setudpchecksum.cc

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

// -*- c-basic-offset: 4 -*-
/*
 * setudpchecksum.{cc,hh} -- sets the UDP header checksum
 * Robert Morris, Eddie Kohler
 *
 * Copyright (c) 1999-2000 Massachusetts Institute of Technology
 * Copyright (c) 2002 International Computer Science Institute
 *
 * 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 "setudpchecksum.hh"
#include <click/glue.hh>
#include <click/error.hh>
#include <clicknet/ip.h>
#include <clicknet/udp.h>
CLICK_DECLS

SetUDPChecksum::SetUDPChecksum()
    : Element(1, 1)
{
}

SetUDPChecksum::~SetUDPChecksum()
{
}

Packet *
SetUDPChecksum::simple_action(Packet *p_in)
{
    WritablePacket *p = p_in->uniqueify();
    if (!p)
	return 0;
    
    // XXX check IP header/UDP protocol?
    click_ip *iph = p->ip_header();
    click_udp *udph = p->udp_header();
    int len = ntohs(udph->uh_ulen);
    if ((unsigned)len > p->length() - p->transport_header_offset()) {
	// packet data too short
	p->kill();
	return 0;
    }

    udph->uh_sum = 0;
    unsigned csum = click_in_cksum((unsigned char *)udph, len);
    udph->uh_sum = click_in_cksum_pseudohdr(csum, iph, len);

    return p;
}

CLICK_ENDDECLS
EXPORT_ELEMENT(SetUDPChecksum)
ELEMENT_MT_SAFE(SetUDPChecksum)