1 /* $OpenBSD: ip6_forward.c,v 1.108 2022/08/09 21:10:02 kn Exp $ */
2 /* $KAME: ip6_forward.c,v 1.75 2001/06/29 12:42:13 jinmei Exp $ */
3
4 /*
5 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of the project nor the names of its contributors
17 * may be used to endorse or promote products derived from this software
18 * without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 */
32
33 #include "pf.h"
34
35 #include <sys/param.h>
36 #include <sys/systm.h>
37 #include <sys/mbuf.h>
38 #include <sys/socket.h>
39 #include <sys/errno.h>
40 #include <sys/time.h>
41 #include <sys/kernel.h>
42 #include <sys/syslog.h>
43
44 #include <net/if.h>
45 #include <net/if_var.h>
46 #include <net/if_enc.h>
47 #include <net/route.h>
48
49 #include <netinet/in.h>
50 #include <netinet/ip_var.h>
51 #include <netinet6/in6_var.h>
52 #include <netinet/ip6.h>
53 #include <netinet6/ip6_var.h>
54 #include <netinet/icmp6.h>
55 #include <netinet6/nd6.h>
56
57 #if NPF > 0
58 #include <net/pfvar.h>
59 #endif
60
61 #ifdef IPSEC
62 #include <netinet/ip_ipsp.h>
63 #include <netinet/ip_ah.h>
64 #include <netinet/ip_esp.h>
65 #include <netinet/udp.h>
66 #include <netinet/tcp.h>
67 #endif
68
69 /*
70 * Forward a packet. If some error occurs return the sender
71 * an icmp packet. Note we can't always generate a meaningful
72 * icmp message because icmp doesn't have a large enough repertoire
73 * of codes and types.
74 *
75 * If not forwarding, just drop the packet. This could be confusing
76 * if ipforwarding was zero but some routing protocol was advancing
77 * us as a gateway to somewhere. However, we must let the routing
78 * protocol deal with that.
79 *
80 */
81
82 void
83 ip6_forward(struct mbuf *m, struct rtentry *rt, int srcrt)
84 {
85 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
86 struct sockaddr_in6 *sin6;
87 struct route_in6 ro;
88 struct ifnet *ifp = NULL;
89 int error = 0, type = 0, code = 0, destmtu = 0;
90 struct mbuf *mcopy = NULL;
91 #ifdef IPSEC
92 struct tdb *tdb = NULL;
93 #endif /* IPSEC */
94 char src6[INET6_ADDRSTRLEN], dst6[INET6_ADDRSTRLEN];
95
96 /*
97 * Do not forward packets to multicast destination (should be handled
98 * by ip6_mforward().
99 * Do not forward packets with unspecified source. It was discussed
100 * in July 2000, on ipngwg mailing list.
101 */
102 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
103 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
104 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
105 ip6stat_inc(ip6s_cantforward);
106 if (ip6_log_time + ip6_log_interval < getuptime()) {
107 ip6_log_time = getuptime();
108 inet_ntop(AF_INET6, &ip6->ip6_src, src6, sizeof(src6));
109 inet_ntop(AF_INET6, &ip6->ip6_dst, dst6, sizeof(dst6));
110 log(LOG_DEBUG,
111 "cannot forward "
112 "from %s to %s nxt %d received on interface %u\n",
113 src6, dst6,
114 ip6->ip6_nxt,
115 m->m_pkthdr.ph_ifidx);
116 }
117 m_freem(m);
118 goto out;
119 }
120
121 if (ip6->ip6_hlim <= IPV6_HLIMDEC) {
122 icmp6_error(m, ICMP6_TIME_EXCEEDED,
123 ICMP6_TIME_EXCEED_TRANSIT, 0);
124 goto out;
125 }
126 ip6->ip6_hlim -= IPV6_HLIMDEC;
127
128 /*
129 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
130 * size of IPv6 + ICMPv6 headers) bytes of the packet in case
131 * we need to generate an ICMP6 message to the src.
132 * Thanks to M_EXT, in most cases copy will not occur.
133 *
134 * It is important to save it before IPsec processing as IPsec
135 * processing may modify the mbuf.
136 */
137 mcopy = m_copym(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN),
138 M_NOWAIT);
139
140 #if NPF > 0
141 reroute:
142 #endif
143
144 #ifdef IPSEC
145 if (ipsec_in_use) {
146 error = ip6_output_ipsec_lookup(m, NULL, &tdb);
147 if (error) {
148 /*
149 * -EINVAL is used to indicate that the packet should
150 * be silently dropped, typically because we've asked
151 * key management for an SA.
152 */
153 if (error == -EINVAL) /* Should silently drop packet */
154 error = 0;
155
156 m_freem(m);
157 goto freecopy;
158 }
159 }
160 #endif /* IPSEC */
161
162 memset(&ro, 0, sizeof(ro));
163 sin6 = &ro.ro_dst;
164 sin6->sin6_family = AF_INET6;
165 sin6->sin6_len = sizeof(*sin6);
166 sin6->sin6_addr = ip6->ip6_dst;
167
168 if (!rtisvalid(rt)) {
169 rtfree(rt);
170 rt = rtalloc_mpath(sin6tosa(sin6), &ip6->ip6_src.s6_addr32[0],
171 m->m_pkthdr.ph_rtableid);
172 if (rt == NULL) {
173 ip6stat_inc(ip6s_noroute);
174 if (mcopy) {
175 icmp6_error(mcopy, ICMP6_DST_UNREACH,
176 ICMP6_DST_UNREACH_NOROUTE, 0);
177 }
178 m_freem(m);
179 goto out;
180 }
181 }
182
183 /*
184 * Scope check: if a packet can't be delivered to its destination
185 * for the reason that the destination is beyond the scope of the
186 * source address, discard the packet and return an icmp6 destination
187 * unreachable error with Code 2 (beyond scope of source address).
188 * [draft-ietf-ipngwg-icmp-v3-00.txt, Section 3.1]
189 */
190 if (in6_addr2scopeid(m->m_pkthdr.ph_ifidx, &ip6->ip6_src) !=
191 in6_addr2scopeid(rt->rt_ifidx, &ip6->ip6_src)) {
192 ip6stat_inc(ip6s_cantforward);
193 ip6stat_inc(ip6s_badscope);
194
195 if (ip6_log_time + ip6_log_interval < getuptime()) {
196 ip6_log_time = getuptime();
197 inet_ntop(AF_INET6, &ip6->ip6_src, src6, sizeof(src6));
198 inet_ntop(AF_INET6, &ip6->ip6_dst, dst6, sizeof(dst6));
199 log(LOG_DEBUG,
200 "cannot forward "
201 "src %s, dst %s, nxt %d, rcvif %u, outif %u\n",
202 src6, dst6,
203 ip6->ip6_nxt,
204 m->m_pkthdr.ph_ifidx, rt->rt_ifidx);
205 }
206 if (mcopy)
207 icmp6_error(mcopy, ICMP6_DST_UNREACH,
208 ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
209 m_freem(m);
210 goto out;
211 }
212
213 #ifdef IPSEC
214 /*
215 * Check if the packet needs encapsulation.
216 * ipsp_process_packet will never come back to here.
217 */
218 if (tdb != NULL) {
219 /* Callee frees mbuf */
220 ro.ro_rt = rt;
221 ro.ro_tableid = m->m_pkthdr.ph_rtableid;
222 error = ip6_output_ipsec_send(tdb, m, &ro, 0, 1);
223 rt = ro.ro_rt;
224 if (error)
225 goto senderr;
226 goto freecopy;
227 }
228 #endif /* IPSEC */
229
230 if (rt->rt_flags & RTF_GATEWAY)
231 sin6 = satosin6(rt->rt_gateway);
232
233 /*
234 * If we are to forward the packet using the same interface
235 * as one we got the packet from, perhaps we should send a redirect
236 * to sender to shortcut a hop.
237 * Only send redirect if source is sending directly to us,
238 * and if packet was not source routed (or has any options).
239 * Also, don't send redirect if forwarding using a route
240 * modified by a redirect.
241 */
242 ifp = if_get(rt->rt_ifidx);
243 if (ifp == NULL) {
244 m_freem(m);
245 goto freecopy;
246 }
247 if (rt->rt_ifidx == m->m_pkthdr.ph_ifidx && !srcrt &&
248 ip6_sendredirects &&
249 (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) {
250 if ((ifp->if_flags & IFF_POINTOPOINT) &&
251 nd6_is_addr_neighbor(&ro.ro_dst, ifp)) {
252 /*
253 * If the incoming interface is equal to the outgoing
254 * one, the link attached to the interface is
255 * point-to-point, and the IPv6 destination is
256 * regarded as on-link on the link, then it will be
257 * highly probable that the destination address does
258 * not exist on the link and that the packet is going
259 * to loop. Thus, we immediately drop the packet and
260 * send an ICMPv6 error message.
261 * For other routing loops, we dare to let the packet
262 * go to the loop, so that a remote diagnosing host
263 * can detect the loop by traceroute.
264 * type/code is based on suggestion by Rich Draves.
265 * not sure if it is the best pick.
266 */
267 if (mcopy)
268 icmp6_error(mcopy, ICMP6_DST_UNREACH,
269 ICMP6_DST_UNREACH_ADDR, 0);
270 m_freem(m);
271 goto out;
272 }
273 type = ND_REDIRECT;
274 }
275
276 /*
277 * Fake scoped addresses. Note that even link-local source or
278 * destination 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 (IN6_IS_SCOPE_EMBED(&ip6->ip6_src))
285 ip6->ip6_src.s6_addr16[1] = 0;
286 if (IN6_IS_SCOPE_EMBED(&ip6->ip6_dst))
287 ip6->ip6_dst.s6_addr16[1] = 0;
288
289 #if NPF > 0
290 if (pf_test(AF_INET6, PF_FWD, ifp, &m) != PF_PASS) {
291 m_freem(m);
292 goto senderr;
293 }
294 if (m == NULL)
295 goto senderr;
296 ip6 = mtod(m, struct ip6_hdr *);
297 if ((m->m_pkthdr.pf.flags & (PF_TAG_REROUTE | PF_TAG_GENERATED)) ==
298 (PF_TAG_REROUTE | PF_TAG_GENERATED)) {
299 /* already rerun the route lookup, go on */
300 m->m_pkthdr.pf.flags &= ~(PF_TAG_GENERATED | PF_TAG_REROUTE);
301 } else if (m->m_pkthdr.pf.flags & PF_TAG_REROUTE) {
302 /* tag as generated to skip over pf_test on rerun */
303 m->m_pkthdr.pf.flags |= PF_TAG_GENERATED;
304 srcrt = 1;
305 rtfree(rt);
306 rt = NULL;
307 if_put(ifp);
308 ifp = NULL;
309 goto reroute;
310 }
311 #endif
312 in6_proto_cksum_out(m, ifp);
313
314 /* Check the size after pf_test to give pf a chance to refragment. */
315 if (m->m_pkthdr.len > ifp->if_mtu) {
316 if (mcopy)
317 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0,
318 ifp->if_mtu);
319 m_freem(m);
320 goto out;
321 }
322
323 error = ifp->if_output(ifp, m, sin6tosa(sin6), rt);
324 if (error) {
325 ip6stat_inc(ip6s_cantforward);
326 } else {
327 ip6stat_inc(ip6s_forward);
328 if (type)
329 ip6stat_inc(ip6s_redirectsent);
330 else {
331 if (mcopy)
332 goto freecopy;
333 }
334 }
335
336 #if NPF > 0 || defined(IPSEC)
337 senderr:
338 #endif
339 if (mcopy == NULL)
340 goto out;
341
342 switch (error) {
343 case 0:
344 if (type == ND_REDIRECT) {
345 icmp6_redirect_output(mcopy, rt);
346 goto out;
347 }
348 goto freecopy;
349
350 case EMSGSIZE:
351 type = ICMP6_PACKET_TOO_BIG;
352 code = 0;
353 if (rt != NULL) {
354 if (rt->rt_mtu) {
355 destmtu = rt->rt_mtu;
356 } else {
357 struct ifnet *destifp;
358
359 destifp = if_get(rt->rt_ifidx);
360 if (destifp != NULL)
361 destmtu = destifp->if_mtu;
362 if_put(destifp);
363 }
364 }
365 ip6stat_inc(ip6s_cantfrag);
366 if (destmtu == 0)
367 goto freecopy;
368 break;
369
370 case EACCES:
371 /*
372 * pf(4) blocked the packet. There is no need to send an ICMP
373 * packet back since pf(4) takes care of it.
374 */
375 goto freecopy;
376
377 case ENOBUFS:
378 /* Tell source to slow down like source quench in IP? */
379 goto freecopy;
380
381 case ENETUNREACH: /* shouldn't happen, checked above */
382 case EHOSTUNREACH:
383 case ENETDOWN:
384 case EHOSTDOWN:
385 default:
386 type = ICMP6_DST_UNREACH;
387 code = ICMP6_DST_UNREACH_ADDR;
388 break;
389 }
390 icmp6_error(mcopy, type, code, destmtu);
391 goto out;
392
393 freecopy:
394 m_freem(mcopy);
395 out:
396 rtfree(rt);
397 if_put(ifp);
398 #ifdef IPSEC
399 tdb_unref(tdb);
400 #endif /* IPSEC */
401 }
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