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(via == source) {
 405                 ifdebug(TRAFFIC) logger(LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 406                 return;
 407         }
 408
 409         if(directonly && subnet->owner != via)
 410                 return route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 411
 412         if(via && packet->len > MAX(via->mtu, 590) && via != myself) {
 413                 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);
 414                 if(packet->data[20] & 0x40) {
 415                         packet->len = MAX(via->mtu, 590);
 416                         route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 417                 } else {
 418                         fragment_ipv4_packet(via, packet);
 419                 }
 420
 421                 return;
 422         }
 423
 424         clamp_mss(source, via, packet);
 425
 426         send_packet(subnet->owner, packet);
 427 }
 428
 429 static void route_ipv4(node_t *source, vpn_packet_t *packet) {
 430         if(!checklength(source, packet, ether_size + ip_size))
 431                 return;
 432
 433         if(broadcast && (((packet->data[30] & 0xf0) == 0xe0) || (
 434                         packet->data[30] == 255 &&
 435                         packet->data[31] == 255 &&
 436                         packet->data[32] == 255 &&
 437                         packet->data[33] == 255)))
 438                 broadcast_packet(source, packet);
 439         else
 440                 route_ipv4_unicast(source, packet);
 441 }
 442
 443 /* RFC 2463 */
 444
 445 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 446         struct ip6_hdr ip6;
 447         struct icmp6_hdr icmp6 = {0};
 448         uint16_t checksum;
 449
 450         struct {
 451                 struct in6_addr ip6_src;        /* source address */
 452                 struct in6_addr ip6_dst;        /* destination address */
 453                 uint32_t length;
 454                 uint32_t next;
 455         } pseudo;
 456
 457         if(ratelimit(3))
 458                 return;
 459
 460         /* Swap Ethernet source and destination addresses */
 461
 462         swap_mac_addresses(packet);
 463
 464         /* Copy headers from packet to structs on the stack */
 465
 466         memcpy(&ip6, packet->data + ether_size, ip6_size);
 467
 468         /* Remember original source and destination */
 469
 470         pseudo.ip6_src = ip6.ip6_dst;
 471         pseudo.ip6_dst = ip6.ip6_src;
 472
 473         pseudo.length = packet->len - ether_size;
 474
 475         if(type == ICMP6_PACKET_TOO_BIG)
 476                 icmp6.icmp6_mtu = htonl(pseudo.length);
 477
 478         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 479                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 480
 481         /* Copy first part of original contents to ICMP message */
 482
 483         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 484
 485         /* Fill in IPv6 header */
 486
 487         ip6.ip6_flow = htonl(0x60000000UL);
 488         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 489         ip6.ip6_nxt = IPPROTO_ICMPV6;
 490         ip6.ip6_hlim = 255;
 491         ip6.ip6_src = pseudo.ip6_src;
 492         ip6.ip6_dst = pseudo.ip6_dst;
 493
 494         /* Fill in ICMP header */
 495
 496         icmp6.icmp6_type = type;
 497         icmp6.icmp6_code = code;
 498         icmp6.icmp6_cksum = 0;
 499
 500         /* Create pseudo header */
 501
 502         pseudo.length = htonl(icmp6_size + pseudo.length);
 503         pseudo.next = htonl(IPPROTO_ICMPV6);
 504
 505         /* Generate checksum */
 506
 507         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 508         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 509         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 510
 511         icmp6.icmp6_cksum = checksum;
 512
 513         /* Copy structs on stack back to packet */
 514
 515         memcpy(packet->data + ether_size, &ip6, ip6_size);
 516         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 517
 518         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 519
 520         send_packet(source, packet);
 521 }
 522
 523 static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet) {
 524         subnet_t *subnet;
 525         node_t *via;
 526         ipv6_t dest;
 527
 528         memcpy(&dest, &packet->data[38], sizeof dest);
 529         subnet = lookup_subnet_ipv6(&dest);
 530
 531         if(!subnet) {
 532                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 533                                 source->name, source->hostname,
 534                                 ntohs(dest.x[0]),
 535                                 ntohs(dest.x[1]),
 536                                 ntohs(dest.x[2]),
 537                                 ntohs(dest.x[3]),
 538                                 ntohs(dest.x[4]),
 539                                 ntohs(dest.x[5]),
 540                                 ntohs(dest.x[6]),
 541                                 ntohs(dest.x[7]));
 542
 543                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 544                 return;
 545         }
 546
 547         if(subnet->owner == source) {
 548                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 549                 return;
 550         }
 551
 552         if(!subnet->owner->status.reachable)
 553                 return route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 554
 555         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 556                 return route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 557
 558         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 559
 560         if(via == source) {
 561                 ifdebug(TRAFFIC) logger(LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 562                 return;
 563         }
 564
 565         if(directonly && subnet->owner != via)
 566                 return route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 567
 568         if(via && packet->len > MAX(via->mtu, 1294) && via != myself) {
 569                 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);
 570                 packet->len = MAX(via->mtu, 1294);
 571                 route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 572                 return;
 573         }
 574
 575         clamp_mss(source, via, packet);
 576
 577         send_packet(subnet->owner, packet);
 578 }
 579
 580 /* RFC 2461 */
 581
 582 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 583         struct ip6_hdr ip6;
 584         struct nd_neighbor_solicit ns;
 585         struct nd_opt_hdr opt;
 586         subnet_t *subnet;
 587         uint16_t checksum;
 588         bool has_opt;
 589
 590         struct {
 591                 struct in6_addr ip6_src;        /* source address */
 592                 struct in6_addr ip6_dst;        /* destination address */
 593                 uint32_t length;
 594                 uint32_t next;
 595         } pseudo;
 596
 597         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 598                 return;
 599
 600         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 601
 602         if(source != myself) {
 603                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname);
 604                 return;
 605         }
 606
 607         /* Copy headers from packet to structs on the stack */
 608
 609         memcpy(&ip6, packet->data + ether_size, ip6_size);
 610         memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
 611         if(has_opt)
 612                 memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 613
 614         /* First, snatch the source address from the neighbor solicitation packet */
 615
 616         if(overwrite_mac)
 617                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 618
 619         /* Check if this is a valid neighbor solicitation request */
 620
 621         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 622            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 623                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request");
 624                 return;
 625         }
 626
 627         /* Create pseudo header */
 628
 629         pseudo.ip6_src = ip6.ip6_src;
 630         pseudo.ip6_dst = ip6.ip6_dst;
 631         if(has_opt)
 632                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 633         else
 634                 pseudo.length = htonl(ns_size);
 635         pseudo.next = htonl(IPPROTO_ICMPV6);
 636
 637         /* Generate checksum */
 638
 639         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 640         checksum = inet_checksum(&ns, ns_size, checksum);
 641         if(has_opt) {
 642                 checksum = inet_checksum(&opt, opt_size, checksum);
 643                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 644         }
 645
 646         if(checksum) {
 647                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request");
 648                 return;
 649         }
 650
 651         /* Check if the IPv6 address exists on the VPN */
 652
 653         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 654
 655         if(!subnet) {
 656                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 657                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 658                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 659                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 660                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 661                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 662                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 663                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 664                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 665
 666                 return;
 667         }
 668
 669         /* Check if it is for our own subnet */
 670
 671         if(subnet->owner == myself)
 672                 return;                                 /* silently ignore */
 673
 674         /* Create neighbor advertation reply */
 675
 676         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 677         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 678
 679         ip6.ip6_dst = ip6.ip6_src;                      /* swap destination and source protocoll address */
 680         ip6.ip6_src = ns.nd_ns_target;
 681
 682         if(has_opt)
 683                 memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 684
 685         ns.nd_ns_cksum = 0;
 686         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 687         ns.nd_ns_reserved = htonl(0x40000000UL);        /* Set solicited flag */
 688         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 689
 690         /* Create pseudo header */
 691
 692         pseudo.ip6_src = ip6.ip6_src;
 693         pseudo.ip6_dst = ip6.ip6_dst;
 694         if(has_opt)
 695                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 696         else
 697                 pseudo.length = htonl(ns_size);
 698         pseudo.next = htonl(IPPROTO_ICMPV6);
 699
 700         /* Generate checksum */
 701
 702         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 703         checksum = inet_checksum(&ns, ns_size, checksum);
 704         if(has_opt) {
 705                 checksum = inet_checksum(&opt, opt_size, checksum);
 706                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 707         }
 708
 709         ns.nd_ns_hdr.icmp6_cksum = checksum;
 710
 711         /* Copy structs on stack back to packet */
 712
 713         memcpy(packet->data + ether_size, &ip6, ip6_size);
 714         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 715         if(has_opt)
 716                 memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 717
 718         send_packet(source, packet);
 719 }
 720
 721 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 722         if(!checklength(source, packet, ether_size + ip6_size))
 723                 return;
 724
 725         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 726                 route_neighborsol(source, packet);
 727                 return;
 728         }
 729
 730         if(broadcast && packet->data[38] == 255)
 731                 broadcast_packet(source, packet);
 732         else
 733                 route_ipv6_unicast(source, packet);
 734 }
 735
 736 /* RFC 826 */
 737
 738 static void route_arp(node_t *source, vpn_packet_t *packet) {
 739         struct ether_arp arp;
 740         subnet_t *subnet;
 741         struct in_addr addr;
 742
 743         if(!checklength(source, packet, ether_size + arp_size))
 744                 return;
 745
 746         if(source != myself) {
 747                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname);
 748                 return;
 749         }
 750
 751         /* First, snatch the source address from the ARP packet */
 752
 753         if(overwrite_mac)
 754                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 755
 756         /* Copy headers from packet to structs on the stack */
 757
 758         memcpy(&arp, packet->data + ether_size, arp_size);
 759
 760         /* Check if this is a valid ARP request */
 761
 762         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 763            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof(addr) || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 764                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type ARP request");
 765                 return;
 766         }
 767
 768         /* Check if the IPv4 address exists on the VPN */
 769
 770         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 771
 772         if(!subnet) {
 773                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d",
 774                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 775                                    arp.arp_tpa[3]);
 776                 return;
 777         }
 778
 779         /* Check if it is for our own subnet */
 780
 781         if(subnet->owner == myself)
 782                 return;                                 /* silently ignore */
 783
 784         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 785         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 786
 787         memcpy(&addr, arp.arp_tpa, sizeof(addr));       /* save protocol addr */
 788         memcpy(arp.arp_tpa, arp.arp_spa, sizeof(addr)); /* swap destination and source protocol address */
 789         memcpy(arp.arp_spa, &addr, sizeof(addr));       /* ... */
 790
 791         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);     /* set target hard/proto addr */
 792         memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN); /* add fake source hard addr */
 793         arp.arp_op = htons(ARPOP_REPLY);
 794
 795         /* Copy structs on stack back to packet */
 796
 797         memcpy(packet->data + ether_size, &arp, arp_size);
 798
 799         send_packet(source, packet);
 800 }
 801
 802 static void route_mac(node_t *source, vpn_packet_t *packet) {
 803         subnet_t *subnet;
 804         mac_t dest;
 805
 806         /* Learn source address */
 807
 808         if(source == myself) {
 809                 mac_t src;
 810                 memcpy(&src, &packet->data[6], sizeof src);
 811                 learn_mac(&src);
 812         }
 813
 814         /* Lookup destination address */
 815
 816         memcpy(&dest, &packet->data[0], sizeof dest);
 817         subnet = lookup_subnet_mac(NULL, &dest);
 818
 819         if(!subnet) {
 820                 if(broadcast)
 821                         broadcast_packet(source, packet);
 822                 return;
 823         }
 824
 825         if(subnet->owner == source) {
 826                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 827                 return;
 828         }
 829
 830         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 831                 return;
 832
 833         // Handle packets larger than PMTU
 834
 835         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 836
 837         if(directonly && subnet->owner != via)
 838                 return;
 839
 840         if(via && packet->len > via->mtu && via != myself) {
 841                 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);
 842                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 843                 if(type == ETH_P_IP && packet->len > 590) {
 844                         if(packet->data[20] & 0x40) {
 845                                 packet->len = via->mtu;
 846                                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 847                         } else {
 848                                 fragment_ipv4_packet(via, packet);
 849                         }
 850                         return;
 851                 } else if(type == ETH_P_IPV6 && packet->len > 1294) {
 852                         packet->len = via->mtu;
 853                         route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 854                         return;
 855                 }
 856         }
 857
 858         clamp_mss(source, via, packet);
 859
 860         send_packet(subnet->owner, packet);
 861 }
 862
 863 static bool do_decrement_ttl(node_t *source, vpn_packet_t *packet) {
 864         uint16_t type = packet->data[12] << 8 | packet->data[13];
 865
 866         switch (type) {
 867                 case ETH_P_IP:
 868                         if(!checklength(source, packet, 14 + 32))
 869                                 return false;
 870
 871                         if(packet->data[22] < 1) {
 872                                 if(packet->data[25] != IPPROTO_ICMP || packet->data[46] != ICMP_TIME_EXCEEDED)
 873                                         route_ipv4_unreachable(source, packet, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL);
 874                                 return false;
 875                         }
 876
 877                         uint16_t old = packet->data[22] << 8 | packet->data[23];
 878                         packet->data[22]--;
 879                         uint16_t new = packet->data[22] << 8 | packet->data[23];
 880
 881                         uint32_t checksum = packet->data[24] << 8 | packet->data[25];
 882                         checksum += old + (~new & 0xFFFF);
 883                         while(checksum >> 16)
 884                                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
 885                         packet->data[24] = checksum >> 8;
 886                         packet->data[25] = checksum & 0xff;
 887
 888                         return true;
 889
 890                 case ETH_P_IPV6:
 891                         if(!checklength(source, packet, 14 + 40))
 892                                 return false;
 893
 894                         if(packet->data[21] < 1) {
 895                                 if(packet->data[20] != IPPROTO_ICMPV6 || packet->data[54] != ICMP6_TIME_EXCEEDED)
 896                                         route_ipv6_unreachable(source, packet, ICMP6_TIME_EXCEEDED, ICMP6_TIME_EXCEED_TRANSIT);
 897                                 return false;
 898                         }
 899
 900                         packet->data[21]--;
 901
 902                         return true;
 903
 904                 default:
 905                         return true;
 906         }
 907 }
 908
 909 void route(node_t *source, vpn_packet_t *packet) {
 910         if(forwarding_mode == FMODE_KERNEL && source != myself) {
 911                 send_packet(myself, packet);
 912                 return;
 913         }
 914
 915         if(!checklength(source, packet, ether_size))
 916                 return;
 917
 918         if(decrement_ttl && source != myself)
 919                 if(!do_decrement_ttl(source, packet))
 920                         return;
 921
 922         switch (routing_mode) {
 923                 case RMODE_ROUTER:
 924                         {
 925                                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 926
 927                                 switch (type) {
 928                                         case ETH_P_ARP:
 929                                                 route_arp(source, packet);
 930                                                 break;
 931
 932                                         case ETH_P_IP:
 933                                                 route_ipv4(source, packet);
 934                                                 break;
 935
 936                                         case ETH_P_IPV6:
 937                                                 route_ipv6(source, packet);
 938                                                 break;
 939
 940                                         default:
 941                                                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type);
 942                                                 break;
 943                                 }
 944                         }
 945                         break;
 946
 947                 case RMODE_SWITCH:
 948                         route_mac(source, packet);
 949                         break;
 950
 951                 case RMODE_HUB:
 952                         broadcast_packet(source, packet);
 953                         break;
 954         }
 955 }