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 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);
184 again:
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
380 pass:
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;
444 bad:
445 m_freem(m);
446 out:
447 if (nh != NULL)
448 NH_FREE(nh);
449 }
450