Line data Source code
1 : /* $OpenBSD: ip6_forward.c,v 1.97 2017/11/28 15:32:51 mpi 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/domain.h>
39 : #include <sys/protosw.h>
40 : #include <sys/socket.h>
41 : #include <sys/errno.h>
42 : #include <sys/time.h>
43 : #include <sys/kernel.h>
44 : #include <sys/syslog.h>
45 :
46 : #include <net/if.h>
47 : #include <net/if_var.h>
48 : #include <net/if_enc.h>
49 : #include <net/route.h>
50 :
51 : #include <netinet/in.h>
52 : #include <netinet/ip_var.h>
53 : #include <netinet6/in6_var.h>
54 : #include <netinet/ip6.h>
55 : #include <netinet6/ip6_var.h>
56 : #include <netinet/icmp6.h>
57 : #include <netinet6/nd6.h>
58 :
59 : #if NPF > 0
60 : #include <net/pfvar.h>
61 : #endif
62 :
63 : #ifdef IPSEC
64 : #include <netinet/ip_ipsp.h>
65 : #include <netinet/ip_ah.h>
66 : #include <netinet/ip_esp.h>
67 : #include <netinet/udp.h>
68 : #include <netinet/tcp.h>
69 : #endif
70 :
71 : /*
72 : * Forward a packet. If some error occurs return the sender
73 : * an icmp packet. Note we can't always generate a meaningful
74 : * icmp message because icmp doesn't have a large enough repertoire
75 : * of codes and types.
76 : *
77 : * If not forwarding, just drop the packet. This could be confusing
78 : * if ipforwarding was zero but some routing protocol was advancing
79 : * us as a gateway to somewhere. However, we must let the routing
80 : * protocol deal with that.
81 : *
82 : */
83 :
84 : void
85 0 : ip6_forward(struct mbuf *m, struct rtentry *rt, int srcrt)
86 : {
87 0 : struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
88 0 : struct sockaddr_in6 *dst, sin6;
89 : struct ifnet *ifp = NULL;
90 0 : int error = 0, type = 0, code = 0;
91 : struct mbuf *mcopy = NULL;
92 : #ifdef IPSEC
93 : struct tdb *tdb = NULL;
94 : #endif /* IPSEC */
95 0 : char src6[INET6_ADDRSTRLEN], dst6[INET6_ADDRSTRLEN];
96 :
97 : /*
98 : * Do not forward packets to multicast destination (should be handled
99 : * by ip6_mforward().
100 : * Do not forward packets with unspecified source. It was discussed
101 : * in July 2000, on ipngwg mailing list.
102 : */
103 0 : if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
104 0 : IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
105 0 : IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
106 0 : ip6stat_inc(ip6s_cantforward);
107 0 : if (ip6_log_time + ip6_log_interval < time_uptime) {
108 0 : ip6_log_time = time_uptime;
109 0 : inet_ntop(AF_INET6, &ip6->ip6_src, src6, sizeof(src6));
110 0 : inet_ntop(AF_INET6, &ip6->ip6_dst, dst6, sizeof(dst6));
111 0 : log(LOG_DEBUG,
112 : "cannot forward "
113 : "from %s to %s nxt %d received on inteface %u\n",
114 : src6, dst6,
115 0 : ip6->ip6_nxt,
116 0 : m->m_pkthdr.ph_ifidx);
117 0 : }
118 0 : m_freem(m);
119 0 : goto out;
120 : }
121 :
122 0 : if (ip6->ip6_hlim <= IPV6_HLIMDEC) {
123 0 : icmp6_error(m, ICMP6_TIME_EXCEEDED,
124 : ICMP6_TIME_EXCEED_TRANSIT, 0);
125 0 : goto out;
126 : }
127 0 : ip6->ip6_hlim -= IPV6_HLIMDEC;
128 :
129 : /*
130 : * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
131 : * size of IPv6 + ICMPv6 headers) bytes of the packet in case
132 : * we need to generate an ICMP6 message to the src.
133 : * Thanks to M_EXT, in most cases copy will not occur.
134 : *
135 : * It is important to save it before IPsec processing as IPsec
136 : * processing may modify the mbuf.
137 : */
138 0 : mcopy = m_copym(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN),
139 : M_NOWAIT);
140 :
141 : #if NPF > 0
142 : reroute:
143 : #endif
144 :
145 : #ifdef IPSEC
146 0 : if (ipsec_in_use) {
147 0 : tdb = ip6_output_ipsec_lookup(m, &error, NULL);
148 0 : if (error != 0) {
149 : /*
150 : * -EINVAL is used to indicate that the packet should
151 : * be silently dropped, typically because we've asked
152 : * key management for an SA.
153 : */
154 0 : if (error == -EINVAL) /* Should silently drop packet */
155 0 : error = 0;
156 :
157 0 : m_freem(m);
158 0 : goto freecopy;
159 : }
160 : }
161 : #endif /* IPSEC */
162 :
163 : dst = &sin6;
164 0 : memset(dst, 0, sizeof(*dst));
165 0 : dst->sin6_len = sizeof(struct sockaddr_in6);
166 0 : dst->sin6_family = AF_INET6;
167 0 : dst->sin6_addr = ip6->ip6_dst;
168 :
169 0 : if (!rtisvalid(rt)) {
170 0 : rtfree(rt);
171 0 : rt = rtalloc_mpath(sin6tosa(dst), &ip6->ip6_src.s6_addr32[0],
172 0 : m->m_pkthdr.ph_rtableid);
173 0 : if (rt == NULL) {
174 0 : ip6stat_inc(ip6s_noroute);
175 0 : if (mcopy) {
176 0 : icmp6_error(mcopy, ICMP6_DST_UNREACH,
177 : ICMP6_DST_UNREACH_NOROUTE, 0);
178 0 : }
179 0 : m_freem(m);
180 0 : goto out;
181 : }
182 : }
183 :
184 : /*
185 : * Scope check: if a packet can't be delivered to its destination
186 : * for the reason that the destination is beyond the scope of the
187 : * source address, discard the packet and return an icmp6 destination
188 : * unreachable error with Code 2 (beyond scope of source address).
189 : * [draft-ietf-ipngwg-icmp-v3-00.txt, Section 3.1]
190 : */
191 0 : if (in6_addr2scopeid(m->m_pkthdr.ph_ifidx, &ip6->ip6_src) !=
192 0 : in6_addr2scopeid(rt->rt_ifidx, &ip6->ip6_src)) {
193 0 : ip6stat_inc(ip6s_cantforward);
194 0 : ip6stat_inc(ip6s_badscope);
195 :
196 0 : if (ip6_log_time + ip6_log_interval < time_uptime) {
197 0 : ip6_log_time = time_uptime;
198 0 : inet_ntop(AF_INET6, &ip6->ip6_src, src6, sizeof(src6));
199 0 : inet_ntop(AF_INET6, &ip6->ip6_dst, dst6, sizeof(dst6));
200 0 : log(LOG_DEBUG,
201 : "cannot forward "
202 : "src %s, dst %s, nxt %d, rcvif %u, outif %u\n",
203 : src6, dst6,
204 0 : ip6->ip6_nxt,
205 0 : m->m_pkthdr.ph_ifidx, rt->rt_ifidx);
206 0 : }
207 0 : if (mcopy)
208 0 : icmp6_error(mcopy, ICMP6_DST_UNREACH,
209 : ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
210 0 : m_freem(m);
211 0 : goto out;
212 : }
213 :
214 : #ifdef IPSEC
215 : /*
216 : * Check if the packet needs encapsulation.
217 : * ipsp_process_packet will never come back to here.
218 : * XXX ipsp_process_packet() calls ip6_output(), and there'll be no
219 : * PMTU notification. is it okay?
220 : */
221 0 : if (tdb != NULL) {
222 : /* Callee frees mbuf */
223 0 : error = ip6_output_ipsec_send(tdb, m, 0, 1);
224 0 : if (error)
225 : goto senderr;
226 : goto freecopy;
227 : }
228 : #endif /* IPSEC */
229 :
230 0 : if (rt->rt_flags & RTF_GATEWAY)
231 0 : dst = 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 0 : ifp = if_get(rt->rt_ifidx);
243 0 : if (ifp == NULL) {
244 0 : m_freem(m);
245 0 : goto freecopy;
246 : }
247 0 : if (rt->rt_ifidx == m->m_pkthdr.ph_ifidx && !srcrt &&
248 0 : ip6_sendredirects &&
249 0 : (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) {
250 0 : if ((ifp->if_flags & IFF_POINTOPOINT) &&
251 0 : nd6_is_addr_neighbor(&sin6, 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 0 : if (mcopy)
268 0 : icmp6_error(mcopy, ICMP6_DST_UNREACH,
269 : ICMP6_DST_UNREACH_ADDR, 0);
270 0 : m_freem(m);
271 0 : goto out;
272 : }
273 : type = ND_REDIRECT;
274 0 : }
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 0 : if (IN6_IS_SCOPE_EMBED(&ip6->ip6_src))
285 0 : ip6->ip6_src.s6_addr16[1] = 0;
286 0 : if (IN6_IS_SCOPE_EMBED(&ip6->ip6_dst))
287 0 : ip6->ip6_dst.s6_addr16[1] = 0;
288 :
289 : #if NPF > 0
290 0 : if (pf_test(AF_INET6, PF_FWD, ifp, &m) != PF_PASS) {
291 0 : m_freem(m);
292 0 : goto senderr;
293 : }
294 0 : if (m == NULL)
295 : goto senderr;
296 0 : ip6 = mtod(m, struct ip6_hdr *);
297 0 : 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 0 : m->m_pkthdr.pf.flags &= ~(PF_TAG_GENERATED | PF_TAG_REROUTE);
301 0 : } else if (m->m_pkthdr.pf.flags & PF_TAG_REROUTE) {
302 : /* tag as generated to skip over pf_test on rerun */
303 0 : m->m_pkthdr.pf.flags |= PF_TAG_GENERATED;
304 : srcrt = 1;
305 0 : rtfree(rt);
306 : rt = NULL;
307 0 : if_put(ifp);
308 : ifp = NULL;
309 0 : goto reroute;
310 : }
311 : #endif
312 0 : in6_proto_cksum_out(m, ifp);
313 :
314 : /* Check the size after pf_test to give pf a chance to refragment. */
315 0 : if (m->m_pkthdr.len > ifp->if_mtu) {
316 0 : if (mcopy)
317 0 : icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0,
318 : ifp->if_mtu);
319 0 : m_freem(m);
320 0 : goto out;
321 : }
322 :
323 0 : error = ifp->if_output(ifp, m, sin6tosa(dst), rt);
324 0 : if (error) {
325 0 : ip6stat_inc(ip6s_cantforward);
326 0 : } else {
327 0 : ip6stat_inc(ip6s_forward);
328 0 : if (type)
329 0 : ip6stat_inc(ip6s_redirectsent);
330 : else {
331 0 : if (mcopy)
332 : goto freecopy;
333 : }
334 : }
335 :
336 : #if NPF > 0 || defined(IPSEC)
337 : senderr:
338 : #endif
339 0 : if (mcopy == NULL)
340 : goto out;
341 0 : switch (error) {
342 : case 0:
343 0 : if (type == ND_REDIRECT) {
344 0 : icmp6_redirect_output(mcopy, rt);
345 0 : goto out;
346 : }
347 : goto freecopy;
348 :
349 : case EMSGSIZE:
350 : /* xxx MTU is constant in PPP? */
351 : goto freecopy;
352 :
353 : case ENOBUFS:
354 : /* Tell source to slow down like source quench in IP? */
355 : goto freecopy;
356 :
357 : case ENETUNREACH: /* shouldn't happen, checked above */
358 : case EHOSTUNREACH:
359 : case ENETDOWN:
360 : case EHOSTDOWN:
361 : default:
362 : type = ICMP6_DST_UNREACH;
363 : code = ICMP6_DST_UNREACH_ADDR;
364 : break;
365 : }
366 0 : icmp6_error(mcopy, type, code, 0);
367 0 : goto out;
368 :
369 : freecopy:
370 0 : m_freem(mcopy);
371 : out:
372 0 : rtfree(rt);
373 0 : if_put(ifp);
374 0 : }
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