slirp/ip_output.c

   1 /*
   2  * Copyright (c) 1982, 1986, 1988, 1990, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  *      @(#)ip_output.c 8.3 (Berkeley) 1/21/94
  30  * ip_output.c,v 1.9 1994/11/16 10:17:10 jkh Exp
  31  */
  32
  33 /*
  34  * Changes and additions relating to SLiRP are
  35  * Copyright (c) 1995 Danny Gasparovski.
  36  *
  37  * Please read the file COPYRIGHT for the
  38  * terms and conditions of the copyright.
  39  */
  40
  41 #include <slirp.h>
  42
  43 u_int16_t ip_id;
  44
  45 /* Number of packets queued before we start sending
  46  * (to prevent allocing too many mbufs) */
  47 #define IF_THRESH 10
  48
  49 /*
  50  * IP output.  The packet in mbuf chain m contains a skeletal IP
  51  * header (with len, off, ttl, proto, tos, src, dst).
  52  * The mbuf chain containing the packet will be freed.
  53  * The mbuf opt, if present, will not be freed.
  54  */
  55 int
  56 ip_output(so, m0)
  57         struct socket *so;
  58         struct mbuf *m0;
  59 {
  60         register struct ip *ip;
  61         register struct mbuf *m = m0;
  62         register int hlen = sizeof(struct ip );
  63         int len, off, error = 0;
  64
  65         DEBUG_CALL("ip_output");
  66         DEBUG_ARG("so = %lx", (long)so);
  67         DEBUG_ARG("m0 = %lx", (long)m0);
  68
  69         /* We do no options */
  70 /*      if (opt) {
  71  *              m = ip_insertoptions(m, opt, &len);
  72  *              hlen = len;
  73  *      }
  74  */
  75         ip = mtod(m, struct ip *);
  76         /*
  77          * Fill in IP header.
  78          */
  79         ip->ip_v = IPVERSION;
  80         ip->ip_off &= IP_DF;
  81         ip->ip_id = htons(ip_id++);
  82         ip->ip_hl = hlen >> 2;
  83         STAT(ipstat.ips_localout++);
  84
  85         /*
  86          * Verify that we have any chance at all of being able to queue
  87          *      the packet or packet fragments
  88          */
  89         /* XXX Hmmm... */
  90 /*      if (if_queued > IF_THRESH && towrite <= 0) {
  91  *              error = ENOBUFS;
  92  *              goto bad;
  93  *      }
  94  */
  95
  96         /*
  97          * If small enough for interface, can just send directly.
  98          */
  99         if ((u_int16_t)ip->ip_len <= IF_MTU) {
 100                 ip->ip_len = htons((u_int16_t)ip->ip_len);
 101                 ip->ip_off = htons((u_int16_t)ip->ip_off);
 102                 ip->ip_sum = 0;
 103                 ip->ip_sum = cksum(m, hlen);
 104
 105                 if_output(so, m);
 106                 goto done;
 107         }
 108
 109         /*
 110          * Too large for interface; fragment if possible.
 111          * Must be able to put at least 8 bytes per fragment.
 112          */
 113         if (ip->ip_off & IP_DF) {
 114                 error = -1;
 115                 STAT(ipstat.ips_cantfrag++);
 116                 goto bad;
 117         }
 118
 119         len = (IF_MTU - hlen) &~ 7;       /* ip databytes per packet */
 120         if (len < 8) {
 121                 error = -1;
 122                 goto bad;
 123         }
 124
 125     {
 126         int mhlen, firstlen = len;
 127         struct mbuf **mnext = &m->m_nextpkt;
 128
 129         /*
 130          * Loop through length of segment after first fragment,
 131          * make new header and copy data of each part and link onto chain.
 132          */
 133         m0 = m;
 134         mhlen = sizeof (struct ip);
 135         for (off = hlen + len; off < (u_int16_t)ip->ip_len; off += len) {
 136           register struct ip *mhip;
 137           m = m_get();
 138           if (m == 0) {
 139             error = -1;
 140             STAT(ipstat.ips_odropped++);
 141             goto sendorfree;
 142           }
 143           m->m_data += IF_MAXLINKHDR;
 144           mhip = mtod(m, struct ip *);
 145           *mhip = *ip;
 146
 147                 /* No options */
 148 /*              if (hlen > sizeof (struct ip)) {
 149  *                      mhlen = ip_optcopy(ip, mhip) + sizeof (struct ip);
 150  *                      mhip->ip_hl = mhlen >> 2;
 151  *              }
 152  */
 153           m->m_len = mhlen;
 154           mhip->ip_off = ((off - hlen) >> 3) + (ip->ip_off & ~IP_MF);
 155           if (ip->ip_off & IP_MF)
 156             mhip->ip_off |= IP_MF;
 157           if (off + len >= (u_int16_t)ip->ip_len)
 158             len = (u_int16_t)ip->ip_len - off;
 159           else
 160             mhip->ip_off |= IP_MF;
 161           mhip->ip_len = htons((u_int16_t)(len + mhlen));
 162
 163           if (m_copy(m, m0, off, len) < 0) {
 164             error = -1;
 165             goto sendorfree;
 166           }
 167
 168           mhip->ip_off = htons((u_int16_t)mhip->ip_off);
 169           mhip->ip_sum = 0;
 170           mhip->ip_sum = cksum(m, mhlen);
 171           *mnext = m;
 172           mnext = &m->m_nextpkt;
 173           STAT(ipstat.ips_ofragments++);
 174         }
 175         /*
 176          * Update first fragment by trimming what's been copied out
 177          * and updating header, then send each fragment (in order).
 178          */
 179         m = m0;
 180         m_adj(m, hlen + firstlen - (u_int16_t)ip->ip_len);
 181         ip->ip_len = htons((u_int16_t)m->m_len);
 182         ip->ip_off = htons((u_int16_t)(ip->ip_off | IP_MF));
 183         ip->ip_sum = 0;
 184         ip->ip_sum = cksum(m, hlen);
 185 sendorfree:
 186         for (m = m0; m; m = m0) {
 187                 m0 = m->m_nextpkt;
 188                 m->m_nextpkt = 0;
 189                 if (error == 0)
 190                         if_output(so, m);
 191                 else
 192                         m_freem(m);
 193         }
 194
 195         if (error == 0)
 196                 STAT(ipstat.ips_fragmented++);
 197     }
 198
 199 done:
 200         return (error);
 201
 202 bad:
 203         m_freem(m0);
 204         goto done;
 205 }