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

/*

 * Copyright (c) 2005 INRIA

 *

 * 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: Mathieu Lacage <mathieu.lacage@sophia.inria.fr>

 */

#include "udp-header.h"

#include "ns3/address-utils.h"

namespace ns3 {

NS_OBJECT_ENSURE_REGISTERED (UdpHeader);

/* The magic values below are used only for debugging.

 * They can be used to easily detect memory corruption

 * problems so you can see the patterns in memory.

 */

UdpHeader::UdpHeader ()

  : m_sourcePort (0xfffd),

    m_destinationPort (0xfffd),

    m_payloadSize (0xfffd),

    m_calcChecksum (false),

    m_goodChecksum (true)

{

}

UdpHeader::~UdpHeader ()

{

  m_sourcePort = 0xfffe;

  m_destinationPort = 0xfffe;

  m_payloadSize = 0xfffe;

}

void 

UdpHeader::EnableChecksums (void)

{

  m_calcChecksum = true;

}

void 

UdpHeader::SetDestinationPort (uint16_t port)

{

  m_destinationPort = port;

}

void 

UdpHeader::SetSourcePort (uint16_t port)

{

  m_sourcePort = port;

}

uint16_t 

UdpHeader::GetSourcePort (void) const

{

  return m_sourcePort;

}

uint16_t 

UdpHeader::GetDestinationPort (void) const

{

  return m_destinationPort;

}

void 

UdpHeader::InitializeChecksum (Ipv4Address source, 

                               Ipv4Address destination,

                               uint8_t protocol)

{

  m_source = source;

  m_destination = destination;

  m_protocol = protocol;

}

uint16_t

UdpHeader::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

UdpHeader::IsChecksumOk (void) const

{

  return m_goodChecksum; 

}

TypeId 

UdpHeader::GetTypeId (void)

{

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

    .SetParent<Header> ()

    .AddConstructor<UdpHeader> ()

  ;

  return tid;

}

TypeId 

UdpHeader::GetInstanceTypeId (void) const

{

  return GetTypeId ();

}

void 

UdpHeader::Print (std::ostream &os) const

{

  os << "length: " << m_payloadSize + GetSerializedSize ()

     << " " 

     << m_sourcePort << " > " << m_destinationPort

  ;

}

uint32_t 

UdpHeader::GetSerializedSize (void) const

{

  return 8;

}

void

UdpHeader::Serialize (Buffer::Iterator start) const

{

  Buffer::Iterator i = start;

  i.WriteHtonU16 (m_sourcePort);

  i.WriteHtonU16 (m_destinationPort);

  i.WriteHtonU16 (start.GetSize ());

  i.WriteU16 (0);

  if (m_calcChecksum)

    {

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

      i = start;

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

      i = start;

      i.Next (6);

      i.WriteU16 (checksum);

    }

}

uint32_t

UdpHeader::Deserialize (Buffer::Iterator start)

{

  Buffer::Iterator i = start;

  m_sourcePort = i.ReadNtohU16 ();

  m_destinationPort = i.ReadNtohU16 ();

  m_payloadSize = i.ReadNtohU16 () - GetSerializedSize ();

  i.Next (2);

  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