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. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by the University of
  16  *      California, Berkeley and its contributors.
  17  * 4. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  *
  33  *      @(#)ip_output.c 8.3 (Berkeley) 1/21/94
  34  * ip_output.c,v 1.9 1994/11/16 10:17:10 jkh Exp
  35  */
  36
  37 /*
  38  * Changes and additions relating to SLiRP are
  39  * Copyright (c) 1995 Danny Gasparovski.
  40  *
  41  * Please read the file COPYRIGHT for the
  42  * terms and conditions of the copyright.
  43  */
  44
  45 #include <slirp.h>
  46
  47 u_int16_t ip_id;
  48
  49 /* Number of packets queued before we start sending
  50  * (to prevent allocing too many mbufs) */
  51 #define IF_THRESH 10
  52
  53 /*
  54  * IP output.  The packet in mbuf chain m contains a skeletal IP
  55  * header (with len, off, ttl, proto, tos, src, dst).
  56  * The mbuf chain containing the packet will be freed.
  57  * The mbuf opt, if present, will not be freed.
  58  */
  59 int
  60 ip_output(so, m0)
  61         struct socket *so;
  62         struct mbuf *m0;
  63 {
  64         register struct ip *ip;
  65         register struct mbuf *m = m0;
  66         register int hlen = sizeof(struct ip );
  67         int len, off, error = 0;
  68
  69         DEBUG_CALL("ip_output");
  70         DEBUG_ARG("so = %lx", (long)so);
  71         DEBUG_ARG("m0 = %lx", (long)m0);
  72
  73         /* We do no options */
  74 /*      if (opt) {
  75  *              m = ip_insertoptions(m, opt, &len);
  76  *              hlen = len;
  77  *      }
  78  */
  79         ip = mtod(m, struct ip *);
  80         /*
  81          * Fill in IP header.
  82          */
  83         ip->ip_v = IPVERSION;
  84         ip->ip_off &= IP_DF;
  85         ip->ip_id = htons(ip_id++);
  86         ip->ip_hl = hlen >> 2;
  87         STAT(ipstat.ips_localout++);
  88
  89         /*
  90          * Verify that we have any chance at all of being able to queue
  91          *      the packet or packet fragments
  92          */
  93         /* XXX Hmmm... */
  94 /*      if (if_queued > IF_THRESH && towrite <= 0) {
  95  *              error = ENOBUFS;
  96  *              goto bad;
  97  *      }
  98  */
  99
 100         /*
 101          * If small enough for interface, can just send directly.
 102          */
 103         if ((u_int16_t)ip->ip_len <= IF_MTU) {
 104                 ip->ip_len = htons((u_int16_t)ip->ip_len);
 105                 ip->ip_off = htons((u_int16_t)ip->ip_off);
 106                 ip->ip_sum = 0;
 107                 ip->ip_sum = cksum(m, hlen);
 108
 109                 if_output(so, m);
 110                 goto done;
 111         }
 112
 113         /*
 114          * Too large for interface; fragment if possible.
 115          * Must be able to put at least 8 bytes per fragment.
 116          */
 117         if (ip->ip_off & IP_DF) {
 118                 error = -1;
 119                 STAT(ipstat.ips_cantfrag++);
 120                 goto bad;
 121         }
 122
 123         len = (IF_MTU - hlen) &~ 7;       /* ip databytes per packet */
 124         if (len < 8) {
 125                 error = -1;
 126                 goto bad;
 127         }
 128
 129     {
 130         int mhlen, firstlen = len;
 131         struct mbuf **mnext = &m->m_nextpkt;
 132
 133         /*
 134          * Loop through length of segment after first fragment,
 135          * make new header and copy data of each part and link onto chain.
 136          */
 137         m0 = m;
 138         mhlen = sizeof (struct ip);
 139         for (off = hlen + len; off < (u_int16_t)ip->ip_len; off += len) {
 140           register struct ip *mhip;
 141           m = m_get();
 142           if (m == 0) {
 143             error = -1;
 144             STAT(ipstat.ips_odropped++);
 145             goto sendorfree;
 146           }
 147           m->m_data += IF_MAXLINKHDR;
 148           mhip = mtod(m, struct ip *);
 149           *mhip = *ip;
 150
 151                 /* No options */
 152 /*              if (hlen > sizeof (struct ip)) {
 153  *                      mhlen = ip_optcopy(ip, mhip) + sizeof (struct ip);
 154  *                      mhip->ip_hl = mhlen >> 2;
 155  *              }
 156  */
 157           m->m_len = mhlen;
 158           mhip->ip_off = ((off - hlen) >> 3) + (ip->ip_off & ~IP_MF);
 159           if (ip->ip_off & IP_MF)
 160             mhip->ip_off |= IP_MF;
 161           if (off + len >= (u_int16_t)ip->ip_len)
 162             len = (u_int16_t)ip->ip_len - off;
 163           else
 164             mhip->ip_off |= IP_MF;
 165           mhip->ip_len = htons((u_int16_t)(len + mhlen));
 166
 167           if (m_copy(m, m0, off, len) < 0) {
 168             error = -1;
 169             goto sendorfree;
 170           }
 171
 172           mhip->ip_off = htons((u_int16_t)mhip->ip_off);
 173           mhip->ip_sum = 0;
 174           mhip->ip_sum = cksum(m, mhlen);
 175           *mnext = m;
 176           mnext = &m->m_nextpkt;
 177           STAT(ipstat.ips_ofragments++);
 178         }
 179         /*
 180          * Update first fragment by trimming what's been copied out
 181          * and updating header, then send each fragment (in order).
 182          */
 183         m = m0;
 184         m_adj(m, hlen + firstlen - (u_int16_t)ip->ip_len);
 185         ip->ip_len = htons((u_int16_t)m->m_len);
 186         ip->ip_off = htons((u_int16_t)(ip->ip_off | IP_MF));
 187         ip->ip_sum = 0;
 188         ip->ip_sum = cksum(m, hlen);
 189 sendorfree:
 190         for (m = m0; m; m = m0) {
 191                 m0 = m->m_nextpkt;
 192                 m->m_nextpkt = 0;
 193                 if (error == 0)
 194                         if_output(so, m);
 195                 else
 196                         m_freem(m);
 197         }
 198
 199         if (error == 0)
 200                 STAT(ipstat.ips_fragmented++);
 201     }
 202
 203 done:
 204         return (error);
 205
 206 bad:
 207         m_freem(m0);
 208         goto done;
 209 }