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      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(struct socket *so, struct mbuf *m0)
     57 {
     58 	register struct ip *ip;
     59 	register struct mbuf *m = m0;
     60 	register int hlen = sizeof(struct ip );
     61 	int len, off, error = 0;
     62 
     63 	DEBUG_CALL("ip_output");
     64 	DEBUG_ARG("so = %lx", (long)so);
     65 	DEBUG_ARG("m0 = %lx", (long)m0);
     66 
     67 	/* We do no options */
     68 /*	if (opt) {
     69  *		m = ip_insertoptions(m, opt, &len);
     70  *		hlen = len;
     71  *	}
     72  */
     73 	ip = mtod(m, struct ip *);
     74 	/*
     75 	 * Fill in IP header.
     76 	 */
     77 	ip->ip_v = IPVERSION;
     78 	ip->ip_off &= IP_DF;
     79 	ip->ip_id = htons(ip_id++);
     80 	ip->ip_hl = hlen >> 2;
     81 	STAT(ipstat.ips_localout++);
     82 
     83 	/*
     84 	 * Verify that we have any chance at all of being able to queue
     85 	 *      the packet or packet fragments
     86 	 */
     87 	/* XXX Hmmm... */
     88 /*	if (if_queued > IF_THRESH && towrite <= 0) {
     89  *		error = ENOBUFS;
     90  *		goto bad;
     91  *	}
     92  */
     93 
     94 	/*
     95 	 * If small enough for interface, can just send directly.
     96 	 */
     97 	if ((u_int16_t)ip->ip_len <= IF_MTU) {
     98 		ip->ip_len = htons((u_int16_t)ip->ip_len);
     99 		ip->ip_off = htons((u_int16_t)ip->ip_off);
    100 		ip->ip_sum = 0;
    101 		ip->ip_sum = cksum(m, hlen);
    102 
    103 		if_output(so, m);
    104 		goto done;
    105 	}
    106 
    107 	/*
    108 	 * Too large for interface; fragment if possible.
    109 	 * Must be able to put at least 8 bytes per fragment.
    110 	 */
    111 	if (ip->ip_off & IP_DF) {
    112 		error = -1;
    113 		STAT(ipstat.ips_cantfrag++);
    114 		goto bad;
    115 	}
    116 
    117 	len = (IF_MTU - hlen) &~ 7;       /* ip databytes per packet */
    118 	if (len < 8) {
    119 		error = -1;
    120 		goto bad;
    121 	}
    122 
    123     {
    124 	int mhlen, firstlen = len;
    125 	struct mbuf **mnext = &m->m_nextpkt;
    126 
    127 	/*
    128 	 * Loop through length of segment after first fragment,
    129 	 * make new header and copy data of each part and link onto chain.
    130 	 */
    131 	m0 = m;
    132 	mhlen = sizeof (struct ip);
    133 	for (off = hlen + len; off < (u_int16_t)ip->ip_len; off += len) {
    134 	  register struct ip *mhip;
    135 	  m = m_get();
    136           if (m == NULL) {
    137 	    error = -1;
    138 	    STAT(ipstat.ips_odropped++);
    139 	    goto sendorfree;
    140 	  }
    141 	  m->m_data += IF_MAXLINKHDR;
    142 	  mhip = mtod(m, struct ip *);
    143 	  *mhip = *ip;
    144 
    145 		/* No options */
    146 /*		if (hlen > sizeof (struct ip)) {
    147  *			mhlen = ip_optcopy(ip, mhip) + sizeof (struct ip);
    148  *			mhip->ip_hl = mhlen >> 2;
    149  *		}
    150  */
    151 	  m->m_len = mhlen;
    152 	  mhip->ip_off = ((off - hlen) >> 3) + (ip->ip_off & ~IP_MF);
    153 	  if (ip->ip_off & IP_MF)
    154 	    mhip->ip_off |= IP_MF;
    155 	  if (off + len >= (u_int16_t)ip->ip_len)
    156 	    len = (u_int16_t)ip->ip_len - off;
    157 	  else
    158 	    mhip->ip_off |= IP_MF;
    159 	  mhip->ip_len = htons((u_int16_t)(len + mhlen));
    160 
    161 	  if (m_copy(m, m0, off, len) < 0) {
    162 	    error = -1;
    163 	    goto sendorfree;
    164 	  }
    165 
    166 	  mhip->ip_off = htons((u_int16_t)mhip->ip_off);
    167 	  mhip->ip_sum = 0;
    168 	  mhip->ip_sum = cksum(m, mhlen);
    169 	  *mnext = m;
    170 	  mnext = &m->m_nextpkt;
    171 	  STAT(ipstat.ips_ofragments++);
    172 	}
    173 	/*
    174 	 * Update first fragment by trimming what's been copied out
    175 	 * and updating header, then send each fragment (in order).
    176 	 */
    177 	m = m0;
    178 	m_adj(m, hlen + firstlen - (u_int16_t)ip->ip_len);
    179 	ip->ip_len = htons((u_int16_t)m->m_len);
    180 	ip->ip_off = htons((u_int16_t)(ip->ip_off | IP_MF));
    181 	ip->ip_sum = 0;
    182 	ip->ip_sum = cksum(m, hlen);
    183 sendorfree:
    184 	for (m = m0; m; m = m0) {
    185 		m0 = m->m_nextpkt;
    186                 m->m_nextpkt = NULL;
    187 		if (error == 0)
    188 			if_output(so, m);
    189 		else
    190 			m_freem(m);
    191 	}
    192 
    193 	if (error == 0)
    194 		STAT(ipstat.ips_fragmented++);
    195     }
    196 
    197 done:
    198 	return (error);
    199 
    200 bad:
    201 	m_freem(m0);
    202 	goto done;
    203 }
    204