text: /*
   * 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>
  
  /* 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(struct socket *so, struct mbuf *m0)
  {
  	Slirp *slirp = m0->slirp;
  	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);
  
  	ip = mtod(m, struct ip *);
  	/*
  	 * Fill in IP header.
  	 */
  	ip->ip_v = IPVERSION;
  	ip->ip_off &= IP_DF;
  	ip->ip_id = htons(slirp->ip_id++);
  	ip->ip_hl = hlen >> 2;
  
  	/*
  	 * If small enough for interface, can just send directly.
  	 */
  	if ((uint16_t)ip->ip_len <= IF_MTU) {
  		ip->ip_len = htons((uint16_t)ip->ip_len);
  		ip->ip_off = htons((uint16_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;
  		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 < (uint16_t)ip->ip_len; off += len) {
  	  register struct ip *mhip;
  	  m = m_get(slirp);
            if (m == NULL) {
  	    error = -1;
  	    goto sendorfree;
  	  }
  	  m->m_data += IF_MAXLINKHDR;
  	  mhip = mtod(m, struct ip *);
  	  *mhip = *ip;
  
  	  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 >= (uint16_t)ip->ip_len)
  	    len = (uint16_t)ip->ip_len - off;
  	  else
  	    mhip->ip_off |= IP_MF;
  	  mhip->ip_len = htons((uint16_t)(len + mhlen));
  
  	  if (m_copy(m, m0, off, len) < 0) {
  	    error = -1;
  	    goto sendorfree;
  	  }
  
  	  mhip->ip_off = htons((uint16_t)mhip->ip_off);
  	  mhip->ip_sum = 0;
  	  mhip->ip_sum = cksum(m, mhlen);
  	  *mnext = m;
  	  mnext = &m->m_nextpkt;
  	}
  	/*
  	 * 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 - (uint16_t)ip->ip_len);
  	ip->ip_len = htons((uint16_t)m->m_len);
  	ip->ip_off = htons((uint16_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 = NULL;
  		if (error == 0)
  			if_output(so, m);
  		else
  			m_freem(m);
  	}
      }
  
  done:
  	return (error);
  
  bad:
  	m_freem(m0);
  	goto done;
  }
  