Attachment #677 for bug #751

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(-)a/src/devices/csma/csma-net-device.cc (+8 lines)

Lines 421-426	Link Here

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  header.SetLengthType (lengthType);

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  header.SetLengthType (lengthType);

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  p->AddHeader (header);

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  p->AddHeader (header);

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  if (Node::ChecksumEnabled ())

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      trailer.EnableFcs (true);

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  trailer.CalcFcs (p);

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  trailer.CalcFcs (p);

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  p->AddTrailer (trailer);

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  p->AddTrailer (trailer);

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Lines 747-752	Link Here

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  EthernetTrailer trailer;

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  EthernetTrailer trailer;

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  packet->RemoveTrailer (trailer);

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  packet->RemoveTrailer (trailer);

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  if (Node::ChecksumEnabled ())

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      trailer.EnableFcs (true);

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  trailer.CheckFcs (packet);

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  trailer.CheckFcs (packet);

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  EthernetHeader header (false);

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  EthernetHeader header (false);





NS_OBJECT_ENSURE_REGISTERED (EthernetTrailer);

bool EthernetTrailer::m_calcFcs = false;

EthernetTrailer::EthernetTrailer ()
  : m_calcFcs (false),
    m_fcs (0)
{}

void EthernetTrailer::Init()
{
  m_fcs = 0;
}

void 
EthernetTrailer::EnableFcs (bool enable)

bool
EthernetTrailer::CheckFcs (Ptr<Packet> p) const
{
  int len = p->GetSize ();
  uint8_t *buffer;
  uint32_t crc;

  if (!m_calcFcs)
    {
      return true;
    } 
  else 
    {
      NS_LOG_WARN ("FCS calculation is not yet enabled");
      return false;
    }

  buffer = new uint8_t[len];
  p->CopyData (buffer, len);
  crc = DoCalcFcs (buffer, len);
  delete[] buffer;
  return (m_fcs == crc);
}

void
EthernetTrailer::CalcFcs (Ptr<Packet> p)
{
  int len = p->GetSize ();
  uint8_t *buffer;

  if (!m_calcFcs)
    {
      return;
    }

  buffer = new uint8_t[len];
  p->CopyData (buffer, len);
  m_fcs = DoCalcFcs (buffer, len);
  delete[] buffer;
}

void

  return size;
}

// This code is copied from /lib/crc32.c in the linux kernel.
// It assumes little endian ordering.
uint32_t
EthernetTrailer::DoCalcFcs (uint8_t *buffer, size_t len) const
{
  uint32_t crc = 0xffffffff;
  int i;

  while (len--)
    {
      crc ^= *buffer++;
      for (i = 0; i < 8; i++)
        {
	  crc = (crc >> 1) ^ ((crc & 1) ? 0xedb88320 : 0);
	}
    }
  return ~crc;
}

}; // namespace ns3




#define ETHERNET_TRAILER_H

#include "ns3/trailer.h"
#include "ns3/packet.h"
#include <string>

namespace ns3 {

class Packet;

/**
 * \ingroup node

  EthernetTrailer ();

  /**
   * \brief Enable or disable FCS checking and calculations
   * \param enable If true, enables FCS calculations.
   */
  void EnableFcs (bool enable);
  /**
   * \brief Updates the Fcs Field to the correct FCS
   * \param p Reference to a packet on which the FCS should be

  virtual void Serialize (Buffer::Iterator end) const;
  virtual uint32_t Deserialize (Buffer::Iterator end);
private:

  /**
   * Initializes the trailer parameters during construction.
   */
  void Init (void);

  /**
   * Enabled FCS calculations. If false, fcs is set to 0 and checkFCS
   * returns true.
   */
  bool m_calcFcs;
  uint32_t m_fcs; /// Value of the fcs contained in the trailer

  uint32_t DoCalcFcs (uint8_t *buffer, size_t len) const;

};

} // namespace ns3

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