ip6_forward.c revision 92716 
1/*	$FreeBSD: head/sys/netinet6/ip6_forward.c 92716 2002-03-19 19:45:41Z alfred $	*/
2/*	$KAME: ip6_forward.c,v 1.69 2001/05/17 03:48:30 itojun Exp $	*/
3
4/*
5 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of the project nor the names of its contributors
17 *    may be used to endorse or promote products derived from this software
18 *    without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 */
32
33#include "opt_ip6fw.h"
34#include "opt_inet.h"
35#include "opt_inet6.h"
36#include "opt_ipsec.h"
37
38#include <sys/param.h>
39#include <sys/systm.h>
40#include <sys/malloc.h>
41#include <sys/mbuf.h>
42#include <sys/domain.h>
43#include <sys/protosw.h>
44#include <sys/socket.h>
45#include <sys/errno.h>
46#include <sys/time.h>
47#include <sys/kernel.h>
48#include <sys/syslog.h>
49
50#include <net/if.h>
51#include <net/route.h>
52#ifdef PFIL_HOOKS
53#include <net/pfil.h>
54#endif
55
56#include <netinet/in.h>
57#include <netinet/in_var.h>
58#include <netinet/in_systm.h>
59#include <netinet/ip.h>
60#include <netinet/ip_var.h>
61#include <netinet6/in6_var.h>
62#include <netinet/ip6.h>
63#include <netinet6/ip6_var.h>
64#include <netinet/icmp6.h>
65#include <netinet6/nd6.h>
66
67#include <netinet/in_pcb.h>
68
69#ifdef IPSEC
70#include <netinet6/ipsec.h>
71#ifdef INET6
72#include <netinet6/ipsec6.h>
73#endif
74#include <netkey/key.h>
75#endif /* IPSEC */
76
77#include <netinet6/ip6_fw.h>
78
79#include <net/net_osdep.h>
80
81#include <netinet6/ip6protosw.h>
82
83struct	route_in6 ip6_forward_rt;
84
85/*
86 * Forward a packet.  If some error occurs return the sender
87 * an icmp packet.  Note we can't always generate a meaningful
88 * icmp message because icmp doesn't have a large enough repertoire
89 * of codes and types.
90 *
91 * If not forwarding, just drop the packet.  This could be confusing
92 * if ipforwarding was zero but some routing protocol was advancing
93 * us as a gateway to somewhere.  However, we must let the routing
94 * protocol deal with that.
95 *
96 */
97
98void
99ip6_forward(m, srcrt)
100	struct mbuf *m;
101	int srcrt;
102{
103	struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
104	struct sockaddr_in6 *dst;
105	struct rtentry *rt;
106	int error, type = 0, code = 0;
107	struct mbuf *mcopy = NULL;
108	struct ifnet *origifp;	/* maybe unnecessary */
109#ifdef PFIL_HOOKS
110	struct packet_filter_hook *pfh;
111	struct mbuf *m1;
112	int rv;
113#endif /* PFIL_HOOKS */
114#ifdef IPSEC
115	struct secpolicy *sp = NULL;
116#endif
117
118#ifdef IPSEC
119	/*
120	 * Check AH/ESP integrity.
121	 */
122	/*
123	 * Don't increment ip6s_cantforward because this is the check
124	 * before forwarding packet actually.
125	 */
126	if (ipsec6_in_reject(m, NULL)) {
127		ipsec6stat.in_polvio++;
128		m_freem(m);
129		return;
130	}
131#endif /*IPSEC*/
132
133	/*
134	 * Do not forward packets to multicast destination (should be handled
135	 * by ip6_mforward().
136	 * Do not forward packets with unspecified source.  It was discussed
137	 * in July 2000, on ipngwg mailing list.
138	 */
139	if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
140	    IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
141	    IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
142		ip6stat.ip6s_cantforward++;
143		/* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
144		if (ip6_log_time + ip6_log_interval < time_second) {
145			ip6_log_time = time_second;
146			log(LOG_DEBUG,
147			    "cannot forward "
148			    "from %s to %s nxt %d received on %s\n",
149			    ip6_sprintf(&ip6->ip6_src),
150			    ip6_sprintf(&ip6->ip6_dst),
151			    ip6->ip6_nxt,
152			    if_name(m->m_pkthdr.rcvif));
153		}
154		m_freem(m);
155		return;
156	}
157
158	if (ip6->ip6_hlim <= IPV6_HLIMDEC) {
159		/* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
160		icmp6_error(m, ICMP6_TIME_EXCEEDED,
161				ICMP6_TIME_EXCEED_TRANSIT, 0);
162		return;
163	}
164	ip6->ip6_hlim -= IPV6_HLIMDEC;
165
166	/*
167	 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
168	 * size of IPv6 + ICMPv6 headers) bytes of the packet in case
169	 * we need to generate an ICMP6 message to the src.
170	 * Thanks to M_EXT, in most cases copy will not occur.
171	 *
172	 * It is important to save it before IPsec processing as IPsec
173	 * processing may modify the mbuf.
174	 */
175	mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN));
176
177#ifdef IPSEC
178	/* get a security policy for this packet */
179	sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, IP_FORWARDING,
180	    &error);
181	if (sp == NULL) {
182		ipsec6stat.out_inval++;
183		ip6stat.ip6s_cantforward++;
184		if (mcopy) {
185#if 0
186			/* XXX: what icmp ? */
187#else
188			m_freem(mcopy);
189#endif
190		}
191		m_freem(m);
192		return;
193	}
194
195	error = 0;
196
197	/* check policy */
198	switch (sp->policy) {
199	case IPSEC_POLICY_DISCARD:
200		/*
201		 * This packet is just discarded.
202		 */
203		ipsec6stat.out_polvio++;
204		ip6stat.ip6s_cantforward++;
205		key_freesp(sp);
206		if (mcopy) {
207#if 0
208			/* XXX: what icmp ? */
209#else
210			m_freem(mcopy);
211#endif
212		}
213		m_freem(m);
214		return;
215
216	case IPSEC_POLICY_BYPASS:
217	case IPSEC_POLICY_NONE:
218		/* no need to do IPsec. */
219		key_freesp(sp);
220		goto skip_ipsec;
221
222	case IPSEC_POLICY_IPSEC:
223		if (sp->req == NULL) {
224			/* XXX should be panic ? */
225			printf("ip6_forward: No IPsec request specified.\n");
226			ip6stat.ip6s_cantforward++;
227			key_freesp(sp);
228			if (mcopy) {
229#if 0
230				/* XXX: what icmp ? */
231#else
232				m_freem(mcopy);
233#endif
234			}
235			m_freem(m);
236			return;
237		}
238		/* do IPsec */
239		break;
240
241	case IPSEC_POLICY_ENTRUST:
242	default:
243		/* should be panic ?? */
244		printf("ip6_forward: Invalid policy found. %d\n", sp->policy);
245		key_freesp(sp);
246		goto skip_ipsec;
247	}
248
249    {
250	struct ipsec_output_state state;
251
252	/*
253	 * All the extension headers will become inaccessible
254	 * (since they can be encrypted).
255	 * Don't panic, we need no more updates to extension headers
256	 * on inner IPv6 packet (since they are now encapsulated).
257	 *
258	 * IPv6 [ESP|AH] IPv6 [extension headers] payload
259	 */
260	bzero(&state, sizeof(state));
261	state.m = m;
262	state.ro = NULL;	/* update at ipsec6_output_tunnel() */
263	state.dst = NULL;	/* update at ipsec6_output_tunnel() */
264
265	error = ipsec6_output_tunnel(&state, sp, 0);
266
267	m = state.m;
268	key_freesp(sp);
269
270	if (error) {
271		/* mbuf is already reclaimed in ipsec6_output_tunnel. */
272		switch (error) {
273		case EHOSTUNREACH:
274		case ENETUNREACH:
275		case EMSGSIZE:
276		case ENOBUFS:
277		case ENOMEM:
278			break;
279		default:
280			printf("ip6_output (ipsec): error code %d\n", error);
281			/*fall through*/
282		case ENOENT:
283			/* don't show these error codes to the user */
284			break;
285		}
286		ip6stat.ip6s_cantforward++;
287		if (mcopy) {
288#if 0
289			/* XXX: what icmp ? */
290#else
291			m_freem(mcopy);
292#endif
293		}
294		m_freem(m);
295		return;
296	}
297    }
298    skip_ipsec:
299#endif /* IPSEC */
300
301	dst = (struct sockaddr_in6 *)&ip6_forward_rt.ro_dst;
302	if (!srcrt) {
303		/*
304		 * ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst
305		 */
306		if (ip6_forward_rt.ro_rt == 0 ||
307		    (ip6_forward_rt.ro_rt->rt_flags & RTF_UP) == 0) {
308			if (ip6_forward_rt.ro_rt) {
309				RTFREE(ip6_forward_rt.ro_rt);
310				ip6_forward_rt.ro_rt = 0;
311			}
312			/* this probably fails but give it a try again */
313			rtalloc_ign((struct route *)&ip6_forward_rt,
314				    RTF_PRCLONING);
315		}
316
317		if (ip6_forward_rt.ro_rt == 0) {
318			ip6stat.ip6s_noroute++;
319			in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
320			if (mcopy) {
321				icmp6_error(mcopy, ICMP6_DST_UNREACH,
322					    ICMP6_DST_UNREACH_NOROUTE, 0);
323			}
324			m_freem(m);
325			return;
326		}
327	} else if ((rt = ip6_forward_rt.ro_rt) == 0 ||
328		 !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) {
329		if (ip6_forward_rt.ro_rt) {
330			RTFREE(ip6_forward_rt.ro_rt);
331			ip6_forward_rt.ro_rt = 0;
332		}
333		bzero(dst, sizeof(*dst));
334		dst->sin6_len = sizeof(struct sockaddr_in6);
335		dst->sin6_family = AF_INET6;
336		dst->sin6_addr = ip6->ip6_dst;
337
338  		rtalloc_ign((struct route *)&ip6_forward_rt, RTF_PRCLONING);
339		if (ip6_forward_rt.ro_rt == 0) {
340			ip6stat.ip6s_noroute++;
341			in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
342			if (mcopy) {
343				icmp6_error(mcopy, ICMP6_DST_UNREACH,
344					    ICMP6_DST_UNREACH_NOROUTE, 0);
345			}
346			m_freem(m);
347			return;
348		}
349	}
350	rt = ip6_forward_rt.ro_rt;
351
352	/*
353	 * Scope check: if a packet can't be delivered to its destination
354	 * for the reason that the destination is beyond the scope of the
355	 * source address, discard the packet and return an icmp6 destination
356	 * unreachable error with Code 2 (beyond scope of source address).
357	 * [draft-ietf-ipngwg-icmp-v3-00.txt, Section 3.1]
358	 */
359	if (in6_addr2scopeid(m->m_pkthdr.rcvif, &ip6->ip6_src) !=
360	    in6_addr2scopeid(rt->rt_ifp, &ip6->ip6_src)) {
361		ip6stat.ip6s_cantforward++;
362		ip6stat.ip6s_badscope++;
363		in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard);
364
365		if (ip6_log_time + ip6_log_interval < time_second) {
366			ip6_log_time = time_second;
367			log(LOG_DEBUG,
368			    "cannot forward "
369			    "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
370			    ip6_sprintf(&ip6->ip6_src),
371			    ip6_sprintf(&ip6->ip6_dst),
372			    ip6->ip6_nxt,
373			    if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp));
374		}
375		if (mcopy)
376			icmp6_error(mcopy, ICMP6_DST_UNREACH,
377				    ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
378		m_freem(m);
379		return;
380	}
381
382	if (m->m_pkthdr.len > rt->rt_ifp->if_mtu) {
383		in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig);
384		if (mcopy) {
385			u_long mtu;
386#ifdef IPSEC
387			struct secpolicy *sp;
388			int ipsecerror;
389			size_t ipsechdrsiz;
390#endif
391
392			mtu = rt->rt_ifp->if_mtu;
393#ifdef IPSEC
394			/*
395			 * When we do IPsec tunnel ingress, we need to play
396			 * with if_mtu value (decrement IPsec header size
397			 * from mtu value).  The code is much simpler than v4
398			 * case, as we have the outgoing interface for
399			 * encapsulated packet as "rt->rt_ifp".
400			 */
401			sp = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND,
402				IP_FORWARDING, &ipsecerror);
403			if (sp) {
404				ipsechdrsiz = ipsec6_hdrsiz(mcopy,
405					IPSEC_DIR_OUTBOUND, NULL);
406				if (ipsechdrsiz < mtu)
407					mtu -= ipsechdrsiz;
408			}
409
410			/*
411			 * if mtu becomes less than minimum MTU,
412			 * tell minimum MTU (and I'll need to fragment it).
413			 */
414			if (mtu < IPV6_MMTU)
415				mtu = IPV6_MMTU;
416#endif
417			icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu);
418		}
419		m_freem(m);
420		return;
421 	}
422
423	if (rt->rt_flags & RTF_GATEWAY)
424		dst = (struct sockaddr_in6 *)rt->rt_gateway;
425
426	/*
427	 * If we are to forward the packet using the same interface
428	 * as one we got the packet from, perhaps we should send a redirect
429	 * to sender to shortcut a hop.
430	 * Only send redirect if source is sending directly to us,
431	 * and if packet was not source routed (or has any options).
432	 * Also, don't send redirect if forwarding using a route
433	 * modified by a redirect.
434	 */
435	if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt &&
436	    (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) {
437		if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) != 0) {
438			/*
439			 * If the incoming interface is equal to the outgoing
440			 * one, and the link attached to the interface is
441			 * point-to-point, then it will be highly probable
442			 * that a routing loop occurs. Thus, we immediately
443			 * drop the packet and send an ICMPv6 error message.
444			 *
445			 * type/code is based on suggestion by Rich Draves.
446			 * not sure if it is the best pick.
447			 */
448			icmp6_error(mcopy, ICMP6_DST_UNREACH,
449				    ICMP6_DST_UNREACH_ADDR, 0);
450			m_freem(m);
451			return;
452		}
453		type = ND_REDIRECT;
454	}
455
456	/*
457	 * Check with the firewall...
458	 */
459	if (ip6_fw_enable && ip6_fw_chk_ptr) {
460		u_short port = 0;
461		/* If ipfw says divert, we have to just drop packet */
462		if ((*ip6_fw_chk_ptr)(&ip6, rt->rt_ifp, &port, &m)) {
463			m_freem(m);
464			goto freecopy;
465		}
466		if (!m)
467			goto freecopy;
468	}
469
470	/*
471	 * Fake scoped addresses. Note that even link-local source or
472	 * destinaion can appear, if the originating node just sends the
473	 * packet to us (without address resolution for the destination).
474	 * Since both icmp6_error and icmp6_redirect_output fill the embedded
475	 * link identifiers, we can do this stuff after making a copy for
476	 * returning an error.
477	 */
478	if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) {
479		/*
480		 * See corresponding comments in ip6_output.
481		 * XXX: but is it possible that ip6_forward() sends a packet
482		 *      to a loopback interface? I don't think so, and thus
483		 *      I bark here. (jinmei@kame.net)
484		 * XXX: it is common to route invalid packets to loopback.
485		 *	also, the codepath will be visited on use of ::1 in
486		 *	rthdr. (itojun)
487		 */
488#if 1
489		if (0)
490#else
491		if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0)
492#endif
493		{
494			printf("ip6_forward: outgoing interface is loopback. "
495				"src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
496				ip6_sprintf(&ip6->ip6_src),
497				ip6_sprintf(&ip6->ip6_dst),
498				ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif),
499				if_name(rt->rt_ifp));
500		}
501
502		/* we can just use rcvif in forwarding. */
503		origifp = m->m_pkthdr.rcvif;
504	}
505	else
506		origifp = rt->rt_ifp;
507#ifndef SCOPEDROUTING
508	/*
509	 * clear embedded scope identifiers if necessary.
510	 * in6_clearscope will touch the addresses only when necessary.
511	 */
512	in6_clearscope(&ip6->ip6_src);
513	in6_clearscope(&ip6->ip6_dst);
514#endif
515
516#ifdef PFIL_HOOKS
517	/*
518	 * Run through list of hooks for output packets.
519	 */
520	m1 = m;
521	pfh = pfil_hook_get(PFIL_OUT, &inet6sw[ip6_protox[IPPROTO_IPV6]].pr_pfh);
522	for (; pfh; pfh = pfh->pfil_link.tqe_next)
523		if (pfh->pfil_func) {
524			rv = pfh->pfil_func(ip6, sizeof(*ip6),
525					    rt->rt_ifp, 1, &m1);
526			if (rv) {
527				error = EHOSTUNREACH;
528				goto freecopy;
529			}
530			m = m1;
531			if (m == NULL)
532				goto freecopy;
533			ip6 = mtod(m, struct ip6_hdr *);
534		}
535#endif /* PFIL_HOOKS */
536
537	error = nd6_output(rt->rt_ifp, origifp, m, dst, rt);
538	if (error) {
539		in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard);
540		ip6stat.ip6s_cantforward++;
541	} else {
542		ip6stat.ip6s_forward++;
543		in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward);
544		if (type)
545			ip6stat.ip6s_redirectsent++;
546		else {
547			if (mcopy)
548				goto freecopy;
549		}
550	}
551	if (mcopy == NULL)
552		return;
553
554	switch (error) {
555	case 0:
556#if 1
557		if (type == ND_REDIRECT) {
558			icmp6_redirect_output(mcopy, rt);
559			return;
560		}
561#endif
562		goto freecopy;
563
564	case EMSGSIZE:
565		/* xxx MTU is constant in PPP? */
566		goto freecopy;
567
568	case ENOBUFS:
569		/* Tell source to slow down like source quench in IP? */
570		goto freecopy;
571
572	case ENETUNREACH:	/* shouldn't happen, checked above */
573	case EHOSTUNREACH:
574	case ENETDOWN:
575	case EHOSTDOWN:
576	default:
577		type = ICMP6_DST_UNREACH;
578		code = ICMP6_DST_UNREACH_ADDR;
579		break;
580	}
581	icmp6_error(mcopy, type, code, 0);
582	return;
583
584 freecopy:
585	m_freem(mcopy);
586	return;
587}
588