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