/* -*- 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-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 (SequenceNumber32 sequenceNumber)
{
  m_sequenceNumber = sequenceNumber;
}
void TcpHeader::SetAckNumber (SequenceNumber32 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;
}
SequenceNumber32 TcpHeader::GetSequenceNumber () const
{
  return m_sequenceNumber;
}
SequenceNumber32 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 ";
        }
      if((m_flags & ECE) != 0)
        {
          os<<" ECE ";
        }
      if((m_flags & CWR) != 0)
        {
          os<<" CWR ";
        }
      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.GetValue ());
  i.WriteHtonU32 (m_ackNumber.GetValue ());
  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