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

   1 /*
   2     route.c -- routing
   3     Copyright (C) 2000-2005 Ivo Timmermans,
   4                   2000-2010 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 "avl_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 fmode_t forwarding_mode = FMODE_INTERNAL;
  37 bool decrement_ttl = true;
  38 bool directonly = false;
  39 bool priorityinheritance = false;
  40 int macexpire = 600;
  41 bool overwrite_mac = false;
  42 bool broadcast = true;
  43 mac_t mymac = {{0xFE, 0xFD, 0, 0, 0, 0}};
  44
  45 /* Sizes of various headers */
  46
  47 static const size_t ether_size = sizeof(struct ether_header);
  48 static const size_t arp_size = sizeof(struct ether_arp);
  49 static const size_t ip_size = sizeof(struct ip);
  50 static const size_t icmp_size = sizeof(struct icmp) - sizeof(struct ip);
  51 static const size_t ip6_size = sizeof(struct ip6_hdr);
  52 static const size_t icmp6_size = sizeof(struct icmp6_hdr);
  53 static const size_t ns_size = sizeof(struct nd_neighbor_solicit);
  54 static const size_t opt_size = sizeof(struct nd_opt_hdr);
  55
  56 #ifndef MAX
  57 #define MAX(a, b) ((a) > (b) ? (a) : (b))
  58 #endif
  59
  60 /* RFC 1071 */
  61
  62 static uint16_t inet_checksum(void *data, int len, uint16_t prevsum) {
  63         uint16_t *p = data;
  64         uint32_t checksum = prevsum ^ 0xFFFF;
  65
  66         while(len >= 2) {
  67                 checksum += *p++;
  68                 len -= 2;
  69         }
  70
  71         if(len)
  72                 checksum += *(uint8_t *)p;
  73
  74         while(checksum >> 16)
  75                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
  76
  77         return ~checksum;
  78 }
  79
  80 static bool ratelimit(int frequency) {
  81         static time_t lasttime = 0;
  82         static int count = 0;
  83
  84         if(lasttime == now) {
  85                 if(count >= frequency)
  86                         return true;
  87         } else {
  88                 lasttime = now;
  89                 count = 0;
  90         }
  91
  92         count++;
  93         return false;
  94 }
  95
  96 static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
  97         if(packet->len < length) {
  98                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got too short packet from %s (%s)", source->name, source->hostname);
  99                 return false;
 100         } else
 101                 return true;
 102 }
 103
 104 static void clamp_mss(const node_t *source, const node_t *via, vpn_packet_t *packet) {
 105         if(!source || !via || !(via->options & OPTION_CLAMP_MSS))
 106                 return;
 107
 108         uint16_t mtu = source->mtu;
 109         if(via != myself && via->mtu < mtu)
 110                 mtu = via->mtu;
 111
 112         /* Find TCP header */
 113         int start = 0;
 114         uint16_t type = packet->data[12] << 8 | packet->data[13];
 115
 116         if(type == ETH_P_IP && packet->data[23] == 6)
 117                 start = 14 + (packet->data[14] & 0xf) * 4;
 118         else if(type == ETH_P_IPV6 && packet->data[20] == 6)
 119                 start = 14 + 40;
 120
 121         if(!start || packet->len <= start + 20)
 122                 return;
 123
 124         /* Use data offset field to calculate length of options field */
 125         int len = ((packet->data[start + 12] >> 4) - 5) * 4;
 126
 127         if(packet->len < start + 20 + len)
 128                 return;
 129
 130         /* Search for MSS option header */
 131         for(int i = 0; i < len;) {
 132                 if(packet->data[start + 20 + i] == 0)
 133                         break;
 134
 135                 if(packet->data[start + 20 + i] == 1) {
 136                         i++;
 137                         continue;
 138                 }
 139
 140                 if(i > len - 2 || i > len - packet->data[start + 21 + i])
 141                         break;
 142
 143                 if(packet->data[start + 20 + i] != 2) {
 144                         if(packet->data[start + 21 + i] < 2)
 145                                 break;
 146                         i += packet->data[start + 21 + i];
 147                         continue;
 148                 }
 149
 150                 if(packet->data[start + 21] != 4)
 151                         break;
 152
 153                 /* Found it */
 154                 uint16_t oldmss = packet->data[start + 22 + i] << 8 | packet->data[start + 23 + i];
 155                 uint16_t newmss = mtu - start - 20;
 156                 uint16_t csum = packet->data[start + 16] << 8 | packet->data[start + 17];
 157
 158                 if(oldmss <= newmss)
 159                         break;
 160
 161                 ifdebug(TRAFFIC) logger(LOG_INFO, "Clamping MSS of packet from %s to %s to %d", source->name, via->name, newmss);
 162
 163                 /* Update the MSS value and the checksum */
 164                 packet->data[start + 22 + i] = newmss >> 8;
 165                 packet->data[start + 23 + i] = newmss & 0xff;
 166                 csum ^= 0xffff;
 167                 csum -= oldmss;
 168                 csum += newmss;
 169                 csum ^= 0xffff;
 170                 packet->data[start + 16] = csum >> 8;
 171                 packet->data[start + 17] = csum & 0xff;
 172                 break;
 173         }
 174 }
 175
 176 static void swap_mac_addresses(vpn_packet_t *packet) {
 177         mac_t tmp;
 178         memcpy(&tmp, &packet->data[0], sizeof tmp);
 179         memcpy(&packet->data[0], &packet->data[6], sizeof tmp);
 180         memcpy(&packet->data[6], &tmp, sizeof tmp);
 181 }
 182
 183 static void learn_mac(mac_t *address) {
 184         subnet_t *subnet;
 185         avl_node_t *node;
 186         connection_t *c;
 187
 188         subnet = lookup_subnet_mac(myself, address);
 189
 190         /* If we don't know this MAC address yet, store it */
 191
 192         if(!subnet) {
 193                 ifdebug(TRAFFIC) logger(LOG_INFO, "Learned new MAC address %hx:%hx:%hx:%hx:%hx:%hx",
 194                                    address->x[0], address->x[1], address->x[2], address->x[3],
 195                                    address->x[4], address->x[5]);
 196
 197                 subnet = new_subnet();
 198                 subnet->type = SUBNET_MAC;
 199                 subnet->expires = now + macexpire;
 200                 subnet->net.mac.address = *address;
 201                 subnet->weight = 10;
 202                 subnet_add(myself, subnet);
 203                 subnet_update(myself, subnet, true);
 204
 205                 /* And tell all other tinc daemons it's our MAC */
 206
 207                 for(node = connection_tree->head; node; node = node->next) {
 208                         c = node->data;
 209                         if(c->status.active)
 210                                 send_add_subnet(c, subnet);
 211                 }
 212         }
 213
 214         if(subnet->expires)
 215                 subnet->expires = now + macexpire;
 216 }
 217
 218 void age_subnets(void) {
 219         subnet_t *s;
 220         connection_t *c;
 221         avl_node_t *node, *next, *node2;
 222
 223         for(node = myself->subnet_tree->head; node; node = next) {
 224                 next = node->next;
 225                 s = node->data;
 226                 if(s->expires && s->expires <= now) {
 227                         ifdebug(TRAFFIC) {
 228                                 char netstr[MAXNETSTR];
 229                                 if(net2str(netstr, sizeof netstr, s))
 230                                         logger(LOG_INFO, "Subnet %s expired", netstr);
 231                         }
 232
 233                         for(node2 = connection_tree->head; node2; node2 = node2->next) {
 234                                 c = node2->data;
 235                                 if(c->status.active)
 236                                         send_del_subnet(c, s);
 237                         }
 238
 239                         subnet_update(myself, s, false);
 240                         subnet_del(myself, s);
 241                 }
 242         }
 243 }
 244
 245 /* RFC 792 */
 246
 247 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 248         struct ip ip = {0};
 249         struct icmp icmp = {0};
 250
 251         struct in_addr ip_src;
 252         struct in_addr ip_dst;
 253         uint32_t oldlen;
 254
 255         if(ratelimit(3))
 256                 return;
 257
 258         /* Swap Ethernet source and destination addresses */
 259
 260         swap_mac_addresses(packet);
 261
 262         /* Copy headers from packet into properly aligned structs on the stack */
 263
 264         memcpy(&ip, packet->data + ether_size, ip_size);
 265
 266         /* Remember original source and destination */
 267
 268         ip_src = ip.ip_src;
 269         ip_dst = ip.ip_dst;
 270
 271         oldlen = packet->len - ether_size;
 272
 273         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 274                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 275
 276         if(oldlen >= IP_MSS - ip_size - icmp_size)
 277                 oldlen = IP_MSS - ip_size - icmp_size;
 278
 279         /* Copy first part of original contents to ICMP message */
 280
 281         memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
 282
 283         /* Fill in IPv4 header */
 284
 285         ip.ip_v = 4;
 286         ip.ip_hl = ip_size / 4;
 287         ip.ip_tos = 0;
 288         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 289         ip.ip_id = 0;
 290         ip.ip_off = 0;
 291         ip.ip_ttl = 255;
 292         ip.ip_p = IPPROTO_ICMP;
 293         ip.ip_sum = 0;
 294         ip.ip_src = ip_dst;
 295         ip.ip_dst = ip_src;
 296
 297         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 298
 299         /* Fill in ICMP header */
 300
 301         icmp.icmp_type = type;
 302         icmp.icmp_code = code;
 303         icmp.icmp_cksum = 0;
 304
 305         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 306         icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 307
 308         /* Copy structs on stack back to packet */
 309
 310         memcpy(packet->data + ether_size, &ip, ip_size);
 311         memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
 312
 313         packet->len = ether_size + ip_size + icmp_size + oldlen;
 314
 315         send_packet(source, packet);
 316 }
 317
 318 /* RFC 791 */
 319
 320 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet) {
 321         struct ip ip;
 322         vpn_packet_t fragment;
 323         int len, maxlen, todo;
 324         uint8_t *offset;
 325         uint16_t ip_off, origf;
 326
 327         memcpy(&ip, packet->data + ether_size, ip_size);
 328         fragment.priority = packet->priority;
 329
 330         if(ip.ip_hl != ip_size / 4)
 331                 return;
 332
 333         todo = ntohs(ip.ip_len) - ip_size;
 334
 335         if(ether_size + ip_size + todo != packet->len) {
 336                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Length of packet (%d) doesn't match length in IPv4 header (%zd)", packet->len, ether_size + ip_size + todo);
 337                 return;
 338         }
 339
 340         ifdebug(TRAFFIC) logger(LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname);
 341
 342         offset = packet->data + ether_size + ip_size;
 343         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 344         ip_off = ntohs(ip.ip_off);
 345         origf = ip_off & ~IP_OFFMASK;
 346         ip_off &= IP_OFFMASK;
 347
 348         while(todo) {
 349                 len = todo > maxlen ? maxlen : todo;
 350                 memcpy(fragment.data + ether_size + ip_size, offset, len);
 351                 todo -= len;
 352                 offset += len;
 353
 354                 ip.ip_len = htons(ip_size + len);
 355                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 356                 ip.ip_sum = 0;
 357                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 358                 memcpy(fragment.data, packet->data, ether_size);
 359                 memcpy(fragment.data + ether_size, &ip, ip_size);
 360                 fragment.len = ether_size + ip_size + len;
 361
 362                 send_packet(dest, &fragment);
 363
 364                 ip_off += len / 8;
 365         }
 366 }
 367
 368 static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet) {
 369         subnet_t *subnet;
 370         node_t *via;
 371         ipv4_t dest;
 372
 373         memcpy(&dest, &packet->data[30], sizeof dest);
 374         subnet = lookup_subnet_ipv4(&dest);
 375
 376         if(!subnet) {
 377                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d",
 378                                 source->name, source->hostname,
 379                                 dest.x[0],
 380                                 dest.x[1],
 381                                 dest.x[2],
 382                                 dest.x[3]);
 383
 384                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 385                 return;
 386         }
 387
 388         if(subnet->owner == source) {
 389                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 390                 return;
 391         }
 392
 393         if(!subnet->owner->status.reachable)
 394                 return route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 395
 396         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 397                 return route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 398
 399         if(priorityinheritance)
 400                 packet->priority = packet->data[15];
 401
 402         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 403
 404         if(directonly && subnet->owner != via)
 405                 return route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 406
 407         if(via && packet->len > MAX(via->mtu, 590) && via != myself) {
 408                 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);
 409                 if(packet->data[20] & 0x40) {
 410                         packet->len = MAX(via->mtu, 590);
 411                         route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 412                 } else {
 413                         fragment_ipv4_packet(via, packet);
 414                 }
 415
 416                 return;
 417         }
 418
 419         clamp_mss(source, via, packet);
 420
 421         send_packet(subnet->owner, packet);
 422 }
 423
 424 static void route_ipv4(node_t *source, vpn_packet_t *packet) {
 425         if(!checklength(source, packet, ether_size + ip_size))
 426                 return;
 427
 428         if(broadcast && (((packet->data[30] & 0xf0) == 0xe0) || (
 429                         packet->data[30] == 255 &&
 430                         packet->data[31] == 255 &&
 431                         packet->data[32] == 255 &&
 432                         packet->data[33] == 255)))
 433                 broadcast_packet(source, packet);
 434         else
 435                 route_ipv4_unicast(source, packet);
 436 }
 437
 438 /* RFC 2463 */
 439
 440 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 441         struct ip6_hdr ip6;
 442         struct icmp6_hdr icmp6 = {0};
 443         uint16_t checksum;
 444
 445         struct {
 446                 struct in6_addr ip6_src;        /* source address */
 447                 struct in6_addr ip6_dst;        /* destination address */
 448                 uint32_t length;
 449                 uint32_t next;
 450         } pseudo;
 451
 452         if(ratelimit(3))
 453                 return;
 454
 455         /* Swap Ethernet source and destination addresses */
 456
 457         swap_mac_addresses(packet);
 458
 459         /* Copy headers from packet to structs on the stack */
 460
 461         memcpy(&ip6, packet->data + ether_size, ip6_size);
 462
 463         /* Remember original source and destination */
 464
 465         pseudo.ip6_src = ip6.ip6_dst;
 466         pseudo.ip6_dst = ip6.ip6_src;
 467
 468         pseudo.length = packet->len - ether_size;
 469
 470         if(type == ICMP6_PACKET_TOO_BIG)
 471                 icmp6.icmp6_mtu = htonl(pseudo.length);
 472
 473         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 474                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 475
 476         /* Copy first part of original contents to ICMP message */
 477
 478         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 479
 480         /* Fill in IPv6 header */
 481
 482         ip6.ip6_flow = htonl(0x60000000UL);
 483         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 484         ip6.ip6_nxt = IPPROTO_ICMPV6;
 485         ip6.ip6_hlim = 255;
 486         ip6.ip6_src = pseudo.ip6_src;
 487         ip6.ip6_dst = pseudo.ip6_dst;
 488
 489         /* Fill in ICMP header */
 490
 491         icmp6.icmp6_type = type;
 492         icmp6.icmp6_code = code;
 493         icmp6.icmp6_cksum = 0;
 494
 495         /* Create pseudo header */
 496
 497         pseudo.length = htonl(icmp6_size + pseudo.length);
 498         pseudo.next = htonl(IPPROTO_ICMPV6);
 499
 500         /* Generate checksum */
 501
 502         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 503         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 504         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 505
 506         icmp6.icmp6_cksum = checksum;
 507
 508         /* Copy structs on stack back to packet */
 509
 510         memcpy(packet->data + ether_size, &ip6, ip6_size);
 511         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 512
 513         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 514
 515         send_packet(source, packet);
 516 }
 517
 518 static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet) {
 519         subnet_t *subnet;
 520         node_t *via;
 521         ipv6_t dest;
 522
 523         memcpy(&dest, &packet->data[38], sizeof dest);
 524         subnet = lookup_subnet_ipv6(&dest);
 525
 526         if(!subnet) {
 527                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 528                                 source->name, source->hostname,
 529                                 ntohs(dest.x[0]),
 530                                 ntohs(dest.x[1]),
 531                                 ntohs(dest.x[2]),
 532                                 ntohs(dest.x[3]),
 533                                 ntohs(dest.x[4]),
 534                                 ntohs(dest.x[5]),
 535                                 ntohs(dest.x[6]),
 536                                 ntohs(dest.x[7]));
 537
 538                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 539                 return;
 540         }
 541
 542         if(subnet->owner == source) {
 543                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 544                 return;
 545         }
 546
 547         if(!subnet->owner->status.reachable)
 548                 return route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 549
 550         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 551                 return route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 552
 553         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 554
 555         if(directonly && subnet->owner != via)
 556                 return route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 557
 558         if(via && packet->len > MAX(via->mtu, 1294) && via != myself) {
 559                 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);
 560                 packet->len = MAX(via->mtu, 1294);
 561                 route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 562                 return;
 563         }
 564
 565         clamp_mss(source, via, packet);
 566
 567         send_packet(subnet->owner, packet);
 568 }
 569
 570 /* RFC 2461 */
 571
 572 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 573         struct ip6_hdr ip6;
 574         struct nd_neighbor_solicit ns;
 575         struct nd_opt_hdr opt;
 576         subnet_t *subnet;
 577         uint16_t checksum;
 578         bool has_opt;
 579
 580         struct {
 581                 struct in6_addr ip6_src;        /* source address */
 582                 struct in6_addr ip6_dst;        /* destination address */
 583                 uint32_t length;
 584                 uint32_t next;
 585         } pseudo;
 586
 587         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 588                 return;
 589
 590         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 591
 592         if(source != myself) {
 593                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname);
 594                 return;
 595         }
 596
 597         /* Copy headers from packet to structs on the stack */
 598
 599         memcpy(&ip6, packet->data + ether_size, ip6_size);
 600         memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
 601         if(has_opt)
 602                 memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 603
 604         /* First, snatch the source address from the neighbor solicitation packet */
 605
 606         if(overwrite_mac)
 607                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 608
 609         /* Check if this is a valid neighbor solicitation request */
 610
 611         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 612            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 613                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request");
 614                 return;
 615         }
 616
 617         /* Create pseudo header */
 618
 619         pseudo.ip6_src = ip6.ip6_src;
 620         pseudo.ip6_dst = ip6.ip6_dst;
 621         if(has_opt)
 622                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 623         else
 624                 pseudo.length = htonl(ns_size);
 625         pseudo.next = htonl(IPPROTO_ICMPV6);
 626
 627         /* Generate checksum */
 628
 629         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 630         checksum = inet_checksum(&ns, ns_size, checksum);
 631         if(has_opt) {
 632                 checksum = inet_checksum(&opt, opt_size, checksum);
 633                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 634         }
 635
 636         if(checksum) {
 637                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request");
 638                 return;
 639         }
 640
 641         /* Check if the IPv6 address exists on the VPN */
 642
 643         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 644
 645         if(!subnet) {
 646                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 647                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 648                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 649                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 650                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 651                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 652                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 653                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 654                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 655
 656                 return;
 657         }
 658
 659         /* Check if it is for our own subnet */
 660
 661         if(subnet->owner == myself)
 662                 return;                                 /* silently ignore */
 663
 664         /* Create neighbor advertation reply */
 665
 666         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 667         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 668
 669         ip6.ip6_dst = ip6.ip6_src;                      /* swap destination and source protocoll address */
 670         ip6.ip6_src = ns.nd_ns_target;
 671
 672         if(has_opt)
 673                 memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 674
 675         ns.nd_ns_cksum = 0;
 676         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 677         ns.nd_ns_reserved = htonl(0x40000000UL);        /* Set solicited flag */
 678         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 679
 680         /* Create pseudo header */
 681
 682         pseudo.ip6_src = ip6.ip6_src;
 683         pseudo.ip6_dst = ip6.ip6_dst;
 684         if(has_opt)
 685                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 686         else
 687                 pseudo.length = htonl(ns_size);
 688         pseudo.next = htonl(IPPROTO_ICMPV6);
 689
 690         /* Generate checksum */
 691
 692         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 693         checksum = inet_checksum(&ns, ns_size, checksum);
 694         if(has_opt) {
 695                 checksum = inet_checksum(&opt, opt_size, checksum);
 696                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 697         }
 698
 699         ns.nd_ns_hdr.icmp6_cksum = checksum;
 700
 701         /* Copy structs on stack back to packet */
 702
 703         memcpy(packet->data + ether_size, &ip6, ip6_size);
 704         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 705         if(has_opt)
 706                 memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 707
 708         send_packet(source, packet);
 709 }
 710
 711 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 712         if(!checklength(source, packet, ether_size + ip6_size))
 713                 return;
 714
 715         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 716                 route_neighborsol(source, packet);
 717                 return;
 718         }
 719
 720         if(broadcast && packet->data[38] == 255)
 721                 broadcast_packet(source, packet);
 722         else
 723                 route_ipv6_unicast(source, packet);
 724 }
 725
 726 /* RFC 826 */
 727
 728 static void route_arp(node_t *source, vpn_packet_t *packet) {
 729         struct ether_arp arp;
 730         subnet_t *subnet;
 731         struct in_addr addr;
 732
 733         if(!checklength(source, packet, ether_size + arp_size))
 734                 return;
 735
 736         if(source != myself) {
 737                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname);
 738                 return;
 739         }
 740
 741         /* First, snatch the source address from the ARP packet */
 742
 743         if(overwrite_mac)
 744                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 745
 746         /* Copy headers from packet to structs on the stack */
 747
 748         memcpy(&arp, packet->data + ether_size, arp_size);
 749
 750         /* Check if this is a valid ARP request */
 751
 752         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 753            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof(addr) || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 754                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type ARP request");
 755                 return;
 756         }
 757
 758         /* Check if the IPv4 address exists on the VPN */
 759
 760         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 761
 762         if(!subnet) {
 763                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d",
 764                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 765                                    arp.arp_tpa[3]);
 766                 return;
 767         }
 768
 769         /* Check if it is for our own subnet */
 770
 771         if(subnet->owner == myself)
 772                 return;                                 /* silently ignore */
 773
 774         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 775         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 776
 777         memcpy(&addr, arp.arp_tpa, sizeof(addr));       /* save protocol addr */
 778         memcpy(arp.arp_tpa, arp.arp_spa, sizeof(addr)); /* swap destination and source protocol address */
 779         memcpy(arp.arp_spa, &addr, sizeof(addr));       /* ... */
 780
 781         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);     /* set target hard/proto addr */
 782         memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN); /* add fake source hard addr */
 783         arp.arp_op = htons(ARPOP_REPLY);
 784
 785         /* Copy structs on stack back to packet */
 786
 787         memcpy(packet->data + ether_size, &arp, arp_size);
 788
 789         send_packet(source, packet);
 790 }
 791
 792 static void route_mac(node_t *source, vpn_packet_t *packet) {
 793         subnet_t *subnet;
 794         mac_t dest;
 795
 796         /* Learn source address */
 797
 798         if(source == myself) {
 799                 mac_t src;
 800                 memcpy(&src, &packet->data[6], sizeof src);
 801                 learn_mac(&src);
 802         }
 803
 804         /* Lookup destination address */
 805
 806         memcpy(&dest, &packet->data[0], sizeof dest);
 807         subnet = lookup_subnet_mac(NULL, &dest);
 808
 809         if(!subnet) {
 810                 if(broadcast)
 811                         broadcast_packet(source, packet);
 812                 return;
 813         }
 814
 815         if(subnet->owner == source) {
 816                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 817                 return;
 818         }
 819
 820         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 821                 return;
 822
 823         // Handle packets larger than PMTU
 824
 825         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 826
 827         if(directonly && subnet->owner != via)
 828                 return;
 829
 830         if(via && packet->len > via->mtu && via != myself) {
 831                 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);
 832                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 833                 if(type == ETH_P_IP && packet->len > 590) {
 834                         if(packet->data[20] & 0x40) {
 835                                 packet->len = via->mtu;
 836                                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 837                         } else {
 838                                 fragment_ipv4_packet(via, packet);
 839                         }
 840                         return;
 841                 } else if(type == ETH_P_IPV6 && packet->len > 1294) {
 842                         packet->len = via->mtu;
 843                         route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 844                         return;
 845                 }
 846         }
 847
 848         clamp_mss(source, via, packet);
 849
 850         send_packet(subnet->owner, packet);
 851 }
 852
 853 static bool do_decrement_ttl(node_t *source, vpn_packet_t *packet) {
 854         uint16_t type = packet->data[12] << 8 | packet->data[13];
 855
 856         switch (type) {
 857                 case ETH_P_IP:
 858                         if(!checklength(source, packet, 14 + 32))
 859                                 return false;
 860
 861                         if(packet->data[22] < 1) {
 862                                 if(packet->data[25] != IPPROTO_ICMP || packet->data[46] != ICMP_TIME_EXCEEDED)
 863                                         route_ipv4_unreachable(source, packet, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL);
 864                                 return false;
 865                         }
 866
 867                         uint16_t old = packet->data[22] << 8 | packet->data[23];
 868                         packet->data[22]--;
 869                         uint16_t new = packet->data[22] << 8 | packet->data[23];
 870
 871                         uint32_t checksum = packet->data[24] << 8 | packet->data[25];
 872                         checksum += old + (~new & 0xFFFF);
 873                         while(checksum >> 16)
 874                                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
 875                         packet->data[24] = checksum >> 8;
 876                         packet->data[25] = checksum & 0xff;
 877
 878                         return true;
 879
 880                 case ETH_P_IPV6:
 881                         if(!checklength(source, packet, 14 + 40))
 882                                 return false;
 883
 884                         if(packet->data[21] < 1) {
 885                                 if(packet->data[20] != IPPROTO_ICMPV6 || packet->data[54] != ICMP6_TIME_EXCEEDED)
 886                                         route_ipv6_unreachable(source, packet, ICMP6_TIME_EXCEEDED, ICMP6_TIME_EXCEED_TRANSIT);
 887                                 return false;
 888                         }
 889
 890                         packet->data[21]--;
 891
 892                         return true;
 893
 894                 default:
 895                         return true;
 896         }
 897 }
 898
 899 void route(node_t *source, vpn_packet_t *packet) {
 900         if(forwarding_mode == FMODE_KERNEL && source != myself) {
 901                 send_packet(myself, packet);
 902                 return;
 903         }
 904
 905         if(!checklength(source, packet, ether_size))
 906                 return;
 907
 908         if(decrement_ttl && source != myself)
 909                 if(!do_decrement_ttl(source, packet))
 910                         return;
 911
 912         switch (routing_mode) {
 913                 case RMODE_ROUTER:
 914                         {
 915                                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 916
 917                                 switch (type) {
 918                                         case ETH_P_ARP:
 919                                                 route_arp(source, packet);
 920                                                 break;
 921
 922                                         case ETH_P_IP:
 923                                                 route_ipv4(source, packet);
 924                                                 break;
 925
 926                                         case ETH_P_IPV6:
 927                                                 route_ipv6(source, packet);
 928                                                 break;
 929
 930                                         default:
 931                                                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type);
 932                                                 break;
 933                                 }
 934                         }
 935                         break;
 936
 937                 case RMODE_SWITCH:
 938                         route_mac(source, packet);
 939                         break;
 940
 941                 case RMODE_HUB:
 942                         broadcast_packet(source, packet);
 943                         break;
 944         }
 945 }