/*
 *  $Id: insert_ipo.c,v 1.2 1999/09/21 15:47:33 dugsong Exp $
 *
 *  libnet
 *  insert_ipo.c - inserts IP options into a prebuilt IP packet
 *
 *  Copyright (c) 1998, 1999 Mike D. Schiffman <mike@infonexus.com>
 *                           route|daemon9 <route@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
#include "../include/libnet.h"

int
insert_ipo(struct ipoption *opt, u_char opt_len, u_char *buf)
{
    struct ip *ip_hdr;
    u_short s, ip_hl, pad;
    u_char *p;

    assert(buf);

    ip_hdr = (struct ip *)(buf);
    ip_hl = ip_hdr->ip_hl * 4;

    s = ntohs(ip_hdr->ip_len);
    
    /* See how much to pad options out (always terminating with EOL). */
    pad = 4 - (((ip_hl - IP_H) + opt_len) & 3);

    if ((s + opt_len + pad) > IP_MAXPACKET)
    {
        /* Nope.  Too big. */
#if (__DEBUG)
        fprintf(stderr,
            "insert_ipo: options list would result in too large of a packet\n");
#endif
        return (-1);
    }

    /* Do we have more then just an IP header? */
    if (s > ip_hl)
    {
        /* Move over whatever's in the way. */
        memmove(buf + ip_hl + opt_len + pad, buf + ip_hl, opt_len + pad);
    }

    /*
     *  Copy over option list.  We rely on the programmer having been
     *  smart enough to allocate enough heap memory here.  Uh oh.
     */
    p = buf + ip_hl;
    memcpy(p, opt->ipopt_list, opt_len);

    /* XXX - this should be 1 if more options are to follow. */
    memset(p + opt_len, 0, pad); 

    ip_hdr->ip_hl   += (opt_len + pad) / 4;
    ip_hdr->ip_len  = htons(s + opt_len + pad);

    return (1);
}

/* EOF */