ip6_forward.c revision 105199 
1/*	$FreeBSD: head/sys/netinet6/ip6_forward.c 105199 2002-10-16 02:25:05Z sam $	*/
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#ifdef FAST_IPSEC
78#include <netipsec/ipsec.h>
79#include <netipsec/ipsec6.h>
80#include <netipsec/key.h>
81#define	IPSEC
82#endif /* FAST_IPSEC */
83
84#include <netinet6/ip6_fw.h>
85
86#include <net/net_osdep.h>
87
88#include <netinet6/ip6protosw.h>
89
90struct	route_in6 ip6_forward_rt;
91
92/*
93 * Forward a packet.  If some error occurs return the sender
94 * an icmp packet.  Note we can't always generate a meaningful
95 * icmp message because icmp doesn't have a large enough repertoire
96 * of codes and types.
97 *
98 * If not forwarding, just drop the packet.  This could be confusing
99 * if ipforwarding was zero but some routing protocol was advancing
100 * us as a gateway to somewhere.  However, we must let the routing
101 * protocol deal with that.
102 *
103 */
104
105void
106ip6_forward(m, srcrt)
107	struct mbuf *m;
108	int srcrt;
109{
110	struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
111	struct sockaddr_in6 *dst;
112	struct rtentry *rt;
113	int error, type = 0, code = 0;
114	struct mbuf *mcopy = NULL;
115	struct ifnet *origifp;	/* maybe unnecessary */
116#ifdef PFIL_HOOKS
117	struct packet_filter_hook *pfh;
118	struct mbuf *m1;
119	int rv;
120#endif /* PFIL_HOOKS */
121#ifdef IPSEC
122	struct secpolicy *sp = NULL;
123#endif
124
125#ifdef IPSEC
126	/*
127	 * Check AH/ESP integrity.
128	 */
129	/*
130	 * Don't increment ip6s_cantforward because this is the check
131	 * before forwarding packet actually.
132	 */
133	if (ipsec6_in_reject(m, NULL)) {
134#if !defined(FAST_IPSEC)
135		ipsec6stat.in_polvio++;
136#endif
137		m_freem(m);
138		return;
139	}
140#endif /* IPSEC */
141
142	/*
143	 * Do not forward packets to multicast destination (should be handled
144	 * by ip6_mforward().
145	 * Do not forward packets with unspecified source.  It was discussed
146	 * in July 2000, on ipngwg mailing list.
147	 */
148	if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
149	    IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
150	    IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
151		ip6stat.ip6s_cantforward++;
152		/* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
153		if (ip6_log_time + ip6_log_interval < time_second) {
154			ip6_log_time = time_second;
155			log(LOG_DEBUG,
156			    "cannot forward "
157			    "from %s to %s nxt %d received on %s\n",
158			    ip6_sprintf(&ip6->ip6_src),
159			    ip6_sprintf(&ip6->ip6_dst),
160			    ip6->ip6_nxt,
161			    if_name(m->m_pkthdr.rcvif));
162		}
163		m_freem(m);
164		return;
165	}
166
167	if (ip6->ip6_hlim <= IPV6_HLIMDEC) {
168		/* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
169		icmp6_error(m, ICMP6_TIME_EXCEEDED,
170				ICMP6_TIME_EXCEED_TRANSIT, 0);
171		return;
172	}
173	ip6->ip6_hlim -= IPV6_HLIMDEC;
174
175	/*
176	 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
177	 * size of IPv6 + ICMPv6 headers) bytes of the packet in case
178	 * we need to generate an ICMP6 message to the src.
179	 * Thanks to M_EXT, in most cases copy will not occur.
180	 *
181	 * It is important to save it before IPsec processing as IPsec
182	 * processing may modify the mbuf.
183	 */
184	mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN));
185
186#ifdef IPSEC
187	/* get a security policy for this packet */
188	sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, IP_FORWARDING,
189	    &error);
190	if (sp == NULL) {
191		ipsec6stat.out_inval++;
192		ip6stat.ip6s_cantforward++;
193		if (mcopy) {
194#if 0
195			/* XXX: what icmp ? */
196#else
197			m_freem(mcopy);
198#endif
199		}
200		m_freem(m);
201		return;
202	}
203
204	error = 0;
205
206	/* check policy */
207	switch (sp->policy) {
208	case IPSEC_POLICY_DISCARD:
209		/*
210		 * This packet is just discarded.
211		 */
212		ipsec6stat.out_polvio++;
213		ip6stat.ip6s_cantforward++;
214		key_freesp(sp);
215		if (mcopy) {
216#if 0
217			/* XXX: what icmp ? */
218#else
219			m_freem(mcopy);
220#endif
221		}
222		m_freem(m);
223		return;
224
225	case IPSEC_POLICY_BYPASS:
226	case IPSEC_POLICY_NONE:
227		/* no need to do IPsec. */
228		key_freesp(sp);
229		goto skip_ipsec;
230
231	case IPSEC_POLICY_IPSEC:
232		if (sp->req == NULL) {
233			/* XXX should be panic ? */
234			printf("ip6_forward: No IPsec request specified.\n");
235			ip6stat.ip6s_cantforward++;
236			key_freesp(sp);
237			if (mcopy) {
238#if 0
239				/* XXX: what icmp ? */
240#else
241				m_freem(mcopy);
242#endif
243			}
244			m_freem(m);
245			return;
246		}
247		/* do IPsec */
248		break;
249
250	case IPSEC_POLICY_ENTRUST:
251	default:
252		/* should be panic ?? */
253		printf("ip6_forward: Invalid policy found. %d\n", sp->policy);
254		key_freesp(sp);
255		goto skip_ipsec;
256	}
257
258    {
259	struct ipsec_output_state state;
260
261	/*
262	 * All the extension headers will become inaccessible
263	 * (since they can be encrypted).
264	 * Don't panic, we need no more updates to extension headers
265	 * on inner IPv6 packet (since they are now encapsulated).
266	 *
267	 * IPv6 [ESP|AH] IPv6 [extension headers] payload
268	 */
269	bzero(&state, sizeof(state));
270	state.m = m;
271	state.ro = NULL;	/* update at ipsec6_output_tunnel() */
272	state.dst = NULL;	/* update at ipsec6_output_tunnel() */
273
274	error = ipsec6_output_tunnel(&state, sp, 0);
275
276	m = state.m;
277	key_freesp(sp);
278
279	if (error) {
280		/* mbuf is already reclaimed in ipsec6_output_tunnel. */
281		switch (error) {
282		case EHOSTUNREACH:
283		case ENETUNREACH:
284		case EMSGSIZE:
285		case ENOBUFS:
286		case ENOMEM:
287			break;
288		default:
289			printf("ip6_output (ipsec): error code %d\n", error);
290			/* fall through */
291		case ENOENT:
292			/* don't show these error codes to the user */
293			break;
294		}
295		ip6stat.ip6s_cantforward++;
296		if (mcopy) {
297#if 0
298			/* XXX: what icmp ? */
299#else
300			m_freem(mcopy);
301#endif
302		}
303		m_freem(m);
304		return;
305	}
306    }
307    skip_ipsec:
308#endif /* IPSEC */
309
310	dst = (struct sockaddr_in6 *)&ip6_forward_rt.ro_dst;
311	if (!srcrt) {
312		/*
313		 * ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst
314		 */
315		if (ip6_forward_rt.ro_rt == 0 ||
316		    (ip6_forward_rt.ro_rt->rt_flags & RTF_UP) == 0) {
317			if (ip6_forward_rt.ro_rt) {
318				RTFREE(ip6_forward_rt.ro_rt);
319				ip6_forward_rt.ro_rt = 0;
320			}
321			/* this probably fails but give it a try again */
322			rtalloc_ign((struct route *)&ip6_forward_rt,
323				    RTF_PRCLONING);
324		}
325
326		if (ip6_forward_rt.ro_rt == 0) {
327			ip6stat.ip6s_noroute++;
328			in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
329			if (mcopy) {
330				icmp6_error(mcopy, ICMP6_DST_UNREACH,
331					    ICMP6_DST_UNREACH_NOROUTE, 0);
332			}
333			m_freem(m);
334			return;
335		}
336	} else if ((rt = ip6_forward_rt.ro_rt) == 0 ||
337		 !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) {
338		if (ip6_forward_rt.ro_rt) {
339			RTFREE(ip6_forward_rt.ro_rt);
340			ip6_forward_rt.ro_rt = 0;
341		}
342		bzero(dst, sizeof(*dst));
343		dst->sin6_len = sizeof(struct sockaddr_in6);
344		dst->sin6_family = AF_INET6;
345		dst->sin6_addr = ip6->ip6_dst;
346
347  		rtalloc_ign((struct route *)&ip6_forward_rt, RTF_PRCLONING);
348		if (ip6_forward_rt.ro_rt == 0) {
349			ip6stat.ip6s_noroute++;
350			in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
351			if (mcopy) {
352				icmp6_error(mcopy, ICMP6_DST_UNREACH,
353					    ICMP6_DST_UNREACH_NOROUTE, 0);
354			}
355			m_freem(m);
356			return;
357		}
358	}
359	rt = ip6_forward_rt.ro_rt;
360
361	/*
362	 * Scope check: if a packet can't be delivered to its destination
363	 * for the reason that the destination is beyond the scope of the
364	 * source address, discard the packet and return an icmp6 destination
365	 * unreachable error with Code 2 (beyond scope of source address).
366	 * [draft-ietf-ipngwg-icmp-v3-02.txt, Section 3.1]
367	 */
368	if (in6_addr2scopeid(m->m_pkthdr.rcvif, &ip6->ip6_src) !=
369	    in6_addr2scopeid(rt->rt_ifp, &ip6->ip6_src)) {
370		ip6stat.ip6s_cantforward++;
371		ip6stat.ip6s_badscope++;
372		in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard);
373
374		if (ip6_log_time + ip6_log_interval < time_second) {
375			ip6_log_time = time_second;
376			log(LOG_DEBUG,
377			    "cannot forward "
378			    "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
379			    ip6_sprintf(&ip6->ip6_src),
380			    ip6_sprintf(&ip6->ip6_dst),
381			    ip6->ip6_nxt,
382			    if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp));
383		}
384		if (mcopy)
385			icmp6_error(mcopy, ICMP6_DST_UNREACH,
386				    ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
387		m_freem(m);
388		return;
389	}
390
391	if (m->m_pkthdr.len > rt->rt_ifp->if_mtu) {
392		in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig);
393		if (mcopy) {
394			u_long mtu;
395#ifdef IPSEC
396			struct secpolicy *sp;
397			int ipsecerror;
398			size_t ipsechdrsiz;
399#endif
400
401			mtu = rt->rt_ifp->if_mtu;
402#ifdef IPSEC
403			/*
404			 * When we do IPsec tunnel ingress, we need to play
405			 * with if_mtu value (decrement IPsec header size
406			 * from mtu value).  The code is much simpler than v4
407			 * case, as we have the outgoing interface for
408			 * encapsulated packet as "rt->rt_ifp".
409			 */
410			sp = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND,
411				IP_FORWARDING, &ipsecerror);
412			if (sp) {
413				ipsechdrsiz = ipsec6_hdrsiz(mcopy,
414					IPSEC_DIR_OUTBOUND, NULL);
415				if (ipsechdrsiz < mtu)
416					mtu -= ipsechdrsiz;
417			}
418
419			/*
420			 * if mtu becomes less than minimum MTU,
421			 * tell minimum MTU (and I'll need to fragment it).
422			 */
423			if (mtu < IPV6_MMTU)
424				mtu = IPV6_MMTU;
425#endif
426			icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu);
427		}
428		m_freem(m);
429		return;
430 	}
431
432	if (rt->rt_flags & RTF_GATEWAY)
433		dst = (struct sockaddr_in6 *)rt->rt_gateway;
434
435	/*
436	 * If we are to forward the packet using the same interface
437	 * as one we got the packet from, perhaps we should send a redirect
438	 * to sender to shortcut a hop.
439	 * Only send redirect if source is sending directly to us,
440	 * and if packet was not source routed (or has any options).
441	 * Also, don't send redirect if forwarding using a route
442	 * modified by a redirect.
443	 */
444	if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt &&
445	    (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) {
446		if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) != 0) {
447			/*
448			 * If the incoming interface is equal to the outgoing
449			 * one, and the link attached to the interface is
450			 * point-to-point, then it will be highly probable
451			 * that a routing loop occurs. Thus, we immediately
452			 * drop the packet and send an ICMPv6 error message.
453			 *
454			 * type/code is based on suggestion by Rich Draves.
455			 * not sure if it is the best pick.
456			 */
457			icmp6_error(mcopy, ICMP6_DST_UNREACH,
458				    ICMP6_DST_UNREACH_ADDR, 0);
459			m_freem(m);
460			return;
461		}
462		type = ND_REDIRECT;
463	}
464
465	/*
466	 * Check with the firewall...
467	 */
468	if (ip6_fw_enable && ip6_fw_chk_ptr) {
469		u_short port = 0;
470		/* If ipfw says divert, we have to just drop packet */
471		if ((*ip6_fw_chk_ptr)(&ip6, rt->rt_ifp, &port, &m)) {
472			m_freem(m);
473			goto freecopy;
474		}
475		if (!m)
476			goto freecopy;
477	}
478
479	/*
480	 * Fake scoped addresses. Note that even link-local source or
481	 * destinaion can appear, if the originating node just sends the
482	 * packet to us (without address resolution for the destination).
483	 * Since both icmp6_error and icmp6_redirect_output fill the embedded
484	 * link identifiers, we can do this stuff after making a copy for
485	 * returning an error.
486	 */
487	if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) {
488		/*
489		 * See corresponding comments in ip6_output.
490		 * XXX: but is it possible that ip6_forward() sends a packet
491		 *      to a loopback interface? I don't think so, and thus
492		 *      I bark here. (jinmei@kame.net)
493		 * XXX: it is common to route invalid packets to loopback.
494		 *	also, the codepath will be visited on use of ::1 in
495		 *	rthdr. (itojun)
496		 */
497#if 1
498		if (0)
499#else
500		if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0)
501#endif
502		{
503			printf("ip6_forward: outgoing interface is loopback. "
504				"src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
505				ip6_sprintf(&ip6->ip6_src),
506				ip6_sprintf(&ip6->ip6_dst),
507				ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif),
508				if_name(rt->rt_ifp));
509		}
510
511		/* we can just use rcvif in forwarding. */
512		origifp = m->m_pkthdr.rcvif;
513	}
514	else
515		origifp = rt->rt_ifp;
516#ifndef SCOPEDROUTING
517	/*
518	 * clear embedded scope identifiers if necessary.
519	 * in6_clearscope will touch the addresses only when necessary.
520	 */
521	in6_clearscope(&ip6->ip6_src);
522	in6_clearscope(&ip6->ip6_dst);
523#endif
524
525#ifdef PFIL_HOOKS
526	/*
527	 * Run through list of hooks for output packets.
528	 */
529	m1 = m;
530	pfh = pfil_hook_get(PFIL_OUT, &inet6sw[ip6_protox[IPPROTO_IPV6]].pr_pfh);
531	for (; pfh; pfh = pfh->pfil_link.tqe_next)
532		if (pfh->pfil_func) {
533			rv = pfh->pfil_func(ip6, sizeof(*ip6),
534					    rt->rt_ifp, 1, &m1);
535			if (rv) {
536				error = EHOSTUNREACH;
537				goto freecopy;
538			}
539			m = m1;
540			if (m == NULL)
541				goto freecopy;
542			ip6 = mtod(m, struct ip6_hdr *);
543		}
544#endif /* PFIL_HOOKS */
545
546	error = nd6_output(rt->rt_ifp, origifp, m, dst, rt);
547	if (error) {
548		in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard);
549		ip6stat.ip6s_cantforward++;
550	} else {
551		ip6stat.ip6s_forward++;
552		in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward);
553		if (type)
554			ip6stat.ip6s_redirectsent++;
555		else {
556			if (mcopy)
557				goto freecopy;
558		}
559	}
560	if (mcopy == NULL)
561		return;
562	switch (error) {
563	case 0:
564#if 1
565		if (type == ND_REDIRECT) {
566			icmp6_redirect_output(mcopy, rt);
567			return;
568		}
569#endif
570		goto freecopy;
571
572	case EMSGSIZE:
573		/* xxx MTU is constant in PPP? */
574		goto freecopy;
575
576	case ENOBUFS:
577		/* Tell source to slow down like source quench in IP? */
578		goto freecopy;
579
580	case ENETUNREACH:	/* shouldn't happen, checked above */
581	case EHOSTUNREACH:
582	case ENETDOWN:
583	case EHOSTDOWN:
584	default:
585		type = ICMP6_DST_UNREACH;
586		code = ICMP6_DST_UNREACH_ADDR;
587		break;
588	}
589	icmp6_error(mcopy, type, code, 0);
590	return;
591
592 freecopy:
593	m_freem(mcopy);
594	return;
595}
596