/* UDP header conversion routines
 * Copyright 1991 Phil Karn, KA9Q
 */
#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 = 0xffffU;
    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);
}
  
