ip6_forward.c revision 1.74.2.3 1 /* $NetBSD: ip6_forward.c,v 1.74.2.3 2016/07/09 20:25:22 skrll Exp $ */
2 /* $KAME: ip6_forward.c,v 1.109 2002/09/11 08:10:17 sakane 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 <sys/cdefs.h>
34 __KERNEL_RCSID(0, "$NetBSD: ip6_forward.c,v 1.74.2.3 2016/07/09 20:25:22 skrll Exp $");
35
36 #ifdef _KERNEL_OPT
37 #include "opt_gateway.h"
38 #include "opt_ipsec.h"
39 #endif
40
41 #include <sys/param.h>
42 #include <sys/systm.h>
43 #include <sys/mbuf.h>
44 #include <sys/domain.h>
45 #include <sys/protosw.h>
46 #include <sys/socket.h>
47 #include <sys/errno.h>
48 #include <sys/time.h>
49 #include <sys/kernel.h>
50 #include <sys/syslog.h>
51
52 #include <net/if.h>
53 #include <net/route.h>
54 #include <net/pfil.h>
55
56 #include <netinet/in.h>
57 #include <netinet/in_var.h>
58 #include <netinet/ip_var.h>
59 #include <netinet/ip6.h>
60 #include <netinet6/ip6_var.h>
61 #include <netinet6/ip6_private.h>
62 #include <netinet6/scope6_var.h>
63 #include <netinet/icmp6.h>
64 #include <netinet6/nd6.h>
65
66 #ifdef IPSEC
67 #include <netipsec/ipsec.h>
68 #include <netipsec/ipsec6.h>
69 #include <netipsec/key.h>
70 #include <netipsec/xform.h>
71 #endif /* IPSEC */
72
73 #include <net/net_osdep.h>
74
75 struct route ip6_forward_rt;
76
77 extern pfil_head_t *inet6_pfil_hook; /* XXX */
78
79 static void __printflike(4, 5)
80 ip6_cantforward(const struct ip6_hdr *ip6, const struct ifnet *srcifp,
81 const struct ifnet *dstifp, const char *fmt, ...)
82 {
83 char sbuf[INET6_ADDRSTRLEN], dbuf[INET6_ADDRSTRLEN];
84 char reason[256];
85 va_list ap;
86 uint64_t *ip6s;
87
88 /* update statistics */
89 ip6s = IP6_STAT_GETREF();
90 ip6s[IP6_STAT_CANTFORWARD]++;
91 if (dstifp)
92 ip6s[IP6_STAT_BADSCOPE]++;
93 IP6_STAT_PUTREF();
94
95 if (dstifp)
96 in6_ifstat_inc(dstifp, ifs6_in_discard);
97
98 if (ip6_log_time + ip6_log_interval >= time_uptime)
99 return;
100 ip6_log_time = time_uptime;
101
102 va_start(ap, fmt);
103 vsnprintf(reason, sizeof(reason), fmt, ap);
104 va_end(ap);
105
106 log(LOG_DEBUG, "Cannot forward from %s@%s to %s@%s nxt %d (%s)\n",
107 IN6_PRINT(sbuf, &ip6->ip6_src), srcifp ? if_name(srcifp) : "?",
108 IN6_PRINT(dbuf, &ip6->ip6_dst), dstifp ? if_name(dstifp) : "?",
109 ip6->ip6_nxt, reason);
110 }
111
112 /*
113 * Forward a packet. If some error occurs return the sender
114 * an icmp packet. Note we can't always generate a meaningful
115 * icmp message because icmp doesn't have a large enough repertoire
116 * of codes and types.
117 *
118 * If not forwarding, just drop the packet. This could be confusing
119 * if ipforwarding was zero but some routing protocol was advancing
120 * us as a gateway to somewhere. However, we must let the routing
121 * protocol deal with that.
122 *
123 */
124
125 void
126 ip6_forward(struct mbuf *m, int srcrt)
127 {
128 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
129 const struct sockaddr_in6 *dst;
130 struct rtentry *rt;
131 int error = 0, type = 0, code = 0;
132 struct mbuf *mcopy = NULL;
133 struct ifnet *origifp; /* maybe unnecessary */
134 uint32_t inzone, outzone;
135 struct in6_addr src_in6, dst_in6;
136 struct ifnet *rcvif = NULL;
137 struct psref psref;
138 #ifdef IPSEC
139 int needipsec = 0;
140 struct secpolicy *sp = NULL;
141 #endif
142
143 /*
144 * Clear any in-bound checksum flags for this packet.
145 */
146 m->m_pkthdr.csum_flags = 0;
147
148 rcvif = m_get_rcvif_psref(m, &psref);
149 if (__predict_false(rcvif == NULL))
150 goto drop;
151
152 /*
153 * Do not forward packets to multicast destination (should be handled
154 * by ip6_mforward().
155 * Do not forward packets with unspecified source. It was discussed
156 * in July 2000, on ipngwg mailing list.
157 */
158 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
159 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
160 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
161 ip6_cantforward(ip6, rcvif, NULL,
162 ((m->m_flags & (M_BCAST|M_MCAST)) != 0) ? "bcast/mcast" :
163 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ? "mcast/dst" :
164 "unspec/src");
165 goto drop;
166 }
167
168 if (ip6->ip6_hlim <= IPV6_HLIMDEC) {
169 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
170 icmp6_error(m, ICMP6_TIME_EXCEEDED,
171 ICMP6_TIME_EXCEED_TRANSIT, 0);
172 goto out;
173 }
174 ip6->ip6_hlim -= IPV6_HLIMDEC;
175
176 /*
177 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
178 * size of IPv6 + ICMPv6 headers) bytes of the packet in case
179 * we need to generate an ICMP6 message to the src.
180 * Thanks to M_EXT, in most cases copy will not occur.
181 *
182 * It is important to save it before IPsec processing as IPsec
183 * processing may modify the mbuf.
184 */
185 mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN));
186
187 #ifdef IPSEC
188 if (ipsec_used) {
189 /* Check the security policy (SP) for the packet */
190
191 sp = ipsec6_check_policy(m, NULL, 0, &needipsec, &error);
192 if (error != 0) {
193 /*
194 * Hack: -EINVAL is used to signal that a packet
195 * should be silently discarded. This is typically
196 * because we asked key management for an SA and
197 * it was delayed (e.g. kicked up to IKE).
198 */
199 if (error == -EINVAL)
200 error = 0;
201 goto freecopy;
202 }
203 }
204 #endif /* IPSEC */
205
206 if (srcrt) {
207 union {
208 struct sockaddr dst;
209 struct sockaddr_in6 dst6;
210 } u;
211
212 sockaddr_in6_init(&u.dst6, &ip6->ip6_dst, 0, 0, 0);
213 if ((rt = rtcache_lookup(&ip6_forward_rt, &u.dst)) == NULL) {
214 IP6_STATINC(IP6_STAT_NOROUTE);
215 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */
216 if (mcopy) {
217 icmp6_error(mcopy, ICMP6_DST_UNREACH,
218 ICMP6_DST_UNREACH_NOROUTE, 0);
219 }
220 goto drop;
221 }
222 } else if ((rt = rtcache_validate(&ip6_forward_rt)) == NULL &&
223 (rt = rtcache_update(&ip6_forward_rt, 1)) == NULL) {
224 /*
225 * rtcache_getdst(ip6_forward_rt)->sin6_addr was equal to
226 * ip6->ip6_dst
227 */
228 IP6_STATINC(IP6_STAT_NOROUTE);
229 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */
230 if (mcopy) {
231 icmp6_error(mcopy, ICMP6_DST_UNREACH,
232 ICMP6_DST_UNREACH_NOROUTE, 0);
233 }
234 goto drop;
235 }
236 dst = satocsin6(rtcache_getdst(&ip6_forward_rt));
237
238 /*
239 * Source scope check: if a packet can't be delivered to its
240 * destination for the reason that the destination is beyond the scope
241 * of the source address, discard the packet and return an icmp6
242 * destination unreachable error with Code 2 (beyond scope of source
243 * address). We use a local copy of ip6_src, since in6_setscope()
244 * will possibly modify its first argument.
245 * [draft-ietf-ipngwg-icmp-v3-07, Section 3.1]
246 */
247 src_in6 = ip6->ip6_src;
248 inzone = outzone = ~0;
249 if (in6_setscope(&src_in6, rt->rt_ifp, &outzone) != 0 ||
250 in6_setscope(&src_in6, rcvif, &inzone) != 0 ||
251 inzone != outzone) {
252 ip6_cantforward(ip6, rcvif, rt->rt_ifp,
253 "src[%s] inzone %d outzone %d",
254 in6_getscopename(&ip6->ip6_src), inzone, outzone);
255 if (mcopy)
256 icmp6_error(mcopy, ICMP6_DST_UNREACH,
257 ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
258 goto drop;
259 }
260
261 #ifdef IPSEC
262 /*
263 * If we need to encapsulate the packet, do it here
264 * ipsec6_proces_packet will send the packet using ip6_output
265 */
266 if (needipsec) {
267 int s = splsoftnet();
268 error = ipsec6_process_packet(m, sp->req);
269 splx(s);
270 if (mcopy)
271 goto freecopy;
272 }
273 #endif
274
275 /*
276 * Destination scope check: if a packet is going to break the scope
277 * zone of packet's destination address, discard it. This case should
278 * usually be prevented by appropriately-configured routing table, but
279 * we need an explicit check because we may mistakenly forward the
280 * packet to a different zone by (e.g.) a default route.
281 */
282 dst_in6 = ip6->ip6_dst;
283 inzone = outzone = ~0;
284 if (in6_setscope(&dst_in6, rcvif, &inzone) != 0 ||
285 in6_setscope(&dst_in6, rt->rt_ifp, &outzone) != 0 ||
286 inzone != outzone) {
287 ip6_cantforward(ip6, rcvif, rt->rt_ifp,
288 "dst[%s] inzone %d outzone %d",
289 in6_getscopename(&ip6->ip6_dst), inzone, outzone);
290 if (mcopy)
291 icmp6_error(mcopy, ICMP6_DST_UNREACH,
292 ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
293 goto drop;
294 }
295
296 if (m->m_pkthdr.len > IN6_LINKMTU(rt->rt_ifp)) {
297 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig);
298 if (mcopy) {
299 u_long mtu;
300
301 mtu = IN6_LINKMTU(rt->rt_ifp);
302 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu);
303 }
304 goto drop;
305 }
306
307 if (rt->rt_flags & RTF_GATEWAY)
308 dst = (struct sockaddr_in6 *)rt->rt_gateway;
309
310 /*
311 * If we are to forward the packet using the same interface
312 * as one we got the packet from, perhaps we should send a redirect
313 * to sender to shortcut a hop.
314 * Only send redirect if source is sending directly to us,
315 * and if packet was not source routed (or has any options).
316 * Also, don't send redirect if forwarding using a route
317 * modified by a redirect.
318 */
319 if (rt->rt_ifp == rcvif && !srcrt && ip6_sendredirects &&
320 (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) {
321 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) &&
322 nd6_is_addr_neighbor(
323 satocsin6(rtcache_getdst(&ip6_forward_rt)),
324 rt->rt_ifp)) {
325 /*
326 * If the incoming interface is equal to the outgoing
327 * one, the link attached to the interface is
328 * point-to-point, and the IPv6 destination is
329 * regarded as on-link on the link, then it will be
330 * highly probable that the destination address does
331 * not exist on the link and that the packet is going
332 * to loop. Thus, we immediately drop the packet and
333 * send an ICMPv6 error message.
334 * For other routing loops, we dare to let the packet
335 * go to the loop, so that a remote diagnosing host
336 * can detect the loop by traceroute.
337 * type/code is based on suggestion by Rich Draves.
338 * not sure if it is the best pick.
339 */
340 icmp6_error(mcopy, ICMP6_DST_UNREACH,
341 ICMP6_DST_UNREACH_ADDR, 0);
342 goto drop;
343 }
344 type = ND_REDIRECT;
345 }
346
347 /*
348 * Fake scoped addresses. Note that even link-local source or
349 * destinaion can appear, if the originating node just sends the
350 * packet to us (without address resolution for the destination).
351 * Since both icmp6_error and icmp6_redirect_output fill the embedded
352 * link identifiers, we can do this stuff after making a copy for
353 * returning an error.
354 */
355 if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) {
356 /*
357 * See corresponding comments in ip6_output.
358 * XXX: but is it possible that ip6_forward() sends a packet
359 * to a loopback interface? I don't think so, and thus
360 * I bark here. (jinmei (at) kame.net)
361 * XXX: it is common to route invalid packets to loopback.
362 * also, the codepath will be visited on use of ::1 in
363 * rthdr. (itojun)
364 */
365 #if 1
366 if (0)
367 #else
368 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0)
369 #endif
370 {
371 printf("ip6_forward: outgoing interface is loopback. "
372 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
373 ip6_sprintf(&ip6->ip6_src),
374 ip6_sprintf(&ip6->ip6_dst),
375 ip6->ip6_nxt, if_name(rcvif),
376 if_name(rt->rt_ifp));
377 }
378
379 /* we can just use rcvif in forwarding. */
380 origifp = rcvif;
381 }
382 else
383 origifp = rt->rt_ifp;
384 /*
385 * clear embedded scope identifiers if necessary.
386 * in6_clearscope will touch the addresses only when necessary.
387 */
388 in6_clearscope(&ip6->ip6_src);
389 in6_clearscope(&ip6->ip6_dst);
390
391 /*
392 * Run through list of hooks for output packets.
393 */
394 if ((error = pfil_run_hooks(inet6_pfil_hook, &m, rt->rt_ifp,
395 PFIL_OUT)) != 0)
396 goto senderr;
397 if (m == NULL)
398 goto freecopy;
399 ip6 = mtod(m, struct ip6_hdr *);
400
401 error = nd6_output(rt->rt_ifp, origifp, m, dst, rt);
402 if (error) {
403 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard);
404 IP6_STATINC(IP6_STAT_CANTFORWARD);
405 } else {
406 IP6_STATINC(IP6_STAT_FORWARD);
407 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward);
408 if (type)
409 IP6_STATINC(IP6_STAT_REDIRECTSENT);
410 else {
411 #ifdef GATEWAY
412 if (m->m_flags & M_CANFASTFWD)
413 ip6flow_create(&ip6_forward_rt, m);
414 #endif
415 if (mcopy)
416 goto freecopy;
417 }
418 }
419
420 senderr:
421 if (mcopy == NULL)
422 goto out;
423 switch (error) {
424 case 0:
425 if (type == ND_REDIRECT) {
426 icmp6_redirect_output(mcopy, rt);
427 goto out;
428 }
429 goto freecopy;
430
431 case EMSGSIZE:
432 /* xxx MTU is constant in PPP? */
433 goto freecopy;
434
435 case ENOBUFS:
436 /* Tell source to slow down like source quench in IP? */
437 goto freecopy;
438
439 case ENETUNREACH: /* shouldn't happen, checked above */
440 case EHOSTUNREACH:
441 case ENETDOWN:
442 case EHOSTDOWN:
443 default:
444 type = ICMP6_DST_UNREACH;
445 code = ICMP6_DST_UNREACH_ADDR;
446 break;
447 }
448 icmp6_error(mcopy, type, code, 0);
449 goto out;
450
451 freecopy:
452 m_freem(mcopy);
453 goto out;
454 drop:
455 m_freem(m);
456 out:
457 if (rcvif != NULL)
458 m_put_rcvif_psref(rcvif, &psref);
459 return;
460 }
461