Adding upstream version 124.0.1.upstream/124.0.1

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

6 files changed, 4416 insertions, 0 deletions

diff --git a/netwerk/sctp/datachannel/DataChannel.cpp b/netwerk/sctp/datachannel/DataChannel.cpp
new file mode 100644
index 0000000000..8af9a558b8
--- /dev/null
+++ b/netwerk/sctp/datachannel/DataChannel.cpp
@@ -0,0 +1,3548 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <algorithm>
+#include <stdio.h>
+#include <stdlib.h>
+#if !defined(__Userspace_os_Windows)
+#  include <arpa/inet.h>
+#endif
+// usrsctp.h expects to have errno definitions prior to its inclusion.
+#include <errno.h>
+
+#define SCTP_DEBUG 1
+#define SCTP_STDINT_INCLUDE <stdint.h>
+
+#ifdef _MSC_VER
+// Disable "warning C4200: nonstandard extension used : zero-sized array in
+//          struct/union"
+// ...which the third-party file usrsctp.h runs afoul of.
+#  pragma warning(push)
+#  pragma warning(disable : 4200)
+#endif
+
+#include "usrsctp.h"
+
+#ifdef _MSC_VER
+#  pragma warning(pop)
+#endif
+
+#include "nsServiceManagerUtils.h"
+#include "nsIInputStream.h"
+#include "nsIPrefBranch.h"
+#include "nsIPrefService.h"
+#include "mozilla/Services.h"
+#include "mozilla/Sprintf.h"
+#include "nsProxyRelease.h"
+#include "nsThread.h"
+#include "nsThreadUtils.h"
+#include "nsNetUtil.h"
+#include "nsNetCID.h"
+#include "mozilla/RandomNum.h"
+#include "mozilla/StaticMutex.h"
+#include "mozilla/UniquePtrExtensions.h"
+#include "mozilla/Unused.h"
+#include "mozilla/dom/RTCDataChannelBinding.h"
+#include "mozilla/dom/RTCStatsReportBinding.h"
+#include "mozilla/media/MediaUtils.h"
+#ifdef MOZ_PEERCONNECTION
+#  include "transport/runnable_utils.h"
+#  include "jsapi/MediaTransportHandler.h"
+#  include "mediapacket.h"
+#endif
+
+#include "DataChannel.h"
+#include "DataChannelProtocol.h"
+
+// Let us turn on and off important assertions in non-debug builds
+#ifdef DEBUG
+#  define ASSERT_WEBRTC(x) MOZ_ASSERT((x))
+#elif defined(MOZ_WEBRTC_ASSERT_ALWAYS)
+#  define ASSERT_WEBRTC(x) \
+    do {                   \
+      if (!(x)) {          \
+        MOZ_CRASH();       \
+      }                    \
+    } while (0)
+#endif
+
+namespace mozilla {
+
+LazyLogModule gDataChannelLog("DataChannel");
+static LazyLogModule gSCTPLog("SCTP");
+
+#define SCTP_LOG(args) \
+  MOZ_LOG(mozilla::gSCTPLog, mozilla::LogLevel::Debug, args)
+
+static void debug_printf(const char* format, ...) {
+  va_list ap;
+  char buffer[1024];
+
+  if (MOZ_LOG_TEST(gSCTPLog, LogLevel::Debug)) {
+    va_start(ap, format);
+#ifdef _WIN32
+    if (vsnprintf_s(buffer, sizeof(buffer), _TRUNCATE, format, ap) > 0) {
+#else
+    if (VsprintfLiteral(buffer, format, ap) > 0) {
+#endif
+      SCTP_LOG(("%s", buffer));
+    }
+    va_end(ap);
+  }
+}
+
+static constexpr const char* ToString(DataChannelState state) {
+  switch (state) {
+    case DataChannelState::Connecting:
+      return "CONNECTING";
+    case DataChannelState::Open:
+      return "OPEN";
+    case DataChannelState::Closing:
+      return "CLOSING";
+    case DataChannelState::Closed:
+      return "CLOSED";
+  }
+  return "";
+};
+
+static constexpr const char* ToString(DataChannelConnectionState state) {
+  switch (state) {
+    case DataChannelConnectionState::Connecting:
+      return "CONNECTING";
+    case DataChannelConnectionState::Open:
+      return "OPEN";
+    case DataChannelConnectionState::Closed:
+      return "CLOSED";
+  }
+  return "";
+};
+
+static constexpr const char* ToString(
+    DataChannelOnMessageAvailable::EventType type) {
+  switch (type) {
+    case DataChannelOnMessageAvailable::EventType::OnConnection:
+      return "ON_CONNECTION";
+    case DataChannelOnMessageAvailable::EventType::OnDisconnected:
+      return "ON_DISCONNECTED";
+    case DataChannelOnMessageAvailable::EventType::OnChannelCreated:
+      return "ON_CHANNEL_CREATED";
+    case DataChannelOnMessageAvailable::EventType::OnDataString:
+      return "ON_DATA_STRING";
+    case DataChannelOnMessageAvailable::EventType::OnDataBinary:
+      return "ON_DATA_BINARY";
+  }
+  return "";
+};
+
+static constexpr const char* ToString(DataChannelConnection::PendingType type) {
+  switch (type) {
+    case DataChannelConnection::PendingType::None:
+      return "NONE";
+    case DataChannelConnection::PendingType::Dcep:
+      return "DCEP";
+    case DataChannelConnection::PendingType::Data:
+      return "DATA";
+  }
+  return "";
+};
+
+static constexpr const char* ToString(DataChannelReliabilityPolicy type) {
+  switch (type) {
+    case DataChannelReliabilityPolicy::Reliable:
+      return "RELIABLE";
+    case DataChannelReliabilityPolicy::LimitedRetransmissions:
+      return "LIMITED_RETRANSMISSIONS";
+    case DataChannelReliabilityPolicy::LimitedLifetime:
+      return "LIMITED_LIFETIME";
+  }
+  return "";
+};
+
+static constexpr uint16_t ToUsrsctpValue(DataChannelReliabilityPolicy type) {
+  switch (type) {
+    case DataChannelReliabilityPolicy::Reliable:
+      return SCTP_PR_SCTP_NONE;
+    case DataChannelReliabilityPolicy::LimitedRetransmissions:
+      return SCTP_PR_SCTP_RTX;
+    case DataChannelReliabilityPolicy::LimitedLifetime:
+      return SCTP_PR_SCTP_TTL;
+  }
+  return SCTP_PR_SCTP_NONE;
+};
+
+class DataChannelRegistry {
+ public:
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(DataChannelRegistry)
+
+  static uintptr_t Register(DataChannelConnection* aConnection) {
+    StaticMutexAutoLock lock(sInstanceMutex);
+    uintptr_t result = EnsureInstance()->RegisterImpl(aConnection);
+    DC_DEBUG(
+        ("Registering connection %p as ulp %p", aConnection, (void*)result));
+    return result;
+  }
+
+  static void Deregister(uintptr_t aId) {
+    RefPtr<DataChannelRegistry> maybeTrash;
+
+    {
+      StaticMutexAutoLock lock(sInstanceMutex);
+      DC_DEBUG(("Deregistering connection ulp = %p", (void*)aId));
+      if (NS_WARN_IF(!Instance())) {
+        return;
+      }
+      Instance()->DeregisterImpl(aId);
+      if (Instance()->Empty()) {
+        // Unset singleton inside mutex lock, but don't call Shutdown until we
+        // unlock, since that involves calling into libusrsctp, which invites
+        // deadlock.
+        maybeTrash = Instance().forget();
+      }
+    }
+  }
+
+  static RefPtr<DataChannelConnection> Lookup(uintptr_t aId) {
+    StaticMutexAutoLock lock(sInstanceMutex);
+    if (NS_WARN_IF(!Instance())) {
+      return nullptr;
+    }
+    return Instance()->LookupImpl(aId);
+  }
+
+ private:
+  // This is a singleton class, so don't let just anyone create one of these
+  DataChannelRegistry() {
+    ASSERT_WEBRTC(NS_IsMainThread());
+    mShutdownBlocker = media::ShutdownBlockingTicket::Create(
+        u"DataChannelRegistry::mShutdownBlocker"_ns,
+        NS_LITERAL_STRING_FROM_CSTRING(__FILE__), __LINE__);
+    InitUsrSctp();
+  }
+
+  static RefPtr<DataChannelRegistry>& Instance() {
+    static RefPtr<DataChannelRegistry> sRegistry;
+    return sRegistry;
+  }
+
+  static RefPtr<DataChannelRegistry>& EnsureInstance() {
+    ASSERT_WEBRTC(NS_IsMainThread());
+    if (!Instance()) {
+      Instance() = new DataChannelRegistry();
+    }
+    return Instance();
+  }
+
+  uintptr_t RegisterImpl(DataChannelConnection* aConnection) {
+    ASSERT_WEBRTC(NS_IsMainThread());
+    mConnections.emplace(mNextId, aConnection);
+    return mNextId++;
+  }
+
+  void DeregisterImpl(uintptr_t aId) {
+    ASSERT_WEBRTC(NS_IsMainThread());
+    mConnections.erase(aId);
+  }
+
+  bool Empty() const { return mConnections.empty(); }
+
+  RefPtr<DataChannelConnection> LookupImpl(uintptr_t aId) {
+    auto it = mConnections.find(aId);
+    if (NS_WARN_IF(it == mConnections.end())) {
+      DC_DEBUG(("Can't find connection ulp %p", (void*)aId));
+      return nullptr;
+    }
+    return it->second;
+  }
+
+  virtual ~DataChannelRegistry() {
+    ASSERT_WEBRTC(NS_IsMainThread());
+
+    if (NS_WARN_IF(!mConnections.empty())) {
+      MOZ_ASSERT(false);
+      mConnections.clear();
+    }
+
+    DeinitUsrSctp();
+  }
+
+#ifdef SCTP_DTLS_SUPPORTED
+  static int SctpDtlsOutput(void* addr, void* buffer, size_t length,
+                            uint8_t tos, uint8_t set_df) {
+    uintptr_t id = reinterpret_cast<uintptr_t>(addr);
+    RefPtr<DataChannelConnection> connection = DataChannelRegistry::Lookup(id);
+    if (NS_WARN_IF(!connection) || connection->InShutdown()) {
+      return 0;
+    }
+    return connection->SctpDtlsOutput(addr, buffer, length, tos, set_df);
+  }
+#endif
+
+  void InitUsrSctp() {
+#ifndef MOZ_PEERCONNECTION
+    MOZ_CRASH("Trying to use SCTP/DTLS without dom/media/webrtc/transport");
+#endif
+
+    DC_DEBUG(("Calling usrsctp_init %p", this));
+
+    usrsctp_init(0, DataChannelRegistry::SctpDtlsOutput, debug_printf);
+
+    // Set logging to SCTP:LogLevel::Debug to get SCTP debugs
+    if (MOZ_LOG_TEST(gSCTPLog, LogLevel::Debug)) {
+      usrsctp_sysctl_set_sctp_debug_on(SCTP_DEBUG_ALL);
+    }
+
+    // Do not send ABORTs in response to INITs (1).
+    // Do not send ABORTs for received Out of the Blue packets (2).
+    usrsctp_sysctl_set_sctp_blackhole(2);
+
+    // Disable the Explicit Congestion Notification extension (currently not
+    // supported by the Firefox code)
+    usrsctp_sysctl_set_sctp_ecn_enable(0);
+
+    // Enable interleaving messages for different streams (incoming)
+    // See: https://tools.ietf.org/html/rfc6458#section-8.1.20
+    usrsctp_sysctl_set_sctp_default_frag_interleave(2);
+
+    // Disabling authentication and dynamic address reconfiguration as neither
+    // of them are used for data channel and only result in additional code
+    // paths being used.
+    usrsctp_sysctl_set_sctp_asconf_enable(0);
+    usrsctp_sysctl_set_sctp_auth_enable(0);
+  }
+
+  void DeinitUsrSctp() {
+    DC_DEBUG(("Calling usrsctp_finish %p", this));
+    usrsctp_finish();
+  }
+
+  uintptr_t mNextId = 1;
+  std::map<uintptr_t, RefPtr<DataChannelConnection>> mConnections;
+  UniquePtr<media::ShutdownBlockingTicket> mShutdownBlocker;
+  static StaticMutex sInstanceMutex MOZ_UNANNOTATED;
+};
+
+StaticMutex DataChannelRegistry::sInstanceMutex;
+
+OutgoingMsg::OutgoingMsg(struct sctp_sendv_spa& info, const uint8_t* data,
+                         size_t length)
+    : mLength(length), mData(data) {
+  mInfo = &info;
+  mPos = 0;
+}
+
+void OutgoingMsg::Advance(size_t offset) {
+  mPos += offset;
+  if (mPos > mLength) {
+    mPos = mLength;
+  }
+}
+
+BufferedOutgoingMsg::BufferedOutgoingMsg(OutgoingMsg& msg) {
+  size_t length = msg.GetLeft();
+  auto* tmp = new uint8_t[length];  // infallible malloc!
+  memcpy(tmp, msg.GetData(), length);
+  mLength = length;
+  mData = tmp;
+  mInfo = new sctp_sendv_spa;
+  *mInfo = msg.GetInfo();
+  mPos = 0;
+}
+
+BufferedOutgoingMsg::~BufferedOutgoingMsg() {
+  delete mInfo;
+  delete[] mData;
+}
+
+static int receive_cb(struct socket* sock, union sctp_sockstore addr,
+                      void* data, size_t datalen, struct sctp_rcvinfo rcv,
+                      int flags, void* ulp_info) {
+  DC_DEBUG(("In receive_cb, ulp_info=%p", ulp_info));
+  uintptr_t id = reinterpret_cast<uintptr_t>(ulp_info);
+  RefPtr<DataChannelConnection> connection = DataChannelRegistry::Lookup(id);
+  if (!connection) {
+    // Unfortunately, we can get callbacks after calling
+    // usrsctp_close(socket), so we need to simply ignore them if we've
+    // already killed the DataChannelConnection object
+    DC_DEBUG((
+        "Ignoring receive callback for terminated Connection ulp=%p, %zu bytes",
+        ulp_info, datalen));
+    return 0;
+  }
+  return connection->ReceiveCallback(sock, data, datalen, rcv, flags);
+}
+
+static RefPtr<DataChannelConnection> GetConnectionFromSocket(
+    struct socket* sock) {
+  struct sockaddr* addrs = nullptr;
+  int naddrs = usrsctp_getladdrs(sock, 0, &addrs);
+  if (naddrs <= 0 || addrs[0].sa_family != AF_CONN) {
+    return nullptr;
+  }
+  // usrsctp_getladdrs() returns the addresses bound to this socket, which
+  // contains the SctpDataMediaChannel* as sconn_addr.  Read the pointer,
+  // then free the list of addresses once we have the pointer.  We only open
+  // AF_CONN sockets, and they should all have the sconn_addr set to the
+  // pointer that created them, so [0] is as good as any other.
+  struct sockaddr_conn* sconn =
+      reinterpret_cast<struct sockaddr_conn*>(&addrs[0]);
+  uintptr_t id = reinterpret_cast<uintptr_t>(sconn->sconn_addr);
+  RefPtr<DataChannelConnection> connection = DataChannelRegistry::Lookup(id);
+  usrsctp_freeladdrs(addrs);
+
+  return connection;
+}
+
+// Called when the buffer empties to the threshold value.  This is called
+// from SctpDtlsInput() through the sctp stack.  SctpDtlsInput() calls
+// usrsctp_conninput() under lock
+int DataChannelConnection::OnThresholdEvent(struct socket* sock,
+                                            uint32_t sb_free, void* ulp_info) {
+  RefPtr<DataChannelConnection> connection = GetConnectionFromSocket(sock);
+  connection->mLock.AssertCurrentThreadOwns();
+  if (connection) {
+    connection->SendDeferredMessages();
+  } else {
+    DC_ERROR(("Can't find connection for socket %p", sock));
+  }
+  return 0;
+}
+
+DataChannelConnection::~DataChannelConnection() {
+  DC_DEBUG(("Deleting DataChannelConnection %p", (void*)this));
+  // This may die on the MainThread, or on the STS thread, or on an
+  // sctp thread if we were in a callback when the DOM side shut things down.
+  ASSERT_WEBRTC(mState == DataChannelConnectionState::Closed);
+  MOZ_ASSERT(!mMasterSocket);
+  MOZ_ASSERT(mPending.GetSize() == 0);
+
+  if (!IsSTSThread()) {
+    // We may be on MainThread *or* on an sctp thread (being called from
+    // receive_cb() or SctpDtlsOutput())
+    if (mInternalIOThread) {
+      // Avoid spinning the event thread from here (which if we're mainthread
+      // is in the event loop already)
+      nsCOMPtr<nsIRunnable> r = WrapRunnable(
+          nsCOMPtr<nsIThread>(mInternalIOThread), &nsIThread::AsyncShutdown);
+      Dispatch(r.forget());
+    }
+  } else {
+    // on STS, safe to call shutdown
+    if (mInternalIOThread) {
+      mInternalIOThread->Shutdown();
+    }
+  }
+}
+
+void DataChannelConnection::Destroy() {
+  // Though it's probably ok to do this and close the sockets;
+  // if we really want it to do true clean shutdowns it can
+  // create a dependant Internal object that would remain around
+  // until the network shut down the association or timed out.
+  DC_DEBUG(("Destroying DataChannelConnection %p", (void*)this));
+  ASSERT_WEBRTC(NS_IsMainThread());
+  CloseAll();
+
+  MutexAutoLock lock(mLock);
+  // If we had a pending reset, we aren't waiting for it - clear the list so
+  // we can deregister this DataChannelConnection without leaking.
+  ClearResets();
+
+  MOZ_ASSERT(mSTS);
+  ASSERT_WEBRTC(NS_IsMainThread());
+  mListener = nullptr;
+  // Finish Destroy on STS thread to avoid bug 876167 - once that's fixed,
+  // the usrsctp_close() calls can move back here (and just proxy the
+  // disconnect_all())
+  RUN_ON_THREAD(mSTS,
+                WrapRunnable(RefPtr<DataChannelConnection>(this),
+                             &DataChannelConnection::DestroyOnSTS, mSocket,
+                             mMasterSocket),
+                NS_DISPATCH_NORMAL);
+
+  // These will be released on STS
+  mSocket = nullptr;
+  mMasterSocket = nullptr;  // also a flag that we've Destroyed this connection
+
+  // We can't get any more *new* callbacks from the SCTP library
+
+  // All existing callbacks have refs to DataChannelConnection - however,
+  // we need to handle their destroying the object off mainthread/STS
+
+  // nsDOMDataChannel objects have refs to DataChannels that have refs to us
+}
+
+void DataChannelConnection::DestroyOnSTS(struct socket* aMasterSocket,
+                                         struct socket* aSocket) {
+  if (aSocket && aSocket != aMasterSocket) usrsctp_close(aSocket);
+  if (aMasterSocket) usrsctp_close(aMasterSocket);
+
+  usrsctp_deregister_address(reinterpret_cast<void*>(mId));
+  DC_DEBUG(
+      ("Deregistered %p from the SCTP stack.", reinterpret_cast<void*>(mId)));
+#ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
+  mShutdown = true;
+  DC_DEBUG(("Shutting down connection %p, id %p", this, (void*)mId));
+#endif
+
+  disconnect_all();
+  mTransportHandler = nullptr;
+  GetMainThreadSerialEventTarget()->Dispatch(NS_NewRunnableFunction(
+      "DataChannelConnection::Destroy",
+      [id = mId]() { DataChannelRegistry::Deregister(id); }));
+}
+
+Maybe<RefPtr<DataChannelConnection>> DataChannelConnection::Create(
+    DataChannelConnection::DataConnectionListener* aListener,
+    nsISerialEventTarget* aTarget, MediaTransportHandler* aHandler,
+    const uint16_t aLocalPort, const uint16_t aNumStreams,
+    const Maybe<uint64_t>& aMaxMessageSize) {
+  ASSERT_WEBRTC(NS_IsMainThread());
+
+  RefPtr<DataChannelConnection> connection = new DataChannelConnection(
+      aListener, aTarget, aHandler);  // Walks into a bar
+  return connection->Init(aLocalPort, aNumStreams, aMaxMessageSize)
+             ? Some(connection)
+             : Nothing();
+}
+
+DataChannelConnection::DataChannelConnection(
+    DataChannelConnection::DataConnectionListener* aListener,
+    nsISerialEventTarget* aTarget, MediaTransportHandler* aHandler)
+    : NeckoTargetHolder(aTarget),
+      mLock("netwerk::sctp::DataChannelConnection"),
+      mListener(aListener),
+      mTransportHandler(aHandler) {
+  DC_VERBOSE(("Constructor DataChannelConnection=%p, listener=%p", this,
+              mListener.get()));
+#ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
+  mShutdown = false;
+#endif
+}
+
+bool DataChannelConnection::Init(const uint16_t aLocalPort,
+                                 const uint16_t aNumStreams,
+                                 const Maybe<uint64_t>& aMaxMessageSize) {
+  ASSERT_WEBRTC(NS_IsMainThread());
+
+  struct sctp_initmsg initmsg = {};
+  struct sctp_assoc_value av = {};
+  struct sctp_event event = {};
+  socklen_t len;
+
+  uint16_t event_types[] = {
+      SCTP_ASSOC_CHANGE,          SCTP_PEER_ADDR_CHANGE,
+      SCTP_REMOTE_ERROR,          SCTP_SHUTDOWN_EVENT,
+      SCTP_ADAPTATION_INDICATION, SCTP_PARTIAL_DELIVERY_EVENT,
+      SCTP_SEND_FAILED_EVENT,     SCTP_STREAM_RESET_EVENT,
+      SCTP_STREAM_CHANGE_EVENT};
+  {
+    // MutexAutoLock lock(mLock); Not needed since we're on mainthread always
+    mLocalPort = aLocalPort;
+    SetMaxMessageSize(aMaxMessageSize.isSome(), aMaxMessageSize.valueOr(0));
+  }
+
+  mId = DataChannelRegistry::Register(this);
+
+  // XXX FIX! make this a global we get once
+  // Find the STS thread
+  nsresult rv;
+  mSTS = do_GetService(NS_SOCKETTRANSPORTSERVICE_CONTRACTID, &rv);
+  MOZ_ASSERT(NS_SUCCEEDED(rv));
+
+  // Open sctp with a callback
+  if ((mMasterSocket =
+           usrsctp_socket(AF_CONN, SOCK_STREAM, IPPROTO_SCTP, receive_cb,
+                          &DataChannelConnection::OnThresholdEvent,
+                          usrsctp_sysctl_get_sctp_sendspace() / 2,
+                          reinterpret_cast<void*>(mId))) == nullptr) {
+    return false;
+  }
+
+  int buf_size = 1024 * 1024;
+
+  if (usrsctp_setsockopt(mMasterSocket, SOL_SOCKET, SO_RCVBUF,
+                         (const void*)&buf_size, sizeof(buf_size)) < 0) {
+    DC_ERROR(("Couldn't change receive buffer size on SCTP socket"));
+    goto error_cleanup;
+  }
+  if (usrsctp_setsockopt(mMasterSocket, SOL_SOCKET, SO_SNDBUF,
+                         (const void*)&buf_size, sizeof(buf_size)) < 0) {
+    DC_ERROR(("Couldn't change send buffer size on SCTP socket"));
+    goto error_cleanup;
+  }
+
+  // Make non-blocking for bind/connect.  SCTP over UDP defaults to non-blocking
+  // in associations for normal IO
+  if (usrsctp_set_non_blocking(mMasterSocket, 1) < 0) {
+    DC_ERROR(("Couldn't set non_blocking on SCTP socket"));
+    // We can't handle connect() safely if it will block, not that this will
+    // even happen.
+    goto error_cleanup;
+  }
+
+  // Make sure when we close the socket, make sure it doesn't call us back
+  // again! This would cause it try to use an invalid DataChannelConnection
+  // pointer
+  struct linger l;
+  l.l_onoff = 1;
+  l.l_linger = 0;
+  if (usrsctp_setsockopt(mMasterSocket, SOL_SOCKET, SO_LINGER, (const void*)&l,
+                         (socklen_t)sizeof(struct linger)) < 0) {
+    DC_ERROR(("Couldn't set SO_LINGER on SCTP socket"));
+    // unsafe to allow it to continue if this fails
+    goto error_cleanup;
+  }
+
+  // XXX Consider disabling this when we add proper SDP negotiation.
+  // We may want to leave enabled for supporting 'cloning' of SDP offers, which
+  // implies re-use of the same pseudo-port number, or forcing a renegotiation.
+  {
+    const int option_value = 1;
+    if (usrsctp_setsockopt(mMasterSocket, IPPROTO_SCTP, SCTP_REUSE_PORT,
+                           (const void*)&option_value,
+                           (socklen_t)sizeof(option_value)) < 0) {
+      DC_WARN(("Couldn't set SCTP_REUSE_PORT on SCTP socket"));
+    }
+    if (usrsctp_setsockopt(mMasterSocket, IPPROTO_SCTP, SCTP_NODELAY,
+                           (const void*)&option_value,
+                           (socklen_t)sizeof(option_value)) < 0) {
+      DC_WARN(("Couldn't set SCTP_NODELAY on SCTP socket"));
+    }
+  }
+
+  // Set explicit EOR
+  {
+    const int option_value = 1;
+    if (usrsctp_setsockopt(mMasterSocket, IPPROTO_SCTP, SCTP_EXPLICIT_EOR,
+                           (const void*)&option_value,
+                           (socklen_t)sizeof(option_value)) < 0) {
+      DC_ERROR(("*** failed to enable explicit EOR mode %d", errno));
+      goto error_cleanup;
+    }
+  }
+
+  // Enable ndata
+  // TODO: Bug 1381145, enable this once ndata has been deployed
+#if 0
+  av.assoc_id = SCTP_FUTURE_ASSOC;
+  av.assoc_value = 1;
+  if (usrsctp_setsockopt(mMasterSocket, IPPROTO_SCTP, SCTP_INTERLEAVING_SUPPORTED, &av,
+                         (socklen_t)sizeof(struct sctp_assoc_value)) < 0) {
+    DC_ERROR(("*** failed enable ndata errno %d", errno));
+    goto error_cleanup;
+  }
+#endif
+
+  av.assoc_id = SCTP_ALL_ASSOC;
+  av.assoc_value = SCTP_ENABLE_RESET_STREAM_REQ | SCTP_ENABLE_CHANGE_ASSOC_REQ;
+  if (usrsctp_setsockopt(mMasterSocket, IPPROTO_SCTP, SCTP_ENABLE_STREAM_RESET,
+                         &av, (socklen_t)sizeof(struct sctp_assoc_value)) < 0) {
+    DC_ERROR(("*** failed enable stream reset errno %d", errno));
+    goto error_cleanup;
+  }
+
+  /* Enable the events of interest. */
+  event.se_assoc_id = SCTP_ALL_ASSOC;
+  event.se_on = 1;
+  for (unsigned short event_type : event_types) {
+    event.se_type = event_type;
+    if (usrsctp_setsockopt(mMasterSocket, IPPROTO_SCTP, SCTP_EVENT, &event,
+                           sizeof(event)) < 0) {
+      DC_ERROR(("*** failed setsockopt SCTP_EVENT errno %d", errno));
+      goto error_cleanup;
+    }
+  }
+
+  len = sizeof(initmsg);
+  if (usrsctp_getsockopt(mMasterSocket, IPPROTO_SCTP, SCTP_INITMSG, &initmsg,
+                         &len) < 0) {
+    DC_ERROR(("*** failed getsockopt SCTP_INITMSG"));
+    goto error_cleanup;
+  }
+  DC_DEBUG(("Setting number of SCTP streams to %u, was %u/%u", aNumStreams,
+            initmsg.sinit_num_ostreams, initmsg.sinit_max_instreams));
+  initmsg.sinit_num_ostreams = aNumStreams;
+  initmsg.sinit_max_instreams = MAX_NUM_STREAMS;
+  if (usrsctp_setsockopt(mMasterSocket, IPPROTO_SCTP, SCTP_INITMSG, &initmsg,
+                         (socklen_t)sizeof(initmsg)) < 0) {
+    DC_ERROR(("*** failed setsockopt SCTP_INITMSG, errno %d", errno));
+    goto error_cleanup;
+  }
+
+  mSocket = nullptr;
+  mSTS->Dispatch(
+      NS_NewRunnableFunction("DataChannelConnection::Init", [id = mId]() {
+        usrsctp_register_address(reinterpret_cast<void*>(id));
+        DC_DEBUG(("Registered %p within the SCTP stack.",
+                  reinterpret_cast<void*>(id)));
+      }));
+
+  return true;
+
+error_cleanup:
+  usrsctp_close(mMasterSocket);
+  mMasterSocket = nullptr;
+  return false;
+}
+
+// Only called on MainThread, mMaxMessageSize is read on other threads
+void DataChannelConnection::SetMaxMessageSize(bool aMaxMessageSizeSet,
+                                              uint64_t aMaxMessageSize) {
+  ASSERT_WEBRTC(NS_IsMainThread());
+  MutexAutoLock lock(mLock);
+
+  if (mMaxMessageSizeSet && !aMaxMessageSizeSet) {
+    // Don't overwrite already set MMS with default values
+    return;
+  }
+
+  mMaxMessageSizeSet = aMaxMessageSizeSet;
+  mMaxMessageSize = aMaxMessageSize;
+
+  nsresult rv;
+  nsCOMPtr<nsIPrefService> prefs =
+      do_GetService("@mozilla.org/preferences-service;1", &rv);
+  if (!NS_WARN_IF(NS_FAILED(rv))) {
+    nsCOMPtr<nsIPrefBranch> branch = do_QueryInterface(prefs);
+
+    if (branch) {
+      int32_t temp;
+      if (!NS_FAILED(branch->GetIntPref(
+              "media.peerconnection.sctp.force_maximum_message_size", &temp))) {
+        if (temp >= 0) {
+          mMaxMessageSize = (uint64_t)temp;
+        }
+      }
+    }
+  }
+
+  // Fix remote MMS. This code exists, so future implementations of
+  // RTCSctpTransport.maxMessageSize can simply provide that value from
+  // GetMaxMessageSize.
+
+  // TODO: Bug 1382779, once resolved, can be increased to
+  // min(Uint8ArrayMaxSize, UINT32_MAX)
+  // TODO: Bug 1381146, once resolved, can be increased to whatever we support
+  // then (hopefully
+  //       SIZE_MAX)
+  if (mMaxMessageSize == 0 ||
+      mMaxMessageSize > WEBRTC_DATACHANNEL_MAX_MESSAGE_SIZE_REMOTE) {
+    mMaxMessageSize = WEBRTC_DATACHANNEL_MAX_MESSAGE_SIZE_REMOTE;
+  }
+
+  DC_DEBUG(("Maximum message size (outgoing data): %" PRIu64
+            " (set=%s, enforced=%s)",
+            mMaxMessageSize, mMaxMessageSizeSet ? "yes" : "no",
+            aMaxMessageSize != mMaxMessageSize ? "yes" : "no"));
+}
+
+uint64_t DataChannelConnection::GetMaxMessageSize() {
+  MutexAutoLock lock(mLock);
+  return mMaxMessageSize;
+}
+
+void DataChannelConnection::AppendStatsToReport(
+    const UniquePtr<dom::RTCStatsCollection>& aReport,
+    const DOMHighResTimeStamp aTimestamp) const {
+  ASSERT_WEBRTC(NS_IsMainThread());
+  nsString temp;
+  for (const RefPtr<DataChannel>& chan : mChannels.GetAll()) {
+    // If channel is empty, ignore
+    if (!chan) {
+      continue;
+    }
+    mozilla::dom::RTCDataChannelStats stats;
+    nsString id = u"dc"_ns;
+    id.AppendInt(chan->GetStream());
+    stats.mId.Construct(id);
+    chan->GetLabel(temp);
+    stats.mTimestamp.Construct(aTimestamp);
+    stats.mType.Construct(mozilla::dom::RTCStatsType::Data_channel);
+    stats.mLabel.Construct(temp);
+    chan->GetProtocol(temp);
+    stats.mProtocol.Construct(temp);
+    stats.mDataChannelIdentifier.Construct(chan->GetStream());
+    {
+      using State = mozilla::dom::RTCDataChannelState;
+      State state;
+      switch (chan->GetReadyState()) {
+        case DataChannelState::Connecting:
+          state = State::Connecting;
+          break;
+        case DataChannelState::Open:
+          state = State::Open;
+          break;
+        case DataChannelState::Closing:
+          state = State::Closing;
+          break;
+        case DataChannelState::Closed:
+          state = State::Closed;
+          break;
+      };
+      stats.mState.Construct(state);
+    }
+    auto counters = chan->GetTrafficCounters();
+    stats.mMessagesSent.Construct(counters.mMessagesSent);
+    stats.mBytesSent.Construct(counters.mBytesSent);
+    stats.mMessagesReceived.Construct(counters.mMessagesReceived);
+    stats.mBytesReceived.Construct(counters.mBytesReceived);
+    if (!aReport->mDataChannelStats.AppendElement(stats, fallible)) {
+      mozalloc_handle_oom(0);
+    }
+  }
+}
+
+#ifdef MOZ_PEERCONNECTION
+
+bool DataChannelConnection::ConnectToTransport(const std::string& aTransportId,
+                                               const bool aClient,
+                                               const uint16_t aLocalPort,
+                                               const uint16_t aRemotePort) {
+  MutexAutoLock lock(mLock);
+
+  MOZ_ASSERT(mMasterSocket,
+             "SCTP wasn't initialized before ConnectToTransport!");
+  static const auto paramString =
+      [](const std::string& tId, const Maybe<bool>& client,
+         const uint16_t localPort, const uint16_t remotePort) -> std::string {
+    std::ostringstream stream;
+    stream << "Transport ID: '" << tId << "', Role: '"
+           << (client ? (client.value() ? "client" : "server") : "")
+           << "', Local Port: '" << localPort << "', Remote Port: '"
+           << remotePort << "'";
+    return stream.str();
+  };
+
+  const auto params =
+      paramString(aTransportId, Some(aClient), aLocalPort, aRemotePort);
+  DC_DEBUG(("ConnectToTransport connecting DTLS transport with parameters: %s",
+            params.c_str()));
+
+  DataChannelConnectionState state = GetState();
+  if (state == DataChannelConnectionState::Open) {
+    if (aTransportId == mTransportId && mAllocateEven.isSome() &&
+        mAllocateEven.value() == aClient && mLocalPort == aLocalPort &&
+        mRemotePort == aRemotePort) {
+      DC_WARN(
+          ("Skipping attempt to connect to an already OPEN transport with "
+           "identical parameters."));
+      return true;
+    }
+    DC_WARN(
+        ("Attempting to connect to an already OPEN transport, because "
+         "different parameters were provided."));
+    DC_WARN(("Original transport parameters: %s",
+             paramString(mTransportId, mAllocateEven, mLocalPort, aRemotePort)
+                 .c_str()));
+    DC_WARN(("New transport parameters: %s", params.c_str()));
+  }
+  if (NS_WARN_IF(aTransportId.empty())) {
+    return false;
+  }
+
+  mLocalPort = aLocalPort;
+  mRemotePort = aRemotePort;
+  SetState(DataChannelConnectionState::Connecting);
+  mAllocateEven = Some(aClient);
+
+  // Could be faster. Probably doesn't matter.
+  while (auto channel = mChannels.Get(INVALID_STREAM)) {
+    mChannels.Remove(channel);
+    channel->mStream = FindFreeStream();
+    if (channel->mStream != INVALID_STREAM) {
+      mChannels.Insert(channel);
+    }
+  }
+  RUN_ON_THREAD(mSTS,
+                WrapRunnable(RefPtr<DataChannelConnection>(this),
+                             &DataChannelConnection::SetSignals, aTransportId),
+                NS_DISPATCH_NORMAL);
+  return true;
+}
+
+void DataChannelConnection::SetSignals(const std::string& aTransportId) {
+  ASSERT_WEBRTC(IsSTSThread());
+  {
+    MutexAutoLock lock(mLock);
+    mTransportId = aTransportId;
+  }
+  if (!mConnectedToTransportHandler) {
+    mTransportHandler->SignalPacketReceived.connect(
+        this, &DataChannelConnection::SctpDtlsInput);
+    mTransportHandler->SignalStateChange.connect(
+        this, &DataChannelConnection::TransportStateChange);
+    mConnectedToTransportHandler = true;
+  }
+  // SignalStateChange() doesn't call you with the initial state
+  if (mTransportHandler->GetState(mTransportId, false) ==
+      TransportLayer::TS_OPEN) {
+    DC_DEBUG(("Setting transport signals, dtls already open"));
+    CompleteConnect();
+  } else {
+    DC_DEBUG(("Setting transport signals, dtls not open yet"));
+  }
+}
+
+void DataChannelConnection::TransportStateChange(
+    const std::string& aTransportId, TransportLayer::State aState) {
+  ASSERT_WEBRTC(IsSTSThread());
+  if (aTransportId == mTransportId) {
+    if (aState == TransportLayer::TS_OPEN) {
+      DC_DEBUG(("Transport is open!"));
+      CompleteConnect();
+    } else if (aState == TransportLayer::TS_CLOSED ||
+               aState == TransportLayer::TS_NONE ||
+               aState == TransportLayer::TS_ERROR) {
+      DC_DEBUG(("Transport is closed!"));
+      Stop();
+    }
+  }
+}
+
+void DataChannelConnection::CompleteConnect() {
+  MutexAutoLock lock(mLock);
+
+  DC_DEBUG(("dtls open"));
+  ASSERT_WEBRTC(IsSTSThread());
+  if (!mMasterSocket) {
+    return;
+  }
+
+  struct sockaddr_conn addr = {};
+  addr.sconn_family = AF_CONN;
+#  if defined(__Userspace_os_Darwin)
+  addr.sconn_len = sizeof(addr);
+#  endif
+  addr.sconn_port = htons(mLocalPort);
+  addr.sconn_addr = reinterpret_cast<void*>(mId);
+
+  DC_DEBUG(("Calling usrsctp_bind"));
+  int r = usrsctp_bind(mMasterSocket, reinterpret_cast<struct sockaddr*>(&addr),
+                       sizeof(addr));
+  if (r < 0) {
+    DC_ERROR(("usrsctp_bind failed: %d", r));
+  } else {
+    // This is the remote addr
+    addr.sconn_port = htons(mRemotePort);
+    DC_DEBUG(("Calling usrsctp_connect"));
+    r = usrsctp_connect(
+        mMasterSocket, reinterpret_cast<struct sockaddr*>(&addr), sizeof(addr));
+    if (r >= 0 || errno == EINPROGRESS) {
+      struct sctp_paddrparams paddrparams = {};
+      socklen_t opt_len;
+
+      memcpy(&paddrparams.spp_address, &addr, sizeof(struct sockaddr_conn));
+      opt_len = (socklen_t)sizeof(struct sctp_paddrparams);
+      r = usrsctp_getsockopt(mMasterSocket, IPPROTO_SCTP, SCTP_PEER_ADDR_PARAMS,
+                             &paddrparams, &opt_len);
+      if (r < 0) {
+        DC_ERROR(("usrsctp_getsockopt failed: %d", r));
+      } else {
+        // This field is misnamed. |spp_pathmtu| represents the maximum
+        // _payload_ size in libusrsctp. So:
+        // 1280 (a reasonable IPV6 MTU according to RFC 8831)
+        //  -12 (sctp header)
+        //  -24 (GCM sipher)
+        //  -13 (DTLS record header)
+        //   -8 (UDP header)
+        //   -4 (TURN ChannelData)
+        //  -40 (IPV6 header)
+        // = 1179
+        // We could further restrict this, because RFC 8831 suggests a starting
+        // IPV4 path MTU of 1200, which would lead to a value of 1115.
+        // I suspect that in practice the path MTU for IPV4 is substantially
+        // larger than 1200.
+        paddrparams.spp_pathmtu = 1179;
+        paddrparams.spp_flags &= ~SPP_PMTUD_ENABLE;
+        paddrparams.spp_flags |= SPP_PMTUD_DISABLE;
+        opt_len = (socklen_t)sizeof(struct sctp_paddrparams);
+        r = usrsctp_setsockopt(mMasterSocket, IPPROTO_SCTP,
+                               SCTP_PEER_ADDR_PARAMS, &paddrparams, opt_len);
+        if (r < 0) {
+          DC_ERROR(("usrsctp_getsockopt failed: %d", r));
+        } else {
+          DC_ERROR(("usrsctp: PMTUD disabled, MTU set to %u",
+                    paddrparams.spp_pathmtu));
+        }
+      }
+    }
+    if (r < 0) {
+      if (errno == EINPROGRESS) {
+        // non-blocking
+        return;
+      }
+      DC_ERROR(("usrsctp_connect failed: %d", errno));
+      SetState(DataChannelConnectionState::Closed);
+    } else {
+      // We fire ON_CONNECTION via SCTP_COMM_UP when we get that
+      return;
+    }
+  }
+  // Note: currently this doesn't actually notify the application
+  Dispatch(do_AddRef(new DataChannelOnMessageAvailable(
+      DataChannelOnMessageAvailable::EventType::OnConnection, this)));
+}
+
+// Process any pending Opens
+void DataChannelConnection::ProcessQueuedOpens() {
+  // The nsDeque holds channels with an AddRef applied.  Another reference
+  // (may) be held by the DOMDataChannel, unless it's been GC'd.  No other
+  // references should exist.
+
+  // Can't copy nsDeque's.  Move into temp array since any that fail will
+  // go back to mPending
+  nsRefPtrDeque<DataChannel> temp;
+  RefPtr<DataChannel> temp_channel;
+  while (nullptr != (temp_channel = mPending.PopFront())) {
+    temp.Push(temp_channel.forget());
+  }
+
+  RefPtr<DataChannel> channel;
+
+  while (nullptr != (channel = temp.PopFront())) {
+    if (channel->mHasFinishedOpen) {
+      DC_DEBUG(("Processing queued open for %p (%u)", channel.get(),
+                channel->mStream));
+      channel->mHasFinishedOpen = false;
+      // OpenFinish returns a reference itself, so we need to take it can
+      // Release it
+      channel = OpenFinish(channel.forget());  // may reset the flag and re-push
+    } else {
+      NS_ASSERTION(false,
+                   "How did a DataChannel get queued without the "
+                   "mHasFinishedOpen flag?");
+    }
+  }
+}
+
+void DataChannelConnection::SctpDtlsInput(const std::string& aTransportId,
+                                          const MediaPacket& packet) {
+  MutexAutoLock lock(mLock);
+  if ((packet.type() != MediaPacket::SCTP) || (mTransportId != aTransportId)) {
+    return;
+  }
+
+  if (MOZ_LOG_TEST(gSCTPLog, LogLevel::Debug)) {
+    char* buf;
+
+    if ((buf = usrsctp_dumppacket((void*)packet.data(), packet.len(),
+                                  SCTP_DUMP_INBOUND)) != nullptr) {
+      SCTP_LOG(("%s", buf));
+      usrsctp_freedumpbuffer(buf);
+    }
+  }
+  // Pass the data to SCTP
+  usrsctp_conninput(reinterpret_cast<void*>(mId), packet.data(), packet.len(),
+                    0);
+}
+
+void DataChannelConnection::SendPacket(std::unique_ptr<MediaPacket>&& packet) {
+  mSTS->Dispatch(NS_NewRunnableFunction(
+      "DataChannelConnection::SendPacket",
+      [this, self = RefPtr<DataChannelConnection>(this),
+       packet = std::move(packet)]() mutable {
+        // DC_DEBUG(("%p: SCTP/DTLS sent %ld bytes", this, len));
+        if (!mTransportId.empty() && mTransportHandler) {
+          mTransportHandler->SendPacket(mTransportId, std::move(*packet));
+        }
+      }));
+}
+
+int DataChannelConnection::SctpDtlsOutput(void* addr, void* buffer,
+                                          size_t length, uint8_t tos,
+                                          uint8_t set_df) {
+  if (MOZ_LOG_TEST(gSCTPLog, LogLevel::Debug)) {
+    char* buf;
+
+    if ((buf = usrsctp_dumppacket(buffer, length, SCTP_DUMP_OUTBOUND)) !=
+        nullptr) {
+      SCTP_LOG(("%s", buf));
+      usrsctp_freedumpbuffer(buf);
+    }
+  }
+
+  // We're async proxying even if on the STSThread because this is called
+  // with internal SCTP locks held in some cases (such as in usrsctp_connect()).
+  // SCTP has an option for Apple, on IP connections only, to release at least
+  // one of the locks before calling a packet output routine; with changes to
+  // the underlying SCTP stack this might remove the need to use an async proxy.
+  std::unique_ptr<MediaPacket> packet(new MediaPacket);
+  packet->SetType(MediaPacket::SCTP);
+  packet->Copy(static_cast<const uint8_t*>(buffer), length);
+
+  if (NS_IsMainThread() && mDeferSend) {
+    mDeferredSend.emplace_back(std::move(packet));
+    return 0;
+  }
+
+  SendPacket(std::move(packet));
+  return 0;  // cheat!  Packets can always be dropped later anyways
+}
+#endif
+
+#ifdef ALLOW_DIRECT_SCTP_LISTEN_CONNECT
+// listen for incoming associations
+// Blocks! - Don't call this from main thread!
+
+bool DataChannelConnection::Listen(unsigned short port) {
+  struct sockaddr_in addr = {};
+  socklen_t addr_len;
+
+  NS_WARNING_ASSERTION(!NS_IsMainThread(),
+                       "Blocks, do not call from main thread!!!");
+
+  /* Acting as the 'server' */
+#  ifdef HAVE_SIN_LEN
+  addr.sin_len = sizeof(struct sockaddr_in);
+#  endif
+  addr.sin_family = AF_INET;
+  addr.sin_port = htons(port);
+  addr.sin_addr.s_addr = htonl(INADDR_ANY);
+  DC_DEBUG(("Waiting for connections on port %u", ntohs(addr.sin_port)));
+  {
+    MutexAutoLock lock(mLock);
+    SetState(DataChannelConnectionState::Connecting);
+  }
+  if (usrsctp_bind(mMasterSocket, reinterpret_cast<struct sockaddr*>(&addr),
+                   sizeof(struct sockaddr_in)) < 0) {
+    DC_ERROR(("***Failed userspace_bind"));
+    return false;
+  }
+  if (usrsctp_listen(mMasterSocket, 1) < 0) {
+    DC_ERROR(("***Failed userspace_listen"));
+    return false;
+  }
+
+  DC_DEBUG(("Accepting connection"));
+  addr_len = 0;
+  if ((mSocket = usrsctp_accept(mMasterSocket, nullptr, &addr_len)) ==
+      nullptr) {
+    DC_ERROR(("***Failed accept"));
+    return false;
+  }
+
+  {
+    MutexAutoLock lock(mLock);
+    SetState(DataChannelConnectionState::Open);
+  }
+
+  struct linger l;
+  l.l_onoff = 1;
+  l.l_linger = 0;
+  if (usrsctp_setsockopt(mSocket, SOL_SOCKET, SO_LINGER, (const void*)&l,
+                         (socklen_t)sizeof(struct linger)) < 0) {
+    DC_WARN(("Couldn't set SO_LINGER on SCTP socket"));
+  }
+
+  // Notify Connection open
+  // XXX We need to make sure connection sticks around until the message is
+  // delivered
+  DC_DEBUG(("%s: sending ON_CONNECTION for %p", __FUNCTION__, this));
+  Dispatch(do_AddRef(new DataChannelOnMessageAvailable(
+      DataChannelOnMessageAvailable::EventType::OnConnection, this,
+      (DataChannel*)nullptr)));
+  return true;
+}
+
+// Blocks! - Don't call this from main thread!
+bool DataChannelConnection::Connect(const char* addr, unsigned short port) {
+  struct sockaddr_in addr4 = {};
+  struct sockaddr_in6 addr6 = {};
+
+  NS_WARNING_ASSERTION(!NS_IsMainThread(),
+                       "Blocks, do not call from main thread!!!");
+
+  /* Acting as the connector */
+  DC_DEBUG(("Connecting to %s, port %u", addr, port));
+#  ifdef HAVE_SIN_LEN
+  addr4.sin_len = sizeof(struct sockaddr_in);
+#  endif
+#  ifdef HAVE_SIN6_LEN
+  addr6.sin6_len = sizeof(struct sockaddr_in6);
+#  endif
+  addr4.sin_family = AF_INET;
+  addr6.sin6_family = AF_INET6;
+  addr4.sin_port = htons(port);
+  addr6.sin6_port = htons(port);
+  {
+    MutexAutoLock lock(mLock);
+    SetState(DataChannelConnectionState::Connecting);
+  }
+#  if !defined(__Userspace_os_Windows)
+  if (inet_pton(AF_INET6, addr, &addr6.sin6_addr) == 1) {
+    if (usrsctp_connect(mMasterSocket,
+                        reinterpret_cast<struct sockaddr*>(&addr6),
+                        sizeof(struct sockaddr_in6)) < 0) {
+      DC_ERROR(("*** Failed userspace_connect"));
+      return false;
+    }
+  } else if (inet_pton(AF_INET, addr, &addr4.sin_addr) == 1) {
+    if (usrsctp_connect(mMasterSocket,
+                        reinterpret_cast<struct sockaddr*>(&addr4),
+                        sizeof(struct sockaddr_in)) < 0) {
+      DC_ERROR(("*** Failed userspace_connect"));
+      return false;
+    }
+  } else {
+    DC_ERROR(("*** Illegal destination address."));
+  }
+#  else
+  {
+    struct sockaddr_storage ss;
+    int sslen = sizeof(ss);
+
+    if (!WSAStringToAddressA(const_cast<char*>(addr), AF_INET6, nullptr,
+                             (struct sockaddr*)&ss, &sslen)) {
+      addr6.sin6_addr =
+          (reinterpret_cast<struct sockaddr_in6*>(&ss))->sin6_addr;
+      if (usrsctp_connect(mMasterSocket,
+                          reinterpret_cast<struct sockaddr*>(&addr6),
+                          sizeof(struct sockaddr_in6)) < 0) {
+        DC_ERROR(("*** Failed userspace_connect"));
+        return false;
+      }
+    } else if (!WSAStringToAddressA(const_cast<char*>(addr), AF_INET, nullptr,
+                                    (struct sockaddr*)&ss, &sslen)) {
+      addr4.sin_addr = (reinterpret_cast<struct sockaddr_in*>(&ss))->sin_addr;
+      if (usrsctp_connect(mMasterSocket,
+                          reinterpret_cast<struct sockaddr*>(&addr4),
+                          sizeof(struct sockaddr_in)) < 0) {
+        DC_ERROR(("*** Failed userspace_connect"));
+        return false;
+      }
+    } else {
+      DC_ERROR(("*** Illegal destination address."));
+    }
+  }
+#  endif
+
+  mSocket = mMasterSocket;
+
+  DC_DEBUG(("connect() succeeded!  Entering connected mode"));
+  {
+    MutexAutoLock lock(mLock);
+    SetState(DataChannelConnectionState::Open);
+  }
+  // Notify Connection open
+  // XXX We need to make sure connection sticks around until the message is
+  // delivered
+  DC_DEBUG(("%s: sending ON_CONNECTION for %p", __FUNCTION__, this));
+  Dispatch(do_AddRef(new DataChannelOnMessageAvailable(
+      DataChannelOnMessageAvailable::EventType::OnConnection, this,
+      (DataChannel*)nullptr)));
+  return true;
+}
+#endif
+
+DataChannel* DataChannelConnection::FindChannelByStream(uint16_t stream) {
+  return mChannels.Get(stream).get();
+}
+
+uint16_t DataChannelConnection::FindFreeStream() const {
+  ASSERT_WEBRTC(NS_IsMainThread());
+  uint16_t i, limit;
+
+  limit = MAX_NUM_STREAMS;
+
+  MOZ_ASSERT(mAllocateEven.isSome());
+  for (i = (*mAllocateEven ? 0 : 1); i < limit; i += 2) {
+    if (mChannels.Get(i)) {
+      continue;
+    }
+
+    // Verify it's not still in the process of closing
+    size_t j;
+    for (j = 0; j < mStreamsResetting.Length(); ++j) {
+      if (mStreamsResetting[j] == i) {
+        break;
+      }
+    }
+
+    if (j == mStreamsResetting.Length()) {
+      return i;
+    }
+  }
+  return INVALID_STREAM;
+}
+
+uint32_t DataChannelConnection::UpdateCurrentStreamIndex() {
+  RefPtr<DataChannel> channel = mChannels.GetNextChannel(mCurrentStream);
+  if (!channel) {
+    mCurrentStream = 0;
+  } else {
+    mCurrentStream = channel->mStream;
+  }
+  return mCurrentStream;
+}
+
+uint32_t DataChannelConnection::GetCurrentStreamIndex() {
+  if (!mChannels.Get(mCurrentStream)) {
+    // The stream muse have been removed, reset
+    DC_DEBUG(("Reset mCurrentChannel"));
+    mCurrentStream = 0;
+  }
+  return mCurrentStream;
+}
+
+bool DataChannelConnection::RequestMoreStreams(int32_t aNeeded) {
+  struct sctp_status status = {};
+  struct sctp_add_streams sas = {};
+  uint32_t outStreamsNeeded;
+  socklen_t len;
+
+  if (aNeeded + mNegotiatedIdLimit > MAX_NUM_STREAMS) {
+    aNeeded = MAX_NUM_STREAMS - mNegotiatedIdLimit;
+  }
+  if (aNeeded <= 0) {
+    return false;
+  }
+
+  len = (socklen_t)sizeof(struct sctp_status);
+  if (usrsctp_getsockopt(mMasterSocket, IPPROTO_SCTP, SCTP_STATUS, &status,
+                         &len) < 0) {
+    DC_ERROR(("***failed: getsockopt SCTP_STATUS"));
+    return false;
+  }
+  outStreamsNeeded = aNeeded;  // number to add
+
+  // Note: if multiple channel opens happen when we don't have enough space,
+  // we'll call RequestMoreStreams() multiple times
+  sas.sas_instrms = 0;
+  sas.sas_outstrms = (uint16_t)outStreamsNeeded; /* XXX error handling */
+  // Doesn't block, we get an event when it succeeds or fails
+  if (usrsctp_setsockopt(mMasterSocket, IPPROTO_SCTP, SCTP_ADD_STREAMS, &sas,
+                         (socklen_t)sizeof(struct sctp_add_streams)) < 0) {
+    if (errno == EALREADY) {
+      DC_DEBUG(("Already have %u output streams", outStreamsNeeded));
+      return true;
+    }
+
+    DC_ERROR(("***failed: setsockopt ADD errno=%d", errno));
+    return false;
+  }
+  DC_DEBUG(("Requested %u more streams", outStreamsNeeded));
+  // We add to mNegotiatedIdLimit when we get a SCTP_STREAM_CHANGE_EVENT and the
+  // values are larger than mNegotiatedIdLimit
+  return true;
+}
+
+// Returns a POSIX error code.
+int DataChannelConnection::SendControlMessage(const uint8_t* data, uint32_t len,
+                                              uint16_t stream) {
+  struct sctp_sendv_spa info = {};
+
+  // General flags
+  info.sendv_flags = SCTP_SEND_SNDINFO_VALID;
+
+  // Set stream identifier, protocol identifier and flags
+  info.sendv_sndinfo.snd_sid = stream;
+  info.sendv_sndinfo.snd_flags = SCTP_EOR;
+  info.sendv_sndinfo.snd_ppid = htonl(DATA_CHANNEL_PPID_CONTROL);
+
+  // Create message instance and send
+  // Note: Main-thread IO, but doesn't block
+#if (UINT32_MAX > SIZE_MAX)
+  if (len > SIZE_MAX) {
+    return EMSGSIZE;
+  }
+#endif
+  OutgoingMsg msg(info, data, (size_t)len);
+  bool buffered;
+  int error = SendMsgInternalOrBuffer(mBufferedControl, msg, buffered, nullptr);
+
+  // Set pending type (if buffered)
+  if (!error && buffered && mPendingType == PendingType::None) {
+    mPendingType = PendingType::Dcep;
+  }
+  return error;
+}
+
+// Returns a POSIX error code.
+int DataChannelConnection::SendOpenAckMessage(uint16_t stream) {
+  struct rtcweb_datachannel_ack ack = {};
+  ack.msg_type = DATA_CHANNEL_ACK;
+
+  return SendControlMessage((const uint8_t*)&ack, sizeof(ack), stream);
+}
+
+// Returns a POSIX error code.
+int DataChannelConnection::SendOpenRequestMessage(
+    const nsACString& label, const nsACString& protocol, uint16_t stream,
+    bool unordered, DataChannelReliabilityPolicy prPolicy, uint32_t prValue) {
+  const size_t label_len = label.Length();     // not including nul
+  const size_t proto_len = protocol.Length();  // not including nul
+  // careful - request struct include one char for the label
+  const size_t req_size = sizeof(struct rtcweb_datachannel_open_request) - 1 +
+                          label_len + proto_len;
+  UniqueFreePtr<struct rtcweb_datachannel_open_request> req(
+      (struct rtcweb_datachannel_open_request*)moz_xmalloc(req_size));
+
+  memset(req.get(), 0, req_size);
+  req->msg_type = DATA_CHANNEL_OPEN_REQUEST;
+  switch (prPolicy) {
+    case DataChannelReliabilityPolicy::Reliable:
+      req->channel_type = DATA_CHANNEL_RELIABLE;
+      break;
+    case DataChannelReliabilityPolicy::LimitedLifetime:
+      req->channel_type = DATA_CHANNEL_PARTIAL_RELIABLE_TIMED;
+      break;
+    case DataChannelReliabilityPolicy::LimitedRetransmissions:
+      req->channel_type = DATA_CHANNEL_PARTIAL_RELIABLE_REXMIT;
+      break;
+    default:
+      return EINVAL;
+  }
+  if (unordered) {
+    // Per the current types, all differ by 0x80 between ordered and unordered
+    req->channel_type |=
+        0x80;  // NOTE: be careful if new types are added in the future
+  }
+
+  req->reliability_param = htonl(prValue);
+  req->priority = htons(0); /* XXX: add support */
+  req->label_length = htons(label_len);
+  req->protocol_length = htons(proto_len);
+  memcpy(&req->label[0], PromiseFlatCString(label).get(), label_len);
+  memcpy(&req->label[label_len], PromiseFlatCString(protocol).get(), proto_len);
+
+  // TODO: req_size is an int... that looks hairy
+  int error = SendControlMessage((const uint8_t*)req.get(), req_size, stream);
+  return error;
+}
+
+// XXX This should use a separate thread (outbound queue) which should
+// select() to know when to *try* to send data to the socket again.
+// Alternatively, it can use a timeout, but that's guaranteed to be wrong
+// (just not sure in what direction).  We could re-implement NSPR's
+// PR_POLL_WRITE/etc handling... with a lot of work.
+
+// Better yet, use the SCTP stack's notifications on buffer state to avoid
+// filling the SCTP's buffers.
+
+// returns if we're still blocked (true)
+bool DataChannelConnection::SendDeferredMessages() {
+  RefPtr<DataChannel> channel;  // we may null out the refs to this
+
+  // This may block while something is modifying channels, but should not block
+  // for IO
+  ASSERT_WEBRTC(!NS_IsMainThread());
+  mLock.AssertCurrentThreadOwns();
+
+  DC_DEBUG(("SendDeferredMessages called, pending type: %s",
+            ToString(mPendingType)));
+  if (mPendingType == PendingType::None) {
+    return false;
+  }
+
+  // Send pending control messages
+  // Note: If ndata is not active, check if DCEP messages are currently
+  // outstanding. These need to
+  //       be sent first before other streams can be used for sending.
+  if (!mBufferedControl.IsEmpty() &&
+      (mSendInterleaved || mPendingType == PendingType::Dcep)) {
+    if (SendBufferedMessages(mBufferedControl, nullptr)) {
+      return true;
+    }
+
+    // Note: There may or may not be pending data messages
+    mPendingType = PendingType::Data;
+  }
+
+  bool blocked = false;
+  uint32_t i = GetCurrentStreamIndex();
+  uint32_t end = i;
+  do {
+    channel = mChannels.Get(i);
+    // Should already be cleared if closing/closed
+    if (!channel || channel->mBufferedData.IsEmpty()) {
+      i = UpdateCurrentStreamIndex();
+      continue;
+    }
+
+    // Send buffered data messages
+    // Warning: This will fail in case ndata is inactive and a previously
+    //          deallocated data channel has not been closed properly. If you
+    //          ever see that no messages can be sent on any channel, this is
+    //          likely the cause (an explicit EOR message partially sent whose
+    //          remaining chunks are still being waited for).
+    size_t written = 0;
+    mDeferSend = true;
+    blocked = SendBufferedMessages(channel->mBufferedData, &written);
+    mDeferSend = false;
+    if (written) {
+      channel->DecrementBufferedAmount(written);
+    }
+
+    for (auto&& packet : mDeferredSend) {
+      MOZ_ASSERT(written);
+      SendPacket(std::move(packet));
+    }
+    mDeferredSend.clear();
+
+    // Update current stream index
+    // Note: If ndata is not active, the outstanding data messages on this
+    //       stream need to be sent first before other streams can be used for
+    //       sending.
+    if (mSendInterleaved || !blocked) {
+      i = UpdateCurrentStreamIndex();
+    }
+  } while (!blocked && i != end);
+
+  if (!blocked) {
+    mPendingType =
+        mBufferedControl.IsEmpty() ? PendingType::None : PendingType::Dcep;
+  }
+  return blocked;
+}
+
+// Called with mLock locked!
+// buffer MUST have at least one item!
+// returns if we're still blocked (true)
+bool DataChannelConnection::SendBufferedMessages(
+    nsTArray<UniquePtr<BufferedOutgoingMsg>>& buffer, size_t* aWritten) {
+  do {
+    // Re-send message
+    int error = SendMsgInternal(*buffer[0], aWritten);
+    switch (error) {
+      case 0:
+        buffer.RemoveElementAt(0);
+        break;
+      case EAGAIN:
+#if (EAGAIN != EWOULDBLOCK)
+      case EWOULDBLOCK:
+#endif
+        return true;
+      default:
+        buffer.RemoveElementAt(0);
+        DC_ERROR(("error on sending: %d", error));
+        break;
+    }
+  } while (!buffer.IsEmpty());
+
+  return false;
+}
+
+// Caller must ensure that length <= SIZE_MAX
+void DataChannelConnection::HandleOpenRequestMessage(
+    const struct rtcweb_datachannel_open_request* req, uint32_t length,
+    uint16_t stream) {
+  RefPtr<DataChannel> channel;
+  uint32_t prValue;
+  DataChannelReliabilityPolicy prPolicy;
+
+  ASSERT_WEBRTC(!NS_IsMainThread());
+  mLock.AssertCurrentThreadOwns();
+
+  const size_t requiredLength = (sizeof(*req) - 1) + ntohs(req->label_length) +
+                                ntohs(req->protocol_length);
+  if (((size_t)length) != requiredLength) {
+    if (((size_t)length) < requiredLength) {
+      DC_ERROR(
+          ("%s: insufficient length: %u, should be %zu. Unable to continue.",
+           __FUNCTION__, length, requiredLength));
+      return;
+    }
+    DC_WARN(("%s: Inconsistent length: %u, should be %zu", __FUNCTION__, length,
+             requiredLength));
+  }
+
+  DC_DEBUG(("%s: length %u, sizeof(*req) = %zu", __FUNCTION__, length,
+            sizeof(*req)));
+
+  switch (req->channel_type) {
+    case DATA_CHANNEL_RELIABLE:
+    case DATA_CHANNEL_RELIABLE_UNORDERED:
+      prPolicy = DataChannelReliabilityPolicy::Reliable;
+      break;
+    case DATA_CHANNEL_PARTIAL_RELIABLE_REXMIT:
+    case DATA_CHANNEL_PARTIAL_RELIABLE_REXMIT_UNORDERED:
+      prPolicy = DataChannelReliabilityPolicy::LimitedRetransmissions;
+      break;
+    case DATA_CHANNEL_PARTIAL_RELIABLE_TIMED:
+    case DATA_CHANNEL_PARTIAL_RELIABLE_TIMED_UNORDERED:
+      prPolicy = DataChannelReliabilityPolicy::LimitedLifetime;
+      break;
+    default:
+      DC_ERROR(("Unknown channel type %d", req->channel_type));
+      /* XXX error handling */
+      return;
+  }
+  prValue = ntohl(req->reliability_param);
+  bool ordered = !(req->channel_type & 0x80);
+
+  if ((channel = FindChannelByStream(stream))) {
+    if (!channel->mNegotiated) {
+      DC_ERROR(
+          ("HandleOpenRequestMessage: channel for pre-existing stream "
+           "%u that was not externally negotiated. JS is lying to us, or "
+           "there's an id collision.",
+           stream));
+      /* XXX: some error handling */
+    } else {
+      DC_DEBUG(("Open for externally negotiated channel %u", stream));
+      // XXX should also check protocol, maybe label
+      if (prPolicy != channel->mPrPolicy || prValue != channel->mPrValue ||
+          ordered != channel->mOrdered) {
+        DC_WARN(
+            ("external negotiation mismatch with OpenRequest:"
+             "channel %u, policy %s/%s, value %u/%u, ordered %d/%d",
+             stream, ToString(prPolicy), ToString(channel->mPrPolicy), prValue,
+             channel->mPrValue, static_cast<int>(ordered),
+             static_cast<int>(channel->mOrdered)));
+      }
+    }
+    return;
+  }
+  if (stream >= mNegotiatedIdLimit) {
+    DC_ERROR(("%s: stream %u out of bounds (%zu)", __FUNCTION__, stream,
+              mNegotiatedIdLimit));
+    return;
+  }
+
+  nsCString label(
+      nsDependentCSubstring(&req->label[0], ntohs(req->label_length)));
+  nsCString protocol(nsDependentCSubstring(
+      &req->label[ntohs(req->label_length)], ntohs(req->protocol_length)));
+
+  channel =
+      new DataChannel(this, stream, DataChannelState::Open, label, protocol,
+                      prPolicy, prValue, ordered, false, nullptr, nullptr);
+  mChannels.Insert(channel);
+
+  DC_DEBUG(("%s: sending ON_CHANNEL_CREATED for %s/%s: %u", __FUNCTION__,
+            channel->mLabel.get(), channel->mProtocol.get(), stream));
+  Dispatch(do_AddRef(new DataChannelOnMessageAvailable(
+      DataChannelOnMessageAvailable::EventType::OnChannelCreated, this,
+      channel)));
+
+  DC_DEBUG(("%s: deferring sending ON_CHANNEL_OPEN for %p", __FUNCTION__,
+            channel.get()));
+  channel->AnnounceOpen();
+
+  // Note that any message can be buffered; SendOpenAckMessage may
+  // error later than this check.
+  const auto error = SendOpenAckMessage(channel->mStream);
+  if (error) {
+    DC_ERROR(("SendOpenRequest failed, error = %d", error));
+    Dispatch(NS_NewRunnableFunction(
+        "DataChannelConnection::HandleOpenRequestMessage",
+        [channel, connection = RefPtr<DataChannelConnection>(this)]() {
+          // Close the channel on failure
+          connection->Close(channel);
+        }));
+    return;
+  }
+  DeliverQueuedData(channel->mStream);
+}
+
+// NOTE: the updated spec from the IETF says we should set in-order until we
+// receive an ACK. That would make this code moot.  Keep it for now for
+// backwards compatibility.
+void DataChannelConnection::DeliverQueuedData(uint16_t stream) {
+  mLock.AssertCurrentThreadOwns();
+
+  mQueuedData.RemoveElementsBy([stream, this](const auto& dataItem) {
+    mLock.AssertCurrentThreadOwns();
+    const bool match = dataItem->mStream == stream;
+    if (match) {
+      DC_DEBUG(("Delivering queued data for stream %u, length %u", stream,
+                dataItem->mLength));
+      // Deliver the queued data
+      HandleDataMessage(dataItem->mData, dataItem->mLength, dataItem->mPpid,
+                        dataItem->mStream, dataItem->mFlags);
+    }
+    return match;
+  });
+}
+
+// Caller must ensure that length <= SIZE_MAX
+void DataChannelConnection::HandleOpenAckMessage(
+    const struct rtcweb_datachannel_ack* ack, uint32_t length,
+    uint16_t stream) {
+  DataChannel* channel;
+
+  mLock.AssertCurrentThreadOwns();
+
+  channel = FindChannelByStream(stream);
+  if (NS_WARN_IF(!channel)) {
+    return;
+  }
+
+  DC_DEBUG(("OpenAck received for stream %u, waiting=%d", stream,
+            channel->mWaitingForAck ? 1 : 0));
+
+  channel->mWaitingForAck = false;
+}
+
+// Caller must ensure that length <= SIZE_MAX
+void DataChannelConnection::HandleUnknownMessage(uint32_t ppid, uint32_t length,
+                                                 uint16_t stream) {
+  /* XXX: Send an error message? */
+  DC_ERROR(("unknown DataChannel message received: %u, len %u on stream %d",
+            ppid, length, stream));
+  // XXX Log to JS error console if possible
+}
+
+uint8_t DataChannelConnection::BufferMessage(nsACString& recvBuffer,
+                                             const void* data, uint32_t length,
+                                             uint32_t ppid, int flags) {
+  const char* buffer = (const char*)data;
+  uint8_t bufferFlags = 0;
+
+  if ((flags & MSG_EOR) && ppid != DATA_CHANNEL_PPID_BINARY_PARTIAL &&
+      ppid != DATA_CHANNEL_PPID_DOMSTRING_PARTIAL) {
+    bufferFlags |= DATA_CHANNEL_BUFFER_MESSAGE_FLAGS_COMPLETE;
+
+    // Return directly if nothing has been buffered
+    if (recvBuffer.IsEmpty()) {
+      return bufferFlags;
+    }
+  }
+
+  // Ensure it doesn't blow up our buffer
+  // TODO: Change 'WEBRTC_DATACHANNEL_MAX_MESSAGE_SIZE_LOCAL' to whatever the
+  //       new buffer is capable of holding.
+  if (((uint64_t)recvBuffer.Length()) + ((uint64_t)length) >
+      WEBRTC_DATACHANNEL_MAX_MESSAGE_SIZE_LOCAL) {
+    bufferFlags |= DATA_CHANNEL_BUFFER_MESSAGE_FLAGS_TOO_LARGE;
+    return bufferFlags;
+  }
+
+  // Copy & add to receive buffer
+  recvBuffer.Append(buffer, length);
+  bufferFlags |= DATA_CHANNEL_BUFFER_MESSAGE_FLAGS_BUFFERED;
+  return bufferFlags;
+}
+
+void DataChannelConnection::HandleDataMessage(const void* data, size_t length,
+                                              uint32_t ppid, uint16_t stream,
+                                              int flags) {
+  DataChannel* channel;
+  const char* buffer = (const char*)data;
+
+  mLock.AssertCurrentThreadOwns();
+  channel = FindChannelByStream(stream);
+
+  // Note: Until we support SIZE_MAX sized messages, we need this check
+#if (SIZE_MAX > UINT32_MAX)
+  if (length > UINT32_MAX) {
+    DC_ERROR(("DataChannel: Cannot handle message of size %zu (max=%" PRIu32
+              ")",
+              length, UINT32_MAX));
+    CloseLocked(channel);
+    return;
+  }
+#endif
+  uint32_t data_length = (uint32_t)length;
+
+  // XXX A closed channel may trip this... check
+  // NOTE: the updated spec from the IETF says we should set in-order until we
+  // receive an ACK. That would make this code moot.  Keep it for now for
+  // backwards compatibility.
+  if (!channel) {
+    // In the updated 0-RTT open case, the sender can send data immediately
+    // after Open, and doesn't set the in-order bit (since we don't have a
+    // response or ack).  Also, with external negotiation, data can come in
+    // before we're told about the external negotiation.  We need to buffer
+    // data until either a) Open comes in, if the ordering get messed up,
+    // or b) the app tells us this channel was externally negotiated.  When
+    // these occur, we deliver the data.
+
+    // Since this is rare and non-performance, keep a single list of queued
+    // data messages to deliver once the channel opens.
+    DC_DEBUG(("Queuing data for stream %u, length %u", stream, data_length));
+    // Copies data
+    mQueuedData.AppendElement(
+        new QueuedDataMessage(stream, ppid, flags, data, data_length));
+    return;
+  }
+
+  // RFC8832: "MUST be sent ordered, ... After the DATA_CHANNEL_ACK **or any
+  // other message** has been received on the data channel".
+  // If the channel was opened on this side, and a message is received, this
+  // indicates that the peer has already received the DATA_CHANNEL_ACK, as the
+  // channel is ordered initially.
+  channel->mWaitingForAck = false;
+
+  bool is_binary = true;
+  uint8_t bufferFlags;
+  DataChannelOnMessageAvailable::EventType type;
+  const char* info = "";
+
+  if (ppid == DATA_CHANNEL_PPID_DOMSTRING_PARTIAL ||
+      ppid == DATA_CHANNEL_PPID_DOMSTRING ||
+      ppid == DATA_CHANNEL_PPID_DOMSTRING_EMPTY) {
+    is_binary = false;
+  }
+  if (is_binary != channel->mIsRecvBinary && !channel->mRecvBuffer.IsEmpty()) {
+    NS_WARNING("DataChannel message aborted by fragment type change!");
+    // TODO: Maybe closing would be better as this is a hard to detect protocol
+    // violation?
+    channel->mRecvBuffer.Truncate(0);
+  }
+  channel->mIsRecvBinary = is_binary;
+
+  // Remaining chunks of previously truncated message (due to the buffer being
+  // full)?
+  if (channel->mClosingTooLarge) {
+    DC_ERROR(
+        ("DataChannel: Ignoring partial message of length %u, buffer full and "
+         "closing",
+         data_length));
+    // Only unblock if unordered
+    if (!channel->mOrdered && (flags & MSG_EOR)) {
+      channel->mClosingTooLarge = false;
+    }
+  }
+
+  // Buffer message until complete
+  bufferFlags =
+      BufferMessage(channel->mRecvBuffer, buffer, data_length, ppid, flags);
+  if (bufferFlags & DATA_CHANNEL_BUFFER_MESSAGE_FLAGS_TOO_LARGE) {
+    DC_ERROR(
+        ("DataChannel: Buffered message would become too large to handle, "
+         "closing channel"));
+    channel->mRecvBuffer.Truncate(0);
+    channel->mClosingTooLarge = true;
+    CloseLocked(channel);
+    return;
+  }
+  if (!(bufferFlags & DATA_CHANNEL_BUFFER_MESSAGE_FLAGS_COMPLETE)) {
+    DC_DEBUG(
+        ("DataChannel: Partial %s message of length %u (total %zu) on channel "
+         "id %u",
+         is_binary ? "binary" : "string", data_length,
+         channel->mRecvBuffer.Length(), channel->mStream));
+    return;  // Not ready to notify application
+  }
+  if (bufferFlags & DATA_CHANNEL_BUFFER_MESSAGE_FLAGS_BUFFERED) {
+    data_length = channel->mRecvBuffer.Length();
+  }
+
+  // Complain about large messages (only complain - we can handle it)
+  if (data_length > WEBRTC_DATACHANNEL_MAX_MESSAGE_SIZE_LOCAL) {
+    DC_WARN(
+        ("DataChannel: Received message of length %u is > announced maximum "
+         "message size (%u)",
+         data_length, WEBRTC_DATACHANNEL_MAX_MESSAGE_SIZE_LOCAL));
+  }
+
+  bool is_empty = false;
+
+  switch (ppid) {
+    case DATA_CHANNEL_PPID_DOMSTRING:
+      DC_DEBUG(
+          ("DataChannel: Received string message of length %u on channel %u",
+           data_length, channel->mStream));
+      type = DataChannelOnMessageAvailable::EventType::OnDataString;
+      if (bufferFlags & DATA_CHANNEL_BUFFER_MESSAGE_FLAGS_BUFFERED) {
+        info = " (string fragmented)";
+      }
+      // else send using recvData normally
+
+      // WebSockets checks IsUTF8() here; we can try to deliver it
+      break;
+
+    case DATA_CHANNEL_PPID_DOMSTRING_EMPTY:
+      DC_DEBUG(
+          ("DataChannel: Received empty string message of length %u on channel "
+           "%u",
+           data_length, channel->mStream));
+      type = DataChannelOnMessageAvailable::EventType::OnDataString;
+      if (bufferFlags & DATA_CHANNEL_BUFFER_MESSAGE_FLAGS_BUFFERED) {
+        info = " (string fragmented)";
+      }
+      is_empty = true;
+      break;
+
+    case DATA_CHANNEL_PPID_BINARY:
+      DC_DEBUG(
+          ("DataChannel: Received binary message of length %u on channel id %u",
+           data_length, channel->mStream));
+      type = DataChannelOnMessageAvailable::EventType::OnDataBinary;
+      if (bufferFlags & DATA_CHANNEL_BUFFER_MESSAGE_FLAGS_BUFFERED) {
+        info = " (binary fragmented)";
+      }
+
+      // else send using recvData normally
+      break;
+
+    case DATA_CHANNEL_PPID_BINARY_EMPTY:
+      DC_DEBUG(
+          ("DataChannel: Received empty binary message of length %u on channel "
+           "id %u",
+           data_length, channel->mStream));
+      type = DataChannelOnMessageAvailable::EventType::OnDataBinary;
+      if (bufferFlags & DATA_CHANNEL_BUFFER_MESSAGE_FLAGS_BUFFERED) {
+        info = " (binary fragmented)";
+      }
+      is_empty = true;
+      break;
+
+    default:
+      NS_ERROR("Unknown data PPID");
+      DC_ERROR(("Unknown data PPID %" PRIu32, ppid));
+      return;
+  }
+
+  channel->WithTrafficCounters(
+      [&data_length](DataChannel::TrafficCounters& counters) {
+        counters.mMessagesReceived++;
+        counters.mBytesReceived += data_length;
+      });
+
+  // Notify onmessage
+  DC_DEBUG(
+      ("%s: sending %s%s for %p", __FUNCTION__, ToString(type), info, channel));
+  if (bufferFlags & DATA_CHANNEL_BUFFER_MESSAGE_FLAGS_BUFFERED) {
+    channel->SendOrQueue(new DataChannelOnMessageAvailable(
+        type, this, channel, channel->mRecvBuffer));
+    channel->mRecvBuffer.Truncate(0);
+  } else {
+    nsAutoCString recvData(is_empty ? "" : buffer,
+                           is_empty ? 0 : data_length);  // allocates >64
+    channel->SendOrQueue(
+        new DataChannelOnMessageAvailable(type, this, channel, recvData));
+  }
+}
+
+void DataChannelConnection::HandleDCEPMessage(const void* buffer, size_t length,
+                                              uint32_t ppid, uint16_t stream,
+                                              int flags) {
+  const struct rtcweb_datachannel_open_request* req;
+  const struct rtcweb_datachannel_ack* ack;
+
+  // Note: Until we support SIZE_MAX sized messages, we need this check
+#if (SIZE_MAX > UINT32_MAX)
+  if (length > UINT32_MAX) {
+    DC_ERROR(("DataChannel: Cannot handle message of size %zu (max=%u)", length,
+              UINT32_MAX));
+    Stop();
+    return;
+  }
+#endif
+  uint32_t data_length = (uint32_t)length;
+
+  mLock.AssertCurrentThreadOwns();
+
+  // Buffer message until complete
+  const uint8_t bufferFlags =
+      BufferMessage(mRecvBuffer, buffer, data_length, ppid, flags);
+  if (bufferFlags & DATA_CHANNEL_BUFFER_MESSAGE_FLAGS_TOO_LARGE) {
+    DC_ERROR(
+        ("DataChannel: Buffered message would become too large to handle, "
+         "closing connection"));
+    mRecvBuffer.Truncate(0);
+    Stop();
+    return;
+  }
+  if (!(bufferFlags & DATA_CHANNEL_BUFFER_MESSAGE_FLAGS_COMPLETE)) {
+    DC_DEBUG(("Buffered partial DCEP message of length %u", data_length));
+    return;
+  }
+  if (bufferFlags & DATA_CHANNEL_BUFFER_MESSAGE_FLAGS_BUFFERED) {
+    buffer = reinterpret_cast<const void*>(mRecvBuffer.BeginReading());
+    data_length = mRecvBuffer.Length();
+  }
+
+  req = static_cast<const struct rtcweb_datachannel_open_request*>(buffer);
+  DC_DEBUG(("Handling DCEP message of length %u", data_length));
+
+  // Ensure minimum message size (ack is the smallest DCEP message)
+  if ((size_t)data_length < sizeof(*ack)) {
+    DC_WARN(("Ignored invalid DCEP message (too short)"));
+    return;
+  }
+
+  switch (req->msg_type) {
+    case DATA_CHANNEL_OPEN_REQUEST:
+      // structure includes a possibly-unused char label[1] (in a packed
+      // structure)
+      if (NS_WARN_IF((size_t)data_length < sizeof(*req) - 1)) {
+        return;
+      }
+
+      HandleOpenRequestMessage(req, data_length, stream);
+      break;
+    case DATA_CHANNEL_ACK:
+      // >= sizeof(*ack) checked above
+
+      ack = static_cast<const struct rtcweb_datachannel_ack*>(buffer);
+      HandleOpenAckMessage(ack, data_length, stream);
+      break;
+    default:
+      HandleUnknownMessage(ppid, data_length, stream);
+      break;
+  }
+
+  // Reset buffer
+  mRecvBuffer.Truncate(0);
+}
+
+// Called with mLock locked!
+void DataChannelConnection::HandleMessage(const void* buffer, size_t length,
+                                          uint32_t ppid, uint16_t stream,
+                                          int flags) {
+  mLock.AssertCurrentThreadOwns();
+
+  switch (ppid) {
+    case DATA_CHANNEL_PPID_CONTROL:
+      HandleDCEPMessage(buffer, length, ppid, stream, flags);
+      break;
+    case DATA_CHANNEL_PPID_DOMSTRING_PARTIAL:
+    case DATA_CHANNEL_PPID_DOMSTRING:
+    case DATA_CHANNEL_PPID_DOMSTRING_EMPTY:
+    case DATA_CHANNEL_PPID_BINARY_PARTIAL:
+    case DATA_CHANNEL_PPID_BINARY:
+    case DATA_CHANNEL_PPID_BINARY_EMPTY:
+      HandleDataMessage(buffer, length, ppid, stream, flags);
+      break;
+    default:
+      DC_ERROR((
+          "Unhandled message of length %zu PPID %u on stream %u received (%s).",
+          length, ppid, stream, (flags & MSG_EOR) ? "complete" : "partial"));
+      break;
+  }
+}
+
+void DataChannelConnection::HandleAssociationChangeEvent(
+    const struct sctp_assoc_change* sac) {
+  mLock.AssertCurrentThreadOwns();
+
+  uint32_t i, n;
+  DataChannelConnectionState state = GetState();
+  switch (sac->sac_state) {
+    case SCTP_COMM_UP:
+      DC_DEBUG(("Association change: SCTP_COMM_UP"));
+      if (state == DataChannelConnectionState::Connecting) {
+        mSocket = mMasterSocket;
+        SetState(DataChannelConnectionState::Open);
+
+        DC_DEBUG(("Negotiated number of incoming streams: %" PRIu16,
+                  sac->sac_inbound_streams));
+        DC_DEBUG(("Negotiated number of outgoing streams: %" PRIu16,
+                  sac->sac_outbound_streams));
+        mNegotiatedIdLimit =
+            std::max(mNegotiatedIdLimit,
+                     static_cast<size_t>(std::max(sac->sac_outbound_streams,
+                                                  sac->sac_inbound_streams)));
+
+        Dispatch(do_AddRef(new DataChannelOnMessageAvailable(
+            DataChannelOnMessageAvailable::EventType::OnConnection, this)));
+        DC_DEBUG(("DTLS connect() succeeded!  Entering connected mode"));
+
+        // Open any streams pending...
+        ProcessQueuedOpens();
+
+      } else if (state == DataChannelConnectionState::Open) {
+        DC_DEBUG(("DataConnection Already OPEN"));
+      } else {
+        DC_ERROR(("Unexpected state: %s", ToString(state)));
+      }
+      break;
+    case SCTP_COMM_LOST:
+      DC_DEBUG(("Association change: SCTP_COMM_LOST"));
+      // This association is toast, so also close all the channels -- from
+      // mainthread!
+      Stop();
+      break;
+    case SCTP_RESTART:
+      DC_DEBUG(("Association change: SCTP_RESTART"));
+      break;
+    case SCTP_SHUTDOWN_COMP:
+      DC_DEBUG(("Association change: SCTP_SHUTDOWN_COMP"));
+      Stop();
+      break;
+    case SCTP_CANT_STR_ASSOC:
+      DC_DEBUG(("Association change: SCTP_CANT_STR_ASSOC"));
+      break;
+    default:
+      DC_DEBUG(("Association change: UNKNOWN"));
+      break;
+  }
+  DC_DEBUG(("Association change: streams (in/out) = (%u/%u)",
+            sac->sac_inbound_streams, sac->sac_outbound_streams));
+
+  if (NS_WARN_IF(!sac)) {
+    return;
+  }
+
+  n = sac->sac_length - sizeof(*sac);
+  if ((sac->sac_state == SCTP_COMM_UP) || (sac->sac_state == SCTP_RESTART)) {
+    if (n > 0) {
+      for (i = 0; i < n; ++i) {
+        switch (sac->sac_info[i]) {
+          case SCTP_ASSOC_SUPPORTS_PR:
+            DC_DEBUG(("Supports: PR"));
+            break;
+          case SCTP_ASSOC_SUPPORTS_AUTH:
+            DC_DEBUG(("Supports: AUTH"));
+            break;
+          case SCTP_ASSOC_SUPPORTS_ASCONF:
+            DC_DEBUG(("Supports: ASCONF"));
+            break;
+          case SCTP_ASSOC_SUPPORTS_MULTIBUF:
+            DC_DEBUG(("Supports: MULTIBUF"));
+            break;
+          case SCTP_ASSOC_SUPPORTS_RE_CONFIG:
+            DC_DEBUG(("Supports: RE-CONFIG"));
+            break;
+#if defined(SCTP_ASSOC_SUPPORTS_INTERLEAVING)
+          case SCTP_ASSOC_SUPPORTS_INTERLEAVING:
+            DC_DEBUG(("Supports: NDATA"));
+            // TODO: This should probably be set earlier above in 'case
+            //       SCTP_COMM_UP' but we also need this for 'SCTP_RESTART'.
+            mSendInterleaved = true;
+            break;
+#endif
+          default:
+            DC_ERROR(("Supports: UNKNOWN(0x%02x)", sac->sac_info[i]));
+            break;
+        }
+      }
+    }
+  } else if (((sac->sac_state == SCTP_COMM_LOST) ||
+              (sac->sac_state == SCTP_CANT_STR_ASSOC)) &&
+             (n > 0)) {
+    DC_DEBUG(("Association: ABORT ="));
+    for (i = 0; i < n; ++i) {
+      DC_DEBUG((" 0x%02x", sac->sac_info[i]));
+    }
+  }
+  if ((sac->sac_state == SCTP_CANT_STR_ASSOC) ||
+      (sac->sac_state == SCTP_SHUTDOWN_COMP) ||
+      (sac->sac_state == SCTP_COMM_LOST)) {
+    return;
+  }
+}
+
+void DataChannelConnection::HandlePeerAddressChangeEvent(
+    const struct sctp_paddr_change* spc) {
+  const char* addr = "";
+#if !defined(__Userspace_os_Windows)
+  char addr_buf[INET6_ADDRSTRLEN];
+  struct sockaddr_in* sin;
+  struct sockaddr_in6* sin6;
+#endif
+
+  switch (spc->spc_aaddr.ss_family) {
+    case AF_INET:
+#if !defined(__Userspace_os_Windows)
+      sin = (struct sockaddr_in*)&spc->spc_aaddr;
+      addr = inet_ntop(AF_INET, &sin->sin_addr, addr_buf, INET6_ADDRSTRLEN);
+#endif
+      break;
+    case AF_INET6:
+#if !defined(__Userspace_os_Windows)
+      sin6 = (struct sockaddr_in6*)&spc->spc_aaddr;
+      addr = inet_ntop(AF_INET6, &sin6->sin6_addr, addr_buf, INET6_ADDRSTRLEN);
+#endif
+      break;
+    case AF_CONN:
+      addr = "DTLS connection";
+      break;
+    default:
+      break;
+  }
+  DC_DEBUG(("Peer address %s is now ", addr));
+  switch (spc->spc_state) {
+    case SCTP_ADDR_AVAILABLE:
+      DC_DEBUG(("SCTP_ADDR_AVAILABLE"));
+      break;
+    case SCTP_ADDR_UNREACHABLE:
+      DC_DEBUG(("SCTP_ADDR_UNREACHABLE"));
+      break;
+    case SCTP_ADDR_REMOVED:
+      DC_DEBUG(("SCTP_ADDR_REMOVED"));
+      break;
+    case SCTP_ADDR_ADDED:
+      DC_DEBUG(("SCTP_ADDR_ADDED"));
+      break;
+    case SCTP_ADDR_MADE_PRIM:
+      DC_DEBUG(("SCTP_ADDR_MADE_PRIM"));
+      break;
+    case SCTP_ADDR_CONFIRMED:
+      DC_DEBUG(("SCTP_ADDR_CONFIRMED"));
+      break;
+    default:
+      DC_ERROR(("UNKNOWN SCP STATE"));
+      break;
+  }
+  if (spc->spc_error) {
+    DC_ERROR((" (error = 0x%08x).\n", spc->spc_error));
+  }
+}
+
+void DataChannelConnection::HandleRemoteErrorEvent(
+    const struct sctp_remote_error* sre) {
+  size_t i, n;
+
+  n = sre->sre_length - sizeof(struct sctp_remote_error);
+  DC_WARN(("Remote Error (error = 0x%04x): ", sre->sre_error));
+  for (i = 0; i < n; ++i) {
+    DC_WARN((" 0x%02x", sre->sre_data[i]));
+  }
+}
+
+void DataChannelConnection::HandleShutdownEvent(
+    const struct sctp_shutdown_event* sse) {
+  DC_DEBUG(("Shutdown event."));
+  /* XXX: notify all channels. */
+  // Attempts to actually send anything will fail
+}
+
+void DataChannelConnection::HandleAdaptationIndication(
+    const struct sctp_adaptation_event* sai) {
+  DC_DEBUG(("Adaptation indication: %x.", sai->sai_adaptation_ind));
+}
+
+void DataChannelConnection::HandlePartialDeliveryEvent(
+    const struct sctp_pdapi_event* spde) {
+  // Note: Be aware that stream and sequence number being u32 instead of u16 is
+  //       a bug in the SCTP API. This may change in the future.
+
+  DC_DEBUG(("Partial delivery event: "));
+  switch (spde->pdapi_indication) {
+    case SCTP_PARTIAL_DELIVERY_ABORTED:
+      DC_DEBUG(("delivery aborted "));
+      break;
+    default:
+      DC_ERROR(("??? "));
+      break;
+  }
+  DC_DEBUG(("(flags = %x), stream = %" PRIu32 ", sn = %" PRIu32,
+            spde->pdapi_flags, spde->pdapi_stream, spde->pdapi_seq));
+
+  // Validate stream ID
+  if (spde->pdapi_stream >= UINT16_MAX) {
+    DC_ERROR(("Invalid stream id in partial delivery event: %" PRIu32 "\n",
+              spde->pdapi_stream));
+    return;
+  }
+
+  // Find channel and reset buffer
+  DataChannel* channel = FindChannelByStream((uint16_t)spde->pdapi_stream);
+  if (channel) {
+    DC_WARN(("Abort partially delivered message of %zu bytes\n",
+             channel->mRecvBuffer.Length()));
+    channel->mRecvBuffer.Truncate(0);
+  }
+}
+
+void DataChannelConnection::HandleSendFailedEvent(
+    const struct sctp_send_failed_event* ssfe) {
+  size_t i, n;
+
+  if (ssfe->ssfe_flags & SCTP_DATA_UNSENT) {
+    DC_DEBUG(("Unsent "));
+  }
+  if (ssfe->ssfe_flags & SCTP_DATA_SENT) {
+    DC_DEBUG(("Sent "));
+  }
+  if (ssfe->ssfe_flags & ~(SCTP_DATA_SENT | SCTP_DATA_UNSENT)) {
+    DC_DEBUG(("(flags = %x) ", ssfe->ssfe_flags));
+  }
+#ifdef XP_WIN
+#  define PRIPPID "lu"
+#else
+#  define PRIPPID "u"
+#endif
+  DC_DEBUG(("message with PPID = %" PRIPPID
+            ", SID = %d, flags: 0x%04x due to error = 0x%08x",
+            ntohl(ssfe->ssfe_info.snd_ppid), ssfe->ssfe_info.snd_sid,
+            ssfe->ssfe_info.snd_flags, ssfe->ssfe_error));
+#undef PRIPPID
+  n = ssfe->ssfe_length - sizeof(struct sctp_send_failed_event);
+  for (i = 0; i < n; ++i) {
+    DC_DEBUG((" 0x%02x", ssfe->ssfe_data[i]));
+  }
+}
+
+void DataChannelConnection::ClearResets() {
+  // Clear all pending resets
+  if (!mStreamsResetting.IsEmpty()) {
+    DC_DEBUG(("Clearing resets for %zu streams", mStreamsResetting.Length()));
+  }
+
+  for (uint32_t i = 0; i < mStreamsResetting.Length(); ++i) {
+    RefPtr<DataChannel> channel;
+    channel = FindChannelByStream(mStreamsResetting[i]);
+    if (channel) {
+      DC_DEBUG(("Forgetting channel %u (%p) with pending reset",
+                channel->mStream, channel.get()));
+      // TODO: Do we _really_ want to remove this? Are we allowed to reuse the
+      // id?
+      mChannels.Remove(channel);
+    }
+  }
+  mStreamsResetting.Clear();
+}
+
+void DataChannelConnection::ResetOutgoingStream(uint16_t stream) {
+  uint32_t i;
+
+  mLock.AssertCurrentThreadOwns();
+  DC_DEBUG(
+      ("Connection %p: Resetting outgoing stream %u", (void*)this, stream));
+  // Rarely has more than a couple items and only for a short time
+  for (i = 0; i < mStreamsResetting.Length(); ++i) {
+    if (mStreamsResetting[i] == stream) {
+      return;
+    }
+  }
+  mStreamsResetting.AppendElement(stream);
+}
+
+void DataChannelConnection::SendOutgoingStreamReset() {
+  struct sctp_reset_streams* srs;
+  uint32_t i;
+  size_t len;
+
+  DC_DEBUG(("Connection %p: Sending outgoing stream reset for %zu streams",
+            (void*)this, mStreamsResetting.Length()));
+  mLock.AssertCurrentThreadOwns();
+  if (mStreamsResetting.IsEmpty()) {
+    DC_DEBUG(("No streams to reset"));
+    return;
+  }
+  len = sizeof(sctp_assoc_t) +
+        (2 + mStreamsResetting.Length()) * sizeof(uint16_t);
+  srs = static_cast<struct sctp_reset_streams*>(
+      moz_xmalloc(len));  // infallible malloc
+  memset(srs, 0, len);
+  srs->srs_flags = SCTP_STREAM_RESET_OUTGOING;
+  srs->srs_number_streams = mStreamsResetting.Length();
+  for (i = 0; i < mStreamsResetting.Length(); ++i) {
+    srs->srs_stream_list[i] = mStreamsResetting[i];
+  }
+  if (usrsctp_setsockopt(mMasterSocket, IPPROTO_SCTP, SCTP_RESET_STREAMS, srs,
+                         (socklen_t)len) < 0) {
+    DC_ERROR(("***failed: setsockopt RESET, errno %d", errno));
+    // if errno == EALREADY, this is normal - we can't send another reset
+    // with one pending.
+    // When we get an incoming reset (which may be a response to our
+    // outstanding one), see if we have any pending outgoing resets and
+    // send them
+  } else {
+    mStreamsResetting.Clear();
+  }
+  free(srs);
+}
+
+void DataChannelConnection::HandleStreamResetEvent(
+    const struct sctp_stream_reset_event* strrst) {
+  uint32_t n, i;
+  RefPtr<DataChannel> channel;  // since we may null out the ref to the channel
+
+  if (!(strrst->strreset_flags & SCTP_STREAM_RESET_DENIED) &&
+      !(strrst->strreset_flags & SCTP_STREAM_RESET_FAILED)) {
+    n = (strrst->strreset_length - sizeof(struct sctp_stream_reset_event)) /
+        sizeof(uint16_t);
+    for (i = 0; i < n; ++i) {
+      if (strrst->strreset_flags & SCTP_STREAM_RESET_INCOMING_SSN) {
+        channel = FindChannelByStream(strrst->strreset_stream_list[i]);
+        if (channel) {
+          // The other side closed the channel
+          // We could be in three states:
+          // 1. Normal state (input and output streams (OPEN)
+          //    Notify application, send a RESET in response on our
+          //    outbound channel.  Go to CLOSED
+          // 2. We sent our own reset (CLOSING); either they crossed on the
+          //    wire, or this is a response to our Reset.
+          //    Go to CLOSED
+          // 3. We've sent a open but haven't gotten a response yet (CONNECTING)
+          //    I believe this is impossible, as we don't have an input stream
+          //    yet.
+
+          DC_DEBUG(("Incoming: Channel %u  closed", channel->mStream));
+          if (mChannels.Remove(channel)) {
+            // Mark the stream for reset (the reset is sent below)
+            ResetOutgoingStream(channel->mStream);
+          }
+
+          DC_DEBUG(("Disconnected DataChannel %p from connection %p",
+                    (void*)channel.get(), (void*)channel->mConnection.get()));
+          channel->StreamClosedLocked();
+        } else {
+          DC_WARN(("Can't find incoming channel %d", i));
+        }
+      }
+    }
+  }
+
+  // Process any pending resets now:
+  if (!mStreamsResetting.IsEmpty()) {
+    DC_DEBUG(("Sending %zu pending resets", mStreamsResetting.Length()));
+    SendOutgoingStreamReset();
+  }
+}
+
+void DataChannelConnection::HandleStreamChangeEvent(
+    const struct sctp_stream_change_event* strchg) {
+  ASSERT_WEBRTC(!NS_IsMainThread());
+  if (strchg->strchange_flags == SCTP_STREAM_CHANGE_DENIED) {
+    DC_ERROR(("*** Failed increasing number of streams from %zu (%u/%u)",
+              mNegotiatedIdLimit, strchg->strchange_instrms,
+              strchg->strchange_outstrms));
+    // XXX FIX! notify pending opens of failure
+    return;
+  }
+  if (strchg->strchange_instrms > mNegotiatedIdLimit) {
+    DC_DEBUG(("Other side increased streams from %zu to %u", mNegotiatedIdLimit,
+              strchg->strchange_instrms));
+  }
+  uint16_t old_limit = mNegotiatedIdLimit;
+  uint16_t new_limit =
+      std::max(strchg->strchange_outstrms, strchg->strchange_instrms);
+  if (new_limit > mNegotiatedIdLimit) {
+    DC_DEBUG(("Increasing number of streams from %u to %u - adding %u (in: %u)",
+              old_limit, new_limit, new_limit - old_limit,
+              strchg->strchange_instrms));
+    // make sure both are the same length
+    mNegotiatedIdLimit = new_limit;
+    DC_DEBUG(("New length = %zu (was %d)", mNegotiatedIdLimit, old_limit));
+    // Re-process any channels waiting for streams.
+    // Linear search, but we don't increase channels often and
+    // the array would only get long in case of an app error normally
+
+    // Make sure we request enough streams if there's a big jump in streams
+    // Could make a more complex API for OpenXxxFinish() and avoid this loop
+    auto channels = mChannels.GetAll();
+    size_t num_needed =
+        channels.Length() ? (channels.LastElement()->mStream + 1) : 0;
+    MOZ_ASSERT(num_needed != INVALID_STREAM);
+    if (num_needed > new_limit) {
+      int32_t more_needed = num_needed - ((int32_t)mNegotiatedIdLimit) + 16;
+      DC_DEBUG(("Not enough new streams, asking for %d more", more_needed));
+      // TODO: parameter is an int32_t but we pass size_t
+      RequestMoreStreams(more_needed);
+    } else if (strchg->strchange_outstrms < strchg->strchange_instrms) {
+      DC_DEBUG(("Requesting %d output streams to match partner",
+                strchg->strchange_instrms - strchg->strchange_outstrms));
+      RequestMoreStreams(strchg->strchange_instrms -
+                         strchg->strchange_outstrms);
+    }
+
+    ProcessQueuedOpens();
+  }
+  // else probably not a change in # of streams
+
+  if ((strchg->strchange_flags & SCTP_STREAM_CHANGE_DENIED) ||
+      (strchg->strchange_flags & SCTP_STREAM_CHANGE_FAILED)) {
+    // Other side denied our request. Need to AnnounceClosed some stuff.
+    for (auto& channel : mChannels.GetAll()) {
+      if (channel->mStream >= mNegotiatedIdLimit) {
+        /* XXX: Signal to the other end. */
+        channel->AnnounceClosed();
+        // maybe fire onError (bug 843625)
+      }
+    }
+  }
+}
+
+// Called with mLock locked!
+void DataChannelConnection::HandleNotification(
+    const union sctp_notification* notif, size_t n) {
+  mLock.AssertCurrentThreadOwns();
+  if (notif->sn_header.sn_length != (uint32_t)n) {
+    return;
+  }
+  switch (notif->sn_header.sn_type) {
+    case SCTP_ASSOC_CHANGE:
+      HandleAssociationChangeEvent(&(notif->sn_assoc_change));
+      break;
+    case SCTP_PEER_ADDR_CHANGE:
+      HandlePeerAddressChangeEvent(&(notif->sn_paddr_change));
+      break;
+    case SCTP_REMOTE_ERROR:
+      HandleRemoteErrorEvent(&(notif->sn_remote_error));
+      break;
+    case SCTP_SHUTDOWN_EVENT:
+      HandleShutdownEvent(&(notif->sn_shutdown_event));
+      break;
+    case SCTP_ADAPTATION_INDICATION:
+      HandleAdaptationIndication(&(notif->sn_adaptation_event));
+      break;
+    case SCTP_AUTHENTICATION_EVENT:
+      DC_DEBUG(("SCTP_AUTHENTICATION_EVENT"));
+      break;
+    case SCTP_SENDER_DRY_EVENT:
+      // DC_DEBUG(("SCTP_SENDER_DRY_EVENT"));
+      break;
+    case SCTP_NOTIFICATIONS_STOPPED_EVENT:
+      DC_DEBUG(("SCTP_NOTIFICATIONS_STOPPED_EVENT"));
+      break;
+    case SCTP_PARTIAL_DELIVERY_EVENT:
+      HandlePartialDeliveryEvent(&(notif->sn_pdapi_event));
+      break;
+    case SCTP_SEND_FAILED_EVENT:
+      HandleSendFailedEvent(&(notif->sn_send_failed_event));
+      break;
+    case SCTP_STREAM_RESET_EVENT:
+      HandleStreamResetEvent(&(notif->sn_strreset_event));
+      break;
+    case SCTP_ASSOC_RESET_EVENT:
+      DC_DEBUG(("SCTP_ASSOC_RESET_EVENT"));
+      break;
+    case SCTP_STREAM_CHANGE_EVENT:
+      HandleStreamChangeEvent(&(notif->sn_strchange_event));
+      break;
+    default:
+      DC_ERROR(("unknown SCTP event: %u", (uint32_t)notif->sn_header.sn_type));
+      break;
+  }
+}
+
+int DataChannelConnection::ReceiveCallback(
+    struct socket* sock, void* data, size_t datalen, struct sctp_rcvinfo rcv,
+    int flags) MOZ_NO_THREAD_SAFETY_ANALYSIS {
+  ASSERT_WEBRTC(!NS_IsMainThread());
+  DC_DEBUG(("In ReceiveCallback"));
+
+  // libusrsctp just went reentrant on us. Put a stop to this.
+  mSTS->Dispatch(NS_NewRunnableFunction(
+      "DataChannelConnection::ReceiveCallback",
+      [data, datalen, rcv, flags, this,
+       self = RefPtr<DataChannelConnection>(this)]() mutable {
+        if (!data) {
+          DC_DEBUG(("ReceiveCallback: SCTP has finished shutting down"));
+        } else {
+          mLock.Lock();
+          if (flags & MSG_NOTIFICATION) {
+            HandleNotification(static_cast<union sctp_notification*>(data),
+                               datalen);
+          } else {
+            HandleMessage(data, datalen, ntohl(rcv.rcv_ppid), rcv.rcv_sid,
+                          flags);
+          }
+          mLock.Unlock();
+          // sctp allocates 'data' with malloc(), and expects the receiver to
+          // free it (presumably with free).
+          // XXX future optimization: try to deliver messages without an
+          // internal alloc/copy, and if so delay the free until later.
+          free(data);
+        }
+      }));
+
+  // usrsctp defines the callback as returning an int, but doesn't use it
+  return 1;
+}
+
+already_AddRefed<DataChannel> DataChannelConnection::Open(
+    const nsACString& label, const nsACString& protocol,
+    DataChannelReliabilityPolicy prPolicy, bool inOrder, uint32_t prValue,
+    DataChannelListener* aListener, nsISupports* aContext,
+    bool aExternalNegotiated, uint16_t aStream) {
+  ASSERT_WEBRTC(NS_IsMainThread());
+  MutexAutoLock lock(mLock);  // OpenFinish assumes this
+  if (!aExternalNegotiated) {
+    if (mAllocateEven.isSome()) {
+      aStream = FindFreeStream();
+      if (aStream == INVALID_STREAM) {
+        return nullptr;
+      }
+    } else {
+      // We do not yet know whether we are client or server, and an id has not
+      // been chosen for us. We will need to choose later.
+      aStream = INVALID_STREAM;
+    }
+  }
+
+  DC_DEBUG(
+      ("DC Open: label %s/%s, type %s, inorder %d, prValue %u, listener %p, "
+       "context %p, external: %s, stream %u",
+       PromiseFlatCString(label).get(), PromiseFlatCString(protocol).get(),
+       ToString(prPolicy), inOrder, prValue, aListener, aContext,
+       aExternalNegotiated ? "true" : "false", aStream));
+
+  if ((prPolicy == DataChannelReliabilityPolicy::Reliable) && (prValue != 0)) {
+    return nullptr;
+  }
+
+  if (aStream != INVALID_STREAM && mChannels.Get(aStream)) {
+    DC_ERROR(("external negotiation of already-open channel %u", aStream));
+    return nullptr;
+  }
+
+  RefPtr<DataChannel> channel(new DataChannel(
+      this, aStream, DataChannelState::Connecting, label, protocol, prPolicy,
+      prValue, inOrder, aExternalNegotiated, aListener, aContext));
+  mChannels.Insert(channel);
+
+  return OpenFinish(channel.forget());
+}
+
+// Separate routine so we can also call it to finish up from pending opens
+already_AddRefed<DataChannel> DataChannelConnection::OpenFinish(
+    already_AddRefed<DataChannel>&& aChannel) {
+  RefPtr<DataChannel> channel(aChannel);  // takes the reference passed in
+  // Normally 1 reference if called from ::Open(), or 2 if called from
+  // ProcessQueuedOpens() unless the DOMDataChannel was gc'd
+  const uint16_t stream = channel->mStream;
+
+  mLock.AssertCurrentThreadOwns();
+
+  // Cases we care about:
+  // Pre-negotiated:
+  //    Not Open:
+  //      Doesn't fit:
+  //         -> change initial ask or renegotiate after open
+  //      -> queue open
+  //    Open:
+  //      Doesn't fit:
+  //         -> RequestMoreStreams && queue
+  //      Does fit:
+  //         -> open
+  // Not negotiated:
+  //    Not Open:
+  //      -> queue open
+  //    Open:
+  //      -> Try to get a stream
+  //      Doesn't fit:
+  //         -> RequestMoreStreams && queue
+  //      Does fit:
+  //         -> open
+  // So the Open cases are basically the same
+  // Not Open cases are simply queue for non-negotiated, and
+  // either change the initial ask or possibly renegotiate after open.
+  DataChannelConnectionState state = GetState();
+  if (state != DataChannelConnectionState::Open ||
+      stream >= mNegotiatedIdLimit) {
+    if (state == DataChannelConnectionState::Open) {
+      MOZ_ASSERT(stream != INVALID_STREAM);
+      // RequestMoreStreams() limits to MAX_NUM_STREAMS -- allocate extra
+      // streams to avoid going back immediately for more if the ask to N, N+1,
+      // etc
+      int32_t more_needed = stream - ((int32_t)mNegotiatedIdLimit) + 16;
+      if (!RequestMoreStreams(more_needed)) {
+        // Something bad happened... we're done
+        goto request_error_cleanup;
+      }
+    }
+    DC_DEBUG(("Queuing channel %p (%u) to finish open", channel.get(), stream));
+    // Also serves to mark we told the app
+    channel->mHasFinishedOpen = true;
+    mPending.Push(channel);
+    return channel.forget();
+  }
+
+  MOZ_ASSERT(stream != INVALID_STREAM);
+  MOZ_ASSERT(stream < mNegotiatedIdLimit);
+
+#ifdef TEST_QUEUED_DATA
+  // It's painful to write a test for this...
+  channel->AnnounceOpen();
+  SendDataMsgInternalOrBuffer(channel, "Help me!", 8,
+                              DATA_CHANNEL_PPID_DOMSTRING);
+#endif
+
+  if (!channel->mNegotiated) {
+    if (!channel->mOrdered) {
+      // Don't send unordered until this gets cleared.
+      channel->mWaitingForAck = true;
+    }
+
+    int error = SendOpenRequestMessage(channel->mLabel, channel->mProtocol,
+                                       stream, !channel->mOrdered,
+                                       channel->mPrPolicy, channel->mPrValue);
+    if (error) {
+      DC_ERROR(("SendOpenRequest failed, error = %d", error));
+      if (channel->mHasFinishedOpen) {
+        // We already returned the channel to the app.
+        NS_ERROR("Failed to send open request");
+        channel->AnnounceClosed();
+      }
+      // If we haven't returned the channel yet, it will get destroyed when we
+      // exit this function.
+      mChannels.Remove(channel);
+      // we'll be destroying the channel
+      return nullptr;
+      /* NOTREACHED */
+    }
+  }
+
+  // Either externally negotiated or we sent Open
+  // FIX?  Move into DOMDataChannel?  I don't think we can send it yet here
+  channel->AnnounceOpen();
+
+  return channel.forget();
+
+request_error_cleanup:
+  if (channel->mHasFinishedOpen) {
+    // We already returned the channel to the app.
+    NS_ERROR("Failed to request more streams");
+    channel->AnnounceClosed();
+    return channel.forget();
+  }
+  // we'll be destroying the channel, but it never really got set up
+  // Alternative would be to RUN_ON_THREAD(channel.forget(),::Destroy,...) and
+  // Dispatch it to ourselves
+  return nullptr;
+}
+
+// Requires mLock to be locked!
+// Returns a POSIX error code directly instead of setting errno.
+int DataChannelConnection::SendMsgInternal(OutgoingMsg& msg, size_t* aWritten) {
+  struct sctp_sndinfo& info = msg.GetInfo().sendv_sndinfo;
+  int error;
+
+  // EOR set?
+  bool eor_set = (info.snd_flags & SCTP_EOR) != 0;
+
+  // Send until buffer is empty
+  size_t left = msg.GetLeft();
+  do {
+    size_t length;
+
+    // Carefully chunk the buffer
+    if (left > DATA_CHANNEL_MAX_BINARY_FRAGMENT) {
+      length = DATA_CHANNEL_MAX_BINARY_FRAGMENT;
+
+      // Unset EOR flag
+      info.snd_flags &= ~SCTP_EOR;
+    } else {
+      length = left;
+
+      // Set EOR flag
+      if (eor_set) {
+        info.snd_flags |= SCTP_EOR;
+      }
+    }
+
+    // Send (or try at least)
+    // SCTP will return EMSGSIZE if the message is bigger than the buffer
+    // size (or EAGAIN if there isn't space). However, we can avoid EMSGSIZE
+    // by carefully crafting small enough message chunks.
+    ssize_t written = usrsctp_sendv(
+        mSocket, msg.GetData(), length, nullptr, 0, (void*)&msg.GetInfo(),
+        (socklen_t)sizeof(struct sctp_sendv_spa), SCTP_SENDV_SPA, 0);
+
+    if (written < 0) {
+      error = errno;
+      goto out;
+    }
+
+    if (aWritten) {
+      *aWritten += written;
+    }
+    DC_DEBUG(("Sent buffer (written=%zu, len=%zu, left=%zu)", (size_t)written,
+              length, left - (size_t)written));
+
+    // TODO: Remove once resolved
+    // (https://github.com/sctplab/usrsctp/issues/132)
+    if (written == 0) {
+      DC_ERROR(("@tuexen: usrsctp_sendv returned 0"));
+      error = EAGAIN;
+      goto out;
+    }
+
+    // If not all bytes have been written, this obviously means that usrsctp's
+    // buffer is full and we need to try again later.
+    if ((size_t)written < length) {
+      msg.Advance((size_t)written);
+      error = EAGAIN;
+      goto out;
+    }
+
+    // Update buffer position
+    msg.Advance((size_t)written);
+
+    // Get amount of bytes left in the buffer
+    left = msg.GetLeft();
+  } while (left > 0);
+
+  // Done
+  error = 0;
+
+out:
+  // Reset EOR flag
+  if (eor_set) {
+    info.snd_flags |= SCTP_EOR;
+  }
+
+  return error;
+}
+
+// Requires mLock to be locked!
+// Returns a POSIX error code directly instead of setting errno.
+// IMPORTANT: Ensure that the buffer passed is guarded by mLock!
+int DataChannelConnection::SendMsgInternalOrBuffer(
+    nsTArray<UniquePtr<BufferedOutgoingMsg>>& buffer, OutgoingMsg& msg,
+    bool& buffered, size_t* aWritten) {
+  NS_WARNING_ASSERTION(msg.GetLength() > 0, "Length is 0?!");
+
+  int error = 0;
+  bool need_buffering = false;
+
+  // Note: Main-thread IO, but doesn't block!
+  // XXX FIX!  to deal with heavy overruns of JS trying to pass data in
+  // (more than the buffersize) queue data onto another thread to do the
+  // actual sends.  See netwerk/protocol/websocket/WebSocketChannel.cpp
+
+  // Avoid a race between buffer-full-failure (where we have to add the
+  // packet to the buffered-data queue) and the buffer-now-only-half-full
+  // callback, which happens on a different thread.  Otherwise we might
+  // fail here, then before we add it to the queue get the half-full
+  // callback, find nothing to do, then on this thread add it to the
+  // queue - which would sit there.  Also, if we later send more data, it
+  // would arrive ahead of the buffered message, but if the buffer ever
+  // got to 1/2 full, the message would get sent - but at a semi-random
+  // time, after other data it was supposed to be in front of.
+
+  // Must lock before empty check for similar reasons!
+  mLock.AssertCurrentThreadOwns();
+  if (buffer.IsEmpty() &&
+      (mSendInterleaved || mPendingType == PendingType::None)) {
+    error = SendMsgInternal(msg, aWritten);
+    switch (error) {
+      case 0:
+        break;
+      case EAGAIN:
+#if (EAGAIN != EWOULDBLOCK)
+      case EWOULDBLOCK:
+#endif
+        need_buffering = true;
+        break;
+      default:
+        DC_ERROR(("error %d on sending", error));
+        break;
+    }
+  } else {
+    need_buffering = true;
+  }
+
+  if (need_buffering) {
+    // queue data for resend!  And queue any further data for the stream until
+    // it is...
+    auto* bufferedMsg = new BufferedOutgoingMsg(msg);  // infallible malloc
+    buffer.AppendElement(bufferedMsg);  // owned by mBufferedData array
+    DC_DEBUG(("Queued %zu buffers (left=%zu, total=%zu)", buffer.Length(),
+              msg.GetLeft(), msg.GetLength()));
+    buffered = true;
+    return 0;
+  }
+
+  buffered = false;
+  return error;
+}
+
+// Caller must ensure that length <= UINT32_MAX
+// Returns a POSIX error code.
+int DataChannelConnection::SendDataMsgInternalOrBuffer(DataChannel& channel,
+                                                       const uint8_t* data,
+                                                       size_t len,
+                                                       uint32_t ppid) {
+  if (NS_WARN_IF(channel.GetReadyState() != DataChannelState::Open)) {
+    return EINVAL;  // TODO: Find a better error code
+  }
+
+  struct sctp_sendv_spa info = {};
+
+  // General flags
+  info.sendv_flags = SCTP_SEND_SNDINFO_VALID;
+
+  // Set stream identifier, protocol identifier and flags
+  info.sendv_sndinfo.snd_sid = channel.mStream;
+  info.sendv_sndinfo.snd_flags = SCTP_EOR;
+  info.sendv_sndinfo.snd_ppid = htonl(ppid);
+
+  // Unordered?
+  // To avoid problems where an in-order OPEN is lost and an
+  // out-of-order data message "beats" it, require data to be in-order
+  // until we get an ACK.
+  if (!channel.mOrdered && !channel.mWaitingForAck) {
+    info.sendv_sndinfo.snd_flags |= SCTP_UNORDERED;
+  }
+
+  // Partial reliability policy
+  if (channel.mPrPolicy != DataChannelReliabilityPolicy::Reliable) {
+    info.sendv_prinfo.pr_policy = ToUsrsctpValue(channel.mPrPolicy);
+    info.sendv_prinfo.pr_value = channel.mPrValue;
+    info.sendv_flags |= SCTP_SEND_PRINFO_VALID;
+  }
+
+  // Create message instance and send
+  OutgoingMsg msg(info, data, len);
+  bool buffered;
+  size_t written = 0;
+  mDeferSend = true;
+  int error =
+      SendMsgInternalOrBuffer(channel.mBufferedData, msg, buffered, &written);
+  mDeferSend = false;
+  if (written && ppid != DATA_CHANNEL_PPID_DOMSTRING_EMPTY &&
+      ppid != DATA_CHANNEL_PPID_BINARY_EMPTY) {
+    channel.DecrementBufferedAmount(written);
+  }
+
+  for (auto&& packet : mDeferredSend) {
+    MOZ_ASSERT(written);
+    SendPacket(std::move(packet));
+  }
+  mDeferredSend.clear();
+
+  // Set pending type and stream index (if buffered)
+  if (!error && buffered && mPendingType == PendingType::None) {
+    mPendingType = PendingType::Data;
+    mCurrentStream = channel.mStream;
+  }
+  return error;
+}
+
+// Caller must ensure that length <= UINT32_MAX
+// Returns a POSIX error code.
+int DataChannelConnection::SendDataMsg(DataChannel& channel,
+                                       const uint8_t* data, size_t len,
+                                       uint32_t ppidPartial,
+                                       uint32_t ppidFinal) {
+  // We *really* don't want to do this from main thread! - and
+  // SendDataMsgInternalOrBuffer avoids blocking.
+  mLock.AssertCurrentThreadOwns();
+
+  if (mMaxMessageSize != 0 && len > mMaxMessageSize) {
+    DC_ERROR(("Message rejected, too large (%zu > %" PRIu64 ")", len,
+              mMaxMessageSize));
+    return EMSGSIZE;
+  }
+
+  // This will use EOR-based fragmentation if the message is too large (> 64
+  // KiB)
+  return SendDataMsgInternalOrBuffer(channel, data, len, ppidFinal);
+}
+
+class ReadBlobRunnable : public Runnable {
+ public:
+  ReadBlobRunnable(DataChannelConnection* aConnection, uint16_t aStream,
+                   nsIInputStream* aBlob)
+      : Runnable("ReadBlobRunnable"),
+        mConnection(aConnection),
+        mStream(aStream),
+        mBlob(aBlob) {}
+
+  NS_IMETHOD Run() override {
+    // ReadBlob() is responsible to releasing the reference
+    DataChannelConnection* self = mConnection;
+    self->ReadBlob(mConnection.forget(), mStream, mBlob);
+    return NS_OK;
+  }
+
+ private:
+  // Make sure the Connection doesn't die while there are jobs outstanding.
+  // Let it die (if released by PeerConnectionImpl while we're running)
+  // when we send our runnable back to MainThread.  Then ~DataChannelConnection
+  // can send the IOThread to MainThread to die in a runnable, avoiding
+  // unsafe event loop recursion.  Evil.
+  RefPtr<DataChannelConnection> mConnection;
+  uint16_t mStream;
+  // Use RefCount for preventing the object is deleted when SendBlob returns.
+  RefPtr<nsIInputStream> mBlob;
+};
+
+// Returns a POSIX error code.
+int DataChannelConnection::SendBlob(uint16_t stream, nsIInputStream* aBlob) {
+  MutexAutoLock lock(mLock);
+  RefPtr<DataChannel> channel = mChannels.Get(stream);
+  if (NS_WARN_IF(!channel)) {
+    return EINVAL;  // TODO: Find a better error code
+  }
+
+  // Spawn a thread to send the data
+  if (!mInternalIOThread) {
+    nsresult rv =
+        NS_NewNamedThread("DataChannel IO", getter_AddRefs(mInternalIOThread));
+    if (NS_FAILED(rv)) {
+      return EINVAL;  // TODO: Find a better error code
+    }
+  }
+
+  mInternalIOThread->Dispatch(
+      do_AddRef(new ReadBlobRunnable(this, stream, aBlob)), NS_DISPATCH_NORMAL);
+  return 0;
+}
+
+class DataChannelBlobSendRunnable : public Runnable {
+ public:
+  DataChannelBlobSendRunnable(
+      already_AddRefed<DataChannelConnection>& aConnection, uint16_t aStream)
+      : Runnable("DataChannelBlobSendRunnable"),
+        mConnection(aConnection),
+        mStream(aStream) {}
+
+  ~DataChannelBlobSendRunnable() override {
+    if (!NS_IsMainThread() && mConnection) {
+      MOZ_ASSERT(false);
+      // explicitly leak the connection if destroyed off mainthread
+      Unused << mConnection.forget().take();
+    }
+  }
+
+  NS_IMETHOD Run() override {
+    ASSERT_WEBRTC(NS_IsMainThread());
+
+    mConnection->SendBinaryMsg(mStream, mData);
+    mConnection = nullptr;
+    return NS_OK;
+  }
+
+  // explicitly public so we can avoid allocating twice and copying
+  nsCString mData;
+
+ private:
+  // Note: we can be destroyed off the target thread, so be careful not to let
+  // this get Released()ed on the temp thread!
+  RefPtr<DataChannelConnection> mConnection;
+  uint16_t mStream;
+};
+
+void DataChannelConnection::SetState(DataChannelConnectionState aState) {
+  mLock.AssertCurrentThreadOwns();
+
+  DC_DEBUG(
+      ("DataChannelConnection labeled %s (%p) switching connection state %s -> "
+       "%s",
+       mTransportId.c_str(), this, ToString(mState), ToString(aState)));
+
+  mState = aState;
+}
+
+void DataChannelConnection::ReadBlob(
+    already_AddRefed<DataChannelConnection> aThis, uint16_t aStream,
+    nsIInputStream* aBlob) {
+  // NOTE: 'aThis' has been forgotten by the caller to avoid releasing
+  // it off mainthread; if PeerConnectionImpl has released then we want
+  // ~DataChannelConnection() to run on MainThread
+
+  // XXX to do this safely, we must enqueue these atomically onto the
+  // output socket.  We need a sender thread(s?) to enqueue data into the
+  // socket and to avoid main-thread IO that might block.  Even on a
+  // background thread, we may not want to block on one stream's data.
+  // I.e. run non-blocking and service multiple channels.
+
+  // Must not let Dispatching it cause the DataChannelConnection to get
+  // released on the wrong thread.  Using
+  // WrapRunnable(RefPtr<DataChannelConnection>(aThis),... will occasionally
+  // cause aThis to get released on this thread.  Also, an explicit Runnable
+  // lets us avoid copying the blob data an extra time.
+  RefPtr<DataChannelBlobSendRunnable> runnable =
+      new DataChannelBlobSendRunnable(aThis, aStream);
+  // avoid copying the blob data by passing the mData from the runnable
+  if (NS_FAILED(NS_ReadInputStreamToString(aBlob, runnable->mData, -1))) {
+    // Bug 966602:  Doesn't return an error to the caller via onerror.
+    // We must release DataChannelConnection on MainThread to avoid issues (bug
+    // 876167) aThis is now owned by the runnable; release it there
+    NS_ReleaseOnMainThread("DataChannelBlobSendRunnable", runnable.forget());
+    return;
+  }
+  aBlob->Close();
+  Dispatch(runnable.forget());
+}
+
+// Returns a POSIX error code.
+int DataChannelConnection::SendDataMsgCommon(uint16_t stream,
+                                             const nsACString& aMsg,
+                                             bool isBinary) {
+  ASSERT_WEBRTC(NS_IsMainThread());
+  // We really could allow this from other threads, so long as we deal with
+  // asynchronosity issues with channels closing, in particular access to
+  // mChannels, and issues with the association closing (access to mSocket).
+
+  const uint8_t* data = (const uint8_t*)aMsg.BeginReading();
+  uint32_t len = aMsg.Length();
+#if (UINT32_MAX > SIZE_MAX)
+  if (len > SIZE_MAX) {
+    return EMSGSIZE;
+  }
+#endif
+
+  DC_DEBUG(("Sending %sto stream %u: %u bytes", isBinary ? "binary " : "",
+            stream, len));
+  // XXX if we want more efficiency, translate flags once at open time
+  RefPtr<DataChannel> channelPtr = mChannels.Get(stream);
+  if (NS_WARN_IF(!channelPtr)) {
+    return EINVAL;  // TODO: Find a better error code
+  }
+  bool is_empty = len == 0;
+  const uint8_t byte = 0;
+  if (is_empty) {
+    data = &byte;
+    len = 1;
+  }
+  auto& channel = *channelPtr;
+  int err = 0;
+  MutexAutoLock lock(mLock);
+  if (isBinary) {
+    err = SendDataMsg(
+        channel, data, len, DATA_CHANNEL_PPID_BINARY_PARTIAL,
+        is_empty ? DATA_CHANNEL_PPID_BINARY_EMPTY : DATA_CHANNEL_PPID_BINARY);
+  } else {
+    err = SendDataMsg(channel, data, len, DATA_CHANNEL_PPID_DOMSTRING_PARTIAL,
+                      is_empty ? DATA_CHANNEL_PPID_DOMSTRING_EMPTY
+                               : DATA_CHANNEL_PPID_DOMSTRING);
+  }
+  if (!err) {
+    channel.WithTrafficCounters([&len](DataChannel::TrafficCounters& counters) {
+      counters.mMessagesSent++;
+      counters.mBytesSent += len;
+    });
+  }
+
+  return err;
+}
+
+void DataChannelConnection::Stop() {
+  // Note: This will call 'CloseAll' from the main thread
+  Dispatch(do_AddRef(new DataChannelOnMessageAvailable(
+      DataChannelOnMessageAvailable::EventType::OnDisconnected, this)));
+}
+
+void DataChannelConnection::Close(DataChannel* aChannel) {
+  MutexAutoLock lock(mLock);
+  CloseLocked(aChannel);
+}
+
+// So we can call Close() with the lock already held
+// Called from someone who holds a ref via ::Close(), or from ~DataChannel
+void DataChannelConnection::CloseLocked(DataChannel* aChannel) {
+  MOZ_ASSERT(aChannel);
+  RefPtr<DataChannel> channel(aChannel);  // make sure it doesn't go away on us
+
+  mLock.AssertCurrentThreadOwns();
+  DC_DEBUG(("Connection %p/Channel %p: Closing stream %u",
+            channel->mConnection.get(), channel.get(), channel->mStream));
+
+  aChannel->mBufferedData.Clear();
+  if (GetState() == DataChannelConnectionState::Closed) {
+    // If we're CLOSING, we might leave this in place until we can send a
+    // reset.
+    mChannels.Remove(channel);
+  }
+
+  // This is supposed to only be accessed from Main thread, but this has
+  // been accessed here from the STS thread for a long time now.
+  // See Bug 1586475
+  DataChannelState channelState = aChannel->GetReadyState();
+  // re-test since it may have closed before the lock was grabbed
+  if (channelState == DataChannelState::Closed ||
+      channelState == DataChannelState::Closing) {
+    DC_DEBUG(("Channel already closing/closed (%s)", ToString(channelState)));
+    return;
+  }
+
+  if (channel->mStream != INVALID_STREAM) {
+    ResetOutgoingStream(channel->mStream);
+    if (GetState() != DataChannelConnectionState::Closed) {
+      // Individual channel is being closed, send reset now.
+      SendOutgoingStreamReset();
+    }
+  }
+  aChannel->SetReadyState(DataChannelState::Closing);
+  if (GetState() == DataChannelConnectionState::Closed) {
+    // we're not going to hang around waiting
+    channel->StreamClosedLocked();
+  }
+  // At this point when we leave here, the object is a zombie held alive only by
+  // the DOM object
+}
+
+void DataChannelConnection::CloseAll() {
+  DC_DEBUG(("Closing all channels (connection %p)", (void*)this));
+
+  // Make sure no more channels will be opened
+  MutexAutoLock lock(mLock);
+  SetState(DataChannelConnectionState::Closed);
+
+  // Close current channels
+  // If there are runnables, they hold a strong ref and keep the channel
+  // and/or connection alive (even if in a CLOSED state)
+  for (auto& channel : mChannels.GetAll()) {
+    MutexAutoUnlock lock(mLock);
+    channel->Close();
+  }
+
+  // Clean up any pending opens for channels
+  RefPtr<DataChannel> channel;
+  while (nullptr != (channel = mPending.PopFront())) {
+    DC_DEBUG(("closing pending channel %p, stream %u", channel.get(),
+              channel->mStream));
+    MutexAutoUnlock lock(mLock);
+    channel->Close();  // also releases the ref on each iteration
+  }
+  // It's more efficient to let the Resets queue in shutdown and then
+  // SendOutgoingStreamReset() here.
+  SendOutgoingStreamReset();
+}
+
+bool DataChannelConnection::Channels::IdComparator::Equals(
+    const RefPtr<DataChannel>& aChannel, uint16_t aId) const {
+  return aChannel->mStream == aId;
+}
+
+bool DataChannelConnection::Channels::IdComparator::LessThan(
+    const RefPtr<DataChannel>& aChannel, uint16_t aId) const {
+  return aChannel->mStream < aId;
+}
+
+bool DataChannelConnection::Channels::IdComparator::Equals(
+    const RefPtr<DataChannel>& a1, const RefPtr<DataChannel>& a2) const {
+  return Equals(a1, a2->mStream);
+}
+
+bool DataChannelConnection::Channels::IdComparator::LessThan(
+    const RefPtr<DataChannel>& a1, const RefPtr<DataChannel>& a2) const {
+  return LessThan(a1, a2->mStream);
+}
+
+void DataChannelConnection::Channels::Insert(
+    const RefPtr<DataChannel>& aChannel) {
+  DC_DEBUG(("Inserting channel %u : %p", aChannel->mStream, aChannel.get()));
+  MutexAutoLock lock(mMutex);
+  if (aChannel->mStream != INVALID_STREAM) {
+    MOZ_ASSERT(!mChannels.ContainsSorted(aChannel, IdComparator()));
+  }
+
+  MOZ_ASSERT(!mChannels.Contains(aChannel));
+
+  mChannels.InsertElementSorted(aChannel, IdComparator());
+}
+
+bool DataChannelConnection::Channels::Remove(
+    const RefPtr<DataChannel>& aChannel) {
+  DC_DEBUG(("Removing channel %u : %p", aChannel->mStream, aChannel.get()));
+  MutexAutoLock lock(mMutex);
+  if (aChannel->mStream == INVALID_STREAM) {
+    return mChannels.RemoveElement(aChannel);
+  }
+
+  return mChannels.RemoveElementSorted(aChannel, IdComparator());
+}
+
+RefPtr<DataChannel> DataChannelConnection::Channels::Get(uint16_t aId) const {
+  MutexAutoLock lock(mMutex);
+  auto index = mChannels.BinaryIndexOf(aId, IdComparator());
+  if (index == ChannelArray::NoIndex) {
+    return nullptr;
+  }
+  return mChannels[index];
+}
+
+RefPtr<DataChannel> DataChannelConnection::Channels::GetNextChannel(
+    uint16_t aCurrentId) const {
+  MutexAutoLock lock(mMutex);
+  if (mChannels.IsEmpty()) {
+    return nullptr;
+  }
+
+  auto index = mChannels.IndexOfFirstElementGt(aCurrentId, IdComparator());
+  if (index == mChannels.Length()) {
+    index = 0;
+  }
+  return mChannels[index];
+}
+
+DataChannel::~DataChannel() {
+  // NS_ASSERTION since this is more "I think I caught all the cases that
+  // can cause this" than a true kill-the-program assertion.  If this is
+  // wrong, nothing bad happens.  A worst it's a leak.
+  NS_ASSERTION(mReadyState == DataChannelState::Closed ||
+                   mReadyState == DataChannelState::Closing,
+               "unexpected state in ~DataChannel");
+}
+
+void DataChannel::Close() {
+  if (mConnection) {
+    // ensure we don't get deleted
+    RefPtr<DataChannelConnection> connection(mConnection);
+    connection->Close(this);
+  }
+}
+
+// Used when disconnecting from the DataChannelConnection
+void DataChannel::StreamClosedLocked() {
+  MOZ_ASSERT(mConnection);
+  if (!mConnection) {
+    return;
+  }
+  mConnection->mLock.AssertCurrentThreadOwns();
+
+  DC_DEBUG(("Destroying Data channel %u", mStream));
+  MOZ_ASSERT_IF(mStream != INVALID_STREAM,
+                !mConnection->FindChannelByStream(mStream));
+  AnnounceClosed();
+  // We leave mConnection live until the DOM releases us, to avoid races
+}
+
+void DataChannel::ReleaseConnection() {
+  ASSERT_WEBRTC(NS_IsMainThread());
+  mConnection = nullptr;
+}
+
+void DataChannel::SetListener(DataChannelListener* aListener,
+                              nsISupports* aContext) {
+  ASSERT_WEBRTC(NS_IsMainThread());
+  mContext = aContext;
+  mListener = aListener;
+}
+
+void DataChannel::SendErrnoToErrorResult(int error, size_t aMessageSize,
+                                         ErrorResult& aRv) {
+  switch (error) {
+    case 0:
+      break;
+    case EMSGSIZE: {
+      nsPrintfCString err("Message size (%zu) exceeds maxMessageSize",
+                          aMessageSize);
+      aRv.ThrowTypeError(err);
+      break;
+    }
+    default:
+      aRv.Throw(NS_ERROR_DOM_OPERATION_ERR);
+      break;
+  }
+}
+
+void DataChannel::IncrementBufferedAmount(uint32_t aSize, ErrorResult& aRv) {
+  ASSERT_WEBRTC(NS_IsMainThread());
+  if (mBufferedAmount > UINT32_MAX - aSize) {
+    aRv.Throw(NS_ERROR_FILE_TOO_BIG);
+    return;
+  }
+
+  mBufferedAmount += aSize;
+}
+
+void DataChannel::DecrementBufferedAmount(uint32_t aSize) {
+  mMainThreadEventTarget->Dispatch(NS_NewRunnableFunction(
+      "DataChannel::DecrementBufferedAmount",
+      [this, self = RefPtr<DataChannel>(this), aSize] {
+        MOZ_ASSERT(aSize <= mBufferedAmount);
+        bool wasLow = mBufferedAmount <= mBufferedThreshold;
+        mBufferedAmount -= aSize;
+        if (!wasLow && mBufferedAmount <= mBufferedThreshold) {
+          DC_DEBUG(("%s: sending BUFFER_LOW_THRESHOLD for %s/%s: %u",
+                    __FUNCTION__, mLabel.get(), mProtocol.get(), mStream));
+          mListener->OnBufferLow(mContext);
+        }
+        if (mBufferedAmount == 0) {
+          DC_DEBUG(("%s: sending NO_LONGER_BUFFERED for %s/%s: %u",
+                    __FUNCTION__, mLabel.get(), mProtocol.get(), mStream));
+          mListener->NotBuffered(mContext);
+        }
+      }));
+}
+
+void DataChannel::AnnounceOpen() {
+  mMainThreadEventTarget->Dispatch(NS_NewRunnableFunction(
+      "DataChannel::AnnounceOpen", [this, self = RefPtr<DataChannel>(this)] {
+        DataChannelState state = GetReadyState();
+        // Special-case; spec says to put brand-new remote-created DataChannel
+        // in "open", but queue the firing of the "open" event.
+        if (state != DataChannelState::Closing &&
+            state != DataChannelState::Closed) {
+          if (!mEverOpened && mConnection && mConnection->mListener) {
+            mEverOpened = true;
+            mConnection->mListener->NotifyDataChannelOpen(this);
+          }
+          SetReadyState(DataChannelState::Open);
+          DC_DEBUG(("%s: sending ON_CHANNEL_OPEN for %s/%s: %u", __FUNCTION__,
+                    mLabel.get(), mProtocol.get(), mStream));
+          if (mListener) {
+            mListener->OnChannelConnected(mContext);
+          }
+        }
+      }));
+}
+
+void DataChannel::AnnounceClosed() {
+  mMainThreadEventTarget->Dispatch(NS_NewRunnableFunction(
+      "DataChannel::AnnounceClosed", [this, self = RefPtr<DataChannel>(this)] {
+        if (GetReadyState() == DataChannelState::Closed) {
+          return;
+        }
+        if (mEverOpened && mConnection && mConnection->mListener) {
+          mConnection->mListener->NotifyDataChannelClosed(this);
+        }
+        SetReadyState(DataChannelState::Closed);
+        mBufferedData.Clear();
+        if (mListener) {
+          DC_DEBUG(("%s: sending ON_CHANNEL_CLOSED for %s/%s: %u", __FUNCTION__,
+                    mLabel.get(), mProtocol.get(), mStream));
+          mListener->OnChannelClosed(mContext);
+        }
+      }));
+}
+
+// Set ready state
+void DataChannel::SetReadyState(const DataChannelState aState) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  DC_DEBUG(
+      ("DataChannelConnection labeled %s(%p) (stream %d) changing ready state "
+       "%s -> %s",
+       mLabel.get(), this, mStream, ToString(mReadyState), ToString(aState)));
+
+  mReadyState = aState;
+}
+
+void DataChannel::SendMsg(const nsACString& aMsg, ErrorResult& aRv) {
+  if (!EnsureValidStream(aRv)) {
+    return;
+  }
+
+  SendErrnoToErrorResult(mConnection->SendMsg(mStream, aMsg), aMsg.Length(),
+                         aRv);
+  if (!aRv.Failed()) {
+    IncrementBufferedAmount(aMsg.Length(), aRv);
+  }
+}
+
+void DataChannel::SendBinaryMsg(const nsACString& aMsg, ErrorResult& aRv) {
+  if (!EnsureValidStream(aRv)) {
+    return;
+  }
+
+  SendErrnoToErrorResult(mConnection->SendBinaryMsg(mStream, aMsg),
+                         aMsg.Length(), aRv);
+  if (!aRv.Failed()) {
+    IncrementBufferedAmount(aMsg.Length(), aRv);
+  }
+}
+
+void DataChannel::SendBinaryBlob(dom::Blob& aBlob, ErrorResult& aRv) {
+  if (!EnsureValidStream(aRv)) {
+    return;
+  }
+
+  uint64_t msgLength = aBlob.GetSize(aRv);
+  if (aRv.Failed()) {
+    return;
+  }
+
+  if (msgLength > UINT32_MAX) {
+    aRv.Throw(NS_ERROR_FILE_TOO_BIG);
+    return;
+  }
+
+  // We convert to an nsIInputStream here, because Blob is not threadsafe, and
+  // we don't convert it earlier because we need to know how large this is so we
+  // can update bufferedAmount.
+  nsCOMPtr<nsIInputStream> msgStream;
+  aBlob.CreateInputStream(getter_AddRefs(msgStream), aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return;
+  }
+
+  SendErrnoToErrorResult(mConnection->SendBlob(mStream, msgStream), msgLength,
+                         aRv);
+  if (!aRv.Failed()) {
+    IncrementBufferedAmount(msgLength, aRv);
+  }
+}
+
+dom::Nullable<uint16_t> DataChannel::GetMaxPacketLifeTime() const {
+  if (mPrPolicy == DataChannelReliabilityPolicy::LimitedLifetime) {
+    return dom::Nullable<uint16_t>(mPrValue);
+  }
+  return dom::Nullable<uint16_t>();
+}
+
+dom::Nullable<uint16_t> DataChannel::GetMaxRetransmits() const {
+  if (mPrPolicy == DataChannelReliabilityPolicy::LimitedRetransmissions) {
+    return dom::Nullable<uint16_t>(mPrValue);
+  }
+  return dom::Nullable<uint16_t>();
+}
+
+uint32_t DataChannel::GetBufferedAmountLowThreshold() const {
+  return mBufferedThreshold;
+}
+
+// Never fire immediately, as it's defined to fire on transitions, not state
+void DataChannel::SetBufferedAmountLowThreshold(uint32_t aThreshold) {
+  mBufferedThreshold = aThreshold;
+}
+
+// Called with mLock locked!
+void DataChannel::SendOrQueue(DataChannelOnMessageAvailable* aMessage) {
+  nsCOMPtr<nsIRunnable> runnable = aMessage;
+  mMainThreadEventTarget->Dispatch(runnable.forget());
+}
+
+DataChannel::TrafficCounters DataChannel::GetTrafficCounters() const {
+  MutexAutoLock lock(mStatsLock);
+  return mTrafficCounters;
+}
+
+bool DataChannel::EnsureValidStream(ErrorResult& aRv) {
+  MOZ_ASSERT(mConnection);
+  if (mConnection && mStream != INVALID_STREAM) {
+    return true;
+  }
+  aRv.Throw(NS_ERROR_DOM_INVALID_STATE_ERR);
+  return false;
+}
+
+void DataChannel::WithTrafficCounters(
+    const std::function<void(TrafficCounters&)>& aFn) {
+  MutexAutoLock lock(mStatsLock);
+  aFn(mTrafficCounters);
+}
+
+nsresult DataChannelOnMessageAvailable::Run() {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  // Note: calling the listeners can indirectly cause the listeners to be
+  // made available for GC (by removing event listeners), especially for
+  // OnChannelClosed().  We hold a ref to the Channel and the listener
+  // while calling this.
+  switch (mType) {
+    case EventType::OnDataString:
+    case EventType::OnDataBinary:
+      if (!mChannel->mListener) {
+        DC_ERROR(("DataChannelOnMessageAvailable (%s) with null Listener!",
+                  ToString(mType)));
+        return NS_OK;
+      }
+
+      if (mChannel->GetReadyState() == DataChannelState::Closed ||
+          mChannel->GetReadyState() == DataChannelState::Closing) {
+        // Closed by JS, probably
+        return NS_OK;
+      }
+
+      if (mType == EventType::OnDataString) {
+        mChannel->mListener->OnMessageAvailable(mChannel->mContext, mData);
+      } else {
+        mChannel->mListener->OnBinaryMessageAvailable(mChannel->mContext,
+                                                      mData);
+      }
+      break;
+    case EventType::OnDisconnected:
+      // If we've disconnected, make sure we close all the streams - from
+      // mainthread!
+      if (mConnection->mListener) {
+        mConnection->mListener->NotifySctpClosed();
+      }
+      mConnection->CloseAll();
+      break;
+    case EventType::OnChannelCreated:
+      if (!mConnection->mListener) {
+        DC_ERROR(("DataChannelOnMessageAvailable (%s) with null Listener!",
+                  ToString(mType)));
+        return NS_OK;
+      }
+
+      // important to give it an already_AddRefed pointer!
+      mConnection->mListener->NotifyDataChannel(mChannel.forget());
+      break;
+    case EventType::OnConnection:
+      if (mConnection->mListener) {
+        mConnection->mListener->NotifySctpConnected();
+      }
+      break;
+  }
+  return NS_OK;
+}
+
+}  // namespace mozilla
diff --git a/netwerk/sctp/datachannel/DataChannel.h b/netwerk/sctp/datachannel/DataChannel.h
new file mode 100644
index 0000000000..76fb6aeced
--- /dev/null
+++ b/netwerk/sctp/datachannel/DataChannel.h
@@ -0,0 +1,670 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef NETWERK_SCTP_DATACHANNEL_DATACHANNEL_H_
+#define NETWERK_SCTP_DATACHANNEL_DATACHANNEL_H_
+
+#ifdef MOZ_WEBRTC_SIGNALING
+#  define SCTP_DTLS_SUPPORTED 1
+#endif
+
+#include <memory>
+#include <string>
+#include <vector>
+#include <errno.h>
+#include "nsISupports.h"
+#include "nsCOMPtr.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/WeakPtr.h"
+#include "nsString.h"
+#include "nsThreadUtils.h"
+#include "nsTArray.h"
+#include "nsDeque.h"
+#include "mozilla/dom/Blob.h"
+#include "mozilla/Mutex.h"
+#include "DataChannelProtocol.h"
+#include "DataChannelListener.h"
+#include "mozilla/net/NeckoTargetHolder.h"
+#include "DataChannelLog.h"
+
+#ifdef SCTP_DTLS_SUPPORTED
+#  include "transport/sigslot.h"
+#  include "transport/transportlayer.h"  // For TransportLayer::State
+#endif
+
+#ifndef EALREADY
+#  define EALREADY WSAEALREADY
+#endif
+
+extern "C" {
+struct socket;
+struct sctp_rcvinfo;
+}
+
+namespace mozilla {
+
+class DataChannelConnection;
+class DataChannel;
+class DataChannelOnMessageAvailable;
+class MediaPacket;
+class MediaTransportHandler;
+namespace dom {
+struct RTCStatsCollection;
+};
+
+enum class DataChannelState { Connecting, Open, Closing, Closed };
+enum class DataChannelConnectionState { Connecting, Open, Closed };
+enum class DataChannelReliabilityPolicy {
+  Reliable,
+  LimitedRetransmissions,
+  LimitedLifetime
+};
+
+// For sending outgoing messages.
+// This class only holds a reference to the data and the info structure but does
+// not copy it.
+class OutgoingMsg {
+ public:
+  OutgoingMsg(struct sctp_sendv_spa& info, const uint8_t* data, size_t length);
+  OutgoingMsg(OutgoingMsg&& other) = default;
+  OutgoingMsg& operator=(OutgoingMsg&& other) = default;
+  ~OutgoingMsg() = default;
+
+  void Advance(size_t offset);
+  struct sctp_sendv_spa& GetInfo() const { return *mInfo; };
+  size_t GetLength() const { return mLength; };
+  size_t GetLeft() const { return mLength - mPos; };
+  const uint8_t* GetData() const { return (const uint8_t*)(mData + mPos); };
+
+ protected:
+  OutgoingMsg()  // Use this for inheritance only
+      : mLength(0), mData(nullptr), mInfo(nullptr), mPos(0){};
+  size_t mLength;
+  const uint8_t* mData;
+  struct sctp_sendv_spa* mInfo;
+  size_t mPos;
+};
+
+// For queuing outgoing messages
+// This class copies data of an outgoing message.
+class BufferedOutgoingMsg : public OutgoingMsg {
+ public:
+  explicit BufferedOutgoingMsg(OutgoingMsg& msg);
+  BufferedOutgoingMsg(BufferedOutgoingMsg&& other) = default;
+  BufferedOutgoingMsg& operator=(BufferedOutgoingMsg&& other) = default;
+  ~BufferedOutgoingMsg();
+};
+
+// for queuing incoming data messages before the Open or
+// external negotiation is indicated to us
+class QueuedDataMessage {
+ public:
+  QueuedDataMessage(uint16_t stream, uint32_t ppid, int flags, const void* data,
+                    uint32_t length)
+      : mStream(stream), mPpid(ppid), mFlags(flags), mLength(length) {
+    mData = static_cast<uint8_t*>(moz_xmalloc((size_t)length));  // infallible
+    memcpy(mData, data, (size_t)length);
+  }
+  QueuedDataMessage(QueuedDataMessage&& other) = default;
+  QueuedDataMessage& operator=(QueuedDataMessage&& other) = default;
+  ~QueuedDataMessage() { free(mData); }
+
+  uint16_t mStream;
+  uint32_t mPpid;
+  int mFlags;
+  uint32_t mLength;
+  uint8_t* mData;
+};
+
+// One per PeerConnection
+class DataChannelConnection final : public net::NeckoTargetHolder
+#ifdef SCTP_DTLS_SUPPORTED
+    ,
+                                    public sigslot::has_slots<>
+#endif
+{
+  friend class DataChannel;
+  friend class DataChannelOnMessageAvailable;
+  friend class DataChannelConnectRunnable;
+
+  virtual ~DataChannelConnection();
+
+ public:
+  enum class PendingType {
+    None,  // No outgoing messages are pending.
+    Dcep,  // Outgoing DCEP messages are pending.
+    Data,  // Outgoing data channel messages are pending.
+  };
+
+  class DataConnectionListener : public SupportsWeakPtr {
+   public:
+    virtual ~DataConnectionListener() = default;
+
+    // Called when a new DataChannel has been opened by the other side.
+    virtual void NotifyDataChannel(already_AddRefed<DataChannel> channel) = 0;
+
+    // Called when a DataChannel transitions to state open
+    virtual void NotifyDataChannelOpen(DataChannel* aChannel) = 0;
+
+    // Called when a DataChannel (that was open at some point in the past)
+    // transitions to state closed
+    virtual void NotifyDataChannelClosed(DataChannel* aChannel) = 0;
+
+    // Called when SCTP connects
+    virtual void NotifySctpConnected() = 0;
+
+    // Called when SCTP closes
+    virtual void NotifySctpClosed() = 0;
+  };
+
+  // Create a new DataChannel Connection
+  // Must be called on Main thread
+  static Maybe<RefPtr<DataChannelConnection>> Create(
+      DataConnectionListener* aListener, nsISerialEventTarget* aTarget,
+      MediaTransportHandler* aHandler, const uint16_t aLocalPort,
+      const uint16_t aNumStreams, const Maybe<uint64_t>& aMaxMessageSize);
+
+  DataChannelConnection(const DataChannelConnection&) = delete;
+  DataChannelConnection& operator=(const DataChannelConnection&) = delete;
+
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(DataChannelConnection)
+
+  void Destroy();  // So we can spawn refs tied to runnables in shutdown
+  // Finish Destroy on STS to avoid SCTP race condition with ABORT from far end
+  void DestroyOnSTS(struct socket* aMasterSocket, struct socket* aSocket);
+  void DestroyOnSTSFinal();
+
+  void SetMaxMessageSize(bool aMaxMessageSizeSet, uint64_t aMaxMessageSize);
+  uint64_t GetMaxMessageSize();
+
+  void AppendStatsToReport(const UniquePtr<dom::RTCStatsCollection>& aReport,
+                           const DOMHighResTimeStamp aTimestamp) const;
+#ifdef ALLOW_DIRECT_SCTP_LISTEN_CONNECT
+  // These block; they require something to decide on listener/connector
+  // (though you can do simultaneous Connect()).  Do not call these from
+  // the main thread!
+  bool Listen(unsigned short port);
+  bool Connect(const char* addr, unsigned short port);
+#endif
+
+#ifdef SCTP_DTLS_SUPPORTED
+  bool ConnectToTransport(const std::string& aTransportId, const bool aClient,
+                          const uint16_t aLocalPort,
+                          const uint16_t aRemotePort);
+  void TransportStateChange(const std::string& aTransportId,
+                            TransportLayer::State aState);
+  void CompleteConnect();
+  void SetSignals(const std::string& aTransportId);
+#endif
+
+  [[nodiscard]] already_AddRefed<DataChannel> Open(
+      const nsACString& label, const nsACString& protocol,
+      DataChannelReliabilityPolicy prPolicy, bool inOrder, uint32_t prValue,
+      DataChannelListener* aListener, nsISupports* aContext,
+      bool aExternalNegotiated, uint16_t aStream);
+
+  void Stop();
+  void Close(DataChannel* aChannel);
+  void CloseLocked(DataChannel* aChannel) MOZ_REQUIRES(mLock);
+  void CloseAll();
+
+  // Returns a POSIX error code.
+  int SendMsg(uint16_t stream, const nsACString& aMsg) {
+    return SendDataMsgCommon(stream, aMsg, false);
+  }
+
+  // Returns a POSIX error code.
+  int SendBinaryMsg(uint16_t stream, const nsACString& aMsg) {
+    return SendDataMsgCommon(stream, aMsg, true);
+  }
+
+  // Returns a POSIX error code.
+  int SendBlob(uint16_t stream, nsIInputStream* aBlob);
+
+  // Called on data reception from the SCTP library
+  // must(?) be public so my c->c++ trampoline can call it
+  // May be called with (STS thread) or without the lock
+  int ReceiveCallback(struct socket* sock, void* data, size_t datalen,
+                      struct sctp_rcvinfo rcv, int flags);
+
+  void ReadBlob(already_AddRefed<DataChannelConnection> aThis, uint16_t aStream,
+                nsIInputStream* aBlob);
+
+  bool SendDeferredMessages() MOZ_REQUIRES(mLock);
+
+#ifdef SCTP_DTLS_SUPPORTED
+  int SctpDtlsOutput(void* addr, void* buffer, size_t length, uint8_t tos,
+                     uint8_t set_df);
+#endif
+
+  bool InShutdown() const {
+#ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
+    return mShutdown;
+#else
+    return false;
+#endif
+  }
+
+ private:
+  class Channels {
+   public:
+    using ChannelArray = AutoTArray<RefPtr<DataChannel>, 16>;
+
+    Channels() : mMutex("DataChannelConnection::Channels::mMutex") {}
+    Channels(const Channels&) = delete;
+    Channels& operator=(const Channels&) = delete;
+
+    void Insert(const RefPtr<DataChannel>& aChannel);
+    bool Remove(const RefPtr<DataChannel>& aChannel);
+    RefPtr<DataChannel> Get(uint16_t aId) const;
+    ChannelArray GetAll() const {
+      MutexAutoLock lock(mMutex);
+      return mChannels.Clone();
+    }
+    RefPtr<DataChannel> GetNextChannel(uint16_t aCurrentId) const;
+
+   private:
+    struct IdComparator {
+      bool Equals(const RefPtr<DataChannel>& aChannel, uint16_t aId) const;
+      bool LessThan(const RefPtr<DataChannel>& aChannel, uint16_t aId) const;
+      bool Equals(const RefPtr<DataChannel>& a1,
+                  const RefPtr<DataChannel>& a2) const;
+      bool LessThan(const RefPtr<DataChannel>& a1,
+                    const RefPtr<DataChannel>& a2) const;
+    };
+    mutable Mutex mMutex;
+    ChannelArray mChannels MOZ_GUARDED_BY(mMutex);
+  };
+
+  DataChannelConnection(DataConnectionListener* aListener,
+                        nsISerialEventTarget* aTarget,
+                        MediaTransportHandler* aHandler);
+
+  bool Init(const uint16_t aLocalPort, const uint16_t aNumStreams,
+            const Maybe<uint64_t>& aMaxMessageSize);
+
+  DataChannelConnectionState GetState() const MOZ_REQUIRES(mLock) {
+    mLock.AssertCurrentThreadOwns();
+
+    return mState;
+  }
+
+  void SetState(DataChannelConnectionState aState) MOZ_REQUIRES(mLock);
+  static int OnThresholdEvent(struct socket* sock, uint32_t sb_free,
+                              void* ulp_info);
+
+#ifdef SCTP_DTLS_SUPPORTED
+  static void DTLSConnectThread(void* data);
+  void SendPacket(std::unique_ptr<MediaPacket>&& packet);
+  void SctpDtlsInput(const std::string& aTransportId,
+                     const MediaPacket& packet);
+#endif
+  DataChannel* FindChannelByStream(uint16_t stream) MOZ_REQUIRES(mLock);
+  uint16_t FindFreeStream() const MOZ_REQUIRES(mLock);
+  bool RequestMoreStreams(int32_t aNeeded = 16) MOZ_REQUIRES(mLock);
+  uint32_t UpdateCurrentStreamIndex() MOZ_REQUIRES(mLock);
+  uint32_t GetCurrentStreamIndex() MOZ_REQUIRES(mLock);
+  int SendControlMessage(const uint8_t* data, uint32_t len, uint16_t stream)
+      MOZ_REQUIRES(mLock);
+  int SendOpenAckMessage(uint16_t stream) MOZ_REQUIRES(mLock);
+  int SendOpenRequestMessage(const nsACString& label,
+                             const nsACString& protocol, uint16_t stream,
+                             bool unordered,
+                             DataChannelReliabilityPolicy prPolicy,
+                             uint32_t prValue) MOZ_REQUIRES(mLock);
+  bool SendBufferedMessages(nsTArray<UniquePtr<BufferedOutgoingMsg>>& buffer,
+                            size_t* aWritten);
+  int SendMsgInternal(OutgoingMsg& msg, size_t* aWritten);
+  int SendMsgInternalOrBuffer(nsTArray<UniquePtr<BufferedOutgoingMsg>>& buffer,
+                              OutgoingMsg& msg, bool& buffered,
+                              size_t* aWritten) MOZ_REQUIRES(mLock);
+  int SendDataMsgInternalOrBuffer(DataChannel& channel, const uint8_t* data,
+                                  size_t len, uint32_t ppid)
+      MOZ_REQUIRES(mLock);
+  int SendDataMsg(DataChannel& channel, const uint8_t* data, size_t len,
+                  uint32_t ppidPartial, uint32_t ppidFinal) MOZ_REQUIRES(mLock);
+  int SendDataMsgCommon(uint16_t stream, const nsACString& aMsg, bool isBinary);
+
+  void DeliverQueuedData(uint16_t stream) MOZ_REQUIRES(mLock);
+
+  already_AddRefed<DataChannel> OpenFinish(
+      already_AddRefed<DataChannel>&& aChannel) MOZ_REQUIRES(mLock);
+
+  void ProcessQueuedOpens() MOZ_REQUIRES(mLock);
+  void ClearResets() MOZ_REQUIRES(mLock);
+  void SendOutgoingStreamReset() MOZ_REQUIRES(mLock);
+  void ResetOutgoingStream(uint16_t stream) MOZ_REQUIRES(mLock);
+  void HandleOpenRequestMessage(
+      const struct rtcweb_datachannel_open_request* req, uint32_t length,
+      uint16_t stream) MOZ_REQUIRES(mLock);
+  void HandleOpenAckMessage(const struct rtcweb_datachannel_ack* ack,
+                            uint32_t length, uint16_t stream);
+  void HandleUnknownMessage(uint32_t ppid, uint32_t length, uint16_t stream)
+      MOZ_REQUIRES(mLock);
+  uint8_t BufferMessage(nsACString& recvBuffer, const void* data,
+                        uint32_t length, uint32_t ppid, int flags);
+  void HandleDataMessage(const void* data, size_t length, uint32_t ppid,
+                         uint16_t stream, int flags) MOZ_REQUIRES(mLock);
+  void HandleDCEPMessage(const void* buffer, size_t length, uint32_t ppid,
+                         uint16_t stream, int flags) MOZ_REQUIRES(mLock);
+  void HandleMessage(const void* buffer, size_t length, uint32_t ppid,
+                     uint16_t stream, int flags) MOZ_REQUIRES(mLock);
+  void HandleAssociationChangeEvent(const struct sctp_assoc_change* sac)
+      MOZ_REQUIRES(mLock);
+  void HandlePeerAddressChangeEvent(const struct sctp_paddr_change* spc)
+      MOZ_REQUIRES(mLock);
+  void HandleRemoteErrorEvent(const struct sctp_remote_error* sre)
+      MOZ_REQUIRES(mLock);
+  void HandleShutdownEvent(const struct sctp_shutdown_event* sse)
+      MOZ_REQUIRES(mLock);
+  void HandleAdaptationIndication(const struct sctp_adaptation_event* sai)
+      MOZ_REQUIRES(mLock);
+  void HandlePartialDeliveryEvent(const struct sctp_pdapi_event* spde)
+      MOZ_REQUIRES(mLock);
+  void HandleSendFailedEvent(const struct sctp_send_failed_event* ssfe)
+      MOZ_REQUIRES(mLock);
+  void HandleStreamResetEvent(const struct sctp_stream_reset_event* strrst)
+      MOZ_REQUIRES(mLock);
+  void HandleStreamChangeEvent(const struct sctp_stream_change_event* strchg)
+      MOZ_REQUIRES(mLock);
+  void HandleNotification(const union sctp_notification* notif, size_t n)
+      MOZ_REQUIRES(mLock);
+
+#ifdef SCTP_DTLS_SUPPORTED
+  bool IsSTSThread() const {
+    bool on = false;
+    if (mSTS) {
+      mSTS->IsOnCurrentThread(&on);
+    }
+    return on;
+  }
+#endif
+
+  mutable Mutex mLock;
+  // Avoid cycles with PeerConnectionImpl
+  // Use from main thread only as WeakPtr is not threadsafe
+  WeakPtr<DataConnectionListener> mListener;
+  bool mSendInterleaved MOZ_GUARDED_BY(mLock) = false;
+  // MainThread only
+  bool mMaxMessageSizeSet = false;
+  // mMaxMessageSize is only set on MainThread, but read off-main-thread
+  uint64_t mMaxMessageSize MOZ_GUARDED_BY(mLock) = 0;
+  // Main thread only
+  Maybe<bool> mAllocateEven;
+  // Data:
+  // NOTE: while this container will auto-expand, increases in the number of
+  // channels available from the stack must be negotiated!
+  // Accessed from both main and sts, API is threadsafe
+  Channels mChannels;
+  // STS only
+  uint32_t mCurrentStream = 0;
+  nsRefPtrDeque<DataChannel> mPending;
+  // STS and main
+  size_t mNegotiatedIdLimit MOZ_GUARDED_BY(mLock) = 0;
+  PendingType mPendingType MOZ_GUARDED_BY(mLock) = PendingType::None;
+  // holds data that's come in before a channel is open
+  nsTArray<UniquePtr<QueuedDataMessage>> mQueuedData MOZ_GUARDED_BY(mLock);
+  // holds outgoing control messages
+  nsTArray<UniquePtr<BufferedOutgoingMsg>> mBufferedControl
+      MOZ_GUARDED_BY(mLock);
+
+  // Streams pending reset. Accessed from main and STS.
+  AutoTArray<uint16_t, 4> mStreamsResetting MOZ_GUARDED_BY(mLock);
+  // accessed from STS thread
+  struct socket* mMasterSocket = nullptr;
+  // cloned from mMasterSocket on successful Connect on STS thread
+  struct socket* mSocket = nullptr;
+  DataChannelConnectionState mState MOZ_GUARDED_BY(mLock) =
+      DataChannelConnectionState::Closed;
+
+#ifdef SCTP_DTLS_SUPPORTED
+  std::string mTransportId;
+  bool mConnectedToTransportHandler = false;
+  RefPtr<MediaTransportHandler> mTransportHandler;
+  nsCOMPtr<nsIEventTarget> mSTS;
+#endif
+  uint16_t mLocalPort = 0;  // Accessed from connect thread
+  uint16_t mRemotePort = 0;
+
+  nsCOMPtr<nsIThread> mInternalIOThread = nullptr;
+  nsCString mRecvBuffer;
+
+  // Workaround to prevent a message from being received on main before the
+  // sender sees the decrease in bufferedAmount.
+  bool mDeferSend = false;
+  std::vector<std::unique_ptr<MediaPacket>> mDeferredSend;
+
+#ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
+  bool mShutdown;
+#endif
+  uintptr_t mId = 0;
+};
+
+class DataChannel {
+  friend class DataChannelOnMessageAvailable;
+  friend class DataChannelConnection;
+
+ public:
+  struct TrafficCounters {
+    uint32_t mMessagesSent = 0;
+    uint64_t mBytesSent = 0;
+    uint32_t mMessagesReceived = 0;
+    uint64_t mBytesReceived = 0;
+  };
+
+  DataChannel(DataChannelConnection* connection, uint16_t stream,
+              DataChannelState state, const nsACString& label,
+              const nsACString& protocol, DataChannelReliabilityPolicy policy,
+              uint32_t value, bool ordered, bool negotiated,
+              DataChannelListener* aListener, nsISupports* aContext)
+      : mListener(aListener),
+        mContext(aContext),
+        mConnection(connection),
+        mLabel(label),
+        mProtocol(protocol),
+        mReadyState(state),
+        mStream(stream),
+        mPrPolicy(policy),
+        mPrValue(value),
+        mNegotiated(negotiated),
+        mOrdered(ordered),
+        mIsRecvBinary(false),
+        mBufferedThreshold(0),  // default from spec
+        mBufferedAmount(0),
+        mMainThreadEventTarget(connection->GetNeckoTarget()),
+        mStatsLock("netwer::sctp::DataChannel::mStatsLock") {
+    NS_ASSERTION(mConnection, "NULL connection");
+  }
+  DataChannel(const DataChannel&) = delete;
+  DataChannel& operator=(const DataChannel&) = delete;
+
+ private:
+  ~DataChannel();
+
+ public:
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(DataChannel)
+
+  // when we disconnect from the connection after stream RESET
+  void StreamClosedLocked();
+
+  // Complete dropping of the link between DataChannel and the connection.
+  // After this, except for a few methods below listed to be safe, you can't
+  // call into DataChannel.
+  void ReleaseConnection();
+
+  // Close this DataChannel.  Can be called multiple times.  MUST be called
+  // before destroying the DataChannel (state must be CLOSED or CLOSING).
+  void Close();
+
+  // Set the listener (especially for channels created from the other side)
+  void SetListener(DataChannelListener* aListener, nsISupports* aContext);
+
+  // Helper for send methods that converts POSIX error codes to an ErrorResult.
+  static void SendErrnoToErrorResult(int error, size_t aMessageSize,
+                                     ErrorResult& aRv);
+
+  // Send a string
+  void SendMsg(const nsACString& aMsg, ErrorResult& aRv);
+
+  // Send a binary message (TypedArray)
+  void SendBinaryMsg(const nsACString& aMsg, ErrorResult& aRv);
+
+  // Send a binary blob
+  void SendBinaryBlob(dom::Blob& aBlob, ErrorResult& aRv);
+
+  DataChannelReliabilityPolicy GetType() const { return mPrPolicy; }
+
+  dom::Nullable<uint16_t> GetMaxPacketLifeTime() const;
+
+  dom::Nullable<uint16_t> GetMaxRetransmits() const;
+
+  bool GetNegotiated() const { return mNegotiated; }
+
+  bool GetOrdered() const { return mOrdered; }
+
+  void IncrementBufferedAmount(uint32_t aSize, ErrorResult& aRv);
+  void DecrementBufferedAmount(uint32_t aSize);
+
+  // Amount of data buffered to send
+  uint32_t GetBufferedAmount() const {
+    MOZ_ASSERT(NS_IsMainThread());
+    return mBufferedAmount;
+  }
+
+  // Trigger amount for generating BufferedAmountLow events
+  uint32_t GetBufferedAmountLowThreshold() const;
+  void SetBufferedAmountLowThreshold(uint32_t aThreshold);
+
+  void AnnounceOpen();
+  // TODO(bug 843625): Optionally pass an error here.
+  void AnnounceClosed();
+
+  // Find out state
+  DataChannelState GetReadyState() const {
+    MOZ_ASSERT(NS_IsMainThread());
+    return mReadyState;
+  }
+
+  // Set ready state
+  void SetReadyState(DataChannelState aState);
+
+  void GetLabel(nsAString& aLabel) { CopyUTF8toUTF16(mLabel, aLabel); }
+  void GetProtocol(nsAString& aProtocol) {
+    CopyUTF8toUTF16(mProtocol, aProtocol);
+  }
+  uint16_t GetStream() const { return mStream; }
+
+  void SendOrQueue(DataChannelOnMessageAvailable* aMessage);
+
+  TrafficCounters GetTrafficCounters() const;
+
+ private:
+  nsresult AddDataToBinaryMsg(const char* data, uint32_t size);
+  bool EnsureValidStream(ErrorResult& aRv);
+  void WithTrafficCounters(const std::function<void(TrafficCounters&)>&);
+
+  // These are both mainthread only
+  DataChannelListener* mListener;
+  nsCOMPtr<nsISupports> mContext;
+
+  RefPtr<DataChannelConnection> mConnection;
+  // mainthread only
+  bool mEverOpened = false;
+  const nsCString mLabel;
+  const nsCString mProtocol;
+  // This is mainthread only
+  DataChannelState mReadyState;
+  uint16_t mStream;
+  const DataChannelReliabilityPolicy mPrPolicy;
+  const uint32_t mPrValue;
+  // Accessed on main and STS
+  const bool mNegotiated;
+  const bool mOrdered;
+  // The data channel has completed the open procedure and the client has been
+  // notified about it.
+  bool mHasFinishedOpen = false;
+  // The channel has been opened, but the peer has not yet acked - ensures that
+  // the messages are sent ordered until this is cleared.
+  bool mWaitingForAck = false;
+  // A too large message was attempted to be sent - closing data channel.
+  bool mClosingTooLarge = false;
+  bool mIsRecvBinary;
+  size_t mBufferedThreshold;
+  // Read/written on main only. Decremented via message-passing, because the
+  // spec requires us to queue a task for this.
+  size_t mBufferedAmount;
+  nsCString mRecvBuffer;
+  nsTArray<UniquePtr<BufferedOutgoingMsg>>
+      mBufferedData;  // MOZ_GUARDED_BY(mConnection->mLock)
+  nsCOMPtr<nsISerialEventTarget> mMainThreadEventTarget;
+  mutable Mutex mStatsLock;
+  TrafficCounters mTrafficCounters MOZ_GUARDED_BY(mStatsLock);
+};
+
+// used to dispatch notifications of incoming data to the main thread
+// Patterned on CallOnMessageAvailable in WebSockets
+// Also used to proxy other items to MainThread
+class DataChannelOnMessageAvailable : public Runnable {
+ public:
+  enum class EventType {
+    OnConnection,
+    OnDisconnected,
+    OnChannelCreated,
+    OnDataString,
+    OnDataBinary,
+  };
+
+  DataChannelOnMessageAvailable(
+      EventType aType, DataChannelConnection* aConnection,
+      DataChannel* aChannel,
+      nsCString& aData)  // XXX this causes inefficiency
+      : Runnable("DataChannelOnMessageAvailable"),
+        mType(aType),
+        mChannel(aChannel),
+        mConnection(aConnection),
+        mData(aData) {}
+
+  DataChannelOnMessageAvailable(EventType aType, DataChannel* aChannel)
+      : Runnable("DataChannelOnMessageAvailable"),
+        mType(aType),
+        mChannel(aChannel) {}
+  // XXX is it safe to leave mData uninitialized?  This should only be
+  // used for notifications that don't use them, but I'd like more
+  // bulletproof compile-time checking.
+
+  DataChannelOnMessageAvailable(EventType aType,
+                                DataChannelConnection* aConnection,
+                                DataChannel* aChannel)
+      : Runnable("DataChannelOnMessageAvailable"),
+        mType(aType),
+        mChannel(aChannel),
+        mConnection(aConnection) {}
+
+  // for ON_CONNECTION/ON_DISCONNECTED
+  DataChannelOnMessageAvailable(EventType aType,
+                                DataChannelConnection* aConnection)
+      : Runnable("DataChannelOnMessageAvailable"),
+        mType(aType),
+        mConnection(aConnection) {}
+  DataChannelOnMessageAvailable(const DataChannelOnMessageAvailable&) = delete;
+  DataChannelOnMessageAvailable& operator=(
+      const DataChannelOnMessageAvailable&) = delete;
+
+  NS_IMETHOD Run() override;
+
+ private:
+  ~DataChannelOnMessageAvailable() = default;
+
+  EventType mType;
+  // XXX should use union
+  RefPtr<DataChannel> mChannel;
+  RefPtr<DataChannelConnection> mConnection;
+  nsCString mData;
+};
+
+}  // namespace mozilla
+
+#endif  // NETWERK_SCTP_DATACHANNEL_DATACHANNEL_H_
diff --git a/netwerk/sctp/datachannel/DataChannelListener.h b/netwerk/sctp/datachannel/DataChannelListener.h
new file mode 100644
index 0000000000..06564b6cc7
--- /dev/null
+++ b/netwerk/sctp/datachannel/DataChannelListener.h
@@ -0,0 +1,45 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef NETWERK_SCTP_DATACHANNEL_DATACHANNELLISTENER_H_
+#define NETWERK_SCTP_DATACHANNEL_DATACHANNELLISTENER_H_
+
+#include "nsISupports.h"
+#include "nsString.h"
+
+namespace mozilla {
+
+// Implemented by consumers of a Channel to receive messages.
+// Can't nest it in DataChannelConnection because C++ doesn't allow forward
+// refs to embedded classes
+class DataChannelListener {
+ public:
+  virtual ~DataChannelListener() = default;
+
+  // Called when a DOMString message is received.
+  virtual nsresult OnMessageAvailable(nsISupports* aContext,
+                                      const nsACString& message) = 0;
+
+  // Called when a binary message is received.
+  virtual nsresult OnBinaryMessageAvailable(nsISupports* aContext,
+                                            const nsACString& message) = 0;
+
+  // Called when the channel is connected
+  virtual nsresult OnChannelConnected(nsISupports* aContext) = 0;
+
+  // Called when the channel is closed
+  virtual nsresult OnChannelClosed(nsISupports* aContext) = 0;
+
+  // Called when the BufferedAmount drops below the BufferedAmountLowThreshold
+  virtual nsresult OnBufferLow(nsISupports* aContext) = 0;
+
+  // Called when the BufferedAmount drops to 0
+  virtual nsresult NotBuffered(nsISupports* aContext) = 0;
+};
+
+}  // namespace mozilla
+
+#endif
diff --git a/netwerk/sctp/datachannel/DataChannelLog.h b/netwerk/sctp/datachannel/DataChannelLog.h
new file mode 100644
index 0000000000..c77fe2e2d8
--- /dev/null
+++ b/netwerk/sctp/datachannel/DataChannelLog.h
@@ -0,0 +1,32 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DataChannelLog_h
+#define DataChannelLog_h
+
+#include "base/basictypes.h"
+#include "mozilla/Logging.h"
+
+namespace mozilla {
+extern mozilla::LazyLogModule gDataChannelLog;
+}
+
+#define DC_ERROR(args) \
+  MOZ_LOG(mozilla::gDataChannelLog, mozilla::LogLevel::Error, args)
+
+#define DC_WARN(args) \
+  MOZ_LOG(mozilla::gDataChannelLog, mozilla::LogLevel::Warning, args)
+
+#define DC_INFO(args) \
+  MOZ_LOG(mozilla::gDataChannelLog, mozilla::LogLevel::Info, args)
+
+#define DC_DEBUG(args) \
+  MOZ_LOG(mozilla::gDataChannelLog, mozilla::LogLevel::Debug, args)
+
+#define DC_VERBOSE(args) \
+  MOZ_LOG(mozilla::gDataChannelLog, mozilla::LogLevel::Verbose, args)
+
+#endif
diff --git a/netwerk/sctp/datachannel/DataChannelProtocol.h b/netwerk/sctp/datachannel/DataChannelProtocol.h
new file mode 100644
index 0000000000..47fe48cdd9
--- /dev/null
+++ b/netwerk/sctp/datachannel/DataChannelProtocol.h
@@ -0,0 +1,85 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef NETWERK_SCTP_DATACHANNEL_DATACHANNELPROTOCOL_H_
+#define NETWERK_SCTP_DATACHANNEL_DATACHANNELPROTOCOL_H_
+
+#if defined(__GNUC__)
+#  define SCTP_PACKED __attribute__((packed))
+#elif defined(_MSC_VER)
+#  pragma pack(push, 1)
+#  define SCTP_PACKED
+#else
+#  error "Unsupported compiler"
+#endif
+
+#define WEBRTC_DATACHANNEL_STREAMS_DEFAULT 256
+// Do not change this value!
+#define WEBRTC_DATACHANNEL_PORT_DEFAULT 5000
+// TODO: Bug 1381146, change once we resolve the nsCString limitation
+#define WEBRTC_DATACHANNEL_MAX_MESSAGE_SIZE_LOCAL 1073741823
+#define WEBRTC_DATACHANNEL_MAX_MESSAGE_SIZE_REMOTE_DEFAULT 65536
+// TODO: Bug 1382779, once resolved, can be increased to min(Uint8ArrayMaxSize,
+// UINT32_MAX)
+// TODO: Bug 1381146, once resolved, can be increased to whatever we support
+//       then (hopefully SIZE_MAX) or be removed
+#define WEBRTC_DATACHANNEL_MAX_MESSAGE_SIZE_REMOTE 2147483637
+
+#define DATA_CHANNEL_PPID_CONTROL 50
+#define DATA_CHANNEL_PPID_BINARY_PARTIAL 52
+#define DATA_CHANNEL_PPID_BINARY 53
+#define DATA_CHANNEL_PPID_DOMSTRING_PARTIAL 54
+#define DATA_CHANNEL_PPID_DOMSTRING 51
+#define DATA_CHANNEL_PPID_DOMSTRING_EMPTY 56
+#define DATA_CHANNEL_PPID_BINARY_EMPTY 57
+
+#define DATA_CHANNEL_MAX_BINARY_FRAGMENT 0x4000
+
+#define DATA_CHANNEL_BUFFER_MESSAGE_FLAGS_TOO_LARGE 0x01
+#define DATA_CHANNEL_BUFFER_MESSAGE_FLAGS_BUFFERED 0x02
+#define DATA_CHANNEL_BUFFER_MESSAGE_FLAGS_COMPLETE 0x04
+
+#define INVALID_STREAM (0xFFFF)
+// max is 0xFFFF: Streams 0 to 0xFFFE = 0xFFFF streams
+#define MAX_NUM_STREAMS (2048)
+
+struct rtcweb_datachannel_open_request {
+  uint8_t msg_type;  // DATA_CHANNEL_OPEN
+  uint8_t channel_type;
+  int16_t priority;
+  uint32_t reliability_param;
+  uint16_t label_length;
+  uint16_t protocol_length;
+  char label[1];  // (and protocol) keep VC++ happy...
+} SCTP_PACKED;
+
+struct rtcweb_datachannel_ack {
+  uint8_t msg_type;  // DATA_CHANNEL_ACK
+} SCTP_PACKED;
+
+/* msg_type values: */
+/* 0-1 were used in an early version of the protocol with 3-way handshakes */
+#define DATA_CHANNEL_ACK 2
+#define DATA_CHANNEL_OPEN_REQUEST 3
+
+/* channel_type values: */
+#define DATA_CHANNEL_RELIABLE 0x00
+#define DATA_CHANNEL_PARTIAL_RELIABLE_REXMIT 0x01
+#define DATA_CHANNEL_PARTIAL_RELIABLE_TIMED 0x02
+
+#define DATA_CHANNEL_RELIABLE_UNORDERED 0x80
+#define DATA_CHANNEL_PARTIAL_RELIABLE_REXMIT_UNORDERED 0x81
+#define DATA_CHANNEL_PARTIAL_RELIABLE_TIMED_UNORDERED 0x82
+
+#define ERR_DATA_CHANNEL_ALREADY_OPEN 1
+#define ERR_DATA_CHANNEL_NONE_AVAILABLE 2
+
+#if defined(_MSC_VER)
+#  pragma pack(pop)
+#  undef SCTP_PACKED
+#endif
+
+#endif
diff --git a/netwerk/sctp/datachannel/moz.build b/netwerk/sctp/datachannel/moz.build
new file mode 100644
index 0000000000..94656f084e
--- /dev/null
+++ b/netwerk/sctp/datachannel/moz.build
@@ -0,0 +1,36 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+EXPORTS.mozilla.net += [
+    "DataChannel.h",
+    "DataChannelListener.h",
+    "DataChannelLog.h",
+    "DataChannelProtocol.h",
+]
+
+SOURCES += [
+    "DataChannel.cpp",
+]
+
+include("/ipc/chromium/chromium-config.mozbuild")
+
+FINAL_LIBRARY = "xul"
+
+LOCAL_INCLUDES += [
+    "/dom/media/webrtc",
+    "/dom/media/webrtc/transport",
+    "/media/webrtc",
+    "/netwerk/sctp/src",
+    "/third_party/libwebrtc",
+    "/third_party/libwebrtc/third_party/abseil-cpp",
+]
+
+DEFINES["SCTP_DEBUG"] = 1
+
+if CONFIG["OS_TARGET"] == "WINNT":
+    DEFINES["__Userspace_os_Windows"] = 1
+else:
+    DEFINES["__Userspace_os_%s" % CONFIG["OS_TARGET"]] = 1