checkxorheader.cc

COPE the first practical network coding scheme which is developped on click

/*
 * checkxorheader.{cc,hh} -- element checks xor header for correctness
 * (checksums, lengths)
 *
 * Wenjun Hu
 *
 * adapted from checksrheader.{cc,hh} by John Bicket
 * adapted from checkwifiheader.{cc,hh} by Douglas S. J. De Couto
 * from checkipheader.{cc,hh} by Robert Morris
 *
 * Copyright (c) 1999-2000 Massachusetts Institute of Technology
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, subject to the conditions
 * listed in the Click LICENSE file. These conditions include: you must
 * preserve this copyright notice, and you cannot mention the copyright
 * holders in advertising related to the Software without their permission.
 * The Software is provided WITHOUT ANY WARRANTY, EXPRESS OR IMPLIED. This
 * notice is a summary of the Click LICENSE file; the license in that file is
 * legally binding.
 */

#include <click/config.h>
//#include <click/confparse.hh>
#include <click/etheraddress.hh>
#include <click/glue.hh>
#include <clicknet/ether.h>
#include <clicknet/ip.h>
#include "encodedheader.hh"
#include "checkxorheader.hh"


CLICK_DECLS

CheckXorHeader::CheckXorHeader()
  : _drops(0)
{
  add_input();
  add_output();
}

CheckXorHeader::~CheckXorHeader()
{
}

void
CheckXorHeader::notify_noutputs(int n)
{
  set_noutputs(n < 2 ? 1 : 2);
}

void
CheckXorHeader::drop_it(Packet *p)
{
  if (_drops == 0)
    click_chatter("CheckXorHeader %s: first drop", id().cc());
  _drops++;
  
  if (noutputs() == 2)
    output(1).push(p);
  else
    p->kill();
}

Packet *
CheckXorHeader::simple_action(Packet *p)
{
  //debugging
  click_chatter("\n entering CheckXorHeader::simple_action\n");

  click_ether *eh = (click_ether *) p->data();
  struct click_xored *xorh = (struct click_xored *) (eh+1);

  if (!xorh) {

  //debugging
  click_chatter("\n in CheckXorHeader::simple_action - no encoded header, packet for drop\n");

    drop_it(p);
    return 0;
  }

  if (p->length() < sizeof(struct click_xored)) { 
    click_chatter("%s: packet truncated", id().cc());
    drop_it(p);
    return 0;
  }

  unsigned int tlen = xorh->hlen_with_data();

  if (tlen > p->length()) { 
    /* can only check inequality, as short packets are padded to a
       minimum frame size for wavelan and ethernet */
    click_chatter("%s: bad packet size, wanted %d, only got %d", id().cc(),
		  tlen + sizeof(click_ether), p->length());
    drop_it(p);
    return 0;
  }

  if (click_in_cksum((unsigned char *) xorh, tlen) != 0) {
    click_chatter("%s: bad xored packet checksum", id().cc());
    click_chatter("%s: length: %d, cksum: 0x%.4x", id().cc(), (unsigned long) ntohs(xorh->_cksum));
    drop_it(p);
    return 0;
  }

  //debugging
  click_chatter("\n leaving CheckXorHeader::simple_action - checks completed\n");


  return(p);  
}


static String 
CheckXorHeader_read_param(Element *e, void *)
{
  CheckXorHeader *td = (CheckXorHeader *)e;
  return "packets dropped: " + String(td->drops()) + "\n";
}
      

void
CheckXorHeader::add_handlers()
{
  add_read_handler("drops", CheckXorHeader_read_param, 0);
}

EXPORT_ELEMENT(CheckXorHeader)
CLICK_ENDDECLS