2 * SPDX-License-Identifier: BSD-3-Clause
4 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
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31 * $KAME: ip6_forward.c,v 1.69 2001/05/17 03:48:30 itojun Exp $
34 #include <sys/cdefs.h>
35 __FBSDID("$FreeBSD$");
38 #include "opt_inet6.h"
39 #include "opt_ipsec.h"
40 #include "opt_ipstealth.h"
43 #include <sys/param.h>
44 #include <sys/systm.h>
45 #include <sys/malloc.h>
47 #include <sys/domain.h>
48 #include <sys/protosw.h>
49 #include <sys/socket.h>
50 #include <sys/errno.h>
52 #include <sys/kernel.h>
53 #include <sys/syslog.h>
56 #include <net/if_var.h>
57 #include <net/netisr.h>
58 #include <net/route.h>
61 #include <netinet/in.h>
62 #include <netinet/in_var.h>
63 #include <netinet/in_systm.h>
64 #include <netinet/ip.h>
65 #include <netinet/ip_var.h>
66 #include <netinet6/in6_var.h>
67 #include <netinet/ip6.h>
68 #include <netinet6/ip6_var.h>
69 #include <netinet6/scope6_var.h>
70 #include <netinet/icmp6.h>
71 #include <netinet6/nd6.h>
73 #include <netinet/in_pcb.h>
75 #include <netipsec/ipsec_support.h>
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
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.
90 ip6_forward(struct mbuf *m, int srcrt)
92 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
93 struct sockaddr_in6 *dst = NULL;
94 struct rtentry *rt = NULL;
95 struct route_in6 rin6;
96 int error, type = 0, code = 0;
97 struct mbuf *mcopy = NULL;
98 struct ifnet *origifp; /* maybe unnecessary */
99 u_int32_t inzone, outzone;
100 struct in6_addr src_in6, dst_in6, odst;
101 struct m_tag *fwd_tag;
102 char ip6bufs[INET6_ADDRSTRLEN], ip6bufd[INET6_ADDRSTRLEN];
105 * Do not forward packets to multicast destination (should be handled
107 * Do not forward packets with unspecified source. It was discussed
108 * in July 2000, on the ipngwg mailing list.
110 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
111 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
112 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
113 IP6STAT_INC(ip6s_cantforward);
114 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
115 if (V_ip6_log_time + V_ip6_log_interval < time_uptime) {
116 V_ip6_log_time = time_uptime;
119 "from %s to %s nxt %d received on %s\n",
120 ip6_sprintf(ip6bufs, &ip6->ip6_src),
121 ip6_sprintf(ip6bufd, &ip6->ip6_dst),
123 if_name(m->m_pkthdr.rcvif));
133 ip6->ip6_hlim <= IPV6_HLIMDEC) {
134 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
135 icmp6_error(m, ICMP6_TIME_EXCEEDED,
136 ICMP6_TIME_EXCEED_TRANSIT, 0);
141 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
142 * size of IPv6 + ICMPv6 headers) bytes of the packet in case
143 * we need to generate an ICMP6 message to the src.
144 * Thanks to M_EXT, in most cases copy will not occur.
146 * It is important to save it before IPsec processing as IPsec
147 * processing may modify the mbuf.
149 mcopy = m_copym(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN),
152 if (V_ip6stealth == 0)
154 ip6->ip6_hlim -= IPV6_HLIMDEC;
156 #if defined(IPSEC) || defined(IPSEC_SUPPORT)
157 if (IPSEC_ENABLED(ipv6)) {
158 if ((error = IPSEC_FORWARD(ipv6, m)) != 0) {
159 /* mbuf consumed by IPsec */
161 if (error != EINPROGRESS)
162 IP6STAT_INC(ip6s_cantforward);
165 /* No IPsec processing required */
169 bzero(&rin6, sizeof(struct route_in6));
170 dst = (struct sockaddr_in6 *)&rin6.ro_dst;
171 dst->sin6_len = sizeof(struct sockaddr_in6);
172 dst->sin6_family = AF_INET6;
173 dst->sin6_addr = ip6->ip6_dst;
175 rin6.ro_rt = in6_rtalloc1((struct sockaddr *)dst, 0, 0, M_GETFIB(m));
177 if (rin6.ro_rt != NULL)
178 RT_UNLOCK(rin6.ro_rt);
180 IP6STAT_INC(ip6s_noroute);
181 in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
183 icmp6_error(mcopy, ICMP6_DST_UNREACH,
184 ICMP6_DST_UNREACH_NOROUTE, 0);
190 * Source scope check: if a packet can't be delivered to its
191 * destination for the reason that the destination is beyond the scope
192 * of the source address, discard the packet and return an icmp6
193 * destination unreachable error with Code 2 (beyond scope of source
194 * address). We use a local copy of ip6_src, since in6_setscope()
195 * will possibly modify its first argument.
196 * [draft-ietf-ipngwg-icmp-v3-04.txt, Section 3.1]
198 src_in6 = ip6->ip6_src;
199 if (in6_setscope(&src_in6, rt->rt_ifp, &outzone)) {
200 /* XXX: this should not happen */
201 IP6STAT_INC(ip6s_cantforward);
202 IP6STAT_INC(ip6s_badscope);
205 if (in6_setscope(&src_in6, m->m_pkthdr.rcvif, &inzone)) {
206 IP6STAT_INC(ip6s_cantforward);
207 IP6STAT_INC(ip6s_badscope);
210 if (inzone != outzone) {
211 IP6STAT_INC(ip6s_cantforward);
212 IP6STAT_INC(ip6s_badscope);
213 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard);
215 if (V_ip6_log_time + V_ip6_log_interval < time_uptime) {
216 V_ip6_log_time = time_uptime;
219 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
220 ip6_sprintf(ip6bufs, &ip6->ip6_src),
221 ip6_sprintf(ip6bufd, &ip6->ip6_dst),
223 if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp));
226 icmp6_error(mcopy, ICMP6_DST_UNREACH,
227 ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
232 * Destination scope check: if a packet is going to break the scope
233 * zone of packet's destination address, discard it. This case should
234 * usually be prevented by appropriately-configured routing table, but
235 * we need an explicit check because we may mistakenly forward the
236 * packet to a different zone by (e.g.) a default route.
238 dst_in6 = ip6->ip6_dst;
239 if (in6_setscope(&dst_in6, m->m_pkthdr.rcvif, &inzone) != 0 ||
240 in6_setscope(&dst_in6, rt->rt_ifp, &outzone) != 0 ||
242 IP6STAT_INC(ip6s_cantforward);
243 IP6STAT_INC(ip6s_badscope);
247 if (rt->rt_flags & RTF_GATEWAY)
248 dst = (struct sockaddr_in6 *)rt->rt_gateway;
251 * If we are to forward the packet using the same interface
252 * as one we got the packet from, perhaps we should send a redirect
253 * to sender to shortcut a hop.
254 * Only send redirect if source is sending directly to us,
255 * and if packet was not source routed (or has any options).
256 * Also, don't send redirect if forwarding using a route
257 * modified by a redirect.
259 if (V_ip6_sendredirects && rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt &&
260 (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) {
261 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) != 0) {
263 * If the incoming interface is equal to the outgoing
264 * one, and the link attached to the interface is
265 * point-to-point, then it will be highly probable
266 * that a routing loop occurs. Thus, we immediately
267 * drop the packet and send an ICMPv6 error message.
269 * type/code is based on suggestion by Rich Draves.
270 * not sure if it is the best pick.
272 icmp6_error(mcopy, ICMP6_DST_UNREACH,
273 ICMP6_DST_UNREACH_ADDR, 0);
280 * Fake scoped addresses. Note that even link-local source or
281 * destinaion can appear, if the originating node just sends the
282 * packet to us (without address resolution for the destination).
283 * Since both icmp6_error and icmp6_redirect_output fill the embedded
284 * link identifiers, we can do this stuff after making a copy for
285 * returning an error.
287 if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) {
289 * See corresponding comments in ip6_output.
290 * XXX: but is it possible that ip6_forward() sends a packet
291 * to a loopback interface? I don't think so, and thus
292 * I bark here. (jinmei@kame.net)
293 * XXX: it is common to route invalid packets to loopback.
294 * also, the codepath will be visited on use of ::1 in
300 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0)
303 printf("ip6_forward: outgoing interface is loopback. "
304 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
305 ip6_sprintf(ip6bufs, &ip6->ip6_src),
306 ip6_sprintf(ip6bufd, &ip6->ip6_dst),
307 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif),
308 if_name(rt->rt_ifp));
311 /* we can just use rcvif in forwarding. */
312 origifp = m->m_pkthdr.rcvif;
315 origifp = rt->rt_ifp;
317 * clear embedded scope identifiers if necessary.
318 * in6_clearscope will touch the addresses only when necessary.
320 in6_clearscope(&ip6->ip6_src);
321 in6_clearscope(&ip6->ip6_dst);
323 /* Jump over all PFIL processing if hooks are not active. */
324 if (!PFIL_HOOKED_OUT(V_inet6_pfil_head))
328 /* Run through list of hooks for forwarded packets. */
329 if (pfil_run_hooks(V_inet6_pfil_head, &m, rt->rt_ifp, PFIL_OUT |
330 PFIL_FWD, NULL) != PFIL_PASS)
332 ip6 = mtod(m, struct ip6_hdr *);
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;
342 goto again; /* Redo the routing table lookup. */
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;
356 if (m->m_pkthdr.csum_flags & CSUM_SCTP_IPV6)
357 m->m_pkthdr.csum_flags |= CSUM_SCTP_VALID;
359 error = netisr_queue(NETISR_IPV6, m);
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);
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);
379 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0,
380 IN6_LINKMTU(rt->rt_ifp));
384 error = nd6_output_ifp(rt->rt_ifp, origifp, m, dst, NULL);
386 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard);
387 IP6STAT_INC(ip6s_cantforward);
389 IP6STAT_INC(ip6s_forward);
390 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward);
392 IP6STAT_INC(ip6s_redirectsent);
403 if (type == ND_REDIRECT) {
404 icmp6_redirect_output(mcopy, rt);
410 /* xxx MTU is constant in PPP? */
414 /* Tell source to slow down like source quench in IP? */
417 case ENETUNREACH: /* shouldn't happen, checked above */
422 type = ICMP6_DST_UNREACH;
423 code = ICMP6_DST_UNREACH_ADDR;
426 icmp6_error(mcopy, type, code, 0);