tcp-socket-base.cc

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/*
 * Copyright (c) 2007 Georgia Tech Research Corporation
 * Copyright (c) 2010 Adrian Sai-wah Tam
 *
 * SPDX-License-Identifier: GPL-2.0-only
 *
 * Author: Adrian Sai-wah Tam <adrian.sw.tam@gmail.com>
 */
 
#define NS_LOG_APPEND_CONTEXT                                                                      \
    if (m_node)                                                                                    \
    {                                                                                              \
        std::clog << " [node " << m_node->GetId() << "] ";                                         \
    }
 
#include "tcp-socket-base.h"
 
#include "ipv4-end-point.h"
#include "ipv4-route.h"
#include "ipv4-routing-protocol.h"
#include "ipv4.h"
#include "ipv6-end-point.h"
#include "ipv6-l3-protocol.h"
#include "ipv6-route.h"
#include "ipv6-routing-protocol.h"
#include "rtt-estimator.h"
#include "tcp-congestion-ops.h"
#include "tcp-header.h"
#include "tcp-l4-protocol.h"
#include "tcp-option-sack-permitted.h"
#include "tcp-option-sack.h"
#include "tcp-option-ts.h"
#include "tcp-option-winscale.h"
#include "tcp-rate-ops.h"
#include "tcp-recovery-ops.h"
#include "tcp-rx-buffer.h"
#include "tcp-tx-buffer.h"
 
#include "ns3/abort.h"
#include "ns3/data-rate.h"
#include "ns3/double.h"
#include "ns3/inet-socket-address.h"
#include "ns3/inet6-socket-address.h"
#include "ns3/log.h"
#include "ns3/node.h"
#include "ns3/object.h"
#include "ns3/packet.h"
#include "ns3/pointer.h"
#include "ns3/simulation-singleton.h"
#include "ns3/simulator.h"
#include "ns3/trace-source-accessor.h"
#include "ns3/uinteger.h"
 
#include <algorithm>
#include <cmath>
 
namespace
{
 
/**
 * @brief map TcpPacketType and EcnMode to boolean value to check whether ECN-marking is allowed or
 * not
 */
const std::map<std::pair<ns3::TcpSocketBase::TcpPacketType_t, ns3::TcpSocketState::EcnMode_t>, bool>
    ECN_RESTRICTION_MAP{
        {{ns3::TcpSocketBase::SYN, ns3::TcpSocketState::ClassicEcn}, false},
        {{ns3::TcpSocketBase::SYN_ACK, ns3::TcpSocketState::ClassicEcn}, false},
        {{ns3::TcpSocketBase::PURE_ACK, ns3::TcpSocketState::ClassicEcn}, false},
        {{ns3::TcpSocketBase::WINDOW_PROBE, ns3::TcpSocketState::ClassicEcn}, false},
        {{ns3::TcpSocketBase::FIN, ns3::TcpSocketState::ClassicEcn}, false},
        {{ns3::TcpSocketBase::RST, ns3::TcpSocketState::ClassicEcn}, false},
        {{ns3::TcpSocketBase::RE_XMT, ns3::TcpSocketState::ClassicEcn}, false},
        {{ns3::TcpSocketBase::DATA, ns3::TcpSocketState::ClassicEcn}, true},
 
        {{ns3::TcpSocketBase::SYN, ns3::TcpSocketState::DctcpEcn}, true},
        {{ns3::TcpSocketBase::SYN_ACK, ns3::TcpSocketState::DctcpEcn}, true},
        {{ns3::TcpSocketBase::PURE_ACK, ns3::TcpSocketState::DctcpEcn}, true},
        {{ns3::TcpSocketBase::WINDOW_PROBE, ns3::TcpSocketState::DctcpEcn}, true},
        {{ns3::TcpSocketBase::FIN, ns3::TcpSocketState::DctcpEcn}, true},
        {{ns3::TcpSocketBase::RST, ns3::TcpSocketState::DctcpEcn}, true},
        {{ns3::TcpSocketBase::RE_XMT, ns3::TcpSocketState::DctcpEcn}, true},
        {{ns3::TcpSocketBase::DATA, ns3::TcpSocketState::DctcpEcn}, true},
    };
} // namespace
 
namespace ns3
{
 
NS_LOG_COMPONENT_DEFINE("TcpSocketBase");
 
NS_OBJECT_ENSURE_REGISTERED(TcpSocketBase);
 
TypeId
TcpSocketBase::GetTypeId()
{
    static TypeId tid =
        TypeId("ns3::TcpSocketBase")
            .SetParent<TcpSocket>()
            .SetGroupName("Internet")
            .AddConstructor<TcpSocketBase>()
            //    .AddAttribute ("TcpState", "State in TCP state machine",
            //                   TypeId::ATTR_GET,
            //                   EnumValue (CLOSED),
            //                   MakeEnumAccessor (&TcpSocketBase::m_state),
            //                   MakeEnumChecker (CLOSED, "Closed"))
            .AddAttribute("MaxSegLifetime",
                          "Maximum segment lifetime in seconds, use for TIME_WAIT state transition "
                          "to CLOSED state",
                          DoubleValue(120), /* RFC793 says MSL=2 minutes*/
                          MakeDoubleAccessor(&TcpSocketBase::m_msl),
                          MakeDoubleChecker<double>(0))
            .AddAttribute("MaxWindowSize",
                          "Max size of advertised window",
                          UintegerValue(65535),
                          MakeUintegerAccessor(&TcpSocketBase::m_maxWinSize),
                          MakeUintegerChecker<uint16_t>())
            .AddAttribute("IcmpCallback",
                          "Callback invoked whenever an icmp error is received on this socket.",
                          CallbackValue(),
                          MakeCallbackAccessor(&TcpSocketBase::m_icmpCallback),
                          MakeCallbackChecker())
            .AddAttribute("IcmpCallback6",
                          "Callback invoked whenever an icmpv6 error is received on this socket.",
                          CallbackValue(),
                          MakeCallbackAccessor(&TcpSocketBase::m_icmpCallback6),
                          MakeCallbackChecker())
            .AddAttribute("WindowScaling",
                          "Enable or disable Window Scaling option",
                          BooleanValue(true),
                          MakeBooleanAccessor(&TcpSocketBase::m_winScalingEnabled),
                          MakeBooleanChecker())
            .AddAttribute("Sack",
                          "Enable or disable Sack option",
                          BooleanValue(true),
                          MakeBooleanAccessor(&TcpSocketBase::m_sackEnabled),
                          MakeBooleanChecker())
            .AddAttribute("Timestamp",
                          "Enable or disable Timestamp option",
                          BooleanValue(true),
                          MakeBooleanAccessor(&TcpSocketBase::m_timestampEnabled),
                          MakeBooleanChecker())
            .AddAttribute("Fack",
                          "Enable or disable FACK option",
                          BooleanValue(false),
                          MakeBooleanAccessor(&TcpSocketBase::m_fackEnabled),
                          MakeBooleanChecker())
            .AddAttribute(
                "MinRto",
                "Minimum retransmit timeout value",
                TimeValue(Seconds(1)), // RFC 6298 says min RTO=1 sec, but Linux uses 200ms.
                // See http://www.postel.org/pipermail/end2end-interest/2004-November/004402.html
                MakeTimeAccessor(&TcpSocketBase::SetMinRto, &TcpSocketBase::GetMinRto),
                MakeTimeChecker())
            .AddAttribute(
                "ClockGranularity",
                "Clock Granularity used in RTO calculations",
                TimeValue(MilliSeconds(1)), // RFC6298 suggest to use fine clock granularity
                MakeTimeAccessor(&TcpSocketBase::SetClockGranularity,
                                 &TcpSocketBase::GetClockGranularity),
                MakeTimeChecker())
            .AddAttribute("TxBuffer",
                          "TCP Tx buffer",
                          PointerValue(),
                          MakePointerAccessor(&TcpSocketBase::GetTxBuffer),
                          MakePointerChecker<TcpTxBuffer>())
            .AddAttribute("RxBuffer",
                          "TCP Rx buffer",
                          PointerValue(),
                          MakePointerAccessor(&TcpSocketBase::GetRxBuffer),
                          MakePointerChecker<TcpRxBuffer>())
            .AddAttribute("CongestionOps",
                          "Pointer to TcpCongestionOps object",
                          PointerValue(),
                          MakePointerAccessor(&TcpSocketBase::m_congestionControl),
                          MakePointerChecker<TcpCongestionOps>())
            .AddAttribute("RecoveryOps",
                          "Pointer to TcpRecoveryOps object",
                          PointerValue(),
                          MakePointerAccessor(&TcpSocketBase::m_recoveryOps),
                          MakePointerChecker<TcpRecoveryOps>())
            .AddAttribute(
                "ReTxThreshold",
                "Threshold for fast retransmit",
                UintegerValue(3),
                MakeUintegerAccessor(&TcpSocketBase::SetRetxThresh, &TcpSocketBase::GetRetxThresh),
                MakeUintegerChecker<uint32_t>())
            .AddAttribute("LimitedTransmit",
                          "Enable limited transmit",
                          BooleanValue(true),
                          MakeBooleanAccessor(&TcpSocketBase::m_limitedTx),
                          MakeBooleanChecker())
            .AddAttribute("UseEcn",
                          "Parameter to set ECN functionality",
                          EnumValue(TcpSocketState::Off),
                          MakeEnumAccessor<TcpSocketState::UseEcn_t>(&TcpSocketBase::SetUseEcn),
                          MakeEnumChecker(TcpSocketState::Off,
                                          "Off",
                                          TcpSocketState::On,
                                          "On",
                                          TcpSocketState::AcceptOnly,
                                          "AcceptOnly"))
            .AddAttribute("UseAbe",
                          "Parameter to set ABE functionality",
                          BooleanValue(false),
                          MakeBooleanAccessor(&TcpSocketBase::m_useAbe),
                          MakeBooleanChecker())
            .AddTraceSource("RTO",
                            "Retransmission timeout",
                            MakeTraceSourceAccessor(&TcpSocketBase::m_rto),
                            "ns3::TracedValueCallback::Time")
            .AddTraceSource("RTT",
                            "Smoothed RTT",
                            MakeTraceSourceAccessor(&TcpSocketBase::m_srttTrace),
                            "ns3::TracedValueCallback::Time")
            .AddTraceSource("LastRTT",
                            "RTT of the last (S)ACKed packet",
                            MakeTraceSourceAccessor(&TcpSocketBase::m_lastRttTrace),
                            "ns3::TracedValueCallback::Time")
            .AddTraceSource("NextTxSequence",
                            "Next sequence number to send (SND.NXT)",
                            MakeTraceSourceAccessor(&TcpSocketBase::m_nextTxSequenceTrace),
                            "ns3::SequenceNumber32TracedValueCallback")
            .AddTraceSource("HighestSequence",
                            "Highest sequence number ever sent in socket's life time",
                            MakeTraceSourceAccessor(&TcpSocketBase::m_highTxMarkTrace),
                            "ns3::TracedValueCallback::SequenceNumber32")
            .AddTraceSource("State",
                            "TCP state",
                            MakeTraceSourceAccessor(&TcpSocketBase::m_state),
                            "ns3::TcpStatesTracedValueCallback")
            .AddTraceSource("CongState",
                            "TCP Congestion machine state",
                            MakeTraceSourceAccessor(&TcpSocketBase::m_congStateTrace),
                            "ns3::TcpSocketState::TcpCongStatesTracedValueCallback")
            .AddTraceSource("EcnState",
                            "Trace ECN state change of socket",
                            MakeTraceSourceAccessor(&TcpSocketBase::m_ecnStateTrace),
                            "ns3::TcpSocketState::EcnStatesTracedValueCallback")
            .AddTraceSource("AdvWND",
                            "Advertised Window Size",
                            MakeTraceSourceAccessor(&TcpSocketBase::m_advWnd),
                            "ns3::TracedValueCallback::Uint32")
            .AddTraceSource("RWND",
                            "Remote side's flow control window",
                            MakeTraceSourceAccessor(&TcpSocketBase::m_rWnd),
                            "ns3::TracedValueCallback::Uint32")
            .AddTraceSource("BytesInFlight",
                            "Socket estimation of bytes in flight",
                            MakeTraceSourceAccessor(&TcpSocketBase::m_bytesInFlightTrace),
                            "ns3::TracedValueCallback::Uint32")
            .AddTraceSource("FackAwnd",
                            "Socket estimation of bytes in flight by FACK",
                            MakeTraceSourceAccessor(&TcpSocketBase::m_fackAwndTrace),
                            "ns3::TracedValueCallback::Uint32")
            .AddTraceSource("HighestRxSequence",
                            "Highest sequence number received from peer",
                            MakeTraceSourceAccessor(&TcpSocketBase::m_highRxMark),
                            "ns3::TracedValueCallback::SequenceNumber32")
            .AddTraceSource("HighestRxAck",
                            "Highest ack received from peer",
                            MakeTraceSourceAccessor(&TcpSocketBase::m_highRxAckMark),
                            "ns3::TracedValueCallback::SequenceNumber32")
            .AddTraceSource("PacingRate",
                            "The current TCP pacing rate",
                            MakeTraceSourceAccessor(&TcpSocketBase::m_pacingRateTrace),
                            "ns3::TracedValueCallback::DataRate")
            .AddTraceSource("CongestionWindow",
                            "The TCP connection's congestion window",
                            MakeTraceSourceAccessor(&TcpSocketBase::m_cWndTrace),
                            "ns3::TracedValueCallback::Uint32")
            .AddTraceSource("CongestionWindowInflated",
                            "The TCP connection's congestion window inflates as in older RFC",
                            MakeTraceSourceAccessor(&TcpSocketBase::m_cWndInflTrace),
                            "ns3::TracedValueCallback::Uint32")
            .AddTraceSource("SlowStartThreshold",
                            "TCP slow start threshold (bytes)",
                            MakeTraceSourceAccessor(&TcpSocketBase::m_ssThTrace),
                            "ns3::TracedValueCallback::Uint32")
            .AddTraceSource("Tx",
                            "Send tcp packet to IP protocol",
                            MakeTraceSourceAccessor(&TcpSocketBase::m_txTrace),
                            "ns3::TcpSocketBase::TcpTxRxTracedCallback")
            .AddTraceSource("Retransmission",
                            "Notification of a TCP retransmission",
                            MakeTraceSourceAccessor(&TcpSocketBase::m_retransmissionTrace),
                            "ns3::TcpSocketBase::RetransmissionCallback")
            .AddTraceSource("Rx",
                            "Receive tcp packet from IP protocol",
                            MakeTraceSourceAccessor(&TcpSocketBase::m_rxTrace),
                            "ns3::TcpSocketBase::TcpTxRxTracedCallback")
            .AddTraceSource("EcnEchoSeq",
                            "Sequence of last received ECN Echo",
                            MakeTraceSourceAccessor(&TcpSocketBase::m_ecnEchoSeq),
                            "ns3::SequenceNumber32TracedValueCallback")
            .AddTraceSource("EcnCeSeq",
                            "Sequence of last received CE",
                            MakeTraceSourceAccessor(&TcpSocketBase::m_ecnCESeq),
                            "ns3::SequenceNumber32TracedValueCallback")
            .AddTraceSource("EcnCwrSeq",
                            "Sequence of last received CWR",
                            MakeTraceSourceAccessor(&TcpSocketBase::m_ecnCWRSeq),
                            "ns3::SequenceNumber32TracedValueCallback");
    return tid;
}
 
TcpSocketBase::TcpSocketBase()
    : TcpSocket()
{
    NS_LOG_FUNCTION(this);
 
    m_txBuffer = CreateObject<TcpTxBuffer>();
    m_txBuffer->SetRWndCallback(MakeCallback(&TcpSocketBase::GetRWnd, this));
    m_tcb = CreateObject<TcpSocketState>();
    m_rateOps = CreateObject<TcpRateLinux>();
 
    m_sndFack = 0;
    m_outstandingRetransBytes = 0;
 
    m_tcb->m_rxBuffer = CreateObject<TcpRxBuffer>();
 
    m_tcb->m_pacingRate = m_tcb->m_maxPacingRate;
    m_pacingTimer.SetFunction(&TcpSocketBase::NotifyPacingPerformed, this);
 
    m_tcb->m_sendEmptyPacketCallback = MakeCallback(&TcpSocketBase::SendEmptyPacket, this);
 
    bool ok;
 
    ok = m_tcb->TraceConnectWithoutContext(
        "PacingRate",
        MakeCallback(&TcpSocketBase::UpdatePacingRateTrace, this));
    NS_ASSERT_MSG(ok, "Could not connect trace source PacingRate");
 
    ok = m_tcb->TraceConnectWithoutContext("CongestionWindow",
                                           MakeCallback(&TcpSocketBase::UpdateCwnd, this));
    NS_ASSERT_MSG(ok, "Could not connect trace source CongestionWindow");
 
    ok = m_tcb->TraceConnectWithoutContext("CongestionWindowInflated",
                                           MakeCallback(&TcpSocketBase::UpdateCwndInfl, this));
    NS_ASSERT_MSG(ok, "Could not connect trace source CongestionWindowInflated");
 
    ok = m_tcb->TraceConnectWithoutContext("SlowStartThreshold",
                                           MakeCallback(&TcpSocketBase::UpdateSsThresh, this));
    NS_ASSERT_MSG(ok, "Could not connect trace source SlowStartThreshold");
 
    ok = m_tcb->TraceConnectWithoutContext("CongState",
                                           MakeCallback(&TcpSocketBase::UpdateCongState, this));
    NS_ASSERT_MSG(ok, "Could not connect trace source CongState");
 
    ok = m_tcb->TraceConnectWithoutContext("EcnState",
                                           MakeCallback(&TcpSocketBase::UpdateEcnState, this));
    NS_ASSERT_MSG(ok, "Could not connect trace source EcnState");
 
    ok =
        m_tcb->TraceConnectWithoutContext("NextTxSequence",
                                          MakeCallback(&TcpSocketBase::UpdateNextTxSequence, this));
    NS_ASSERT_MSG(ok, "Could not connect trace source NextTxSequence");
 
    ok = m_tcb->TraceConnectWithoutContext("HighestSequence",
                                           MakeCallback(&TcpSocketBase::UpdateHighTxMark, this));
    NS_ASSERT_MSG(ok, "Could not connect trace source HighestSequence");
 
    ok = m_tcb->TraceConnectWithoutContext("BytesInFlight",
                                           MakeCallback(&TcpSocketBase::UpdateBytesInFlight, this));
    NS_ASSERT_MSG(ok, "Could not connect trace source BytesInFlight");
 
    ok = m_tcb->TraceConnectWithoutContext("FackAwnd",
                                           MakeCallback(&TcpSocketBase::UpdateFackAwnd, this));
    NS_ASSERT_MSG(ok, "Could not connect trace source FackAwnd");
 
    ok = m_tcb->TraceConnectWithoutContext("RTT", MakeCallback(&TcpSocketBase::UpdateRtt, this));
    NS_ASSERT_MSG(ok, "Could not connect trace source RTT");
 
    ok = m_tcb->TraceConnectWithoutContext("LastRTT",
                                           MakeCallback(&TcpSocketBase::UpdateLastRtt, this));
    NS_ASSERT_MSG(ok, "Could not connect trace source LastRTT");
}
 
void
TcpSocketBase::NotifyConstructionCompleted()
{
    NS_LOG_FUNCTION(this);
 
    SetUseAbe(m_useAbe);
}
 
TcpSocketBase::TcpSocketBase(const TcpSocketBase& sock)
    : TcpSocket(sock),
      // copy object::m_tid and socket::callbacks
      m_dupAckCount(sock.m_dupAckCount),
      m_delAckCount(0),
      m_delAckMaxCount(sock.m_delAckMaxCount),
      m_noDelay(sock.m_noDelay),
      m_synCount(sock.m_synCount),
      m_synRetries(sock.m_synRetries),
      m_dataRetrCount(sock.m_dataRetrCount),
      m_dataRetries(sock.m_dataRetries),
      m_rto(sock.m_rto),
      m_minRto(sock.m_minRto),
      m_clockGranularity(sock.m_clockGranularity),
      m_delAckTimeout(sock.m_delAckTimeout),
      m_persistTimeout(sock.m_persistTimeout),
      m_cnTimeout(sock.m_cnTimeout),
      m_endPoint(nullptr),
      m_endPoint6(nullptr),
      m_node(sock.m_node),
      m_tcp(sock.m_tcp),
      m_state(sock.m_state),
      m_errno(sock.m_errno),
      m_closeNotified(sock.m_closeNotified),
      m_closeOnEmpty(sock.m_closeOnEmpty),
      m_shutdownSend(sock.m_shutdownSend),
      m_shutdownRecv(sock.m_shutdownRecv),
      m_connected(sock.m_connected),
      m_msl(sock.m_msl),
      m_maxWinSize(sock.m_maxWinSize),
      m_bytesAckedNotProcessed(sock.m_bytesAckedNotProcessed),
      m_rWnd(sock.m_rWnd),
      m_highRxMark(sock.m_highRxMark),
      m_highRxAckMark(sock.m_highRxAckMark),
      m_sackEnabled(sock.m_sackEnabled),
      m_winScalingEnabled(sock.m_winScalingEnabled),
      m_rcvWindShift(sock.m_rcvWindShift),
      m_sndWindShift(sock.m_sndWindShift),
      m_timestampEnabled(sock.m_timestampEnabled),
      m_timestampToEcho(sock.m_timestampToEcho),
      m_fackEnabled(sock.m_fackEnabled),
      m_recover(sock.m_recover),
      m_recoverActive(sock.m_recoverActive),
      m_retxThresh(sock.m_retxThresh),
      m_limitedTx(sock.m_limitedTx),
      m_isFirstPartialAck(sock.m_isFirstPartialAck),
      m_txTrace(sock.m_txTrace),
      m_rxTrace(sock.m_rxTrace),
      m_pacingTimer(Timer::CANCEL_ON_DESTROY),
      m_ecnEchoSeq(sock.m_ecnEchoSeq),
      m_ecnCESeq(sock.m_ecnCESeq),
      m_ecnCWRSeq(sock.m_ecnCWRSeq)
{
    NS_LOG_FUNCTION(this);
    NS_LOG_LOGIC("Invoked the copy constructor");
    // Copy the rtt estimator if it is set
    if (sock.m_rtt)
    {
        m_rtt = sock.m_rtt->Copy();
    }
    // Reset all callbacks to null
    Callback<void, Ptr<Socket>> vPS = MakeNullCallback<void, Ptr<Socket>>();
    Callback<void, Ptr<Socket>, const Address&> vPSA =
        MakeNullCallback<void, Ptr<Socket>, const Address&>();
    Callback<void, Ptr<Socket>, uint32_t> vPSUI = MakeNullCallback<void, Ptr<Socket>, uint32_t>();
    SetConnectCallback(vPS, vPS);
    SetDataSentCallback(vPSUI);
    SetSendCallback(vPSUI);
    SetRecvCallback(vPS);
    m_txBuffer = CopyObject(sock.m_txBuffer);
    m_txBuffer->SetRWndCallback(MakeCallback(&TcpSocketBase::GetRWnd, this));
    m_tcb = CopyObject(sock.m_tcb);
    m_tcb->m_rxBuffer = CopyObject(sock.m_tcb->m_rxBuffer);
 
    m_tcb->m_pacingRate = m_tcb->m_maxPacingRate;
    m_pacingTimer.SetFunction(&TcpSocketBase::NotifyPacingPerformed, this);
 
    m_rateOps = CreateObject<TcpRateLinux>();
 
    if (sock.m_congestionControl)
    {
        m_congestionControl = sock.m_congestionControl->Fork();
        m_congestionControl->Init(m_tcb);
        m_congestionControl->SetRateOps(m_rateOps);
    }
 
    if (sock.m_recoveryOps)
    {
        m_recoveryOps = sock.m_recoveryOps->Fork();
    }
 
    if (m_tcb->m_sendEmptyPacketCallback.IsNull())
    {
        m_tcb->m_sendEmptyPacketCallback = MakeCallback(&TcpSocketBase::SendEmptyPacket, this);
    }
 
    m_sndFack = sock.m_sndFack;
    m_outstandingRetransBytes = sock.m_outstandingRetransBytes;
 
    bool ok;
 
    ok = m_tcb->TraceConnectWithoutContext(
        "PacingRate",
        MakeCallback(&TcpSocketBase::UpdatePacingRateTrace, this));
    NS_ASSERT_MSG(ok, "Could not connect trace source PacingRate");
 
    ok = m_tcb->TraceConnectWithoutContext("CongestionWindow",
                                           MakeCallback(&TcpSocketBase::UpdateCwnd, this));
    NS_ASSERT_MSG(ok, "Could not connect trace source CongestionWindow");
 
    ok = m_tcb->TraceConnectWithoutContext("CongestionWindowInflated",
                                           MakeCallback(&TcpSocketBase::UpdateCwndInfl, this));
    NS_ASSERT_MSG(ok, "Could not connect trace source CongestionWindowInflated");
 
    ok = m_tcb->TraceConnectWithoutContext("SlowStartThreshold",
                                           MakeCallback(&TcpSocketBase::UpdateSsThresh, this));
    NS_ASSERT_MSG(ok, "Could not connect trace source SlowStartThreshold");
 
    ok = m_tcb->TraceConnectWithoutContext("CongState",
                                           MakeCallback(&TcpSocketBase::UpdateCongState, this));
    NS_ASSERT_MSG(ok, "Could not connect trace source CongState");
 
    ok = m_tcb->TraceConnectWithoutContext("EcnState",
                                           MakeCallback(&TcpSocketBase::UpdateEcnState, this));
    NS_ASSERT_MSG(ok, "Could not connect trace source EcnState");
 
    ok =
        m_tcb->TraceConnectWithoutContext("NextTxSequence",
                                          MakeCallback(&TcpSocketBase::UpdateNextTxSequence, this));
    NS_ASSERT_MSG(ok, "Could not connect trace source NextTxSequence");
 
    ok = m_tcb->TraceConnectWithoutContext("HighestSequence",
                                           MakeCallback(&TcpSocketBase::UpdateHighTxMark, this));
    NS_ASSERT_MSG(ok, "Could not connect trace source HighestSequence");
    ok = m_tcb->TraceConnectWithoutContext("BytesInFlight",
                                           MakeCallback(&TcpSocketBase::UpdateBytesInFlight, this));
    NS_ASSERT_MSG(ok, "Could not connect trace source BytesInFlight");
 
    ok = m_tcb->TraceConnectWithoutContext("FackAwnd",
                                           MakeCallback(&TcpSocketBase::UpdateFackAwnd, this));
 
    ok = m_tcb->TraceConnectWithoutContext("RTT", MakeCallback(&TcpSocketBase::UpdateRtt, this));
    NS_ASSERT_MSG(ok, "Could not connect trace source RTT");
 
    ok = m_tcb->TraceConnectWithoutContext("LastRTT",
                                           MakeCallback(&TcpSocketBase::UpdateLastRtt, this));
    NS_ASSERT_MSG(ok, "Could not connect trace source LastRTT");
}
 
TcpSocketBase::~TcpSocketBase()
{
    NS_LOG_FUNCTION(this);
    m_node = nullptr;
    if (m_endPoint != nullptr)
    {
        NS_ASSERT(m_tcp);
        /*
         * Upon Bind, an Ipv4Endpoint is allocated and set to m_endPoint, and
         * DestroyCallback is set to TcpSocketBase::Destroy. If we called
         * m_tcp->DeAllocate, it will destroy its Ipv4EndpointDemux::DeAllocate,
         * which in turn destroys my m_endPoint, and in turn invokes
         * TcpSocketBase::Destroy to nullify m_node, m_endPoint, and m_tcp.
         */
        NS_ASSERT(m_endPoint != nullptr);
        m_tcp->DeAllocate(m_endPoint);
        NS_ASSERT(m_endPoint == nullptr);
    }
    if (m_endPoint6 != nullptr)
    {
        NS_ASSERT(m_tcp);
        NS_ASSERT(m_endPoint6 != nullptr);
        m_tcp->DeAllocate(m_endPoint6);
        NS_ASSERT(m_endPoint6 == nullptr);
    }
    m_tcp = nullptr;
    CancelAllTimers();
}
 
/* Associate a node with this TCP socket */
void
TcpSocketBase::SetNode(Ptr<Node> node)
{
    m_node = node;
}
 
/* Associate the L4 protocol (e.g. mux/demux) with this socket */
void
TcpSocketBase::SetTcp(Ptr<TcpL4Protocol> tcp)
{
    m_tcp = tcp;
}
 
/* Set an RTT estimator with this socket */
void
TcpSocketBase::SetRtt(Ptr<RttEstimator> rtt)
{
    m_rtt = rtt;
}
 
/* Inherit from Socket class: Returns error code */
Socket::SocketErrno
TcpSocketBase::GetErrno() const
{
    return m_errno;
}
 
/* Inherit from Socket class: Returns socket type, NS3_SOCK_STREAM */
Socket::SocketType
TcpSocketBase::GetSocketType() const
{
    return NS3_SOCK_STREAM;
}
 
/* Inherit from Socket class: Returns associated node */
Ptr<Node>
TcpSocketBase::GetNode() const
{
    return m_node;
}
 
/* Inherit from Socket class: Bind socket to an end-point in TcpL4Protocol */
int
TcpSocketBase::Bind()
{
    NS_LOG_FUNCTION(this);
    m_endPoint = m_tcp->Allocate();
    if (nullptr == m_endPoint)
    {
        m_errno = ERROR_ADDRNOTAVAIL;
        return -1;
    }
 
    m_tcp->AddSocket(this);
 
    return SetupCallback();
}
 
int
TcpSocketBase::Bind6()
{
    NS_LOG_FUNCTION(this);
    m_endPoint6 = m_tcp->Allocate6();
    if (nullptr == m_endPoint6)
    {
        m_errno = ERROR_ADDRNOTAVAIL;
        return -1;
    }
 
    m_tcp->AddSocket(this);
 
    return SetupCallback();
}
 
/* Inherit from Socket class: Bind socket (with specific address) to an end-point in TcpL4Protocol
 */
int
TcpSocketBase::Bind(const Address& address)
{
    NS_LOG_FUNCTION(this << address);
    if (InetSocketAddress::IsMatchingType(address))
    {
        InetSocketAddress transport = InetSocketAddress::ConvertFrom(address);
        Ipv4Address ipv4 = transport.GetIpv4();
        uint16_t port = transport.GetPort();
        if (ipv4 == Ipv4Address::GetAny() && port == 0)
        {
            m_endPoint = m_tcp->Allocate();
        }
        else if (ipv4 == Ipv4Address::GetAny() && port != 0)
        {
            m_endPoint = m_tcp->Allocate(GetBoundNetDevice(), port);
        }
        else if (ipv4 != Ipv4Address::GetAny() && port == 0)
        {
            m_endPoint = m_tcp->Allocate(ipv4);
        }
        else if (ipv4 != Ipv4Address::GetAny() && port != 0)
        {
            m_endPoint = m_tcp->Allocate(GetBoundNetDevice(), ipv4, port);
        }
        if (nullptr == m_endPoint)
        {
            m_errno = port ? ERROR_ADDRINUSE : ERROR_ADDRNOTAVAIL;
            return -1;
        }
    }
    else if (Inet6SocketAddress::IsMatchingType(address))
    {
        Inet6SocketAddress transport = Inet6SocketAddress::ConvertFrom(address);
        Ipv6Address ipv6 = transport.GetIpv6();
        uint16_t port = transport.GetPort();
        if (ipv6 == Ipv6Address::GetAny() && port == 0)
        {
            m_endPoint6 = m_tcp->Allocate6();
        }
        else if (ipv6 == Ipv6Address::GetAny() && port != 0)
        {
            m_endPoint6 = m_tcp->Allocate6(GetBoundNetDevice(), port);
        }
        else if (ipv6 != Ipv6Address::GetAny() && port == 0)
        {
            m_endPoint6 = m_tcp->Allocate6(ipv6);
        }
        else if (ipv6 != Ipv6Address::GetAny() && port != 0)
        {
            m_endPoint6 = m_tcp->Allocate6(GetBoundNetDevice(), ipv6, port);
        }
        if (nullptr == m_endPoint6)
        {
            m_errno = port ? ERROR_ADDRINUSE : ERROR_ADDRNOTAVAIL;
            return -1;
        }
    }
    else
    {
        m_errno = ERROR_INVAL;
        return -1;
    }
 
    m_tcp->AddSocket(this);
 
    NS_LOG_LOGIC("TcpSocketBase " << this << " got an endpoint: " << m_endPoint);
 
    return SetupCallback();
}
 
void
TcpSocketBase::SetInitialSSThresh(uint32_t threshold)
{
    NS_ABORT_MSG_UNLESS(
        (m_state == CLOSED) || threshold == m_tcb->m_initialSsThresh,
        "TcpSocketBase::SetSSThresh() cannot change initial ssThresh after connection started.");
 
    m_tcb->m_initialSsThresh = threshold;
}
 
uint32_t
TcpSocketBase::GetInitialSSThresh() const
{
    return m_tcb->m_initialSsThresh;
}
 
void
TcpSocketBase::SetInitialCwnd(uint32_t cwnd)
{
    NS_ABORT_MSG_UNLESS(
        (m_state == CLOSED) || cwnd == m_tcb->m_initialCWnd,
        "TcpSocketBase::SetInitialCwnd() cannot change initial cwnd after connection started.");
 
    m_tcb->m_initialCWnd = cwnd;
}
 
uint32_t
TcpSocketBase::GetInitialCwnd() const
{
    return m_tcb->m_initialCWnd;
}
 
/* Inherit from Socket class: Initiate connection to a remote address:port */
int
TcpSocketBase::Connect(const Address& address)
{
    NS_LOG_FUNCTION(this << address);
 
    // If haven't do so, Bind() this socket first
    if (InetSocketAddress::IsMatchingType(address))
    {
        if (m_endPoint == nullptr)
        {
            if (Bind() == -1)
            {
                NS_ASSERT(m_endPoint == nullptr);
                return -1; // Bind() failed
            }
            NS_ASSERT(m_endPoint != nullptr);
        }
        InetSocketAddress transport = InetSocketAddress::ConvertFrom(address);
        m_endPoint->SetPeer(transport.GetIpv4(), transport.GetPort());
        m_endPoint6 = nullptr;
 
        // Get the appropriate local address and port number from the routing protocol and set up
        // endpoint
        if (SetupEndpoint() != 0)
        {
            NS_LOG_ERROR("Route to destination does not exist ?!");
            return -1;
        }
    }
    else if (Inet6SocketAddress::IsMatchingType(address))
    {
        // If we are operating on a v4-mapped address, translate the address to
        // a v4 address and re-call this function
        Inet6SocketAddress transport = Inet6SocketAddress::ConvertFrom(address);
        Ipv6Address v6Addr = transport.GetIpv6();
        if (v6Addr.IsIpv4MappedAddress())
        {
            Ipv4Address v4Addr = v6Addr.GetIpv4MappedAddress();
            return Connect(InetSocketAddress(v4Addr, transport.GetPort()));
        }
 
        if (m_endPoint6 == nullptr)
        {
            if (Bind6() == -1)
            {
                NS_ASSERT(m_endPoint6 == nullptr);
                return -1; // Bind() failed
            }
            NS_ASSERT(m_endPoint6 != nullptr);
        }
        m_endPoint6->SetPeer(v6Addr, transport.GetPort());
        m_endPoint = nullptr;
 
        // Get the appropriate local address and port number from the routing protocol and set up
        // endpoint
        if (SetupEndpoint6() != 0)
        {
            NS_LOG_ERROR("Route to destination does not exist ?!");
            return -1;
        }
    }
    else
    {
        m_errno = ERROR_INVAL;
        return -1;
    }
 
    // Re-initialize parameters in case this socket is being reused after CLOSE
    m_rtt->Reset();
    m_synCount = m_synRetries;
    m_dataRetrCount = m_dataRetries;
 
    // DoConnect() will do state-checking and send a SYN packet
    return DoConnect();
}
 
/* Inherit from Socket class: Listen on the endpoint for an incoming connection */
int
TcpSocketBase::Listen()
{
    NS_LOG_FUNCTION(this);
 
    // Linux quits EINVAL if we're not in CLOSED state, so match what they do
    if (m_state != CLOSED)
    {
        m_errno = ERROR_INVAL;
        return -1;
    }
    // In other cases, set the state to LISTEN and done
    NS_LOG_DEBUG("CLOSED -> LISTEN");
    m_state = LISTEN;
    return 0;
}
 
/* Inherit from Socket class: Kill this socket and signal the peer (if any) */
int
TcpSocketBase::Close()
{
    NS_LOG_FUNCTION(this);
    /// @internal
    /// First we check to see if there is any unread rx data.
    /// \bugid{426} claims we should send reset in this case.
    if (m_tcb->m_rxBuffer->Size() != 0)
    {
        NS_LOG_WARN("Socket " << this << " << unread rx data during close.  Sending reset."
                              << "This is probably due to a bad sink application; check its code");
        SendRST();
        return 0;
    }
 
    if (m_txBuffer->SizeFromSequence(m_tcb->m_nextTxSequence) > 0)
    { // App close with pending data must wait until all data transmitted
        if (!m_closeOnEmpty)
        {
            m_closeOnEmpty = true;
            NS_LOG_INFO("Socket " << this << " deferring close, state " << TcpStateName[m_state]);
        }
        return 0;
    }
    return DoClose();
}
 
/* Inherit from Socket class: Signal a termination of send */
int
TcpSocketBase::ShutdownSend()
{
    NS_LOG_FUNCTION(this);
 
    // this prevents data from being added to the buffer
    m_shutdownSend = true;
    m_closeOnEmpty = true;
    // if buffer is already empty, send a fin now
    // otherwise fin will go when buffer empties.
    if (m_txBuffer->Size() == 0)
    {
        if (m_state == ESTABLISHED || m_state == CLOSE_WAIT)
        {
            NS_LOG_INFO("Empty tx buffer, send fin");
            SendEmptyPacket(TcpHeader::FIN);
 
            if (m_state == ESTABLISHED)
            { // On active close: I am the first one to send FIN
                NS_LOG_DEBUG("ESTABLISHED -> FIN_WAIT_1");
                m_state = FIN_WAIT_1;
            }
            else
            { // On passive close: Peer sent me FIN already
                NS_LOG_DEBUG("CLOSE_WAIT -> LAST_ACK");
                m_state = LAST_ACK;
            }
        }
    }
 
    return 0;
}
 
/* Inherit from Socket class: Signal a termination of receive */
int
TcpSocketBase::ShutdownRecv()
{
    NS_LOG_FUNCTION(this);
    m_shutdownRecv = true;
    return 0;
}
 
/* Inherit from Socket class: Send a packet. Parameter flags is not used.
    Packet has no TCP header. Invoked by upper-layer application */
int
TcpSocketBase::Send(Ptr<Packet> p, uint32_t flags)
{
    NS_LOG_FUNCTION(this << p);
    NS_ABORT_MSG_IF(flags, "use of flags is not supported in TcpSocketBase::Send()");
    if (m_state == ESTABLISHED || m_state == SYN_SENT || m_state == CLOSE_WAIT)
    {
        // Store the packet into Tx buffer
        if (!m_txBuffer->Add(p))
        { // TxBuffer overflow, send failed
            m_errno = ERROR_MSGSIZE;
            return -1;
        }
        if (m_shutdownSend)
        {
            m_errno = ERROR_SHUTDOWN;
            return -1;
        }
 
        m_rateOps->CalculateAppLimited(m_tcb->m_cWnd,
                                       m_tcb->m_bytesInFlight,
                                       m_tcb->m_segmentSize,
                                       m_txBuffer->TailSequence(),
                                       m_tcb->m_nextTxSequence,
                                       m_txBuffer->GetLost(),
                                       m_txBuffer->GetRetransmitsCount());
 
        // Submit the data to lower layers
        NS_LOG_LOGIC("txBufSize=" << m_txBuffer->Size() << " state " << TcpStateName[m_state]);
        if ((m_state == ESTABLISHED || m_state == CLOSE_WAIT) && AvailableWindow() > 0)
        { // Try to send the data out: Add a little step to allow the application
            // to fill the buffer
            if (!m_sendPendingDataEvent.IsPending())
            {
                m_sendPendingDataEvent = Simulator::Schedule(TimeStep(1),
                                                             &TcpSocketBase::SendPendingData,
                                                             this,
                                                             m_connected);
            }
        }
        return p->GetSize();
    }
    else
    { // Connection not established yet
        m_errno = ERROR_NOTCONN;
        return -1; // Send failure
    }
}
 
/* Inherit from Socket class: In TcpSocketBase, it is same as Send() call */
int
TcpSocketBase::SendTo(Ptr<Packet> p, uint32_t flags, const Address& /* address */)
{
    return Send(p, flags); // SendTo() and Send() are the same
}
 
/* Inherit from Socket class: Return data to upper-layer application. Parameter flags
   is not used. Data is returned as a packet of size no larger than maxSize */
Ptr<Packet>
TcpSocketBase::Recv(uint32_t maxSize, uint32_t flags)
{
    NS_LOG_FUNCTION(this);
    NS_ABORT_MSG_IF(flags, "use of flags is not supported in TcpSocketBase::Recv()");
    if (m_tcb->m_rxBuffer->Size() == 0 && m_state == CLOSE_WAIT)
    {
        return Create<Packet>(); // Send EOF on connection close
    }
    Ptr<Packet> outPacket = m_tcb->m_rxBuffer->Extract(maxSize);
    return outPacket;
}
 
/* Inherit from Socket class: Recv and return the remote's address */
Ptr<Packet>
TcpSocketBase::RecvFrom(uint32_t maxSize, uint32_t flags, Address& fromAddress)
{
    NS_LOG_FUNCTION(this << maxSize << flags);
    Ptr<Packet> packet = Recv(maxSize, flags);
    // Null packet means no data to read, and an empty packet indicates EOF
    if (packet && packet->GetSize() != 0)
    {
        if (m_endPoint != nullptr)
        {
            fromAddress =
                InetSocketAddress(m_endPoint->GetPeerAddress(), m_endPoint->GetPeerPort());
        }
        else if (m_endPoint6 != nullptr)
        {
            fromAddress =
                Inet6SocketAddress(m_endPoint6->GetPeerAddress(), m_endPoint6->GetPeerPort());
        }
        else
        {
            fromAddress = InetSocketAddress(Ipv4Address::GetZero(), 0);
        }
    }
    return packet;
}
 
/* Inherit from Socket class: Get the max number of bytes an app can send */
uint32_t
TcpSocketBase::GetTxAvailable() const
{
    NS_LOG_FUNCTION(this);
    return m_txBuffer->Available();
}
 
/* Inherit from Socket class: Get the max number of bytes an app can read */
uint32_t
TcpSocketBase::GetRxAvailable() const
{
    NS_LOG_FUNCTION(this);
    return m_tcb->m_rxBuffer->Available();
}
 
/* Inherit from Socket class: Return local address:port */
int
TcpSocketBase::GetSockName(Address& address) const
{
    NS_LOG_FUNCTION(this);
    if (m_endPoint != nullptr)
    {
        address = InetSocketAddress(m_endPoint->GetLocalAddress(), m_endPoint->GetLocalPort());
    }
    else if (m_endPoint6 != nullptr)
    {
        address = Inet6SocketAddress(m_endPoint6->GetLocalAddress(), m_endPoint6->GetLocalPort());
    }
    else
    { // It is possible to call this method on a socket without a name
        // in which case, behavior is unspecified
        // Should this return an InetSocketAddress or an Inet6SocketAddress?
        address = InetSocketAddress(Ipv4Address::GetZero(), 0);
    }
    return 0;
}
 
int
TcpSocketBase::GetPeerName(Address& address) const
{
    NS_LOG_FUNCTION(this << address);
 
    if (!m_endPoint && !m_endPoint6)
    {
        m_errno = ERROR_NOTCONN;
        return -1;
    }
 
    if (m_endPoint)
    {
        address = InetSocketAddress(m_endPoint->GetPeerAddress(), m_endPoint->GetPeerPort());
    }
    else if (m_endPoint6)
    {
        address = Inet6SocketAddress(m_endPoint6->GetPeerAddress(), m_endPoint6->GetPeerPort());
    }
    else
    {
        NS_ASSERT(false);
    }
 
    return 0;
}
 
/* Inherit from Socket class: Bind this socket to the specified NetDevice */
void
TcpSocketBase::BindToNetDevice(Ptr<NetDevice> netdevice)
{
    NS_LOG_FUNCTION(netdevice);
    Socket::BindToNetDevice(netdevice); // Includes sanity check
    if (m_endPoint != nullptr)
    {
        m_endPoint->BindToNetDevice(netdevice);
    }
 
    if (m_endPoint6 != nullptr)
    {
        m_endPoint6->BindToNetDevice(netdevice);
    }
}
 
/* Clean up after Bind. Set up callback functions in the end-point. */
int
TcpSocketBase::SetupCallback()
{
    NS_LOG_FUNCTION(this);
 
    if (m_endPoint == nullptr && m_endPoint6 == nullptr)
    {
        return -1;
    }
    if (m_endPoint != nullptr)
    {
        m_endPoint->SetRxCallback(
            MakeCallback(&TcpSocketBase::ForwardUp, Ptr<TcpSocketBase>(this)));
        m_endPoint->SetIcmpCallback(
            MakeCallback(&TcpSocketBase::ForwardIcmp, Ptr<TcpSocketBase>(this)));
        m_endPoint->SetDestroyCallback(
            MakeCallback(&TcpSocketBase::Destroy, Ptr<TcpSocketBase>(this)));
    }
    if (m_endPoint6 != nullptr)
    {
        m_endPoint6->SetRxCallback(
            MakeCallback(&TcpSocketBase::ForwardUp6, Ptr<TcpSocketBase>(this)));
        m_endPoint6->SetIcmpCallback(
            MakeCallback(&TcpSocketBase::ForwardIcmp6, Ptr<TcpSocketBase>(this)));
        m_endPoint6->SetDestroyCallback(
            MakeCallback(&TcpSocketBase::Destroy6, Ptr<TcpSocketBase>(this)));
    }
 
    return 0;
}
 
/* Perform the real connection tasks: Send SYN if allowed, RST if invalid */
int
TcpSocketBase::DoConnect()
{
    NS_LOG_FUNCTION(this);
 
    // A new connection is allowed only if this socket does not have a connection
    if (m_state == CLOSED || m_state == LISTEN || m_state == SYN_SENT || m_state == LAST_ACK ||
        m_state == CLOSE_WAIT)
    { // send a SYN packet and change state into SYN_SENT
        // send a SYN packet with ECE and CWR flags set if sender is ECN capable
        if (m_tcb->m_useEcn == TcpSocketState::On)
        {
            SendEmptyPacket(TcpHeader::SYN | TcpHeader::ECE | TcpHeader::CWR);
        }
        else
        {
            SendEmptyPacket(TcpHeader::SYN);
        }
        NS_LOG_DEBUG(TcpStateName[m_state] << " -> SYN_SENT");
        m_state = SYN_SENT;
        m_tcb->m_ecnState = TcpSocketState::ECN_DISABLED; // because sender is not yet aware about
                                                          // receiver's ECN capability
    }
    else if (m_state != TIME_WAIT)
    { // In states SYN_RCVD, ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, and CLOSING, an connection
        // exists. We send RST, tear down everything, and close this socket.
        SendRST();
        CloseAndNotify();
    }
    return 0;
}
 
/* Do the action to close the socket. Usually send a packet with appropriate
    flags depended on the current m_state. */
int
TcpSocketBase::DoClose()
{
    NS_LOG_FUNCTION(this);
    switch (m_state)
    {
    case SYN_RCVD:
    case ESTABLISHED:
        // send FIN to close the peer
        SendEmptyPacket(TcpHeader::FIN);
        NS_LOG_DEBUG("ESTABLISHED -> FIN_WAIT_1");
        m_state = FIN_WAIT_1;
        break;
    case CLOSE_WAIT:
        // send FIN+ACK to close the peer
        SendEmptyPacket(TcpHeader::FIN | TcpHeader::ACK);
        NS_LOG_DEBUG("CLOSE_WAIT -> LAST_ACK");
        m_state = LAST_ACK;
        break;
    case SYN_SENT:
    case CLOSING:
        // Send RST if application closes in SYN_SENT and CLOSING
        SendRST();
        CloseAndNotify();
        break;
    case LISTEN:
        // In this state, move to CLOSED and tear down the end point
        CloseAndNotify();
        break;
    case LAST_ACK:
    case CLOSED:
    case FIN_WAIT_1:
    case FIN_WAIT_2:
    case TIME_WAIT:
    default: /* mute compiler */
        // Do nothing in these five states
        break;
    }
    return 0;
}
 
/* Peacefully close the socket by notifying the upper layer and deallocate end point */
void
TcpSocketBase::CloseAndNotify()
{
    NS_LOG_FUNCTION(this);
 
    if (!m_closeNotified)
    {
        NotifyNormalClose();
        m_closeNotified = true;
    }
    if (m_lastAckEvent.IsPending())
    {
        m_lastAckEvent.Cancel();
    }
    NS_LOG_DEBUG(TcpStateName[m_state] << " -> CLOSED");
    m_state = CLOSED;
    DeallocateEndPoint();
}
 
/* Tell if a sequence number range is out side the range that my rx buffer can
    accept */
bool
TcpSocketBase::OutOfRange(SequenceNumber32 head, SequenceNumber32 tail) const
{
    if (m_state == LISTEN || m_state == SYN_SENT || m_state == SYN_RCVD)
    { // Rx buffer in these states are not initialized.
        return false;
    }
    if (m_state == LAST_ACK || m_state == CLOSING || m_state == CLOSE_WAIT)
    { // In LAST_ACK and CLOSING states, it only wait for an ACK and the
        // sequence number must equals to m_rxBuffer->NextRxSequence ()
        return (m_tcb->m_rxBuffer->NextRxSequence() != head);
    }
 
    // In all other cases, check if the sequence number is in range
    return (tail < m_tcb->m_rxBuffer->NextRxSequence() ||
            m_tcb->m_rxBuffer->MaxRxSequence() <= head);
}
 
/* Function called by the L3 protocol when it received a packet to pass on to
    the TCP. This function is registered as the "RxCallback" function in
    SetupCallback(), which invoked by Bind(), and CompleteFork() */
void
TcpSocketBase::ForwardUp(Ptr<Packet> packet,
                         Ipv4Header header,
                         uint16_t port,
                         Ptr<Ipv4Interface> incomingInterface)
{
    NS_LOG_LOGIC("Socket " << this << " forward up " << m_endPoint->GetPeerAddress() << ":"
                           << m_endPoint->GetPeerPort() << " to " << m_endPoint->GetLocalAddress()
                           << ":" << m_endPoint->GetLocalPort());
 
    Address fromAddress = InetSocketAddress(header.GetSource(), port);
    Address toAddress = InetSocketAddress(header.GetDestination(), m_endPoint->GetLocalPort());
 
    TcpHeader tcpHeader;
    uint32_t bytesRemoved = packet->PeekHeader(tcpHeader);
 
    if (!IsValidTcpSegment(tcpHeader.GetSequenceNumber(),
                           bytesRemoved,
                           packet->GetSize() - bytesRemoved))
    {
        return;
    }
 
    if (header.GetEcn() == Ipv4Header::ECN_CE && m_ecnCESeq < tcpHeader.GetSequenceNumber())
    {
        NS_LOG_INFO("Received CE flag is valid");
        NS_LOG_DEBUG(TcpSocketState::EcnStateName[m_tcb->m_ecnState] << " -> ECN_CE_RCVD");
        m_ecnCESeq = tcpHeader.GetSequenceNumber();
        m_tcb->m_ecnState = TcpSocketState::ECN_CE_RCVD;
        m_congestionControl->CwndEvent(m_tcb, TcpSocketState::CA_EVENT_ECN_IS_CE);
    }
    else if (header.GetEcn() != Ipv4Header::ECN_NotECT &&
             m_tcb->m_ecnState != TcpSocketState::ECN_DISABLED)
    {
        m_congestionControl->CwndEvent(m_tcb, TcpSocketState::CA_EVENT_ECN_NO_CE);
    }
 
    DoForwardUp(packet, fromAddress, toAddress);
}
 
void
TcpSocketBase::ForwardUp6(Ptr<Packet> packet,
                          Ipv6Header header,
                          uint16_t port,
                          Ptr<Ipv6Interface> incomingInterface)
{
    NS_LOG_LOGIC("Socket " << this << " forward up " << m_endPoint6->GetPeerAddress() << ":"
                           << m_endPoint6->GetPeerPort() << " to " << m_endPoint6->GetLocalAddress()
                           << ":" << m_endPoint6->GetLocalPort());
 
    Address fromAddress = Inet6SocketAddress(header.GetSource(), port);
    Address toAddress = Inet6SocketAddress(header.GetDestination(), m_endPoint6->GetLocalPort());
 
    TcpHeader tcpHeader;
    uint32_t bytesRemoved = packet->PeekHeader(tcpHeader);
 
    if (!IsValidTcpSegment(tcpHeader.GetSequenceNumber(),
                           bytesRemoved,
                           packet->GetSize() - bytesRemoved))
    {
        return;
    }
 
    if (header.GetEcn() == Ipv6Header::ECN_CE && m_ecnCESeq < tcpHeader.GetSequenceNumber())
    {
        NS_LOG_INFO("Received CE flag is valid");
        NS_LOG_DEBUG(TcpSocketState::EcnStateName[m_tcb->m_ecnState] << " -> ECN_CE_RCVD");
        m_ecnCESeq = tcpHeader.GetSequenceNumber();
        m_tcb->m_ecnState = TcpSocketState::ECN_CE_RCVD;
        m_congestionControl->CwndEvent(m_tcb, TcpSocketState::CA_EVENT_ECN_IS_CE);
    }
    else if (header.GetEcn() != Ipv6Header::ECN_NotECT)
    {
        m_congestionControl->CwndEvent(m_tcb, TcpSocketState::CA_EVENT_ECN_NO_CE);
    }
 
    DoForwardUp(packet, fromAddress, toAddress);
}
 
void
TcpSocketBase::ForwardIcmp(Ipv4Address icmpSource,
                           uint8_t icmpTtl,
                           uint8_t icmpType,
                           uint8_t icmpCode,
                           uint32_t icmpInfo)
{
    NS_LOG_FUNCTION(this << icmpSource << static_cast<uint32_t>(icmpTtl)
                         << static_cast<uint32_t>(icmpType) << static_cast<uint32_t>(icmpCode)
                         << icmpInfo);
    if (!m_icmpCallback.IsNull())
    {
        m_icmpCallback(icmpSource, icmpTtl, icmpType, icmpCode, icmpInfo);
    }
}
 
void
TcpSocketBase::ForwardIcmp6(Ipv6Address icmpSource,
                            uint8_t icmpTtl,
                            uint8_t icmpType,
                            uint8_t icmpCode,
                            uint32_t icmpInfo)
{
    NS_LOG_FUNCTION(this << icmpSource << static_cast<uint32_t>(icmpTtl)
                         << static_cast<uint32_t>(icmpType) << static_cast<uint32_t>(icmpCode)
                         << icmpInfo);
    if (!m_icmpCallback6.IsNull())
    {
        m_icmpCallback6(icmpSource, icmpTtl, icmpType, icmpCode, icmpInfo);
    }
}
 
bool
TcpSocketBase::IsValidTcpSegment(const SequenceNumber32 seq,
                                 const uint32_t tcpHeaderSize,
                                 const uint32_t tcpPayloadSize)
{
    if (tcpHeaderSize == 0 || tcpHeaderSize > 60)
    {
        NS_LOG_ERROR("Bytes removed: " << tcpHeaderSize << " invalid");
        return false; // Discard invalid packet
    }
    else if (tcpPayloadSize > 0 && OutOfRange(seq, seq + tcpPayloadSize))
    {
        // Discard fully out of range data packets
        NS_LOG_WARN("At state " << TcpStateName[m_state] << " received packet of seq [" << seq
                                << ":" << seq + tcpPayloadSize << ") out of range ["
                                << m_tcb->m_rxBuffer->NextRxSequence() << ":"
                                << m_tcb->m_rxBuffer->MaxRxSequence() << ")");
        // Acknowledgement should be sent for all unacceptable packets (RFC793, p.69)
        SendEmptyPacket(TcpHeader::ACK);
        return false;
    }
    return true;
}
 
void
TcpSocketBase::DoForwardUp(Ptr<Packet> packet, const Address& fromAddress, const Address& toAddress)
{
    // in case the packet still has a priority tag attached, remove it
    SocketPriorityTag priorityTag;
    packet->RemovePacketTag(priorityTag);
 
    // Peel off TCP header
    TcpHeader tcpHeader;
    packet->RemoveHeader(tcpHeader);
    SequenceNumber32 seq = tcpHeader.GetSequenceNumber();
 
    if (m_state == ESTABLISHED && !(tcpHeader.GetFlags() & TcpHeader::RST))
    {
        // Check if the sender has responded to ECN echo by reducing the Congestion Window
        if (tcpHeader.GetFlags() & TcpHeader::CWR)
        {
            // Check if a packet with CE bit set is received. If there is no CE bit set, then change
            // the state to ECN_IDLE to stop sending ECN Echo messages. If there is CE bit set, the
            // packet should continue sending ECN Echo messages
            //
            if (m_tcb->m_ecnState != TcpSocketState::ECN_CE_RCVD)
            {
                NS_LOG_DEBUG(TcpSocketState::EcnStateName[m_tcb->m_ecnState] << " -> ECN_IDLE");
                m_tcb->m_ecnState = TcpSocketState::ECN_IDLE;
            }
        }
    }
 
    m_rxTrace(packet, tcpHeader, this);
 
    if (tcpHeader.GetFlags() & TcpHeader::SYN)
    {
        /* The window field in a segment where the SYN bit is set (i.e., a <SYN>
         * or <SYN,ACK>) MUST NOT be scaled (from RFC 7323 page 9). But should be
         * saved anyway..
         */
        m_rWnd = tcpHeader.GetWindowSize();
 
        if (tcpHeader.HasOption(TcpOption::WINSCALE) && m_winScalingEnabled)
        {
            ProcessOptionWScale(tcpHeader.GetOption(TcpOption::WINSCALE));
        }
        else
        {
            m_winScalingEnabled = false;
        }
 
        if (tcpHeader.HasOption(TcpOption::SACKPERMITTED) && m_sackEnabled)
        {
            ProcessOptionSackPermitted(tcpHeader.GetOption(TcpOption::SACKPERMITTED));
        }
        else
        {
            m_sackEnabled = false;
            m_txBuffer->SetSackEnabled(false);
        }
 
        // When receiving a <SYN> or <SYN-ACK> we should adapt TS to the other end
        if (tcpHeader.HasOption(TcpOption::TS) && m_timestampEnabled)
        {
            ProcessOptionTimestamp(tcpHeader.GetOption(TcpOption::TS),
                                   tcpHeader.GetSequenceNumber());
        }
        else
        {
            m_timestampEnabled = false;
        }
 
        // Initialize cWnd and ssThresh
        m_tcb->m_cWnd = GetInitialCwnd() * GetSegSize();
        m_tcb->m_cWndInfl = m_tcb->m_cWnd;
        m_tcb->m_ssThresh = GetInitialSSThresh();
 
        if (tcpHeader.GetFlags() & TcpHeader::ACK)
        {
            EstimateRtt(tcpHeader);
            m_highRxAckMark = tcpHeader.GetAckNumber();
        }
    }
    else if (tcpHeader.GetFlags() & TcpHeader::ACK)
    {
        NS_ASSERT(!(tcpHeader.GetFlags() & TcpHeader::SYN));
        if (m_timestampEnabled)
        {
            if (!tcpHeader.HasOption(TcpOption::TS))
            {
                // Ignoring segment without TS, RFC 7323
                NS_LOG_LOGIC("At state " << TcpStateName[m_state] << " received packet of seq ["
                                         << seq << ":" << seq + packet->GetSize()
                                         << ") without TS option. Silently discard it");
                return;
            }
            else
            {
                ProcessOptionTimestamp(tcpHeader.GetOption(TcpOption::TS),
                                       tcpHeader.GetSequenceNumber());
            }
        }
 
        EstimateRtt(tcpHeader);
        UpdateWindowSize(tcpHeader);
    }
 
    if (m_rWnd.Get() == 0 && m_persistEvent.IsExpired())
    { // Zero window: Enter persist state to send 1 byte to probe
        NS_LOG_LOGIC(this << " Enter zerowindow persist state");
        NS_LOG_LOGIC(
            this << " Cancelled ReTxTimeout event which was set to expire at "
                 << (Simulator::Now() + Simulator::GetDelayLeft(m_retxEvent)).GetSeconds());
        m_retxEvent.Cancel();
        NS_LOG_LOGIC("Schedule persist timeout at time "
                     << Simulator::Now().GetSeconds() << " to expire at time "
                     << (Simulator::Now() + m_persistTimeout).GetSeconds());
        m_persistEvent =
            Simulator::Schedule(m_persistTimeout, &TcpSocketBase::PersistTimeout, this);
        NS_ASSERT(m_persistTimeout == Simulator::GetDelayLeft(m_persistEvent));
    }
 
    // TCP state machine code in different process functions
    // C.f.: tcp_rcv_state_process() in tcp_input.c in Linux kernel
    switch (m_state)
    {
    case ESTABLISHED:
        ProcessEstablished(packet, tcpHeader);
        break;
    case LISTEN:
        ProcessListen(packet, tcpHeader, fromAddress, toAddress);
        break;
    case TIME_WAIT:
        // Do nothing
        break;
    case CLOSED:
        // Send RST if the incoming packet is not a RST
        if ((tcpHeader.GetFlags() & ~(TcpHeader::PSH | TcpHeader::URG)) != TcpHeader::RST)
        { // Since m_endPoint is not configured yet, we cannot use SendRST here
            TcpHeader h;
            Ptr<Packet> p = Create<Packet>();
            h.SetFlags(TcpHeader::RST);
            h.SetSequenceNumber(m_tcb->m_nextTxSequence);
            h.SetAckNumber(m_tcb->m_rxBuffer->NextRxSequence());
            h.SetSourcePort(tcpHeader.GetDestinationPort());
            h.SetDestinationPort(tcpHeader.GetSourcePort());
            h.SetWindowSize(AdvertisedWindowSize());
            AddOptions(h);
            m_txTrace(p, h, this);
            m_tcp->SendPacket(p, h, toAddress, fromAddress, m_boundnetdevice);
        }
        break;
    case SYN_SENT:
        ProcessSynSent(packet, tcpHeader);
        break;
    case SYN_RCVD:
        ProcessSynRcvd(packet, tcpHeader, fromAddress, toAddress);
        break;
    case FIN_WAIT_1:
    case FIN_WAIT_2:
    case CLOSE_WAIT:
        ProcessWait(packet, tcpHeader);
        break;
    case CLOSING:
        ProcessClosing(packet, tcpHeader);
        break;
    case LAST_ACK:
        ProcessLastAck(packet, tcpHeader);
        break;
    default: // mute compiler
        break;
    }
 
    if (m_rWnd.Get() != 0 && m_persistEvent.IsPending())
    { // persist probes end, the other end has increased the window
        NS_ASSERT(m_connected);
        NS_LOG_LOGIC(this << " Leaving zerowindow persist state");
        m_persistEvent.Cancel();
 
        SendPendingData(m_connected);
    }
}
 
/* Received a packet upon ESTABLISHED state. This function is mimicking the
    role of tcp_rcv_established() in tcp_input.c in Linux kernel. */
void
TcpSocketBase::ProcessEstablished(Ptr<Packet> packet, const TcpHeader& tcpHeader)
{
    NS_LOG_FUNCTION(this << tcpHeader);
 
    // Extract the flags. PSH, URG, CWR and ECE are disregarded.
    uint8_t tcpflags =
        tcpHeader.GetFlags() & ~(TcpHeader::PSH | TcpHeader::URG | TcpHeader::CWR | TcpHeader::ECE);
 
    // Different flags are different events
    if (tcpflags == TcpHeader::ACK)
    {
        if (tcpHeader.GetAckNumber() < m_txBuffer->HeadSequence())
        {
            // Case 1:  If the ACK is a duplicate (SEG.ACK < SND.UNA), it can be ignored.
            // Pag. 72 RFC 793
            NS_LOG_WARN("Ignored ack of " << tcpHeader.GetAckNumber()
                                          << " SND.UNA = " << m_txBuffer->HeadSequence());
 
            // TODO: RFC 5961 5.2 [Blind Data Injection Attack].[Mitigation]
        }
        else if (tcpHeader.GetAckNumber() > m_tcb->m_highTxMark)
        {
            // If the ACK acks something not yet sent (SEG.ACK > HighTxMark) then
            // send an ACK, drop the segment, and return.
            // Pag. 72 RFC 793
            NS_LOG_WARN("Ignored ack of " << tcpHeader.GetAckNumber()
                                          << " HighTxMark = " << m_tcb->m_highTxMark);
 
            // Receiver sets ECE flags when it receives a packet with CE bit on or sender hasn't
            // responded to ECN echo sent by receiver
            if (m_tcb->m_ecnState == TcpSocketState::ECN_CE_RCVD ||
                m_tcb->m_ecnState == TcpSocketState::ECN_SENDING_ECE)
            {
                SendEmptyPacket(TcpHeader::ACK | TcpHeader::ECE);
                NS_LOG_DEBUG(TcpSocketState::EcnStateName[m_tcb->m_ecnState]
                             << " -> ECN_SENDING_ECE");
                m_tcb->m_ecnState = TcpSocketState::ECN_SENDING_ECE;
            }
            else
            {
                SendEmptyPacket(TcpHeader::ACK);
            }
        }
        else
        {
            // SND.UNA < SEG.ACK =< HighTxMark
            // Pag. 72 RFC 793
            ReceivedAck(packet, tcpHeader);
        }
    }
    else if (tcpflags == TcpHeader::SYN || tcpflags == (TcpHeader::SYN | TcpHeader::ACK))
    {
        // (a) Received SYN, old NS-3 behaviour is to set state to SYN_RCVD and
        // respond with a SYN+ACK. But it is not a legal state transition as of
        // RFC793. Thus this is ignored.
 
        // (b) No action for received SYN+ACK, it is probably a duplicated packet
    }
    else if (tcpflags == TcpHeader::FIN || tcpflags == (TcpHeader::FIN | TcpHeader::ACK))
    { // Received FIN or FIN+ACK, bring down this socket nicely
        PeerClose(packet, tcpHeader);
    }
    else if (tcpflags == 0)
    { // No flags means there is only data
        ReceivedData(packet, tcpHeader);
        if (m_tcb->m_rxBuffer->Finished())
        {
            PeerClose(packet, tcpHeader);
        }
    }
    else
    { // Received RST or the TCP flags is invalid, in either case, terminate this socket
        if (tcpflags != TcpHeader::RST)
        { // this must be an invalid flag, send reset
            NS_LOG_LOGIC("Illegal flag " << TcpHeader::FlagsToString(tcpflags)
                                         << " received. Reset packet is sent.");
            SendRST();
        }
        CloseAndNotify();
    }
}
 
bool
TcpSocketBase::IsTcpOptionEnabled(uint8_t kind) const
{
    NS_LOG_FUNCTION(this << static_cast<uint32_t>(kind));
 
    switch (kind)
    {
    case TcpOption::TS:
        return m_timestampEnabled;
    case TcpOption::WINSCALE:
        return m_winScalingEnabled;
    case TcpOption::SACKPERMITTED:
    case TcpOption::SACK:
        return m_sackEnabled;
    default:
        break;
    }
    return false;
}
 
void
TcpSocketBase::ReadOptions(const TcpHeader& tcpHeader, uint32_t* bytesSacked)
{
    NS_LOG_FUNCTION(this << tcpHeader);
 
    for (const auto& option : tcpHeader.GetOptionList())
    {
        // Check only for ACK options here
        switch (option->GetKind())
        {
        case TcpOption::SACK:
            *bytesSacked = ProcessOptionSack(option);
            break;
        default:
            continue;
        }
    }
}
 
// Sender should reduce the Congestion Window as a response to receiver's
// ECN Echo notification only once per window
void
TcpSocketBase::EnterCwr(uint32_t currentDelivered)
{
    NS_LOG_FUNCTION(this << currentDelivered);
    m_tcb->m_ssThresh = m_congestionControl->GetSsThresh(m_tcb, BytesInFlight());
    NS_LOG_DEBUG("Reduce ssThresh to " << m_tcb->m_ssThresh);
    // Do not update m_cWnd, under assumption that recovery process will
    // gradually bring it down to m_ssThresh.  Update the 'inflated' value of
    // cWnd used for tracing, however.
    m_tcb->m_cWndInfl = m_tcb->m_ssThresh;
    NS_ASSERT(m_tcb->m_congState != TcpSocketState::CA_CWR);
    NS_LOG_DEBUG(TcpSocketState::TcpCongStateName[m_tcb->m_congState] << " -> CA_CWR");
    m_congestionControl->CongestionStateSet(m_tcb, TcpSocketState::CA_CWR);
    m_tcb->m_congState = TcpSocketState::CA_CWR;
    // CWR state will be exited when the ack exceeds the m_recover variable.
    // Do not set m_recoverActive (which applies to a loss-based recovery)
    // m_recover corresponds to Linux tp->high_seq
    m_recover = m_tcb->m_highTxMark;
    if (!m_congestionControl->HasCongControl())
    {
        // If there is a recovery algorithm, invoke it.
        m_recoveryOps->EnterRecovery(m_tcb, m_dupAckCount, UnAckDataCount(), currentDelivered);
        NS_LOG_INFO("Enter CWR recovery mode; set cwnd to " << m_tcb->m_cWnd << ", ssthresh to "
                                                            << m_tcb->m_ssThresh << ", recover to "
                                                            << m_recover);
    }
}
 
void
TcpSocketBase::EnterRecovery(uint32_t currentDelivered)
{
    NS_LOG_FUNCTION(this);
    NS_ASSERT(m_tcb->m_congState != TcpSocketState::CA_RECOVERY);
 
    NS_LOG_DEBUG(TcpSocketState::TcpCongStateName[m_tcb->m_congState] << " -> CA_RECOVERY");
 
    if (!m_sackEnabled)
    {
        // One segment has left the network, PLUS the head is lost
        m_txBuffer->AddRenoSack();
        m_txBuffer->MarkHeadAsLost();
    }
    else
    {
        if (!m_txBuffer->IsLost(m_txBuffer->HeadSequence()))
        {
            // We received 3 dupacks, but the head is not marked as lost
            // (received less than 3 SACK block ahead).
            // Manually set it as lost.
            m_txBuffer->MarkHeadAsLost();
        }
    }
 
    // RFC 6675, point (4):
    // (4) Invoke fast retransmit and enter loss recovery as follows:
    // (4.1) RecoveryPoint = HighData
    m_recover = m_tcb->m_highTxMark;
    m_recoverActive = true;
 
    m_congestionControl->CongestionStateSet(m_tcb, TcpSocketState::CA_RECOVERY);
    m_tcb->m_congState = TcpSocketState::CA_RECOVERY;
 
    // (4.2) ssthresh = cwnd = (FlightSize / 2)
    // If SACK is not enabled, still consider the head as 'in flight' for
    // compatibility with old ns-3 versions
    uint32_t bytesInFlight =
        m_sackEnabled ? BytesInFlight() : BytesInFlight() + m_tcb->m_segmentSize;
    m_tcb->m_ssThresh = m_congestionControl->GetSsThresh(m_tcb, bytesInFlight);
 
    if (!m_congestionControl->HasCongControl())
    {
        m_recoveryOps->EnterRecovery(m_tcb, m_dupAckCount, UnAckDataCount(), currentDelivered);
        NS_LOG_INFO(m_dupAckCount << " dupack. Enter fast recovery mode."
                                  << "Reset cwnd to " << m_tcb->m_cWnd << ", ssthresh to "
                                  << m_tcb->m_ssThresh << " at fast recovery seqnum " << m_recover
                                  << " calculated in flight: " << bytesInFlight);
    }
 
    // (4.3) Retransmit the first data segment presumed dropped
    uint32_t sz = SendDataPacket(m_highRxAckMark, m_tcb->m_segmentSize, true);
    NS_ASSERT_MSG(sz > 0, "SendDataPacket returned zero, indicating zero bytes were sent");
    // (4.4) Run SetPipe ()
    // (4.5) Proceed to step (C)
    // these steps are done after the ProcessAck function (SendPendingData)
}
 
void
TcpSocketBase::DupAck(uint32_t currentDelivered)
{
    NS_LOG_FUNCTION(this);
    // NOTE: We do not count the DupAcks received in CA_LOSS, because we
    // don't know if they are generated by a spurious retransmission or because
    // of a real packet loss. With SACK, it is easy to know, but we do not consider
    // dupacks. Without SACK, there are some heuristics in the RFC 6582, but
    // for now, we do not implement it, leading to ignoring the dupacks.
    if (m_tcb->m_congState == TcpSocketState::CA_LOSS)
    {
        return;
    }
 
    // RFC 6675, Section 5, 3rd paragraph:
    // If the incoming ACK is a duplicate acknowledgment per the definition
    // in Section 2 (regardless of its status as a cumulative
    // acknowledgment), and the TCP is not currently in loss recovery
    // the TCP MUST increase DupAcks by one ...
    if (m_tcb->m_congState != TcpSocketState::CA_RECOVERY)
    {
        ++m_dupAckCount;
    }
 
    if (m_tcb->m_congState == TcpSocketState::CA_OPEN)
    {
        // From Open we go Disorder
        NS_ASSERT_MSG(m_dupAckCount == 1,
                      "From OPEN->DISORDER but with " << m_dupAckCount << " dup ACKs");
 
        m_congestionControl->CongestionStateSet(m_tcb, TcpSocketState::CA_DISORDER);
        m_tcb->m_congState = TcpSocketState::CA_DISORDER;
 
        NS_LOG_DEBUG("CA_OPEN -> CA_DISORDER");
    }
 
    if (m_tcb->m_congState == TcpSocketState::CA_RECOVERY)
    {
        if (!m_sackEnabled)
        {
            // If we are in recovery and we receive a dupack, one segment
            // has left the network. This is equivalent to a SACK of one block.
            m_txBuffer->AddRenoSack();
        }
        if (!m_congestionControl->HasCongControl())
        {
            m_recoveryOps->DoRecovery(m_tcb, currentDelivered, true);
            NS_LOG_INFO(m_dupAckCount << " Dupack received in fast recovery mode."
                                         "Increase cwnd to "
                                      << m_tcb->m_cWnd);
        }
    }
    else if (m_tcb->m_congState == TcpSocketState::CA_DISORDER)
    {
        // m_dupackCount should not exceed its threshold in CA_DISORDER state
        // when m_recoverActive has not been set. When recovery point
        // have been set after timeout, the sender could enter into CA_DISORDER
        // after receiving new ACK smaller than m_recover. After that, m_dupackCount
        // can be equal and larger than m_retxThresh and we should avoid entering
        // CA_RECOVERY and reducing sending rate again.
        NS_ASSERT((m_dupAckCount <= m_retxThresh) || m_recoverActive);
 
        uint32_t fackDiff = 0;
        if (m_fackEnabled)
        {
            uint32_t headSeq = m_txBuffer->HeadSequence().GetValue();
            if (m_sndFack > headSeq)
            {
                fackDiff = m_sndFack - headSeq;
            }
        }
 
        // RFC 6675, Section 5, continuing:
        // ... and take the following steps:
        // (1) If DupAcks >= DupThresh, go to step (4).
        //     Sequence number comparison (m_highRxAckMark >= m_recover) will take
        //     effect only when m_recover has been set. Hence, we can avoid to use
        //     m_recover in the last congestion event and fail to enter
        //     CA_RECOVERY when sequence number is advanced significantly since
        //     the last congestion event, which could be common for
        //     bandwidth-greedy application in high speed and reliable network
        //     (such as datacenter network) whose sending rate is constrained by
        //     TCP socket buffer size at receiver side.
 
        // Check FACK recovery condition
 
        if ((m_fackEnabled && fackDiff > m_tcb->m_segmentSize * 3) ||
            ((m_dupAckCount == m_retxThresh) &&
             (m_highRxAckMark >= m_recover || (!m_recoverActive))))
        {
            EnterRecovery(currentDelivered);
            NS_ASSERT(m_tcb->m_congState == TcpSocketState::CA_RECOVERY);
        }
        // (2) If DupAcks < DupThresh but IsLost (HighACK + 1) returns true
        // (indicating at least three segments have arrived above the current
        // cumulative acknowledgment point, which is taken to indicate loss)
        // go to step (4).  Note that m_highRxAckMark is (HighACK + 1)
        else if (m_txBuffer->IsLost(m_highRxAckMark))
        {
            EnterRecovery(currentDelivered);
            NS_ASSERT(m_tcb->m_congState == TcpSocketState::CA_RECOVERY);
        }
        else
        {
            // (3) The TCP MAY transmit previously unsent data segments as per
            // Limited Transmit [RFC5681] ...except that the number of octets
            // which may be sent is governed by pipe and cwnd as follows:
            //
            // (3.1) Set HighRxt to HighACK.
            // Not clear in RFC. We don't do this here, since we still have
            // to retransmit the segment.
 
            if (!m_sackEnabled && m_limitedTx)
            {
                m_txBuffer->AddRenoSack();
 
                // In limited transmit, cwnd Infl is not updated.
            }
        }
    }
}
 
/* Process the newly received ACK */
void
TcpSocketBase::ReceivedAck(Ptr<Packet> packet, const TcpHeader& tcpHeader)
{
    NS_LOG_FUNCTION(this << tcpHeader);
 
    NS_ASSERT(0 != (tcpHeader.GetFlags() & TcpHeader::ACK));
    NS_ASSERT(m_tcb->m_segmentSize > 0);
 
    uint32_t previousLost = m_txBuffer->GetLost();
    uint32_t priorInFlight = m_tcb->m_bytesInFlight.Get();
 
    // RFC 6675, Section 5, 1st paragraph:
    // Upon the receipt of any ACK containing SACK information, the
    // scoreboard MUST be updated via the Update () routine (done in ReadOptions)
    uint32_t bytesSacked = 0;
    uint64_t previousDelivered = m_rateOps->GetConnectionRate().m_delivered;
    ReadOptions(tcpHeader, &bytesSacked);
 
    SequenceNumber32 ackNumber = tcpHeader.GetAckNumber();
    SequenceNumber32 oldHeadSequence = m_txBuffer->HeadSequence();
 
    if (ackNumber < oldHeadSequence)
    {
        NS_LOG_DEBUG("Possibly received a stale ACK (ack number < head sequence)");
        // If there is any data piggybacked, store it into m_rxBuffer
        if (packet->GetSize() > 0)
        {
            ReceivedData(packet, tcpHeader);
        }
        return;
    }
    if ((ackNumber > oldHeadSequence) && (ackNumber < m_recover) &&
        (m_tcb->m_congState == TcpSocketState::CA_RECOVERY))
    {
        uint32_t segAcked = (ackNumber - oldHeadSequence) / m_tcb->m_segmentSize;
        for (uint32_t i = 0; i < segAcked; i++)
        {
            if (m_txBuffer->IsRetransmittedDataAcked(ackNumber - (i * m_tcb->m_segmentSize)))
            {
                m_tcb->m_isRetransDataAcked = true;
                NS_LOG_DEBUG("Ack Number " << ackNumber << "is ACK of retransmitted packet.");
            }
        }
    }
 
    m_txBuffer->DiscardUpTo(ackNumber, MakeCallback(&TcpRateOps::SkbDelivered, m_rateOps));
 
    auto currentDelivered =
        static_cast<uint32_t>(m_rateOps->GetConnectionRate().m_delivered - previousDelivered);
    m_tcb->m_lastAckedSackedBytes = currentDelivered;
 
    if (m_tcb->m_congState == TcpSocketState::CA_CWR && (ackNumber > m_recover))
    {
        // Recovery is over after the window exceeds m_recover
        // (although it may be re-entered below if ECE is still set)
        NS_LOG_DEBUG(TcpSocketState::TcpCongStateName[m_tcb->m_congState] << " -> CA_OPEN");
        m_congestionControl->CongestionStateSet(m_tcb, TcpSocketState::CA_OPEN);
        m_tcb->m_congState = TcpSocketState::CA_OPEN;
        if (!m_congestionControl->HasCongControl())
        {
            m_tcb->m_cWnd = m_tcb->m_ssThresh.Get();
            m_recoveryOps->ExitRecovery(m_tcb);
            m_congestionControl->CwndEvent(m_tcb, TcpSocketState::CA_EVENT_COMPLETE_CWR);
        }
    }
 
    if (ackNumber > oldHeadSequence && (m_tcb->m_ecnState != TcpSocketState::ECN_DISABLED) &&
        (tcpHeader.GetFlags() & TcpHeader::ECE))
    {
        if (m_ecnEchoSeq < ackNumber)
        {
            NS_LOG_INFO("Received ECN Echo is valid");
            m_ecnEchoSeq = ackNumber;
            NS_LOG_DEBUG(TcpSocketState::EcnStateName[m_tcb->m_ecnState] << " -> ECN_ECE_RCVD");
            m_tcb->m_ecnState = TcpSocketState::ECN_ECE_RCVD;
            if (m_tcb->m_congState != TcpSocketState::CA_CWR)
            {
                EnterCwr(currentDelivered);
            }
        }
    }
    else if (m_tcb->m_ecnState == TcpSocketState::ECN_ECE_RCVD &&
             !(tcpHeader.GetFlags() & TcpHeader::ECE))
    {
        m_tcb->m_ecnState = TcpSocketState::ECN_IDLE;
    }
 
    // Update bytes in flight before processing the ACK for proper calculation of congestion window
    NS_LOG_INFO("Update bytes in flight before processing the ACK.");
    BytesInFlight();
 
    bool receivedData = packet->GetSize() > 0;
 
    // RFC 6675 Section 5: 2nd, 3rd paragraph and point (A), (B) implementation
    // are inside the function ProcessAck
    ProcessAck(ackNumber, (bytesSacked > 0), currentDelivered, oldHeadSequence, receivedData);
    m_tcb->m_isRetransDataAcked = false;
 
    if (m_congestionControl->HasCongControl())
    {
        uint32_t currentLost = m_txBuffer->GetLost();
        uint32_t lost =
            (currentLost > previousLost) ? currentLost - previousLost : previousLost - currentLost;
        auto rateSample = m_rateOps->GenerateSample(currentDelivered,
                                                    lost,
                                                    false,
                                                    priorInFlight,
                                                    m_tcb->m_minRtt);
        auto rateConn = m_rateOps->GetConnectionRate();
        m_congestionControl->CongControl(m_tcb, rateConn, rateSample);
    }
 
    // If there is any data piggybacked, store it into m_rxBuffer
    if (receivedData)
    {
        ReceivedData(packet, tcpHeader);
    }
 
    // RFC 6675, Section 5, point (C), try to send more data. NB: (C) is implemented
    // inside SendPendingData
    SendPendingData(m_connected);
}
 
void
TcpSocketBase::ProcessAck(const SequenceNumber32& ackNumber,
                          bool scoreboardUpdated,
                          uint32_t currentDelivered,
                          const SequenceNumber32& oldHeadSequence,
                          bool receivedData)
{
    NS_LOG_FUNCTION(this << ackNumber << scoreboardUpdated << currentDelivered << oldHeadSequence);
    // RFC 6675, Section 5, 2nd paragraph:
    // If the incoming ACK is a cumulative acknowledgment, the TCP MUST
    // reset DupAcks to zero.
    bool exitedFastRecovery = false;
    uint32_t oldDupAckCount = m_dupAckCount; // remember the old value
    m_tcb->m_lastAckedSeq = ackNumber;       // Update lastAckedSeq
    uint32_t bytesAcked = 0;
 
    /* In RFC 5681 the definition of duplicate acknowledgment was strict:
     *
     * (a) the receiver of the ACK has outstanding data,
     * (b) the incoming acknowledgment carries no data,
     * (c) the SYN and FIN bits are both off,
     * (d) the acknowledgment number is equal to the greatest acknowledgment
     *     received on the given connection (TCP.UNA from [RFC793]),
     * (e) the advertised window in the incoming acknowledgment equals the
     *     advertised window in the last incoming acknowledgment.
     *
     * With RFC 6675, this definition has been reduced:
     *
     * (a) the ACK is carrying a SACK block that identifies previously
     *     unacknowledged and un-SACKed octets between HighACK (TCP.UNA) and
     *     HighData (m_highTxMark)
     *
     * The check below implements conditions a), b), and d), and c) is prevented by virtue of not
     * reaching this code if SYN or FIN is set, and e) is not supported.
     */
 
    if (m_fackEnabled && ackNumber == m_txBuffer->HeadSequence() &&
        m_tcb->m_congState == TcpSocketState::CA_RECOVERY)
    {
        if (m_outstandingRetransBytes > m_tcb->m_segmentSize)
        {
            m_outstandingRetransBytes -= m_tcb->m_segmentSize;
        }
        else
        {
            m_outstandingRetransBytes = 0;
        }
    }
 
    bool isDupack = m_sackEnabled ? scoreboardUpdated
                                  : (ackNumber == oldHeadSequence &&
                                     ackNumber < m_tcb->m_highTxMark && !receivedData);
 
    NS_LOG_DEBUG("ACK of " << ackNumber << " SND.UNA=" << oldHeadSequence
                           << " SND.NXT=" << m_tcb->m_nextTxSequence
                           << " in state: " << TcpSocketState::TcpCongStateName[m_tcb->m_congState]
                           << " with m_recover: " << m_recover);
 
    // RFC 6675, Section 5, 3rd paragraph:
    // If the incoming ACK is a duplicate acknowledgment per the definition
    // in Section 2 (regardless of its status as a cumulative
    // acknowledgment), and the TCP is not currently in loss recovery
    if (isDupack)
    {
        // loss recovery check is done inside this function thanks to
        // the congestion state machine
        DupAck(currentDelivered);
    }
 
    if (ackNumber == oldHeadSequence && ackNumber == m_tcb->m_highTxMark)
    {
        // Dupack, but the ACK is precisely equal to the nextTxSequence
        return;
    }
    else if (ackNumber == oldHeadSequence && ackNumber > m_tcb->m_highTxMark)
    {
        // ACK of the FIN bit ... nextTxSequence is not updated since we
        // don't have anything to transmit
        NS_LOG_DEBUG("Update nextTxSequence manually to " << ackNumber);
        m_tcb->m_nextTxSequence = ackNumber;
    }
    else if (ackNumber == oldHeadSequence)
    {
        // DupAck. Artificially call PktsAcked: after all, one segment has been ACKed.
        m_congestionControl->PktsAcked(m_tcb, 1, m_tcb->m_srtt);
    }
    else if (ackNumber > oldHeadSequence)
    {
        // Please remember that, with SACK, we can enter here even if we
        // received a dupack.
        bytesAcked = currentDelivered;
        uint32_t segsAcked = bytesAcked / m_tcb->m_segmentSize;
        m_bytesAckedNotProcessed += bytesAcked % m_tcb->m_segmentSize;
        bytesAcked -= bytesAcked % m_tcb->m_segmentSize;
 
        if (m_bytesAckedNotProcessed >= m_tcb->m_segmentSize)
        {
            segsAcked += 1;
            bytesAcked += m_tcb->m_segmentSize;
            m_bytesAckedNotProcessed -= m_tcb->m_segmentSize;
        }
        NS_LOG_DEBUG("Set segsAcked: " << segsAcked
                                       << " based on currentDelivered: " << currentDelivered);
 
        // Dupack count is reset to eventually fast-retransmit after 3 dupacks.
        // Any SACK-ed segment will be cleaned up by DiscardUpTo.
        // In the case that we advanced SND.UNA, but the ack contains SACK blocks,
        // we do not reset. At the third one we will retransmit.
        // If we are already in recovery, this check is useless since dupAcks
        // are not considered in this phase. When from Recovery we go back
        // to open, then dupAckCount is reset anyway.
        if (!isDupack)
        {
            m_dupAckCount = 0;
        }
 
        // RFC 6675, Section 5, part (B)
        // (B) Upon receipt of an ACK that does not cover RecoveryPoint, the
        // following actions MUST be taken:
        //
        // (B.1) Use Update () to record the new SACK information conveyed
        //       by the incoming ACK.
        // (B.2) Use SetPipe () to re-calculate the number of octets still
        //       in the network.
        //
        // (B.1) is done at the beginning, while (B.2) is delayed to part (C) while
        // trying to transmit with SendPendingData. We are not allowed to exit
        // the CA_RECOVERY phase. Just process this partial ack (RFC 5681)
        if (ackNumber < m_recover && m_tcb->m_congState == TcpSocketState::CA_RECOVERY)
        {
            if (!m_sackEnabled)
            {
                // Manually set the head as lost, it will be retransmitted.
                NS_LOG_INFO("Partial ACK. Manually setting head as lost");
                m_txBuffer->MarkHeadAsLost();
            }
 
            // Before retransmitting the packet perform DoRecovery and check if
            // there is available window
            if (!m_congestionControl->HasCongControl() && segsAcked >= 1)
            {
                m_recoveryOps->DoRecovery(m_tcb, currentDelivered, false);
            }
 
            // If the packet is already retransmitted do not retransmit it
            if (!m_txBuffer->IsRetransmittedDataAcked(ackNumber + m_tcb->m_segmentSize))
            {
                DoRetransmit(); // Assume the next seq is lost. Retransmit lost packet
                m_tcb->m_cWndInfl = SafeSubtraction(m_tcb->m_cWndInfl, bytesAcked);
            }
 
            // This partial ACK acknowledge the fact that one segment has been
            // previously lost and now successfully received. All others have
            // been processed when they come under the form of dupACKs
            m_congestionControl->PktsAcked(m_tcb, 1, m_tcb->m_srtt);
            NewAck(ackNumber, m_isFirstPartialAck);
 
            if (m_isFirstPartialAck)
            {
                NS_LOG_DEBUG("Partial ACK of " << ackNumber
                                               << " and this is the first (RTO will be reset);"
                                                  " cwnd set to "
                                               << m_tcb->m_cWnd << " recover seq: " << m_recover
                                               << " dupAck count: " << m_dupAckCount);
                m_isFirstPartialAck = false;
            }
            else
            {
                NS_LOG_DEBUG("Partial ACK of "
                             << ackNumber
                             << " and this is NOT the first (RTO will not be reset)"
                                " cwnd set to "
                             << m_tcb->m_cWnd << " recover seq: " << m_recover
                             << " dupAck count: " << m_dupAckCount);
            }
        }
        // From RFC 6675 section 5.1
        // In addition, a new recovery phase (as described in Section 5) MUST NOT
        // be initiated until HighACK is greater than or equal to the new value
        // of RecoveryPoint.
        else if (ackNumber < m_recover && m_tcb->m_congState == TcpSocketState::CA_LOSS)
        {
            m_congestionControl->PktsAcked(m_tcb, segsAcked, m_tcb->m_srtt);
            m_congestionControl->IncreaseWindow(m_tcb, segsAcked);
 
            NS_LOG_DEBUG(" Cong Control Called, cWnd=" << m_tcb->m_cWnd
                                                       << " ssTh=" << m_tcb->m_ssThresh);
            if (!m_sackEnabled)
            {
                NS_ASSERT_MSG(
                    m_txBuffer->GetSacked() == 0,
                    "Some segment got dup-acked in CA_LOSS state: " << m_txBuffer->GetSacked());
            }
            NewAck(ackNumber, true);
        }
        else if (m_tcb->m_congState == TcpSocketState::CA_CWR)
        {
            m_congestionControl->PktsAcked(m_tcb, segsAcked, m_tcb->m_srtt);
            // TODO: need to check behavior if marking is compounded by loss
            // and/or packet reordering
            if (!m_congestionControl->HasCongControl() && segsAcked >= 1)
            {
                m_recoveryOps->DoRecovery(m_tcb, currentDelivered, false);
            }
            NewAck(ackNumber, true);
        }
        else
        {
            if (m_tcb->m_congState == TcpSocketState::CA_OPEN)
            {
                m_congestionControl->PktsAcked(m_tcb, segsAcked, m_tcb->m_srtt);
            }
            else if (m_tcb->m_congState == TcpSocketState::CA_DISORDER)
            {
                if (segsAcked >= oldDupAckCount)
                {
                    m_congestionControl->PktsAcked(m_tcb,
                                                   segsAcked - oldDupAckCount,
                                                   m_tcb->m_srtt);
                }
 
                if (!isDupack)
                {
                    // The network reorder packets. Linux changes the counting lost
                    // packet algorithm from FACK to NewReno. We simply go back in Open.
                    m_congestionControl->CongestionStateSet(m_tcb, TcpSocketState::CA_OPEN);
                    m_tcb->m_congState = TcpSocketState::CA_OPEN;
                    NS_LOG_DEBUG(segsAcked << " segments acked in CA_DISORDER, ack of " << ackNumber
                                           << " exiting CA_DISORDER -> CA_OPEN");
                }
                else
                {
                    NS_LOG_DEBUG(segsAcked << " segments acked in CA_DISORDER, ack of " << ackNumber
                                           << " but still in CA_DISORDER");
                }
            }
            // RFC 6675, Section 5:
            // Once a TCP is in the loss recovery phase, the following procedure
            // MUST be used for each arriving ACK:
            // (A) An incoming cumulative ACK for a sequence number greater than
            // RecoveryPoint signals the end of loss recovery, and the loss
            // recovery phase MUST be terminated.  Any information contained in
            // the scoreboard for sequence numbers greater than the new value of
            // HighACK SHOULD NOT be cleared when leaving the loss recovery
            // phase.
            else if (m_tcb->m_congState == TcpSocketState::CA_RECOVERY)
            {
                m_isFirstPartialAck = true;
 
                // Recalculate the segs acked, that are from m_recover to ackNumber
                // (which are the ones we have not passed to PktsAcked and that
                // can increase cWnd)
                // TODO:  check consistency for dynamic segment size
                segsAcked =
                    static_cast<uint32_t>(ackNumber - oldHeadSequence) / m_tcb->m_segmentSize;
                m_congestionControl->PktsAcked(m_tcb, segsAcked, m_tcb->m_srtt);
                m_congestionControl->CwndEvent(m_tcb, TcpSocketState::CA_EVENT_COMPLETE_CWR);
                m_congestionControl->CongestionStateSet(m_tcb, TcpSocketState::CA_OPEN);
                m_tcb->m_congState = TcpSocketState::CA_OPEN;
                exitedFastRecovery = true;
                m_dupAckCount = 0; // From recovery to open, reset dupack
 
                NS_LOG_DEBUG(segsAcked << " segments acked in CA_RECOVER, ack of " << ackNumber
                                       << ", exiting CA_RECOVERY -> CA_OPEN");
            }
            else if (m_tcb->m_congState == TcpSocketState::CA_LOSS)
            {
                m_isFirstPartialAck = true;
 
                // Recalculate the segs acked, that are from m_recover to ackNumber
                // (which are the ones we have not passed to PktsAcked and that
                // can increase cWnd)
                segsAcked = (ackNumber - m_recover) / m_tcb->m_segmentSize;
 
                m_congestionControl->PktsAcked(m_tcb, segsAcked, m_tcb->m_srtt);
 
                m_congestionControl->CongestionStateSet(m_tcb, TcpSocketState::CA_OPEN);
                m_tcb->m_congState = TcpSocketState::CA_OPEN;
                NS_LOG_DEBUG(segsAcked << " segments acked in CA_LOSS, ack of" << ackNumber
                                       << ", exiting CA_LOSS -> CA_OPEN");
            }
 
            if (ackNumber >= m_recover)
            {
                // All lost segments in the congestion event have been
                // retransmitted successfully. The recovery point (m_recover)
                // should be deactivated.
                m_recoverActive = false;
            }
 
            if (exitedFastRecovery)
            {
                NewAck(ackNumber, true);
                m_tcb->m_cWnd = m_tcb->m_ssThresh.Get();
                m_recoveryOps->ExitRecovery(m_tcb);
                NS_LOG_DEBUG("Leaving Fast Recovery; BytesInFlight() = "
                             << BytesInFlight() << "; cWnd = " << m_tcb->m_cWnd);
            }
            if (m_tcb->m_congState == TcpSocketState::CA_OPEN)
            {
                m_congestionControl->IncreaseWindow(m_tcb, segsAcked);
 
                m_tcb->m_cWndInfl = m_tcb->m_cWnd;
 
                NS_LOG_LOGIC("Congestion control called: cWnd: " << m_tcb->m_cWnd
                                                                 << " ssTh: " << m_tcb->m_ssThresh
                                                                 << " segsAcked: " << segsAcked);
 
                NewAck(ackNumber, true);
            }
        }
    }
    // Update the pacing rate, since m_congestionControl->IncreaseWindow() or
    // m_congestionControl->PktsAcked () may change m_tcb->m_cWnd
    // Make sure that control reaches the end of this function and there is no
    // return in between
    UpdatePacingRate();
}
 
/* Received a packet upon LISTEN state. */
void
TcpSocketBase::ProcessListen(Ptr<Packet> packet,
                             const TcpHeader& tcpHeader,
                             const Address& fromAddress,
                             const Address& toAddress)
{
    NS_LOG_FUNCTION(this << tcpHeader);
 
    // Extract the flags. PSH, URG, CWR and ECE are disregarded.
    uint8_t tcpflags =
        tcpHeader.GetFlags() & ~(TcpHeader::PSH | TcpHeader::URG | TcpHeader::CWR | TcpHeader::ECE);
 
    // Fork a socket if received a SYN. Do nothing otherwise.
    // C.f.: the LISTEN part in tcp_v4_do_rcv() in tcp_ipv4.c in Linux kernel
    if (tcpflags != TcpHeader::SYN)
    {
        return;
    }
 
    // Call socket's notify function to let the server app know we got a SYN
    // If the server app refuses the connection, do nothing
    if (!NotifyConnectionRequest(fromAddress))
    {
        return;
    }
    // Clone the socket, simulate fork
    Ptr<TcpSocketBase> newSock = Fork();
    NS_LOG_LOGIC("Cloned a TcpSocketBase " << newSock);
    Simulator::ScheduleNow(&TcpSocketBase::CompleteFork,
                           newSock,
                           packet,
                           tcpHeader,
                           fromAddress,
                           toAddress);
}
 
/* Received a packet upon SYN_SENT */
void
TcpSocketBase::ProcessSynSent(Ptr<Packet> packet, const TcpHeader& tcpHeader)
{
    NS_LOG_FUNCTION(this << tcpHeader);
 
    // Extract the flags. PSH and URG are disregarded.
    uint8_t tcpflags = tcpHeader.GetFlags() & ~(TcpHeader::PSH | TcpHeader::URG);
 
    if (tcpflags == 0)
    { // Bare data, accept it and move to ESTABLISHED state. This is not a normal behaviour. Remove
      // this?
        NS_LOG_DEBUG("SYN_SENT -> ESTABLISHED");
        m_congestionControl->CongestionStateSet(m_tcb, TcpSocketState::CA_OPEN);
        m_tcb->m_congState = TcpSocketState::CA_OPEN;
        m_state = ESTABLISHED;
        m_connected = true;
        m_retxEvent.Cancel();
        m_delAckCount = m_delAckMaxCount;
        ReceivedData(packet, tcpHeader);
        Simulator::ScheduleNow(&TcpSocketBase::ConnectionSucceeded, this);
    }
    else if (tcpflags & TcpHeader::ACK && !(tcpflags & TcpHeader::SYN))
    { // Ignore ACK in SYN_SENT
    }
    else if (tcpflags & TcpHeader::SYN && !(tcpflags & TcpHeader::ACK))
    { // Received SYN, move to SYN_RCVD state and respond with SYN+ACK
        NS_LOG_DEBUG("SYN_SENT -> SYN_RCVD");
        m_state = SYN_RCVD;
        m_synCount = m_synRetries;
        m_tcb->m_rxBuffer->SetNextRxSequence(tcpHeader.GetSequenceNumber() + SequenceNumber32(1));
        /* Check if we received an ECN SYN packet. Change the ECN state of receiver to ECN_IDLE if
         * the traffic is ECN capable and sender has sent ECN SYN packet
         */
 
        if (m_tcb->m_useEcn != TcpSocketState::Off &&
            (tcpflags & (TcpHeader::CWR | TcpHeader::ECE)) == (TcpHeader::CWR | TcpHeader::ECE))
        {
            NS_LOG_INFO("Received ECN SYN packet");
            SendEmptyPacket(TcpHeader::SYN | TcpHeader::ACK | TcpHeader::ECE);
            NS_LOG_DEBUG(TcpSocketState::EcnStateName[m_tcb->m_ecnState] << " -> ECN_IDLE");
            m_tcb->m_ecnState = TcpSocketState::ECN_IDLE;
        }
        else
        {
            m_tcb->m_ecnState = TcpSocketState::ECN_DISABLED;
            SendEmptyPacket(TcpHeader::SYN | TcpHeader::ACK);
        }
    }
    else if (tcpflags & (TcpHeader::SYN | TcpHeader::ACK) &&
             m_tcb->m_nextTxSequence + SequenceNumber32(1) == tcpHeader.GetAckNumber())
    { // Handshake completed
        NS_LOG_DEBUG("SYN_SENT -> ESTABLISHED");
        m_congestionControl->CongestionStateSet(m_tcb, TcpSocketState::CA_OPEN);
        m_tcb->m_congState = TcpSocketState::CA_OPEN;
        m_state = ESTABLISHED;
        m_connected = true;
        m_retxEvent.Cancel();
        m_tcb->m_rxBuffer->SetNextRxSequence(tcpHeader.GetSequenceNumber() + SequenceNumber32(1));
        m_tcb->m_highTxMark = ++m_tcb->m_nextTxSequence;
        m_txBuffer->SetHeadSequence(m_tcb->m_nextTxSequence);
        // Before sending packets, update the pacing rate based on RTT measurement so far
        UpdatePacingRate();
        SendEmptyPacket(TcpHeader::ACK);
 
        /* Check if we received an ECN SYN-ACK packet. Change the ECN state of sender to ECN_IDLE if
         * receiver has sent an ECN SYN-ACK packet and the  traffic is ECN Capable
         */
        if (m_tcb->m_useEcn != TcpSocketState::Off &&
            (tcpflags & (TcpHeader::CWR | TcpHeader::ECE)) == (TcpHeader::ECE))
        {
            NS_LOG_INFO("Received ECN SYN-ACK packet.");
            NS_LOG_DEBUG(TcpSocketState::EcnStateName[m_tcb->m_ecnState] << " -> ECN_IDLE");
            m_tcb->m_ecnState = TcpSocketState::ECN_IDLE;
        }
        else
        {
            m_tcb->m_ecnState = TcpSocketState::ECN_DISABLED;
        }
        SendPendingData(m_connected);
        Simulator::ScheduleNow(&TcpSocketBase::ConnectionSucceeded, this);
        // Always respond to first data packet to speed up the connection.
        // Remove to get the behaviour of old NS-3 code.
        m_delAckCount = m_delAckMaxCount;
    }
    else
    { // Other in-sequence input
        if (!(tcpflags & TcpHeader::RST))
        { // When (1) rx of FIN+ACK; (2) rx of FIN; (3) rx of bad flags
            NS_LOG_LOGIC("Illegal flag combination "
                         << TcpHeader::FlagsToString(tcpHeader.GetFlags())
                         << " received in SYN_SENT. Reset packet is sent.");
            SendRST();
        }
        CloseAndNotify();
    }
}
 
/* Received a packet upon SYN_RCVD */
void
TcpSocketBase::ProcessSynRcvd(Ptr<Packet> packet,
                              const TcpHeader& tcpHeader,
                              const Address& fromAddress,
                              const Address& /* toAddress */)
{
    NS_LOG_FUNCTION(this << tcpHeader);
 
    // Extract the flags. PSH, URG, CWR and ECE are disregarded.
    uint8_t tcpflags =
        tcpHeader.GetFlags() & ~(TcpHeader::PSH | TcpHeader::URG | TcpHeader::CWR | TcpHeader::ECE);
 
    if (tcpflags == 0 ||
        (tcpflags == TcpHeader::ACK &&
         m_tcb->m_nextTxSequence + SequenceNumber32(1) == tcpHeader.GetAckNumber()))
    { // If it is bare data, accept it and move to ESTABLISHED state. This is
        // possibly due to ACK lost in 3WHS. If in-sequence ACK is received, the
        // handshake is completed nicely.
        NS_LOG_DEBUG("SYN_RCVD -> ESTABLISHED");
        m_congestionControl->CongestionStateSet(m_tcb, TcpSocketState::CA_OPEN);
        m_tcb->m_congState = TcpSocketState::CA_OPEN;
        m_state = ESTABLISHED;
        m_connected = true;
        m_retxEvent.Cancel();
        m_tcb->m_highTxMark = ++m_tcb->m_nextTxSequence;
        m_txBuffer->SetHeadSequence(m_tcb->m_nextTxSequence);
        if (m_endPoint)
        {
            m_endPoint->SetPeer(InetSocketAddress::ConvertFrom(fromAddress).GetIpv4(),
                                InetSocketAddress::ConvertFrom(fromAddress).GetPort());
        }
        else if (m_endPoint6)
        {
            m_endPoint6->SetPeer(Inet6SocketAddress::ConvertFrom(fromAddress).GetIpv6(),
                                 Inet6SocketAddress::ConvertFrom(fromAddress).GetPort());
        }
        // Always respond to first data packet to speed up the connection.
        // Remove to get the behaviour of old NS-3 code.
        m_delAckCount = m_delAckMaxCount;
        NotifyNewConnectionCreated(this, fromAddress);
        ReceivedAck(packet, tcpHeader);
        // Update the pacing rate based on RTT measurement so far
        UpdatePacingRate();
        // As this connection is established, the socket is available to send data now
        if (GetTxAvailable() > 0)
        {
            NotifySend(GetTxAvailable());
        }
    }
    else if (tcpflags == TcpHeader::SYN)
    { // Probably the peer lost my SYN+ACK
        m_tcb->m_rxBuffer->SetNextRxSequence(tcpHeader.GetSequenceNumber() + SequenceNumber32(1));
        /* Check if we received an ECN SYN packet. Change the ECN state of receiver to ECN_IDLE if
         * sender has sent an ECN SYN packet and the  traffic is ECN Capable
         */
        if (m_tcb->m_useEcn != TcpSocketState::Off &&
            (tcpHeader.GetFlags() & (TcpHeader::CWR | TcpHeader::ECE)) ==
                (TcpHeader::CWR | TcpHeader::ECE))
        {
            NS_LOG_INFO("Received ECN SYN packet");
            SendEmptyPacket(TcpHeader::SYN | TcpHeader::ACK | TcpHeader::ECE);
            NS_LOG_DEBUG(TcpSocketState::EcnStateName[m_tcb->m_ecnState] << " -> ECN_IDLE");
            m_tcb->m_ecnState = TcpSocketState::ECN_IDLE;
        }
        else
        {
            m_tcb->m_ecnState = TcpSocketState::ECN_DISABLED;
            SendEmptyPacket(TcpHeader::SYN | TcpHeader::ACK);
        }
    }
    else if (tcpflags == (TcpHeader::FIN | TcpHeader::ACK))
    {
        if (tcpHeader.GetSequenceNumber() == m_tcb->m_rxBuffer->NextRxSequence())
        { // In-sequence FIN before connection complete. Set up connection and close.
            m_connected = true;
            m_retxEvent.Cancel();
            m_tcb->m_highTxMark = ++m_tcb->m_nextTxSequence;
            m_txBuffer->SetHeadSequence(m_tcb->m_nextTxSequence);
            if (m_endPoint)
            {
                m_endPoint->SetPeer(InetSocketAddress::ConvertFrom(fromAddress).GetIpv4(),
                                    InetSocketAddress::ConvertFrom(fromAddress).GetPort());
            }
            else if (m_endPoint6)
            {
                m_endPoint6->SetPeer(Inet6SocketAddress::ConvertFrom(fromAddress).GetIpv6(),
                                     Inet6SocketAddress::ConvertFrom(fromAddress).GetPort());
            }
            NotifyNewConnectionCreated(this, fromAddress);
            PeerClose(packet, tcpHeader);
        }
    }
    else
    { // Other in-sequence input
        if (tcpflags != TcpHeader::RST)
        { // When (1) rx of SYN+ACK; (2) rx of FIN; (3) rx of bad flags
            NS_LOG_LOGIC("Illegal flag " << TcpHeader::FlagsToString(tcpflags)
                                         << " received. Reset packet is sent.");
            if (m_endPoint)
            {
                m_endPoint->SetPeer(InetSocketAddress::ConvertFrom(fromAddress).GetIpv4(),
                                    InetSocketAddress::ConvertFrom(fromAddress).GetPort());
            }
            else if (m_endPoint6)
            {
                m_endPoint6->SetPeer(Inet6SocketAddress::ConvertFrom(fromAddress).GetIpv6(),
                                     Inet6SocketAddress::ConvertFrom(fromAddress).GetPort());
            }
            SendRST();
        }
        CloseAndNotify();
    }
}
 
/* Received a packet upon CLOSE_WAIT, FIN_WAIT_1, or FIN_WAIT_2 states */
void
TcpSocketBase::ProcessWait(Ptr<Packet> packet, const TcpHeader& tcpHeader)
{
    NS_LOG_FUNCTION(this << tcpHeader);
 
    // Extract the flags. PSH, URG, CWR and ECE are disregarded.
    uint8_t tcpflags =
        tcpHeader.GetFlags() & ~(TcpHeader::PSH | TcpHeader::URG | TcpHeader::CWR | TcpHeader::ECE);
 
    if (packet->GetSize() > 0 && !(tcpflags & TcpHeader::ACK))
    { // Bare data, accept it
        ReceivedData(packet, tcpHeader);
    }
    else if (tcpflags == TcpHeader::ACK)
    { // Process the ACK, and if in FIN_WAIT_1, conditionally move to FIN_WAIT_2
        ReceivedAck(packet, tcpHeader);
        if (m_state == FIN_WAIT_1 && m_txBuffer->Size() == 0 &&
            tcpHeader.GetAckNumber() == m_tcb->m_highTxMark + SequenceNumber32(1))
        { // This ACK corresponds to the FIN sent
            NS_LOG_DEBUG("FIN_WAIT_1 -> FIN_WAIT_2");
            m_state = FIN_WAIT_2;
        }
    }
    else if (tcpflags == TcpHeader::FIN || tcpflags == (TcpHeader::FIN | TcpHeader::ACK))
    { // Got FIN, respond with ACK and move to next state
        if (tcpflags & TcpHeader::ACK)
        { // Process the ACK first
            ReceivedAck(packet, tcpHeader);
        }
        m_tcb->m_rxBuffer->SetFinSequence(tcpHeader.GetSequenceNumber());
    }
    else if (tcpflags == TcpHeader::SYN || tcpflags == (TcpHeader::SYN | TcpHeader::ACK))
    { // Duplicated SYN or SYN+ACK, possibly due to spurious retransmission
        return;
    }
    else
    { // This is a RST or bad flags
        if (tcpflags != TcpHeader::RST)
        {
            NS_LOG_LOGIC("Illegal flag " << TcpHeader::FlagsToString(tcpflags)
                                         << " received. Reset packet is sent.");
            SendRST();
        }
        CloseAndNotify();
        return;
    }
 
    // Check if the close responder sent an in-sequence FIN, if so, respond ACK
    if ((m_state == FIN_WAIT_1 || m_state == FIN_WAIT_2) && m_tcb->m_rxBuffer->Finished())
    {
        if (m_state == FIN_WAIT_1)
        {
            NS_LOG_DEBUG("FIN_WAIT_1 -> CLOSING");
            m_state = CLOSING;
            if (m_txBuffer->Size() == 0 &&
                tcpHeader.GetAckNumber() == m_tcb->m_highTxMark + SequenceNumber32(1))
            { // This ACK corresponds to the FIN sent
                TimeWait();
            }
        }
        else if (m_state == FIN_WAIT_2)
        {
            TimeWait();
        }
        SendEmptyPacket(TcpHeader::ACK);
        if (!m_shutdownRecv)
        {
            NotifyDataRecv();
        }
    }
}
 
/* Received a packet upon CLOSING */
void
TcpSocketBase::ProcessClosing(Ptr<Packet> packet, const TcpHeader& tcpHeader)
{
    NS_LOG_FUNCTION(this << tcpHeader);
 
    // Extract the flags. PSH and URG are disregarded.
    uint8_t tcpflags = tcpHeader.GetFlags() & ~(TcpHeader::PSH | TcpHeader::URG);
 
    if (tcpflags == TcpHeader::ACK)
    {
        if (tcpHeader.GetSequenceNumber() == m_tcb->m_rxBuffer->NextRxSequence())
        { // This ACK corresponds to the FIN sent
            TimeWait();
        }
    }
    else
    { // CLOSING state means simultaneous close, i.e. no one is sending data to
        // anyone. If anything other than ACK is received, respond with a reset.
        if (tcpflags == TcpHeader::FIN || tcpflags == (TcpHeader::FIN | TcpHeader::ACK))
        { // FIN from the peer as well. We can close immediately.
            SendEmptyPacket(TcpHeader::ACK);
        }
        else if (tcpflags != TcpHeader::RST)
        { // Receive of SYN or SYN+ACK or bad flags or pure data
            NS_LOG_LOGIC("Illegal flag " << TcpHeader::FlagsToString(tcpflags)
                                         << " received. Reset packet is sent.");
            SendRST();
        }
        CloseAndNotify();
    }
}
 
/* Received a packet upon LAST_ACK */
void
TcpSocketBase::ProcessLastAck(Ptr<Packet> packet, const TcpHeader& tcpHeader)
{
    NS_LOG_FUNCTION(this << tcpHeader);
 
    // Extract the flags. PSH and URG are disregarded.
    uint8_t tcpflags = tcpHeader.GetFlags() & ~(TcpHeader::PSH | TcpHeader::URG);
 
    if (tcpflags == 0)
    {
        ReceivedData(packet, tcpHeader);
    }
    else if (tcpflags == TcpHeader::ACK)
    {
        if (tcpHeader.GetSequenceNumber() == m_tcb->m_rxBuffer->NextRxSequence())
        { // This ACK corresponds to the FIN sent. This socket closed peacefully.
            CloseAndNotify();
        }
    }
    else if (tcpflags == TcpHeader::FIN)
    { // Received FIN again, the peer probably lost the FIN+ACK
        SendEmptyPacket(TcpHeader::FIN | TcpHeader::ACK);
    }
    else if (tcpflags == (TcpHeader::FIN | TcpHeader::ACK) || tcpflags == TcpHeader::RST)
    {
        CloseAndNotify();
    }
    else
    { // Received a SYN or SYN+ACK or bad flags
        NS_LOG_LOGIC("Illegal flag " << TcpHeader::FlagsToString(tcpflags)
                                     << " received. Reset packet is sent.");
        SendRST();
        CloseAndNotify();
    }
}
 
/* Peer sent me a FIN. Remember its sequence in rx buffer. */
void
TcpSocketBase::PeerClose(Ptr<Packet> p, const TcpHeader& tcpHeader)
{
    NS_LOG_FUNCTION(this << tcpHeader);
 
    // Ignore all out of range packets
    if (tcpHeader.GetSequenceNumber() < m_tcb->m_rxBuffer->NextRxSequence() ||
        tcpHeader.GetSequenceNumber() > m_tcb->m_rxBuffer->MaxRxSequence())
    {
        return;
    }
    // For any case, remember the FIN position in rx buffer first
    m_tcb->m_rxBuffer->SetFinSequence(tcpHeader.GetSequenceNumber() +
                                      SequenceNumber32(p->GetSize()));
    NS_LOG_LOGIC("Accepted FIN at seq "
                 << tcpHeader.GetSequenceNumber() + SequenceNumber32(p->GetSize()));
    // If there is any piggybacked data, process it
    if (p->GetSize())
    {
        ReceivedData(p, tcpHeader);
    }
    // Return if FIN is out of sequence, otherwise move to CLOSE_WAIT state by DoPeerClose
    if (!m_tcb->m_rxBuffer->Finished())
    {
        return;
    }
 
    // Simultaneous close: Application invoked Close() when we are processing this FIN packet
    if (m_state == FIN_WAIT_1)
    {
        NS_LOG_DEBUG("FIN_WAIT_1 -> CLOSING");
        m_state = CLOSING;
        return;
    }
 
    DoPeerClose(); // Change state, respond with ACK
}
 
/* Received a in-sequence FIN. Close down this socket. */
void
TcpSocketBase::DoPeerClose()
{
    NS_ASSERT(m_state == ESTABLISHED || m_state == SYN_RCVD || m_state == FIN_WAIT_1 ||
              m_state == FIN_WAIT_2);
 
    // Move the state to CLOSE_WAIT
    NS_LOG_DEBUG(TcpStateName[m_state] << " -> CLOSE_WAIT");
    m_state = CLOSE_WAIT;
 
    if (!m_closeNotified)
    {
        // The normal behaviour for an application is that, when the peer sent a in-sequence
        // FIN, the app should prepare to close. The app has two choices at this point: either
        // respond with ShutdownSend() call to declare that it has nothing more to send and
        // the socket can be closed immediately; or remember the peer's close request, wait
        // until all its existing data are pushed into the TCP socket, then call Close()
        // explicitly.
        NS_LOG_LOGIC("TCP " << this << " calling NotifyNormalClose");
        NotifyNormalClose();
        m_closeNotified = true;
    }
    if (m_shutdownSend)
    { // The application declares that it would not sent any more, close this socket
        Close();
    }
    else
    { // Need to ack, the application will close later
        SendEmptyPacket(TcpHeader::ACK);
    }
    if (m_state == LAST_ACK)
    {
        m_dataRetrCount = m_dataRetries; // prevent endless FINs
        NS_LOG_LOGIC("TcpSocketBase " << this << " scheduling LATO1");
        Time lastRto = m_rtt->GetEstimate() + Max(m_clockGranularity, m_rtt->GetVariation() * 4);
        m_lastAckEvent = Simulator::Schedule(lastRto, &TcpSocketBase::LastAckTimeout, this);
    }
}
 
/* Kill this socket. This is a callback function configured to m_endpoint in
   SetupCallback(), invoked when the endpoint is destroyed. */
void
TcpSocketBase::Destroy()
{
    NS_LOG_FUNCTION(this);
    m_endPoint = nullptr;
    if (m_tcp)
    {
        m_tcp->RemoveSocket(this);
    }
    NS_LOG_LOGIC(this << " Cancelled ReTxTimeout event which was set to expire at "
                      << (Simulator::Now() + Simulator::GetDelayLeft(m_retxEvent)).GetSeconds());
    CancelAllTimers();
}
 
/* Kill this socket. This is a callback function configured to m_endpoint in
   SetupCallback(), invoked when the endpoint is destroyed. */
void
TcpSocketBase::Destroy6()
{
    NS_LOG_FUNCTION(this);
    m_endPoint6 = nullptr;
    if (m_tcp)
    {
        m_tcp->RemoveSocket(this);
    }
    NS_LOG_LOGIC(this << " Cancelled ReTxTimeout event which was set to expire at "
                      << (Simulator::Now() + Simulator::GetDelayLeft(m_retxEvent)).GetSeconds());
    CancelAllTimers();
}
 
/* Send an empty packet with specified TCP flags */
void
TcpSocketBase::SendEmptyPacket(uint8_t flags)
{
    NS_LOG_FUNCTION(this << static_cast<uint32_t>(flags));
 
    if (m_endPoint == nullptr && m_endPoint6 == nullptr)
    {
        NS_LOG_WARN("Failed to send empty packet due to null endpoint");
        return;
    }
 
    Ptr<Packet> p = Create<Packet>();
    TcpHeader header;
    SequenceNumber32 s = m_tcb->m_nextTxSequence;
    TcpPacketType_t packetType = INVALID;
 
    if (flags & TcpHeader::FIN)
    {
        packetType = TcpPacketType_t::FIN;
        flags |= TcpHeader::ACK;
    }
    else if (m_state == FIN_WAIT_1 || m_state == LAST_ACK || m_state == CLOSING)
    {
        ++s;
    }
 
    if (flags & TcpHeader::SYN)
    {
        packetType = TcpPacketType_t::SYN;
        if (flags & TcpHeader::ACK)
        {
            packetType = TcpPacketType_t::SYN_ACK;
        }
    }
    else if (flags & TcpHeader::ACK)
    {
        packetType = TcpPacketType_t::PURE_ACK;
    }
 
    if (flags & TcpHeader::RST)
    {
        packetType = TcpPacketType_t::RST;
    }
 
    NS_ASSERT_MSG(packetType != TcpPacketType_t::INVALID, "Invalid TCP packet type");
    AddSocketTags(p, IsEct(packetType));
 
    header.SetFlags(flags);
    header.SetSequenceNumber(s);
    header.SetAckNumber(m_tcb->m_rxBuffer->NextRxSequence());
    if (m_endPoint != nullptr)
    {
        header.SetSourcePort(m_endPoint->GetLocalPort());
        header.SetDestinationPort(m_endPoint->GetPeerPort());
    }
    else
    {
        header.SetSourcePort(m_endPoint6->GetLocalPort());
        header.SetDestinationPort(m_endPoint6->GetPeerPort());
    }
    AddOptions(header);
 
    // RFC 6298, clause 2.4
    m_rto =
        Max(m_rtt->GetEstimate() + Max(m_clockGranularity, m_rtt->GetVariation() * 4), m_minRto);
 
    uint16_t windowSize = AdvertisedWindowSize();
    bool hasSyn = flags & TcpHeader::SYN;
    bool hasFin = flags & TcpHeader::FIN;
    bool isAck = flags == TcpHeader::ACK;
    if (hasSyn)
    {
        if (m_winScalingEnabled)
        { // The window scaling option is set only on SYN packets
            AddOptionWScale(header);
        }
 
        if (m_sackEnabled)
        {
            AddOptionSackPermitted(header);
        }
 
        if (m_synCount == 0)
        { // No more connection retries, give up
            NS_LOG_LOGIC("Connection failed.");
            m_rtt->Reset(); // According to recommendation -> RFC 6298
            NotifyConnectionFailed();
            m_state = CLOSED;
            DeallocateEndPoint();
            return;
        }
        else
        { // Exponential backoff of connection time out
            int backoffCount = 0x1 << (m_synRetries - m_synCount);
            m_rto = m_cnTimeout * backoffCount;
            m_synCount--;
        }
 
        if (m_synRetries - 1 == m_synCount)
        {
            UpdateRttHistory(s, 0, false);
        }
        else
        { // This is SYN retransmission
            UpdateRttHistory(s, 0, true);
        }
 
        windowSize = AdvertisedWindowSize(false);
    }
    header.SetWindowSize(windowSize);
 
    if (flags & TcpHeader::ACK)
    { // If sending an ACK, cancel the delay ACK as well
        m_delAckEvent.Cancel();
        m_delAckCount = 0;
        if (m_highTxAck < header.GetAckNumber())
        {
            m_highTxAck = header.GetAckNumber();
        }
        if (m_sackEnabled && m_tcb->m_rxBuffer->GetSackListSize() > 0)
        {
            AddOptionSack(header);
        }
        NS_LOG_INFO("Sending a pure ACK, acking seq " << m_tcb->m_rxBuffer->NextRxSequence());
    }
 
    m_txTrace(p, header, this);
 
    if (m_endPoint != nullptr)
    {
        m_tcp->SendPacket(p,
                          header,
                          m_endPoint->GetLocalAddress(),
                          m_endPoint->GetPeerAddress(),
                          m_boundnetdevice);
    }
    else
    {
        m_tcp->SendPacket(p,
                          header,
                          m_endPoint6->GetLocalAddress(),
                          m_endPoint6->GetPeerAddress(),
                          m_boundnetdevice);
    }
 
    if (m_retxEvent.IsExpired() && (hasSyn || hasFin) && !isAck)
    { // Retransmit SYN / SYN+ACK / FIN / FIN+ACK to guard against lost
        NS_LOG_LOGIC("Schedule retransmission timeout at time "
                     << Simulator::Now().GetSeconds() << " to expire at time "
                     << (Simulator::Now() + m_rto.Get()).GetSeconds());
        m_retxEvent = Simulator::Schedule(m_rto, &TcpSocketBase::SendEmptyPacket, this, flags);
    }
}
 
/* This function closes the endpoint completely. Called upon RST_TX action. */
void
TcpSocketBase::SendRST()
{
    NS_LOG_FUNCTION(this);
    SendEmptyPacket(TcpHeader::RST);
    NotifyErrorClose();
    DeallocateEndPoint();
}
 
/* Deallocate the end point and cancel all the timers */
void
TcpSocketBase::DeallocateEndPoint()
{
    // note: it shouldn't be necessary to invalidate the callback and manually call
    // TcpL4Protocol::RemoveSocket. Alas, if one relies on the endpoint destruction
    // callback, there's a weird memory access to a free'd area. Harmless, but valgrind
    // considers it an error.
 
    if (m_endPoint != nullptr)
    {
        CancelAllTimers();
        m_endPoint->SetDestroyCallback(MakeNullCallback<void>());
        m_tcp->DeAllocate(m_endPoint);
        m_endPoint = nullptr;
        m_tcp->RemoveSocket(this);
    }
    else if (m_endPoint6 != nullptr)
    {
        CancelAllTimers();
        m_endPoint6->SetDestroyCallback(MakeNullCallback<void>());
        m_tcp->DeAllocate(m_endPoint6);
        m_endPoint6 = nullptr;
        m_tcp->RemoveSocket(this);
    }
}
 
/* Configure the endpoint to a local address. Called by Connect() if Bind() didn't specify one. */
int
TcpSocketBase::SetupEndpoint()
{
    NS_LOG_FUNCTION(this);
    Ptr<Ipv4> ipv4 = m_node->GetObject<Ipv4>();
    NS_ASSERT(ipv4);
    if (!ipv4->GetRoutingProtocol())
    {
        NS_FATAL_ERROR("No Ipv4RoutingProtocol in the node");
    }
    // Create a dummy packet, then ask the routing function for the best output
    // interface's address
    Ipv4Header header;
    header.SetDestination(m_endPoint->GetPeerAddress());
    Socket::SocketErrno errno_;
    Ptr<Ipv4Route> route;
    Ptr<NetDevice> oif = m_boundnetdevice;
    route = ipv4->GetRoutingProtocol()->RouteOutput(Ptr<Packet>(), header, oif, errno_);
    if (!route)
    {
        NS_LOG_LOGIC("Route to " << m_endPoint->GetPeerAddress() << " does not exist");
        NS_LOG_ERROR(errno_);
        m_errno = errno_;
        return -1;
    }
    NS_LOG_LOGIC("Route exists");
    m_endPoint->SetLocalAddress(route->GetSource());
    return 0;
}
 
int
TcpSocketBase::SetupEndpoint6()
{
    NS_LOG_FUNCTION(this);
    Ptr<Ipv6L3Protocol> ipv6 = m_node->GetObject<Ipv6L3Protocol>();
    NS_ASSERT(ipv6);
    if (!ipv6->GetRoutingProtocol())
    {
        NS_FATAL_ERROR("No Ipv6RoutingProtocol in the node");
    }
    // Create a dummy packet, then ask the routing function for the best output
    // interface's address
    Ipv6Header header;
    header.SetDestination(m_endPoint6->GetPeerAddress());
    Socket::SocketErrno errno_;
    Ptr<Ipv6Route> route;
    Ptr<NetDevice> oif = m_boundnetdevice;
    route = ipv6->GetRoutingProtocol()->RouteOutput(Ptr<Packet>(), header, oif, errno_);
    if (!route)
    {
        NS_LOG_LOGIC("Route to " << m_endPoint6->GetPeerAddress() << " does not exist");
        NS_LOG_ERROR(errno_);
        m_errno = errno_;
        return -1;
    }
    NS_LOG_LOGIC("Route exists");
    m_endPoint6->SetLocalAddress(route->GetSource());
    return 0;
}
 
/* This function is called only if a SYN received in LISTEN state. After
   TcpSocketBase cloned, allocate a new end point to handle the incoming
   connection and send a SYN+ACK to complete the handshake. */
void
TcpSocketBase::CompleteFork(Ptr<Packet> p [[maybe_unused]],
                            const TcpHeader& h,
                            const Address& fromAddress,
                            const Address& toAddress)
{
    NS_LOG_FUNCTION(this << p << h << fromAddress << toAddress);
    // Get port and address from peer (connecting host)
    if (InetSocketAddress::IsMatchingType(toAddress))
    {
        m_endPoint = m_tcp->Allocate(GetBoundNetDevice(),
                                     InetSocketAddress::ConvertFrom(toAddress).GetIpv4(),
                                     InetSocketAddress::ConvertFrom(toAddress).GetPort(),
                                     InetSocketAddress::ConvertFrom(fromAddress).GetIpv4(),
                                     InetSocketAddress::ConvertFrom(fromAddress).GetPort());
        m_endPoint6 = nullptr;
    }
    else if (Inet6SocketAddress::IsMatchingType(toAddress))
    {
        m_endPoint6 = m_tcp->Allocate6(GetBoundNetDevice(),
                                       Inet6SocketAddress::ConvertFrom(toAddress).GetIpv6(),
                                       Inet6SocketAddress::ConvertFrom(toAddress).GetPort(),
                                       Inet6SocketAddress::ConvertFrom(fromAddress).GetIpv6(),
                                       Inet6SocketAddress::ConvertFrom(fromAddress).GetPort());
        m_endPoint = nullptr;
    }
    m_tcp->AddSocket(this);
 
    // Change the cloned socket from LISTEN state to SYN_RCVD
    NS_LOG_DEBUG("LISTEN -> SYN_RCVD");
    m_state = SYN_RCVD;
    m_synCount = m_synRetries;
    m_dataRetrCount = m_dataRetries;
    SetupCallback();
    // Set the sequence number and send SYN+ACK
    m_tcb->m_rxBuffer->SetNextRxSequence(h.GetSequenceNumber() + SequenceNumber32(1));
 
    /* Check if we received an ECN SYN packet. Change the ECN state of receiver to ECN_IDLE if
     * sender has sent an ECN SYN packet and the traffic is ECN Capable
     */
    if (m_tcb->m_useEcn != TcpSocketState::Off &&
        (h.GetFlags() & (TcpHeader::CWR | TcpHeader::ECE)) == (TcpHeader::CWR | TcpHeader::ECE))
    {
        SendEmptyPacket(TcpHeader::SYN | TcpHeader::ACK | TcpHeader::ECE);
        NS_LOG_DEBUG(TcpSocketState::EcnStateName[m_tcb->m_ecnState] << " -> ECN_IDLE");
        m_tcb->m_ecnState = TcpSocketState::ECN_IDLE;
    }
    else
    {
        SendEmptyPacket(TcpHeader::SYN | TcpHeader::ACK);
        m_tcb->m_ecnState = TcpSocketState::ECN_DISABLED;
    }
}
 
void
TcpSocketBase::ConnectionSucceeded()
{ // Wrapper to protected function NotifyConnectionSucceeded() so that it can
    // be called as a scheduled event
    NotifyConnectionSucceeded();
    // The if-block below was moved from ProcessSynSent() to here because we need
    // to invoke the NotifySend() only after NotifyConnectionSucceeded() to
    // reflect the behaviour in the real world.
    if (GetTxAvailable() > 0)
    {
        NotifySend(GetTxAvailable());
    }
}
 
void
TcpSocketBase::AddSocketTags(const Ptr<Packet>& p, bool isEct) const
{
    /*
     * Add tags for each socket option.
     * Note that currently the socket adds both IPv4 tag and IPv6 tag
     * if both options are set. Once the packet got to layer three, only
     * the corresponding tags will be read.
     */
    if (GetIpTos())
    {
        SocketIpTosTag ipTosTag;
        if (m_tcb->m_ecnState != TcpSocketState::ECN_DISABLED && !CheckNoEcn(GetIpTos()) && isEct)
        {
            ipTosTag.SetTos(MarkEcnCodePoint(GetIpTos(), m_tcb->m_ectCodePoint));
        }
        else
        {
            // Set the last received ipTos
            ipTosTag.SetTos(GetIpTos());
        }
        p->AddPacketTag(ipTosTag);
    }
    else
    {
        if ((m_tcb->m_ecnState != TcpSocketState::ECN_DISABLED && p->GetSize() > 0 && isEct) ||
            m_tcb->m_ecnMode == TcpSocketState::DctcpEcn)
        {
            SocketIpTosTag ipTosTag;
            ipTosTag.SetTos(MarkEcnCodePoint(GetIpTos(), m_tcb->m_ectCodePoint));
            p->AddPacketTag(ipTosTag);
        }
    }
 
    if (IsManualIpv6Tclass())
    {
        SocketIpv6TclassTag ipTclassTag;
        if (m_tcb->m_ecnState != TcpSocketState::ECN_DISABLED && !CheckNoEcn(GetIpv6Tclass()) &&
            isEct)
        {
            ipTclassTag.SetTclass(MarkEcnCodePoint(GetIpv6Tclass(), m_tcb->m_ectCodePoint));
        }
        else
        {
            // Set the last received ipTos
            ipTclassTag.SetTclass(GetIpv6Tclass());
        }
        p->AddPacketTag(ipTclassTag);
    }
    else
    {
        if ((m_tcb->m_ecnState != TcpSocketState::ECN_DISABLED && p->GetSize() > 0 && isEct) ||
            m_tcb->m_ecnMode == TcpSocketState::DctcpEcn)
        {
            SocketIpv6TclassTag ipTclassTag;
            ipTclassTag.SetTclass(MarkEcnCodePoint(GetIpv6Tclass(), m_tcb->m_ectCodePoint));
            p->AddPacketTag(ipTclassTag);
        }
    }
 
    if (IsManualIpTtl())
    {
        SocketIpTtlTag ipTtlTag;
        ipTtlTag.SetTtl(GetIpTtl());
        p->AddPacketTag(ipTtlTag);
    }
 
    if (IsManualIpv6HopLimit())
    {
        SocketIpv6HopLimitTag ipHopLimitTag;
        ipHopLimitTag.SetHopLimit(GetIpv6HopLimit());
        p->AddPacketTag(ipHopLimitTag);
    }
 
    uint8_t priority = GetPriority();
    if (priority)
    {
        SocketPriorityTag priorityTag;
        priorityTag.SetPriority(priority);
        p->ReplacePacketTag(priorityTag);
    }
}
 
/* Extract at most maxSize bytes from the TxBuffer at sequence seq, add the
    TCP header, and send to TcpL4Protocol */
uint32_t
TcpSocketBase::SendDataPacket(SequenceNumber32 seq, uint32_t maxSize, bool withAck)
{
    NS_LOG_FUNCTION(this << seq << maxSize << withAck);
 
    bool isStartOfTransmission = BytesInFlight() == 0U;
    TcpTxItem* outItem = m_txBuffer->CopyFromSequence(maxSize, seq);
 
    m_rateOps->SkbSent(outItem, isStartOfTransmission);
 
    bool isRetransmission = outItem->IsRetrans();
    Ptr<Packet> p = outItem->GetPacketCopy();
    uint32_t sz = p->GetSize(); // Size of packet
    uint8_t flags = withAck ? TcpHeader::ACK : 0;
    uint32_t remainingData = m_txBuffer->SizeFromSequence(seq + SequenceNumber32(sz));
 
    // TCP sender should not send data out of the window advertised by the
    // peer when it is not retransmission.
    NS_ASSERT(isRetransmission ||
              ((m_highRxAckMark + SequenceNumber32(m_rWnd)) >= (seq + SequenceNumber32(maxSize))));
 
    if (IsPacingEnabled())
    {
        NS_LOG_INFO("Pacing is enabled");
        if (m_pacingTimer.IsExpired())
        {
            NS_LOG_DEBUG("Current Pacing Rate " << m_tcb->m_pacingRate);
            NS_LOG_DEBUG("Timer is in expired state, activate it "
                         << m_tcb->m_pacingRate.Get().CalculateBytesTxTime(sz));
            m_pacingTimer.Schedule(m_tcb->m_pacingRate.Get().CalculateBytesTxTime(sz));
        }
        else
        {
            NS_LOG_INFO("Timer is already in running state");
        }
    }
    else
    {
        NS_LOG_INFO("Pacing is disabled");
    }
 
    if (withAck)
    {
        m_delAckEvent.Cancel();
        m_delAckCount = 0;
    }
 
    if (m_tcb->m_ecnState == TcpSocketState::ECN_ECE_RCVD &&
        m_ecnEchoSeq.Get() > m_ecnCWRSeq.Get() && !isRetransmission)
    {
        NS_LOG_DEBUG(TcpSocketState::EcnStateName[m_tcb->m_ecnState] << " -> ECN_CWR_SENT");
        m_tcb->m_ecnState = TcpSocketState::ECN_CWR_SENT;
        m_ecnCWRSeq = seq;
        flags |= TcpHeader::CWR;
        NS_LOG_INFO("CWR flags set");
    }
 
    bool isEct = IsEct(isRetransmission ? TcpPacketType_t::RE_XMT : TcpPacketType_t::DATA);
    AddSocketTags(p, isEct);
 
    if (m_closeOnEmpty && (remainingData == 0))
    {
        flags |= TcpHeader::FIN;
        if (m_state == ESTABLISHED)
        { // On active close: I am the first one to send FIN
            NS_LOG_DEBUG("ESTABLISHED -> FIN_WAIT_1");
            m_state = FIN_WAIT_1;
        }
        else if (m_state == CLOSE_WAIT)
        { // On passive close: Peer sent me FIN already
            NS_LOG_DEBUG("CLOSE_WAIT -> LAST_ACK");
            m_state = LAST_ACK;
        }
    }
    TcpHeader header;
    header.SetFlags(flags);
    header.SetSequenceNumber(seq);
    header.SetAckNumber(m_tcb->m_rxBuffer->NextRxSequence());
    if (m_endPoint)
    {
        header.SetSourcePort(m_endPoint->GetLocalPort());
        header.SetDestinationPort(m_endPoint->GetPeerPort());
    }
    else
    {
        header.SetSourcePort(m_endPoint6->GetLocalPort());
        header.SetDestinationPort(m_endPoint6->GetPeerPort());
    }
    header.SetWindowSize(AdvertisedWindowSize());
    AddOptions(header);
 
    if (m_retxEvent.IsExpired())
    {
        // Schedules retransmit timeout. m_rto should be already doubled.
 
        NS_LOG_LOGIC(this << " SendDataPacket Schedule ReTxTimeout at time "
                          << Simulator::Now().GetSeconds() << " to expire at time "
                          << (Simulator::Now() + m_rto.Get()).GetSeconds());
        m_retxEvent = Simulator::Schedule(m_rto, &TcpSocketBase::ReTxTimeout, this);
    }
 
    m_txTrace(p, header, this);
    if (isRetransmission)
    {
        if (m_endPoint)
        {
            m_retransmissionTrace(p,
                                  header,
                                  m_endPoint->GetLocalAddress(),
                                  m_endPoint->GetPeerAddress(),
                                  this);
        }
        else
        {
            m_retransmissionTrace(p,
                                  header,
                                  m_endPoint6->GetLocalAddress(),
                                  m_endPoint6->GetPeerAddress(),
                                  this);
        }
    }
 
    if (m_endPoint)
    {
        m_tcp->SendPacket(p,
                          header,
                          m_endPoint->GetLocalAddress(),
                          m_endPoint->GetPeerAddress(),
                          m_boundnetdevice);
        NS_LOG_DEBUG("Send segment of size "
                     << sz << " with remaining data " << remainingData << " via TcpL4Protocol to "
                     << m_endPoint->GetPeerAddress() << ". Header " << header);
    }
    else
    {
        m_tcp->SendPacket(p,
                          header,
                          m_endPoint6->GetLocalAddress(),
                          m_endPoint6->GetPeerAddress(),
                          m_boundnetdevice);
        NS_LOG_DEBUG("Send segment of size "
                     << sz << " with remaining data " << remainingData << " via TcpL4Protocol to "
                     << m_endPoint6->GetPeerAddress() << ". Header " << header);
    }
 
    // Signal to congestion control whether the cwnd is fully used
    // This is a simple version of Linux tcp_cwnd_validate() but following
    // the principle implemented in Linux that limits the updating of cwnd
    // (in the congestion controls) when flight size is >= cwnd
    // send will also be cwnd limited if less then one segment of cwnd is available
    m_tcb->m_isCwndLimited = (m_tcb->m_cWnd < BytesInFlight() + m_tcb->m_segmentSize);
 
    UpdateRttHistory(seq, sz, isRetransmission);
 
    // Update bytes sent during recovery phase
    if (m_tcb->m_congState == TcpSocketState::CA_RECOVERY ||
        m_tcb->m_congState == TcpSocketState::CA_CWR)
    {
        m_recoveryOps->UpdateBytesSent(sz);
    }
 
    // Notify the application of the data being sent unless this is a retransmit
    if (!isRetransmission)
    {
        Simulator::ScheduleNow(&TcpSocketBase::NotifyDataSent,
                               this,
                               (seq + sz - m_tcb->m_highTxMark.Get()));
    }
    // Update highTxMark
    m_tcb->m_highTxMark = std::max(seq + sz, m_tcb->m_highTxMark.Get());
    return sz;
}
 
void
TcpSocketBase::UpdateRttHistory(const SequenceNumber32& seq, uint32_t sz, bool isRetransmission)
{
    NS_LOG_FUNCTION(this);
 
    // update the history of sequence numbers used to calculate the RTT
    if (!isRetransmission)
    { // This is the next expected one, just log at end
        m_history.emplace_back(seq, sz, Simulator::Now());
    }
    else
    { // This is a retransmit, find in list and mark as re-tx
        for (auto i = m_history.begin(); i != m_history.end(); ++i)
        {
            if ((seq >= i->seq) && (seq < (i->seq + SequenceNumber32(i->count))))
            { // Found it
                i->retx = true;
                i->count = ((seq + SequenceNumber32(sz)) - i->seq); // And update count in hist
                break;
            }
        }
    }
}
 
// Note that this function did not implement the PSH flag
uint32_t
TcpSocketBase::SendPendingData(bool withAck)
{
    NS_LOG_FUNCTION(this << withAck);
    if (m_txBuffer->Size() == 0)
    {
        return 0; // Nothing to send
    }
    if (m_endPoint == nullptr && m_endPoint6 == nullptr)
    {
        NS_LOG_INFO(
            "TcpSocketBase::SendPendingData: No endpoint; m_shutdownSend=" << m_shutdownSend);
        return 0; // Is this the right way to handle this condition?
    }
 
    uint32_t nPacketsSent = 0;
    uint32_t availableWindow = AvailableWindow();
 
    // RFC 6675, Section (C)
    // If cwnd - pipe >= 1 SMSS, the sender SHOULD transmit one or more
    // segments as follows:
    // (NOTE: We check > 0, and do the checks for segmentSize in the following
    // else branch to control silly window syndrome and Nagle)
    while (availableWindow > 0)
    {
        if (IsPacingEnabled())
        {
            NS_LOG_INFO("Pacing is enabled");
            if (m_pacingTimer.IsRunning())
            {
                NS_LOG_INFO("Skipping Packet due to pacing" << m_pacingTimer.GetDelayLeft());
                break;
            }
            NS_LOG_INFO("Timer is not running");
        }
 
        if (m_tcb->m_congState == TcpSocketState::CA_OPEN && m_state == TcpSocket::FIN_WAIT_1)
        {
            NS_LOG_INFO("FIN_WAIT and OPEN state; no data to transmit");
            break;
        }
        // (C.1) The scoreboard MUST be queried via NextSeg () for the
        //       sequence number range of the next segment to transmit (if
        //       any), and the given segment sent.  If NextSeg () returns
        //       failure (no data to send), return without sending anything
        //       (i.e., terminate steps C.1 -- C.5).
        SequenceNumber32 next;
        SequenceNumber32 nextHigh;
        bool enableRule3 = m_sackEnabled && m_tcb->m_congState == TcpSocketState::CA_RECOVERY;
        if (!m_txBuffer->NextSeg(&next, &nextHigh, enableRule3))
        {
            NS_LOG_INFO("no valid seq to transmit, or no data available");
            break;
        }
        else
        {
            // It's time to transmit, but before do silly window and Nagle's check
            uint32_t availableData = m_txBuffer->SizeFromSequence(next);
 
            // If there's less app data than the full window, ask the app for more
            // data before trying to send
            if (availableData < availableWindow)
            {
                NotifySend(GetTxAvailable());
            }
 
            // Stop sending if we need to wait for a larger Tx window (prevent silly window
            // syndrome) but continue if we don't have data
            if (availableWindow < m_tcb->m_segmentSize && availableData > availableWindow)
            {
                NS_LOG_LOGIC("Preventing Silly Window Syndrome. Wait to send.");
                break; // No more
            }
            // Nagle's algorithm (RFC896): Hold off sending if there is unacked data
            // in the buffer and the amount of data to send is less than one segment
            if (!m_noDelay && UnAckDataCount() > 0 && availableData < m_tcb->m_segmentSize)
            {
                NS_LOG_DEBUG("Invoking Nagle's algorithm for seq "
                             << next << ", SFS: " << m_txBuffer->SizeFromSequence(next)
                             << ". Wait to send.");
                break;
            }
 
            uint32_t s = std::min(availableWindow, m_tcb->m_segmentSize);
            // NextSeg () may have further constrained the segment size
            auto maxSizeToSend = static_cast<uint32_t>(nextHigh - next);
            s = std::min(s, maxSizeToSend);
 
            // (C.2) If any of the data octets sent in (C.1) are below HighData,
            //       HighRxt MUST be set to the highest sequence number of the
            //       retransmitted segment unless NextSeg () rule (4) was
            //       invoked for this retransmission.
            // (C.3) If any of the data octets sent in (C.1) are above HighData,
            //       HighData must be updated to reflect the transmission of
            //       previously unsent data.
            //
            // These steps are done in m_txBuffer with the tags.
            if (m_tcb->m_nextTxSequence != next)
            {
                m_tcb->m_nextTxSequence = next;
            }
            if (m_tcb->m_bytesInFlight.Get() == 0)
            {
                m_congestionControl->CwndEvent(m_tcb, TcpSocketState::CA_EVENT_TX_START);
            }
            uint32_t sz = SendDataPacket(m_tcb->m_nextTxSequence, s, withAck);
 
            NS_LOG_LOGIC(" rxwin " << m_rWnd << " segsize " << m_tcb->m_segmentSize
                                   << " highestRxAck " << m_txBuffer->HeadSequence() << " pd->Size "
                                   << m_txBuffer->Size() << " pd->SFS "
                                   << m_txBuffer->SizeFromSequence(m_tcb->m_nextTxSequence));
 
            NS_LOG_DEBUG("cWnd: " << m_tcb->m_cWnd << " total unAck: " << UnAckDataCount()
                                  << " sent seq " << m_tcb->m_nextTxSequence << " size " << sz);
            m_tcb->m_nextTxSequence += sz;
            ++nPacketsSent;
            if (IsPacingEnabled())
            {
                NS_LOG_INFO("Pacing is enabled");
                if (m_pacingTimer.IsExpired())
                {
                    NS_LOG_DEBUG("Current Pacing Rate " << m_tcb->m_pacingRate);
                    NS_LOG_DEBUG("Timer is in expired state, activate it "
                                 << m_tcb->m_pacingRate.Get().CalculateBytesTxTime(sz));
                    m_pacingTimer.Schedule(m_tcb->m_pacingRate.Get().CalculateBytesTxTime(sz));
                    break;
                }
            }
        }
 
        // (C.4) The estimate of the amount of data outstanding in the
        //       network must be updated by incrementing pipe by the number
        //       of octets transmitted in (C.1).
        //
        // Done in BytesInFlight, inside AvailableWindow.
        availableWindow = AvailableWindow();
 
        // (C.5) If cwnd - pipe >= 1 SMSS, return to (C.1)
        // loop again!
    }
 
    if (nPacketsSent > 0)
    {
        if (!m_sackEnabled)
        {
            if (!m_limitedTx)
            {
                // We can't transmit in CA_DISORDER without limitedTx active
                NS_ASSERT(m_tcb->m_congState != TcpSocketState::CA_DISORDER);
            }
        }
 
        NS_LOG_DEBUG("SendPendingData sent " << nPacketsSent << " segments");
    }
    else
    {
        NS_LOG_DEBUG("SendPendingData no segments sent");
    }
    return nPacketsSent;
}
 
uint32_t
TcpSocketBase::UnAckDataCount() const
{
    return m_tcb->m_highTxMark - m_txBuffer->HeadSequence();
}
 
uint32_t
TcpSocketBase::BytesInFlight() const
{
    uint32_t bytesInFlight = m_txBuffer->BytesInFlight();
    // Ugly, but we are not modifying the state; m_bytesInFlight is used
    // only for tracing purpose.
    m_tcb->m_bytesInFlight = bytesInFlight;
 
    NS_LOG_DEBUG("Returning calculated bytesInFlight: " << bytesInFlight);
    return bytesInFlight;
}
 
uint32_t
TcpSocketBase::Window() const
{
    return std::min(m_rWnd.Get(), m_tcb->m_cWnd.Get());
}
 
uint32_t
TcpSocketBase::AvailableWindow() const
{
    uint32_t win = Window(); // Number of bytes allowed to be outstanding
 
    if (m_sackEnabled && m_fackEnabled && win >= m_tcb->m_ssThresh)
    {
        // Update awnd (Data sender's estimate of the actual quantity of data outstanding in the
        // network)
        NS_LOG_DEBUG("FACK is enabled and win >= ssthresh (" << m_tcb->m_ssThresh << ")");
 
        uint32_t sndNxt = (m_tcb->m_highTxMark.Get().GetValue());
        uint32_t retranData = m_txBuffer->GetRetransmitsCount();
        uint32_t awnd = sndNxt - m_sndFack + retranData;
        m_tcb->m_fackAwnd = awnd;
 
        NS_LOG_DEBUG("SndNxt: " << sndNxt << ", SndFack: " << m_sndFack << ", AWND: " << awnd
                                << ", RetranData :" << retranData);
 
        uint32_t awndDiff = (win > awnd) ? (win - awnd) : 0;
        NS_LOG_DEBUG("AWND: " << awnd << ", win: " << win << ", AWND_DIFF: " << awndDiff);
        return awndDiff;
    }
 
    uint32_t inflight = BytesInFlight();
 
    if (inflight >= win)
    {
        return 0;
    }
 
    return win - inflight;
}
 
uint16_t
TcpSocketBase::AdvertisedWindowSize(bool scale) const
{
    NS_LOG_FUNCTION(this << scale);
    uint32_t w;
 
    // We don't want to advertise 0 after a FIN is received. So, we just use
    // the previous value of the advWnd.
    if (m_tcb->m_rxBuffer->GotFin())
    {
        w = m_advWnd;
    }
    else
    {
        NS_ASSERT_MSG(m_tcb->m_rxBuffer->MaxRxSequence() - m_tcb->m_rxBuffer->NextRxSequence() >= 0,
                      "Unexpected sequence number values");
        w = static_cast<uint32_t>(m_tcb->m_rxBuffer->MaxRxSequence() -
                                  m_tcb->m_rxBuffer->NextRxSequence());
    }
 
    // Ugly, but we are not modifying the state, that variable
    // is used only for tracing purpose.
    if (w != m_advWnd)
    {
        const_cast<TcpSocketBase*>(this)->m_advWnd = w;
    }
    if (scale)
    {
        w >>= m_rcvWindShift;
    }
    if (w > m_maxWinSize)
    {
        w = m_maxWinSize;
        NS_LOG_WARN("Adv window size truncated to "
                    << m_maxWinSize << "; possibly to avoid overflow of the 16-bit integer");
    }
    NS_LOG_LOGIC("Returning AdvertisedWindowSize of " << static_cast<uint16_t>(w));
    return static_cast<uint16_t>(w);
}
 
// Receipt of new packet, put into Rx buffer
void
TcpSocketBase::ReceivedData(Ptr<Packet> p, const TcpHeader& tcpHeader)
{
    NS_LOG_FUNCTION(this << tcpHeader);
    NS_LOG_DEBUG("Data segment, seq=" << tcpHeader.GetSequenceNumber()
                                      << " pkt size=" << p->GetSize());
 
    // Put into Rx buffer
    SequenceNumber32 expectedSeq = m_tcb->m_rxBuffer->NextRxSequence();
    if (!m_tcb->m_rxBuffer->Add(p, tcpHeader))
    { // Insert failed: No data or RX buffer full
        if (m_tcb->m_ecnState == TcpSocketState::ECN_CE_RCVD ||
            m_tcb->m_ecnState == TcpSocketState::ECN_SENDING_ECE)
        {
            SendEmptyPacket(TcpHeader::ACK | TcpHeader::ECE);
            NS_LOG_DEBUG(TcpSocketState::EcnStateName[m_tcb->m_ecnState] << " -> ECN_SENDING_ECE");
            m_tcb->m_ecnState = TcpSocketState::ECN_SENDING_ECE;
        }
        else
        {
            SendEmptyPacket(TcpHeader::ACK);
        }
        return;
    }
    // Notify app to receive if necessary
    if (expectedSeq < m_tcb->m_rxBuffer->NextRxSequence())
    { // NextRxSeq advanced, we have something to send to the app
        if (!m_shutdownRecv)
        {
            NotifyDataRecv();
        }
        // Handle exceptions
        if (m_closeNotified)
        {
            NS_LOG_WARN("Why TCP " << this << " got data after close notification?");
        }
        // If we received FIN before and now completed all "holes" in rx buffer,
        // invoke peer close procedure
        if (m_tcb->m_rxBuffer->Finished() && (tcpHeader.GetFlags() & TcpHeader::FIN) == 0)
        {
            DoPeerClose();
            return;
        }
    }
    // Now send a new ACK packet acknowledging all received and delivered data
    if (m_tcb->m_rxBuffer->Size() > m_tcb->m_rxBuffer->Available() ||
        m_tcb->m_rxBuffer->NextRxSequence() > expectedSeq + p->GetSize())
    { // A gap exists in the buffer, or we filled a gap: Always ACK
        m_congestionControl->CwndEvent(m_tcb, TcpSocketState::CA_EVENT_NON_DELAYED_ACK);
        if (m_tcb->m_ecnState == TcpSocketState::ECN_CE_RCVD ||
            m_tcb->m_ecnState == TcpSocketState::ECN_SENDING_ECE)
        {
            SendEmptyPacket(TcpHeader::ACK | TcpHeader::ECE);
            NS_LOG_DEBUG(TcpSocketState::EcnStateName[m_tcb->m_ecnState] << " -> ECN_SENDING_ECE");
            m_tcb->m_ecnState = TcpSocketState::ECN_SENDING_ECE;
        }
        else
        {
            SendEmptyPacket(TcpHeader::ACK);
        }
    }
    else
    { // In-sequence packet: ACK if delayed ack count allows
        if (++m_delAckCount >= m_delAckMaxCount)
        {
            m_delAckEvent.Cancel();
            m_delAckCount = 0;
            m_congestionControl->CwndEvent(m_tcb, TcpSocketState::CA_EVENT_NON_DELAYED_ACK);
            if (m_tcb->m_ecnState == TcpSocketState::ECN_CE_RCVD ||
                m_tcb->m_ecnState == TcpSocketState::ECN_SENDING_ECE)
            {
                NS_LOG_DEBUG("Congestion algo " << m_congestionControl->GetName());
                SendEmptyPacket(TcpHeader::ACK | TcpHeader::ECE);
                NS_LOG_DEBUG(TcpSocketState::EcnStateName[m_tcb->m_ecnState]
                             << " -> ECN_SENDING_ECE");
                m_tcb->m_ecnState = TcpSocketState::ECN_SENDING_ECE;
            }
            else
            {
                SendEmptyPacket(TcpHeader::ACK);
            }
        }
        else if (!m_delAckEvent.IsExpired())
        {
            m_congestionControl->CwndEvent(m_tcb, TcpSocketState::CA_EVENT_DELAYED_ACK);
        }
        else if (m_delAckEvent.IsExpired())
        {
            m_congestionControl->CwndEvent(m_tcb, TcpSocketState::CA_EVENT_DELAYED_ACK);
            m_delAckEvent =
                Simulator::Schedule(m_delAckTimeout, &TcpSocketBase::DelAckTimeout, this);
            NS_LOG_LOGIC(
                this << " scheduled delayed ACK at "
                     << (Simulator::Now() + Simulator::GetDelayLeft(m_delAckEvent)).GetSeconds());
        }
    }
}
 
Time
TcpSocketBase::CalculateRttSample(const TcpHeader& tcpHeader, const RttHistory& rttHistory)
{
    NS_LOG_FUNCTION(this);
    SequenceNumber32 ackSeq = tcpHeader.GetAckNumber();
    Time rtt;
 
    if (ackSeq >= (rttHistory.seq + SequenceNumber32(rttHistory.count)))
    {
        // As per RFC 6298 (Section 3)
        // RTT samples MUST NOT be made using segments that were
        // retransmitted (and thus for which it is ambiguous whether the reply
        // was for the first instance of the packet or a later instance).  The
        // only case when TCP can safely take RTT samples from retransmitted
        // segments is when the TCP timestamp option is employed, since
        // the timestamp option removes the ambiguity regarding which instance
        // of the data segment triggered the acknowledgment.
        if (m_timestampEnabled && tcpHeader.HasOption(TcpOption::TS))
        {
            Ptr<const TcpOptionTS> ts;
            ts = DynamicCast<const TcpOptionTS>(tcpHeader.GetOption(TcpOption::TS));
            rtt = TcpOptionTS::ElapsedTimeFromTsValue(ts->GetEcho());
            if (rtt.IsZero())
            {
                NS_LOG_LOGIC("TcpSocketBase::EstimateRtt - RTT calculated from TcpOption::TS "
                             "is zero, approximating to 1us.");
                NS_LOG_DEBUG("RTT calculated from TcpOption::TS is zero, updating rtt to 1us.");
                rtt = MicroSeconds(1);
            }
        }
        else if (!rttHistory.retx)
        {
            // Elapsed time since the packet was transmitted
            rtt = Simulator::Now() - rttHistory.time;
        }
    }
    return rtt;
}
 
void
TcpSocketBase::EstimateRtt(const TcpHeader& tcpHeader)
{
    NS_LOG_FUNCTION(this);
    SequenceNumber32 ackSeq = tcpHeader.GetAckNumber();
    Time rtt;
 
    // An ack has been received, calculate rtt and log this measurement
    // Note we use a linear search (O(n)) for this since for the common
    // case the ack'ed packet will be at the head of the list
    if (!m_history.empty())
    {
        RttHistory& earliestTransmittedPktHistory = m_history.front();
        rtt = CalculateRttSample(tcpHeader, earliestTransmittedPktHistory);
 
        // Store ACKed packet that has the latest transmission time to update `lastRtt`
        RttHistory latestTransmittedPktHistory = earliestTransmittedPktHistory;
 
        // Delete all ACK history with seq <= ack
        while (!m_history.empty())
        {
            RttHistory& rttHistory = m_history.front();
            if ((rttHistory.seq + SequenceNumber32(rttHistory.count)) > ackSeq)
            {
                break; // Done removing
            }
 
            latestTransmittedPktHistory = rttHistory;
            m_history.pop_front(); // Remove
        }
 
        // In case of multiple packets being ACKed in a single acknowledgement, `m_lastRtt` is
        // RTT of the last (S)ACKed packet calculated using the data packet with the latest
        // transmission time
        Time lastRtt = CalculateRttSample(tcpHeader, latestTransmittedPktHistory);
        if (!lastRtt.IsZero())
        {
            NS_LOG_DEBUG("Last RTT sample updated to: " << lastRtt);
            m_tcb->m_lastRtt = lastRtt;
        }
    }
 
    if (!rtt.IsZero())
    {
        m_rtt->Measurement(rtt); // Log the measurement
        // RFC 6298, clause 2.4
        m_rto = Max(m_rtt->GetEstimate() + Max(m_clockGranularity, m_rtt->GetVariation() * 4),
                    m_minRto);
        m_tcb->m_srtt = m_rtt->GetEstimate();
        m_tcb->m_minRtt = std::min(m_tcb->m_srtt.Get(), m_tcb->m_minRtt);
        NS_LOG_INFO(this << m_tcb->m_srtt << m_tcb->m_minRtt);
    }
}
 
// Called by the ReceivedAck() when new ACK received and by ProcessSynRcvd()
// when the three-way handshake completed. This cancels retransmission timer
// and advances Tx window
void
TcpSocketBase::NewAck(const SequenceNumber32& ack, bool resetRTO)
{
    NS_LOG_FUNCTION(this << ack);
 
    // Reset the data retransmission count. We got a new ACK!
    m_dataRetrCount = m_dataRetries;
 
    // Update m_sndFack if possible
    if (m_fackEnabled && ack.GetValue() > m_sndFack)
    {
        NS_LOG_INFO(" m_sndFack " << m_sndFack << " updated by normal ack to " << ack.GetValue());
        m_sndFack = ack.GetValue();
    }
 
    if (m_state != SYN_RCVD && resetRTO)
    { // Set RTO unless the ACK is received in SYN_RCVD state
        NS_LOG_LOGIC(
            this << " Cancelled ReTxTimeout event which was set to expire at "
                 << (Simulator::Now() + Simulator::GetDelayLeft(m_retxEvent)).GetSeconds());
        m_retxEvent.Cancel();
        // On receiving a "New" ack we restart retransmission timer .. RFC 6298
        // RFC 6298, clause 2.4
        m_rto = Max(m_rtt->GetEstimate() + Max(m_clockGranularity, m_rtt->GetVariation() * 4),
                    m_minRto);
 
        NS_LOG_LOGIC(this << " Schedule ReTxTimeout at time " << Simulator::Now().GetSeconds()
                          << " to expire at time "
                          << (Simulator::Now() + m_rto.Get()).GetSeconds());
        m_retxEvent = Simulator::Schedule(m_rto, &TcpSocketBase::ReTxTimeout, this);
    }
 
    // Note the highest ACK and tell app to send more
    NS_LOG_LOGIC("TCP " << this << " NewAck " << ack << " numberAck "
                        << (ack - m_txBuffer->HeadSequence())); // Number bytes ack'ed
 
    if (GetTxAvailable() > 0)
    {
        NotifySend(GetTxAvailable());
    }
    if (ack > m_tcb->m_nextTxSequence)
    {
        m_tcb->m_nextTxSequence = ack; // If advanced
    }
    if (m_txBuffer->Size() == 0 && m_state != FIN_WAIT_1 && m_state != CLOSING)
    { // No retransmit timer if no data to retransmit
        NS_LOG_LOGIC(
            this << " Cancelled ReTxTimeout event which was set to expire at "
                 << (Simulator::Now() + Simulator::GetDelayLeft(m_retxEvent)).GetSeconds());
        m_retxEvent.Cancel();
    }
}
 
// Retransmit timeout
void
TcpSocketBase::ReTxTimeout()
{
    NS_LOG_FUNCTION(this);
    NS_LOG_LOGIC(this << " ReTxTimeout Expired at time " << Simulator::Now().GetSeconds());
    // If erroneous timeout in closed/timed-wait state, just return
    if (m_state == CLOSED || m_state == TIME_WAIT)
    {
        return;
    }
 
    if (m_state == SYN_SENT)
    {
        NS_ASSERT(m_synCount > 0);
        if (m_tcb->m_useEcn == TcpSocketState::On)
        {
            SendEmptyPacket(TcpHeader::SYN | TcpHeader::ECE | TcpHeader::CWR);
        }
        else
        {
            SendEmptyPacket(TcpHeader::SYN);
        }
        return;
    }
 
    // Retransmit non-data packet: Only if in FIN_WAIT_1 or CLOSING state
    if (m_txBuffer->Size() == 0)
    {
        if (m_state == FIN_WAIT_1 || m_state == CLOSING)
        { // Must have lost FIN, re-send
            SendEmptyPacket(TcpHeader::FIN);
        }
        return;
    }
 
    NS_LOG_DEBUG("Checking if Connection is Established");
    // If all data are received (non-closing socket and nothing to send), just return
    if (m_state <= ESTABLISHED && m_txBuffer->HeadSequence() >= m_tcb->m_highTxMark &&
        m_txBuffer->Size() == 0)
    {
        NS_LOG_DEBUG("Already Sent full data" << m_txBuffer->HeadSequence() << " "
                                              << m_tcb->m_highTxMark);
        return;
    }
 
    if (m_dataRetrCount == 0)
    {
        NS_LOG_INFO("No more data retries available. Dropping connection");
        NotifyErrorClose();
        DeallocateEndPoint();
        return;
    }
    else
    {
        --m_dataRetrCount;
    }
 
    uint32_t inFlightBeforeRto = BytesInFlight();
    bool resetSack = !m_sackEnabled; // Reset SACK information if SACK is not enabled.
                                     // The information in the TcpTxBuffer is guessed, in this case.
 
    // Reset dupAckCount
    m_dupAckCount = 0;
    if (!m_sackEnabled)
    {
        m_txBuffer->ResetRenoSack();
    }
 
    // From RFC 6675, Section 5.1
    // [RFC2018] suggests that a TCP sender SHOULD expunge the SACK
    // information gathered from a receiver upon a retransmission timeout
    // (RTO) "since the timeout might indicate that the data receiver has
    // reneged."  Additionally, a TCP sender MUST "ignore prior SACK
    // information in determining which data to retransmit."
    // It has been suggested that, as long as robust tests for
    // reneging are present, an implementation can retain and use SACK
    // information across a timeout event [Errata1610].
    // The head of the sent list will not be marked as sacked, therefore
    // will be retransmitted, if the receiver renegotiate the SACK blocks
    // that we received.
    m_txBuffer->SetSentListLost(resetSack);
 
    // From RFC 6675, Section 5.1
    // If an RTO occurs during loss recovery as specified in this document,
    // RecoveryPoint MUST be set to HighData.  Further, the new value of
    // RecoveryPoint MUST be preserved and the loss recovery algorithm
    // outlined in this document MUST be terminated.
    m_recover = m_tcb->m_highTxMark;
    m_recoverActive = true;
 
    // RFC 6298, clause 2.5, double the timer
    Time doubledRto = m_rto + m_rto;
    m_rto = Min(doubledRto, Time::FromDouble(60, Time::S));
 
    // Empty RTT history
    m_history.clear();
 
    // Please don't reset highTxMark, it is used for retransmission detection
 
    // When a TCP sender detects segment loss using the retransmission timer
    // and the given segment has not yet been resent by way of the
    // retransmission timer, decrease ssThresh
    if (m_tcb->m_congState != TcpSocketState::CA_LOSS || !m_txBuffer->IsHeadRetransmitted())
    {
        m_tcb->m_ssThresh = m_congestionControl->GetSsThresh(m_tcb, inFlightBeforeRto);
    }
 
    // Cwnd set to 1 MSS
    m_congestionControl->CwndEvent(m_tcb, TcpSocketState::CA_EVENT_LOSS);
    m_congestionControl->CongestionStateSet(m_tcb, TcpSocketState::CA_LOSS);
    m_tcb->m_congState = TcpSocketState::CA_LOSS;
    m_tcb->m_cWnd = m_tcb->m_segmentSize;
    m_tcb->m_cWndInfl = m_tcb->m_cWnd;
 
    m_pacingTimer.Cancel();
 
    NS_LOG_DEBUG("RTO. Reset cwnd to " << m_tcb->m_cWnd << ", ssthresh to " << m_tcb->m_ssThresh
                                       << ", restart from seqnum " << m_txBuffer->HeadSequence()
                                       << " doubled rto to " << m_rto.Get().GetSeconds() << " s");
 
    NS_ASSERT_MSG(BytesInFlight() == 0,
                  "There are some bytes in flight after an RTO: " << BytesInFlight());
 
    SendPendingData(m_connected);
 
    NS_ASSERT_MSG(BytesInFlight() <= m_tcb->m_segmentSize,
                  "In flight (" << BytesInFlight() << ") there is more than one segment ("
                                << m_tcb->m_segmentSize << ")");
}
 
void
TcpSocketBase::DelAckTimeout()
{
    m_delAckCount = 0;
    m_congestionControl->CwndEvent(m_tcb, TcpSocketState::CA_EVENT_DELAYED_ACK);
    if (m_tcb->m_ecnState == TcpSocketState::ECN_CE_RCVD ||
        m_tcb->m_ecnState == TcpSocketState::ECN_SENDING_ECE)
    {
        SendEmptyPacket(TcpHeader::ACK | TcpHeader::ECE);
        m_tcb->m_ecnState = TcpSocketState::ECN_SENDING_ECE;
    }
    else
    {
        SendEmptyPacket(TcpHeader::ACK);
    }
}
 
void
TcpSocketBase::LastAckTimeout()
{
    NS_LOG_FUNCTION(this);
 
    m_lastAckEvent.Cancel();
    if (m_state == LAST_ACK)
    {
        if (m_dataRetrCount == 0)
        {
            NS_LOG_INFO("LAST-ACK: No more data retries available. Dropping connection");
            NotifyErrorClose();
            DeallocateEndPoint();
            return;
        }
        m_dataRetrCount--;
        SendEmptyPacket(TcpHeader::FIN | TcpHeader::ACK);
        NS_LOG_LOGIC("TcpSocketBase " << this << " rescheduling LATO1");
        Time lastRto = m_rtt->GetEstimate() + Max(m_clockGranularity, m_rtt->GetVariation() * 4);
        m_lastAckEvent = Simulator::Schedule(lastRto, &TcpSocketBase::LastAckTimeout, this);
    }
}
 
// Send 1-byte data to probe for the window size at the receiver when
// the local knowledge tells that the receiver has zero window size
// C.f.: RFC793 p.42, RFC1112 sec.4.2.2.17
void
TcpSocketBase::PersistTimeout()
{
    NS_LOG_LOGIC("PersistTimeout expired at " << Simulator::Now().GetSeconds());
    m_persistTimeout =
        std::min(Seconds(60), Time(2 * m_persistTimeout)); // max persist timeout = 60s
    Ptr<Packet> p = m_txBuffer->CopyFromSequence(1, m_tcb->m_nextTxSequence)->GetPacketCopy();
    m_txBuffer->ResetLastSegmentSent();
    TcpHeader tcpHeader;
    tcpHeader.SetSequenceNumber(m_tcb->m_nextTxSequence);
    tcpHeader.SetAckNumber(m_tcb->m_rxBuffer->NextRxSequence());
    tcpHeader.SetWindowSize(AdvertisedWindowSize());
    if (m_endPoint != nullptr)
    {
        tcpHeader.SetSourcePort(m_endPoint->GetLocalPort());
        tcpHeader.SetDestinationPort(m_endPoint->GetPeerPort());
    }
    else
    {
        tcpHeader.SetSourcePort(m_endPoint6->GetLocalPort());
        tcpHeader.SetDestinationPort(m_endPoint6->GetPeerPort());
    }
    AddOptions(tcpHeader);
    // Send a packet tag for setting ECT bits in IP header
    if (m_tcb->m_ecnState != TcpSocketState::ECN_DISABLED)
    {
        AddSocketTags(p, IsEct(TcpPacketType_t::WINDOW_PROBE));
    }
    m_txTrace(p, tcpHeader, this);
 
    if (m_endPoint != nullptr)
    {
        m_tcp->SendPacket(p,
                          tcpHeader,
                          m_endPoint->GetLocalAddress(),
                          m_endPoint->GetPeerAddress(),
                          m_boundnetdevice);
    }
    else
    {
        m_tcp->SendPacket(p,
                          tcpHeader,
                          m_endPoint6->GetLocalAddress(),
                          m_endPoint6->GetPeerAddress(),
                          m_boundnetdevice);
    }
 
    NS_LOG_LOGIC("Schedule persist timeout at time "
                 << Simulator::Now().GetSeconds() << " to expire at time "
                 << (Simulator::Now() + m_persistTimeout).GetSeconds());
    m_persistEvent = Simulator::Schedule(m_persistTimeout, &TcpSocketBase::PersistTimeout, this);
}
 
void
TcpSocketBase::DoRetransmit()
{
    NS_LOG_FUNCTION(this);
    bool res;
    SequenceNumber32 seq;
    SequenceNumber32 seqHigh;
    uint32_t maxSizeToSend;
 
    // Find the first segment marked as lost and not retransmitted. With Reno,
    // that should be the head
    res = m_txBuffer->NextSeg(&seq, &seqHigh, false);
    if (!res)
    {
        // We have already retransmitted the head. However, we still received
        // three dupacks, or the RTO expired, but no data to transmit.
        // Therefore, re-send again the head.
        seq = m_txBuffer->HeadSequence();
        maxSizeToSend = m_tcb->m_segmentSize;
    }
    else
    {
        // NextSeg() may constrain the segment size when res is true
        maxSizeToSend = static_cast<uint32_t>(seqHigh - seq);
    }
    NS_ASSERT(m_sackEnabled || seq == m_txBuffer->HeadSequence());
 
    NS_LOG_INFO("Retransmitting " << seq);
    // Update the trace and retransmit the segment
    m_tcb->m_nextTxSequence = seq;
    uint32_t sz = SendDataPacket(m_tcb->m_nextTxSequence, maxSizeToSend, true);
 
    NS_ASSERT(sz > 0);
}
 
void
TcpSocketBase::CancelAllTimers()
{
    m_retxEvent.Cancel();
    m_persistEvent.Cancel();
    m_delAckEvent.Cancel();
    m_lastAckEvent.Cancel();
    m_timewaitEvent.Cancel();
    m_sendPendingDataEvent.Cancel();
    m_pacingTimer.Cancel();
}
 
/* Move TCP to Time_Wait state and schedule a transition to Closed state */
void
TcpSocketBase::TimeWait()
{
    NS_LOG_DEBUG(TcpStateName[m_state] << " -> TIME_WAIT");
    m_state = TIME_WAIT;
    CancelAllTimers();
    if (!m_closeNotified)
    {
        // Technically the connection is not fully closed, but we notify now
        // because an implementation (real socket) would behave as if closed.
        // Notify normal close when entering TIME_WAIT or leaving LAST_ACK.
        NotifyNormalClose();
        m_closeNotified = true;
    }
    // Move from TIME_WAIT to CLOSED after 2*MSL. Max segment lifetime is 2 min
    // according to RFC793, p.28
    m_timewaitEvent = Simulator::Schedule(Seconds(2 * m_msl), &TcpSocketBase::CloseAndNotify, this);
}
 
/* Below are the attribute get/set functions */
 
void
TcpSocketBase::SetSndBufSize(uint32_t size)
{
    NS_LOG_FUNCTION(this << size);
    m_txBuffer->SetMaxBufferSize(size);
}
 
uint32_t
TcpSocketBase::GetSndBufSize() const
{
    return m_txBuffer->MaxBufferSize();
}
 
uint32_t
TcpSocketBase::GetSndFack() const
{
    return m_sndFack;
}
 
bool
TcpSocketBase::GetFackEnabled() const
{
    return m_fackEnabled;
}
 
void
TcpSocketBase::SetRcvBufSize(uint32_t size)
{
    NS_LOG_FUNCTION(this << size);
    uint32_t oldSize = GetRcvBufSize();
 
    m_tcb->m_rxBuffer->SetMaxBufferSize(size);
 
    /* The size has (manually) increased. Actively inform the other end to prevent
     * stale zero-window states.
     */
    if (oldSize < size && m_connected)
    {
        if (m_tcb->m_ecnState == TcpSocketState::ECN_CE_RCVD ||
            m_tcb->m_ecnState == TcpSocketState::ECN_SENDING_ECE)
        {
            SendEmptyPacket(TcpHeader::ACK | TcpHeader::ECE);
            NS_LOG_DEBUG(TcpSocketState::EcnStateName[m_tcb->m_ecnState] << " -> ECN_SENDING_ECE");
            m_tcb->m_ecnState = TcpSocketState::ECN_SENDING_ECE;
        }
        else
        {
            SendEmptyPacket(TcpHeader::ACK);
        }
    }
}
 
uint32_t
TcpSocketBase::GetRcvBufSize() const
{
    return m_tcb->m_rxBuffer->MaxBufferSize();
}
 
void
TcpSocketBase::SetSegSize(uint32_t size)
{
    NS_LOG_FUNCTION(this << size);
    m_tcb->m_segmentSize = size;
    m_txBuffer->SetSegmentSize(size);
 
    NS_ABORT_MSG_UNLESS(m_state == CLOSED, "Cannot change segment size dynamically.");
}
 
uint32_t
TcpSocketBase::GetSegSize() const
{
    return m_tcb->m_segmentSize;
}
 
void
TcpSocketBase::SetConnTimeout(Time timeout)
{
    NS_LOG_FUNCTION(this << timeout);
    m_cnTimeout = timeout;
}
 
Time
TcpSocketBase::GetConnTimeout() const
{
    return m_cnTimeout;
}
 
void
TcpSocketBase::SetSynRetries(uint32_t count)
{
    NS_LOG_FUNCTION(this << count);
    m_synRetries = count;
}
 
uint32_t
TcpSocketBase::GetSynRetries() const
{
    return m_synRetries;
}
 
void
TcpSocketBase::SetDataRetries(uint32_t retries)
{
    NS_LOG_FUNCTION(this << retries);
    m_dataRetries = retries;
}
 
uint32_t
TcpSocketBase::GetDataRetries() const
{
    NS_LOG_FUNCTION(this);
    return m_dataRetries;
}
 
void
TcpSocketBase::SetDelAckTimeout(Time timeout)
{
    NS_LOG_FUNCTION(this << timeout);
    m_delAckTimeout = timeout;
}
 
Time
TcpSocketBase::GetDelAckTimeout() const
{
    return m_delAckTimeout;
}
 
void
TcpSocketBase::SetDelAckMaxCount(uint32_t count)
{
    NS_LOG_FUNCTION(this << count);
    m_delAckMaxCount = count;
}
 
uint32_t
TcpSocketBase::GetDelAckMaxCount() const
{
    return m_delAckMaxCount;
}
 
void
TcpSocketBase::SetTcpNoDelay(bool noDelay)
{
    NS_LOG_FUNCTION(this << noDelay);
    m_noDelay = noDelay;
}
 
bool
TcpSocketBase::GetTcpNoDelay() const
{
    return m_noDelay;
}
 
void
TcpSocketBase::SetPersistTimeout(Time timeout)
{
    NS_LOG_FUNCTION(this << timeout);
    m_persistTimeout = timeout;
}
 
Time
TcpSocketBase::GetPersistTimeout() const
{
    return m_persistTimeout;
}
 
bool
TcpSocketBase::SetAllowBroadcast(bool allowBroadcast)
{
    // Broadcast is not implemented. Return true only if allowBroadcast==false
    return (!allowBroadcast);
}
 
bool
TcpSocketBase::GetAllowBroadcast() const
{
    return false;
}
 
void
TcpSocketBase::AddOptions(TcpHeader& header)
{
    NS_LOG_FUNCTION(this << header);
 
    if (m_timestampEnabled)
    {
        AddOptionTimestamp(header);
    }
}
 
void
TcpSocketBase::ProcessOptionWScale(const Ptr<const TcpOption> option)
{
    NS_LOG_FUNCTION(this << option);
 
    Ptr<const TcpOptionWinScale> ws = DynamicCast<const TcpOptionWinScale>(option);
 
    // In naming, we do the contrary of RFC 1323. The received scaling factor
    // is Rcv.Wind.Scale (and not Snd.Wind.Scale)
    m_sndWindShift = ws->GetScale();
 
    if (m_sndWindShift > 14)
    {
        NS_LOG_WARN("Possible error; m_sndWindShift exceeds 14: " << m_sndWindShift);
        m_sndWindShift = 14;
    }
 
    NS_LOG_INFO(m_node->GetId() << " Received a scale factor of "
                                << static_cast<int>(m_sndWindShift));
}
 
uint8_t
TcpSocketBase::CalculateWScale() const
{
    NS_LOG_FUNCTION(this);
    uint32_t maxSpace = m_tcb->m_rxBuffer->MaxBufferSize();
    uint8_t scale = 0;
 
    while (maxSpace > m_maxWinSize)
    {
        maxSpace = maxSpace >> 1;
        ++scale;
    }
 
    if (scale > 14)
    {
        NS_LOG_WARN("Possible error; scale exceeds 14: " << scale);
        scale = 14;
    }
 
    NS_LOG_INFO("Node " << m_node->GetId() << " calculated wscale factor of "
                        << static_cast<int>(scale) << " for buffer size "
                        << m_tcb->m_rxBuffer->MaxBufferSize());
    return scale;
}
 
void
TcpSocketBase::AddOptionWScale(TcpHeader& header)
{
    NS_LOG_FUNCTION(this << header);
    NS_ASSERT(header.GetFlags() & TcpHeader::SYN);
 
    Ptr<TcpOptionWinScale> option = CreateObject<TcpOptionWinScale>();
 
    // In naming, we do the contrary of RFC 1323. The sended scaling factor
    // is Snd.Wind.Scale (and not Rcv.Wind.Scale)
 
    m_rcvWindShift = CalculateWScale();
    option->SetScale(m_rcvWindShift);
 
    header.AppendOption(option);
 
    NS_LOG_INFO(m_node->GetId() << " Send a scaling factor of "
                                << static_cast<int>(m_rcvWindShift));
}
 
uint32_t
TcpSocketBase::ProcessOptionSack(const Ptr<const TcpOption> option)
{
    NS_LOG_FUNCTION(this << option);
 
    Ptr<const TcpOptionSack> s = DynamicCast<const TcpOptionSack>(option);
 
    // Update m_sndFack with the highest sequence number acknowledged from the SACK blocks
    if (m_fackEnabled)
    {
        for (const auto& [leftEdge, rightEdge] : s->GetSackList())
        {
            if (rightEdge.GetValue() > m_sndFack)
            {
                NS_LOG_INFO(" m_sndFack updated from " << m_sndFack << " to "
                                                       << rightEdge.GetValue());
                m_sndFack = rightEdge.GetValue();
            }
        }
    }
 
    return m_txBuffer->Update(s->GetSackList(), MakeCallback(&TcpRateOps::SkbDelivered, m_rateOps));
}
 
void
TcpSocketBase::ProcessOptionSackPermitted(const Ptr<const TcpOption> option)
{
    NS_LOG_FUNCTION(this << option);
 
    Ptr<const TcpOptionSackPermitted> s = DynamicCast<const TcpOptionSackPermitted>(option);
 
    NS_ASSERT(m_sackEnabled == true);
    NS_LOG_INFO(m_node->GetId() << " Received a SACK_PERMITTED option " << s);
}
 
void
TcpSocketBase::AddOptionSackPermitted(TcpHeader& header)
{
    NS_LOG_FUNCTION(this << header);
    NS_ASSERT(header.GetFlags() & TcpHeader::SYN);
 
    Ptr<TcpOptionSackPermitted> option = CreateObject<TcpOptionSackPermitted>();
    header.AppendOption(option);
    NS_LOG_INFO(m_node->GetId() << " Add option SACK-PERMITTED");
}
 
void
TcpSocketBase::AddOptionSack(TcpHeader& header)
{
    NS_LOG_FUNCTION(this << header);
 
    // Calculate the number of SACK blocks allowed in this packet
    uint8_t optionLenAvail = header.GetMaxOptionLength() - header.GetOptionLength();
    uint8_t allowedSackBlocks = (optionLenAvail - 2) / 8;
 
    TcpOptionSack::SackList sackList = m_tcb->m_rxBuffer->GetSackList();
    if (allowedSackBlocks == 0 || sackList.empty())
    {
        NS_LOG_LOGIC("No space available or sack list empty, not adding sack blocks");
        return;
    }
 
    // Append the allowed number of SACK blocks
    Ptr<TcpOptionSack> option = CreateObject<TcpOptionSack>();
 
    for (auto i = sackList.begin(); allowedSackBlocks > 0 && i != sackList.end(); ++i)
    {
        option->AddSackBlock(*i);
        allowedSackBlocks--;
    }
 
    header.AppendOption(option);
    NS_LOG_INFO(m_node->GetId() << " Add option SACK " << *option);
}
 
void
TcpSocketBase::ProcessOptionTimestamp(const Ptr<const TcpOption> option,
                                      const SequenceNumber32& seq)
{
    NS_LOG_FUNCTION(this << option);
 
    Ptr<const TcpOptionTS> ts = DynamicCast<const TcpOptionTS>(option);
 
    // This is valid only when no overflow occurs. It happens
    // when a connection last longer than 50 days.
    if (m_tcb->m_rcvTimestampValue > ts->GetTimestamp())
    {
        // Do not save a smaller timestamp (probably there is reordering)
        return;
    }
 
    m_tcb->m_rcvTimestampValue = ts->GetTimestamp();
    m_tcb->m_rcvTimestampEchoReply = ts->GetEcho();
 
    if (seq == m_tcb->m_rxBuffer->NextRxSequence() && seq <= m_highTxAck)
    {
        m_timestampToEcho = ts->GetTimestamp();
    }
 
    NS_LOG_INFO(m_node->GetId() << " Got timestamp=" << m_timestampToEcho
                                << " and Echo=" << ts->GetEcho());
}
 
void
TcpSocketBase::AddOptionTimestamp(TcpHeader& header)
{
    NS_LOG_FUNCTION(this << header);
 
    Ptr<TcpOptionTS> option = CreateObject<TcpOptionTS>();
 
    option->SetTimestamp(TcpOptionTS::NowToTsValue());
    option->SetEcho(m_timestampToEcho);
 
    header.AppendOption(option);
    NS_LOG_INFO(m_node->GetId() << " Add option TS, ts=" << option->GetTimestamp()
                                << " echo=" << m_timestampToEcho);
}
 
void
TcpSocketBase::UpdateWindowSize(const TcpHeader& header)
{
    NS_LOG_FUNCTION(this << header);
    //  If the connection is not established, the window size is always
    //  updated
    uint32_t receivedWindow = header.GetWindowSize();
    receivedWindow <<= m_sndWindShift;
    NS_LOG_INFO("Received (scaled) window is " << receivedWindow << " bytes");
    if (m_state < ESTABLISHED)
    {
        m_rWnd = receivedWindow;
        NS_LOG_LOGIC("State less than ESTABLISHED; updating rWnd to " << m_rWnd);
        return;
    }
 
    // Test for conditions that allow updating of the window
    // 1) segment contains new data (advancing the right edge of the receive
    // buffer),
    // 2) segment does not contain new data but the segment acks new data
    // (highest sequence number acked advances), or
    // 3) the advertised window is larger than the current send window
    bool update = false;
    if (header.GetAckNumber() == m_highRxAckMark && receivedWindow > m_rWnd)
    {
        // right edge of the send window is increased (window update)
        update = true;
    }
    if (header.GetAckNumber() > m_highRxAckMark)
    {
        m_highRxAckMark = header.GetAckNumber();
        update = true;
    }
    if (header.GetSequenceNumber() > m_highRxMark)
    {
        m_highRxMark = header.GetSequenceNumber();
        update = true;
    }
    if (update)
    {
        m_rWnd = receivedWindow;
        NS_LOG_LOGIC("updating rWnd to " << m_rWnd);
    }
}
 
void
TcpSocketBase::SetMinRto(Time minRto)
{
    NS_LOG_FUNCTION(this << minRto);
    m_minRto = minRto;
}
 
Time
TcpSocketBase::GetMinRto() const
{
    return m_minRto;
}
 
void
TcpSocketBase::SetClockGranularity(Time clockGranularity)
{
    NS_LOG_FUNCTION(this << clockGranularity);
    m_clockGranularity = clockGranularity;
}
 
Time
TcpSocketBase::GetClockGranularity() const
{
    return m_clockGranularity;
}
 
Ptr<TcpTxBuffer>
TcpSocketBase::GetTxBuffer() const
{
    return m_txBuffer;
}
 
Ptr<TcpRxBuffer>
TcpSocketBase::GetRxBuffer() const
{
    return m_tcb->m_rxBuffer;
}
 
void
TcpSocketBase::SetRetxThresh(uint32_t retxThresh)
{
    m_retxThresh = retxThresh;
    m_txBuffer->SetDupAckThresh(retxThresh);
}
 
void
TcpSocketBase::UpdatePacingRateTrace(DataRate oldValue, DataRate newValue) const
{
    m_pacingRateTrace(oldValue, newValue);
}
 
void
TcpSocketBase::UpdateCwnd(uint32_t oldValue, uint32_t newValue) const
{
    m_cWndTrace(oldValue, newValue);
}
 
void
TcpSocketBase::UpdateCwndInfl(uint32_t oldValue, uint32_t newValue) const
{
    m_cWndInflTrace(oldValue, newValue);
}
 
void
TcpSocketBase::UpdateSsThresh(uint32_t oldValue, uint32_t newValue) const
{
    m_ssThTrace(oldValue, newValue);
}
 
void
TcpSocketBase::UpdateCongState(TcpSocketState::TcpCongState_t oldValue,
                               TcpSocketState::TcpCongState_t newValue) const
{
    m_congStateTrace(oldValue, newValue);
}
 
void
TcpSocketBase::UpdateEcnState(TcpSocketState::EcnState_t oldValue,
                              TcpSocketState::EcnState_t newValue) const
{
    m_ecnStateTrace(oldValue, newValue);
}
 
void
TcpSocketBase::UpdateNextTxSequence(SequenceNumber32 oldValue, SequenceNumber32 newValue) const
 
{
    m_nextTxSequenceTrace(oldValue, newValue);
}
 
void
TcpSocketBase::UpdateHighTxMark(SequenceNumber32 oldValue, SequenceNumber32 newValue) const
{
    m_highTxMarkTrace(oldValue, newValue);
}
 
void
TcpSocketBase::UpdateBytesInFlight(uint32_t oldValue, uint32_t newValue) const
{
    m_bytesInFlightTrace(oldValue, newValue);
}
 
void
TcpSocketBase::UpdateFackAwnd(uint32_t oldValue, uint32_t newValue) const
{
    m_fackAwndTrace(oldValue, newValue);
}
 
void
TcpSocketBase::UpdateRtt(Time oldValue, Time newValue) const
{
    m_srttTrace(oldValue, newValue);
}
 
void
TcpSocketBase::UpdateLastRtt(Time oldValue, Time newValue) const
{
    m_lastRttTrace(oldValue, newValue);
}
 
void
TcpSocketBase::SetCongestionControlAlgorithm(Ptr<TcpCongestionOps> algo)
{
    NS_LOG_FUNCTION(this << algo);
    m_congestionControl = algo;
    m_congestionControl->Init(m_tcb);
    m_congestionControl->SetRateOps(m_rateOps);
}
 
void
TcpSocketBase::SetRecoveryAlgorithm(Ptr<TcpRecoveryOps> recovery)
{
    NS_LOG_FUNCTION(this << recovery);
    m_recoveryOps = recovery;
}
 
Ptr<TcpSocketBase>
TcpSocketBase::Fork()
{
    return CopyObject<TcpSocketBase>(this);
}
 
uint32_t
TcpSocketBase::SafeSubtraction(uint32_t a, uint32_t b)
{
    if (a > b)
    {
        return a - b;
    }
 
    return 0;
}
 
void
TcpSocketBase::NotifyPacingPerformed()
{
    NS_LOG_FUNCTION(this);
    NS_LOG_INFO("Performing Pacing");
    SendPendingData(m_connected);
}
 
bool
TcpSocketBase::IsPacingEnabled() const
{
    if (!m_tcb->m_pacing)
    {
        return false;
    }
    else
    {
        if (m_tcb->m_paceInitialWindow)
        {
            return true;
        }
        SequenceNumber32 highTxMark = m_tcb->m_highTxMark; // cast traced value
        if (highTxMark.GetValue() > (GetInitialCwnd() * m_tcb->m_segmentSize))
        {
            return true;
        }
    }
    return false;
}
 
void
TcpSocketBase::UpdatePacingRate()
{
    NS_LOG_FUNCTION(this << m_tcb);
 
    // According to Linux, set base pacing rate to (cwnd * mss) / srtt
    //
    // In (early) slow start, multiply base by the slow start factor.
    // In late slow start and congestion avoidance, multiply base by
    // the congestion avoidance factor.
    // Comment from Linux code regarding early/late slow start:
    // Normal Slow Start condition is (tp->snd_cwnd < tp->snd_ssthresh)
    // If snd_cwnd >= (tp->snd_ssthresh / 2), we are approaching
    // end of slow start and should slow down.
 
    // Similar to Linux, do not update pacing rate here if the
    // congestion control implements TcpCongestionOps::CongControl ()
    if (m_congestionControl->HasCongControl() || !m_tcb->m_pacing)
    {
        return;
    }
 
    double factor;
    if (m_tcb->m_cWnd < m_tcb->m_ssThresh / 2)
    {
        NS_LOG_DEBUG("Pacing according to slow start factor; " << m_tcb->m_cWnd << " "
                                                               << m_tcb->m_ssThresh);
        factor = static_cast<double>(m_tcb->m_pacingSsRatio) / 100;
    }
    else
    {
        NS_LOG_DEBUG("Pacing according to congestion avoidance factor; " << m_tcb->m_cWnd << " "
                                                                         << m_tcb->m_ssThresh);
        factor = static_cast<double>(m_tcb->m_pacingCaRatio) / 100;
    }
    Time srtt = m_tcb->m_srtt.Get(); // Get underlying Time value
    NS_LOG_DEBUG("Smoothed RTT is " << srtt.GetSeconds());
 
    // Multiply by 8 to convert from bytes per second to bits per second
    DataRate pacingRate((std::max(m_tcb->m_cWnd, m_tcb->m_bytesInFlight) * 8 * factor) /
                        srtt.GetSeconds());
    if (pacingRate < m_tcb->m_maxPacingRate)
    {
        NS_LOG_DEBUG("Pacing rate updated to: " << pacingRate);
        m_tcb->m_pacingRate = pacingRate;
    }
    else
    {
        NS_LOG_DEBUG("Pacing capped by max pacing rate: " << m_tcb->m_maxPacingRate);
        m_tcb->m_pacingRate = m_tcb->m_maxPacingRate;
    }
}
 
void
TcpSocketBase::SetPacingStatus(bool pacing)
{
    NS_LOG_FUNCTION(this << pacing);
    m_tcb->m_pacing = pacing;
}
 
void
TcpSocketBase::SetPaceInitialWindow(bool paceWindow)
{
    NS_LOG_FUNCTION(this << paceWindow);
    m_tcb->m_paceInitialWindow = paceWindow;
}
 
bool
TcpSocketBase::IsEct(TcpPacketType_t packetType) const
{
    NS_LOG_FUNCTION(this << packetType);
    NS_ASSERT_MSG(packetType != TcpPacketType_t::INVALID, "Invalid TCP packet type");
    if (m_tcb->m_ecnState == TcpSocketState::ECN_DISABLED)
    {
        return false;
    }
 
    NS_ABORT_MSG_IF(!ECN_RESTRICTION_MAP.contains(std::make_pair(packetType, m_tcb->m_ecnMode)),
                    "Invalid packetType and ecnMode");
 
    return ECN_RESTRICTION_MAP.at(std::make_pair(packetType, m_tcb->m_ecnMode));
}
 
void
TcpSocketBase::SetUseEcn(TcpSocketState::UseEcn_t useEcn)
{
    NS_LOG_FUNCTION(this << useEcn);
    m_tcb->m_useEcn = useEcn;
}
 
void
TcpSocketBase::SetUseAbe(bool useAbe)
{
    NS_LOG_FUNCTION(this << useAbe);
    if (m_tcb->m_useEcn == TcpSocketState::Off && useAbe)
    {
        NS_LOG_INFO("Enabling ECN along with ABE");
        m_tcb->m_useEcn = TcpSocketState::On;
    }
    m_tcb->m_abeEnabled = useAbe;
}
 
bool
TcpSocketBase::GetUseAbe() const
{
    return m_tcb->m_abeEnabled;
}
 
uint32_t
TcpSocketBase::GetRWnd() const
{
    return m_rWnd.Get();
}
 
SequenceNumber32
TcpSocketBase::GetHighRxAck() const
{
    return m_highRxAckMark.Get();
}
 
// RttHistory methods
RttHistory::RttHistory(SequenceNumber32 s, uint32_t c, Time t)
    : seq(s),
      count(c),
      time(t),
      retx(false)
{
}
 
RttHistory::RttHistory(const RttHistory& h)
    : seq(h.seq),
      count(h.count),
      time(h.time),
      retx(h.retx)
{
}
 
} // namespace ns3