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diff --git a/third_party/libwebrtc/p2p/base/pseudo_tcp.h b/third_party/libwebrtc/p2p/base/pseudo_tcp.h
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+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_BASE_PSEUDO_TCP_H_
+#define P2P_BASE_PSEUDO_TCP_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <list>
+#include <memory>
+
+#include "rtc_base/synchronization/mutex.h"
+#include "rtc_base/system/rtc_export.h"
+
+namespace cricket {
+
+//////////////////////////////////////////////////////////////////////
+// IPseudoTcpNotify
+//////////////////////////////////////////////////////////////////////
+
+class PseudoTcp;
+
+class IPseudoTcpNotify {
+ public:
+  // Notification of tcp events
+  virtual void OnTcpOpen(PseudoTcp* tcp) = 0;
+  virtual void OnTcpReadable(PseudoTcp* tcp) = 0;
+  virtual void OnTcpWriteable(PseudoTcp* tcp) = 0;
+  virtual void OnTcpClosed(PseudoTcp* tcp, uint32_t error) = 0;
+
+  // Write the packet onto the network
+  enum WriteResult { WR_SUCCESS, WR_TOO_LARGE, WR_FAIL };
+  virtual WriteResult TcpWritePacket(PseudoTcp* tcp,
+                                     const char* buffer,
+                                     size_t len) = 0;
+
+ protected:
+  virtual ~IPseudoTcpNotify() {}
+};
+
+//////////////////////////////////////////////////////////////////////
+// PseudoTcp
+//////////////////////////////////////////////////////////////////////
+
+class RTC_EXPORT PseudoTcp {
+ public:
+  static uint32_t Now();
+
+  PseudoTcp(IPseudoTcpNotify* notify, uint32_t conv);
+  virtual ~PseudoTcp();
+
+  int Connect();
+  int Recv(char* buffer, size_t len);
+  int Send(const char* buffer, size_t len);
+  void Close(bool force);
+  int GetError();
+
+  enum TcpState {
+    TCP_LISTEN,
+    TCP_SYN_SENT,
+    TCP_SYN_RECEIVED,
+    TCP_ESTABLISHED,
+    TCP_CLOSED
+  };
+  TcpState State() const { return m_state; }
+
+  // Call this when the PMTU changes.
+  void NotifyMTU(uint16_t mtu);
+
+  // Call this based on timeout value returned from GetNextClock.
+  // It's ok to call this too frequently.
+  void NotifyClock(uint32_t now);
+
+  // Call this whenever a packet arrives.
+  // Returns true if the packet was processed successfully.
+  bool NotifyPacket(const char* buffer, size_t len);
+
+  // Call this to determine the next time NotifyClock should be called.
+  // Returns false if the socket is ready to be destroyed.
+  bool GetNextClock(uint32_t now, long& timeout);
+
+  // Call these to get/set option values to tailor this PseudoTcp
+  // instance's behaviour for the kind of data it will carry.
+  // If an unrecognized option is set or got, an assertion will fire.
+  //
+  // Setting options for OPT_RCVBUF or OPT_SNDBUF after Connect() is called
+  // will result in an assertion.
+  enum Option {
+    OPT_NODELAY,   // Whether to enable Nagle's algorithm (0 == off)
+    OPT_ACKDELAY,  // The Delayed ACK timeout (0 == off).
+    OPT_RCVBUF,    // Set the receive buffer size, in bytes.
+    OPT_SNDBUF,    // Set the send buffer size, in bytes.
+  };
+  void GetOption(Option opt, int* value);
+  void SetOption(Option opt, int value);
+
+  // Returns current congestion window in bytes.
+  uint32_t GetCongestionWindow() const;
+
+  // Returns amount of data in bytes that has been sent, but haven't
+  // been acknowledged.
+  uint32_t GetBytesInFlight() const;
+
+  // Returns number of bytes that were written in buffer and haven't
+  // been sent.
+  uint32_t GetBytesBufferedNotSent() const;
+
+  // Returns current round-trip time estimate in milliseconds.
+  uint32_t GetRoundTripTimeEstimateMs() const;
+
+ protected:
+  enum SendFlags { sfNone, sfDelayedAck, sfImmediateAck };
+
+  struct Segment {
+    uint32_t conv, seq, ack;
+    uint8_t flags;
+    uint16_t wnd;
+    const char* data;
+    uint32_t len;
+    uint32_t tsval, tsecr;
+  };
+
+  struct SSegment {
+    SSegment(uint32_t s, uint32_t l, bool c)
+        : seq(s), len(l), /*tstamp(0),*/ xmit(0), bCtrl(c) {}
+    uint32_t seq, len;
+    // uint32_t tstamp;
+    uint8_t xmit;
+    bool bCtrl;
+  };
+  typedef std::list<SSegment> SList;
+
+  struct RSegment {
+    uint32_t seq, len;
+  };
+
+  uint32_t queue(const char* data, uint32_t len, bool bCtrl);
+
+  // Creates a packet and submits it to the network. This method can either
+  // send payload or just an ACK packet.
+  //
+  // `seq` is the sequence number of this packet.
+  // `flags` is the flags for sending this packet.
+  // `offset` is the offset to read from `m_sbuf`.
+  // `len` is the number of bytes to read from `m_sbuf` as payload. If this
+  // value is 0 then this is an ACK packet, otherwise this packet has payload.
+  IPseudoTcpNotify::WriteResult packet(uint32_t seq,
+                                       uint8_t flags,
+                                       uint32_t offset,
+                                       uint32_t len);
+  bool parse(const uint8_t* buffer, uint32_t size);
+
+  void attemptSend(SendFlags sflags = sfNone);
+
+  void closedown(uint32_t err = 0);
+
+  bool clock_check(uint32_t now, long& nTimeout);
+
+  bool process(Segment& seg);
+  bool transmit(const SList::iterator& seg, uint32_t now);
+
+  void adjustMTU();
+
+ protected:
+  // This method is used in test only to query receive buffer state.
+  bool isReceiveBufferFull() const;
+
+  // This method is only used in tests, to disable window scaling
+  // support for testing backward compatibility.
+  void disableWindowScale();
+
+ private:
+  // Queue the connect message with TCP options.
+  void queueConnectMessage();
+
+  // Parse TCP options in the header.
+  void parseOptions(const char* data, uint32_t len);
+
+  // Apply a TCP option that has been read from the header.
+  void applyOption(char kind, const char* data, uint32_t len);
+
+  // Apply window scale option.
+  void applyWindowScaleOption(uint8_t scale_factor);
+
+  // Resize the send buffer with `new_size` in bytes.
+  void resizeSendBuffer(uint32_t new_size);
+
+  // Resize the receive buffer with `new_size` in bytes. This call adjusts
+  // window scale factor `m_swnd_scale` accordingly.
+  void resizeReceiveBuffer(uint32_t new_size);
+
+  class LockedFifoBuffer final {
+   public:
+    explicit LockedFifoBuffer(size_t size);
+    ~LockedFifoBuffer();
+
+    size_t GetBuffered() const;
+    bool SetCapacity(size_t size);
+    bool ReadOffset(void* buffer,
+                    size_t bytes,
+                    size_t offset,
+                    size_t* bytes_read);
+    bool WriteOffset(const void* buffer,
+                     size_t bytes,
+                     size_t offset,
+                     size_t* bytes_written);
+    bool Read(void* buffer, size_t bytes, size_t* bytes_read);
+    bool Write(const void* buffer, size_t bytes, size_t* bytes_written);
+    void ConsumeReadData(size_t size);
+    void ConsumeWriteBuffer(size_t size);
+    bool GetWriteRemaining(size_t* size) const;
+
+   private:
+    bool ReadOffsetLocked(void* buffer,
+                          size_t bytes,
+                          size_t offset,
+                          size_t* bytes_read)
+        RTC_EXCLUSIVE_LOCKS_REQUIRED(mutex_);
+    bool WriteOffsetLocked(const void* buffer,
+                           size_t bytes,
+                           size_t offset,
+                           size_t* bytes_written)
+        RTC_EXCLUSIVE_LOCKS_REQUIRED(mutex_);
+
+    // the allocated buffer
+    std::unique_ptr<char[]> buffer_ RTC_GUARDED_BY(mutex_);
+    // size of the allocated buffer
+    size_t buffer_length_ RTC_GUARDED_BY(mutex_);
+    // amount of readable data in the buffer
+    size_t data_length_ RTC_GUARDED_BY(mutex_);
+    // offset to the readable data
+    size_t read_position_ RTC_GUARDED_BY(mutex_);
+    mutable webrtc::Mutex mutex_;
+  };
+
+  IPseudoTcpNotify* m_notify;
+  enum Shutdown { SD_NONE, SD_GRACEFUL, SD_FORCEFUL } m_shutdown;
+  int m_error;
+
+  // TCB data
+  TcpState m_state;
+  uint32_t m_conv;
+  bool m_bReadEnable, m_bWriteEnable, m_bOutgoing;
+  uint32_t m_lasttraffic;
+
+  // Incoming data
+  typedef std::list<RSegment> RList;
+  RList m_rlist;
+  uint32_t m_rbuf_len, m_rcv_nxt, m_rcv_wnd, m_lastrecv;
+  uint8_t m_rwnd_scale;  // Window scale factor.
+  LockedFifoBuffer m_rbuf;
+
+  // Outgoing data
+  SList m_slist;
+  uint32_t m_sbuf_len, m_snd_nxt, m_snd_wnd, m_lastsend, m_snd_una;
+  uint8_t m_swnd_scale;  // Window scale factor.
+  LockedFifoBuffer m_sbuf;
+
+  // Maximum segment size, estimated protocol level, largest segment sent
+  uint32_t m_mss, m_msslevel, m_largest, m_mtu_advise;
+  // Retransmit timer
+  uint32_t m_rto_base;
+
+  // Timestamp tracking
+  uint32_t m_ts_recent, m_ts_lastack;
+
+  // Round-trip calculation
+  uint32_t m_rx_rttvar, m_rx_srtt, m_rx_rto;
+
+  // Congestion avoidance, Fast retransmit/recovery, Delayed ACKs
+  uint32_t m_ssthresh, m_cwnd;
+  uint8_t m_dup_acks;
+  uint32_t m_recover;
+  uint32_t m_t_ack;
+
+  // Configuration options
+  bool m_use_nagling;
+  uint32_t m_ack_delay;
+
+  // This is used by unit tests to test backward compatibility of
+  // PseudoTcp implementations that don't support window scaling.
+  bool m_support_wnd_scale;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_PSEUDO_TCP_H_