/* -*- 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>
 */

#ifndef UDP_HEADER_H
#define UDP_HEADER_H

#include <stdint.h>
#include <string>
#include "ns3/header.h"
#include "ns3/ipv4-address.h"
#include "ns3/ipv6-address.h"

namespace ns3 {
/**
 * \ingroup udp
 * \brief Packet header for UDP packets
 *
 * This class has fields corresponding to those in a network UDP header
 * (port numbers, payload size, checksum) as well as methods for serialization
 * to and deserialization from a byte buffer.
 */
class UdpHeader : public Header 
{
public:

  /**
   * \brief Constructor
   *
   * Creates a null header
   */
  UdpHeader ();
  ~UdpHeader ();

  /**
   * \brief Enable checksum calculation for UDP 
   */
  void EnableChecksums (void);
  /**
   * \param port the destination port for this UdpHeader
   */
  void SetDestinationPort (uint16_t port);
  /**
   * \param port The source port for this UdpHeader
   */
  void SetSourcePort (uint16_t port);
  /**
   * \return The source port for this UdpHeader
   */
  uint16_t GetSourcePort (void) const;
  /**
   * \return the destination port for this UdpHeader
   */
  uint16_t GetDestinationPort (void) const;

  /**
   * \param source the ip source to use in the underlying
   *        ip packet.
   * \param destination the ip destination to use in the
   *        underlying ip packet.
   * \param protocol the protocol number to use in the underlying
   *        ip packet.
   *
   * If you want to use udp checksums, you should call this
   * method prior to adding the header to a packet.
   */
  void InitializeChecksum (Address source, 
                           Address destination,
                           uint8_t protocol);

  /**
   * \param source the ip source to use in the underlying
   *        ip packet.
   * \param destination the ip destination to use in the
   *        underlying ip packet.
   * \param protocol the protocol number to use in the underlying
   *        ip packet.
   *
   * If you want to use udp checksums, you should call this
   * method prior to adding the header to a packet.
   */
  void InitializeChecksum (Ipv4Address source, 
                           Ipv4Address destination,
                           uint8_t protocol);

  /**
   * \param source the ip source to use in the underlying
   *        ip packet.
   * \param destination the ip destination to use in the
   *        underlying ip packet.
   * \param protocol the protocol number to use in the underlying
   *        ip packet.
   *
   * If you want to use udp checksums, you should call this
   * method prior to adding the header to a packet.
   */
  void InitializeChecksum (Ipv6Address source, 
                           Ipv6Address destination,
                           uint8_t protocol);

  /**
   * \brief Get the type ID.
   * \return the object TypeId
   */
  static TypeId GetTypeId (void);
  virtual TypeId GetInstanceTypeId (void) const;
  virtual void Print (std::ostream &os) const;
  virtual uint32_t GetSerializedSize (void) const;
  virtual void Serialize (Buffer::Iterator start) const;
  virtual uint32_t Deserialize (Buffer::Iterator start);

  /**
   * \brief Is the UDP checksum correct ?
   * \returns true if the checksum is correct, false otherwise.
   */
  bool IsChecksumOk (void) const;

  /**
   * \brief Force the UDP checksum to a given value.
   *
   * This might be useful for test purposes or to
   * restore the UDP checksum when the UDP header
   * has been compressed (e.g., in 6LoWPAN).
   * Note that, normally, the header checksum is
   * calculated on the fly when the packet is
   * serialized.
   *
   * When this option is used, the UDP checksum is written in
   * the header, regardless of the global ChecksumEnabled option.
   *
   * \note The checksum value must be a big endian number.
   *
   * \param checksum the checksum to use (big endian).
   */
  void ForceChecksum (uint16_t checksum);

  /**
   * \brief Force the UDP payload length to a given value.
   *
   * This might be useful when forging a packet for test
   * purposes.
   *
   * \param payloadSize the payload length to use.
   */
  void ForcePayloadSize (uint16_t payloadSize);

  /**
   * \brief Return the checksum (only known after a Deserialize)
   * \return The checksum for this UdpHeader
   */
  uint16_t GetChecksum ();

private:
  /**
   * \brief Calculate the header checksum
   * \param size packet size
   * \returns the checksum
   */
  uint16_t CalculateHeaderChecksum (uint16_t size) const;
  uint16_t m_sourcePort;      //!< Source port
  uint16_t m_destinationPort; //!< Destination port
  uint16_t m_payloadSize;     //!< Payload size

  Address m_source;           //!< Source IP address
  Address m_destination;      //!< Destination IP address
  uint8_t m_protocol;         //!< Protocol number
  uint16_t m_checksum;        //!< Forced Checksum value
  bool m_calcChecksum;        //!< Flag to calculate checksum
  bool m_goodChecksum;        //!< Flag to indicate that checksum is correct
};

} // namespace ns3

#endif /* UDP_HEADER */