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 */
90 void
ip6_forward(struct mbuf * m,int srcrt)91 ip6_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 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_dst)) {
114 IP6STAT_INC(ip6s_cantforward);
115 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
116 if (V_ip6_log_cannot_forward && ip6_log_ratelimit()) {
117 log(LOG_DEBUG,
118 "cannot forward "
119 "from %s to %s nxt %d received on %s\n",
120 ip6_sprintf(ip6bufs, &ip6->ip6_src),
121 ip6_sprintf(ip6bufd, &ip6->ip6_dst),
122 ip6->ip6_nxt,
123 if_name(m->m_pkthdr.rcvif));
124 }
125 m_freem(m);
126 return;
127 }
128
129 if (
130 #ifdef IPSTEALTH
131 V_ip6stealth == 0 &&
132 #endif
133 ip6->ip6_hlim <= IPV6_HLIMDEC) {
134 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
135 icmp6_error(m, ICMP6_TIME_EXCEEDED,
136 ICMP6_TIME_EXCEED_TRANSIT, 0);
137 return;
138 }
139
140 /*
141 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
142 * size of IPv6 + ICMPv6 headers) bytes of the packet in case
143 * we need to generate an ICMP6 message to the src.
144 * Thanks to M_EXT, in most cases copy will not occur.
145 *
146 * It is important to save it before IPsec processing as IPsec
147 * processing may modify the mbuf.
148 */
149 mcopy = m_copym(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN),
150 M_NOWAIT);
151 #ifdef IPSTEALTH
152 if (V_ip6stealth == 0)
153 #endif
154 ip6->ip6_hlim -= IPV6_HLIMDEC;
155
156 #if defined(IPSEC) || defined(IPSEC_SUPPORT)
157 if (IPSEC_ENABLED(ipv6)) {
158 if ((error = IPSEC_FORWARD(ipv6, m)) != 0) {
159 /* mbuf consumed by IPsec */
160 m_freem(mcopy);
161 if (error != EINPROGRESS)
162 IP6STAT_INC(ip6s_cantforward);
163 return;
164 }
165 /* No IPsec processing required */
166 }
167 #endif
168 /*
169 * ip6_forward() operates with IPv6 addresses with deembedded scope.
170 *
171 * There are 3 sources of IPv6 destination address:
172 *
173 * 1) ip6_input(), where ip6_dst contains deembedded address.
174 * In order to deal with forwarding of link-local packets,
175 * calculate the scope based on input interface (RFC 4007, clause 9).
176 * 2) packet filters changing ip6_dst directly. It would embed scope
177 * for LL addresses, so in6_localip() performs properly.
178 * 3) packet filters attaching PACKET_TAG_IPFORWARD would embed
179 * scope for the nexthop.
180 */
181 bzero(&dst, sizeof(struct sockaddr_in6));
182 dst.sin6_family = AF_INET6;
183 dst.sin6_addr = ip6->ip6_dst;
184 dst.sin6_scope_id = in6_get_unicast_scopeid(&ip6->ip6_dst, m->m_pkthdr.rcvif);
185 again:
186 nh = fib6_lookup(M_GETFIB(m), &dst.sin6_addr, dst.sin6_scope_id,
187 NHR_REF, m->m_pkthdr.flowid);
188 if (nh == NULL) {
189 IP6STAT_INC(ip6s_noroute);
190 in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
191 if (mcopy) {
192 icmp6_error(mcopy, ICMP6_DST_UNREACH,
193 ICMP6_DST_UNREACH_NOROUTE, 0);
194 }
195 goto bad;
196 }
197
198 if (nh->nh_flags & (NHF_BLACKHOLE | NHF_REJECT)) {
199 IP6STAT_INC(ip6s_cantforward);
200 if (mcopy != NULL) {
201 if (nh->nh_flags & NHF_REJECT) {
202 icmp6_error(mcopy, ICMP6_DST_UNREACH,
203 ICMP6_DST_UNREACH_REJECT, 0);
204 } else
205 m_freem(mcopy);
206 }
207 goto bad;
208 }
209
210 /*
211 * Source scope check: if a packet can't be delivered to its
212 * destination for the reason that the destination is beyond the scope
213 * of the source address, discard the packet and return an icmp6
214 * destination unreachable error with Code 2 (beyond scope of source
215 * address).
216 * [draft-ietf-ipngwg-icmp-v3-04.txt, Section 3.1]
217 */
218 outzone = in6_get_unicast_scopeid(&ip6->ip6_src, nh->nh_ifp);
219 inzone = in6_get_unicast_scopeid(&ip6->ip6_src, m->m_pkthdr.rcvif);
220 if (inzone != outzone) {
221 IP6STAT_INC(ip6s_cantforward);
222 IP6STAT_INC(ip6s_badscope);
223 in6_ifstat_inc(nh->nh_ifp, ifs6_in_discard);
224
225 if (V_ip6_log_cannot_forward && ip6_log_ratelimit()) {
226 log(LOG_DEBUG,
227 "cannot forward "
228 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
229 ip6_sprintf(ip6bufs, &ip6->ip6_src),
230 ip6_sprintf(ip6bufd, &ip6->ip6_dst),
231 ip6->ip6_nxt,
232 if_name(m->m_pkthdr.rcvif), if_name(nh->nh_ifp));
233 }
234 if (mcopy)
235 icmp6_error(mcopy, ICMP6_DST_UNREACH,
236 ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
237 goto bad;
238 }
239
240 /*
241 * Destination scope check: if a packet is going to break the scope
242 * zone of packet's destination address, discard it. This case should
243 * usually be prevented by appropriately-configured routing table, but
244 * we need an explicit check because we may mistakenly forward the
245 * packet to a different zone by (e.g.) a default route.
246 */
247 inzone = in6_get_unicast_scopeid(&ip6->ip6_dst, m->m_pkthdr.rcvif);
248 outzone = in6_get_unicast_scopeid(&ip6->ip6_dst, nh->nh_ifp);
249
250 if (inzone != outzone) {
251 IP6STAT_INC(ip6s_cantforward);
252 IP6STAT_INC(ip6s_badscope);
253 goto bad;
254 }
255
256 if (nh->nh_flags & NHF_GATEWAY) {
257 /* Store gateway address in deembedded form */
258 dst.sin6_addr = nh->gw6_sa.sin6_addr;
259 dst.sin6_scope_id = ntohs(in6_getscope(&dst.sin6_addr));
260 in6_clearscope(&dst.sin6_addr);
261 }
262
263 /*
264 * If we are to forward the packet using the same interface
265 * as one we got the packet from, perhaps we should send a redirect
266 * to sender to shortcut a hop.
267 * Only send redirect if source is sending directly to us,
268 * and if packet was not source routed (or has any options).
269 * Also, don't send redirect if forwarding using a route
270 * modified by a redirect.
271 */
272 if (V_ip6_sendredirects && nh->nh_ifp == m->m_pkthdr.rcvif && !srcrt &&
273 (nh->nh_flags & NHF_REDIRECT) == 0)
274 type = ND_REDIRECT;
275
276 /*
277 * Fake scoped addresses. Note that even link-local source or
278 * destinaion can appear, if the originating node just sends the
279 * packet to us (without address resolution for the destination).
280 * Since both icmp6_error and icmp6_redirect_output fill the embedded
281 * link identifiers, we can do this stuff after making a copy for
282 * returning an error.
283 */
284 if ((nh->nh_ifp->if_flags & IFF_LOOPBACK) != 0) {
285 /*
286 * See corresponding comments in ip6_output.
287 * XXX: but is it possible that ip6_forward() sends a packet
288 * to a loopback interface? I don't think so, and thus
289 * I bark here. (jinmei@kame.net)
290 * XXX: it is common to route invalid packets to loopback.
291 * also, the codepath will be visited on use of ::1 in
292 * rthdr. (itojun)
293 */
294 #if 1
295 if (0)
296 #else
297 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0)
298 #endif
299 {
300 printf("ip6_forward: outgoing interface is loopback. "
301 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
302 ip6_sprintf(ip6bufs, &ip6->ip6_src),
303 ip6_sprintf(ip6bufd, &ip6->ip6_dst),
304 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif),
305 if_name(nh->nh_ifp));
306 }
307
308 /* we can just use rcvif in forwarding. */
309 origifp = m->m_pkthdr.rcvif;
310 }
311 else
312 origifp = nh->nh_ifp;
313 /*
314 * clear embedded scope identifiers if necessary.
315 * in6_clearscope will touch the addresses only when necessary.
316 */
317 in6_clearscope(&ip6->ip6_src);
318 in6_clearscope(&ip6->ip6_dst);
319
320 /* Jump over all PFIL processing if hooks are not active. */
321 if (!PFIL_HOOKED_OUT(V_inet6_pfil_head))
322 goto pass;
323
324 odst = ip6->ip6_dst;
325 /* Run through list of hooks for forwarded packets. */
326 if (pfil_mbuf_fwd(V_inet6_pfil_head, &m, nh->nh_ifp,
327 NULL) != PFIL_PASS)
328 goto freecopy;
329 ip6 = mtod(m, struct ip6_hdr *);
330
331 /* See if destination IP address was changed by packet filter. */
332 if (!IN6_ARE_ADDR_EQUAL(&odst, &ip6->ip6_dst)) {
333 m->m_flags |= M_SKIP_FIREWALL;
334 /* If destination is now ourself drop to ip6_input(). */
335 if (in6_localip(&ip6->ip6_dst))
336 m->m_flags |= M_FASTFWD_OURS;
337 else {
338 NH_FREE(nh);
339
340 /* Update address and scopeid. Assume scope is embedded */
341 dst.sin6_scope_id = ntohs(in6_getscope(&ip6->ip6_dst));
342 dst.sin6_addr = ip6->ip6_dst;
343 in6_clearscope(&dst.sin6_addr);
344 goto again; /* Redo the routing table lookup. */
345 }
346 }
347
348 /* See if local, if yes, send it to netisr. */
349 if (m->m_flags & M_FASTFWD_OURS) {
350 if (m->m_pkthdr.rcvif == NULL)
351 m->m_pkthdr.rcvif = V_loif;
352 if (m->m_pkthdr.csum_flags & CSUM_DELAY_DATA_IPV6) {
353 m->m_pkthdr.csum_flags |=
354 CSUM_DATA_VALID_IPV6 | CSUM_PSEUDO_HDR;
355 m->m_pkthdr.csum_data = 0xffff;
356 }
357 #if defined(SCTP) || defined(SCTP_SUPPORT)
358 if (m->m_pkthdr.csum_flags & CSUM_SCTP_IPV6)
359 m->m_pkthdr.csum_flags |= CSUM_SCTP_VALID;
360 #endif
361 error = netisr_queue(NETISR_IPV6, m);
362 goto out;
363 }
364 /* Or forward to some other address? */
365 if ((m->m_flags & M_IP6_NEXTHOP) &&
366 (fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL)) != NULL) {
367 struct sockaddr_in6 *gw6 = (struct sockaddr_in6 *)(fwd_tag + 1);
368
369 /* Update address and scopeid. Assume scope is embedded */
370 dst.sin6_scope_id = ntohs(in6_getscope(&gw6->sin6_addr));
371 dst.sin6_addr = gw6->sin6_addr;
372 in6_clearscope(&dst.sin6_addr);
373
374 m->m_flags |= M_SKIP_FIREWALL;
375 m->m_flags &= ~M_IP6_NEXTHOP;
376 m_tag_delete(m, fwd_tag);
377 NH_FREE(nh);
378 goto again;
379 }
380
381 pass:
382 /* See if the size was changed by the packet filter. */
383 /* TODO: change to nh->nh_mtu */
384 if (m->m_pkthdr.len > IN6_LINKMTU(nh->nh_ifp)) {
385 in6_ifstat_inc(nh->nh_ifp, ifs6_in_toobig);
386 if (mcopy)
387 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0,
388 IN6_LINKMTU(nh->nh_ifp));
389 goto bad;
390 }
391
392 /* Currently LLE layer stores embedded IPv6 addresses */
393 if (IN6_IS_SCOPE_LINKLOCAL(&dst.sin6_addr)) {
394 in6_set_unicast_scopeid(&dst.sin6_addr, dst.sin6_scope_id);
395 dst.sin6_scope_id = 0;
396 }
397 error = nd6_output_ifp(nh->nh_ifp, origifp, m, &dst, NULL);
398 if (error) {
399 in6_ifstat_inc(nh->nh_ifp, ifs6_out_discard);
400 IP6STAT_INC(ip6s_cantforward);
401 } else {
402 IP6STAT_INC(ip6s_forward);
403 in6_ifstat_inc(nh->nh_ifp, ifs6_out_forward);
404 if (type)
405 IP6STAT_INC(ip6s_redirectsent);
406 else {
407 if (mcopy)
408 goto freecopy;
409 }
410 }
411
412 if (mcopy == NULL)
413 goto out;
414 switch (error) {
415 case 0:
416 if (type == ND_REDIRECT) {
417 icmp6_redirect_output(mcopy, nh);
418 goto out;
419 }
420 goto freecopy;
421
422 case EMSGSIZE:
423 /* xxx MTU is constant in PPP? */
424 goto freecopy;
425
426 case ENOBUFS:
427 /* Tell source to slow down like source quench in IP? */
428 goto freecopy;
429
430 case ENETUNREACH: /* shouldn't happen, checked above */
431 case EHOSTUNREACH:
432 case ENETDOWN:
433 case EHOSTDOWN:
434 default:
435 type = ICMP6_DST_UNREACH;
436 code = ICMP6_DST_UNREACH_ADDR;
437 break;
438 }
439 icmp6_error(mcopy, type, code, 0);
440 goto out;
441
442 freecopy:
443 m_freem(mcopy);
444 goto out;
445 bad:
446 m_freem(m);
447 out:
448 if (nh != NULL)
449 NH_FREE(nh);
450 }
451