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 __FBSDID("$FreeBSD: releng/12.0/sys/netinet6/ip6_forward.c 331436 2018-03-23 16:56:44Z kp $");
36
37 #include "opt_inet.h"
38 #include "opt_inet6.h"
39 #include "opt_ipsec.h"
40 #include "opt_ipstealth.h"
41
42 #include <sys/param.h>
43 #include <sys/systm.h>
44 #include <sys/malloc.h>
45 #include <sys/mbuf.h>
46 #include <sys/domain.h>
47 #include <sys/protosw.h>
48 #include <sys/socket.h>
49 #include <sys/errno.h>
50 #include <sys/time.h>
51 #include <sys/kernel.h>
52 #include <sys/syslog.h>
53
54 #include <net/if.h>
55 #include <net/if_var.h>
56 #include <net/netisr.h>
57 #include <net/route.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/ip6_var.h>
68 #include <netinet6/scope6_var.h>
69 #include <netinet/icmp6.h>
70 #include <netinet6/nd6.h>
71
72 #include <netinet/in_pcb.h>
73
74 #include <netipsec/ipsec_support.h>
75
76 /*
77 * Forward a packet. If some error occurs return the sender
78 * an icmp packet. Note we can't always generate a meaningful
79 * icmp message because icmp doesn't have a large enough repertoire
80 * of codes and types.
81 *
82 * If not forwarding, just drop the packet. This could be confusing
83 * if ipforwarding was zero but some routing protocol was advancing
84 * us as a gateway to somewhere. However, we must let the routing
85 * protocol deal with that.
86 *
87 */
88 void
89 ip6_forward(struct mbuf *m, int srcrt)
90 {
91 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
92 struct sockaddr_in6 *dst = NULL;
93 struct rtentry *rt = NULL;
94 struct route_in6 rin6;
95 int error, type = 0, code = 0;
96 struct mbuf *mcopy = NULL;
97 struct ifnet *origifp; /* maybe unnecessary */
98 u_int32_t inzone, outzone;
99 struct in6_addr src_in6, dst_in6, odst;
100 struct m_tag *fwd_tag;
101 char ip6bufs[INET6_ADDRSTRLEN], ip6bufd[INET6_ADDRSTRLEN];
102
103 /*
104 * Do not forward packets to multicast destination (should be handled
105 * by ip6_mforward().
106 * Do not forward packets with unspecified source. It was discussed
107 * in July 2000, on the ipngwg mailing list.
108 */
109 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
110 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
111 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
112 IP6STAT_INC(ip6s_cantforward);
113 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
114 if (V_ip6_log_time + V_ip6_log_interval < time_uptime) {
115 V_ip6_log_time = time_uptime;
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 again:
168 bzero(&rin6, sizeof(struct route_in6));
169 dst = (struct sockaddr_in6 *)&rin6.ro_dst;
170 dst->sin6_len = sizeof(struct sockaddr_in6);
171 dst->sin6_family = AF_INET6;
172 dst->sin6_addr = ip6->ip6_dst;
173 again2:
174 rin6.ro_rt = in6_rtalloc1((struct sockaddr *)dst, 0, 0, M_GETFIB(m));
175 rt = rin6.ro_rt;
176 if (rin6.ro_rt != NULL)
177 RT_UNLOCK(rin6.ro_rt);
178 else {
179 IP6STAT_INC(ip6s_noroute);
180 in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
181 if (mcopy) {
182 icmp6_error(mcopy, ICMP6_DST_UNREACH,
183 ICMP6_DST_UNREACH_NOROUTE, 0);
184 }
185 goto bad;
186 }
187
188 /*
189 * Source scope check: if a packet can't be delivered to its
190 * destination for the reason that the destination is beyond the scope
191 * of the source address, discard the packet and return an icmp6
192 * destination unreachable error with Code 2 (beyond scope of source
193 * address). We use a local copy of ip6_src, since in6_setscope()
194 * will possibly modify its first argument.
195 * [draft-ietf-ipngwg-icmp-v3-04.txt, Section 3.1]
196 */
197 src_in6 = ip6->ip6_src;
198 if (in6_setscope(&src_in6, rt->rt_ifp, &outzone)) {
199 /* XXX: this should not happen */
200 IP6STAT_INC(ip6s_cantforward);
201 IP6STAT_INC(ip6s_badscope);
202 goto bad;
203 }
204 if (in6_setscope(&src_in6, m->m_pkthdr.rcvif, &inzone)) {
205 IP6STAT_INC(ip6s_cantforward);
206 IP6STAT_INC(ip6s_badscope);
207 goto bad;
208 }
209 if (inzone != outzone) {
210 IP6STAT_INC(ip6s_cantforward);
211 IP6STAT_INC(ip6s_badscope);
212 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard);
213
214 if (V_ip6_log_time + V_ip6_log_interval < time_uptime) {
215 V_ip6_log_time = time_uptime;
216 log(LOG_DEBUG,
217 "cannot forward "
218 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
219 ip6_sprintf(ip6bufs, &ip6->ip6_src),
220 ip6_sprintf(ip6bufd, &ip6->ip6_dst),
221 ip6->ip6_nxt,
222 if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp));
223 }
224 if (mcopy)
225 icmp6_error(mcopy, ICMP6_DST_UNREACH,
226 ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
227 goto bad;
228 }
229
230 /*
231 * Destination scope check: if a packet is going to break the scope
232 * zone of packet's destination address, discard it. This case should
233 * usually be prevented by appropriately-configured routing table, but
234 * we need an explicit check because we may mistakenly forward the
235 * packet to a different zone by (e.g.) a default route.
236 */
237 dst_in6 = ip6->ip6_dst;
238 if (in6_setscope(&dst_in6, m->m_pkthdr.rcvif, &inzone) != 0 ||
239 in6_setscope(&dst_in6, rt->rt_ifp, &outzone) != 0 ||
240 inzone != outzone) {
241 IP6STAT_INC(ip6s_cantforward);
242 IP6STAT_INC(ip6s_badscope);
243 goto bad;
244 }
245
246 if (rt->rt_flags & RTF_GATEWAY)
247 dst = (struct sockaddr_in6 *)rt->rt_gateway;
248
249 /*
250 * If we are to forward the packet using the same interface
251 * as one we got the packet from, perhaps we should send a redirect
252 * to sender to shortcut a hop.
253 * Only send redirect if source is sending directly to us,
254 * and if packet was not source routed (or has any options).
255 * Also, don't send redirect if forwarding using a route
256 * modified by a redirect.
257 */
258 if (V_ip6_sendredirects && rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt &&
259 (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) {
260 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) != 0) {
261 /*
262 * If the incoming interface is equal to the outgoing
263 * one, and the link attached to the interface is
264 * point-to-point, then it will be highly probable
265 * that a routing loop occurs. Thus, we immediately
266 * drop the packet and send an ICMPv6 error message.
267 *
268 * type/code is based on suggestion by Rich Draves.
269 * not sure if it is the best pick.
270 */
271 icmp6_error(mcopy, ICMP6_DST_UNREACH,
272 ICMP6_DST_UNREACH_ADDR, 0);
273 goto bad;
274 }
275 type = ND_REDIRECT;
276 }
277
278 /*
279 * Fake scoped addresses. Note that even link-local source or
280 * destinaion can appear, if the originating node just sends the
281 * packet to us (without address resolution for the destination).
282 * Since both icmp6_error and icmp6_redirect_output fill the embedded
283 * link identifiers, we can do this stuff after making a copy for
284 * returning an error.
285 */
286 if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) {
287 /*
288 * See corresponding comments in ip6_output.
289 * XXX: but is it possible that ip6_forward() sends a packet
290 * to a loopback interface? I don't think so, and thus
291 * I bark here. (jinmei@kame.net)
292 * XXX: it is common to route invalid packets to loopback.
293 * also, the codepath will be visited on use of ::1 in
294 * rthdr. (itojun)
295 */
296 #if 1
297 if (0)
298 #else
299 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0)
300 #endif
301 {
302 printf("ip6_forward: outgoing interface is loopback. "
303 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
304 ip6_sprintf(ip6bufs, &ip6->ip6_src),
305 ip6_sprintf(ip6bufd, &ip6->ip6_dst),
306 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif),
307 if_name(rt->rt_ifp));
308 }
309
310 /* we can just use rcvif in forwarding. */
311 origifp = m->m_pkthdr.rcvif;
312 }
313 else
314 origifp = rt->rt_ifp;
315 /*
316 * clear embedded scope identifiers if necessary.
317 * in6_clearscope will touch the addresses only when necessary.
318 */
319 in6_clearscope(&ip6->ip6_src);
320 in6_clearscope(&ip6->ip6_dst);
321
322 /* Jump over all PFIL processing if hooks are not active. */
323 if (!PFIL_HOOKED(&V_inet6_pfil_hook))
324 goto pass;
325
326 odst = ip6->ip6_dst;
327 /* Run through list of hooks for forwarded packets. */
328 error = pfil_run_hooks(&V_inet6_pfil_hook, &m, rt->rt_ifp, PFIL_OUT,
329 PFIL_FWD, NULL);
330 if (error != 0 || m == NULL)
331 goto freecopy; /* consumed by filter */
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 RTFREE(rt);
342 goto again; /* Redo the routing table lookup. */
343 }
344 }
345
346 /* See if local, if yes, send it to netisr. */
347 if (m->m_flags & M_FASTFWD_OURS) {
348 if (m->m_pkthdr.rcvif == NULL)
349 m->m_pkthdr.rcvif = V_loif;
350 if (m->m_pkthdr.csum_flags & CSUM_DELAY_DATA_IPV6) {
351 m->m_pkthdr.csum_flags |=
352 CSUM_DATA_VALID_IPV6 | CSUM_PSEUDO_HDR;
353 m->m_pkthdr.csum_data = 0xffff;
354 }
355 #ifdef SCTP
356 if (m->m_pkthdr.csum_flags & CSUM_SCTP_IPV6)
357 m->m_pkthdr.csum_flags |= CSUM_SCTP_VALID;
358 #endif
359 error = netisr_queue(NETISR_IPV6, m);
360 goto out;
361 }
362 /* Or forward to some other address? */
363 if ((m->m_flags & M_IP6_NEXTHOP) &&
364 (fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL)) != NULL) {
365 dst = (struct sockaddr_in6 *)&rin6.ro_dst;
366 bcopy((fwd_tag+1), dst, sizeof(struct sockaddr_in6));
367 m->m_flags |= M_SKIP_FIREWALL;
368 m->m_flags &= ~M_IP6_NEXTHOP;
369 m_tag_delete(m, fwd_tag);
370 RTFREE(rt);
371 goto again2;
372 }
373
374 pass:
375 /* See if the size was changed by the packet filter. */
376 if (m->m_pkthdr.len > IN6_LINKMTU(rt->rt_ifp)) {
377 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig);
378 if (mcopy)
379 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0,
380 IN6_LINKMTU(rt->rt_ifp));
381 goto bad;
382 }
383
384 error = nd6_output_ifp(rt->rt_ifp, origifp, m, dst, NULL);
385 if (error) {
386 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard);
387 IP6STAT_INC(ip6s_cantforward);
388 } else {
389 IP6STAT_INC(ip6s_forward);
390 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward);
391 if (type)
392 IP6STAT_INC(ip6s_redirectsent);
393 else {
394 if (mcopy)
395 goto freecopy;
396 }
397 }
398
399 if (mcopy == NULL)
400 goto out;
401 switch (error) {
402 case 0:
403 if (type == ND_REDIRECT) {
404 icmp6_redirect_output(mcopy, rt);
405 goto out;
406 }
407 goto freecopy;
408
409 case EMSGSIZE:
410 /* xxx MTU is constant in PPP? */
411 goto freecopy;
412
413 case ENOBUFS:
414 /* Tell source to slow down like source quench in IP? */
415 goto freecopy;
416
417 case ENETUNREACH: /* shouldn't happen, checked above */
418 case EHOSTUNREACH:
419 case ENETDOWN:
420 case EHOSTDOWN:
421 default:
422 type = ICMP6_DST_UNREACH;
423 code = ICMP6_DST_UNREACH_ADDR;
424 break;
425 }
426 icmp6_error(mcopy, type, code, 0);
427 goto out;
428
429 freecopy:
430 m_freem(mcopy);
431 goto out;
432 bad:
433 m_freem(m);
434 out:
435 if (rt != NULL)
436 RTFREE(rt);
437 }
Cache object: ba7ff50123ff310337715909083a3c1b
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