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 "opt_inet.h"
35 #include "opt_inet6.h"
36 #include "opt_ipsec.h"
37 #include "opt_ipstealth.h"
38 #include "opt_sctp.h"
39
40 #include <sys/param.h>
41 #include <sys/systm.h>
42 #include <sys/malloc.h>
43 #include <sys/mbuf.h>
44 #include <sys/domain.h>
45 #include <sys/protosw.h>
46 #include <sys/socket.h>
47 #include <sys/errno.h>
48 #include <sys/time.h>
49 #include <sys/kernel.h>
50 #include <sys/syslog.h>
51
52 #include <net/if.h>
53 #include <net/if_var.h>
54 #include <net/if_private.h>
55 #include <net/netisr.h>
56 #include <net/route.h>
57 #include <net/route/nhop.h>
58 #include <net/pfil.h>
59
60 #include <netinet/in.h>
61 #include <netinet/in_var.h>
62 #include <netinet/in_systm.h>
63 #include <netinet/ip.h>
64 #include <netinet/ip_var.h>
65 #include <netinet6/in6_var.h>
66 #include <netinet/ip6.h>
67 #include <netinet6/in6_fib.h>
68 #include <netinet6/ip6_var.h>
69 #include <netinet6/scope6_var.h>
70 #include <netinet/icmp6.h>
71 #include <netinet6/nd6.h>
72
73 #include <netinet/in_pcb.h>
74
75 #include <netipsec/ipsec_support.h>
76
77 #if defined(SCTP) || defined(SCTP_SUPPORT)
78 #include <netinet/sctp_crc32.h>
79 #endif
80
81 /*
82 * Forward a packet. If some error occurs return the sender
83 * an icmp packet. Note we can't always generate a meaningful
84 * icmp message because icmp doesn't have a large enough repertoire
85 * of codes and types.
86 *
87 * If not forwarding, just drop the packet. This could be confusing
88 * if ipforwarding was zero but some routing protocol was advancing
89 * us as a gateway to somewhere. However, we must let the routing
90 * protocol deal with that.
91 *
92 */
93 void
ip6_forward(struct mbuf * m,int srcrt)94 ip6_forward(struct mbuf *m, int srcrt)
95 {
96 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
97 struct sockaddr_in6 dst;
98 struct nhop_object *nh = NULL;
99 int error, type = 0, code = 0;
100 struct mbuf *mcopy = NULL;
101 struct ifnet *origifp; /* maybe unnecessary */
102 u_int32_t inzone, outzone;
103 struct in6_addr odst;
104 struct m_tag *fwd_tag;
105 char ip6bufs[INET6_ADDRSTRLEN], ip6bufd[INET6_ADDRSTRLEN];
106
107 /*
108 * Do not forward packets to multicast destination (should be handled
109 * by ip6_mforward().
110 * Do not forward packets with unspecified source. It was discussed
111 * in July 2000, on the ipngwg mailing list.
112 */
113 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
114 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
115 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src) ||
116 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_dst)) {
117 IP6STAT_INC(ip6s_cantforward);
118 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
119 if (V_ip6_log_cannot_forward && ip6_log_ratelimit()) {
120 log(LOG_DEBUG,
121 "cannot forward "
122 "from %s to %s nxt %d received on %s\n",
123 ip6_sprintf(ip6bufs, &ip6->ip6_src),
124 ip6_sprintf(ip6bufd, &ip6->ip6_dst),
125 ip6->ip6_nxt,
126 if_name(m->m_pkthdr.rcvif));
127 }
128 m_freem(m);
129 return;
130 }
131
132 if (
133 #ifdef IPSTEALTH
134 V_ip6stealth == 0 &&
135 #endif
136 ip6->ip6_hlim <= IPV6_HLIMDEC) {
137 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
138 icmp6_error(m, ICMP6_TIME_EXCEEDED,
139 ICMP6_TIME_EXCEED_TRANSIT, 0);
140 return;
141 }
142
143 /*
144 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
145 * size of IPv6 + ICMPv6 headers) bytes of the packet in case
146 * we need to generate an ICMP6 message to the src.
147 * Thanks to M_EXT, in most cases copy will not occur.
148 *
149 * It is important to save it before IPsec processing as IPsec
150 * processing may modify the mbuf.
151 */
152 mcopy = m_copym(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN),
153 M_NOWAIT);
154 #ifdef IPSTEALTH
155 if (V_ip6stealth == 0)
156 #endif
157 ip6->ip6_hlim -= IPV6_HLIMDEC;
158
159 #if defined(IPSEC) || defined(IPSEC_SUPPORT)
160 if (IPSEC_ENABLED(ipv6)) {
161 if ((error = IPSEC_FORWARD(ipv6, m)) != 0) {
162 /* mbuf consumed by IPsec */
163 m_freem(mcopy);
164 if (error != EINPROGRESS)
165 IP6STAT_INC(ip6s_cantforward);
166 return;
167 }
168 /* No IPsec processing required */
169 }
170 #endif
171 /*
172 * ip6_forward() operates with IPv6 addresses with deembedded scope.
173 *
174 * There are 3 sources of IPv6 destination address:
175 *
176 * 1) ip6_input(), where ip6_dst contains deembedded address.
177 * In order to deal with forwarding of link-local packets,
178 * calculate the scope based on input interface (RFC 4007, clause 9).
179 * 2) packet filters changing ip6_dst directly. It would embed scope
180 * for LL addresses, so in6_localip() performs properly.
181 * 3) packet filters attaching PACKET_TAG_IPFORWARD would embed
182 * scope for the nexthop.
183 */
184 bzero(&dst, sizeof(struct sockaddr_in6));
185 dst.sin6_family = AF_INET6;
186 dst.sin6_addr = ip6->ip6_dst;
187 dst.sin6_scope_id = in6_get_unicast_scopeid(&ip6->ip6_dst, m->m_pkthdr.rcvif);
188 again:
189 nh = fib6_lookup(M_GETFIB(m), &dst.sin6_addr, dst.sin6_scope_id,
190 NHR_REF, m->m_pkthdr.flowid);
191 if (nh == NULL) {
192 IP6STAT_INC(ip6s_noroute);
193 in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
194 if (mcopy) {
195 icmp6_error(mcopy, ICMP6_DST_UNREACH,
196 ICMP6_DST_UNREACH_NOROUTE, 0);
197 }
198 goto bad;
199 }
200
201 if (nh->nh_flags & (NHF_BLACKHOLE | NHF_REJECT)) {
202 IP6STAT_INC(ip6s_cantforward);
203 if (mcopy != NULL) {
204 if (nh->nh_flags & NHF_REJECT) {
205 icmp6_error(mcopy, ICMP6_DST_UNREACH,
206 ICMP6_DST_UNREACH_REJECT, 0);
207 } else
208 m_freem(mcopy);
209 }
210 goto bad;
211 }
212
213 /*
214 * Source scope check: if a packet can't be delivered to its
215 * destination for the reason that the destination is beyond the scope
216 * of the source address, discard the packet and return an icmp6
217 * destination unreachable error with Code 2 (beyond scope of source
218 * address).
219 * [draft-ietf-ipngwg-icmp-v3-04.txt, Section 3.1]
220 */
221 outzone = in6_get_unicast_scopeid(&ip6->ip6_src, nh->nh_ifp);
222 inzone = in6_get_unicast_scopeid(&ip6->ip6_src, m->m_pkthdr.rcvif);
223 if (inzone != outzone) {
224 IP6STAT_INC(ip6s_cantforward);
225 IP6STAT_INC(ip6s_badscope);
226 in6_ifstat_inc(nh->nh_ifp, ifs6_in_discard);
227
228 if (V_ip6_log_cannot_forward && ip6_log_ratelimit()) {
229 log(LOG_DEBUG,
230 "cannot forward "
231 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
232 ip6_sprintf(ip6bufs, &ip6->ip6_src),
233 ip6_sprintf(ip6bufd, &ip6->ip6_dst),
234 ip6->ip6_nxt,
235 if_name(m->m_pkthdr.rcvif), if_name(nh->nh_ifp));
236 }
237 if (mcopy)
238 icmp6_error(mcopy, ICMP6_DST_UNREACH,
239 ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
240 goto bad;
241 }
242
243 /*
244 * Destination scope check: if a packet is going to break the scope
245 * zone of packet's destination address, discard it. This case should
246 * usually be prevented by appropriately-configured routing table, but
247 * we need an explicit check because we may mistakenly forward the
248 * packet to a different zone by (e.g.) a default route.
249 */
250 inzone = in6_get_unicast_scopeid(&ip6->ip6_dst, m->m_pkthdr.rcvif);
251 outzone = in6_get_unicast_scopeid(&ip6->ip6_dst, nh->nh_ifp);
252
253 if (inzone != outzone) {
254 IP6STAT_INC(ip6s_cantforward);
255 IP6STAT_INC(ip6s_badscope);
256 goto bad;
257 }
258
259 if (nh->nh_flags & NHF_GATEWAY) {
260 /* Store gateway address in deembedded form */
261 dst.sin6_addr = nh->gw6_sa.sin6_addr;
262 dst.sin6_scope_id = ntohs(in6_getscope(&dst.sin6_addr));
263 in6_clearscope(&dst.sin6_addr);
264 }
265
266 /*
267 * If we are to forward the packet using the same interface
268 * as one we got the packet from, perhaps we should send a redirect
269 * to sender to shortcut a hop.
270 * Only send redirect if source is sending directly to us,
271 * and if packet was not source routed (or has any options).
272 * Also, don't send redirect if forwarding using a route
273 * modified by a redirect.
274 */
275 if (V_ip6_sendredirects && nh->nh_ifp == m->m_pkthdr.rcvif && !srcrt &&
276 (nh->nh_flags & NHF_REDIRECT) == 0)
277 type = ND_REDIRECT;
278
279 /*
280 * Fake scoped addresses. Note that even link-local source or
281 * destinaion can appear, if the originating node just sends the
282 * packet to us (without address resolution for the destination).
283 * Since both icmp6_error and icmp6_redirect_output fill the embedded
284 * link identifiers, we can do this stuff after making a copy for
285 * returning an error.
286 */
287 if ((nh->nh_ifp->if_flags & IFF_LOOPBACK) != 0) {
288 /*
289 * See corresponding comments in ip6_output.
290 * XXX: but is it possible that ip6_forward() sends a packet
291 * to a loopback interface? I don't think so, and thus
292 * I bark here. (jinmei@kame.net)
293 * XXX: it is common to route invalid packets to loopback.
294 * also, the codepath will be visited on use of ::1 in
295 * rthdr. (itojun)
296 */
297 #if 1
298 if (0)
299 #else
300 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0)
301 #endif
302 {
303 printf("ip6_forward: outgoing interface is loopback. "
304 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
305 ip6_sprintf(ip6bufs, &ip6->ip6_src),
306 ip6_sprintf(ip6bufd, &ip6->ip6_dst),
307 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif),
308 if_name(nh->nh_ifp));
309 }
310
311 /* we can just use rcvif in forwarding. */
312 origifp = m->m_pkthdr.rcvif;
313 }
314 else
315 origifp = nh->nh_ifp;
316 /*
317 * clear embedded scope identifiers if necessary.
318 * in6_clearscope will touch the addresses only when necessary.
319 */
320 in6_clearscope(&ip6->ip6_src);
321 in6_clearscope(&ip6->ip6_dst);
322
323 /* Jump over all PFIL processing if hooks are not active. */
324 if (!PFIL_HOOKED_OUT(V_inet6_pfil_head))
325 goto pass;
326
327 odst = ip6->ip6_dst;
328 /* Run through list of hooks for forwarded packets. */
329 if (pfil_mbuf_fwd(V_inet6_pfil_head, &m, nh->nh_ifp,
330 NULL) != PFIL_PASS)
331 goto freecopy;
332 ip6 = mtod(m, struct ip6_hdr *);
333
334 /* See if destination IP address was changed by packet filter. */
335 if (!IN6_ARE_ADDR_EQUAL(&odst, &ip6->ip6_dst)) {
336 m->m_flags |= M_SKIP_FIREWALL;
337 /* If destination is now ourself drop to ip6_input(). */
338 if (in6_localip(&ip6->ip6_dst))
339 m->m_flags |= M_FASTFWD_OURS;
340 else {
341 NH_FREE(nh);
342
343 /* Update address and scopeid. Assume scope is embedded */
344 dst.sin6_scope_id = ntohs(in6_getscope(&ip6->ip6_dst));
345 dst.sin6_addr = ip6->ip6_dst;
346 in6_clearscope(&dst.sin6_addr);
347 goto again; /* Redo the routing table lookup. */
348 }
349 }
350
351 /* See if local, if yes, send it to netisr. */
352 if (m->m_flags & M_FASTFWD_OURS) {
353 if (m->m_pkthdr.rcvif == NULL)
354 m->m_pkthdr.rcvif = V_loif;
355 if (m->m_pkthdr.csum_flags & CSUM_DELAY_DATA_IPV6) {
356 m->m_pkthdr.csum_flags |=
357 CSUM_DATA_VALID_IPV6 | CSUM_PSEUDO_HDR;
358 m->m_pkthdr.csum_data = 0xffff;
359 }
360 #if defined(SCTP) || defined(SCTP_SUPPORT)
361 if (m->m_pkthdr.csum_flags & CSUM_SCTP_IPV6)
362 m->m_pkthdr.csum_flags |= CSUM_SCTP_VALID;
363 #endif
364 error = netisr_queue(NETISR_IPV6, m);
365 goto out;
366 }
367 /* Or forward to some other address? */
368 if ((m->m_flags & M_IP6_NEXTHOP) &&
369 (fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL)) != NULL) {
370 struct sockaddr_in6 *gw6 = (struct sockaddr_in6 *)(fwd_tag + 1);
371
372 /* Update address and scopeid. Assume scope is embedded */
373 dst.sin6_scope_id = ntohs(in6_getscope(&gw6->sin6_addr));
374 dst.sin6_addr = gw6->sin6_addr;
375 in6_clearscope(&dst.sin6_addr);
376
377 m->m_flags |= M_SKIP_FIREWALL;
378 m->m_flags &= ~M_IP6_NEXTHOP;
379 m_tag_delete(m, fwd_tag);
380 NH_FREE(nh);
381 goto again;
382 }
383
384 pass:
385 /* See if the size was changed by the packet filter. */
386 /* TODO: change to nh->nh_mtu */
387 if (m->m_pkthdr.len > in6_ifmtu(nh->nh_ifp)) {
388 in6_ifstat_inc(nh->nh_ifp, ifs6_in_toobig);
389 if (mcopy)
390 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0,
391 in6_ifmtu(nh->nh_ifp));
392 goto bad;
393 }
394
395 /*
396 * If TCP/UDP header still needs a valid checksum and interface will not
397 * calculate it for us, do it here.
398 */
399 if (__predict_false(m->m_pkthdr.csum_flags & CSUM_DELAY_DATA_IPV6 &
400 ~nh->nh_ifp->if_hwassist)) {
401 int offset = ip6_lasthdr(m, 0, IPPROTO_IPV6, NULL);
402
403 if (offset < sizeof(struct ip6_hdr) || offset > m->m_pkthdr.len)
404 goto bad;
405 in6_delayed_cksum(m, m->m_pkthdr.len - offset, offset);
406 m->m_pkthdr.csum_flags &= ~CSUM_DELAY_DATA_IPV6;
407 }
408 #if defined(SCTP) || defined(SCTP_SUPPORT)
409 if (__predict_false(m->m_pkthdr.csum_flags & CSUM_IP6_SCTP &
410 ~nh->nh_ifp->if_hwassist)) {
411 int offset = ip6_lasthdr(m, 0, IPPROTO_IPV6, NULL);
412
413 sctp_delayed_cksum(m, offset);
414 m->m_pkthdr.csum_flags &= ~CSUM_IP6_SCTP;
415 }
416 #endif
417
418 /* Currently LLE layer stores embedded IPv6 addresses */
419 if (IN6_IS_SCOPE_LINKLOCAL(&dst.sin6_addr)) {
420 in6_set_unicast_scopeid(&dst.sin6_addr, dst.sin6_scope_id);
421 dst.sin6_scope_id = 0;
422 }
423 error = nd6_output_ifp(nh->nh_ifp, origifp, m, &dst, NULL);
424 if (error) {
425 in6_ifstat_inc(nh->nh_ifp, ifs6_out_discard);
426 IP6STAT_INC(ip6s_cantforward);
427 } else {
428 IP6STAT_INC(ip6s_forward);
429 in6_ifstat_inc(nh->nh_ifp, ifs6_out_forward);
430 if (type)
431 IP6STAT_INC(ip6s_redirectsent);
432 else {
433 if (mcopy)
434 goto freecopy;
435 }
436 }
437
438 if (mcopy == NULL)
439 goto out;
440 switch (error) {
441 case 0:
442 if (type == ND_REDIRECT) {
443 icmp6_redirect_output(mcopy, nh);
444 goto out;
445 }
446 goto freecopy;
447
448 case EMSGSIZE:
449 /* xxx MTU is constant in PPP? */
450 goto freecopy;
451
452 case ENOBUFS:
453 /* Tell source to slow down like source quench in IP? */
454 goto freecopy;
455
456 case ENETUNREACH: /* shouldn't happen, checked above */
457 case EHOSTUNREACH:
458 case ENETDOWN:
459 case EHOSTDOWN:
460 default:
461 type = ICMP6_DST_UNREACH;
462 code = ICMP6_DST_UNREACH_ADDR;
463 break;
464 }
465 icmp6_error(mcopy, type, code, 0);
466 goto out;
467
468 freecopy:
469 m_freem(mcopy);
470 goto out;
471 bad:
472 m_freem(m);
473 out:
474 if (nh != NULL)
475 NH_FREE(nh);
476 }
477