initial user mode network support

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@733 c046a42c-6fe2-441c-8c8c-71466251a162

1 files changed, 697 insertions, 0 deletions

diff --git a/slirp/ip_input.c b/slirp/ip_input.c
new file mode 100644
index 0000000000..74b9223160
--- /dev/null
+++ b/slirp/ip_input.c
@@ -0,0 +1,697 @@
+/*
+ * Copyright (c) 1982, 1986, 1988, 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. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *	This product includes software developed by the University of
+ *	California, Berkeley and its contributors.
+ * 4. 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_input.c	8.2 (Berkeley) 1/4/94
+ * ip_input.c,v 1.11 1994/11/16 10:17:08 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>
+#include "ip_icmp.h"
+
+int ip_defttl;
+struct ipstat ipstat;
+struct ipq ipq;
+
+/*
+ * IP initialization: fill in IP protocol switch table.
+ * All protocols not implemented in kernel go to raw IP protocol handler.
+ */
+void
+ip_init()
+{
+	ipq.next = ipq.prev = (ipqp_32)&ipq;
+	ip_id = tt.tv_sec & 0xffff;
+	udp_init();
+	tcp_init();
+	ip_defttl = IPDEFTTL;
+}
+
+/*
+ * Ip input routine.  Checksum and byte swap header.  If fragmented
+ * try to reassemble.  Process options.  Pass to next level.
+ */
+void
+ip_input(m)
+	struct mbuf *m;
+{
+	register struct ip *ip;
+	int hlen;
+	
+	DEBUG_CALL("ip_input");
+	DEBUG_ARG("m = %lx", (long)m);
+	DEBUG_ARG("m_len = %d", m->m_len);
+
+	ipstat.ips_total++;
+	
+	if (m->m_len < sizeof (struct ip)) {
+		ipstat.ips_toosmall++;
+		return;
+	}
+	
+	ip = mtod(m, struct ip *);
+	
+	if (ip->ip_v != IPVERSION) {
+		ipstat.ips_badvers++;
+		goto bad;
+	}
+
+	hlen = ip->ip_hl << 2;
+	if (hlen<sizeof(struct ip ) || hlen>m->m_len) {/* min header length */
+	  ipstat.ips_badhlen++;                     /* or packet too short */
+	  goto bad;
+	}
+
+        /* keep ip header intact for ICMP reply
+	 * ip->ip_sum = cksum(m, hlen); 
+	 * if (ip->ip_sum) { 
+	 */
+	if(cksum(m,hlen)) {
+	  ipstat.ips_badsum++;
+	  goto bad;
+	}
+
+	/*
+	 * Convert fields to host representation.
+	 */
+	NTOHS(ip->ip_len);
+	if (ip->ip_len < hlen) {
+		ipstat.ips_badlen++;
+		goto bad;
+	}
+	NTOHS(ip->ip_id);
+	NTOHS(ip->ip_off);
+
+	/*
+	 * Check that the amount of data in the buffers
+	 * is as at least much as the IP header would have us expect.
+	 * Trim mbufs if longer than we expect.
+	 * Drop packet if shorter than we expect.
+	 */
+	if (m->m_len < ip->ip_len) {
+		ipstat.ips_tooshort++;
+		goto bad;
+	}
+	/* Should drop packet if mbuf too long? hmmm... */
+	if (m->m_len > ip->ip_len)
+	   m_adj(m, ip->ip_len - m->m_len);
+
+	/* check ip_ttl for a correct ICMP reply */
+	if(ip->ip_ttl==0 || ip->ip_ttl==1) {
+	  icmp_error(m, ICMP_TIMXCEED,ICMP_TIMXCEED_INTRANS, 0,"ttl");
+	  goto bad;
+	}
+
+	/*
+	 * Process options and, if not destined for us,
+	 * ship it on.  ip_dooptions returns 1 when an
+	 * error was detected (causing an icmp message
+	 * to be sent and the original packet to be freed).
+	 */
+/* We do no IP options */
+/*	if (hlen > sizeof (struct ip) && ip_dooptions(m))
+ *		goto next;
+ */
+	/*
+	 * If offset or IP_MF are set, must reassemble.
+	 * Otherwise, nothing need be done.
+	 * (We could look in the reassembly queue to see
+	 * if the packet was previously fragmented,
+	 * but it's not worth the time; just let them time out.)
+	 * 
+	 * XXX This should fail, don't fragment yet
+	 */
+	if (ip->ip_off &~ IP_DF) {
+	  register struct ipq *fp;
+		/*
+		 * Look for queue of fragments
+		 * of this datagram.
+		 */
+		for (fp = (struct ipq *) ipq.next; fp != &ipq;
+		     fp = (struct ipq *) fp->next)
+		  if (ip->ip_id == fp->ipq_id &&
+		      ip->ip_src.s_addr == fp->ipq_src.s_addr &&
+		      ip->ip_dst.s_addr == fp->ipq_dst.s_addr &&
+		      ip->ip_p == fp->ipq_p)
+		    goto found;
+		fp = 0;
+	found:
+
+		/*
+		 * Adjust ip_len to not reflect header,
+		 * set ip_mff if more fragments are expected,
+		 * convert offset of this to bytes.
+		 */
+		ip->ip_len -= hlen;
+		if (ip->ip_off & IP_MF)
+		  ((struct ipasfrag *)ip)->ipf_mff |= 1;
+		else 
+		  ((struct ipasfrag *)ip)->ipf_mff &= ~1;
+
+		ip->ip_off <<= 3;
+
+		/*
+		 * If datagram marked as having more fragments
+		 * or if this is not the first fragment,
+		 * attempt reassembly; if it succeeds, proceed.
+		 */
+		if (((struct ipasfrag *)ip)->ipf_mff & 1 || ip->ip_off) {
+			ipstat.ips_fragments++;
+			ip = ip_reass((struct ipasfrag *)ip, fp);
+			if (ip == 0)
+				return;
+			ipstat.ips_reassembled++;
+			m = dtom(ip);
+		} else
+			if (fp)
+		   	   ip_freef(fp);
+
+	} else
+		ip->ip_len -= hlen;
+
+	/*
+	 * Switch out to protocol's input routine.
+	 */
+	ipstat.ips_delivered++;
+	switch (ip->ip_p) {
+	 case IPPROTO_TCP:
+		tcp_input(m, hlen, (struct socket *)NULL);
+		break;
+	 case IPPROTO_UDP:
+		udp_input(m, hlen);
+		break;
+	 case IPPROTO_ICMP:
+		icmp_input(m, hlen);
+		break;
+	 default:
+		ipstat.ips_noproto++;
+		m_free(m);
+	}
+	return;
+bad:
+	m_freem(m);
+	return;
+}
+
+/*
+ * Take incoming datagram fragment and try to
+ * reassemble it into whole datagram.  If a chain for
+ * reassembly of this datagram already exists, then it
+ * is given as fp; otherwise have to make a chain.
+ */
+struct ip *
+ip_reass(ip, fp)
+	register struct ipasfrag *ip;
+	register struct ipq *fp;
+{
+	register struct mbuf *m = dtom(ip);
+	register struct ipasfrag *q;
+	int hlen = ip->ip_hl << 2;
+	int i, next;
+	
+	DEBUG_CALL("ip_reass");
+	DEBUG_ARG("ip = %lx", (long)ip);
+	DEBUG_ARG("fp = %lx", (long)fp);
+	DEBUG_ARG("m = %lx", (long)m);
+
+	/*
+	 * Presence of header sizes in mbufs
+	 * would confuse code below.
+         * Fragment m_data is concatenated.
+	 */
+	m->m_data += hlen;
+	m->m_len -= hlen;
+
+	/*
+	 * If first fragment to arrive, create a reassembly queue.
+	 */
+	if (fp == 0) {
+	  struct mbuf *t;
+	  if ((t = m_get()) == NULL) goto dropfrag;
+	  fp = mtod(t, struct ipq *);
+	  insque_32(fp, &ipq);
+	  fp->ipq_ttl = IPFRAGTTL;
+	  fp->ipq_p = ip->ip_p;
+	  fp->ipq_id = ip->ip_id;
+	  fp->ipq_next = fp->ipq_prev = (ipasfragp_32)fp;
+	  fp->ipq_src = ((struct ip *)ip)->ip_src;
+	  fp->ipq_dst = ((struct ip *)ip)->ip_dst;
+	  q = (struct ipasfrag *)fp;
+	  goto insert;
+	}
+	
+	/*
+	 * Find a segment which begins after this one does.
+	 */
+	for (q = (struct ipasfrag *)fp->ipq_next; q != (struct ipasfrag *)fp;
+	    q = (struct ipasfrag *)q->ipf_next)
+		if (q->ip_off > ip->ip_off)
+			break;
+
+	/*
+	 * If there is a preceding segment, it may provide some of
+	 * our data already.  If so, drop the data from the incoming
+	 * segment.  If it provides all of our data, drop us.
+	 */
+	if (q->ipf_prev != (ipasfragp_32)fp) {
+		i = ((struct ipasfrag *)(q->ipf_prev))->ip_off +
+		  ((struct ipasfrag *)(q->ipf_prev))->ip_len - ip->ip_off;
+		if (i > 0) {
+			if (i >= ip->ip_len)
+				goto dropfrag;
+			m_adj(dtom(ip), i);
+			ip->ip_off += i;
+			ip->ip_len -= i;
+		}
+	}
+
+	/*
+	 * While we overlap succeeding segments trim them or,
+	 * if they are completely covered, dequeue them.
+	 */
+	while (q != (struct ipasfrag *)fp && ip->ip_off + ip->ip_len > q->ip_off) {
+		i = (ip->ip_off + ip->ip_len) - q->ip_off;
+		if (i < q->ip_len) {
+			q->ip_len -= i;
+			q->ip_off += i;
+			m_adj(dtom(q), i);
+			break;
+		}
+		q = (struct ipasfrag *) q->ipf_next;
+		m_freem(dtom((struct ipasfrag *) q->ipf_prev));
+		ip_deq((struct ipasfrag *) q->ipf_prev);
+	}
+
+insert:
+	/*
+	 * Stick new segment in its place;
+	 * check for complete reassembly.
+	 */
+	ip_enq(ip, (struct ipasfrag *) q->ipf_prev);
+	next = 0;
+	for (q = (struct ipasfrag *) fp->ipq_next; q != (struct ipasfrag *)fp;
+	     q = (struct ipasfrag *) q->ipf_next) {
+		if (q->ip_off != next)
+			return (0);
+		next += q->ip_len;
+	}
+	if (((struct ipasfrag *)(q->ipf_prev))->ipf_mff & 1)
+		return (0);
+
+	/*
+	 * Reassembly is complete; concatenate fragments.
+	 */
+	q = (struct ipasfrag *) fp->ipq_next;
+	m = dtom(q);
+
+	q = (struct ipasfrag *) q->ipf_next;
+	while (q != (struct ipasfrag *)fp) {
+	  struct mbuf *t;
+	  t = dtom(q);
+	  m_cat(m, t);
+	  q = (struct ipasfrag *) q->ipf_next;
+	}
+
+	/*
+	 * Create header for new ip packet by
+	 * modifying header of first packet;
+	 * dequeue and discard fragment reassembly header.
+	 * Make header visible.
+	 */
+	ip = (struct ipasfrag *) fp->ipq_next;
+
+	/*
+	 * If the fragments concatenated to an mbuf that's
+	 * bigger than the total size of the fragment, then and
+	 * m_ext buffer was alloced. But fp->ipq_next points to
+	 * the old buffer (in the mbuf), so we must point ip
+	 * into the new buffer.
+	 */
+	if (m->m_flags & M_EXT) {
+	  int delta;
+	  delta = (char *)ip - m->m_dat;
+	  ip = (struct ipasfrag *)(m->m_ext + delta);
+	}
+
+	/* DEBUG_ARG("ip = %lx", (long)ip); 
+	 * ip=(struct ipasfrag *)m->m_data; */
+
+	ip->ip_len = next;
+	ip->ipf_mff &= ~1;
+	((struct ip *)ip)->ip_src = fp->ipq_src;
+	((struct ip *)ip)->ip_dst = fp->ipq_dst;
+	remque_32(fp);
+	(void) m_free(dtom(fp));
+	m = dtom(ip);
+	m->m_len += (ip->ip_hl << 2);
+	m->m_data -= (ip->ip_hl << 2);
+
+	return ((struct ip *)ip);
+
+dropfrag:
+	ipstat.ips_fragdropped++;
+	m_freem(m);
+	return (0);
+}
+
+/*
+ * Free a fragment reassembly header and all
+ * associated datagrams.
+ */
+void
+ip_freef(fp)
+	struct ipq *fp;
+{
+	register struct ipasfrag *q, *p;
+
+	for (q = (struct ipasfrag *) fp->ipq_next; q != (struct ipasfrag *)fp;
+	    q = p) {
+		p = (struct ipasfrag *) q->ipf_next;
+		ip_deq(q);
+		m_freem(dtom(q));
+	}
+	remque_32(fp);
+	(void) m_free(dtom(fp));
+}
+
+/*
+ * Put an ip fragment on a reassembly chain.
+ * Like insque, but pointers in middle of structure.
+ */
+void
+ip_enq(p, prev)
+	register struct ipasfrag *p, *prev;
+{
+	DEBUG_CALL("ip_enq");
+	DEBUG_ARG("prev = %lx", (long)prev);
+	p->ipf_prev = (ipasfragp_32) prev;
+	p->ipf_next = prev->ipf_next;
+	((struct ipasfrag *)(prev->ipf_next))->ipf_prev = (ipasfragp_32) p;
+	prev->ipf_next = (ipasfragp_32) p;
+}
+
+/*
+ * To ip_enq as remque is to insque.
+ */
+void
+ip_deq(p)
+	register struct ipasfrag *p;
+{
+	((struct ipasfrag *)(p->ipf_prev))->ipf_next = p->ipf_next;
+	((struct ipasfrag *)(p->ipf_next))->ipf_prev = p->ipf_prev;
+}
+
+/*
+ * IP timer processing;
+ * if a timer expires on a reassembly
+ * queue, discard it.
+ */
+void
+ip_slowtimo()
+{
+	register struct ipq *fp;
+	
+	DEBUG_CALL("ip_slowtimo");
+	
+	fp = (struct ipq *) ipq.next;
+	if (fp == 0)
+	   return;
+
+	while (fp != &ipq) {
+		--fp->ipq_ttl;
+		fp = (struct ipq *) fp->next;
+		if (((struct ipq *)(fp->prev))->ipq_ttl == 0) {
+			ipstat.ips_fragtimeout++;
+			ip_freef((struct ipq *) fp->prev);
+		}
+	}
+}
+
+/*
+ * Do option processing on a datagram,
+ * possibly discarding it if bad options are encountered,
+ * or forwarding it if source-routed.
+ * Returns 1 if packet has been forwarded/freed,
+ * 0 if the packet should be processed further.
+ */
+
+#ifdef notdef
+
+int
+ip_dooptions(m)
+	struct mbuf *m;
+{
+	register struct ip *ip = mtod(m, struct ip *);
+	register u_char *cp;
+	register struct ip_timestamp *ipt;
+	register struct in_ifaddr *ia;
+/*	int opt, optlen, cnt, off, code, type = ICMP_PARAMPROB, forward = 0; */
+	int opt, optlen, cnt, off, code, type, forward = 0;
+	struct in_addr *sin, dst;
+typedef u_int32_t n_time;
+	n_time ntime;
+
+	dst = ip->ip_dst;
+	cp = (u_char *)(ip + 1);
+	cnt = (ip->ip_hl << 2) - sizeof (struct ip);
+	for (; cnt > 0; cnt -= optlen, cp += optlen) {
+		opt = cp[IPOPT_OPTVAL];
+		if (opt == IPOPT_EOL)
+			break;
+		if (opt == IPOPT_NOP)
+			optlen = 1;
+		else {
+			optlen = cp[IPOPT_OLEN];
+			if (optlen <= 0 || optlen > cnt) {
+				code = &cp[IPOPT_OLEN] - (u_char *)ip;
+				goto bad;
+			}
+		}
+		switch (opt) {
+
+		default:
+			break;
+
+		/*
+		 * Source routing with record.
+		 * Find interface with current destination address.
+		 * If none on this machine then drop if strictly routed,
+		 * or do nothing if loosely routed.
+		 * Record interface address and bring up next address
+		 * component.  If strictly routed make sure next
+		 * address is on directly accessible net.
+		 */
+		case IPOPT_LSRR:
+		case IPOPT_SSRR:
+			if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
+				code = &cp[IPOPT_OFFSET] - (u_char *)ip;
+				goto bad;
+			}
+			ipaddr.sin_addr = ip->ip_dst;
+			ia = (struct in_ifaddr *)
+				ifa_ifwithaddr((struct sockaddr *)&ipaddr);
+			if (ia == 0) {
+				if (opt == IPOPT_SSRR) {
+					type = ICMP_UNREACH;
+					code = ICMP_UNREACH_SRCFAIL;
+					goto bad;
+				}
+				/*
+				 * Loose routing, and not at next destination
+				 * yet; nothing to do except forward.
+				 */
+				break;
+			}
+			off--;			/ * 0 origin *  /
+			if (off > optlen - sizeof(struct in_addr)) {
+				/*
+				 * End of source route.  Should be for us.
+				 */
+				save_rte(cp, ip->ip_src);
+				break;
+			}
+			/*
+			 * locate outgoing interface
+			 */
+			bcopy((caddr_t)(cp + off), (caddr_t)&ipaddr.sin_addr,
+			    sizeof(ipaddr.sin_addr));
+			if (opt == IPOPT_SSRR) {
+#define	INA	struct in_ifaddr *
+#define	SA	struct sockaddr *
+ 			    if ((ia = (INA)ifa_ifwithdstaddr((SA)&ipaddr)) == 0)
+				ia = (INA)ifa_ifwithnet((SA)&ipaddr);
+			} else
+				ia = ip_rtaddr(ipaddr.sin_addr);
+			if (ia == 0) {
+				type = ICMP_UNREACH;
+				code = ICMP_UNREACH_SRCFAIL;
+				goto bad;
+			}
+			ip->ip_dst = ipaddr.sin_addr;
+			bcopy((caddr_t)&(IA_SIN(ia)->sin_addr),
+			    (caddr_t)(cp + off), sizeof(struct in_addr));
+			cp[IPOPT_OFFSET] += sizeof(struct in_addr);
+			/*
+			 * Let ip_intr's mcast routing check handle mcast pkts
+			 */
+			forward = !IN_MULTICAST(ntohl(ip->ip_dst.s_addr));
+			break;
+
+		case IPOPT_RR:
+			if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
+				code = &cp[IPOPT_OFFSET] - (u_char *)ip;
+				goto bad;
+			}
+			/*
+			 * If no space remains, ignore.
+			 */
+			off--;			 * 0 origin *
+			if (off > optlen - sizeof(struct in_addr))
+				break;
+			bcopy((caddr_t)(&ip->ip_dst), (caddr_t)&ipaddr.sin_addr,
+			    sizeof(ipaddr.sin_addr));
+			/*
+			 * locate outgoing interface; if we're the destination,
+			 * use the incoming interface (should be same).
+			 */
+			if ((ia = (INA)ifa_ifwithaddr((SA)&ipaddr)) == 0 &&
+			    (ia = ip_rtaddr(ipaddr.sin_addr)) == 0) {
+				type = ICMP_UNREACH;
+				code = ICMP_UNREACH_HOST;
+				goto bad;
+			}
+			bcopy((caddr_t)&(IA_SIN(ia)->sin_addr),
+			    (caddr_t)(cp + off), sizeof(struct in_addr));
+			cp[IPOPT_OFFSET] += sizeof(struct in_addr);
+			break;
+
+		case IPOPT_TS:
+			code = cp - (u_char *)ip;
+			ipt = (struct ip_timestamp *)cp;
+			if (ipt->ipt_len < 5)
+				goto bad;
+			if (ipt->ipt_ptr > ipt->ipt_len - sizeof (int32_t)) {
+				if (++ipt->ipt_oflw == 0)
+					goto bad;
+				break;
+			}
+			sin = (struct in_addr *)(cp + ipt->ipt_ptr - 1);
+			switch (ipt->ipt_flg) {
+
+			case IPOPT_TS_TSONLY:
+				break;
+
+			case IPOPT_TS_TSANDADDR:
+				if (ipt->ipt_ptr + sizeof(n_time) +
+				    sizeof(struct in_addr) > ipt->ipt_len)
+					goto bad;
+				ipaddr.sin_addr = dst;
+				ia = (INA)ifaof_ i f p foraddr((SA)&ipaddr,
+							    m->m_pkthdr.rcvif);
+				if (ia == 0)
+					continue;
+				bcopy((caddr_t)&IA_SIN(ia)->sin_addr,
+				    (caddr_t)sin, sizeof(struct in_addr));
+				ipt->ipt_ptr += sizeof(struct in_addr);
+				break;
+
+			case IPOPT_TS_PRESPEC:
+				if (ipt->ipt_ptr + sizeof(n_time) +
+				    sizeof(struct in_addr) > ipt->ipt_len)
+					goto bad;
+				bcopy((caddr_t)sin, (caddr_t)&ipaddr.sin_addr,
+				    sizeof(struct in_addr));
+				if (ifa_ifwithaddr((SA)&ipaddr) == 0)
+					continue;
+				ipt->ipt_ptr += sizeof(struct in_addr);
+				break;
+
+			default:
+				goto bad;
+			}
+			ntime = iptime();
+			bcopy((caddr_t)&ntime, (caddr_t)cp + ipt->ipt_ptr - 1,
+			    sizeof(n_time));
+			ipt->ipt_ptr += sizeof(n_time);
+		}
+	}
+	if (forward) {
+		ip_forward(m, 1);
+		return (1);
+	}
+		}
+	}
+	return (0);
+bad:
+	/* ip->ip_len -= ip->ip_hl << 2;   XXX icmp_error adds in hdr length */
+
+/* Not yet */
+ 	icmp_error(m, type, code, 0, 0);
+
+	ipstat.ips_badoptions++;
+	return (1);
+}
+
+#endif /* notdef */
+
+/*
+ * Strip out IP options, at higher
+ * level protocol in the kernel.
+ * Second argument is buffer to which options
+ * will be moved, and return value is their length.
+ * (XXX) should be deleted; last arg currently ignored.
+ */
+void
+ip_stripoptions(m, mopt)
+	register struct mbuf *m;
+	struct mbuf *mopt;
+{
+	register int i;
+	struct ip *ip = mtod(m, struct ip *);
+	register caddr_t opts;
+	int olen;
+
+	olen = (ip->ip_hl<<2) - sizeof (struct ip);
+	opts = (caddr_t)(ip + 1);
+	i = m->m_len - (sizeof (struct ip) + olen);
+	memcpy(opts, opts  + olen, (unsigned)i);
+	m->m_len -= olen;
+	
+	ip->ip_hl = sizeof(struct ip) >> 2;
+}