xref: /freebsd/sys/netinet6/ip6_forward.c (revision 5129159789cc9d7bc514e4546b88e3427695002d)
1 /*
2  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  * 3. Neither the name of the project nor the names of its contributors
14  *    may be used to endorse or promote products derived from this software
15  *    without specific prior written permission.
16  *
17  * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27  * SUCH DAMAGE.
28  *
29  * $FreeBSD$
30  */
31 
32 #include "opt_key.h"
33 
34 #include <sys/param.h>
35 #include <sys/systm.h>
36 #include <sys/malloc.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/route.h>
48 
49 #include <netinet/in.h>
50 #include <netinet/in_var.h>
51 #include <netinet6/ip6.h>
52 #include <netinet6/ip6_var.h>
53 #include <netinet6/icmp6.h>
54 #include <netinet6/nd6.h>
55 
56 #ifdef IPSEC_IPV6FWD
57 #include <netinet6/ipsec.h>
58 #include <netinet6/ipsec6.h>
59 #include <netkey/key.h>
60 #ifdef KEY_DEBUG
61 #include <netkey/key_debug.h>
62 #else
63 #define DPRINTF(lev,arg)
64 #define DDO(lev, stmt)
65 #define DP(x, y, z)
66 #endif /* KEY_DEBUG */
67 #endif /* IPSEC_IPV6FWD */
68 
69 #ifdef IPV6FIREWALL
70 #include <netinet6/ip6_fw.h>
71 #endif
72 
73 #include <net/net_osdep.h>
74 
75 struct	route_in6 ip6_forward_rt;
76 
77 /*
78  * Forward a packet.  If some error occurs return the sender
79  * an icmp packet.  Note we can't always generate a meaningful
80  * icmp message because icmp doesn't have a large enough repertoire
81  * of codes and types.
82  *
83  * If not forwarding, just drop the packet.  This could be confusing
84  * if ipforwarding was zero but some routing protocol was advancing
85  * us as a gateway to somewhere.  However, we must let the routing
86  * protocol deal with that.
87  *
88  */
89 
90 void
91 ip6_forward(m, srcrt)
92 	struct mbuf *m;
93 	int srcrt;
94 {
95 	struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
96 	register struct sockaddr_in6 *dst;
97 	register struct rtentry *rt;
98 	int error, type = 0, code = 0;
99 	struct mbuf *mcopy;
100 #ifdef IPSEC_IPV6FWD
101 	struct secpolicy *sp = NULL;
102 #endif
103 
104 #ifdef IPSEC_IPV6FWD
105 	/*
106 	 * Check AH/ESP integrity.
107 	 */
108 	/*
109 	 * Don't increment ip6s_cantforward because this is the check
110 	 * before forwarding packet actually.
111 	 */
112 	if (ipsec6_in_reject(m, NULL)) {
113 		ipsec6stat.in_polvio++;
114 		m_freem(m);
115 		return;
116 	}
117 #endif /*IPSEC_IPV6FWD*/
118 
119 	if (m->m_flags & (M_BCAST|M_MCAST) ||
120 	   in6_canforward(&ip6->ip6_src, &ip6->ip6_dst) == 0) {
121 		ip6stat.ip6s_cantforward++;
122 		ip6stat.ip6s_badscope++;
123 		/* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
124 		if (ip6_log_time + ip6_log_interval < time_second) {
125 			char addr[INET6_ADDRSTRLEN];
126 			ip6_log_time = time_second;
127 			strncpy(addr, ip6_sprintf(&ip6->ip6_src), sizeof(addr));
128 			log(LOG_DEBUG,
129 			    "cannot forward "
130 			    "from %s to %s nxt %d received on %s\n",
131 			    addr, ip6_sprintf(&ip6->ip6_dst),
132 			    ip6->ip6_nxt,
133 			    if_name(m->m_pkthdr.rcvif));
134 		}
135 		m_freem(m);
136 		return;
137 	}
138 
139 	if (ip6->ip6_hlim <= IPV6_HLIMDEC) {
140 		/* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
141 		icmp6_error(m, ICMP6_TIME_EXCEEDED,
142 				ICMP6_TIME_EXCEED_TRANSIT, 0);
143 		return;
144 	}
145 	ip6->ip6_hlim -= IPV6_HLIMDEC;
146 
147 #ifdef IPSEC_IPV6FWD
148 	/* get a security policy for this packet */
149 	sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, 0, &error);
150 	if (sp == NULL) {
151 		ipsec6stat.out_inval++;
152 		ip6stat.ip6s_cantforward++;
153 		/* XXX: any icmp ? */
154 		m_freem(m);
155 		return;
156 	}
157 
158 	error = 0;
159 
160 	/* check policy */
161 	switch (sp->policy) {
162 	case IPSEC_POLICY_DISCARD:
163 		/*
164 		 * This packet is just discarded.
165 		 */
166 		ipsec6stat.out_polvio++;
167 		ip6stat.ip6s_cantforward++;
168 		key_freesp(sp);
169 		/* XXX: any icmp ? */
170 		m_freem(m);
171 		return;
172 
173 	case IPSEC_POLICY_BYPASS:
174 	case IPSEC_POLICY_NONE:
175 		/* no need to do IPsec. */
176 		key_freesp(sp);
177 		goto skip_ipsec;
178 
179 	case IPSEC_POLICY_IPSEC:
180 		if (sp->req == NULL) {
181 			/* XXX should be panic ? */
182 			printf("ip6_forward: No IPsec request specified.\n");
183 			ip6stat.ip6s_cantforward++;
184 			key_freesp(sp);
185 			/* XXX: any icmp ? */
186 			m_freem(m);
187 			return;
188 		}
189 		/* do IPsec */
190 		break;
191 
192 	case IPSEC_POLICY_ENTRUST:
193 	default:
194 		/* should be panic ?? */
195 		printf("ip6_forward: Invalid policy found. %d\n", sp->policy);
196 		key_freesp(sp);
197 		goto skip_ipsec;
198 	}
199 
200     {
201 	struct ipsec_output_state state;
202 
203 	/*
204 	 * All the extension headers will become inaccessible
205 	 * (since they can be encrypted).
206 	 * Don't panic, we need no more updates to extension headers
207 	 * on inner IPv6 packet (since they are now encapsulated).
208 	 *
209 	 * IPv6 [ESP|AH] IPv6 [extension headers] payload
210 	 */
211 	bzero(&state, sizeof(state));
212 	state.m = m;
213 	state.ro = NULL;	/* update at ipsec6_output_tunnel() */
214 	state.dst = NULL;	/* update at ipsec6_output_tunnel() */
215 
216 	error = ipsec6_output_tunnel(&state, sp, 0);
217 
218 	m = state.m;
219 	/* XXX allocate a route (ro, dst) again later */
220 	key_freesp(sp);
221 
222 	if (error) {
223 		/* mbuf is already reclaimed in ipsec6_output_tunnel. */
224 		switch (error) {
225 		case EHOSTUNREACH:
226 		case ENETUNREACH:
227 		case EMSGSIZE:
228 		case ENOBUFS:
229 		case ENOMEM:
230 			break;
231 		default:
232 			printf("ip6_output (ipsec): error code %d\n", error);
233 			/*fall through*/
234 		case ENOENT:
235 			/* don't show these error codes to the user */
236 			break;
237 		}
238 		ip6stat.ip6s_cantforward++;
239 		/* XXX: any icmp ? */
240 		m_freem(m);
241 		return;
242 	}
243     }
244     skip_ipsec:
245 #endif /* IPSEC_IPV6FWD */
246 
247 	dst = &ip6_forward_rt.ro_dst;
248 	if (!srcrt) {
249 		/*
250 		 * ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst
251 		 */
252 		if (ip6_forward_rt.ro_rt == 0 ||
253 		    (ip6_forward_rt.ro_rt->rt_flags & RTF_UP) == 0) {
254 			if (ip6_forward_rt.ro_rt) {
255 				RTFREE(ip6_forward_rt.ro_rt);
256 				ip6_forward_rt.ro_rt = 0;
257 			}
258 			/* this probably fails but give it a try again */
259 			rtalloc_ign((struct route *)&ip6_forward_rt,
260 				    RTF_PRCLONING);
261 		}
262 
263 		if (ip6_forward_rt.ro_rt == 0) {
264 			ip6stat.ip6s_noroute++;
265 			/* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */
266 			icmp6_error(m, ICMP6_DST_UNREACH,
267 				    ICMP6_DST_UNREACH_NOROUTE, 0);
268 			return;
269 		}
270 	} else if ((rt = ip6_forward_rt.ro_rt) == 0 ||
271 		 !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) {
272 		if (ip6_forward_rt.ro_rt) {
273 			RTFREE(ip6_forward_rt.ro_rt);
274 			ip6_forward_rt.ro_rt = 0;
275 		}
276 		bzero(dst, sizeof(*dst));
277 		dst->sin6_len = sizeof(struct sockaddr_in6);
278 		dst->sin6_family = AF_INET6;
279 		dst->sin6_addr = ip6->ip6_dst;
280 
281   		rtalloc_ign((struct route *)&ip6_forward_rt, RTF_PRCLONING);
282 		if (ip6_forward_rt.ro_rt == 0) {
283 			ip6stat.ip6s_noroute++;
284 			/* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */
285 			icmp6_error(m, ICMP6_DST_UNREACH,
286 				    ICMP6_DST_UNREACH_NOROUTE, 0);
287 			return;
288 		}
289 	}
290 	rt = ip6_forward_rt.ro_rt;
291 	if (m->m_pkthdr.len > rt->rt_ifp->if_mtu){
292 		in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig);
293  		icmp6_error(m, ICMP6_PACKET_TOO_BIG, 0, rt->rt_ifp->if_mtu);
294 		return;
295  	}
296 
297 	if (rt->rt_flags & RTF_GATEWAY)
298 		dst = (struct sockaddr_in6 *)rt->rt_gateway;
299 	/*
300 	 * Save at most 528 bytes of the packet in case
301 	 * we need to generate an ICMP6 message to the src.
302 	 * Thanks to M_EXT, in most cases copy will not occur.
303 	 */
304 	mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN));
305 
306 	/*
307 	 * If we are to forward the packet using the same interface
308 	 * as one we got the packet from, perhaps we should send a redirect
309 	 * to sender to shortcut a hop.
310 	 * Only send redirect if source is sending directly to us,
311 	 * and if packet was not source routed (or has any options).
312 	 * Also, don't send redirect if forwarding using a route
313 	 * modified by a redirect.
314 	 */
315 	if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt &&
316 	    (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0)
317 		type = ND_REDIRECT;
318 
319 #ifdef IPV6FIREWALL
320 	/*
321 	 * Check with the firewall...
322 	 */
323 	if (ip6_fw_chk_ptr) {
324 		u_short port = 0;
325 		/* If ipfw says divert, we have to just drop packet */
326 		if ((*ip6_fw_chk_ptr)(&ip6, rt->rt_ifp, &port, &m)) {
327 			m_freem(m);
328 			goto freecopy;
329 		}
330 		if (!m)
331 			goto freecopy;
332 	}
333 #endif
334 
335 	error = nd6_output(rt->rt_ifp, m, dst, rt);
336 	if (error) {
337 		in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard);
338 		ip6stat.ip6s_cantforward++;
339 	} else {
340 		ip6stat.ip6s_forward++;
341 		in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward);
342 		if (type)
343 			ip6stat.ip6s_redirectsent++;
344 		else {
345 			if (mcopy)
346 				goto freecopy;
347 		}
348 	}
349 	if (mcopy == NULL)
350 		return;
351 
352 	switch (error) {
353 	case 0:
354 		if (type == ND_REDIRECT) {
355 			icmp6_redirect_output(mcopy, rt);
356 			return;
357 		}
358 		goto freecopy;
359 
360 	case EMSGSIZE:
361 		/* xxx MTU is constant in PPP? */
362 		goto freecopy;
363 
364 	case ENOBUFS:
365 		/* Tell source to slow down like source quench in IP? */
366 		goto freecopy;
367 
368 	case ENETUNREACH:	/* shouldn't happen, checked above */
369 	case EHOSTUNREACH:
370 	case ENETDOWN:
371 	case EHOSTDOWN:
372 	default:
373 		type = ICMP6_DST_UNREACH;
374 		code = ICMP6_DST_UNREACH_ADDR;
375 		break;
376 	}
377 	icmp6_error(mcopy, type, code, 0);
378 	return;
379 
380  freecopy:
381 	m_freem(mcopy);
382 	return;
383 }
384