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