if_gre.c revision 103394
1/* $NetBSD: if_gre.c,v 1.42 2002/08/14 00:23:27 itojun Exp $ */ 2/* $FreeBSD: head/sys/net/if_gre.c 103394 2002-09-16 10:10:18Z bde $ */ 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 <sys/cdefs.h> 50__RCSID("@(#) $FreeBSD: head/sys/net/if_gre.c 103394 2002-09-16 10:10:18Z bde $"); 51 52#include "opt_atalk.h" 53#include "opt_inet.h" 54#include "opt_ns.h" 55#include "bpf.h" 56 57#include <sys/param.h> 58#include <sys/kernel.h> 59#include <sys/malloc.h> 60#include <sys/mbuf.h> 61#include <sys/protosw.h> 62#include <sys/socket.h> 63#include <sys/sockio.h> 64#include <sys/sysctl.h> 65#include <sys/systm.h> 66 67#include <net/ethernet.h> 68#include <net/if.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#if NBPF > 0 85#include <net/bpf.h> 86#endif 87 88#include <net/net_osdep.h> 89#include <net/if_gre.h> 90 91/* 92 * It is not easy to calculate the right value for a GRE MTU. 93 * We leave this task to the admin and use the same default that 94 * other vendors use. 95 */ 96#define GREMTU 1476 97 98#define GRENAME "gre" 99 100static MALLOC_DEFINE(M_GRE, GRENAME, "Generic Routing Encapsulation"); 101 102struct gre_softc_head gre_softc_list; 103 104static int gre_clone_create __P((struct if_clone *, int)); 105static void gre_clone_destroy __P((struct ifnet *)); 106static int gre_ioctl(struct ifnet *, u_long, caddr_t); 107static int gre_output(struct ifnet *, struct mbuf *, struct sockaddr *, 108 struct rtentry *rt); 109 110static struct if_clone gre_cloner = 111 IF_CLONE_INITIALIZER("gre", gre_clone_create, gre_clone_destroy, 0, IF_MAXUNIT); 112 113static int gre_compute_route(struct gre_softc *sc); 114 115static void greattach __P((void)); 116 117#ifdef INET 118extern struct domain inetdomain; 119static const struct protosw in_gre_protosw = 120{ SOCK_RAW, &inetdomain, IPPROTO_GRE, PR_ATOMIC|PR_ADDR, 121 (pr_input_t*)gre_input, (pr_output_t*)rip_output, rip_ctlinput, rip_ctloutput, 122 0, 123 0, 0, 0, 0, 124 &rip_usrreqs 125}; 126static const struct protosw in_mobile_protosw = 127{ SOCK_RAW, &inetdomain, IPPROTO_MOBILE, PR_ATOMIC|PR_ADDR, 128 (pr_input_t*)gre_mobile_input, (pr_output_t*)rip_output, rip_ctlinput, rip_ctloutput, 129 0, 130 0, 0, 0, 0, 131 &rip_usrreqs 132}; 133#endif 134 135SYSCTL_DECL(_net_link); 136SYSCTL_NODE(_net_link, IFT_OTHER, gre, CTLFLAG_RW, 0, 137 "Generic Routing Encapsulation"); 138#ifndef MAX_GRE_NEST 139/* 140 * This macro controls the default upper limitation on nesting of gre tunnels. 141 * Since, setting a large value to this macro with a careless configuration 142 * may introduce system crash, we don't allow any nestings by default. 143 * If you need to configure nested gre tunnels, you can define this macro 144 * in your kernel configuration file. However, if you do so, please be 145 * careful to configure the tunnels so that it won't make a loop. 146 */ 147#define MAX_GRE_NEST 1 148#endif 149static int max_gre_nesting = MAX_GRE_NEST; 150SYSCTL_INT(_net_link_gre, OID_AUTO, max_nesting, CTLFLAG_RW, 151 &max_gre_nesting, 0, "Max nested tunnels"); 152 153/* ARGSUSED */ 154static void 155greattach(void) 156{ 157 158 LIST_INIT(&gre_softc_list); 159 if_clone_attach(&gre_cloner); 160} 161 162static int 163gre_clone_create(ifc, unit) 164 struct if_clone *ifc; 165 int unit; 166{ 167 struct gre_softc *sc; 168 169 sc = malloc(sizeof(struct gre_softc), M_GRE, M_WAITOK); 170 memset(sc, 0, sizeof(struct gre_softc)); 171 172 sc->sc_if.if_name = GRENAME; 173 sc->sc_if.if_softc = sc; 174 sc->sc_if.if_unit = unit; 175 sc->sc_if.if_snd.ifq_maxlen = IFQ_MAXLEN; 176 sc->sc_if.if_type = IFT_OTHER; 177 sc->sc_if.if_addrlen = 0; 178 sc->sc_if.if_hdrlen = 24; /* IP + GRE */ 179 sc->sc_if.if_mtu = GREMTU; 180 sc->sc_if.if_flags = IFF_POINTOPOINT|IFF_MULTICAST; 181 sc->sc_if.if_output = gre_output; 182 sc->sc_if.if_ioctl = gre_ioctl; 183 sc->g_dst.s_addr = sc->g_src.s_addr = INADDR_ANY; 184 sc->g_proto = IPPROTO_GRE; 185 sc->sc_if.if_flags |= IFF_LINK0; 186 sc->encap = NULL; 187 sc->called = 0; 188 if_attach(&sc->sc_if); 189#if NBPF 190 bpfattach(&sc->sc_if, DLT_NULL, sizeof(u_int32_t)); 191#endif 192 LIST_INSERT_HEAD(&gre_softc_list, sc, sc_list); 193 return (0); 194} 195 196static void 197gre_clone_destroy(ifp) 198 struct ifnet *ifp; 199{ 200 struct gre_softc *sc = ifp->if_softc; 201 202#ifdef INET 203 if (sc->encap != NULL) 204 encap_detach(sc->encap); 205#endif 206 LIST_REMOVE(sc, sc_list); 207#if NBPF 208 bpfdetach(ifp); 209#endif 210 if_detach(ifp); 211 free(sc, M_GRE); 212} 213 214/* 215 * The output routine. Takes a packet and encapsulates it in the protocol 216 * given by sc->g_proto. See also RFC 1701 and RFC 2004 217 */ 218static int 219gre_output(struct ifnet *ifp, struct mbuf *m, struct sockaddr *dst, 220 struct rtentry *rt) 221{ 222 int error = 0; 223 struct gre_softc *sc = ifp->if_softc; 224 struct greip *gh; 225 struct ip *ip; 226 u_char osrc; 227 u_short etype = 0; 228 struct mobile_h mob_h; 229 230 /* 231 * gre may cause infinite recursion calls when misconfigured. 232 * We'll prevent this by introducing upper limit. 233 */ 234 if (++(sc->called) > max_gre_nesting) { 235 printf("%s: gre_output: recursively called too many " 236 "times(%d)\n", if_name(&sc->sc_if), sc->called); 237 m_freem(m); 238 error = EIO; /* is there better errno? */ 239 goto end; 240 } 241 242 if ((ifp->if_flags & (IFF_UP | IFF_RUNNING)) == 0 || 243 sc->g_src.s_addr == INADDR_ANY || sc->g_dst.s_addr == INADDR_ANY) { 244 m_freem(m); 245 error = ENETDOWN; 246 goto end; 247 } 248 249 gh = NULL; 250 ip = NULL; 251 osrc = 0; 252 253#if NBPF 254 if (ifp->if_bpf) { 255 /* see comment of other if_foo.c files */ 256 struct mbuf m0; 257 u_int32_t af = dst->sa_family; 258 259 m0.m_next = m; 260 m0.m_len = 4; 261 m0.m_data = (char *)⁡ 262 263 bpf_mtap(ifp, &m0); 264 } 265#endif 266 267 m->m_flags &= ~(M_BCAST|M_MCAST); 268 269 if (sc->g_proto == IPPROTO_MOBILE) { 270 if (dst->sa_family == AF_INET) { 271 struct mbuf *m0; 272 int msiz; 273 274 ip = mtod(m, struct ip *); 275 276 /* 277 * RFC2004 specifies that fragmented diagrams shouldn't 278 * be encapsulated. 279 */ 280 if ((ip->ip_off & IP_MF) != 0) { 281 _IF_DROP(&ifp->if_snd); 282 m_freem(m); 283 error = EINVAL; /* is there better errno? */ 284 goto end; 285 } 286 memset(&mob_h, 0, MOB_H_SIZ_L); 287 mob_h.proto = (ip->ip_p) << 8; 288 mob_h.odst = ip->ip_dst.s_addr; 289 ip->ip_dst.s_addr = sc->g_dst.s_addr; 290 291 /* 292 * If the packet comes from our host, we only change 293 * the destination address in the IP header. 294 * Else we also need to save and change the source 295 */ 296 if (in_hosteq(ip->ip_src, sc->g_src)) { 297 msiz = MOB_H_SIZ_S; 298 } else { 299 mob_h.proto |= MOB_H_SBIT; 300 mob_h.osrc = ip->ip_src.s_addr; 301 ip->ip_src.s_addr = sc->g_src.s_addr; 302 msiz = MOB_H_SIZ_L; 303 } 304 mob_h.proto = htons(mob_h.proto); 305 mob_h.hcrc = gre_in_cksum((u_short *)&mob_h, msiz); 306 307 if ((m->m_data - msiz) < m->m_pktdat) { 308 /* need new mbuf */ 309 MGETHDR(m0, M_DONTWAIT, MT_HEADER); 310 if (m0 == NULL) { 311 _IF_DROP(&ifp->if_snd); 312 m_freem(m); 313 error = ENOBUFS; 314 goto end; 315 } 316 m0->m_next = m; 317 m->m_data += sizeof(struct ip); 318 m->m_len -= sizeof(struct ip); 319 m0->m_pkthdr.len = m->m_pkthdr.len + msiz; 320 m0->m_len = msiz + sizeof(struct ip); 321 m0->m_data += max_linkhdr; 322 memcpy(mtod(m0, caddr_t), (caddr_t)ip, 323 sizeof(struct ip)); 324 m = m0; 325 } else { /* we have some space left in the old one */ 326 m->m_data -= msiz; 327 m->m_len += msiz; 328 m->m_pkthdr.len += msiz; 329 bcopy(ip, mtod(m, caddr_t), 330 sizeof(struct ip)); 331 } 332 ip = mtod(m, struct ip *); 333 memcpy((caddr_t)(ip + 1), &mob_h, (unsigned)msiz); 334 ip->ip_len = ntohs(ip->ip_len) + msiz; 335 } else { /* AF_INET */ 336 _IF_DROP(&ifp->if_snd); 337 m_freem(m); 338 error = EINVAL; 339 goto end; 340 } 341 } else if (sc->g_proto == IPPROTO_GRE) { 342 switch (dst->sa_family) { 343 case AF_INET: 344 ip = mtod(m, struct ip *); 345 etype = ETHERTYPE_IP; 346 break; 347#ifdef NETATALK 348 case AF_APPLETALK: 349 etype = ETHERTYPE_ATALK; 350 break; 351#endif 352#ifdef NS 353 case AF_NS: 354 etype = ETHERTYPE_NS; 355 break; 356#endif 357 default: 358 _IF_DROP(&ifp->if_snd); 359 m_freem(m); 360 error = EAFNOSUPPORT; 361 goto end; 362 } 363 M_PREPEND(m, sizeof(struct greip), M_DONTWAIT); 364 } else { 365 _IF_DROP(&ifp->if_snd); 366 m_freem(m); 367 error = EINVAL; 368 goto end; 369 } 370 371 if (m == NULL) { /* impossible */ 372 _IF_DROP(&ifp->if_snd); 373 error = ENOBUFS; 374 goto end; 375 } 376 377 gh = mtod(m, struct greip *); 378 if (sc->g_proto == IPPROTO_GRE) { 379 /* we don't have any GRE flags for now */ 380 381 memset((void *)&gh->gi_g, 0, sizeof(struct gre_h)); 382 gh->gi_ptype = htons(etype); 383 } 384 385 gh->gi_pr = sc->g_proto; 386 if (sc->g_proto != IPPROTO_MOBILE) { 387 gh->gi_src = sc->g_src; 388 gh->gi_dst = sc->g_dst; 389 ((struct ip*)gh)->ip_hl = (sizeof(struct ip)) >> 2; 390 ((struct ip*)gh)->ip_ttl = GRE_TTL; 391 ((struct ip*)gh)->ip_tos = ip->ip_tos; 392 ((struct ip*)gh)->ip_id = ip->ip_id; 393 gh->gi_len = m->m_pkthdr.len; 394 } 395 396 ifp->if_opackets++; 397 ifp->if_obytes += m->m_pkthdr.len; 398 /* send it off */ 399 error = ip_output(m, NULL, &sc->route, 0, NULL); 400 end: 401 sc->called = 0; 402 if (error) 403 ifp->if_oerrors++; 404 return (error); 405} 406 407static int 408gre_ioctl(struct ifnet *ifp, u_long cmd, caddr_t data) 409{ 410 struct ifreq *ifr = (struct ifreq *)data; 411 struct if_laddrreq *lifr = (struct if_laddrreq *)data; 412 struct in_aliasreq *aifr = (struct in_aliasreq *)data; 413 struct gre_softc *sc = ifp->if_softc; 414 int s; 415 struct sockaddr_in si; 416 struct sockaddr *sa = NULL; 417 int error; 418 struct sockaddr_in sp, sm, dp, dm; 419 420 error = 0; 421 422 s = splnet(); 423 switch (cmd) { 424 case SIOCSIFADDR: 425 ifp->if_flags |= IFF_UP; 426 break; 427 case SIOCSIFDSTADDR: 428 break; 429 case SIOCSIFFLAGS: 430 if ((error = suser(curthread)) != 0) 431 break; 432 if ((ifr->ifr_flags & IFF_LINK0) != 0) 433 sc->g_proto = IPPROTO_GRE; 434 else 435 sc->g_proto = IPPROTO_MOBILE; 436 goto recompute; 437 case SIOCSIFMTU: 438 if ((error = suser(curthread)) != 0) 439 break; 440 if (ifr->ifr_mtu < 576) { 441 error = EINVAL; 442 break; 443 } 444 ifp->if_mtu = ifr->ifr_mtu; 445 break; 446 case SIOCGIFMTU: 447 ifr->ifr_mtu = sc->sc_if.if_mtu; 448 break; 449 case SIOCADDMULTI: 450 case SIOCDELMULTI: 451 if ((error = suser(curthread)) != 0) 452 break; 453 if (ifr == 0) { 454 error = EAFNOSUPPORT; 455 break; 456 } 457 switch (ifr->ifr_addr.sa_family) { 458#ifdef INET 459 case AF_INET: 460 break; 461#endif 462 default: 463 error = EAFNOSUPPORT; 464 break; 465 } 466 break; 467 case GRESPROTO: 468 if ((error = suser(curthread)) != 0) 469 break; 470 sc->g_proto = ifr->ifr_flags; 471 switch (sc->g_proto) { 472 case IPPROTO_GRE: 473 ifp->if_flags |= IFF_LINK0; 474 break; 475 case IPPROTO_MOBILE: 476 ifp->if_flags &= ~IFF_LINK0; 477 break; 478 default: 479 error = EPROTONOSUPPORT; 480 break; 481 } 482 goto recompute; 483 case GREGPROTO: 484 ifr->ifr_flags = sc->g_proto; 485 break; 486 case GRESADDRS: 487 case GRESADDRD: 488 if ((error = suser(curthread)) != 0) 489 break; 490 /* 491 * set tunnel endpoints, compute a less specific route 492 * to the remote end and mark if as up 493 */ 494 sa = &ifr->ifr_addr; 495 if (cmd == GRESADDRS) 496 sc->g_src = (satosin(sa))->sin_addr; 497 if (cmd == GRESADDRD) 498 sc->g_dst = (satosin(sa))->sin_addr; 499 recompute: 500#ifdef INET 501 if (sc->encap != NULL) { 502 encap_detach(sc->encap); 503 sc->encap = NULL; 504 } 505#endif 506 if ((sc->g_src.s_addr != INADDR_ANY) && 507 (sc->g_dst.s_addr != INADDR_ANY)) { 508 bzero(&sp, sizeof(sp)); 509 bzero(&sm, sizeof(sm)); 510 bzero(&dp, sizeof(dp)); 511 bzero(&dm, sizeof(dm)); 512 sp.sin_len = sm.sin_len = dp.sin_len = dm.sin_len = 513 sizeof(struct sockaddr_in); 514 sp.sin_family = sm.sin_family = dp.sin_family = 515 dm.sin_family = AF_INET; 516 sp.sin_addr = sc->g_src; 517 dp.sin_addr = sc->g_dst; 518 sm.sin_addr.s_addr = dm.sin_addr.s_addr = 519 INADDR_BROADCAST; 520#ifdef INET 521 sc->encap = encap_attach(AF_INET, sc->g_proto, 522 sintosa(&sp), sintosa(&sm), sintosa(&dp), 523 sintosa(&dm), (sc->g_proto == IPPROTO_GRE) ? 524 &in_gre_protosw : &in_mobile_protosw, sc); 525 if (sc->encap == NULL) 526 printf("%s: unable to attach encap\n", 527 if_name(&sc->sc_if)); 528#endif 529 if (sc->route.ro_rt != 0) /* free old route */ 530 RTFREE(sc->route.ro_rt); 531 if (gre_compute_route(sc) == 0) 532 ifp->if_flags |= IFF_RUNNING; 533 else 534 ifp->if_flags &= ~IFF_RUNNING; 535 } 536 break; 537 case GREGADDRS: 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_src.s_addr; 542 sa = sintosa(&si); 543 ifr->ifr_addr = *sa; 544 break; 545 case GREGADDRD: 546 memset(&si, 0, sizeof(si)); 547 si.sin_family = AF_INET; 548 si.sin_len = sizeof(struct sockaddr_in); 549 si.sin_addr.s_addr = sc->g_dst.s_addr; 550 sa = sintosa(&si); 551 ifr->ifr_addr = *sa; 552 break; 553 case SIOCSIFPHYADDR: 554 if ((error = suser(curthread)) != 0) 555 break; 556 if (aifr->ifra_addr.sin_family != AF_INET || 557 aifr->ifra_dstaddr.sin_family != AF_INET) { 558 error = EAFNOSUPPORT; 559 break; 560 } 561 if (aifr->ifra_addr.sin_len != sizeof(si) || 562 aifr->ifra_dstaddr.sin_len != sizeof(si)) { 563 error = EINVAL; 564 break; 565 } 566 sc->g_src = aifr->ifra_addr.sin_addr; 567 sc->g_dst = aifr->ifra_dstaddr.sin_addr; 568 goto recompute; 569 case SIOCSLIFPHYADDR: 570 if ((error = suser(curthread)) != 0) 571 break; 572 if (lifr->addr.ss_family != AF_INET || 573 lifr->dstaddr.ss_family != AF_INET) { 574 error = EAFNOSUPPORT; 575 break; 576 } 577 if (lifr->addr.ss_len != sizeof(si) || 578 lifr->dstaddr.ss_len != sizeof(si)) { 579 error = EINVAL; 580 break; 581 } 582 sc->g_src = (satosin((struct sockadrr *)&lifr->addr))->sin_addr; 583 sc->g_dst = 584 (satosin((struct sockadrr *)&lifr->dstaddr))->sin_addr; 585 goto recompute; 586 case SIOCDIFPHYADDR: 587 if ((error = suser(curthread)) != 0) 588 break; 589 sc->g_src.s_addr = INADDR_ANY; 590 sc->g_dst.s_addr = INADDR_ANY; 591 goto recompute; 592 case SIOCGLIFPHYADDR: 593 if (sc->g_src.s_addr == INADDR_ANY || 594 sc->g_dst.s_addr == INADDR_ANY) { 595 error = EADDRNOTAVAIL; 596 break; 597 } 598 memset(&si, 0, sizeof(si)); 599 si.sin_family = AF_INET; 600 si.sin_len = sizeof(struct sockaddr_in); 601 si.sin_addr.s_addr = sc->g_src.s_addr; 602 memcpy(&lifr->addr, &si, sizeof(si)); 603 si.sin_addr.s_addr = sc->g_dst.s_addr; 604 memcpy(&lifr->dstaddr, &si, sizeof(si)); 605 break; 606 case SIOCGIFPSRCADDR: 607 if (sc->g_src.s_addr == INADDR_ANY) { 608 error = EADDRNOTAVAIL; 609 break; 610 } 611 memset(&si, 0, sizeof(si)); 612 si.sin_family = AF_INET; 613 si.sin_len = sizeof(struct sockaddr_in); 614 si.sin_addr.s_addr = sc->g_src.s_addr; 615 bcopy(&si, &ifr->ifr_addr, sizeof(ifr->ifr_addr)); 616 break; 617 case SIOCGIFPDSTADDR: 618 if (sc->g_dst.s_addr == INADDR_ANY) { 619 error = EADDRNOTAVAIL; 620 break; 621 } 622 memset(&si, 0, sizeof(si)); 623 si.sin_family = AF_INET; 624 si.sin_len = sizeof(struct sockaddr_in); 625 si.sin_addr.s_addr = sc->g_dst.s_addr; 626 bcopy(&si, &ifr->ifr_addr, sizeof(ifr->ifr_addr)); 627 break; 628 default: 629 error = EINVAL; 630 break; 631 } 632 633 splx(s); 634 return (error); 635} 636 637/* 638 * computes a route to our destination that is not the one 639 * which would be taken by ip_output(), as this one will loop back to 640 * us. If the interface is p2p as a--->b, then a routing entry exists 641 * If we now send a packet to b (e.g. ping b), this will come down here 642 * gets src=a, dst=b tacked on and would from ip_ouput() sent back to 643 * if_gre. 644 * Goal here is to compute a route to b that is less specific than 645 * a-->b. We know that this one exists as in normal operation we have 646 * at least a default route which matches. 647 */ 648static int 649gre_compute_route(struct gre_softc *sc) 650{ 651 struct route *ro; 652 u_int32_t a, b, c; 653 654 ro = &sc->route; 655 656 memset(ro, 0, sizeof(struct route)); 657 ((struct sockaddr_in *)&ro->ro_dst)->sin_addr = sc->g_dst; 658 ro->ro_dst.sa_family = AF_INET; 659 ro->ro_dst.sa_len = sizeof(ro->ro_dst); 660 661 /* 662 * toggle last bit, so our interface is not found, but a less 663 * specific route. I'd rather like to specify a shorter mask, 664 * but this is not possible. Should work though. XXX 665 * there is a simpler way ... 666 */ 667 if ((sc->sc_if.if_flags & IFF_LINK1) == 0) { 668 a = ntohl(sc->g_dst.s_addr); 669 b = a & 0x01; 670 c = a & 0xfffffffe; 671 b = b ^ 0x01; 672 a = b | c; 673 ((struct sockaddr_in *)&ro->ro_dst)->sin_addr.s_addr 674 = htonl(a); 675 } 676 677#ifdef DIAGNOSTIC 678 printf("%s: searching a route to %s", if_name(&sc->sc_if), 679 inet_ntoa(((struct sockaddr_in *)&ro->ro_dst)->sin_addr)); 680#endif 681 682 rtalloc(ro); 683 684 /* 685 * check if this returned a route at all and this route is no 686 * recursion to ourself 687 */ 688 if (ro->ro_rt == NULL || ro->ro_rt->rt_ifp->if_softc == sc) { 689#ifdef DIAGNOSTIC 690 if (ro->ro_rt == NULL) 691 printf(" - no route found!\n"); 692 else 693 printf(" - route loops back to ourself!\n"); 694#endif 695 return EADDRNOTAVAIL; 696 } 697 698 /* 699 * now change it back - else ip_output will just drop 700 * the route and search one to this interface ... 701 */ 702 if ((sc->sc_if.if_flags & IFF_LINK1) == 0) 703 ((struct sockaddr_in *)&ro->ro_dst)->sin_addr = sc->g_dst; 704 705#ifdef DIAGNOSTIC 706 printf(", choosing %s with gateway %s", if_name(ro->ro_rt->rt_ifp), 707 inet_ntoa(((struct sockaddr_in *)(ro->ro_rt->rt_gateway))->sin_addr)); 708 printf("\n"); 709#endif 710 711 return 0; 712} 713 714/* 715 * do a checksum of a buffer - much like in_cksum, which operates on 716 * mbufs. 717 */ 718u_short 719gre_in_cksum(u_short *p, u_int len) 720{ 721 u_int sum = 0; 722 int nwords = len >> 1; 723 724 while (nwords-- != 0) 725 sum += *p++; 726 727 if (len & 1) { 728 union { 729 u_short w; 730 u_char c[2]; 731 } u; 732 u.c[0] = *(u_char *)p; 733 u.c[1] = 0; 734 sum += u.w; 735 } 736 737 /* end-around-carry */ 738 sum = (sum >> 16) + (sum & 0xffff); 739 sum += (sum >> 16); 740 return (~sum); 741} 742 743static int 744gremodevent(module_t mod, int type, void *data) 745{ 746 747 switch (type) { 748 case MOD_LOAD: 749 greattach(); 750 break; 751 case MOD_UNLOAD: 752 if_clone_detach(&gre_cloner); 753 754 while (!LIST_EMPTY(&gre_softc_list)) 755 gre_clone_destroy(&LIST_FIRST(&gre_softc_list)->sc_if); 756 break; 757 } 758 return 0; 759} 760 761static moduledata_t gre_mod = { 762 "if_gre", 763 gremodevent, 764 0 765}; 766 767DECLARE_MODULE(if_gre, gre_mod, SI_SUB_PSEUDO, SI_ORDER_ANY); 768MODULE_VERSION(if_gre, 1); 769