/* -*- 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-tahoe.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 ("TcpTahoe");

namespace ns3 {

NS_OBJECT_ENSURE_REGISTERED (TcpTahoe);

TypeId

TcpTahoe::GetTypeId (void)

{

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

    .SetParent<TcpSocketBase> ()

    .AddConstructor<TcpTahoe> ()

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

                    UintegerValue (3),

                    MakeUintegerAccessor (&TcpTahoe::m_retxThresh),

                    MakeUintegerChecker<uint32_t> ())

    .AddTraceSource ("CongestionWindow",

                     "The TCP connection's congestion window",

                     MakeTraceSourceAccessor (&TcpTahoe::m_cWnd))

  ;

  return tid;

}

TcpTahoe::TcpTahoe (void) : m_initialCWnd (1), m_retxThresh (3)

{

  NS_LOG_FUNCTION (this);

}

TcpTahoe::TcpTahoe (const TcpTahoe& sock)

  : TcpSocketBase (sock),

    m_cWnd (sock.m_cWnd),

    m_ssThresh (sock.m_ssThresh),

    m_initialCWnd (sock.m_initialCWnd),

    m_retxThresh (sock.m_retxThresh)

{

  NS_LOG_FUNCTION (this);

  NS_LOG_LOGIC ("Invoked the copy constructor");

}

TcpTahoe::~TcpTahoe (void)

{

}

/* We initialize m_cWnd from this function, after attributes initialized */

int

TcpTahoe::Listen (void)

{

  NS_LOG_FUNCTION (this);

  InitializeCwnd ();

  return TcpSocketBase::Listen ();

}

/* We initialize m_cWnd from this function, after attributes initialized */

int

TcpTahoe::Connect (const Address & address)

{

  NS_LOG_FUNCTION (this << address);

  InitializeCwnd ();

  return TcpSocketBase::Connect (address);

}

/* Limit the size of in-flight data by cwnd and receiver's rxwin */

uint32_t

TcpTahoe::Window (void)

{

  NS_LOG_FUNCTION (this);

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

}

Ptr<TcpSocketBase>

TcpTahoe::Fork (void)

{

  return CopyObject<TcpTahoe> (this);

}

/* New ACK (up to seqnum seq) received. Increase cwnd and call TcpSocketBase::NewAck() */

void

TcpTahoe::NewAck (SequenceNumber32 const& seq)

{

  NS_LOG_FUNCTION (this << seq);

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

                " cwnd " << m_cWnd <<

                " ssthresh " << m_ssThresh);

  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);

    }

  TcpSocketBase::NewAck (seq);           // Complete newAck processing

}

/* Cut down ssthresh upon triple dupack */

void

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

{

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

  if (count == m_retxThresh)

    { // triple duplicate ack triggers fast retransmit (RFC2001, sec.3)

      NS_LOG_INFO ("Triple Dup Ack: old ssthresh " << m_ssThresh << " cwnd " << m_cWnd);

      // fast retransmit in Tahoe means triggering RTO earlier. Tx is restarted

      // from the highest ack and run slow start again.

      // (Fall & Floyd 1996, sec.1)

      m_ssThresh = std::max (static_cast<unsigned> (m_cWnd / 2), m_segmentSize * 2);  // Half ssthresh

      m_cWnd = m_segmentSize; // Run slow start again

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

      NS_LOG_INFO ("Triple Dup Ack: new ssthresh " << m_ssThresh << " cwnd " << m_cWnd);

      NS_LOG_LOGIC ("Triple Dup Ack: retransmit missing segment at " << Simulator::Now ().GetSeconds ());

      DoRetransmit ();

    }

}

/* Retransmit timeout */

void TcpTahoe::Retransmit (void)

{

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

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

  m_ssThresh = std::max (static_cast<unsigned> (m_cWnd / 2), m_segmentSize * 2);  // Half ssthresh

  m_cWnd = m_segmentSize;                   // Set cwnd to 1 segSize (RFC2001, sec.2)

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

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

  DoRetransmit ();                          // Retransmit the packet

}

void

TcpTahoe::SetSegSize (uint32_t size)

{

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

  m_segmentSize = size;

}

void

TcpTahoe::SetSSThresh (uint32_t threshold)

{

  m_ssThresh = threshold;

}

uint32_t

TcpTahoe::GetSSThresh (void) const

{

  return m_ssThresh;

}

void

TcpTahoe::SetInitialCwnd (uint32_t cwnd)

{

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

  m_initialCWnd = cwnd;

}

uint32_t

TcpTahoe::GetInitialCwnd (void) const

{

  return m_initialCWnd;

}

void 

TcpTahoe::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