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 #if defined(SCTP) || defined(SCTP_SUPPORT)
79 #include <netinet/sctp_crc32.h>
80 #endif
81
82 /*
83 * Forward a packet. If some error occurs return the sender
84 * an icmp packet. Note we can't always generate a meaningful
85 * icmp message because icmp doesn't have a large enough repertoire
86 * of codes and types.
87 *
88 * If not forwarding, just drop the packet. This could be confusing
89 * if ipforwarding was zero but some routing protocol was advancing
90 * us as a gateway to somewhere. However, we must let the routing
91 * protocol deal with that.
92 *
93 */
94 void
ip6_forward(struct mbuf * m,int srcrt)95 ip6_forward(struct mbuf *m, int srcrt)
96 {
97 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
98 struct sockaddr_in6 dst;
99 struct nhop_object *nh = NULL;
100 int error, type = 0, code = 0;
101 struct mbuf *mcopy = NULL;
102 struct ifnet *origifp; /* maybe unnecessary */
103 u_int32_t inzone, outzone;
104 struct in6_addr odst;
105 struct m_tag *fwd_tag;
106 char ip6bufs[INET6_ADDRSTRLEN], ip6bufd[INET6_ADDRSTRLEN];
107
108 /*
109 * Do not forward packets to multicast destination (should be handled
110 * by ip6_mforward().
111 * Do not forward packets with unspecified source. It was discussed
112 * in July 2000, on the ipngwg mailing list.
113 */
114 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
115 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
116 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src) ||
117 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_dst)) {
118 IP6STAT_INC(ip6s_cantforward);
119 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
120 if (V_ip6_log_cannot_forward && ip6_log_ratelimit()) {
121 log(LOG_DEBUG,
122 "cannot forward "
123 "from %s to %s nxt %d received on %s\n",
124 ip6_sprintf(ip6bufs, &ip6->ip6_src),
125 ip6_sprintf(ip6bufd, &ip6->ip6_dst),
126 ip6->ip6_nxt,
127 if_name(m->m_pkthdr.rcvif));
128 }
129 m_freem(m);
130 return;
131 }
132
133 if (
134 #ifdef IPSTEALTH
135 V_ip6stealth == 0 &&
136 #endif
137 ip6->ip6_hlim <= IPV6_HLIMDEC) {
138 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
139 icmp6_error(m, ICMP6_TIME_EXCEEDED,
140 ICMP6_TIME_EXCEED_TRANSIT, 0);
141 return;
142 }
143
144 /*
145 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
146 * size of IPv6 + ICMPv6 headers) bytes of the packet in case
147 * we need to generate an ICMP6 message to the src.
148 * Thanks to M_EXT, in most cases copy will not occur.
149 *
150 * It is important to save it before IPsec processing as IPsec
151 * processing may modify the mbuf.
152 */
153 mcopy = m_copym(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN),
154 M_NOWAIT);
155 #ifdef IPSTEALTH
156 if (V_ip6stealth == 0)
157 #endif
158 ip6->ip6_hlim -= IPV6_HLIMDEC;
159
160 #if defined(IPSEC) || defined(IPSEC_SUPPORT)
161 if (IPSEC_ENABLED(ipv6)) {
162 if ((error = IPSEC_FORWARD(ipv6, m)) != 0) {
163 /* mbuf consumed by IPsec */
164 m_freem(mcopy);
165 if (error != EINPROGRESS)
166 IP6STAT_INC(ip6s_cantforward);
167 return;
168 }
169 /* No IPsec processing required */
170 }
171 #endif
172 /*
173 * ip6_forward() operates with IPv6 addresses with deembedded scope.
174 *
175 * There are 3 sources of IPv6 destination address:
176 *
177 * 1) ip6_input(), where ip6_dst contains deembedded address.
178 * In order to deal with forwarding of link-local packets,
179 * calculate the scope based on input interface (RFC 4007, clause 9).
180 * 2) packet filters changing ip6_dst directly. It would embed scope
181 * for LL addresses, so in6_localip() performs properly.
182 * 3) packet filters attaching PACKET_TAG_IPFORWARD would embed
183 * scope for the nexthop.
184 */
185 bzero(&dst, sizeof(struct sockaddr_in6));
186 dst.sin6_family = AF_INET6;
187 dst.sin6_addr = ip6->ip6_dst;
188 dst.sin6_scope_id = in6_get_unicast_scopeid(&ip6->ip6_dst, m->m_pkthdr.rcvif);
189 again:
190 nh = fib6_lookup(M_GETFIB(m), &dst.sin6_addr, dst.sin6_scope_id,
191 NHR_REF, m->m_pkthdr.flowid);
192 if (nh == NULL) {
193 IP6STAT_INC(ip6s_noroute);
194 in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
195 if (mcopy) {
196 icmp6_error(mcopy, ICMP6_DST_UNREACH,
197 ICMP6_DST_UNREACH_NOROUTE, 0);
198 }
199 goto bad;
200 }
201
202 if (nh->nh_flags & (NHF_BLACKHOLE | NHF_REJECT)) {
203 IP6STAT_INC(ip6s_cantforward);
204 if (mcopy != NULL) {
205 if (nh->nh_flags & NHF_REJECT) {
206 icmp6_error(mcopy, ICMP6_DST_UNREACH,
207 ICMP6_DST_UNREACH_REJECT, 0);
208 } else
209 m_freem(mcopy);
210 }
211 goto bad;
212 }
213
214 /*
215 * Source scope check: if a packet can't be delivered to its
216 * destination for the reason that the destination is beyond the scope
217 * of the source address, discard the packet and return an icmp6
218 * destination unreachable error with Code 2 (beyond scope of source
219 * address).
220 * [draft-ietf-ipngwg-icmp-v3-04.txt, Section 3.1]
221 */
222 outzone = in6_get_unicast_scopeid(&ip6->ip6_src, nh->nh_ifp);
223 inzone = in6_get_unicast_scopeid(&ip6->ip6_src, m->m_pkthdr.rcvif);
224 if (inzone != outzone) {
225 IP6STAT_INC(ip6s_cantforward);
226 IP6STAT_INC(ip6s_badscope);
227 in6_ifstat_inc(nh->nh_ifp, ifs6_in_discard);
228
229 if (V_ip6_log_cannot_forward && ip6_log_ratelimit()) {
230 log(LOG_DEBUG,
231 "cannot forward "
232 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
233 ip6_sprintf(ip6bufs, &ip6->ip6_src),
234 ip6_sprintf(ip6bufd, &ip6->ip6_dst),
235 ip6->ip6_nxt,
236 if_name(m->m_pkthdr.rcvif), if_name(nh->nh_ifp));
237 }
238 if (mcopy)
239 icmp6_error(mcopy, ICMP6_DST_UNREACH,
240 ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
241 goto bad;
242 }
243
244 /*
245 * Destination scope check: if a packet is going to break the scope
246 * zone of packet's destination address, discard it. This case should
247 * usually be prevented by appropriately-configured routing table, but
248 * we need an explicit check because we may mistakenly forward the
249 * packet to a different zone by (e.g.) a default route.
250 */
251 inzone = in6_get_unicast_scopeid(&ip6->ip6_dst, m->m_pkthdr.rcvif);
252 outzone = in6_get_unicast_scopeid(&ip6->ip6_dst, nh->nh_ifp);
253
254 if (inzone != outzone) {
255 IP6STAT_INC(ip6s_cantforward);
256 IP6STAT_INC(ip6s_badscope);
257 goto bad;
258 }
259
260 if (nh->nh_flags & NHF_GATEWAY) {
261 /* Store gateway address in deembedded form */
262 dst.sin6_addr = nh->gw6_sa.sin6_addr;
263 dst.sin6_scope_id = ntohs(in6_getscope(&dst.sin6_addr));
264 in6_clearscope(&dst.sin6_addr);
265 }
266
267 /*
268 * If we are to forward the packet using the same interface
269 * as one we got the packet from, perhaps we should send a redirect
270 * to sender to shortcut a hop.
271 * Only send redirect if source is sending directly to us,
272 * and if packet was not source routed (or has any options).
273 * Also, don't send redirect if forwarding using a route
274 * modified by a redirect.
275 */
276 if (V_ip6_sendredirects && nh->nh_ifp == m->m_pkthdr.rcvif && !srcrt &&
277 (nh->nh_flags & NHF_REDIRECT) == 0)
278 type = ND_REDIRECT;
279
280 /*
281 * Fake scoped addresses. Note that even link-local source or
282 * destinaion can appear, if the originating node just sends the
283 * packet to us (without address resolution for the destination).
284 * Since both icmp6_error and icmp6_redirect_output fill the embedded
285 * link identifiers, we can do this stuff after making a copy for
286 * returning an error.
287 */
288 if ((nh->nh_ifp->if_flags & IFF_LOOPBACK) != 0) {
289 /*
290 * See corresponding comments in ip6_output.
291 * XXX: but is it possible that ip6_forward() sends a packet
292 * to a loopback interface? I don't think so, and thus
293 * I bark here. (jinmei@kame.net)
294 * XXX: it is common to route invalid packets to loopback.
295 * also, the codepath will be visited on use of ::1 in
296 * rthdr. (itojun)
297 */
298 #if 1
299 if (0)
300 #else
301 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0)
302 #endif
303 {
304 printf("ip6_forward: outgoing interface is loopback. "
305 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
306 ip6_sprintf(ip6bufs, &ip6->ip6_src),
307 ip6_sprintf(ip6bufd, &ip6->ip6_dst),
308 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif),
309 if_name(nh->nh_ifp));
310 }
311
312 /* we can just use rcvif in forwarding. */
313 origifp = m->m_pkthdr.rcvif;
314 }
315 else
316 origifp = nh->nh_ifp;
317 /*
318 * clear embedded scope identifiers if necessary.
319 * in6_clearscope will touch the addresses only when necessary.
320 */
321 in6_clearscope(&ip6->ip6_src);
322 in6_clearscope(&ip6->ip6_dst);
323
324 /* Jump over all PFIL processing if hooks are not active. */
325 if (!PFIL_HOOKED_OUT(V_inet6_pfil_head))
326 goto pass;
327
328 odst = ip6->ip6_dst;
329 /* Run through list of hooks for forwarded packets. */
330 if (pfil_mbuf_fwd(V_inet6_pfil_head, &m, nh->nh_ifp,
331 NULL) != PFIL_PASS)
332 goto freecopy;
333 ip6 = mtod(m, struct ip6_hdr *);
334
335 /* See if destination IP address was changed by packet filter. */
336 if (!IN6_ARE_ADDR_EQUAL(&odst, &ip6->ip6_dst)) {
337 m->m_flags |= M_SKIP_FIREWALL;
338 /* If destination is now ourself drop to ip6_input(). */
339 if (in6_localip(&ip6->ip6_dst))
340 m->m_flags |= M_FASTFWD_OURS;
341 else {
342 NH_FREE(nh);
343
344 /* Update address and scopeid. Assume scope is embedded */
345 dst.sin6_scope_id = ntohs(in6_getscope(&ip6->ip6_dst));
346 dst.sin6_addr = ip6->ip6_dst;
347 in6_clearscope(&dst.sin6_addr);
348 goto again; /* Redo the routing table lookup. */
349 }
350 }
351
352 /* See if local, if yes, send it to netisr. */
353 if (m->m_flags & M_FASTFWD_OURS) {
354 if (m->m_pkthdr.rcvif == NULL)
355 m->m_pkthdr.rcvif = V_loif;
356 if (m->m_pkthdr.csum_flags & CSUM_DELAY_DATA_IPV6) {
357 m->m_pkthdr.csum_flags |=
358 CSUM_DATA_VALID_IPV6 | CSUM_PSEUDO_HDR;
359 m->m_pkthdr.csum_data = 0xffff;
360 }
361 #if defined(SCTP) || defined(SCTP_SUPPORT)
362 if (m->m_pkthdr.csum_flags & CSUM_SCTP_IPV6)
363 m->m_pkthdr.csum_flags |= CSUM_SCTP_VALID;
364 #endif
365 error = netisr_queue(NETISR_IPV6, m);
366 goto out;
367 }
368 /* Or forward to some other address? */
369 if ((m->m_flags & M_IP6_NEXTHOP) &&
370 (fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL)) != NULL) {
371 struct sockaddr_in6 *gw6 = (struct sockaddr_in6 *)(fwd_tag + 1);
372
373 /* Update address and scopeid. Assume scope is embedded */
374 dst.sin6_scope_id = ntohs(in6_getscope(&gw6->sin6_addr));
375 dst.sin6_addr = gw6->sin6_addr;
376 in6_clearscope(&dst.sin6_addr);
377
378 m->m_flags |= M_SKIP_FIREWALL;
379 m->m_flags &= ~M_IP6_NEXTHOP;
380 m_tag_delete(m, fwd_tag);
381 NH_FREE(nh);
382 goto again;
383 }
384
385 pass:
386 /* See if the size was changed by the packet filter. */
387 /* TODO: change to nh->nh_mtu */
388 if (m->m_pkthdr.len > IN6_LINKMTU(nh->nh_ifp)) {
389 in6_ifstat_inc(nh->nh_ifp, ifs6_in_toobig);
390 if (mcopy)
391 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0,
392 IN6_LINKMTU(nh->nh_ifp));
393 goto bad;
394 }
395
396 /*
397 * If TCP/UDP header still needs a valid checksum and interface will not
398 * calculate it for us, do it here.
399 */
400 if (__predict_false(m->m_pkthdr.csum_flags & CSUM_DELAY_DATA_IPV6 &
401 ~nh->nh_ifp->if_hwassist)) {
402 int offset = ip6_lasthdr(m, 0, IPPROTO_IPV6, NULL);
403
404 if (offset < sizeof(struct ip6_hdr) || offset > m->m_pkthdr.len)
405 goto bad;
406 in6_delayed_cksum(m, m->m_pkthdr.len - offset, offset);
407 m->m_pkthdr.csum_flags &= ~CSUM_DELAY_DATA_IPV6;
408 }
409 #if defined(SCTP) || defined(SCTP_SUPPORT)
410 if (__predict_false(m->m_pkthdr.csum_flags & CSUM_IP6_SCTP &
411 ~nh->nh_ifp->if_hwassist)) {
412 int offset = ip6_lasthdr(m, 0, IPPROTO_IPV6, NULL);
413
414 sctp_delayed_cksum(m, offset);
415 m->m_pkthdr.csum_flags &= ~CSUM_IP6_SCTP;
416 }
417 #endif
418
419 /* Currently LLE layer stores embedded IPv6 addresses */
420 if (IN6_IS_SCOPE_LINKLOCAL(&dst.sin6_addr)) {
421 in6_set_unicast_scopeid(&dst.sin6_addr, dst.sin6_scope_id);
422 dst.sin6_scope_id = 0;
423 }
424 error = nd6_output_ifp(nh->nh_ifp, origifp, m, &dst, NULL);
425 if (error) {
426 in6_ifstat_inc(nh->nh_ifp, ifs6_out_discard);
427 IP6STAT_INC(ip6s_cantforward);
428 } else {
429 IP6STAT_INC(ip6s_forward);
430 in6_ifstat_inc(nh->nh_ifp, ifs6_out_forward);
431 if (type)
432 IP6STAT_INC(ip6s_redirectsent);
433 else {
434 if (mcopy)
435 goto freecopy;
436 }
437 }
438
439 if (mcopy == NULL)
440 goto out;
441 switch (error) {
442 case 0:
443 if (type == ND_REDIRECT) {
444 icmp6_redirect_output(mcopy, nh);
445 goto out;
446 }
447 goto freecopy;
448
449 case EMSGSIZE:
450 /* xxx MTU is constant in PPP? */
451 goto freecopy;
452
453 case ENOBUFS:
454 /* Tell source to slow down like source quench in IP? */
455 goto freecopy;
456
457 case ENETUNREACH: /* shouldn't happen, checked above */
458 case EHOSTUNREACH:
459 case ENETDOWN:
460 case EHOSTDOWN:
461 default:
462 type = ICMP6_DST_UNREACH;
463 code = ICMP6_DST_UNREACH_ADDR;
464 break;
465 }
466 icmp6_error(mcopy, type, code, 0);
467 goto out;
468
469 freecopy:
470 m_freem(mcopy);
471 goto out;
472 bad:
473 m_freem(m);
474 out:
475 if (nh != NULL)
476 NH_FREE(nh);
477 }
478