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ip_output.c

/*
 * Copyright (c) 1982, 1986, 1988, 1990, 1993
 *    The Regents of the University of California.  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.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
 *
 *    @(#)ip_output.c   8.3 (Berkeley) 1/21/94
 * ip_output.c,v 1.9 1994/11/16 10:17:10 jkh Exp
 */

/*
 * Changes and additions relating to SLiRP are
 * Copyright (c) 1995 Danny Gasparovski.
 *
 * Please read the file COPYRIGHT for the
 * terms and conditions of the copyright.
 */

#include <slirp.h>

u_int16_t ip_id;

/* Number of packets queued before we start sending
 * (to prevent allocing too many mbufs) */
#define IF_THRESH 10

/*
 * IP output.  The packet in mbuf chain m contains a skeletal IP
 * header (with len, off, ttl, proto, tos, src, dst).
 * The mbuf chain containing the packet will be freed.
 * The mbuf opt, if present, will not be freed.
 */
int
ip_output(so, m0)
      struct socket *so;
      struct mbuf *m0;
{
      register struct ip *ip;
      register struct mbuf *m = m0;
      register int hlen = sizeof(struct ip );
      int len, off, error = 0;

      DEBUG_CALL("ip_output");
      DEBUG_ARG("so = %lx", (long)so);
      DEBUG_ARG("m0 = %lx", (long)m0);

      /* We do no options */
/*    if (opt) {
 *          m = ip_insertoptions(m, opt, &len);
 *          hlen = len;
 *    }
 */
      ip = mtod(m, struct ip *);
      /*
       * Fill in IP header.
       */
      ip->ip_v = IPVERSION;
      ip->ip_off &= IP_DF;
      ip->ip_id = htons(ip_id++);
      ip->ip_hl = hlen >> 2;
      STAT(ipstat.ips_localout++);

      /*
       * Verify that we have any chance at all of being able to queue
       *      the packet or packet fragments
       */
      /* XXX Hmmm... */
/*    if (if_queued > IF_THRESH && towrite <= 0) {
 *          error = ENOBUFS;
 *          goto bad;
 *    }
 */

      /*
       * If small enough for interface, can just send directly.
       */
      if ((u_int16_t)ip->ip_len <= IF_MTU) {
            ip->ip_len = htons((u_int16_t)ip->ip_len);
            ip->ip_off = htons((u_int16_t)ip->ip_off);
            ip->ip_sum = 0;
            ip->ip_sum = cksum(m, hlen);

            if_output(so, m);
            goto done;
      }

      /*
       * Too large for interface; fragment if possible.
       * Must be able to put at least 8 bytes per fragment.
       */
      if (ip->ip_off & IP_DF) {
            error = -1;
            STAT(ipstat.ips_cantfrag++);
            goto bad;
      }

      len = (IF_MTU - hlen) &~ 7;       /* ip databytes per packet */
      if (len < 8) {
            error = -1;
            goto bad;
      }

    {
      int mhlen, firstlen = len;
      struct mbuf **mnext = &m->m_nextpkt;

      /*
       * Loop through length of segment after first fragment,
       * make new header and copy data of each part and link onto chain.
       */
      m0 = m;
      mhlen = sizeof (struct ip);
      for (off = hlen + len; off < (u_int16_t)ip->ip_len; off += len) {
        register struct ip *mhip;
        m = m_get();
        if (m == 0) {
          error = -1;
          STAT(ipstat.ips_odropped++);
          goto sendorfree;
        }
        m->m_data += IF_MAXLINKHDR;
        mhip = mtod(m, struct ip *);
        *mhip = *ip;

            /* No options */
/*          if (hlen > sizeof (struct ip)) {
 *                mhlen = ip_optcopy(ip, mhip) + sizeof (struct ip);
 *                mhip->ip_hl = mhlen >> 2;
 *          }
 */
        m->m_len = mhlen;
        mhip->ip_off = ((off - hlen) >> 3) + (ip->ip_off & ~IP_MF);
        if (ip->ip_off & IP_MF)
          mhip->ip_off |= IP_MF;
        if (off + len >= (u_int16_t)ip->ip_len)
          len = (u_int16_t)ip->ip_len - off;
        else
          mhip->ip_off |= IP_MF;
        mhip->ip_len = htons((u_int16_t)(len + mhlen));

        if (m_copy(m, m0, off, len) < 0) {
          error = -1;
          goto sendorfree;
        }

        mhip->ip_off = htons((u_int16_t)mhip->ip_off);
        mhip->ip_sum = 0;
        mhip->ip_sum = cksum(m, mhlen);
        *mnext = m;
        mnext = &m->m_nextpkt;
        STAT(ipstat.ips_ofragments++);
      }
      /*
       * Update first fragment by trimming what's been copied out
       * and updating header, then send each fragment (in order).
       */
      m = m0;
      m_adj(m, hlen + firstlen - (u_int16_t)ip->ip_len);
      ip->ip_len = htons((u_int16_t)m->m_len);
      ip->ip_off = htons((u_int16_t)(ip->ip_off | IP_MF));
      ip->ip_sum = 0;
      ip->ip_sum = cksum(m, hlen);
sendorfree:
      for (m = m0; m; m = m0) {
            m0 = m->m_nextpkt;
            m->m_nextpkt = 0;
            if (error == 0)
                  if_output(so, m);
            else
                  m_freem(m);
      }

      if (error == 0)
            STAT(ipstat.ips_fragmented++);
    }

done:
      return (error);

bad:
      m_freem(m0);
      goto done;
}

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