xref: /dragonfly/sys/net/gre/if_gre.c (revision 25a2db75)
1 /*	$NetBSD: if_gre.c,v 1.42 2002/08/14 00:23:27 itojun Exp $ */
2 /*	$FreeBSD: src/sys/net/if_gre.c,v 1.9.2.3 2003/01/23 21:06:44 sam Exp $ */
3 
4 /*
5  * Copyright (c) 1998 The NetBSD Foundation, Inc.
6  * All rights reserved.
7  *
8  * This code is derived from software contributed to The NetBSD Foundation
9  * by Heiko W.Rupp <hwr@pilhuhn.de>
10  *
11  * Redistribution and use in source and binary forms, with or without
12  * modification, are permitted provided that the following conditions
13  * are met:
14  * 1. Redistributions of source code must retain the above copyright
15  *    notice, this list of conditions and the following disclaimer.
16  * 2. Redistributions in binary form must reproduce the above copyright
17  *    notice, this list of conditions and the following disclaimer in the
18  *    documentation and/or other materials provided with the distribution.
19  * 3. All advertising materials mentioning features or use of this software
20  *    must display the following acknowledgement:
21  *        This product includes software developed by the NetBSD
22  *        Foundation, Inc. and its contributors.
23  * 4. Neither the name of The NetBSD Foundation nor the names of its
24  *    contributors may be used to endorse or promote products derived
25  *    from this software without specific prior written permission.
26  *
27  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
28  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
29  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
30  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
31  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
32  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
33  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
34  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
35  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
36  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
37  * POSSIBILITY OF SUCH DAMAGE.
38  */
39 
40 /*
41  * Encapsulate L3 protocols into IP
42  * See RFC 1701 and 1702 for more details.
43  * If_gre is compatible with Cisco GRE tunnels, so you can
44  * have a NetBSD box as the other end of a tunnel interface of a Cisco
45  * router. See gre(4) for more details.
46  * Also supported:  IP in IP encaps (proto 55) as of RFC 2004
47  */
48 
49 #include "opt_inet.h"
50 
51 #include <sys/param.h>
52 #include <sys/kernel.h>
53 #include <sys/bus.h>
54 #include <sys/malloc.h>
55 #include <sys/mbuf.h>
56 #include <sys/proc.h>
57 #include <sys/priv.h>
58 #include <sys/protosw.h>
59 #include <sys/socket.h>
60 #include <sys/sockio.h>
61 #include <sys/sysctl.h>
62 #include <sys/systm.h>
63 #include <sys/thread2.h>
64 
65 #include <net/ethernet.h>
66 #include <net/if.h>
67 #include <net/if_types.h>
68 #include <net/ifq_var.h>
69 #include <net/route.h>
70 #include <net/if_clone.h>
71 
72 #ifdef INET
73 #include <netinet/in.h>
74 #include <netinet/in_systm.h>
75 #include <netinet/in_var.h>
76 #include <netinet/ip.h>
77 #include <netinet/ip_gre.h>
78 #include <netinet/ip_var.h>
79 #include <netinet/ip_encap.h>
80 #else
81 #error "Huh? if_gre without inet?"
82 #endif
83 
84 #include <net/bpf.h>
85 
86 #include <net/net_osdep.h>
87 #include "if_gre.h"
88 
89 /*
90  * It is not easy to calculate the right value for a GRE MTU.
91  * We leave this task to the admin and use the same default that
92  * other vendors use.
93  */
94 #define GREMTU	1476
95 
96 #define GRENAME	"gre"
97 
98 static MALLOC_DEFINE(M_GRE, GRENAME, "Generic Routing Encapsulation");
99 
100 struct gre_softc_head gre_softc_list;
101 
102 static int	gre_clone_create(struct if_clone *, int, caddr_t);
103 static int	gre_clone_destroy(struct ifnet *);
104 static int	gre_ioctl(struct ifnet *, u_long, caddr_t, struct ucred *);
105 static int	gre_output(struct ifnet *, struct mbuf *, struct sockaddr *,
106 		    struct rtentry *rt);
107 
108 static struct if_clone gre_cloner = IF_CLONE_INITIALIZER("gre",
109     gre_clone_create, gre_clone_destroy, 0, IF_MAXUNIT);
110 
111 static int gre_compute_route(struct gre_softc *sc);
112 
113 static void	greattach(void);
114 
115 #ifdef INET
116 
117 extern struct domain inetdomain;
118 
119 static const struct protosw in_gre_protosw =
120     {
121 	.pr_type = SOCK_RAW,
122 	.pr_domain = &inetdomain,
123 	.pr_protocol = IPPROTO_GRE,
124 	.pr_flags = PR_ATOMIC|PR_ADDR,
125 
126 	.pr_input = gre_input,
127 	.pr_output = rip_output,
128 	.pr_ctlinput = rip_ctlinput,
129 	.pr_ctloutput = rip_ctloutput,
130 
131 	.pr_ctlport = cpu0_ctlport,
132 	.pr_usrreqs = &rip_usrreqs
133     };
134 
135 static const struct protosw in_mobile_protosw =
136     {
137 	.pr_type = SOCK_RAW,
138 	.pr_domain = &inetdomain,
139 	.pr_protocol = IPPROTO_MOBILE,
140 	.pr_flags = PR_ATOMIC|PR_ADDR,
141 
142 	.pr_input = gre_mobile_input,
143 	.pr_output = rip_output,
144 	.pr_ctlinput = rip_ctlinput,
145 	.pr_ctloutput = rip_ctloutput,
146 
147 	.pr_ctlport = cpu0_ctlport,
148 	.pr_usrreqs = &rip_usrreqs
149     };
150 
151 #endif
152 
153 SYSCTL_DECL(_net_link);
154 SYSCTL_NODE(_net_link, IFT_OTHER, gre, CTLFLAG_RW, 0,
155     "Generic Routing Encapsulation");
156 #ifndef MAX_GRE_NEST
157 /*
158  * This macro controls the default upper limitation on nesting of gre tunnels.
159  * Since, setting a large value to this macro with a careless configuration
160  * may introduce system crash, we don't allow any nestings by default.
161  * If you need to configure nested gre tunnels, you can define this macro
162  * in your kernel configuration file.  However, if you do so, please be
163  * careful to configure the tunnels so that it won't make a loop.
164  */
165 #define MAX_GRE_NEST 1
166 #endif
167 static int max_gre_nesting = MAX_GRE_NEST;
168 SYSCTL_INT(_net_link_gre, OID_AUTO, max_nesting, CTLFLAG_RW,
169     &max_gre_nesting, 0, "Max nested tunnels");
170 
171 /* ARGSUSED */
172 static void
173 greattach(void)
174 {
175 
176 	LIST_INIT(&gre_softc_list);
177 	if_clone_attach(&gre_cloner);
178 }
179 
180 static int
181 gre_clone_create(struct if_clone *ifc, int unit, caddr_t param __unused)
182 {
183 	struct gre_softc *sc;
184 
185 	sc = kmalloc(sizeof(struct gre_softc), M_GRE, M_WAITOK);
186 	memset(sc, 0, sizeof(struct gre_softc));
187 
188 	sc->sc_if.if_softc = sc;
189 	if_initname(&(sc->sc_if), GRENAME, unit);
190 	ifq_set_maxlen(&sc->sc_if.if_snd, IFQ_MAXLEN);
191 	sc->sc_if.if_type = IFT_OTHER;
192 	sc->sc_if.if_addrlen = 0;
193 	sc->sc_if.if_hdrlen = 24; /* IP + GRE */
194 	sc->sc_if.if_mtu = GREMTU;
195 	sc->sc_if.if_flags = IFF_POINTOPOINT|IFF_MULTICAST;
196 	sc->sc_if.if_output = gre_output;
197 	sc->sc_if.if_ioctl = gre_ioctl;
198 	sc->g_dst.s_addr = sc->g_src.s_addr = INADDR_ANY;
199 	sc->g_proto = IPPROTO_GRE;
200 	sc->sc_if.if_flags |= IFF_LINK0;
201 	sc->encap = NULL;
202 	sc->called = 0;
203 	if_attach(&sc->sc_if, NULL);
204 	bpfattach(&sc->sc_if, DLT_NULL, sizeof(u_int32_t));
205 	LIST_INSERT_HEAD(&gre_softc_list, sc, sc_list);
206 	return (0);
207 }
208 
209 static int
210 gre_clone_destroy(struct ifnet *ifp)
211 {
212 	struct gre_softc *sc = ifp->if_softc;
213 
214 #ifdef INET
215 	if (sc->encap != NULL)
216 		encap_detach(sc->encap);
217 #endif
218 	LIST_REMOVE(sc, sc_list);
219 	bpfdetach(ifp);
220 	if_detach(ifp);
221 
222 	kfree(sc, M_GRE);
223 
224 	return 0;
225 }
226 
227 /*
228  * The output routine. Takes a packet and encapsulates it in the protocol
229  * given by sc->g_proto. See also RFC 1701 and RFC 2004
230  */
231 static int
232 gre_output_serialized(struct ifnet *ifp, struct mbuf *m, struct sockaddr *dst,
233 		      struct rtentry *rt)
234 {
235 	int error = 0;
236 	struct gre_softc *sc = ifp->if_softc;
237 	struct greip *gh;
238 	struct ip *ip;
239 	u_short etype = 0;
240 	struct mobile_h mob_h;
241 
242 	/*
243 	 * gre may cause infinite recursion calls when misconfigured.
244 	 * We'll prevent this by introducing upper limit.
245 	 */
246 	if (++(sc->called) > max_gre_nesting) {
247 		kprintf("%s: gre_output: recursively called too many "
248 		       "times(%d)\n", if_name(&sc->sc_if), sc->called);
249 		m_freem(m);
250 		error = EIO;    /* is there better errno? */
251 		goto end;
252 	}
253 
254 	if ((ifp->if_flags & (IFF_UP | IFF_RUNNING)) == 0 ||
255 	    sc->g_src.s_addr == INADDR_ANY || sc->g_dst.s_addr == INADDR_ANY) {
256 		m_freem(m);
257 		error = ENETDOWN;
258 		goto end;
259 	}
260 
261 	gh = NULL;
262 	ip = NULL;
263 
264 	if (ifp->if_bpf) {
265 		bpf_gettoken();
266 		if (ifp->if_bpf) {
267 			uint32_t af = dst->sa_family;
268 
269 			bpf_ptap(ifp->if_bpf, m, &af, sizeof(af));
270 		}
271 		bpf_reltoken();
272 	}
273 
274 	m->m_flags &= ~(M_BCAST|M_MCAST);
275 
276 	if (sc->g_proto == IPPROTO_MOBILE) {
277 		if (dst->sa_family == AF_INET) {
278 			struct mbuf *m0;
279 			int msiz;
280 
281 			ip = mtod(m, struct ip *);
282 
283 			/*
284 			 * RFC2004 specifies that fragmented datagrams shouldn't
285 			 * be encapsulated.
286 			 */
287 			if (ip->ip_off & (IP_MF | IP_OFFMASK)) {
288 				m_freem(m);
289 				error = EINVAL;    /* is there better errno? */
290 				goto end;
291 			}
292 			memset(&mob_h, 0, MOB_H_SIZ_L);
293 			mob_h.proto = (ip->ip_p) << 8;
294 			mob_h.odst = ip->ip_dst.s_addr;
295 			ip->ip_dst.s_addr = sc->g_dst.s_addr;
296 
297 			/*
298 			 * If the packet comes from our host, we only change
299 			 * the destination address in the IP header.
300 			 * Else we also need to save and change the source
301 			 */
302 			if (in_hosteq(ip->ip_src, sc->g_src)) {
303 				msiz = MOB_H_SIZ_S;
304 			} else {
305 				mob_h.proto |= MOB_H_SBIT;
306 				mob_h.osrc = ip->ip_src.s_addr;
307 				ip->ip_src.s_addr = sc->g_src.s_addr;
308 				msiz = MOB_H_SIZ_L;
309 			}
310 			mob_h.proto = htons(mob_h.proto);
311 			mob_h.hcrc = gre_in_cksum((u_short *)&mob_h, msiz);
312 
313 			if ((m->m_data - msiz) < m->m_pktdat) {
314 				/* need new mbuf */
315 				MGETHDR(m0, MB_DONTWAIT, MT_HEADER);
316 				if (m0 == NULL) {
317 					m_freem(m);
318 					error = ENOBUFS;
319 					goto end;
320 				}
321 				m0->m_next = m;
322 				m->m_data += sizeof(struct ip);
323 				m->m_len -= sizeof(struct ip);
324 				m0->m_pkthdr.len = m->m_pkthdr.len + msiz;
325 				m0->m_len = msiz + sizeof(struct ip);
326 				m0->m_data += max_linkhdr;
327 				memcpy(mtod(m0, caddr_t), (caddr_t)ip,
328 				       sizeof(struct ip));
329 				m = m0;
330 			} else {  /* we have some space left in the old one */
331 				m->m_data -= msiz;
332 				m->m_len += msiz;
333 				m->m_pkthdr.len += msiz;
334 				bcopy(ip, mtod(m, caddr_t),
335 					sizeof(struct ip));
336 			}
337 			ip = mtod(m, struct ip *);
338 			memcpy((caddr_t)(ip + 1), &mob_h, (unsigned)msiz);
339 			ip->ip_len = ntohs(ip->ip_len) + msiz;
340 		} else {  /* AF_INET */
341 			m_freem(m);
342 			error = EINVAL;
343 			goto end;
344 		}
345 	} else if (sc->g_proto == IPPROTO_GRE) {
346 		switch (dst->sa_family) {
347 		case AF_INET:
348 			ip = mtod(m, struct ip *);
349 			etype = ETHERTYPE_IP;
350 			break;
351 		default:
352 			m_freem(m);
353 			error = EAFNOSUPPORT;
354 			goto end;
355 		}
356 		M_PREPEND(m, sizeof(struct greip), MB_DONTWAIT);
357 	} else {
358 		m_freem(m);
359 		error = EINVAL;
360 		goto end;
361 	}
362 
363 	if (m == NULL) {	/* impossible */
364 		error = ENOBUFS;
365 		goto end;
366 	}
367 
368 	gh = mtod(m, struct greip *);
369 	if (sc->g_proto == IPPROTO_GRE) {
370 		/* we don't have any GRE flags for now */
371 
372 		memset((void *)&gh->gi_g, 0, sizeof(struct gre_h));
373 		gh->gi_ptype = htons(etype);
374 	}
375 
376 	gh->gi_pr = sc->g_proto;
377 	if (sc->g_proto != IPPROTO_MOBILE) {
378 		gh->gi_src = sc->g_src;
379 		gh->gi_dst = sc->g_dst;
380 		((struct ip*)gh)->ip_hl = (sizeof(struct ip)) >> 2;
381 		((struct ip*)gh)->ip_ttl = GRE_TTL;
382 		((struct ip*)gh)->ip_tos = ip->ip_tos;
383 		((struct ip*)gh)->ip_id = ip->ip_id;
384 		gh->gi_len = m->m_pkthdr.len;
385 	}
386 
387 	IFNET_STAT_INC(ifp, opackets, 1);
388 	IFNET_STAT_INC(ifp, obytes, m->m_pkthdr.len);
389 	/* send it off */
390 	error = ip_output(m, NULL, &sc->route, 0, NULL, NULL);
391   end:
392 	sc->called = 0;
393 	if (error)
394 		IFNET_STAT_INC(ifp, oerrors, 1);
395 	return (error);
396 }
397 
398 static int
399 gre_output(struct ifnet *ifp, struct mbuf *m, struct sockaddr *dst,
400 	   struct rtentry *rt)
401 {
402 	struct ifaltq_subque *ifsq = ifq_get_subq_default(&ifp->if_snd);
403 	int error;
404 
405 	ifsq_serialize_hw(ifsq);
406 	error = gre_output_serialized(ifp, m, dst, rt);
407 	ifsq_deserialize_hw(ifsq);
408 
409 	return error;
410 }
411 
412 static int
413 gre_ioctl(struct ifnet *ifp, u_long cmd, caddr_t data, struct ucred *cr)
414 {
415 	struct ifreq *ifr = (struct ifreq *)data;
416 	struct if_laddrreq *lifr = (struct if_laddrreq *)data;
417 	struct in_aliasreq *aifr = (struct in_aliasreq *)data;
418 	struct gre_softc *sc = ifp->if_softc;
419 	struct sockaddr_in si;
420 	struct sockaddr *sa = NULL;
421 	int error;
422 	struct sockaddr_in sp, sm, dp, dm;
423 
424 	error = 0;
425 
426 	crit_enter();
427 	switch (cmd) {
428 	case SIOCSIFADDR:
429 		ifp->if_flags |= IFF_UP;
430 		break;
431 	case SIOCSIFDSTADDR:
432 		break;
433 	case SIOCSIFFLAGS:
434 		if ((error = priv_check_cred(cr, PRIV_ROOT, NULL_CRED_OKAY)) != 0)
435 			break;
436 		if ((ifr->ifr_flags & IFF_LINK0) != 0)
437 			sc->g_proto = IPPROTO_GRE;
438 		else
439 			sc->g_proto = IPPROTO_MOBILE;
440 		goto recompute;
441 	case SIOCSIFMTU:
442 		if ((error = priv_check_cred(cr, PRIV_ROOT, NULL_CRED_OKAY)) != 0)
443 			break;
444 		if (ifr->ifr_mtu < 576) {
445 			error = EINVAL;
446 			break;
447 		}
448 		ifp->if_mtu = ifr->ifr_mtu;
449 		break;
450 	case SIOCGIFMTU:
451 		ifr->ifr_mtu = sc->sc_if.if_mtu;
452 		break;
453 	case SIOCADDMULTI:
454 	case SIOCDELMULTI:
455 		if ((error = priv_check_cred(cr, PRIV_ROOT, NULL_CRED_OKAY)) != 0)
456 			break;
457 		if (ifr == NULL) {
458 			error = EAFNOSUPPORT;
459 			break;
460 		}
461 		switch (ifr->ifr_addr.sa_family) {
462 #ifdef INET
463 		case AF_INET:
464 			break;
465 #endif
466 		default:
467 			error = EAFNOSUPPORT;
468 			break;
469 		}
470 		break;
471 	case GRESPROTO:
472 		if ((error = priv_check_cred(cr, PRIV_ROOT, NULL_CRED_OKAY)) != 0)
473 			break;
474 		sc->g_proto = ifr->ifr_flags;
475 		switch (sc->g_proto) {
476 		case IPPROTO_GRE:
477 			ifp->if_flags |= IFF_LINK0;
478 			break;
479 		case IPPROTO_MOBILE:
480 			ifp->if_flags &= ~IFF_LINK0;
481 			break;
482 		default:
483 			error = EPROTONOSUPPORT;
484 			break;
485 		}
486 		goto recompute;
487 	case GREGPROTO:
488 		ifr->ifr_flags = sc->g_proto;
489 		break;
490 	case GRESADDRS:
491 	case GRESADDRD:
492 		if ((error = priv_check_cred(cr, PRIV_ROOT, NULL_CRED_OKAY)) != 0)
493 			break;
494 		/*
495 		 * set tunnel endpoints, compute a less specific route
496 		 * to the remote end and mark if as up
497 		 */
498 		sa = &ifr->ifr_addr;
499 		if (cmd == GRESADDRS)
500 			sc->g_src = (satosin(sa))->sin_addr;
501 		if (cmd == GRESADDRD)
502 			sc->g_dst = (satosin(sa))->sin_addr;
503 	recompute:
504 #ifdef INET
505 		if (sc->encap != NULL) {
506 			encap_detach(sc->encap);
507 			sc->encap = NULL;
508 		}
509 #endif
510 		if ((sc->g_src.s_addr != INADDR_ANY) &&
511 		    (sc->g_dst.s_addr != INADDR_ANY)) {
512 			bzero(&sp, sizeof(sp));
513 			bzero(&sm, sizeof(sm));
514 			bzero(&dp, sizeof(dp));
515 			bzero(&dm, sizeof(dm));
516 			sp.sin_len = sm.sin_len = dp.sin_len = dm.sin_len =
517 			    sizeof(struct sockaddr_in);
518 			sp.sin_family = sm.sin_family = dp.sin_family =
519 			    dm.sin_family = AF_INET;
520 			sp.sin_addr = sc->g_src;
521 			dp.sin_addr = sc->g_dst;
522 			sm.sin_addr.s_addr = dm.sin_addr.s_addr =
523 			    INADDR_BROADCAST;
524 #ifdef INET
525 			sc->encap = encap_attach(AF_INET, sc->g_proto,
526 			    sintosa(&sp), sintosa(&sm), sintosa(&dp),
527 			    sintosa(&dm), (sc->g_proto == IPPROTO_GRE) ?
528 				&in_gre_protosw : &in_mobile_protosw, sc);
529 			if (sc->encap == NULL)
530 				kprintf("%s: unable to attach encap\n",
531 				    if_name(&sc->sc_if));
532 #endif
533 			if (sc->route.ro_rt != 0) /* free old route */
534 				RTFREE(sc->route.ro_rt);
535 			if (gre_compute_route(sc) == 0)
536 				ifp->if_flags |= IFF_RUNNING;
537 			else
538 				ifp->if_flags &= ~IFF_RUNNING;
539 		}
540 		break;
541 	case GREGADDRS:
542 		memset(&si, 0, sizeof(si));
543 		si.sin_family = AF_INET;
544 		si.sin_len = sizeof(struct sockaddr_in);
545 		si.sin_addr.s_addr = sc->g_src.s_addr;
546 		sa = sintosa(&si);
547 		ifr->ifr_addr = *sa;
548 		break;
549 	case GREGADDRD:
550 		memset(&si, 0, sizeof(si));
551 		si.sin_family = AF_INET;
552 		si.sin_len = sizeof(struct sockaddr_in);
553 		si.sin_addr.s_addr = sc->g_dst.s_addr;
554 		sa = sintosa(&si);
555 		ifr->ifr_addr = *sa;
556 		break;
557 	case SIOCSIFPHYADDR:
558 		if ((error = priv_check_cred(cr, PRIV_ROOT, NULL_CRED_OKAY)) != 0)
559 			break;
560 		if (aifr->ifra_addr.sin_family != AF_INET ||
561 		    aifr->ifra_dstaddr.sin_family != AF_INET) {
562 			error = EAFNOSUPPORT;
563 			break;
564 		}
565 		if (aifr->ifra_addr.sin_len != sizeof(si) ||
566 		    aifr->ifra_dstaddr.sin_len != sizeof(si)) {
567 			error = EINVAL;
568 			break;
569 		}
570 		sc->g_src = aifr->ifra_addr.sin_addr;
571 		sc->g_dst = aifr->ifra_dstaddr.sin_addr;
572 		goto recompute;
573 	case SIOCSLIFPHYADDR:
574 		if ((error = priv_check_cred(cr, PRIV_ROOT, NULL_CRED_OKAY)) != 0)
575 			break;
576 		if (lifr->addr.ss_family != AF_INET ||
577 		    lifr->dstaddr.ss_family != AF_INET) {
578 			error = EAFNOSUPPORT;
579 			break;
580 		}
581 		if (lifr->addr.ss_len != sizeof(si) ||
582 		    lifr->dstaddr.ss_len != sizeof(si)) {
583 			error = EINVAL;
584 			break;
585 		}
586 		sc->g_src = (satosin((struct sockadrr *)&lifr->addr))->sin_addr;
587 		sc->g_dst =
588 		    (satosin((struct sockadrr *)&lifr->dstaddr))->sin_addr;
589 		goto recompute;
590 	case SIOCDIFPHYADDR:
591 		if ((error = priv_check_cred(cr, PRIV_ROOT, NULL_CRED_OKAY)) != 0)
592 			break;
593 		sc->g_src.s_addr = INADDR_ANY;
594 		sc->g_dst.s_addr = INADDR_ANY;
595 		goto recompute;
596 	case SIOCGLIFPHYADDR:
597 		if (sc->g_src.s_addr == INADDR_ANY ||
598 		    sc->g_dst.s_addr == INADDR_ANY) {
599 			error = EADDRNOTAVAIL;
600 			break;
601 		}
602 		memset(&si, 0, sizeof(si));
603 		si.sin_family = AF_INET;
604 		si.sin_len = sizeof(struct sockaddr_in);
605 		si.sin_addr.s_addr = sc->g_src.s_addr;
606 		memcpy(&lifr->addr, &si, sizeof(si));
607 		si.sin_addr.s_addr = sc->g_dst.s_addr;
608 		memcpy(&lifr->dstaddr, &si, sizeof(si));
609 		break;
610 	case SIOCGIFPSRCADDR:
611 		if (sc->g_src.s_addr == INADDR_ANY) {
612 			error = EADDRNOTAVAIL;
613 			break;
614 		}
615 		memset(&si, 0, sizeof(si));
616 		si.sin_family = AF_INET;
617 		si.sin_len = sizeof(struct sockaddr_in);
618 		si.sin_addr.s_addr = sc->g_src.s_addr;
619 		bcopy(&si, &ifr->ifr_addr, sizeof(ifr->ifr_addr));
620 		break;
621 	case SIOCGIFPDSTADDR:
622 		if (sc->g_dst.s_addr == INADDR_ANY) {
623 			error = EADDRNOTAVAIL;
624 			break;
625 		}
626 		memset(&si, 0, sizeof(si));
627 		si.sin_family = AF_INET;
628 		si.sin_len = sizeof(struct sockaddr_in);
629 		si.sin_addr.s_addr = sc->g_dst.s_addr;
630 		bcopy(&si, &ifr->ifr_addr, sizeof(ifr->ifr_addr));
631 		break;
632 	default:
633 		error = EINVAL;
634 		break;
635 	}
636 
637 	crit_exit();
638 	return (error);
639 }
640 
641 /*
642  * computes a route to our destination that is not the one
643  * which would be taken by ip_output(), as this one will loop back to
644  * us. If the interface is p2p as  a--->b, then a routing entry exists
645  * If we now send a packet to b (e.g. ping b), this will come down here
646  * gets src=a, dst=b tacked on and would from ip_ouput() sent back to
647  * if_gre.
648  * Goal here is to compute a route to b that is less specific than
649  * a-->b. We know that this one exists as in normal operation we have
650  * at least a default route which matches.
651  */
652 static int
653 gre_compute_route(struct gre_softc *sc)
654 {
655 	struct route *ro;
656 	u_int32_t a, b, c;
657 
658 	ro = &sc->route;
659 
660 	memset(ro, 0, sizeof(struct route));
661 	((struct sockaddr_in *)&ro->ro_dst)->sin_addr = sc->g_dst;
662 	ro->ro_dst.sa_family = AF_INET;
663 	ro->ro_dst.sa_len = sizeof(ro->ro_dst);
664 
665 	/*
666 	 * toggle last bit, so our interface is not found, but a less
667 	 * specific route. I'd rather like to specify a shorter mask,
668 	 * but this is not possible. Should work though. XXX
669 	 * there is a simpler way ...
670 	 */
671 	if ((sc->sc_if.if_flags & IFF_LINK1) == 0) {
672 		a = ntohl(sc->g_dst.s_addr);
673 		b = a & 0x01;
674 		c = a & 0xfffffffe;
675 		b = b ^ 0x01;
676 		a = b | c;
677 		((struct sockaddr_in *)&ro->ro_dst)->sin_addr.s_addr
678 		    = htonl(a);
679 	}
680 
681 #ifdef DIAGNOSTIC
682 	kprintf("%s: searching a route to %s", if_name(&sc->sc_if),
683 	    inet_ntoa(((struct sockaddr_in *)&ro->ro_dst)->sin_addr));
684 #endif
685 
686 	rtalloc(ro);
687 
688 	/*
689 	 * check if this returned a route at all and this route is no
690 	 * recursion to ourself
691 	 */
692 	if (ro->ro_rt == NULL || ro->ro_rt->rt_ifp->if_softc == sc) {
693 #ifdef DIAGNOSTIC
694 		if (ro->ro_rt == NULL)
695 			kprintf(" - no route found!\n");
696 		else
697 			kprintf(" - route loops back to ourself!\n");
698 #endif
699 		return EADDRNOTAVAIL;
700 	}
701 
702 	/*
703 	 * now change it back - else ip_output will just drop
704 	 * the route and search one to this interface ...
705 	 */
706 	if ((sc->sc_if.if_flags & IFF_LINK1) == 0)
707 		((struct sockaddr_in *)&ro->ro_dst)->sin_addr = sc->g_dst;
708 
709 #ifdef DIAGNOSTIC
710 	kprintf(", choosing %s with gateway %s", if_name(ro->ro_rt->rt_ifp),
711 	    inet_ntoa(((struct sockaddr_in *)(ro->ro_rt->rt_gateway))->sin_addr));
712 	kprintf("\n");
713 #endif
714 
715 	return 0;
716 }
717 
718 /*
719  * do a checksum of a buffer - much like in_cksum, which operates on
720  * mbufs.
721  */
722 u_short
723 gre_in_cksum(u_short *p, u_int len)
724 {
725 	u_int sum = 0;
726 	int nwords = len >> 1;
727 
728 	while (nwords-- != 0)
729 		sum += *p++;
730 
731 	if (len & 1) {
732 		union {
733 			u_short w;
734 			u_char c[2];
735 		} u;
736 		u.c[0] = *(u_char *)p;
737 		u.c[1] = 0;
738 		sum += u.w;
739 	}
740 
741 	/* end-around-carry */
742 	sum = (sum >> 16) + (sum & 0xffff);
743 	sum += (sum >> 16);
744 	return (~sum);
745 }
746 
747 static int
748 gremodevent(module_t mod, int type, void *data)
749 {
750 
751 	switch (type) {
752 	case MOD_LOAD:
753 		greattach();
754 		break;
755 	case MOD_UNLOAD:
756 		if_clone_detach(&gre_cloner);
757 
758 		while (!LIST_EMPTY(&gre_softc_list))
759 			gre_clone_destroy(&LIST_FIRST(&gre_softc_list)->sc_if);
760 
761 		break;
762 	}
763 	return 0;
764 }
765 
766 static moduledata_t gre_mod = {
767 	"if_gre",
768 	gremodevent,
769 	0
770 };
771 
772 DECLARE_MODULE(if_gre, gre_mod, SI_SUB_PSEUDO, SI_ORDER_ANY);
773 MODULE_VERSION(if_gre, 1);
774