udp.c

单片机tcpip_c51源程序.rar

#include <stdio.h>
#include <string.h>
#include "ethernet.h"
#include "ip.h"
#include "udp.h"
/* Return UDP data length (-1 if no data), 0 if not UDP */
int is_udp(IPKT *ip, int len)
{
    UDPKT *udp;
    WORD sum;
    int dlen=0;
                                       /* Check protocol & minimum length */
    if (ip->i.pcol==PUDP && len>=sizeof(UDPHDR))
    {
        udp = (UDPKT *)ip;              /* Do checksum */
        sum = check_udp(udp, ip->i.sip, ip->i.dip, len);
        if (!udp->u.check || sum==0xffff)
        {                               /* If zero or correct.. */
            len -= sizeof(UDPHDR);      /* Subtract header len */
            dlen = len>0 ? len : -1;    /* Return -1 if data len=0 */
        }
    }
    return(dlen);
}

/* Make a UDP datagram given the source & destination, data len */
int make_udp(ETHERFRAME * efp, NODE *srcep, NODE *destp, WORD dlen)
{
    UDPKT *udp;
    int ulen, ilen;
    udp = (UDPKT *)(efp->edata);
    udp->u.sport = srcep->port;          /* Set ports */
    udp->u.dport = destp->port;
	ulen = dlen + sizeof(UDPHDR);
    udp->u.len = ulen; 
    udp->u.check = 0;
    ilen = make_ip(efp, srcep, destp, PUDP, (WORD)(ulen));
    udp->u.check = ~check_udp(udp, udp->i.sip, udp->i.dip, ulen);
    if (udp->u.check == 0)              /* Change sum of 0 to FFFF */
        udp->u.check = 0xffff;
    return(ilen);                       /* Return IP length */
}

/* Return TCP checksum, given UDP (header + data) length.
** The values must be in network byte-order */
WORD check_udp(UDPKT *udp, LWORD sip, LWORD dip, int ulen)
{
    PHDR tph;
    LWORD sum;
    sum = csum(&udp->u, (WORD)ulen);            /* Checksum TCP segment */
	tph.len=ulen;
    tph.srce = sip;
    tph.dest = dip;
    tph.z = 0;
    tph.pcol = udp->i.pcol;
    sum += csum(&tph, sizeof(tph));             /* Checksum pseudo-header */
    return((WORD)(sum + (sum /0x10000)));          /* Return total plus carry */
}

/* Send a UDP datagram, given destination node, data and length */
void udp_transmit(ETHERFRAME *efp, NODE *sp, NODE *dp, void *dat, int len)
{
    UDPKT *udp;
    udp = (UDPKT *)efp->edata;
    memmove(udp->udpdata, dat, len);
    put_ethernet(efp, make_udp(efp, sp, dp, (WORD)max(len, 0)));
}


/* Get the frame driver type, source port, IP and Ethernet addrs */
void getudp_srce(ETHERFRAME *efp, NODE *np)
{
    UDPKT *udp;
    memset(np, 0, sizeof(NODE));        /* Clear unused fields */
    getip_srce(efp, np);                /* Get dtype, srce IP and Ether addrs */
    udp = (UDPKT *)(efp->edata);
    np->port = udp->u.sport;            /* Get source port */
}

/* Get complete TCP local node data corresponding to frame dest IP address
** Return 0 if no matching node */
int getudp_locdest(ETHERFRAME *efp, NODE *np)
{
    UDPKT *udp;
    int ok;
    ok = getip_locdest(efp, np);          /* Get addresses, dtype & netmask */
    udp = (UDPKT *)(efp->edata);          /* Get dest port */
    np->port = udp->u.dport;
    return(ok);
}