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udphdr.c
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C/C++ Source or Header
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1994-09-16
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2KB
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77 lines
/* UDP header conversion routines
* Copyright 1991 Phil Karn, KA9Q
*/
/****************************************************************************
* $Id: udphdr.c 1.2 93/07/16 11:52:07 ROOT_DOS Exp $
* 09 May 93 1.2 GT Fix warnings. *
****************************************************************************/
#include "global.h"
#include "mbuf.h"
#include "ip.h"
#include "internet.h"
#include "udp.h"
/* Convert UDP header in internal format to an mbuf in external format */
struct mbuf *
htonudp(udp,data,ph)
struct udp *udp;
struct mbuf *data;
struct pseudo_header *ph;
{
struct mbuf *bp;
register char *cp;
int16 checksum;
/* Allocate UDP protocol header and fill it in */
if((bp = pushdown(data,UDPHDR)) == NULLBUF)
return NULLBUF;
cp = bp->data;
cp = put16(cp,udp->source); /* Source port */
cp = put16(cp,udp->dest); /* Destination port */
cp = put16(cp,udp->length); /* Length */
*cp++ = 0; /* Clear checksum */
*cp-- = 0;
/* All zeros and all ones is equivalent in one's complement arithmetic;
* the spec requires us to change zeros into ones to distinguish an
* all-zero checksum from no checksum at all
*/
if((checksum = cksum(ph,bp,ph->length)) == 0)
checksum = 0xffffffffL;
put16(cp,checksum);
return bp;
}
/* Convert UDP header in mbuf to internal structure */
int
ntohudp(udp,bpp)
struct udp *udp;
struct mbuf **bpp;
{
char udpbuf[UDPHDR];
if(pullup(bpp,udpbuf,UDPHDR) != UDPHDR)
return -1;
udp->source = get16(&udpbuf[0]);
udp->dest = get16(&udpbuf[2]);
udp->length = get16(&udpbuf[4]);
udp->checksum = get16(&udpbuf[6]);
return 0;
}
/* Extract UDP checksum value from a network-format header without
* disturbing the header
*/
int16
udpcksum(bp)
struct mbuf *bp;
{
struct mbuf *dup;
if(dup_p(&dup,bp,6,2) != 2)
return 0;
return pull16(&dup);
}