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