xref: /freebsd/sys/netinet/ip_encap.c (revision d9f0ce31900a48d1a2bfc1c8c86f79d1e831451a) 
1 /*	$KAME: ip_encap.c,v 1.41 2001/03/15 08:35:08 itojun Exp $	*/
2 
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 /*
32  * My grandfather said that there's a devil inside tunnelling technology...
33  *
34  * We have surprisingly many protocols that want packets with IP protocol
35  * #4 or #41.  Here's a list of protocols that want protocol #41:
36  *	RFC1933 configured tunnel
37  *	RFC1933 automatic tunnel
38  *	RFC2401 IPsec tunnel
39  *	RFC2473 IPv6 generic packet tunnelling
40  *	RFC2529 6over4 tunnel
41  *	mobile-ip6 (uses RFC2473)
42  *	RFC3056 6to4 tunnel
43  *	isatap tunnel
44  * Here's a list of protocol that want protocol #4:
45  *	RFC1853 IPv4-in-IPv4 tunnelling
46  *	RFC2003 IPv4 encapsulation within IPv4
47  *	RFC2344 reverse tunnelling for mobile-ip4
48  *	RFC2401 IPsec tunnel
49  * Well, what can I say.  They impose different en/decapsulation mechanism
50  * from each other, so they need separate protocol handler.  The only one
51  * we can easily determine by protocol # is IPsec, which always has
52  * AH/ESP/IPComp header right after outer IP header.
53  *
54  * So, clearly good old protosw does not work for protocol #4 and #41.
55  * The code will let you match protocol via src/dst address pair.
56  */
57 /* XXX is M_NETADDR correct? */
58 
59 #include <sys/cdefs.h>
60 __FBSDID("$FreeBSD$");
61 
62 #include "opt_mrouting.h"
63 #include "opt_inet.h"
64 #include "opt_inet6.h"
65 
66 #include <sys/param.h>
67 #include <sys/systm.h>
68 #include <sys/lock.h>
69 #include <sys/mutex.h>
70 #include <sys/socket.h>
71 #include <sys/sockio.h>
72 #include <sys/mbuf.h>
73 #include <sys/errno.h>
74 #include <sys/protosw.h>
75 #include <sys/queue.h>
76 
77 #include <net/if.h>
78 #include <net/route.h>
79 
80 #include <netinet/in.h>
81 #include <netinet/in_systm.h>
82 #include <netinet/ip.h>
83 #include <netinet/ip_var.h>
84 #include <netinet/ip_encap.h>
85 
86 #ifdef INET6
87 #include <netinet/ip6.h>
88 #include <netinet6/ip6_var.h>
89 #endif
90 
91 #include <machine/stdarg.h>
92 
93 #include <sys/kernel.h>
94 #include <sys/malloc.h>
95 static MALLOC_DEFINE(M_NETADDR, "encap_export_host", "Export host address structure");
96 
97 static void encap_add(struct encaptab *);
98 static int mask_match(const struct encaptab *, const struct sockaddr *,
99 		const struct sockaddr *);
100 static void encap_fillarg(struct mbuf *, void *);
101 
102 /*
103  * All global variables in ip_encap.c are locked using encapmtx.
104  */
105 static struct mtx encapmtx;
106 MTX_SYSINIT(encapmtx, &encapmtx, "encapmtx", MTX_DEF);
107 static LIST_HEAD(, encaptab) encaptab = LIST_HEAD_INITIALIZER(encaptab);
108 
109 /*
110  * We currently keey encap_init() for source code compatibility reasons --
111  * it's referenced by KAME pieces in netinet6.
112  */
113 void
114 encap_init(void)
115 {
116 }
117 
118 #ifdef INET
119 int
120 encap4_input(struct mbuf **mp, int *offp, int proto)
121 {
122 	struct ip *ip;
123 	struct mbuf *m;
124 	struct sockaddr_in s, d;
125 	const struct protosw *psw;
126 	struct encaptab *ep, *match;
127 	void *arg;
128 	int matchprio, off, prio;
129 
130 	m = *mp;
131 	off = *offp;
132 	ip = mtod(m, struct ip *);
133 
134 	bzero(&s, sizeof(s));
135 	s.sin_family = AF_INET;
136 	s.sin_len = sizeof(struct sockaddr_in);
137 	s.sin_addr = ip->ip_src;
138 	bzero(&d, sizeof(d));
139 	d.sin_family = AF_INET;
140 	d.sin_len = sizeof(struct sockaddr_in);
141 	d.sin_addr = ip->ip_dst;
142 
143 	arg = NULL;
144 	psw = NULL;
145 	match = NULL;
146 	matchprio = 0;
147 	mtx_lock(&encapmtx);
148 	LIST_FOREACH(ep, &encaptab, chain) {
149 		if (ep->af != AF_INET)
150 			continue;
151 		if (ep->proto >= 0 && ep->proto != proto)
152 			continue;
153 		if (ep->func)
154 			prio = (*ep->func)(m, off, proto, ep->arg);
155 		else {
156 			/*
157 			 * it's inbound traffic, we need to match in reverse
158 			 * order
159 			 */
160 			prio = mask_match(ep, (struct sockaddr *)&d,
161 			    (struct sockaddr *)&s);
162 		}
163 
164 		/*
165 		 * We prioritize the matches by using bit length of the
166 		 * matches.  mask_match() and user-supplied matching function
167 		 * should return the bit length of the matches (for example,
168 		 * if both src/dst are matched for IPv4, 64 should be returned).
169 		 * 0 or negative return value means "it did not match".
170 		 *
171 		 * The question is, since we have two "mask" portion, we
172 		 * cannot really define total order between entries.
173 		 * For example, which of these should be preferred?
174 		 * mask_match() returns 48 (32 + 16) for both of them.
175 		 *	src=3ffe::/16, dst=3ffe:501::/32
176 		 *	src=3ffe:501::/32, dst=3ffe::/16
177 		 *
178 		 * We need to loop through all the possible candidates
179 		 * to get the best match - the search takes O(n) for
180 		 * n attachments (i.e. interfaces).
181 		 */
182 		if (prio <= 0)
183 			continue;
184 		if (prio > matchprio) {
185 			matchprio = prio;
186 			match = ep;
187 		}
188 	}
189 	if (match != NULL) {
190 		psw = match->psw;
191 		arg = match->arg;
192 	}
193 	mtx_unlock(&encapmtx);
194 
195 	if (match != NULL) {
196 		/* found a match, "match" has the best one */
197 		if (psw != NULL && psw->pr_input != NULL) {
198 			encap_fillarg(m, arg);
199 			(*psw->pr_input)(mp, offp, proto);
200 		} else
201 			m_freem(m);
202 		return (IPPROTO_DONE);
203 	}
204 
205 	/* last resort: inject to raw socket */
206 	return (rip_input(mp, offp, proto));
207 }
208 #endif
209 
210 #ifdef INET6
211 int
212 encap6_input(struct mbuf **mp, int *offp, int proto)
213 {
214 	struct mbuf *m = *mp;
215 	struct ip6_hdr *ip6;
216 	struct sockaddr_in6 s, d;
217 	const struct protosw *psw;
218 	struct encaptab *ep, *match;
219 	void *arg;
220 	int prio, matchprio;
221 
222 	ip6 = mtod(m, struct ip6_hdr *);
223 
224 	bzero(&s, sizeof(s));
225 	s.sin6_family = AF_INET6;
226 	s.sin6_len = sizeof(struct sockaddr_in6);
227 	s.sin6_addr = ip6->ip6_src;
228 	bzero(&d, sizeof(d));
229 	d.sin6_family = AF_INET6;
230 	d.sin6_len = sizeof(struct sockaddr_in6);
231 	d.sin6_addr = ip6->ip6_dst;
232 
233 	arg = NULL;
234 	psw = NULL;
235 	match = NULL;
236 	matchprio = 0;
237 	mtx_lock(&encapmtx);
238 	LIST_FOREACH(ep, &encaptab, chain) {
239 		if (ep->af != AF_INET6)
240 			continue;
241 		if (ep->proto >= 0 && ep->proto != proto)
242 			continue;
243 		if (ep->func)
244 			prio = (*ep->func)(m, *offp, proto, ep->arg);
245 		else {
246 			/*
247 			 * it's inbound traffic, we need to match in reverse
248 			 * order
249 			 */
250 			prio = mask_match(ep, (struct sockaddr *)&d,
251 			    (struct sockaddr *)&s);
252 		}
253 
254 		/* see encap4_input() for issues here */
255 		if (prio <= 0)
256 			continue;
257 		if (prio > matchprio) {
258 			matchprio = prio;
259 			match = ep;
260 		}
261 	}
262 	if (match != NULL) {
263 		psw = match->psw;
264 		arg = match->arg;
265 	}
266 	mtx_unlock(&encapmtx);
267 
268 	if (match != NULL) {
269 		/* found a match */
270 		if (psw != NULL && psw->pr_input != NULL) {
271 			encap_fillarg(m, arg);
272 			return (*psw->pr_input)(mp, offp, proto);
273 		} else {
274 			m_freem(m);
275 			return (IPPROTO_DONE);
276 		}
277 	}
278 
279 	/* last resort: inject to raw socket */
280 	return rip6_input(mp, offp, proto);
281 }
282 #endif
283 
284 /*lint -sem(encap_add, custodial(1)) */
285 static void
286 encap_add(struct encaptab *ep)
287 {
288 
289 	mtx_assert(&encapmtx, MA_OWNED);
290 	LIST_INSERT_HEAD(&encaptab, ep, chain);
291 }
292 
293 /*
294  * sp (src ptr) is always my side, and dp (dst ptr) is always remote side.
295  * length of mask (sm and dm) is assumed to be same as sp/dp.
296  * Return value will be necessary as input (cookie) for encap_detach().
297  */
298 const struct encaptab *
299 encap_attach(int af, int proto, const struct sockaddr *sp,
300     const struct sockaddr *sm, const struct sockaddr *dp,
301     const struct sockaddr *dm, const struct protosw *psw, void *arg)
302 {
303 	struct encaptab *ep;
304 
305 	/* sanity check on args */
306 	if (sp->sa_len > sizeof(ep->src) || dp->sa_len > sizeof(ep->dst))
307 		return (NULL);
308 	if (sp->sa_len != dp->sa_len)
309 		return (NULL);
310 	if (af != sp->sa_family || af != dp->sa_family)
311 		return (NULL);
312 
313 	/* check if anyone have already attached with exactly same config */
314 	mtx_lock(&encapmtx);
315 	LIST_FOREACH(ep, &encaptab, chain) {
316 		if (ep->af != af)
317 			continue;
318 		if (ep->proto != proto)
319 			continue;
320 		if (ep->src.ss_len != sp->sa_len ||
321 		    bcmp(&ep->src, sp, sp->sa_len) != 0 ||
322 		    bcmp(&ep->srcmask, sm, sp->sa_len) != 0)
323 			continue;
324 		if (ep->dst.ss_len != dp->sa_len ||
325 		    bcmp(&ep->dst, dp, dp->sa_len) != 0 ||
326 		    bcmp(&ep->dstmask, dm, dp->sa_len) != 0)
327 			continue;
328 
329 		mtx_unlock(&encapmtx);
330 		return (NULL);
331 	}
332 
333 	ep = malloc(sizeof(*ep), M_NETADDR, M_NOWAIT);	/*XXX*/
334 	if (ep == NULL) {
335 		mtx_unlock(&encapmtx);
336 		return (NULL);
337 	}
338 	bzero(ep, sizeof(*ep));
339 
340 	ep->af = af;
341 	ep->proto = proto;
342 	bcopy(sp, &ep->src, sp->sa_len);
343 	bcopy(sm, &ep->srcmask, sp->sa_len);
344 	bcopy(dp, &ep->dst, dp->sa_len);
345 	bcopy(dm, &ep->dstmask, dp->sa_len);
346 	ep->psw = psw;
347 	ep->arg = arg;
348 
349 	encap_add(ep);
350 	mtx_unlock(&encapmtx);
351 	return (ep);
352 }
353 
354 const struct encaptab *
355 encap_attach_func(int af, int proto,
356     int (*func)(const struct mbuf *, int, int, void *),
357     const struct protosw *psw, void *arg)
358 {
359 	struct encaptab *ep;
360 
361 	/* sanity check on args */
362 	if (!func)
363 		return (NULL);
364 
365 	ep = malloc(sizeof(*ep), M_NETADDR, M_NOWAIT);	/*XXX*/
366 	if (ep == NULL)
367 		return (NULL);
368 	bzero(ep, sizeof(*ep));
369 
370 	ep->af = af;
371 	ep->proto = proto;
372 	ep->func = func;
373 	ep->psw = psw;
374 	ep->arg = arg;
375 
376 	mtx_lock(&encapmtx);
377 	encap_add(ep);
378 	mtx_unlock(&encapmtx);
379 	return (ep);
380 }
381 
382 int
383 encap_detach(const struct encaptab *cookie)
384 {
385 	const struct encaptab *ep = cookie;
386 	struct encaptab *p;
387 
388 	mtx_lock(&encapmtx);
389 	LIST_FOREACH(p, &encaptab, chain) {
390 		if (p == ep) {
391 			LIST_REMOVE(p, chain);
392 			mtx_unlock(&encapmtx);
393 			free(p, M_NETADDR);	/*XXX*/
394 			return 0;
395 		}
396 	}
397 	mtx_unlock(&encapmtx);
398 
399 	return EINVAL;
400 }
401 
402 static int
403 mask_match(const struct encaptab *ep, const struct sockaddr *sp,
404     const struct sockaddr *dp)
405 {
406 	struct sockaddr_storage s;
407 	struct sockaddr_storage d;
408 	int i;
409 	const u_int8_t *p, *q;
410 	u_int8_t *r;
411 	int matchlen;
412 
413 	if (sp->sa_len > sizeof(s) || dp->sa_len > sizeof(d))
414 		return 0;
415 	if (sp->sa_family != ep->af || dp->sa_family != ep->af)
416 		return 0;
417 	if (sp->sa_len != ep->src.ss_len || dp->sa_len != ep->dst.ss_len)
418 		return 0;
419 
420 	matchlen = 0;
421 
422 	p = (const u_int8_t *)sp;
423 	q = (const u_int8_t *)&ep->srcmask;
424 	r = (u_int8_t *)&s;
425 	for (i = 0 ; i < sp->sa_len; i++) {
426 		r[i] = p[i] & q[i];
427 		/* XXX estimate */
428 		matchlen += (q[i] ? 8 : 0);
429 	}
430 
431 	p = (const u_int8_t *)dp;
432 	q = (const u_int8_t *)&ep->dstmask;
433 	r = (u_int8_t *)&d;
434 	for (i = 0 ; i < dp->sa_len; i++) {
435 		r[i] = p[i] & q[i];
436 		/* XXX rough estimate */
437 		matchlen += (q[i] ? 8 : 0);
438 	}
439 
440 	/* need to overwrite len/family portion as we don't compare them */
441 	s.ss_len = sp->sa_len;
442 	s.ss_family = sp->sa_family;
443 	d.ss_len = dp->sa_len;
444 	d.ss_family = dp->sa_family;
445 
446 	if (bcmp(&s, &ep->src, ep->src.ss_len) == 0 &&
447 	    bcmp(&d, &ep->dst, ep->dst.ss_len) == 0) {
448 		return matchlen;
449 	} else
450 		return 0;
451 }
452 
453 static void
454 encap_fillarg(struct mbuf *m, void *arg)
455 {
456 	struct m_tag *tag;
457 
458 	if (arg != NULL) {
459 		tag = m_tag_get(PACKET_TAG_ENCAP, sizeof(void *), M_NOWAIT);
460 		if (tag != NULL) {
461 			*(void**)(tag+1) = arg;
462 			m_tag_prepend(m, tag);
463 		}
464 	}
465 }
466 
467 void *
468 encap_getarg(struct mbuf *m)
469 {
470 	void *p = NULL;
471 	struct m_tag *tag;
472 
473 	tag = m_tag_find(m, PACKET_TAG_ENCAP, NULL);
474 	if (tag) {
475 		p = *(void**)(tag+1);
476 		m_tag_delete(m, tag);
477 	}
478 	return p;
479 }
480