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 /* $DragonFly: src/sys/net/gre/if_gre.c,v 1.7 2004/01/06 01:40:51 dillon Exp $ */ 4 5 /* 6 * Copyright (c) 1998 The NetBSD Foundation, Inc. 7 * All rights reserved. 8 * 9 * This code is derived from software contributed to The NetBSD Foundation 10 * by Heiko W.Rupp <hwr@pilhuhn.de> 11 * 12 * Redistribution and use in source and binary forms, with or without 13 * modification, are permitted provided that the following conditions 14 * are met: 15 * 1. Redistributions of source code must retain the above copyright 16 * notice, this list of conditions and the following disclaimer. 17 * 2. Redistributions in binary form must reproduce the above copyright 18 * notice, this list of conditions and the following disclaimer in the 19 * documentation and/or other materials provided with the distribution. 20 * 3. All advertising materials mentioning features or use of this software 21 * must display the following acknowledgement: 22 * This product includes software developed by the NetBSD 23 * Foundation, Inc. and its contributors. 24 * 4. Neither the name of The NetBSD Foundation nor the names of its 25 * contributors may be used to endorse or promote products derived 26 * from this software without specific prior written permission. 27 * 28 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 29 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 30 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 31 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 32 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 33 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 34 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 35 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 36 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 37 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 38 * POSSIBILITY OF SUCH DAMAGE. 39 */ 40 41 /* 42 * Encapsulate L3 protocols into IP 43 * See RFC 1701 and 1702 for more details. 44 * If_gre is compatible with Cisco GRE tunnels, so you can 45 * have a NetBSD box as the other end of a tunnel interface of a Cisco 46 * router. See gre(4) for more details. 47 * Also supported: IP in IP encaps (proto 55) as of RFC 2004 48 */ 49 50 #include "opt_atalk.h" 51 #include "opt_inet.h" 52 #include "opt_ns.h" 53 54 #include <sys/param.h> 55 #include <sys/kernel.h> 56 #include <sys/malloc.h> 57 #include <sys/mbuf.h> 58 #include <sys/proc.h> 59 #include <sys/protosw.h> 60 #include <machine/bus.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_types.h> 69 #include <net/route.h> 70 71 #ifdef INET 72 #include <netinet/in.h> 73 #include <netinet/in_systm.h> 74 #include <netinet/in_var.h> 75 #include <netinet/ip.h> 76 #include <netinet/ip_gre.h> 77 #include <netinet/ip_var.h> 78 #include <netinet/ip_encap.h> 79 #else 80 #error "Huh? if_gre without inet?" 81 #endif 82 83 #include <net/bpf.h> 84 85 #include <net/net_osdep.h> 86 #include "if_gre.h" 87 88 /* 89 * It is not easy to calculate the right value for a GRE MTU. 90 * We leave this task to the admin and use the same default that 91 * other vendors use. 92 */ 93 #define GREMTU 1476 94 95 #define GRENAME "gre" 96 97 static MALLOC_DEFINE(M_GRE, GRENAME, "Generic Routing Encapsulation"); 98 99 struct gre_softc_head gre_softc_list; 100 101 static int gre_clone_create(struct if_clone *, int); 102 static void gre_clone_destroy(struct ifnet *); 103 static int gre_ioctl(struct ifnet *, u_long, caddr_t); 104 static int gre_output(struct ifnet *, struct mbuf *, struct sockaddr *, 105 struct rtentry *rt); 106 107 static struct if_clone gre_cloner = IF_CLONE_INITIALIZER("gre", 108 gre_clone_create, gre_clone_destroy, 0, IF_MAXUNIT); 109 110 static int gre_compute_route(struct gre_softc *sc); 111 112 static void greattach(void); 113 114 #ifdef INET 115 extern struct domain inetdomain; 116 static const struct protosw in_gre_protosw = 117 { SOCK_RAW, &inetdomain, IPPROTO_GRE, PR_ATOMIC|PR_ADDR, 118 gre_input, rip_output, rip_ctlinput, rip_ctloutput, 119 0, 120 0, 0, 0, 0, 121 &rip_usrreqs 122 }; 123 static const struct protosw in_mobile_protosw = 124 { SOCK_RAW, &inetdomain, IPPROTO_MOBILE, PR_ATOMIC|PR_ADDR, 125 gre_mobile_input, rip_output, rip_ctlinput, rip_ctloutput, 126 0, 127 0, 0, 0, 0, 128 &rip_usrreqs 129 }; 130 #endif 131 132 SYSCTL_DECL(_net_link); 133 SYSCTL_NODE(_net_link, IFT_OTHER, gre, CTLFLAG_RW, 0, 134 "Generic Routing Encapsulation"); 135 #ifndef MAX_GRE_NEST 136 /* 137 * This macro controls the default upper limitation on nesting of gre tunnels. 138 * Since, setting a large value to this macro with a careless configuration 139 * may introduce system crash, we don't allow any nestings by default. 140 * If you need to configure nested gre tunnels, you can define this macro 141 * in your kernel configuration file. However, if you do so, please be 142 * careful to configure the tunnels so that it won't make a loop. 143 */ 144 #define MAX_GRE_NEST 1 145 #endif 146 static int max_gre_nesting = MAX_GRE_NEST; 147 SYSCTL_INT(_net_link_gre, OID_AUTO, max_nesting, CTLFLAG_RW, 148 &max_gre_nesting, 0, "Max nested tunnels"); 149 150 /* ARGSUSED */ 151 static void 152 greattach(void) 153 { 154 155 LIST_INIT(&gre_softc_list); 156 if_clone_attach(&gre_cloner); 157 } 158 159 static int 160 gre_clone_create(ifc, unit) 161 struct if_clone *ifc; 162 int unit; 163 { 164 struct gre_softc *sc; 165 166 sc = malloc(sizeof(struct gre_softc), M_GRE, M_WAITOK); 167 memset(sc, 0, sizeof(struct gre_softc)); 168 169 sc->sc_if.if_softc = sc; 170 if_initname(&(sc->sc_if), GRENAME, unit); 171 sc->sc_if.if_snd.ifq_maxlen = IFQ_MAXLEN; 172 sc->sc_if.if_type = IFT_OTHER; 173 sc->sc_if.if_addrlen = 0; 174 sc->sc_if.if_hdrlen = 24; /* IP + GRE */ 175 sc->sc_if.if_mtu = GREMTU; 176 sc->sc_if.if_flags = IFF_POINTOPOINT|IFF_MULTICAST; 177 sc->sc_if.if_output = gre_output; 178 sc->sc_if.if_ioctl = gre_ioctl; 179 sc->g_dst.s_addr = sc->g_src.s_addr = INADDR_ANY; 180 sc->g_proto = IPPROTO_GRE; 181 sc->sc_if.if_flags |= IFF_LINK0; 182 sc->encap = NULL; 183 sc->called = 0; 184 if_attach(&sc->sc_if); 185 bpfattach(&sc->sc_if, DLT_NULL, sizeof(u_int32_t)); 186 LIST_INSERT_HEAD(&gre_softc_list, sc, sc_list); 187 return (0); 188 } 189 190 static void 191 gre_clone_destroy(ifp) 192 struct ifnet *ifp; 193 { 194 struct gre_softc *sc = ifp->if_softc; 195 196 #ifdef INET 197 if (sc->encap != NULL) 198 encap_detach(sc->encap); 199 #endif 200 LIST_REMOVE(sc, sc_list); 201 bpfdetach(ifp); 202 if_detach(ifp); 203 204 free(sc, M_GRE); 205 } 206 207 /* 208 * The output routine. Takes a packet and encapsulates it in the protocol 209 * given by sc->g_proto. See also RFC 1701 and RFC 2004 210 */ 211 static int 212 gre_output(struct ifnet *ifp, struct mbuf *m, struct sockaddr *dst, 213 struct rtentry *rt) 214 { 215 int error = 0; 216 struct gre_softc *sc = ifp->if_softc; 217 struct greip *gh; 218 struct ip *ip; 219 u_char osrc; 220 u_short etype = 0; 221 struct mobile_h mob_h; 222 223 /* 224 * gre may cause infinite recursion calls when misconfigured. 225 * We'll prevent this by introducing upper limit. 226 */ 227 if (++(sc->called) > max_gre_nesting) { 228 printf("%s: gre_output: recursively called too many " 229 "times(%d)\n", if_name(&sc->sc_if), sc->called); 230 m_freem(m); 231 error = EIO; /* is there better errno? */ 232 goto end; 233 } 234 235 if ((ifp->if_flags & (IFF_UP | IFF_RUNNING)) == 0 || 236 sc->g_src.s_addr == INADDR_ANY || sc->g_dst.s_addr == INADDR_ANY) { 237 m_freem(m); 238 error = ENETDOWN; 239 goto end; 240 } 241 242 gh = NULL; 243 ip = NULL; 244 osrc = 0; 245 246 if (ifp->if_bpf) { 247 /* see comment of other if_foo.c files */ 248 struct mbuf m0; 249 u_int32_t af = dst->sa_family; 250 251 m0.m_next = m; 252 m0.m_len = 4; 253 m0.m_data = (char *)⁡ 254 255 bpf_mtap(ifp, &m0); 256 } 257 258 m->m_flags &= ~(M_BCAST|M_MCAST); 259 260 if (sc->g_proto == IPPROTO_MOBILE) { 261 if (dst->sa_family == AF_INET) { 262 struct mbuf *m0; 263 int msiz; 264 265 ip = mtod(m, struct ip *); 266 267 /* 268 * RFC2004 specifies that fragmented diagrams shouldn't 269 * be encapsulated. 270 */ 271 if ((ip->ip_off & IP_MF) != 0) { 272 IF_DROP(&ifp->if_snd); 273 m_freem(m); 274 error = EINVAL; /* is there better errno? */ 275 goto end; 276 } 277 memset(&mob_h, 0, MOB_H_SIZ_L); 278 mob_h.proto = (ip->ip_p) << 8; 279 mob_h.odst = ip->ip_dst.s_addr; 280 ip->ip_dst.s_addr = sc->g_dst.s_addr; 281 282 /* 283 * If the packet comes from our host, we only change 284 * the destination address in the IP header. 285 * Else we also need to save and change the source 286 */ 287 if (in_hosteq(ip->ip_src, sc->g_src)) { 288 msiz = MOB_H_SIZ_S; 289 } else { 290 mob_h.proto |= MOB_H_SBIT; 291 mob_h.osrc = ip->ip_src.s_addr; 292 ip->ip_src.s_addr = sc->g_src.s_addr; 293 msiz = MOB_H_SIZ_L; 294 } 295 mob_h.proto = htons(mob_h.proto); 296 mob_h.hcrc = gre_in_cksum((u_short *)&mob_h, msiz); 297 298 if ((m->m_data - msiz) < m->m_pktdat) { 299 /* need new mbuf */ 300 MGETHDR(m0, M_DONTWAIT, MT_HEADER); 301 if (m0 == NULL) { 302 IF_DROP(&ifp->if_snd); 303 m_freem(m); 304 error = ENOBUFS; 305 goto end; 306 } 307 m0->m_next = m; 308 m->m_data += sizeof(struct ip); 309 m->m_len -= sizeof(struct ip); 310 m0->m_pkthdr.len = m->m_pkthdr.len + msiz; 311 m0->m_len = msiz + sizeof(struct ip); 312 m0->m_data += max_linkhdr; 313 memcpy(mtod(m0, caddr_t), (caddr_t)ip, 314 sizeof(struct ip)); 315 m = m0; 316 } else { /* we have some space left in the old one */ 317 m->m_data -= msiz; 318 m->m_len += msiz; 319 m->m_pkthdr.len += msiz; 320 bcopy(ip, mtod(m, caddr_t), 321 sizeof(struct ip)); 322 } 323 ip = mtod(m, struct ip *); 324 memcpy((caddr_t)(ip + 1), &mob_h, (unsigned)msiz); 325 ip->ip_len = ntohs(ip->ip_len) + msiz; 326 } else { /* AF_INET */ 327 IF_DROP(&ifp->if_snd); 328 m_freem(m); 329 error = EINVAL; 330 goto end; 331 } 332 } else if (sc->g_proto == IPPROTO_GRE) { 333 switch (dst->sa_family) { 334 case AF_INET: 335 ip = mtod(m, struct ip *); 336 etype = ETHERTYPE_IP; 337 break; 338 #ifdef NETATALK 339 case AF_APPLETALK: 340 etype = ETHERTYPE_ATALK; 341 break; 342 #endif 343 #ifdef NS 344 case AF_NS: 345 etype = ETHERTYPE_NS; 346 break; 347 #endif 348 default: 349 IF_DROP(&ifp->if_snd); 350 m_freem(m); 351 error = EAFNOSUPPORT; 352 goto end; 353 } 354 M_PREPEND(m, sizeof(struct greip), M_DONTWAIT); 355 } else { 356 IF_DROP(&ifp->if_snd); 357 m_freem(m); 358 error = EINVAL; 359 goto end; 360 } 361 362 if (m == NULL) { /* impossible */ 363 IF_DROP(&ifp->if_snd); 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 ifp->if_opackets++; 388 ifp->if_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 ifp->if_oerrors++; 395 return (error); 396 } 397 398 static int 399 gre_ioctl(struct ifnet *ifp, u_long cmd, caddr_t data) 400 { 401 struct ifreq *ifr = (struct ifreq *)data; 402 struct if_laddrreq *lifr = (struct if_laddrreq *)data; 403 struct in_aliasreq *aifr = (struct in_aliasreq *)data; 404 struct gre_softc *sc = ifp->if_softc; 405 int s; 406 struct sockaddr_in si; 407 struct sockaddr *sa = NULL; 408 int error; 409 struct sockaddr_in sp, sm, dp, dm; 410 struct thread *td = curthread; 411 412 error = 0; 413 414 s = splnet(); 415 switch (cmd) { 416 case SIOCSIFADDR: 417 ifp->if_flags |= IFF_UP; 418 break; 419 case SIOCSIFDSTADDR: 420 break; 421 case SIOCSIFFLAGS: 422 if ((error = suser(td)) != 0) 423 break; 424 if ((ifr->ifr_flags & IFF_LINK0) != 0) 425 sc->g_proto = IPPROTO_GRE; 426 else 427 sc->g_proto = IPPROTO_MOBILE; 428 goto recompute; 429 case SIOCSIFMTU: 430 if ((error = suser(td)) != 0) 431 break; 432 if (ifr->ifr_mtu < 576) { 433 error = EINVAL; 434 break; 435 } 436 ifp->if_mtu = ifr->ifr_mtu; 437 break; 438 case SIOCGIFMTU: 439 ifr->ifr_mtu = sc->sc_if.if_mtu; 440 break; 441 case SIOCADDMULTI: 442 case SIOCDELMULTI: 443 if ((error = suser(td)) != 0) 444 break; 445 if (ifr == 0) { 446 error = EAFNOSUPPORT; 447 break; 448 } 449 switch (ifr->ifr_addr.sa_family) { 450 #ifdef INET 451 case AF_INET: 452 break; 453 #endif 454 default: 455 error = EAFNOSUPPORT; 456 break; 457 } 458 break; 459 case GRESPROTO: 460 if ((error = suser(td)) != 0) 461 break; 462 sc->g_proto = ifr->ifr_flags; 463 switch (sc->g_proto) { 464 case IPPROTO_GRE: 465 ifp->if_flags |= IFF_LINK0; 466 break; 467 case IPPROTO_MOBILE: 468 ifp->if_flags &= ~IFF_LINK0; 469 break; 470 default: 471 error = EPROTONOSUPPORT; 472 break; 473 } 474 goto recompute; 475 case GREGPROTO: 476 ifr->ifr_flags = sc->g_proto; 477 break; 478 case GRESADDRS: 479 case GRESADDRD: 480 if ((error = suser(td)) != 0) 481 break; 482 /* 483 * set tunnel endpoints, compute a less specific route 484 * to the remote end and mark if as up 485 */ 486 sa = &ifr->ifr_addr; 487 if (cmd == GRESADDRS) 488 sc->g_src = (satosin(sa))->sin_addr; 489 if (cmd == GRESADDRD) 490 sc->g_dst = (satosin(sa))->sin_addr; 491 recompute: 492 #ifdef INET 493 if (sc->encap != NULL) { 494 encap_detach(sc->encap); 495 sc->encap = NULL; 496 } 497 #endif 498 if ((sc->g_src.s_addr != INADDR_ANY) && 499 (sc->g_dst.s_addr != INADDR_ANY)) { 500 bzero(&sp, sizeof(sp)); 501 bzero(&sm, sizeof(sm)); 502 bzero(&dp, sizeof(dp)); 503 bzero(&dm, sizeof(dm)); 504 sp.sin_len = sm.sin_len = dp.sin_len = dm.sin_len = 505 sizeof(struct sockaddr_in); 506 sp.sin_family = sm.sin_family = dp.sin_family = 507 dm.sin_family = AF_INET; 508 sp.sin_addr = sc->g_src; 509 dp.sin_addr = sc->g_dst; 510 sm.sin_addr.s_addr = dm.sin_addr.s_addr = 511 INADDR_BROADCAST; 512 #ifdef INET 513 sc->encap = encap_attach(AF_INET, sc->g_proto, 514 sintosa(&sp), sintosa(&sm), sintosa(&dp), 515 sintosa(&dm), (sc->g_proto == IPPROTO_GRE) ? 516 &in_gre_protosw : &in_mobile_protosw, sc); 517 if (sc->encap == NULL) 518 printf("%s: unable to attach encap\n", 519 if_name(&sc->sc_if)); 520 #endif 521 if (sc->route.ro_rt != 0) /* free old route */ 522 RTFREE(sc->route.ro_rt); 523 if (gre_compute_route(sc) == 0) 524 ifp->if_flags |= IFF_RUNNING; 525 else 526 ifp->if_flags &= ~IFF_RUNNING; 527 } 528 break; 529 case GREGADDRS: 530 memset(&si, 0, sizeof(si)); 531 si.sin_family = AF_INET; 532 si.sin_len = sizeof(struct sockaddr_in); 533 si.sin_addr.s_addr = sc->g_src.s_addr; 534 sa = sintosa(&si); 535 ifr->ifr_addr = *sa; 536 break; 537 case GREGADDRD: 538 memset(&si, 0, sizeof(si)); 539 si.sin_family = AF_INET; 540 si.sin_len = sizeof(struct sockaddr_in); 541 si.sin_addr.s_addr = sc->g_dst.s_addr; 542 sa = sintosa(&si); 543 ifr->ifr_addr = *sa; 544 break; 545 case SIOCSIFPHYADDR: 546 if ((error = suser(td)) != 0) 547 break; 548 if (aifr->ifra_addr.sin_family != AF_INET || 549 aifr->ifra_dstaddr.sin_family != AF_INET) { 550 error = EAFNOSUPPORT; 551 break; 552 } 553 if (aifr->ifra_addr.sin_len != sizeof(si) || 554 aifr->ifra_dstaddr.sin_len != sizeof(si)) { 555 error = EINVAL; 556 break; 557 } 558 sc->g_src = aifr->ifra_addr.sin_addr; 559 sc->g_dst = aifr->ifra_dstaddr.sin_addr; 560 goto recompute; 561 case SIOCSLIFPHYADDR: 562 if ((error = suser(td)) != 0) 563 break; 564 if (lifr->addr.ss_family != AF_INET || 565 lifr->dstaddr.ss_family != AF_INET) { 566 error = EAFNOSUPPORT; 567 break; 568 } 569 if (lifr->addr.ss_len != sizeof(si) || 570 lifr->dstaddr.ss_len != sizeof(si)) { 571 error = EINVAL; 572 break; 573 } 574 sc->g_src = (satosin((struct sockadrr *)&lifr->addr))->sin_addr; 575 sc->g_dst = 576 (satosin((struct sockadrr *)&lifr->dstaddr))->sin_addr; 577 goto recompute; 578 case SIOCDIFPHYADDR: 579 if ((error = suser(td)) != 0) 580 break; 581 sc->g_src.s_addr = INADDR_ANY; 582 sc->g_dst.s_addr = INADDR_ANY; 583 goto recompute; 584 case SIOCGLIFPHYADDR: 585 if (sc->g_src.s_addr == INADDR_ANY || 586 sc->g_dst.s_addr == INADDR_ANY) { 587 error = EADDRNOTAVAIL; 588 break; 589 } 590 memset(&si, 0, sizeof(si)); 591 si.sin_family = AF_INET; 592 si.sin_len = sizeof(struct sockaddr_in); 593 si.sin_addr.s_addr = sc->g_src.s_addr; 594 memcpy(&lifr->addr, &si, sizeof(si)); 595 si.sin_addr.s_addr = sc->g_dst.s_addr; 596 memcpy(&lifr->dstaddr, &si, sizeof(si)); 597 break; 598 case SIOCGIFPSRCADDR: 599 if (sc->g_src.s_addr == INADDR_ANY) { 600 error = EADDRNOTAVAIL; 601 break; 602 } 603 memset(&si, 0, sizeof(si)); 604 si.sin_family = AF_INET; 605 si.sin_len = sizeof(struct sockaddr_in); 606 si.sin_addr.s_addr = sc->g_src.s_addr; 607 bcopy(&si, &ifr->ifr_addr, sizeof(ifr->ifr_addr)); 608 break; 609 case SIOCGIFPDSTADDR: 610 if (sc->g_dst.s_addr == INADDR_ANY) { 611 error = EADDRNOTAVAIL; 612 break; 613 } 614 memset(&si, 0, sizeof(si)); 615 si.sin_family = AF_INET; 616 si.sin_len = sizeof(struct sockaddr_in); 617 si.sin_addr.s_addr = sc->g_dst.s_addr; 618 bcopy(&si, &ifr->ifr_addr, sizeof(ifr->ifr_addr)); 619 break; 620 default: 621 error = EINVAL; 622 break; 623 } 624 625 splx(s); 626 return (error); 627 } 628 629 /* 630 * computes a route to our destination that is not the one 631 * which would be taken by ip_output(), as this one will loop back to 632 * us. If the interface is p2p as a--->b, then a routing entry exists 633 * If we now send a packet to b (e.g. ping b), this will come down here 634 * gets src=a, dst=b tacked on and would from ip_ouput() sent back to 635 * if_gre. 636 * Goal here is to compute a route to b that is less specific than 637 * a-->b. We know that this one exists as in normal operation we have 638 * at least a default route which matches. 639 */ 640 static int 641 gre_compute_route(struct gre_softc *sc) 642 { 643 struct route *ro; 644 u_int32_t a, b, c; 645 646 ro = &sc->route; 647 648 memset(ro, 0, sizeof(struct route)); 649 ((struct sockaddr_in *)&ro->ro_dst)->sin_addr = sc->g_dst; 650 ro->ro_dst.sa_family = AF_INET; 651 ro->ro_dst.sa_len = sizeof(ro->ro_dst); 652 653 /* 654 * toggle last bit, so our interface is not found, but a less 655 * specific route. I'd rather like to specify a shorter mask, 656 * but this is not possible. Should work though. XXX 657 * there is a simpler way ... 658 */ 659 if ((sc->sc_if.if_flags & IFF_LINK1) == 0) { 660 a = ntohl(sc->g_dst.s_addr); 661 b = a & 0x01; 662 c = a & 0xfffffffe; 663 b = b ^ 0x01; 664 a = b | c; 665 ((struct sockaddr_in *)&ro->ro_dst)->sin_addr.s_addr 666 = htonl(a); 667 } 668 669 #ifdef DIAGNOSTIC 670 printf("%s: searching a route to %s", if_name(&sc->sc_if), 671 inet_ntoa(((struct sockaddr_in *)&ro->ro_dst)->sin_addr)); 672 #endif 673 674 rtalloc(ro); 675 676 /* 677 * check if this returned a route at all and this route is no 678 * recursion to ourself 679 */ 680 if (ro->ro_rt == NULL || ro->ro_rt->rt_ifp->if_softc == sc) { 681 #ifdef DIAGNOSTIC 682 if (ro->ro_rt == NULL) 683 printf(" - no route found!\n"); 684 else 685 printf(" - route loops back to ourself!\n"); 686 #endif 687 return EADDRNOTAVAIL; 688 } 689 690 /* 691 * now change it back - else ip_output will just drop 692 * the route and search one to this interface ... 693 */ 694 if ((sc->sc_if.if_flags & IFF_LINK1) == 0) 695 ((struct sockaddr_in *)&ro->ro_dst)->sin_addr = sc->g_dst; 696 697 #ifdef DIAGNOSTIC 698 printf(", choosing %s with gateway %s", if_name(ro->ro_rt->rt_ifp), 699 inet_ntoa(((struct sockaddr_in *)(ro->ro_rt->rt_gateway))->sin_addr)); 700 printf("\n"); 701 #endif 702 703 return 0; 704 } 705 706 /* 707 * do a checksum of a buffer - much like in_cksum, which operates on 708 * mbufs. 709 */ 710 u_short 711 gre_in_cksum(u_short *p, u_int len) 712 { 713 u_int sum = 0; 714 int nwords = len >> 1; 715 716 while (nwords-- != 0) 717 sum += *p++; 718 719 if (len & 1) { 720 union { 721 u_short w; 722 u_char c[2]; 723 } u; 724 u.c[0] = *(u_char *)p; 725 u.c[1] = 0; 726 sum += u.w; 727 } 728 729 /* end-around-carry */ 730 sum = (sum >> 16) + (sum & 0xffff); 731 sum += (sum >> 16); 732 return (~sum); 733 } 734 735 static int 736 gremodevent(module_t mod, int type, void *data) 737 { 738 739 switch (type) { 740 case MOD_LOAD: 741 greattach(); 742 break; 743 case MOD_UNLOAD: 744 if_clone_detach(&gre_cloner); 745 746 while (!LIST_EMPTY(&gre_softc_list)) 747 gre_clone_destroy(&LIST_FIRST(&gre_softc_list)->sc_if); 748 749 break; 750 } 751 return 0; 752 } 753 754 static moduledata_t gre_mod = { 755 "if_gre", 756 gremodevent, 757 0 758 }; 759 760 DECLARE_MODULE(if_gre, gre_mod, SI_SUB_PSEUDO, SI_ORDER_ANY); 761 MODULE_VERSION(if_gre, 1); 762