xref: /freebsd/sys/netinet/ip_encap.c (revision d8a0fe102c0cfdfcd5b818f850eff09d8536c9bc) 
1 /*	$KAME: ip_encap.c,v 1.41 2001/03/15 08:35:08 itojun Exp $	*/
2 
3 /*-
4  * SPDX-License-Identifier: BSD-3-Clause
5  *
6  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
7  * All rights reserved.
8  *
9  * Redistribution and use in source and binary forms, with or without
10  * modification, are permitted provided that the following conditions
11  * are met:
12  * 1. Redistributions of source code must retain the above copyright
13  *    notice, this list of conditions and the following disclaimer.
14  * 2. Redistributions in binary form must reproduce the above copyright
15  *    notice, this list of conditions and the following disclaimer in the
16  *    documentation and/or other materials provided with the distribution.
17  * 3. Neither the name of the project nor the names of its contributors
18  *    may be used to endorse or promote products derived from this software
19  *    without specific prior written permission.
20  *
21  * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31  * SUCH DAMAGE.
32  */
33 /*
34  * My grandfather said that there's a devil inside tunnelling technology...
35  *
36  * We have surprisingly many protocols that want packets with IP protocol
37  * #4 or #41.  Here's a list of protocols that want protocol #41:
38  *	RFC1933 configured tunnel
39  *	RFC1933 automatic tunnel
40  *	RFC2401 IPsec tunnel
41  *	RFC2473 IPv6 generic packet tunnelling
42  *	RFC2529 6over4 tunnel
43  *	mobile-ip6 (uses RFC2473)
44  *	RFC3056 6to4 tunnel
45  *	isatap tunnel
46  * Here's a list of protocol that want protocol #4:
47  *	RFC1853 IPv4-in-IPv4 tunnelling
48  *	RFC2003 IPv4 encapsulation within IPv4
49  *	RFC2344 reverse tunnelling for mobile-ip4
50  *	RFC2401 IPsec tunnel
51  * Well, what can I say.  They impose different en/decapsulation mechanism
52  * from each other, so they need separate protocol handler.  The only one
53  * we can easily determine by protocol # is IPsec, which always has
54  * AH/ESP/IPComp header right after outer IP header.
55  *
56  * So, clearly good old protosw does not work for protocol #4 and #41.
57  * The code will let you match protocol via src/dst address pair.
58  */
59 /* XXX is M_NETADDR correct? */
60 
61 #include <sys/cdefs.h>
62 __FBSDID("$FreeBSD$");
63 
64 #include "opt_mrouting.h"
65 #include "opt_inet.h"
66 #include "opt_inet6.h"
67 
68 #include <sys/param.h>
69 #include <sys/systm.h>
70 #include <sys/lock.h>
71 #include <sys/mutex.h>
72 #include <sys/socket.h>
73 #include <sys/sockio.h>
74 #include <sys/mbuf.h>
75 #include <sys/errno.h>
76 #include <sys/protosw.h>
77 #include <sys/queue.h>
78 
79 #include <net/if.h>
80 #include <net/route.h>
81 
82 #include <netinet/in.h>
83 #include <netinet/in_systm.h>
84 #include <netinet/ip.h>
85 #include <netinet/ip_var.h>
86 #include <netinet/ip_encap.h>
87 
88 #ifdef INET6
89 #include <netinet/ip6.h>
90 #include <netinet6/ip6_var.h>
91 #endif
92 
93 #include <machine/stdarg.h>
94 
95 #include <sys/kernel.h>
96 #include <sys/malloc.h>
97 static MALLOC_DEFINE(M_NETADDR, "encap_export_host", "Export host address structure");
98 
99 static void encap_add(struct encaptab *);
100 static int mask_match(const struct encaptab *, const struct sockaddr *,
101 		const struct sockaddr *);
102 static void encap_fillarg(struct mbuf *, void *);
103 
104 /*
105  * All global variables in ip_encap.c are locked using encapmtx.
106  */
107 static struct mtx encapmtx;
108 MTX_SYSINIT(encapmtx, &encapmtx, "encapmtx", MTX_DEF);
109 static LIST_HEAD(, encaptab) encaptab = LIST_HEAD_INITIALIZER(encaptab);
110 
111 /*
112  * We currently keey encap_init() for source code compatibility reasons --
113  * it's referenced by KAME pieces in netinet6.
114  */
115 void
116 encap_init(void)
117 {
118 }
119 
120 #ifdef INET
121 int
122 encap4_input(struct mbuf **mp, int *offp, int proto)
123 {
124 	struct ip *ip;
125 	struct mbuf *m;
126 	struct sockaddr_in s, d;
127 	const struct protosw *psw;
128 	struct encaptab *ep, *match;
129 	void *arg;
130 	int matchprio, off, prio;
131 
132 	m = *mp;
133 	off = *offp;
134 	ip = mtod(m, struct ip *);
135 
136 	bzero(&s, sizeof(s));
137 	s.sin_family = AF_INET;
138 	s.sin_len = sizeof(struct sockaddr_in);
139 	s.sin_addr = ip->ip_src;
140 	bzero(&d, sizeof(d));
141 	d.sin_family = AF_INET;
142 	d.sin_len = sizeof(struct sockaddr_in);
143 	d.sin_addr = ip->ip_dst;
144 
145 	arg = NULL;
146 	psw = NULL;
147 	match = NULL;
148 	matchprio = 0;
149 	mtx_lock(&encapmtx);
150 	LIST_FOREACH(ep, &encaptab, chain) {
151 		if (ep->af != AF_INET)
152 			continue;
153 		if (ep->proto >= 0 && ep->proto != proto)
154 			continue;
155 		if (ep->func)
156 			prio = (*ep->func)(m, off, proto, ep->arg);
157 		else {
158 			/*
159 			 * it's inbound traffic, we need to match in reverse
160 			 * order
161 			 */
162 			prio = mask_match(ep, (struct sockaddr *)&d,
163 			    (struct sockaddr *)&s);
164 		}
165 
166 		/*
167 		 * We prioritize the matches by using bit length of the
168 		 * matches.  mask_match() and user-supplied matching function
169 		 * should return the bit length of the matches (for example,
170 		 * if both src/dst are matched for IPv4, 64 should be returned).
171 		 * 0 or negative return value means "it did not match".
172 		 *
173 		 * The question is, since we have two "mask" portion, we
174 		 * cannot really define total order between entries.
175 		 * For example, which of these should be preferred?
176 		 * mask_match() returns 48 (32 + 16) for both of them.
177 		 *	src=3ffe::/16, dst=3ffe:501::/32
178 		 *	src=3ffe:501::/32, dst=3ffe::/16
179 		 *
180 		 * We need to loop through all the possible candidates
181 		 * to get the best match - the search takes O(n) for
182 		 * n attachments (i.e. interfaces).
183 		 */
184 		if (prio <= 0)
185 			continue;
186 		if (prio > matchprio) {
187 			matchprio = prio;
188 			match = ep;
189 		}
190 	}
191 	if (match != NULL) {
192 		psw = match->psw;
193 		arg = match->arg;
194 	}
195 	mtx_unlock(&encapmtx);
196 
197 	if (match != NULL) {
198 		/* found a match, "match" has the best one */
199 		if (psw != NULL && psw->pr_input != NULL) {
200 			encap_fillarg(m, arg);
201 			(*psw->pr_input)(mp, offp, proto);
202 		} else
203 			m_freem(m);
204 		return (IPPROTO_DONE);
205 	}
206 
207 	/* last resort: inject to raw socket */
208 	return (rip_input(mp, offp, proto));
209 }
210 #endif
211 
212 #ifdef INET6
213 int
214 encap6_input(struct mbuf **mp, int *offp, int proto)
215 {
216 	struct mbuf *m = *mp;
217 	struct ip6_hdr *ip6;
218 	struct sockaddr_in6 s, d;
219 	const struct protosw *psw;
220 	struct encaptab *ep, *match;
221 	void *arg;
222 	int prio, matchprio;
223 
224 	ip6 = mtod(m, struct ip6_hdr *);
225 
226 	bzero(&s, sizeof(s));
227 	s.sin6_family = AF_INET6;
228 	s.sin6_len = sizeof(struct sockaddr_in6);
229 	s.sin6_addr = ip6->ip6_src;
230 	bzero(&d, sizeof(d));
231 	d.sin6_family = AF_INET6;
232 	d.sin6_len = sizeof(struct sockaddr_in6);
233 	d.sin6_addr = ip6->ip6_dst;
234 
235 	arg = NULL;
236 	psw = NULL;
237 	match = NULL;
238 	matchprio = 0;
239 	mtx_lock(&encapmtx);
240 	LIST_FOREACH(ep, &encaptab, chain) {
241 		if (ep->af != AF_INET6)
242 			continue;
243 		if (ep->proto >= 0 && ep->proto != proto)
244 			continue;
245 		if (ep->func)
246 			prio = (*ep->func)(m, *offp, proto, ep->arg);
247 		else {
248 			/*
249 			 * it's inbound traffic, we need to match in reverse
250 			 * order
251 			 */
252 			prio = mask_match(ep, (struct sockaddr *)&d,
253 			    (struct sockaddr *)&s);
254 		}
255 
256 		/* see encap4_input() for issues here */
257 		if (prio <= 0)
258 			continue;
259 		if (prio > matchprio) {
260 			matchprio = prio;
261 			match = ep;
262 		}
263 	}
264 	if (match != NULL) {
265 		psw = match->psw;
266 		arg = match->arg;
267 	}
268 	mtx_unlock(&encapmtx);
269 
270 	if (match != NULL) {
271 		/* found a match */
272 		if (psw != NULL && psw->pr_input != NULL) {
273 			encap_fillarg(m, arg);
274 			return (*psw->pr_input)(mp, offp, proto);
275 		} else {
276 			m_freem(m);
277 			return (IPPROTO_DONE);
278 		}
279 	}
280 
281 	/* last resort: inject to raw socket */
282 	return rip6_input(mp, offp, proto);
283 }
284 #endif
285 
286 /*lint -sem(encap_add, custodial(1)) */
287 static void
288 encap_add(struct encaptab *ep)
289 {
290 
291 	mtx_assert(&encapmtx, MA_OWNED);
292 	LIST_INSERT_HEAD(&encaptab, ep, chain);
293 }
294 
295 /*
296  * sp (src ptr) is always my side, and dp (dst ptr) is always remote side.
297  * length of mask (sm and dm) is assumed to be same as sp/dp.
298  * Return value will be necessary as input (cookie) for encap_detach().
299  */
300 const struct encaptab *
301 encap_attach(int af, int proto, const struct sockaddr *sp,
302     const struct sockaddr *sm, const struct sockaddr *dp,
303     const struct sockaddr *dm, const struct protosw *psw, void *arg)
304 {
305 	struct encaptab *ep;
306 
307 	/* sanity check on args */
308 	if (sp->sa_len > sizeof(ep->src) || dp->sa_len > sizeof(ep->dst))
309 		return (NULL);
310 	if (sp->sa_len != dp->sa_len)
311 		return (NULL);
312 	if (af != sp->sa_family || af != dp->sa_family)
313 		return (NULL);
314 
315 	/* check if anyone have already attached with exactly same config */
316 	mtx_lock(&encapmtx);
317 	LIST_FOREACH(ep, &encaptab, chain) {
318 		if (ep->af != af)
319 			continue;
320 		if (ep->proto != proto)
321 			continue;
322 		if (ep->src.ss_len != sp->sa_len ||
323 		    bcmp(&ep->src, sp, sp->sa_len) != 0 ||
324 		    bcmp(&ep->srcmask, sm, sp->sa_len) != 0)
325 			continue;
326 		if (ep->dst.ss_len != dp->sa_len ||
327 		    bcmp(&ep->dst, dp, dp->sa_len) != 0 ||
328 		    bcmp(&ep->dstmask, dm, dp->sa_len) != 0)
329 			continue;
330 
331 		mtx_unlock(&encapmtx);
332 		return (NULL);
333 	}
334 
335 	ep = malloc(sizeof(*ep), M_NETADDR, M_NOWAIT);	/*XXX*/
336 	if (ep == NULL) {
337 		mtx_unlock(&encapmtx);
338 		return (NULL);
339 	}
340 	bzero(ep, sizeof(*ep));
341 
342 	ep->af = af;
343 	ep->proto = proto;
344 	bcopy(sp, &ep->src, sp->sa_len);
345 	bcopy(sm, &ep->srcmask, sp->sa_len);
346 	bcopy(dp, &ep->dst, dp->sa_len);
347 	bcopy(dm, &ep->dstmask, dp->sa_len);
348 	ep->psw = psw;
349 	ep->arg = arg;
350 
351 	encap_add(ep);
352 	mtx_unlock(&encapmtx);
353 	return (ep);
354 }
355 
356 const struct encaptab *
357 encap_attach_func(int af, int proto,
358     int (*func)(const struct mbuf *, int, int, void *),
359     const struct protosw *psw, void *arg)
360 {
361 	struct encaptab *ep;
362 
363 	/* sanity check on args */
364 	if (!func)
365 		return (NULL);
366 
367 	ep = malloc(sizeof(*ep), M_NETADDR, M_NOWAIT);	/*XXX*/
368 	if (ep == NULL)
369 		return (NULL);
370 	bzero(ep, sizeof(*ep));
371 
372 	ep->af = af;
373 	ep->proto = proto;
374 	ep->func = func;
375 	ep->psw = psw;
376 	ep->arg = arg;
377 
378 	mtx_lock(&encapmtx);
379 	encap_add(ep);
380 	mtx_unlock(&encapmtx);
381 	return (ep);
382 }
383 
384 int
385 encap_detach(const struct encaptab *cookie)
386 {
387 	const struct encaptab *ep = cookie;
388 	struct encaptab *p;
389 
390 	mtx_lock(&encapmtx);
391 	LIST_FOREACH(p, &encaptab, chain) {
392 		if (p == ep) {
393 			LIST_REMOVE(p, chain);
394 			mtx_unlock(&encapmtx);
395 			free(p, M_NETADDR);	/*XXX*/
396 			return 0;
397 		}
398 	}
399 	mtx_unlock(&encapmtx);
400 
401 	return EINVAL;
402 }
403 
404 static int
405 mask_match(const struct encaptab *ep, const struct sockaddr *sp,
406     const struct sockaddr *dp)
407 {
408 	struct sockaddr_storage s;
409 	struct sockaddr_storage d;
410 	int i;
411 	const u_int8_t *p, *q;
412 	u_int8_t *r;
413 	int matchlen;
414 
415 	if (sp->sa_len > sizeof(s) || dp->sa_len > sizeof(d))
416 		return 0;
417 	if (sp->sa_family != ep->af || dp->sa_family != ep->af)
418 		return 0;
419 	if (sp->sa_len != ep->src.ss_len || dp->sa_len != ep->dst.ss_len)
420 		return 0;
421 
422 	matchlen = 0;
423 
424 	p = (const u_int8_t *)sp;
425 	q = (const u_int8_t *)&ep->srcmask;
426 	r = (u_int8_t *)&s;
427 	for (i = 0 ; i < sp->sa_len; i++) {
428 		r[i] = p[i] & q[i];
429 		/* XXX estimate */
430 		matchlen += (q[i] ? 8 : 0);
431 	}
432 
433 	p = (const u_int8_t *)dp;
434 	q = (const u_int8_t *)&ep->dstmask;
435 	r = (u_int8_t *)&d;
436 	for (i = 0 ; i < dp->sa_len; i++) {
437 		r[i] = p[i] & q[i];
438 		/* XXX rough estimate */
439 		matchlen += (q[i] ? 8 : 0);
440 	}
441 
442 	/* need to overwrite len/family portion as we don't compare them */
443 	s.ss_len = sp->sa_len;
444 	s.ss_family = sp->sa_family;
445 	d.ss_len = dp->sa_len;
446 	d.ss_family = dp->sa_family;
447 
448 	if (bcmp(&s, &ep->src, ep->src.ss_len) == 0 &&
449 	    bcmp(&d, &ep->dst, ep->dst.ss_len) == 0) {
450 		return matchlen;
451 	} else
452 		return 0;
453 }
454 
455 static void
456 encap_fillarg(struct mbuf *m, void *arg)
457 {
458 	struct m_tag *tag;
459 
460 	if (arg != NULL) {
461 		tag = m_tag_get(PACKET_TAG_ENCAP, sizeof(void *), M_NOWAIT);
462 		if (tag != NULL) {
463 			*(void**)(tag+1) = arg;
464 			m_tag_prepend(m, tag);
465 		}
466 	}
467 }
468 
469 void *
470 encap_getarg(struct mbuf *m)
471 {
472 	void *p = NULL;
473 	struct m_tag *tag;
474 
475 	tag = m_tag_find(m, PACKET_TAG_ENCAP, NULL);
476 	if (tag) {
477 		p = *(void**)(tag+1);
478 		m_tag_delete(m, tag);
479 	}
480 	return p;
481 }
482