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 along
  17     with this program; if not, write to the Free Software Foundation, Inc.,
  18     51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  19 */
  20
  21 #include "system.h"
  22
  23 #include "splay_tree.h"
  24 #include "connection.h"
  25 #include "ethernet.h"
  26 #include "ipv4.h"
  27 #include "ipv6.h"
  28 #include "logger.h"
  29 #include "net.h"
  30 #include "protocol.h"
  31 #include "route.h"
  32 #include "subnet.h"
  33 #include "utils.h"
  34
  35 rmode_t routing_mode = RMODE_ROUTER;
  36 bool priorityinheritance = false;
  37 int macexpire = 600;
  38 bool overwrite_mac = false;
  39 mac_t mymac = {{0xFE, 0xFD, 0, 0, 0, 0}};
  40
  41 /* Sizes of various headers */
  42
  43 static const size_t ether_size = sizeof(struct ether_header);
  44 static const size_t arp_size = sizeof(struct ether_arp);
  45 static const size_t ip_size = sizeof(struct ip);
  46 static const size_t icmp_size = sizeof(struct icmp) - sizeof(struct ip);
  47 static const size_t ip6_size = sizeof(struct ip6_hdr);
  48 static const size_t icmp6_size = sizeof(struct icmp6_hdr);
  49 static const size_t ns_size = sizeof(struct nd_neighbor_solicit);
  50 static const size_t opt_size = sizeof(struct nd_opt_hdr);
  51
  52 static struct event age_subnets_event;
  53
  54 /* RFC 1071 */
  55
  56 static uint16_t inet_checksum(void *data, int len, uint16_t prevsum) {
  57         uint16_t *p = data;
  58         uint32_t checksum = prevsum ^ 0xFFFF;
  59
  60         while(len >= 2) {
  61                 checksum += *p++;
  62                 len -= 2;
  63         }
  64
  65         if(len)
  66                 checksum += *(uint8_t *)p;
  67
  68         while(checksum >> 16)
  69                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
  70
  71         return ~checksum;
  72 }
  73
  74 static bool ratelimit(int frequency) {
  75         static time_t lasttime = 0;
  76         static int count = 0;
  77         time_t now = time(NULL);
  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 age_subnets(int fd, short events, void *data) {
 106         subnet_t *s;
 107         connection_t *c;
 108         splay_node_t *node, *next, *node2;
 109         bool left = false;
 110         time_t now = time(NULL);
 111
 112         for(node = myself->subnet_tree->head; node; node = next) {
 113                 next = node->next;
 114                 s = node->data;
 115                 if(s->expires && s->expires < now) {
 116                         ifdebug(TRAFFIC) {
 117                                 char netstr[MAXNETSTR];
 118                                 if(net2str(netstr, sizeof netstr, s))
 119                                         logger(LOG_INFO, "Subnet %s expired", netstr);
 120                         }
 121
 122                         for(node2 = connection_tree->head; node2; node2 = node2->next) {
 123                                 c = node2->data;
 124                                 if(c->status.active)
 125                                         send_del_subnet(c, s);
 126                         }
 127
 128                         subnet_del(myself, s);
 129                 } else {
 130                         if(s->expires)
 131                                 left = true;
 132                 }
 133         }
 134
 135         if(left)
 136                 event_add(&age_subnets_event, &(struct timeval){10, 0});
 137 }
 138
 139 static void learn_mac(mac_t *address) {
 140         subnet_t *subnet;
 141         splay_node_t *node;
 142         connection_t *c;
 143
 144         subnet = lookup_subnet_mac(address);
 145
 146         /* If we don't know this MAC address yet, store it */
 147
 148         if(!subnet) {
 149                 ifdebug(TRAFFIC) logger(LOG_INFO, "Learned new MAC address %hx:%hx:%hx:%hx:%hx:%hx",
 150                                    address->x[0], address->x[1], address->x[2], address->x[3],
 151                                    address->x[4], address->x[5]);
 152
 153                 subnet = new_subnet();
 154                 subnet->type = SUBNET_MAC;
 155                 subnet->expires = time(NULL) + macexpire;
 156                 subnet->net.mac.address = *address;
 157                 subnet->weight = 10;
 158                 subnet_add(myself, subnet);
 159
 160                 /* And tell all other tinc daemons it's our MAC */
 161
 162                 for(node = connection_tree->head; node; node = node->next) {
 163                         c = node->data;
 164                         if(c->status.active)
 165                                 send_add_subnet(c, subnet);
 166                 }
 167
 168                 if(!timeout_initialized(&age_subnets_event))
 169                         timeout_set(&age_subnets_event, age_subnets, NULL);
 170                 event_add(&age_subnets_event, &(struct timeval){10, 0});
 171         } else {
 172                 if(subnet->expires)
 173                         subnet->expires = time(NULL) + macexpire;
 174         }
 175 }
 176
 177 /* RFC 792 */
 178
 179 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 180         struct ip ip = {0};
 181         struct icmp icmp = {0};
 182
 183         struct in_addr ip_src;
 184         struct in_addr ip_dst;
 185         uint32_t oldlen;
 186
 187         if(ratelimit(3))
 188                 return;
 189
 190         /* Swap Ethernet source and destination addresses */
 191
 192         swap_mac_addresses(packet);
 193
 194         /* Copy headers from packet into properly aligned structs on the stack */
 195
 196         memcpy(&ip, packet->data + ether_size, ip_size);
 197
 198         /* Remember original source and destination */
 199
 200         ip_src = ip.ip_src;
 201         ip_dst = ip.ip_dst;
 202
 203         oldlen = packet->len - ether_size;
 204
 205         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 206                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 207
 208         if(oldlen >= IP_MSS - ip_size - icmp_size)
 209                 oldlen = IP_MSS - ip_size - icmp_size;
 210
 211         /* Copy first part of original contents to ICMP message */
 212
 213         memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
 214
 215         /* Fill in IPv4 header */
 216
 217         ip.ip_v = 4;
 218         ip.ip_hl = ip_size / 4;
 219         ip.ip_tos = 0;
 220         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 221         ip.ip_id = 0;
 222         ip.ip_off = 0;
 223         ip.ip_ttl = 255;
 224         ip.ip_p = IPPROTO_ICMP;
 225         ip.ip_sum = 0;
 226         ip.ip_src = ip_dst;
 227         ip.ip_dst = ip_src;
 228
 229         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 230
 231         /* Fill in ICMP header */
 232
 233         icmp.icmp_type = type;
 234         icmp.icmp_code = code;
 235         icmp.icmp_cksum = 0;
 236
 237         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 238         icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 239
 240         /* Copy structs on stack back to packet */
 241
 242         memcpy(packet->data + ether_size, &ip, ip_size);
 243         memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
 244
 245         packet->len = ether_size + ip_size + icmp_size + oldlen;
 246
 247         send_packet(source, packet);
 248 }
 249
 250 /* RFC 791 */
 251
 252 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet) {
 253         struct ip ip;
 254         vpn_packet_t fragment;
 255         int len, maxlen, todo;
 256         uint8_t *offset;
 257         uint16_t ip_off, origf;
 258
 259         memcpy(&ip, packet->data + ether_size, ip_size);
 260         fragment.priority = packet->priority;
 261
 262         if(ip.ip_hl != ip_size / 4)
 263                 return;
 264
 265         todo = ntohs(ip.ip_len) - ip_size;
 266
 267         if(ether_size + ip_size + todo != packet->len) {
 268                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Length of packet (%d) doesn't match length in IPv4 header (%zd)", packet->len, ether_size + ip_size + todo);
 269                 return;
 270         }
 271
 272         ifdebug(TRAFFIC) logger(LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname);
 273
 274         offset = packet->data + ether_size + ip_size;
 275         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 276         ip_off = ntohs(ip.ip_off);
 277         origf = ip_off & ~IP_OFFMASK;
 278         ip_off &= IP_OFFMASK;
 279
 280         while(todo) {
 281                 len = todo > maxlen ? maxlen : todo;
 282                 memcpy(fragment.data + ether_size + ip_size, offset, len);
 283                 todo -= len;
 284                 offset += len;
 285
 286                 ip.ip_len = htons(ip_size + len);
 287                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 288                 ip.ip_sum = 0;
 289                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 290                 memcpy(fragment.data, packet->data, ether_size);
 291                 memcpy(fragment.data + ether_size, &ip, ip_size);
 292                 fragment.len = ether_size + ip_size + len;
 293
 294                 send_packet(dest, &fragment);
 295
 296                 ip_off += len / 8;
 297         }
 298 }
 299
 300 static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet) {
 301         subnet_t *subnet;
 302         node_t *via;
 303         ipv4_t dest;
 304
 305         memcpy(&dest, &packet->data[30], sizeof dest);
 306         subnet = lookup_subnet_ipv4(&dest);
 307
 308         if(!subnet) {
 309                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d",
 310                                 source->name, source->hostname,
 311                                 dest.x[0],
 312                                 dest.x[1],
 313                                 dest.x[2],
 314                                 dest.x[3]);
 315
 316                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 317                 return;
 318         }
 319
 320         if(subnet->owner == source) {
 321                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 322                 return;
 323         }
 324
 325         if(!subnet->owner->status.reachable)
 326                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 327
 328         if(priorityinheritance)
 329                 packet->priority = packet->data[15];
 330
 331         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 332
 333         if(via && packet->len > via->mtu && via != myself) {
 334                 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);
 335                 if(packet->data[20] & 0x40) {
 336                         packet->len = via->mtu;
 337                         route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 338                 } else {
 339                         fragment_ipv4_packet(via, packet);
 340                 }
 341
 342                 return;
 343         }
 344
 345         send_packet(subnet->owner, packet);
 346 }
 347
 348 static void route_ipv4(node_t *source, vpn_packet_t *packet) {
 349         if(!checklength(source, packet, ether_size + ip_size))
 350                 return;
 351
 352         if(((packet->data[30] & 0xf0) == 0xe0) || (
 353                         packet->data[30] == 255 &&
 354                         packet->data[31] == 255 &&
 355                         packet->data[32] == 255 &&
 356                         packet->data[33] == 255))
 357                 broadcast_packet(source, packet);
 358         else
 359                 route_ipv4_unicast(source, packet);
 360 }
 361
 362 /* RFC 2463 */
 363
 364 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 365         struct ip6_hdr ip6;
 366         struct icmp6_hdr icmp6 = {0};
 367         uint16_t checksum;
 368
 369         struct {
 370                 struct in6_addr ip6_src;        /* source address */
 371                 struct in6_addr ip6_dst;        /* destination address */
 372                 uint32_t length;
 373                 uint32_t next;
 374         } pseudo;
 375
 376         if(ratelimit(3))
 377                 return;
 378
 379         /* Swap Ethernet source and destination addresses */
 380
 381         swap_mac_addresses(packet);
 382
 383         /* Copy headers from packet to structs on the stack */
 384
 385         memcpy(&ip6, packet->data + ether_size, ip6_size);
 386
 387         /* Remember original source and destination */
 388
 389         pseudo.ip6_src = ip6.ip6_dst;
 390         pseudo.ip6_dst = ip6.ip6_src;
 391
 392         pseudo.length = packet->len - ether_size;
 393
 394         if(type == ICMP6_PACKET_TOO_BIG)
 395                 icmp6.icmp6_mtu = htonl(pseudo.length);
 396
 397         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 398                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 399
 400         /* Copy first part of original contents to ICMP message */
 401
 402         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 403
 404         /* Fill in IPv6 header */
 405
 406         ip6.ip6_flow = htonl(0x60000000UL);
 407         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 408         ip6.ip6_nxt = IPPROTO_ICMPV6;
 409         ip6.ip6_hlim = 255;
 410         ip6.ip6_src = pseudo.ip6_src;
 411         ip6.ip6_dst = pseudo.ip6_dst;
 412
 413         /* Fill in ICMP header */
 414
 415         icmp6.icmp6_type = type;
 416         icmp6.icmp6_code = code;
 417         icmp6.icmp6_cksum = 0;
 418
 419         /* Create pseudo header */
 420
 421         pseudo.length = htonl(icmp6_size + pseudo.length);
 422         pseudo.next = htonl(IPPROTO_ICMPV6);
 423
 424         /* Generate checksum */
 425
 426         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 427         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 428         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 429
 430         icmp6.icmp6_cksum = checksum;
 431
 432         /* Copy structs on stack back to packet */
 433
 434         memcpy(packet->data + ether_size, &ip6, ip6_size);
 435         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 436
 437         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 438
 439         send_packet(source, packet);
 440 }
 441
 442 static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet) {
 443         subnet_t *subnet;
 444         node_t *via;
 445         ipv6_t dest;
 446
 447         memcpy(&dest, &packet->data[38], sizeof dest);
 448         subnet = lookup_subnet_ipv6(&dest);
 449
 450         if(!subnet) {
 451                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 452                                 source->name, source->hostname,
 453                                 ntohs(dest.x[0]),
 454                                 ntohs(dest.x[1]),
 455                                 ntohs(dest.x[2]),
 456                                 ntohs(dest.x[3]),
 457                                 ntohs(dest.x[4]),
 458                                 ntohs(dest.x[5]),
 459                                 ntohs(dest.x[6]),
 460                                 ntohs(dest.x[7]));
 461
 462                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 463                 return;
 464         }
 465
 466         if(subnet->owner == source) {
 467                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 468                 return;
 469         }
 470
 471         if(!subnet->owner->status.reachable)
 472                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 473
 474         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 475
 476         if(via && packet->len > via->mtu && via != myself) {
 477                 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);
 478                 packet->len = via->mtu;
 479                 route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 480                 return;
 481         }
 482
 483         send_packet(subnet->owner, packet);
 484 }
 485
 486 /* RFC 2461 */
 487
 488 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 489         struct ip6_hdr ip6;
 490         struct nd_neighbor_solicit ns;
 491         struct nd_opt_hdr opt;
 492         subnet_t *subnet;
 493         uint16_t checksum;
 494         bool has_opt;
 495
 496         struct {
 497                 struct in6_addr ip6_src;        /* source address */
 498                 struct in6_addr ip6_dst;        /* destination address */
 499                 uint32_t length;
 500                 uint32_t next;
 501         } pseudo;
 502
 503         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 504                 return;
 505
 506         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 507
 508         if(source != myself) {
 509                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname);
 510                 return;
 511         }
 512
 513         /* Copy headers from packet to structs on the stack */
 514
 515         memcpy(&ip6, packet->data + ether_size, ip6_size);
 516         memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
 517         if(has_opt)
 518                 memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 519
 520         /* First, snatch the source address from the neighbor solicitation packet */
 521
 522         if(overwrite_mac)
 523                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 524
 525         /* Check if this is a valid neighbor solicitation request */
 526
 527         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 528            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 529                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request");
 530                 return;
 531         }
 532
 533         /* Create pseudo header */
 534
 535         pseudo.ip6_src = ip6.ip6_src;
 536         pseudo.ip6_dst = ip6.ip6_dst;
 537         if(has_opt)
 538                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 539         else
 540                 pseudo.length = htonl(ns_size);
 541         pseudo.next = htonl(IPPROTO_ICMPV6);
 542
 543         /* Generate checksum */
 544
 545         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 546         checksum = inet_checksum(&ns, ns_size, checksum);
 547         if(has_opt) {
 548                 checksum = inet_checksum(&opt, opt_size, checksum);
 549                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 550         }
 551
 552         if(checksum) {
 553                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request");
 554                 return;
 555         }
 556
 557         /* Check if the IPv6 address exists on the VPN */
 558
 559         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 560
 561         if(!subnet) {
 562                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 563                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 564                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 565                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 566                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 567                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 568                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 569                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 570                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 571
 572                 return;
 573         }
 574
 575         /* Check if it is for our own subnet */
 576
 577         if(subnet->owner == myself)
 578                 return;                                 /* silently ignore */
 579
 580         /* Create neighbor advertation reply */
 581
 582         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 583         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 584
 585         ip6.ip6_dst = ip6.ip6_src;                      /* swap destination and source protocoll address */
 586         ip6.ip6_src = ns.nd_ns_target;
 587
 588         if(has_opt)
 589                 memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 590
 591         ns.nd_ns_cksum = 0;
 592         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 593         ns.nd_ns_reserved = htonl(0x40000000UL);        /* Set solicited flag */
 594         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 595
 596         /* Create pseudo header */
 597
 598         pseudo.ip6_src = ip6.ip6_src;
 599         pseudo.ip6_dst = ip6.ip6_dst;
 600         if(has_opt)
 601                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 602         else
 603                 pseudo.length = htonl(ns_size);
 604         pseudo.next = htonl(IPPROTO_ICMPV6);
 605
 606         /* Generate checksum */
 607
 608         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 609         checksum = inet_checksum(&ns, ns_size, checksum);
 610         if(has_opt) {
 611                 checksum = inet_checksum(&opt, opt_size, checksum);
 612                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 613         }
 614
 615         ns.nd_ns_hdr.icmp6_cksum = checksum;
 616
 617         /* Copy structs on stack back to packet */
 618
 619         memcpy(packet->data + ether_size, &ip6, ip6_size);
 620         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 621         if(has_opt)
 622                 memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 623
 624         send_packet(source, packet);
 625 }
 626
 627 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 628         if(!checklength(source, packet, ether_size + ip6_size))
 629                 return;
 630
 631         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 632                 route_neighborsol(source, packet);
 633                 return;
 634         }
 635
 636         if(packet->data[38] == 255)
 637                 broadcast_packet(source, packet);
 638         else
 639                 route_ipv6_unicast(source, packet);
 640 }
 641
 642 /* RFC 826 */
 643
 644 static void route_arp(node_t *source, vpn_packet_t *packet) {
 645         struct ether_arp arp;
 646         subnet_t *subnet;
 647         struct in_addr addr;
 648
 649         if(!checklength(source, packet, ether_size + arp_size))
 650                 return;
 651
 652         if(source != myself) {
 653                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname);
 654                 return;
 655         }
 656
 657         /* First, snatch the source address from the ARP packet */
 658
 659         if(overwrite_mac)
 660                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 661
 662         /* Copy headers from packet to structs on the stack */
 663
 664         memcpy(&arp, packet->data + ether_size, arp_size);
 665
 666         /* Check if this is a valid ARP request */
 667
 668         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 669            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof addr || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 670                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type ARP request");
 671                 return;
 672         }
 673
 674         /* Check if the IPv4 address exists on the VPN */
 675
 676         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 677
 678         if(!subnet) {
 679                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d",
 680                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 681                                    arp.arp_tpa[3]);
 682                 return;
 683         }
 684
 685         /* Check if it is for our own subnet */
 686
 687         if(subnet->owner == myself)
 688                 return;                                 /* silently ignore */
 689
 690         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 691         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 692
 693         memcpy(&addr, arp.arp_tpa, sizeof addr);        /* save protocol addr */
 694         memcpy(arp.arp_tpa, arp.arp_spa, sizeof addr);  /* swap destination and source protocol address */
 695         memcpy(arp.arp_spa, &addr, sizeof addr);        /* ... */
 696
 697         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);     /* set target hard/proto addr */
 698         memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN); /* add fake source hard addr */
 699         arp.arp_op = htons(ARPOP_REPLY);
 700
 701         /* Copy structs on stack back to packet */
 702
 703         memcpy(packet->data + ether_size, &arp, arp_size);
 704
 705         send_packet(source, packet);
 706 }
 707
 708 static void route_mac(node_t *source, vpn_packet_t *packet) {
 709         subnet_t *subnet;
 710         mac_t dest;
 711
 712         /* Learn source address */
 713
 714         if(source == myself) {
 715                 mac_t src;
 716                 memcpy(&src, &packet->data[6], sizeof src);
 717                 learn_mac(&src);
 718         }
 719
 720         /* Lookup destination address */
 721
 722         memcpy(&dest, &packet->data[0], sizeof dest);
 723         subnet = lookup_subnet_mac(&dest);
 724
 725         if(!subnet) {
 726                 broadcast_packet(source, packet);
 727                 return;
 728         }
 729
 730         if(subnet->owner == source) {
 731                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 732                 return;
 733         }
 734
 735         // Handle packets larger than PMTU
 736
 737         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 738
 739         if(via && packet->len > via->mtu && via != myself) {
 740                 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);
 741                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 742                 if(type == ETH_P_IP) {
 743                         if(packet->data[20] & 0x40) {
 744                                 packet->len = via->mtu;
 745                                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 746                         } else {
 747                                 fragment_ipv4_packet(via, packet);
 748                         }
 749                         return;
 750                 } else if(type == ETH_P_IPV6) {
 751                         packet->len = via->mtu;
 752                         route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 753                         return;
 754                 }
 755         }
 756
 757         send_packet(subnet->owner, packet);
 758 }
 759
 760 void route(node_t *source, vpn_packet_t *packet) {
 761         if(!checklength(source, packet, ether_size))
 762                 return;
 763
 764         switch (routing_mode) {
 765                 case RMODE_ROUTER:
 766                         {
 767                                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 768
 769                                 switch (type) {
 770                                         case ETH_P_ARP:
 771                                                 route_arp(source, packet);
 772                                                 break;
 773
 774                                         case ETH_P_IP:
 775                                                 route_ipv4(source, packet);
 776                                                 break;
 777
 778                                         case ETH_P_IPV6:
 779                                                 route_ipv6(source, packet);
 780                                                 break;
 781
 782                                         default:
 783                                                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type);
 784                                                 break;
 785                                 }
 786                         }
 787                         break;
 788
 789                 case RMODE_SWITCH:
 790                         route_mac(source, packet);
 791                         break;
 792
 793                 case RMODE_HUB:
 794                         broadcast_packet(source, packet);
 795                         break;
 796         }
 797 }