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

   1 /*
   2     route.c -- routing
   3     Copyright (C) 2000-2005 Ivo Timmermans,
   4                   2000-2006 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 static struct event age_subnets_event;
  55
  56 /* RFC 1071 */
  57
  58 static uint16_t inet_checksum(void *data, int len, uint16_t prevsum)
  59 {
  60         uint16_t *p = data;
  61         uint32_t checksum = prevsum ^ 0xFFFF;
  62
  63         while(len >= 2) {
  64                 checksum += *p++;
  65                 len -= 2;
  66         }
  67
  68         if(len)
  69                 checksum += *(uint8_t *)p;
  70
  71         while(checksum >> 16)
  72                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
  73
  74         return ~checksum;
  75 }
  76
  77 static bool ratelimit(int frequency) {
  78         static time_t lasttime = 0;
  79         static int count = 0;
  80         time_t now = time(NULL);
  81
  82         if(lasttime == now) {
  83                 if(++count > frequency)
  84                         return true;
  85         } else {
  86                 lasttime = now;
  87                 count = 0;
  88         }
  89
  90         return false;
  91 }
  92
  93 static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
  94         if(packet->len < length) {
  95                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Got too short packet from %s (%s)"), source->name, source->hostname);
  96                 return false;
  97         } else
  98                 return true;
  99 }
 100
 101 static void age_subnets(int fd, short events, void *data)
 102 {
 103         subnet_t *s;
 104         connection_t *c;
 105         avl_node_t *node, *next, *node2;
 106         bool left = false;
 107         time_t now = time(NULL);
 108
 109         cp();
 110
 111         for(node = myself->subnet_tree->head; node; node = next) {
 112                 next = node->next;
 113                 s = node->data;
 114                 if(s->expires && s->expires < now) {
 115                         ifdebug(TRAFFIC) {
 116                                 char netstr[MAXNETSTR];
 117                                 if(net2str(netstr, sizeof netstr, s))
 118                                         logger(LOG_INFO, _("Subnet %s expired"), netstr);
 119                         }
 120
 121                         for(node2 = connection_tree->head; node2; node2 = node2->next) {
 122                                 c = node2->data;
 123                                 if(c->status.active)
 124                                         send_del_subnet(c, s);
 125                         }
 126
 127                         subnet_del(myself, s);
 128                 } else {
 129                         if(s->expires)
 130                                 left = true;
 131                 }
 132         }
 133
 134         if(left)
 135                 event_add(&age_subnets_event, &(struct timeval){10, 0});
 136 }
 137
 138 static void learn_mac(mac_t *address)
 139 {
 140         subnet_t *subnet;
 141         avl_node_t *node;
 142         connection_t *c;
 143
 144         cp();
 145
 146         subnet = lookup_subnet_mac(address);
 147
 148         /* If we don't know this MAC address yet, store it */
 149
 150         if(!subnet) {
 151                 ifdebug(TRAFFIC) logger(LOG_INFO, _("Learned new MAC address %hx:%hx:%hx:%hx:%hx:%hx"),
 152                                    address->x[0], address->x[1], address->x[2], address->x[3],
 153                                    address->x[4], address->x[5]);
 154
 155                 subnet = new_subnet();
 156                 subnet->type = SUBNET_MAC;
 157                 subnet->expires = time(NULL) + macexpire;
 158                 subnet->net.mac.address = *address;
 159                 subnet_add(myself, subnet);
 160
 161                 /* And tell all other tinc daemons it's our MAC */
 162
 163                 for(node = connection_tree->head; node; node = node->next) {
 164                         c = node->data;
 165                         if(c->status.active)
 166                                 send_add_subnet(c, subnet);
 167                 }
 168
 169                 if(!timeout_initialized(&age_subnets_event))
 170                         timeout_set(&age_subnets_event, age_subnets, NULL);
 171                 event_add(&age_subnets_event, &(struct timeval){10, 0});
 172         } else {
 173                 if(subnet->expires)
 174                         subnet->expires = time(NULL) + macexpire;
 175         }
 176 }
 177
 178 static void route_mac(node_t *source, vpn_packet_t *packet)
 179 {
 180         subnet_t *subnet;
 181         mac_t dest;
 182
 183         cp();
 184
 185
 186         /* Learn source address */
 187
 188         if(source == myself) {
 189                 mac_t src;
 190                 memcpy(&src, &packet->data[6], sizeof src);
 191                 learn_mac(&src);
 192         }
 193
 194         /* Lookup destination address */
 195
 196         memcpy(&dest, &packet->data[0], sizeof dest);
 197         subnet = lookup_subnet_mac(&dest);
 198
 199         if(!subnet) {
 200                 broadcast_packet(source, packet);
 201                 return;
 202         }
 203
 204         if(subnet->owner == source) {
 205                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Packet looping back to %s (%s)!"), source->name, source->hostname);
 206                 return;
 207         }
 208
 209         send_packet(subnet->owner, packet);
 210 }
 211
 212 /* RFC 792 */
 213
 214 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code)
 215 {
 216         struct ip ip = {0};
 217         struct icmp icmp = {0};
 218
 219         struct in_addr ip_src;
 220         struct in_addr ip_dst;
 221         uint32_t oldlen;
 222
 223         if(ratelimit(3))
 224                 return;
 225
 226         cp();
 227
 228         /* Copy headers from packet into properly aligned structs on the stack */
 229
 230         memcpy(&ip, packet->data + ether_size, ip_size);
 231
 232         /* Remember original source and destination */
 233
 234         ip_src = ip.ip_src;
 235         ip_dst = ip.ip_dst;
 236
 237         oldlen = packet->len - ether_size;
 238
 239         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 240                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 241
 242         if(oldlen >= IP_MSS - ip_size - icmp_size)
 243                 oldlen = IP_MSS - ip_size - icmp_size;
 244
 245         /* Copy first part of original contents to ICMP message */
 246
 247         memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
 248
 249         /* Fill in IPv4 header */
 250
 251         ip.ip_v = 4;
 252         ip.ip_hl = ip_size / 4;
 253         ip.ip_tos = 0;
 254         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 255         ip.ip_id = 0;
 256         ip.ip_off = 0;
 257         ip.ip_ttl = 255;
 258         ip.ip_p = IPPROTO_ICMP;
 259         ip.ip_sum = 0;
 260         ip.ip_src = ip_dst;
 261         ip.ip_dst = ip_src;
 262
 263         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 264
 265         /* Fill in ICMP header */
 266
 267         icmp.icmp_type = type;
 268         icmp.icmp_code = code;
 269         icmp.icmp_cksum = 0;
 270
 271         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 272         icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 273
 274         /* Copy structs on stack back to packet */
 275
 276         memcpy(packet->data + ether_size, &ip, ip_size);
 277         memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
 278
 279         packet->len = ether_size + ip_size + icmp_size + oldlen;
 280
 281         send_packet(source, packet);
 282 }
 283
 284 /* RFC 791 */
 285
 286 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet) {
 287         struct ip ip;
 288         vpn_packet_t fragment;
 289         int len, maxlen, todo;
 290         uint8_t *offset;
 291         uint16_t ip_off, origf;
 292
 293         cp();
 294
 295         memcpy(&ip, packet->data + ether_size, ip_size);
 296         fragment.priority = packet->priority;
 297
 298         if(ip.ip_hl != ip_size / 4)
 299                 return;
 300
 301         todo = ntohs(ip.ip_len) - ip_size;
 302
 303         if(ether_size + ip_size + todo != packet->len) {
 304                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Length of packet (%d) doesn't match length in IPv4 header (%zd)"), packet->len, ether_size + ip_size + todo);
 305                 return;
 306         }
 307
 308         ifdebug(TRAFFIC) logger(LOG_INFO, _("Fragmenting packet of %d bytes to %s (%s)"), packet->len, dest->name, dest->hostname);
 309
 310         offset = packet->data + ether_size + ip_size;
 311         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 312         ip_off = ntohs(ip.ip_off);
 313         origf = ip_off & ~IP_OFFMASK;
 314         ip_off &= IP_OFFMASK;
 315
 316         while(todo) {
 317                 len = todo > maxlen ? maxlen : todo;
 318                 memcpy(fragment.data + ether_size + ip_size, offset, len);
 319                 todo -= len;
 320                 offset += len;
 321
 322                 ip.ip_len = htons(ip_size + len);
 323                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 324                 ip.ip_sum = 0;
 325                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 326                 memcpy(fragment.data, packet->data, ether_size);
 327                 memcpy(fragment.data + ether_size, &ip, ip_size);
 328                 fragment.len = ether_size + ip_size + len;
 329
 330                 send_packet(dest, &fragment);
 331
 332                 ip_off += len / 8;
 333         }
 334 }
 335
 336 static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet)
 337 {
 338         subnet_t *subnet;
 339         node_t *via;
 340         ipv4_t dest;
 341
 342         cp();
 343
 344         memcpy(&dest, &packet->data[30], sizeof dest);
 345         subnet = lookup_subnet_ipv4(&dest);
 346
 347         if(!subnet) {
 348                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d"),
 349                                 source->name, source->hostname,
 350                                 dest.x[0],
 351                                 dest.x[1],
 352                                 dest.x[2],
 353                                 dest.x[3]);
 354
 355                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 356                 return;
 357         }
 358
 359         if(subnet->owner == source) {
 360                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Packet looping back to %s (%s)!"), source->name, source->hostname);
 361                 return;
 362         }
 363
 364         if(!subnet->owner->status.reachable)
 365                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 366
 367         if(priorityinheritance)
 368                 packet->priority = packet->data[15];
 369
 370         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 371
 372         if(via && packet->len > via->mtu && via != myself) {
 373                 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);
 374                 if(packet->data[20] & 0x40) {
 375                         packet->len = via->mtu;
 376                         route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 377                 } else {
 378                         fragment_ipv4_packet(via, packet);
 379                 }
 380
 381                 return;
 382         }
 383
 384         send_packet(subnet->owner, packet);
 385 }
 386
 387 static void route_ipv4(node_t *source, vpn_packet_t *packet)
 388 {
 389         cp();
 390
 391         if(!checklength(source, packet, ether_size + ip_size))
 392                 return;
 393
 394         route_ipv4_unicast(source, packet);
 395 }
 396
 397 /* RFC 2463 */
 398
 399 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code)
 400 {
 401         struct ip6_hdr ip6;
 402         struct icmp6_hdr icmp6 = {0};
 403         uint16_t checksum;
 404
 405         struct {
 406                 struct in6_addr ip6_src;        /* source address */
 407                 struct in6_addr ip6_dst;        /* destination address */
 408                 uint32_t length;
 409                 uint32_t next;
 410         } pseudo;
 411
 412         if(ratelimit(3))
 413                 return;
 414
 415         cp();
 416
 417         /* Copy headers from packet to structs on the stack */
 418
 419         memcpy(&ip6, packet->data + ether_size, ip6_size);
 420
 421         /* Remember original source and destination */
 422
 423         pseudo.ip6_src = ip6.ip6_dst;
 424         pseudo.ip6_dst = ip6.ip6_src;
 425
 426         pseudo.length = packet->len - ether_size;
 427
 428         if(type == ICMP6_PACKET_TOO_BIG)
 429                 icmp6.icmp6_mtu = htonl(pseudo.length);
 430
 431         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 432                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 433
 434         /* Copy first part of original contents to ICMP message */
 435
 436         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 437
 438         /* Fill in IPv6 header */
 439
 440         ip6.ip6_flow = htonl(0x60000000UL);
 441         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 442         ip6.ip6_nxt = IPPROTO_ICMPV6;
 443         ip6.ip6_hlim = 255;
 444         ip6.ip6_src = pseudo.ip6_src;
 445         ip6.ip6_dst = pseudo.ip6_dst;
 446
 447         /* Fill in ICMP header */
 448
 449         icmp6.icmp6_type = type;
 450         icmp6.icmp6_code = code;
 451         icmp6.icmp6_cksum = 0;
 452
 453         /* Create pseudo header */
 454
 455         pseudo.length = htonl(icmp6_size + pseudo.length);
 456         pseudo.next = htonl(IPPROTO_ICMPV6);
 457
 458         /* Generate checksum */
 459
 460         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 461         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 462         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 463
 464         icmp6.icmp6_cksum = checksum;
 465
 466         /* Copy structs on stack back to packet */
 467
 468         memcpy(packet->data + ether_size, &ip6, ip6_size);
 469         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 470
 471         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 472
 473         send_packet(source, packet);
 474 }
 475
 476 static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet)
 477 {
 478         subnet_t *subnet;
 479         node_t *via;
 480         ipv6_t dest;
 481
 482         cp();
 483
 484         memcpy(&dest, &packet->data[38], sizeof dest);
 485         subnet = lookup_subnet_ipv6(&dest);
 486
 487         if(!subnet) {
 488                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx"),
 489                                 source->name, source->hostname,
 490                                 ntohs(dest.x[0]),
 491                                 ntohs(dest.x[1]),
 492                                 ntohs(dest.x[2]),
 493                                 ntohs(dest.x[3]),
 494                                 ntohs(dest.x[4]),
 495                                 ntohs(dest.x[5]),
 496                                 ntohs(dest.x[6]),
 497                                 ntohs(dest.x[7]));
 498
 499                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 500                 return;
 501         }
 502
 503         if(subnet->owner == source) {
 504                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Packet looping back to %s (%s)!"), source->name, source->hostname);
 505                 return;
 506         }
 507
 508         if(!subnet->owner->status.reachable)
 509                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 510
 511         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 512
 513         if(via && packet->len > via->mtu && via != myself) {
 514                 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);
 515                 packet->len = via->mtu;
 516                 route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 517                 return;
 518         }
 519
 520         send_packet(subnet->owner, packet);
 521 }
 522
 523 /* RFC 2461 */
 524
 525 static void route_neighborsol(node_t *source, vpn_packet_t *packet)
 526 {
 527         struct ip6_hdr ip6;
 528         struct nd_neighbor_solicit ns;
 529         struct nd_opt_hdr opt;
 530         subnet_t *subnet;
 531         uint16_t checksum;
 532
 533         struct {
 534                 struct in6_addr ip6_src;        /* source address */
 535                 struct in6_addr ip6_dst;        /* destination address */
 536                 uint32_t length;
 537                 uint32_t next;
 538         } pseudo;
 539
 540         cp();
 541
 542         if(!checklength(source, packet, ether_size + ip6_size + ns_size + opt_size + ETH_ALEN))
 543                 return;
 544
 545         if(source != myself) {
 546                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Got neighbor solicitation request from %s (%s) while in router mode!"), source->name, source->hostname);
 547                 return;
 548         }
 549
 550         /* Copy headers from packet to structs on the stack */
 551
 552         memcpy(&ip6, packet->data + ether_size, ip6_size);
 553         memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
 554         memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 555
 556         /* First, snatch the source address from the neighbor solicitation packet */
 557
 558         if(overwrite_mac)
 559                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 560
 561         /* Check if this is a valid neighbor solicitation request */
 562
 563         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 564            opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR) {
 565                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: received unknown type neighbor solicitation request"));
 566                 return;
 567         }
 568
 569         /* Create pseudo header */
 570
 571         pseudo.ip6_src = ip6.ip6_src;
 572         pseudo.ip6_dst = ip6.ip6_dst;
 573         pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 574         pseudo.next = htonl(IPPROTO_ICMPV6);
 575
 576         /* Generate checksum */
 577
 578         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 579         checksum = inet_checksum(&ns, ns_size, checksum);
 580         checksum = inet_checksum(&opt, opt_size, checksum);
 581         checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 582
 583         if(checksum) {
 584                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: checksum error for neighbor solicitation request"));
 585                 return;
 586         }
 587
 588         /* Check if the IPv6 address exists on the VPN */
 589
 590         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 591
 592         if(!subnet) {
 593                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx"),
 594                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 595                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 596                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 597                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 598                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 599                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 600                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 601                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 602
 603                 return;
 604         }
 605
 606         /* Check if it is for our own subnet */
 607
 608         if(subnet->owner == myself)
 609                 return;                                 /* silently ignore */
 610
 611         /* Create neighbor advertation reply */
 612
 613         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 614         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 615
 616         ip6.ip6_dst = ip6.ip6_src;                      /* swap destination and source protocoll address */
 617         ip6.ip6_src = ns.nd_ns_target;
 618
 619         memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 620
 621         ns.nd_ns_cksum = 0;
 622         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 623         ns.nd_ns_reserved = htonl(0x40000000UL);        /* Set solicited flag */
 624         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 625
 626         /* Create pseudo header */
 627
 628         pseudo.ip6_src = ip6.ip6_src;
 629         pseudo.ip6_dst = ip6.ip6_dst;
 630         pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 631         pseudo.next = htonl(IPPROTO_ICMPV6);
 632
 633         /* Generate checksum */
 634
 635         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 636         checksum = inet_checksum(&ns, ns_size, checksum);
 637         checksum = inet_checksum(&opt, opt_size, checksum);
 638         checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 639
 640         ns.nd_ns_hdr.icmp6_cksum = checksum;
 641
 642         /* Copy structs on stack back to packet */
 643
 644         memcpy(packet->data + ether_size, &ip6, ip6_size);
 645         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 646         memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 647
 648         send_packet(source, packet);
 649 }
 650
 651 static void route_ipv6(node_t *source, vpn_packet_t *packet)
 652 {
 653         cp();
 654
 655         if(!checklength(source, packet, ether_size + ip6_size))
 656                 return;
 657
 658         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 659                 route_neighborsol(source, packet);
 660                 return;
 661         }
 662
 663         route_ipv6_unicast(source, packet);
 664 }
 665
 666 /* RFC 826 */
 667
 668 static void route_arp(node_t *source, vpn_packet_t *packet)
 669 {
 670         struct ether_arp arp;
 671         subnet_t *subnet;
 672         struct in_addr addr;
 673
 674         cp();
 675
 676         if(!checklength(source, packet, ether_size + arp_size))
 677                 return;
 678
 679         if(source != myself) {
 680                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Got ARP request from %s (%s) while in router mode!"), source->name, source->hostname);
 681                 return;
 682         }
 683
 684         /* First, snatch the source address from the ARP packet */
 685
 686         if(overwrite_mac)
 687                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 688
 689         /* Copy headers from packet to structs on the stack */
 690
 691         memcpy(&arp, packet->data + ether_size, arp_size);
 692
 693         /* Check if this is a valid ARP request */
 694
 695         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 696            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof(addr) || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 697                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: received unknown type ARP request"));
 698                 return;
 699         }
 700
 701         /* Check if the IPv4 address exists on the VPN */
 702
 703         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 704
 705         if(!subnet) {
 706                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: ARP request for unknown address %d.%d.%d.%d"),
 707                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 708                                    arp.arp_tpa[3]);
 709                 return;
 710         }
 711
 712         /* Check if it is for our own subnet */
 713
 714         if(subnet->owner == myself)
 715                 return;                                 /* silently ignore */
 716
 717         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 718         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 719
 720         memcpy(&addr, arp.arp_tpa, sizeof(addr));       /* save protocol addr */
 721         memcpy(arp.arp_tpa, arp.arp_spa, sizeof(addr)); /* swap destination and source protocol address */
 722         memcpy(arp.arp_spa, &addr, sizeof(addr));       /* ... */
 723
 724         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);     /* set target hard/proto addr */
 725         memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN); /* add fake source hard addr */
 726         arp.arp_op = htons(ARPOP_REPLY);
 727
 728         /* Copy structs on stack back to packet */
 729
 730         memcpy(packet->data + ether_size, &arp, arp_size);
 731
 732         send_packet(source, packet);
 733 }
 734
 735 void route(node_t *source, vpn_packet_t *packet)
 736 {
 737         cp();
 738
 739         if(!checklength(source, packet, ether_size))
 740                 return;
 741
 742         switch (routing_mode) {
 743                 case RMODE_ROUTER:
 744                         {
 745                                 uint16_t type;
 746
 747                                 type = ntohs(*((uint16_t *)(&packet->data[12])));
 748                                 switch (type) {
 749                                         case ETH_P_ARP:
 750                                                 route_arp(source, packet);
 751                                                 break;
 752
 753                                         case ETH_P_IP:
 754                                                 route_ipv4(source, packet);
 755                                                 break;
 756
 757                                         case ETH_P_IPV6:
 758                                                 route_ipv6(source, packet);
 759                                                 break;
 760
 761                                         default:
 762                                                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet from %s (%s): unknown type %hx"), source->name, source->hostname, type);
 763                                                 break;
 764                                 }
 765                         }
 766                         break;
 767
 768                 case RMODE_SWITCH:
 769                         route_mac(source, packet);
 770                         break;
 771
 772                 case RMODE_HUB:
 773                         broadcast_packet(source, packet);
 774                         break;
 775         }
 776 }