Adding upstream version 115.7.0esr.upstream/115.7.0esr

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

1 files changed, 1432 insertions, 0 deletions

diff --git a/third_party/libwebrtc/p2p/base/pseudo_tcp.cc b/third_party/libwebrtc/p2p/base/pseudo_tcp.cc
new file mode 100644
index 0000000000..eff86e849e
--- /dev/null
+++ b/third_party/libwebrtc/p2p/base/pseudo_tcp.cc
@@ -0,0 +1,1432 @@
+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "p2p/base/pseudo_tcp.h"
+
+#include <errno.h>
+#include <stdio.h>
+#include <string.h>
+
+#include <algorithm>
+#include <cstdint>
+#include <memory>
+#include <set>
+
+#include "rtc_base/byte_buffer.h"
+#include "rtc_base/byte_order.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/logging.h"
+#include "rtc_base/numerics/safe_minmax.h"
+#include "rtc_base/socket.h"
+#include "rtc_base/time_utils.h"
+
+// The following logging is for detailed (packet-level) analysis only.
+#define _DBG_NONE 0
+#define _DBG_NORMAL 1
+#define _DBG_VERBOSE 2
+#define _DEBUGMSG _DBG_NONE
+
+namespace cricket {
+
+//////////////////////////////////////////////////////////////////////
+// Network Constants
+//////////////////////////////////////////////////////////////////////
+
+// Standard MTUs
+const uint16_t PACKET_MAXIMUMS[] = {
+    65535,  // Theoretical maximum, Hyperchannel
+    32000,  // Nothing
+    17914,  // 16Mb IBM Token Ring
+    8166,   // IEEE 802.4
+    // 4464,   // IEEE 802.5 (4Mb max)
+    4352,  // FDDI
+    // 2048,   // Wideband Network
+    2002,  // IEEE 802.5 (4Mb recommended)
+    // 1536,   // Expermental Ethernet Networks
+    // 1500,   // Ethernet, Point-to-Point (default)
+    1492,  // IEEE 802.3
+    1006,  // SLIP, ARPANET
+    // 576,    // X.25 Networks
+    // 544,    // DEC IP Portal
+    // 512,    // NETBIOS
+    508,  // IEEE 802/Source-Rt Bridge, ARCNET
+    296,  // Point-to-Point (low delay)
+    // 68,     // Official minimum
+    0,  // End of list marker
+};
+
+const uint32_t MAX_PACKET = 65535;
+// Note: we removed lowest level because packet overhead was larger!
+const uint32_t MIN_PACKET = 296;
+
+const uint32_t IP_HEADER_SIZE = 20;  // (+ up to 40 bytes of options?)
+const uint32_t UDP_HEADER_SIZE = 8;
+// TODO(?): Make JINGLE_HEADER_SIZE transparent to this code?
+const uint32_t JINGLE_HEADER_SIZE = 64;  // when relay framing is in use
+
+// Default size for receive and send buffer.
+const uint32_t DEFAULT_RCV_BUF_SIZE = 60 * 1024;
+const uint32_t DEFAULT_SND_BUF_SIZE = 90 * 1024;
+
+//////////////////////////////////////////////////////////////////////
+// Global Constants and Functions
+//////////////////////////////////////////////////////////////////////
+//
+//    0                   1                   2                   3
+//    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+//    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+//  0 |                      Conversation Number                      |
+//    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+//  4 |                        Sequence Number                        |
+//    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+//  8 |                     Acknowledgment Number                     |
+//    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+//    |               |   |U|A|P|R|S|F|                               |
+// 12 |    Control    |   |R|C|S|S|Y|I|            Window             |
+//    |               |   |G|K|H|T|N|N|                               |
+//    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// 16 |                       Timestamp sending                       |
+//    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// 20 |                      Timestamp receiving                      |
+//    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// 24 |                             data                              |
+//    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+//
+//////////////////////////////////////////////////////////////////////
+
+#define PSEUDO_KEEPALIVE 0
+
+const uint32_t HEADER_SIZE = 24;
+const uint32_t PACKET_OVERHEAD =
+    HEADER_SIZE + UDP_HEADER_SIZE + IP_HEADER_SIZE + JINGLE_HEADER_SIZE;
+
+const uint32_t MIN_RTO =
+    250;  // 250 ms (RFC1122, Sec 4.2.3.1 "fractions of a second")
+const uint32_t DEF_RTO = 3000;       // 3 seconds (RFC1122, Sec 4.2.3.1)
+const uint32_t MAX_RTO = 60000;      // 60 seconds
+const uint32_t DEF_ACK_DELAY = 100;  // 100 milliseconds
+
+const uint8_t FLAG_CTL = 0x02;
+const uint8_t FLAG_RST = 0x04;
+
+const uint8_t CTL_CONNECT = 0;
+
+// TCP options.
+const uint8_t TCP_OPT_EOL = 0;        // End of list.
+const uint8_t TCP_OPT_NOOP = 1;       // No-op.
+const uint8_t TCP_OPT_MSS = 2;        // Maximum segment size.
+const uint8_t TCP_OPT_WND_SCALE = 3;  // Window scale factor.
+
+const long DEFAULT_TIMEOUT =
+    4000;  // If there are no pending clocks, wake up every 4 seconds
+const long CLOSED_TIMEOUT =
+    60 * 1000;  // If the connection is closed, once per minute
+
+#if PSEUDO_KEEPALIVE
+// !?! Rethink these times
+const uint32_t IDLE_PING =
+    20 *
+    1000;  // 20 seconds (note: WinXP SP2 firewall udp timeout is 90 seconds)
+const uint32_t IDLE_TIMEOUT = 90 * 1000;  // 90 seconds;
+#endif                                    // PSEUDO_KEEPALIVE
+
+//////////////////////////////////////////////////////////////////////
+// Helper Functions
+//////////////////////////////////////////////////////////////////////
+
+inline void long_to_bytes(uint32_t val, void* buf) {
+  *static_cast<uint32_t*>(buf) = rtc::HostToNetwork32(val);
+}
+
+inline void short_to_bytes(uint16_t val, void* buf) {
+  *static_cast<uint16_t*>(buf) = rtc::HostToNetwork16(val);
+}
+
+inline uint32_t bytes_to_long(const void* buf) {
+  return rtc::NetworkToHost32(*static_cast<const uint32_t*>(buf));
+}
+
+inline uint16_t bytes_to_short(const void* buf) {
+  return rtc::NetworkToHost16(*static_cast<const uint16_t*>(buf));
+}
+
+//////////////////////////////////////////////////////////////////////
+// Debugging Statistics
+//////////////////////////////////////////////////////////////////////
+
+#if 0  // Not used yet
+
+enum Stat {
+  S_SENT_PACKET,    // All packet sends
+  S_RESENT_PACKET,  // All packet sends that are retransmits
+  S_RECV_PACKET,    // All packet receives
+  S_RECV_NEW,       // All packet receives that are too new
+  S_RECV_OLD,       // All packet receives that are too old
+  S_NUM_STATS
+};
+
+const char* const STAT_NAMES[S_NUM_STATS] = {
+  "snt",
+  "snt-r",
+  "rcv"
+  "rcv-n",
+  "rcv-o"
+};
+
+int g_stats[S_NUM_STATS];
+inline void Incr(Stat s) { ++g_stats[s]; }
+void ReportStats() {
+  char buffer[256];
+  size_t len = 0;
+  for (int i = 0; i < S_NUM_STATS; ++i) {
+    len += snprintf(buffer, arraysize(buffer), "%s%s:%d",
+                          (i == 0) ? "" : ",", STAT_NAMES[i], g_stats[i]);
+    g_stats[i] = 0;
+  }
+  RTC_LOG(LS_INFO) << "Stats[" << buffer << "]";
+}
+
+#endif
+
+//////////////////////////////////////////////////////////////////////
+// PseudoTcp
+//////////////////////////////////////////////////////////////////////
+
+uint32_t PseudoTcp::Now() {
+#if 0  // Use this to synchronize timers with logging timestamps (easier debug)
+  return static_cast<uint32_t>(rtc::TimeSince(StartTime()));
+#else
+  return rtc::Time32();
+#endif
+}
+
+PseudoTcp::PseudoTcp(IPseudoTcpNotify* notify, uint32_t conv)
+    : m_notify(notify),
+      m_shutdown(SD_NONE),
+      m_error(0),
+      m_rbuf_len(DEFAULT_RCV_BUF_SIZE),
+      m_rbuf(m_rbuf_len),
+      m_sbuf_len(DEFAULT_SND_BUF_SIZE),
+      m_sbuf(m_sbuf_len) {
+  // Sanity check on buffer sizes (needed for OnTcpWriteable notification logic)
+  RTC_DCHECK(m_rbuf_len + MIN_PACKET < m_sbuf_len);
+
+  uint32_t now = Now();
+
+  m_state = TCP_LISTEN;
+  m_conv = conv;
+  m_rcv_wnd = m_rbuf_len;
+  m_rwnd_scale = m_swnd_scale = 0;
+  m_snd_nxt = 0;
+  m_snd_wnd = 1;
+  m_snd_una = m_rcv_nxt = 0;
+  m_bReadEnable = true;
+  m_bWriteEnable = false;
+  m_t_ack = 0;
+
+  m_msslevel = 0;
+  m_largest = 0;
+  RTC_DCHECK(MIN_PACKET > PACKET_OVERHEAD);
+  m_mss = MIN_PACKET - PACKET_OVERHEAD;
+  m_mtu_advise = MAX_PACKET;
+
+  m_rto_base = 0;
+
+  m_cwnd = 2 * m_mss;
+  m_ssthresh = m_rbuf_len;
+  m_lastrecv = m_lastsend = m_lasttraffic = now;
+  m_bOutgoing = false;
+
+  m_dup_acks = 0;
+  m_recover = 0;
+
+  m_ts_recent = m_ts_lastack = 0;
+
+  m_rx_rto = DEF_RTO;
+  m_rx_srtt = m_rx_rttvar = 0;
+
+  m_use_nagling = true;
+  m_ack_delay = DEF_ACK_DELAY;
+  m_support_wnd_scale = true;
+}
+
+PseudoTcp::~PseudoTcp() {}
+
+int PseudoTcp::Connect() {
+  if (m_state != TCP_LISTEN) {
+    m_error = EINVAL;
+    return -1;
+  }
+
+  m_state = TCP_SYN_SENT;
+  RTC_LOG(LS_INFO) << "State: TCP_SYN_SENT";
+
+  queueConnectMessage();
+  attemptSend();
+
+  return 0;
+}
+
+void PseudoTcp::NotifyMTU(uint16_t mtu) {
+  m_mtu_advise = mtu;
+  if (m_state == TCP_ESTABLISHED) {
+    adjustMTU();
+  }
+}
+
+void PseudoTcp::NotifyClock(uint32_t now) {
+  if (m_state == TCP_CLOSED)
+    return;
+
+  // Check if it's time to retransmit a segment
+  if (m_rto_base && (rtc::TimeDiff32(m_rto_base + m_rx_rto, now) <= 0)) {
+    if (m_slist.empty()) {
+      RTC_DCHECK_NOTREACHED();
+    } else {
+// Note: (m_slist.front().xmit == 0)) {
+// retransmit segments
+#if _DEBUGMSG >= _DBG_NORMAL
+      RTC_LOG(LS_INFO) << "timeout retransmit (rto: " << m_rx_rto
+                       << ") (rto_base: " << m_rto_base << ") (now: " << now
+                       << ") (dup_acks: " << static_cast<unsigned>(m_dup_acks)
+                       << ")";
+#endif  // _DEBUGMSG
+      if (!transmit(m_slist.begin(), now)) {
+        closedown(ECONNABORTED);
+        return;
+      }
+
+      uint32_t nInFlight = m_snd_nxt - m_snd_una;
+      m_ssthresh = std::max(nInFlight / 2, 2 * m_mss);
+      // RTC_LOG(LS_INFO) << "m_ssthresh: " << m_ssthresh << "  nInFlight: " <<
+      // nInFlight << "  m_mss: " << m_mss;
+      m_cwnd = m_mss;
+
+      // Back off retransmit timer.  Note: the limit is lower when connecting.
+      uint32_t rto_limit = (m_state < TCP_ESTABLISHED) ? DEF_RTO : MAX_RTO;
+      m_rx_rto = std::min(rto_limit, m_rx_rto * 2);
+      m_rto_base = now;
+    }
+  }
+
+  // Check if it's time to probe closed windows
+  if ((m_snd_wnd == 0) && (rtc::TimeDiff32(m_lastsend + m_rx_rto, now) <= 0)) {
+    if (rtc::TimeDiff32(now, m_lastrecv) >= 15000) {
+      closedown(ECONNABORTED);
+      return;
+    }
+
+    // probe the window
+    packet(m_snd_nxt - 1, 0, 0, 0);
+    m_lastsend = now;
+
+    // back off retransmit timer
+    m_rx_rto = std::min(MAX_RTO, m_rx_rto * 2);
+  }
+
+  // Check if it's time to send delayed acks
+  if (m_t_ack && (rtc::TimeDiff32(m_t_ack + m_ack_delay, now) <= 0)) {
+    packet(m_snd_nxt, 0, 0, 0);
+  }
+
+#if PSEUDO_KEEPALIVE
+  // Check for idle timeout
+  if ((m_state == TCP_ESTABLISHED) &&
+      (TimeDiff32(m_lastrecv + IDLE_TIMEOUT, now) <= 0)) {
+    closedown(ECONNABORTED);
+    return;
+  }
+
+  // Check for ping timeout (to keep udp mapping open)
+  if ((m_state == TCP_ESTABLISHED) &&
+      (TimeDiff32(m_lasttraffic + (m_bOutgoing ? IDLE_PING * 3 / 2 : IDLE_PING),
+                  now) <= 0)) {
+    packet(m_snd_nxt, 0, 0, 0);
+  }
+#endif  // PSEUDO_KEEPALIVE
+}
+
+bool PseudoTcp::NotifyPacket(const char* buffer, size_t len) {
+  if (len > MAX_PACKET) {
+    RTC_LOG_F(LS_WARNING) << "packet too large";
+    return false;
+  }
+  return parse(reinterpret_cast<const uint8_t*>(buffer), uint32_t(len));
+}
+
+bool PseudoTcp::GetNextClock(uint32_t now, long& timeout) {
+  return clock_check(now, timeout);
+}
+
+void PseudoTcp::GetOption(Option opt, int* value) {
+  if (opt == OPT_NODELAY) {
+    *value = m_use_nagling ? 0 : 1;
+  } else if (opt == OPT_ACKDELAY) {
+    *value = m_ack_delay;
+  } else if (opt == OPT_SNDBUF) {
+    *value = m_sbuf_len;
+  } else if (opt == OPT_RCVBUF) {
+    *value = m_rbuf_len;
+  } else {
+    RTC_DCHECK_NOTREACHED();
+  }
+}
+void PseudoTcp::SetOption(Option opt, int value) {
+  if (opt == OPT_NODELAY) {
+    m_use_nagling = value == 0;
+  } else if (opt == OPT_ACKDELAY) {
+    m_ack_delay = value;
+  } else if (opt == OPT_SNDBUF) {
+    RTC_DCHECK(m_state == TCP_LISTEN);
+    resizeSendBuffer(value);
+  } else if (opt == OPT_RCVBUF) {
+    RTC_DCHECK(m_state == TCP_LISTEN);
+    resizeReceiveBuffer(value);
+  } else {
+    RTC_DCHECK_NOTREACHED();
+  }
+}
+
+uint32_t PseudoTcp::GetCongestionWindow() const {
+  return m_cwnd;
+}
+
+uint32_t PseudoTcp::GetBytesInFlight() const {
+  return m_snd_nxt - m_snd_una;
+}
+
+uint32_t PseudoTcp::GetBytesBufferedNotSent() const {
+  return static_cast<uint32_t>(m_snd_una + m_sbuf.GetBuffered() - m_snd_nxt);
+}
+
+uint32_t PseudoTcp::GetRoundTripTimeEstimateMs() const {
+  return m_rx_srtt;
+}
+
+//
+// IPStream Implementation
+//
+
+int PseudoTcp::Recv(char* buffer, size_t len) {
+  if (m_state != TCP_ESTABLISHED) {
+    m_error = ENOTCONN;
+    return SOCKET_ERROR;
+  }
+
+  size_t read = 0;
+  if (!m_rbuf.Read(buffer, len, &read)) {
+    m_bReadEnable = true;
+    m_error = EWOULDBLOCK;
+    return SOCKET_ERROR;
+  }
+
+  size_t available_space = 0;
+  m_rbuf.GetWriteRemaining(&available_space);
+
+  if (uint32_t(available_space) - m_rcv_wnd >=
+      std::min<uint32_t>(m_rbuf_len / 2, m_mss)) {
+    // TODO(jbeda): !?! Not sure about this was closed business
+    bool bWasClosed = (m_rcv_wnd == 0);
+    m_rcv_wnd = static_cast<uint32_t>(available_space);
+
+    if (bWasClosed) {
+      attemptSend(sfImmediateAck);
+    }
+  }
+
+  return static_cast<int>(read);
+}
+
+int PseudoTcp::Send(const char* buffer, size_t len) {
+  if (m_state != TCP_ESTABLISHED) {
+    m_error = ENOTCONN;
+    return SOCKET_ERROR;
+  }
+
+  size_t available_space = 0;
+  m_sbuf.GetWriteRemaining(&available_space);
+
+  if (!available_space) {
+    m_bWriteEnable = true;
+    m_error = EWOULDBLOCK;
+    return SOCKET_ERROR;
+  }
+
+  int written = queue(buffer, uint32_t(len), false);
+  attemptSend();
+  return written;
+}
+
+void PseudoTcp::Close(bool force) {
+  RTC_LOG_F(LS_VERBOSE) << "(" << (force ? "true" : "false") << ")";
+  m_shutdown = force ? SD_FORCEFUL : SD_GRACEFUL;
+}
+
+int PseudoTcp::GetError() {
+  return m_error;
+}
+
+//
+// Internal Implementation
+//
+
+uint32_t PseudoTcp::queue(const char* data, uint32_t len, bool bCtrl) {
+  size_t available_space = 0;
+  m_sbuf.GetWriteRemaining(&available_space);
+
+  if (len > static_cast<uint32_t>(available_space)) {
+    RTC_DCHECK(!bCtrl);
+    len = static_cast<uint32_t>(available_space);
+  }
+
+  // We can concatenate data if the last segment is the same type
+  // (control v. regular data), and has not been transmitted yet
+  if (!m_slist.empty() && (m_slist.back().bCtrl == bCtrl) &&
+      (m_slist.back().xmit == 0)) {
+    m_slist.back().len += len;
+  } else {
+    SSegment sseg(static_cast<uint32_t>(m_snd_una + m_sbuf.GetBuffered()), len,
+                  bCtrl);
+    m_slist.push_back(sseg);
+  }
+
+  size_t written = 0;
+  m_sbuf.Write(data, len, &written);
+  return static_cast<uint32_t>(written);
+}
+
+IPseudoTcpNotify::WriteResult PseudoTcp::packet(uint32_t seq,
+                                                uint8_t flags,
+                                                uint32_t offset,
+                                                uint32_t len) {
+  RTC_DCHECK(HEADER_SIZE + len <= MAX_PACKET);
+
+  uint32_t now = Now();
+
+  std::unique_ptr<uint8_t[]> buffer(new uint8_t[MAX_PACKET]);
+  long_to_bytes(m_conv, buffer.get());
+  long_to_bytes(seq, buffer.get() + 4);
+  long_to_bytes(m_rcv_nxt, buffer.get() + 8);
+  buffer[12] = 0;
+  buffer[13] = flags;
+  short_to_bytes(static_cast<uint16_t>(m_rcv_wnd >> m_rwnd_scale),
+                 buffer.get() + 14);
+
+  // Timestamp computations
+  long_to_bytes(now, buffer.get() + 16);
+  long_to_bytes(m_ts_recent, buffer.get() + 20);
+  m_ts_lastack = m_rcv_nxt;
+
+  if (len) {
+    size_t bytes_read = 0;
+    bool result =
+        m_sbuf.ReadOffset(buffer.get() + HEADER_SIZE, len, offset, &bytes_read);
+    RTC_DCHECK(result);
+    RTC_DCHECK(static_cast<uint32_t>(bytes_read) == len);
+  }
+
+#if _DEBUGMSG >= _DBG_VERBOSE
+  RTC_LOG(LS_INFO) << "<-- <CONV=" << m_conv
+                   << "><FLG=" << static_cast<unsigned>(flags)
+                   << "><SEQ=" << seq << ":" << seq + len
+                   << "><ACK=" << m_rcv_nxt << "><WND=" << m_rcv_wnd
+                   << "><TS=" << (now % 10000)
+                   << "><TSR=" << (m_ts_recent % 10000) << "><LEN=" << len
+                   << ">";
+#endif  // _DEBUGMSG
+
+  IPseudoTcpNotify::WriteResult wres = m_notify->TcpWritePacket(
+      this, reinterpret_cast<char*>(buffer.get()), len + HEADER_SIZE);
+  // Note: When len is 0, this is an ACK packet.  We don't read the return value
+  // for those, and thus we won't retry.  So go ahead and treat the packet as a
+  // success (basically simulate as if it were dropped), which will prevent our
+  // timers from being messed up.
+  if ((wres != IPseudoTcpNotify::WR_SUCCESS) && (0 != len))
+    return wres;
+
+  m_t_ack = 0;
+  if (len > 0) {
+    m_lastsend = now;
+  }
+  m_lasttraffic = now;
+  m_bOutgoing = true;
+
+  return IPseudoTcpNotify::WR_SUCCESS;
+}
+
+bool PseudoTcp::parse(const uint8_t* buffer, uint32_t size) {
+  if (size < HEADER_SIZE)
+    return false;
+
+  Segment seg;
+  seg.conv = bytes_to_long(buffer);
+  seg.seq = bytes_to_long(buffer + 4);
+  seg.ack = bytes_to_long(buffer + 8);
+  seg.flags = buffer[13];
+  seg.wnd = bytes_to_short(buffer + 14);
+
+  seg.tsval = bytes_to_long(buffer + 16);
+  seg.tsecr = bytes_to_long(buffer + 20);
+
+  seg.data = reinterpret_cast<const char*>(buffer) + HEADER_SIZE;
+  seg.len = size - HEADER_SIZE;
+
+#if _DEBUGMSG >= _DBG_VERBOSE
+  RTC_LOG(LS_INFO) << "--> <CONV=" << seg.conv
+                   << "><FLG=" << static_cast<unsigned>(seg.flags)
+                   << "><SEQ=" << seg.seq << ":" << seg.seq + seg.len
+                   << "><ACK=" << seg.ack << "><WND=" << seg.wnd
+                   << "><TS=" << (seg.tsval % 10000)
+                   << "><TSR=" << (seg.tsecr % 10000) << "><LEN=" << seg.len
+                   << ">";
+#endif  // _DEBUGMSG
+
+  return process(seg);
+}
+
+bool PseudoTcp::clock_check(uint32_t now, long& nTimeout) {
+  if (m_shutdown == SD_FORCEFUL)
+    return false;
+
+  if ((m_shutdown == SD_GRACEFUL) &&
+      ((m_state != TCP_ESTABLISHED) ||
+       ((m_sbuf.GetBuffered() == 0) && (m_t_ack == 0)))) {
+    return false;
+  }
+
+  if (m_state == TCP_CLOSED) {
+    nTimeout = CLOSED_TIMEOUT;
+    return true;
+  }
+
+  nTimeout = DEFAULT_TIMEOUT;
+
+  if (m_t_ack) {
+    nTimeout = std::min<int32_t>(nTimeout,
+                                 rtc::TimeDiff32(m_t_ack + m_ack_delay, now));
+  }
+  if (m_rto_base) {
+    nTimeout = std::min<int32_t>(nTimeout,
+                                 rtc::TimeDiff32(m_rto_base + m_rx_rto, now));
+  }
+  if (m_snd_wnd == 0) {
+    nTimeout = std::min<int32_t>(nTimeout,
+                                 rtc::TimeDiff32(m_lastsend + m_rx_rto, now));
+  }
+#if PSEUDO_KEEPALIVE
+  if (m_state == TCP_ESTABLISHED) {
+    nTimeout = std::min<int32_t>(
+        nTimeout,
+        rtc::TimeDiff32(
+            m_lasttraffic + (m_bOutgoing ? IDLE_PING * 3 / 2 : IDLE_PING),
+            now));
+  }
+#endif  // PSEUDO_KEEPALIVE
+  return true;
+}
+
+bool PseudoTcp::process(Segment& seg) {
+  // If this is the wrong conversation, send a reset!?! (with the correct
+  // conversation?)
+  if (seg.conv != m_conv) {
+    // if ((seg.flags & FLAG_RST) == 0) {
+    //  packet(tcb, seg.ack, 0, FLAG_RST, 0, 0);
+    //}
+    RTC_LOG_F(LS_ERROR) << "wrong conversation";
+    return false;
+  }
+
+  uint32_t now = Now();
+  m_lasttraffic = m_lastrecv = now;
+  m_bOutgoing = false;
+
+  if (m_state == TCP_CLOSED) {
+    // !?! send reset?
+    RTC_LOG_F(LS_ERROR) << "closed";
+    return false;
+  }
+
+  // Check if this is a reset segment
+  if (seg.flags & FLAG_RST) {
+    closedown(ECONNRESET);
+    return false;
+  }
+
+  // Check for control data
+  bool bConnect = false;
+  if (seg.flags & FLAG_CTL) {
+    if (seg.len == 0) {
+      RTC_LOG_F(LS_ERROR) << "Missing control code";
+      return false;
+    } else if (seg.data[0] == CTL_CONNECT) {
+      bConnect = true;
+
+      // TCP options are in the remainder of the payload after CTL_CONNECT.
+      parseOptions(&seg.data[1], seg.len - 1);
+
+      if (m_state == TCP_LISTEN) {
+        m_state = TCP_SYN_RECEIVED;
+        RTC_LOG(LS_INFO) << "State: TCP_SYN_RECEIVED";
+        // m_notify->associate(addr);
+        queueConnectMessage();
+      } else if (m_state == TCP_SYN_SENT) {
+        m_state = TCP_ESTABLISHED;
+        RTC_LOG(LS_INFO) << "State: TCP_ESTABLISHED";
+        adjustMTU();
+        if (m_notify) {
+          m_notify->OnTcpOpen(this);
+        }
+        // notify(evOpen);
+      }
+    } else {
+      RTC_LOG_F(LS_WARNING) << "Unknown control code: " << seg.data[0];
+      return false;
+    }
+  }
+
+  // Update timestamp
+  if ((seg.seq <= m_ts_lastack) && (m_ts_lastack < seg.seq + seg.len)) {
+    m_ts_recent = seg.tsval;
+  }
+
+  // Check if this is a valuable ack
+  if ((seg.ack > m_snd_una) && (seg.ack <= m_snd_nxt)) {
+    // Calculate round-trip time
+    if (seg.tsecr) {
+      int32_t rtt = rtc::TimeDiff32(now, seg.tsecr);
+      if (rtt >= 0) {
+        if (m_rx_srtt == 0) {
+          m_rx_srtt = rtt;
+          m_rx_rttvar = rtt / 2;
+        } else {
+          uint32_t unsigned_rtt = static_cast<uint32_t>(rtt);
+          uint32_t abs_err = unsigned_rtt > m_rx_srtt
+                                 ? unsigned_rtt - m_rx_srtt
+                                 : m_rx_srtt - unsigned_rtt;
+          m_rx_rttvar = (3 * m_rx_rttvar + abs_err) / 4;
+          m_rx_srtt = (7 * m_rx_srtt + rtt) / 8;
+        }
+        m_rx_rto = rtc::SafeClamp(m_rx_srtt + rtc::SafeMax(1, 4 * m_rx_rttvar),
+                                  MIN_RTO, MAX_RTO);
+#if _DEBUGMSG >= _DBG_VERBOSE
+        RTC_LOG(LS_INFO) << "rtt: " << rtt << "  srtt: " << m_rx_srtt
+                         << "  rto: " << m_rx_rto;
+#endif  // _DEBUGMSG
+      } else {
+        RTC_LOG(LS_WARNING) << "rtt < 0";
+      }
+    }
+
+    m_snd_wnd = static_cast<uint32_t>(seg.wnd) << m_swnd_scale;
+
+    uint32_t nAcked = seg.ack - m_snd_una;
+    m_snd_una = seg.ack;
+
+    m_rto_base = (m_snd_una == m_snd_nxt) ? 0 : now;
+
+    m_sbuf.ConsumeReadData(nAcked);
+
+    for (uint32_t nFree = nAcked; nFree > 0;) {
+      RTC_DCHECK(!m_slist.empty());
+      if (nFree < m_slist.front().len) {
+        m_slist.front().len -= nFree;
+        nFree = 0;
+      } else {
+        if (m_slist.front().len > m_largest) {
+          m_largest = m_slist.front().len;
+        }
+        nFree -= m_slist.front().len;
+        m_slist.pop_front();
+      }
+    }
+
+    if (m_dup_acks >= 3) {
+      if (m_snd_una >= m_recover) {  // NewReno
+        uint32_t nInFlight = m_snd_nxt - m_snd_una;
+        m_cwnd = std::min(m_ssthresh, nInFlight + m_mss);  // (Fast Retransmit)
+#if _DEBUGMSG >= _DBG_NORMAL
+        RTC_LOG(LS_INFO) << "exit recovery";
+#endif  // _DEBUGMSG
+        m_dup_acks = 0;
+      } else {
+#if _DEBUGMSG >= _DBG_NORMAL
+        RTC_LOG(LS_INFO) << "recovery retransmit";
+#endif  // _DEBUGMSG
+        if (!transmit(m_slist.begin(), now)) {
+          closedown(ECONNABORTED);
+          return false;
+        }
+        m_cwnd += m_mss - std::min(nAcked, m_cwnd);
+      }
+    } else {
+      m_dup_acks = 0;
+      // Slow start, congestion avoidance
+      if (m_cwnd < m_ssthresh) {
+        m_cwnd += m_mss;
+      } else {
+        m_cwnd += std::max<uint32_t>(1, m_mss * m_mss / m_cwnd);
+      }
+    }
+  } else if (seg.ack == m_snd_una) {
+    // !?! Note, tcp says don't do this... but otherwise how does a closed
+    // window become open?
+    m_snd_wnd = static_cast<uint32_t>(seg.wnd) << m_swnd_scale;
+
+    // Check duplicate acks
+    if (seg.len > 0) {
+      // it's a dup ack, but with a data payload, so don't modify m_dup_acks
+    } else if (m_snd_una != m_snd_nxt) {
+      m_dup_acks += 1;
+      if (m_dup_acks == 3) {  // (Fast Retransmit)
+#if _DEBUGMSG >= _DBG_NORMAL
+        RTC_LOG(LS_INFO) << "enter recovery";
+        RTC_LOG(LS_INFO) << "recovery retransmit";
+#endif  // _DEBUGMSG
+        if (!transmit(m_slist.begin(), now)) {
+          closedown(ECONNABORTED);
+          return false;
+        }
+        m_recover = m_snd_nxt;
+        uint32_t nInFlight = m_snd_nxt - m_snd_una;
+        m_ssthresh = std::max(nInFlight / 2, 2 * m_mss);
+        // RTC_LOG(LS_INFO) << "m_ssthresh: " << m_ssthresh << "  nInFlight: "
+        // << nInFlight << "  m_mss: " << m_mss;
+        m_cwnd = m_ssthresh + 3 * m_mss;
+      } else if (m_dup_acks > 3) {
+        m_cwnd += m_mss;
+      }
+    } else {
+      m_dup_acks = 0;
+    }
+  }
+
+  // !?! A bit hacky
+  if ((m_state == TCP_SYN_RECEIVED) && !bConnect) {
+    m_state = TCP_ESTABLISHED;
+    RTC_LOG(LS_INFO) << "State: TCP_ESTABLISHED";
+    adjustMTU();
+    if (m_notify) {
+      m_notify->OnTcpOpen(this);
+    }
+    // notify(evOpen);
+  }
+
+  // If we make room in the send queue, notify the user
+  // The goal it to make sure we always have at least enough data to fill the
+  // window.  We'd like to notify the app when we are halfway to that point.
+  const uint32_t kIdealRefillSize = (m_sbuf_len + m_rbuf_len) / 2;
+  if (m_bWriteEnable &&
+      static_cast<uint32_t>(m_sbuf.GetBuffered()) < kIdealRefillSize) {
+    m_bWriteEnable = false;
+    if (m_notify) {
+      m_notify->OnTcpWriteable(this);
+    }
+    // notify(evWrite);
+  }
+
+  // Conditions were acks must be sent:
+  // 1) Segment is too old (they missed an ACK) (immediately)
+  // 2) Segment is too new (we missed a segment) (immediately)
+  // 3) Segment has data (so we need to ACK!) (delayed)
+  // ... so the only time we don't need to ACK, is an empty segment that points
+  // to rcv_nxt!
+
+  SendFlags sflags = sfNone;
+  if (seg.seq != m_rcv_nxt) {
+    sflags = sfImmediateAck;  // (Fast Recovery)
+  } else if (seg.len != 0) {
+    if (m_ack_delay == 0) {
+      sflags = sfImmediateAck;
+    } else {
+      sflags = sfDelayedAck;
+    }
+  }
+#if _DEBUGMSG >= _DBG_NORMAL
+  if (sflags == sfImmediateAck) {
+    if (seg.seq > m_rcv_nxt) {
+      RTC_LOG_F(LS_INFO) << "too new";
+    } else if (seg.seq + seg.len <= m_rcv_nxt) {
+      RTC_LOG_F(LS_INFO) << "too old";
+    }
+  }
+#endif  // _DEBUGMSG
+
+  // Adjust the incoming segment to fit our receive buffer
+  if (seg.seq < m_rcv_nxt) {
+    uint32_t nAdjust = m_rcv_nxt - seg.seq;
+    if (nAdjust < seg.len) {
+      seg.seq += nAdjust;
+      seg.data += nAdjust;
+      seg.len -= nAdjust;
+    } else {
+      seg.len = 0;
+    }
+  }
+
+  size_t available_space = 0;
+  m_rbuf.GetWriteRemaining(&available_space);
+
+  if ((seg.seq + seg.len - m_rcv_nxt) >
+      static_cast<uint32_t>(available_space)) {
+    uint32_t nAdjust =
+        seg.seq + seg.len - m_rcv_nxt - static_cast<uint32_t>(available_space);
+    if (nAdjust < seg.len) {
+      seg.len -= nAdjust;
+    } else {
+      seg.len = 0;
+    }
+  }
+
+  bool bIgnoreData = (seg.flags & FLAG_CTL) || (m_shutdown != SD_NONE);
+  bool bNewData = false;
+
+  if (seg.len > 0) {
+    bool bRecover = false;
+    if (bIgnoreData) {
+      if (seg.seq == m_rcv_nxt) {
+        m_rcv_nxt += seg.len;
+        // If we received a data segment out of order relative to a control
+        // segment, then we wrote it into the receive buffer at an offset (see
+        // "WriteOffset") below. So we need to advance the position in the
+        // buffer to avoid corrupting data. See bugs.webrtc.org/9208
+        //
+        // We advance the position in the buffer by N bytes by acting like we
+        // wrote N bytes and then immediately read them. We can only do this if
+        // there's not already data ready to read, but this should always be
+        // true in the problematic scenario, since control frames are always
+        // sent first in the stream.
+        if (m_rbuf.GetBuffered() == 0) {
+          m_rbuf.ConsumeWriteBuffer(seg.len);
+          m_rbuf.ConsumeReadData(seg.len);
+          // After shifting the position in the buffer, we may have
+          // out-of-order packets ready to be recovered.
+          bRecover = true;
+        }
+      }
+    } else {
+      uint32_t nOffset = seg.seq - m_rcv_nxt;
+
+      if (!m_rbuf.WriteOffset(seg.data, seg.len, nOffset, NULL)) {
+        // Ignore incoming packets outside of the receive window.
+        return false;
+      }
+
+      if (seg.seq == m_rcv_nxt) {
+        m_rbuf.ConsumeWriteBuffer(seg.len);
+        m_rcv_nxt += seg.len;
+        m_rcv_wnd -= seg.len;
+        bNewData = true;
+        // May be able to recover packets previously received out-of-order
+        // now.
+        bRecover = true;
+      } else {
+#if _DEBUGMSG >= _DBG_NORMAL
+        RTC_LOG(LS_INFO) << "Saving " << seg.len << " bytes (" << seg.seq
+                         << " -> " << seg.seq + seg.len << ")";
+#endif  // _DEBUGMSG
+        RSegment rseg;
+        rseg.seq = seg.seq;
+        rseg.len = seg.len;
+        RList::iterator it = m_rlist.begin();
+        while ((it != m_rlist.end()) && (it->seq < rseg.seq)) {
+          ++it;
+        }
+        m_rlist.insert(it, rseg);
+      }
+    }
+    if (bRecover) {
+      RList::iterator it = m_rlist.begin();
+      while ((it != m_rlist.end()) && (it->seq <= m_rcv_nxt)) {
+        if (it->seq + it->len > m_rcv_nxt) {
+          sflags = sfImmediateAck;  // (Fast Recovery)
+          uint32_t nAdjust = (it->seq + it->len) - m_rcv_nxt;
+#if _DEBUGMSG >= _DBG_NORMAL
+          RTC_LOG(LS_INFO) << "Recovered " << nAdjust << " bytes (" << m_rcv_nxt
+                           << " -> " << m_rcv_nxt + nAdjust << ")";
+#endif  // _DEBUGMSG
+          m_rbuf.ConsumeWriteBuffer(nAdjust);
+          m_rcv_nxt += nAdjust;
+          m_rcv_wnd -= nAdjust;
+          bNewData = true;
+        }
+        it = m_rlist.erase(it);
+      }
+    }
+  }
+
+  attemptSend(sflags);
+
+  // If we have new data, notify the user
+  if (bNewData && m_bReadEnable) {
+    m_bReadEnable = false;
+    if (m_notify) {
+      m_notify->OnTcpReadable(this);
+    }
+    // notify(evRead);
+  }
+
+  return true;
+}
+
+bool PseudoTcp::transmit(const SList::iterator& seg, uint32_t now) {
+  if (seg->xmit >= ((m_state == TCP_ESTABLISHED) ? 15 : 30)) {
+    RTC_LOG_F(LS_VERBOSE) << "too many retransmits";
+    return false;
+  }
+
+  uint32_t nTransmit = std::min(seg->len, m_mss);
+
+  while (true) {
+    uint32_t seq = seg->seq;
+    uint8_t flags = (seg->bCtrl ? FLAG_CTL : 0);
+    IPseudoTcpNotify::WriteResult wres =
+        packet(seq, flags, seg->seq - m_snd_una, nTransmit);
+
+    if (wres == IPseudoTcpNotify::WR_SUCCESS)
+      break;
+
+    if (wres == IPseudoTcpNotify::WR_FAIL) {
+      RTC_LOG_F(LS_VERBOSE) << "packet failed";
+      return false;
+    }
+
+    RTC_DCHECK(wres == IPseudoTcpNotify::WR_TOO_LARGE);
+
+    while (true) {
+      if (PACKET_MAXIMUMS[m_msslevel + 1] == 0) {
+        RTC_LOG_F(LS_VERBOSE) << "MTU too small";
+        return false;
+      }
+      // !?! We need to break up all outstanding and pending packets and then
+      // retransmit!?!
+
+      m_mss = PACKET_MAXIMUMS[++m_msslevel] - PACKET_OVERHEAD;
+      m_cwnd = 2 * m_mss;  // I added this... haven't researched actual formula
+      if (m_mss < nTransmit) {
+        nTransmit = m_mss;
+        break;
+      }
+    }
+#if _DEBUGMSG >= _DBG_NORMAL
+    RTC_LOG(LS_INFO) << "Adjusting mss to " << m_mss << " bytes";
+#endif  // _DEBUGMSG
+  }
+
+  if (nTransmit < seg->len) {
+    RTC_LOG_F(LS_VERBOSE) << "mss reduced to " << m_mss;
+
+    SSegment subseg(seg->seq + nTransmit, seg->len - nTransmit, seg->bCtrl);
+    // subseg.tstamp = seg->tstamp;
+    subseg.xmit = seg->xmit;
+    seg->len = nTransmit;
+
+    SList::iterator next = seg;
+    m_slist.insert(++next, subseg);
+  }
+
+  if (seg->xmit == 0) {
+    m_snd_nxt += seg->len;
+  }
+  seg->xmit += 1;
+  // seg->tstamp = now;
+  if (m_rto_base == 0) {
+    m_rto_base = now;
+  }
+
+  return true;
+}
+
+void PseudoTcp::attemptSend(SendFlags sflags) {
+  uint32_t now = Now();
+
+  if (rtc::TimeDiff32(now, m_lastsend) > static_cast<long>(m_rx_rto)) {
+    m_cwnd = m_mss;
+  }
+
+#if _DEBUGMSG
+  bool bFirst = true;
+#endif  // _DEBUGMSG
+
+  while (true) {
+    uint32_t cwnd = m_cwnd;
+    if ((m_dup_acks == 1) || (m_dup_acks == 2)) {  // Limited Transmit
+      cwnd += m_dup_acks * m_mss;
+    }
+    uint32_t nWindow = std::min(m_snd_wnd, cwnd);
+    uint32_t nInFlight = m_snd_nxt - m_snd_una;
+    uint32_t nUseable = (nInFlight < nWindow) ? (nWindow - nInFlight) : 0;
+
+    size_t snd_buffered = m_sbuf.GetBuffered();
+    uint32_t nAvailable =
+        std::min(static_cast<uint32_t>(snd_buffered) - nInFlight, m_mss);
+
+    if (nAvailable > nUseable) {
+      if (nUseable * 4 < nWindow) {
+        // RFC 813 - avoid SWS
+        nAvailable = 0;
+      } else {
+        nAvailable = nUseable;
+      }
+    }
+
+#if _DEBUGMSG >= _DBG_VERBOSE
+    if (bFirst) {
+      size_t available_space = 0;
+      m_sbuf.GetWriteRemaining(&available_space);
+
+      bFirst = false;
+      RTC_LOG(LS_INFO) << "[cwnd: " << m_cwnd << "  nWindow: " << nWindow
+                       << "  nInFlight: " << nInFlight
+                       << "  nAvailable: " << nAvailable
+                       << "  nQueued: " << snd_buffered
+                       << "  nEmpty: " << available_space
+                       << "  ssthresh: " << m_ssthresh << "]";
+    }
+#endif  // _DEBUGMSG
+
+    if (nAvailable == 0) {
+      if (sflags == sfNone)
+        return;
+
+      // If this is an immediate ack, or the second delayed ack
+      if ((sflags == sfImmediateAck) || m_t_ack) {
+        packet(m_snd_nxt, 0, 0, 0);
+      } else {
+        m_t_ack = Now();
+      }
+      return;
+    }
+
+    // Nagle's algorithm.
+    // If there is data already in-flight, and we haven't a full segment of
+    // data ready to send then hold off until we get more to send, or the
+    // in-flight data is acknowledged.
+    if (m_use_nagling && (m_snd_nxt > m_snd_una) && (nAvailable < m_mss)) {
+      return;
+    }
+
+    // Find the next segment to transmit
+    SList::iterator it = m_slist.begin();
+    while (it->xmit > 0) {
+      ++it;
+      RTC_DCHECK(it != m_slist.end());
+    }
+    SList::iterator seg = it;
+
+    // If the segment is too large, break it into two
+    if (seg->len > nAvailable) {
+      SSegment subseg(seg->seq + nAvailable, seg->len - nAvailable, seg->bCtrl);
+      seg->len = nAvailable;
+      m_slist.insert(++it, subseg);
+    }
+
+    if (!transmit(seg, now)) {
+      RTC_LOG_F(LS_VERBOSE) << "transmit failed";
+      // TODO(?): consider closing socket
+      return;
+    }
+
+    sflags = sfNone;
+  }
+}
+
+void PseudoTcp::closedown(uint32_t err) {
+  RTC_LOG(LS_INFO) << "State: TCP_CLOSED";
+  m_state = TCP_CLOSED;
+  if (m_notify) {
+    m_notify->OnTcpClosed(this, err);
+  }
+  // notify(evClose, err);
+}
+
+void PseudoTcp::adjustMTU() {
+  // Determine our current mss level, so that we can adjust appropriately later
+  for (m_msslevel = 0; PACKET_MAXIMUMS[m_msslevel + 1] > 0; ++m_msslevel) {
+    if (static_cast<uint16_t>(PACKET_MAXIMUMS[m_msslevel]) <= m_mtu_advise) {
+      break;
+    }
+  }
+  m_mss = m_mtu_advise - PACKET_OVERHEAD;
+// !?! Should we reset m_largest here?
+#if _DEBUGMSG >= _DBG_NORMAL
+  RTC_LOG(LS_INFO) << "Adjusting mss to " << m_mss << " bytes";
+#endif  // _DEBUGMSG
+  // Enforce minimums on ssthresh and cwnd
+  m_ssthresh = std::max(m_ssthresh, 2 * m_mss);
+  m_cwnd = std::max(m_cwnd, m_mss);
+}
+
+bool PseudoTcp::isReceiveBufferFull() const {
+  size_t available_space = 0;
+  m_rbuf.GetWriteRemaining(&available_space);
+  return !available_space;
+}
+
+void PseudoTcp::disableWindowScale() {
+  m_support_wnd_scale = false;
+}
+
+void PseudoTcp::queueConnectMessage() {
+  rtc::ByteBufferWriter buf;
+
+  buf.WriteUInt8(CTL_CONNECT);
+  if (m_support_wnd_scale) {
+    buf.WriteUInt8(TCP_OPT_WND_SCALE);
+    buf.WriteUInt8(1);
+    buf.WriteUInt8(m_rwnd_scale);
+  }
+  m_snd_wnd = static_cast<uint32_t>(buf.Length());
+  queue(buf.Data(), static_cast<uint32_t>(buf.Length()), true);
+}
+
+void PseudoTcp::parseOptions(const char* data, uint32_t len) {
+  std::set<uint8_t> options_specified;
+
+  // See http://www.freesoft.org/CIE/Course/Section4/8.htm for
+  // parsing the options list.
+  rtc::ByteBufferReader buf(data, len);
+  while (buf.Length()) {
+    uint8_t kind = TCP_OPT_EOL;
+    buf.ReadUInt8(&kind);
+
+    if (kind == TCP_OPT_EOL) {
+      // End of option list.
+      break;
+    } else if (kind == TCP_OPT_NOOP) {
+      // No op.
+      continue;
+    }
+
+    // Length of this option.
+    RTC_DCHECK(len != 0);
+    uint8_t opt_len = 0;
+    buf.ReadUInt8(&opt_len);
+
+    // Content of this option.
+    if (opt_len <= buf.Length()) {
+      applyOption(kind, buf.Data(), opt_len);
+      buf.Consume(opt_len);
+    } else {
+      RTC_LOG(LS_ERROR) << "Invalid option length received.";
+      return;
+    }
+    options_specified.insert(kind);
+  }
+
+  if (options_specified.find(TCP_OPT_WND_SCALE) == options_specified.end()) {
+    RTC_LOG(LS_WARNING) << "Peer doesn't support window scaling";
+
+    if (m_rwnd_scale > 0) {
+      // Peer doesn't support TCP options and window scaling.
+      // Revert receive buffer size to default value.
+      resizeReceiveBuffer(DEFAULT_RCV_BUF_SIZE);
+      m_swnd_scale = 0;
+    }
+  }
+}
+
+void PseudoTcp::applyOption(char kind, const char* data, uint32_t len) {
+  if (kind == TCP_OPT_MSS) {
+    RTC_LOG(LS_WARNING) << "Peer specified MSS option which is not supported.";
+    // TODO(?): Implement.
+  } else if (kind == TCP_OPT_WND_SCALE) {
+    // Window scale factor.
+    // http://www.ietf.org/rfc/rfc1323.txt
+    if (len != 1) {
+      RTC_LOG_F(LS_WARNING) << "Invalid window scale option received.";
+      return;
+    }
+    applyWindowScaleOption(data[0]);
+  }
+}
+
+void PseudoTcp::applyWindowScaleOption(uint8_t scale_factor) {
+  m_swnd_scale = scale_factor;
+}
+
+void PseudoTcp::resizeSendBuffer(uint32_t new_size) {
+  m_sbuf_len = new_size;
+  m_sbuf.SetCapacity(new_size);
+}
+
+void PseudoTcp::resizeReceiveBuffer(uint32_t new_size) {
+  uint8_t scale_factor = 0;
+
+  // Determine the scale factor such that the scaled window size can fit
+  // in a 16-bit unsigned integer.
+  while (new_size > 0xFFFF) {
+    ++scale_factor;
+    new_size >>= 1;
+  }
+
+  // Determine the proper size of the buffer.
+  new_size <<= scale_factor;
+  bool result = m_rbuf.SetCapacity(new_size);
+
+  // Make sure the new buffer is large enough to contain data in the old
+  // buffer. This should always be true because this method is called either
+  // before connection is established or when peers are exchanging connect
+  // messages.
+  RTC_DCHECK(result);
+  m_rbuf_len = new_size;
+  m_rwnd_scale = scale_factor;
+  m_ssthresh = new_size;
+
+  size_t available_space = 0;
+  m_rbuf.GetWriteRemaining(&available_space);
+  m_rcv_wnd = static_cast<uint32_t>(available_space);
+}
+
+PseudoTcp::LockedFifoBuffer::LockedFifoBuffer(size_t size)
+    : buffer_(new char[size]),
+      buffer_length_(size),
+      data_length_(0),
+      read_position_(0) {}
+
+PseudoTcp::LockedFifoBuffer::~LockedFifoBuffer() {}
+
+size_t PseudoTcp::LockedFifoBuffer::GetBuffered() const {
+  webrtc::MutexLock lock(&mutex_);
+  return data_length_;
+}
+
+bool PseudoTcp::LockedFifoBuffer::SetCapacity(size_t size) {
+  webrtc::MutexLock lock(&mutex_);
+  if (data_length_ > size)
+    return false;
+
+  if (size != buffer_length_) {
+    char* buffer = new char[size];
+    const size_t copy = data_length_;
+    const size_t tail_copy = std::min(copy, buffer_length_ - read_position_);
+    memcpy(buffer, &buffer_[read_position_], tail_copy);
+    memcpy(buffer + tail_copy, &buffer_[0], copy - tail_copy);
+    buffer_.reset(buffer);
+    read_position_ = 0;
+    buffer_length_ = size;
+  }
+
+  return true;
+}
+
+bool PseudoTcp::LockedFifoBuffer::ReadOffset(void* buffer,
+                                             size_t bytes,
+                                             size_t offset,
+                                             size_t* bytes_read) {
+  webrtc::MutexLock lock(&mutex_);
+  return ReadOffsetLocked(buffer, bytes, offset, bytes_read);
+}
+
+bool PseudoTcp::LockedFifoBuffer::WriteOffset(const void* buffer,
+                                              size_t bytes,
+                                              size_t offset,
+                                              size_t* bytes_written) {
+  webrtc::MutexLock lock(&mutex_);
+  return WriteOffsetLocked(buffer, bytes, offset, bytes_written);
+}
+
+bool PseudoTcp::LockedFifoBuffer::Read(void* buffer,
+                                       size_t bytes,
+                                       size_t* bytes_read) {
+  webrtc::MutexLock lock(&mutex_);
+  size_t copy = 0;
+  if (!ReadOffsetLocked(buffer, bytes, 0, &copy))
+    return false;
+
+  // If read was successful then adjust the read position and number of
+  // bytes buffered.
+  read_position_ = (read_position_ + copy) % buffer_length_;
+  data_length_ -= copy;
+  if (bytes_read)
+    *bytes_read = copy;
+
+  return true;
+}
+
+bool PseudoTcp::LockedFifoBuffer::Write(const void* buffer,
+                                        size_t bytes,
+                                        size_t* bytes_written) {
+  webrtc::MutexLock lock(&mutex_);
+  size_t copy = 0;
+  if (!WriteOffsetLocked(buffer, bytes, 0, &copy))
+    return false;
+
+  // If write was successful then adjust the number of readable bytes.
+  data_length_ += copy;
+  if (bytes_written) {
+    *bytes_written = copy;
+  }
+
+  return true;
+}
+
+void PseudoTcp::LockedFifoBuffer::ConsumeReadData(size_t size) {
+  webrtc::MutexLock lock(&mutex_);
+  RTC_DCHECK(size <= data_length_);
+  read_position_ = (read_position_ + size) % buffer_length_;
+  data_length_ -= size;
+}
+
+void PseudoTcp::LockedFifoBuffer::ConsumeWriteBuffer(size_t size) {
+  webrtc::MutexLock lock(&mutex_);
+  RTC_DCHECK(size <= buffer_length_ - data_length_);
+  data_length_ += size;
+}
+
+bool PseudoTcp::LockedFifoBuffer::GetWriteRemaining(size_t* size) const {
+  webrtc::MutexLock lock(&mutex_);
+  *size = buffer_length_ - data_length_;
+  return true;
+}
+
+bool PseudoTcp::LockedFifoBuffer::ReadOffsetLocked(void* buffer,
+                                                   size_t bytes,
+                                                   size_t offset,
+                                                   size_t* bytes_read) {
+  if (offset >= data_length_)
+    return false;
+
+  const size_t available = data_length_ - offset;
+  const size_t read_position = (read_position_ + offset) % buffer_length_;
+  const size_t copy = std::min(bytes, available);
+  const size_t tail_copy = std::min(copy, buffer_length_ - read_position);
+  char* const p = static_cast<char*>(buffer);
+  memcpy(p, &buffer_[read_position], tail_copy);
+  memcpy(p + tail_copy, &buffer_[0], copy - tail_copy);
+
+  if (bytes_read)
+    *bytes_read = copy;
+
+  return true;
+}
+
+bool PseudoTcp::LockedFifoBuffer::WriteOffsetLocked(const void* buffer,
+                                                    size_t bytes,
+                                                    size_t offset,
+                                                    size_t* bytes_written) {
+  if (data_length_ + offset >= buffer_length_)
+    return false;
+
+  const size_t available = buffer_length_ - data_length_ - offset;
+  const size_t write_position =
+      (read_position_ + data_length_ + offset) % buffer_length_;
+  const size_t copy = std::min(bytes, available);
+  const size_t tail_copy = std::min(copy, buffer_length_ - write_position);
+  const char* const p = static_cast<const char*>(buffer);
+  memcpy(&buffer_[write_position], p, tail_copy);
+  memcpy(&buffer_[0], p + tail_copy, copy - tail_copy);
+
+  if (bytes_written)
+    *bytes_written = copy;
+
+  return true;
+}
+
+}  // namespace cricket