ip6_forward.c revision 120971 
1/*	$FreeBSD: head/sys/netinet6/ip6_forward.c 120971 2003-10-10 16:04:00Z ume $	*/
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#include "opt_pfil_hooks.h"
38
39#include <sys/param.h>
40#include <sys/systm.h>
41#include <sys/malloc.h>
42#include <sys/mbuf.h>
43#include <sys/domain.h>
44#include <sys/protosw.h>
45#include <sys/socket.h>
46#include <sys/errno.h>
47#include <sys/time.h>
48#include <sys/kernel.h>
49#include <sys/syslog.h>
50
51#include <net/if.h>
52#include <net/route.h>
53#ifdef PFIL_HOOKS
54#include <net/pfil.h>
55#endif
56
57#include <netinet/in.h>
58#include <netinet/in_var.h>
59#include <netinet/in_systm.h>
60#include <netinet/ip.h>
61#include <netinet/ip_var.h>
62#include <netinet6/in6_var.h>
63#include <netinet/ip6.h>
64#include <netinet6/ip6_var.h>
65#include <netinet/icmp6.h>
66#include <netinet6/nd6.h>
67
68#include <netinet/in_pcb.h>
69
70#ifdef IPSEC
71#include <netinet6/ipsec.h>
72#ifdef INET6
73#include <netinet6/ipsec6.h>
74#endif
75#include <netkey/key.h>
76#endif /* IPSEC */
77
78#ifdef FAST_IPSEC
79#include <netipsec/ipsec.h>
80#include <netipsec/ipsec6.h>
81#include <netipsec/key.h>
82#define	IPSEC
83#endif /* FAST_IPSEC */
84
85#include <netinet6/ip6_fw.h>
86
87#include <net/net_osdep.h>
88
89#include <netinet6/ip6protosw.h>
90
91struct	route_in6 ip6_forward_rt;
92
93/*
94 * Forward a packet.  If some error occurs return the sender
95 * an icmp packet.  Note we can't always generate a meaningful
96 * icmp message because icmp doesn't have a large enough repertoire
97 * of codes and types.
98 *
99 * If not forwarding, just drop the packet.  This could be confusing
100 * if ipforwarding was zero but some routing protocol was advancing
101 * us as a gateway to somewhere.  However, we must let the routing
102 * protocol deal with that.
103 *
104 */
105
106void
107ip6_forward(m, srcrt)
108	struct mbuf *m;
109	int srcrt;
110{
111	struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
112	struct sockaddr_in6 *dst;
113	struct rtentry *rt;
114	int error, type = 0, code = 0;
115	struct mbuf *mcopy = NULL;
116	struct ifnet *origifp;	/* maybe unnecessary */
117#ifdef IPSEC
118	struct secpolicy *sp = NULL;
119#endif
120
121#ifdef IPSEC
122	/*
123	 * Check AH/ESP integrity.
124	 */
125	/*
126	 * Don't increment ip6s_cantforward because this is the check
127	 * before forwarding packet actually.
128	 */
129	if (ipsec6_in_reject(m, NULL)) {
130#if !defined(FAST_IPSEC)
131		ipsec6stat.in_polvio++;
132#endif
133		m_freem(m);
134		return;
135	}
136#endif /* IPSEC */
137
138	/*
139	 * Do not forward packets to multicast destination (should be handled
140	 * by ip6_mforward().
141	 * Do not forward packets with unspecified source.  It was discussed
142	 * in July 2000, on the ipngwg mailing list.
143	 */
144	if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
145	    IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
146	    IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
147		ip6stat.ip6s_cantforward++;
148		/* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
149		if (ip6_log_time + ip6_log_interval < time_second) {
150			ip6_log_time = time_second;
151			log(LOG_DEBUG,
152			    "cannot forward "
153			    "from %s to %s nxt %d received on %s\n",
154			    ip6_sprintf(&ip6->ip6_src),
155			    ip6_sprintf(&ip6->ip6_dst),
156			    ip6->ip6_nxt,
157			    if_name(m->m_pkthdr.rcvif));
158		}
159		m_freem(m);
160		return;
161	}
162
163	if (ip6->ip6_hlim <= IPV6_HLIMDEC) {
164		/* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
165		icmp6_error(m, ICMP6_TIME_EXCEEDED,
166				ICMP6_TIME_EXCEED_TRANSIT, 0);
167		return;
168	}
169	ip6->ip6_hlim -= IPV6_HLIMDEC;
170
171	/*
172	 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
173	 * size of IPv6 + ICMPv6 headers) bytes of the packet in case
174	 * we need to generate an ICMP6 message to the src.
175	 * Thanks to M_EXT, in most cases copy will not occur.
176	 *
177	 * It is important to save it before IPsec processing as IPsec
178	 * processing may modify the mbuf.
179	 */
180	mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN));
181
182#ifdef IPSEC
183	/* get a security policy for this packet */
184	sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND,
185	    IP_FORWARDING, &error);
186	if (sp == NULL) {
187		ipsec6stat.out_inval++;
188		ip6stat.ip6s_cantforward++;
189		if (mcopy) {
190#if 0
191			/* XXX: what icmp ? */
192#else
193			m_freem(mcopy);
194#endif
195		}
196		m_freem(m);
197		return;
198	}
199
200	error = 0;
201
202	/* check policy */
203	switch (sp->policy) {
204	case IPSEC_POLICY_DISCARD:
205		/*
206		 * This packet is just discarded.
207		 */
208		ipsec6stat.out_polvio++;
209		ip6stat.ip6s_cantforward++;
210		key_freesp(sp);
211		if (mcopy) {
212#if 0
213			/* XXX: what icmp ? */
214#else
215			m_freem(mcopy);
216#endif
217		}
218		m_freem(m);
219		return;
220
221	case IPSEC_POLICY_BYPASS:
222	case IPSEC_POLICY_NONE:
223		/* no need to do IPsec. */
224		key_freesp(sp);
225		goto skip_ipsec;
226
227	case IPSEC_POLICY_IPSEC:
228		if (sp->req == NULL) {
229			/* XXX should be panic ? */
230			printf("ip6_forward: No IPsec request specified.\n");
231			ip6stat.ip6s_cantforward++;
232			key_freesp(sp);
233			if (mcopy) {
234#if 0
235				/* XXX: what icmp ? */
236#else
237				m_freem(mcopy);
238#endif
239			}
240			m_freem(m);
241			return;
242		}
243		/* do IPsec */
244		break;
245
246	case IPSEC_POLICY_ENTRUST:
247	default:
248		/* should be panic ?? */
249		printf("ip6_forward: Invalid policy found. %d\n", sp->policy);
250		key_freesp(sp);
251		goto skip_ipsec;
252	}
253
254    {
255	struct ipsec_output_state state;
256
257	/*
258	 * All the extension headers will become inaccessible
259	 * (since they can be encrypted).
260	 * Don't panic, we need no more updates to extension headers
261	 * on inner IPv6 packet (since they are now encapsulated).
262	 *
263	 * IPv6 [ESP|AH] IPv6 [extension headers] payload
264	 */
265	bzero(&state, sizeof(state));
266	state.m = m;
267	state.ro = NULL;	/* update at ipsec6_output_tunnel() */
268	state.dst = NULL;	/* update at ipsec6_output_tunnel() */
269
270	error = ipsec6_output_tunnel(&state, sp, 0);
271
272	m = state.m;
273	key_freesp(sp);
274
275	if (error) {
276		/* mbuf is already reclaimed in ipsec6_output_tunnel. */
277		switch (error) {
278		case EHOSTUNREACH:
279		case ENETUNREACH:
280		case EMSGSIZE:
281		case ENOBUFS:
282		case ENOMEM:
283			break;
284		default:
285			printf("ip6_output (ipsec): error code %d\n", error);
286			/* FALLTHROUGH */
287		case ENOENT:
288			/* don't show these error codes to the user */
289			break;
290		}
291		ip6stat.ip6s_cantforward++;
292		if (mcopy) {
293#if 0
294			/* XXX: what icmp ? */
295#else
296			m_freem(mcopy);
297#endif
298		}
299		m_freem(m);
300		return;
301	}
302    }
303    skip_ipsec:
304#endif /* IPSEC */
305
306	dst = (struct sockaddr_in6 *)&ip6_forward_rt.ro_dst;
307	if (!srcrt) {
308		/* ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst */
309		if (ip6_forward_rt.ro_rt == 0 ||
310		    (ip6_forward_rt.ro_rt->rt_flags & RTF_UP) == 0) {
311			if (ip6_forward_rt.ro_rt) {
312				RTFREE(ip6_forward_rt.ro_rt);
313				ip6_forward_rt.ro_rt = 0;
314			}
315
316			/* this probably fails but give it a try again */
317			rtalloc_ign((struct route *)&ip6_forward_rt,
318				    RTF_PRCLONING);
319		}
320
321		if (ip6_forward_rt.ro_rt == 0) {
322			ip6stat.ip6s_noroute++;
323			in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
324			if (mcopy) {
325				icmp6_error(mcopy, ICMP6_DST_UNREACH,
326					    ICMP6_DST_UNREACH_NOROUTE, 0);
327			}
328			m_freem(m);
329			return;
330		}
331	} else if ((rt = ip6_forward_rt.ro_rt) == 0 ||
332		   !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) {
333		if (ip6_forward_rt.ro_rt) {
334			RTFREE(ip6_forward_rt.ro_rt);
335			ip6_forward_rt.ro_rt = 0;
336		}
337		bzero(dst, sizeof(*dst));
338		dst->sin6_len = sizeof(struct sockaddr_in6);
339		dst->sin6_family = AF_INET6;
340		dst->sin6_addr = ip6->ip6_dst;
341
342  		rtalloc_ign((struct route *)&ip6_forward_rt, RTF_PRCLONING);
343		if (ip6_forward_rt.ro_rt == 0) {
344			ip6stat.ip6s_noroute++;
345			in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
346			if (mcopy) {
347				icmp6_error(mcopy, ICMP6_DST_UNREACH,
348					    ICMP6_DST_UNREACH_NOROUTE, 0);
349			}
350			m_freem(m);
351			return;
352		}
353	}
354	rt = ip6_forward_rt.ro_rt;
355
356	/*
357	 * Scope check: if a packet can't be delivered to its destination
358	 * for the reason that the destination is beyond the scope of the
359	 * source address, discard the packet and return an icmp6 destination
360	 * unreachable error with Code 2 (beyond scope of source address).
361	 * [draft-ietf-ipngwg-icmp-v3-02.txt, Section 3.1]
362	 */
363	if (in6_addr2scopeid(m->m_pkthdr.rcvif, &ip6->ip6_src) !=
364	    in6_addr2scopeid(rt->rt_ifp, &ip6->ip6_src)) {
365		ip6stat.ip6s_cantforward++;
366		ip6stat.ip6s_badscope++;
367		in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard);
368
369		if (ip6_log_time + ip6_log_interval < time_second) {
370			ip6_log_time = time_second;
371			log(LOG_DEBUG,
372			    "cannot forward "
373			    "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
374			    ip6_sprintf(&ip6->ip6_src),
375			    ip6_sprintf(&ip6->ip6_dst),
376			    ip6->ip6_nxt,
377			    if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp));
378		}
379		if (mcopy)
380			icmp6_error(mcopy, ICMP6_DST_UNREACH,
381				    ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
382		m_freem(m);
383		return;
384	}
385
386	if (m->m_pkthdr.len > rt->rt_ifp->if_mtu) {
387		in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig);
388		if (mcopy) {
389			u_long mtu;
390#ifdef IPSEC
391			struct secpolicy *sp;
392			int ipsecerror;
393			size_t ipsechdrsiz;
394#endif
395
396			mtu = rt->rt_ifp->if_mtu;
397#ifdef IPSEC
398			/*
399			 * When we do IPsec tunnel ingress, we need to play
400			 * with if_mtu value (decrement IPsec header size
401			 * from mtu value).  The code is much simpler than v4
402			 * case, as we have the outgoing interface for
403			 * encapsulated packet as "rt->rt_ifp".
404			 */
405			sp = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND,
406				IP_FORWARDING, &ipsecerror);
407			if (sp) {
408				ipsechdrsiz = ipsec6_hdrsiz(mcopy,
409					IPSEC_DIR_OUTBOUND, NULL);
410				if (ipsechdrsiz < mtu)
411					mtu -= ipsechdrsiz;
412			}
413
414			/*
415			 * if mtu becomes less than minimum MTU,
416			 * tell minimum MTU (and I'll need to fragment it).
417			 */
418			if (mtu < IPV6_MMTU)
419				mtu = IPV6_MMTU;
420#endif
421			icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu);
422		}
423		m_freem(m);
424		return;
425	}
426
427	if (rt->rt_flags & RTF_GATEWAY)
428		dst = (struct sockaddr_in6 *)rt->rt_gateway;
429
430	/*
431	 * If we are to forward the packet using the same interface
432	 * as one we got the packet from, perhaps we should send a redirect
433	 * to sender to shortcut a hop.
434	 * Only send redirect if source is sending directly to us,
435	 * and if packet was not source routed (or has any options).
436	 * Also, don't send redirect if forwarding using a route
437	 * modified by a redirect.
438	 */
439	if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt &&
440	    (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) {
441		if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) != 0) {
442			/*
443			 * If the incoming interface is equal to the outgoing
444			 * one, and the link attached to the interface is
445			 * point-to-point, then it will be highly probable
446			 * that a routing loop occurs. Thus, we immediately
447			 * drop the packet and send an ICMPv6 error message.
448			 *
449			 * type/code is based on suggestion by Rich Draves.
450			 * not sure if it is the best pick.
451			 */
452			icmp6_error(mcopy, ICMP6_DST_UNREACH,
453				    ICMP6_DST_UNREACH_ADDR, 0);
454			m_freem(m);
455			return;
456		}
457		type = ND_REDIRECT;
458	}
459
460	/*
461	 * Check with the firewall...
462	 */
463	if (ip6_fw_enable && ip6_fw_chk_ptr) {
464		u_short port = 0;
465		/* If ipfw says divert, we have to just drop packet */
466		if ((*ip6_fw_chk_ptr)(&ip6, rt->rt_ifp, &port, &m)) {
467			m_freem(m);
468			goto freecopy;
469		}
470		if (!m)
471			goto freecopy;
472	}
473
474	/*
475	 * Fake scoped addresses. Note that even link-local source or
476	 * destinaion can appear, if the originating node just sends the
477	 * packet to us (without address resolution for the destination).
478	 * Since both icmp6_error and icmp6_redirect_output fill the embedded
479	 * link identifiers, we can do this stuff after making a copy for
480	 * returning an error.
481	 */
482	if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) {
483		/*
484		 * See corresponding comments in ip6_output.
485		 * XXX: but is it possible that ip6_forward() sends a packet
486		 *      to a loopback interface? I don't think so, and thus
487		 *      I bark here. (jinmei@kame.net)
488		 * XXX: it is common to route invalid packets to loopback.
489		 *	also, the codepath will be visited on use of ::1 in
490		 *	rthdr. (itojun)
491		 */
492#if 1
493		if (0)
494#else
495		if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0)
496#endif
497		{
498			printf("ip6_forward: outgoing interface is loopback. "
499			       "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
500			       ip6_sprintf(&ip6->ip6_src),
501			       ip6_sprintf(&ip6->ip6_dst),
502			       ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif),
503			       if_name(rt->rt_ifp));
504		}
505
506		/* we can just use rcvif in forwarding. */
507		origifp = m->m_pkthdr.rcvif;
508	}
509	else
510		origifp = rt->rt_ifp;
511	/*
512	 * clear embedded scope identifiers if necessary.
513	 * in6_clearscope will touch the addresses only when necessary.
514	 */
515	in6_clearscope(&ip6->ip6_src);
516	in6_clearscope(&ip6->ip6_dst);
517
518#ifdef PFIL_HOOKS
519	/*
520	 * Run through list of hooks for output packets.
521	 */
522	error = pfil_run_hooks(&inet6_pfil_hook, &m, rt->rt_ifp, PFIL_OUT);
523	if (error != 0)
524		goto senderr;
525	if (m == NULL)
526		goto freecopy;
527	ip6 = mtod(m, struct ip6_hdr *);
528#endif /* PFIL_HOOKS */
529
530	error = nd6_output(rt->rt_ifp, origifp, m, dst, rt);
531	if (error) {
532		in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard);
533		ip6stat.ip6s_cantforward++;
534	} else {
535		ip6stat.ip6s_forward++;
536		in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward);
537		if (type)
538			ip6stat.ip6s_redirectsent++;
539		else {
540			if (mcopy)
541				goto freecopy;
542		}
543	}
544
545#ifdef PFIL_HOOKS
546senderr:
547#endif
548	if (mcopy == NULL)
549		return;
550	switch (error) {
551	case 0:
552		if (type == ND_REDIRECT) {
553			icmp6_redirect_output(mcopy, rt);
554			return;
555		}
556		goto freecopy;
557
558	case EMSGSIZE:
559		/* xxx MTU is constant in PPP? */
560		goto freecopy;
561
562	case ENOBUFS:
563		/* Tell source to slow down like source quench in IP? */
564		goto freecopy;
565
566	case ENETUNREACH:	/* shouldn't happen, checked above */
567	case EHOSTUNREACH:
568	case ENETDOWN:
569	case EHOSTDOWN:
570	default:
571		type = ICMP6_DST_UNREACH;
572		code = ICMP6_DST_UNREACH_ADDR;
573		break;
574	}
575	icmp6_error(mcopy, type, code, 0);
576	return;
577
578 freecopy:
579	m_freem(mcopy);
580	return;
581}
582