/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */

/*

 * Copyright (c) 2010 Adrian Sai-wah Tam

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation;

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

 *

 * Author: Adrian Sai-wah Tam <adrian.sw.tam@gmail.com>

 */

#define NS_LOG_APPEND_CONTEXT \

  if (m_node) { std::clog << Simulator::Now ().GetSeconds () << " [node " << m_node->GetId () << "] "; }

#include "tcp-reno.h"

#include "ns3/log.h"

#include "ns3/trace-source-accessor.h"

#include "ns3/simulator.h"

#include "ns3/abort.h"

#include "ns3/node.h"

NS_LOG_COMPONENT_DEFINE ("TcpReno");

namespace ns3 {

NS_OBJECT_ENSURE_REGISTERED (TcpReno)

  ;

TypeId

TcpReno::GetTypeId (void)

{

  static TypeId tid = TypeId ("ns3::TcpReno")

    .SetParent<TcpSocketBase> ()

    .AddConstructor<TcpReno> ()

    .AddAttribute ("ReTxThreshold", "Threshold for fast retransmit",

                    UintegerValue (3),

                    MakeUintegerAccessor (&TcpReno::m_retxThresh),

                    MakeUintegerChecker<uint32_t> ())

    .AddTraceSource ("CongestionWindow",

                     "The TCP connection's congestion window",

                     MakeTraceSourceAccessor (&TcpReno::m_cWnd))

  ;

  return tid;

}

TcpReno::TcpReno (void) : m_retxThresh (3), m_inFastRec (false)

{

  NS_LOG_FUNCTION (this);

}

TcpReno::TcpReno (const TcpReno& sock)

  : TcpSocketBase (sock),

    m_cWnd (sock.m_cWnd),

    m_ssThresh (sock.m_ssThresh),

    m_initialCWnd (sock.m_initialCWnd),

    m_retxThresh (sock.m_retxThresh),

    m_inFastRec (false)

{

  NS_LOG_FUNCTION (this);

  NS_LOG_LOGIC ("Invoked the copy constructor");

}

TcpReno::~TcpReno (void)

{

}

int

TcpReno::Listen (void)

{

  NS_LOG_FUNCTION (this);

  InitializeCwnd ();

  return TcpSocketBase::Listen ();

}

int

TcpReno::Connect (const Address & address)

{

  NS_LOG_FUNCTION (this << address);

  InitializeCwnd ();

  return TcpSocketBase::Connect (address);

}

uint32_t

TcpReno::Window (void)

{

  NS_LOG_FUNCTION (this);

  return std::min (m_rWnd.Get (), m_cWnd.Get ());

}

Ptr<TcpSocketBase>

TcpReno::Fork (void)

{

  return CopyObject<TcpReno> (this);

}

void

TcpReno::NewAck (const SequenceNumber32& seq)

{

  NS_LOG_FUNCTION (this << seq);

  NS_LOG_LOGIC ("TcpReno receieved ACK for seq " << seq <<

                " cwnd " << m_cWnd <<

                " ssthresh " << m_ssThresh);

  // Check for exit condition of fast recovery

  if (m_inFastRec)

    { // RFC2001, sec.4; RFC2581, sec.3.2

      // First new ACK after fast recovery: reset cwnd

      m_cWnd = m_ssThresh;

      m_inFastRec = false;

      NS_LOG_INFO ("Reset cwnd to " << m_cWnd);

    };

  // Increase of cwnd based on current phase (slow start or congestion avoidance)

  if (m_cWnd < m_ssThresh)

    { // Slow start mode, add one segSize to cWnd. Default m_ssThresh is 65535. (RFC2001, sec.1)

      m_cWnd += m_segmentSize;

      NS_LOG_INFO ("In SlowStart, updated to cwnd " << m_cWnd << " ssthresh " << m_ssThresh);

    }

  else

    { // Congestion avoidance mode, increase by (segSize*segSize)/cwnd. (RFC2581, sec.3.1)

      // To increase cwnd for one segSize per RTT, it should be (ackBytes*segSize)/cwnd

      double adder = static_cast<double> (m_segmentSize * m_segmentSize) / m_cWnd.Get ();

      adder = std::max (1.0, adder);

      m_cWnd += static_cast<uint32_t> (adder);

      NS_LOG_INFO ("In CongAvoid, updated to cwnd " << m_cWnd << " ssthresh " << m_ssThresh);

    }

  // Complete newAck processing

  TcpSocketBase::NewAck (seq);

}

// Fast recovery and fast retransmit

void

TcpReno::DupAck (const TcpHeader& t, uint32_t count)

{

  NS_LOG_FUNCTION (this << "t " << count);

  if (count == m_retxThresh && !m_inFastRec)

    { // triple duplicate ack triggers fast retransmit (RFC2581, sec.3.2)

      m_ssThresh = std::max (2 * m_segmentSize, BytesInFlight () / 2);

      m_cWnd = m_ssThresh + 3 * m_segmentSize;

      m_inFastRec = true;

      NS_LOG_INFO ("Triple dupack. Reset cwnd to " << m_cWnd << ", ssthresh to " << m_ssThresh);

      DoRetransmit ();

    }

  else if (m_inFastRec)

    { // In fast recovery, inc cwnd for every additional dupack (RFC2581, sec.3.2)

      m_cWnd += m_segmentSize;

      NS_LOG_INFO ("Increased cwnd to " << m_cWnd);

      SendPendingData (m_connected);

    };

}

// Retransmit timeout

void TcpReno::Retransmit (void)

{

  NS_LOG_FUNCTION (this);

  NS_LOG_LOGIC (this << " ReTxTimeout Expired at time " << Simulator::Now ().GetSeconds ());

  m_inFastRec = false;

  // If erroneous timeout in closed/timed-wait state, just return

  if (m_state == CLOSED || m_state == TIME_WAIT) return;

  // If all data are received (non-closing socket and nothing to send), just return

  if (m_state <= ESTABLISHED && m_txBuffer.HeadSequence () >= m_highTxMark) return;

  // According to RFC2581 sec.3.1, upon RTO, ssthresh is set to half of flight

  // size and cwnd is set to 1*MSS, then the lost packet is retransmitted and

  // TCP back to slow start

  m_ssThresh = std::max (2 * m_segmentSize, BytesInFlight () / 2);

  m_cWnd = m_segmentSize;

  m_nextTxSequence = m_txBuffer.HeadSequence (); // Restart from highest Ack

  NS_LOG_INFO ("RTO. Reset cwnd to " << m_cWnd <<

               ", ssthresh to " << m_ssThresh << ", restart from seqnum " << m_nextTxSequence);

  m_rtt->IncreaseMultiplier ();             // Double the next RTO

  DoRetransmit ();                          // Retransmit the packet

}

void

TcpReno::SetSegSize (uint32_t size)

{

  NS_ABORT_MSG_UNLESS (m_state == CLOSED, "TcpReno::SetSegSize() cannot change segment size after connection started.");

  m_segmentSize = size;

}

void

TcpReno::SetSSThresh (uint32_t threshold)

{

  m_ssThresh = threshold;

}

uint32_t

TcpReno::GetSSThresh (void) const

{

  return m_ssThresh;

}

void

TcpReno::SetInitialCwnd (uint32_t cwnd)

{

  NS_ABORT_MSG_UNLESS (m_state == CLOSED, "TcpReno::SetInitialCwnd() cannot change initial cwnd after connection started.");

  m_initialCWnd = cwnd;

}

uint32_t

TcpReno::GetInitialCwnd (void) const

{

  return m_initialCWnd;

}

void 

TcpReno::InitializeCwnd (void)

{

  /*

   * Initialize congestion window, default to 1 MSS (RFC2001, sec.1) and must

   * not be larger than 2 MSS (RFC2581, sec.3.1). Both m_initiaCWnd and

   * m_segmentSize are set by the attribute system in ns3::TcpSocket.

   */

  m_cWnd = m_initialCWnd * m_segmentSize;

}

} // namespace ns3