xref: /freebsd/sys/netinet/ip_encap.c (revision aa0a1e58) 
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/socket.h>
69 #include <sys/sockio.h>
70 #include <sys/mbuf.h>
71 #include <sys/errno.h>
72 #include <sys/protosw.h>
73 #include <sys/queue.h>
74 
75 #include <net/if.h>
76 #include <net/route.h>
77 
78 #include <netinet/in.h>
79 #include <netinet/in_systm.h>
80 #include <netinet/ip.h>
81 #include <netinet/ip_var.h>
82 #include <netinet/ip_encap.h>
83 
84 #ifdef INET6
85 #include <netinet/ip6.h>
86 #include <netinet6/ip6_var.h>
87 #include <netinet6/ip6protosw.h>
88 #endif
89 
90 #include <machine/stdarg.h>
91 
92 #include <sys/kernel.h>
93 #include <sys/malloc.h>
94 static MALLOC_DEFINE(M_NETADDR, "encap_export_host", "Export host address structure");
95 
96 static void encap_add(struct encaptab *);
97 static int mask_match(const struct encaptab *, const struct sockaddr *,
98 		const struct sockaddr *);
99 static void encap_fillarg(struct mbuf *, const struct encaptab *);
100 
101 /*
102  * All global variables in ip_encap.c are locked using encapmtx.
103  */
104 static struct mtx encapmtx;
105 MTX_SYSINIT(encapmtx, &encapmtx, "encapmtx", MTX_DEF);
106 LIST_HEAD(, encaptab) encaptab = LIST_HEAD_INITIALIZER(encaptab);
107 
108 /*
109  * We currently keey encap_init() for source code compatibility reasons --
110  * it's referenced by KAME pieces in netinet6.
111  */
112 void
113 encap_init(void)
114 {
115 }
116 
117 #ifdef INET
118 void
119 encap4_input(struct mbuf *m, int off)
120 {
121 	struct ip *ip;
122 	int proto;
123 	struct sockaddr_in s, d;
124 	const struct protosw *psw;
125 	struct encaptab *ep, *match;
126 	int prio, matchprio;
127 
128 	ip = mtod(m, struct ip *);
129 	proto = ip->ip_p;
130 
131 	bzero(&s, sizeof(s));
132 	s.sin_family = AF_INET;
133 	s.sin_len = sizeof(struct sockaddr_in);
134 	s.sin_addr = ip->ip_src;
135 	bzero(&d, sizeof(d));
136 	d.sin_family = AF_INET;
137 	d.sin_len = sizeof(struct sockaddr_in);
138 	d.sin_addr = ip->ip_dst;
139 
140 	match = NULL;
141 	matchprio = 0;
142 	mtx_lock(&encapmtx);
143 	LIST_FOREACH(ep, &encaptab, chain) {
144 		if (ep->af != AF_INET)
145 			continue;
146 		if (ep->proto >= 0 && ep->proto != proto)
147 			continue;
148 		if (ep->func)
149 			prio = (*ep->func)(m, off, proto, ep->arg);
150 		else {
151 			/*
152 			 * it's inbound traffic, we need to match in reverse
153 			 * order
154 			 */
155 			prio = mask_match(ep, (struct sockaddr *)&d,
156 			    (struct sockaddr *)&s);
157 		}
158 
159 		/*
160 		 * We prioritize the matches by using bit length of the
161 		 * matches.  mask_match() and user-supplied matching function
162 		 * should return the bit length of the matches (for example,
163 		 * if both src/dst are matched for IPv4, 64 should be returned).
164 		 * 0 or negative return value means "it did not match".
165 		 *
166 		 * The question is, since we have two "mask" portion, we
167 		 * cannot really define total order between entries.
168 		 * For example, which of these should be preferred?
169 		 * mask_match() returns 48 (32 + 16) for both of them.
170 		 *	src=3ffe::/16, dst=3ffe:501::/32
171 		 *	src=3ffe:501::/32, dst=3ffe::/16
172 		 *
173 		 * We need to loop through all the possible candidates
174 		 * to get the best match - the search takes O(n) for
175 		 * n attachments (i.e. interfaces).
176 		 */
177 		if (prio <= 0)
178 			continue;
179 		if (prio > matchprio) {
180 			matchprio = prio;
181 			match = ep;
182 		}
183 	}
184 	mtx_unlock(&encapmtx);
185 
186 	if (match) {
187 		/* found a match, "match" has the best one */
188 		psw = match->psw;
189 		if (psw && psw->pr_input) {
190 			encap_fillarg(m, match);
191 			(*psw->pr_input)(m, off);
192 		} else
193 			m_freem(m);
194 		return;
195 	}
196 
197 	/* last resort: inject to raw socket */
198 	rip_input(m, off);
199 }
200 #endif
201 
202 #ifdef INET6
203 int
204 encap6_input(struct mbuf **mp, int *offp, int proto)
205 {
206 	struct mbuf *m = *mp;
207 	struct ip6_hdr *ip6;
208 	struct sockaddr_in6 s, d;
209 	const struct ip6protosw *psw;
210 	struct encaptab *ep, *match;
211 	int prio, matchprio;
212 
213 	ip6 = mtod(m, struct ip6_hdr *);
214 
215 	bzero(&s, sizeof(s));
216 	s.sin6_family = AF_INET6;
217 	s.sin6_len = sizeof(struct sockaddr_in6);
218 	s.sin6_addr = ip6->ip6_src;
219 	bzero(&d, sizeof(d));
220 	d.sin6_family = AF_INET6;
221 	d.sin6_len = sizeof(struct sockaddr_in6);
222 	d.sin6_addr = ip6->ip6_dst;
223 
224 	match = NULL;
225 	matchprio = 0;
226 	mtx_lock(&encapmtx);
227 	LIST_FOREACH(ep, &encaptab, chain) {
228 		if (ep->af != AF_INET6)
229 			continue;
230 		if (ep->proto >= 0 && ep->proto != proto)
231 			continue;
232 		if (ep->func)
233 			prio = (*ep->func)(m, *offp, proto, ep->arg);
234 		else {
235 			/*
236 			 * it's inbound traffic, we need to match in reverse
237 			 * order
238 			 */
239 			prio = mask_match(ep, (struct sockaddr *)&d,
240 			    (struct sockaddr *)&s);
241 		}
242 
243 		/* see encap4_input() for issues here */
244 		if (prio <= 0)
245 			continue;
246 		if (prio > matchprio) {
247 			matchprio = prio;
248 			match = ep;
249 		}
250 	}
251 	mtx_unlock(&encapmtx);
252 
253 	if (match) {
254 		/* found a match */
255 		psw = (const struct ip6protosw *)match->psw;
256 		if (psw && psw->pr_input) {
257 			encap_fillarg(m, match);
258 			return (*psw->pr_input)(mp, offp, proto);
259 		} else {
260 			m_freem(m);
261 			return IPPROTO_DONE;
262 		}
263 	}
264 
265 	/* last resort: inject to raw socket */
266 	return rip6_input(mp, offp, proto);
267 }
268 #endif
269 
270 /*lint -sem(encap_add, custodial(1)) */
271 static void
272 encap_add(struct encaptab *ep)
273 {
274 
275 	mtx_assert(&encapmtx, MA_OWNED);
276 	LIST_INSERT_HEAD(&encaptab, ep, chain);
277 }
278 
279 /*
280  * sp (src ptr) is always my side, and dp (dst ptr) is always remote side.
281  * length of mask (sm and dm) is assumed to be same as sp/dp.
282  * Return value will be necessary as input (cookie) for encap_detach().
283  */
284 const struct encaptab *
285 encap_attach(int af, int proto, const struct sockaddr *sp,
286     const struct sockaddr *sm, const struct sockaddr *dp,
287     const struct sockaddr *dm, const struct protosw *psw, void *arg)
288 {
289 	struct encaptab *ep;
290 
291 	/* sanity check on args */
292 	if (sp->sa_len > sizeof(ep->src) || dp->sa_len > sizeof(ep->dst))
293 		return (NULL);
294 	if (sp->sa_len != dp->sa_len)
295 		return (NULL);
296 	if (af != sp->sa_family || af != dp->sa_family)
297 		return (NULL);
298 
299 	/* check if anyone have already attached with exactly same config */
300 	mtx_lock(&encapmtx);
301 	LIST_FOREACH(ep, &encaptab, chain) {
302 		if (ep->af != af)
303 			continue;
304 		if (ep->proto != proto)
305 			continue;
306 		if (ep->src.ss_len != sp->sa_len ||
307 		    bcmp(&ep->src, sp, sp->sa_len) != 0 ||
308 		    bcmp(&ep->srcmask, sm, sp->sa_len) != 0)
309 			continue;
310 		if (ep->dst.ss_len != dp->sa_len ||
311 		    bcmp(&ep->dst, dp, dp->sa_len) != 0 ||
312 		    bcmp(&ep->dstmask, dm, dp->sa_len) != 0)
313 			continue;
314 
315 		mtx_unlock(&encapmtx);
316 		return (NULL);
317 	}
318 
319 	ep = malloc(sizeof(*ep), M_NETADDR, M_NOWAIT);	/*XXX*/
320 	if (ep == NULL) {
321 		mtx_unlock(&encapmtx);
322 		return (NULL);
323 	}
324 	bzero(ep, sizeof(*ep));
325 
326 	ep->af = af;
327 	ep->proto = proto;
328 	bcopy(sp, &ep->src, sp->sa_len);
329 	bcopy(sm, &ep->srcmask, sp->sa_len);
330 	bcopy(dp, &ep->dst, dp->sa_len);
331 	bcopy(dm, &ep->dstmask, dp->sa_len);
332 	ep->psw = psw;
333 	ep->arg = arg;
334 
335 	encap_add(ep);
336 	mtx_unlock(&encapmtx);
337 	return (ep);
338 }
339 
340 const struct encaptab *
341 encap_attach_func(int af, int proto,
342     int (*func)(const struct mbuf *, int, int, void *),
343     const struct protosw *psw, void *arg)
344 {
345 	struct encaptab *ep;
346 
347 	/* sanity check on args */
348 	if (!func)
349 		return (NULL);
350 
351 	ep = malloc(sizeof(*ep), M_NETADDR, M_NOWAIT);	/*XXX*/
352 	if (ep == NULL)
353 		return (NULL);
354 	bzero(ep, sizeof(*ep));
355 
356 	ep->af = af;
357 	ep->proto = proto;
358 	ep->func = func;
359 	ep->psw = psw;
360 	ep->arg = arg;
361 
362 	mtx_lock(&encapmtx);
363 	encap_add(ep);
364 	mtx_unlock(&encapmtx);
365 	return (ep);
366 }
367 
368 int
369 encap_detach(const struct encaptab *cookie)
370 {
371 	const struct encaptab *ep = cookie;
372 	struct encaptab *p;
373 
374 	mtx_lock(&encapmtx);
375 	LIST_FOREACH(p, &encaptab, chain) {
376 		if (p == ep) {
377 			LIST_REMOVE(p, chain);
378 			mtx_unlock(&encapmtx);
379 			free(p, M_NETADDR);	/*XXX*/
380 			return 0;
381 		}
382 	}
383 	mtx_unlock(&encapmtx);
384 
385 	return EINVAL;
386 }
387 
388 static int
389 mask_match(const struct encaptab *ep, const struct sockaddr *sp,
390     const struct sockaddr *dp)
391 {
392 	struct sockaddr_storage s;
393 	struct sockaddr_storage d;
394 	int i;
395 	const u_int8_t *p, *q;
396 	u_int8_t *r;
397 	int matchlen;
398 
399 	if (sp->sa_len > sizeof(s) || dp->sa_len > sizeof(d))
400 		return 0;
401 	if (sp->sa_family != ep->af || dp->sa_family != ep->af)
402 		return 0;
403 	if (sp->sa_len != ep->src.ss_len || dp->sa_len != ep->dst.ss_len)
404 		return 0;
405 
406 	matchlen = 0;
407 
408 	p = (const u_int8_t *)sp;
409 	q = (const u_int8_t *)&ep->srcmask;
410 	r = (u_int8_t *)&s;
411 	for (i = 0 ; i < sp->sa_len; i++) {
412 		r[i] = p[i] & q[i];
413 		/* XXX estimate */
414 		matchlen += (q[i] ? 8 : 0);
415 	}
416 
417 	p = (const u_int8_t *)dp;
418 	q = (const u_int8_t *)&ep->dstmask;
419 	r = (u_int8_t *)&d;
420 	for (i = 0 ; i < dp->sa_len; i++) {
421 		r[i] = p[i] & q[i];
422 		/* XXX rough estimate */
423 		matchlen += (q[i] ? 8 : 0);
424 	}
425 
426 	/* need to overwrite len/family portion as we don't compare them */
427 	s.ss_len = sp->sa_len;
428 	s.ss_family = sp->sa_family;
429 	d.ss_len = dp->sa_len;
430 	d.ss_family = dp->sa_family;
431 
432 	if (bcmp(&s, &ep->src, ep->src.ss_len) == 0 &&
433 	    bcmp(&d, &ep->dst, ep->dst.ss_len) == 0) {
434 		return matchlen;
435 	} else
436 		return 0;
437 }
438 
439 static void
440 encap_fillarg(struct mbuf *m, const struct encaptab *ep)
441 {
442 	struct m_tag *tag;
443 
444 	tag = m_tag_get(PACKET_TAG_ENCAP, sizeof (void*), M_NOWAIT);
445 	if (tag) {
446 		*(void**)(tag+1) = ep->arg;
447 		m_tag_prepend(m, tag);
448 	}
449 }
450 
451 void *
452 encap_getarg(struct mbuf *m)
453 {
454 	void *p = NULL;
455 	struct m_tag *tag;
456 
457 	tag = m_tag_find(m, PACKET_TAG_ENCAP, NULL);
458 	if (tag) {
459 		p = *(void**)(tag+1);
460 		m_tag_delete(m, tag);
461 	}
462 	return p;
463 }
464