tinc-vpn.org Git - tinc/blob - src/route.c

   1 /*
   2     route.c -- routing
   3     Copyright (C) 2000-2005 Ivo Timmermans,
   4                   2000-2009 Guus Sliepen <guus@tinc-vpn.org>
   5
   6     This program is free software; you can redistribute it and/or modify
   7     it under the terms of the GNU General Public License as published by
   8     the Free Software Foundation; either version 2 of the License, or
   9     (at your option) any later version.
  10
  11     This program is distributed in the hope that it will be useful,
  12     but WITHOUT ANY WARRANTY; without even the implied warranty of
  13     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14     GNU General Public License for more details.
  15
  16     You should have received a copy of the GNU General Public License
  17     along with this program; if not, write to the Free Software
  18     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19
  20     $Id$
  21 */
  22
  23 #include "system.h"
  24
  25 #include "avl_tree.h"
  26 #include "connection.h"
  27 #include "ethernet.h"
  28 #include "ipv4.h"
  29 #include "ipv6.h"
  30 #include "logger.h"
  31 #include "net.h"
  32 #include "protocol.h"
  33 #include "route.h"
  34 #include "subnet.h"
  35 #include "utils.h"
  36
  37 rmode_t routing_mode = RMODE_ROUTER;
  38 bool priorityinheritance = false;
  39 int macexpire = 600;
  40 bool overwrite_mac = false;
  41 mac_t mymac = {{0xFE, 0xFD, 0, 0, 0, 0}};
  42
  43 /* Sizes of various headers */
  44
  45 static const size_t ether_size = sizeof(struct ether_header);
  46 static const size_t arp_size = sizeof(struct ether_arp);
  47 static const size_t ip_size = sizeof(struct ip);
  48 static const size_t icmp_size = sizeof(struct icmp) - sizeof(struct ip);
  49 static const size_t ip6_size = sizeof(struct ip6_hdr);
  50 static const size_t icmp6_size = sizeof(struct icmp6_hdr);
  51 static const size_t ns_size = sizeof(struct nd_neighbor_solicit);
  52 static const size_t opt_size = sizeof(struct nd_opt_hdr);
  53
  54 /* RFC 1071 */
  55
  56 static uint16_t inet_checksum(void *data, int len, uint16_t prevsum)
  57 {
  58         uint16_t *p = data;
  59         uint32_t checksum = prevsum ^ 0xFFFF;
  60
  61         while(len >= 2) {
  62                 checksum += *p++;
  63                 len -= 2;
  64         }
  65
  66         if(len)
  67                 checksum += *(uint8_t *)p;
  68
  69         while(checksum >> 16)
  70                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
  71
  72         return ~checksum;
  73 }
  74
  75 static bool ratelimit(int frequency) {
  76         static time_t lasttime = 0;
  77         static int count = 0;
  78
  79         if(lasttime == now) {
  80                 if(++count > frequency)
  81                         return true;
  82         } else {
  83                 lasttime = now;
  84                 count = 0;
  85         }
  86
  87         return false;
  88 }
  89
  90 static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
  91         if(packet->len < length) {
  92                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Got too short packet from %s (%s)"), source->name, source->hostname);
  93                 return false;
  94         } else
  95                 return true;
  96 }
  97
  98 static void swap_mac_addresses(vpn_packet_t *packet) {
  99         mac_t tmp;
 100         memcpy(&tmp, &packet->data[0], sizeof tmp);
 101         memcpy(&packet->data[0], &packet->data[6], sizeof tmp);
 102         memcpy(&packet->data[6], &tmp, sizeof tmp);
 103 }
 104
 105 static void learn_mac(mac_t *address)
 106 {
 107         subnet_t *subnet;
 108         avl_node_t *node;
 109         connection_t *c;
 110
 111         cp();
 112
 113         subnet = lookup_subnet_mac(address);
 114
 115         /* If we don't know this MAC address yet, store it */
 116
 117         if(!subnet) {
 118                 ifdebug(TRAFFIC) logger(LOG_INFO, _("Learned new MAC address %hx:%hx:%hx:%hx:%hx:%hx"),
 119                                    address->x[0], address->x[1], address->x[2], address->x[3],
 120                                    address->x[4], address->x[5]);
 121
 122                 subnet = new_subnet();
 123                 subnet->type = SUBNET_MAC;
 124                 subnet->expires = now + macexpire;
 125                 subnet->net.mac.address = *address;
 126                 subnet_add(myself, subnet);
 127
 128                 /* And tell all other tinc daemons it's our MAC */
 129
 130                 for(node = connection_tree->head; node; node = node->next) {
 131                         c = node->data;
 132                         if(c->status.active)
 133                                 send_add_subnet(c, subnet);
 134                 }
 135         }
 136
 137         if(subnet->expires)
 138                 subnet->expires = now + macexpire;
 139 }
 140
 141 void age_subnets(void)
 142 {
 143         subnet_t *s;
 144         connection_t *c;
 145         avl_node_t *node, *next, *node2;
 146
 147         cp();
 148
 149         for(node = myself->subnet_tree->head; node; node = next) {
 150                 next = node->next;
 151                 s = node->data;
 152                 if(s->expires && s->expires < now) {
 153                         ifdebug(TRAFFIC) {
 154                                 char netstr[MAXNETSTR];
 155                                 if(net2str(netstr, sizeof netstr, s))
 156                                         logger(LOG_INFO, _("Subnet %s expired"), netstr);
 157                         }
 158
 159                         for(node2 = connection_tree->head; node2; node2 = node2->next) {
 160                                 c = node2->data;
 161                                 if(c->status.active)
 162                                         send_del_subnet(c, s);
 163                         }
 164
 165                         subnet_del(myself, s);
 166                 }
 167         }
 168 }
 169
 170 /* RFC 792 */
 171
 172 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code)
 173 {
 174         struct ip ip = {0};
 175         struct icmp icmp = {0};
 176
 177         struct in_addr ip_src;
 178         struct in_addr ip_dst;
 179         uint32_t oldlen;
 180
 181         if(ratelimit(3))
 182                 return;
 183
 184         cp();
 185
 186         /* Swap Ethernet source and destination addresses */
 187
 188         swap_mac_addresses(packet);
 189
 190         /* Copy headers from packet into properly aligned structs on the stack */
 191
 192         memcpy(&ip, packet->data + ether_size, ip_size);
 193
 194         /* Remember original source and destination */
 195
 196         ip_src = ip.ip_src;
 197         ip_dst = ip.ip_dst;
 198
 199         oldlen = packet->len - ether_size;
 200
 201         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 202                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 203
 204         if(oldlen >= IP_MSS - ip_size - icmp_size)
 205                 oldlen = IP_MSS - ip_size - icmp_size;
 206
 207         /* Copy first part of original contents to ICMP message */
 208
 209         memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
 210
 211         /* Fill in IPv4 header */
 212
 213         ip.ip_v = 4;
 214         ip.ip_hl = ip_size / 4;
 215         ip.ip_tos = 0;
 216         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 217         ip.ip_id = 0;
 218         ip.ip_off = 0;
 219         ip.ip_ttl = 255;
 220         ip.ip_p = IPPROTO_ICMP;
 221         ip.ip_sum = 0;
 222         ip.ip_src = ip_dst;
 223         ip.ip_dst = ip_src;
 224
 225         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 226
 227         /* Fill in ICMP header */
 228
 229         icmp.icmp_type = type;
 230         icmp.icmp_code = code;
 231         icmp.icmp_cksum = 0;
 232
 233         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 234         icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 235
 236         /* Copy structs on stack back to packet */
 237
 238         memcpy(packet->data + ether_size, &ip, ip_size);
 239         memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
 240
 241         packet->len = ether_size + ip_size + icmp_size + oldlen;
 242
 243         send_packet(source, packet);
 244 }
 245
 246 /* RFC 791 */
 247
 248 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet) {
 249         struct ip ip;
 250         vpn_packet_t fragment;
 251         int len, maxlen, todo;
 252         uint8_t *offset;
 253         uint16_t ip_off, origf;
 254
 255         cp();
 256
 257         memcpy(&ip, packet->data + ether_size, ip_size);
 258         fragment.priority = packet->priority;
 259
 260         if(ip.ip_hl != ip_size / 4)
 261                 return;
 262
 263         todo = ntohs(ip.ip_len) - ip_size;
 264
 265         if(ether_size + ip_size + todo != packet->len) {
 266                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Length of packet (%d) doesn't match length in IPv4 header (%zd)"), packet->len, ether_size + ip_size + todo);
 267                 return;
 268         }
 269
 270         ifdebug(TRAFFIC) logger(LOG_INFO, _("Fragmenting packet of %d bytes to %s (%s)"), packet->len, dest->name, dest->hostname);
 271
 272         offset = packet->data + ether_size + ip_size;
 273         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 274         ip_off = ntohs(ip.ip_off);
 275         origf = ip_off & ~IP_OFFMASK;
 276         ip_off &= IP_OFFMASK;
 277
 278         while(todo) {
 279                 len = todo > maxlen ? maxlen : todo;
 280                 memcpy(fragment.data + ether_size + ip_size, offset, len);
 281                 todo -= len;
 282                 offset += len;
 283
 284                 ip.ip_len = htons(ip_size + len);
 285                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 286                 ip.ip_sum = 0;
 287                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 288                 memcpy(fragment.data, packet->data, ether_size);
 289                 memcpy(fragment.data + ether_size, &ip, ip_size);
 290                 fragment.len = ether_size + ip_size + len;
 291
 292                 send_packet(dest, &fragment);
 293
 294                 ip_off += len / 8;
 295         }
 296 }
 297
 298 static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet)
 299 {
 300         subnet_t *subnet;
 301         node_t *via;
 302         ipv4_t dest;
 303
 304         cp();
 305
 306         memcpy(&dest, &packet->data[30], sizeof dest);
 307         subnet = lookup_subnet_ipv4(&dest);
 308
 309         if(!subnet) {
 310                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d"),
 311                                 source->name, source->hostname,
 312                                 dest.x[0],
 313                                 dest.x[1],
 314                                 dest.x[2],
 315                                 dest.x[3]);
 316
 317                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 318                 return;
 319         }
 320
 321         if(subnet->owner == source) {
 322                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Packet looping back to %s (%s)!"), source->name, source->hostname);
 323                 return;
 324         }
 325
 326         if(!subnet->owner->status.reachable)
 327                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 328
 329         if(priorityinheritance)
 330                 packet->priority = packet->data[15];
 331
 332         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 333
 334         if(via && packet->len > via->mtu && via != myself) {
 335                 ifdebug(TRAFFIC) logger(LOG_INFO, _("Packet for %s (%s) length %d larger than MTU %d"), subnet->owner->name, subnet->owner->hostname, packet->len, via->mtu);
 336                 if(packet->data[20] & 0x40) {
 337                         packet->len = via->mtu;
 338                         route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 339                 } else {
 340                         fragment_ipv4_packet(via, packet);
 341                 }
 342
 343                 return;
 344         }
 345
 346         send_packet(subnet->owner, packet);
 347 }
 348
 349 static void route_ipv4(node_t *source, vpn_packet_t *packet)
 350 {
 351         cp();
 352
 353         if(!checklength(source, packet, ether_size + ip_size))
 354                 return;
 355
 356         if(((packet->data[30] & 0xf0) == 0xe0) || (
 357                         packet->data[30] == 255 &&
 358                         packet->data[31] == 255 &&
 359                         packet->data[32] == 255 &&
 360                         packet->data[33] == 255))
 361                 broadcast_packet(source, packet);
 362         else
 363                 route_ipv4_unicast(source, packet);
 364 }
 365
 366 /* RFC 2463 */
 367
 368 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code)
 369 {
 370         struct ip6_hdr ip6;
 371         struct icmp6_hdr icmp6 = {0};
 372         uint16_t checksum;
 373
 374         struct {
 375                 struct in6_addr ip6_src;        /* source address */
 376                 struct in6_addr ip6_dst;        /* destination address */
 377                 uint32_t length;
 378                 uint32_t next;
 379         } pseudo;
 380
 381         if(ratelimit(3))
 382                 return;
 383
 384         cp();
 385
 386         /* Swap Ethernet source and destination addresses */
 387
 388         swap_mac_addresses(packet);
 389
 390         /* Copy headers from packet to structs on the stack */
 391
 392         memcpy(&ip6, packet->data + ether_size, ip6_size);
 393
 394         /* Remember original source and destination */
 395
 396         pseudo.ip6_src = ip6.ip6_dst;
 397         pseudo.ip6_dst = ip6.ip6_src;
 398
 399         pseudo.length = packet->len - ether_size;
 400
 401         if(type == ICMP6_PACKET_TOO_BIG)
 402                 icmp6.icmp6_mtu = htonl(pseudo.length);
 403
 404         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 405                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 406
 407         /* Copy first part of original contents to ICMP message */
 408
 409         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 410
 411         /* Fill in IPv6 header */
 412
 413         ip6.ip6_flow = htonl(0x60000000UL);
 414         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 415         ip6.ip6_nxt = IPPROTO_ICMPV6;
 416         ip6.ip6_hlim = 255;
 417         ip6.ip6_src = pseudo.ip6_src;
 418         ip6.ip6_dst = pseudo.ip6_dst;
 419
 420         /* Fill in ICMP header */
 421
 422         icmp6.icmp6_type = type;
 423         icmp6.icmp6_code = code;
 424         icmp6.icmp6_cksum = 0;
 425
 426         /* Create pseudo header */
 427
 428         pseudo.length = htonl(icmp6_size + pseudo.length);
 429         pseudo.next = htonl(IPPROTO_ICMPV6);
 430
 431         /* Generate checksum */
 432
 433         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 434         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 435         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 436
 437         icmp6.icmp6_cksum = checksum;
 438
 439         /* Copy structs on stack back to packet */
 440
 441         memcpy(packet->data + ether_size, &ip6, ip6_size);
 442         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 443
 444         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 445
 446         send_packet(source, packet);
 447 }
 448
 449 static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet)
 450 {
 451         subnet_t *subnet;
 452         node_t *via;
 453         ipv6_t dest;
 454
 455         cp();
 456
 457         memcpy(&dest, &packet->data[38], sizeof dest);
 458         subnet = lookup_subnet_ipv6(&dest);
 459
 460         if(!subnet) {
 461                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx"),
 462                                 source->name, source->hostname,
 463                                 ntohs(dest.x[0]),
 464                                 ntohs(dest.x[1]),
 465                                 ntohs(dest.x[2]),
 466                                 ntohs(dest.x[3]),
 467                                 ntohs(dest.x[4]),
 468                                 ntohs(dest.x[5]),
 469                                 ntohs(dest.x[6]),
 470                                 ntohs(dest.x[7]));
 471
 472                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 473                 return;
 474         }
 475
 476         if(subnet->owner == source) {
 477                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Packet looping back to %s (%s)!"), source->name, source->hostname);
 478                 return;
 479         }
 480
 481         if(!subnet->owner->status.reachable)
 482                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 483
 484         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 485
 486         if(via && packet->len > via->mtu && via != myself) {
 487                 ifdebug(TRAFFIC) logger(LOG_INFO, _("Packet for %s (%s) length %d larger than MTU %d"), subnet->owner->name, subnet->owner->hostname, packet->len, via->mtu);
 488                 packet->len = via->mtu;
 489                 route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 490                 return;
 491         }
 492
 493         send_packet(subnet->owner, packet);
 494 }
 495
 496 /* RFC 2461 */
 497
 498 static void route_neighborsol(node_t *source, vpn_packet_t *packet)
 499 {
 500         struct ip6_hdr ip6;
 501         struct nd_neighbor_solicit ns;
 502         struct nd_opt_hdr opt;
 503         subnet_t *subnet;
 504         uint16_t checksum;
 505         bool has_opt;
 506
 507         struct {
 508                 struct in6_addr ip6_src;        /* source address */
 509                 struct in6_addr ip6_dst;        /* destination address */
 510                 uint32_t length;
 511                 uint32_t next;
 512         } pseudo;
 513
 514         cp();
 515
 516         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 517                 return;
 518
 519         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 520
 521         if(source != myself) {
 522                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Got neighbor solicitation request from %s (%s) while in router mode!"), source->name, source->hostname);
 523                 return;
 524         }
 525
 526         /* Copy headers from packet to structs on the stack */
 527
 528         memcpy(&ip6, packet->data + ether_size, ip6_size);
 529         memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
 530         if(has_opt)
 531                 memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 532
 533         /* First, snatch the source address from the neighbor solicitation packet */
 534
 535         if(overwrite_mac)
 536                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 537
 538         /* Check if this is a valid neighbor solicitation request */
 539
 540         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 541            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 542                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: received unknown type neighbor solicitation request"));
 543                 return;
 544         }
 545
 546         /* Create pseudo header */
 547
 548         pseudo.ip6_src = ip6.ip6_src;
 549         pseudo.ip6_dst = ip6.ip6_dst;
 550         if(has_opt)
 551                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 552         else
 553                 pseudo.length = htonl(ns_size);
 554         pseudo.next = htonl(IPPROTO_ICMPV6);
 555
 556         /* Generate checksum */
 557
 558         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 559         checksum = inet_checksum(&ns, ns_size, checksum);
 560         if(has_opt) {
 561                 checksum = inet_checksum(&opt, opt_size, checksum);
 562                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 563         }
 564
 565         if(checksum) {
 566                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: checksum error for neighbor solicitation request"));
 567                 return;
 568         }
 569
 570         /* Check if the IPv6 address exists on the VPN */
 571
 572         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 573
 574         if(!subnet) {
 575                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx"),
 576                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 577                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 578                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 579                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 580                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 581                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 582                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 583                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 584
 585                 return;
 586         }
 587
 588         /* Check if it is for our own subnet */
 589
 590         if(subnet->owner == myself)
 591                 return;                                 /* silently ignore */
 592
 593         /* Create neighbor advertation reply */
 594
 595         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 596         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 597
 598         ip6.ip6_dst = ip6.ip6_src;                      /* swap destination and source protocoll address */
 599         ip6.ip6_src = ns.nd_ns_target;
 600
 601         if(has_opt)
 602                 memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 603
 604         ns.nd_ns_cksum = 0;
 605         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 606         ns.nd_ns_reserved = htonl(0x40000000UL);        /* Set solicited flag */
 607         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 608
 609         /* Create pseudo header */
 610
 611         pseudo.ip6_src = ip6.ip6_src;
 612         pseudo.ip6_dst = ip6.ip6_dst;
 613         if(has_opt)
 614                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 615         else
 616                 pseudo.length = htonl(ns_size);
 617         pseudo.next = htonl(IPPROTO_ICMPV6);
 618
 619         /* Generate checksum */
 620
 621         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 622         checksum = inet_checksum(&ns, ns_size, checksum);
 623         if(has_opt) {
 624                 checksum = inet_checksum(&opt, opt_size, checksum);
 625                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 626         }
 627
 628         ns.nd_ns_hdr.icmp6_cksum = checksum;
 629
 630         /* Copy structs on stack back to packet */
 631
 632         memcpy(packet->data + ether_size, &ip6, ip6_size);
 633         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 634         if(has_opt)
 635                 memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 636
 637         send_packet(source, packet);
 638 }
 639
 640 static void route_ipv6(node_t *source, vpn_packet_t *packet)
 641 {
 642         cp();
 643
 644         if(!checklength(source, packet, ether_size + ip6_size))
 645                 return;
 646
 647         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 648                 route_neighborsol(source, packet);
 649                 return;
 650         }
 651
 652         if(packet->data[38] == 255)
 653                 broadcast_packet(source, packet);
 654         else
 655                 route_ipv6_unicast(source, packet);
 656 }
 657
 658 /* RFC 826 */
 659
 660 static void route_arp(node_t *source, vpn_packet_t *packet)
 661 {
 662         struct ether_arp arp;
 663         subnet_t *subnet;
 664         struct in_addr addr;
 665
 666         cp();
 667
 668         if(!checklength(source, packet, ether_size + arp_size))
 669                 return;
 670
 671         if(source != myself) {
 672                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Got ARP request from %s (%s) while in router mode!"), source->name, source->hostname);
 673                 return;
 674         }
 675
 676         /* First, snatch the source address from the ARP packet */
 677
 678         if(overwrite_mac)
 679                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 680
 681         /* Copy headers from packet to structs on the stack */
 682
 683         memcpy(&arp, packet->data + ether_size, arp_size);
 684
 685         /* Check if this is a valid ARP request */
 686
 687         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 688            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof(addr) || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 689                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: received unknown type ARP request"));
 690                 return;
 691         }
 692
 693         /* Check if the IPv4 address exists on the VPN */
 694
 695         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 696
 697         if(!subnet) {
 698                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: ARP request for unknown address %d.%d.%d.%d"),
 699                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 700                                    arp.arp_tpa[3]);
 701                 return;
 702         }
 703
 704         /* Check if it is for our own subnet */
 705
 706         if(subnet->owner == myself)
 707                 return;                                 /* silently ignore */
 708
 709         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 710         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 711
 712         memcpy(&addr, arp.arp_tpa, sizeof(addr));       /* save protocol addr */
 713         memcpy(arp.arp_tpa, arp.arp_spa, sizeof(addr)); /* swap destination and source protocol address */
 714         memcpy(arp.arp_spa, &addr, sizeof(addr));       /* ... */
 715
 716         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);     /* set target hard/proto addr */
 717         memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN); /* add fake source hard addr */
 718         arp.arp_op = htons(ARPOP_REPLY);
 719
 720         /* Copy structs on stack back to packet */
 721
 722         memcpy(packet->data + ether_size, &arp, arp_size);
 723
 724         send_packet(source, packet);
 725 }
 726
 727 static void route_mac(node_t *source, vpn_packet_t *packet)
 728 {
 729         subnet_t *subnet;
 730         mac_t dest;
 731
 732         cp();
 733
 734
 735         /* Learn source address */
 736
 737         if(source == myself) {
 738                 mac_t src;
 739                 memcpy(&src, &packet->data[6], sizeof src);
 740                 learn_mac(&src);
 741         }
 742
 743         /* Lookup destination address */
 744
 745         memcpy(&dest, &packet->data[0], sizeof dest);
 746         subnet = lookup_subnet_mac(&dest);
 747
 748         if(!subnet) {
 749                 broadcast_packet(source, packet);
 750                 return;
 751         }
 752
 753         if(subnet->owner == source) {
 754                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Packet looping back to %s (%s)!"), source->name, source->hostname);
 755                 return;
 756         }
 757
 758         // Handle packets larger than PMTU
 759
 760         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 761
 762         if(via && packet->len > via->mtu && via != myself) {
 763                 ifdebug(TRAFFIC) logger(LOG_INFO, _("Packet for %s (%s) length %d larger than MTU %d"), subnet->owner->name, subnet->owner->hostname, packet->len, via->mtu);
 764                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 765                 if(type == ETH_P_IP) {
 766                         if(packet->data[20] & 0x40) {
 767                                 packet->len = via->mtu;
 768                                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 769                         } else {
 770                                 fragment_ipv4_packet(via, packet);
 771                         }
 772                 } else if(type == ETH_P_IPV6) {
 773                         packet->len = via->mtu;
 774                         route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 775                 } else
 776                         ifdebug(TRAFFIC) logger(LOG_INFO, _("Large packet of unhandled type %hx dropped"), type);
 777
 778                 return;
 779         }
 780
 781         send_packet(subnet->owner, packet);
 782 }
 783
 784
 785 void route(node_t *source, vpn_packet_t *packet)
 786 {
 787         cp();
 788
 789         if(!checklength(source, packet, ether_size))
 790                 return;
 791
 792         switch (routing_mode) {
 793                 case RMODE_ROUTER:
 794                         {
 795                                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 796
 797                                 switch (type) {
 798                                         case ETH_P_ARP:
 799                                                 route_arp(source, packet);
 800                                                 break;
 801
 802                                         case ETH_P_IP:
 803                                                 route_ipv4(source, packet);
 804                                                 break;
 805
 806                                         case ETH_P_IPV6:
 807                                                 route_ipv6(source, packet);
 808                                                 break;
 809
 810                                         default:
 811                                                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet from %s (%s): unknown type %hx"), source->name, source->hostname, type);
 812                                                 break;
 813                                 }
 814                         }
 815                         break;
 816
 817                 case RMODE_SWITCH:
 818                         route_mac(source, packet);
 819                         break;
 820
 821                 case RMODE_HUB:
 822                         broadcast_packet(source, packet);
 823                         break;
 824         }
 825 }