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("$FreeBSD$");
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 */
88void
89ip6_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
167again:
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;
173again2:
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
374pass:
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;
432bad:
433	m_freem(m);
434out:
435	if (rt != NULL)
436		RTFREE(rt);
437}
438