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

/*

 * Copyright (c) 2007 Georgia Tech Research Corporation

 *

 * 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: Raj Bhattacharjea <raj.b@gatech.edu>

 */

#include <stdint.h>

#include <iostream>

#include "tcp-socket-impl.h"

#include "tcp-header.h"

#include "ns3/buffer.h"

#include "ns3/address-utils.h"

namespace ns3 {

NS_OBJECT_ENSURE_REGISTERED (TcpHeader);

TcpHeader::TcpHeader ()

  : m_sourcePort (0),

    m_destinationPort (0),

    m_sequenceNumber (0),

    m_ackNumber (0),

    m_length (5),

    m_flags (0),

    m_windowSize (0xffff),

    m_urgentPointer (0),

    m_calcChecksum(false),

    m_goodChecksum(true)

{}

TcpHeader::~TcpHeader ()

{}

void

TcpHeader::EnableChecksums (void)

{

  m_calcChecksum = true;

}

void TcpHeader::SetSourcePort (uint16_t port)

{

  m_sourcePort = port;

}

void TcpHeader::SetDestinationPort (uint16_t port)

{

  m_destinationPort = port;

}

void TcpHeader::SetSequenceNumber (SequenceNumber sequenceNumber)

{

  m_sequenceNumber = sequenceNumber;

}

void TcpHeader::SetAckNumber (SequenceNumber ackNumber)

{

  m_ackNumber = ackNumber;

}

void TcpHeader::SetLength (uint8_t length)

{

  m_length = length;

}

void TcpHeader::SetFlags (uint8_t flags)

{

  m_flags = flags;

}

void TcpHeader::SetWindowSize (uint16_t windowSize)

{

  m_windowSize = windowSize;

}

void TcpHeader::SetUrgentPointer (uint16_t urgentPointer)

{

  m_urgentPointer = urgentPointer;

}

uint16_t TcpHeader::GetSourcePort () const

{

  return m_sourcePort;

}

uint16_t TcpHeader::GetDestinationPort () const

{

  return m_destinationPort;

}

SequenceNumber TcpHeader::GetSequenceNumber () const

{

  return m_sequenceNumber;

}

SequenceNumber TcpHeader::GetAckNumber () const

{

  return m_ackNumber;

}

uint8_t  TcpHeader::GetLength () const

{

  return m_length;

}

uint8_t  TcpHeader::GetFlags () const

{

  return m_flags;

}

uint16_t TcpHeader::GetWindowSize () const

{

  return m_windowSize;

}

uint16_t TcpHeader::GetUrgentPointer () const

{

  return m_urgentPointer;

}

void 

TcpHeader::InitializeChecksum (Ipv4Address source, 

                               Ipv4Address destination,

                               uint8_t protocol)

{

  m_source = source;

  m_destination = destination;

  m_protocol = protocol;

}

uint16_t

TcpHeader::CalculateHeaderChecksum (uint16_t size) const

{

  Buffer buf = Buffer (12);

  buf.AddAtStart (12);

  Buffer::Iterator it = buf.Begin ();

  WriteTo (it, m_source);

  WriteTo (it, m_destination);

  it.WriteU8 (0); /* protocol */

  it.WriteU8 (m_protocol); /* protocol */

  it.WriteU8 (size >> 8); /* length */

  it.WriteU8 (size & 0xff); /* length */

  it = buf.Begin ();

  /* we don't CompleteChecksum ( ~ ) now */

  return ~(it.CalculateIpChecksum (12));

}

bool

TcpHeader::IsChecksumOk (void) const

{

  return m_goodChecksum;

}

TypeId 

TcpHeader::GetTypeId (void)

{

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

    .SetParent<Header> ()

    .AddConstructor<TcpHeader> ()

    ;

  return tid;

}

TypeId 

TcpHeader::GetInstanceTypeId (void) const

{

  return GetTypeId ();

}

void TcpHeader::Print (std::ostream &os)  const

{

  os << m_sourcePort << " > " << m_destinationPort;

  if(m_flags!=0)

  {

    os<<" [";

    if((m_flags & FIN) != 0)

    {

      os<<" FIN ";

    }

    if((m_flags & SYN) != 0)

    {

      os<<" SYN ";

    }

    if((m_flags & RST) != 0)

    {

      os<<" RST ";

    }

    if((m_flags & PSH) != 0)

    {

      os<<" PSH ";

    }

    if((m_flags & ACK) != 0)

    {

      os<<" ACK ";

    }

    if((m_flags & URG) != 0)

    {

      os<<" URG ";

    }

    os<<"]";

  }

  os<<" Seq="<<m_sequenceNumber<<" Ack="<<m_ackNumber<<" Win="<<m_windowSize;

}

uint32_t TcpHeader::GetSerializedSize (void)  const

{

  return 4*m_length;

}

void TcpHeader::Serialize (Buffer::Iterator start)  const

{

  Buffer::Iterator i = start;

  i.WriteHtonU16 (m_sourcePort);

  i.WriteHtonU16 (m_destinationPort);

  i.WriteHtonU32 (m_sequenceNumber);

  i.WriteHtonU32 (m_ackNumber);

  i.WriteHtonU16 (m_length << 12 | m_flags); //reserved bits are all zero

  i.WriteHtonU16 (m_windowSize);

  i.WriteHtonU16 (0);

  i.WriteHtonU16 (m_urgentPointer);

  if(m_calcChecksum)

  {

    uint16_t headerChecksum = CalculateHeaderChecksum (start.GetSize ());

    i = start;

    uint16_t checksum = i.CalculateIpChecksum(start.GetSize (), headerChecksum);

    i = start;

    i.Next(16);

    i.WriteU16(checksum);

  }

}

uint32_t TcpHeader::Deserialize (Buffer::Iterator start)

{

  Buffer::Iterator i = start;

  m_sourcePort = i.ReadNtohU16 ();

  m_destinationPort = i.ReadNtohU16 ();

  m_sequenceNumber = i.ReadNtohU32 ();

  m_ackNumber = i.ReadNtohU32 ();

  uint16_t field = i.ReadNtohU16 ();

  m_flags = field & 0x3F;

  m_length = field>>12;

  m_windowSize = i.ReadNtohU16 ();

  i.Next (2);

  m_urgentPointer = i.ReadNtohU16 ();

  if(m_calcChecksum)

    {

      uint16_t headerChecksum = CalculateHeaderChecksum (start.GetSize ());

      i = start;

      uint16_t checksum = i.CalculateIpChecksum(start.GetSize (), headerChecksum);

      m_goodChecksum = (checksum == 0);

    }

  return GetSerializedSize ();

}

}; // namespace ns3