1/*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the project nor the names of its contributors
16 *    may be used to endorse or promote products derived from this software
17 *    without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 *
31 *	$KAME: ip6_forward.c,v 1.69 2001/05/17 03:48:30 itojun Exp $
32 */
33
34#include <sys/cdefs.h>
35#include "opt_inet.h"
36#include "opt_inet6.h"
37#include "opt_ipsec.h"
38#include "opt_ipstealth.h"
39#include "opt_sctp.h"
40
41#include <sys/param.h>
42#include <sys/systm.h>
43#include <sys/malloc.h>
44#include <sys/mbuf.h>
45#include <sys/domain.h>
46#include <sys/protosw.h>
47#include <sys/socket.h>
48#include <sys/errno.h>
49#include <sys/time.h>
50#include <sys/kernel.h>
51#include <sys/syslog.h>
52
53#include <net/if.h>
54#include <net/if_var.h>
55#include <net/if_private.h>
56#include <net/netisr.h>
57#include <net/route.h>
58#include <net/route/nhop.h>
59#include <net/pfil.h>
60
61#include <netinet/in.h>
62#include <netinet/in_var.h>
63#include <netinet/in_systm.h>
64#include <netinet/ip.h>
65#include <netinet/ip_var.h>
66#include <netinet6/in6_var.h>
67#include <netinet/ip6.h>
68#include <netinet6/in6_fib.h>
69#include <netinet6/ip6_var.h>
70#include <netinet6/scope6_var.h>
71#include <netinet/icmp6.h>
72#include <netinet6/nd6.h>
73
74#include <netinet/in_pcb.h>
75
76#include <netipsec/ipsec_support.h>
77
78/*
79 * Forward a packet.  If some error occurs return the sender
80 * an icmp packet.  Note we can't always generate a meaningful
81 * icmp message because icmp doesn't have a large enough repertoire
82 * of codes and types.
83 *
84 * If not forwarding, just drop the packet.  This could be confusing
85 * if ipforwarding was zero but some routing protocol was advancing
86 * us as a gateway to somewhere.  However, we must let the routing
87 * protocol deal with that.
88 *
89 */
90void
91ip6_forward(struct mbuf *m, int srcrt)
92{
93	struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
94	struct sockaddr_in6 dst;
95	struct nhop_object *nh = NULL;
96	int error, type = 0, code = 0;
97	struct mbuf *mcopy = NULL;
98	struct ifnet *origifp;	/* maybe unnecessary */
99	u_int32_t inzone, outzone;
100	struct in6_addr odst;
101	struct m_tag *fwd_tag;
102	char ip6bufs[INET6_ADDRSTRLEN], ip6bufd[INET6_ADDRSTRLEN];
103
104	/*
105	 * Do not forward packets to multicast destination (should be handled
106	 * by ip6_mforward().
107	 * Do not forward packets with unspecified source.  It was discussed
108	 * in July 2000, on the ipngwg mailing list.
109	 */
110	if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
111	    IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
112	    IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
113		IP6STAT_INC(ip6s_cantforward);
114		/* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
115		if (V_ip6_log_cannot_forward && ip6_log_ratelimit()) {
116			log(LOG_DEBUG,
117			    "cannot forward "
118			    "from %s to %s nxt %d received on %s\n",
119			    ip6_sprintf(ip6bufs, &ip6->ip6_src),
120			    ip6_sprintf(ip6bufd, &ip6->ip6_dst),
121			    ip6->ip6_nxt,
122			    if_name(m->m_pkthdr.rcvif));
123		}
124		m_freem(m);
125		return;
126	}
127
128	if (
129#ifdef IPSTEALTH
130	    V_ip6stealth == 0 &&
131#endif
132	    ip6->ip6_hlim <= IPV6_HLIMDEC) {
133		/* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
134		icmp6_error(m, ICMP6_TIME_EXCEEDED,
135		    ICMP6_TIME_EXCEED_TRANSIT, 0);
136		return;
137	}
138
139	/*
140	 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
141	 * size of IPv6 + ICMPv6 headers) bytes of the packet in case
142	 * we need to generate an ICMP6 message to the src.
143	 * Thanks to M_EXT, in most cases copy will not occur.
144	 *
145	 * It is important to save it before IPsec processing as IPsec
146	 * processing may modify the mbuf.
147	 */
148	mcopy = m_copym(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN),
149	    M_NOWAIT);
150#ifdef IPSTEALTH
151	if (V_ip6stealth == 0)
152#endif
153		ip6->ip6_hlim -= IPV6_HLIMDEC;
154
155#if defined(IPSEC) || defined(IPSEC_SUPPORT)
156	if (IPSEC_ENABLED(ipv6)) {
157		if ((error = IPSEC_FORWARD(ipv6, m)) != 0) {
158			/* mbuf consumed by IPsec */
159			m_freem(mcopy);
160			if (error != EINPROGRESS)
161				IP6STAT_INC(ip6s_cantforward);
162			return;
163		}
164		/* No IPsec processing required */
165	}
166#endif
167	/*
168	 * ip6_forward() operates with IPv6 addresses with deembedded scope.
169	 *
170	 * There are 3 sources of IPv6 destination address:
171	 *
172	 * 1) ip6_input(), where ip6_dst contains deembedded address.
173	 *   In order to deal with forwarding of link-local packets,
174	 *   calculate the scope based on input interface (RFC 4007, clause 9).
175	 * 2) packet filters changing ip6_dst directly. It would embed scope
176	 *   for LL addresses, so in6_localip() performs properly.
177	 * 3) packet filters attaching PACKET_TAG_IPFORWARD would embed
178	 *   scope for the nexthop.
179	 */
180	bzero(&dst, sizeof(struct sockaddr_in6));
181	dst.sin6_family = AF_INET6;
182	dst.sin6_addr = ip6->ip6_dst;
183	dst.sin6_scope_id = in6_get_unicast_scopeid(&ip6->ip6_dst, m->m_pkthdr.rcvif);
184again:
185	nh = fib6_lookup(M_GETFIB(m), &dst.sin6_addr, dst.sin6_scope_id,
186	    NHR_REF, m->m_pkthdr.flowid);
187	if (nh == NULL) {
188		IP6STAT_INC(ip6s_noroute);
189		in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
190		if (mcopy) {
191			icmp6_error(mcopy, ICMP6_DST_UNREACH,
192			ICMP6_DST_UNREACH_NOROUTE, 0);
193		}
194		goto bad;
195	}
196
197	if (nh->nh_flags & (NHF_BLACKHOLE | NHF_REJECT)) {
198		IP6STAT_INC(ip6s_cantforward);
199		if (mcopy != NULL) {
200			if (nh->nh_flags & NHF_REJECT) {
201				icmp6_error(mcopy, ICMP6_DST_UNREACH,
202				    ICMP6_DST_UNREACH_REJECT, 0);
203			} else
204				m_freem(mcopy);
205		}
206		goto bad;
207	}
208
209	/*
210	 * Source scope check: if a packet can't be delivered to its
211	 * destination for the reason that the destination is beyond the scope
212	 * of the source address, discard the packet and return an icmp6
213	 * destination unreachable error with Code 2 (beyond scope of source
214	 * address).
215	 * [draft-ietf-ipngwg-icmp-v3-04.txt, Section 3.1]
216	 */
217	outzone = in6_get_unicast_scopeid(&ip6->ip6_src, nh->nh_ifp);
218	inzone = in6_get_unicast_scopeid(&ip6->ip6_src, m->m_pkthdr.rcvif);
219	if (inzone != outzone) {
220		IP6STAT_INC(ip6s_cantforward);
221		IP6STAT_INC(ip6s_badscope);
222		in6_ifstat_inc(nh->nh_ifp, ifs6_in_discard);
223
224		if (V_ip6_log_cannot_forward && ip6_log_ratelimit()) {
225			log(LOG_DEBUG,
226			    "cannot forward "
227			    "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
228			    ip6_sprintf(ip6bufs, &ip6->ip6_src),
229			    ip6_sprintf(ip6bufd, &ip6->ip6_dst),
230			    ip6->ip6_nxt,
231			    if_name(m->m_pkthdr.rcvif), if_name(nh->nh_ifp));
232		}
233		if (mcopy)
234			icmp6_error(mcopy, ICMP6_DST_UNREACH,
235				    ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
236		goto bad;
237	}
238
239	/*
240	 * Destination scope check: if a packet is going to break the scope
241	 * zone of packet's destination address, discard it.  This case should
242	 * usually be prevented by appropriately-configured routing table, but
243	 * we need an explicit check because we may mistakenly forward the
244	 * packet to a different zone by (e.g.) a default route.
245	 */
246	inzone = in6_get_unicast_scopeid(&ip6->ip6_dst, m->m_pkthdr.rcvif);
247	outzone = in6_get_unicast_scopeid(&ip6->ip6_dst, nh->nh_ifp);
248
249	if (inzone != outzone) {
250		IP6STAT_INC(ip6s_cantforward);
251		IP6STAT_INC(ip6s_badscope);
252		goto bad;
253	}
254
255	if (nh->nh_flags & NHF_GATEWAY) {
256		/* Store gateway address in deembedded form */
257		dst.sin6_addr = nh->gw6_sa.sin6_addr;
258		dst.sin6_scope_id = ntohs(in6_getscope(&dst.sin6_addr));
259		in6_clearscope(&dst.sin6_addr);
260	}
261
262	/*
263	 * If we are to forward the packet using the same interface
264	 * as one we got the packet from, perhaps we should send a redirect
265	 * to sender to shortcut a hop.
266	 * Only send redirect if source is sending directly to us,
267	 * and if packet was not source routed (or has any options).
268	 * Also, don't send redirect if forwarding using a route
269	 * modified by a redirect.
270	 */
271	if (V_ip6_sendredirects && nh->nh_ifp == m->m_pkthdr.rcvif && !srcrt &&
272	    (nh->nh_flags & NHF_REDIRECT) == 0)
273		type = ND_REDIRECT;
274
275	/*
276	 * Fake scoped addresses. Note that even link-local source or
277	 * destinaion can appear, if the originating node just sends the
278	 * packet to us (without address resolution for the destination).
279	 * Since both icmp6_error and icmp6_redirect_output fill the embedded
280	 * link identifiers, we can do this stuff after making a copy for
281	 * returning an error.
282	 */
283	if ((nh->nh_ifp->if_flags & IFF_LOOPBACK) != 0) {
284		/*
285		 * See corresponding comments in ip6_output.
286		 * XXX: but is it possible that ip6_forward() sends a packet
287		 *      to a loopback interface? I don't think so, and thus
288		 *      I bark here. (jinmei@kame.net)
289		 * XXX: it is common to route invalid packets to loopback.
290		 *	also, the codepath will be visited on use of ::1 in
291		 *	rthdr. (itojun)
292		 */
293#if 1
294		if (0)
295#else
296		if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0)
297#endif
298		{
299			printf("ip6_forward: outgoing interface is loopback. "
300			       "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
301			       ip6_sprintf(ip6bufs, &ip6->ip6_src),
302			       ip6_sprintf(ip6bufd, &ip6->ip6_dst),
303			       ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif),
304			       if_name(nh->nh_ifp));
305		}
306
307		/* we can just use rcvif in forwarding. */
308		origifp = m->m_pkthdr.rcvif;
309	}
310	else
311		origifp = nh->nh_ifp;
312	/*
313	 * clear embedded scope identifiers if necessary.
314	 * in6_clearscope will touch the addresses only when necessary.
315	 */
316	in6_clearscope(&ip6->ip6_src);
317	in6_clearscope(&ip6->ip6_dst);
318
319	/* Jump over all PFIL processing if hooks are not active. */
320	if (!PFIL_HOOKED_OUT(V_inet6_pfil_head))
321		goto pass;
322
323	odst = ip6->ip6_dst;
324	/* Run through list of hooks for forwarded packets. */
325	if (pfil_mbuf_fwd(V_inet6_pfil_head, &m, nh->nh_ifp,
326	    NULL) != PFIL_PASS)
327		goto freecopy;
328	ip6 = mtod(m, struct ip6_hdr *);
329
330	/* See if destination IP address was changed by packet filter. */
331	if (!IN6_ARE_ADDR_EQUAL(&odst, &ip6->ip6_dst)) {
332		m->m_flags |= M_SKIP_FIREWALL;
333		/* If destination is now ourself drop to ip6_input(). */
334		if (in6_localip(&ip6->ip6_dst))
335			m->m_flags |= M_FASTFWD_OURS;
336		else {
337			NH_FREE(nh);
338
339			/* Update address and scopeid. Assume scope is embedded */
340			dst.sin6_scope_id = ntohs(in6_getscope(&ip6->ip6_dst));
341			dst.sin6_addr = ip6->ip6_dst;
342			in6_clearscope(&dst.sin6_addr);
343			goto again;	/* Redo the routing table lookup. */
344		}
345	}
346
347	/* See if local, if yes, send it to netisr. */
348	if (m->m_flags & M_FASTFWD_OURS) {
349		if (m->m_pkthdr.rcvif == NULL)
350			m->m_pkthdr.rcvif = V_loif;
351		if (m->m_pkthdr.csum_flags & CSUM_DELAY_DATA_IPV6) {
352			m->m_pkthdr.csum_flags |=
353			    CSUM_DATA_VALID_IPV6 | CSUM_PSEUDO_HDR;
354			m->m_pkthdr.csum_data = 0xffff;
355		}
356#if defined(SCTP) || defined(SCTP_SUPPORT)
357		if (m->m_pkthdr.csum_flags & CSUM_SCTP_IPV6)
358			m->m_pkthdr.csum_flags |= CSUM_SCTP_VALID;
359#endif
360		error = netisr_queue(NETISR_IPV6, m);
361		goto out;
362	}
363	/* Or forward to some other address? */
364	if ((m->m_flags & M_IP6_NEXTHOP) &&
365	    (fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL)) != NULL) {
366		struct sockaddr_in6 *gw6 = (struct sockaddr_in6 *)(fwd_tag + 1);
367
368		/* Update address and scopeid. Assume scope is embedded */
369		dst.sin6_scope_id = ntohs(in6_getscope(&gw6->sin6_addr));
370		dst.sin6_addr = gw6->sin6_addr;
371		in6_clearscope(&dst.sin6_addr);
372
373		m->m_flags |= M_SKIP_FIREWALL;
374		m->m_flags &= ~M_IP6_NEXTHOP;
375		m_tag_delete(m, fwd_tag);
376		NH_FREE(nh);
377		goto again;
378	}
379
380pass:
381	/* See if the size was changed by the packet filter. */
382	/* TODO: change to nh->nh_mtu */
383	if (m->m_pkthdr.len > IN6_LINKMTU(nh->nh_ifp)) {
384		in6_ifstat_inc(nh->nh_ifp, ifs6_in_toobig);
385		if (mcopy)
386			icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0,
387			    IN6_LINKMTU(nh->nh_ifp));
388		goto bad;
389	}
390
391	/* Currently LLE layer stores embedded IPv6 addresses */
392	if (IN6_IS_SCOPE_LINKLOCAL(&dst.sin6_addr)) {
393		in6_set_unicast_scopeid(&dst.sin6_addr, dst.sin6_scope_id);
394		dst.sin6_scope_id = 0;
395	}
396	error = nd6_output_ifp(nh->nh_ifp, origifp, m, &dst, NULL);
397	if (error) {
398		in6_ifstat_inc(nh->nh_ifp, ifs6_out_discard);
399		IP6STAT_INC(ip6s_cantforward);
400	} else {
401		IP6STAT_INC(ip6s_forward);
402		in6_ifstat_inc(nh->nh_ifp, ifs6_out_forward);
403		if (type)
404			IP6STAT_INC(ip6s_redirectsent);
405		else {
406			if (mcopy)
407				goto freecopy;
408		}
409	}
410
411	if (mcopy == NULL)
412		goto out;
413	switch (error) {
414	case 0:
415		if (type == ND_REDIRECT) {
416			icmp6_redirect_output(mcopy, nh);
417			goto out;
418		}
419		goto freecopy;
420
421	case EMSGSIZE:
422		/* xxx MTU is constant in PPP? */
423		goto freecopy;
424
425	case ENOBUFS:
426		/* Tell source to slow down like source quench in IP? */
427		goto freecopy;
428
429	case ENETUNREACH:	/* shouldn't happen, checked above */
430	case EHOSTUNREACH:
431	case ENETDOWN:
432	case EHOSTDOWN:
433	default:
434		type = ICMP6_DST_UNREACH;
435		code = ICMP6_DST_UNREACH_ADDR;
436		break;
437	}
438	icmp6_error(mcopy, type, code, 0);
439	goto out;
440
441 freecopy:
442	m_freem(mcopy);
443	goto out;
444bad:
445	m_freem(m);
446out:
447	if (nh != NULL)
448		NH_FREE(nh);
449}
450