Adding upstream version 1:115.7.0.upstream/1%115.7.0upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

101 files changed, 41039 insertions, 0 deletions

diff --git a/third_party/libwebrtc/p2p/base/active_ice_controller_factory_interface.h b/third_party/libwebrtc/p2p/base/active_ice_controller_factory_interface.h
new file mode 100644
index 0000000000..6a47f2253f
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/active_ice_controller_factory_interface.h
@@ -0,0 +1,39 @@
+/*
+ *  Copyright 2022 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_ACTIVE_ICE_CONTROLLER_FACTORY_INTERFACE_H_
+#define P2P_BASE_ACTIVE_ICE_CONTROLLER_FACTORY_INTERFACE_H_
+
+#include <memory>
+
+#include "p2p/base/active_ice_controller_interface.h"
+#include "p2p/base/ice_agent_interface.h"
+#include "p2p/base/ice_controller_factory_interface.h"
+
+namespace cricket {
+
+// An active ICE controller may be constructed with the same arguments as a
+// legacy ICE controller. Additionally, an ICE agent must be provided for the
+// active ICE controller to interact with.
+struct ActiveIceControllerFactoryArgs {
+  IceControllerFactoryArgs legacy_args;
+  IceAgentInterface* ice_agent;
+};
+
+class ActiveIceControllerFactoryInterface {
+ public:
+  virtual ~ActiveIceControllerFactoryInterface() = default;
+  virtual std::unique_ptr<ActiveIceControllerInterface> Create(
+      const ActiveIceControllerFactoryArgs&) = 0;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_ACTIVE_ICE_CONTROLLER_FACTORY_INTERFACE_H_
diff --git a/third_party/libwebrtc/p2p/base/active_ice_controller_interface.h b/third_party/libwebrtc/p2p/base/active_ice_controller_interface.h
new file mode 100644
index 0000000000..e54838ee64
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/active_ice_controller_interface.h
@@ -0,0 +1,84 @@
+/*
+ *  Copyright 2022 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_ACTIVE_ICE_CONTROLLER_INTERFACE_H_
+#define P2P_BASE_ACTIVE_ICE_CONTROLLER_INTERFACE_H_
+
+#include "absl/types/optional.h"
+#include "api/array_view.h"
+#include "p2p/base/connection.h"
+#include "p2p/base/ice_switch_reason.h"
+#include "p2p/base/ice_transport_internal.h"
+#include "p2p/base/transport_description.h"
+
+namespace cricket {
+
+// ActiveIceControllerInterface defines the methods for a module that actively
+// manages the connection used by an ICE transport.
+//
+// An active ICE controller receives updates from the ICE transport when
+//   - the connections state is mutated
+//   - a new connection should be selected as a result of an external event (eg.
+//     a different connection nominated by the remote peer)
+//
+// The active ICE controller takes the appropriate decisions and requests the
+// ICE agent to perform the necessary actions through the IceAgentInterface.
+class ActiveIceControllerInterface {
+ public:
+  virtual ~ActiveIceControllerInterface() = default;
+
+  // Sets the current ICE configuration.
+  virtual void SetIceConfig(const IceConfig& config) = 0;
+
+  // Called when a new connection is added to the ICE transport.
+  virtual void OnConnectionAdded(const Connection* connection) = 0;
+
+  // Called when the transport switches that connection in active use.
+  virtual void OnConnectionSwitched(const Connection* connection) = 0;
+
+  // Called when a connection is destroyed.
+  virtual void OnConnectionDestroyed(const Connection* connection) = 0;
+
+  // Called when a STUN ping has been sent on a connection. This does not
+  // indicate that a STUN response has been received.
+  virtual void OnConnectionPinged(const Connection* connection) = 0;
+
+  // Called when one of the following changes for a connection.
+  // - rtt estimate
+  // - write state
+  // - receiving
+  // - connected
+  // - nominated
+  virtual void OnConnectionUpdated(const Connection* connection) = 0;
+
+  // Compute "STUN_ATTR_USE_CANDIDATE" for a STUN ping on the given connection.
+  virtual bool GetUseCandidateAttribute(const Connection* connection,
+                                        NominationMode mode,
+                                        IceMode remote_ice_mode) const = 0;
+
+  // Called to enque a request to pick and switch to the best available
+  // connection.
+  virtual void OnSortAndSwitchRequest(IceSwitchReason reason) = 0;
+
+  // Called to pick and switch to the best available connection immediately.
+  virtual void OnImmediateSortAndSwitchRequest(IceSwitchReason reason) = 0;
+
+  // Called to switch to the given connection immediately without checking for
+  // the best available connection.
+  virtual bool OnImmediateSwitchRequest(IceSwitchReason reason,
+                                        const Connection* selected) = 0;
+
+  // Only for unit tests
+  virtual const Connection* FindNextPingableConnection() = 0;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_ACTIVE_ICE_CONTROLLER_INTERFACE_H_
diff --git a/third_party/libwebrtc/p2p/base/async_stun_tcp_socket.cc b/third_party/libwebrtc/p2p/base/async_stun_tcp_socket.cc
new file mode 100644
index 0000000000..5f8f07227f
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/async_stun_tcp_socket.cc
@@ -0,0 +1,156 @@
+/*
+ *  Copyright 2013 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/async_stun_tcp_socket.h"
+
+#include <errno.h>
+#include <stdint.h>
+#include <string.h>
+
+#include "api/transport/stun.h"
+#include "rtc_base/byte_order.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/network/sent_packet.h"
+#include "rtc_base/third_party/sigslot/sigslot.h"
+#include "rtc_base/time_utils.h"
+
+namespace cricket {
+
+static const size_t kMaxPacketSize = 64 * 1024;
+
+typedef uint16_t PacketLength;
+static const size_t kPacketLenSize = sizeof(PacketLength);
+static const size_t kPacketLenOffset = 2;
+static const size_t kBufSize = kMaxPacketSize + kStunHeaderSize;
+static const size_t kTurnChannelDataHdrSize = 4;
+
+inline bool IsStunMessage(uint16_t msg_type) {
+  // The first two bits of a channel data message are 0b01.
+  return (msg_type & 0xC000) ? false : true;
+}
+
+// AsyncStunTCPSocket
+// Binds and connects `socket` and creates AsyncTCPSocket for
+// it. Takes ownership of `socket`. Returns NULL if bind() or
+// connect() fail (`socket` is destroyed in that case).
+AsyncStunTCPSocket* AsyncStunTCPSocket::Create(
+    rtc::Socket* socket,
+    const rtc::SocketAddress& bind_address,
+    const rtc::SocketAddress& remote_address) {
+  return new AsyncStunTCPSocket(
+      AsyncTCPSocketBase::ConnectSocket(socket, bind_address, remote_address));
+}
+
+AsyncStunTCPSocket::AsyncStunTCPSocket(rtc::Socket* socket)
+    : rtc::AsyncTCPSocketBase(socket, kBufSize) {}
+
+int AsyncStunTCPSocket::Send(const void* pv,
+                             size_t cb,
+                             const rtc::PacketOptions& options) {
+  if (cb > kBufSize || cb < kPacketLenSize + kPacketLenOffset) {
+    SetError(EMSGSIZE);
+    return -1;
+  }
+
+  // If we are blocking on send, then silently drop this packet
+  if (!IsOutBufferEmpty())
+    return static_cast<int>(cb);
+
+  int pad_bytes;
+  size_t expected_pkt_len = GetExpectedLength(pv, cb, &pad_bytes);
+
+  // Accepts only complete STUN/ChannelData packets.
+  if (cb != expected_pkt_len)
+    return -1;
+
+  AppendToOutBuffer(pv, cb);
+
+  RTC_DCHECK(pad_bytes < 4);
+  char padding[4] = {0};
+  AppendToOutBuffer(padding, pad_bytes);
+
+  int res = FlushOutBuffer();
+  if (res <= 0) {
+    // drop packet if we made no progress
+    ClearOutBuffer();
+    return res;
+  }
+
+  rtc::SentPacket sent_packet(options.packet_id, rtc::TimeMillis());
+  SignalSentPacket(this, sent_packet);
+
+  // We claim to have sent the whole thing, even if we only sent partial
+  return static_cast<int>(cb);
+}
+
+void AsyncStunTCPSocket::ProcessInput(char* data, size_t* len) {
+  rtc::SocketAddress remote_addr(GetRemoteAddress());
+  // STUN packet - First 4 bytes. Total header size is 20 bytes.
+  // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+  // |0 0|     STUN Message Type     |         Message Length        |
+  // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+  // TURN ChannelData
+  // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+  // |         Channel Number        |            Length             |
+  // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+  while (true) {
+    // We need at least 4 bytes to read the STUN or ChannelData packet length.
+    if (*len < kPacketLenOffset + kPacketLenSize)
+      return;
+
+    int pad_bytes;
+    size_t expected_pkt_len = GetExpectedLength(data, *len, &pad_bytes);
+    size_t actual_length = expected_pkt_len + pad_bytes;
+
+    if (*len < actual_length) {
+      return;
+    }
+
+    SignalReadPacket(this, data, expected_pkt_len, remote_addr,
+                     rtc::TimeMicros());
+
+    *len -= actual_length;
+    if (*len > 0) {
+      memmove(data, data + actual_length, *len);
+    }
+  }
+}
+
+size_t AsyncStunTCPSocket::GetExpectedLength(const void* data,
+                                             size_t len,
+                                             int* pad_bytes) {
+  *pad_bytes = 0;
+  PacketLength pkt_len =
+      rtc::GetBE16(static_cast<const char*>(data) + kPacketLenOffset);
+  size_t expected_pkt_len;
+  uint16_t msg_type = rtc::GetBE16(data);
+  if (IsStunMessage(msg_type)) {
+    // STUN message.
+    expected_pkt_len = kStunHeaderSize + pkt_len;
+  } else {
+    // TURN ChannelData message.
+    expected_pkt_len = kTurnChannelDataHdrSize + pkt_len;
+    // From RFC 5766 section 11.5
+    // Over TCP and TLS-over-TCP, the ChannelData message MUST be padded to
+    // a multiple of four bytes in order to ensure the alignment of
+    // subsequent messages.  The padding is not reflected in the length
+    // field of the ChannelData message, so the actual size of a ChannelData
+    // message (including padding) is (4 + Length) rounded up to the nearest
+    // multiple of 4.  Over UDP, the padding is not required but MAY be
+    // included.
+    if (expected_pkt_len % 4)
+      *pad_bytes = 4 - (expected_pkt_len % 4);
+  }
+  return expected_pkt_len;
+}
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/async_stun_tcp_socket.h b/third_party/libwebrtc/p2p/base/async_stun_tcp_socket.h
new file mode 100644
index 0000000000..f0df42b52a
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/async_stun_tcp_socket.h
@@ -0,0 +1,51 @@
+/*
+ *  Copyright 2013 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_ASYNC_STUN_TCP_SOCKET_H_
+#define P2P_BASE_ASYNC_STUN_TCP_SOCKET_H_
+
+#include <stddef.h>
+
+#include "rtc_base/async_packet_socket.h"
+#include "rtc_base/async_tcp_socket.h"
+#include "rtc_base/socket.h"
+#include "rtc_base/socket_address.h"
+
+namespace cricket {
+
+class AsyncStunTCPSocket : public rtc::AsyncTCPSocketBase {
+ public:
+  // Binds and connects `socket` and creates AsyncTCPSocket for
+  // it. Takes ownership of `socket`. Returns NULL if bind() or
+  // connect() fail (`socket` is destroyed in that case).
+  static AsyncStunTCPSocket* Create(rtc::Socket* socket,
+                                    const rtc::SocketAddress& bind_address,
+                                    const rtc::SocketAddress& remote_address);
+
+  explicit AsyncStunTCPSocket(rtc::Socket* socket);
+
+  AsyncStunTCPSocket(const AsyncStunTCPSocket&) = delete;
+  AsyncStunTCPSocket& operator=(const AsyncStunTCPSocket&) = delete;
+
+  int Send(const void* pv,
+           size_t cb,
+           const rtc::PacketOptions& options) override;
+  void ProcessInput(char* data, size_t* len) override;
+
+ private:
+  // This method returns the message hdr + length written in the header.
+  // This method also returns the number of padding bytes needed/added to the
+  // turn message. `pad_bytes` should be used only when `is_turn` is true.
+  size_t GetExpectedLength(const void* data, size_t len, int* pad_bytes);
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_ASYNC_STUN_TCP_SOCKET_H_
diff --git a/third_party/libwebrtc/p2p/base/async_stun_tcp_socket_unittest.cc b/third_party/libwebrtc/p2p/base/async_stun_tcp_socket_unittest.cc
new file mode 100644
index 0000000000..72d6a7fde0
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/async_stun_tcp_socket_unittest.cc
@@ -0,0 +1,288 @@
+/*
+ *  Copyright 2013 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/async_stun_tcp_socket.h"
+
+#include <stdint.h>
+#include <string.h>
+
+#include <list>
+#include <memory>
+#include <string>
+#include <utility>
+
+#include "absl/memory/memory.h"
+#include "rtc_base/network/sent_packet.h"
+#include "rtc_base/socket.h"
+#include "rtc_base/third_party/sigslot/sigslot.h"
+#include "rtc_base/thread.h"
+#include "rtc_base/virtual_socket_server.h"
+#include "test/gtest.h"
+
+namespace cricket {
+
+static unsigned char kStunMessageWithZeroLength[] = {
+    0x00, 0x01, 0x00, 0x00,  // length of 0 (last 2 bytes)
+    0x21, 0x12, 0xA4, 0x42, '0', '1', '2', '3',
+    '4',  '5',  '6',  '7',  '8', '9', 'a', 'b',
+};
+
+static unsigned char kTurnChannelDataMessageWithZeroLength[] = {
+    0x40, 0x00, 0x00, 0x00,  // length of 0 (last 2 bytes)
+};
+
+static unsigned char kTurnChannelDataMessage[] = {
+    0x40, 0x00, 0x00, 0x10, 0x21, 0x12, 0xA4, 0x42, '0', '1',
+    '2',  '3',  '4',  '5',  '6',  '7',  '8',  '9',  'a', 'b',
+};
+
+static unsigned char kStunMessageWithInvalidLength[] = {
+    0x00, 0x01, 0x00, 0x10, 0x21, 0x12, 0xA4, 0x42, '0', '1',
+    '2',  '3',  '4',  '5',  '6',  '7',  '8',  '9',  'a', 'b',
+};
+
+static unsigned char kTurnChannelDataMessageWithInvalidLength[] = {
+    0x80, 0x00, 0x00, 0x20, 0x21, 0x12, 0xA4, 0x42, '0', '1',
+    '2',  '3',  '4',  '5',  '6',  '7',  '8',  '9',  'a', 'b',
+};
+
+static unsigned char kTurnChannelDataMessageWithOddLength[] = {
+    0x40, 0x00, 0x00, 0x05, 0x21, 0x12, 0xA4, 0x42, '0',
+};
+
+static const rtc::SocketAddress kClientAddr("11.11.11.11", 0);
+static const rtc::SocketAddress kServerAddr("22.22.22.22", 0);
+
+class AsyncStunServerTCPSocket : public rtc::AsyncTcpListenSocket {
+ public:
+  explicit AsyncStunServerTCPSocket(std::unique_ptr<rtc::Socket> socket)
+      : AsyncTcpListenSocket(std::move(socket)) {}
+  void HandleIncomingConnection(rtc::Socket* socket) override {
+    SignalNewConnection(this, new AsyncStunTCPSocket(socket));
+  }
+};
+
+class AsyncStunTCPSocketTest : public ::testing::Test,
+                               public sigslot::has_slots<> {
+ protected:
+  AsyncStunTCPSocketTest()
+      : vss_(new rtc::VirtualSocketServer()), thread_(vss_.get()) {}
+
+  virtual void SetUp() { CreateSockets(); }
+
+  void CreateSockets() {
+    std::unique_ptr<rtc::Socket> server =
+        absl::WrapUnique(vss_->CreateSocket(kServerAddr.family(), SOCK_STREAM));
+    server->Bind(kServerAddr);
+    listen_socket_ =
+        std::make_unique<AsyncStunServerTCPSocket>(std::move(server));
+    listen_socket_->SignalNewConnection.connect(
+        this, &AsyncStunTCPSocketTest::OnNewConnection);
+
+    rtc::Socket* client = vss_->CreateSocket(kClientAddr.family(), SOCK_STREAM);
+    send_socket_.reset(AsyncStunTCPSocket::Create(
+        client, kClientAddr, listen_socket_->GetLocalAddress()));
+    send_socket_->SignalSentPacket.connect(
+        this, &AsyncStunTCPSocketTest::OnSentPacket);
+    ASSERT_TRUE(send_socket_.get() != NULL);
+    vss_->ProcessMessagesUntilIdle();
+  }
+
+  void OnReadPacket(rtc::AsyncPacketSocket* socket,
+                    const char* data,
+                    size_t len,
+                    const rtc::SocketAddress& remote_addr,
+                    const int64_t& /* packet_time_us */) {
+    recv_packets_.push_back(std::string(data, len));
+  }
+
+  void OnSentPacket(rtc::AsyncPacketSocket* socket,
+                    const rtc::SentPacket& packet) {
+    ++sent_packets_;
+  }
+
+  void OnNewConnection(rtc::AsyncListenSocket* /*server*/,
+                       rtc::AsyncPacketSocket* new_socket) {
+    recv_socket_ = absl::WrapUnique(new_socket);
+    new_socket->SignalReadPacket.connect(this,
+                                         &AsyncStunTCPSocketTest::OnReadPacket);
+  }
+
+  bool Send(const void* data, size_t len) {
+    rtc::PacketOptions options;
+    int ret =
+        send_socket_->Send(reinterpret_cast<const char*>(data), len, options);
+    vss_->ProcessMessagesUntilIdle();
+    return (ret == static_cast<int>(len));
+  }
+
+  bool CheckData(const void* data, int len) {
+    bool ret = false;
+    if (recv_packets_.size()) {
+      std::string packet = recv_packets_.front();
+      recv_packets_.pop_front();
+      ret = (memcmp(data, packet.c_str(), len) == 0);
+    }
+    return ret;
+  }
+
+  std::unique_ptr<rtc::VirtualSocketServer> vss_;
+  rtc::AutoSocketServerThread thread_;
+  std::unique_ptr<AsyncStunTCPSocket> send_socket_;
+  std::unique_ptr<rtc::AsyncListenSocket> listen_socket_;
+  std::unique_ptr<rtc::AsyncPacketSocket> recv_socket_;
+  std::list<std::string> recv_packets_;
+  int sent_packets_ = 0;
+};
+
+// Testing a stun packet sent/recv properly.
+TEST_F(AsyncStunTCPSocketTest, TestSingleStunPacket) {
+  EXPECT_TRUE(
+      Send(kStunMessageWithZeroLength, sizeof(kStunMessageWithZeroLength)));
+  EXPECT_EQ(1u, recv_packets_.size());
+  EXPECT_TRUE(CheckData(kStunMessageWithZeroLength,
+                        sizeof(kStunMessageWithZeroLength)));
+}
+
+// Verify sending multiple packets.
+TEST_F(AsyncStunTCPSocketTest, TestMultipleStunPackets) {
+  EXPECT_TRUE(
+      Send(kStunMessageWithZeroLength, sizeof(kStunMessageWithZeroLength)));
+  EXPECT_TRUE(
+      Send(kStunMessageWithZeroLength, sizeof(kStunMessageWithZeroLength)));
+  EXPECT_TRUE(
+      Send(kStunMessageWithZeroLength, sizeof(kStunMessageWithZeroLength)));
+  EXPECT_TRUE(
+      Send(kStunMessageWithZeroLength, sizeof(kStunMessageWithZeroLength)));
+  EXPECT_EQ(4u, recv_packets_.size());
+}
+
+// Verifying TURN channel data message with zero length.
+TEST_F(AsyncStunTCPSocketTest, TestTurnChannelDataWithZeroLength) {
+  EXPECT_TRUE(Send(kTurnChannelDataMessageWithZeroLength,
+                   sizeof(kTurnChannelDataMessageWithZeroLength)));
+  EXPECT_EQ(1u, recv_packets_.size());
+  EXPECT_TRUE(CheckData(kTurnChannelDataMessageWithZeroLength,
+                        sizeof(kTurnChannelDataMessageWithZeroLength)));
+}
+
+// Verifying TURN channel data message.
+TEST_F(AsyncStunTCPSocketTest, TestTurnChannelData) {
+  EXPECT_TRUE(Send(kTurnChannelDataMessage, sizeof(kTurnChannelDataMessage)));
+  EXPECT_EQ(1u, recv_packets_.size());
+  EXPECT_TRUE(
+      CheckData(kTurnChannelDataMessage, sizeof(kTurnChannelDataMessage)));
+}
+
+// Verifying TURN channel messages which needs padding handled properly.
+TEST_F(AsyncStunTCPSocketTest, TestTurnChannelDataPadding) {
+  EXPECT_TRUE(Send(kTurnChannelDataMessageWithOddLength,
+                   sizeof(kTurnChannelDataMessageWithOddLength)));
+  EXPECT_EQ(1u, recv_packets_.size());
+  EXPECT_TRUE(CheckData(kTurnChannelDataMessageWithOddLength,
+                        sizeof(kTurnChannelDataMessageWithOddLength)));
+}
+
+// Verifying stun message with invalid length.
+TEST_F(AsyncStunTCPSocketTest, TestStunInvalidLength) {
+  EXPECT_FALSE(Send(kStunMessageWithInvalidLength,
+                    sizeof(kStunMessageWithInvalidLength)));
+  EXPECT_EQ(0u, recv_packets_.size());
+
+  // Modify the message length to larger value.
+  kStunMessageWithInvalidLength[2] = 0xFF;
+  kStunMessageWithInvalidLength[3] = 0xFF;
+  EXPECT_FALSE(Send(kStunMessageWithInvalidLength,
+                    sizeof(kStunMessageWithInvalidLength)));
+
+  // Modify the message length to smaller value.
+  kStunMessageWithInvalidLength[2] = 0x00;
+  kStunMessageWithInvalidLength[3] = 0x01;
+  EXPECT_FALSE(Send(kStunMessageWithInvalidLength,
+                    sizeof(kStunMessageWithInvalidLength)));
+}
+
+// Verifying TURN channel data message with invalid length.
+TEST_F(AsyncStunTCPSocketTest, TestTurnChannelDataWithInvalidLength) {
+  EXPECT_FALSE(Send(kTurnChannelDataMessageWithInvalidLength,
+                    sizeof(kTurnChannelDataMessageWithInvalidLength)));
+  // Modify the length to larger value.
+  kTurnChannelDataMessageWithInvalidLength[2] = 0xFF;
+  kTurnChannelDataMessageWithInvalidLength[3] = 0xF0;
+  EXPECT_FALSE(Send(kTurnChannelDataMessageWithInvalidLength,
+                    sizeof(kTurnChannelDataMessageWithInvalidLength)));
+
+  // Modify the length to smaller value.
+  kTurnChannelDataMessageWithInvalidLength[2] = 0x00;
+  kTurnChannelDataMessageWithInvalidLength[3] = 0x00;
+  EXPECT_FALSE(Send(kTurnChannelDataMessageWithInvalidLength,
+                    sizeof(kTurnChannelDataMessageWithInvalidLength)));
+}
+
+// Verifying a small buffer handled (dropped) properly. This will be
+// a common one for both stun and turn.
+TEST_F(AsyncStunTCPSocketTest, TestTooSmallMessageBuffer) {
+  char data[1];
+  EXPECT_FALSE(Send(data, sizeof(data)));
+}
+
+// Verifying a legal large turn message.
+TEST_F(AsyncStunTCPSocketTest, TestMaximumSizeTurnPacket) {
+  unsigned char packet[65539];
+  packet[0] = 0x40;
+  packet[1] = 0x00;
+  packet[2] = 0xFF;
+  packet[3] = 0xFF;
+  EXPECT_TRUE(Send(packet, sizeof(packet)));
+}
+
+// Verifying a legal large stun message.
+TEST_F(AsyncStunTCPSocketTest, TestMaximumSizeStunPacket) {
+  unsigned char packet[65552];
+  packet[0] = 0x00;
+  packet[1] = 0x01;
+  packet[2] = 0xFF;
+  packet[3] = 0xFC;
+  EXPECT_TRUE(Send(packet, sizeof(packet)));
+}
+
+// Test that a turn message is sent completely even if it exceeds the socket
+// send buffer capacity.
+TEST_F(AsyncStunTCPSocketTest, TestWithSmallSendBuffer) {
+  vss_->set_send_buffer_capacity(1);
+  Send(kTurnChannelDataMessageWithOddLength,
+       sizeof(kTurnChannelDataMessageWithOddLength));
+  EXPECT_EQ(1u, recv_packets_.size());
+  EXPECT_TRUE(CheckData(kTurnChannelDataMessageWithOddLength,
+                        sizeof(kTurnChannelDataMessageWithOddLength)));
+}
+
+// Test that SignalSentPacket is fired when a packet is sent.
+TEST_F(AsyncStunTCPSocketTest, SignalSentPacketFiredWhenPacketSent) {
+  ASSERT_TRUE(
+      Send(kStunMessageWithZeroLength, sizeof(kStunMessageWithZeroLength)));
+  EXPECT_EQ(1, sent_packets_);
+  // Send another packet for good measure.
+  ASSERT_TRUE(
+      Send(kStunMessageWithZeroLength, sizeof(kStunMessageWithZeroLength)));
+  EXPECT_EQ(2, sent_packets_);
+}
+
+// Test that SignalSentPacket isn't fired when a packet isn't sent (for
+// example, because it's invalid).
+TEST_F(AsyncStunTCPSocketTest, SignalSentPacketNotFiredWhenPacketNotSent) {
+  // Attempt to send a packet that's too small; since it isn't sent,
+  // SignalSentPacket shouldn't fire.
+  char data[1];
+  ASSERT_FALSE(Send(data, sizeof(data)));
+  EXPECT_EQ(0, sent_packets_);
+}
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/basic_async_resolver_factory.cc b/third_party/libwebrtc/p2p/base/basic_async_resolver_factory.cc
new file mode 100644
index 0000000000..3fdf75b12f
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/basic_async_resolver_factory.cc
@@ -0,0 +1,53 @@
+/*
+ *  Copyright 2018 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/basic_async_resolver_factory.h"
+
+#include <memory>
+#include <utility>
+
+#include "absl/memory/memory.h"
+#include "api/async_dns_resolver.h"
+#include "api/wrapping_async_dns_resolver.h"
+#include "rtc_base/async_resolver.h"
+#include "rtc_base/logging.h"
+
+namespace webrtc {
+
+rtc::AsyncResolverInterface* BasicAsyncResolverFactory::Create() {
+  return new rtc::AsyncResolver();
+}
+
+
+std::unique_ptr<webrtc::AsyncDnsResolverInterface>
+WrappingAsyncDnsResolverFactory::Create() {
+  return std::make_unique<WrappingAsyncDnsResolver>(wrapped_factory_->Create());
+}
+
+std::unique_ptr<webrtc::AsyncDnsResolverInterface>
+WrappingAsyncDnsResolverFactory::CreateAndResolve(
+    const rtc::SocketAddress& addr,
+    std::function<void()> callback) {
+  std::unique_ptr<webrtc::AsyncDnsResolverInterface> resolver = Create();
+  resolver->Start(addr, std::move(callback));
+  return resolver;
+}
+
+std::unique_ptr<webrtc::AsyncDnsResolverInterface>
+WrappingAsyncDnsResolverFactory::CreateAndResolve(
+    const rtc::SocketAddress& addr,
+    int family,
+    std::function<void()> callback) {
+  std::unique_ptr<webrtc::AsyncDnsResolverInterface> resolver = Create();
+  resolver->Start(addr, family, std::move(callback));
+  return resolver;
+}
+
+}  // namespace webrtc
diff --git a/third_party/libwebrtc/p2p/base/basic_async_resolver_factory.h b/third_party/libwebrtc/p2p/base/basic_async_resolver_factory.h
new file mode 100644
index 0000000000..9a0ba1ab28
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/basic_async_resolver_factory.h
@@ -0,0 +1,62 @@
+/*
+ *  Copyright 2018 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_BASIC_ASYNC_RESOLVER_FACTORY_H_
+#define P2P_BASE_BASIC_ASYNC_RESOLVER_FACTORY_H_
+
+#include <functional>
+#include <memory>
+#include <utility>
+
+#include "api/async_dns_resolver.h"
+#include "api/async_resolver_factory.h"
+#include "rtc_base/async_resolver_interface.h"
+
+namespace webrtc {
+
+class BasicAsyncResolverFactory final : public AsyncResolverFactory {
+ public:
+  rtc::AsyncResolverInterface* Create() override;
+};
+
+// This class wraps a factory using the older webrtc::AsyncResolverFactory API,
+// and produces webrtc::AsyncDnsResolver objects that contain an
+// rtc::AsyncResolver object.
+class WrappingAsyncDnsResolverFactory final
+    : public AsyncDnsResolverFactoryInterface {
+ public:
+  explicit WrappingAsyncDnsResolverFactory(
+      std::unique_ptr<AsyncResolverFactory> wrapped_factory)
+      : owned_factory_(std::move(wrapped_factory)),
+        wrapped_factory_(owned_factory_.get()) {}
+
+  explicit WrappingAsyncDnsResolverFactory(
+      AsyncResolverFactory* non_owned_factory)
+      : wrapped_factory_(non_owned_factory) {}
+
+  std::unique_ptr<webrtc::AsyncDnsResolverInterface> CreateAndResolve(
+      const rtc::SocketAddress& addr,
+      std::function<void()> callback) override;
+
+  std::unique_ptr<webrtc::AsyncDnsResolverInterface> CreateAndResolve(
+      const rtc::SocketAddress& addr,
+      int family,
+      std::function<void()> callback) override;
+
+  std::unique_ptr<webrtc::AsyncDnsResolverInterface> Create() override;
+
+ private:
+  const std::unique_ptr<AsyncResolverFactory> owned_factory_;
+  AsyncResolverFactory* const wrapped_factory_;
+};
+
+}  // namespace webrtc
+
+#endif  // P2P_BASE_BASIC_ASYNC_RESOLVER_FACTORY_H_
diff --git a/third_party/libwebrtc/p2p/base/basic_async_resolver_factory_unittest.cc b/third_party/libwebrtc/p2p/base/basic_async_resolver_factory_unittest.cc
new file mode 100644
index 0000000000..77b97e75e6
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/basic_async_resolver_factory_unittest.cc
@@ -0,0 +1,111 @@
+/*
+ *  Copyright 2018 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/basic_async_resolver_factory.h"
+
+#include "api/test/mock_async_dns_resolver.h"
+#include "p2p/base/mock_async_resolver.h"
+#include "rtc_base/async_resolver.h"
+#include "rtc_base/gunit.h"
+#include "rtc_base/socket_address.h"
+#include "rtc_base/third_party/sigslot/sigslot.h"
+#include "test/gmock.h"
+#include "test/gtest.h"
+#include "test/testsupport/rtc_expect_death.h"
+
+namespace webrtc {
+
+class BasicAsyncResolverFactoryTest : public ::testing::Test,
+                                      public sigslot::has_slots<> {
+ public:
+  void TestCreate() {
+    BasicAsyncResolverFactory factory;
+    rtc::AsyncResolverInterface* resolver = factory.Create();
+    ASSERT_TRUE(resolver);
+    resolver->SignalDone.connect(
+        this, &BasicAsyncResolverFactoryTest::SetAddressResolved);
+
+    rtc::SocketAddress address("", 0);
+    resolver->Start(address);
+    ASSERT_TRUE_WAIT(address_resolved_, 10000 /*ms*/);
+    resolver->Destroy(false);
+  }
+
+  void SetAddressResolved(rtc::AsyncResolverInterface* resolver) {
+    address_resolved_ = true;
+  }
+
+ private:
+  bool address_resolved_ = false;
+};
+
+// This test is primarily intended to let tools check that the created resolver
+// doesn't leak.
+TEST_F(BasicAsyncResolverFactoryTest, TestCreate) {
+  rtc::AutoThread main_thread;
+  TestCreate();
+}
+
+TEST(WrappingAsyncDnsResolverFactoryTest, TestCreateAndResolve) {
+  rtc::AutoThread main_thread;
+  WrappingAsyncDnsResolverFactory factory(
+      std::make_unique<BasicAsyncResolverFactory>());
+
+  std::unique_ptr<AsyncDnsResolverInterface> resolver(factory.Create());
+  ASSERT_TRUE(resolver);
+
+  bool address_resolved = false;
+  rtc::SocketAddress address("", 0);
+  resolver->Start(address, [&address_resolved]() { address_resolved = true; });
+  ASSERT_TRUE_WAIT(address_resolved, 10000 /*ms*/);
+  resolver.reset();
+}
+
+TEST(WrappingAsyncDnsResolverFactoryTest, WrapOtherResolver) {
+  rtc::AutoThread main_thread;
+  BasicAsyncResolverFactory non_owned_factory;
+  WrappingAsyncDnsResolverFactory factory(&non_owned_factory);
+  std::unique_ptr<AsyncDnsResolverInterface> resolver(factory.Create());
+  ASSERT_TRUE(resolver);
+
+  bool address_resolved = false;
+  rtc::SocketAddress address("", 0);
+  resolver->Start(address, [&address_resolved]() { address_resolved = true; });
+  ASSERT_TRUE_WAIT(address_resolved, 10000 /*ms*/);
+  resolver.reset();
+}
+
+#if GTEST_HAS_DEATH_TEST && defined(WEBRTC_LINUX)
+// Tests that the prohibition against deleting the resolver from the callback
+// is enforced. This is required by the use of sigslot in the wrapped resolver.
+// Checking the error message fails on a number of platforms, so run this
+// test only on the platforms where it works.
+void CallResolver(WrappingAsyncDnsResolverFactory& factory) {
+  rtc::SocketAddress address("", 0);
+  std::unique_ptr<AsyncDnsResolverInterface> resolver(factory.Create());
+  resolver->Start(address, [&resolver]() { resolver.reset(); });
+  WAIT(!resolver.get(), 10000 /*ms*/);
+}
+
+TEST(WrappingAsyncDnsResolverFactoryDeathTest, DestroyResolverInCallback) {
+  rtc::AutoThread main_thread;
+  // TODO(bugs.webrtc.org/12652): Rewrite as death test in loop style when it
+  // works.
+  WrappingAsyncDnsResolverFactory factory(
+      std::make_unique<BasicAsyncResolverFactory>());
+
+  // Since EXPECT_DEATH is thread sensitive, and the resolver creates a thread,
+  // we wrap the whole creation section in EXPECT_DEATH.
+  RTC_EXPECT_DEATH(CallResolver(factory),
+                   "Check failed: !within_resolve_result_");
+}
+#endif
+
+}  // namespace webrtc
diff --git a/third_party/libwebrtc/p2p/base/basic_ice_controller.cc b/third_party/libwebrtc/p2p/base/basic_ice_controller.cc
new file mode 100644
index 0000000000..55f187cb9a
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/basic_ice_controller.cc
@@ -0,0 +1,855 @@
+/*
+ *  Copyright 2019 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/basic_ice_controller.h"
+
+namespace {
+
+// The minimum improvement in RTT that justifies a switch.
+const int kMinImprovement = 10;
+
+bool IsRelayRelay(const cricket::Connection* conn) {
+  return conn->local_candidate().type() == cricket::RELAY_PORT_TYPE &&
+         conn->remote_candidate().type() == cricket::RELAY_PORT_TYPE;
+}
+
+bool IsUdp(const cricket::Connection* conn) {
+  return conn->local_candidate().relay_protocol() == cricket::UDP_PROTOCOL_NAME;
+}
+
+// TODO(qingsi) Use an enum to replace the following constants for all
+// comparision results.
+static constexpr int a_is_better = 1;
+static constexpr int b_is_better = -1;
+static constexpr int a_and_b_equal = 0;
+
+bool LocalCandidateUsesPreferredNetwork(
+    const cricket::Connection* conn,
+    absl::optional<rtc::AdapterType> network_preference) {
+  rtc::AdapterType network_type = conn->network()->type();
+  return network_preference.has_value() && (network_type == network_preference);
+}
+
+int CompareCandidatePairsByNetworkPreference(
+    const cricket::Connection* a,
+    const cricket::Connection* b,
+    absl::optional<rtc::AdapterType> network_preference) {
+  bool a_uses_preferred_network =
+      LocalCandidateUsesPreferredNetwork(a, network_preference);
+  bool b_uses_preferred_network =
+      LocalCandidateUsesPreferredNetwork(b, network_preference);
+  if (a_uses_preferred_network && !b_uses_preferred_network) {
+    return a_is_better;
+  } else if (!a_uses_preferred_network && b_uses_preferred_network) {
+    return b_is_better;
+  }
+  return a_and_b_equal;
+}
+
+}  // namespace
+
+namespace cricket {
+
+BasicIceController::BasicIceController(const IceControllerFactoryArgs& args)
+    : ice_transport_state_func_(args.ice_transport_state_func),
+      ice_role_func_(args.ice_role_func),
+      is_connection_pruned_func_(args.is_connection_pruned_func),
+      field_trials_(args.ice_field_trials) {}
+
+BasicIceController::~BasicIceController() {}
+
+void BasicIceController::SetIceConfig(const IceConfig& config) {
+  config_ = config;
+}
+
+void BasicIceController::SetSelectedConnection(
+    const Connection* selected_connection) {
+  selected_connection_ = selected_connection;
+}
+
+void BasicIceController::AddConnection(const Connection* connection) {
+  connections_.push_back(connection);
+  unpinged_connections_.insert(connection);
+}
+
+void BasicIceController::OnConnectionDestroyed(const Connection* connection) {
+  pinged_connections_.erase(connection);
+  unpinged_connections_.erase(connection);
+  connections_.erase(absl::c_find(connections_, connection));
+  if (selected_connection_ == connection)
+    selected_connection_ = nullptr;
+}
+
+bool BasicIceController::HasPingableConnection() const {
+  int64_t now = rtc::TimeMillis();
+  return absl::c_any_of(connections_, [this, now](const Connection* c) {
+    return IsPingable(c, now);
+  });
+}
+
+IceControllerInterface::PingResult BasicIceController::SelectConnectionToPing(
+    int64_t last_ping_sent_ms) {
+  // When the selected connection is not receiving or not writable, or any
+  // active connection has not been pinged enough times, use the weak ping
+  // interval.
+  bool need_more_pings_at_weak_interval =
+      absl::c_any_of(connections_, [](const Connection* conn) {
+        return conn->active() &&
+               conn->num_pings_sent() < MIN_PINGS_AT_WEAK_PING_INTERVAL;
+      });
+  int ping_interval = (weak() || need_more_pings_at_weak_interval)
+                          ? weak_ping_interval()
+                          : strong_ping_interval();
+
+  const Connection* conn = nullptr;
+  if (rtc::TimeMillis() >= last_ping_sent_ms + ping_interval) {
+    conn = FindNextPingableConnection();
+  }
+  PingResult res(conn, std::min(ping_interval, check_receiving_interval()));
+  return res;
+}
+
+void BasicIceController::MarkConnectionPinged(const Connection* conn) {
+  if (conn && pinged_connections_.insert(conn).second) {
+    unpinged_connections_.erase(conn);
+  }
+}
+
+// Returns the next pingable connection to ping.
+const Connection* BasicIceController::FindNextPingableConnection() {
+  int64_t now = rtc::TimeMillis();
+
+  // Rule 1: Selected connection takes priority over non-selected ones.
+  if (selected_connection_ && selected_connection_->connected() &&
+      selected_connection_->writable() &&
+      WritableConnectionPastPingInterval(selected_connection_, now)) {
+    return selected_connection_;
+  }
+
+  // Rule 2: If the channel is weak, we need to find a new writable and
+  // receiving connection, probably on a different network. If there are lots of
+  // connections, it may take several seconds between two pings for every
+  // non-selected connection. This will cause the receiving state of those
+  // connections to be false, and thus they won't be selected. This is
+  // problematic for network fail-over. We want to make sure at least one
+  // connection per network is pinged frequently enough in order for it to be
+  // selectable. So we prioritize one connection per network.
+  // Rule 2.1: Among such connections, pick the one with the earliest
+  // last-ping-sent time.
+  if (weak()) {
+    std::vector<const Connection*> pingable_selectable_connections;
+    absl::c_copy_if(GetBestWritableConnectionPerNetwork(),
+                    std::back_inserter(pingable_selectable_connections),
+                    [this, now](const Connection* conn) {
+                      return WritableConnectionPastPingInterval(conn, now);
+                    });
+    auto iter = absl::c_min_element(
+        pingable_selectable_connections,
+        [](const Connection* conn1, const Connection* conn2) {
+          return conn1->last_ping_sent() < conn2->last_ping_sent();
+        });
+    if (iter != pingable_selectable_connections.end()) {
+      return *iter;
+    }
+  }
+
+  // Rule 3: Triggered checks have priority over non-triggered connections.
+  // Rule 3.1: Among triggered checks, oldest takes precedence.
+  const Connection* oldest_triggered_check =
+      FindOldestConnectionNeedingTriggeredCheck(now);
+  if (oldest_triggered_check) {
+    return oldest_triggered_check;
+  }
+
+  // Rule 4: Unpinged connections have priority over pinged ones.
+  RTC_CHECK(connections_.size() ==
+            pinged_connections_.size() + unpinged_connections_.size());
+  // If there are unpinged and pingable connections, only ping those.
+  // Otherwise, treat everything as unpinged.
+  // TODO(honghaiz): Instead of adding two separate vectors, we can add a state
+  // "pinged" to filter out unpinged connections.
+  if (absl::c_none_of(unpinged_connections_,
+                      [this, now](const Connection* conn) {
+                        return this->IsPingable(conn, now);
+                      })) {
+    unpinged_connections_.insert(pinged_connections_.begin(),
+                                 pinged_connections_.end());
+    pinged_connections_.clear();
+  }
+
+  // Among un-pinged pingable connections, "more pingable" takes precedence.
+  std::vector<const Connection*> pingable_connections;
+  absl::c_copy_if(
+      unpinged_connections_, std::back_inserter(pingable_connections),
+      [this, now](const Connection* conn) { return IsPingable(conn, now); });
+  auto iter = absl::c_max_element(
+      pingable_connections,
+      [this](const Connection* conn1, const Connection* conn2) {
+        // Some implementations of max_element
+        // compare an element with itself.
+        if (conn1 == conn2) {
+          return false;
+        }
+        return MorePingable(conn1, conn2) == conn2;
+      });
+  if (iter != pingable_connections.end()) {
+    return *iter;
+  }
+  return nullptr;
+}
+
+// Find "triggered checks".  We ping first those connections that have
+// received a ping but have not sent a ping since receiving it
+// (last_ping_received > last_ping_sent).  But we shouldn't do
+// triggered checks if the connection is already writable.
+const Connection* BasicIceController::FindOldestConnectionNeedingTriggeredCheck(
+    int64_t now) {
+  const Connection* oldest_needing_triggered_check = nullptr;
+  for (auto* conn : connections_) {
+    if (!IsPingable(conn, now)) {
+      continue;
+    }
+    bool needs_triggered_check =
+        (!conn->writable() &&
+         conn->last_ping_received() > conn->last_ping_sent());
+    if (needs_triggered_check &&
+        (!oldest_needing_triggered_check ||
+         (conn->last_ping_received() <
+          oldest_needing_triggered_check->last_ping_received()))) {
+      oldest_needing_triggered_check = conn;
+    }
+  }
+
+  if (oldest_needing_triggered_check) {
+    RTC_LOG(LS_INFO) << "Selecting connection for triggered check: "
+                     << oldest_needing_triggered_check->ToString();
+  }
+  return oldest_needing_triggered_check;
+}
+
+bool BasicIceController::WritableConnectionPastPingInterval(
+    const Connection* conn,
+    int64_t now) const {
+  int interval = CalculateActiveWritablePingInterval(conn, now);
+  return conn->last_ping_sent() + interval <= now;
+}
+
+int BasicIceController::CalculateActiveWritablePingInterval(
+    const Connection* conn,
+    int64_t now) const {
+  // Ping each connection at a higher rate at least
+  // MIN_PINGS_AT_WEAK_PING_INTERVAL times.
+  if (conn->num_pings_sent() < MIN_PINGS_AT_WEAK_PING_INTERVAL) {
+    return weak_ping_interval();
+  }
+
+  int stable_interval =
+      config_.stable_writable_connection_ping_interval_or_default();
+  int weak_or_stablizing_interval = std::min(
+      stable_interval, WEAK_OR_STABILIZING_WRITABLE_CONNECTION_PING_INTERVAL);
+  // If the channel is weak or the connection is not stable yet, use the
+  // weak_or_stablizing_interval.
+  return (!weak() && conn->stable(now)) ? stable_interval
+                                        : weak_or_stablizing_interval;
+}
+
+// Is the connection in a state for us to even consider pinging the other side?
+// We consider a connection pingable even if it's not connected because that's
+// how a TCP connection is kicked into reconnecting on the active side.
+bool BasicIceController::IsPingable(const Connection* conn, int64_t now) const {
+  const Candidate& remote = conn->remote_candidate();
+  // We should never get this far with an empty remote ufrag.
+  RTC_DCHECK(!remote.username().empty());
+  if (remote.username().empty() || remote.password().empty()) {
+    // If we don't have an ICE ufrag and pwd, there's no way we can ping.
+    return false;
+  }
+
+  // A failed connection will not be pinged.
+  if (conn->state() == IceCandidatePairState::FAILED) {
+    return false;
+  }
+
+  // An never connected connection cannot be written to at all, so pinging is
+  // out of the question. However, if it has become WRITABLE, it is in the
+  // reconnecting state so ping is needed.
+  if (!conn->connected() && !conn->writable()) {
+    return false;
+  }
+
+  // If we sent a number of pings wo/ reply, skip sending more
+  // until we get one.
+  if (conn->TooManyOutstandingPings(field_trials_->max_outstanding_pings)) {
+    return false;
+  }
+
+  // If the channel is weakly connected, ping all connections.
+  if (weak()) {
+    return true;
+  }
+
+  // Always ping active connections regardless whether the channel is completed
+  // or not, but backup connections are pinged at a slower rate.
+  if (IsBackupConnection(conn)) {
+    return conn->rtt_samples() == 0 ||
+           (now >= conn->last_ping_response_received() +
+                       config_.backup_connection_ping_interval_or_default());
+  }
+  // Don't ping inactive non-backup connections.
+  if (!conn->active()) {
+    return false;
+  }
+
+  // Do ping unwritable, active connections.
+  if (!conn->writable()) {
+    return true;
+  }
+
+  // Ping writable, active connections if it's been long enough since the last
+  // ping.
+  return WritableConnectionPastPingInterval(conn, now);
+}
+
+// A connection is considered a backup connection if the channel state
+// is completed, the connection is not the selected connection and it is active.
+bool BasicIceController::IsBackupConnection(const Connection* conn) const {
+  return ice_transport_state_func_() == IceTransportState::STATE_COMPLETED &&
+         conn != selected_connection_ && conn->active();
+}
+
+const Connection* BasicIceController::MorePingable(const Connection* conn1,
+                                                   const Connection* conn2) {
+  RTC_DCHECK(conn1 != conn2);
+  if (config_.prioritize_most_likely_candidate_pairs) {
+    const Connection* most_likely_to_work_conn = MostLikelyToWork(conn1, conn2);
+    if (most_likely_to_work_conn) {
+      return most_likely_to_work_conn;
+    }
+  }
+
+  const Connection* least_recently_pinged_conn =
+      LeastRecentlyPinged(conn1, conn2);
+  if (least_recently_pinged_conn) {
+    return least_recently_pinged_conn;
+  }
+
+  // During the initial state when nothing has been pinged yet, return the first
+  // one in the ordered `connections_`.
+  auto connections = connections_;
+  return *(std::find_if(connections.begin(), connections.end(),
+                        [conn1, conn2](const Connection* conn) {
+                          return conn == conn1 || conn == conn2;
+                        }));
+}
+
+const Connection* BasicIceController::MostLikelyToWork(
+    const Connection* conn1,
+    const Connection* conn2) {
+  bool rr1 = IsRelayRelay(conn1);
+  bool rr2 = IsRelayRelay(conn2);
+  if (rr1 && !rr2) {
+    return conn1;
+  } else if (rr2 && !rr1) {
+    return conn2;
+  } else if (rr1 && rr2) {
+    bool udp1 = IsUdp(conn1);
+    bool udp2 = IsUdp(conn2);
+    if (udp1 && !udp2) {
+      return conn1;
+    } else if (udp2 && udp1) {
+      return conn2;
+    }
+  }
+  return nullptr;
+}
+
+const Connection* BasicIceController::LeastRecentlyPinged(
+    const Connection* conn1,
+    const Connection* conn2) {
+  if (conn1->last_ping_sent() < conn2->last_ping_sent()) {
+    return conn1;
+  }
+  if (conn1->last_ping_sent() > conn2->last_ping_sent()) {
+    return conn2;
+  }
+  return nullptr;
+}
+
+std::map<const rtc::Network*, const Connection*>
+BasicIceController::GetBestConnectionByNetwork() const {
+  // `connections_` has been sorted, so the first one in the list on a given
+  // network is the best connection on the network, except that the selected
+  // connection is always the best connection on the network.
+  std::map<const rtc::Network*, const Connection*> best_connection_by_network;
+  if (selected_connection_) {
+    best_connection_by_network[selected_connection_->network()] =
+        selected_connection_;
+  }
+  // TODO(honghaiz): Need to update this if `connections_` are not sorted.
+  for (const Connection* conn : connections_) {
+    const rtc::Network* network = conn->network();
+    // This only inserts when the network does not exist in the map.
+    best_connection_by_network.insert(std::make_pair(network, conn));
+  }
+  return best_connection_by_network;
+}
+
+std::vector<const Connection*>
+BasicIceController::GetBestWritableConnectionPerNetwork() const {
+  std::vector<const Connection*> connections;
+  for (auto kv : GetBestConnectionByNetwork()) {
+    const Connection* conn = kv.second;
+    if (conn->writable() && conn->connected()) {
+      connections.push_back(conn);
+    }
+  }
+  return connections;
+}
+
+IceControllerInterface::SwitchResult
+BasicIceController::HandleInitialSelectDampening(
+    IceSwitchReason reason,
+    const Connection* new_connection) {
+  if (!field_trials_->initial_select_dampening.has_value() &&
+      !field_trials_->initial_select_dampening_ping_received.has_value()) {
+    // experiment not enabled => select connection.
+    return {new_connection, absl::nullopt};
+  }
+
+  int64_t now = rtc::TimeMillis();
+  int64_t max_delay = 0;
+  if (new_connection->last_ping_received() > 0 &&
+      field_trials_->initial_select_dampening_ping_received.has_value()) {
+    max_delay = *field_trials_->initial_select_dampening_ping_received;
+  } else if (field_trials_->initial_select_dampening.has_value()) {
+    max_delay = *field_trials_->initial_select_dampening;
+  }
+
+  int64_t start_wait =
+      initial_select_timestamp_ms_ == 0 ? now : initial_select_timestamp_ms_;
+  int64_t max_wait_until = start_wait + max_delay;
+
+  if (now >= max_wait_until) {
+    RTC_LOG(LS_INFO) << "reset initial_select_timestamp_ = "
+                     << initial_select_timestamp_ms_
+                     << " selection delayed by: " << (now - start_wait) << "ms";
+    initial_select_timestamp_ms_ = 0;
+    return {new_connection, absl::nullopt};
+  }
+
+  // We are not yet ready to select first connection...
+  if (initial_select_timestamp_ms_ == 0) {
+    // Set timestamp on first time...
+    // but run the delayed invokation everytime to
+    // avoid possibility that we miss it.
+    initial_select_timestamp_ms_ = now;
+    RTC_LOG(LS_INFO) << "set initial_select_timestamp_ms_ = "
+                     << initial_select_timestamp_ms_;
+  }
+
+  int min_delay = max_delay;
+  if (field_trials_->initial_select_dampening.has_value()) {
+    min_delay = std::min(min_delay, *field_trials_->initial_select_dampening);
+  }
+  if (field_trials_->initial_select_dampening_ping_received.has_value()) {
+    min_delay = std::min(
+        min_delay, *field_trials_->initial_select_dampening_ping_received);
+  }
+
+  RTC_LOG(LS_INFO) << "delay initial selection up to " << min_delay << "ms";
+  return {.connection = absl::nullopt,
+          .recheck_event = IceRecheckEvent(
+              IceSwitchReason::ICE_CONTROLLER_RECHECK, min_delay)};
+}
+
+IceControllerInterface::SwitchResult BasicIceController::ShouldSwitchConnection(
+    IceSwitchReason reason,
+    const Connection* new_connection) {
+  if (!ReadyToSend(new_connection) || selected_connection_ == new_connection) {
+    return {absl::nullopt, absl::nullopt};
+  }
+
+  if (selected_connection_ == nullptr) {
+    return HandleInitialSelectDampening(reason, new_connection);
+  }
+
+  // Do not switch to a connection that is not receiving if it is not on a
+  // preferred network or it has higher cost because it may be just spuriously
+  // better.
+  int compare_a_b_by_networks = CompareCandidatePairNetworks(
+      new_connection, selected_connection_, config_.network_preference);
+  if (compare_a_b_by_networks == b_is_better && !new_connection->receiving()) {
+    return {absl::nullopt, absl::nullopt};
+  }
+
+  bool missed_receiving_unchanged_threshold = false;
+  absl::optional<int64_t> receiving_unchanged_threshold(
+      rtc::TimeMillis() - config_.receiving_switching_delay_or_default());
+  int cmp = CompareConnections(selected_connection_, new_connection,
+                               receiving_unchanged_threshold,
+                               &missed_receiving_unchanged_threshold);
+
+  absl::optional<IceRecheckEvent> recheck_event;
+  if (missed_receiving_unchanged_threshold &&
+      config_.receiving_switching_delay_or_default()) {
+    // If we do not switch to the connection because it missed the receiving
+    // threshold, the new connection is in a better receiving state than the
+    // currently selected connection. So we need to re-check whether it needs
+    // to be switched at a later time.
+    recheck_event.emplace(reason,
+                          config_.receiving_switching_delay_or_default());
+  }
+
+  if (cmp < 0) {
+    return {new_connection, absl::nullopt};
+  } else if (cmp > 0) {
+    return {absl::nullopt, recheck_event};
+  }
+
+  // If everything else is the same, switch only if rtt has improved by
+  // a margin.
+  if (new_connection->rtt() <= selected_connection_->rtt() - kMinImprovement) {
+    return {new_connection, absl::nullopt};
+  }
+
+  return {absl::nullopt, recheck_event};
+}
+
+IceControllerInterface::SwitchResult
+BasicIceController::SortAndSwitchConnection(IceSwitchReason reason) {
+  // Find the best alternative connection by sorting.  It is important to note
+  // that amongst equal preference, writable connections, this will choose the
+  // one whose estimated latency is lowest.  So it is the only one that we
+  // need to consider switching to.
+  // TODO(honghaiz): Don't sort;  Just use std::max_element in the right places.
+  absl::c_stable_sort(
+      connections_, [this](const Connection* a, const Connection* b) {
+        int cmp = CompareConnections(a, b, absl::nullopt, nullptr);
+        if (cmp != 0) {
+          return cmp > 0;
+        }
+        // Otherwise, sort based on latency estimate.
+        return a->rtt() < b->rtt();
+      });
+
+  RTC_LOG(LS_VERBOSE) << "Sorting " << connections_.size()
+                      << " available connections";
+  for (size_t i = 0; i < connections_.size(); ++i) {
+    RTC_LOG(LS_VERBOSE) << connections_[i]->ToString();
+  }
+
+  const Connection* top_connection =
+      (!connections_.empty()) ? connections_[0] : nullptr;
+
+  return ShouldSwitchConnection(reason, top_connection);
+}
+
+bool BasicIceController::ReadyToSend(const Connection* connection) const {
+  // Note that we allow sending on an unreliable connection, because it's
+  // possible that it became unreliable simply due to bad chance.
+  // So this shouldn't prevent attempting to send media.
+  return connection != nullptr &&
+         (connection->writable() ||
+          connection->write_state() == Connection::STATE_WRITE_UNRELIABLE ||
+          PresumedWritable(connection));
+}
+
+bool BasicIceController::PresumedWritable(const Connection* conn) const {
+  return (conn->write_state() == Connection::STATE_WRITE_INIT &&
+          config_.presume_writable_when_fully_relayed &&
+          conn->local_candidate().type() == RELAY_PORT_TYPE &&
+          (conn->remote_candidate().type() == RELAY_PORT_TYPE ||
+           conn->remote_candidate().type() == PRFLX_PORT_TYPE));
+}
+
+// Compare two connections based on their writing, receiving, and connected
+// states.
+int BasicIceController::CompareConnectionStates(
+    const Connection* a,
+    const Connection* b,
+    absl::optional<int64_t> receiving_unchanged_threshold,
+    bool* missed_receiving_unchanged_threshold) const {
+  // First, prefer a connection that's writable or presumed writable over
+  // one that's not writable.
+  bool a_writable = a->writable() || PresumedWritable(a);
+  bool b_writable = b->writable() || PresumedWritable(b);
+  if (a_writable && !b_writable) {
+    return a_is_better;
+  }
+  if (!a_writable && b_writable) {
+    return b_is_better;
+  }
+
+  // Sort based on write-state. Better states have lower values.
+  if (a->write_state() < b->write_state()) {
+    return a_is_better;
+  }
+  if (b->write_state() < a->write_state()) {
+    return b_is_better;
+  }
+
+  // We prefer a receiving connection to a non-receiving, higher-priority
+  // connection when sorting connections and choosing which connection to
+  // switch to.
+  if (a->receiving() && !b->receiving()) {
+    return a_is_better;
+  }
+  if (!a->receiving() && b->receiving()) {
+    if (!receiving_unchanged_threshold ||
+        (a->receiving_unchanged_since() <= *receiving_unchanged_threshold &&
+         b->receiving_unchanged_since() <= *receiving_unchanged_threshold)) {
+      return b_is_better;
+    }
+    *missed_receiving_unchanged_threshold = true;
+  }
+
+  // WARNING: Some complexity here about TCP reconnecting.
+  // When a TCP connection fails because of a TCP socket disconnecting, the
+  // active side of the connection will attempt to reconnect for 5 seconds while
+  // pretending to be writable (the connection is not set to the unwritable
+  // state).  On the passive side, the connection also remains writable even
+  // though it is disconnected, and a new connection is created when the active
+  // side connects.  At that point, there are two TCP connections on the passive
+  // side: 1. the old, disconnected one that is pretending to be writable, and
+  // 2.  the new, connected one that is maybe not yet writable.  For purposes of
+  // pruning, pinging, and selecting the selected connection, we want to treat
+  // the new connection as "better" than the old one. We could add a method
+  // called something like Connection::ImReallyBadEvenThoughImWritable, but that
+  // is equivalent to the existing Connection::connected(), which we already
+  // have. So, in code throughout this file, we'll check whether the connection
+  // is connected() or not, and if it is not, treat it as "worse" than a
+  // connected one, even though it's writable.  In the code below, we're doing
+  // so to make sure we treat a new writable connection as better than an old
+  // disconnected connection.
+
+  // In the case where we reconnect TCP connections, the original best
+  // connection is disconnected without changing to WRITE_TIMEOUT. In this case,
+  // the new connection, when it becomes writable, should have higher priority.
+  if (a->write_state() == Connection::STATE_WRITABLE &&
+      b->write_state() == Connection::STATE_WRITABLE) {
+    if (a->connected() && !b->connected()) {
+      return a_is_better;
+    }
+    if (!a->connected() && b->connected()) {
+      return b_is_better;
+    }
+  }
+
+  return 0;
+}
+
+// Compares two connections based only on the candidate and network information.
+// Returns positive if `a` is better than `b`.
+int BasicIceController::CompareConnectionCandidates(const Connection* a,
+                                                    const Connection* b) const {
+  int compare_a_b_by_networks =
+      CompareCandidatePairNetworks(a, b, config_.network_preference);
+  if (compare_a_b_by_networks != a_and_b_equal) {
+    return compare_a_b_by_networks;
+  }
+
+  // Compare connection priority. Lower values get sorted last.
+  if (a->priority() > b->priority()) {
+    return a_is_better;
+  }
+  if (a->priority() < b->priority()) {
+    return b_is_better;
+  }
+
+  // If we're still tied at this point, prefer a younger generation.
+  // (Younger generation means a larger generation number).
+  int cmp = (a->remote_candidate().generation() + a->generation()) -
+            (b->remote_candidate().generation() + b->generation());
+  if (cmp != 0) {
+    return cmp;
+  }
+
+  // A periodic regather (triggered by the regather_all_networks_interval_range)
+  // will produce candidates that appear the same but would use a new port. We
+  // want to use the new candidates and purge the old candidates as they come
+  // in, so use the fact that the old ports get pruned immediately to rank the
+  // candidates with an active port/remote candidate higher.
+  bool a_pruned = is_connection_pruned_func_(a);
+  bool b_pruned = is_connection_pruned_func_(b);
+  if (!a_pruned && b_pruned) {
+    return a_is_better;
+  }
+  if (a_pruned && !b_pruned) {
+    return b_is_better;
+  }
+
+  // Otherwise, must be equal
+  return 0;
+}
+
+int BasicIceController::CompareConnections(
+    const Connection* a,
+    const Connection* b,
+    absl::optional<int64_t> receiving_unchanged_threshold,
+    bool* missed_receiving_unchanged_threshold) const {
+  RTC_CHECK(a != nullptr);
+  RTC_CHECK(b != nullptr);
+
+  // We prefer to switch to a writable and receiving connection over a
+  // non-writable or non-receiving connection, even if the latter has
+  // been nominated by the controlling side.
+  int state_cmp = CompareConnectionStates(a, b, receiving_unchanged_threshold,
+                                          missed_receiving_unchanged_threshold);
+  if (state_cmp != 0) {
+    return state_cmp;
+  }
+
+  if (ice_role_func_() == ICEROLE_CONTROLLED) {
+    // Compare the connections based on the nomination states and the last data
+    // received time if this is on the controlled side.
+    if (a->remote_nomination() > b->remote_nomination()) {
+      return a_is_better;
+    }
+    if (a->remote_nomination() < b->remote_nomination()) {
+      return b_is_better;
+    }
+
+    if (a->last_data_received() > b->last_data_received()) {
+      return a_is_better;
+    }
+    if (a->last_data_received() < b->last_data_received()) {
+      return b_is_better;
+    }
+  }
+
+  // Compare the network cost and priority.
+  return CompareConnectionCandidates(a, b);
+}
+
+int BasicIceController::CompareCandidatePairNetworks(
+    const Connection* a,
+    const Connection* b,
+    absl::optional<rtc::AdapterType> network_preference) const {
+  int compare_a_b_by_network_preference =
+      CompareCandidatePairsByNetworkPreference(a, b,
+                                               config_.network_preference);
+  // The network preference has a higher precedence than the network cost.
+  if (compare_a_b_by_network_preference != a_and_b_equal) {
+    return compare_a_b_by_network_preference;
+  }
+
+  bool a_vpn = a->network()->IsVpn();
+  bool b_vpn = b->network()->IsVpn();
+  switch (config_.vpn_preference) {
+    case webrtc::VpnPreference::kDefault:
+      break;
+    case webrtc::VpnPreference::kOnlyUseVpn:
+    case webrtc::VpnPreference::kPreferVpn:
+      if (a_vpn && !b_vpn) {
+        return a_is_better;
+      } else if (!a_vpn && b_vpn) {
+        return b_is_better;
+      }
+      break;
+    case webrtc::VpnPreference::kNeverUseVpn:
+    case webrtc::VpnPreference::kAvoidVpn:
+      if (a_vpn && !b_vpn) {
+        return b_is_better;
+      } else if (!a_vpn && b_vpn) {
+        return a_is_better;
+      }
+      break;
+    default:
+      break;
+  }
+
+  uint32_t a_cost = a->ComputeNetworkCost();
+  uint32_t b_cost = b->ComputeNetworkCost();
+  // Prefer lower network cost.
+  if (a_cost < b_cost) {
+    return a_is_better;
+  }
+  if (a_cost > b_cost) {
+    return b_is_better;
+  }
+  return a_and_b_equal;
+}
+
+std::vector<const Connection*> BasicIceController::PruneConnections() {
+  // We can prune any connection for which there is a connected, writable
+  // connection on the same network with better or equal priority.  We leave
+  // those with better priority just in case they become writable later (at
+  // which point, we would prune out the current selected connection).  We leave
+  // connections on other networks because they may not be using the same
+  // resources and they may represent very distinct paths over which we can
+  // switch. If `best_conn_on_network` is not connected, we may be reconnecting
+  // a TCP connection and should not prune connections in this network.
+  // See the big comment in CompareConnectionStates.
+  //
+  // An exception is made for connections on an "any address" network, meaning
+  // not bound to any specific network interface. We don't want to keep one of
+  // these alive as a backup, since it could be using the same network
+  // interface as the higher-priority, selected candidate pair.
+  std::vector<const Connection*> connections_to_prune;
+  auto best_connection_by_network = GetBestConnectionByNetwork();
+  for (const Connection* conn : connections_) {
+    const Connection* best_conn = selected_connection_;
+    if (!rtc::IPIsAny(conn->network()->GetBestIP())) {
+      // If the connection is bound to a specific network interface (not an
+      // "any address" network), compare it against the best connection for
+      // that network interface rather than the best connection overall. This
+      // ensures that at least one connection per network will be left
+      // unpruned.
+      best_conn = best_connection_by_network[conn->network()];
+    }
+    // Do not prune connections if the connection being compared against is
+    // weak. Otherwise, it may delete connections prematurely.
+    if (best_conn && conn != best_conn && !best_conn->weak() &&
+        CompareConnectionCandidates(best_conn, conn) >= 0) {
+      connections_to_prune.push_back(conn);
+    }
+  }
+  return connections_to_prune;
+}
+
+bool BasicIceController::GetUseCandidateAttr(const Connection* conn,
+                                             NominationMode mode,
+                                             IceMode remote_ice_mode) const {
+  switch (mode) {
+    case NominationMode::REGULAR:
+      // TODO(honghaiz): Implement regular nomination.
+      return false;
+    case NominationMode::AGGRESSIVE:
+      if (remote_ice_mode == ICEMODE_LITE) {
+        return GetUseCandidateAttr(conn, NominationMode::REGULAR,
+                                   remote_ice_mode);
+      }
+      return true;
+    case NominationMode::SEMI_AGGRESSIVE: {
+      // Nominate if
+      // a) Remote is in FULL ICE AND
+      //    a.1) `conn` is the selected connection OR
+      //    a.2) there is no selected connection OR
+      //    a.3) the selected connection is unwritable OR
+      //    a.4) `conn` has higher priority than selected_connection.
+      // b) Remote is in LITE ICE AND
+      //    b.1) `conn` is the selected_connection AND
+      //    b.2) `conn` is writable.
+      bool selected = conn == selected_connection_;
+      if (remote_ice_mode == ICEMODE_LITE) {
+        return selected && conn->writable();
+      }
+      bool better_than_selected =
+          !selected_connection_ || !selected_connection_->writable() ||
+          CompareConnectionCandidates(selected_connection_, conn) < 0;
+      return selected || better_than_selected;
+    }
+    default:
+      RTC_DCHECK_NOTREACHED();
+      return false;
+  }
+}
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/basic_ice_controller.h b/third_party/libwebrtc/p2p/base/basic_ice_controller.h
new file mode 100644
index 0000000000..b941a0dd7e
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/basic_ice_controller.h
@@ -0,0 +1,165 @@
+/*
+ *  Copyright 2019 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_BASIC_ICE_CONTROLLER_H_
+#define P2P_BASE_BASIC_ICE_CONTROLLER_H_
+
+#include <algorithm>
+#include <map>
+#include <set>
+#include <utility>
+#include <vector>
+
+#include "p2p/base/ice_controller_factory_interface.h"
+#include "p2p/base/ice_controller_interface.h"
+#include "p2p/base/p2p_transport_channel.h"
+
+namespace cricket {
+
+class BasicIceController : public IceControllerInterface {
+ public:
+  explicit BasicIceController(const IceControllerFactoryArgs& args);
+  virtual ~BasicIceController();
+
+  void SetIceConfig(const IceConfig& config) override;
+  void SetSelectedConnection(const Connection* selected_connection) override;
+  void AddConnection(const Connection* connection) override;
+  void OnConnectionDestroyed(const Connection* connection) override;
+  rtc::ArrayView<const Connection*> connections() const override {
+    return rtc::ArrayView<const Connection*>(
+        const_cast<const Connection**>(connections_.data()),
+        connections_.size());
+  }
+
+  bool HasPingableConnection() const override;
+
+  PingResult SelectConnectionToPing(int64_t last_ping_sent_ms) override;
+
+  bool GetUseCandidateAttr(const Connection* conn,
+                           NominationMode mode,
+                           IceMode remote_ice_mode) const override;
+
+  SwitchResult ShouldSwitchConnection(IceSwitchReason reason,
+                                      const Connection* connection) override;
+  SwitchResult SortAndSwitchConnection(IceSwitchReason reason) override;
+
+  std::vector<const Connection*> PruneConnections() override;
+
+  // These methods are only for tests.
+  const Connection* FindNextPingableConnection() override;
+  void MarkConnectionPinged(const Connection* conn) override;
+
+ private:
+  // A transport channel is weak if the current best connection is either
+  // not receiving or not writable, or if there is no best connection at all.
+  bool weak() const {
+    return !selected_connection_ || selected_connection_->weak();
+  }
+
+  int weak_ping_interval() const {
+    return std::max(config_.ice_check_interval_weak_connectivity_or_default(),
+                    config_.ice_check_min_interval_or_default());
+  }
+
+  int strong_ping_interval() const {
+    return std::max(config_.ice_check_interval_strong_connectivity_or_default(),
+                    config_.ice_check_min_interval_or_default());
+  }
+
+  int check_receiving_interval() const {
+    return std::max(MIN_CHECK_RECEIVING_INTERVAL,
+                    config_.receiving_timeout_or_default() / 10);
+  }
+
+  const Connection* FindOldestConnectionNeedingTriggeredCheck(int64_t now);
+  // Between `conn1` and `conn2`, this function returns the one which should
+  // be pinged first.
+  const Connection* MorePingable(const Connection* conn1,
+                                 const Connection* conn2);
+  // Select the connection which is Relay/Relay. If both of them are,
+  // UDP relay protocol takes precedence.
+  const Connection* MostLikelyToWork(const Connection* conn1,
+                                     const Connection* conn2);
+  // Compare the last_ping_sent time and return the one least recently pinged.
+  const Connection* LeastRecentlyPinged(const Connection* conn1,
+                                        const Connection* conn2);
+
+  bool IsPingable(const Connection* conn, int64_t now) const;
+  bool IsBackupConnection(const Connection* conn) const;
+  // Whether a writable connection is past its ping interval and needs to be
+  // pinged again.
+  bool WritableConnectionPastPingInterval(const Connection* conn,
+                                          int64_t now) const;
+  int CalculateActiveWritablePingInterval(const Connection* conn,
+                                          int64_t now) const;
+
+  std::map<const rtc::Network*, const Connection*> GetBestConnectionByNetwork()
+      const;
+  std::vector<const Connection*> GetBestWritableConnectionPerNetwork() const;
+
+  bool ReadyToSend(const Connection* connection) const;
+  bool PresumedWritable(const Connection* conn) const;
+
+  int CompareCandidatePairNetworks(
+      const Connection* a,
+      const Connection* b,
+      absl::optional<rtc::AdapterType> network_preference) const;
+
+  // The methods below return a positive value if `a` is preferable to `b`,
+  // a negative value if `b` is preferable, and 0 if they're equally preferable.
+  // If `receiving_unchanged_threshold` is set, then when `b` is receiving and
+  // `a` is not, returns a negative value only if `b` has been in receiving
+  // state and `a` has been in not receiving state since
+  // `receiving_unchanged_threshold` and sets
+  // `missed_receiving_unchanged_threshold` to true otherwise.
+  int CompareConnectionStates(
+      const Connection* a,
+      const Connection* b,
+      absl::optional<int64_t> receiving_unchanged_threshold,
+      bool* missed_receiving_unchanged_threshold) const;
+  int CompareConnectionCandidates(const Connection* a,
+                                  const Connection* b) const;
+  // Compares two connections based on the connection states
+  // (writable/receiving/connected), nomination states, last data received time,
+  // and static preferences. Does not include latency. Used by both sorting
+  // and ShouldSwitchSelectedConnection().
+  // Returns a positive value if `a` is better than `b`.
+  int CompareConnections(const Connection* a,
+                         const Connection* b,
+                         absl::optional<int64_t> receiving_unchanged_threshold,
+                         bool* missed_receiving_unchanged_threshold) const;
+
+  SwitchResult HandleInitialSelectDampening(IceSwitchReason reason,
+                                            const Connection* new_connection);
+
+  std::function<IceTransportState()> ice_transport_state_func_;
+  std::function<IceRole()> ice_role_func_;
+  std::function<bool(const Connection*)> is_connection_pruned_func_;
+
+  IceConfig config_;
+  const IceFieldTrials* field_trials_;
+
+  // `connections_` is a sorted list with the first one always be the
+  // `selected_connection_` when it's not nullptr. The combination of
+  // `pinged_connections_` and `unpinged_connections_` has the same
+  // connections as `connections_`. These 2 sets maintain whether a
+  // connection should be pinged next or not.
+  const Connection* selected_connection_ = nullptr;
+  std::vector<const Connection*> connections_;
+  std::set<const Connection*> pinged_connections_;
+  std::set<const Connection*> unpinged_connections_;
+
+  // Timestamp for when we got the first selectable connection.
+  int64_t initial_select_timestamp_ms_ = 0;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_BASIC_ICE_CONTROLLER_H_
diff --git a/third_party/libwebrtc/p2p/base/basic_packet_socket_factory.cc b/third_party/libwebrtc/p2p/base/basic_packet_socket_factory.cc
new file mode 100644
index 0000000000..5bc02dd0f0
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/basic_packet_socket_factory.cc
@@ -0,0 +1,210 @@
+/*
+ *  Copyright 2011 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/basic_packet_socket_factory.h"
+
+#include <stddef.h>
+
+#include <string>
+
+#include "absl/memory/memory.h"
+#include "api/async_dns_resolver.h"
+#include "api/wrapping_async_dns_resolver.h"
+#include "p2p/base/async_stun_tcp_socket.h"
+#include "rtc_base/async_tcp_socket.h"
+#include "rtc_base/async_udp_socket.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/logging.h"
+#include "rtc_base/socket.h"
+#include "rtc_base/socket_adapters.h"
+#include "rtc_base/ssl_adapter.h"
+
+namespace rtc {
+
+BasicPacketSocketFactory::BasicPacketSocketFactory(
+    SocketFactory* socket_factory)
+    : socket_factory_(socket_factory) {}
+
+BasicPacketSocketFactory::~BasicPacketSocketFactory() {}
+
+AsyncPacketSocket* BasicPacketSocketFactory::CreateUdpSocket(
+    const SocketAddress& address,
+    uint16_t min_port,
+    uint16_t max_port) {
+  // UDP sockets are simple.
+  Socket* socket = socket_factory_->CreateSocket(address.family(), SOCK_DGRAM);
+  if (!socket) {
+    return NULL;
+  }
+  if (BindSocket(socket, address, min_port, max_port) < 0) {
+    RTC_LOG(LS_ERROR) << "UDP bind failed with error " << socket->GetError();
+    delete socket;
+    return NULL;
+  }
+  return new AsyncUDPSocket(socket);
+}
+
+AsyncListenSocket* BasicPacketSocketFactory::CreateServerTcpSocket(
+    const SocketAddress& local_address,
+    uint16_t min_port,
+    uint16_t max_port,
+    int opts) {
+  // Fail if TLS is required.
+  if (opts & PacketSocketFactory::OPT_TLS) {
+    RTC_LOG(LS_ERROR) << "TLS support currently is not available.";
+    return NULL;
+  }
+
+  if (opts & PacketSocketFactory::OPT_TLS_FAKE) {
+    RTC_LOG(LS_ERROR) << "Fake TLS not supported.";
+    return NULL;
+  }
+  Socket* socket =
+      socket_factory_->CreateSocket(local_address.family(), SOCK_STREAM);
+  if (!socket) {
+    return NULL;
+  }
+
+  if (BindSocket(socket, local_address, min_port, max_port) < 0) {
+    RTC_LOG(LS_ERROR) << "TCP bind failed with error " << socket->GetError();
+    delete socket;
+    return NULL;
+  }
+
+  RTC_CHECK(!(opts & PacketSocketFactory::OPT_STUN));
+
+  return new AsyncTcpListenSocket(absl::WrapUnique(socket));
+}
+
+AsyncPacketSocket* BasicPacketSocketFactory::CreateClientTcpSocket(
+    const SocketAddress& local_address,
+    const SocketAddress& remote_address,
+    const ProxyInfo& proxy_info,
+    const std::string& user_agent,
+    const PacketSocketTcpOptions& tcp_options) {
+  Socket* socket =
+      socket_factory_->CreateSocket(local_address.family(), SOCK_STREAM);
+  if (!socket) {
+    return NULL;
+  }
+
+  if (BindSocket(socket, local_address, 0, 0) < 0) {
+    // Allow BindSocket to fail if we're binding to the ANY address, since this
+    // is mostly redundant in the first place. The socket will be bound when we
+    // call Connect() instead.
+    if (local_address.IsAnyIP()) {
+      RTC_LOG(LS_WARNING) << "TCP bind failed with error " << socket->GetError()
+                          << "; ignoring since socket is using 'any' address.";
+    } else {
+      RTC_LOG(LS_ERROR) << "TCP bind failed with error " << socket->GetError();
+      delete socket;
+      return NULL;
+    }
+  }
+
+  // Set TCP_NODELAY (via OPT_NODELAY) for improved performance; this causes
+  // small media packets to be sent immediately rather than being buffered up,
+  // reducing latency.
+  //
+  // Must be done before calling Connect, otherwise it may fail.
+  if (socket->SetOption(Socket::OPT_NODELAY, 1) != 0) {
+    RTC_LOG(LS_ERROR) << "Setting TCP_NODELAY option failed with error "
+                      << socket->GetError();
+  }
+
+  // If using a proxy, wrap the socket in a proxy socket.
+  if (proxy_info.type == PROXY_SOCKS5) {
+    socket = new AsyncSocksProxySocket(
+        socket, proxy_info.address, proxy_info.username, proxy_info.password);
+  } else if (proxy_info.type == PROXY_HTTPS) {
+    socket =
+        new AsyncHttpsProxySocket(socket, user_agent, proxy_info.address,
+                                  proxy_info.username, proxy_info.password);
+  }
+
+  // Assert that at most one TLS option is used.
+  int tlsOpts = tcp_options.opts & (PacketSocketFactory::OPT_TLS |
+                                    PacketSocketFactory::OPT_TLS_FAKE |
+                                    PacketSocketFactory::OPT_TLS_INSECURE);
+  RTC_DCHECK((tlsOpts & (tlsOpts - 1)) == 0);
+
+  if ((tlsOpts & PacketSocketFactory::OPT_TLS) ||
+      (tlsOpts & PacketSocketFactory::OPT_TLS_INSECURE)) {
+    // Using TLS, wrap the socket in an SSL adapter.
+    SSLAdapter* ssl_adapter = SSLAdapter::Create(socket);
+    if (!ssl_adapter) {
+      return NULL;
+    }
+
+    if (tlsOpts & PacketSocketFactory::OPT_TLS_INSECURE) {
+      ssl_adapter->SetIgnoreBadCert(true);
+    }
+
+    ssl_adapter->SetAlpnProtocols(tcp_options.tls_alpn_protocols);
+    ssl_adapter->SetEllipticCurves(tcp_options.tls_elliptic_curves);
+    ssl_adapter->SetCertVerifier(tcp_options.tls_cert_verifier);
+
+    socket = ssl_adapter;
+
+    if (ssl_adapter->StartSSL(remote_address.hostname().c_str()) != 0) {
+      delete ssl_adapter;
+      return NULL;
+    }
+
+  } else if (tlsOpts & PacketSocketFactory::OPT_TLS_FAKE) {
+    // Using fake TLS, wrap the TCP socket in a pseudo-SSL socket.
+    socket = new AsyncSSLSocket(socket);
+  }
+
+  if (socket->Connect(remote_address) < 0) {
+    RTC_LOG(LS_ERROR) << "TCP connect failed with error " << socket->GetError();
+    delete socket;
+    return NULL;
+  }
+
+  // Finally, wrap that socket in a TCP or STUN TCP packet socket.
+  AsyncPacketSocket* tcp_socket;
+  if (tcp_options.opts & PacketSocketFactory::OPT_STUN) {
+    tcp_socket = new cricket::AsyncStunTCPSocket(socket);
+  } else {
+    tcp_socket = new AsyncTCPSocket(socket);
+  }
+
+  return tcp_socket;
+}
+
+AsyncResolverInterface* BasicPacketSocketFactory::CreateAsyncResolver() {
+  return new AsyncResolver();
+}
+
+std::unique_ptr<webrtc::AsyncDnsResolverInterface>
+BasicPacketSocketFactory::CreateAsyncDnsResolver() {
+  return std::make_unique<webrtc::WrappingAsyncDnsResolver>(
+      new AsyncResolver());
+}
+
+int BasicPacketSocketFactory::BindSocket(Socket* socket,
+                                         const SocketAddress& local_address,
+                                         uint16_t min_port,
+                                         uint16_t max_port) {
+  int ret = -1;
+  if (min_port == 0 && max_port == 0) {
+    // If there's no port range, let the OS pick a port for us.
+    ret = socket->Bind(local_address);
+  } else {
+    // Otherwise, try to find a port in the provided range.
+    for (int port = min_port; ret < 0 && port <= max_port; ++port) {
+      ret = socket->Bind(SocketAddress(local_address.ipaddr(), port));
+    }
+  }
+  return ret;
+}
+
+}  // namespace rtc
diff --git a/third_party/libwebrtc/p2p/base/basic_packet_socket_factory.h b/third_party/libwebrtc/p2p/base/basic_packet_socket_factory.h
new file mode 100644
index 0000000000..396a8ba4eb
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/basic_packet_socket_factory.h
@@ -0,0 +1,69 @@
+/*
+ *  Copyright 2011 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_BASIC_PACKET_SOCKET_FACTORY_H_
+#define P2P_BASE_BASIC_PACKET_SOCKET_FACTORY_H_
+
+#include <stdint.h>
+
+#include <memory>
+#include <string>
+
+#include "api/async_dns_resolver.h"
+#include "api/packet_socket_factory.h"
+#include "rtc_base/async_packet_socket.h"
+#include "rtc_base/proxy_info.h"
+#include "rtc_base/socket.h"
+#include "rtc_base/socket_address.h"
+#include "rtc_base/socket_factory.h"
+#include "rtc_base/system/rtc_export.h"
+
+namespace rtc {
+
+class SocketFactory;
+
+class RTC_EXPORT BasicPacketSocketFactory : public PacketSocketFactory {
+ public:
+  explicit BasicPacketSocketFactory(SocketFactory* socket_factory);
+  ~BasicPacketSocketFactory() override;
+
+  AsyncPacketSocket* CreateUdpSocket(const SocketAddress& local_address,
+                                     uint16_t min_port,
+                                     uint16_t max_port) override;
+  AsyncListenSocket* CreateServerTcpSocket(const SocketAddress& local_address,
+                                           uint16_t min_port,
+                                           uint16_t max_port,
+                                           int opts) override;
+  AsyncPacketSocket* CreateClientTcpSocket(
+      const SocketAddress& local_address,
+      const SocketAddress& remote_address,
+      const ProxyInfo& proxy_info,
+      const std::string& user_agent,
+      const PacketSocketTcpOptions& tcp_options) override;
+
+  // TODO(bugs.webrtc.org/12598) Remove when downstream stops using it.
+  ABSL_DEPRECATED("Use CreateAsyncDnsResolver")
+  AsyncResolverInterface* CreateAsyncResolver() override;
+
+  std::unique_ptr<webrtc::AsyncDnsResolverInterface> CreateAsyncDnsResolver()
+      override;
+
+ private:
+  int BindSocket(Socket* socket,
+                 const SocketAddress& local_address,
+                 uint16_t min_port,
+                 uint16_t max_port);
+
+  SocketFactory* socket_factory_;
+};
+
+}  // namespace rtc
+
+#endif  // P2P_BASE_BASIC_PACKET_SOCKET_FACTORY_H_
diff --git a/third_party/libwebrtc/p2p/base/candidate_pair_interface.h b/third_party/libwebrtc/p2p/base/candidate_pair_interface.h
new file mode 100644
index 0000000000..2b68fd7ea9
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/candidate_pair_interface.h
@@ -0,0 +1,28 @@
+/*
+ *  Copyright 2016 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_CANDIDATE_PAIR_INTERFACE_H_
+#define P2P_BASE_CANDIDATE_PAIR_INTERFACE_H_
+
+namespace cricket {
+
+class Candidate;
+
+class CandidatePairInterface {
+ public:
+  virtual ~CandidatePairInterface() {}
+
+  virtual const Candidate& local_candidate() const = 0;
+  virtual const Candidate& remote_candidate() const = 0;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_CANDIDATE_PAIR_INTERFACE_H_
diff --git a/third_party/libwebrtc/p2p/base/connection.cc b/third_party/libwebrtc/p2p/base/connection.cc
new file mode 100644
index 0000000000..c5e6993c87
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/connection.cc
@@ -0,0 +1,1720 @@
+/*
+ *  Copyright 2019 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/connection.h"
+
+#include <math.h>
+
+#include <algorithm>
+#include <memory>
+#include <utility>
+#include <vector>
+
+#include "absl/algorithm/container.h"
+#include "absl/strings/escaping.h"
+#include "absl/strings/match.h"
+#include "absl/strings/string_view.h"
+#include "p2p/base/port_allocator.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/crc32.h"
+#include "rtc_base/helpers.h"
+#include "rtc_base/logging.h"
+#include "rtc_base/mdns_responder_interface.h"
+#include "rtc_base/message_digest.h"
+#include "rtc_base/network.h"
+#include "rtc_base/numerics/safe_minmax.h"
+#include "rtc_base/string_encode.h"
+#include "rtc_base/string_utils.h"
+#include "rtc_base/strings/string_builder.h"
+#include "rtc_base/third_party/base64/base64.h"
+
+namespace cricket {
+namespace {
+
+// Determines whether we have seen at least the given maximum number of
+// pings fail to have a response.
+inline bool TooManyFailures(
+    const std::vector<Connection::SentPing>& pings_since_last_response,
+    uint32_t maximum_failures,
+    int rtt_estimate,
+    int64_t now) {
+  // If we haven't sent that many pings, then we can't have failed that many.
+  if (pings_since_last_response.size() < maximum_failures)
+    return false;
+
+  // Check if the window in which we would expect a response to the ping has
+  // already elapsed.
+  int64_t expected_response_time =
+      pings_since_last_response[maximum_failures - 1].sent_time + rtt_estimate;
+  return now > expected_response_time;
+}
+
+// Determines whether we have gone too long without seeing any response.
+inline bool TooLongWithoutResponse(
+    const std::vector<Connection::SentPing>& pings_since_last_response,
+    int64_t maximum_time,
+    int64_t now) {
+  if (pings_since_last_response.size() == 0)
+    return false;
+
+  auto first = pings_since_last_response[0];
+  return now > (first.sent_time + maximum_time);
+}
+
+// Helper methods for converting string values of log description fields to
+// enum.
+webrtc::IceCandidateType GetCandidateTypeByString(absl::string_view type) {
+  if (type == LOCAL_PORT_TYPE) {
+    return webrtc::IceCandidateType::kLocal;
+  } else if (type == STUN_PORT_TYPE) {
+    return webrtc::IceCandidateType::kStun;
+  } else if (type == PRFLX_PORT_TYPE) {
+    return webrtc::IceCandidateType::kPrflx;
+  } else if (type == RELAY_PORT_TYPE) {
+    return webrtc::IceCandidateType::kRelay;
+  }
+  return webrtc::IceCandidateType::kUnknown;
+}
+
+webrtc::IceCandidatePairProtocol GetProtocolByString(
+    absl::string_view protocol) {
+  if (protocol == UDP_PROTOCOL_NAME) {
+    return webrtc::IceCandidatePairProtocol::kUdp;
+  } else if (protocol == TCP_PROTOCOL_NAME) {
+    return webrtc::IceCandidatePairProtocol::kTcp;
+  } else if (protocol == SSLTCP_PROTOCOL_NAME) {
+    return webrtc::IceCandidatePairProtocol::kSsltcp;
+  } else if (protocol == TLS_PROTOCOL_NAME) {
+    return webrtc::IceCandidatePairProtocol::kTls;
+  }
+  return webrtc::IceCandidatePairProtocol::kUnknown;
+}
+
+webrtc::IceCandidatePairAddressFamily GetAddressFamilyByInt(
+    int address_family) {
+  if (address_family == AF_INET) {
+    return webrtc::IceCandidatePairAddressFamily::kIpv4;
+  } else if (address_family == AF_INET6) {
+    return webrtc::IceCandidatePairAddressFamily::kIpv6;
+  }
+  return webrtc::IceCandidatePairAddressFamily::kUnknown;
+}
+
+webrtc::IceCandidateNetworkType ConvertNetworkType(rtc::AdapterType type) {
+  switch (type) {
+    case rtc::ADAPTER_TYPE_ETHERNET:
+      return webrtc::IceCandidateNetworkType::kEthernet;
+    case rtc::ADAPTER_TYPE_LOOPBACK:
+      return webrtc::IceCandidateNetworkType::kLoopback;
+    case rtc::ADAPTER_TYPE_WIFI:
+      return webrtc::IceCandidateNetworkType::kWifi;
+    case rtc::ADAPTER_TYPE_VPN:
+      return webrtc::IceCandidateNetworkType::kVpn;
+    case rtc::ADAPTER_TYPE_CELLULAR:
+    case rtc::ADAPTER_TYPE_CELLULAR_2G:
+    case rtc::ADAPTER_TYPE_CELLULAR_3G:
+    case rtc::ADAPTER_TYPE_CELLULAR_4G:
+    case rtc::ADAPTER_TYPE_CELLULAR_5G:
+      return webrtc::IceCandidateNetworkType::kCellular;
+    default:
+      return webrtc::IceCandidateNetworkType::kUnknown;
+  }
+}
+
+// When we don't have any RTT data, we have to pick something reasonable.  We
+// use a large value just in case the connection is really slow.
+const int DEFAULT_RTT = 3000;  // 3 seconds
+
+// We will restrict RTT estimates (when used for determining state) to be
+// within a reasonable range.
+const int MINIMUM_RTT = 100;    // 0.1 seconds
+const int MAXIMUM_RTT = 60000;  // 60 seconds
+
+const int DEFAULT_RTT_ESTIMATE_HALF_TIME_MS = 500;
+
+// Computes our estimate of the RTT given the current estimate.
+inline int ConservativeRTTEstimate(int rtt) {
+  return rtc::SafeClamp(2 * rtt, MINIMUM_RTT, MAXIMUM_RTT);
+}
+
+// Weighting of the old rtt value to new data.
+const int RTT_RATIO = 3;  // 3 : 1
+
+constexpr int64_t kMinExtraPingDelayMs = 100;
+
+// Default field trials.
+const IceFieldTrials kDefaultFieldTrials;
+
+constexpr int kSupportGoogPingVersionRequestIndex = static_cast<int>(
+    IceGoogMiscInfoBindingRequestAttributeIndex::SUPPORT_GOOG_PING_VERSION);
+
+constexpr int kSupportGoogPingVersionResponseIndex = static_cast<int>(
+    IceGoogMiscInfoBindingResponseAttributeIndex::SUPPORT_GOOG_PING_VERSION);
+
+}  // namespace
+
+// A ConnectionRequest is a STUN binding used to determine writability.
+class Connection::ConnectionRequest : public StunRequest {
+ public:
+  ConnectionRequest(StunRequestManager& manager,
+                    Connection* connection,
+                    std::unique_ptr<IceMessage> message);
+  void OnResponse(StunMessage* response) override;
+  void OnErrorResponse(StunMessage* response) override;
+  void OnTimeout() override;
+  void OnSent() override;
+  int resend_delay() override;
+
+ private:
+  Connection* const connection_;
+};
+
+Connection::ConnectionRequest::ConnectionRequest(
+    StunRequestManager& manager,
+    Connection* connection,
+    std::unique_ptr<IceMessage> message)
+    : StunRequest(manager, std::move(message)), connection_(connection) {}
+
+void Connection::ConnectionRequest::OnResponse(StunMessage* response) {
+  RTC_DCHECK_RUN_ON(connection_->network_thread_);
+  connection_->OnConnectionRequestResponse(this, response);
+}
+
+void Connection::ConnectionRequest::OnErrorResponse(StunMessage* response) {
+  RTC_DCHECK_RUN_ON(connection_->network_thread_);
+  connection_->OnConnectionRequestErrorResponse(this, response);
+}
+
+void Connection::ConnectionRequest::OnTimeout() {
+  RTC_DCHECK_RUN_ON(connection_->network_thread_);
+  connection_->OnConnectionRequestTimeout(this);
+}
+
+void Connection::ConnectionRequest::OnSent() {
+  RTC_DCHECK_RUN_ON(connection_->network_thread_);
+  connection_->OnConnectionRequestSent(this);
+  // Each request is sent only once.  After a single delay , the request will
+  // time out.
+  set_timed_out();
+}
+
+int Connection::ConnectionRequest::resend_delay() {
+  return CONNECTION_RESPONSE_TIMEOUT;
+}
+
+Connection::Connection(rtc::WeakPtr<Port> port,
+                       size_t index,
+                       const Candidate& remote_candidate)
+    : network_thread_(port->thread()),
+      id_(rtc::CreateRandomId()),
+      port_(std::move(port)),
+      local_candidate_(port_->Candidates()[index]),
+      remote_candidate_(remote_candidate),
+      recv_rate_tracker_(100, 10u),
+      send_rate_tracker_(100, 10u),
+      write_state_(STATE_WRITE_INIT),
+      receiving_(false),
+      connected_(true),
+      pruned_(false),
+      use_candidate_attr_(false),
+      requests_(port_->thread(),
+                [this](const void* data, size_t size, StunRequest* request) {
+                  OnSendStunPacket(data, size, request);
+                }),
+      rtt_(DEFAULT_RTT),
+      last_ping_sent_(0),
+      last_ping_received_(0),
+      last_data_received_(0),
+      last_ping_response_received_(0),
+      state_(IceCandidatePairState::WAITING),
+      time_created_ms_(rtc::TimeMillis()),
+      delta_internal_unix_epoch_ms_(rtc::TimeUTCMillis() - rtc::TimeMillis()),
+      field_trials_(&kDefaultFieldTrials),
+      rtt_estimate_(DEFAULT_RTT_ESTIMATE_HALF_TIME_MS) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  RTC_DCHECK(port_);
+  RTC_LOG(LS_INFO) << ToString() << ": Connection created";
+}
+
+Connection::~Connection() {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  RTC_DCHECK(!port_);
+}
+
+webrtc::TaskQueueBase* Connection::network_thread() const {
+  return network_thread_;
+}
+
+const Candidate& Connection::local_candidate() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return local_candidate_;
+}
+
+const Candidate& Connection::remote_candidate() const {
+  return remote_candidate_;
+}
+
+const rtc::Network* Connection::network() const {
+  return port()->Network();
+}
+
+int Connection::generation() const {
+  return port()->generation();
+}
+
+uint64_t Connection::priority() const {
+  if (!port_)
+    return 0;
+
+  uint64_t priority = 0;
+  // RFC 5245 - 5.7.2.  Computing Pair Priority and Ordering Pairs
+  // Let G be the priority for the candidate provided by the controlling
+  // agent.  Let D be the priority for the candidate provided by the
+  // controlled agent.
+  // pair priority = 2^32*MIN(G,D) + 2*MAX(G,D) + (G>D?1:0)
+  IceRole role = port_->GetIceRole();
+  if (role != ICEROLE_UNKNOWN) {
+    uint32_t g = 0;
+    uint32_t d = 0;
+    if (role == ICEROLE_CONTROLLING) {
+      g = local_candidate().priority();
+      d = remote_candidate_.priority();
+    } else {
+      g = remote_candidate_.priority();
+      d = local_candidate().priority();
+    }
+    priority = std::min(g, d);
+    priority = priority << 32;
+    priority += 2 * std::max(g, d) + (g > d ? 1 : 0);
+  }
+  return priority;
+}
+
+void Connection::set_write_state(WriteState value) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  WriteState old_value = write_state_;
+  write_state_ = value;
+  if (value != old_value) {
+    RTC_LOG(LS_VERBOSE) << ToString() << ": set_write_state from: " << old_value
+                        << " to " << value;
+    SignalStateChange(this);
+  }
+}
+
+void Connection::UpdateReceiving(int64_t now) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  bool receiving;
+  if (last_ping_sent() < last_ping_response_received()) {
+    // We consider any candidate pair that has its last connectivity check
+    // acknowledged by a response as receiving, particularly for backup
+    // candidate pairs that send checks at a much slower pace than the selected
+    // one. Otherwise, a backup candidate pair constantly becomes not receiving
+    // as a side effect of a long ping interval, since we do not have a separate
+    // receiving timeout for backup candidate pairs. See
+    // IceConfig.ice_backup_candidate_pair_ping_interval,
+    // IceConfig.ice_connection_receiving_timeout and their default value.
+    receiving = true;
+  } else {
+    receiving =
+        last_received() > 0 && now <= last_received() + receiving_timeout();
+  }
+  if (receiving_ == receiving) {
+    return;
+  }
+  RTC_LOG(LS_VERBOSE) << ToString() << ": set_receiving to " << receiving;
+  receiving_ = receiving;
+  receiving_unchanged_since_ = now;
+  SignalStateChange(this);
+}
+
+void Connection::set_state(IceCandidatePairState state) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  IceCandidatePairState old_state = state_;
+  state_ = state;
+  if (state != old_state) {
+    RTC_LOG(LS_VERBOSE) << ToString() << ": set_state";
+  }
+}
+
+void Connection::set_connected(bool value) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  bool old_value = connected_;
+  connected_ = value;
+  if (value != old_value) {
+    RTC_LOG(LS_VERBOSE) << ToString() << ": Change connected_ to " << value;
+    SignalStateChange(this);
+  }
+}
+
+bool Connection::use_candidate_attr() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return use_candidate_attr_;
+}
+
+void Connection::set_use_candidate_attr(bool enable) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  use_candidate_attr_ = enable;
+}
+
+void Connection::set_nomination(uint32_t value) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  nomination_ = value;
+}
+
+uint32_t Connection::remote_nomination() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return remote_nomination_;
+}
+
+bool Connection::nominated() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return acked_nomination_ || remote_nomination_;
+}
+
+int Connection::unwritable_timeout() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return unwritable_timeout_.value_or(CONNECTION_WRITE_CONNECT_TIMEOUT);
+}
+
+void Connection::set_unwritable_timeout(const absl::optional<int>& value_ms) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  unwritable_timeout_ = value_ms;
+}
+
+int Connection::unwritable_min_checks() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return unwritable_min_checks_.value_or(CONNECTION_WRITE_CONNECT_FAILURES);
+}
+
+void Connection::set_unwritable_min_checks(const absl::optional<int>& value) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  unwritable_min_checks_ = value;
+}
+
+int Connection::inactive_timeout() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return inactive_timeout_.value_or(CONNECTION_WRITE_TIMEOUT);
+}
+
+void Connection::set_inactive_timeout(const absl::optional<int>& value) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  inactive_timeout_ = value;
+}
+
+int Connection::receiving_timeout() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return receiving_timeout_.value_or(WEAK_CONNECTION_RECEIVE_TIMEOUT);
+}
+
+void Connection::set_receiving_timeout(
+    absl::optional<int> receiving_timeout_ms) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  receiving_timeout_ = receiving_timeout_ms;
+}
+
+void Connection::SetIceFieldTrials(const IceFieldTrials* field_trials) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  field_trials_ = field_trials;
+  rtt_estimate_.SetHalfTime(field_trials->rtt_estimate_halftime_ms);
+}
+
+void Connection::OnSendStunPacket(const void* data,
+                                  size_t size,
+                                  StunRequest* req) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  rtc::PacketOptions options(port_->StunDscpValue());
+  options.info_signaled_after_sent.packet_type =
+      rtc::PacketType::kIceConnectivityCheck;
+  auto err =
+      port_->SendTo(data, size, remote_candidate_.address(), options, false);
+  if (err < 0) {
+    RTC_LOG(LS_WARNING) << ToString()
+                        << ": Failed to send STUN ping "
+                           " err="
+                        << err << " id=" << rtc::hex_encode(req->id());
+  }
+}
+
+void Connection::OnReadPacket(const char* data,
+                              size_t size,
+                              int64_t packet_time_us) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  std::unique_ptr<IceMessage> msg;
+  std::string remote_ufrag;
+  const rtc::SocketAddress& addr(remote_candidate_.address());
+  if (!port_->GetStunMessage(data, size, addr, &msg, &remote_ufrag)) {
+    // The packet did not parse as a valid STUN message
+    // This is a data packet, pass it along.
+    last_data_received_ = rtc::TimeMillis();
+    UpdateReceiving(last_data_received_);
+    recv_rate_tracker_.AddSamples(size);
+    stats_.packets_received++;
+    SignalReadPacket(this, data, size, packet_time_us);
+
+    // If timed out sending writability checks, start up again
+    if (!pruned_ && (write_state_ == STATE_WRITE_TIMEOUT)) {
+      RTC_LOG(LS_WARNING)
+          << "Received a data packet on a timed-out Connection. "
+             "Resetting state to STATE_WRITE_INIT.";
+      set_write_state(STATE_WRITE_INIT);
+    }
+    return;
+  } else if (!msg) {
+    // The packet was STUN, but failed a check and was handled internally.
+    return;
+  }
+
+  // The packet is STUN and passed the Port checks.
+  // Perform our own checks to ensure this packet is valid.
+  // If this is a STUN request, then update the receiving bit and respond.
+  // If this is a STUN response, then update the writable bit.
+  // Log at LS_INFO if we receive a ping on an unwritable connection.
+
+  // REQUESTs   have msg->integrity() already checked in Port
+  // RESPONSEs  have msg->integrity() checked below.
+  // INDICATION does not have any integrity.
+  if (IsStunRequestType(msg->type())) {
+    if (msg->integrity() != StunMessage::IntegrityStatus::kIntegrityOk) {
+      // "silently" discard the request.
+      RTC_LOG(LS_VERBOSE) << ToString() << ": Discarding "
+                          << StunMethodToString(msg->type())
+                          << ", id=" << rtc::hex_encode(msg->transaction_id())
+                          << " with invalid message integrity: "
+                          << static_cast<int>(msg->integrity());
+      return;
+    }
+    // fall-through
+  } else if (IsStunSuccessResponseType(msg->type()) ||
+             IsStunErrorResponseType(msg->type())) {
+    RTC_DCHECK(msg->integrity() == StunMessage::IntegrityStatus::kNotSet);
+    if (msg->ValidateMessageIntegrity(remote_candidate().password()) !=
+        StunMessage::IntegrityStatus::kIntegrityOk) {
+      // "silently" discard the response.
+      RTC_LOG(LS_VERBOSE) << ToString() << ": Discarding "
+                          << StunMethodToString(msg->type())
+                          << ", id=" << rtc::hex_encode(msg->transaction_id())
+                          << " with invalid message integrity: "
+                          << static_cast<int>(msg->integrity());
+      return;
+    }
+  } else {
+    RTC_DCHECK(IsStunIndicationType(msg->type()));
+    // No message integrity.
+  }
+
+  rtc::LoggingSeverity sev = (!writable() ? rtc::LS_INFO : rtc::LS_VERBOSE);
+  switch (msg->type()) {
+    case STUN_BINDING_REQUEST:
+      RTC_LOG_V(sev) << ToString() << ": Received "
+                     << StunMethodToString(msg->type())
+                     << ", id=" << rtc::hex_encode(msg->transaction_id());
+      if (remote_ufrag == remote_candidate_.username()) {
+        HandleStunBindingOrGoogPingRequest(msg.get());
+      } else {
+        // The packet had the right local username, but the remote username
+        // was not the right one for the remote address.
+        RTC_LOG(LS_ERROR) << ToString()
+                          << ": Received STUN request with bad remote username "
+                          << remote_ufrag;
+        port_->SendBindingErrorResponse(msg.get(), addr,
+                                        STUN_ERROR_UNAUTHORIZED,
+                                        STUN_ERROR_REASON_UNAUTHORIZED);
+      }
+      break;
+
+      // Response from remote peer. Does it match request sent?
+      // This doesn't just check, it makes callbacks if transaction
+      // id's match.
+    case STUN_BINDING_RESPONSE:
+    case STUN_BINDING_ERROR_RESPONSE:
+      requests_.CheckResponse(msg.get());
+      break;
+
+      // Remote end point sent an STUN indication instead of regular binding
+      // request. In this case `last_ping_received_` will be updated but no
+      // response will be sent.
+    case STUN_BINDING_INDICATION:
+      ReceivedPing(msg->transaction_id());
+      break;
+    case GOOG_PING_REQUEST:
+      // Checked in Port::GetStunMessage.
+      HandleStunBindingOrGoogPingRequest(msg.get());
+      break;
+    case GOOG_PING_RESPONSE:
+    case GOOG_PING_ERROR_RESPONSE:
+      requests_.CheckResponse(msg.get());
+      break;
+    default:
+      RTC_DCHECK_NOTREACHED();
+      break;
+  }
+}
+
+void Connection::HandleStunBindingOrGoogPingRequest(IceMessage* msg) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  // This connection should now be receiving.
+  ReceivedPing(msg->transaction_id());
+  if (field_trials_->extra_ice_ping && last_ping_response_received_ == 0) {
+    if (local_candidate().type() == RELAY_PORT_TYPE ||
+        local_candidate().type() == PRFLX_PORT_TYPE ||
+        remote_candidate().type() == RELAY_PORT_TYPE ||
+        remote_candidate().type() == PRFLX_PORT_TYPE) {
+      const int64_t now = rtc::TimeMillis();
+      if (last_ping_sent_ + kMinExtraPingDelayMs <= now) {
+        RTC_LOG(LS_INFO) << ToString()
+                         << "WebRTC-ExtraICEPing/Sending extra ping"
+                            " last_ping_sent_: "
+                         << last_ping_sent_ << " now: " << now
+                         << " (diff: " << (now - last_ping_sent_) << ")";
+        Ping(now);
+      } else {
+        RTC_LOG(LS_INFO) << ToString()
+                         << "WebRTC-ExtraICEPing/Not sending extra ping"
+                            " last_ping_sent_: "
+                         << last_ping_sent_ << " now: " << now
+                         << " (diff: " << (now - last_ping_sent_) << ")";
+      }
+    }
+  }
+
+  const rtc::SocketAddress& remote_addr = remote_candidate_.address();
+  if (msg->type() == STUN_BINDING_REQUEST) {
+    // Check for role conflicts.
+    const std::string& remote_ufrag = remote_candidate_.username();
+    if (!port_->MaybeIceRoleConflict(remote_addr, msg, remote_ufrag)) {
+      // Received conflicting role from the peer.
+      RTC_LOG(LS_INFO) << "Received conflicting role from the peer.";
+      return;
+    }
+  }
+
+  stats_.recv_ping_requests++;
+  LogCandidatePairEvent(webrtc::IceCandidatePairEventType::kCheckReceived,
+                        msg->reduced_transaction_id());
+
+  // This is a validated stun request from remote peer.
+  if (msg->type() == STUN_BINDING_REQUEST) {
+    SendStunBindingResponse(msg);
+  } else {
+    RTC_DCHECK(msg->type() == GOOG_PING_REQUEST);
+    SendGoogPingResponse(msg);
+  }
+
+  // If it timed out on writing check, start up again
+  if (!pruned_ && write_state_ == STATE_WRITE_TIMEOUT) {
+    set_write_state(STATE_WRITE_INIT);
+  }
+
+  if (port_->GetIceRole() == ICEROLE_CONTROLLED) {
+    const StunUInt32Attribute* nomination_attr =
+        msg->GetUInt32(STUN_ATTR_NOMINATION);
+    uint32_t nomination = 0;
+    if (nomination_attr) {
+      nomination = nomination_attr->value();
+      if (nomination == 0) {
+        RTC_LOG(LS_ERROR) << "Invalid nomination: " << nomination;
+      }
+    } else {
+      const StunByteStringAttribute* use_candidate_attr =
+          msg->GetByteString(STUN_ATTR_USE_CANDIDATE);
+      if (use_candidate_attr) {
+        nomination = 1;
+      }
+    }
+    // We don't un-nominate a connection, so we only keep a larger nomination.
+    if (nomination > remote_nomination_) {
+      set_remote_nomination(nomination);
+      SignalNominated(this);
+    }
+  }
+  // Set the remote cost if the network_info attribute is available.
+  // Note: If packets are re-ordered, we may get incorrect network cost
+  // temporarily, but it should get the correct value shortly after that.
+  const StunUInt32Attribute* network_attr =
+      msg->GetUInt32(STUN_ATTR_GOOG_NETWORK_INFO);
+  if (network_attr) {
+    uint32_t network_info = network_attr->value();
+    uint16_t network_cost = static_cast<uint16_t>(network_info);
+    if (network_cost != remote_candidate_.network_cost()) {
+      remote_candidate_.set_network_cost(network_cost);
+      // Network cost change will affect the connection ranking, so signal
+      // state change to force a re-sort in P2PTransportChannel.
+      SignalStateChange(this);
+    }
+  }
+
+  if (field_trials_->piggyback_ice_check_acknowledgement) {
+    HandlePiggybackCheckAcknowledgementIfAny(msg);
+  }
+}
+
+void Connection::SendStunBindingResponse(const StunMessage* message) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  RTC_DCHECK_EQ(message->type(), STUN_BINDING_REQUEST);
+
+  // Retrieve the username from the `message`.
+  const StunByteStringAttribute* username_attr =
+      message->GetByteString(STUN_ATTR_USERNAME);
+  RTC_DCHECK(username_attr != NULL);
+  if (username_attr == NULL) {
+    // No valid username, skip the response.
+    return;
+  }
+
+  // Fill in the response.
+  StunMessage response(STUN_BINDING_RESPONSE, message->transaction_id());
+  const StunUInt32Attribute* retransmit_attr =
+      message->GetUInt32(STUN_ATTR_RETRANSMIT_COUNT);
+  if (retransmit_attr) {
+    // Inherit the incoming retransmit value in the response so the other side
+    // can see our view of lost pings.
+    response.AddAttribute(std::make_unique<StunUInt32Attribute>(
+        STUN_ATTR_RETRANSMIT_COUNT, retransmit_attr->value()));
+
+    if (retransmit_attr->value() > CONNECTION_WRITE_CONNECT_FAILURES) {
+      RTC_LOG(LS_INFO)
+          << ToString()
+          << ": Received a remote ping with high retransmit count: "
+          << retransmit_attr->value();
+    }
+  }
+
+  response.AddAttribute(std::make_unique<StunXorAddressAttribute>(
+      STUN_ATTR_XOR_MAPPED_ADDRESS, remote_candidate_.address()));
+
+  if (field_trials_->announce_goog_ping) {
+    // Check if message contains a announce-request.
+    auto goog_misc = message->GetUInt16List(STUN_ATTR_GOOG_MISC_INFO);
+    if (goog_misc != nullptr &&
+        goog_misc->Size() >= kSupportGoogPingVersionRequestIndex &&
+        // Which version can we handle...currently any >= 1
+        goog_misc->GetType(kSupportGoogPingVersionRequestIndex) >= 1) {
+      auto list =
+          StunAttribute::CreateUInt16ListAttribute(STUN_ATTR_GOOG_MISC_INFO);
+      list->AddTypeAtIndex(kSupportGoogPingVersionResponseIndex,
+                           kGoogPingVersion);
+      response.AddAttribute(std::move(list));
+    }
+  }
+
+  response.AddMessageIntegrity(local_candidate().password());
+  response.AddFingerprint();
+
+  SendResponseMessage(response);
+}
+
+void Connection::SendGoogPingResponse(const StunMessage* message) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  RTC_DCHECK(message->type() == GOOG_PING_REQUEST);
+
+  // Fill in the response.
+  StunMessage response(GOOG_PING_RESPONSE, message->transaction_id());
+  response.AddMessageIntegrity32(local_candidate().password());
+  SendResponseMessage(response);
+}
+
+void Connection::SendResponseMessage(const StunMessage& response) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  // Where I send the response.
+  const rtc::SocketAddress& addr = remote_candidate_.address();
+
+  // Send the response.
+  rtc::ByteBufferWriter buf;
+  response.Write(&buf);
+  rtc::PacketOptions options(port_->StunDscpValue());
+  options.info_signaled_after_sent.packet_type =
+      rtc::PacketType::kIceConnectivityCheckResponse;
+  auto err = port_->SendTo(buf.Data(), buf.Length(), addr, options, false);
+  if (err < 0) {
+    RTC_LOG(LS_ERROR) << ToString() << ": Failed to send "
+                      << StunMethodToString(response.type())
+                      << ", to=" << addr.ToSensitiveString() << ", err=" << err
+                      << ", id=" << rtc::hex_encode(response.transaction_id());
+  } else {
+    // Log at LS_INFO if we send a stun ping response on an unwritable
+    // connection.
+    rtc::LoggingSeverity sev = (!writable()) ? rtc::LS_INFO : rtc::LS_VERBOSE;
+    RTC_LOG_V(sev) << ToString() << ": Sent "
+                   << StunMethodToString(response.type())
+                   << ", to=" << addr.ToSensitiveString()
+                   << ", id=" << rtc::hex_encode(response.transaction_id());
+
+    stats_.sent_ping_responses++;
+    LogCandidatePairEvent(webrtc::IceCandidatePairEventType::kCheckResponseSent,
+                          response.reduced_transaction_id());
+  }
+}
+
+uint32_t Connection::acked_nomination() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return acked_nomination_;
+}
+
+void Connection::set_remote_nomination(uint32_t remote_nomination) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  remote_nomination_ = remote_nomination;
+}
+
+void Connection::OnReadyToSend() {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  SignalReadyToSend(this);
+}
+
+bool Connection::pruned() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return pruned_;
+}
+
+void Connection::Prune() {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (!pruned_ || active()) {
+    RTC_LOG(LS_INFO) << ToString() << ": Connection pruned";
+    pruned_ = true;
+    requests_.Clear();
+    set_write_state(STATE_WRITE_TIMEOUT);
+  }
+}
+
+void Connection::Destroy() {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  RTC_DCHECK(port_) << "Calling Destroy() twice?";
+  if (port_)
+    port_->DestroyConnection(this);
+}
+
+bool Connection::Shutdown() {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (!port_)
+    return false;  // already shut down.
+
+  RTC_DLOG(LS_VERBOSE) << ToString() << ": Connection destroyed";
+
+  // Fire the 'destroyed' event before deleting the object. This is done
+  // intentionally to avoid a situation whereby the signal might have dangling
+  // pointers to objects that have been deleted by the time the async task
+  // that deletes the connection object runs.
+  auto destroyed_signals = SignalDestroyed;
+  SignalDestroyed.disconnect_all();
+  destroyed_signals(this);
+
+  LogCandidatePairConfig(webrtc::IceCandidatePairConfigType::kDestroyed);
+
+  // Reset the `port_` after logging and firing the destroyed signal since
+  // information required for logging needs access to `port_`.
+  port_.reset();
+
+  return true;
+}
+
+void Connection::FailAndPrune() {
+  RTC_DCHECK_RUN_ON(network_thread_);
+
+  // TODO(bugs.webrtc.org/13865): There's a circular dependency between Port
+  // and Connection. In some cases (Port dtor), a Connection object is deleted
+  // without using the `Destroy` method (port_ won't be nulled and some
+  // functionality won't run as expected), while in other cases
+  // the Connection object is deleted asynchronously and in that case `port_`
+  // will be nulled.
+  // In such a case, there's a chance that the Port object gets
+  // deleted before the Connection object ends up being deleted.
+  if (!port_)
+    return;
+
+  set_state(IceCandidatePairState::FAILED);
+  Prune();
+}
+
+void Connection::PrintPingsSinceLastResponse(std::string* s, size_t max) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  rtc::StringBuilder oss;
+  if (pings_since_last_response_.size() > max) {
+    for (size_t i = 0; i < max; i++) {
+      const SentPing& ping = pings_since_last_response_[i];
+      oss << rtc::hex_encode(ping.id) << " ";
+    }
+    oss << "... " << (pings_since_last_response_.size() - max) << " more";
+  } else {
+    for (const SentPing& ping : pings_since_last_response_) {
+      oss << rtc::hex_encode(ping.id) << " ";
+    }
+  }
+  *s = oss.str();
+}
+
+bool Connection::selected() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return selected_;
+}
+
+void Connection::set_selected(bool selected) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  selected_ = selected;
+}
+
+void Connection::UpdateState(int64_t now) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (!port_)
+    return;
+
+  int rtt = ConservativeRTTEstimate(rtt_);
+
+  if (RTC_LOG_CHECK_LEVEL(LS_VERBOSE)) {
+    std::string pings;
+    PrintPingsSinceLastResponse(&pings, 5);
+    RTC_LOG(LS_VERBOSE) << ToString()
+                        << ": UpdateState()"
+                           ", ms since last received response="
+                        << now - last_ping_response_received_
+                        << ", ms since last received data="
+                        << now - last_data_received_ << ", rtt=" << rtt
+                        << ", pings_since_last_response=" << pings;
+  }
+
+  // Check the writable state.  (The order of these checks is important.)
+  //
+  // Before becoming unwritable, we allow for a fixed number of pings to fail
+  // (i.e., receive no response).  We also have to give the response time to
+  // get back, so we include a conservative estimate of this.
+  //
+  // Before timing out writability, we give a fixed amount of time.  This is to
+  // allow for changes in network conditions.
+
+  if ((write_state_ == STATE_WRITABLE) &&
+      TooManyFailures(pings_since_last_response_, unwritable_min_checks(), rtt,
+                      now) &&
+      TooLongWithoutResponse(pings_since_last_response_, unwritable_timeout(),
+                             now)) {
+    uint32_t max_pings = unwritable_min_checks();
+    RTC_LOG(LS_INFO) << ToString() << ": Unwritable after " << max_pings
+                     << " ping failures and "
+                     << now - pings_since_last_response_[0].sent_time
+                     << " ms without a response,"
+                        " ms since last received ping="
+                     << now - last_ping_received_
+                     << " ms since last received data="
+                     << now - last_data_received_ << " rtt=" << rtt;
+    set_write_state(STATE_WRITE_UNRELIABLE);
+  }
+  if ((write_state_ == STATE_WRITE_UNRELIABLE ||
+       write_state_ == STATE_WRITE_INIT) &&
+      TooLongWithoutResponse(pings_since_last_response_, inactive_timeout(),
+                             now)) {
+    RTC_LOG(LS_INFO) << ToString() << ": Timed out after "
+                     << now - pings_since_last_response_[0].sent_time
+                     << " ms without a response, rtt=" << rtt;
+    set_write_state(STATE_WRITE_TIMEOUT);
+  }
+
+  // Update the receiving state.
+  UpdateReceiving(now);
+  if (dead(now)) {
+    port_->DestroyConnectionAsync(this);
+  }
+}
+
+void Connection::UpdateLocalIceParameters(int component,
+                                          absl::string_view username_fragment,
+                                          absl::string_view password) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  local_candidate_.set_component(component);
+  local_candidate_.set_username(username_fragment);
+  local_candidate_.set_password(password);
+}
+
+int64_t Connection::last_ping_sent() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return last_ping_sent_;
+}
+
+void Connection::Ping(int64_t now) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (!port_)
+    return;
+
+  last_ping_sent_ = now;
+
+  // If not using renomination, we use "1" to mean "nominated" and "0" to mean
+  // "not nominated". If using renomination, values greater than 1 are used for
+  // re-nominated pairs.
+  int nomination = use_candidate_attr_ ? 1 : 0;
+  if (nomination_ > 0) {
+    nomination = nomination_;
+  }
+
+  auto req =
+      std::make_unique<ConnectionRequest>(requests_, this, BuildPingRequest());
+
+  if (ShouldSendGoogPing(req->msg())) {
+    auto message = std::make_unique<IceMessage>(GOOG_PING_REQUEST, req->id());
+    message->AddMessageIntegrity32(remote_candidate_.password());
+    req.reset(new ConnectionRequest(requests_, this, std::move(message)));
+  }
+
+  pings_since_last_response_.push_back(SentPing(req->id(), now, nomination));
+  RTC_LOG(LS_VERBOSE) << ToString() << ": Sending STUN ping, id="
+                      << rtc::hex_encode(req->id())
+                      << ", nomination=" << nomination_;
+  requests_.Send(req.release());
+  state_ = IceCandidatePairState::IN_PROGRESS;
+  num_pings_sent_++;
+}
+
+std::unique_ptr<IceMessage> Connection::BuildPingRequest() {
+  auto message = std::make_unique<IceMessage>(STUN_BINDING_REQUEST);
+  // Note that the order of attributes does not impact the parsing on the
+  // receiver side. The attribute is retrieved then by iterating and matching
+  // over all parsed attributes. See StunMessage::GetAttribute.
+  message->AddAttribute(std::make_unique<StunByteStringAttribute>(
+      STUN_ATTR_USERNAME,
+      port()->CreateStunUsername(remote_candidate_.username())));
+  message->AddAttribute(std::make_unique<StunUInt32Attribute>(
+      STUN_ATTR_GOOG_NETWORK_INFO,
+      (port_->Network()->id() << 16) | port_->network_cost()));
+
+  if (field_trials_->piggyback_ice_check_acknowledgement &&
+      last_ping_id_received_) {
+    message->AddAttribute(std::make_unique<StunByteStringAttribute>(
+        STUN_ATTR_GOOG_LAST_ICE_CHECK_RECEIVED, *last_ping_id_received_));
+  }
+
+  // Adding ICE_CONTROLLED or ICE_CONTROLLING attribute based on the role.
+  IceRole ice_role = port_->GetIceRole();
+  RTC_DCHECK(ice_role == ICEROLE_CONTROLLING || ice_role == ICEROLE_CONTROLLED);
+  message->AddAttribute(std::make_unique<StunUInt64Attribute>(
+      ice_role == ICEROLE_CONTROLLING ? STUN_ATTR_ICE_CONTROLLING
+                                      : STUN_ATTR_ICE_CONTROLLED,
+      port_->IceTiebreaker()));
+
+  if (ice_role == ICEROLE_CONTROLLING) {
+    // We should have either USE_CANDIDATE attribute or ICE_NOMINATION
+    // attribute but not both. That was enforced in p2ptransportchannel.
+    if (use_candidate_attr()) {
+      message->AddAttribute(
+          std::make_unique<StunByteStringAttribute>(STUN_ATTR_USE_CANDIDATE));
+    }
+    if (nomination_ && nomination_ != acked_nomination()) {
+      message->AddAttribute(std::make_unique<StunUInt32Attribute>(
+          STUN_ATTR_NOMINATION, nomination_));
+    }
+  }
+
+  message->AddAttribute(std::make_unique<StunUInt32Attribute>(
+      STUN_ATTR_PRIORITY, prflx_priority()));
+
+  if (port()->send_retransmit_count_attribute()) {
+    message->AddAttribute(std::make_unique<StunUInt32Attribute>(
+        STUN_ATTR_RETRANSMIT_COUNT, pings_since_last_response_.size()));
+  }
+  if (field_trials_->enable_goog_ping &&
+      !remote_support_goog_ping_.has_value()) {
+    // Check if remote supports GOOG PING by announcing which version we
+    // support. This is sent on all STUN_BINDING_REQUEST until we get a
+    // STUN_BINDING_RESPONSE.
+    auto list =
+        StunAttribute::CreateUInt16ListAttribute(STUN_ATTR_GOOG_MISC_INFO);
+    list->AddTypeAtIndex(kSupportGoogPingVersionRequestIndex, kGoogPingVersion);
+    message->AddAttribute(std::move(list));
+  }
+  message->AddMessageIntegrity(remote_candidate_.password());
+  message->AddFingerprint();
+
+  return message;
+}
+
+int64_t Connection::last_ping_response_received() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return last_ping_response_received_;
+}
+
+const absl::optional<std::string>& Connection::last_ping_id_received() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return last_ping_id_received_;
+}
+
+// Used to check if any STUN ping response has been received.
+int Connection::rtt_samples() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return rtt_samples_;
+}
+
+// Called whenever a valid ping is received on this connection.  This is
+// public because the connection intercepts the first ping for us.
+int64_t Connection::last_ping_received() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return last_ping_received_;
+}
+
+void Connection::ReceivedPing(const absl::optional<std::string>& request_id) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  last_ping_received_ = rtc::TimeMillis();
+  last_ping_id_received_ = request_id;
+  UpdateReceiving(last_ping_received_);
+}
+
+void Connection::HandlePiggybackCheckAcknowledgementIfAny(StunMessage* msg) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  RTC_DCHECK(msg->type() == STUN_BINDING_REQUEST ||
+             msg->type() == GOOG_PING_REQUEST);
+  const StunByteStringAttribute* last_ice_check_received_attr =
+      msg->GetByteString(STUN_ATTR_GOOG_LAST_ICE_CHECK_RECEIVED);
+  if (last_ice_check_received_attr) {
+    const absl::string_view request_id =
+        last_ice_check_received_attr->string_view();
+    auto iter = absl::c_find_if(
+        pings_since_last_response_,
+        [&request_id](const SentPing& ping) { return ping.id == request_id; });
+    if (iter != pings_since_last_response_.end()) {
+      rtc::LoggingSeverity sev = !writable() ? rtc::LS_INFO : rtc::LS_VERBOSE;
+      RTC_LOG_V(sev) << ToString()
+                     << ": Received piggyback STUN ping response, id="
+                     << rtc::hex_encode(request_id);
+      const int64_t rtt = rtc::TimeMillis() - iter->sent_time;
+      ReceivedPingResponse(rtt, request_id, iter->nomination);
+    }
+  }
+}
+
+int64_t Connection::last_send_data() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return last_send_data_;
+}
+
+int64_t Connection::last_data_received() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return last_data_received_;
+}
+
+void Connection::ReceivedPingResponse(
+    int rtt,
+    absl::string_view request_id,
+    const absl::optional<uint32_t>& nomination) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  RTC_DCHECK_GE(rtt, 0);
+  // We've already validated that this is a STUN binding response with
+  // the correct local and remote username for this connection.
+  // So if we're not already, become writable. We may be bringing a pruned
+  // connection back to life, but if we don't really want it, we can always
+  // prune it again.
+  if (nomination && nomination.value() > acked_nomination_) {
+    acked_nomination_ = nomination.value();
+  }
+
+  int64_t now = rtc::TimeMillis();
+  total_round_trip_time_ms_ += rtt;
+  current_round_trip_time_ms_ = static_cast<uint32_t>(rtt);
+  rtt_estimate_.AddSample(now, rtt);
+
+  pings_since_last_response_.clear();
+  last_ping_response_received_ = now;
+  UpdateReceiving(last_ping_response_received_);
+  set_write_state(STATE_WRITABLE);
+  set_state(IceCandidatePairState::SUCCEEDED);
+  if (rtt_samples_ > 0) {
+    rtt_ = rtc::GetNextMovingAverage(rtt_, rtt, RTT_RATIO);
+  } else {
+    rtt_ = rtt;
+  }
+  rtt_samples_++;
+}
+
+Connection::WriteState Connection::write_state() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return write_state_;
+}
+
+bool Connection::writable() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return write_state_ == STATE_WRITABLE;
+}
+
+bool Connection::receiving() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return receiving_;
+}
+
+// Determines whether the connection has finished connecting.  This can only
+// be false for TCP connections.
+bool Connection::connected() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return connected_;
+}
+
+bool Connection::weak() const {
+  return !(writable() && receiving() && connected());
+}
+
+bool Connection::active() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return write_state_ != STATE_WRITE_TIMEOUT;
+}
+
+bool Connection::dead(int64_t now) const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (last_received() > 0) {
+    // If it has ever received anything, we keep it alive
+    // - if it has recevied last DEAD_CONNECTION_RECEIVE_TIMEOUT (30s)
+    // - if it has a ping outstanding shorter than
+    // DEAD_CONNECTION_RECEIVE_TIMEOUT (30s)
+    // - else if IDLE let it live field_trials_->dead_connection_timeout_ms
+    //
+    // This covers the normal case of a successfully used connection that stops
+    // working. This also allows a remote peer to continue pinging over a
+    // locally inactive (pruned) connection. This also allows the local agent to
+    // ping with longer interval than 30s as long as it shorter than
+    // `dead_connection_timeout_ms`.
+    if (now <= (last_received() + DEAD_CONNECTION_RECEIVE_TIMEOUT)) {
+      // Not dead since we have received the last 30s.
+      return false;
+    }
+    if (!pings_since_last_response_.empty()) {
+      // Outstanding pings: let it live until the ping is unreplied for
+      // DEAD_CONNECTION_RECEIVE_TIMEOUT.
+      return now > (pings_since_last_response_[0].sent_time +
+                    DEAD_CONNECTION_RECEIVE_TIMEOUT);
+    }
+
+    // No outstanding pings: let it live until
+    // field_trials_->dead_connection_timeout_ms has passed.
+    return now > (last_received() + field_trials_->dead_connection_timeout_ms);
+  }
+
+  if (active()) {
+    // If it has never received anything, keep it alive as long as it is
+    // actively pinging and not pruned. Otherwise, the connection might be
+    // deleted before it has a chance to ping. This is the normal case for a
+    // new connection that is pinging but hasn't received anything yet.
+    return false;
+  }
+
+  // If it has never received anything and is not actively pinging (pruned), we
+  // keep it around for at least MIN_CONNECTION_LIFETIME to prevent connections
+  // from being pruned too quickly during a network change event when two
+  // networks would be up simultaneously but only for a brief period.
+  return now > (time_created_ms_ + MIN_CONNECTION_LIFETIME);
+}
+
+int Connection::rtt() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return rtt_;
+}
+
+bool Connection::stable(int64_t now) const {
+  // A connection is stable if it's RTT has converged and it isn't missing any
+  // responses.  We should send pings at a higher rate until the RTT converges
+  // and whenever a ping response is missing (so that we can detect
+  // unwritability faster)
+  return rtt_converged() && !missing_responses(now);
+}
+
+std::string Connection::ToDebugId() const {
+  return rtc::ToHex(reinterpret_cast<uintptr_t>(this));
+}
+
+uint32_t Connection::ComputeNetworkCost() const {
+  // TODO(honghaiz): Will add rtt as part of the network cost.
+  return port()->network_cost() + remote_candidate_.network_cost();
+}
+
+std::string Connection::ToString() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  constexpr absl::string_view CONNECT_STATE_ABBREV[2] = {
+      "-",  // not connected (false)
+      "C",  // connected (true)
+  };
+  constexpr absl::string_view RECEIVE_STATE_ABBREV[2] = {
+      "-",  // not receiving (false)
+      "R",  // receiving (true)
+  };
+  constexpr absl::string_view WRITE_STATE_ABBREV[4] = {
+      "W",  // STATE_WRITABLE
+      "w",  // STATE_WRITE_UNRELIABLE
+      "-",  // STATE_WRITE_INIT
+      "x",  // STATE_WRITE_TIMEOUT
+  };
+  constexpr absl::string_view ICESTATE[4] = {
+      "W",  // STATE_WAITING
+      "I",  // STATE_INPROGRESS
+      "S",  // STATE_SUCCEEDED
+      "F"   // STATE_FAILED
+  };
+  constexpr absl::string_view SELECTED_STATE_ABBREV[2] = {
+      "-",  // candidate pair not selected (false)
+      "S",  // selected (true)
+  };
+  rtc::StringBuilder ss;
+  ss << "Conn[" << ToDebugId();
+
+  if (!port_) {
+    // No content or network names for pending delete. Temporarily substitute
+    // the names with a hash (rhyming with trash).
+    ss << ":#:#:";
+  } else {
+    ss << ":" << port_->content_name() << ":" << port_->Network()->ToString()
+       << ":";
+  }
+
+  const Candidate& local = local_candidate();
+  const Candidate& remote = remote_candidate();
+  ss << local.id() << ":" << local.component() << ":" << local.generation()
+     << ":" << local.type() << ":" << local.protocol() << ":"
+     << local.address().ToSensitiveString() << "->" << remote.id() << ":"
+     << remote.component() << ":" << remote.priority() << ":" << remote.type()
+     << ":" << remote.protocol() << ":" << remote.address().ToSensitiveString()
+     << "|";
+
+  ss << CONNECT_STATE_ABBREV[connected_] << RECEIVE_STATE_ABBREV[receiving_]
+     << WRITE_STATE_ABBREV[write_state_] << ICESTATE[static_cast<int>(state_)]
+     << "|" << SELECTED_STATE_ABBREV[selected_] << "|" << remote_nomination_
+     << "|" << nomination_ << "|";
+
+  if (port_)
+    ss << priority() << "|";
+
+  if (rtt_ < DEFAULT_RTT) {
+    ss << rtt_ << "]";
+  } else {
+    ss << "-]";
+  }
+
+  return ss.Release();
+}
+
+std::string Connection::ToSensitiveString() const {
+  return ToString();
+}
+
+const webrtc::IceCandidatePairDescription& Connection::ToLogDescription() {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (log_description_.has_value()) {
+    return log_description_.value();
+  }
+  const Candidate& local = local_candidate();
+  const Candidate& remote = remote_candidate();
+  const rtc::Network* network = port()->Network();
+  log_description_ = webrtc::IceCandidatePairDescription();
+  log_description_->local_candidate_type =
+      GetCandidateTypeByString(local.type());
+  log_description_->local_relay_protocol =
+      GetProtocolByString(local.relay_protocol());
+  log_description_->local_network_type = ConvertNetworkType(network->type());
+  log_description_->local_address_family =
+      GetAddressFamilyByInt(local.address().family());
+  log_description_->remote_candidate_type =
+      GetCandidateTypeByString(remote.type());
+  log_description_->remote_address_family =
+      GetAddressFamilyByInt(remote.address().family());
+  log_description_->candidate_pair_protocol =
+      GetProtocolByString(local.protocol());
+  return log_description_.value();
+}
+
+void Connection::set_ice_event_log(webrtc::IceEventLog* ice_event_log) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  ice_event_log_ = ice_event_log;
+}
+
+void Connection::LogCandidatePairConfig(
+    webrtc::IceCandidatePairConfigType type) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (ice_event_log_ == nullptr) {
+    return;
+  }
+  ice_event_log_->LogCandidatePairConfig(type, id(), ToLogDescription());
+}
+
+void Connection::LogCandidatePairEvent(webrtc::IceCandidatePairEventType type,
+                                       uint32_t transaction_id) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (ice_event_log_ == nullptr) {
+    return;
+  }
+  ice_event_log_->LogCandidatePairEvent(type, id(), transaction_id);
+}
+
+void Connection::OnConnectionRequestResponse(StunRequest* request,
+                                             StunMessage* response) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  // Log at LS_INFO if we receive a ping response on an unwritable
+  // connection.
+  rtc::LoggingSeverity sev = !writable() ? rtc::LS_INFO : rtc::LS_VERBOSE;
+
+  int rtt = request->Elapsed();
+
+  if (RTC_LOG_CHECK_LEVEL_V(sev)) {
+    std::string pings;
+    PrintPingsSinceLastResponse(&pings, 5);
+    RTC_LOG_V(sev) << ToString() << ": Received "
+                   << StunMethodToString(response->type())
+                   << ", id=" << rtc::hex_encode(request->id())
+                   << ", code=0"  // Makes logging easier to parse.
+                      ", rtt="
+                   << rtt << ", pings_since_last_response=" << pings;
+  }
+  absl::optional<uint32_t> nomination;
+  const std::string request_id = request->id();
+  auto iter = absl::c_find_if(
+      pings_since_last_response_,
+      [&request_id](const SentPing& ping) { return ping.id == request_id; });
+  if (iter != pings_since_last_response_.end()) {
+    nomination.emplace(iter->nomination);
+  }
+  ReceivedPingResponse(rtt, request_id, nomination);
+
+  stats_.recv_ping_responses++;
+  LogCandidatePairEvent(
+      webrtc::IceCandidatePairEventType::kCheckResponseReceived,
+      response->reduced_transaction_id());
+
+  if (request->msg()->type() == STUN_BINDING_REQUEST) {
+    if (!remote_support_goog_ping_.has_value()) {
+      auto goog_misc = response->GetUInt16List(STUN_ATTR_GOOG_MISC_INFO);
+      if (goog_misc != nullptr &&
+          goog_misc->Size() >= kSupportGoogPingVersionResponseIndex) {
+        // The remote peer has indicated that it {does/does not} supports
+        // GOOG_PING.
+        remote_support_goog_ping_ =
+            goog_misc->GetType(kSupportGoogPingVersionResponseIndex) >=
+            kGoogPingVersion;
+      } else {
+        remote_support_goog_ping_ = false;
+      }
+    }
+
+    MaybeUpdateLocalCandidate(request, response);
+
+    if (field_trials_->enable_goog_ping && remote_support_goog_ping_) {
+      cached_stun_binding_ = request->msg()->Clone();
+    }
+  }
+}
+
+void Connection::OnConnectionRequestErrorResponse(ConnectionRequest* request,
+                                                  StunMessage* response) {
+  if (!port_)
+    return;
+
+  int error_code = response->GetErrorCodeValue();
+  RTC_LOG(LS_WARNING) << ToString() << ": Received "
+                      << StunMethodToString(response->type())
+                      << " id=" << rtc::hex_encode(request->id())
+                      << " code=" << error_code
+                      << " rtt=" << request->Elapsed();
+
+  cached_stun_binding_.reset();
+  if (error_code == STUN_ERROR_UNKNOWN_ATTRIBUTE ||
+      error_code == STUN_ERROR_SERVER_ERROR ||
+      error_code == STUN_ERROR_UNAUTHORIZED) {
+    // Recoverable error, retry
+  } else if (error_code == STUN_ERROR_ROLE_CONFLICT) {
+    port_->SignalRoleConflict(port_.get());
+  } else if (request->msg()->type() == GOOG_PING_REQUEST) {
+    // Race, retry.
+  } else {
+    // This is not a valid connection.
+    RTC_LOG(LS_ERROR) << ToString()
+                      << ": Received STUN error response, code=" << error_code
+                      << "; killing connection";
+    set_state(IceCandidatePairState::FAILED);
+    port_->DestroyConnectionAsync(this);
+  }
+}
+
+void Connection::OnConnectionRequestTimeout(ConnectionRequest* request) {
+  // Log at LS_INFO if we miss a ping on a writable connection.
+  rtc::LoggingSeverity sev = writable() ? rtc::LS_INFO : rtc::LS_VERBOSE;
+  RTC_LOG_V(sev) << ToString() << ": Timing-out STUN ping "
+                 << rtc::hex_encode(request->id()) << " after "
+                 << request->Elapsed() << " ms";
+}
+
+void Connection::OnConnectionRequestSent(ConnectionRequest* request) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  // Log at LS_INFO if we send a ping on an unwritable connection.
+  rtc::LoggingSeverity sev = !writable() ? rtc::LS_INFO : rtc::LS_VERBOSE;
+  RTC_LOG_V(sev) << ToString() << ": Sent "
+                 << StunMethodToString(request->msg()->type())
+                 << ", id=" << rtc::hex_encode(request->id())
+                 << ", use_candidate=" << use_candidate_attr()
+                 << ", nomination=" << nomination_;
+  stats_.sent_ping_requests_total++;
+  LogCandidatePairEvent(webrtc::IceCandidatePairEventType::kCheckSent,
+                        request->reduced_transaction_id());
+  if (stats_.recv_ping_responses == 0) {
+    stats_.sent_ping_requests_before_first_response++;
+  }
+}
+
+IceCandidatePairState Connection::state() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return state_;
+}
+
+int Connection::num_pings_sent() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return num_pings_sent_;
+}
+
+void Connection::MaybeSetRemoteIceParametersAndGeneration(
+    const IceParameters& ice_params,
+    int generation) {
+  if (remote_candidate_.username() == ice_params.ufrag &&
+      remote_candidate_.password().empty()) {
+    remote_candidate_.set_password(ice_params.pwd);
+  }
+  // TODO(deadbeef): A value of '0' for the generation is used for both
+  // generation 0 and "generation unknown". It should be changed to an
+  // absl::optional to fix this.
+  if (remote_candidate_.username() == ice_params.ufrag &&
+      remote_candidate_.password() == ice_params.pwd &&
+      remote_candidate_.generation() == 0) {
+    remote_candidate_.set_generation(generation);
+  }
+}
+
+void Connection::MaybeUpdatePeerReflexiveCandidate(
+    const Candidate& new_candidate) {
+  if (remote_candidate_.type() == PRFLX_PORT_TYPE &&
+      new_candidate.type() != PRFLX_PORT_TYPE &&
+      remote_candidate_.protocol() == new_candidate.protocol() &&
+      remote_candidate_.address() == new_candidate.address() &&
+      remote_candidate_.username() == new_candidate.username() &&
+      remote_candidate_.password() == new_candidate.password() &&
+      remote_candidate_.generation() == new_candidate.generation()) {
+    remote_candidate_ = new_candidate;
+  }
+}
+
+int64_t Connection::last_received() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return std::max(last_data_received_,
+                  std::max(last_ping_received_, last_ping_response_received_));
+}
+
+int64_t Connection::receiving_unchanged_since() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return receiving_unchanged_since_;
+}
+
+uint32_t Connection::prflx_priority() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  // PRIORITY Attribute.
+  // Changing the type preference to Peer Reflexive and local preference
+  // and component id information is unchanged from the original priority.
+  // priority = (2^24)*(type preference) +
+  //           (2^8)*(local preference) +
+  //           (2^0)*(256 - component ID)
+  IcePriorityValue type_preference =
+      (local_candidate_.protocol() == TCP_PROTOCOL_NAME)
+          ? ICE_TYPE_PREFERENCE_PRFLX_TCP
+          : ICE_TYPE_PREFERENCE_PRFLX;
+  return type_preference << 24 | (local_candidate_.priority() & 0x00FFFFFF);
+}
+
+ConnectionInfo Connection::stats() {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  stats_.recv_bytes_second = round(recv_rate_tracker_.ComputeRate());
+  stats_.recv_total_bytes = recv_rate_tracker_.TotalSampleCount();
+  stats_.sent_bytes_second = round(send_rate_tracker_.ComputeRate());
+  stats_.sent_total_bytes = send_rate_tracker_.TotalSampleCount();
+  stats_.receiving = receiving_;
+  stats_.writable = write_state_ == STATE_WRITABLE;
+  stats_.timeout = write_state_ == STATE_WRITE_TIMEOUT;
+  stats_.rtt = rtt_;
+  stats_.key = this;
+  stats_.state = state_;
+  if (port_) {
+    stats_.priority = priority();
+    stats_.local_candidate = local_candidate();
+  }
+  stats_.nominated = nominated();
+  stats_.total_round_trip_time_ms = total_round_trip_time_ms_;
+  stats_.current_round_trip_time_ms = current_round_trip_time_ms_;
+  stats_.remote_candidate = remote_candidate();
+  if (last_data_received_ > 0) {
+    stats_.last_data_received = webrtc::Timestamp::Millis(
+        last_data_received_ + delta_internal_unix_epoch_ms_);
+  }
+  if (last_send_data_ > 0) {
+    stats_.last_data_sent = webrtc::Timestamp::Millis(
+        last_send_data_ + delta_internal_unix_epoch_ms_);
+  }
+  return stats_;
+}
+
+void Connection::MaybeUpdateLocalCandidate(StunRequest* request,
+                                           StunMessage* response) {
+  if (!port_)
+    return;
+
+  // RFC 5245
+  // The agent checks the mapped address from the STUN response.  If the
+  // transport address does not match any of the local candidates that the
+  // agent knows about, the mapped address represents a new candidate -- a
+  // peer reflexive candidate.
+  const StunAddressAttribute* addr =
+      response->GetAddress(STUN_ATTR_XOR_MAPPED_ADDRESS);
+  if (!addr) {
+    RTC_LOG(LS_WARNING)
+        << "Connection::OnConnectionRequestResponse - "
+           "No MAPPED-ADDRESS or XOR-MAPPED-ADDRESS found in the "
+           "stun response message";
+    return;
+  }
+
+  for (const Candidate& candidate : port_->Candidates()) {
+    if (candidate.address() == addr->GetAddress()) {
+      if (local_candidate_ != candidate) {
+        RTC_LOG(LS_INFO) << ToString()
+                         << ": Updating local candidate type to srflx.";
+        local_candidate_ = candidate;
+        // SignalStateChange to force a re-sort in P2PTransportChannel as this
+        // Connection's local candidate has changed.
+        SignalStateChange(this);
+      }
+      return;
+    }
+  }
+
+  // RFC 5245
+  // Its priority is set equal to the value of the PRIORITY attribute
+  // in the Binding request.
+  const StunUInt32Attribute* priority_attr =
+      request->msg()->GetUInt32(STUN_ATTR_PRIORITY);
+  if (!priority_attr) {
+    RTC_LOG(LS_WARNING) << "Connection::OnConnectionRequestResponse - "
+                           "No STUN_ATTR_PRIORITY found in the "
+                           "stun response message";
+    return;
+  }
+  const uint32_t priority = priority_attr->value();
+  std::string id = rtc::CreateRandomString(8);
+
+  // Create a peer-reflexive candidate based on the local candidate.
+  local_candidate_.set_id(id);
+  local_candidate_.set_type(PRFLX_PORT_TYPE);
+  // Set the related address and foundation attributes before changing the
+  // address.
+  local_candidate_.set_related_address(local_candidate_.address());
+  local_candidate_.set_foundation(port()->ComputeFoundation(
+      PRFLX_PORT_TYPE, local_candidate_.protocol(),
+      local_candidate_.relay_protocol(), local_candidate_.address()));
+  local_candidate_.set_priority(priority);
+  local_candidate_.set_address(addr->GetAddress());
+
+  // Change the local candidate of this Connection to the new prflx candidate.
+  RTC_LOG(LS_INFO) << ToString() << ": Updating local candidate type to prflx.";
+  port_->AddPrflxCandidate(local_candidate_);
+
+  // SignalStateChange to force a re-sort in P2PTransportChannel as this
+  // Connection's local candidate has changed.
+  SignalStateChange(this);
+}
+
+bool Connection::rtt_converged() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return rtt_samples_ > (RTT_RATIO + 1);
+}
+
+bool Connection::missing_responses(int64_t now) const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (pings_since_last_response_.empty()) {
+    return false;
+  }
+
+  int64_t waiting = now - pings_since_last_response_[0].sent_time;
+  return waiting > 2 * rtt();
+}
+
+bool Connection::TooManyOutstandingPings(
+    const absl::optional<int>& max_outstanding_pings) const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (!max_outstanding_pings.has_value()) {
+    return false;
+  }
+  if (static_cast<int>(pings_since_last_response_.size()) <
+      *max_outstanding_pings) {
+    return false;
+  }
+  return true;
+}
+
+void Connection::SetLocalCandidateNetworkCost(uint16_t cost) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+
+  if (cost == local_candidate_.network_cost())
+    return;
+
+  local_candidate_.set_network_cost(cost);
+
+  // Network cost change will affect the connection selection criteria.
+  // Signal the connection state change to force a re-sort in
+  // P2PTransportChannel.
+  SignalStateChange(this);
+}
+
+bool Connection::ShouldSendGoogPing(const StunMessage* message) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (remote_support_goog_ping_ == true && cached_stun_binding_ &&
+      cached_stun_binding_->EqualAttributes(message, [](int type) {
+        // Ignore these attributes.
+        // NOTE: Consider what to do if adding more content to
+        // STUN_ATTR_GOOG_MISC_INFO
+        return type != STUN_ATTR_FINGERPRINT &&
+               type != STUN_ATTR_MESSAGE_INTEGRITY &&
+               type != STUN_ATTR_RETRANSMIT_COUNT &&
+               type != STUN_ATTR_GOOG_MISC_INFO;
+      })) {
+    return true;
+  }
+  return false;
+}
+
+void Connection::ForgetLearnedState() {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  RTC_LOG(LS_INFO) << ToString() << ": Connection forget learned state";
+  requests_.Clear();
+  receiving_ = false;
+  write_state_ = STATE_WRITE_INIT;
+  rtt_estimate_.Reset();
+  pings_since_last_response_.clear();
+}
+
+ProxyConnection::ProxyConnection(rtc::WeakPtr<Port> port,
+                                 size_t index,
+                                 const Candidate& remote_candidate)
+    : Connection(std::move(port), index, remote_candidate) {}
+
+int ProxyConnection::Send(const void* data,
+                          size_t size,
+                          const rtc::PacketOptions& options) {
+  if (!port_)
+    return SOCKET_ERROR;
+
+  stats_.sent_total_packets++;
+  int sent =
+      port_->SendTo(data, size, remote_candidate_.address(), options, true);
+  int64_t now = rtc::TimeMillis();
+  if (sent <= 0) {
+    RTC_DCHECK(sent < 0);
+    error_ = port_->GetError();
+    stats_.sent_discarded_packets++;
+    stats_.sent_discarded_bytes += size;
+  } else {
+    send_rate_tracker_.AddSamplesAtTime(now, sent);
+  }
+  last_send_data_ = now;
+  return sent;
+}
+
+int ProxyConnection::GetError() {
+  return error_;
+}
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/connection.h b/third_party/libwebrtc/p2p/base/connection.h
new file mode 100644
index 0000000000..4e6c7d91be
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/connection.h
@@ -0,0 +1,498 @@
+/*
+ *  Copyright 2019 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_CONNECTION_H_
+#define P2P_BASE_CONNECTION_H_
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "absl/strings/string_view.h"
+#include "absl/types/optional.h"
+#include "api/candidate.h"
+#include "api/transport/stun.h"
+#include "logging/rtc_event_log/ice_logger.h"
+#include "p2p/base/candidate_pair_interface.h"
+#include "p2p/base/connection_info.h"
+#include "p2p/base/p2p_transport_channel_ice_field_trials.h"
+#include "p2p/base/stun_request.h"
+#include "p2p/base/transport_description.h"
+#include "rtc_base/async_packet_socket.h"
+#include "rtc_base/network.h"
+#include "rtc_base/numerics/event_based_exponential_moving_average.h"
+#include "rtc_base/rate_tracker.h"
+#include "rtc_base/system/rtc_export.h"
+#include "rtc_base/weak_ptr.h"
+
+namespace cricket {
+
+// Version number for GOOG_PING, this is added to have the option of
+// adding other flavors in the future.
+constexpr int kGoogPingVersion = 1;
+
+// Connection and Port has circular dependencies.
+// So we use forward declaration rather than include.
+class Port;
+
+// Forward declaration so that a ConnectionRequest can contain a Connection.
+class Connection;
+
+struct CandidatePair final : public CandidatePairInterface {
+  ~CandidatePair() override = default;
+
+  const Candidate& local_candidate() const override { return local; }
+  const Candidate& remote_candidate() const override { return remote; }
+
+  Candidate local;
+  Candidate remote;
+};
+
+// Represents a communication link between a port on the local client and a
+// port on the remote client.
+class RTC_EXPORT Connection : public CandidatePairInterface {
+ public:
+  struct SentPing {
+    SentPing(absl::string_view id, int64_t sent_time, uint32_t nomination)
+        : id(id), sent_time(sent_time), nomination(nomination) {}
+
+    std::string id;
+    int64_t sent_time;
+    uint32_t nomination;
+  };
+
+  ~Connection() override;
+
+  // A unique ID assigned when the connection is created.
+  uint32_t id() const { return id_; }
+
+  webrtc::TaskQueueBase* network_thread() const;
+
+  // Implementation of virtual methods in CandidatePairInterface.
+  // Returns the description of the local port
+  const Candidate& local_candidate() const override;
+  // Returns the description of the remote port to which we communicate.
+  const Candidate& remote_candidate() const override;
+
+  // Return local network for this connection.
+  virtual const rtc::Network* network() const;
+  // Return generation for this connection.
+  virtual int generation() const;
+
+  // Returns the pair priority.
+  virtual uint64_t priority() const;
+
+  enum WriteState {
+    STATE_WRITABLE = 0,          // we have received ping responses recently
+    STATE_WRITE_UNRELIABLE = 1,  // we have had a few ping failures
+    STATE_WRITE_INIT = 2,        // we have yet to receive a ping response
+    STATE_WRITE_TIMEOUT = 3,     // we have had a large number of ping failures
+  };
+
+  WriteState write_state() const;
+  bool writable() const;
+  bool receiving() const;
+
+  const Port* port() const {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    return port_.get();
+  }
+
+  // Determines whether the connection has finished connecting.  This can only
+  // be false for TCP connections.
+  bool connected() const;
+  bool weak() const;
+  bool active() const;
+
+  // A connection is dead if it can be safely deleted.
+  bool dead(int64_t now) const;
+
+  // Estimate of the round-trip time over this connection.
+  int rtt() const;
+
+  int unwritable_timeout() const;
+  void set_unwritable_timeout(const absl::optional<int>& value_ms);
+  int unwritable_min_checks() const;
+  void set_unwritable_min_checks(const absl::optional<int>& value);
+  int inactive_timeout() const;
+  void set_inactive_timeout(const absl::optional<int>& value);
+
+  // Gets the `ConnectionInfo` stats, where `best_connection` has not been
+  // populated (default value false).
+  ConnectionInfo stats();
+
+  sigslot::signal1<Connection*> SignalStateChange;
+
+  // Sent when the connection has decided that it is no longer of value.  It
+  // will delete itself immediately after this call.
+  sigslot::signal1<Connection*> SignalDestroyed;
+
+  // The connection can send and receive packets asynchronously.  This matches
+  // the interface of AsyncPacketSocket, which may use UDP or TCP under the
+  // covers.
+  virtual int Send(const void* data,
+                   size_t size,
+                   const rtc::PacketOptions& options) = 0;
+
+  // Error if Send() returns < 0
+  virtual int GetError() = 0;
+
+  sigslot::signal4<Connection*, const char*, size_t, int64_t> SignalReadPacket;
+
+  sigslot::signal1<Connection*> SignalReadyToSend;
+
+  // Called when a packet is received on this connection.
+  void OnReadPacket(const char* data, size_t size, int64_t packet_time_us);
+
+  // Called when the socket is currently able to send.
+  void OnReadyToSend();
+
+  // Called when a connection is determined to be no longer useful to us.  We
+  // still keep it around in case the other side wants to use it.  But we can
+  // safely stop pinging on it and we can allow it to time out if the other
+  // side stops using it as well.
+  bool pruned() const;
+  void Prune();
+
+  bool use_candidate_attr() const;
+  void set_use_candidate_attr(bool enable);
+
+  void set_nomination(uint32_t value);
+
+  uint32_t remote_nomination() const;
+  // One or several pairs may be nominated based on if Regular or Aggressive
+  // Nomination is used. https://tools.ietf.org/html/rfc5245#section-8
+  // `nominated` is defined both for the controlling or controlled agent based
+  // on if a nomination has been pinged or acknowledged. The controlled agent
+  // gets its `remote_nomination_` set when pinged by the controlling agent with
+  // a nomination value. The controlling agent gets its `acked_nomination_` set
+  // when receiving a response to a nominating ping.
+  bool nominated() const;
+
+  int receiving_timeout() const;
+  void set_receiving_timeout(absl::optional<int> receiving_timeout_ms);
+
+  // Deletes a `Connection` instance is by calling the `DestroyConnection`
+  // method in `Port`.
+  // Note: When the function returns, the object has been deleted.
+  void Destroy();
+
+  // Signals object destruction, releases outstanding references and performs
+  // final logging.
+  // The function will return `true` when shutdown was performed, signals
+  // emitted and outstanding references released. If the function returns
+  // `false`, `Shutdown()` has previously been called.
+  bool Shutdown();
+
+  // Prunes the connection and sets its state to STATE_FAILED,
+  // It will not be used or send pings although it can still receive packets.
+  void FailAndPrune();
+
+  // Checks that the state of this connection is up-to-date.  The argument is
+  // the current time, which is compared against various timeouts.
+  void UpdateState(int64_t now);
+
+  void UpdateLocalIceParameters(int component,
+                                absl::string_view username_fragment,
+                                absl::string_view password);
+
+  // Called when this connection should try checking writability again.
+  int64_t last_ping_sent() const;
+  void Ping(int64_t now);
+  void ReceivedPingResponse(
+      int rtt,
+      absl::string_view request_id,
+      const absl::optional<uint32_t>& nomination = absl::nullopt);
+  std::unique_ptr<IceMessage> BuildPingRequest() RTC_RUN_ON(network_thread_);
+
+  int64_t last_ping_response_received() const;
+  const absl::optional<std::string>& last_ping_id_received() const;
+
+  // Used to check if any STUN ping response has been received.
+  int rtt_samples() const;
+
+  // Called whenever a valid ping is received on this connection.  This is
+  // public because the connection intercepts the first ping for us.
+  int64_t last_ping_received() const;
+
+  void ReceivedPing(
+      const absl::optional<std::string>& request_id = absl::nullopt);
+  // Handles the binding request; sends a response if this is a valid request.
+  void HandleStunBindingOrGoogPingRequest(IceMessage* msg);
+  // Handles the piggyback acknowledgement of the lastest connectivity check
+  // that the remote peer has received, if it is indicated in the incoming
+  // connectivity check from the peer.
+  void HandlePiggybackCheckAcknowledgementIfAny(StunMessage* msg);
+  // Timestamp when data was last sent (or attempted to be sent).
+  int64_t last_send_data() const;
+  int64_t last_data_received() const;
+
+  // Debugging description of this connection
+  std::string ToDebugId() const;
+  std::string ToString() const;
+  std::string ToSensitiveString() const;
+  // Structured description of this candidate pair.
+  const webrtc::IceCandidatePairDescription& ToLogDescription();
+  void set_ice_event_log(webrtc::IceEventLog* ice_event_log);
+
+  // Prints pings_since_last_response_ into a string.
+  void PrintPingsSinceLastResponse(std::string* pings, size_t max);
+
+  // `set_selected` is only used for logging in ToString above.  The flag is
+  // set true by P2PTransportChannel for its selected candidate pair.
+  // TODO(tommi): Remove `selected()` once not referenced downstream.
+  bool selected() const;
+  void set_selected(bool selected);
+
+  // This signal will be fired if this connection is nominated by the
+  // controlling side.
+  sigslot::signal1<Connection*> SignalNominated;
+
+  IceCandidatePairState state() const;
+
+  int num_pings_sent() const;
+
+  uint32_t ComputeNetworkCost() const;
+
+  // Update the ICE password and/or generation of the remote candidate if the
+  // ufrag in `params` matches the candidate's ufrag, and the
+  // candidate's password and/or ufrag has not been set.
+  void MaybeSetRemoteIceParametersAndGeneration(const IceParameters& params,
+                                                int generation);
+
+  // If `remote_candidate_` is peer reflexive and is equivalent to
+  // `new_candidate` except the type, update `remote_candidate_` to
+  // `new_candidate`.
+  void MaybeUpdatePeerReflexiveCandidate(const Candidate& new_candidate);
+
+  // Returns the last received time of any data, stun request, or stun
+  // response in milliseconds
+  int64_t last_received() const;
+  // Returns the last time when the connection changed its receiving state.
+  int64_t receiving_unchanged_since() const;
+
+  // Constructs the prflx priority as described in
+  // https://datatracker.ietf.org/doc/html/rfc5245#section-4.1.2.1
+  uint32_t prflx_priority() const;
+
+  bool stable(int64_t now) const;
+
+  // Check if we sent `val` pings without receving a response.
+  bool TooManyOutstandingPings(const absl::optional<int>& val) const;
+
+  // Called by Port when the network cost changes.
+  void SetLocalCandidateNetworkCost(uint16_t cost);
+
+  void SetIceFieldTrials(const IceFieldTrials* field_trials);
+  const rtc::EventBasedExponentialMovingAverage& GetRttEstimate() const {
+    return rtt_estimate_;
+  }
+
+  // Reset the connection to a state of a newly connected.
+  // - STATE_WRITE_INIT
+  // - receving = false
+  // - throw away all pending request
+  // - reset RttEstimate
+  //
+  // Keep the following unchanged:
+  // - connected
+  // - remote_candidate
+  // - statistics
+  //
+  // Does not trigger SignalStateChange
+  void ForgetLearnedState();
+
+  void SendStunBindingResponse(const StunMessage* message);
+  void SendGoogPingResponse(const StunMessage* message);
+  void SendResponseMessage(const StunMessage& response);
+
+  // An accessor for unit tests.
+  Port* PortForTest() { return port_.get(); }
+  const Port* PortForTest() const { return port_.get(); }
+
+  std::unique_ptr<IceMessage> BuildPingRequestForTest() {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    return BuildPingRequest();
+  }
+
+  // Public for unit tests.
+  uint32_t acked_nomination() const;
+  void set_remote_nomination(uint32_t remote_nomination);
+
+  const std::string& remote_password_for_test() const {
+    return remote_candidate().password();
+  }
+  void set_remote_password_for_test(absl::string_view pwd) {
+    remote_candidate_.set_password(pwd);
+  }
+
+ protected:
+  // A ConnectionRequest is a simple STUN ping used to determine writability.
+  class ConnectionRequest;
+
+  // Constructs a new connection to the given remote port.
+  Connection(rtc::WeakPtr<Port> port, size_t index, const Candidate& candidate);
+
+  // Called back when StunRequestManager has a stun packet to send
+  void OnSendStunPacket(const void* data, size_t size, StunRequest* req);
+
+  // Callbacks from ConnectionRequest
+  virtual void OnConnectionRequestResponse(StunRequest* req,
+                                           StunMessage* response);
+  void OnConnectionRequestErrorResponse(ConnectionRequest* req,
+                                        StunMessage* response)
+      RTC_RUN_ON(network_thread_);
+  void OnConnectionRequestTimeout(ConnectionRequest* req)
+      RTC_RUN_ON(network_thread_);
+  void OnConnectionRequestSent(ConnectionRequest* req)
+      RTC_RUN_ON(network_thread_);
+
+  bool rtt_converged() const;
+
+  // If the response is not received within 2 * RTT, the response is assumed to
+  // be missing.
+  bool missing_responses(int64_t now) const;
+
+  // Changes the state and signals if necessary.
+  void set_write_state(WriteState value);
+  void UpdateReceiving(int64_t now);
+  void set_state(IceCandidatePairState state);
+  void set_connected(bool value);
+
+  // The local port where this connection sends and receives packets.
+  Port* port() { return port_.get(); }
+
+  // NOTE: A pointer to the network thread is held by `port_` so in theory we
+  // shouldn't need to hold on to this pointer here, but rather defer to
+  // port_->thread(). However, some tests delete the classes in the wrong order
+  // so `port_` may be deleted before an instance of this class is deleted.
+  // TODO(tommi): This ^^^ should be fixed.
+  webrtc::TaskQueueBase* const network_thread_;
+  const uint32_t id_;
+  rtc::WeakPtr<Port> port_;
+  Candidate local_candidate_ RTC_GUARDED_BY(network_thread_);
+  Candidate remote_candidate_;
+
+  ConnectionInfo stats_;
+  rtc::RateTracker recv_rate_tracker_;
+  rtc::RateTracker send_rate_tracker_;
+  int64_t last_send_data_ = 0;
+
+ private:
+  // Update the local candidate based on the mapped address attribute.
+  // If the local candidate changed, fires SignalStateChange.
+  void MaybeUpdateLocalCandidate(StunRequest* request, StunMessage* response)
+      RTC_RUN_ON(network_thread_);
+
+  void LogCandidatePairConfig(webrtc::IceCandidatePairConfigType type)
+      RTC_RUN_ON(network_thread_);
+  void LogCandidatePairEvent(webrtc::IceCandidatePairEventType type,
+                             uint32_t transaction_id)
+      RTC_RUN_ON(network_thread_);
+
+  // Check if this IceMessage is identical
+  // to last message ack:ed STUN_BINDING_REQUEST.
+  bool ShouldSendGoogPing(const StunMessage* message)
+      RTC_RUN_ON(network_thread_);
+
+  WriteState write_state_ RTC_GUARDED_BY(network_thread_);
+  bool receiving_ RTC_GUARDED_BY(network_thread_);
+  bool connected_ RTC_GUARDED_BY(network_thread_);
+  bool pruned_ RTC_GUARDED_BY(network_thread_);
+  bool selected_ RTC_GUARDED_BY(network_thread_) = false;
+  // By default `use_candidate_attr_` flag will be true,
+  // as we will be using aggressive nomination.
+  // But when peer is ice-lite, this flag "must" be initialized to false and
+  // turn on when connection becomes "best connection".
+  bool use_candidate_attr_ RTC_GUARDED_BY(network_thread_);
+  // Used by the controlling side to indicate that this connection will be
+  // selected for transmission if the peer supports ICE-renomination when this
+  // value is positive. A larger-value indicates that a connection is nominated
+  // later and should be selected by the controlled side with higher precedence.
+  // A zero-value indicates not nominating this connection.
+  uint32_t nomination_ RTC_GUARDED_BY(network_thread_) = 0;
+  // The last nomination that has been acknowledged.
+  uint32_t acked_nomination_ RTC_GUARDED_BY(network_thread_) = 0;
+  // Used by the controlled side to remember the nomination value received from
+  // the controlling side. When the peer does not support ICE re-nomination, its
+  // value will be 1 if the connection has been nominated.
+  uint32_t remote_nomination_ RTC_GUARDED_BY(network_thread_) = 0;
+
+  StunRequestManager requests_ RTC_GUARDED_BY(network_thread_);
+  int rtt_ RTC_GUARDED_BY(network_thread_);
+  int rtt_samples_ RTC_GUARDED_BY(network_thread_) = 0;
+  // https://w3c.github.io/webrtc-stats/#dom-rtcicecandidatepairstats-totalroundtriptime
+  uint64_t total_round_trip_time_ms_ RTC_GUARDED_BY(network_thread_) = 0;
+  // https://w3c.github.io/webrtc-stats/#dom-rtcicecandidatepairstats-currentroundtriptime
+  absl::optional<uint32_t> current_round_trip_time_ms_
+      RTC_GUARDED_BY(network_thread_);
+  int64_t last_ping_sent_ RTC_GUARDED_BY(
+      network_thread_);  // last time we sent a ping to the other side
+  int64_t last_ping_received_
+      RTC_GUARDED_BY(network_thread_);  // last time we received a ping from the
+                                        // other side
+  int64_t last_data_received_ RTC_GUARDED_BY(network_thread_);
+  int64_t last_ping_response_received_ RTC_GUARDED_BY(network_thread_);
+  int64_t receiving_unchanged_since_ RTC_GUARDED_BY(network_thread_) = 0;
+  std::vector<SentPing> pings_since_last_response_
+      RTC_GUARDED_BY(network_thread_);
+  // Transaction ID of the last connectivity check received. Null if having not
+  // received a ping yet.
+  absl::optional<std::string> last_ping_id_received_
+      RTC_GUARDED_BY(network_thread_);
+
+  absl::optional<int> unwritable_timeout_ RTC_GUARDED_BY(network_thread_);
+  absl::optional<int> unwritable_min_checks_ RTC_GUARDED_BY(network_thread_);
+  absl::optional<int> inactive_timeout_ RTC_GUARDED_BY(network_thread_);
+
+  IceCandidatePairState state_ RTC_GUARDED_BY(network_thread_);
+  // Time duration to switch from receiving to not receiving.
+  absl::optional<int> receiving_timeout_ RTC_GUARDED_BY(network_thread_);
+  const int64_t time_created_ms_ RTC_GUARDED_BY(network_thread_);
+  const int64_t delta_internal_unix_epoch_ms_ RTC_GUARDED_BY(network_thread_);
+  int num_pings_sent_ RTC_GUARDED_BY(network_thread_) = 0;
+
+  absl::optional<webrtc::IceCandidatePairDescription> log_description_
+      RTC_GUARDED_BY(network_thread_);
+  webrtc::IceEventLog* ice_event_log_ RTC_GUARDED_BY(network_thread_) = nullptr;
+
+  // GOOG_PING_REQUEST is sent in place of STUN_BINDING_REQUEST
+  // if configured via field trial, the remote peer supports it (signaled
+  // in STUN_BINDING) and if the last STUN BINDING is identical to the one
+  // that is about to be sent.
+  absl::optional<bool> remote_support_goog_ping_
+      RTC_GUARDED_BY(network_thread_);
+  std::unique_ptr<StunMessage> cached_stun_binding_
+      RTC_GUARDED_BY(network_thread_);
+
+  const IceFieldTrials* field_trials_;
+  rtc::EventBasedExponentialMovingAverage rtt_estimate_
+      RTC_GUARDED_BY(network_thread_);
+};
+
+// ProxyConnection defers all the interesting work to the port.
+class ProxyConnection : public Connection {
+ public:
+  ProxyConnection(rtc::WeakPtr<Port> port,
+                  size_t index,
+                  const Candidate& remote_candidate);
+
+  int Send(const void* data,
+           size_t size,
+           const rtc::PacketOptions& options) override;
+  int GetError() override;
+
+ private:
+  int error_ = 0;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_CONNECTION_H_
diff --git a/third_party/libwebrtc/p2p/base/connection_info.cc b/third_party/libwebrtc/p2p/base/connection_info.cc
new file mode 100644
index 0000000000..363d32954e
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/connection_info.cc
@@ -0,0 +1,44 @@
+/*
+ *  Copyright 2019 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/connection_info.h"
+
+namespace cricket {
+
+ConnectionInfo::ConnectionInfo()
+    : best_connection(false),
+      writable(false),
+      receiving(false),
+      timeout(false),
+      rtt(0),
+      sent_discarded_bytes(0),
+      sent_total_bytes(0),
+      sent_bytes_second(0),
+      sent_discarded_packets(0),
+      sent_total_packets(0),
+      sent_ping_requests_total(0),
+      sent_ping_requests_before_first_response(0),
+      sent_ping_responses(0),
+      recv_total_bytes(0),
+      recv_bytes_second(0),
+      packets_received(0),
+      recv_ping_requests(0),
+      recv_ping_responses(0),
+      key(nullptr),
+      state(IceCandidatePairState::WAITING),
+      priority(0),
+      nominated(false),
+      total_round_trip_time_ms(0) {}
+
+ConnectionInfo::ConnectionInfo(const ConnectionInfo&) = default;
+
+ConnectionInfo::~ConnectionInfo() = default;
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/connection_info.h b/third_party/libwebrtc/p2p/base/connection_info.h
new file mode 100644
index 0000000000..cd2a913451
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/connection_info.h
@@ -0,0 +1,87 @@
+/*
+ *  Copyright 2019 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_CONNECTION_INFO_H_
+#define P2P_BASE_CONNECTION_INFO_H_
+
+#include <vector>
+
+#include "absl/types/optional.h"
+#include "api/candidate.h"
+#include "api/units/timestamp.h"
+
+namespace cricket {
+
+// States are from RFC 5245. http://tools.ietf.org/html/rfc5245#section-5.7.4
+enum class IceCandidatePairState {
+  WAITING = 0,  // Check has not been performed, Waiting pair on CL.
+  IN_PROGRESS,  // Check has been sent, transaction is in progress.
+  SUCCEEDED,    // Check already done, produced a successful result.
+  FAILED,       // Check for this connection failed.
+  // According to spec there should also be a frozen state, but nothing is ever
+  // frozen because we have not implemented ICE freezing logic.
+};
+
+// Stats that we can return about the connections for a transport channel.
+// TODO(hta): Rename to ConnectionStats
+struct ConnectionInfo {
+  ConnectionInfo();
+  ConnectionInfo(const ConnectionInfo&);
+  ~ConnectionInfo();
+
+  bool best_connection;      // Is this the best connection we have?
+  bool writable;             // Has this connection received a STUN response?
+  bool receiving;            // Has this connection received anything?
+  bool timeout;              // Has this connection timed out?
+  size_t rtt;                // The STUN RTT for this connection.
+  size_t sent_discarded_bytes;  // Number of outgoing bytes discarded due to
+                                // socket errors.
+  size_t sent_total_bytes;      // Total bytes sent on this connection. Does not
+                                // include discarded bytes.
+  size_t sent_bytes_second;  // Bps over the last measurement interval.
+  size_t sent_discarded_packets;  // Number of outgoing packets discarded due to
+                                  // socket errors.
+  size_t sent_total_packets;  // Number of total outgoing packets attempted for
+                              // sending, including discarded packets.
+  size_t sent_ping_requests_total;  // Number of STUN ping request sent.
+  size_t sent_ping_requests_before_first_response;  // Number of STUN ping
+  // sent before receiving the first response.
+  size_t sent_ping_responses;  // Number of STUN ping response sent.
+
+  size_t recv_total_bytes;     // Total bytes received on this connection.
+  size_t recv_bytes_second;    // Bps over the last measurement interval.
+  size_t packets_received;     // Number of packets that were received.
+  size_t recv_ping_requests;   // Number of STUN ping request received.
+  size_t recv_ping_responses;  // Number of STUN ping response received.
+  Candidate local_candidate;   // The local candidate for this connection.
+  Candidate remote_candidate;  // The remote candidate for this connection.
+  void* key;                   // A static value that identifies this conn.
+  // https://w3c.github.io/webrtc-stats/#dom-rtcicecandidatepairstats-state
+  IceCandidatePairState state;
+  // https://w3c.github.io/webrtc-stats/#dom-rtcicecandidatepairstats-priority
+  uint64_t priority;
+  // https://w3c.github.io/webrtc-stats/#dom-rtcicecandidatepairstats-nominated
+  bool nominated;
+  // https://w3c.github.io/webrtc-stats/#dom-rtcicecandidatepairstats-totalroundtriptime
+  uint64_t total_round_trip_time_ms;
+  // https://w3c.github.io/webrtc-stats/#dom-rtcicecandidatepairstats-currentroundtriptime
+  absl::optional<uint32_t> current_round_trip_time_ms;
+
+  // https://w3c.github.io/webrtc-stats/#dom-rtcicecandidatepairstats-lastpacketreceivedtimestamp
+  absl::optional<webrtc::Timestamp> last_data_received;
+  absl::optional<webrtc::Timestamp> last_data_sent;
+};
+
+// Information about all the candidate pairs of a channel.
+typedef std::vector<ConnectionInfo> ConnectionInfos;
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_CONNECTION_INFO_H_
diff --git a/third_party/libwebrtc/p2p/base/default_ice_transport_factory.cc b/third_party/libwebrtc/p2p/base/default_ice_transport_factory.cc
new file mode 100644
index 0000000000..313d608750
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/default_ice_transport_factory.cc
@@ -0,0 +1,54 @@
+/*
+ *  Copyright 2019 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/default_ice_transport_factory.h"
+
+#include <utility>
+
+#include "api/make_ref_counted.h"
+#include "p2p/base/basic_ice_controller.h"
+#include "p2p/base/ice_controller_factory_interface.h"
+
+namespace {
+
+class BasicIceControllerFactory
+    : public cricket::IceControllerFactoryInterface {
+ public:
+  std::unique_ptr<cricket::IceControllerInterface> Create(
+      const cricket::IceControllerFactoryArgs& args) override {
+    return std::make_unique<cricket::BasicIceController>(args);
+  }
+};
+
+}  // namespace
+
+namespace webrtc {
+
+DefaultIceTransport::DefaultIceTransport(
+    std::unique_ptr<cricket::P2PTransportChannel> internal)
+    : internal_(std::move(internal)) {}
+
+DefaultIceTransport::~DefaultIceTransport() {
+  RTC_DCHECK_RUN_ON(&thread_checker_);
+}
+
+rtc::scoped_refptr<IceTransportInterface>
+DefaultIceTransportFactory::CreateIceTransport(
+    const std::string& transport_name,
+    int component,
+    IceTransportInit init) {
+  BasicIceControllerFactory factory;
+  init.set_ice_controller_factory(&factory);
+  return rtc::make_ref_counted<DefaultIceTransport>(
+      cricket::P2PTransportChannel::Create(transport_name, component,
+                                           std::move(init)));
+}
+
+}  // namespace webrtc
diff --git a/third_party/libwebrtc/p2p/base/default_ice_transport_factory.h b/third_party/libwebrtc/p2p/base/default_ice_transport_factory.h
new file mode 100644
index 0000000000..e46680d480
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/default_ice_transport_factory.h
@@ -0,0 +1,58 @@
+/*
+ *  Copyright 2019 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_DEFAULT_ICE_TRANSPORT_FACTORY_H_
+#define P2P_BASE_DEFAULT_ICE_TRANSPORT_FACTORY_H_
+
+#include <memory>
+#include <string>
+
+#include "api/ice_transport_interface.h"
+#include "p2p/base/p2p_transport_channel.h"
+#include "rtc_base/thread.h"
+
+namespace webrtc {
+
+// The default ICE transport wraps the implementation of IceTransportInternal
+// provided by P2PTransportChannel. This default transport is not thread safe
+// and must be constructed, used and destroyed on the same network thread on
+// which the internal P2PTransportChannel lives.
+class DefaultIceTransport : public IceTransportInterface {
+ public:
+  explicit DefaultIceTransport(
+      std::unique_ptr<cricket::P2PTransportChannel> internal);
+  ~DefaultIceTransport();
+
+  cricket::IceTransportInternal* internal() override {
+    RTC_DCHECK_RUN_ON(&thread_checker_);
+    return internal_.get();
+  }
+
+ private:
+  const SequenceChecker thread_checker_{};
+  std::unique_ptr<cricket::P2PTransportChannel> internal_
+      RTC_GUARDED_BY(thread_checker_);
+};
+
+class DefaultIceTransportFactory : public IceTransportFactory {
+ public:
+  DefaultIceTransportFactory() = default;
+  ~DefaultIceTransportFactory() = default;
+
+  // Must be called on the network thread and returns a DefaultIceTransport.
+  rtc::scoped_refptr<IceTransportInterface> CreateIceTransport(
+      const std::string& transport_name,
+      int component,
+      IceTransportInit init) override;
+};
+
+}  // namespace webrtc
+
+#endif  // P2P_BASE_DEFAULT_ICE_TRANSPORT_FACTORY_H_
diff --git a/third_party/libwebrtc/p2p/base/dtls_transport.cc b/third_party/libwebrtc/p2p/base/dtls_transport.cc
new file mode 100644
index 0000000000..af16efad78
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/dtls_transport.cc
@@ -0,0 +1,870 @@
+/*
+ *  Copyright 2011 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/dtls_transport.h"
+
+#include <algorithm>
+#include <memory>
+#include <utility>
+
+#include "absl/memory/memory.h"
+#include "absl/strings/string_view.h"
+#include "api/array_view.h"
+#include "api/dtls_transport_interface.h"
+#include "api/rtc_event_log/rtc_event_log.h"
+#include "logging/rtc_event_log/events/rtc_event_dtls_transport_state.h"
+#include "logging/rtc_event_log/events/rtc_event_dtls_writable_state.h"
+#include "p2p/base/packet_transport_internal.h"
+#include "rtc_base/buffer.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/dscp.h"
+#include "rtc_base/logging.h"
+#include "rtc_base/rtc_certificate.h"
+#include "rtc_base/ssl_stream_adapter.h"
+#include "rtc_base/stream.h"
+#include "rtc_base/thread.h"
+
+namespace cricket {
+
+// We don't pull the RTP constants from rtputils.h, to avoid a layer violation.
+static const size_t kDtlsRecordHeaderLen = 13;
+static const size_t kMaxDtlsPacketLen = 2048;
+static const size_t kMinRtpPacketLen = 12;
+
+// Maximum number of pending packets in the queue. Packets are read immediately
+// after they have been written, so a capacity of "1" is sufficient.
+//
+// However, this bug seems to indicate that's not the case: crbug.com/1063834
+// So, temporarily increasing it to 2 to see if that makes a difference.
+static const size_t kMaxPendingPackets = 2;
+
+// Minimum and maximum values for the initial DTLS handshake timeout. We'll pick
+// an initial timeout based on ICE RTT estimates, but clamp it to this range.
+static const int kMinHandshakeTimeout = 50;
+static const int kMaxHandshakeTimeout = 3000;
+
+static bool IsDtlsPacket(const char* data, size_t len) {
+  const uint8_t* u = reinterpret_cast<const uint8_t*>(data);
+  return (len >= kDtlsRecordHeaderLen && (u[0] > 19 && u[0] < 64));
+}
+static bool IsDtlsClientHelloPacket(const char* data, size_t len) {
+  if (!IsDtlsPacket(data, len)) {
+    return false;
+  }
+  const uint8_t* u = reinterpret_cast<const uint8_t*>(data);
+  return len > 17 && u[0] == 22 && u[13] == 1;
+}
+static bool IsRtpPacket(const char* data, size_t len) {
+  const uint8_t* u = reinterpret_cast<const uint8_t*>(data);
+  return (len >= kMinRtpPacketLen && (u[0] & 0xC0) == 0x80);
+}
+
+StreamInterfaceChannel::StreamInterfaceChannel(
+    IceTransportInternal* ice_transport)
+    : ice_transport_(ice_transport),
+      state_(rtc::SS_OPEN),
+      packets_(kMaxPendingPackets, kMaxDtlsPacketLen) {}
+
+rtc::StreamResult StreamInterfaceChannel::Read(rtc::ArrayView<uint8_t> buffer,
+                                               size_t& read,
+                                               int& error) {
+  RTC_DCHECK_RUN_ON(&sequence_checker_);
+
+  if (state_ == rtc::SS_CLOSED)
+    return rtc::SR_EOS;
+  if (state_ == rtc::SS_OPENING)
+    return rtc::SR_BLOCK;
+
+  if (!packets_.ReadFront(buffer.data(), buffer.size(), &read)) {
+    return rtc::SR_BLOCK;
+  }
+
+  return rtc::SR_SUCCESS;
+}
+
+rtc::StreamResult StreamInterfaceChannel::Write(
+    rtc::ArrayView<const uint8_t> data,
+    size_t& written,
+    int& error) {
+  RTC_DCHECK_RUN_ON(&sequence_checker_);
+  // Always succeeds, since this is an unreliable transport anyway.
+  // TODO(zhihuang): Should this block if ice_transport_'s temporarily
+  // unwritable?
+  rtc::PacketOptions packet_options;
+  ice_transport_->SendPacket(reinterpret_cast<const char*>(data.data()),
+                             data.size(), packet_options);
+  written = data.size();
+  return rtc::SR_SUCCESS;
+}
+
+bool StreamInterfaceChannel::OnPacketReceived(const char* data, size_t size) {
+  RTC_DCHECK_RUN_ON(&sequence_checker_);
+  if (packets_.size() > 0) {
+    RTC_LOG(LS_WARNING) << "Packet already in queue.";
+  }
+  bool ret = packets_.WriteBack(data, size, NULL);
+  if (!ret) {
+    // Somehow we received another packet before the SSLStreamAdapter read the
+    // previous one out of our temporary buffer. In this case, we'll log an
+    // error and still signal the read event, hoping that it will read the
+    // packet currently in packets_.
+    RTC_LOG(LS_ERROR) << "Failed to write packet to queue.";
+  }
+  SignalEvent(this, rtc::SE_READ, 0);
+  return ret;
+}
+
+rtc::StreamState StreamInterfaceChannel::GetState() const {
+  RTC_DCHECK_RUN_ON(&sequence_checker_);
+  return state_;
+}
+
+void StreamInterfaceChannel::Close() {
+  RTC_DCHECK_RUN_ON(&sequence_checker_);
+  packets_.Clear();
+  state_ = rtc::SS_CLOSED;
+}
+
+DtlsTransport::DtlsTransport(IceTransportInternal* ice_transport,
+                             const webrtc::CryptoOptions& crypto_options,
+                             webrtc::RtcEventLog* event_log,
+                             rtc::SSLProtocolVersion max_version)
+    : component_(ice_transport->component()),
+      ice_transport_(ice_transport),
+      downward_(NULL),
+      srtp_ciphers_(crypto_options.GetSupportedDtlsSrtpCryptoSuites()),
+      ssl_max_version_(max_version),
+      event_log_(event_log) {
+  RTC_DCHECK(ice_transport_);
+  ConnectToIceTransport();
+}
+
+DtlsTransport::~DtlsTransport() = default;
+
+webrtc::DtlsTransportState DtlsTransport::dtls_state() const {
+  return dtls_state_;
+}
+
+const std::string& DtlsTransport::transport_name() const {
+  return ice_transport_->transport_name();
+}
+
+int DtlsTransport::component() const {
+  return component_;
+}
+
+bool DtlsTransport::IsDtlsActive() const {
+  return dtls_active_;
+}
+
+bool DtlsTransport::SetLocalCertificate(
+    const rtc::scoped_refptr<rtc::RTCCertificate>& certificate) {
+  if (dtls_active_) {
+    if (certificate == local_certificate_) {
+      // This may happen during renegotiation.
+      RTC_LOG(LS_INFO) << ToString() << ": Ignoring identical DTLS identity";
+      return true;
+    } else {
+      RTC_LOG(LS_ERROR) << ToString()
+                        << ": Can't change DTLS local identity in this state";
+      return false;
+    }
+  }
+
+  if (certificate) {
+    local_certificate_ = certificate;
+    dtls_active_ = true;
+  } else {
+    RTC_LOG(LS_INFO) << ToString()
+                     << ": NULL DTLS identity supplied. Not doing DTLS";
+  }
+
+  return true;
+}
+
+rtc::scoped_refptr<rtc::RTCCertificate> DtlsTransport::GetLocalCertificate()
+    const {
+  return local_certificate_;
+}
+
+bool DtlsTransport::SetDtlsRole(rtc::SSLRole role) {
+  if (dtls_) {
+    RTC_DCHECK(dtls_role_);
+    if (*dtls_role_ != role) {
+      RTC_LOG(LS_ERROR)
+          << "SSL Role can't be reversed after the session is setup.";
+      return false;
+    }
+    return true;
+  }
+
+  dtls_role_ = role;
+  return true;
+}
+
+bool DtlsTransport::GetDtlsRole(rtc::SSLRole* role) const {
+  if (!dtls_role_) {
+    return false;
+  }
+  *role = *dtls_role_;
+  return true;
+}
+
+bool DtlsTransport::GetSslCipherSuite(int* cipher) {
+  if (dtls_state() != webrtc::DtlsTransportState::kConnected) {
+    return false;
+  }
+
+  return dtls_->GetSslCipherSuite(cipher);
+}
+
+webrtc::RTCError DtlsTransport::SetRemoteParameters(
+    absl::string_view digest_alg,
+    const uint8_t* digest,
+    size_t digest_len,
+    absl::optional<rtc::SSLRole> role) {
+  rtc::Buffer remote_fingerprint_value(digest, digest_len);
+  bool is_dtls_restart =
+      dtls_active_ && remote_fingerprint_value_ != remote_fingerprint_value;
+  // Set SSL role. Role must be set before fingerprint is applied, which
+  // initiates DTLS setup.
+  if (role) {
+    if (is_dtls_restart) {
+      dtls_role_ = *role;
+    } else {
+      if (!SetDtlsRole(*role)) {
+        return webrtc::RTCError(webrtc::RTCErrorType::INVALID_PARAMETER,
+                                "Failed to set SSL role for the transport.");
+      }
+    }
+  }
+  // Apply remote fingerprint.
+  if (!SetRemoteFingerprint(digest_alg, digest, digest_len)) {
+    return webrtc::RTCError(webrtc::RTCErrorType::INVALID_PARAMETER,
+                            "Failed to apply remote fingerprint.");
+  }
+  return webrtc::RTCError::OK();
+}
+
+bool DtlsTransport::SetRemoteFingerprint(absl::string_view digest_alg,
+                                         const uint8_t* digest,
+                                         size_t digest_len) {
+  rtc::Buffer remote_fingerprint_value(digest, digest_len);
+
+  // Once we have the local certificate, the same remote fingerprint can be set
+  // multiple times.
+  if (dtls_active_ && remote_fingerprint_value_ == remote_fingerprint_value &&
+      !digest_alg.empty()) {
+    // This may happen during renegotiation.
+    RTC_LOG(LS_INFO) << ToString()
+                     << ": Ignoring identical remote DTLS fingerprint";
+    return true;
+  }
+
+  // If the other side doesn't support DTLS, turn off `dtls_active_`.
+  // TODO(deadbeef): Remove this. It's dangerous, because it relies on higher
+  // level code to ensure DTLS is actually used, but there are tests that
+  // depend on it, for the case where an m= section is rejected. In that case
+  // SetRemoteFingerprint shouldn't even be called though.
+  if (digest_alg.empty()) {
+    RTC_DCHECK(!digest_len);
+    RTC_LOG(LS_INFO) << ToString() << ": Other side didn't support DTLS.";
+    dtls_active_ = false;
+    return true;
+  }
+
+  // Otherwise, we must have a local certificate before setting remote
+  // fingerprint.
+  if (!dtls_active_) {
+    RTC_LOG(LS_ERROR) << ToString()
+                      << ": Can't set DTLS remote settings in this state.";
+    return false;
+  }
+
+  // At this point we know we are doing DTLS
+  bool fingerprint_changing = remote_fingerprint_value_.size() > 0u;
+  remote_fingerprint_value_ = std::move(remote_fingerprint_value);
+  remote_fingerprint_algorithm_ = std::string(digest_alg);
+
+  if (dtls_ && !fingerprint_changing) {
+    // This can occur if DTLS is set up before a remote fingerprint is
+    // received. For instance, if we set up DTLS due to receiving an early
+    // ClientHello.
+    rtc::SSLPeerCertificateDigestError err;
+    if (!dtls_->SetPeerCertificateDigest(
+            remote_fingerprint_algorithm_,
+            reinterpret_cast<unsigned char*>(remote_fingerprint_value_.data()),
+            remote_fingerprint_value_.size(), &err)) {
+      RTC_LOG(LS_ERROR) << ToString()
+                        << ": Couldn't set DTLS certificate digest.";
+      set_dtls_state(webrtc::DtlsTransportState::kFailed);
+      // If the error is "verification failed", don't return false, because
+      // this means the fingerprint was formatted correctly but didn't match
+      // the certificate from the DTLS handshake. Thus the DTLS state should go
+      // to "failed", but SetRemoteDescription shouldn't fail.
+      return err == rtc::SSLPeerCertificateDigestError::VERIFICATION_FAILED;
+    }
+    return true;
+  }
+
+  // If the fingerprint is changing, we'll tear down the DTLS association and
+  // create a new one, resetting our state.
+  if (dtls_ && fingerprint_changing) {
+    dtls_.reset(nullptr);
+    set_dtls_state(webrtc::DtlsTransportState::kNew);
+    set_writable(false);
+  }
+
+  if (!SetupDtls()) {
+    set_dtls_state(webrtc::DtlsTransportState::kFailed);
+    return false;
+  }
+
+  return true;
+}
+
+std::unique_ptr<rtc::SSLCertChain> DtlsTransport::GetRemoteSSLCertChain()
+    const {
+  if (!dtls_) {
+    return nullptr;
+  }
+
+  return dtls_->GetPeerSSLCertChain();
+}
+
+bool DtlsTransport::ExportKeyingMaterial(absl::string_view label,
+                                         const uint8_t* context,
+                                         size_t context_len,
+                                         bool use_context,
+                                         uint8_t* result,
+                                         size_t result_len) {
+  return (dtls_.get())
+             ? dtls_->ExportKeyingMaterial(label, context, context_len,
+                                           use_context, result, result_len)
+             : false;
+}
+
+bool DtlsTransport::SetupDtls() {
+  RTC_DCHECK(dtls_role_);
+  {
+    auto downward = std::make_unique<StreamInterfaceChannel>(ice_transport_);
+    StreamInterfaceChannel* downward_ptr = downward.get();
+
+    dtls_ = rtc::SSLStreamAdapter::Create(std::move(downward));
+    if (!dtls_) {
+      RTC_LOG(LS_ERROR) << ToString() << ": Failed to create DTLS adapter.";
+      return false;
+    }
+    downward_ = downward_ptr;
+  }
+
+  dtls_->SetIdentity(local_certificate_->identity()->Clone());
+  dtls_->SetMode(rtc::SSL_MODE_DTLS);
+  dtls_->SetMaxProtocolVersion(ssl_max_version_);
+  dtls_->SetServerRole(*dtls_role_);
+  dtls_->SignalEvent.connect(this, &DtlsTransport::OnDtlsEvent);
+  dtls_->SignalSSLHandshakeError.connect(this,
+                                         &DtlsTransport::OnDtlsHandshakeError);
+  if (remote_fingerprint_value_.size() &&
+      !dtls_->SetPeerCertificateDigest(
+          remote_fingerprint_algorithm_,
+          reinterpret_cast<unsigned char*>(remote_fingerprint_value_.data()),
+          remote_fingerprint_value_.size())) {
+    RTC_LOG(LS_ERROR) << ToString()
+                      << ": Couldn't set DTLS certificate digest.";
+    return false;
+  }
+
+  // Set up DTLS-SRTP, if it's been enabled.
+  if (!srtp_ciphers_.empty()) {
+    if (!dtls_->SetDtlsSrtpCryptoSuites(srtp_ciphers_)) {
+      RTC_LOG(LS_ERROR) << ToString() << ": Couldn't set DTLS-SRTP ciphers.";
+      return false;
+    }
+  } else {
+    RTC_LOG(LS_INFO) << ToString() << ": Not using DTLS-SRTP.";
+  }
+
+  RTC_LOG(LS_INFO) << ToString() << ": DTLS setup complete.";
+
+  // If the underlying ice_transport is already writable at this point, we may
+  // be able to start DTLS right away.
+  MaybeStartDtls();
+  return true;
+}
+
+bool DtlsTransport::GetSrtpCryptoSuite(int* cipher) {
+  if (dtls_state() != webrtc::DtlsTransportState::kConnected) {
+    return false;
+  }
+
+  return dtls_->GetDtlsSrtpCryptoSuite(cipher);
+}
+
+bool DtlsTransport::GetSslVersionBytes(int* version) const {
+  if (dtls_state() != webrtc::DtlsTransportState::kConnected) {
+    return false;
+  }
+
+  return dtls_->GetSslVersionBytes(version);
+}
+
+// Called from upper layers to send a media packet.
+int DtlsTransport::SendPacket(const char* data,
+                              size_t size,
+                              const rtc::PacketOptions& options,
+                              int flags) {
+  if (!dtls_active_) {
+    // Not doing DTLS.
+    return ice_transport_->SendPacket(data, size, options);
+  }
+
+  switch (dtls_state()) {
+    case webrtc::DtlsTransportState::kNew:
+      // Can't send data until the connection is active.
+      // TODO(ekr@rtfm.com): assert here if dtls_ is NULL?
+      return -1;
+    case webrtc::DtlsTransportState::kConnecting:
+      // Can't send data until the connection is active.
+      return -1;
+    case webrtc::DtlsTransportState::kConnected:
+      if (flags & PF_SRTP_BYPASS) {
+        RTC_DCHECK(!srtp_ciphers_.empty());
+        if (!IsRtpPacket(data, size)) {
+          return -1;
+        }
+
+        return ice_transport_->SendPacket(data, size, options);
+      } else {
+        size_t written;
+        int error;
+        return (dtls_->WriteAll(
+                    rtc::MakeArrayView(reinterpret_cast<const uint8_t*>(data),
+                                       size),
+                    written, error) == rtc::SR_SUCCESS)
+                   ? static_cast<int>(size)
+                   : -1;
+      }
+    case webrtc::DtlsTransportState::kFailed:
+      // Can't send anything when we're failed.
+      RTC_LOG(LS_ERROR) << ToString()
+                        << ": Couldn't send packet due to "
+                           "webrtc::DtlsTransportState::kFailed.";
+      return -1;
+    case webrtc::DtlsTransportState::kClosed:
+      // Can't send anything when we're closed.
+      RTC_LOG(LS_ERROR) << ToString()
+                        << ": Couldn't send packet due to "
+                           "webrtc::DtlsTransportState::kClosed.";
+      return -1;
+    default:
+      RTC_DCHECK_NOTREACHED();
+      return -1;
+  }
+}
+
+IceTransportInternal* DtlsTransport::ice_transport() {
+  return ice_transport_;
+}
+
+bool DtlsTransport::IsDtlsConnected() {
+  return dtls_ && dtls_->IsTlsConnected();
+}
+
+bool DtlsTransport::receiving() const {
+  return receiving_;
+}
+
+bool DtlsTransport::writable() const {
+  return writable_;
+}
+
+int DtlsTransport::GetError() {
+  return ice_transport_->GetError();
+}
+
+absl::optional<rtc::NetworkRoute> DtlsTransport::network_route() const {
+  return ice_transport_->network_route();
+}
+
+bool DtlsTransport::GetOption(rtc::Socket::Option opt, int* value) {
+  return ice_transport_->GetOption(opt, value);
+}
+
+int DtlsTransport::SetOption(rtc::Socket::Option opt, int value) {
+  return ice_transport_->SetOption(opt, value);
+}
+
+void DtlsTransport::ConnectToIceTransport() {
+  RTC_DCHECK(ice_transport_);
+  ice_transport_->SignalWritableState.connect(this,
+                                              &DtlsTransport::OnWritableState);
+  ice_transport_->SignalReadPacket.connect(this, &DtlsTransport::OnReadPacket);
+  ice_transport_->SignalSentPacket.connect(this, &DtlsTransport::OnSentPacket);
+  ice_transport_->SignalReadyToSend.connect(this,
+                                            &DtlsTransport::OnReadyToSend);
+  ice_transport_->SignalReceivingState.connect(
+      this, &DtlsTransport::OnReceivingState);
+  ice_transport_->SignalNetworkRouteChanged.connect(
+      this, &DtlsTransport::OnNetworkRouteChanged);
+}
+
+// The state transition logic here is as follows:
+// (1) If we're not doing DTLS-SRTP, then the state is just the
+//     state of the underlying impl()
+// (2) If we're doing DTLS-SRTP:
+//     - Prior to the DTLS handshake, the state is neither receiving nor
+//       writable
+//     - When the impl goes writable for the first time we
+//       start the DTLS handshake
+//     - Once the DTLS handshake completes, the state is that of the
+//       impl again
+void DtlsTransport::OnWritableState(rtc::PacketTransportInternal* transport) {
+  RTC_DCHECK_RUN_ON(&thread_checker_);
+  RTC_DCHECK(transport == ice_transport_);
+  RTC_LOG(LS_VERBOSE) << ToString()
+                      << ": ice_transport writable state changed to "
+                      << ice_transport_->writable();
+
+  if (!dtls_active_) {
+    // Not doing DTLS.
+    // Note: SignalWritableState fired by set_writable.
+    set_writable(ice_transport_->writable());
+    return;
+  }
+
+  switch (dtls_state()) {
+    case webrtc::DtlsTransportState::kNew:
+      MaybeStartDtls();
+      break;
+    case webrtc::DtlsTransportState::kConnected:
+      // Note: SignalWritableState fired by set_writable.
+      set_writable(ice_transport_->writable());
+      break;
+    case webrtc::DtlsTransportState::kConnecting:
+      // Do nothing.
+      break;
+    case webrtc::DtlsTransportState::kFailed:
+      // Should not happen. Do nothing.
+      RTC_LOG(LS_ERROR) << ToString()
+                        << ": OnWritableState() called in state "
+                           "webrtc::DtlsTransportState::kFailed.";
+      break;
+    case webrtc::DtlsTransportState::kClosed:
+      // Should not happen. Do nothing.
+      RTC_LOG(LS_ERROR) << ToString()
+                        << ": OnWritableState() called in state "
+                           "webrtc::DtlsTransportState::kClosed.";
+      break;
+    case webrtc::DtlsTransportState::kNumValues:
+      RTC_DCHECK_NOTREACHED();
+      break;
+  }
+}
+
+void DtlsTransport::OnReceivingState(rtc::PacketTransportInternal* transport) {
+  RTC_DCHECK_RUN_ON(&thread_checker_);
+  RTC_DCHECK(transport == ice_transport_);
+  RTC_LOG(LS_VERBOSE) << ToString()
+                      << ": ice_transport "
+                         "receiving state changed to "
+                      << ice_transport_->receiving();
+  if (!dtls_active_ || dtls_state() == webrtc::DtlsTransportState::kConnected) {
+    // Note: SignalReceivingState fired by set_receiving.
+    set_receiving(ice_transport_->receiving());
+  }
+}
+
+void DtlsTransport::OnReadPacket(rtc::PacketTransportInternal* transport,
+                                 const char* data,
+                                 size_t size,
+                                 const int64_t& packet_time_us,
+                                 int flags) {
+  RTC_DCHECK_RUN_ON(&thread_checker_);
+  RTC_DCHECK(transport == ice_transport_);
+  RTC_DCHECK(flags == 0);
+
+  if (!dtls_active_) {
+    // Not doing DTLS.
+    SignalReadPacket(this, data, size, packet_time_us, 0);
+    return;
+  }
+
+  switch (dtls_state()) {
+    case webrtc::DtlsTransportState::kNew:
+      if (dtls_) {
+        RTC_LOG(LS_INFO) << ToString()
+                         << ": Packet received before DTLS started.";
+      } else {
+        RTC_LOG(LS_WARNING) << ToString()
+                            << ": Packet received before we know if we are "
+                               "doing DTLS or not.";
+      }
+      // Cache a client hello packet received before DTLS has actually started.
+      if (IsDtlsClientHelloPacket(data, size)) {
+        RTC_LOG(LS_INFO) << ToString()
+                         << ": Caching DTLS ClientHello packet until DTLS is "
+                            "started.";
+        cached_client_hello_.SetData(data, size);
+        // If we haven't started setting up DTLS yet (because we don't have a
+        // remote fingerprint/role), we can use the client hello as a clue that
+        // the peer has chosen the client role, and proceed with the handshake.
+        // The fingerprint will be verified when it's set.
+        if (!dtls_ && local_certificate_) {
+          SetDtlsRole(rtc::SSL_SERVER);
+          SetupDtls();
+        }
+      } else {
+        RTC_LOG(LS_INFO) << ToString()
+                         << ": Not a DTLS ClientHello packet; dropping.";
+      }
+      break;
+
+    case webrtc::DtlsTransportState::kConnecting:
+    case webrtc::DtlsTransportState::kConnected:
+      // We should only get DTLS or SRTP packets; STUN's already been demuxed.
+      // Is this potentially a DTLS packet?
+      if (IsDtlsPacket(data, size)) {
+        if (!HandleDtlsPacket(data, size)) {
+          RTC_LOG(LS_ERROR) << ToString() << ": Failed to handle DTLS packet.";
+          return;
+        }
+      } else {
+        // Not a DTLS packet; our handshake should be complete by now.
+        if (dtls_state() != webrtc::DtlsTransportState::kConnected) {
+          RTC_LOG(LS_ERROR) << ToString()
+                            << ": Received non-DTLS packet before DTLS "
+                               "complete.";
+          return;
+        }
+
+        // And it had better be a SRTP packet.
+        if (!IsRtpPacket(data, size)) {
+          RTC_LOG(LS_ERROR)
+              << ToString() << ": Received unexpected non-DTLS packet.";
+          return;
+        }
+
+        // Sanity check.
+        RTC_DCHECK(!srtp_ciphers_.empty());
+
+        // Signal this upwards as a bypass packet.
+        SignalReadPacket(this, data, size, packet_time_us, PF_SRTP_BYPASS);
+      }
+      break;
+    case webrtc::DtlsTransportState::kFailed:
+    case webrtc::DtlsTransportState::kClosed:
+    case webrtc::DtlsTransportState::kNumValues:
+      // This shouldn't be happening. Drop the packet.
+      break;
+  }
+}
+
+void DtlsTransport::OnSentPacket(rtc::PacketTransportInternal* transport,
+                                 const rtc::SentPacket& sent_packet) {
+  RTC_DCHECK_RUN_ON(&thread_checker_);
+  SignalSentPacket(this, sent_packet);
+}
+
+void DtlsTransport::OnReadyToSend(rtc::PacketTransportInternal* transport) {
+  RTC_DCHECK_RUN_ON(&thread_checker_);
+  if (writable()) {
+    SignalReadyToSend(this);
+  }
+}
+
+void DtlsTransport::OnDtlsEvent(rtc::StreamInterface* dtls, int sig, int err) {
+  RTC_DCHECK_RUN_ON(&thread_checker_);
+  RTC_DCHECK(dtls == dtls_.get());
+  if (sig & rtc::SE_OPEN) {
+    // This is the first time.
+    RTC_LOG(LS_INFO) << ToString() << ": DTLS handshake complete.";
+    if (dtls_->GetState() == rtc::SS_OPEN) {
+      // The check for OPEN shouldn't be necessary but let's make
+      // sure we don't accidentally frob the state if it's closed.
+      set_dtls_state(webrtc::DtlsTransportState::kConnected);
+      set_writable(true);
+    }
+  }
+  if (sig & rtc::SE_READ) {
+    uint8_t buf[kMaxDtlsPacketLen];
+    size_t read;
+    int read_error;
+    rtc::StreamResult ret;
+    // The underlying DTLS stream may have received multiple DTLS records in
+    // one packet, so read all of them.
+    do {
+      ret = dtls_->Read(buf, read, read_error);
+      if (ret == rtc::SR_SUCCESS) {
+        SignalReadPacket(this, reinterpret_cast<const char*>(buf), read,
+                         rtc::TimeMicros(), 0);
+      } else if (ret == rtc::SR_EOS) {
+        // Remote peer shut down the association with no error.
+        RTC_LOG(LS_INFO) << ToString() << ": DTLS transport closed by remote";
+        set_writable(false);
+        set_dtls_state(webrtc::DtlsTransportState::kClosed);
+        SignalClosed(this);
+      } else if (ret == rtc::SR_ERROR) {
+        // Remote peer shut down the association with an error.
+        RTC_LOG(LS_INFO)
+            << ToString()
+            << ": Closed by remote with DTLS transport error, code="
+            << read_error;
+        set_writable(false);
+        set_dtls_state(webrtc::DtlsTransportState::kFailed);
+        SignalClosed(this);
+      }
+    } while (ret == rtc::SR_SUCCESS);
+  }
+  if (sig & rtc::SE_CLOSE) {
+    RTC_DCHECK(sig == rtc::SE_CLOSE);  // SE_CLOSE should be by itself.
+    set_writable(false);
+    if (!err) {
+      RTC_LOG(LS_INFO) << ToString() << ": DTLS transport closed";
+      set_dtls_state(webrtc::DtlsTransportState::kClosed);
+    } else {
+      RTC_LOG(LS_INFO) << ToString() << ": DTLS transport error, code=" << err;
+      set_dtls_state(webrtc::DtlsTransportState::kFailed);
+    }
+  }
+}
+
+void DtlsTransport::OnNetworkRouteChanged(
+    absl::optional<rtc::NetworkRoute> network_route) {
+  RTC_DCHECK_RUN_ON(&thread_checker_);
+  SignalNetworkRouteChanged(network_route);
+}
+
+void DtlsTransport::MaybeStartDtls() {
+  if (dtls_ && ice_transport_->writable()) {
+    ConfigureHandshakeTimeout();
+
+    if (dtls_->StartSSL()) {
+      // This should never fail:
+      // Because we are operating in a nonblocking mode and all
+      // incoming packets come in via OnReadPacket(), which rejects
+      // packets in this state, the incoming queue must be empty. We
+      // ignore write errors, thus any errors must be because of
+      // configuration and therefore are our fault.
+      RTC_DCHECK_NOTREACHED() << "StartSSL failed.";
+      RTC_LOG(LS_ERROR) << ToString() << ": Couldn't start DTLS handshake";
+      set_dtls_state(webrtc::DtlsTransportState::kFailed);
+      return;
+    }
+    RTC_LOG(LS_INFO) << ToString()
+                     << ": DtlsTransport: Started DTLS handshake active="
+                     << IsDtlsActive();
+    set_dtls_state(webrtc::DtlsTransportState::kConnecting);
+    // Now that the handshake has started, we can process a cached ClientHello
+    // (if one exists).
+    if (cached_client_hello_.size()) {
+      if (*dtls_role_ == rtc::SSL_SERVER) {
+        RTC_LOG(LS_INFO) << ToString()
+                         << ": Handling cached DTLS ClientHello packet.";
+        if (!HandleDtlsPacket(cached_client_hello_.data<char>(),
+                              cached_client_hello_.size())) {
+          RTC_LOG(LS_ERROR) << ToString() << ": Failed to handle DTLS packet.";
+        }
+      } else {
+        RTC_LOG(LS_WARNING) << ToString()
+                            << ": Discarding cached DTLS ClientHello packet "
+                               "because we don't have the server role.";
+      }
+      cached_client_hello_.Clear();
+    }
+  }
+}
+
+// Called from OnReadPacket when a DTLS packet is received.
+bool DtlsTransport::HandleDtlsPacket(const char* data, size_t size) {
+  // Sanity check we're not passing junk that
+  // just looks like DTLS.
+  const uint8_t* tmp_data = reinterpret_cast<const uint8_t*>(data);
+  size_t tmp_size = size;
+  while (tmp_size > 0) {
+    if (tmp_size < kDtlsRecordHeaderLen)
+      return false;  // Too short for the header
+
+    size_t record_len = (tmp_data[11] << 8) | (tmp_data[12]);
+    if ((record_len + kDtlsRecordHeaderLen) > tmp_size)
+      return false;  // Body too short
+
+    tmp_data += record_len + kDtlsRecordHeaderLen;
+    tmp_size -= record_len + kDtlsRecordHeaderLen;
+  }
+
+  // Looks good. Pass to the SIC which ends up being passed to
+  // the DTLS stack.
+  return downward_->OnPacketReceived(data, size);
+}
+
+void DtlsTransport::set_receiving(bool receiving) {
+  if (receiving_ == receiving) {
+    return;
+  }
+  receiving_ = receiving;
+  SignalReceivingState(this);
+}
+
+void DtlsTransport::set_writable(bool writable) {
+  if (writable_ == writable) {
+    return;
+  }
+  if (event_log_) {
+    event_log_->Log(
+        std::make_unique<webrtc::RtcEventDtlsWritableState>(writable));
+  }
+  RTC_LOG(LS_VERBOSE) << ToString() << ": set_writable to: " << writable;
+  writable_ = writable;
+  if (writable_) {
+    SignalReadyToSend(this);
+  }
+  SignalWritableState(this);
+}
+
+void DtlsTransport::set_dtls_state(webrtc::DtlsTransportState state) {
+  if (dtls_state_ == state) {
+    return;
+  }
+  if (event_log_) {
+    event_log_->Log(
+        std::make_unique<webrtc::RtcEventDtlsTransportState>(state));
+  }
+  RTC_LOG(LS_VERBOSE) << ToString() << ": set_dtls_state from:"
+                      << static_cast<int>(dtls_state_) << " to "
+                      << static_cast<int>(state);
+  dtls_state_ = state;
+  SendDtlsState(this, state);
+}
+
+void DtlsTransport::OnDtlsHandshakeError(rtc::SSLHandshakeError error) {
+  SendDtlsHandshakeError(error);
+}
+
+void DtlsTransport::ConfigureHandshakeTimeout() {
+  RTC_DCHECK(dtls_);
+  absl::optional<int> rtt = ice_transport_->GetRttEstimate();
+  if (rtt) {
+    // Limit the timeout to a reasonable range in case the ICE RTT takes
+    // extreme values.
+    int initial_timeout = std::max(kMinHandshakeTimeout,
+                                   std::min(kMaxHandshakeTimeout, 2 * (*rtt)));
+    RTC_LOG(LS_INFO) << ToString() << ": configuring DTLS handshake timeout "
+                     << initial_timeout << " based on ICE RTT " << *rtt;
+
+    dtls_->SetInitialRetransmissionTimeout(initial_timeout);
+  } else {
+    RTC_LOG(LS_INFO)
+        << ToString()
+        << ": no RTT estimate - using default DTLS handshake timeout";
+  }
+}
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/dtls_transport.h b/third_party/libwebrtc/p2p/base/dtls_transport.h
new file mode 100644
index 0000000000..4e21410b76
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/dtls_transport.h
@@ -0,0 +1,264 @@
+/*
+ *  Copyright 2011 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_DTLS_TRANSPORT_H_
+#define P2P_BASE_DTLS_TRANSPORT_H_
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "absl/strings/string_view.h"
+#include "api/crypto/crypto_options.h"
+#include "api/dtls_transport_interface.h"
+#include "api/sequence_checker.h"
+#include "p2p/base/dtls_transport_internal.h"
+#include "p2p/base/ice_transport_internal.h"
+#include "rtc_base/buffer.h"
+#include "rtc_base/buffer_queue.h"
+#include "rtc_base/ssl_stream_adapter.h"
+#include "rtc_base/stream.h"
+#include "rtc_base/strings/string_builder.h"
+#include "rtc_base/system/no_unique_address.h"
+
+namespace rtc {
+class PacketTransportInternal;
+}
+
+namespace cricket {
+
+// A bridge between a packet-oriented/transport-type interface on
+// the bottom and a StreamInterface on the top.
+class StreamInterfaceChannel : public rtc::StreamInterface {
+ public:
+  explicit StreamInterfaceChannel(IceTransportInternal* ice_transport);
+
+  StreamInterfaceChannel(const StreamInterfaceChannel&) = delete;
+  StreamInterfaceChannel& operator=(const StreamInterfaceChannel&) = delete;
+
+  // Push in a packet; this gets pulled out from Read().
+  bool OnPacketReceived(const char* data, size_t size);
+
+  // Implementations of StreamInterface
+  rtc::StreamState GetState() const override;
+  void Close() override;
+  rtc::StreamResult Read(rtc::ArrayView<uint8_t> buffer,
+                         size_t& read,
+                         int& error) override;
+  rtc::StreamResult Write(rtc::ArrayView<const uint8_t> data,
+                          size_t& written,
+                          int& error) override;
+
+ private:
+  RTC_NO_UNIQUE_ADDRESS webrtc::SequenceChecker sequence_checker_;
+  IceTransportInternal* const ice_transport_;  // owned by DtlsTransport
+  rtc::StreamState state_ RTC_GUARDED_BY(sequence_checker_);
+  rtc::BufferQueue packets_ RTC_GUARDED_BY(sequence_checker_);
+};
+
+// This class provides a DTLS SSLStreamAdapter inside a TransportChannel-style
+// packet-based interface, wrapping an existing TransportChannel instance
+// (e.g a P2PTransportChannel)
+// Here's the way this works:
+//
+//   DtlsTransport {
+//       SSLStreamAdapter* dtls_ {
+//           StreamInterfaceChannel downward_ {
+//               IceTransportInternal* ice_transport_;
+//           }
+//       }
+//   }
+//
+//   - Data which comes into DtlsTransport from the underlying
+//     ice_transport_ via OnReadPacket() is checked for whether it is DTLS
+//     or not, and if it is, is passed to DtlsTransport::HandleDtlsPacket,
+//     which pushes it into to downward_. dtls_ is listening for events on
+//     downward_, so it immediately calls downward_->Read().
+//
+//   - Data written to DtlsTransport is passed either to downward_ or directly
+//     to ice_transport_, depending on whether DTLS is negotiated and whether
+//     the flags include PF_SRTP_BYPASS
+//
+//   - The SSLStreamAdapter writes to downward_->Write() which translates it
+//     into packet writes on ice_transport_.
+//
+// This class is not thread safe; all methods must be called on the same thread
+// as the constructor.
+class DtlsTransport : public DtlsTransportInternal {
+ public:
+  // `ice_transport` is the ICE transport this DTLS transport is wrapping.  It
+  // must outlive this DTLS transport.
+  //
+  // `crypto_options` are the options used for the DTLS handshake. This affects
+  // whether GCM crypto suites are negotiated.
+  //
+  // `event_log` is an optional RtcEventLog for logging state changes. It should
+  // outlive the DtlsTransport.
+  DtlsTransport(
+      IceTransportInternal* ice_transport,
+      const webrtc::CryptoOptions& crypto_options,
+      webrtc::RtcEventLog* event_log,
+      rtc::SSLProtocolVersion max_version = rtc::SSL_PROTOCOL_DTLS_12);
+
+  ~DtlsTransport() override;
+
+  DtlsTransport(const DtlsTransport&) = delete;
+  DtlsTransport& operator=(const DtlsTransport&) = delete;
+
+  webrtc::DtlsTransportState dtls_state() const override;
+  const std::string& transport_name() const override;
+  int component() const override;
+
+  // DTLS is active if a local certificate was set. Otherwise this acts in a
+  // "passthrough" mode, sending packets directly through the underlying ICE
+  // transport.
+  // TODO(deadbeef): Remove this weirdness, and handle it in the upper layers.
+  bool IsDtlsActive() const override;
+
+  // SetLocalCertificate is what makes DTLS active. It must be called before
+  // SetRemoteFinterprint.
+  // TODO(deadbeef): Once DtlsTransport no longer has the concept of being
+  // "active" or not (acting as a passthrough if not active), just require this
+  // certificate on construction or "Start".
+  bool SetLocalCertificate(
+      const rtc::scoped_refptr<rtc::RTCCertificate>& certificate) override;
+  rtc::scoped_refptr<rtc::RTCCertificate> GetLocalCertificate() const override;
+
+  // SetRemoteFingerprint must be called after SetLocalCertificate, and any
+  // other methods like SetDtlsRole. It's what triggers the actual DTLS setup.
+  // TODO(deadbeef): Rename to "Start" like in ORTC?
+  bool SetRemoteFingerprint(absl::string_view digest_alg,
+                            const uint8_t* digest,
+                            size_t digest_len) override;
+
+  // SetRemoteParameters must be called after SetLocalCertificate.
+  webrtc::RTCError SetRemoteParameters(
+      absl::string_view digest_alg,
+      const uint8_t* digest,
+      size_t digest_len,
+      absl::optional<rtc::SSLRole> role) override;
+
+  // Called to send a packet (via DTLS, if turned on).
+  int SendPacket(const char* data,
+                 size_t size,
+                 const rtc::PacketOptions& options,
+                 int flags) override;
+
+  bool GetOption(rtc::Socket::Option opt, int* value) override;
+
+  // Find out which TLS version was negotiated
+  bool GetSslVersionBytes(int* version) const override;
+  // Find out which DTLS-SRTP cipher was negotiated
+  bool GetSrtpCryptoSuite(int* cipher) override;
+
+  bool GetDtlsRole(rtc::SSLRole* role) const override;
+  bool SetDtlsRole(rtc::SSLRole role) override;
+
+  // Find out which DTLS cipher was negotiated
+  bool GetSslCipherSuite(int* cipher) override;
+
+  // Once DTLS has been established, this method retrieves the certificate
+  // chain in use by the remote peer, for use in external identity
+  // verification.
+  std::unique_ptr<rtc::SSLCertChain> GetRemoteSSLCertChain() const override;
+
+  // Once DTLS has established (i.e., this ice_transport is writable), this
+  // method extracts the keys negotiated during the DTLS handshake, for use in
+  // external encryption. DTLS-SRTP uses this to extract the needed SRTP keys.
+  // See the SSLStreamAdapter documentation for info on the specific parameters.
+  bool ExportKeyingMaterial(absl::string_view label,
+                            const uint8_t* context,
+                            size_t context_len,
+                            bool use_context,
+                            uint8_t* result,
+                            size_t result_len) override;
+
+  IceTransportInternal* ice_transport() override;
+
+  // For informational purposes. Tells if the DTLS handshake has finished.
+  // This may be true even if writable() is false, if the remote fingerprint
+  // has not yet been verified.
+  bool IsDtlsConnected();
+
+  bool receiving() const override;
+  bool writable() const override;
+
+  int GetError() override;
+
+  absl::optional<rtc::NetworkRoute> network_route() const override;
+
+  int SetOption(rtc::Socket::Option opt, int value) override;
+
+  std::string ToString() const {
+    const absl::string_view RECEIVING_ABBREV[2] = {"_", "R"};
+    const absl::string_view WRITABLE_ABBREV[2] = {"_", "W"};
+    rtc::StringBuilder sb;
+    sb << "DtlsTransport[" << transport_name() << "|" << component_ << "|"
+       << RECEIVING_ABBREV[receiving()] << WRITABLE_ABBREV[writable()] << "]";
+    return sb.Release();
+  }
+
+ private:
+  void ConnectToIceTransport();
+
+  void OnWritableState(rtc::PacketTransportInternal* transport);
+  void OnReadPacket(rtc::PacketTransportInternal* transport,
+                    const char* data,
+                    size_t size,
+                    const int64_t& packet_time_us,
+                    int flags);
+  void OnSentPacket(rtc::PacketTransportInternal* transport,
+                    const rtc::SentPacket& sent_packet);
+  void OnReadyToSend(rtc::PacketTransportInternal* transport);
+  void OnReceivingState(rtc::PacketTransportInternal* transport);
+  void OnDtlsEvent(rtc::StreamInterface* stream_, int sig, int err);
+  void OnNetworkRouteChanged(absl::optional<rtc::NetworkRoute> network_route);
+  bool SetupDtls();
+  void MaybeStartDtls();
+  bool HandleDtlsPacket(const char* data, size_t size);
+  void OnDtlsHandshakeError(rtc::SSLHandshakeError error);
+  void ConfigureHandshakeTimeout();
+
+  void set_receiving(bool receiving);
+  void set_writable(bool writable);
+  // Sets the DTLS state, signaling if necessary.
+  void set_dtls_state(webrtc::DtlsTransportState state);
+
+  webrtc::SequenceChecker thread_checker_;
+
+  const int component_;
+  webrtc::DtlsTransportState dtls_state_ = webrtc::DtlsTransportState::kNew;
+  // Underlying ice_transport, not owned by this class.
+  IceTransportInternal* const ice_transport_;
+  std::unique_ptr<rtc::SSLStreamAdapter> dtls_;  // The DTLS stream
+  StreamInterfaceChannel*
+      downward_;  // Wrapper for ice_transport_, owned by dtls_.
+  const std::vector<int> srtp_ciphers_;  // SRTP ciphers to use with DTLS.
+  bool dtls_active_ = false;
+  rtc::scoped_refptr<rtc::RTCCertificate> local_certificate_;
+  absl::optional<rtc::SSLRole> dtls_role_;
+  const rtc::SSLProtocolVersion ssl_max_version_;
+  rtc::Buffer remote_fingerprint_value_;
+  std::string remote_fingerprint_algorithm_;
+
+  // Cached DTLS ClientHello packet that was received before we started the
+  // DTLS handshake. This could happen if the hello was received before the
+  // ice transport became writable, or before a remote fingerprint was received.
+  rtc::Buffer cached_client_hello_;
+
+  bool receiving_ = false;
+  bool writable_ = false;
+
+  webrtc::RtcEventLog* const event_log_;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_DTLS_TRANSPORT_H_
diff --git a/third_party/libwebrtc/p2p/base/dtls_transport_factory.h b/third_party/libwebrtc/p2p/base/dtls_transport_factory.h
new file mode 100644
index 0000000000..7c4a24adc8
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/dtls_transport_factory.h
@@ -0,0 +1,40 @@
+/*
+ *  Copyright 2018 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_DTLS_TRANSPORT_FACTORY_H_
+#define P2P_BASE_DTLS_TRANSPORT_FACTORY_H_
+
+#include <memory>
+#include <string>
+
+#include "p2p/base/dtls_transport_internal.h"
+#include "p2p/base/ice_transport_internal.h"
+
+namespace cricket {
+
+// This interface is used to create DTLS transports. The external transports
+// can be injected into the JsepTransportController through it.
+//
+// TODO(qingsi): Remove this factory in favor of one that produces
+// DtlsTransportInterface given by the public API if this is going to be
+// injectable.
+class DtlsTransportFactory {
+ public:
+  virtual ~DtlsTransportFactory() = default;
+
+  virtual std::unique_ptr<DtlsTransportInternal> CreateDtlsTransport(
+      IceTransportInternal* ice,
+      const webrtc::CryptoOptions& crypto_options,
+      rtc::SSLProtocolVersion max_version) = 0;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_DTLS_TRANSPORT_FACTORY_H_
diff --git a/third_party/libwebrtc/p2p/base/dtls_transport_internal.cc b/third_party/libwebrtc/p2p/base/dtls_transport_internal.cc
new file mode 100644
index 0000000000..6997dbc702
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/dtls_transport_internal.cc
@@ -0,0 +1,19 @@
+/*
+ *  Copyright 2017 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/dtls_transport_internal.h"
+
+namespace cricket {
+
+DtlsTransportInternal::DtlsTransportInternal() = default;
+
+DtlsTransportInternal::~DtlsTransportInternal() = default;
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/dtls_transport_internal.h b/third_party/libwebrtc/p2p/base/dtls_transport_internal.h
new file mode 100644
index 0000000000..3d20d1bfd6
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/dtls_transport_internal.h
@@ -0,0 +1,157 @@
+/*
+ *  Copyright 2016 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_DTLS_TRANSPORT_INTERNAL_H_
+#define P2P_BASE_DTLS_TRANSPORT_INTERNAL_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <memory>
+#include <string>
+#include <utility>
+
+#include "absl/base/attributes.h"
+#include "absl/strings/string_view.h"
+#include "api/crypto/crypto_options.h"
+#include "api/dtls_transport_interface.h"
+#include "api/scoped_refptr.h"
+#include "p2p/base/ice_transport_internal.h"
+#include "p2p/base/packet_transport_internal.h"
+#include "rtc_base/callback_list.h"
+#include "rtc_base/ssl_certificate.h"
+#include "rtc_base/ssl_fingerprint.h"
+#include "rtc_base/ssl_stream_adapter.h"
+
+namespace cricket {
+
+enum PacketFlags {
+  PF_NORMAL = 0x00,       // A normal packet.
+  PF_SRTP_BYPASS = 0x01,  // An encrypted SRTP packet; bypass any additional
+                          // crypto provided by the transport (e.g. DTLS)
+};
+
+// DtlsTransportInternal is an internal interface that does DTLS, also
+// negotiating SRTP crypto suites so that it may be used for DTLS-SRTP.
+//
+// Once the public interface is supported,
+// (https://www.w3.org/TR/webrtc/#rtcdtlstransport-interface)
+// the DtlsTransportInterface will be split from this class.
+class DtlsTransportInternal : public rtc::PacketTransportInternal {
+ public:
+  ~DtlsTransportInternal() override;
+
+  DtlsTransportInternal(const DtlsTransportInternal&) = delete;
+  DtlsTransportInternal& operator=(const DtlsTransportInternal&) = delete;
+
+  virtual webrtc::DtlsTransportState dtls_state() const = 0;
+
+  virtual int component() const = 0;
+
+  virtual bool IsDtlsActive() const = 0;
+
+  virtual bool GetDtlsRole(rtc::SSLRole* role) const = 0;
+
+  virtual bool SetDtlsRole(rtc::SSLRole role) = 0;
+
+  // Finds out which TLS/DTLS version is running.
+  virtual bool GetSslVersionBytes(int* version) const = 0;
+  // Finds out which DTLS-SRTP cipher was negotiated.
+  // TODO(zhihuang): Remove this once all dependencies implement this.
+  virtual bool GetSrtpCryptoSuite(int* cipher) = 0;
+
+  // Finds out which DTLS cipher was negotiated.
+  // TODO(zhihuang): Remove this once all dependencies implement this.
+  virtual bool GetSslCipherSuite(int* cipher) = 0;
+
+  // Gets the local RTCCertificate used for DTLS.
+  virtual rtc::scoped_refptr<rtc::RTCCertificate> GetLocalCertificate()
+      const = 0;
+
+  virtual bool SetLocalCertificate(
+      const rtc::scoped_refptr<rtc::RTCCertificate>& certificate) = 0;
+
+  // Gets a copy of the remote side's SSL certificate chain.
+  virtual std::unique_ptr<rtc::SSLCertChain> GetRemoteSSLCertChain() const = 0;
+
+  // Allows key material to be extracted for external encryption.
+  virtual bool ExportKeyingMaterial(absl::string_view label,
+                                    const uint8_t* context,
+                                    size_t context_len,
+                                    bool use_context,
+                                    uint8_t* result,
+                                    size_t result_len) = 0;
+
+  // Set DTLS remote fingerprint. Must be after local identity set.
+  ABSL_DEPRECATED("Use SetRemoteParameters instead.")
+  virtual bool SetRemoteFingerprint(absl::string_view digest_alg,
+                                    const uint8_t* digest,
+                                    size_t digest_len) = 0;
+
+  // Set DTLS remote fingerprint and role. Must be after local identity set.
+  virtual webrtc::RTCError SetRemoteParameters(
+      absl::string_view digest_alg,
+      const uint8_t* digest,
+      size_t digest_len,
+      absl::optional<rtc::SSLRole> role) = 0;
+
+  ABSL_DEPRECATED("Set the max version via construction.")
+  bool SetSslMaxProtocolVersion(rtc::SSLProtocolVersion version) {
+    return true;
+  }
+
+  // Expose the underneath IceTransport.
+  virtual IceTransportInternal* ice_transport() = 0;
+
+  // F: void(DtlsTransportInternal*, const webrtc::DtlsTransportState)
+  template <typename F>
+  void SubscribeDtlsTransportState(F&& callback) {
+    dtls_transport_state_callback_list_.AddReceiver(std::forward<F>(callback));
+  }
+
+  template <typename F>
+  void SubscribeDtlsTransportState(const void* id, F&& callback) {
+    dtls_transport_state_callback_list_.AddReceiver(id,
+                                                    std::forward<F>(callback));
+  }
+  // Unsubscribe the subscription with given id.
+  void UnsubscribeDtlsTransportState(const void* id) {
+    dtls_transport_state_callback_list_.RemoveReceivers(id);
+  }
+
+  void SendDtlsState(DtlsTransportInternal* transport,
+                     webrtc::DtlsTransportState state) {
+    dtls_transport_state_callback_list_.Send(transport, state);
+  }
+
+  // Emitted whenever the Dtls handshake failed on some transport channel.
+  // F: void(rtc::SSLHandshakeError)
+  template <typename F>
+  void SubscribeDtlsHandshakeError(F&& callback) {
+    dtls_handshake_error_callback_list_.AddReceiver(std::forward<F>(callback));
+  }
+
+  void SendDtlsHandshakeError(rtc::SSLHandshakeError error) {
+    dtls_handshake_error_callback_list_.Send(error);
+  }
+
+ protected:
+  DtlsTransportInternal();
+
+ private:
+  webrtc::CallbackList<const rtc::SSLHandshakeError>
+      dtls_handshake_error_callback_list_;
+  webrtc::CallbackList<DtlsTransportInternal*, const webrtc::DtlsTransportState>
+      dtls_transport_state_callback_list_;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_DTLS_TRANSPORT_INTERNAL_H_
diff --git a/third_party/libwebrtc/p2p/base/dtls_transport_unittest.cc b/third_party/libwebrtc/p2p/base/dtls_transport_unittest.cc
new file mode 100644
index 0000000000..e338ab6a49
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/dtls_transport_unittest.cc
@@ -0,0 +1,748 @@
+/*
+ *  Copyright 2011 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/dtls_transport.h"
+
+#include <algorithm>
+#include <memory>
+#include <set>
+#include <utility>
+
+#include "absl/strings/string_view.h"
+#include "api/dtls_transport_interface.h"
+#include "p2p/base/fake_ice_transport.h"
+#include "p2p/base/packet_transport_internal.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/dscp.h"
+#include "rtc_base/gunit.h"
+#include "rtc_base/helpers.h"
+#include "rtc_base/rtc_certificate.h"
+#include "rtc_base/ssl_adapter.h"
+#include "rtc_base/ssl_identity.h"
+#include "rtc_base/ssl_stream_adapter.h"
+
+#define MAYBE_SKIP_TEST(feature)                                  \
+  if (!(rtc::SSLStreamAdapter::feature())) {                      \
+    RTC_LOG(LS_INFO) << #feature " feature disabled... skipping"; \
+    return;                                                       \
+  }
+
+namespace cricket {
+
+static const size_t kPacketNumOffset = 8;
+static const size_t kPacketHeaderLen = 12;
+static const int kFakePacketId = 0x1234;
+static const int kTimeout = 10000;
+
+static bool IsRtpLeadByte(uint8_t b) {
+  return ((b & 0xC0) == 0x80);
+}
+
+// `modify_digest` is used to set modified fingerprints that are meant to fail
+// validation.
+void SetRemoteFingerprintFromCert(
+    DtlsTransport* transport,
+    const rtc::scoped_refptr<rtc::RTCCertificate>& cert,
+    bool modify_digest = false) {
+  std::unique_ptr<rtc::SSLFingerprint> fingerprint =
+      rtc::SSLFingerprint::CreateFromCertificate(*cert);
+  if (modify_digest) {
+    ++fingerprint->digest.MutableData()[0];
+  }
+
+  // Even if digest is verified to be incorrect, should fail asynchronously.
+  EXPECT_TRUE(
+      transport
+          ->SetRemoteParameters(
+              fingerprint->algorithm,
+              reinterpret_cast<const uint8_t*>(fingerprint->digest.data()),
+              fingerprint->digest.size(), absl::nullopt)
+          .ok());
+}
+
+class DtlsTestClient : public sigslot::has_slots<> {
+ public:
+  explicit DtlsTestClient(absl::string_view name) : name_(name) {}
+  void CreateCertificate(rtc::KeyType key_type) {
+    certificate_ =
+        rtc::RTCCertificate::Create(rtc::SSLIdentity::Create(name_, key_type));
+  }
+  const rtc::scoped_refptr<rtc::RTCCertificate>& certificate() {
+    return certificate_;
+  }
+  void SetupMaxProtocolVersion(rtc::SSLProtocolVersion version) {
+    ssl_max_version_ = version;
+  }
+  // Set up fake ICE transport and real DTLS transport under test.
+  void SetupTransports(IceRole role, int async_delay_ms = 0) {
+    fake_ice_transport_.reset(new FakeIceTransport("fake", 0));
+    fake_ice_transport_->SetAsync(true);
+    fake_ice_transport_->SetAsyncDelay(async_delay_ms);
+    fake_ice_transport_->SetIceRole(role);
+    fake_ice_transport_->SetIceTiebreaker((role == ICEROLE_CONTROLLING) ? 1
+                                                                        : 2);
+    // Hook the raw packets so that we can verify they are encrypted.
+    fake_ice_transport_->SignalReadPacket.connect(
+        this, &DtlsTestClient::OnFakeIceTransportReadPacket);
+
+    dtls_transport_ = std::make_unique<DtlsTransport>(
+        fake_ice_transport_.get(), webrtc::CryptoOptions(),
+        /*event_log=*/nullptr, ssl_max_version_);
+    // Note: Certificate may be null here if testing passthrough.
+    dtls_transport_->SetLocalCertificate(certificate_);
+    dtls_transport_->SignalWritableState.connect(
+        this, &DtlsTestClient::OnTransportWritableState);
+    dtls_transport_->SignalReadPacket.connect(
+        this, &DtlsTestClient::OnTransportReadPacket);
+    dtls_transport_->SignalSentPacket.connect(
+        this, &DtlsTestClient::OnTransportSentPacket);
+  }
+
+  FakeIceTransport* fake_ice_transport() {
+    return static_cast<FakeIceTransport*>(dtls_transport_->ice_transport());
+  }
+
+  DtlsTransport* dtls_transport() { return dtls_transport_.get(); }
+
+  // Simulate fake ICE transports connecting.
+  bool Connect(DtlsTestClient* peer, bool asymmetric) {
+    fake_ice_transport()->SetDestination(peer->fake_ice_transport(),
+                                         asymmetric);
+    return true;
+  }
+
+  int received_dtls_client_hellos() const {
+    return received_dtls_client_hellos_;
+  }
+
+  int received_dtls_server_hellos() const {
+    return received_dtls_server_hellos_;
+  }
+
+  void CheckRole(rtc::SSLRole role) {
+    if (role == rtc::SSL_CLIENT) {
+      ASSERT_EQ(0, received_dtls_client_hellos_);
+      ASSERT_GT(received_dtls_server_hellos_, 0);
+    } else {
+      ASSERT_GT(received_dtls_client_hellos_, 0);
+      ASSERT_EQ(0, received_dtls_server_hellos_);
+    }
+  }
+
+  void CheckSrtp(int expected_crypto_suite) {
+    int crypto_suite;
+    bool rv = dtls_transport_->GetSrtpCryptoSuite(&crypto_suite);
+    if (dtls_transport_->IsDtlsActive() && expected_crypto_suite) {
+      ASSERT_TRUE(rv);
+      ASSERT_EQ(crypto_suite, expected_crypto_suite);
+    } else {
+      ASSERT_FALSE(rv);
+    }
+  }
+
+  void CheckSsl() {
+    int cipher;
+    bool rv = dtls_transport_->GetSslCipherSuite(&cipher);
+    if (dtls_transport_->IsDtlsActive()) {
+      ASSERT_TRUE(rv);
+      EXPECT_TRUE(
+          rtc::SSLStreamAdapter::IsAcceptableCipher(cipher, rtc::KT_DEFAULT));
+    } else {
+      ASSERT_FALSE(rv);
+    }
+  }
+
+  void SendPackets(size_t size, size_t count, bool srtp) {
+    std::unique_ptr<char[]> packet(new char[size]);
+    size_t sent = 0;
+    do {
+      // Fill the packet with a known value and a sequence number to check
+      // against, and make sure that it doesn't look like DTLS.
+      memset(packet.get(), sent & 0xff, size);
+      packet[0] = (srtp) ? 0x80 : 0x00;
+      rtc::SetBE32(packet.get() + kPacketNumOffset,
+                   static_cast<uint32_t>(sent));
+
+      // Only set the bypass flag if we've activated DTLS.
+      int flags = (certificate_ && srtp) ? PF_SRTP_BYPASS : 0;
+      rtc::PacketOptions packet_options;
+      packet_options.packet_id = kFakePacketId;
+      int rv = dtls_transport_->SendPacket(packet.get(), size, packet_options,
+                                           flags);
+      ASSERT_GT(rv, 0);
+      ASSERT_EQ(size, static_cast<size_t>(rv));
+      ++sent;
+    } while (sent < count);
+  }
+
+  int SendInvalidSrtpPacket(size_t size) {
+    std::unique_ptr<char[]> packet(new char[size]);
+    // Fill the packet with 0 to form an invalid SRTP packet.
+    memset(packet.get(), 0, size);
+
+    rtc::PacketOptions packet_options;
+    return dtls_transport_->SendPacket(packet.get(), size, packet_options,
+                                       PF_SRTP_BYPASS);
+  }
+
+  void ExpectPackets(size_t size) {
+    packet_size_ = size;
+    received_.clear();
+  }
+
+  size_t NumPacketsReceived() { return received_.size(); }
+
+  // Inverse of SendPackets.
+  bool VerifyPacket(const char* data, size_t size, uint32_t* out_num) {
+    if (size != packet_size_ ||
+        (data[0] != 0 && static_cast<uint8_t>(data[0]) != 0x80)) {
+      return false;
+    }
+    uint32_t packet_num = rtc::GetBE32(data + kPacketNumOffset);
+    for (size_t i = kPacketHeaderLen; i < size; ++i) {
+      if (static_cast<uint8_t>(data[i]) != (packet_num & 0xff)) {
+        return false;
+      }
+    }
+    if (out_num) {
+      *out_num = packet_num;
+    }
+    return true;
+  }
+  bool VerifyEncryptedPacket(const char* data, size_t size) {
+    // This is an encrypted data packet; let's make sure it's mostly random;
+    // less than 10% of the bytes should be equal to the cleartext packet.
+    if (size <= packet_size_) {
+      return false;
+    }
+    uint32_t packet_num = rtc::GetBE32(data + kPacketNumOffset);
+    int num_matches = 0;
+    for (size_t i = kPacketNumOffset; i < size; ++i) {
+      if (static_cast<uint8_t>(data[i]) == (packet_num & 0xff)) {
+        ++num_matches;
+      }
+    }
+    return (num_matches < ((static_cast<int>(size) - 5) / 10));
+  }
+
+  // Transport callbacks
+  void OnTransportWritableState(rtc::PacketTransportInternal* transport) {
+    RTC_LOG(LS_INFO) << name_ << ": Transport '" << transport->transport_name()
+                     << "' is writable";
+  }
+
+  void OnTransportReadPacket(rtc::PacketTransportInternal* transport,
+                             const char* data,
+                             size_t size,
+                             const int64_t& /* packet_time_us */,
+                             int flags) {
+    uint32_t packet_num = 0;
+    ASSERT_TRUE(VerifyPacket(data, size, &packet_num));
+    received_.insert(packet_num);
+    // Only DTLS-SRTP packets should have the bypass flag set.
+    int expected_flags =
+        (certificate_ && IsRtpLeadByte(data[0])) ? PF_SRTP_BYPASS : 0;
+    ASSERT_EQ(expected_flags, flags);
+  }
+
+  void OnTransportSentPacket(rtc::PacketTransportInternal* transport,
+                             const rtc::SentPacket& sent_packet) {
+    sent_packet_ = sent_packet;
+  }
+
+  rtc::SentPacket sent_packet() const { return sent_packet_; }
+
+  // Hook into the raw packet stream to make sure DTLS packets are encrypted.
+  void OnFakeIceTransportReadPacket(rtc::PacketTransportInternal* transport,
+                                    const char* data,
+                                    size_t size,
+                                    const int64_t& /* packet_time_us */,
+                                    int flags) {
+    // Flags shouldn't be set on the underlying Transport packets.
+    ASSERT_EQ(0, flags);
+
+    // Look at the handshake packets to see what role we played.
+    // Check that non-handshake packets are DTLS data or SRTP bypass.
+    if (data[0] == 22 && size > 17) {
+      if (data[13] == 1) {
+        ++received_dtls_client_hellos_;
+      } else if (data[13] == 2) {
+        ++received_dtls_server_hellos_;
+      }
+    } else if (dtls_transport_->IsDtlsActive() &&
+               !(data[0] >= 20 && data[0] <= 22)) {
+      ASSERT_TRUE(data[0] == 23 || IsRtpLeadByte(data[0]));
+      if (data[0] == 23) {
+        ASSERT_TRUE(VerifyEncryptedPacket(data, size));
+      } else if (IsRtpLeadByte(data[0])) {
+        ASSERT_TRUE(VerifyPacket(data, size, NULL));
+      }
+    }
+  }
+
+ private:
+  std::string name_;
+  rtc::scoped_refptr<rtc::RTCCertificate> certificate_;
+  std::unique_ptr<FakeIceTransport> fake_ice_transport_;
+  std::unique_ptr<DtlsTransport> dtls_transport_;
+  size_t packet_size_ = 0u;
+  std::set<int> received_;
+  rtc::SSLProtocolVersion ssl_max_version_ = rtc::SSL_PROTOCOL_DTLS_12;
+  int received_dtls_client_hellos_ = 0;
+  int received_dtls_server_hellos_ = 0;
+  rtc::SentPacket sent_packet_;
+};
+
+// Base class for DtlsTransportTest and DtlsEventOrderingTest, which
+// inherit from different variants of ::testing::Test.
+//
+// Note that this test always uses a FakeClock, due to the `fake_clock_` member
+// variable.
+class DtlsTransportTestBase {
+ public:
+  DtlsTransportTestBase() : client1_("P1"), client2_("P2"), use_dtls_(false) {}
+
+  void SetMaxProtocolVersions(rtc::SSLProtocolVersion c1,
+                              rtc::SSLProtocolVersion c2) {
+    client1_.SetupMaxProtocolVersion(c1);
+    client2_.SetupMaxProtocolVersion(c2);
+  }
+  // If not called, DtlsTransport will be used in SRTP bypass mode.
+  void PrepareDtls(rtc::KeyType key_type) {
+    client1_.CreateCertificate(key_type);
+    client2_.CreateCertificate(key_type);
+    use_dtls_ = true;
+  }
+
+  // This test negotiates DTLS parameters before the underlying transports are
+  // writable. DtlsEventOrderingTest is responsible for exercising differerent
+  // orderings.
+  bool Connect(bool client1_server = true) {
+    Negotiate(client1_server);
+    EXPECT_TRUE(client1_.Connect(&client2_, false));
+
+    EXPECT_TRUE_SIMULATED_WAIT(client1_.dtls_transport()->writable() &&
+                                   client2_.dtls_transport()->writable(),
+                               kTimeout, fake_clock_);
+    if (!client1_.dtls_transport()->writable() ||
+        !client2_.dtls_transport()->writable())
+      return false;
+
+    // Check that we used the right roles.
+    if (use_dtls_) {
+      client1_.CheckRole(client1_server ? rtc::SSL_SERVER : rtc::SSL_CLIENT);
+      client2_.CheckRole(client1_server ? rtc::SSL_CLIENT : rtc::SSL_SERVER);
+    }
+
+    if (use_dtls_) {
+      // Check that we negotiated the right ciphers. Since GCM ciphers are not
+      // negotiated by default, we should end up with kSrtpAes128CmSha1_80.
+      client1_.CheckSrtp(rtc::kSrtpAes128CmSha1_80);
+      client2_.CheckSrtp(rtc::kSrtpAes128CmSha1_80);
+    } else {
+      // If DTLS isn't actually being used, GetSrtpCryptoSuite should return
+      // false.
+      client1_.CheckSrtp(rtc::kSrtpInvalidCryptoSuite);
+      client2_.CheckSrtp(rtc::kSrtpInvalidCryptoSuite);
+    }
+
+    client1_.CheckSsl();
+    client2_.CheckSsl();
+
+    return true;
+  }
+
+  void Negotiate(bool client1_server = true) {
+    client1_.SetupTransports(ICEROLE_CONTROLLING);
+    client2_.SetupTransports(ICEROLE_CONTROLLED);
+    client1_.dtls_transport()->SetDtlsRole(client1_server ? rtc::SSL_SERVER
+                                                          : rtc::SSL_CLIENT);
+    client2_.dtls_transport()->SetDtlsRole(client1_server ? rtc::SSL_CLIENT
+                                                          : rtc::SSL_SERVER);
+    if (client2_.certificate()) {
+      SetRemoteFingerprintFromCert(client1_.dtls_transport(),
+                                   client2_.certificate());
+    }
+    if (client1_.certificate()) {
+      SetRemoteFingerprintFromCert(client2_.dtls_transport(),
+                                   client1_.certificate());
+    }
+  }
+
+  void TestTransfer(size_t size, size_t count, bool srtp) {
+    RTC_LOG(LS_INFO) << "Expect packets, size=" << size;
+    client2_.ExpectPackets(size);
+    client1_.SendPackets(size, count, srtp);
+    EXPECT_EQ_SIMULATED_WAIT(count, client2_.NumPacketsReceived(), kTimeout,
+                             fake_clock_);
+  }
+
+ protected:
+  rtc::AutoThread main_thread_;
+  rtc::ScopedFakeClock fake_clock_;
+  DtlsTestClient client1_;
+  DtlsTestClient client2_;
+  bool use_dtls_;
+  rtc::SSLProtocolVersion ssl_expected_version_;
+};
+
+class DtlsTransportTest : public DtlsTransportTestBase,
+                          public ::testing::Test {};
+
+// Connect without DTLS, and transfer RTP data.
+TEST_F(DtlsTransportTest, TestTransferRtp) {
+  ASSERT_TRUE(Connect());
+  TestTransfer(1000, 100, /*srtp=*/false);
+}
+
+// Test that the SignalSentPacket signal is wired up.
+TEST_F(DtlsTransportTest, TestSignalSentPacket) {
+  ASSERT_TRUE(Connect());
+  // Sanity check default value (-1).
+  ASSERT_EQ(client1_.sent_packet().send_time_ms, -1);
+  TestTransfer(1000, 100, false);
+  // Check that we get the expected fake packet ID, and a time of 0 from the
+  // fake clock.
+  EXPECT_EQ(kFakePacketId, client1_.sent_packet().packet_id);
+  EXPECT_GE(client1_.sent_packet().send_time_ms, 0);
+}
+
+// Connect without DTLS, and transfer SRTP data.
+TEST_F(DtlsTransportTest, TestTransferSrtp) {
+  ASSERT_TRUE(Connect());
+  TestTransfer(1000, 100, /*srtp=*/true);
+}
+
+// Connect with DTLS, and transfer data over DTLS.
+TEST_F(DtlsTransportTest, TestTransferDtls) {
+  PrepareDtls(rtc::KT_DEFAULT);
+  ASSERT_TRUE(Connect());
+  TestTransfer(1000, 100, /*srtp=*/false);
+}
+
+// Connect with DTLS, combine multiple DTLS records into one packet.
+// Our DTLS implementation doesn't do this, but other implementations may;
+// see https://tools.ietf.org/html/rfc6347#section-4.1.1.
+// This has caused interoperability problems with ORTCLib in the past.
+TEST_F(DtlsTransportTest, TestTransferDtlsCombineRecords) {
+  PrepareDtls(rtc::KT_DEFAULT);
+  ASSERT_TRUE(Connect());
+  // Our DTLS implementation always sends one record per packet, so to simulate
+  // an endpoint that sends multiple records per packet, we configure the fake
+  // ICE transport to combine every two consecutive packets into a single
+  // packet.
+  FakeIceTransport* transport = client1_.fake_ice_transport();
+  transport->combine_outgoing_packets(true);
+  TestTransfer(500, 100, /*srtp=*/false);
+}
+
+class DtlsTransportVersionTest
+    : public DtlsTransportTestBase,
+      public ::testing::TestWithParam<
+          ::testing::tuple<rtc::SSLProtocolVersion, rtc::SSLProtocolVersion>> {
+};
+
+// Test that an acceptable cipher suite is negotiated when different versions
+// of DTLS are supported. Note that it's IsAcceptableCipher that does the actual
+// work.
+TEST_P(DtlsTransportVersionTest, TestCipherSuiteNegotiation) {
+  PrepareDtls(rtc::KT_DEFAULT);
+  SetMaxProtocolVersions(::testing::get<0>(GetParam()),
+                         ::testing::get<1>(GetParam()));
+  ASSERT_TRUE(Connect());
+}
+
+// Will test every combination of 1.0/1.2 on the client and server.
+INSTANTIATE_TEST_SUITE_P(
+    TestCipherSuiteNegotiation,
+    DtlsTransportVersionTest,
+    ::testing::Combine(::testing::Values(rtc::SSL_PROTOCOL_DTLS_10,
+                                         rtc::SSL_PROTOCOL_DTLS_12),
+                       ::testing::Values(rtc::SSL_PROTOCOL_DTLS_10,
+                                         rtc::SSL_PROTOCOL_DTLS_12)));
+
+// Connect with DTLS, negotiating DTLS-SRTP, and transfer SRTP using bypass.
+TEST_F(DtlsTransportTest, TestTransferDtlsSrtp) {
+  PrepareDtls(rtc::KT_DEFAULT);
+  ASSERT_TRUE(Connect());
+  TestTransfer(1000, 100, /*srtp=*/true);
+}
+
+// Connect with DTLS-SRTP, transfer an invalid SRTP packet, and expects -1
+// returned.
+TEST_F(DtlsTransportTest, TestTransferDtlsInvalidSrtpPacket) {
+  PrepareDtls(rtc::KT_DEFAULT);
+  ASSERT_TRUE(Connect());
+  EXPECT_EQ(-1, client1_.SendInvalidSrtpPacket(100));
+}
+
+// Create a single transport with DTLS, and send normal data and SRTP data on
+// it.
+TEST_F(DtlsTransportTest, TestTransferDtlsSrtpDemux) {
+  PrepareDtls(rtc::KT_DEFAULT);
+  ASSERT_TRUE(Connect());
+  TestTransfer(1000, 100, /*srtp=*/false);
+  TestTransfer(1000, 100, /*srtp=*/true);
+}
+
+// Test transferring when the "answerer" has the server role.
+TEST_F(DtlsTransportTest, TestTransferDtlsSrtpAnswererIsPassive) {
+  PrepareDtls(rtc::KT_DEFAULT);
+  ASSERT_TRUE(Connect(/*client1_server=*/false));
+  TestTransfer(1000, 100, /*srtp=*/true);
+}
+
+// Test that renegotiation (setting same role and fingerprint again) can be
+// started before the clients become connected in the first negotiation.
+TEST_F(DtlsTransportTest, TestRenegotiateBeforeConnect) {
+  PrepareDtls(rtc::KT_DEFAULT);
+  // Note: This is doing the same thing Connect normally does, minus some
+  // additional checks not relevant for this test.
+  Negotiate();
+  Negotiate();
+  EXPECT_TRUE(client1_.Connect(&client2_, false));
+  EXPECT_TRUE_SIMULATED_WAIT(client1_.dtls_transport()->writable() &&
+                                 client2_.dtls_transport()->writable(),
+                             kTimeout, fake_clock_);
+  TestTransfer(1000, 100, true);
+}
+
+// Test Certificates state after negotiation but before connection.
+TEST_F(DtlsTransportTest, TestCertificatesBeforeConnect) {
+  PrepareDtls(rtc::KT_DEFAULT);
+  Negotiate();
+
+  // After negotiation, each side has a distinct local certificate, but still no
+  // remote certificate, because connection has not yet occurred.
+  auto certificate1 = client1_.dtls_transport()->GetLocalCertificate();
+  auto certificate2 = client2_.dtls_transport()->GetLocalCertificate();
+  ASSERT_NE(certificate1->GetSSLCertificate().ToPEMString(),
+            certificate2->GetSSLCertificate().ToPEMString());
+  ASSERT_FALSE(client1_.dtls_transport()->GetRemoteSSLCertChain());
+  ASSERT_FALSE(client2_.dtls_transport()->GetRemoteSSLCertChain());
+}
+
+// Test Certificates state after connection.
+TEST_F(DtlsTransportTest, TestCertificatesAfterConnect) {
+  PrepareDtls(rtc::KT_DEFAULT);
+  ASSERT_TRUE(Connect());
+
+  // After connection, each side has a distinct local certificate.
+  auto certificate1 = client1_.dtls_transport()->GetLocalCertificate();
+  auto certificate2 = client2_.dtls_transport()->GetLocalCertificate();
+  ASSERT_NE(certificate1->GetSSLCertificate().ToPEMString(),
+            certificate2->GetSSLCertificate().ToPEMString());
+
+  // Each side's remote certificate is the other side's local certificate.
+  std::unique_ptr<rtc::SSLCertChain> remote_cert1 =
+      client1_.dtls_transport()->GetRemoteSSLCertChain();
+  ASSERT_TRUE(remote_cert1);
+  ASSERT_EQ(1u, remote_cert1->GetSize());
+  ASSERT_EQ(remote_cert1->Get(0).ToPEMString(),
+            certificate2->GetSSLCertificate().ToPEMString());
+  std::unique_ptr<rtc::SSLCertChain> remote_cert2 =
+      client2_.dtls_transport()->GetRemoteSSLCertChain();
+  ASSERT_TRUE(remote_cert2);
+  ASSERT_EQ(1u, remote_cert2->GetSize());
+  ASSERT_EQ(remote_cert2->Get(0).ToPEMString(),
+            certificate1->GetSSLCertificate().ToPEMString());
+}
+
+// Test that packets are retransmitted according to the expected schedule.
+// Each time a timeout occurs, the retransmission timer should be doubled up to
+// 60 seconds. The timer defaults to 1 second, but for WebRTC we should be
+// initializing it to 50ms.
+TEST_F(DtlsTransportTest, TestRetransmissionSchedule) {
+  // We can only change the retransmission schedule with a recently-added
+  // BoringSSL API. Skip the test if not built with BoringSSL.
+  MAYBE_SKIP_TEST(IsBoringSsl);
+
+  PrepareDtls(rtc::KT_DEFAULT);
+  // Exchange fingerprints and set SSL roles.
+  Negotiate();
+
+  // Make client2_ writable, but not client1_.
+  // This means client1_ will send DTLS client hellos but get no response.
+  EXPECT_TRUE(client2_.Connect(&client1_, true));
+  EXPECT_TRUE_SIMULATED_WAIT(client2_.fake_ice_transport()->writable(),
+                             kTimeout, fake_clock_);
+
+  // Wait for the first client hello to be sent.
+  EXPECT_EQ_WAIT(1, client1_.received_dtls_client_hellos(), kTimeout);
+  EXPECT_FALSE(client1_.fake_ice_transport()->writable());
+
+  static int timeout_schedule_ms[] = {50,   100,  200,   400,   800,   1600,
+                                      3200, 6400, 12800, 25600, 51200, 60000};
+
+  int expected_hellos = 1;
+  for (size_t i = 0;
+       i < (sizeof(timeout_schedule_ms) / sizeof(timeout_schedule_ms[0]));
+       ++i) {
+    // For each expected retransmission time, advance the fake clock a
+    // millisecond before the expected time and verify that no unexpected
+    // retransmissions were sent. Then advance it the final millisecond and
+    // verify that the expected retransmission was sent.
+    fake_clock_.AdvanceTime(
+        webrtc::TimeDelta::Millis(timeout_schedule_ms[i] - 1));
+    EXPECT_EQ(expected_hellos, client1_.received_dtls_client_hellos());
+    fake_clock_.AdvanceTime(webrtc::TimeDelta::Millis(1));
+    EXPECT_EQ(++expected_hellos, client1_.received_dtls_client_hellos());
+  }
+}
+
+// The following events can occur in many different orders:
+// 1. Caller receives remote fingerprint.
+// 2. Caller is writable.
+// 3. Caller receives ClientHello.
+// 4. DTLS handshake finishes.
+//
+// The tests below cover all causally consistent permutations of these events;
+// the caller must be writable and receive a ClientHello before the handshake
+// finishes, but otherwise any ordering is possible.
+//
+// For each permutation, the test verifies that a connection is established and
+// fingerprint verified without any DTLS packet needing to be retransmitted.
+//
+// Each permutation is also tested with valid and invalid fingerprints,
+// ensuring that the handshake fails with an invalid fingerprint.
+enum DtlsTransportEvent {
+  CALLER_RECEIVES_FINGERPRINT,
+  CALLER_WRITABLE,
+  CALLER_RECEIVES_CLIENTHELLO,
+  HANDSHAKE_FINISHES
+};
+
+class DtlsEventOrderingTest
+    : public DtlsTransportTestBase,
+      public ::testing::TestWithParam<
+          ::testing::tuple<std::vector<DtlsTransportEvent>, bool>> {
+ protected:
+  // If `valid_fingerprint` is false, the caller will receive a fingerprint
+  // that doesn't match the callee's certificate, so the handshake should fail.
+  void TestEventOrdering(const std::vector<DtlsTransportEvent>& events,
+                         bool valid_fingerprint) {
+    // Pre-setup: Set local certificate on both caller and callee, and
+    // remote fingerprint on callee, but neither is writable and the caller
+    // doesn't have the callee's fingerprint.
+    PrepareDtls(rtc::KT_DEFAULT);
+    // Simulate packets being sent and arriving asynchronously.
+    // Otherwise the entire DTLS handshake would occur in one clock tick, and
+    // we couldn't inject method calls in the middle of it.
+    int simulated_delay_ms = 10;
+    client1_.SetupTransports(ICEROLE_CONTROLLING, simulated_delay_ms);
+    client2_.SetupTransports(ICEROLE_CONTROLLED, simulated_delay_ms);
+    // Similar to how NegotiateOrdering works.
+    client1_.dtls_transport()->SetDtlsRole(rtc::SSL_SERVER);
+    client2_.dtls_transport()->SetDtlsRole(rtc::SSL_CLIENT);
+    SetRemoteFingerprintFromCert(client2_.dtls_transport(),
+                                 client1_.certificate());
+
+    for (DtlsTransportEvent e : events) {
+      switch (e) {
+        case CALLER_RECEIVES_FINGERPRINT:
+          if (valid_fingerprint) {
+            SetRemoteFingerprintFromCert(client1_.dtls_transport(),
+                                         client2_.certificate());
+          } else {
+            SetRemoteFingerprintFromCert(client1_.dtls_transport(),
+                                         client2_.certificate(),
+                                         true /*modify_digest*/);
+          }
+          break;
+        case CALLER_WRITABLE:
+          EXPECT_TRUE(client1_.Connect(&client2_, true));
+          EXPECT_TRUE_SIMULATED_WAIT(client1_.fake_ice_transport()->writable(),
+                                     kTimeout, fake_clock_);
+          break;
+        case CALLER_RECEIVES_CLIENTHELLO:
+          // Sanity check that a ClientHello hasn't already been received.
+          EXPECT_EQ(0, client1_.received_dtls_client_hellos());
+          // Making client2_ writable will cause it to send the ClientHello.
+          EXPECT_TRUE(client2_.Connect(&client1_, true));
+          EXPECT_TRUE_SIMULATED_WAIT(client2_.fake_ice_transport()->writable(),
+                                     kTimeout, fake_clock_);
+          EXPECT_EQ_SIMULATED_WAIT(1, client1_.received_dtls_client_hellos(),
+                                   kTimeout, fake_clock_);
+          break;
+        case HANDSHAKE_FINISHES:
+          // Sanity check that the handshake hasn't already finished.
+          EXPECT_FALSE(client1_.dtls_transport()->IsDtlsConnected() ||
+                       client1_.dtls_transport()->dtls_state() ==
+                           webrtc::DtlsTransportState::kFailed);
+          EXPECT_TRUE_SIMULATED_WAIT(
+              client1_.dtls_transport()->IsDtlsConnected() ||
+                  client1_.dtls_transport()->dtls_state() ==
+                      webrtc::DtlsTransportState::kFailed,
+              kTimeout, fake_clock_);
+          break;
+      }
+    }
+
+    webrtc::DtlsTransportState expected_final_state =
+        valid_fingerprint ? webrtc::DtlsTransportState::kConnected
+                          : webrtc::DtlsTransportState::kFailed;
+    EXPECT_EQ_SIMULATED_WAIT(expected_final_state,
+                             client1_.dtls_transport()->dtls_state(), kTimeout,
+                             fake_clock_);
+    EXPECT_EQ_SIMULATED_WAIT(expected_final_state,
+                             client2_.dtls_transport()->dtls_state(), kTimeout,
+                             fake_clock_);
+
+    // Transports should be writable iff there was a valid fingerprint.
+    EXPECT_EQ(valid_fingerprint, client1_.dtls_transport()->writable());
+    EXPECT_EQ(valid_fingerprint, client2_.dtls_transport()->writable());
+
+    // Check that no hello needed to be retransmitted.
+    EXPECT_EQ(1, client1_.received_dtls_client_hellos());
+    EXPECT_EQ(1, client2_.received_dtls_server_hellos());
+
+    if (valid_fingerprint) {
+      TestTransfer(1000, 100, false);
+    }
+  }
+};
+
+TEST_P(DtlsEventOrderingTest, TestEventOrdering) {
+  TestEventOrdering(::testing::get<0>(GetParam()),
+                    ::testing::get<1>(GetParam()));
+}
+
+INSTANTIATE_TEST_SUITE_P(
+    TestEventOrdering,
+    DtlsEventOrderingTest,
+    ::testing::Combine(
+        ::testing::Values(
+            std::vector<DtlsTransportEvent>{
+                CALLER_RECEIVES_FINGERPRINT, CALLER_WRITABLE,
+                CALLER_RECEIVES_CLIENTHELLO, HANDSHAKE_FINISHES},
+            std::vector<DtlsTransportEvent>{
+                CALLER_WRITABLE, CALLER_RECEIVES_FINGERPRINT,
+                CALLER_RECEIVES_CLIENTHELLO, HANDSHAKE_FINISHES},
+            std::vector<DtlsTransportEvent>{
+                CALLER_WRITABLE, CALLER_RECEIVES_CLIENTHELLO,
+                CALLER_RECEIVES_FINGERPRINT, HANDSHAKE_FINISHES},
+            std::vector<DtlsTransportEvent>{
+                CALLER_WRITABLE, CALLER_RECEIVES_CLIENTHELLO,
+                HANDSHAKE_FINISHES, CALLER_RECEIVES_FINGERPRINT},
+            std::vector<DtlsTransportEvent>{
+                CALLER_RECEIVES_FINGERPRINT, CALLER_RECEIVES_CLIENTHELLO,
+                CALLER_WRITABLE, HANDSHAKE_FINISHES},
+            std::vector<DtlsTransportEvent>{
+                CALLER_RECEIVES_CLIENTHELLO, CALLER_RECEIVES_FINGERPRINT,
+                CALLER_WRITABLE, HANDSHAKE_FINISHES},
+            std::vector<DtlsTransportEvent>{
+                CALLER_RECEIVES_CLIENTHELLO, CALLER_WRITABLE,
+                CALLER_RECEIVES_FINGERPRINT, HANDSHAKE_FINISHES},
+            std::vector<DtlsTransportEvent>{CALLER_RECEIVES_CLIENTHELLO,
+                                            CALLER_WRITABLE, HANDSHAKE_FINISHES,
+                                            CALLER_RECEIVES_FINGERPRINT}),
+        ::testing::Bool()));
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/fake_dtls_transport.h b/third_party/libwebrtc/p2p/base/fake_dtls_transport.h
new file mode 100644
index 0000000000..283488bc38
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/fake_dtls_transport.h
@@ -0,0 +1,318 @@
+/*
+ *  Copyright 2017 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_FAKE_DTLS_TRANSPORT_H_
+#define P2P_BASE_FAKE_DTLS_TRANSPORT_H_
+
+#include <memory>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "absl/strings/string_view.h"
+#include "api/crypto/crypto_options.h"
+#include "api/dtls_transport_interface.h"
+#include "p2p/base/dtls_transport_internal.h"
+#include "p2p/base/fake_ice_transport.h"
+#include "rtc_base/fake_ssl_identity.h"
+#include "rtc_base/rtc_certificate.h"
+
+namespace cricket {
+
+// Fake DTLS transport which is implemented by wrapping a fake ICE transport.
+// Doesn't interact directly with fake ICE transport for anything other than
+// sending packets.
+class FakeDtlsTransport : public DtlsTransportInternal {
+ public:
+  explicit FakeDtlsTransport(FakeIceTransport* ice_transport)
+      : ice_transport_(ice_transport),
+        transport_name_(ice_transport->transport_name()),
+        component_(ice_transport->component()),
+        dtls_fingerprint_("", nullptr) {
+    RTC_DCHECK(ice_transport_);
+    ice_transport_->SignalReadPacket.connect(
+        this, &FakeDtlsTransport::OnIceTransportReadPacket);
+    ice_transport_->SignalNetworkRouteChanged.connect(
+        this, &FakeDtlsTransport::OnNetworkRouteChanged);
+  }
+
+  explicit FakeDtlsTransport(std::unique_ptr<FakeIceTransport> ice)
+      : owned_ice_transport_(std::move(ice)),
+        transport_name_(owned_ice_transport_->transport_name()),
+        component_(owned_ice_transport_->component()),
+        dtls_fingerprint_("", rtc::ArrayView<const uint8_t>()) {
+    ice_transport_ = owned_ice_transport_.get();
+    ice_transport_->SignalReadPacket.connect(
+        this, &FakeDtlsTransport::OnIceTransportReadPacket);
+    ice_transport_->SignalNetworkRouteChanged.connect(
+        this, &FakeDtlsTransport::OnNetworkRouteChanged);
+  }
+
+  // If this constructor is called, a new fake ICE transport will be created,
+  // and this FakeDtlsTransport will take the ownership.
+  FakeDtlsTransport(const std::string& name, int component)
+      : FakeDtlsTransport(std::make_unique<FakeIceTransport>(name, component)) {
+  }
+  FakeDtlsTransport(const std::string& name,
+                    int component,
+                    rtc::Thread* network_thread)
+      : FakeDtlsTransport(std::make_unique<FakeIceTransport>(name,
+                                                             component,
+                                                             network_thread)) {}
+
+  ~FakeDtlsTransport() override {
+    if (dest_ && dest_->dest_ == this) {
+      dest_->dest_ = nullptr;
+    }
+  }
+
+  // Get inner fake ICE transport.
+  FakeIceTransport* fake_ice_transport() { return ice_transport_; }
+
+  // If async, will send packets by "Post"-ing to message queue instead of
+  // synchronously "Send"-ing.
+  void SetAsync(bool async) { ice_transport_->SetAsync(async); }
+  void SetAsyncDelay(int delay_ms) { ice_transport_->SetAsyncDelay(delay_ms); }
+
+  // SetWritable, SetReceiving and SetDestination are the main methods that can
+  // be used for testing, to simulate connectivity or lack thereof.
+  void SetWritable(bool writable) {
+    ice_transport_->SetWritable(writable);
+    set_writable(writable);
+  }
+  void SetReceiving(bool receiving) {
+    ice_transport_->SetReceiving(receiving);
+    set_receiving(receiving);
+  }
+  void SetDtlsState(webrtc::DtlsTransportState state) {
+    dtls_state_ = state;
+    SendDtlsState(this, dtls_state_);
+  }
+
+  // Simulates the two DTLS transports connecting to each other.
+  // If `asymmetric` is true this method only affects this FakeDtlsTransport.
+  // If false, it affects `dest` as well.
+  void SetDestination(FakeDtlsTransport* dest, bool asymmetric = false) {
+    if (dest == dest_) {
+      return;
+    }
+    RTC_DCHECK(!dest || !dest_)
+        << "Changing fake destination from one to another is not supported.";
+    if (dest && !dest_) {
+      // This simulates the DTLS handshake.
+      dest_ = dest;
+      if (local_cert_ && dest_->local_cert_) {
+        do_dtls_ = true;
+        RTC_LOG(LS_INFO) << "FakeDtlsTransport is doing DTLS";
+      } else {
+        do_dtls_ = false;
+        RTC_LOG(LS_INFO) << "FakeDtlsTransport is not doing DTLS";
+      }
+      SetWritable(true);
+      if (!asymmetric) {
+        dest->SetDestination(this, true);
+      }
+      // If the `dtls_role_` is unset, set it to SSL_CLIENT by default.
+      if (!dtls_role_) {
+        dtls_role_ = std::move(rtc::SSL_CLIENT);
+      }
+      SetDtlsState(webrtc::DtlsTransportState::kConnected);
+      ice_transport_->SetDestination(
+          static_cast<FakeIceTransport*>(dest->ice_transport()), asymmetric);
+    } else {
+      // Simulates loss of connectivity, by asymmetrically forgetting dest_.
+      dest_ = nullptr;
+      SetWritable(false);
+      ice_transport_->SetDestination(nullptr, asymmetric);
+    }
+  }
+
+  // Fake DtlsTransportInternal implementation.
+  webrtc::DtlsTransportState dtls_state() const override { return dtls_state_; }
+  const std::string& transport_name() const override { return transport_name_; }
+  int component() const override { return component_; }
+  const rtc::SSLFingerprint& dtls_fingerprint() const {
+    return dtls_fingerprint_;
+  }
+  webrtc::RTCError SetRemoteParameters(absl::string_view alg,
+                                       const uint8_t* digest,
+                                       size_t digest_len,
+                                       absl::optional<rtc::SSLRole> role) {
+    if (role) {
+      SetDtlsRole(*role);
+    }
+    SetRemoteFingerprint(alg, digest, digest_len);
+    return webrtc::RTCError::OK();
+  }
+  bool SetRemoteFingerprint(absl::string_view alg,
+                            const uint8_t* digest,
+                            size_t digest_len) {
+    dtls_fingerprint_ =
+        rtc::SSLFingerprint(alg, rtc::MakeArrayView(digest, digest_len));
+    return true;
+  }
+  bool SetDtlsRole(rtc::SSLRole role) override {
+    dtls_role_ = std::move(role);
+    return true;
+  }
+  bool GetDtlsRole(rtc::SSLRole* role) const override {
+    if (!dtls_role_) {
+      return false;
+    }
+    *role = *dtls_role_;
+    return true;
+  }
+  bool SetLocalCertificate(
+      const rtc::scoped_refptr<rtc::RTCCertificate>& certificate) override {
+    do_dtls_ = true;
+    local_cert_ = certificate;
+    return true;
+  }
+  void SetRemoteSSLCertificate(rtc::FakeSSLCertificate* cert) {
+    remote_cert_ = cert;
+  }
+  bool IsDtlsActive() const override { return do_dtls_; }
+  bool GetSslVersionBytes(int* version) const override {
+    if (!do_dtls_) {
+      return false;
+    }
+    *version = 0x0102;
+    return true;
+  }
+  bool GetSrtpCryptoSuite(int* crypto_suite) override {
+    if (!do_dtls_) {
+      return false;
+    }
+    *crypto_suite = crypto_suite_;
+    return true;
+  }
+  void SetSrtpCryptoSuite(int crypto_suite) { crypto_suite_ = crypto_suite; }
+
+  bool GetSslCipherSuite(int* cipher_suite) override {
+    if (ssl_cipher_suite_) {
+      *cipher_suite = *ssl_cipher_suite_;
+      return true;
+    }
+    return false;
+  }
+  void SetSslCipherSuite(absl::optional<int> cipher_suite) {
+    ssl_cipher_suite_ = cipher_suite;
+  }
+  rtc::scoped_refptr<rtc::RTCCertificate> GetLocalCertificate() const override {
+    return local_cert_;
+  }
+  std::unique_ptr<rtc::SSLCertChain> GetRemoteSSLCertChain() const override {
+    if (!remote_cert_) {
+      return nullptr;
+    }
+    return std::make_unique<rtc::SSLCertChain>(remote_cert_->Clone());
+  }
+  bool ExportKeyingMaterial(absl::string_view label,
+                            const uint8_t* context,
+                            size_t context_len,
+                            bool use_context,
+                            uint8_t* result,
+                            size_t result_len) override {
+    if (!do_dtls_) {
+      return false;
+    }
+    memset(result, 0xff, result_len);
+    return true;
+  }
+  void set_ssl_max_protocol_version(rtc::SSLProtocolVersion version) {
+    ssl_max_version_ = version;
+  }
+  rtc::SSLProtocolVersion ssl_max_protocol_version() const {
+    return ssl_max_version_;
+  }
+
+  IceTransportInternal* ice_transport() override { return ice_transport_; }
+
+  // PacketTransportInternal implementation, which passes through to fake ICE
+  // transport for sending actual packets.
+  bool writable() const override { return writable_; }
+  bool receiving() const override { return receiving_; }
+  int SendPacket(const char* data,
+                 size_t len,
+                 const rtc::PacketOptions& options,
+                 int flags) override {
+    // We expect only SRTP packets to be sent through this interface.
+    if (flags != PF_SRTP_BYPASS && flags != 0) {
+      return -1;
+    }
+    return ice_transport_->SendPacket(data, len, options, flags);
+  }
+  int SetOption(rtc::Socket::Option opt, int value) override {
+    return ice_transport_->SetOption(opt, value);
+  }
+  bool GetOption(rtc::Socket::Option opt, int* value) override {
+    return ice_transport_->GetOption(opt, value);
+  }
+  int GetError() override { return ice_transport_->GetError(); }
+
+  absl::optional<rtc::NetworkRoute> network_route() const override {
+    return ice_transport_->network_route();
+  }
+
+ private:
+  void OnIceTransportReadPacket(PacketTransportInternal* ice_,
+                                const char* data,
+                                size_t len,
+                                const int64_t& packet_time_us,
+                                int flags) {
+    SignalReadPacket(this, data, len, packet_time_us, flags);
+  }
+
+  void set_receiving(bool receiving) {
+    if (receiving_ == receiving) {
+      return;
+    }
+    receiving_ = receiving;
+    SignalReceivingState(this);
+  }
+
+  void set_writable(bool writable) {
+    if (writable_ == writable) {
+      return;
+    }
+    writable_ = writable;
+    if (writable_) {
+      SignalReadyToSend(this);
+    }
+    SignalWritableState(this);
+  }
+
+  void OnNetworkRouteChanged(absl::optional<rtc::NetworkRoute> network_route) {
+    SignalNetworkRouteChanged(network_route);
+  }
+
+  FakeIceTransport* ice_transport_;
+  std::unique_ptr<FakeIceTransport> owned_ice_transport_;
+  std::string transport_name_;
+  int component_;
+  FakeDtlsTransport* dest_ = nullptr;
+  rtc::scoped_refptr<rtc::RTCCertificate> local_cert_;
+  rtc::FakeSSLCertificate* remote_cert_ = nullptr;
+  bool do_dtls_ = false;
+  rtc::SSLProtocolVersion ssl_max_version_ = rtc::SSL_PROTOCOL_DTLS_12;
+  rtc::SSLFingerprint dtls_fingerprint_;
+  absl::optional<rtc::SSLRole> dtls_role_;
+  int crypto_suite_ = rtc::kSrtpAes128CmSha1_80;
+  absl::optional<int> ssl_cipher_suite_;
+
+  webrtc::DtlsTransportState dtls_state_ = webrtc::DtlsTransportState::kNew;
+
+  bool receiving_ = false;
+  bool writable_ = false;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_FAKE_DTLS_TRANSPORT_H_
diff --git a/third_party/libwebrtc/p2p/base/fake_ice_transport.h b/third_party/libwebrtc/p2p/base/fake_ice_transport.h
new file mode 100644
index 0000000000..ae7bf8947e
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/fake_ice_transport.h
@@ -0,0 +1,446 @@
+/*
+ *  Copyright 2017 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_FAKE_ICE_TRANSPORT_H_
+#define P2P_BASE_FAKE_ICE_TRANSPORT_H_
+
+#include <map>
+#include <memory>
+#include <string>
+#include <utility>
+
+#include "absl/algorithm/container.h"
+#include "absl/strings/string_view.h"
+#include "absl/types/optional.h"
+#include "api/ice_transport_interface.h"
+#include "api/task_queue/pending_task_safety_flag.h"
+#include "api/units/time_delta.h"
+#include "p2p/base/ice_transport_internal.h"
+#include "rtc_base/copy_on_write_buffer.h"
+#include "rtc_base/task_queue_for_test.h"
+
+namespace cricket {
+using ::webrtc::SafeTask;
+using ::webrtc::TimeDelta;
+
+// All methods must be called on the network thread (which is either the thread
+// calling the constructor, or the separate thread explicitly passed to the
+// constructor).
+class FakeIceTransport : public IceTransportInternal {
+ public:
+  explicit FakeIceTransport(absl::string_view name,
+                            int component,
+                            rtc::Thread* network_thread = nullptr)
+      : name_(name),
+        component_(component),
+        network_thread_(network_thread ? network_thread
+                                       : rtc::Thread::Current()) {
+    RTC_DCHECK(network_thread_);
+  }
+  // Must be called either on the network thread, or after the network thread
+  // has been shut down.
+  ~FakeIceTransport() override {
+    if (dest_ && dest_->dest_ == this) {
+      dest_->dest_ = nullptr;
+    }
+  }
+
+  // If async, will send packets by "Post"-ing to message queue instead of
+  // synchronously "Send"-ing.
+  void SetAsync(bool async) {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    async_ = async;
+  }
+  void SetAsyncDelay(int delay_ms) {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    async_delay_ms_ = delay_ms;
+  }
+
+  // SetWritable, SetReceiving and SetDestination are the main methods that can
+  // be used for testing, to simulate connectivity or lack thereof.
+  void SetWritable(bool writable) {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    set_writable(writable);
+  }
+  void SetReceiving(bool receiving) {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    set_receiving(receiving);
+  }
+
+  // Simulates the two transports connecting to each other.
+  // If `asymmetric` is true this method only affects this FakeIceTransport.
+  // If false, it affects `dest` as well.
+  void SetDestination(FakeIceTransport* dest, bool asymmetric = false) {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    if (dest == dest_) {
+      return;
+    }
+    RTC_DCHECK(!dest || !dest_)
+        << "Changing fake destination from one to another is not supported.";
+    if (dest) {
+      // This simulates the delivery of candidates.
+      dest_ = dest;
+      set_writable(true);
+      if (!asymmetric) {
+        dest->SetDestination(this, true);
+      }
+    } else {
+      // Simulates loss of connectivity, by asymmetrically forgetting dest_.
+      dest_ = nullptr;
+      set_writable(false);
+    }
+  }
+
+  void SetTransportState(webrtc::IceTransportState state,
+                         IceTransportState legacy_state) {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    transport_state_ = state;
+    legacy_transport_state_ = legacy_state;
+    SignalIceTransportStateChanged(this);
+  }
+
+  void SetConnectionCount(size_t connection_count) {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    size_t old_connection_count = connection_count_;
+    connection_count_ = connection_count;
+    if (connection_count) {
+      had_connection_ = true;
+    }
+    // In this fake transport channel, `connection_count_` determines the
+    // transport state.
+    if (connection_count_ < old_connection_count) {
+      SignalStateChanged(this);
+    }
+  }
+
+  void SetCandidatesGatheringComplete() {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    if (gathering_state_ != kIceGatheringComplete) {
+      gathering_state_ = kIceGatheringComplete;
+      SignalGatheringState(this);
+    }
+  }
+
+  // Convenience functions for accessing ICE config and other things.
+  int receiving_timeout() const {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    return ice_config_.receiving_timeout_or_default();
+  }
+  bool gather_continually() const {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    return ice_config_.gather_continually();
+  }
+  const Candidates& remote_candidates() const {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    return remote_candidates_;
+  }
+
+  // Fake IceTransportInternal implementation.
+  const std::string& transport_name() const override { return name_; }
+  int component() const override { return component_; }
+  uint64_t IceTiebreaker() const {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    return tiebreaker_;
+  }
+  IceMode remote_ice_mode() const {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    return remote_ice_mode_;
+  }
+  const std::string& ice_ufrag() const { return ice_parameters_.ufrag; }
+  const std::string& ice_pwd() const { return ice_parameters_.pwd; }
+  const std::string& remote_ice_ufrag() const {
+    return remote_ice_parameters_.ufrag;
+  }
+  const std::string& remote_ice_pwd() const {
+    return remote_ice_parameters_.pwd;
+  }
+  const IceParameters& ice_parameters() const { return ice_parameters_; }
+  const IceParameters& remote_ice_parameters() const {
+    return remote_ice_parameters_;
+  }
+
+  IceTransportState GetState() const override {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    if (legacy_transport_state_) {
+      return *legacy_transport_state_;
+    }
+
+    if (connection_count_ == 0) {
+      return had_connection_ ? IceTransportState::STATE_FAILED
+                             : IceTransportState::STATE_INIT;
+    }
+
+    if (connection_count_ == 1) {
+      return IceTransportState::STATE_COMPLETED;
+    }
+
+    return IceTransportState::STATE_CONNECTING;
+  }
+
+  webrtc::IceTransportState GetIceTransportState() const override {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    if (transport_state_) {
+      return *transport_state_;
+    }
+
+    if (connection_count_ == 0) {
+      return had_connection_ ? webrtc::IceTransportState::kFailed
+                             : webrtc::IceTransportState::kNew;
+    }
+
+    if (connection_count_ == 1) {
+      return webrtc::IceTransportState::kCompleted;
+    }
+
+    return webrtc::IceTransportState::kConnected;
+  }
+
+  void SetIceRole(IceRole role) override {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    role_ = role;
+  }
+  IceRole GetIceRole() const override {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    return role_;
+  }
+  void SetIceTiebreaker(uint64_t tiebreaker) override {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    tiebreaker_ = tiebreaker;
+  }
+  void SetIceParameters(const IceParameters& ice_params) override {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    ice_parameters_ = ice_params;
+  }
+  void SetRemoteIceParameters(const IceParameters& params) override {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    remote_ice_parameters_ = params;
+  }
+
+  void SetRemoteIceMode(IceMode mode) override {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    remote_ice_mode_ = mode;
+  }
+
+  void MaybeStartGathering() override {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    if (gathering_state_ == kIceGatheringNew) {
+      gathering_state_ = kIceGatheringGathering;
+      SignalGatheringState(this);
+    }
+  }
+
+  IceGatheringState gathering_state() const override {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    return gathering_state_;
+  }
+
+  void SetIceConfig(const IceConfig& config) override {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    ice_config_ = config;
+  }
+
+  void AddRemoteCandidate(const Candidate& candidate) override {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    remote_candidates_.push_back(candidate);
+  }
+  void RemoveRemoteCandidate(const Candidate& candidate) override {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    auto it = absl::c_find(remote_candidates_, candidate);
+    if (it == remote_candidates_.end()) {
+      RTC_LOG(LS_INFO) << "Trying to remove a candidate which doesn't exist.";
+      return;
+    }
+
+    remote_candidates_.erase(it);
+  }
+
+  void RemoveAllRemoteCandidates() override {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    remote_candidates_.clear();
+  }
+
+  bool GetStats(IceTransportStats* ice_transport_stats) override {
+    CandidateStats candidate_stats;
+    ConnectionInfo candidate_pair_stats;
+    ice_transport_stats->candidate_stats_list.clear();
+    ice_transport_stats->candidate_stats_list.push_back(candidate_stats);
+    ice_transport_stats->connection_infos.clear();
+    ice_transport_stats->connection_infos.push_back(candidate_pair_stats);
+    return true;
+  }
+
+  absl::optional<int> GetRttEstimate() override { return absl::nullopt; }
+
+  const Connection* selected_connection() const override { return nullptr; }
+  absl::optional<const CandidatePair> GetSelectedCandidatePair()
+      const override {
+    return absl::nullopt;
+  }
+
+  // Fake PacketTransportInternal implementation.
+  bool writable() const override {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    return writable_;
+  }
+  bool receiving() const override {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    return receiving_;
+  }
+  // If combine is enabled, every two consecutive packets to be sent with
+  // "SendPacket" will be combined into one outgoing packet.
+  void combine_outgoing_packets(bool combine) {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    combine_outgoing_packets_ = combine;
+  }
+  int SendPacket(const char* data,
+                 size_t len,
+                 const rtc::PacketOptions& options,
+                 int flags) override {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    if (!dest_) {
+      return -1;
+    }
+
+    send_packet_.AppendData(data, len);
+    if (!combine_outgoing_packets_ || send_packet_.size() > len) {
+      rtc::CopyOnWriteBuffer packet(std::move(send_packet_));
+      if (async_) {
+        network_thread_->PostDelayedTask(
+            SafeTask(task_safety_.flag(),
+                     [this, packet] {
+                       RTC_DCHECK_RUN_ON(network_thread_);
+                       FakeIceTransport::SendPacketInternal(packet);
+                     }),
+            TimeDelta::Millis(async_delay_ms_));
+      } else {
+        SendPacketInternal(packet);
+      }
+    }
+    rtc::SentPacket sent_packet(options.packet_id, rtc::TimeMillis());
+    SignalSentPacket(this, sent_packet);
+    return static_cast<int>(len);
+  }
+
+  int SetOption(rtc::Socket::Option opt, int value) override {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    socket_options_[opt] = value;
+    return true;
+  }
+  bool GetOption(rtc::Socket::Option opt, int* value) override {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    auto it = socket_options_.find(opt);
+    if (it != socket_options_.end()) {
+      *value = it->second;
+      return true;
+    } else {
+      return false;
+    }
+  }
+
+  int GetError() override { return 0; }
+
+  rtc::CopyOnWriteBuffer last_sent_packet() {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    return last_sent_packet_;
+  }
+
+  absl::optional<rtc::NetworkRoute> network_route() const override {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    return network_route_;
+  }
+  void SetNetworkRoute(absl::optional<rtc::NetworkRoute> network_route) {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    network_route_ = network_route;
+    SendTask(network_thread_, [this] {
+      RTC_DCHECK_RUN_ON(network_thread_);
+      SignalNetworkRouteChanged(network_route_);
+    });
+  }
+
+ private:
+  void set_writable(bool writable)
+      RTC_EXCLUSIVE_LOCKS_REQUIRED(network_thread_) {
+    if (writable_ == writable) {
+      return;
+    }
+    RTC_LOG(LS_INFO) << "Change writable_ to " << writable;
+    writable_ = writable;
+    if (writable_) {
+      SignalReadyToSend(this);
+    }
+    SignalWritableState(this);
+  }
+
+  void set_receiving(bool receiving)
+      RTC_EXCLUSIVE_LOCKS_REQUIRED(network_thread_) {
+    if (receiving_ == receiving) {
+      return;
+    }
+    receiving_ = receiving;
+    SignalReceivingState(this);
+  }
+
+  void SendPacketInternal(const rtc::CopyOnWriteBuffer& packet)
+      RTC_EXCLUSIVE_LOCKS_REQUIRED(network_thread_) {
+    if (dest_) {
+      last_sent_packet_ = packet;
+      dest_->SignalReadPacket(dest_, packet.data<char>(), packet.size(),
+                              rtc::TimeMicros(), 0);
+    }
+  }
+
+  const std::string name_;
+  const int component_;
+  FakeIceTransport* dest_ RTC_GUARDED_BY(network_thread_) = nullptr;
+  bool async_ RTC_GUARDED_BY(network_thread_) = false;
+  int async_delay_ms_ RTC_GUARDED_BY(network_thread_) = 0;
+  Candidates remote_candidates_ RTC_GUARDED_BY(network_thread_);
+  IceConfig ice_config_ RTC_GUARDED_BY(network_thread_);
+  IceRole role_ RTC_GUARDED_BY(network_thread_) = ICEROLE_UNKNOWN;
+  uint64_t tiebreaker_ RTC_GUARDED_BY(network_thread_) = 0;
+  IceParameters ice_parameters_ RTC_GUARDED_BY(network_thread_);
+  IceParameters remote_ice_parameters_ RTC_GUARDED_BY(network_thread_);
+  IceMode remote_ice_mode_ RTC_GUARDED_BY(network_thread_) = ICEMODE_FULL;
+  size_t connection_count_ RTC_GUARDED_BY(network_thread_) = 0;
+  absl::optional<webrtc::IceTransportState> transport_state_
+      RTC_GUARDED_BY(network_thread_);
+  absl::optional<IceTransportState> legacy_transport_state_
+      RTC_GUARDED_BY(network_thread_);
+  IceGatheringState gathering_state_ RTC_GUARDED_BY(network_thread_) =
+      kIceGatheringNew;
+  bool had_connection_ RTC_GUARDED_BY(network_thread_) = false;
+  bool writable_ RTC_GUARDED_BY(network_thread_) = false;
+  bool receiving_ RTC_GUARDED_BY(network_thread_) = false;
+  bool combine_outgoing_packets_ RTC_GUARDED_BY(network_thread_) = false;
+  rtc::CopyOnWriteBuffer send_packet_ RTC_GUARDED_BY(network_thread_);
+  absl::optional<rtc::NetworkRoute> network_route_
+      RTC_GUARDED_BY(network_thread_);
+  std::map<rtc::Socket::Option, int> socket_options_
+      RTC_GUARDED_BY(network_thread_);
+  rtc::CopyOnWriteBuffer last_sent_packet_ RTC_GUARDED_BY(network_thread_);
+  rtc::Thread* const network_thread_;
+  webrtc::ScopedTaskSafetyDetached task_safety_;
+};
+
+class FakeIceTransportWrapper : public webrtc::IceTransportInterface {
+ public:
+  explicit FakeIceTransportWrapper(
+      std::unique_ptr<cricket::FakeIceTransport> internal)
+      : internal_(std::move(internal)) {}
+
+  cricket::IceTransportInternal* internal() override { return internal_.get(); }
+
+ private:
+  std::unique_ptr<cricket::FakeIceTransport> internal_;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_FAKE_ICE_TRANSPORT_H_
diff --git a/third_party/libwebrtc/p2p/base/fake_packet_transport.h b/third_party/libwebrtc/p2p/base/fake_packet_transport.h
new file mode 100644
index 0000000000..e80af0e008
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/fake_packet_transport.h
@@ -0,0 +1,143 @@
+/*
+ *  Copyright 2017 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_FAKE_PACKET_TRANSPORT_H_
+#define P2P_BASE_FAKE_PACKET_TRANSPORT_H_
+
+#include <map>
+#include <string>
+
+#include "p2p/base/packet_transport_internal.h"
+#include "rtc_base/copy_on_write_buffer.h"
+
+namespace rtc {
+
+// Used to simulate a packet-based transport.
+class FakePacketTransport : public PacketTransportInternal {
+ public:
+  explicit FakePacketTransport(const std::string& transport_name)
+      : transport_name_(transport_name) {}
+  ~FakePacketTransport() override {
+    if (dest_ && dest_->dest_ == this) {
+      dest_->dest_ = nullptr;
+    }
+  }
+
+  // SetWritable, SetReceiving and SetDestination are the main methods that can
+  // be used for testing, to simulate connectivity or lack thereof.
+  void SetWritable(bool writable) { set_writable(writable); }
+  void SetReceiving(bool receiving) { set_receiving(receiving); }
+
+  // Simulates the two transports connecting to each other.
+  // If `asymmetric` is true this method only affects this FakePacketTransport.
+  // If false, it affects `dest` as well.
+  void SetDestination(FakePacketTransport* dest, bool asymmetric) {
+    if (dest) {
+      dest_ = dest;
+      set_writable(true);
+      if (!asymmetric) {
+        dest->SetDestination(this, true);
+      }
+    } else {
+      // Simulates loss of connectivity, by asymmetrically forgetting dest_.
+      dest_ = nullptr;
+      set_writable(false);
+    }
+  }
+
+  // Fake PacketTransportInternal implementation.
+  const std::string& transport_name() const override { return transport_name_; }
+  bool writable() const override { return writable_; }
+  bool receiving() const override { return receiving_; }
+  int SendPacket(const char* data,
+                 size_t len,
+                 const PacketOptions& options,
+                 int flags) override {
+    if (!dest_) {
+      return -1;
+    }
+    CopyOnWriteBuffer packet(data, len);
+    SendPacketInternal(packet);
+
+    SentPacket sent_packet(options.packet_id, TimeMillis());
+    SignalSentPacket(this, sent_packet);
+    return static_cast<int>(len);
+  }
+
+  int SetOption(Socket::Option opt, int value) override {
+    options_[opt] = value;
+    return 0;
+  }
+
+  bool GetOption(Socket::Option opt, int* value) override {
+    auto it = options_.find(opt);
+    if (it == options_.end()) {
+      return false;
+    }
+    *value = it->second;
+    return true;
+  }
+
+  int GetError() override { return error_; }
+  void SetError(int error) { error_ = error; }
+
+  const CopyOnWriteBuffer* last_sent_packet() { return &last_sent_packet_; }
+
+  absl::optional<NetworkRoute> network_route() const override {
+    return network_route_;
+  }
+  void SetNetworkRoute(absl::optional<NetworkRoute> network_route) {
+    network_route_ = network_route;
+    SignalNetworkRouteChanged(network_route);
+  }
+
+ private:
+  void set_writable(bool writable) {
+    if (writable_ == writable) {
+      return;
+    }
+    writable_ = writable;
+    if (writable_) {
+      SignalReadyToSend(this);
+    }
+    SignalWritableState(this);
+  }
+
+  void set_receiving(bool receiving) {
+    if (receiving_ == receiving) {
+      return;
+    }
+    receiving_ = receiving;
+    SignalReceivingState(this);
+  }
+
+  void SendPacketInternal(const CopyOnWriteBuffer& packet) {
+    last_sent_packet_ = packet;
+    if (dest_) {
+      dest_->SignalReadPacket(dest_, packet.data<char>(), packet.size(),
+                              TimeMicros(), 0);
+    }
+  }
+
+  CopyOnWriteBuffer last_sent_packet_;
+  std::string transport_name_;
+  FakePacketTransport* dest_ = nullptr;
+  bool writable_ = false;
+  bool receiving_ = false;
+
+  std::map<Socket::Option, int> options_;
+  int error_ = 0;
+
+  absl::optional<NetworkRoute> network_route_;
+};
+
+}  // namespace rtc
+
+#endif  // P2P_BASE_FAKE_PACKET_TRANSPORT_H_
diff --git a/third_party/libwebrtc/p2p/base/fake_port_allocator.h b/third_party/libwebrtc/p2p/base/fake_port_allocator.h
new file mode 100644
index 0000000000..05c631361f
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/fake_port_allocator.h
@@ -0,0 +1,279 @@
+/*
+ *  Copyright 2010 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_FAKE_PORT_ALLOCATOR_H_
+#define P2P_BASE_FAKE_PORT_ALLOCATOR_H_
+
+#include <memory>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "absl/strings/string_view.h"
+#include "p2p/base/basic_packet_socket_factory.h"
+#include "p2p/base/port_allocator.h"
+#include "p2p/base/udp_port.h"
+#include "rtc_base/memory/always_valid_pointer.h"
+#include "rtc_base/net_helpers.h"
+#include "rtc_base/task_queue_for_test.h"
+#include "rtc_base/thread.h"
+
+namespace rtc {
+class SocketFactory;
+}
+
+namespace cricket {
+
+class TestUDPPort : public UDPPort {
+ public:
+  static TestUDPPort* Create(rtc::Thread* thread,
+                             rtc::PacketSocketFactory* factory,
+                             const rtc::Network* network,
+                             uint16_t min_port,
+                             uint16_t max_port,
+                             absl::string_view username,
+                             absl::string_view password,
+                             bool emit_localhost_for_anyaddress,
+                             const webrtc::FieldTrialsView* field_trials) {
+    TestUDPPort* port =
+        new TestUDPPort(thread, factory, network, min_port, max_port, username,
+                        password, emit_localhost_for_anyaddress, field_trials);
+    if (!port->Init()) {
+      delete port;
+      port = nullptr;
+    }
+    return port;
+  }
+
+ protected:
+  TestUDPPort(rtc::Thread* thread,
+              rtc::PacketSocketFactory* factory,
+              const rtc::Network* network,
+              uint16_t min_port,
+              uint16_t max_port,
+              absl::string_view username,
+              absl::string_view password,
+              bool emit_localhost_for_anyaddress,
+              const webrtc::FieldTrialsView* field_trials)
+      : UDPPort(thread,
+                factory,
+                network,
+                min_port,
+                max_port,
+                username,
+                password,
+                emit_localhost_for_anyaddress,
+                field_trials) {}
+};
+
+// A FakePortAllocatorSession can be used with either a real or fake socket
+// factory. It gathers a single loopback port, using IPv6 if available and
+// not disabled.
+class FakePortAllocatorSession : public PortAllocatorSession {
+ public:
+  FakePortAllocatorSession(PortAllocator* allocator,
+                           rtc::Thread* network_thread,
+                           rtc::PacketSocketFactory* factory,
+                           absl::string_view content_name,
+                           int component,
+                           absl::string_view ice_ufrag,
+                           absl::string_view ice_pwd,
+                           const webrtc::FieldTrialsView* field_trials)
+      : PortAllocatorSession(content_name,
+                             component,
+                             ice_ufrag,
+                             ice_pwd,
+                             allocator->flags()),
+        network_thread_(network_thread),
+        factory_(factory),
+        ipv4_network_("network",
+                      "unittest",
+                      rtc::IPAddress(INADDR_LOOPBACK),
+                      32),
+        ipv6_network_("network",
+                      "unittest",
+                      rtc::IPAddress(in6addr_loopback),
+                      64),
+        port_(),
+        port_config_count_(0),
+        stun_servers_(allocator->stun_servers()),
+        turn_servers_(allocator->turn_servers()),
+        field_trials_(field_trials) {
+    ipv4_network_.AddIP(rtc::IPAddress(INADDR_LOOPBACK));
+    ipv6_network_.AddIP(rtc::IPAddress(in6addr_loopback));
+    set_ice_tiebreaker(/*kTiebreakerDefault = */ 44444);
+  }
+
+  void SetCandidateFilter(uint32_t filter) override {
+    candidate_filter_ = filter;
+  }
+
+  void StartGettingPorts() override {
+    if (!port_) {
+      rtc::Network& network =
+          (rtc::HasIPv6Enabled() && (flags() & PORTALLOCATOR_ENABLE_IPV6))
+              ? ipv6_network_
+              : ipv4_network_;
+      port_.reset(TestUDPPort::Create(network_thread_, factory_, &network, 0, 0,
+                                      username(), password(), false,
+                                      field_trials_));
+      RTC_DCHECK(port_);
+      port_->SetIceTiebreaker(ice_tiebreaker());
+      port_->SubscribePortDestroyed(
+          [this](PortInterface* port) { OnPortDestroyed(port); });
+      AddPort(port_.get());
+    }
+    ++port_config_count_;
+    running_ = true;
+  }
+
+  void StopGettingPorts() override { running_ = false; }
+  bool IsGettingPorts() override { return running_; }
+  void ClearGettingPorts() override { is_cleared = true; }
+  bool IsCleared() const override { return is_cleared; }
+
+  void RegatherOnFailedNetworks() override {
+    SignalIceRegathering(this, IceRegatheringReason::NETWORK_FAILURE);
+  }
+
+  std::vector<PortInterface*> ReadyPorts() const override {
+    return ready_ports_;
+  }
+  std::vector<Candidate> ReadyCandidates() const override {
+    return candidates_;
+  }
+  void PruneAllPorts() override { port_->Prune(); }
+  bool CandidatesAllocationDone() const override { return allocation_done_; }
+
+  int port_config_count() { return port_config_count_; }
+
+  const ServerAddresses& stun_servers() const { return stun_servers_; }
+
+  const std::vector<RelayServerConfig>& turn_servers() const {
+    return turn_servers_;
+  }
+
+  uint32_t candidate_filter() const { return candidate_filter_; }
+
+  int transport_info_update_count() const {
+    return transport_info_update_count_;
+  }
+
+ protected:
+  void UpdateIceParametersInternal() override {
+    // Since this class is a fake and this method only is overridden for tests,
+    // we don't need to actually update the transport info.
+    ++transport_info_update_count_;
+  }
+
+ private:
+  void AddPort(cricket::Port* port) {
+    port->set_component(component());
+    port->set_generation(generation());
+    port->SignalPortComplete.connect(this,
+                                     &FakePortAllocatorSession::OnPortComplete);
+    port->PrepareAddress();
+    ready_ports_.push_back(port);
+    SignalPortReady(this, port);
+    port->KeepAliveUntilPruned();
+  }
+  void OnPortComplete(cricket::Port* port) {
+    const std::vector<Candidate>& candidates = port->Candidates();
+    candidates_.insert(candidates_.end(), candidates.begin(), candidates.end());
+    SignalCandidatesReady(this, candidates);
+
+    allocation_done_ = true;
+    SignalCandidatesAllocationDone(this);
+  }
+  void OnPortDestroyed(cricket::PortInterface* port) {
+    // Don't want to double-delete port if it deletes itself.
+    port_.release();
+  }
+
+  rtc::Thread* network_thread_;
+  rtc::PacketSocketFactory* factory_;
+  rtc::Network ipv4_network_;
+  rtc::Network ipv6_network_;
+  std::unique_ptr<cricket::Port> port_;
+  int port_config_count_;
+  std::vector<Candidate> candidates_;
+  std::vector<PortInterface*> ready_ports_;
+  bool allocation_done_ = false;
+  bool is_cleared = false;
+  ServerAddresses stun_servers_;
+  std::vector<RelayServerConfig> turn_servers_;
+  uint32_t candidate_filter_ = CF_ALL;
+  int transport_info_update_count_ = 0;
+  bool running_ = false;
+  const webrtc::FieldTrialsView* field_trials_;
+};
+
+class FakePortAllocator : public cricket::PortAllocator {
+ public:
+  FakePortAllocator(rtc::Thread* network_thread,
+                    rtc::PacketSocketFactory* factory,
+                    webrtc::FieldTrialsView* field_trials)
+      : FakePortAllocator(network_thread, factory, nullptr, field_trials) {}
+
+  FakePortAllocator(rtc::Thread* network_thread,
+                    std::unique_ptr<rtc::PacketSocketFactory> factory,
+                    webrtc::FieldTrialsView* field_trials)
+      : FakePortAllocator(network_thread,
+                          nullptr,
+                          std::move(factory),
+                          field_trials) {}
+
+  void SetNetworkIgnoreMask(int network_ignore_mask) override {}
+
+  cricket::PortAllocatorSession* CreateSessionInternal(
+      absl::string_view content_name,
+      int component,
+      absl::string_view ice_ufrag,
+      absl::string_view ice_pwd) override {
+    return new FakePortAllocatorSession(
+        this, network_thread_, factory_.get(), std::string(content_name),
+        component, std::string(ice_ufrag), std::string(ice_pwd), field_trials_);
+  }
+
+  bool initialized() const { return initialized_; }
+
+  // For testing: Manipulate MdnsObfuscationEnabled()
+  bool MdnsObfuscationEnabled() const override {
+    return mdns_obfuscation_enabled_;
+  }
+  void SetMdnsObfuscationEnabledForTesting(bool enabled) {
+    mdns_obfuscation_enabled_ = enabled;
+  }
+
+ private:
+  FakePortAllocator(rtc::Thread* network_thread,
+                    rtc::PacketSocketFactory* factory,
+                    std::unique_ptr<rtc::PacketSocketFactory> owned_factory,
+                    webrtc::FieldTrialsView* field_trials)
+      : network_thread_(network_thread),
+        factory_(std::move(owned_factory), factory),
+        field_trials_(field_trials) {
+    if (network_thread_ == nullptr) {
+      network_thread_ = rtc::Thread::Current();
+      Initialize();
+      return;
+    }
+    SendTask(network_thread_, [this] { Initialize(); });
+  }
+
+  rtc::Thread* network_thread_;
+  const webrtc::AlwaysValidPointerNoDefault<rtc::PacketSocketFactory> factory_;
+  const webrtc::FieldTrialsView* field_trials_;
+  bool mdns_obfuscation_enabled_ = false;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_FAKE_PORT_ALLOCATOR_H_
diff --git a/third_party/libwebrtc/p2p/base/ice_agent_interface.h b/third_party/libwebrtc/p2p/base/ice_agent_interface.h
new file mode 100644
index 0000000000..30b6ade6e6
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/ice_agent_interface.h
@@ -0,0 +1,80 @@
+/*
+ *  Copyright 2022 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_ICE_AGENT_INTERFACE_H_
+#define P2P_BASE_ICE_AGENT_INTERFACE_H_
+
+#include "api/array_view.h"
+#include "p2p/base/connection.h"
+#include "p2p/base/ice_switch_reason.h"
+
+namespace cricket {
+
+// IceAgentInterface provides methods that allow an ICE controller to manipulate
+// the connections available to a transport, and used by the transport to
+// transfer data.
+class IceAgentInterface {
+ public:
+  virtual ~IceAgentInterface() = default;
+
+  // Get the time when the last ping was sent.
+  // This is only needed in some scenarios if the agent decides to ping on its
+  // own, eg. in some switchover scenarios. Otherwise the ICE controller could
+  // keep this state on its own.
+  // TODO(bugs.webrtc.org/14367): route extra pings through the ICE controller.
+  virtual int64_t GetLastPingSentMs() const = 0;
+
+  // Get the ICE role of this ICE agent.
+  virtual IceRole GetIceRole() const = 0;
+
+  // Called when a pingable connection first becomes available.
+  virtual void OnStartedPinging() = 0;
+
+  // Update the state of all available connections.
+  virtual void UpdateConnectionStates() = 0;
+
+  // Update the internal state of the ICE agent. An ICE controller should call
+  // this at the end of a sequence of actions to combine several mutations into
+  // a single state refresh.
+  // TODO(bugs.webrtc.org/14431): ICE agent state updates should be internal to
+  // the agent. If batching is necessary, use a more appropriate interface.
+  virtual void UpdateState() = 0;
+
+  // Reset the given connections to a state of newly connected connections.
+  // - STATE_WRITE_INIT
+  // - receving = false
+  // - throw away all pending request
+  // - reset RttEstimate
+  //
+  // Keep the following unchanged:
+  // - connected
+  // - remote_candidate
+  // - statistics
+  //
+  // SignalStateChange will not be triggered.
+  virtual void ForgetLearnedStateForConnections(
+      rtc::ArrayView<const Connection* const> connections) = 0;
+
+  // Send a STUN ping request for the given connection.
+  virtual void SendPingRequest(const Connection* connection) = 0;
+
+  // Switch the transport to use the given connection.
+  virtual void SwitchSelectedConnection(const Connection* new_connection,
+                                        IceSwitchReason reason) = 0;
+
+  // Prune away the given connections. Returns true if pruning is permitted and
+  // successfully performed.
+  virtual bool PruneConnections(
+      rtc::ArrayView<const Connection* const> connections) = 0;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_ICE_AGENT_INTERFACE_H_
diff --git a/third_party/libwebrtc/p2p/base/ice_controller_factory_interface.h b/third_party/libwebrtc/p2p/base/ice_controller_factory_interface.h
new file mode 100644
index 0000000000..bae8b8f19d
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/ice_controller_factory_interface.h
@@ -0,0 +1,40 @@
+/*
+ *  Copyright 2019 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_ICE_CONTROLLER_FACTORY_INTERFACE_H_
+#define P2P_BASE_ICE_CONTROLLER_FACTORY_INTERFACE_H_
+
+#include <memory>
+#include <string>
+
+#include "p2p/base/ice_controller_interface.h"
+#include "p2p/base/ice_transport_internal.h"
+
+namespace cricket {
+
+// struct with arguments to IceControllerFactoryInterface::Create
+struct IceControllerFactoryArgs {
+  std::function<IceTransportState()> ice_transport_state_func;
+  std::function<IceRole()> ice_role_func;
+  std::function<bool(const Connection*)> is_connection_pruned_func;
+  const IceFieldTrials* ice_field_trials;
+  std::string ice_controller_field_trials;
+};
+
+class IceControllerFactoryInterface {
+ public:
+  virtual ~IceControllerFactoryInterface() = default;
+  virtual std::unique_ptr<IceControllerInterface> Create(
+      const IceControllerFactoryArgs& args) = 0;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_ICE_CONTROLLER_FACTORY_INTERFACE_H_
diff --git a/third_party/libwebrtc/p2p/base/ice_controller_interface.cc b/third_party/libwebrtc/p2p/base/ice_controller_interface.cc
new file mode 100644
index 0000000000..9fb3b055f9
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/ice_controller_interface.cc
@@ -0,0 +1,27 @@
+/*
+ *  Copyright 2019 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/ice_controller_interface.h"
+
+#include <string>
+
+#include "p2p/base/ice_switch_reason.h"
+
+namespace cricket {
+
+std::string IceRecheckEvent::ToString() const {
+  std::string str = IceSwitchReasonToString(reason);
+  if (recheck_delay_ms) {
+    str += " (after delay: " + std::to_string(recheck_delay_ms) + ")";
+  }
+  return str;
+}
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/ice_controller_interface.h b/third_party/libwebrtc/p2p/base/ice_controller_interface.h
new file mode 100644
index 0000000000..482043ef35
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/ice_controller_interface.h
@@ -0,0 +1,138 @@
+/*
+ *  Copyright 2019 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_ICE_CONTROLLER_INTERFACE_H_
+#define P2P_BASE_ICE_CONTROLLER_INTERFACE_H_
+
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "absl/types/optional.h"
+#include "p2p/base/connection.h"
+#include "p2p/base/ice_switch_reason.h"
+#include "p2p/base/ice_transport_internal.h"
+
+namespace cricket {
+
+struct IceFieldTrials;  // Forward declaration to avoid circular dependency.
+
+struct IceRecheckEvent {
+  IceRecheckEvent(IceSwitchReason _reason, int _recheck_delay_ms)
+      : reason(_reason), recheck_delay_ms(_recheck_delay_ms) {}
+
+  std::string ToString() const;
+
+  IceSwitchReason reason;
+  int recheck_delay_ms;
+};
+
+// Defines the interface for a module that control
+// - which connection to ping
+// - which connection to use
+// - which connection to prune
+// - which connection to forget learned state on
+//
+// The P2PTransportChannel owns (creates and destroys) Connections,
+// but P2PTransportChannel gives const pointers to the the IceController using
+// `AddConnection`, i.e the IceController should not call any non-const methods
+// on a Connection but signal back in the interface if any mutable function
+// shall be called.
+//
+// Current these are limited to:
+// Connection::Ping               - returned in PingResult
+// Connection::Prune              - retuned in PruneConnections
+// Connection::ForgetLearnedState - return in SwitchResult
+//
+// The IceController shall keep track of all connections added
+// (and not destroyed) and give them back using the connections()-function-
+//
+// When a Connection gets destroyed
+// - signals on Connection::SignalDestroyed
+// - P2PTransportChannel calls IceController::OnConnectionDestroyed
+class IceControllerInterface {
+ public:
+  // This represents the result of a switch call.
+  struct SwitchResult {
+    // Connection that we should (optionally) switch to.
+    absl::optional<const Connection*> connection;
+
+    // An optional recheck event for when a Switch() should be attempted again.
+    absl::optional<IceRecheckEvent> recheck_event;
+
+    // A vector with connection to run ForgetLearnedState on.
+    std::vector<const Connection*> connections_to_forget_state_on;
+  };
+
+  // This represents the result of a call to SelectConnectionToPing.
+  struct PingResult {
+    PingResult(const Connection* conn, int _recheck_delay_ms)
+        : connection(conn ? absl::optional<const Connection*>(conn)
+                          : absl::nullopt),
+          recheck_delay_ms(_recheck_delay_ms) {}
+
+    // Connection that we should (optionally) ping.
+    const absl::optional<const Connection*> connection;
+
+    // The delay before P2PTransportChannel shall call SelectConnectionToPing()
+    // again.
+    //
+    // Since the IceController determines which connection to ping and
+    // only returns one connection at a time, the recheck_delay_ms does not have
+    // any obvious implication on bitrate for pings. E.g the recheck_delay_ms
+    // will be shorter if there are more connections available.
+    const int recheck_delay_ms = 0;
+  };
+
+  virtual ~IceControllerInterface() = default;
+
+  // These setters are called when the state of P2PTransportChannel is mutated.
+  virtual void SetIceConfig(const IceConfig& config) = 0;
+  virtual void SetSelectedConnection(const Connection* selected_connection) = 0;
+  virtual void AddConnection(const Connection* connection) = 0;
+  virtual void OnConnectionDestroyed(const Connection* connection) = 0;
+
+  // These are all connections that has been added and not destroyed.
+  virtual rtc::ArrayView<const Connection*> connections() const = 0;
+
+  // Is there a pingable connection ?
+  // This function is used to boot-strap pinging, after this returns true
+  // SelectConnectionToPing() will be called periodically.
+  virtual bool HasPingableConnection() const = 0;
+
+  // Select a connection to Ping, or nullptr if none.
+  virtual PingResult SelectConnectionToPing(int64_t last_ping_sent_ms) = 0;
+
+  // Compute the "STUN_ATTR_USE_CANDIDATE" for `conn`.
+  virtual bool GetUseCandidateAttr(const Connection* conn,
+                                   NominationMode mode,
+                                   IceMode remote_ice_mode) const = 0;
+
+  // These methods is only added to not have to change all unit tests
+  // that simulate pinging by marking a connection pinged.
+  virtual const Connection* FindNextPingableConnection() = 0;
+  virtual void MarkConnectionPinged(const Connection* con) = 0;
+
+  // Check if we should switch to `connection`.
+  // This method is called for IceSwitchReasons that can switch directly
+  // i.e without resorting.
+  virtual SwitchResult ShouldSwitchConnection(IceSwitchReason reason,
+                                              const Connection* connection) = 0;
+
+  // Sort connections and check if we should switch.
+  virtual SwitchResult SortAndSwitchConnection(IceSwitchReason reason) = 0;
+
+  // Prune connections.
+  virtual std::vector<const Connection*> PruneConnections() = 0;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_ICE_CONTROLLER_INTERFACE_H_
diff --git a/third_party/libwebrtc/p2p/base/ice_credentials_iterator.cc b/third_party/libwebrtc/p2p/base/ice_credentials_iterator.cc
new file mode 100644
index 0000000000..373c8510ac
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/ice_credentials_iterator.cc
@@ -0,0 +1,38 @@
+/*
+ *  Copyright 2018 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/ice_credentials_iterator.h"
+
+#include "p2p/base/p2p_constants.h"
+#include "rtc_base/helpers.h"
+
+namespace cricket {
+
+IceCredentialsIterator::IceCredentialsIterator(
+    const std::vector<IceParameters>& pooled_credentials)
+    : pooled_ice_credentials_(pooled_credentials) {}
+
+IceCredentialsIterator::~IceCredentialsIterator() = default;
+
+IceParameters IceCredentialsIterator::CreateRandomIceCredentials() {
+  return IceParameters(rtc::CreateRandomString(ICE_UFRAG_LENGTH),
+                       rtc::CreateRandomString(ICE_PWD_LENGTH), false);
+}
+
+IceParameters IceCredentialsIterator::GetIceCredentials() {
+  if (pooled_ice_credentials_.empty()) {
+    return CreateRandomIceCredentials();
+  }
+  IceParameters credentials = pooled_ice_credentials_.back();
+  pooled_ice_credentials_.pop_back();
+  return credentials;
+}
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/ice_credentials_iterator.h b/third_party/libwebrtc/p2p/base/ice_credentials_iterator.h
new file mode 100644
index 0000000000..fa331cc6eb
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/ice_credentials_iterator.h
@@ -0,0 +1,37 @@
+/*
+ *  Copyright 2018 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_ICE_CREDENTIALS_ITERATOR_H_
+#define P2P_BASE_ICE_CREDENTIALS_ITERATOR_H_
+
+#include <vector>
+
+#include "p2p/base/transport_description.h"
+
+namespace cricket {
+
+class IceCredentialsIterator {
+ public:
+  explicit IceCredentialsIterator(const std::vector<IceParameters>&);
+  virtual ~IceCredentialsIterator();
+
+  // Get next pooled ice credentials.
+  // Returns a new random credential if the pool is empty.
+  IceParameters GetIceCredentials();
+
+  static IceParameters CreateRandomIceCredentials();
+
+ private:
+  std::vector<IceParameters> pooled_ice_credentials_;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_ICE_CREDENTIALS_ITERATOR_H_
diff --git a/third_party/libwebrtc/p2p/base/ice_credentials_iterator_unittest.cc b/third_party/libwebrtc/p2p/base/ice_credentials_iterator_unittest.cc
new file mode 100644
index 0000000000..470efe3e45
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/ice_credentials_iterator_unittest.cc
@@ -0,0 +1,48 @@
+/*
+ *  Copyright 2018 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/ice_credentials_iterator.h"
+
+#include <vector>
+
+#include "test/gtest.h"
+
+using cricket::IceCredentialsIterator;
+using cricket::IceParameters;
+
+TEST(IceCredentialsIteratorTest, GetEmpty) {
+  std::vector<IceParameters> empty;
+  IceCredentialsIterator iterator(empty);
+  // Verify that we can get credentials even if input is empty.
+  IceParameters credentials1 = iterator.GetIceCredentials();
+}
+
+TEST(IceCredentialsIteratorTest, GetOne) {
+  std::vector<IceParameters> one = {
+      IceCredentialsIterator::CreateRandomIceCredentials()};
+  IceCredentialsIterator iterator(one);
+  EXPECT_EQ(iterator.GetIceCredentials(), one[0]);
+  auto random = iterator.GetIceCredentials();
+  EXPECT_NE(random, one[0]);
+  EXPECT_NE(random, iterator.GetIceCredentials());
+}
+
+TEST(IceCredentialsIteratorTest, GetTwo) {
+  std::vector<IceParameters> two = {
+      IceCredentialsIterator::CreateRandomIceCredentials(),
+      IceCredentialsIterator::CreateRandomIceCredentials()};
+  IceCredentialsIterator iterator(two);
+  EXPECT_EQ(iterator.GetIceCredentials(), two[1]);
+  EXPECT_EQ(iterator.GetIceCredentials(), two[0]);
+  auto random = iterator.GetIceCredentials();
+  EXPECT_NE(random, two[0]);
+  EXPECT_NE(random, two[1]);
+  EXPECT_NE(random, iterator.GetIceCredentials());
+}
diff --git a/third_party/libwebrtc/p2p/base/ice_switch_reason.cc b/third_party/libwebrtc/p2p/base/ice_switch_reason.cc
new file mode 100644
index 0000000000..61f0fa7d5b
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/ice_switch_reason.cc
@@ -0,0 +1,44 @@
+/*
+ *  Copyright 2022 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/ice_switch_reason.h"
+
+#include <string>
+
+namespace cricket {
+
+std::string IceSwitchReasonToString(IceSwitchReason reason) {
+  switch (reason) {
+    case IceSwitchReason::REMOTE_CANDIDATE_GENERATION_CHANGE:
+      return "remote candidate generation maybe changed";
+    case IceSwitchReason::NETWORK_PREFERENCE_CHANGE:
+      return "network preference changed";
+    case IceSwitchReason::NEW_CONNECTION_FROM_LOCAL_CANDIDATE:
+      return "new candidate pairs created from a new local candidate";
+    case IceSwitchReason::NEW_CONNECTION_FROM_REMOTE_CANDIDATE:
+      return "new candidate pairs created from a new remote candidate";
+    case IceSwitchReason::NEW_CONNECTION_FROM_UNKNOWN_REMOTE_ADDRESS:
+      return "a new candidate pair created from an unknown remote address";
+    case IceSwitchReason::NOMINATION_ON_CONTROLLED_SIDE:
+      return "nomination on the controlled side";
+    case IceSwitchReason::DATA_RECEIVED:
+      return "data received";
+    case IceSwitchReason::CONNECT_STATE_CHANGE:
+      return "candidate pair state changed";
+    case IceSwitchReason::SELECTED_CONNECTION_DESTROYED:
+      return "selected candidate pair destroyed";
+    case IceSwitchReason::ICE_CONTROLLER_RECHECK:
+      return "ice-controller-request-recheck";
+    default:
+      return "unknown";
+  }
+}
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/ice_switch_reason.h b/third_party/libwebrtc/p2p/base/ice_switch_reason.h
new file mode 100644
index 0000000000..2c4fe31884
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/ice_switch_reason.h
@@ -0,0 +1,38 @@
+/*
+ *  Copyright 2022 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_ICE_SWITCH_REASON_H_
+#define P2P_BASE_ICE_SWITCH_REASON_H_
+
+#include <string>
+
+namespace cricket {
+
+enum class IceSwitchReason {
+  REMOTE_CANDIDATE_GENERATION_CHANGE,
+  NETWORK_PREFERENCE_CHANGE,
+  NEW_CONNECTION_FROM_LOCAL_CANDIDATE,
+  NEW_CONNECTION_FROM_REMOTE_CANDIDATE,
+  NEW_CONNECTION_FROM_UNKNOWN_REMOTE_ADDRESS,
+  NOMINATION_ON_CONTROLLED_SIDE,
+  DATA_RECEIVED,
+  CONNECT_STATE_CHANGE,
+  SELECTED_CONNECTION_DESTROYED,
+  // The ICE_CONTROLLER_RECHECK enum value lets an IceController request
+  // P2PTransportChannel to recheck a switch periodically without an event
+  // taking place.
+  ICE_CONTROLLER_RECHECK,
+};
+
+std::string IceSwitchReasonToString(IceSwitchReason reason);
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_ICE_SWITCH_REASON_H_
diff --git a/third_party/libwebrtc/p2p/base/ice_transport_internal.cc b/third_party/libwebrtc/p2p/base/ice_transport_internal.cc
new file mode 100644
index 0000000000..fab6f2037a
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/ice_transport_internal.cc
@@ -0,0 +1,140 @@
+/*
+ *  Copyright 2017 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/ice_transport_internal.h"
+
+#include "absl/strings/string_view.h"
+#include "p2p/base/p2p_constants.h"
+
+namespace cricket {
+
+using webrtc::RTCError;
+using webrtc::RTCErrorType;
+
+RTCError VerifyCandidate(const Candidate& cand) {
+  // No address zero.
+  if (cand.address().IsNil() || cand.address().IsAnyIP()) {
+    return RTCError(RTCErrorType::INVALID_PARAMETER,
+                    "candidate has address of zero");
+  }
+
+  // Disallow all ports below 1024, except for 80 and 443 on public addresses.
+  int port = cand.address().port();
+  if (cand.protocol() == cricket::TCP_PROTOCOL_NAME &&
+      (cand.tcptype() == cricket::TCPTYPE_ACTIVE_STR || port == 0)) {
+    // Expected for active-only candidates per
+    // http://tools.ietf.org/html/rfc6544#section-4.5 so no error.
+    // Libjingle clients emit port 0, in "active" mode.
+    return RTCError::OK();
+  }
+  if (port < 1024) {
+    if ((port != 80) && (port != 443)) {
+      return RTCError(RTCErrorType::INVALID_PARAMETER,
+                      "candidate has port below 1024, but not 80 or 443");
+    }
+
+    if (cand.address().IsPrivateIP()) {
+      return RTCError(
+          RTCErrorType::INVALID_PARAMETER,
+          "candidate has port of 80 or 443 with private IP address");
+    }
+  }
+
+  return RTCError::OK();
+}
+
+RTCError VerifyCandidates(const Candidates& candidates) {
+  for (const Candidate& candidate : candidates) {
+    RTCError error = VerifyCandidate(candidate);
+    if (!error.ok())
+      return error;
+  }
+  return RTCError::OK();
+}
+
+IceConfig::IceConfig() = default;
+
+IceConfig::IceConfig(int receiving_timeout_ms,
+                     int backup_connection_ping_interval,
+                     ContinualGatheringPolicy gathering_policy,
+                     bool prioritize_most_likely_candidate_pairs,
+                     int stable_writable_connection_ping_interval_ms,
+                     bool presume_writable_when_fully_relayed,
+                     int regather_on_failed_networks_interval_ms,
+                     int receiving_switching_delay_ms)
+    : receiving_timeout(receiving_timeout_ms),
+      backup_connection_ping_interval(backup_connection_ping_interval),
+      continual_gathering_policy(gathering_policy),
+      prioritize_most_likely_candidate_pairs(
+          prioritize_most_likely_candidate_pairs),
+      stable_writable_connection_ping_interval(
+          stable_writable_connection_ping_interval_ms),
+      presume_writable_when_fully_relayed(presume_writable_when_fully_relayed),
+      regather_on_failed_networks_interval(
+          regather_on_failed_networks_interval_ms),
+      receiving_switching_delay(receiving_switching_delay_ms) {}
+
+IceConfig::~IceConfig() = default;
+
+int IceConfig::receiving_timeout_or_default() const {
+  return receiving_timeout.value_or(RECEIVING_TIMEOUT);
+}
+int IceConfig::backup_connection_ping_interval_or_default() const {
+  return backup_connection_ping_interval.value_or(
+      BACKUP_CONNECTION_PING_INTERVAL);
+}
+int IceConfig::stable_writable_connection_ping_interval_or_default() const {
+  return stable_writable_connection_ping_interval.value_or(
+      STRONG_AND_STABLE_WRITABLE_CONNECTION_PING_INTERVAL);
+}
+int IceConfig::regather_on_failed_networks_interval_or_default() const {
+  return regather_on_failed_networks_interval.value_or(
+      REGATHER_ON_FAILED_NETWORKS_INTERVAL);
+}
+int IceConfig::receiving_switching_delay_or_default() const {
+  return receiving_switching_delay.value_or(RECEIVING_SWITCHING_DELAY);
+}
+int IceConfig::ice_check_interval_strong_connectivity_or_default() const {
+  return ice_check_interval_strong_connectivity.value_or(STRONG_PING_INTERVAL);
+}
+int IceConfig::ice_check_interval_weak_connectivity_or_default() const {
+  return ice_check_interval_weak_connectivity.value_or(WEAK_PING_INTERVAL);
+}
+int IceConfig::ice_check_min_interval_or_default() const {
+  return ice_check_min_interval.value_or(-1);
+}
+int IceConfig::ice_unwritable_timeout_or_default() const {
+  return ice_unwritable_timeout.value_or(CONNECTION_WRITE_CONNECT_TIMEOUT);
+}
+int IceConfig::ice_unwritable_min_checks_or_default() const {
+  return ice_unwritable_min_checks.value_or(CONNECTION_WRITE_CONNECT_FAILURES);
+}
+int IceConfig::ice_inactive_timeout_or_default() const {
+  return ice_inactive_timeout.value_or(CONNECTION_WRITE_TIMEOUT);
+}
+int IceConfig::stun_keepalive_interval_or_default() const {
+  return stun_keepalive_interval.value_or(STUN_KEEPALIVE_INTERVAL);
+}
+
+IceTransportInternal::IceTransportInternal() = default;
+
+IceTransportInternal::~IceTransportInternal() = default;
+
+void IceTransportInternal::SetIceCredentials(absl::string_view ice_ufrag,
+                                             absl::string_view ice_pwd) {
+  SetIceParameters(IceParameters(ice_ufrag, ice_pwd, false));
+}
+
+void IceTransportInternal::SetRemoteIceCredentials(absl::string_view ice_ufrag,
+                                                   absl::string_view ice_pwd) {
+  SetRemoteIceParameters(IceParameters(ice_ufrag, ice_pwd, false));
+}
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/ice_transport_internal.h b/third_party/libwebrtc/p2p/base/ice_transport_internal.h
new file mode 100644
index 0000000000..3a93ab0484
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/ice_transport_internal.h
@@ -0,0 +1,347 @@
+/*
+ *  Copyright 2016 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_ICE_TRANSPORT_INTERNAL_H_
+#define P2P_BASE_ICE_TRANSPORT_INTERNAL_H_
+
+#include <stdint.h>
+
+#include <string>
+#include <vector>
+
+#include "absl/strings/string_view.h"
+#include "absl/types/optional.h"
+#include "api/candidate.h"
+#include "api/rtc_error.h"
+#include "api/transport/enums.h"
+#include "p2p/base/connection.h"
+#include "p2p/base/packet_transport_internal.h"
+#include "p2p/base/port.h"
+#include "p2p/base/transport_description.h"
+#include "rtc_base/network_constants.h"
+#include "rtc_base/system/rtc_export.h"
+#include "rtc_base/third_party/sigslot/sigslot.h"
+#include "rtc_base/time_utils.h"
+
+namespace cricket {
+
+struct IceTransportStats {
+  CandidateStatsList candidate_stats_list;
+  ConnectionInfos connection_infos;
+  // Number of times the selected candidate pair has changed
+  // Initially 0 and 1 once the first candidate pair has been selected.
+  // The counter is increase also when "unselecting" a connection.
+  uint32_t selected_candidate_pair_changes = 0;
+
+  // Bytes/packets sent/received.
+  // note: Is not the same as sum(connection_infos.bytes_sent)
+  // as connections are created and destroyed while the ICE transport
+  // is alive.
+  uint64_t bytes_sent = 0;
+  uint64_t bytes_received = 0;
+  uint64_t packets_sent = 0;
+  uint64_t packets_received = 0;
+
+  IceRole ice_role = ICEROLE_UNKNOWN;
+  std::string ice_local_username_fragment;
+  webrtc::IceTransportState ice_state = webrtc::IceTransportState::kNew;
+};
+
+typedef std::vector<Candidate> Candidates;
+
+enum IceConnectionState {
+  kIceConnectionConnecting = 0,
+  kIceConnectionFailed,
+  kIceConnectionConnected,  // Writable, but still checking one or more
+                            // connections
+  kIceConnectionCompleted,
+};
+
+// TODO(deadbeef): Unify with PeerConnectionInterface::IceConnectionState
+// once /talk/ and /webrtc/ are combined, and also switch to ENUM_NAME naming
+// style.
+enum IceGatheringState {
+  kIceGatheringNew = 0,
+  kIceGatheringGathering,
+  kIceGatheringComplete,
+};
+
+enum ContinualGatheringPolicy {
+  // All port allocator sessions will stop after a writable connection is found.
+  GATHER_ONCE = 0,
+  // The most recent port allocator session will keep on running.
+  GATHER_CONTINUALLY,
+};
+
+// ICE Nomination mode.
+enum class NominationMode {
+  REGULAR,         // Nominate once per ICE restart (Not implemented yet).
+  AGGRESSIVE,      // Nominate every connection except that it will behave as if
+                   // REGULAR when the remote is an ICE-LITE endpoint.
+  SEMI_AGGRESSIVE  // Our current implementation of the nomination algorithm.
+                   // The details are described in P2PTransportChannel.
+};
+
+// Utility method that checks if various required Candidate fields are filled in
+// and contain valid values. If conditions are not met, an RTCError with the
+// appropriated error number and description is returned. If the configuration
+// is valid RTCError::OK() is returned.
+webrtc::RTCError VerifyCandidate(const Candidate& cand);
+
+// Runs through a list of cricket::Candidate instances and calls VerifyCandidate
+// for each one, stopping on the first error encounted and returning that error
+// value if so. On success returns RTCError::OK().
+webrtc::RTCError VerifyCandidates(const Candidates& candidates);
+
+// Information about ICE configuration.
+// TODO(deadbeef): Use absl::optional to represent unset values, instead of
+// -1.
+struct IceConfig {
+  // The ICE connection receiving timeout value in milliseconds.
+  absl::optional<int> receiving_timeout;
+  // Time interval in milliseconds to ping a backup connection when the ICE
+  // channel is strongly connected.
+  absl::optional<int> backup_connection_ping_interval;
+
+  ContinualGatheringPolicy continual_gathering_policy = GATHER_ONCE;
+
+  bool gather_continually() const {
+    return continual_gathering_policy == GATHER_CONTINUALLY;
+  }
+
+  // Whether we should prioritize Relay/Relay candidate when nothing
+  // is writable yet.
+  bool prioritize_most_likely_candidate_pairs = false;
+
+  // Writable connections are pinged at a slower rate once stablized.
+  absl::optional<int> stable_writable_connection_ping_interval;
+
+  // If set to true, this means the ICE transport should presume TURN-to-TURN
+  // candidate pairs will succeed, even before a binding response is received.
+  bool presume_writable_when_fully_relayed = false;
+
+  // If true, after the ICE transport type (as the candidate filter used by the
+  // port allocator) is changed such that new types of ICE candidates are
+  // allowed by the new filter, e.g. from CF_RELAY to CF_ALL, candidates that
+  // have been gathered by the ICE transport but filtered out and not signaled
+  // to the upper layers, will be surfaced.
+  bool surface_ice_candidates_on_ice_transport_type_changed = false;
+
+  // Interval to check on all networks and to perform ICE regathering on any
+  // active network having no connection on it.
+  absl::optional<int> regather_on_failed_networks_interval;
+
+  // The time period in which we will not switch the selected connection
+  // when a new connection becomes receiving but the selected connection is not
+  // in case that the selected connection may become receiving soon.
+  absl::optional<int> receiving_switching_delay;
+
+  // TODO(honghaiz): Change the default to regular nomination.
+  // Default nomination mode if the remote does not support renomination.
+  NominationMode default_nomination_mode = NominationMode::SEMI_AGGRESSIVE;
+
+  // The interval in milliseconds at which ICE checks (STUN pings) will be sent
+  // for a candidate pair when it is both writable and receiving (strong
+  // connectivity). This parameter overrides the default value given by
+  // `STRONG_PING_INTERVAL` in p2ptransport.h if set.
+  absl::optional<int> ice_check_interval_strong_connectivity;
+  // The interval in milliseconds at which ICE checks (STUN pings) will be sent
+  // for a candidate pair when it is either not writable or not receiving (weak
+  // connectivity). This parameter overrides the default value given by
+  // `WEAK_PING_INTERVAL` in p2ptransport.h if set.
+  absl::optional<int> ice_check_interval_weak_connectivity;
+  // ICE checks (STUN pings) will not be sent at higher rate (lower interval)
+  // than this, no matter what other settings there are.
+  // Measure in milliseconds.
+  //
+  // Note that this parameter overrides both the above check intervals for
+  // candidate pairs with strong or weak connectivity, if either of the above
+  // interval is shorter than the min interval.
+  absl::optional<int> ice_check_min_interval;
+  // The min time period for which a candidate pair must wait for response to
+  // connectivity checks before it becomes unwritable. This parameter
+  // overrides the default value given by `CONNECTION_WRITE_CONNECT_TIMEOUT`
+  // in port.h if set, when determining the writability of a candidate pair.
+  absl::optional<int> ice_unwritable_timeout;
+
+  // The min number of connectivity checks that a candidate pair must sent
+  // without receiving response before it becomes unwritable. This parameter
+  // overrides the default value given by `CONNECTION_WRITE_CONNECT_FAILURES` in
+  // port.h if set, when determining the writability of a candidate pair.
+  absl::optional<int> ice_unwritable_min_checks;
+
+  // The min time period for which a candidate pair must wait for response to
+  // connectivity checks it becomes inactive. This parameter overrides the
+  // default value given by `CONNECTION_WRITE_TIMEOUT` in port.h if set, when
+  // determining the writability of a candidate pair.
+  absl::optional<int> ice_inactive_timeout;
+
+  // The interval in milliseconds at which STUN candidates will resend STUN
+  // binding requests to keep NAT bindings open.
+  absl::optional<int> stun_keepalive_interval;
+
+  absl::optional<rtc::AdapterType> network_preference;
+
+  webrtc::VpnPreference vpn_preference = webrtc::VpnPreference::kDefault;
+
+  IceConfig();
+  IceConfig(int receiving_timeout_ms,
+            int backup_connection_ping_interval,
+            ContinualGatheringPolicy gathering_policy,
+            bool prioritize_most_likely_candidate_pairs,
+            int stable_writable_connection_ping_interval_ms,
+            bool presume_writable_when_fully_relayed,
+            int regather_on_failed_networks_interval_ms,
+            int receiving_switching_delay_ms);
+  ~IceConfig();
+
+  // Helper getters for parameters with implementation-specific default value.
+  // By convention, parameters with default value are represented by
+  // absl::optional and setting a parameter to null restores its default value.
+  int receiving_timeout_or_default() const;
+  int backup_connection_ping_interval_or_default() const;
+  int stable_writable_connection_ping_interval_or_default() const;
+  int regather_on_failed_networks_interval_or_default() const;
+  int receiving_switching_delay_or_default() const;
+  int ice_check_interval_strong_connectivity_or_default() const;
+  int ice_check_interval_weak_connectivity_or_default() const;
+  int ice_check_min_interval_or_default() const;
+  int ice_unwritable_timeout_or_default() const;
+  int ice_unwritable_min_checks_or_default() const;
+  int ice_inactive_timeout_or_default() const;
+  int stun_keepalive_interval_or_default() const;
+};
+
+// TODO(zhihuang): Replace this with
+// PeerConnectionInterface::IceConnectionState.
+enum class IceTransportState {
+  STATE_INIT,
+  STATE_CONNECTING,  // Will enter this state once a connection is created
+  STATE_COMPLETED,
+  STATE_FAILED
+};
+
+// TODO(zhihuang): Remove this once it's no longer used in
+// remoting/protocol/libjingle_transport_factory.cc
+enum IceProtocolType {
+  ICEPROTO_RFC5245  // Standard RFC 5245 version of ICE.
+};
+
+// IceTransportInternal is an internal abstract class that does ICE.
+// Once the public interface is supported,
+// (https://www.w3.org/TR/webrtc/#rtcicetransport)
+// the IceTransportInterface will be split from this class.
+class RTC_EXPORT IceTransportInternal : public rtc::PacketTransportInternal {
+ public:
+  IceTransportInternal();
+  ~IceTransportInternal() override;
+
+  // TODO(bugs.webrtc.org/9308): Remove GetState once all uses have been
+  // migrated to GetIceTransportState.
+  virtual IceTransportState GetState() const = 0;
+  virtual webrtc::IceTransportState GetIceTransportState() const = 0;
+
+  virtual int component() const = 0;
+
+  virtual IceRole GetIceRole() const = 0;
+
+  virtual void SetIceRole(IceRole role) = 0;
+
+  virtual void SetIceTiebreaker(uint64_t tiebreaker) = 0;
+
+  // TODO(zhihuang): Remove this once it's no longer called in
+  // remoting/protocol/libjingle_transport_factory.cc
+  virtual void SetIceProtocolType(IceProtocolType type) {}
+
+  virtual void SetIceCredentials(absl::string_view ice_ufrag,
+                                 absl::string_view ice_pwd);
+
+  virtual void SetRemoteIceCredentials(absl::string_view ice_ufrag,
+                                       absl::string_view ice_pwd);
+
+  // The ufrag and pwd in `ice_params` must be set
+  // before candidate gathering can start.
+  virtual void SetIceParameters(const IceParameters& ice_params) = 0;
+
+  virtual void SetRemoteIceParameters(const IceParameters& ice_params) = 0;
+
+  virtual void SetRemoteIceMode(IceMode mode) = 0;
+
+  virtual void SetIceConfig(const IceConfig& config) = 0;
+
+  // Start gathering candidates if not already started, or if an ICE restart
+  // occurred.
+  virtual void MaybeStartGathering() = 0;
+
+  virtual void AddRemoteCandidate(const Candidate& candidate) = 0;
+
+  virtual void RemoveRemoteCandidate(const Candidate& candidate) = 0;
+
+  virtual void RemoveAllRemoteCandidates() = 0;
+
+  virtual IceGatheringState gathering_state() const = 0;
+
+  // Returns the current stats for this connection.
+  virtual bool GetStats(IceTransportStats* ice_transport_stats) = 0;
+
+  // Returns RTT estimate over the currently active connection, or an empty
+  // absl::optional if there is none.
+  virtual absl::optional<int> GetRttEstimate() = 0;
+
+  // TODO(qingsi): Remove this method once Chrome does not depend on it anymore.
+  virtual const Connection* selected_connection() const = 0;
+
+  // Returns the selected candidate pair, or an empty absl::optional if there is
+  // none.
+  virtual absl::optional<const CandidatePair> GetSelectedCandidatePair()
+      const = 0;
+
+  sigslot::signal1<IceTransportInternal*> SignalGatheringState;
+
+  // Handles sending and receiving of candidates.
+  sigslot::signal2<IceTransportInternal*, const Candidate&>
+      SignalCandidateGathered;
+
+  sigslot::signal2<IceTransportInternal*, const IceCandidateErrorEvent&>
+      SignalCandidateError;
+
+  sigslot::signal2<IceTransportInternal*, const Candidates&>
+      SignalCandidatesRemoved;
+
+  // Deprecated by PacketTransportInternal::SignalNetworkRouteChanged.
+  // This signal occurs when there is a change in the way that packets are
+  // being routed, i.e. to a different remote location. The candidate
+  // indicates where and how we are currently sending media.
+  // TODO(zhihuang): Update the Chrome remoting to use the new
+  // SignalNetworkRouteChanged.
+  sigslot::signal2<IceTransportInternal*, const Candidate&> SignalRouteChange;
+
+  sigslot::signal1<const cricket::CandidatePairChangeEvent&>
+      SignalCandidatePairChanged;
+
+  // Invoked when there is conflict in the ICE role between local and remote
+  // agents.
+  sigslot::signal1<IceTransportInternal*> SignalRoleConflict;
+
+  // Emitted whenever the transport state changed.
+  // TODO(bugs.webrtc.org/9308): Remove once all uses have migrated to the new
+  // IceTransportState.
+  sigslot::signal1<IceTransportInternal*> SignalStateChanged;
+
+  // Emitted whenever the new standards-compliant transport state changed.
+  sigslot::signal1<IceTransportInternal*> SignalIceTransportStateChanged;
+
+  // Invoked when the transport is being destroyed.
+  sigslot::signal1<IceTransportInternal*> SignalDestroyed;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_ICE_TRANSPORT_INTERNAL_H_
diff --git a/third_party/libwebrtc/p2p/base/mock_active_ice_controller.h b/third_party/libwebrtc/p2p/base/mock_active_ice_controller.h
new file mode 100644
index 0000000000..908967bd1d
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/mock_active_ice_controller.h
@@ -0,0 +1,89 @@
+/*
+ *  Copyright 2018 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_MOCK_ACTIVE_ICE_CONTROLLER_H_
+#define P2P_BASE_MOCK_ACTIVE_ICE_CONTROLLER_H_
+
+#include <memory>
+
+#include "p2p/base/active_ice_controller_factory_interface.h"
+#include "p2p/base/active_ice_controller_interface.h"
+#include "test/gmock.h"
+
+namespace cricket {
+
+class MockActiveIceController : public cricket::ActiveIceControllerInterface {
+ public:
+  explicit MockActiveIceController(
+      const cricket::ActiveIceControllerFactoryArgs& args) {}
+  ~MockActiveIceController() override = default;
+
+  MOCK_METHOD(void, SetIceConfig, (const cricket::IceConfig&), (override));
+  MOCK_METHOD(void,
+              OnConnectionAdded,
+              (const cricket::Connection*),
+              (override));
+  MOCK_METHOD(void,
+              OnConnectionSwitched,
+              (const cricket::Connection*),
+              (override));
+  MOCK_METHOD(void,
+              OnConnectionDestroyed,
+              (const cricket::Connection*),
+              (override));
+  MOCK_METHOD(void,
+              OnConnectionPinged,
+              (const cricket::Connection*),
+              (override));
+  MOCK_METHOD(void,
+              OnConnectionUpdated,
+              (const cricket::Connection*),
+              (override));
+  MOCK_METHOD(bool,
+              GetUseCandidateAttribute,
+              (const cricket::Connection*,
+               cricket::NominationMode,
+               cricket::IceMode),
+              (const, override));
+  MOCK_METHOD(void,
+              OnSortAndSwitchRequest,
+              (cricket::IceSwitchReason),
+              (override));
+  MOCK_METHOD(void,
+              OnImmediateSortAndSwitchRequest,
+              (cricket::IceSwitchReason),
+              (override));
+  MOCK_METHOD(bool,
+              OnImmediateSwitchRequest,
+              (cricket::IceSwitchReason, const cricket::Connection*),
+              (override));
+  MOCK_METHOD(const cricket::Connection*,
+              FindNextPingableConnection,
+              (),
+              (override));
+};
+
+class MockActiveIceControllerFactory
+    : public cricket::ActiveIceControllerFactoryInterface {
+ public:
+  ~MockActiveIceControllerFactory() override = default;
+
+  std::unique_ptr<cricket::ActiveIceControllerInterface> Create(
+      const cricket::ActiveIceControllerFactoryArgs& args) {
+    RecordActiveIceControllerCreated();
+    return std::make_unique<MockActiveIceController>(args);
+  }
+
+  MOCK_METHOD(void, RecordActiveIceControllerCreated, ());
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_MOCK_ACTIVE_ICE_CONTROLLER_H_
diff --git a/third_party/libwebrtc/p2p/base/mock_async_resolver.h b/third_party/libwebrtc/p2p/base/mock_async_resolver.h
new file mode 100644
index 0000000000..44164716b2
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/mock_async_resolver.h
@@ -0,0 +1,57 @@
+/*
+ *  Copyright 2018 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_MOCK_ASYNC_RESOLVER_H_
+#define P2P_BASE_MOCK_ASYNC_RESOLVER_H_
+
+#include "api/async_resolver_factory.h"
+#include "rtc_base/async_resolver_interface.h"
+#include "test/gmock.h"
+
+namespace rtc {
+
+using ::testing::_;
+using ::testing::InvokeWithoutArgs;
+
+class MockAsyncResolver : public AsyncResolverInterface {
+ public:
+  MockAsyncResolver() {
+    ON_CALL(*this, Start(_)).WillByDefault(InvokeWithoutArgs([this] {
+      SignalDone(this);
+    }));
+  }
+  ~MockAsyncResolver() = default;
+
+  MOCK_METHOD(void, Start, (const rtc::SocketAddress&), (override));
+  MOCK_METHOD(void, Start, (const rtc::SocketAddress&, int family), (override));
+  MOCK_METHOD(bool,
+              GetResolvedAddress,
+              (int family, SocketAddress* addr),
+              (const, override));
+  MOCK_METHOD(int, GetError, (), (const, override));
+
+  // Note that this won't delete the object like AsyncResolverInterface says in
+  // order to avoid sanitizer failures caused by this being a synchronous
+  // implementation. The test code should delete the object instead.
+  MOCK_METHOD(void, Destroy, (bool), (override));
+};
+
+}  // namespace rtc
+
+namespace webrtc {
+
+class MockAsyncResolverFactory : public AsyncResolverFactory {
+ public:
+  MOCK_METHOD(rtc::AsyncResolverInterface*, Create, (), (override));
+};
+
+}  // namespace webrtc
+
+#endif  // P2P_BASE_MOCK_ASYNC_RESOLVER_H_
diff --git a/third_party/libwebrtc/p2p/base/mock_dns_resolving_packet_socket_factory.h b/third_party/libwebrtc/p2p/base/mock_dns_resolving_packet_socket_factory.h
new file mode 100644
index 0000000000..8f18e9b0e1
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/mock_dns_resolving_packet_socket_factory.h
@@ -0,0 +1,53 @@
+/*
+ *  Copyright (c) 2022 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_MOCK_DNS_RESOLVING_PACKET_SOCKET_FACTORY_H_
+#define P2P_BASE_MOCK_DNS_RESOLVING_PACKET_SOCKET_FACTORY_H_
+
+#include <functional>
+#include <memory>
+
+#include "api/test/mock_async_dns_resolver.h"
+#include "p2p/base/basic_packet_socket_factory.h"
+
+namespace rtc {
+
+// A PacketSocketFactory implementation for tests that uses a mock DnsResolver
+// and allows setting expectations on the resolver and results.
+class MockDnsResolvingPacketSocketFactory : public BasicPacketSocketFactory {
+ public:
+  using Expectations = std::function<void(webrtc::MockAsyncDnsResolver*,
+                                          webrtc::MockAsyncDnsResolverResult*)>;
+
+  explicit MockDnsResolvingPacketSocketFactory(SocketFactory* socket_factory)
+      : BasicPacketSocketFactory(socket_factory) {}
+
+  std::unique_ptr<webrtc::AsyncDnsResolverInterface> CreateAsyncDnsResolver()
+      override {
+    std::unique_ptr<webrtc::MockAsyncDnsResolver> resolver =
+        std::make_unique<webrtc::MockAsyncDnsResolver>();
+    if (expectations_) {
+      expectations_(resolver.get(), &resolver_result_);
+    }
+    return resolver;
+  }
+
+  void SetExpectations(Expectations expectations) {
+    expectations_ = expectations;
+  }
+
+ private:
+  webrtc::MockAsyncDnsResolverResult resolver_result_;
+  Expectations expectations_;
+};
+
+}  // namespace rtc
+
+#endif  // P2P_BASE_MOCK_DNS_RESOLVING_PACKET_SOCKET_FACTORY_H_
diff --git a/third_party/libwebrtc/p2p/base/mock_ice_agent.h b/third_party/libwebrtc/p2p/base/mock_ice_agent.h
new file mode 100644
index 0000000000..a1c0ebffbf
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/mock_ice_agent.h
@@ -0,0 +1,50 @@
+/*
+ *  Copyright 2018 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_MOCK_ICE_AGENT_H_
+#define P2P_BASE_MOCK_ICE_AGENT_H_
+
+#include <vector>
+
+#include "p2p/base/connection.h"
+#include "p2p/base/ice_agent_interface.h"
+#include "p2p/base/ice_switch_reason.h"
+#include "p2p/base/transport_description.h"
+#include "test/gmock.h"
+
+namespace cricket {
+
+class MockIceAgent : public IceAgentInterface {
+ public:
+  ~MockIceAgent() override = default;
+
+  MOCK_METHOD(int64_t, GetLastPingSentMs, (), (override, const));
+  MOCK_METHOD(IceRole, GetIceRole, (), (override, const));
+  MOCK_METHOD(void, OnStartedPinging, (), (override));
+  MOCK_METHOD(void, UpdateConnectionStates, (), (override));
+  MOCK_METHOD(void, UpdateState, (), (override));
+  MOCK_METHOD(void,
+              ForgetLearnedStateForConnections,
+              (rtc::ArrayView<const Connection* const>),
+              (override));
+  MOCK_METHOD(void, SendPingRequest, (const Connection*), (override));
+  MOCK_METHOD(void,
+              SwitchSelectedConnection,
+              (const Connection*, IceSwitchReason),
+              (override));
+  MOCK_METHOD(bool,
+              PruneConnections,
+              (rtc::ArrayView<const Connection* const>),
+              (override));
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_MOCK_ICE_AGENT_H_
diff --git a/third_party/libwebrtc/p2p/base/mock_ice_controller.h b/third_party/libwebrtc/p2p/base/mock_ice_controller.h
new file mode 100644
index 0000000000..bde9254e7d
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/mock_ice_controller.h
@@ -0,0 +1,90 @@
+/*
+ *  Copyright 2018 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_MOCK_ICE_CONTROLLER_H_
+#define P2P_BASE_MOCK_ICE_CONTROLLER_H_
+
+#include <memory>
+#include <vector>
+
+#include "p2p/base/ice_controller_factory_interface.h"
+#include "p2p/base/ice_controller_interface.h"
+#include "test/gmock.h"
+
+namespace cricket {
+
+class MockIceController : public cricket::IceControllerInterface {
+ public:
+  explicit MockIceController(const cricket::IceControllerFactoryArgs& args) {}
+  ~MockIceController() override = default;
+
+  MOCK_METHOD(void, SetIceConfig, (const cricket::IceConfig&), (override));
+  MOCK_METHOD(void,
+              SetSelectedConnection,
+              (const cricket::Connection*),
+              (override));
+  MOCK_METHOD(void, AddConnection, (const cricket::Connection*), (override));
+  MOCK_METHOD(void,
+              OnConnectionDestroyed,
+              (const cricket::Connection*),
+              (override));
+  MOCK_METHOD(rtc::ArrayView<const cricket::Connection*>,
+              connections,
+              (),
+              (const, override));
+  MOCK_METHOD(bool, HasPingableConnection, (), (const, override));
+  MOCK_METHOD(cricket::IceControllerInterface::PingResult,
+              SelectConnectionToPing,
+              (int64_t),
+              (override));
+  MOCK_METHOD(bool,
+              GetUseCandidateAttr,
+              (const cricket::Connection*,
+               cricket::NominationMode,
+               cricket::IceMode),
+              (const, override));
+  MOCK_METHOD(const cricket::Connection*,
+              FindNextPingableConnection,
+              (),
+              (override));
+  MOCK_METHOD(void,
+              MarkConnectionPinged,
+              (const cricket::Connection*),
+              (override));
+  MOCK_METHOD(cricket::IceControllerInterface::SwitchResult,
+              ShouldSwitchConnection,
+              (cricket::IceSwitchReason, const cricket::Connection*),
+              (override));
+  MOCK_METHOD(cricket::IceControllerInterface::SwitchResult,
+              SortAndSwitchConnection,
+              (cricket::IceSwitchReason),
+              (override));
+  MOCK_METHOD(std::vector<const cricket::Connection*>,
+              PruneConnections,
+              (),
+              (override));
+};
+
+class MockIceControllerFactory : public cricket::IceControllerFactoryInterface {
+ public:
+  ~MockIceControllerFactory() override = default;
+
+  std::unique_ptr<cricket::IceControllerInterface> Create(
+      const cricket::IceControllerFactoryArgs& args) override {
+    RecordIceControllerCreated();
+    return std::make_unique<MockIceController>(args);
+  }
+
+  MOCK_METHOD(void, RecordIceControllerCreated, ());
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_MOCK_ICE_CONTROLLER_H_
diff --git a/third_party/libwebrtc/p2p/base/mock_ice_transport.h b/third_party/libwebrtc/p2p/base/mock_ice_transport.h
new file mode 100644
index 0000000000..ef6bdce3c0
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/mock_ice_transport.h
@@ -0,0 +1,90 @@
+/*
+ *  Copyright 2016 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_MOCK_ICE_TRANSPORT_H_
+#define P2P_BASE_MOCK_ICE_TRANSPORT_H_
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "p2p/base/ice_transport_internal.h"
+#include "rtc_base/gunit.h"
+#include "test/gmock.h"
+
+using ::testing::_;
+using ::testing::Return;
+
+namespace cricket {
+
+// Used in Chromium/remoting/protocol/channel_socket_adapter_unittest.cc
+class MockIceTransport : public IceTransportInternal {
+ public:
+  MockIceTransport() {
+    SignalReadyToSend(this);
+    SignalWritableState(this);
+  }
+
+  MOCK_METHOD(int,
+              SendPacket,
+              (const char* data,
+               size_t len,
+               const rtc::PacketOptions& options,
+               int flags),
+              (override));
+  MOCK_METHOD(int, SetOption, (rtc::Socket::Option opt, int value), (override));
+  MOCK_METHOD(int, GetError, (), (override));
+  MOCK_METHOD(cricket::IceRole, GetIceRole, (), (const, override));
+  MOCK_METHOD(bool,
+              GetStats,
+              (cricket::IceTransportStats * ice_transport_stats),
+              (override));
+
+  IceTransportState GetState() const override {
+    return IceTransportState::STATE_INIT;
+  }
+  webrtc::IceTransportState GetIceTransportState() const override {
+    return webrtc::IceTransportState::kNew;
+  }
+
+  const std::string& transport_name() const override { return transport_name_; }
+  int component() const override { return 0; }
+  void SetIceRole(IceRole role) override {}
+  void SetIceTiebreaker(uint64_t tiebreaker) override {}
+  // The ufrag and pwd in `ice_params` must be set
+  // before candidate gathering can start.
+  void SetIceParameters(const IceParameters& ice_params) override {}
+  void SetRemoteIceParameters(const IceParameters& ice_params) override {}
+  void SetRemoteIceMode(IceMode mode) override {}
+  void SetIceConfig(const IceConfig& config) override {}
+  absl::optional<int> GetRttEstimate() override { return absl::nullopt; }
+  const Connection* selected_connection() const override { return nullptr; }
+  absl::optional<const CandidatePair> GetSelectedCandidatePair()
+      const override {
+    return absl::nullopt;
+  }
+  void MaybeStartGathering() override {}
+  void AddRemoteCandidate(const Candidate& candidate) override {}
+  void RemoveRemoteCandidate(const Candidate& candidate) override {}
+  void RemoveAllRemoteCandidates() override {}
+  IceGatheringState gathering_state() const override {
+    return IceGatheringState::kIceGatheringComplete;
+  }
+
+  bool receiving() const override { return true; }
+  bool writable() const override { return true; }
+
+ private:
+  std::string transport_name_;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_MOCK_ICE_TRANSPORT_H_
diff --git a/third_party/libwebrtc/p2p/base/p2p_constants.cc b/third_party/libwebrtc/p2p/base/p2p_constants.cc
new file mode 100644
index 0000000000..3414939a6f
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/p2p_constants.cc
@@ -0,0 +1,75 @@
+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/p2p_constants.h"
+
+namespace cricket {
+
+const char CN_AUDIO[] = "audio";
+const char CN_VIDEO[] = "video";
+const char CN_DATA[] = "data";
+const char CN_OTHER[] = "main";
+
+const char GROUP_TYPE_BUNDLE[] = "BUNDLE";
+
+// Minimum ufrag length is 4 characters as per RFC5245.
+const int ICE_UFRAG_LENGTH = 4;
+// Minimum password length of 22 characters as per RFC5245. We chose 24 because
+// some internal systems expect password to be multiple of 4.
+const int ICE_PWD_LENGTH = 24;
+const size_t ICE_UFRAG_MIN_LENGTH = 4;
+const size_t ICE_PWD_MIN_LENGTH = 22;
+const size_t ICE_UFRAG_MAX_LENGTH = 256;
+const size_t ICE_PWD_MAX_LENGTH = 256;
+
+// This is media-specific, so might belong
+// somewhere like media/base/mediaconstants.h
+const int ICE_CANDIDATE_COMPONENT_RTP = 1;
+const int ICE_CANDIDATE_COMPONENT_RTCP = 2;
+const int ICE_CANDIDATE_COMPONENT_DEFAULT = 1;
+
+// From RFC 4145, SDP setup attribute values.
+const char CONNECTIONROLE_ACTIVE_STR[] = "active";
+const char CONNECTIONROLE_PASSIVE_STR[] = "passive";
+const char CONNECTIONROLE_ACTPASS_STR[] = "actpass";
+const char CONNECTIONROLE_HOLDCONN_STR[] = "holdconn";
+
+const char LOCAL_TLD[] = ".local";
+
+const int MIN_CHECK_RECEIVING_INTERVAL = 50;
+const int RECEIVING_TIMEOUT = MIN_CHECK_RECEIVING_INTERVAL * 50;
+const int RECEIVING_SWITCHING_DELAY = 1000;
+const int BACKUP_CONNECTION_PING_INTERVAL = 25 * 1000;
+const int REGATHER_ON_FAILED_NETWORKS_INTERVAL = 5 * 60 * 1000;
+
+// When the socket is unwritable, we will use 10 Kbps (ignoring IP+UDP headers)
+// for pinging. When the socket is writable, we will use only 1 Kbps because we
+// don't want to degrade the quality on a modem.  These numbers should work well
+// on a 28.8K modem, which is the slowest connection on which the voice quality
+// is reasonable at all.
+const int STUN_PING_PACKET_SIZE = 60 * 8;
+const int STRONG_PING_INTERVAL = 1000 * STUN_PING_PACKET_SIZE / 1000;  // 480ms.
+const int WEAK_PING_INTERVAL = 1000 * STUN_PING_PACKET_SIZE / 10000;   // 48ms.
+const int WEAK_OR_STABILIZING_WRITABLE_CONNECTION_PING_INTERVAL = 900;
+const int STRONG_AND_STABLE_WRITABLE_CONNECTION_PING_INTERVAL = 2500;
+const int CONNECTION_WRITE_CONNECT_TIMEOUT = 5 * 1000;  // 5 seconds
+const uint32_t CONNECTION_WRITE_CONNECT_FAILURES = 5;   // 5 pings
+
+const int STUN_KEEPALIVE_INTERVAL = 10 * 1000;  // 10 seconds
+
+const int MIN_CONNECTION_LIFETIME = 10 * 1000;          // 10 seconds.
+const int DEAD_CONNECTION_RECEIVE_TIMEOUT = 30 * 1000;  // 30 seconds.
+const int WEAK_CONNECTION_RECEIVE_TIMEOUT = 2500;       // 2.5 seconds
+const int CONNECTION_WRITE_TIMEOUT = 15 * 1000;         // 15 seconds
+// There is no harm to keep this value high other than a small amount
+// of increased memory, but in some networks (2G), we observe up to 60s RTTs.
+const int CONNECTION_RESPONSE_TIMEOUT = 60 * 1000;  // 60 seconds
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/p2p_constants.h b/third_party/libwebrtc/p2p/base/p2p_constants.h
new file mode 100644
index 0000000000..d51ee17a07
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/p2p_constants.h
@@ -0,0 +1,114 @@
+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_P2P_CONSTANTS_H_
+#define P2P_BASE_P2P_CONSTANTS_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "rtc_base/system/rtc_export.h"
+
+namespace cricket {
+
+// CN_ == "content name".  When we initiate a session, we choose the
+// name, and when we receive a Gingle session, we provide default
+// names (since Gingle has no content names).  But when we receive a
+// Jingle call, the content name can be anything, so don't rely on
+// these values being the same as the ones received.
+extern const char CN_AUDIO[];
+extern const char CN_VIDEO[];
+extern const char CN_DATA[];
+extern const char CN_OTHER[];
+
+// GN stands for group name
+extern const char GROUP_TYPE_BUNDLE[];
+
+RTC_EXPORT extern const int ICE_UFRAG_LENGTH;
+RTC_EXPORT extern const int ICE_PWD_LENGTH;
+extern const size_t ICE_UFRAG_MIN_LENGTH;
+extern const size_t ICE_PWD_MIN_LENGTH;
+extern const size_t ICE_UFRAG_MAX_LENGTH;
+extern const size_t ICE_PWD_MAX_LENGTH;
+
+RTC_EXPORT extern const int ICE_CANDIDATE_COMPONENT_RTP;
+RTC_EXPORT extern const int ICE_CANDIDATE_COMPONENT_RTCP;
+RTC_EXPORT extern const int ICE_CANDIDATE_COMPONENT_DEFAULT;
+
+// RFC 4145, SDP setup attribute values.
+extern const char CONNECTIONROLE_ACTIVE_STR[];
+extern const char CONNECTIONROLE_PASSIVE_STR[];
+extern const char CONNECTIONROLE_ACTPASS_STR[];
+extern const char CONNECTIONROLE_HOLDCONN_STR[];
+
+// RFC 6762, the .local pseudo-top-level domain used for mDNS names.
+extern const char LOCAL_TLD[];
+
+// Constants for time intervals are in milliseconds unless otherwise stated.
+//
+// Most of the following constants are the default values of IceConfig
+// paramters. See IceConfig for detailed definition.
+//
+// Default value of IceConfig.receiving_timeout.
+extern const int RECEIVING_TIMEOUT;
+// Default value IceConfig.ice_check_min_interval.
+extern const int MIN_CHECK_RECEIVING_INTERVAL;
+// The next two ping intervals are at the ICE transport level.
+//
+// STRONG_PING_INTERVAL is applied when the selected connection is both
+// writable and receiving.
+//
+// Default value of IceConfig.ice_check_interval_strong_connectivity.
+extern const int STRONG_PING_INTERVAL;
+// WEAK_PING_INTERVAL is applied when the selected connection is either
+// not writable or not receiving.
+//
+// Defaul value of IceConfig.ice_check_interval_weak_connectivity.
+extern const int WEAK_PING_INTERVAL;
+// The next two ping intervals are at the candidate pair level.
+//
+// Writable candidate pairs are pinged at a slower rate once they are stabilized
+// and the channel is strongly connected.
+extern const int STRONG_AND_STABLE_WRITABLE_CONNECTION_PING_INTERVAL;
+// Writable candidate pairs are pinged at a faster rate while the connections
+// are stabilizing or the channel is weak.
+extern const int WEAK_OR_STABILIZING_WRITABLE_CONNECTION_PING_INTERVAL;
+// Default value of IceConfig.backup_connection_ping_interval
+extern const int BACKUP_CONNECTION_PING_INTERVAL;
+// Defualt value of IceConfig.receiving_switching_delay.
+extern const int RECEIVING_SWITCHING_DELAY;
+// Default value of IceConfig.regather_on_failed_networks_interval.
+extern const int REGATHER_ON_FAILED_NETWORKS_INTERVAL;
+// Default vaule of IceConfig.ice_unwritable_timeout.
+extern const int CONNECTION_WRITE_CONNECT_TIMEOUT;
+// Default vaule of IceConfig.ice_unwritable_min_checks.
+extern const uint32_t CONNECTION_WRITE_CONNECT_FAILURES;
+// Default value of IceConfig.ice_inactive_timeout;
+extern const int CONNECTION_WRITE_TIMEOUT;
+// Default value of IceConfig.stun_keepalive_interval;
+extern const int STUN_KEEPALIVE_INTERVAL;
+
+// The following constants are used at the candidate pair level to determine the
+// state of a candidate pair.
+//
+// The timeout duration when a connection does not receive anything.
+extern const int WEAK_CONNECTION_RECEIVE_TIMEOUT;
+// A connection will be declared dead if it has not received anything for this
+// long.
+extern const int DEAD_CONNECTION_RECEIVE_TIMEOUT;
+// This is the length of time that we wait for a ping response to come back.
+extern const int CONNECTION_RESPONSE_TIMEOUT;
+// The minimum time we will wait before destroying a connection after creating
+// it.
+extern const int MIN_CONNECTION_LIFETIME;
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_P2P_CONSTANTS_H_
diff --git a/third_party/libwebrtc/p2p/base/p2p_transport_channel.cc b/third_party/libwebrtc/p2p/base/p2p_transport_channel.cc
new file mode 100644
index 0000000000..15b1cf6f87
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/p2p_transport_channel.cc
@@ -0,0 +1,2636 @@
+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/p2p_transport_channel.h"
+
+#include <errno.h>
+#include <stdlib.h>
+
+#include <algorithm>
+#include <functional>
+#include <memory>
+#include <set>
+#include <utility>
+
+#include "absl/algorithm/container.h"
+#include "absl/memory/memory.h"
+#include "absl/strings/match.h"
+#include "absl/strings/string_view.h"
+#include "api/async_dns_resolver.h"
+#include "api/candidate.h"
+#include "api/field_trials_view.h"
+#include "api/units/time_delta.h"
+#include "logging/rtc_event_log/ice_logger.h"
+#include "p2p/base/basic_async_resolver_factory.h"
+#include "p2p/base/basic_ice_controller.h"
+#include "p2p/base/connection.h"
+#include "p2p/base/connection_info.h"
+#include "p2p/base/port.h"
+#include "p2p/base/wrapping_active_ice_controller.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/crc32.h"
+#include "rtc_base/experiments/struct_parameters_parser.h"
+#include "rtc_base/ip_address.h"
+#include "rtc_base/logging.h"
+#include "rtc_base/net_helper.h"
+#include "rtc_base/network.h"
+#include "rtc_base/network_constants.h"
+#include "rtc_base/string_encode.h"
+#include "rtc_base/third_party/sigslot/sigslot.h"
+#include "rtc_base/time_utils.h"
+#include "rtc_base/trace_event.h"
+#include "system_wrappers/include/metrics.h"
+
+namespace {
+
+cricket::PortInterface::CandidateOrigin GetOrigin(
+    cricket::PortInterface* port,
+    cricket::PortInterface* origin_port) {
+  if (!origin_port)
+    return cricket::PortInterface::ORIGIN_MESSAGE;
+  else if (port == origin_port)
+    return cricket::PortInterface::ORIGIN_THIS_PORT;
+  else
+    return cricket::PortInterface::ORIGIN_OTHER_PORT;
+}
+
+uint32_t GetWeakPingIntervalInFieldTrial(
+    const webrtc::FieldTrialsView* field_trials) {
+  if (field_trials != nullptr) {
+    uint32_t weak_ping_interval =
+        ::strtoul(field_trials->Lookup("WebRTC-StunInterPacketDelay").c_str(),
+                  nullptr, 10);
+    if (weak_ping_interval) {
+      return static_cast<int>(weak_ping_interval);
+    }
+  }
+  return cricket::WEAK_PING_INTERVAL;
+}
+
+rtc::RouteEndpoint CreateRouteEndpointFromCandidate(
+    bool local,
+    const cricket::Candidate& candidate,
+    bool uses_turn) {
+  auto adapter_type = candidate.network_type();
+  if (!local && adapter_type == rtc::ADAPTER_TYPE_UNKNOWN) {
+    bool vpn;
+    std::tie(adapter_type, vpn) =
+        rtc::Network::GuessAdapterFromNetworkCost(candidate.network_cost());
+  }
+
+  // TODO(bugs.webrtc.org/9446) : Rewrite if information about remote network
+  // adapter becomes available. The implication of this implementation is that
+  // we will only ever report 1 adapter per type. In practice this is probably
+  // fine, since the endpoint also contains network-id.
+  uint16_t adapter_id = static_cast<int>(adapter_type);
+  return rtc::RouteEndpoint(adapter_type, adapter_id, candidate.network_id(),
+                            uses_turn);
+}
+
+bool UseActiveIceControllerFieldTrialEnabled(
+    const webrtc::FieldTrialsView* field_trials) {
+  // Feature to refactor ICE controller and enable active ICE controllers.
+  // Field trial key reserved in bugs.webrtc.org/14367
+  return field_trials &&
+         field_trials->IsEnabled("WebRTC-UseActiveIceController");
+}
+
+using ::webrtc::RTCError;
+using ::webrtc::RTCErrorType;
+using ::webrtc::SafeTask;
+using ::webrtc::TimeDelta;
+
+}  // unnamed namespace
+
+namespace cricket {
+
+bool IceCredentialsChanged(absl::string_view old_ufrag,
+                           absl::string_view old_pwd,
+                           absl::string_view new_ufrag,
+                           absl::string_view new_pwd) {
+  // The standard (RFC 5245 Section 9.1.1.1) says that ICE restarts MUST change
+  // both the ufrag and password. However, section 9.2.1.1 says changing the
+  // ufrag OR password indicates an ICE restart. So, to keep compatibility with
+  // endpoints that only change one, we'll treat this as an ICE restart.
+  return (old_ufrag != new_ufrag) || (old_pwd != new_pwd);
+}
+
+std::unique_ptr<P2PTransportChannel> P2PTransportChannel::Create(
+    absl::string_view transport_name,
+    int component,
+    webrtc::IceTransportInit init) {
+  if (init.async_resolver_factory()) {
+    return absl::WrapUnique(new P2PTransportChannel(
+        transport_name, component, init.port_allocator(), nullptr,
+        std::make_unique<webrtc::WrappingAsyncDnsResolverFactory>(
+            init.async_resolver_factory()),
+        init.event_log(), init.ice_controller_factory(),
+        init.active_ice_controller_factory(), init.field_trials()));
+  } else {
+    return absl::WrapUnique(new P2PTransportChannel(
+        transport_name, component, init.port_allocator(),
+        init.async_dns_resolver_factory(), nullptr, init.event_log(),
+        init.ice_controller_factory(), init.active_ice_controller_factory(),
+        init.field_trials()));
+  }
+}
+
+P2PTransportChannel::P2PTransportChannel(
+    absl::string_view transport_name,
+    int component,
+    PortAllocator* allocator,
+    const webrtc::FieldTrialsView* field_trials)
+    : P2PTransportChannel(transport_name,
+                          component,
+                          allocator,
+                          /* async_dns_resolver_factory= */ nullptr,
+                          /* owned_dns_resolver_factory= */ nullptr,
+                          /* event_log= */ nullptr,
+                          /* ice_controller_factory= */ nullptr,
+                          /* active_ice_controller_factory= */ nullptr,
+                          field_trials) {}
+
+// Private constructor, called from Create()
+P2PTransportChannel::P2PTransportChannel(
+    absl::string_view transport_name,
+    int component,
+    PortAllocator* allocator,
+    webrtc::AsyncDnsResolverFactoryInterface* async_dns_resolver_factory,
+    std::unique_ptr<webrtc::AsyncDnsResolverFactoryInterface>
+        owned_dns_resolver_factory,
+    webrtc::RtcEventLog* event_log,
+    IceControllerFactoryInterface* ice_controller_factory,
+    ActiveIceControllerFactoryInterface* active_ice_controller_factory,
+    const webrtc::FieldTrialsView* field_trials)
+    : transport_name_(transport_name),
+      component_(component),
+      allocator_(allocator),
+      // If owned_dns_resolver_factory is given, async_dns_resolver_factory is
+      // ignored.
+      async_dns_resolver_factory_(owned_dns_resolver_factory
+                                      ? owned_dns_resolver_factory.get()
+                                      : async_dns_resolver_factory),
+      owned_dns_resolver_factory_(std::move(owned_dns_resolver_factory)),
+      network_thread_(rtc::Thread::Current()),
+      incoming_only_(false),
+      error_(0),
+      sort_dirty_(false),
+      remote_ice_mode_(ICEMODE_FULL),
+      ice_role_(ICEROLE_UNKNOWN),
+      tiebreaker_(0),
+      gathering_state_(kIceGatheringNew),
+      weak_ping_interval_(GetWeakPingIntervalInFieldTrial(field_trials)),
+      config_(RECEIVING_TIMEOUT,
+              BACKUP_CONNECTION_PING_INTERVAL,
+              GATHER_ONCE /* continual_gathering_policy */,
+              false /* prioritize_most_likely_candidate_pairs */,
+              STRONG_AND_STABLE_WRITABLE_CONNECTION_PING_INTERVAL,
+              true /* presume_writable_when_fully_relayed */,
+              REGATHER_ON_FAILED_NETWORKS_INTERVAL,
+              RECEIVING_SWITCHING_DELAY) {
+  TRACE_EVENT0("webrtc", "P2PTransportChannel::P2PTransportChannel");
+  RTC_DCHECK(allocator_ != nullptr);
+  // Validate IceConfig even for mostly built-in constant default values in case
+  // we change them.
+  RTC_DCHECK(ValidateIceConfig(config_).ok());
+  webrtc::BasicRegatheringController::Config regathering_config;
+  regathering_config.regather_on_failed_networks_interval =
+      config_.regather_on_failed_networks_interval_or_default();
+  regathering_controller_ =
+      std::make_unique<webrtc::BasicRegatheringController>(
+          regathering_config, this, network_thread_);
+  // We populate the change in the candidate filter to the session taken by
+  // the transport.
+  allocator_->SignalCandidateFilterChanged.connect(
+      this, &P2PTransportChannel::OnCandidateFilterChanged);
+  ice_event_log_.set_event_log(event_log);
+
+  ParseFieldTrials(field_trials);
+
+  IceControllerFactoryArgs args{
+      [this] { return GetState(); }, [this] { return GetIceRole(); },
+      [this](const Connection* connection) {
+        return IsPortPruned(connection->port()) ||
+               IsRemoteCandidatePruned(connection->remote_candidate());
+      },
+      &ice_field_trials_,
+      field_trials ? field_trials->Lookup("WebRTC-IceControllerFieldTrials")
+                   : ""};
+  ice_adapter_ = std::make_unique<IceControllerAdapter>(
+      args, ice_controller_factory, active_ice_controller_factory, field_trials,
+      /* transport= */ this);
+}
+
+P2PTransportChannel::~P2PTransportChannel() {
+  TRACE_EVENT0("webrtc", "P2PTransportChannel::~P2PTransportChannel");
+  RTC_DCHECK_RUN_ON(network_thread_);
+  std::vector<Connection*> copy(connections().begin(), connections().end());
+  for (Connection* connection : copy) {
+    connection->SignalDestroyed.disconnect(this);
+    RemoveConnection(connection);
+    connection->Destroy();
+  }
+  resolvers_.clear();
+}
+
+// Add the allocator session to our list so that we know which sessions
+// are still active.
+void P2PTransportChannel::AddAllocatorSession(
+    std::unique_ptr<PortAllocatorSession> session) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+
+  session->set_generation(static_cast<uint32_t>(allocator_sessions_.size()));
+  session->SignalPortReady.connect(this, &P2PTransportChannel::OnPortReady);
+  session->SignalPortsPruned.connect(this, &P2PTransportChannel::OnPortsPruned);
+  session->SignalCandidatesReady.connect(
+      this, &P2PTransportChannel::OnCandidatesReady);
+  session->SignalCandidateError.connect(this,
+                                        &P2PTransportChannel::OnCandidateError);
+  session->SignalCandidatesRemoved.connect(
+      this, &P2PTransportChannel::OnCandidatesRemoved);
+  session->SignalCandidatesAllocationDone.connect(
+      this, &P2PTransportChannel::OnCandidatesAllocationDone);
+  if (!allocator_sessions_.empty()) {
+    allocator_session()->PruneAllPorts();
+  }
+  allocator_sessions_.push_back(std::move(session));
+  regathering_controller_->set_allocator_session(allocator_session());
+
+  // We now only want to apply new candidates that we receive to the ports
+  // created by this new session because these are replacing those of the
+  // previous sessions.
+  PruneAllPorts();
+}
+
+void P2PTransportChannel::AddConnection(Connection* connection) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  connection->set_receiving_timeout(config_.receiving_timeout);
+  connection->set_unwritable_timeout(config_.ice_unwritable_timeout);
+  connection->set_unwritable_min_checks(config_.ice_unwritable_min_checks);
+  connection->set_inactive_timeout(config_.ice_inactive_timeout);
+  connection->SignalReadPacket.connect(this,
+                                       &P2PTransportChannel::OnReadPacket);
+  connection->SignalReadyToSend.connect(this,
+                                        &P2PTransportChannel::OnReadyToSend);
+  connection->SignalStateChange.connect(
+      this, &P2PTransportChannel::OnConnectionStateChange);
+  connection->SignalDestroyed.connect(
+      this, &P2PTransportChannel::OnConnectionDestroyed);
+  connection->SignalNominated.connect(this, &P2PTransportChannel::OnNominated);
+
+  had_connection_ = true;
+
+  connection->set_ice_event_log(&ice_event_log_);
+  connection->SetIceFieldTrials(&ice_field_trials_);
+  LogCandidatePairConfig(connection,
+                         webrtc::IceCandidatePairConfigType::kAdded);
+
+  connections_.push_back(connection);
+  ice_adapter_->OnConnectionAdded(connection);
+}
+
+// TODO(bugs.webrtc.org/14367) remove once refactor lands.
+bool P2PTransportChannel::MaybeSwitchSelectedConnection(
+    const Connection* new_connection,
+    IceSwitchReason reason) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+
+  return MaybeSwitchSelectedConnection(
+      reason,
+      ice_adapter_->LegacyShouldSwitchConnection(reason, new_connection));
+}
+
+// TODO(bugs.webrtc.org/14367) remove once refactor lands.
+bool P2PTransportChannel::MaybeSwitchSelectedConnection(
+    IceSwitchReason reason,
+    IceControllerInterface::SwitchResult result) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (result.connection.has_value()) {
+    RTC_LOG(LS_INFO) << "Switching selected connection due to: "
+                     << IceSwitchReasonToString(reason);
+    SwitchSelectedConnection(FromIceController(*result.connection), reason);
+  }
+
+  if (result.recheck_event.has_value()) {
+    // If we do not switch to the connection because it missed the receiving
+    // threshold, the new connection is in a better receiving state than the
+    // currently selected connection. So we need to re-check whether it needs
+    // to be switched at a later time.
+    network_thread_->PostDelayedTask(
+        SafeTask(task_safety_.flag(),
+                 [this, reason = result.recheck_event->reason]() {
+                   SortConnectionsAndUpdateState(reason);
+                 }),
+        TimeDelta::Millis(result.recheck_event->recheck_delay_ms));
+  }
+
+  for (const auto* con : result.connections_to_forget_state_on) {
+    FromIceController(con)->ForgetLearnedState();
+  }
+
+  return result.connection.has_value();
+}
+
+void P2PTransportChannel::ForgetLearnedStateForConnections(
+    rtc::ArrayView<const Connection* const> connections) {
+  for (const Connection* con : connections) {
+    FromIceController(con)->ForgetLearnedState();
+  }
+}
+
+void P2PTransportChannel::SetIceRole(IceRole ice_role) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (ice_role_ != ice_role) {
+    ice_role_ = ice_role;
+    for (PortInterface* port : ports_) {
+      port->SetIceRole(ice_role);
+    }
+    // Update role on pruned ports as well, because they may still have
+    // connections alive that should be using the correct role.
+    for (PortInterface* port : pruned_ports_) {
+      port->SetIceRole(ice_role);
+    }
+  }
+}
+
+IceRole P2PTransportChannel::GetIceRole() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return ice_role_;
+}
+
+void P2PTransportChannel::SetIceTiebreaker(uint64_t tiebreaker) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (!ports_.empty() || !pruned_ports_.empty()) {
+    RTC_LOG(LS_ERROR)
+        << "Attempt to change tiebreaker after Port has been allocated.";
+    return;
+  }
+
+  tiebreaker_ = tiebreaker;
+}
+
+IceTransportState P2PTransportChannel::GetState() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return state_;
+}
+
+webrtc::IceTransportState P2PTransportChannel::GetIceTransportState() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return standardized_state_;
+}
+
+const std::string& P2PTransportChannel::transport_name() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return transport_name_;
+}
+
+int P2PTransportChannel::component() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return component_;
+}
+
+bool P2PTransportChannel::writable() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return writable_;
+}
+
+bool P2PTransportChannel::receiving() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return receiving_;
+}
+
+IceGatheringState P2PTransportChannel::gathering_state() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return gathering_state_;
+}
+
+absl::optional<int> P2PTransportChannel::GetRttEstimate() {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (selected_connection_ != nullptr &&
+      selected_connection_->rtt_samples() > 0) {
+    return selected_connection_->rtt();
+  } else {
+    return absl::nullopt;
+  }
+}
+
+absl::optional<const CandidatePair>
+P2PTransportChannel::GetSelectedCandidatePair() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (selected_connection_ == nullptr) {
+    return absl::nullopt;
+  }
+
+  CandidatePair pair;
+  pair.local = SanitizeLocalCandidate(selected_connection_->local_candidate());
+  pair.remote =
+      SanitizeRemoteCandidate(selected_connection_->remote_candidate());
+  return pair;
+}
+
+// A channel is considered ICE completed once there is at most one active
+// connection per network and at least one active connection.
+IceTransportState P2PTransportChannel::ComputeState() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (!had_connection_) {
+    return IceTransportState::STATE_INIT;
+  }
+
+  std::vector<Connection*> active_connections;
+  for (Connection* connection : connections()) {
+    if (connection->active()) {
+      active_connections.push_back(connection);
+    }
+  }
+  if (active_connections.empty()) {
+    return IceTransportState::STATE_FAILED;
+  }
+
+  std::set<const rtc::Network*> networks;
+  for (Connection* connection : active_connections) {
+    const rtc::Network* network = connection->network();
+    if (networks.find(network) == networks.end()) {
+      networks.insert(network);
+    } else {
+      RTC_LOG(LS_VERBOSE) << ToString()
+                          << ": Ice not completed yet for this channel as "
+                          << network->ToString()
+                          << " has more than 1 connection.";
+      return IceTransportState::STATE_CONNECTING;
+    }
+  }
+
+  ice_event_log_.DumpCandidatePairDescriptionToMemoryAsConfigEvents();
+  return IceTransportState::STATE_COMPLETED;
+}
+
+// Compute the current RTCIceTransportState as described in
+// https://www.w3.org/TR/webrtc/#dom-rtcicetransportstate
+// TODO(bugs.webrtc.org/9218): Start signaling kCompleted once we have
+// implemented end-of-candidates signalling.
+webrtc::IceTransportState P2PTransportChannel::ComputeIceTransportState()
+    const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  bool has_connection = false;
+  for (Connection* connection : connections()) {
+    if (connection->active()) {
+      has_connection = true;
+      break;
+    }
+  }
+
+  if (had_connection_ && !has_connection) {
+    return webrtc::IceTransportState::kFailed;
+  }
+
+  if (!writable() && has_been_writable_) {
+    return webrtc::IceTransportState::kDisconnected;
+  }
+
+  if (!had_connection_ && !has_connection) {
+    return webrtc::IceTransportState::kNew;
+  }
+
+  if (has_connection && !writable()) {
+    // A candidate pair has been formed by adding a remote candidate
+    // and gathering a local candidate.
+    return webrtc::IceTransportState::kChecking;
+  }
+
+  return webrtc::IceTransportState::kConnected;
+}
+
+void P2PTransportChannel::SetIceParameters(const IceParameters& ice_params) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  RTC_LOG(LS_INFO) << "Set ICE ufrag: " << ice_params.ufrag
+                   << " pwd: " << ice_params.pwd << " on transport "
+                   << transport_name();
+  ice_parameters_ = ice_params;
+  // Note: Candidate gathering will restart when MaybeStartGathering is next
+  // called.
+}
+
+void P2PTransportChannel::SetRemoteIceParameters(
+    const IceParameters& ice_params) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  RTC_LOG(LS_INFO) << "Received remote ICE parameters: ufrag="
+                   << ice_params.ufrag << ", renomination "
+                   << (ice_params.renomination ? "enabled" : "disabled");
+  IceParameters* current_ice = remote_ice();
+  if (!current_ice || *current_ice != ice_params) {
+    // Keep the ICE credentials so that newer connections
+    // are prioritized over the older ones.
+    remote_ice_parameters_.push_back(ice_params);
+  }
+
+  // Update the pwd of remote candidate if needed.
+  for (RemoteCandidate& candidate : remote_candidates_) {
+    if (candidate.username() == ice_params.ufrag &&
+        candidate.password().empty()) {
+      candidate.set_password(ice_params.pwd);
+    }
+  }
+  // We need to update the credentials and generation for any peer reflexive
+  // candidates.
+  for (Connection* conn : connections()) {
+    conn->MaybeSetRemoteIceParametersAndGeneration(
+        ice_params, static_cast<int>(remote_ice_parameters_.size() - 1));
+  }
+  // Updating the remote ICE candidate generation could change the sort order.
+  ice_adapter_->OnSortAndSwitchRequest(
+      IceSwitchReason::REMOTE_CANDIDATE_GENERATION_CHANGE);
+}
+
+void P2PTransportChannel::SetRemoteIceMode(IceMode mode) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  remote_ice_mode_ = mode;
+}
+
+// TODO(qingsi): We apply the convention that setting a absl::optional parameter
+// to null restores its default value in the implementation. However, some
+// absl::optional parameters are only processed below if non-null, e.g.,
+// regather_on_failed_networks_interval, and thus there is no way to restore the
+// defaults. Fix this issue later for consistency.
+void P2PTransportChannel::SetIceConfig(const IceConfig& config) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (config_.continual_gathering_policy != config.continual_gathering_policy) {
+    if (!allocator_sessions_.empty()) {
+      RTC_LOG(LS_ERROR) << "Trying to change continual gathering policy "
+                           "when gathering has already started!";
+    } else {
+      config_.continual_gathering_policy = config.continual_gathering_policy;
+      RTC_LOG(LS_INFO) << "Set continual_gathering_policy to "
+                       << config_.continual_gathering_policy;
+    }
+  }
+
+  if (config_.backup_connection_ping_interval !=
+      config.backup_connection_ping_interval) {
+    config_.backup_connection_ping_interval =
+        config.backup_connection_ping_interval;
+    RTC_LOG(LS_INFO) << "Set backup connection ping interval to "
+                     << config_.backup_connection_ping_interval_or_default()
+                     << " milliseconds.";
+  }
+  if (config_.receiving_timeout != config.receiving_timeout) {
+    config_.receiving_timeout = config.receiving_timeout;
+    for (Connection* connection : connections()) {
+      connection->set_receiving_timeout(config_.receiving_timeout);
+    }
+    RTC_LOG(LS_INFO) << "Set ICE receiving timeout to "
+                     << config_.receiving_timeout_or_default()
+                     << " milliseconds";
+  }
+
+  config_.prioritize_most_likely_candidate_pairs =
+      config.prioritize_most_likely_candidate_pairs;
+  RTC_LOG(LS_INFO) << "Set ping most likely connection to "
+                   << config_.prioritize_most_likely_candidate_pairs;
+
+  if (config_.stable_writable_connection_ping_interval !=
+      config.stable_writable_connection_ping_interval) {
+    config_.stable_writable_connection_ping_interval =
+        config.stable_writable_connection_ping_interval;
+    RTC_LOG(LS_INFO)
+        << "Set stable_writable_connection_ping_interval to "
+        << config_.stable_writable_connection_ping_interval_or_default();
+  }
+
+  if (config_.presume_writable_when_fully_relayed !=
+      config.presume_writable_when_fully_relayed) {
+    if (!connections().empty()) {
+      RTC_LOG(LS_ERROR) << "Trying to change 'presume writable' "
+                           "while connections already exist!";
+    } else {
+      config_.presume_writable_when_fully_relayed =
+          config.presume_writable_when_fully_relayed;
+      RTC_LOG(LS_INFO) << "Set presume writable when fully relayed to "
+                       << config_.presume_writable_when_fully_relayed;
+    }
+  }
+
+  config_.surface_ice_candidates_on_ice_transport_type_changed =
+      config.surface_ice_candidates_on_ice_transport_type_changed;
+  if (config_.surface_ice_candidates_on_ice_transport_type_changed &&
+      config_.continual_gathering_policy != GATHER_CONTINUALLY) {
+    RTC_LOG(LS_WARNING)
+        << "surface_ice_candidates_on_ice_transport_type_changed is "
+           "ineffective since we do not gather continually.";
+  }
+
+  if (config_.regather_on_failed_networks_interval !=
+      config.regather_on_failed_networks_interval) {
+    config_.regather_on_failed_networks_interval =
+        config.regather_on_failed_networks_interval;
+    RTC_LOG(LS_INFO)
+        << "Set regather_on_failed_networks_interval to "
+        << config_.regather_on_failed_networks_interval_or_default();
+  }
+
+  if (config_.receiving_switching_delay != config.receiving_switching_delay) {
+    config_.receiving_switching_delay = config.receiving_switching_delay;
+    RTC_LOG(LS_INFO) << "Set receiving_switching_delay to "
+                     << config_.receiving_switching_delay_or_default();
+  }
+
+  if (config_.default_nomination_mode != config.default_nomination_mode) {
+    config_.default_nomination_mode = config.default_nomination_mode;
+    RTC_LOG(LS_INFO) << "Set default nomination mode to "
+                     << static_cast<int>(config_.default_nomination_mode);
+  }
+
+  if (config_.ice_check_interval_strong_connectivity !=
+      config.ice_check_interval_strong_connectivity) {
+    config_.ice_check_interval_strong_connectivity =
+        config.ice_check_interval_strong_connectivity;
+    RTC_LOG(LS_INFO)
+        << "Set strong ping interval to "
+        << config_.ice_check_interval_strong_connectivity_or_default();
+  }
+
+  if (config_.ice_check_interval_weak_connectivity !=
+      config.ice_check_interval_weak_connectivity) {
+    config_.ice_check_interval_weak_connectivity =
+        config.ice_check_interval_weak_connectivity;
+    RTC_LOG(LS_INFO)
+        << "Set weak ping interval to "
+        << config_.ice_check_interval_weak_connectivity_or_default();
+  }
+
+  if (config_.ice_check_min_interval != config.ice_check_min_interval) {
+    config_.ice_check_min_interval = config.ice_check_min_interval;
+    RTC_LOG(LS_INFO) << "Set min ping interval to "
+                     << config_.ice_check_min_interval_or_default();
+  }
+
+  if (config_.ice_unwritable_timeout != config.ice_unwritable_timeout) {
+    config_.ice_unwritable_timeout = config.ice_unwritable_timeout;
+    for (Connection* conn : connections()) {
+      conn->set_unwritable_timeout(config_.ice_unwritable_timeout);
+    }
+    RTC_LOG(LS_INFO) << "Set unwritable timeout to "
+                     << config_.ice_unwritable_timeout_or_default();
+  }
+
+  if (config_.ice_unwritable_min_checks != config.ice_unwritable_min_checks) {
+    config_.ice_unwritable_min_checks = config.ice_unwritable_min_checks;
+    for (Connection* conn : connections()) {
+      conn->set_unwritable_min_checks(config_.ice_unwritable_min_checks);
+    }
+    RTC_LOG(LS_INFO) << "Set unwritable min checks to "
+                     << config_.ice_unwritable_min_checks_or_default();
+  }
+
+  if (config_.ice_inactive_timeout != config.ice_inactive_timeout) {
+    config_.ice_inactive_timeout = config.ice_inactive_timeout;
+    for (Connection* conn : connections()) {
+      conn->set_inactive_timeout(config_.ice_inactive_timeout);
+    }
+    RTC_LOG(LS_INFO) << "Set inactive timeout to "
+                     << config_.ice_inactive_timeout_or_default();
+  }
+
+  if (config_.network_preference != config.network_preference) {
+    config_.network_preference = config.network_preference;
+    ice_adapter_->OnSortAndSwitchRequest(
+        IceSwitchReason::NETWORK_PREFERENCE_CHANGE);
+    RTC_LOG(LS_INFO) << "Set network preference to "
+                     << (config_.network_preference.has_value()
+                             ? config_.network_preference.value()
+                             : -1);  // network_preference cannot be bound to
+                                     // int with value_or.
+  }
+
+  // TODO(qingsi): Resolve the naming conflict of stun_keepalive_delay in
+  // UDPPort and stun_keepalive_interval.
+  if (config_.stun_keepalive_interval != config.stun_keepalive_interval) {
+    config_.stun_keepalive_interval = config.stun_keepalive_interval;
+    allocator_session()->SetStunKeepaliveIntervalForReadyPorts(
+        config_.stun_keepalive_interval);
+    RTC_LOG(LS_INFO) << "Set STUN keepalive interval to "
+                     << config.stun_keepalive_interval_or_default();
+  }
+
+  webrtc::BasicRegatheringController::Config regathering_config;
+  regathering_config.regather_on_failed_networks_interval =
+      config_.regather_on_failed_networks_interval_or_default();
+  regathering_controller_->SetConfig(regathering_config);
+
+  config_.vpn_preference = config.vpn_preference;
+  allocator_->SetVpnPreference(config_.vpn_preference);
+
+  ice_adapter_->SetIceConfig(config_);
+
+  RTC_DCHECK(ValidateIceConfig(config_).ok());
+}
+
+void P2PTransportChannel::ParseFieldTrials(
+    const webrtc::FieldTrialsView* field_trials) {
+  if (field_trials == nullptr) {
+    return;
+  }
+
+  if (field_trials->IsEnabled("WebRTC-ExtraICEPing")) {
+    RTC_LOG(LS_INFO) << "Set WebRTC-ExtraICEPing: Enabled";
+  }
+
+  webrtc::StructParametersParser::Create(
+      // go/skylift-light
+      "skip_relay_to_non_relay_connections",
+      &ice_field_trials_.skip_relay_to_non_relay_connections,
+      // Limiting pings sent.
+      "max_outstanding_pings", &ice_field_trials_.max_outstanding_pings,
+      // Delay initial selection of connection.
+      "initial_select_dampening", &ice_field_trials_.initial_select_dampening,
+      // Delay initial selection of connections, that are receiving.
+      "initial_select_dampening_ping_received",
+      &ice_field_trials_.initial_select_dampening_ping_received,
+      // Reply that we support goog ping.
+      "announce_goog_ping", &ice_field_trials_.announce_goog_ping,
+      // Use goog ping if remote support it.
+      "enable_goog_ping", &ice_field_trials_.enable_goog_ping,
+      // How fast does a RTT sample decay.
+      "rtt_estimate_halftime_ms", &ice_field_trials_.rtt_estimate_halftime_ms,
+      // Make sure that nomination reaching ICE controlled asap.
+      "send_ping_on_switch_ice_controlling",
+      &ice_field_trials_.send_ping_on_switch_ice_controlling,
+      // Make sure that nomination reaching ICE controlled asap.
+      "send_ping_on_selected_ice_controlling",
+      &ice_field_trials_.send_ping_on_selected_ice_controlling,
+      // Reply to nomination ASAP.
+      "send_ping_on_nomination_ice_controlled",
+      &ice_field_trials_.send_ping_on_nomination_ice_controlled,
+      // Allow connections to live untouched longer that 30s.
+      "dead_connection_timeout_ms",
+      &ice_field_trials_.dead_connection_timeout_ms,
+      // Stop gathering on strongly connected.
+      "stop_gather_on_strongly_connected",
+      &ice_field_trials_.stop_gather_on_strongly_connected)
+      ->Parse(field_trials->Lookup("WebRTC-IceFieldTrials"));
+
+  if (ice_field_trials_.dead_connection_timeout_ms < 30000) {
+    RTC_LOG(LS_WARNING) << "dead_connection_timeout_ms set to "
+                        << ice_field_trials_.dead_connection_timeout_ms
+                        << " increasing it to 30000";
+    ice_field_trials_.dead_connection_timeout_ms = 30000;
+  }
+
+  if (ice_field_trials_.skip_relay_to_non_relay_connections) {
+    RTC_LOG(LS_INFO) << "Set skip_relay_to_non_relay_connections";
+  }
+
+  if (ice_field_trials_.max_outstanding_pings.has_value()) {
+    RTC_LOG(LS_INFO) << "Set max_outstanding_pings: "
+                     << *ice_field_trials_.max_outstanding_pings;
+  }
+
+  if (ice_field_trials_.initial_select_dampening.has_value()) {
+    RTC_LOG(LS_INFO) << "Set initial_select_dampening: "
+                     << *ice_field_trials_.initial_select_dampening;
+  }
+
+  if (ice_field_trials_.initial_select_dampening_ping_received.has_value()) {
+    RTC_LOG(LS_INFO)
+        << "Set initial_select_dampening_ping_received: "
+        << *ice_field_trials_.initial_select_dampening_ping_received;
+  }
+
+  // DSCP override, allow user to specify (any) int value
+  // that will be used for tagging all packets.
+  webrtc::StructParametersParser::Create("override_dscp",
+                                         &ice_field_trials_.override_dscp)
+      ->Parse(field_trials->Lookup("WebRTC-DscpFieldTrial"));
+
+  if (ice_field_trials_.override_dscp) {
+    SetOption(rtc::Socket::OPT_DSCP, *ice_field_trials_.override_dscp);
+  }
+
+  std::string field_trial_string =
+      field_trials->Lookup("WebRTC-SetSocketReceiveBuffer");
+  int receive_buffer_size_kb = 0;
+  sscanf(field_trial_string.c_str(), "Enabled-%d", &receive_buffer_size_kb);
+  if (receive_buffer_size_kb > 0) {
+    RTC_LOG(LS_INFO) << "Set WebRTC-SetSocketReceiveBuffer: Enabled and set to "
+                     << receive_buffer_size_kb << "kb";
+    SetOption(rtc::Socket::OPT_RCVBUF, receive_buffer_size_kb * 1024);
+  }
+
+  ice_field_trials_.piggyback_ice_check_acknowledgement =
+      field_trials->IsEnabled("WebRTC-PiggybackIceCheckAcknowledgement");
+
+  ice_field_trials_.extra_ice_ping =
+      field_trials->IsEnabled("WebRTC-ExtraICEPing");
+}
+
+const IceConfig& P2PTransportChannel::config() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return config_;
+}
+
+// TODO(qingsi): Add tests for the config validation starting from
+// PeerConnection::SetConfiguration.
+// Static
+RTCError P2PTransportChannel::ValidateIceConfig(const IceConfig& config) {
+  if (config.ice_check_interval_strong_connectivity_or_default() <
+      config.ice_check_interval_weak_connectivity.value_or(
+          GetWeakPingIntervalInFieldTrial(nullptr))) {
+    return RTCError(RTCErrorType::INVALID_PARAMETER,
+                    "Ping interval of candidate pairs is shorter when ICE is "
+                    "strongly connected than that when ICE is weakly "
+                    "connected");
+  }
+
+  if (config.receiving_timeout_or_default() <
+      std::max(config.ice_check_interval_strong_connectivity_or_default(),
+               config.ice_check_min_interval_or_default())) {
+    return RTCError(
+        RTCErrorType::INVALID_PARAMETER,
+        "Receiving timeout is shorter than the minimal ping interval.");
+  }
+
+  if (config.backup_connection_ping_interval_or_default() <
+      config.ice_check_interval_strong_connectivity_or_default()) {
+    return RTCError(RTCErrorType::INVALID_PARAMETER,
+                    "Ping interval of backup candidate pairs is shorter than "
+                    "that of general candidate pairs when ICE is strongly "
+                    "connected");
+  }
+
+  if (config.stable_writable_connection_ping_interval_or_default() <
+      config.ice_check_interval_strong_connectivity_or_default()) {
+    return RTCError(RTCErrorType::INVALID_PARAMETER,
+                    "Ping interval of stable and writable candidate pairs is "
+                    "shorter than that of general candidate pairs when ICE is "
+                    "strongly connected");
+  }
+
+  if (config.ice_unwritable_timeout_or_default() >
+      config.ice_inactive_timeout_or_default()) {
+    return RTCError(RTCErrorType::INVALID_PARAMETER,
+                    "The timeout period for the writability state to become "
+                    "UNRELIABLE is longer than that to become TIMEOUT.");
+  }
+
+  return RTCError::OK();
+}
+
+const Connection* P2PTransportChannel::selected_connection() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return selected_connection_;
+}
+
+int P2PTransportChannel::check_receiving_interval() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return std::max(MIN_CHECK_RECEIVING_INTERVAL,
+                  config_.receiving_timeout_or_default() / 10);
+}
+
+void P2PTransportChannel::MaybeStartGathering() {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  // TODO(bugs.webrtc.org/14605): ensure tie_breaker_ is set.
+  if (ice_parameters_.ufrag.empty() || ice_parameters_.pwd.empty()) {
+    RTC_LOG(LS_ERROR)
+        << "Cannot gather candidates because ICE parameters are empty"
+           " ufrag: "
+        << ice_parameters_.ufrag << " pwd: " << ice_parameters_.pwd;
+    return;
+  }
+  // Start gathering if we never started before, or if an ICE restart occurred.
+  if (allocator_sessions_.empty() ||
+      IceCredentialsChanged(allocator_sessions_.back()->ice_ufrag(),
+                            allocator_sessions_.back()->ice_pwd(),
+                            ice_parameters_.ufrag, ice_parameters_.pwd)) {
+    if (gathering_state_ != kIceGatheringGathering) {
+      gathering_state_ = kIceGatheringGathering;
+      SignalGatheringState(this);
+    }
+
+    if (!allocator_sessions_.empty()) {
+      IceRestartState state;
+      if (writable()) {
+        state = IceRestartState::CONNECTED;
+      } else if (IsGettingPorts()) {
+        state = IceRestartState::CONNECTING;
+      } else {
+        state = IceRestartState::DISCONNECTED;
+      }
+      RTC_HISTOGRAM_ENUMERATION("WebRTC.PeerConnection.IceRestartState",
+                                static_cast<int>(state),
+                                static_cast<int>(IceRestartState::MAX_VALUE));
+    }
+
+    for (const auto& session : allocator_sessions_) {
+      if (session->IsStopped()) {
+        continue;
+      }
+      session->StopGettingPorts();
+    }
+
+    // Time for a new allocator.
+    std::unique_ptr<PortAllocatorSession> pooled_session =
+        allocator_->TakePooledSession(transport_name(), component(),
+                                      ice_parameters_.ufrag,
+                                      ice_parameters_.pwd);
+    if (pooled_session) {
+      pooled_session->set_ice_tiebreaker(tiebreaker_);
+      AddAllocatorSession(std::move(pooled_session));
+      PortAllocatorSession* raw_pooled_session =
+          allocator_sessions_.back().get();
+      // Process the pooled session's existing candidates/ports, if they exist.
+      OnCandidatesReady(raw_pooled_session,
+                        raw_pooled_session->ReadyCandidates());
+      for (PortInterface* port : allocator_sessions_.back()->ReadyPorts()) {
+        OnPortReady(raw_pooled_session, port);
+      }
+      if (allocator_sessions_.back()->CandidatesAllocationDone()) {
+        OnCandidatesAllocationDone(raw_pooled_session);
+      }
+    } else {
+      AddAllocatorSession(allocator_->CreateSession(
+          transport_name(), component(), ice_parameters_.ufrag,
+          ice_parameters_.pwd));
+      allocator_sessions_.back()->set_ice_tiebreaker(tiebreaker_);
+      allocator_sessions_.back()->StartGettingPorts();
+    }
+  }
+}
+
+// A new port is available, attempt to make connections for it
+void P2PTransportChannel::OnPortReady(PortAllocatorSession* session,
+                                      PortInterface* port) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+
+  // Set in-effect options on the new port
+  for (OptionMap::const_iterator it = options_.begin(); it != options_.end();
+       ++it) {
+    int val = port->SetOption(it->first, it->second);
+    if (val < 0) {
+      // Errors are frequent, so use LS_INFO. bugs.webrtc.org/9221
+      RTC_LOG(LS_INFO) << port->ToString() << ": SetOption(" << it->first
+                       << ", " << it->second
+                       << ") failed: " << port->GetError();
+    }
+  }
+
+  // Remember the ports and candidates, and signal that candidates are ready.
+  // The session will handle this, and send an initiate/accept/modify message
+  // if one is pending.
+
+  port->SetIceRole(ice_role_);
+  port->SetIceTiebreaker(tiebreaker_);
+  ports_.push_back(port);
+  port->SignalUnknownAddress.connect(this,
+                                     &P2PTransportChannel::OnUnknownAddress);
+  port->SubscribePortDestroyed(
+      [this](PortInterface* port) { OnPortDestroyed(port); });
+
+  port->SignalRoleConflict.connect(this, &P2PTransportChannel::OnRoleConflict);
+  port->SignalSentPacket.connect(this, &P2PTransportChannel::OnSentPacket);
+
+  // Attempt to create a connection from this new port to all of the remote
+  // candidates that we were given so far.
+
+  std::vector<RemoteCandidate>::iterator iter;
+  for (iter = remote_candidates_.begin(); iter != remote_candidates_.end();
+       ++iter) {
+    CreateConnection(port, *iter, iter->origin_port());
+  }
+
+  ice_adapter_->OnImmediateSortAndSwitchRequest(
+      IceSwitchReason::NEW_CONNECTION_FROM_LOCAL_CANDIDATE);
+}
+
+// A new candidate is available, let listeners know
+void P2PTransportChannel::OnCandidatesReady(
+    PortAllocatorSession* session,
+    const std::vector<Candidate>& candidates) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  for (size_t i = 0; i < candidates.size(); ++i) {
+    SignalCandidateGathered(this, candidates[i]);
+  }
+}
+
+void P2PTransportChannel::OnCandidateError(
+    PortAllocatorSession* session,
+    const IceCandidateErrorEvent& event) {
+  RTC_DCHECK(network_thread_ == rtc::Thread::Current());
+  SignalCandidateError(this, event);
+}
+
+void P2PTransportChannel::OnCandidatesAllocationDone(
+    PortAllocatorSession* session) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (config_.gather_continually()) {
+    RTC_LOG(LS_INFO) << "P2PTransportChannel: " << transport_name()
+                     << ", component " << component()
+                     << " gathering complete, but using continual "
+                        "gathering so not changing gathering state.";
+    return;
+  }
+  gathering_state_ = kIceGatheringComplete;
+  RTC_LOG(LS_INFO) << "P2PTransportChannel: " << transport_name()
+                   << ", component " << component() << " gathering complete";
+  SignalGatheringState(this);
+}
+
+// Handle stun packets
+void P2PTransportChannel::OnUnknownAddress(PortInterface* port,
+                                           const rtc::SocketAddress& address,
+                                           ProtocolType proto,
+                                           IceMessage* stun_msg,
+                                           const std::string& remote_username,
+                                           bool port_muxed) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+
+  // Port has received a valid stun packet from an address that no Connection
+  // is currently available for. See if we already have a candidate with the
+  // address. If it isn't we need to create new candidate for it.
+  //
+  // TODO(qingsi): There is a caveat of the logic below if we have remote
+  // candidates with hostnames. We could create a prflx candidate that is
+  // identical to a host candidate that are currently in the process of name
+  // resolution. We would not have a duplicate candidate since when adding the
+  // resolved host candidate, FinishingAddingRemoteCandidate does
+  // MaybeUpdatePeerReflexiveCandidate, and the prflx candidate would be updated
+  // to a host candidate. As a result, for a brief moment we would have a prflx
+  // candidate showing a private IP address, though we do not signal prflx
+  // candidates to applications and we could obfuscate the IP addresses of prflx
+  // candidates in P2PTransportChannel::GetStats. The difficulty of preventing
+  // creating the prflx from the beginning is that we do not have a reliable way
+  // to claim two candidates are identical without the address information. If
+  // we always pause the addition of a prflx candidate when there is ongoing
+  // name resolution and dedup after we have a resolved address, we run into the
+  // risk of losing/delaying the addition of a non-identical candidate that
+  // could be the only way to have a connection, if the resolution never
+  // completes or is significantly delayed.
+  const Candidate* candidate = nullptr;
+  for (const Candidate& c : remote_candidates_) {
+    if (c.username() == remote_username && c.address() == address &&
+        c.protocol() == ProtoToString(proto)) {
+      candidate = &c;
+      break;
+    }
+  }
+
+  uint32_t remote_generation = 0;
+  std::string remote_password;
+  // The STUN binding request may arrive after setRemoteDescription and before
+  // adding remote candidate, so we need to set the password to the shared
+  // password and set the generation if the user name matches.
+  const IceParameters* ice_param =
+      FindRemoteIceFromUfrag(remote_username, &remote_generation);
+  // Note: if not found, the remote_generation will still be 0.
+  if (ice_param != nullptr) {
+    remote_password = ice_param->pwd;
+  }
+
+  Candidate remote_candidate;
+  bool remote_candidate_is_new = (candidate == nullptr);
+  if (!remote_candidate_is_new) {
+    remote_candidate = *candidate;
+  } else {
+    // Create a new candidate with this address.
+    // The priority of the candidate is set to the PRIORITY attribute
+    // from the request.
+    const StunUInt32Attribute* priority_attr =
+        stun_msg->GetUInt32(STUN_ATTR_PRIORITY);
+    if (!priority_attr) {
+      RTC_LOG(LS_WARNING) << "P2PTransportChannel::OnUnknownAddress - "
+                             "No STUN_ATTR_PRIORITY found in the "
+                             "stun request message";
+      port->SendBindingErrorResponse(stun_msg, address, STUN_ERROR_BAD_REQUEST,
+                                     STUN_ERROR_REASON_BAD_REQUEST);
+      return;
+    }
+    int remote_candidate_priority = priority_attr->value();
+
+    uint16_t network_id = 0;
+    uint16_t network_cost = 0;
+    const StunUInt32Attribute* network_attr =
+        stun_msg->GetUInt32(STUN_ATTR_GOOG_NETWORK_INFO);
+    if (network_attr) {
+      uint32_t network_info = network_attr->value();
+      network_id = static_cast<uint16_t>(network_info >> 16);
+      network_cost = static_cast<uint16_t>(network_info);
+    }
+
+    // RFC 5245
+    // If the source transport address of the request does not match any
+    // existing remote candidates, it represents a new peer reflexive remote
+    // candidate.
+    remote_candidate = Candidate(
+        component(), ProtoToString(proto), address, remote_candidate_priority,
+        remote_username, remote_password, PRFLX_PORT_TYPE, remote_generation,
+        "", network_id, network_cost);
+    if (proto == PROTO_TCP) {
+      remote_candidate.set_tcptype(TCPTYPE_ACTIVE_STR);
+    }
+
+    // From RFC 5245, section-7.2.1.3:
+    // The foundation of the candidate is set to an arbitrary value, different
+    // from the foundation for all other remote candidates.
+    remote_candidate.set_foundation(
+        rtc::ToString(rtc::ComputeCrc32(remote_candidate.id())));
+  }
+
+  // RFC5245, the agent constructs a pair whose local candidate is equal to
+  // the transport address on which the STUN request was received, and a
+  // remote candidate equal to the source transport address where the
+  // request came from.
+
+  // There shouldn't be an existing connection with this remote address.
+  // When ports are muxed, this channel might get multiple unknown address
+  // signals. In that case if the connection is already exists, we should
+  // simply ignore the signal otherwise send server error.
+  if (port->GetConnection(remote_candidate.address())) {
+    if (port_muxed) {
+      RTC_LOG(LS_INFO) << "Connection already exists for peer reflexive "
+                          "candidate: "
+                       << remote_candidate.ToSensitiveString();
+      return;
+    } else {
+      RTC_DCHECK_NOTREACHED();
+      port->SendBindingErrorResponse(stun_msg, address, STUN_ERROR_SERVER_ERROR,
+                                     STUN_ERROR_REASON_SERVER_ERROR);
+      return;
+    }
+  }
+
+  Connection* connection =
+      port->CreateConnection(remote_candidate, PortInterface::ORIGIN_THIS_PORT);
+  if (!connection) {
+    // This could happen in some scenarios. For example, a TurnPort may have
+    // had a refresh request timeout, so it won't create connections.
+    port->SendBindingErrorResponse(stun_msg, address, STUN_ERROR_SERVER_ERROR,
+                                   STUN_ERROR_REASON_SERVER_ERROR);
+    return;
+  }
+
+  RTC_LOG(LS_INFO) << "Adding connection from "
+                   << (remote_candidate_is_new ? "peer reflexive"
+                                               : "resurrected")
+                   << " candidate: " << remote_candidate.ToSensitiveString();
+  AddConnection(connection);
+  connection->HandleStunBindingOrGoogPingRequest(stun_msg);
+
+  // Update the list of connections since we just added another.  We do this
+  // after sending the response since it could (in principle) delete the
+  // connection in question.
+  ice_adapter_->OnImmediateSortAndSwitchRequest(
+      IceSwitchReason::NEW_CONNECTION_FROM_UNKNOWN_REMOTE_ADDRESS);
+}
+
+void P2PTransportChannel::OnCandidateFilterChanged(uint32_t prev_filter,
+                                                   uint32_t cur_filter) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (prev_filter == cur_filter || allocator_session() == nullptr) {
+    return;
+  }
+  if (config_.surface_ice_candidates_on_ice_transport_type_changed) {
+    allocator_session()->SetCandidateFilter(cur_filter);
+  }
+}
+
+void P2PTransportChannel::OnRoleConflict(PortInterface* port) {
+  SignalRoleConflict(this);  // STUN ping will be sent when SetRole is called
+                             // from Transport.
+}
+
+const IceParameters* P2PTransportChannel::FindRemoteIceFromUfrag(
+    absl::string_view ufrag,
+    uint32_t* generation) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  const auto& params = remote_ice_parameters_;
+  auto it = std::find_if(
+      params.rbegin(), params.rend(),
+      [ufrag](const IceParameters& param) { return param.ufrag == ufrag; });
+  if (it == params.rend()) {
+    // Not found.
+    return nullptr;
+  }
+  *generation = params.rend() - it - 1;
+  return &(*it);
+}
+
+void P2PTransportChannel::OnNominated(Connection* conn) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  RTC_DCHECK(ice_role_ == ICEROLE_CONTROLLED);
+
+  if (selected_connection_ == conn) {
+    return;
+  }
+
+  if (ice_field_trials_.send_ping_on_nomination_ice_controlled &&
+      conn != nullptr) {
+    SendPingRequestInternal(conn);
+  }
+
+  // TODO(qingsi): RequestSortAndStateUpdate will eventually call
+  // MaybeSwitchSelectedConnection again. Rewrite this logic.
+  if (ice_adapter_->OnImmediateSwitchRequest(
+          IceSwitchReason::NOMINATION_ON_CONTROLLED_SIDE, conn)) {
+    // Now that we have selected a connection, it is time to prune other
+    // connections and update the read/write state of the channel.
+    ice_adapter_->OnSortAndSwitchRequest(
+        IceSwitchReason::NOMINATION_ON_CONTROLLED_SIDE);
+  } else {
+    RTC_LOG(LS_INFO)
+        << "Not switching the selected connection on controlled side yet: "
+        << conn->ToString();
+  }
+}
+
+void P2PTransportChannel::ResolveHostnameCandidate(const Candidate& candidate) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (!async_dns_resolver_factory_) {
+    RTC_LOG(LS_WARNING) << "Dropping ICE candidate with hostname address "
+                           "(no AsyncResolverFactory)";
+    return;
+  }
+
+  auto resolver = async_dns_resolver_factory_->Create();
+  auto resptr = resolver.get();
+  resolvers_.emplace_back(candidate, std::move(resolver));
+  resptr->Start(candidate.address(),
+                [this, resptr]() { OnCandidateResolved(resptr); });
+  RTC_LOG(LS_INFO) << "Asynchronously resolving ICE candidate hostname "
+                   << candidate.address().HostAsSensitiveURIString();
+}
+
+void P2PTransportChannel::AddRemoteCandidate(const Candidate& candidate) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+
+  uint32_t generation = GetRemoteCandidateGeneration(candidate);
+  // If a remote candidate with a previous generation arrives, drop it.
+  if (generation < remote_ice_generation()) {
+    RTC_LOG(LS_WARNING) << "Dropping a remote candidate because its ufrag "
+                        << candidate.username()
+                        << " indicates it was for a previous generation.";
+    return;
+  }
+
+  Candidate new_remote_candidate(candidate);
+  new_remote_candidate.set_generation(generation);
+  // ICE candidates don't need to have username and password set, but
+  // the code below this (specifically, ConnectionRequest::Prepare in
+  // port.cc) uses the remote candidates's username.  So, we set it
+  // here.
+  if (remote_ice()) {
+    if (candidate.username().empty()) {
+      new_remote_candidate.set_username(remote_ice()->ufrag);
+    }
+    if (new_remote_candidate.username() == remote_ice()->ufrag) {
+      if (candidate.password().empty()) {
+        new_remote_candidate.set_password(remote_ice()->pwd);
+      }
+    } else {
+      // The candidate belongs to the next generation. Its pwd will be set
+      // when the new remote ICE credentials arrive.
+      RTC_LOG(LS_WARNING)
+          << "A remote candidate arrives with an unknown ufrag: "
+          << candidate.username();
+    }
+  }
+
+  if (new_remote_candidate.address().IsUnresolvedIP()) {
+    // Don't do DNS lookups if the IceTransportPolicy is "none" or "relay".
+    bool sharing_host = ((allocator_->candidate_filter() & CF_HOST) != 0);
+    bool sharing_stun = ((allocator_->candidate_filter() & CF_REFLEXIVE) != 0);
+    if (sharing_host || sharing_stun) {
+      ResolveHostnameCandidate(new_remote_candidate);
+    }
+    return;
+  }
+
+  FinishAddingRemoteCandidate(new_remote_candidate);
+}
+
+P2PTransportChannel::CandidateAndResolver::CandidateAndResolver(
+    const Candidate& candidate,
+    std::unique_ptr<webrtc::AsyncDnsResolverInterface>&& resolver)
+    : candidate_(candidate), resolver_(std::move(resolver)) {}
+
+P2PTransportChannel::CandidateAndResolver::~CandidateAndResolver() {}
+
+void P2PTransportChannel::OnCandidateResolved(
+    webrtc::AsyncDnsResolverInterface* resolver) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  auto p =
+      absl::c_find_if(resolvers_, [resolver](const CandidateAndResolver& cr) {
+        return cr.resolver_.get() == resolver;
+      });
+  if (p == resolvers_.end()) {
+    RTC_LOG(LS_ERROR) << "Unexpected AsyncDnsResolver return";
+    RTC_DCHECK_NOTREACHED();
+    return;
+  }
+  Candidate candidate = p->candidate_;
+  AddRemoteCandidateWithResult(candidate, resolver->result());
+  // Now we can delete the resolver.
+  // TODO(bugs.webrtc.org/12651): Replace the stuff below with
+  // resolvers_.erase(p);
+  std::unique_ptr<webrtc::AsyncDnsResolverInterface> to_delete =
+      std::move(p->resolver_);
+  // Delay the actual deletion of the resolver until the lambda executes.
+  network_thread_->PostTask([to_delete = std::move(to_delete)] {});
+  resolvers_.erase(p);
+}
+
+void P2PTransportChannel::AddRemoteCandidateWithResult(
+    Candidate candidate,
+    const webrtc::AsyncDnsResolverResult& result) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (result.GetError()) {
+    RTC_LOG(LS_WARNING) << "Failed to resolve ICE candidate hostname "
+                        << candidate.address().HostAsSensitiveURIString()
+                        << " with error " << result.GetError();
+    return;
+  }
+
+  rtc::SocketAddress resolved_address;
+  // Prefer IPv6 to IPv4 if we have it (see RFC 5245 Section 15.1).
+  // TODO(zstein): This won't work if we only have IPv4 locally but receive an
+  // AAAA DNS record.
+  bool have_address = result.GetResolvedAddress(AF_INET6, &resolved_address) ||
+                      result.GetResolvedAddress(AF_INET, &resolved_address);
+  if (!have_address) {
+    RTC_LOG(LS_INFO) << "ICE candidate hostname "
+                     << candidate.address().HostAsSensitiveURIString()
+                     << " could not be resolved";
+    return;
+  }
+
+  RTC_LOG(LS_INFO) << "Resolved ICE candidate hostname "
+                   << candidate.address().HostAsSensitiveURIString() << " to "
+                   << resolved_address.ipaddr().ToSensitiveString();
+  candidate.set_address(resolved_address);
+  FinishAddingRemoteCandidate(candidate);
+}
+
+void P2PTransportChannel::FinishAddingRemoteCandidate(
+    const Candidate& new_remote_candidate) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  // If this candidate matches what was thought to be a peer reflexive
+  // candidate, we need to update the candidate priority/etc.
+  for (Connection* conn : connections()) {
+    conn->MaybeUpdatePeerReflexiveCandidate(new_remote_candidate);
+  }
+
+  // Create connections to this remote candidate.
+  CreateConnections(new_remote_candidate, NULL);
+
+  // Resort the connections list, which may have new elements.
+  ice_adapter_->OnImmediateSortAndSwitchRequest(
+      IceSwitchReason::NEW_CONNECTION_FROM_REMOTE_CANDIDATE);
+}
+
+void P2PTransportChannel::RemoveRemoteCandidate(
+    const Candidate& cand_to_remove) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  auto iter =
+      std::remove_if(remote_candidates_.begin(), remote_candidates_.end(),
+                     [cand_to_remove](const Candidate& candidate) {
+                       return cand_to_remove.MatchesForRemoval(candidate);
+                     });
+  if (iter != remote_candidates_.end()) {
+    RTC_LOG(LS_VERBOSE) << "Removed remote candidate "
+                        << cand_to_remove.ToSensitiveString();
+    remote_candidates_.erase(iter, remote_candidates_.end());
+  }
+}
+
+void P2PTransportChannel::RemoveAllRemoteCandidates() {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  remote_candidates_.clear();
+}
+
+// Creates connections from all of the ports that we care about to the given
+// remote candidate.  The return value is true if we created a connection from
+// the origin port.
+bool P2PTransportChannel::CreateConnections(const Candidate& remote_candidate,
+                                            PortInterface* origin_port) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+
+  // If we've already seen the new remote candidate (in the current candidate
+  // generation), then we shouldn't try creating connections for it.
+  // We either already have a connection for it, or we previously created one
+  // and then later pruned it. If we don't return, the channel will again
+  // re-create any connections that were previously pruned, which will then
+  // immediately be re-pruned, churning the network for no purpose.
+  // This only applies to candidates received over signaling (i.e. origin_port
+  // is NULL).
+  if (!origin_port && IsDuplicateRemoteCandidate(remote_candidate)) {
+    // return true to indicate success, without creating any new connections.
+    return true;
+  }
+
+  // Add a new connection for this candidate to every port that allows such a
+  // connection (i.e., if they have compatible protocols) and that does not
+  // already have a connection to an equivalent candidate.  We must be careful
+  // to make sure that the origin port is included, even if it was pruned,
+  // since that may be the only port that can create this connection.
+  bool created = false;
+  std::vector<PortInterface*>::reverse_iterator it;
+  for (it = ports_.rbegin(); it != ports_.rend(); ++it) {
+    if (CreateConnection(*it, remote_candidate, origin_port)) {
+      if (*it == origin_port)
+        created = true;
+    }
+  }
+
+  if ((origin_port != NULL) && !absl::c_linear_search(ports_, origin_port)) {
+    if (CreateConnection(origin_port, remote_candidate, origin_port))
+      created = true;
+  }
+
+  // Remember this remote candidate so that we can add it to future ports.
+  RememberRemoteCandidate(remote_candidate, origin_port);
+
+  return created;
+}
+
+// Setup a connection object for the local and remote candidate combination.
+// And then listen to connection object for changes.
+bool P2PTransportChannel::CreateConnection(PortInterface* port,
+                                           const Candidate& remote_candidate,
+                                           PortInterface* origin_port) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (!port->SupportsProtocol(remote_candidate.protocol())) {
+    return false;
+  }
+
+  if (ice_field_trials_.skip_relay_to_non_relay_connections) {
+    if ((port->Type() != remote_candidate.type()) &&
+        (port->Type() == RELAY_PORT_TYPE ||
+         remote_candidate.type() == RELAY_PORT_TYPE)) {
+      RTC_LOG(LS_INFO) << ToString() << ": skip creating connection "
+                       << port->Type() << " to " << remote_candidate.type();
+      return false;
+    }
+  }
+
+  // Look for an existing connection with this remote address.  If one is not
+  // found or it is found but the existing remote candidate has an older
+  // generation, then we can create a new connection for this address.
+  Connection* connection = port->GetConnection(remote_candidate.address());
+  if (connection == nullptr || connection->remote_candidate().generation() <
+                                   remote_candidate.generation()) {
+    // Don't create a connection if this is a candidate we received in a
+    // message and we are not allowed to make outgoing connections.
+    PortInterface::CandidateOrigin origin = GetOrigin(port, origin_port);
+    if (origin == PortInterface::ORIGIN_MESSAGE && incoming_only_) {
+      return false;
+    }
+    Connection* connection = port->CreateConnection(remote_candidate, origin);
+    if (!connection) {
+      return false;
+    }
+    AddConnection(connection);
+    RTC_LOG(LS_INFO) << ToString()
+                     << ": Created connection with origin: " << origin
+                     << ", total: " << connections().size();
+    return true;
+  }
+
+  // No new connection was created.
+  // It is not legal to try to change any of the parameters of an existing
+  // connection; however, the other side can send a duplicate candidate.
+  if (!remote_candidate.IsEquivalent(connection->remote_candidate())) {
+    RTC_LOG(LS_INFO) << "Attempt to change a remote candidate."
+                        " Existing remote candidate: "
+                     << connection->remote_candidate().ToSensitiveString()
+                     << "New remote candidate: "
+                     << remote_candidate.ToSensitiveString();
+  }
+  return false;
+}
+
+bool P2PTransportChannel::FindConnection(const Connection* connection) const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return absl::c_linear_search(connections(), connection);
+}
+
+uint32_t P2PTransportChannel::GetRemoteCandidateGeneration(
+    const Candidate& candidate) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  // If the candidate has a ufrag, use it to find the generation.
+  if (!candidate.username().empty()) {
+    uint32_t generation = 0;
+    if (!FindRemoteIceFromUfrag(candidate.username(), &generation)) {
+      // If the ufrag is not found, assume the next/future generation.
+      generation = static_cast<uint32_t>(remote_ice_parameters_.size());
+    }
+    return generation;
+  }
+  // If candidate generation is set, use that.
+  if (candidate.generation() > 0) {
+    return candidate.generation();
+  }
+  // Otherwise, assume the generation from remote ice parameters.
+  return remote_ice_generation();
+}
+
+// Check if remote candidate is already cached.
+bool P2PTransportChannel::IsDuplicateRemoteCandidate(
+    const Candidate& candidate) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  for (size_t i = 0; i < remote_candidates_.size(); ++i) {
+    if (remote_candidates_[i].IsEquivalent(candidate)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+// Maintain our remote candidate list, adding this new remote one.
+void P2PTransportChannel::RememberRemoteCandidate(
+    const Candidate& remote_candidate,
+    PortInterface* origin_port) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  // Remove any candidates whose generation is older than this one.  The
+  // presence of a new generation indicates that the old ones are not useful.
+  size_t i = 0;
+  while (i < remote_candidates_.size()) {
+    if (remote_candidates_[i].generation() < remote_candidate.generation()) {
+      RTC_LOG(LS_INFO) << "Pruning candidate from old generation: "
+                       << remote_candidates_[i].address().ToSensitiveString();
+      remote_candidates_.erase(remote_candidates_.begin() + i);
+    } else {
+      i += 1;
+    }
+  }
+
+  // Make sure this candidate is not a duplicate.
+  if (IsDuplicateRemoteCandidate(remote_candidate)) {
+    RTC_LOG(LS_INFO) << "Duplicate candidate: "
+                     << remote_candidate.ToSensitiveString();
+    return;
+  }
+
+  // Try this candidate for all future ports.
+  remote_candidates_.push_back(RemoteCandidate(remote_candidate, origin_port));
+}
+
+// Set options on ourselves is simply setting options on all of our available
+// port objects.
+int P2PTransportChannel::SetOption(rtc::Socket::Option opt, int value) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (ice_field_trials_.override_dscp && opt == rtc::Socket::OPT_DSCP) {
+    value = *ice_field_trials_.override_dscp;
+  }
+
+  OptionMap::iterator it = options_.find(opt);
+  if (it == options_.end()) {
+    options_.insert(std::make_pair(opt, value));
+  } else if (it->second == value) {
+    return 0;
+  } else {
+    it->second = value;
+  }
+
+  for (PortInterface* port : ports_) {
+    int val = port->SetOption(opt, value);
+    if (val < 0) {
+      // Because this also occurs deferred, probably no point in reporting an
+      // error
+      RTC_LOG(LS_WARNING) << "SetOption(" << opt << ", " << value
+                          << ") failed: " << port->GetError();
+    }
+  }
+  return 0;
+}
+
+bool P2PTransportChannel::GetOption(rtc::Socket::Option opt, int* value) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+
+  const auto& found = options_.find(opt);
+  if (found == options_.end()) {
+    return false;
+  }
+  *value = found->second;
+  return true;
+}
+
+int P2PTransportChannel::GetError() {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return error_;
+}
+
+// Send data to the other side, using our selected connection.
+int P2PTransportChannel::SendPacket(const char* data,
+                                    size_t len,
+                                    const rtc::PacketOptions& options,
+                                    int flags) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (flags != 0) {
+    error_ = EINVAL;
+    return -1;
+  }
+  // If we don't think the connection is working yet, return ENOTCONN
+  // instead of sending a packet that will probably be dropped.
+  if (!ReadyToSend(selected_connection_)) {
+    error_ = ENOTCONN;
+    return -1;
+  }
+
+  packets_sent_++;
+  last_sent_packet_id_ = options.packet_id;
+  rtc::PacketOptions modified_options(options);
+  modified_options.info_signaled_after_sent.packet_type =
+      rtc::PacketType::kData;
+  int sent = selected_connection_->Send(data, len, modified_options);
+  if (sent <= 0) {
+    RTC_DCHECK(sent < 0);
+    error_ = selected_connection_->GetError();
+    return sent;
+  }
+
+  bytes_sent_ += sent;
+  return sent;
+}
+
+bool P2PTransportChannel::GetStats(IceTransportStats* ice_transport_stats) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  // Gather candidate and candidate pair stats.
+  ice_transport_stats->candidate_stats_list.clear();
+  ice_transport_stats->connection_infos.clear();
+
+  if (!allocator_sessions_.empty()) {
+    allocator_session()->GetCandidateStatsFromReadyPorts(
+        &ice_transport_stats->candidate_stats_list);
+  }
+
+  // TODO(qingsi): Remove naming inconsistency for candidate pair/connection.
+  for (Connection* connection : connections()) {
+    ConnectionInfo stats = connection->stats();
+    stats.local_candidate = SanitizeLocalCandidate(stats.local_candidate);
+    stats.remote_candidate = SanitizeRemoteCandidate(stats.remote_candidate);
+    stats.best_connection = (selected_connection_ == connection);
+    ice_transport_stats->connection_infos.push_back(std::move(stats));
+  }
+
+  ice_transport_stats->selected_candidate_pair_changes =
+      selected_candidate_pair_changes_;
+
+  ice_transport_stats->bytes_sent = bytes_sent_;
+  ice_transport_stats->bytes_received = bytes_received_;
+  ice_transport_stats->packets_sent = packets_sent_;
+  ice_transport_stats->packets_received = packets_received_;
+
+  ice_transport_stats->ice_role = GetIceRole();
+  ice_transport_stats->ice_local_username_fragment = ice_parameters_.ufrag;
+  ice_transport_stats->ice_state = ComputeIceTransportState();
+
+  return true;
+}
+
+absl::optional<rtc::NetworkRoute> P2PTransportChannel::network_route() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return network_route_;
+}
+
+rtc::DiffServCodePoint P2PTransportChannel::DefaultDscpValue() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  OptionMap::const_iterator it = options_.find(rtc::Socket::OPT_DSCP);
+  if (it == options_.end()) {
+    return rtc::DSCP_NO_CHANGE;
+  }
+  return static_cast<rtc::DiffServCodePoint>(it->second);
+}
+
+rtc::ArrayView<Connection*> P2PTransportChannel::connections() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return ice_adapter_->LegacyConnections();
+}
+
+void P2PTransportChannel::RemoveConnectionForTest(Connection* connection) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  RTC_DCHECK(FindConnection(connection));
+  connection->SignalDestroyed.disconnect(this);
+  RemoveConnection(connection);
+  RTC_DCHECK(!FindConnection(connection));
+  if (selected_connection_ == connection)
+    selected_connection_ = nullptr;
+  connection->Destroy();
+}
+
+// Monitor connection states.
+void P2PTransportChannel::UpdateConnectionStates() {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  int64_t now = rtc::TimeMillis();
+
+  // We need to copy the list of connections since some may delete themselves
+  // when we call UpdateState.
+  // NOTE: We copy the connections() vector in case `UpdateState` triggers the
+  // Connection to be destroyed (which will cause a callback that alters
+  // the connections() vector).
+  std::vector<Connection*> copy(connections().begin(), connections().end());
+  for (Connection* c : copy) {
+    c->UpdateState(now);
+  }
+}
+
+// Prepare for best candidate sorting.
+// TODO(bugs.webrtc.org/14367) remove once refactor lands.
+void P2PTransportChannel::RequestSortAndStateUpdate(
+    IceSwitchReason reason_to_sort) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (!sort_dirty_) {
+    network_thread_->PostTask(
+        SafeTask(task_safety_.flag(), [this, reason_to_sort]() {
+          SortConnectionsAndUpdateState(reason_to_sort);
+        }));
+    sort_dirty_ = true;
+  }
+}
+
+// TODO(bugs.webrtc.org/14367) remove once refactor lands.
+void P2PTransportChannel::MaybeStartPinging() {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (started_pinging_) {
+    return;
+  }
+
+  if (ice_adapter_->LegacyHasPingableConnection()) {
+    RTC_LOG(LS_INFO) << ToString()
+                     << ": Have a pingable connection for the first time; "
+                        "starting to ping.";
+    network_thread_->PostTask(
+        SafeTask(task_safety_.flag(), [this]() { CheckAndPing(); }));
+    regathering_controller_->Start();
+    started_pinging_ = true;
+  }
+}
+
+void P2PTransportChannel::OnStartedPinging() {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  RTC_LOG(LS_INFO) << ToString()
+                   << ": Have a pingable connection for the first time; "
+                      "starting to ping.";
+  regathering_controller_->Start();
+}
+
+bool P2PTransportChannel::IsPortPruned(const Port* port) const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return !absl::c_linear_search(ports_, port);
+}
+
+bool P2PTransportChannel::IsRemoteCandidatePruned(const Candidate& cand) const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return !absl::c_linear_search(remote_candidates_, cand);
+}
+
+bool P2PTransportChannel::PresumedWritable(const Connection* conn) const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return (conn->write_state() == Connection::STATE_WRITE_INIT &&
+          config_.presume_writable_when_fully_relayed &&
+          conn->local_candidate().type() == RELAY_PORT_TYPE &&
+          (conn->remote_candidate().type() == RELAY_PORT_TYPE ||
+           conn->remote_candidate().type() == PRFLX_PORT_TYPE));
+}
+
+// Sort the available connections to find the best one.  We also monitor
+// the number of available connections and the current state.
+// TODO(bugs.webrtc.org/14367) remove once refactor lands.
+void P2PTransportChannel::SortConnectionsAndUpdateState(
+    IceSwitchReason reason_to_sort) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+
+  // Make sure the connection states are up-to-date since this affects how they
+  // will be sorted.
+  UpdateConnectionStates();
+
+  // Any changes after this point will require a re-sort.
+  sort_dirty_ = false;
+
+  // If necessary, switch to the new choice. Note that `top_connection` doesn't
+  // have to be writable to become the selected connection although it will
+  // have higher priority if it is writable.
+  MaybeSwitchSelectedConnection(
+      reason_to_sort,
+      ice_adapter_->LegacySortAndSwitchConnection(reason_to_sort));
+
+  // The controlled side can prune only if the selected connection has been
+  // nominated because otherwise it may prune the connection that will be
+  // selected by the controlling side.
+  // TODO(honghaiz): This is not enough to prevent a connection from being
+  // pruned too early because with aggressive nomination, the controlling side
+  // will nominate every connection until it becomes writable.
+  if (AllowedToPruneConnections()) {
+    PruneConnections();
+  }
+
+  // Check if all connections are timedout.
+  bool all_connections_timedout = true;
+  for (const Connection* conn : connections()) {
+    if (conn->write_state() != Connection::STATE_WRITE_TIMEOUT) {
+      all_connections_timedout = false;
+      break;
+    }
+  }
+
+  // Now update the writable state of the channel with the information we have
+  // so far.
+  if (all_connections_timedout) {
+    HandleAllTimedOut();
+  }
+
+  // Update the state of this channel.
+  UpdateTransportState();
+
+  // Also possibly start pinging.
+  // We could start pinging if:
+  // * The first connection was created.
+  // * ICE credentials were provided.
+  // * A TCP connection became connected.
+  MaybeStartPinging();
+}
+
+void P2PTransportChannel::UpdateState() {
+  // Check if all connections are timedout.
+  bool all_connections_timedout = true;
+  for (const Connection* conn : connections()) {
+    if (conn->write_state() != Connection::STATE_WRITE_TIMEOUT) {
+      all_connections_timedout = false;
+      break;
+    }
+  }
+
+  // Now update the writable state of the channel with the information we have
+  // so far.
+  if (all_connections_timedout) {
+    HandleAllTimedOut();
+  }
+
+  // Update the state of this channel.
+  UpdateTransportState();
+}
+
+bool P2PTransportChannel::AllowedToPruneConnections() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return ice_role_ == ICEROLE_CONTROLLING ||
+         (selected_connection_ && selected_connection_->nominated());
+}
+
+// TODO(bugs.webrtc.org/14367) remove once refactor lands.
+void P2PTransportChannel::PruneConnections() {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  std::vector<const Connection*> connections_to_prune =
+      ice_adapter_->LegacyPruneConnections();
+  PruneConnections(connections_to_prune);
+}
+
+bool P2PTransportChannel::PruneConnections(
+    rtc::ArrayView<const Connection* const> connections) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (!AllowedToPruneConnections()) {
+    RTC_LOG(LS_WARNING) << "Not allowed to prune connections";
+    return false;
+  }
+  for (const Connection* conn : connections) {
+    FromIceController(conn)->Prune();
+  }
+  return true;
+}
+
+rtc::NetworkRoute P2PTransportChannel::ConfigureNetworkRoute(
+    const Connection* conn) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return {
+      .connected = ReadyToSend(conn),
+      .local = CreateRouteEndpointFromCandidate(
+          /* local= */ true, conn->local_candidate(),
+          /* uses_turn= */
+          conn->port()->Type() == RELAY_PORT_TYPE),
+      .remote = CreateRouteEndpointFromCandidate(
+          /* local= */ false, conn->remote_candidate(),
+          /* uses_turn= */ conn->remote_candidate().type() == RELAY_PORT_TYPE),
+      .last_sent_packet_id = last_sent_packet_id_,
+      .packet_overhead =
+          conn->local_candidate().address().ipaddr().overhead() +
+          GetProtocolOverhead(conn->local_candidate().protocol())};
+}
+
+void P2PTransportChannel::SwitchSelectedConnection(
+    const Connection* new_connection,
+    IceSwitchReason reason) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  SwitchSelectedConnectionInternal(FromIceController(new_connection), reason);
+}
+
+// Change the selected connection, and let listeners know.
+void P2PTransportChannel::SwitchSelectedConnectionInternal(
+    Connection* conn,
+    IceSwitchReason reason) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  // Note: if conn is NULL, the previous `selected_connection_` has been
+  // destroyed, so don't use it.
+  Connection* old_selected_connection = selected_connection_;
+  selected_connection_ = conn;
+  LogCandidatePairConfig(conn, webrtc::IceCandidatePairConfigType::kSelected);
+  network_route_.reset();
+  if (old_selected_connection) {
+    old_selected_connection->set_selected(false);
+  }
+  if (selected_connection_) {
+    ++nomination_;
+    selected_connection_->set_selected(true);
+    if (old_selected_connection) {
+      RTC_LOG(LS_INFO) << ToString() << ": Previous selected connection: "
+                       << old_selected_connection->ToString();
+    }
+    RTC_LOG(LS_INFO) << ToString() << ": New selected connection: "
+                     << selected_connection_->ToString();
+    SignalRouteChange(this, selected_connection_->remote_candidate());
+    // This is a temporary, but safe fix to webrtc issue 5705.
+    // TODO(honghaiz): Make all ENOTCONN error routed through the transport
+    // channel so that it knows whether the media channel is allowed to
+    // send; then it will only signal ready-to-send if the media channel
+    // has been disallowed to send.
+    if (selected_connection_->writable() ||
+        PresumedWritable(selected_connection_)) {
+      SignalReadyToSend(this);
+    }
+
+    network_route_.emplace(ConfigureNetworkRoute(selected_connection_));
+  } else {
+    RTC_LOG(LS_INFO) << ToString() << ": No selected connection";
+  }
+
+  if (conn != nullptr && ice_role_ == ICEROLE_CONTROLLING &&
+      ((ice_field_trials_.send_ping_on_switch_ice_controlling &&
+        old_selected_connection != nullptr) ||
+       ice_field_trials_.send_ping_on_selected_ice_controlling)) {
+    SendPingRequestInternal(conn);
+  }
+
+  SignalNetworkRouteChanged(network_route_);
+
+  // Create event for candidate pair change.
+  if (selected_connection_) {
+    CandidatePairChangeEvent pair_change;
+    pair_change.reason = IceSwitchReasonToString(reason);
+    pair_change.selected_candidate_pair = *GetSelectedCandidatePair();
+    pair_change.last_data_received_ms =
+        selected_connection_->last_data_received();
+
+    if (old_selected_connection) {
+      pair_change.estimated_disconnected_time_ms =
+          ComputeEstimatedDisconnectedTimeMs(rtc::TimeMillis(),
+                                             old_selected_connection);
+    } else {
+      pair_change.estimated_disconnected_time_ms = 0;
+    }
+
+    SignalCandidatePairChanged(pair_change);
+  }
+
+  ++selected_candidate_pair_changes_;
+
+  ice_adapter_->OnConnectionSwitched(selected_connection_);
+}
+
+int64_t P2PTransportChannel::ComputeEstimatedDisconnectedTimeMs(
+    int64_t now_ms,
+    Connection* old_connection) {
+  // TODO(jonaso): nicer keeps estimate of how frequently data _should_ be
+  // received, this could be used to give better estimate (if needed).
+  int64_t last_data_or_old_ping =
+      std::max(old_connection->last_received(), last_data_received_ms_);
+  return (now_ms - last_data_or_old_ping);
+}
+
+// Warning: UpdateTransportState should eventually be called whenever a
+// connection is added, deleted, or the write state of any connection changes so
+// that the transport controller will get the up-to-date channel state. However
+// it should not be called too often; in the case that multiple connection
+// states change, it should be called after all the connection states have
+// changed. For example, we call this at the end of
+// SortConnectionsAndUpdateState.
+void P2PTransportChannel::UpdateTransportState() {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  // If our selected connection is "presumed writable" (TURN-TURN with no
+  // CreatePermission required), act like we're already writable to the upper
+  // layers, so they can start media quicker.
+  bool writable =
+      selected_connection_ && (selected_connection_->writable() ||
+                               PresumedWritable(selected_connection_));
+  SetWritable(writable);
+
+  bool receiving = false;
+  for (const Connection* connection : connections()) {
+    if (connection->receiving()) {
+      receiving = true;
+      break;
+    }
+  }
+  SetReceiving(receiving);
+
+  IceTransportState state = ComputeState();
+  webrtc::IceTransportState current_standardized_state =
+      ComputeIceTransportState();
+
+  if (state_ != state) {
+    RTC_LOG(LS_INFO) << ToString() << ": Transport channel state changed from "
+                     << static_cast<int>(state_) << " to "
+                     << static_cast<int>(state);
+    // Check that the requested transition is allowed. Note that
+    // P2PTransportChannel does not (yet) implement a direct mapping of the
+    // ICE states from the standard; the difference is covered by
+    // TransportController and PeerConnection.
+    switch (state_) {
+      case IceTransportState::STATE_INIT:
+        // TODO(deadbeef): Once we implement end-of-candidates signaling,
+        // we shouldn't go from INIT to COMPLETED.
+        RTC_DCHECK(state == IceTransportState::STATE_CONNECTING ||
+                   state == IceTransportState::STATE_COMPLETED ||
+                   state == IceTransportState::STATE_FAILED);
+        break;
+      case IceTransportState::STATE_CONNECTING:
+        RTC_DCHECK(state == IceTransportState::STATE_COMPLETED ||
+                   state == IceTransportState::STATE_FAILED);
+        break;
+      case IceTransportState::STATE_COMPLETED:
+        // TODO(deadbeef): Once we implement end-of-candidates signaling,
+        // we shouldn't go from COMPLETED to CONNECTING.
+        // Though we *can* go from COMPlETED to FAILED, if consent expires.
+        RTC_DCHECK(state == IceTransportState::STATE_CONNECTING ||
+                   state == IceTransportState::STATE_FAILED);
+        break;
+      case IceTransportState::STATE_FAILED:
+        // TODO(deadbeef): Once we implement end-of-candidates signaling,
+        // we shouldn't go from FAILED to CONNECTING or COMPLETED.
+        RTC_DCHECK(state == IceTransportState::STATE_CONNECTING ||
+                   state == IceTransportState::STATE_COMPLETED);
+        break;
+      default:
+        RTC_DCHECK_NOTREACHED();
+        break;
+    }
+    state_ = state;
+    SignalStateChanged(this);
+  }
+
+  if (standardized_state_ != current_standardized_state) {
+    standardized_state_ = current_standardized_state;
+    SignalIceTransportStateChanged(this);
+  }
+}
+
+void P2PTransportChannel::MaybeStopPortAllocatorSessions() {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (!IsGettingPorts()) {
+    return;
+  }
+
+  for (const auto& session : allocator_sessions_) {
+    if (session->IsStopped()) {
+      continue;
+    }
+    // If gathering continually, keep the last session running so that
+    // it can gather candidates if the networks change.
+    if (config_.gather_continually() && session == allocator_sessions_.back()) {
+      session->ClearGettingPorts();
+    } else {
+      session->StopGettingPorts();
+    }
+  }
+}
+
+void P2PTransportChannel::OnSelectedConnectionDestroyed() {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  RTC_LOG(LS_INFO) << "Selected connection destroyed. Will choose a new one.";
+  IceSwitchReason reason = IceSwitchReason::SELECTED_CONNECTION_DESTROYED;
+  SwitchSelectedConnectionInternal(nullptr, reason);
+  ice_adapter_->OnSortAndSwitchRequest(reason);
+}
+
+// If all connections timed out, delete them all.
+void P2PTransportChannel::HandleAllTimedOut() {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  bool update_selected_connection = false;
+  std::vector<Connection*> copy(connections().begin(), connections().end());
+  for (Connection* connection : copy) {
+    if (selected_connection_ == connection) {
+      selected_connection_ = nullptr;
+      update_selected_connection = true;
+    }
+    connection->SignalDestroyed.disconnect(this);
+    RemoveConnection(connection);
+    connection->Destroy();
+  }
+
+  if (update_selected_connection)
+    OnSelectedConnectionDestroyed();
+}
+
+bool P2PTransportChannel::ReadyToSend(const Connection* connection) const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  // Note that we allow sending on an unreliable connection, because it's
+  // possible that it became unreliable simply due to bad chance.
+  // So this shouldn't prevent attempting to send media.
+  return connection != nullptr &&
+         (connection->writable() ||
+          connection->write_state() == Connection::STATE_WRITE_UNRELIABLE ||
+          PresumedWritable(connection));
+}
+
+// Handle queued up check-and-ping request
+// TODO(bugs.webrtc.org/14367) remove once refactor lands.
+void P2PTransportChannel::CheckAndPing() {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  // Make sure the states of the connections are up-to-date (since this
+  // affects which ones are pingable).
+  UpdateConnectionStates();
+
+  auto result = ice_adapter_->LegacySelectConnectionToPing(last_ping_sent_ms_);
+  TimeDelta delay = TimeDelta::Millis(result.recheck_delay_ms);
+
+  if (result.connection.value_or(nullptr)) {
+    SendPingRequest(result.connection.value());
+  }
+
+  network_thread_->PostDelayedTask(
+      SafeTask(task_safety_.flag(), [this]() { CheckAndPing(); }), delay);
+}
+
+// This method is only for unit testing.
+Connection* P2PTransportChannel::FindNextPingableConnection() {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  const Connection* conn = ice_adapter_->FindNextPingableConnection();
+  if (conn) {
+    return FromIceController(conn);
+  } else {
+    return nullptr;
+  }
+}
+
+int64_t P2PTransportChannel::GetLastPingSentMs() const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return last_ping_sent_ms_;
+}
+
+void P2PTransportChannel::SendPingRequest(const Connection* connection) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  SendPingRequestInternal(FromIceController(connection));
+}
+
+void P2PTransportChannel::SendPingRequestInternal(Connection* connection) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  PingConnection(connection);
+  MarkConnectionPinged(connection);
+}
+
+// A connection is considered a backup connection if the channel state
+// is completed, the connection is not the selected connection and it is
+// active.
+void P2PTransportChannel::MarkConnectionPinged(Connection* conn) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  ice_adapter_->OnConnectionPinged(conn);
+}
+
+// Apart from sending ping from `conn` this method also updates
+// `use_candidate_attr` and `nomination` flags. One of the flags is set to
+// nominate `conn` if this channel is in CONTROLLING.
+void P2PTransportChannel::PingConnection(Connection* conn) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  bool use_candidate_attr = false;
+  uint32_t nomination = 0;
+  if (ice_role_ == ICEROLE_CONTROLLING) {
+    bool renomination_supported = ice_parameters_.renomination &&
+                                  !remote_ice_parameters_.empty() &&
+                                  remote_ice_parameters_.back().renomination;
+    if (renomination_supported) {
+      nomination = GetNominationAttr(conn);
+    } else {
+      use_candidate_attr = GetUseCandidateAttr(conn);
+    }
+  }
+  conn->set_nomination(nomination);
+  conn->set_use_candidate_attr(use_candidate_attr);
+  last_ping_sent_ms_ = rtc::TimeMillis();
+  conn->Ping(last_ping_sent_ms_);
+}
+
+uint32_t P2PTransportChannel::GetNominationAttr(Connection* conn) const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return (conn == selected_connection_) ? nomination_ : 0;
+}
+
+// Nominate a connection based on the NominationMode.
+bool P2PTransportChannel::GetUseCandidateAttr(Connection* conn) const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return ice_adapter_->GetUseCandidateAttribute(
+      conn, config_.default_nomination_mode, remote_ice_mode_);
+}
+
+// When a connection's state changes, we need to figure out who to use as
+// the selected connection again.  It could have become usable, or become
+// unusable.
+void P2PTransportChannel::OnConnectionStateChange(Connection* connection) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+
+  // May stop the allocator session when at least one connection becomes
+  // strongly connected after starting to get ports and the local candidate of
+  // the connection is at the latest generation. It is not enough to check
+  // that the connection becomes weakly connected because the connection may
+  // be changing from (writable, receiving) to (writable, not receiving).
+  if (ice_field_trials_.stop_gather_on_strongly_connected) {
+    bool strongly_connected = !connection->weak();
+    bool latest_generation = connection->local_candidate().generation() >=
+                             allocator_session()->generation();
+    if (strongly_connected && latest_generation) {
+      MaybeStopPortAllocatorSessions();
+    }
+  }
+  // We have to unroll the stack before doing this because we may be changing
+  // the state of connections while sorting.
+  ice_adapter_->OnSortAndSwitchRequest(
+      IceSwitchReason::CONNECT_STATE_CHANGE);  // "candidate pair state
+                                               // changed");
+}
+
+// When a connection is removed, edit it out, and then update our best
+// connection.
+void P2PTransportChannel::OnConnectionDestroyed(Connection* connection) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+
+  // Note: the previous selected_connection_ may be destroyed by now, so don't
+  // use it.
+
+  // Remove this connection from the list.
+  RemoveConnection(connection);
+
+  RTC_LOG(LS_INFO) << ToString() << ": Removed connection " << connection
+                   << " (" << connections().size() << " remaining)";
+
+  // If this is currently the selected connection, then we need to pick a new
+  // one. The call to SortConnectionsAndUpdateState will pick a new one. It
+  // looks at the current selected connection in order to avoid switching
+  // between fairly similar ones. Since this connection is no longer an
+  // option, we can just set selected to nullptr and re-choose a best assuming
+  // that there was no selected connection.
+  if (selected_connection_ == connection) {
+    OnSelectedConnectionDestroyed();
+  } else {
+    // If a non-selected connection was destroyed, we don't need to re-sort but
+    // we do need to update state, because we could be switching to "failed" or
+    // "completed".
+    UpdateTransportState();
+  }
+}
+
+void P2PTransportChannel::RemoveConnection(const Connection* connection) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  auto it = absl::c_find(connections_, connection);
+  RTC_DCHECK(it != connections_.end());
+  connections_.erase(it);
+  ice_adapter_->OnConnectionDestroyed(connection);
+}
+
+// When a port is destroyed, remove it from our list of ports to use for
+// connection attempts.
+void P2PTransportChannel::OnPortDestroyed(PortInterface* port) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+
+  ports_.erase(std::remove(ports_.begin(), ports_.end(), port), ports_.end());
+  pruned_ports_.erase(
+      std::remove(pruned_ports_.begin(), pruned_ports_.end(), port),
+      pruned_ports_.end());
+  RTC_LOG(LS_INFO) << "Removed port because it is destroyed: " << ports_.size()
+                   << " remaining";
+}
+
+void P2PTransportChannel::OnPortsPruned(
+    PortAllocatorSession* session,
+    const std::vector<PortInterface*>& ports) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  for (PortInterface* port : ports) {
+    if (PrunePort(port)) {
+      RTC_LOG(LS_INFO) << "Removed port: " << port->ToString() << " "
+                       << ports_.size() << " remaining";
+    }
+  }
+}
+
+void P2PTransportChannel::OnCandidatesRemoved(
+    PortAllocatorSession* session,
+    const std::vector<Candidate>& candidates) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  // Do not signal candidate removals if continual gathering is not enabled,
+  // or if this is not the last session because an ICE restart would have
+  // signaled the remote side to remove all candidates in previous sessions.
+  if (!config_.gather_continually() || session != allocator_session()) {
+    return;
+  }
+
+  std::vector<Candidate> candidates_to_remove;
+  for (Candidate candidate : candidates) {
+    candidate.set_transport_name(transport_name());
+    candidates_to_remove.push_back(candidate);
+  }
+  SignalCandidatesRemoved(this, candidates_to_remove);
+}
+
+void P2PTransportChannel::PruneAllPorts() {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  pruned_ports_.insert(pruned_ports_.end(), ports_.begin(), ports_.end());
+  ports_.clear();
+}
+
+bool P2PTransportChannel::PrunePort(PortInterface* port) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  auto it = absl::c_find(ports_, port);
+  // Don't need to do anything if the port has been deleted from the port
+  // list.
+  if (it == ports_.end()) {
+    return false;
+  }
+  ports_.erase(it);
+  pruned_ports_.push_back(port);
+  return true;
+}
+
+// We data is available, let listeners know
+void P2PTransportChannel::OnReadPacket(Connection* connection,
+                                       const char* data,
+                                       size_t len,
+                                       int64_t packet_time_us) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+
+  if (connection == selected_connection_) {
+    // Let the client know of an incoming packet
+    packets_received_++;
+    bytes_received_ += len;
+    RTC_DCHECK(connection->last_data_received() >= last_data_received_ms_);
+    last_data_received_ms_ =
+        std::max(last_data_received_ms_, connection->last_data_received());
+    SignalReadPacket(this, data, len, packet_time_us, 0);
+    return;
+  }
+
+  // Do not deliver, if packet doesn't belong to the correct transport
+  // channel.
+  if (!FindConnection(connection))
+    return;
+
+  packets_received_++;
+  bytes_received_ += len;
+  RTC_DCHECK(connection->last_data_received() >= last_data_received_ms_);
+  last_data_received_ms_ =
+      std::max(last_data_received_ms_, connection->last_data_received());
+
+  // Let the client know of an incoming packet
+  SignalReadPacket(this, data, len, packet_time_us, 0);
+
+  // May need to switch the sending connection based on the receiving media
+  // path if this is the controlled side.
+  if (ice_role_ == ICEROLE_CONTROLLED) {
+    ice_adapter_->OnImmediateSwitchRequest(IceSwitchReason::DATA_RECEIVED,
+                                           connection);
+  }
+}
+
+void P2PTransportChannel::OnSentPacket(const rtc::SentPacket& sent_packet) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+
+  SignalSentPacket(this, sent_packet);
+}
+
+void P2PTransportChannel::OnReadyToSend(Connection* connection) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (connection == selected_connection_ && writable()) {
+    SignalReadyToSend(this);
+  }
+}
+
+void P2PTransportChannel::SetWritable(bool writable) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (writable_ == writable) {
+    return;
+  }
+  RTC_LOG(LS_VERBOSE) << ToString() << ": Changed writable_ to " << writable;
+  writable_ = writable;
+  if (writable_) {
+    has_been_writable_ = true;
+    SignalReadyToSend(this);
+  }
+  SignalWritableState(this);
+}
+
+void P2PTransportChannel::SetReceiving(bool receiving) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (receiving_ == receiving) {
+    return;
+  }
+  receiving_ = receiving;
+  SignalReceivingState(this);
+}
+
+Candidate P2PTransportChannel::SanitizeLocalCandidate(
+    const Candidate& c) const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  // Delegates to the port allocator.
+  return allocator_->SanitizeCandidate(c);
+}
+
+Candidate P2PTransportChannel::SanitizeRemoteCandidate(
+    const Candidate& c) const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  // If the remote endpoint signaled us an mDNS candidate, we assume it
+  // is supposed to be sanitized.
+  bool use_hostname_address = absl::EndsWith(c.address().hostname(), LOCAL_TLD);
+  // Remove the address for prflx remote candidates. See
+  // https://w3c.github.io/webrtc-stats/#dom-rtcicecandidatestats.
+  use_hostname_address |= c.type() == PRFLX_PORT_TYPE;
+  return c.ToSanitizedCopy(use_hostname_address,
+                           false /* filter_related_address */);
+}
+
+void P2PTransportChannel::LogCandidatePairConfig(
+    Connection* conn,
+    webrtc::IceCandidatePairConfigType type) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (conn == nullptr) {
+    return;
+  }
+  ice_event_log_.LogCandidatePairConfig(type, conn->id(),
+                                        conn->ToLogDescription());
+}
+
+P2PTransportChannel::IceControllerAdapter::IceControllerAdapter(
+    const IceControllerFactoryArgs& args,
+    IceControllerFactoryInterface* ice_controller_factory,
+    ActiveIceControllerFactoryInterface* active_ice_controller_factory,
+    const webrtc::FieldTrialsView* field_trials,
+    P2PTransportChannel* transport)
+    : transport_(transport) {
+  if (UseActiveIceControllerFieldTrialEnabled(field_trials)) {
+    if (active_ice_controller_factory) {
+      ActiveIceControllerFactoryArgs active_args{args,
+                                                 /* ice_agent= */ transport};
+      active_ice_controller_ =
+          active_ice_controller_factory->Create(active_args);
+    } else {
+      active_ice_controller_ = std::make_unique<WrappingActiveIceController>(
+          /* ice_agent= */ transport, ice_controller_factory, args);
+    }
+  } else {
+    if (ice_controller_factory != nullptr) {
+      legacy_ice_controller_ = ice_controller_factory->Create(args);
+    } else {
+      legacy_ice_controller_ = std::make_unique<BasicIceController>(args);
+    }
+  }
+}
+
+P2PTransportChannel::IceControllerAdapter::~IceControllerAdapter() = default;
+
+void P2PTransportChannel::IceControllerAdapter::SetIceConfig(
+    const IceConfig& config) {
+  active_ice_controller_ ? active_ice_controller_->SetIceConfig(config)
+                         : legacy_ice_controller_->SetIceConfig(config);
+}
+
+void P2PTransportChannel::IceControllerAdapter::OnConnectionAdded(
+    const Connection* connection) {
+  active_ice_controller_ ? active_ice_controller_->OnConnectionAdded(connection)
+                         : legacy_ice_controller_->AddConnection(connection);
+}
+
+void P2PTransportChannel::IceControllerAdapter::OnConnectionSwitched(
+    const Connection* connection) {
+  active_ice_controller_
+      ? active_ice_controller_->OnConnectionSwitched(connection)
+      : legacy_ice_controller_->SetSelectedConnection(connection);
+}
+
+void P2PTransportChannel::IceControllerAdapter::OnConnectionPinged(
+    const Connection* connection) {
+  active_ice_controller_
+      ? active_ice_controller_->OnConnectionPinged(connection)
+      : legacy_ice_controller_->MarkConnectionPinged(connection);
+}
+
+void P2PTransportChannel::IceControllerAdapter::OnConnectionDestroyed(
+    const Connection* connection) {
+  active_ice_controller_
+      ? active_ice_controller_->OnConnectionDestroyed(connection)
+      : legacy_ice_controller_->OnConnectionDestroyed(connection);
+}
+
+void P2PTransportChannel::IceControllerAdapter::OnConnectionUpdated(
+    const Connection* connection) {
+  if (active_ice_controller_) {
+    active_ice_controller_->OnConnectionUpdated(connection);
+    return;
+  }
+  RTC_DCHECK_NOTREACHED();
+}
+
+void P2PTransportChannel::IceControllerAdapter::OnSortAndSwitchRequest(
+    IceSwitchReason reason) {
+  active_ice_controller_
+      ? active_ice_controller_->OnSortAndSwitchRequest(reason)
+      : transport_->RequestSortAndStateUpdate(reason);
+}
+
+void P2PTransportChannel::IceControllerAdapter::OnImmediateSortAndSwitchRequest(
+    IceSwitchReason reason) {
+  active_ice_controller_
+      ? active_ice_controller_->OnImmediateSortAndSwitchRequest(reason)
+      : transport_->SortConnectionsAndUpdateState(reason);
+}
+
+bool P2PTransportChannel::IceControllerAdapter::OnImmediateSwitchRequest(
+    IceSwitchReason reason,
+    const Connection* connection) {
+  return active_ice_controller_
+             ? active_ice_controller_->OnImmediateSwitchRequest(reason,
+                                                                connection)
+             : transport_->MaybeSwitchSelectedConnection(connection, reason);
+}
+
+bool P2PTransportChannel::IceControllerAdapter::GetUseCandidateAttribute(
+    const cricket::Connection* connection,
+    cricket::NominationMode mode,
+    cricket::IceMode remote_ice_mode) const {
+  return active_ice_controller_
+             ? active_ice_controller_->GetUseCandidateAttribute(
+                   connection, mode, remote_ice_mode)
+             : legacy_ice_controller_->GetUseCandidateAttr(connection, mode,
+                                                           remote_ice_mode);
+}
+
+const Connection*
+P2PTransportChannel::IceControllerAdapter::FindNextPingableConnection() {
+  return active_ice_controller_
+             ? active_ice_controller_->FindNextPingableConnection()
+             : legacy_ice_controller_->FindNextPingableConnection();
+}
+
+rtc::ArrayView<Connection*>
+P2PTransportChannel::IceControllerAdapter::LegacyConnections() const {
+  RTC_DCHECK_RUN_ON(transport_->network_thread_);
+  if (active_ice_controller_) {
+    return rtc::ArrayView<Connection*>(transport_->connections_.data(),
+                                       transport_->connections_.size());
+  }
+
+  rtc::ArrayView<const Connection*> res = legacy_ice_controller_->connections();
+  return rtc::ArrayView<Connection*>(const_cast<Connection**>(res.data()),
+                                     res.size());
+}
+
+bool P2PTransportChannel::IceControllerAdapter::LegacyHasPingableConnection()
+    const {
+  if (active_ice_controller_) {
+    RTC_DCHECK_NOTREACHED();
+  }
+  return legacy_ice_controller_->HasPingableConnection();
+}
+
+IceControllerInterface::PingResult
+P2PTransportChannel::IceControllerAdapter::LegacySelectConnectionToPing(
+    int64_t last_ping_sent_ms) {
+  if (active_ice_controller_) {
+    RTC_DCHECK_NOTREACHED();
+  }
+  return legacy_ice_controller_->SelectConnectionToPing(last_ping_sent_ms);
+}
+
+IceControllerInterface::SwitchResult
+P2PTransportChannel::IceControllerAdapter::LegacyShouldSwitchConnection(
+    IceSwitchReason reason,
+    const Connection* connection) {
+  if (active_ice_controller_) {
+    RTC_DCHECK_NOTREACHED();
+  }
+  return legacy_ice_controller_->ShouldSwitchConnection(reason, connection);
+}
+
+IceControllerInterface::SwitchResult
+P2PTransportChannel::IceControllerAdapter::LegacySortAndSwitchConnection(
+    IceSwitchReason reason) {
+  if (active_ice_controller_) {
+    RTC_DCHECK_NOTREACHED();
+  }
+  return legacy_ice_controller_->SortAndSwitchConnection(reason);
+}
+
+std::vector<const Connection*>
+P2PTransportChannel::IceControllerAdapter::LegacyPruneConnections() {
+  if (active_ice_controller_) {
+    RTC_DCHECK_NOTREACHED();
+  }
+  return legacy_ice_controller_->PruneConnections();
+}
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/p2p_transport_channel.h b/third_party/libwebrtc/p2p/base/p2p_transport_channel.h
new file mode 100644
index 0000000000..f7bfce0e17
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/p2p_transport_channel.h
@@ -0,0 +1,590 @@
+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+// P2PTransportChannel wraps up the state management of the connection between
+// two P2P clients.  Clients have candidate ports for connecting, and
+// connections which are combinations of candidates from each end (Alice and
+// Bob each have candidates, one candidate from Alice and one candidate from
+// Bob are used to make a connection, repeat to make many connections).
+//
+// When all of the available connections become invalid (non-writable), we
+// kick off a process of determining more candidates and more connections.
+//
+#ifndef P2P_BASE_P2P_TRANSPORT_CHANNEL_H_
+#define P2P_BASE_P2P_TRANSPORT_CHANNEL_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <algorithm>
+#include <map>
+#include <memory>
+#include <set>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "absl/base/attributes.h"
+#include "absl/strings/string_view.h"
+#include "absl/types/optional.h"
+#include "api/array_view.h"
+#include "api/async_dns_resolver.h"
+#include "api/async_resolver_factory.h"
+#include "api/candidate.h"
+#include "api/ice_transport_interface.h"
+#include "api/rtc_error.h"
+#include "api/sequence_checker.h"
+#include "api/task_queue/pending_task_safety_flag.h"
+#include "api/transport/enums.h"
+#include "api/transport/stun.h"
+#include "logging/rtc_event_log/events/rtc_event_ice_candidate_pair_config.h"
+#include "logging/rtc_event_log/ice_logger.h"
+#include "p2p/base/active_ice_controller_factory_interface.h"
+#include "p2p/base/basic_async_resolver_factory.h"
+#include "p2p/base/candidate_pair_interface.h"
+#include "p2p/base/connection.h"
+#include "p2p/base/ice_agent_interface.h"
+#include "p2p/base/ice_controller_factory_interface.h"
+#include "p2p/base/ice_controller_interface.h"
+#include "p2p/base/ice_switch_reason.h"
+#include "p2p/base/ice_transport_internal.h"
+#include "p2p/base/p2p_constants.h"
+#include "p2p/base/p2p_transport_channel_ice_field_trials.h"
+#include "p2p/base/port.h"
+#include "p2p/base/port_allocator.h"
+#include "p2p/base/port_interface.h"
+#include "p2p/base/regathering_controller.h"
+#include "p2p/base/transport_description.h"
+#include "rtc_base/async_packet_socket.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/dscp.h"
+#include "rtc_base/network/sent_packet.h"
+#include "rtc_base/network_route.h"
+#include "rtc_base/socket.h"
+#include "rtc_base/socket_address.h"
+#include "rtc_base/strings/string_builder.h"
+#include "rtc_base/system/rtc_export.h"
+#include "rtc_base/third_party/sigslot/sigslot.h"
+#include "rtc_base/thread.h"
+#include "rtc_base/thread_annotations.h"
+
+namespace webrtc {
+class RtcEventLog;
+}  // namespace webrtc
+
+namespace cricket {
+
+// Enum for UMA metrics, used to record whether the channel is
+// connected/connecting/disconnected when ICE restart happens.
+enum class IceRestartState { CONNECTING, CONNECTED, DISCONNECTED, MAX_VALUE };
+
+static const int MIN_PINGS_AT_WEAK_PING_INTERVAL = 3;
+
+bool IceCredentialsChanged(absl::string_view old_ufrag,
+                           absl::string_view old_pwd,
+                           absl::string_view new_ufrag,
+                           absl::string_view new_pwd);
+
+// Adds the port on which the candidate originated.
+class RemoteCandidate : public Candidate {
+ public:
+  RemoteCandidate(const Candidate& c, PortInterface* origin_port)
+      : Candidate(c), origin_port_(origin_port) {}
+
+  PortInterface* origin_port() { return origin_port_; }
+
+ private:
+  PortInterface* origin_port_;
+};
+
+// P2PTransportChannel manages the candidates and connection process to keep
+// two P2P clients connected to each other.
+class RTC_EXPORT P2PTransportChannel : public IceTransportInternal,
+                                       public IceAgentInterface {
+ public:
+  static std::unique_ptr<P2PTransportChannel> Create(
+      absl::string_view transport_name,
+      int component,
+      webrtc::IceTransportInit init);
+
+  // For testing only.
+  // TODO(zstein): Remove once AsyncDnsResolverFactory is required.
+  P2PTransportChannel(absl::string_view transport_name,
+                      int component,
+                      PortAllocator* allocator,
+                      const webrtc::FieldTrialsView* field_trials = nullptr);
+
+  ~P2PTransportChannel() override;
+
+  P2PTransportChannel(const P2PTransportChannel&) = delete;
+  P2PTransportChannel& operator=(const P2PTransportChannel&) = delete;
+
+  // From TransportChannelImpl:
+  IceTransportState GetState() const override;
+  webrtc::IceTransportState GetIceTransportState() const override;
+
+  const std::string& transport_name() const override;
+  int component() const override;
+  bool writable() const override;
+  bool receiving() const override;
+  void SetIceRole(IceRole role) override;
+  IceRole GetIceRole() const override;
+  void SetIceTiebreaker(uint64_t tiebreaker) override;
+  void SetIceParameters(const IceParameters& ice_params) override;
+  void SetRemoteIceParameters(const IceParameters& ice_params) override;
+  void SetRemoteIceMode(IceMode mode) override;
+  // TODO(deadbeef): Deprecated. Remove when Chromium's
+  // IceTransportChannel does not depend on this.
+  void Connect() {}
+  void MaybeStartGathering() override;
+  IceGatheringState gathering_state() const override;
+  void ResolveHostnameCandidate(const Candidate& candidate);
+  void AddRemoteCandidate(const Candidate& candidate) override;
+  void RemoveRemoteCandidate(const Candidate& candidate) override;
+  void RemoveAllRemoteCandidates() override;
+  // Sets the parameters in IceConfig. We do not set them blindly. Instead, we
+  // only update the parameter if it is considered set in `config`. For example,
+  // a negative value of receiving_timeout will be considered "not set" and we
+  // will not use it to update the respective parameter in `config_`.
+  // TODO(deadbeef): Use absl::optional instead of negative values.
+  void SetIceConfig(const IceConfig& config) override;
+  const IceConfig& config() const;
+  static webrtc::RTCError ValidateIceConfig(const IceConfig& config);
+
+  // From TransportChannel:
+  int SendPacket(const char* data,
+                 size_t len,
+                 const rtc::PacketOptions& options,
+                 int flags) override;
+  int SetOption(rtc::Socket::Option opt, int value) override;
+  bool GetOption(rtc::Socket::Option opt, int* value) override;
+  int GetError() override;
+  bool GetStats(IceTransportStats* ice_transport_stats) override;
+  absl::optional<int> GetRttEstimate() override;
+  const Connection* selected_connection() const override;
+  absl::optional<const CandidatePair> GetSelectedCandidatePair() const override;
+
+  // From IceAgentInterface
+  void OnStartedPinging() override;
+  int64_t GetLastPingSentMs() const override;
+  void UpdateConnectionStates() override;
+  void UpdateState() override;
+  void SendPingRequest(const Connection* connection) override;
+  void SwitchSelectedConnection(const Connection* connection,
+                                IceSwitchReason reason) override;
+  void ForgetLearnedStateForConnections(
+      rtc::ArrayView<const Connection* const> connections) override;
+  bool PruneConnections(
+      rtc::ArrayView<const Connection* const> connections) override;
+
+  // TODO(honghaiz): Remove this method once the reference of it in
+  // Chromoting is removed.
+  const Connection* best_connection() const {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    return selected_connection_;
+  }
+
+  void set_incoming_only(bool value) {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    incoming_only_ = value;
+  }
+
+  // Note: These are only for testing purpose.
+  // `ports_` and `pruned_ports` should not be changed from outside.
+  const std::vector<PortInterface*>& ports() {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    return ports_;
+  }
+  const std::vector<PortInterface*>& pruned_ports() {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    return pruned_ports_;
+  }
+
+  IceMode remote_ice_mode() const {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    return remote_ice_mode_;
+  }
+
+  void PruneAllPorts();
+  int check_receiving_interval() const;
+  absl::optional<rtc::NetworkRoute> network_route() const override;
+
+  void RemoveConnection(const Connection* connection);
+
+  // Helper method used only in unittest.
+  rtc::DiffServCodePoint DefaultDscpValue() const;
+
+  // Public for unit tests.
+  Connection* FindNextPingableConnection();
+  void MarkConnectionPinged(Connection* conn);
+
+  // Public for unit tests.
+  rtc::ArrayView<Connection*> connections() const;
+  void RemoveConnectionForTest(Connection* connection);
+
+  // Public for unit tests.
+  PortAllocatorSession* allocator_session() const {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    if (allocator_sessions_.empty()) {
+      return nullptr;
+    }
+    return allocator_sessions_.back().get();
+  }
+
+  // Public for unit tests.
+  const std::vector<RemoteCandidate>& remote_candidates() const {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    return remote_candidates_;
+  }
+
+  std::string ToString() const {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    const std::string RECEIVING_ABBREV[2] = {"_", "R"};
+    const std::string WRITABLE_ABBREV[2] = {"_", "W"};
+    rtc::StringBuilder ss;
+    ss << "Channel[" << transport_name_ << "|" << component_ << "|"
+       << RECEIVING_ABBREV[receiving_] << WRITABLE_ABBREV[writable_] << "]";
+    return ss.Release();
+  }
+
+ private:
+  P2PTransportChannel(
+      absl::string_view transport_name,
+      int component,
+      PortAllocator* allocator,
+      // DNS resolver factory
+      webrtc::AsyncDnsResolverFactoryInterface* async_dns_resolver_factory,
+      // If the P2PTransportChannel has to delete the DNS resolver factory
+      // on release, this pointer is set.
+      std::unique_ptr<webrtc::AsyncDnsResolverFactoryInterface>
+          owned_dns_resolver_factory,
+      webrtc::RtcEventLog* event_log,
+      IceControllerFactoryInterface* ice_controller_factory,
+      ActiveIceControllerFactoryInterface* active_ice_controller_factory,
+      const webrtc::FieldTrialsView* field_trials);
+
+  bool IsGettingPorts() {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    return allocator_session()->IsGettingPorts();
+  }
+
+  // Returns true if it's possible to send packets on `connection`.
+  bool ReadyToSend(const Connection* connection) const;
+  bool PresumedWritable(const Connection* conn) const;
+  // TODO(bugs.webrtc.org/14367) remove once refactor lands.
+  void RequestSortAndStateUpdate(IceSwitchReason reason_to_sort);
+  // Start pinging if we haven't already started, and we now have a connection
+  // that's pingable.
+  // TODO(bugs.webrtc.org/14367) remove once refactor lands.
+  void MaybeStartPinging();
+  void SendPingRequestInternal(Connection* connection);
+
+  // TODO(bugs.webrtc.org/14367) remove once refactor lands.
+  void SortConnectionsAndUpdateState(IceSwitchReason reason_to_sort);
+  rtc::NetworkRoute ConfigureNetworkRoute(const Connection* conn);
+  void SwitchSelectedConnectionInternal(Connection* conn,
+                                        IceSwitchReason reason);
+  void UpdateTransportState();
+  void HandleAllTimedOut();
+  void MaybeStopPortAllocatorSessions();
+  void OnSelectedConnectionDestroyed() RTC_RUN_ON(network_thread_);
+
+  // ComputeIceTransportState computes the RTCIceTransportState as described in
+  // https://w3c.github.io/webrtc-pc/#dom-rtcicetransportstate. ComputeState
+  // computes the value we currently export as RTCIceTransportState.
+  // TODO(bugs.webrtc.org/9308): Remove ComputeState once it's no longer used.
+  IceTransportState ComputeState() const;
+  webrtc::IceTransportState ComputeIceTransportState() const;
+
+  bool CreateConnections(const Candidate& remote_candidate,
+                         PortInterface* origin_port);
+  bool CreateConnection(PortInterface* port,
+                        const Candidate& remote_candidate,
+                        PortInterface* origin_port);
+  bool FindConnection(const Connection* connection) const;
+
+  uint32_t GetRemoteCandidateGeneration(const Candidate& candidate);
+  bool IsDuplicateRemoteCandidate(const Candidate& candidate);
+  void RememberRemoteCandidate(const Candidate& remote_candidate,
+                               PortInterface* origin_port);
+  void PingConnection(Connection* conn);
+  void AddAllocatorSession(std::unique_ptr<PortAllocatorSession> session);
+  void AddConnection(Connection* connection);
+
+  void OnPortReady(PortAllocatorSession* session, PortInterface* port);
+  void OnPortsPruned(PortAllocatorSession* session,
+                     const std::vector<PortInterface*>& ports);
+  void OnCandidatesReady(PortAllocatorSession* session,
+                         const std::vector<Candidate>& candidates);
+  void OnCandidateError(PortAllocatorSession* session,
+                        const IceCandidateErrorEvent& event);
+  void OnCandidatesRemoved(PortAllocatorSession* session,
+                           const std::vector<Candidate>& candidates);
+  void OnCandidatesAllocationDone(PortAllocatorSession* session);
+  void OnUnknownAddress(PortInterface* port,
+                        const rtc::SocketAddress& addr,
+                        ProtocolType proto,
+                        IceMessage* stun_msg,
+                        const std::string& remote_username,
+                        bool port_muxed);
+  void OnCandidateFilterChanged(uint32_t prev_filter, uint32_t cur_filter);
+
+  // When a port is destroyed, remove it from both lists `ports_`
+  // and `pruned_ports_`.
+  void OnPortDestroyed(PortInterface* port);
+  // When pruning a port, move it from `ports_` to `pruned_ports_`.
+  // Returns true if the port is found and removed from `ports_`.
+  bool PrunePort(PortInterface* port);
+  void OnRoleConflict(PortInterface* port);
+
+  void OnConnectionStateChange(Connection* connection);
+  void OnReadPacket(Connection* connection,
+                    const char* data,
+                    size_t len,
+                    int64_t packet_time_us);
+  void OnSentPacket(const rtc::SentPacket& sent_packet);
+  void OnReadyToSend(Connection* connection);
+  void OnConnectionDestroyed(Connection* connection);
+
+  void OnNominated(Connection* conn);
+
+  // TODO(bugs.webrtc.org/14367) remove once refactor lands.
+  void CheckAndPing();
+
+  void LogCandidatePairConfig(Connection* conn,
+                              webrtc::IceCandidatePairConfigType type);
+
+  uint32_t GetNominationAttr(Connection* conn) const;
+  bool GetUseCandidateAttr(Connection* conn) const;
+
+  // Returns true if the new_connection is selected for transmission.
+  // TODO(bugs.webrtc.org/14367) remove once refactor lands.
+  bool MaybeSwitchSelectedConnection(const Connection* new_connection,
+                                     IceSwitchReason reason);
+  // TODO(bugs.webrtc.org/14367) remove once refactor lands.
+  bool MaybeSwitchSelectedConnection(
+      IceSwitchReason reason,
+      IceControllerInterface::SwitchResult result);
+  bool AllowedToPruneConnections() const;
+  // TODO(bugs.webrtc.org/14367) remove once refactor lands.
+  void PruneConnections();
+
+  // Returns the latest remote ICE parameters or nullptr if there are no remote
+  // ICE parameters yet.
+  IceParameters* remote_ice() {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    return remote_ice_parameters_.empty() ? nullptr
+                                          : &remote_ice_parameters_.back();
+  }
+  // Returns the remote IceParameters and generation that match `ufrag`
+  // if found, and returns nullptr otherwise.
+  const IceParameters* FindRemoteIceFromUfrag(absl::string_view ufrag,
+                                              uint32_t* generation);
+  // Returns the index of the latest remote ICE parameters, or 0 if no remote
+  // ICE parameters have been received.
+  uint32_t remote_ice_generation() {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    return remote_ice_parameters_.empty()
+               ? 0
+               : static_cast<uint32_t>(remote_ice_parameters_.size() - 1);
+  }
+
+  // Indicates if the given local port has been pruned.
+  bool IsPortPruned(const Port* port) const;
+
+  // Indicates if the given remote candidate has been pruned.
+  bool IsRemoteCandidatePruned(const Candidate& cand) const;
+
+  // Sets the writable state, signaling if necessary.
+  void SetWritable(bool writable);
+  // Sets the receiving state, signaling if necessary.
+  void SetReceiving(bool receiving);
+  // Clears the address and the related address fields of a local candidate to
+  // avoid IP leakage. This is applicable in several scenarios as commented in
+  // `PortAllocator::SanitizeCandidate`.
+  Candidate SanitizeLocalCandidate(const Candidate& c) const;
+  // Clears the address field of a remote candidate to avoid IP leakage. This is
+  // applicable in the following scenarios:
+  // 1. mDNS candidates are received.
+  // 2. Peer-reflexive remote candidates.
+  Candidate SanitizeRemoteCandidate(const Candidate& c) const;
+
+  // Cast a Connection returned from IceController and verify that it exists.
+  // (P2P owns all Connections, and only gives const pointers to IceController,
+  // see IceControllerInterface).
+  Connection* FromIceController(const Connection* conn) {
+    // Verify that IceController does not return a connection
+    // that we have destroyed.
+    RTC_DCHECK(FindConnection(conn));
+    return const_cast<Connection*>(conn);
+  }
+
+  int64_t ComputeEstimatedDisconnectedTimeMs(int64_t now,
+                                             Connection* old_connection);
+
+  void ParseFieldTrials(const webrtc::FieldTrialsView* field_trials);
+
+  // TODO(bugs.webrtc.org/14367) remove once refactor lands.
+  webrtc::ScopedTaskSafety task_safety_;
+  std::string transport_name_ RTC_GUARDED_BY(network_thread_);
+  int component_ RTC_GUARDED_BY(network_thread_);
+  PortAllocator* allocator_ RTC_GUARDED_BY(network_thread_);
+  webrtc::AsyncDnsResolverFactoryInterface* const async_dns_resolver_factory_
+      RTC_GUARDED_BY(network_thread_);
+  const std::unique_ptr<webrtc::AsyncDnsResolverFactoryInterface>
+      owned_dns_resolver_factory_;
+  rtc::Thread* const network_thread_;
+  bool incoming_only_ RTC_GUARDED_BY(network_thread_);
+  int error_ RTC_GUARDED_BY(network_thread_);
+  std::vector<std::unique_ptr<PortAllocatorSession>> allocator_sessions_
+      RTC_GUARDED_BY(network_thread_);
+  // `ports_` contains ports that are used to form new connections when
+  // new remote candidates are added.
+  std::vector<PortInterface*> ports_ RTC_GUARDED_BY(network_thread_);
+  // `pruned_ports_` contains ports that have been removed from `ports_` and
+  // are not being used to form new connections, but that aren't yet destroyed.
+  // They may have existing connections, and they still fire signals such as
+  // SignalUnknownAddress.
+  std::vector<PortInterface*> pruned_ports_ RTC_GUARDED_BY(network_thread_);
+
+  Connection* selected_connection_ RTC_GUARDED_BY(network_thread_) = nullptr;
+  std::vector<Connection*> connections_ RTC_GUARDED_BY(network_thread_);
+
+  std::vector<RemoteCandidate> remote_candidates_
+      RTC_GUARDED_BY(network_thread_);
+  // TODO(bugs.webrtc.org/14367) remove once refactor lands.
+  bool sort_dirty_ RTC_GUARDED_BY(
+      network_thread_);  // indicates whether another sort is needed right now
+  bool had_connection_ RTC_GUARDED_BY(network_thread_) =
+      false;  // if connections_ has ever been nonempty
+  typedef std::map<rtc::Socket::Option, int> OptionMap;
+  OptionMap options_ RTC_GUARDED_BY(network_thread_);
+  IceParameters ice_parameters_ RTC_GUARDED_BY(network_thread_);
+  std::vector<IceParameters> remote_ice_parameters_
+      RTC_GUARDED_BY(network_thread_);
+  IceMode remote_ice_mode_ RTC_GUARDED_BY(network_thread_);
+  IceRole ice_role_ RTC_GUARDED_BY(network_thread_);
+  uint64_t tiebreaker_ RTC_GUARDED_BY(network_thread_);
+  IceGatheringState gathering_state_ RTC_GUARDED_BY(network_thread_);
+  std::unique_ptr<webrtc::BasicRegatheringController> regathering_controller_
+      RTC_GUARDED_BY(network_thread_);
+  int64_t last_ping_sent_ms_ RTC_GUARDED_BY(network_thread_) = 0;
+  int weak_ping_interval_ RTC_GUARDED_BY(network_thread_) = WEAK_PING_INTERVAL;
+  // TODO(jonasolsson): Remove state_ and rename standardized_state_ once state_
+  // is no longer used to compute the ICE connection state.
+  IceTransportState state_ RTC_GUARDED_BY(network_thread_) =
+      IceTransportState::STATE_INIT;
+  webrtc::IceTransportState standardized_state_
+      RTC_GUARDED_BY(network_thread_) = webrtc::IceTransportState::kNew;
+  IceConfig config_ RTC_GUARDED_BY(network_thread_);
+  int last_sent_packet_id_ RTC_GUARDED_BY(network_thread_) =
+      -1;  // -1 indicates no packet was sent before.
+  // TODO(bugs.webrtc.org/14367) remove once refactor lands.
+  bool started_pinging_ RTC_GUARDED_BY(network_thread_) = false;
+  // The value put in the "nomination" attribute for the next nominated
+  // connection. A zero-value indicates the connection will not be nominated.
+  uint32_t nomination_ RTC_GUARDED_BY(network_thread_) = 0;
+  bool receiving_ RTC_GUARDED_BY(network_thread_) = false;
+  bool writable_ RTC_GUARDED_BY(network_thread_) = false;
+  bool has_been_writable_ RTC_GUARDED_BY(network_thread_) =
+      false;  // if writable_ has ever been true
+
+  absl::optional<rtc::NetworkRoute> network_route_
+      RTC_GUARDED_BY(network_thread_);
+  webrtc::IceEventLog ice_event_log_ RTC_GUARDED_BY(network_thread_);
+
+  // The adapter transparently delegates ICE controller interactions to either
+  // the legacy or the active ICE controller depending on field trials.
+  // TODO(bugs.webrtc.org/14367) replace with active ICE controller eventually.
+  class IceControllerAdapter : public ActiveIceControllerInterface {
+   public:
+    IceControllerAdapter(
+        const IceControllerFactoryArgs& args,
+        IceControllerFactoryInterface* ice_controller_factory,
+        ActiveIceControllerFactoryInterface* active_ice_controller_factory,
+        const webrtc::FieldTrialsView* field_trials,
+        P2PTransportChannel* transport);
+    ~IceControllerAdapter() override;
+
+    // ActiveIceControllerInterface overrides
+    void SetIceConfig(const IceConfig& config) override;
+    void OnConnectionAdded(const Connection* connection) override;
+    void OnConnectionSwitched(const Connection* connection) override;
+    void OnConnectionPinged(const Connection* connection) override;
+    void OnConnectionDestroyed(const Connection* connection) override;
+    void OnConnectionUpdated(const Connection* connection) override;
+    void OnSortAndSwitchRequest(IceSwitchReason reason) override;
+    void OnImmediateSortAndSwitchRequest(IceSwitchReason reason) override;
+    bool OnImmediateSwitchRequest(IceSwitchReason reason,
+                                  const Connection* connection) override;
+    bool GetUseCandidateAttribute(const Connection* connection,
+                                  NominationMode mode,
+                                  IceMode remote_ice_mode) const override;
+    const Connection* FindNextPingableConnection() override;
+
+    // Methods only available with legacy ICE controller.
+    rtc::ArrayView<Connection*> LegacyConnections() const;
+    bool LegacyHasPingableConnection() const;
+    IceControllerInterface::PingResult LegacySelectConnectionToPing(
+        int64_t last_ping_sent_ms);
+    IceControllerInterface::SwitchResult LegacyShouldSwitchConnection(
+        IceSwitchReason reason,
+        const Connection* connection);
+    IceControllerInterface::SwitchResult LegacySortAndSwitchConnection(
+        IceSwitchReason reason);
+    std::vector<const Connection*> LegacyPruneConnections();
+
+   private:
+    P2PTransportChannel* transport_;
+    std::unique_ptr<IceControllerInterface> legacy_ice_controller_;
+    std::unique_ptr<ActiveIceControllerInterface> active_ice_controller_;
+  };
+  std::unique_ptr<IceControllerAdapter> ice_adapter_
+      RTC_GUARDED_BY(network_thread_);
+
+  struct CandidateAndResolver final {
+    CandidateAndResolver(
+        const Candidate& candidate,
+        std::unique_ptr<webrtc::AsyncDnsResolverInterface>&& resolver);
+    ~CandidateAndResolver();
+    // Moveable, but not copyable.
+    CandidateAndResolver(CandidateAndResolver&&) = default;
+    CandidateAndResolver& operator=(CandidateAndResolver&&) = default;
+
+    Candidate candidate_;
+    std::unique_ptr<webrtc::AsyncDnsResolverInterface> resolver_;
+  };
+  std::vector<CandidateAndResolver> resolvers_ RTC_GUARDED_BY(network_thread_);
+  void FinishAddingRemoteCandidate(const Candidate& new_remote_candidate);
+  void OnCandidateResolved(webrtc::AsyncDnsResolverInterface* resolver);
+  void AddRemoteCandidateWithResult(
+      Candidate candidate,
+      const webrtc::AsyncDnsResolverResult& result);
+
+  // Bytes/packets sent/received on this channel.
+  uint64_t bytes_sent_ = 0;
+  uint64_t bytes_received_ = 0;
+  uint64_t packets_sent_ = 0;
+  uint64_t packets_received_ = 0;
+
+  // Number of times the selected_connection_ has been modified.
+  uint32_t selected_candidate_pair_changes_ = 0;
+
+  // When was last data received on a existing connection,
+  // from connection->last_data_received() that uses rtc::TimeMillis().
+  int64_t last_data_received_ms_ = 0;
+
+  // Parsed field trials.
+  IceFieldTrials ice_field_trials_;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_P2P_TRANSPORT_CHANNEL_H_
diff --git a/third_party/libwebrtc/p2p/base/p2p_transport_channel_ice_field_trials.h b/third_party/libwebrtc/p2p/base/p2p_transport_channel_ice_field_trials.h
new file mode 100644
index 0000000000..f19823b21e
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/p2p_transport_channel_ice_field_trials.h
@@ -0,0 +1,77 @@
+/*
+ *  Copyright 2019 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_P2P_TRANSPORT_CHANNEL_ICE_FIELD_TRIALS_H_
+#define P2P_BASE_P2P_TRANSPORT_CHANNEL_ICE_FIELD_TRIALS_H_
+
+#include "absl/types/optional.h"
+
+namespace cricket {
+
+// Field trials for P2PTransportChannel and friends,
+// put in separate file so that they can be shared e.g
+// with Connection.
+struct IceFieldTrials {
+  // This struct is built using the FieldTrialParser, and then not modified.
+  // TODO(jonaso) : Consider how members of this struct can be made const.
+
+  bool skip_relay_to_non_relay_connections = false;
+  absl::optional<int> max_outstanding_pings;
+
+  // Wait X ms before selecting a connection when having none.
+  // This will make media slower, but will give us chance to find
+  // a better connection before starting.
+  absl::optional<int> initial_select_dampening;
+
+  // If the connection has recevied a ping-request, delay by
+  // maximum this delay. This will make media slower, but will
+  // give us chance to find a better connection before starting.
+  absl::optional<int> initial_select_dampening_ping_received;
+
+  // Announce GOOG_PING support in STUN_BINDING_RESPONSE if requested
+  // by peer.
+  bool announce_goog_ping = true;
+
+  // Enable sending GOOG_PING if remote announce it.
+  bool enable_goog_ping = false;
+
+  // Decay rate for RTT estimate using EventBasedExponentialMovingAverage
+  // expressed as halving time.
+  int rtt_estimate_halftime_ms = 500;
+
+  // Sending a PING directly after a switch on ICE_CONTROLLING-side.
+  // TODO(jonaso) : Deprecate this in favor of
+  // `send_ping_on_selected_ice_controlling`.
+  bool send_ping_on_switch_ice_controlling = false;
+
+  // Sending a PING directly after selecting a connection
+  // (i.e either a switch or the inital selection).
+  bool send_ping_on_selected_ice_controlling = false;
+
+  // Sending a PING directly after a nomination on ICE_CONTROLLED-side.
+  bool send_ping_on_nomination_ice_controlled = false;
+
+  // The timeout after which the connection will be considered dead if no
+  // traffic is received.
+  int dead_connection_timeout_ms = 30000;
+
+  // Stop gathering when having a strong connection.
+  bool stop_gather_on_strongly_connected = true;
+
+  // DSCP taging.
+  absl::optional<int> override_dscp;
+
+  bool piggyback_ice_check_acknowledgement = false;
+  bool extra_ice_ping = false;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_P2P_TRANSPORT_CHANNEL_ICE_FIELD_TRIALS_H_
diff --git a/third_party/libwebrtc/p2p/base/p2p_transport_channel_unittest.cc b/third_party/libwebrtc/p2p/base/p2p_transport_channel_unittest.cc
new file mode 100644
index 0000000000..4d73f013fb
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/p2p_transport_channel_unittest.cc
@@ -0,0 +1,6630 @@
+/*
+ *  Copyright 2009 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/p2p_transport_channel.h"
+
+#include <list>
+#include <memory>
+#include <string>
+#include <tuple>
+#include <utility>
+
+#include "absl/algorithm/container.h"
+#include "absl/strings/string_view.h"
+#include "api/test/mock_async_dns_resolver.h"
+#include "p2p/base/active_ice_controller_factory_interface.h"
+#include "p2p/base/active_ice_controller_interface.h"
+#include "p2p/base/basic_ice_controller.h"
+#include "p2p/base/connection.h"
+#include "p2p/base/fake_port_allocator.h"
+#include "p2p/base/ice_transport_internal.h"
+#include "p2p/base/mock_active_ice_controller.h"
+#include "p2p/base/mock_async_resolver.h"
+#include "p2p/base/mock_ice_controller.h"
+#include "p2p/base/packet_transport_internal.h"
+#include "p2p/base/test_stun_server.h"
+#include "p2p/base/test_turn_server.h"
+#include "p2p/client/basic_port_allocator.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/dscp.h"
+#include "rtc_base/fake_clock.h"
+#include "rtc_base/fake_mdns_responder.h"
+#include "rtc_base/fake_network.h"
+#include "rtc_base/firewall_socket_server.h"
+#include "rtc_base/gunit.h"
+#include "rtc_base/helpers.h"
+#include "rtc_base/internal/default_socket_server.h"
+#include "rtc_base/logging.h"
+#include "rtc_base/mdns_responder_interface.h"
+#include "rtc_base/nat_server.h"
+#include "rtc_base/nat_socket_factory.h"
+#include "rtc_base/proxy_server.h"
+#include "rtc_base/socket_address.h"
+#include "rtc_base/ssl_adapter.h"
+#include "rtc_base/strings/string_builder.h"
+#include "rtc_base/thread.h"
+#include "rtc_base/virtual_socket_server.h"
+#include "system_wrappers/include/metrics.h"
+#include "test/scoped_key_value_config.h"
+
+namespace {
+
+using rtc::SocketAddress;
+using ::testing::_;
+using ::testing::Assign;
+using ::testing::Combine;
+using ::testing::Contains;
+using ::testing::DoAll;
+using ::testing::InSequence;
+using ::testing::InvokeArgument;
+using ::testing::InvokeWithoutArgs;
+using ::testing::Return;
+using ::testing::ReturnRef;
+using ::testing::SaveArg;
+using ::testing::SetArgPointee;
+using ::testing::SizeIs;
+using ::testing::TestWithParam;
+using ::testing::Values;
+using ::testing::WithParamInterface;
+using ::webrtc::PendingTaskSafetyFlag;
+using ::webrtc::SafeTask;
+
+// Default timeout for tests in this file.
+// Should be large enough for slow buildbots to run the tests reliably.
+static const int kDefaultTimeout = 10000;
+static const int kMediumTimeout = 3000;
+static const int kShortTimeout = 1000;
+
+static const int kOnlyLocalPorts = cricket::PORTALLOCATOR_DISABLE_STUN |
+                                   cricket::PORTALLOCATOR_DISABLE_RELAY |
+                                   cricket::PORTALLOCATOR_DISABLE_TCP;
+static const int LOW_RTT = 20;
+// Addresses on the public internet.
+static const SocketAddress kPublicAddrs[2] = {SocketAddress("11.11.11.11", 0),
+                                              SocketAddress("22.22.22.22", 0)};
+// IPv6 Addresses on the public internet.
+static const SocketAddress kIPv6PublicAddrs[2] = {
+    SocketAddress("2400:4030:1:2c00:be30:abcd:efab:cdef", 0),
+    SocketAddress("2600:0:1000:1b03:2e41:38ff:fea6:f2a4", 0)};
+// For configuring multihomed clients.
+static const SocketAddress kAlternateAddrs[2] = {
+    SocketAddress("101.101.101.101", 0), SocketAddress("202.202.202.202", 0)};
+static const SocketAddress kIPv6AlternateAddrs[2] = {
+    SocketAddress("2401:4030:1:2c00:be30:abcd:efab:cdef", 0),
+    SocketAddress("2601:0:1000:1b03:2e41:38ff:fea6:f2a4", 0)};
+// Addresses for HTTP proxy servers.
+static const SocketAddress kHttpsProxyAddrs[2] = {
+    SocketAddress("11.11.11.1", 443), SocketAddress("22.22.22.1", 443)};
+// Addresses for SOCKS proxy servers.
+static const SocketAddress kSocksProxyAddrs[2] = {
+    SocketAddress("11.11.11.1", 1080), SocketAddress("22.22.22.1", 1080)};
+// Internal addresses for NAT boxes.
+static const SocketAddress kNatAddrs[2] = {SocketAddress("192.168.1.1", 0),
+                                           SocketAddress("192.168.2.1", 0)};
+// Private addresses inside the NAT private networks.
+static const SocketAddress kPrivateAddrs[2] = {
+    SocketAddress("192.168.1.11", 0), SocketAddress("192.168.2.22", 0)};
+// For cascaded NATs, the internal addresses of the inner NAT boxes.
+static const SocketAddress kCascadedNatAddrs[2] = {
+    SocketAddress("192.168.10.1", 0), SocketAddress("192.168.20.1", 0)};
+// For cascaded NATs, private addresses inside the inner private networks.
+static const SocketAddress kCascadedPrivateAddrs[2] = {
+    SocketAddress("192.168.10.11", 0), SocketAddress("192.168.20.22", 0)};
+// The address of the public STUN server.
+static const SocketAddress kStunAddr("99.99.99.1", cricket::STUN_SERVER_PORT);
+// The addresses for the public turn server.
+static const SocketAddress kTurnUdpIntAddr("99.99.99.3",
+                                           cricket::STUN_SERVER_PORT);
+static const SocketAddress kTurnTcpIntAddr("99.99.99.4",
+                                           cricket::STUN_SERVER_PORT + 1);
+static const SocketAddress kTurnUdpExtAddr("99.99.99.5", 0);
+static const cricket::RelayCredentials kRelayCredentials("test", "test");
+
+// Based on ICE_UFRAG_LENGTH
+const char* kIceUfrag[4] = {"UF00", "UF01", "UF02", "UF03"};
+// Based on ICE_PWD_LENGTH
+const char* kIcePwd[4] = {
+    "TESTICEPWD00000000000000", "TESTICEPWD00000000000001",
+    "TESTICEPWD00000000000002", "TESTICEPWD00000000000003"};
+const cricket::IceParameters kIceParams[4] = {
+    {kIceUfrag[0], kIcePwd[0], false},
+    {kIceUfrag[1], kIcePwd[1], false},
+    {kIceUfrag[2], kIcePwd[2], false},
+    {kIceUfrag[3], kIcePwd[3], false}};
+
+const uint64_t kLowTiebreaker = 11111;
+const uint64_t kHighTiebreaker = 22222;
+const uint64_t kTiebreakerDefault = 44444;
+
+cricket::IceConfig CreateIceConfig(
+    int receiving_timeout,
+    cricket::ContinualGatheringPolicy continual_gathering_policy,
+    absl::optional<int> backup_ping_interval = absl::nullopt) {
+  cricket::IceConfig config;
+  config.receiving_timeout = receiving_timeout;
+  config.continual_gathering_policy = continual_gathering_policy;
+  config.backup_connection_ping_interval = backup_ping_interval;
+  return config;
+}
+
+cricket::Candidate CreateUdpCandidate(absl::string_view type,
+                                      absl::string_view ip,
+                                      int port,
+                                      int priority,
+                                      absl::string_view ufrag = "") {
+  cricket::Candidate c;
+  c.set_address(rtc::SocketAddress(ip, port));
+  c.set_component(cricket::ICE_CANDIDATE_COMPONENT_DEFAULT);
+  c.set_protocol(cricket::UDP_PROTOCOL_NAME);
+  c.set_priority(priority);
+  c.set_username(ufrag);
+  c.set_type(type);
+  return c;
+}
+
+cricket::BasicPortAllocator* CreateBasicPortAllocator(
+    rtc::NetworkManager* network_manager,
+    rtc::SocketServer* socket_server,
+    const cricket::ServerAddresses& stun_servers,
+    const rtc::SocketAddress& turn_server_udp,
+    const rtc::SocketAddress& turn_server_tcp) {
+  cricket::RelayServerConfig turn_server;
+  turn_server.credentials = kRelayCredentials;
+  if (!turn_server_udp.IsNil()) {
+    turn_server.ports.push_back(
+        cricket::ProtocolAddress(turn_server_udp, cricket::PROTO_UDP));
+  }
+  if (!turn_server_tcp.IsNil()) {
+    turn_server.ports.push_back(
+        cricket::ProtocolAddress(turn_server_tcp, cricket::PROTO_TCP));
+  }
+  std::vector<cricket::RelayServerConfig> turn_servers(1, turn_server);
+
+  std::unique_ptr<cricket::BasicPortAllocator> allocator =
+      std::make_unique<cricket::BasicPortAllocator>(
+          network_manager,
+          std::make_unique<rtc::BasicPacketSocketFactory>(socket_server));
+  allocator->Initialize();
+  allocator->SetConfiguration(stun_servers, turn_servers, 0, webrtc::NO_PRUNE);
+  return allocator.release();
+}
+
+// An one-shot resolver factory with default return arguments.
+// Resolution is immediate, always succeeds, and returns nonsense.
+class ResolverFactoryFixture : public webrtc::MockAsyncDnsResolverFactory {
+ public:
+  ResolverFactoryFixture() {
+    mock_async_dns_resolver_ = std::make_unique<webrtc::MockAsyncDnsResolver>();
+    EXPECT_CALL(*mock_async_dns_resolver_, Start(_, _))
+        .WillRepeatedly(InvokeArgument<1>());
+    EXPECT_CALL(*mock_async_dns_resolver_, result())
+        .WillOnce(ReturnRef(mock_async_dns_resolver_result_));
+
+    // A default action for GetResolvedAddress. Will be overruled
+    // by SetAddressToReturn.
+    EXPECT_CALL(mock_async_dns_resolver_result_, GetResolvedAddress(_, _))
+        .WillRepeatedly(Return(true));
+
+    EXPECT_CALL(mock_async_dns_resolver_result_, GetError())
+        .WillOnce(Return(0));
+    EXPECT_CALL(*this, Create()).WillOnce([this]() {
+      return std::move(mock_async_dns_resolver_);
+    });
+  }
+
+  void SetAddressToReturn(rtc::SocketAddress address_to_return) {
+    EXPECT_CALL(mock_async_dns_resolver_result_, GetResolvedAddress(_, _))
+        .WillOnce(DoAll(SetArgPointee<1>(address_to_return), Return(true)));
+  }
+  void DelayResolution() {
+    // This function must be called before Create().
+    ASSERT_TRUE(!!mock_async_dns_resolver_);
+    EXPECT_CALL(*mock_async_dns_resolver_, Start(_, _))
+        .WillOnce(SaveArg<1>(&saved_callback_));
+  }
+  void FireDelayedResolution() {
+    // This function must be called after Create().
+    ASSERT_TRUE(saved_callback_);
+    saved_callback_();
+  }
+
+ private:
+  std::unique_ptr<webrtc::MockAsyncDnsResolver> mock_async_dns_resolver_;
+  webrtc::MockAsyncDnsResolverResult mock_async_dns_resolver_result_;
+  std::function<void()> saved_callback_;
+};
+
+bool HasLocalAddress(const cricket::CandidatePairInterface* pair,
+                     const SocketAddress& address) {
+  return pair->local_candidate().address().EqualIPs(address);
+}
+
+bool HasRemoteAddress(const cricket::CandidatePairInterface* pair,
+                      const SocketAddress& address) {
+  return pair->remote_candidate().address().EqualIPs(address);
+}
+
+}  // namespace
+
+namespace cricket {
+
+// This test simulates 2 P2P endpoints that want to establish connectivity
+// with each other over various network topologies and conditions, which can be
+// specified in each individial test.
+// A virtual network (via VirtualSocketServer) along with virtual firewalls and
+// NATs (via Firewall/NATSocketServer) are used to simulate the various network
+// conditions. We can configure the IP addresses of the endpoints,
+// block various types of connectivity, or add arbitrary levels of NAT.
+// We also run a STUN server and a relay server on the virtual network to allow
+// our typical P2P mechanisms to do their thing.
+// For each case, we expect the P2P stack to eventually settle on a specific
+// form of connectivity to the other side. The test checks that the P2P
+// negotiation successfully establishes connectivity within a certain time,
+// and that the result is what we expect.
+// Note that this class is a base class for use by other tests, who will provide
+// specialized test behavior.
+class P2PTransportChannelTestBase : public ::testing::Test,
+                                    public sigslot::has_slots<> {
+ public:
+  explicit P2PTransportChannelTestBase(absl::string_view field_trials)
+      : field_trials_(field_trials),
+        vss_(new rtc::VirtualSocketServer()),
+        nss_(new rtc::NATSocketServer(vss_.get())),
+        ss_(new rtc::FirewallSocketServer(nss_.get())),
+        main_(ss_.get()),
+        stun_server_(TestStunServer::Create(ss_.get(), kStunAddr)),
+        turn_server_(&main_, ss_.get(), kTurnUdpIntAddr, kTurnUdpExtAddr),
+        socks_server1_(ss_.get(),
+                       kSocksProxyAddrs[0],
+                       ss_.get(),
+                       kSocksProxyAddrs[0]),
+        socks_server2_(ss_.get(),
+                       kSocksProxyAddrs[1],
+                       ss_.get(),
+                       kSocksProxyAddrs[1]),
+        force_relay_(false) {
+    ep1_.role_ = ICEROLE_CONTROLLING;
+    ep2_.role_ = ICEROLE_CONTROLLED;
+
+    ServerAddresses stun_servers;
+    stun_servers.insert(kStunAddr);
+    ep1_.allocator_.reset(CreateBasicPortAllocator(
+        &ep1_.network_manager_, ss_.get(), stun_servers, kTurnUdpIntAddr,
+        rtc::SocketAddress()));
+    ep2_.allocator_.reset(CreateBasicPortAllocator(
+        &ep2_.network_manager_, ss_.get(), stun_servers, kTurnUdpIntAddr,
+        rtc::SocketAddress()));
+
+    ep1_.SetIceTiebreaker(kTiebreakerDefault);
+    ep1_.allocator_->SetIceTiebreaker(kTiebreakerDefault);
+    ep2_.SetIceTiebreaker(kTiebreakerDefault);
+    ep2_.allocator_->SetIceTiebreaker(kTiebreakerDefault);
+    webrtc::metrics::Reset();
+  }
+
+  P2PTransportChannelTestBase()
+      : P2PTransportChannelTestBase(absl::string_view()) {}
+
+ protected:
+  enum Config {
+    OPEN,                         // Open to the Internet
+    NAT_FULL_CONE,                // NAT, no filtering
+    NAT_ADDR_RESTRICTED,          // NAT, must send to an addr to recv
+    NAT_PORT_RESTRICTED,          // NAT, must send to an addr+port to recv
+    NAT_SYMMETRIC,                // NAT, endpoint-dependent bindings
+    NAT_DOUBLE_CONE,              // Double NAT, both cone
+    NAT_SYMMETRIC_THEN_CONE,      // Double NAT, symmetric outer, cone inner
+    BLOCK_UDP,                    // Firewall, UDP in/out blocked
+    BLOCK_UDP_AND_INCOMING_TCP,   // Firewall, UDP in/out and TCP in blocked
+    BLOCK_ALL_BUT_OUTGOING_HTTP,  // Firewall, only TCP out on 80/443
+    PROXY_HTTPS,                  // All traffic through HTTPS proxy
+    PROXY_SOCKS,                  // All traffic through SOCKS proxy
+    NUM_CONFIGS
+  };
+
+  struct Result {
+    Result(absl::string_view controlling_type,
+           absl::string_view controlling_protocol,
+           absl::string_view controlled_type,
+           absl::string_view controlled_protocol,
+           int wait)
+        : controlling_type(controlling_type),
+          controlling_protocol(controlling_protocol),
+          controlled_type(controlled_type),
+          controlled_protocol(controlled_protocol),
+          connect_wait(wait) {}
+
+    // The expected candidate type and protocol of the controlling ICE agent.
+    std::string controlling_type;
+    std::string controlling_protocol;
+    // The expected candidate type and protocol of the controlled ICE agent.
+    std::string controlled_type;
+    std::string controlled_protocol;
+    // How long to wait before the correct candidate pair is selected.
+    int connect_wait;
+  };
+
+  struct ChannelData {
+    bool CheckData(const char* data, int len) {
+      bool ret = false;
+      if (!ch_packets_.empty()) {
+        std::string packet = ch_packets_.front();
+        ret = (packet == std::string(data, len));
+        ch_packets_.pop_front();
+      }
+      return ret;
+    }
+
+    std::string name_;  // TODO(?) - Currently not used.
+    std::list<std::string> ch_packets_;
+    std::unique_ptr<P2PTransportChannel> ch_;
+  };
+
+  struct CandidateData {
+    IceTransportInternal* channel;
+    Candidate candidate;
+  };
+
+  struct Endpoint : public sigslot::has_slots<> {
+    Endpoint()
+        : role_(ICEROLE_UNKNOWN),
+          tiebreaker_(0),
+          role_conflict_(false),
+          save_candidates_(false) {}
+    bool HasTransport(const rtc::PacketTransportInternal* transport) {
+      return (transport == cd1_.ch_.get() || transport == cd2_.ch_.get());
+    }
+    ChannelData* GetChannelData(rtc::PacketTransportInternal* transport) {
+      if (!HasTransport(transport))
+        return NULL;
+      if (cd1_.ch_.get() == transport)
+        return &cd1_;
+      else
+        return &cd2_;
+    }
+
+    void SetIceRole(IceRole role) { role_ = role; }
+    IceRole ice_role() { return role_; }
+    void SetIceTiebreaker(uint64_t tiebreaker) { tiebreaker_ = tiebreaker; }
+    uint64_t GetIceTiebreaker() { return tiebreaker_; }
+    void OnRoleConflict(bool role_conflict) { role_conflict_ = role_conflict; }
+    bool role_conflict() { return role_conflict_; }
+    void SetAllocationStepDelay(uint32_t delay) {
+      allocator_->set_step_delay(delay);
+    }
+    void SetAllowTcpListen(bool allow_tcp_listen) {
+      allocator_->set_allow_tcp_listen(allow_tcp_listen);
+    }
+
+    void OnIceRegathering(PortAllocatorSession*, IceRegatheringReason reason) {
+      ++ice_regathering_counter_[reason];
+    }
+
+    int GetIceRegatheringCountForReason(IceRegatheringReason reason) {
+      return ice_regathering_counter_[reason];
+    }
+
+    rtc::FakeNetworkManager network_manager_;
+    std::unique_ptr<BasicPortAllocator> allocator_;
+    webrtc::AsyncDnsResolverFactoryInterface* async_dns_resolver_factory_;
+    ChannelData cd1_;
+    ChannelData cd2_;
+    IceRole role_;
+    uint64_t tiebreaker_;
+    bool role_conflict_;
+    bool save_candidates_;
+    std::vector<CandidateData> saved_candidates_;
+    bool ready_to_send_ = false;
+    std::map<IceRegatheringReason, int> ice_regathering_counter_;
+  };
+
+  ChannelData* GetChannelData(rtc::PacketTransportInternal* transport) {
+    if (ep1_.HasTransport(transport))
+      return ep1_.GetChannelData(transport);
+    else
+      return ep2_.GetChannelData(transport);
+  }
+
+  IceParameters IceParamsWithRenomination(const IceParameters& ice,
+                                          bool renomination) {
+    IceParameters new_ice = ice;
+    new_ice.renomination = renomination;
+    return new_ice;
+  }
+
+  void CreateChannels(const IceConfig& ep1_config,
+                      const IceConfig& ep2_config,
+                      bool renomination = false) {
+    IceParameters ice_ep1_cd1_ch =
+        IceParamsWithRenomination(kIceParams[0], renomination);
+    IceParameters ice_ep2_cd1_ch =
+        IceParamsWithRenomination(kIceParams[1], renomination);
+    ep1_.cd1_.ch_ = CreateChannel(0, ICE_CANDIDATE_COMPONENT_DEFAULT,
+                                  ice_ep1_cd1_ch, ice_ep2_cd1_ch);
+    ep2_.cd1_.ch_ = CreateChannel(1, ICE_CANDIDATE_COMPONENT_DEFAULT,
+                                  ice_ep2_cd1_ch, ice_ep1_cd1_ch);
+    ep1_.cd1_.ch_->SetIceConfig(ep1_config);
+    ep2_.cd1_.ch_->SetIceConfig(ep2_config);
+    ep1_.cd1_.ch_->MaybeStartGathering();
+    ep2_.cd1_.ch_->MaybeStartGathering();
+    ep1_.cd1_.ch_->allocator_session()->SignalIceRegathering.connect(
+        &ep1_, &Endpoint::OnIceRegathering);
+    ep2_.cd1_.ch_->allocator_session()->SignalIceRegathering.connect(
+        &ep2_, &Endpoint::OnIceRegathering);
+  }
+
+  void CreateChannels() {
+    IceConfig default_config;
+    CreateChannels(default_config, default_config, false);
+  }
+
+  std::unique_ptr<P2PTransportChannel> CreateChannel(
+      int endpoint,
+      int component,
+      const IceParameters& local_ice,
+      const IceParameters& remote_ice) {
+    webrtc::IceTransportInit init;
+    init.set_port_allocator(GetAllocator(endpoint));
+    init.set_async_dns_resolver_factory(
+        GetEndpoint(endpoint)->async_dns_resolver_factory_);
+    init.set_field_trials(&field_trials_);
+    auto channel = P2PTransportChannel::Create("test content name", component,
+                                               std::move(init));
+    channel->SignalReadyToSend.connect(
+        this, &P2PTransportChannelTestBase::OnReadyToSend);
+    channel->SignalCandidateGathered.connect(
+        this, &P2PTransportChannelTestBase::OnCandidateGathered);
+    channel->SignalCandidatesRemoved.connect(
+        this, &P2PTransportChannelTestBase::OnCandidatesRemoved);
+    channel->SignalReadPacket.connect(
+        this, &P2PTransportChannelTestBase::OnReadPacket);
+    channel->SignalRoleConflict.connect(
+        this, &P2PTransportChannelTestBase::OnRoleConflict);
+    channel->SignalNetworkRouteChanged.connect(
+        this, &P2PTransportChannelTestBase::OnNetworkRouteChanged);
+    channel->SignalSentPacket.connect(
+        this, &P2PTransportChannelTestBase::OnSentPacket);
+    channel->SetIceParameters(local_ice);
+    if (remote_ice_parameter_source_ == FROM_SETICEPARAMETERS) {
+      channel->SetRemoteIceParameters(remote_ice);
+    }
+    channel->SetIceRole(GetEndpoint(endpoint)->ice_role());
+    channel->SetIceTiebreaker(GetEndpoint(endpoint)->GetIceTiebreaker());
+    return channel;
+  }
+
+  void DestroyChannels() {
+    safety_->SetNotAlive();
+    ep1_.cd1_.ch_.reset();
+    ep2_.cd1_.ch_.reset();
+    ep1_.cd2_.ch_.reset();
+    ep2_.cd2_.ch_.reset();
+    // Process pending tasks that need to run for cleanup purposes such as
+    // pending deletion of Connection objects (see Connection::Destroy).
+    rtc::Thread::Current()->ProcessMessages(0);
+  }
+  P2PTransportChannel* ep1_ch1() { return ep1_.cd1_.ch_.get(); }
+  P2PTransportChannel* ep1_ch2() { return ep1_.cd2_.ch_.get(); }
+  P2PTransportChannel* ep2_ch1() { return ep2_.cd1_.ch_.get(); }
+  P2PTransportChannel* ep2_ch2() { return ep2_.cd2_.ch_.get(); }
+
+  TestTurnServer* test_turn_server() { return &turn_server_; }
+  rtc::VirtualSocketServer* virtual_socket_server() { return vss_.get(); }
+
+  // Common results.
+  static const Result kLocalUdpToLocalUdp;
+  static const Result kLocalUdpToStunUdp;
+  static const Result kLocalUdpToPrflxUdp;
+  static const Result kPrflxUdpToLocalUdp;
+  static const Result kStunUdpToLocalUdp;
+  static const Result kStunUdpToStunUdp;
+  static const Result kStunUdpToPrflxUdp;
+  static const Result kPrflxUdpToStunUdp;
+  static const Result kLocalUdpToRelayUdp;
+  static const Result kPrflxUdpToRelayUdp;
+  static const Result kRelayUdpToPrflxUdp;
+  static const Result kLocalTcpToLocalTcp;
+  static const Result kLocalTcpToPrflxTcp;
+  static const Result kPrflxTcpToLocalTcp;
+
+  rtc::NATSocketServer* nat() { return nss_.get(); }
+  rtc::FirewallSocketServer* fw() { return ss_.get(); }
+
+  Endpoint* GetEndpoint(int endpoint) {
+    if (endpoint == 0) {
+      return &ep1_;
+    } else if (endpoint == 1) {
+      return &ep2_;
+    } else {
+      return NULL;
+    }
+  }
+  BasicPortAllocator* GetAllocator(int endpoint) {
+    return GetEndpoint(endpoint)->allocator_.get();
+  }
+  void AddAddress(int endpoint, const SocketAddress& addr) {
+    GetEndpoint(endpoint)->network_manager_.AddInterface(addr);
+  }
+  void AddAddress(int endpoint,
+                  const SocketAddress& addr,
+                  absl::string_view ifname,
+                  rtc::AdapterType adapter_type,
+                  absl::optional<rtc::AdapterType> underlying_vpn_adapter_type =
+                      absl::nullopt) {
+    GetEndpoint(endpoint)->network_manager_.AddInterface(
+        addr, ifname, adapter_type, underlying_vpn_adapter_type);
+  }
+  void RemoveAddress(int endpoint, const SocketAddress& addr) {
+    GetEndpoint(endpoint)->network_manager_.RemoveInterface(addr);
+    fw()->AddRule(false, rtc::FP_ANY, rtc::FD_ANY, addr);
+  }
+  void SetProxy(int endpoint, rtc::ProxyType type) {
+    rtc::ProxyInfo info;
+    info.type = type;
+    info.address = (type == rtc::PROXY_HTTPS) ? kHttpsProxyAddrs[endpoint]
+                                              : kSocksProxyAddrs[endpoint];
+    GetAllocator(endpoint)->set_proxy("unittest/1.0", info);
+  }
+  void SetAllocatorFlags(int endpoint, int flags) {
+    GetAllocator(endpoint)->set_flags(flags);
+  }
+  void SetIceRole(int endpoint, IceRole role) {
+    GetEndpoint(endpoint)->SetIceRole(role);
+  }
+  void SetIceTiebreaker(int endpoint, uint64_t tiebreaker) {
+    GetEndpoint(endpoint)->SetIceTiebreaker(tiebreaker);
+  }
+  bool GetRoleConflict(int endpoint) {
+    return GetEndpoint(endpoint)->role_conflict();
+  }
+  void SetAllocationStepDelay(int endpoint, uint32_t delay) {
+    return GetEndpoint(endpoint)->SetAllocationStepDelay(delay);
+  }
+  void SetAllowTcpListen(int endpoint, bool allow_tcp_listen) {
+    return GetEndpoint(endpoint)->SetAllowTcpListen(allow_tcp_listen);
+  }
+
+  // Return true if the approprite parts of the expected Result, based
+  // on the local and remote candidate of ep1_ch1, match.  This can be
+  // used in an EXPECT_TRUE_WAIT.
+  bool CheckCandidate1(const Result& expected) {
+    const std::string& local_type = LocalCandidate(ep1_ch1())->type();
+    const std::string& local_protocol = LocalCandidate(ep1_ch1())->protocol();
+    const std::string& remote_type = RemoteCandidate(ep1_ch1())->type();
+    const std::string& remote_protocol = RemoteCandidate(ep1_ch1())->protocol();
+    return (local_protocol == expected.controlling_protocol &&
+            remote_protocol == expected.controlled_protocol &&
+            local_type == expected.controlling_type &&
+            remote_type == expected.controlled_type);
+  }
+
+  // EXPECT_EQ on the approprite parts of the expected Result, based
+  // on the local and remote candidate of ep1_ch1.  This is like
+  // CheckCandidate1, except that it will provide more detail about
+  // what didn't match.
+  void ExpectCandidate1(const Result& expected) {
+    if (CheckCandidate1(expected)) {
+      return;
+    }
+
+    const std::string& local_type = LocalCandidate(ep1_ch1())->type();
+    const std::string& local_protocol = LocalCandidate(ep1_ch1())->protocol();
+    const std::string& remote_type = RemoteCandidate(ep1_ch1())->type();
+    const std::string& remote_protocol = RemoteCandidate(ep1_ch1())->protocol();
+    EXPECT_EQ(expected.controlling_type, local_type);
+    EXPECT_EQ(expected.controlled_type, remote_type);
+    EXPECT_EQ(expected.controlling_protocol, local_protocol);
+    EXPECT_EQ(expected.controlled_protocol, remote_protocol);
+  }
+
+  // Return true if the approprite parts of the expected Result, based
+  // on the local and remote candidate of ep2_ch1, match.  This can be
+  // used in an EXPECT_TRUE_WAIT.
+  bool CheckCandidate2(const Result& expected) {
+    const std::string& local_type = LocalCandidate(ep2_ch1())->type();
+    const std::string& local_protocol = LocalCandidate(ep2_ch1())->protocol();
+    const std::string& remote_type = RemoteCandidate(ep2_ch1())->type();
+    const std::string& remote_protocol = RemoteCandidate(ep2_ch1())->protocol();
+    return (local_protocol == expected.controlled_protocol &&
+            remote_protocol == expected.controlling_protocol &&
+            local_type == expected.controlled_type &&
+            remote_type == expected.controlling_type);
+  }
+
+  // EXPECT_EQ on the approprite parts of the expected Result, based
+  // on the local and remote candidate of ep2_ch1.  This is like
+  // CheckCandidate2, except that it will provide more detail about
+  // what didn't match.
+  void ExpectCandidate2(const Result& expected) {
+    if (CheckCandidate2(expected)) {
+      return;
+    }
+
+    const std::string& local_type = LocalCandidate(ep2_ch1())->type();
+    const std::string& local_protocol = LocalCandidate(ep2_ch1())->protocol();
+    const std::string& remote_type = RemoteCandidate(ep2_ch1())->type();
+    const std::string& remote_protocol = RemoteCandidate(ep2_ch1())->protocol();
+    EXPECT_EQ(expected.controlled_type, local_type);
+    EXPECT_EQ(expected.controlling_type, remote_type);
+    EXPECT_EQ(expected.controlled_protocol, local_protocol);
+    EXPECT_EQ(expected.controlling_protocol, remote_protocol);
+  }
+
+  static bool CheckCandidate(P2PTransportChannel* channel,
+                             SocketAddress from,
+                             SocketAddress to) {
+    auto local_candidate = LocalCandidate(channel);
+    auto remote_candidate = RemoteCandidate(channel);
+    return local_candidate != nullptr &&
+           local_candidate->address().EqualIPs(from) &&
+           remote_candidate != nullptr &&
+           remote_candidate->address().EqualIPs(to);
+  }
+
+  static bool CheckCandidatePair(P2PTransportChannel* ch1,
+                                 P2PTransportChannel* ch2,
+                                 SocketAddress from,
+                                 SocketAddress to) {
+    return CheckCandidate(ch1, from, to) && CheckCandidate(ch2, to, from);
+  }
+
+  static bool CheckConnected(P2PTransportChannel* ch1,
+                             P2PTransportChannel* ch2) {
+    return ch1 != nullptr && ch1->receiving() && ch1->writable() &&
+           ch2 != nullptr && ch2->receiving() && ch2->writable();
+  }
+
+  static bool CheckCandidatePairAndConnected(P2PTransportChannel* ch1,
+                                             P2PTransportChannel* ch2,
+                                             SocketAddress from,
+                                             SocketAddress to) {
+    return CheckConnected(ch1, ch2) && CheckCandidatePair(ch1, ch2, from, to);
+  }
+
+  virtual void Test(const Result& expected) {
+    rtc::ScopedFakeClock clock;
+    int64_t connect_start = rtc::TimeMillis();
+    int64_t connect_time;
+
+    // Create the channels and wait for them to connect.
+    CreateChannels();
+    EXPECT_TRUE_SIMULATED_WAIT(CheckConnected(ep1_ch1(), ep2_ch1()),
+                               expected.connect_wait + kShortTimeout, clock);
+    connect_time = rtc::TimeMillis() - connect_start;
+    if (connect_time < expected.connect_wait) {
+      RTC_LOG(LS_INFO) << "Connect time: " << connect_time << " ms";
+    } else {
+      RTC_LOG(LS_INFO) << "Connect time: TIMEOUT (" << expected.connect_wait
+                       << " ms)";
+    }
+
+    // Allow a few turns of the crank for the selected connections to emerge.
+    // This may take up to 2 seconds.
+    if (ep1_ch1()->selected_connection() && ep2_ch1()->selected_connection()) {
+      int64_t converge_start = rtc::TimeMillis();
+      int64_t converge_time;
+      // Verifying local and remote channel selected connection information.
+      // This is done only for the RFC 5245 as controlled agent will use
+      // USE-CANDIDATE from controlling (ep1) agent. We can easily predict from
+      // EP1 result matrix.
+      EXPECT_TRUE_SIMULATED_WAIT(
+          CheckCandidate1(expected) && CheckCandidate2(expected),
+          kDefaultTimeout, clock);
+      // Also do EXPECT_EQ on each part so that failures are more verbose.
+      ExpectCandidate1(expected);
+      ExpectCandidate2(expected);
+
+      converge_time = rtc::TimeMillis() - converge_start;
+      int64_t converge_wait = 2000;
+      if (converge_time < converge_wait) {
+        RTC_LOG(LS_INFO) << "Converge time: " << converge_time << " ms";
+      } else {
+        RTC_LOG(LS_INFO) << "Converge time: TIMEOUT (" << converge_time
+                         << " ms)";
+      }
+    }
+    // Try sending some data to other end.
+    TestSendRecv(&clock);
+
+    // Destroy the channels, and wait for them to be fully cleaned up.
+    DestroyChannels();
+  }
+
+  void TestSendRecv(rtc::ThreadProcessingFakeClock* clock) {
+    for (int i = 0; i < 10; ++i) {
+      const char* data = "ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";
+      int len = static_cast<int>(strlen(data));
+      // local_channel1 <==> remote_channel1
+      EXPECT_EQ_SIMULATED_WAIT(len, SendData(ep1_ch1(), data, len),
+                               kMediumTimeout, *clock);
+      EXPECT_TRUE_SIMULATED_WAIT(CheckDataOnChannel(ep2_ch1(), data, len),
+                                 kMediumTimeout, *clock);
+      EXPECT_EQ_SIMULATED_WAIT(len, SendData(ep2_ch1(), data, len),
+                               kMediumTimeout, *clock);
+      EXPECT_TRUE_SIMULATED_WAIT(CheckDataOnChannel(ep1_ch1(), data, len),
+                                 kMediumTimeout, *clock);
+    }
+  }
+
+  // This test waits for the transport to become receiving and writable on both
+  // end points. Once they are, the end points set new local ice parameters and
+  // restart the ice gathering. Finally it waits for the transport to select a
+  // new connection using the newly generated ice candidates.
+  // Before calling this function the end points must be configured.
+  void TestHandleIceUfragPasswordChanged() {
+    rtc::ScopedFakeClock clock;
+    ep1_ch1()->SetRemoteIceParameters(kIceParams[1]);
+    ep2_ch1()->SetRemoteIceParameters(kIceParams[0]);
+    EXPECT_TRUE_SIMULATED_WAIT(CheckConnected(ep1_ch1(), ep2_ch1()),
+                               kMediumTimeout, clock);
+
+    const Candidate* old_local_candidate1 = LocalCandidate(ep1_ch1());
+    const Candidate* old_local_candidate2 = LocalCandidate(ep2_ch1());
+    const Candidate* old_remote_candidate1 = RemoteCandidate(ep1_ch1());
+    const Candidate* old_remote_candidate2 = RemoteCandidate(ep2_ch1());
+
+    ep1_ch1()->SetIceParameters(kIceParams[2]);
+    ep1_ch1()->SetRemoteIceParameters(kIceParams[3]);
+    ep1_ch1()->MaybeStartGathering();
+    ep2_ch1()->SetIceParameters(kIceParams[3]);
+
+    ep2_ch1()->SetRemoteIceParameters(kIceParams[2]);
+    ep2_ch1()->MaybeStartGathering();
+
+    EXPECT_TRUE_SIMULATED_WAIT(LocalCandidate(ep1_ch1())->generation() !=
+                                   old_local_candidate1->generation(),
+                               kMediumTimeout, clock);
+    EXPECT_TRUE_SIMULATED_WAIT(LocalCandidate(ep2_ch1())->generation() !=
+                                   old_local_candidate2->generation(),
+                               kMediumTimeout, clock);
+    EXPECT_TRUE_SIMULATED_WAIT(RemoteCandidate(ep1_ch1())->generation() !=
+                                   old_remote_candidate1->generation(),
+                               kMediumTimeout, clock);
+    EXPECT_TRUE_SIMULATED_WAIT(RemoteCandidate(ep2_ch1())->generation() !=
+                                   old_remote_candidate2->generation(),
+                               kMediumTimeout, clock);
+    EXPECT_EQ(1u, RemoteCandidate(ep2_ch1())->generation());
+    EXPECT_EQ(1u, RemoteCandidate(ep1_ch1())->generation());
+  }
+
+  void TestSignalRoleConflict() {
+    rtc::ScopedFakeClock clock;
+    // Default EP1 is in controlling state.
+    SetIceTiebreaker(0, kLowTiebreaker);
+
+    SetIceRole(1, ICEROLE_CONTROLLING);
+    SetIceTiebreaker(1, kHighTiebreaker);
+
+    // Creating channels with both channels role set to CONTROLLING.
+    CreateChannels();
+    // Since both the channels initiated with controlling state and channel2
+    // has higher tiebreaker value, channel1 should receive SignalRoleConflict.
+    EXPECT_TRUE_SIMULATED_WAIT(GetRoleConflict(0), kShortTimeout, clock);
+    EXPECT_FALSE(GetRoleConflict(1));
+
+    EXPECT_TRUE_SIMULATED_WAIT(CheckConnected(ep1_ch1(), ep2_ch1()),
+                               kShortTimeout, clock);
+
+    EXPECT_TRUE(ep1_ch1()->selected_connection() &&
+                ep2_ch1()->selected_connection());
+
+    TestSendRecv(&clock);
+    DestroyChannels();
+  }
+
+  void TestPacketInfoIsSet(rtc::PacketInfo info) {
+    EXPECT_NE(info.packet_type, rtc::PacketType::kUnknown);
+    EXPECT_NE(info.protocol, rtc::PacketInfoProtocolType::kUnknown);
+    EXPECT_TRUE(info.network_id.has_value());
+  }
+
+  void OnReadyToSend(rtc::PacketTransportInternal* transport) {
+    GetEndpoint(transport)->ready_to_send_ = true;
+  }
+
+  // We pass the candidates directly to the other side.
+  void OnCandidateGathered(IceTransportInternal* ch, const Candidate& c) {
+    if (force_relay_ && c.type() != RELAY_PORT_TYPE)
+      return;
+
+    if (GetEndpoint(ch)->save_candidates_) {
+      GetEndpoint(ch)->saved_candidates_.push_back(
+          {.channel = ch, .candidate = c});
+    } else {
+      main_.PostTask(SafeTask(
+          safety_, [this, ch, c = c]() mutable { AddCandidate(ch, c); }));
+    }
+  }
+
+  void OnNetworkRouteChanged(absl::optional<rtc::NetworkRoute> network_route) {
+    // If the `network_route` is unset, don't count. This is used in the case
+    // when the network on remote side is down, the signal will be fired with an
+    // unset network route and it shouldn't trigger a connection switch.
+    if (network_route) {
+      ++selected_candidate_pair_switches_;
+    }
+  }
+
+  int reset_selected_candidate_pair_switches() {
+    int switches = selected_candidate_pair_switches_;
+    selected_candidate_pair_switches_ = 0;
+    return switches;
+  }
+
+  void PauseCandidates(int endpoint) {
+    GetEndpoint(endpoint)->save_candidates_ = true;
+  }
+
+  void OnCandidatesRemoved(IceTransportInternal* ch,
+                           const std::vector<Candidate>& candidates) {
+    // Candidate removals are not paused.
+    main_.PostTask(SafeTask(safety_, [this, ch, candidates]() mutable {
+      P2PTransportChannel* rch = GetRemoteChannel(ch);
+      if (rch == nullptr) {
+        return;
+      }
+      for (const Candidate& c : candidates) {
+        RTC_LOG(LS_INFO) << "Removed remote candidate " << c.ToString();
+        rch->RemoveRemoteCandidate(c);
+      }
+    }));
+  }
+
+  // Tcp candidate verification has to be done when they are generated.
+  void VerifySavedTcpCandidates(int endpoint, absl::string_view tcptype) {
+    for (auto& data : GetEndpoint(endpoint)->saved_candidates_) {
+      EXPECT_EQ(data.candidate.protocol(), TCP_PROTOCOL_NAME);
+      EXPECT_EQ(data.candidate.tcptype(), tcptype);
+      if (data.candidate.tcptype() == TCPTYPE_ACTIVE_STR) {
+        EXPECT_EQ(data.candidate.address().port(), DISCARD_PORT);
+      } else if (data.candidate.tcptype() == TCPTYPE_PASSIVE_STR) {
+        EXPECT_NE(data.candidate.address().port(), DISCARD_PORT);
+      } else {
+        FAIL() << "Unknown tcptype: " << data.candidate.tcptype();
+      }
+    }
+  }
+
+  void ResumeCandidates(int endpoint) {
+    Endpoint* ed = GetEndpoint(endpoint);
+    std::vector<CandidateData> candidates = std::move(ed->saved_candidates_);
+    if (!candidates.empty()) {
+      main_.PostTask(SafeTask(
+          safety_, [this, candidates = std::move(candidates)]() mutable {
+            for (CandidateData& data : candidates) {
+              AddCandidate(data.channel, data.candidate);
+            }
+          }));
+    }
+    ed->saved_candidates_.clear();
+    ed->save_candidates_ = false;
+  }
+
+  void AddCandidate(IceTransportInternal* channel, Candidate& candidate) {
+    P2PTransportChannel* rch = GetRemoteChannel(channel);
+    if (rch == nullptr) {
+      return;
+    }
+    if (remote_ice_parameter_source_ != FROM_CANDIDATE) {
+      candidate.set_username("");
+      candidate.set_password("");
+    }
+    RTC_LOG(LS_INFO) << "Candidate(" << channel->component() << "->"
+                     << rch->component() << "): " << candidate.ToString();
+    rch->AddRemoteCandidate(candidate);
+  }
+
+  void OnReadPacket(rtc::PacketTransportInternal* transport,
+                    const char* data,
+                    size_t len,
+                    const int64_t& /* packet_time_us */,
+                    int flags) {
+    std::list<std::string>& packets = GetPacketList(transport);
+    packets.push_front(std::string(data, len));
+  }
+
+  void OnRoleConflict(IceTransportInternal* channel) {
+    GetEndpoint(channel)->OnRoleConflict(true);
+    IceRole new_role = GetEndpoint(channel)->ice_role() == ICEROLE_CONTROLLING
+                           ? ICEROLE_CONTROLLED
+                           : ICEROLE_CONTROLLING;
+    channel->SetIceRole(new_role);
+  }
+
+  void OnSentPacket(rtc::PacketTransportInternal* transport,
+                    const rtc::SentPacket& packet) {
+    TestPacketInfoIsSet(packet.info);
+  }
+
+  int SendData(IceTransportInternal* channel, const char* data, size_t len) {
+    rtc::PacketOptions options;
+    return channel->SendPacket(data, len, options, 0);
+  }
+  bool CheckDataOnChannel(IceTransportInternal* channel,
+                          const char* data,
+                          int len) {
+    return GetChannelData(channel)->CheckData(data, len);
+  }
+  static const Candidate* LocalCandidate(P2PTransportChannel* ch) {
+    return (ch && ch->selected_connection())
+               ? &ch->selected_connection()->local_candidate()
+               : NULL;
+  }
+  static const Candidate* RemoteCandidate(P2PTransportChannel* ch) {
+    return (ch && ch->selected_connection())
+               ? &ch->selected_connection()->remote_candidate()
+               : NULL;
+  }
+  Endpoint* GetEndpoint(rtc::PacketTransportInternal* transport) {
+    if (ep1_.HasTransport(transport)) {
+      return &ep1_;
+    } else if (ep2_.HasTransport(transport)) {
+      return &ep2_;
+    } else {
+      return NULL;
+    }
+  }
+  P2PTransportChannel* GetRemoteChannel(IceTransportInternal* ch) {
+    if (ch == ep1_ch1())
+      return ep2_ch1();
+    else if (ch == ep1_ch2())
+      return ep2_ch2();
+    else if (ch == ep2_ch1())
+      return ep1_ch1();
+    else if (ch == ep2_ch2())
+      return ep1_ch2();
+    else
+      return NULL;
+  }
+  std::list<std::string>& GetPacketList(
+      rtc::PacketTransportInternal* transport) {
+    return GetChannelData(transport)->ch_packets_;
+  }
+
+  enum RemoteIceParameterSource { FROM_CANDIDATE, FROM_SETICEPARAMETERS };
+
+  // How does the test pass ICE parameters to the P2PTransportChannel?
+  // On the candidate itself, or through SetRemoteIceParameters?
+  // Goes through the candidate itself by default.
+  void set_remote_ice_parameter_source(RemoteIceParameterSource source) {
+    remote_ice_parameter_source_ = source;
+  }
+
+  void set_force_relay(bool relay) { force_relay_ = relay; }
+
+  void ConnectSignalNominated(Connection* conn) {
+    conn->SignalNominated.connect(this,
+                                  &P2PTransportChannelTestBase::OnNominated);
+  }
+
+  void OnNominated(Connection* conn) { nominated_ = true; }
+  bool nominated() { return nominated_; }
+
+  webrtc::test::ScopedKeyValueConfig field_trials_;
+
+ private:
+  std::unique_ptr<rtc::VirtualSocketServer> vss_;
+  std::unique_ptr<rtc::NATSocketServer> nss_;
+  std::unique_ptr<rtc::FirewallSocketServer> ss_;
+  rtc::AutoSocketServerThread main_;
+  rtc::scoped_refptr<PendingTaskSafetyFlag> safety_ =
+      PendingTaskSafetyFlag::Create();
+  std::unique_ptr<TestStunServer> stun_server_;
+  TestTurnServer turn_server_;
+  rtc::SocksProxyServer socks_server1_;
+  rtc::SocksProxyServer socks_server2_;
+  Endpoint ep1_;
+  Endpoint ep2_;
+  RemoteIceParameterSource remote_ice_parameter_source_ = FROM_CANDIDATE;
+  bool force_relay_;
+  int selected_candidate_pair_switches_ = 0;
+
+  bool nominated_ = false;
+};
+
+// The tests have only a few outcomes, which we predefine.
+const P2PTransportChannelTestBase::Result
+    P2PTransportChannelTestBase::kLocalUdpToLocalUdp("local",
+                                                     "udp",
+                                                     "local",
+                                                     "udp",
+                                                     1000);
+const P2PTransportChannelTestBase::Result
+    P2PTransportChannelTestBase::kLocalUdpToStunUdp("local",
+                                                    "udp",
+                                                    "stun",
+                                                    "udp",
+                                                    1000);
+const P2PTransportChannelTestBase::Result
+    P2PTransportChannelTestBase::kLocalUdpToPrflxUdp("local",
+                                                     "udp",
+                                                     "prflx",
+                                                     "udp",
+                                                     1000);
+const P2PTransportChannelTestBase::Result
+    P2PTransportChannelTestBase::kPrflxUdpToLocalUdp("prflx",
+                                                     "udp",
+                                                     "local",
+                                                     "udp",
+                                                     1000);
+const P2PTransportChannelTestBase::Result
+    P2PTransportChannelTestBase::kStunUdpToLocalUdp("stun",
+                                                    "udp",
+                                                    "local",
+                                                    "udp",
+                                                    1000);
+const P2PTransportChannelTestBase::Result
+    P2PTransportChannelTestBase::kStunUdpToStunUdp("stun",
+                                                   "udp",
+                                                   "stun",
+                                                   "udp",
+                                                   1000);
+const P2PTransportChannelTestBase::Result
+    P2PTransportChannelTestBase::kStunUdpToPrflxUdp("stun",
+                                                    "udp",
+                                                    "prflx",
+                                                    "udp",
+                                                    1000);
+const P2PTransportChannelTestBase::Result
+    P2PTransportChannelTestBase::kPrflxUdpToStunUdp("prflx",
+                                                    "udp",
+                                                    "stun",
+                                                    "udp",
+                                                    1000);
+const P2PTransportChannelTestBase::Result
+    P2PTransportChannelTestBase::kLocalUdpToRelayUdp("local",
+                                                     "udp",
+                                                     "relay",
+                                                     "udp",
+                                                     2000);
+const P2PTransportChannelTestBase::Result
+    P2PTransportChannelTestBase::kPrflxUdpToRelayUdp("prflx",
+                                                     "udp",
+                                                     "relay",
+                                                     "udp",
+                                                     2000);
+const P2PTransportChannelTestBase::Result
+    P2PTransportChannelTestBase::kRelayUdpToPrflxUdp("relay",
+                                                     "udp",
+                                                     "prflx",
+                                                     "udp",
+                                                     2000);
+const P2PTransportChannelTestBase::Result
+    P2PTransportChannelTestBase::kLocalTcpToLocalTcp("local",
+                                                     "tcp",
+                                                     "local",
+                                                     "tcp",
+                                                     3000);
+const P2PTransportChannelTestBase::Result
+    P2PTransportChannelTestBase::kLocalTcpToPrflxTcp("local",
+                                                     "tcp",
+                                                     "prflx",
+                                                     "tcp",
+                                                     3000);
+const P2PTransportChannelTestBase::Result
+    P2PTransportChannelTestBase::kPrflxTcpToLocalTcp("prflx",
+                                                     "tcp",
+                                                     "local",
+                                                     "tcp",
+                                                     3000);
+
+// Test the matrix of all the connectivity types we expect to see in the wild.
+// Just test every combination of the configs in the Config enum.
+class P2PTransportChannelTest : public P2PTransportChannelTestBase {
+ public:
+  P2PTransportChannelTest() : P2PTransportChannelTestBase() {}
+  explicit P2PTransportChannelTest(absl::string_view field_trials)
+      : P2PTransportChannelTestBase(field_trials) {}
+
+ protected:
+  void ConfigureEndpoints(Config config1,
+                          Config config2,
+                          int allocator_flags1,
+                          int allocator_flags2) {
+    ConfigureEndpoint(0, config1);
+    SetAllocatorFlags(0, allocator_flags1);
+    SetAllocationStepDelay(0, kMinimumStepDelay);
+    ConfigureEndpoint(1, config2);
+    SetAllocatorFlags(1, allocator_flags2);
+    SetAllocationStepDelay(1, kMinimumStepDelay);
+
+    set_remote_ice_parameter_source(FROM_SETICEPARAMETERS);
+  }
+  void ConfigureEndpoint(int endpoint, Config config) {
+    switch (config) {
+      case OPEN:
+        AddAddress(endpoint, kPublicAddrs[endpoint]);
+        break;
+      case NAT_FULL_CONE:
+      case NAT_ADDR_RESTRICTED:
+      case NAT_PORT_RESTRICTED:
+      case NAT_SYMMETRIC:
+        AddAddress(endpoint, kPrivateAddrs[endpoint]);
+        // Add a single NAT of the desired type
+        nat()
+            ->AddTranslator(kPublicAddrs[endpoint], kNatAddrs[endpoint],
+                            static_cast<rtc::NATType>(config - NAT_FULL_CONE))
+            ->AddClient(kPrivateAddrs[endpoint]);
+        break;
+      case NAT_DOUBLE_CONE:
+      case NAT_SYMMETRIC_THEN_CONE:
+        AddAddress(endpoint, kCascadedPrivateAddrs[endpoint]);
+        // Add a two cascaded NATs of the desired types
+        nat()
+            ->AddTranslator(kPublicAddrs[endpoint], kNatAddrs[endpoint],
+                            (config == NAT_DOUBLE_CONE) ? rtc::NAT_OPEN_CONE
+                                                        : rtc::NAT_SYMMETRIC)
+            ->AddTranslator(kPrivateAddrs[endpoint],
+                            kCascadedNatAddrs[endpoint], rtc::NAT_OPEN_CONE)
+            ->AddClient(kCascadedPrivateAddrs[endpoint]);
+        break;
+      case BLOCK_UDP:
+      case BLOCK_UDP_AND_INCOMING_TCP:
+      case BLOCK_ALL_BUT_OUTGOING_HTTP:
+      case PROXY_HTTPS:
+      case PROXY_SOCKS:
+        AddAddress(endpoint, kPublicAddrs[endpoint]);
+        // Block all UDP
+        fw()->AddRule(false, rtc::FP_UDP, rtc::FD_ANY, kPublicAddrs[endpoint]);
+        if (config == BLOCK_UDP_AND_INCOMING_TCP) {
+          // Block TCP inbound to the endpoint
+          fw()->AddRule(false, rtc::FP_TCP, SocketAddress(),
+                        kPublicAddrs[endpoint]);
+        } else if (config == BLOCK_ALL_BUT_OUTGOING_HTTP) {
+          // Block all TCP to/from the endpoint except 80/443 out
+          fw()->AddRule(true, rtc::FP_TCP, kPublicAddrs[endpoint],
+                        SocketAddress(rtc::IPAddress(INADDR_ANY), 80));
+          fw()->AddRule(true, rtc::FP_TCP, kPublicAddrs[endpoint],
+                        SocketAddress(rtc::IPAddress(INADDR_ANY), 443));
+          fw()->AddRule(false, rtc::FP_TCP, rtc::FD_ANY,
+                        kPublicAddrs[endpoint]);
+        } else if (config == PROXY_HTTPS) {
+          // Block all TCP to/from the endpoint except to the proxy server
+          fw()->AddRule(true, rtc::FP_TCP, kPublicAddrs[endpoint],
+                        kHttpsProxyAddrs[endpoint]);
+          fw()->AddRule(false, rtc::FP_TCP, rtc::FD_ANY,
+                        kPublicAddrs[endpoint]);
+          SetProxy(endpoint, rtc::PROXY_HTTPS);
+        } else if (config == PROXY_SOCKS) {
+          // Block all TCP to/from the endpoint except to the proxy server
+          fw()->AddRule(true, rtc::FP_TCP, kPublicAddrs[endpoint],
+                        kSocksProxyAddrs[endpoint]);
+          fw()->AddRule(false, rtc::FP_TCP, rtc::FD_ANY,
+                        kPublicAddrs[endpoint]);
+          SetProxy(endpoint, rtc::PROXY_SOCKS5);
+        }
+        break;
+      default:
+        RTC_DCHECK_NOTREACHED();
+        break;
+    }
+  }
+};
+
+class P2PTransportChannelTestWithFieldTrials
+    : public P2PTransportChannelTest,
+      public WithParamInterface<std::string> {
+ public:
+  P2PTransportChannelTestWithFieldTrials()
+      : P2PTransportChannelTest(GetParam()) {}
+};
+
+class P2PTransportChannelMatrixTest
+    : public P2PTransportChannelTestWithFieldTrials {
+ protected:
+  static const Result* kMatrix[NUM_CONFIGS][NUM_CONFIGS];
+};
+
+// Shorthands for use in the test matrix.
+#define LULU &kLocalUdpToLocalUdp
+#define LUSU &kLocalUdpToStunUdp
+#define LUPU &kLocalUdpToPrflxUdp
+#define PULU &kPrflxUdpToLocalUdp
+#define SULU &kStunUdpToLocalUdp
+#define SUSU &kStunUdpToStunUdp
+#define SUPU &kStunUdpToPrflxUdp
+#define PUSU &kPrflxUdpToStunUdp
+#define LURU &kLocalUdpToRelayUdp
+#define PURU &kPrflxUdpToRelayUdp
+#define RUPU &kRelayUdpToPrflxUdp
+#define LTLT &kLocalTcpToLocalTcp
+#define LTPT &kLocalTcpToPrflxTcp
+#define PTLT &kPrflxTcpToLocalTcp
+// TODO(?): Enable these once TestRelayServer can accept external TCP.
+#define LTRT NULL
+#define LSRS NULL
+
+// Test matrix. Originator behavior defined by rows, receiever by columns.
+
+// TODO(?): Fix NULLs caused by lack of TCP support in NATSocket.
+// TODO(?): Fix NULLs caused by no HTTP proxy support.
+// TODO(?): Rearrange rows/columns from best to worst.
+const P2PTransportChannelMatrixTest::Result*
+    P2PTransportChannelMatrixTest::kMatrix[NUM_CONFIGS][NUM_CONFIGS] = {
+        //      OPEN  CONE  ADDR  PORT  SYMM  2CON  SCON  !UDP  !TCP  HTTP  PRXH
+        //      PRXS
+        /*OP*/ {LULU, LUSU, LUSU, LUSU, LUPU, LUSU, LUPU, LTPT, LTPT, LSRS,
+                NULL, LTPT},
+        /*CO*/
+        {SULU, SUSU, SUSU, SUSU, SUPU, SUSU, SUPU, NULL, NULL, LSRS, NULL,
+         LTRT},
+        /*AD*/
+        {SULU, SUSU, SUSU, SUSU, SUPU, SUSU, SUPU, NULL, NULL, LSRS, NULL,
+         LTRT},
+        /*PO*/
+        {SULU, SUSU, SUSU, SUSU, RUPU, SUSU, RUPU, NULL, NULL, LSRS, NULL,
+         LTRT},
+        /*SY*/
+        {PULU, PUSU, PUSU, PURU, PURU, PUSU, PURU, NULL, NULL, LSRS, NULL,
+         LTRT},
+        /*2C*/
+        {SULU, SUSU, SUSU, SUSU, SUPU, SUSU, SUPU, NULL, NULL, LSRS, NULL,
+         LTRT},
+        /*SC*/
+        {PULU, PUSU, PUSU, PURU, PURU, PUSU, PURU, NULL, NULL, LSRS, NULL,
+         LTRT},
+        /*!U*/
+        {LTPT, NULL, NULL, NULL, NULL, NULL, NULL, LTPT, LTPT, LSRS, NULL,
+         LTRT},
+        /*!T*/
+        {PTLT, NULL, NULL, NULL, NULL, NULL, NULL, PTLT, LTRT, LSRS, NULL,
+         LTRT},
+        /*HT*/
+        {LSRS, LSRS, LSRS, LSRS, LSRS, LSRS, LSRS, LSRS, LSRS, LSRS, NULL,
+         LSRS},
+        /*PR*/
+        {NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
+         NULL},
+        /*PR*/
+        {LTRT, LTRT, LTRT, LTRT, LTRT, LTRT, LTRT, LTRT, LTRT, LSRS, NULL,
+         LTRT},
+};
+
+// The actual tests that exercise all the various configurations.
+// Test names are of the form P2PTransportChannelTest_TestOPENToNAT_FULL_CONE
+#define P2P_TEST_DECLARATION(x, y, z)                            \
+  TEST_P(P2PTransportChannelMatrixTest, z##Test##x##To##y) {     \
+    ConfigureEndpoints(x, y, PORTALLOCATOR_ENABLE_SHARED_SOCKET, \
+                       PORTALLOCATOR_ENABLE_SHARED_SOCKET);      \
+    if (kMatrix[x][y] != NULL)                                   \
+      Test(*kMatrix[x][y]);                                      \
+    else                                                         \
+      RTC_LOG(LS_WARNING) << "Not yet implemented";              \
+  }
+
+#define P2P_TEST(x, y) P2P_TEST_DECLARATION(x, y, /* empty argument */)
+
+#define P2P_TEST_SET(x)                    \
+  P2P_TEST(x, OPEN)                        \
+  P2P_TEST(x, NAT_FULL_CONE)               \
+  P2P_TEST(x, NAT_ADDR_RESTRICTED)         \
+  P2P_TEST(x, NAT_PORT_RESTRICTED)         \
+  P2P_TEST(x, NAT_SYMMETRIC)               \
+  P2P_TEST(x, NAT_DOUBLE_CONE)             \
+  P2P_TEST(x, NAT_SYMMETRIC_THEN_CONE)     \
+  P2P_TEST(x, BLOCK_UDP)                   \
+  P2P_TEST(x, BLOCK_UDP_AND_INCOMING_TCP)  \
+  P2P_TEST(x, BLOCK_ALL_BUT_OUTGOING_HTTP) \
+  P2P_TEST(x, PROXY_HTTPS)                 \
+  P2P_TEST(x, PROXY_SOCKS)
+
+P2P_TEST_SET(OPEN)
+P2P_TEST_SET(NAT_FULL_CONE)
+P2P_TEST_SET(NAT_ADDR_RESTRICTED)
+P2P_TEST_SET(NAT_PORT_RESTRICTED)
+P2P_TEST_SET(NAT_SYMMETRIC)
+P2P_TEST_SET(NAT_DOUBLE_CONE)
+P2P_TEST_SET(NAT_SYMMETRIC_THEN_CONE)
+P2P_TEST_SET(BLOCK_UDP)
+P2P_TEST_SET(BLOCK_UDP_AND_INCOMING_TCP)
+P2P_TEST_SET(BLOCK_ALL_BUT_OUTGOING_HTTP)
+P2P_TEST_SET(PROXY_HTTPS)
+P2P_TEST_SET(PROXY_SOCKS)
+
+INSTANTIATE_TEST_SUITE_P(
+    Legacy,
+    P2PTransportChannelMatrixTest,
+    // Each field-trial is ~144 tests (some return not-yet-implemented).
+    Values("", "WebRTC-IceFieldTrials/enable_goog_ping:true/"));
+INSTANTIATE_TEST_SUITE_P(
+    Active,
+    P2PTransportChannelMatrixTest,
+    // Each field-trial is ~144 tests (some return not-yet-implemented).
+    Values("WebRTC-UseActiveIceController/Enabled/",
+           "WebRTC-IceFieldTrials/enable_goog_ping:true/"
+           "WebRTC-UseActiveIceController/Enabled/"));
+
+INSTANTIATE_TEST_SUITE_P(Legacy,
+                         P2PTransportChannelTestWithFieldTrials,
+                         Values(""));
+INSTANTIATE_TEST_SUITE_P(Active,
+                         P2PTransportChannelTestWithFieldTrials,
+                         Values("WebRTC-UseActiveIceController/Enabled/"));
+
+// Test that we restart candidate allocation when local ufrag&pwd changed.
+// Standard Ice protocol is used.
+TEST_P(P2PTransportChannelTestWithFieldTrials, HandleUfragPwdChange) {
+  ConfigureEndpoints(OPEN, OPEN, kDefaultPortAllocatorFlags,
+                     kDefaultPortAllocatorFlags);
+  CreateChannels();
+  TestHandleIceUfragPasswordChanged();
+  DestroyChannels();
+}
+
+// Same as above test, but with a symmetric NAT.
+// We should end up with relay<->prflx candidate pairs, with generation "1".
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       HandleUfragPwdChangeSymmetricNat) {
+  ConfigureEndpoints(NAT_SYMMETRIC, NAT_SYMMETRIC, kDefaultPortAllocatorFlags,
+                     kDefaultPortAllocatorFlags);
+  CreateChannels();
+  TestHandleIceUfragPasswordChanged();
+  DestroyChannels();
+}
+
+// Test the operation of GetStats.
+TEST_P(P2PTransportChannelTestWithFieldTrials, GetStats) {
+  rtc::ScopedFakeClock clock;
+  ConfigureEndpoints(OPEN, OPEN, kDefaultPortAllocatorFlags,
+                     kDefaultPortAllocatorFlags);
+  CreateChannels();
+  EXPECT_TRUE_SIMULATED_WAIT(ep1_ch1()->receiving() && ep1_ch1()->writable() &&
+                                 ep2_ch1()->receiving() &&
+                                 ep2_ch1()->writable(),
+                             kMediumTimeout, clock);
+  // Sends and receives 10 packets.
+  TestSendRecv(&clock);
+
+  // Try sending a packet which is discarded due to the socket being blocked.
+  virtual_socket_server()->SetSendingBlocked(true);
+  const char* data = "ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";
+  int len = static_cast<int>(strlen(data));
+  EXPECT_EQ(-1, SendData(ep1_ch1(), data, len));
+
+  IceTransportStats ice_transport_stats;
+  ASSERT_TRUE(ep1_ch1()->GetStats(&ice_transport_stats));
+  ASSERT_GE(ice_transport_stats.connection_infos.size(), 1u);
+  ASSERT_GE(ice_transport_stats.candidate_stats_list.size(), 1u);
+  EXPECT_EQ(ice_transport_stats.selected_candidate_pair_changes, 1u);
+  ConnectionInfo* best_conn_info = nullptr;
+  for (ConnectionInfo& info : ice_transport_stats.connection_infos) {
+    if (info.best_connection) {
+      best_conn_info = &info;
+      break;
+    }
+  }
+  ASSERT_TRUE(best_conn_info != nullptr);
+  EXPECT_TRUE(best_conn_info->receiving);
+  EXPECT_TRUE(best_conn_info->writable);
+  EXPECT_FALSE(best_conn_info->timeout);
+  // Note that discarded packets are counted in sent_total_packets but not
+  // sent_total_bytes.
+  EXPECT_EQ(11U, best_conn_info->sent_total_packets);
+  EXPECT_EQ(1U, best_conn_info->sent_discarded_packets);
+  EXPECT_EQ(10 * 36U, best_conn_info->sent_total_bytes);
+  EXPECT_EQ(36U, best_conn_info->sent_discarded_bytes);
+  EXPECT_EQ(10 * 36U, best_conn_info->recv_total_bytes);
+  EXPECT_EQ(10U, best_conn_info->packets_received);
+
+  EXPECT_EQ(10 * 36U, ice_transport_stats.bytes_sent);
+  EXPECT_EQ(10 * 36U, ice_transport_stats.bytes_received);
+
+  DestroyChannels();
+}
+
+TEST_P(P2PTransportChannelTestWithFieldTrials, GetStatsSwitchConnection) {
+  rtc::ScopedFakeClock clock;
+  IceConfig continual_gathering_config =
+      CreateIceConfig(1000, GATHER_CONTINUALLY);
+
+  ConfigureEndpoints(OPEN, OPEN, kDefaultPortAllocatorFlags,
+                     kDefaultPortAllocatorFlags);
+
+  AddAddress(0, kAlternateAddrs[1], "rmnet0", rtc::ADAPTER_TYPE_CELLULAR);
+
+  CreateChannels(continual_gathering_config, continual_gathering_config);
+  EXPECT_TRUE_SIMULATED_WAIT(ep1_ch1()->receiving() && ep1_ch1()->writable() &&
+                                 ep2_ch1()->receiving() &&
+                                 ep2_ch1()->writable(),
+                             kMediumTimeout, clock);
+  // Sends and receives 10 packets.
+  TestSendRecv(&clock);
+
+  IceTransportStats ice_transport_stats;
+  ASSERT_TRUE(ep1_ch1()->GetStats(&ice_transport_stats));
+  ASSERT_GE(ice_transport_stats.connection_infos.size(), 2u);
+  ASSERT_GE(ice_transport_stats.candidate_stats_list.size(), 2u);
+  EXPECT_EQ(ice_transport_stats.selected_candidate_pair_changes, 1u);
+
+  ConnectionInfo* best_conn_info = nullptr;
+  for (ConnectionInfo& info : ice_transport_stats.connection_infos) {
+    if (info.best_connection) {
+      best_conn_info = &info;
+      break;
+    }
+  }
+  ASSERT_TRUE(best_conn_info != nullptr);
+  EXPECT_TRUE(best_conn_info->receiving);
+  EXPECT_TRUE(best_conn_info->writable);
+  EXPECT_FALSE(best_conn_info->timeout);
+
+  EXPECT_EQ(10 * 36U, best_conn_info->sent_total_bytes);
+  EXPECT_EQ(10 * 36U, best_conn_info->recv_total_bytes);
+  EXPECT_EQ(10 * 36U, ice_transport_stats.bytes_sent);
+  EXPECT_EQ(10 * 36U, ice_transport_stats.bytes_received);
+
+  auto old_selected_connection = ep1_ch1()->selected_connection();
+  ep1_ch1()->RemoveConnectionForTest(
+      const_cast<Connection*>(old_selected_connection));
+
+  EXPECT_TRUE_SIMULATED_WAIT(ep1_ch1()->selected_connection() != nullptr,
+                             kMediumTimeout, clock);
+
+  // Sends and receives 10 packets.
+  TestSendRecv(&clock);
+
+  IceTransportStats ice_transport_stats2;
+  ASSERT_TRUE(ep1_ch1()->GetStats(&ice_transport_stats2));
+
+  int64_t sum_bytes_sent = 0;
+  int64_t sum_bytes_received = 0;
+  for (ConnectionInfo& info : ice_transport_stats.connection_infos) {
+    sum_bytes_sent += info.sent_total_bytes;
+    sum_bytes_received += info.recv_total_bytes;
+  }
+
+  EXPECT_EQ(10 * 36U, sum_bytes_sent);
+  EXPECT_EQ(10 * 36U, sum_bytes_received);
+
+  EXPECT_EQ(20 * 36U, ice_transport_stats2.bytes_sent);
+  EXPECT_EQ(20 * 36U, ice_transport_stats2.bytes_received);
+
+  DestroyChannels();
+}
+
+// Tests that UMAs are recorded when ICE restarts while the channel
+// is disconnected.
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       TestUMAIceRestartWhileDisconnected) {
+  rtc::ScopedFakeClock clock;
+  ConfigureEndpoints(OPEN, OPEN, kOnlyLocalPorts, kOnlyLocalPorts);
+
+  CreateChannels();
+  EXPECT_TRUE_SIMULATED_WAIT(CheckConnected(ep1_ch1(), ep2_ch1()),
+                             kDefaultTimeout, clock);
+
+  // Drop all packets so that both channels become not writable.
+  fw()->AddRule(false, rtc::FP_ANY, rtc::FD_ANY, kPublicAddrs[0]);
+  const int kWriteTimeoutDelay = 8000;
+  EXPECT_TRUE_SIMULATED_WAIT(!ep1_ch1()->writable() && !ep2_ch1()->writable(),
+                             kWriteTimeoutDelay, clock);
+
+  ep1_ch1()->SetIceParameters(kIceParams[2]);
+  ep1_ch1()->SetRemoteIceParameters(kIceParams[3]);
+  ep1_ch1()->MaybeStartGathering();
+  EXPECT_METRIC_EQ(1, webrtc::metrics::NumEvents(
+                          "WebRTC.PeerConnection.IceRestartState",
+                          static_cast<int>(IceRestartState::DISCONNECTED)));
+
+  ep2_ch1()->SetIceParameters(kIceParams[3]);
+  ep2_ch1()->SetRemoteIceParameters(kIceParams[2]);
+  ep2_ch1()->MaybeStartGathering();
+  EXPECT_METRIC_EQ(2, webrtc::metrics::NumEvents(
+                          "WebRTC.PeerConnection.IceRestartState",
+                          static_cast<int>(IceRestartState::DISCONNECTED)));
+
+  DestroyChannels();
+}
+
+// Tests that UMAs are recorded when ICE restarts while the channel
+// is connected.
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       TestUMAIceRestartWhileConnected) {
+  rtc::ScopedFakeClock clock;
+  ConfigureEndpoints(OPEN, OPEN, kOnlyLocalPorts, kOnlyLocalPorts);
+
+  CreateChannels();
+  EXPECT_TRUE_SIMULATED_WAIT(CheckConnected(ep1_ch1(), ep2_ch1()),
+                             kDefaultTimeout, clock);
+
+  ep1_ch1()->SetIceParameters(kIceParams[2]);
+  ep1_ch1()->SetRemoteIceParameters(kIceParams[3]);
+  ep1_ch1()->MaybeStartGathering();
+  EXPECT_METRIC_EQ(1, webrtc::metrics::NumEvents(
+                          "WebRTC.PeerConnection.IceRestartState",
+                          static_cast<int>(IceRestartState::CONNECTED)));
+
+  ep2_ch1()->SetIceParameters(kIceParams[3]);
+  ep2_ch1()->SetRemoteIceParameters(kIceParams[2]);
+  ep2_ch1()->MaybeStartGathering();
+  EXPECT_METRIC_EQ(2, webrtc::metrics::NumEvents(
+                          "WebRTC.PeerConnection.IceRestartState",
+                          static_cast<int>(IceRestartState::CONNECTED)));
+
+  DestroyChannels();
+}
+
+// Tests that UMAs are recorded when ICE restarts while the channel
+// is connecting.
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       TestUMAIceRestartWhileConnecting) {
+  rtc::ScopedFakeClock clock;
+  ConfigureEndpoints(OPEN, OPEN, kOnlyLocalPorts, kOnlyLocalPorts);
+
+  // Create the channels without waiting for them to become connected.
+  CreateChannels();
+
+  ep1_ch1()->SetIceParameters(kIceParams[2]);
+  ep1_ch1()->SetRemoteIceParameters(kIceParams[3]);
+  ep1_ch1()->MaybeStartGathering();
+  EXPECT_METRIC_EQ(1, webrtc::metrics::NumEvents(
+                          "WebRTC.PeerConnection.IceRestartState",
+                          static_cast<int>(IceRestartState::CONNECTING)));
+
+  ep2_ch1()->SetIceParameters(kIceParams[3]);
+  ep2_ch1()->SetRemoteIceParameters(kIceParams[2]);
+  ep2_ch1()->MaybeStartGathering();
+  EXPECT_METRIC_EQ(2, webrtc::metrics::NumEvents(
+                          "WebRTC.PeerConnection.IceRestartState",
+                          static_cast<int>(IceRestartState::CONNECTING)));
+
+  DestroyChannels();
+}
+
+// Tests that a UMA on ICE regathering is recorded when there is a network
+// change if and only if continual gathering is enabled.
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       TestIceRegatheringReasonContinualGatheringByNetworkChange) {
+  rtc::ScopedFakeClock clock;
+  ConfigureEndpoints(OPEN, OPEN, kOnlyLocalPorts, kOnlyLocalPorts);
+
+  // ep1 gathers continually but ep2 does not.
+  IceConfig continual_gathering_config =
+      CreateIceConfig(1000, GATHER_CONTINUALLY);
+  IceConfig default_config;
+  CreateChannels(continual_gathering_config, default_config);
+
+  EXPECT_TRUE_SIMULATED_WAIT(CheckConnected(ep1_ch1(), ep2_ch1()),
+                             kDefaultTimeout, clock);
+
+  // Adding address in ep1 will trigger continual gathering.
+  AddAddress(0, kAlternateAddrs[0]);
+  EXPECT_EQ_SIMULATED_WAIT(1,
+                           GetEndpoint(0)->GetIceRegatheringCountForReason(
+                               IceRegatheringReason::NETWORK_CHANGE),
+                           kDefaultTimeout, clock);
+
+  ep2_ch1()->SetIceParameters(kIceParams[3]);
+  ep2_ch1()->SetRemoteIceParameters(kIceParams[2]);
+  ep2_ch1()->MaybeStartGathering();
+
+  AddAddress(1, kAlternateAddrs[1]);
+  SIMULATED_WAIT(false, kDefaultTimeout, clock);
+  // ep2 has not enabled continual gathering.
+  EXPECT_EQ(0, GetEndpoint(1)->GetIceRegatheringCountForReason(
+                   IceRegatheringReason::NETWORK_CHANGE));
+
+  DestroyChannels();
+}
+
+// Tests that a UMA on ICE regathering is recorded when there is a network
+// failure if and only if continual gathering is enabled.
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       TestIceRegatheringReasonContinualGatheringByNetworkFailure) {
+  rtc::ScopedFakeClock clock;
+  ConfigureEndpoints(OPEN, OPEN, kOnlyLocalPorts, kOnlyLocalPorts);
+
+  // ep1 gathers continually but ep2 does not.
+  IceConfig config1 = CreateIceConfig(1000, GATHER_CONTINUALLY);
+  config1.regather_on_failed_networks_interval = 2000;
+  IceConfig config2;
+  config2.regather_on_failed_networks_interval = 2000;
+  CreateChannels(config1, config2);
+
+  EXPECT_TRUE_SIMULATED_WAIT(CheckConnected(ep1_ch1(), ep2_ch1()),
+                             kDefaultTimeout, clock);
+
+  fw()->AddRule(false, rtc::FP_ANY, rtc::FD_ANY, kPublicAddrs[0]);
+  // Timeout value such that all connections are deleted.
+  const int kNetworkFailureTimeout = 35000;
+  SIMULATED_WAIT(false, kNetworkFailureTimeout, clock);
+  EXPECT_LE(1, GetEndpoint(0)->GetIceRegatheringCountForReason(
+                   IceRegatheringReason::NETWORK_FAILURE));
+  EXPECT_METRIC_LE(
+      1, webrtc::metrics::NumEvents(
+             "WebRTC.PeerConnection.IceRegatheringReason",
+             static_cast<int>(IceRegatheringReason::NETWORK_FAILURE)));
+  EXPECT_EQ(0, GetEndpoint(1)->GetIceRegatheringCountForReason(
+                   IceRegatheringReason::NETWORK_FAILURE));
+
+  DestroyChannels();
+}
+
+// Test that we properly create a connection on a STUN ping from unknown address
+// when the signaling is slow.
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       PeerReflexiveCandidateBeforeSignaling) {
+  ConfigureEndpoints(OPEN, OPEN, kDefaultPortAllocatorFlags,
+                     kDefaultPortAllocatorFlags);
+  // Emulate no remote parameters coming in.
+  set_remote_ice_parameter_source(FROM_CANDIDATE);
+  CreateChannels();
+  // Only have remote parameters come in for ep2, not ep1.
+  ep2_ch1()->SetRemoteIceParameters(kIceParams[0]);
+
+  // Pause sending ep2's candidates to ep1 until ep1 receives the peer reflexive
+  // candidate.
+  PauseCandidates(1);
+
+  // Wait until the callee becomes writable to make sure that a ping request is
+  // received by the caller before their remote ICE credentials are set.
+  ASSERT_TRUE_WAIT(ep2_ch1()->selected_connection() != nullptr, kMediumTimeout);
+  // Add two sets of remote ICE credentials, so that the ones used by the
+  // candidate will be generation 1 instead of 0.
+  ep1_ch1()->SetRemoteIceParameters(kIceParams[3]);
+  ep1_ch1()->SetRemoteIceParameters(kIceParams[1]);
+  // The caller should have the selected connection connected to the peer
+  // reflexive candidate.
+  const Connection* selected_connection = nullptr;
+  ASSERT_TRUE_WAIT(
+      (selected_connection = ep1_ch1()->selected_connection()) != nullptr,
+      kMediumTimeout);
+  EXPECT_EQ(PRFLX_PORT_TYPE, selected_connection->remote_candidate().type());
+  EXPECT_EQ(kIceUfrag[1], selected_connection->remote_candidate().username());
+  EXPECT_EQ(kIcePwd[1], selected_connection->remote_candidate().password());
+  EXPECT_EQ(1u, selected_connection->remote_candidate().generation());
+
+  ResumeCandidates(1);
+  // Verify ep1's selected connection is updated to use the 'local' candidate.
+  EXPECT_EQ_WAIT(LOCAL_PORT_TYPE,
+                 ep1_ch1()->selected_connection()->remote_candidate().type(),
+                 kMediumTimeout);
+  EXPECT_EQ(selected_connection, ep1_ch1()->selected_connection());
+  DestroyChannels();
+}
+
+// Test that if we learn a prflx remote candidate, its address is concealed in
+// 1. the selected candidate pair accessed via the public API, and
+// 2. the candidate pair stats
+// until we learn the same address from signaling.
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       PeerReflexiveRemoteCandidateIsSanitized) {
+  ConfigureEndpoints(OPEN, OPEN, kOnlyLocalPorts, kOnlyLocalPorts);
+  // Emulate no remote parameters coming in.
+  set_remote_ice_parameter_source(FROM_CANDIDATE);
+  CreateChannels();
+  // Only have remote parameters come in for ep2, not ep1.
+  ep2_ch1()->SetRemoteIceParameters(kIceParams[0]);
+
+  // Pause sending ep2's candidates to ep1 until ep1 receives the peer reflexive
+  // candidate.
+  PauseCandidates(1);
+
+  ASSERT_TRUE_WAIT(ep2_ch1()->selected_connection() != nullptr, kMediumTimeout);
+  ep1_ch1()->SetRemoteIceParameters(kIceParams[1]);
+  ASSERT_TRUE_WAIT(ep1_ch1()->selected_connection() != nullptr, kMediumTimeout);
+
+  // Check the selected candidate pair.
+  auto pair_ep1 = ep1_ch1()->GetSelectedCandidatePair();
+  ASSERT_TRUE(pair_ep1.has_value());
+  EXPECT_EQ(PRFLX_PORT_TYPE, pair_ep1->remote_candidate().type());
+  EXPECT_TRUE(pair_ep1->remote_candidate().address().ipaddr().IsNil());
+
+  IceTransportStats ice_transport_stats;
+  ep1_ch1()->GetStats(&ice_transport_stats);
+  // Check the candidate pair stats.
+  ASSERT_EQ(1u, ice_transport_stats.connection_infos.size());
+  EXPECT_EQ(PRFLX_PORT_TYPE,
+            ice_transport_stats.connection_infos[0].remote_candidate.type());
+  EXPECT_TRUE(ice_transport_stats.connection_infos[0]
+                  .remote_candidate.address()
+                  .ipaddr()
+                  .IsNil());
+
+  // Let ep1 receive the remote candidate to update its type from prflx to host.
+  ResumeCandidates(1);
+  ASSERT_TRUE_WAIT(
+      ep1_ch1()->selected_connection() != nullptr &&
+          ep1_ch1()->selected_connection()->remote_candidate().type() ==
+              LOCAL_PORT_TYPE,
+      kMediumTimeout);
+
+  // We should be able to reveal the address after it is learnt via
+  // AddIceCandidate.
+  //
+  // Check the selected candidate pair.
+  auto updated_pair_ep1 = ep1_ch1()->GetSelectedCandidatePair();
+  ASSERT_TRUE(updated_pair_ep1.has_value());
+  EXPECT_EQ(LOCAL_PORT_TYPE, updated_pair_ep1->remote_candidate().type());
+  EXPECT_TRUE(HasRemoteAddress(&updated_pair_ep1.value(), kPublicAddrs[1]));
+
+  ep1_ch1()->GetStats(&ice_transport_stats);
+  // Check the candidate pair stats.
+  ASSERT_EQ(1u, ice_transport_stats.connection_infos.size());
+  EXPECT_EQ(LOCAL_PORT_TYPE,
+            ice_transport_stats.connection_infos[0].remote_candidate.type());
+  EXPECT_TRUE(ice_transport_stats.connection_infos[0]
+                  .remote_candidate.address()
+                  .EqualIPs(kPublicAddrs[1]));
+
+  DestroyChannels();
+}
+
+// Test that we properly create a connection on a STUN ping from unknown address
+// when the signaling is slow and the end points are behind NAT.
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       PeerReflexiveCandidateBeforeSignalingWithNAT) {
+  ConfigureEndpoints(OPEN, NAT_SYMMETRIC, kDefaultPortAllocatorFlags,
+                     kDefaultPortAllocatorFlags);
+  // Emulate no remote parameters coming in.
+  set_remote_ice_parameter_source(FROM_CANDIDATE);
+  CreateChannels();
+  // Only have remote parameters come in for ep2, not ep1.
+  ep2_ch1()->SetRemoteIceParameters(kIceParams[0]);
+  // Pause sending ep2's candidates to ep1 until ep1 receives the peer reflexive
+  // candidate.
+  PauseCandidates(1);
+
+  // Wait until the callee becomes writable to make sure that a ping request is
+  // received by the caller before their remote ICE credentials are set.
+  ASSERT_TRUE_WAIT(ep2_ch1()->selected_connection() != nullptr, kMediumTimeout);
+  // Add two sets of remote ICE credentials, so that the ones used by the
+  // candidate will be generation 1 instead of 0.
+  ep1_ch1()->SetRemoteIceParameters(kIceParams[3]);
+  ep1_ch1()->SetRemoteIceParameters(kIceParams[1]);
+
+  // The caller's selected connection should be connected to the peer reflexive
+  // candidate.
+  const Connection* selected_connection = nullptr;
+  ASSERT_TRUE_WAIT(
+      (selected_connection = ep1_ch1()->selected_connection()) != nullptr,
+      kMediumTimeout);
+  EXPECT_EQ(PRFLX_PORT_TYPE, selected_connection->remote_candidate().type());
+  EXPECT_EQ(kIceUfrag[1], selected_connection->remote_candidate().username());
+  EXPECT_EQ(kIcePwd[1], selected_connection->remote_candidate().password());
+  EXPECT_EQ(1u, selected_connection->remote_candidate().generation());
+
+  ResumeCandidates(1);
+
+  EXPECT_EQ_WAIT(PRFLX_PORT_TYPE,
+                 ep1_ch1()->selected_connection()->remote_candidate().type(),
+                 kMediumTimeout);
+  EXPECT_EQ(selected_connection, ep1_ch1()->selected_connection());
+  DestroyChannels();
+}
+
+// Test that we properly create a connection on a STUN ping from unknown address
+// when the signaling is slow, even if the new candidate is created due to the
+// remote peer doing an ICE restart, pairing this candidate across generations.
+//
+// Previously this wasn't working due to a bug where the peer reflexive
+// candidate was only updated for the newest generation candidate pairs, and
+// not older-generation candidate pairs created by pairing candidates across
+// generations. This resulted in the old-generation prflx candidate being
+// prioritized above new-generation candidate pairs.
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       PeerReflexiveCandidateBeforeSignalingWithIceRestart) {
+  ConfigureEndpoints(OPEN, OPEN, kDefaultPortAllocatorFlags,
+                     kDefaultPortAllocatorFlags);
+  // Only gather relay candidates, so that when the prflx candidate arrives
+  // it's prioritized above the current candidate pair.
+  GetEndpoint(0)->allocator_->SetCandidateFilter(CF_RELAY);
+  GetEndpoint(1)->allocator_->SetCandidateFilter(CF_RELAY);
+  // Setting this allows us to control when SetRemoteIceParameters is called.
+  set_remote_ice_parameter_source(FROM_CANDIDATE);
+  CreateChannels();
+  // Wait for the initial connection to be made.
+  ep1_ch1()->SetRemoteIceParameters(kIceParams[1]);
+  ep2_ch1()->SetRemoteIceParameters(kIceParams[0]);
+  EXPECT_TRUE_WAIT(CheckConnected(ep1_ch1(), ep2_ch1()), kDefaultTimeout);
+
+  // Simulate an ICE restart on ep2, but don't signal the candidate or new
+  // ICE parameters until after a prflx connection has been made.
+  PauseCandidates(1);
+  ep2_ch1()->SetIceParameters(kIceParams[3]);
+
+  ep1_ch1()->SetRemoteIceParameters(kIceParams[3]);
+  ep2_ch1()->MaybeStartGathering();
+
+  // The caller should have the selected connection connected to the peer
+  // reflexive candidate.
+  EXPECT_EQ_WAIT(PRFLX_PORT_TYPE,
+                 ep1_ch1()->selected_connection()->remote_candidate().type(),
+                 kDefaultTimeout);
+  const Connection* prflx_selected_connection =
+      ep1_ch1()->selected_connection();
+
+  // Now simulate the ICE restart on ep1.
+  ep1_ch1()->SetIceParameters(kIceParams[2]);
+
+  ep2_ch1()->SetRemoteIceParameters(kIceParams[2]);
+  ep1_ch1()->MaybeStartGathering();
+
+  // Finally send the candidates from ep2's ICE restart and verify that ep1 uses
+  // their information to update the peer reflexive candidate.
+  ResumeCandidates(1);
+
+  EXPECT_EQ_WAIT(RELAY_PORT_TYPE,
+                 ep1_ch1()->selected_connection()->remote_candidate().type(),
+                 kDefaultTimeout);
+  EXPECT_EQ(prflx_selected_connection, ep1_ch1()->selected_connection());
+  DestroyChannels();
+}
+
+// Test that if remote candidates don't have ufrag and pwd, we still work.
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       RemoteCandidatesWithoutUfragPwd) {
+  rtc::ScopedFakeClock clock;
+  set_remote_ice_parameter_source(FROM_SETICEPARAMETERS);
+  ConfigureEndpoints(OPEN, OPEN, kDefaultPortAllocatorFlags,
+                     kDefaultPortAllocatorFlags);
+  CreateChannels();
+  const Connection* selected_connection = NULL;
+  // Wait until the callee's connections are created.
+  EXPECT_TRUE_SIMULATED_WAIT(
+      (selected_connection = ep2_ch1()->selected_connection()) != NULL,
+      kMediumTimeout, clock);
+  // Wait to make sure the selected connection is not changed.
+  SIMULATED_WAIT(ep2_ch1()->selected_connection() != selected_connection,
+                 kShortTimeout, clock);
+  EXPECT_TRUE(ep2_ch1()->selected_connection() == selected_connection);
+  DestroyChannels();
+}
+
+// Test that a host behind NAT cannot be reached when incoming_only
+// is set to true.
+TEST_P(P2PTransportChannelTestWithFieldTrials, IncomingOnlyBlocked) {
+  rtc::ScopedFakeClock clock;
+  ConfigureEndpoints(NAT_FULL_CONE, OPEN, kDefaultPortAllocatorFlags,
+                     kDefaultPortAllocatorFlags);
+
+  SetAllocatorFlags(0, kOnlyLocalPorts);
+  CreateChannels();
+  ep1_ch1()->set_incoming_only(true);
+
+  // Pump for 1 second and verify that the channels are not connected.
+  SIMULATED_WAIT(false, kShortTimeout, clock);
+
+  EXPECT_FALSE(ep1_ch1()->receiving());
+  EXPECT_FALSE(ep1_ch1()->writable());
+  EXPECT_FALSE(ep2_ch1()->receiving());
+  EXPECT_FALSE(ep2_ch1()->writable());
+
+  DestroyChannels();
+}
+
+// Test that a peer behind NAT can connect to a peer that has
+// incoming_only flag set.
+TEST_P(P2PTransportChannelTestWithFieldTrials, IncomingOnlyOpen) {
+  rtc::ScopedFakeClock clock;
+  ConfigureEndpoints(OPEN, NAT_FULL_CONE, kDefaultPortAllocatorFlags,
+                     kDefaultPortAllocatorFlags);
+
+  SetAllocatorFlags(0, kOnlyLocalPorts);
+  CreateChannels();
+  ep1_ch1()->set_incoming_only(true);
+
+  EXPECT_TRUE_SIMULATED_WAIT(CheckConnected(ep1_ch1(), ep2_ch1()),
+                             kMediumTimeout, clock);
+
+  DestroyChannels();
+}
+
+// Test that two peers can connect when one can only make outgoing TCP
+// connections. This has been observed in some scenarios involving
+// VPNs/firewalls.
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       CanOnlyMakeOutgoingTcpConnections) {
+  // The PORTALLOCATOR_ENABLE_ANY_ADDRESS_PORTS flag is required if the
+  // application needs this use case to work, since the application must accept
+  // the tradeoff that more candidates need to be allocated.
+  //
+  // TODO(deadbeef): Later, make this flag the default, and do more elegant
+  // things to ensure extra candidates don't waste resources?
+  ConfigureEndpoints(
+      OPEN, OPEN,
+      kDefaultPortAllocatorFlags | PORTALLOCATOR_ENABLE_ANY_ADDRESS_PORTS,
+      kDefaultPortAllocatorFlags);
+  // In order to simulate nothing working but outgoing TCP connections, prevent
+  // the endpoint from binding to its interface's address as well as the
+  // "any" addresses. It can then only make a connection by using "Connect()".
+  fw()->SetUnbindableIps({rtc::GetAnyIP(AF_INET), rtc::GetAnyIP(AF_INET6),
+                          kPublicAddrs[0].ipaddr()});
+  CreateChannels();
+  // Expect a "prflx" candidate on the side that can only make outgoing
+  // connections, endpoint 0.
+  Test(kPrflxTcpToLocalTcp);
+  DestroyChannels();
+}
+
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       TestTcpConnectionsFromActiveToPassive) {
+  rtc::ScopedFakeClock clock;
+  AddAddress(0, kPublicAddrs[0]);
+  AddAddress(1, kPublicAddrs[1]);
+
+  SetAllocationStepDelay(0, kMinimumStepDelay);
+  SetAllocationStepDelay(1, kMinimumStepDelay);
+
+  int kOnlyLocalTcpPorts = PORTALLOCATOR_DISABLE_UDP |
+                           PORTALLOCATOR_DISABLE_STUN |
+                           PORTALLOCATOR_DISABLE_RELAY;
+  // Disable all protocols except TCP.
+  SetAllocatorFlags(0, kOnlyLocalTcpPorts);
+  SetAllocatorFlags(1, kOnlyLocalTcpPorts);
+
+  SetAllowTcpListen(0, true);   // actpass.
+  SetAllowTcpListen(1, false);  // active.
+
+  // We want SetRemoteIceParameters to be called as it normally would.
+  // Otherwise we won't know what parameters to use for the expected
+  // prflx TCP candidates.
+  set_remote_ice_parameter_source(FROM_SETICEPARAMETERS);
+
+  // Pause candidate so we could verify the candidate properties.
+  PauseCandidates(0);
+  PauseCandidates(1);
+  CreateChannels();
+
+  // Verify tcp candidates.
+  VerifySavedTcpCandidates(0, TCPTYPE_PASSIVE_STR);
+  VerifySavedTcpCandidates(1, TCPTYPE_ACTIVE_STR);
+
+  // Resume candidates.
+  ResumeCandidates(0);
+  ResumeCandidates(1);
+
+  EXPECT_TRUE_SIMULATED_WAIT(
+      CheckCandidatePairAndConnected(ep1_ch1(), ep2_ch1(), kPublicAddrs[0],
+                                     kPublicAddrs[1]),
+      kShortTimeout, clock);
+
+  TestSendRecv(&clock);
+  DestroyChannels();
+}
+
+// Test that tcptype is set on all candidates for a connection running over TCP.
+TEST_P(P2PTransportChannelTestWithFieldTrials, TestTcpConnectionTcptypeSet) {
+  rtc::ScopedFakeClock clock;
+  ConfigureEndpoints(BLOCK_UDP_AND_INCOMING_TCP, OPEN,
+                     PORTALLOCATOR_ENABLE_SHARED_SOCKET,
+                     PORTALLOCATOR_ENABLE_SHARED_SOCKET);
+
+  SetAllowTcpListen(0, false);  // active.
+  SetAllowTcpListen(1, true);   // actpass.
+  CreateChannels();
+
+  EXPECT_TRUE_SIMULATED_WAIT(CheckConnected(ep1_ch1(), ep2_ch1()),
+                             kMediumTimeout, clock);
+  SIMULATED_WAIT(false, kDefaultTimeout, clock);
+
+  EXPECT_EQ(RemoteCandidate(ep1_ch1())->tcptype(), "passive");
+  EXPECT_EQ(LocalCandidate(ep1_ch1())->tcptype(), "active");
+  EXPECT_EQ(RemoteCandidate(ep2_ch1())->tcptype(), "active");
+  EXPECT_EQ(LocalCandidate(ep2_ch1())->tcptype(), "passive");
+
+  DestroyChannels();
+}
+
+TEST_P(P2PTransportChannelTestWithFieldTrials, TestIceRoleConflict) {
+  AddAddress(0, kPublicAddrs[0]);
+  AddAddress(1, kPublicAddrs[1]);
+  TestSignalRoleConflict();
+}
+
+// Tests that the ice configs (protocol, tiebreaker and role) can be passed
+// down to ports.
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       TestIceConfigWillPassDownToPort) {
+  rtc::ScopedFakeClock clock;
+  AddAddress(0, kPublicAddrs[0]);
+  AddAddress(1, kPublicAddrs[1]);
+
+  // Give the first connection the higher tiebreaker so its role won't
+  // change unless we tell it to.
+  SetIceRole(0, ICEROLE_CONTROLLING);
+  SetIceTiebreaker(0, kHighTiebreaker);
+  SetIceRole(1, ICEROLE_CONTROLLING);
+  SetIceTiebreaker(1, kLowTiebreaker);
+
+  CreateChannels();
+
+  EXPECT_EQ_SIMULATED_WAIT(2u, ep1_ch1()->ports().size(), kShortTimeout, clock);
+
+  const std::vector<PortInterface*> ports_before = ep1_ch1()->ports();
+  for (size_t i = 0; i < ports_before.size(); ++i) {
+    EXPECT_EQ(ICEROLE_CONTROLLING, ports_before[i]->GetIceRole());
+    EXPECT_EQ(kHighTiebreaker, ports_before[i]->IceTiebreaker());
+  }
+
+  ep1_ch1()->SetIceRole(ICEROLE_CONTROLLED);
+  ep1_ch1()->SetIceTiebreaker(kLowTiebreaker);
+
+  const std::vector<PortInterface*> ports_after = ep1_ch1()->ports();
+  for (size_t i = 0; i < ports_after.size(); ++i) {
+    EXPECT_EQ(ICEROLE_CONTROLLED, ports_before[i]->GetIceRole());
+    // SetIceTiebreaker after ports have been created will fail. So expect the
+    // original value.
+    EXPECT_EQ(kHighTiebreaker, ports_before[i]->IceTiebreaker());
+  }
+
+  EXPECT_TRUE_SIMULATED_WAIT(CheckConnected(ep1_ch1(), ep2_ch1()),
+                             kShortTimeout, clock);
+
+  EXPECT_TRUE(ep1_ch1()->selected_connection() &&
+              ep2_ch1()->selected_connection());
+
+  TestSendRecv(&clock);
+  DestroyChannels();
+}
+
+// Verify that we can set DSCP value and retrieve properly from P2PTC.
+TEST_P(P2PTransportChannelTestWithFieldTrials, TestDefaultDscpValue) {
+  AddAddress(0, kPublicAddrs[0]);
+  AddAddress(1, kPublicAddrs[1]);
+
+  CreateChannels();
+  EXPECT_EQ(rtc::DSCP_NO_CHANGE, GetEndpoint(0)->cd1_.ch_->DefaultDscpValue());
+  EXPECT_EQ(rtc::DSCP_NO_CHANGE, GetEndpoint(1)->cd1_.ch_->DefaultDscpValue());
+  GetEndpoint(0)->cd1_.ch_->SetOption(rtc::Socket::OPT_DSCP, rtc::DSCP_CS6);
+  GetEndpoint(1)->cd1_.ch_->SetOption(rtc::Socket::OPT_DSCP, rtc::DSCP_CS6);
+  EXPECT_EQ(rtc::DSCP_CS6, GetEndpoint(0)->cd1_.ch_->DefaultDscpValue());
+  EXPECT_EQ(rtc::DSCP_CS6, GetEndpoint(1)->cd1_.ch_->DefaultDscpValue());
+  GetEndpoint(0)->cd1_.ch_->SetOption(rtc::Socket::OPT_DSCP, rtc::DSCP_AF41);
+  GetEndpoint(1)->cd1_.ch_->SetOption(rtc::Socket::OPT_DSCP, rtc::DSCP_AF41);
+  EXPECT_EQ(rtc::DSCP_AF41, GetEndpoint(0)->cd1_.ch_->DefaultDscpValue());
+  EXPECT_EQ(rtc::DSCP_AF41, GetEndpoint(1)->cd1_.ch_->DefaultDscpValue());
+  DestroyChannels();
+}
+
+// Verify IPv6 connection is preferred over IPv4.
+TEST_P(P2PTransportChannelTestWithFieldTrials, TestIPv6Connections) {
+  rtc::ScopedFakeClock clock;
+  AddAddress(0, kIPv6PublicAddrs[0]);
+  AddAddress(0, kPublicAddrs[0]);
+  AddAddress(1, kIPv6PublicAddrs[1]);
+  AddAddress(1, kPublicAddrs[1]);
+
+  SetAllocationStepDelay(0, kMinimumStepDelay);
+  SetAllocationStepDelay(1, kMinimumStepDelay);
+
+  // Enable IPv6
+  SetAllocatorFlags(
+      0, PORTALLOCATOR_ENABLE_IPV6 | PORTALLOCATOR_ENABLE_IPV6_ON_WIFI);
+  SetAllocatorFlags(
+      1, PORTALLOCATOR_ENABLE_IPV6 | PORTALLOCATOR_ENABLE_IPV6_ON_WIFI);
+
+  CreateChannels();
+
+  EXPECT_TRUE_SIMULATED_WAIT(
+      CheckCandidatePairAndConnected(ep1_ch1(), ep2_ch1(), kIPv6PublicAddrs[0],
+                                     kIPv6PublicAddrs[1]),
+      kShortTimeout, clock);
+
+  TestSendRecv(&clock);
+  DestroyChannels();
+}
+
+// Testing forceful TURN connections.
+TEST_P(P2PTransportChannelTestWithFieldTrials, TestForceTurn) {
+  rtc::ScopedFakeClock clock;
+  ConfigureEndpoints(
+      NAT_PORT_RESTRICTED, NAT_SYMMETRIC,
+      kDefaultPortAllocatorFlags | PORTALLOCATOR_ENABLE_SHARED_SOCKET,
+      kDefaultPortAllocatorFlags | PORTALLOCATOR_ENABLE_SHARED_SOCKET);
+  set_force_relay(true);
+
+  SetAllocationStepDelay(0, kMinimumStepDelay);
+  SetAllocationStepDelay(1, kMinimumStepDelay);
+
+  CreateChannels();
+
+  EXPECT_TRUE_SIMULATED_WAIT(CheckConnected(ep1_ch1(), ep2_ch1()),
+                             kMediumTimeout, clock);
+
+  EXPECT_TRUE(ep1_ch1()->selected_connection() &&
+              ep2_ch1()->selected_connection());
+
+  EXPECT_EQ(RELAY_PORT_TYPE, RemoteCandidate(ep1_ch1())->type());
+  EXPECT_EQ(RELAY_PORT_TYPE, LocalCandidate(ep1_ch1())->type());
+  EXPECT_EQ(RELAY_PORT_TYPE, RemoteCandidate(ep2_ch1())->type());
+  EXPECT_EQ(RELAY_PORT_TYPE, LocalCandidate(ep2_ch1())->type());
+
+  TestSendRecv(&clock);
+  DestroyChannels();
+}
+
+// Test that if continual gathering is set to true, ICE gathering state will
+// not change to "Complete", and vice versa.
+TEST_P(P2PTransportChannelTestWithFieldTrials, TestContinualGathering) {
+  rtc::ScopedFakeClock clock;
+  ConfigureEndpoints(OPEN, OPEN, kDefaultPortAllocatorFlags,
+                     kDefaultPortAllocatorFlags);
+  SetAllocationStepDelay(0, kDefaultStepDelay);
+  SetAllocationStepDelay(1, kDefaultStepDelay);
+  IceConfig continual_gathering_config =
+      CreateIceConfig(1000, GATHER_CONTINUALLY);
+  // By default, ep2 does not gather continually.
+  IceConfig default_config;
+  CreateChannels(continual_gathering_config, default_config);
+
+  EXPECT_TRUE_SIMULATED_WAIT(CheckConnected(ep1_ch1(), ep2_ch1()),
+                             kMediumTimeout, clock);
+  SIMULATED_WAIT(
+      IceGatheringState::kIceGatheringComplete == ep1_ch1()->gathering_state(),
+      kShortTimeout, clock);
+  EXPECT_EQ(IceGatheringState::kIceGatheringGathering,
+            ep1_ch1()->gathering_state());
+  // By now, ep2 should have completed gathering.
+  EXPECT_EQ(IceGatheringState::kIceGatheringComplete,
+            ep2_ch1()->gathering_state());
+
+  DestroyChannels();
+}
+
+// Test that a connection succeeds when the P2PTransportChannel uses a pooled
+// PortAllocatorSession that has not yet finished gathering candidates.
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       TestUsingPooledSessionBeforeDoneGathering) {
+  rtc::ScopedFakeClock clock;
+  ConfigureEndpoints(OPEN, OPEN, kDefaultPortAllocatorFlags,
+                     kDefaultPortAllocatorFlags);
+  // First create a pooled session for each endpoint.
+  auto& allocator_1 = GetEndpoint(0)->allocator_;
+  auto& allocator_2 = GetEndpoint(1)->allocator_;
+  int pool_size = 1;
+  allocator_1->SetConfiguration(allocator_1->stun_servers(),
+                                allocator_1->turn_servers(), pool_size,
+                                webrtc::NO_PRUNE);
+  allocator_2->SetConfiguration(allocator_2->stun_servers(),
+                                allocator_2->turn_servers(), pool_size,
+                                webrtc::NO_PRUNE);
+  const PortAllocatorSession* pooled_session_1 =
+      allocator_1->GetPooledSession();
+  const PortAllocatorSession* pooled_session_2 =
+      allocator_2->GetPooledSession();
+  ASSERT_NE(nullptr, pooled_session_1);
+  ASSERT_NE(nullptr, pooled_session_2);
+  // Sanity check that pooled sessions haven't gathered anything yet.
+  EXPECT_TRUE(pooled_session_1->ReadyPorts().empty());
+  EXPECT_TRUE(pooled_session_1->ReadyCandidates().empty());
+  EXPECT_TRUE(pooled_session_2->ReadyPorts().empty());
+  EXPECT_TRUE(pooled_session_2->ReadyCandidates().empty());
+  // Now let the endpoints connect and try exchanging some data.
+  CreateChannels();
+  EXPECT_TRUE_SIMULATED_WAIT(CheckConnected(ep1_ch1(), ep2_ch1()),
+                             kMediumTimeout, clock);
+  TestSendRecv(&clock);
+  // Make sure the P2PTransportChannels are actually using ports from the
+  // pooled sessions.
+  auto pooled_ports_1 = pooled_session_1->ReadyPorts();
+  auto pooled_ports_2 = pooled_session_2->ReadyPorts();
+  EXPECT_THAT(pooled_ports_1,
+              Contains(ep1_ch1()->selected_connection()->PortForTest()));
+  EXPECT_THAT(pooled_ports_2,
+              Contains(ep2_ch1()->selected_connection()->PortForTest()));
+  DestroyChannels();
+}
+
+// Test that a connection succeeds when the P2PTransportChannel uses a pooled
+// PortAllocatorSession that already finished gathering candidates.
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       TestUsingPooledSessionAfterDoneGathering) {
+  rtc::ScopedFakeClock clock;
+  ConfigureEndpoints(OPEN, OPEN, kDefaultPortAllocatorFlags,
+                     kDefaultPortAllocatorFlags);
+  // First create a pooled session for each endpoint.
+  auto& allocator_1 = GetEndpoint(0)->allocator_;
+  auto& allocator_2 = GetEndpoint(1)->allocator_;
+  int pool_size = 1;
+  allocator_1->SetConfiguration(allocator_1->stun_servers(),
+                                allocator_1->turn_servers(), pool_size,
+                                webrtc::NO_PRUNE);
+  allocator_2->SetConfiguration(allocator_2->stun_servers(),
+                                allocator_2->turn_servers(), pool_size,
+                                webrtc::NO_PRUNE);
+  const PortAllocatorSession* pooled_session_1 =
+      allocator_1->GetPooledSession();
+  const PortAllocatorSession* pooled_session_2 =
+      allocator_2->GetPooledSession();
+  ASSERT_NE(nullptr, pooled_session_1);
+  ASSERT_NE(nullptr, pooled_session_2);
+  // Wait for the pooled sessions to finish gathering before the
+  // P2PTransportChannels try to use them.
+  EXPECT_TRUE_SIMULATED_WAIT(pooled_session_1->CandidatesAllocationDone() &&
+                                 pooled_session_2->CandidatesAllocationDone(),
+                             kDefaultTimeout, clock);
+  // Now let the endpoints connect and try exchanging some data.
+  CreateChannels();
+  EXPECT_TRUE_SIMULATED_WAIT(CheckConnected(ep1_ch1(), ep2_ch1()),
+                             kMediumTimeout, clock);
+  TestSendRecv(&clock);
+  // Make sure the P2PTransportChannels are actually using ports from the
+  // pooled sessions.
+  auto pooled_ports_1 = pooled_session_1->ReadyPorts();
+  auto pooled_ports_2 = pooled_session_2->ReadyPorts();
+  EXPECT_THAT(pooled_ports_1,
+              Contains(ep1_ch1()->selected_connection()->PortForTest()));
+  EXPECT_THAT(pooled_ports_2,
+              Contains(ep2_ch1()->selected_connection()->PortForTest()));
+  DestroyChannels();
+}
+
+// Test that when the "presume_writable_when_fully_relayed" flag is set to
+// true and there's a TURN-TURN candidate pair, it's presumed to be writable
+// as soon as it's created.
+// TODO(deadbeef): Move this and other "presumed writable" tests into a test
+// class that operates on a single P2PTransportChannel, once an appropriate one
+// (which supports TURN servers and TURN candidate gathering) is available.
+TEST_P(P2PTransportChannelTestWithFieldTrials, TurnToTurnPresumedWritable) {
+  ConfigureEndpoints(OPEN, OPEN, kDefaultPortAllocatorFlags,
+                     kDefaultPortAllocatorFlags);
+  // Only configure one channel so we can control when the remote candidate
+  // is added.
+  GetEndpoint(0)->cd1_.ch_ = CreateChannel(0, ICE_CANDIDATE_COMPONENT_DEFAULT,
+                                           kIceParams[0], kIceParams[1]);
+  IceConfig config;
+  config.presume_writable_when_fully_relayed = true;
+  ep1_ch1()->SetIceConfig(config);
+  ep1_ch1()->MaybeStartGathering();
+  EXPECT_EQ_WAIT(IceGatheringState::kIceGatheringComplete,
+                 ep1_ch1()->gathering_state(), kDefaultTimeout);
+  // Add two remote candidates; a host candidate (with higher priority)
+  // and TURN candidate.
+  ep1_ch1()->AddRemoteCandidate(
+      CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 100));
+  ep1_ch1()->AddRemoteCandidate(
+      CreateUdpCandidate(RELAY_PORT_TYPE, "2.2.2.2", 2, 0));
+  // Expect that the TURN-TURN candidate pair will be prioritized since it's
+  // "probably writable".
+  EXPECT_TRUE_WAIT(ep1_ch1()->selected_connection() != nullptr, kShortTimeout);
+  EXPECT_EQ(RELAY_PORT_TYPE, LocalCandidate(ep1_ch1())->type());
+  EXPECT_EQ(RELAY_PORT_TYPE, RemoteCandidate(ep1_ch1())->type());
+  // Also expect that the channel instantly indicates that it's writable since
+  // it has a TURN-TURN pair.
+  EXPECT_TRUE(ep1_ch1()->writable());
+  EXPECT_TRUE(GetEndpoint(0)->ready_to_send_);
+  // Also make sure we can immediately send packets.
+  const char* data = "test";
+  int len = static_cast<int>(strlen(data));
+  EXPECT_EQ(len, SendData(ep1_ch1(), data, len));
+  // Prevent pending messages to access endpoints after their destruction.
+  DestroyChannels();
+}
+
+// Test that a TURN/peer reflexive candidate pair is also presumed writable.
+TEST_P(P2PTransportChannelTestWithFieldTrials, TurnToPrflxPresumedWritable) {
+  rtc::ScopedFakeClock fake_clock;
+
+  // We need to add artificial network delay to verify that the connection
+  // is presumed writable before it's actually writable. Without this delay
+  // it would become writable instantly.
+  virtual_socket_server()->set_delay_mean(50);
+  virtual_socket_server()->UpdateDelayDistribution();
+
+  ConfigureEndpoints(NAT_SYMMETRIC, NAT_SYMMETRIC, kDefaultPortAllocatorFlags,
+                     kDefaultPortAllocatorFlags);
+  // We want the remote TURN candidate to show up as prflx. To do this we need
+  // to configure the server to accept packets from an address we haven't
+  // explicitly installed permission for.
+  test_turn_server()->set_enable_permission_checks(false);
+  IceConfig config;
+  config.presume_writable_when_fully_relayed = true;
+  GetEndpoint(0)->cd1_.ch_ = CreateChannel(0, ICE_CANDIDATE_COMPONENT_DEFAULT,
+                                           kIceParams[0], kIceParams[1]);
+  GetEndpoint(1)->cd1_.ch_ = CreateChannel(1, ICE_CANDIDATE_COMPONENT_DEFAULT,
+                                           kIceParams[1], kIceParams[0]);
+  ep1_ch1()->SetIceConfig(config);
+  ep2_ch1()->SetIceConfig(config);
+  // Don't signal candidates from channel 2, so that channel 1 sees the TURN
+  // candidate as peer reflexive.
+  PauseCandidates(1);
+  ep1_ch1()->MaybeStartGathering();
+  ep2_ch1()->MaybeStartGathering();
+
+  // Wait for the TURN<->prflx connection.
+  EXPECT_TRUE_SIMULATED_WAIT(ep1_ch1()->receiving() && ep1_ch1()->writable(),
+                             kShortTimeout, fake_clock);
+  ASSERT_NE(nullptr, ep1_ch1()->selected_connection());
+  EXPECT_EQ(RELAY_PORT_TYPE, LocalCandidate(ep1_ch1())->type());
+  EXPECT_EQ(PRFLX_PORT_TYPE, RemoteCandidate(ep1_ch1())->type());
+  // Make sure that at this point the connection is only presumed writable,
+  // not fully writable.
+  EXPECT_FALSE(ep1_ch1()->selected_connection()->writable());
+
+  // Now wait for it to actually become writable.
+  EXPECT_TRUE_SIMULATED_WAIT(ep1_ch1()->selected_connection()->writable(),
+                             kShortTimeout, fake_clock);
+
+  // Explitly destroy channels, before fake clock is destroyed.
+  DestroyChannels();
+}
+
+// Test that a presumed-writable TURN<->TURN connection is preferred above an
+// unreliable connection (one that has failed to be pinged for some time).
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       PresumedWritablePreferredOverUnreliable) {
+  rtc::ScopedFakeClock fake_clock;
+
+  ConfigureEndpoints(NAT_SYMMETRIC, NAT_SYMMETRIC, kDefaultPortAllocatorFlags,
+                     kDefaultPortAllocatorFlags);
+  IceConfig config;
+  config.presume_writable_when_fully_relayed = true;
+  GetEndpoint(0)->cd1_.ch_ = CreateChannel(0, ICE_CANDIDATE_COMPONENT_DEFAULT,
+                                           kIceParams[0], kIceParams[1]);
+  GetEndpoint(1)->cd1_.ch_ = CreateChannel(1, ICE_CANDIDATE_COMPONENT_DEFAULT,
+                                           kIceParams[1], kIceParams[0]);
+  ep1_ch1()->SetIceConfig(config);
+  ep2_ch1()->SetIceConfig(config);
+  ep1_ch1()->MaybeStartGathering();
+  ep2_ch1()->MaybeStartGathering();
+  // Wait for initial connection as usual.
+  EXPECT_TRUE_SIMULATED_WAIT(CheckConnected(ep1_ch1(), ep2_ch1()),
+                             kShortTimeout, fake_clock);
+  const Connection* old_selected_connection = ep1_ch1()->selected_connection();
+  // Destroy the second channel and wait for the current connection on the
+  // first channel to become "unreliable", making it no longer writable.
+  GetEndpoint(1)->cd1_.ch_.reset();
+  EXPECT_TRUE_SIMULATED_WAIT(!ep1_ch1()->writable(), kDefaultTimeout,
+                             fake_clock);
+  EXPECT_NE(nullptr, ep1_ch1()->selected_connection());
+  // Add a remote TURN candidate. The first channel should still have a TURN
+  // port available to make a TURN<->TURN pair that's presumed writable.
+  ep1_ch1()->AddRemoteCandidate(
+      CreateUdpCandidate(RELAY_PORT_TYPE, "2.2.2.2", 2, 0));
+  EXPECT_EQ(RELAY_PORT_TYPE, LocalCandidate(ep1_ch1())->type());
+  EXPECT_EQ(RELAY_PORT_TYPE, RemoteCandidate(ep1_ch1())->type());
+  EXPECT_TRUE(ep1_ch1()->writable());
+  EXPECT_TRUE(GetEndpoint(0)->ready_to_send_);
+  EXPECT_NE(old_selected_connection, ep1_ch1()->selected_connection());
+  // Explitly destroy channels, before fake clock is destroyed.
+  DestroyChannels();
+}
+
+// Ensure that "SignalReadyToSend" is fired as expected with a "presumed
+// writable" connection. Previously this did not work.
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       SignalReadyToSendWithPresumedWritable) {
+  ConfigureEndpoints(OPEN, OPEN, kDefaultPortAllocatorFlags,
+                     kDefaultPortAllocatorFlags);
+  // Only test one endpoint, so we can ensure the connection doesn't receive a
+  // binding response and advance beyond being "presumed" writable.
+  GetEndpoint(0)->cd1_.ch_ = CreateChannel(0, ICE_CANDIDATE_COMPONENT_DEFAULT,
+                                           kIceParams[0], kIceParams[1]);
+  IceConfig config;
+  config.presume_writable_when_fully_relayed = true;
+  ep1_ch1()->SetIceConfig(config);
+  ep1_ch1()->MaybeStartGathering();
+  EXPECT_EQ_WAIT(IceGatheringState::kIceGatheringComplete,
+                 ep1_ch1()->gathering_state(), kDefaultTimeout);
+  ep1_ch1()->AddRemoteCandidate(
+      CreateUdpCandidate(RELAY_PORT_TYPE, "1.1.1.1", 1, 0));
+  // Sanity checking the type of the connection.
+  EXPECT_TRUE_WAIT(ep1_ch1()->selected_connection() != nullptr, kShortTimeout);
+  EXPECT_EQ(RELAY_PORT_TYPE, LocalCandidate(ep1_ch1())->type());
+  EXPECT_EQ(RELAY_PORT_TYPE, RemoteCandidate(ep1_ch1())->type());
+
+  // Tell the socket server to block packets (returning EWOULDBLOCK).
+  virtual_socket_server()->SetSendingBlocked(true);
+  const char* data = "test";
+  int len = static_cast<int>(strlen(data));
+  EXPECT_EQ(-1, SendData(ep1_ch1(), data, len));
+
+  // Reset `ready_to_send_` flag, which is set to true if the event fires as it
+  // should.
+  GetEndpoint(0)->ready_to_send_ = false;
+  virtual_socket_server()->SetSendingBlocked(false);
+  EXPECT_TRUE(GetEndpoint(0)->ready_to_send_);
+  EXPECT_EQ(len, SendData(ep1_ch1(), data, len));
+  DestroyChannels();
+}
+
+// Test that role conflict error responses are sent as expected when receiving a
+// ping from an unknown address over a TURN connection. Regression test for
+// crbug.com/webrtc/9034.
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       TurnToPrflxSelectedAfterResolvingIceControllingRoleConflict) {
+  rtc::ScopedFakeClock clock;
+  // Gather only relay candidates.
+  ConfigureEndpoints(NAT_SYMMETRIC, NAT_SYMMETRIC,
+                     kDefaultPortAllocatorFlags | PORTALLOCATOR_DISABLE_UDP |
+                         PORTALLOCATOR_DISABLE_STUN | PORTALLOCATOR_DISABLE_TCP,
+                     kDefaultPortAllocatorFlags | PORTALLOCATOR_DISABLE_UDP |
+                         PORTALLOCATOR_DISABLE_STUN |
+                         PORTALLOCATOR_DISABLE_TCP);
+  // With conflicting ICE roles, endpoint 1 has the higher tie breaker and will
+  // send a binding error response.
+  SetIceRole(0, ICEROLE_CONTROLLING);
+  SetIceTiebreaker(0, kHighTiebreaker);
+  SetIceRole(1, ICEROLE_CONTROLLING);
+  SetIceTiebreaker(1, kLowTiebreaker);
+  // We want the remote TURN candidate to show up as prflx. To do this we need
+  // to configure the server to accept packets from an address we haven't
+  // explicitly installed permission for.
+  test_turn_server()->set_enable_permission_checks(false);
+  GetEndpoint(0)->cd1_.ch_ = CreateChannel(0, ICE_CANDIDATE_COMPONENT_DEFAULT,
+                                           kIceParams[0], kIceParams[1]);
+  GetEndpoint(1)->cd1_.ch_ = CreateChannel(1, ICE_CANDIDATE_COMPONENT_DEFAULT,
+                                           kIceParams[1], kIceParams[0]);
+  // Don't signal candidates from channel 2, so that channel 1 sees the TURN
+  // candidate as peer reflexive.
+  PauseCandidates(1);
+  ep1_ch1()->MaybeStartGathering();
+  ep2_ch1()->MaybeStartGathering();
+
+  EXPECT_TRUE_SIMULATED_WAIT(ep1_ch1()->receiving() && ep1_ch1()->writable(),
+                             kMediumTimeout, clock);
+
+  ASSERT_NE(nullptr, ep1_ch1()->selected_connection());
+
+  EXPECT_EQ(RELAY_PORT_TYPE, LocalCandidate(ep1_ch1())->type());
+  EXPECT_EQ(PRFLX_PORT_TYPE, RemoteCandidate(ep1_ch1())->type());
+
+  DestroyChannels();
+}
+
+// Test that the writability can be established with the piggyback
+// acknowledgement in the connectivity check from the remote peer.
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       CanConnectWithPiggybackCheckAcknowledgementWhenCheckResponseBlocked) {
+  webrtc::test::ScopedKeyValueConfig field_trials(
+      field_trials_, "WebRTC-PiggybackIceCheckAcknowledgement/Enabled/");
+  rtc::ScopedFakeClock clock;
+  ConfigureEndpoints(OPEN, OPEN, kOnlyLocalPorts, kOnlyLocalPorts);
+  IceConfig ep1_config;
+  IceConfig ep2_config = CreateIceConfig(1000, GATHER_CONTINUALLY);
+  // Let ep2 be tolerable of the loss of connectivity checks, so that it keeps
+  // sending pings even after ep1 becomes unwritable as we configure the
+  // firewall below.
+  ep2_config.receiving_timeout = 30 * 1000;
+  ep2_config.ice_unwritable_timeout = 30 * 1000;
+  ep2_config.ice_unwritable_min_checks = 30;
+  ep2_config.ice_inactive_timeout = 60 * 1000;
+
+  CreateChannels(ep1_config, ep2_config);
+
+  // Wait until both sides become writable for the first time.
+  EXPECT_TRUE_SIMULATED_WAIT(CheckConnected(ep1_ch1(), ep2_ch1()),
+                             kDefaultTimeout, clock);
+  // Block the ingress traffic to ep1 so that there is no check response from
+  // ep2.
+  ASSERT_NE(nullptr, LocalCandidate(ep1_ch1()));
+  fw()->AddRule(false, rtc::FP_ANY, rtc::FD_IN,
+                LocalCandidate(ep1_ch1())->address());
+  // Wait until ep1 becomes unwritable. At the same time ep2 should be still
+  // fine so that it will keep sending pings.
+  EXPECT_TRUE_SIMULATED_WAIT(ep1_ch1() != nullptr && !ep1_ch1()->writable(),
+                             kDefaultTimeout, clock);
+  EXPECT_TRUE(ep2_ch1() != nullptr && ep2_ch1()->writable());
+  // Now let the pings from ep2 to flow but block any pings from ep1, so that
+  // ep1 can only become writable again after receiving an incoming ping from
+  // ep2 with piggyback acknowledgement of its previously sent pings. Note
+  // though that ep1 should have stopped sending pings after becoming unwritable
+  // in the current design.
+  fw()->ClearRules();
+  fw()->AddRule(false, rtc::FP_ANY, rtc::FD_OUT,
+                LocalCandidate(ep1_ch1())->address());
+  EXPECT_TRUE_SIMULATED_WAIT(ep1_ch1() != nullptr && ep1_ch1()->writable(),
+                             kDefaultTimeout, clock);
+  DestroyChannels();
+}
+
+// Test what happens when we have 2 users behind the same NAT. This can lead
+// to interesting behavior because the STUN server will only give out the
+// address of the outermost NAT.
+class P2PTransportChannelSameNatTest : public P2PTransportChannelTestBase,
+                                       public WithParamInterface<std::string> {
+ public:
+  P2PTransportChannelSameNatTest() : P2PTransportChannelTestBase(GetParam()) {}
+
+ protected:
+  void ConfigureEndpoints(Config nat_type, Config config1, Config config2) {
+    RTC_CHECK_GE(nat_type, NAT_FULL_CONE);
+    RTC_CHECK_LE(nat_type, NAT_SYMMETRIC);
+    rtc::NATSocketServer::Translator* outer_nat = nat()->AddTranslator(
+        kPublicAddrs[0], kNatAddrs[0],
+        static_cast<rtc::NATType>(nat_type - NAT_FULL_CONE));
+    ConfigureEndpoint(outer_nat, 0, config1);
+    ConfigureEndpoint(outer_nat, 1, config2);
+    set_remote_ice_parameter_source(FROM_SETICEPARAMETERS);
+  }
+  void ConfigureEndpoint(rtc::NATSocketServer::Translator* nat,
+                         int endpoint,
+                         Config config) {
+    RTC_CHECK(config <= NAT_SYMMETRIC);
+    if (config == OPEN) {
+      AddAddress(endpoint, kPrivateAddrs[endpoint]);
+      nat->AddClient(kPrivateAddrs[endpoint]);
+    } else {
+      AddAddress(endpoint, kCascadedPrivateAddrs[endpoint]);
+      nat->AddTranslator(kPrivateAddrs[endpoint], kCascadedNatAddrs[endpoint],
+                         static_cast<rtc::NATType>(config - NAT_FULL_CONE))
+          ->AddClient(kCascadedPrivateAddrs[endpoint]);
+    }
+  }
+};
+
+INSTANTIATE_TEST_SUITE_P(Legacy, P2PTransportChannelSameNatTest, Values(""));
+INSTANTIATE_TEST_SUITE_P(Active,
+                         P2PTransportChannelSameNatTest,
+                         Values("WebRTC-UseActiveIceController/Enabled/"));
+
+TEST_P(P2PTransportChannelSameNatTest, TestConesBehindSameCone) {
+  ConfigureEndpoints(NAT_FULL_CONE, NAT_FULL_CONE, NAT_FULL_CONE);
+  Test(
+      P2PTransportChannelTestBase::Result("prflx", "udp", "stun", "udp", 1000));
+}
+
+// Test what happens when we have multiple available pathways.
+// In the future we will try different RTTs and configs for the different
+// interfaces, so that we can simulate a user with Ethernet and VPN networks.
+class P2PTransportChannelMultihomedTest
+    : public P2PTransportChannelTestWithFieldTrials {
+ public:
+  const Connection* GetConnectionWithRemoteAddress(
+      P2PTransportChannel* channel,
+      const SocketAddress& address) {
+    for (Connection* conn : channel->connections()) {
+      if (HasRemoteAddress(conn, address)) {
+        return conn;
+      }
+    }
+    return nullptr;
+  }
+
+  Connection* GetConnectionWithLocalAddress(P2PTransportChannel* channel,
+                                            const SocketAddress& address) {
+    for (Connection* conn : channel->connections()) {
+      if (HasLocalAddress(conn, address)) {
+        return conn;
+      }
+    }
+    return nullptr;
+  }
+
+  Connection* GetConnection(P2PTransportChannel* channel,
+                            const SocketAddress& local,
+                            const SocketAddress& remote) {
+    for (Connection* conn : channel->connections()) {
+      if (HasLocalAddress(conn, local) && HasRemoteAddress(conn, remote)) {
+        return conn;
+      }
+    }
+    return nullptr;
+  }
+
+  Connection* GetBestConnection(P2PTransportChannel* channel) {
+    rtc::ArrayView<Connection*> connections = channel->connections();
+    auto it = absl::c_find(connections, channel->selected_connection());
+    if (it == connections.end()) {
+      return nullptr;
+    }
+    return *it;
+  }
+
+  Connection* GetBackupConnection(P2PTransportChannel* channel) {
+    rtc::ArrayView<Connection*> connections = channel->connections();
+    auto it = absl::c_find_if_not(connections, [channel](Connection* conn) {
+      return conn == channel->selected_connection();
+    });
+    if (it == connections.end()) {
+      return nullptr;
+    }
+    return *it;
+  }
+
+  void DestroyAllButBestConnection(P2PTransportChannel* channel) {
+    const Connection* selected_connection = channel->selected_connection();
+    // Copy the list of connections since the original will be modified.
+    rtc::ArrayView<Connection*> view = channel->connections();
+    std::vector<Connection*> connections(view.begin(), view.end());
+    for (Connection* conn : connections) {
+      if (conn != selected_connection)
+        channel->RemoveConnectionForTest(conn);
+    }
+  }
+};
+
+INSTANTIATE_TEST_SUITE_P(Legacy, P2PTransportChannelMultihomedTest, Values(""));
+INSTANTIATE_TEST_SUITE_P(Active,
+                         P2PTransportChannelMultihomedTest,
+                         Values("WebRTC-UseActiveIceController/Enabled/"));
+
+// Test that we can establish connectivity when both peers are multihomed.
+TEST_P(P2PTransportChannelMultihomedTest, TestBasic) {
+  AddAddress(0, kPublicAddrs[0]);
+  AddAddress(0, kAlternateAddrs[0]);
+  AddAddress(1, kPublicAddrs[1]);
+  AddAddress(1, kAlternateAddrs[1]);
+  Test(kLocalUdpToLocalUdp);
+}
+
+// Test that we can quickly switch links if an interface goes down.
+// The controlled side has two interfaces and one will die.
+TEST_P(P2PTransportChannelMultihomedTest, TestFailoverControlledSide) {
+  rtc::ScopedFakeClock clock;
+  AddAddress(0, kPublicAddrs[0]);
+  // Simulate failing over from Wi-Fi to cell interface.
+  AddAddress(1, kPublicAddrs[1], "eth0", rtc::ADAPTER_TYPE_WIFI);
+  AddAddress(1, kAlternateAddrs[1], "wlan0", rtc::ADAPTER_TYPE_CELLULAR);
+
+  // Use only local ports for simplicity.
+  SetAllocatorFlags(0, kOnlyLocalPorts);
+  SetAllocatorFlags(1, kOnlyLocalPorts);
+
+  // Make the receiving timeout shorter for testing.
+  IceConfig config = CreateIceConfig(1000, GATHER_ONCE);
+  // Create channels and let them go writable, as usual.
+  CreateChannels(config, config);
+
+  EXPECT_TRUE_SIMULATED_WAIT(
+      CheckCandidatePairAndConnected(ep1_ch1(), ep2_ch1(), kPublicAddrs[0],
+                                     kPublicAddrs[1]),
+      kMediumTimeout, clock);
+
+  // Blackhole any traffic to or from the public addrs.
+  RTC_LOG(LS_INFO) << "Failing over...";
+  fw()->AddRule(false, rtc::FP_ANY, rtc::FD_ANY, kPublicAddrs[1]);
+  // The selected connections may switch, so keep references to them.
+  const Connection* selected_connection1 = ep1_ch1()->selected_connection();
+  // We should detect loss of receiving within 1 second or so.
+  EXPECT_TRUE_SIMULATED_WAIT(!selected_connection1->receiving(), kMediumTimeout,
+                             clock);
+
+  // We should switch over to use the alternate addr on both sides
+  // when we are not receiving.
+  EXPECT_TRUE_SIMULATED_WAIT(ep1_ch1()->selected_connection()->receiving() &&
+                                 ep2_ch1()->selected_connection()->receiving(),
+                             kMediumTimeout, clock);
+  EXPECT_TRUE(LocalCandidate(ep1_ch1())->address().EqualIPs(kPublicAddrs[0]));
+  EXPECT_TRUE(
+      RemoteCandidate(ep1_ch1())->address().EqualIPs(kAlternateAddrs[1]));
+  EXPECT_TRUE(
+      LocalCandidate(ep2_ch1())->address().EqualIPs(kAlternateAddrs[1]));
+
+  DestroyChannels();
+}
+
+// Test that we can quickly switch links if an interface goes down.
+// The controlling side has two interfaces and one will die.
+TEST_P(P2PTransportChannelMultihomedTest, TestFailoverControllingSide) {
+  rtc::ScopedFakeClock clock;
+  // Simulate failing over from Wi-Fi to cell interface.
+  AddAddress(0, kPublicAddrs[0], "eth0", rtc::ADAPTER_TYPE_WIFI);
+  AddAddress(0, kAlternateAddrs[0], "wlan0", rtc::ADAPTER_TYPE_CELLULAR);
+  AddAddress(1, kPublicAddrs[1]);
+
+  // Use only local ports for simplicity.
+  SetAllocatorFlags(0, kOnlyLocalPorts);
+  SetAllocatorFlags(1, kOnlyLocalPorts);
+
+  // Make the receiving timeout shorter for testing.
+  IceConfig config = CreateIceConfig(1000, GATHER_ONCE);
+  // Create channels and let them go writable, as usual.
+  CreateChannels(config, config);
+  EXPECT_TRUE_SIMULATED_WAIT(
+      CheckCandidatePairAndConnected(ep1_ch1(), ep2_ch1(), kPublicAddrs[0],
+                                     kPublicAddrs[1]),
+      kMediumTimeout, clock);
+
+  // Blackhole any traffic to or from the public addrs.
+  RTC_LOG(LS_INFO) << "Failing over...";
+  fw()->AddRule(false, rtc::FP_ANY, rtc::FD_ANY, kPublicAddrs[0]);
+
+  // We should detect loss of receiving within 1 second or so.
+  // We should switch over to use the alternate addr on both sides
+  // when we are not receiving.
+  EXPECT_TRUE_SIMULATED_WAIT(
+      CheckCandidatePairAndConnected(ep1_ch1(), ep2_ch1(), kAlternateAddrs[0],
+                                     kPublicAddrs[1]),
+      kMediumTimeout, clock);
+
+  DestroyChannels();
+}
+
+// Tests that we can quickly switch links if an interface goes down when
+// there are many connections.
+TEST_P(P2PTransportChannelMultihomedTest, TestFailoverWithManyConnections) {
+  rtc::ScopedFakeClock clock;
+  test_turn_server()->AddInternalSocket(kTurnTcpIntAddr, PROTO_TCP);
+  RelayServerConfig turn_server;
+  turn_server.credentials = kRelayCredentials;
+  turn_server.ports.push_back(ProtocolAddress(kTurnTcpIntAddr, PROTO_TCP));
+  GetAllocator(0)->AddTurnServerForTesting(turn_server);
+  GetAllocator(1)->AddTurnServerForTesting(turn_server);
+  // Enable IPv6
+  SetAllocatorFlags(
+      0, PORTALLOCATOR_ENABLE_IPV6 | PORTALLOCATOR_ENABLE_IPV6_ON_WIFI);
+  SetAllocatorFlags(
+      1, PORTALLOCATOR_ENABLE_IPV6 | PORTALLOCATOR_ENABLE_IPV6_ON_WIFI);
+  SetAllocationStepDelay(0, kMinimumStepDelay);
+  SetAllocationStepDelay(1, kMinimumStepDelay);
+
+  auto& wifi = kPublicAddrs;
+  auto& cellular = kAlternateAddrs;
+  auto& wifiIpv6 = kIPv6PublicAddrs;
+  auto& cellularIpv6 = kIPv6AlternateAddrs;
+  AddAddress(0, wifi[0], "wifi0", rtc::ADAPTER_TYPE_WIFI);
+  AddAddress(0, wifiIpv6[0], "wifi0", rtc::ADAPTER_TYPE_WIFI);
+  AddAddress(0, cellular[0], "cellular0", rtc::ADAPTER_TYPE_CELLULAR);
+  AddAddress(0, cellularIpv6[0], "cellular0", rtc::ADAPTER_TYPE_CELLULAR);
+  AddAddress(1, wifi[1], "wifi1", rtc::ADAPTER_TYPE_WIFI);
+  AddAddress(1, wifiIpv6[1], "wifi1", rtc::ADAPTER_TYPE_WIFI);
+  AddAddress(1, cellular[1], "cellular1", rtc::ADAPTER_TYPE_CELLULAR);
+  AddAddress(1, cellularIpv6[1], "cellular1", rtc::ADAPTER_TYPE_CELLULAR);
+
+  // Set smaller delay on the TCP TURN server so that TCP TURN candidates
+  // will be created in time.
+  virtual_socket_server()->SetDelayOnAddress(kTurnTcpIntAddr, 1);
+  virtual_socket_server()->SetDelayOnAddress(kTurnUdpExtAddr, 1);
+  virtual_socket_server()->set_delay_mean(500);
+  virtual_socket_server()->UpdateDelayDistribution();
+
+  // Make the receiving timeout shorter for testing.
+  IceConfig config = CreateIceConfig(1000, GATHER_CONTINUALLY);
+  // Create channels and let them go writable, as usual.
+  CreateChannels(config, config, true /* ice_renomination */);
+  EXPECT_TRUE_SIMULATED_WAIT(
+      CheckCandidatePairAndConnected(ep1_ch1(), ep2_ch1(), wifiIpv6[0],
+                                     wifiIpv6[1]),
+      kMediumTimeout, clock);
+
+  // Blackhole any traffic to or from the wifi on endpoint 1.
+  RTC_LOG(LS_INFO) << "Failing over...";
+  fw()->AddRule(false, rtc::FP_ANY, rtc::FD_ANY, wifi[0]);
+  fw()->AddRule(false, rtc::FP_ANY, rtc::FD_ANY, wifiIpv6[0]);
+
+  // The selected connections may switch, so keep references to them.
+  const Connection* selected_connection1 = ep1_ch1()->selected_connection();
+  const Connection* selected_connection2 = ep2_ch1()->selected_connection();
+  EXPECT_TRUE_SIMULATED_WAIT(
+      !selected_connection1->receiving() && !selected_connection2->receiving(),
+      kMediumTimeout, clock);
+
+  // Per-network best connections will be pinged at relatively higher rate when
+  // the selected connection becomes not receiving.
+  Connection* per_network_best_connection1 =
+      GetConnection(ep1_ch1(), cellularIpv6[0], wifiIpv6[1]);
+  ASSERT_NE(nullptr, per_network_best_connection1);
+  int64_t last_ping_sent1 = per_network_best_connection1->last_ping_sent();
+  int num_pings_sent1 = per_network_best_connection1->num_pings_sent();
+  EXPECT_TRUE_SIMULATED_WAIT(
+      num_pings_sent1 < per_network_best_connection1->num_pings_sent(),
+      kMediumTimeout, clock);
+  ASSERT_GT(per_network_best_connection1->num_pings_sent() - num_pings_sent1,
+            0);
+  int64_t ping_interval1 =
+      (per_network_best_connection1->last_ping_sent() - last_ping_sent1) /
+      (per_network_best_connection1->num_pings_sent() - num_pings_sent1);
+  constexpr int SCHEDULING_DELAY = 200;
+  EXPECT_LT(
+      ping_interval1,
+      WEAK_OR_STABILIZING_WRITABLE_CONNECTION_PING_INTERVAL + SCHEDULING_DELAY);
+
+  // It should switch over to use the cellular IPv6 addr on endpoint 1 before
+  // it timed out on writing.
+  EXPECT_TRUE_SIMULATED_WAIT(
+      CheckCandidatePairAndConnected(ep1_ch1(), ep2_ch1(), cellularIpv6[0],
+                                     wifiIpv6[1]),
+      kMediumTimeout, clock);
+
+  DestroyChannels();
+}
+
+// Test that when the controlling side switches the selected connection,
+// the nomination of the selected connection on the controlled side will
+// increase.
+TEST_P(P2PTransportChannelMultihomedTest, TestIceRenomination) {
+  rtc::ScopedFakeClock clock;
+  // Simulate failing over from Wi-Fi to cell interface.
+  AddAddress(0, kPublicAddrs[0], "eth0", rtc::ADAPTER_TYPE_WIFI);
+  AddAddress(0, kAlternateAddrs[0], "wlan0", rtc::ADAPTER_TYPE_CELLULAR);
+  AddAddress(1, kPublicAddrs[1]);
+
+  // Use only local ports for simplicity.
+  SetAllocatorFlags(0, kOnlyLocalPorts);
+  SetAllocatorFlags(1, kOnlyLocalPorts);
+
+  // We want it to set the remote ICE parameters when creating channels.
+  set_remote_ice_parameter_source(FROM_SETICEPARAMETERS);
+  // Make the receiving timeout shorter for testing.
+  IceConfig config = CreateIceConfig(1000, GATHER_ONCE);
+  // Create channels with ICE renomination and let them go writable as usual.
+  CreateChannels(config, config, true);
+  ASSERT_TRUE_SIMULATED_WAIT(CheckConnected(ep1_ch1(), ep2_ch1()),
+                             kMediumTimeout, clock);
+  EXPECT_TRUE_SIMULATED_WAIT(
+      ep2_ch1()->selected_connection()->remote_nomination() > 0 &&
+          ep1_ch1()->selected_connection()->acked_nomination() > 0,
+      kDefaultTimeout, clock);
+  const Connection* selected_connection1 = ep1_ch1()->selected_connection();
+  Connection* selected_connection2 =
+      const_cast<Connection*>(ep2_ch1()->selected_connection());
+  uint32_t remote_nomination2 = selected_connection2->remote_nomination();
+  // `selected_connection2` should not be nominated any more since the previous
+  // nomination has been acknowledged.
+  ConnectSignalNominated(selected_connection2);
+  SIMULATED_WAIT(nominated(), kMediumTimeout, clock);
+  EXPECT_FALSE(nominated());
+
+  // Blackhole any traffic to or from the public addrs.
+  RTC_LOG(LS_INFO) << "Failing over...";
+  fw()->AddRule(false, rtc::FP_ANY, rtc::FD_ANY, kPublicAddrs[0]);
+
+  // The selected connection on the controlling side should switch.
+  EXPECT_TRUE_SIMULATED_WAIT(
+      ep1_ch1()->selected_connection() != selected_connection1, kMediumTimeout,
+      clock);
+  // The connection on the controlled side should be nominated again
+  // and have an increased nomination.
+  EXPECT_TRUE_SIMULATED_WAIT(
+      ep2_ch1()->selected_connection()->remote_nomination() >
+          remote_nomination2,
+      kDefaultTimeout, clock);
+
+  DestroyChannels();
+}
+
+// Test that if an interface fails temporarily and then recovers quickly,
+// the selected connection will not switch.
+// The case that it will switch over to the backup connection if the selected
+// connection does not recover after enough time is covered in
+// TestFailoverControlledSide and TestFailoverControllingSide.
+TEST_P(P2PTransportChannelMultihomedTest,
+       TestConnectionSwitchDampeningControlledSide) {
+  rtc::ScopedFakeClock clock;
+  AddAddress(0, kPublicAddrs[0]);
+  // Simulate failing over from Wi-Fi to cell interface.
+  AddAddress(1, kPublicAddrs[1], "eth0", rtc::ADAPTER_TYPE_WIFI);
+  AddAddress(1, kAlternateAddrs[1], "wlan0", rtc::ADAPTER_TYPE_CELLULAR);
+
+  // Use only local ports for simplicity.
+  SetAllocatorFlags(0, kOnlyLocalPorts);
+  SetAllocatorFlags(1, kOnlyLocalPorts);
+
+  // Create channels and let them go writable, as usual.
+  CreateChannels();
+
+  EXPECT_TRUE_SIMULATED_WAIT(
+      CheckCandidatePairAndConnected(ep1_ch1(), ep2_ch1(), kPublicAddrs[0],
+                                     kPublicAddrs[1]),
+      kMediumTimeout, clock);
+
+  // Make the receiving timeout shorter for testing.
+  IceConfig config = CreateIceConfig(1000, GATHER_ONCE);
+  ep1_ch1()->SetIceConfig(config);
+  ep2_ch1()->SetIceConfig(config);
+  reset_selected_candidate_pair_switches();
+
+  // Blackhole any traffic to or from the public addrs.
+  RTC_LOG(LS_INFO) << "Failing over...";
+  fw()->AddRule(false, rtc::FP_ANY, rtc::FD_ANY, kPublicAddrs[1]);
+
+  // The selected connections may switch, so keep references to them.
+  const Connection* selected_connection1 = ep1_ch1()->selected_connection();
+  // We should detect loss of receiving within 1 second or so.
+  EXPECT_TRUE_SIMULATED_WAIT(!selected_connection1->receiving(), kMediumTimeout,
+                             clock);
+  // After a short while, the link recovers itself.
+  SIMULATED_WAIT(false, 10, clock);
+  fw()->ClearRules();
+
+  // We should remain on the public address on both sides and no connection
+  // switches should have happened.
+  EXPECT_TRUE_SIMULATED_WAIT(ep1_ch1()->selected_connection()->receiving() &&
+                                 ep2_ch1()->selected_connection()->receiving(),
+                             kMediumTimeout, clock);
+  EXPECT_TRUE(RemoteCandidate(ep1_ch1())->address().EqualIPs(kPublicAddrs[1]));
+  EXPECT_TRUE(LocalCandidate(ep2_ch1())->address().EqualIPs(kPublicAddrs[1]));
+  EXPECT_EQ(0, reset_selected_candidate_pair_switches());
+
+  DestroyChannels();
+}
+
+// Test that if an interface fails temporarily and then recovers quickly,
+// the selected connection will not switch.
+TEST_P(P2PTransportChannelMultihomedTest,
+       TestConnectionSwitchDampeningControllingSide) {
+  rtc::ScopedFakeClock clock;
+  // Simulate failing over from Wi-Fi to cell interface.
+  AddAddress(0, kPublicAddrs[0], "eth0", rtc::ADAPTER_TYPE_WIFI);
+  AddAddress(0, kAlternateAddrs[0], "wlan0", rtc::ADAPTER_TYPE_CELLULAR);
+  AddAddress(1, kPublicAddrs[1]);
+
+  // Use only local ports for simplicity.
+  SetAllocatorFlags(0, kOnlyLocalPorts);
+  SetAllocatorFlags(1, kOnlyLocalPorts);
+
+  // Create channels and let them go writable, as usual.
+  CreateChannels();
+  EXPECT_TRUE_SIMULATED_WAIT(
+      CheckCandidatePairAndConnected(ep1_ch1(), ep2_ch1(), kPublicAddrs[0],
+                                     kPublicAddrs[1]),
+      kMediumTimeout, clock);
+
+  // Make the receiving timeout shorter for testing.
+  IceConfig config = CreateIceConfig(1000, GATHER_ONCE);
+  ep1_ch1()->SetIceConfig(config);
+  ep2_ch1()->SetIceConfig(config);
+  reset_selected_candidate_pair_switches();
+
+  // Blackhole any traffic to or from the public addrs.
+  RTC_LOG(LS_INFO) << "Failing over...";
+  fw()->AddRule(false, rtc::FP_ANY, rtc::FD_ANY, kPublicAddrs[0]);
+  // The selected connections may switch, so keep references to them.
+  const Connection* selected_connection1 = ep1_ch1()->selected_connection();
+  // We should detect loss of receiving within 1 second or so.
+  EXPECT_TRUE_SIMULATED_WAIT(!selected_connection1->receiving(), kMediumTimeout,
+                             clock);
+  // The link recovers after a short while.
+  SIMULATED_WAIT(false, 10, clock);
+  fw()->ClearRules();
+
+  // We should not switch to the alternate addr on both sides because of the
+  // dampening.
+  EXPECT_TRUE_SIMULATED_WAIT(
+      CheckCandidatePairAndConnected(ep1_ch1(), ep2_ch1(), kPublicAddrs[0],
+                                     kPublicAddrs[1]),
+      kMediumTimeout, clock);
+  EXPECT_EQ(0, reset_selected_candidate_pair_switches());
+  DestroyChannels();
+}
+
+// Tests that if the remote side's network failed, it won't cause the local
+// side to switch connections and networks.
+TEST_P(P2PTransportChannelMultihomedTest, TestRemoteFailover) {
+  rtc::ScopedFakeClock clock;
+  // The interface names are chosen so that `cellular` would have higher
+  // candidate priority and higher cost.
+  auto& wifi = kPublicAddrs;
+  auto& cellular = kAlternateAddrs;
+  AddAddress(0, wifi[0], "wifi0", rtc::ADAPTER_TYPE_WIFI);
+  AddAddress(0, cellular[0], "cellular0", rtc::ADAPTER_TYPE_CELLULAR);
+  AddAddress(1, wifi[1], "wifi0", rtc::ADAPTER_TYPE_WIFI);
+
+  // Use only local ports for simplicity.
+  SetAllocatorFlags(0, kOnlyLocalPorts);
+  SetAllocatorFlags(1, kOnlyLocalPorts);
+  // Create channels and let them go writable, as usual.
+  CreateChannels();
+  // Make the receiving timeout shorter for testing.
+  // Set the backup connection ping interval to 25s.
+  IceConfig config = CreateIceConfig(1000, GATHER_ONCE, 25000);
+  // Ping the best connection more frequently since we don't have traffic.
+  config.stable_writable_connection_ping_interval = 900;
+  ep1_ch1()->SetIceConfig(config);
+  ep2_ch1()->SetIceConfig(config);
+  // Need to wait to make sure the connections on both networks are writable.
+  EXPECT_TRUE_SIMULATED_WAIT(
+      CheckCandidatePairAndConnected(ep1_ch1(), ep2_ch1(), wifi[0], wifi[1]),
+      kDefaultTimeout, clock);
+  Connection* backup_conn =
+      GetConnectionWithLocalAddress(ep1_ch1(), cellular[0]);
+  ASSERT_NE(nullptr, backup_conn);
+  // After a short while, the backup connection will be writable but not
+  // receiving because backup connection is pinged at a slower rate.
+  EXPECT_TRUE_SIMULATED_WAIT(
+      backup_conn->writable() && !backup_conn->receiving(), kDefaultTimeout,
+      clock);
+  reset_selected_candidate_pair_switches();
+  // Blackhole any traffic to or from the remote WiFi networks.
+  RTC_LOG(LS_INFO) << "Failing over...";
+  fw()->AddRule(false, rtc::FP_ANY, rtc::FD_ANY, wifi[1]);
+
+  int num_switches = 0;
+  SIMULATED_WAIT((num_switches = reset_selected_candidate_pair_switches()) > 0,
+                 20000, clock);
+  EXPECT_EQ(0, num_switches);
+  DestroyChannels();
+}
+
+// Tests that a Wifi-Wifi connection has the highest precedence.
+TEST_P(P2PTransportChannelMultihomedTest, TestPreferWifiToWifiConnection) {
+  // The interface names are chosen so that `cellular` would have higher
+  // candidate priority if it is not for the network type.
+  auto& wifi = kAlternateAddrs;
+  auto& cellular = kPublicAddrs;
+  AddAddress(0, wifi[0], "test0", rtc::ADAPTER_TYPE_WIFI);
+  AddAddress(0, cellular[0], "test1", rtc::ADAPTER_TYPE_CELLULAR);
+  AddAddress(1, wifi[1], "test0", rtc::ADAPTER_TYPE_WIFI);
+  AddAddress(1, cellular[1], "test1", rtc::ADAPTER_TYPE_CELLULAR);
+
+  // Use only local ports for simplicity.
+  SetAllocatorFlags(0, kOnlyLocalPorts);
+  SetAllocatorFlags(1, kOnlyLocalPorts);
+
+  // Create channels and let them go writable, as usual.
+  CreateChannels();
+
+  EXPECT_TRUE_WAIT_MARGIN(CheckConnected(ep1_ch1(), ep2_ch1()), 1000, 1000);
+  // Need to wait to make sure the connections on both networks are writable.
+  EXPECT_TRUE_WAIT(
+      CheckCandidatePairAndConnected(ep1_ch1(), ep2_ch1(), wifi[0], wifi[1]),
+      1000);
+  DestroyChannels();
+}
+
+// Tests that a Wifi-Cellular connection has higher precedence than
+// a Cellular-Cellular connection.
+TEST_P(P2PTransportChannelMultihomedTest, TestPreferWifiOverCellularNetwork) {
+  // The interface names are chosen so that `cellular` would have higher
+  // candidate priority if it is not for the network type.
+  auto& wifi = kAlternateAddrs;
+  auto& cellular = kPublicAddrs;
+  AddAddress(0, cellular[0], "test1", rtc::ADAPTER_TYPE_CELLULAR);
+  AddAddress(1, wifi[1], "test0", rtc::ADAPTER_TYPE_WIFI);
+  AddAddress(1, cellular[1], "test1", rtc::ADAPTER_TYPE_CELLULAR);
+
+  // Use only local ports for simplicity.
+  SetAllocatorFlags(0, kOnlyLocalPorts);
+  SetAllocatorFlags(1, kOnlyLocalPorts);
+
+  // Create channels and let them go writable, as usual.
+  CreateChannels();
+
+  EXPECT_TRUE_WAIT_MARGIN(CheckCandidatePairAndConnected(ep1_ch1(), ep2_ch1(),
+                                                         cellular[0], wifi[1]),
+                          1000, 1000);
+  DestroyChannels();
+}
+
+// Test that the backup connection is pinged at a rate no faster than
+// what was configured.
+TEST_P(P2PTransportChannelMultihomedTest, TestPingBackupConnectionRate) {
+  AddAddress(0, kPublicAddrs[0]);
+  // Adding alternate address will make sure `kPublicAddrs` has the higher
+  // priority than others. This is due to FakeNetwork::AddInterface method.
+  AddAddress(1, kAlternateAddrs[1]);
+  AddAddress(1, kPublicAddrs[1]);
+
+  // Use only local ports for simplicity.
+  SetAllocatorFlags(0, kOnlyLocalPorts);
+  SetAllocatorFlags(1, kOnlyLocalPorts);
+
+  // Create channels and let them go writable, as usual.
+  CreateChannels();
+  EXPECT_TRUE_WAIT_MARGIN(CheckConnected(ep1_ch1(), ep2_ch1()), 1000, 1000);
+  int backup_ping_interval = 2000;
+  ep2_ch1()->SetIceConfig(
+      CreateIceConfig(2000, GATHER_ONCE, backup_ping_interval));
+  // After the state becomes COMPLETED, the backup connection will be pinged
+  // once every `backup_ping_interval` milliseconds.
+  ASSERT_TRUE_WAIT(ep2_ch1()->GetState() == IceTransportState::STATE_COMPLETED,
+                   1000);
+  auto connections = ep2_ch1()->connections();
+  ASSERT_EQ(2U, connections.size());
+  Connection* backup_conn = GetBackupConnection(ep2_ch1());
+  EXPECT_TRUE_WAIT(backup_conn->writable(), kMediumTimeout);
+  int64_t last_ping_response_ms = backup_conn->last_ping_response_received();
+  EXPECT_TRUE_WAIT(
+      last_ping_response_ms < backup_conn->last_ping_response_received(),
+      kDefaultTimeout);
+  int time_elapsed =
+      backup_conn->last_ping_response_received() - last_ping_response_ms;
+  RTC_LOG(LS_INFO) << "Time elapsed: " << time_elapsed;
+  EXPECT_GE(time_elapsed, backup_ping_interval);
+
+  DestroyChannels();
+}
+
+// Test that the connection is pinged at a rate no faster than
+// what was configured when stable and writable.
+TEST_P(P2PTransportChannelMultihomedTest, TestStableWritableRate) {
+  AddAddress(0, kPublicAddrs[0]);
+  // Adding alternate address will make sure `kPublicAddrs` has the higher
+  // priority than others. This is due to FakeNetwork::AddInterface method.
+  AddAddress(1, kAlternateAddrs[1]);
+  AddAddress(1, kPublicAddrs[1]);
+
+  // Use only local ports for simplicity.
+  SetAllocatorFlags(0, kOnlyLocalPorts);
+  SetAllocatorFlags(1, kOnlyLocalPorts);
+
+  // Create channels and let them go writable, as usual.
+  CreateChannels();
+  EXPECT_TRUE_WAIT_MARGIN(CheckConnected(ep1_ch1(), ep2_ch1()), 1000, 1000);
+  // Set a value larger than the default value of 2500 ms
+  int ping_interval_ms = 3456;
+  IceConfig config = CreateIceConfig(2 * ping_interval_ms, GATHER_ONCE);
+  config.stable_writable_connection_ping_interval = ping_interval_ms;
+  ep2_ch1()->SetIceConfig(config);
+  // After the state becomes COMPLETED and is stable and writable, the
+  // connection will be pinged once every `ping_interval_ms` milliseconds.
+  ASSERT_TRUE_WAIT(ep2_ch1()->GetState() == IceTransportState::STATE_COMPLETED,
+                   1000);
+  auto connections = ep2_ch1()->connections();
+  ASSERT_EQ(2U, connections.size());
+  Connection* conn = GetBestConnection(ep2_ch1());
+  EXPECT_TRUE_WAIT(conn->writable(), kMediumTimeout);
+
+  int64_t last_ping_response_ms;
+  // Burn through some pings so the connection is stable.
+  for (int i = 0; i < 5; i++) {
+    last_ping_response_ms = conn->last_ping_response_received();
+    EXPECT_TRUE_WAIT(
+        last_ping_response_ms < conn->last_ping_response_received(),
+        kDefaultTimeout);
+  }
+  EXPECT_TRUE(conn->stable(last_ping_response_ms)) << "Connection not stable";
+  int time_elapsed =
+      conn->last_ping_response_received() - last_ping_response_ms;
+  RTC_LOG(LS_INFO) << "Time elapsed: " << time_elapsed;
+  EXPECT_GE(time_elapsed, ping_interval_ms);
+
+  DestroyChannels();
+}
+
+TEST_P(P2PTransportChannelMultihomedTest, TestGetState) {
+  rtc::ScopedFakeClock clock;
+  AddAddress(0, kAlternateAddrs[0]);
+  AddAddress(0, kPublicAddrs[0]);
+  AddAddress(1, kPublicAddrs[1]);
+  // Create channels and let them go writable, as usual.
+  CreateChannels();
+
+  // Both transport channels will reach STATE_COMPLETED quickly.
+  EXPECT_EQ_SIMULATED_WAIT(IceTransportState::STATE_COMPLETED,
+                           ep1_ch1()->GetState(), kShortTimeout, clock);
+  EXPECT_EQ_SIMULATED_WAIT(IceTransportState::STATE_COMPLETED,
+                           ep2_ch1()->GetState(), kShortTimeout, clock);
+  DestroyChannels();
+}
+
+// Tests that when a network interface becomes inactive, if Continual Gathering
+// policy is GATHER_CONTINUALLY, the ports associated with that network
+// will be removed from the port list of the channel, and the respective
+// remote candidates on the other participant will be removed eventually.
+TEST_P(P2PTransportChannelMultihomedTest, TestNetworkBecomesInactive) {
+  rtc::ScopedFakeClock clock;
+  AddAddress(0, kPublicAddrs[0]);
+  AddAddress(1, kPublicAddrs[1]);
+  // Create channels and let them go writable, as usual.
+  IceConfig ep1_config = CreateIceConfig(2000, GATHER_CONTINUALLY);
+  IceConfig ep2_config = CreateIceConfig(2000, GATHER_ONCE);
+  CreateChannels(ep1_config, ep2_config);
+
+  SetAllocatorFlags(0, kOnlyLocalPorts);
+  SetAllocatorFlags(1, kOnlyLocalPorts);
+  ASSERT_TRUE_SIMULATED_WAIT(CheckConnected(ep1_ch1(), ep2_ch1()),
+                             kDefaultTimeout, clock);
+  // More than one port has been created.
+  EXPECT_LE(1U, ep1_ch1()->ports().size());
+  // Endpoint 1 enabled continual gathering; the port will be removed
+  // when the interface is removed.
+  RemoveAddress(0, kPublicAddrs[0]);
+  EXPECT_TRUE(ep1_ch1()->ports().empty());
+  // The remote candidates will be removed eventually.
+  EXPECT_TRUE_SIMULATED_WAIT(ep2_ch1()->remote_candidates().empty(), 1000,
+                             clock);
+
+  size_t num_ports = ep2_ch1()->ports().size();
+  EXPECT_LE(1U, num_ports);
+  size_t num_remote_candidates = ep1_ch1()->remote_candidates().size();
+  // Endpoint 2 did not enable continual gathering; the local port will still be
+  // removed when the interface is removed but the remote candidates on the
+  // other participant will not be removed.
+  RemoveAddress(1, kPublicAddrs[1]);
+
+  EXPECT_EQ_SIMULATED_WAIT(0U, ep2_ch1()->ports().size(), kDefaultTimeout,
+                           clock);
+  SIMULATED_WAIT(0U == ep1_ch1()->remote_candidates().size(), 500, clock);
+  EXPECT_EQ(num_remote_candidates, ep1_ch1()->remote_candidates().size());
+
+  DestroyChannels();
+}
+
+// Tests that continual gathering will create new connections when a new
+// interface is added.
+TEST_P(P2PTransportChannelMultihomedTest,
+       TestContinualGatheringOnNewInterface) {
+  auto& wifi = kAlternateAddrs;
+  auto& cellular = kPublicAddrs;
+  AddAddress(0, wifi[0], "test_wifi0", rtc::ADAPTER_TYPE_WIFI);
+  AddAddress(1, cellular[1], "test_cell1", rtc::ADAPTER_TYPE_CELLULAR);
+  // Set continual gathering policy.
+  IceConfig continual_gathering_config =
+      CreateIceConfig(1000, GATHER_CONTINUALLY);
+  CreateChannels(continual_gathering_config, continual_gathering_config);
+  SetAllocatorFlags(0, kOnlyLocalPorts);
+  SetAllocatorFlags(1, kOnlyLocalPorts);
+  EXPECT_TRUE_WAIT_MARGIN(CheckConnected(ep1_ch1(), ep2_ch1()), kDefaultTimeout,
+                          kDefaultTimeout);
+
+  // Add a new wifi interface on end point 2. We should expect a new connection
+  // to be created and the new one will be the best connection.
+  AddAddress(1, wifi[1], "test_wifi1", rtc::ADAPTER_TYPE_WIFI);
+  const Connection* conn;
+  EXPECT_TRUE_WAIT((conn = ep1_ch1()->selected_connection()) != nullptr &&
+                       HasRemoteAddress(conn, wifi[1]),
+                   kDefaultTimeout);
+  EXPECT_TRUE_WAIT((conn = ep2_ch1()->selected_connection()) != nullptr &&
+                       HasLocalAddress(conn, wifi[1]),
+                   kDefaultTimeout);
+
+  // Add a new cellular interface on end point 1, we should expect a new
+  // backup connection created using this new interface.
+  AddAddress(0, cellular[0], "test_cellular0", rtc::ADAPTER_TYPE_CELLULAR);
+  EXPECT_TRUE_WAIT(
+      ep1_ch1()->GetState() == IceTransportState::STATE_COMPLETED &&
+          absl::c_any_of(ep1_ch1()->connections(),
+                         [channel = ep1_ch1(),
+                          address = cellular[0]](const Connection* conn) {
+                           return HasLocalAddress(conn, address) &&
+                                  conn != channel->selected_connection() &&
+                                  conn->writable();
+                         }),
+      kDefaultTimeout);
+  EXPECT_TRUE_WAIT(
+      ep2_ch1()->GetState() == IceTransportState::STATE_COMPLETED &&
+          absl::c_any_of(ep2_ch1()->connections(),
+                         [channel = ep2_ch1(),
+                          address = cellular[0]](const Connection* conn) {
+                           return HasRemoteAddress(conn, address) &&
+                                  conn != channel->selected_connection() &&
+                                  conn->receiving();
+                         }),
+      kDefaultTimeout);
+
+  DestroyChannels();
+}
+
+// Tests that we can switch links via continual gathering.
+TEST_P(P2PTransportChannelMultihomedTest,
+       TestSwitchLinksViaContinualGathering) {
+  rtc::ScopedFakeClock clock;
+  AddAddress(0, kPublicAddrs[0]);
+  AddAddress(1, kPublicAddrs[1]);
+  // Use only local ports for simplicity.
+  SetAllocatorFlags(0, kOnlyLocalPorts);
+  SetAllocatorFlags(1, kOnlyLocalPorts);
+
+  // Set continual gathering policy.
+  IceConfig continual_gathering_config =
+      CreateIceConfig(1000, GATHER_CONTINUALLY);
+  // Create channels and let them go writable, as usual.
+  CreateChannels(continual_gathering_config, continual_gathering_config);
+  EXPECT_TRUE_SIMULATED_WAIT(
+      CheckCandidatePairAndConnected(ep1_ch1(), ep2_ch1(), kPublicAddrs[0],
+                                     kPublicAddrs[1]),
+      kMediumTimeout, clock);
+
+  // Add the new address first and then remove the other one.
+  RTC_LOG(LS_INFO) << "Draining...";
+  AddAddress(1, kAlternateAddrs[1]);
+  RemoveAddress(1, kPublicAddrs[1]);
+  // We should switch to use the alternate address after an exchange of pings.
+  EXPECT_TRUE_SIMULATED_WAIT(
+      CheckCandidatePairAndConnected(ep1_ch1(), ep2_ch1(), kPublicAddrs[0],
+                                     kAlternateAddrs[1]),
+      kMediumTimeout, clock);
+
+  // Remove one address first and then add another address.
+  RTC_LOG(LS_INFO) << "Draining again...";
+  RemoveAddress(1, kAlternateAddrs[1]);
+  AddAddress(1, kAlternateAddrs[0]);
+  EXPECT_TRUE_SIMULATED_WAIT(
+      CheckCandidatePairAndConnected(ep1_ch1(), ep2_ch1(), kPublicAddrs[0],
+                                     kAlternateAddrs[0]),
+      kMediumTimeout, clock);
+
+  DestroyChannels();
+}
+
+// Tests that the backup connection will be restored after it is destroyed.
+TEST_P(P2PTransportChannelMultihomedTest, TestRestoreBackupConnection) {
+  rtc::ScopedFakeClock clock;
+  auto& wifi = kAlternateAddrs;
+  auto& cellular = kPublicAddrs;
+  AddAddress(0, wifi[0], "test_wifi0", rtc::ADAPTER_TYPE_WIFI);
+  AddAddress(0, cellular[0], "test_cell0", rtc::ADAPTER_TYPE_CELLULAR);
+  AddAddress(1, wifi[1], "test_wifi1", rtc::ADAPTER_TYPE_WIFI);
+  AddAddress(1, cellular[1], "test_cell1", rtc::ADAPTER_TYPE_CELLULAR);
+  // Use only local ports for simplicity.
+  SetAllocatorFlags(0, kOnlyLocalPorts);
+  SetAllocatorFlags(1, kOnlyLocalPorts);
+
+  // Create channels and let them go writable, as usual.
+  IceConfig config = CreateIceConfig(1000, GATHER_CONTINUALLY);
+  config.regather_on_failed_networks_interval = 2000;
+  CreateChannels(config, config);
+  EXPECT_TRUE_SIMULATED_WAIT(
+      CheckCandidatePairAndConnected(ep1_ch1(), ep2_ch1(), wifi[0], wifi[1]),
+      kMediumTimeout, clock);
+
+  // Destroy all backup connections.
+  DestroyAllButBestConnection(ep1_ch1());
+  // Ensure the backup connection is removed first.
+  EXPECT_TRUE_SIMULATED_WAIT(
+      GetConnectionWithLocalAddress(ep1_ch1(), cellular[0]) == nullptr,
+      kDefaultTimeout, clock);
+  const Connection* conn;
+  EXPECT_TRUE_SIMULATED_WAIT(
+      (conn = GetConnectionWithLocalAddress(ep1_ch1(), cellular[0])) !=
+              nullptr &&
+          conn != ep1_ch1()->selected_connection() && conn->writable(),
+      kDefaultTimeout, clock);
+
+  DestroyChannels();
+}
+
+TEST_P(P2PTransportChannelMultihomedTest, TestVpnDefault) {
+  rtc::ScopedFakeClock clock;
+  AddAddress(0, kPublicAddrs[0], "eth0", rtc::ADAPTER_TYPE_ETHERNET);
+  AddAddress(0, kAlternateAddrs[0], "vpn0", rtc::ADAPTER_TYPE_VPN);
+  AddAddress(1, kPublicAddrs[1]);
+
+  IceConfig config;
+  CreateChannels(config, config, false);
+  EXPECT_TRUE_SIMULATED_WAIT(
+      CheckConnected(ep1_ch1(), ep2_ch1()) &&
+          !ep1_ch1()->selected_connection()->network()->IsVpn(),
+      kDefaultTimeout, clock);
+}
+
+TEST_P(P2PTransportChannelMultihomedTest, TestVpnPreferVpn) {
+  rtc::ScopedFakeClock clock;
+  AddAddress(0, kPublicAddrs[0], "eth0", rtc::ADAPTER_TYPE_ETHERNET);
+  AddAddress(0, kAlternateAddrs[0], "vpn0", rtc::ADAPTER_TYPE_VPN,
+             rtc::ADAPTER_TYPE_CELLULAR);
+  AddAddress(1, kPublicAddrs[1]);
+
+  IceConfig config;
+  config.vpn_preference = webrtc::VpnPreference::kPreferVpn;
+  RTC_LOG(LS_INFO) << "KESO: config.vpn_preference: " << config.vpn_preference;
+  CreateChannels(config, config, false);
+  EXPECT_TRUE_SIMULATED_WAIT(
+      CheckConnected(ep1_ch1(), ep2_ch1()) &&
+          ep1_ch1()->selected_connection()->network()->IsVpn(),
+      kDefaultTimeout, clock);
+
+  // Block VPN.
+  fw()->AddRule(false, rtc::FP_ANY, rtc::FD_ANY, kAlternateAddrs[0]);
+
+  // Check that it switches to non-VPN
+  EXPECT_TRUE_SIMULATED_WAIT(
+      CheckConnected(ep1_ch1(), ep2_ch1()) &&
+          !ep1_ch1()->selected_connection()->network()->IsVpn(),
+      kDefaultTimeout, clock);
+}
+
+TEST_P(P2PTransportChannelMultihomedTest, TestVpnAvoidVpn) {
+  rtc::ScopedFakeClock clock;
+  AddAddress(0, kPublicAddrs[0], "eth0", rtc::ADAPTER_TYPE_CELLULAR);
+  AddAddress(0, kAlternateAddrs[0], "vpn0", rtc::ADAPTER_TYPE_VPN,
+             rtc::ADAPTER_TYPE_ETHERNET);
+  AddAddress(1, kPublicAddrs[1]);
+
+  IceConfig config;
+  config.vpn_preference = webrtc::VpnPreference::kAvoidVpn;
+  CreateChannels(config, config, false);
+  EXPECT_TRUE_SIMULATED_WAIT(
+      CheckConnected(ep1_ch1(), ep2_ch1()) &&
+          !ep1_ch1()->selected_connection()->network()->IsVpn(),
+      kDefaultTimeout, clock);
+
+  // Block non-VPN.
+  fw()->AddRule(false, rtc::FP_ANY, rtc::FD_ANY, kPublicAddrs[0]);
+
+  // Check that it switches to VPN
+  EXPECT_TRUE_SIMULATED_WAIT(
+      CheckConnected(ep1_ch1(), ep2_ch1()) &&
+          ep1_ch1()->selected_connection()->network()->IsVpn(),
+      kDefaultTimeout, clock);
+}
+
+TEST_P(P2PTransportChannelMultihomedTest, TestVpnNeverVpn) {
+  rtc::ScopedFakeClock clock;
+  AddAddress(0, kPublicAddrs[0], "eth0", rtc::ADAPTER_TYPE_CELLULAR);
+  AddAddress(0, kAlternateAddrs[0], "vpn0", rtc::ADAPTER_TYPE_VPN,
+             rtc::ADAPTER_TYPE_ETHERNET);
+  AddAddress(1, kPublicAddrs[1]);
+
+  IceConfig config;
+  config.vpn_preference = webrtc::VpnPreference::kNeverUseVpn;
+  CreateChannels(config, config, false);
+  EXPECT_TRUE_SIMULATED_WAIT(
+      CheckConnected(ep1_ch1(), ep2_ch1()) &&
+          !ep1_ch1()->selected_connection()->network()->IsVpn(),
+      kDefaultTimeout, clock);
+
+  // Block non-VPN.
+  fw()->AddRule(false, rtc::FP_ANY, rtc::FD_ANY, kPublicAddrs[0]);
+
+  // Check that it does not switches to VPN
+  clock.AdvanceTime(webrtc::TimeDelta::Millis(kDefaultTimeout));
+  EXPECT_TRUE_SIMULATED_WAIT(!CheckConnected(ep1_ch1(), ep2_ch1()),
+                             kDefaultTimeout, clock);
+}
+
+TEST_P(P2PTransportChannelMultihomedTest, TestVpnOnlyVpn) {
+  rtc::ScopedFakeClock clock;
+  AddAddress(0, kPublicAddrs[0], "eth0", rtc::ADAPTER_TYPE_CELLULAR);
+  AddAddress(0, kAlternateAddrs[0], "vpn0", rtc::ADAPTER_TYPE_VPN,
+             rtc::ADAPTER_TYPE_ETHERNET);
+  AddAddress(1, kPublicAddrs[1]);
+
+  IceConfig config;
+  config.vpn_preference = webrtc::VpnPreference::kOnlyUseVpn;
+  CreateChannels(config, config, false);
+  EXPECT_TRUE_SIMULATED_WAIT(
+      CheckConnected(ep1_ch1(), ep2_ch1()) &&
+          ep1_ch1()->selected_connection()->network()->IsVpn(),
+      kDefaultTimeout, clock);
+
+  // Block VPN.
+  fw()->AddRule(false, rtc::FP_ANY, rtc::FD_ANY, kAlternateAddrs[0]);
+
+  // Check that it does not switch to non-VPN
+  clock.AdvanceTime(webrtc::TimeDelta::Millis(kDefaultTimeout));
+  EXPECT_TRUE_SIMULATED_WAIT(!CheckConnected(ep1_ch1(), ep2_ch1()),
+                             kDefaultTimeout, clock);
+}
+
+// A collection of tests which tests a single P2PTransportChannel by sending
+// pings.
+class P2PTransportChannelPingTest : public TestWithParam<std::string>,
+                                    public sigslot::has_slots<> {
+ public:
+  P2PTransportChannelPingTest()
+      : field_trials_(GetParam()),
+        vss_(std::make_unique<rtc::VirtualSocketServer>()),
+        packet_socket_factory_(
+            std::make_unique<rtc::BasicPacketSocketFactory>(vss_.get())),
+        thread_(vss_.get()) {}
+
+ protected:
+  void PrepareChannel(P2PTransportChannel* ch) {
+    ch->SetIceRole(ICEROLE_CONTROLLING);
+    ch->SetIceTiebreaker(kTiebreakerDefault);
+    ch->SetIceParameters(kIceParams[0]);
+    ch->SetRemoteIceParameters(kIceParams[1]);
+    ch->SignalNetworkRouteChanged.connect(
+        this, &P2PTransportChannelPingTest::OnNetworkRouteChanged);
+    ch->SignalReadyToSend.connect(this,
+                                  &P2PTransportChannelPingTest::OnReadyToSend);
+    ch->SignalStateChanged.connect(
+        this, &P2PTransportChannelPingTest::OnChannelStateChanged);
+    ch->SignalCandidatePairChanged.connect(
+        this, &P2PTransportChannelPingTest::OnCandidatePairChanged);
+  }
+
+  Connection* WaitForConnectionTo(
+      P2PTransportChannel* ch,
+      absl::string_view ip,
+      int port_num,
+      rtc::ThreadProcessingFakeClock* clock = nullptr) {
+    if (clock == nullptr) {
+      EXPECT_TRUE_WAIT(GetConnectionTo(ch, ip, port_num) != nullptr,
+                       kMediumTimeout);
+    } else {
+      EXPECT_TRUE_SIMULATED_WAIT(GetConnectionTo(ch, ip, port_num) != nullptr,
+                                 kMediumTimeout, *clock);
+    }
+    return GetConnectionTo(ch, ip, port_num);
+  }
+
+  Port* GetPort(P2PTransportChannel* ch) {
+    if (ch->ports().empty()) {
+      return nullptr;
+    }
+    return static_cast<Port*>(ch->ports()[0]);
+  }
+
+  Port* GetPrunedPort(P2PTransportChannel* ch) {
+    if (ch->pruned_ports().empty()) {
+      return nullptr;
+    }
+    return static_cast<Port*>(ch->pruned_ports()[0]);
+  }
+
+  Connection* GetConnectionTo(P2PTransportChannel* ch,
+                              absl::string_view ip,
+                              int port_num) {
+    Port* port = GetPort(ch);
+    if (!port) {
+      return nullptr;
+    }
+    return port->GetConnection(rtc::SocketAddress(ip, port_num));
+  }
+
+  Connection* FindNextPingableConnectionAndPingIt(P2PTransportChannel* ch) {
+    Connection* conn = ch->FindNextPingableConnection();
+    if (conn) {
+      ch->MarkConnectionPinged(conn);
+    }
+    return conn;
+  }
+
+  int SendData(IceTransportInternal* channel,
+               const char* data,
+               size_t len,
+               int packet_id) {
+    rtc::PacketOptions options;
+    options.packet_id = packet_id;
+    return channel->SendPacket(data, len, options, 0);
+  }
+
+  Connection* CreateConnectionWithCandidate(P2PTransportChannel* channel,
+                                            rtc::ScopedFakeClock* clock,
+                                            absl::string_view ip_addr,
+                                            int port,
+                                            int priority,
+                                            bool writable) {
+    channel->AddRemoteCandidate(
+        CreateUdpCandidate(LOCAL_PORT_TYPE, ip_addr, port, priority));
+    EXPECT_TRUE_SIMULATED_WAIT(
+        GetConnectionTo(channel, ip_addr, port) != nullptr, kMediumTimeout,
+        *clock);
+    Connection* conn = GetConnectionTo(channel, ip_addr, port);
+
+    if (conn && writable) {
+      conn->ReceivedPingResponse(LOW_RTT, "id");  // make it writable
+    }
+    return conn;
+  }
+
+  void NominateConnection(Connection* conn, uint32_t remote_nomination = 1U) {
+    conn->set_remote_nomination(remote_nomination);
+    conn->SignalNominated(conn);
+  }
+
+  void OnNetworkRouteChanged(absl::optional<rtc::NetworkRoute> network_route) {
+    last_network_route_ = network_route;
+    if (last_network_route_) {
+      last_sent_packet_id_ = last_network_route_->last_sent_packet_id;
+    }
+    ++selected_candidate_pair_switches_;
+  }
+
+  void ReceivePingOnConnection(
+      Connection* conn,
+      absl::string_view remote_ufrag,
+      int priority,
+      uint32_t nomination,
+      const absl::optional<std::string>& piggyback_ping_id) {
+    IceMessage msg(STUN_BINDING_REQUEST);
+    msg.AddAttribute(std::make_unique<StunByteStringAttribute>(
+        STUN_ATTR_USERNAME,
+        conn->local_candidate().username() + ":" + std::string(remote_ufrag)));
+    msg.AddAttribute(
+        std::make_unique<StunUInt32Attribute>(STUN_ATTR_PRIORITY, priority));
+    if (nomination != 0) {
+      msg.AddAttribute(std::make_unique<StunUInt32Attribute>(
+          STUN_ATTR_NOMINATION, nomination));
+    }
+    if (piggyback_ping_id) {
+      msg.AddAttribute(std::make_unique<StunByteStringAttribute>(
+          STUN_ATTR_GOOG_LAST_ICE_CHECK_RECEIVED, piggyback_ping_id.value()));
+    }
+    msg.AddMessageIntegrity(conn->local_candidate().password());
+    msg.AddFingerprint();
+    rtc::ByteBufferWriter buf;
+    msg.Write(&buf);
+    conn->OnReadPacket(buf.Data(), buf.Length(), rtc::TimeMicros());
+  }
+
+  void ReceivePingOnConnection(Connection* conn,
+                               absl::string_view remote_ufrag,
+                               int priority,
+                               uint32_t nomination = 0) {
+    ReceivePingOnConnection(conn, remote_ufrag, priority, nomination,
+                            absl::nullopt);
+  }
+
+  void OnReadyToSend(rtc::PacketTransportInternal* transport) {
+    channel_ready_to_send_ = true;
+  }
+  void OnChannelStateChanged(IceTransportInternal* channel) {
+    channel_state_ = channel->GetState();
+  }
+  void OnCandidatePairChanged(const CandidatePairChangeEvent& event) {
+    last_candidate_change_event_ = event;
+  }
+
+  int last_sent_packet_id() { return last_sent_packet_id_; }
+  bool channel_ready_to_send() { return channel_ready_to_send_; }
+  void reset_channel_ready_to_send() { channel_ready_to_send_ = false; }
+  IceTransportState channel_state() { return channel_state_; }
+  int reset_selected_candidate_pair_switches() {
+    int switches = selected_candidate_pair_switches_;
+    selected_candidate_pair_switches_ = 0;
+    return switches;
+  }
+
+  // Return true if the `pair` matches the last network route.
+  bool CandidatePairMatchesNetworkRoute(CandidatePairInterface* pair) {
+    if (!pair) {
+      return !last_network_route_.has_value();
+    } else {
+      return pair->local_candidate().network_id() ==
+                 last_network_route_->local.network_id() &&
+             pair->remote_candidate().network_id() ==
+                 last_network_route_->remote.network_id();
+    }
+  }
+
+  bool ConnectionMatchesChangeEvent(Connection* conn,
+                                    absl::string_view reason) {
+    if (!conn) {
+      return !last_candidate_change_event_.has_value();
+    } else {
+      const auto& last_selected_pair =
+          last_candidate_change_event_->selected_candidate_pair;
+      return last_selected_pair.local_candidate().IsEquivalent(
+                 conn->local_candidate()) &&
+             last_selected_pair.remote_candidate().IsEquivalent(
+                 conn->remote_candidate()) &&
+             last_candidate_change_event_->last_data_received_ms ==
+                 conn->last_data_received() &&
+             last_candidate_change_event_->reason == reason;
+    }
+  }
+
+  int64_t LastEstimatedDisconnectedTimeMs() const {
+    if (!last_candidate_change_event_.has_value()) {
+      return 0;
+    } else {
+      return last_candidate_change_event_->estimated_disconnected_time_ms;
+    }
+  }
+
+  rtc::SocketServer* ss() const { return vss_.get(); }
+
+  rtc::PacketSocketFactory* packet_socket_factory() const {
+    return packet_socket_factory_.get();
+  }
+
+  webrtc::test::ScopedKeyValueConfig field_trials_;
+
+ private:
+  std::unique_ptr<rtc::VirtualSocketServer> vss_;
+  std::unique_ptr<rtc::PacketSocketFactory> packet_socket_factory_;
+  rtc::AutoSocketServerThread thread_;
+  int selected_candidate_pair_switches_ = 0;
+  int last_sent_packet_id_ = -1;
+  bool channel_ready_to_send_ = false;
+  absl::optional<CandidatePairChangeEvent> last_candidate_change_event_;
+  IceTransportState channel_state_ = IceTransportState::STATE_INIT;
+  absl::optional<rtc::NetworkRoute> last_network_route_;
+};
+
+INSTANTIATE_TEST_SUITE_P(Legacy, P2PTransportChannelPingTest, Values(""));
+INSTANTIATE_TEST_SUITE_P(Active,
+                         P2PTransportChannelPingTest,
+                         Values("WebRTC-UseActiveIceController/Enabled/"));
+
+TEST_P(P2PTransportChannelPingTest, TestTriggeredChecks) {
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("trigger checks", 1, &pa, &field_trials_);
+  PrepareChannel(&ch);
+  ch.MaybeStartGathering();
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 1));
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "2.2.2.2", 2, 2));
+
+  Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1);
+  Connection* conn2 = WaitForConnectionTo(&ch, "2.2.2.2", 2);
+  ASSERT_TRUE(conn1 != nullptr);
+  ASSERT_TRUE(conn2 != nullptr);
+
+  // Before a triggered check, the first connection to ping is the
+  // highest priority one.
+  EXPECT_EQ(conn2, FindNextPingableConnectionAndPingIt(&ch));
+
+  // Receiving a ping causes a triggered check which should make conn1
+  // be pinged first instead of conn2, even though conn2 has a higher
+  // priority.
+  conn1->ReceivedPing();
+  EXPECT_EQ(conn1, FindNextPingableConnectionAndPingIt(&ch));
+}
+
+TEST_P(P2PTransportChannelPingTest, TestAllConnectionsPingedSufficiently) {
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("ping sufficiently", 1, &pa, &field_trials_);
+  PrepareChannel(&ch);
+  ch.MaybeStartGathering();
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 1));
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "2.2.2.2", 2, 2));
+
+  Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1);
+  Connection* conn2 = WaitForConnectionTo(&ch, "2.2.2.2", 2);
+  ASSERT_TRUE(conn1 != nullptr);
+  ASSERT_TRUE(conn2 != nullptr);
+
+  // Low-priority connection becomes writable so that the other connection
+  // is not pruned.
+  conn1->ReceivedPingResponse(LOW_RTT, "id");
+  EXPECT_TRUE_WAIT(
+      conn1->num_pings_sent() >= MIN_PINGS_AT_WEAK_PING_INTERVAL &&
+          conn2->num_pings_sent() >= MIN_PINGS_AT_WEAK_PING_INTERVAL,
+      kDefaultTimeout);
+}
+
+// Verify that the connections are pinged at the right time.
+TEST_P(P2PTransportChannelPingTest, TestStunPingIntervals) {
+  rtc::ScopedFakeClock clock;
+  int RTT_RATIO = 4;
+  int SCHEDULING_RANGE = 200;
+  int RTT_RANGE = 10;
+
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("TestChannel", 1, &pa, &field_trials_);
+  PrepareChannel(&ch);
+  ch.MaybeStartGathering();
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 1));
+  Connection* conn = WaitForConnectionTo(&ch, "1.1.1.1", 1);
+
+  ASSERT_TRUE(conn != nullptr);
+  SIMULATED_WAIT(conn->num_pings_sent() == 1, kDefaultTimeout, clock);
+
+  // Initializing.
+
+  int64_t start = clock.TimeNanos();
+  SIMULATED_WAIT(conn->num_pings_sent() >= MIN_PINGS_AT_WEAK_PING_INTERVAL,
+                 kDefaultTimeout, clock);
+  int64_t ping_interval_ms = (clock.TimeNanos() - start) /
+                             rtc::kNumNanosecsPerMillisec /
+                             (MIN_PINGS_AT_WEAK_PING_INTERVAL - 1);
+  EXPECT_EQ(ping_interval_ms, WEAK_PING_INTERVAL);
+
+  // Stabilizing.
+
+  conn->ReceivedPingResponse(LOW_RTT, "id");
+  int ping_sent_before = conn->num_pings_sent();
+  start = clock.TimeNanos();
+  // The connection becomes strong but not stable because we haven't been able
+  // to converge the RTT.
+  SIMULATED_WAIT(conn->num_pings_sent() == ping_sent_before + 1, kMediumTimeout,
+                 clock);
+  ping_interval_ms = (clock.TimeNanos() - start) / rtc::kNumNanosecsPerMillisec;
+  EXPECT_GE(ping_interval_ms,
+            WEAK_OR_STABILIZING_WRITABLE_CONNECTION_PING_INTERVAL);
+  EXPECT_LE(
+      ping_interval_ms,
+      WEAK_OR_STABILIZING_WRITABLE_CONNECTION_PING_INTERVAL + SCHEDULING_RANGE);
+
+  // Stabilized.
+
+  // The connection becomes stable after receiving more than RTT_RATIO rtt
+  // samples.
+  for (int i = 0; i < RTT_RATIO; i++) {
+    conn->ReceivedPingResponse(LOW_RTT, "id");
+  }
+  ping_sent_before = conn->num_pings_sent();
+  start = clock.TimeNanos();
+  SIMULATED_WAIT(conn->num_pings_sent() == ping_sent_before + 1, kMediumTimeout,
+                 clock);
+  ping_interval_ms = (clock.TimeNanos() - start) / rtc::kNumNanosecsPerMillisec;
+  EXPECT_GE(ping_interval_ms,
+            STRONG_AND_STABLE_WRITABLE_CONNECTION_PING_INTERVAL);
+  EXPECT_LE(
+      ping_interval_ms,
+      STRONG_AND_STABLE_WRITABLE_CONNECTION_PING_INTERVAL + SCHEDULING_RANGE);
+
+  // Destabilized.
+
+  conn->ReceivedPingResponse(LOW_RTT, "id");
+  // Create a in-flight ping.
+  conn->Ping(clock.TimeNanos() / rtc::kNumNanosecsPerMillisec);
+  start = clock.TimeNanos();
+  // In-flight ping timeout and the connection will be unstable.
+  SIMULATED_WAIT(
+      !conn->stable(clock.TimeNanos() / rtc::kNumNanosecsPerMillisec),
+      kMediumTimeout, clock);
+  int64_t duration_ms =
+      (clock.TimeNanos() - start) / rtc::kNumNanosecsPerMillisec;
+  EXPECT_GE(duration_ms, 2 * conn->rtt() - RTT_RANGE);
+  EXPECT_LE(duration_ms, 2 * conn->rtt() + RTT_RANGE);
+  // The connection become unstable due to not receiving ping responses.
+  ping_sent_before = conn->num_pings_sent();
+  SIMULATED_WAIT(conn->num_pings_sent() == ping_sent_before + 1, kMediumTimeout,
+                 clock);
+  // The interval is expected to be
+  // WEAK_OR_STABILIZING_WRITABLE_CONNECTION_PING_INTERVAL.
+  start = clock.TimeNanos();
+  ping_sent_before = conn->num_pings_sent();
+  SIMULATED_WAIT(conn->num_pings_sent() == ping_sent_before + 1, kMediumTimeout,
+                 clock);
+  ping_interval_ms = (clock.TimeNanos() - start) / rtc::kNumNanosecsPerMillisec;
+  EXPECT_GE(ping_interval_ms,
+            WEAK_OR_STABILIZING_WRITABLE_CONNECTION_PING_INTERVAL);
+  EXPECT_LE(
+      ping_interval_ms,
+      WEAK_OR_STABILIZING_WRITABLE_CONNECTION_PING_INTERVAL + SCHEDULING_RANGE);
+}
+
+// Test that we start pinging as soon as we have a connection and remote ICE
+// parameters.
+TEST_P(P2PTransportChannelPingTest, PingingStartedAsSoonAsPossible) {
+  rtc::ScopedFakeClock clock;
+
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("TestChannel", 1, &pa, &field_trials_);
+  ch.SetIceRole(ICEROLE_CONTROLLING);
+  ch.SetIceTiebreaker(kTiebreakerDefault);
+  ch.SetIceParameters(kIceParams[0]);
+  ch.MaybeStartGathering();
+  EXPECT_EQ_WAIT(IceGatheringState::kIceGatheringComplete, ch.gathering_state(),
+                 kDefaultTimeout);
+
+  // Simulate a binding request being received, creating a peer reflexive
+  // candidate pair while we still don't have remote ICE parameters.
+  IceMessage request(STUN_BINDING_REQUEST);
+  request.AddAttribute(std::make_unique<StunByteStringAttribute>(
+      STUN_ATTR_USERNAME, kIceUfrag[1]));
+  uint32_t prflx_priority = ICE_TYPE_PREFERENCE_PRFLX << 24;
+  request.AddAttribute(std::make_unique<StunUInt32Attribute>(STUN_ATTR_PRIORITY,
+                                                             prflx_priority));
+  Port* port = GetPort(&ch);
+  ASSERT_NE(nullptr, port);
+  port->SignalUnknownAddress(port, rtc::SocketAddress("1.1.1.1", 1), PROTO_UDP,
+                             &request, kIceUfrag[1], false);
+  Connection* conn = GetConnectionTo(&ch, "1.1.1.1", 1);
+  ASSERT_NE(nullptr, conn);
+
+  // Simulate waiting for a second (and change) and verify that no pings were
+  // sent, since we don't yet have remote ICE parameters.
+  SIMULATED_WAIT(conn->num_pings_sent() > 0, 1025, clock);
+  EXPECT_EQ(0, conn->num_pings_sent());
+
+  // Set remote ICE parameters. Now we should be able to ping. Ensure that
+  // the first ping is sent as soon as possible, within one simulated clock
+  // tick.
+  ch.SetRemoteIceParameters(kIceParams[1]);
+  EXPECT_TRUE_SIMULATED_WAIT(conn->num_pings_sent() > 0, 1, clock);
+}
+
+TEST_P(P2PTransportChannelPingTest, TestNoTriggeredChecksWhenWritable) {
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("trigger checks", 1, &pa, &field_trials_);
+  PrepareChannel(&ch);
+  ch.MaybeStartGathering();
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 1));
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "2.2.2.2", 2, 2));
+
+  Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1);
+  Connection* conn2 = WaitForConnectionTo(&ch, "2.2.2.2", 2);
+  ASSERT_TRUE(conn1 != nullptr);
+  ASSERT_TRUE(conn2 != nullptr);
+
+  EXPECT_EQ(conn2, FindNextPingableConnectionAndPingIt(&ch));
+  EXPECT_EQ(conn1, FindNextPingableConnectionAndPingIt(&ch));
+  conn1->ReceivedPingResponse(LOW_RTT, "id");
+  ASSERT_TRUE(conn1->writable());
+  conn1->ReceivedPing();
+
+  // Ping received, but the connection is already writable, so no
+  // "triggered check" and conn2 is pinged before conn1 because it has
+  // a higher priority.
+  EXPECT_EQ(conn2, FindNextPingableConnectionAndPingIt(&ch));
+}
+
+TEST_P(P2PTransportChannelPingTest, TestFailedConnectionNotPingable) {
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("Do not ping failed connections", 1, &pa,
+                         &field_trials_);
+  PrepareChannel(&ch);
+  ch.MaybeStartGathering();
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 1));
+
+  Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1);
+  ASSERT_TRUE(conn1 != nullptr);
+
+  EXPECT_EQ(conn1, ch.FindNextPingableConnection());
+  conn1->Prune();  // A pruned connection may still be pingable.
+  EXPECT_EQ(conn1, ch.FindNextPingableConnection());
+  conn1->FailAndPrune();
+  EXPECT_TRUE(nullptr == ch.FindNextPingableConnection());
+}
+
+TEST_P(P2PTransportChannelPingTest, TestSignalStateChanged) {
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("state change", 1, &pa, &field_trials_);
+  PrepareChannel(&ch);
+  ch.MaybeStartGathering();
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 1));
+  Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1);
+  ASSERT_TRUE(conn1 != nullptr);
+  // Pruning the connection reduces the set of active connections and changes
+  // the channel state.
+  conn1->Prune();
+  EXPECT_EQ_WAIT(IceTransportState::STATE_FAILED, channel_state(),
+                 kDefaultTimeout);
+}
+
+// Test adding remote candidates with different ufrags. If a remote candidate
+// is added with an old ufrag, it will be discarded. If it is added with a
+// ufrag that was not seen before, it will be used to create connections
+// although the ICE pwd in the remote candidate will be set when the ICE
+// parameters arrive. If a remote candidate is added with the current ICE
+// ufrag, its pwd and generation will be set properly.
+TEST_P(P2PTransportChannelPingTest, TestAddRemoteCandidateWithVariousUfrags) {
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("add candidate", 1, &pa, &field_trials_);
+  PrepareChannel(&ch);
+  ch.MaybeStartGathering();
+  // Add a candidate with a future ufrag.
+  ch.AddRemoteCandidate(
+      CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 1, kIceUfrag[2]));
+  Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1);
+  ASSERT_TRUE(conn1 != nullptr);
+  const Candidate& candidate = conn1->remote_candidate();
+  EXPECT_EQ(kIceUfrag[2], candidate.username());
+  EXPECT_TRUE(candidate.password().empty());
+  EXPECT_TRUE(FindNextPingableConnectionAndPingIt(&ch) == nullptr);
+
+  // Set the remote ICE parameters with the "future" ufrag.
+  // This should set the ICE pwd in the remote candidate of `conn1`, making
+  // it pingable.
+  ch.SetRemoteIceParameters(kIceParams[2]);
+  EXPECT_EQ(kIceUfrag[2], candidate.username());
+  EXPECT_EQ(kIcePwd[2], candidate.password());
+  EXPECT_EQ(conn1, FindNextPingableConnectionAndPingIt(&ch));
+
+  // Add a candidate with an old ufrag. No connection will be created.
+  ch.AddRemoteCandidate(
+      CreateUdpCandidate(LOCAL_PORT_TYPE, "2.2.2.2", 2, 2, kIceUfrag[1]));
+  rtc::Thread::Current()->ProcessMessages(500);
+  EXPECT_TRUE(GetConnectionTo(&ch, "2.2.2.2", 2) == nullptr);
+
+  // Add a candidate with the current ufrag, its pwd and generation will be
+  // assigned, even if the generation is not set.
+  ch.AddRemoteCandidate(
+      CreateUdpCandidate(LOCAL_PORT_TYPE, "3.3.3.3", 3, 0, kIceUfrag[2]));
+  Connection* conn3 = nullptr;
+  ASSERT_TRUE_WAIT((conn3 = GetConnectionTo(&ch, "3.3.3.3", 3)) != nullptr,
+                   kMediumTimeout);
+  const Candidate& new_candidate = conn3->remote_candidate();
+  EXPECT_EQ(kIcePwd[2], new_candidate.password());
+  EXPECT_EQ(1U, new_candidate.generation());
+
+  // Check that the pwd of all remote candidates are properly assigned.
+  for (const RemoteCandidate& candidate : ch.remote_candidates()) {
+    EXPECT_TRUE(candidate.username() == kIceUfrag[1] ||
+                candidate.username() == kIceUfrag[2]);
+    if (candidate.username() == kIceUfrag[1]) {
+      EXPECT_EQ(kIcePwd[1], candidate.password());
+    } else if (candidate.username() == kIceUfrag[2]) {
+      EXPECT_EQ(kIcePwd[2], candidate.password());
+    }
+  }
+}
+
+TEST_P(P2PTransportChannelPingTest, ConnectionResurrection) {
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("connection resurrection", 1, &pa, &field_trials_);
+  PrepareChannel(&ch);
+  ch.MaybeStartGathering();
+
+  // Create conn1 and keep track of original candidate priority.
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 1));
+  Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1);
+  ASSERT_TRUE(conn1 != nullptr);
+  uint32_t remote_priority = conn1->remote_candidate().priority();
+
+  // Create a higher priority candidate and make the connection
+  // receiving/writable. This will prune conn1.
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "2.2.2.2", 2, 2));
+  Connection* conn2 = WaitForConnectionTo(&ch, "2.2.2.2", 2);
+  ASSERT_TRUE(conn2 != nullptr);
+  conn2->ReceivedPing();
+  conn2->ReceivedPingResponse(LOW_RTT, "id");
+
+  // Wait for conn2 to be selected.
+  EXPECT_EQ_WAIT(conn2, ch.selected_connection(), kMediumTimeout);
+  // Destroy the connection to test SignalUnknownAddress.
+  ch.RemoveConnectionForTest(conn1);
+  EXPECT_TRUE_WAIT(GetConnectionTo(&ch, "1.1.1.1", 1) == nullptr,
+                   kMediumTimeout);
+
+  // Create a minimal STUN message with prflx priority.
+  IceMessage request(STUN_BINDING_REQUEST);
+  request.AddAttribute(std::make_unique<StunByteStringAttribute>(
+      STUN_ATTR_USERNAME, kIceUfrag[1]));
+  uint32_t prflx_priority = ICE_TYPE_PREFERENCE_PRFLX << 24;
+  request.AddAttribute(std::make_unique<StunUInt32Attribute>(STUN_ATTR_PRIORITY,
+                                                             prflx_priority));
+  EXPECT_NE(prflx_priority, remote_priority);
+
+  Port* port = GetPort(&ch);
+  // conn1 should be resurrected with original priority.
+  port->SignalUnknownAddress(port, rtc::SocketAddress("1.1.1.1", 1), PROTO_UDP,
+                             &request, kIceUfrag[1], false);
+  conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1);
+  ASSERT_TRUE(conn1 != nullptr);
+  EXPECT_EQ(conn1->remote_candidate().priority(), remote_priority);
+
+  // conn3, a real prflx connection, should have prflx priority.
+  port->SignalUnknownAddress(port, rtc::SocketAddress("3.3.3.3", 1), PROTO_UDP,
+                             &request, kIceUfrag[1], false);
+  Connection* conn3 = WaitForConnectionTo(&ch, "3.3.3.3", 1);
+  ASSERT_TRUE(conn3 != nullptr);
+  EXPECT_EQ(conn3->remote_candidate().priority(), prflx_priority);
+}
+
+TEST_P(P2PTransportChannelPingTest, TestReceivingStateChange) {
+  rtc::ScopedFakeClock clock;
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("receiving state change", 1, &pa, &field_trials_);
+  PrepareChannel(&ch);
+  // Default receiving timeout and checking receiving interval should not be too
+  // small.
+  EXPECT_LE(1000, ch.config().receiving_timeout_or_default());
+  EXPECT_LE(200, ch.check_receiving_interval());
+  ch.SetIceConfig(CreateIceConfig(500, GATHER_ONCE));
+  EXPECT_EQ(500, ch.config().receiving_timeout_or_default());
+  EXPECT_EQ(50, ch.check_receiving_interval());
+  ch.MaybeStartGathering();
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 1));
+  Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1, &clock);
+  ASSERT_TRUE(conn1 != nullptr);
+
+  clock.AdvanceTime(webrtc::TimeDelta::Seconds(1));
+  conn1->ReceivedPing();
+  conn1->OnReadPacket("ABC", 3, rtc::TimeMicros());
+  EXPECT_TRUE_SIMULATED_WAIT(ch.receiving(), kShortTimeout, clock);
+  EXPECT_TRUE_SIMULATED_WAIT(!ch.receiving(), kShortTimeout, clock);
+}
+
+// The controlled side will select a connection as the "selected connection"
+// based on priority until the controlling side nominates a connection, at which
+// point the controlled side will select that connection as the
+// "selected connection". Plus, SignalNetworkRouteChanged will be fired if the
+// selected connection changes and SignalReadyToSend will be fired if the new
+// selected connection is writable.
+TEST_P(P2PTransportChannelPingTest, TestSelectConnectionBeforeNomination) {
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("receiving state change", 1, &pa, &field_trials_);
+  PrepareChannel(&ch);
+  ch.SetIceRole(ICEROLE_CONTROLLED);
+  ch.MaybeStartGathering();
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 1));
+  Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1);
+  ASSERT_TRUE(conn1 != nullptr);
+  // Channel is not ready to send because it is not writable.
+  EXPECT_FALSE(channel_ready_to_send());
+  int last_packet_id = 0;
+  const char* data = "ABCDEFGH";
+  int len = static_cast<int>(strlen(data));
+  EXPECT_EQ(-1, SendData(&ch, data, len, ++last_packet_id));
+  EXPECT_EQ(-1, last_sent_packet_id());
+
+  // A connection needs to be writable before it is selected for transmission.
+  conn1->ReceivedPingResponse(LOW_RTT, "id");
+  EXPECT_EQ_WAIT(conn1, ch.selected_connection(), kDefaultTimeout);
+  EXPECT_TRUE(CandidatePairMatchesNetworkRoute(conn1));
+  EXPECT_TRUE(ConnectionMatchesChangeEvent(
+      conn1, "remote candidate generation maybe changed"));
+  EXPECT_EQ(len, SendData(&ch, data, len, ++last_packet_id));
+
+  // When a higher priority candidate comes in, the new connection is chosen
+  // as the selected connection.
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "2.2.2.2", 2, 10));
+  Connection* conn2 = WaitForConnectionTo(&ch, "2.2.2.2", 2);
+  ASSERT_TRUE(conn2 != nullptr);
+  conn2->ReceivedPingResponse(LOW_RTT, "id");
+  EXPECT_EQ_WAIT(conn2, ch.selected_connection(), kDefaultTimeout);
+  EXPECT_TRUE(CandidatePairMatchesNetworkRoute(conn2));
+  EXPECT_TRUE(
+      ConnectionMatchesChangeEvent(conn2, "candidate pair state changed"));
+  EXPECT_TRUE(channel_ready_to_send());
+  EXPECT_EQ(last_packet_id, last_sent_packet_id());
+
+  // If a stun request with use-candidate attribute arrives, the receiving
+  // connection will be set as the selected connection, even though
+  // its priority is lower.
+  EXPECT_EQ(len, SendData(&ch, data, len, ++last_packet_id));
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "3.3.3.3", 3, 1));
+  Connection* conn3 = WaitForConnectionTo(&ch, "3.3.3.3", 3);
+  ASSERT_TRUE(conn3 != nullptr);
+  // Because it has a lower priority, the selected connection is still conn2.
+  EXPECT_EQ(conn2, ch.selected_connection());
+  conn3->ReceivedPingResponse(LOW_RTT, "id");  // Become writable.
+  // But if it is nominated via use_candidate, it is chosen as the selected
+  // connection.
+  NominateConnection(conn3);
+  ASSERT_EQ(conn3, ch.selected_connection());
+
+  EXPECT_TRUE(CandidatePairMatchesNetworkRoute(conn3));
+  EXPECT_TRUE(
+      ConnectionMatchesChangeEvent(conn3, "nomination on the controlled side"));
+  EXPECT_EQ(last_packet_id, last_sent_packet_id());
+  EXPECT_TRUE(channel_ready_to_send());
+
+  // Even if another higher priority candidate arrives, it will not be set as
+  // the selected connection because the selected connection is nominated by
+  // the controlling side.
+  EXPECT_EQ(len, SendData(&ch, data, len, ++last_packet_id));
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "4.4.4.4", 4, 100));
+  Connection* conn4 = WaitForConnectionTo(&ch, "4.4.4.4", 4);
+  ASSERT_TRUE(conn4 != nullptr);
+  EXPECT_EQ(conn3, ch.selected_connection());
+  // But if it is nominated via use_candidate and writable, it will be set as
+  // the selected connection.
+  NominateConnection(conn4);
+  // Not switched yet because conn4 is not writable.
+  EXPECT_EQ(conn3, ch.selected_connection());
+  reset_channel_ready_to_send();
+  // The selected connection switches after conn4 becomes writable.
+  conn4->ReceivedPingResponse(LOW_RTT, "id");
+  EXPECT_EQ_WAIT(conn4, ch.selected_connection(), kDefaultTimeout);
+  EXPECT_TRUE(CandidatePairMatchesNetworkRoute(conn4));
+  EXPECT_TRUE(
+      ConnectionMatchesChangeEvent(conn4, "candidate pair state changed"));
+  EXPECT_EQ(last_packet_id, last_sent_packet_id());
+  // SignalReadyToSend is fired again because conn4 is writable.
+  EXPECT_TRUE(channel_ready_to_send());
+}
+
+// Test the field trial send_ping_on_nomination_ice_controlled
+// that sends a ping directly when a connection has been nominated
+// i.e on the ICE_CONTROLLED-side.
+TEST_P(P2PTransportChannelPingTest, TestPingOnNomination) {
+  webrtc::test::ScopedKeyValueConfig field_trials(
+      field_trials_,
+      "WebRTC-IceFieldTrials/send_ping_on_nomination_ice_controlled:true/");
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("receiving state change", 1, &pa, &field_trials);
+  PrepareChannel(&ch);
+  ch.SetIceConfig(ch.config());
+  ch.SetIceRole(ICEROLE_CONTROLLED);
+  ch.MaybeStartGathering();
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 1));
+  Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1);
+  ASSERT_TRUE(conn1 != nullptr);
+
+  // A connection needs to be writable before it is selected for transmission.
+  conn1->ReceivedPingResponse(LOW_RTT, "id");
+  EXPECT_EQ_WAIT(conn1, ch.selected_connection(), kDefaultTimeout);
+  EXPECT_TRUE(CandidatePairMatchesNetworkRoute(conn1));
+
+  // When a higher priority candidate comes in, the new connection is chosen
+  // as the selected connection.
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "2.2.2.2", 2, 10));
+  Connection* conn2 = WaitForConnectionTo(&ch, "2.2.2.2", 2);
+  ASSERT_TRUE(conn2 != nullptr);
+  conn2->ReceivedPingResponse(LOW_RTT, "id");
+  EXPECT_EQ_WAIT(conn2, ch.selected_connection(), kDefaultTimeout);
+  EXPECT_TRUE(CandidatePairMatchesNetworkRoute(conn2));
+
+  // Now nominate conn1 (low prio), it shall be choosen.
+  const int before = conn1->num_pings_sent();
+  NominateConnection(conn1);
+  ASSERT_EQ(conn1, ch.selected_connection());
+  EXPECT_TRUE(CandidatePairMatchesNetworkRoute(conn1));
+
+  // And the additional ping should have been sent directly.
+  EXPECT_EQ(conn1->num_pings_sent(), before + 1);
+}
+
+// Test the field trial send_ping_on_switch_ice_controlling
+// that sends a ping directly when switching to a new connection
+// on the ICE_CONTROLLING-side.
+TEST_P(P2PTransportChannelPingTest, TestPingOnSwitch) {
+  webrtc::test::ScopedKeyValueConfig field_trials(
+      field_trials_,
+      "WebRTC-IceFieldTrials/send_ping_on_switch_ice_controlling:true/");
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("receiving state change", 1, &pa, &field_trials);
+  PrepareChannel(&ch);
+  ch.SetIceConfig(ch.config());
+  ch.SetIceRole(ICEROLE_CONTROLLING);
+  ch.MaybeStartGathering();
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 1));
+  Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1);
+  ASSERT_TRUE(conn1 != nullptr);
+
+  // A connection needs to be writable before it is selected for transmission.
+  conn1->ReceivedPingResponse(LOW_RTT, "id");
+  EXPECT_EQ_WAIT(conn1, ch.selected_connection(), kDefaultTimeout);
+  EXPECT_TRUE(CandidatePairMatchesNetworkRoute(conn1));
+
+  // When a higher priority candidate comes in, the new connection is chosen
+  // as the selected connection.
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "2.2.2.2", 2, 10));
+  Connection* conn2 = WaitForConnectionTo(&ch, "2.2.2.2", 2);
+  ASSERT_TRUE(conn2 != nullptr);
+
+  const int before = conn2->num_pings_sent();
+
+  conn2->ReceivedPingResponse(LOW_RTT, "id");
+  EXPECT_EQ_WAIT(conn2, ch.selected_connection(), kDefaultTimeout);
+  EXPECT_TRUE(CandidatePairMatchesNetworkRoute(conn2));
+
+  // And the additional ping should have been sent directly.
+  EXPECT_EQ(conn2->num_pings_sent(), before + 1);
+}
+
+// Test the field trial send_ping_on_switch_ice_controlling
+// that sends a ping directly when selecteing a new connection
+// on the ICE_CONTROLLING-side (i.e also initial selection).
+TEST_P(P2PTransportChannelPingTest, TestPingOnSelected) {
+  webrtc::test::ScopedKeyValueConfig field_trials(
+      field_trials_,
+      "WebRTC-IceFieldTrials/send_ping_on_selected_ice_controlling:true/");
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("receiving state change", 1, &pa, &field_trials);
+  PrepareChannel(&ch);
+  ch.SetIceConfig(ch.config());
+  ch.SetIceRole(ICEROLE_CONTROLLING);
+  ch.MaybeStartGathering();
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 1));
+  Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1);
+  ASSERT_TRUE(conn1 != nullptr);
+
+  const int before = conn1->num_pings_sent();
+
+  // A connection needs to be writable before it is selected for transmission.
+  conn1->ReceivedPingResponse(LOW_RTT, "id");
+  EXPECT_EQ_WAIT(conn1, ch.selected_connection(), kDefaultTimeout);
+  EXPECT_TRUE(CandidatePairMatchesNetworkRoute(conn1));
+
+  // And the additional ping should have been sent directly.
+  EXPECT_EQ(conn1->num_pings_sent(), before + 1);
+}
+
+// The controlled side will select a connection as the "selected connection"
+// based on requests from an unknown address before the controlling side
+// nominates a connection, and will nominate a connection from an unknown
+// address if the request contains the use_candidate attribute. Plus, it will
+// also sends back a ping response and set the ICE pwd in the remote candidate
+// appropriately.
+TEST_P(P2PTransportChannelPingTest, TestSelectConnectionFromUnknownAddress) {
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("receiving state change", 1, &pa, &field_trials_);
+  PrepareChannel(&ch);
+  ch.SetIceRole(ICEROLE_CONTROLLED);
+  ch.MaybeStartGathering();
+  // A minimal STUN message with prflx priority.
+  IceMessage request(STUN_BINDING_REQUEST);
+  request.AddAttribute(std::make_unique<StunByteStringAttribute>(
+      STUN_ATTR_USERNAME, kIceUfrag[1]));
+  uint32_t prflx_priority = ICE_TYPE_PREFERENCE_PRFLX << 24;
+  request.AddAttribute(std::make_unique<StunUInt32Attribute>(STUN_ATTR_PRIORITY,
+                                                             prflx_priority));
+  TestUDPPort* port = static_cast<TestUDPPort*>(GetPort(&ch));
+  port->SignalUnknownAddress(port, rtc::SocketAddress("1.1.1.1", 1), PROTO_UDP,
+                             &request, kIceUfrag[1], false);
+  Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1);
+  ASSERT_TRUE(conn1 != nullptr);
+  EXPECT_EQ(conn1->stats().sent_ping_responses, 1u);
+  EXPECT_NE(conn1, ch.selected_connection());
+  conn1->ReceivedPingResponse(LOW_RTT, "id");
+  EXPECT_EQ_WAIT(conn1, ch.selected_connection(), kDefaultTimeout);
+
+  // Another connection is nominated via use_candidate.
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "2.2.2.2", 2, 1));
+  Connection* conn2 = WaitForConnectionTo(&ch, "2.2.2.2", 2);
+  ASSERT_TRUE(conn2 != nullptr);
+  // Because it has a lower priority, the selected connection is still conn1.
+  EXPECT_EQ(conn1, ch.selected_connection());
+  // When it is nominated via use_candidate and writable, it is chosen as the
+  // selected connection.
+  conn2->ReceivedPingResponse(LOW_RTT, "id");  // Become writable.
+  NominateConnection(conn2);
+  EXPECT_EQ(conn2, ch.selected_connection());
+
+  // Another request with unknown address, it will not be set as the selected
+  // connection because the selected connection was nominated by the controlling
+  // side.
+  port->SignalUnknownAddress(port, rtc::SocketAddress("3.3.3.3", 3), PROTO_UDP,
+                             &request, kIceUfrag[1], false);
+  Connection* conn3 = WaitForConnectionTo(&ch, "3.3.3.3", 3);
+  ASSERT_TRUE(conn3 != nullptr);
+  EXPECT_EQ(conn3->stats().sent_ping_responses, 1u);
+  conn3->ReceivedPingResponse(LOW_RTT, "id");  // Become writable.
+  EXPECT_EQ(conn2, ch.selected_connection());
+
+  // However if the request contains use_candidate attribute, it will be
+  // selected as the selected connection.
+  request.AddAttribute(
+      std::make_unique<StunByteStringAttribute>(STUN_ATTR_USE_CANDIDATE));
+  port->SignalUnknownAddress(port, rtc::SocketAddress("4.4.4.4", 4), PROTO_UDP,
+                             &request, kIceUfrag[1], false);
+  Connection* conn4 = WaitForConnectionTo(&ch, "4.4.4.4", 4);
+  ASSERT_TRUE(conn4 != nullptr);
+  EXPECT_EQ(conn4->stats().sent_ping_responses, 1u);
+  // conn4 is not the selected connection yet because it is not writable.
+  EXPECT_EQ(conn2, ch.selected_connection());
+  conn4->ReceivedPingResponse(LOW_RTT, "id");  // Become writable.
+  EXPECT_EQ_WAIT(conn4, ch.selected_connection(), kDefaultTimeout);
+
+  // Test that the request from an unknown address contains a ufrag from an old
+  // generation.
+  // port->set_sent_binding_response(false);
+  ch.SetRemoteIceParameters(kIceParams[2]);
+  ch.SetRemoteIceParameters(kIceParams[3]);
+  port->SignalUnknownAddress(port, rtc::SocketAddress("5.5.5.5", 5), PROTO_UDP,
+                             &request, kIceUfrag[2], false);
+  Connection* conn5 = WaitForConnectionTo(&ch, "5.5.5.5", 5);
+  ASSERT_TRUE(conn5 != nullptr);
+  EXPECT_EQ(conn5->stats().sent_ping_responses, 1u);
+  EXPECT_EQ(kIcePwd[2], conn5->remote_candidate().password());
+}
+
+// The controlled side will select a connection as the "selected connection"
+// based on media received until the controlling side nominates a connection,
+// at which point the controlled side will select that connection as
+// the "selected connection".
+TEST_P(P2PTransportChannelPingTest, TestSelectConnectionBasedOnMediaReceived) {
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("receiving state change", 1, &pa, &field_trials_);
+  PrepareChannel(&ch);
+  ch.SetIceRole(ICEROLE_CONTROLLED);
+  ch.MaybeStartGathering();
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 10));
+  Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1);
+  ASSERT_TRUE(conn1 != nullptr);
+  conn1->ReceivedPingResponse(LOW_RTT, "id");
+  EXPECT_EQ_WAIT(conn1, ch.selected_connection(), kDefaultTimeout);
+
+  // If a data packet is received on conn2, the selected connection should
+  // switch to conn2 because the controlled side must mirror the media path
+  // chosen by the controlling side.
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "2.2.2.2", 2, 1));
+  Connection* conn2 = WaitForConnectionTo(&ch, "2.2.2.2", 2);
+  ASSERT_TRUE(conn2 != nullptr);
+  conn2->ReceivedPingResponse(LOW_RTT, "id");  // Become writable and receiving.
+  conn2->OnReadPacket("ABC", 3, rtc::TimeMicros());
+  EXPECT_EQ(conn2, ch.selected_connection());
+  conn2->ReceivedPingResponse(LOW_RTT, "id");  // Become writable.
+
+  // Now another STUN message with an unknown address and use_candidate will
+  // nominate the selected connection.
+  IceMessage request(STUN_BINDING_REQUEST);
+  request.AddAttribute(std::make_unique<StunByteStringAttribute>(
+      STUN_ATTR_USERNAME, kIceUfrag[1]));
+  uint32_t prflx_priority = ICE_TYPE_PREFERENCE_PRFLX << 24;
+  request.AddAttribute(std::make_unique<StunUInt32Attribute>(STUN_ATTR_PRIORITY,
+                                                             prflx_priority));
+  request.AddAttribute(
+      std::make_unique<StunByteStringAttribute>(STUN_ATTR_USE_CANDIDATE));
+  Port* port = GetPort(&ch);
+  port->SignalUnknownAddress(port, rtc::SocketAddress("3.3.3.3", 3), PROTO_UDP,
+                             &request, kIceUfrag[1], false);
+  Connection* conn3 = WaitForConnectionTo(&ch, "3.3.3.3", 3);
+  ASSERT_TRUE(conn3 != nullptr);
+  EXPECT_NE(conn3, ch.selected_connection());  // Not writable yet.
+  conn3->ReceivedPingResponse(LOW_RTT, "id");  // Become writable.
+  EXPECT_EQ_WAIT(conn3, ch.selected_connection(), kDefaultTimeout);
+
+  // Now another data packet will not switch the selected connection because the
+  // selected connection was nominated by the controlling side.
+  conn2->ReceivedPing();
+  conn2->ReceivedPingResponse(LOW_RTT, "id");
+  conn2->OnReadPacket("XYZ", 3, rtc::TimeMicros());
+  EXPECT_EQ_WAIT(conn3, ch.selected_connection(), kDefaultTimeout);
+}
+
+TEST_P(P2PTransportChannelPingTest,
+       TestControlledAgentDataReceivingTakesHigherPrecedenceThanPriority) {
+  rtc::ScopedFakeClock clock;
+  clock.AdvanceTime(webrtc::TimeDelta::Seconds(1));
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("SwitchSelectedConnection", 1, &pa, &field_trials_);
+  PrepareChannel(&ch);
+  ch.SetIceRole(ICEROLE_CONTROLLED);
+  ch.MaybeStartGathering();
+  // The connections have decreasing priority.
+  Connection* conn1 =
+      CreateConnectionWithCandidate(&ch, &clock, "1.1.1.1", 1, 10, true);
+  ASSERT_TRUE(conn1 != nullptr);
+  Connection* conn2 =
+      CreateConnectionWithCandidate(&ch, &clock, "2.2.2.2", 2, 9, true);
+  ASSERT_TRUE(conn2 != nullptr);
+
+  // Initially, connections are selected based on priority.
+  EXPECT_EQ(1, reset_selected_candidate_pair_switches());
+  EXPECT_TRUE(CandidatePairMatchesNetworkRoute(conn1));
+
+  // conn2 receives data; it becomes selected.
+  // Advance the clock by 1ms so that the last data receiving timestamp of
+  // conn2 is larger.
+  SIMULATED_WAIT(false, 1, clock);
+  conn2->OnReadPacket("XYZ", 3, rtc::TimeMicros());
+  EXPECT_EQ(1, reset_selected_candidate_pair_switches());
+  EXPECT_TRUE(CandidatePairMatchesNetworkRoute(conn2));
+
+  // conn1 also receives data; it becomes selected due to priority again.
+  conn1->OnReadPacket("XYZ", 3, rtc::TimeMicros());
+  EXPECT_EQ(1, reset_selected_candidate_pair_switches());
+  EXPECT_TRUE(CandidatePairMatchesNetworkRoute(conn2));
+
+  // conn2 received data more recently; it is selected now because it
+  // received data more recently.
+  SIMULATED_WAIT(false, 1, clock);
+  // Need to become writable again because it was pruned.
+  conn2->ReceivedPingResponse(LOW_RTT, "id");
+  conn2->OnReadPacket("XYZ", 3, rtc::TimeMicros());
+  EXPECT_EQ(1, reset_selected_candidate_pair_switches());
+  EXPECT_TRUE(CandidatePairMatchesNetworkRoute(conn2));
+
+  // Make sure sorting won't reselect candidate pair.
+  SIMULATED_WAIT(false, 10, clock);
+  EXPECT_EQ(0, reset_selected_candidate_pair_switches());
+}
+
+TEST_P(P2PTransportChannelPingTest,
+       TestControlledAgentNominationTakesHigherPrecedenceThanDataReceiving) {
+  rtc::ScopedFakeClock clock;
+  clock.AdvanceTime(webrtc::TimeDelta::Seconds(1));
+
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("SwitchSelectedConnection", 1, &pa, &field_trials_);
+  PrepareChannel(&ch);
+  ch.SetIceRole(ICEROLE_CONTROLLED);
+  ch.MaybeStartGathering();
+  // The connections have decreasing priority.
+  Connection* conn1 =
+      CreateConnectionWithCandidate(&ch, &clock, "1.1.1.1", 1, 10, true);
+  ASSERT_TRUE(conn1 != nullptr);
+  Connection* conn2 =
+      CreateConnectionWithCandidate(&ch, &clock, "2.2.2.2", 2, 9, true);
+  ASSERT_TRUE(conn2 != nullptr);
+
+  // conn1 received data; it is the selected connection.
+  // Advance the clock to have a non-zero last-data-receiving time.
+  SIMULATED_WAIT(false, 1, clock);
+  conn1->OnReadPacket("XYZ", 3, rtc::TimeMicros());
+  EXPECT_EQ(1, reset_selected_candidate_pair_switches());
+  EXPECT_TRUE(CandidatePairMatchesNetworkRoute(conn1));
+
+  // conn2 is nominated; it becomes the selected connection.
+  NominateConnection(conn2);
+  EXPECT_EQ(1, reset_selected_candidate_pair_switches());
+  EXPECT_TRUE(CandidatePairMatchesNetworkRoute(conn2));
+
+  // conn1 is selected because it has higher priority and also nominated.
+  NominateConnection(conn1);
+  EXPECT_EQ(1, reset_selected_candidate_pair_switches());
+  EXPECT_TRUE(CandidatePairMatchesNetworkRoute(conn2));
+
+  // Make sure sorting won't reselect candidate pair.
+  SIMULATED_WAIT(false, 10, clock);
+  EXPECT_EQ(0, reset_selected_candidate_pair_switches());
+}
+
+TEST_P(P2PTransportChannelPingTest,
+       TestControlledAgentSelectsConnectionWithHigherNomination) {
+  rtc::ScopedFakeClock clock;
+  clock.AdvanceTime(webrtc::TimeDelta::Seconds(1));
+
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("test", 1, &pa, &field_trials_);
+  PrepareChannel(&ch);
+  ch.SetIceRole(ICEROLE_CONTROLLED);
+  ch.MaybeStartGathering();
+  // The connections have decreasing priority.
+  Connection* conn1 =
+      CreateConnectionWithCandidate(&ch, &clock, "1.1.1.1", 1, 10, true);
+  ASSERT_TRUE(conn1 != nullptr);
+  Connection* conn2 =
+      CreateConnectionWithCandidate(&ch, &clock, "2.2.2.2", 2, 9, true);
+  ASSERT_TRUE(conn2 != nullptr);
+
+  // conn1 is the selected connection because it has a higher priority,
+  EXPECT_EQ_SIMULATED_WAIT(conn1, ch.selected_connection(), kDefaultTimeout,
+                           clock);
+  EXPECT_TRUE(CandidatePairMatchesNetworkRoute(conn1));
+  reset_selected_candidate_pair_switches();
+
+  // conn2 is nominated; it becomes selected.
+  NominateConnection(conn2);
+  EXPECT_EQ(1, reset_selected_candidate_pair_switches());
+  EXPECT_EQ(conn2, ch.selected_connection());
+  EXPECT_TRUE(CandidatePairMatchesNetworkRoute(conn2));
+
+  // conn1 is selected because of its priority.
+  NominateConnection(conn1);
+  EXPECT_EQ(1, reset_selected_candidate_pair_switches());
+  EXPECT_EQ(conn1, ch.selected_connection());
+  EXPECT_TRUE(CandidatePairMatchesNetworkRoute(conn1));
+
+  // conn2 gets higher remote nomination; it is selected again.
+  NominateConnection(conn2, 2U);
+  EXPECT_EQ(1, reset_selected_candidate_pair_switches());
+  EXPECT_EQ(conn2, ch.selected_connection());
+  EXPECT_TRUE(CandidatePairMatchesNetworkRoute(conn2));
+
+  // Make sure sorting won't reselect candidate pair.
+  SIMULATED_WAIT(false, 100, clock);
+  EXPECT_EQ(0, reset_selected_candidate_pair_switches());
+}
+
+TEST_P(P2PTransportChannelPingTest, TestEstimatedDisconnectedTime) {
+  rtc::ScopedFakeClock clock;
+  clock.AdvanceTime(webrtc::TimeDelta::Seconds(1));
+
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("test", 1, &pa, &field_trials_);
+  PrepareChannel(&ch);
+  ch.SetIceRole(ICEROLE_CONTROLLED);
+  ch.MaybeStartGathering();
+  // The connections have decreasing priority.
+  Connection* conn1 =
+      CreateConnectionWithCandidate(&ch, &clock, "1.1.1.1", /* port= */ 1,
+                                    /* priority= */ 10, /* writable= */ true);
+  ASSERT_TRUE(conn1 != nullptr);
+  Connection* conn2 =
+      CreateConnectionWithCandidate(&ch, &clock, "2.2.2.2", /* port= */ 2,
+                                    /* priority= */ 9, /* writable= */ true);
+  ASSERT_TRUE(conn2 != nullptr);
+
+  // conn1 is the selected connection because it has a higher priority,
+  EXPECT_EQ_SIMULATED_WAIT(conn1, ch.selected_connection(), kDefaultTimeout,
+                           clock);
+  EXPECT_TRUE(CandidatePairMatchesNetworkRoute(conn1));
+  // No estimateded disconnect time at first connect <=> value is 0.
+  EXPECT_EQ(LastEstimatedDisconnectedTimeMs(), 0);
+
+  // Use nomination to force switching of selected connection.
+  int nomination = 1;
+
+  {
+    clock.AdvanceTime(webrtc::TimeDelta::Seconds(1));
+    // This will not parse as STUN, and is considered data
+    conn1->OnReadPacket("XYZ", 3, rtc::TimeMicros());
+    clock.AdvanceTime(webrtc::TimeDelta::Seconds(2));
+
+    // conn2 is nominated; it becomes selected.
+    NominateConnection(conn2, nomination++);
+    EXPECT_EQ(conn2, ch.selected_connection());
+    // We got data 2s ago...guess that we lost 2s of connectivity.
+    EXPECT_EQ(LastEstimatedDisconnectedTimeMs(), 2000);
+  }
+
+  {
+    clock.AdvanceTime(webrtc::TimeDelta::Seconds(1));
+    conn2->OnReadPacket("XYZ", 3, rtc::TimeMicros());
+
+    clock.AdvanceTime(webrtc::TimeDelta::Seconds(2));
+    ReceivePingOnConnection(conn2, kIceUfrag[1], 1, nomination++);
+
+    clock.AdvanceTime(webrtc::TimeDelta::Millis(500));
+
+    ReceivePingOnConnection(conn1, kIceUfrag[1], 1, nomination++);
+    EXPECT_EQ(conn1, ch.selected_connection());
+    // We got ping 500ms ago...guess that we lost 500ms of connectivity.
+    EXPECT_EQ(LastEstimatedDisconnectedTimeMs(), 500);
+  }
+}
+
+TEST_P(P2PTransportChannelPingTest,
+       TestControlledAgentIgnoresSmallerNomination) {
+  rtc::ScopedFakeClock clock;
+  clock.AdvanceTime(webrtc::TimeDelta::Seconds(1));
+
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("test", 1, &pa, &field_trials_);
+  PrepareChannel(&ch);
+  ch.SetIceRole(ICEROLE_CONTROLLED);
+  ch.MaybeStartGathering();
+  Connection* conn =
+      CreateConnectionWithCandidate(&ch, &clock, "1.1.1.1", 1, 10, false);
+  ReceivePingOnConnection(conn, kIceUfrag[1], 1, 2U);
+  EXPECT_EQ(2U, conn->remote_nomination());
+  // Smaller nomination is ignored.
+  ReceivePingOnConnection(conn, kIceUfrag[1], 1, 1U);
+  EXPECT_EQ(2U, conn->remote_nomination());
+}
+
+TEST_P(P2PTransportChannelPingTest,
+       TestControlledAgentWriteStateTakesHigherPrecedenceThanNomination) {
+  rtc::ScopedFakeClock clock;
+
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("SwitchSelectedConnection", 1, &pa, &field_trials_);
+  PrepareChannel(&ch);
+  ch.SetIceRole(ICEROLE_CONTROLLED);
+  ch.MaybeStartGathering();
+  // The connections have decreasing priority.
+  Connection* conn1 =
+      CreateConnectionWithCandidate(&ch, &clock, "1.1.1.1", 1, 10, false);
+  ASSERT_TRUE(conn1 != nullptr);
+  Connection* conn2 =
+      CreateConnectionWithCandidate(&ch, &clock, "2.2.2.2", 2, 9, false);
+  ASSERT_TRUE(conn2 != nullptr);
+
+  NominateConnection(conn1);
+  // There is no selected connection because no connection is writable.
+  EXPECT_EQ(0, reset_selected_candidate_pair_switches());
+
+  // conn2 becomes writable; it is selected even though it is not nominated.
+  conn2->ReceivedPingResponse(LOW_RTT, "id");
+  EXPECT_EQ_SIMULATED_WAIT(1, reset_selected_candidate_pair_switches(),
+                           kDefaultTimeout, clock);
+  EXPECT_EQ_SIMULATED_WAIT(conn2, ch.selected_connection(), kDefaultTimeout,
+                           clock);
+  EXPECT_TRUE(CandidatePairMatchesNetworkRoute(conn2));
+
+  // If conn1 is also writable, it will become selected.
+  conn1->ReceivedPingResponse(LOW_RTT, "id");
+  EXPECT_EQ_SIMULATED_WAIT(1, reset_selected_candidate_pair_switches(),
+                           kDefaultTimeout, clock);
+  EXPECT_EQ_SIMULATED_WAIT(conn1, ch.selected_connection(), kDefaultTimeout,
+                           clock);
+  EXPECT_TRUE(CandidatePairMatchesNetworkRoute(conn1));
+
+  // Make sure sorting won't reselect candidate pair.
+  SIMULATED_WAIT(false, 10, clock);
+  EXPECT_EQ(0, reset_selected_candidate_pair_switches());
+}
+
+// Test that if a new remote candidate has the same address and port with
+// an old one, it will be used to create a new connection.
+TEST_P(P2PTransportChannelPingTest, TestAddRemoteCandidateWithAddressReuse) {
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("candidate reuse", 1, &pa, &field_trials_);
+  PrepareChannel(&ch);
+  ch.MaybeStartGathering();
+  const std::string host_address = "1.1.1.1";
+  const int port_num = 1;
+
+  // kIceUfrag[1] is the current generation ufrag.
+  Candidate candidate = CreateUdpCandidate(LOCAL_PORT_TYPE, host_address,
+                                           port_num, 1, kIceUfrag[1]);
+  ch.AddRemoteCandidate(candidate);
+  Connection* conn1 = WaitForConnectionTo(&ch, host_address, port_num);
+  ASSERT_TRUE(conn1 != nullptr);
+  EXPECT_EQ(0u, conn1->remote_candidate().generation());
+
+  // Simply adding the same candidate again won't create a new connection.
+  ch.AddRemoteCandidate(candidate);
+  Connection* conn2 = GetConnectionTo(&ch, host_address, port_num);
+  EXPECT_EQ(conn1, conn2);
+
+  // Update the ufrag of the candidate and add it again.
+  candidate.set_username(kIceUfrag[2]);
+  ch.AddRemoteCandidate(candidate);
+  conn2 = GetConnectionTo(&ch, host_address, port_num);
+  EXPECT_NE(conn1, conn2);
+  EXPECT_EQ(kIceUfrag[2], conn2->remote_candidate().username());
+  EXPECT_EQ(1u, conn2->remote_candidate().generation());
+
+  // Verify that a ping with the new ufrag can be received on the new
+  // connection.
+  EXPECT_EQ(0, conn2->last_ping_received());
+  ReceivePingOnConnection(conn2, kIceUfrag[2], 1 /* priority */);
+  EXPECT_GT(conn2->last_ping_received(), 0);
+}
+
+// When the current selected connection is strong, lower-priority connections
+// will be pruned. Otherwise, lower-priority connections are kept.
+TEST_P(P2PTransportChannelPingTest, TestDontPruneWhenWeak) {
+  rtc::ScopedFakeClock clock;
+  clock.AdvanceTime(webrtc::TimeDelta::Seconds(1));
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("test channel", 1, &pa, &field_trials_);
+  PrepareChannel(&ch);
+  ch.SetIceRole(ICEROLE_CONTROLLED);
+  ch.MaybeStartGathering();
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 1));
+  Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1);
+  ASSERT_TRUE(conn1 != nullptr);
+  EXPECT_EQ(nullptr, ch.selected_connection());
+  conn1->ReceivedPingResponse(LOW_RTT, "id");  // Becomes writable and receiving
+
+  // When a higher-priority, nominated candidate comes in, the connections with
+  // lower-priority are pruned.
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "2.2.2.2", 2, 10));
+  Connection* conn2 = WaitForConnectionTo(&ch, "2.2.2.2", 2, &clock);
+  ASSERT_TRUE(conn2 != nullptr);
+  conn2->ReceivedPingResponse(LOW_RTT, "id");  // Becomes writable and receiving
+  NominateConnection(conn2);
+  EXPECT_TRUE_SIMULATED_WAIT(conn1->pruned(), kMediumTimeout, clock);
+
+  ch.SetIceConfig(CreateIceConfig(500, GATHER_ONCE));
+  // Wait until conn2 becomes not receiving.
+  EXPECT_TRUE_SIMULATED_WAIT(!conn2->receiving(), kMediumTimeout, clock);
+
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "3.3.3.3", 3, 1));
+  Connection* conn3 = WaitForConnectionTo(&ch, "3.3.3.3", 3, &clock);
+  ASSERT_TRUE(conn3 != nullptr);
+  // The selected connection should still be conn2. Even through conn3 has lower
+  // priority and is not receiving/writable, it is not pruned because the
+  // selected connection is not receiving.
+  SIMULATED_WAIT(conn3->pruned(), kShortTimeout, clock);
+  EXPECT_FALSE(conn3->pruned());
+}
+
+TEST_P(P2PTransportChannelPingTest, TestDontPruneHighPriorityConnections) {
+  rtc::ScopedFakeClock clock;
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("test channel", 1, &pa, &field_trials_);
+  PrepareChannel(&ch);
+  ch.SetIceRole(ICEROLE_CONTROLLED);
+  ch.MaybeStartGathering();
+  Connection* conn1 =
+      CreateConnectionWithCandidate(&ch, &clock, "1.1.1.1", 1, 100, true);
+  ASSERT_TRUE(conn1 != nullptr);
+  Connection* conn2 =
+      CreateConnectionWithCandidate(&ch, &clock, "2.2.2.2", 2, 200, false);
+  ASSERT_TRUE(conn2 != nullptr);
+  // Even if conn1 is writable, nominated, receiving data, it should not prune
+  // conn2.
+  NominateConnection(conn1);
+  SIMULATED_WAIT(false, 1, clock);
+  conn1->OnReadPacket("XYZ", 3, rtc::TimeMicros());
+  SIMULATED_WAIT(conn2->pruned(), 100, clock);
+  EXPECT_FALSE(conn2->pruned());
+}
+
+// Test that GetState returns the state correctly.
+TEST_P(P2PTransportChannelPingTest, TestGetState) {
+  rtc::ScopedFakeClock clock;
+  clock.AdvanceTime(webrtc::TimeDelta::Seconds(1));
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("test channel", 1, &pa, &field_trials_);
+  EXPECT_EQ(webrtc::IceTransportState::kNew, ch.GetIceTransportState());
+  PrepareChannel(&ch);
+  ch.MaybeStartGathering();
+  // After gathering we are still in the kNew state because we aren't checking
+  // any connections yet.
+  EXPECT_EQ(webrtc::IceTransportState::kNew, ch.GetIceTransportState());
+  EXPECT_EQ(IceTransportState::STATE_INIT, ch.GetState());
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 100));
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "2.2.2.2", 2, 1));
+  // Checking candidates that have been added with gathered candidates.
+  ASSERT_GT(ch.connections().size(), 0u);
+  EXPECT_EQ(webrtc::IceTransportState::kChecking, ch.GetIceTransportState());
+  Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1, &clock);
+  Connection* conn2 = WaitForConnectionTo(&ch, "2.2.2.2", 2, &clock);
+  ASSERT_TRUE(conn1 != nullptr);
+  ASSERT_TRUE(conn2 != nullptr);
+  // Now there are two connections, so the transport channel is connecting.
+  EXPECT_EQ(IceTransportState::STATE_CONNECTING, ch.GetState());
+  // No connections are writable yet, so we should still be in the kChecking
+  // state.
+  EXPECT_EQ(webrtc::IceTransportState::kChecking, ch.GetIceTransportState());
+  // `conn1` becomes writable and receiving; it then should prune `conn2`.
+  conn1->ReceivedPingResponse(LOW_RTT, "id");
+  EXPECT_TRUE_SIMULATED_WAIT(conn2->pruned(), kShortTimeout, clock);
+  EXPECT_EQ(IceTransportState::STATE_COMPLETED, ch.GetState());
+  EXPECT_EQ(webrtc::IceTransportState::kConnected, ch.GetIceTransportState());
+  conn1->Prune();  // All connections are pruned.
+  // Need to wait until the channel state is updated.
+  EXPECT_EQ_SIMULATED_WAIT(IceTransportState::STATE_FAILED, ch.GetState(),
+                           kShortTimeout, clock);
+  EXPECT_EQ(webrtc::IceTransportState::kFailed, ch.GetIceTransportState());
+}
+
+// Test that when a low-priority connection is pruned, it is not deleted
+// right away, and it can become active and be pruned again.
+TEST_P(P2PTransportChannelPingTest, TestConnectionPrunedAgain) {
+  rtc::ScopedFakeClock clock;
+  clock.AdvanceTime(webrtc::TimeDelta::Seconds(1));
+
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("test channel", 1, &pa, &field_trials_);
+  PrepareChannel(&ch);
+  IceConfig config = CreateIceConfig(1000, GATHER_ONCE);
+  config.receiving_switching_delay = 800;
+  ch.SetIceConfig(config);
+  ch.MaybeStartGathering();
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 100));
+  Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1, &clock);
+  ASSERT_TRUE(conn1 != nullptr);
+  EXPECT_EQ(nullptr, ch.selected_connection());
+  conn1->ReceivedPingResponse(LOW_RTT, "id");  // Becomes writable and receiving
+  EXPECT_EQ_SIMULATED_WAIT(conn1, ch.selected_connection(), kDefaultTimeout,
+                           clock);
+
+  // Add a low-priority connection `conn2`, which will be pruned, but it will
+  // not be deleted right away. Once the current selected connection becomes not
+  // receiving, `conn2` will start to ping and upon receiving the ping response,
+  // it will become the selected connection.
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "2.2.2.2", 2, 1));
+  Connection* conn2 = WaitForConnectionTo(&ch, "2.2.2.2", 2, &clock);
+  ASSERT_TRUE(conn2 != nullptr);
+  EXPECT_TRUE_SIMULATED_WAIT(!conn2->active(), kDefaultTimeout, clock);
+  // `conn2` should not send a ping yet.
+  EXPECT_EQ(IceCandidatePairState::WAITING, conn2->state());
+  EXPECT_EQ(IceTransportState::STATE_COMPLETED, ch.GetState());
+  // Wait for `conn1` becoming not receiving.
+  EXPECT_TRUE_SIMULATED_WAIT(!conn1->receiving(), kMediumTimeout, clock);
+  // Make sure conn2 is not deleted.
+  conn2 = WaitForConnectionTo(&ch, "2.2.2.2", 2, &clock);
+  ASSERT_TRUE(conn2 != nullptr);
+  EXPECT_EQ_SIMULATED_WAIT(IceCandidatePairState::IN_PROGRESS, conn2->state(),
+                           kDefaultTimeout, clock);
+  conn2->ReceivedPingResponse(LOW_RTT, "id");
+  EXPECT_EQ_SIMULATED_WAIT(conn2, ch.selected_connection(), kDefaultTimeout,
+                           clock);
+  EXPECT_EQ(IceTransportState::STATE_CONNECTING, ch.GetState());
+
+  // When `conn1` comes back again, `conn2` will be pruned again.
+  conn1->ReceivedPingResponse(LOW_RTT, "id");
+  EXPECT_EQ_SIMULATED_WAIT(conn1, ch.selected_connection(), kDefaultTimeout,
+                           clock);
+  EXPECT_TRUE_SIMULATED_WAIT(!conn2->active(), kDefaultTimeout, clock);
+  EXPECT_EQ(IceTransportState::STATE_COMPLETED, ch.GetState());
+}
+
+// Test that if all connections in a channel has timed out on writing, they
+// will all be deleted. We use Prune to simulate write_time_out.
+TEST_P(P2PTransportChannelPingTest, TestDeleteConnectionsIfAllWriteTimedout) {
+  rtc::ScopedFakeClock clock;
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("test channel", 1, &pa, &field_trials_);
+  PrepareChannel(&ch);
+  ch.MaybeStartGathering();
+  // Have one connection only but later becomes write-time-out.
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 100));
+  Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1, &clock);
+  ASSERT_TRUE(conn1 != nullptr);
+  conn1->ReceivedPing();  // Becomes receiving
+  conn1->Prune();
+  EXPECT_TRUE_SIMULATED_WAIT(ch.connections().empty(), kShortTimeout, clock);
+
+  // Have two connections but both become write-time-out later.
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "2.2.2.2", 2, 1));
+  Connection* conn2 = WaitForConnectionTo(&ch, "2.2.2.2", 2, &clock);
+  ASSERT_TRUE(conn2 != nullptr);
+  conn2->ReceivedPing();  // Becomes receiving
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "3.3.3.3", 3, 2));
+  Connection* conn3 = WaitForConnectionTo(&ch, "3.3.3.3", 3, &clock);
+  ASSERT_TRUE(conn3 != nullptr);
+  conn3->ReceivedPing();  // Becomes receiving
+  // Now prune both conn2 and conn3; they will be deleted soon.
+  conn2->Prune();
+  conn3->Prune();
+  EXPECT_TRUE_SIMULATED_WAIT(ch.connections().empty(), kShortTimeout, clock);
+}
+
+// Tests that after a port allocator session is started, it will be stopped
+// when a new connection becomes writable and receiving. Also tests that if a
+// connection belonging to an old session becomes writable, it won't stop
+// the current port allocator session.
+TEST_P(P2PTransportChannelPingTest, TestStopPortAllocatorSessions) {
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("test channel", 1, &pa, &field_trials_);
+  PrepareChannel(&ch);
+  ch.SetIceConfig(CreateIceConfig(2000, GATHER_ONCE));
+  ch.MaybeStartGathering();
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 100));
+  Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1);
+  ASSERT_TRUE(conn1 != nullptr);
+  conn1->ReceivedPingResponse(LOW_RTT, "id");  // Becomes writable and receiving
+  EXPECT_TRUE(!ch.allocator_session()->IsGettingPorts());
+
+  // Start a new session. Even though conn1, which belongs to an older
+  // session, becomes unwritable and writable again, it should not stop the
+  // current session.
+  ch.SetIceParameters(kIceParams[1]);
+  ch.MaybeStartGathering();
+  conn1->Prune();
+  conn1->ReceivedPingResponse(LOW_RTT, "id");
+  EXPECT_TRUE(ch.allocator_session()->IsGettingPorts());
+
+  // But if a new connection created from the new session becomes writable,
+  // it will stop the current session.
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "2.2.2.2", 2, 100));
+  Connection* conn2 = WaitForConnectionTo(&ch, "2.2.2.2", 2);
+  ASSERT_TRUE(conn2 != nullptr);
+  conn2->ReceivedPingResponse(LOW_RTT, "id");  // Becomes writable and receiving
+  EXPECT_TRUE(!ch.allocator_session()->IsGettingPorts());
+}
+
+// Test that the ICE role is updated even on ports that has been removed.
+// These ports may still have connections that need a correct role, in case that
+// the connections on it may still receive stun pings.
+TEST_P(P2PTransportChannelPingTest, TestIceRoleUpdatedOnRemovedPort) {
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("test channel", ICE_CANDIDATE_COMPONENT_DEFAULT, &pa,
+                         &field_trials_);
+  // Starts with ICEROLE_CONTROLLING.
+  PrepareChannel(&ch);
+  IceConfig config = CreateIceConfig(1000, GATHER_CONTINUALLY);
+  ch.SetIceConfig(config);
+  ch.MaybeStartGathering();
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 1));
+
+  Connection* conn = WaitForConnectionTo(&ch, "1.1.1.1", 1);
+  ASSERT_TRUE(conn != nullptr);
+
+  // Make a fake signal to remove the ports in the p2ptransportchannel. then
+  // change the ICE role and expect it to be updated.
+  std::vector<PortInterface*> ports(1, conn->PortForTest());
+  ch.allocator_session()->SignalPortsPruned(ch.allocator_session(), ports);
+  ch.SetIceRole(ICEROLE_CONTROLLED);
+  EXPECT_EQ(ICEROLE_CONTROLLED, conn->PortForTest()->GetIceRole());
+}
+
+// Test that the ICE role is updated even on ports with inactive networks.
+// These ports may still have connections that need a correct role, for the
+// pings sent by those connections until they're replaced by newer-generation
+// connections.
+TEST_P(P2PTransportChannelPingTest, TestIceRoleUpdatedOnPortAfterIceRestart) {
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("test channel", ICE_CANDIDATE_COMPONENT_DEFAULT, &pa,
+                         &field_trials_);
+  // Starts with ICEROLE_CONTROLLING.
+  PrepareChannel(&ch);
+  ch.MaybeStartGathering();
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 1));
+
+  Connection* conn = WaitForConnectionTo(&ch, "1.1.1.1", 1);
+  ASSERT_TRUE(conn != nullptr);
+
+  // Do an ICE restart, change the role, and expect the old port to have its
+  // role updated.
+  ch.SetIceParameters(kIceParams[1]);
+  ch.MaybeStartGathering();
+  ch.SetIceRole(ICEROLE_CONTROLLED);
+  EXPECT_EQ(ICEROLE_CONTROLLED, conn->PortForTest()->GetIceRole());
+}
+
+// Test that after some amount of time without receiving data, the connection
+// will be destroyed. The port will only be destroyed after it is marked as
+// "pruned."
+TEST_P(P2PTransportChannelPingTest, TestPortDestroyedAfterTimeoutAndPruned) {
+  rtc::ScopedFakeClock fake_clock;
+
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("test channel", ICE_CANDIDATE_COMPONENT_DEFAULT, &pa,
+                         &field_trials_);
+  PrepareChannel(&ch);
+  ch.SetIceRole(ICEROLE_CONTROLLED);
+  ch.MaybeStartGathering();
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 1));
+
+  Connection* conn = WaitForConnectionTo(&ch, "1.1.1.1", 1);
+  ASSERT_TRUE(conn != nullptr);
+
+  // Simulate 2 minutes going by. This should be enough time for the port to
+  // time out.
+  for (int second = 0; second < 120; ++second) {
+    fake_clock.AdvanceTime(webrtc::TimeDelta::Seconds(1));
+  }
+  EXPECT_EQ(nullptr, GetConnectionTo(&ch, "1.1.1.1", 1));
+  // Port will not be removed because it is not pruned yet.
+  PortInterface* port = GetPort(&ch);
+  ASSERT_NE(nullptr, port);
+
+  // If the session prunes all ports, the port will be destroyed.
+  ch.allocator_session()->PruneAllPorts();
+  EXPECT_EQ_SIMULATED_WAIT(nullptr, GetPort(&ch), 1, fake_clock);
+  EXPECT_EQ_SIMULATED_WAIT(nullptr, GetPrunedPort(&ch), 1, fake_clock);
+}
+
+TEST_P(P2PTransportChannelPingTest, TestMaxOutstandingPingsFieldTrial) {
+  webrtc::test::ScopedKeyValueConfig field_trials(
+      field_trials_, "WebRTC-IceFieldTrials/max_outstanding_pings:3/");
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("max", 1, &pa, &field_trials);
+  ch.SetIceConfig(ch.config());
+  PrepareChannel(&ch);
+  ch.MaybeStartGathering();
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 1));
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "2.2.2.2", 2, 2));
+
+  Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1);
+  Connection* conn2 = WaitForConnectionTo(&ch, "2.2.2.2", 2);
+  ASSERT_TRUE(conn1 != nullptr);
+  ASSERT_TRUE(conn2 != nullptr);
+
+  EXPECT_TRUE_WAIT(conn1->num_pings_sent() == 3 && conn2->num_pings_sent() == 3,
+                   kDefaultTimeout);
+
+  // Check that these connections don't send any more pings.
+  EXPECT_EQ(nullptr, ch.FindNextPingableConnection());
+}
+
+class P2PTransportChannelMostLikelyToWorkFirstTest
+    : public P2PTransportChannelPingTest {
+ public:
+  P2PTransportChannelMostLikelyToWorkFirstTest()
+      : turn_server_(rtc::Thread::Current(),
+                     ss(),
+                     kTurnUdpIntAddr,
+                     kTurnUdpExtAddr) {
+    network_manager_.AddInterface(kPublicAddrs[0]);
+    allocator_.reset(
+        CreateBasicPortAllocator(&network_manager_, ss(), ServerAddresses(),
+                                 kTurnUdpIntAddr, rtc::SocketAddress()));
+    allocator_->set_flags(allocator_->flags() | PORTALLOCATOR_DISABLE_STUN |
+                          PORTALLOCATOR_DISABLE_TCP);
+    allocator_->set_step_delay(kMinimumStepDelay);
+  }
+
+  P2PTransportChannel& StartTransportChannel(
+      bool prioritize_most_likely_to_work,
+      int stable_writable_connection_ping_interval,
+      const webrtc::FieldTrialsView* field_trials = nullptr) {
+    channel_.reset(
+        new P2PTransportChannel("checks", 1, allocator(), field_trials));
+    IceConfig config = channel_->config();
+    config.prioritize_most_likely_candidate_pairs =
+        prioritize_most_likely_to_work;
+    config.stable_writable_connection_ping_interval =
+        stable_writable_connection_ping_interval;
+    channel_->SetIceConfig(config);
+    PrepareChannel(channel_.get());
+    channel_->MaybeStartGathering();
+    return *channel_.get();
+  }
+
+  BasicPortAllocator* allocator() { return allocator_.get(); }
+  TestTurnServer* turn_server() { return &turn_server_; }
+
+  // This verifies the next pingable connection has the expected candidates'
+  // types and, for relay local candidate, the expected relay protocol and ping
+  // it.
+  void VerifyNextPingableConnection(
+      absl::string_view local_candidate_type,
+      absl::string_view remote_candidate_type,
+      absl::string_view relay_protocol_type = UDP_PROTOCOL_NAME) {
+    Connection* conn = FindNextPingableConnectionAndPingIt(channel_.get());
+    ASSERT_TRUE(conn != nullptr);
+    EXPECT_EQ(conn->local_candidate().type(), local_candidate_type);
+    if (conn->local_candidate().type() == RELAY_PORT_TYPE) {
+      EXPECT_EQ(conn->local_candidate().relay_protocol(), relay_protocol_type);
+    }
+    EXPECT_EQ(conn->remote_candidate().type(), remote_candidate_type);
+  }
+
+ private:
+  std::unique_ptr<BasicPortAllocator> allocator_;
+  rtc::FakeNetworkManager network_manager_;
+  TestTurnServer turn_server_;
+  std::unique_ptr<P2PTransportChannel> channel_;
+};
+
+INSTANTIATE_TEST_SUITE_P(Legacy,
+                         P2PTransportChannelMostLikelyToWorkFirstTest,
+                         Values(""));
+INSTANTIATE_TEST_SUITE_P(Active,
+                         P2PTransportChannelMostLikelyToWorkFirstTest,
+                         Values("WebRTC-UseActiveIceController/Enabled/"));
+
+// Test that Relay/Relay connections will be pinged first when no other
+// connections have been pinged yet, unless we need to ping a trigger check or
+// we have a selected connection.
+TEST_P(P2PTransportChannelMostLikelyToWorkFirstTest,
+       TestRelayRelayFirstWhenNothingPingedYet) {
+  const int max_strong_interval = 500;
+  P2PTransportChannel& ch =
+      StartTransportChannel(true, max_strong_interval, &field_trials_);
+  EXPECT_TRUE_WAIT(ch.ports().size() == 2, kDefaultTimeout);
+  EXPECT_EQ(ch.ports()[0]->Type(), LOCAL_PORT_TYPE);
+  EXPECT_EQ(ch.ports()[1]->Type(), RELAY_PORT_TYPE);
+
+  ch.AddRemoteCandidate(CreateUdpCandidate(RELAY_PORT_TYPE, "1.1.1.1", 1, 1));
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "2.2.2.2", 2, 2));
+
+  EXPECT_TRUE_WAIT(ch.connections().size() == 4, kDefaultTimeout);
+
+  // Relay/Relay should be the first pingable connection.
+  Connection* conn = FindNextPingableConnectionAndPingIt(&ch);
+  ASSERT_TRUE(conn != nullptr);
+  EXPECT_EQ(conn->local_candidate().type(), RELAY_PORT_TYPE);
+  EXPECT_EQ(conn->remote_candidate().type(), RELAY_PORT_TYPE);
+
+  // Unless that we have a trigger check waiting to be pinged.
+  Connection* conn2 = WaitForConnectionTo(&ch, "2.2.2.2", 2);
+  ASSERT_TRUE(conn2 != nullptr);
+  EXPECT_EQ(conn2->local_candidate().type(), LOCAL_PORT_TYPE);
+  EXPECT_EQ(conn2->remote_candidate().type(), LOCAL_PORT_TYPE);
+  conn2->ReceivedPing();
+  EXPECT_EQ(conn2, FindNextPingableConnectionAndPingIt(&ch));
+
+  // Make conn3 the selected connection.
+  Connection* conn3 = WaitForConnectionTo(&ch, "1.1.1.1", 1);
+  ASSERT_TRUE(conn3 != nullptr);
+  EXPECT_EQ(conn3->local_candidate().type(), LOCAL_PORT_TYPE);
+  EXPECT_EQ(conn3->remote_candidate().type(), RELAY_PORT_TYPE);
+  conn3->ReceivedPingResponse(LOW_RTT, "id");
+  ASSERT_TRUE(conn3->writable());
+  conn3->ReceivedPing();
+
+  /*
+
+  TODO(honghaiz): Re-enable this once we use fake clock for this test to fix
+  the flakiness. The following test becomes flaky because we now ping the
+  connections with fast rates until every connection is pinged at least three
+  times. The selected connection may have been pinged before
+  `max_strong_interval`, so it may not be the next connection to be pinged as
+  expected in the test.
+
+  // Verify that conn3 will be the "selected connection" since it is readable
+  // and writable. After `MAX_CURRENT_STRONG_INTERVAL`, it should be the next
+  // pingable connection.
+  EXPECT_TRUE_WAIT(conn3 == ch.selected_connection(), kDefaultTimeout);
+  WAIT(false, max_strong_interval + 100);
+  conn3->ReceivedPingResponse(LOW_RTT, "id");
+  ASSERT_TRUE(conn3->writable());
+  EXPECT_EQ(conn3, FindNextPingableConnectionAndPingIt(&ch));
+
+  */
+}
+
+// Test that Relay/Relay connections will be pinged first when everything has
+// been pinged even if the Relay/Relay connection wasn't the first to be pinged
+// in the first round.
+TEST_P(P2PTransportChannelMostLikelyToWorkFirstTest,
+       TestRelayRelayFirstWhenEverythingPinged) {
+  P2PTransportChannel& ch = StartTransportChannel(true, 500, &field_trials_);
+  EXPECT_TRUE_WAIT(ch.ports().size() == 2, kDefaultTimeout);
+  EXPECT_EQ(ch.ports()[0]->Type(), LOCAL_PORT_TYPE);
+  EXPECT_EQ(ch.ports()[1]->Type(), RELAY_PORT_TYPE);
+
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 1));
+  EXPECT_TRUE_WAIT(ch.connections().size() == 2, kDefaultTimeout);
+
+  // Initially, only have Local/Local and Local/Relay.
+  VerifyNextPingableConnection(LOCAL_PORT_TYPE, LOCAL_PORT_TYPE);
+  VerifyNextPingableConnection(RELAY_PORT_TYPE, LOCAL_PORT_TYPE);
+
+  // Remote Relay candidate arrives.
+  ch.AddRemoteCandidate(CreateUdpCandidate(RELAY_PORT_TYPE, "2.2.2.2", 2, 2));
+  EXPECT_TRUE_WAIT(ch.connections().size() == 4, kDefaultTimeout);
+
+  // Relay/Relay should be the first since it hasn't been pinged before.
+  VerifyNextPingableConnection(RELAY_PORT_TYPE, RELAY_PORT_TYPE);
+
+  // Local/Relay is the final one.
+  VerifyNextPingableConnection(LOCAL_PORT_TYPE, RELAY_PORT_TYPE);
+
+  // Now, every connection has been pinged once. The next one should be
+  // Relay/Relay.
+  VerifyNextPingableConnection(RELAY_PORT_TYPE, RELAY_PORT_TYPE);
+}
+
+// Test that when we receive a new remote candidate, they will be tried first
+// before we re-ping Relay/Relay connections again.
+TEST_P(P2PTransportChannelMostLikelyToWorkFirstTest,
+       TestNoStarvationOnNonRelayConnection) {
+  P2PTransportChannel& ch = StartTransportChannel(true, 500, &field_trials_);
+  EXPECT_TRUE_WAIT(ch.ports().size() == 2, kDefaultTimeout);
+  EXPECT_EQ(ch.ports()[0]->Type(), LOCAL_PORT_TYPE);
+  EXPECT_EQ(ch.ports()[1]->Type(), RELAY_PORT_TYPE);
+
+  ch.AddRemoteCandidate(CreateUdpCandidate(RELAY_PORT_TYPE, "1.1.1.1", 1, 1));
+  EXPECT_TRUE_WAIT(ch.connections().size() == 2, kDefaultTimeout);
+
+  // Initially, only have Relay/Relay and Local/Relay. Ping Relay/Relay first.
+  VerifyNextPingableConnection(RELAY_PORT_TYPE, RELAY_PORT_TYPE);
+
+  // Next, ping Local/Relay.
+  VerifyNextPingableConnection(LOCAL_PORT_TYPE, RELAY_PORT_TYPE);
+
+  // Remote Local candidate arrives.
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "2.2.2.2", 2, 2));
+  EXPECT_TRUE_WAIT(ch.connections().size() == 4, kDefaultTimeout);
+
+  // Local/Local should be the first since it hasn't been pinged before.
+  VerifyNextPingableConnection(LOCAL_PORT_TYPE, LOCAL_PORT_TYPE);
+
+  // Relay/Local is the final one.
+  VerifyNextPingableConnection(RELAY_PORT_TYPE, LOCAL_PORT_TYPE);
+
+  // Now, every connection has been pinged once. The next one should be
+  // Relay/Relay.
+  VerifyNextPingableConnection(RELAY_PORT_TYPE, RELAY_PORT_TYPE);
+}
+
+// Test skip_relay_to_non_relay_connections field-trial.
+// I.e that we never create connection between relay and non-relay.
+TEST_P(P2PTransportChannelMostLikelyToWorkFirstTest,
+       TestSkipRelayToNonRelayConnectionsFieldTrial) {
+  webrtc::test::ScopedKeyValueConfig field_trials(
+      field_trials_,
+      "WebRTC-IceFieldTrials/skip_relay_to_non_relay_connections:true/");
+  P2PTransportChannel& ch = StartTransportChannel(true, 500, &field_trials);
+  EXPECT_TRUE_WAIT(ch.ports().size() == 2, kDefaultTimeout);
+  EXPECT_EQ(ch.ports()[0]->Type(), LOCAL_PORT_TYPE);
+  EXPECT_EQ(ch.ports()[1]->Type(), RELAY_PORT_TYPE);
+
+  // Remote Relay candidate arrives.
+  ch.AddRemoteCandidate(CreateUdpCandidate(RELAY_PORT_TYPE, "1.1.1.1", 1, 1));
+  EXPECT_TRUE_WAIT(ch.connections().size() == 1, kDefaultTimeout);
+
+  // Remote Local candidate arrives.
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "2.2.2.2", 2, 2));
+  EXPECT_TRUE_WAIT(ch.connections().size() == 2, kDefaultTimeout);
+}
+
+// Test the ping sequence is UDP Relay/Relay followed by TCP Relay/Relay,
+// followed by the rest.
+TEST_P(P2PTransportChannelMostLikelyToWorkFirstTest, TestTcpTurn) {
+  // Add a Tcp Turn server.
+  turn_server()->AddInternalSocket(kTurnTcpIntAddr, PROTO_TCP);
+  RelayServerConfig config;
+  config.credentials = kRelayCredentials;
+  config.ports.push_back(ProtocolAddress(kTurnTcpIntAddr, PROTO_TCP));
+  allocator()->AddTurnServerForTesting(config);
+
+  P2PTransportChannel& ch = StartTransportChannel(true, 500, &field_trials_);
+  EXPECT_TRUE_WAIT(ch.ports().size() == 3, kDefaultTimeout);
+  EXPECT_EQ(ch.ports()[0]->Type(), LOCAL_PORT_TYPE);
+  EXPECT_EQ(ch.ports()[1]->Type(), RELAY_PORT_TYPE);
+  EXPECT_EQ(ch.ports()[2]->Type(), RELAY_PORT_TYPE);
+
+  // Remote Relay candidate arrives.
+  ch.AddRemoteCandidate(CreateUdpCandidate(RELAY_PORT_TYPE, "1.1.1.1", 1, 1));
+  EXPECT_TRUE_WAIT(ch.connections().size() == 3, kDefaultTimeout);
+
+  // UDP Relay/Relay should be pinged first.
+  VerifyNextPingableConnection(RELAY_PORT_TYPE, RELAY_PORT_TYPE);
+
+  // TCP Relay/Relay is the next.
+  VerifyNextPingableConnection(RELAY_PORT_TYPE, RELAY_PORT_TYPE,
+                               TCP_PROTOCOL_NAME);
+
+  // Finally, Local/Relay will be pinged.
+  VerifyNextPingableConnection(LOCAL_PORT_TYPE, RELAY_PORT_TYPE);
+}
+
+class P2PTransportChannelResolverTest : public TestWithParam<std::string> {};
+
+INSTANTIATE_TEST_SUITE_P(Legacy, P2PTransportChannelResolverTest, Values(""));
+INSTANTIATE_TEST_SUITE_P(Active,
+                         P2PTransportChannelResolverTest,
+                         Values("WebRTC-UseActiveIceController/Enabled/"));
+
+// Test that a resolver is created, asked for a result, and destroyed
+// when the address is a hostname. The destruction should happen even
+// if the channel is not destroyed.
+TEST_P(P2PTransportChannelResolverTest, HostnameCandidateIsResolved) {
+  webrtc::test::ScopedKeyValueConfig field_trials(GetParam());
+  ResolverFactoryFixture resolver_fixture;
+  std::unique_ptr<rtc::SocketServer> socket_server =
+      rtc::CreateDefaultSocketServer();
+  rtc::AutoSocketServerThread main_thread(socket_server.get());
+  rtc::BasicPacketSocketFactory packet_socket_factory(socket_server.get());
+  FakePortAllocator allocator(rtc::Thread::Current(), &packet_socket_factory,
+                              &field_trials);
+  webrtc::IceTransportInit init;
+  init.set_port_allocator(&allocator);
+  init.set_async_dns_resolver_factory(&resolver_fixture);
+  init.set_field_trials(&field_trials);
+  auto channel = P2PTransportChannel::Create("tn", 0, std::move(init));
+  Candidate hostname_candidate;
+  SocketAddress hostname_address("fake.test", 1000);
+  hostname_candidate.set_address(hostname_address);
+  channel->AddRemoteCandidate(hostname_candidate);
+
+  ASSERT_EQ_WAIT(1u, channel->remote_candidates().size(), kDefaultTimeout);
+  const RemoteCandidate& candidate = channel->remote_candidates()[0];
+  EXPECT_FALSE(candidate.address().IsUnresolvedIP());
+}
+
+// Test that if we signal a hostname candidate after the remote endpoint
+// discovers a prflx remote candidate with the same underlying IP address, the
+// prflx candidate is updated to a host candidate after the name resolution is
+// done.
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       PeerReflexiveCandidateBeforeSignalingWithMdnsName) {
+  // ep1 and ep2 will only gather host candidates with addresses
+  // kPublicAddrs[0] and kPublicAddrs[1], respectively.
+  ConfigureEndpoints(OPEN, OPEN, kOnlyLocalPorts, kOnlyLocalPorts);
+  // ICE parameter will be set up when creating the channels.
+  set_remote_ice_parameter_source(FROM_SETICEPARAMETERS);
+  GetEndpoint(0)->network_manager_.set_mdns_responder(
+      std::make_unique<webrtc::FakeMdnsResponder>(rtc::Thread::Current()));
+
+  ResolverFactoryFixture resolver_fixture;
+  GetEndpoint(1)->async_dns_resolver_factory_ = &resolver_fixture;
+  CreateChannels();
+  // Pause sending candidates from both endpoints until we find out what port
+  // number is assgined to ep1's host candidate.
+  PauseCandidates(0);
+  PauseCandidates(1);
+  ASSERT_EQ_WAIT(1u, GetEndpoint(0)->saved_candidates_.size(), kMediumTimeout);
+  const auto& local_candidate = GetEndpoint(0)->saved_candidates_[0].candidate;
+  // The IP address of ep1's host candidate should be obfuscated.
+  EXPECT_TRUE(local_candidate.address().IsUnresolvedIP());
+  // This is the underlying private IP address of the same candidate at ep1.
+  const auto local_address = rtc::SocketAddress(
+      kPublicAddrs[0].ipaddr(), local_candidate.address().port());
+
+  // Let ep2 signal its candidate to ep1. ep1 should form a candidate
+  // pair and start to ping. After receiving the ping, ep2 discovers a prflx
+  // remote candidate and form a candidate pair as well.
+  ResumeCandidates(1);
+  ASSERT_TRUE_WAIT(ep1_ch1()->selected_connection() != nullptr, kMediumTimeout);
+  // ep2 should have the selected connection connected to the prflx remote
+  // candidate.
+  const Connection* selected_connection = nullptr;
+  ASSERT_TRUE_WAIT(
+      (selected_connection = ep2_ch1()->selected_connection()) != nullptr,
+      kMediumTimeout);
+  EXPECT_EQ(PRFLX_PORT_TYPE, selected_connection->remote_candidate().type());
+  EXPECT_EQ(kIceUfrag[0], selected_connection->remote_candidate().username());
+  EXPECT_EQ(kIcePwd[0], selected_connection->remote_candidate().password());
+  // Set expectation before ep1 signals a hostname candidate.
+  resolver_fixture.SetAddressToReturn(local_address);
+  ResumeCandidates(0);
+  // Verify ep2's selected connection is updated to use the 'local' candidate.
+  EXPECT_EQ_WAIT(LOCAL_PORT_TYPE,
+                 ep2_ch1()->selected_connection()->remote_candidate().type(),
+                 kMediumTimeout);
+  EXPECT_EQ(selected_connection, ep2_ch1()->selected_connection());
+
+  DestroyChannels();
+}
+
+// Test that if we discover a prflx candidate during the process of name
+// resolution for a remote hostname candidate, we update the prflx candidate to
+// a host candidate if the hostname candidate turns out to have the same IP
+// address after the resolution completes.
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       PeerReflexiveCandidateDuringResolvingHostCandidateWithMdnsName) {
+  ResolverFactoryFixture resolver_fixture;
+  // Prevent resolution until triggered by FireDelayedResolution.
+  resolver_fixture.DelayResolution();
+
+  // ep1 and ep2 will only gather host candidates with addresses
+  // kPublicAddrs[0] and kPublicAddrs[1], respectively.
+  ConfigureEndpoints(OPEN, OPEN, kOnlyLocalPorts, kOnlyLocalPorts);
+  // ICE parameter will be set up when creating the channels.
+  set_remote_ice_parameter_source(FROM_SETICEPARAMETERS);
+  GetEndpoint(0)->network_manager_.set_mdns_responder(
+      std::make_unique<webrtc::FakeMdnsResponder>(rtc::Thread::Current()));
+  GetEndpoint(1)->async_dns_resolver_factory_ = &resolver_fixture;
+  CreateChannels();
+  // Pause sending candidates from both endpoints until we find out what port
+  // number is assgined to ep1's host candidate.
+  PauseCandidates(0);
+  PauseCandidates(1);
+
+  ASSERT_EQ_WAIT(1u, GetEndpoint(0)->saved_candidates_.size(), kMediumTimeout);
+  const auto& local_candidate = GetEndpoint(0)->saved_candidates_[0].candidate;
+  // The IP address of ep1's host candidate should be obfuscated.
+  ASSERT_TRUE(local_candidate.address().IsUnresolvedIP());
+  // This is the underlying private IP address of the same candidate at ep1.
+  const auto local_address = rtc::SocketAddress(
+      kPublicAddrs[0].ipaddr(), local_candidate.address().port());
+  // Let ep1 signal its hostname candidate to ep2.
+  ResumeCandidates(0);
+  // Now that ep2 is in the process of resolving the hostname candidate signaled
+  // by ep1. Let ep2 signal its host candidate with an IP address to ep1, so
+  // that ep1 can form a candidate pair, select it and start to ping ep2.
+  ResumeCandidates(1);
+  ASSERT_TRUE_WAIT(ep1_ch1()->selected_connection() != nullptr, kMediumTimeout);
+  // Let the mock resolver of ep2 receives the correct resolution.
+  resolver_fixture.SetAddressToReturn(local_address);
+
+  // Upon receiving a ping from ep1, ep2 adds a prflx candidate from the
+  // unknown address and establishes a connection.
+  //
+  // There is a caveat in our implementation associated with this expectation.
+  // See the big comment in P2PTransportChannel::OnUnknownAddress.
+  ASSERT_TRUE_WAIT(ep2_ch1()->selected_connection() != nullptr, kMediumTimeout);
+  EXPECT_EQ(PRFLX_PORT_TYPE,
+            ep2_ch1()->selected_connection()->remote_candidate().type());
+  // ep2 should also be able resolve the hostname candidate. The resolved remote
+  // host candidate should be merged with the prflx remote candidate.
+
+  resolver_fixture.FireDelayedResolution();
+
+  EXPECT_EQ_WAIT(LOCAL_PORT_TYPE,
+                 ep2_ch1()->selected_connection()->remote_candidate().type(),
+                 kMediumTimeout);
+  EXPECT_EQ(1u, ep2_ch1()->remote_candidates().size());
+
+  DestroyChannels();
+}
+
+// Test that if we only gather and signal a host candidate, the IP address of
+// which is obfuscated by an mDNS name, and if the peer can complete the name
+// resolution with the correct IP address, we can have a p2p connection.
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       CanConnectWithHostCandidateWithMdnsName) {
+  ResolverFactoryFixture resolver_fixture;
+
+  // ep1 and ep2 will only gather host candidates with addresses
+  // kPublicAddrs[0] and kPublicAddrs[1], respectively.
+  ConfigureEndpoints(OPEN, OPEN, kOnlyLocalPorts, kOnlyLocalPorts);
+  // ICE parameter will be set up when creating the channels.
+  set_remote_ice_parameter_source(FROM_SETICEPARAMETERS);
+  GetEndpoint(0)->network_manager_.set_mdns_responder(
+      std::make_unique<webrtc::FakeMdnsResponder>(rtc::Thread::Current()));
+  GetEndpoint(1)->async_dns_resolver_factory_ = &resolver_fixture;
+  CreateChannels();
+  // Pause sending candidates from both endpoints until we find out what port
+  // number is assgined to ep1's host candidate.
+  PauseCandidates(0);
+  PauseCandidates(1);
+  ASSERT_EQ_WAIT(1u, GetEndpoint(0)->saved_candidates_.size(), kMediumTimeout);
+  const auto& local_candidate_ep1 =
+      GetEndpoint(0)->saved_candidates_[0].candidate;
+  // The IP address of ep1's host candidate should be obfuscated.
+  EXPECT_TRUE(local_candidate_ep1.address().IsUnresolvedIP());
+  // This is the underlying private IP address of the same candidate at ep1,
+  // and let the mock resolver of ep2 receive the correct resolution.
+  rtc::SocketAddress resolved_address_ep1(local_candidate_ep1.address());
+  resolved_address_ep1.SetResolvedIP(kPublicAddrs[0].ipaddr());
+
+  resolver_fixture.SetAddressToReturn(resolved_address_ep1);
+  // Let ep1 signal its hostname candidate to ep2.
+  ResumeCandidates(0);
+
+  // We should be able to receive a ping from ep2 and establish a connection
+  // with a peer reflexive candidate from ep2.
+  ASSERT_TRUE_WAIT((ep1_ch1()->selected_connection()) != nullptr,
+                   kMediumTimeout);
+  EXPECT_EQ(LOCAL_PORT_TYPE,
+            ep1_ch1()->selected_connection()->local_candidate().type());
+  EXPECT_EQ(PRFLX_PORT_TYPE,
+            ep1_ch1()->selected_connection()->remote_candidate().type());
+
+  DestroyChannels();
+}
+
+// Test that when the IP of a host candidate is concealed by an mDNS name, the
+// stats from the gathering ICE endpoint do not reveal the address of this local
+// host candidate or the related address of a local srflx candidate from the
+// same endpoint. Also, the remote ICE endpoint that successfully resolves a
+// signaled host candidate with an mDNS name should not reveal the address of
+// this remote host candidate in stats.
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       CandidatesSanitizedInStatsWhenMdnsObfuscationEnabled) {
+  ResolverFactoryFixture resolver_fixture;
+
+  // ep1 and ep2 will gather host candidates with addresses
+  // kPublicAddrs[0] and kPublicAddrs[1], respectively. ep1 also gathers a srflx
+  // and a relay candidates.
+  ConfigureEndpoints(OPEN, OPEN,
+                     kDefaultPortAllocatorFlags | PORTALLOCATOR_DISABLE_TCP,
+                     kOnlyLocalPorts);
+  // ICE parameter will be set up when creating the channels.
+  set_remote_ice_parameter_source(FROM_SETICEPARAMETERS);
+  GetEndpoint(0)->network_manager_.set_mdns_responder(
+      std::make_unique<webrtc::FakeMdnsResponder>(rtc::Thread::Current()));
+  GetEndpoint(1)->async_dns_resolver_factory_ = &resolver_fixture;
+  CreateChannels();
+  // Pause sending candidates from both endpoints until we find out what port
+  // number is assigned to ep1's host candidate.
+  PauseCandidates(0);
+  PauseCandidates(1);
+  // Ep1 has a UDP host, a srflx and a relay candidates.
+  ASSERT_EQ_WAIT(3u, GetEndpoint(0)->saved_candidates_.size(), kMediumTimeout);
+  ASSERT_EQ_WAIT(1u, GetEndpoint(1)->saved_candidates_.size(), kMediumTimeout);
+
+  for (const auto& candidates_data : GetEndpoint(0)->saved_candidates_) {
+    const auto& local_candidate_ep1 = candidates_data.candidate;
+    if (local_candidate_ep1.type() == LOCAL_PORT_TYPE) {
+      // This is the underlying private IP address of the same candidate at ep1,
+      // and let the mock resolver of ep2 receive the correct resolution.
+      rtc::SocketAddress resolved_address_ep1(local_candidate_ep1.address());
+      resolved_address_ep1.SetResolvedIP(kPublicAddrs[0].ipaddr());
+      resolver_fixture.SetAddressToReturn(resolved_address_ep1);
+      break;
+    }
+  }
+  ResumeCandidates(0);
+  ResumeCandidates(1);
+
+  ASSERT_EQ_WAIT(kIceGatheringComplete, ep1_ch1()->gathering_state(),
+                 kMediumTimeout);
+  // We should have the following candidate pairs on both endpoints:
+  // ep1_host <-> ep2_host, ep1_srflx <-> ep2_host, ep1_relay <-> ep2_host
+  ASSERT_EQ_WAIT(3u, ep1_ch1()->connections().size(), kMediumTimeout);
+  ASSERT_EQ_WAIT(3u, ep2_ch1()->connections().size(), kMediumTimeout);
+
+  IceTransportStats ice_transport_stats1;
+  IceTransportStats ice_transport_stats2;
+  ep1_ch1()->GetStats(&ice_transport_stats1);
+  ep2_ch1()->GetStats(&ice_transport_stats2);
+  EXPECT_EQ(3u, ice_transport_stats1.connection_infos.size());
+  EXPECT_EQ(3u, ice_transport_stats1.candidate_stats_list.size());
+  EXPECT_EQ(3u, ice_transport_stats2.connection_infos.size());
+  // Check the stats of ep1 seen by ep1.
+  for (const auto& connection_info : ice_transport_stats1.connection_infos) {
+    const auto& local_candidate = connection_info.local_candidate;
+    if (local_candidate.type() == LOCAL_PORT_TYPE) {
+      EXPECT_TRUE(local_candidate.address().IsUnresolvedIP());
+    } else if (local_candidate.type() == STUN_PORT_TYPE) {
+      EXPECT_TRUE(local_candidate.related_address().IsAnyIP());
+    } else if (local_candidate.type() == RELAY_PORT_TYPE) {
+      // The related address of the relay candidate should be equal to the
+      // srflx address. Note that NAT is not configured, hence the following
+      // expectation.
+      EXPECT_EQ(kPublicAddrs[0].ipaddr(),
+                local_candidate.related_address().ipaddr());
+    } else {
+      FAIL();
+    }
+  }
+  // Check the stats of ep1 seen by ep2.
+  for (const auto& connection_info : ice_transport_stats2.connection_infos) {
+    const auto& remote_candidate = connection_info.remote_candidate;
+    if (remote_candidate.type() == LOCAL_PORT_TYPE) {
+      EXPECT_TRUE(remote_candidate.address().IsUnresolvedIP());
+    } else if (remote_candidate.type() == STUN_PORT_TYPE) {
+      EXPECT_TRUE(remote_candidate.related_address().IsAnyIP());
+    } else if (remote_candidate.type() == RELAY_PORT_TYPE) {
+      EXPECT_EQ(kPublicAddrs[0].ipaddr(),
+                remote_candidate.related_address().ipaddr());
+    } else {
+      FAIL();
+    }
+  }
+  DestroyChannels();
+}
+
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       ConnectingIncreasesSelectedCandidatePairChanges) {
+  rtc::ScopedFakeClock clock;
+  ConfigureEndpoints(OPEN, OPEN, kDefaultPortAllocatorFlags,
+                     kDefaultPortAllocatorFlags);
+  CreateChannels();
+
+  IceTransportStats ice_transport_stats;
+  ASSERT_TRUE(ep1_ch1()->GetStats(&ice_transport_stats));
+  EXPECT_EQ(0u, ice_transport_stats.selected_candidate_pair_changes);
+
+  // Let the channels connect.
+  EXPECT_TRUE_SIMULATED_WAIT(ep1_ch1()->selected_connection() != nullptr,
+                             kMediumTimeout, clock);
+
+  ASSERT_TRUE(ep1_ch1()->GetStats(&ice_transport_stats));
+  EXPECT_EQ(1u, ice_transport_stats.selected_candidate_pair_changes);
+
+  DestroyChannels();
+}
+
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       DisconnectedIncreasesSelectedCandidatePairChanges) {
+  rtc::ScopedFakeClock clock;
+  ConfigureEndpoints(OPEN, OPEN, kDefaultPortAllocatorFlags,
+                     kDefaultPortAllocatorFlags);
+  CreateChannels();
+
+  IceTransportStats ice_transport_stats;
+  ASSERT_TRUE(ep1_ch1()->GetStats(&ice_transport_stats));
+  EXPECT_EQ(0u, ice_transport_stats.selected_candidate_pair_changes);
+
+  // Let the channels connect.
+  EXPECT_TRUE_SIMULATED_WAIT(ep1_ch1()->selected_connection() != nullptr,
+                             kMediumTimeout, clock);
+
+  ASSERT_TRUE(ep1_ch1()->GetStats(&ice_transport_stats));
+  EXPECT_EQ(1u, ice_transport_stats.selected_candidate_pair_changes);
+
+  // Prune connections and wait for disconnect.
+  for (Connection* con : ep1_ch1()->connections()) {
+    con->Prune();
+  }
+  EXPECT_TRUE_SIMULATED_WAIT(ep1_ch1()->selected_connection() == nullptr,
+                             kMediumTimeout, clock);
+
+  ASSERT_TRUE(ep1_ch1()->GetStats(&ice_transport_stats));
+  EXPECT_EQ(2u, ice_transport_stats.selected_candidate_pair_changes);
+
+  DestroyChannels();
+}
+
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       NewSelectionIncreasesSelectedCandidatePairChanges) {
+  rtc::ScopedFakeClock clock;
+  ConfigureEndpoints(OPEN, OPEN, kDefaultPortAllocatorFlags,
+                     kDefaultPortAllocatorFlags);
+  CreateChannels();
+
+  IceTransportStats ice_transport_stats;
+  ASSERT_TRUE(ep1_ch1()->GetStats(&ice_transport_stats));
+  EXPECT_EQ(0u, ice_transport_stats.selected_candidate_pair_changes);
+
+  // Let the channels connect.
+  EXPECT_TRUE_SIMULATED_WAIT(ep1_ch1()->selected_connection() != nullptr,
+                             kMediumTimeout, clock);
+
+  ASSERT_TRUE(ep1_ch1()->GetStats(&ice_transport_stats));
+  EXPECT_EQ(1u, ice_transport_stats.selected_candidate_pair_changes);
+
+  // Prune the currently selected connection and wait for selection
+  // of a new one.
+  const Connection* selected_connection = ep1_ch1()->selected_connection();
+  for (Connection* con : ep1_ch1()->connections()) {
+    if (con == selected_connection) {
+      con->Prune();
+    }
+  }
+  EXPECT_TRUE_SIMULATED_WAIT(
+      ep1_ch1()->selected_connection() != nullptr &&
+          (ep1_ch1()->GetStats(&ice_transport_stats),
+           ice_transport_stats.selected_candidate_pair_changes >= 2u),
+      kMediumTimeout, clock);
+
+  ASSERT_TRUE(ep1_ch1()->GetStats(&ice_transport_stats));
+  EXPECT_GE(ice_transport_stats.selected_candidate_pair_changes, 2u);
+
+  DestroyChannels();
+}
+
+// A similar test as above to check the selected candidate pair is sanitized
+// when it is queried via GetSelectedCandidatePair.
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       SelectedCandidatePairSanitizedWhenMdnsObfuscationEnabled) {
+  ResolverFactoryFixture resolver_fixture;
+
+  // ep1 and ep2 will gather host candidates with addresses
+  // kPublicAddrs[0] and kPublicAddrs[1], respectively.
+  ConfigureEndpoints(OPEN, OPEN, kOnlyLocalPorts, kOnlyLocalPorts);
+  // ICE parameter will be set up when creating the channels.
+  set_remote_ice_parameter_source(FROM_SETICEPARAMETERS);
+  GetEndpoint(0)->network_manager_.set_mdns_responder(
+      std::make_unique<webrtc::FakeMdnsResponder>(rtc::Thread::Current()));
+  GetEndpoint(1)->async_dns_resolver_factory_ = &resolver_fixture;
+  CreateChannels();
+  // Pause sending candidates from both endpoints until we find out what port
+  // number is assigned to ep1's host candidate.
+  PauseCandidates(0);
+  PauseCandidates(1);
+  ASSERT_EQ_WAIT(1u, GetEndpoint(0)->saved_candidates_.size(), kMediumTimeout);
+  const auto& candidates_data = GetEndpoint(0)->saved_candidates_[0];
+  const auto& local_candidate_ep1 = candidates_data.candidate;
+  ASSERT_TRUE(local_candidate_ep1.type() == LOCAL_PORT_TYPE);
+  // This is the underlying private IP address of the same candidate at ep1,
+  // and let the mock resolver of ep2 receive the correct resolution.
+  rtc::SocketAddress resolved_address_ep1(local_candidate_ep1.address());
+  resolved_address_ep1.SetResolvedIP(kPublicAddrs[0].ipaddr());
+  resolver_fixture.SetAddressToReturn(resolved_address_ep1);
+
+  ResumeCandidates(0);
+  ResumeCandidates(1);
+
+  ASSERT_TRUE_WAIT(ep1_ch1()->selected_connection() != nullptr &&
+                       ep2_ch1()->selected_connection() != nullptr,
+                   kMediumTimeout);
+
+  const auto pair_ep1 = ep1_ch1()->GetSelectedCandidatePair();
+  ASSERT_TRUE(pair_ep1.has_value());
+  EXPECT_EQ(LOCAL_PORT_TYPE, pair_ep1->local_candidate().type());
+  EXPECT_TRUE(pair_ep1->local_candidate().address().IsUnresolvedIP());
+
+  const auto pair_ep2 = ep2_ch1()->GetSelectedCandidatePair();
+  ASSERT_TRUE(pair_ep2.has_value());
+  EXPECT_EQ(LOCAL_PORT_TYPE, pair_ep2->remote_candidate().type());
+  EXPECT_TRUE(pair_ep2->remote_candidate().address().IsUnresolvedIP());
+
+  DestroyChannels();
+}
+
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       NoPairOfLocalRelayCandidateWithRemoteMdnsCandidate) {
+  const int kOnlyRelayPorts = cricket::PORTALLOCATOR_DISABLE_UDP |
+                              cricket::PORTALLOCATOR_DISABLE_STUN |
+                              cricket::PORTALLOCATOR_DISABLE_TCP;
+  // We use one endpoint to test the behavior of adding remote candidates, and
+  // this endpoint only gathers relay candidates.
+  ConfigureEndpoints(OPEN, OPEN, kOnlyRelayPorts, kDefaultPortAllocatorFlags);
+  GetEndpoint(0)->cd1_.ch_ = CreateChannel(0, ICE_CANDIDATE_COMPONENT_DEFAULT,
+                                           kIceParams[0], kIceParams[1]);
+  IceConfig config;
+  // Start gathering and we should have only a single relay port.
+  ep1_ch1()->SetIceConfig(config);
+  ep1_ch1()->MaybeStartGathering();
+  EXPECT_EQ_WAIT(IceGatheringState::kIceGatheringComplete,
+                 ep1_ch1()->gathering_state(), kDefaultTimeout);
+  EXPECT_EQ(1u, ep1_ch1()->ports().size());
+  // Add a plain remote host candidate and three remote mDNS candidates with the
+  // host, srflx and relay types. Note that the candidates differ in their
+  // ports.
+  cricket::Candidate host_candidate = CreateUdpCandidate(
+      LOCAL_PORT_TYPE, "1.1.1.1", 1 /* port */, 0 /* priority */);
+  ep1_ch1()->AddRemoteCandidate(host_candidate);
+
+  std::vector<cricket::Candidate> mdns_candidates;
+  mdns_candidates.push_back(CreateUdpCandidate(LOCAL_PORT_TYPE, "example.local",
+                                               2 /* port */, 0 /* priority */));
+  mdns_candidates.push_back(CreateUdpCandidate(STUN_PORT_TYPE, "example.local",
+                                               3 /* port */, 0 /* priority */));
+  mdns_candidates.push_back(CreateUdpCandidate(RELAY_PORT_TYPE, "example.local",
+                                               4 /* port */, 0 /* priority */));
+  // We just resolve the hostname to 1.1.1.1, and add the candidates with this
+  // address directly to simulate the process of adding remote candidates with
+  // the name resolution.
+  for (auto& mdns_candidate : mdns_candidates) {
+    rtc::SocketAddress resolved_address(mdns_candidate.address());
+    resolved_address.SetResolvedIP(0x1111);  // 1.1.1.1
+    mdns_candidate.set_address(resolved_address);
+    EXPECT_FALSE(mdns_candidate.address().IsUnresolvedIP());
+    ep1_ch1()->AddRemoteCandidate(mdns_candidate);
+  }
+
+  // All remote candidates should have been successfully added.
+  EXPECT_EQ(4u, ep1_ch1()->remote_candidates().size());
+
+  // Expect that there is no connection paired with any mDNS candidate.
+  ASSERT_EQ(1u, ep1_ch1()->connections().size());
+  ASSERT_NE(nullptr, ep1_ch1()->connections()[0]);
+  EXPECT_EQ(
+      "1.1.1.1:1",
+      ep1_ch1()->connections()[0]->remote_candidate().address().ToString());
+  DestroyChannels();
+}
+
+class MockMdnsResponder : public webrtc::MdnsResponderInterface {
+ public:
+  MOCK_METHOD(void,
+              CreateNameForAddress,
+              (const rtc::IPAddress&, NameCreatedCallback),
+              (override));
+  MOCK_METHOD(void,
+              RemoveNameForAddress,
+              (const rtc::IPAddress&, NameRemovedCallback),
+              (override));
+};
+
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       SrflxCandidateCanBeGatheredBeforeMdnsCandidateToCreateConnection) {
+  // ep1 and ep2 will only gather host and srflx candidates with base addresses
+  // kPublicAddrs[0] and kPublicAddrs[1], respectively, and we use a shared
+  // socket in gathering.
+  const auto kOnlyLocalAndStunPorts =
+      cricket::PORTALLOCATOR_DISABLE_RELAY |
+      cricket::PORTALLOCATOR_DISABLE_TCP |
+      cricket::PORTALLOCATOR_ENABLE_SHARED_SOCKET;
+  // ep1 is configured with a NAT so that we do gather a srflx candidate.
+  ConfigureEndpoints(NAT_FULL_CONE, OPEN, kOnlyLocalAndStunPorts,
+                     kOnlyLocalAndStunPorts);
+  // ICE parameter will be set up when creating the channels.
+  set_remote_ice_parameter_source(FROM_SETICEPARAMETERS);
+  // Use a mock mDNS responder, which does not complete the name registration by
+  // ignoring the completion callback.
+  auto mock_mdns_responder = std::make_unique<MockMdnsResponder>();
+  EXPECT_CALL(*mock_mdns_responder, CreateNameForAddress(_, _))
+      .Times(1)
+      .WillOnce(Return());
+  GetEndpoint(0)->network_manager_.set_mdns_responder(
+      std::move(mock_mdns_responder));
+
+  CreateChannels();
+
+  // We should be able to form a srflx-host connection to ep2.
+  ASSERT_TRUE_WAIT((ep1_ch1()->selected_connection()) != nullptr,
+                   kMediumTimeout);
+  EXPECT_EQ(STUN_PORT_TYPE,
+            ep1_ch1()->selected_connection()->local_candidate().type());
+  EXPECT_EQ(LOCAL_PORT_TYPE,
+            ep1_ch1()->selected_connection()->remote_candidate().type());
+
+  DestroyChannels();
+}
+
+// Test that after changing the candidate filter from relay-only to allowing all
+// types of candidates when doing continual gathering, we can gather without ICE
+// restart the other types of candidates that are now enabled and form candidate
+// pairs. Also, we verify that the relay candidates gathered previously are not
+// removed and are still usable for necessary route switching.
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       SurfaceHostCandidateOnCandidateFilterChangeFromRelayToAll) {
+  rtc::ScopedFakeClock clock;
+
+  ConfigureEndpoints(
+      OPEN, OPEN,
+      kDefaultPortAllocatorFlags | PORTALLOCATOR_ENABLE_SHARED_SOCKET,
+      kDefaultPortAllocatorFlags | PORTALLOCATOR_ENABLE_SHARED_SOCKET);
+  auto* ep1 = GetEndpoint(0);
+  auto* ep2 = GetEndpoint(1);
+  ep1->allocator_->SetCandidateFilter(CF_RELAY);
+  ep2->allocator_->SetCandidateFilter(CF_RELAY);
+  // Enable continual gathering and also resurfacing gathered candidates upon
+  // the candidate filter changed in the ICE configuration.
+  IceConfig ice_config = CreateIceConfig(1000, GATHER_CONTINUALLY);
+  ice_config.surface_ice_candidates_on_ice_transport_type_changed = true;
+  CreateChannels(ice_config, ice_config);
+  ASSERT_TRUE_SIMULATED_WAIT(ep1_ch1()->selected_connection() != nullptr,
+                             kDefaultTimeout, clock);
+  ASSERT_TRUE_SIMULATED_WAIT(ep2_ch1()->selected_connection() != nullptr,
+                             kDefaultTimeout, clock);
+  EXPECT_EQ(RELAY_PORT_TYPE,
+            ep1_ch1()->selected_connection()->local_candidate().type());
+  EXPECT_EQ(RELAY_PORT_TYPE,
+            ep2_ch1()->selected_connection()->local_candidate().type());
+
+  // Loosen the candidate filter at ep1.
+  ep1->allocator_->SetCandidateFilter(CF_ALL);
+  EXPECT_TRUE_SIMULATED_WAIT(
+      ep1_ch1()->selected_connection() != nullptr &&
+          ep1_ch1()->selected_connection()->local_candidate().type() ==
+              LOCAL_PORT_TYPE,
+      kDefaultTimeout, clock);
+  EXPECT_EQ(RELAY_PORT_TYPE,
+            ep1_ch1()->selected_connection()->remote_candidate().type());
+
+  // Loosen the candidate filter at ep2.
+  ep2->allocator_->SetCandidateFilter(CF_ALL);
+  EXPECT_TRUE_SIMULATED_WAIT(
+      ep2_ch1()->selected_connection() != nullptr &&
+          ep2_ch1()->selected_connection()->local_candidate().type() ==
+              LOCAL_PORT_TYPE,
+      kDefaultTimeout, clock);
+  // We have migrated to a host-host candidate pair.
+  EXPECT_EQ(LOCAL_PORT_TYPE,
+            ep2_ch1()->selected_connection()->remote_candidate().type());
+
+  // Block the traffic over non-relay-to-relay routes and expect a route change.
+  fw()->AddRule(false, rtc::FP_ANY, kPublicAddrs[0], kPublicAddrs[1]);
+  fw()->AddRule(false, rtc::FP_ANY, kPublicAddrs[1], kPublicAddrs[0]);
+  fw()->AddRule(false, rtc::FP_ANY, kPublicAddrs[0], kTurnUdpExtAddr);
+  fw()->AddRule(false, rtc::FP_ANY, kPublicAddrs[1], kTurnUdpExtAddr);
+
+  // We should be able to reuse the previously gathered relay candidates.
+  EXPECT_EQ_SIMULATED_WAIT(
+      RELAY_PORT_TYPE,
+      ep1_ch1()->selected_connection()->local_candidate().type(),
+      kDefaultTimeout, clock);
+  EXPECT_EQ(RELAY_PORT_TYPE,
+            ep1_ch1()->selected_connection()->remote_candidate().type());
+  DestroyChannels();
+}
+
+// A similar test as SurfaceHostCandidateOnCandidateFilterChangeFromRelayToAll,
+// and we should surface server-reflexive candidates that are enabled after
+// changing the candidate filter.
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       SurfaceSrflxCandidateOnCandidateFilterChangeFromRelayToNoHost) {
+  rtc::ScopedFakeClock clock;
+  // We need an actual NAT so that the host candidate is not equivalent to the
+  // srflx candidate; otherwise, the host candidate would still surface even
+  // though we disable it via the candidate filter below. This is a result of
+  // the following limitation in the current implementation:
+  //  1. We don't generate the srflx candidate when we have public IP.
+  //  2. We keep the host candidate in this case in CheckCandidateFilter even
+  //     though we intend to filter them.
+  ConfigureEndpoints(
+      NAT_FULL_CONE, NAT_FULL_CONE,
+      kDefaultPortAllocatorFlags | PORTALLOCATOR_ENABLE_SHARED_SOCKET,
+      kDefaultPortAllocatorFlags | PORTALLOCATOR_ENABLE_SHARED_SOCKET);
+  auto* ep1 = GetEndpoint(0);
+  auto* ep2 = GetEndpoint(1);
+  ep1->allocator_->SetCandidateFilter(CF_RELAY);
+  ep2->allocator_->SetCandidateFilter(CF_RELAY);
+  // Enable continual gathering and also resurfacing gathered candidates upon
+  // the candidate filter changed in the ICE configuration.
+  IceConfig ice_config = CreateIceConfig(1000, GATHER_CONTINUALLY);
+  ice_config.surface_ice_candidates_on_ice_transport_type_changed = true;
+  CreateChannels(ice_config, ice_config);
+  ASSERT_TRUE_SIMULATED_WAIT(ep1_ch1()->selected_connection() != nullptr,
+                             kDefaultTimeout, clock);
+  ASSERT_TRUE_SIMULATED_WAIT(ep2_ch1()->selected_connection() != nullptr,
+                             kDefaultTimeout, clock);
+  const uint32_t kCandidateFilterNoHost = CF_ALL & ~CF_HOST;
+  // Loosen the candidate filter at ep1.
+  ep1->allocator_->SetCandidateFilter(kCandidateFilterNoHost);
+  EXPECT_TRUE_SIMULATED_WAIT(
+      ep1_ch1()->selected_connection() != nullptr &&
+          ep1_ch1()->selected_connection()->local_candidate().type() ==
+              STUN_PORT_TYPE,
+      kDefaultTimeout, clock);
+  EXPECT_EQ(RELAY_PORT_TYPE,
+            ep1_ch1()->selected_connection()->remote_candidate().type());
+
+  // Loosen the candidate filter at ep2.
+  ep2->allocator_->SetCandidateFilter(kCandidateFilterNoHost);
+  EXPECT_TRUE_SIMULATED_WAIT(
+      ep2_ch1()->selected_connection() != nullptr &&
+          ep2_ch1()->selected_connection()->local_candidate().type() ==
+              STUN_PORT_TYPE,
+      kDefaultTimeout, clock);
+  // We have migrated to a srflx-srflx candidate pair.
+  EXPECT_EQ(STUN_PORT_TYPE,
+            ep2_ch1()->selected_connection()->remote_candidate().type());
+
+  // Block the traffic over non-relay-to-relay routes and expect a route change.
+  fw()->AddRule(false, rtc::FP_ANY, kPrivateAddrs[0], kPublicAddrs[1]);
+  fw()->AddRule(false, rtc::FP_ANY, kPrivateAddrs[1], kPublicAddrs[0]);
+  fw()->AddRule(false, rtc::FP_ANY, kPrivateAddrs[0], kTurnUdpExtAddr);
+  fw()->AddRule(false, rtc::FP_ANY, kPrivateAddrs[1], kTurnUdpExtAddr);
+  // We should be able to reuse the previously gathered relay candidates.
+  EXPECT_EQ_SIMULATED_WAIT(
+      RELAY_PORT_TYPE,
+      ep1_ch1()->selected_connection()->local_candidate().type(),
+      kDefaultTimeout, clock);
+  EXPECT_EQ(RELAY_PORT_TYPE,
+            ep1_ch1()->selected_connection()->remote_candidate().type());
+  DestroyChannels();
+}
+
+// This is the complement to
+// SurfaceHostCandidateOnCandidateFilterChangeFromRelayToAll, and instead of
+// gathering continually we only gather once, which makes the config
+// `surface_ice_candidates_on_ice_transport_type_changed` ineffective after the
+// gathering stopped.
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       CannotSurfaceTheNewlyAllowedOnFilterChangeIfNotGatheringContinually) {
+  rtc::ScopedFakeClock clock;
+
+  ConfigureEndpoints(
+      OPEN, OPEN,
+      kDefaultPortAllocatorFlags | PORTALLOCATOR_ENABLE_SHARED_SOCKET,
+      kDefaultPortAllocatorFlags | PORTALLOCATOR_ENABLE_SHARED_SOCKET);
+  auto* ep1 = GetEndpoint(0);
+  auto* ep2 = GetEndpoint(1);
+  ep1->allocator_->SetCandidateFilter(CF_RELAY);
+  ep2->allocator_->SetCandidateFilter(CF_RELAY);
+  // Only gather once.
+  IceConfig ice_config = CreateIceConfig(1000, GATHER_ONCE);
+  ice_config.surface_ice_candidates_on_ice_transport_type_changed = true;
+  CreateChannels(ice_config, ice_config);
+  ASSERT_TRUE_SIMULATED_WAIT(ep1_ch1()->selected_connection() != nullptr,
+                             kDefaultTimeout, clock);
+  ASSERT_TRUE_SIMULATED_WAIT(ep2_ch1()->selected_connection() != nullptr,
+                             kDefaultTimeout, clock);
+  // Loosen the candidate filter at ep1.
+  ep1->allocator_->SetCandidateFilter(CF_ALL);
+  // Wait for a period for any potential surfacing of new candidates.
+  SIMULATED_WAIT(false, kDefaultTimeout, clock);
+  EXPECT_EQ(RELAY_PORT_TYPE,
+            ep1_ch1()->selected_connection()->local_candidate().type());
+
+  // Loosen the candidate filter at ep2.
+  ep2->allocator_->SetCandidateFilter(CF_ALL);
+  EXPECT_EQ(RELAY_PORT_TYPE,
+            ep2_ch1()->selected_connection()->local_candidate().type());
+  DestroyChannels();
+}
+
+// Test that when the candidate filter is updated to be more restrictive,
+// candidates that 1) have already been gathered and signaled 2) but no longer
+// match the filter, are not removed.
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       RestrictingCandidateFilterDoesNotRemoveRegatheredCandidates) {
+  rtc::ScopedFakeClock clock;
+
+  ConfigureEndpoints(
+      OPEN, OPEN,
+      kDefaultPortAllocatorFlags | PORTALLOCATOR_ENABLE_SHARED_SOCKET,
+      kDefaultPortAllocatorFlags | PORTALLOCATOR_ENABLE_SHARED_SOCKET);
+  auto* ep1 = GetEndpoint(0);
+  auto* ep2 = GetEndpoint(1);
+  ep1->allocator_->SetCandidateFilter(CF_ALL);
+  ep2->allocator_->SetCandidateFilter(CF_ALL);
+  // Enable continual gathering and also resurfacing gathered candidates upon
+  // the candidate filter changed in the ICE configuration.
+  IceConfig ice_config = CreateIceConfig(1000, GATHER_CONTINUALLY);
+  ice_config.surface_ice_candidates_on_ice_transport_type_changed = true;
+  // Pause candidates so we can gather all types of candidates. See
+  // P2PTransportChannel::OnConnectionStateChange, where we would stop the
+  // gathering when we have a strongly connected candidate pair.
+  PauseCandidates(0);
+  PauseCandidates(1);
+  CreateChannels(ice_config, ice_config);
+
+  // We have gathered host, srflx and relay candidates.
+  EXPECT_TRUE_SIMULATED_WAIT(ep1->saved_candidates_.size() == 3u,
+                             kDefaultTimeout, clock);
+  ResumeCandidates(0);
+  ResumeCandidates(1);
+  ASSERT_TRUE_SIMULATED_WAIT(
+      ep1_ch1()->selected_connection() != nullptr &&
+          LOCAL_PORT_TYPE ==
+              ep1_ch1()->selected_connection()->local_candidate().type() &&
+          ep2_ch1()->selected_connection() != nullptr &&
+          LOCAL_PORT_TYPE ==
+              ep1_ch1()->selected_connection()->remote_candidate().type(),
+      kDefaultTimeout, clock);
+  ASSERT_TRUE_SIMULATED_WAIT(ep2_ch1()->selected_connection() != nullptr,
+                             kDefaultTimeout, clock);
+  // Test that we have a host-host candidate pair selected and the number of
+  // candidates signaled to the remote peer stays the same.
+  auto test_invariants = [this]() {
+    EXPECT_EQ(LOCAL_PORT_TYPE,
+              ep1_ch1()->selected_connection()->local_candidate().type());
+    EXPECT_EQ(LOCAL_PORT_TYPE,
+              ep1_ch1()->selected_connection()->remote_candidate().type());
+    EXPECT_THAT(ep2_ch1()->remote_candidates(), SizeIs(3));
+  };
+
+  test_invariants();
+
+  // Set a more restrictive candidate filter at ep1.
+  ep1->allocator_->SetCandidateFilter(CF_HOST | CF_REFLEXIVE);
+  SIMULATED_WAIT(false, kDefaultTimeout, clock);
+  test_invariants();
+
+  ep1->allocator_->SetCandidateFilter(CF_HOST);
+  SIMULATED_WAIT(false, kDefaultTimeout, clock);
+  test_invariants();
+
+  ep1->allocator_->SetCandidateFilter(CF_NONE);
+  SIMULATED_WAIT(false, kDefaultTimeout, clock);
+  test_invariants();
+  DestroyChannels();
+}
+
+// Verify that things break unless
+// - both parties use the surface_ice_candidates_on_ice_transport_type_changed
+// - both parties loosen candidate filter at the same time (approx.).
+//
+// i.e surface_ice_candidates_on_ice_transport_type_changed requires
+// coordination outside of webrtc to function properly.
+TEST_P(P2PTransportChannelTestWithFieldTrials, SurfaceRequiresCoordination) {
+  webrtc::test::ScopedKeyValueConfig field_trials(
+      field_trials_,
+      "WebRTC-IceFieldTrials/skip_relay_to_non_relay_connections:true/");
+  rtc::ScopedFakeClock clock;
+
+  ConfigureEndpoints(
+      OPEN, OPEN,
+      kDefaultPortAllocatorFlags | PORTALLOCATOR_ENABLE_SHARED_SOCKET,
+      kDefaultPortAllocatorFlags | PORTALLOCATOR_ENABLE_SHARED_SOCKET);
+  auto* ep1 = GetEndpoint(0);
+  auto* ep2 = GetEndpoint(1);
+  ep1->allocator_->SetCandidateFilter(CF_RELAY);
+  ep2->allocator_->SetCandidateFilter(CF_ALL);
+  // Enable continual gathering and also resurfacing gathered candidates upon
+  // the candidate filter changed in the ICE configuration.
+  IceConfig ice_config = CreateIceConfig(1000, GATHER_CONTINUALLY);
+  ice_config.surface_ice_candidates_on_ice_transport_type_changed = true;
+  // Pause candidates gathering so we can gather all types of candidates. See
+  // P2PTransportChannel::OnConnectionStateChange, where we would stop the
+  // gathering when we have a strongly connected candidate pair.
+  PauseCandidates(0);
+  PauseCandidates(1);
+  CreateChannels(ice_config, ice_config);
+
+  // On the caller we only have relay,
+  // on the callee we have host, srflx and relay.
+  EXPECT_TRUE_SIMULATED_WAIT(ep1->saved_candidates_.size() == 1u,
+                             kDefaultTimeout, clock);
+  EXPECT_TRUE_SIMULATED_WAIT(ep2->saved_candidates_.size() == 3u,
+                             kDefaultTimeout, clock);
+
+  ResumeCandidates(0);
+  ResumeCandidates(1);
+  ASSERT_TRUE_SIMULATED_WAIT(
+      ep1_ch1()->selected_connection() != nullptr &&
+          RELAY_PORT_TYPE ==
+              ep1_ch1()->selected_connection()->local_candidate().type() &&
+          ep2_ch1()->selected_connection() != nullptr &&
+          RELAY_PORT_TYPE ==
+              ep1_ch1()->selected_connection()->remote_candidate().type(),
+      kDefaultTimeout, clock);
+  ASSERT_TRUE_SIMULATED_WAIT(ep2_ch1()->selected_connection() != nullptr,
+                             kDefaultTimeout, clock);
+
+  // Wait until the callee discards it's candidates
+  // since they don't manage to connect.
+  SIMULATED_WAIT(false, 300000, clock);
+
+  // And then loosen caller candidate filter.
+  ep1->allocator_->SetCandidateFilter(CF_ALL);
+
+  SIMULATED_WAIT(false, kDefaultTimeout, clock);
+
+  // No p2p connection will be made, it will remain on relay.
+  EXPECT_TRUE(ep1_ch1()->selected_connection() != nullptr &&
+              RELAY_PORT_TYPE ==
+                  ep1_ch1()->selected_connection()->local_candidate().type() &&
+              ep2_ch1()->selected_connection() != nullptr &&
+              RELAY_PORT_TYPE ==
+                  ep1_ch1()->selected_connection()->remote_candidate().type());
+
+  DestroyChannels();
+}
+
+TEST_P(P2PTransportChannelPingTest, TestInitialSelectDampening0) {
+  webrtc::test::ScopedKeyValueConfig field_trials(
+      field_trials_, "WebRTC-IceFieldTrials/initial_select_dampening:0/");
+
+  constexpr int kMargin = 10;
+  rtc::ScopedFakeClock clock;
+  clock.AdvanceTime(webrtc::TimeDelta::Seconds(1));
+
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("test channel", 1, &pa, &field_trials);
+  PrepareChannel(&ch);
+  ch.SetIceConfig(ch.config());
+  ch.MaybeStartGathering();
+
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 100));
+  Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1, &clock);
+  ASSERT_TRUE(conn1 != nullptr);
+  EXPECT_EQ(nullptr, ch.selected_connection());
+  conn1->ReceivedPingResponse(LOW_RTT, "id");  // Becomes writable and receiving
+  // It shall not be selected until 0ms has passed....i.e it should be connected
+  // directly.
+  EXPECT_EQ_SIMULATED_WAIT(conn1, ch.selected_connection(), kMargin, clock);
+}
+
+TEST_P(P2PTransportChannelPingTest, TestInitialSelectDampening) {
+  webrtc::test::ScopedKeyValueConfig field_trials(
+      field_trials_, "WebRTC-IceFieldTrials/initial_select_dampening:100/");
+
+  constexpr int kMargin = 10;
+  rtc::ScopedFakeClock clock;
+  clock.AdvanceTime(webrtc::TimeDelta::Seconds(1));
+
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("test channel", 1, &pa, &field_trials);
+  PrepareChannel(&ch);
+  ch.SetIceConfig(ch.config());
+  ch.MaybeStartGathering();
+
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 100));
+  Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1, &clock);
+  ASSERT_TRUE(conn1 != nullptr);
+  EXPECT_EQ(nullptr, ch.selected_connection());
+  conn1->ReceivedPingResponse(LOW_RTT, "id");  // Becomes writable and receiving
+  // It shall not be selected until 100ms has passed.
+  SIMULATED_WAIT(conn1 == ch.selected_connection(), 100 - kMargin, clock);
+  EXPECT_EQ_SIMULATED_WAIT(conn1, ch.selected_connection(), 2 * kMargin, clock);
+}
+
+TEST_P(P2PTransportChannelPingTest, TestInitialSelectDampeningPingReceived) {
+  webrtc::test::ScopedKeyValueConfig field_trials(
+      field_trials_,
+      "WebRTC-IceFieldTrials/initial_select_dampening_ping_received:100/");
+
+  constexpr int kMargin = 10;
+  rtc::ScopedFakeClock clock;
+  clock.AdvanceTime(webrtc::TimeDelta::Seconds(1));
+
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("test channel", 1, &pa, &field_trials);
+  PrepareChannel(&ch);
+  ch.SetIceConfig(ch.config());
+  ch.MaybeStartGathering();
+
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 100));
+  Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1, &clock);
+  ASSERT_TRUE(conn1 != nullptr);
+  EXPECT_EQ(nullptr, ch.selected_connection());
+  conn1->ReceivedPingResponse(LOW_RTT, "id");  // Becomes writable and receiving
+  conn1->ReceivedPing("id1");                  //
+  // It shall not be selected until 100ms has passed.
+  SIMULATED_WAIT(conn1 == ch.selected_connection(), 100 - kMargin, clock);
+  EXPECT_EQ_SIMULATED_WAIT(conn1, ch.selected_connection(), 2 * kMargin, clock);
+}
+
+TEST_P(P2PTransportChannelPingTest, TestInitialSelectDampeningBoth) {
+  webrtc::test::ScopedKeyValueConfig field_trials(
+      field_trials_,
+      "WebRTC-IceFieldTrials/"
+      "initial_select_dampening:100,initial_select_dampening_ping_received:"
+      "50/");
+
+  constexpr int kMargin = 10;
+  rtc::ScopedFakeClock clock;
+  clock.AdvanceTime(webrtc::TimeDelta::Seconds(1));
+
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  P2PTransportChannel ch("test channel", 1, &pa, &field_trials);
+  PrepareChannel(&ch);
+  ch.SetIceConfig(ch.config());
+  ch.MaybeStartGathering();
+
+  ch.AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 100));
+  Connection* conn1 = WaitForConnectionTo(&ch, "1.1.1.1", 1, &clock);
+  ASSERT_TRUE(conn1 != nullptr);
+  EXPECT_EQ(nullptr, ch.selected_connection());
+  conn1->ReceivedPingResponse(LOW_RTT, "id");  // Becomes writable and receiving
+  // It shall not be selected until 100ms has passed....but only wait ~50 now.
+  SIMULATED_WAIT(conn1 == ch.selected_connection(), 50 - kMargin, clock);
+  // Now receiving ping and new timeout should kick in.
+  conn1->ReceivedPing("id1");  //
+  EXPECT_EQ_SIMULATED_WAIT(conn1, ch.selected_connection(), 2 * kMargin, clock);
+}
+
+class P2PTransportChannelIceControllerTest : public TestWithParam<std::string> {
+};
+
+INSTANTIATE_TEST_SUITE_P(Legacy,
+                         P2PTransportChannelIceControllerTest,
+                         Values(""));
+INSTANTIATE_TEST_SUITE_P(Active,
+                         P2PTransportChannelIceControllerTest,
+                         Values("WebRTC-UseActiveIceController/Enabled/"));
+
+TEST_P(P2PTransportChannelIceControllerTest, InjectIceController) {
+  webrtc::test::ScopedKeyValueConfig field_trials(GetParam());
+  std::unique_ptr<rtc::SocketServer> socket_server =
+      rtc::CreateDefaultSocketServer();
+  rtc::AutoSocketServerThread main_thread(socket_server.get());
+  rtc::BasicPacketSocketFactory packet_socket_factory(socket_server.get());
+  MockIceControllerFactory factory;
+  FakePortAllocator pa(rtc::Thread::Current(), &packet_socket_factory,
+                       &field_trials);
+  EXPECT_CALL(factory, RecordIceControllerCreated()).Times(1);
+  webrtc::IceTransportInit init;
+  init.set_port_allocator(&pa);
+  init.set_ice_controller_factory(&factory);
+  init.set_field_trials(&field_trials);
+  auto dummy =
+      P2PTransportChannel::Create("transport_name",
+                                  /* component= */ 77, std::move(init));
+}
+
+TEST(P2PTransportChannel, InjectActiveIceController) {
+  webrtc::test::ScopedKeyValueConfig field_trials(
+      "WebRTC-UseActiveIceController/Enabled/");
+  std::unique_ptr<rtc::SocketServer> socket_server =
+      rtc::CreateDefaultSocketServer();
+  rtc::AutoSocketServerThread main_thread(socket_server.get());
+  rtc::BasicPacketSocketFactory packet_socket_factory(socket_server.get());
+  MockActiveIceControllerFactory factory;
+  FakePortAllocator pa(rtc::Thread::Current(), &packet_socket_factory,
+                       &field_trials);
+  EXPECT_CALL(factory, RecordActiveIceControllerCreated()).Times(1);
+  webrtc::IceTransportInit init;
+  init.set_port_allocator(&pa);
+  init.set_active_ice_controller_factory(&factory);
+  init.set_field_trials(&field_trials);
+  auto dummy =
+      P2PTransportChannel::Create("transport_name",
+                                  /* component= */ 77, std::move(init));
+}
+
+class ForgetLearnedStateController : public cricket::BasicIceController {
+ public:
+  explicit ForgetLearnedStateController(
+      const cricket::IceControllerFactoryArgs& args)
+      : cricket::BasicIceController(args) {}
+
+  SwitchResult SortAndSwitchConnection(IceSwitchReason reason) override {
+    auto result = cricket::BasicIceController::SortAndSwitchConnection(reason);
+    if (forget_connnection_) {
+      result.connections_to_forget_state_on.push_back(forget_connnection_);
+      forget_connnection_ = nullptr;
+    }
+    result.recheck_event.emplace(IceSwitchReason::ICE_CONTROLLER_RECHECK, 100);
+    return result;
+  }
+
+  void ForgetThisConnectionNextTimeSortAndSwitchConnectionIsCalled(
+      Connection* con) {
+    forget_connnection_ = con;
+  }
+
+ private:
+  Connection* forget_connnection_ = nullptr;
+};
+
+class ForgetLearnedStateControllerFactory
+    : public cricket::IceControllerFactoryInterface {
+ public:
+  std::unique_ptr<cricket::IceControllerInterface> Create(
+      const cricket::IceControllerFactoryArgs& args) override {
+    auto controller = std::make_unique<ForgetLearnedStateController>(args);
+    // Keep a pointer to allow modifying calls.
+    // Must not be used after the p2ptransportchannel has been destructed.
+    controller_ = controller.get();
+    return controller;
+  }
+  virtual ~ForgetLearnedStateControllerFactory() = default;
+
+  ForgetLearnedStateController* controller_;
+};
+
+TEST_P(P2PTransportChannelPingTest, TestForgetLearnedState) {
+  ForgetLearnedStateControllerFactory factory;
+  FakePortAllocator pa(rtc::Thread::Current(), packet_socket_factory(),
+                       &field_trials_);
+  webrtc::IceTransportInit init;
+  init.set_port_allocator(&pa);
+  init.set_ice_controller_factory(&factory);
+  init.set_field_trials(&field_trials_);
+  auto ch =
+      P2PTransportChannel::Create("ping sufficiently", 1, std::move(init));
+
+  PrepareChannel(ch.get());
+  ch->MaybeStartGathering();
+  ch->AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "1.1.1.1", 1, 1));
+  ch->AddRemoteCandidate(CreateUdpCandidate(LOCAL_PORT_TYPE, "2.2.2.2", 2, 2));
+
+  Connection* conn1 = WaitForConnectionTo(ch.get(), "1.1.1.1", 1);
+  Connection* conn2 = WaitForConnectionTo(ch.get(), "2.2.2.2", 2);
+  ASSERT_TRUE(conn1 != nullptr);
+  ASSERT_TRUE(conn2 != nullptr);
+
+  // Wait for conn1 to be selected.
+  conn1->ReceivedPingResponse(LOW_RTT, "id");
+  EXPECT_EQ_WAIT(conn1, ch->selected_connection(), kMediumTimeout);
+
+  conn2->ReceivedPingResponse(LOW_RTT, "id");
+  EXPECT_TRUE(conn2->writable());
+
+  // Now let the ice controller signal to P2PTransportChannel that it
+  // should Forget conn2.
+  factory.controller_
+      ->ForgetThisConnectionNextTimeSortAndSwitchConnectionIsCalled(conn2);
+
+  // We don't have a mock Connection, so verify this by checking that it
+  // is no longer writable.
+  EXPECT_EQ_WAIT(false, conn2->writable(), kMediumTimeout);
+}
+
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       DisableDnsLookupsWithTransportPolicyRelay) {
+  ConfigureEndpoints(OPEN, OPEN, kDefaultPortAllocatorFlags,
+                     kDefaultPortAllocatorFlags);
+  auto* ep1 = GetEndpoint(0);
+  ep1->allocator_->SetCandidateFilter(CF_RELAY);
+
+  std::unique_ptr<webrtc::MockAsyncDnsResolver> mock_async_resolver =
+      std::make_unique<webrtc::MockAsyncDnsResolver>();
+  // This test expects resolution to not be started.
+  EXPECT_CALL(*mock_async_resolver, Start(_, _)).Times(0);
+
+  webrtc::MockAsyncDnsResolverFactory mock_async_resolver_factory;
+  ON_CALL(mock_async_resolver_factory, Create())
+      .WillByDefault(
+          [&mock_async_resolver]() { return std::move(mock_async_resolver); });
+
+  ep1->async_dns_resolver_factory_ = &mock_async_resolver_factory;
+
+  CreateChannels();
+
+  ep1_ch1()->AddRemoteCandidate(
+      CreateUdpCandidate(LOCAL_PORT_TYPE, "hostname.test", 1, 100));
+
+  DestroyChannels();
+}
+
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       DisableDnsLookupsWithTransportPolicyNone) {
+  ConfigureEndpoints(OPEN, OPEN, kDefaultPortAllocatorFlags,
+                     kDefaultPortAllocatorFlags);
+  auto* ep1 = GetEndpoint(0);
+  ep1->allocator_->SetCandidateFilter(CF_NONE);
+
+  std::unique_ptr<webrtc::MockAsyncDnsResolver> mock_async_resolver =
+      std::make_unique<webrtc::MockAsyncDnsResolver>();
+  // This test expects resolution to not be started.
+  EXPECT_CALL(*mock_async_resolver, Start(_, _)).Times(0);
+
+  webrtc::MockAsyncDnsResolverFactory mock_async_resolver_factory;
+  ON_CALL(mock_async_resolver_factory, Create())
+      .WillByDefault(
+          [&mock_async_resolver]() { return std::move(mock_async_resolver); });
+
+  ep1->async_dns_resolver_factory_ = &mock_async_resolver_factory;
+
+  CreateChannels();
+
+  ep1_ch1()->AddRemoteCandidate(
+      CreateUdpCandidate(LOCAL_PORT_TYPE, "hostname.test", 1, 100));
+
+  DestroyChannels();
+}
+
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       EnableDnsLookupsWithTransportPolicyNoHost) {
+  ConfigureEndpoints(OPEN, OPEN, kDefaultPortAllocatorFlags,
+                     kDefaultPortAllocatorFlags);
+  auto* ep1 = GetEndpoint(0);
+  ep1->allocator_->SetCandidateFilter(CF_ALL & ~CF_HOST);
+
+  std::unique_ptr<webrtc::MockAsyncDnsResolver> mock_async_resolver =
+      std::make_unique<webrtc::MockAsyncDnsResolver>();
+  bool lookup_started = false;
+  EXPECT_CALL(*mock_async_resolver, Start(_, _))
+      .WillOnce(Assign(&lookup_started, true));
+
+  webrtc::MockAsyncDnsResolverFactory mock_async_resolver_factory;
+  EXPECT_CALL(mock_async_resolver_factory, Create())
+      .WillOnce(
+          [&mock_async_resolver]() { return std::move(mock_async_resolver); });
+
+  ep1->async_dns_resolver_factory_ = &mock_async_resolver_factory;
+
+  CreateChannels();
+
+  ep1_ch1()->AddRemoteCandidate(
+      CreateUdpCandidate(LOCAL_PORT_TYPE, "hostname.test", 1, 100));
+
+  EXPECT_TRUE(lookup_started);
+
+  DestroyChannels();
+}
+
+class GatherAfterConnectedTest
+    : public P2PTransportChannelTest,
+      public WithParamInterface<std::tuple<bool, std::string>> {
+ public:
+  GatherAfterConnectedTest()
+      : P2PTransportChannelTest(std::get<1>(GetParam())) {}
+};
+
+TEST_P(GatherAfterConnectedTest, GatherAfterConnected) {
+  const bool stop_gather_on_strongly_connected = std::get<0>(GetParam());
+  const std::string field_trial =
+      std::string("WebRTC-IceFieldTrials/stop_gather_on_strongly_connected:") +
+      (stop_gather_on_strongly_connected ? "true/" : "false/");
+  webrtc::test::ScopedKeyValueConfig field_trials(field_trials_, field_trial);
+
+  rtc::ScopedFakeClock clock;
+  // Use local + relay
+  constexpr uint32_t flags =
+      kDefaultPortAllocatorFlags | PORTALLOCATOR_ENABLE_SHARED_SOCKET |
+      PORTALLOCATOR_DISABLE_STUN | PORTALLOCATOR_DISABLE_TCP;
+  ConfigureEndpoints(OPEN, OPEN, flags, flags);
+  auto* ep1 = GetEndpoint(0);
+  auto* ep2 = GetEndpoint(1);
+  ep1->allocator_->SetCandidateFilter(CF_ALL);
+  ep2->allocator_->SetCandidateFilter(CF_ALL);
+
+  // Use step delay 3s which is long enough for
+  // connection to be established before managing to gather relay candidates.
+  int delay = 3000;
+  SetAllocationStepDelay(0, delay);
+  SetAllocationStepDelay(1, delay);
+  IceConfig ice_config = CreateIceConfig(1000, GATHER_CONTINUALLY);
+  CreateChannels(ice_config, ice_config);
+
+  PauseCandidates(0);
+  PauseCandidates(1);
+
+  // We have gathered host candidates but not relay.
+  ASSERT_TRUE_SIMULATED_WAIT(ep1->saved_candidates_.size() == 1u &&
+                                 ep2->saved_candidates_.size() == 1u,
+                             kDefaultTimeout, clock);
+
+  ResumeCandidates(0);
+  ResumeCandidates(1);
+
+  PauseCandidates(0);
+  PauseCandidates(1);
+
+  ASSERT_TRUE_SIMULATED_WAIT(ep1_ch1()->remote_candidates().size() == 1 &&
+                                 ep2_ch1()->remote_candidates().size() == 1,
+                             kDefaultTimeout, clock);
+
+  ASSERT_TRUE_SIMULATED_WAIT(
+      ep1_ch1()->selected_connection() && ep2_ch1()->selected_connection(),
+      kDefaultTimeout, clock);
+
+  clock.AdvanceTime(webrtc::TimeDelta::Millis(10 * delay));
+
+  if (stop_gather_on_strongly_connected) {
+    // The relay candidates gathered has not been propagated to channel.
+    EXPECT_EQ(ep1->saved_candidates_.size(), 0u);
+    EXPECT_EQ(ep2->saved_candidates_.size(), 0u);
+  } else {
+    // The relay candidates gathered has been propagated to channel.
+    EXPECT_EQ(ep1->saved_candidates_.size(), 1u);
+    EXPECT_EQ(ep2->saved_candidates_.size(), 1u);
+  }
+}
+
+TEST_P(GatherAfterConnectedTest, GatherAfterConnectedMultiHomed) {
+  const bool stop_gather_on_strongly_connected = std::get<0>(GetParam());
+  const std::string field_trial =
+      std::string("WebRTC-IceFieldTrials/stop_gather_on_strongly_connected:") +
+      (stop_gather_on_strongly_connected ? "true/" : "false/");
+  webrtc::test::ScopedKeyValueConfig field_trials(field_trials_, field_trial);
+
+  rtc::ScopedFakeClock clock;
+  // Use local + relay
+  constexpr uint32_t flags =
+      kDefaultPortAllocatorFlags | PORTALLOCATOR_ENABLE_SHARED_SOCKET |
+      PORTALLOCATOR_DISABLE_STUN | PORTALLOCATOR_DISABLE_TCP;
+  AddAddress(0, kAlternateAddrs[0]);
+  ConfigureEndpoints(OPEN, OPEN, flags, flags);
+  auto* ep1 = GetEndpoint(0);
+  auto* ep2 = GetEndpoint(1);
+  ep1->allocator_->SetCandidateFilter(CF_ALL);
+  ep2->allocator_->SetCandidateFilter(CF_ALL);
+
+  // Use step delay 3s which is long enough for
+  // connection to be established before managing to gather relay candidates.
+  int delay = 3000;
+  SetAllocationStepDelay(0, delay);
+  SetAllocationStepDelay(1, delay);
+  IceConfig ice_config = CreateIceConfig(1000, GATHER_CONTINUALLY);
+  CreateChannels(ice_config, ice_config);
+
+  PauseCandidates(0);
+  PauseCandidates(1);
+
+  // We have gathered host candidates but not relay.
+  ASSERT_TRUE_SIMULATED_WAIT(ep1->saved_candidates_.size() == 2u &&
+                                 ep2->saved_candidates_.size() == 1u,
+                             kDefaultTimeout, clock);
+
+  ResumeCandidates(0);
+  ResumeCandidates(1);
+
+  PauseCandidates(0);
+  PauseCandidates(1);
+
+  ASSERT_TRUE_SIMULATED_WAIT(ep1_ch1()->remote_candidates().size() == 1 &&
+                                 ep2_ch1()->remote_candidates().size() == 2,
+                             kDefaultTimeout, clock);
+
+  ASSERT_TRUE_SIMULATED_WAIT(
+      ep1_ch1()->selected_connection() && ep2_ch1()->selected_connection(),
+      kDefaultTimeout, clock);
+
+  clock.AdvanceTime(webrtc::TimeDelta::Millis(10 * delay));
+
+  if (stop_gather_on_strongly_connected) {
+    // The relay candidates gathered has not been propagated to channel.
+    EXPECT_EQ(ep1->saved_candidates_.size(), 0u);
+    EXPECT_EQ(ep2->saved_candidates_.size(), 0u);
+  } else {
+    // The relay candidates gathered has been propagated.
+    EXPECT_EQ(ep1->saved_candidates_.size(), 2u);
+    EXPECT_EQ(ep2->saved_candidates_.size(), 1u);
+  }
+}
+
+INSTANTIATE_TEST_SUITE_P(Legacy,
+                         GatherAfterConnectedTest,
+                         Combine(Values(true, false), Values("")));
+INSTANTIATE_TEST_SUITE_P(
+    Active,
+    GatherAfterConnectedTest,
+    Combine(Values(true, false),
+            Values("WebRTC-UseActiveIceController/Enabled/")));
+
+// Tests no candidates are generated with old ice ufrag/passwd after an ice
+// restart even if continual gathering is enabled.
+TEST_P(P2PTransportChannelTestWithFieldTrials,
+       TestIceNoOldCandidatesAfterIceRestart) {
+  rtc::ScopedFakeClock clock;
+  AddAddress(0, kAlternateAddrs[0]);
+  ConfigureEndpoints(OPEN, OPEN, kDefaultPortAllocatorFlags,
+                     kDefaultPortAllocatorFlags);
+
+  // gathers continually.
+  IceConfig config = CreateIceConfig(1000, GATHER_CONTINUALLY);
+  CreateChannels(config, config);
+
+  EXPECT_TRUE_SIMULATED_WAIT(CheckConnected(ep1_ch1(), ep2_ch1()),
+                             kDefaultTimeout, clock);
+
+  PauseCandidates(0);
+
+  ep1_ch1()->SetIceParameters(kIceParams[3]);
+  ep1_ch1()->MaybeStartGathering();
+
+  EXPECT_TRUE_SIMULATED_WAIT(GetEndpoint(0)->saved_candidates_.size() > 0,
+                             kDefaultTimeout, clock);
+
+  for (const auto& cd : GetEndpoint(0)->saved_candidates_) {
+    EXPECT_EQ(cd.candidate.username(), kIceUfrag[3]);
+  }
+
+  DestroyChannels();
+}
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/packet_transport_internal.cc b/third_party/libwebrtc/p2p/base/packet_transport_internal.cc
new file mode 100644
index 0000000000..0904cb2d3e
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/packet_transport_internal.cc
@@ -0,0 +1,27 @@
+/*
+ *  Copyright 2017 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/packet_transport_internal.h"
+
+namespace rtc {
+
+PacketTransportInternal::PacketTransportInternal() = default;
+
+PacketTransportInternal::~PacketTransportInternal() = default;
+
+bool PacketTransportInternal::GetOption(rtc::Socket::Option opt, int* value) {
+  return false;
+}
+
+absl::optional<NetworkRoute> PacketTransportInternal::network_route() const {
+  return absl::optional<NetworkRoute>();
+}
+
+}  // namespace rtc
diff --git a/third_party/libwebrtc/p2p/base/packet_transport_internal.h b/third_party/libwebrtc/p2p/base/packet_transport_internal.h
new file mode 100644
index 0000000000..2ca47d533d
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/packet_transport_internal.h
@@ -0,0 +1,108 @@
+/*
+ *  Copyright 2017 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_PACKET_TRANSPORT_INTERNAL_H_
+#define P2P_BASE_PACKET_TRANSPORT_INTERNAL_H_
+
+#include <string>
+#include <vector>
+
+#include "absl/types/optional.h"
+#include "p2p/base/port.h"
+#include "rtc_base/async_packet_socket.h"
+#include "rtc_base/network_route.h"
+#include "rtc_base/socket.h"
+#include "rtc_base/system/rtc_export.h"
+#include "rtc_base/third_party/sigslot/sigslot.h"
+
+namespace rtc {
+struct PacketOptions;
+struct SentPacket;
+
+class RTC_EXPORT PacketTransportInternal : public sigslot::has_slots<> {
+ public:
+  virtual const std::string& transport_name() const = 0;
+
+  // The transport has been established.
+  virtual bool writable() const = 0;
+
+  // The transport has received a packet in the last X milliseconds, here X is
+  // configured by each implementation.
+  virtual bool receiving() const = 0;
+
+  // Attempts to send the given packet.
+  // The return value is < 0 on failure. The return value in failure case is not
+  // descriptive. Depending on failure cause and implementation details
+  // GetError() returns an descriptive errno.h error value.
+  // This mimics posix socket send() or sendto() behavior.
+  // TODO(johan): Reliable, meaningful, consistent error codes for all
+  // implementations would be nice.
+  // TODO(johan): Remove the default argument once channel code is updated.
+  virtual int SendPacket(const char* data,
+                         size_t len,
+                         const rtc::PacketOptions& options,
+                         int flags = 0) = 0;
+
+  // Sets a socket option. Note that not all options are
+  // supported by all transport types.
+  virtual int SetOption(rtc::Socket::Option opt, int value) = 0;
+
+  // TODO(pthatcher): Once Chrome's MockPacketTransportInterface implements
+  // this, remove the default implementation.
+  virtual bool GetOption(rtc::Socket::Option opt, int* value);
+
+  // Returns the most recent error that occurred on this channel.
+  virtual int GetError() = 0;
+
+  // Returns the current network route with transport overhead.
+  // TODO(zhihuang): Make it pure virtual once the Chrome/remoting is updated.
+  virtual absl::optional<NetworkRoute> network_route() const;
+
+  // Emitted when the writable state, represented by `writable()`, changes.
+  sigslot::signal1<PacketTransportInternal*> SignalWritableState;
+
+  //  Emitted when the PacketTransportInternal is ready to send packets. "Ready
+  //  to send" is more sensitive than the writable state; a transport may be
+  //  writable, but temporarily not able to send packets. For example, the
+  //  underlying transport's socket buffer may be full, as indicated by
+  //  SendPacket's return code and/or GetError.
+  sigslot::signal1<PacketTransportInternal*> SignalReadyToSend;
+
+  // Emitted when receiving state changes to true.
+  sigslot::signal1<PacketTransportInternal*> SignalReceivingState;
+
+  // Signalled each time a packet is received on this channel.
+  sigslot::signal5<PacketTransportInternal*,
+                   const char*,
+                   size_t,
+                   // TODO(bugs.webrtc.org/9584): Change to passing the int64_t
+                   // timestamp by value.
+                   const int64_t&,
+                   int>
+      SignalReadPacket;
+
+  // Signalled each time a packet is sent on this channel.
+  sigslot::signal2<PacketTransportInternal*, const rtc::SentPacket&>
+      SignalSentPacket;
+
+  // Signalled when the current network route has changed.
+  sigslot::signal1<absl::optional<rtc::NetworkRoute>> SignalNetworkRouteChanged;
+
+  // Signalled when the transport is closed.
+  sigslot::signal1<PacketTransportInternal*> SignalClosed;
+
+ protected:
+  PacketTransportInternal();
+  ~PacketTransportInternal() override;
+};
+
+}  // namespace rtc
+
+#endif  // P2P_BASE_PACKET_TRANSPORT_INTERNAL_H_
diff --git a/third_party/libwebrtc/p2p/base/port.cc b/third_party/libwebrtc/p2p/base/port.cc
new file mode 100644
index 0000000000..5c5ac6319c
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/port.cc
@@ -0,0 +1,969 @@
+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/port.h"
+
+#include <math.h>
+
+#include <algorithm>
+#include <memory>
+#include <utility>
+#include <vector>
+
+#include "absl/algorithm/container.h"
+#include "absl/memory/memory.h"
+#include "absl/strings/match.h"
+#include "absl/strings/string_view.h"
+#include "p2p/base/connection.h"
+#include "p2p/base/port_allocator.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/crc32.h"
+#include "rtc_base/helpers.h"
+#include "rtc_base/logging.h"
+#include "rtc_base/mdns_responder_interface.h"
+#include "rtc_base/message_digest.h"
+#include "rtc_base/network.h"
+#include "rtc_base/numerics/safe_minmax.h"
+#include "rtc_base/string_encode.h"
+#include "rtc_base/string_utils.h"
+#include "rtc_base/strings/string_builder.h"
+#include "rtc_base/third_party/base64/base64.h"
+#include "rtc_base/trace_event.h"
+
+namespace cricket {
+namespace {
+
+using ::webrtc::RTCError;
+using ::webrtc::RTCErrorType;
+using ::webrtc::TaskQueueBase;
+using ::webrtc::TimeDelta;
+
+rtc::PacketInfoProtocolType ConvertProtocolTypeToPacketInfoProtocolType(
+    cricket::ProtocolType type) {
+  switch (type) {
+    case cricket::ProtocolType::PROTO_UDP:
+      return rtc::PacketInfoProtocolType::kUdp;
+    case cricket::ProtocolType::PROTO_TCP:
+      return rtc::PacketInfoProtocolType::kTcp;
+    case cricket::ProtocolType::PROTO_SSLTCP:
+      return rtc::PacketInfoProtocolType::kSsltcp;
+    case cricket::ProtocolType::PROTO_TLS:
+      return rtc::PacketInfoProtocolType::kTls;
+    default:
+      return rtc::PacketInfoProtocolType::kUnknown;
+  }
+}
+
+// The delay before we begin checking if this port is useless. We set
+// it to a little higher than a total STUN timeout.
+const int kPortTimeoutDelay = cricket::STUN_TOTAL_TIMEOUT + 5000;
+
+}  // namespace
+
+// TODO(ronghuawu): Use "local", "srflx", "prflx" and "relay". But this requires
+// the signaling part be updated correspondingly as well.
+const char LOCAL_PORT_TYPE[] = "local";
+const char STUN_PORT_TYPE[] = "stun";
+const char PRFLX_PORT_TYPE[] = "prflx";
+const char RELAY_PORT_TYPE[] = "relay";
+
+static const char* const PROTO_NAMES[] = {UDP_PROTOCOL_NAME, TCP_PROTOCOL_NAME,
+                                          SSLTCP_PROTOCOL_NAME,
+                                          TLS_PROTOCOL_NAME};
+
+const char* ProtoToString(ProtocolType proto) {
+  return PROTO_NAMES[proto];
+}
+
+absl::optional<ProtocolType> StringToProto(absl::string_view proto_name) {
+  for (size_t i = 0; i <= PROTO_LAST; ++i) {
+    if (absl::EqualsIgnoreCase(PROTO_NAMES[i], proto_name)) {
+      return static_cast<ProtocolType>(i);
+    }
+  }
+  return absl::nullopt;
+}
+
+// RFC 6544, TCP candidate encoding rules.
+const int DISCARD_PORT = 9;
+const char TCPTYPE_ACTIVE_STR[] = "active";
+const char TCPTYPE_PASSIVE_STR[] = "passive";
+const char TCPTYPE_SIMOPEN_STR[] = "so";
+
+std::string Port::ComputeFoundation(absl::string_view type,
+                                    absl::string_view protocol,
+                                    absl::string_view relay_protocol,
+                                    const rtc::SocketAddress& base_address) {
+  // TODO(bugs.webrtc.org/14605): ensure IceTiebreaker() is set.
+  rtc::StringBuilder sb;
+  sb << type << base_address.ipaddr().ToString() << protocol << relay_protocol
+     << rtc::ToString(IceTiebreaker());
+  return rtc::ToString(rtc::ComputeCrc32(sb.Release()));
+}
+
+Port::Port(TaskQueueBase* thread,
+           absl::string_view type,
+           rtc::PacketSocketFactory* factory,
+           const rtc::Network* network,
+           absl::string_view username_fragment,
+           absl::string_view password,
+           const webrtc::FieldTrialsView* field_trials)
+    : thread_(thread),
+      factory_(factory),
+      type_(type),
+      send_retransmit_count_attribute_(false),
+      network_(network),
+      min_port_(0),
+      max_port_(0),
+      component_(ICE_CANDIDATE_COMPONENT_DEFAULT),
+      generation_(0),
+      ice_username_fragment_(username_fragment),
+      password_(password),
+      timeout_delay_(kPortTimeoutDelay),
+      enable_port_packets_(false),
+      ice_role_(ICEROLE_UNKNOWN),
+      tiebreaker_(0),
+      shared_socket_(true),
+      weak_factory_(this),
+      field_trials_(field_trials) {
+  RTC_DCHECK(factory_ != NULL);
+  Construct();
+}
+
+Port::Port(TaskQueueBase* thread,
+           absl::string_view type,
+           rtc::PacketSocketFactory* factory,
+           const rtc::Network* network,
+           uint16_t min_port,
+           uint16_t max_port,
+           absl::string_view username_fragment,
+           absl::string_view password,
+           const webrtc::FieldTrialsView* field_trials)
+    : thread_(thread),
+      factory_(factory),
+      type_(type),
+      send_retransmit_count_attribute_(false),
+      network_(network),
+      min_port_(min_port),
+      max_port_(max_port),
+      component_(ICE_CANDIDATE_COMPONENT_DEFAULT),
+      generation_(0),
+      ice_username_fragment_(username_fragment),
+      password_(password),
+      timeout_delay_(kPortTimeoutDelay),
+      enable_port_packets_(false),
+      ice_role_(ICEROLE_UNKNOWN),
+      tiebreaker_(0),
+      shared_socket_(false),
+      weak_factory_(this),
+      field_trials_(field_trials) {
+  RTC_DCHECK(factory_ != NULL);
+  Construct();
+}
+
+void Port::Construct() {
+  // TODO(pthatcher): Remove this old behavior once we're sure no one
+  // relies on it.  If the username_fragment and password are empty,
+  // we should just create one.
+  if (ice_username_fragment_.empty()) {
+    RTC_DCHECK(password_.empty());
+    ice_username_fragment_ = rtc::CreateRandomString(ICE_UFRAG_LENGTH);
+    password_ = rtc::CreateRandomString(ICE_PWD_LENGTH);
+  }
+  network_->SignalTypeChanged.connect(this, &Port::OnNetworkTypeChanged);
+  network_cost_ = network_->GetCost(field_trials());
+
+  PostDestroyIfDead(/*delayed=*/true);
+  RTC_LOG(LS_INFO) << ToString() << ": Port created with network cost "
+                   << network_cost_;
+}
+
+Port::~Port() {
+  RTC_DCHECK_RUN_ON(thread_);
+  CancelPendingTasks();
+  DestroyAllConnections();
+}
+
+const std::string& Port::Type() const {
+  return type_;
+}
+const rtc::Network* Port::Network() const {
+  return network_;
+}
+
+IceRole Port::GetIceRole() const {
+  return ice_role_;
+}
+
+void Port::SetIceRole(IceRole role) {
+  ice_role_ = role;
+}
+
+void Port::SetIceTiebreaker(uint64_t tiebreaker) {
+  tiebreaker_ = tiebreaker;
+}
+
+uint64_t Port::IceTiebreaker() const {
+  return tiebreaker_;
+}
+
+bool Port::SharedSocket() const {
+  return shared_socket_;
+}
+
+void Port::SetIceParameters(int component,
+                            absl::string_view username_fragment,
+                            absl::string_view password) {
+  RTC_DCHECK_RUN_ON(thread_);
+  component_ = component;
+  ice_username_fragment_ = std::string(username_fragment);
+  password_ = std::string(password);
+  for (Candidate& c : candidates_) {
+    c.set_component(component);
+    c.set_username(username_fragment);
+    c.set_password(password);
+  }
+
+  // In case any connections exist make sure we update them too.
+  for (auto& [unused, connection] : connections_) {
+    connection->UpdateLocalIceParameters(component, username_fragment,
+                                         password);
+  }
+}
+
+const std::vector<Candidate>& Port::Candidates() const {
+  return candidates_;
+}
+
+Connection* Port::GetConnection(const rtc::SocketAddress& remote_addr) {
+  AddressMap::const_iterator iter = connections_.find(remote_addr);
+  if (iter != connections_.end())
+    return iter->second;
+  else
+    return NULL;
+}
+
+void Port::AddAddress(const rtc::SocketAddress& address,
+                      const rtc::SocketAddress& base_address,
+                      const rtc::SocketAddress& related_address,
+                      absl::string_view protocol,
+                      absl::string_view relay_protocol,
+                      absl::string_view tcptype,
+                      absl::string_view type,
+                      uint32_t type_preference,
+                      uint32_t relay_preference,
+                      absl::string_view url,
+                      bool is_final) {
+  RTC_DCHECK_RUN_ON(thread_);
+  if (protocol == TCP_PROTOCOL_NAME && type == LOCAL_PORT_TYPE) {
+    RTC_DCHECK(!tcptype.empty());
+  }
+
+  std::string foundation =
+      ComputeFoundation(type, protocol, relay_protocol, base_address);
+  Candidate c(component_, protocol, address, 0U, username_fragment(), password_,
+              type, generation_, foundation, network_->id(), network_cost_);
+  c.set_priority(
+      c.GetPriority(type_preference, network_->preference(), relay_preference));
+  c.set_relay_protocol(relay_protocol);
+  c.set_tcptype(tcptype);
+  c.set_network_name(network_->name());
+  c.set_network_type(network_->type());
+  c.set_underlying_type_for_vpn(network_->underlying_type_for_vpn());
+  c.set_url(url);
+  c.set_related_address(related_address);
+
+  bool pending = MaybeObfuscateAddress(&c, type, is_final);
+
+  if (!pending) {
+    FinishAddingAddress(c, is_final);
+  }
+}
+
+bool Port::MaybeObfuscateAddress(Candidate* c,
+                                 absl::string_view type,
+                                 bool is_final) {
+  // TODO(bugs.webrtc.org/9723): Use a config to control the feature of IP
+  // handling with mDNS.
+  if (network_->GetMdnsResponder() == nullptr) {
+    return false;
+  }
+  if (type != LOCAL_PORT_TYPE) {
+    return false;
+  }
+
+  auto copy = *c;
+  auto weak_ptr = weak_factory_.GetWeakPtr();
+  auto callback = [weak_ptr, copy, is_final](const rtc::IPAddress& addr,
+                                             absl::string_view name) mutable {
+    RTC_DCHECK(copy.address().ipaddr() == addr);
+    rtc::SocketAddress hostname_address(name, copy.address().port());
+    // In Port and Connection, we need the IP address information to
+    // correctly handle the update of candidate type to prflx. The removal
+    // of IP address when signaling this candidate will take place in
+    // BasicPortAllocatorSession::OnCandidateReady, via SanitizeCandidate.
+    hostname_address.SetResolvedIP(addr);
+    copy.set_address(hostname_address);
+    copy.set_related_address(rtc::SocketAddress());
+    if (weak_ptr != nullptr) {
+      RTC_DCHECK_RUN_ON(weak_ptr->thread_);
+      weak_ptr->set_mdns_name_registration_status(
+          MdnsNameRegistrationStatus::kCompleted);
+      weak_ptr->FinishAddingAddress(copy, is_final);
+    }
+  };
+  set_mdns_name_registration_status(MdnsNameRegistrationStatus::kInProgress);
+  network_->GetMdnsResponder()->CreateNameForAddress(copy.address().ipaddr(),
+                                                     callback);
+  return true;
+}
+
+void Port::FinishAddingAddress(const Candidate& c, bool is_final) {
+  candidates_.push_back(c);
+  SignalCandidateReady(this, c);
+
+  PostAddAddress(is_final);
+}
+
+void Port::PostAddAddress(bool is_final) {
+  if (is_final) {
+    SignalPortComplete(this);
+  }
+}
+
+void Port::AddOrReplaceConnection(Connection* conn) {
+  auto ret = connections_.insert(
+      std::make_pair(conn->remote_candidate().address(), conn));
+  // If there is a different connection on the same remote address, replace
+  // it with the new one and destroy the old one.
+  if (ret.second == false && ret.first->second != conn) {
+    RTC_LOG(LS_WARNING)
+        << ToString()
+        << ": A new connection was created on an existing remote address. "
+           "New remote candidate: "
+        << conn->remote_candidate().ToSensitiveString();
+    std::unique_ptr<Connection> old_conn = absl::WrapUnique(ret.first->second);
+    ret.first->second = conn;
+    HandleConnectionDestroyed(old_conn.get());
+    old_conn->Shutdown();
+  }
+}
+
+void Port::OnReadPacket(const char* data,
+                        size_t size,
+                        const rtc::SocketAddress& addr,
+                        ProtocolType proto) {
+  // If the user has enabled port packets, just hand this over.
+  if (enable_port_packets_) {
+    SignalReadPacket(this, data, size, addr);
+    return;
+  }
+
+  // If this is an authenticated STUN request, then signal unknown address and
+  // send back a proper binding response.
+  std::unique_ptr<IceMessage> msg;
+  std::string remote_username;
+  if (!GetStunMessage(data, size, addr, &msg, &remote_username)) {
+    RTC_LOG(LS_ERROR) << ToString()
+                      << ": Received non-STUN packet from unknown address: "
+                      << addr.ToSensitiveString();
+  } else if (!msg) {
+    // STUN message handled already
+  } else if (msg->type() == STUN_BINDING_REQUEST) {
+    RTC_LOG(LS_INFO) << "Received " << StunMethodToString(msg->type())
+                     << " id=" << rtc::hex_encode(msg->transaction_id())
+                     << " from unknown address " << addr.ToSensitiveString();
+    // We need to signal an unknown address before we handle any role conflict
+    // below. Otherwise there would be no candidate pair and TURN entry created
+    // to send the error response in case of a role conflict.
+    SignalUnknownAddress(this, addr, proto, msg.get(), remote_username, false);
+    // Check for role conflicts.
+    if (!MaybeIceRoleConflict(addr, msg.get(), remote_username)) {
+      RTC_LOG(LS_INFO) << "Received conflicting role from the peer.";
+      return;
+    }
+  } else if (msg->type() == GOOG_PING_REQUEST) {
+    // This is a PING sent to a connection that was destroyed.
+    // Send back that this is the case and a authenticated BINDING
+    // is needed.
+    SendBindingErrorResponse(msg.get(), addr, STUN_ERROR_BAD_REQUEST,
+                             STUN_ERROR_REASON_BAD_REQUEST);
+  } else {
+    // NOTE(tschmelcher): STUN_BINDING_RESPONSE is benign. It occurs if we
+    // pruned a connection for this port while it had STUN requests in flight,
+    // because we then get back responses for them, which this code correctly
+    // does not handle.
+    if (msg->type() != STUN_BINDING_RESPONSE &&
+        msg->type() != GOOG_PING_RESPONSE &&
+        msg->type() != GOOG_PING_ERROR_RESPONSE) {
+      RTC_LOG(LS_ERROR) << ToString()
+                        << ": Received unexpected STUN message type: "
+                        << msg->type() << " from unknown address: "
+                        << addr.ToSensitiveString();
+    }
+  }
+}
+
+void Port::OnReadyToSend() {
+  AddressMap::iterator iter = connections_.begin();
+  for (; iter != connections_.end(); ++iter) {
+    iter->second->OnReadyToSend();
+  }
+}
+
+void Port::AddPrflxCandidate(const Candidate& local) {
+  RTC_DCHECK_RUN_ON(thread_);
+  candidates_.push_back(local);
+}
+
+bool Port::GetStunMessage(const char* data,
+                          size_t size,
+                          const rtc::SocketAddress& addr,
+                          std::unique_ptr<IceMessage>* out_msg,
+                          std::string* out_username) {
+  // NOTE: This could clearly be optimized to avoid allocating any memory.
+  //       However, at the data rates we'll be looking at on the client side,
+  //       this probably isn't worth worrying about.
+  RTC_DCHECK(out_msg != NULL);
+  RTC_DCHECK(out_username != NULL);
+  out_username->clear();
+
+  // Don't bother parsing the packet if we can tell it's not STUN.
+  // In ICE mode, all STUN packets will have a valid fingerprint.
+  // Except GOOG_PING_REQUEST/RESPONSE that does not send fingerprint.
+  int types[] = {GOOG_PING_REQUEST, GOOG_PING_RESPONSE,
+                 GOOG_PING_ERROR_RESPONSE};
+  if (!StunMessage::IsStunMethod(types, data, size) &&
+      !StunMessage::ValidateFingerprint(data, size)) {
+    return false;
+  }
+
+  // Parse the request message.  If the packet is not a complete and correct
+  // STUN message, then ignore it.
+  std::unique_ptr<IceMessage> stun_msg(new IceMessage());
+  rtc::ByteBufferReader buf(data, size);
+  if (!stun_msg->Read(&buf) || (buf.Length() > 0)) {
+    return false;
+  }
+
+  // Get list of attributes in the "comprehension-required" range that were not
+  // comprehended. If one or more is found, the behavior differs based on the
+  // type of the incoming message; see below.
+  std::vector<uint16_t> unknown_attributes =
+      stun_msg->GetNonComprehendedAttributes();
+
+  if (stun_msg->type() == STUN_BINDING_REQUEST) {
+    // Check for the presence of USERNAME and MESSAGE-INTEGRITY (if ICE) first.
+    // If not present, fail with a 400 Bad Request.
+    if (!stun_msg->GetByteString(STUN_ATTR_USERNAME) ||
+        !stun_msg->GetByteString(STUN_ATTR_MESSAGE_INTEGRITY)) {
+      RTC_LOG(LS_ERROR) << ToString() << ": Received "
+                        << StunMethodToString(stun_msg->type())
+                        << " without username/M-I from: "
+                        << addr.ToSensitiveString();
+      SendBindingErrorResponse(stun_msg.get(), addr, STUN_ERROR_BAD_REQUEST,
+                               STUN_ERROR_REASON_BAD_REQUEST);
+      return true;
+    }
+
+    // If the username is bad or unknown, fail with a 401 Unauthorized.
+    std::string local_ufrag;
+    std::string remote_ufrag;
+    if (!ParseStunUsername(stun_msg.get(), &local_ufrag, &remote_ufrag) ||
+        local_ufrag != username_fragment()) {
+      RTC_LOG(LS_ERROR) << ToString() << ": Received "
+                        << StunMethodToString(stun_msg->type())
+                        << " with bad local username " << local_ufrag
+                        << " from " << addr.ToSensitiveString();
+      SendBindingErrorResponse(stun_msg.get(), addr, STUN_ERROR_UNAUTHORIZED,
+                               STUN_ERROR_REASON_UNAUTHORIZED);
+      return true;
+    }
+
+    // If ICE, and the MESSAGE-INTEGRITY is bad, fail with a 401 Unauthorized
+    if (stun_msg->ValidateMessageIntegrity(password_) !=
+        StunMessage::IntegrityStatus::kIntegrityOk) {
+      RTC_LOG(LS_ERROR) << ToString() << ": Received "
+                        << StunMethodToString(stun_msg->type())
+                        << " with bad M-I from " << addr.ToSensitiveString()
+                        << ", password_=" << password_;
+      SendBindingErrorResponse(stun_msg.get(), addr, STUN_ERROR_UNAUTHORIZED,
+                               STUN_ERROR_REASON_UNAUTHORIZED);
+      return true;
+    }
+
+    // If a request contains unknown comprehension-required attributes, reply
+    // with an error. See RFC5389 section 7.3.1.
+    if (!unknown_attributes.empty()) {
+      SendUnknownAttributesErrorResponse(stun_msg.get(), addr,
+                                         unknown_attributes);
+      return true;
+    }
+
+    out_username->assign(remote_ufrag);
+  } else if ((stun_msg->type() == STUN_BINDING_RESPONSE) ||
+             (stun_msg->type() == STUN_BINDING_ERROR_RESPONSE)) {
+    if (stun_msg->type() == STUN_BINDING_ERROR_RESPONSE) {
+      if (const StunErrorCodeAttribute* error_code = stun_msg->GetErrorCode()) {
+        RTC_LOG(LS_ERROR) << ToString() << ": Received "
+                          << StunMethodToString(stun_msg->type())
+                          << ": class=" << error_code->eclass()
+                          << " number=" << error_code->number() << " reason='"
+                          << error_code->reason() << "' from "
+                          << addr.ToSensitiveString();
+        // Return message to allow error-specific processing
+      } else {
+        RTC_LOG(LS_ERROR) << ToString() << ": Received "
+                          << StunMethodToString(stun_msg->type())
+                          << " without a error code from "
+                          << addr.ToSensitiveString();
+        return true;
+      }
+    }
+    // If a response contains unknown comprehension-required attributes, it's
+    // simply discarded and the transaction is considered failed. See RFC5389
+    // sections 7.3.3 and 7.3.4.
+    if (!unknown_attributes.empty()) {
+      RTC_LOG(LS_ERROR) << ToString()
+                        << ": Discarding STUN response due to unknown "
+                           "comprehension-required attribute";
+      return true;
+    }
+    // NOTE: Username should not be used in verifying response messages.
+    out_username->clear();
+  } else if (stun_msg->type() == STUN_BINDING_INDICATION) {
+    RTC_LOG(LS_VERBOSE) << ToString() << ": Received "
+                        << StunMethodToString(stun_msg->type()) << ": from "
+                        << addr.ToSensitiveString();
+    out_username->clear();
+
+    // If an indication contains unknown comprehension-required attributes,[]
+    // it's simply discarded. See RFC5389 section 7.3.2.
+    if (!unknown_attributes.empty()) {
+      RTC_LOG(LS_ERROR) << ToString()
+                        << ": Discarding STUN indication due to "
+                           "unknown comprehension-required attribute";
+      return true;
+    }
+    // No stun attributes will be verified, if it's stun indication message.
+    // Returning from end of the this method.
+  } else if (stun_msg->type() == GOOG_PING_REQUEST) {
+    if (stun_msg->ValidateMessageIntegrity(password_) !=
+        StunMessage::IntegrityStatus::kIntegrityOk) {
+      RTC_LOG(LS_ERROR) << ToString() << ": Received "
+                        << StunMethodToString(stun_msg->type())
+                        << " with bad M-I from " << addr.ToSensitiveString()
+                        << ", password_=" << password_;
+      SendBindingErrorResponse(stun_msg.get(), addr, STUN_ERROR_UNAUTHORIZED,
+                               STUN_ERROR_REASON_UNAUTHORIZED);
+      return true;
+    }
+    RTC_LOG(LS_VERBOSE) << ToString() << ": Received "
+                        << StunMethodToString(stun_msg->type()) << " from "
+                        << addr.ToSensitiveString();
+    out_username->clear();
+  } else if (stun_msg->type() == GOOG_PING_RESPONSE ||
+             stun_msg->type() == GOOG_PING_ERROR_RESPONSE) {
+    // note: the MessageIntegrity32 will be verified in Connection.cc
+    RTC_LOG(LS_VERBOSE) << ToString() << ": Received "
+                        << StunMethodToString(stun_msg->type()) << " from "
+                        << addr.ToSensitiveString();
+    out_username->clear();
+  } else {
+    RTC_LOG(LS_ERROR) << ToString()
+                      << ": Received STUN packet with invalid type ("
+                      << stun_msg->type() << ") from "
+                      << addr.ToSensitiveString();
+    return true;
+  }
+
+  // Return the STUN message found.
+  *out_msg = std::move(stun_msg);
+  return true;
+}
+
+bool Port::IsCompatibleAddress(const rtc::SocketAddress& addr) {
+  // Get a representative IP for the Network this port is configured to use.
+  rtc::IPAddress ip = network_->GetBestIP();
+  // We use single-stack sockets, so families must match.
+  if (addr.family() != ip.family()) {
+    return false;
+  }
+  // Link-local IPv6 ports can only connect to other link-local IPv6 ports.
+  if (ip.family() == AF_INET6 &&
+      (IPIsLinkLocal(ip) != IPIsLinkLocal(addr.ipaddr()))) {
+    return false;
+  }
+  return true;
+}
+
+rtc::DiffServCodePoint Port::StunDscpValue() const {
+  // By default, inherit from whatever the MediaChannel sends.
+  return rtc::DSCP_NO_CHANGE;
+}
+
+void Port::DestroyAllConnections() {
+  RTC_DCHECK_RUN_ON(thread_);
+  for (auto& [unused, connection] : connections_) {
+    connection->Shutdown();
+    delete connection;
+  }
+  connections_.clear();
+}
+
+void Port::set_timeout_delay(int delay) {
+  RTC_DCHECK_RUN_ON(thread_);
+  // Although this method is meant to only be used by tests, some downstream
+  // projects have started using it. Ideally we should update our tests to not
+  // require to modify this state and instead use a testing harness that allows
+  // adjusting the clock and then just use the kPortTimeoutDelay constant
+  // directly.
+  timeout_delay_ = delay;
+}
+
+bool Port::ParseStunUsername(const StunMessage* stun_msg,
+                             std::string* local_ufrag,
+                             std::string* remote_ufrag) const {
+  // The packet must include a username that either begins or ends with our
+  // fragment.  It should begin with our fragment if it is a request and it
+  // should end with our fragment if it is a response.
+  local_ufrag->clear();
+  remote_ufrag->clear();
+  const StunByteStringAttribute* username_attr =
+      stun_msg->GetByteString(STUN_ATTR_USERNAME);
+  if (username_attr == NULL)
+    return false;
+
+  // RFRAG:LFRAG
+  const absl::string_view username = username_attr->string_view();
+  size_t colon_pos = username.find(':');
+  if (colon_pos == absl::string_view::npos) {
+    return false;
+  }
+
+  *local_ufrag = std::string(username.substr(0, colon_pos));
+  *remote_ufrag = std::string(username.substr(colon_pos + 1, username.size()));
+  return true;
+}
+
+bool Port::MaybeIceRoleConflict(const rtc::SocketAddress& addr,
+                                IceMessage* stun_msg,
+                                absl::string_view remote_ufrag) {
+  // Validate ICE_CONTROLLING or ICE_CONTROLLED attributes.
+  bool ret = true;
+  IceRole remote_ice_role = ICEROLE_UNKNOWN;
+  uint64_t remote_tiebreaker = 0;
+  const StunUInt64Attribute* stun_attr =
+      stun_msg->GetUInt64(STUN_ATTR_ICE_CONTROLLING);
+  if (stun_attr) {
+    remote_ice_role = ICEROLE_CONTROLLING;
+    remote_tiebreaker = stun_attr->value();
+  }
+
+  // If `remote_ufrag` is same as port local username fragment and
+  // tie breaker value received in the ping message matches port
+  // tiebreaker value this must be a loopback call.
+  // We will treat this as valid scenario.
+  if (remote_ice_role == ICEROLE_CONTROLLING &&
+      username_fragment() == remote_ufrag &&
+      remote_tiebreaker == IceTiebreaker()) {
+    return true;
+  }
+
+  stun_attr = stun_msg->GetUInt64(STUN_ATTR_ICE_CONTROLLED);
+  if (stun_attr) {
+    remote_ice_role = ICEROLE_CONTROLLED;
+    remote_tiebreaker = stun_attr->value();
+  }
+
+  switch (ice_role_) {
+    case ICEROLE_CONTROLLING:
+      if (ICEROLE_CONTROLLING == remote_ice_role) {
+        if (remote_tiebreaker >= tiebreaker_) {
+          SignalRoleConflict(this);
+        } else {
+          // Send Role Conflict (487) error response.
+          SendBindingErrorResponse(stun_msg, addr, STUN_ERROR_ROLE_CONFLICT,
+                                   STUN_ERROR_REASON_ROLE_CONFLICT);
+          ret = false;
+        }
+      }
+      break;
+    case ICEROLE_CONTROLLED:
+      if (ICEROLE_CONTROLLED == remote_ice_role) {
+        if (remote_tiebreaker < tiebreaker_) {
+          SignalRoleConflict(this);
+        } else {
+          // Send Role Conflict (487) error response.
+          SendBindingErrorResponse(stun_msg, addr, STUN_ERROR_ROLE_CONFLICT,
+                                   STUN_ERROR_REASON_ROLE_CONFLICT);
+          ret = false;
+        }
+      }
+      break;
+    default:
+      RTC_DCHECK_NOTREACHED();
+  }
+  return ret;
+}
+
+std::string Port::CreateStunUsername(absl::string_view remote_username) const {
+  return std::string(remote_username) + ":" + username_fragment();
+}
+
+bool Port::HandleIncomingPacket(rtc::AsyncPacketSocket* socket,
+                                const char* data,
+                                size_t size,
+                                const rtc::SocketAddress& remote_addr,
+                                int64_t packet_time_us) {
+  RTC_DCHECK_NOTREACHED();
+  return false;
+}
+
+bool Port::CanHandleIncomingPacketsFrom(const rtc::SocketAddress&) const {
+  return false;
+}
+
+void Port::SendBindingErrorResponse(StunMessage* message,
+                                    const rtc::SocketAddress& addr,
+                                    int error_code,
+                                    absl::string_view reason) {
+  RTC_DCHECK(message->type() == STUN_BINDING_REQUEST ||
+             message->type() == GOOG_PING_REQUEST);
+
+  // Fill in the response message.
+  StunMessage response(message->type() == STUN_BINDING_REQUEST
+                           ? STUN_BINDING_ERROR_RESPONSE
+                           : GOOG_PING_ERROR_RESPONSE,
+                       message->transaction_id());
+
+  // When doing GICE, we need to write out the error code incorrectly to
+  // maintain backwards compatiblility.
+  auto error_attr = StunAttribute::CreateErrorCode();
+  error_attr->SetCode(error_code);
+  error_attr->SetReason(std::string(reason));
+  response.AddAttribute(std::move(error_attr));
+
+  // Per Section 10.1.2, certain error cases don't get a MESSAGE-INTEGRITY,
+  // because we don't have enough information to determine the shared secret.
+  if (error_code != STUN_ERROR_BAD_REQUEST &&
+      error_code != STUN_ERROR_UNAUTHORIZED &&
+      message->type() != GOOG_PING_REQUEST) {
+    if (message->type() == STUN_BINDING_REQUEST) {
+      response.AddMessageIntegrity(password_);
+    } else {
+      response.AddMessageIntegrity32(password_);
+    }
+  }
+
+  if (message->type() == STUN_BINDING_REQUEST) {
+    response.AddFingerprint();
+  }
+
+  // Send the response message.
+  rtc::ByteBufferWriter buf;
+  response.Write(&buf);
+  rtc::PacketOptions options(StunDscpValue());
+  options.info_signaled_after_sent.packet_type =
+      rtc::PacketType::kIceConnectivityCheckResponse;
+  SendTo(buf.Data(), buf.Length(), addr, options, false);
+  RTC_LOG(LS_INFO) << ToString() << ": Sending STUN "
+                   << StunMethodToString(response.type())
+                   << ": reason=" << reason << " to "
+                   << addr.ToSensitiveString();
+}
+
+void Port::SendUnknownAttributesErrorResponse(
+    StunMessage* message,
+    const rtc::SocketAddress& addr,
+    const std::vector<uint16_t>& unknown_types) {
+  RTC_DCHECK(message->type() == STUN_BINDING_REQUEST);
+
+  // Fill in the response message.
+  StunMessage response(STUN_BINDING_ERROR_RESPONSE, message->transaction_id());
+
+  auto error_attr = StunAttribute::CreateErrorCode();
+  error_attr->SetCode(STUN_ERROR_UNKNOWN_ATTRIBUTE);
+  error_attr->SetReason(STUN_ERROR_REASON_UNKNOWN_ATTRIBUTE);
+  response.AddAttribute(std::move(error_attr));
+
+  std::unique_ptr<StunUInt16ListAttribute> unknown_attr =
+      StunAttribute::CreateUnknownAttributes();
+  for (uint16_t type : unknown_types) {
+    unknown_attr->AddType(type);
+  }
+  response.AddAttribute(std::move(unknown_attr));
+
+  response.AddMessageIntegrity(password_);
+  response.AddFingerprint();
+
+  // Send the response message.
+  rtc::ByteBufferWriter buf;
+  response.Write(&buf);
+  rtc::PacketOptions options(StunDscpValue());
+  options.info_signaled_after_sent.packet_type =
+      rtc::PacketType::kIceConnectivityCheckResponse;
+  SendTo(buf.Data(), buf.Length(), addr, options, false);
+  RTC_LOG(LS_ERROR) << ToString() << ": Sending STUN binding error: reason="
+                    << STUN_ERROR_UNKNOWN_ATTRIBUTE << " to "
+                    << addr.ToSensitiveString();
+}
+
+void Port::KeepAliveUntilPruned() {
+  // If it is pruned, we won't bring it up again.
+  if (state_ == State::INIT) {
+    state_ = State::KEEP_ALIVE_UNTIL_PRUNED;
+  }
+}
+
+void Port::Prune() {
+  state_ = State::PRUNED;
+  PostDestroyIfDead(/*delayed=*/false);
+}
+
+// Call to stop any currently pending operations from running.
+void Port::CancelPendingTasks() {
+  TRACE_EVENT0("webrtc", "Port::CancelPendingTasks");
+  RTC_DCHECK_RUN_ON(thread_);
+  weak_factory_.InvalidateWeakPtrs();
+}
+
+void Port::PostDestroyIfDead(bool delayed) {
+  rtc::WeakPtr<Port> weak_ptr = NewWeakPtr();
+  auto task = [weak_ptr = std::move(weak_ptr)] {
+    if (weak_ptr) {
+      weak_ptr->DestroyIfDead();
+    }
+  };
+  if (delayed) {
+    thread_->PostDelayedTask(std::move(task),
+                             TimeDelta::Millis(timeout_delay_));
+  } else {
+    thread_->PostTask(std::move(task));
+  }
+}
+
+void Port::DestroyIfDead() {
+  RTC_DCHECK_RUN_ON(thread_);
+  bool dead =
+      (state_ == State::INIT || state_ == State::PRUNED) &&
+      connections_.empty() &&
+      rtc::TimeMillis() - last_time_all_connections_removed_ >= timeout_delay_;
+  if (dead) {
+    Destroy();
+  }
+}
+
+void Port::SubscribePortDestroyed(
+    std::function<void(PortInterface*)> callback) {
+  port_destroyed_callback_list_.AddReceiver(callback);
+}
+
+void Port::SendPortDestroyed(Port* port) {
+  port_destroyed_callback_list_.Send(port);
+}
+void Port::OnNetworkTypeChanged(const rtc::Network* network) {
+  RTC_DCHECK(network == network_);
+
+  UpdateNetworkCost();
+}
+
+std::string Port::ToString() const {
+  rtc::StringBuilder ss;
+  ss << "Port[" << rtc::ToHex(reinterpret_cast<uintptr_t>(this)) << ":"
+     << content_name_ << ":" << component_ << ":" << generation_ << ":" << type_
+     << ":" << network_->ToString() << "]";
+  return ss.Release();
+}
+
+// TODO(honghaiz): Make the network cost configurable from user setting.
+void Port::UpdateNetworkCost() {
+  RTC_DCHECK_RUN_ON(thread_);
+  uint16_t new_cost = network_->GetCost(field_trials());
+  if (network_cost_ == new_cost) {
+    return;
+  }
+  RTC_LOG(LS_INFO) << "Network cost changed from " << network_cost_ << " to "
+                   << new_cost
+                   << ". Number of candidates created: " << candidates_.size()
+                   << ". Number of connections created: "
+                   << connections_.size();
+  network_cost_ = new_cost;
+  for (cricket::Candidate& candidate : candidates_)
+    candidate.set_network_cost(network_cost_);
+
+  for (auto& [unused, connection] : connections_)
+    connection->SetLocalCandidateNetworkCost(network_cost_);
+}
+
+void Port::EnablePortPackets() {
+  enable_port_packets_ = true;
+}
+
+bool Port::OnConnectionDestroyed(Connection* conn) {
+  if (connections_.erase(conn->remote_candidate().address()) == 0) {
+    // This could indicate a programmer error outside of webrtc so while we
+    // do have this check here to alert external developers, we also need to
+    // handle it since it might be a corner case not caught in tests.
+    RTC_DCHECK_NOTREACHED() << "Calling Destroy recursively?";
+    return false;
+  }
+
+  HandleConnectionDestroyed(conn);
+
+  // Ports time out after all connections fail if it is not marked as
+  // "keep alive until pruned."
+  // Note: If a new connection is added after this message is posted, but it
+  // fails and is removed before kPortTimeoutDelay, then this message will
+  // not cause the Port to be destroyed.
+  if (connections_.empty()) {
+    last_time_all_connections_removed_ = rtc::TimeMillis();
+    PostDestroyIfDead(/*delayed=*/true);
+  }
+
+  return true;
+}
+
+void Port::DestroyConnectionInternal(Connection* conn, bool async) {
+  RTC_DCHECK_RUN_ON(thread_);
+  if (!OnConnectionDestroyed(conn))
+    return;
+
+  conn->Shutdown();
+  if (async) {
+    // Unwind the stack before deleting the object in case upstream callers
+    // need to refer to the Connection's state as part of teardown.
+    // NOTE: We move ownership of `conn` into the capture section of the lambda
+    // so that the object will always be deleted, including if PostTask fails.
+    // In such a case (only tests), deletion would happen inside of the call
+    // to `DestroyConnection()`.
+    thread_->PostTask([conn = absl::WrapUnique(conn)]() {});
+  } else {
+    delete conn;
+  }
+}
+
+void Port::Destroy() {
+  RTC_DCHECK(connections_.empty());
+  RTC_LOG(LS_INFO) << ToString() << ": Port deleted";
+  SendPortDestroyed(this);
+  delete this;
+}
+
+const std::string Port::username_fragment() const {
+  return ice_username_fragment_;
+}
+
+void Port::CopyPortInformationToPacketInfo(rtc::PacketInfo* info) const {
+  info->protocol = ConvertProtocolTypeToPacketInfoProtocolType(GetProtocol());
+  info->network_id = Network()->id();
+}
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/port.h b/third_party/libwebrtc/p2p/base/port.h
new file mode 100644
index 0000000000..31091eb273
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/port.h
@@ -0,0 +1,540 @@
+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_PORT_H_
+#define P2P_BASE_PORT_H_
+
+#include <map>
+#include <memory>
+#include <set>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "absl/strings/string_view.h"
+#include "absl/types/optional.h"
+#include "api/candidate.h"
+#include "api/field_trials_view.h"
+#include "api/packet_socket_factory.h"
+#include "api/rtc_error.h"
+#include "api/task_queue/task_queue_base.h"
+#include "api/transport/field_trial_based_config.h"
+#include "api/transport/stun.h"
+#include "logging/rtc_event_log/events/rtc_event_ice_candidate_pair.h"
+#include "logging/rtc_event_log/events/rtc_event_ice_candidate_pair_config.h"
+#include "logging/rtc_event_log/ice_logger.h"
+#include "p2p/base/candidate_pair_interface.h"
+#include "p2p/base/connection.h"
+#include "p2p/base/connection_info.h"
+#include "p2p/base/p2p_constants.h"
+#include "p2p/base/port_interface.h"
+#include "p2p/base/stun_request.h"
+#include "rtc_base/async_packet_socket.h"
+#include "rtc_base/callback_list.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/memory/always_valid_pointer.h"
+#include "rtc_base/net_helper.h"
+#include "rtc_base/network.h"
+#include "rtc_base/proxy_info.h"
+#include "rtc_base/rate_tracker.h"
+#include "rtc_base/socket_address.h"
+#include "rtc_base/system/rtc_export.h"
+#include "rtc_base/third_party/sigslot/sigslot.h"
+#include "rtc_base/weak_ptr.h"
+
+namespace cricket {
+
+RTC_EXPORT extern const char LOCAL_PORT_TYPE[];
+RTC_EXPORT extern const char STUN_PORT_TYPE[];
+RTC_EXPORT extern const char PRFLX_PORT_TYPE[];
+RTC_EXPORT extern const char RELAY_PORT_TYPE[];
+
+// RFC 6544, TCP candidate encoding rules.
+extern const int DISCARD_PORT;
+extern const char TCPTYPE_ACTIVE_STR[];
+extern const char TCPTYPE_PASSIVE_STR[];
+extern const char TCPTYPE_SIMOPEN_STR[];
+
+// The type preference MUST be an integer from 0 to 126 inclusive.
+// https://datatracker.ietf.org/doc/html/rfc5245#section-4.1.2.1
+enum IcePriorityValue : uint8_t {
+  ICE_TYPE_PREFERENCE_RELAY_TLS = 0,
+  ICE_TYPE_PREFERENCE_RELAY_TCP = 1,
+  ICE_TYPE_PREFERENCE_RELAY_UDP = 2,
+  ICE_TYPE_PREFERENCE_PRFLX_TCP = 80,
+  ICE_TYPE_PREFERENCE_HOST_TCP = 90,
+  ICE_TYPE_PREFERENCE_SRFLX = 100,
+  ICE_TYPE_PREFERENCE_PRFLX = 110,
+  ICE_TYPE_PREFERENCE_HOST = 126
+};
+
+enum class MdnsNameRegistrationStatus {
+  // IP concealment with mDNS is not enabled or the name registration process is
+  // not started yet.
+  kNotStarted,
+  // A request to create and register an mDNS name for a local IP address of a
+  // host candidate is sent to the mDNS responder.
+  kInProgress,
+  // The name registration is complete and the created name is returned by the
+  // mDNS responder.
+  kCompleted,
+};
+
+// Stats that we can return about the port of a STUN candidate.
+class StunStats {
+ public:
+  StunStats() = default;
+  StunStats(const StunStats&) = default;
+  ~StunStats() = default;
+
+  StunStats& operator=(const StunStats& other) = default;
+
+  int stun_binding_requests_sent = 0;
+  int stun_binding_responses_received = 0;
+  double stun_binding_rtt_ms_total = 0;
+  double stun_binding_rtt_ms_squared_total = 0;
+};
+
+// Stats that we can return about a candidate.
+class CandidateStats {
+ public:
+  CandidateStats() = default;
+  CandidateStats(const CandidateStats&) = default;
+  CandidateStats(CandidateStats&&) = default;
+  CandidateStats(Candidate candidate,
+                 absl::optional<StunStats> stats = absl::nullopt)
+      : candidate_(std::move(candidate)), stun_stats_(std::move(stats)) {}
+  ~CandidateStats() = default;
+
+  CandidateStats& operator=(const CandidateStats& other) = default;
+
+  const Candidate& candidate() const { return candidate_; }
+
+  const absl::optional<StunStats>& stun_stats() const { return stun_stats_; }
+
+ private:
+  Candidate candidate_;
+  // STUN port stats if this candidate is a STUN candidate.
+  absl::optional<StunStats> stun_stats_;
+};
+
+typedef std::vector<CandidateStats> CandidateStatsList;
+
+const char* ProtoToString(ProtocolType proto);
+absl::optional<ProtocolType> StringToProto(absl::string_view proto_name);
+
+struct ProtocolAddress {
+  rtc::SocketAddress address;
+  ProtocolType proto;
+
+  ProtocolAddress(const rtc::SocketAddress& a, ProtocolType p)
+      : address(a), proto(p) {}
+
+  bool operator==(const ProtocolAddress& o) const {
+    return address == o.address && proto == o.proto;
+  }
+  bool operator!=(const ProtocolAddress& o) const { return !(*this == o); }
+};
+
+struct IceCandidateErrorEvent {
+  IceCandidateErrorEvent() = default;
+  IceCandidateErrorEvent(absl::string_view address,
+                         int port,
+                         absl::string_view url,
+                         int error_code,
+                         absl::string_view error_text)
+      : address(std::move(address)),
+        port(port),
+        url(std::move(url)),
+        error_code(error_code),
+        error_text(std::move(error_text)) {}
+
+  std::string address;
+  int port = 0;
+  std::string url;
+  int error_code = 0;
+  std::string error_text;
+};
+
+struct CandidatePairChangeEvent {
+  CandidatePair selected_candidate_pair;
+  int64_t last_data_received_ms;
+  std::string reason;
+  // How long do we estimate that we've been disconnected.
+  int64_t estimated_disconnected_time_ms;
+};
+
+typedef std::set<rtc::SocketAddress> ServerAddresses;
+
+// Represents a local communication mechanism that can be used to create
+// connections to similar mechanisms of the other client.  Subclasses of this
+// one add support for specific mechanisms like local UDP ports.
+class RTC_EXPORT Port : public PortInterface, public sigslot::has_slots<> {
+ public:
+  // INIT: The state when a port is just created.
+  // KEEP_ALIVE_UNTIL_PRUNED: A port should not be destroyed even if no
+  // connection is using it.
+  // PRUNED: It will be destroyed if no connection is using it for a period of
+  // 30 seconds.
+  enum class State { INIT, KEEP_ALIVE_UNTIL_PRUNED, PRUNED };
+  Port(webrtc::TaskQueueBase* thread,
+       absl::string_view type,
+       rtc::PacketSocketFactory* factory,
+       const rtc::Network* network,
+       absl::string_view username_fragment,
+       absl::string_view password,
+       const webrtc::FieldTrialsView* field_trials = nullptr);
+  Port(webrtc::TaskQueueBase* thread,
+       absl::string_view type,
+       rtc::PacketSocketFactory* factory,
+       const rtc::Network* network,
+       uint16_t min_port,
+       uint16_t max_port,
+       absl::string_view username_fragment,
+       absl::string_view password,
+       const webrtc::FieldTrialsView* field_trials = nullptr);
+  ~Port() override;
+
+  // Note that the port type does NOT uniquely identify different subclasses of
+  // Port. Use the 2-tuple of the port type AND the protocol (GetProtocol()) to
+  // uniquely identify subclasses. Whenever a new subclass of Port introduces a
+  // conflit in the value of the 2-tuple, make sure that the implementation that
+  // relies on this 2-tuple for RTTI is properly changed.
+  const std::string& Type() const override;
+  const rtc::Network* Network() const override;
+
+  // Methods to set/get ICE role and tiebreaker values.
+  IceRole GetIceRole() const override;
+  void SetIceRole(IceRole role) override;
+
+  void SetIceTiebreaker(uint64_t tiebreaker) override;
+  uint64_t IceTiebreaker() const override;
+
+  bool SharedSocket() const override;
+  void ResetSharedSocket() { shared_socket_ = false; }
+
+  // Should not destroy the port even if no connection is using it. Called when
+  // a port is ready to use.
+  void KeepAliveUntilPruned();
+  // Allows a port to be destroyed if no connection is using it.
+  void Prune();
+
+  // Call to stop any currently pending operations from running.
+  void CancelPendingTasks();
+
+  // The thread on which this port performs its I/O.
+  webrtc::TaskQueueBase* thread() { return thread_; }
+
+  // The factory used to create the sockets of this port.
+  rtc::PacketSocketFactory* socket_factory() const { return factory_; }
+
+  // For debugging purposes.
+  const std::string& content_name() const { return content_name_; }
+  void set_content_name(absl::string_view content_name) {
+    content_name_ = std::string(content_name);
+  }
+
+  int component() const { return component_; }
+  void set_component(int component) { component_ = component; }
+
+  bool send_retransmit_count_attribute() const {
+    return send_retransmit_count_attribute_;
+  }
+  void set_send_retransmit_count_attribute(bool enable) {
+    send_retransmit_count_attribute_ = enable;
+  }
+
+  // Identifies the generation that this port was created in.
+  uint32_t generation() const { return generation_; }
+  void set_generation(uint32_t generation) { generation_ = generation; }
+
+  const std::string username_fragment() const;
+  const std::string& password() const { return password_; }
+
+  // May be called when this port was initially created by a pooled
+  // PortAllocatorSession, and is now being assigned to an ICE transport.
+  // Updates the information for candidates as well.
+  void SetIceParameters(int component,
+                        absl::string_view username_fragment,
+                        absl::string_view password);
+
+  // Fired when candidates are discovered by the port. When all candidates
+  // are discovered that belong to port SignalAddressReady is fired.
+  sigslot::signal2<Port*, const Candidate&> SignalCandidateReady;
+  // Provides all of the above information in one handy object.
+  const std::vector<Candidate>& Candidates() const override;
+  // Fired when candidate discovery failed using certain server.
+  sigslot::signal2<Port*, const IceCandidateErrorEvent&> SignalCandidateError;
+
+  // SignalPortComplete is sent when port completes the task of candidates
+  // allocation.
+  sigslot::signal1<Port*> SignalPortComplete;
+  // This signal sent when port fails to allocate candidates and this port
+  // can't be used in establishing the connections. When port is in shared mode
+  // and port fails to allocate one of the candidates, port shouldn't send
+  // this signal as other candidates might be usefull in establishing the
+  // connection.
+  sigslot::signal1<Port*> SignalPortError;
+
+  void SubscribePortDestroyed(
+      std::function<void(PortInterface*)> callback) override;
+  void SendPortDestroyed(Port* port);
+  // Returns a map containing all of the connections of this port, keyed by the
+  // remote address.
+  typedef std::map<rtc::SocketAddress, Connection*> AddressMap;
+  const AddressMap& connections() { return connections_; }
+
+  // Returns the connection to the given address or NULL if none exists.
+  Connection* GetConnection(const rtc::SocketAddress& remote_addr) override;
+
+  // Removes and deletes a connection object. `DestroyConnection` will
+  // delete the connection object directly whereas `DestroyConnectionAsync`
+  // defers the `delete` operation to when the call stack has been unwound.
+  // Async may be needed when deleting a connection object from within a
+  // callback.
+  void DestroyConnection(Connection* conn) {
+    DestroyConnectionInternal(conn, false);
+  }
+
+  void DestroyConnectionAsync(Connection* conn) {
+    DestroyConnectionInternal(conn, true);
+  }
+
+  // In a shared socket mode each port which shares the socket will decide
+  // to accept the packet based on the `remote_addr`. Currently only UDP
+  // port implemented this method.
+  // TODO(mallinath) - Make it pure virtual.
+  virtual bool HandleIncomingPacket(rtc::AsyncPacketSocket* socket,
+                                    const char* data,
+                                    size_t size,
+                                    const rtc::SocketAddress& remote_addr,
+                                    int64_t packet_time_us);
+
+  // Shall the port handle packet from this `remote_addr`.
+  // This method is overridden by TurnPort.
+  virtual bool CanHandleIncomingPacketsFrom(
+      const rtc::SocketAddress& remote_addr) const;
+
+  // Sends a response error to the given request.
+  void SendBindingErrorResponse(StunMessage* message,
+                                const rtc::SocketAddress& addr,
+                                int error_code,
+                                absl::string_view reason) override;
+  void SendUnknownAttributesErrorResponse(
+      StunMessage* message,
+      const rtc::SocketAddress& addr,
+      const std::vector<uint16_t>& unknown_types);
+
+  void set_proxy(absl::string_view user_agent, const rtc::ProxyInfo& proxy) {
+    user_agent_ = std::string(user_agent);
+    proxy_ = proxy;
+  }
+  const std::string& user_agent() { return user_agent_; }
+  const rtc::ProxyInfo& proxy() { return proxy_; }
+
+  void EnablePortPackets() override;
+
+  // Called if the port has no connections and is no longer useful.
+  void Destroy();
+
+  // Debugging description of this port
+  std::string ToString() const override;
+  uint16_t min_port() { return min_port_; }
+  uint16_t max_port() { return max_port_; }
+
+  // Timeout shortening function to speed up unit tests.
+  void set_timeout_delay(int delay);
+
+  // This method will return local and remote username fragements from the
+  // stun username attribute if present.
+  bool ParseStunUsername(const StunMessage* stun_msg,
+                         std::string* local_username,
+                         std::string* remote_username) const;
+  std::string CreateStunUsername(absl::string_view remote_username) const;
+
+  bool MaybeIceRoleConflict(const rtc::SocketAddress& addr,
+                            IceMessage* stun_msg,
+                            absl::string_view remote_ufrag);
+
+  // Called when a packet has been sent to the socket.
+  // This is made pure virtual to notify subclasses of Port that they MUST
+  // listen to AsyncPacketSocket::SignalSentPacket and then call
+  // PortInterface::OnSentPacket.
+  virtual void OnSentPacket(rtc::AsyncPacketSocket* socket,
+                            const rtc::SentPacket& sent_packet) = 0;
+
+  // Called when the socket is currently able to send.
+  void OnReadyToSend();
+
+  // Called when the Connection discovers a local peer reflexive candidate.
+  void AddPrflxCandidate(const Candidate& local);
+
+  int16_t network_cost() const { return network_cost_; }
+
+  void GetStunStats(absl::optional<StunStats>* stats) override {}
+
+  // Foundation:  An arbitrary string that is the same for two candidates
+  //   that have the same type, base IP address, protocol (UDP, TCP,
+  //   etc.), and STUN or TURN server.  If any of these are different,
+  //   then the foundation will be different.  Two candidate pairs with
+  //   the same foundation pairs are likely to have similar network
+  //   characteristics. Foundations are used in the frozen algorithm.
+  std::string ComputeFoundation(absl::string_view type,
+                                absl::string_view protocol,
+                                absl::string_view relay_protocol,
+                                const rtc::SocketAddress& base_address);
+
+ protected:
+  virtual void UpdateNetworkCost();
+
+  void set_type(absl::string_view type) { type_ = std::string(type); }
+
+  rtc::WeakPtr<Port> NewWeakPtr() { return weak_factory_.GetWeakPtr(); }
+
+  void AddAddress(const rtc::SocketAddress& address,
+                  const rtc::SocketAddress& base_address,
+                  const rtc::SocketAddress& related_address,
+                  absl::string_view protocol,
+                  absl::string_view relay_protocol,
+                  absl::string_view tcptype,
+                  absl::string_view type,
+                  uint32_t type_preference,
+                  uint32_t relay_preference,
+                  absl::string_view url,
+                  bool is_final);
+
+  void FinishAddingAddress(const Candidate& c, bool is_final)
+      RTC_RUN_ON(thread_);
+
+  virtual void PostAddAddress(bool is_final);
+
+  // Adds the given connection to the map keyed by the remote candidate address.
+  // If an existing connection has the same address, the existing one will be
+  // replaced and destroyed.
+  void AddOrReplaceConnection(Connection* conn);
+
+  // Called when a packet is received from an unknown address that is not
+  // currently a connection.  If this is an authenticated STUN binding request,
+  // then we will signal the client.
+  void OnReadPacket(const char* data,
+                    size_t size,
+                    const rtc::SocketAddress& addr,
+                    ProtocolType proto);
+
+  // If the given data comprises a complete and correct STUN message then the
+  // return value is true, otherwise false. If the message username corresponds
+  // with this port's username fragment, msg will contain the parsed STUN
+  // message.  Otherwise, the function may send a STUN response internally.
+  // remote_username contains the remote fragment of the STUN username.
+  bool GetStunMessage(const char* data,
+                      size_t size,
+                      const rtc::SocketAddress& addr,
+                      std::unique_ptr<IceMessage>* out_msg,
+                      std::string* out_username);
+
+  // Checks if the address in addr is compatible with the port's ip.
+  bool IsCompatibleAddress(const rtc::SocketAddress& addr);
+
+  // Returns DSCP value packets generated by the port itself should use.
+  virtual rtc::DiffServCodePoint StunDscpValue() const;
+
+  // Extra work to be done in subclasses when a connection is destroyed.
+  virtual void HandleConnectionDestroyed(Connection* conn) {}
+
+  void DestroyAllConnections();
+
+  void CopyPortInformationToPacketInfo(rtc::PacketInfo* info) const;
+
+  MdnsNameRegistrationStatus mdns_name_registration_status() const {
+    return mdns_name_registration_status_;
+  }
+  void set_mdns_name_registration_status(MdnsNameRegistrationStatus status) {
+    mdns_name_registration_status_ = status;
+  }
+
+  const webrtc::FieldTrialsView& field_trials() const { return *field_trials_; }
+
+ private:
+  void Construct();
+
+  void PostDestroyIfDead(bool delayed);
+  void DestroyIfDead();
+
+  // Called internally when deleting a connection object.
+  // Returns true if the connection object was removed from the `connections_`
+  // list and the state updated accordingly. If the connection was not found
+  // in the list, the return value is false. Note that this may indicate
+  // incorrect behavior of external code that might be attempting to delete
+  // connection objects from within a 'on destroyed' callback notification
+  // for the connection object itself.
+  bool OnConnectionDestroyed(Connection* conn);
+
+  // Private implementation of DestroyConnection to keep the async usage
+  // distinct.
+  void DestroyConnectionInternal(Connection* conn, bool async);
+
+  void OnNetworkTypeChanged(const rtc::Network* network);
+
+  webrtc::TaskQueueBase* const thread_;
+  rtc::PacketSocketFactory* const factory_;
+  std::string type_;
+  bool send_retransmit_count_attribute_;
+  const rtc::Network* network_;
+  uint16_t min_port_;
+  uint16_t max_port_;
+  std::string content_name_;
+  int component_;
+  uint32_t generation_;
+  // In order to establish a connection to this Port (so that real data can be
+  // sent through), the other side must send us a STUN binding request that is
+  // authenticated with this username_fragment and password.
+  // PortAllocatorSession will provide these username_fragment and password.
+  //
+  // Note: we should always use username_fragment() instead of using
+  // `ice_username_fragment_` directly. For the details see the comment on
+  // username_fragment().
+  std::string ice_username_fragment_;
+  std::string password_;
+  std::vector<Candidate> candidates_ RTC_GUARDED_BY(thread_);
+  AddressMap connections_;
+  int timeout_delay_;
+  bool enable_port_packets_;
+  IceRole ice_role_;
+  uint64_t tiebreaker_;
+  bool shared_socket_;
+  // Information to use when going through a proxy.
+  std::string user_agent_;
+  rtc::ProxyInfo proxy_;
+
+  // A virtual cost perceived by the user, usually based on the network type
+  // (WiFi. vs. Cellular). It takes precedence over the priority when
+  // comparing two connections.
+  int16_t network_cost_;
+  State state_ = State::INIT;
+  int64_t last_time_all_connections_removed_ = 0;
+  MdnsNameRegistrationStatus mdns_name_registration_status_ =
+      MdnsNameRegistrationStatus::kNotStarted;
+
+  rtc::WeakPtrFactory<Port> weak_factory_;
+  webrtc::AlwaysValidPointer<const webrtc::FieldTrialsView,
+                             webrtc::FieldTrialBasedConfig>
+      field_trials_;
+
+  bool MaybeObfuscateAddress(Candidate* c,
+                             absl::string_view type,
+                             bool is_final) RTC_RUN_ON(thread_);
+
+  friend class Connection;
+  webrtc::CallbackList<PortInterface*> port_destroyed_callback_list_;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_PORT_H_
diff --git a/third_party/libwebrtc/p2p/base/port_allocator.cc b/third_party/libwebrtc/p2p/base/port_allocator.cc
new file mode 100644
index 0000000000..522f0beb98
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/port_allocator.cc
@@ -0,0 +1,349 @@
+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/port_allocator.h"
+
+#include <iterator>
+#include <set>
+#include <utility>
+
+#include "absl/strings/string_view.h"
+#include "p2p/base/ice_credentials_iterator.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/logging.h"
+
+namespace cricket {
+
+RelayServerConfig::RelayServerConfig() {}
+
+RelayServerConfig::RelayServerConfig(const rtc::SocketAddress& address,
+                                     absl::string_view username,
+                                     absl::string_view password,
+                                     ProtocolType proto)
+    : credentials(username, password) {
+  ports.push_back(ProtocolAddress(address, proto));
+}
+
+RelayServerConfig::RelayServerConfig(absl::string_view address,
+                                     int port,
+                                     absl::string_view username,
+                                     absl::string_view password,
+                                     ProtocolType proto)
+    : RelayServerConfig(rtc::SocketAddress(address, port),
+                        username,
+                        password,
+                        proto) {}
+
+// Legacy constructor where "secure" and PROTO_TCP implies PROTO_TLS.
+RelayServerConfig::RelayServerConfig(absl::string_view address,
+                                     int port,
+                                     absl::string_view username,
+                                     absl::string_view password,
+                                     ProtocolType proto,
+                                     bool secure)
+    : RelayServerConfig(address,
+                        port,
+                        username,
+                        password,
+                        (proto == PROTO_TCP && secure ? PROTO_TLS : proto)) {}
+
+RelayServerConfig::RelayServerConfig(const RelayServerConfig&) = default;
+
+RelayServerConfig::~RelayServerConfig() = default;
+
+PortAllocatorSession::PortAllocatorSession(absl::string_view content_name,
+                                           int component,
+                                           absl::string_view ice_ufrag,
+                                           absl::string_view ice_pwd,
+                                           uint32_t flags)
+    : flags_(flags),
+      generation_(0),
+      content_name_(content_name),
+      component_(component),
+      ice_ufrag_(ice_ufrag),
+      ice_pwd_(ice_pwd),
+      tiebreaker_(0) {
+  // Pooled sessions are allowed to be created with empty content name,
+  // component, ufrag and password.
+  RTC_DCHECK(ice_ufrag.empty() == ice_pwd.empty());
+}
+
+PortAllocatorSession::~PortAllocatorSession() = default;
+
+bool PortAllocatorSession::IsCleared() const {
+  return false;
+}
+
+bool PortAllocatorSession::IsStopped() const {
+  return false;
+}
+
+uint32_t PortAllocatorSession::generation() {
+  return generation_;
+}
+
+void PortAllocatorSession::set_generation(uint32_t generation) {
+  generation_ = generation;
+}
+
+PortAllocator::PortAllocator()
+    : flags_(kDefaultPortAllocatorFlags),
+      min_port_(0),
+      max_port_(0),
+      max_ipv6_networks_(kDefaultMaxIPv6Networks),
+      step_delay_(kDefaultStepDelay),
+      allow_tcp_listen_(true),
+      candidate_filter_(CF_ALL),
+      tiebreaker_(0) {
+  // The allocator will be attached to a thread in Initialize.
+  thread_checker_.Detach();
+}
+
+void PortAllocator::Initialize() {
+  RTC_DCHECK(thread_checker_.IsCurrent());
+  initialized_ = true;
+}
+
+PortAllocator::~PortAllocator() {
+  CheckRunOnValidThreadIfInitialized();
+}
+
+void PortAllocator::set_restrict_ice_credentials_change(bool value) {
+  restrict_ice_credentials_change_ = value;
+}
+
+// Deprecated
+bool PortAllocator::SetConfiguration(
+    const ServerAddresses& stun_servers,
+    const std::vector<RelayServerConfig>& turn_servers,
+    int candidate_pool_size,
+    bool prune_turn_ports,
+    webrtc::TurnCustomizer* turn_customizer,
+    const absl::optional<int>& stun_candidate_keepalive_interval) {
+  webrtc::PortPrunePolicy turn_port_prune_policy =
+      prune_turn_ports ? webrtc::PRUNE_BASED_ON_PRIORITY : webrtc::NO_PRUNE;
+  return SetConfiguration(stun_servers, turn_servers, candidate_pool_size,
+                          turn_port_prune_policy, turn_customizer,
+                          stun_candidate_keepalive_interval);
+}
+
+bool PortAllocator::SetConfiguration(
+    const ServerAddresses& stun_servers,
+    const std::vector<RelayServerConfig>& turn_servers,
+    int candidate_pool_size,
+    webrtc::PortPrunePolicy turn_port_prune_policy,
+    webrtc::TurnCustomizer* turn_customizer,
+    const absl::optional<int>& stun_candidate_keepalive_interval) {
+  CheckRunOnValidThreadIfInitialized();
+  // A positive candidate pool size would lead to the creation of a pooled
+  // allocator session and starting getting ports, which we should only do on
+  // the network thread.
+  RTC_DCHECK(candidate_pool_size == 0 || thread_checker_.IsCurrent());
+  bool ice_servers_changed =
+      (stun_servers != stun_servers_ || turn_servers != turn_servers_);
+  stun_servers_ = stun_servers;
+  turn_servers_ = turn_servers;
+  turn_port_prune_policy_ = turn_port_prune_policy;
+
+  if (candidate_pool_frozen_) {
+    if (candidate_pool_size != candidate_pool_size_) {
+      RTC_LOG(LS_ERROR)
+          << "Trying to change candidate pool size after pool was frozen.";
+      return false;
+    }
+    return true;
+  }
+
+  if (candidate_pool_size < 0) {
+    RTC_LOG(LS_ERROR) << "Can't set negative pool size.";
+    return false;
+  }
+
+  candidate_pool_size_ = candidate_pool_size;
+
+  // If ICE servers changed, throw away any existing pooled sessions and create
+  // new ones.
+  if (ice_servers_changed) {
+    pooled_sessions_.clear();
+  }
+
+  turn_customizer_ = turn_customizer;
+
+  // If `candidate_pool_size_` is less than the number of pooled sessions, get
+  // rid of the extras.
+  while (candidate_pool_size_ < static_cast<int>(pooled_sessions_.size())) {
+    pooled_sessions_.back().reset(nullptr);
+    pooled_sessions_.pop_back();
+  }
+
+  // `stun_candidate_keepalive_interval_` will be used in STUN port allocation
+  // in future sessions. We also update the ready ports in the pooled sessions.
+  // Ports in sessions that are taken and owned by P2PTransportChannel will be
+  // updated there via IceConfig.
+  stun_candidate_keepalive_interval_ = stun_candidate_keepalive_interval;
+  for (const auto& session : pooled_sessions_) {
+    session->SetStunKeepaliveIntervalForReadyPorts(
+        stun_candidate_keepalive_interval_);
+  }
+
+  // If `candidate_pool_size_` is greater than the number of pooled sessions,
+  // create new sessions.
+  while (static_cast<int>(pooled_sessions_.size()) < candidate_pool_size_) {
+    IceParameters iceCredentials =
+        IceCredentialsIterator::CreateRandomIceCredentials();
+    PortAllocatorSession* pooled_session =
+        CreateSessionInternal("", 0, iceCredentials.ufrag, iceCredentials.pwd);
+    pooled_session->set_pooled(true);
+    pooled_session->set_ice_tiebreaker(tiebreaker_);
+    pooled_session->StartGettingPorts();
+    pooled_sessions_.push_back(
+        std::unique_ptr<PortAllocatorSession>(pooled_session));
+  }
+  return true;
+}
+
+void PortAllocator::SetIceTiebreaker(uint64_t tiebreaker) {
+  tiebreaker_ = tiebreaker;
+  for (auto& pooled_session : pooled_sessions_) {
+    pooled_session->set_ice_tiebreaker(tiebreaker_);
+  }
+}
+
+std::unique_ptr<PortAllocatorSession> PortAllocator::CreateSession(
+    absl::string_view content_name,
+    int component,
+    absl::string_view ice_ufrag,
+    absl::string_view ice_pwd) {
+  CheckRunOnValidThreadAndInitialized();
+  auto session = std::unique_ptr<PortAllocatorSession>(
+      CreateSessionInternal(content_name, component, ice_ufrag, ice_pwd));
+  session->SetCandidateFilter(candidate_filter());
+  session->set_ice_tiebreaker(tiebreaker_);
+  return session;
+}
+
+std::unique_ptr<PortAllocatorSession> PortAllocator::TakePooledSession(
+    absl::string_view content_name,
+    int component,
+    absl::string_view ice_ufrag,
+    absl::string_view ice_pwd) {
+  CheckRunOnValidThreadAndInitialized();
+  RTC_DCHECK(!ice_ufrag.empty());
+  RTC_DCHECK(!ice_pwd.empty());
+  if (pooled_sessions_.empty()) {
+    return nullptr;
+  }
+
+  IceParameters credentials(ice_ufrag, ice_pwd, false);
+  // If restrict_ice_credentials_change_ is TRUE, then call FindPooledSession
+  // with ice credentials. Otherwise call it with nullptr which means
+  // "find any" pooled session.
+  auto cit = FindPooledSession(restrict_ice_credentials_change_ ? &credentials
+                                                                : nullptr);
+  if (cit == pooled_sessions_.end()) {
+    return nullptr;
+  }
+
+  auto it =
+      pooled_sessions_.begin() + std::distance(pooled_sessions_.cbegin(), cit);
+  std::unique_ptr<PortAllocatorSession> ret = std::move(*it);
+  ret->SetIceParameters(content_name, component, ice_ufrag, ice_pwd);
+  ret->set_pooled(false);
+  // According to JSEP, a pooled session should filter candidates only
+  // after it's taken out of the pool.
+  ret->SetCandidateFilter(candidate_filter());
+  pooled_sessions_.erase(it);
+  return ret;
+}
+
+const PortAllocatorSession* PortAllocator::GetPooledSession(
+    const IceParameters* ice_credentials) const {
+  CheckRunOnValidThreadAndInitialized();
+  auto it = FindPooledSession(ice_credentials);
+  if (it == pooled_sessions_.end()) {
+    return nullptr;
+  } else {
+    return it->get();
+  }
+}
+
+std::vector<std::unique_ptr<PortAllocatorSession>>::const_iterator
+PortAllocator::FindPooledSession(const IceParameters* ice_credentials) const {
+  for (auto it = pooled_sessions_.begin(); it != pooled_sessions_.end(); ++it) {
+    if (ice_credentials == nullptr ||
+        ((*it)->ice_ufrag() == ice_credentials->ufrag &&
+         (*it)->ice_pwd() == ice_credentials->pwd)) {
+      return it;
+    }
+  }
+  return pooled_sessions_.end();
+}
+
+void PortAllocator::FreezeCandidatePool() {
+  CheckRunOnValidThreadAndInitialized();
+  candidate_pool_frozen_ = true;
+}
+
+void PortAllocator::DiscardCandidatePool() {
+  CheckRunOnValidThreadIfInitialized();
+  pooled_sessions_.clear();
+}
+
+void PortAllocator::SetCandidateFilter(uint32_t filter) {
+  CheckRunOnValidThreadIfInitialized();
+  if (candidate_filter_ == filter) {
+    return;
+  }
+  uint32_t prev_filter = candidate_filter_;
+  candidate_filter_ = filter;
+  SignalCandidateFilterChanged(prev_filter, filter);
+}
+
+void PortAllocator::GetCandidateStatsFromPooledSessions(
+    CandidateStatsList* candidate_stats_list) {
+  CheckRunOnValidThreadAndInitialized();
+  for (const auto& session : pooled_sessions()) {
+    session->GetCandidateStatsFromReadyPorts(candidate_stats_list);
+  }
+}
+
+std::vector<IceParameters> PortAllocator::GetPooledIceCredentials() {
+  CheckRunOnValidThreadAndInitialized();
+  std::vector<IceParameters> list;
+  for (const auto& session : pooled_sessions_) {
+    list.push_back(
+        IceParameters(session->ice_ufrag(), session->ice_pwd(), false));
+  }
+  return list;
+}
+
+Candidate PortAllocator::SanitizeCandidate(const Candidate& c) const {
+  CheckRunOnValidThreadAndInitialized();
+  // For a local host candidate, we need to conceal its IP address candidate if
+  // the mDNS obfuscation is enabled.
+  bool use_hostname_address =
+      (c.type() == LOCAL_PORT_TYPE || c.type() == PRFLX_PORT_TYPE) &&
+      MdnsObfuscationEnabled();
+  // If adapter enumeration is disabled or host candidates are disabled,
+  // clear the raddr of STUN candidates to avoid local address leakage.
+  bool filter_stun_related_address =
+      ((flags() & PORTALLOCATOR_DISABLE_ADAPTER_ENUMERATION) &&
+       (flags() & PORTALLOCATOR_DISABLE_DEFAULT_LOCAL_CANDIDATE)) ||
+      !(candidate_filter_ & CF_HOST) || MdnsObfuscationEnabled();
+  // If the candidate filter doesn't allow reflexive addresses, empty TURN raddr
+  // to avoid reflexive address leakage.
+  bool filter_turn_related_address = !(candidate_filter_ & CF_REFLEXIVE);
+  bool filter_related_address =
+      ((c.type() == STUN_PORT_TYPE && filter_stun_related_address) ||
+       (c.type() == RELAY_PORT_TYPE && filter_turn_related_address));
+  return c.ToSanitizedCopy(use_hostname_address, filter_related_address);
+}
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/port_allocator.h b/third_party/libwebrtc/p2p/base/port_allocator.h
new file mode 100644
index 0000000000..3ca63cbd41
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/port_allocator.h
@@ -0,0 +1,683 @@
+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_PORT_ALLOCATOR_H_
+#define P2P_BASE_PORT_ALLOCATOR_H_
+
+#include <deque>
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "absl/strings/string_view.h"
+#include "api/sequence_checker.h"
+#include "api/transport/enums.h"
+#include "p2p/base/port.h"
+#include "p2p/base/port_interface.h"
+#include "rtc_base/helpers.h"
+#include "rtc_base/proxy_info.h"
+#include "rtc_base/ssl_certificate.h"
+#include "rtc_base/system/rtc_export.h"
+#include "rtc_base/third_party/sigslot/sigslot.h"
+#include "rtc_base/thread.h"
+
+namespace webrtc {
+class TurnCustomizer;
+}  // namespace webrtc
+
+namespace cricket {
+
+// PortAllocator is responsible for allocating Port types for a given
+// P2PSocket. It also handles port freeing.
+//
+// Clients can override this class to control port allocation, including
+// what kinds of ports are allocated.
+
+enum {
+  // Disable local UDP ports. This doesn't impact how we connect to relay
+  // servers.
+  PORTALLOCATOR_DISABLE_UDP = 0x01,
+  PORTALLOCATOR_DISABLE_STUN = 0x02,
+  PORTALLOCATOR_DISABLE_RELAY = 0x04,
+  // Disable local TCP ports. This doesn't impact how we connect to relay
+  // servers.
+  PORTALLOCATOR_DISABLE_TCP = 0x08,
+  PORTALLOCATOR_ENABLE_IPV6 = 0x40,
+  PORTALLOCATOR_ENABLE_SHARED_SOCKET = 0x100,
+  PORTALLOCATOR_ENABLE_STUN_RETRANSMIT_ATTRIBUTE = 0x200,
+  // When specified, we'll only allocate the STUN candidate for the public
+  // interface as seen by regular http traffic and the HOST candidate associated
+  // with the default local interface.
+  PORTALLOCATOR_DISABLE_ADAPTER_ENUMERATION = 0x400,
+  // When specified along with PORTALLOCATOR_DISABLE_ADAPTER_ENUMERATION, the
+  // default local candidate mentioned above will not be allocated. Only the
+  // STUN candidate will be.
+  PORTALLOCATOR_DISABLE_DEFAULT_LOCAL_CANDIDATE = 0x800,
+  // Disallow use of UDP when connecting to a relay server. Since proxy servers
+  // usually don't handle UDP, using UDP will leak the IP address.
+  PORTALLOCATOR_DISABLE_UDP_RELAY = 0x1000,
+
+  // When multiple networks exist, do not gather candidates on the ones with
+  // high cost. So if both Wi-Fi and cellular networks exist, gather only on the
+  // Wi-Fi network. If a network type is "unknown", it has a cost lower than
+  // cellular but higher than Wi-Fi/Ethernet. So if an unknown network exists,
+  // cellular networks will not be used to gather candidates and if a Wi-Fi
+  // network is present, "unknown" networks will not be usd to gather
+  // candidates. Doing so ensures that even if a cellular network type was not
+  // detected initially, it would not be used if a Wi-Fi network is present.
+  PORTALLOCATOR_DISABLE_COSTLY_NETWORKS = 0x2000,
+
+  // When specified, do not collect IPv6 ICE candidates on Wi-Fi.
+  PORTALLOCATOR_ENABLE_IPV6_ON_WIFI = 0x4000,
+
+  // When this flag is set, ports not bound to any specific network interface
+  // will be used, in addition to normal ports bound to the enumerated
+  // interfaces. Without this flag, these "any address" ports would only be
+  // used when network enumeration fails or is disabled. But under certain
+  // conditions, these ports may succeed where others fail, so they may allow
+  // the application to work in a wider variety of environments, at the expense
+  // of having to allocate additional candidates.
+  PORTALLOCATOR_ENABLE_ANY_ADDRESS_PORTS = 0x8000,
+
+  // Exclude link-local network interfaces
+  // from considertaion after adapter enumeration.
+  PORTALLOCATOR_DISABLE_LINK_LOCAL_NETWORKS = 0x10000,
+};
+
+// Defines various reasons that have caused ICE regathering.
+enum class IceRegatheringReason {
+  NETWORK_CHANGE,      // Network interfaces on the device changed
+  NETWORK_FAILURE,     // Regather only on networks that have failed
+  OCCASIONAL_REFRESH,  // Periodic regather on all networks
+  MAX_VALUE
+};
+
+const uint32_t kDefaultPortAllocatorFlags = 0;
+
+const uint32_t kDefaultStepDelay = 1000;  // 1 sec step delay.
+// As per RFC 5245 Appendix B.1, STUN transactions need to be paced at certain
+// internal. Less than 20ms is not acceptable. We choose 50ms as our default.
+const uint32_t kMinimumStepDelay = 50;
+
+// Turning on IPv6 could make many IPv6 interfaces available for connectivity
+// check and delay the call setup time. kDefaultMaxIPv6Networks is the default
+// upper limit of IPv6 networks but could be changed by
+// set_max_ipv6_networks().
+constexpr int kDefaultMaxIPv6Networks = 5;
+
+// CF = CANDIDATE FILTER
+enum : uint32_t {
+  CF_NONE = 0x0,
+  CF_HOST = 0x1,
+  CF_REFLEXIVE = 0x2,
+  CF_RELAY = 0x4,
+  CF_ALL = 0x7,
+};
+
+// TLS certificate policy.
+enum class TlsCertPolicy {
+  // For TLS based protocols, ensure the connection is secure by not
+  // circumventing certificate validation.
+  TLS_CERT_POLICY_SECURE,
+  // For TLS based protocols, disregard security completely by skipping
+  // certificate validation. This is insecure and should never be used unless
+  // security is irrelevant in that particular context.
+  TLS_CERT_POLICY_INSECURE_NO_CHECK,
+};
+
+// TODO(deadbeef): Rename to TurnCredentials (and username to ufrag).
+struct RelayCredentials {
+  RelayCredentials() {}
+  RelayCredentials(absl::string_view username, absl::string_view password)
+      : username(username), password(password) {}
+
+  bool operator==(const RelayCredentials& o) const {
+    return username == o.username && password == o.password;
+  }
+  bool operator!=(const RelayCredentials& o) const { return !(*this == o); }
+
+  std::string username;
+  std::string password;
+};
+
+typedef std::vector<ProtocolAddress> PortList;
+// TODO(deadbeef): Rename to TurnServerConfig.
+struct RTC_EXPORT RelayServerConfig {
+  RelayServerConfig();
+  RelayServerConfig(const rtc::SocketAddress& address,
+                    absl::string_view username,
+                    absl::string_view password,
+                    ProtocolType proto);
+  RelayServerConfig(absl::string_view address,
+                    int port,
+                    absl::string_view username,
+                    absl::string_view password,
+                    ProtocolType proto);
+  // Legacy constructor where "secure" and PROTO_TCP implies PROTO_TLS.
+  RelayServerConfig(absl::string_view address,
+                    int port,
+                    absl::string_view username,
+                    absl::string_view password,
+                    ProtocolType proto,
+                    bool secure);
+  RelayServerConfig(const RelayServerConfig&);
+  ~RelayServerConfig();
+
+  bool operator==(const RelayServerConfig& o) const {
+    return ports == o.ports && credentials == o.credentials;
+  }
+  bool operator!=(const RelayServerConfig& o) const { return !(*this == o); }
+
+  PortList ports;
+  RelayCredentials credentials;
+  TlsCertPolicy tls_cert_policy = TlsCertPolicy::TLS_CERT_POLICY_SECURE;
+  std::vector<std::string> tls_alpn_protocols;
+  std::vector<std::string> tls_elliptic_curves;
+  rtc::SSLCertificateVerifier* tls_cert_verifier = nullptr;
+  std::string turn_logging_id;
+};
+
+class RTC_EXPORT PortAllocatorSession : public sigslot::has_slots<> {
+ public:
+  // Content name passed in mostly for logging and debugging.
+  PortAllocatorSession(absl::string_view content_name,
+                       int component,
+                       absl::string_view ice_ufrag,
+                       absl::string_view ice_pwd,
+                       uint32_t flags);
+
+  // Subclasses should clean up any ports created.
+  ~PortAllocatorSession() override;
+
+  uint32_t flags() const { return flags_; }
+  void set_flags(uint32_t flags) { flags_ = flags; }
+  std::string content_name() const { return content_name_; }
+  int component() const { return component_; }
+  const std::string& ice_ufrag() const { return ice_ufrag_; }
+  const std::string& ice_pwd() const { return ice_pwd_; }
+  bool pooled() const { return pooled_; }
+
+  // TODO(bugs.webrtc.org/14605): move this to the constructor
+  void set_ice_tiebreaker(uint64_t tiebreaker) { tiebreaker_ = tiebreaker; }
+  uint64_t ice_tiebreaker() const { return tiebreaker_; }
+
+  // Setting this filter should affect not only candidates gathered in the
+  // future, but candidates already gathered and ports already "ready",
+  // which would be returned by ReadyCandidates() and ReadyPorts().
+  //
+  // Default filter should be CF_ALL.
+  virtual void SetCandidateFilter(uint32_t filter) = 0;
+
+  // Starts gathering ports and ICE candidates.
+  virtual void StartGettingPorts() = 0;
+  // Completely stops gathering. Will not gather again unless StartGettingPorts
+  // is called again.
+  virtual void StopGettingPorts() = 0;
+  // Whether the session is actively getting ports.
+  virtual bool IsGettingPorts() = 0;
+
+  //
+  // NOTE: The group of methods below is only used for continual gathering.
+  //
+
+  // ClearGettingPorts should have the same immediate effect as
+  // StopGettingPorts, but if the implementation supports continual gathering,
+  // ClearGettingPorts allows additional ports/candidates to be gathered if the
+  // network conditions change.
+  virtual void ClearGettingPorts() = 0;
+  // Whether it is in the state where the existing gathering process is stopped,
+  // but new ones may be started (basically after calling ClearGettingPorts).
+  virtual bool IsCleared() const;
+  // Whether the session has completely stopped.
+  virtual bool IsStopped() const;
+  // Re-gathers candidates on networks that do not have any connections. More
+  // precisely, a network interface may have more than one IP addresses (e.g.,
+  // IPv4 and IPv6 addresses). Each address subnet will be used to create a
+  // network. Only if all networks of an interface have no connection, the
+  // implementation should start re-gathering on all networks of that interface.
+  virtual void RegatherOnFailedNetworks() {}
+  // Get candidate-level stats from all candidates on the ready ports and return
+  // the stats to the given list.
+  virtual void GetCandidateStatsFromReadyPorts(
+      CandidateStatsList* candidate_stats_list) const {}
+  // Set the interval at which STUN candidates will resend STUN binding requests
+  // on the underlying ports to keep NAT bindings open.
+  // The default value of the interval in implementation is restored if a null
+  // optional value is passed.
+  virtual void SetStunKeepaliveIntervalForReadyPorts(
+      const absl::optional<int>& stun_keepalive_interval) {}
+  // Another way of getting the information provided by the signals below.
+  //
+  // Ports and candidates are not guaranteed to be in the same order as the
+  // signals were emitted in.
+  virtual std::vector<PortInterface*> ReadyPorts() const = 0;
+  virtual std::vector<Candidate> ReadyCandidates() const = 0;
+  virtual bool CandidatesAllocationDone() const = 0;
+  // Marks all ports in the current session as "pruned" so that they may be
+  // destroyed if no connection is using them.
+  virtual void PruneAllPorts() {}
+
+  sigslot::signal2<PortAllocatorSession*, PortInterface*> SignalPortReady;
+  // Fires this signal when the network of the ports failed (either because the
+  // interface is down, or because there is no connection on the interface),
+  // or when TURN ports are pruned because a higher-priority TURN port becomes
+  // ready(pairable).
+  sigslot::signal2<PortAllocatorSession*, const std::vector<PortInterface*>&>
+      SignalPortsPruned;
+  sigslot::signal2<PortAllocatorSession*, const std::vector<Candidate>&>
+      SignalCandidatesReady;
+  sigslot::signal2<PortAllocatorSession*, const IceCandidateErrorEvent&>
+      SignalCandidateError;
+  // Candidates should be signaled to be removed when the port that generated
+  // the candidates is removed.
+  sigslot::signal2<PortAllocatorSession*, const std::vector<Candidate>&>
+      SignalCandidatesRemoved;
+  sigslot::signal1<PortAllocatorSession*> SignalCandidatesAllocationDone;
+
+  sigslot::signal2<PortAllocatorSession*, IceRegatheringReason>
+      SignalIceRegathering;
+
+  virtual uint32_t generation();
+  virtual void set_generation(uint32_t generation);
+
+ protected:
+  // This method is called when a pooled session (which doesn't have these
+  // properties initially) is returned by PortAllocator::TakePooledSession,
+  // and the content name, component, and ICE ufrag/pwd are updated.
+  //
+  // A subclass may need to override this method to perform additional actions,
+  // such as applying the updated information to ports and candidates.
+  virtual void UpdateIceParametersInternal() {}
+
+  // TODO(deadbeef): Get rid of these when everyone switches to ice_ufrag and
+  // ice_pwd.
+  const std::string& username() const { return ice_ufrag_; }
+  const std::string& password() const { return ice_pwd_; }
+
+ private:
+  void SetIceParameters(absl::string_view content_name,
+                        int component,
+                        absl::string_view ice_ufrag,
+                        absl::string_view ice_pwd) {
+    content_name_ = std::string(content_name);
+    component_ = component;
+    ice_ufrag_ = std::string(ice_ufrag);
+    ice_pwd_ = std::string(ice_pwd);
+    UpdateIceParametersInternal();
+  }
+
+  void set_pooled(bool value) { pooled_ = value; }
+
+  uint32_t flags_;
+  uint32_t generation_;
+  std::string content_name_;
+  int component_;
+  std::string ice_ufrag_;
+  std::string ice_pwd_;
+
+  bool pooled_ = false;
+
+  // TODO(bugs.webrtc.org/14605): move this to the constructor
+  uint64_t tiebreaker_;
+
+  // SetIceParameters is an implementation detail which only PortAllocator
+  // should be able to call.
+  friend class PortAllocator;
+};
+
+// Every method of PortAllocator (including the destructor) must be called on
+// the same thread after Initialize is called.
+//
+// This allows a PortAllocator subclass to be constructed and configured on one
+// thread, and passed into an object that uses it on a different thread.
+class RTC_EXPORT PortAllocator : public sigslot::has_slots<> {
+ public:
+  PortAllocator();
+  ~PortAllocator() override;
+
+  // This MUST be called on the PortAllocator's thread after finishing
+  // constructing and configuring the PortAllocator subclasses.
+  virtual void Initialize();
+
+  // Set to true if some Ports need to know the ICE credentials when they are
+  // created. This will ensure that the PortAllocator will only match pooled
+  // allocator sessions to the ICE transport with the same credentials.
+  virtual void set_restrict_ice_credentials_change(bool value);
+
+  // Set STUN and TURN servers to be used in future sessions, and set
+  // candidate pool size, as described in JSEP.
+  //
+  // If the servers are changing, and the candidate pool size is nonzero, and
+  // FreezeCandidatePool hasn't been called, existing pooled sessions will be
+  // destroyed and new ones created.
+  //
+  // If the servers are not changing but the candidate pool size is, and
+  // FreezeCandidatePool hasn't been called, pooled sessions will be either
+  // created or destroyed as necessary.
+  //
+  // Returns true if the configuration could successfully be changed.
+  // Deprecated
+  bool SetConfiguration(const ServerAddresses& stun_servers,
+                        const std::vector<RelayServerConfig>& turn_servers,
+                        int candidate_pool_size,
+                        bool prune_turn_ports,
+                        webrtc::TurnCustomizer* turn_customizer = nullptr,
+                        const absl::optional<int>&
+                            stun_candidate_keepalive_interval = absl::nullopt);
+  bool SetConfiguration(const ServerAddresses& stun_servers,
+                        const std::vector<RelayServerConfig>& turn_servers,
+                        int candidate_pool_size,
+                        webrtc::PortPrunePolicy turn_port_prune_policy,
+                        webrtc::TurnCustomizer* turn_customizer = nullptr,
+                        const absl::optional<int>&
+                            stun_candidate_keepalive_interval = absl::nullopt);
+
+  void SetIceTiebreaker(uint64_t tiebreaker);
+  uint64_t IceTiebreaker() const { return tiebreaker_; }
+
+  const ServerAddresses& stun_servers() const {
+    CheckRunOnValidThreadIfInitialized();
+    return stun_servers_;
+  }
+
+  const std::vector<RelayServerConfig>& turn_servers() const {
+    CheckRunOnValidThreadIfInitialized();
+    return turn_servers_;
+  }
+
+  int candidate_pool_size() const {
+    CheckRunOnValidThreadIfInitialized();
+    return candidate_pool_size_;
+  }
+
+  const absl::optional<int>& stun_candidate_keepalive_interval() const {
+    CheckRunOnValidThreadIfInitialized();
+    return stun_candidate_keepalive_interval_;
+  }
+
+  // Sets the network types to ignore.
+  // Values are defined by the AdapterType enum.
+  // For instance, calling this with
+  // ADAPTER_TYPE_ETHERNET | ADAPTER_TYPE_LOOPBACK will ignore Ethernet and
+  // loopback interfaces.
+  virtual void SetNetworkIgnoreMask(int network_ignore_mask) = 0;
+
+  // Set whether VPN connections should be preferred, avoided, mandated or
+  // blocked.
+  virtual void SetVpnPreference(webrtc::VpnPreference preference) {
+    vpn_preference_ = preference;
+  }
+
+  // Set list of <ipaddress, mask> that shall be categorized as VPN.
+  // Implemented by BasicPortAllocator.
+  virtual void SetVpnList(const std::vector<rtc::NetworkMask>& vpn_list) {}
+
+  std::unique_ptr<PortAllocatorSession> CreateSession(
+      absl::string_view content_name,
+      int component,
+      absl::string_view ice_ufrag,
+      absl::string_view ice_pwd);
+
+  // Get an available pooled session and set the transport information on it.
+  //
+  // Caller takes ownership of the returned session.
+  //
+  // If restrict_ice_credentials_change is TRUE, then it will only
+  //   return a pooled session with matching ice credentials.
+  // If no pooled sessions are available, returns null.
+  std::unique_ptr<PortAllocatorSession> TakePooledSession(
+      absl::string_view content_name,
+      int component,
+      absl::string_view ice_ufrag,
+      absl::string_view ice_pwd);
+
+  // Returns the next session that would be returned by TakePooledSession
+  // optionally restricting it to sessions with specified ice credentials.
+  const PortAllocatorSession* GetPooledSession(
+      const IceParameters* ice_credentials = nullptr) const;
+
+  // After FreezeCandidatePool is called, changing the candidate pool size will
+  // no longer be allowed, and changing ICE servers will not cause pooled
+  // sessions to be recreated.
+  //
+  // Expected to be called when SetLocalDescription is called on a
+  // PeerConnection. Can be called safely on any thread as long as not
+  // simultaneously with SetConfiguration.
+  void FreezeCandidatePool();
+
+  // Discard any remaining pooled sessions.
+  void DiscardCandidatePool();
+
+  // Clears the address and the related address fields of a local candidate to
+  // avoid IP leakage. This is applicable in several scenarios:
+  // 1. Sanitization is configured via the candidate filter.
+  // 2. Sanitization is configured via the port allocator flags.
+  // 3. mDNS concealment of private IPs is enabled.
+  Candidate SanitizeCandidate(const Candidate& c) const;
+
+  uint32_t flags() const {
+    CheckRunOnValidThreadIfInitialized();
+    return flags_;
+  }
+
+  void set_flags(uint32_t flags) {
+    CheckRunOnValidThreadIfInitialized();
+    flags_ = flags;
+  }
+
+  // These three methods are deprecated. If connections need to go through a
+  // proxy, the application should create a BasicPortAllocator given a custom
+  // PacketSocketFactory that creates proxy sockets.
+  const std::string& user_agent() const {
+    CheckRunOnValidThreadIfInitialized();
+    return agent_;
+  }
+
+  const rtc::ProxyInfo& proxy() const {
+    CheckRunOnValidThreadIfInitialized();
+    return proxy_;
+  }
+
+  void set_proxy(absl::string_view agent, const rtc::ProxyInfo& proxy) {
+    CheckRunOnValidThreadIfInitialized();
+    agent_ = std::string(agent);
+    proxy_ = proxy;
+  }
+
+  // Gets/Sets the port range to use when choosing client ports.
+  int min_port() const {
+    CheckRunOnValidThreadIfInitialized();
+    return min_port_;
+  }
+
+  int max_port() const {
+    CheckRunOnValidThreadIfInitialized();
+    return max_port_;
+  }
+
+  bool SetPortRange(int min_port, int max_port) {
+    CheckRunOnValidThreadIfInitialized();
+    if (min_port > max_port) {
+      return false;
+    }
+
+    min_port_ = min_port;
+    max_port_ = max_port;
+    return true;
+  }
+
+  // Can be used to change the default numer of IPv6 network interfaces used
+  // (5). Can set to INT_MAX to effectively disable the limit.
+  //
+  // TODO(deadbeef): Applications shouldn't have to arbitrarily limit the
+  // number of available IPv6 network interfaces just because they could slow
+  // ICE down. We should work on making our ICE logic smarter (for example,
+  // prioritizing pinging connections that are most likely to work) so that
+  // every network interface can be used without impacting ICE's speed.
+  void set_max_ipv6_networks(int networks) {
+    CheckRunOnValidThreadIfInitialized();
+    max_ipv6_networks_ = networks;
+  }
+
+  int max_ipv6_networks() {
+    CheckRunOnValidThreadIfInitialized();
+    return max_ipv6_networks_;
+  }
+
+  // Delay between different candidate gathering phases (UDP, TURN, TCP).
+  // Defaults to 1 second, but PeerConnection sets it to 50ms.
+  // TODO(deadbeef): Get rid of this. Its purpose is to avoid sending too many
+  // STUN transactions at once, but that's already happening if you configure
+  // multiple STUN servers or have multiple network interfaces. We should
+  // implement some global pacing logic instead if that's our goal.
+  uint32_t step_delay() const {
+    CheckRunOnValidThreadIfInitialized();
+    return step_delay_;
+  }
+
+  void set_step_delay(uint32_t delay) {
+    CheckRunOnValidThreadIfInitialized();
+    step_delay_ = delay;
+  }
+
+  bool allow_tcp_listen() const {
+    CheckRunOnValidThreadIfInitialized();
+    return allow_tcp_listen_;
+  }
+
+  void set_allow_tcp_listen(bool allow_tcp_listen) {
+    CheckRunOnValidThreadIfInitialized();
+    allow_tcp_listen_ = allow_tcp_listen;
+  }
+
+  uint32_t candidate_filter() {
+    CheckRunOnValidThreadIfInitialized();
+    return candidate_filter_;
+  }
+
+  // The new filter value will be populated to future allocation sessions, when
+  // they are created via CreateSession, and also pooled sessions when one is
+  // taken via TakePooledSession.
+  //
+  // A change in the candidate filter also fires a signal
+  // `SignalCandidateFilterChanged`, so that objects subscribed to this signal
+  // can, for example, update the candidate filter for sessions created by this
+  // allocator and already taken by the object.
+  //
+  // Specifically for the session taken by the ICE transport, we currently do
+  // not support removing candidate pairs formed with local candidates from this
+  // session that are disabled by the new candidate filter.
+  void SetCandidateFilter(uint32_t filter);
+  // Deprecated.
+  // TODO(qingsi): Remove this after Chromium migrates to the new method.
+  void set_candidate_filter(uint32_t filter) { SetCandidateFilter(filter); }
+
+  // Deprecated (by the next method).
+  bool prune_turn_ports() const {
+    CheckRunOnValidThreadIfInitialized();
+    return turn_port_prune_policy_ == webrtc::PRUNE_BASED_ON_PRIORITY;
+  }
+
+  webrtc::PortPrunePolicy turn_port_prune_policy() const {
+    CheckRunOnValidThreadIfInitialized();
+    return turn_port_prune_policy_;
+  }
+
+  webrtc::TurnCustomizer* turn_customizer() {
+    CheckRunOnValidThreadIfInitialized();
+    return turn_customizer_;
+  }
+
+  // Collect candidate stats from pooled allocator sessions. This can be used to
+  // collect candidate stats without creating an offer/answer or setting local
+  // description. After the local description is set, the ownership of the
+  // pooled session is taken by P2PTransportChannel, and the
+  // candidate stats can be collected from P2PTransportChannel::GetStats.
+  virtual void GetCandidateStatsFromPooledSessions(
+      CandidateStatsList* candidate_stats_list);
+
+  // Return IceParameters of the pooled sessions.
+  std::vector<IceParameters> GetPooledIceCredentials();
+
+  // Fired when `candidate_filter_` changes.
+  sigslot::signal2<uint32_t /* prev_filter */, uint32_t /* cur_filter */>
+      SignalCandidateFilterChanged;
+
+ protected:
+  // TODO(webrtc::13579): Remove std::string version once downstream users have
+  // migrated to the absl::string_view version.
+  virtual PortAllocatorSession* CreateSessionInternal(
+      absl::string_view content_name,
+      int component,
+      absl::string_view ice_ufrag,
+      absl::string_view ice_pwd) = 0;
+
+  const std::vector<std::unique_ptr<PortAllocatorSession>>& pooled_sessions() {
+    return pooled_sessions_;
+  }
+
+  // Returns true if there is an mDNS responder attached to the network manager.
+  virtual bool MdnsObfuscationEnabled() const { return false; }
+
+  // The following thread checks are only done in DCHECK for the consistency
+  // with the exsiting thread checks.
+  void CheckRunOnValidThreadIfInitialized() const {
+    RTC_DCHECK(!initialized_ || thread_checker_.IsCurrent());
+  }
+
+  void CheckRunOnValidThreadAndInitialized() const {
+    RTC_DCHECK(initialized_ && thread_checker_.IsCurrent());
+  }
+
+  bool initialized_ = false;
+  uint32_t flags_;
+  std::string agent_;
+  rtc::ProxyInfo proxy_;
+  int min_port_;
+  int max_port_;
+  int max_ipv6_networks_;
+  uint32_t step_delay_;
+  bool allow_tcp_listen_;
+  uint32_t candidate_filter_;
+  std::string origin_;
+  webrtc::SequenceChecker thread_checker_;
+  webrtc::VpnPreference vpn_preference_ = webrtc::VpnPreference::kDefault;
+
+ private:
+  ServerAddresses stun_servers_;
+  std::vector<RelayServerConfig> turn_servers_;
+  int candidate_pool_size_ = 0;  // Last value passed into SetConfiguration.
+  std::vector<std::unique_ptr<PortAllocatorSession>> pooled_sessions_;
+  bool candidate_pool_frozen_ = false;
+  webrtc::PortPrunePolicy turn_port_prune_policy_ = webrtc::NO_PRUNE;
+
+  // Customizer for TURN messages.
+  // The instance is owned by application and will be shared among
+  // all TurnPort(s) created.
+  webrtc::TurnCustomizer* turn_customizer_ = nullptr;
+
+  absl::optional<int> stun_candidate_keepalive_interval_;
+
+  // If true, TakePooledSession() will only return sessions that has same ice
+  // credentials as requested.
+  bool restrict_ice_credentials_change_ = false;
+
+  // Returns iterator to pooled session with specified ice_credentials or first
+  // if ice_credentials is nullptr.
+  std::vector<std::unique_ptr<PortAllocatorSession>>::const_iterator
+  FindPooledSession(const IceParameters* ice_credentials = nullptr) const;
+
+  // ICE tie breaker.
+  uint64_t tiebreaker_;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_PORT_ALLOCATOR_H_
diff --git a/third_party/libwebrtc/p2p/base/port_allocator_unittest.cc b/third_party/libwebrtc/p2p/base/port_allocator_unittest.cc
new file mode 100644
index 0000000000..f70997179e
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/port_allocator_unittest.cc
@@ -0,0 +1,371 @@
+/*
+ *  Copyright 2016 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/port_allocator.h"
+
+#include <memory>
+
+#include "absl/strings/string_view.h"
+#include "p2p/base/fake_port_allocator.h"
+#include "rtc_base/thread.h"
+#include "rtc_base/virtual_socket_server.h"
+#include "test/gtest.h"
+#include "test/scoped_key_value_config.h"
+
+static const char kContentName[] = "test content";
+// Based on ICE_UFRAG_LENGTH
+static const char kIceUfrag[] = "UF00";
+// Based on ICE_PWD_LENGTH
+static const char kIcePwd[] = "TESTICEPWD00000000000000";
+static const char kTurnUsername[] = "test";
+static const char kTurnPassword[] = "test";
+constexpr uint64_t kTiebreakerDefault = 44444;
+
+class PortAllocatorTest : public ::testing::Test, public sigslot::has_slots<> {
+ public:
+  PortAllocatorTest()
+      : vss_(std::make_unique<rtc::VirtualSocketServer>()),
+        main_(vss_.get()),
+        packet_socket_factory_(
+            std::make_unique<rtc::BasicPacketSocketFactory>(vss_.get())),
+        allocator_(std::make_unique<cricket::FakePortAllocator>(
+            rtc::Thread::Current(),
+            packet_socket_factory_.get(),
+            &field_trials_)) {
+    allocator_->SetIceTiebreaker(kTiebreakerDefault);
+  }
+
+ protected:
+  void SetConfigurationWithPoolSize(int candidate_pool_size) {
+    EXPECT_TRUE(allocator_->SetConfiguration(
+        cricket::ServerAddresses(), std::vector<cricket::RelayServerConfig>(),
+        candidate_pool_size, webrtc::NO_PRUNE));
+  }
+
+  void SetConfigurationWithPoolSizeExpectFailure(int candidate_pool_size) {
+    EXPECT_FALSE(allocator_->SetConfiguration(
+        cricket::ServerAddresses(), std::vector<cricket::RelayServerConfig>(),
+        candidate_pool_size, webrtc::NO_PRUNE));
+  }
+
+  std::unique_ptr<cricket::FakePortAllocatorSession> CreateSession(
+      absl::string_view content_name,
+      int component,
+      absl::string_view ice_ufrag,
+      absl::string_view ice_pwd) {
+    return std::unique_ptr<cricket::FakePortAllocatorSession>(
+        static_cast<cricket::FakePortAllocatorSession*>(
+            allocator_
+                ->CreateSession(content_name, component, ice_ufrag, ice_pwd)
+                .release()));
+  }
+
+  const cricket::FakePortAllocatorSession* GetPooledSession() const {
+    return static_cast<const cricket::FakePortAllocatorSession*>(
+        allocator_->GetPooledSession());
+  }
+
+  std::unique_ptr<cricket::FakePortAllocatorSession> TakePooledSession() {
+    return std::unique_ptr<cricket::FakePortAllocatorSession>(
+        static_cast<cricket::FakePortAllocatorSession*>(
+            allocator_->TakePooledSession(kContentName, 0, kIceUfrag, kIcePwd)
+                .release()));
+  }
+
+  int GetAllPooledSessionsReturnCount() {
+    int count = 0;
+    while (TakePooledSession() != nullptr) {
+      ++count;
+    }
+    return count;
+  }
+
+  webrtc::test::ScopedKeyValueConfig field_trials_;
+  std::unique_ptr<rtc::VirtualSocketServer> vss_;
+  rtc::AutoSocketServerThread main_;
+  std::unique_ptr<rtc::PacketSocketFactory> packet_socket_factory_;
+  std::unique_ptr<cricket::FakePortAllocator> allocator_;
+  rtc::SocketAddress stun_server_1{"11.11.11.11", 3478};
+  rtc::SocketAddress stun_server_2{"22.22.22.22", 3478};
+  cricket::RelayServerConfig turn_server_1{"11.11.11.11",      3478,
+                                           kTurnUsername,      kTurnPassword,
+                                           cricket::PROTO_UDP, false};
+  cricket::RelayServerConfig turn_server_2{"22.22.22.22",      3478,
+                                           kTurnUsername,      kTurnPassword,
+                                           cricket::PROTO_UDP, false};
+};
+
+TEST_F(PortAllocatorTest, TestDefaults) {
+  EXPECT_EQ(0UL, allocator_->stun_servers().size());
+  EXPECT_EQ(0UL, allocator_->turn_servers().size());
+  EXPECT_EQ(0, allocator_->candidate_pool_size());
+  EXPECT_EQ(0, GetAllPooledSessionsReturnCount());
+}
+
+// Call CreateSession and verify that the parameters passed in and the
+// candidate filter are applied as expected.
+TEST_F(PortAllocatorTest, CreateSession) {
+  allocator_->SetCandidateFilter(cricket::CF_RELAY);
+  auto session = CreateSession(kContentName, 1, kIceUfrag, kIcePwd);
+  ASSERT_NE(nullptr, session);
+  EXPECT_EQ(cricket::CF_RELAY, session->candidate_filter());
+  EXPECT_EQ(kContentName, session->content_name());
+  EXPECT_EQ(1, session->component());
+  EXPECT_EQ(kIceUfrag, session->ice_ufrag());
+  EXPECT_EQ(kIcePwd, session->ice_pwd());
+}
+
+TEST_F(PortAllocatorTest, SetConfigurationUpdatesIceServers) {
+  cricket::ServerAddresses stun_servers_1 = {stun_server_1};
+  std::vector<cricket::RelayServerConfig> turn_servers_1 = {turn_server_1};
+  EXPECT_TRUE(allocator_->SetConfiguration(stun_servers_1, turn_servers_1, 0,
+                                           webrtc::NO_PRUNE));
+  EXPECT_EQ(stun_servers_1, allocator_->stun_servers());
+  EXPECT_EQ(turn_servers_1, allocator_->turn_servers());
+
+  // Update with a different set of servers.
+  cricket::ServerAddresses stun_servers_2 = {stun_server_2};
+  std::vector<cricket::RelayServerConfig> turn_servers_2 = {turn_server_2};
+  EXPECT_TRUE(allocator_->SetConfiguration(stun_servers_2, turn_servers_2, 0,
+                                           webrtc::NO_PRUNE));
+  EXPECT_EQ(stun_servers_2, allocator_->stun_servers());
+  EXPECT_EQ(turn_servers_2, allocator_->turn_servers());
+}
+
+TEST_F(PortAllocatorTest, SetConfigurationUpdatesCandidatePoolSize) {
+  SetConfigurationWithPoolSize(2);
+  EXPECT_EQ(2, allocator_->candidate_pool_size());
+  SetConfigurationWithPoolSize(3);
+  EXPECT_EQ(3, allocator_->candidate_pool_size());
+  SetConfigurationWithPoolSize(1);
+  EXPECT_EQ(1, allocator_->candidate_pool_size());
+  SetConfigurationWithPoolSize(4);
+  EXPECT_EQ(4, allocator_->candidate_pool_size());
+}
+
+// A negative pool size should just be treated as zero.
+TEST_F(PortAllocatorTest, SetConfigurationWithNegativePoolSizeFails) {
+  SetConfigurationWithPoolSizeExpectFailure(-1);
+}
+
+// Test that if the candidate pool size is nonzero, pooled sessions are
+// created, and StartGettingPorts is called on them.
+TEST_F(PortAllocatorTest, SetConfigurationCreatesPooledSessions) {
+  SetConfigurationWithPoolSize(2);
+  auto session_1 = TakePooledSession();
+  auto session_2 = TakePooledSession();
+  ASSERT_NE(nullptr, session_1.get());
+  ASSERT_NE(nullptr, session_2.get());
+  EXPECT_EQ(1, session_1->port_config_count());
+  EXPECT_EQ(1, session_2->port_config_count());
+  EXPECT_EQ(0, GetAllPooledSessionsReturnCount());
+}
+
+// Test that if the candidate pool size is increased, pooled sessions are
+// created as necessary.
+TEST_F(PortAllocatorTest, SetConfigurationCreatesMorePooledSessions) {
+  SetConfigurationWithPoolSize(1);
+  SetConfigurationWithPoolSize(2);
+  EXPECT_EQ(2, GetAllPooledSessionsReturnCount());
+}
+
+// Test that if the candidate pool size is reduced, extra sessions are
+// destroyed.
+TEST_F(PortAllocatorTest, SetConfigurationDestroysPooledSessions) {
+  SetConfigurationWithPoolSize(2);
+  SetConfigurationWithPoolSize(1);
+  EXPECT_EQ(1, GetAllPooledSessionsReturnCount());
+}
+
+// According to JSEP, existing pooled sessions should be destroyed and new
+// ones created when the ICE servers change.
+TEST_F(PortAllocatorTest,
+       SetConfigurationRecreatesPooledSessionsWhenIceServersChange) {
+  cricket::ServerAddresses stun_servers_1 = {stun_server_1};
+  std::vector<cricket::RelayServerConfig> turn_servers_1 = {turn_server_1};
+  allocator_->SetConfiguration(stun_servers_1, turn_servers_1, 1,
+                               webrtc::NO_PRUNE);
+  EXPECT_EQ(stun_servers_1, allocator_->stun_servers());
+  EXPECT_EQ(turn_servers_1, allocator_->turn_servers());
+
+  // Update with a different set of servers (and also change pool size).
+  cricket::ServerAddresses stun_servers_2 = {stun_server_2};
+  std::vector<cricket::RelayServerConfig> turn_servers_2 = {turn_server_2};
+  allocator_->SetConfiguration(stun_servers_2, turn_servers_2, 2,
+                               webrtc::NO_PRUNE);
+  EXPECT_EQ(stun_servers_2, allocator_->stun_servers());
+  EXPECT_EQ(turn_servers_2, allocator_->turn_servers());
+  auto session_1 = TakePooledSession();
+  auto session_2 = TakePooledSession();
+  ASSERT_NE(nullptr, session_1.get());
+  ASSERT_NE(nullptr, session_2.get());
+  EXPECT_EQ(stun_servers_2, session_1->stun_servers());
+  EXPECT_EQ(turn_servers_2, session_1->turn_servers());
+  EXPECT_EQ(stun_servers_2, session_2->stun_servers());
+  EXPECT_EQ(turn_servers_2, session_2->turn_servers());
+  EXPECT_EQ(0, GetAllPooledSessionsReturnCount());
+}
+
+// According to JSEP, after SetLocalDescription, setting different ICE servers
+// will not cause the pool to be refilled. This is implemented by the
+// PeerConnection calling FreezeCandidatePool when a local description is set.
+TEST_F(PortAllocatorTest,
+       SetConfigurationDoesNotRecreatePooledSessionsAfterFreezeCandidatePool) {
+  cricket::ServerAddresses stun_servers_1 = {stun_server_1};
+  std::vector<cricket::RelayServerConfig> turn_servers_1 = {turn_server_1};
+  allocator_->SetConfiguration(stun_servers_1, turn_servers_1, 1,
+                               webrtc::NO_PRUNE);
+  EXPECT_EQ(stun_servers_1, allocator_->stun_servers());
+  EXPECT_EQ(turn_servers_1, allocator_->turn_servers());
+
+  // Update with a different set of servers, but first freeze the pool.
+  allocator_->FreezeCandidatePool();
+  cricket::ServerAddresses stun_servers_2 = {stun_server_2};
+  std::vector<cricket::RelayServerConfig> turn_servers_2 = {turn_server_2};
+  allocator_->SetConfiguration(stun_servers_2, turn_servers_2, 2,
+                               webrtc::NO_PRUNE);
+  EXPECT_EQ(stun_servers_2, allocator_->stun_servers());
+  EXPECT_EQ(turn_servers_2, allocator_->turn_servers());
+  auto session = TakePooledSession();
+  ASSERT_NE(nullptr, session.get());
+  EXPECT_EQ(stun_servers_1, session->stun_servers());
+  EXPECT_EQ(turn_servers_1, session->turn_servers());
+  EXPECT_EQ(0, GetAllPooledSessionsReturnCount());
+}
+
+TEST_F(PortAllocatorTest, GetPooledSessionReturnsNextSession) {
+  SetConfigurationWithPoolSize(2);
+  auto peeked_session_1 = GetPooledSession();
+  auto session_1 = TakePooledSession();
+  EXPECT_EQ(session_1.get(), peeked_session_1);
+  auto peeked_session_2 = GetPooledSession();
+  auto session_2 = TakePooledSession();
+  EXPECT_EQ(session_2.get(), peeked_session_2);
+}
+
+// Verify that subclasses of PortAllocatorSession are given a chance to update
+// ICE parameters when TakePooledSession is called, and the base class updates
+// the info itself.
+TEST_F(PortAllocatorTest, TakePooledSessionUpdatesIceParameters) {
+  SetConfigurationWithPoolSize(1);
+  auto peeked_session = GetPooledSession();
+  ASSERT_NE(nullptr, peeked_session);
+  EXPECT_EQ(0, peeked_session->transport_info_update_count());
+  std::unique_ptr<cricket::FakePortAllocatorSession> session(
+      static_cast<cricket::FakePortAllocatorSession*>(
+          allocator_->TakePooledSession(kContentName, 1, kIceUfrag, kIcePwd)
+              .release()));
+  EXPECT_EQ(1, session->transport_info_update_count());
+  EXPECT_EQ(kContentName, session->content_name());
+  EXPECT_EQ(1, session->component());
+  EXPECT_EQ(kIceUfrag, session->ice_ufrag());
+  EXPECT_EQ(kIcePwd, session->ice_pwd());
+}
+
+// According to JSEP, candidate filtering should be done when the pooled
+// candidates are surfaced to the application. This means when a pooled
+// session is taken. So a pooled session should gather candidates
+// unfiltered until it's returned by TakePooledSession.
+TEST_F(PortAllocatorTest, TakePooledSessionUpdatesCandidateFilter) {
+  allocator_->SetCandidateFilter(cricket::CF_RELAY);
+  SetConfigurationWithPoolSize(1);
+  auto peeked_session = GetPooledSession();
+  ASSERT_NE(nullptr, peeked_session);
+  EXPECT_EQ(cricket::CF_ALL, peeked_session->candidate_filter());
+  auto session = TakePooledSession();
+  EXPECT_EQ(cricket::CF_RELAY, session->candidate_filter());
+}
+
+// Verify that after DiscardCandidatePool, TakePooledSession doesn't return
+// anything.
+TEST_F(PortAllocatorTest, DiscardCandidatePool) {
+  SetConfigurationWithPoolSize(1);
+  allocator_->DiscardCandidatePool();
+  EXPECT_EQ(0, GetAllPooledSessionsReturnCount());
+}
+
+TEST_F(PortAllocatorTest, RestrictIceCredentialsChange) {
+  SetConfigurationWithPoolSize(1);
+  EXPECT_EQ(1, GetAllPooledSessionsReturnCount());
+  allocator_->DiscardCandidatePool();
+
+  // Only return pooled sessions with the ice credentials that
+  // match those requested in TakePooledSession().
+  allocator_->set_restrict_ice_credentials_change(true);
+  SetConfigurationWithPoolSize(1);
+  EXPECT_EQ(0, GetAllPooledSessionsReturnCount());
+  allocator_->DiscardCandidatePool();
+
+  SetConfigurationWithPoolSize(1);
+  auto credentials = allocator_->GetPooledIceCredentials();
+  ASSERT_EQ(1u, credentials.size());
+  EXPECT_EQ(nullptr,
+            allocator_->TakePooledSession(kContentName, 0, kIceUfrag, kIcePwd));
+  EXPECT_NE(nullptr,
+            allocator_->TakePooledSession(kContentName, 0, credentials[0].ufrag,
+                                          credentials[0].pwd));
+  EXPECT_EQ(nullptr,
+            allocator_->TakePooledSession(kContentName, 0, credentials[0].ufrag,
+                                          credentials[0].pwd));
+  allocator_->DiscardCandidatePool();
+}
+
+// Constants for testing candidates
+const char kIpv4Address[] = "12.34.56.78";
+const char kIpv4AddressWithPort[] = "12.34.56.78:443";
+
+TEST_F(PortAllocatorTest, SanitizeEmptyCandidateDefaultConfig) {
+  cricket::Candidate input;
+  cricket::Candidate output = allocator_->SanitizeCandidate(input);
+  EXPECT_EQ("", output.address().ipaddr().ToString());
+}
+
+TEST_F(PortAllocatorTest, SanitizeIpv4CandidateDefaultConfig) {
+  cricket::Candidate input(1, "udp", rtc::SocketAddress(kIpv4Address, 443), 1,
+                           "username", "password", cricket::LOCAL_PORT_TYPE, 1,
+                           "foundation", 1, 1);
+  cricket::Candidate output = allocator_->SanitizeCandidate(input);
+  EXPECT_EQ(kIpv4AddressWithPort, output.address().ToString());
+  EXPECT_EQ(kIpv4Address, output.address().ipaddr().ToString());
+}
+
+TEST_F(PortAllocatorTest, SanitizeIpv4CandidateMdnsObfuscationEnabled) {
+  allocator_->SetMdnsObfuscationEnabledForTesting(true);
+  cricket::Candidate input(1, "udp", rtc::SocketAddress(kIpv4Address, 443), 1,
+                           "username", "password", cricket::LOCAL_PORT_TYPE, 1,
+                           "foundation", 1, 1);
+  cricket::Candidate output = allocator_->SanitizeCandidate(input);
+  EXPECT_NE(kIpv4AddressWithPort, output.address().ToString());
+  EXPECT_EQ("", output.address().ipaddr().ToString());
+}
+
+TEST_F(PortAllocatorTest, SanitizePrflxCandidateMdnsObfuscationEnabled) {
+  allocator_->SetMdnsObfuscationEnabledForTesting(true);
+  // Create the candidate from an IP literal. This populates the hostname.
+  cricket::Candidate input(1, "udp", rtc::SocketAddress(kIpv4Address, 443), 1,
+                           "username", "password", cricket::PRFLX_PORT_TYPE, 1,
+                           "foundation", 1, 1);
+  cricket::Candidate output = allocator_->SanitizeCandidate(input);
+  EXPECT_NE(kIpv4AddressWithPort, output.address().ToString());
+  EXPECT_EQ("", output.address().ipaddr().ToString());
+}
+
+TEST_F(PortAllocatorTest, SanitizeIpv4NonLiteralMdnsObfuscationEnabled) {
+  // Create the candidate with an empty hostname.
+  allocator_->SetMdnsObfuscationEnabledForTesting(true);
+  rtc::IPAddress ip;
+  EXPECT_TRUE(IPFromString(kIpv4Address, &ip));
+  cricket::Candidate input(1, "udp", rtc::SocketAddress(ip, 443), 1, "username",
+                           "password", cricket::LOCAL_PORT_TYPE, 1,
+                           "foundation", 1, 1);
+  cricket::Candidate output = allocator_->SanitizeCandidate(input);
+  EXPECT_NE(kIpv4AddressWithPort, output.address().ToString());
+  EXPECT_EQ("", output.address().ipaddr().ToString());
+}
diff --git a/third_party/libwebrtc/p2p/base/port_interface.cc b/third_party/libwebrtc/p2p/base/port_interface.cc
new file mode 100644
index 0000000000..b07cdf9ee6
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/port_interface.cc
@@ -0,0 +1,23 @@
+/*
+ *  Copyright 2017 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/port_interface.h"
+
+#include <string>
+
+#include "absl/strings/string_view.h"
+
+namespace cricket {
+
+PortInterface::PortInterface() = default;
+
+PortInterface::~PortInterface() = default;
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/port_interface.h b/third_party/libwebrtc/p2p/base/port_interface.h
new file mode 100644
index 0000000000..29c2741bab
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/port_interface.h
@@ -0,0 +1,146 @@
+/*
+ *  Copyright 2012 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_PORT_INTERFACE_H_
+#define P2P_BASE_PORT_INTERFACE_H_
+
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "absl/strings/string_view.h"
+#include "absl/types/optional.h"
+#include "api/candidate.h"
+#include "p2p/base/transport_description.h"
+#include "rtc_base/async_packet_socket.h"
+#include "rtc_base/callback_list.h"
+#include "rtc_base/socket_address.h"
+
+namespace rtc {
+class Network;
+struct PacketOptions;
+}  // namespace rtc
+
+namespace cricket {
+class Connection;
+class IceMessage;
+class StunMessage;
+class StunStats;
+
+enum ProtocolType {
+  PROTO_UDP,
+  PROTO_TCP,
+  PROTO_SSLTCP,  // Pseudo-TLS.
+  PROTO_TLS,
+  PROTO_LAST = PROTO_TLS
+};
+
+// Defines the interface for a port, which represents a local communication
+// mechanism that can be used to create connections to similar mechanisms of
+// the other client. Various types of ports will implement this interface.
+class PortInterface {
+ public:
+  virtual ~PortInterface();
+
+  virtual const std::string& Type() const = 0;
+  virtual const rtc::Network* Network() const = 0;
+
+  // Methods to set/get ICE role and tiebreaker values.
+  virtual void SetIceRole(IceRole role) = 0;
+  virtual IceRole GetIceRole() const = 0;
+
+  virtual void SetIceTiebreaker(uint64_t tiebreaker) = 0;
+  virtual uint64_t IceTiebreaker() const = 0;
+
+  virtual bool SharedSocket() const = 0;
+
+  virtual bool SupportsProtocol(absl::string_view protocol) const = 0;
+
+  // PrepareAddress will attempt to get an address for this port that other
+  // clients can send to.  It may take some time before the address is ready.
+  // Once it is ready, we will send SignalAddressReady.  If errors are
+  // preventing the port from getting an address, it may send
+  // SignalAddressError.
+  virtual void PrepareAddress() = 0;
+
+  // Returns the connection to the given address or NULL if none exists.
+  virtual Connection* GetConnection(const rtc::SocketAddress& remote_addr) = 0;
+
+  // Creates a new connection to the given address.
+  enum CandidateOrigin { ORIGIN_THIS_PORT, ORIGIN_OTHER_PORT, ORIGIN_MESSAGE };
+  virtual Connection* CreateConnection(const Candidate& remote_candidate,
+                                       CandidateOrigin origin) = 0;
+
+  // Functions on the underlying socket(s).
+  virtual int SetOption(rtc::Socket::Option opt, int value) = 0;
+  virtual int GetOption(rtc::Socket::Option opt, int* value) = 0;
+  virtual int GetError() = 0;
+
+  virtual ProtocolType GetProtocol() const = 0;
+
+  virtual const std::vector<Candidate>& Candidates() const = 0;
+
+  // Sends the given packet to the given address, provided that the address is
+  // that of a connection or an address that has sent to us already.
+  virtual int SendTo(const void* data,
+                     size_t size,
+                     const rtc::SocketAddress& addr,
+                     const rtc::PacketOptions& options,
+                     bool payload) = 0;
+
+  // Indicates that we received a successful STUN binding request from an
+  // address that doesn't correspond to any current connection.  To turn this
+  // into a real connection, call CreateConnection.
+  sigslot::signal6<PortInterface*,
+                   const rtc::SocketAddress&,
+                   ProtocolType,
+                   IceMessage*,
+                   const std::string&,
+                   bool>
+      SignalUnknownAddress;
+
+  // Sends a response message (normal or error) to the given request.  One of
+  // these methods should be called as a response to SignalUnknownAddress.
+  virtual void SendBindingErrorResponse(StunMessage* message,
+                                        const rtc::SocketAddress& addr,
+                                        int error_code,
+                                        absl::string_view reason) = 0;
+
+  // Signaled when this port decides to delete itself because it no longer has
+  // any usefulness.
+  virtual void SubscribePortDestroyed(
+      std::function<void(PortInterface*)> callback) = 0;
+
+  // Signaled when Port discovers ice role conflict with the peer.
+  sigslot::signal1<PortInterface*> SignalRoleConflict;
+
+  // Normally, packets arrive through a connection (or they result signaling of
+  // unknown address).  Calling this method turns off delivery of packets
+  // through their respective connection and instead delivers every packet
+  // through this port.
+  virtual void EnablePortPackets() = 0;
+  sigslot::
+      signal4<PortInterface*, const char*, size_t, const rtc::SocketAddress&>
+          SignalReadPacket;
+
+  // Emitted each time a packet is sent on this port.
+  sigslot::signal1<const rtc::SentPacket&> SignalSentPacket;
+
+  virtual std::string ToString() const = 0;
+
+  virtual void GetStunStats(absl::optional<StunStats>* stats) = 0;
+
+ protected:
+  PortInterface();
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_PORT_INTERFACE_H_
diff --git a/third_party/libwebrtc/p2p/base/port_unittest.cc b/third_party/libwebrtc/p2p/base/port_unittest.cc
new file mode 100644
index 0000000000..3a0021699c
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/port_unittest.cc
@@ -0,0 +1,3844 @@
+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/port.h"
+
+#include <string.h>
+
+#include <cstdint>
+#include <limits>
+#include <list>
+#include <memory>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "absl/strings/string_view.h"
+#include "absl/types/optional.h"
+#include "api/candidate.h"
+#include "api/packet_socket_factory.h"
+#include "api/transport/stun.h"
+#include "api/units/time_delta.h"
+#include "p2p/base/basic_packet_socket_factory.h"
+#include "p2p/base/p2p_constants.h"
+#include "p2p/base/port_allocator.h"
+#include "p2p/base/port_interface.h"
+#include "p2p/base/stun_port.h"
+#include "p2p/base/stun_server.h"
+#include "p2p/base/tcp_port.h"
+#include "p2p/base/test_stun_server.h"
+#include "p2p/base/test_turn_server.h"
+#include "p2p/base/transport_description.h"
+#include "p2p/base/turn_port.h"
+#include "p2p/base/turn_server.h"
+#include "p2p/client/relay_port_factory_interface.h"
+#include "rtc_base/arraysize.h"
+#include "rtc_base/async_packet_socket.h"
+#include "rtc_base/buffer.h"
+#include "rtc_base/byte_buffer.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/dscp.h"
+#include "rtc_base/fake_clock.h"
+#include "rtc_base/gunit.h"
+#include "rtc_base/helpers.h"
+#include "rtc_base/logging.h"
+#include "rtc_base/nat_server.h"
+#include "rtc_base/nat_socket_factory.h"
+#include "rtc_base/nat_types.h"
+#include "rtc_base/net_helper.h"
+#include "rtc_base/network.h"
+#include "rtc_base/network/sent_packet.h"
+#include "rtc_base/network_constants.h"
+#include "rtc_base/proxy_info.h"
+#include "rtc_base/socket.h"
+#include "rtc_base/socket_adapters.h"
+#include "rtc_base/socket_address.h"
+#include "rtc_base/third_party/sigslot/sigslot.h"
+#include "rtc_base/thread.h"
+#include "rtc_base/time_utils.h"
+#include "rtc_base/virtual_socket_server.h"
+#include "test/gtest.h"
+#include "test/scoped_key_value_config.h"
+
+using rtc::AsyncListenSocket;
+using rtc::AsyncPacketSocket;
+using rtc::ByteBufferReader;
+using rtc::ByteBufferWriter;
+using rtc::NAT_ADDR_RESTRICTED;
+using rtc::NAT_OPEN_CONE;
+using rtc::NAT_PORT_RESTRICTED;
+using rtc::NAT_SYMMETRIC;
+using rtc::NATType;
+using rtc::PacketSocketFactory;
+using rtc::Socket;
+using rtc::SocketAddress;
+
+namespace cricket {
+namespace {
+
+constexpr int kDefaultTimeout = 3000;
+constexpr int kShortTimeout = 1000;
+constexpr int kMaxExpectedSimulatedRtt = 200;
+const SocketAddress kLocalAddr1("192.168.1.2", 0);
+const SocketAddress kLocalAddr2("192.168.1.3", 0);
+const SocketAddress kLinkLocalIPv6Addr("fe80::aabb:ccff:fedd:eeff", 0);
+const SocketAddress kNatAddr1("77.77.77.77", rtc::NAT_SERVER_UDP_PORT);
+const SocketAddress kNatAddr2("88.88.88.88", rtc::NAT_SERVER_UDP_PORT);
+const SocketAddress kStunAddr("99.99.99.1", STUN_SERVER_PORT);
+const SocketAddress kTurnUdpIntAddr("99.99.99.4", STUN_SERVER_PORT);
+const SocketAddress kTurnTcpIntAddr("99.99.99.4", 5010);
+const SocketAddress kTurnUdpExtAddr("99.99.99.5", 0);
+const RelayCredentials kRelayCredentials("test", "test");
+
+// TODO(?): Update these when RFC5245 is completely supported.
+// Magic value of 30 is from RFC3484, for IPv4 addresses.
+const uint32_t kDefaultPrflxPriority = ICE_TYPE_PREFERENCE_PRFLX << 24 |
+                                       30 << 8 |
+                                       (256 - ICE_CANDIDATE_COMPONENT_DEFAULT);
+
+constexpr int kTiebreaker1 = 11111;
+constexpr int kTiebreaker2 = 22222;
+constexpr int kTiebreakerDefault = 44444;
+
+const char* data = "ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";
+
+Candidate GetCandidate(Port* port) {
+  RTC_DCHECK_GE(port->Candidates().size(), 1);
+  return port->Candidates()[0];
+}
+
+SocketAddress GetAddress(Port* port) {
+  return GetCandidate(port).address();
+}
+
+std::unique_ptr<IceMessage> CopyStunMessage(const IceMessage& src) {
+  auto dst = std::make_unique<IceMessage>();
+  ByteBufferWriter buf;
+  src.Write(&buf);
+  ByteBufferReader read_buf(buf);
+  dst->Read(&read_buf);
+  return dst;
+}
+
+bool WriteStunMessage(const StunMessage& msg, ByteBufferWriter* buf) {
+  buf->Resize(0);  // clear out any existing buffer contents
+  return msg.Write(buf);
+}
+
+}  // namespace
+
+// Stub port class for testing STUN generation and processing.
+class TestPort : public Port {
+ public:
+  TestPort(rtc::Thread* thread,
+           absl::string_view type,
+           rtc::PacketSocketFactory* factory,
+           const rtc::Network* network,
+           uint16_t min_port,
+           uint16_t max_port,
+           absl::string_view username_fragment,
+           absl::string_view password)
+      : Port(thread,
+             type,
+             factory,
+             network,
+             min_port,
+             max_port,
+             username_fragment,
+             password) {}
+  ~TestPort() {}
+
+  // Expose GetStunMessage so that we can test it.
+  using cricket::Port::GetStunMessage;
+
+  // The last StunMessage that was sent on this Port.
+  // TODO(?): Make these const; requires changes to SendXXXXResponse.
+  rtc::BufferT<uint8_t>* last_stun_buf() { return last_stun_buf_.get(); }
+  IceMessage* last_stun_msg() { return last_stun_msg_.get(); }
+  int last_stun_error_code() {
+    int code = 0;
+    if (last_stun_msg_) {
+      const StunErrorCodeAttribute* error_attr = last_stun_msg_->GetErrorCode();
+      if (error_attr) {
+        code = error_attr->code();
+      }
+    }
+    return code;
+  }
+
+  virtual void PrepareAddress() {
+    // Act as if the socket was bound to the best IP on the network, to the
+    // first port in the allowed range.
+    rtc::SocketAddress addr(Network()->GetBestIP(), min_port());
+    AddAddress(addr, addr, rtc::SocketAddress(), "udp", "", "", Type(),
+               ICE_TYPE_PREFERENCE_HOST, 0, "", true);
+  }
+
+  virtual bool SupportsProtocol(absl::string_view protocol) const {
+    return true;
+  }
+
+  virtual ProtocolType GetProtocol() const { return PROTO_UDP; }
+
+  // Exposed for testing candidate building.
+  void AddCandidateAddress(const rtc::SocketAddress& addr) {
+    AddAddress(addr, addr, rtc::SocketAddress(), "udp", "", "", Type(),
+               type_preference_, 0, "", false);
+  }
+  void AddCandidateAddress(const rtc::SocketAddress& addr,
+                           const rtc::SocketAddress& base_address,
+                           absl::string_view type,
+                           int type_preference,
+                           bool final) {
+    AddAddress(addr, base_address, rtc::SocketAddress(), "udp", "", "", type,
+               type_preference, 0, "", final);
+  }
+
+  virtual Connection* CreateConnection(const Candidate& remote_candidate,
+                                       CandidateOrigin origin) {
+    Connection* conn = new ProxyConnection(NewWeakPtr(), 0, remote_candidate);
+    AddOrReplaceConnection(conn);
+    // Set use-candidate attribute flag as this will add USE-CANDIDATE attribute
+    // in STUN binding requests.
+    conn->set_use_candidate_attr(true);
+    return conn;
+  }
+  virtual int SendTo(const void* data,
+                     size_t size,
+                     const rtc::SocketAddress& addr,
+                     const rtc::PacketOptions& options,
+                     bool payload) {
+    if (!payload) {
+      auto msg = std::make_unique<IceMessage>();
+      auto buf = std::make_unique<rtc::BufferT<uint8_t>>(
+          static_cast<const char*>(data), size);
+      ByteBufferReader read_buf(*buf);
+      if (!msg->Read(&read_buf)) {
+        return -1;
+      }
+      last_stun_buf_ = std::move(buf);
+      last_stun_msg_ = std::move(msg);
+    }
+    return static_cast<int>(size);
+  }
+  virtual int SetOption(rtc::Socket::Option opt, int value) { return 0; }
+  virtual int GetOption(rtc::Socket::Option opt, int* value) { return -1; }
+  virtual int GetError() { return 0; }
+  void Reset() {
+    last_stun_buf_.reset();
+    last_stun_msg_.reset();
+  }
+  void set_type_preference(int type_preference) {
+    type_preference_ = type_preference;
+  }
+
+ private:
+  void OnSentPacket(rtc::AsyncPacketSocket* socket,
+                    const rtc::SentPacket& sent_packet) {
+    PortInterface::SignalSentPacket(sent_packet);
+  }
+  std::unique_ptr<rtc::BufferT<uint8_t>> last_stun_buf_;
+  std::unique_ptr<IceMessage> last_stun_msg_;
+  int type_preference_ = 0;
+};
+
+static void SendPingAndReceiveResponse(Connection* lconn,
+                                       TestPort* lport,
+                                       Connection* rconn,
+                                       TestPort* rport,
+                                       rtc::ScopedFakeClock* clock,
+                                       int64_t ms) {
+  lconn->Ping(rtc::TimeMillis());
+  ASSERT_TRUE_WAIT(lport->last_stun_msg(), kDefaultTimeout);
+  ASSERT_TRUE(lport->last_stun_buf());
+  rconn->OnReadPacket(lport->last_stun_buf()->data<char>(),
+                      lport->last_stun_buf()->size(), /* packet_time_us */ -1);
+  clock->AdvanceTime(webrtc::TimeDelta::Millis(ms));
+  ASSERT_TRUE_WAIT(rport->last_stun_msg(), kDefaultTimeout);
+  ASSERT_TRUE(rport->last_stun_buf());
+  lconn->OnReadPacket(rport->last_stun_buf()->data<char>(),
+                      rport->last_stun_buf()->size(), /* packet_time_us */ -1);
+}
+
+class TestChannel : public sigslot::has_slots<> {
+ public:
+  // Takes ownership of `p1` (but not `p2`).
+  explicit TestChannel(std::unique_ptr<Port> p1) : port_(std::move(p1)) {
+    port_->SignalPortComplete.connect(this, &TestChannel::OnPortComplete);
+    port_->SignalUnknownAddress.connect(this, &TestChannel::OnUnknownAddress);
+    port_->SubscribePortDestroyed(
+        [this](PortInterface* port) { OnSrcPortDestroyed(port); });
+  }
+
+  ~TestChannel() { Stop(); }
+
+  int complete_count() { return complete_count_; }
+  Connection* conn() { return conn_; }
+  const SocketAddress& remote_address() { return remote_address_; }
+  const std::string remote_fragment() { return remote_frag_; }
+
+  void Start() { port_->PrepareAddress(); }
+  void CreateConnection(const Candidate& remote_candidate) {
+    RTC_DCHECK(!conn_);
+    conn_ = port_->CreateConnection(remote_candidate, Port::ORIGIN_MESSAGE);
+    IceMode remote_ice_mode =
+        (ice_mode_ == ICEMODE_FULL) ? ICEMODE_LITE : ICEMODE_FULL;
+    conn_->set_use_candidate_attr(remote_ice_mode == ICEMODE_FULL);
+    conn_->SignalStateChange.connect(this,
+                                     &TestChannel::OnConnectionStateChange);
+    conn_->SignalDestroyed.connect(this, &TestChannel::OnDestroyed);
+    conn_->SignalReadyToSend.connect(this,
+                                     &TestChannel::OnConnectionReadyToSend);
+    connection_ready_to_send_ = false;
+  }
+
+  void OnConnectionStateChange(Connection* conn) {
+    if (conn->write_state() == Connection::STATE_WRITABLE) {
+      conn->set_use_candidate_attr(true);
+      nominated_ = true;
+    }
+  }
+  void AcceptConnection(const Candidate& remote_candidate) {
+    if (conn_) {
+      conn_->SignalDestroyed.disconnect(this);
+      conn_ = nullptr;
+    }
+    ASSERT_TRUE(remote_request_.get() != NULL);
+    Candidate c = remote_candidate;
+    c.set_address(remote_address_);
+    conn_ = port_->CreateConnection(c, Port::ORIGIN_MESSAGE);
+    conn_->SignalDestroyed.connect(this, &TestChannel::OnDestroyed);
+    conn_->SendStunBindingResponse(remote_request_.get());
+    remote_request_.reset();
+  }
+  void Ping() { Ping(0); }
+  void Ping(int64_t now) { conn_->Ping(now); }
+  void Stop() {
+    if (conn_) {
+      port_->DestroyConnection(conn_);
+      conn_ = nullptr;
+    }
+  }
+
+  void OnPortComplete(Port* port) { complete_count_++; }
+  void SetIceMode(IceMode ice_mode) { ice_mode_ = ice_mode; }
+
+  int SendData(const char* data, size_t len) {
+    rtc::PacketOptions options;
+    return conn_->Send(data, len, options);
+  }
+
+  void OnUnknownAddress(PortInterface* port,
+                        const SocketAddress& addr,
+                        ProtocolType proto,
+                        IceMessage* msg,
+                        const std::string& rf,
+                        bool /*port_muxed*/) {
+    ASSERT_EQ(port_.get(), port);
+    if (!remote_address_.IsNil()) {
+      ASSERT_EQ(remote_address_, addr);
+    }
+    const cricket::StunUInt32Attribute* priority_attr =
+        msg->GetUInt32(STUN_ATTR_PRIORITY);
+    const cricket::StunByteStringAttribute* mi_attr =
+        msg->GetByteString(STUN_ATTR_MESSAGE_INTEGRITY);
+    const cricket::StunUInt32Attribute* fingerprint_attr =
+        msg->GetUInt32(STUN_ATTR_FINGERPRINT);
+    EXPECT_TRUE(priority_attr != NULL);
+    EXPECT_TRUE(mi_attr != NULL);
+    EXPECT_TRUE(fingerprint_attr != NULL);
+    remote_address_ = addr;
+    remote_request_ = CopyStunMessage(*msg);
+    remote_frag_ = rf;
+  }
+
+  void OnDestroyed(Connection* conn) {
+    ASSERT_EQ(conn_, conn);
+    RTC_LOG(LS_INFO) << "OnDestroy connection " << conn << " deleted";
+    conn_ = nullptr;
+    // When the connection is destroyed, also clear these fields so future
+    // connections are possible.
+    remote_request_.reset();
+    remote_address_.Clear();
+  }
+
+  void OnSrcPortDestroyed(PortInterface* port) {
+    Port* destroyed_src = port_.release();
+    ASSERT_EQ(destroyed_src, port);
+  }
+
+  Port* port() { return port_.get(); }
+
+  bool nominated() const { return nominated_; }
+
+  void set_connection_ready_to_send(bool ready) {
+    connection_ready_to_send_ = ready;
+  }
+  bool connection_ready_to_send() const { return connection_ready_to_send_; }
+
+ private:
+  // ReadyToSend will only issue after a Connection recovers from ENOTCONN
+  void OnConnectionReadyToSend(Connection* conn) {
+    ASSERT_EQ(conn, conn_);
+    connection_ready_to_send_ = true;
+  }
+
+  IceMode ice_mode_ = ICEMODE_FULL;
+  std::unique_ptr<Port> port_;
+
+  int complete_count_ = 0;
+  Connection* conn_ = nullptr;
+  SocketAddress remote_address_;
+  std::unique_ptr<StunMessage> remote_request_;
+  std::string remote_frag_;
+  bool nominated_ = false;
+  bool connection_ready_to_send_ = false;
+};
+
+class PortTest : public ::testing::Test, public sigslot::has_slots<> {
+ public:
+  PortTest()
+      : ss_(new rtc::VirtualSocketServer()),
+        main_(ss_.get()),
+        socket_factory_(ss_.get()),
+        nat_factory1_(ss_.get(), kNatAddr1, SocketAddress()),
+        nat_factory2_(ss_.get(), kNatAddr2, SocketAddress()),
+        nat_socket_factory1_(&nat_factory1_),
+        nat_socket_factory2_(&nat_factory2_),
+        stun_server_(TestStunServer::Create(ss_.get(), kStunAddr)),
+        turn_server_(&main_, ss_.get(), kTurnUdpIntAddr, kTurnUdpExtAddr),
+        username_(rtc::CreateRandomString(ICE_UFRAG_LENGTH)),
+        password_(rtc::CreateRandomString(ICE_PWD_LENGTH)),
+        role_conflict_(false),
+        ports_destroyed_(0) {}
+
+  ~PortTest() {
+    // Workaround for tests that trigger async destruction of objects that we
+    // need to give an opportunity here to run, before proceeding with other
+    // teardown.
+    rtc::Thread::Current()->ProcessMessages(0);
+  }
+
+ protected:
+  std::string password() { return password_; }
+
+  void TestLocalToLocal() {
+    auto port1 = CreateUdpPort(kLocalAddr1);
+    port1->SetIceRole(cricket::ICEROLE_CONTROLLING);
+    auto port2 = CreateUdpPort(kLocalAddr2);
+    port2->SetIceRole(cricket::ICEROLE_CONTROLLED);
+    TestConnectivity("udp", std::move(port1), "udp", std::move(port2), true,
+                     true, true, true);
+  }
+  void TestLocalToStun(NATType ntype) {
+    auto port1 = CreateUdpPort(kLocalAddr1);
+    port1->SetIceRole(cricket::ICEROLE_CONTROLLING);
+    nat_server2_ = CreateNatServer(kNatAddr2, ntype);
+    auto port2 = CreateStunPort(kLocalAddr2, &nat_socket_factory2_);
+    port2->SetIceRole(cricket::ICEROLE_CONTROLLED);
+    TestConnectivity("udp", std::move(port1), StunName(ntype), std::move(port2),
+                     ntype == NAT_OPEN_CONE, true, ntype != NAT_SYMMETRIC,
+                     true);
+  }
+  void TestLocalToRelay(ProtocolType proto) {
+    auto port1 = CreateUdpPort(kLocalAddr1);
+    port1->SetIceRole(cricket::ICEROLE_CONTROLLING);
+    auto port2 = CreateRelayPort(kLocalAddr2, proto, PROTO_UDP);
+    port2->SetIceRole(cricket::ICEROLE_CONTROLLED);
+    TestConnectivity("udp", std::move(port1), RelayName(proto),
+                     std::move(port2), false, true, true, true);
+  }
+  void TestStunToLocal(NATType ntype) {
+    nat_server1_ = CreateNatServer(kNatAddr1, ntype);
+    auto port1 = CreateStunPort(kLocalAddr1, &nat_socket_factory1_);
+    port1->SetIceRole(cricket::ICEROLE_CONTROLLING);
+    auto port2 = CreateUdpPort(kLocalAddr2);
+    port2->SetIceRole(cricket::ICEROLE_CONTROLLED);
+    TestConnectivity(StunName(ntype), std::move(port1), "udp", std::move(port2),
+                     true, ntype != NAT_SYMMETRIC, true, true);
+  }
+  void TestStunToStun(NATType ntype1, NATType ntype2) {
+    nat_server1_ = CreateNatServer(kNatAddr1, ntype1);
+    auto port1 = CreateStunPort(kLocalAddr1, &nat_socket_factory1_);
+    port1->SetIceRole(cricket::ICEROLE_CONTROLLING);
+    nat_server2_ = CreateNatServer(kNatAddr2, ntype2);
+    auto port2 = CreateStunPort(kLocalAddr2, &nat_socket_factory2_);
+    port2->SetIceRole(cricket::ICEROLE_CONTROLLED);
+    TestConnectivity(StunName(ntype1), std::move(port1), StunName(ntype2),
+                     std::move(port2), ntype2 == NAT_OPEN_CONE,
+                     ntype1 != NAT_SYMMETRIC, ntype2 != NAT_SYMMETRIC,
+                     ntype1 + ntype2 < (NAT_PORT_RESTRICTED + NAT_SYMMETRIC));
+  }
+  void TestStunToRelay(NATType ntype, ProtocolType proto) {
+    nat_server1_ = CreateNatServer(kNatAddr1, ntype);
+    auto port1 = CreateStunPort(kLocalAddr1, &nat_socket_factory1_);
+    port1->SetIceRole(cricket::ICEROLE_CONTROLLING);
+    auto port2 = CreateRelayPort(kLocalAddr2, proto, PROTO_UDP);
+    port2->SetIceRole(cricket::ICEROLE_CONTROLLED);
+    TestConnectivity(StunName(ntype), std::move(port1), RelayName(proto),
+                     std::move(port2), false, ntype != NAT_SYMMETRIC, true,
+                     true);
+  }
+  void TestTcpToTcp() {
+    auto port1 = CreateTcpPort(kLocalAddr1);
+    port1->SetIceRole(cricket::ICEROLE_CONTROLLING);
+    auto port2 = CreateTcpPort(kLocalAddr2);
+    port2->SetIceRole(cricket::ICEROLE_CONTROLLED);
+    TestConnectivity("tcp", std::move(port1), "tcp", std::move(port2), true,
+                     false, true, true);
+  }
+  void TestTcpToRelay(ProtocolType proto) {
+    auto port1 = CreateTcpPort(kLocalAddr1);
+    port1->SetIceRole(cricket::ICEROLE_CONTROLLING);
+    auto port2 = CreateRelayPort(kLocalAddr2, proto, PROTO_TCP);
+    port2->SetIceRole(cricket::ICEROLE_CONTROLLED);
+    TestConnectivity("tcp", std::move(port1), RelayName(proto),
+                     std::move(port2), false, false, true, true);
+  }
+  void TestSslTcpToRelay(ProtocolType proto) {
+    auto port1 = CreateTcpPort(kLocalAddr1);
+    port1->SetIceRole(cricket::ICEROLE_CONTROLLING);
+    auto port2 = CreateRelayPort(kLocalAddr2, proto, PROTO_SSLTCP);
+    port2->SetIceRole(cricket::ICEROLE_CONTROLLED);
+    TestConnectivity("ssltcp", std::move(port1), RelayName(proto),
+                     std::move(port2), false, false, true, true);
+  }
+
+  rtc::Network* MakeNetwork(const SocketAddress& addr) {
+    networks_.emplace_back("unittest", "unittest", addr.ipaddr(), 32);
+    networks_.back().AddIP(addr.ipaddr());
+    return &networks_.back();
+  }
+
+  rtc::Network* MakeNetworkMultipleAddrs(
+      const SocketAddress& global_addr,
+      const SocketAddress& link_local_addr,
+      const webrtc::FieldTrialsView* field_trials) {
+    networks_.emplace_back("unittest", "unittest", global_addr.ipaddr(), 32,
+                           rtc::ADAPTER_TYPE_UNKNOWN, field_trials);
+    networks_.back().AddIP(link_local_addr.ipaddr());
+    networks_.back().AddIP(global_addr.ipaddr());
+    networks_.back().AddIP(link_local_addr.ipaddr());
+    return &networks_.back();
+  }
+
+  // helpers for above functions
+  std::unique_ptr<UDPPort> CreateUdpPort(const SocketAddress& addr) {
+    return CreateUdpPort(addr, &socket_factory_);
+  }
+  std::unique_ptr<UDPPort> CreateUdpPort(const SocketAddress& addr,
+                                         PacketSocketFactory* socket_factory) {
+    auto port = UDPPort::Create(&main_, socket_factory, MakeNetwork(addr), 0, 0,
+                                username_, password_, true, absl::nullopt,
+                                &field_trials_);
+    port->SetIceTiebreaker(kTiebreakerDefault);
+    return port;
+  }
+
+  std::unique_ptr<UDPPort> CreateUdpPortMultipleAddrs(
+      const SocketAddress& global_addr,
+      const SocketAddress& link_local_addr,
+      PacketSocketFactory* socket_factory,
+      const webrtc::test::ScopedKeyValueConfig& field_trials) {
+    auto port = UDPPort::Create(
+        &main_, socket_factory,
+        MakeNetworkMultipleAddrs(global_addr, link_local_addr, &field_trials),
+        0, 0, username_, password_, true, absl::nullopt, &field_trials);
+    port->SetIceTiebreaker(kTiebreakerDefault);
+    return port;
+  }
+  std::unique_ptr<TCPPort> CreateTcpPort(const SocketAddress& addr) {
+    return CreateTcpPort(addr, &socket_factory_);
+  }
+  std::unique_ptr<TCPPort> CreateTcpPort(const SocketAddress& addr,
+                                         PacketSocketFactory* socket_factory) {
+    auto port = TCPPort::Create(&main_, socket_factory, MakeNetwork(addr), 0, 0,
+                                username_, password_, true, &field_trials_);
+    port->SetIceTiebreaker(kTiebreakerDefault);
+    return port;
+  }
+  std::unique_ptr<StunPort> CreateStunPort(const SocketAddress& addr,
+                                           rtc::PacketSocketFactory* factory) {
+    ServerAddresses stun_servers;
+    stun_servers.insert(kStunAddr);
+    auto port = StunPort::Create(&main_, factory, MakeNetwork(addr), 0, 0,
+                                 username_, password_, stun_servers,
+                                 absl::nullopt, &field_trials_);
+    port->SetIceTiebreaker(kTiebreakerDefault);
+    return port;
+  }
+  std::unique_ptr<Port> CreateRelayPort(const SocketAddress& addr,
+                                        ProtocolType int_proto,
+                                        ProtocolType ext_proto) {
+    return CreateTurnPort(addr, &socket_factory_, int_proto, ext_proto);
+  }
+  std::unique_ptr<TurnPort> CreateTurnPort(const SocketAddress& addr,
+                                           PacketSocketFactory* socket_factory,
+                                           ProtocolType int_proto,
+                                           ProtocolType ext_proto) {
+    SocketAddress server_addr =
+        int_proto == PROTO_TCP ? kTurnTcpIntAddr : kTurnUdpIntAddr;
+    return CreateTurnPort(addr, socket_factory, int_proto, ext_proto,
+                          server_addr);
+  }
+  std::unique_ptr<TurnPort> CreateTurnPort(
+      const SocketAddress& addr,
+      PacketSocketFactory* socket_factory,
+      ProtocolType int_proto,
+      ProtocolType ext_proto,
+      const rtc::SocketAddress& server_addr) {
+    RelayServerConfig config;
+    config.credentials = kRelayCredentials;
+    ProtocolAddress server_address(server_addr, int_proto);
+    CreateRelayPortArgs args;
+    args.network_thread = &main_;
+    args.socket_factory = socket_factory;
+    args.network = MakeNetwork(addr);
+    args.username = username_;
+    args.password = password_;
+    args.server_address = &server_address;
+    args.config = &config;
+    args.field_trials = &field_trials_;
+
+    auto port = TurnPort::Create(args, 0, 0);
+    port->SetIceTiebreaker(kTiebreakerDefault);
+    return port;
+  }
+
+  std::unique_ptr<rtc::NATServer> CreateNatServer(const SocketAddress& addr,
+                                                  rtc::NATType type) {
+    return std::make_unique<rtc::NATServer>(type, ss_.get(), addr, addr,
+                                            ss_.get(), addr);
+  }
+  static const char* StunName(NATType type) {
+    switch (type) {
+      case NAT_OPEN_CONE:
+        return "stun(open cone)";
+      case NAT_ADDR_RESTRICTED:
+        return "stun(addr restricted)";
+      case NAT_PORT_RESTRICTED:
+        return "stun(port restricted)";
+      case NAT_SYMMETRIC:
+        return "stun(symmetric)";
+      default:
+        return "stun(?)";
+    }
+  }
+  static const char* RelayName(ProtocolType proto) {
+    switch (proto) {
+      case PROTO_UDP:
+        return "turn(udp)";
+      case PROTO_TCP:
+        return "turn(tcp)";
+      case PROTO_SSLTCP:
+        return "turn(ssltcp)";
+      case PROTO_TLS:
+        return "turn(tls)";
+      default:
+        return "turn(?)";
+    }
+  }
+
+  void TestCrossFamilyPorts(int type);
+
+  void ExpectPortsCanConnect(bool can_connect, Port* p1, Port* p2);
+
+  // This does all the work and then deletes `port1` and `port2`.
+  void TestConnectivity(absl::string_view name1,
+                        std::unique_ptr<Port> port1,
+                        absl::string_view name2,
+                        std::unique_ptr<Port> port2,
+                        bool accept,
+                        bool same_addr1,
+                        bool same_addr2,
+                        bool possible);
+
+  // This connects the provided channels which have already started.  `ch1`
+  // should have its Connection created (either through CreateConnection() or
+  // TCP reconnecting mechanism before entering this function.
+  void ConnectStartedChannels(TestChannel* ch1, TestChannel* ch2) {
+    ASSERT_TRUE(ch1->conn());
+    EXPECT_TRUE_WAIT(ch1->conn()->connected(),
+                     kDefaultTimeout);  // for TCP connect
+    ch1->Ping();
+    WAIT(!ch2->remote_address().IsNil(), kShortTimeout);
+
+    // Send a ping from dst to src.
+    ch2->AcceptConnection(GetCandidate(ch1->port()));
+    ch2->Ping();
+    EXPECT_EQ_WAIT(Connection::STATE_WRITABLE, ch2->conn()->write_state(),
+                   kDefaultTimeout);
+  }
+
+  // This connects and disconnects the provided channels in the same sequence as
+  // TestConnectivity with all options set to `true`.  It does not delete either
+  // channel.
+  void StartConnectAndStopChannels(TestChannel* ch1, TestChannel* ch2) {
+    // Acquire addresses.
+    ch1->Start();
+    ch2->Start();
+
+    ch1->CreateConnection(GetCandidate(ch2->port()));
+    ConnectStartedChannels(ch1, ch2);
+
+    // Destroy the connections.
+    ch1->Stop();
+    ch2->Stop();
+  }
+
+  // This disconnects both end's Connection and make sure ch2 ready for new
+  // connection.
+  void DisconnectTcpTestChannels(TestChannel* ch1, TestChannel* ch2) {
+    TCPConnection* tcp_conn1 = static_cast<TCPConnection*>(ch1->conn());
+    TCPConnection* tcp_conn2 = static_cast<TCPConnection*>(ch2->conn());
+    ASSERT_TRUE(
+        ss_->CloseTcpConnections(tcp_conn1->socket()->GetLocalAddress(),
+                                 tcp_conn2->socket()->GetLocalAddress()));
+
+    // Wait for both OnClose are delivered.
+    EXPECT_TRUE_WAIT(!ch1->conn()->connected(), kDefaultTimeout);
+    EXPECT_TRUE_WAIT(!ch2->conn()->connected(), kDefaultTimeout);
+
+    // Ensure redundant SignalClose events on TcpConnection won't break tcp
+    // reconnection. Chromium will fire SignalClose for all outstanding IPC
+    // packets during reconnection.
+    tcp_conn1->socket()->NotifyClosedForTest(0);
+    tcp_conn2->socket()->NotifyClosedForTest(0);
+
+    // Speed up destroying ch2's connection such that the test is ready to
+    // accept a new connection from ch1 before ch1's connection destroys itself.
+    ch2->Stop();
+    EXPECT_TRUE_WAIT(ch2->conn() == NULL, kDefaultTimeout);
+  }
+
+  void TestTcpReconnect(bool ping_after_disconnected,
+                        bool send_after_disconnected) {
+    auto port1 = CreateTcpPort(kLocalAddr1);
+    port1->SetIceRole(cricket::ICEROLE_CONTROLLING);
+    auto port2 = CreateTcpPort(kLocalAddr2);
+    port2->SetIceRole(cricket::ICEROLE_CONTROLLED);
+
+    port1->set_component(cricket::ICE_CANDIDATE_COMPONENT_DEFAULT);
+    port2->set_component(cricket::ICE_CANDIDATE_COMPONENT_DEFAULT);
+
+    // Set up channels and ensure both ports will be deleted.
+    TestChannel ch1(std::move(port1));
+    TestChannel ch2(std::move(port2));
+    EXPECT_EQ(0, ch1.complete_count());
+    EXPECT_EQ(0, ch2.complete_count());
+
+    ch1.Start();
+    ch2.Start();
+    ASSERT_EQ_WAIT(1, ch1.complete_count(), kDefaultTimeout);
+    ASSERT_EQ_WAIT(1, ch2.complete_count(), kDefaultTimeout);
+
+    // Initial connecting the channel, create connection on channel1.
+    ch1.CreateConnection(GetCandidate(ch2.port()));
+    ConnectStartedChannels(&ch1, &ch2);
+
+    // Shorten the timeout period.
+    const int kTcpReconnectTimeout = kDefaultTimeout;
+    static_cast<TCPConnection*>(ch1.conn())
+        ->set_reconnection_timeout(kTcpReconnectTimeout);
+    static_cast<TCPConnection*>(ch2.conn())
+        ->set_reconnection_timeout(kTcpReconnectTimeout);
+
+    EXPECT_FALSE(ch1.connection_ready_to_send());
+    EXPECT_FALSE(ch2.connection_ready_to_send());
+
+    // Once connected, disconnect them.
+    DisconnectTcpTestChannels(&ch1, &ch2);
+
+    if (send_after_disconnected || ping_after_disconnected) {
+      if (send_after_disconnected) {
+        // First SendData after disconnect should fail but will trigger
+        // reconnect.
+        EXPECT_EQ(-1, ch1.SendData(data, static_cast<int>(strlen(data))));
+      }
+
+      if (ping_after_disconnected) {
+        // Ping should trigger reconnect.
+        ch1.Ping();
+      }
+
+      // Wait for channel's outgoing TCPConnection connected.
+      EXPECT_TRUE_WAIT(ch1.conn()->connected(), kDefaultTimeout);
+
+      // Verify that we could still connect channels.
+      ConnectStartedChannels(&ch1, &ch2);
+      EXPECT_TRUE_WAIT(ch1.connection_ready_to_send(), kTcpReconnectTimeout);
+      // Channel2 is the passive one so a new connection is created during
+      // reconnect. This new connection should never have issued ENOTCONN
+      // hence the connection_ready_to_send() should be false.
+      EXPECT_FALSE(ch2.connection_ready_to_send());
+    } else {
+      EXPECT_EQ(ch1.conn()->write_state(), Connection::STATE_WRITABLE);
+      // Since the reconnection never happens, the connections should have been
+      // destroyed after the timeout.
+      EXPECT_TRUE_WAIT(!ch1.conn(), kTcpReconnectTimeout + kDefaultTimeout);
+      EXPECT_TRUE(!ch2.conn());
+    }
+
+    // Tear down and ensure that goes smoothly.
+    ch1.Stop();
+    ch2.Stop();
+    EXPECT_TRUE_WAIT(ch1.conn() == NULL, kDefaultTimeout);
+    EXPECT_TRUE_WAIT(ch2.conn() == NULL, kDefaultTimeout);
+  }
+
+  std::unique_ptr<IceMessage> CreateStunMessage(StunMessageType type) {
+    auto msg = std::make_unique<IceMessage>(type, "TESTTESTTEST");
+    return msg;
+  }
+  std::unique_ptr<IceMessage> CreateStunMessageWithUsername(
+      StunMessageType type,
+      absl::string_view username) {
+    std::unique_ptr<IceMessage> msg = CreateStunMessage(type);
+    msg->AddAttribute(std::make_unique<StunByteStringAttribute>(
+        STUN_ATTR_USERNAME, std::string(username)));
+    return msg;
+  }
+  std::unique_ptr<TestPort> CreateTestPort(const rtc::SocketAddress& addr,
+                                           absl::string_view username,
+                                           absl::string_view password) {
+    auto port =
+        std::make_unique<TestPort>(&main_, "test", &socket_factory_,
+                                   MakeNetwork(addr), 0, 0, username, password);
+    port->SignalRoleConflict.connect(this, &PortTest::OnRoleConflict);
+    return port;
+  }
+  std::unique_ptr<TestPort> CreateTestPort(const rtc::SocketAddress& addr,
+                                           absl::string_view username,
+                                           absl::string_view password,
+                                           cricket::IceRole role,
+                                           int tiebreaker) {
+    auto port = CreateTestPort(addr, username, password);
+    port->SetIceRole(role);
+    port->SetIceTiebreaker(tiebreaker);
+    return port;
+  }
+  // Overload to create a test port given an rtc::Network directly.
+  std::unique_ptr<TestPort> CreateTestPort(const rtc::Network* network,
+                                           absl::string_view username,
+                                           absl::string_view password) {
+    auto port = std::make_unique<TestPort>(&main_, "test", &socket_factory_,
+                                           network, 0, 0, username, password);
+    port->SignalRoleConflict.connect(this, &PortTest::OnRoleConflict);
+    return port;
+  }
+
+  void OnRoleConflict(PortInterface* port) { role_conflict_ = true; }
+  bool role_conflict() const { return role_conflict_; }
+
+  void ConnectToSignalDestroyed(PortInterface* port) {
+    port->SubscribePortDestroyed(
+        [this](PortInterface* port) { OnDestroyed(port); });
+  }
+
+  void OnDestroyed(PortInterface* port) { ++ports_destroyed_; }
+  int ports_destroyed() const { return ports_destroyed_; }
+
+  rtc::BasicPacketSocketFactory* nat_socket_factory1() {
+    return &nat_socket_factory1_;
+  }
+
+  rtc::VirtualSocketServer* vss() { return ss_.get(); }
+
+ private:
+  // When a "create port" helper method is called with an IP, we create a
+  // Network with that IP and add it to this list. Using a list instead of a
+  // vector so that when it grows, pointers aren't invalidated.
+  std::list<rtc::Network> networks_;
+  std::unique_ptr<rtc::VirtualSocketServer> ss_;
+  rtc::AutoSocketServerThread main_;
+  rtc::BasicPacketSocketFactory socket_factory_;
+  std::unique_ptr<rtc::NATServer> nat_server1_;
+  std::unique_ptr<rtc::NATServer> nat_server2_;
+  rtc::NATSocketFactory nat_factory1_;
+  rtc::NATSocketFactory nat_factory2_;
+  rtc::BasicPacketSocketFactory nat_socket_factory1_;
+  rtc::BasicPacketSocketFactory nat_socket_factory2_;
+  std::unique_ptr<TestStunServer> stun_server_;
+  TestTurnServer turn_server_;
+  std::string username_;
+  std::string password_;
+  bool role_conflict_;
+  int ports_destroyed_;
+  webrtc::test::ScopedKeyValueConfig field_trials_;
+};
+
+void PortTest::TestConnectivity(absl::string_view name1,
+                                std::unique_ptr<Port> port1,
+                                absl::string_view name2,
+                                std::unique_ptr<Port> port2,
+                                bool accept,
+                                bool same_addr1,
+                                bool same_addr2,
+                                bool possible) {
+  rtc::ScopedFakeClock clock;
+  RTC_LOG(LS_INFO) << "Test: " << name1 << " to " << name2 << ": ";
+  port1->set_component(cricket::ICE_CANDIDATE_COMPONENT_DEFAULT);
+  port2->set_component(cricket::ICE_CANDIDATE_COMPONENT_DEFAULT);
+
+  // Set up channels and ensure both ports will be deleted.
+  TestChannel ch1(std::move(port1));
+  TestChannel ch2(std::move(port2));
+  EXPECT_EQ(0, ch1.complete_count());
+  EXPECT_EQ(0, ch2.complete_count());
+
+  // Acquire addresses.
+  ch1.Start();
+  ch2.Start();
+  ASSERT_EQ_SIMULATED_WAIT(1, ch1.complete_count(), kDefaultTimeout, clock);
+  ASSERT_EQ_SIMULATED_WAIT(1, ch2.complete_count(), kDefaultTimeout, clock);
+
+  // Send a ping from src to dst. This may or may not make it.
+  ch1.CreateConnection(GetCandidate(ch2.port()));
+  ASSERT_TRUE(ch1.conn() != NULL);
+  EXPECT_TRUE_SIMULATED_WAIT(ch1.conn()->connected(), kDefaultTimeout,
+                             clock);  // for TCP connect
+  ch1.Ping();
+  SIMULATED_WAIT(!ch2.remote_address().IsNil(), kShortTimeout, clock);
+
+  if (accept) {
+    // We are able to send a ping from src to dst. This is the case when
+    // sending to UDP ports and cone NATs.
+    EXPECT_TRUE(ch1.remote_address().IsNil());
+    EXPECT_EQ(ch2.remote_fragment(), ch1.port()->username_fragment());
+
+    // Ensure the ping came from the same address used for src.
+    // This is the case unless the source NAT was symmetric.
+    if (same_addr1)
+      EXPECT_EQ(ch2.remote_address(), GetAddress(ch1.port()));
+    EXPECT_TRUE(same_addr2);
+
+    // Send a ping from dst to src.
+    ch2.AcceptConnection(GetCandidate(ch1.port()));
+    ASSERT_TRUE(ch2.conn() != NULL);
+    ch2.Ping();
+    EXPECT_EQ_SIMULATED_WAIT(Connection::STATE_WRITABLE,
+                             ch2.conn()->write_state(), kDefaultTimeout, clock);
+  } else {
+    // We can't send a ping from src to dst, so flip it around. This will happen
+    // when the destination NAT is addr/port restricted or symmetric.
+    EXPECT_TRUE(ch1.remote_address().IsNil());
+    EXPECT_TRUE(ch2.remote_address().IsNil());
+
+    // Send a ping from dst to src. Again, this may or may not make it.
+    ch2.CreateConnection(GetCandidate(ch1.port()));
+    ASSERT_TRUE(ch2.conn() != NULL);
+    ch2.Ping();
+    SIMULATED_WAIT(ch2.conn()->write_state() == Connection::STATE_WRITABLE,
+                   kShortTimeout, clock);
+
+    if (same_addr1 && same_addr2) {
+      // The new ping got back to the source.
+      EXPECT_TRUE(ch1.conn()->receiving());
+      EXPECT_EQ(Connection::STATE_WRITABLE, ch2.conn()->write_state());
+
+      // First connection may not be writable if the first ping did not get
+      // through.  So we will have to do another.
+      if (ch1.conn()->write_state() == Connection::STATE_WRITE_INIT) {
+        ch1.Ping();
+        EXPECT_EQ_SIMULATED_WAIT(Connection::STATE_WRITABLE,
+                                 ch1.conn()->write_state(), kDefaultTimeout,
+                                 clock);
+      }
+    } else if (!same_addr1 && possible) {
+      // The new ping went to the candidate address, but that address was bad.
+      // This will happen when the source NAT is symmetric.
+      EXPECT_TRUE(ch1.remote_address().IsNil());
+      EXPECT_TRUE(ch2.remote_address().IsNil());
+
+      // However, since we have now sent a ping to the source IP, we should be
+      // able to get a ping from it. This gives us the real source address.
+      ch1.Ping();
+      EXPECT_TRUE_SIMULATED_WAIT(!ch2.remote_address().IsNil(), kDefaultTimeout,
+                                 clock);
+      EXPECT_FALSE(ch2.conn()->receiving());
+      EXPECT_TRUE(ch1.remote_address().IsNil());
+
+      // Pick up the actual address and establish the connection.
+      ch2.AcceptConnection(GetCandidate(ch1.port()));
+      ASSERT_TRUE(ch2.conn() != NULL);
+      ch2.Ping();
+      EXPECT_EQ_SIMULATED_WAIT(Connection::STATE_WRITABLE,
+                               ch2.conn()->write_state(), kDefaultTimeout,
+                               clock);
+    } else if (!same_addr2 && possible) {
+      // The new ping came in, but from an unexpected address. This will happen
+      // when the destination NAT is symmetric.
+      EXPECT_FALSE(ch1.remote_address().IsNil());
+      EXPECT_FALSE(ch1.conn()->receiving());
+
+      // Update our address and complete the connection.
+      ch1.AcceptConnection(GetCandidate(ch2.port()));
+      ch1.Ping();
+      EXPECT_EQ_SIMULATED_WAIT(Connection::STATE_WRITABLE,
+                               ch1.conn()->write_state(), kDefaultTimeout,
+                               clock);
+    } else {  // (!possible)
+      // There should be s no way for the pings to reach each other. Check it.
+      EXPECT_TRUE(ch1.remote_address().IsNil());
+      EXPECT_TRUE(ch2.remote_address().IsNil());
+      ch1.Ping();
+      SIMULATED_WAIT(!ch2.remote_address().IsNil(), kShortTimeout, clock);
+      EXPECT_TRUE(ch1.remote_address().IsNil());
+      EXPECT_TRUE(ch2.remote_address().IsNil());
+    }
+  }
+
+  // Everything should be good, unless we know the situation is impossible.
+  ASSERT_TRUE(ch1.conn() != NULL);
+  ASSERT_TRUE(ch2.conn() != NULL);
+  if (possible) {
+    EXPECT_TRUE(ch1.conn()->receiving());
+    EXPECT_EQ(Connection::STATE_WRITABLE, ch1.conn()->write_state());
+    EXPECT_TRUE(ch2.conn()->receiving());
+    EXPECT_EQ(Connection::STATE_WRITABLE, ch2.conn()->write_state());
+  } else {
+    EXPECT_FALSE(ch1.conn()->receiving());
+    EXPECT_NE(Connection::STATE_WRITABLE, ch1.conn()->write_state());
+    EXPECT_FALSE(ch2.conn()->receiving());
+    EXPECT_NE(Connection::STATE_WRITABLE, ch2.conn()->write_state());
+  }
+
+  // Tear down and ensure that goes smoothly.
+  ch1.Stop();
+  ch2.Stop();
+  EXPECT_TRUE_SIMULATED_WAIT(ch1.conn() == NULL, kDefaultTimeout, clock);
+  EXPECT_TRUE_SIMULATED_WAIT(ch2.conn() == NULL, kDefaultTimeout, clock);
+}
+
+class FakePacketSocketFactory : public rtc::PacketSocketFactory {
+ public:
+  FakePacketSocketFactory()
+      : next_udp_socket_(NULL), next_server_tcp_socket_(NULL) {}
+  ~FakePacketSocketFactory() override {}
+
+  AsyncPacketSocket* CreateUdpSocket(const SocketAddress& address,
+                                     uint16_t min_port,
+                                     uint16_t max_port) override {
+    EXPECT_TRUE(next_udp_socket_ != NULL);
+    AsyncPacketSocket* result = next_udp_socket_;
+    next_udp_socket_ = NULL;
+    return result;
+  }
+
+  AsyncListenSocket* CreateServerTcpSocket(const SocketAddress& local_address,
+                                           uint16_t min_port,
+                                           uint16_t max_port,
+                                           int opts) override {
+    EXPECT_TRUE(next_server_tcp_socket_ != NULL);
+    AsyncListenSocket* result = next_server_tcp_socket_;
+    next_server_tcp_socket_ = NULL;
+    return result;
+  }
+
+  AsyncPacketSocket* CreateClientTcpSocket(
+      const SocketAddress& local_address,
+      const SocketAddress& remote_address,
+      const rtc::ProxyInfo& proxy_info,
+      const std::string& user_agent,
+      const rtc::PacketSocketTcpOptions& opts) override {
+    EXPECT_TRUE(next_client_tcp_socket_.has_value());
+    AsyncPacketSocket* result = *next_client_tcp_socket_;
+    next_client_tcp_socket_ = nullptr;
+    return result;
+  }
+
+  void set_next_udp_socket(AsyncPacketSocket* next_udp_socket) {
+    next_udp_socket_ = next_udp_socket;
+  }
+  void set_next_server_tcp_socket(AsyncListenSocket* next_server_tcp_socket) {
+    next_server_tcp_socket_ = next_server_tcp_socket;
+  }
+  void set_next_client_tcp_socket(AsyncPacketSocket* next_client_tcp_socket) {
+    next_client_tcp_socket_ = next_client_tcp_socket;
+  }
+  std::unique_ptr<webrtc::AsyncDnsResolverInterface> CreateAsyncDnsResolver()
+      override {
+    return nullptr;
+  }
+
+ private:
+  AsyncPacketSocket* next_udp_socket_;
+  AsyncListenSocket* next_server_tcp_socket_;
+  absl::optional<AsyncPacketSocket*> next_client_tcp_socket_;
+};
+
+class FakeAsyncPacketSocket : public AsyncPacketSocket {
+ public:
+  // Returns current local address. Address may be set to NULL if the
+  // socket is not bound yet (GetState() returns STATE_BINDING).
+  virtual SocketAddress GetLocalAddress() const { return local_address_; }
+
+  // Returns remote address. Returns zeroes if this is not a client TCP socket.
+  virtual SocketAddress GetRemoteAddress() const { return remote_address_; }
+
+  // Send a packet.
+  virtual int Send(const void* pv,
+                   size_t cb,
+                   const rtc::PacketOptions& options) {
+    if (error_ == 0) {
+      return static_cast<int>(cb);
+    } else {
+      return -1;
+    }
+  }
+  virtual int SendTo(const void* pv,
+                     size_t cb,
+                     const SocketAddress& addr,
+                     const rtc::PacketOptions& options) {
+    if (error_ == 0) {
+      return static_cast<int>(cb);
+    } else {
+      return -1;
+    }
+  }
+  virtual int Close() { return 0; }
+
+  virtual State GetState() const { return state_; }
+  virtual int GetOption(Socket::Option opt, int* value) { return 0; }
+  virtual int SetOption(Socket::Option opt, int value) { return 0; }
+  virtual int GetError() const { return 0; }
+  virtual void SetError(int error) { error_ = error; }
+
+  void set_state(State state) { state_ = state; }
+
+  SocketAddress local_address_;
+  SocketAddress remote_address_;
+
+ private:
+  int error_ = 0;
+  State state_;
+};
+
+class FakeAsyncListenSocket : public AsyncListenSocket {
+ public:
+  // Returns current local address. Address may be set to NULL if the
+  // socket is not bound yet (GetState() returns STATE_BINDING).
+  virtual SocketAddress GetLocalAddress() const { return local_address_; }
+  void Bind(const SocketAddress& address) {
+    local_address_ = address;
+    state_ = State::kBound;
+  }
+  virtual int GetOption(Socket::Option opt, int* value) { return 0; }
+  virtual int SetOption(Socket::Option opt, int value) { return 0; }
+  virtual State GetState() const { return state_; }
+
+ private:
+  SocketAddress local_address_;
+  State state_ = State::kClosed;
+};
+
+// Local -> XXXX
+TEST_F(PortTest, TestLocalToLocal) {
+  TestLocalToLocal();
+}
+
+TEST_F(PortTest, TestLocalToConeNat) {
+  TestLocalToStun(NAT_OPEN_CONE);
+}
+
+TEST_F(PortTest, TestLocalToARNat) {
+  TestLocalToStun(NAT_ADDR_RESTRICTED);
+}
+
+TEST_F(PortTest, TestLocalToPRNat) {
+  TestLocalToStun(NAT_PORT_RESTRICTED);
+}
+
+TEST_F(PortTest, TestLocalToSymNat) {
+  TestLocalToStun(NAT_SYMMETRIC);
+}
+
+// Flaky: https://code.google.com/p/webrtc/issues/detail?id=3316.
+TEST_F(PortTest, DISABLED_TestLocalToTurn) {
+  TestLocalToRelay(PROTO_UDP);
+}
+
+// Cone NAT -> XXXX
+TEST_F(PortTest, TestConeNatToLocal) {
+  TestStunToLocal(NAT_OPEN_CONE);
+}
+
+TEST_F(PortTest, TestConeNatToConeNat) {
+  TestStunToStun(NAT_OPEN_CONE, NAT_OPEN_CONE);
+}
+
+TEST_F(PortTest, TestConeNatToARNat) {
+  TestStunToStun(NAT_OPEN_CONE, NAT_ADDR_RESTRICTED);
+}
+
+TEST_F(PortTest, TestConeNatToPRNat) {
+  TestStunToStun(NAT_OPEN_CONE, NAT_PORT_RESTRICTED);
+}
+
+TEST_F(PortTest, TestConeNatToSymNat) {
+  TestStunToStun(NAT_OPEN_CONE, NAT_SYMMETRIC);
+}
+
+TEST_F(PortTest, TestConeNatToTurn) {
+  TestStunToRelay(NAT_OPEN_CONE, PROTO_UDP);
+}
+
+// Address-restricted NAT -> XXXX
+TEST_F(PortTest, TestARNatToLocal) {
+  TestStunToLocal(NAT_ADDR_RESTRICTED);
+}
+
+TEST_F(PortTest, TestARNatToConeNat) {
+  TestStunToStun(NAT_ADDR_RESTRICTED, NAT_OPEN_CONE);
+}
+
+TEST_F(PortTest, TestARNatToARNat) {
+  TestStunToStun(NAT_ADDR_RESTRICTED, NAT_ADDR_RESTRICTED);
+}
+
+TEST_F(PortTest, TestARNatToPRNat) {
+  TestStunToStun(NAT_ADDR_RESTRICTED, NAT_PORT_RESTRICTED);
+}
+
+TEST_F(PortTest, TestARNatToSymNat) {
+  TestStunToStun(NAT_ADDR_RESTRICTED, NAT_SYMMETRIC);
+}
+
+TEST_F(PortTest, TestARNatToTurn) {
+  TestStunToRelay(NAT_ADDR_RESTRICTED, PROTO_UDP);
+}
+
+// Port-restricted NAT -> XXXX
+TEST_F(PortTest, TestPRNatToLocal) {
+  TestStunToLocal(NAT_PORT_RESTRICTED);
+}
+
+TEST_F(PortTest, TestPRNatToConeNat) {
+  TestStunToStun(NAT_PORT_RESTRICTED, NAT_OPEN_CONE);
+}
+
+TEST_F(PortTest, TestPRNatToARNat) {
+  TestStunToStun(NAT_PORT_RESTRICTED, NAT_ADDR_RESTRICTED);
+}
+
+TEST_F(PortTest, TestPRNatToPRNat) {
+  TestStunToStun(NAT_PORT_RESTRICTED, NAT_PORT_RESTRICTED);
+}
+
+TEST_F(PortTest, TestPRNatToSymNat) {
+  // Will "fail"
+  TestStunToStun(NAT_PORT_RESTRICTED, NAT_SYMMETRIC);
+}
+
+TEST_F(PortTest, TestPRNatToTurn) {
+  TestStunToRelay(NAT_PORT_RESTRICTED, PROTO_UDP);
+}
+
+// Symmetric NAT -> XXXX
+TEST_F(PortTest, TestSymNatToLocal) {
+  TestStunToLocal(NAT_SYMMETRIC);
+}
+
+TEST_F(PortTest, TestSymNatToConeNat) {
+  TestStunToStun(NAT_SYMMETRIC, NAT_OPEN_CONE);
+}
+
+TEST_F(PortTest, TestSymNatToARNat) {
+  TestStunToStun(NAT_SYMMETRIC, NAT_ADDR_RESTRICTED);
+}
+
+TEST_F(PortTest, TestSymNatToPRNat) {
+  // Will "fail"
+  TestStunToStun(NAT_SYMMETRIC, NAT_PORT_RESTRICTED);
+}
+
+TEST_F(PortTest, TestSymNatToSymNat) {
+  // Will "fail"
+  TestStunToStun(NAT_SYMMETRIC, NAT_SYMMETRIC);
+}
+
+TEST_F(PortTest, TestSymNatToTurn) {
+  TestStunToRelay(NAT_SYMMETRIC, PROTO_UDP);
+}
+
+// Outbound TCP -> XXXX
+TEST_F(PortTest, TestTcpToTcp) {
+  TestTcpToTcp();
+}
+
+TEST_F(PortTest, TestTcpReconnectOnSendPacket) {
+  TestTcpReconnect(false /* ping */, true /* send */);
+}
+
+TEST_F(PortTest, TestTcpReconnectOnPing) {
+  TestTcpReconnect(true /* ping */, false /* send */);
+}
+
+TEST_F(PortTest, TestTcpReconnectTimeout) {
+  TestTcpReconnect(false /* ping */, false /* send */);
+}
+
+// Test when TcpConnection never connects, the OnClose() will be called to
+// destroy the connection.
+TEST_F(PortTest, TestTcpNeverConnect) {
+  auto port1 = CreateTcpPort(kLocalAddr1);
+  port1->SetIceRole(cricket::ICEROLE_CONTROLLING);
+  port1->set_component(cricket::ICE_CANDIDATE_COMPONENT_DEFAULT);
+
+  // Set up a channel and ensure the port will be deleted.
+  TestChannel ch1(std::move(port1));
+  EXPECT_EQ(0, ch1.complete_count());
+
+  ch1.Start();
+  ASSERT_EQ_WAIT(1, ch1.complete_count(), kDefaultTimeout);
+
+  std::unique_ptr<rtc::Socket> server(
+      vss()->CreateSocket(kLocalAddr2.family(), SOCK_STREAM));
+  // Bind but not listen.
+  EXPECT_EQ(0, server->Bind(kLocalAddr2));
+
+  Candidate c = GetCandidate(ch1.port());
+  c.set_address(server->GetLocalAddress());
+
+  ch1.CreateConnection(c);
+  EXPECT_TRUE(ch1.conn());
+  EXPECT_TRUE_WAIT(!ch1.conn(), kDefaultTimeout);  // for TCP connect
+}
+
+/* TODO(?): Enable these once testrelayserver can accept external TCP.
+TEST_F(PortTest, TestTcpToTcpRelay) {
+  TestTcpToRelay(PROTO_TCP);
+}
+
+TEST_F(PortTest, TestTcpToSslTcpRelay) {
+  TestTcpToRelay(PROTO_SSLTCP);
+}
+*/
+
+// Outbound SSLTCP -> XXXX
+/* TODO(?): Enable these once testrelayserver can accept external SSL.
+TEST_F(PortTest, TestSslTcpToTcpRelay) {
+  TestSslTcpToRelay(PROTO_TCP);
+}
+
+TEST_F(PortTest, TestSslTcpToSslTcpRelay) {
+  TestSslTcpToRelay(PROTO_SSLTCP);
+}
+*/
+
+// Test that a connection will be dead and deleted if
+// i) it has never received anything for MIN_CONNECTION_LIFETIME milliseconds
+//    since it was created, or
+// ii) it has not received anything for DEAD_CONNECTION_RECEIVE_TIMEOUT
+//     milliseconds since last receiving.
+TEST_F(PortTest, TestConnectionDead) {
+  TestChannel ch1(CreateUdpPort(kLocalAddr1));
+  TestChannel ch2(CreateUdpPort(kLocalAddr2));
+  // Acquire address.
+  ch1.Start();
+  ch2.Start();
+  ASSERT_EQ_WAIT(1, ch1.complete_count(), kDefaultTimeout);
+  ASSERT_EQ_WAIT(1, ch2.complete_count(), kDefaultTimeout);
+
+  // Test case that the connection has never received anything.
+  int64_t before_created = rtc::TimeMillis();
+  ch1.CreateConnection(GetCandidate(ch2.port()));
+  int64_t after_created = rtc::TimeMillis();
+  Connection* conn = ch1.conn();
+  ASSERT_NE(conn, nullptr);
+  // It is not dead if it is after MIN_CONNECTION_LIFETIME but not pruned.
+  conn->UpdateState(after_created + MIN_CONNECTION_LIFETIME + 1);
+  rtc::Thread::Current()->ProcessMessages(0);
+  EXPECT_TRUE(ch1.conn() != nullptr);
+  // It is not dead if it is before MIN_CONNECTION_LIFETIME and pruned.
+  conn->UpdateState(before_created + MIN_CONNECTION_LIFETIME - 1);
+  conn->Prune();
+  rtc::Thread::Current()->ProcessMessages(0);
+  EXPECT_TRUE(ch1.conn() != nullptr);
+  // It will be dead after MIN_CONNECTION_LIFETIME and pruned.
+  conn->UpdateState(after_created + MIN_CONNECTION_LIFETIME + 1);
+  EXPECT_TRUE_WAIT(ch1.conn() == nullptr, kDefaultTimeout);
+
+  // Test case that the connection has received something.
+  // Create a connection again and receive a ping.
+  ch1.CreateConnection(GetCandidate(ch2.port()));
+  conn = ch1.conn();
+  ASSERT_NE(conn, nullptr);
+  int64_t before_last_receiving = rtc::TimeMillis();
+  conn->ReceivedPing();
+  int64_t after_last_receiving = rtc::TimeMillis();
+  // The connection will be dead after DEAD_CONNECTION_RECEIVE_TIMEOUT
+  conn->UpdateState(before_last_receiving + DEAD_CONNECTION_RECEIVE_TIMEOUT -
+                    1);
+  rtc::Thread::Current()->ProcessMessages(100);
+  EXPECT_TRUE(ch1.conn() != nullptr);
+  conn->UpdateState(after_last_receiving + DEAD_CONNECTION_RECEIVE_TIMEOUT + 1);
+  EXPECT_TRUE_WAIT(ch1.conn() == nullptr, kDefaultTimeout);
+}
+
+TEST_F(PortTest, TestConnectionDeadWithDeadConnectionTimeout) {
+  TestChannel ch1(CreateUdpPort(kLocalAddr1));
+  TestChannel ch2(CreateUdpPort(kLocalAddr2));
+  // Acquire address.
+  ch1.Start();
+  ch2.Start();
+  ASSERT_EQ_WAIT(1, ch1.complete_count(), kDefaultTimeout);
+  ASSERT_EQ_WAIT(1, ch2.complete_count(), kDefaultTimeout);
+
+  // Note: set field trials manually since they are parsed by
+  // P2PTransportChannel but P2PTransportChannel is not used in this test.
+  IceFieldTrials field_trials;
+  field_trials.dead_connection_timeout_ms = 90000;
+
+  // Create a connection again and receive a ping.
+  ch1.CreateConnection(GetCandidate(ch2.port()));
+  auto conn = ch1.conn();
+  conn->SetIceFieldTrials(&field_trials);
+
+  ASSERT_NE(conn, nullptr);
+  int64_t before_last_receiving = rtc::TimeMillis();
+  conn->ReceivedPing();
+  int64_t after_last_receiving = rtc::TimeMillis();
+  // The connection will be dead after 90s
+  conn->UpdateState(before_last_receiving + 90000 - 1);
+  rtc::Thread::Current()->ProcessMessages(100);
+  EXPECT_TRUE(ch1.conn() != nullptr);
+  conn->UpdateState(after_last_receiving + 90000 + 1);
+  EXPECT_TRUE_WAIT(ch1.conn() == nullptr, kDefaultTimeout);
+}
+
+TEST_F(PortTest, TestConnectionDeadOutstandingPing) {
+  auto port1 = CreateUdpPort(kLocalAddr1);
+  port1->SetIceRole(cricket::ICEROLE_CONTROLLING);
+  port1->SetIceTiebreaker(kTiebreaker1);
+  auto port2 = CreateUdpPort(kLocalAddr2);
+  port2->SetIceRole(cricket::ICEROLE_CONTROLLED);
+  port2->SetIceTiebreaker(kTiebreaker2);
+
+  TestChannel ch1(std::move(port1));
+  TestChannel ch2(std::move(port2));
+  // Acquire address.
+  ch1.Start();
+  ch2.Start();
+  ASSERT_EQ_WAIT(1, ch1.complete_count(), kDefaultTimeout);
+  ASSERT_EQ_WAIT(1, ch2.complete_count(), kDefaultTimeout);
+
+  // Note: set field trials manually since they are parsed by
+  // P2PTransportChannel but P2PTransportChannel is not used in this test.
+  IceFieldTrials field_trials;
+  field_trials.dead_connection_timeout_ms = 360000;
+
+  // Create a connection again and receive a ping and then send
+  // a ping and keep it outstanding.
+  ch1.CreateConnection(GetCandidate(ch2.port()));
+  auto conn = ch1.conn();
+  conn->SetIceFieldTrials(&field_trials);
+
+  ASSERT_NE(conn, nullptr);
+  conn->ReceivedPing();
+  int64_t send_ping_timestamp = rtc::TimeMillis();
+  conn->Ping(send_ping_timestamp);
+
+  // The connection will be dead 30s after the ping was sent.
+  conn->UpdateState(send_ping_timestamp + DEAD_CONNECTION_RECEIVE_TIMEOUT - 1);
+  rtc::Thread::Current()->ProcessMessages(100);
+  EXPECT_TRUE(ch1.conn() != nullptr);
+  conn->UpdateState(send_ping_timestamp + DEAD_CONNECTION_RECEIVE_TIMEOUT + 1);
+  EXPECT_TRUE_WAIT(ch1.conn() == nullptr, kDefaultTimeout);
+}
+
+// This test case verifies standard ICE features in STUN messages. Currently it
+// verifies Message Integrity attribute in STUN messages and username in STUN
+// binding request will have colon (":") between remote and local username.
+TEST_F(PortTest, TestLocalToLocalStandard) {
+  auto port1 = CreateUdpPort(kLocalAddr1);
+  port1->SetIceRole(cricket::ICEROLE_CONTROLLING);
+  port1->SetIceTiebreaker(kTiebreaker1);
+  auto port2 = CreateUdpPort(kLocalAddr2);
+  port2->SetIceRole(cricket::ICEROLE_CONTROLLED);
+  port2->SetIceTiebreaker(kTiebreaker2);
+  // Same parameters as TestLocalToLocal above.
+  TestConnectivity("udp", std::move(port1), "udp", std::move(port2), true, true,
+                   true, true);
+}
+
+// This test is trying to validate a successful and failure scenario in a
+// loopback test when protocol is RFC5245. For success IceTiebreaker, username
+// should remain equal to the request generated by the port and role of port
+// must be in controlling.
+TEST_F(PortTest, TestLoopbackCall) {
+  auto lport = CreateTestPort(kLocalAddr1, "lfrag", "lpass");
+  lport->SetIceRole(cricket::ICEROLE_CONTROLLING);
+  lport->SetIceTiebreaker(kTiebreaker1);
+  lport->PrepareAddress();
+  ASSERT_FALSE(lport->Candidates().empty());
+  Connection* conn =
+      lport->CreateConnection(lport->Candidates()[0], Port::ORIGIN_MESSAGE);
+  conn->Ping(0);
+
+  ASSERT_TRUE_WAIT(lport->last_stun_msg() != NULL, kDefaultTimeout);
+  IceMessage* msg = lport->last_stun_msg();
+  EXPECT_EQ(STUN_BINDING_REQUEST, msg->type());
+  conn->OnReadPacket(lport->last_stun_buf()->data<char>(),
+                     lport->last_stun_buf()->size(), /* packet_time_us */ -1);
+  ASSERT_TRUE_WAIT(lport->last_stun_msg() != NULL, kDefaultTimeout);
+  msg = lport->last_stun_msg();
+  EXPECT_EQ(STUN_BINDING_RESPONSE, msg->type());
+
+  // If the tiebreaker value is different from port, we expect a error
+  // response.
+  lport->Reset();
+  lport->AddCandidateAddress(kLocalAddr2);
+  // Creating a different connection as `conn` is receiving.
+  Connection* conn1 =
+      lport->CreateConnection(lport->Candidates()[1], Port::ORIGIN_MESSAGE);
+  conn1->Ping(0);
+
+  ASSERT_TRUE_WAIT(lport->last_stun_msg() != NULL, kDefaultTimeout);
+  msg = lport->last_stun_msg();
+  EXPECT_EQ(STUN_BINDING_REQUEST, msg->type());
+  std::unique_ptr<IceMessage> modified_req(
+      CreateStunMessage(STUN_BINDING_REQUEST));
+  const StunByteStringAttribute* username_attr =
+      msg->GetByteString(STUN_ATTR_USERNAME);
+  modified_req->AddAttribute(std::make_unique<StunByteStringAttribute>(
+      STUN_ATTR_USERNAME, username_attr->string_view()));
+  // To make sure we receive error response, adding tiebreaker less than
+  // what's present in request.
+  modified_req->AddAttribute(std::make_unique<StunUInt64Attribute>(
+      STUN_ATTR_ICE_CONTROLLING, kTiebreaker1 - 1));
+  modified_req->AddMessageIntegrity("lpass");
+  modified_req->AddFingerprint();
+
+  lport->Reset();
+  auto buf = std::make_unique<ByteBufferWriter>();
+  WriteStunMessage(*modified_req, buf.get());
+  conn1->OnReadPacket(buf->Data(), buf->Length(), /* packet_time_us */ -1);
+  ASSERT_TRUE_WAIT(lport->last_stun_msg() != NULL, kDefaultTimeout);
+  msg = lport->last_stun_msg();
+  EXPECT_EQ(STUN_BINDING_ERROR_RESPONSE, msg->type());
+}
+
+// This test verifies role conflict signal is received when there is
+// conflict in the role. In this case both ports are in controlling and
+// `rport` has higher tiebreaker value than `lport`. Since `lport` has lower
+// value of tiebreaker, when it receives ping request from `rport` it will
+// send role conflict signal.
+TEST_F(PortTest, TestIceRoleConflict) {
+  auto lport = CreateTestPort(kLocalAddr1, "lfrag", "lpass");
+  lport->SetIceRole(cricket::ICEROLE_CONTROLLING);
+  lport->SetIceTiebreaker(kTiebreaker1);
+  auto rport = CreateTestPort(kLocalAddr2, "rfrag", "rpass");
+  rport->SetIceRole(cricket::ICEROLE_CONTROLLING);
+  rport->SetIceTiebreaker(kTiebreaker2);
+
+  lport->PrepareAddress();
+  rport->PrepareAddress();
+  ASSERT_FALSE(lport->Candidates().empty());
+  ASSERT_FALSE(rport->Candidates().empty());
+  Connection* lconn =
+      lport->CreateConnection(rport->Candidates()[0], Port::ORIGIN_MESSAGE);
+  Connection* rconn =
+      rport->CreateConnection(lport->Candidates()[0], Port::ORIGIN_MESSAGE);
+  rconn->Ping(0);
+
+  ASSERT_TRUE_WAIT(rport->last_stun_msg() != NULL, kDefaultTimeout);
+  IceMessage* msg = rport->last_stun_msg();
+  EXPECT_EQ(STUN_BINDING_REQUEST, msg->type());
+  // Send rport binding request to lport.
+  lconn->OnReadPacket(rport->last_stun_buf()->data<char>(),
+                      rport->last_stun_buf()->size(), /* packet_time_us */ -1);
+
+  ASSERT_TRUE_WAIT(lport->last_stun_msg() != NULL, kDefaultTimeout);
+  EXPECT_EQ(STUN_BINDING_RESPONSE, lport->last_stun_msg()->type());
+  EXPECT_TRUE(role_conflict());
+}
+
+TEST_F(PortTest, TestTcpNoDelay) {
+  rtc::ScopedFakeClock clock;
+  auto port1 = CreateTcpPort(kLocalAddr1);
+  port1->SetIceRole(cricket::ICEROLE_CONTROLLING);
+  int option_value = -1;
+  int success = port1->GetOption(rtc::Socket::OPT_NODELAY, &option_value);
+  ASSERT_EQ(0, success);  // GetOption() should complete successfully w/ 0
+  EXPECT_EQ(1, option_value);
+
+  auto port2 = CreateTcpPort(kLocalAddr2);
+  port2->SetIceRole(cricket::ICEROLE_CONTROLLED);
+
+  // Set up a connection, and verify that option is set on connected sockets at
+  // both ends.
+  TestChannel ch1(std::move(port1));
+  TestChannel ch2(std::move(port2));
+  // Acquire addresses.
+  ch1.Start();
+  ch2.Start();
+  ASSERT_EQ_SIMULATED_WAIT(1, ch1.complete_count(), kDefaultTimeout, clock);
+  ASSERT_EQ_SIMULATED_WAIT(1, ch2.complete_count(), kDefaultTimeout, clock);
+  // Connect and send a ping from src to dst.
+  ch1.CreateConnection(GetCandidate(ch2.port()));
+  ASSERT_TRUE(ch1.conn() != NULL);
+  EXPECT_TRUE_SIMULATED_WAIT(ch1.conn()->connected(), kDefaultTimeout,
+                             clock);  // for TCP connect
+  ch1.Ping();
+  SIMULATED_WAIT(!ch2.remote_address().IsNil(), kShortTimeout, clock);
+
+  // Accept the connection.
+  ch2.AcceptConnection(GetCandidate(ch1.port()));
+  ASSERT_TRUE(ch2.conn() != NULL);
+
+  option_value = -1;
+  success = static_cast<TCPConnection*>(ch1.conn())
+                ->socket()
+                ->GetOption(rtc::Socket::OPT_NODELAY, &option_value);
+  ASSERT_EQ(0, success);
+  EXPECT_EQ(1, option_value);
+
+  option_value = -1;
+  success = static_cast<TCPConnection*>(ch2.conn())
+                ->socket()
+                ->GetOption(rtc::Socket::OPT_NODELAY, &option_value);
+  ASSERT_EQ(0, success);
+  EXPECT_EQ(1, option_value);
+}
+
+TEST_F(PortTest, TestDelayedBindingUdp) {
+  FakeAsyncPacketSocket* socket = new FakeAsyncPacketSocket();
+  FakePacketSocketFactory socket_factory;
+
+  socket_factory.set_next_udp_socket(socket);
+  auto port = CreateUdpPort(kLocalAddr1, &socket_factory);
+
+  socket->set_state(AsyncPacketSocket::STATE_BINDING);
+  port->PrepareAddress();
+
+  EXPECT_EQ(0U, port->Candidates().size());
+  socket->SignalAddressReady(socket, kLocalAddr2);
+
+  EXPECT_EQ(1U, port->Candidates().size());
+}
+
+TEST_F(PortTest, TestDisableInterfaceOfTcpPort) {
+  FakeAsyncListenSocket* lsocket = new FakeAsyncListenSocket();
+  FakeAsyncListenSocket* rsocket = new FakeAsyncListenSocket();
+  FakePacketSocketFactory socket_factory;
+
+  socket_factory.set_next_server_tcp_socket(lsocket);
+  auto lport = CreateTcpPort(kLocalAddr1, &socket_factory);
+
+  socket_factory.set_next_server_tcp_socket(rsocket);
+  auto rport = CreateTcpPort(kLocalAddr2, &socket_factory);
+
+  lsocket->Bind(kLocalAddr1);
+  rsocket->Bind(kLocalAddr2);
+
+  lport->SetIceRole(cricket::ICEROLE_CONTROLLING);
+  lport->SetIceTiebreaker(kTiebreaker1);
+  rport->SetIceRole(cricket::ICEROLE_CONTROLLED);
+  rport->SetIceTiebreaker(kTiebreaker2);
+
+  lport->PrepareAddress();
+  rport->PrepareAddress();
+  ASSERT_FALSE(rport->Candidates().empty());
+
+  // A client socket.
+  FakeAsyncPacketSocket* socket = new FakeAsyncPacketSocket();
+  socket->local_address_ = kLocalAddr1;
+  socket->remote_address_ = kLocalAddr2;
+  socket_factory.set_next_client_tcp_socket(socket);
+  Connection* lconn =
+      lport->CreateConnection(rport->Candidates()[0], Port::ORIGIN_MESSAGE);
+  ASSERT_NE(lconn, nullptr);
+  socket->SignalConnect(socket);
+  lconn->Ping(0);
+
+  // Now disconnect the client socket...
+  socket->NotifyClosedForTest(1);
+
+  // And prevent new sockets from being created.
+  socket_factory.set_next_client_tcp_socket(nullptr);
+
+  // Test that Ping() does not cause SEGV.
+  lconn->Ping(0);
+}
+
+void PortTest::TestCrossFamilyPorts(int type) {
+  FakePacketSocketFactory factory;
+  std::unique_ptr<Port> ports[4];
+  SocketAddress addresses[4] = {
+      SocketAddress("192.168.1.3", 0), SocketAddress("192.168.1.4", 0),
+      SocketAddress("2001:db8::1", 0), SocketAddress("2001:db8::2", 0)};
+  for (int i = 0; i < 4; i++) {
+    if (type == SOCK_DGRAM) {
+      FakeAsyncPacketSocket* socket = new FakeAsyncPacketSocket();
+      factory.set_next_udp_socket(socket);
+      ports[i] = CreateUdpPort(addresses[i], &factory);
+      socket->set_state(AsyncPacketSocket::STATE_BINDING);
+      socket->SignalAddressReady(socket, addresses[i]);
+    } else if (type == SOCK_STREAM) {
+      FakeAsyncListenSocket* socket = new FakeAsyncListenSocket();
+      factory.set_next_server_tcp_socket(socket);
+      ports[i] = CreateTcpPort(addresses[i], &factory);
+      socket->Bind(addresses[i]);
+    }
+    ports[i]->PrepareAddress();
+  }
+
+  // IPv4 Port, connects to IPv6 candidate and then to IPv4 candidate.
+  if (type == SOCK_STREAM) {
+    FakeAsyncPacketSocket* clientsocket = new FakeAsyncPacketSocket();
+    factory.set_next_client_tcp_socket(clientsocket);
+  }
+  Connection* c = ports[0]->CreateConnection(GetCandidate(ports[2].get()),
+                                             Port::ORIGIN_MESSAGE);
+  EXPECT_TRUE(NULL == c);
+  EXPECT_EQ(0U, ports[0]->connections().size());
+  c = ports[0]->CreateConnection(GetCandidate(ports[1].get()),
+                                 Port::ORIGIN_MESSAGE);
+  EXPECT_FALSE(NULL == c);
+  EXPECT_EQ(1U, ports[0]->connections().size());
+
+  // IPv6 Port, connects to IPv4 candidate and to IPv6 candidate.
+  if (type == SOCK_STREAM) {
+    FakeAsyncPacketSocket* clientsocket = new FakeAsyncPacketSocket();
+    factory.set_next_client_tcp_socket(clientsocket);
+  }
+  c = ports[2]->CreateConnection(GetCandidate(ports[0].get()),
+                                 Port::ORIGIN_MESSAGE);
+  EXPECT_TRUE(NULL == c);
+  EXPECT_EQ(0U, ports[2]->connections().size());
+  c = ports[2]->CreateConnection(GetCandidate(ports[3].get()),
+                                 Port::ORIGIN_MESSAGE);
+  EXPECT_FALSE(NULL == c);
+  EXPECT_EQ(1U, ports[2]->connections().size());
+}
+
+TEST_F(PortTest, TestSkipCrossFamilyTcp) {
+  TestCrossFamilyPorts(SOCK_STREAM);
+}
+
+TEST_F(PortTest, TestSkipCrossFamilyUdp) {
+  TestCrossFamilyPorts(SOCK_DGRAM);
+}
+
+void PortTest::ExpectPortsCanConnect(bool can_connect, Port* p1, Port* p2) {
+  Connection* c = p1->CreateConnection(GetCandidate(p2), Port::ORIGIN_MESSAGE);
+  if (can_connect) {
+    EXPECT_FALSE(NULL == c);
+    EXPECT_EQ(1U, p1->connections().size());
+  } else {
+    EXPECT_TRUE(NULL == c);
+    EXPECT_EQ(0U, p1->connections().size());
+  }
+}
+
+TEST_F(PortTest, TestUdpSingleAddressV6CrossTypePorts) {
+  FakePacketSocketFactory factory;
+  std::unique_ptr<Port> ports[4];
+  SocketAddress addresses[4] = {
+      SocketAddress("2001:db8::1", 0), SocketAddress("fe80::1", 0),
+      SocketAddress("fe80::2", 0), SocketAddress("::1", 0)};
+  for (int i = 0; i < 4; i++) {
+    FakeAsyncPacketSocket* socket = new FakeAsyncPacketSocket();
+    factory.set_next_udp_socket(socket);
+    ports[i] = CreateUdpPort(addresses[i], &factory);
+    socket->set_state(AsyncPacketSocket::STATE_BINDING);
+    socket->SignalAddressReady(socket, addresses[i]);
+    ports[i]->PrepareAddress();
+  }
+
+  Port* standard = ports[0].get();
+  Port* link_local1 = ports[1].get();
+  Port* link_local2 = ports[2].get();
+  Port* localhost = ports[3].get();
+
+  ExpectPortsCanConnect(false, link_local1, standard);
+  ExpectPortsCanConnect(false, standard, link_local1);
+  ExpectPortsCanConnect(false, link_local1, localhost);
+  ExpectPortsCanConnect(false, localhost, link_local1);
+
+  ExpectPortsCanConnect(true, link_local1, link_local2);
+  ExpectPortsCanConnect(true, localhost, standard);
+  ExpectPortsCanConnect(true, standard, localhost);
+}
+
+TEST_F(PortTest, TestUdpMultipleAddressesV6CrossTypePorts) {
+  webrtc::test::ScopedKeyValueConfig field_trials(
+      "WebRTC-IPv6NetworkResolutionFixes/"
+      "Enabled,PreferGlobalIPv6Address:true/");
+  FakePacketSocketFactory factory;
+  std::unique_ptr<Port> ports[5];
+  SocketAddress addresses[5] = {
+      SocketAddress("2001:db8::1", 0), SocketAddress("2001:db8::2", 0),
+      SocketAddress("fe80::1", 0), SocketAddress("fe80::2", 0),
+      SocketAddress("::1", 0)};
+  for (int i = 0; i < 5; i++) {
+    FakeAsyncPacketSocket* socket = new FakeAsyncPacketSocket();
+    factory.set_next_udp_socket(socket);
+    ports[i] = CreateUdpPortMultipleAddrs(addresses[i], kLinkLocalIPv6Addr,
+                                          &factory, field_trials);
+    ports[i]->SetIceTiebreaker(kTiebreakerDefault);
+    socket->set_state(AsyncPacketSocket::STATE_BINDING);
+    socket->SignalAddressReady(socket, addresses[i]);
+    ports[i]->PrepareAddress();
+  }
+
+  Port* standard1 = ports[0].get();
+  Port* standard2 = ports[1].get();
+  Port* link_local1 = ports[2].get();
+  Port* link_local2 = ports[3].get();
+  Port* localhost = ports[4].get();
+
+  ExpectPortsCanConnect(false, link_local1, standard1);
+  ExpectPortsCanConnect(false, standard1, link_local1);
+  ExpectPortsCanConnect(false, link_local1, localhost);
+  ExpectPortsCanConnect(false, localhost, link_local1);
+
+  ExpectPortsCanConnect(true, link_local1, link_local2);
+  ExpectPortsCanConnect(true, localhost, standard1);
+  ExpectPortsCanConnect(true, standard1, localhost);
+  ExpectPortsCanConnect(true, standard2, standard1);
+}
+
+// This test verifies DSCP value set through SetOption interface can be
+// get through DefaultDscpValue.
+TEST_F(PortTest, TestDefaultDscpValue) {
+  int dscp;
+  auto udpport = CreateUdpPort(kLocalAddr1);
+  EXPECT_EQ(0, udpport->SetOption(rtc::Socket::OPT_DSCP, rtc::DSCP_CS6));
+  EXPECT_EQ(0, udpport->GetOption(rtc::Socket::OPT_DSCP, &dscp));
+  auto tcpport = CreateTcpPort(kLocalAddr1);
+  EXPECT_EQ(0, tcpport->SetOption(rtc::Socket::OPT_DSCP, rtc::DSCP_AF31));
+  EXPECT_EQ(0, tcpport->GetOption(rtc::Socket::OPT_DSCP, &dscp));
+  EXPECT_EQ(rtc::DSCP_AF31, dscp);
+  auto stunport = CreateStunPort(kLocalAddr1, nat_socket_factory1());
+  EXPECT_EQ(0, stunport->SetOption(rtc::Socket::OPT_DSCP, rtc::DSCP_AF41));
+  EXPECT_EQ(0, stunport->GetOption(rtc::Socket::OPT_DSCP, &dscp));
+  EXPECT_EQ(rtc::DSCP_AF41, dscp);
+  auto turnport1 =
+      CreateTurnPort(kLocalAddr1, nat_socket_factory1(), PROTO_UDP, PROTO_UDP);
+  // Socket is created in PrepareAddress.
+  turnport1->PrepareAddress();
+  EXPECT_EQ(0, turnport1->SetOption(rtc::Socket::OPT_DSCP, rtc::DSCP_CS7));
+  EXPECT_EQ(0, turnport1->GetOption(rtc::Socket::OPT_DSCP, &dscp));
+  EXPECT_EQ(rtc::DSCP_CS7, dscp);
+  // This will verify correct value returned without the socket.
+  auto turnport2 =
+      CreateTurnPort(kLocalAddr1, nat_socket_factory1(), PROTO_UDP, PROTO_UDP);
+  EXPECT_EQ(0, turnport2->SetOption(rtc::Socket::OPT_DSCP, rtc::DSCP_CS6));
+  EXPECT_EQ(0, turnport2->GetOption(rtc::Socket::OPT_DSCP, &dscp));
+  EXPECT_EQ(rtc::DSCP_CS6, dscp);
+}
+
+// Test sending STUN messages.
+TEST_F(PortTest, TestSendStunMessage) {
+  auto lport = CreateTestPort(kLocalAddr1, "lfrag", "lpass");
+  auto rport = CreateTestPort(kLocalAddr2, "rfrag", "rpass");
+  lport->SetIceRole(cricket::ICEROLE_CONTROLLING);
+  lport->SetIceTiebreaker(kTiebreaker1);
+  rport->SetIceRole(cricket::ICEROLE_CONTROLLED);
+  rport->SetIceTiebreaker(kTiebreaker2);
+
+  // Send a fake ping from lport to rport.
+  lport->PrepareAddress();
+  rport->PrepareAddress();
+  ASSERT_FALSE(rport->Candidates().empty());
+  Connection* lconn =
+      lport->CreateConnection(rport->Candidates()[0], Port::ORIGIN_MESSAGE);
+  Connection* rconn =
+      rport->CreateConnection(lport->Candidates()[0], Port::ORIGIN_MESSAGE);
+  lconn->Ping(0);
+
+  // Check that it's a proper BINDING-REQUEST.
+  ASSERT_TRUE_WAIT(lport->last_stun_msg() != NULL, kDefaultTimeout);
+  IceMessage* msg = lport->last_stun_msg();
+  EXPECT_EQ(STUN_BINDING_REQUEST, msg->type());
+  EXPECT_FALSE(msg->IsLegacy());
+  const StunByteStringAttribute* username_attr =
+      msg->GetByteString(STUN_ATTR_USERNAME);
+  ASSERT_TRUE(username_attr != NULL);
+  const StunUInt32Attribute* priority_attr = msg->GetUInt32(STUN_ATTR_PRIORITY);
+  ASSERT_TRUE(priority_attr != NULL);
+  EXPECT_EQ(kDefaultPrflxPriority, priority_attr->value());
+  EXPECT_EQ("rfrag:lfrag", username_attr->string_view());
+  EXPECT_TRUE(msg->GetByteString(STUN_ATTR_MESSAGE_INTEGRITY) != NULL);
+  EXPECT_EQ(StunMessage::IntegrityStatus::kIntegrityOk,
+            msg->ValidateMessageIntegrity("rpass"));
+  const StunUInt64Attribute* ice_controlling_attr =
+      msg->GetUInt64(STUN_ATTR_ICE_CONTROLLING);
+  ASSERT_TRUE(ice_controlling_attr != NULL);
+  EXPECT_EQ(lport->IceTiebreaker(), ice_controlling_attr->value());
+  EXPECT_TRUE(msg->GetByteString(STUN_ATTR_ICE_CONTROLLED) == NULL);
+  EXPECT_TRUE(msg->GetByteString(STUN_ATTR_USE_CANDIDATE) != NULL);
+  EXPECT_TRUE(msg->GetUInt32(STUN_ATTR_FINGERPRINT) != NULL);
+  EXPECT_TRUE(StunMessage::ValidateFingerprint(
+      lport->last_stun_buf()->data<char>(), lport->last_stun_buf()->size()));
+
+  // Request should not include ping count.
+  ASSERT_TRUE(msg->GetUInt32(STUN_ATTR_RETRANSMIT_COUNT) == NULL);
+
+  // Save a copy of the BINDING-REQUEST for use below.
+  std::unique_ptr<IceMessage> request = CopyStunMessage(*msg);
+
+  // Receive the BINDING-REQUEST and respond with BINDING-RESPONSE.
+  rconn->OnReadPacket(lport->last_stun_buf()->data<char>(),
+                      lport->last_stun_buf()->size(), /* packet_time_us */ -1);
+  msg = rport->last_stun_msg();
+  ASSERT_TRUE(msg != NULL);
+  EXPECT_EQ(STUN_BINDING_RESPONSE, msg->type());
+  // Received a BINDING-RESPONSE.
+  lconn->OnReadPacket(rport->last_stun_buf()->data<char>(),
+                      rport->last_stun_buf()->size(), /* packet_time_us */ -1);
+  // Verify the STUN Stats.
+  EXPECT_EQ(1U, lconn->stats().sent_ping_requests_total);
+  EXPECT_EQ(1U, lconn->stats().sent_ping_requests_before_first_response);
+  EXPECT_EQ(1U, lconn->stats().recv_ping_responses);
+  EXPECT_EQ(1U, rconn->stats().recv_ping_requests);
+  EXPECT_EQ(1U, rconn->stats().sent_ping_responses);
+
+  EXPECT_FALSE(msg->IsLegacy());
+  const StunAddressAttribute* addr_attr =
+      msg->GetAddress(STUN_ATTR_XOR_MAPPED_ADDRESS);
+  ASSERT_TRUE(addr_attr != NULL);
+  EXPECT_EQ(lport->Candidates()[0].address(), addr_attr->GetAddress());
+  EXPECT_TRUE(msg->GetByteString(STUN_ATTR_MESSAGE_INTEGRITY) != NULL);
+  EXPECT_EQ(StunMessage::IntegrityStatus::kIntegrityOk,
+            msg->ValidateMessageIntegrity("rpass"));
+  EXPECT_TRUE(msg->GetUInt32(STUN_ATTR_FINGERPRINT) != NULL);
+  EXPECT_TRUE(StunMessage::ValidateFingerprint(
+      lport->last_stun_buf()->data<char>(), lport->last_stun_buf()->size()));
+  // No USERNAME or PRIORITY in ICE responses.
+  EXPECT_TRUE(msg->GetByteString(STUN_ATTR_USERNAME) == NULL);
+  EXPECT_TRUE(msg->GetByteString(STUN_ATTR_PRIORITY) == NULL);
+  EXPECT_TRUE(msg->GetByteString(STUN_ATTR_MAPPED_ADDRESS) == NULL);
+  EXPECT_TRUE(msg->GetByteString(STUN_ATTR_ICE_CONTROLLING) == NULL);
+  EXPECT_TRUE(msg->GetByteString(STUN_ATTR_ICE_CONTROLLED) == NULL);
+  EXPECT_TRUE(msg->GetByteString(STUN_ATTR_USE_CANDIDATE) == NULL);
+
+  // Response should not include ping count.
+  ASSERT_TRUE(msg->GetUInt32(STUN_ATTR_RETRANSMIT_COUNT) == NULL);
+
+  // Respond with a BINDING-ERROR-RESPONSE. This wouldn't happen in real life,
+  // but we can do it here.
+  rport->SendBindingErrorResponse(
+      request.get(), lport->Candidates()[0].address(), STUN_ERROR_SERVER_ERROR,
+      STUN_ERROR_REASON_SERVER_ERROR);
+  msg = rport->last_stun_msg();
+  ASSERT_TRUE(msg != NULL);
+  EXPECT_EQ(STUN_BINDING_ERROR_RESPONSE, msg->type());
+  EXPECT_FALSE(msg->IsLegacy());
+  const StunErrorCodeAttribute* error_attr = msg->GetErrorCode();
+  ASSERT_TRUE(error_attr != NULL);
+  EXPECT_EQ(STUN_ERROR_SERVER_ERROR, error_attr->code());
+  EXPECT_EQ(std::string(STUN_ERROR_REASON_SERVER_ERROR), error_attr->reason());
+  EXPECT_TRUE(msg->GetByteString(STUN_ATTR_MESSAGE_INTEGRITY) != NULL);
+  EXPECT_EQ(StunMessage::IntegrityStatus::kIntegrityOk,
+            msg->ValidateMessageIntegrity("rpass"));
+  EXPECT_TRUE(msg->GetUInt32(STUN_ATTR_FINGERPRINT) != NULL);
+  EXPECT_TRUE(StunMessage::ValidateFingerprint(
+      lport->last_stun_buf()->data<char>(), lport->last_stun_buf()->size()));
+  // No USERNAME with ICE.
+  EXPECT_TRUE(msg->GetByteString(STUN_ATTR_USERNAME) == NULL);
+  EXPECT_TRUE(msg->GetByteString(STUN_ATTR_PRIORITY) == NULL);
+
+  // Testing STUN binding requests from rport --> lport, having ICE_CONTROLLED
+  // and (incremented) RETRANSMIT_COUNT attributes.
+  rport->Reset();
+  rport->set_send_retransmit_count_attribute(true);
+  rconn->Ping(0);
+  rconn->Ping(0);
+  rconn->Ping(0);
+  ASSERT_TRUE_WAIT(rport->last_stun_msg() != NULL, kDefaultTimeout);
+  msg = rport->last_stun_msg();
+  EXPECT_EQ(STUN_BINDING_REQUEST, msg->type());
+  const StunUInt64Attribute* ice_controlled_attr =
+      msg->GetUInt64(STUN_ATTR_ICE_CONTROLLED);
+  ASSERT_TRUE(ice_controlled_attr != NULL);
+  EXPECT_EQ(rport->IceTiebreaker(), ice_controlled_attr->value());
+  EXPECT_TRUE(msg->GetByteString(STUN_ATTR_USE_CANDIDATE) == NULL);
+
+  // Request should include ping count.
+  const StunUInt32Attribute* retransmit_attr =
+      msg->GetUInt32(STUN_ATTR_RETRANSMIT_COUNT);
+  ASSERT_TRUE(retransmit_attr != NULL);
+  EXPECT_EQ(2U, retransmit_attr->value());
+
+  // Respond with a BINDING-RESPONSE.
+  request = CopyStunMessage(*msg);
+  lconn->OnReadPacket(rport->last_stun_buf()->data<char>(),
+                      rport->last_stun_buf()->size(), /* packet_time_us */ -1);
+  msg = lport->last_stun_msg();
+  // Receive the BINDING-RESPONSE.
+  rconn->OnReadPacket(lport->last_stun_buf()->data<char>(),
+                      lport->last_stun_buf()->size(), /* packet_time_us */ -1);
+
+  // Verify the Stun ping stats.
+  EXPECT_EQ(3U, rconn->stats().sent_ping_requests_total);
+  EXPECT_EQ(3U, rconn->stats().sent_ping_requests_before_first_response);
+  EXPECT_EQ(1U, rconn->stats().recv_ping_responses);
+  EXPECT_EQ(1U, lconn->stats().sent_ping_responses);
+  EXPECT_EQ(1U, lconn->stats().recv_ping_requests);
+  // Ping after receiver the first response
+  rconn->Ping(0);
+  rconn->Ping(0);
+  EXPECT_EQ(5U, rconn->stats().sent_ping_requests_total);
+  EXPECT_EQ(3U, rconn->stats().sent_ping_requests_before_first_response);
+
+  // Response should include same ping count.
+  retransmit_attr = msg->GetUInt32(STUN_ATTR_RETRANSMIT_COUNT);
+  ASSERT_TRUE(retransmit_attr != NULL);
+  EXPECT_EQ(2U, retransmit_attr->value());
+}
+
+TEST_F(PortTest, TestNomination) {
+  auto lport = CreateTestPort(kLocalAddr1, "lfrag", "lpass");
+  auto rport = CreateTestPort(kLocalAddr2, "rfrag", "rpass");
+  lport->SetIceRole(cricket::ICEROLE_CONTROLLING);
+  lport->SetIceTiebreaker(kTiebreaker1);
+  rport->SetIceRole(cricket::ICEROLE_CONTROLLED);
+  rport->SetIceTiebreaker(kTiebreaker2);
+
+  lport->PrepareAddress();
+  rport->PrepareAddress();
+  ASSERT_FALSE(lport->Candidates().empty());
+  ASSERT_FALSE(rport->Candidates().empty());
+  Connection* lconn =
+      lport->CreateConnection(rport->Candidates()[0], Port::ORIGIN_MESSAGE);
+  Connection* rconn =
+      rport->CreateConnection(lport->Candidates()[0], Port::ORIGIN_MESSAGE);
+
+  // `lconn` is controlling, `rconn` is controlled.
+  uint32_t nomination = 1234;
+  lconn->set_nomination(nomination);
+
+  EXPECT_FALSE(lconn->nominated());
+  EXPECT_FALSE(rconn->nominated());
+  EXPECT_EQ(lconn->nominated(), lconn->stats().nominated);
+  EXPECT_EQ(rconn->nominated(), rconn->stats().nominated);
+
+  // Send ping (including the nomination value) from `lconn` to `rconn`. This
+  // should set the remote nomination of `rconn`.
+  lconn->Ping(0);
+  ASSERT_TRUE_WAIT(lport->last_stun_msg(), kDefaultTimeout);
+  ASSERT_TRUE(lport->last_stun_buf());
+  rconn->OnReadPacket(lport->last_stun_buf()->data<char>(),
+                      lport->last_stun_buf()->size(), /* packet_time_us */ -1);
+  EXPECT_EQ(nomination, rconn->remote_nomination());
+  EXPECT_FALSE(lconn->nominated());
+  EXPECT_TRUE(rconn->nominated());
+  EXPECT_EQ(lconn->nominated(), lconn->stats().nominated);
+  EXPECT_EQ(rconn->nominated(), rconn->stats().nominated);
+
+  // This should result in an acknowledgment sent back from `rconn` to `lconn`,
+  // updating the acknowledged nomination of `lconn`.
+  ASSERT_TRUE_WAIT(rport->last_stun_msg(), kDefaultTimeout);
+  ASSERT_TRUE(rport->last_stun_buf());
+  lconn->OnReadPacket(rport->last_stun_buf()->data<char>(),
+                      rport->last_stun_buf()->size(), /* packet_time_us */ -1);
+  EXPECT_EQ(nomination, lconn->acked_nomination());
+  EXPECT_TRUE(lconn->nominated());
+  EXPECT_TRUE(rconn->nominated());
+  EXPECT_EQ(lconn->nominated(), lconn->stats().nominated);
+  EXPECT_EQ(rconn->nominated(), rconn->stats().nominated);
+}
+
+TEST_F(PortTest, TestRoundTripTime) {
+  rtc::ScopedFakeClock clock;
+
+  auto lport = CreateTestPort(kLocalAddr1, "lfrag", "lpass");
+  auto rport = CreateTestPort(kLocalAddr2, "rfrag", "rpass");
+  lport->SetIceRole(cricket::ICEROLE_CONTROLLING);
+  lport->SetIceTiebreaker(kTiebreaker1);
+  rport->SetIceRole(cricket::ICEROLE_CONTROLLED);
+  rport->SetIceTiebreaker(kTiebreaker2);
+
+  lport->PrepareAddress();
+  rport->PrepareAddress();
+  ASSERT_FALSE(lport->Candidates().empty());
+  ASSERT_FALSE(rport->Candidates().empty());
+  Connection* lconn =
+      lport->CreateConnection(rport->Candidates()[0], Port::ORIGIN_MESSAGE);
+  Connection* rconn =
+      rport->CreateConnection(lport->Candidates()[0], Port::ORIGIN_MESSAGE);
+
+  EXPECT_EQ(0u, lconn->stats().total_round_trip_time_ms);
+  EXPECT_FALSE(lconn->stats().current_round_trip_time_ms);
+
+  SendPingAndReceiveResponse(lconn, lport.get(), rconn, rport.get(), &clock,
+                             10);
+  EXPECT_EQ(10u, lconn->stats().total_round_trip_time_ms);
+  ASSERT_TRUE(lconn->stats().current_round_trip_time_ms);
+  EXPECT_EQ(10u, *lconn->stats().current_round_trip_time_ms);
+
+  SendPingAndReceiveResponse(lconn, lport.get(), rconn, rport.get(), &clock,
+                             20);
+  EXPECT_EQ(30u, lconn->stats().total_round_trip_time_ms);
+  ASSERT_TRUE(lconn->stats().current_round_trip_time_ms);
+  EXPECT_EQ(20u, *lconn->stats().current_round_trip_time_ms);
+
+  SendPingAndReceiveResponse(lconn, lport.get(), rconn, rport.get(), &clock,
+                             30);
+  EXPECT_EQ(60u, lconn->stats().total_round_trip_time_ms);
+  ASSERT_TRUE(lconn->stats().current_round_trip_time_ms);
+  EXPECT_EQ(30u, *lconn->stats().current_round_trip_time_ms);
+}
+
+TEST_F(PortTest, TestUseCandidateAttribute) {
+  auto lport = CreateTestPort(kLocalAddr1, "lfrag", "lpass");
+  auto rport = CreateTestPort(kLocalAddr2, "rfrag", "rpass");
+  lport->SetIceRole(cricket::ICEROLE_CONTROLLING);
+  lport->SetIceTiebreaker(kTiebreaker1);
+  rport->SetIceRole(cricket::ICEROLE_CONTROLLED);
+  rport->SetIceTiebreaker(kTiebreaker2);
+
+  // Send a fake ping from lport to rport.
+  lport->PrepareAddress();
+  rport->PrepareAddress();
+  ASSERT_FALSE(rport->Candidates().empty());
+  Connection* lconn =
+      lport->CreateConnection(rport->Candidates()[0], Port::ORIGIN_MESSAGE);
+  lconn->Ping(0);
+  ASSERT_TRUE_WAIT(lport->last_stun_msg() != NULL, kDefaultTimeout);
+  IceMessage* msg = lport->last_stun_msg();
+  const StunUInt64Attribute* ice_controlling_attr =
+      msg->GetUInt64(STUN_ATTR_ICE_CONTROLLING);
+  ASSERT_TRUE(ice_controlling_attr != NULL);
+  const StunByteStringAttribute* use_candidate_attr =
+      msg->GetByteString(STUN_ATTR_USE_CANDIDATE);
+  ASSERT_TRUE(use_candidate_attr != NULL);
+}
+
+// Tests that when the network type changes, the network cost of the port will
+// change, the network cost of the local candidates will change. Also tests that
+// the remote network costs are updated with the stun binding requests.
+TEST_F(PortTest, TestNetworkCostChange) {
+  rtc::Network* test_network = MakeNetwork(kLocalAddr1);
+  auto lport = CreateTestPort(test_network, "lfrag", "lpass");
+  auto rport = CreateTestPort(test_network, "rfrag", "rpass");
+  lport->SetIceRole(cricket::ICEROLE_CONTROLLING);
+  lport->SetIceTiebreaker(kTiebreaker1);
+  rport->SetIceRole(cricket::ICEROLE_CONTROLLED);
+  rport->SetIceTiebreaker(kTiebreaker2);
+  lport->PrepareAddress();
+  rport->PrepareAddress();
+
+  // Default local port cost is rtc::kNetworkCostUnknown.
+  EXPECT_EQ(rtc::kNetworkCostUnknown, lport->network_cost());
+  ASSERT_TRUE(!lport->Candidates().empty());
+  for (const cricket::Candidate& candidate : lport->Candidates()) {
+    EXPECT_EQ(rtc::kNetworkCostUnknown, candidate.network_cost());
+  }
+
+  // Change the network type to wifi.
+  test_network->set_type(rtc::ADAPTER_TYPE_WIFI);
+  EXPECT_EQ(rtc::kNetworkCostLow, lport->network_cost());
+  for (const cricket::Candidate& candidate : lport->Candidates()) {
+    EXPECT_EQ(rtc::kNetworkCostLow, candidate.network_cost());
+  }
+
+  // Add a connection and then change the network type.
+  Connection* lconn =
+      lport->CreateConnection(rport->Candidates()[0], Port::ORIGIN_MESSAGE);
+  // Change the network type to cellular.
+  test_network->set_type(rtc::ADAPTER_TYPE_CELLULAR);
+  EXPECT_EQ(rtc::kNetworkCostHigh, lport->network_cost());
+  for (const cricket::Candidate& candidate : lport->Candidates()) {
+    EXPECT_EQ(rtc::kNetworkCostHigh, candidate.network_cost());
+  }
+
+  test_network->set_type(rtc::ADAPTER_TYPE_WIFI);
+  Connection* rconn =
+      rport->CreateConnection(lport->Candidates()[0], Port::ORIGIN_MESSAGE);
+  test_network->set_type(rtc::ADAPTER_TYPE_CELLULAR);
+  lconn->Ping(0);
+  // The rconn's remote candidate cost is rtc::kNetworkCostLow, but the ping
+  // contains an attribute of network cost of rtc::kNetworkCostHigh. Once the
+  // message is handled in rconn, The rconn's remote candidate will have cost
+  // rtc::kNetworkCostHigh;
+  EXPECT_EQ(rtc::kNetworkCostLow, rconn->remote_candidate().network_cost());
+  ASSERT_TRUE_WAIT(lport->last_stun_msg() != NULL, kDefaultTimeout);
+  IceMessage* msg = lport->last_stun_msg();
+  EXPECT_EQ(STUN_BINDING_REQUEST, msg->type());
+  // Pass the binding request to rport.
+  rconn->OnReadPacket(lport->last_stun_buf()->data<char>(),
+                      lport->last_stun_buf()->size(), /* packet_time_us */ -1);
+  // Wait until rport sends the response and then check the remote network cost.
+  ASSERT_TRUE_WAIT(rport->last_stun_msg() != NULL, kDefaultTimeout);
+  EXPECT_EQ(rtc::kNetworkCostHigh, rconn->remote_candidate().network_cost());
+}
+
+TEST_F(PortTest, TestNetworkInfoAttribute) {
+  rtc::Network* test_network = MakeNetwork(kLocalAddr1);
+  auto lport = CreateTestPort(test_network, "lfrag", "lpass");
+  auto rport = CreateTestPort(test_network, "rfrag", "rpass");
+  lport->SetIceRole(cricket::ICEROLE_CONTROLLING);
+  lport->SetIceTiebreaker(kTiebreaker1);
+  rport->SetIceRole(cricket::ICEROLE_CONTROLLED);
+  rport->SetIceTiebreaker(kTiebreaker2);
+
+  uint16_t lnetwork_id = 9;
+  test_network->set_id(lnetwork_id);
+  // Send a fake ping from lport to rport.
+  lport->PrepareAddress();
+  rport->PrepareAddress();
+  Connection* lconn =
+      lport->CreateConnection(rport->Candidates()[0], Port::ORIGIN_MESSAGE);
+  lconn->Ping(0);
+  ASSERT_TRUE_WAIT(lport->last_stun_msg() != NULL, kDefaultTimeout);
+  IceMessage* msg = lport->last_stun_msg();
+  const StunUInt32Attribute* network_info_attr =
+      msg->GetUInt32(STUN_ATTR_GOOG_NETWORK_INFO);
+  ASSERT_TRUE(network_info_attr != NULL);
+  uint32_t network_info = network_info_attr->value();
+  EXPECT_EQ(lnetwork_id, network_info >> 16);
+  // Default network has unknown type and cost kNetworkCostUnknown.
+  EXPECT_EQ(rtc::kNetworkCostUnknown, network_info & 0xFFFF);
+
+  // Set the network type to be cellular so its cost will be kNetworkCostHigh.
+  // Send a fake ping from rport to lport.
+  test_network->set_type(rtc::ADAPTER_TYPE_CELLULAR);
+  uint16_t rnetwork_id = 8;
+  test_network->set_id(rnetwork_id);
+  Connection* rconn =
+      rport->CreateConnection(lport->Candidates()[0], Port::ORIGIN_MESSAGE);
+  rconn->Ping(0);
+  ASSERT_TRUE_WAIT(rport->last_stun_msg() != NULL, kDefaultTimeout);
+  msg = rport->last_stun_msg();
+  network_info_attr = msg->GetUInt32(STUN_ATTR_GOOG_NETWORK_INFO);
+  ASSERT_TRUE(network_info_attr != NULL);
+  network_info = network_info_attr->value();
+  EXPECT_EQ(rnetwork_id, network_info >> 16);
+  EXPECT_EQ(rtc::kNetworkCostHigh, network_info & 0xFFFF);
+}
+
+// Test handling STUN messages.
+TEST_F(PortTest, TestHandleStunMessage) {
+  // Our port will act as the "remote" port.
+  auto port = CreateTestPort(kLocalAddr2, "rfrag", "rpass");
+
+  std::unique_ptr<IceMessage> in_msg, out_msg;
+  auto buf = std::make_unique<ByteBufferWriter>();
+  rtc::SocketAddress addr(kLocalAddr1);
+  std::string username;
+
+  // BINDING-REQUEST from local to remote with valid ICE username,
+  // MESSAGE-INTEGRITY, and FINGERPRINT.
+  in_msg = CreateStunMessageWithUsername(STUN_BINDING_REQUEST, "rfrag:lfrag");
+  in_msg->AddMessageIntegrity("rpass");
+  in_msg->AddFingerprint();
+  WriteStunMessage(*in_msg, buf.get());
+  EXPECT_TRUE(port->GetStunMessage(buf->Data(), buf->Length(), addr, &out_msg,
+                                   &username));
+  EXPECT_TRUE(out_msg.get() != NULL);
+  EXPECT_EQ("lfrag", username);
+
+  // BINDING-RESPONSE without username, with MESSAGE-INTEGRITY and FINGERPRINT.
+  in_msg = CreateStunMessage(STUN_BINDING_RESPONSE);
+  in_msg->AddAttribute(std::make_unique<StunXorAddressAttribute>(
+      STUN_ATTR_XOR_MAPPED_ADDRESS, kLocalAddr2));
+  in_msg->AddMessageIntegrity("rpass");
+  in_msg->AddFingerprint();
+  WriteStunMessage(*in_msg, buf.get());
+  EXPECT_TRUE(port->GetStunMessage(buf->Data(), buf->Length(), addr, &out_msg,
+                                   &username));
+  EXPECT_TRUE(out_msg.get() != NULL);
+  EXPECT_EQ("", username);
+
+  // BINDING-ERROR-RESPONSE without username, with error, M-I, and FINGERPRINT.
+  in_msg = CreateStunMessage(STUN_BINDING_ERROR_RESPONSE);
+  in_msg->AddAttribute(std::make_unique<StunErrorCodeAttribute>(
+      STUN_ATTR_ERROR_CODE, STUN_ERROR_SERVER_ERROR,
+      STUN_ERROR_REASON_SERVER_ERROR));
+  in_msg->AddFingerprint();
+  WriteStunMessage(*in_msg, buf.get());
+  EXPECT_TRUE(port->GetStunMessage(buf->Data(), buf->Length(), addr, &out_msg,
+                                   &username));
+  EXPECT_TRUE(out_msg.get() != NULL);
+  EXPECT_EQ("", username);
+  ASSERT_TRUE(out_msg->GetErrorCode() != NULL);
+  EXPECT_EQ(STUN_ERROR_SERVER_ERROR, out_msg->GetErrorCode()->code());
+  EXPECT_EQ(std::string(STUN_ERROR_REASON_SERVER_ERROR),
+            out_msg->GetErrorCode()->reason());
+}
+
+// Tests handling of ICE binding requests with missing or incorrect usernames.
+TEST_F(PortTest, TestHandleStunMessageBadUsername) {
+  auto port = CreateTestPort(kLocalAddr2, "rfrag", "rpass");
+
+  std::unique_ptr<IceMessage> in_msg, out_msg;
+  auto buf = std::make_unique<ByteBufferWriter>();
+  rtc::SocketAddress addr(kLocalAddr1);
+  std::string username;
+
+  // BINDING-REQUEST with no username.
+  in_msg = CreateStunMessage(STUN_BINDING_REQUEST);
+  in_msg->AddMessageIntegrity("rpass");
+  in_msg->AddFingerprint();
+  WriteStunMessage(*in_msg, buf.get());
+  EXPECT_TRUE(port->GetStunMessage(buf->Data(), buf->Length(), addr, &out_msg,
+                                   &username));
+  EXPECT_TRUE(out_msg.get() == NULL);
+  EXPECT_EQ("", username);
+  EXPECT_EQ(STUN_ERROR_BAD_REQUEST, port->last_stun_error_code());
+
+  // BINDING-REQUEST with empty username.
+  in_msg = CreateStunMessageWithUsername(STUN_BINDING_REQUEST, "");
+  in_msg->AddMessageIntegrity("rpass");
+  in_msg->AddFingerprint();
+  WriteStunMessage(*in_msg, buf.get());
+  EXPECT_TRUE(port->GetStunMessage(buf->Data(), buf->Length(), addr, &out_msg,
+                                   &username));
+  EXPECT_TRUE(out_msg.get() == NULL);
+  EXPECT_EQ("", username);
+  EXPECT_EQ(STUN_ERROR_UNAUTHORIZED, port->last_stun_error_code());
+
+  // BINDING-REQUEST with too-short username.
+  in_msg = CreateStunMessageWithUsername(STUN_BINDING_REQUEST, "rfra");
+  in_msg->AddMessageIntegrity("rpass");
+  in_msg->AddFingerprint();
+  WriteStunMessage(*in_msg, buf.get());
+  EXPECT_TRUE(port->GetStunMessage(buf->Data(), buf->Length(), addr, &out_msg,
+                                   &username));
+  EXPECT_TRUE(out_msg.get() == NULL);
+  EXPECT_EQ("", username);
+  EXPECT_EQ(STUN_ERROR_UNAUTHORIZED, port->last_stun_error_code());
+
+  // BINDING-REQUEST with reversed username.
+  in_msg = CreateStunMessageWithUsername(STUN_BINDING_REQUEST, "lfrag:rfrag");
+  in_msg->AddMessageIntegrity("rpass");
+  in_msg->AddFingerprint();
+  WriteStunMessage(*in_msg, buf.get());
+  EXPECT_TRUE(port->GetStunMessage(buf->Data(), buf->Length(), addr, &out_msg,
+                                   &username));
+  EXPECT_TRUE(out_msg.get() == NULL);
+  EXPECT_EQ("", username);
+  EXPECT_EQ(STUN_ERROR_UNAUTHORIZED, port->last_stun_error_code());
+
+  // BINDING-REQUEST with garbage username.
+  in_msg = CreateStunMessageWithUsername(STUN_BINDING_REQUEST, "abcd:efgh");
+  in_msg->AddMessageIntegrity("rpass");
+  in_msg->AddFingerprint();
+  WriteStunMessage(*in_msg, buf.get());
+  EXPECT_TRUE(port->GetStunMessage(buf->Data(), buf->Length(), addr, &out_msg,
+                                   &username));
+  EXPECT_TRUE(out_msg.get() == NULL);
+  EXPECT_EQ("", username);
+  EXPECT_EQ(STUN_ERROR_UNAUTHORIZED, port->last_stun_error_code());
+}
+
+// Test handling STUN messages with missing or malformed M-I.
+TEST_F(PortTest, TestHandleStunMessageBadMessageIntegrity) {
+  // Our port will act as the "remote" port.
+  auto port = CreateTestPort(kLocalAddr2, "rfrag", "rpass");
+
+  std::unique_ptr<IceMessage> in_msg, out_msg;
+  auto buf = std::make_unique<ByteBufferWriter>();
+  rtc::SocketAddress addr(kLocalAddr1);
+  std::string username;
+
+  // BINDING-REQUEST from local to remote with valid ICE username and
+  // FINGERPRINT, but no MESSAGE-INTEGRITY.
+  in_msg = CreateStunMessageWithUsername(STUN_BINDING_REQUEST, "rfrag:lfrag");
+  in_msg->AddFingerprint();
+  WriteStunMessage(*in_msg, buf.get());
+  EXPECT_TRUE(port->GetStunMessage(buf->Data(), buf->Length(), addr, &out_msg,
+                                   &username));
+  EXPECT_TRUE(out_msg.get() == NULL);
+  EXPECT_EQ("", username);
+  EXPECT_EQ(STUN_ERROR_BAD_REQUEST, port->last_stun_error_code());
+
+  // BINDING-REQUEST from local to remote with valid ICE username and
+  // FINGERPRINT, but invalid MESSAGE-INTEGRITY.
+  in_msg = CreateStunMessageWithUsername(STUN_BINDING_REQUEST, "rfrag:lfrag");
+  in_msg->AddMessageIntegrity("invalid");
+  in_msg->AddFingerprint();
+  WriteStunMessage(*in_msg, buf.get());
+  EXPECT_TRUE(port->GetStunMessage(buf->Data(), buf->Length(), addr, &out_msg,
+                                   &username));
+  EXPECT_TRUE(out_msg.get() == NULL);
+  EXPECT_EQ("", username);
+  EXPECT_EQ(STUN_ERROR_UNAUTHORIZED, port->last_stun_error_code());
+
+  // TODO(?): BINDING-RESPONSES and BINDING-ERROR-RESPONSES are checked
+  // by the Connection, not the Port, since they require the remote username.
+  // Change this test to pass in data via Connection::OnReadPacket instead.
+}
+
+// Test handling STUN messages with missing or malformed FINGERPRINT.
+TEST_F(PortTest, TestHandleStunMessageBadFingerprint) {
+  // Our port will act as the "remote" port.
+  auto port = CreateTestPort(kLocalAddr2, "rfrag", "rpass");
+
+  std::unique_ptr<IceMessage> in_msg, out_msg;
+  auto buf = std::make_unique<ByteBufferWriter>();
+  rtc::SocketAddress addr(kLocalAddr1);
+  std::string username;
+
+  // BINDING-REQUEST from local to remote with valid ICE username and
+  // MESSAGE-INTEGRITY, but no FINGERPRINT; GetStunMessage should fail.
+  in_msg = CreateStunMessageWithUsername(STUN_BINDING_REQUEST, "rfrag:lfrag");
+  in_msg->AddMessageIntegrity("rpass");
+  WriteStunMessage(*in_msg, buf.get());
+  EXPECT_FALSE(port->GetStunMessage(buf->Data(), buf->Length(), addr, &out_msg,
+                                    &username));
+  EXPECT_EQ(0, port->last_stun_error_code());
+
+  // Now, add a fingerprint, but munge the message so it's not valid.
+  in_msg->AddFingerprint();
+  in_msg->SetTransactionIdForTesting("TESTTESTBADD");
+  WriteStunMessage(*in_msg, buf.get());
+  EXPECT_FALSE(port->GetStunMessage(buf->Data(), buf->Length(), addr, &out_msg,
+                                    &username));
+  EXPECT_EQ(0, port->last_stun_error_code());
+
+  // Valid BINDING-RESPONSE, except no FINGERPRINT.
+  in_msg = CreateStunMessage(STUN_BINDING_RESPONSE);
+  in_msg->AddAttribute(std::make_unique<StunXorAddressAttribute>(
+      STUN_ATTR_XOR_MAPPED_ADDRESS, kLocalAddr2));
+  in_msg->AddMessageIntegrity("rpass");
+  WriteStunMessage(*in_msg, buf.get());
+  EXPECT_FALSE(port->GetStunMessage(buf->Data(), buf->Length(), addr, &out_msg,
+                                    &username));
+  EXPECT_EQ(0, port->last_stun_error_code());
+
+  // Now, add a fingerprint, but munge the message so it's not valid.
+  in_msg->AddFingerprint();
+  in_msg->SetTransactionIdForTesting("TESTTESTBADD");
+  WriteStunMessage(*in_msg, buf.get());
+  EXPECT_FALSE(port->GetStunMessage(buf->Data(), buf->Length(), addr, &out_msg,
+                                    &username));
+  EXPECT_EQ(0, port->last_stun_error_code());
+
+  // Valid BINDING-ERROR-RESPONSE, except no FINGERPRINT.
+  in_msg = CreateStunMessage(STUN_BINDING_ERROR_RESPONSE);
+  in_msg->AddAttribute(std::make_unique<StunErrorCodeAttribute>(
+      STUN_ATTR_ERROR_CODE, STUN_ERROR_SERVER_ERROR,
+      STUN_ERROR_REASON_SERVER_ERROR));
+  in_msg->AddMessageIntegrity("rpass");
+  WriteStunMessage(*in_msg, buf.get());
+  EXPECT_FALSE(port->GetStunMessage(buf->Data(), buf->Length(), addr, &out_msg,
+                                    &username));
+  EXPECT_EQ(0, port->last_stun_error_code());
+
+  // Now, add a fingerprint, but munge the message so it's not valid.
+  in_msg->AddFingerprint();
+  in_msg->SetTransactionIdForTesting("TESTTESTBADD");
+  WriteStunMessage(*in_msg, buf.get());
+  EXPECT_FALSE(port->GetStunMessage(buf->Data(), buf->Length(), addr, &out_msg,
+                                    &username));
+  EXPECT_EQ(0, port->last_stun_error_code());
+}
+
+// Test handling a STUN message with unknown attributes in the
+// "comprehension-required" range. Should respond with an error with the
+// unknown attributes' IDs.
+TEST_F(PortTest,
+       TestHandleStunRequestWithUnknownComprehensionRequiredAttribute) {
+  // Our port will act as the "remote" port.
+  std::unique_ptr<TestPort> port(CreateTestPort(kLocalAddr2, "rfrag", "rpass"));
+
+  std::unique_ptr<IceMessage> in_msg, out_msg;
+  auto buf = std::make_unique<ByteBufferWriter>();
+  rtc::SocketAddress addr(kLocalAddr1);
+  std::string username;
+
+  // Build ordinary message with valid ufrag/pass.
+  in_msg = CreateStunMessageWithUsername(STUN_BINDING_REQUEST, "rfrag:lfrag");
+  in_msg->AddMessageIntegrity("rpass");
+  // Add a couple attributes with ID in comprehension-required range.
+  in_msg->AddAttribute(StunAttribute::CreateUInt32(0x7777));
+  in_msg->AddAttribute(StunAttribute::CreateUInt32(0x4567));
+  // ... And one outside the range.
+  in_msg->AddAttribute(StunAttribute::CreateUInt32(0xdead));
+  in_msg->AddFingerprint();
+  WriteStunMessage(*in_msg, buf.get());
+  ASSERT_TRUE(port->GetStunMessage(buf->Data(), buf->Length(), addr, &out_msg,
+                                   &username));
+  IceMessage* error_response = port->last_stun_msg();
+  ASSERT_NE(nullptr, error_response);
+
+  // Verify that the "unknown attribute" error response has the right error
+  // code, and includes an attribute that lists out the unrecognized attribute
+  // types.
+  EXPECT_EQ(STUN_ERROR_UNKNOWN_ATTRIBUTE, error_response->GetErrorCodeValue());
+  const StunUInt16ListAttribute* unknown_attributes =
+      error_response->GetUnknownAttributes();
+  ASSERT_NE(nullptr, unknown_attributes);
+  ASSERT_EQ(2u, unknown_attributes->Size());
+  EXPECT_EQ(0x7777, unknown_attributes->GetType(0));
+  EXPECT_EQ(0x4567, unknown_attributes->GetType(1));
+}
+
+// Similar to the above, but with a response instead of a request. In this
+// case the response should just be ignored and transaction treated is failed.
+TEST_F(PortTest,
+       TestHandleStunResponseWithUnknownComprehensionRequiredAttribute) {
+  // Generic setup.
+  auto lport = CreateTestPort(kLocalAddr1, "lfrag", "lpass",
+                              cricket::ICEROLE_CONTROLLING, kTiebreakerDefault);
+  auto rport = CreateTestPort(kLocalAddr2, "rfrag", "rpass",
+                              cricket::ICEROLE_CONTROLLED, kTiebreakerDefault);
+  lport->PrepareAddress();
+  rport->PrepareAddress();
+  ASSERT_FALSE(lport->Candidates().empty());
+  ASSERT_FALSE(rport->Candidates().empty());
+  Connection* lconn =
+      lport->CreateConnection(rport->Candidates()[0], Port::ORIGIN_MESSAGE);
+  Connection* rconn =
+      rport->CreateConnection(lport->Candidates()[0], Port::ORIGIN_MESSAGE);
+
+  // Send request.
+  lconn->Ping(0);
+  ASSERT_TRUE_WAIT(lport->last_stun_msg() != NULL, kDefaultTimeout);
+  rconn->OnReadPacket(lport->last_stun_buf()->data<char>(),
+                      lport->last_stun_buf()->size(), /* packet_time_us */ -1);
+
+  // Intercept request and add comprehension required attribute.
+  ASSERT_TRUE_WAIT(rport->last_stun_msg() != NULL, kDefaultTimeout);
+  auto modified_response = rport->last_stun_msg()->Clone();
+  modified_response->AddAttribute(StunAttribute::CreateUInt32(0x7777));
+  modified_response->RemoveAttribute(STUN_ATTR_FINGERPRINT);
+  modified_response->AddFingerprint();
+  ByteBufferWriter buf;
+  WriteStunMessage(*modified_response, &buf);
+  lconn->OnReadPacket(buf.Data(), buf.Length(), /* packet_time_us */ -1);
+  // Response should have been ignored, leaving us unwritable still.
+  EXPECT_FALSE(lconn->writable());
+}
+
+// Similar to the above, but with an indication. As with a response, it should
+// just be ignored.
+TEST_F(PortTest,
+       TestHandleStunIndicationWithUnknownComprehensionRequiredAttribute) {
+  // Generic set up.
+  auto lport = CreateTestPort(kLocalAddr2, "lfrag", "lpass",
+                              cricket::ICEROLE_CONTROLLING, kTiebreakerDefault);
+  auto rport = CreateTestPort(kLocalAddr2, "rfrag", "rpass",
+                              cricket::ICEROLE_CONTROLLED, kTiebreakerDefault);
+  lport->PrepareAddress();
+  rport->PrepareAddress();
+  ASSERT_FALSE(lport->Candidates().empty());
+  ASSERT_FALSE(rport->Candidates().empty());
+  Connection* lconn =
+      lport->CreateConnection(rport->Candidates()[0], Port::ORIGIN_MESSAGE);
+
+  // Generate indication with comprehension required attribute and verify it
+  // doesn't update last_ping_received.
+  auto in_msg = CreateStunMessage(STUN_BINDING_INDICATION);
+  in_msg->AddAttribute(StunAttribute::CreateUInt32(0x7777));
+  in_msg->AddFingerprint();
+  ByteBufferWriter buf;
+  WriteStunMessage(*in_msg, &buf);
+  lconn->OnReadPacket(buf.Data(), buf.Length(), /* packet_time_us */ -1);
+  EXPECT_EQ(0u, lconn->last_ping_received());
+}
+
+// Test handling of STUN binding indication messages . STUN binding
+// indications are allowed only to the connection which is in read mode.
+TEST_F(PortTest, TestHandleStunBindingIndication) {
+  auto lport = CreateTestPort(kLocalAddr2, "lfrag", "lpass",
+                              cricket::ICEROLE_CONTROLLING, kTiebreaker1);
+
+  // Verifying encoding and decoding STUN indication message.
+  std::unique_ptr<IceMessage> in_msg, out_msg;
+  std::unique_ptr<ByteBufferWriter> buf(new ByteBufferWriter());
+  rtc::SocketAddress addr(kLocalAddr1);
+  std::string username;
+
+  in_msg = CreateStunMessage(STUN_BINDING_INDICATION);
+  in_msg->AddFingerprint();
+  WriteStunMessage(*in_msg, buf.get());
+  EXPECT_TRUE(lport->GetStunMessage(buf->Data(), buf->Length(), addr, &out_msg,
+                                    &username));
+  EXPECT_TRUE(out_msg.get() != NULL);
+  EXPECT_EQ(out_msg->type(), STUN_BINDING_INDICATION);
+  EXPECT_EQ("", username);
+
+  // Verify connection can handle STUN indication and updates
+  // last_ping_received.
+  auto rport = CreateTestPort(kLocalAddr2, "rfrag", "rpass");
+  rport->SetIceRole(cricket::ICEROLE_CONTROLLED);
+  rport->SetIceTiebreaker(kTiebreaker2);
+
+  lport->PrepareAddress();
+  rport->PrepareAddress();
+  ASSERT_FALSE(lport->Candidates().empty());
+  ASSERT_FALSE(rport->Candidates().empty());
+
+  Connection* lconn =
+      lport->CreateConnection(rport->Candidates()[0], Port::ORIGIN_MESSAGE);
+  Connection* rconn =
+      rport->CreateConnection(lport->Candidates()[0], Port::ORIGIN_MESSAGE);
+  rconn->Ping(0);
+
+  ASSERT_TRUE_WAIT(rport->last_stun_msg() != NULL, kDefaultTimeout);
+  IceMessage* msg = rport->last_stun_msg();
+  EXPECT_EQ(STUN_BINDING_REQUEST, msg->type());
+  // Send rport binding request to lport.
+  lconn->OnReadPacket(rport->last_stun_buf()->data<char>(),
+                      rport->last_stun_buf()->size(), /* packet_time_us */ -1);
+  ASSERT_TRUE_WAIT(lport->last_stun_msg() != NULL, kDefaultTimeout);
+  EXPECT_EQ(STUN_BINDING_RESPONSE, lport->last_stun_msg()->type());
+  int64_t last_ping_received1 = lconn->last_ping_received();
+
+  // Adding a delay of 100ms.
+  rtc::Thread::Current()->ProcessMessages(100);
+  // Pinging lconn using stun indication message.
+  lconn->OnReadPacket(buf->Data(), buf->Length(), /* packet_time_us */ -1);
+  int64_t last_ping_received2 = lconn->last_ping_received();
+  EXPECT_GT(last_ping_received2, last_ping_received1);
+}
+
+TEST_F(PortTest, TestComputeCandidatePriority) {
+  auto port = CreateTestPort(kLocalAddr1, "name", "pass");
+  port->SetIceTiebreaker(kTiebreakerDefault);
+  port->set_type_preference(90);
+  port->set_component(177);
+  port->AddCandidateAddress(SocketAddress("192.168.1.4", 1234));
+  port->AddCandidateAddress(SocketAddress("2001:db8::1234", 1234));
+  port->AddCandidateAddress(SocketAddress("fc12:3456::1234", 1234));
+  port->AddCandidateAddress(SocketAddress("::ffff:192.168.1.4", 1234));
+  port->AddCandidateAddress(SocketAddress("::192.168.1.4", 1234));
+  port->AddCandidateAddress(SocketAddress("2002::1234:5678", 1234));
+  port->AddCandidateAddress(SocketAddress("2001::1234:5678", 1234));
+  port->AddCandidateAddress(SocketAddress("fecf::1234:5678", 1234));
+  port->AddCandidateAddress(SocketAddress("3ffe::1234:5678", 1234));
+  // These should all be:
+  // (90 << 24) | ([rfc3484 pref value] << 8) | (256 - 177)
+  uint32_t expected_priority_v4 = 1509957199U;
+  uint32_t expected_priority_v6 = 1509959759U;
+  uint32_t expected_priority_ula = 1509962319U;
+  uint32_t expected_priority_v4mapped = expected_priority_v4;
+  uint32_t expected_priority_v4compat = 1509949775U;
+  uint32_t expected_priority_6to4 = 1509954639U;
+  uint32_t expected_priority_teredo = 1509952079U;
+  uint32_t expected_priority_sitelocal = 1509949775U;
+  uint32_t expected_priority_6bone = 1509949775U;
+  ASSERT_EQ(expected_priority_v4, port->Candidates()[0].priority());
+  ASSERT_EQ(expected_priority_v6, port->Candidates()[1].priority());
+  ASSERT_EQ(expected_priority_ula, port->Candidates()[2].priority());
+  ASSERT_EQ(expected_priority_v4mapped, port->Candidates()[3].priority());
+  ASSERT_EQ(expected_priority_v4compat, port->Candidates()[4].priority());
+  ASSERT_EQ(expected_priority_6to4, port->Candidates()[5].priority());
+  ASSERT_EQ(expected_priority_teredo, port->Candidates()[6].priority());
+  ASSERT_EQ(expected_priority_sitelocal, port->Candidates()[7].priority());
+  ASSERT_EQ(expected_priority_6bone, port->Candidates()[8].priority());
+}
+
+// In the case of shared socket, one port may be shared by local and stun.
+// Test that candidates with different types will have different foundation.
+TEST_F(PortTest, TestFoundation) {
+  auto testport = CreateTestPort(kLocalAddr1, "name", "pass");
+  testport->SetIceTiebreaker(kTiebreakerDefault);
+  testport->AddCandidateAddress(kLocalAddr1, kLocalAddr1, LOCAL_PORT_TYPE,
+                                cricket::ICE_TYPE_PREFERENCE_HOST, false);
+  testport->AddCandidateAddress(kLocalAddr2, kLocalAddr1, STUN_PORT_TYPE,
+                                cricket::ICE_TYPE_PREFERENCE_SRFLX, true);
+  EXPECT_NE(testport->Candidates()[0].foundation(),
+            testport->Candidates()[1].foundation());
+}
+
+// This test verifies the foundation of different types of ICE candidates.
+TEST_F(PortTest, TestCandidateFoundation) {
+  std::unique_ptr<rtc::NATServer> nat_server(
+      CreateNatServer(kNatAddr1, NAT_OPEN_CONE));
+  auto udpport1 = CreateUdpPort(kLocalAddr1);
+  udpport1->PrepareAddress();
+  auto udpport2 = CreateUdpPort(kLocalAddr1);
+  udpport2->PrepareAddress();
+  EXPECT_EQ(udpport1->Candidates()[0].foundation(),
+            udpport2->Candidates()[0].foundation());
+  auto tcpport1 = CreateTcpPort(kLocalAddr1);
+  tcpport1->PrepareAddress();
+  auto tcpport2 = CreateTcpPort(kLocalAddr1);
+  tcpport2->PrepareAddress();
+  EXPECT_EQ(tcpport1->Candidates()[0].foundation(),
+            tcpport2->Candidates()[0].foundation());
+  auto stunport = CreateStunPort(kLocalAddr1, nat_socket_factory1());
+  stunport->PrepareAddress();
+  ASSERT_EQ_WAIT(1U, stunport->Candidates().size(), kDefaultTimeout);
+  EXPECT_NE(tcpport1->Candidates()[0].foundation(),
+            stunport->Candidates()[0].foundation());
+  EXPECT_NE(tcpport2->Candidates()[0].foundation(),
+            stunport->Candidates()[0].foundation());
+  EXPECT_NE(udpport1->Candidates()[0].foundation(),
+            stunport->Candidates()[0].foundation());
+  EXPECT_NE(udpport2->Candidates()[0].foundation(),
+            stunport->Candidates()[0].foundation());
+  // Verifying TURN candidate foundation.
+  auto turnport1 =
+      CreateTurnPort(kLocalAddr1, nat_socket_factory1(), PROTO_UDP, PROTO_UDP);
+  turnport1->PrepareAddress();
+  ASSERT_EQ_WAIT(1U, turnport1->Candidates().size(), kDefaultTimeout);
+  EXPECT_NE(udpport1->Candidates()[0].foundation(),
+            turnport1->Candidates()[0].foundation());
+  EXPECT_NE(udpport2->Candidates()[0].foundation(),
+            turnport1->Candidates()[0].foundation());
+  EXPECT_NE(stunport->Candidates()[0].foundation(),
+            turnport1->Candidates()[0].foundation());
+  auto turnport2 =
+      CreateTurnPort(kLocalAddr1, nat_socket_factory1(), PROTO_UDP, PROTO_UDP);
+  turnport2->PrepareAddress();
+  ASSERT_EQ_WAIT(1U, turnport2->Candidates().size(), kDefaultTimeout);
+  EXPECT_EQ(turnport1->Candidates()[0].foundation(),
+            turnport2->Candidates()[0].foundation());
+
+  // Running a second turn server, to get different base IP address.
+  SocketAddress kTurnUdpIntAddr2("99.99.98.4", STUN_SERVER_PORT);
+  SocketAddress kTurnUdpExtAddr2("99.99.98.5", 0);
+  TestTurnServer turn_server2(rtc::Thread::Current(), vss(), kTurnUdpIntAddr2,
+                              kTurnUdpExtAddr2);
+  auto turnport3 = CreateTurnPort(kLocalAddr1, nat_socket_factory1(), PROTO_UDP,
+                                  PROTO_UDP, kTurnUdpIntAddr2);
+  turnport3->PrepareAddress();
+  ASSERT_EQ_WAIT(1U, turnport3->Candidates().size(), kDefaultTimeout);
+  EXPECT_NE(turnport3->Candidates()[0].foundation(),
+            turnport2->Candidates()[0].foundation());
+
+  // Start a TCP turn server, and check that two turn candidates have
+  // different foundations if their relay protocols are different.
+  TestTurnServer turn_server3(rtc::Thread::Current(), vss(), kTurnTcpIntAddr,
+                              kTurnUdpExtAddr, PROTO_TCP);
+  auto turnport4 =
+      CreateTurnPort(kLocalAddr1, nat_socket_factory1(), PROTO_TCP, PROTO_UDP);
+  turnport4->PrepareAddress();
+  ASSERT_EQ_WAIT(1U, turnport4->Candidates().size(), kDefaultTimeout);
+  EXPECT_NE(turnport2->Candidates()[0].foundation(),
+            turnport4->Candidates()[0].foundation());
+}
+
+// This test verifies the related addresses of different types of
+// ICE candidates.
+TEST_F(PortTest, TestCandidateRelatedAddress) {
+  auto nat_server = CreateNatServer(kNatAddr1, NAT_OPEN_CONE);
+  auto udpport = CreateUdpPort(kLocalAddr1);
+  udpport->PrepareAddress();
+  // For UDPPort, related address will be empty.
+  EXPECT_TRUE(udpport->Candidates()[0].related_address().IsNil());
+  // Testing related address for stun candidates.
+  // For stun candidate related address must be equal to the base
+  // socket address.
+  auto stunport = CreateStunPort(kLocalAddr1, nat_socket_factory1());
+  stunport->PrepareAddress();
+  ASSERT_EQ_WAIT(1U, stunport->Candidates().size(), kDefaultTimeout);
+  // Check STUN candidate address.
+  EXPECT_EQ(stunport->Candidates()[0].address().ipaddr(), kNatAddr1.ipaddr());
+  // Check STUN candidate related address.
+  EXPECT_EQ(stunport->Candidates()[0].related_address(),
+            stunport->GetLocalAddress());
+  // Verifying the related address for TURN candidate.
+  // For TURN related address must be equal to the mapped address.
+  auto turnport =
+      CreateTurnPort(kLocalAddr1, nat_socket_factory1(), PROTO_UDP, PROTO_UDP);
+  turnport->PrepareAddress();
+  ASSERT_EQ_WAIT(1U, turnport->Candidates().size(), kDefaultTimeout);
+  EXPECT_EQ(kTurnUdpExtAddr.ipaddr(),
+            turnport->Candidates()[0].address().ipaddr());
+  EXPECT_EQ(kNatAddr1.ipaddr(),
+            turnport->Candidates()[0].related_address().ipaddr());
+}
+
+// Test priority value overflow handling when preference is set to 3.
+TEST_F(PortTest, TestCandidatePriority) {
+  cricket::Candidate cand1;
+  cand1.set_priority(3);
+  cricket::Candidate cand2;
+  cand2.set_priority(1);
+  EXPECT_TRUE(cand1.priority() > cand2.priority());
+}
+
+// Test the Connection priority is calculated correctly.
+TEST_F(PortTest, TestConnectionPriority) {
+  auto lport = CreateTestPort(kLocalAddr1, "lfrag", "lpass");
+  lport->SetIceTiebreaker(kTiebreakerDefault);
+  lport->set_type_preference(cricket::ICE_TYPE_PREFERENCE_HOST);
+
+  auto rport = CreateTestPort(kLocalAddr2, "rfrag", "rpass");
+  rport->SetIceTiebreaker(kTiebreakerDefault);
+  rport->set_type_preference(cricket::ICE_TYPE_PREFERENCE_RELAY_UDP);
+  lport->set_component(123);
+  lport->AddCandidateAddress(SocketAddress("192.168.1.4", 1234));
+  rport->set_component(23);
+  rport->AddCandidateAddress(SocketAddress("10.1.1.100", 1234));
+
+  EXPECT_EQ(0x7E001E85U, lport->Candidates()[0].priority());
+  EXPECT_EQ(0x2001EE9U, rport->Candidates()[0].priority());
+
+  // RFC 5245
+  // pair priority = 2^32*MIN(G,D) + 2*MAX(G,D) + (G>D?1:0)
+  lport->SetIceRole(cricket::ICEROLE_CONTROLLING);
+  rport->SetIceRole(cricket::ICEROLE_CONTROLLED);
+  Connection* lconn =
+      lport->CreateConnection(rport->Candidates()[0], Port::ORIGIN_MESSAGE);
+#if defined(WEBRTC_WIN)
+  EXPECT_EQ(0x2001EE9FC003D0BU, lconn->priority());
+#else
+  EXPECT_EQ(0x2001EE9FC003D0BLLU, lconn->priority());
+#endif
+
+  lport->SetIceRole(cricket::ICEROLE_CONTROLLED);
+  rport->SetIceRole(cricket::ICEROLE_CONTROLLING);
+  Connection* rconn =
+      rport->CreateConnection(lport->Candidates()[0], Port::ORIGIN_MESSAGE);
+#if defined(WEBRTC_WIN)
+  EXPECT_EQ(0x2001EE9FC003D0AU, rconn->priority());
+#else
+  EXPECT_EQ(0x2001EE9FC003D0ALLU, rconn->priority());
+#endif
+}
+
+// Note that UpdateState takes into account the estimated RTT, and the
+// correctness of using `kMaxExpectedSimulatedRtt` as an upper bound of RTT in
+// the following tests depends on the link rate and the delay distriubtion
+// configured in VirtualSocketServer::AddPacketToNetwork. The tests below use
+// the default setup where the RTT is deterministically one, which generates an
+// estimate given by `MINIMUM_RTT` = 100.
+TEST_F(PortTest, TestWritableState) {
+  rtc::ScopedFakeClock clock;
+  auto port1 = CreateUdpPort(kLocalAddr1);
+  port1->SetIceRole(cricket::ICEROLE_CONTROLLING);
+  auto port2 = CreateUdpPort(kLocalAddr2);
+  port2->SetIceRole(cricket::ICEROLE_CONTROLLED);
+
+  // Set up channels.
+  TestChannel ch1(std::move(port1));
+  TestChannel ch2(std::move(port2));
+
+  // Acquire addresses.
+  ch1.Start();
+  ch2.Start();
+  ASSERT_EQ_SIMULATED_WAIT(1, ch1.complete_count(), kDefaultTimeout, clock);
+  ASSERT_EQ_SIMULATED_WAIT(1, ch2.complete_count(), kDefaultTimeout, clock);
+
+  // Send a ping from src to dst.
+  ch1.CreateConnection(GetCandidate(ch2.port()));
+  ASSERT_TRUE(ch1.conn() != NULL);
+  EXPECT_EQ(Connection::STATE_WRITE_INIT, ch1.conn()->write_state());
+  // for TCP connect
+  EXPECT_TRUE_SIMULATED_WAIT(ch1.conn()->connected(), kDefaultTimeout, clock);
+  ch1.Ping();
+  SIMULATED_WAIT(!ch2.remote_address().IsNil(), kShortTimeout, clock);
+
+  // Data should be sendable before the connection is accepted.
+  char data[] = "abcd";
+  int data_size = arraysize(data);
+  rtc::PacketOptions options;
+  EXPECT_EQ(data_size, ch1.conn()->Send(data, data_size, options));
+
+  // Accept the connection to return the binding response, transition to
+  // writable, and allow data to be sent.
+  ch2.AcceptConnection(GetCandidate(ch1.port()));
+  EXPECT_EQ_SIMULATED_WAIT(Connection::STATE_WRITABLE,
+                           ch1.conn()->write_state(), kDefaultTimeout, clock);
+  EXPECT_EQ(data_size, ch1.conn()->Send(data, data_size, options));
+
+  // Ask the connection to update state as if enough time has passed to lose
+  // full writability and 5 pings went unresponded to. We'll accomplish the
+  // latter by sending pings but not pumping messages.
+  for (uint32_t i = 1; i <= CONNECTION_WRITE_CONNECT_FAILURES; ++i) {
+    ch1.Ping(i);
+  }
+  int unreliable_timeout_delay =
+      CONNECTION_WRITE_CONNECT_TIMEOUT + kMaxExpectedSimulatedRtt;
+  ch1.conn()->UpdateState(unreliable_timeout_delay);
+  EXPECT_EQ(Connection::STATE_WRITE_UNRELIABLE, ch1.conn()->write_state());
+
+  // Data should be able to be sent in this state.
+  EXPECT_EQ(data_size, ch1.conn()->Send(data, data_size, options));
+
+  // And now allow the other side to process the pings and send binding
+  // responses.
+  EXPECT_EQ_SIMULATED_WAIT(Connection::STATE_WRITABLE,
+                           ch1.conn()->write_state(), kDefaultTimeout, clock);
+  // Wait long enough for a full timeout (past however long we've already
+  // waited).
+  for (uint32_t i = 1; i <= CONNECTION_WRITE_CONNECT_FAILURES; ++i) {
+    ch1.Ping(unreliable_timeout_delay + i);
+  }
+  ch1.conn()->UpdateState(unreliable_timeout_delay + CONNECTION_WRITE_TIMEOUT +
+                          kMaxExpectedSimulatedRtt);
+  EXPECT_EQ(Connection::STATE_WRITE_TIMEOUT, ch1.conn()->write_state());
+
+  // Even if the connection has timed out, the Connection shouldn't block
+  // the sending of data.
+  EXPECT_EQ(data_size, ch1.conn()->Send(data, data_size, options));
+
+  ch1.Stop();
+  ch2.Stop();
+}
+
+// Test writability states using the configured threshold value to replace
+// the default value given by `CONNECTION_WRITE_CONNECT_TIMEOUT` and
+// `CONNECTION_WRITE_CONNECT_FAILURES`.
+TEST_F(PortTest, TestWritableStateWithConfiguredThreshold) {
+  rtc::ScopedFakeClock clock;
+  auto port1 = CreateUdpPort(kLocalAddr1);
+  port1->SetIceRole(cricket::ICEROLE_CONTROLLING);
+  auto port2 = CreateUdpPort(kLocalAddr2);
+  port2->SetIceRole(cricket::ICEROLE_CONTROLLED);
+
+  // Set up channels.
+  TestChannel ch1(std::move(port1));
+  TestChannel ch2(std::move(port2));
+
+  // Acquire addresses.
+  ch1.Start();
+  ch2.Start();
+  ASSERT_EQ_SIMULATED_WAIT(1, ch1.complete_count(), kDefaultTimeout, clock);
+  ASSERT_EQ_SIMULATED_WAIT(1, ch2.complete_count(), kDefaultTimeout, clock);
+
+  // Send a ping from src to dst.
+  ch1.CreateConnection(GetCandidate(ch2.port()));
+  ASSERT_TRUE(ch1.conn() != NULL);
+  ch1.Ping();
+  SIMULATED_WAIT(!ch2.remote_address().IsNil(), kShortTimeout, clock);
+
+  // Accept the connection to return the binding response, transition to
+  // writable, and allow data to be sent.
+  ch2.AcceptConnection(GetCandidate(ch1.port()));
+  EXPECT_EQ_SIMULATED_WAIT(Connection::STATE_WRITABLE,
+                           ch1.conn()->write_state(), kDefaultTimeout, clock);
+
+  ch1.conn()->set_unwritable_timeout(1000);
+  ch1.conn()->set_unwritable_min_checks(3);
+  // Send two checks.
+  ch1.Ping(1);
+  ch1.Ping(2);
+  // We have not reached the timeout nor have we sent the minimum number of
+  // checks to change the state to Unreliable.
+  ch1.conn()->UpdateState(999);
+  EXPECT_EQ(Connection::STATE_WRITABLE, ch1.conn()->write_state());
+  // We have not sent the minimum number of checks without responses.
+  ch1.conn()->UpdateState(1000 + kMaxExpectedSimulatedRtt);
+  EXPECT_EQ(Connection::STATE_WRITABLE, ch1.conn()->write_state());
+  // Last ping after which the candidate pair should become Unreliable after
+  // timeout.
+  ch1.Ping(3);
+  // We have not reached the timeout.
+  ch1.conn()->UpdateState(999);
+  EXPECT_EQ(Connection::STATE_WRITABLE, ch1.conn()->write_state());
+  // We should be in the state Unreliable now.
+  ch1.conn()->UpdateState(1000 + kMaxExpectedSimulatedRtt);
+  EXPECT_EQ(Connection::STATE_WRITE_UNRELIABLE, ch1.conn()->write_state());
+
+  ch1.Stop();
+  ch2.Stop();
+}
+
+TEST_F(PortTest, TestTimeoutForNeverWritable) {
+  auto port1 = CreateUdpPort(kLocalAddr1);
+  port1->SetIceRole(cricket::ICEROLE_CONTROLLING);
+  auto port2 = CreateUdpPort(kLocalAddr2);
+  port2->SetIceRole(cricket::ICEROLE_CONTROLLED);
+
+  // Set up channels.
+  TestChannel ch1(std::move(port1));
+  TestChannel ch2(std::move(port2));
+
+  // Acquire addresses.
+  ch1.Start();
+  ch2.Start();
+
+  ch1.CreateConnection(GetCandidate(ch2.port()));
+  ASSERT_TRUE(ch1.conn() != NULL);
+  EXPECT_EQ(Connection::STATE_WRITE_INIT, ch1.conn()->write_state());
+
+  // Attempt to go directly to write timeout.
+  for (uint32_t i = 1; i <= CONNECTION_WRITE_CONNECT_FAILURES; ++i) {
+    ch1.Ping(i);
+  }
+  ch1.conn()->UpdateState(CONNECTION_WRITE_TIMEOUT + kMaxExpectedSimulatedRtt);
+  EXPECT_EQ(Connection::STATE_WRITE_TIMEOUT, ch1.conn()->write_state());
+}
+
+// This test verifies the connection setup between ICEMODE_FULL
+// and ICEMODE_LITE.
+// In this test `ch1` behaves like FULL mode client and we have created
+// port which responds to the ping message just like LITE client.
+TEST_F(PortTest, TestIceLiteConnectivity) {
+  auto ice_full_port =
+      CreateTestPort(kLocalAddr1, "lfrag", "lpass",
+                     cricket::ICEROLE_CONTROLLING, kTiebreaker1);
+  auto* ice_full_port_ptr = ice_full_port.get();
+
+  auto ice_lite_port = CreateTestPort(
+      kLocalAddr2, "rfrag", "rpass", cricket::ICEROLE_CONTROLLED, kTiebreaker2);
+  // Setup TestChannel. This behaves like FULL mode client.
+  TestChannel ch1(std::move(ice_full_port));
+  ch1.SetIceMode(ICEMODE_FULL);
+
+  // Start gathering candidates.
+  ch1.Start();
+  ice_lite_port->PrepareAddress();
+
+  ASSERT_EQ_WAIT(1, ch1.complete_count(), kDefaultTimeout);
+  ASSERT_FALSE(ice_lite_port->Candidates().empty());
+
+  ch1.CreateConnection(GetCandidate(ice_lite_port.get()));
+  ASSERT_TRUE(ch1.conn() != NULL);
+  EXPECT_EQ(Connection::STATE_WRITE_INIT, ch1.conn()->write_state());
+
+  // Send ping from full mode client.
+  // This ping must not have USE_CANDIDATE_ATTR.
+  ch1.Ping();
+
+  // Verify stun ping is without USE_CANDIDATE_ATTR. Getting message directly
+  // from port.
+  ASSERT_TRUE_WAIT(ice_full_port_ptr->last_stun_msg() != NULL, kDefaultTimeout);
+  IceMessage* msg = ice_full_port_ptr->last_stun_msg();
+  EXPECT_TRUE(msg->GetByteString(STUN_ATTR_USE_CANDIDATE) == NULL);
+
+  // Respond with a BINDING-RESPONSE from litemode client.
+  // NOTE: Ideally we should't create connection at this stage from lite
+  // port, as it should be done only after receiving ping with USE_CANDIDATE.
+  // But we need a connection to send a response message.
+  auto* con = ice_lite_port->CreateConnection(
+      ice_full_port_ptr->Candidates()[0], cricket::Port::ORIGIN_MESSAGE);
+  std::unique_ptr<IceMessage> request = CopyStunMessage(*msg);
+  con->SendStunBindingResponse(request.get());
+
+  // Feeding the respone message from litemode to the full mode connection.
+  ch1.conn()->OnReadPacket(ice_lite_port->last_stun_buf()->data<char>(),
+                           ice_lite_port->last_stun_buf()->size(),
+                           /* packet_time_us */ -1);
+  // Verifying full mode connection becomes writable from the response.
+  EXPECT_EQ_WAIT(Connection::STATE_WRITABLE, ch1.conn()->write_state(),
+                 kDefaultTimeout);
+  EXPECT_TRUE_WAIT(ch1.nominated(), kDefaultTimeout);
+
+  // Clear existing stun messsages. Otherwise we will process old stun
+  // message right after we send ping.
+  ice_full_port_ptr->Reset();
+  // Send ping. This must have USE_CANDIDATE_ATTR.
+  ch1.Ping();
+  ASSERT_TRUE_WAIT(ice_full_port_ptr->last_stun_msg() != NULL, kDefaultTimeout);
+  msg = ice_full_port_ptr->last_stun_msg();
+  EXPECT_TRUE(msg->GetByteString(STUN_ATTR_USE_CANDIDATE) != NULL);
+  ch1.Stop();
+}
+
+namespace {
+
+// Utility function for testing goog ping.
+absl::optional<int> GetSupportedGoogPingVersion(const StunMessage* msg) {
+  auto goog_misc = msg->GetUInt16List(STUN_ATTR_GOOG_MISC_INFO);
+  if (goog_misc == nullptr) {
+    return absl::nullopt;
+  }
+
+  if (msg->type() == STUN_BINDING_REQUEST) {
+    if (goog_misc->Size() <
+        static_cast<int>(cricket::IceGoogMiscInfoBindingRequestAttributeIndex::
+                             SUPPORT_GOOG_PING_VERSION)) {
+      return absl::nullopt;
+    }
+
+    return goog_misc->GetType(
+        static_cast<int>(cricket::IceGoogMiscInfoBindingRequestAttributeIndex::
+                             SUPPORT_GOOG_PING_VERSION));
+  }
+
+  if (msg->type() == STUN_BINDING_RESPONSE) {
+    if (goog_misc->Size() <
+        static_cast<int>(cricket::IceGoogMiscInfoBindingResponseAttributeIndex::
+                             SUPPORT_GOOG_PING_VERSION)) {
+      return absl::nullopt;
+    }
+
+    return goog_misc->GetType(
+        static_cast<int>(cricket::IceGoogMiscInfoBindingResponseAttributeIndex::
+                             SUPPORT_GOOG_PING_VERSION));
+  }
+  return absl::nullopt;
+}
+
+}  // namespace
+
+class GoogPingTest
+    : public PortTest,
+      public ::testing::WithParamInterface<std::pair<bool, bool>> {};
+
+// This test verifies the announce/enable on/off behavior
+TEST_P(GoogPingTest, TestGoogPingAnnounceEnable) {
+  IceFieldTrials trials;
+  trials.announce_goog_ping = GetParam().first;
+  trials.enable_goog_ping = GetParam().second;
+  RTC_LOG(LS_INFO) << "Testing combination: "
+                      " announce: "
+                   << trials.announce_goog_ping
+                   << " enable:" << trials.enable_goog_ping;
+
+  auto port1_unique =
+      CreateTestPort(kLocalAddr1, "lfrag", "lpass",
+                     cricket::ICEROLE_CONTROLLING, kTiebreaker1);
+  auto* port1 = port1_unique.get();
+  auto port2 = CreateTestPort(kLocalAddr2, "rfrag", "rpass",
+                              cricket::ICEROLE_CONTROLLED, kTiebreaker2);
+
+  TestChannel ch1(std::move(port1_unique));
+  // Block usage of STUN_ATTR_USE_CANDIDATE so that
+  // ch1.conn() will sent GOOG_PING_REQUEST directly.
+  // This only makes test a bit shorter...
+  ch1.SetIceMode(ICEMODE_LITE);
+  // Start gathering candidates.
+  ch1.Start();
+  port2->PrepareAddress();
+
+  ASSERT_EQ_WAIT(1, ch1.complete_count(), kDefaultTimeout);
+  ASSERT_FALSE(port2->Candidates().empty());
+
+  ch1.CreateConnection(GetCandidate(port2.get()));
+  ASSERT_TRUE(ch1.conn() != NULL);
+  EXPECT_EQ(Connection::STATE_WRITE_INIT, ch1.conn()->write_state());
+  ch1.conn()->SetIceFieldTrials(&trials);
+
+  // Send ping.
+  ch1.Ping();
+
+  ASSERT_TRUE_WAIT(port1->last_stun_msg() != NULL, kDefaultTimeout);
+  const IceMessage* request1 = port1->last_stun_msg();
+
+  ASSERT_EQ(trials.enable_goog_ping,
+            GetSupportedGoogPingVersion(request1) &&
+                GetSupportedGoogPingVersion(request1) >= kGoogPingVersion);
+
+  auto* con = port2->CreateConnection(port1->Candidates()[0],
+                                      cricket::Port::ORIGIN_MESSAGE);
+  con->SetIceFieldTrials(&trials);
+
+  con->SendStunBindingResponse(request1);
+
+  // Then check the response matches the settings.
+  const auto* response = port2->last_stun_msg();
+  EXPECT_EQ(response->type(), STUN_BINDING_RESPONSE);
+  EXPECT_EQ(trials.enable_goog_ping && trials.announce_goog_ping,
+            GetSupportedGoogPingVersion(response) &&
+                GetSupportedGoogPingVersion(response) >= kGoogPingVersion);
+
+  // Feeding the respone message back.
+  ch1.conn()->OnReadPacket(port2->last_stun_buf()->data<char>(),
+                           port2->last_stun_buf()->size(),
+                           /* packet_time_us */ -1);
+
+  port1->Reset();
+  port2->Reset();
+
+  ch1.Ping();
+  ASSERT_TRUE_WAIT(port1->last_stun_msg() != NULL, kDefaultTimeout);
+  const IceMessage* request2 = port1->last_stun_msg();
+
+  // It should be a GOOG_PING if both of these are TRUE
+  if (trials.announce_goog_ping && trials.enable_goog_ping) {
+    ASSERT_EQ(request2->type(), GOOG_PING_REQUEST);
+    con->SendGoogPingResponse(request2);
+  } else {
+    ASSERT_EQ(request2->type(), STUN_BINDING_REQUEST);
+    // If we sent a BINDING with enable, and we got a reply that
+    // didn't contain announce, the next ping should not contain
+    // the enable again.
+    ASSERT_FALSE(GetSupportedGoogPingVersion(request2).has_value());
+    con->SendStunBindingResponse(request2);
+  }
+
+  const auto* response2 = port2->last_stun_msg();
+  ASSERT_TRUE(response2 != nullptr);
+
+  // It should be a GOOG_PING_RESPONSE if both of these are TRUE
+  if (trials.announce_goog_ping && trials.enable_goog_ping) {
+    ASSERT_EQ(response2->type(), GOOG_PING_RESPONSE);
+  } else {
+    ASSERT_EQ(response2->type(), STUN_BINDING_RESPONSE);
+  }
+
+  ch1.Stop();
+}
+
+// This test if a someone send a STUN_BINDING with unsupported version
+// (kGoogPingVersion == 0)
+TEST_F(PortTest, TestGoogPingUnsupportedVersionInStunBinding) {
+  IceFieldTrials trials;
+  trials.announce_goog_ping = true;
+  trials.enable_goog_ping = true;
+
+  auto port1_unique =
+      CreateTestPort(kLocalAddr1, "lfrag", "lpass",
+                     cricket::ICEROLE_CONTROLLING, kTiebreaker1);
+  auto* port1 = port1_unique.get();
+  auto port2 = CreateTestPort(kLocalAddr2, "rfrag", "rpass",
+                              cricket::ICEROLE_CONTROLLED, kTiebreaker2);
+
+  TestChannel ch1(std::move(port1_unique));
+  // Block usage of STUN_ATTR_USE_CANDIDATE so that
+  // ch1.conn() will sent GOOG_PING_REQUEST directly.
+  // This only makes test a bit shorter...
+  ch1.SetIceMode(ICEMODE_LITE);
+  // Start gathering candidates.
+  ch1.Start();
+  port2->PrepareAddress();
+
+  ASSERT_EQ_WAIT(1, ch1.complete_count(), kDefaultTimeout);
+  ASSERT_FALSE(port2->Candidates().empty());
+
+  ch1.CreateConnection(GetCandidate(port2.get()));
+  ASSERT_TRUE(ch1.conn() != NULL);
+  EXPECT_EQ(Connection::STATE_WRITE_INIT, ch1.conn()->write_state());
+  ch1.conn()->SetIceFieldTrials(&trials);
+
+  // Send ping.
+  ch1.Ping();
+
+  ASSERT_TRUE_WAIT(port1->last_stun_msg() != NULL, kDefaultTimeout);
+  const IceMessage* request1 = port1->last_stun_msg();
+
+  ASSERT_TRUE(GetSupportedGoogPingVersion(request1) &&
+              GetSupportedGoogPingVersion(request1) >= kGoogPingVersion);
+
+  // Modify the STUN message request1 to send GetSupportedGoogPingVersion == 0
+  auto modified_request1 = request1->Clone();
+  ASSERT_TRUE(modified_request1->RemoveAttribute(STUN_ATTR_GOOG_MISC_INFO) !=
+              nullptr);
+  ASSERT_TRUE(modified_request1->RemoveAttribute(STUN_ATTR_MESSAGE_INTEGRITY) !=
+              nullptr);
+  {
+    auto list =
+        StunAttribute::CreateUInt16ListAttribute(STUN_ATTR_GOOG_MISC_INFO);
+    list->AddTypeAtIndex(
+        static_cast<uint16_t>(
+            cricket::IceGoogMiscInfoBindingRequestAttributeIndex::
+                SUPPORT_GOOG_PING_VERSION),
+        /* version */ 0);
+    modified_request1->AddAttribute(std::move(list));
+    modified_request1->AddMessageIntegrity("rpass");
+  }
+  auto* con = port2->CreateConnection(port1->Candidates()[0],
+                                      cricket::Port::ORIGIN_MESSAGE);
+  con->SetIceFieldTrials(&trials);
+
+  con->SendStunBindingResponse(modified_request1.get());
+
+  // Then check the response matches the settings.
+  const auto* response = port2->last_stun_msg();
+  EXPECT_EQ(response->type(), STUN_BINDING_RESPONSE);
+  EXPECT_FALSE(GetSupportedGoogPingVersion(response));
+
+  ch1.Stop();
+}
+
+// This test if a someone send a STUN_BINDING_RESPONSE with unsupported version
+// (kGoogPingVersion == 0)
+TEST_F(PortTest, TestGoogPingUnsupportedVersionInStunBindingResponse) {
+  IceFieldTrials trials;
+  trials.announce_goog_ping = true;
+  trials.enable_goog_ping = true;
+
+  auto port1_unique =
+      CreateTestPort(kLocalAddr1, "lfrag", "lpass",
+                     cricket::ICEROLE_CONTROLLING, kTiebreaker1);
+  auto* port1 = port1_unique.get();
+  auto port2 = CreateTestPort(kLocalAddr2, "rfrag", "rpass",
+                              cricket::ICEROLE_CONTROLLED, kTiebreaker2);
+
+  TestChannel ch1(std::move(port1_unique));
+  // Block usage of STUN_ATTR_USE_CANDIDATE so that
+  // ch1.conn() will sent GOOG_PING_REQUEST directly.
+  // This only makes test a bit shorter...
+  ch1.SetIceMode(ICEMODE_LITE);
+  // Start gathering candidates.
+  ch1.Start();
+  port2->PrepareAddress();
+
+  ASSERT_EQ_WAIT(1, ch1.complete_count(), kDefaultTimeout);
+  ASSERT_FALSE(port2->Candidates().empty());
+
+  ch1.CreateConnection(GetCandidate(port2.get()));
+  ASSERT_TRUE(ch1.conn() != NULL);
+  EXPECT_EQ(Connection::STATE_WRITE_INIT, ch1.conn()->write_state());
+  ch1.conn()->SetIceFieldTrials(&trials);
+
+  // Send ping.
+  ch1.Ping();
+
+  ASSERT_TRUE_WAIT(port1->last_stun_msg() != NULL, kDefaultTimeout);
+  const IceMessage* request1 = port1->last_stun_msg();
+
+  ASSERT_TRUE(GetSupportedGoogPingVersion(request1) &&
+              GetSupportedGoogPingVersion(request1) >= kGoogPingVersion);
+
+  auto* con = port2->CreateConnection(port1->Candidates()[0],
+                                      cricket::Port::ORIGIN_MESSAGE);
+  con->SetIceFieldTrials(&trials);
+
+  con->SendStunBindingResponse(request1);
+
+  // Then check the response matches the settings.
+  const auto* response = port2->last_stun_msg();
+  EXPECT_EQ(response->type(), STUN_BINDING_RESPONSE);
+  EXPECT_TRUE(GetSupportedGoogPingVersion(response));
+
+  // Modify the STUN message response to contain GetSupportedGoogPingVersion ==
+  // 0
+  auto modified_response = response->Clone();
+  ASSERT_TRUE(modified_response->RemoveAttribute(STUN_ATTR_GOOG_MISC_INFO) !=
+              nullptr);
+  ASSERT_TRUE(modified_response->RemoveAttribute(STUN_ATTR_MESSAGE_INTEGRITY) !=
+              nullptr);
+  ASSERT_TRUE(modified_response->RemoveAttribute(STUN_ATTR_FINGERPRINT) !=
+              nullptr);
+  {
+    auto list =
+        StunAttribute::CreateUInt16ListAttribute(STUN_ATTR_GOOG_MISC_INFO);
+    list->AddTypeAtIndex(
+        static_cast<uint16_t>(
+            cricket::IceGoogMiscInfoBindingResponseAttributeIndex::
+                SUPPORT_GOOG_PING_VERSION),
+        /* version */ 0);
+    modified_response->AddAttribute(std::move(list));
+    modified_response->AddMessageIntegrity("rpass");
+    modified_response->AddFingerprint();
+  }
+
+  rtc::ByteBufferWriter buf;
+  modified_response->Write(&buf);
+
+  // Feeding the modified respone message back.
+  ch1.conn()->OnReadPacket(buf.Data(), buf.Length(), /* packet_time_us */ -1);
+
+  port1->Reset();
+  port2->Reset();
+
+  ch1.Ping();
+  ASSERT_TRUE_WAIT(port1->last_stun_msg() != NULL, kDefaultTimeout);
+
+  // This should now be a STUN_BINDING...without a kGoogPingVersion
+  const IceMessage* request2 = port1->last_stun_msg();
+  EXPECT_EQ(request2->type(), STUN_BINDING_REQUEST);
+  EXPECT_FALSE(GetSupportedGoogPingVersion(request2));
+
+  ch1.Stop();
+}
+
+INSTANTIATE_TEST_SUITE_P(GoogPingTest,
+                         GoogPingTest,
+                         // test all combinations of <announce, enable> pairs.
+                         ::testing::Values(std::make_pair(false, false),
+                                           std::make_pair(true, false),
+                                           std::make_pair(false, true),
+                                           std::make_pair(true, true)));
+
+// This test checks that a change in attributes falls back to STUN_BINDING
+TEST_F(PortTest, TestChangeInAttributeMakesGoogPingFallsbackToStunBinding) {
+  IceFieldTrials trials;
+  trials.announce_goog_ping = true;
+  trials.enable_goog_ping = true;
+
+  auto port1_unique =
+      CreateTestPort(kLocalAddr1, "lfrag", "lpass",
+                     cricket::ICEROLE_CONTROLLING, kTiebreaker1);
+  auto* port1 = port1_unique.get();
+  auto port2 = CreateTestPort(kLocalAddr2, "rfrag", "rpass",
+                              cricket::ICEROLE_CONTROLLED, kTiebreaker2);
+
+  TestChannel ch1(std::move(port1_unique));
+  // Block usage of STUN_ATTR_USE_CANDIDATE so that
+  // ch1.conn() will sent GOOG_PING_REQUEST directly.
+  // This only makes test a bit shorter...
+  ch1.SetIceMode(ICEMODE_LITE);
+  // Start gathering candidates.
+  ch1.Start();
+  port2->PrepareAddress();
+
+  ASSERT_EQ_WAIT(1, ch1.complete_count(), kDefaultTimeout);
+  ASSERT_FALSE(port2->Candidates().empty());
+
+  ch1.CreateConnection(GetCandidate(port2.get()));
+  ASSERT_TRUE(ch1.conn() != nullptr);
+  EXPECT_EQ(Connection::STATE_WRITE_INIT, ch1.conn()->write_state());
+  ch1.conn()->SetIceFieldTrials(&trials);
+
+  // Send ping.
+  ch1.Ping();
+
+  ASSERT_TRUE_WAIT(port1->last_stun_msg() != NULL, kDefaultTimeout);
+  const IceMessage* msg = port1->last_stun_msg();
+  auto* con = port2->CreateConnection(port1->Candidates()[0],
+                                      cricket::Port::ORIGIN_MESSAGE);
+  con->SetIceFieldTrials(&trials);
+
+  // Feed the message into the connection.
+  con->SendStunBindingResponse(msg);
+
+  // The check reply wrt to settings.
+  const auto* response = port2->last_stun_msg();
+  ASSERT_EQ(response->type(), STUN_BINDING_RESPONSE);
+  ASSERT_TRUE(GetSupportedGoogPingVersion(response) >= kGoogPingVersion);
+
+  // Feeding the respone message back.
+  ch1.conn()->OnReadPacket(port2->last_stun_buf()->data<char>(),
+                           port2->last_stun_buf()->size(),
+                           /* packet_time_us */ -1);
+
+  port1->Reset();
+  port2->Reset();
+
+  ch1.Ping();
+  ASSERT_TRUE_WAIT(port1->last_stun_msg() != NULL, kDefaultTimeout);
+  const IceMessage* msg2 = port1->last_stun_msg();
+
+  // It should be a GOOG_PING if both of these are TRUE
+  ASSERT_EQ(msg2->type(), GOOG_PING_REQUEST);
+  con->SendGoogPingResponse(msg2);
+
+  const auto* response2 = port2->last_stun_msg();
+  ASSERT_TRUE(response2 != nullptr);
+
+  // It should be a GOOG_PING_RESPONSE.
+  ASSERT_EQ(response2->type(), GOOG_PING_RESPONSE);
+
+  // And now the third ping.
+  port1->Reset();
+  port2->Reset();
+
+  // Modify the message to be sent.
+  ch1.conn()->set_use_candidate_attr(!ch1.conn()->use_candidate_attr());
+
+  ch1.Ping();
+  ASSERT_TRUE_WAIT(port1->last_stun_msg() != NULL, kDefaultTimeout);
+  const IceMessage* msg3 = port1->last_stun_msg();
+
+  // It should be a STUN_BINDING_REQUEST
+  ASSERT_EQ(msg3->type(), STUN_BINDING_REQUEST);
+
+  ch1.Stop();
+}
+
+// This test that an error response fall back to STUN_BINDING.
+TEST_F(PortTest, TestErrorResponseMakesGoogPingFallBackToStunBinding) {
+  IceFieldTrials trials;
+  trials.announce_goog_ping = true;
+  trials.enable_goog_ping = true;
+
+  auto port1_unique =
+      CreateTestPort(kLocalAddr1, "lfrag", "lpass",
+                     cricket::ICEROLE_CONTROLLING, kTiebreaker1);
+  auto* port1 = port1_unique.get();
+  auto port2 = CreateTestPort(kLocalAddr2, "rfrag", "rpass",
+                              cricket::ICEROLE_CONTROLLED, kTiebreaker2);
+
+  TestChannel ch1(std::move(port1_unique));
+  // Block usage of STUN_ATTR_USE_CANDIDATE so that
+  // ch1.conn() will sent GOOG_PING_REQUEST directly.
+  // This only makes test a bit shorter...
+  ch1.SetIceMode(ICEMODE_LITE);
+  // Start gathering candidates.
+  ch1.Start();
+  port2->PrepareAddress();
+
+  ASSERT_EQ_WAIT(1, ch1.complete_count(), kDefaultTimeout);
+  ASSERT_FALSE(port2->Candidates().empty());
+
+  ch1.CreateConnection(GetCandidate(port2.get()));
+  ASSERT_TRUE(ch1.conn() != NULL);
+  EXPECT_EQ(Connection::STATE_WRITE_INIT, ch1.conn()->write_state());
+  ch1.conn()->SetIceFieldTrials(&trials);
+
+  // Send ping.
+  ch1.Ping();
+
+  ASSERT_TRUE_WAIT(port1->last_stun_msg() != NULL, kDefaultTimeout);
+  const IceMessage* msg = port1->last_stun_msg();
+  auto* con = port2->CreateConnection(port1->Candidates()[0],
+                                      cricket::Port::ORIGIN_MESSAGE);
+  con->SetIceFieldTrials(&trials);
+
+  // Feed the message into the connection.
+  con->SendStunBindingResponse(msg);
+
+  // The check reply wrt to settings.
+  const auto* response = port2->last_stun_msg();
+  ASSERT_EQ(response->type(), STUN_BINDING_RESPONSE);
+  ASSERT_TRUE(GetSupportedGoogPingVersion(response) >= kGoogPingVersion);
+
+  // Feeding the respone message back.
+  ch1.conn()->OnReadPacket(port2->last_stun_buf()->data<char>(),
+                           port2->last_stun_buf()->size(),
+                           /* packet_time_us */ -1);
+
+  port1->Reset();
+  port2->Reset();
+
+  ch1.Ping();
+  ASSERT_TRUE_WAIT(port1->last_stun_msg() != NULL, kDefaultTimeout);
+  const IceMessage* msg2 = port1->last_stun_msg();
+
+  // It should be a GOOG_PING.
+  ASSERT_EQ(msg2->type(), GOOG_PING_REQUEST);
+  con->SendGoogPingResponse(msg2);
+
+  const auto* response2 = port2->last_stun_msg();
+  ASSERT_TRUE(response2 != nullptr);
+
+  // It should be a GOOG_PING_RESPONSE.
+  ASSERT_EQ(response2->type(), GOOG_PING_RESPONSE);
+
+  // But rather than the RESPONSE...feedback an error.
+  StunMessage error_response(GOOG_PING_ERROR_RESPONSE);
+  error_response.SetTransactionIdForTesting(response2->transaction_id());
+  error_response.AddMessageIntegrity32("rpass");
+  rtc::ByteBufferWriter buf;
+  error_response.Write(&buf);
+
+  ch1.conn()->OnReadPacket(buf.Data(), buf.Length(),
+                           /* packet_time_us */ -1);
+
+  // And now the third ping...this should be a binding.
+  port1->Reset();
+  port2->Reset();
+
+  ch1.Ping();
+  ASSERT_TRUE_WAIT(port1->last_stun_msg() != NULL, kDefaultTimeout);
+  const IceMessage* msg3 = port1->last_stun_msg();
+
+  // It should be a STUN_BINDING_REQUEST
+  ASSERT_EQ(msg3->type(), STUN_BINDING_REQUEST);
+
+  ch1.Stop();
+}
+
+// This test case verifies that both the controlling port and the controlled
+// port will time out after connectivity is lost, if they are not marked as
+// "keep alive until pruned."
+TEST_F(PortTest, TestPortTimeoutIfNotKeptAlive) {
+  rtc::ScopedFakeClock clock;
+  int timeout_delay = 100;
+  auto port1 = CreateUdpPort(kLocalAddr1);
+  ConnectToSignalDestroyed(port1.get());
+  port1->set_timeout_delay(timeout_delay);  // milliseconds
+  port1->SetIceRole(cricket::ICEROLE_CONTROLLING);
+  port1->SetIceTiebreaker(kTiebreaker1);
+
+  auto port2 = CreateUdpPort(kLocalAddr2);
+  ConnectToSignalDestroyed(port2.get());
+  port2->set_timeout_delay(timeout_delay);  // milliseconds
+  port2->SetIceRole(cricket::ICEROLE_CONTROLLED);
+  port2->SetIceTiebreaker(kTiebreaker2);
+
+  // Set up channels and ensure both ports will be deleted.
+  TestChannel ch1(std::move(port1));
+  TestChannel ch2(std::move(port2));
+
+  // Simulate a connection that succeeds, and then is destroyed.
+  StartConnectAndStopChannels(&ch1, &ch2);
+  // After the connection is destroyed, the port will be destroyed because
+  // none of them is marked as "keep alive until pruned.
+  EXPECT_EQ_SIMULATED_WAIT(2, ports_destroyed(), 110, clock);
+}
+
+// Test that if after all connection are destroyed, new connections are created
+// and destroyed again, ports won't be destroyed until a timeout period passes
+// after the last set of connections are all destroyed.
+TEST_F(PortTest, TestPortTimeoutAfterNewConnectionCreatedAndDestroyed) {
+  rtc::ScopedFakeClock clock;
+  int timeout_delay = 100;
+  auto port1 = CreateUdpPort(kLocalAddr1);
+  ConnectToSignalDestroyed(port1.get());
+  port1->set_timeout_delay(timeout_delay);  // milliseconds
+  port1->SetIceRole(cricket::ICEROLE_CONTROLLING);
+  port1->SetIceTiebreaker(kTiebreaker1);
+
+  auto port2 = CreateUdpPort(kLocalAddr2);
+  ConnectToSignalDestroyed(port2.get());
+  port2->set_timeout_delay(timeout_delay);  // milliseconds
+
+  port2->SetIceRole(cricket::ICEROLE_CONTROLLED);
+  port2->SetIceTiebreaker(kTiebreaker2);
+
+  // Set up channels and ensure both ports will be deleted.
+  TestChannel ch1(std::move(port1));
+  TestChannel ch2(std::move(port2));
+
+  // Simulate a connection that succeeds, and then is destroyed.
+  StartConnectAndStopChannels(&ch1, &ch2);
+  SIMULATED_WAIT(ports_destroyed() > 0, 80, clock);
+  EXPECT_EQ(0, ports_destroyed());
+
+  // Start the second set of connection and destroy them.
+  ch1.CreateConnection(GetCandidate(ch2.port()));
+  ch2.CreateConnection(GetCandidate(ch1.port()));
+  ch1.Stop();
+  ch2.Stop();
+
+  SIMULATED_WAIT(ports_destroyed() > 0, 80, clock);
+  EXPECT_EQ(0, ports_destroyed());
+
+  // The ports on both sides should be destroyed after timeout.
+  EXPECT_TRUE_SIMULATED_WAIT(ports_destroyed() == 2, 30, clock);
+}
+
+// This test case verifies that neither the controlling port nor the controlled
+// port will time out after connectivity is lost if they are marked as "keep
+// alive until pruned". They will time out after they are pruned.
+TEST_F(PortTest, TestPortNotTimeoutUntilPruned) {
+  rtc::ScopedFakeClock clock;
+  int timeout_delay = 100;
+  auto port1 = CreateUdpPort(kLocalAddr1);
+  ConnectToSignalDestroyed(port1.get());
+  port1->set_timeout_delay(timeout_delay);  // milliseconds
+  port1->SetIceRole(cricket::ICEROLE_CONTROLLING);
+  port1->SetIceTiebreaker(kTiebreaker1);
+
+  auto port2 = CreateUdpPort(kLocalAddr2);
+  ConnectToSignalDestroyed(port2.get());
+  port2->set_timeout_delay(timeout_delay);  // milliseconds
+  port2->SetIceRole(cricket::ICEROLE_CONTROLLED);
+  port2->SetIceTiebreaker(kTiebreaker2);
+  // The connection must not be destroyed before a connection is attempted.
+  EXPECT_EQ(0, ports_destroyed());
+
+  port1->set_component(cricket::ICE_CANDIDATE_COMPONENT_DEFAULT);
+  port2->set_component(cricket::ICE_CANDIDATE_COMPONENT_DEFAULT);
+
+  // Set up channels and keep the port alive.
+  TestChannel ch1(std::move(port1));
+  TestChannel ch2(std::move(port2));
+  // Simulate a connection that succeeds, and then is destroyed. But ports
+  // are kept alive. Ports won't be destroyed.
+  StartConnectAndStopChannels(&ch1, &ch2);
+  ch1.port()->KeepAliveUntilPruned();
+  ch2.port()->KeepAliveUntilPruned();
+  SIMULATED_WAIT(ports_destroyed() > 0, 150, clock);
+  EXPECT_EQ(0, ports_destroyed());
+
+  // If they are pruned now, they will be destroyed right away.
+  ch1.port()->Prune();
+  ch2.port()->Prune();
+  // The ports on both sides should be destroyed after timeout.
+  EXPECT_TRUE_SIMULATED_WAIT(ports_destroyed() == 2, 1, clock);
+}
+
+TEST_F(PortTest, TestSupportsProtocol) {
+  auto udp_port = CreateUdpPort(kLocalAddr1);
+  EXPECT_TRUE(udp_port->SupportsProtocol(UDP_PROTOCOL_NAME));
+  EXPECT_FALSE(udp_port->SupportsProtocol(TCP_PROTOCOL_NAME));
+
+  auto stun_port = CreateStunPort(kLocalAddr1, nat_socket_factory1());
+  EXPECT_TRUE(stun_port->SupportsProtocol(UDP_PROTOCOL_NAME));
+  EXPECT_FALSE(stun_port->SupportsProtocol(TCP_PROTOCOL_NAME));
+
+  auto tcp_port = CreateTcpPort(kLocalAddr1);
+  EXPECT_TRUE(tcp_port->SupportsProtocol(TCP_PROTOCOL_NAME));
+  EXPECT_TRUE(tcp_port->SupportsProtocol(SSLTCP_PROTOCOL_NAME));
+  EXPECT_FALSE(tcp_port->SupportsProtocol(UDP_PROTOCOL_NAME));
+
+  auto turn_port =
+      CreateTurnPort(kLocalAddr1, nat_socket_factory1(), PROTO_UDP, PROTO_UDP);
+  EXPECT_TRUE(turn_port->SupportsProtocol(UDP_PROTOCOL_NAME));
+  EXPECT_FALSE(turn_port->SupportsProtocol(TCP_PROTOCOL_NAME));
+}
+
+// Test that SetIceParameters updates the component, ufrag and password
+// on both the port itself and its candidates.
+TEST_F(PortTest, TestSetIceParameters) {
+  auto port = CreateTestPort(kLocalAddr1, "ufrag1", "password1");
+  port->SetIceTiebreaker(kTiebreakerDefault);
+  port->PrepareAddress();
+  EXPECT_EQ(1UL, port->Candidates().size());
+  port->SetIceParameters(1, "ufrag2", "password2");
+  EXPECT_EQ(1, port->component());
+  EXPECT_EQ("ufrag2", port->username_fragment());
+  EXPECT_EQ("password2", port->password());
+  const Candidate& candidate = port->Candidates()[0];
+  EXPECT_EQ(1, candidate.component());
+  EXPECT_EQ("ufrag2", candidate.username());
+  EXPECT_EQ("password2", candidate.password());
+}
+
+TEST_F(PortTest, TestAddConnectionWithSameAddress) {
+  auto port = CreateTestPort(kLocalAddr1, "ufrag1", "password1");
+  port->SetIceTiebreaker(kTiebreakerDefault);
+  port->PrepareAddress();
+  EXPECT_EQ(1u, port->Candidates().size());
+  rtc::SocketAddress address("1.1.1.1", 5000);
+  cricket::Candidate candidate(1, "udp", address, 0, "", "", "relay", 0, "");
+  cricket::Connection* conn1 =
+      port->CreateConnection(candidate, Port::ORIGIN_MESSAGE);
+  cricket::Connection* conn_in_use = port->GetConnection(address);
+  EXPECT_EQ(conn1, conn_in_use);
+  EXPECT_EQ(0u, conn_in_use->remote_candidate().generation());
+
+  // Creating with a candidate with the same address again will get us a
+  // different connection with the new candidate.
+  candidate.set_generation(2);
+  cricket::Connection* conn2 =
+      port->CreateConnection(candidate, Port::ORIGIN_MESSAGE);
+  EXPECT_NE(conn1, conn2);
+  conn_in_use = port->GetConnection(address);
+  EXPECT_EQ(conn2, conn_in_use);
+  EXPECT_EQ(2u, conn_in_use->remote_candidate().generation());
+
+  // Make sure the new connection was not deleted.
+  rtc::Thread::Current()->ProcessMessages(300);
+  EXPECT_TRUE(port->GetConnection(address) != nullptr);
+}
+
+// TODO(webrtc:11463) : Move Connection tests into separate unit test
+// splitting out shared test code as needed.
+
+class ConnectionTest : public PortTest {
+ public:
+  ConnectionTest() {
+    lport_ = CreateTestPort(kLocalAddr1, "lfrag", "lpass");
+    rport_ = CreateTestPort(kLocalAddr2, "rfrag", "rpass");
+    lport_->SetIceRole(cricket::ICEROLE_CONTROLLING);
+    lport_->SetIceTiebreaker(kTiebreaker1);
+    rport_->SetIceRole(cricket::ICEROLE_CONTROLLED);
+    rport_->SetIceTiebreaker(kTiebreaker2);
+
+    lport_->PrepareAddress();
+    rport_->PrepareAddress();
+  }
+
+  rtc::ScopedFakeClock clock_;
+  int num_state_changes_ = 0;
+
+  Connection* CreateConnection(IceRole role) {
+    Connection* conn;
+    if (role == cricket::ICEROLE_CONTROLLING) {
+      conn = lport_->CreateConnection(rport_->Candidates()[0],
+                                      Port::ORIGIN_MESSAGE);
+    } else {
+      conn = rport_->CreateConnection(lport_->Candidates()[0],
+                                      Port::ORIGIN_MESSAGE);
+    }
+    conn->SignalStateChange.connect(this,
+                                    &ConnectionTest::OnConnectionStateChange);
+    return conn;
+  }
+
+  void SendPingAndCaptureReply(Connection* lconn,
+                               Connection* rconn,
+                               int64_t ms,
+                               rtc::BufferT<uint8_t>* reply) {
+    TestPort* lport =
+        lconn->PortForTest() == lport_.get() ? lport_.get() : rport_.get();
+    TestPort* rport =
+        rconn->PortForTest() == rport_.get() ? rport_.get() : lport_.get();
+    lconn->Ping(rtc::TimeMillis());
+    ASSERT_TRUE_WAIT(lport->last_stun_msg(), kDefaultTimeout);
+    ASSERT_TRUE(lport->last_stun_buf());
+    rconn->OnReadPacket(lport->last_stun_buf()->data<char>(),
+                        lport->last_stun_buf()->size(),
+                        /* packet_time_us */ -1);
+    clock_.AdvanceTime(webrtc::TimeDelta::Millis(ms));
+    ASSERT_TRUE_WAIT(rport->last_stun_msg(), kDefaultTimeout);
+    ASSERT_TRUE(rport->last_stun_buf());
+    *reply = std::move(*rport->last_stun_buf());
+  }
+
+  void SendPingAndReceiveResponse(Connection* lconn,
+                                  Connection* rconn,
+                                  int64_t ms) {
+    rtc::BufferT<uint8_t> reply;
+    SendPingAndCaptureReply(lconn, rconn, ms, &reply);
+    lconn->OnReadPacket(reply.data<char>(), reply.size(),
+                        /* packet_time_us */ -1);
+  }
+
+  void OnConnectionStateChange(Connection* connection) { num_state_changes_++; }
+
+ private:
+  std::unique_ptr<TestPort> lport_;
+  std::unique_ptr<TestPort> rport_;
+};
+
+TEST_F(ConnectionTest, ConnectionForgetLearnedState) {
+  Connection* lconn = CreateConnection(ICEROLE_CONTROLLING);
+  Connection* rconn = CreateConnection(ICEROLE_CONTROLLED);
+
+  EXPECT_FALSE(lconn->writable());
+  EXPECT_FALSE(lconn->receiving());
+  EXPECT_TRUE(std::isnan(lconn->GetRttEstimate().GetAverage()));
+  EXPECT_EQ(lconn->GetRttEstimate().GetVariance(),
+            std::numeric_limits<double>::infinity());
+
+  SendPingAndReceiveResponse(lconn, rconn, 10);
+
+  EXPECT_TRUE(lconn->writable());
+  EXPECT_TRUE(lconn->receiving());
+  EXPECT_EQ(lconn->GetRttEstimate().GetAverage(), 10);
+  EXPECT_EQ(lconn->GetRttEstimate().GetVariance(),
+            std::numeric_limits<double>::infinity());
+
+  SendPingAndReceiveResponse(lconn, rconn, 11);
+
+  EXPECT_TRUE(lconn->writable());
+  EXPECT_TRUE(lconn->receiving());
+  EXPECT_NEAR(lconn->GetRttEstimate().GetAverage(), 10, 0.5);
+  EXPECT_LT(lconn->GetRttEstimate().GetVariance(),
+            std::numeric_limits<double>::infinity());
+
+  lconn->ForgetLearnedState();
+
+  EXPECT_FALSE(lconn->writable());
+  EXPECT_FALSE(lconn->receiving());
+  EXPECT_TRUE(std::isnan(lconn->GetRttEstimate().GetAverage()));
+  EXPECT_EQ(lconn->GetRttEstimate().GetVariance(),
+            std::numeric_limits<double>::infinity());
+}
+
+TEST_F(ConnectionTest, ConnectionForgetLearnedStateDiscardsPendingPings) {
+  Connection* lconn = CreateConnection(ICEROLE_CONTROLLING);
+  Connection* rconn = CreateConnection(ICEROLE_CONTROLLED);
+
+  SendPingAndReceiveResponse(lconn, rconn, 10);
+
+  EXPECT_TRUE(lconn->writable());
+  EXPECT_TRUE(lconn->receiving());
+
+  rtc::BufferT<uint8_t> reply;
+  SendPingAndCaptureReply(lconn, rconn, 10, &reply);
+
+  lconn->ForgetLearnedState();
+
+  EXPECT_FALSE(lconn->writable());
+  EXPECT_FALSE(lconn->receiving());
+
+  lconn->OnReadPacket(reply.data<char>(), reply.size(),
+                      /* packet_time_us */ -1);
+
+  // That reply was discarded due to the ForgetLearnedState() while it was
+  // outstanding.
+  EXPECT_FALSE(lconn->writable());
+  EXPECT_FALSE(lconn->receiving());
+
+  // But sending a new ping and getting a reply works.
+  SendPingAndReceiveResponse(lconn, rconn, 11);
+  EXPECT_TRUE(lconn->writable());
+  EXPECT_TRUE(lconn->receiving());
+}
+
+TEST_F(ConnectionTest, ConnectionForgetLearnedStateDoesNotTriggerStateChange) {
+  Connection* lconn = CreateConnection(ICEROLE_CONTROLLING);
+  Connection* rconn = CreateConnection(ICEROLE_CONTROLLED);
+
+  EXPECT_EQ(num_state_changes_, 0);
+  SendPingAndReceiveResponse(lconn, rconn, 10);
+
+  EXPECT_TRUE(lconn->writable());
+  EXPECT_TRUE(lconn->receiving());
+  EXPECT_EQ(num_state_changes_, 2);
+
+  lconn->ForgetLearnedState();
+
+  EXPECT_FALSE(lconn->writable());
+  EXPECT_FALSE(lconn->receiving());
+  EXPECT_EQ(num_state_changes_, 2);
+}
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/pseudo_tcp.cc b/third_party/libwebrtc/p2p/base/pseudo_tcp.cc
new file mode 100644
index 0000000000..eff86e849e
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/pseudo_tcp.cc
@@ -0,0 +1,1432 @@
+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/pseudo_tcp.h"
+
+#include <errno.h>
+#include <stdio.h>
+#include <string.h>
+
+#include <algorithm>
+#include <cstdint>
+#include <memory>
+#include <set>
+
+#include "rtc_base/byte_buffer.h"
+#include "rtc_base/byte_order.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/logging.h"
+#include "rtc_base/numerics/safe_minmax.h"
+#include "rtc_base/socket.h"
+#include "rtc_base/time_utils.h"
+
+// The following logging is for detailed (packet-level) analysis only.
+#define _DBG_NONE 0
+#define _DBG_NORMAL 1
+#define _DBG_VERBOSE 2
+#define _DEBUGMSG _DBG_NONE
+
+namespace cricket {
+
+//////////////////////////////////////////////////////////////////////
+// Network Constants
+//////////////////////////////////////////////////////////////////////
+
+// Standard MTUs
+const uint16_t PACKET_MAXIMUMS[] = {
+    65535,  // Theoretical maximum, Hyperchannel
+    32000,  // Nothing
+    17914,  // 16Mb IBM Token Ring
+    8166,   // IEEE 802.4
+    // 4464,   // IEEE 802.5 (4Mb max)
+    4352,  // FDDI
+    // 2048,   // Wideband Network
+    2002,  // IEEE 802.5 (4Mb recommended)
+    // 1536,   // Expermental Ethernet Networks
+    // 1500,   // Ethernet, Point-to-Point (default)
+    1492,  // IEEE 802.3
+    1006,  // SLIP, ARPANET
+    // 576,    // X.25 Networks
+    // 544,    // DEC IP Portal
+    // 512,    // NETBIOS
+    508,  // IEEE 802/Source-Rt Bridge, ARCNET
+    296,  // Point-to-Point (low delay)
+    // 68,     // Official minimum
+    0,  // End of list marker
+};
+
+const uint32_t MAX_PACKET = 65535;
+// Note: we removed lowest level because packet overhead was larger!
+const uint32_t MIN_PACKET = 296;
+
+const uint32_t IP_HEADER_SIZE = 20;  // (+ up to 40 bytes of options?)
+const uint32_t UDP_HEADER_SIZE = 8;
+// TODO(?): Make JINGLE_HEADER_SIZE transparent to this code?
+const uint32_t JINGLE_HEADER_SIZE = 64;  // when relay framing is in use
+
+// Default size for receive and send buffer.
+const uint32_t DEFAULT_RCV_BUF_SIZE = 60 * 1024;
+const uint32_t DEFAULT_SND_BUF_SIZE = 90 * 1024;
+
+//////////////////////////////////////////////////////////////////////
+// Global Constants and Functions
+//////////////////////////////////////////////////////////////////////
+//
+//    0                   1                   2                   3
+//    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+//    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+//  0 |                      Conversation Number                      |
+//    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+//  4 |                        Sequence Number                        |
+//    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+//  8 |                     Acknowledgment Number                     |
+//    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+//    |               |   |U|A|P|R|S|F|                               |
+// 12 |    Control    |   |R|C|S|S|Y|I|            Window             |
+//    |               |   |G|K|H|T|N|N|                               |
+//    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// 16 |                       Timestamp sending                       |
+//    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// 20 |                      Timestamp receiving                      |
+//    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// 24 |                             data                              |
+//    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+//
+//////////////////////////////////////////////////////////////////////
+
+#define PSEUDO_KEEPALIVE 0
+
+const uint32_t HEADER_SIZE = 24;
+const uint32_t PACKET_OVERHEAD =
+    HEADER_SIZE + UDP_HEADER_SIZE + IP_HEADER_SIZE + JINGLE_HEADER_SIZE;
+
+const uint32_t MIN_RTO =
+    250;  // 250 ms (RFC1122, Sec 4.2.3.1 "fractions of a second")
+const uint32_t DEF_RTO = 3000;       // 3 seconds (RFC1122, Sec 4.2.3.1)
+const uint32_t MAX_RTO = 60000;      // 60 seconds
+const uint32_t DEF_ACK_DELAY = 100;  // 100 milliseconds
+
+const uint8_t FLAG_CTL = 0x02;
+const uint8_t FLAG_RST = 0x04;
+
+const uint8_t CTL_CONNECT = 0;
+
+// TCP options.
+const uint8_t TCP_OPT_EOL = 0;        // End of list.
+const uint8_t TCP_OPT_NOOP = 1;       // No-op.
+const uint8_t TCP_OPT_MSS = 2;        // Maximum segment size.
+const uint8_t TCP_OPT_WND_SCALE = 3;  // Window scale factor.
+
+const long DEFAULT_TIMEOUT =
+    4000;  // If there are no pending clocks, wake up every 4 seconds
+const long CLOSED_TIMEOUT =
+    60 * 1000;  // If the connection is closed, once per minute
+
+#if PSEUDO_KEEPALIVE
+// !?! Rethink these times
+const uint32_t IDLE_PING =
+    20 *
+    1000;  // 20 seconds (note: WinXP SP2 firewall udp timeout is 90 seconds)
+const uint32_t IDLE_TIMEOUT = 90 * 1000;  // 90 seconds;
+#endif                                    // PSEUDO_KEEPALIVE
+
+//////////////////////////////////////////////////////////////////////
+// Helper Functions
+//////////////////////////////////////////////////////////////////////
+
+inline void long_to_bytes(uint32_t val, void* buf) {
+  *static_cast<uint32_t*>(buf) = rtc::HostToNetwork32(val);
+}
+
+inline void short_to_bytes(uint16_t val, void* buf) {
+  *static_cast<uint16_t*>(buf) = rtc::HostToNetwork16(val);
+}
+
+inline uint32_t bytes_to_long(const void* buf) {
+  return rtc::NetworkToHost32(*static_cast<const uint32_t*>(buf));
+}
+
+inline uint16_t bytes_to_short(const void* buf) {
+  return rtc::NetworkToHost16(*static_cast<const uint16_t*>(buf));
+}
+
+//////////////////////////////////////////////////////////////////////
+// Debugging Statistics
+//////////////////////////////////////////////////////////////////////
+
+#if 0  // Not used yet
+
+enum Stat {
+  S_SENT_PACKET,    // All packet sends
+  S_RESENT_PACKET,  // All packet sends that are retransmits
+  S_RECV_PACKET,    // All packet receives
+  S_RECV_NEW,       // All packet receives that are too new
+  S_RECV_OLD,       // All packet receives that are too old
+  S_NUM_STATS
+};
+
+const char* const STAT_NAMES[S_NUM_STATS] = {
+  "snt",
+  "snt-r",
+  "rcv"
+  "rcv-n",
+  "rcv-o"
+};
+
+int g_stats[S_NUM_STATS];
+inline void Incr(Stat s) { ++g_stats[s]; }
+void ReportStats() {
+  char buffer[256];
+  size_t len = 0;
+  for (int i = 0; i < S_NUM_STATS; ++i) {
+    len += snprintf(buffer, arraysize(buffer), "%s%s:%d",
+                          (i == 0) ? "" : ",", STAT_NAMES[i], g_stats[i]);
+    g_stats[i] = 0;
+  }
+  RTC_LOG(LS_INFO) << "Stats[" << buffer << "]";
+}
+
+#endif
+
+//////////////////////////////////////////////////////////////////////
+// PseudoTcp
+//////////////////////////////////////////////////////////////////////
+
+uint32_t PseudoTcp::Now() {
+#if 0  // Use this to synchronize timers with logging timestamps (easier debug)
+  return static_cast<uint32_t>(rtc::TimeSince(StartTime()));
+#else
+  return rtc::Time32();
+#endif
+}
+
+PseudoTcp::PseudoTcp(IPseudoTcpNotify* notify, uint32_t conv)
+    : m_notify(notify),
+      m_shutdown(SD_NONE),
+      m_error(0),
+      m_rbuf_len(DEFAULT_RCV_BUF_SIZE),
+      m_rbuf(m_rbuf_len),
+      m_sbuf_len(DEFAULT_SND_BUF_SIZE),
+      m_sbuf(m_sbuf_len) {
+  // Sanity check on buffer sizes (needed for OnTcpWriteable notification logic)
+  RTC_DCHECK(m_rbuf_len + MIN_PACKET < m_sbuf_len);
+
+  uint32_t now = Now();
+
+  m_state = TCP_LISTEN;
+  m_conv = conv;
+  m_rcv_wnd = m_rbuf_len;
+  m_rwnd_scale = m_swnd_scale = 0;
+  m_snd_nxt = 0;
+  m_snd_wnd = 1;
+  m_snd_una = m_rcv_nxt = 0;
+  m_bReadEnable = true;
+  m_bWriteEnable = false;
+  m_t_ack = 0;
+
+  m_msslevel = 0;
+  m_largest = 0;
+  RTC_DCHECK(MIN_PACKET > PACKET_OVERHEAD);
+  m_mss = MIN_PACKET - PACKET_OVERHEAD;
+  m_mtu_advise = MAX_PACKET;
+
+  m_rto_base = 0;
+
+  m_cwnd = 2 * m_mss;
+  m_ssthresh = m_rbuf_len;
+  m_lastrecv = m_lastsend = m_lasttraffic = now;
+  m_bOutgoing = false;
+
+  m_dup_acks = 0;
+  m_recover = 0;
+
+  m_ts_recent = m_ts_lastack = 0;
+
+  m_rx_rto = DEF_RTO;
+  m_rx_srtt = m_rx_rttvar = 0;
+
+  m_use_nagling = true;
+  m_ack_delay = DEF_ACK_DELAY;
+  m_support_wnd_scale = true;
+}
+
+PseudoTcp::~PseudoTcp() {}
+
+int PseudoTcp::Connect() {
+  if (m_state != TCP_LISTEN) {
+    m_error = EINVAL;
+    return -1;
+  }
+
+  m_state = TCP_SYN_SENT;
+  RTC_LOG(LS_INFO) << "State: TCP_SYN_SENT";
+
+  queueConnectMessage();
+  attemptSend();
+
+  return 0;
+}
+
+void PseudoTcp::NotifyMTU(uint16_t mtu) {
+  m_mtu_advise = mtu;
+  if (m_state == TCP_ESTABLISHED) {
+    adjustMTU();
+  }
+}
+
+void PseudoTcp::NotifyClock(uint32_t now) {
+  if (m_state == TCP_CLOSED)
+    return;
+
+  // Check if it's time to retransmit a segment
+  if (m_rto_base && (rtc::TimeDiff32(m_rto_base + m_rx_rto, now) <= 0)) {
+    if (m_slist.empty()) {
+      RTC_DCHECK_NOTREACHED();
+    } else {
+// Note: (m_slist.front().xmit == 0)) {
+// retransmit segments
+#if _DEBUGMSG >= _DBG_NORMAL
+      RTC_LOG(LS_INFO) << "timeout retransmit (rto: " << m_rx_rto
+                       << ") (rto_base: " << m_rto_base << ") (now: " << now
+                       << ") (dup_acks: " << static_cast<unsigned>(m_dup_acks)
+                       << ")";
+#endif  // _DEBUGMSG
+      if (!transmit(m_slist.begin(), now)) {
+        closedown(ECONNABORTED);
+        return;
+      }
+
+      uint32_t nInFlight = m_snd_nxt - m_snd_una;
+      m_ssthresh = std::max(nInFlight / 2, 2 * m_mss);
+      // RTC_LOG(LS_INFO) << "m_ssthresh: " << m_ssthresh << "  nInFlight: " <<
+      // nInFlight << "  m_mss: " << m_mss;
+      m_cwnd = m_mss;
+
+      // Back off retransmit timer.  Note: the limit is lower when connecting.
+      uint32_t rto_limit = (m_state < TCP_ESTABLISHED) ? DEF_RTO : MAX_RTO;
+      m_rx_rto = std::min(rto_limit, m_rx_rto * 2);
+      m_rto_base = now;
+    }
+  }
+
+  // Check if it's time to probe closed windows
+  if ((m_snd_wnd == 0) && (rtc::TimeDiff32(m_lastsend + m_rx_rto, now) <= 0)) {
+    if (rtc::TimeDiff32(now, m_lastrecv) >= 15000) {
+      closedown(ECONNABORTED);
+      return;
+    }
+
+    // probe the window
+    packet(m_snd_nxt - 1, 0, 0, 0);
+    m_lastsend = now;
+
+    // back off retransmit timer
+    m_rx_rto = std::min(MAX_RTO, m_rx_rto * 2);
+  }
+
+  // Check if it's time to send delayed acks
+  if (m_t_ack && (rtc::TimeDiff32(m_t_ack + m_ack_delay, now) <= 0)) {
+    packet(m_snd_nxt, 0, 0, 0);
+  }
+
+#if PSEUDO_KEEPALIVE
+  // Check for idle timeout
+  if ((m_state == TCP_ESTABLISHED) &&
+      (TimeDiff32(m_lastrecv + IDLE_TIMEOUT, now) <= 0)) {
+    closedown(ECONNABORTED);
+    return;
+  }
+
+  // Check for ping timeout (to keep udp mapping open)
+  if ((m_state == TCP_ESTABLISHED) &&
+      (TimeDiff32(m_lasttraffic + (m_bOutgoing ? IDLE_PING * 3 / 2 : IDLE_PING),
+                  now) <= 0)) {
+    packet(m_snd_nxt, 0, 0, 0);
+  }
+#endif  // PSEUDO_KEEPALIVE
+}
+
+bool PseudoTcp::NotifyPacket(const char* buffer, size_t len) {
+  if (len > MAX_PACKET) {
+    RTC_LOG_F(LS_WARNING) << "packet too large";
+    return false;
+  }
+  return parse(reinterpret_cast<const uint8_t*>(buffer), uint32_t(len));
+}
+
+bool PseudoTcp::GetNextClock(uint32_t now, long& timeout) {
+  return clock_check(now, timeout);
+}
+
+void PseudoTcp::GetOption(Option opt, int* value) {
+  if (opt == OPT_NODELAY) {
+    *value = m_use_nagling ? 0 : 1;
+  } else if (opt == OPT_ACKDELAY) {
+    *value = m_ack_delay;
+  } else if (opt == OPT_SNDBUF) {
+    *value = m_sbuf_len;
+  } else if (opt == OPT_RCVBUF) {
+    *value = m_rbuf_len;
+  } else {
+    RTC_DCHECK_NOTREACHED();
+  }
+}
+void PseudoTcp::SetOption(Option opt, int value) {
+  if (opt == OPT_NODELAY) {
+    m_use_nagling = value == 0;
+  } else if (opt == OPT_ACKDELAY) {
+    m_ack_delay = value;
+  } else if (opt == OPT_SNDBUF) {
+    RTC_DCHECK(m_state == TCP_LISTEN);
+    resizeSendBuffer(value);
+  } else if (opt == OPT_RCVBUF) {
+    RTC_DCHECK(m_state == TCP_LISTEN);
+    resizeReceiveBuffer(value);
+  } else {
+    RTC_DCHECK_NOTREACHED();
+  }
+}
+
+uint32_t PseudoTcp::GetCongestionWindow() const {
+  return m_cwnd;
+}
+
+uint32_t PseudoTcp::GetBytesInFlight() const {
+  return m_snd_nxt - m_snd_una;
+}
+
+uint32_t PseudoTcp::GetBytesBufferedNotSent() const {
+  return static_cast<uint32_t>(m_snd_una + m_sbuf.GetBuffered() - m_snd_nxt);
+}
+
+uint32_t PseudoTcp::GetRoundTripTimeEstimateMs() const {
+  return m_rx_srtt;
+}
+
+//
+// IPStream Implementation
+//
+
+int PseudoTcp::Recv(char* buffer, size_t len) {
+  if (m_state != TCP_ESTABLISHED) {
+    m_error = ENOTCONN;
+    return SOCKET_ERROR;
+  }
+
+  size_t read = 0;
+  if (!m_rbuf.Read(buffer, len, &read)) {
+    m_bReadEnable = true;
+    m_error = EWOULDBLOCK;
+    return SOCKET_ERROR;
+  }
+
+  size_t available_space = 0;
+  m_rbuf.GetWriteRemaining(&available_space);
+
+  if (uint32_t(available_space) - m_rcv_wnd >=
+      std::min<uint32_t>(m_rbuf_len / 2, m_mss)) {
+    // TODO(jbeda): !?! Not sure about this was closed business
+    bool bWasClosed = (m_rcv_wnd == 0);
+    m_rcv_wnd = static_cast<uint32_t>(available_space);
+
+    if (bWasClosed) {
+      attemptSend(sfImmediateAck);
+    }
+  }
+
+  return static_cast<int>(read);
+}
+
+int PseudoTcp::Send(const char* buffer, size_t len) {
+  if (m_state != TCP_ESTABLISHED) {
+    m_error = ENOTCONN;
+    return SOCKET_ERROR;
+  }
+
+  size_t available_space = 0;
+  m_sbuf.GetWriteRemaining(&available_space);
+
+  if (!available_space) {
+    m_bWriteEnable = true;
+    m_error = EWOULDBLOCK;
+    return SOCKET_ERROR;
+  }
+
+  int written = queue(buffer, uint32_t(len), false);
+  attemptSend();
+  return written;
+}
+
+void PseudoTcp::Close(bool force) {
+  RTC_LOG_F(LS_VERBOSE) << "(" << (force ? "true" : "false") << ")";
+  m_shutdown = force ? SD_FORCEFUL : SD_GRACEFUL;
+}
+
+int PseudoTcp::GetError() {
+  return m_error;
+}
+
+//
+// Internal Implementation
+//
+
+uint32_t PseudoTcp::queue(const char* data, uint32_t len, bool bCtrl) {
+  size_t available_space = 0;
+  m_sbuf.GetWriteRemaining(&available_space);
+
+  if (len > static_cast<uint32_t>(available_space)) {
+    RTC_DCHECK(!bCtrl);
+    len = static_cast<uint32_t>(available_space);
+  }
+
+  // We can concatenate data if the last segment is the same type
+  // (control v. regular data), and has not been transmitted yet
+  if (!m_slist.empty() && (m_slist.back().bCtrl == bCtrl) &&
+      (m_slist.back().xmit == 0)) {
+    m_slist.back().len += len;
+  } else {
+    SSegment sseg(static_cast<uint32_t>(m_snd_una + m_sbuf.GetBuffered()), len,
+                  bCtrl);
+    m_slist.push_back(sseg);
+  }
+
+  size_t written = 0;
+  m_sbuf.Write(data, len, &written);
+  return static_cast<uint32_t>(written);
+}
+
+IPseudoTcpNotify::WriteResult PseudoTcp::packet(uint32_t seq,
+                                                uint8_t flags,
+                                                uint32_t offset,
+                                                uint32_t len) {
+  RTC_DCHECK(HEADER_SIZE + len <= MAX_PACKET);
+
+  uint32_t now = Now();
+
+  std::unique_ptr<uint8_t[]> buffer(new uint8_t[MAX_PACKET]);
+  long_to_bytes(m_conv, buffer.get());
+  long_to_bytes(seq, buffer.get() + 4);
+  long_to_bytes(m_rcv_nxt, buffer.get() + 8);
+  buffer[12] = 0;
+  buffer[13] = flags;
+  short_to_bytes(static_cast<uint16_t>(m_rcv_wnd >> m_rwnd_scale),
+                 buffer.get() + 14);
+
+  // Timestamp computations
+  long_to_bytes(now, buffer.get() + 16);
+  long_to_bytes(m_ts_recent, buffer.get() + 20);
+  m_ts_lastack = m_rcv_nxt;
+
+  if (len) {
+    size_t bytes_read = 0;
+    bool result =
+        m_sbuf.ReadOffset(buffer.get() + HEADER_SIZE, len, offset, &bytes_read);
+    RTC_DCHECK(result);
+    RTC_DCHECK(static_cast<uint32_t>(bytes_read) == len);
+  }
+
+#if _DEBUGMSG >= _DBG_VERBOSE
+  RTC_LOG(LS_INFO) << "<-- <CONV=" << m_conv
+                   << "><FLG=" << static_cast<unsigned>(flags)
+                   << "><SEQ=" << seq << ":" << seq + len
+                   << "><ACK=" << m_rcv_nxt << "><WND=" << m_rcv_wnd
+                   << "><TS=" << (now % 10000)
+                   << "><TSR=" << (m_ts_recent % 10000) << "><LEN=" << len
+                   << ">";
+#endif  // _DEBUGMSG
+
+  IPseudoTcpNotify::WriteResult wres = m_notify->TcpWritePacket(
+      this, reinterpret_cast<char*>(buffer.get()), len + HEADER_SIZE);
+  // Note: When len is 0, this is an ACK packet.  We don't read the return value
+  // for those, and thus we won't retry.  So go ahead and treat the packet as a
+  // success (basically simulate as if it were dropped), which will prevent our
+  // timers from being messed up.
+  if ((wres != IPseudoTcpNotify::WR_SUCCESS) && (0 != len))
+    return wres;
+
+  m_t_ack = 0;
+  if (len > 0) {
+    m_lastsend = now;
+  }
+  m_lasttraffic = now;
+  m_bOutgoing = true;
+
+  return IPseudoTcpNotify::WR_SUCCESS;
+}
+
+bool PseudoTcp::parse(const uint8_t* buffer, uint32_t size) {
+  if (size < HEADER_SIZE)
+    return false;
+
+  Segment seg;
+  seg.conv = bytes_to_long(buffer);
+  seg.seq = bytes_to_long(buffer + 4);
+  seg.ack = bytes_to_long(buffer + 8);
+  seg.flags = buffer[13];
+  seg.wnd = bytes_to_short(buffer + 14);
+
+  seg.tsval = bytes_to_long(buffer + 16);
+  seg.tsecr = bytes_to_long(buffer + 20);
+
+  seg.data = reinterpret_cast<const char*>(buffer) + HEADER_SIZE;
+  seg.len = size - HEADER_SIZE;
+
+#if _DEBUGMSG >= _DBG_VERBOSE
+  RTC_LOG(LS_INFO) << "--> <CONV=" << seg.conv
+                   << "><FLG=" << static_cast<unsigned>(seg.flags)
+                   << "><SEQ=" << seg.seq << ":" << seg.seq + seg.len
+                   << "><ACK=" << seg.ack << "><WND=" << seg.wnd
+                   << "><TS=" << (seg.tsval % 10000)
+                   << "><TSR=" << (seg.tsecr % 10000) << "><LEN=" << seg.len
+                   << ">";
+#endif  // _DEBUGMSG
+
+  return process(seg);
+}
+
+bool PseudoTcp::clock_check(uint32_t now, long& nTimeout) {
+  if (m_shutdown == SD_FORCEFUL)
+    return false;
+
+  if ((m_shutdown == SD_GRACEFUL) &&
+      ((m_state != TCP_ESTABLISHED) ||
+       ((m_sbuf.GetBuffered() == 0) && (m_t_ack == 0)))) {
+    return false;
+  }
+
+  if (m_state == TCP_CLOSED) {
+    nTimeout = CLOSED_TIMEOUT;
+    return true;
+  }
+
+  nTimeout = DEFAULT_TIMEOUT;
+
+  if (m_t_ack) {
+    nTimeout = std::min<int32_t>(nTimeout,
+                                 rtc::TimeDiff32(m_t_ack + m_ack_delay, now));
+  }
+  if (m_rto_base) {
+    nTimeout = std::min<int32_t>(nTimeout,
+                                 rtc::TimeDiff32(m_rto_base + m_rx_rto, now));
+  }
+  if (m_snd_wnd == 0) {
+    nTimeout = std::min<int32_t>(nTimeout,
+                                 rtc::TimeDiff32(m_lastsend + m_rx_rto, now));
+  }
+#if PSEUDO_KEEPALIVE
+  if (m_state == TCP_ESTABLISHED) {
+    nTimeout = std::min<int32_t>(
+        nTimeout,
+        rtc::TimeDiff32(
+            m_lasttraffic + (m_bOutgoing ? IDLE_PING * 3 / 2 : IDLE_PING),
+            now));
+  }
+#endif  // PSEUDO_KEEPALIVE
+  return true;
+}
+
+bool PseudoTcp::process(Segment& seg) {
+  // If this is the wrong conversation, send a reset!?! (with the correct
+  // conversation?)
+  if (seg.conv != m_conv) {
+    // if ((seg.flags & FLAG_RST) == 0) {
+    //  packet(tcb, seg.ack, 0, FLAG_RST, 0, 0);
+    //}
+    RTC_LOG_F(LS_ERROR) << "wrong conversation";
+    return false;
+  }
+
+  uint32_t now = Now();
+  m_lasttraffic = m_lastrecv = now;
+  m_bOutgoing = false;
+
+  if (m_state == TCP_CLOSED) {
+    // !?! send reset?
+    RTC_LOG_F(LS_ERROR) << "closed";
+    return false;
+  }
+
+  // Check if this is a reset segment
+  if (seg.flags & FLAG_RST) {
+    closedown(ECONNRESET);
+    return false;
+  }
+
+  // Check for control data
+  bool bConnect = false;
+  if (seg.flags & FLAG_CTL) {
+    if (seg.len == 0) {
+      RTC_LOG_F(LS_ERROR) << "Missing control code";
+      return false;
+    } else if (seg.data[0] == CTL_CONNECT) {
+      bConnect = true;
+
+      // TCP options are in the remainder of the payload after CTL_CONNECT.
+      parseOptions(&seg.data[1], seg.len - 1);
+
+      if (m_state == TCP_LISTEN) {
+        m_state = TCP_SYN_RECEIVED;
+        RTC_LOG(LS_INFO) << "State: TCP_SYN_RECEIVED";
+        // m_notify->associate(addr);
+        queueConnectMessage();
+      } else if (m_state == TCP_SYN_SENT) {
+        m_state = TCP_ESTABLISHED;
+        RTC_LOG(LS_INFO) << "State: TCP_ESTABLISHED";
+        adjustMTU();
+        if (m_notify) {
+          m_notify->OnTcpOpen(this);
+        }
+        // notify(evOpen);
+      }
+    } else {
+      RTC_LOG_F(LS_WARNING) << "Unknown control code: " << seg.data[0];
+      return false;
+    }
+  }
+
+  // Update timestamp
+  if ((seg.seq <= m_ts_lastack) && (m_ts_lastack < seg.seq + seg.len)) {
+    m_ts_recent = seg.tsval;
+  }
+
+  // Check if this is a valuable ack
+  if ((seg.ack > m_snd_una) && (seg.ack <= m_snd_nxt)) {
+    // Calculate round-trip time
+    if (seg.tsecr) {
+      int32_t rtt = rtc::TimeDiff32(now, seg.tsecr);
+      if (rtt >= 0) {
+        if (m_rx_srtt == 0) {
+          m_rx_srtt = rtt;
+          m_rx_rttvar = rtt / 2;
+        } else {
+          uint32_t unsigned_rtt = static_cast<uint32_t>(rtt);
+          uint32_t abs_err = unsigned_rtt > m_rx_srtt
+                                 ? unsigned_rtt - m_rx_srtt
+                                 : m_rx_srtt - unsigned_rtt;
+          m_rx_rttvar = (3 * m_rx_rttvar + abs_err) / 4;
+          m_rx_srtt = (7 * m_rx_srtt + rtt) / 8;
+        }
+        m_rx_rto = rtc::SafeClamp(m_rx_srtt + rtc::SafeMax(1, 4 * m_rx_rttvar),
+                                  MIN_RTO, MAX_RTO);
+#if _DEBUGMSG >= _DBG_VERBOSE
+        RTC_LOG(LS_INFO) << "rtt: " << rtt << "  srtt: " << m_rx_srtt
+                         << "  rto: " << m_rx_rto;
+#endif  // _DEBUGMSG
+      } else {
+        RTC_LOG(LS_WARNING) << "rtt < 0";
+      }
+    }
+
+    m_snd_wnd = static_cast<uint32_t>(seg.wnd) << m_swnd_scale;
+
+    uint32_t nAcked = seg.ack - m_snd_una;
+    m_snd_una = seg.ack;
+
+    m_rto_base = (m_snd_una == m_snd_nxt) ? 0 : now;
+
+    m_sbuf.ConsumeReadData(nAcked);
+
+    for (uint32_t nFree = nAcked; nFree > 0;) {
+      RTC_DCHECK(!m_slist.empty());
+      if (nFree < m_slist.front().len) {
+        m_slist.front().len -= nFree;
+        nFree = 0;
+      } else {
+        if (m_slist.front().len > m_largest) {
+          m_largest = m_slist.front().len;
+        }
+        nFree -= m_slist.front().len;
+        m_slist.pop_front();
+      }
+    }
+
+    if (m_dup_acks >= 3) {
+      if (m_snd_una >= m_recover) {  // NewReno
+        uint32_t nInFlight = m_snd_nxt - m_snd_una;
+        m_cwnd = std::min(m_ssthresh, nInFlight + m_mss);  // (Fast Retransmit)
+#if _DEBUGMSG >= _DBG_NORMAL
+        RTC_LOG(LS_INFO) << "exit recovery";
+#endif  // _DEBUGMSG
+        m_dup_acks = 0;
+      } else {
+#if _DEBUGMSG >= _DBG_NORMAL
+        RTC_LOG(LS_INFO) << "recovery retransmit";
+#endif  // _DEBUGMSG
+        if (!transmit(m_slist.begin(), now)) {
+          closedown(ECONNABORTED);
+          return false;
+        }
+        m_cwnd += m_mss - std::min(nAcked, m_cwnd);
+      }
+    } else {
+      m_dup_acks = 0;
+      // Slow start, congestion avoidance
+      if (m_cwnd < m_ssthresh) {
+        m_cwnd += m_mss;
+      } else {
+        m_cwnd += std::max<uint32_t>(1, m_mss * m_mss / m_cwnd);
+      }
+    }
+  } else if (seg.ack == m_snd_una) {
+    // !?! Note, tcp says don't do this... but otherwise how does a closed
+    // window become open?
+    m_snd_wnd = static_cast<uint32_t>(seg.wnd) << m_swnd_scale;
+
+    // Check duplicate acks
+    if (seg.len > 0) {
+      // it's a dup ack, but with a data payload, so don't modify m_dup_acks
+    } else if (m_snd_una != m_snd_nxt) {
+      m_dup_acks += 1;
+      if (m_dup_acks == 3) {  // (Fast Retransmit)
+#if _DEBUGMSG >= _DBG_NORMAL
+        RTC_LOG(LS_INFO) << "enter recovery";
+        RTC_LOG(LS_INFO) << "recovery retransmit";
+#endif  // _DEBUGMSG
+        if (!transmit(m_slist.begin(), now)) {
+          closedown(ECONNABORTED);
+          return false;
+        }
+        m_recover = m_snd_nxt;
+        uint32_t nInFlight = m_snd_nxt - m_snd_una;
+        m_ssthresh = std::max(nInFlight / 2, 2 * m_mss);
+        // RTC_LOG(LS_INFO) << "m_ssthresh: " << m_ssthresh << "  nInFlight: "
+        // << nInFlight << "  m_mss: " << m_mss;
+        m_cwnd = m_ssthresh + 3 * m_mss;
+      } else if (m_dup_acks > 3) {
+        m_cwnd += m_mss;
+      }
+    } else {
+      m_dup_acks = 0;
+    }
+  }
+
+  // !?! A bit hacky
+  if ((m_state == TCP_SYN_RECEIVED) && !bConnect) {
+    m_state = TCP_ESTABLISHED;
+    RTC_LOG(LS_INFO) << "State: TCP_ESTABLISHED";
+    adjustMTU();
+    if (m_notify) {
+      m_notify->OnTcpOpen(this);
+    }
+    // notify(evOpen);
+  }
+
+  // If we make room in the send queue, notify the user
+  // The goal it to make sure we always have at least enough data to fill the
+  // window.  We'd like to notify the app when we are halfway to that point.
+  const uint32_t kIdealRefillSize = (m_sbuf_len + m_rbuf_len) / 2;
+  if (m_bWriteEnable &&
+      static_cast<uint32_t>(m_sbuf.GetBuffered()) < kIdealRefillSize) {
+    m_bWriteEnable = false;
+    if (m_notify) {
+      m_notify->OnTcpWriteable(this);
+    }
+    // notify(evWrite);
+  }
+
+  // Conditions were acks must be sent:
+  // 1) Segment is too old (they missed an ACK) (immediately)
+  // 2) Segment is too new (we missed a segment) (immediately)
+  // 3) Segment has data (so we need to ACK!) (delayed)
+  // ... so the only time we don't need to ACK, is an empty segment that points
+  // to rcv_nxt!
+
+  SendFlags sflags = sfNone;
+  if (seg.seq != m_rcv_nxt) {
+    sflags = sfImmediateAck;  // (Fast Recovery)
+  } else if (seg.len != 0) {
+    if (m_ack_delay == 0) {
+      sflags = sfImmediateAck;
+    } else {
+      sflags = sfDelayedAck;
+    }
+  }
+#if _DEBUGMSG >= _DBG_NORMAL
+  if (sflags == sfImmediateAck) {
+    if (seg.seq > m_rcv_nxt) {
+      RTC_LOG_F(LS_INFO) << "too new";
+    } else if (seg.seq + seg.len <= m_rcv_nxt) {
+      RTC_LOG_F(LS_INFO) << "too old";
+    }
+  }
+#endif  // _DEBUGMSG
+
+  // Adjust the incoming segment to fit our receive buffer
+  if (seg.seq < m_rcv_nxt) {
+    uint32_t nAdjust = m_rcv_nxt - seg.seq;
+    if (nAdjust < seg.len) {
+      seg.seq += nAdjust;
+      seg.data += nAdjust;
+      seg.len -= nAdjust;
+    } else {
+      seg.len = 0;
+    }
+  }
+
+  size_t available_space = 0;
+  m_rbuf.GetWriteRemaining(&available_space);
+
+  if ((seg.seq + seg.len - m_rcv_nxt) >
+      static_cast<uint32_t>(available_space)) {
+    uint32_t nAdjust =
+        seg.seq + seg.len - m_rcv_nxt - static_cast<uint32_t>(available_space);
+    if (nAdjust < seg.len) {
+      seg.len -= nAdjust;
+    } else {
+      seg.len = 0;
+    }
+  }
+
+  bool bIgnoreData = (seg.flags & FLAG_CTL) || (m_shutdown != SD_NONE);
+  bool bNewData = false;
+
+  if (seg.len > 0) {
+    bool bRecover = false;
+    if (bIgnoreData) {
+      if (seg.seq == m_rcv_nxt) {
+        m_rcv_nxt += seg.len;
+        // If we received a data segment out of order relative to a control
+        // segment, then we wrote it into the receive buffer at an offset (see
+        // "WriteOffset") below. So we need to advance the position in the
+        // buffer to avoid corrupting data. See bugs.webrtc.org/9208
+        //
+        // We advance the position in the buffer by N bytes by acting like we
+        // wrote N bytes and then immediately read them. We can only do this if
+        // there's not already data ready to read, but this should always be
+        // true in the problematic scenario, since control frames are always
+        // sent first in the stream.
+        if (m_rbuf.GetBuffered() == 0) {
+          m_rbuf.ConsumeWriteBuffer(seg.len);
+          m_rbuf.ConsumeReadData(seg.len);
+          // After shifting the position in the buffer, we may have
+          // out-of-order packets ready to be recovered.
+          bRecover = true;
+        }
+      }
+    } else {
+      uint32_t nOffset = seg.seq - m_rcv_nxt;
+
+      if (!m_rbuf.WriteOffset(seg.data, seg.len, nOffset, NULL)) {
+        // Ignore incoming packets outside of the receive window.
+        return false;
+      }
+
+      if (seg.seq == m_rcv_nxt) {
+        m_rbuf.ConsumeWriteBuffer(seg.len);
+        m_rcv_nxt += seg.len;
+        m_rcv_wnd -= seg.len;
+        bNewData = true;
+        // May be able to recover packets previously received out-of-order
+        // now.
+        bRecover = true;
+      } else {
+#if _DEBUGMSG >= _DBG_NORMAL
+        RTC_LOG(LS_INFO) << "Saving " << seg.len << " bytes (" << seg.seq
+                         << " -> " << seg.seq + seg.len << ")";
+#endif  // _DEBUGMSG
+        RSegment rseg;
+        rseg.seq = seg.seq;
+        rseg.len = seg.len;
+        RList::iterator it = m_rlist.begin();
+        while ((it != m_rlist.end()) && (it->seq < rseg.seq)) {
+          ++it;
+        }
+        m_rlist.insert(it, rseg);
+      }
+    }
+    if (bRecover) {
+      RList::iterator it = m_rlist.begin();
+      while ((it != m_rlist.end()) && (it->seq <= m_rcv_nxt)) {
+        if (it->seq + it->len > m_rcv_nxt) {
+          sflags = sfImmediateAck;  // (Fast Recovery)
+          uint32_t nAdjust = (it->seq + it->len) - m_rcv_nxt;
+#if _DEBUGMSG >= _DBG_NORMAL
+          RTC_LOG(LS_INFO) << "Recovered " << nAdjust << " bytes (" << m_rcv_nxt
+                           << " -> " << m_rcv_nxt + nAdjust << ")";
+#endif  // _DEBUGMSG
+          m_rbuf.ConsumeWriteBuffer(nAdjust);
+          m_rcv_nxt += nAdjust;
+          m_rcv_wnd -= nAdjust;
+          bNewData = true;
+        }
+        it = m_rlist.erase(it);
+      }
+    }
+  }
+
+  attemptSend(sflags);
+
+  // If we have new data, notify the user
+  if (bNewData && m_bReadEnable) {
+    m_bReadEnable = false;
+    if (m_notify) {
+      m_notify->OnTcpReadable(this);
+    }
+    // notify(evRead);
+  }
+
+  return true;
+}
+
+bool PseudoTcp::transmit(const SList::iterator& seg, uint32_t now) {
+  if (seg->xmit >= ((m_state == TCP_ESTABLISHED) ? 15 : 30)) {
+    RTC_LOG_F(LS_VERBOSE) << "too many retransmits";
+    return false;
+  }
+
+  uint32_t nTransmit = std::min(seg->len, m_mss);
+
+  while (true) {
+    uint32_t seq = seg->seq;
+    uint8_t flags = (seg->bCtrl ? FLAG_CTL : 0);
+    IPseudoTcpNotify::WriteResult wres =
+        packet(seq, flags, seg->seq - m_snd_una, nTransmit);
+
+    if (wres == IPseudoTcpNotify::WR_SUCCESS)
+      break;
+
+    if (wres == IPseudoTcpNotify::WR_FAIL) {
+      RTC_LOG_F(LS_VERBOSE) << "packet failed";
+      return false;
+    }
+
+    RTC_DCHECK(wres == IPseudoTcpNotify::WR_TOO_LARGE);
+
+    while (true) {
+      if (PACKET_MAXIMUMS[m_msslevel + 1] == 0) {
+        RTC_LOG_F(LS_VERBOSE) << "MTU too small";
+        return false;
+      }
+      // !?! We need to break up all outstanding and pending packets and then
+      // retransmit!?!
+
+      m_mss = PACKET_MAXIMUMS[++m_msslevel] - PACKET_OVERHEAD;
+      m_cwnd = 2 * m_mss;  // I added this... haven't researched actual formula
+      if (m_mss < nTransmit) {
+        nTransmit = m_mss;
+        break;
+      }
+    }
+#if _DEBUGMSG >= _DBG_NORMAL
+    RTC_LOG(LS_INFO) << "Adjusting mss to " << m_mss << " bytes";
+#endif  // _DEBUGMSG
+  }
+
+  if (nTransmit < seg->len) {
+    RTC_LOG_F(LS_VERBOSE) << "mss reduced to " << m_mss;
+
+    SSegment subseg(seg->seq + nTransmit, seg->len - nTransmit, seg->bCtrl);
+    // subseg.tstamp = seg->tstamp;
+    subseg.xmit = seg->xmit;
+    seg->len = nTransmit;
+
+    SList::iterator next = seg;
+    m_slist.insert(++next, subseg);
+  }
+
+  if (seg->xmit == 0) {
+    m_snd_nxt += seg->len;
+  }
+  seg->xmit += 1;
+  // seg->tstamp = now;
+  if (m_rto_base == 0) {
+    m_rto_base = now;
+  }
+
+  return true;
+}
+
+void PseudoTcp::attemptSend(SendFlags sflags) {
+  uint32_t now = Now();
+
+  if (rtc::TimeDiff32(now, m_lastsend) > static_cast<long>(m_rx_rto)) {
+    m_cwnd = m_mss;
+  }
+
+#if _DEBUGMSG
+  bool bFirst = true;
+#endif  // _DEBUGMSG
+
+  while (true) {
+    uint32_t cwnd = m_cwnd;
+    if ((m_dup_acks == 1) || (m_dup_acks == 2)) {  // Limited Transmit
+      cwnd += m_dup_acks * m_mss;
+    }
+    uint32_t nWindow = std::min(m_snd_wnd, cwnd);
+    uint32_t nInFlight = m_snd_nxt - m_snd_una;
+    uint32_t nUseable = (nInFlight < nWindow) ? (nWindow - nInFlight) : 0;
+
+    size_t snd_buffered = m_sbuf.GetBuffered();
+    uint32_t nAvailable =
+        std::min(static_cast<uint32_t>(snd_buffered) - nInFlight, m_mss);
+
+    if (nAvailable > nUseable) {
+      if (nUseable * 4 < nWindow) {
+        // RFC 813 - avoid SWS
+        nAvailable = 0;
+      } else {
+        nAvailable = nUseable;
+      }
+    }
+
+#if _DEBUGMSG >= _DBG_VERBOSE
+    if (bFirst) {
+      size_t available_space = 0;
+      m_sbuf.GetWriteRemaining(&available_space);
+
+      bFirst = false;
+      RTC_LOG(LS_INFO) << "[cwnd: " << m_cwnd << "  nWindow: " << nWindow
+                       << "  nInFlight: " << nInFlight
+                       << "  nAvailable: " << nAvailable
+                       << "  nQueued: " << snd_buffered
+                       << "  nEmpty: " << available_space
+                       << "  ssthresh: " << m_ssthresh << "]";
+    }
+#endif  // _DEBUGMSG
+
+    if (nAvailable == 0) {
+      if (sflags == sfNone)
+        return;
+
+      // If this is an immediate ack, or the second delayed ack
+      if ((sflags == sfImmediateAck) || m_t_ack) {
+        packet(m_snd_nxt, 0, 0, 0);
+      } else {
+        m_t_ack = Now();
+      }
+      return;
+    }
+
+    // Nagle's algorithm.
+    // If there is data already in-flight, and we haven't a full segment of
+    // data ready to send then hold off until we get more to send, or the
+    // in-flight data is acknowledged.
+    if (m_use_nagling && (m_snd_nxt > m_snd_una) && (nAvailable < m_mss)) {
+      return;
+    }
+
+    // Find the next segment to transmit
+    SList::iterator it = m_slist.begin();
+    while (it->xmit > 0) {
+      ++it;
+      RTC_DCHECK(it != m_slist.end());
+    }
+    SList::iterator seg = it;
+
+    // If the segment is too large, break it into two
+    if (seg->len > nAvailable) {
+      SSegment subseg(seg->seq + nAvailable, seg->len - nAvailable, seg->bCtrl);
+      seg->len = nAvailable;
+      m_slist.insert(++it, subseg);
+    }
+
+    if (!transmit(seg, now)) {
+      RTC_LOG_F(LS_VERBOSE) << "transmit failed";
+      // TODO(?): consider closing socket
+      return;
+    }
+
+    sflags = sfNone;
+  }
+}
+
+void PseudoTcp::closedown(uint32_t err) {
+  RTC_LOG(LS_INFO) << "State: TCP_CLOSED";
+  m_state = TCP_CLOSED;
+  if (m_notify) {
+    m_notify->OnTcpClosed(this, err);
+  }
+  // notify(evClose, err);
+}
+
+void PseudoTcp::adjustMTU() {
+  // Determine our current mss level, so that we can adjust appropriately later
+  for (m_msslevel = 0; PACKET_MAXIMUMS[m_msslevel + 1] > 0; ++m_msslevel) {
+    if (static_cast<uint16_t>(PACKET_MAXIMUMS[m_msslevel]) <= m_mtu_advise) {
+      break;
+    }
+  }
+  m_mss = m_mtu_advise - PACKET_OVERHEAD;
+// !?! Should we reset m_largest here?
+#if _DEBUGMSG >= _DBG_NORMAL
+  RTC_LOG(LS_INFO) << "Adjusting mss to " << m_mss << " bytes";
+#endif  // _DEBUGMSG
+  // Enforce minimums on ssthresh and cwnd
+  m_ssthresh = std::max(m_ssthresh, 2 * m_mss);
+  m_cwnd = std::max(m_cwnd, m_mss);
+}
+
+bool PseudoTcp::isReceiveBufferFull() const {
+  size_t available_space = 0;
+  m_rbuf.GetWriteRemaining(&available_space);
+  return !available_space;
+}
+
+void PseudoTcp::disableWindowScale() {
+  m_support_wnd_scale = false;
+}
+
+void PseudoTcp::queueConnectMessage() {
+  rtc::ByteBufferWriter buf;
+
+  buf.WriteUInt8(CTL_CONNECT);
+  if (m_support_wnd_scale) {
+    buf.WriteUInt8(TCP_OPT_WND_SCALE);
+    buf.WriteUInt8(1);
+    buf.WriteUInt8(m_rwnd_scale);
+  }
+  m_snd_wnd = static_cast<uint32_t>(buf.Length());
+  queue(buf.Data(), static_cast<uint32_t>(buf.Length()), true);
+}
+
+void PseudoTcp::parseOptions(const char* data, uint32_t len) {
+  std::set<uint8_t> options_specified;
+
+  // See http://www.freesoft.org/CIE/Course/Section4/8.htm for
+  // parsing the options list.
+  rtc::ByteBufferReader buf(data, len);
+  while (buf.Length()) {
+    uint8_t kind = TCP_OPT_EOL;
+    buf.ReadUInt8(&kind);
+
+    if (kind == TCP_OPT_EOL) {
+      // End of option list.
+      break;
+    } else if (kind == TCP_OPT_NOOP) {
+      // No op.
+      continue;
+    }
+
+    // Length of this option.
+    RTC_DCHECK(len != 0);
+    uint8_t opt_len = 0;
+    buf.ReadUInt8(&opt_len);
+
+    // Content of this option.
+    if (opt_len <= buf.Length()) {
+      applyOption(kind, buf.Data(), opt_len);
+      buf.Consume(opt_len);
+    } else {
+      RTC_LOG(LS_ERROR) << "Invalid option length received.";
+      return;
+    }
+    options_specified.insert(kind);
+  }
+
+  if (options_specified.find(TCP_OPT_WND_SCALE) == options_specified.end()) {
+    RTC_LOG(LS_WARNING) << "Peer doesn't support window scaling";
+
+    if (m_rwnd_scale > 0) {
+      // Peer doesn't support TCP options and window scaling.
+      // Revert receive buffer size to default value.
+      resizeReceiveBuffer(DEFAULT_RCV_BUF_SIZE);
+      m_swnd_scale = 0;
+    }
+  }
+}
+
+void PseudoTcp::applyOption(char kind, const char* data, uint32_t len) {
+  if (kind == TCP_OPT_MSS) {
+    RTC_LOG(LS_WARNING) << "Peer specified MSS option which is not supported.";
+    // TODO(?): Implement.
+  } else if (kind == TCP_OPT_WND_SCALE) {
+    // Window scale factor.
+    // http://www.ietf.org/rfc/rfc1323.txt
+    if (len != 1) {
+      RTC_LOG_F(LS_WARNING) << "Invalid window scale option received.";
+      return;
+    }
+    applyWindowScaleOption(data[0]);
+  }
+}
+
+void PseudoTcp::applyWindowScaleOption(uint8_t scale_factor) {
+  m_swnd_scale = scale_factor;
+}
+
+void PseudoTcp::resizeSendBuffer(uint32_t new_size) {
+  m_sbuf_len = new_size;
+  m_sbuf.SetCapacity(new_size);
+}
+
+void PseudoTcp::resizeReceiveBuffer(uint32_t new_size) {
+  uint8_t scale_factor = 0;
+
+  // Determine the scale factor such that the scaled window size can fit
+  // in a 16-bit unsigned integer.
+  while (new_size > 0xFFFF) {
+    ++scale_factor;
+    new_size >>= 1;
+  }
+
+  // Determine the proper size of the buffer.
+  new_size <<= scale_factor;
+  bool result = m_rbuf.SetCapacity(new_size);
+
+  // Make sure the new buffer is large enough to contain data in the old
+  // buffer. This should always be true because this method is called either
+  // before connection is established or when peers are exchanging connect
+  // messages.
+  RTC_DCHECK(result);
+  m_rbuf_len = new_size;
+  m_rwnd_scale = scale_factor;
+  m_ssthresh = new_size;
+
+  size_t available_space = 0;
+  m_rbuf.GetWriteRemaining(&available_space);
+  m_rcv_wnd = static_cast<uint32_t>(available_space);
+}
+
+PseudoTcp::LockedFifoBuffer::LockedFifoBuffer(size_t size)
+    : buffer_(new char[size]),
+      buffer_length_(size),
+      data_length_(0),
+      read_position_(0) {}
+
+PseudoTcp::LockedFifoBuffer::~LockedFifoBuffer() {}
+
+size_t PseudoTcp::LockedFifoBuffer::GetBuffered() const {
+  webrtc::MutexLock lock(&mutex_);
+  return data_length_;
+}
+
+bool PseudoTcp::LockedFifoBuffer::SetCapacity(size_t size) {
+  webrtc::MutexLock lock(&mutex_);
+  if (data_length_ > size)
+    return false;
+
+  if (size != buffer_length_) {
+    char* buffer = new char[size];
+    const size_t copy = data_length_;
+    const size_t tail_copy = std::min(copy, buffer_length_ - read_position_);
+    memcpy(buffer, &buffer_[read_position_], tail_copy);
+    memcpy(buffer + tail_copy, &buffer_[0], copy - tail_copy);
+    buffer_.reset(buffer);
+    read_position_ = 0;
+    buffer_length_ = size;
+  }
+
+  return true;
+}
+
+bool PseudoTcp::LockedFifoBuffer::ReadOffset(void* buffer,
+                                             size_t bytes,
+                                             size_t offset,
+                                             size_t* bytes_read) {
+  webrtc::MutexLock lock(&mutex_);
+  return ReadOffsetLocked(buffer, bytes, offset, bytes_read);
+}
+
+bool PseudoTcp::LockedFifoBuffer::WriteOffset(const void* buffer,
+                                              size_t bytes,
+                                              size_t offset,
+                                              size_t* bytes_written) {
+  webrtc::MutexLock lock(&mutex_);
+  return WriteOffsetLocked(buffer, bytes, offset, bytes_written);
+}
+
+bool PseudoTcp::LockedFifoBuffer::Read(void* buffer,
+                                       size_t bytes,
+                                       size_t* bytes_read) {
+  webrtc::MutexLock lock(&mutex_);
+  size_t copy = 0;
+  if (!ReadOffsetLocked(buffer, bytes, 0, &copy))
+    return false;
+
+  // If read was successful then adjust the read position and number of
+  // bytes buffered.
+  read_position_ = (read_position_ + copy) % buffer_length_;
+  data_length_ -= copy;
+  if (bytes_read)
+    *bytes_read = copy;
+
+  return true;
+}
+
+bool PseudoTcp::LockedFifoBuffer::Write(const void* buffer,
+                                        size_t bytes,
+                                        size_t* bytes_written) {
+  webrtc::MutexLock lock(&mutex_);
+  size_t copy = 0;
+  if (!WriteOffsetLocked(buffer, bytes, 0, &copy))
+    return false;
+
+  // If write was successful then adjust the number of readable bytes.
+  data_length_ += copy;
+  if (bytes_written) {
+    *bytes_written = copy;
+  }
+
+  return true;
+}
+
+void PseudoTcp::LockedFifoBuffer::ConsumeReadData(size_t size) {
+  webrtc::MutexLock lock(&mutex_);
+  RTC_DCHECK(size <= data_length_);
+  read_position_ = (read_position_ + size) % buffer_length_;
+  data_length_ -= size;
+}
+
+void PseudoTcp::LockedFifoBuffer::ConsumeWriteBuffer(size_t size) {
+  webrtc::MutexLock lock(&mutex_);
+  RTC_DCHECK(size <= buffer_length_ - data_length_);
+  data_length_ += size;
+}
+
+bool PseudoTcp::LockedFifoBuffer::GetWriteRemaining(size_t* size) const {
+  webrtc::MutexLock lock(&mutex_);
+  *size = buffer_length_ - data_length_;
+  return true;
+}
+
+bool PseudoTcp::LockedFifoBuffer::ReadOffsetLocked(void* buffer,
+                                                   size_t bytes,
+                                                   size_t offset,
+                                                   size_t* bytes_read) {
+  if (offset >= data_length_)
+    return false;
+
+  const size_t available = data_length_ - offset;
+  const size_t read_position = (read_position_ + offset) % buffer_length_;
+  const size_t copy = std::min(bytes, available);
+  const size_t tail_copy = std::min(copy, buffer_length_ - read_position);
+  char* const p = static_cast<char*>(buffer);
+  memcpy(p, &buffer_[read_position], tail_copy);
+  memcpy(p + tail_copy, &buffer_[0], copy - tail_copy);
+
+  if (bytes_read)
+    *bytes_read = copy;
+
+  return true;
+}
+
+bool PseudoTcp::LockedFifoBuffer::WriteOffsetLocked(const void* buffer,
+                                                    size_t bytes,
+                                                    size_t offset,
+                                                    size_t* bytes_written) {
+  if (data_length_ + offset >= buffer_length_)
+    return false;
+
+  const size_t available = buffer_length_ - data_length_ - offset;
+  const size_t write_position =
+      (read_position_ + data_length_ + offset) % buffer_length_;
+  const size_t copy = std::min(bytes, available);
+  const size_t tail_copy = std::min(copy, buffer_length_ - write_position);
+  const char* const p = static_cast<const char*>(buffer);
+  memcpy(&buffer_[write_position], p, tail_copy);
+  memcpy(&buffer_[0], p + tail_copy, copy - tail_copy);
+
+  if (bytes_written)
+    *bytes_written = copy;
+
+  return true;
+}
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/pseudo_tcp.h b/third_party/libwebrtc/p2p/base/pseudo_tcp.h
new file mode 100644
index 0000000000..65b54ba125
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/pseudo_tcp.h
@@ -0,0 +1,295 @@
+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_PSEUDO_TCP_H_
+#define P2P_BASE_PSEUDO_TCP_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <list>
+#include <memory>
+
+#include "rtc_base/synchronization/mutex.h"
+#include "rtc_base/system/rtc_export.h"
+
+namespace cricket {
+
+//////////////////////////////////////////////////////////////////////
+// IPseudoTcpNotify
+//////////////////////////////////////////////////////////////////////
+
+class PseudoTcp;
+
+class IPseudoTcpNotify {
+ public:
+  // Notification of tcp events
+  virtual void OnTcpOpen(PseudoTcp* tcp) = 0;
+  virtual void OnTcpReadable(PseudoTcp* tcp) = 0;
+  virtual void OnTcpWriteable(PseudoTcp* tcp) = 0;
+  virtual void OnTcpClosed(PseudoTcp* tcp, uint32_t error) = 0;
+
+  // Write the packet onto the network
+  enum WriteResult { WR_SUCCESS, WR_TOO_LARGE, WR_FAIL };
+  virtual WriteResult TcpWritePacket(PseudoTcp* tcp,
+                                     const char* buffer,
+                                     size_t len) = 0;
+
+ protected:
+  virtual ~IPseudoTcpNotify() {}
+};
+
+//////////////////////////////////////////////////////////////////////
+// PseudoTcp
+//////////////////////////////////////////////////////////////////////
+
+class RTC_EXPORT PseudoTcp {
+ public:
+  static uint32_t Now();
+
+  PseudoTcp(IPseudoTcpNotify* notify, uint32_t conv);
+  virtual ~PseudoTcp();
+
+  int Connect();
+  int Recv(char* buffer, size_t len);
+  int Send(const char* buffer, size_t len);
+  void Close(bool force);
+  int GetError();
+
+  enum TcpState {
+    TCP_LISTEN,
+    TCP_SYN_SENT,
+    TCP_SYN_RECEIVED,
+    TCP_ESTABLISHED,
+    TCP_CLOSED
+  };
+  TcpState State() const { return m_state; }
+
+  // Call this when the PMTU changes.
+  void NotifyMTU(uint16_t mtu);
+
+  // Call this based on timeout value returned from GetNextClock.
+  // It's ok to call this too frequently.
+  void NotifyClock(uint32_t now);
+
+  // Call this whenever a packet arrives.
+  // Returns true if the packet was processed successfully.
+  bool NotifyPacket(const char* buffer, size_t len);
+
+  // Call this to determine the next time NotifyClock should be called.
+  // Returns false if the socket is ready to be destroyed.
+  bool GetNextClock(uint32_t now, long& timeout);
+
+  // Call these to get/set option values to tailor this PseudoTcp
+  // instance's behaviour for the kind of data it will carry.
+  // If an unrecognized option is set or got, an assertion will fire.
+  //
+  // Setting options for OPT_RCVBUF or OPT_SNDBUF after Connect() is called
+  // will result in an assertion.
+  enum Option {
+    OPT_NODELAY,   // Whether to enable Nagle's algorithm (0 == off)
+    OPT_ACKDELAY,  // The Delayed ACK timeout (0 == off).
+    OPT_RCVBUF,    // Set the receive buffer size, in bytes.
+    OPT_SNDBUF,    // Set the send buffer size, in bytes.
+  };
+  void GetOption(Option opt, int* value);
+  void SetOption(Option opt, int value);
+
+  // Returns current congestion window in bytes.
+  uint32_t GetCongestionWindow() const;
+
+  // Returns amount of data in bytes that has been sent, but haven't
+  // been acknowledged.
+  uint32_t GetBytesInFlight() const;
+
+  // Returns number of bytes that were written in buffer and haven't
+  // been sent.
+  uint32_t GetBytesBufferedNotSent() const;
+
+  // Returns current round-trip time estimate in milliseconds.
+  uint32_t GetRoundTripTimeEstimateMs() const;
+
+ protected:
+  enum SendFlags { sfNone, sfDelayedAck, sfImmediateAck };
+
+  struct Segment {
+    uint32_t conv, seq, ack;
+    uint8_t flags;
+    uint16_t wnd;
+    const char* data;
+    uint32_t len;
+    uint32_t tsval, tsecr;
+  };
+
+  struct SSegment {
+    SSegment(uint32_t s, uint32_t l, bool c)
+        : seq(s), len(l), /*tstamp(0),*/ xmit(0), bCtrl(c) {}
+    uint32_t seq, len;
+    // uint32_t tstamp;
+    uint8_t xmit;
+    bool bCtrl;
+  };
+  typedef std::list<SSegment> SList;
+
+  struct RSegment {
+    uint32_t seq, len;
+  };
+
+  uint32_t queue(const char* data, uint32_t len, bool bCtrl);
+
+  // Creates a packet and submits it to the network. This method can either
+  // send payload or just an ACK packet.
+  //
+  // `seq` is the sequence number of this packet.
+  // `flags` is the flags for sending this packet.
+  // `offset` is the offset to read from `m_sbuf`.
+  // `len` is the number of bytes to read from `m_sbuf` as payload. If this
+  // value is 0 then this is an ACK packet, otherwise this packet has payload.
+  IPseudoTcpNotify::WriteResult packet(uint32_t seq,
+                                       uint8_t flags,
+                                       uint32_t offset,
+                                       uint32_t len);
+  bool parse(const uint8_t* buffer, uint32_t size);
+
+  void attemptSend(SendFlags sflags = sfNone);
+
+  void closedown(uint32_t err = 0);
+
+  bool clock_check(uint32_t now, long& nTimeout);
+
+  bool process(Segment& seg);
+  bool transmit(const SList::iterator& seg, uint32_t now);
+
+  void adjustMTU();
+
+ protected:
+  // This method is used in test only to query receive buffer state.
+  bool isReceiveBufferFull() const;
+
+  // This method is only used in tests, to disable window scaling
+  // support for testing backward compatibility.
+  void disableWindowScale();
+
+ private:
+  // Queue the connect message with TCP options.
+  void queueConnectMessage();
+
+  // Parse TCP options in the header.
+  void parseOptions(const char* data, uint32_t len);
+
+  // Apply a TCP option that has been read from the header.
+  void applyOption(char kind, const char* data, uint32_t len);
+
+  // Apply window scale option.
+  void applyWindowScaleOption(uint8_t scale_factor);
+
+  // Resize the send buffer with `new_size` in bytes.
+  void resizeSendBuffer(uint32_t new_size);
+
+  // Resize the receive buffer with `new_size` in bytes. This call adjusts
+  // window scale factor `m_swnd_scale` accordingly.
+  void resizeReceiveBuffer(uint32_t new_size);
+
+  class LockedFifoBuffer final {
+   public:
+    explicit LockedFifoBuffer(size_t size);
+    ~LockedFifoBuffer();
+
+    size_t GetBuffered() const;
+    bool SetCapacity(size_t size);
+    bool ReadOffset(void* buffer,
+                    size_t bytes,
+                    size_t offset,
+                    size_t* bytes_read);
+    bool WriteOffset(const void* buffer,
+                     size_t bytes,
+                     size_t offset,
+                     size_t* bytes_written);
+    bool Read(void* buffer, size_t bytes, size_t* bytes_read);
+    bool Write(const void* buffer, size_t bytes, size_t* bytes_written);
+    void ConsumeReadData(size_t size);
+    void ConsumeWriteBuffer(size_t size);
+    bool GetWriteRemaining(size_t* size) const;
+
+   private:
+    bool ReadOffsetLocked(void* buffer,
+                          size_t bytes,
+                          size_t offset,
+                          size_t* bytes_read)
+        RTC_EXCLUSIVE_LOCKS_REQUIRED(mutex_);
+    bool WriteOffsetLocked(const void* buffer,
+                           size_t bytes,
+                           size_t offset,
+                           size_t* bytes_written)
+        RTC_EXCLUSIVE_LOCKS_REQUIRED(mutex_);
+
+    // the allocated buffer
+    std::unique_ptr<char[]> buffer_ RTC_GUARDED_BY(mutex_);
+    // size of the allocated buffer
+    size_t buffer_length_ RTC_GUARDED_BY(mutex_);
+    // amount of readable data in the buffer
+    size_t data_length_ RTC_GUARDED_BY(mutex_);
+    // offset to the readable data
+    size_t read_position_ RTC_GUARDED_BY(mutex_);
+    mutable webrtc::Mutex mutex_;
+  };
+
+  IPseudoTcpNotify* m_notify;
+  enum Shutdown { SD_NONE, SD_GRACEFUL, SD_FORCEFUL } m_shutdown;
+  int m_error;
+
+  // TCB data
+  TcpState m_state;
+  uint32_t m_conv;
+  bool m_bReadEnable, m_bWriteEnable, m_bOutgoing;
+  uint32_t m_lasttraffic;
+
+  // Incoming data
+  typedef std::list<RSegment> RList;
+  RList m_rlist;
+  uint32_t m_rbuf_len, m_rcv_nxt, m_rcv_wnd, m_lastrecv;
+  uint8_t m_rwnd_scale;  // Window scale factor.
+  LockedFifoBuffer m_rbuf;
+
+  // Outgoing data
+  SList m_slist;
+  uint32_t m_sbuf_len, m_snd_nxt, m_snd_wnd, m_lastsend, m_snd_una;
+  uint8_t m_swnd_scale;  // Window scale factor.
+  LockedFifoBuffer m_sbuf;
+
+  // Maximum segment size, estimated protocol level, largest segment sent
+  uint32_t m_mss, m_msslevel, m_largest, m_mtu_advise;
+  // Retransmit timer
+  uint32_t m_rto_base;
+
+  // Timestamp tracking
+  uint32_t m_ts_recent, m_ts_lastack;
+
+  // Round-trip calculation
+  uint32_t m_rx_rttvar, m_rx_srtt, m_rx_rto;
+
+  // Congestion avoidance, Fast retransmit/recovery, Delayed ACKs
+  uint32_t m_ssthresh, m_cwnd;
+  uint8_t m_dup_acks;
+  uint32_t m_recover;
+  uint32_t m_t_ack;
+
+  // Configuration options
+  bool m_use_nagling;
+  uint32_t m_ack_delay;
+
+  // This is used by unit tests to test backward compatibility of
+  // PseudoTcp implementations that don't support window scaling.
+  bool m_support_wnd_scale;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_PSEUDO_TCP_H_
diff --git a/third_party/libwebrtc/p2p/base/pseudo_tcp_unittest.cc b/third_party/libwebrtc/p2p/base/pseudo_tcp_unittest.cc
new file mode 100644
index 0000000000..e56c6fa2c5
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/pseudo_tcp_unittest.cc
@@ -0,0 +1,880 @@
+/*
+ *  Copyright 2011 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/pseudo_tcp.h"
+
+#include <string.h>
+
+#include <algorithm>
+#include <cstddef>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "api/task_queue/pending_task_safety_flag.h"
+#include "api/task_queue/task_queue_base.h"
+#include "api/units/time_delta.h"
+#include "rtc_base/gunit.h"
+#include "rtc_base/helpers.h"
+#include "rtc_base/logging.h"
+#include "rtc_base/memory_stream.h"
+#include "rtc_base/time_utils.h"
+#include "test/gtest.h"
+
+using ::cricket::PseudoTcp;
+using ::webrtc::ScopedTaskSafety;
+using ::webrtc::TaskQueueBase;
+using ::webrtc::TimeDelta;
+
+static const int kConnectTimeoutMs = 10000;  // ~3 * default RTO of 3000ms
+static const int kTransferTimeoutMs = 15000;
+static const int kBlockSize = 4096;
+
+class PseudoTcpForTest : public cricket::PseudoTcp {
+ public:
+  PseudoTcpForTest(cricket::IPseudoTcpNotify* notify, uint32_t conv)
+      : PseudoTcp(notify, conv) {}
+
+  bool isReceiveBufferFull() const { return PseudoTcp::isReceiveBufferFull(); }
+
+  void disableWindowScale() { PseudoTcp::disableWindowScale(); }
+};
+
+class PseudoTcpTestBase : public ::testing::Test,
+                          public cricket::IPseudoTcpNotify {
+ public:
+  PseudoTcpTestBase()
+      : local_(this, 1),
+        remote_(this, 1),
+        have_connected_(false),
+        have_disconnected_(false),
+        local_mtu_(65535),
+        remote_mtu_(65535),
+        delay_(0),
+        loss_(0) {
+    // Set use of the test RNG to get predictable loss patterns. Otherwise,
+    // this test would occasionally get really unlucky loss and time out.
+    rtc::SetRandomTestMode(true);
+  }
+  ~PseudoTcpTestBase() {
+    // Put it back for the next test.
+    rtc::SetRandomTestMode(false);
+  }
+  // If true, both endpoints will send the "connect" segment simultaneously,
+  // rather than `local_` sending it followed by a response from `remote_`.
+  // Note that this is what chromoting ends up doing.
+  void SetSimultaneousOpen(bool enabled) { simultaneous_open_ = enabled; }
+  void SetLocalMtu(int mtu) {
+    local_.NotifyMTU(mtu);
+    local_mtu_ = mtu;
+  }
+  void SetRemoteMtu(int mtu) {
+    remote_.NotifyMTU(mtu);
+    remote_mtu_ = mtu;
+  }
+  void SetDelay(int delay) { delay_ = delay; }
+  void SetLoss(int percent) { loss_ = percent; }
+  // Used to cause the initial "connect" segment to be lost, needed for a
+  // regression test.
+  void DropNextPacket() { drop_next_packet_ = true; }
+  void SetOptNagling(bool enable_nagles) {
+    local_.SetOption(PseudoTcp::OPT_NODELAY, !enable_nagles);
+    remote_.SetOption(PseudoTcp::OPT_NODELAY, !enable_nagles);
+  }
+  void SetOptAckDelay(int ack_delay) {
+    local_.SetOption(PseudoTcp::OPT_ACKDELAY, ack_delay);
+    remote_.SetOption(PseudoTcp::OPT_ACKDELAY, ack_delay);
+  }
+  void SetOptSndBuf(int size) {
+    local_.SetOption(PseudoTcp::OPT_SNDBUF, size);
+    remote_.SetOption(PseudoTcp::OPT_SNDBUF, size);
+  }
+  void SetRemoteOptRcvBuf(int size) {
+    remote_.SetOption(PseudoTcp::OPT_RCVBUF, size);
+  }
+  void SetLocalOptRcvBuf(int size) {
+    local_.SetOption(PseudoTcp::OPT_RCVBUF, size);
+  }
+  void DisableRemoteWindowScale() { remote_.disableWindowScale(); }
+  void DisableLocalWindowScale() { local_.disableWindowScale(); }
+
+ protected:
+  int Connect() {
+    int ret = local_.Connect();
+    if (ret == 0) {
+      UpdateLocalClock();
+    }
+    if (simultaneous_open_) {
+      ret = remote_.Connect();
+      if (ret == 0) {
+        UpdateRemoteClock();
+      }
+    }
+    return ret;
+  }
+  void Close() {
+    local_.Close(false);
+    UpdateLocalClock();
+  }
+
+  virtual void OnTcpOpen(PseudoTcp* tcp) {
+    // Consider ourselves connected when the local side gets OnTcpOpen.
+    // OnTcpWriteable isn't fired at open, so we trigger it now.
+    RTC_LOG(LS_VERBOSE) << "Opened";
+    if (tcp == &local_) {
+      have_connected_ = true;
+      OnTcpWriteable(tcp);
+    }
+  }
+  // Test derived from the base should override
+  //   virtual void OnTcpReadable(PseudoTcp* tcp)
+  // and
+  //   virtual void OnTcpWritable(PseudoTcp* tcp)
+  virtual void OnTcpClosed(PseudoTcp* tcp, uint32_t error) {
+    // Consider ourselves closed when the remote side gets OnTcpClosed.
+    // TODO(?): OnTcpClosed is only ever notified in case of error in
+    // the current implementation.  Solicited close is not (yet) supported.
+    RTC_LOG(LS_VERBOSE) << "Closed";
+    EXPECT_EQ(0U, error);
+    if (tcp == &remote_) {
+      have_disconnected_ = true;
+    }
+  }
+  virtual WriteResult TcpWritePacket(PseudoTcp* tcp,
+                                     const char* buffer,
+                                     size_t len) {
+    // Drop a packet if the test called DropNextPacket.
+    if (drop_next_packet_) {
+      drop_next_packet_ = false;
+      RTC_LOG(LS_VERBOSE) << "Dropping packet due to DropNextPacket, size="
+                          << len;
+      return WR_SUCCESS;
+    }
+    // Randomly drop the desired percentage of packets.
+    if (rtc::CreateRandomId() % 100 < static_cast<uint32_t>(loss_)) {
+      RTC_LOG(LS_VERBOSE) << "Randomly dropping packet, size=" << len;
+      return WR_SUCCESS;
+    }
+    // Also drop packets that are larger than the configured MTU.
+    if (len > static_cast<size_t>(std::min(local_mtu_, remote_mtu_))) {
+      RTC_LOG(LS_VERBOSE) << "Dropping packet that exceeds path MTU, size="
+                          << len;
+      return WR_SUCCESS;
+    }
+    PseudoTcp* other;
+    ScopedTaskSafety* timer;
+    if (tcp == &local_) {
+      other = &remote_;
+      timer = &remote_timer_;
+    } else {
+      other = &local_;
+      timer = &local_timer_;
+    }
+    std::string packet(buffer, len);
+    ++packets_in_flight_;
+    TaskQueueBase::Current()->PostDelayedTask(
+        [other, timer, packet = std::move(packet), this] {
+          --packets_in_flight_;
+          other->NotifyPacket(packet.c_str(), packet.size());
+          UpdateClock(*other, *timer);
+        },
+        TimeDelta::Millis(delay_));
+    return WR_SUCCESS;
+  }
+
+  void UpdateLocalClock() { UpdateClock(local_, local_timer_); }
+  void UpdateRemoteClock() { UpdateClock(remote_, remote_timer_); }
+  static void UpdateClock(PseudoTcp& tcp, ScopedTaskSafety& timer) {
+    long interval = 0;  // NOLINT
+    tcp.GetNextClock(PseudoTcp::Now(), interval);
+    interval = std::max<int>(interval, 0L);  // sometimes interval is < 0
+    timer.reset();
+    TaskQueueBase::Current()->PostDelayedTask(
+        SafeTask(timer.flag(),
+                 [&tcp, &timer] {
+                   tcp.NotifyClock(PseudoTcp::Now());
+                   UpdateClock(tcp, timer);
+                 }),
+        TimeDelta::Millis(interval));
+  }
+
+  rtc::AutoThread main_thread_;
+  PseudoTcpForTest local_;
+  PseudoTcpForTest remote_;
+  ScopedTaskSafety local_timer_;
+  ScopedTaskSafety remote_timer_;
+  rtc::MemoryStream send_stream_;
+  rtc::MemoryStream recv_stream_;
+  bool have_connected_;
+  bool have_disconnected_;
+  int local_mtu_;
+  int remote_mtu_;
+  int delay_;
+  int loss_;
+  bool drop_next_packet_ = false;
+  bool simultaneous_open_ = false;
+  int packets_in_flight_ = 0;
+};
+
+class PseudoTcpTest : public PseudoTcpTestBase {
+ public:
+  void TestTransfer(int size) {
+    uint32_t start;
+    int32_t elapsed;
+    size_t received;
+    // Create some dummy data to send.
+    send_stream_.ReserveSize(size);
+    for (int i = 0; i < size; ++i) {
+      uint8_t ch = static_cast<uint8_t>(i);
+      size_t written;
+      int error;
+      send_stream_.Write(rtc::MakeArrayView(&ch, 1), written, error);
+    }
+    send_stream_.Rewind();
+    // Prepare the receive stream.
+    recv_stream_.ReserveSize(size);
+    // Connect and wait until connected.
+    start = rtc::Time32();
+    EXPECT_EQ(0, Connect());
+    EXPECT_TRUE_WAIT(have_connected_, kConnectTimeoutMs);
+    // Sending will start from OnTcpWriteable and complete when all data has
+    // been received.
+    EXPECT_TRUE_WAIT(have_disconnected_, kTransferTimeoutMs);
+    elapsed = rtc::Time32() - start;
+    recv_stream_.GetSize(&received);
+    // Ensure we closed down OK and we got the right data.
+    // TODO(?): Ensure the errors are cleared properly.
+    // EXPECT_EQ(0, local_.GetError());
+    // EXPECT_EQ(0, remote_.GetError());
+    EXPECT_EQ(static_cast<size_t>(size), received);
+    EXPECT_EQ(0,
+              memcmp(send_stream_.GetBuffer(), recv_stream_.GetBuffer(), size));
+    RTC_LOG(LS_INFO) << "Transferred " << received << " bytes in " << elapsed
+                     << " ms (" << size * 8 / elapsed << " Kbps)";
+  }
+
+ private:
+  // IPseudoTcpNotify interface
+
+  virtual void OnTcpReadable(PseudoTcp* tcp) {
+    // Stream bytes to the recv stream as they arrive.
+    if (tcp == &remote_) {
+      ReadData();
+
+      // TODO(?): OnTcpClosed() is currently only notified on error -
+      // there is no on-the-wire equivalent of TCP FIN.
+      // So we fake the notification when all the data has been read.
+      size_t received, required;
+      recv_stream_.GetPosition(&received);
+      send_stream_.GetSize(&required);
+      if (received == required)
+        OnTcpClosed(&remote_, 0);
+    }
+  }
+  virtual void OnTcpWriteable(PseudoTcp* tcp) {
+    // Write bytes from the send stream when we can.
+    // Shut down when we've sent everything.
+    if (tcp == &local_) {
+      RTC_LOG(LS_VERBOSE) << "Flow Control Lifted";
+      bool done;
+      WriteData(&done);
+      if (done) {
+        Close();
+      }
+    }
+  }
+
+  void ReadData() {
+    char block[kBlockSize];
+    size_t position;
+    int rcvd;
+    do {
+      rcvd = remote_.Recv(block, sizeof(block));
+      if (rcvd != -1) {
+        size_t written;
+        int error;
+        recv_stream_.Write(
+            rtc::MakeArrayView(reinterpret_cast<uint8_t*>(block), rcvd),
+            written, error);
+        recv_stream_.GetPosition(&position);
+        RTC_LOG(LS_VERBOSE) << "Received: " << position;
+      }
+    } while (rcvd > 0);
+  }
+  void WriteData(bool* done) {
+    size_t position, tosend;
+    int sent;
+    char block[kBlockSize];
+    do {
+      send_stream_.GetPosition(&position);
+      int error;
+      if (send_stream_.Read(
+              rtc::MakeArrayView(reinterpret_cast<uint8_t*>(block), kBlockSize),
+              tosend, error) != rtc::SR_EOS) {
+        sent = local_.Send(block, tosend);
+        UpdateLocalClock();
+        if (sent != -1) {
+          send_stream_.SetPosition(position + sent);
+          RTC_LOG(LS_VERBOSE) << "Sent: " << position + sent;
+        } else {
+          send_stream_.SetPosition(position);
+          RTC_LOG(LS_VERBOSE) << "Flow Controlled";
+        }
+      } else {
+        sent = static_cast<int>(tosend = 0);
+      }
+    } while (sent > 0);
+    *done = (tosend == 0);
+  }
+
+ private:
+  rtc::MemoryStream send_stream_;
+  rtc::MemoryStream recv_stream_;
+};
+
+class PseudoTcpTestPingPong : public PseudoTcpTestBase {
+ public:
+  PseudoTcpTestPingPong()
+      : iterations_remaining_(0),
+        sender_(NULL),
+        receiver_(NULL),
+        bytes_per_send_(0) {}
+  void SetBytesPerSend(int bytes) { bytes_per_send_ = bytes; }
+  void TestPingPong(int size, int iterations) {
+    uint32_t start, elapsed;
+    iterations_remaining_ = iterations;
+    receiver_ = &remote_;
+    sender_ = &local_;
+    // Create some dummy data to send.
+    send_stream_.ReserveSize(size);
+    for (int i = 0; i < size; ++i) {
+      uint8_t ch = static_cast<uint8_t>(i);
+      size_t written;
+      int error;
+      send_stream_.Write(rtc::MakeArrayView(&ch, 1), written, error);
+    }
+    send_stream_.Rewind();
+    // Prepare the receive stream.
+    recv_stream_.ReserveSize(size);
+    // Connect and wait until connected.
+    start = rtc::Time32();
+    EXPECT_EQ(0, Connect());
+    EXPECT_TRUE_WAIT(have_connected_, kConnectTimeoutMs);
+    // Sending will start from OnTcpWriteable and stop when the required
+    // number of iterations have completed.
+    EXPECT_TRUE_WAIT(have_disconnected_, kTransferTimeoutMs);
+    elapsed = rtc::TimeSince(start);
+    RTC_LOG(LS_INFO) << "Performed " << iterations << " pings in " << elapsed
+                     << " ms";
+  }
+
+ private:
+  // IPseudoTcpNotify interface
+
+  virtual void OnTcpReadable(PseudoTcp* tcp) {
+    if (tcp != receiver_) {
+      RTC_LOG_F(LS_ERROR) << "unexpected OnTcpReadable";
+      return;
+    }
+    // Stream bytes to the recv stream as they arrive.
+    ReadData();
+    // If we've received the desired amount of data, rewind things
+    // and send it back the other way!
+    size_t position, desired;
+    recv_stream_.GetPosition(&position);
+    send_stream_.GetSize(&desired);
+    if (position == desired) {
+      if (receiver_ == &local_ && --iterations_remaining_ == 0) {
+        Close();
+        // TODO(?): Fake OnTcpClosed() on the receiver for now.
+        OnTcpClosed(&remote_, 0);
+        return;
+      }
+      PseudoTcp* tmp = receiver_;
+      receiver_ = sender_;
+      sender_ = tmp;
+      recv_stream_.Rewind();
+      send_stream_.Rewind();
+      OnTcpWriteable(sender_);
+    }
+  }
+  virtual void OnTcpWriteable(PseudoTcp* tcp) {
+    if (tcp != sender_)
+      return;
+    // Write bytes from the send stream when we can.
+    // Shut down when we've sent everything.
+    RTC_LOG(LS_VERBOSE) << "Flow Control Lifted";
+    WriteData();
+  }
+
+  void ReadData() {
+    char block[kBlockSize];
+    size_t position;
+    int rcvd;
+    do {
+      rcvd = receiver_->Recv(block, sizeof(block));
+      if (rcvd != -1) {
+        size_t written;
+        int error;
+        recv_stream_.Write(
+            rtc::MakeArrayView(reinterpret_cast<const uint8_t*>(block), rcvd),
+            written, error);
+        recv_stream_.GetPosition(&position);
+        RTC_LOG(LS_VERBOSE) << "Received: " << position;
+      }
+    } while (rcvd > 0);
+  }
+  void WriteData() {
+    size_t position, tosend;
+    int sent;
+    char block[kBlockSize];
+    do {
+      send_stream_.GetPosition(&position);
+      tosend = bytes_per_send_ ? bytes_per_send_ : sizeof(block);
+      int error;
+      if (send_stream_.Read(
+              rtc::MakeArrayView(reinterpret_cast<uint8_t*>(block), tosend),
+              tosend, error) != rtc::SR_EOS) {
+        sent = sender_->Send(block, tosend);
+        UpdateLocalClock();
+        if (sent != -1) {
+          send_stream_.SetPosition(position + sent);
+          RTC_LOG(LS_VERBOSE) << "Sent: " << position + sent;
+        } else {
+          send_stream_.SetPosition(position);
+          RTC_LOG(LS_VERBOSE) << "Flow Controlled";
+        }
+      } else {
+        sent = static_cast<int>(tosend = 0);
+      }
+    } while (sent > 0);
+  }
+
+ private:
+  int iterations_remaining_;
+  PseudoTcp* sender_;
+  PseudoTcp* receiver_;
+  int bytes_per_send_;
+};
+
+// Fill the receiver window until it is full, drain it and then
+// fill it with the same amount. This is to test that receiver window
+// contracts and enlarges correctly.
+class PseudoTcpTestReceiveWindow : public PseudoTcpTestBase {
+ public:
+  // Not all the data are transfered, `size` just need to be big enough
+  // to fill up the receiver window twice.
+  void TestTransfer(int size) {
+    // Create some dummy data to send.
+    send_stream_.ReserveSize(size);
+    for (int i = 0; i < size; ++i) {
+      uint8_t ch = static_cast<uint8_t>(i);
+      size_t written;
+      int error;
+      send_stream_.Write(rtc::MakeArrayView(&ch, 1), written, error);
+    }
+    send_stream_.Rewind();
+
+    // Prepare the receive stream.
+    recv_stream_.ReserveSize(size);
+
+    // Connect and wait until connected.
+    EXPECT_EQ(0, Connect());
+    EXPECT_TRUE_WAIT(have_connected_, kConnectTimeoutMs);
+
+    TaskQueueBase::Current()->PostTask([this] { WriteData(); });
+    EXPECT_TRUE_WAIT(have_disconnected_, kTransferTimeoutMs);
+
+    ASSERT_EQ(2u, send_position_.size());
+    ASSERT_EQ(2u, recv_position_.size());
+
+    const size_t estimated_recv_window = EstimateReceiveWindowSize();
+
+    // The difference in consecutive send positions should equal the
+    // receive window size or match very closely. This verifies that receive
+    // window is open after receiver drained all the data.
+    const size_t send_position_diff = send_position_[1] - send_position_[0];
+    EXPECT_GE(1024u, estimated_recv_window - send_position_diff);
+
+    // Receiver drained the receive window twice.
+    EXPECT_EQ(2 * estimated_recv_window, recv_position_[1]);
+  }
+
+  uint32_t EstimateReceiveWindowSize() const {
+    return static_cast<uint32_t>(recv_position_[0]);
+  }
+
+  uint32_t EstimateSendWindowSize() const {
+    return static_cast<uint32_t>(send_position_[0] - recv_position_[0]);
+  }
+
+ private:
+  // IPseudoTcpNotify interface
+  virtual void OnTcpReadable(PseudoTcp* tcp) {}
+
+  virtual void OnTcpWriteable(PseudoTcp* tcp) {}
+
+  void ReadUntilIOPending() {
+    char block[kBlockSize];
+    size_t position;
+    int rcvd;
+
+    do {
+      rcvd = remote_.Recv(block, sizeof(block));
+      if (rcvd != -1) {
+        size_t written;
+        int error;
+        recv_stream_.Write(
+            rtc::MakeArrayView(reinterpret_cast<uint8_t*>(block), rcvd),
+            written, error);
+        recv_stream_.GetPosition(&position);
+        RTC_LOG(LS_VERBOSE) << "Received: " << position;
+      }
+    } while (rcvd > 0);
+
+    recv_stream_.GetPosition(&position);
+    recv_position_.push_back(position);
+
+    // Disconnect if we have done two transfers.
+    if (recv_position_.size() == 2u) {
+      Close();
+      OnTcpClosed(&remote_, 0);
+    } else {
+      WriteData();
+    }
+  }
+
+  void WriteData() {
+    size_t position, tosend;
+    int sent;
+    char block[kBlockSize];
+    do {
+      send_stream_.GetPosition(&position);
+      int error;
+      if (send_stream_.Read(
+              rtc::MakeArrayView(reinterpret_cast<uint8_t*>(block),
+                                 sizeof(block)),
+              tosend, error) != rtc::SR_EOS) {
+        sent = local_.Send(block, tosend);
+        UpdateLocalClock();
+        if (sent != -1) {
+          send_stream_.SetPosition(position + sent);
+          RTC_LOG(LS_VERBOSE) << "Sent: " << position + sent;
+        } else {
+          send_stream_.SetPosition(position);
+          RTC_LOG(LS_VERBOSE) << "Flow Controlled";
+        }
+      } else {
+        sent = static_cast<int>(tosend = 0);
+      }
+    } while (sent > 0);
+    // At this point, we've filled up the available space in the send queue.
+
+    if (packets_in_flight_ > 0) {
+      // If there are packet tasks, attempt to continue sending after giving
+      // those packets time to process, which should free up the send buffer.
+      rtc::Thread::Current()->PostDelayedTask([this] { WriteData(); },
+                                              TimeDelta::Millis(10));
+    } else {
+      if (!remote_.isReceiveBufferFull()) {
+        RTC_LOG(LS_ERROR) << "This shouldn't happen - the send buffer is full, "
+                             "the receive buffer is not, and there are no "
+                             "remaining messages to process.";
+      }
+      send_stream_.GetPosition(&position);
+      send_position_.push_back(position);
+
+      // Drain the receiver buffer.
+      ReadUntilIOPending();
+    }
+  }
+
+ private:
+  rtc::MemoryStream send_stream_;
+  rtc::MemoryStream recv_stream_;
+
+  std::vector<size_t> send_position_;
+  std::vector<size_t> recv_position_;
+};
+
+// Basic end-to-end data transfer tests
+
+// Test the normal case of sending data from one side to the other.
+TEST_F(PseudoTcpTest, TestSend) {
+  SetLocalMtu(1500);
+  SetRemoteMtu(1500);
+  TestTransfer(1000000);
+}
+
+// Test sending data with a 50 ms RTT. Transmission should take longer due
+// to a slower ramp-up in send rate.
+TEST_F(PseudoTcpTest, TestSendWithDelay) {
+  SetLocalMtu(1500);
+  SetRemoteMtu(1500);
+  SetDelay(50);
+  TestTransfer(1000000);
+}
+
+// Test sending data with packet loss. Transmission should take much longer due
+// to send back-off when loss occurs.
+TEST_F(PseudoTcpTest, TestSendWithLoss) {
+  SetLocalMtu(1500);
+  SetRemoteMtu(1500);
+  SetLoss(10);
+  TestTransfer(100000);  // less data so test runs faster
+}
+
+// Test sending data with a 50 ms RTT and 10% packet loss. Transmission should
+// take much longer due to send back-off and slower detection of loss.
+TEST_F(PseudoTcpTest, TestSendWithDelayAndLoss) {
+  SetLocalMtu(1500);
+  SetRemoteMtu(1500);
+  SetDelay(50);
+  SetLoss(10);
+  TestTransfer(100000);  // less data so test runs faster
+}
+
+// Test sending data with 10% packet loss and Nagling disabled.  Transmission
+// should take about the same time as with Nagling enabled.
+TEST_F(PseudoTcpTest, TestSendWithLossAndOptNaglingOff) {
+  SetLocalMtu(1500);
+  SetRemoteMtu(1500);
+  SetLoss(10);
+  SetOptNagling(false);
+  TestTransfer(100000);  // less data so test runs faster
+}
+
+// Regression test for bugs.webrtc.org/9208.
+//
+// This bug resulted in corrupted data if a "connect" segment was received after
+// a data segment. This is only possible if:
+//
+// * The initial "connect" segment is lost, and retransmitted later.
+// * Both sides send "connect"s simultaneously, such that the local side thinks
+//   a connection is established even before its "connect" has been
+//   acknowledged.
+// * Nagle algorithm disabled, allowing a data segment to be sent before the
+//   "connect" has been acknowledged.
+TEST_F(PseudoTcpTest,
+       TestSendWhenFirstPacketLostWithOptNaglingOffAndSimultaneousOpen) {
+  SetLocalMtu(1500);
+  SetRemoteMtu(1500);
+  DropNextPacket();
+  SetOptNagling(false);
+  SetSimultaneousOpen(true);
+  TestTransfer(10000);
+}
+
+// Test sending data with 10% packet loss and Delayed ACK disabled.
+// Transmission should be slightly faster than with it enabled.
+TEST_F(PseudoTcpTest, TestSendWithLossAndOptAckDelayOff) {
+  SetLocalMtu(1500);
+  SetRemoteMtu(1500);
+  SetLoss(10);
+  SetOptAckDelay(0);
+  TestTransfer(100000);
+}
+
+// Test sending data with 50ms delay and Nagling disabled.
+TEST_F(PseudoTcpTest, TestSendWithDelayAndOptNaglingOff) {
+  SetLocalMtu(1500);
+  SetRemoteMtu(1500);
+  SetDelay(50);
+  SetOptNagling(false);
+  TestTransfer(100000);  // less data so test runs faster
+}
+
+// Test sending data with 50ms delay and Delayed ACK disabled.
+TEST_F(PseudoTcpTest, TestSendWithDelayAndOptAckDelayOff) {
+  SetLocalMtu(1500);
+  SetRemoteMtu(1500);
+  SetDelay(50);
+  SetOptAckDelay(0);
+  TestTransfer(100000);  // less data so test runs faster
+}
+
+// Test a large receive buffer with a sender that doesn't support scaling.
+TEST_F(PseudoTcpTest, TestSendRemoteNoWindowScale) {
+  SetLocalMtu(1500);
+  SetRemoteMtu(1500);
+  SetLocalOptRcvBuf(100000);
+  DisableRemoteWindowScale();
+  TestTransfer(1000000);
+}
+
+// Test a large sender-side receive buffer with a receiver that doesn't support
+// scaling.
+TEST_F(PseudoTcpTest, TestSendLocalNoWindowScale) {
+  SetLocalMtu(1500);
+  SetRemoteMtu(1500);
+  SetRemoteOptRcvBuf(100000);
+  DisableLocalWindowScale();
+  TestTransfer(1000000);
+}
+
+// Test when both sides use window scaling.
+TEST_F(PseudoTcpTest, TestSendBothUseWindowScale) {
+  SetLocalMtu(1500);
+  SetRemoteMtu(1500);
+  SetRemoteOptRcvBuf(100000);
+  SetLocalOptRcvBuf(100000);
+  TestTransfer(1000000);
+}
+
+// Test using a large window scale value.
+TEST_F(PseudoTcpTest, TestSendLargeInFlight) {
+  SetLocalMtu(1500);
+  SetRemoteMtu(1500);
+  SetRemoteOptRcvBuf(100000);
+  SetLocalOptRcvBuf(100000);
+  SetOptSndBuf(150000);
+  TestTransfer(1000000);
+}
+
+TEST_F(PseudoTcpTest, TestSendBothUseLargeWindowScale) {
+  SetLocalMtu(1500);
+  SetRemoteMtu(1500);
+  SetRemoteOptRcvBuf(1000000);
+  SetLocalOptRcvBuf(1000000);
+  TestTransfer(10000000);
+}
+
+// Test using a small receive buffer.
+TEST_F(PseudoTcpTest, TestSendSmallReceiveBuffer) {
+  SetLocalMtu(1500);
+  SetRemoteMtu(1500);
+  SetRemoteOptRcvBuf(10000);
+  SetLocalOptRcvBuf(10000);
+  TestTransfer(1000000);
+}
+
+// Test using a very small receive buffer.
+TEST_F(PseudoTcpTest, TestSendVerySmallReceiveBuffer) {
+  SetLocalMtu(1500);
+  SetRemoteMtu(1500);
+  SetRemoteOptRcvBuf(100);
+  SetLocalOptRcvBuf(100);
+  TestTransfer(100000);
+}
+
+// Ping-pong (request/response) tests
+
+// Test sending <= 1x MTU of data in each ping/pong.  Should take <10ms.
+TEST_F(PseudoTcpTestPingPong, TestPingPong1xMtu) {
+  SetLocalMtu(1500);
+  SetRemoteMtu(1500);
+  TestPingPong(100, 100);
+}
+
+// Test sending 2x-3x MTU of data in each ping/pong.  Should take <10ms.
+TEST_F(PseudoTcpTestPingPong, TestPingPong3xMtu) {
+  SetLocalMtu(1500);
+  SetRemoteMtu(1500);
+  TestPingPong(400, 100);
+}
+
+// Test sending 1x-2x MTU of data in each ping/pong.
+// Should take ~1s, due to interaction between Nagling and Delayed ACK.
+TEST_F(PseudoTcpTestPingPong, TestPingPong2xMtu) {
+  SetLocalMtu(1500);
+  SetRemoteMtu(1500);
+  TestPingPong(2000, 5);
+}
+
+// Test sending 1x-2x MTU of data in each ping/pong with Delayed ACK off.
+// Should take <10ms.
+TEST_F(PseudoTcpTestPingPong, TestPingPong2xMtuWithAckDelayOff) {
+  SetLocalMtu(1500);
+  SetRemoteMtu(1500);
+  SetOptAckDelay(0);
+  TestPingPong(2000, 100);
+}
+
+// Test sending 1x-2x MTU of data in each ping/pong with Nagling off.
+// Should take <10ms.
+TEST_F(PseudoTcpTestPingPong, TestPingPong2xMtuWithNaglingOff) {
+  SetLocalMtu(1500);
+  SetRemoteMtu(1500);
+  SetOptNagling(false);
+  TestPingPong(2000, 5);
+}
+
+// Test sending a ping as pair of short (non-full) segments.
+// Should take ~1s, due to Delayed ACK interaction with Nagling.
+TEST_F(PseudoTcpTestPingPong, TestPingPongShortSegments) {
+  SetLocalMtu(1500);
+  SetRemoteMtu(1500);
+  SetOptAckDelay(5000);
+  SetBytesPerSend(50);  // i.e. two Send calls per payload
+  TestPingPong(100, 5);
+}
+
+// Test sending ping as a pair of short (non-full) segments, with Nagling off.
+// Should take <10ms.
+TEST_F(PseudoTcpTestPingPong, TestPingPongShortSegmentsWithNaglingOff) {
+  SetLocalMtu(1500);
+  SetRemoteMtu(1500);
+  SetOptNagling(false);
+  SetBytesPerSend(50);  // i.e. two Send calls per payload
+  TestPingPong(100, 5);
+}
+
+// Test sending <= 1x MTU of data ping/pong, in two segments, no Delayed ACK.
+// Should take ~1s.
+TEST_F(PseudoTcpTestPingPong, TestPingPongShortSegmentsWithAckDelayOff) {
+  SetLocalMtu(1500);
+  SetRemoteMtu(1500);
+  SetBytesPerSend(50);  // i.e. two Send calls per payload
+  SetOptAckDelay(0);
+  TestPingPong(100, 5);
+}
+
+// Test that receive window expands and contract correctly.
+TEST_F(PseudoTcpTestReceiveWindow, TestReceiveWindow) {
+  SetLocalMtu(1500);
+  SetRemoteMtu(1500);
+  SetOptNagling(false);
+  SetOptAckDelay(0);
+  TestTransfer(1024 * 1000);
+}
+
+// Test setting send window size to a very small value.
+TEST_F(PseudoTcpTestReceiveWindow, TestSetVerySmallSendWindowSize) {
+  SetLocalMtu(1500);
+  SetRemoteMtu(1500);
+  SetOptNagling(false);
+  SetOptAckDelay(0);
+  SetOptSndBuf(900);
+  TestTransfer(1024 * 1000);
+  EXPECT_EQ(900u, EstimateSendWindowSize());
+}
+
+// Test setting receive window size to a value other than default.
+TEST_F(PseudoTcpTestReceiveWindow, TestSetReceiveWindowSize) {
+  SetLocalMtu(1500);
+  SetRemoteMtu(1500);
+  SetOptNagling(false);
+  SetOptAckDelay(0);
+  SetRemoteOptRcvBuf(100000);
+  SetLocalOptRcvBuf(100000);
+  TestTransfer(1024 * 1000);
+  EXPECT_EQ(100000u, EstimateReceiveWindowSize());
+}
+
+/* Test sending data with mismatched MTUs. We should detect this and reduce
+// our packet size accordingly.
+// TODO(?): This doesn't actually work right now. The current code
+// doesn't detect if the MTU is set too high on either side.
+TEST_F(PseudoTcpTest, TestSendWithMismatchedMtus) {
+  SetLocalMtu(1500);
+  SetRemoteMtu(1280);
+  TestTransfer(1000000);
+}
+*/
diff --git a/third_party/libwebrtc/p2p/base/regathering_controller.cc b/third_party/libwebrtc/p2p/base/regathering_controller.cc
new file mode 100644
index 0000000000..572c2a616f
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/regathering_controller.cc
@@ -0,0 +1,80 @@
+/*
+ *  Copyright 2018 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/regathering_controller.h"
+
+#include "api/task_queue/pending_task_safety_flag.h"
+#include "api/units/time_delta.h"
+
+namespace webrtc {
+
+BasicRegatheringController::BasicRegatheringController(
+    const Config& config,
+    cricket::IceTransportInternal* ice_transport,
+    rtc::Thread* thread)
+    : config_(config), ice_transport_(ice_transport), thread_(thread) {
+  RTC_DCHECK(thread_);
+  RTC_DCHECK_RUN_ON(thread_);
+  RTC_DCHECK(ice_transport_);
+  ice_transport_->SignalStateChanged.connect(
+      this, &BasicRegatheringController::OnIceTransportStateChanged);
+  ice_transport->SignalWritableState.connect(
+      this, &BasicRegatheringController::OnIceTransportWritableState);
+  ice_transport->SignalReceivingState.connect(
+      this, &BasicRegatheringController::OnIceTransportReceivingState);
+  ice_transport->SignalNetworkRouteChanged.connect(
+      this, &BasicRegatheringController::OnIceTransportNetworkRouteChanged);
+}
+
+BasicRegatheringController::~BasicRegatheringController() {
+  RTC_DCHECK_RUN_ON(thread_);
+}
+
+void BasicRegatheringController::Start() {
+  RTC_DCHECK_RUN_ON(thread_);
+  ScheduleRecurringRegatheringOnFailedNetworks();
+}
+
+void BasicRegatheringController::SetConfig(const Config& config) {
+  RTC_DCHECK_RUN_ON(thread_);
+  bool need_reschedule_on_failed_networks =
+      pending_regathering_ && (config_.regather_on_failed_networks_interval !=
+                               config.regather_on_failed_networks_interval);
+  config_ = config;
+  if (need_reschedule_on_failed_networks) {
+    ScheduleRecurringRegatheringOnFailedNetworks();
+  }
+}
+
+void BasicRegatheringController::
+    ScheduleRecurringRegatheringOnFailedNetworks() {
+  RTC_DCHECK_RUN_ON(thread_);
+  RTC_DCHECK(config_.regather_on_failed_networks_interval >= 0);
+  // Reset pending_regathering_ to cancel any potentially pending tasks.
+  pending_regathering_.reset(new ScopedTaskSafety());
+
+  thread_->PostDelayedTask(
+      SafeTask(pending_regathering_->flag(),
+               [this]() {
+                 RTC_DCHECK_RUN_ON(thread_);
+                 // Only regather when the current session is in the CLEARED
+                 // state (i.e., not running or stopped). It is only
+                 // possible to enter this state when we gather continually,
+                 // so there is an implicit check on continual gathering
+                 // here.
+                 if (allocator_session_ && allocator_session_->IsCleared()) {
+                   allocator_session_->RegatherOnFailedNetworks();
+                 }
+                 ScheduleRecurringRegatheringOnFailedNetworks();
+               }),
+      TimeDelta::Millis(config_.regather_on_failed_networks_interval));
+}
+
+}  // namespace webrtc
diff --git a/third_party/libwebrtc/p2p/base/regathering_controller.h b/third_party/libwebrtc/p2p/base/regathering_controller.h
new file mode 100644
index 0000000000..a0dfb8053d
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/regathering_controller.h
@@ -0,0 +1,97 @@
+/*
+ *  Copyright 2018 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_REGATHERING_CONTROLLER_H_
+#define P2P_BASE_REGATHERING_CONTROLLER_H_
+
+#include <memory>
+
+#include "api/task_queue/pending_task_safety_flag.h"
+#include "p2p/base/ice_transport_internal.h"
+#include "p2p/base/port_allocator.h"
+#include "rtc_base/thread.h"
+
+namespace webrtc {
+
+// Controls regathering of candidates for the ICE transport passed into it,
+// reacting to signals like SignalWritableState, SignalNetworkRouteChange, etc.,
+// using methods like GetStats to get additional information, and calling
+// methods like RegatherOnFailedNetworks on the PortAllocatorSession when
+// regathering is desired.
+//
+// "Regathering" is defined as gathering additional candidates within a single
+// ICE generation (or in other words, PortAllocatorSession), and is possible
+// when "continual gathering" is enabled. This may allow connectivity to be
+// maintained and/or restored without a full ICE restart.
+//
+// Regathering will only begin after PortAllocationSession is set via
+// set_allocator_session. This should be called any time the "active"
+// PortAllocatorSession is changed (in other words, when an ICE restart occurs),
+// so that candidates are gathered for the "current" ICE generation.
+//
+// All methods of BasicRegatheringController should be called on the same
+// thread as the one passed to the constructor, and this thread should be the
+// same one where PortAllocatorSession runs, which is also identical to the
+// network thread of the ICE transport, as given by
+// P2PTransportChannel::thread().
+class BasicRegatheringController : public sigslot::has_slots<> {
+ public:
+  struct Config {
+    int regather_on_failed_networks_interval =
+        cricket::REGATHER_ON_FAILED_NETWORKS_INTERVAL;
+  };
+
+  BasicRegatheringController() = delete;
+  BasicRegatheringController(const Config& config,
+                             cricket::IceTransportInternal* ice_transport,
+                             rtc::Thread* thread);
+  ~BasicRegatheringController() override;
+  // TODO(qingsi): Remove this method after implementing a new signal in
+  // P2PTransportChannel and reacting to that signal for the initial schedules
+  // of regathering.
+  void Start();
+  void set_allocator_session(cricket::PortAllocatorSession* allocator_session) {
+    allocator_session_ = allocator_session;
+  }
+  // Setting a different config of the regathering interval range on all
+  // networks cancels and reschedules the recurring schedules, if any, of
+  // regathering on all networks. The same applies to the change of the
+  // regathering interval on the failed networks. This rescheduling behavior is
+  // seperately defined for the two config parameters.
+  void SetConfig(const Config& config);
+
+ private:
+  // TODO(qingsi): Implement the following methods and use methods from the ICE
+  // transport like GetStats to get additional information for the decision
+  // making in regathering.
+  void OnIceTransportStateChanged(cricket::IceTransportInternal*) {}
+  void OnIceTransportWritableState(rtc::PacketTransportInternal*) {}
+  void OnIceTransportReceivingState(rtc::PacketTransportInternal*) {}
+  void OnIceTransportNetworkRouteChanged(absl::optional<rtc::NetworkRoute>) {}
+  // Schedules delayed and repeated regathering of local candidates on failed
+  // networks, where the delay in milliseconds is given by the config. Each
+  // repetition is separated by the same delay. When scheduled, all previous
+  // schedules are canceled.
+  void ScheduleRecurringRegatheringOnFailedNetworks();
+  // Cancels regathering scheduled by ScheduleRecurringRegatheringOnAllNetworks.
+  void CancelScheduledRecurringRegatheringOnAllNetworks();
+
+  // We use a flag to be able to cancel pending regathering operations when
+  // the object goes out of scope or the config changes.
+  std::unique_ptr<ScopedTaskSafety> pending_regathering_;
+  Config config_;
+  cricket::IceTransportInternal* ice_transport_;
+  cricket::PortAllocatorSession* allocator_session_ = nullptr;
+  rtc::Thread* const thread_;
+};
+
+}  // namespace webrtc
+
+#endif  // P2P_BASE_REGATHERING_CONTROLLER_H_
diff --git a/third_party/libwebrtc/p2p/base/regathering_controller_unittest.cc b/third_party/libwebrtc/p2p/base/regathering_controller_unittest.cc
new file mode 100644
index 0000000000..91b7270f77
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/regathering_controller_unittest.cc
@@ -0,0 +1,189 @@
+/*
+ *  Copyright 2018 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/regathering_controller.h"
+
+#include <map>
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "api/scoped_refptr.h"
+#include "p2p/base/fake_port_allocator.h"
+#include "p2p/base/mock_ice_transport.h"
+#include "p2p/base/p2p_constants.h"
+#include "p2p/base/port.h"
+#include "p2p/base/stun_server.h"
+#include "rtc_base/gunit.h"
+#include "rtc_base/socket_address.h"
+#include "rtc_base/thread.h"
+#include "rtc_base/virtual_socket_server.h"
+#include "test/scoped_key_value_config.h"
+
+namespace {
+
+const int kOnlyLocalPorts = cricket::PORTALLOCATOR_DISABLE_STUN |
+                            cricket::PORTALLOCATOR_DISABLE_RELAY |
+                            cricket::PORTALLOCATOR_DISABLE_TCP;
+// The address of the public STUN server.
+const rtc::SocketAddress kStunAddr("99.99.99.1", cricket::STUN_SERVER_PORT);
+// The addresses for the public TURN server.
+const rtc::SocketAddress kTurnUdpIntAddr("99.99.99.3",
+                                         cricket::STUN_SERVER_PORT);
+const cricket::RelayCredentials kRelayCredentials("test", "test");
+const char kIceUfrag[] = "UF00";
+const char kIcePwd[] = "TESTICEPWD00000000000000";
+constexpr uint64_t kTiebreakerDefault = 44444;
+
+}  // namespace
+
+namespace webrtc {
+
+class RegatheringControllerTest : public ::testing::Test,
+                                  public sigslot::has_slots<> {
+ public:
+  RegatheringControllerTest()
+      : vss_(std::make_unique<rtc::VirtualSocketServer>()),
+        thread_(vss_.get()),
+        ice_transport_(std::make_unique<cricket::MockIceTransport>()),
+        packet_socket_factory_(
+            std::make_unique<rtc::BasicPacketSocketFactory>(vss_.get())),
+        allocator_(std::make_unique<cricket::FakePortAllocator>(
+            rtc::Thread::Current(),
+            packet_socket_factory_.get(),
+            &field_trials_)) {
+    allocator_->SetIceTiebreaker(kTiebreakerDefault);
+    BasicRegatheringController::Config regathering_config;
+    regathering_config.regather_on_failed_networks_interval = 0;
+    regathering_controller_.reset(new BasicRegatheringController(
+        regathering_config, ice_transport_.get(), rtc::Thread::Current()));
+  }
+
+  // Initializes the allocator and gathers candidates once by StartGettingPorts.
+  void InitializeAndGatherOnce() {
+    cricket::ServerAddresses stun_servers;
+    stun_servers.insert(kStunAddr);
+    cricket::RelayServerConfig turn_server;
+    turn_server.credentials = kRelayCredentials;
+    turn_server.ports.push_back(
+        cricket::ProtocolAddress(kTurnUdpIntAddr, cricket::PROTO_UDP));
+    std::vector<cricket::RelayServerConfig> turn_servers(1, turn_server);
+    allocator_->set_flags(kOnlyLocalPorts);
+    allocator_->SetConfiguration(stun_servers, turn_servers, 0 /* pool size */,
+                                 webrtc::NO_PRUNE);
+    allocator_session_ = allocator_->CreateSession(
+        "test", cricket::ICE_CANDIDATE_COMPONENT_RTP, kIceUfrag, kIcePwd);
+    // The gathering will take place on the current thread and the following
+    // call of StartGettingPorts is blocking. We will not ClearGettingPorts
+    // prematurely.
+    allocator_session_->StartGettingPorts();
+    allocator_session_->SignalIceRegathering.connect(
+        this, &RegatheringControllerTest::OnIceRegathering);
+    regathering_controller_->set_allocator_session(allocator_session_.get());
+  }
+
+  // The regathering controller is initialized with the allocator session
+  // cleared. Only after clearing the session, we would be able to regather. See
+  // the comments for BasicRegatheringController in regatheringcontroller.h.
+  void InitializeAndGatherOnceWithSessionCleared() {
+    InitializeAndGatherOnce();
+    allocator_session_->ClearGettingPorts();
+  }
+
+  void OnIceRegathering(cricket::PortAllocatorSession* allocator_session,
+                        cricket::IceRegatheringReason reason) {
+    ++count_[reason];
+  }
+
+  int GetRegatheringReasonCount(cricket::IceRegatheringReason reason) {
+    return count_[reason];
+  }
+
+  BasicRegatheringController* regathering_controller() {
+    return regathering_controller_.get();
+  }
+
+ private:
+  webrtc::test::ScopedKeyValueConfig field_trials_;
+  std::unique_ptr<rtc::VirtualSocketServer> vss_;
+  rtc::AutoSocketServerThread thread_;
+  std::unique_ptr<cricket::IceTransportInternal> ice_transport_;
+  std::unique_ptr<BasicRegatheringController> regathering_controller_;
+  std::unique_ptr<rtc::PacketSocketFactory> packet_socket_factory_;
+  std::unique_ptr<cricket::PortAllocator> allocator_;
+  std::unique_ptr<cricket::PortAllocatorSession> allocator_session_;
+  std::map<cricket::IceRegatheringReason, int> count_;
+};
+
+// Tests that ICE regathering occurs only if the port allocator session is
+// cleared. A port allocation session is not cleared if the initial gathering is
+// still in progress or the continual gathering is not enabled.
+TEST_F(RegatheringControllerTest,
+       IceRegatheringDoesNotOccurIfSessionNotCleared) {
+  rtc::ScopedFakeClock clock;
+  InitializeAndGatherOnce();  // Session not cleared.
+
+  BasicRegatheringController::Config config;
+  config.regather_on_failed_networks_interval = 2000;
+  regathering_controller()->SetConfig(config);
+  regathering_controller()->Start();
+  SIMULATED_WAIT(false, 10000, clock);
+  // Expect no regathering in the last 10s.
+  EXPECT_EQ(0, GetRegatheringReasonCount(
+                   cricket::IceRegatheringReason::NETWORK_FAILURE));
+}
+
+TEST_F(RegatheringControllerTest, IceRegatheringRepeatsAsScheduled) {
+  rtc::ScopedFakeClock clock;
+  InitializeAndGatherOnceWithSessionCleared();
+
+  BasicRegatheringController::Config config;
+  config.regather_on_failed_networks_interval = 2000;
+  regathering_controller()->SetConfig(config);
+  regathering_controller()->Start();
+  SIMULATED_WAIT(false, 2000 - 1, clock);
+  // Expect no regathering.
+  EXPECT_EQ(0, GetRegatheringReasonCount(
+                   cricket::IceRegatheringReason::NETWORK_FAILURE));
+  SIMULATED_WAIT(false, 2, clock);
+  // Expect regathering on all networks and on failed networks to happen once
+  // respectively in that last 2s with 2s interval.
+  EXPECT_EQ(1, GetRegatheringReasonCount(
+                   cricket::IceRegatheringReason::NETWORK_FAILURE));
+  SIMULATED_WAIT(false, 11000, clock);
+  // Expect regathering to happen for another 5 times in 11s with 2s interval.
+  EXPECT_EQ(6, GetRegatheringReasonCount(
+                   cricket::IceRegatheringReason::NETWORK_FAILURE));
+}
+
+// Tests that the schedule of ICE regathering on failed networks can be canceled
+// and replaced by a new recurring schedule.
+TEST_F(RegatheringControllerTest,
+       ScheduleOfIceRegatheringOnFailedNetworksCanBeReplaced) {
+  rtc::ScopedFakeClock clock;
+  InitializeAndGatherOnceWithSessionCleared();
+
+  BasicRegatheringController::Config config;
+  config.regather_on_failed_networks_interval = 2000;
+  regathering_controller()->SetConfig(config);
+  regathering_controller()->Start();
+  config.regather_on_failed_networks_interval = 5000;
+  regathering_controller()->SetConfig(config);
+  SIMULATED_WAIT(false, 3000, clock);
+  // Expect no regathering from the previous schedule.
+  EXPECT_EQ(0, GetRegatheringReasonCount(
+                   cricket::IceRegatheringReason::NETWORK_FAILURE));
+  SIMULATED_WAIT(false, 11000 - 3000, clock);
+  // Expect regathering to happen twice in the last 11s with 5s interval.
+  EXPECT_EQ(2, GetRegatheringReasonCount(
+                   cricket::IceRegatheringReason::NETWORK_FAILURE));
+}
+
+}  // namespace webrtc
diff --git a/third_party/libwebrtc/p2p/base/stun_port.cc b/third_party/libwebrtc/p2p/base/stun_port.cc
new file mode 100644
index 0000000000..9fd39da8f3
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/stun_port.cc
@@ -0,0 +1,700 @@
+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/stun_port.h"
+
+#include <utility>
+#include <vector>
+
+#include "absl/memory/memory.h"
+#include "absl/strings/string_view.h"
+#include "api/transport/stun.h"
+#include "p2p/base/connection.h"
+#include "p2p/base/p2p_constants.h"
+#include "p2p/base/port_allocator.h"
+#include "rtc_base/async_resolver_interface.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/experiments/field_trial_parser.h"
+#include "rtc_base/helpers.h"
+#include "rtc_base/ip_address.h"
+#include "rtc_base/logging.h"
+#include "rtc_base/strings/string_builder.h"
+
+namespace cricket {
+
+namespace {
+
+bool ResolveStunHostnameForFamily(const webrtc::FieldTrialsView& field_trials) {
+  // Bug fix for STUN hostname resolution on IPv6.
+  // Field trial key reserved in bugs.webrtc.org/14334
+  static constexpr char field_trial_name[] =
+      "WebRTC-IPv6NetworkResolutionFixes";
+  if (!field_trials.IsEnabled(field_trial_name)) {
+    return false;
+  }
+
+  webrtc::FieldTrialParameter<bool> resolve_stun_hostname_for_family(
+      "ResolveStunHostnameForFamily", /*default_value=*/false);
+  webrtc::ParseFieldTrial({&resolve_stun_hostname_for_family},
+                          field_trials.Lookup(field_trial_name));
+  return resolve_stun_hostname_for_family;
+}
+
+}  // namespace
+
+// TODO(?): Move these to a common place (used in relayport too)
+const int RETRY_TIMEOUT = 50 * 1000;  // 50 seconds
+
+// Stop logging errors in UDPPort::SendTo after we have logged
+// `kSendErrorLogLimit` messages. Start again after a successful send.
+const int kSendErrorLogLimit = 5;
+
+// Handles a binding request sent to the STUN server.
+class StunBindingRequest : public StunRequest {
+ public:
+  StunBindingRequest(UDPPort* port,
+                     const rtc::SocketAddress& addr,
+                     int64_t start_time)
+      : StunRequest(port->request_manager(),
+                    std::make_unique<StunMessage>(STUN_BINDING_REQUEST)),
+        port_(port),
+        server_addr_(addr),
+        start_time_(start_time) {}
+
+  const rtc::SocketAddress& server_addr() const { return server_addr_; }
+
+  void OnResponse(StunMessage* response) override {
+    const StunAddressAttribute* addr_attr =
+        response->GetAddress(STUN_ATTR_MAPPED_ADDRESS);
+    if (!addr_attr) {
+      RTC_LOG(LS_ERROR) << "Binding response missing mapped address.";
+    } else if (addr_attr->family() != STUN_ADDRESS_IPV4 &&
+               addr_attr->family() != STUN_ADDRESS_IPV6) {
+      RTC_LOG(LS_ERROR) << "Binding address has bad family";
+    } else {
+      rtc::SocketAddress addr(addr_attr->ipaddr(), addr_attr->port());
+      port_->OnStunBindingRequestSucceeded(this->Elapsed(), server_addr_, addr);
+    }
+
+    // The keep-alive requests will be stopped after its lifetime has passed.
+    if (WithinLifetime(rtc::TimeMillis())) {
+      port_->request_manager_.SendDelayed(
+          new StunBindingRequest(port_, server_addr_, start_time_),
+          port_->stun_keepalive_delay());
+    }
+  }
+
+  void OnErrorResponse(StunMessage* response) override {
+    const StunErrorCodeAttribute* attr = response->GetErrorCode();
+    if (!attr) {
+      RTC_LOG(LS_ERROR) << "Missing binding response error code.";
+    } else {
+      RTC_LOG(LS_ERROR) << "Binding error response:"
+                           " class="
+                        << attr->eclass() << " number=" << attr->number()
+                        << " reason=" << attr->reason();
+    }
+
+    port_->OnStunBindingOrResolveRequestFailed(
+        server_addr_, attr ? attr->number() : STUN_ERROR_GLOBAL_FAILURE,
+        attr ? attr->reason()
+             : "STUN binding response with no error code attribute.");
+
+    int64_t now = rtc::TimeMillis();
+    if (WithinLifetime(now) &&
+        rtc::TimeDiff(now, start_time_) < RETRY_TIMEOUT) {
+      port_->request_manager_.SendDelayed(
+          new StunBindingRequest(port_, server_addr_, start_time_),
+          port_->stun_keepalive_delay());
+    }
+  }
+  void OnTimeout() override {
+    RTC_LOG(LS_ERROR) << "Binding request timed out from "
+                      << port_->GetLocalAddress().ToSensitiveString() << " ("
+                      << port_->Network()->name() << ")";
+    port_->OnStunBindingOrResolveRequestFailed(
+        server_addr_, SERVER_NOT_REACHABLE_ERROR,
+        "STUN binding request timed out.");
+  }
+
+ private:
+  // Returns true if `now` is within the lifetime of the request (a negative
+  // lifetime means infinite).
+  bool WithinLifetime(int64_t now) const {
+    int lifetime = port_->stun_keepalive_lifetime();
+    return lifetime < 0 || rtc::TimeDiff(now, start_time_) <= lifetime;
+  }
+
+  UDPPort* port_;
+  const rtc::SocketAddress server_addr_;
+
+  int64_t start_time_;
+};
+
+UDPPort::AddressResolver::AddressResolver(
+    rtc::PacketSocketFactory* factory,
+    std::function<void(const rtc::SocketAddress&, int)> done_callback)
+    : socket_factory_(factory), done_(std::move(done_callback)) {}
+
+void UDPPort::AddressResolver::Resolve(
+    const rtc::SocketAddress& address,
+    int family,
+    const webrtc::FieldTrialsView& field_trials) {
+  if (resolvers_.find(address) != resolvers_.end())
+    return;
+
+  auto resolver = socket_factory_->CreateAsyncDnsResolver();
+  auto resolver_ptr = resolver.get();
+  std::pair<rtc::SocketAddress,
+            std::unique_ptr<webrtc::AsyncDnsResolverInterface>>
+      pair = std::make_pair(address, std::move(resolver));
+
+  resolvers_.insert(std::move(pair));
+  auto callback = [this, address] {
+    ResolverMap::const_iterator it = resolvers_.find(address);
+    if (it != resolvers_.end()) {
+      done_(it->first, it->second->result().GetError());
+    }
+  };
+  if (ResolveStunHostnameForFamily(field_trials)) {
+    resolver_ptr->Start(address, family, std::move(callback));
+  } else {
+    resolver_ptr->Start(address, std::move(callback));
+  }
+}
+
+bool UDPPort::AddressResolver::GetResolvedAddress(
+    const rtc::SocketAddress& input,
+    int family,
+    rtc::SocketAddress* output) const {
+  ResolverMap::const_iterator it = resolvers_.find(input);
+  if (it == resolvers_.end())
+    return false;
+
+  return it->second->result().GetResolvedAddress(family, output);
+}
+
+UDPPort::UDPPort(rtc::Thread* thread,
+                 rtc::PacketSocketFactory* factory,
+                 const rtc::Network* network,
+                 rtc::AsyncPacketSocket* socket,
+                 absl::string_view username,
+                 absl::string_view password,
+                 bool emit_local_for_anyaddress,
+                 const webrtc::FieldTrialsView* field_trials)
+    : Port(thread,
+           LOCAL_PORT_TYPE,
+           factory,
+           network,
+           username,
+           password,
+           field_trials),
+      request_manager_(
+          thread,
+          [this](const void* data, size_t size, StunRequest* request) {
+            OnSendPacket(data, size, request);
+          }),
+      socket_(socket),
+      error_(0),
+      ready_(false),
+      stun_keepalive_delay_(STUN_KEEPALIVE_INTERVAL),
+      dscp_(rtc::DSCP_NO_CHANGE),
+      emit_local_for_anyaddress_(emit_local_for_anyaddress) {}
+
+UDPPort::UDPPort(rtc::Thread* thread,
+                 rtc::PacketSocketFactory* factory,
+                 const rtc::Network* network,
+                 uint16_t min_port,
+                 uint16_t max_port,
+                 absl::string_view username,
+                 absl::string_view password,
+                 bool emit_local_for_anyaddress,
+                 const webrtc::FieldTrialsView* field_trials)
+    : Port(thread,
+           LOCAL_PORT_TYPE,
+           factory,
+           network,
+           min_port,
+           max_port,
+           username,
+           password,
+           field_trials),
+      request_manager_(
+          thread,
+          [this](const void* data, size_t size, StunRequest* request) {
+            OnSendPacket(data, size, request);
+          }),
+      socket_(nullptr),
+      error_(0),
+      ready_(false),
+      stun_keepalive_delay_(STUN_KEEPALIVE_INTERVAL),
+      dscp_(rtc::DSCP_NO_CHANGE),
+      emit_local_for_anyaddress_(emit_local_for_anyaddress) {}
+
+bool UDPPort::Init() {
+  stun_keepalive_lifetime_ = GetStunKeepaliveLifetime();
+  if (!SharedSocket()) {
+    RTC_DCHECK(socket_ == nullptr);
+    socket_ = socket_factory()->CreateUdpSocket(
+        rtc::SocketAddress(Network()->GetBestIP(), 0), min_port(), max_port());
+    if (!socket_) {
+      RTC_LOG(LS_WARNING) << ToString() << ": UDP socket creation failed";
+      return false;
+    }
+    socket_->SignalReadPacket.connect(this, &UDPPort::OnReadPacket);
+  }
+  socket_->SignalSentPacket.connect(this, &UDPPort::OnSentPacket);
+  socket_->SignalReadyToSend.connect(this, &UDPPort::OnReadyToSend);
+  socket_->SignalAddressReady.connect(this, &UDPPort::OnLocalAddressReady);
+  return true;
+}
+
+UDPPort::~UDPPort() {
+  if (!SharedSocket())
+    delete socket_;
+}
+
+void UDPPort::PrepareAddress() {
+  RTC_DCHECK(request_manager_.empty());
+  if (socket_->GetState() == rtc::AsyncPacketSocket::STATE_BOUND) {
+    OnLocalAddressReady(socket_, socket_->GetLocalAddress());
+  }
+}
+
+void UDPPort::MaybePrepareStunCandidate() {
+  // Sending binding request to the STUN server if address is available to
+  // prepare STUN candidate.
+  if (!server_addresses_.empty()) {
+    SendStunBindingRequests();
+  } else {
+    // Port is done allocating candidates.
+    MaybeSetPortCompleteOrError();
+  }
+}
+
+Connection* UDPPort::CreateConnection(const Candidate& address,
+                                      CandidateOrigin origin) {
+  if (!SupportsProtocol(address.protocol())) {
+    return nullptr;
+  }
+
+  if (!IsCompatibleAddress(address.address())) {
+    return nullptr;
+  }
+
+  // In addition to DCHECK-ing the non-emptiness of local candidates, we also
+  // skip this Port with null if there are latent bugs to violate it; otherwise
+  // it would lead to a crash when accessing the local candidate of the
+  // connection that would be created below.
+  if (Candidates().empty()) {
+    RTC_DCHECK_NOTREACHED();
+    return nullptr;
+  }
+  // When the socket is shared, the srflx candidate is gathered by the UDPPort.
+  // The assumption here is that
+  //  1) if the IP concealment with mDNS is not enabled, the gathering of the
+  //     host candidate of this port (which is synchronous),
+  //  2) or otherwise if enabled, the start of name registration of the host
+  //     candidate (as the start of asynchronous gathering)
+  // is always before the gathering of a srflx candidate (and any prflx
+  // candidate).
+  //
+  // See also the definition of MdnsNameRegistrationStatus::kNotStarted in
+  // port.h.
+  RTC_DCHECK(!SharedSocket() || Candidates()[0].type() == LOCAL_PORT_TYPE ||
+             mdns_name_registration_status() !=
+                 MdnsNameRegistrationStatus::kNotStarted);
+
+  Connection* conn = new ProxyConnection(NewWeakPtr(), 0, address);
+  AddOrReplaceConnection(conn);
+  return conn;
+}
+
+int UDPPort::SendTo(const void* data,
+                    size_t size,
+                    const rtc::SocketAddress& addr,
+                    const rtc::PacketOptions& options,
+                    bool payload) {
+  rtc::PacketOptions modified_options(options);
+  CopyPortInformationToPacketInfo(&modified_options.info_signaled_after_sent);
+  int sent = socket_->SendTo(data, size, addr, modified_options);
+  if (sent < 0) {
+    error_ = socket_->GetError();
+    // Rate limiting added for crbug.com/856088.
+    // TODO(webrtc:9622): Use general rate limiting mechanism once it exists.
+    if (send_error_count_ < kSendErrorLogLimit) {
+      ++send_error_count_;
+      RTC_LOG(LS_ERROR) << ToString() << ": UDP send of " << size
+                        << " bytes to host "
+                        << addr.ToSensitiveNameAndAddressString()
+                        << " failed with error " << error_;
+    }
+  } else {
+    send_error_count_ = 0;
+  }
+  return sent;
+}
+
+void UDPPort::UpdateNetworkCost() {
+  Port::UpdateNetworkCost();
+  stun_keepalive_lifetime_ = GetStunKeepaliveLifetime();
+}
+
+rtc::DiffServCodePoint UDPPort::StunDscpValue() const {
+  return dscp_;
+}
+
+int UDPPort::SetOption(rtc::Socket::Option opt, int value) {
+  if (opt == rtc::Socket::OPT_DSCP) {
+    // Save value for future packets we instantiate.
+    dscp_ = static_cast<rtc::DiffServCodePoint>(value);
+  }
+  return socket_->SetOption(opt, value);
+}
+
+int UDPPort::GetOption(rtc::Socket::Option opt, int* value) {
+  return socket_->GetOption(opt, value);
+}
+
+int UDPPort::GetError() {
+  return error_;
+}
+
+bool UDPPort::HandleIncomingPacket(rtc::AsyncPacketSocket* socket,
+                                   const char* data,
+                                   size_t size,
+                                   const rtc::SocketAddress& remote_addr,
+                                   int64_t packet_time_us) {
+  // All packets given to UDP port will be consumed.
+  OnReadPacket(socket, data, size, remote_addr, packet_time_us);
+  return true;
+}
+
+bool UDPPort::SupportsProtocol(absl::string_view protocol) const {
+  return protocol == UDP_PROTOCOL_NAME;
+}
+
+ProtocolType UDPPort::GetProtocol() const {
+  return PROTO_UDP;
+}
+
+void UDPPort::GetStunStats(absl::optional<StunStats>* stats) {
+  *stats = stats_;
+}
+
+void UDPPort::set_stun_keepalive_delay(const absl::optional<int>& delay) {
+  stun_keepalive_delay_ = delay.value_or(STUN_KEEPALIVE_INTERVAL);
+}
+
+void UDPPort::OnLocalAddressReady(rtc::AsyncPacketSocket* socket,
+                                  const rtc::SocketAddress& address) {
+  // When adapter enumeration is disabled and binding to the any address, the
+  // default local address will be issued as a candidate instead if
+  // `emit_local_for_anyaddress` is true. This is to allow connectivity for
+  // applications which absolutely requires a HOST candidate.
+  rtc::SocketAddress addr = address;
+
+  // If MaybeSetDefaultLocalAddress fails, we keep the "any" IP so that at
+  // least the port is listening.
+  MaybeSetDefaultLocalAddress(&addr);
+
+  AddAddress(addr, addr, rtc::SocketAddress(), UDP_PROTOCOL_NAME, "", "",
+             LOCAL_PORT_TYPE, ICE_TYPE_PREFERENCE_HOST, 0, "", false);
+  MaybePrepareStunCandidate();
+}
+
+void UDPPort::PostAddAddress(bool is_final) {
+  MaybeSetPortCompleteOrError();
+}
+
+void UDPPort::OnReadPacket(rtc::AsyncPacketSocket* socket,
+                           const char* data,
+                           size_t size,
+                           const rtc::SocketAddress& remote_addr,
+                           const int64_t& packet_time_us) {
+  RTC_DCHECK(socket == socket_);
+  RTC_DCHECK(!remote_addr.IsUnresolvedIP());
+
+  // Look for a response from the STUN server.
+  // Even if the response doesn't match one of our outstanding requests, we
+  // will eat it because it might be a response to a retransmitted packet, and
+  // we already cleared the request when we got the first response.
+  if (server_addresses_.find(remote_addr) != server_addresses_.end()) {
+    request_manager_.CheckResponse(data, size);
+    return;
+  }
+
+  if (Connection* conn = GetConnection(remote_addr)) {
+    conn->OnReadPacket(data, size, packet_time_us);
+  } else {
+    Port::OnReadPacket(data, size, remote_addr, PROTO_UDP);
+  }
+}
+
+void UDPPort::OnSentPacket(rtc::AsyncPacketSocket* socket,
+                           const rtc::SentPacket& sent_packet) {
+  PortInterface::SignalSentPacket(sent_packet);
+}
+
+void UDPPort::OnReadyToSend(rtc::AsyncPacketSocket* socket) {
+  Port::OnReadyToSend();
+}
+
+void UDPPort::SendStunBindingRequests() {
+  // We will keep pinging the stun server to make sure our NAT pin-hole stays
+  // open until the deadline (specified in SendStunBindingRequest).
+  RTC_DCHECK(request_manager_.empty());
+
+  for (ServerAddresses::const_iterator it = server_addresses_.begin();
+       it != server_addresses_.end();) {
+    // sending a STUN binding request may cause the current SocketAddress to be
+    // erased from the set, invalidating the loop iterator before it is
+    // incremented (even if the SocketAddress itself still exists). So make a
+    // copy of the loop iterator, which may be safely invalidated.
+    ServerAddresses::const_iterator addr = it++;
+    SendStunBindingRequest(*addr);
+  }
+}
+
+void UDPPort::ResolveStunAddress(const rtc::SocketAddress& stun_addr) {
+  if (!resolver_) {
+    resolver_.reset(new AddressResolver(
+        socket_factory(), [&](const rtc::SocketAddress& input, int error) {
+          OnResolveResult(input, error);
+        }));
+  }
+
+  RTC_LOG(LS_INFO) << ToString() << ": Starting STUN host lookup for "
+                   << stun_addr.ToSensitiveString();
+  resolver_->Resolve(stun_addr, Network()->family(), field_trials());
+}
+
+void UDPPort::OnResolveResult(const rtc::SocketAddress& input, int error) {
+  RTC_DCHECK(resolver_.get() != nullptr);
+
+  rtc::SocketAddress resolved;
+  if (error != 0 || !resolver_->GetResolvedAddress(
+                        input, Network()->GetBestIP().family(), &resolved)) {
+    RTC_LOG(LS_WARNING) << ToString()
+                        << ": StunPort: stun host lookup received error "
+                        << error;
+    OnStunBindingOrResolveRequestFailed(input, SERVER_NOT_REACHABLE_ERROR,
+                                        "STUN host lookup received error.");
+    return;
+  }
+
+  server_addresses_.erase(input);
+
+  if (server_addresses_.find(resolved) == server_addresses_.end()) {
+    server_addresses_.insert(resolved);
+    SendStunBindingRequest(resolved);
+  }
+}
+
+void UDPPort::SendStunBindingRequest(const rtc::SocketAddress& stun_addr) {
+  if (stun_addr.IsUnresolvedIP()) {
+    ResolveStunAddress(stun_addr);
+
+  } else if (socket_->GetState() == rtc::AsyncPacketSocket::STATE_BOUND) {
+    // Check if `server_addr_` is compatible with the port's ip.
+    if (IsCompatibleAddress(stun_addr)) {
+      request_manager_.Send(
+          new StunBindingRequest(this, stun_addr, rtc::TimeMillis()));
+    } else {
+      // Since we can't send stun messages to the server, we should mark this
+      // port ready.
+      const char* reason = "STUN server address is incompatible.";
+      RTC_LOG(LS_WARNING) << reason;
+      OnStunBindingOrResolveRequestFailed(stun_addr, SERVER_NOT_REACHABLE_ERROR,
+                                          reason);
+    }
+  }
+}
+
+bool UDPPort::MaybeSetDefaultLocalAddress(rtc::SocketAddress* addr) const {
+  if (!addr->IsAnyIP() || !emit_local_for_anyaddress_ ||
+      !Network()->default_local_address_provider()) {
+    return true;
+  }
+  rtc::IPAddress default_address;
+  bool result =
+      Network()->default_local_address_provider()->GetDefaultLocalAddress(
+          addr->family(), &default_address);
+  if (!result || default_address.IsNil()) {
+    return false;
+  }
+
+  addr->SetIP(default_address);
+  return true;
+}
+
+void UDPPort::OnStunBindingRequestSucceeded(
+    int rtt_ms,
+    const rtc::SocketAddress& stun_server_addr,
+    const rtc::SocketAddress& stun_reflected_addr) {
+  RTC_DCHECK(stats_.stun_binding_responses_received <
+             stats_.stun_binding_requests_sent);
+  stats_.stun_binding_responses_received++;
+  stats_.stun_binding_rtt_ms_total += rtt_ms;
+  stats_.stun_binding_rtt_ms_squared_total += rtt_ms * rtt_ms;
+  if (bind_request_succeeded_servers_.find(stun_server_addr) !=
+      bind_request_succeeded_servers_.end()) {
+    return;
+  }
+  bind_request_succeeded_servers_.insert(stun_server_addr);
+  // If socket is shared and `stun_reflected_addr` is equal to local socket
+  // address and mDNS obfuscation is not enabled, or if the same address has
+  // been added by another STUN server, then discarding the stun address.
+  // For STUN, related address is the local socket address.
+  if ((!SharedSocket() || stun_reflected_addr != socket_->GetLocalAddress() ||
+       Network()->GetMdnsResponder() != nullptr) &&
+      !HasStunCandidateWithAddress(stun_reflected_addr)) {
+    rtc::SocketAddress related_address = socket_->GetLocalAddress();
+    // If we can't stamp the related address correctly, empty it to avoid leak.
+    if (!MaybeSetDefaultLocalAddress(&related_address)) {
+      related_address =
+          rtc::EmptySocketAddressWithFamily(related_address.family());
+    }
+
+    rtc::StringBuilder url;
+    url << "stun:" << stun_server_addr.hostname() << ":"
+        << stun_server_addr.port();
+    AddAddress(stun_reflected_addr, socket_->GetLocalAddress(), related_address,
+               UDP_PROTOCOL_NAME, "", "", STUN_PORT_TYPE,
+               ICE_TYPE_PREFERENCE_SRFLX, 0, url.str(), false);
+  }
+  MaybeSetPortCompleteOrError();
+}
+
+void UDPPort::OnStunBindingOrResolveRequestFailed(
+    const rtc::SocketAddress& stun_server_addr,
+    int error_code,
+    absl::string_view reason) {
+  rtc::StringBuilder url;
+  url << "stun:" << stun_server_addr.ToString();
+  SignalCandidateError(
+      this, IceCandidateErrorEvent(GetLocalAddress().HostAsSensitiveURIString(),
+                                   GetLocalAddress().port(), url.str(),
+                                   error_code, reason));
+  if (bind_request_failed_servers_.find(stun_server_addr) !=
+      bind_request_failed_servers_.end()) {
+    return;
+  }
+  bind_request_failed_servers_.insert(stun_server_addr);
+  MaybeSetPortCompleteOrError();
+}
+
+void UDPPort::MaybeSetPortCompleteOrError() {
+  if (mdns_name_registration_status() ==
+      MdnsNameRegistrationStatus::kInProgress) {
+    return;
+  }
+
+  if (ready_) {
+    return;
+  }
+
+  // Do not set port ready if we are still waiting for bind responses.
+  const size_t servers_done_bind_request =
+      bind_request_failed_servers_.size() +
+      bind_request_succeeded_servers_.size();
+  if (server_addresses_.size() != servers_done_bind_request) {
+    return;
+  }
+
+  // Setting ready status.
+  ready_ = true;
+
+  // The port is "completed" if there is no stun server provided, or the bind
+  // request succeeded for any stun server, or the socket is shared.
+  if (server_addresses_.empty() || bind_request_succeeded_servers_.size() > 0 ||
+      SharedSocket()) {
+    SignalPortComplete(this);
+  } else {
+    SignalPortError(this);
+  }
+}
+
+// TODO(?): merge this with SendTo above.
+void UDPPort::OnSendPacket(const void* data, size_t size, StunRequest* req) {
+  StunBindingRequest* sreq = static_cast<StunBindingRequest*>(req);
+  rtc::PacketOptions options(StunDscpValue());
+  options.info_signaled_after_sent.packet_type = rtc::PacketType::kStunMessage;
+  CopyPortInformationToPacketInfo(&options.info_signaled_after_sent);
+  if (socket_->SendTo(data, size, sreq->server_addr(), options) < 0) {
+    RTC_LOG_ERR_EX(LS_ERROR, socket_->GetError())
+        << "UDP send of " << size << " bytes to host "
+        << sreq->server_addr().ToSensitiveNameAndAddressString()
+        << " failed with error " << error_;
+  }
+  stats_.stun_binding_requests_sent++;
+}
+
+bool UDPPort::HasStunCandidateWithAddress(
+    const rtc::SocketAddress& addr) const {
+  const std::vector<Candidate>& existing_candidates = Candidates();
+  std::vector<Candidate>::const_iterator it = existing_candidates.begin();
+  for (; it != existing_candidates.end(); ++it) {
+    if (it->type() == STUN_PORT_TYPE && it->address() == addr)
+      return true;
+  }
+  return false;
+}
+
+std::unique_ptr<StunPort> StunPort::Create(
+    rtc::Thread* thread,
+    rtc::PacketSocketFactory* factory,
+    const rtc::Network* network,
+    uint16_t min_port,
+    uint16_t max_port,
+    absl::string_view username,
+    absl::string_view password,
+    const ServerAddresses& servers,
+    absl::optional<int> stun_keepalive_interval,
+    const webrtc::FieldTrialsView* field_trials) {
+  // Using `new` to access a non-public constructor.
+  auto port = absl::WrapUnique(new StunPort(thread, factory, network, min_port,
+                                            max_port, username, password,
+                                            servers, field_trials));
+  port->set_stun_keepalive_delay(stun_keepalive_interval);
+  if (!port->Init()) {
+    return nullptr;
+  }
+  return port;
+}
+
+StunPort::StunPort(rtc::Thread* thread,
+                   rtc::PacketSocketFactory* factory,
+                   const rtc::Network* network,
+                   uint16_t min_port,
+                   uint16_t max_port,
+                   absl::string_view username,
+                   absl::string_view password,
+                   const ServerAddresses& servers,
+                   const webrtc::FieldTrialsView* field_trials)
+    : UDPPort(thread,
+              factory,
+              network,
+              min_port,
+              max_port,
+              username,
+              password,
+              false,
+              field_trials) {
+  // UDPPort will set these to local udp, updating these to STUN.
+  set_type(STUN_PORT_TYPE);
+  set_server_addresses(servers);
+}
+
+void StunPort::PrepareAddress() {
+  SendStunBindingRequests();
+}
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/stun_port.h b/third_party/libwebrtc/p2p/base/stun_port.h
new file mode 100644
index 0000000000..380dbecd2d
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/stun_port.h
@@ -0,0 +1,301 @@
+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_STUN_PORT_H_
+#define P2P_BASE_STUN_PORT_H_
+
+#include <functional>
+#include <map>
+#include <memory>
+#include <string>
+
+#include "absl/memory/memory.h"
+#include "absl/strings/string_view.h"
+#include "api/task_queue/pending_task_safety_flag.h"
+#include "p2p/base/port.h"
+#include "p2p/base/stun_request.h"
+#include "rtc_base/async_packet_socket.h"
+#include "rtc_base/system/rtc_export.h"
+
+namespace cricket {
+
+// Lifetime chosen for STUN ports on low-cost networks.
+static const int INFINITE_LIFETIME = -1;
+// Lifetime for STUN ports on high-cost networks: 2 minutes
+static const int HIGH_COST_PORT_KEEPALIVE_LIFETIME = 2 * 60 * 1000;
+
+// Communicates using the address on the outside of a NAT.
+class RTC_EXPORT UDPPort : public Port {
+ public:
+  static std::unique_ptr<UDPPort> Create(
+      rtc::Thread* thread,
+      rtc::PacketSocketFactory* factory,
+      const rtc::Network* network,
+      rtc::AsyncPacketSocket* socket,
+      absl::string_view username,
+      absl::string_view password,
+      bool emit_local_for_anyaddress,
+      absl::optional<int> stun_keepalive_interval,
+      const webrtc::FieldTrialsView* field_trials = nullptr) {
+    // Using `new` to access a non-public constructor.
+    auto port = absl::WrapUnique(
+        new UDPPort(thread, factory, network, socket, username, password,
+                    emit_local_for_anyaddress, field_trials));
+    port->set_stun_keepalive_delay(stun_keepalive_interval);
+    if (!port->Init()) {
+      return nullptr;
+    }
+    return port;
+  }
+
+  static std::unique_ptr<UDPPort> Create(
+      rtc::Thread* thread,
+      rtc::PacketSocketFactory* factory,
+      const rtc::Network* network,
+      uint16_t min_port,
+      uint16_t max_port,
+      absl::string_view username,
+      absl::string_view password,
+      bool emit_local_for_anyaddress,
+      absl::optional<int> stun_keepalive_interval,
+      const webrtc::FieldTrialsView* field_trials = nullptr) {
+    // Using `new` to access a non-public constructor.
+    auto port = absl::WrapUnique(
+        new UDPPort(thread, factory, network, min_port, max_port, username,
+                    password, emit_local_for_anyaddress, field_trials));
+    port->set_stun_keepalive_delay(stun_keepalive_interval);
+    if (!port->Init()) {
+      return nullptr;
+    }
+    return port;
+  }
+
+  ~UDPPort() override;
+
+  rtc::SocketAddress GetLocalAddress() const {
+    return socket_->GetLocalAddress();
+  }
+
+  const ServerAddresses& server_addresses() const { return server_addresses_; }
+  void set_server_addresses(const ServerAddresses& addresses) {
+    server_addresses_ = addresses;
+  }
+
+  void PrepareAddress() override;
+
+  Connection* CreateConnection(const Candidate& address,
+                               CandidateOrigin origin) override;
+  int SetOption(rtc::Socket::Option opt, int value) override;
+  int GetOption(rtc::Socket::Option opt, int* value) override;
+  int GetError() override;
+
+  bool HandleIncomingPacket(rtc::AsyncPacketSocket* socket,
+                            const char* data,
+                            size_t size,
+                            const rtc::SocketAddress& remote_addr,
+                            int64_t packet_time_us) override;
+
+  bool SupportsProtocol(absl::string_view protocol) const override;
+  ProtocolType GetProtocol() const override;
+
+  void GetStunStats(absl::optional<StunStats>* stats) override;
+
+  void set_stun_keepalive_delay(const absl::optional<int>& delay);
+  int stun_keepalive_delay() const { return stun_keepalive_delay_; }
+
+  // Visible for testing.
+  int stun_keepalive_lifetime() const { return stun_keepalive_lifetime_; }
+  void set_stun_keepalive_lifetime(int lifetime) {
+    stun_keepalive_lifetime_ = lifetime;
+  }
+
+  StunRequestManager& request_manager() { return request_manager_; }
+
+ protected:
+  UDPPort(rtc::Thread* thread,
+          rtc::PacketSocketFactory* factory,
+          const rtc::Network* network,
+          uint16_t min_port,
+          uint16_t max_port,
+          absl::string_view username,
+          absl::string_view password,
+          bool emit_local_for_anyaddress,
+          const webrtc::FieldTrialsView* field_trials);
+
+  UDPPort(rtc::Thread* thread,
+          rtc::PacketSocketFactory* factory,
+          const rtc::Network* network,
+          rtc::AsyncPacketSocket* socket,
+          absl::string_view username,
+          absl::string_view password,
+          bool emit_local_for_anyaddress,
+          const webrtc::FieldTrialsView* field_trials);
+
+  bool Init();
+
+  int SendTo(const void* data,
+             size_t size,
+             const rtc::SocketAddress& addr,
+             const rtc::PacketOptions& options,
+             bool payload) override;
+
+  void UpdateNetworkCost() override;
+
+  rtc::DiffServCodePoint StunDscpValue() const override;
+
+  void OnLocalAddressReady(rtc::AsyncPacketSocket* socket,
+                           const rtc::SocketAddress& address);
+
+  void PostAddAddress(bool is_final) override;
+
+  void OnReadPacket(rtc::AsyncPacketSocket* socket,
+                    const char* data,
+                    size_t size,
+                    const rtc::SocketAddress& remote_addr,
+                    const int64_t& packet_time_us);
+
+  void OnSentPacket(rtc::AsyncPacketSocket* socket,
+                    const rtc::SentPacket& sent_packet) override;
+
+  void OnReadyToSend(rtc::AsyncPacketSocket* socket);
+
+  // This method will send STUN binding request if STUN server address is set.
+  void MaybePrepareStunCandidate();
+
+  void SendStunBindingRequests();
+
+  // Helper function which will set `addr`'s IP to the default local address if
+  // `addr` is the "any" address and `emit_local_for_anyaddress_` is true. When
+  // returning false, it indicates that the operation has failed and the
+  // address shouldn't be used by any candidate.
+  bool MaybeSetDefaultLocalAddress(rtc::SocketAddress* addr) const;
+
+ private:
+  // A helper class which can be called repeatedly to resolve multiple
+  // addresses, as opposed to rtc::AsyncDnsResolverInterface, which can only
+  // resolve one address per instance.
+  class AddressResolver {
+   public:
+    explicit AddressResolver(
+        rtc::PacketSocketFactory* factory,
+        std::function<void(const rtc::SocketAddress&, int)> done_callback);
+
+    void Resolve(const rtc::SocketAddress& address,
+                 int family,
+                 const webrtc::FieldTrialsView& field_trials);
+    bool GetResolvedAddress(const rtc::SocketAddress& input,
+                            int family,
+                            rtc::SocketAddress* output) const;
+
+   private:
+    typedef std::map<rtc::SocketAddress,
+                     std::unique_ptr<webrtc::AsyncDnsResolverInterface>>
+        ResolverMap;
+
+    rtc::PacketSocketFactory* socket_factory_;
+    // The function is called when resolving the specified address is finished.
+    // The first argument is the input address, the second argument is the error
+    // or 0 if it succeeded.
+    std::function<void(const rtc::SocketAddress&, int)> done_;
+    // Resolver may fire callbacks that refer to done_, so ensure
+    // that all resolvers are destroyed first.
+    ResolverMap resolvers_;
+  };
+
+  // DNS resolution of the STUN server.
+  void ResolveStunAddress(const rtc::SocketAddress& stun_addr);
+  void OnResolveResult(const rtc::SocketAddress& input, int error);
+
+  // Send a STUN binding request to the given address. Calling this method may
+  // cause the set of known server addresses to be modified, eg. by replacing an
+  // unresolved server address with a resolved address.
+  void SendStunBindingRequest(const rtc::SocketAddress& stun_addr);
+
+  // Below methods handles binding request responses.
+  void OnStunBindingRequestSucceeded(
+      int rtt_ms,
+      const rtc::SocketAddress& stun_server_addr,
+      const rtc::SocketAddress& stun_reflected_addr);
+  void OnStunBindingOrResolveRequestFailed(
+      const rtc::SocketAddress& stun_server_addr,
+      int error_code,
+      absl::string_view reason);
+
+  // Sends STUN requests to the server.
+  void OnSendPacket(const void* data, size_t size, StunRequest* req);
+
+  // TODO(mallinaht) - Move this up to cricket::Port when SignalAddressReady is
+  // changed to SignalPortReady.
+  void MaybeSetPortCompleteOrError();
+
+  bool HasStunCandidateWithAddress(const rtc::SocketAddress& addr) const;
+
+  // If this is a low-cost network, it will keep on sending STUN binding
+  // requests indefinitely to keep the NAT binding alive. Otherwise, stop
+  // sending STUN binding requests after HIGH_COST_PORT_KEEPALIVE_LIFETIME.
+  int GetStunKeepaliveLifetime() {
+    return (network_cost() >= rtc::kNetworkCostHigh)
+               ? HIGH_COST_PORT_KEEPALIVE_LIFETIME
+               : INFINITE_LIFETIME;
+  }
+
+  ServerAddresses server_addresses_;
+  ServerAddresses bind_request_succeeded_servers_;
+  ServerAddresses bind_request_failed_servers_;
+  StunRequestManager request_manager_;
+  rtc::AsyncPacketSocket* socket_;
+  int error_;
+  int send_error_count_ = 0;
+  std::unique_ptr<AddressResolver> resolver_;
+  bool ready_;
+  int stun_keepalive_delay_;
+  int stun_keepalive_lifetime_ = INFINITE_LIFETIME;
+  rtc::DiffServCodePoint dscp_;
+
+  StunStats stats_;
+
+  // This is true by default and false when
+  // PORTALLOCATOR_DISABLE_DEFAULT_LOCAL_CANDIDATE is specified.
+  bool emit_local_for_anyaddress_;
+
+  friend class StunBindingRequest;
+};
+
+class StunPort : public UDPPort {
+ public:
+  static std::unique_ptr<StunPort> Create(
+      rtc::Thread* thread,
+      rtc::PacketSocketFactory* factory,
+      const rtc::Network* network,
+      uint16_t min_port,
+      uint16_t max_port,
+      absl::string_view username,
+      absl::string_view password,
+      const ServerAddresses& servers,
+      absl::optional<int> stun_keepalive_interval,
+      const webrtc::FieldTrialsView* field_trials);
+
+  void PrepareAddress() override;
+
+ protected:
+  StunPort(rtc::Thread* thread,
+           rtc::PacketSocketFactory* factory,
+           const rtc::Network* network,
+           uint16_t min_port,
+           uint16_t max_port,
+           absl::string_view username,
+           absl::string_view password,
+           const ServerAddresses& servers,
+           const webrtc::FieldTrialsView* field_trials);
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_STUN_PORT_H_
diff --git a/third_party/libwebrtc/p2p/base/stun_port_unittest.cc b/third_party/libwebrtc/p2p/base/stun_port_unittest.cc
new file mode 100644
index 0000000000..3d56636a9b
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/stun_port_unittest.cc
@@ -0,0 +1,765 @@
+/*
+ *  Copyright 2009 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/stun_port.h"
+
+#include <memory>
+
+#include "api/test/mock_async_dns_resolver.h"
+#include "p2p/base/basic_packet_socket_factory.h"
+#include "p2p/base/mock_dns_resolving_packet_socket_factory.h"
+#include "p2p/base/test_stun_server.h"
+#include "rtc_base/gunit.h"
+#include "rtc_base/helpers.h"
+#include "rtc_base/socket_address.h"
+#include "rtc_base/ssl_adapter.h"
+#include "rtc_base/virtual_socket_server.h"
+#include "test/gmock.h"
+#include "test/scoped_key_value_config.h"
+
+namespace {
+
+using cricket::ServerAddresses;
+using rtc::SocketAddress;
+using ::testing::_;
+using ::testing::DoAll;
+using ::testing::InvokeArgument;
+using ::testing::Return;
+using ::testing::ReturnPointee;
+using ::testing::SetArgPointee;
+
+static const SocketAddress kLocalAddr("127.0.0.1", 0);
+static const SocketAddress kIPv6LocalAddr("::1", 0);
+static const SocketAddress kStunAddr1("127.0.0.1", 5000);
+static const SocketAddress kStunAddr2("127.0.0.1", 4000);
+static const SocketAddress kStunAddr3("127.0.0.1", 3000);
+static const SocketAddress kIPv6StunAddr1("::1", 5000);
+static const SocketAddress kBadAddr("0.0.0.1", 5000);
+static const SocketAddress kValidHostnameAddr("valid-hostname", 5000);
+static const SocketAddress kBadHostnameAddr("not-a-real-hostname", 5000);
+// STUN timeout (with all retries) is cricket::STUN_TOTAL_TIMEOUT.
+// Add some margin of error for slow bots.
+static const int kTimeoutMs = cricket::STUN_TOTAL_TIMEOUT;
+// stun prio = 100 (srflx) << 24 | 30 (IPv4) << 8 | 256 - 1 (component)
+static const uint32_t kStunCandidatePriority =
+    (100 << 24) | (30 << 8) | (256 - 1);
+// stun prio = 100 (srflx) << 24 | 60 (loopback IPv6) << 8 | 256 - 1 (component)
+static const uint32_t kIPv6StunCandidatePriority =
+    (100 << 24) | (60 << 8) | (256 - 1);
+static const int kInfiniteLifetime = -1;
+static const int kHighCostPortKeepaliveLifetimeMs = 2 * 60 * 1000;
+
+constexpr uint64_t kTiebreakerDefault = 44444;
+
+class FakeMdnsResponder : public webrtc::MdnsResponderInterface {
+ public:
+  void CreateNameForAddress(const rtc::IPAddress& addr,
+                            NameCreatedCallback callback) override {
+    callback(addr, std::string("unittest-mdns-host-name.local"));
+  }
+
+  void RemoveNameForAddress(const rtc::IPAddress& addr,
+                            NameRemovedCallback callback) override {}
+};
+
+class FakeMdnsResponderProvider : public rtc::MdnsResponderProvider {
+ public:
+  FakeMdnsResponderProvider() : mdns_responder_(new FakeMdnsResponder()) {}
+
+  webrtc::MdnsResponderInterface* GetMdnsResponder() const override {
+    return mdns_responder_.get();
+  }
+
+ private:
+  std::unique_ptr<webrtc::MdnsResponderInterface> mdns_responder_;
+};
+
+// Base class for tests connecting a StunPort to a fake STUN server
+// (cricket::StunServer).
+class StunPortTestBase : public ::testing::Test, public sigslot::has_slots<> {
+ public:
+  StunPortTestBase()
+      : StunPortTestBase(
+            rtc::Network("unittest", "unittest", kLocalAddr.ipaddr(), 32),
+            kLocalAddr.ipaddr()) {}
+
+  StunPortTestBase(rtc::Network network, const rtc::IPAddress address)
+      : ss_(new rtc::VirtualSocketServer()),
+        thread_(ss_.get()),
+        network_(network),
+        socket_factory_(ss_.get()),
+        stun_server_1_(cricket::TestStunServer::Create(ss_.get(), kStunAddr1)),
+        stun_server_2_(cricket::TestStunServer::Create(ss_.get(), kStunAddr2)),
+        mdns_responder_provider_(new FakeMdnsResponderProvider()),
+        done_(false),
+        error_(false),
+        stun_keepalive_delay_(1),
+        stun_keepalive_lifetime_(-1) {
+    network_.AddIP(address);
+  }
+
+  virtual rtc::PacketSocketFactory* socket_factory() {
+    return &socket_factory_;
+  }
+
+  rtc::VirtualSocketServer* ss() const { return ss_.get(); }
+  cricket::UDPPort* port() const { return stun_port_.get(); }
+  rtc::AsyncPacketSocket* socket() const { return socket_.get(); }
+  bool done() const { return done_; }
+  bool error() const { return error_; }
+
+  bool HasPendingRequest(int msg_type) {
+    return stun_port_->request_manager().HasRequestForTest(msg_type);
+  }
+
+  void SetNetworkType(rtc::AdapterType adapter_type) {
+    network_.set_type(adapter_type);
+  }
+
+  void CreateStunPort(const rtc::SocketAddress& server_addr,
+                      const webrtc::FieldTrialsView* field_trials = nullptr) {
+    ServerAddresses stun_servers;
+    stun_servers.insert(server_addr);
+    CreateStunPort(stun_servers, field_trials);
+  }
+
+  void CreateStunPort(const ServerAddresses& stun_servers,
+                      const webrtc::FieldTrialsView* field_trials = nullptr) {
+    stun_port_ = cricket::StunPort::Create(
+        rtc::Thread::Current(), socket_factory(), &network_, 0, 0,
+        rtc::CreateRandomString(16), rtc::CreateRandomString(22), stun_servers,
+        absl::nullopt, field_trials);
+    stun_port_->SetIceTiebreaker(kTiebreakerDefault);
+    stun_port_->set_stun_keepalive_delay(stun_keepalive_delay_);
+    // If `stun_keepalive_lifetime_` is negative, let the stun port
+    // choose its lifetime from the network type.
+    if (stun_keepalive_lifetime_ >= 0) {
+      stun_port_->set_stun_keepalive_lifetime(stun_keepalive_lifetime_);
+    }
+    stun_port_->SignalPortComplete.connect(this,
+                                           &StunPortTestBase::OnPortComplete);
+    stun_port_->SignalPortError.connect(this, &StunPortTestBase::OnPortError);
+    stun_port_->SignalCandidateError.connect(
+        this, &StunPortTestBase::OnCandidateError);
+  }
+
+  void CreateSharedUdpPort(
+      const rtc::SocketAddress& server_addr,
+      rtc::AsyncPacketSocket* socket,
+      const webrtc::FieldTrialsView* field_trials = nullptr) {
+    if (socket) {
+      socket_.reset(socket);
+    } else {
+      socket_.reset(socket_factory()->CreateUdpSocket(
+          rtc::SocketAddress(kLocalAddr.ipaddr(), 0), 0, 0));
+    }
+    ASSERT_TRUE(socket_ != NULL);
+    socket_->SignalReadPacket.connect(this, &StunPortTestBase::OnReadPacket);
+    stun_port_ = cricket::UDPPort::Create(
+        rtc::Thread::Current(), socket_factory(), &network_, socket_.get(),
+        rtc::CreateRandomString(16), rtc::CreateRandomString(22), false,
+        absl::nullopt, field_trials);
+    ASSERT_TRUE(stun_port_ != NULL);
+    stun_port_->SetIceTiebreaker(kTiebreakerDefault);
+    ServerAddresses stun_servers;
+    stun_servers.insert(server_addr);
+    stun_port_->set_server_addresses(stun_servers);
+    stun_port_->SignalPortComplete.connect(this,
+                                           &StunPortTestBase::OnPortComplete);
+    stun_port_->SignalPortError.connect(this, &StunPortTestBase::OnPortError);
+  }
+
+  void PrepareAddress() { stun_port_->PrepareAddress(); }
+
+  void OnReadPacket(rtc::AsyncPacketSocket* socket,
+                    const char* data,
+                    size_t size,
+                    const rtc::SocketAddress& remote_addr,
+                    const int64_t& /* packet_time_us */) {
+    stun_port_->HandleIncomingPacket(socket, data, size, remote_addr,
+                                     /* packet_time_us */ -1);
+  }
+
+  void SendData(const char* data, size_t len) {
+    stun_port_->HandleIncomingPacket(socket_.get(), data, len,
+                                     rtc::SocketAddress("22.22.22.22", 0),
+                                     /* packet_time_us */ -1);
+  }
+
+  void EnableMdnsObfuscation() {
+    network_.set_mdns_responder_provider(mdns_responder_provider_.get());
+  }
+
+ protected:
+  static void SetUpTestSuite() {
+    // Ensure the RNG is inited.
+    rtc::InitRandom(NULL, 0);
+  }
+
+  void OnPortComplete(cricket::Port* port) {
+    ASSERT_FALSE(done_);
+    done_ = true;
+    error_ = false;
+  }
+  void OnPortError(cricket::Port* port) {
+    done_ = true;
+    error_ = true;
+  }
+  void OnCandidateError(cricket::Port* port,
+                        const cricket::IceCandidateErrorEvent& event) {
+    error_event_ = event;
+  }
+  void SetKeepaliveDelay(int delay) { stun_keepalive_delay_ = delay; }
+
+  void SetKeepaliveLifetime(int lifetime) {
+    stun_keepalive_lifetime_ = lifetime;
+  }
+
+  cricket::TestStunServer* stun_server_1() { return stun_server_1_.get(); }
+  cricket::TestStunServer* stun_server_2() { return stun_server_2_.get(); }
+
+ private:
+  std::unique_ptr<rtc::VirtualSocketServer> ss_;
+  rtc::AutoSocketServerThread thread_;
+  rtc::Network network_;
+  rtc::BasicPacketSocketFactory socket_factory_;
+  std::unique_ptr<cricket::UDPPort> stun_port_;
+  std::unique_ptr<cricket::TestStunServer> stun_server_1_;
+  std::unique_ptr<cricket::TestStunServer> stun_server_2_;
+  std::unique_ptr<rtc::AsyncPacketSocket> socket_;
+  std::unique_ptr<rtc::MdnsResponderProvider> mdns_responder_provider_;
+  bool done_;
+  bool error_;
+  int stun_keepalive_delay_;
+  int stun_keepalive_lifetime_;
+
+ protected:
+  cricket::IceCandidateErrorEvent error_event_;
+};
+
+class StunPortTestWithRealClock : public StunPortTestBase {};
+
+class FakeClockBase {
+ public:
+  rtc::ScopedFakeClock fake_clock;
+};
+
+class StunPortTest : public FakeClockBase, public StunPortTestBase {};
+
+// Test that we can create a STUN port.
+TEST_F(StunPortTest, TestCreateStunPort) {
+  CreateStunPort(kStunAddr1);
+  EXPECT_EQ("stun", port()->Type());
+  EXPECT_EQ(0U, port()->Candidates().size());
+}
+
+// Test that we can create a UDP port.
+TEST_F(StunPortTest, TestCreateUdpPort) {
+  CreateSharedUdpPort(kStunAddr1, nullptr);
+  EXPECT_EQ("local", port()->Type());
+  EXPECT_EQ(0U, port()->Candidates().size());
+}
+
+// Test that we can get an address from a STUN server.
+TEST_F(StunPortTest, TestPrepareAddress) {
+  CreateStunPort(kStunAddr1);
+  PrepareAddress();
+  EXPECT_TRUE_SIMULATED_WAIT(done(), kTimeoutMs, fake_clock);
+  ASSERT_EQ(1U, port()->Candidates().size());
+  EXPECT_TRUE(kLocalAddr.EqualIPs(port()->Candidates()[0].address()));
+  std::string expected_server_url = "stun:127.0.0.1:5000";
+  EXPECT_EQ(port()->Candidates()[0].url(), expected_server_url);
+}
+
+// Test that we fail properly if we can't get an address.
+TEST_F(StunPortTest, TestPrepareAddressFail) {
+  CreateStunPort(kBadAddr);
+  PrepareAddress();
+  EXPECT_TRUE_SIMULATED_WAIT(done(), kTimeoutMs, fake_clock);
+  EXPECT_TRUE(error());
+  EXPECT_EQ(0U, port()->Candidates().size());
+  EXPECT_EQ_SIMULATED_WAIT(error_event_.error_code,
+                           cricket::SERVER_NOT_REACHABLE_ERROR, kTimeoutMs,
+                           fake_clock);
+  ASSERT_NE(error_event_.error_text.find('.'), std::string::npos);
+  ASSERT_NE(error_event_.address.find(kLocalAddr.HostAsSensitiveURIString()),
+            std::string::npos);
+  std::string server_url = "stun:" + kBadAddr.ToString();
+  ASSERT_EQ(error_event_.url, server_url);
+}
+
+class StunPortWithMockDnsResolverTest : public StunPortTest {
+ public:
+  StunPortWithMockDnsResolverTest() : StunPortTest(), socket_factory_(ss()) {}
+
+  rtc::PacketSocketFactory* socket_factory() override {
+    return &socket_factory_;
+  }
+
+  void SetDnsResolverExpectations(
+      rtc::MockDnsResolvingPacketSocketFactory::Expectations expectations) {
+    socket_factory_.SetExpectations(expectations);
+  }
+
+ private:
+  rtc::MockDnsResolvingPacketSocketFactory socket_factory_;
+};
+
+// Test that we can get an address from a STUN server specified by a hostname.
+TEST_F(StunPortWithMockDnsResolverTest, TestPrepareAddressHostname) {
+  SetDnsResolverExpectations(
+      [](webrtc::MockAsyncDnsResolver* resolver,
+         webrtc::MockAsyncDnsResolverResult* resolver_result) {
+        EXPECT_CALL(*resolver, Start(kValidHostnameAddr, _))
+            .WillOnce(InvokeArgument<1>());
+        EXPECT_CALL(*resolver, result)
+            .WillRepeatedly(ReturnPointee(resolver_result));
+        EXPECT_CALL(*resolver_result, GetError).WillOnce(Return(0));
+        EXPECT_CALL(*resolver_result, GetResolvedAddress(AF_INET, _))
+            .WillOnce(DoAll(SetArgPointee<1>(SocketAddress("127.0.0.1", 5000)),
+                            Return(true)));
+      });
+  CreateStunPort(kValidHostnameAddr);
+  PrepareAddress();
+  EXPECT_TRUE_SIMULATED_WAIT(done(), kTimeoutMs, fake_clock);
+  ASSERT_EQ(1U, port()->Candidates().size());
+  EXPECT_TRUE(kLocalAddr.EqualIPs(port()->Candidates()[0].address()));
+  EXPECT_EQ(kStunCandidatePriority, port()->Candidates()[0].priority());
+}
+
+// Test that we handle hostname lookup failures properly.
+TEST_F(StunPortTestWithRealClock, TestPrepareAddressHostnameFail) {
+  CreateStunPort(kBadHostnameAddr);
+  PrepareAddress();
+  EXPECT_TRUE_WAIT(done(), kTimeoutMs);
+  EXPECT_TRUE(error());
+  EXPECT_EQ(0U, port()->Candidates().size());
+  EXPECT_EQ_WAIT(error_event_.error_code, cricket::SERVER_NOT_REACHABLE_ERROR,
+                 kTimeoutMs);
+}
+
+// This test verifies keepalive response messages don't result in
+// additional candidate generation.
+TEST_F(StunPortTest, TestKeepAliveResponse) {
+  SetKeepaliveDelay(500);  // 500ms of keepalive delay.
+  CreateStunPort(kStunAddr1);
+  PrepareAddress();
+  EXPECT_TRUE_SIMULATED_WAIT(done(), kTimeoutMs, fake_clock);
+  ASSERT_EQ(1U, port()->Candidates().size());
+  EXPECT_TRUE(kLocalAddr.EqualIPs(port()->Candidates()[0].address()));
+  SIMULATED_WAIT(false, 1000, fake_clock);
+  EXPECT_EQ(1U, port()->Candidates().size());
+}
+
+// Test that a local candidate can be generated using a shared socket.
+TEST_F(StunPortTest, TestSharedSocketPrepareAddress) {
+  CreateSharedUdpPort(kStunAddr1, nullptr);
+  PrepareAddress();
+  EXPECT_TRUE_SIMULATED_WAIT(done(), kTimeoutMs, fake_clock);
+  ASSERT_EQ(1U, port()->Candidates().size());
+  EXPECT_TRUE(kLocalAddr.EqualIPs(port()->Candidates()[0].address()));
+}
+
+// Test that we still get a local candidate with invalid stun server hostname.
+// Also verifing that UDPPort can receive packets when stun address can't be
+// resolved.
+TEST_F(StunPortTestWithRealClock,
+       TestSharedSocketPrepareAddressInvalidHostname) {
+  CreateSharedUdpPort(kBadHostnameAddr, nullptr);
+  PrepareAddress();
+  EXPECT_TRUE_WAIT(done(), kTimeoutMs);
+  ASSERT_EQ(1U, port()->Candidates().size());
+  EXPECT_TRUE(kLocalAddr.EqualIPs(port()->Candidates()[0].address()));
+
+  // Send data to port after it's ready. This is to make sure, UDP port can
+  // handle data with unresolved stun server address.
+  std::string data = "some random data, sending to cricket::Port.";
+  SendData(data.c_str(), data.length());
+  // No crash is success.
+}
+
+// Test that a stun candidate (srflx candidate) is discarded whose address is
+// equal to that of a local candidate if mDNS obfuscation is not enabled.
+TEST_F(StunPortTest, TestStunCandidateDiscardedWithMdnsObfuscationNotEnabled) {
+  CreateSharedUdpPort(kStunAddr1, nullptr);
+  PrepareAddress();
+  EXPECT_TRUE_SIMULATED_WAIT(done(), kTimeoutMs, fake_clock);
+  ASSERT_EQ(1U, port()->Candidates().size());
+  EXPECT_TRUE(kLocalAddr.EqualIPs(port()->Candidates()[0].address()));
+  EXPECT_EQ(port()->Candidates()[0].type(), cricket::LOCAL_PORT_TYPE);
+}
+
+// Test that a stun candidate (srflx candidate) is generated whose address is
+// equal to that of a local candidate if mDNS obfuscation is enabled.
+TEST_F(StunPortTest, TestStunCandidateGeneratedWithMdnsObfuscationEnabled) {
+  EnableMdnsObfuscation();
+  CreateSharedUdpPort(kStunAddr1, nullptr);
+  PrepareAddress();
+  EXPECT_TRUE_SIMULATED_WAIT(done(), kTimeoutMs, fake_clock);
+  ASSERT_EQ(2U, port()->Candidates().size());
+
+  // The addresses of the candidates are both equal to kLocalAddr.
+  EXPECT_TRUE(kLocalAddr.EqualIPs(port()->Candidates()[0].address()));
+  EXPECT_TRUE(kLocalAddr.EqualIPs(port()->Candidates()[1].address()));
+
+  // One of the generated candidates is a local candidate and the other is a
+  // stun candidate.
+  EXPECT_NE(port()->Candidates()[0].type(), port()->Candidates()[1].type());
+  if (port()->Candidates()[0].type() == cricket::LOCAL_PORT_TYPE) {
+    EXPECT_EQ(port()->Candidates()[1].type(), cricket::STUN_PORT_TYPE);
+  } else {
+    EXPECT_EQ(port()->Candidates()[0].type(), cricket::STUN_PORT_TYPE);
+    EXPECT_EQ(port()->Candidates()[1].type(), cricket::LOCAL_PORT_TYPE);
+  }
+}
+
+// Test that the same address is added only once if two STUN servers are in
+// use.
+TEST_F(StunPortTest, TestNoDuplicatedAddressWithTwoStunServers) {
+  ServerAddresses stun_servers;
+  stun_servers.insert(kStunAddr1);
+  stun_servers.insert(kStunAddr2);
+  CreateStunPort(stun_servers);
+  EXPECT_EQ("stun", port()->Type());
+  PrepareAddress();
+  EXPECT_TRUE_SIMULATED_WAIT(done(), kTimeoutMs, fake_clock);
+  EXPECT_EQ(1U, port()->Candidates().size());
+  EXPECT_EQ(port()->Candidates()[0].relay_protocol(), "");
+}
+
+// Test that candidates can be allocated for multiple STUN servers, one of
+// which is not reachable.
+TEST_F(StunPortTest, TestMultipleStunServersWithBadServer) {
+  ServerAddresses stun_servers;
+  stun_servers.insert(kStunAddr1);
+  stun_servers.insert(kBadAddr);
+  CreateStunPort(stun_servers);
+  EXPECT_EQ("stun", port()->Type());
+  PrepareAddress();
+  EXPECT_TRUE_SIMULATED_WAIT(done(), kTimeoutMs, fake_clock);
+  EXPECT_EQ(1U, port()->Candidates().size());
+  std::string server_url = "stun:" + kBadAddr.ToString();
+  ASSERT_EQ_SIMULATED_WAIT(error_event_.url, server_url, kTimeoutMs,
+                           fake_clock);
+}
+
+// Test that two candidates are allocated if the two STUN servers return
+// different mapped addresses.
+TEST_F(StunPortTest, TestTwoCandidatesWithTwoStunServersAcrossNat) {
+  const SocketAddress kStunMappedAddr1("77.77.77.77", 0);
+  const SocketAddress kStunMappedAddr2("88.77.77.77", 0);
+  stun_server_1()->set_fake_stun_addr(kStunMappedAddr1);
+  stun_server_2()->set_fake_stun_addr(kStunMappedAddr2);
+
+  ServerAddresses stun_servers;
+  stun_servers.insert(kStunAddr1);
+  stun_servers.insert(kStunAddr2);
+  CreateStunPort(stun_servers);
+  EXPECT_EQ("stun", port()->Type());
+  PrepareAddress();
+  EXPECT_TRUE_SIMULATED_WAIT(done(), kTimeoutMs, fake_clock);
+  EXPECT_EQ(2U, port()->Candidates().size());
+  EXPECT_EQ(port()->Candidates()[0].relay_protocol(), "");
+  EXPECT_EQ(port()->Candidates()[1].relay_protocol(), "");
+}
+
+// Test that the stun_keepalive_lifetime is set correctly based on the network
+// type on a STUN port. Also test that it will be updated if the network type
+// changes.
+TEST_F(StunPortTest, TestStunPortGetStunKeepaliveLifetime) {
+  // Lifetime for the default (unknown) network type is `kInfiniteLifetime`.
+  CreateStunPort(kStunAddr1);
+  EXPECT_EQ(kInfiniteLifetime, port()->stun_keepalive_lifetime());
+  // Lifetime for the cellular network is `kHighCostPortKeepaliveLifetimeMs`
+  SetNetworkType(rtc::ADAPTER_TYPE_CELLULAR);
+  EXPECT_EQ(kHighCostPortKeepaliveLifetimeMs,
+            port()->stun_keepalive_lifetime());
+
+  // Lifetime for the wifi network is `kInfiniteLifetime`.
+  SetNetworkType(rtc::ADAPTER_TYPE_WIFI);
+  CreateStunPort(kStunAddr2);
+  EXPECT_EQ(kInfiniteLifetime, port()->stun_keepalive_lifetime());
+}
+
+// Test that the stun_keepalive_lifetime is set correctly based on the network
+// type on a shared STUN port (UDPPort). Also test that it will be updated
+// if the network type changes.
+TEST_F(StunPortTest, TestUdpPortGetStunKeepaliveLifetime) {
+  // Lifetime for the default (unknown) network type is `kInfiniteLifetime`.
+  CreateSharedUdpPort(kStunAddr1, nullptr);
+  EXPECT_EQ(kInfiniteLifetime, port()->stun_keepalive_lifetime());
+  // Lifetime for the cellular network is `kHighCostPortKeepaliveLifetimeMs`.
+  SetNetworkType(rtc::ADAPTER_TYPE_CELLULAR);
+  EXPECT_EQ(kHighCostPortKeepaliveLifetimeMs,
+            port()->stun_keepalive_lifetime());
+
+  // Lifetime for the wifi network type is `kInfiniteLifetime`.
+  SetNetworkType(rtc::ADAPTER_TYPE_WIFI);
+  CreateSharedUdpPort(kStunAddr2, nullptr);
+  EXPECT_EQ(kInfiniteLifetime, port()->stun_keepalive_lifetime());
+}
+
+// Test that STUN binding requests will be stopped shortly if the keep-alive
+// lifetime is short.
+TEST_F(StunPortTest, TestStunBindingRequestShortLifetime) {
+  SetKeepaliveDelay(101);
+  SetKeepaliveLifetime(100);
+  CreateStunPort(kStunAddr1);
+  PrepareAddress();
+  EXPECT_TRUE_SIMULATED_WAIT(done(), kTimeoutMs, fake_clock);
+  EXPECT_TRUE_SIMULATED_WAIT(!HasPendingRequest(cricket::STUN_BINDING_REQUEST),
+                             2000, fake_clock);
+}
+
+// Test that by default, the STUN binding requests will last for a long time.
+TEST_F(StunPortTest, TestStunBindingRequestLongLifetime) {
+  SetKeepaliveDelay(101);
+  CreateStunPort(kStunAddr1);
+  PrepareAddress();
+  EXPECT_TRUE_SIMULATED_WAIT(done(), kTimeoutMs, fake_clock);
+  EXPECT_TRUE_SIMULATED_WAIT(HasPendingRequest(cricket::STUN_BINDING_REQUEST),
+                             1000, fake_clock);
+}
+
+class MockAsyncPacketSocket : public rtc::AsyncPacketSocket {
+ public:
+  ~MockAsyncPacketSocket() = default;
+
+  MOCK_METHOD(SocketAddress, GetLocalAddress, (), (const, override));
+  MOCK_METHOD(SocketAddress, GetRemoteAddress, (), (const, override));
+  MOCK_METHOD(int,
+              Send,
+              (const void* pv, size_t cb, const rtc::PacketOptions& options),
+              (override));
+
+  MOCK_METHOD(int,
+              SendTo,
+              (const void* pv,
+               size_t cb,
+               const SocketAddress& addr,
+               const rtc::PacketOptions& options),
+              (override));
+  MOCK_METHOD(int, Close, (), (override));
+  MOCK_METHOD(State, GetState, (), (const, override));
+  MOCK_METHOD(int,
+              GetOption,
+              (rtc::Socket::Option opt, int* value),
+              (override));
+  MOCK_METHOD(int, SetOption, (rtc::Socket::Option opt, int value), (override));
+  MOCK_METHOD(int, GetError, (), (const, override));
+  MOCK_METHOD(void, SetError, (int error), (override));
+};
+
+// Test that outbound packets inherit the dscp value assigned to the socket.
+TEST_F(StunPortTest, TestStunPacketsHaveDscpPacketOption) {
+  MockAsyncPacketSocket* socket = new MockAsyncPacketSocket();
+  CreateSharedUdpPort(kStunAddr1, socket);
+  EXPECT_CALL(*socket, GetLocalAddress()).WillRepeatedly(Return(kLocalAddr));
+  EXPECT_CALL(*socket, GetState())
+      .WillRepeatedly(Return(rtc::AsyncPacketSocket::STATE_BOUND));
+  EXPECT_CALL(*socket, SetOption(_, _)).WillRepeatedly(Return(0));
+
+  // If DSCP is not set on the socket, stun packets should have no value.
+  EXPECT_CALL(*socket,
+              SendTo(_, _, _,
+                     ::testing::Field(&rtc::PacketOptions::dscp,
+                                      ::testing::Eq(rtc::DSCP_NO_CHANGE))))
+      .WillOnce(Return(100));
+  PrepareAddress();
+
+  // Once it is set transport wide, they should inherit that value.
+  port()->SetOption(rtc::Socket::OPT_DSCP, rtc::DSCP_AF41);
+  EXPECT_CALL(*socket, SendTo(_, _, _,
+                              ::testing::Field(&rtc::PacketOptions::dscp,
+                                               ::testing::Eq(rtc::DSCP_AF41))))
+      .WillRepeatedly(Return(100));
+  EXPECT_TRUE_SIMULATED_WAIT(done(), kTimeoutMs, fake_clock);
+}
+
+class StunIPv6PortTestBase : public StunPortTestBase {
+ public:
+  StunIPv6PortTestBase()
+      : StunPortTestBase(rtc::Network("unittestipv6",
+                                      "unittestipv6",
+                                      kIPv6LocalAddr.ipaddr(),
+                                      128),
+                         kIPv6LocalAddr.ipaddr()) {
+    stun_server_ipv6_1_.reset(
+        cricket::TestStunServer::Create(ss(), kIPv6StunAddr1));
+  }
+
+ protected:
+  std::unique_ptr<cricket::TestStunServer> stun_server_ipv6_1_;
+};
+
+class StunIPv6PortTestWithRealClock : public StunIPv6PortTestBase {};
+
+class StunIPv6PortTest : public FakeClockBase, public StunIPv6PortTestBase {};
+
+// Test that we can get an address from a STUN server.
+TEST_F(StunIPv6PortTest, TestPrepareAddress) {
+  CreateStunPort(kIPv6StunAddr1);
+  PrepareAddress();
+  EXPECT_TRUE_SIMULATED_WAIT(done(), kTimeoutMs, fake_clock);
+  ASSERT_EQ(1U, port()->Candidates().size());
+  EXPECT_TRUE(kIPv6LocalAddr.EqualIPs(port()->Candidates()[0].address()));
+  std::string expected_server_url = "stun:::1:5000";
+  EXPECT_EQ(port()->Candidates()[0].url(), expected_server_url);
+}
+
+// Test that we fail properly if we can't get an address.
+TEST_F(StunIPv6PortTest, TestPrepareAddressFail) {
+  CreateStunPort(kBadAddr);
+  PrepareAddress();
+  EXPECT_TRUE_SIMULATED_WAIT(done(), kTimeoutMs, fake_clock);
+  EXPECT_TRUE(error());
+  EXPECT_EQ(0U, port()->Candidates().size());
+  EXPECT_EQ_SIMULATED_WAIT(error_event_.error_code,
+                           cricket::SERVER_NOT_REACHABLE_ERROR, kTimeoutMs,
+                           fake_clock);
+  ASSERT_NE(error_event_.error_text.find('.'), std::string::npos);
+  ASSERT_NE(
+      error_event_.address.find(kIPv6LocalAddr.HostAsSensitiveURIString()),
+      std::string::npos);
+  std::string server_url = "stun:" + kBadAddr.ToString();
+  ASSERT_EQ(error_event_.url, server_url);
+}
+
+// Test that we handle hostname lookup failures properly with a real clock.
+TEST_F(StunIPv6PortTestWithRealClock, TestPrepareAddressHostnameFail) {
+  CreateStunPort(kBadHostnameAddr);
+  PrepareAddress();
+  EXPECT_TRUE_WAIT(done(), kTimeoutMs);
+  EXPECT_TRUE(error());
+  EXPECT_EQ(0U, port()->Candidates().size());
+  EXPECT_EQ_WAIT(error_event_.error_code, cricket::SERVER_NOT_REACHABLE_ERROR,
+                 kTimeoutMs);
+}
+
+class StunIPv6PortTestWithMockDnsResolver : public StunIPv6PortTest {
+ public:
+  StunIPv6PortTestWithMockDnsResolver()
+      : StunIPv6PortTest(), socket_factory_(ss()) {}
+
+  rtc::PacketSocketFactory* socket_factory() override {
+    return &socket_factory_;
+  }
+
+  void SetDnsResolverExpectations(
+      rtc::MockDnsResolvingPacketSocketFactory::Expectations expectations) {
+    socket_factory_.SetExpectations(expectations);
+  }
+
+ private:
+  rtc::MockDnsResolvingPacketSocketFactory socket_factory_;
+};
+
+// Test that we can get an address from a STUN server specified by a hostname.
+TEST_F(StunIPv6PortTestWithMockDnsResolver, TestPrepareAddressHostname) {
+  SetDnsResolverExpectations(
+      [](webrtc::MockAsyncDnsResolver* resolver,
+         webrtc::MockAsyncDnsResolverResult* resolver_result) {
+        // Expect to call Resolver::Start without family arg.
+        EXPECT_CALL(*resolver, Start(kValidHostnameAddr, _))
+            .WillOnce(InvokeArgument<1>());
+        EXPECT_CALL(*resolver, result)
+            .WillRepeatedly(ReturnPointee(resolver_result));
+        EXPECT_CALL(*resolver_result, GetError).WillOnce(Return(0));
+        EXPECT_CALL(*resolver_result, GetResolvedAddress(AF_INET6, _))
+            .WillOnce(DoAll(SetArgPointee<1>(SocketAddress("::1", 5000)),
+                            Return(true)));
+      });
+  CreateStunPort(kValidHostnameAddr);
+  PrepareAddress();
+  EXPECT_TRUE_SIMULATED_WAIT(done(), kTimeoutMs, fake_clock);
+  ASSERT_EQ(1U, port()->Candidates().size());
+  EXPECT_TRUE(kIPv6LocalAddr.EqualIPs(port()->Candidates()[0].address()));
+  EXPECT_EQ(kIPv6StunCandidatePriority, port()->Candidates()[0].priority());
+}
+
+TEST_F(StunIPv6PortTestWithMockDnsResolver,
+       TestPrepareAddressHostnameFamilyFieldTrialDisabled) {
+  webrtc::test::ScopedKeyValueConfig field_trials(
+      "WebRTC-IPv6NetworkResolutionFixes/Disabled/");
+  SetDnsResolverExpectations(
+      [](webrtc::MockAsyncDnsResolver* resolver,
+         webrtc::MockAsyncDnsResolverResult* resolver_result) {
+        // Expect to call Resolver::Start without family arg.
+        EXPECT_CALL(*resolver, Start(kValidHostnameAddr, _))
+            .WillOnce(InvokeArgument<1>());
+        EXPECT_CALL(*resolver, result)
+            .WillRepeatedly(ReturnPointee(resolver_result));
+        EXPECT_CALL(*resolver_result, GetError).WillOnce(Return(0));
+        EXPECT_CALL(*resolver_result, GetResolvedAddress(AF_INET6, _))
+            .WillOnce(DoAll(SetArgPointee<1>(SocketAddress("::1", 5000)),
+                            Return(true)));
+      });
+  CreateStunPort(kValidHostnameAddr, &field_trials);
+  PrepareAddress();
+  EXPECT_TRUE_SIMULATED_WAIT(done(), kTimeoutMs, fake_clock);
+  ASSERT_EQ(1U, port()->Candidates().size());
+  EXPECT_TRUE(kIPv6LocalAddr.EqualIPs(port()->Candidates()[0].address()));
+  EXPECT_EQ(kIPv6StunCandidatePriority, port()->Candidates()[0].priority());
+}
+
+TEST_F(StunIPv6PortTestWithMockDnsResolver,
+       TestPrepareAddressHostnameFamilyFieldTrialParamDisabled) {
+  webrtc::test::ScopedKeyValueConfig field_trials(
+      "WebRTC-IPv6NetworkResolutionFixes/"
+      "Enabled,ResolveStunHostnameForFamily:false/");
+  SetDnsResolverExpectations(
+      [](webrtc::MockAsyncDnsResolver* resolver,
+         webrtc::MockAsyncDnsResolverResult* resolver_result) {
+        // Expect to call Resolver::Start without family arg.
+        EXPECT_CALL(*resolver, Start(kValidHostnameAddr, _))
+            .WillOnce(InvokeArgument<1>());
+        EXPECT_CALL(*resolver, result)
+            .WillRepeatedly(ReturnPointee(resolver_result));
+        EXPECT_CALL(*resolver_result, GetError).WillOnce(Return(0));
+        EXPECT_CALL(*resolver_result, GetResolvedAddress(AF_INET6, _))
+            .WillOnce(DoAll(SetArgPointee<1>(SocketAddress("::1", 5000)),
+                            Return(true)));
+      });
+  CreateStunPort(kValidHostnameAddr, &field_trials);
+  PrepareAddress();
+  EXPECT_TRUE_SIMULATED_WAIT(done(), kTimeoutMs, fake_clock);
+  ASSERT_EQ(1U, port()->Candidates().size());
+  EXPECT_TRUE(kIPv6LocalAddr.EqualIPs(port()->Candidates()[0].address()));
+  EXPECT_EQ(kIPv6StunCandidatePriority, port()->Candidates()[0].priority());
+}
+
+TEST_F(StunIPv6PortTestWithMockDnsResolver,
+       TestPrepareAddressHostnameFamilyFieldTrialEnabled) {
+  webrtc::test::ScopedKeyValueConfig field_trials(
+      "WebRTC-IPv6NetworkResolutionFixes/"
+      "Enabled,ResolveStunHostnameForFamily:true/");
+  SetDnsResolverExpectations(
+      [](webrtc::MockAsyncDnsResolver* resolver,
+         webrtc::MockAsyncDnsResolverResult* resolver_result) {
+        // Expect to call Resolver::Start _with_ family arg.
+        EXPECT_CALL(*resolver,
+                    Start(kValidHostnameAddr, /*family=*/AF_INET6, _))
+            .WillOnce(InvokeArgument<2>());
+        EXPECT_CALL(*resolver, result)
+            .WillRepeatedly(ReturnPointee(resolver_result));
+        EXPECT_CALL(*resolver_result, GetError).WillOnce(Return(0));
+        EXPECT_CALL(*resolver_result, GetResolvedAddress(AF_INET6, _))
+            .WillOnce(DoAll(SetArgPointee<1>(SocketAddress("::1", 5000)),
+                            Return(true)));
+      });
+  CreateStunPort(kValidHostnameAddr, &field_trials);
+  PrepareAddress();
+  EXPECT_TRUE_SIMULATED_WAIT(done(), kTimeoutMs, fake_clock);
+  ASSERT_EQ(1U, port()->Candidates().size());
+  EXPECT_TRUE(kIPv6LocalAddr.EqualIPs(port()->Candidates()[0].address()));
+  EXPECT_EQ(kIPv6StunCandidatePriority, port()->Candidates()[0].priority());
+}
+
+}  // namespace
diff --git a/third_party/libwebrtc/p2p/base/stun_request.cc b/third_party/libwebrtc/p2p/base/stun_request.cc
new file mode 100644
index 0000000000..d15a3e65e2
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/stun_request.cc
@@ -0,0 +1,310 @@
+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/stun_request.h"
+
+#include <algorithm>
+#include <memory>
+#include <utility>
+#include <vector>
+
+#include "absl/memory/memory.h"
+#include "api/task_queue/pending_task_safety_flag.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/helpers.h"
+#include "rtc_base/logging.h"
+#include "rtc_base/string_encode.h"
+#include "rtc_base/time_utils.h"  // For TimeMillis
+
+namespace cricket {
+using ::webrtc::SafeTask;
+
+// RFC 5389 says SHOULD be 500ms.
+// For years, this was 100ms, but for networks that
+// experience moments of high RTT (such as 2G networks), this doesn't
+// work well.
+const int STUN_INITIAL_RTO = 250;  // milliseconds
+
+// The timeout doubles each retransmission, up to this many times
+// RFC 5389 says SHOULD retransmit 7 times.
+// This has been 8 for years (not sure why).
+const int STUN_MAX_RETRANSMISSIONS = 8;           // Total sends: 9
+
+// We also cap the doubling, even though the standard doesn't say to.
+// This has been 1.6 seconds for years, but for networks that
+// experience moments of high RTT (such as 2G networks), this doesn't
+// work well.
+const int STUN_MAX_RTO = 8000;  // milliseconds, or 5 doublings
+
+StunRequestManager::StunRequestManager(
+    webrtc::TaskQueueBase* thread,
+    std::function<void(const void*, size_t, StunRequest*)> send_packet)
+    : thread_(thread), send_packet_(std::move(send_packet)) {}
+
+StunRequestManager::~StunRequestManager() = default;
+
+void StunRequestManager::Send(StunRequest* request) {
+  SendDelayed(request, 0);
+}
+
+void StunRequestManager::SendDelayed(StunRequest* request, int delay) {
+  RTC_DCHECK_RUN_ON(thread_);
+  RTC_DCHECK_EQ(this, request->manager());
+  auto [iter, was_inserted] =
+      requests_.emplace(request->id(), absl::WrapUnique(request));
+  RTC_DCHECK(was_inserted);
+  request->Send(webrtc::TimeDelta::Millis(delay));
+}
+
+void StunRequestManager::FlushForTest(int msg_type) {
+  RTC_DCHECK_RUN_ON(thread_);
+  for (const auto& [unused, request] : requests_) {
+    if (msg_type == kAllRequestsForTest || msg_type == request->type()) {
+      // Calling `Send` implies starting the send operation which may be posted
+      // on a timer and be repeated on a timer until timeout. To make sure that
+      // a call to `Send` doesn't conflict with a previously started `Send`
+      // operation, we reset the `task_safety_` flag here, which has the effect
+      // of canceling any outstanding tasks and prepare a new flag for
+      // operations related to this call to `Send`.
+      request->ResetTasksForTest();
+      request->Send(webrtc::TimeDelta::Zero());
+    }
+  }
+}
+
+bool StunRequestManager::HasRequestForTest(int msg_type) {
+  RTC_DCHECK_RUN_ON(thread_);
+  RTC_DCHECK_NE(msg_type, kAllRequestsForTest);
+  for (const auto& [unused, request] : requests_) {
+    if (msg_type == request->type()) {
+      return true;
+    }
+  }
+  return false;
+}
+
+void StunRequestManager::Clear() {
+  RTC_DCHECK_RUN_ON(thread_);
+  requests_.clear();
+}
+
+bool StunRequestManager::CheckResponse(StunMessage* msg) {
+  RTC_DCHECK_RUN_ON(thread_);
+  RequestMap::iterator iter = requests_.find(msg->transaction_id());
+  if (iter == requests_.end())
+    return false;
+
+  StunRequest* request = iter->second.get();
+
+  // Now that we know the request, we can see if the response is
+  // integrity-protected or not.
+  // For some tests, the message integrity is not set in the request.
+  // Complain, and then don't check.
+  bool skip_integrity_checking =
+      (request->msg()->integrity() == StunMessage::IntegrityStatus::kNotSet);
+  if (skip_integrity_checking) {
+    // This indicates lazy test writing (not adding integrity attribute).
+    // Complain, but only in debug mode (while developing).
+    RTC_DLOG(LS_ERROR)
+        << "CheckResponse called on a passwordless request. Fix test!";
+  } else {
+    if (msg->integrity() == StunMessage::IntegrityStatus::kNotSet) {
+      // Checking status for the first time. Normal.
+      msg->ValidateMessageIntegrity(request->msg()->password());
+    } else if (msg->integrity() == StunMessage::IntegrityStatus::kIntegrityOk &&
+               msg->password() == request->msg()->password()) {
+      // Status is already checked, with the same password. This is the case
+      // we would want to see happen.
+    } else if (msg->integrity() ==
+               StunMessage::IntegrityStatus::kIntegrityBad) {
+      // This indicates that the original check had the wrong password.
+      // Bad design, needs revisiting.
+      // TODO(crbug.com/1177125): Fix this.
+      msg->RevalidateMessageIntegrity(request->msg()->password());
+    } else {
+      RTC_CHECK_NOTREACHED();
+    }
+  }
+
+  bool success = true;
+
+  if (!msg->GetNonComprehendedAttributes().empty()) {
+    // If a response contains unknown comprehension-required attributes, it's
+    // simply discarded and the transaction is considered failed. See RFC5389
+    // sections 7.3.3 and 7.3.4.
+    RTC_LOG(LS_ERROR) << ": Discarding response due to unknown "
+                         "comprehension-required attribute.";
+    success = false;
+  } else if (msg->type() == GetStunSuccessResponseType(request->type())) {
+    if (!msg->IntegrityOk() && !skip_integrity_checking) {
+      return false;
+    }
+    request->OnResponse(msg);
+  } else if (msg->type() == GetStunErrorResponseType(request->type())) {
+    request->OnErrorResponse(msg);
+  } else {
+    RTC_LOG(LS_ERROR) << "Received response with wrong type: " << msg->type()
+                      << " (expecting "
+                      << GetStunSuccessResponseType(request->type()) << ")";
+    return false;
+  }
+
+  requests_.erase(iter);
+  return success;
+}
+
+bool StunRequestManager::empty() const {
+  RTC_DCHECK_RUN_ON(thread_);
+  return requests_.empty();
+}
+
+bool StunRequestManager::CheckResponse(const char* data, size_t size) {
+  RTC_DCHECK_RUN_ON(thread_);
+  // Check the appropriate bytes of the stream to see if they match the
+  // transaction ID of a response we are expecting.
+
+  if (size < 20)
+    return false;
+
+  std::string id;
+  id.append(data + kStunTransactionIdOffset, kStunTransactionIdLength);
+
+  RequestMap::iterator iter = requests_.find(id);
+  if (iter == requests_.end())
+    return false;
+
+  // Parse the STUN message and continue processing as usual.
+
+  rtc::ByteBufferReader buf(data, size);
+  std::unique_ptr<StunMessage> response(iter->second->msg_->CreateNew());
+  if (!response->Read(&buf)) {
+    RTC_LOG(LS_WARNING) << "Failed to read STUN response "
+                        << rtc::hex_encode(id);
+    return false;
+  }
+
+  return CheckResponse(response.get());
+}
+
+void StunRequestManager::OnRequestTimedOut(StunRequest* request) {
+  RTC_DCHECK_RUN_ON(thread_);
+  requests_.erase(request->id());
+}
+
+void StunRequestManager::SendPacket(const void* data,
+                                    size_t size,
+                                    StunRequest* request) {
+  RTC_DCHECK_EQ(this, request->manager());
+  send_packet_(data, size, request);
+}
+
+StunRequest::StunRequest(StunRequestManager& manager)
+    : manager_(manager),
+      msg_(new StunMessage(STUN_INVALID_MESSAGE_TYPE)),
+      tstamp_(0),
+      count_(0),
+      timeout_(false) {
+  RTC_DCHECK_RUN_ON(network_thread());
+}
+
+StunRequest::StunRequest(StunRequestManager& manager,
+                         std::unique_ptr<StunMessage> message)
+    : manager_(manager),
+      msg_(std::move(message)),
+      tstamp_(0),
+      count_(0),
+      timeout_(false) {
+  RTC_DCHECK_RUN_ON(network_thread());
+  RTC_DCHECK(!msg_->transaction_id().empty());
+}
+
+StunRequest::~StunRequest() {}
+
+int StunRequest::type() {
+  RTC_DCHECK(msg_ != NULL);
+  return msg_->type();
+}
+
+const StunMessage* StunRequest::msg() const {
+  return msg_.get();
+}
+
+int StunRequest::Elapsed() const {
+  RTC_DCHECK_RUN_ON(network_thread());
+  return static_cast<int>(rtc::TimeMillis() - tstamp_);
+}
+
+void StunRequest::SendInternal() {
+  RTC_DCHECK_RUN_ON(network_thread());
+  if (timeout_) {
+    OnTimeout();
+    manager_.OnRequestTimedOut(this);
+    return;
+  }
+
+  tstamp_ = rtc::TimeMillis();
+
+  rtc::ByteBufferWriter buf;
+  msg_->Write(&buf);
+  manager_.SendPacket(buf.Data(), buf.Length(), this);
+
+  OnSent();
+  SendDelayed(webrtc::TimeDelta::Millis(resend_delay()));
+}
+
+void StunRequest::SendDelayed(webrtc::TimeDelta delay) {
+  network_thread()->PostDelayedTask(
+      SafeTask(task_safety_.flag(), [this]() { SendInternal(); }), delay);
+}
+
+void StunRequest::Send(webrtc::TimeDelta delay) {
+  RTC_DCHECK_RUN_ON(network_thread());
+  RTC_DCHECK_GE(delay.ms(), 0);
+
+  RTC_DCHECK(!task_safety_.flag()->alive()) << "Send already called?";
+  task_safety_.flag()->SetAlive();
+
+  delay.IsZero() ? SendInternal() : SendDelayed(delay);
+}
+
+void StunRequest::ResetTasksForTest() {
+  RTC_DCHECK_RUN_ON(network_thread());
+  task_safety_.reset(webrtc::PendingTaskSafetyFlag::CreateDetachedInactive());
+  count_ = 0;
+  RTC_DCHECK(!timeout_);
+}
+
+void StunRequest::OnSent() {
+  RTC_DCHECK_RUN_ON(network_thread());
+  count_ += 1;
+  int retransmissions = (count_ - 1);
+  if (retransmissions >= STUN_MAX_RETRANSMISSIONS) {
+    timeout_ = true;
+  }
+  RTC_DLOG(LS_VERBOSE) << "Sent STUN request " << count_
+                       << "; resend delay = " << resend_delay();
+}
+
+int StunRequest::resend_delay() {
+  RTC_DCHECK_RUN_ON(network_thread());
+  if (count_ == 0) {
+    return 0;
+  }
+  int retransmissions = (count_ - 1);
+  int rto = STUN_INITIAL_RTO << retransmissions;
+  return std::min(rto, STUN_MAX_RTO);
+}
+
+void StunRequest::set_timed_out() {
+  RTC_DCHECK_RUN_ON(network_thread());
+  timeout_ = true;
+}
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/stun_request.h b/third_party/libwebrtc/p2p/base/stun_request.h
new file mode 100644
index 0000000000..6e83be3830
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/stun_request.h
@@ -0,0 +1,162 @@
+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_STUN_REQUEST_H_
+#define P2P_BASE_STUN_REQUEST_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <functional>
+#include <map>
+#include <memory>
+#include <string>
+
+#include "api/task_queue/pending_task_safety_flag.h"
+#include "api/task_queue/task_queue_base.h"
+#include "api/transport/stun.h"
+#include "api/units/time_delta.h"
+
+namespace cricket {
+
+class StunRequest;
+
+const int kAllRequestsForTest = 0;
+
+// Total max timeouts: 39.75 seconds
+// For years, this was 9.5 seconds, but for networks that experience moments of
+// high RTT (such as 40s on 2G networks), this doesn't work well.
+const int STUN_TOTAL_TIMEOUT = 39750;  // milliseconds
+
+// Manages a set of STUN requests, sending and resending until we receive a
+// response or determine that the request has timed out.
+class StunRequestManager {
+ public:
+  StunRequestManager(
+      webrtc::TaskQueueBase* thread,
+      std::function<void(const void*, size_t, StunRequest*)> send_packet);
+  ~StunRequestManager();
+
+  // Starts sending the given request (perhaps after a delay).
+  void Send(StunRequest* request);
+  void SendDelayed(StunRequest* request, int delay);
+
+  // If `msg_type` is kAllRequestsForTest, sends all pending requests right
+  // away. Otherwise, sends those that have a matching type right away. Only for
+  // testing.
+  // TODO(tommi): Remove this method and update tests that use it to simulate
+  // production code.
+  void FlushForTest(int msg_type);
+
+  // Returns true if at least one request with `msg_type` is scheduled for
+  // transmission. For testing only.
+  // TODO(tommi): Remove this method and update tests that use it to simulate
+  // production code.
+  bool HasRequestForTest(int msg_type);
+
+  // Removes all stun requests that were added previously.
+  void Clear();
+
+  // Determines whether the given message is a response to one of the
+  // outstanding requests, and if so, processes it appropriately.
+  bool CheckResponse(StunMessage* msg);
+  bool CheckResponse(const char* data, size_t size);
+
+  // Called from a StunRequest when a timeout occurs.
+  void OnRequestTimedOut(StunRequest* request);
+
+  bool empty() const;
+
+  webrtc::TaskQueueBase* network_thread() const { return thread_; }
+
+  void SendPacket(const void* data, size_t size, StunRequest* request);
+
+ private:
+  typedef std::map<std::string, std::unique_ptr<StunRequest>> RequestMap;
+
+  webrtc::TaskQueueBase* const thread_;
+  RequestMap requests_ RTC_GUARDED_BY(thread_);
+  const std::function<void(const void*, size_t, StunRequest*)> send_packet_;
+};
+
+// Represents an individual request to be sent.  The STUN message can either be
+// constructed beforehand or built on demand.
+class StunRequest {
+ public:
+  explicit StunRequest(StunRequestManager& manager);
+  StunRequest(StunRequestManager& manager,
+              std::unique_ptr<StunMessage> message);
+  virtual ~StunRequest();
+
+  // The manager handling this request (if it has been scheduled for sending).
+  StunRequestManager* manager() { return &manager_; }
+
+  // Returns the transaction ID of this request.
+  const std::string& id() const { return msg_->transaction_id(); }
+
+  // Returns the reduced transaction ID of this request.
+  uint32_t reduced_transaction_id() const {
+    return msg_->reduced_transaction_id();
+  }
+
+  // Returns the STUN type of the request message.
+  int type();
+
+  // Returns a const pointer to `msg_`.
+  const StunMessage* msg() const;
+
+  // Time elapsed since last send (in ms)
+  int Elapsed() const;
+
+ protected:
+  friend class StunRequestManager;
+
+  // Called by StunRequestManager.
+  void Send(webrtc::TimeDelta delay);
+
+  // Called from FlushForTest.
+  // TODO(tommi): Remove when FlushForTest gets removed.
+  void ResetTasksForTest();
+
+  StunMessage* mutable_msg() { return msg_.get(); }
+
+  // Called when the message receives a response or times out.
+  virtual void OnResponse(StunMessage* response) {}
+  virtual void OnErrorResponse(StunMessage* response) {}
+  virtual void OnTimeout() {}
+  // Called when the message is sent.
+  virtual void OnSent();
+  // Returns the next delay for resends in milliseconds.
+  virtual int resend_delay();
+
+  webrtc::TaskQueueBase* network_thread() const {
+    return manager_.network_thread();
+  }
+
+  void set_timed_out();
+
+ private:
+  void SendInternal();
+  // Calls `PostDelayedTask` to queue up a call to SendInternal after the
+  // specified timeout.
+  void SendDelayed(webrtc::TimeDelta delay);
+
+  StunRequestManager& manager_;
+  const std::unique_ptr<StunMessage> msg_;
+  int64_t tstamp_ RTC_GUARDED_BY(network_thread());
+  int count_ RTC_GUARDED_BY(network_thread());
+  bool timeout_ RTC_GUARDED_BY(network_thread());
+  webrtc::ScopedTaskSafety task_safety_{
+      webrtc::PendingTaskSafetyFlag::CreateDetachedInactive()};
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_STUN_REQUEST_H_
diff --git a/third_party/libwebrtc/p2p/base/stun_request_unittest.cc b/third_party/libwebrtc/p2p/base/stun_request_unittest.cc
new file mode 100644
index 0000000000..6831d9ffa2
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/stun_request_unittest.cc
@@ -0,0 +1,219 @@
+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/stun_request.h"
+
+#include <utility>
+#include <vector>
+
+#include "rtc_base/fake_clock.h"
+#include "rtc_base/gunit.h"
+#include "rtc_base/helpers.h"
+#include "rtc_base/logging.h"
+#include "rtc_base/time_utils.h"
+#include "test/gtest.h"
+
+namespace cricket {
+namespace {
+std::unique_ptr<StunMessage> CreateStunMessage(
+    StunMessageType type,
+    const StunMessage* req = nullptr) {
+  std::unique_ptr<StunMessage> msg = std::make_unique<StunMessage>(
+      type, req ? req->transaction_id() : StunMessage::GenerateTransactionId());
+  return msg;
+}
+
+int TotalDelay(int sends) {
+  std::vector<int> delays = {0,    250,   750,   1750,  3750,
+                             7750, 15750, 23750, 31750, 39750};
+  return delays[sends];
+}
+}  // namespace
+
+class StunRequestTest : public ::testing::Test {
+ public:
+  StunRequestTest()
+      : manager_(rtc::Thread::Current(),
+                 [this](const void* data, size_t size, StunRequest* request) {
+                   OnSendPacket(data, size, request);
+                 }),
+        request_count_(0),
+        response_(NULL),
+        success_(false),
+        failure_(false),
+        timeout_(false) {}
+
+  void OnSendPacket(const void* data, size_t size, StunRequest* req) {
+    request_count_++;
+  }
+
+  void OnResponse(StunMessage* res) {
+    response_ = res;
+    success_ = true;
+  }
+  void OnErrorResponse(StunMessage* res) {
+    response_ = res;
+    failure_ = true;
+  }
+  void OnTimeout() { timeout_ = true; }
+
+ protected:
+  rtc::AutoThread main_thread_;
+  StunRequestManager manager_;
+  int request_count_;
+  StunMessage* response_;
+  bool success_;
+  bool failure_;
+  bool timeout_;
+};
+
+// Forwards results to the test class.
+class StunRequestThunker : public StunRequest {
+ public:
+  StunRequestThunker(StunRequestManager& manager, StunRequestTest* test)
+      : StunRequest(manager, CreateStunMessage(STUN_BINDING_REQUEST)),
+        test_(test) {}
+
+  std::unique_ptr<StunMessage> CreateResponseMessage(StunMessageType type) {
+    return CreateStunMessage(type, msg());
+  }
+
+ private:
+  virtual void OnResponse(StunMessage* res) { test_->OnResponse(res); }
+  virtual void OnErrorResponse(StunMessage* res) {
+    test_->OnErrorResponse(res);
+  }
+  virtual void OnTimeout() { test_->OnTimeout(); }
+
+  StunRequestTest* test_;
+};
+
+// Test handling of a normal binding response.
+TEST_F(StunRequestTest, TestSuccess) {
+  auto* request = new StunRequestThunker(manager_, this);
+  std::unique_ptr<StunMessage> res =
+      request->CreateResponseMessage(STUN_BINDING_RESPONSE);
+  manager_.Send(request);
+  EXPECT_TRUE(manager_.CheckResponse(res.get()));
+
+  EXPECT_TRUE(response_ == res.get());
+  EXPECT_TRUE(success_);
+  EXPECT_FALSE(failure_);
+  EXPECT_FALSE(timeout_);
+}
+
+// Test handling of an error binding response.
+TEST_F(StunRequestTest, TestError) {
+  auto* request = new StunRequestThunker(manager_, this);
+  std::unique_ptr<StunMessage> res =
+      request->CreateResponseMessage(STUN_BINDING_ERROR_RESPONSE);
+  manager_.Send(request);
+  EXPECT_TRUE(manager_.CheckResponse(res.get()));
+
+  EXPECT_TRUE(response_ == res.get());
+  EXPECT_FALSE(success_);
+  EXPECT_TRUE(failure_);
+  EXPECT_FALSE(timeout_);
+}
+
+// Test handling of a binding response with the wrong transaction id.
+TEST_F(StunRequestTest, TestUnexpected) {
+  auto* request = new StunRequestThunker(manager_, this);
+  std::unique_ptr<StunMessage> res = CreateStunMessage(STUN_BINDING_RESPONSE);
+
+  manager_.Send(request);
+  EXPECT_FALSE(manager_.CheckResponse(res.get()));
+
+  EXPECT_TRUE(response_ == NULL);
+  EXPECT_FALSE(success_);
+  EXPECT_FALSE(failure_);
+  EXPECT_FALSE(timeout_);
+}
+
+// Test that requests are sent at the right times.
+TEST_F(StunRequestTest, TestBackoff) {
+  rtc::ScopedFakeClock fake_clock;
+  auto* request = new StunRequestThunker(manager_, this);
+  std::unique_ptr<StunMessage> res =
+      request->CreateResponseMessage(STUN_BINDING_RESPONSE);
+
+  int64_t start = rtc::TimeMillis();
+  manager_.Send(request);
+  for (int i = 0; i < 9; ++i) {
+    EXPECT_TRUE_SIMULATED_WAIT(request_count_ != i, STUN_TOTAL_TIMEOUT,
+                               fake_clock);
+    int64_t elapsed = rtc::TimeMillis() - start;
+    RTC_DLOG(LS_INFO) << "STUN request #" << (i + 1) << " sent at " << elapsed
+                      << " ms";
+    EXPECT_EQ(TotalDelay(i), elapsed);
+  }
+  EXPECT_TRUE(manager_.CheckResponse(res.get()));
+
+  EXPECT_TRUE(response_ == res.get());
+  EXPECT_TRUE(success_);
+  EXPECT_FALSE(failure_);
+  EXPECT_FALSE(timeout_);
+}
+
+// Test that we timeout properly if no response is received.
+TEST_F(StunRequestTest, TestTimeout) {
+  rtc::ScopedFakeClock fake_clock;
+  auto* request = new StunRequestThunker(manager_, this);
+  std::unique_ptr<StunMessage> res =
+      request->CreateResponseMessage(STUN_BINDING_RESPONSE);
+
+  manager_.Send(request);
+  SIMULATED_WAIT(false, cricket::STUN_TOTAL_TIMEOUT, fake_clock);
+
+  EXPECT_FALSE(manager_.CheckResponse(res.get()));
+  EXPECT_TRUE(response_ == NULL);
+  EXPECT_FALSE(success_);
+  EXPECT_FALSE(failure_);
+  EXPECT_TRUE(timeout_);
+}
+
+// Regression test for specific crash where we receive a response with the
+// same id as a request that doesn't have an underlying StunMessage yet.
+TEST_F(StunRequestTest, TestNoEmptyRequest) {
+  StunRequestThunker* request = new StunRequestThunker(manager_, this);
+
+  manager_.SendDelayed(request, 100);
+
+  StunMessage dummy_req(0, request->id());
+  std::unique_ptr<StunMessage> res =
+      CreateStunMessage(STUN_BINDING_RESPONSE, &dummy_req);
+
+  EXPECT_TRUE(manager_.CheckResponse(res.get()));
+
+  EXPECT_TRUE(response_ == res.get());
+  EXPECT_TRUE(success_);
+  EXPECT_FALSE(failure_);
+  EXPECT_FALSE(timeout_);
+}
+
+// If the response contains an attribute in the "comprehension required" range
+// which is not recognized, the transaction should be considered a failure and
+// the response should be ignored.
+TEST_F(StunRequestTest, TestUnrecognizedComprehensionRequiredAttribute) {
+  auto* request = new StunRequestThunker(manager_, this);
+  std::unique_ptr<StunMessage> res =
+      request->CreateResponseMessage(STUN_BINDING_ERROR_RESPONSE);
+
+  manager_.Send(request);
+  res->AddAttribute(StunAttribute::CreateUInt32(0x7777));
+  EXPECT_FALSE(manager_.CheckResponse(res.get()));
+
+  EXPECT_EQ(nullptr, response_);
+  EXPECT_FALSE(success_);
+  EXPECT_FALSE(failure_);
+  EXPECT_FALSE(timeout_);
+}
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/stun_server.cc b/third_party/libwebrtc/p2p/base/stun_server.cc
new file mode 100644
index 0000000000..7827a0bb81
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/stun_server.cc
@@ -0,0 +1,104 @@
+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/stun_server.h"
+
+#include <string>
+#include <utility>
+
+#include "absl/strings/string_view.h"
+#include "rtc_base/byte_buffer.h"
+#include "rtc_base/logging.h"
+
+namespace cricket {
+
+StunServer::StunServer(rtc::AsyncUDPSocket* socket) : socket_(socket) {
+  socket_->SignalReadPacket.connect(this, &StunServer::OnPacket);
+}
+
+StunServer::~StunServer() {
+  socket_->SignalReadPacket.disconnect(this);
+}
+
+void StunServer::OnPacket(rtc::AsyncPacketSocket* socket,
+                          const char* buf,
+                          size_t size,
+                          const rtc::SocketAddress& remote_addr,
+                          const int64_t& /* packet_time_us */) {
+  // Parse the STUN message; eat any messages that fail to parse.
+  rtc::ByteBufferReader bbuf(buf, size);
+  StunMessage msg;
+  if (!msg.Read(&bbuf)) {
+    return;
+  }
+
+  // TODO(?): If unknown non-optional (<= 0x7fff) attributes are found, send a
+  //          420 "Unknown Attribute" response.
+
+  // Send the message to the appropriate handler function.
+  switch (msg.type()) {
+    case STUN_BINDING_REQUEST:
+      OnBindingRequest(&msg, remote_addr);
+      break;
+
+    default:
+      SendErrorResponse(msg, remote_addr, 600, "Operation Not Supported");
+  }
+}
+
+void StunServer::OnBindingRequest(StunMessage* msg,
+                                  const rtc::SocketAddress& remote_addr) {
+  StunMessage response(STUN_BINDING_RESPONSE, msg->transaction_id());
+  GetStunBindResponse(msg, remote_addr, &response);
+  SendResponse(response, remote_addr);
+}
+
+void StunServer::SendErrorResponse(const StunMessage& msg,
+                                   const rtc::SocketAddress& addr,
+                                   int error_code,
+                                   absl::string_view error_desc) {
+  StunMessage err_msg(GetStunErrorResponseType(msg.type()),
+                      msg.transaction_id());
+
+  auto err_code = StunAttribute::CreateErrorCode();
+  err_code->SetCode(error_code);
+  err_code->SetReason(std::string(error_desc));
+  err_msg.AddAttribute(std::move(err_code));
+
+  SendResponse(err_msg, addr);
+}
+
+void StunServer::SendResponse(const StunMessage& msg,
+                              const rtc::SocketAddress& addr) {
+  rtc::ByteBufferWriter buf;
+  msg.Write(&buf);
+  rtc::PacketOptions options;
+  if (socket_->SendTo(buf.Data(), buf.Length(), addr, options) < 0)
+    RTC_LOG_ERR(LS_ERROR) << "sendto";
+}
+
+void StunServer::GetStunBindResponse(StunMessage* message,
+                                     const rtc::SocketAddress& remote_addr,
+                                     StunMessage* response) const {
+  RTC_DCHECK_EQ(response->type(), STUN_BINDING_RESPONSE);
+  RTC_DCHECK_EQ(response->transaction_id(), message->transaction_id());
+
+  // Tell the user the address that we received their message from.
+  std::unique_ptr<StunAddressAttribute> mapped_addr;
+  if (message->IsLegacy()) {
+    mapped_addr = StunAttribute::CreateAddress(STUN_ATTR_MAPPED_ADDRESS);
+  } else {
+    mapped_addr = StunAttribute::CreateXorAddress(STUN_ATTR_XOR_MAPPED_ADDRESS);
+  }
+  mapped_addr->SetAddress(remote_addr);
+  response->AddAttribute(std::move(mapped_addr));
+}
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/stun_server.h b/third_party/libwebrtc/p2p/base/stun_server.h
new file mode 100644
index 0000000000..505773b052
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/stun_server.h
@@ -0,0 +1,72 @@
+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_STUN_SERVER_H_
+#define P2P_BASE_STUN_SERVER_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <memory>
+
+#include "absl/strings/string_view.h"
+#include "api/transport/stun.h"
+#include "rtc_base/async_packet_socket.h"
+#include "rtc_base/async_udp_socket.h"
+#include "rtc_base/socket_address.h"
+#include "rtc_base/third_party/sigslot/sigslot.h"
+
+namespace cricket {
+
+const int STUN_SERVER_PORT = 3478;
+
+class StunServer : public sigslot::has_slots<> {
+ public:
+  // Creates a STUN server, which will listen on the given socket.
+  explicit StunServer(rtc::AsyncUDPSocket* socket);
+  // Removes the STUN server from the socket and deletes the socket.
+  ~StunServer() override;
+
+ protected:
+  // Slot for Socket.PacketRead:
+  void OnPacket(rtc::AsyncPacketSocket* socket,
+                const char* buf,
+                size_t size,
+                const rtc::SocketAddress& remote_addr,
+                const int64_t& packet_time_us);
+
+  // Handlers for the different types of STUN/TURN requests:
+  virtual void OnBindingRequest(StunMessage* msg,
+                                const rtc::SocketAddress& addr);
+  void OnAllocateRequest(StunMessage* msg, const rtc::SocketAddress& addr);
+  void OnSharedSecretRequest(StunMessage* msg, const rtc::SocketAddress& addr);
+  void OnSendRequest(StunMessage* msg, const rtc::SocketAddress& addr);
+
+  // Sends an error response to the given message back to the user.
+  void SendErrorResponse(const StunMessage& msg,
+                         const rtc::SocketAddress& addr,
+                         int error_code,
+                         absl::string_view error_desc);
+
+  // Sends the given message to the appropriate destination.
+  void SendResponse(const StunMessage& msg, const rtc::SocketAddress& addr);
+
+  // A helper method to compose a STUN binding response.
+  void GetStunBindResponse(StunMessage* message,
+                           const rtc::SocketAddress& remote_addr,
+                           StunMessage* response) const;
+
+ private:
+  std::unique_ptr<rtc::AsyncUDPSocket> socket_;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_STUN_SERVER_H_
diff --git a/third_party/libwebrtc/p2p/base/stun_server_unittest.cc b/third_party/libwebrtc/p2p/base/stun_server_unittest.cc
new file mode 100644
index 0000000000..5d3f31fb98
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/stun_server_unittest.cc
@@ -0,0 +1,145 @@
+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/stun_server.h"
+
+#include <string.h>
+
+#include <memory>
+#include <string>
+
+#include "absl/memory/memory.h"
+#include "rtc_base/byte_buffer.h"
+#include "rtc_base/ip_address.h"
+#include "rtc_base/logging.h"
+#include "rtc_base/test_client.h"
+#include "rtc_base/thread.h"
+#include "rtc_base/virtual_socket_server.h"
+#include "test/gtest.h"
+
+namespace cricket {
+
+namespace {
+const rtc::SocketAddress server_addr("99.99.99.1", 3478);
+const rtc::SocketAddress client_addr("1.2.3.4", 1234);
+}  // namespace
+
+class StunServerTest : public ::testing::Test {
+ public:
+  StunServerTest() : ss_(new rtc::VirtualSocketServer()), network_(ss_.get()) {
+    server_.reset(
+        new StunServer(rtc::AsyncUDPSocket::Create(ss_.get(), server_addr)));
+    client_.reset(new rtc::TestClient(
+        absl::WrapUnique(rtc::AsyncUDPSocket::Create(ss_.get(), client_addr))));
+
+    network_.Start();
+  }
+  ~StunServerTest() override { network_.Stop(); }
+
+  void Send(const StunMessage& msg) {
+    rtc::ByteBufferWriter buf;
+    msg.Write(&buf);
+    Send(buf.Data(), static_cast<int>(buf.Length()));
+  }
+  void Send(const char* buf, int len) {
+    client_->SendTo(buf, len, server_addr);
+  }
+  bool ReceiveFails() { return (client_->CheckNoPacket()); }
+  StunMessage* Receive() {
+    StunMessage* msg = NULL;
+    std::unique_ptr<rtc::TestClient::Packet> packet =
+        client_->NextPacket(rtc::TestClient::kTimeoutMs);
+    if (packet) {
+      rtc::ByteBufferReader buf(packet->buf, packet->size);
+      msg = new StunMessage();
+      msg->Read(&buf);
+    }
+    return msg;
+  }
+
+ private:
+  rtc::AutoThread main_thread;
+  std::unique_ptr<rtc::VirtualSocketServer> ss_;
+  rtc::Thread network_;
+  std::unique_ptr<StunServer> server_;
+  std::unique_ptr<rtc::TestClient> client_;
+};
+
+TEST_F(StunServerTest, TestGood) {
+  // kStunLegacyTransactionIdLength = 16 for legacy RFC 3489 request
+  std::string transaction_id = "0123456789abcdef";
+  StunMessage req(STUN_BINDING_REQUEST, transaction_id);
+  Send(req);
+
+  StunMessage* msg = Receive();
+  ASSERT_TRUE(msg != NULL);
+  EXPECT_EQ(STUN_BINDING_RESPONSE, msg->type());
+  EXPECT_EQ(req.transaction_id(), msg->transaction_id());
+
+  const StunAddressAttribute* mapped_addr =
+      msg->GetAddress(STUN_ATTR_MAPPED_ADDRESS);
+  EXPECT_TRUE(mapped_addr != NULL);
+  EXPECT_EQ(1, mapped_addr->family());
+  EXPECT_EQ(client_addr.port(), mapped_addr->port());
+
+  delete msg;
+}
+
+TEST_F(StunServerTest, TestGoodXorMappedAddr) {
+  // kStunTransactionIdLength = 12 for RFC 5389 request
+  // StunMessage::Write will automatically insert magic cookie (0x2112A442)
+  std::string transaction_id = "0123456789ab";
+  StunMessage req(STUN_BINDING_REQUEST, transaction_id);
+  Send(req);
+
+  StunMessage* msg = Receive();
+  ASSERT_TRUE(msg != NULL);
+  EXPECT_EQ(STUN_BINDING_RESPONSE, msg->type());
+  EXPECT_EQ(req.transaction_id(), msg->transaction_id());
+
+  const StunAddressAttribute* mapped_addr =
+      msg->GetAddress(STUN_ATTR_XOR_MAPPED_ADDRESS);
+  EXPECT_TRUE(mapped_addr != NULL);
+  EXPECT_EQ(1, mapped_addr->family());
+  EXPECT_EQ(client_addr.port(), mapped_addr->port());
+
+  delete msg;
+}
+
+// Send legacy RFC 3489 request, should not get xor mapped addr
+TEST_F(StunServerTest, TestNoXorMappedAddr) {
+  // kStunLegacyTransactionIdLength = 16 for legacy RFC 3489 request
+  std::string transaction_id = "0123456789abcdef";
+  StunMessage req(STUN_BINDING_REQUEST, transaction_id);
+  Send(req);
+
+  StunMessage* msg = Receive();
+  ASSERT_TRUE(msg != NULL);
+  EXPECT_EQ(STUN_BINDING_RESPONSE, msg->type());
+  EXPECT_EQ(req.transaction_id(), msg->transaction_id());
+
+  const StunAddressAttribute* mapped_addr =
+      msg->GetAddress(STUN_ATTR_XOR_MAPPED_ADDRESS);
+  EXPECT_TRUE(mapped_addr == NULL);
+
+  delete msg;
+}
+
+TEST_F(StunServerTest, TestBad) {
+  const char* bad =
+      "this is a completely nonsensical message whose only "
+      "purpose is to make the parser go 'ack'.  it doesn't "
+      "look anything like a normal stun message";
+  Send(bad, static_cast<int>(strlen(bad)));
+
+  ASSERT_TRUE(ReceiveFails());
+}
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/tcp_port.cc b/third_party/libwebrtc/p2p/base/tcp_port.cc
new file mode 100644
index 0000000000..fbda2999f9
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/tcp_port.cc
@@ -0,0 +1,620 @@
+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+/*
+ *  This is a diagram of how TCP reconnect works for the active side. The
+ *  passive side just waits for an incoming connection.
+ *
+ *  - Connected: Indicate whether the TCP socket is connected.
+ *
+ *  - Writable: Whether the stun binding is completed. Sending a data packet
+ *    before stun binding completed will trigger IPC socket layer to shutdown
+ *    the connection.
+ *
+ *  - PendingTCP: `connection_pending_` indicates whether there is an
+ *    outstanding TCP connection in progress.
+ *
+ *  - PretendWri: Tracked by `pretending_to_be_writable_`. Marking connection as
+ *    WRITE_TIMEOUT will cause the connection be deleted. Instead, we're
+ *    "pretending" we're still writable for a period of time such that reconnect
+ *    could work.
+ *
+ *  Data could only be sent in state 3. Sening data during state 2 & 6 will get
+ *  EWOULDBLOCK, 4 & 5 EPIPE.
+ *
+ *         OS Timeout         7 -------------+
+ *   +----------------------->|Connected: N  |
+ *   |                        |Writable:  N  |     Timeout
+ *   |       Timeout          |Connection is |<----------------+
+ *   |   +------------------->|Dead          |                 |
+ *   |   |                    +--------------+                 |
+ *   |   |                               ^                     |
+ *   |   |            OnClose            |                     |
+ *   |   |    +-----------------------+  |                     |
+ *   |   |    |                       |  |Timeout              |
+ *   |   |    v                       |  |                     |
+ *   | 4 +----------+          5 -----+--+--+           6 -----+-----+
+ *   | |Connected: N|Send() or |Connected: N|           |Connected: Y|
+ *   | |Writable:  Y|Ping()    |Writable:  Y|OnConnect  |Writable:  Y|
+ *   | |PendingTCP:N+--------> |PendingTCP:Y+---------> |PendingTCP:N|
+ *   | |PretendWri:Y|          |PretendWri:Y|           |PretendWri:Y|
+ *   | +-----+------+          +------------+           +---+--+-----+
+ *   |   ^   ^                                              |  |
+ *   |   |   |                     OnClose                  |  |
+ *   |   |   +----------------------------------------------+  |
+ *   |   |                                                     |
+ *   |   |                              Stun Binding Completed |
+ *   |   |                                                     |
+ *   |   |                    OnClose                          |
+ *   |   +------------------------------------------------+    |
+ *   |                                                    |    v
+ *  1 -----------+           2 -----------+Stun      3 -----------+
+ *  |Connected: N|           |Connected: Y|Binding   |Connected: Y|
+ *  |Writable:  N|OnConnect  |Writable:  N|Completed |Writable:  Y|
+ *  |PendingTCP:Y+---------> |PendingTCP:N+--------> |PendingTCP:N|
+ *  |PretendWri:N|           |PretendWri:N|          |PretendWri:N|
+ *  +------------+           +------------+          +------------+
+ *
+ */
+
+#include "p2p/base/tcp_port.h"
+
+#include <errno.h>
+
+#include <utility>
+#include <vector>
+
+#include "absl/algorithm/container.h"
+#include "absl/memory/memory.h"
+#include "absl/strings/string_view.h"
+#include "api/task_queue/pending_task_safety_flag.h"
+#include "api/units/time_delta.h"
+#include "p2p/base/p2p_constants.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/ip_address.h"
+#include "rtc_base/logging.h"
+#include "rtc_base/net_helper.h"
+#include "rtc_base/rate_tracker.h"
+#include "rtc_base/third_party/sigslot/sigslot.h"
+
+namespace cricket {
+using ::webrtc::SafeTask;
+using ::webrtc::TimeDelta;
+
+TCPPort::TCPPort(rtc::Thread* thread,
+                 rtc::PacketSocketFactory* factory,
+                 const rtc::Network* network,
+                 uint16_t min_port,
+                 uint16_t max_port,
+                 absl::string_view username,
+                 absl::string_view password,
+                 bool allow_listen,
+                 const webrtc::FieldTrialsView* field_trials)
+    : Port(thread,
+           LOCAL_PORT_TYPE,
+           factory,
+           network,
+           min_port,
+           max_port,
+           username,
+           password,
+           field_trials),
+      allow_listen_(allow_listen),
+      error_(0) {
+  // TODO(mallinath) - Set preference value as per RFC 6544.
+  // http://b/issue?id=7141794
+  if (allow_listen_) {
+    TryCreateServerSocket();
+  }
+  // Set TCP_NODELAY (via OPT_NODELAY) for improved performance; this causes
+  // small media packets to be sent immediately rather than being buffered up,
+  // reducing latency.
+  SetOption(rtc::Socket::OPT_NODELAY, 1);
+}
+
+TCPPort::~TCPPort() {
+  listen_socket_ = nullptr;
+  std::list<Incoming>::iterator it;
+  for (it = incoming_.begin(); it != incoming_.end(); ++it)
+    delete it->socket;
+  incoming_.clear();
+}
+
+Connection* TCPPort::CreateConnection(const Candidate& address,
+                                      CandidateOrigin origin) {
+  if (!SupportsProtocol(address.protocol())) {
+    return NULL;
+  }
+
+  if ((address.tcptype() == TCPTYPE_ACTIVE_STR &&
+       address.type() != PRFLX_PORT_TYPE) ||
+      (address.tcptype().empty() && address.address().port() == 0)) {
+    // It's active only candidate, we should not try to create connections
+    // for these candidates.
+    return NULL;
+  }
+
+  // We can't accept TCP connections incoming on other ports
+  if (origin == ORIGIN_OTHER_PORT)
+    return NULL;
+
+  // We don't know how to act as an ssl server yet
+  if ((address.protocol() == SSLTCP_PROTOCOL_NAME) &&
+      (origin == ORIGIN_THIS_PORT)) {
+    return NULL;
+  }
+
+  if (!IsCompatibleAddress(address.address())) {
+    return NULL;
+  }
+
+  TCPConnection* conn = NULL;
+  if (rtc::AsyncPacketSocket* socket = GetIncoming(address.address(), true)) {
+    // Incoming connection; we already created a socket and connected signals,
+    // so we need to hand off the "read packet" responsibility to
+    // TCPConnection.
+    socket->SignalReadPacket.disconnect(this);
+    conn = new TCPConnection(NewWeakPtr(), address, socket);
+  } else {
+    // Outgoing connection, which will create a new socket for which we still
+    // need to connect SignalReadyToSend and SignalSentPacket.
+    conn = new TCPConnection(NewWeakPtr(), address);
+    if (conn->socket()) {
+      conn->socket()->SignalReadyToSend.connect(this, &TCPPort::OnReadyToSend);
+      conn->socket()->SignalSentPacket.connect(this, &TCPPort::OnSentPacket);
+    }
+  }
+  AddOrReplaceConnection(conn);
+  return conn;
+}
+
+void TCPPort::PrepareAddress() {
+  if (listen_socket_) {
+    // Socket may be in the CLOSED state if Listen()
+    // failed, we still want to add the socket address.
+    RTC_LOG(LS_VERBOSE) << "Preparing TCP address, current state: "
+                        << static_cast<int>(listen_socket_->GetState());
+    AddAddress(listen_socket_->GetLocalAddress(),
+               listen_socket_->GetLocalAddress(), rtc::SocketAddress(),
+               TCP_PROTOCOL_NAME, "", TCPTYPE_PASSIVE_STR, LOCAL_PORT_TYPE,
+               ICE_TYPE_PREFERENCE_HOST_TCP, 0, "", true);
+  } else {
+    RTC_LOG(LS_INFO) << ToString()
+                     << ": Not listening due to firewall restrictions.";
+    // Note: We still add the address, since otherwise the remote side won't
+    // recognize our incoming TCP connections. According to
+    // https://tools.ietf.org/html/rfc6544#section-4.5, for active candidate,
+    // the port must be set to the discard port, i.e. 9. We can't be 100% sure
+    // which IP address will actually be used, so GetBestIP is as good as we
+    // can do.
+    // TODO(deadbeef): We could do something like create a dummy socket just to
+    // see what IP we get. But that may be overkill.
+    AddAddress(rtc::SocketAddress(Network()->GetBestIP(), DISCARD_PORT),
+               rtc::SocketAddress(Network()->GetBestIP(), 0),
+               rtc::SocketAddress(), TCP_PROTOCOL_NAME, "", TCPTYPE_ACTIVE_STR,
+               LOCAL_PORT_TYPE, ICE_TYPE_PREFERENCE_HOST_TCP, 0, "", true);
+  }
+}
+
+int TCPPort::SendTo(const void* data,
+                    size_t size,
+                    const rtc::SocketAddress& addr,
+                    const rtc::PacketOptions& options,
+                    bool payload) {
+  rtc::AsyncPacketSocket* socket = NULL;
+  TCPConnection* conn = static_cast<TCPConnection*>(GetConnection(addr));
+
+  // For Connection, this is the code path used by Ping() to establish
+  // WRITABLE. It has to send through the socket directly as TCPConnection::Send
+  // checks writability.
+  if (conn) {
+    if (!conn->connected()) {
+      conn->MaybeReconnect();
+      return SOCKET_ERROR;
+    }
+    socket = conn->socket();
+    if (!socket) {
+      // The failure to initialize should have been logged elsewhere,
+      // so this log is not important.
+      RTC_LOG(LS_INFO) << ToString()
+                       << ": Attempted to send to an uninitialized socket: "
+                       << addr.ToSensitiveString();
+      error_ = EHOSTUNREACH;
+      return SOCKET_ERROR;
+    }
+  } else {
+    socket = GetIncoming(addr);
+    if (!socket) {
+      RTC_LOG(LS_ERROR) << ToString()
+                        << ": Attempted to send to an unknown destination: "
+                        << addr.ToSensitiveString();
+      error_ = EHOSTUNREACH;
+      return SOCKET_ERROR;
+    }
+  }
+  rtc::PacketOptions modified_options(options);
+  CopyPortInformationToPacketInfo(&modified_options.info_signaled_after_sent);
+  int sent = socket->Send(data, size, modified_options);
+  if (sent < 0) {
+    error_ = socket->GetError();
+    // Error from this code path for a Connection (instead of from a bare
+    // socket) will not trigger reconnecting. In theory, this shouldn't matter
+    // as OnClose should always be called and set connected to false.
+    RTC_LOG(LS_ERROR) << ToString() << ": TCP send of " << size
+                      << " bytes failed with error " << error_;
+  }
+  return sent;
+}
+
+int TCPPort::GetOption(rtc::Socket::Option opt, int* value) {
+  auto const& it = socket_options_.find(opt);
+  if (it == socket_options_.end()) {
+    return -1;
+  }
+  *value = it->second;
+  return 0;
+}
+
+int TCPPort::SetOption(rtc::Socket::Option opt, int value) {
+  socket_options_[opt] = value;
+  return 0;
+}
+
+int TCPPort::GetError() {
+  return error_;
+}
+
+bool TCPPort::SupportsProtocol(absl::string_view protocol) const {
+  return protocol == TCP_PROTOCOL_NAME || protocol == SSLTCP_PROTOCOL_NAME;
+}
+
+ProtocolType TCPPort::GetProtocol() const {
+  return PROTO_TCP;
+}
+
+void TCPPort::OnNewConnection(rtc::AsyncListenSocket* socket,
+                              rtc::AsyncPacketSocket* new_socket) {
+  RTC_DCHECK_EQ(socket, listen_socket_.get());
+
+  for (const auto& option : socket_options_) {
+    new_socket->SetOption(option.first, option.second);
+  }
+  Incoming incoming;
+  incoming.addr = new_socket->GetRemoteAddress();
+  incoming.socket = new_socket;
+  incoming.socket->SignalReadPacket.connect(this, &TCPPort::OnReadPacket);
+  incoming.socket->SignalReadyToSend.connect(this, &TCPPort::OnReadyToSend);
+  incoming.socket->SignalSentPacket.connect(this, &TCPPort::OnSentPacket);
+
+  RTC_LOG(LS_VERBOSE) << ToString() << ": Accepted connection from "
+                      << incoming.addr.ToSensitiveString();
+  incoming_.push_back(incoming);
+}
+
+void TCPPort::TryCreateServerSocket() {
+  listen_socket_ = absl::WrapUnique(socket_factory()->CreateServerTcpSocket(
+      rtc::SocketAddress(Network()->GetBestIP(), 0), min_port(), max_port(),
+      false /* ssl */));
+  if (!listen_socket_) {
+    RTC_LOG(LS_WARNING)
+        << ToString()
+        << ": TCP server socket creation failed; continuing anyway.";
+    return;
+  }
+  listen_socket_->SignalNewConnection.connect(this, &TCPPort::OnNewConnection);
+}
+
+rtc::AsyncPacketSocket* TCPPort::GetIncoming(const rtc::SocketAddress& addr,
+                                             bool remove) {
+  rtc::AsyncPacketSocket* socket = NULL;
+  for (std::list<Incoming>::iterator it = incoming_.begin();
+       it != incoming_.end(); ++it) {
+    if (it->addr == addr) {
+      socket = it->socket;
+      if (remove)
+        incoming_.erase(it);
+      break;
+    }
+  }
+  return socket;
+}
+
+void TCPPort::OnReadPacket(rtc::AsyncPacketSocket* socket,
+                           const char* data,
+                           size_t size,
+                           const rtc::SocketAddress& remote_addr,
+                           const int64_t& packet_time_us) {
+  Port::OnReadPacket(data, size, remote_addr, PROTO_TCP);
+}
+
+void TCPPort::OnSentPacket(rtc::AsyncPacketSocket* socket,
+                           const rtc::SentPacket& sent_packet) {
+  PortInterface::SignalSentPacket(sent_packet);
+}
+
+void TCPPort::OnReadyToSend(rtc::AsyncPacketSocket* socket) {
+  Port::OnReadyToSend();
+}
+
+// TODO(qingsi): `CONNECTION_WRITE_CONNECT_TIMEOUT` is overriden by
+// `ice_unwritable_timeout` in IceConfig when determining the writability state.
+// Replace this constant with the config parameter assuming the default value if
+// we decide it is also applicable here.
+TCPConnection::TCPConnection(rtc::WeakPtr<Port> tcp_port,
+                             const Candidate& candidate,
+                             rtc::AsyncPacketSocket* socket)
+    : Connection(std::move(tcp_port), 0, candidate),
+      socket_(socket),
+      error_(0),
+      outgoing_(socket == NULL),
+      connection_pending_(false),
+      pretending_to_be_writable_(false),
+      reconnection_timeout_(cricket::CONNECTION_WRITE_CONNECT_TIMEOUT) {
+  RTC_DCHECK_EQ(port()->GetProtocol(), PROTO_TCP);  // Needs to be TCPPort.
+  if (outgoing_) {
+    CreateOutgoingTcpSocket();
+  } else {
+    // Incoming connections should match one of the network addresses. Same as
+    // what's being checked in OnConnect, but just DCHECKing here.
+    RTC_LOG(LS_VERBOSE) << ToString() << ": socket ipaddr: "
+                        << socket_->GetLocalAddress().ToSensitiveString()
+                        << ", port() Network:" << port()->Network()->ToString();
+    RTC_DCHECK(absl::c_any_of(
+        port_->Network()->GetIPs(), [this](const rtc::InterfaceAddress& addr) {
+          return socket_->GetLocalAddress().ipaddr() == addr;
+        }));
+    ConnectSocketSignals(socket);
+  }
+}
+
+TCPConnection::~TCPConnection() {
+  RTC_DCHECK_RUN_ON(network_thread_);
+}
+
+int TCPConnection::Send(const void* data,
+                        size_t size,
+                        const rtc::PacketOptions& options) {
+  if (!socket_) {
+    error_ = ENOTCONN;
+    return SOCKET_ERROR;
+  }
+
+  // Sending after OnClose on active side will trigger a reconnect for a
+  // outgoing connection. Note that the write state is still WRITABLE as we want
+  // to spend a few seconds attempting a reconnect before saying we're
+  // unwritable.
+  if (!connected()) {
+    MaybeReconnect();
+    return SOCKET_ERROR;
+  }
+
+  // Note that this is important to put this after the previous check to give
+  // the connection a chance to reconnect.
+  if (pretending_to_be_writable_ || write_state() != STATE_WRITABLE) {
+    // TODO(?): Should STATE_WRITE_TIMEOUT return a non-blocking error?
+    error_ = ENOTCONN;
+    return SOCKET_ERROR;
+  }
+  stats_.sent_total_packets++;
+  rtc::PacketOptions modified_options(options);
+  tcp_port()->CopyPortInformationToPacketInfo(
+      &modified_options.info_signaled_after_sent);
+  int sent = socket_->Send(data, size, modified_options);
+  int64_t now = rtc::TimeMillis();
+  if (sent < 0) {
+    stats_.sent_discarded_packets++;
+    error_ = socket_->GetError();
+  } else {
+    send_rate_tracker_.AddSamplesAtTime(now, sent);
+  }
+  last_send_data_ = now;
+  return sent;
+}
+
+int TCPConnection::GetError() {
+  return error_;
+}
+
+void TCPConnection::OnConnectionRequestResponse(StunRequest* req,
+                                                StunMessage* response) {
+  // Process the STUN response before we inform upper layer ready to send.
+  Connection::OnConnectionRequestResponse(req, response);
+
+  // If we're in the state of pretending to be writeable, we should inform the
+  // upper layer it's ready to send again as previous EWOULDLBLOCK from socket
+  // would have stopped the outgoing stream.
+  if (pretending_to_be_writable_) {
+    Connection::OnReadyToSend();
+  }
+  pretending_to_be_writable_ = false;
+  RTC_DCHECK(write_state() == STATE_WRITABLE);
+}
+
+void TCPConnection::OnConnect(rtc::AsyncPacketSocket* socket) {
+  RTC_DCHECK_EQ(socket, socket_.get());
+
+  if (!port_) {
+    RTC_LOG(LS_ERROR) << "TCPConnection: Port has been deleted.";
+    return;
+  }
+
+  // Do not use this port if the socket bound to an address not associated with
+  // the desired network interface. This is seen in Chrome, where TCP sockets
+  // cannot be given a binding address, and the platform is expected to pick
+  // the correct local address.
+  //
+  // However, there are two situations in which we allow the bound address to
+  // not be one of the addresses of the requested interface:
+  // 1. The bound address is the loopback address. This happens when a proxy
+  // forces TCP to bind to only the localhost address (see issue 3927).
+  // 2. The bound address is the "any address". This happens when
+  // multiple_routes is disabled (see issue 4780).
+  //
+  // Note that, aside from minor differences in log statements, this logic is
+  // identical to that in TurnPort.
+  const rtc::SocketAddress& socket_address = socket->GetLocalAddress();
+  if (absl::c_any_of(port_->Network()->GetIPs(),
+                     [socket_address](const rtc::InterfaceAddress& addr) {
+                       return socket_address.ipaddr() == addr;
+                     })) {
+    RTC_LOG(LS_VERBOSE) << ToString() << ": Connection established to "
+                        << socket->GetRemoteAddress().ToSensitiveString();
+  } else {
+    if (socket->GetLocalAddress().IsLoopbackIP()) {
+      RTC_LOG(LS_WARNING) << "Socket is bound to the address:"
+                          << socket_address.ipaddr().ToSensitiveString()
+                          << ", rather than an address associated with network:"
+                          << port_->Network()->ToString()
+                          << ". Still allowing it since it's localhost.";
+    } else if (IPIsAny(port_->Network()->GetBestIP())) {
+      RTC_LOG(LS_WARNING)
+          << "Socket is bound to the address:"
+          << socket_address.ipaddr().ToSensitiveString()
+          << ", rather than an address associated with network:"
+          << port_->Network()->ToString()
+          << ". Still allowing it since it's the 'any' address"
+             ", possibly caused by multiple_routes being disabled.";
+    } else {
+      RTC_LOG(LS_WARNING) << "Dropping connection as TCP socket bound to IP "
+                          << socket_address.ipaddr().ToSensitiveString()
+                          << ", rather than an address associated with network:"
+                          << port_->Network()->ToString();
+      OnClose(socket, 0);
+      return;
+    }
+  }
+
+  // Connection is established successfully.
+  set_connected(true);
+  connection_pending_ = false;
+}
+
+void TCPConnection::OnClose(rtc::AsyncPacketSocket* socket, int error) {
+  RTC_DCHECK_EQ(socket, socket_.get());
+  RTC_LOG(LS_INFO) << ToString() << ": Connection closed with error " << error;
+
+  if (!port_) {
+    RTC_LOG(LS_ERROR) << "TCPConnection: Port has been deleted.";
+    return;
+  }
+
+  // Guard against the condition where IPC socket will call OnClose for every
+  // packet it can't send.
+  if (connected()) {
+    set_connected(false);
+
+    // Prevent the connection from being destroyed by redundant SignalClose
+    // events.
+    pretending_to_be_writable_ = true;
+
+    // If this connection can't become connected and writable again in 5
+    // seconds, it's time to tear this down. This is the case for the original
+    // TCP connection on passive side during a reconnect.
+    // We don't attempt reconnect right here. This is to avoid a case where the
+    // shutdown is intentional and reconnect is not necessary. We only reconnect
+    // when the connection is used to Send() or Ping().
+    network_thread()->PostDelayedTask(
+        SafeTask(network_safety_.flag(),
+                 [this]() {
+                   if (pretending_to_be_writable_) {
+                     Destroy();
+                   }
+                 }),
+        TimeDelta::Millis(reconnection_timeout()));
+  } else if (!pretending_to_be_writable_) {
+    // OnClose could be called when the underneath socket times out during the
+    // initial connect() (i.e. `pretending_to_be_writable_` is false) . We have
+    // to manually destroy here as this connection, as never connected, will not
+    // be scheduled for ping to trigger destroy.
+    socket_->UnsubscribeClose(this);
+    port()->DestroyConnectionAsync(this);
+  }
+}
+
+void TCPConnection::MaybeReconnect() {
+  // Only reconnect for an outgoing TCPConnection when OnClose was signaled and
+  // no outstanding reconnect is pending.
+  if (connected() || connection_pending_ || !outgoing_) {
+    return;
+  }
+
+  RTC_LOG(LS_INFO) << ToString()
+                   << ": TCP Connection with remote is closed, "
+                      "trying to reconnect";
+
+  CreateOutgoingTcpSocket();
+  error_ = EPIPE;
+}
+
+void TCPConnection::OnReadPacket(rtc::AsyncPacketSocket* socket,
+                                 const char* data,
+                                 size_t size,
+                                 const rtc::SocketAddress& remote_addr,
+                                 const int64_t& packet_time_us) {
+  RTC_DCHECK_EQ(socket, socket_.get());
+  Connection::OnReadPacket(data, size, packet_time_us);
+}
+
+void TCPConnection::OnReadyToSend(rtc::AsyncPacketSocket* socket) {
+  RTC_DCHECK_EQ(socket, socket_.get());
+  Connection::OnReadyToSend();
+}
+
+void TCPConnection::CreateOutgoingTcpSocket() {
+  RTC_DCHECK(outgoing_);
+  int opts = (remote_candidate().protocol() == SSLTCP_PROTOCOL_NAME)
+                 ? rtc::PacketSocketFactory::OPT_TLS_FAKE
+                 : 0;
+
+  if (socket_) {
+    socket_->UnsubscribeClose(this);
+  }
+
+  rtc::PacketSocketTcpOptions tcp_opts;
+  tcp_opts.opts = opts;
+  socket_.reset(port()->socket_factory()->CreateClientTcpSocket(
+      rtc::SocketAddress(port()->Network()->GetBestIP(), 0),
+      remote_candidate().address(), port()->proxy(), port()->user_agent(),
+      tcp_opts));
+  if (socket_) {
+    RTC_LOG(LS_VERBOSE) << ToString() << ": Connecting from "
+                        << socket_->GetLocalAddress().ToSensitiveString()
+                        << " to "
+                        << remote_candidate().address().ToSensitiveString();
+    set_connected(false);
+    connection_pending_ = true;
+    ConnectSocketSignals(socket_.get());
+  } else {
+    RTC_LOG(LS_WARNING) << ToString() << ": Failed to create connection to "
+                        << remote_candidate().address().ToSensitiveString();
+    set_state(IceCandidatePairState::FAILED);
+    // We can't FailAndPrune directly here. FailAndPrune and deletes all
+    // the StunRequests from the request_map_. And if this is in the stack
+    // of Connection::Ping(), we are still using the request.
+    // Unwind the stack and defer the FailAndPrune.
+    network_thread()->PostTask(
+        SafeTask(network_safety_.flag(), [this]() { FailAndPrune(); }));
+  }
+}
+
+void TCPConnection::ConnectSocketSignals(rtc::AsyncPacketSocket* socket) {
+  if (outgoing_) {
+    socket->SignalConnect.connect(this, &TCPConnection::OnConnect);
+  }
+  socket->SignalReadPacket.connect(this, &TCPConnection::OnReadPacket);
+  socket->SignalReadyToSend.connect(this, &TCPConnection::OnReadyToSend);
+  socket->SubscribeClose(this, [this, safety = network_safety_.flag()](
+                                   rtc::AsyncPacketSocket* s, int err) {
+    if (safety->alive())
+      OnClose(s, err);
+  });
+}
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/tcp_port.h b/third_party/libwebrtc/p2p/base/tcp_port.h
new file mode 100644
index 0000000000..ff69e6e48b
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/tcp_port.h
@@ -0,0 +1,203 @@
+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_TCP_PORT_H_
+#define P2P_BASE_TCP_PORT_H_
+
+#include <list>
+#include <memory>
+#include <string>
+
+#include "absl/memory/memory.h"
+#include "absl/strings/string_view.h"
+#include "api/task_queue/pending_task_safety_flag.h"
+#include "p2p/base/connection.h"
+#include "p2p/base/port.h"
+#include "rtc_base/async_packet_socket.h"
+#include "rtc_base/containers/flat_map.h"
+
+namespace cricket {
+
+class TCPConnection;
+
+// Communicates using a local TCP port.
+//
+// This class is designed to allow subclasses to take advantage of the
+// connection management provided by this class.  A subclass should take of all
+// packet sending and preparation, but when a packet is received, it should
+// call this TCPPort::OnReadPacket (3 arg) to dispatch to a connection.
+class TCPPort : public Port {
+ public:
+  static std::unique_ptr<TCPPort> Create(
+      rtc::Thread* thread,
+      rtc::PacketSocketFactory* factory,
+      const rtc::Network* network,
+      uint16_t min_port,
+      uint16_t max_port,
+      absl::string_view username,
+      absl::string_view password,
+      bool allow_listen,
+      const webrtc::FieldTrialsView* field_trials = nullptr) {
+    // Using `new` to access a non-public constructor.
+    return absl::WrapUnique(new TCPPort(thread, factory, network, min_port,
+                                        max_port, username, password,
+                                        allow_listen, field_trials));
+  }
+  ~TCPPort() override;
+
+  Connection* CreateConnection(const Candidate& address,
+                               CandidateOrigin origin) override;
+
+  void PrepareAddress() override;
+
+  // Options apply to accepted sockets.
+  // TODO(bugs.webrtc.org/13065): Apply also to outgoing and existing
+  // connections.
+  int GetOption(rtc::Socket::Option opt, int* value) override;
+  int SetOption(rtc::Socket::Option opt, int value) override;
+  int GetError() override;
+  bool SupportsProtocol(absl::string_view protocol) const override;
+  ProtocolType GetProtocol() const override;
+
+ protected:
+  TCPPort(rtc::Thread* thread,
+          rtc::PacketSocketFactory* factory,
+          const rtc::Network* network,
+          uint16_t min_port,
+          uint16_t max_port,
+          absl::string_view username,
+          absl::string_view password,
+          bool allow_listen,
+          const webrtc::FieldTrialsView* field_trials);
+
+  // Handles sending using the local TCP socket.
+  int SendTo(const void* data,
+             size_t size,
+             const rtc::SocketAddress& addr,
+             const rtc::PacketOptions& options,
+             bool payload) override;
+
+  // Accepts incoming TCP connection.
+  void OnNewConnection(rtc::AsyncListenSocket* socket,
+                       rtc::AsyncPacketSocket* new_socket);
+
+ private:
+  struct Incoming {
+    rtc::SocketAddress addr;
+    rtc::AsyncPacketSocket* socket;
+  };
+
+  void TryCreateServerSocket();
+
+  rtc::AsyncPacketSocket* GetIncoming(const rtc::SocketAddress& addr,
+                                      bool remove = false);
+
+  // Receives packet signal from the local TCP Socket.
+  void OnReadPacket(rtc::AsyncPacketSocket* socket,
+                    const char* data,
+                    size_t size,
+                    const rtc::SocketAddress& remote_addr,
+                    const int64_t& packet_time_us);
+
+  void OnSentPacket(rtc::AsyncPacketSocket* socket,
+                    const rtc::SentPacket& sent_packet) override;
+
+  void OnReadyToSend(rtc::AsyncPacketSocket* socket);
+
+  bool allow_listen_;
+  std::unique_ptr<rtc::AsyncListenSocket> listen_socket_;
+  // Options to be applied to accepted sockets.
+  // TODO(bugs.webrtc:13065): Configure connect/accept in the same way, but
+  // currently, setting OPT_NODELAY for client sockets is done (unconditionally)
+  // by BasicPacketSocketFactory::CreateClientTcpSocket.
+  webrtc::flat_map<rtc::Socket::Option, int> socket_options_;
+
+  int error_;
+  std::list<Incoming> incoming_;
+
+  friend class TCPConnection;
+};
+
+class TCPConnection : public Connection, public sigslot::has_slots<> {
+ public:
+  // Connection is outgoing unless socket is specified
+  TCPConnection(rtc::WeakPtr<Port> tcp_port,
+                const Candidate& candidate,
+                rtc::AsyncPacketSocket* socket = nullptr);
+  ~TCPConnection() override;
+
+  int Send(const void* data,
+           size_t size,
+           const rtc::PacketOptions& options) override;
+  int GetError() override;
+
+  rtc::AsyncPacketSocket* socket() { return socket_.get(); }
+
+  // Allow test cases to overwrite the default timeout period.
+  int reconnection_timeout() const { return reconnection_timeout_; }
+  void set_reconnection_timeout(int timeout_in_ms) {
+    reconnection_timeout_ = timeout_in_ms;
+  }
+
+ protected:
+  // Set waiting_for_stun_binding_complete_ to false to allow data packets in
+  // addition to what Port::OnConnectionRequestResponse does.
+  void OnConnectionRequestResponse(StunRequest* req,
+                                   StunMessage* response) override;
+
+ private:
+  // Helper function to handle the case when Ping or Send fails with error
+  // related to socket close.
+  void MaybeReconnect();
+
+  void CreateOutgoingTcpSocket();
+
+  void ConnectSocketSignals(rtc::AsyncPacketSocket* socket);
+
+  void OnConnect(rtc::AsyncPacketSocket* socket);
+  void OnClose(rtc::AsyncPacketSocket* socket, int error);
+  void OnReadPacket(rtc::AsyncPacketSocket* socket,
+                    const char* data,
+                    size_t size,
+                    const rtc::SocketAddress& remote_addr,
+                    const int64_t& packet_time_us);
+  void OnReadyToSend(rtc::AsyncPacketSocket* socket);
+
+  TCPPort* tcp_port() {
+    RTC_DCHECK_EQ(port()->GetProtocol(), PROTO_TCP);
+    return static_cast<TCPPort*>(port());
+  }
+
+  std::unique_ptr<rtc::AsyncPacketSocket> socket_;
+  int error_;
+  bool outgoing_;
+
+  // Guard against multiple outgoing tcp connection during a reconnect.
+  bool connection_pending_;
+
+  // Guard against data packets sent when we reconnect a TCP connection. During
+  // reconnecting, when a new tcp connection has being made, we can't send data
+  // packets out until the STUN binding is completed (i.e. the write state is
+  // set to WRITABLE again by Connection::OnConnectionRequestResponse). IPC
+  // socket, when receiving data packets before that, will trigger OnError which
+  // will terminate the newly created connection.
+  bool pretending_to_be_writable_;
+
+  // Allow test case to overwrite the default timeout period.
+  int reconnection_timeout_;
+
+  webrtc::ScopedTaskSafety network_safety_;
+
+  friend class TCPPort;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_TCP_PORT_H_
diff --git a/third_party/libwebrtc/p2p/base/tcp_port_unittest.cc b/third_party/libwebrtc/p2p/base/tcp_port_unittest.cc
new file mode 100644
index 0000000000..1bb59811b8
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/tcp_port_unittest.cc
@@ -0,0 +1,259 @@
+/*
+ *  Copyright 2016 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/tcp_port.h"
+
+#include <list>
+#include <memory>
+#include <vector>
+
+#include "p2p/base/basic_packet_socket_factory.h"
+#include "p2p/base/p2p_constants.h"
+#include "p2p/base/transport_description.h"
+#include "rtc_base/gunit.h"
+#include "rtc_base/helpers.h"
+#include "rtc_base/ip_address.h"
+#include "rtc_base/third_party/sigslot/sigslot.h"
+#include "rtc_base/thread.h"
+#include "rtc_base/time_utils.h"
+#include "rtc_base/virtual_socket_server.h"
+#include "test/gtest.h"
+#include "test/scoped_key_value_config.h"
+
+using cricket::Connection;
+using cricket::ICE_PWD_LENGTH;
+using cricket::ICE_UFRAG_LENGTH;
+using cricket::Port;
+using cricket::TCPPort;
+using rtc::SocketAddress;
+
+static int kTimeout = 1000;
+static const SocketAddress kLocalAddr("11.11.11.11", 0);
+static const SocketAddress kLocalIPv6Addr("2401:fa00:4:1000:be30:5bff:fee5:c3",
+                                          0);
+static const SocketAddress kAlternateLocalAddr("1.2.3.4", 0);
+static const SocketAddress kRemoteAddr("22.22.22.22", 0);
+static const SocketAddress kRemoteIPv6Addr("2401:fa00:4:1000:be30:5bff:fee5:c4",
+                                           0);
+
+constexpr uint64_t kTiebreakerDefault = 44444;
+
+class ConnectionObserver : public sigslot::has_slots<> {
+ public:
+  explicit ConnectionObserver(Connection* conn) : conn_(conn) {
+    conn->SignalDestroyed.connect(this, &ConnectionObserver::OnDestroyed);
+  }
+
+  ~ConnectionObserver() {
+    if (!connection_destroyed_) {
+      RTC_DCHECK(conn_);
+      conn_->SignalDestroyed.disconnect(this);
+    }
+  }
+
+  bool connection_destroyed() { return connection_destroyed_; }
+
+ private:
+  void OnDestroyed(Connection*) { connection_destroyed_ = true; }
+
+  Connection* const conn_;
+  bool connection_destroyed_ = false;
+};
+
+class TCPPortTest : public ::testing::Test, public sigslot::has_slots<> {
+ public:
+  TCPPortTest()
+      : ss_(new rtc::VirtualSocketServer()),
+        main_(ss_.get()),
+        socket_factory_(ss_.get()),
+        username_(rtc::CreateRandomString(ICE_UFRAG_LENGTH)),
+        password_(rtc::CreateRandomString(ICE_PWD_LENGTH)) {}
+
+  rtc::Network* MakeNetwork(const SocketAddress& addr) {
+    networks_.emplace_back("unittest", "unittest", addr.ipaddr(), 32);
+    networks_.back().AddIP(addr.ipaddr());
+    return &networks_.back();
+  }
+
+  std::unique_ptr<TCPPort> CreateTCPPort(const SocketAddress& addr) {
+    auto port = std::unique_ptr<TCPPort>(
+        TCPPort::Create(&main_, &socket_factory_, MakeNetwork(addr), 0, 0,
+                        username_, password_, true, &field_trials_));
+    port->SetIceTiebreaker(kTiebreakerDefault);
+    return port;
+  }
+
+  std::unique_ptr<TCPPort> CreateTCPPort(const rtc::Network* network) {
+    auto port = std::unique_ptr<TCPPort>(
+        TCPPort::Create(&main_, &socket_factory_, network, 0, 0, username_,
+                        password_, true, &field_trials_));
+    port->SetIceTiebreaker(kTiebreakerDefault);
+    return port;
+  }
+
+ protected:
+  // When a "create port" helper method is called with an IP, we create a
+  // Network with that IP and add it to this list. Using a list instead of a
+  // vector so that when it grows, pointers aren't invalidated.
+  std::list<rtc::Network> networks_;
+  std::unique_ptr<rtc::VirtualSocketServer> ss_;
+  rtc::AutoSocketServerThread main_;
+  rtc::BasicPacketSocketFactory socket_factory_;
+  std::string username_;
+  std::string password_;
+  webrtc::test::ScopedKeyValueConfig field_trials_;
+};
+
+TEST_F(TCPPortTest, TestTCPPortWithLocalhostAddress) {
+  SocketAddress local_address("127.0.0.1", 0);
+  // After calling this, when TCPPort attempts to get a socket bound to
+  // kLocalAddr, it will end up using localhost instead.
+  ss_->SetAlternativeLocalAddress(kLocalAddr.ipaddr(), local_address.ipaddr());
+  auto local_port = CreateTCPPort(kLocalAddr);
+  auto remote_port = CreateTCPPort(kRemoteAddr);
+  local_port->PrepareAddress();
+  remote_port->PrepareAddress();
+  Connection* conn = local_port->CreateConnection(remote_port->Candidates()[0],
+                                                  Port::ORIGIN_MESSAGE);
+  EXPECT_TRUE_WAIT(conn->connected(), kTimeout);
+  // Verify that the socket actually used localhost, otherwise this test isn't
+  // doing what it meant to.
+  ASSERT_EQ(local_address.ipaddr(),
+            local_port->Candidates()[0].address().ipaddr());
+}
+
+// If the address the socket ends up bound to does not match any address of the
+// TCPPort's Network, then the socket should be discarded and no candidates
+// should be signaled. In the context of ICE, where one TCPPort is created for
+// each Network, when this happens it's likely that the unexpected address is
+// associated with some other Network, which another TCPPort is already
+// covering.
+TEST_F(TCPPortTest, TCPPortDiscardedIfBoundAddressDoesNotMatchNetwork) {
+  // Sockets bound to kLocalAddr will actually end up with kAlternateLocalAddr.
+  ss_->SetAlternativeLocalAddress(kLocalAddr.ipaddr(),
+                                  kAlternateLocalAddr.ipaddr());
+
+  // Create ports (local_port is the one whose IP will end up reassigned).
+  auto local_port = CreateTCPPort(kLocalAddr);
+  auto remote_port = CreateTCPPort(kRemoteAddr);
+  local_port->PrepareAddress();
+  remote_port->PrepareAddress();
+
+  // Tell port to create a connection; it should be destroyed when it's
+  // realized that it's using an unexpected address.
+  Connection* conn = local_port->CreateConnection(remote_port->Candidates()[0],
+                                                  Port::ORIGIN_MESSAGE);
+  ConnectionObserver observer(conn);
+  EXPECT_TRUE_WAIT(observer.connection_destroyed(), kTimeout);
+}
+
+// A caveat for the above logic: if the socket ends up bound to one of the IPs
+// associated with the Network, just not the "best" one, this is ok.
+TEST_F(TCPPortTest, TCPPortNotDiscardedIfNotBoundToBestIP) {
+  // Sockets bound to kLocalAddr will actually end up with kAlternateLocalAddr.
+  ss_->SetAlternativeLocalAddress(kLocalAddr.ipaddr(),
+                                  kAlternateLocalAddr.ipaddr());
+
+  // Set up a network with kLocalAddr1 as the "best" IP, and kAlternateLocalAddr
+  // as an alternate.
+  rtc::Network* network = MakeNetwork(kLocalAddr);
+  network->AddIP(kAlternateLocalAddr.ipaddr());
+  ASSERT_EQ(kLocalAddr.ipaddr(), network->GetBestIP());
+
+  // Create ports (using our special 2-IP Network for local_port).
+  auto local_port = CreateTCPPort(network);
+  auto remote_port = CreateTCPPort(kRemoteAddr);
+  local_port->PrepareAddress();
+  remote_port->PrepareAddress();
+
+  // Expect connection to succeed.
+  Connection* conn = local_port->CreateConnection(remote_port->Candidates()[0],
+                                                  Port::ORIGIN_MESSAGE);
+  EXPECT_TRUE_WAIT(conn->connected(), kTimeout);
+
+  // Verify that the socket actually used the alternate address, otherwise this
+  // test isn't doing what it meant to.
+  ASSERT_EQ(kAlternateLocalAddr.ipaddr(),
+            local_port->Candidates()[0].address().ipaddr());
+}
+
+// Regression test for crbug.com/webrtc/8972, caused by buggy comparison
+// between rtc::IPAddress and rtc::InterfaceAddress.
+TEST_F(TCPPortTest, TCPPortNotDiscardedIfBoundToTemporaryIP) {
+  networks_.emplace_back("unittest", "unittest", kLocalIPv6Addr.ipaddr(), 32);
+  networks_.back().AddIP(rtc::InterfaceAddress(
+      kLocalIPv6Addr.ipaddr(), rtc::IPV6_ADDRESS_FLAG_TEMPORARY));
+
+  auto local_port = CreateTCPPort(&networks_.back());
+  auto remote_port = CreateTCPPort(kRemoteIPv6Addr);
+  local_port->PrepareAddress();
+  remote_port->PrepareAddress();
+
+  // Connection should succeed if the port isn't discarded.
+  Connection* conn = local_port->CreateConnection(remote_port->Candidates()[0],
+                                                  Port::ORIGIN_MESSAGE);
+  ASSERT_NE(nullptr, conn);
+  EXPECT_TRUE_WAIT(conn->connected(), kTimeout);
+}
+
+class SentPacketCounter : public sigslot::has_slots<> {
+ public:
+  explicit SentPacketCounter(TCPPort* p) {
+    p->SignalSentPacket.connect(this, &SentPacketCounter::OnSentPacket);
+  }
+
+  int sent_packets() const { return sent_packets_; }
+
+ private:
+  void OnSentPacket(const rtc::SentPacket&) { ++sent_packets_; }
+
+  int sent_packets_ = 0;
+};
+
+// Test that SignalSentPacket is fired when a packet is successfully sent, for
+// both TCP client and server sockets.
+TEST_F(TCPPortTest, SignalSentPacket) {
+  std::unique_ptr<TCPPort> client(CreateTCPPort(kLocalAddr));
+  std::unique_ptr<TCPPort> server(CreateTCPPort(kRemoteAddr));
+  client->SetIceRole(cricket::ICEROLE_CONTROLLING);
+  server->SetIceRole(cricket::ICEROLE_CONTROLLED);
+  client->PrepareAddress();
+  server->PrepareAddress();
+
+  Connection* client_conn =
+      client->CreateConnection(server->Candidates()[0], Port::ORIGIN_MESSAGE);
+  ASSERT_NE(nullptr, client_conn);
+  ASSERT_TRUE_WAIT(client_conn->connected(), kTimeout);
+
+  // Need to get the port of the actual outgoing socket, not the server socket..
+  cricket::Candidate client_candidate = client->Candidates()[0];
+  client_candidate.set_address(static_cast<cricket::TCPConnection*>(client_conn)
+                                   ->socket()
+                                   ->GetLocalAddress());
+  Connection* server_conn =
+      server->CreateConnection(client_candidate, Port::ORIGIN_THIS_PORT);
+  ASSERT_NE(nullptr, server_conn);
+  ASSERT_TRUE_WAIT(server_conn->connected(), kTimeout);
+
+  client_conn->Ping(rtc::TimeMillis());
+  server_conn->Ping(rtc::TimeMillis());
+  ASSERT_TRUE_WAIT(client_conn->writable(), kTimeout);
+  ASSERT_TRUE_WAIT(server_conn->writable(), kTimeout);
+
+  SentPacketCounter client_counter(client.get());
+  SentPacketCounter server_counter(server.get());
+  static const char kData[] = "hello";
+  for (int i = 0; i < 10; ++i) {
+    client_conn->Send(&kData, sizeof(kData), rtc::PacketOptions());
+    server_conn->Send(&kData, sizeof(kData), rtc::PacketOptions());
+  }
+  EXPECT_EQ_WAIT(10, client_counter.sent_packets(), kTimeout);
+  EXPECT_EQ_WAIT(10, server_counter.sent_packets(), kTimeout);
+}
diff --git a/third_party/libwebrtc/p2p/base/test_stun_server.cc b/third_party/libwebrtc/p2p/base/test_stun_server.cc
new file mode 100644
index 0000000000..d4c3b2d851
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/test_stun_server.cc
@@ -0,0 +1,37 @@
+/*
+ *  Copyright 2017 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/test_stun_server.h"
+
+#include "rtc_base/socket.h"
+#include "rtc_base/socket_server.h"
+
+namespace cricket {
+
+TestStunServer* TestStunServer::Create(rtc::SocketServer* ss,
+                                       const rtc::SocketAddress& addr) {
+  rtc::Socket* socket = ss->CreateSocket(addr.family(), SOCK_DGRAM);
+  rtc::AsyncUDPSocket* udp_socket = rtc::AsyncUDPSocket::Create(socket, addr);
+
+  return new TestStunServer(udp_socket);
+}
+
+void TestStunServer::OnBindingRequest(StunMessage* msg,
+                                      const rtc::SocketAddress& remote_addr) {
+  if (fake_stun_addr_.IsNil()) {
+    StunServer::OnBindingRequest(msg, remote_addr);
+  } else {
+    StunMessage response(STUN_BINDING_RESPONSE, msg->transaction_id());
+    GetStunBindResponse(msg, fake_stun_addr_, &response);
+    SendResponse(response, remote_addr);
+  }
+}
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/test_stun_server.h b/third_party/libwebrtc/p2p/base/test_stun_server.h
new file mode 100644
index 0000000000..11ac620bb8
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/test_stun_server.h
@@ -0,0 +1,45 @@
+/*
+ *  Copyright 2008 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_TEST_STUN_SERVER_H_
+#define P2P_BASE_TEST_STUN_SERVER_H_
+
+#include "api/transport/stun.h"
+#include "p2p/base/stun_server.h"
+#include "rtc_base/async_udp_socket.h"
+#include "rtc_base/socket_address.h"
+#include "rtc_base/socket_server.h"
+
+namespace cricket {
+
+// A test STUN server. Useful for unit tests.
+class TestStunServer : StunServer {
+ public:
+  static TestStunServer* Create(rtc::SocketServer* ss,
+                                const rtc::SocketAddress& addr);
+
+  // Set a fake STUN address to return to the client.
+  void set_fake_stun_addr(const rtc::SocketAddress& addr) {
+    fake_stun_addr_ = addr;
+  }
+
+ private:
+  explicit TestStunServer(rtc::AsyncUDPSocket* socket) : StunServer(socket) {}
+
+  void OnBindingRequest(StunMessage* msg,
+                        const rtc::SocketAddress& remote_addr) override;
+
+ private:
+  rtc::SocketAddress fake_stun_addr_;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_TEST_STUN_SERVER_H_
diff --git a/third_party/libwebrtc/p2p/base/test_turn_customizer.h b/third_party/libwebrtc/p2p/base/test_turn_customizer.h
new file mode 100644
index 0000000000..415b13fbf2
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/test_turn_customizer.h
@@ -0,0 +1,59 @@
+/*
+ *  Copyright 2017 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_TEST_TURN_CUSTOMIZER_H_
+#define P2P_BASE_TEST_TURN_CUSTOMIZER_H_
+
+#include <memory>
+
+#include "api/turn_customizer.h"
+#include "rtc_base/gunit.h"
+
+namespace cricket {
+
+class TestTurnCustomizer : public webrtc::TurnCustomizer {
+ public:
+  TestTurnCustomizer() {}
+  virtual ~TestTurnCustomizer() {}
+
+  enum TestTurnAttributeExtensions {
+    // Test only attribute
+    STUN_ATTR_COUNTER = 0xFF02  // Number
+  };
+
+  void MaybeModifyOutgoingStunMessage(cricket::PortInterface* port,
+                                      cricket::StunMessage* message) override {
+    modify_cnt_++;
+
+    ASSERT_NE(0, message->type());
+    if (add_counter_) {
+      message->AddAttribute(std::make_unique<cricket::StunUInt32Attribute>(
+          STUN_ATTR_COUNTER, modify_cnt_));
+    }
+    return;
+  }
+
+  bool AllowChannelData(cricket::PortInterface* port,
+                        const void* data,
+                        size_t size,
+                        bool payload) override {
+    allow_channel_data_cnt_++;
+    return allow_channel_data_;
+  }
+
+  bool add_counter_ = false;
+  bool allow_channel_data_ = true;
+  unsigned int modify_cnt_ = 0;
+  unsigned int allow_channel_data_cnt_ = 0;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_TEST_TURN_CUSTOMIZER_H_
diff --git a/third_party/libwebrtc/p2p/base/test_turn_server.h b/third_party/libwebrtc/p2p/base/test_turn_server.h
new file mode 100644
index 0000000000..4070372db2
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/test_turn_server.h
@@ -0,0 +1,161 @@
+/*
+ *  Copyright 2012 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_TEST_TURN_SERVER_H_
+#define P2P_BASE_TEST_TURN_SERVER_H_
+
+#include <memory>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "absl/strings/string_view.h"
+#include "api/sequence_checker.h"
+#include "api/transport/stun.h"
+#include "p2p/base/basic_packet_socket_factory.h"
+#include "p2p/base/turn_server.h"
+#include "rtc_base/async_udp_socket.h"
+#include "rtc_base/ssl_adapter.h"
+#include "rtc_base/ssl_identity.h"
+#include "rtc_base/thread.h"
+
+namespace cricket {
+
+static const char kTestRealm[] = "example.org";
+static const char kTestSoftware[] = "TestTurnServer";
+
+class TestTurnRedirector : public TurnRedirectInterface {
+ public:
+  explicit TestTurnRedirector(const std::vector<rtc::SocketAddress>& addresses)
+      : alternate_server_addresses_(addresses),
+        iter_(alternate_server_addresses_.begin()) {}
+
+  virtual bool ShouldRedirect(const rtc::SocketAddress&,
+                              rtc::SocketAddress* out) {
+    if (!out || iter_ == alternate_server_addresses_.end()) {
+      return false;
+    }
+    *out = *iter_++;
+    return true;
+  }
+
+ private:
+  const std::vector<rtc::SocketAddress>& alternate_server_addresses_;
+  std::vector<rtc::SocketAddress>::const_iterator iter_;
+};
+
+class TestTurnServer : public TurnAuthInterface {
+ public:
+  TestTurnServer(rtc::Thread* thread,
+                 rtc::SocketFactory* socket_factory,
+                 const rtc::SocketAddress& int_addr,
+                 const rtc::SocketAddress& udp_ext_addr,
+                 ProtocolType int_protocol = PROTO_UDP,
+                 bool ignore_bad_cert = true,
+                 absl::string_view common_name = "test turn server")
+      : server_(thread), socket_factory_(socket_factory) {
+    AddInternalSocket(int_addr, int_protocol, ignore_bad_cert, common_name);
+    server_.SetExternalSocketFactory(
+        new rtc::BasicPacketSocketFactory(socket_factory), udp_ext_addr);
+    server_.set_realm(kTestRealm);
+    server_.set_software(kTestSoftware);
+    server_.set_auth_hook(this);
+  }
+
+  ~TestTurnServer() { RTC_DCHECK(thread_checker_.IsCurrent()); }
+
+  void set_enable_otu_nonce(bool enable) {
+    RTC_DCHECK(thread_checker_.IsCurrent());
+    server_.set_enable_otu_nonce(enable);
+  }
+
+  TurnServer* server() {
+    RTC_DCHECK(thread_checker_.IsCurrent());
+    return &server_;
+  }
+
+  void set_redirect_hook(TurnRedirectInterface* redirect_hook) {
+    RTC_DCHECK(thread_checker_.IsCurrent());
+    server_.set_redirect_hook(redirect_hook);
+  }
+
+  void set_enable_permission_checks(bool enable) {
+    RTC_DCHECK(thread_checker_.IsCurrent());
+    server_.set_enable_permission_checks(enable);
+  }
+
+  void AddInternalSocket(const rtc::SocketAddress& int_addr,
+                         ProtocolType proto,
+                         bool ignore_bad_cert = true,
+                         absl::string_view common_name = "test turn server") {
+    RTC_DCHECK(thread_checker_.IsCurrent());
+    if (proto == cricket::PROTO_UDP) {
+      server_.AddInternalSocket(
+          rtc::AsyncUDPSocket::Create(socket_factory_, int_addr), proto);
+    } else if (proto == cricket::PROTO_TCP || proto == cricket::PROTO_TLS) {
+      // For TCP we need to create a server socket which can listen for incoming
+      // new connections.
+      rtc::Socket* socket = socket_factory_->CreateSocket(AF_INET, SOCK_STREAM);
+      socket->Bind(int_addr);
+      socket->Listen(5);
+      if (proto == cricket::PROTO_TLS) {
+        // For TLS, wrap the TCP socket with an SSL adapter. The adapter must
+        // be configured with a self-signed certificate for testing.
+        // Additionally, the client will not present a valid certificate, so we
+        // must not fail when checking the peer's identity.
+        std::unique_ptr<rtc::SSLAdapterFactory> ssl_adapter_factory =
+            rtc::SSLAdapterFactory::Create();
+        ssl_adapter_factory->SetRole(rtc::SSL_SERVER);
+        ssl_adapter_factory->SetIdentity(
+            rtc::SSLIdentity::Create(common_name, rtc::KeyParams()));
+        ssl_adapter_factory->SetIgnoreBadCert(ignore_bad_cert);
+        server_.AddInternalServerSocket(socket, proto,
+                                        std::move(ssl_adapter_factory));
+      } else {
+        server_.AddInternalServerSocket(socket, proto);
+      }
+    } else {
+      RTC_DCHECK_NOTREACHED() << "Unknown protocol type: " << proto;
+    }
+  }
+
+  // Finds the first allocation in the server allocation map with a source
+  // ip and port matching the socket address provided.
+  TurnServerAllocation* FindAllocation(const rtc::SocketAddress& src) {
+    RTC_DCHECK(thread_checker_.IsCurrent());
+    const TurnServer::AllocationMap& map = server_.allocations();
+    for (TurnServer::AllocationMap::const_iterator it = map.begin();
+         it != map.end(); ++it) {
+      if (src == it->first.src()) {
+        return it->second.get();
+      }
+    }
+    return NULL;
+  }
+
+ private:
+  // For this test server, succeed if the password is the same as the username.
+  // Obviously, do not use this in a production environment.
+  virtual bool GetKey(absl::string_view username,
+                      absl::string_view realm,
+                      std::string* key) {
+    RTC_DCHECK(thread_checker_.IsCurrent());
+    return ComputeStunCredentialHash(std::string(username), std::string(realm),
+                                     std::string(username), key);
+  }
+
+  TurnServer server_;
+  rtc::SocketFactory* socket_factory_;
+  webrtc::SequenceChecker thread_checker_;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_TEST_TURN_SERVER_H_
diff --git a/third_party/libwebrtc/p2p/base/transport_description.cc b/third_party/libwebrtc/p2p/base/transport_description.cc
new file mode 100644
index 0000000000..f3b1fbb6ea
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/transport_description.cc
@@ -0,0 +1,196 @@
+/*
+ *  Copyright 2013 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/transport_description.h"
+
+#include "absl/strings/ascii.h"
+#include "absl/strings/match.h"
+#include "absl/strings/string_view.h"
+#include "p2p/base/p2p_constants.h"
+#include "rtc_base/arraysize.h"
+#include "rtc_base/logging.h"
+#include "rtc_base/strings/string_builder.h"
+
+using webrtc::RTCError;
+using webrtc::RTCErrorOr;
+using webrtc::RTCErrorType;
+
+namespace cricket {
+namespace {
+
+bool IsIceChar(char c) {
+  // Note: '-', '=', '#' and '_' are *not* valid ice-chars but temporarily
+  // permitted in order to allow external software to upgrade.
+  if (c == '-' || c == '=' || c == '#' || c == '_') {
+    RTC_LOG(LS_WARNING)
+        << "'-', '=', '#' and '-' are not valid ice-char and thus not "
+        << "permitted in ufrag or pwd. This is a protocol violation that "
+        << "is permitted to allow upgrading but will be rejected in "
+        << "the future. See https://crbug.com/1053756";
+    return true;
+  }
+  return absl::ascii_isalnum(c) || c == '+' || c == '/';
+}
+
+RTCError ValidateIceUfrag(absl::string_view raw_ufrag) {
+  if (!(ICE_UFRAG_MIN_LENGTH <= raw_ufrag.size() &&
+        raw_ufrag.size() <= ICE_UFRAG_MAX_LENGTH)) {
+    rtc::StringBuilder sb;
+    sb << "ICE ufrag must be between " << ICE_UFRAG_MIN_LENGTH << " and "
+       << ICE_UFRAG_MAX_LENGTH << " characters long.";
+    return RTCError(RTCErrorType::SYNTAX_ERROR, sb.Release());
+  }
+
+  if (!absl::c_all_of(raw_ufrag, IsIceChar)) {
+    return RTCError(
+        RTCErrorType::SYNTAX_ERROR,
+        "ICE ufrag must contain only alphanumeric characters, '+', and '/'.");
+  }
+
+  return RTCError::OK();
+}
+
+RTCError ValidateIcePwd(absl::string_view raw_pwd) {
+  if (!(ICE_PWD_MIN_LENGTH <= raw_pwd.size() &&
+        raw_pwd.size() <= ICE_PWD_MAX_LENGTH)) {
+    rtc::StringBuilder sb;
+    sb << "ICE pwd must be between " << ICE_PWD_MIN_LENGTH << " and "
+       << ICE_PWD_MAX_LENGTH << " characters long.";
+    return RTCError(RTCErrorType::SYNTAX_ERROR, sb.Release());
+  }
+
+  if (!absl::c_all_of(raw_pwd, IsIceChar)) {
+    return RTCError(
+        RTCErrorType::SYNTAX_ERROR,
+        "ICE pwd must contain only alphanumeric characters, '+', and '/'.");
+  }
+
+  return RTCError::OK();
+}
+
+}  // namespace
+
+RTCErrorOr<IceParameters> IceParameters::Parse(absl::string_view raw_ufrag,
+                                               absl::string_view raw_pwd) {
+  IceParameters parameters(std::string(raw_ufrag), std::string(raw_pwd),
+                           /* renomination= */ false);
+  auto result = parameters.Validate();
+  if (!result.ok()) {
+    return result;
+  }
+  return parameters;
+}
+
+RTCError IceParameters::Validate() const {
+  // For legacy protocols.
+  // TODO(zhihuang): Remove this once the legacy protocol is no longer
+  // supported.
+  if (ufrag.empty() && pwd.empty()) {
+    return RTCError::OK();
+  }
+
+  auto ufrag_result = ValidateIceUfrag(ufrag);
+  if (!ufrag_result.ok()) {
+    return ufrag_result;
+  }
+
+  auto pwd_result = ValidateIcePwd(pwd);
+  if (!pwd_result.ok()) {
+    return pwd_result;
+  }
+
+  return RTCError::OK();
+}
+
+absl::optional<ConnectionRole> StringToConnectionRole(
+    absl::string_view role_str) {
+  const char* const roles[] = {
+      CONNECTIONROLE_ACTIVE_STR, CONNECTIONROLE_PASSIVE_STR,
+      CONNECTIONROLE_ACTPASS_STR, CONNECTIONROLE_HOLDCONN_STR};
+
+  for (size_t i = 0; i < arraysize(roles); ++i) {
+    if (absl::EqualsIgnoreCase(roles[i], role_str)) {
+      return static_cast<ConnectionRole>(CONNECTIONROLE_ACTIVE + i);
+    }
+  }
+  return absl::nullopt;
+}
+
+bool ConnectionRoleToString(const ConnectionRole& role, std::string* role_str) {
+  switch (role) {
+    case cricket::CONNECTIONROLE_ACTIVE:
+      *role_str = cricket::CONNECTIONROLE_ACTIVE_STR;
+      break;
+    case cricket::CONNECTIONROLE_ACTPASS:
+      *role_str = cricket::CONNECTIONROLE_ACTPASS_STR;
+      break;
+    case cricket::CONNECTIONROLE_PASSIVE:
+      *role_str = cricket::CONNECTIONROLE_PASSIVE_STR;
+      break;
+    case cricket::CONNECTIONROLE_HOLDCONN:
+      *role_str = cricket::CONNECTIONROLE_HOLDCONN_STR;
+      break;
+    default:
+      return false;
+  }
+  return true;
+}
+
+TransportDescription::TransportDescription()
+    : ice_mode(ICEMODE_FULL), connection_role(CONNECTIONROLE_NONE) {}
+
+TransportDescription::TransportDescription(
+    const std::vector<std::string>& transport_options,
+    absl::string_view ice_ufrag,
+    absl::string_view ice_pwd,
+    IceMode ice_mode,
+    ConnectionRole role,
+    const rtc::SSLFingerprint* identity_fingerprint)
+    : transport_options(transport_options),
+      ice_ufrag(ice_ufrag),
+      ice_pwd(ice_pwd),
+      ice_mode(ice_mode),
+      connection_role(role),
+      identity_fingerprint(CopyFingerprint(identity_fingerprint)) {}
+
+TransportDescription::TransportDescription(absl::string_view ice_ufrag,
+                                           absl::string_view ice_pwd)
+    : ice_ufrag(ice_ufrag),
+      ice_pwd(ice_pwd),
+      ice_mode(ICEMODE_FULL),
+      connection_role(CONNECTIONROLE_NONE) {}
+
+TransportDescription::TransportDescription(const TransportDescription& from)
+    : transport_options(from.transport_options),
+      ice_ufrag(from.ice_ufrag),
+      ice_pwd(from.ice_pwd),
+      ice_mode(from.ice_mode),
+      connection_role(from.connection_role),
+      identity_fingerprint(CopyFingerprint(from.identity_fingerprint.get())) {}
+
+TransportDescription::~TransportDescription() = default;
+
+TransportDescription& TransportDescription::operator=(
+    const TransportDescription& from) {
+  // Self-assignment
+  if (this == &from)
+    return *this;
+
+  transport_options = from.transport_options;
+  ice_ufrag = from.ice_ufrag;
+  ice_pwd = from.ice_pwd;
+  ice_mode = from.ice_mode;
+  connection_role = from.connection_role;
+
+  identity_fingerprint.reset(CopyFingerprint(from.identity_fingerprint.get()));
+  return *this;
+}
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/transport_description.h b/third_party/libwebrtc/p2p/base/transport_description.h
new file mode 100644
index 0000000000..7d28ad52e9
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/transport_description.h
@@ -0,0 +1,154 @@
+/*
+ *  Copyright 2012 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_TRANSPORT_DESCRIPTION_H_
+#define P2P_BASE_TRANSPORT_DESCRIPTION_H_
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "absl/algorithm/container.h"
+#include "absl/strings/string_view.h"
+#include "absl/types/optional.h"
+#include "api/rtc_error.h"
+#include "p2p/base/p2p_constants.h"
+#include "rtc_base/ssl_fingerprint.h"
+#include "rtc_base/system/rtc_export.h"
+
+namespace cricket {
+
+// SEC_ENABLED and SEC_REQUIRED should only be used if the session
+// was negotiated over TLS, to protect the inline crypto material
+// exchange.
+// SEC_DISABLED: No crypto in outgoing offer, ignore any supplied crypto.
+// SEC_ENABLED:  Crypto in outgoing offer and answer (if supplied in offer).
+// SEC_REQUIRED: Crypto in outgoing offer and answer. Fail any offer with absent
+//               or unsupported crypto.
+// TODO(deadbeef): Remove this or rename it to something more appropriate, like
+// SdesPolicy.
+enum SecurePolicy { SEC_DISABLED, SEC_ENABLED, SEC_REQUIRED };
+
+// Whether our side of the call is driving the negotiation, or the other side.
+enum IceRole { ICEROLE_CONTROLLING = 0, ICEROLE_CONTROLLED, ICEROLE_UNKNOWN };
+
+// ICE RFC 5245 implementation type.
+enum IceMode {
+  ICEMODE_FULL,  // As defined in http://tools.ietf.org/html/rfc5245#section-4.1
+  ICEMODE_LITE   // As defined in http://tools.ietf.org/html/rfc5245#section-4.2
+};
+
+// RFC 4145 - http://tools.ietf.org/html/rfc4145#section-4
+// 'active':  The endpoint will initiate an outgoing connection.
+// 'passive': The endpoint will accept an incoming connection.
+// 'actpass': The endpoint is willing to accept an incoming
+//            connection or to initiate an outgoing connection.
+enum ConnectionRole {
+  CONNECTIONROLE_NONE = 0,
+  CONNECTIONROLE_ACTIVE,
+  CONNECTIONROLE_PASSIVE,
+  CONNECTIONROLE_ACTPASS,
+  CONNECTIONROLE_HOLDCONN,
+};
+
+struct IceParameters {
+  // Constructs an IceParameters from a user-provided ufrag/pwd combination.
+  // Returns a SyntaxError if the ufrag or pwd are malformed.
+  static RTC_EXPORT webrtc::RTCErrorOr<IceParameters> Parse(
+      absl::string_view raw_ufrag,
+      absl::string_view raw_pwd);
+
+  // TODO(honghaiz): Include ICE mode in this structure to match the ORTC
+  // struct:
+  // http://ortc.org/wp-content/uploads/2016/03/ortc.html#idl-def-RTCIceParameters
+  std::string ufrag;
+  std::string pwd;
+  bool renomination = false;
+  IceParameters() = default;
+  IceParameters(absl::string_view ice_ufrag,
+                absl::string_view ice_pwd,
+                bool ice_renomination)
+      : ufrag(ice_ufrag), pwd(ice_pwd), renomination(ice_renomination) {}
+
+  bool operator==(const IceParameters& other) const {
+    return ufrag == other.ufrag && pwd == other.pwd &&
+           renomination == other.renomination;
+  }
+  bool operator!=(const IceParameters& other) const {
+    return !(*this == other);
+  }
+
+  // Validate IceParameters, returns a SyntaxError if the ufrag or pwd are
+  // malformed.
+  webrtc::RTCError Validate() const;
+};
+
+extern const char CONNECTIONROLE_ACTIVE_STR[];
+extern const char CONNECTIONROLE_PASSIVE_STR[];
+extern const char CONNECTIONROLE_ACTPASS_STR[];
+extern const char CONNECTIONROLE_HOLDCONN_STR[];
+
+constexpr auto* ICE_OPTION_TRICKLE = "trickle";
+constexpr auto* ICE_OPTION_RENOMINATION = "renomination";
+
+absl::optional<ConnectionRole> StringToConnectionRole(
+    absl::string_view role_str);
+bool ConnectionRoleToString(const ConnectionRole& role, std::string* role_str);
+
+struct TransportDescription {
+  TransportDescription();
+  TransportDescription(const std::vector<std::string>& transport_options,
+                       absl::string_view ice_ufrag,
+                       absl::string_view ice_pwd,
+                       IceMode ice_mode,
+                       ConnectionRole role,
+                       const rtc::SSLFingerprint* identity_fingerprint);
+  TransportDescription(absl::string_view ice_ufrag, absl::string_view ice_pwd);
+  TransportDescription(const TransportDescription& from);
+  ~TransportDescription();
+
+  TransportDescription& operator=(const TransportDescription& from);
+
+  // TODO(deadbeef): Rename to HasIceOption, etc.
+  bool HasOption(absl::string_view option) const {
+    return absl::c_linear_search(transport_options, option);
+  }
+  void AddOption(absl::string_view option) {
+    transport_options.emplace_back(option);
+  }
+  bool secure() const { return identity_fingerprint != nullptr; }
+
+  IceParameters GetIceParameters() const {
+    return IceParameters(ice_ufrag, ice_pwd,
+                         HasOption(ICE_OPTION_RENOMINATION));
+  }
+
+  static rtc::SSLFingerprint* CopyFingerprint(const rtc::SSLFingerprint* from) {
+    if (!from)
+      return NULL;
+
+    return new rtc::SSLFingerprint(*from);
+  }
+
+  // These are actually ICE options (appearing in the ice-options attribute in
+  // SDP).
+  // TODO(deadbeef): Rename to ice_options.
+  std::vector<std::string> transport_options;
+  std::string ice_ufrag;
+  std::string ice_pwd;
+  IceMode ice_mode;
+  ConnectionRole connection_role;
+
+  std::unique_ptr<rtc::SSLFingerprint> identity_fingerprint;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_TRANSPORT_DESCRIPTION_H_
diff --git a/third_party/libwebrtc/p2p/base/transport_description_factory.cc b/third_party/libwebrtc/p2p/base/transport_description_factory.cc
new file mode 100644
index 0000000000..7eb21da166
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/transport_description_factory.cc
@@ -0,0 +1,151 @@
+/*
+ *  Copyright 2012 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/transport_description_factory.h"
+
+#include <stddef.h>
+
+#include <memory>
+#include <string>
+
+#include "p2p/base/transport_description.h"
+#include "rtc_base/logging.h"
+#include "rtc_base/ssl_fingerprint.h"
+
+namespace cricket {
+
+TransportDescriptionFactory::TransportDescriptionFactory(
+    const webrtc::FieldTrialsView& field_trials)
+    : secure_(SEC_DISABLED), field_trials_(field_trials) {}
+
+TransportDescriptionFactory::~TransportDescriptionFactory() = default;
+
+std::unique_ptr<TransportDescription> TransportDescriptionFactory::CreateOffer(
+    const TransportOptions& options,
+    const TransportDescription* current_description,
+    IceCredentialsIterator* ice_credentials) const {
+  auto desc = std::make_unique<TransportDescription>();
+
+  // Generate the ICE credentials if we don't already have them.
+  if (!current_description || options.ice_restart) {
+    IceParameters credentials = ice_credentials->GetIceCredentials();
+    desc->ice_ufrag = credentials.ufrag;
+    desc->ice_pwd = credentials.pwd;
+  } else {
+    desc->ice_ufrag = current_description->ice_ufrag;
+    desc->ice_pwd = current_description->ice_pwd;
+  }
+  desc->AddOption(ICE_OPTION_TRICKLE);
+  if (options.enable_ice_renomination) {
+    desc->AddOption(ICE_OPTION_RENOMINATION);
+  }
+
+  // If we are trying to establish a secure transport, add a fingerprint.
+  if (secure_ == SEC_ENABLED || secure_ == SEC_REQUIRED) {
+    // Fail if we can't create the fingerprint.
+    // If we are the initiator set role to "actpass".
+    if (!SetSecurityInfo(desc.get(), CONNECTIONROLE_ACTPASS)) {
+      return NULL;
+    }
+  }
+
+  return desc;
+}
+
+std::unique_ptr<TransportDescription> TransportDescriptionFactory::CreateAnswer(
+    const TransportDescription* offer,
+    const TransportOptions& options,
+    bool require_transport_attributes,
+    const TransportDescription* current_description,
+    IceCredentialsIterator* ice_credentials) const {
+  // TODO(juberti): Figure out why we get NULL offers, and fix this upstream.
+  if (!offer) {
+    RTC_LOG(LS_WARNING) << "Failed to create TransportDescription answer "
+                           "because offer is NULL";
+    return NULL;
+  }
+
+  auto desc = std::make_unique<TransportDescription>();
+  // Generate the ICE credentials if we don't already have them or ice is
+  // being restarted.
+  if (!current_description || options.ice_restart) {
+    IceParameters credentials = ice_credentials->GetIceCredentials();
+    desc->ice_ufrag = credentials.ufrag;
+    desc->ice_pwd = credentials.pwd;
+  } else {
+    desc->ice_ufrag = current_description->ice_ufrag;
+    desc->ice_pwd = current_description->ice_pwd;
+  }
+  desc->AddOption(ICE_OPTION_TRICKLE);
+  if (options.enable_ice_renomination) {
+    desc->AddOption(ICE_OPTION_RENOMINATION);
+  }
+
+  // Negotiate security params.
+  if (offer && offer->identity_fingerprint.get()) {
+    // The offer supports DTLS, so answer with DTLS, as long as we support it.
+    if (secure_ == SEC_ENABLED || secure_ == SEC_REQUIRED) {
+      ConnectionRole role = CONNECTIONROLE_NONE;
+      // If the offer does not constrain the role, go with preference.
+      if (offer->connection_role == CONNECTIONROLE_ACTPASS) {
+        role = (options.prefer_passive_role) ? CONNECTIONROLE_PASSIVE
+                                             : CONNECTIONROLE_ACTIVE;
+      } else if (offer->connection_role == CONNECTIONROLE_ACTIVE) {
+        role = CONNECTIONROLE_PASSIVE;
+      } else if (offer->connection_role == CONNECTIONROLE_PASSIVE) {
+        role = CONNECTIONROLE_ACTIVE;
+      } else if (offer->connection_role == CONNECTIONROLE_NONE) {
+        // This case may be reached if a=setup is not present in the SDP.
+        RTC_LOG(LS_WARNING) << "Remote offer connection role is NONE, which is "
+                               "a protocol violation";
+        role = (options.prefer_passive_role) ? CONNECTIONROLE_PASSIVE
+                                             : CONNECTIONROLE_ACTIVE;
+      } else {
+        RTC_LOG(LS_ERROR) << "Remote offer connection role is " << role
+                          << " which is a protocol violation";
+        RTC_DCHECK_NOTREACHED();
+      }
+
+      if (!SetSecurityInfo(desc.get(), role)) {
+        return NULL;
+      }
+    }
+  } else if (require_transport_attributes && secure_ == SEC_REQUIRED) {
+    // We require DTLS, but the other side didn't offer it. Fail.
+    RTC_LOG(LS_WARNING) << "Failed to create TransportDescription answer "
+                           "because of incompatible security settings";
+    return NULL;
+  }
+
+  return desc;
+}
+
+bool TransportDescriptionFactory::SetSecurityInfo(TransportDescription* desc,
+                                                  ConnectionRole role) const {
+  if (!certificate_) {
+    RTC_LOG(LS_ERROR) << "Cannot create identity digest with no certificate";
+    return false;
+  }
+
+  // This digest algorithm is used to produce the a=fingerprint lines in SDP.
+  // RFC 4572 Section 5 requires that those lines use the same hash function as
+  // the certificate's signature, which is what CreateFromCertificate does.
+  desc->identity_fingerprint =
+      rtc::SSLFingerprint::CreateFromCertificate(*certificate_);
+  if (!desc->identity_fingerprint) {
+    return false;
+  }
+
+  // Assign security role.
+  desc->connection_role = role;
+  return true;
+}
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/transport_description_factory.h b/third_party/libwebrtc/p2p/base/transport_description_factory.h
new file mode 100644
index 0000000000..11352f88b4
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/transport_description_factory.h
@@ -0,0 +1,91 @@
+/*
+ *  Copyright 2012 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_TRANSPORT_DESCRIPTION_FACTORY_H_
+#define P2P_BASE_TRANSPORT_DESCRIPTION_FACTORY_H_
+
+#include <memory>
+#include <utility>
+
+#include "api/field_trials_view.h"
+#include "p2p/base/ice_credentials_iterator.h"
+#include "p2p/base/transport_description.h"
+#include "rtc_base/rtc_certificate.h"
+
+namespace rtc {
+class SSLIdentity;
+}
+
+namespace cricket {
+
+struct TransportOptions {
+  bool ice_restart = false;
+  bool prefer_passive_role = false;
+  // If true, ICE renomination is supported and will be used if it is also
+  // supported by the remote side.
+  bool enable_ice_renomination = false;
+};
+
+// Creates transport descriptions according to the supplied configuration.
+// When creating answers, performs the appropriate negotiation
+// of the various fields to determine the proper result.
+class TransportDescriptionFactory {
+ public:
+  // Default ctor; use methods below to set configuration.
+  explicit TransportDescriptionFactory(
+      const webrtc::FieldTrialsView& field_trials);
+  ~TransportDescriptionFactory();
+
+  SecurePolicy secure() const { return secure_; }
+  // The certificate to use when setting up DTLS.
+  const rtc::scoped_refptr<rtc::RTCCertificate>& certificate() const {
+    return certificate_;
+  }
+
+  // Specifies the transport security policy to use.
+  void set_secure(SecurePolicy s) { secure_ = s; }
+  // Specifies the certificate to use (only used when secure != SEC_DISABLED).
+  void set_certificate(rtc::scoped_refptr<rtc::RTCCertificate> certificate) {
+    certificate_ = std::move(certificate);
+  }
+
+  // Creates a transport description suitable for use in an offer.
+  std::unique_ptr<TransportDescription> CreateOffer(
+      const TransportOptions& options,
+      const TransportDescription* current_description,
+      IceCredentialsIterator* ice_credentials) const;
+  // Create a transport description that is a response to an offer.
+  //
+  // If `require_transport_attributes` is true, then TRANSPORT category
+  // attributes are expected to be present in `offer`, as defined by
+  // sdp-mux-attributes, and null will be returned otherwise. It's expected
+  // that this will be set to false for an m= section that's in a BUNDLE group
+  // but isn't the first m= section in the group.
+  std::unique_ptr<TransportDescription> CreateAnswer(
+      const TransportDescription* offer,
+      const TransportOptions& options,
+      bool require_transport_attributes,
+      const TransportDescription* current_description,
+      IceCredentialsIterator* ice_credentials) const;
+
+  const webrtc::FieldTrialsView& trials() const { return field_trials_; }
+
+ private:
+  bool SetSecurityInfo(TransportDescription* description,
+                       ConnectionRole role) const;
+
+  SecurePolicy secure_;
+  rtc::scoped_refptr<rtc::RTCCertificate> certificate_;
+  const webrtc::FieldTrialsView& field_trials_;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_TRANSPORT_DESCRIPTION_FACTORY_H_
diff --git a/third_party/libwebrtc/p2p/base/transport_description_factory_unittest.cc b/third_party/libwebrtc/p2p/base/transport_description_factory_unittest.cc
new file mode 100644
index 0000000000..0da5b7c294
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/transport_description_factory_unittest.cc
@@ -0,0 +1,406 @@
+/*
+ *  Copyright 2012 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/transport_description_factory.h"
+
+#include <stddef.h>
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "absl/strings/string_view.h"
+#include "p2p/base/p2p_constants.h"
+#include "p2p/base/transport_description.h"
+#include "rtc_base/copy_on_write_buffer.h"
+#include "rtc_base/fake_ssl_identity.h"
+#include "rtc_base/ssl_certificate.h"
+#include "rtc_base/ssl_fingerprint.h"
+#include "rtc_base/ssl_identity.h"
+#include "test/gmock.h"
+#include "test/gtest.h"
+#include "test/scoped_key_value_config.h"
+
+using cricket::TransportDescription;
+using cricket::TransportDescriptionFactory;
+using cricket::TransportOptions;
+using ::testing::Contains;
+using ::testing::Not;
+
+class TransportDescriptionFactoryTest : public ::testing::Test {
+ public:
+  TransportDescriptionFactoryTest()
+      : ice_credentials_({}),
+        f1_(field_trials_),
+        f2_(field_trials_),
+        cert1_(rtc::RTCCertificate::Create(std::unique_ptr<rtc::SSLIdentity>(
+            new rtc::FakeSSLIdentity("User1")))),
+        cert2_(rtc::RTCCertificate::Create(std::unique_ptr<rtc::SSLIdentity>(
+            new rtc::FakeSSLIdentity("User2")))) {}
+
+  void CheckDesc(const TransportDescription* desc,
+                 absl::string_view opt,
+                 absl::string_view ice_ufrag,
+                 absl::string_view ice_pwd,
+                 absl::string_view dtls_alg) {
+    ASSERT_TRUE(desc != NULL);
+    EXPECT_EQ(!opt.empty(), desc->HasOption(opt));
+    if (ice_ufrag.empty() && ice_pwd.empty()) {
+      EXPECT_EQ(static_cast<size_t>(cricket::ICE_UFRAG_LENGTH),
+                desc->ice_ufrag.size());
+      EXPECT_EQ(static_cast<size_t>(cricket::ICE_PWD_LENGTH),
+                desc->ice_pwd.size());
+    } else {
+      EXPECT_EQ(ice_ufrag, desc->ice_ufrag);
+      EXPECT_EQ(ice_pwd, desc->ice_pwd);
+    }
+    if (dtls_alg.empty()) {
+      EXPECT_TRUE(desc->identity_fingerprint.get() == NULL);
+    } else {
+      ASSERT_TRUE(desc->identity_fingerprint.get() != NULL);
+      EXPECT_EQ(desc->identity_fingerprint->algorithm, dtls_alg);
+      EXPECT_GT(desc->identity_fingerprint->digest.size(), 0U);
+    }
+  }
+
+  // This test ice restart by doing two offer answer exchanges. On the second
+  // exchange ice is restarted. The test verifies that the ufrag and password
+  // in the offer and answer is changed.
+  // If `dtls` is true, the test verifies that the finger print is not changed.
+  void TestIceRestart(bool dtls) {
+    SetDtls(dtls);
+    cricket::TransportOptions options;
+    // The initial offer / answer exchange.
+    std::unique_ptr<TransportDescription> offer =
+        f1_.CreateOffer(options, NULL, &ice_credentials_);
+    std::unique_ptr<TransportDescription> answer =
+        f2_.CreateAnswer(offer.get(), options, true, NULL, &ice_credentials_);
+
+    // Create an updated offer where we restart ice.
+    options.ice_restart = true;
+    std::unique_ptr<TransportDescription> restart_offer =
+        f1_.CreateOffer(options, offer.get(), &ice_credentials_);
+
+    VerifyUfragAndPasswordChanged(dtls, offer.get(), restart_offer.get());
+
+    // Create a new answer. The transport ufrag and password is changed since
+    // |options.ice_restart == true|
+    std::unique_ptr<TransportDescription> restart_answer = f2_.CreateAnswer(
+        restart_offer.get(), options, true, answer.get(), &ice_credentials_);
+    ASSERT_TRUE(restart_answer.get() != NULL);
+
+    VerifyUfragAndPasswordChanged(dtls, answer.get(), restart_answer.get());
+  }
+
+  void VerifyUfragAndPasswordChanged(bool dtls,
+                                     const TransportDescription* org_desc,
+                                     const TransportDescription* restart_desc) {
+    EXPECT_NE(org_desc->ice_pwd, restart_desc->ice_pwd);
+    EXPECT_NE(org_desc->ice_ufrag, restart_desc->ice_ufrag);
+    EXPECT_EQ(static_cast<size_t>(cricket::ICE_UFRAG_LENGTH),
+              restart_desc->ice_ufrag.size());
+    EXPECT_EQ(static_cast<size_t>(cricket::ICE_PWD_LENGTH),
+              restart_desc->ice_pwd.size());
+    // If DTLS is enabled, make sure the finger print is unchanged.
+    if (dtls) {
+      EXPECT_FALSE(
+          org_desc->identity_fingerprint->GetRfc4572Fingerprint().empty());
+      EXPECT_EQ(org_desc->identity_fingerprint->GetRfc4572Fingerprint(),
+                restart_desc->identity_fingerprint->GetRfc4572Fingerprint());
+    }
+  }
+
+  void TestIceRenomination(bool dtls) {
+    SetDtls(dtls);
+
+    cricket::TransportOptions options;
+    // The initial offer / answer exchange.
+    std::unique_ptr<TransportDescription> offer =
+        f1_.CreateOffer(options, nullptr, &ice_credentials_);
+    ASSERT_TRUE(offer);
+    EXPECT_THAT(offer->transport_options, Not(Contains("renomination")));
+
+    std::unique_ptr<TransportDescription> answer = f2_.CreateAnswer(
+        offer.get(), options, true, nullptr, &ice_credentials_);
+    ASSERT_TRUE(answer);
+    EXPECT_THAT(answer->transport_options, Not(Contains("renomination")));
+
+    options.enable_ice_renomination = true;
+    std::unique_ptr<TransportDescription> renomination_offer =
+        f1_.CreateOffer(options, offer.get(), &ice_credentials_);
+    ASSERT_TRUE(renomination_offer);
+    EXPECT_THAT(renomination_offer->transport_options,
+                Contains("renomination"));
+
+    std::unique_ptr<TransportDescription> renomination_answer =
+        f2_.CreateAnswer(renomination_offer.get(), options, true, answer.get(),
+                         &ice_credentials_);
+    ASSERT_TRUE(renomination_answer);
+    EXPECT_THAT(renomination_answer->transport_options,
+                Contains("renomination"));
+  }
+
+ protected:
+  void SetDtls(bool dtls) {
+    if (dtls) {
+      f1_.set_secure(cricket::SEC_ENABLED);
+      f2_.set_secure(cricket::SEC_ENABLED);
+      f1_.set_certificate(cert1_);
+      f2_.set_certificate(cert2_);
+    } else {
+      f1_.set_secure(cricket::SEC_DISABLED);
+      f2_.set_secure(cricket::SEC_DISABLED);
+    }
+  }
+
+  webrtc::test::ScopedKeyValueConfig field_trials_;
+  cricket::IceCredentialsIterator ice_credentials_;
+  TransportDescriptionFactory f1_;
+  TransportDescriptionFactory f2_;
+
+  rtc::scoped_refptr<rtc::RTCCertificate> cert1_;
+  rtc::scoped_refptr<rtc::RTCCertificate> cert2_;
+};
+
+TEST_F(TransportDescriptionFactoryTest, TestOfferDefault) {
+  std::unique_ptr<TransportDescription> desc =
+      f1_.CreateOffer(TransportOptions(), NULL, &ice_credentials_);
+  CheckDesc(desc.get(), "", "", "", "");
+}
+
+TEST_F(TransportDescriptionFactoryTest, TestOfferDtls) {
+  f1_.set_secure(cricket::SEC_ENABLED);
+  f1_.set_certificate(cert1_);
+  std::string digest_alg;
+  ASSERT_TRUE(
+      cert1_->GetSSLCertificate().GetSignatureDigestAlgorithm(&digest_alg));
+  std::unique_ptr<TransportDescription> desc =
+      f1_.CreateOffer(TransportOptions(), NULL, &ice_credentials_);
+  CheckDesc(desc.get(), "", "", "", digest_alg);
+  // Ensure it also works with SEC_REQUIRED.
+  f1_.set_secure(cricket::SEC_REQUIRED);
+  desc = f1_.CreateOffer(TransportOptions(), NULL, &ice_credentials_);
+  CheckDesc(desc.get(), "", "", "", digest_alg);
+}
+
+// Test generating an offer with DTLS fails with no identity.
+TEST_F(TransportDescriptionFactoryTest, TestOfferDtlsWithNoIdentity) {
+  f1_.set_secure(cricket::SEC_ENABLED);
+  std::unique_ptr<TransportDescription> desc =
+      f1_.CreateOffer(TransportOptions(), NULL, &ice_credentials_);
+  ASSERT_TRUE(desc.get() == NULL);
+}
+
+// Test updating an offer with DTLS to pick ICE.
+// The ICE credentials should stay the same in the new offer.
+TEST_F(TransportDescriptionFactoryTest, TestOfferDtlsReofferDtls) {
+  f1_.set_secure(cricket::SEC_ENABLED);
+  f1_.set_certificate(cert1_);
+  std::string digest_alg;
+  ASSERT_TRUE(
+      cert1_->GetSSLCertificate().GetSignatureDigestAlgorithm(&digest_alg));
+  std::unique_ptr<TransportDescription> old_desc =
+      f1_.CreateOffer(TransportOptions(), NULL, &ice_credentials_);
+  ASSERT_TRUE(old_desc.get() != NULL);
+  std::unique_ptr<TransportDescription> desc =
+      f1_.CreateOffer(TransportOptions(), old_desc.get(), &ice_credentials_);
+  CheckDesc(desc.get(), "", old_desc->ice_ufrag, old_desc->ice_pwd, digest_alg);
+}
+
+TEST_F(TransportDescriptionFactoryTest, TestAnswerDefault) {
+  std::unique_ptr<TransportDescription> offer =
+      f1_.CreateOffer(TransportOptions(), NULL, &ice_credentials_);
+  ASSERT_TRUE(offer.get() != NULL);
+  std::unique_ptr<TransportDescription> desc = f2_.CreateAnswer(
+      offer.get(), TransportOptions(), true, NULL, &ice_credentials_);
+  CheckDesc(desc.get(), "", "", "", "");
+  desc = f2_.CreateAnswer(offer.get(), TransportOptions(), true, NULL,
+                          &ice_credentials_);
+  CheckDesc(desc.get(), "", "", "", "");
+}
+
+// Test that we can update an answer properly; ICE credentials shouldn't change.
+TEST_F(TransportDescriptionFactoryTest, TestReanswer) {
+  std::unique_ptr<TransportDescription> offer =
+      f1_.CreateOffer(TransportOptions(), NULL, &ice_credentials_);
+  ASSERT_TRUE(offer.get() != NULL);
+  std::unique_ptr<TransportDescription> old_desc = f2_.CreateAnswer(
+      offer.get(), TransportOptions(), true, NULL, &ice_credentials_);
+  ASSERT_TRUE(old_desc.get() != NULL);
+  std::unique_ptr<TransportDescription> desc = f2_.CreateAnswer(
+      offer.get(), TransportOptions(), true, old_desc.get(), &ice_credentials_);
+  ASSERT_TRUE(desc.get() != NULL);
+  CheckDesc(desc.get(), "", old_desc->ice_ufrag, old_desc->ice_pwd, "");
+}
+
+// Test that we handle answering an offer with DTLS with no DTLS.
+TEST_F(TransportDescriptionFactoryTest, TestAnswerDtlsToNoDtls) {
+  f1_.set_secure(cricket::SEC_ENABLED);
+  f1_.set_certificate(cert1_);
+  std::unique_ptr<TransportDescription> offer =
+      f1_.CreateOffer(TransportOptions(), NULL, &ice_credentials_);
+  ASSERT_TRUE(offer.get() != NULL);
+  std::unique_ptr<TransportDescription> desc = f2_.CreateAnswer(
+      offer.get(), TransportOptions(), true, NULL, &ice_credentials_);
+  CheckDesc(desc.get(), "", "", "", "");
+}
+
+// Test that we handle answering an offer without DTLS if we have DTLS enabled,
+// but fail if we require DTLS.
+TEST_F(TransportDescriptionFactoryTest, TestAnswerNoDtlsToDtls) {
+  f2_.set_secure(cricket::SEC_ENABLED);
+  f2_.set_certificate(cert2_);
+  std::unique_ptr<TransportDescription> offer =
+      f1_.CreateOffer(TransportOptions(), NULL, &ice_credentials_);
+  ASSERT_TRUE(offer.get() != NULL);
+  std::unique_ptr<TransportDescription> desc = f2_.CreateAnswer(
+      offer.get(), TransportOptions(), true, NULL, &ice_credentials_);
+  CheckDesc(desc.get(), "", "", "", "");
+  f2_.set_secure(cricket::SEC_REQUIRED);
+  desc = f2_.CreateAnswer(offer.get(), TransportOptions(), true, NULL,
+                          &ice_credentials_);
+  ASSERT_TRUE(desc.get() == NULL);
+}
+
+// Test that we handle answering an DTLS offer with DTLS, both if we have
+// DTLS enabled and required.
+TEST_F(TransportDescriptionFactoryTest, TestAnswerDtlsToDtls) {
+  f1_.set_secure(cricket::SEC_ENABLED);
+  f1_.set_certificate(cert1_);
+
+  f2_.set_secure(cricket::SEC_ENABLED);
+  f2_.set_certificate(cert2_);
+  // f2_ produces the answer that is being checked in this test, so the
+  // answer must contain fingerprint lines with cert2_'s digest algorithm.
+  std::string digest_alg2;
+  ASSERT_TRUE(
+      cert2_->GetSSLCertificate().GetSignatureDigestAlgorithm(&digest_alg2));
+
+  std::unique_ptr<TransportDescription> offer =
+      f1_.CreateOffer(TransportOptions(), NULL, &ice_credentials_);
+  ASSERT_TRUE(offer.get() != NULL);
+  std::unique_ptr<TransportDescription> desc = f2_.CreateAnswer(
+      offer.get(), TransportOptions(), true, NULL, &ice_credentials_);
+  CheckDesc(desc.get(), "", "", "", digest_alg2);
+  f2_.set_secure(cricket::SEC_REQUIRED);
+  desc = f2_.CreateAnswer(offer.get(), TransportOptions(), true, NULL,
+                          &ice_credentials_);
+  CheckDesc(desc.get(), "", "", "", digest_alg2);
+}
+
+// Test that ice ufrag and password is changed in an updated offer and answer
+// if `TransportDescriptionOptions::ice_restart` is true.
+TEST_F(TransportDescriptionFactoryTest, TestIceRestart) {
+  TestIceRestart(false);
+}
+
+// Test that ice ufrag and password is changed in an updated offer and answer
+// if `TransportDescriptionOptions::ice_restart` is true and DTLS is enabled.
+TEST_F(TransportDescriptionFactoryTest, TestIceRestartWithDtls) {
+  TestIceRestart(true);
+}
+
+// Test that ice renomination is set in an updated offer and answer
+// if `TransportDescriptionOptions::enable_ice_renomination` is true.
+TEST_F(TransportDescriptionFactoryTest, TestIceRenomination) {
+  TestIceRenomination(false);
+}
+
+// Test that ice renomination is set in an updated offer and answer
+// if `TransportDescriptionOptions::enable_ice_renomination` is true and DTLS
+// is enabled.
+TEST_F(TransportDescriptionFactoryTest, TestIceRenominationWithDtls) {
+  TestIceRenomination(true);
+}
+
+// Test that offers and answers have ice-option:trickle.
+TEST_F(TransportDescriptionFactoryTest, AddsTrickleIceOption) {
+  cricket::TransportOptions options;
+  std::unique_ptr<TransportDescription> offer =
+      f1_.CreateOffer(options, nullptr, &ice_credentials_);
+  EXPECT_TRUE(offer->HasOption("trickle"));
+  std::unique_ptr<TransportDescription> answer =
+      f2_.CreateAnswer(offer.get(), options, true, nullptr, &ice_credentials_);
+  EXPECT_TRUE(answer->HasOption("trickle"));
+}
+
+// Test CreateOffer with IceCredentialsIterator.
+TEST_F(TransportDescriptionFactoryTest, CreateOfferIceCredentialsIterator) {
+  std::vector<cricket::IceParameters> credentials = {
+      cricket::IceParameters("kalle", "anka", false)};
+  cricket::IceCredentialsIterator credentialsIterator(credentials);
+  cricket::TransportOptions options;
+  std::unique_ptr<TransportDescription> offer =
+      f1_.CreateOffer(options, nullptr, &credentialsIterator);
+  EXPECT_EQ(offer->GetIceParameters().ufrag, credentials[0].ufrag);
+  EXPECT_EQ(offer->GetIceParameters().pwd, credentials[0].pwd);
+}
+
+// Test CreateAnswer with IceCredentialsIterator.
+TEST_F(TransportDescriptionFactoryTest, CreateAnswerIceCredentialsIterator) {
+  cricket::TransportOptions options;
+  std::unique_ptr<TransportDescription> offer =
+      f1_.CreateOffer(options, nullptr, &ice_credentials_);
+
+  std::vector<cricket::IceParameters> credentials = {
+      cricket::IceParameters("kalle", "anka", false)};
+  cricket::IceCredentialsIterator credentialsIterator(credentials);
+  std::unique_ptr<TransportDescription> answer = f1_.CreateAnswer(
+      offer.get(), options, false, nullptr, &credentialsIterator);
+  EXPECT_EQ(answer->GetIceParameters().ufrag, credentials[0].ufrag);
+  EXPECT_EQ(answer->GetIceParameters().pwd, credentials[0].pwd);
+}
+
+TEST_F(TransportDescriptionFactoryTest, CreateAnswerToDtlsActpassOffer) {
+  f1_.set_secure(cricket::SEC_ENABLED);
+  f1_.set_certificate(cert1_);
+
+  f2_.set_secure(cricket::SEC_ENABLED);
+  f2_.set_certificate(cert2_);
+  cricket::TransportOptions options;
+  std::unique_ptr<TransportDescription> offer =
+      f1_.CreateOffer(options, nullptr, &ice_credentials_);
+
+  std::unique_ptr<TransportDescription> answer =
+      f2_.CreateAnswer(offer.get(), options, false, nullptr, &ice_credentials_);
+  EXPECT_EQ(answer->connection_role, cricket::CONNECTIONROLE_ACTIVE);
+}
+
+TEST_F(TransportDescriptionFactoryTest, CreateAnswerToDtlsActiveOffer) {
+  f1_.set_secure(cricket::SEC_ENABLED);
+  f1_.set_certificate(cert1_);
+
+  f2_.set_secure(cricket::SEC_ENABLED);
+  f2_.set_certificate(cert2_);
+  cricket::TransportOptions options;
+  std::unique_ptr<TransportDescription> offer =
+      f1_.CreateOffer(options, nullptr, &ice_credentials_);
+  offer->connection_role = cricket::CONNECTIONROLE_ACTIVE;
+
+  std::unique_ptr<TransportDescription> answer =
+      f2_.CreateAnswer(offer.get(), options, false, nullptr, &ice_credentials_);
+  EXPECT_EQ(answer->connection_role, cricket::CONNECTIONROLE_PASSIVE);
+}
+
+TEST_F(TransportDescriptionFactoryTest, CreateAnswerToDtlsPassiveOffer) {
+  f1_.set_secure(cricket::SEC_ENABLED);
+  f1_.set_certificate(cert1_);
+
+  f2_.set_secure(cricket::SEC_ENABLED);
+  f2_.set_certificate(cert2_);
+  cricket::TransportOptions options;
+  std::unique_ptr<TransportDescription> offer =
+      f1_.CreateOffer(options, nullptr, &ice_credentials_);
+  offer->connection_role = cricket::CONNECTIONROLE_PASSIVE;
+
+  std::unique_ptr<TransportDescription> answer =
+      f2_.CreateAnswer(offer.get(), options, false, nullptr, &ice_credentials_);
+  EXPECT_EQ(answer->connection_role, cricket::CONNECTIONROLE_ACTIVE);
+}
diff --git a/third_party/libwebrtc/p2p/base/transport_description_unittest.cc b/third_party/libwebrtc/p2p/base/transport_description_unittest.cc
new file mode 100644
index 0000000000..41d7336ff6
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/transport_description_unittest.cc
@@ -0,0 +1,58 @@
+/*
+ *  Copyright 2020 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/transport_description.h"
+#include "test/gtest.h"
+
+using webrtc::RTCErrorType;
+
+namespace cricket {
+
+TEST(IceParameters, SuccessfulParse) {
+  auto result = IceParameters::Parse("ufrag", "22+characters+long+pwd");
+  ASSERT_TRUE(result.ok());
+  IceParameters parameters = result.MoveValue();
+  EXPECT_EQ("ufrag", parameters.ufrag);
+  EXPECT_EQ("22+characters+long+pwd", parameters.pwd);
+}
+
+TEST(IceParameters, FailedParseShortUfrag) {
+  auto result = IceParameters::Parse("3ch", "22+characters+long+pwd");
+  EXPECT_EQ(RTCErrorType::SYNTAX_ERROR, result.error().type());
+}
+
+TEST(IceParameters, FailedParseLongUfrag) {
+  std::string ufrag(257, '+');
+  auto result = IceParameters::Parse(ufrag, "22+characters+long+pwd");
+  EXPECT_EQ(RTCErrorType::SYNTAX_ERROR, result.error().type());
+}
+
+TEST(IceParameters, FailedParseShortPwd) {
+  auto result = IceParameters::Parse("ufrag", "21+character+long+pwd");
+  EXPECT_EQ(RTCErrorType::SYNTAX_ERROR, result.error().type());
+}
+
+TEST(IceParameters, FailedParseLongPwd) {
+  std::string pwd(257, '+');
+  auto result = IceParameters::Parse("ufrag", pwd);
+  EXPECT_EQ(RTCErrorType::SYNTAX_ERROR, result.error().type());
+}
+
+TEST(IceParameters, FailedParseBadUfragChar) {
+  auto result = IceParameters::Parse("ufrag\r\n", "22+characters+long+pwd");
+  EXPECT_EQ(RTCErrorType::SYNTAX_ERROR, result.error().type());
+}
+
+TEST(IceParameters, FailedParseBadPwdChar) {
+  auto result = IceParameters::Parse("ufrag", "22+characters+long+pwd\r\n");
+  EXPECT_EQ(RTCErrorType::SYNTAX_ERROR, result.error().type());
+}
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/transport_info.h b/third_party/libwebrtc/p2p/base/transport_info.h
new file mode 100644
index 0000000000..1f60b64012
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/transport_info.h
@@ -0,0 +1,42 @@
+/*
+ *  Copyright 2012 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_TRANSPORT_INFO_H_
+#define P2P_BASE_TRANSPORT_INFO_H_
+
+#include <string>
+#include <vector>
+
+#include "api/candidate.h"
+#include "p2p/base/p2p_constants.h"
+#include "p2p/base/transport_description.h"
+#include "rtc_base/helpers.h"
+
+namespace cricket {
+
+// A TransportInfo is NOT a transport-info message.  It is comparable
+// to a "ContentInfo". A transport-infos message is basically just a
+// collection of TransportInfos.
+struct TransportInfo {
+  TransportInfo() {}
+
+  TransportInfo(const std::string& content_name,
+                const TransportDescription& description)
+      : content_name(content_name), description(description) {}
+
+  std::string content_name;
+  TransportDescription description;
+};
+
+typedef std::vector<TransportInfo> TransportInfos;
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_TRANSPORT_INFO_H_
diff --git a/third_party/libwebrtc/p2p/base/turn_port.cc b/third_party/libwebrtc/p2p/base/turn_port.cc
new file mode 100644
index 0000000000..089910e072
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/turn_port.cc
@@ -0,0 +1,1900 @@
+/*
+ *  Copyright 2012 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/turn_port.h"
+
+#include <functional>
+#include <memory>
+#include <utility>
+#include <vector>
+
+#include "absl/algorithm/container.h"
+#include "absl/strings/match.h"
+#include "absl/strings/string_view.h"
+#include "absl/types/optional.h"
+#include "api/task_queue/pending_task_safety_flag.h"
+#include "api/transport/stun.h"
+#include "p2p/base/connection.h"
+#include "p2p/base/p2p_constants.h"
+#include "rtc_base/async_packet_socket.h"
+#include "rtc_base/byte_order.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/experiments/field_trial_parser.h"
+#include "rtc_base/logging.h"
+#include "rtc_base/net_helpers.h"
+#include "rtc_base/socket_address.h"
+#include "rtc_base/strings/string_builder.h"
+
+namespace cricket {
+
+namespace {
+
+bool ResolveTurnHostnameForFamily(const webrtc::FieldTrialsView& field_trials) {
+  // Bug fix for TURN hostname resolution on IPv6.
+  // Field trial key reserved in bugs.webrtc.org/14334
+  static constexpr char field_trial_name[] =
+      "WebRTC-IPv6NetworkResolutionFixes";
+  if (!field_trials.IsEnabled(field_trial_name)) {
+    return false;
+  }
+
+  webrtc::FieldTrialParameter<bool> resolve_turn_hostname_for_family(
+      "ResolveTurnHostnameForFamily", /*default_value=*/false);
+  webrtc::ParseFieldTrial({&resolve_turn_hostname_for_family},
+                          field_trials.Lookup(field_trial_name));
+  return resolve_turn_hostname_for_family;
+}
+
+}  // namespace
+
+using ::webrtc::SafeTask;
+using ::webrtc::TaskQueueBase;
+using ::webrtc::TimeDelta;
+
+// TODO(juberti): Move to stun.h when relay messages have been renamed.
+static const int TURN_ALLOCATE_REQUEST = STUN_ALLOCATE_REQUEST;
+
+// Attributes in comprehension-optional range,
+// ignored by TURN server that doesn't know about them.
+// https://tools.ietf.org/html/rfc5389#section-18.2
+const int STUN_ATTR_TURN_LOGGING_ID = 0xff05;
+
+// TODO(juberti): Extract to turnmessage.h
+static const int TURN_DEFAULT_PORT = 3478;
+static const int TURN_CHANNEL_NUMBER_START = 0x4000;
+
+static constexpr TimeDelta kTurnPermissionTimeout = TimeDelta::Minutes(5);
+
+static const size_t TURN_CHANNEL_HEADER_SIZE = 4U;
+
+// Retry at most twice (i.e. three different ALLOCATE requests) on
+// STUN_ERROR_ALLOCATION_MISMATCH error per rfc5766.
+static const size_t MAX_ALLOCATE_MISMATCH_RETRIES = 2;
+
+static const int TURN_SUCCESS_RESULT_CODE = 0;
+
+inline bool IsTurnChannelData(uint16_t msg_type) {
+  return ((msg_type & 0xC000) == 0x4000);  // MSB are 0b01
+}
+
+static int GetRelayPreference(cricket::ProtocolType proto) {
+  switch (proto) {
+    case cricket::PROTO_TCP:
+      return ICE_TYPE_PREFERENCE_RELAY_TCP;
+    case cricket::PROTO_TLS:
+      return ICE_TYPE_PREFERENCE_RELAY_TLS;
+    default:
+      RTC_DCHECK(proto == PROTO_UDP);
+      return ICE_TYPE_PREFERENCE_RELAY_UDP;
+  }
+}
+
+class TurnAllocateRequest : public StunRequest {
+ public:
+  explicit TurnAllocateRequest(TurnPort* port);
+  void OnSent() override;
+  void OnResponse(StunMessage* response) override;
+  void OnErrorResponse(StunMessage* response) override;
+  void OnTimeout() override;
+
+ private:
+  // Handles authentication challenge from the server.
+  void OnAuthChallenge(StunMessage* response, int code);
+  void OnTryAlternate(StunMessage* response, int code);
+  void OnUnknownAttribute(StunMessage* response);
+
+  TurnPort* port_;
+};
+
+class TurnRefreshRequest : public StunRequest {
+ public:
+  explicit TurnRefreshRequest(TurnPort* port, int lifetime = -1);
+  void OnSent() override;
+  void OnResponse(StunMessage* response) override;
+  void OnErrorResponse(StunMessage* response) override;
+  void OnTimeout() override;
+
+ private:
+  TurnPort* port_;
+};
+
+class TurnCreatePermissionRequest : public StunRequest {
+ public:
+  TurnCreatePermissionRequest(TurnPort* port,
+                              TurnEntry* entry,
+                              const rtc::SocketAddress& ext_addr);
+  ~TurnCreatePermissionRequest() override;
+  void OnSent() override;
+  void OnResponse(StunMessage* response) override;
+  void OnErrorResponse(StunMessage* response) override;
+  void OnTimeout() override;
+
+ private:
+  TurnPort* port_;
+  TurnEntry* entry_;
+  rtc::SocketAddress ext_addr_;
+};
+
+class TurnChannelBindRequest : public StunRequest {
+ public:
+  TurnChannelBindRequest(TurnPort* port,
+                         TurnEntry* entry,
+                         int channel_id,
+                         const rtc::SocketAddress& ext_addr);
+  ~TurnChannelBindRequest() override;
+  void OnSent() override;
+  void OnResponse(StunMessage* response) override;
+  void OnErrorResponse(StunMessage* response) override;
+  void OnTimeout() override;
+
+ private:
+  TurnPort* port_;
+  TurnEntry* entry_;
+  int channel_id_;
+  rtc::SocketAddress ext_addr_;
+};
+
+// Manages a "connection" to a remote destination. We will attempt to bring up
+// a channel for this remote destination to reduce the overhead of sending data.
+class TurnEntry : public sigslot::has_slots<> {
+ public:
+  enum BindState { STATE_UNBOUND, STATE_BINDING, STATE_BOUND };
+  TurnEntry(TurnPort* port, Connection* conn, int channel_id);
+  ~TurnEntry();
+
+  TurnPort* port() { return port_; }
+
+  int channel_id() const { return channel_id_; }
+  // For testing only.
+  void set_channel_id(int channel_id) { channel_id_ = channel_id; }
+
+  const rtc::SocketAddress& address() const { return ext_addr_; }
+  BindState state() const { return state_; }
+
+  // Adds a new connection object to the list of connections that are associated
+  // with this entry. If prior to this call there were no connections being
+  // tracked (i.e. count goes from 0 -> 1), the internal safety flag is reset
+  // which cancels any potential pending deletion tasks.
+  void TrackConnection(Connection* conn);
+
+  // Removes a connection from the list of tracked connections.
+  // * If `conn` was the last connection removed, the function returns a
+  //   safety flag that's used to schedule the deletion of the entry after a
+  //   timeout expires. If during this timeout `TrackConnection` is called, the
+  //   flag will be reset and pending tasks associated with it, cancelled.
+  // * If `conn` was not the last connection, the return value will be nullptr.
+  rtc::scoped_refptr<webrtc::PendingTaskSafetyFlag> UntrackConnection(
+      Connection* conn);
+
+  // Helper methods to send permission and channel bind requests.
+  void SendCreatePermissionRequest(int delay);
+  void SendChannelBindRequest(int delay);
+  // Sends a packet to the given destination address.
+  // This will wrap the packet in STUN if necessary.
+  int Send(const void* data,
+           size_t size,
+           bool payload,
+           const rtc::PacketOptions& options);
+
+  void OnCreatePermissionSuccess();
+  void OnCreatePermissionError(StunMessage* response, int code);
+  void OnCreatePermissionTimeout();
+  void OnChannelBindSuccess();
+  void OnChannelBindError(StunMessage* response, int code);
+  void OnChannelBindTimeout();
+  // Signal sent when TurnEntry is destroyed.
+  webrtc::CallbackList<TurnEntry*> destroyed_callback_list_;
+
+ private:
+  TurnPort* port_;
+  int channel_id_;
+  rtc::SocketAddress ext_addr_;
+  BindState state_;
+  // List of associated connection instances to keep track of how many and
+  // which connections are associated with this entry. Once this is empty,
+  // the entry can be deleted.
+  std::vector<Connection*> connections_;
+  webrtc::ScopedTaskSafety task_safety_;
+};
+
+TurnPort::TurnPort(TaskQueueBase* thread,
+                   rtc::PacketSocketFactory* factory,
+                   const rtc::Network* network,
+                   rtc::AsyncPacketSocket* socket,
+                   absl::string_view username,
+                   absl::string_view password,
+                   const ProtocolAddress& server_address,
+                   const RelayCredentials& credentials,
+                   int server_priority,
+                   const std::vector<std::string>& tls_alpn_protocols,
+                   const std::vector<std::string>& tls_elliptic_curves,
+                   webrtc::TurnCustomizer* customizer,
+                   rtc::SSLCertificateVerifier* tls_cert_verifier,
+                   const webrtc::FieldTrialsView* field_trials)
+    : Port(thread,
+           RELAY_PORT_TYPE,
+           factory,
+           network,
+           username,
+           password,
+           field_trials),
+      server_address_(server_address),
+      tls_alpn_protocols_(tls_alpn_protocols),
+      tls_elliptic_curves_(tls_elliptic_curves),
+      tls_cert_verifier_(tls_cert_verifier),
+      credentials_(credentials),
+      socket_(socket),
+      error_(0),
+      stun_dscp_value_(rtc::DSCP_NO_CHANGE),
+      request_manager_(
+          thread,
+          [this](const void* data, size_t size, StunRequest* request) {
+            OnSendStunPacket(data, size, request);
+          }),
+      next_channel_number_(TURN_CHANNEL_NUMBER_START),
+      state_(STATE_CONNECTING),
+      server_priority_(server_priority),
+      allocate_mismatch_retries_(0),
+      turn_customizer_(customizer) {}
+
+TurnPort::TurnPort(TaskQueueBase* thread,
+                   rtc::PacketSocketFactory* factory,
+                   const rtc::Network* network,
+                   uint16_t min_port,
+                   uint16_t max_port,
+                   absl::string_view username,
+                   absl::string_view password,
+                   const ProtocolAddress& server_address,
+                   const RelayCredentials& credentials,
+                   int server_priority,
+                   const std::vector<std::string>& tls_alpn_protocols,
+                   const std::vector<std::string>& tls_elliptic_curves,
+                   webrtc::TurnCustomizer* customizer,
+                   rtc::SSLCertificateVerifier* tls_cert_verifier,
+                   const webrtc::FieldTrialsView* field_trials)
+    : Port(thread,
+           RELAY_PORT_TYPE,
+           factory,
+           network,
+           min_port,
+           max_port,
+           username,
+           password,
+           field_trials),
+      server_address_(server_address),
+      tls_alpn_protocols_(tls_alpn_protocols),
+      tls_elliptic_curves_(tls_elliptic_curves),
+      tls_cert_verifier_(tls_cert_verifier),
+      credentials_(credentials),
+      socket_(nullptr),
+      error_(0),
+      stun_dscp_value_(rtc::DSCP_NO_CHANGE),
+      request_manager_(
+          thread,
+          [this](const void* data, size_t size, StunRequest* request) {
+            OnSendStunPacket(data, size, request);
+          }),
+      next_channel_number_(TURN_CHANNEL_NUMBER_START),
+      state_(STATE_CONNECTING),
+      server_priority_(server_priority),
+      allocate_mismatch_retries_(0),
+      turn_customizer_(customizer) {}
+
+TurnPort::~TurnPort() {
+  // TODO(juberti): Should this even be necessary?
+
+  // release the allocation by sending a refresh with
+  // lifetime 0.
+  if (ready()) {
+    Release();
+  }
+
+  entries_.clear();
+
+  if (socket_)
+    socket_->UnsubscribeClose(this);
+
+  if (!SharedSocket()) {
+    delete socket_;
+  }
+}
+
+rtc::SocketAddress TurnPort::GetLocalAddress() const {
+  return socket_ ? socket_->GetLocalAddress() : rtc::SocketAddress();
+}
+
+ProtocolType TurnPort::GetProtocol() const {
+  return server_address_.proto;
+}
+
+TlsCertPolicy TurnPort::GetTlsCertPolicy() const {
+  return tls_cert_policy_;
+}
+
+void TurnPort::SetTlsCertPolicy(TlsCertPolicy tls_cert_policy) {
+  tls_cert_policy_ = tls_cert_policy;
+}
+
+void TurnPort::SetTurnLoggingId(absl::string_view turn_logging_id) {
+  turn_logging_id_ = std::string(turn_logging_id);
+}
+
+std::vector<std::string> TurnPort::GetTlsAlpnProtocols() const {
+  return tls_alpn_protocols_;
+}
+
+std::vector<std::string> TurnPort::GetTlsEllipticCurves() const {
+  return tls_elliptic_curves_;
+}
+
+void TurnPort::PrepareAddress() {
+  if (credentials_.username.empty() || credentials_.password.empty()) {
+    RTC_LOG(LS_ERROR) << "Allocation can't be started without setting the"
+                         " TURN server credentials for the user.";
+    OnAllocateError(STUN_ERROR_UNAUTHORIZED,
+                    "Missing TURN server credentials.");
+    return;
+  }
+
+  if (!server_address_.address.port()) {
+    // We will set default TURN port, if no port is set in the address.
+    server_address_.address.SetPort(TURN_DEFAULT_PORT);
+  }
+
+  if (!AllowedTurnPort(server_address_.address.port(), &field_trials())) {
+    // This can only happen after a 300 ALTERNATE SERVER, since the port can't
+    // be created with a disallowed port number.
+    RTC_LOG(LS_ERROR) << "Attempt to start allocation with disallowed port# "
+                      << server_address_.address.port();
+    OnAllocateError(STUN_ERROR_SERVER_ERROR,
+                    "Attempt to start allocation to a disallowed port");
+    return;
+  }
+  if (server_address_.address.IsUnresolvedIP()) {
+    ResolveTurnAddress(server_address_.address);
+  } else {
+    // If protocol family of server address doesn't match with local, return.
+    if (!IsCompatibleAddress(server_address_.address)) {
+      RTC_LOG(LS_ERROR) << "IP address family does not match. server: "
+                        << server_address_.address.family()
+                        << " local: " << Network()->GetBestIP().family();
+      OnAllocateError(STUN_ERROR_GLOBAL_FAILURE,
+                      "IP address family does not match.");
+      return;
+    }
+
+    // Insert the current address to prevent redirection pingpong.
+    attempted_server_addresses_.insert(server_address_.address);
+
+    RTC_LOG(LS_INFO)
+        << ToString() << ": Trying to connect to TURN server via "
+        << ProtoToString(server_address_.proto) << " @ "
+        << server_address_.address.ToSensitiveNameAndAddressString();
+    if (!CreateTurnClientSocket()) {
+      RTC_LOG(LS_ERROR) << "Failed to create TURN client socket";
+      OnAllocateError(SERVER_NOT_REACHABLE_ERROR,
+                      "Failed to create TURN client socket.");
+      return;
+    }
+    if (server_address_.proto == PROTO_UDP) {
+      // If its UDP, send AllocateRequest now.
+      // For TCP and TLS AllcateRequest will be sent by OnSocketConnect.
+      SendRequest(new TurnAllocateRequest(this), 0);
+    }
+  }
+}
+
+bool TurnPort::CreateTurnClientSocket() {
+  RTC_DCHECK(!socket_ || SharedSocket());
+
+  if (server_address_.proto == PROTO_UDP && !SharedSocket()) {
+    socket_ = socket_factory()->CreateUdpSocket(
+        rtc::SocketAddress(Network()->GetBestIP(), 0), min_port(), max_port());
+  } else if (server_address_.proto == PROTO_TCP ||
+             server_address_.proto == PROTO_TLS) {
+    RTC_DCHECK(!SharedSocket());
+    int opts = rtc::PacketSocketFactory::OPT_STUN;
+
+    // Apply server address TLS and insecure bits to options.
+    if (server_address_.proto == PROTO_TLS) {
+      if (tls_cert_policy_ ==
+          TlsCertPolicy::TLS_CERT_POLICY_INSECURE_NO_CHECK) {
+        opts |= rtc::PacketSocketFactory::OPT_TLS_INSECURE;
+      } else {
+        opts |= rtc::PacketSocketFactory::OPT_TLS;
+      }
+    }
+
+    rtc::PacketSocketTcpOptions tcp_options;
+    tcp_options.opts = opts;
+    tcp_options.tls_alpn_protocols = tls_alpn_protocols_;
+    tcp_options.tls_elliptic_curves = tls_elliptic_curves_;
+    tcp_options.tls_cert_verifier = tls_cert_verifier_;
+    socket_ = socket_factory()->CreateClientTcpSocket(
+        rtc::SocketAddress(Network()->GetBestIP(), 0), server_address_.address,
+        proxy(), user_agent(), tcp_options);
+  }
+
+  if (!socket_) {
+    error_ = SOCKET_ERROR;
+    return false;
+  }
+
+  // Apply options if any.
+  for (SocketOptionsMap::iterator iter = socket_options_.begin();
+       iter != socket_options_.end(); ++iter) {
+    socket_->SetOption(iter->first, iter->second);
+  }
+
+  if (!SharedSocket()) {
+    // If socket is shared, AllocationSequence will receive the packet.
+    socket_->SignalReadPacket.connect(this, &TurnPort::OnReadPacket);
+  }
+
+  socket_->SignalReadyToSend.connect(this, &TurnPort::OnReadyToSend);
+
+  socket_->SignalSentPacket.connect(this, &TurnPort::OnSentPacket);
+
+  // TCP port is ready to send stun requests after the socket is connected,
+  // while UDP port is ready to do so once the socket is created.
+  if (server_address_.proto == PROTO_TCP ||
+      server_address_.proto == PROTO_TLS) {
+    socket_->SignalConnect.connect(this, &TurnPort::OnSocketConnect);
+    socket_->SubscribeClose(this, [this](rtc::AsyncPacketSocket* s, int err) {
+      OnSocketClose(s, err);
+    });
+  } else {
+    state_ = STATE_CONNECTED;
+  }
+  return true;
+}
+
+void TurnPort::OnSocketConnect(rtc::AsyncPacketSocket* socket) {
+  // This slot should only be invoked if we're using a connection-oriented
+  // protocol.
+  RTC_DCHECK(server_address_.proto == PROTO_TCP ||
+             server_address_.proto == PROTO_TLS);
+
+  // Do not use this port if the socket bound to an address not associated with
+  // the desired network interface. This is seen in Chrome, where TCP sockets
+  // cannot be given a binding address, and the platform is expected to pick
+  // the correct local address.
+  //
+  // However, there are two situations in which we allow the bound address to
+  // not be one of the addresses of the requested interface:
+  // 1. The bound address is the loopback address. This happens when a proxy
+  // forces TCP to bind to only the localhost address (see issue 3927).
+  // 2. The bound address is the "any address". This happens when
+  // multiple_routes is disabled (see issue 4780).
+  //
+  // Note that, aside from minor differences in log statements, this logic is
+  // identical to that in TcpPort.
+  const rtc::SocketAddress& socket_address = socket->GetLocalAddress();
+  if (absl::c_none_of(Network()->GetIPs(),
+                      [socket_address](const rtc::InterfaceAddress& addr) {
+                        return socket_address.ipaddr() == addr;
+                      })) {
+    if (socket->GetLocalAddress().IsLoopbackIP()) {
+      RTC_LOG(LS_WARNING) << "Socket is bound to the address:"
+                          << socket_address.ToSensitiveNameAndAddressString()
+                          << ", rather than an address associated with network:"
+                          << Network()->ToString()
+                          << ". Still allowing it since it's localhost.";
+    } else if (IPIsAny(Network()->GetBestIP())) {
+      RTC_LOG(LS_WARNING)
+          << "Socket is bound to the address:"
+          << socket_address.ToSensitiveNameAndAddressString()
+          << ", rather than an address associated with network:"
+          << Network()->ToString()
+          << ". Still allowing it since it's the 'any' address"
+             ", possibly caused by multiple_routes being disabled.";
+    } else {
+      RTC_LOG(LS_WARNING) << "Socket is bound to the address:"
+                          << socket_address.ToSensitiveNameAndAddressString()
+                          << ", rather than an address associated with network:"
+                          << Network()->ToString() << ". Discarding TURN port.";
+      OnAllocateError(
+          STUN_ERROR_GLOBAL_FAILURE,
+          "Address not associated with the desired network interface.");
+      return;
+    }
+  }
+
+  state_ = STATE_CONNECTED;  // It is ready to send stun requests.
+  if (server_address_.address.IsUnresolvedIP()) {
+    server_address_.address = socket_->GetRemoteAddress();
+  }
+
+  RTC_LOG(LS_INFO) << "TurnPort connected to "
+                   << socket->GetRemoteAddress().ToSensitiveString()
+                   << " using tcp.";
+  SendRequest(new TurnAllocateRequest(this), 0);
+}
+
+void TurnPort::OnSocketClose(rtc::AsyncPacketSocket* socket, int error) {
+  RTC_LOG(LS_WARNING) << ToString()
+                      << ": Connection with server failed with error: "
+                      << error;
+  RTC_DCHECK(socket == socket_);
+  Close();
+}
+
+void TurnPort::OnAllocateMismatch() {
+  if (allocate_mismatch_retries_ >= MAX_ALLOCATE_MISMATCH_RETRIES) {
+    RTC_LOG(LS_WARNING) << ToString() << ": Giving up on the port after "
+                        << allocate_mismatch_retries_
+                        << " retries for STUN_ERROR_ALLOCATION_MISMATCH";
+    OnAllocateError(STUN_ERROR_ALLOCATION_MISMATCH,
+                    "Maximum retries reached for allocation mismatch.");
+    return;
+  }
+
+  RTC_LOG(LS_INFO) << ToString()
+                   << ": Allocating a new socket after "
+                      "STUN_ERROR_ALLOCATION_MISMATCH, retry: "
+                   << allocate_mismatch_retries_ + 1;
+
+  socket_->UnsubscribeClose(this);
+
+  if (SharedSocket()) {
+    ResetSharedSocket();
+  } else {
+    delete socket_;
+  }
+  socket_ = nullptr;
+
+  ResetNonce();
+  PrepareAddress();
+  ++allocate_mismatch_retries_;
+}
+
+Connection* TurnPort::CreateConnection(const Candidate& remote_candidate,
+                                       CandidateOrigin origin) {
+  // TURN-UDP can only connect to UDP candidates.
+  if (!SupportsProtocol(remote_candidate.protocol())) {
+    return nullptr;
+  }
+
+  if (state_ == STATE_DISCONNECTED || state_ == STATE_RECEIVEONLY) {
+    return nullptr;
+  }
+
+  // If the remote endpoint signaled us an mDNS candidate, we do not form a pair
+  // with the relay candidate to avoid IP leakage in the CreatePermission
+  // request.
+  if (absl::EndsWith(remote_candidate.address().hostname(), LOCAL_TLD)) {
+    return nullptr;
+  }
+
+  // A TURN port will have two candidates, STUN and TURN. STUN may not
+  // present in all cases. If present stun candidate will be added first
+  // and TURN candidate later.
+  for (size_t index = 0; index < Candidates().size(); ++index) {
+    const Candidate& local_candidate = Candidates()[index];
+    if (local_candidate.type() == RELAY_PORT_TYPE &&
+        local_candidate.address().family() ==
+            remote_candidate.address().family()) {
+      ProxyConnection* conn =
+          new ProxyConnection(NewWeakPtr(), index, remote_candidate);
+      // Create an entry, if needed, so we can get our permissions set up
+      // correctly.
+      if (CreateOrRefreshEntry(conn, next_channel_number_)) {
+        next_channel_number_++;
+      }
+      AddOrReplaceConnection(conn);
+      return conn;
+    }
+  }
+  return nullptr;
+}
+
+bool TurnPort::FailAndPruneConnection(const rtc::SocketAddress& address) {
+  Connection* conn = GetConnection(address);
+  if (conn != nullptr) {
+    conn->FailAndPrune();
+    return true;
+  }
+  return false;
+}
+
+int TurnPort::SetOption(rtc::Socket::Option opt, int value) {
+  // Remember the last requested DSCP value, for STUN traffic.
+  if (opt == rtc::Socket::OPT_DSCP)
+    stun_dscp_value_ = static_cast<rtc::DiffServCodePoint>(value);
+
+  if (!socket_) {
+    // If socket is not created yet, these options will be applied during socket
+    // creation.
+    socket_options_[opt] = value;
+    return 0;
+  }
+  return socket_->SetOption(opt, value);
+}
+
+int TurnPort::GetOption(rtc::Socket::Option opt, int* value) {
+  if (!socket_) {
+    SocketOptionsMap::const_iterator it = socket_options_.find(opt);
+    if (it == socket_options_.end()) {
+      return -1;
+    }
+    *value = it->second;
+    return 0;
+  }
+
+  return socket_->GetOption(opt, value);
+}
+
+int TurnPort::GetError() {
+  return error_;
+}
+
+int TurnPort::SendTo(const void* data,
+                     size_t size,
+                     const rtc::SocketAddress& addr,
+                     const rtc::PacketOptions& options,
+                     bool payload) {
+  // Try to find an entry for this specific address; we should have one.
+  TurnEntry* entry = FindEntry(addr);
+  RTC_DCHECK(entry);
+
+  if (!ready()) {
+    error_ = ENOTCONN;
+    return SOCKET_ERROR;
+  }
+
+  // Send the actual contents to the server using the usual mechanism.
+  rtc::PacketOptions modified_options(options);
+  CopyPortInformationToPacketInfo(&modified_options.info_signaled_after_sent);
+  int sent = entry->Send(data, size, payload, modified_options);
+  if (sent <= 0) {
+    error_ = socket_->GetError();
+    return SOCKET_ERROR;
+  }
+
+  // The caller of the function is expecting the number of user data bytes,
+  // rather than the size of the packet.
+  return static_cast<int>(size);
+}
+
+bool TurnPort::CanHandleIncomingPacketsFrom(
+    const rtc::SocketAddress& addr) const {
+  return server_address_.address == addr;
+}
+
+void TurnPort::SendBindingErrorResponse(StunMessage* message,
+                                        const rtc::SocketAddress& addr,
+                                        int error_code,
+                                        absl::string_view reason) {
+  if (!GetConnection(addr))
+    return;
+
+  Port::SendBindingErrorResponse(message, addr, error_code, reason);
+}
+
+bool TurnPort::HandleIncomingPacket(rtc::AsyncPacketSocket* socket,
+                                    const char* data,
+                                    size_t size,
+                                    const rtc::SocketAddress& remote_addr,
+                                    int64_t packet_time_us) {
+  if (socket != socket_) {
+    // The packet was received on a shared socket after we've allocated a new
+    // socket for this TURN port.
+    return false;
+  }
+
+  // This is to guard against a STUN response from previous server after
+  // alternative server redirection. TODO(guoweis): add a unit test for this
+  // race condition.
+  if (remote_addr != server_address_.address) {
+    RTC_LOG(LS_WARNING)
+        << ToString() << ": Discarding TURN message from unknown address: "
+        << remote_addr.ToSensitiveNameAndAddressString() << " server_address_: "
+        << server_address_.address.ToSensitiveNameAndAddressString();
+    return false;
+  }
+
+  // The message must be at least the size of a channel header.
+  if (size < TURN_CHANNEL_HEADER_SIZE) {
+    RTC_LOG(LS_WARNING) << ToString()
+                        << ": Received TURN message that was too short";
+    return false;
+  }
+
+  if (state_ == STATE_DISCONNECTED) {
+    RTC_LOG(LS_WARNING)
+        << ToString()
+        << ": Received TURN message while the TURN port is disconnected";
+    return false;
+  }
+
+  // Check the message type, to see if is a Channel Data message.
+  // The message will either be channel data, a TURN data indication, or
+  // a response to a previous request.
+  uint16_t msg_type = rtc::GetBE16(data);
+  if (IsTurnChannelData(msg_type)) {
+    HandleChannelData(msg_type, data, size, packet_time_us);
+    return true;
+  }
+
+  if (msg_type == TURN_DATA_INDICATION) {
+    HandleDataIndication(data, size, packet_time_us);
+    return true;
+  }
+
+  if (SharedSocket() && (msg_type == STUN_BINDING_RESPONSE ||
+                         msg_type == STUN_BINDING_ERROR_RESPONSE)) {
+    RTC_LOG(LS_VERBOSE)
+        << ToString()
+        << ": Ignoring STUN binding response message on shared socket.";
+    return false;
+  }
+
+  request_manager_.CheckResponse(data, size);
+
+  return true;
+}
+
+void TurnPort::OnReadPacket(rtc::AsyncPacketSocket* socket,
+                            const char* data,
+                            size_t size,
+                            const rtc::SocketAddress& remote_addr,
+                            const int64_t& packet_time_us) {
+  HandleIncomingPacket(socket, data, size, remote_addr, packet_time_us);
+}
+
+void TurnPort::OnSentPacket(rtc::AsyncPacketSocket* socket,
+                            const rtc::SentPacket& sent_packet) {
+  PortInterface::SignalSentPacket(sent_packet);
+}
+
+void TurnPort::OnReadyToSend(rtc::AsyncPacketSocket* socket) {
+  if (ready()) {
+    Port::OnReadyToSend();
+  }
+}
+
+bool TurnPort::SupportsProtocol(absl::string_view protocol) const {
+  // Turn port only connects to UDP candidates.
+  return protocol == UDP_PROTOCOL_NAME;
+}
+
+// Update current server address port with the alternate server address port.
+bool TurnPort::SetAlternateServer(const rtc::SocketAddress& address) {
+  // Check if we have seen this address before and reject if we did.
+  AttemptedServerSet::iterator iter = attempted_server_addresses_.find(address);
+  if (iter != attempted_server_addresses_.end()) {
+    RTC_LOG(LS_WARNING) << ToString() << ": Redirection to ["
+                        << address.ToSensitiveNameAndAddressString()
+                        << "] ignored, allocation failed.";
+    return false;
+  }
+
+  // If protocol family of server address doesn't match with local, return.
+  if (!IsCompatibleAddress(address)) {
+    RTC_LOG(LS_WARNING) << "Server IP address family does not match with "
+                           "local host address family type";
+    return false;
+  }
+
+  // Block redirects to a loopback address.
+  // See: https://bugs.chromium.org/p/chromium/issues/detail?id=649118
+  if (address.IsLoopbackIP()) {
+    RTC_LOG(LS_WARNING) << ToString()
+                        << ": Blocking attempted redirect to loopback address.";
+    return false;
+  }
+
+  RTC_LOG(LS_INFO) << ToString() << ": Redirecting from TURN server ["
+                   << server_address_.address.ToSensitiveNameAndAddressString()
+                   << "] to TURN server ["
+                   << address.ToSensitiveNameAndAddressString() << "]";
+  server_address_ = ProtocolAddress(address, server_address_.proto);
+
+  // Insert the current address to prevent redirection pingpong.
+  attempted_server_addresses_.insert(server_address_.address);
+  return true;
+}
+
+void TurnPort::ResolveTurnAddress(const rtc::SocketAddress& address) {
+  if (resolver_)
+    return;
+
+  RTC_LOG(LS_INFO) << ToString() << ": Starting TURN host lookup for "
+                   << address.ToSensitiveString();
+  resolver_ = socket_factory()->CreateAsyncDnsResolver();
+  auto callback = [this] {
+    // If DNS resolve is failed when trying to connect to the server using TCP,
+    // one of the reason could be due to DNS queries blocked by firewall.
+    // In such cases we will try to connect to the server with hostname,
+    // assuming socket layer will resolve the hostname through a HTTP proxy (if
+    // any).
+    auto& result = resolver_->result();
+    if (result.GetError() != 0 && (server_address_.proto == PROTO_TCP ||
+                                   server_address_.proto == PROTO_TLS)) {
+      if (!CreateTurnClientSocket()) {
+        OnAllocateError(SERVER_NOT_REACHABLE_ERROR,
+                        "TURN host lookup received error.");
+      }
+      return;
+    }
+
+    // Copy the original server address in `resolved_address`. For TLS based
+    // sockets we need hostname along with resolved address.
+    rtc::SocketAddress resolved_address = server_address_.address;
+    if (result.GetError() != 0 ||
+        !result.GetResolvedAddress(Network()->GetBestIP().family(),
+                                   &resolved_address)) {
+      RTC_LOG(LS_WARNING) << ToString() << ": TURN host lookup received error "
+                          << result.GetError();
+      error_ = result.GetError();
+      OnAllocateError(SERVER_NOT_REACHABLE_ERROR,
+                      "TURN host lookup received error.");
+      return;
+    }
+    server_address_.address = resolved_address;
+    PrepareAddress();
+  };
+  // TODO(bugs.webrtc.org/14733): remove duplicate resolution with STUN port.
+  if (ResolveTurnHostnameForFamily(field_trials())) {
+    resolver_->Start(address, Network()->family(), std::move(callback));
+  } else {
+    resolver_->Start(address, std::move(callback));
+  }
+}
+
+void TurnPort::OnSendStunPacket(const void* data,
+                                size_t size,
+                                StunRequest* request) {
+  RTC_DCHECK(connected());
+  rtc::PacketOptions options(StunDscpValue());
+  options.info_signaled_after_sent.packet_type = rtc::PacketType::kTurnMessage;
+  CopyPortInformationToPacketInfo(&options.info_signaled_after_sent);
+  if (Send(data, size, options) < 0) {
+    RTC_LOG(LS_ERROR) << ToString() << ": Failed to send TURN message, error: "
+                      << socket_->GetError();
+  }
+}
+
+void TurnPort::OnStunAddress(const rtc::SocketAddress& address) {
+  // STUN Port will discover STUN candidate, as it's supplied with first TURN
+  // server address.
+  // Why not using this address? - P2PTransportChannel will start creating
+  // connections after first candidate, which means it could start creating the
+  // connections before TURN candidate added. For that to handle, we need to
+  // supply STUN candidate from this port to UDPPort, and TurnPort should have
+  // handle to UDPPort to pass back the address.
+}
+
+void TurnPort::OnAllocateSuccess(const rtc::SocketAddress& address,
+                                 const rtc::SocketAddress& stun_address) {
+  state_ = STATE_READY;
+
+  rtc::SocketAddress related_address = stun_address;
+
+  // For relayed candidate, Base is the candidate itself.
+  AddAddress(address,          // Candidate address.
+             address,          // Base address.
+             related_address,  // Related address.
+             UDP_PROTOCOL_NAME,
+             ProtoToString(server_address_.proto),  // The first hop protocol.
+             "",  // TCP candidate type, empty for turn candidates.
+             RELAY_PORT_TYPE, GetRelayPreference(server_address_.proto),
+             server_priority_, ReconstructedServerUrl(), true);
+}
+
+void TurnPort::OnAllocateError(int error_code, absl::string_view reason) {
+  // We will send SignalPortError asynchronously as this can be sent during
+  // port initialization. This way it will not be blocking other port
+  // creation.
+  thread()->PostTask(
+      SafeTask(task_safety_.flag(), [this] { SignalPortError(this); }));
+  std::string address = GetLocalAddress().HostAsSensitiveURIString();
+  int port = GetLocalAddress().port();
+  if (server_address_.proto == PROTO_TCP &&
+      server_address_.address.IsPrivateIP()) {
+    address.clear();
+    port = 0;
+  }
+  SignalCandidateError(
+      this, IceCandidateErrorEvent(address, port, ReconstructedServerUrl(),
+                                   error_code, reason));
+}
+
+void TurnPort::OnRefreshError() {
+  // Need to clear the requests asynchronously because otherwise, the refresh
+  // request may be deleted twice: once at the end of the message processing
+  // and the other in HandleRefreshError().
+  thread()->PostTask(
+      SafeTask(task_safety_.flag(), [this] { HandleRefreshError(); }));
+}
+
+void TurnPort::HandleRefreshError() {
+  request_manager_.Clear();
+  state_ = STATE_RECEIVEONLY;
+  // Fail and prune all connections; stop sending data.
+  for (auto kv : connections()) {
+    kv.second->FailAndPrune();
+  }
+}
+
+void TurnPort::Release() {
+  // Remove any pending refresh requests.
+  request_manager_.Clear();
+
+  // Send refresh with lifetime 0.
+  TurnRefreshRequest* req = new TurnRefreshRequest(this, 0);
+  SendRequest(req, 0);
+
+  state_ = STATE_RECEIVEONLY;
+}
+
+void TurnPort::Close() {
+  if (!ready()) {
+    OnAllocateError(SERVER_NOT_REACHABLE_ERROR, "");
+  }
+  request_manager_.Clear();
+  // Stop the port from creating new connections.
+  state_ = STATE_DISCONNECTED;
+  // Delete all existing connections; stop sending data.
+  DestroyAllConnections();
+  if (callbacks_for_test_) {
+    callbacks_for_test_->OnTurnPortClosed();
+  }
+}
+
+rtc::DiffServCodePoint TurnPort::StunDscpValue() const {
+  return stun_dscp_value_;
+}
+
+// static
+bool TurnPort::AllowedTurnPort(int port,
+                               const webrtc::FieldTrialsView* field_trials) {
+  // Port 53, 80 and 443 are used for existing deployments.
+  // Ports above 1024 are assumed to be OK to use.
+  if (port == 53 || port == 80 || port == 443 || port >= 1024) {
+    return true;
+  }
+  // Allow any port if relevant field trial is set. This allows disabling the
+  // check.
+  if (field_trials && field_trials->IsEnabled("WebRTC-Turn-AllowSystemPorts")) {
+    return true;
+  }
+  return false;
+}
+
+void TurnPort::TryAlternateServer() {
+  if (server_address().proto == PROTO_UDP) {
+    // Send another allocate request to alternate server, with the received
+    // realm and nonce values.
+    SendRequest(new TurnAllocateRequest(this), 0);
+  } else {
+    // Since it's TCP, we have to delete the connected socket and reconnect
+    // with the alternate server. PrepareAddress will send stun binding once
+    // the new socket is connected.
+    RTC_DCHECK(server_address().proto == PROTO_TCP ||
+               server_address().proto == PROTO_TLS);
+    RTC_DCHECK(!SharedSocket());
+    delete socket_;
+    socket_ = nullptr;
+    PrepareAddress();
+  }
+}
+
+void TurnPort::OnAllocateRequestTimeout() {
+  OnAllocateError(SERVER_NOT_REACHABLE_ERROR,
+                  "TURN allocate request timed out.");
+}
+
+void TurnPort::HandleDataIndication(const char* data,
+                                    size_t size,
+                                    int64_t packet_time_us) {
+  // Read in the message, and process according to RFC5766, Section 10.4.
+  rtc::ByteBufferReader buf(data, size);
+  TurnMessage msg;
+  if (!msg.Read(&buf)) {
+    RTC_LOG(LS_WARNING) << ToString()
+                        << ": Received invalid TURN data indication";
+    return;
+  }
+
+  // Check mandatory attributes.
+  const StunAddressAttribute* addr_attr =
+      msg.GetAddress(STUN_ATTR_XOR_PEER_ADDRESS);
+  if (!addr_attr) {
+    RTC_LOG(LS_WARNING) << ToString()
+                        << ": Missing STUN_ATTR_XOR_PEER_ADDRESS attribute "
+                           "in data indication.";
+    return;
+  }
+
+  const StunByteStringAttribute* data_attr = msg.GetByteString(STUN_ATTR_DATA);
+  if (!data_attr) {
+    RTC_LOG(LS_WARNING) << ToString()
+                        << ": Missing STUN_ATTR_DATA attribute in "
+                           "data indication.";
+    return;
+  }
+
+  // Log a warning if the data didn't come from an address that we think we have
+  // a permission for.
+  rtc::SocketAddress ext_addr(addr_attr->GetAddress());
+  if (!HasPermission(ext_addr.ipaddr())) {
+    RTC_LOG(LS_WARNING) << ToString()
+                        << ": Received TURN data indication with unknown "
+                           "peer address, addr: "
+                        << ext_addr.ToSensitiveString();
+  }
+
+  DispatchPacket(data_attr->bytes(), data_attr->length(), ext_addr, PROTO_UDP,
+                 packet_time_us);
+}
+
+void TurnPort::HandleChannelData(int channel_id,
+                                 const char* data,
+                                 size_t size,
+                                 int64_t packet_time_us) {
+  // Read the message, and process according to RFC5766, Section 11.6.
+  //    0                   1                   2                   3
+  //    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+  //   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+  //   |         Channel Number        |            Length             |
+  //   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+  //   |                                                               |
+  //   /                       Application Data                        /
+  //   /                                                               /
+  //   |                                                               |
+  //   |                               +-------------------------------+
+  //   |                               |
+  //   +-------------------------------+
+
+  // Extract header fields from the message.
+  uint16_t len = rtc::GetBE16(data + 2);
+  if (len > size - TURN_CHANNEL_HEADER_SIZE) {
+    RTC_LOG(LS_WARNING) << ToString()
+                        << ": Received TURN channel data message with "
+                           "incorrect length, len: "
+                        << len;
+    return;
+  }
+  // Allowing messages larger than `len`, as ChannelData can be padded.
+
+  TurnEntry* entry = FindEntry(channel_id);
+  if (!entry) {
+    RTC_LOG(LS_WARNING) << ToString()
+                        << ": Received TURN channel data message for invalid "
+                           "channel, channel_id: "
+                        << channel_id;
+    return;
+  }
+
+  DispatchPacket(data + TURN_CHANNEL_HEADER_SIZE, len, entry->address(),
+                 PROTO_UDP, packet_time_us);
+}
+
+void TurnPort::DispatchPacket(const char* data,
+                              size_t size,
+                              const rtc::SocketAddress& remote_addr,
+                              ProtocolType proto,
+                              int64_t packet_time_us) {
+  if (Connection* conn = GetConnection(remote_addr)) {
+    conn->OnReadPacket(data, size, packet_time_us);
+  } else {
+    Port::OnReadPacket(data, size, remote_addr, proto);
+  }
+}
+
+bool TurnPort::ScheduleRefresh(uint32_t lifetime) {
+  // Lifetime is in seconds, delay is in milliseconds.
+  int delay = 1 * 60 * 1000;
+
+  // Cutoff lifetime bigger than 1h.
+  constexpr uint32_t max_lifetime = 60 * 60;
+
+  if (lifetime < 2 * 60) {
+    // The RFC does not mention a lower limit on lifetime.
+    // So if server sends a value less than 2 minutes, we schedule a refresh
+    // for half lifetime.
+    RTC_LOG(LS_WARNING) << ToString()
+                        << ": Received response with short lifetime: "
+                        << lifetime << " seconds.";
+    delay = (lifetime * 1000) / 2;
+  } else if (lifetime > max_lifetime) {
+    // Make 1 hour largest delay, and then we schedule a refresh for one minute
+    // less than max lifetime.
+    RTC_LOG(LS_WARNING) << ToString()
+                        << ": Received response with long lifetime: "
+                        << lifetime << " seconds.";
+    delay = (max_lifetime - 60) * 1000;
+  } else {
+    // Normal case,
+    // we schedule a refresh for one minute less than requested lifetime.
+    delay = (lifetime - 60) * 1000;
+  }
+
+  SendRequest(new TurnRefreshRequest(this), delay);
+  RTC_LOG(LS_INFO) << ToString() << ": Scheduled refresh in " << delay << "ms.";
+  return true;
+}
+
+void TurnPort::SendRequest(StunRequest* req, int delay) {
+  request_manager_.SendDelayed(req, delay);
+}
+
+void TurnPort::AddRequestAuthInfo(StunMessage* msg) {
+  // If we've gotten the necessary data from the server, add it to our request.
+  RTC_DCHECK(!hash_.empty());
+  msg->AddAttribute(std::make_unique<StunByteStringAttribute>(
+      STUN_ATTR_USERNAME, credentials_.username));
+  msg->AddAttribute(
+      std::make_unique<StunByteStringAttribute>(STUN_ATTR_REALM, realm_));
+  msg->AddAttribute(
+      std::make_unique<StunByteStringAttribute>(STUN_ATTR_NONCE, nonce_));
+  const bool success = msg->AddMessageIntegrity(hash());
+  RTC_DCHECK(success);
+}
+
+int TurnPort::Send(const void* data,
+                   size_t len,
+                   const rtc::PacketOptions& options) {
+  return socket_->SendTo(data, len, server_address_.address, options);
+}
+
+void TurnPort::UpdateHash() {
+  const bool success = ComputeStunCredentialHash(credentials_.username, realm_,
+                                                 credentials_.password, &hash_);
+  RTC_DCHECK(success);
+}
+
+bool TurnPort::UpdateNonce(StunMessage* response) {
+  // When stale nonce error received, we should update
+  // hash and store realm and nonce.
+  // Check the mandatory attributes.
+  const StunByteStringAttribute* realm_attr =
+      response->GetByteString(STUN_ATTR_REALM);
+  if (!realm_attr) {
+    RTC_LOG(LS_ERROR) << "Missing STUN_ATTR_REALM attribute in "
+                         "stale nonce error response.";
+    return false;
+  }
+  set_realm(realm_attr->string_view());
+
+  const StunByteStringAttribute* nonce_attr =
+      response->GetByteString(STUN_ATTR_NONCE);
+  if (!nonce_attr) {
+    RTC_LOG(LS_ERROR) << "Missing STUN_ATTR_NONCE attribute in "
+                         "stale nonce error response.";
+    return false;
+  }
+  set_nonce(nonce_attr->string_view());
+  return true;
+}
+
+void TurnPort::ResetNonce() {
+  hash_.clear();
+  nonce_.clear();
+  realm_.clear();
+}
+
+bool TurnPort::HasPermission(const rtc::IPAddress& ipaddr) const {
+  return absl::c_any_of(entries_, [&ipaddr](const auto& e) {
+    return e->address().ipaddr() == ipaddr;
+  });
+}
+
+TurnEntry* TurnPort::FindEntry(const rtc::SocketAddress& addr) const {
+  auto it = absl::c_find_if(
+      entries_, [&addr](const auto& e) { return e->address() == addr; });
+  return (it != entries_.end()) ? it->get() : nullptr;
+}
+
+TurnEntry* TurnPort::FindEntry(int channel_id) const {
+  auto it = absl::c_find_if(entries_, [&channel_id](const auto& e) {
+    return e->channel_id() == channel_id;
+  });
+  return (it != entries_.end()) ? it->get() : nullptr;
+}
+
+bool TurnPort::CreateOrRefreshEntry(Connection* conn, int channel_number) {
+  const Candidate& remote_candidate = conn->remote_candidate();
+  TurnEntry* entry = FindEntry(remote_candidate.address());
+  if (entry == nullptr) {
+    entries_.push_back(std::make_unique<TurnEntry>(this, conn, channel_number));
+    return true;
+  }
+
+  // Associate this connection object with an existing entry. If the entry
+  // has been scheduled for deletion, this will cancel that task.
+  entry->TrackConnection(conn);
+
+  return false;
+}
+
+void TurnPort::HandleConnectionDestroyed(Connection* conn) {
+  // Schedule an event to destroy TurnEntry for the connection, which is
+  // being destroyed.
+  const rtc::SocketAddress& remote_address = conn->remote_candidate().address();
+  // We should always have an entry for this connection.
+  TurnEntry* entry = FindEntry(remote_address);
+  rtc::scoped_refptr<webrtc::PendingTaskSafetyFlag> flag =
+      entry->UntrackConnection(conn);
+  if (flag) {
+    // An assumption here is that the lifetime flag for the entry, is within
+    // the lifetime scope of `task_safety_` and therefore use of `this` is safe.
+    // If an entry gets reused (associated with a new connection) while this
+    // task is pending, the entry will reset the safety flag, thus cancel this
+    // task.
+    thread()->PostDelayedTask(SafeTask(flag,
+                                       [this, entry] {
+                                         entries_.erase(absl::c_find_if(
+                                             entries_, [entry](const auto& e) {
+                                               return e.get() == entry;
+                                             }));
+                                       }),
+                              kTurnPermissionTimeout);
+  }
+}
+
+void TurnPort::SetCallbacksForTest(CallbacksForTest* callbacks) {
+  RTC_DCHECK(!callbacks_for_test_);
+  callbacks_for_test_ = callbacks;
+}
+
+bool TurnPort::SetEntryChannelId(const rtc::SocketAddress& address,
+                                 int channel_id) {
+  TurnEntry* entry = FindEntry(address);
+  if (!entry) {
+    return false;
+  }
+  entry->set_channel_id(channel_id);
+  return true;
+}
+
+std::string TurnPort::ReconstructedServerUrl() {
+  // draft-petithuguenin-behave-turn-uris-01
+  // turnURI       = scheme ":" turn-host [ ":" turn-port ]
+  //                 [ "?transport=" transport ]
+  // scheme        = "turn" / "turns"
+  // transport     = "udp" / "tcp" / transport-ext
+  // transport-ext = 1*unreserved
+  // turn-host     = IP-literal / IPv4address / reg-name
+  // turn-port     = *DIGIT
+  std::string scheme = "turn";
+  std::string transport = "tcp";
+  switch (server_address_.proto) {
+    case PROTO_SSLTCP:
+    case PROTO_TLS:
+      scheme = "turns";
+      break;
+    case PROTO_UDP:
+      transport = "udp";
+      break;
+    case PROTO_TCP:
+      break;
+  }
+  rtc::StringBuilder url;
+  url << scheme << ":" << server_address_.address.hostname() << ":"
+      << server_address_.address.port() << "?transport=" << transport;
+  return url.Release();
+}
+
+void TurnPort::TurnCustomizerMaybeModifyOutgoingStunMessage(
+    StunMessage* message) {
+  if (turn_customizer_ == nullptr) {
+    return;
+  }
+
+  turn_customizer_->MaybeModifyOutgoingStunMessage(this, message);
+}
+
+bool TurnPort::TurnCustomizerAllowChannelData(const void* data,
+                                              size_t size,
+                                              bool payload) {
+  if (turn_customizer_ == nullptr) {
+    return true;
+  }
+
+  return turn_customizer_->AllowChannelData(this, data, size, payload);
+}
+
+void TurnPort::MaybeAddTurnLoggingId(StunMessage* msg) {
+  if (!turn_logging_id_.empty()) {
+    msg->AddAttribute(std::make_unique<StunByteStringAttribute>(
+        STUN_ATTR_TURN_LOGGING_ID, turn_logging_id_));
+  }
+}
+
+TurnAllocateRequest::TurnAllocateRequest(TurnPort* port)
+    : StunRequest(port->request_manager(),
+                  std::make_unique<TurnMessage>(TURN_ALLOCATE_REQUEST)),
+      port_(port) {
+  StunMessage* message = mutable_msg();
+  // Create the request as indicated in RFC 5766, Section 6.1.
+  RTC_DCHECK_EQ(message->type(), TURN_ALLOCATE_REQUEST);
+  auto transport_attr =
+      StunAttribute::CreateUInt32(STUN_ATTR_REQUESTED_TRANSPORT);
+  transport_attr->SetValue(IPPROTO_UDP << 24);
+  message->AddAttribute(std::move(transport_attr));
+  if (!port_->hash().empty()) {
+    port_->AddRequestAuthInfo(message);
+  }
+  port_->MaybeAddTurnLoggingId(message);
+  port_->TurnCustomizerMaybeModifyOutgoingStunMessage(message);
+}
+
+void TurnAllocateRequest::OnSent() {
+  RTC_LOG(LS_INFO) << port_->ToString() << ": TURN allocate request sent, id="
+                   << rtc::hex_encode(id());
+  StunRequest::OnSent();
+}
+
+void TurnAllocateRequest::OnResponse(StunMessage* response) {
+  RTC_LOG(LS_INFO) << port_->ToString()
+                   << ": TURN allocate requested successfully, id="
+                   << rtc::hex_encode(id())
+                   << ", code=0"  // Makes logging easier to parse.
+                      ", rtt="
+                   << Elapsed();
+
+  // Check mandatory attributes as indicated in RFC5766, Section 6.3.
+  const StunAddressAttribute* mapped_attr =
+      response->GetAddress(STUN_ATTR_XOR_MAPPED_ADDRESS);
+  if (!mapped_attr) {
+    RTC_LOG(LS_WARNING) << port_->ToString()
+                        << ": Missing STUN_ATTR_XOR_MAPPED_ADDRESS "
+                           "attribute in allocate success response";
+    return;
+  }
+  // Using XOR-Mapped-Address for stun.
+  port_->OnStunAddress(mapped_attr->GetAddress());
+
+  const StunAddressAttribute* relayed_attr =
+      response->GetAddress(STUN_ATTR_XOR_RELAYED_ADDRESS);
+  if (!relayed_attr) {
+    RTC_LOG(LS_WARNING) << port_->ToString()
+                        << ": Missing STUN_ATTR_XOR_RELAYED_ADDRESS "
+                           "attribute in allocate success response";
+    return;
+  }
+
+  const StunUInt32Attribute* lifetime_attr =
+      response->GetUInt32(STUN_ATTR_TURN_LIFETIME);
+  if (!lifetime_attr) {
+    RTC_LOG(LS_WARNING) << port_->ToString()
+                        << ": Missing STUN_ATTR_TURN_LIFETIME attribute in "
+                           "allocate success response";
+    return;
+  }
+  // Notify the port the allocate succeeded, and schedule a refresh request.
+  port_->OnAllocateSuccess(relayed_attr->GetAddress(),
+                           mapped_attr->GetAddress());
+  port_->ScheduleRefresh(lifetime_attr->value());
+}
+
+void TurnAllocateRequest::OnErrorResponse(StunMessage* response) {
+  // Process error response according to RFC5766, Section 6.4.
+  int error_code = response->GetErrorCodeValue();
+
+  RTC_LOG(LS_INFO) << port_->ToString()
+                   << ": Received TURN allocate error response, id="
+                   << rtc::hex_encode(id()) << ", code=" << error_code
+                   << ", rtt=" << Elapsed();
+
+  switch (error_code) {
+    case STUN_ERROR_UNAUTHORIZED:  // Unauthrorized.
+      OnAuthChallenge(response, error_code);
+      break;
+    case STUN_ERROR_TRY_ALTERNATE:
+      OnTryAlternate(response, error_code);
+      break;
+    case STUN_ERROR_ALLOCATION_MISMATCH: {
+      // We must handle this error async because trying to delete the socket in
+      // OnErrorResponse will cause a deadlock on the socket.
+      TurnPort* port = port_;
+      port->thread()->PostTask(SafeTask(
+          port->task_safety_.flag(), [port] { port->OnAllocateMismatch(); }));
+    } break;
+    default:
+      RTC_LOG(LS_WARNING) << port_->ToString()
+                          << ": Received TURN allocate error response, id="
+                          << rtc::hex_encode(id()) << ", code=" << error_code
+                          << ", rtt=" << Elapsed();
+      const StunErrorCodeAttribute* attr = response->GetErrorCode();
+      port_->OnAllocateError(error_code, attr ? attr->reason() : "");
+  }
+}
+
+void TurnAllocateRequest::OnTimeout() {
+  RTC_LOG(LS_WARNING) << port_->ToString() << ": TURN allocate request "
+                      << rtc::hex_encode(id()) << " timeout";
+  port_->OnAllocateRequestTimeout();
+}
+
+void TurnAllocateRequest::OnAuthChallenge(StunMessage* response, int code) {
+  // If we failed to authenticate even after we sent our credentials, fail hard.
+  if (code == STUN_ERROR_UNAUTHORIZED && !port_->hash().empty()) {
+    RTC_LOG(LS_WARNING) << port_->ToString()
+                        << ": Failed to authenticate with the server "
+                           "after challenge.";
+    const StunErrorCodeAttribute* attr = response->GetErrorCode();
+    port_->OnAllocateError(STUN_ERROR_UNAUTHORIZED, attr ? attr->reason() : "");
+    return;
+  }
+
+  // Check the mandatory attributes.
+  const StunByteStringAttribute* realm_attr =
+      response->GetByteString(STUN_ATTR_REALM);
+  if (!realm_attr) {
+    RTC_LOG(LS_WARNING) << port_->ToString()
+                        << ": Missing STUN_ATTR_REALM attribute in "
+                           "allocate unauthorized response.";
+    return;
+  }
+  port_->set_realm(realm_attr->string_view());
+
+  const StunByteStringAttribute* nonce_attr =
+      response->GetByteString(STUN_ATTR_NONCE);
+  if (!nonce_attr) {
+    RTC_LOG(LS_WARNING) << port_->ToString()
+                        << ": Missing STUN_ATTR_NONCE attribute in "
+                           "allocate unauthorized response.";
+    return;
+  }
+  port_->set_nonce(nonce_attr->string_view());
+
+  // Send another allocate request, with the received realm and nonce values.
+  port_->SendRequest(new TurnAllocateRequest(port_), 0);
+}
+
+void TurnAllocateRequest::OnTryAlternate(StunMessage* response, int code) {
+  // According to RFC 5389 section 11, there are use cases where
+  // authentication of response is not possible, we're not validating
+  // message integrity.
+  const StunErrorCodeAttribute* error_code_attr = response->GetErrorCode();
+  // Get the alternate server address attribute value.
+  const StunAddressAttribute* alternate_server_attr =
+      response->GetAddress(STUN_ATTR_ALTERNATE_SERVER);
+  if (!alternate_server_attr) {
+    RTC_LOG(LS_WARNING) << port_->ToString()
+                        << ": Missing STUN_ATTR_ALTERNATE_SERVER "
+                           "attribute in try alternate error response";
+    port_->OnAllocateError(STUN_ERROR_TRY_ALTERNATE,
+                           error_code_attr ? error_code_attr->reason() : "");
+    return;
+  }
+  if (!port_->SetAlternateServer(alternate_server_attr->GetAddress())) {
+    port_->OnAllocateError(STUN_ERROR_TRY_ALTERNATE,
+                           error_code_attr ? error_code_attr->reason() : "");
+    return;
+  }
+
+  // Check the attributes.
+  const StunByteStringAttribute* realm_attr =
+      response->GetByteString(STUN_ATTR_REALM);
+  if (realm_attr) {
+    RTC_LOG(LS_INFO) << port_->ToString()
+                     << ": Applying STUN_ATTR_REALM attribute in "
+                        "try alternate error response.";
+    port_->set_realm(realm_attr->string_view());
+  }
+
+  const StunByteStringAttribute* nonce_attr =
+      response->GetByteString(STUN_ATTR_NONCE);
+  if (nonce_attr) {
+    RTC_LOG(LS_INFO) << port_->ToString()
+                     << ": Applying STUN_ATTR_NONCE attribute in "
+                        "try alternate error response.";
+    port_->set_nonce(nonce_attr->string_view());
+  }
+
+  // For TCP, we can't close the original Tcp socket during handling a 300 as
+  // we're still inside that socket's event handler. Doing so will cause
+  // deadlock.
+  TurnPort* port = port_;
+  port->thread()->PostTask(SafeTask(port->task_safety_.flag(),
+                                    [port] { port->TryAlternateServer(); }));
+}
+
+TurnRefreshRequest::TurnRefreshRequest(TurnPort* port, int lifetime /*= -1*/)
+    : StunRequest(port->request_manager(),
+                  std::make_unique<TurnMessage>(TURN_REFRESH_REQUEST)),
+      port_(port) {
+  StunMessage* message = mutable_msg();
+  // Create the request as indicated in RFC 5766, Section 7.1.
+  // No attributes need to be included.
+  RTC_DCHECK_EQ(message->type(), TURN_REFRESH_REQUEST);
+  if (lifetime > -1) {
+    message->AddAttribute(
+        std::make_unique<StunUInt32Attribute>(STUN_ATTR_LIFETIME, lifetime));
+  }
+
+  port_->AddRequestAuthInfo(message);
+  port_->TurnCustomizerMaybeModifyOutgoingStunMessage(message);
+}
+
+void TurnRefreshRequest::OnSent() {
+  RTC_LOG(LS_INFO) << port_->ToString() << ": TURN refresh request sent, id="
+                   << rtc::hex_encode(id());
+  StunRequest::OnSent();
+}
+
+void TurnRefreshRequest::OnResponse(StunMessage* response) {
+  RTC_LOG(LS_INFO) << port_->ToString()
+                   << ": TURN refresh requested successfully, id="
+                   << rtc::hex_encode(id())
+                   << ", code=0"  // Makes logging easier to parse.
+                      ", rtt="
+                   << Elapsed();
+
+  // Check mandatory attributes as indicated in RFC5766, Section 7.3.
+  const StunUInt32Attribute* lifetime_attr =
+      response->GetUInt32(STUN_ATTR_TURN_LIFETIME);
+  if (!lifetime_attr) {
+    RTC_LOG(LS_WARNING) << port_->ToString()
+                        << ": Missing STUN_ATTR_TURN_LIFETIME attribute in "
+                           "refresh success response.";
+    return;
+  }
+
+  if (lifetime_attr->value() > 0) {
+    // Schedule a refresh based on the returned lifetime value.
+    port_->ScheduleRefresh(lifetime_attr->value());
+  } else {
+    // If we scheduled a refresh with lifetime 0, we're releasing this
+    // allocation; see TurnPort::Release.
+    TurnPort* port = port_;
+    port->thread()->PostTask(
+        SafeTask(port->task_safety_.flag(), [port] { port->Close(); }));
+  }
+
+  if (port_->callbacks_for_test_) {
+    port_->callbacks_for_test_->OnTurnRefreshResult(TURN_SUCCESS_RESULT_CODE);
+  }
+}
+
+void TurnRefreshRequest::OnErrorResponse(StunMessage* response) {
+  int error_code = response->GetErrorCodeValue();
+
+  if (error_code == STUN_ERROR_STALE_NONCE) {
+    if (port_->UpdateNonce(response)) {
+      // Send RefreshRequest immediately.
+      port_->SendRequest(new TurnRefreshRequest(port_), 0);
+    }
+  } else {
+    RTC_LOG(LS_WARNING) << port_->ToString()
+                        << ": Received TURN refresh error response, id="
+                        << rtc::hex_encode(id()) << ", code=" << error_code
+                        << ", rtt=" << Elapsed();
+    port_->OnRefreshError();
+    if (port_->callbacks_for_test_) {
+      port_->callbacks_for_test_->OnTurnRefreshResult(error_code);
+    }
+  }
+}
+
+void TurnRefreshRequest::OnTimeout() {
+  RTC_LOG(LS_WARNING) << port_->ToString() << ": TURN refresh timeout "
+                      << rtc::hex_encode(id());
+  port_->OnRefreshError();
+}
+
+TurnCreatePermissionRequest::TurnCreatePermissionRequest(
+    TurnPort* port,
+    TurnEntry* entry,
+    const rtc::SocketAddress& ext_addr)
+    : StunRequest(
+          port->request_manager(),
+          std::make_unique<TurnMessage>(TURN_CREATE_PERMISSION_REQUEST)),
+      port_(port),
+      entry_(entry),
+      ext_addr_(ext_addr) {
+  RTC_DCHECK(entry_);
+  entry_->destroyed_callback_list_.AddReceiver(this, [this](TurnEntry* entry) {
+    RTC_DCHECK(entry_ == entry);
+    entry_ = nullptr;
+  });
+  StunMessage* message = mutable_msg();
+  // Create the request as indicated in RFC5766, Section 9.1.
+  RTC_DCHECK_EQ(message->type(), TURN_CREATE_PERMISSION_REQUEST);
+  message->AddAttribute(std::make_unique<StunXorAddressAttribute>(
+      STUN_ATTR_XOR_PEER_ADDRESS, ext_addr_));
+  port_->AddRequestAuthInfo(message);
+  port_->TurnCustomizerMaybeModifyOutgoingStunMessage(message);
+}
+
+TurnCreatePermissionRequest::~TurnCreatePermissionRequest() {
+  if (entry_) {
+    entry_->destroyed_callback_list_.RemoveReceivers(this);
+  }
+}
+
+void TurnCreatePermissionRequest::OnSent() {
+  RTC_LOG(LS_INFO) << port_->ToString()
+                   << ": TURN create permission request sent, id="
+                   << rtc::hex_encode(id());
+  StunRequest::OnSent();
+}
+
+void TurnCreatePermissionRequest::OnResponse(StunMessage* response) {
+  RTC_LOG(LS_INFO) << port_->ToString()
+                   << ": TURN permission requested successfully, id="
+                   << rtc::hex_encode(id())
+                   << ", code=0"  // Makes logging easier to parse.
+                      ", rtt="
+                   << Elapsed();
+
+  if (entry_) {
+    entry_->OnCreatePermissionSuccess();
+  }
+}
+
+void TurnCreatePermissionRequest::OnErrorResponse(StunMessage* response) {
+  int error_code = response->GetErrorCodeValue();
+  RTC_LOG(LS_WARNING) << port_->ToString()
+                      << ": Received TURN create permission error response, id="
+                      << rtc::hex_encode(id()) << ", code=" << error_code
+                      << ", rtt=" << Elapsed();
+  if (entry_) {
+    entry_->OnCreatePermissionError(response, error_code);
+  }
+}
+
+void TurnCreatePermissionRequest::OnTimeout() {
+  RTC_LOG(LS_WARNING) << port_->ToString()
+                      << ": TURN create permission timeout "
+                      << rtc::hex_encode(id());
+  if (entry_) {
+    entry_->OnCreatePermissionTimeout();
+  }
+}
+
+TurnChannelBindRequest::TurnChannelBindRequest(
+    TurnPort* port,
+    TurnEntry* entry,
+    int channel_id,
+    const rtc::SocketAddress& ext_addr)
+    : StunRequest(port->request_manager(),
+                  std::make_unique<TurnMessage>(TURN_CHANNEL_BIND_REQUEST)),
+      port_(port),
+      entry_(entry),
+      channel_id_(channel_id),
+      ext_addr_(ext_addr) {
+  RTC_DCHECK(entry_);
+  entry_->destroyed_callback_list_.AddReceiver(this, [this](TurnEntry* entry) {
+    RTC_DCHECK(entry_ == entry);
+    entry_ = nullptr;
+  });
+  StunMessage* message = mutable_msg();
+  // Create the request as indicated in RFC5766, Section 11.1.
+  RTC_DCHECK_EQ(message->type(), TURN_CHANNEL_BIND_REQUEST);
+  message->AddAttribute(std::make_unique<StunUInt32Attribute>(
+      STUN_ATTR_CHANNEL_NUMBER, channel_id_ << 16));
+  message->AddAttribute(std::make_unique<StunXorAddressAttribute>(
+      STUN_ATTR_XOR_PEER_ADDRESS, ext_addr_));
+  port_->AddRequestAuthInfo(message);
+  port_->TurnCustomizerMaybeModifyOutgoingStunMessage(message);
+}
+
+TurnChannelBindRequest::~TurnChannelBindRequest() {
+  if (entry_) {
+    entry_->destroyed_callback_list_.RemoveReceivers(this);
+  }
+}
+
+void TurnChannelBindRequest::OnSent() {
+  RTC_LOG(LS_INFO) << port_->ToString()
+                   << ": TURN channel bind request sent, id="
+                   << rtc::hex_encode(id());
+  StunRequest::OnSent();
+}
+
+void TurnChannelBindRequest::OnResponse(StunMessage* response) {
+  RTC_LOG(LS_INFO) << port_->ToString()
+                   << ": TURN channel bind requested successfully, id="
+                   << rtc::hex_encode(id())
+                   << ", code=0"  // Makes logging easier to parse.
+                      ", rtt="
+                   << Elapsed();
+
+  if (entry_) {
+    entry_->OnChannelBindSuccess();
+    // Refresh the channel binding just under the permission timeout
+    // threshold. The channel binding has a longer lifetime, but
+    // this is the easiest way to keep both the channel and the
+    // permission from expiring.
+    TimeDelta delay = kTurnPermissionTimeout - TimeDelta::Minutes(1);
+    entry_->SendChannelBindRequest(delay.ms());
+    RTC_LOG(LS_INFO) << port_->ToString() << ": Scheduled channel bind in "
+                     << delay.ms() << "ms.";
+  }
+}
+
+void TurnChannelBindRequest::OnErrorResponse(StunMessage* response) {
+  int error_code = response->GetErrorCodeValue();
+  RTC_LOG(LS_WARNING) << port_->ToString()
+                      << ": Received TURN channel bind error response, id="
+                      << rtc::hex_encode(id()) << ", code=" << error_code
+                      << ", rtt=" << Elapsed();
+  if (entry_) {
+    entry_->OnChannelBindError(response, error_code);
+  }
+}
+
+void TurnChannelBindRequest::OnTimeout() {
+  RTC_LOG(LS_WARNING) << port_->ToString() << ": TURN channel bind timeout "
+                      << rtc::hex_encode(id());
+  if (entry_) {
+    entry_->OnChannelBindTimeout();
+  }
+}
+
+TurnEntry::TurnEntry(TurnPort* port, Connection* conn, int channel_id)
+    : port_(port),
+      channel_id_(channel_id),
+      ext_addr_(conn->remote_candidate().address()),
+      state_(STATE_UNBOUND),
+      connections_({conn}) {
+  // Creating permission for `ext_addr_`.
+  SendCreatePermissionRequest(0);
+}
+
+TurnEntry::~TurnEntry() {
+  destroyed_callback_list_.Send(this);
+}
+
+void TurnEntry::TrackConnection(Connection* conn) {
+  RTC_DCHECK(absl::c_find(connections_, conn) == connections_.end());
+  if (connections_.empty()) {
+    task_safety_.reset();
+  }
+  connections_.push_back(conn);
+}
+
+rtc::scoped_refptr<webrtc::PendingTaskSafetyFlag> TurnEntry::UntrackConnection(
+    Connection* conn) {
+  connections_.erase(absl::c_find(connections_, conn));
+  return connections_.empty() ? task_safety_.flag() : nullptr;
+}
+
+void TurnEntry::SendCreatePermissionRequest(int delay) {
+  port_->SendRequest(new TurnCreatePermissionRequest(port_, this, ext_addr_),
+                     delay);
+}
+
+void TurnEntry::SendChannelBindRequest(int delay) {
+  port_->SendRequest(
+      new TurnChannelBindRequest(port_, this, channel_id_, ext_addr_), delay);
+}
+
+int TurnEntry::Send(const void* data,
+                    size_t size,
+                    bool payload,
+                    const rtc::PacketOptions& options) {
+  rtc::ByteBufferWriter buf;
+  if (state_ != STATE_BOUND ||
+      !port_->TurnCustomizerAllowChannelData(data, size, payload)) {
+    // If we haven't bound the channel yet, we have to use a Send Indication.
+    // The turn_customizer_ can also make us use Send Indication.
+    TurnMessage msg(TURN_SEND_INDICATION);
+    msg.AddAttribute(std::make_unique<StunXorAddressAttribute>(
+        STUN_ATTR_XOR_PEER_ADDRESS, ext_addr_));
+    msg.AddAttribute(
+        std::make_unique<StunByteStringAttribute>(STUN_ATTR_DATA, data, size));
+
+    port_->TurnCustomizerMaybeModifyOutgoingStunMessage(&msg);
+
+    const bool success = msg.Write(&buf);
+    RTC_DCHECK(success);
+
+    // If we're sending real data, request a channel bind that we can use later.
+    if (state_ == STATE_UNBOUND && payload) {
+      SendChannelBindRequest(0);
+      state_ = STATE_BINDING;
+    }
+  } else {
+    // If the channel is bound, we can send the data as a Channel Message.
+    buf.WriteUInt16(channel_id_);
+    buf.WriteUInt16(static_cast<uint16_t>(size));
+    buf.WriteBytes(reinterpret_cast<const char*>(data), size);
+  }
+  rtc::PacketOptions modified_options(options);
+  modified_options.info_signaled_after_sent.turn_overhead_bytes =
+      buf.Length() - size;
+  return port_->Send(buf.Data(), buf.Length(), modified_options);
+}
+
+void TurnEntry::OnCreatePermissionSuccess() {
+  RTC_LOG(LS_INFO) << port_->ToString() << ": Create permission for "
+                   << ext_addr_.ToSensitiveString() << " succeeded";
+  if (port_->callbacks_for_test_) {
+    port_->callbacks_for_test_->OnTurnCreatePermissionResult(
+        TURN_SUCCESS_RESULT_CODE);
+  }
+
+  // If `state_` is STATE_BOUND, the permission will be refreshed
+  // by ChannelBindRequest.
+  if (state_ != STATE_BOUND) {
+    // Refresh the permission request about 1 minute before the permission
+    // times out.
+    TimeDelta delay = kTurnPermissionTimeout - TimeDelta::Minutes(1);
+    SendCreatePermissionRequest(delay.ms());
+    RTC_LOG(LS_INFO) << port_->ToString()
+                     << ": Scheduled create-permission-request in "
+                     << delay.ms() << "ms.";
+  }
+}
+
+void TurnEntry::OnCreatePermissionError(StunMessage* response, int code) {
+  if (code == STUN_ERROR_STALE_NONCE) {
+    if (port_->UpdateNonce(response)) {
+      SendCreatePermissionRequest(0);
+    }
+  } else {
+    bool found = port_->FailAndPruneConnection(ext_addr_);
+    if (found) {
+      RTC_LOG(LS_ERROR) << "Received TURN CreatePermission error response, "
+                           "code="
+                        << code << "; pruned connection.";
+    }
+  }
+  if (port_->callbacks_for_test_) {
+    port_->callbacks_for_test_->OnTurnCreatePermissionResult(code);
+  }
+}
+
+void TurnEntry::OnCreatePermissionTimeout() {
+  port_->FailAndPruneConnection(ext_addr_);
+}
+
+void TurnEntry::OnChannelBindSuccess() {
+  RTC_LOG(LS_INFO) << port_->ToString() << ": Successful channel bind for "
+                   << ext_addr_.ToSensitiveString();
+  RTC_DCHECK(state_ == STATE_BINDING || state_ == STATE_BOUND);
+  state_ = STATE_BOUND;
+}
+
+void TurnEntry::OnChannelBindError(StunMessage* response, int code) {
+  // If the channel bind fails due to errors other than STATE_NONCE,
+  // we will fail and prune the connection and rely on ICE restart to
+  // re-establish a new connection if needed.
+  if (code == STUN_ERROR_STALE_NONCE) {
+    if (port_->UpdateNonce(response)) {
+      // Send channel bind request with fresh nonce.
+      SendChannelBindRequest(0);
+    }
+  } else {
+    state_ = STATE_UNBOUND;
+    port_->FailAndPruneConnection(ext_addr_);
+  }
+}
+void TurnEntry::OnChannelBindTimeout() {
+  state_ = STATE_UNBOUND;
+  port_->FailAndPruneConnection(ext_addr_);
+}
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/turn_port.h b/third_party/libwebrtc/p2p/base/turn_port.h
new file mode 100644
index 0000000000..ac660d6599
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/turn_port.h
@@ -0,0 +1,375 @@
+/*
+ *  Copyright 2012 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_TURN_PORT_H_
+#define P2P_BASE_TURN_PORT_H_
+
+#include <stdio.h>
+
+#include <map>
+#include <memory>
+#include <set>
+#include <string>
+#include <vector>
+
+#include "absl/memory/memory.h"
+#include "absl/strings/string_view.h"
+#include "api/async_dns_resolver.h"
+#include "api/task_queue/pending_task_safety_flag.h"
+#include "api/task_queue/task_queue_base.h"
+#include "p2p/base/port.h"
+#include "p2p/client/basic_port_allocator.h"
+#include "rtc_base/async_packet_socket.h"
+#include "rtc_base/ssl_certificate.h"
+
+namespace webrtc {
+class TurnCustomizer;
+}
+
+namespace cricket {
+
+const int kMaxTurnUsernameLength = 509;  // RFC 8489 section 14.3
+
+extern const int STUN_ATTR_TURN_LOGGING_ID;
+extern const char TURN_PORT_TYPE[];
+class TurnAllocateRequest;
+class TurnEntry;
+
+class TurnPort : public Port {
+ public:
+  enum PortState {
+    STATE_CONNECTING,    // Initial state, cannot send any packets.
+    STATE_CONNECTED,     // Socket connected, ready to send stun requests.
+    STATE_READY,         // Received allocate success, can send any packets.
+    STATE_RECEIVEONLY,   // Had REFRESH_REQUEST error, cannot send any packets.
+    STATE_DISCONNECTED,  // TCP connection died, cannot send/receive any
+                         // packets.
+  };
+
+  static bool Validate(const CreateRelayPortArgs& args) {
+    // Do basic parameter validation.
+    if (args.config->credentials.username.size() > kMaxTurnUsernameLength) {
+      RTC_LOG(LS_ERROR) << "Attempt to use TURN with a too long username "
+                        << "of length "
+                        << args.config->credentials.username.size();
+      return false;
+    }
+    // Do not connect to low-numbered ports. The default STUN port is 3478.
+    if (!AllowedTurnPort(args.server_address->address.port(),
+                         args.field_trials)) {
+      RTC_LOG(LS_ERROR) << "Attempt to use TURN to connect to port "
+                        << args.server_address->address.port();
+      return false;
+    }
+    return true;
+  }
+
+  // Create a TURN port using the shared UDP socket, `socket`.
+  static std::unique_ptr<TurnPort> Create(const CreateRelayPortArgs& args,
+                                          rtc::AsyncPacketSocket* socket) {
+    if (!Validate(args)) {
+      return nullptr;
+    }
+    // Using `new` to access a non-public constructor.
+    return absl::WrapUnique(
+        new TurnPort(args.network_thread, args.socket_factory, args.network,
+                     socket, args.username, args.password, *args.server_address,
+                     args.config->credentials, args.relative_priority,
+                     args.config->tls_alpn_protocols,
+                     args.config->tls_elliptic_curves, args.turn_customizer,
+                     args.config->tls_cert_verifier, args.field_trials));
+  }
+
+  // Create a TURN port that will use a new socket, bound to `network` and
+  // using a port in the range between `min_port` and `max_port`.
+  static std::unique_ptr<TurnPort> Create(const CreateRelayPortArgs& args,
+                                          int min_port,
+                                          int max_port) {
+    if (!Validate(args)) {
+      return nullptr;
+    }
+    // Using `new` to access a non-public constructor.
+    return absl::WrapUnique(
+        new TurnPort(args.network_thread, args.socket_factory, args.network,
+                     min_port, max_port, args.username, args.password,
+                     *args.server_address, args.config->credentials,
+                     args.relative_priority, args.config->tls_alpn_protocols,
+                     args.config->tls_elliptic_curves, args.turn_customizer,
+                     args.config->tls_cert_verifier, args.field_trials));
+  }
+
+  ~TurnPort() override;
+
+  const ProtocolAddress& server_address() const { return server_address_; }
+  // Returns an empty address if the local address has not been assigned.
+  rtc::SocketAddress GetLocalAddress() const;
+
+  bool ready() const { return state_ == STATE_READY; }
+  bool connected() const {
+    return state_ == STATE_READY || state_ == STATE_CONNECTED;
+  }
+  const RelayCredentials& credentials() const { return credentials_; }
+
+  ProtocolType GetProtocol() const override;
+
+  virtual TlsCertPolicy GetTlsCertPolicy() const;
+  virtual void SetTlsCertPolicy(TlsCertPolicy tls_cert_policy);
+
+  void SetTurnLoggingId(absl::string_view turn_logging_id);
+
+  virtual std::vector<std::string> GetTlsAlpnProtocols() const;
+  virtual std::vector<std::string> GetTlsEllipticCurves() const;
+
+  // Release a TURN allocation by sending a refresh with lifetime 0.
+  // Sets state to STATE_RECEIVEONLY.
+  void Release();
+
+  void PrepareAddress() override;
+  Connection* CreateConnection(const Candidate& c,
+                               PortInterface::CandidateOrigin origin) override;
+  int SendTo(const void* data,
+             size_t size,
+             const rtc::SocketAddress& addr,
+             const rtc::PacketOptions& options,
+             bool payload) override;
+  int SetOption(rtc::Socket::Option opt, int value) override;
+  int GetOption(rtc::Socket::Option opt, int* value) override;
+  int GetError() override;
+
+  bool HandleIncomingPacket(rtc::AsyncPacketSocket* socket,
+                            const char* data,
+                            size_t size,
+                            const rtc::SocketAddress& remote_addr,
+                            int64_t packet_time_us) override;
+  bool CanHandleIncomingPacketsFrom(
+      const rtc::SocketAddress& addr) const override;
+
+  // Checks if a connection exists for `addr` before forwarding the call to
+  // the base class.
+  void SendBindingErrorResponse(StunMessage* message,
+                                const rtc::SocketAddress& addr,
+                                int error_code,
+                                absl::string_view reason) override;
+
+  virtual void OnReadPacket(rtc::AsyncPacketSocket* socket,
+                            const char* data,
+                            size_t size,
+                            const rtc::SocketAddress& remote_addr,
+                            const int64_t& packet_time_us);
+
+  void OnSentPacket(rtc::AsyncPacketSocket* socket,
+                    const rtc::SentPacket& sent_packet) override;
+  virtual void OnReadyToSend(rtc::AsyncPacketSocket* socket);
+  bool SupportsProtocol(absl::string_view protocol) const override;
+
+  void OnSocketConnect(rtc::AsyncPacketSocket* socket);
+  void OnSocketClose(rtc::AsyncPacketSocket* socket, int error);
+
+  const std::string& hash() const { return hash_; }
+  const std::string& nonce() const { return nonce_; }
+
+  int error() const { return error_; }
+
+  void OnAllocateMismatch();
+
+  rtc::AsyncPacketSocket* socket() const { return socket_; }
+  StunRequestManager& request_manager() { return request_manager_; }
+
+  bool HasRequests() { return !request_manager_.empty(); }
+  void set_credentials(const RelayCredentials& credentials) {
+    credentials_ = credentials;
+  }
+  // Finds the turn entry with `address` and sets its channel id.
+  // Returns true if the entry is found.
+  bool SetEntryChannelId(const rtc::SocketAddress& address, int channel_id);
+
+  void HandleConnectionDestroyed(Connection* conn) override;
+
+  void CloseForTest() { Close(); }
+
+  // TODO(solenberg): Tests should be refactored to not peek at internal state.
+  class CallbacksForTest {
+   public:
+    virtual ~CallbacksForTest() {}
+    virtual void OnTurnCreatePermissionResult(int code) = 0;
+    virtual void OnTurnRefreshResult(int code) = 0;
+    virtual void OnTurnPortClosed() = 0;
+  };
+  void SetCallbacksForTest(CallbacksForTest* callbacks);
+
+ protected:
+  TurnPort(webrtc::TaskQueueBase* thread,
+           rtc::PacketSocketFactory* factory,
+           const rtc::Network* network,
+           rtc::AsyncPacketSocket* socket,
+           absl::string_view username,
+           absl::string_view password,
+           const ProtocolAddress& server_address,
+           const RelayCredentials& credentials,
+           int server_priority,
+           const std::vector<std::string>& tls_alpn_protocols,
+           const std::vector<std::string>& tls_elliptic_curves,
+           webrtc::TurnCustomizer* customizer,
+           rtc::SSLCertificateVerifier* tls_cert_verifier = nullptr,
+           const webrtc::FieldTrialsView* field_trials = nullptr);
+
+  TurnPort(webrtc::TaskQueueBase* thread,
+           rtc::PacketSocketFactory* factory,
+           const rtc::Network* network,
+           uint16_t min_port,
+           uint16_t max_port,
+           absl::string_view username,
+           absl::string_view password,
+           const ProtocolAddress& server_address,
+           const RelayCredentials& credentials,
+           int server_priority,
+           const std::vector<std::string>& tls_alpn_protocols,
+           const std::vector<std::string>& tls_elliptic_curves,
+           webrtc::TurnCustomizer* customizer,
+           rtc::SSLCertificateVerifier* tls_cert_verifier = nullptr,
+           const webrtc::FieldTrialsView* field_trials = nullptr);
+
+  // NOTE: This method needs to be accessible for StunPort
+  // return true if entry was created (i.e channel_number consumed).
+  bool CreateOrRefreshEntry(Connection* conn, int channel_number);
+
+  rtc::DiffServCodePoint StunDscpValue() const override;
+
+  // Shuts down the turn port, frees requests and deletes connections.
+  void Close();
+
+ private:
+  typedef std::map<rtc::Socket::Option, int> SocketOptionsMap;
+  typedef std::set<rtc::SocketAddress> AttemptedServerSet;
+
+  static bool AllowedTurnPort(int port,
+                              const webrtc::FieldTrialsView* field_trials);
+  void TryAlternateServer();
+
+  bool CreateTurnClientSocket();
+
+  void set_nonce(absl::string_view nonce) { nonce_ = std::string(nonce); }
+  void set_realm(absl::string_view realm) {
+    if (realm != realm_) {
+      realm_ = std::string(realm);
+      UpdateHash();
+    }
+  }
+
+  void OnRefreshError();
+  void HandleRefreshError();
+  bool SetAlternateServer(const rtc::SocketAddress& address);
+  void ResolveTurnAddress(const rtc::SocketAddress& address);
+  void OnResolveResult(rtc::AsyncResolverInterface* resolver);
+
+  void AddRequestAuthInfo(StunMessage* msg);
+  void OnSendStunPacket(const void* data, size_t size, StunRequest* request);
+  // Stun address from allocate success response.
+  // Currently used only for testing.
+  void OnStunAddress(const rtc::SocketAddress& address);
+  void OnAllocateSuccess(const rtc::SocketAddress& address,
+                         const rtc::SocketAddress& stun_address);
+  void OnAllocateError(int error_code, absl::string_view reason);
+  void OnAllocateRequestTimeout();
+
+  void HandleDataIndication(const char* data,
+                            size_t size,
+                            int64_t packet_time_us);
+  void HandleChannelData(int channel_id,
+                         const char* data,
+                         size_t size,
+                         int64_t packet_time_us);
+  void DispatchPacket(const char* data,
+                      size_t size,
+                      const rtc::SocketAddress& remote_addr,
+                      ProtocolType proto,
+                      int64_t packet_time_us);
+
+  bool ScheduleRefresh(uint32_t lifetime);
+  void SendRequest(StunRequest* request, int delay);
+  int Send(const void* data, size_t size, const rtc::PacketOptions& options);
+  void UpdateHash();
+  bool UpdateNonce(StunMessage* response);
+  void ResetNonce();
+
+  bool HasPermission(const rtc::IPAddress& ipaddr) const;
+  TurnEntry* FindEntry(const rtc::SocketAddress& address) const;
+  TurnEntry* FindEntry(int channel_id) const;
+
+  // Marks the connection with remote address `address` failed and
+  // pruned (a.k.a. write-timed-out). Returns true if a connection is found.
+  bool FailAndPruneConnection(const rtc::SocketAddress& address);
+
+  // Reconstruct the URL of the server which the candidate is gathered from.
+  std::string ReconstructedServerUrl();
+
+  void MaybeAddTurnLoggingId(StunMessage* message);
+
+  void TurnCustomizerMaybeModifyOutgoingStunMessage(StunMessage* message);
+  bool TurnCustomizerAllowChannelData(const void* data,
+                                      size_t size,
+                                      bool payload);
+
+  ProtocolAddress server_address_;
+  TlsCertPolicy tls_cert_policy_ = TlsCertPolicy::TLS_CERT_POLICY_SECURE;
+  std::vector<std::string> tls_alpn_protocols_;
+  std::vector<std::string> tls_elliptic_curves_;
+  rtc::SSLCertificateVerifier* tls_cert_verifier_;
+  RelayCredentials credentials_;
+  AttemptedServerSet attempted_server_addresses_;
+
+  rtc::AsyncPacketSocket* socket_;
+  SocketOptionsMap socket_options_;
+  std::unique_ptr<webrtc::AsyncDnsResolverInterface> resolver_;
+  int error_;
+  rtc::DiffServCodePoint stun_dscp_value_;
+
+  StunRequestManager request_manager_;
+  std::string realm_;  // From 401/438 response message.
+  std::string nonce_;  // From 401/438 response message.
+  std::string hash_;   // Digest of username:realm:password
+
+  int next_channel_number_;
+  std::vector<std::unique_ptr<TurnEntry>> entries_;
+
+  PortState state_;
+  // By default the value will be set to 0. This value will be used in
+  // calculating the candidate priority.
+  int server_priority_;
+
+  // The number of retries made due to allocate mismatch error.
+  size_t allocate_mismatch_retries_;
+
+  // Optional TurnCustomizer that can modify outgoing messages. Once set, this
+  // must outlive the TurnPort's lifetime.
+  webrtc::TurnCustomizer* turn_customizer_ = nullptr;
+
+  // Optional TurnLoggingId.
+  // An identifier set by application that is added to TURN_ALLOCATE_REQUEST
+  // and can be used to match client/backend logs.
+  // TODO(jonaso): This should really be initialized in constructor,
+  // but that is currently so terrible. Fix once constructor is changed
+  // to be more easy to work with.
+  std::string turn_logging_id_;
+
+  webrtc::ScopedTaskSafety task_safety_;
+
+  CallbacksForTest* callbacks_for_test_ = nullptr;
+
+  friend class TurnEntry;
+  friend class TurnAllocateRequest;
+  friend class TurnRefreshRequest;
+  friend class TurnCreatePermissionRequest;
+  friend class TurnChannelBindRequest;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_TURN_PORT_H_
diff --git a/third_party/libwebrtc/p2p/base/turn_port_unittest.cc b/third_party/libwebrtc/p2p/base/turn_port_unittest.cc
new file mode 100644
index 0000000000..d63dd4a75c
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/turn_port_unittest.cc
@@ -0,0 +1,2026 @@
+/*
+ *  Copyright 2012 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+#if defined(WEBRTC_POSIX)
+#include <dirent.h>
+
+#include "absl/strings/string_view.h"
+#endif
+
+#include <list>
+#include <memory>
+#include <utility>
+#include <vector>
+
+#include "absl/types/optional.h"
+#include "api/units/time_delta.h"
+#include "p2p/base/basic_packet_socket_factory.h"
+#include "p2p/base/connection.h"
+#include "p2p/base/mock_dns_resolving_packet_socket_factory.h"
+#include "p2p/base/p2p_constants.h"
+#include "p2p/base/port_allocator.h"
+#include "p2p/base/stun_port.h"
+#include "p2p/base/test_turn_customizer.h"
+#include "p2p/base/test_turn_server.h"
+#include "p2p/base/transport_description.h"
+#include "p2p/base/turn_port.h"
+#include "p2p/base/turn_server.h"
+#include "rtc_base/buffer.h"
+#include "rtc_base/byte_buffer.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/fake_clock.h"
+#include "rtc_base/gunit.h"
+#include "rtc_base/net_helper.h"
+#include "rtc_base/socket.h"
+#include "rtc_base/socket_address.h"
+#include "rtc_base/thread.h"
+#include "rtc_base/time_utils.h"
+#include "rtc_base/virtual_socket_server.h"
+#include "test/gtest.h"
+#include "test/scoped_key_value_config.h"
+
+namespace {
+using rtc::SocketAddress;
+
+using ::testing::_;
+using ::testing::DoAll;
+using ::testing::InvokeArgument;
+using ::testing::Return;
+using ::testing::ReturnPointee;
+using ::testing::SetArgPointee;
+
+static const SocketAddress kLocalAddr1("11.11.11.11", 0);
+static const SocketAddress kLocalAddr2("22.22.22.22", 0);
+static const SocketAddress kLocalIPv6Addr("2401:fa00:4:1000:be30:5bff:fee5:c3",
+                                          0);
+static const SocketAddress kLocalIPv6Addr2("2401:fa00:4:2000:be30:5bff:fee5:d4",
+                                           0);
+static const SocketAddress kTurnUdpIntAddr("99.99.99.3",
+                                           cricket::TURN_SERVER_PORT);
+static const SocketAddress kTurnTcpIntAddr("99.99.99.4",
+                                           cricket::TURN_SERVER_PORT);
+static const SocketAddress kTurnUdpExtAddr("99.99.99.5", 0);
+static const SocketAddress kTurnAlternateIntAddr("99.99.99.6",
+                                                 cricket::TURN_SERVER_PORT);
+// Port for redirecting to a TCP Web server. Should not work.
+static const SocketAddress kTurnDangerousAddr("99.99.99.7", 81);
+// Port 53 (the DNS port); should work.
+static const SocketAddress kTurnPort53Addr("99.99.99.7", 53);
+// Port 80 (the HTTP port); should work.
+static const SocketAddress kTurnPort80Addr("99.99.99.7", 80);
+// Port 443 (the HTTPS port); should work.
+static const SocketAddress kTurnPort443Addr("99.99.99.7", 443);
+// The default TURN server port.
+static const SocketAddress kTurnIntAddr("99.99.99.7",
+                                        cricket::TURN_SERVER_PORT);
+static const SocketAddress kTurnIPv6IntAddr(
+    "2400:4030:2:2c00:be30:abcd:efab:cdef",
+    cricket::TURN_SERVER_PORT);
+static const SocketAddress kTurnUdpIPv6IntAddr(
+    "2400:4030:1:2c00:be30:abcd:efab:cdef",
+    cricket::TURN_SERVER_PORT);
+static const SocketAddress kTurnInvalidAddr("www.google.invalid.", 3478);
+static const SocketAddress kTurnValidAddr("www.google.valid.", 3478);
+
+static const char kCandidateFoundation[] = "foundation";
+static const char kIceUfrag1[] = "TESTICEUFRAG0001";
+static const char kIceUfrag2[] = "TESTICEUFRAG0002";
+static const char kIcePwd1[] = "TESTICEPWD00000000000001";
+static const char kIcePwd2[] = "TESTICEPWD00000000000002";
+static const char kTurnUsername[] = "test";
+static const char kTurnPassword[] = "test";
+// This test configures the virtual socket server to simulate delay so that we
+// can verify operations take no more than the expected number of round trips.
+static constexpr unsigned int kSimulatedRtt = 50;
+// Connection destruction may happen asynchronously, but it should only
+// take one simulated clock tick.
+static constexpr unsigned int kConnectionDestructionDelay = 1;
+// This used to be 1 second, but that's not always enough for getaddrinfo().
+// See: https://bugs.chromium.org/p/webrtc/issues/detail?id=5191
+static constexpr unsigned int kResolverTimeout = 10000;
+
+constexpr uint64_t kTiebreakerDefault = 44444;
+
+static const cricket::ProtocolAddress kTurnUdpProtoAddr(kTurnUdpIntAddr,
+                                                        cricket::PROTO_UDP);
+static const cricket::ProtocolAddress kTurnTcpProtoAddr(kTurnTcpIntAddr,
+                                                        cricket::PROTO_TCP);
+static const cricket::ProtocolAddress kTurnTlsProtoAddr(kTurnTcpIntAddr,
+                                                        cricket::PROTO_TLS);
+static const cricket::ProtocolAddress kTurnUdpIPv6ProtoAddr(kTurnUdpIPv6IntAddr,
+                                                            cricket::PROTO_UDP);
+static const cricket::ProtocolAddress kTurnDangerousProtoAddr(
+    kTurnDangerousAddr,
+    cricket::PROTO_TCP);
+static const cricket::ProtocolAddress kTurnPort53ProtoAddr(kTurnPort53Addr,
+                                                           cricket::PROTO_TCP);
+static const cricket::ProtocolAddress kTurnPort80ProtoAddr(kTurnPort80Addr,
+                                                           cricket::PROTO_TCP);
+static const cricket::ProtocolAddress kTurnPort443ProtoAddr(kTurnPort443Addr,
+                                                            cricket::PROTO_TCP);
+static const cricket::ProtocolAddress kTurnPortInvalidHostnameProtoAddr(
+    kTurnInvalidAddr,
+    cricket::PROTO_UDP);
+static const cricket::ProtocolAddress kTurnPortValidHostnameProtoAddr(
+    kTurnValidAddr,
+    cricket::PROTO_UDP);
+
+#if defined(WEBRTC_LINUX) && !defined(WEBRTC_ANDROID)
+static int GetFDCount() {
+  struct dirent* dp;
+  int fd_count = 0;
+  DIR* dir = opendir("/proc/self/fd/");
+  while ((dp = readdir(dir)) != NULL) {
+    if (dp->d_name[0] == '.')
+      continue;
+    ++fd_count;
+  }
+  closedir(dir);
+  return fd_count;
+}
+#endif
+
+}  // unnamed namespace
+
+namespace cricket {
+
+class TurnPortTestVirtualSocketServer : public rtc::VirtualSocketServer {
+ public:
+  TurnPortTestVirtualSocketServer() {
+    // This configures the virtual socket server to always add a simulated
+    // delay of exactly half of kSimulatedRtt.
+    set_delay_mean(kSimulatedRtt / 2);
+    UpdateDelayDistribution();
+  }
+
+  using rtc::VirtualSocketServer::LookupBinding;
+};
+
+class TestConnectionWrapper : public sigslot::has_slots<> {
+ public:
+  explicit TestConnectionWrapper(Connection* conn) : connection_(conn) {
+    conn->SignalDestroyed.connect(
+        this, &TestConnectionWrapper::OnConnectionDestroyed);
+  }
+
+  ~TestConnectionWrapper() {
+    if (connection_) {
+      connection_->SignalDestroyed.disconnect(this);
+    }
+  }
+
+  Connection* connection() { return connection_; }
+
+ private:
+  void OnConnectionDestroyed(Connection* conn) {
+    ASSERT_TRUE(conn == connection_);
+    connection_ = nullptr;
+  }
+
+  Connection* connection_;
+};
+
+// Note: This test uses a fake clock with a simulated network round trip
+// (between local port and TURN server) of kSimulatedRtt.
+class TurnPortTest : public ::testing::Test,
+                     public TurnPort::CallbacksForTest,
+                     public sigslot::has_slots<> {
+ public:
+  TurnPortTest()
+      : ss_(new TurnPortTestVirtualSocketServer()),
+        main_(ss_.get()),
+        turn_server_(&main_, ss_.get(), kTurnUdpIntAddr, kTurnUdpExtAddr),
+        socket_factory_(ss_.get()) {
+    // Some code uses "last received time == 0" to represent "nothing received
+    // so far", so we need to start the fake clock at a nonzero time...
+    // TODO(deadbeef): Fix this.
+    fake_clock_.AdvanceTime(webrtc::TimeDelta::Seconds(1));
+  }
+
+  void OnTurnPortComplete(Port* port) { turn_ready_ = true; }
+  void OnTurnPortError(Port* port) { turn_error_ = true; }
+  void OnCandidateError(Port* port,
+                        const cricket::IceCandidateErrorEvent& event) {
+    error_event_ = event;
+  }
+  void OnTurnUnknownAddress(PortInterface* port,
+                            const SocketAddress& addr,
+                            ProtocolType proto,
+                            IceMessage* msg,
+                            const std::string& rf,
+                            bool /*port_muxed*/) {
+    turn_unknown_address_ = true;
+  }
+  void OnTurnReadPacket(Connection* conn,
+                        const char* data,
+                        size_t size,
+                        int64_t packet_time_us) {
+    turn_packets_.push_back(rtc::Buffer(data, size));
+  }
+  void OnUdpPortComplete(Port* port) { udp_ready_ = true; }
+  void OnUdpReadPacket(Connection* conn,
+                       const char* data,
+                       size_t size,
+                       int64_t packet_time_us) {
+    udp_packets_.push_back(rtc::Buffer(data, size));
+  }
+  void OnSocketReadPacket(rtc::AsyncPacketSocket* socket,
+                          const char* data,
+                          size_t size,
+                          const rtc::SocketAddress& remote_addr,
+                          const int64_t& packet_time_us) {
+    turn_port_->HandleIncomingPacket(socket, data, size, remote_addr,
+                                     packet_time_us);
+  }
+  void OnTurnPortDestroyed(PortInterface* port) { turn_port_destroyed_ = true; }
+
+  // TurnPort::TestCallbacks
+  void OnTurnCreatePermissionResult(int code) override {
+    turn_create_permission_success_ = (code == 0);
+  }
+  void OnTurnRefreshResult(int code) override {
+    turn_refresh_success_ = (code == 0);
+  }
+  void OnTurnPortClosed() override { turn_port_closed_ = true; }
+
+  rtc::Socket* CreateServerSocket(const SocketAddress addr) {
+    rtc::Socket* socket = ss_->CreateSocket(AF_INET, SOCK_STREAM);
+    EXPECT_GE(socket->Bind(addr), 0);
+    EXPECT_GE(socket->Listen(5), 0);
+    return socket;
+  }
+
+  rtc::Network* MakeNetwork(const SocketAddress& addr) {
+    networks_.emplace_back("unittest", "unittest", addr.ipaddr(), 32);
+    networks_.back().AddIP(addr.ipaddr());
+    return &networks_.back();
+  }
+
+  bool CreateTurnPort(absl::string_view username,
+                      absl::string_view password,
+                      const ProtocolAddress& server_address) {
+    return CreateTurnPortWithAllParams(MakeNetwork(kLocalAddr1), username,
+                                       password, server_address);
+  }
+  bool CreateTurnPort(const rtc::SocketAddress& local_address,
+                      absl::string_view username,
+                      absl::string_view password,
+                      const ProtocolAddress& server_address) {
+    return CreateTurnPortWithAllParams(MakeNetwork(local_address), username,
+                                       password, server_address);
+  }
+
+  bool CreateTurnPortWithNetwork(const rtc::Network* network,
+                                 absl::string_view username,
+                                 absl::string_view password,
+                                 const ProtocolAddress& server_address) {
+    return CreateTurnPortWithAllParams(network, username, password,
+                                       server_address);
+  }
+
+  // Version of CreateTurnPort that takes all possible parameters; all other
+  // helper methods call this, such that "SetIceRole" and "ConnectSignals" (and
+  // possibly other things in the future) only happen in one place.
+  bool CreateTurnPortWithAllParams(const rtc::Network* network,
+                                   absl::string_view username,
+                                   absl::string_view password,
+                                   const ProtocolAddress& server_address) {
+    RelayServerConfig config;
+    config.credentials = RelayCredentials(username, password);
+    CreateRelayPortArgs args;
+    args.network_thread = &main_;
+    args.socket_factory = socket_factory();
+    args.network = network;
+    args.username = kIceUfrag1;
+    args.password = kIcePwd1;
+    args.server_address = &server_address;
+    args.config = &config;
+    args.turn_customizer = turn_customizer_.get();
+    args.field_trials = &field_trials_;
+
+    turn_port_ = TurnPort::Create(args, 0, 0);
+    if (!turn_port_) {
+      return false;
+    }
+    // This TURN port will be the controlling.
+    turn_port_->SetIceRole(ICEROLE_CONTROLLING);
+    turn_port_->SetIceTiebreaker(kTiebreakerDefault);
+    ConnectSignals();
+
+    if (server_address.proto == cricket::PROTO_TLS) {
+      // The test TURN server has a self-signed certificate so will not pass
+      // the normal client validation. Instruct the client to ignore certificate
+      // errors for testing only.
+      turn_port_->SetTlsCertPolicy(
+          TlsCertPolicy::TLS_CERT_POLICY_INSECURE_NO_CHECK);
+    }
+    return true;
+  }
+
+  void CreateSharedTurnPort(absl::string_view username,
+                            absl::string_view password,
+                            const ProtocolAddress& server_address) {
+    RTC_CHECK(server_address.proto == PROTO_UDP);
+
+    if (!socket_) {
+      socket_.reset(socket_factory()->CreateUdpSocket(
+          rtc::SocketAddress(kLocalAddr1.ipaddr(), 0), 0, 0));
+      ASSERT_TRUE(socket_ != NULL);
+      socket_->SignalReadPacket.connect(this,
+                                        &TurnPortTest::OnSocketReadPacket);
+    }
+
+    RelayServerConfig config;
+    config.credentials = RelayCredentials(username, password);
+    CreateRelayPortArgs args;
+    args.network_thread = &main_;
+    args.socket_factory = socket_factory();
+    args.network = MakeNetwork(kLocalAddr1);
+    args.username = kIceUfrag1;
+    args.password = kIcePwd1;
+    args.server_address = &server_address;
+    args.config = &config;
+    args.turn_customizer = turn_customizer_.get();
+    args.field_trials = &field_trials_;
+    turn_port_ = TurnPort::Create(args, socket_.get());
+    // This TURN port will be the controlling.
+    turn_port_->SetIceRole(ICEROLE_CONTROLLING);
+    turn_port_->SetIceTiebreaker(kTiebreakerDefault);
+    ConnectSignals();
+  }
+
+  void ConnectSignals() {
+    turn_port_->SignalPortComplete.connect(this,
+                                           &TurnPortTest::OnTurnPortComplete);
+    turn_port_->SignalPortError.connect(this, &TurnPortTest::OnTurnPortError);
+    turn_port_->SignalCandidateError.connect(this,
+                                             &TurnPortTest::OnCandidateError);
+    turn_port_->SignalUnknownAddress.connect(
+        this, &TurnPortTest::OnTurnUnknownAddress);
+    turn_port_->SubscribePortDestroyed(
+        [this](PortInterface* port) { OnTurnPortDestroyed(port); });
+    turn_port_->SetCallbacksForTest(this);
+  }
+
+  void CreateUdpPort() { CreateUdpPort(kLocalAddr2); }
+
+  void CreateUdpPort(const SocketAddress& address) {
+    udp_port_ = UDPPort::Create(&main_, socket_factory(), MakeNetwork(address),
+                                0, 0, kIceUfrag2, kIcePwd2, false,
+                                absl::nullopt, &field_trials_);
+    // UDP port will be controlled.
+    udp_port_->SetIceRole(ICEROLE_CONTROLLED);
+    udp_port_->SetIceTiebreaker(kTiebreakerDefault);
+    udp_port_->SignalPortComplete.connect(this,
+                                          &TurnPortTest::OnUdpPortComplete);
+  }
+
+  void PrepareTurnAndUdpPorts(ProtocolType protocol_type) {
+    // turn_port_ should have been created.
+    ASSERT_TRUE(turn_port_ != nullptr);
+    turn_port_->PrepareAddress();
+    ASSERT_TRUE_SIMULATED_WAIT(
+        turn_ready_, TimeToGetTurnCandidate(protocol_type), fake_clock_);
+
+    CreateUdpPort();
+    udp_port_->PrepareAddress();
+    ASSERT_TRUE_SIMULATED_WAIT(udp_ready_, kSimulatedRtt, fake_clock_);
+  }
+
+  // Returns the fake clock time to establish a connection over the given
+  // protocol.
+  int TimeToConnect(ProtocolType protocol_type) {
+    switch (protocol_type) {
+      case PROTO_TCP:
+        // The virtual socket server will delay by a fixed half a round trip
+        // for a TCP connection.
+        return kSimulatedRtt / 2;
+      case PROTO_TLS:
+        // TLS operates over TCP and additionally has a round of HELLO for
+        // negotiating ciphers and a round for exchanging certificates.
+        return 2 * kSimulatedRtt + TimeToConnect(PROTO_TCP);
+      case PROTO_UDP:
+      default:
+        // UDP requires no round trips to set up the connection.
+        return 0;
+    }
+  }
+
+  // Returns the total fake clock time to establish a connection with a TURN
+  // server over the given protocol and to allocate a TURN candidate.
+  int TimeToGetTurnCandidate(ProtocolType protocol_type) {
+    // For a simple allocation, the first Allocate message will return with an
+    // error asking for credentials and will succeed after the second Allocate
+    // message.
+    return 2 * kSimulatedRtt + TimeToConnect(protocol_type);
+  }
+
+  // Total fake clock time to do the following:
+  // 1. Connect to primary TURN server
+  // 2. Send Allocate and receive a redirect from the primary TURN server
+  // 3. Connect to alternate TURN server
+  // 4. Send Allocate and receive a request for credentials
+  // 5. Send Allocate with credentials and receive allocation
+  int TimeToGetAlternateTurnCandidate(ProtocolType protocol_type) {
+    return 3 * kSimulatedRtt + 2 * TimeToConnect(protocol_type);
+  }
+
+  bool CheckConnectionFailedAndPruned(Connection* conn) {
+    return conn && !conn->active() &&
+           conn->state() == IceCandidatePairState::FAILED;
+  }
+
+  // Checks that `turn_port_` has a nonempty set of connections and they are all
+  // failed and pruned.
+  bool CheckAllConnectionsFailedAndPruned() {
+    auto& connections = turn_port_->connections();
+    if (connections.empty()) {
+      return false;
+    }
+    for (const auto& kv : connections) {
+      if (!CheckConnectionFailedAndPruned(kv.second)) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  void TestTurnAllocateSucceeds(unsigned int timeout) {
+    ASSERT_TRUE(turn_port_);
+    turn_port_->PrepareAddress();
+    EXPECT_TRUE_SIMULATED_WAIT(turn_ready_, timeout, fake_clock_);
+    ASSERT_EQ(1U, turn_port_->Candidates().size());
+    EXPECT_EQ(kTurnUdpExtAddr.ipaddr(),
+              turn_port_->Candidates()[0].address().ipaddr());
+    EXPECT_NE(0, turn_port_->Candidates()[0].address().port());
+  }
+
+  void TestReconstructedServerUrl(ProtocolType protocol_type,
+                                  absl::string_view expected_url) {
+    ASSERT_TRUE(turn_port_);
+    turn_port_->PrepareAddress();
+    ASSERT_TRUE_SIMULATED_WAIT(
+        turn_ready_, TimeToGetTurnCandidate(protocol_type), fake_clock_);
+    ASSERT_EQ(1U, turn_port_->Candidates().size());
+    EXPECT_EQ(turn_port_->Candidates()[0].url(), expected_url);
+  }
+
+  void TestTurnAlternateServer(ProtocolType protocol_type) {
+    std::vector<rtc::SocketAddress> redirect_addresses;
+    redirect_addresses.push_back(kTurnAlternateIntAddr);
+
+    TestTurnRedirector redirector(redirect_addresses);
+
+    turn_server_.AddInternalSocket(kTurnIntAddr, protocol_type);
+    turn_server_.AddInternalSocket(kTurnAlternateIntAddr, protocol_type);
+    turn_server_.set_redirect_hook(&redirector);
+    CreateTurnPort(kTurnUsername, kTurnPassword,
+                   ProtocolAddress(kTurnIntAddr, protocol_type));
+
+    // Retrieve the address before we run the state machine.
+    const SocketAddress old_addr = turn_port_->server_address().address;
+
+    turn_port_->PrepareAddress();
+    EXPECT_TRUE_SIMULATED_WAIT(turn_ready_,
+                               TimeToGetAlternateTurnCandidate(protocol_type),
+                               fake_clock_);
+    // Retrieve the address again, the turn port's address should be
+    // changed.
+    const SocketAddress new_addr = turn_port_->server_address().address;
+    EXPECT_NE(old_addr, new_addr);
+    ASSERT_EQ(1U, turn_port_->Candidates().size());
+    EXPECT_EQ(kTurnUdpExtAddr.ipaddr(),
+              turn_port_->Candidates()[0].address().ipaddr());
+    EXPECT_NE(0, turn_port_->Candidates()[0].address().port());
+  }
+
+  void TestTurnAlternateServerV4toV6(ProtocolType protocol_type) {
+    std::vector<rtc::SocketAddress> redirect_addresses;
+    redirect_addresses.push_back(kTurnIPv6IntAddr);
+
+    TestTurnRedirector redirector(redirect_addresses);
+    turn_server_.AddInternalSocket(kTurnIntAddr, protocol_type);
+    turn_server_.set_redirect_hook(&redirector);
+    CreateTurnPort(kTurnUsername, kTurnPassword,
+                   ProtocolAddress(kTurnIntAddr, protocol_type));
+    turn_port_->PrepareAddress();
+    // Need time to connect to TURN server, send Allocate request and receive
+    // redirect notice.
+    EXPECT_TRUE_SIMULATED_WAIT(
+        turn_error_, kSimulatedRtt + TimeToConnect(protocol_type), fake_clock_);
+  }
+
+  void TestTurnAlternateServerPingPong(ProtocolType protocol_type) {
+    std::vector<rtc::SocketAddress> redirect_addresses;
+    redirect_addresses.push_back(kTurnAlternateIntAddr);
+    redirect_addresses.push_back(kTurnIntAddr);
+
+    TestTurnRedirector redirector(redirect_addresses);
+
+    turn_server_.AddInternalSocket(kTurnIntAddr, protocol_type);
+    turn_server_.AddInternalSocket(kTurnAlternateIntAddr, protocol_type);
+    turn_server_.set_redirect_hook(&redirector);
+    CreateTurnPort(kTurnUsername, kTurnPassword,
+                   ProtocolAddress(kTurnIntAddr, protocol_type));
+
+    turn_port_->PrepareAddress();
+    EXPECT_TRUE_SIMULATED_WAIT(turn_error_,
+                               TimeToGetAlternateTurnCandidate(protocol_type),
+                               fake_clock_);
+    ASSERT_EQ(0U, turn_port_->Candidates().size());
+    rtc::SocketAddress address;
+    // Verify that we have exhausted all alternate servers instead of
+    // failure caused by other errors.
+    EXPECT_FALSE(redirector.ShouldRedirect(address, &address));
+  }
+
+  void TestTurnAlternateServerDetectRepetition(ProtocolType protocol_type) {
+    std::vector<rtc::SocketAddress> redirect_addresses;
+    redirect_addresses.push_back(kTurnAlternateIntAddr);
+    redirect_addresses.push_back(kTurnAlternateIntAddr);
+
+    TestTurnRedirector redirector(redirect_addresses);
+
+    turn_server_.AddInternalSocket(kTurnIntAddr, protocol_type);
+    turn_server_.AddInternalSocket(kTurnAlternateIntAddr, protocol_type);
+    turn_server_.set_redirect_hook(&redirector);
+    CreateTurnPort(kTurnUsername, kTurnPassword,
+                   ProtocolAddress(kTurnIntAddr, protocol_type));
+
+    turn_port_->PrepareAddress();
+    EXPECT_TRUE_SIMULATED_WAIT(turn_error_,
+                               TimeToGetAlternateTurnCandidate(protocol_type),
+                               fake_clock_);
+    ASSERT_EQ(0U, turn_port_->Candidates().size());
+  }
+
+  // A certain security exploit works by redirecting to a loopback address,
+  // which doesn't ever actually make sense. So redirects to loopback should
+  // be treated as errors.
+  // See: https://bugs.chromium.org/p/chromium/issues/detail?id=649118
+  void TestTurnAlternateServerLoopback(ProtocolType protocol_type, bool ipv6) {
+    const SocketAddress& local_address = ipv6 ? kLocalIPv6Addr : kLocalAddr1;
+    const SocketAddress& server_address =
+        ipv6 ? kTurnIPv6IntAddr : kTurnIntAddr;
+
+    std::vector<rtc::SocketAddress> redirect_addresses;
+    // Pick an unusual address in the 127.0.0.0/8 range to make sure more than
+    // 127.0.0.1 is covered.
+    SocketAddress loopback_address(ipv6 ? "::1" : "127.1.2.3",
+                                   TURN_SERVER_PORT);
+    redirect_addresses.push_back(loopback_address);
+
+    // Make a socket and bind it to the local port, to make extra sure no
+    // packet is sent to this address.
+    std::unique_ptr<rtc::Socket> loopback_socket(ss_->CreateSocket(
+        AF_INET, protocol_type == PROTO_UDP ? SOCK_DGRAM : SOCK_STREAM));
+    ASSERT_NE(nullptr, loopback_socket.get());
+    ASSERT_EQ(0, loopback_socket->Bind(loopback_address));
+    if (protocol_type == PROTO_TCP) {
+      ASSERT_EQ(0, loopback_socket->Listen(1));
+    }
+
+    TestTurnRedirector redirector(redirect_addresses);
+
+    turn_server_.AddInternalSocket(server_address, protocol_type);
+    turn_server_.set_redirect_hook(&redirector);
+    CreateTurnPort(local_address, kTurnUsername, kTurnPassword,
+                   ProtocolAddress(server_address, protocol_type));
+
+    turn_port_->PrepareAddress();
+    EXPECT_TRUE_SIMULATED_WAIT(
+        turn_error_, TimeToGetTurnCandidate(protocol_type), fake_clock_);
+
+    // Wait for some extra time, and make sure no packets were received on the
+    // loopback port we created (or in the case of TCP, no connection attempt
+    // occurred).
+    SIMULATED_WAIT(false, kSimulatedRtt, fake_clock_);
+    if (protocol_type == PROTO_UDP) {
+      char buf[1];
+      EXPECT_EQ(-1, loopback_socket->Recv(&buf, 1, nullptr));
+    } else {
+      std::unique_ptr<rtc::Socket> accepted_socket(
+          loopback_socket->Accept(nullptr));
+      EXPECT_EQ(nullptr, accepted_socket.get());
+    }
+  }
+
+  void TestTurnConnection(ProtocolType protocol_type) {
+    // Create ports and prepare addresses.
+    PrepareTurnAndUdpPorts(protocol_type);
+
+    // Send ping from UDP to TURN.
+    ASSERT_GE(turn_port_->Candidates().size(), 1U);
+    Connection* conn1 = udp_port_->CreateConnection(turn_port_->Candidates()[0],
+                                                    Port::ORIGIN_MESSAGE);
+    ASSERT_TRUE(conn1 != NULL);
+    conn1->Ping(0);
+    SIMULATED_WAIT(!turn_unknown_address_, kSimulatedRtt * 2, fake_clock_);
+    EXPECT_FALSE(turn_unknown_address_);
+    EXPECT_FALSE(conn1->receiving());
+    EXPECT_EQ(Connection::STATE_WRITE_INIT, conn1->write_state());
+
+    // Send ping from TURN to UDP.
+    Connection* conn2 = turn_port_->CreateConnection(udp_port_->Candidates()[0],
+                                                     Port::ORIGIN_MESSAGE);
+    ASSERT_TRUE(conn2 != NULL);
+    ASSERT_TRUE_SIMULATED_WAIT(turn_create_permission_success_, kSimulatedRtt,
+                               fake_clock_);
+    conn2->Ping(0);
+
+    // Two hops from TURN port to UDP port through TURN server, thus two RTTs.
+    EXPECT_EQ_SIMULATED_WAIT(Connection::STATE_WRITABLE, conn2->write_state(),
+                             kSimulatedRtt * 2, fake_clock_);
+    EXPECT_TRUE(conn1->receiving());
+    EXPECT_TRUE(conn2->receiving());
+    EXPECT_EQ(Connection::STATE_WRITE_INIT, conn1->write_state());
+
+    // Send another ping from UDP to TURN.
+    conn1->Ping(0);
+    EXPECT_EQ_SIMULATED_WAIT(Connection::STATE_WRITABLE, conn1->write_state(),
+                             kSimulatedRtt * 2, fake_clock_);
+    EXPECT_TRUE(conn2->receiving());
+  }
+
+  void TestDestroyTurnConnection() {
+    PrepareTurnAndUdpPorts(PROTO_UDP);
+
+    // Create connections on both ends.
+    Connection* conn1 = udp_port_->CreateConnection(turn_port_->Candidates()[0],
+                                                    Port::ORIGIN_MESSAGE);
+    Connection* conn2 = turn_port_->CreateConnection(udp_port_->Candidates()[0],
+                                                     Port::ORIGIN_MESSAGE);
+
+    // Increased to 10 minutes, to ensure that the TurnEntry times out before
+    // the TurnPort.
+    turn_port_->set_timeout_delay(10 * 60 * 1000);
+
+    ASSERT_TRUE(conn2 != NULL);
+    ASSERT_TRUE_SIMULATED_WAIT(turn_create_permission_success_, kSimulatedRtt,
+                               fake_clock_);
+    // Make sure turn connection can receive.
+    conn1->Ping(0);
+    EXPECT_EQ_SIMULATED_WAIT(Connection::STATE_WRITABLE, conn1->write_state(),
+                             kSimulatedRtt * 2, fake_clock_);
+    EXPECT_FALSE(turn_unknown_address_);
+
+    // Destroy the connection on the TURN port. The TurnEntry still exists, so
+    // the TURN port should still process a ping from an unknown address.
+    turn_port_->DestroyConnection(conn2);
+
+    conn1->Ping(0);
+    EXPECT_TRUE_SIMULATED_WAIT(turn_unknown_address_, kSimulatedRtt,
+                               fake_clock_);
+
+    // Wait for TurnEntry to expire. Timeout is 5 minutes.
+    // Expect that it still processes an incoming ping and signals the
+    // unknown address.
+    turn_unknown_address_ = false;
+    fake_clock_.AdvanceTime(webrtc::TimeDelta::Seconds(5 * 60));
+
+    // TODO(chromium:1395625): When `TurnPort` doesn't find connection objects
+    // for incoming packets, it forwards calls to the parent class, `Port`. This
+    // happens inside `TurnPort::DispatchPacket`. The `Port` implementation may
+    // need to send a binding error back over a connection which, unless the
+    // `TurnPort` implementation handles it, could result in a null deref.
+    // This special check tests if dispatching messages via `TurnPort` for which
+    // there's no connection, results in a no-op rather than crashing.
+    // See `TurnPort::SendBindingErrorResponse` for the check.
+    // This should probably be done in a neater way both from a testing pov and
+    // how incoming messages are handled in the `Port` class, when an assumption
+    // is made about connection objects existing and when those assumptions
+    // may not hold.
+    std::string pwd = conn1->remote_password_for_test();
+    conn1->set_remote_password_for_test("bad");
+    auto msg = conn1->BuildPingRequestForTest();
+
+    rtc::ByteBufferWriter buf;
+    msg->Write(&buf);
+    conn1->Send(buf.Data(), buf.Length(), options);
+
+    // Now restore the password before continuing.
+    conn1->set_remote_password_for_test(pwd);
+
+    conn1->Ping(0);
+    EXPECT_TRUE_SIMULATED_WAIT(turn_unknown_address_, kSimulatedRtt,
+                               fake_clock_);
+
+    // If the connection is created again, it will start to receive pings.
+    conn2 = turn_port_->CreateConnection(udp_port_->Candidates()[0],
+                                         Port::ORIGIN_MESSAGE);
+    conn1->Ping(0);
+    EXPECT_TRUE_SIMULATED_WAIT(conn2->receiving(), kSimulatedRtt, fake_clock_);
+  }
+
+  void TestTurnSendData(ProtocolType protocol_type) {
+    PrepareTurnAndUdpPorts(protocol_type);
+
+    // Create connections and send pings.
+    Connection* conn1 = turn_port_->CreateConnection(udp_port_->Candidates()[0],
+                                                     Port::ORIGIN_MESSAGE);
+    Connection* conn2 = udp_port_->CreateConnection(turn_port_->Candidates()[0],
+                                                    Port::ORIGIN_MESSAGE);
+    ASSERT_TRUE(conn1 != NULL);
+    ASSERT_TRUE(conn2 != NULL);
+    conn1->SignalReadPacket.connect(static_cast<TurnPortTest*>(this),
+                                    &TurnPortTest::OnTurnReadPacket);
+    conn2->SignalReadPacket.connect(static_cast<TurnPortTest*>(this),
+                                    &TurnPortTest::OnUdpReadPacket);
+    conn1->Ping(0);
+    EXPECT_EQ_SIMULATED_WAIT(Connection::STATE_WRITABLE, conn1->write_state(),
+                             kSimulatedRtt * 2, fake_clock_);
+    conn2->Ping(0);
+    EXPECT_EQ_SIMULATED_WAIT(Connection::STATE_WRITABLE, conn2->write_state(),
+                             kSimulatedRtt * 2, fake_clock_);
+
+    // Send some data.
+    size_t num_packets = 256;
+    for (size_t i = 0; i < num_packets; ++i) {
+      unsigned char buf[256] = {0};
+      for (size_t j = 0; j < i + 1; ++j) {
+        buf[j] = 0xFF - static_cast<unsigned char>(j);
+      }
+      conn1->Send(buf, i + 1, options);
+      conn2->Send(buf, i + 1, options);
+      SIMULATED_WAIT(false, kSimulatedRtt, fake_clock_);
+    }
+
+    // Check the data.
+    ASSERT_EQ(num_packets, turn_packets_.size());
+    ASSERT_EQ(num_packets, udp_packets_.size());
+    for (size_t i = 0; i < num_packets; ++i) {
+      EXPECT_EQ(i + 1, turn_packets_[i].size());
+      EXPECT_EQ(i + 1, udp_packets_[i].size());
+      EXPECT_EQ(turn_packets_[i], udp_packets_[i]);
+    }
+  }
+
+  // Test that a TURN allocation is released when the port is closed.
+  void TestTurnReleaseAllocation(ProtocolType protocol_type) {
+    PrepareTurnAndUdpPorts(protocol_type);
+    turn_port_.reset();
+    EXPECT_EQ_SIMULATED_WAIT(0U, turn_server_.server()->allocations().size(),
+                             kSimulatedRtt, fake_clock_);
+  }
+
+  // Test that the TURN allocation is released by sending a refresh request
+  // with lifetime 0 when Release is called.
+  void TestTurnGracefulReleaseAllocation(ProtocolType protocol_type) {
+    PrepareTurnAndUdpPorts(protocol_type);
+
+    // Create connections and send pings.
+    Connection* conn1 = turn_port_->CreateConnection(udp_port_->Candidates()[0],
+                                                     Port::ORIGIN_MESSAGE);
+    Connection* conn2 = udp_port_->CreateConnection(turn_port_->Candidates()[0],
+                                                    Port::ORIGIN_MESSAGE);
+    ASSERT_TRUE(conn1 != NULL);
+    ASSERT_TRUE(conn2 != NULL);
+    conn1->SignalReadPacket.connect(static_cast<TurnPortTest*>(this),
+                                    &TurnPortTest::OnTurnReadPacket);
+    conn2->SignalReadPacket.connect(static_cast<TurnPortTest*>(this),
+                                    &TurnPortTest::OnUdpReadPacket);
+    conn1->Ping(0);
+    EXPECT_EQ_SIMULATED_WAIT(Connection::STATE_WRITABLE, conn1->write_state(),
+                             kSimulatedRtt * 2, fake_clock_);
+    conn2->Ping(0);
+    EXPECT_EQ_SIMULATED_WAIT(Connection::STATE_WRITABLE, conn2->write_state(),
+                             kSimulatedRtt * 2, fake_clock_);
+
+    // Send some data from Udp to TurnPort.
+    unsigned char buf[256] = {0};
+    conn2->Send(buf, sizeof(buf), options);
+
+    // Now release the TurnPort allocation.
+    // This will send a REFRESH with lifetime 0 to server.
+    turn_port_->Release();
+
+    // Wait for the TurnPort to signal closed.
+    ASSERT_TRUE_SIMULATED_WAIT(turn_port_closed_, kSimulatedRtt, fake_clock_);
+
+    // But the data should have arrived first.
+    ASSERT_EQ(1ul, turn_packets_.size());
+    EXPECT_EQ(sizeof(buf), turn_packets_[0].size());
+
+    // The allocation is released at server.
+    EXPECT_EQ(0U, turn_server_.server()->allocations().size());
+  }
+
+ protected:
+  virtual rtc::PacketSocketFactory* socket_factory() {
+    return &socket_factory_;
+  }
+
+  webrtc::test::ScopedKeyValueConfig field_trials_;
+  rtc::ScopedFakeClock fake_clock_;
+  // When a "create port" helper method is called with an IP, we create a
+  // Network with that IP and add it to this list. Using a list instead of a
+  // vector so that when it grows, pointers aren't invalidated.
+  std::list<rtc::Network> networks_;
+  std::unique_ptr<TurnPortTestVirtualSocketServer> ss_;
+  rtc::AutoSocketServerThread main_;
+  std::unique_ptr<rtc::AsyncPacketSocket> socket_;
+  TestTurnServer turn_server_;
+  std::unique_ptr<TurnPort> turn_port_;
+  std::unique_ptr<UDPPort> udp_port_;
+  bool turn_ready_ = false;
+  bool turn_error_ = false;
+  bool turn_unknown_address_ = false;
+  bool turn_create_permission_success_ = false;
+  bool turn_port_closed_ = false;
+  bool turn_port_destroyed_ = false;
+  bool udp_ready_ = false;
+  bool test_finish_ = false;
+  bool turn_refresh_success_ = false;
+  std::vector<rtc::Buffer> turn_packets_;
+  std::vector<rtc::Buffer> udp_packets_;
+  rtc::PacketOptions options;
+  std::unique_ptr<webrtc::TurnCustomizer> turn_customizer_;
+  cricket::IceCandidateErrorEvent error_event_;
+
+ private:
+  rtc::BasicPacketSocketFactory socket_factory_;
+};
+
+TEST_F(TurnPortTest, TestTurnPortType) {
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnUdpProtoAddr);
+  EXPECT_EQ(cricket::RELAY_PORT_TYPE, turn_port_->Type());
+}
+
+// Tests that the URL of the servers can be correctly reconstructed when
+// gathering the candidates.
+TEST_F(TurnPortTest, TestReconstructedServerUrlForUdpIPv4) {
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnUdpProtoAddr);
+  TestReconstructedServerUrl(PROTO_UDP, "turn:99.99.99.3:3478?transport=udp");
+}
+
+TEST_F(TurnPortTest, TestReconstructedServerUrlForUdpIPv6) {
+  turn_server_.AddInternalSocket(kTurnUdpIPv6IntAddr, PROTO_UDP);
+  CreateTurnPort(kLocalIPv6Addr, kTurnUsername, kTurnPassword,
+                 kTurnUdpIPv6ProtoAddr);
+  TestReconstructedServerUrl(
+      PROTO_UDP,
+      "turn:2400:4030:1:2c00:be30:abcd:efab:cdef:3478?transport=udp");
+}
+
+TEST_F(TurnPortTest, TestReconstructedServerUrlForTcp) {
+  turn_server_.AddInternalSocket(kTurnTcpIntAddr, PROTO_TCP);
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnTcpProtoAddr);
+  TestReconstructedServerUrl(PROTO_TCP, "turn:99.99.99.4:3478?transport=tcp");
+}
+
+TEST_F(TurnPortTest, TestReconstructedServerUrlForTls) {
+  turn_server_.AddInternalSocket(kTurnTcpIntAddr, PROTO_TLS);
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnTlsProtoAddr);
+  TestReconstructedServerUrl(PROTO_TLS, "turns:99.99.99.4:3478?transport=tcp");
+}
+
+TEST_F(TurnPortTest, TestReconstructedServerUrlForHostname) {
+  CreateTurnPort(kTurnUsername, kTurnPassword,
+                 kTurnPortInvalidHostnameProtoAddr);
+  // This test follows the pattern from TestTurnTcpOnAddressResolveFailure.
+  // As VSS doesn't provide DNS resolution, name resolve will fail,
+  // the error will be set and contain the url.
+  turn_port_->PrepareAddress();
+  EXPECT_TRUE_WAIT(turn_error_, kResolverTimeout);
+  std::string server_url =
+      "turn:" + kTurnInvalidAddr.ToString() + "?transport=udp";
+  ASSERT_EQ(error_event_.url, server_url);
+}
+
+// Do a normal TURN allocation.
+TEST_F(TurnPortTest, TestTurnAllocate) {
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnUdpProtoAddr);
+  EXPECT_EQ(0, turn_port_->SetOption(rtc::Socket::OPT_SNDBUF, 10 * 1024));
+  TestTurnAllocateSucceeds(kSimulatedRtt * 2);
+}
+
+class TurnLoggingIdValidator : public StunMessageObserver {
+ public:
+  explicit TurnLoggingIdValidator(const char* expect_val)
+      : expect_val_(expect_val) {}
+  ~TurnLoggingIdValidator() {}
+  void ReceivedMessage(const TurnMessage* msg) override {
+    if (msg->type() == cricket::STUN_ALLOCATE_REQUEST) {
+      const StunByteStringAttribute* attr =
+          msg->GetByteString(cricket::STUN_ATTR_TURN_LOGGING_ID);
+      if (expect_val_) {
+        ASSERT_NE(nullptr, attr);
+        ASSERT_EQ(expect_val_, attr->string_view());
+      } else {
+        EXPECT_EQ(nullptr, attr);
+      }
+    }
+  }
+  void ReceivedChannelData(const char* data, size_t size) override {}
+
+ private:
+  const char* expect_val_;
+};
+
+TEST_F(TurnPortTest, TestTurnAllocateWithLoggingId) {
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnUdpProtoAddr);
+  turn_port_->SetTurnLoggingId("KESO");
+  turn_server_.server()->SetStunMessageObserver(
+      std::make_unique<TurnLoggingIdValidator>("KESO"));
+  TestTurnAllocateSucceeds(kSimulatedRtt * 2);
+}
+
+TEST_F(TurnPortTest, TestTurnAllocateWithoutLoggingId) {
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnUdpProtoAddr);
+  turn_server_.server()->SetStunMessageObserver(
+      std::make_unique<TurnLoggingIdValidator>(nullptr));
+  TestTurnAllocateSucceeds(kSimulatedRtt * 2);
+}
+
+// Test bad credentials.
+TEST_F(TurnPortTest, TestTurnBadCredentials) {
+  CreateTurnPort(kTurnUsername, "bad", kTurnUdpProtoAddr);
+  turn_port_->PrepareAddress();
+  EXPECT_TRUE_SIMULATED_WAIT(turn_error_, kSimulatedRtt * 3, fake_clock_);
+  ASSERT_EQ(0U, turn_port_->Candidates().size());
+  EXPECT_EQ_SIMULATED_WAIT(error_event_.error_code, STUN_ERROR_UNAUTHORIZED,
+                           kSimulatedRtt * 3, fake_clock_);
+  EXPECT_EQ(error_event_.error_text, "Unauthorized");
+}
+
+// Testing a normal UDP allocation using TCP connection.
+TEST_F(TurnPortTest, TestTurnTcpAllocate) {
+  turn_server_.AddInternalSocket(kTurnTcpIntAddr, PROTO_TCP);
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnTcpProtoAddr);
+  EXPECT_EQ(0, turn_port_->SetOption(rtc::Socket::OPT_SNDBUF, 10 * 1024));
+  TestTurnAllocateSucceeds(kSimulatedRtt * 3);
+}
+
+// Test case for WebRTC issue 3927 where a proxy binds to the local host address
+// instead the address that TurnPort originally bound to. The candidate pair
+// impacted by this behavior should still be used.
+TEST_F(TurnPortTest, TestTurnTcpAllocationWhenProxyChangesAddressToLocalHost) {
+  SocketAddress local_address("127.0.0.1", 0);
+  // After calling this, when TurnPort attempts to get a socket bound to
+  // kLocalAddr, it will end up using localhost instead.
+  ss_->SetAlternativeLocalAddress(kLocalAddr1.ipaddr(), local_address.ipaddr());
+
+  turn_server_.AddInternalSocket(kTurnTcpIntAddr, PROTO_TCP);
+  CreateTurnPort(kLocalAddr1, kTurnUsername, kTurnPassword, kTurnTcpProtoAddr);
+  EXPECT_EQ(0, turn_port_->SetOption(rtc::Socket::OPT_SNDBUF, 10 * 1024));
+  TestTurnAllocateSucceeds(kSimulatedRtt * 3);
+
+  // Verify that the socket actually used localhost, otherwise this test isn't
+  // doing what it meant to.
+  ASSERT_EQ(local_address.ipaddr(),
+            turn_port_->Candidates()[0].related_address().ipaddr());
+}
+
+// If the address the socket ends up bound to does not match any address of the
+// TurnPort's Network, then the socket should be discarded and no candidates
+// should be signaled. In the context of ICE, where one TurnPort is created for
+// each Network, when this happens it's likely that the unexpected address is
+// associated with some other Network, which another TurnPort is already
+// covering.
+TEST_F(TurnPortTest,
+       TurnTcpAllocationDiscardedIfBoundAddressDoesNotMatchNetwork) {
+  // Sockets bound to kLocalAddr1 will actually end up with kLocalAddr2.
+  ss_->SetAlternativeLocalAddress(kLocalAddr1.ipaddr(), kLocalAddr2.ipaddr());
+
+  // Set up TURN server to use TCP (this logic only exists for TCP).
+  turn_server_.AddInternalSocket(kTurnTcpIntAddr, PROTO_TCP);
+
+  // Create TURN port and tell it to start allocation.
+  CreateTurnPort(kLocalAddr1, kTurnUsername, kTurnPassword, kTurnTcpProtoAddr);
+  turn_port_->PrepareAddress();
+
+  // Shouldn't take more than 1 RTT to realize the bound address isn't the one
+  // expected.
+  EXPECT_TRUE_SIMULATED_WAIT(turn_error_, kSimulatedRtt, fake_clock_);
+  EXPECT_EQ_SIMULATED_WAIT(error_event_.error_code, STUN_ERROR_GLOBAL_FAILURE,
+                           kSimulatedRtt, fake_clock_);
+  ASSERT_NE(error_event_.error_text.find('.'), std::string::npos);
+  ASSERT_NE(error_event_.address.find(kLocalAddr2.HostAsSensitiveURIString()),
+            std::string::npos);
+  ASSERT_NE(error_event_.port, 0);
+  std::string server_url =
+      "turn:" + kTurnTcpIntAddr.ToString() + "?transport=tcp";
+  ASSERT_EQ(error_event_.url, server_url);
+}
+
+// A caveat for the above logic: if the socket ends up bound to one of the IPs
+// associated with the Network, just not the "best" one, this is ok.
+TEST_F(TurnPortTest, TurnTcpAllocationNotDiscardedIfNotBoundToBestIP) {
+  // Sockets bound to kLocalAddr1 will actually end up with kLocalAddr2.
+  ss_->SetAlternativeLocalAddress(kLocalAddr1.ipaddr(), kLocalAddr2.ipaddr());
+
+  // Set up a network with kLocalAddr1 as the "best" IP, and kLocalAddr2 as an
+  // alternate.
+  rtc::Network* network = MakeNetwork(kLocalAddr1);
+  network->AddIP(kLocalAddr2.ipaddr());
+  ASSERT_EQ(kLocalAddr1.ipaddr(), network->GetBestIP());
+
+  // Set up TURN server to use TCP (this logic only exists for TCP).
+  turn_server_.AddInternalSocket(kTurnTcpIntAddr, PROTO_TCP);
+
+  // Create TURN port using our special Network, and tell it to start
+  // allocation.
+  CreateTurnPortWithNetwork(network, kTurnUsername, kTurnPassword,
+                            kTurnTcpProtoAddr);
+  turn_port_->PrepareAddress();
+
+  // Candidate should be gathered as normally.
+  EXPECT_TRUE_SIMULATED_WAIT(turn_ready_, kSimulatedRtt * 3, fake_clock_);
+  ASSERT_EQ(1U, turn_port_->Candidates().size());
+
+  // Verify that the socket actually used the alternate address, otherwise this
+  // test isn't doing what it meant to.
+  ASSERT_EQ(kLocalAddr2.ipaddr(),
+            turn_port_->Candidates()[0].related_address().ipaddr());
+}
+
+// Regression test for crbug.com/webrtc/8972, caused by buggy comparison
+// between rtc::IPAddress and rtc::InterfaceAddress.
+TEST_F(TurnPortTest, TCPPortNotDiscardedIfBoundToTemporaryIP) {
+  networks_.emplace_back("unittest", "unittest", kLocalIPv6Addr.ipaddr(), 32);
+  networks_.back().AddIP(rtc::InterfaceAddress(
+      kLocalIPv6Addr.ipaddr(), rtc::IPV6_ADDRESS_FLAG_TEMPORARY));
+
+  // Set up TURN server to use TCP (this logic only exists for TCP).
+  turn_server_.AddInternalSocket(kTurnIPv6IntAddr, PROTO_TCP);
+
+  // Create TURN port using our special Network, and tell it to start
+  // allocation.
+  CreateTurnPortWithNetwork(
+      &networks_.back(), kTurnUsername, kTurnPassword,
+      cricket::ProtocolAddress(kTurnIPv6IntAddr, PROTO_TCP));
+  turn_port_->PrepareAddress();
+
+  // Candidate should be gathered as normally.
+  EXPECT_TRUE_SIMULATED_WAIT(turn_ready_, kSimulatedRtt * 3, fake_clock_);
+  ASSERT_EQ(1U, turn_port_->Candidates().size());
+}
+
+// Testing turn port will attempt to create TCP socket on address resolution
+// failure.
+TEST_F(TurnPortTest, TestTurnTcpOnAddressResolveFailure) {
+  turn_server_.AddInternalSocket(kTurnTcpIntAddr, PROTO_TCP);
+  CreateTurnPort(kTurnUsername, kTurnPassword,
+                 ProtocolAddress(kTurnInvalidAddr, PROTO_TCP));
+  turn_port_->PrepareAddress();
+  EXPECT_TRUE_WAIT(turn_error_, kResolverTimeout);
+  // As VSS doesn't provide DNS resolution, name resolve will fail. TurnPort
+  // will proceed in creating a TCP socket which will fail as there is no
+  // server on the above domain and error will be set to SOCKET_ERROR.
+  EXPECT_EQ(SOCKET_ERROR, turn_port_->error());
+  EXPECT_EQ_SIMULATED_WAIT(error_event_.error_code, SERVER_NOT_REACHABLE_ERROR,
+                           kSimulatedRtt, fake_clock_);
+  std::string server_url =
+      "turn:" + kTurnInvalidAddr.ToString() + "?transport=tcp";
+  ASSERT_EQ(error_event_.url, server_url);
+}
+
+// Testing turn port will attempt to create TLS socket on address resolution
+// failure.
+TEST_F(TurnPortTest, TestTurnTlsOnAddressResolveFailure) {
+  turn_server_.AddInternalSocket(kTurnTcpIntAddr, PROTO_TLS);
+  CreateTurnPort(kTurnUsername, kTurnPassword,
+                 ProtocolAddress(kTurnInvalidAddr, PROTO_TLS));
+  turn_port_->PrepareAddress();
+  EXPECT_TRUE_WAIT(turn_error_, kResolverTimeout);
+  EXPECT_EQ(SOCKET_ERROR, turn_port_->error());
+}
+
+// In case of UDP on address resolve failure, TurnPort will not create socket
+// and return allocate failure.
+TEST_F(TurnPortTest, TestTurnUdpOnAddressResolveFailure) {
+  CreateTurnPort(kTurnUsername, kTurnPassword,
+                 ProtocolAddress(kTurnInvalidAddr, PROTO_UDP));
+  turn_port_->PrepareAddress();
+  EXPECT_TRUE_WAIT(turn_error_, kResolverTimeout);
+  // Error from turn port will not be socket error.
+  EXPECT_NE(SOCKET_ERROR, turn_port_->error());
+}
+
+// Try to do a TURN allocation with an invalid password.
+TEST_F(TurnPortTest, TestTurnAllocateBadPassword) {
+  CreateTurnPort(kTurnUsername, "bad", kTurnUdpProtoAddr);
+  turn_port_->PrepareAddress();
+  EXPECT_TRUE_SIMULATED_WAIT(turn_error_, kSimulatedRtt * 2, fake_clock_);
+  ASSERT_EQ(0U, turn_port_->Candidates().size());
+}
+
+// Tests that TURN port nonce will be reset when receiving an ALLOCATE MISMATCH
+// error.
+TEST_F(TurnPortTest, TestTurnAllocateNonceResetAfterAllocateMismatch) {
+  // Do a normal allocation first.
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnUdpProtoAddr);
+  turn_port_->PrepareAddress();
+  EXPECT_TRUE_SIMULATED_WAIT(turn_ready_, kSimulatedRtt * 2, fake_clock_);
+  rtc::SocketAddress first_addr(turn_port_->socket()->GetLocalAddress());
+  // Destroy the turnport while keeping the drop probability to 1 to
+  // suppress the release of the allocation at the server.
+  ss_->set_drop_probability(1.0);
+  turn_port_.reset();
+  SIMULATED_WAIT(false, kSimulatedRtt, fake_clock_);
+  ss_->set_drop_probability(0.0);
+
+  // Force the socket server to assign the same port.
+  ss_->SetNextPortForTesting(first_addr.port());
+  turn_ready_ = false;
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnUdpProtoAddr);
+
+  // It is expected that the turn port will first get a nonce from the server
+  // using timestamp `ts_before` but then get an allocate mismatch error and
+  // receive an even newer nonce based on the system clock. `ts_before` is
+  // chosen so that the two NONCEs generated by the server will be different.
+  int64_t ts_before = rtc::TimeMillis() - 1;
+  std::string first_nonce =
+      turn_server_.server()->SetTimestampForNextNonce(ts_before);
+  turn_port_->PrepareAddress();
+
+  // Four round trips; first we'll get "stale nonce", then
+  // "allocate mismatch", then "stale nonce" again, then finally it will
+  // succeed.
+  EXPECT_TRUE_SIMULATED_WAIT(turn_ready_, kSimulatedRtt * 4, fake_clock_);
+  EXPECT_NE(first_nonce, turn_port_->nonce());
+}
+
+// Tests that a new local address is created after
+// STUN_ERROR_ALLOCATION_MISMATCH.
+TEST_F(TurnPortTest, TestTurnAllocateMismatch) {
+  // Do a normal allocation first.
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnUdpProtoAddr);
+  turn_port_->PrepareAddress();
+  EXPECT_TRUE_SIMULATED_WAIT(turn_ready_, kSimulatedRtt * 2, fake_clock_);
+  rtc::SocketAddress first_addr(turn_port_->socket()->GetLocalAddress());
+
+  // Clear connected_ flag on turnport to suppress the release of
+  // the allocation.
+  turn_port_->OnSocketClose(turn_port_->socket(), 0);
+
+  // Forces the socket server to assign the same port.
+  ss_->SetNextPortForTesting(first_addr.port());
+
+  turn_ready_ = false;
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnUdpProtoAddr);
+  turn_port_->PrepareAddress();
+
+  // Verifies that the new port has the same address.
+  EXPECT_EQ(first_addr, turn_port_->socket()->GetLocalAddress());
+
+  // Four round trips; first we'll get "stale nonce", then
+  // "allocate mismatch", then "stale nonce" again, then finally it will
+  // succeed.
+  EXPECT_TRUE_SIMULATED_WAIT(turn_ready_, kSimulatedRtt * 4, fake_clock_);
+
+  // Verifies that the new port has a different address now.
+  EXPECT_NE(first_addr, turn_port_->socket()->GetLocalAddress());
+
+  // Verify that all packets received from the shared socket are ignored.
+  std::string test_packet = "Test packet";
+  EXPECT_FALSE(turn_port_->HandleIncomingPacket(
+      socket_.get(), test_packet.data(), test_packet.size(),
+      rtc::SocketAddress(kTurnUdpExtAddr.ipaddr(), 0), rtc::TimeMicros()));
+}
+
+// Tests that a shared-socket-TurnPort creates its own socket after
+// STUN_ERROR_ALLOCATION_MISMATCH.
+TEST_F(TurnPortTest, TestSharedSocketAllocateMismatch) {
+  // Do a normal allocation first.
+  CreateSharedTurnPort(kTurnUsername, kTurnPassword, kTurnUdpProtoAddr);
+  turn_port_->PrepareAddress();
+  EXPECT_TRUE_SIMULATED_WAIT(turn_ready_, kSimulatedRtt * 2, fake_clock_);
+  rtc::SocketAddress first_addr(turn_port_->socket()->GetLocalAddress());
+
+  // Clear connected_ flag on turnport to suppress the release of
+  // the allocation.
+  turn_port_->OnSocketClose(turn_port_->socket(), 0);
+
+  turn_ready_ = false;
+  CreateSharedTurnPort(kTurnUsername, kTurnPassword, kTurnUdpProtoAddr);
+
+  // Verifies that the new port has the same address.
+  EXPECT_EQ(first_addr, turn_port_->socket()->GetLocalAddress());
+  EXPECT_TRUE(turn_port_->SharedSocket());
+
+  turn_port_->PrepareAddress();
+  // Extra 2 round trips due to allocate mismatch.
+  EXPECT_TRUE_SIMULATED_WAIT(turn_ready_, kSimulatedRtt * 4, fake_clock_);
+
+  // Verifies that the new port has a different address now.
+  EXPECT_NE(first_addr, turn_port_->socket()->GetLocalAddress());
+  EXPECT_FALSE(turn_port_->SharedSocket());
+}
+
+TEST_F(TurnPortTest, TestTurnTcpAllocateMismatch) {
+  turn_server_.AddInternalSocket(kTurnTcpIntAddr, PROTO_TCP);
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnTcpProtoAddr);
+
+  // Do a normal allocation first.
+  turn_port_->PrepareAddress();
+  EXPECT_TRUE_SIMULATED_WAIT(turn_ready_, kSimulatedRtt * 3, fake_clock_);
+  rtc::SocketAddress first_addr(turn_port_->socket()->GetLocalAddress());
+
+  // Clear connected_ flag on turnport to suppress the release of
+  // the allocation.
+  turn_port_->OnSocketClose(turn_port_->socket(), 0);
+
+  // Forces the socket server to assign the same port.
+  ss_->SetNextPortForTesting(first_addr.port());
+
+  turn_ready_ = false;
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnTcpProtoAddr);
+  turn_port_->PrepareAddress();
+
+  // Verifies that the new port has the same address.
+  EXPECT_EQ(first_addr, turn_port_->socket()->GetLocalAddress());
+
+  // Extra 2 round trips due to allocate mismatch.
+  EXPECT_TRUE_SIMULATED_WAIT(turn_ready_, kSimulatedRtt * 5, fake_clock_);
+
+  // Verifies that the new port has a different address now.
+  EXPECT_NE(first_addr, turn_port_->socket()->GetLocalAddress());
+}
+
+TEST_F(TurnPortTest, TestRefreshRequestGetsErrorResponse) {
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnUdpProtoAddr);
+  PrepareTurnAndUdpPorts(PROTO_UDP);
+  turn_port_->CreateConnection(udp_port_->Candidates()[0],
+                               Port::ORIGIN_MESSAGE);
+  // Set bad credentials.
+  RelayCredentials bad_credentials("bad_user", "bad_pwd");
+  turn_port_->set_credentials(bad_credentials);
+  turn_refresh_success_ = false;
+  // This sends out the first RefreshRequest with correct credentials.
+  // When this succeeds, it will schedule a new RefreshRequest with the bad
+  // credential.
+  turn_port_->request_manager().FlushForTest(TURN_REFRESH_REQUEST);
+  EXPECT_TRUE_SIMULATED_WAIT(turn_refresh_success_, kSimulatedRtt, fake_clock_);
+  // Flush it again, it will receive a bad response.
+  turn_port_->request_manager().FlushForTest(TURN_REFRESH_REQUEST);
+  EXPECT_TRUE_SIMULATED_WAIT(!turn_refresh_success_, kSimulatedRtt,
+                             fake_clock_);
+  EXPECT_FALSE(turn_port_->connected());
+  EXPECT_TRUE(CheckAllConnectionsFailedAndPruned());
+  EXPECT_FALSE(turn_port_->HasRequests());
+}
+
+// Test that TurnPort will not handle any incoming packets once it has been
+// closed.
+TEST_F(TurnPortTest, TestStopProcessingPacketsAfterClosed) {
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnUdpProtoAddr);
+  PrepareTurnAndUdpPorts(PROTO_UDP);
+  Connection* conn1 = turn_port_->CreateConnection(udp_port_->Candidates()[0],
+                                                   Port::ORIGIN_MESSAGE);
+  Connection* conn2 = udp_port_->CreateConnection(turn_port_->Candidates()[0],
+                                                  Port::ORIGIN_MESSAGE);
+  ASSERT_TRUE(conn1 != NULL);
+  ASSERT_TRUE(conn2 != NULL);
+  // Make sure conn2 is writable.
+  conn2->Ping(0);
+  EXPECT_EQ_SIMULATED_WAIT(Connection::STATE_WRITABLE, conn2->write_state(),
+                           kSimulatedRtt * 2, fake_clock_);
+
+  turn_port_->CloseForTest();
+  SIMULATED_WAIT(false, kSimulatedRtt, fake_clock_);
+  turn_unknown_address_ = false;
+  conn2->Ping(0);
+  SIMULATED_WAIT(false, kSimulatedRtt, fake_clock_);
+  // Since the turn port does not handle packets any more, it should not
+  // SignalUnknownAddress.
+  EXPECT_FALSE(turn_unknown_address_);
+}
+
+// Test that CreateConnection will return null if port becomes disconnected.
+TEST_F(TurnPortTest, TestCreateConnectionWhenSocketClosed) {
+  turn_server_.AddInternalSocket(kTurnTcpIntAddr, PROTO_TCP);
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnTcpProtoAddr);
+  PrepareTurnAndUdpPorts(PROTO_TCP);
+  // Create a connection.
+  Connection* conn1 = turn_port_->CreateConnection(udp_port_->Candidates()[0],
+                                                   Port::ORIGIN_MESSAGE);
+  ASSERT_TRUE(conn1 != NULL);
+
+  // Close the socket and create a connection again.
+  turn_port_->OnSocketClose(turn_port_->socket(), 1);
+  conn1 = turn_port_->CreateConnection(udp_port_->Candidates()[0],
+                                       Port::ORIGIN_MESSAGE);
+  ASSERT_TRUE(conn1 == NULL);
+}
+
+// Tests that when a TCP socket is closed, the respective TURN connection will
+// be destroyed.
+TEST_F(TurnPortTest, TestSocketCloseWillDestroyConnection) {
+  turn_server_.AddInternalSocket(kTurnTcpIntAddr, PROTO_TCP);
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnTcpProtoAddr);
+  PrepareTurnAndUdpPorts(PROTO_TCP);
+  Connection* conn = turn_port_->CreateConnection(udp_port_->Candidates()[0],
+                                                  Port::ORIGIN_MESSAGE);
+  EXPECT_NE(nullptr, conn);
+  EXPECT_TRUE(!turn_port_->connections().empty());
+  turn_port_->socket()->NotifyClosedForTest(1);
+  EXPECT_TRUE_SIMULATED_WAIT(turn_port_->connections().empty(),
+                             kConnectionDestructionDelay, fake_clock_);
+}
+
+// Test try-alternate-server feature.
+TEST_F(TurnPortTest, TestTurnAlternateServerUDP) {
+  TestTurnAlternateServer(PROTO_UDP);
+}
+
+TEST_F(TurnPortTest, TestTurnAlternateServerTCP) {
+  TestTurnAlternateServer(PROTO_TCP);
+}
+
+TEST_F(TurnPortTest, TestTurnAlternateServerTLS) {
+  TestTurnAlternateServer(PROTO_TLS);
+}
+
+// Test that we fail when we redirect to an address different from
+// current IP family.
+TEST_F(TurnPortTest, TestTurnAlternateServerV4toV6UDP) {
+  TestTurnAlternateServerV4toV6(PROTO_UDP);
+}
+
+TEST_F(TurnPortTest, TestTurnAlternateServerV4toV6TCP) {
+  TestTurnAlternateServerV4toV6(PROTO_TCP);
+}
+
+TEST_F(TurnPortTest, TestTurnAlternateServerV4toV6TLS) {
+  TestTurnAlternateServerV4toV6(PROTO_TLS);
+}
+
+// Test try-alternate-server catches the case of pingpong.
+TEST_F(TurnPortTest, TestTurnAlternateServerPingPongUDP) {
+  TestTurnAlternateServerPingPong(PROTO_UDP);
+}
+
+TEST_F(TurnPortTest, TestTurnAlternateServerPingPongTCP) {
+  TestTurnAlternateServerPingPong(PROTO_TCP);
+}
+
+TEST_F(TurnPortTest, TestTurnAlternateServerPingPongTLS) {
+  TestTurnAlternateServerPingPong(PROTO_TLS);
+}
+
+// Test try-alternate-server catch the case of repeated server.
+TEST_F(TurnPortTest, TestTurnAlternateServerDetectRepetitionUDP) {
+  TestTurnAlternateServerDetectRepetition(PROTO_UDP);
+}
+
+TEST_F(TurnPortTest, TestTurnAlternateServerDetectRepetitionTCP) {
+  TestTurnAlternateServerDetectRepetition(PROTO_TCP);
+}
+
+TEST_F(TurnPortTest, TestTurnAlternateServerDetectRepetitionTLS) {
+  TestTurnAlternateServerDetectRepetition(PROTO_TCP);
+}
+
+// Test catching the case of a redirect to loopback.
+TEST_F(TurnPortTest, TestTurnAlternateServerLoopbackUdpIpv4) {
+  TestTurnAlternateServerLoopback(PROTO_UDP, false);
+}
+
+TEST_F(TurnPortTest, TestTurnAlternateServerLoopbackUdpIpv6) {
+  TestTurnAlternateServerLoopback(PROTO_UDP, true);
+}
+
+TEST_F(TurnPortTest, TestTurnAlternateServerLoopbackTcpIpv4) {
+  TestTurnAlternateServerLoopback(PROTO_TCP, false);
+}
+
+TEST_F(TurnPortTest, TestTurnAlternateServerLoopbackTcpIpv6) {
+  TestTurnAlternateServerLoopback(PROTO_TCP, true);
+}
+
+TEST_F(TurnPortTest, TestTurnAlternateServerLoopbackTlsIpv4) {
+  TestTurnAlternateServerLoopback(PROTO_TLS, false);
+}
+
+TEST_F(TurnPortTest, TestTurnAlternateServerLoopbackTlsIpv6) {
+  TestTurnAlternateServerLoopback(PROTO_TLS, true);
+}
+
+// Do a TURN allocation and try to send a packet to it from the outside.
+// The packet should be dropped. Then, try to send a packet from TURN to the
+// outside. It should reach its destination. Finally, try again from the
+// outside. It should now work as well.
+TEST_F(TurnPortTest, TestTurnConnection) {
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnUdpProtoAddr);
+  TestTurnConnection(PROTO_UDP);
+}
+
+// Similar to above, except that this test will use the shared socket.
+TEST_F(TurnPortTest, TestTurnConnectionUsingSharedSocket) {
+  CreateSharedTurnPort(kTurnUsername, kTurnPassword, kTurnUdpProtoAddr);
+  TestTurnConnection(PROTO_UDP);
+}
+
+// Test that we can establish a TCP connection with TURN server.
+TEST_F(TurnPortTest, TestTurnTcpConnection) {
+  turn_server_.AddInternalSocket(kTurnTcpIntAddr, PROTO_TCP);
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnTcpProtoAddr);
+  TestTurnConnection(PROTO_TCP);
+}
+
+// Test that we can establish a TLS connection with TURN server.
+TEST_F(TurnPortTest, TestTurnTlsConnection) {
+  turn_server_.AddInternalSocket(kTurnTcpIntAddr, PROTO_TLS);
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnTlsProtoAddr);
+  TestTurnConnection(PROTO_TLS);
+}
+
+// Test that if a connection on a TURN port is destroyed, the TURN port can
+// still receive ping on that connection as if it is from an unknown address.
+// If the connection is created again, it will be used to receive ping.
+TEST_F(TurnPortTest, TestDestroyTurnConnection) {
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnUdpProtoAddr);
+  TestDestroyTurnConnection();
+}
+
+// Similar to above, except that this test will use the shared socket.
+TEST_F(TurnPortTest, TestDestroyTurnConnectionUsingSharedSocket) {
+  CreateSharedTurnPort(kTurnUsername, kTurnPassword, kTurnUdpProtoAddr);
+  TestDestroyTurnConnection();
+}
+
+// Run TurnConnectionTest with one-time-use nonce feature.
+// Here server will send a 438 STALE_NONCE error message for
+// every TURN transaction.
+TEST_F(TurnPortTest, TestTurnConnectionUsingOTUNonce) {
+  turn_server_.set_enable_otu_nonce(true);
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnUdpProtoAddr);
+  TestTurnConnection(PROTO_UDP);
+}
+
+// Test that CreatePermissionRequest will be scheduled after the success
+// of the first create permission request and the request will get an
+// ErrorResponse if the ufrag and pwd are incorrect.
+TEST_F(TurnPortTest, TestRefreshCreatePermissionRequest) {
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnUdpProtoAddr);
+  PrepareTurnAndUdpPorts(PROTO_UDP);
+
+  Connection* conn = turn_port_->CreateConnection(udp_port_->Candidates()[0],
+                                                  Port::ORIGIN_MESSAGE);
+  ASSERT_TRUE(conn != NULL);
+  EXPECT_TRUE_SIMULATED_WAIT(turn_create_permission_success_, kSimulatedRtt,
+                             fake_clock_);
+  turn_create_permission_success_ = false;
+  // A create-permission-request should be pending.
+  // After the next create-permission-response is received, it will schedule
+  // another request with bad_ufrag and bad_pwd.
+  RelayCredentials bad_credentials("bad_user", "bad_pwd");
+  turn_port_->set_credentials(bad_credentials);
+  turn_port_->request_manager().FlushForTest(kAllRequestsForTest);
+  EXPECT_TRUE_SIMULATED_WAIT(turn_create_permission_success_, kSimulatedRtt,
+                             fake_clock_);
+  // Flush the requests again; the create-permission-request will fail.
+  turn_port_->request_manager().FlushForTest(kAllRequestsForTest);
+  EXPECT_TRUE_SIMULATED_WAIT(!turn_create_permission_success_, kSimulatedRtt,
+                             fake_clock_);
+  EXPECT_TRUE(CheckConnectionFailedAndPruned(conn));
+}
+
+TEST_F(TurnPortTest, TestChannelBindGetErrorResponse) {
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnUdpProtoAddr);
+  PrepareTurnAndUdpPorts(PROTO_UDP);
+  Connection* conn1 = turn_port_->CreateConnection(udp_port_->Candidates()[0],
+                                                   Port::ORIGIN_MESSAGE);
+  ASSERT_TRUE(conn1 != nullptr);
+  Connection* conn2 = udp_port_->CreateConnection(turn_port_->Candidates()[0],
+                                                  Port::ORIGIN_MESSAGE);
+
+  ASSERT_TRUE(conn2 != nullptr);
+  conn1->Ping(0);
+  EXPECT_TRUE_SIMULATED_WAIT(conn1->writable(), kSimulatedRtt * 2, fake_clock_);
+  // TODO(deadbeef): SetEntryChannelId should not be a public method.
+  // Instead we should set an option on the fake TURN server to force it to
+  // send a channel bind errors.
+  ASSERT_TRUE(
+      turn_port_->SetEntryChannelId(udp_port_->Candidates()[0].address(), -1));
+
+  std::string data = "ABC";
+  conn1->Send(data.data(), data.length(), options);
+
+  EXPECT_TRUE_SIMULATED_WAIT(CheckConnectionFailedAndPruned(conn1),
+                             kSimulatedRtt, fake_clock_);
+  // Verify that packets are allowed to be sent after a bind request error.
+  // They'll just use a send indication instead.
+  conn2->SignalReadPacket.connect(static_cast<TurnPortTest*>(this),
+                                  &TurnPortTest::OnUdpReadPacket);
+  conn1->Send(data.data(), data.length(), options);
+  EXPECT_TRUE_SIMULATED_WAIT(!udp_packets_.empty(), kSimulatedRtt, fake_clock_);
+}
+
+// Do a TURN allocation, establish a UDP connection, and send some data.
+TEST_F(TurnPortTest, TestTurnSendDataTurnUdpToUdp) {
+  // Create ports and prepare addresses.
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnUdpProtoAddr);
+  TestTurnSendData(PROTO_UDP);
+  EXPECT_EQ(UDP_PROTOCOL_NAME, turn_port_->Candidates()[0].relay_protocol());
+}
+
+// Do a TURN allocation, establish a TCP connection, and send some data.
+TEST_F(TurnPortTest, TestTurnSendDataTurnTcpToUdp) {
+  turn_server_.AddInternalSocket(kTurnTcpIntAddr, PROTO_TCP);
+  // Create ports and prepare addresses.
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnTcpProtoAddr);
+  TestTurnSendData(PROTO_TCP);
+  EXPECT_EQ(TCP_PROTOCOL_NAME, turn_port_->Candidates()[0].relay_protocol());
+}
+
+// Do a TURN allocation, establish a TLS connection, and send some data.
+TEST_F(TurnPortTest, TestTurnSendDataTurnTlsToUdp) {
+  turn_server_.AddInternalSocket(kTurnTcpIntAddr, PROTO_TLS);
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnTlsProtoAddr);
+  TestTurnSendData(PROTO_TLS);
+  EXPECT_EQ(TLS_PROTOCOL_NAME, turn_port_->Candidates()[0].relay_protocol());
+}
+
+// Test TURN fails to make a connection from IPv6 address to a server which has
+// IPv4 address.
+TEST_F(TurnPortTest, TestTurnLocalIPv6AddressServerIPv4) {
+  turn_server_.AddInternalSocket(kTurnUdpIPv6IntAddr, PROTO_UDP);
+  CreateTurnPort(kLocalIPv6Addr, kTurnUsername, kTurnPassword,
+                 kTurnUdpProtoAddr);
+  turn_port_->PrepareAddress();
+  ASSERT_TRUE_SIMULATED_WAIT(turn_error_, kSimulatedRtt, fake_clock_);
+  EXPECT_TRUE(turn_port_->Candidates().empty());
+}
+
+// Test TURN make a connection from IPv6 address to a server which has
+// IPv6 intenal address. But in this test external address is a IPv4 address,
+// hence allocated address will be a IPv4 address.
+TEST_F(TurnPortTest, TestTurnLocalIPv6AddressServerIPv6ExtenalIPv4) {
+  turn_server_.AddInternalSocket(kTurnUdpIPv6IntAddr, PROTO_UDP);
+  CreateTurnPort(kLocalIPv6Addr, kTurnUsername, kTurnPassword,
+                 kTurnUdpIPv6ProtoAddr);
+  TestTurnAllocateSucceeds(kSimulatedRtt * 2);
+}
+
+// Tests that the local and remote candidate address families should match when
+// a connection is created. Specifically, if a TURN port has an IPv6 address,
+// its local candidate will still be an IPv4 address and it can only create
+// connections with IPv4 remote candidates.
+TEST_F(TurnPortTest, TestCandidateAddressFamilyMatch) {
+  turn_server_.AddInternalSocket(kTurnUdpIPv6IntAddr, PROTO_UDP);
+
+  CreateTurnPort(kLocalIPv6Addr, kTurnUsername, kTurnPassword,
+                 kTurnUdpIPv6ProtoAddr);
+  turn_port_->PrepareAddress();
+  EXPECT_TRUE_SIMULATED_WAIT(turn_ready_, kSimulatedRtt * 2, fake_clock_);
+  ASSERT_EQ(1U, turn_port_->Candidates().size());
+
+  // Create an IPv4 candidate. It will match the TURN candidate.
+  Candidate remote_candidate(ICE_CANDIDATE_COMPONENT_RTP, "udp", kLocalAddr2, 0,
+                             "", "", "local", 0, kCandidateFoundation);
+  remote_candidate.set_address(kLocalAddr2);
+  Connection* conn =
+      turn_port_->CreateConnection(remote_candidate, Port::ORIGIN_MESSAGE);
+  EXPECT_NE(nullptr, conn);
+
+  // Set the candidate address family to IPv6. It won't match the TURN
+  // candidate.
+  remote_candidate.set_address(kLocalIPv6Addr2);
+  conn = turn_port_->CreateConnection(remote_candidate, Port::ORIGIN_MESSAGE);
+  EXPECT_EQ(nullptr, conn);
+}
+
+// Test that a CreatePermission failure will result in the connection being
+// pruned and failed.
+TEST_F(TurnPortTest, TestConnectionFailedAndPrunedOnCreatePermissionFailure) {
+  turn_server_.AddInternalSocket(kTurnTcpIntAddr, PROTO_TCP);
+  turn_server_.server()->set_reject_private_addresses(true);
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnTcpProtoAddr);
+  turn_port_->PrepareAddress();
+  EXPECT_TRUE_SIMULATED_WAIT(turn_ready_, kSimulatedRtt * 3, fake_clock_);
+
+  CreateUdpPort(SocketAddress("10.0.0.10", 0));
+  udp_port_->PrepareAddress();
+  EXPECT_TRUE_SIMULATED_WAIT(udp_ready_, kSimulatedRtt, fake_clock_);
+  // Create a connection.
+  TestConnectionWrapper conn(turn_port_->CreateConnection(
+      udp_port_->Candidates()[0], Port::ORIGIN_MESSAGE));
+  EXPECT_TRUE(conn.connection() != nullptr);
+
+  // Asynchronously, CreatePermission request should be sent and fail, which
+  // will make the connection pruned and failed.
+  EXPECT_TRUE_SIMULATED_WAIT(CheckConnectionFailedAndPruned(conn.connection()),
+                             kSimulatedRtt, fake_clock_);
+  EXPECT_TRUE_SIMULATED_WAIT(!turn_create_permission_success_, kSimulatedRtt,
+                             fake_clock_);
+  // Check that the connection is not deleted asynchronously.
+  SIMULATED_WAIT(conn.connection() == nullptr, kConnectionDestructionDelay,
+                 fake_clock_);
+  EXPECT_NE(nullptr, conn.connection());
+}
+
+// Test that a TURN allocation is released when the port is closed.
+TEST_F(TurnPortTest, TestTurnReleaseAllocation) {
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnUdpProtoAddr);
+  TestTurnReleaseAllocation(PROTO_UDP);
+}
+
+// Test that a TURN TCP allocation is released when the port is closed.
+TEST_F(TurnPortTest, TestTurnTCPReleaseAllocation) {
+  turn_server_.AddInternalSocket(kTurnTcpIntAddr, PROTO_TCP);
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnTcpProtoAddr);
+  TestTurnReleaseAllocation(PROTO_TCP);
+}
+
+TEST_F(TurnPortTest, TestTurnTLSReleaseAllocation) {
+  turn_server_.AddInternalSocket(kTurnTcpIntAddr, PROTO_TLS);
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnTlsProtoAddr);
+  TestTurnReleaseAllocation(PROTO_TLS);
+}
+
+TEST_F(TurnPortTest, TestTurnUDPGracefulReleaseAllocation) {
+  turn_server_.AddInternalSocket(kTurnTcpIntAddr, PROTO_UDP);
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnUdpProtoAddr);
+  TestTurnGracefulReleaseAllocation(PROTO_UDP);
+}
+
+TEST_F(TurnPortTest, TestTurnTCPGracefulReleaseAllocation) {
+  turn_server_.AddInternalSocket(kTurnTcpIntAddr, PROTO_TCP);
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnTcpProtoAddr);
+  TestTurnGracefulReleaseAllocation(PROTO_TCP);
+}
+
+TEST_F(TurnPortTest, TestTurnTLSGracefulReleaseAllocation) {
+  turn_server_.AddInternalSocket(kTurnTcpIntAddr, PROTO_TLS);
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnTlsProtoAddr);
+  TestTurnGracefulReleaseAllocation(PROTO_TLS);
+}
+
+// Test that nothing bad happens if we try to create a connection to the same
+// remote address twice. Previously there was a bug that caused this to hit a
+// DCHECK.
+TEST_F(TurnPortTest, CanCreateTwoConnectionsToSameAddress) {
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnUdpProtoAddr);
+  PrepareTurnAndUdpPorts(PROTO_UDP);
+  Connection* conn1 = turn_port_->CreateConnection(udp_port_->Candidates()[0],
+                                                   Port::ORIGIN_MESSAGE);
+  Connection* conn2 = turn_port_->CreateConnection(udp_port_->Candidates()[0],
+                                                   Port::ORIGIN_MESSAGE);
+  EXPECT_NE(conn1, conn2);
+}
+
+// This test verifies any FD's are not leaked after TurnPort is destroyed.
+// https://code.google.com/p/webrtc/issues/detail?id=2651
+#if defined(WEBRTC_LINUX) && !defined(WEBRTC_ANDROID)
+
+TEST_F(TurnPortTest, TestResolverShutdown) {
+  turn_server_.AddInternalSocket(kTurnUdpIPv6IntAddr, PROTO_UDP);
+  int last_fd_count = GetFDCount();
+  // Need to supply unresolved address to kick off resolver.
+  CreateTurnPort(kLocalIPv6Addr, kTurnUsername, kTurnPassword,
+                 ProtocolAddress(kTurnInvalidAddr, PROTO_UDP));
+  turn_port_->PrepareAddress();
+  ASSERT_TRUE_WAIT(turn_error_, kResolverTimeout);
+  EXPECT_TRUE(turn_port_->Candidates().empty());
+  turn_port_.reset();
+  rtc::Thread::Current()->PostTask([this] { test_finish_ = true; });
+  // Waiting for above message to be processed.
+  ASSERT_TRUE_SIMULATED_WAIT(test_finish_, 1, fake_clock_);
+  EXPECT_EQ(last_fd_count, GetFDCount());
+}
+#endif
+
+class MessageObserver : public StunMessageObserver {
+ public:
+  MessageObserver(unsigned int* message_counter,
+                  unsigned int* channel_data_counter,
+                  unsigned int* attr_counter)
+      : message_counter_(message_counter),
+        channel_data_counter_(channel_data_counter),
+        attr_counter_(attr_counter) {}
+  virtual ~MessageObserver() {}
+  void ReceivedMessage(const TurnMessage* msg) override {
+    if (message_counter_ != nullptr) {
+      (*message_counter_)++;
+    }
+    // Implementation defined attributes are returned as ByteString
+    const StunByteStringAttribute* attr =
+        msg->GetByteString(TestTurnCustomizer::STUN_ATTR_COUNTER);
+    if (attr != nullptr && attr_counter_ != nullptr) {
+      rtc::ByteBufferReader buf(attr->bytes(), attr->length());
+      unsigned int val = ~0u;
+      buf.ReadUInt32(&val);
+      (*attr_counter_)++;
+    }
+  }
+
+  void ReceivedChannelData(const char* data, size_t size) override {
+    if (channel_data_counter_ != nullptr) {
+      (*channel_data_counter_)++;
+    }
+  }
+
+  // Number of TurnMessages observed.
+  unsigned int* message_counter_ = nullptr;
+
+  // Number of channel data observed.
+  unsigned int* channel_data_counter_ = nullptr;
+
+  // Number of TurnMessages that had STUN_ATTR_COUNTER.
+  unsigned int* attr_counter_ = nullptr;
+};
+
+// Do a TURN allocation, establish a TLS connection, and send some data.
+// Add customizer and check that it get called.
+TEST_F(TurnPortTest, TestTurnCustomizerCount) {
+  unsigned int observer_message_counter = 0;
+  unsigned int observer_channel_data_counter = 0;
+  unsigned int observer_attr_counter = 0;
+  TestTurnCustomizer* customizer = new TestTurnCustomizer();
+  std::unique_ptr<MessageObserver> validator(new MessageObserver(
+      &observer_message_counter, &observer_channel_data_counter,
+      &observer_attr_counter));
+
+  turn_server_.AddInternalSocket(kTurnTcpIntAddr, PROTO_TLS);
+  turn_customizer_.reset(customizer);
+  turn_server_.server()->SetStunMessageObserver(std::move(validator));
+
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnTlsProtoAddr);
+  TestTurnSendData(PROTO_TLS);
+  EXPECT_EQ(TLS_PROTOCOL_NAME, turn_port_->Candidates()[0].relay_protocol());
+
+  // There should have been at least turn_packets_.size() calls to `customizer`.
+  EXPECT_GE(customizer->modify_cnt_ + customizer->allow_channel_data_cnt_,
+            turn_packets_.size());
+
+  // Some channel data should be received.
+  EXPECT_GE(observer_channel_data_counter, 0u);
+
+  // Need to release TURN port before the customizer.
+  turn_port_.reset(nullptr);
+}
+
+// Do a TURN allocation, establish a TLS connection, and send some data.
+// Add customizer and check that it can can prevent usage of channel data.
+TEST_F(TurnPortTest, TestTurnCustomizerDisallowChannelData) {
+  unsigned int observer_message_counter = 0;
+  unsigned int observer_channel_data_counter = 0;
+  unsigned int observer_attr_counter = 0;
+  TestTurnCustomizer* customizer = new TestTurnCustomizer();
+  std::unique_ptr<MessageObserver> validator(new MessageObserver(
+      &observer_message_counter, &observer_channel_data_counter,
+      &observer_attr_counter));
+  customizer->allow_channel_data_ = false;
+  turn_server_.AddInternalSocket(kTurnTcpIntAddr, PROTO_TLS);
+  turn_customizer_.reset(customizer);
+  turn_server_.server()->SetStunMessageObserver(std::move(validator));
+
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnTlsProtoAddr);
+  TestTurnSendData(PROTO_TLS);
+  EXPECT_EQ(TLS_PROTOCOL_NAME, turn_port_->Candidates()[0].relay_protocol());
+
+  // There should have been at least turn_packets_.size() calls to `customizer`.
+  EXPECT_GE(customizer->modify_cnt_, turn_packets_.size());
+
+  // No channel data should be received.
+  EXPECT_EQ(observer_channel_data_counter, 0u);
+
+  // Need to release TURN port before the customizer.
+  turn_port_.reset(nullptr);
+}
+
+// Do a TURN allocation, establish a TLS connection, and send some data.
+// Add customizer and check that it can add attribute to messages.
+TEST_F(TurnPortTest, TestTurnCustomizerAddAttribute) {
+  unsigned int observer_message_counter = 0;
+  unsigned int observer_channel_data_counter = 0;
+  unsigned int observer_attr_counter = 0;
+  TestTurnCustomizer* customizer = new TestTurnCustomizer();
+  std::unique_ptr<MessageObserver> validator(new MessageObserver(
+      &observer_message_counter, &observer_channel_data_counter,
+      &observer_attr_counter));
+  customizer->allow_channel_data_ = false;
+  customizer->add_counter_ = true;
+  turn_server_.AddInternalSocket(kTurnTcpIntAddr, PROTO_TLS);
+  turn_customizer_.reset(customizer);
+  turn_server_.server()->SetStunMessageObserver(std::move(validator));
+
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnTlsProtoAddr);
+  TestTurnSendData(PROTO_TLS);
+  EXPECT_EQ(TLS_PROTOCOL_NAME, turn_port_->Candidates()[0].relay_protocol());
+
+  // There should have been at least turn_packets_.size() calls to `customizer`.
+  EXPECT_GE(customizer->modify_cnt_, turn_packets_.size());
+
+  // Everything will be sent as messages since channel data is disallowed.
+  EXPECT_GE(customizer->modify_cnt_, observer_message_counter);
+
+  // All messages should have attribute.
+  EXPECT_EQ(observer_message_counter, observer_attr_counter);
+
+  // At least allow_channel_data_cnt_ messages should have been sent.
+  EXPECT_GE(customizer->modify_cnt_, customizer->allow_channel_data_cnt_);
+  EXPECT_GE(customizer->allow_channel_data_cnt_, 0u);
+
+  // No channel data should be received.
+  EXPECT_EQ(observer_channel_data_counter, 0u);
+
+  // Need to release TURN port before the customizer.
+  turn_port_.reset(nullptr);
+}
+
+TEST_F(TurnPortTest, TestOverlongUsername) {
+  std::string overlong_username(513, 'x');
+  RelayCredentials credentials(overlong_username, kTurnPassword);
+  EXPECT_FALSE(
+      CreateTurnPort(overlong_username, kTurnPassword, kTurnTlsProtoAddr));
+}
+
+TEST_F(TurnPortTest, TestTurnDangerousServer) {
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnDangerousProtoAddr);
+  ASSERT_FALSE(turn_port_);
+}
+
+TEST_F(TurnPortTest, TestTurnDangerousServerPermits53) {
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnPort53ProtoAddr);
+  ASSERT_TRUE(turn_port_);
+}
+
+TEST_F(TurnPortTest, TestTurnDangerousServerPermits80) {
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnPort80ProtoAddr);
+  ASSERT_TRUE(turn_port_);
+}
+
+TEST_F(TurnPortTest, TestTurnDangerousServerPermits443) {
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnPort443ProtoAddr);
+  ASSERT_TRUE(turn_port_);
+}
+
+TEST_F(TurnPortTest, TestTurnDangerousAlternateServer) {
+  const ProtocolType protocol_type = PROTO_TCP;
+  std::vector<rtc::SocketAddress> redirect_addresses;
+  redirect_addresses.push_back(kTurnDangerousAddr);
+
+  TestTurnRedirector redirector(redirect_addresses);
+
+  turn_server_.AddInternalSocket(kTurnIntAddr, protocol_type);
+  turn_server_.AddInternalSocket(kTurnDangerousAddr, protocol_type);
+  turn_server_.set_redirect_hook(&redirector);
+  CreateTurnPort(kTurnUsername, kTurnPassword,
+                 ProtocolAddress(kTurnIntAddr, protocol_type));
+
+  // Retrieve the address before we run the state machine.
+  const SocketAddress old_addr = turn_port_->server_address().address;
+
+  turn_port_->PrepareAddress();
+  // This should result in an error event.
+  EXPECT_TRUE_SIMULATED_WAIT(error_event_.error_code != 0,
+                             TimeToGetAlternateTurnCandidate(protocol_type),
+                             fake_clock_);
+  // but should NOT result in the port turning ready, and no candidates
+  // should be gathered.
+  EXPECT_FALSE(turn_ready_);
+  ASSERT_EQ(0U, turn_port_->Candidates().size());
+}
+
+TEST_F(TurnPortTest, TestTurnDangerousServerAllowedWithFieldTrial) {
+  webrtc::test::ScopedKeyValueConfig override_field_trials(
+      field_trials_, "WebRTC-Turn-AllowSystemPorts/Enabled/");
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnDangerousProtoAddr);
+  ASSERT_TRUE(turn_port_);
+}
+
+class TurnPortWithMockDnsResolverTest : public TurnPortTest {
+ public:
+  TurnPortWithMockDnsResolverTest()
+      : TurnPortTest(), socket_factory_(ss_.get()) {}
+
+  rtc::PacketSocketFactory* socket_factory() override {
+    return &socket_factory_;
+  }
+
+  void SetDnsResolverExpectations(
+      rtc::MockDnsResolvingPacketSocketFactory::Expectations expectations) {
+    socket_factory_.SetExpectations(expectations);
+  }
+
+ private:
+  rtc::MockDnsResolvingPacketSocketFactory socket_factory_;
+};
+
+// Test an allocation from a TURN server specified by a hostname.
+TEST_F(TurnPortWithMockDnsResolverTest, TestHostnameResolved) {
+  CreateTurnPort(kTurnUsername, kTurnPassword, kTurnPortValidHostnameProtoAddr);
+  SetDnsResolverExpectations(
+      [](webrtc::MockAsyncDnsResolver* resolver,
+         webrtc::MockAsyncDnsResolverResult* resolver_result) {
+        EXPECT_CALL(*resolver, Start(kTurnValidAddr, _))
+            .WillOnce(InvokeArgument<1>());
+        EXPECT_CALL(*resolver, result)
+            .WillRepeatedly(ReturnPointee(resolver_result));
+        EXPECT_CALL(*resolver_result, GetError).WillRepeatedly(Return(0));
+        EXPECT_CALL(*resolver_result, GetResolvedAddress(AF_INET, _))
+            .WillOnce(DoAll(SetArgPointee<1>(kTurnUdpIntAddr), Return(true)));
+      });
+  TestTurnAllocateSucceeds(kSimulatedRtt * 2);
+}
+
+// Test an allocation from a TURN server specified by a hostname on an IPv6
+// network.
+TEST_F(TurnPortWithMockDnsResolverTest, TestHostnameResolvedIPv6Network) {
+  turn_server_.AddInternalSocket(kTurnUdpIPv6IntAddr, PROTO_UDP);
+  CreateTurnPort(kLocalIPv6Addr, kTurnUsername, kTurnPassword,
+                 kTurnPortValidHostnameProtoAddr);
+  SetDnsResolverExpectations(
+      [](webrtc::MockAsyncDnsResolver* resolver,
+         webrtc::MockAsyncDnsResolverResult* resolver_result) {
+        EXPECT_CALL(*resolver, Start(kTurnValidAddr, _))
+            .WillOnce(InvokeArgument<1>());
+        EXPECT_CALL(*resolver, result)
+            .WillRepeatedly(ReturnPointee(resolver_result));
+        EXPECT_CALL(*resolver_result, GetError).WillRepeatedly(Return(0));
+        EXPECT_CALL(*resolver_result, GetResolvedAddress(AF_INET6, _))
+            .WillOnce(
+                DoAll(SetArgPointee<1>(kTurnUdpIPv6IntAddr), Return(true)));
+      });
+  TestTurnAllocateSucceeds(kSimulatedRtt * 2);
+}
+
+// Test an allocation from a TURN server specified by a hostname on an IPv6
+// network, without network family-specific resolution.
+TEST_F(TurnPortWithMockDnsResolverTest,
+       TestHostnameResolvedIPv6NetworkFamilyFieldTrialDisabled) {
+  webrtc::test::ScopedKeyValueConfig override_field_trials(
+      field_trials_, "WebRTC-IPv6NetworkResolutionFixes/Disabled/");
+  turn_server_.AddInternalSocket(kTurnUdpIPv6IntAddr, PROTO_UDP);
+  CreateTurnPort(kLocalIPv6Addr, kTurnUsername, kTurnPassword,
+                 kTurnPortValidHostnameProtoAddr);
+  SetDnsResolverExpectations(
+      [](webrtc::MockAsyncDnsResolver* resolver,
+         webrtc::MockAsyncDnsResolverResult* resolver_result) {
+        // Expect to call Resolver::Start without family arg.
+        EXPECT_CALL(*resolver, Start(kTurnValidAddr, _))
+            .WillOnce(InvokeArgument<1>());
+        EXPECT_CALL(*resolver, result)
+            .WillRepeatedly(ReturnPointee(resolver_result));
+        EXPECT_CALL(*resolver_result, GetError).WillRepeatedly(Return(0));
+        EXPECT_CALL(*resolver_result, GetResolvedAddress(AF_INET6, _))
+            .WillOnce(
+                DoAll(SetArgPointee<1>(kTurnUdpIPv6IntAddr), Return(true)));
+      });
+  TestTurnAllocateSucceeds(kSimulatedRtt * 2);
+}
+
+// Test an allocation from a TURN server specified by a hostname on an IPv6
+// network, without network family-specific resolution.
+TEST_F(TurnPortWithMockDnsResolverTest,
+       TestHostnameResolvedIPv6NetworkFamilyFieldTrialParamDisabled) {
+  webrtc::test::ScopedKeyValueConfig override_field_trials(
+      field_trials_,
+      "WebRTC-IPv6NetworkResolutionFixes/"
+      "Enabled,ResolveTurnHostnameForFamily:false/");
+  turn_server_.AddInternalSocket(kTurnUdpIPv6IntAddr, PROTO_UDP);
+  CreateTurnPort(kLocalIPv6Addr, kTurnUsername, kTurnPassword,
+                 kTurnPortValidHostnameProtoAddr);
+  SetDnsResolverExpectations(
+      [](webrtc::MockAsyncDnsResolver* resolver,
+         webrtc::MockAsyncDnsResolverResult* resolver_result) {
+        // Expect to call Resolver::Start without family arg.
+        EXPECT_CALL(*resolver, Start(kTurnValidAddr, _))
+            .WillOnce(InvokeArgument<1>());
+        EXPECT_CALL(*resolver, result)
+            .WillRepeatedly(ReturnPointee(resolver_result));
+        EXPECT_CALL(*resolver_result, GetError).WillRepeatedly(Return(0));
+        EXPECT_CALL(*resolver_result, GetResolvedAddress(AF_INET6, _))
+            .WillOnce(
+                DoAll(SetArgPointee<1>(kTurnUdpIPv6IntAddr), Return(true)));
+      });
+  TestTurnAllocateSucceeds(kSimulatedRtt * 2);
+}
+
+// Test an allocation from a TURN server specified by a hostname on an IPv6
+// network, with network family-specific resolution.
+TEST_F(TurnPortWithMockDnsResolverTest,
+       TestHostnameResolvedIPv6NetworkFieldTrialEnabled) {
+  webrtc::test::ScopedKeyValueConfig override_field_trials(
+      field_trials_,
+      "WebRTC-IPv6NetworkResolutionFixes/"
+      "Enabled,ResolveTurnHostnameForFamily:true/");
+  turn_server_.AddInternalSocket(kTurnUdpIPv6IntAddr, PROTO_UDP);
+  CreateTurnPort(kLocalIPv6Addr, kTurnUsername, kTurnPassword,
+                 kTurnPortValidHostnameProtoAddr);
+  SetDnsResolverExpectations(
+      [](webrtc::MockAsyncDnsResolver* resolver,
+         webrtc::MockAsyncDnsResolverResult* resolver_result) {
+        // Expect to call Resolver::Start _with_ family arg.
+        EXPECT_CALL(*resolver, Start(kTurnValidAddr, /*family=*/AF_INET6, _))
+            .WillOnce(InvokeArgument<2>());
+        EXPECT_CALL(*resolver, result)
+            .WillRepeatedly(ReturnPointee(resolver_result));
+        EXPECT_CALL(*resolver_result, GetError).WillRepeatedly(Return(0));
+        EXPECT_CALL(*resolver_result, GetResolvedAddress(AF_INET6, _))
+            .WillOnce(
+                DoAll(SetArgPointee<1>(kTurnUdpIPv6IntAddr), Return(true)));
+      });
+  TestTurnAllocateSucceeds(kSimulatedRtt * 2);
+}
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/turn_server.cc b/third_party/libwebrtc/p2p/base/turn_server.cc
new file mode 100644
index 0000000000..e11b52aecd
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/turn_server.cc
@@ -0,0 +1,881 @@
+/*
+ *  Copyright 2012 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/turn_server.h"
+
+#include <algorithm>
+#include <memory>
+#include <tuple>  // for std::tie
+#include <utility>
+
+#include "absl/algorithm/container.h"
+#include "absl/memory/memory.h"
+#include "absl/strings/string_view.h"
+#include "api/array_view.h"
+#include "api/packet_socket_factory.h"
+#include "api/task_queue/task_queue_base.h"
+#include "api/transport/stun.h"
+#include "p2p/base/async_stun_tcp_socket.h"
+#include "rtc_base/byte_buffer.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/helpers.h"
+#include "rtc_base/logging.h"
+#include "rtc_base/message_digest.h"
+#include "rtc_base/socket_adapters.h"
+#include "rtc_base/strings/string_builder.h"
+
+namespace cricket {
+namespace {
+using ::webrtc::TimeDelta;
+
+// TODO(juberti): Move this all to a future turnmessage.h
+//  static const int IPPROTO_UDP = 17;
+constexpr TimeDelta kNonceTimeout = TimeDelta::Minutes(60);
+constexpr TimeDelta kDefaultAllocationTimeout = TimeDelta::Minutes(10);
+constexpr TimeDelta kPermissionTimeout = TimeDelta::Minutes(5);
+constexpr TimeDelta kChannelTimeout = TimeDelta::Minutes(10);
+
+constexpr int kMinChannelNumber = 0x4000;
+constexpr int kMaxChannelNumber = 0x7FFF;
+
+constexpr size_t kNonceKeySize = 16;
+constexpr size_t kNonceSize = 48;
+
+constexpr size_t TURN_CHANNEL_HEADER_SIZE = 4U;
+
+// TODO(mallinath) - Move these to a common place.
+bool IsTurnChannelData(uint16_t msg_type) {
+  // The first two bits of a channel data message are 0b01.
+  return ((msg_type & 0xC000) == 0x4000);
+}
+
+}  // namespace
+
+int GetStunSuccessResponseTypeOrZero(const StunMessage& req) {
+  const int resp_type = GetStunSuccessResponseType(req.type());
+  return resp_type == -1 ? 0 : resp_type;
+}
+
+int GetStunErrorResponseTypeOrZero(const StunMessage& req) {
+  const int resp_type = GetStunErrorResponseType(req.type());
+  return resp_type == -1 ? 0 : resp_type;
+}
+
+static void InitErrorResponse(int code,
+                              absl::string_view reason,
+                              StunMessage* resp) {
+  resp->AddAttribute(std::make_unique<cricket::StunErrorCodeAttribute>(
+      STUN_ATTR_ERROR_CODE, code, std::string(reason)));
+}
+
+TurnServer::TurnServer(webrtc::TaskQueueBase* thread)
+    : thread_(thread),
+      nonce_key_(rtc::CreateRandomString(kNonceKeySize)),
+      auth_hook_(NULL),
+      redirect_hook_(NULL),
+      enable_otu_nonce_(false) {}
+
+TurnServer::~TurnServer() {
+  RTC_DCHECK_RUN_ON(thread_);
+  for (InternalSocketMap::iterator it = server_sockets_.begin();
+       it != server_sockets_.end(); ++it) {
+    rtc::AsyncPacketSocket* socket = it->first;
+    delete socket;
+  }
+
+  for (ServerSocketMap::iterator it = server_listen_sockets_.begin();
+       it != server_listen_sockets_.end(); ++it) {
+    rtc::Socket* socket = it->first;
+    delete socket;
+  }
+}
+
+void TurnServer::AddInternalSocket(rtc::AsyncPacketSocket* socket,
+                                   ProtocolType proto) {
+  RTC_DCHECK_RUN_ON(thread_);
+  RTC_DCHECK(server_sockets_.end() == server_sockets_.find(socket));
+  server_sockets_[socket] = proto;
+  socket->SignalReadPacket.connect(this, &TurnServer::OnInternalPacket);
+}
+
+void TurnServer::AddInternalServerSocket(
+    rtc::Socket* socket,
+    ProtocolType proto,
+    std::unique_ptr<rtc::SSLAdapterFactory> ssl_adapter_factory) {
+  RTC_DCHECK_RUN_ON(thread_);
+
+  RTC_DCHECK(server_listen_sockets_.end() ==
+             server_listen_sockets_.find(socket));
+  server_listen_sockets_[socket] = {proto, std::move(ssl_adapter_factory)};
+  socket->SignalReadEvent.connect(this, &TurnServer::OnNewInternalConnection);
+}
+
+void TurnServer::SetExternalSocketFactory(
+    rtc::PacketSocketFactory* factory,
+    const rtc::SocketAddress& external_addr) {
+  RTC_DCHECK_RUN_ON(thread_);
+  external_socket_factory_.reset(factory);
+  external_addr_ = external_addr;
+}
+
+void TurnServer::OnNewInternalConnection(rtc::Socket* socket) {
+  RTC_DCHECK_RUN_ON(thread_);
+  RTC_DCHECK(server_listen_sockets_.find(socket) !=
+             server_listen_sockets_.end());
+  AcceptConnection(socket);
+}
+
+void TurnServer::AcceptConnection(rtc::Socket* server_socket) {
+  // Check if someone is trying to connect to us.
+  rtc::SocketAddress accept_addr;
+  rtc::Socket* accepted_socket = server_socket->Accept(&accept_addr);
+  if (accepted_socket != NULL) {
+    const ServerSocketInfo& info = server_listen_sockets_[server_socket];
+    if (info.ssl_adapter_factory) {
+      rtc::SSLAdapter* ssl_adapter =
+          info.ssl_adapter_factory->CreateAdapter(accepted_socket);
+      ssl_adapter->StartSSL("");
+      accepted_socket = ssl_adapter;
+    }
+    cricket::AsyncStunTCPSocket* tcp_socket =
+        new cricket::AsyncStunTCPSocket(accepted_socket);
+
+    tcp_socket->SubscribeClose(this,
+                               [this](rtc::AsyncPacketSocket* s, int err) {
+                                 OnInternalSocketClose(s, err);
+                               });
+    // Finally add the socket so it can start communicating with the client.
+    AddInternalSocket(tcp_socket, info.proto);
+  }
+}
+
+void TurnServer::OnInternalSocketClose(rtc::AsyncPacketSocket* socket,
+                                       int err) {
+  RTC_DCHECK_RUN_ON(thread_);
+  DestroyInternalSocket(socket);
+}
+
+void TurnServer::OnInternalPacket(rtc::AsyncPacketSocket* socket,
+                                  const char* data,
+                                  size_t size,
+                                  const rtc::SocketAddress& addr,
+                                  const int64_t& /* packet_time_us */) {
+  RTC_DCHECK_RUN_ON(thread_);
+  // Fail if the packet is too small to even contain a channel header.
+  if (size < TURN_CHANNEL_HEADER_SIZE) {
+    return;
+  }
+  InternalSocketMap::iterator iter = server_sockets_.find(socket);
+  RTC_DCHECK(iter != server_sockets_.end());
+  TurnServerConnection conn(addr, iter->second, socket);
+  uint16_t msg_type = rtc::GetBE16(data);
+  if (!IsTurnChannelData(msg_type)) {
+    // This is a STUN message.
+    HandleStunMessage(&conn, data, size);
+  } else {
+    // This is a channel message; let the allocation handle it.
+    TurnServerAllocation* allocation = FindAllocation(&conn);
+    if (allocation) {
+      allocation->HandleChannelData(data, size);
+    }
+    if (stun_message_observer_ != nullptr) {
+      stun_message_observer_->ReceivedChannelData(data, size);
+    }
+  }
+}
+
+void TurnServer::HandleStunMessage(TurnServerConnection* conn,
+                                   const char* data,
+                                   size_t size) {
+  TurnMessage msg;
+  rtc::ByteBufferReader buf(data, size);
+  if (!msg.Read(&buf) || (buf.Length() > 0)) {
+    RTC_LOG(LS_WARNING) << "Received invalid STUN message";
+    return;
+  }
+
+  if (stun_message_observer_ != nullptr) {
+    stun_message_observer_->ReceivedMessage(&msg);
+  }
+
+  // If it's a STUN binding request, handle that specially.
+  if (msg.type() == STUN_BINDING_REQUEST) {
+    HandleBindingRequest(conn, &msg);
+    return;
+  }
+
+  if (redirect_hook_ != NULL && msg.type() == STUN_ALLOCATE_REQUEST) {
+    rtc::SocketAddress address;
+    if (redirect_hook_->ShouldRedirect(conn->src(), &address)) {
+      SendErrorResponseWithAlternateServer(conn, &msg, address);
+      return;
+    }
+  }
+
+  // Look up the key that we'll use to validate the M-I. If we have an
+  // existing allocation, the key will already be cached.
+  TurnServerAllocation* allocation = FindAllocation(conn);
+  std::string key;
+  if (!allocation) {
+    GetKey(&msg, &key);
+  } else {
+    key = allocation->key();
+  }
+
+  // Ensure the message is authorized; only needed for requests.
+  if (IsStunRequestType(msg.type())) {
+    if (!CheckAuthorization(conn, &msg, data, size, key)) {
+      return;
+    }
+  }
+
+  if (!allocation && msg.type() == STUN_ALLOCATE_REQUEST) {
+    HandleAllocateRequest(conn, &msg, key);
+  } else if (allocation &&
+             (msg.type() != STUN_ALLOCATE_REQUEST ||
+              msg.transaction_id() == allocation->transaction_id())) {
+    // This is a non-allocate request, or a retransmit of an allocate.
+    // Check that the username matches the previous username used.
+    if (IsStunRequestType(msg.type()) &&
+        msg.GetByteString(STUN_ATTR_USERNAME)->string_view() !=
+            allocation->username()) {
+      SendErrorResponse(conn, &msg, STUN_ERROR_WRONG_CREDENTIALS,
+                        STUN_ERROR_REASON_WRONG_CREDENTIALS);
+      return;
+    }
+    allocation->HandleTurnMessage(&msg);
+  } else {
+    // Allocation mismatch.
+    SendErrorResponse(conn, &msg, STUN_ERROR_ALLOCATION_MISMATCH,
+                      STUN_ERROR_REASON_ALLOCATION_MISMATCH);
+  }
+}
+
+bool TurnServer::GetKey(const StunMessage* msg, std::string* key) {
+  const StunByteStringAttribute* username_attr =
+      msg->GetByteString(STUN_ATTR_USERNAME);
+  if (!username_attr) {
+    return false;
+  }
+
+  return (auth_hook_ != NULL &&
+          auth_hook_->GetKey(std::string(username_attr->string_view()), realm_,
+                             key));
+}
+
+bool TurnServer::CheckAuthorization(TurnServerConnection* conn,
+                                    StunMessage* msg,
+                                    const char* data,
+                                    size_t size,
+                                    absl::string_view key) {
+  // RFC 5389, 10.2.2.
+  RTC_DCHECK(IsStunRequestType(msg->type()));
+  const StunByteStringAttribute* mi_attr =
+      msg->GetByteString(STUN_ATTR_MESSAGE_INTEGRITY);
+  const StunByteStringAttribute* username_attr =
+      msg->GetByteString(STUN_ATTR_USERNAME);
+  const StunByteStringAttribute* realm_attr =
+      msg->GetByteString(STUN_ATTR_REALM);
+  const StunByteStringAttribute* nonce_attr =
+      msg->GetByteString(STUN_ATTR_NONCE);
+
+  // Fail if no MESSAGE_INTEGRITY.
+  if (!mi_attr) {
+    SendErrorResponseWithRealmAndNonce(conn, msg, STUN_ERROR_UNAUTHORIZED,
+                                       STUN_ERROR_REASON_UNAUTHORIZED);
+    return false;
+  }
+
+  // Fail if there is MESSAGE_INTEGRITY but no username, nonce, or realm.
+  if (!username_attr || !realm_attr || !nonce_attr) {
+    SendErrorResponse(conn, msg, STUN_ERROR_BAD_REQUEST,
+                      STUN_ERROR_REASON_BAD_REQUEST);
+    return false;
+  }
+
+  // Fail if bad nonce.
+  if (!ValidateNonce(nonce_attr->string_view())) {
+    SendErrorResponseWithRealmAndNonce(conn, msg, STUN_ERROR_STALE_NONCE,
+                                       STUN_ERROR_REASON_STALE_NONCE);
+    return false;
+  }
+
+  // Fail if bad MESSAGE_INTEGRITY.
+  if (key.empty() || msg->ValidateMessageIntegrity(std::string(key)) !=
+                         StunMessage::IntegrityStatus::kIntegrityOk) {
+    SendErrorResponseWithRealmAndNonce(conn, msg, STUN_ERROR_UNAUTHORIZED,
+                                       STUN_ERROR_REASON_UNAUTHORIZED);
+    return false;
+  }
+
+  // Fail if one-time-use nonce feature is enabled.
+  TurnServerAllocation* allocation = FindAllocation(conn);
+  if (enable_otu_nonce_ && allocation &&
+      allocation->last_nonce() == nonce_attr->string_view()) {
+    SendErrorResponseWithRealmAndNonce(conn, msg, STUN_ERROR_STALE_NONCE,
+                                       STUN_ERROR_REASON_STALE_NONCE);
+    return false;
+  }
+
+  if (allocation) {
+    allocation->set_last_nonce(nonce_attr->string_view());
+  }
+  // Success.
+  return true;
+}
+
+void TurnServer::HandleBindingRequest(TurnServerConnection* conn,
+                                      const StunMessage* req) {
+  StunMessage response(GetStunSuccessResponseTypeOrZero(*req),
+                       req->transaction_id());
+  // Tell the user the address that we received their request from.
+  auto mapped_addr_attr = std::make_unique<StunXorAddressAttribute>(
+      STUN_ATTR_XOR_MAPPED_ADDRESS, conn->src());
+  response.AddAttribute(std::move(mapped_addr_attr));
+
+  SendStun(conn, &response);
+}
+
+void TurnServer::HandleAllocateRequest(TurnServerConnection* conn,
+                                       const TurnMessage* msg,
+                                       absl::string_view key) {
+  // Check the parameters in the request.
+  const StunUInt32Attribute* transport_attr =
+      msg->GetUInt32(STUN_ATTR_REQUESTED_TRANSPORT);
+  if (!transport_attr) {
+    SendErrorResponse(conn, msg, STUN_ERROR_BAD_REQUEST,
+                      STUN_ERROR_REASON_BAD_REQUEST);
+    return;
+  }
+
+  // Only UDP is supported right now.
+  int proto = transport_attr->value() >> 24;
+  if (proto != IPPROTO_UDP) {
+    SendErrorResponse(conn, msg, STUN_ERROR_UNSUPPORTED_PROTOCOL,
+                      STUN_ERROR_REASON_UNSUPPORTED_PROTOCOL);
+    return;
+  }
+
+  // Create the allocation and let it send the success response.
+  // If the actual socket allocation fails, send an internal error.
+  TurnServerAllocation* alloc = CreateAllocation(conn, proto, key);
+  if (alloc) {
+    alloc->HandleTurnMessage(msg);
+  } else {
+    SendErrorResponse(conn, msg, STUN_ERROR_SERVER_ERROR,
+                      "Failed to allocate socket");
+  }
+}
+
+std::string TurnServer::GenerateNonce(int64_t now) const {
+  // Generate a nonce of the form hex(now + HMAC-MD5(nonce_key_, now))
+  std::string input(reinterpret_cast<const char*>(&now), sizeof(now));
+  std::string nonce = rtc::hex_encode(input);
+  nonce += rtc::ComputeHmac(rtc::DIGEST_MD5, nonce_key_, input);
+  RTC_DCHECK(nonce.size() == kNonceSize);
+
+  return nonce;
+}
+
+bool TurnServer::ValidateNonce(absl::string_view nonce) const {
+  // Check the size.
+  if (nonce.size() != kNonceSize) {
+    return false;
+  }
+
+  // Decode the timestamp.
+  int64_t then;
+  char* p = reinterpret_cast<char*>(&then);
+  size_t len = rtc::hex_decode(rtc::ArrayView<char>(p, sizeof(then)),
+                               nonce.substr(0, sizeof(then) * 2));
+  if (len != sizeof(then)) {
+    return false;
+  }
+
+  // Verify the HMAC.
+  if (nonce.substr(sizeof(then) * 2) !=
+      rtc::ComputeHmac(rtc::DIGEST_MD5, nonce_key_,
+                       std::string(p, sizeof(then)))) {
+    return false;
+  }
+
+  // Validate the timestamp.
+  return TimeDelta::Millis(rtc::TimeMillis() - then) < kNonceTimeout;
+}
+
+TurnServerAllocation* TurnServer::FindAllocation(TurnServerConnection* conn) {
+  AllocationMap::const_iterator it = allocations_.find(*conn);
+  return (it != allocations_.end()) ? it->second.get() : nullptr;
+}
+
+TurnServerAllocation* TurnServer::CreateAllocation(TurnServerConnection* conn,
+                                                   int proto,
+                                                   absl::string_view key) {
+  rtc::AsyncPacketSocket* external_socket =
+      (external_socket_factory_)
+          ? external_socket_factory_->CreateUdpSocket(external_addr_, 0, 0)
+          : NULL;
+  if (!external_socket) {
+    return NULL;
+  }
+
+  // The Allocation takes ownership of the socket.
+  TurnServerAllocation* allocation =
+      new TurnServerAllocation(this, thread_, *conn, external_socket, key);
+  allocations_[*conn].reset(allocation);
+  return allocation;
+}
+
+void TurnServer::SendErrorResponse(TurnServerConnection* conn,
+                                   const StunMessage* req,
+                                   int code,
+                                   absl::string_view reason) {
+  RTC_DCHECK_RUN_ON(thread_);
+  TurnMessage resp(GetStunErrorResponseTypeOrZero(*req), req->transaction_id());
+  InitErrorResponse(code, reason, &resp);
+
+  RTC_LOG(LS_INFO) << "Sending error response, type=" << resp.type()
+                   << ", code=" << code << ", reason=" << reason;
+  SendStun(conn, &resp);
+}
+
+void TurnServer::SendErrorResponseWithRealmAndNonce(TurnServerConnection* conn,
+                                                    const StunMessage* msg,
+                                                    int code,
+                                                    absl::string_view reason) {
+  TurnMessage resp(GetStunErrorResponseTypeOrZero(*msg), msg->transaction_id());
+  InitErrorResponse(code, reason, &resp);
+
+  int64_t timestamp = rtc::TimeMillis();
+  if (ts_for_next_nonce_) {
+    timestamp = ts_for_next_nonce_;
+    ts_for_next_nonce_ = 0;
+  }
+  resp.AddAttribute(std::make_unique<StunByteStringAttribute>(
+      STUN_ATTR_NONCE, GenerateNonce(timestamp)));
+  resp.AddAttribute(
+      std::make_unique<StunByteStringAttribute>(STUN_ATTR_REALM, realm_));
+  SendStun(conn, &resp);
+}
+
+void TurnServer::SendErrorResponseWithAlternateServer(
+    TurnServerConnection* conn,
+    const StunMessage* msg,
+    const rtc::SocketAddress& addr) {
+  TurnMessage resp(GetStunErrorResponseTypeOrZero(*msg), msg->transaction_id());
+  InitErrorResponse(STUN_ERROR_TRY_ALTERNATE,
+                    STUN_ERROR_REASON_TRY_ALTERNATE_SERVER, &resp);
+  resp.AddAttribute(
+      std::make_unique<StunAddressAttribute>(STUN_ATTR_ALTERNATE_SERVER, addr));
+  SendStun(conn, &resp);
+}
+
+void TurnServer::SendStun(TurnServerConnection* conn, StunMessage* msg) {
+  RTC_DCHECK_RUN_ON(thread_);
+  rtc::ByteBufferWriter buf;
+  // Add a SOFTWARE attribute if one is set.
+  if (!software_.empty()) {
+    msg->AddAttribute(std::make_unique<StunByteStringAttribute>(
+        STUN_ATTR_SOFTWARE, software_));
+  }
+  msg->Write(&buf);
+  Send(conn, buf);
+}
+
+void TurnServer::Send(TurnServerConnection* conn,
+                      const rtc::ByteBufferWriter& buf) {
+  RTC_DCHECK_RUN_ON(thread_);
+  rtc::PacketOptions options;
+  conn->socket()->SendTo(buf.Data(), buf.Length(), conn->src(), options);
+}
+
+void TurnServer::DestroyAllocation(TurnServerAllocation* allocation) {
+  // Removing the internal socket if the connection is not udp.
+  rtc::AsyncPacketSocket* socket = allocation->conn()->socket();
+  InternalSocketMap::iterator iter = server_sockets_.find(socket);
+  // Skip if the socket serving this allocation is UDP, as this will be shared
+  // by all allocations.
+  // Note: We may not find a socket if it's a TCP socket that was closed, and
+  // the allocation is only now timing out.
+  if (iter != server_sockets_.end() && iter->second != cricket::PROTO_UDP) {
+    DestroyInternalSocket(socket);
+  }
+
+  allocations_.erase(*(allocation->conn()));
+}
+
+void TurnServer::DestroyInternalSocket(rtc::AsyncPacketSocket* socket) {
+  InternalSocketMap::iterator iter = server_sockets_.find(socket);
+  if (iter != server_sockets_.end()) {
+    rtc::AsyncPacketSocket* socket = iter->first;
+    socket->UnsubscribeClose(this);
+    socket->SignalReadPacket.disconnect(this);
+    server_sockets_.erase(iter);
+    std::unique_ptr<rtc::AsyncPacketSocket> socket_to_delete =
+        absl::WrapUnique(socket);
+    // We must destroy the socket async to avoid invalidating the sigslot
+    // callback list iterator inside a sigslot callback. (In other words,
+    // deleting an object from within a callback from that object).
+    thread_->PostTask([socket_to_delete = std::move(socket_to_delete)] {});
+  }
+}
+
+TurnServerConnection::TurnServerConnection(const rtc::SocketAddress& src,
+                                           ProtocolType proto,
+                                           rtc::AsyncPacketSocket* socket)
+    : src_(src),
+      dst_(socket->GetRemoteAddress()),
+      proto_(proto),
+      socket_(socket) {}
+
+bool TurnServerConnection::operator==(const TurnServerConnection& c) const {
+  return src_ == c.src_ && dst_ == c.dst_ && proto_ == c.proto_;
+}
+
+bool TurnServerConnection::operator<(const TurnServerConnection& c) const {
+  return std::tie(src_, dst_, proto_) < std::tie(c.src_, c.dst_, c.proto_);
+}
+
+std::string TurnServerConnection::ToString() const {
+  const char* const kProtos[] = {"unknown", "udp", "tcp", "ssltcp"};
+  rtc::StringBuilder ost;
+  ost << src_.ToSensitiveString() << "-" << dst_.ToSensitiveString() << ":"
+      << kProtos[proto_];
+  return ost.Release();
+}
+
+TurnServerAllocation::TurnServerAllocation(TurnServer* server,
+                                           webrtc::TaskQueueBase* thread,
+                                           const TurnServerConnection& conn,
+                                           rtc::AsyncPacketSocket* socket,
+                                           absl::string_view key)
+    : server_(server),
+      thread_(thread),
+      conn_(conn),
+      external_socket_(socket),
+      key_(key) {
+  external_socket_->SignalReadPacket.connect(
+      this, &TurnServerAllocation::OnExternalPacket);
+}
+
+TurnServerAllocation::~TurnServerAllocation() {
+  channels_.clear();
+  perms_.clear();
+  RTC_LOG(LS_INFO) << ToString() << ": Allocation destroyed";
+}
+
+std::string TurnServerAllocation::ToString() const {
+  rtc::StringBuilder ost;
+  ost << "Alloc[" << conn_.ToString() << "]";
+  return ost.Release();
+}
+
+void TurnServerAllocation::HandleTurnMessage(const TurnMessage* msg) {
+  RTC_DCHECK(msg != NULL);
+  switch (msg->type()) {
+    case STUN_ALLOCATE_REQUEST:
+      HandleAllocateRequest(msg);
+      break;
+    case TURN_REFRESH_REQUEST:
+      HandleRefreshRequest(msg);
+      break;
+    case TURN_SEND_INDICATION:
+      HandleSendIndication(msg);
+      break;
+    case TURN_CREATE_PERMISSION_REQUEST:
+      HandleCreatePermissionRequest(msg);
+      break;
+    case TURN_CHANNEL_BIND_REQUEST:
+      HandleChannelBindRequest(msg);
+      break;
+    default:
+      // Not sure what to do with this, just eat it.
+      RTC_LOG(LS_WARNING) << ToString()
+                          << ": Invalid TURN message type received: "
+                          << msg->type();
+  }
+}
+
+void TurnServerAllocation::HandleAllocateRequest(const TurnMessage* msg) {
+  // Copy the important info from the allocate request.
+  transaction_id_ = msg->transaction_id();
+  const StunByteStringAttribute* username_attr =
+      msg->GetByteString(STUN_ATTR_USERNAME);
+  RTC_DCHECK(username_attr != NULL);
+  username_ = std::string(username_attr->string_view());
+
+  // Figure out the lifetime and start the allocation timer.
+  TimeDelta lifetime = ComputeLifetime(*msg);
+  PostDeleteSelf(lifetime);
+
+  RTC_LOG(LS_INFO) << ToString() << ": Created allocation with lifetime="
+                   << lifetime.seconds();
+
+  // We've already validated all the important bits; just send a response here.
+  TurnMessage response(GetStunSuccessResponseTypeOrZero(*msg),
+                       msg->transaction_id());
+
+  auto mapped_addr_attr = std::make_unique<StunXorAddressAttribute>(
+      STUN_ATTR_XOR_MAPPED_ADDRESS, conn_.src());
+  auto relayed_addr_attr = std::make_unique<StunXorAddressAttribute>(
+      STUN_ATTR_XOR_RELAYED_ADDRESS, external_socket_->GetLocalAddress());
+  auto lifetime_attr = std::make_unique<StunUInt32Attribute>(
+      STUN_ATTR_LIFETIME, lifetime.seconds());
+  response.AddAttribute(std::move(mapped_addr_attr));
+  response.AddAttribute(std::move(relayed_addr_attr));
+  response.AddAttribute(std::move(lifetime_attr));
+
+  SendResponse(&response);
+}
+
+void TurnServerAllocation::HandleRefreshRequest(const TurnMessage* msg) {
+  // Figure out the new lifetime.
+  TimeDelta lifetime = ComputeLifetime(*msg);
+
+  // Reset the expiration timer.
+  safety_.reset();
+  PostDeleteSelf(lifetime);
+
+  RTC_LOG(LS_INFO) << ToString()
+                   << ": Refreshed allocation, lifetime=" << lifetime.seconds();
+
+  // Send a success response with a LIFETIME attribute.
+  TurnMessage response(GetStunSuccessResponseTypeOrZero(*msg),
+                       msg->transaction_id());
+
+  auto lifetime_attr = std::make_unique<StunUInt32Attribute>(
+      STUN_ATTR_LIFETIME, lifetime.seconds());
+  response.AddAttribute(std::move(lifetime_attr));
+
+  SendResponse(&response);
+}
+
+void TurnServerAllocation::HandleSendIndication(const TurnMessage* msg) {
+  // Check mandatory attributes.
+  const StunByteStringAttribute* data_attr = msg->GetByteString(STUN_ATTR_DATA);
+  const StunAddressAttribute* peer_attr =
+      msg->GetAddress(STUN_ATTR_XOR_PEER_ADDRESS);
+  if (!data_attr || !peer_attr) {
+    RTC_LOG(LS_WARNING) << ToString() << ": Received invalid send indication";
+    return;
+  }
+
+  // If a permission exists, send the data on to the peer.
+  if (HasPermission(peer_attr->GetAddress().ipaddr())) {
+    SendExternal(data_attr->bytes(), data_attr->length(),
+                 peer_attr->GetAddress());
+  } else {
+    RTC_LOG(LS_WARNING) << ToString()
+                        << ": Received send indication without permission"
+                           " peer="
+                        << peer_attr->GetAddress().ToSensitiveString();
+  }
+}
+
+void TurnServerAllocation::HandleCreatePermissionRequest(
+    const TurnMessage* msg) {
+  // Check mandatory attributes.
+  const StunAddressAttribute* peer_attr =
+      msg->GetAddress(STUN_ATTR_XOR_PEER_ADDRESS);
+  if (!peer_attr) {
+    SendBadRequestResponse(msg);
+    return;
+  }
+
+  if (server_->reject_private_addresses_ &&
+      rtc::IPIsPrivate(peer_attr->GetAddress().ipaddr())) {
+    SendErrorResponse(msg, STUN_ERROR_FORBIDDEN, STUN_ERROR_REASON_FORBIDDEN);
+    return;
+  }
+
+  // Add this permission.
+  AddPermission(peer_attr->GetAddress().ipaddr());
+
+  RTC_LOG(LS_INFO) << ToString() << ": Created permission, peer="
+                   << peer_attr->GetAddress().ToSensitiveString();
+
+  // Send a success response.
+  TurnMessage response(GetStunSuccessResponseTypeOrZero(*msg),
+                       msg->transaction_id());
+  SendResponse(&response);
+}
+
+void TurnServerAllocation::HandleChannelBindRequest(const TurnMessage* msg) {
+  // Check mandatory attributes.
+  const StunUInt32Attribute* channel_attr =
+      msg->GetUInt32(STUN_ATTR_CHANNEL_NUMBER);
+  const StunAddressAttribute* peer_attr =
+      msg->GetAddress(STUN_ATTR_XOR_PEER_ADDRESS);
+  if (!channel_attr || !peer_attr) {
+    SendBadRequestResponse(msg);
+    return;
+  }
+
+  // Check that channel id is valid.
+  int channel_id = channel_attr->value() >> 16;
+  if (channel_id < kMinChannelNumber || channel_id > kMaxChannelNumber) {
+    SendBadRequestResponse(msg);
+    return;
+  }
+
+  // Check that this channel id isn't bound to another transport address, and
+  // that this transport address isn't bound to another channel id.
+  auto channel1 = FindChannel(channel_id);
+  auto channel2 = FindChannel(peer_attr->GetAddress());
+  if (channel1 != channel2) {
+    SendBadRequestResponse(msg);
+    return;
+  }
+
+  // Add or refresh this channel.
+  if (channel1 == channels_.end()) {
+    channel1 = channels_.insert(
+        channels_.end(), {.id = channel_id, .peer = peer_attr->GetAddress()});
+  } else {
+    channel1->pending_delete.reset();
+  }
+  thread_->PostDelayedTask(
+      SafeTask(channel1->pending_delete.flag(),
+               [this, channel1] { channels_.erase(channel1); }),
+      kChannelTimeout);
+
+  // Channel binds also refresh permissions.
+  AddPermission(peer_attr->GetAddress().ipaddr());
+
+  RTC_LOG(LS_INFO) << ToString() << ": Bound channel, id=" << channel_id
+                   << ", peer=" << peer_attr->GetAddress().ToSensitiveString();
+
+  // Send a success response.
+  TurnMessage response(GetStunSuccessResponseTypeOrZero(*msg),
+                       msg->transaction_id());
+  SendResponse(&response);
+}
+
+void TurnServerAllocation::HandleChannelData(const char* data, size_t size) {
+  // Extract the channel number from the data.
+  uint16_t channel_id = rtc::GetBE16(data);
+  auto channel = FindChannel(channel_id);
+  if (channel != channels_.end()) {
+    // Send the data to the peer address.
+    SendExternal(data + TURN_CHANNEL_HEADER_SIZE,
+                 size - TURN_CHANNEL_HEADER_SIZE, channel->peer);
+  } else {
+    RTC_LOG(LS_WARNING) << ToString()
+                        << ": Received channel data for invalid channel, id="
+                        << channel_id;
+  }
+}
+
+void TurnServerAllocation::OnExternalPacket(
+    rtc::AsyncPacketSocket* socket,
+    const char* data,
+    size_t size,
+    const rtc::SocketAddress& addr,
+    const int64_t& /* packet_time_us */) {
+  RTC_DCHECK(external_socket_.get() == socket);
+  auto channel = FindChannel(addr);
+  if (channel != channels_.end()) {
+    // There is a channel bound to this address. Send as a channel message.
+    rtc::ByteBufferWriter buf;
+    buf.WriteUInt16(channel->id);
+    buf.WriteUInt16(static_cast<uint16_t>(size));
+    buf.WriteBytes(data, size);
+    server_->Send(&conn_, buf);
+  } else if (!server_->enable_permission_checks_ ||
+             HasPermission(addr.ipaddr())) {
+    // No channel, but a permission exists. Send as a data indication.
+    TurnMessage msg(TURN_DATA_INDICATION);
+    msg.AddAttribute(std::make_unique<StunXorAddressAttribute>(
+        STUN_ATTR_XOR_PEER_ADDRESS, addr));
+    msg.AddAttribute(
+        std::make_unique<StunByteStringAttribute>(STUN_ATTR_DATA, data, size));
+    server_->SendStun(&conn_, &msg);
+  } else {
+    RTC_LOG(LS_WARNING)
+        << ToString() << ": Received external packet without permission, peer="
+        << addr.ToSensitiveString();
+  }
+}
+
+TimeDelta TurnServerAllocation::ComputeLifetime(const TurnMessage& msg) {
+  if (const StunUInt32Attribute* attr = msg.GetUInt32(STUN_ATTR_LIFETIME)) {
+    return std::min(TimeDelta::Seconds(static_cast<int>(attr->value())),
+                    kDefaultAllocationTimeout);
+  }
+  return kDefaultAllocationTimeout;
+}
+
+bool TurnServerAllocation::HasPermission(const rtc::IPAddress& addr) {
+  return FindPermission(addr) != perms_.end();
+}
+
+void TurnServerAllocation::AddPermission(const rtc::IPAddress& addr) {
+  auto perm = FindPermission(addr);
+  if (perm == perms_.end()) {
+    perm = perms_.insert(perms_.end(), {.peer = addr});
+  } else {
+    perm->pending_delete.reset();
+  }
+  thread_->PostDelayedTask(SafeTask(perm->pending_delete.flag(),
+                                    [this, perm] { perms_.erase(perm); }),
+                           kPermissionTimeout);
+}
+
+TurnServerAllocation::PermissionList::iterator
+TurnServerAllocation::FindPermission(const rtc::IPAddress& addr) {
+  return absl::c_find_if(perms_,
+                         [&](const Permission& p) { return p.peer == addr; });
+}
+
+TurnServerAllocation::ChannelList::iterator TurnServerAllocation::FindChannel(
+    int channel_id) {
+  return absl::c_find_if(channels_,
+                         [&](const Channel& c) { return c.id == channel_id; });
+}
+
+TurnServerAllocation::ChannelList::iterator TurnServerAllocation::FindChannel(
+    const rtc::SocketAddress& addr) {
+  return absl::c_find_if(channels_,
+                         [&](const Channel& c) { return c.peer == addr; });
+}
+
+void TurnServerAllocation::SendResponse(TurnMessage* msg) {
+  // Success responses always have M-I.
+  msg->AddMessageIntegrity(key_);
+  server_->SendStun(&conn_, msg);
+}
+
+void TurnServerAllocation::SendBadRequestResponse(const TurnMessage* req) {
+  SendErrorResponse(req, STUN_ERROR_BAD_REQUEST, STUN_ERROR_REASON_BAD_REQUEST);
+}
+
+void TurnServerAllocation::SendErrorResponse(const TurnMessage* req,
+                                             int code,
+                                             absl::string_view reason) {
+  server_->SendErrorResponse(&conn_, req, code, reason);
+}
+
+void TurnServerAllocation::SendExternal(const void* data,
+                                        size_t size,
+                                        const rtc::SocketAddress& peer) {
+  rtc::PacketOptions options;
+  external_socket_->SendTo(data, size, peer, options);
+}
+
+void TurnServerAllocation::PostDeleteSelf(TimeDelta delay) {
+  auto delete_self = [this] {
+    RTC_DCHECK_RUN_ON(server_->thread_);
+    server_->DestroyAllocation(this);
+  };
+  thread_->PostDelayedTask(SafeTask(safety_.flag(), std::move(delete_self)),
+                           delay);
+}
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/turn_server.h b/third_party/libwebrtc/p2p/base/turn_server.h
new file mode 100644
index 0000000000..e951d089af
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/turn_server.h
@@ -0,0 +1,373 @@
+/*
+ *  Copyright 2012 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_TURN_SERVER_H_
+#define P2P_BASE_TURN_SERVER_H_
+
+#include <list>
+#include <map>
+#include <memory>
+#include <set>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "absl/strings/string_view.h"
+#include "api/sequence_checker.h"
+#include "api/task_queue/pending_task_safety_flag.h"
+#include "api/task_queue/task_queue_base.h"
+#include "api/units/time_delta.h"
+#include "p2p/base/port_interface.h"
+#include "rtc_base/async_packet_socket.h"
+#include "rtc_base/socket_address.h"
+#include "rtc_base/ssl_adapter.h"
+#include "rtc_base/third_party/sigslot/sigslot.h"
+
+namespace rtc {
+class ByteBufferWriter;
+class PacketSocketFactory;
+}  // namespace rtc
+
+namespace cricket {
+
+class StunMessage;
+class TurnMessage;
+class TurnServer;
+
+// The default server port for TURN, as specified in RFC5766.
+const int TURN_SERVER_PORT = 3478;
+
+// Encapsulates the client's connection to the server.
+class TurnServerConnection {
+ public:
+  TurnServerConnection() : proto_(PROTO_UDP), socket_(NULL) {}
+  TurnServerConnection(const rtc::SocketAddress& src,
+                       ProtocolType proto,
+                       rtc::AsyncPacketSocket* socket);
+  const rtc::SocketAddress& src() const { return src_; }
+  rtc::AsyncPacketSocket* socket() { return socket_; }
+  bool operator==(const TurnServerConnection& t) const;
+  bool operator<(const TurnServerConnection& t) const;
+  std::string ToString() const;
+
+ private:
+  rtc::SocketAddress src_;
+  rtc::SocketAddress dst_;
+  cricket::ProtocolType proto_;
+  rtc::AsyncPacketSocket* socket_;
+};
+
+// Encapsulates a TURN allocation.
+// The object is created when an allocation request is received, and then
+// handles TURN messages (via HandleTurnMessage) and channel data messages
+// (via HandleChannelData) for this allocation when received by the server.
+// The object informs the server when its lifetime timer expires.
+class TurnServerAllocation : public sigslot::has_slots<> {
+ public:
+  TurnServerAllocation(TurnServer* server_,
+                       webrtc::TaskQueueBase* thread,
+                       const TurnServerConnection& conn,
+                       rtc::AsyncPacketSocket* server_socket,
+                       absl::string_view key);
+  ~TurnServerAllocation() override;
+
+  TurnServerConnection* conn() { return &conn_; }
+  const std::string& key() const { return key_; }
+  const std::string& transaction_id() const { return transaction_id_; }
+  const std::string& username() const { return username_; }
+  const std::string& last_nonce() const { return last_nonce_; }
+  void set_last_nonce(absl::string_view nonce) {
+    last_nonce_ = std::string(nonce);
+  }
+
+  std::string ToString() const;
+
+  void HandleTurnMessage(const TurnMessage* msg);
+  void HandleChannelData(const char* data, size_t size);
+
+ private:
+  struct Channel {
+    webrtc::ScopedTaskSafety pending_delete;
+    int id;
+    rtc::SocketAddress peer;
+  };
+  struct Permission {
+    webrtc::ScopedTaskSafety pending_delete;
+    rtc::IPAddress peer;
+  };
+  using PermissionList = std::list<Permission>;
+  using ChannelList = std::list<Channel>;
+
+  void PostDeleteSelf(webrtc::TimeDelta delay);
+
+  void HandleAllocateRequest(const TurnMessage* msg);
+  void HandleRefreshRequest(const TurnMessage* msg);
+  void HandleSendIndication(const TurnMessage* msg);
+  void HandleCreatePermissionRequest(const TurnMessage* msg);
+  void HandleChannelBindRequest(const TurnMessage* msg);
+
+  void OnExternalPacket(rtc::AsyncPacketSocket* socket,
+                        const char* data,
+                        size_t size,
+                        const rtc::SocketAddress& addr,
+                        const int64_t& packet_time_us);
+
+  static webrtc::TimeDelta ComputeLifetime(const TurnMessage& msg);
+  bool HasPermission(const rtc::IPAddress& addr);
+  void AddPermission(const rtc::IPAddress& addr);
+  PermissionList::iterator FindPermission(const rtc::IPAddress& addr);
+  ChannelList::iterator FindChannel(int channel_id);
+  ChannelList::iterator FindChannel(const rtc::SocketAddress& addr);
+
+  void SendResponse(TurnMessage* msg);
+  void SendBadRequestResponse(const TurnMessage* req);
+  void SendErrorResponse(const TurnMessage* req,
+                         int code,
+                         absl::string_view reason);
+  void SendExternal(const void* data,
+                    size_t size,
+                    const rtc::SocketAddress& peer);
+
+  TurnServer* const server_;
+  webrtc::TaskQueueBase* const thread_;
+  TurnServerConnection conn_;
+  std::unique_ptr<rtc::AsyncPacketSocket> external_socket_;
+  std::string key_;
+  std::string transaction_id_;
+  std::string username_;
+  std::string last_nonce_;
+  PermissionList perms_;
+  ChannelList channels_;
+  webrtc::ScopedTaskSafety safety_;
+};
+
+// An interface through which the MD5 credential hash can be retrieved.
+class TurnAuthInterface {
+ public:
+  // Gets HA1 for the specified user and realm.
+  // HA1 = MD5(A1) = MD5(username:realm:password).
+  // Return true if the given username and realm are valid, or false if not.
+  virtual bool GetKey(absl::string_view username,
+                      absl::string_view realm,
+                      std::string* key) = 0;
+  virtual ~TurnAuthInterface() = default;
+};
+
+// An interface enables Turn Server to control redirection behavior.
+class TurnRedirectInterface {
+ public:
+  virtual bool ShouldRedirect(const rtc::SocketAddress& address,
+                              rtc::SocketAddress* out) = 0;
+  virtual ~TurnRedirectInterface() {}
+};
+
+class StunMessageObserver {
+ public:
+  virtual void ReceivedMessage(const TurnMessage* msg) = 0;
+  virtual void ReceivedChannelData(const char* data, size_t size) = 0;
+  virtual ~StunMessageObserver() {}
+};
+
+// The core TURN server class. Give it a socket to listen on via
+// AddInternalServerSocket, and a factory to create external sockets via
+// SetExternalSocketFactory, and it's ready to go.
+// Not yet wired up: TCP support.
+class TurnServer : public sigslot::has_slots<> {
+ public:
+  typedef std::map<TurnServerConnection, std::unique_ptr<TurnServerAllocation>>
+      AllocationMap;
+
+  explicit TurnServer(webrtc::TaskQueueBase* thread);
+  ~TurnServer() override;
+
+  // Gets/sets the realm value to use for the server.
+  const std::string& realm() const {
+    RTC_DCHECK_RUN_ON(thread_);
+    return realm_;
+  }
+  void set_realm(absl::string_view realm) {
+    RTC_DCHECK_RUN_ON(thread_);
+    realm_ = std::string(realm);
+  }
+
+  // Gets/sets the value for the SOFTWARE attribute for TURN messages.
+  const std::string& software() const {
+    RTC_DCHECK_RUN_ON(thread_);
+    return software_;
+  }
+  void set_software(absl::string_view software) {
+    RTC_DCHECK_RUN_ON(thread_);
+    software_ = std::string(software);
+  }
+
+  const AllocationMap& allocations() const {
+    RTC_DCHECK_RUN_ON(thread_);
+    return allocations_;
+  }
+
+  // Sets the authentication callback; does not take ownership.
+  void set_auth_hook(TurnAuthInterface* auth_hook) {
+    RTC_DCHECK_RUN_ON(thread_);
+    auth_hook_ = auth_hook;
+  }
+
+  void set_redirect_hook(TurnRedirectInterface* redirect_hook) {
+    RTC_DCHECK_RUN_ON(thread_);
+    redirect_hook_ = redirect_hook;
+  }
+
+  void set_enable_otu_nonce(bool enable) {
+    RTC_DCHECK_RUN_ON(thread_);
+    enable_otu_nonce_ = enable;
+  }
+
+  // If set to true, reject CreatePermission requests to RFC1918 addresses.
+  void set_reject_private_addresses(bool filter) {
+    RTC_DCHECK_RUN_ON(thread_);
+    reject_private_addresses_ = filter;
+  }
+
+  void set_enable_permission_checks(bool enable) {
+    RTC_DCHECK_RUN_ON(thread_);
+    enable_permission_checks_ = enable;
+  }
+
+  // Starts listening for packets from internal clients.
+  void AddInternalSocket(rtc::AsyncPacketSocket* socket, ProtocolType proto);
+  // Starts listening for the connections on this socket. When someone tries
+  // to connect, the connection will be accepted and a new internal socket
+  // will be added.
+  void AddInternalServerSocket(
+      rtc::Socket* socket,
+      ProtocolType proto,
+      std::unique_ptr<rtc::SSLAdapterFactory> ssl_adapter_factory = nullptr);
+  // Specifies the factory to use for creating external sockets.
+  void SetExternalSocketFactory(rtc::PacketSocketFactory* factory,
+                                const rtc::SocketAddress& address);
+  // For testing only.
+  std::string SetTimestampForNextNonce(int64_t timestamp) {
+    RTC_DCHECK_RUN_ON(thread_);
+    ts_for_next_nonce_ = timestamp;
+    return GenerateNonce(timestamp);
+  }
+
+  void SetStunMessageObserver(std::unique_ptr<StunMessageObserver> observer) {
+    RTC_DCHECK_RUN_ON(thread_);
+    stun_message_observer_ = std::move(observer);
+  }
+
+ private:
+  // All private member functions and variables should have access restricted to
+  // thread_. But compile-time annotations are missing for members access from
+  // TurnServerAllocation (via friend declaration), and the On* methods, which
+  // are called via sigslot.
+  std::string GenerateNonce(int64_t now) const RTC_RUN_ON(thread_);
+  void OnInternalPacket(rtc::AsyncPacketSocket* socket,
+                        const char* data,
+                        size_t size,
+                        const rtc::SocketAddress& address,
+                        const int64_t& packet_time_us);
+
+  void OnNewInternalConnection(rtc::Socket* socket);
+
+  // Accept connections on this server socket.
+  void AcceptConnection(rtc::Socket* server_socket) RTC_RUN_ON(thread_);
+  void OnInternalSocketClose(rtc::AsyncPacketSocket* socket, int err);
+
+  void HandleStunMessage(TurnServerConnection* conn,
+                         const char* data,
+                         size_t size) RTC_RUN_ON(thread_);
+  void HandleBindingRequest(TurnServerConnection* conn, const StunMessage* msg)
+      RTC_RUN_ON(thread_);
+  void HandleAllocateRequest(TurnServerConnection* conn,
+                             const TurnMessage* msg,
+                             absl::string_view key) RTC_RUN_ON(thread_);
+
+  bool GetKey(const StunMessage* msg, std::string* key) RTC_RUN_ON(thread_);
+  bool CheckAuthorization(TurnServerConnection* conn,
+                          StunMessage* msg,
+                          const char* data,
+                          size_t size,
+                          absl::string_view key) RTC_RUN_ON(thread_);
+  bool ValidateNonce(absl::string_view nonce) const RTC_RUN_ON(thread_);
+
+  TurnServerAllocation* FindAllocation(TurnServerConnection* conn)
+      RTC_RUN_ON(thread_);
+  TurnServerAllocation* CreateAllocation(TurnServerConnection* conn,
+                                         int proto,
+                                         absl::string_view key)
+      RTC_RUN_ON(thread_);
+
+  void SendErrorResponse(TurnServerConnection* conn,
+                         const StunMessage* req,
+                         int code,
+                         absl::string_view reason);
+
+  void SendErrorResponseWithRealmAndNonce(TurnServerConnection* conn,
+                                          const StunMessage* req,
+                                          int code,
+                                          absl::string_view reason)
+      RTC_RUN_ON(thread_);
+
+  void SendErrorResponseWithAlternateServer(TurnServerConnection* conn,
+                                            const StunMessage* req,
+                                            const rtc::SocketAddress& addr)
+      RTC_RUN_ON(thread_);
+
+  void SendStun(TurnServerConnection* conn, StunMessage* msg);
+  void Send(TurnServerConnection* conn, const rtc::ByteBufferWriter& buf);
+
+  void DestroyAllocation(TurnServerAllocation* allocation) RTC_RUN_ON(thread_);
+  void DestroyInternalSocket(rtc::AsyncPacketSocket* socket)
+      RTC_RUN_ON(thread_);
+
+  typedef std::map<rtc::AsyncPacketSocket*, ProtocolType> InternalSocketMap;
+  struct ServerSocketInfo {
+    ProtocolType proto;
+    // If non-null, used to wrap accepted sockets.
+    std::unique_ptr<rtc::SSLAdapterFactory> ssl_adapter_factory;
+  };
+  typedef std::map<rtc::Socket*, ServerSocketInfo> ServerSocketMap;
+
+  webrtc::TaskQueueBase* const thread_;
+  const std::string nonce_key_;
+  std::string realm_ RTC_GUARDED_BY(thread_);
+  std::string software_ RTC_GUARDED_BY(thread_);
+  TurnAuthInterface* auth_hook_ RTC_GUARDED_BY(thread_);
+  TurnRedirectInterface* redirect_hook_ RTC_GUARDED_BY(thread_);
+  // otu - one-time-use. Server will respond with 438 if it's
+  // sees the same nonce in next transaction.
+  bool enable_otu_nonce_ RTC_GUARDED_BY(thread_);
+  bool reject_private_addresses_ = false;
+  // Check for permission when receiving an external packet.
+  bool enable_permission_checks_ = true;
+
+  InternalSocketMap server_sockets_ RTC_GUARDED_BY(thread_);
+  ServerSocketMap server_listen_sockets_ RTC_GUARDED_BY(thread_);
+  std::unique_ptr<rtc::PacketSocketFactory> external_socket_factory_
+      RTC_GUARDED_BY(thread_);
+  rtc::SocketAddress external_addr_ RTC_GUARDED_BY(thread_);
+
+  AllocationMap allocations_ RTC_GUARDED_BY(thread_);
+
+  // For testing only. If this is non-zero, the next NONCE will be generated
+  // from this value, and it will be reset to 0 after generating the NONCE.
+  int64_t ts_for_next_nonce_ RTC_GUARDED_BY(thread_) = 0;
+
+  // For testing only. Used to observe STUN messages received.
+  std::unique_ptr<StunMessageObserver> stun_message_observer_
+      RTC_GUARDED_BY(thread_);
+
+  friend class TurnServerAllocation;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_TURN_SERVER_H_
diff --git a/third_party/libwebrtc/p2p/base/turn_server_unittest.cc b/third_party/libwebrtc/p2p/base/turn_server_unittest.cc
new file mode 100644
index 0000000000..e534f6598c
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/turn_server_unittest.cc
@@ -0,0 +1,65 @@
+/*
+ *  Copyright 2016 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/turn_server.h"
+
+#include "p2p/base/basic_packet_socket_factory.h"
+#include "rtc_base/virtual_socket_server.h"
+#include "test/gtest.h"
+
+// NOTE: This is a work in progress. Currently this file only has tests for
+// TurnServerConnection, a primitive class used by TurnServer.
+
+namespace cricket {
+
+class TurnServerConnectionTest : public ::testing::Test {
+ public:
+  TurnServerConnectionTest() : thread_(&vss_), socket_factory_(&vss_) {}
+
+  void ExpectEqual(const TurnServerConnection& a,
+                   const TurnServerConnection& b) {
+    EXPECT_TRUE(a == b);
+    EXPECT_FALSE(a < b);
+    EXPECT_FALSE(b < a);
+  }
+
+  void ExpectNotEqual(const TurnServerConnection& a,
+                      const TurnServerConnection& b) {
+    EXPECT_FALSE(a == b);
+    // We don't care which is less than the other, as long as only one is less
+    // than the other.
+    EXPECT_TRUE((a < b) != (b < a));
+  }
+
+ protected:
+  rtc::VirtualSocketServer vss_;
+  rtc::AutoSocketServerThread thread_;
+  rtc::BasicPacketSocketFactory socket_factory_;
+};
+
+TEST_F(TurnServerConnectionTest, ComparisonOperators) {
+  std::unique_ptr<rtc::AsyncPacketSocket> socket1(
+      socket_factory_.CreateUdpSocket(rtc::SocketAddress("1.1.1.1", 1), 0, 0));
+  std::unique_ptr<rtc::AsyncPacketSocket> socket2(
+      socket_factory_.CreateUdpSocket(rtc::SocketAddress("2.2.2.2", 2), 0, 0));
+  TurnServerConnection connection1(socket2->GetLocalAddress(), PROTO_UDP,
+                                   socket1.get());
+  TurnServerConnection connection2(socket2->GetLocalAddress(), PROTO_UDP,
+                                   socket1.get());
+  TurnServerConnection connection3(socket1->GetLocalAddress(), PROTO_UDP,
+                                   socket2.get());
+  TurnServerConnection connection4(socket2->GetLocalAddress(), PROTO_TCP,
+                                   socket1.get());
+  ExpectEqual(connection1, connection2);
+  ExpectNotEqual(connection1, connection3);
+  ExpectNotEqual(connection1, connection4);
+}
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/udp_port.h b/third_party/libwebrtc/p2p/base/udp_port.h
new file mode 100644
index 0000000000..2fd68680cf
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/udp_port.h
@@ -0,0 +1,17 @@
+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_UDP_PORT_H_
+#define P2P_BASE_UDP_PORT_H_
+
+// StunPort will be handling UDPPort functionality.
+#include "p2p/base/stun_port.h"
+
+#endif  // P2P_BASE_UDP_PORT_H_
diff --git a/third_party/libwebrtc/p2p/base/wrapping_active_ice_controller.cc b/third_party/libwebrtc/p2p/base/wrapping_active_ice_controller.cc
new file mode 100644
index 0000000000..c6659217fc
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/wrapping_active_ice_controller.cc
@@ -0,0 +1,253 @@
+/*
+ *  Copyright 2022 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/wrapping_active_ice_controller.h"
+
+#include <memory>
+#include <utility>
+#include <vector>
+
+#include "api/sequence_checker.h"
+#include "api/task_queue/pending_task_safety_flag.h"
+#include "api/units/time_delta.h"
+#include "p2p/base/basic_ice_controller.h"
+#include "p2p/base/connection.h"
+#include "p2p/base/ice_agent_interface.h"
+#include "p2p/base/ice_controller_interface.h"
+#include "p2p/base/ice_switch_reason.h"
+#include "p2p/base/ice_transport_internal.h"
+#include "p2p/base/transport_description.h"
+#include "rtc_base/logging.h"
+#include "rtc_base/thread.h"
+#include "rtc_base/time_utils.h"
+
+namespace {
+using ::webrtc::SafeTask;
+using ::webrtc::TimeDelta;
+}  // unnamed namespace
+
+namespace cricket {
+
+WrappingActiveIceController::WrappingActiveIceController(
+    IceAgentInterface* ice_agent,
+    std::unique_ptr<IceControllerInterface> wrapped)
+    : network_thread_(rtc::Thread::Current()),
+      wrapped_(std::move(wrapped)),
+      agent_(*ice_agent) {
+  RTC_DCHECK(ice_agent != nullptr);
+}
+
+WrappingActiveIceController::WrappingActiveIceController(
+    IceAgentInterface* ice_agent,
+    IceControllerFactoryInterface* wrapped_factory,
+    const IceControllerFactoryArgs& wrapped_factory_args)
+    : network_thread_(rtc::Thread::Current()), agent_(*ice_agent) {
+  RTC_DCHECK(ice_agent != nullptr);
+  if (wrapped_factory) {
+    wrapped_ = wrapped_factory->Create(wrapped_factory_args);
+  } else {
+    wrapped_ = std::make_unique<BasicIceController>(wrapped_factory_args);
+  }
+}
+
+WrappingActiveIceController::~WrappingActiveIceController() {}
+
+void WrappingActiveIceController::SetIceConfig(const IceConfig& config) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  wrapped_->SetIceConfig(config);
+}
+
+bool WrappingActiveIceController::GetUseCandidateAttribute(
+    const Connection* connection,
+    NominationMode mode,
+    IceMode remote_ice_mode) const {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return wrapped_->GetUseCandidateAttr(connection, mode, remote_ice_mode);
+}
+
+void WrappingActiveIceController::OnConnectionAdded(
+    const Connection* connection) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  wrapped_->AddConnection(connection);
+}
+
+void WrappingActiveIceController::OnConnectionPinged(
+    const Connection* connection) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  wrapped_->MarkConnectionPinged(connection);
+}
+
+void WrappingActiveIceController::OnConnectionUpdated(
+    const Connection* connection) {
+  RTC_LOG(LS_VERBOSE) << "Connection report for " << connection->ToString();
+  // Do nothing. Native ICE controllers have direct access to Connection, so no
+  // need to update connection state separately.
+}
+
+void WrappingActiveIceController::OnConnectionSwitched(
+    const Connection* connection) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  selected_connection_ = connection;
+  wrapped_->SetSelectedConnection(connection);
+}
+
+void WrappingActiveIceController::OnConnectionDestroyed(
+    const Connection* connection) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  wrapped_->OnConnectionDestroyed(connection);
+}
+
+void WrappingActiveIceController::MaybeStartPinging() {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (started_pinging_) {
+    return;
+  }
+
+  if (wrapped_->HasPingableConnection()) {
+    network_thread_->PostTask(
+        SafeTask(task_safety_.flag(), [this]() { SelectAndPingConnection(); }));
+    agent_.OnStartedPinging();
+    started_pinging_ = true;
+  }
+}
+
+void WrappingActiveIceController::SelectAndPingConnection() {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  agent_.UpdateConnectionStates();
+
+  IceControllerInterface::PingResult result =
+      wrapped_->SelectConnectionToPing(agent_.GetLastPingSentMs());
+  HandlePingResult(result);
+}
+
+void WrappingActiveIceController::HandlePingResult(
+    IceControllerInterface::PingResult result) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+
+  if (result.connection.has_value()) {
+    agent_.SendPingRequest(result.connection.value());
+  }
+
+  network_thread_->PostDelayedTask(
+      SafeTask(task_safety_.flag(), [this]() { SelectAndPingConnection(); }),
+      TimeDelta::Millis(result.recheck_delay_ms));
+}
+
+void WrappingActiveIceController::OnSortAndSwitchRequest(
+    IceSwitchReason reason) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (!sort_pending_) {
+    network_thread_->PostTask(SafeTask(task_safety_.flag(), [this, reason]() {
+      SortAndSwitchToBestConnection(reason);
+    }));
+    sort_pending_ = true;
+  }
+}
+
+void WrappingActiveIceController::OnImmediateSortAndSwitchRequest(
+    IceSwitchReason reason) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  SortAndSwitchToBestConnection(reason);
+}
+
+void WrappingActiveIceController::SortAndSwitchToBestConnection(
+    IceSwitchReason reason) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+
+  // Make sure the connection states are up-to-date since this affects how they
+  // will be sorted.
+  agent_.UpdateConnectionStates();
+
+  // Any changes after this point will require a re-sort.
+  sort_pending_ = false;
+
+  IceControllerInterface::SwitchResult result =
+      wrapped_->SortAndSwitchConnection(reason);
+  HandleSwitchResult(reason, result);
+  UpdateStateOnConnectionsResorted();
+}
+
+bool WrappingActiveIceController::OnImmediateSwitchRequest(
+    IceSwitchReason reason,
+    const Connection* selected) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  IceControllerInterface::SwitchResult result =
+      wrapped_->ShouldSwitchConnection(reason, selected);
+  HandleSwitchResult(reason, result);
+  return result.connection.has_value();
+}
+
+void WrappingActiveIceController::HandleSwitchResult(
+    IceSwitchReason reason_for_switch,
+    IceControllerInterface::SwitchResult result) {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  if (result.connection.has_value()) {
+    RTC_LOG(LS_INFO) << "Switching selected connection due to: "
+                     << IceSwitchReasonToString(reason_for_switch);
+    agent_.SwitchSelectedConnection(result.connection.value(),
+                                    reason_for_switch);
+  }
+
+  if (result.recheck_event.has_value()) {
+    // If we do not switch to the connection because it missed the receiving
+    // threshold, the new connection is in a better receiving state than the
+    // currently selected connection. So we need to re-check whether it needs
+    // to be switched at a later time.
+    network_thread_->PostDelayedTask(
+        SafeTask(task_safety_.flag(),
+                 [this, recheck_reason = result.recheck_event->reason]() {
+                   SortAndSwitchToBestConnection(recheck_reason);
+                 }),
+        TimeDelta::Millis(result.recheck_event->recheck_delay_ms));
+  }
+
+  agent_.ForgetLearnedStateForConnections(
+      result.connections_to_forget_state_on);
+}
+
+void WrappingActiveIceController::UpdateStateOnConnectionsResorted() {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  PruneConnections();
+
+  // Update the internal state of the ICE agentl.
+  agent_.UpdateState();
+
+  // Also possibly start pinging.
+  // We could start pinging if:
+  // * The first connection was created.
+  // * ICE credentials were provided.
+  // * A TCP connection became connected.
+  MaybeStartPinging();
+}
+
+void WrappingActiveIceController::PruneConnections() {
+  RTC_DCHECK_RUN_ON(network_thread_);
+
+  // The controlled side can prune only if the selected connection has been
+  // nominated because otherwise it may prune the connection that will be
+  // selected by the controlling side.
+  // TODO(honghaiz): This is not enough to prevent a connection from being
+  // pruned too early because with aggressive nomination, the controlling side
+  // will nominate every connection until it becomes writable.
+  if (agent_.GetIceRole() == ICEROLE_CONTROLLING ||
+      (selected_connection_ && selected_connection_->nominated())) {
+    std::vector<const Connection*> connections_to_prune =
+        wrapped_->PruneConnections();
+    agent_.PruneConnections(connections_to_prune);
+  }
+}
+
+// Only for unit tests
+const Connection* WrappingActiveIceController::FindNextPingableConnection() {
+  RTC_DCHECK_RUN_ON(network_thread_);
+  return wrapped_->FindNextPingableConnection();
+}
+
+}  // namespace cricket
diff --git a/third_party/libwebrtc/p2p/base/wrapping_active_ice_controller.h b/third_party/libwebrtc/p2p/base/wrapping_active_ice_controller.h
new file mode 100644
index 0000000000..449c0f0ee1
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/wrapping_active_ice_controller.h
@@ -0,0 +1,97 @@
+/*
+ *  Copyright 2022 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_WRAPPING_ACTIVE_ICE_CONTROLLER_H_
+#define P2P_BASE_WRAPPING_ACTIVE_ICE_CONTROLLER_H_
+
+#include <memory>
+
+#include "absl/types/optional.h"
+#include "api/task_queue/pending_task_safety_flag.h"
+#include "p2p/base/active_ice_controller_interface.h"
+#include "p2p/base/connection.h"
+#include "p2p/base/ice_agent_interface.h"
+#include "p2p/base/ice_controller_factory_interface.h"
+#include "p2p/base/ice_controller_interface.h"
+#include "p2p/base/ice_switch_reason.h"
+#include "p2p/base/ice_transport_internal.h"
+#include "p2p/base/transport_description.h"
+#include "rtc_base/thread.h"
+#include "rtc_base/thread_annotations.h"
+
+namespace cricket {
+
+// WrappingActiveIceController provides the functionality of a legacy passive
+// ICE controller but packaged as an active ICE Controller.
+class WrappingActiveIceController : public ActiveIceControllerInterface {
+ public:
+  // Constructs an active ICE controller wrapping an already constructed legacy
+  // ICE controller. Does not take ownership of the ICE agent, which must
+  // already exist and outlive the ICE controller.
+  WrappingActiveIceController(IceAgentInterface* ice_agent,
+                              std::unique_ptr<IceControllerInterface> wrapped);
+  // Constructs an active ICE controller that wraps over a legacy ICE
+  // controller. The legacy ICE controller is constructed through a factory, if
+  // one is supplied. If not, a default BasicIceController is wrapped instead.
+  // Does not take ownership of the ICE agent, which must already exist and
+  // outlive the ICE controller.
+  WrappingActiveIceController(
+      IceAgentInterface* ice_agent,
+      IceControllerFactoryInterface* wrapped_factory,
+      const IceControllerFactoryArgs& wrapped_factory_args);
+  virtual ~WrappingActiveIceController();
+
+  void SetIceConfig(const IceConfig& config) override;
+  bool GetUseCandidateAttribute(const Connection* connection,
+                                NominationMode mode,
+                                IceMode remote_ice_mode) const override;
+
+  void OnConnectionAdded(const Connection* connection) override;
+  void OnConnectionPinged(const Connection* connection) override;
+  void OnConnectionUpdated(const Connection* connection) override;
+  void OnConnectionSwitched(const Connection* connection) override;
+  void OnConnectionDestroyed(const Connection* connection) override;
+
+  void OnSortAndSwitchRequest(IceSwitchReason reason) override;
+  void OnImmediateSortAndSwitchRequest(IceSwitchReason reason) override;
+  bool OnImmediateSwitchRequest(IceSwitchReason reason,
+                                const Connection* selected) override;
+
+  // Only for unit tests
+  const Connection* FindNextPingableConnection() override;
+
+ private:
+  void MaybeStartPinging();
+  void SelectAndPingConnection();
+  void HandlePingResult(IceControllerInterface::PingResult result);
+
+  void SortAndSwitchToBestConnection(IceSwitchReason reason);
+  void HandleSwitchResult(IceSwitchReason reason_for_switch,
+                          IceControllerInterface::SwitchResult result);
+  void UpdateStateOnConnectionsResorted();
+
+  void PruneConnections();
+
+  rtc::Thread* const network_thread_;
+  webrtc::ScopedTaskSafety task_safety_;
+
+  bool started_pinging_ RTC_GUARDED_BY(network_thread_) = false;
+  bool sort_pending_ RTC_GUARDED_BY(network_thread_) = false;
+  const Connection* selected_connection_ RTC_GUARDED_BY(network_thread_) =
+      nullptr;
+
+  std::unique_ptr<IceControllerInterface> wrapped_
+      RTC_GUARDED_BY(network_thread_);
+  IceAgentInterface& agent_ RTC_GUARDED_BY(network_thread_);
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_WRAPPING_ACTIVE_ICE_CONTROLLER_H_
diff --git a/third_party/libwebrtc/p2p/base/wrapping_active_ice_controller_unittest.cc b/third_party/libwebrtc/p2p/base/wrapping_active_ice_controller_unittest.cc
new file mode 100644
index 0000000000..b4811bd297
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/wrapping_active_ice_controller_unittest.cc
@@ -0,0 +1,315 @@
+/*
+ *  Copyright 2009 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/wrapping_active_ice_controller.h"
+
+#include <memory>
+#include <utility>
+#include <vector>
+
+#include "p2p/base/connection.h"
+#include "p2p/base/mock_ice_agent.h"
+#include "p2p/base/mock_ice_controller.h"
+#include "rtc_base/fake_clock.h"
+#include "rtc_base/gunit.h"
+#include "rtc_base/thread.h"
+
+namespace {
+
+using ::cricket::Connection;
+using ::cricket::IceConfig;
+using ::cricket::IceControllerFactoryArgs;
+using ::cricket::IceControllerInterface;
+using ::cricket::IceMode;
+using ::cricket::IceRecheckEvent;
+using ::cricket::IceSwitchReason;
+using ::cricket::MockIceAgent;
+using ::cricket::MockIceController;
+using ::cricket::MockIceControllerFactory;
+using ::cricket::NominationMode;
+using ::cricket::WrappingActiveIceController;
+
+using ::testing::_;
+using ::testing::ElementsAreArray;
+using ::testing::IsEmpty;
+using ::testing::NiceMock;
+using ::testing::Ref;
+using ::testing::Return;
+using ::testing::Sequence;
+
+using ::rtc::AutoThread;
+using ::rtc::Event;
+using ::rtc::ScopedFakeClock;
+using ::webrtc::TimeDelta;
+
+using NiceMockIceController = NiceMock<MockIceController>;
+
+static const Connection* kConnection =
+    reinterpret_cast<const Connection*>(0xabcd);
+static const Connection* kConnectionTwo =
+    reinterpret_cast<const Connection*>(0xbcde);
+static const Connection* kConnectionThree =
+    reinterpret_cast<const Connection*>(0xcdef);
+
+static const std::vector<const Connection*> kEmptyConnsList =
+    std::vector<const Connection*>();
+
+static const TimeDelta kTick = TimeDelta::Millis(1);
+
+TEST(WrappingActiveIceControllerTest, CreateLegacyIceControllerFromFactory) {
+  AutoThread main;
+  MockIceAgent agent;
+  IceControllerFactoryArgs args;
+  MockIceControllerFactory legacy_controller_factory;
+  EXPECT_CALL(legacy_controller_factory, RecordIceControllerCreated()).Times(1);
+  WrappingActiveIceController controller(&agent, &legacy_controller_factory,
+                                         args);
+}
+
+TEST(WrappingActiveIceControllerTest, PassthroughIceControllerInterface) {
+  AutoThread main;
+  MockIceAgent agent;
+  std::unique_ptr<MockIceController> will_move =
+      std::make_unique<MockIceController>(IceControllerFactoryArgs{});
+  MockIceController* wrapped = will_move.get();
+  WrappingActiveIceController controller(&agent, std::move(will_move));
+
+  IceConfig config{};
+  EXPECT_CALL(*wrapped, SetIceConfig(Ref(config)));
+  controller.SetIceConfig(config);
+
+  EXPECT_CALL(*wrapped,
+              GetUseCandidateAttr(kConnection, NominationMode::AGGRESSIVE,
+                                  IceMode::ICEMODE_LITE))
+      .WillOnce(Return(true));
+  EXPECT_TRUE(controller.GetUseCandidateAttribute(
+      kConnection, NominationMode::AGGRESSIVE, IceMode::ICEMODE_LITE));
+
+  EXPECT_CALL(*wrapped, AddConnection(kConnection));
+  controller.OnConnectionAdded(kConnection);
+
+  EXPECT_CALL(*wrapped, OnConnectionDestroyed(kConnection));
+  controller.OnConnectionDestroyed(kConnection);
+
+  EXPECT_CALL(*wrapped, SetSelectedConnection(kConnection));
+  controller.OnConnectionSwitched(kConnection);
+
+  EXPECT_CALL(*wrapped, MarkConnectionPinged(kConnection));
+  controller.OnConnectionPinged(kConnection);
+
+  EXPECT_CALL(*wrapped, FindNextPingableConnection())
+      .WillOnce(Return(kConnection));
+  EXPECT_EQ(controller.FindNextPingableConnection(), kConnection);
+}
+
+TEST(WrappingActiveIceControllerTest, HandlesImmediateSwitchRequest) {
+  AutoThread main;
+  ScopedFakeClock clock;
+  NiceMock<MockIceAgent> agent;
+  std::unique_ptr<NiceMockIceController> will_move =
+      std::make_unique<NiceMockIceController>(IceControllerFactoryArgs{});
+  NiceMockIceController* wrapped = will_move.get();
+  WrappingActiveIceController controller(&agent, std::move(will_move));
+
+  IceSwitchReason reason = IceSwitchReason::NOMINATION_ON_CONTROLLED_SIDE;
+  std::vector<const Connection*> conns_to_forget{kConnectionTwo};
+  int recheck_delay_ms = 10;
+  IceControllerInterface::SwitchResult switch_result{
+      kConnection,
+      IceRecheckEvent(IceSwitchReason::ICE_CONTROLLER_RECHECK,
+                      recheck_delay_ms),
+      conns_to_forget};
+
+  // ICE controller should switch to given connection immediately.
+  Sequence check_then_switch;
+  EXPECT_CALL(*wrapped, ShouldSwitchConnection(reason, kConnection))
+      .InSequence(check_then_switch)
+      .WillOnce(Return(switch_result));
+  EXPECT_CALL(agent, SwitchSelectedConnection(kConnection, reason))
+      .InSequence(check_then_switch);
+  EXPECT_CALL(agent, ForgetLearnedStateForConnections(
+                         ElementsAreArray(conns_to_forget)));
+
+  EXPECT_TRUE(controller.OnImmediateSwitchRequest(reason, kConnection));
+
+  // No rechecks before recheck delay.
+  clock.AdvanceTime(TimeDelta::Millis(recheck_delay_ms - 1));
+
+  // ICE controller should recheck for best connection after the recheck delay.
+  Sequence recheck_sort;
+  EXPECT_CALL(agent, UpdateConnectionStates()).InSequence(recheck_sort);
+  EXPECT_CALL(*wrapped,
+              SortAndSwitchConnection(IceSwitchReason::ICE_CONTROLLER_RECHECK))
+      .InSequence(recheck_sort)
+      .WillOnce(Return(IceControllerInterface::SwitchResult{}));
+  EXPECT_CALL(agent, ForgetLearnedStateForConnections(IsEmpty()));
+
+  clock.AdvanceTime(kTick);
+}
+
+TEST(WrappingActiveIceControllerTest, HandlesImmediateSortAndSwitchRequest) {
+  AutoThread main;
+  ScopedFakeClock clock;
+  NiceMock<MockIceAgent> agent;
+  std::unique_ptr<NiceMockIceController> will_move =
+      std::make_unique<NiceMockIceController>(IceControllerFactoryArgs{});
+  NiceMockIceController* wrapped = will_move.get();
+  WrappingActiveIceController controller(&agent, std::move(will_move));
+
+  IceSwitchReason reason = IceSwitchReason::NEW_CONNECTION_FROM_LOCAL_CANDIDATE;
+  std::vector<const Connection*> conns_to_forget{kConnectionTwo};
+  std::vector<const Connection*> conns_to_prune{kConnectionThree};
+  int recheck_delay_ms = 10;
+  IceControllerInterface::SwitchResult switch_result{
+      kConnection,
+      IceRecheckEvent(IceSwitchReason::ICE_CONTROLLER_RECHECK,
+                      recheck_delay_ms),
+      conns_to_forget};
+
+  Sequence sort_and_switch;
+  EXPECT_CALL(agent, UpdateConnectionStates()).InSequence(sort_and_switch);
+  EXPECT_CALL(*wrapped, SortAndSwitchConnection(reason))
+      .InSequence(sort_and_switch)
+      .WillOnce(Return(switch_result));
+  EXPECT_CALL(agent, SwitchSelectedConnection(kConnection, reason))
+      .InSequence(sort_and_switch);
+  EXPECT_CALL(*wrapped, PruneConnections())
+      .InSequence(sort_and_switch)
+      .WillOnce(Return(conns_to_prune));
+  EXPECT_CALL(agent, PruneConnections(ElementsAreArray(conns_to_prune)))
+      .InSequence(sort_and_switch);
+
+  controller.OnImmediateSortAndSwitchRequest(reason);
+
+  // No rechecks before recheck delay.
+  clock.AdvanceTime(TimeDelta::Millis(recheck_delay_ms - 1));
+
+  // ICE controller should recheck for best connection after the recheck delay.
+  Sequence recheck_sort;
+  EXPECT_CALL(agent, UpdateConnectionStates()).InSequence(recheck_sort);
+  EXPECT_CALL(*wrapped,
+              SortAndSwitchConnection(IceSwitchReason::ICE_CONTROLLER_RECHECK))
+      .InSequence(recheck_sort)
+      .WillOnce(Return(IceControllerInterface::SwitchResult{}));
+  EXPECT_CALL(*wrapped, PruneConnections())
+      .InSequence(recheck_sort)
+      .WillOnce(Return(kEmptyConnsList));
+  EXPECT_CALL(agent, PruneConnections(IsEmpty())).InSequence(recheck_sort);
+
+  clock.AdvanceTime(kTick);
+}
+
+TEST(WrappingActiveIceControllerTest, HandlesSortAndSwitchRequest) {
+  AutoThread main;
+  ScopedFakeClock clock;
+
+  // Block the main task queue until ready.
+  Event init;
+  TimeDelta init_delay = TimeDelta::Millis(10);
+  main.PostTask([&init, &init_delay] { init.Wait(init_delay); });
+
+  NiceMock<MockIceAgent> agent;
+  std::unique_ptr<NiceMockIceController> will_move =
+      std::make_unique<NiceMockIceController>(IceControllerFactoryArgs{});
+  NiceMockIceController* wrapped = will_move.get();
+  WrappingActiveIceController controller(&agent, std::move(will_move));
+
+  IceSwitchReason reason = IceSwitchReason::NETWORK_PREFERENCE_CHANGE;
+
+  // No action should occur immediately
+  EXPECT_CALL(agent, UpdateConnectionStates()).Times(0);
+  EXPECT_CALL(*wrapped, SortAndSwitchConnection(_)).Times(0);
+  EXPECT_CALL(agent, SwitchSelectedConnection(_, _)).Times(0);
+
+  controller.OnSortAndSwitchRequest(reason);
+
+  std::vector<const Connection*> conns_to_forget{kConnectionTwo};
+  int recheck_delay_ms = 10;
+  IceControllerInterface::SwitchResult switch_result{
+      kConnection,
+      IceRecheckEvent(IceSwitchReason::ICE_CONTROLLER_RECHECK,
+                      recheck_delay_ms),
+      conns_to_forget};
+
+  // Sort and switch should take place as the subsequent task.
+  Sequence sort_and_switch;
+  EXPECT_CALL(agent, UpdateConnectionStates()).InSequence(sort_and_switch);
+  EXPECT_CALL(*wrapped, SortAndSwitchConnection(reason))
+      .InSequence(sort_and_switch)
+      .WillOnce(Return(switch_result));
+  EXPECT_CALL(agent, SwitchSelectedConnection(kConnection, reason))
+      .InSequence(sort_and_switch);
+
+  // Unblock the init task.
+  clock.AdvanceTime(init_delay);
+}
+
+TEST(WrappingActiveIceControllerTest, StartPingingAfterSortAndSwitch) {
+  AutoThread main;
+  ScopedFakeClock clock;
+
+  // Block the main task queue until ready.
+  Event init;
+  TimeDelta init_delay = TimeDelta::Millis(10);
+  main.PostTask([&init, &init_delay] { init.Wait(init_delay); });
+
+  NiceMock<MockIceAgent> agent;
+  std::unique_ptr<NiceMockIceController> will_move =
+      std::make_unique<NiceMockIceController>(IceControllerFactoryArgs{});
+  NiceMockIceController* wrapped = will_move.get();
+  WrappingActiveIceController controller(&agent, std::move(will_move));
+
+  // Pinging does not start automatically, unless triggered through a sort.
+  EXPECT_CALL(*wrapped, HasPingableConnection()).Times(0);
+  EXPECT_CALL(*wrapped, SelectConnectionToPing(_)).Times(0);
+  EXPECT_CALL(agent, OnStartedPinging()).Times(0);
+
+  controller.OnSortAndSwitchRequest(IceSwitchReason::DATA_RECEIVED);
+
+  // Pinging does not start if no pingable connection.
+  EXPECT_CALL(*wrapped, HasPingableConnection()).WillOnce(Return(false));
+  EXPECT_CALL(*wrapped, SelectConnectionToPing(_)).Times(0);
+  EXPECT_CALL(agent, OnStartedPinging()).Times(0);
+
+  // Unblock the init task.
+  clock.AdvanceTime(init_delay);
+
+  int recheck_delay_ms = 10;
+  IceControllerInterface::PingResult ping_result(kConnection, recheck_delay_ms);
+
+  // Pinging starts when there is a pingable connection.
+  Sequence start_pinging;
+  EXPECT_CALL(*wrapped, HasPingableConnection())
+      .InSequence(start_pinging)
+      .WillOnce(Return(true));
+  EXPECT_CALL(agent, OnStartedPinging()).InSequence(start_pinging);
+  EXPECT_CALL(agent, GetLastPingSentMs())
+      .InSequence(start_pinging)
+      .WillOnce(Return(123));
+  EXPECT_CALL(*wrapped, SelectConnectionToPing(123))
+      .InSequence(start_pinging)
+      .WillOnce(Return(ping_result));
+  EXPECT_CALL(agent, SendPingRequest(kConnection)).InSequence(start_pinging);
+
+  controller.OnSortAndSwitchRequest(IceSwitchReason::DATA_RECEIVED);
+  clock.AdvanceTime(kTick);
+
+  // ICE controller should recheck and ping after the recheck delay.
+  // No ping should be sent if no connection selected to ping.
+  EXPECT_CALL(agent, GetLastPingSentMs()).WillOnce(Return(456));
+  EXPECT_CALL(*wrapped, SelectConnectionToPing(456))
+      .WillOnce(Return(IceControllerInterface::PingResult(
+          /* connection= */ nullptr, recheck_delay_ms)));
+  EXPECT_CALL(agent, SendPingRequest(kConnection)).Times(0);
+
+  clock.AdvanceTime(TimeDelta::Millis(recheck_delay_ms));
+}
+
+}  // namespace