xref: /freebsd/sys/net/if_gre.c (revision 3642298923e528d795e3a30ec165d2b469e28b40)
1 /*	$NetBSD: if_gre.c,v 1.49 2003/12/11 00:22:29 itojun Exp $ */
2 /*	 $FreeBSD$ */
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  * IPv6-over-GRE contributed by Gert Doering <gert@greenie.muc.de>
12  *
13  * Redistribution and use in source and binary forms, with or without
14  * modification, are permitted provided that the following conditions
15  * are met:
16  * 1. Redistributions of source code must retain the above copyright
17  *    notice, this list of conditions and the following disclaimer.
18  * 2. Redistributions in binary form must reproduce the above copyright
19  *    notice, this list of conditions and the following disclaimer in the
20  *    documentation and/or other materials provided with the distribution.
21  * 3. All advertising materials mentioning features or use of this software
22  *    must display the following acknowledgement:
23  *        This product includes software developed by the NetBSD
24  *        Foundation, Inc. and its contributors.
25  * 4. Neither the name of The NetBSD Foundation nor the names of its
26  *    contributors may be used to endorse or promote products derived
27  *    from this software without specific prior written permission.
28  *
29  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
30  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
31  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
32  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
33  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
34  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
35  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
36  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
37  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
38  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
39  * POSSIBILITY OF SUCH DAMAGE.
40  */
41 
42 /*
43  * Encapsulate L3 protocols into IP
44  * See RFC 2784 (successor of RFC 1701 and 1702) for more details.
45  * If_gre is compatible with Cisco GRE tunnels, so you can
46  * have a NetBSD box as the other end of a tunnel interface of a Cisco
47  * router. See gre(4) for more details.
48  * Also supported:  IP in IP encaps (proto 55) as of RFC 2004
49  */
50 
51 #include "opt_atalk.h"
52 #include "opt_inet.h"
53 #include "opt_inet6.h"
54 
55 #include <sys/param.h>
56 #include <sys/kernel.h>
57 #include <sys/malloc.h>
58 #include <sys/module.h>
59 #include <sys/mbuf.h>
60 #include <sys/protosw.h>
61 #include <sys/socket.h>
62 #include <sys/sockio.h>
63 #include <sys/sysctl.h>
64 #include <sys/systm.h>
65 
66 #include <net/ethernet.h>
67 #include <net/if.h>
68 #include <net/if_clone.h>
69 #include <net/if_types.h>
70 #include <net/route.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 <net/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 /*
99  * gre_mtx protects all global variables in if_gre.c.
100  * XXX: gre_softc data not protected yet.
101  */
102 struct mtx gre_mtx;
103 static MALLOC_DEFINE(M_GRE, GRENAME, "Generic Routing Encapsulation");
104 
105 struct gre_softc_head gre_softc_list;
106 
107 static int	gre_clone_create(struct if_clone *, int);
108 static void	gre_clone_destroy(struct ifnet *);
109 static int	gre_ioctl(struct ifnet *, u_long, caddr_t);
110 static int	gre_output(struct ifnet *, struct mbuf *, struct sockaddr *,
111 		    struct rtentry *rt);
112 
113 IFC_SIMPLE_DECLARE(gre, 0);
114 
115 static int gre_compute_route(struct gre_softc *sc);
116 
117 static void	greattach(void);
118 
119 #ifdef INET
120 extern struct domain inetdomain;
121 static const struct protosw in_gre_protosw =
122 { SOCK_RAW,     &inetdomain,    IPPROTO_GRE,    PR_ATOMIC|PR_ADDR,
123   (pr_input_t*)gre_input, (pr_output_t*)rip_output, rip_ctlinput, rip_ctloutput,
124   0,
125   0,		0,		0,		0,
126   &rip_usrreqs
127 };
128 static const struct protosw in_mobile_protosw =
129 { SOCK_RAW,     &inetdomain,    IPPROTO_MOBILE, PR_ATOMIC|PR_ADDR,
130   (pr_input_t*)gre_mobile_input, (pr_output_t*)rip_output, rip_ctlinput, rip_ctloutput,
131   0,
132   0,		0,		0,		0,
133   &rip_usrreqs
134 };
135 #endif
136 
137 SYSCTL_DECL(_net_link);
138 SYSCTL_NODE(_net_link, IFT_TUNNEL, gre, CTLFLAG_RW, 0,
139     "Generic Routing Encapsulation");
140 #ifndef MAX_GRE_NEST
141 /*
142  * This macro controls the default upper limitation on nesting of gre tunnels.
143  * Since, setting a large value to this macro with a careless configuration
144  * may introduce system crash, we don't allow any nestings by default.
145  * If you need to configure nested gre tunnels, you can define this macro
146  * in your kernel configuration file.  However, if you do so, please be
147  * careful to configure the tunnels so that it won't make a loop.
148  */
149 #define MAX_GRE_NEST 1
150 #endif
151 static int max_gre_nesting = MAX_GRE_NEST;
152 SYSCTL_INT(_net_link_gre, OID_AUTO, max_nesting, CTLFLAG_RW,
153     &max_gre_nesting, 0, "Max nested tunnels");
154 
155 /* ARGSUSED */
156 static void
157 greattach(void)
158 {
159 
160 	mtx_init(&gre_mtx, "gre_mtx", NULL, MTX_DEF);
161 	LIST_INIT(&gre_softc_list);
162 	if_clone_attach(&gre_cloner);
163 }
164 
165 static int
166 gre_clone_create(ifc, unit)
167 	struct if_clone *ifc;
168 	int unit;
169 {
170 	struct gre_softc *sc;
171 
172 	sc = malloc(sizeof(struct gre_softc), M_GRE, M_WAITOK | M_ZERO);
173 
174 	GRE2IFP(sc) = if_alloc(IFT_TUNNEL);
175 	if (GRE2IFP(sc) == NULL) {
176 		free(sc, M_GRE);
177 		return (ENOSPC);
178 	}
179 
180 	GRE2IFP(sc)->if_softc = sc;
181 	if_initname(GRE2IFP(sc), ifc->ifc_name, unit);
182 
183 	GRE2IFP(sc)->if_snd.ifq_maxlen = IFQ_MAXLEN;
184 	GRE2IFP(sc)->if_addrlen = 0;
185 	GRE2IFP(sc)->if_hdrlen = 24; /* IP + GRE */
186 	GRE2IFP(sc)->if_mtu = GREMTU;
187 	GRE2IFP(sc)->if_flags = IFF_POINTOPOINT|IFF_MULTICAST;
188 	GRE2IFP(sc)->if_output = gre_output;
189 	GRE2IFP(sc)->if_ioctl = gre_ioctl;
190 	sc->g_dst.s_addr = sc->g_src.s_addr = INADDR_ANY;
191 	sc->g_proto = IPPROTO_GRE;
192 	GRE2IFP(sc)->if_flags |= IFF_LINK0;
193 	sc->encap = NULL;
194 	sc->called = 0;
195 	sc->wccp_ver = WCCP_V1;
196 	if_attach(GRE2IFP(sc));
197 	bpfattach(GRE2IFP(sc), DLT_NULL, sizeof(u_int32_t));
198 	mtx_lock(&gre_mtx);
199 	LIST_INSERT_HEAD(&gre_softc_list, sc, sc_list);
200 	mtx_unlock(&gre_mtx);
201 	return (0);
202 }
203 
204 static void
205 gre_destroy(struct gre_softc *sc)
206 {
207 
208 #ifdef INET
209 	if (sc->encap != NULL)
210 		encap_detach(sc->encap);
211 #endif
212 	bpfdetach(GRE2IFP(sc));
213 	if_detach(GRE2IFP(sc));
214 	if_free(GRE2IFP(sc));
215 	free(sc, M_GRE);
216 }
217 
218 static void
219 gre_clone_destroy(ifp)
220 	struct ifnet *ifp;
221 {
222 	struct gre_softc *sc = ifp->if_softc;
223 
224 	mtx_lock(&gre_mtx);
225 	LIST_REMOVE(sc, sc_list);
226 	mtx_unlock(&gre_mtx);
227 	gre_destroy(sc);
228 }
229 
230 /*
231  * The output routine. Takes a packet and encapsulates it in the protocol
232  * given by sc->g_proto. See also RFC 1701 and RFC 2004
233  */
234 static int
235 gre_output(struct ifnet *ifp, struct mbuf *m, struct sockaddr *dst,
236 	   struct rtentry *rt)
237 {
238 	int error = 0;
239 	struct gre_softc *sc = ifp->if_softc;
240 	struct greip *gh;
241 	struct ip *ip;
242 	u_short ip_id = 0;
243 	uint8_t ip_tos = 0;
244 	u_int16_t etype = 0;
245 	struct mobile_h mob_h;
246 	u_int32_t af;
247 
248 	/*
249 	 * gre may cause infinite recursion calls when misconfigured.
250 	 * We'll prevent this by introducing upper limit.
251 	 */
252 	if (++(sc->called) > max_gre_nesting) {
253 		printf("%s: gre_output: recursively called too many "
254 		       "times(%d)\n", if_name(GRE2IFP(sc)), sc->called);
255 		m_freem(m);
256 		error = EIO;    /* is there better errno? */
257 		goto end;
258 	}
259 
260 	if (!((ifp->if_flags & IFF_UP) &&
261 	    (ifp->if_drv_flags & IFF_DRV_RUNNING)) ||
262 	    sc->g_src.s_addr == INADDR_ANY || sc->g_dst.s_addr == INADDR_ANY) {
263 		m_freem(m);
264 		error = ENETDOWN;
265 		goto end;
266 	}
267 
268 	gh = NULL;
269 	ip = NULL;
270 
271 	/* BPF writes need to be handled specially. */
272 	if (dst->sa_family == AF_UNSPEC) {
273 		bcopy(dst->sa_data, &af, sizeof(af));
274 		dst->sa_family = af;
275 	}
276 
277 	if (ifp->if_bpf) {
278 		af = dst->sa_family;
279 		bpf_mtap2(ifp->if_bpf, &af, sizeof(af), m);
280 	}
281 
282 	m->m_flags &= ~(M_BCAST|M_MCAST);
283 
284 	if (sc->g_proto == IPPROTO_MOBILE) {
285 		if (dst->sa_family == AF_INET) {
286 			struct mbuf *m0;
287 			int msiz;
288 
289 			ip = mtod(m, struct ip *);
290 
291 			/*
292 			 * RFC2004 specifies that fragmented diagrams shouldn't
293 			 * be encapsulated.
294 			 */
295 			if ((ip->ip_off & IP_MF) != 0) {
296 				_IF_DROP(&ifp->if_snd);
297 				m_freem(m);
298 				error = EINVAL;    /* is there better errno? */
299 				goto end;
300 			}
301 			memset(&mob_h, 0, MOB_H_SIZ_L);
302 			mob_h.proto = (ip->ip_p) << 8;
303 			mob_h.odst = ip->ip_dst.s_addr;
304 			ip->ip_dst.s_addr = sc->g_dst.s_addr;
305 
306 			/*
307 			 * If the packet comes from our host, we only change
308 			 * the destination address in the IP header.
309 			 * Else we also need to save and change the source
310 			 */
311 			if (in_hosteq(ip->ip_src, sc->g_src)) {
312 				msiz = MOB_H_SIZ_S;
313 			} else {
314 				mob_h.proto |= MOB_H_SBIT;
315 				mob_h.osrc = ip->ip_src.s_addr;
316 				ip->ip_src.s_addr = sc->g_src.s_addr;
317 				msiz = MOB_H_SIZ_L;
318 			}
319 			mob_h.proto = htons(mob_h.proto);
320 			mob_h.hcrc = gre_in_cksum((u_int16_t *)&mob_h, msiz);
321 
322 			if ((m->m_data - msiz) < m->m_pktdat) {
323 				/* need new mbuf */
324 				MGETHDR(m0, M_DONTWAIT, MT_HEADER);
325 				if (m0 == NULL) {
326 					_IF_DROP(&ifp->if_snd);
327 					m_freem(m);
328 					error = ENOBUFS;
329 					goto end;
330 				}
331 				m0->m_next = m;
332 				m->m_data += sizeof(struct ip);
333 				m->m_len -= sizeof(struct ip);
334 				m0->m_pkthdr.len = m->m_pkthdr.len + msiz;
335 				m0->m_len = msiz + sizeof(struct ip);
336 				m0->m_data += max_linkhdr;
337 				memcpy(mtod(m0, caddr_t), (caddr_t)ip,
338 				       sizeof(struct ip));
339 				m = m0;
340 			} else {  /* we have some space left in the old one */
341 				m->m_data -= msiz;
342 				m->m_len += msiz;
343 				m->m_pkthdr.len += msiz;
344 				bcopy(ip, mtod(m, caddr_t),
345 					sizeof(struct ip));
346 			}
347 			ip = mtod(m, struct ip *);
348 			memcpy((caddr_t)(ip + 1), &mob_h, (unsigned)msiz);
349 			ip->ip_len = ntohs(ip->ip_len) + msiz;
350 		} else {  /* AF_INET */
351 			_IF_DROP(&ifp->if_snd);
352 			m_freem(m);
353 			error = EINVAL;
354 			goto end;
355 		}
356 	} else if (sc->g_proto == IPPROTO_GRE) {
357 		switch (dst->sa_family) {
358 		case AF_INET:
359 			ip = mtod(m, struct ip *);
360 			ip_tos = ip->ip_tos;
361 			ip_id = ip->ip_id;
362 			etype = ETHERTYPE_IP;
363 			break;
364 #ifdef INET6
365 		case AF_INET6:
366 			ip_id = ip_newid();
367 			etype = ETHERTYPE_IPV6;
368 			break;
369 #endif
370 #ifdef NETATALK
371 		case AF_APPLETALK:
372 			etype = ETHERTYPE_ATALK;
373 			break;
374 #endif
375 		default:
376 			_IF_DROP(&ifp->if_snd);
377 			m_freem(m);
378 			error = EAFNOSUPPORT;
379 			goto end;
380 		}
381 		M_PREPEND(m, sizeof(struct greip), M_DONTWAIT);
382 	} else {
383 		_IF_DROP(&ifp->if_snd);
384 		m_freem(m);
385 		error = EINVAL;
386 		goto end;
387 	}
388 
389 	if (m == NULL) {	/* mbuf allocation failed */
390 		_IF_DROP(&ifp->if_snd);
391 		error = ENOBUFS;
392 		goto end;
393 	}
394 
395 	gh = mtod(m, struct greip *);
396 	if (sc->g_proto == IPPROTO_GRE) {
397 		/* we don't have any GRE flags for now */
398 		memset((void *)gh, 0, sizeof(struct greip));
399 		gh->gi_ptype = htons(etype);
400 	}
401 
402 	gh->gi_pr = sc->g_proto;
403 	if (sc->g_proto != IPPROTO_MOBILE) {
404 		gh->gi_src = sc->g_src;
405 		gh->gi_dst = sc->g_dst;
406 		((struct ip*)gh)->ip_v = IPPROTO_IPV4;
407 		((struct ip*)gh)->ip_hl = (sizeof(struct ip)) >> 2;
408 		((struct ip*)gh)->ip_ttl = GRE_TTL;
409 		((struct ip*)gh)->ip_tos = ip_tos;
410 		((struct ip*)gh)->ip_id = ip_id;
411 		gh->gi_len = m->m_pkthdr.len;
412 	}
413 
414 	ifp->if_opackets++;
415 	ifp->if_obytes += m->m_pkthdr.len;
416 	/*
417 	 * Send it off and with IP_FORWARD flag to prevent it from
418 	 * overwriting the ip_id again.  ip_id is already set to the
419 	 * ip_id of the encapsulated packet.
420 	 */
421 	error = ip_output(m, NULL, &sc->route, IP_FORWARDING,
422 	    (struct ip_moptions *)NULL, (struct inpcb *)NULL);
423   end:
424 	sc->called = 0;
425 	if (error)
426 		ifp->if_oerrors++;
427 	return (error);
428 }
429 
430 static int
431 gre_ioctl(struct ifnet *ifp, u_long cmd, caddr_t data)
432 {
433 	struct ifreq *ifr = (struct ifreq *)data;
434 	struct if_laddrreq *lifr = (struct if_laddrreq *)data;
435 	struct in_aliasreq *aifr = (struct in_aliasreq *)data;
436 	struct gre_softc *sc = ifp->if_softc;
437 	int s;
438 	struct sockaddr_in si;
439 	struct sockaddr *sa = NULL;
440 	int error;
441 	struct sockaddr_in sp, sm, dp, dm;
442 
443 	error = 0;
444 
445 	s = splnet();
446 	switch (cmd) {
447 	case SIOCSIFADDR:
448 		ifp->if_flags |= IFF_UP;
449 		break;
450 	case SIOCSIFDSTADDR:
451 		break;
452 	case SIOCSIFFLAGS:
453 		if ((error = suser(curthread)) != 0)
454 			break;
455 		if ((ifr->ifr_flags & IFF_LINK0) != 0)
456 			sc->g_proto = IPPROTO_GRE;
457 		else
458 			sc->g_proto = IPPROTO_MOBILE;
459 		if ((ifr->ifr_flags & IFF_LINK2) != 0)
460 			sc->wccp_ver = WCCP_V2;
461 		else
462 			sc->wccp_ver = WCCP_V1;
463 		goto recompute;
464 	case SIOCSIFMTU:
465 		if ((error = suser(curthread)) != 0)
466 			break;
467 		if (ifr->ifr_mtu < 576) {
468 			error = EINVAL;
469 			break;
470 		}
471 		ifp->if_mtu = ifr->ifr_mtu;
472 		break;
473 	case SIOCGIFMTU:
474 		ifr->ifr_mtu = GRE2IFP(sc)->if_mtu;
475 		break;
476 	case SIOCADDMULTI:
477 	case SIOCDELMULTI:
478 		if ((error = suser(curthread)) != 0)
479 			break;
480 		if (ifr == 0) {
481 			error = EAFNOSUPPORT;
482 			break;
483 		}
484 		switch (ifr->ifr_addr.sa_family) {
485 #ifdef INET
486 		case AF_INET:
487 			break;
488 #endif
489 #ifdef INET6
490 		case AF_INET6:
491 			break;
492 #endif
493 		default:
494 			error = EAFNOSUPPORT;
495 			break;
496 		}
497 		break;
498 	case GRESPROTO:
499 		if ((error = suser(curthread)) != 0)
500 			break;
501 		sc->g_proto = ifr->ifr_flags;
502 		switch (sc->g_proto) {
503 		case IPPROTO_GRE:
504 			ifp->if_flags |= IFF_LINK0;
505 			break;
506 		case IPPROTO_MOBILE:
507 			ifp->if_flags &= ~IFF_LINK0;
508 			break;
509 		default:
510 			error = EPROTONOSUPPORT;
511 			break;
512 		}
513 		goto recompute;
514 	case GREGPROTO:
515 		ifr->ifr_flags = sc->g_proto;
516 		break;
517 	case GRESADDRS:
518 	case GRESADDRD:
519 		if ((error = suser(curthread)) != 0)
520 			break;
521 		/*
522 		 * set tunnel endpoints, compute a less specific route
523 		 * to the remote end and mark if as up
524 		 */
525 		sa = &ifr->ifr_addr;
526 		if (cmd == GRESADDRS)
527 			sc->g_src = (satosin(sa))->sin_addr;
528 		if (cmd == GRESADDRD)
529 			sc->g_dst = (satosin(sa))->sin_addr;
530 	recompute:
531 #ifdef INET
532 		if (sc->encap != NULL) {
533 			encap_detach(sc->encap);
534 			sc->encap = NULL;
535 		}
536 #endif
537 		if ((sc->g_src.s_addr != INADDR_ANY) &&
538 		    (sc->g_dst.s_addr != INADDR_ANY)) {
539 			bzero(&sp, sizeof(sp));
540 			bzero(&sm, sizeof(sm));
541 			bzero(&dp, sizeof(dp));
542 			bzero(&dm, sizeof(dm));
543 			sp.sin_len = sm.sin_len = dp.sin_len = dm.sin_len =
544 			    sizeof(struct sockaddr_in);
545 			sp.sin_family = sm.sin_family = dp.sin_family =
546 			    dm.sin_family = AF_INET;
547 			sp.sin_addr = sc->g_src;
548 			dp.sin_addr = sc->g_dst;
549 			sm.sin_addr.s_addr = dm.sin_addr.s_addr =
550 			    INADDR_BROADCAST;
551 #ifdef INET
552 			sc->encap = encap_attach(AF_INET, sc->g_proto,
553 			    sintosa(&sp), sintosa(&sm), sintosa(&dp),
554 			    sintosa(&dm), (sc->g_proto == IPPROTO_GRE) ?
555 				&in_gre_protosw : &in_mobile_protosw, sc);
556 			if (sc->encap == NULL)
557 				printf("%s: unable to attach encap\n",
558 				    if_name(GRE2IFP(sc)));
559 #endif
560 			if (sc->route.ro_rt != 0) /* free old route */
561 				RTFREE(sc->route.ro_rt);
562 			if (gre_compute_route(sc) == 0)
563 				ifp->if_drv_flags |= IFF_DRV_RUNNING;
564 			else
565 				ifp->if_drv_flags &= ~IFF_DRV_RUNNING;
566 		}
567 		break;
568 	case GREGADDRS:
569 		memset(&si, 0, sizeof(si));
570 		si.sin_family = AF_INET;
571 		si.sin_len = sizeof(struct sockaddr_in);
572 		si.sin_addr.s_addr = sc->g_src.s_addr;
573 		sa = sintosa(&si);
574 		ifr->ifr_addr = *sa;
575 		break;
576 	case GREGADDRD:
577 		memset(&si, 0, sizeof(si));
578 		si.sin_family = AF_INET;
579 		si.sin_len = sizeof(struct sockaddr_in);
580 		si.sin_addr.s_addr = sc->g_dst.s_addr;
581 		sa = sintosa(&si);
582 		ifr->ifr_addr = *sa;
583 		break;
584 	case SIOCSIFPHYADDR:
585 		if ((error = suser(curthread)) != 0)
586 			break;
587 		if (aifr->ifra_addr.sin_family != AF_INET ||
588 		    aifr->ifra_dstaddr.sin_family != AF_INET) {
589 			error = EAFNOSUPPORT;
590 			break;
591 		}
592 		if (aifr->ifra_addr.sin_len != sizeof(si) ||
593 		    aifr->ifra_dstaddr.sin_len != sizeof(si)) {
594 			error = EINVAL;
595 			break;
596 		}
597 		sc->g_src = aifr->ifra_addr.sin_addr;
598 		sc->g_dst = aifr->ifra_dstaddr.sin_addr;
599 		goto recompute;
600 	case SIOCSLIFPHYADDR:
601 		if ((error = suser(curthread)) != 0)
602 			break;
603 		if (lifr->addr.ss_family != AF_INET ||
604 		    lifr->dstaddr.ss_family != AF_INET) {
605 			error = EAFNOSUPPORT;
606 			break;
607 		}
608 		if (lifr->addr.ss_len != sizeof(si) ||
609 		    lifr->dstaddr.ss_len != sizeof(si)) {
610 			error = EINVAL;
611 			break;
612 		}
613 		sc->g_src = (satosin((struct sockadrr *)&lifr->addr))->sin_addr;
614 		sc->g_dst =
615 		    (satosin((struct sockadrr *)&lifr->dstaddr))->sin_addr;
616 		goto recompute;
617 	case SIOCDIFPHYADDR:
618 		if ((error = suser(curthread)) != 0)
619 			break;
620 		sc->g_src.s_addr = INADDR_ANY;
621 		sc->g_dst.s_addr = INADDR_ANY;
622 		goto recompute;
623 	case SIOCGLIFPHYADDR:
624 		if (sc->g_src.s_addr == INADDR_ANY ||
625 		    sc->g_dst.s_addr == INADDR_ANY) {
626 			error = EADDRNOTAVAIL;
627 			break;
628 		}
629 		memset(&si, 0, sizeof(si));
630 		si.sin_family = AF_INET;
631 		si.sin_len = sizeof(struct sockaddr_in);
632 		si.sin_addr.s_addr = sc->g_src.s_addr;
633 		memcpy(&lifr->addr, &si, sizeof(si));
634 		si.sin_addr.s_addr = sc->g_dst.s_addr;
635 		memcpy(&lifr->dstaddr, &si, sizeof(si));
636 		break;
637 	case SIOCGIFPSRCADDR:
638 #ifdef INET6
639 	case SIOCGIFPSRCADDR_IN6:
640 #endif
641 		if (sc->g_src.s_addr == INADDR_ANY) {
642 			error = EADDRNOTAVAIL;
643 			break;
644 		}
645 		memset(&si, 0, sizeof(si));
646 		si.sin_family = AF_INET;
647 		si.sin_len = sizeof(struct sockaddr_in);
648 		si.sin_addr.s_addr = sc->g_src.s_addr;
649 		bcopy(&si, &ifr->ifr_addr, sizeof(ifr->ifr_addr));
650 		break;
651 	case SIOCGIFPDSTADDR:
652 #ifdef INET6
653 	case SIOCGIFPDSTADDR_IN6:
654 #endif
655 		if (sc->g_dst.s_addr == INADDR_ANY) {
656 			error = EADDRNOTAVAIL;
657 			break;
658 		}
659 		memset(&si, 0, sizeof(si));
660 		si.sin_family = AF_INET;
661 		si.sin_len = sizeof(struct sockaddr_in);
662 		si.sin_addr.s_addr = sc->g_dst.s_addr;
663 		bcopy(&si, &ifr->ifr_addr, sizeof(ifr->ifr_addr));
664 		break;
665 	default:
666 		error = EINVAL;
667 		break;
668 	}
669 
670 	splx(s);
671 	return (error);
672 }
673 
674 /*
675  * computes a route to our destination that is not the one
676  * which would be taken by ip_output(), as this one will loop back to
677  * us. If the interface is p2p as  a--->b, then a routing entry exists
678  * If we now send a packet to b (e.g. ping b), this will come down here
679  * gets src=a, dst=b tacked on and would from ip_output() sent back to
680  * if_gre.
681  * Goal here is to compute a route to b that is less specific than
682  * a-->b. We know that this one exists as in normal operation we have
683  * at least a default route which matches.
684  */
685 static int
686 gre_compute_route(struct gre_softc *sc)
687 {
688 	struct route *ro;
689 	u_int32_t a, b, c;
690 
691 	ro = &sc->route;
692 
693 	memset(ro, 0, sizeof(struct route));
694 	((struct sockaddr_in *)&ro->ro_dst)->sin_addr = sc->g_dst;
695 	ro->ro_dst.sa_family = AF_INET;
696 	ro->ro_dst.sa_len = sizeof(ro->ro_dst);
697 
698 	/*
699 	 * toggle last bit, so our interface is not found, but a less
700 	 * specific route. I'd rather like to specify a shorter mask,
701 	 * but this is not possible. Should work though. XXX
702 	 * there is a simpler way ...
703 	 */
704 	if ((GRE2IFP(sc)->if_flags & IFF_LINK1) == 0) {
705 		a = ntohl(sc->g_dst.s_addr);
706 		b = a & 0x01;
707 		c = a & 0xfffffffe;
708 		b = b ^ 0x01;
709 		a = b | c;
710 		((struct sockaddr_in *)&ro->ro_dst)->sin_addr.s_addr
711 		    = htonl(a);
712 	}
713 
714 #ifdef DIAGNOSTIC
715 	printf("%s: searching for a route to %s", if_name(GRE2IFP(sc)),
716 	    inet_ntoa(((struct sockaddr_in *)&ro->ro_dst)->sin_addr));
717 #endif
718 
719 	rtalloc(ro);
720 
721 	/*
722 	 * check if this returned a route at all and this route is no
723 	 * recursion to ourself
724 	 */
725 	if (ro->ro_rt == NULL || ro->ro_rt->rt_ifp->if_softc == sc) {
726 #ifdef DIAGNOSTIC
727 		if (ro->ro_rt == NULL)
728 			printf(" - no route found!\n");
729 		else
730 			printf(" - route loops back to ourself!\n");
731 #endif
732 		return EADDRNOTAVAIL;
733 	}
734 
735 	/*
736 	 * now change it back - else ip_output will just drop
737 	 * the route and search one to this interface ...
738 	 */
739 	if ((GRE2IFP(sc)->if_flags & IFF_LINK1) == 0)
740 		((struct sockaddr_in *)&ro->ro_dst)->sin_addr = sc->g_dst;
741 
742 #ifdef DIAGNOSTIC
743 	printf(", choosing %s with gateway %s", if_name(ro->ro_rt->rt_ifp),
744 	    inet_ntoa(((struct sockaddr_in *)(ro->ro_rt->rt_gateway))->sin_addr));
745 	printf("\n");
746 #endif
747 
748 	return 0;
749 }
750 
751 /*
752  * do a checksum of a buffer - much like in_cksum, which operates on
753  * mbufs.
754  */
755 u_int16_t
756 gre_in_cksum(u_int16_t *p, u_int len)
757 {
758 	u_int32_t sum = 0;
759 	int nwords = len >> 1;
760 
761 	while (nwords-- != 0)
762 		sum += *p++;
763 
764 	if (len & 1) {
765 		union {
766 			u_short w;
767 			u_char c[2];
768 		} u;
769 		u.c[0] = *(u_char *)p;
770 		u.c[1] = 0;
771 		sum += u.w;
772 	}
773 
774 	/* end-around-carry */
775 	sum = (sum >> 16) + (sum & 0xffff);
776 	sum += (sum >> 16);
777 	return (~sum);
778 }
779 
780 static int
781 gremodevent(module_t mod, int type, void *data)
782 {
783 	struct gre_softc *sc;
784 
785 	switch (type) {
786 	case MOD_LOAD:
787 		greattach();
788 		break;
789 	case MOD_UNLOAD:
790 		if_clone_detach(&gre_cloner);
791 
792 		mtx_lock(&gre_mtx);
793 		while ((sc = LIST_FIRST(&gre_softc_list)) != NULL) {
794 			LIST_REMOVE(sc, sc_list);
795 			mtx_unlock(&gre_mtx);
796 			gre_destroy(sc);
797 			mtx_lock(&gre_mtx);
798 		}
799 		mtx_unlock(&gre_mtx);
800 		mtx_destroy(&gre_mtx);
801 		break;
802 	default:
803 		return EOPNOTSUPP;
804 	}
805 	return 0;
806 }
807 
808 static moduledata_t gre_mod = {
809 	"if_gre",
810 	gremodevent,
811 	0
812 };
813 
814 DECLARE_MODULE(if_gre, gre_mod, SI_SUB_PSEUDO, SI_ORDER_ANY);
815 MODULE_VERSION(if_gre, 1);
816