libnet_build_udp.c

/*
 *  $Id: libnet_build_udp.c,v 1.11 2004/04/13 17:32:28 mike Exp $
 *
 *  libnet
 *  libnet_build_udp.c - UDP packet assembler
 *
 *  Copyright (c) 1998 - 2004 Mike D. Schiffman <mike@infonexus.com>
 *  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 */

#if (HAVE_CONFIG_H)
#include "../include/config.h"
#endif
#if (!(_WIN32) || (__CYGWIN__)) 
#include "../include/libnet.h"
#else
#include "../include/win32/libnet.h"
#endif

libnet_ptag_t
libnet_build_udp(uint16_t sp, uint16_t dp, uint16_t len, uint16_t sum,
const uint8_t *payload, uint32_t payload_s, libnet_t *l, libnet_ptag_t ptag)
{
    uint32_t n;
    libnet_pblock_t *p;
    struct libnet_udp_hdr udp_hdr;

    if (l == NULL)
    { 
        return (-1);
    } 

    n = LIBNET_UDP_H + payload_s;               /* size of memory block */

    /*
     *  Find the existing protocol block if a ptag is specified, or create
     *  a new one.
     */
    p = libnet_pblock_probe(l, ptag, n, LIBNET_PBLOCK_UDP_H);
    if (p == NULL)
    {
        return (-1);
    }

    memset(&udp_hdr, 0, sizeof(udp_hdr));
    udp_hdr.uh_sport   = htons(sp);             /* source port */
    udp_hdr.uh_dport   = htons(dp);             /* destination port */
    udp_hdr.uh_ulen    = htons(len);            /* total length of UDP packet*/
    udp_hdr.uh_sum     = (sum ? htons(sum) : 0);/* checksum */

    n = libnet_pblock_append(l, p, (uint8_t *)&udp_hdr, LIBNET_UDP_H);
    if (n == -1)
    {
        goto bad;
    }

    /* boilerplate payload sanity check / append macro */
    LIBNET_DO_PAYLOAD(l, p);
 
    if (sum == 0)
    {
        /*
         *  If checksum is zero, by default libnet will compute a checksum
         *  for the user.  The programmer can override this by calling
         *  libnet_toggle_checksum(l, ptag, 1);
         */
        libnet_pblock_setflags(p, LIBNET_PBLOCK_DO_CHECKSUM);
    }
    return (ptag ? ptag : libnet_pblock_update(l, p, len, LIBNET_PBLOCK_UDP_H));
bad:
    libnet_pblock_delete(l, p);
    return (-1);
}

/* EOF */