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

   1 /*
   2     route.c -- routing
   3     Copyright (C) 2000-2005 Ivo Timmermans,
   4                   2000-2013 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 bmode_t broadcast_mode = BMODE_MST;
  38 bool decrement_ttl = false;
  39 bool directonly = false;
  40 bool priorityinheritance = false;
  41 int macexpire = 600;
  42 bool overwrite_mac = false;
  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 = ether_size;
 114         uint16_t type = packet->data[12] << 8 | packet->data[13];
 115
 116         if(type == ETH_P_8021Q) {
 117                 start += 4;
 118                 type = packet->data[16] << 8 | packet->data[17];
 119         }
 120
 121         if(type == ETH_P_IP && packet->data[start + 9] == 6)
 122                 start += (packet->data[start] & 0xf) * 4;
 123         else if(type == ETH_P_IPV6 && packet->data[start + 6] == 6)
 124                 start += 40;
 125         else
 126                 return;
 127
 128         if(packet->len <= start + 20)
 129                 return;
 130
 131         /* Use data offset field to calculate length of options field */
 132         int len = ((packet->data[start + 12] >> 4) - 5) * 4;
 133
 134         if(packet->len < start + 20 + len)
 135                 return;
 136
 137         /* Search for MSS option header */
 138         for(int i = 0; i < len;) {
 139                 if(packet->data[start + 20 + i] == 0)
 140                         break;
 141
 142                 if(packet->data[start + 20 + i] == 1) {
 143                         i++;
 144                         continue;
 145                 }
 146
 147                 if(i > len - 2 || i > len - packet->data[start + 21 + i])
 148                         break;
 149
 150                 if(packet->data[start + 20 + i] != 2) {
 151                         if(packet->data[start + 21 + i] < 2)
 152                                 break;
 153                         i += packet->data[start + 21 + i];
 154                         continue;
 155                 }
 156
 157                 if(packet->data[start + 21] != 4)
 158                         break;
 159
 160                 /* Found it */
 161                 uint16_t oldmss = packet->data[start + 22 + i] << 8 | packet->data[start + 23 + i];
 162                 uint16_t newmss = mtu - start - 20;
 163                 uint16_t csum = packet->data[start + 16] << 8 | packet->data[start + 17];
 164
 165                 if(oldmss <= newmss)
 166                         break;
 167
 168                 ifdebug(TRAFFIC) logger(LOG_INFO, "Clamping MSS of packet from %s to %s to %d", source->name, via->name, newmss);
 169
 170                 /* Update the MSS value and the checksum */
 171                 packet->data[start + 22 + i] = newmss >> 8;
 172                 packet->data[start + 23 + i] = newmss & 0xff;
 173                 csum ^= 0xffff;
 174                 csum -= oldmss;
 175                 csum += newmss;
 176                 csum ^= 0xffff;
 177                 packet->data[start + 16] = csum >> 8;
 178                 packet->data[start + 17] = csum & 0xff;
 179                 break;
 180         }
 181 }
 182
 183 static void swap_mac_addresses(vpn_packet_t *packet) {
 184         mac_t tmp;
 185         memcpy(&tmp, &packet->data[0], sizeof tmp);
 186         memcpy(&packet->data[0], &packet->data[6], sizeof tmp);
 187         memcpy(&packet->data[6], &tmp, sizeof tmp);
 188 }
 189
 190 static void learn_mac(mac_t *address) {
 191         subnet_t *subnet;
 192         avl_node_t *node;
 193         connection_t *c;
 194
 195         subnet = lookup_subnet_mac(myself, address);
 196
 197         /* If we don't know this MAC address yet, store it */
 198
 199         if(!subnet) {
 200                 ifdebug(TRAFFIC) logger(LOG_INFO, "Learned new MAC address %hx:%hx:%hx:%hx:%hx:%hx",
 201                                    address->x[0], address->x[1], address->x[2], address->x[3],
 202                                    address->x[4], address->x[5]);
 203
 204                 subnet = new_subnet();
 205                 subnet->type = SUBNET_MAC;
 206                 subnet->expires = now + macexpire;
 207                 subnet->net.mac.address = *address;
 208                 subnet->weight = 10;
 209                 subnet_add(myself, subnet);
 210                 subnet_update(myself, subnet, true);
 211
 212                 /* And tell all other tinc daemons it's our MAC */
 213
 214                 for(node = connection_tree->head; node; node = node->next) {
 215                         c = node->data;
 216                         if(c->status.active)
 217                                 send_add_subnet(c, subnet);
 218                 }
 219         }
 220
 221         if(subnet->expires)
 222                 subnet->expires = now + macexpire;
 223 }
 224
 225 void age_subnets(void) {
 226         subnet_t *s;
 227         connection_t *c;
 228         avl_node_t *node, *next, *node2;
 229
 230         for(node = myself->subnet_tree->head; node; node = next) {
 231                 next = node->next;
 232                 s = node->data;
 233                 if(s->expires && s->expires <= now) {
 234                         ifdebug(TRAFFIC) {
 235                                 char netstr[MAXNETSTR];
 236                                 if(net2str(netstr, sizeof netstr, s))
 237                                         logger(LOG_INFO, "Subnet %s expired", netstr);
 238                         }
 239
 240                         for(node2 = connection_tree->head; node2; node2 = node2->next) {
 241                                 c = node2->data;
 242                                 if(c->status.active)
 243                                         send_del_subnet(c, s);
 244                         }
 245
 246                         subnet_update(myself, s, false);
 247                         subnet_del(myself, s);
 248                 }
 249         }
 250 }
 251
 252 /* RFC 792 */
 253
 254 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, uint8_t type, uint8_t code) {
 255         struct ip ip = {0};
 256         struct icmp icmp = {0};
 257
 258         struct in_addr ip_src;
 259         struct in_addr ip_dst;
 260         uint32_t oldlen;
 261
 262         if(ratelimit(3))
 263                 return;
 264
 265         /* Swap Ethernet source and destination addresses */
 266
 267         swap_mac_addresses(packet);
 268
 269         /* Copy headers from packet into properly aligned structs on the stack */
 270
 271         memcpy(&ip, packet->data + ether_size, ip_size);
 272
 273         /* Remember original source and destination */
 274
 275         ip_src = ip.ip_src;
 276         ip_dst = ip.ip_dst;
 277
 278         oldlen = packet->len - ether_size;
 279
 280         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 281                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 282
 283         if(oldlen >= IP_MSS - ip_size - icmp_size)
 284                 oldlen = IP_MSS - ip_size - icmp_size;
 285
 286         /* Copy first part of original contents to ICMP message */
 287
 288         memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
 289
 290         /* Fill in IPv4 header */
 291
 292         ip.ip_v = 4;
 293         ip.ip_hl = ip_size / 4;
 294         ip.ip_tos = 0;
 295         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 296         ip.ip_id = 0;
 297         ip.ip_off = 0;
 298         ip.ip_ttl = 255;
 299         ip.ip_p = IPPROTO_ICMP;
 300         ip.ip_sum = 0;
 301         ip.ip_src = ip_dst;
 302         ip.ip_dst = ip_src;
 303
 304         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 305
 306         /* Fill in ICMP header */
 307
 308         icmp.icmp_type = type;
 309         icmp.icmp_code = code;
 310         icmp.icmp_cksum = 0;
 311
 312         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 313         icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 314
 315         /* Copy structs on stack back to packet */
 316
 317         memcpy(packet->data + ether_size, &ip, ip_size);
 318         memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
 319
 320         packet->len = ether_size + ip_size + icmp_size + oldlen;
 321
 322         send_packet(source, packet);
 323 }
 324
 325 /* RFC 791 */
 326
 327 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet, length_t ether_size) {
 328         struct ip ip;
 329         vpn_packet_t fragment;
 330         int len, maxlen, todo;
 331         uint8_t *offset;
 332         uint16_t ip_off, origf;
 333
 334         memcpy(&ip, packet->data + ether_size, ip_size);
 335         fragment.priority = packet->priority;
 336
 337         if(ip.ip_hl != ip_size / 4)
 338                 return;
 339
 340         todo = ntohs(ip.ip_len) - ip_size;
 341
 342         if(ether_size + ip_size + todo != packet->len) {
 343                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Length of packet (%d) doesn't match length in IPv4 header (%d)", packet->len, (int)(ether_size + ip_size + todo));
 344                 return;
 345         }
 346
 347         ifdebug(TRAFFIC) logger(LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname);
 348
 349         offset = packet->data + ether_size + ip_size;
 350         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 351         ip_off = ntohs(ip.ip_off);
 352         origf = ip_off & ~IP_OFFMASK;
 353         ip_off &= IP_OFFMASK;
 354
 355         while(todo) {
 356                 len = todo > maxlen ? maxlen : todo;
 357                 memcpy(fragment.data + ether_size + ip_size, offset, len);
 358                 todo -= len;
 359                 offset += len;
 360
 361                 ip.ip_len = htons(ip_size + len);
 362                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 363                 ip.ip_sum = 0;
 364                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 365                 memcpy(fragment.data, packet->data, ether_size);
 366                 memcpy(fragment.data + ether_size, &ip, ip_size);
 367                 fragment.len = ether_size + ip_size + len;
 368
 369                 send_packet(dest, &fragment);
 370
 371                 ip_off += len / 8;
 372         }
 373 }
 374
 375 static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet) {
 376         subnet_t *subnet;
 377         node_t *via;
 378         ipv4_t dest;
 379
 380         memcpy(&dest, &packet->data[30], sizeof dest);
 381         subnet = lookup_subnet_ipv4(&dest);
 382
 383         if(!subnet) {
 384                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d",
 385                                 source->name, source->hostname,
 386                                 dest.x[0],
 387                                 dest.x[1],
 388                                 dest.x[2],
 389                                 dest.x[3]);
 390
 391                 route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 392                 return;
 393         }
 394
 395         if(subnet->owner == source) {
 396                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 397                 return;
 398         }
 399
 400         if(!subnet->owner->status.reachable)
 401                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 402
 403         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 404                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 405
 406         if(priorityinheritance)
 407                 packet->priority = packet->data[15];
 408
 409         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 410
 411         if(via == source) {
 412                 ifdebug(TRAFFIC) logger(LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 413                 return;
 414         }
 415
 416         if(directonly && subnet->owner != via)
 417                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 418
 419         if(via && packet->len > MAX(via->mtu, 590) && via != myself) {
 420                 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);
 421                 if(packet->data[20] & 0x40) {
 422                         packet->len = MAX(via->mtu, 590);
 423                         route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 424                 } else {
 425                         fragment_ipv4_packet(via, packet, ether_size);
 426                 }
 427
 428                 return;
 429         }
 430
 431         clamp_mss(source, via, packet);
 432
 433         send_packet(subnet->owner, packet);
 434 }
 435
 436 static void route_ipv4(node_t *source, vpn_packet_t *packet) {
 437         if(!checklength(source, packet, ether_size + ip_size))
 438                 return;
 439
 440         if(broadcast_mode && (((packet->data[30] & 0xf0) == 0xe0) || (
 441                         packet->data[30] == 255 &&
 442                         packet->data[31] == 255 &&
 443                         packet->data[32] == 255 &&
 444                         packet->data[33] == 255)))
 445                 broadcast_packet(source, packet);
 446         else
 447                 route_ipv4_unicast(source, packet);
 448 }
 449
 450 /* RFC 2463 */
 451
 452 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, uint8_t type, uint8_t code) {
 453         struct ip6_hdr ip6;
 454         struct icmp6_hdr icmp6 = {0};
 455         uint16_t checksum;
 456
 457         struct {
 458                 struct in6_addr ip6_src;        /* source address */
 459                 struct in6_addr ip6_dst;        /* destination address */
 460                 uint32_t length;
 461                 uint32_t next;
 462         } pseudo;
 463
 464         if(ratelimit(3))
 465                 return;
 466
 467         /* Swap Ethernet source and destination addresses */
 468
 469         swap_mac_addresses(packet);
 470
 471         /* Copy headers from packet to structs on the stack */
 472
 473         memcpy(&ip6, packet->data + ether_size, ip6_size);
 474
 475         /* Remember original source and destination */
 476
 477         pseudo.ip6_src = ip6.ip6_dst;
 478         pseudo.ip6_dst = ip6.ip6_src;
 479
 480         pseudo.length = packet->len - ether_size;
 481
 482         if(type == ICMP6_PACKET_TOO_BIG)
 483                 icmp6.icmp6_mtu = htonl(pseudo.length);
 484
 485         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 486                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 487
 488         /* Copy first part of original contents to ICMP message */
 489
 490         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 491
 492         /* Fill in IPv6 header */
 493
 494         ip6.ip6_flow = htonl(0x60000000UL);
 495         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 496         ip6.ip6_nxt = IPPROTO_ICMPV6;
 497         ip6.ip6_hlim = 255;
 498         ip6.ip6_src = pseudo.ip6_src;
 499         ip6.ip6_dst = pseudo.ip6_dst;
 500
 501         /* Fill in ICMP header */
 502
 503         icmp6.icmp6_type = type;
 504         icmp6.icmp6_code = code;
 505         icmp6.icmp6_cksum = 0;
 506
 507         /* Create pseudo header */
 508
 509         pseudo.length = htonl(icmp6_size + pseudo.length);
 510         pseudo.next = htonl(IPPROTO_ICMPV6);
 511
 512         /* Generate checksum */
 513
 514         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 515         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 516         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 517
 518         icmp6.icmp6_cksum = checksum;
 519
 520         /* Copy structs on stack back to packet */
 521
 522         memcpy(packet->data + ether_size, &ip6, ip6_size);
 523         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 524
 525         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 526
 527         send_packet(source, packet);
 528 }
 529
 530 static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet) {
 531         subnet_t *subnet;
 532         node_t *via;
 533         ipv6_t dest;
 534
 535         memcpy(&dest, &packet->data[38], sizeof dest);
 536         subnet = lookup_subnet_ipv6(&dest);
 537
 538         if(!subnet) {
 539                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 540                                 source->name, source->hostname,
 541                                 ntohs(dest.x[0]),
 542                                 ntohs(dest.x[1]),
 543                                 ntohs(dest.x[2]),
 544                                 ntohs(dest.x[3]),
 545                                 ntohs(dest.x[4]),
 546                                 ntohs(dest.x[5]),
 547                                 ntohs(dest.x[6]),
 548                                 ntohs(dest.x[7]));
 549
 550                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 551                 return;
 552         }
 553
 554         if(subnet->owner == source) {
 555                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 556                 return;
 557         }
 558
 559         if(!subnet->owner->status.reachable)
 560                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 561
 562         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 563                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 564
 565         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 566
 567         if(via == source) {
 568                 ifdebug(TRAFFIC) logger(LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 569                 return;
 570         }
 571
 572         if(directonly && subnet->owner != via)
 573                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 574
 575         if(via && packet->len > MAX(via->mtu, 1294) && via != myself) {
 576                 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);
 577                 packet->len = MAX(via->mtu, 1294);
 578                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_PACKET_TOO_BIG, 0);
 579                 return;
 580         }
 581
 582         clamp_mss(source, via, packet);
 583
 584         send_packet(subnet->owner, packet);
 585 }
 586
 587 /* RFC 2461 */
 588
 589 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 590         struct ip6_hdr ip6;
 591         struct nd_neighbor_solicit ns;
 592         struct nd_opt_hdr opt;
 593         subnet_t *subnet;
 594         uint16_t checksum;
 595         bool has_opt;
 596
 597         struct {
 598                 struct in6_addr ip6_src;        /* source address */
 599                 struct in6_addr ip6_dst;        /* destination address */
 600                 uint32_t length;
 601                 uint32_t next;
 602         } pseudo;
 603
 604         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 605                 return;
 606
 607         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 608
 609         if(source != myself) {
 610                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname);
 611                 return;
 612         }
 613
 614         /* Copy headers from packet to structs on the stack */
 615
 616         memcpy(&ip6, packet->data + ether_size, ip6_size);
 617         memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
 618         if(has_opt)
 619                 memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 620
 621         /* First, snatch the source address from the neighbor solicitation packet */
 622
 623         if(overwrite_mac)
 624                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 625
 626         /* Check if this is a valid neighbor solicitation request */
 627
 628         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 629            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 630                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request");
 631                 return;
 632         }
 633
 634         /* Create pseudo header */
 635
 636         pseudo.ip6_src = ip6.ip6_src;
 637         pseudo.ip6_dst = ip6.ip6_dst;
 638         if(has_opt)
 639                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 640         else
 641                 pseudo.length = htonl(ns_size);
 642         pseudo.next = htonl(IPPROTO_ICMPV6);
 643
 644         /* Generate checksum */
 645
 646         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 647         checksum = inet_checksum(&ns, ns_size, checksum);
 648         if(has_opt) {
 649                 checksum = inet_checksum(&opt, opt_size, checksum);
 650                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 651         }
 652
 653         if(checksum) {
 654                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request");
 655                 return;
 656         }
 657
 658         /* Check if the IPv6 address exists on the VPN */
 659
 660         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 661
 662         if(!subnet) {
 663                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 664                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 665                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 666                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 667                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 668                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 669                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 670                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 671                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 672
 673                 return;
 674         }
 675
 676         /* Check if it is for our own subnet */
 677
 678         if(subnet->owner == myself)
 679                 return;                                 /* silently ignore */
 680
 681         /* Create neighbor advertation reply */
 682
 683         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 684         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 685
 686         ip6.ip6_dst = ip6.ip6_src;                      /* swap destination and source protocoll address */
 687         ip6.ip6_src = ns.nd_ns_target;
 688
 689         if(has_opt)
 690                 memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 691
 692         ns.nd_ns_cksum = 0;
 693         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 694         ns.nd_ns_reserved = htonl(0x40000000UL);        /* Set solicited flag */
 695         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 696
 697         /* Create pseudo header */
 698
 699         pseudo.ip6_src = ip6.ip6_src;
 700         pseudo.ip6_dst = ip6.ip6_dst;
 701         if(has_opt)
 702                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 703         else
 704                 pseudo.length = htonl(ns_size);
 705         pseudo.next = htonl(IPPROTO_ICMPV6);
 706
 707         /* Generate checksum */
 708
 709         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 710         checksum = inet_checksum(&ns, ns_size, checksum);
 711         if(has_opt) {
 712                 checksum = inet_checksum(&opt, opt_size, checksum);
 713                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 714         }
 715
 716         ns.nd_ns_hdr.icmp6_cksum = checksum;
 717
 718         /* Copy structs on stack back to packet */
 719
 720         memcpy(packet->data + ether_size, &ip6, ip6_size);
 721         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 722         if(has_opt)
 723                 memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 724
 725         send_packet(source, packet);
 726 }
 727
 728 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 729         if(!checklength(source, packet, ether_size + ip6_size))
 730                 return;
 731
 732         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 733                 route_neighborsol(source, packet);
 734                 return;
 735         }
 736
 737         if(broadcast_mode && packet->data[38] == 255)
 738                 broadcast_packet(source, packet);
 739         else
 740                 route_ipv6_unicast(source, packet);
 741 }
 742
 743 /* RFC 826 */
 744
 745 static void route_arp(node_t *source, vpn_packet_t *packet) {
 746         struct ether_arp arp;
 747         subnet_t *subnet;
 748         struct in_addr addr;
 749
 750         if(!checklength(source, packet, ether_size + arp_size))
 751                 return;
 752
 753         if(source != myself) {
 754                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname);
 755                 return;
 756         }
 757
 758         /* First, snatch the source address from the ARP packet */
 759
 760         if(overwrite_mac)
 761                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 762
 763         /* Copy headers from packet to structs on the stack */
 764
 765         memcpy(&arp, packet->data + ether_size, arp_size);
 766
 767         /* Check if this is a valid ARP request */
 768
 769         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 770            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof(addr) || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 771                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type ARP request");
 772                 return;
 773         }
 774
 775         /* Check if the IPv4 address exists on the VPN */
 776
 777         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 778
 779         if(!subnet) {
 780                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d",
 781                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 782                                    arp.arp_tpa[3]);
 783                 return;
 784         }
 785
 786         /* Check if it is for our own subnet */
 787
 788         if(subnet->owner == myself)
 789                 return;                                 /* silently ignore */
 790
 791         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 792         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 793
 794         memcpy(&addr, arp.arp_tpa, sizeof(addr));       /* save protocol addr */
 795         memcpy(arp.arp_tpa, arp.arp_spa, sizeof(addr)); /* swap destination and source protocol address */
 796         memcpy(arp.arp_spa, &addr, sizeof(addr));       /* ... */
 797
 798         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);     /* set target hard/proto addr */
 799         memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN); /* add fake source hard addr */
 800         arp.arp_op = htons(ARPOP_REPLY);
 801
 802         /* Copy structs on stack back to packet */
 803
 804         memcpy(packet->data + ether_size, &arp, arp_size);
 805
 806         send_packet(source, packet);
 807 }
 808
 809 static void route_mac(node_t *source, vpn_packet_t *packet) {
 810         subnet_t *subnet;
 811         mac_t dest;
 812
 813         /* Learn source address */
 814
 815         if(source == myself) {
 816                 mac_t src;
 817                 memcpy(&src, &packet->data[6], sizeof src);
 818                 learn_mac(&src);
 819         }
 820
 821         /* Lookup destination address */
 822
 823         memcpy(&dest, &packet->data[0], sizeof dest);
 824         subnet = lookup_subnet_mac(NULL, &dest);
 825
 826         if(!subnet) {
 827                 broadcast_packet(source, packet);
 828                 return;
 829         }
 830
 831         if(subnet->owner == source) {
 832                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 833                 return;
 834         }
 835
 836         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 837                 return;
 838
 839         uint16_t type = packet->data[12] << 8 | packet->data[13];
 840
 841         if(priorityinheritance && type == ETH_P_IP && packet->len >= ether_size + ip_size)
 842                 packet->priority = packet->data[15];
 843
 844         // Handle packets larger than PMTU
 845
 846         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 847
 848         if(directonly && subnet->owner != via)
 849                 return;
 850
 851         if(via && packet->len > via->mtu && via != myself) {
 852                 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);
 853                 length_t ethlen = 14;
 854
 855                 if(type == ETH_P_8021Q) {
 856                         type = packet->data[16] << 8 | packet->data[17];
 857                         ethlen += 4;
 858                 }
 859
 860                 if(type == ETH_P_IP && packet->len > 576 + ethlen) {
 861                         if(packet->data[6 + ethlen] & 0x40) {
 862                                 packet->len = via->mtu;
 863                                 route_ipv4_unreachable(source, packet, ethlen, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 864                         } else {
 865                                 fragment_ipv4_packet(via, packet, ethlen);
 866                         }
 867                         return;
 868                 } else if(type == ETH_P_IPV6 && packet->len > 1280 + ethlen) {
 869                         packet->len = via->mtu;
 870                         route_ipv6_unreachable(source, packet, ethlen, ICMP6_PACKET_TOO_BIG, 0);
 871                         return;
 872                 }
 873         }
 874
 875         clamp_mss(source, via, packet);
 876
 877         send_packet(subnet->owner, packet);
 878 }
 879
 880 static bool do_decrement_ttl(node_t *source, vpn_packet_t *packet) {
 881         uint16_t type = packet->data[12] << 8 | packet->data[13];
 882         length_t ethlen = ether_size;
 883
 884         if(type == ETH_P_8021Q) {
 885                 type = packet->data[16] << 8 | packet->data[17];
 886                 ethlen += 4;
 887         }
 888
 889         switch (type) {
 890                 case ETH_P_IP:
 891                         if(!checklength(source, packet, ethlen + ip_size))
 892                                 return false;
 893
 894                         if(packet->data[ethlen + 8] < 1) {
 895                                 if(packet->data[ethlen + 11] != IPPROTO_ICMP || packet->data[ethlen + 32] != ICMP_TIME_EXCEEDED)
 896                                         route_ipv4_unreachable(source, packet, ethlen, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL);
 897                                 return false;
 898                         }
 899
 900                         uint16_t old = packet->data[ethlen + 8] << 8 | packet->data[ethlen + 9];
 901                         packet->data[ethlen + 8]--;
 902                         uint16_t new = packet->data[ethlen + 8] << 8 | packet->data[ethlen + 9];
 903
 904                         uint32_t checksum = packet->data[ethlen + 10] << 8 | packet->data[ethlen + 11];
 905                         checksum += old + (~new & 0xFFFF);
 906                         while(checksum >> 16)
 907                                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
 908                         packet->data[ethlen + 10] = checksum >> 8;
 909                         packet->data[ethlen + 11] = checksum & 0xff;
 910
 911                         return true;
 912
 913                 case ETH_P_IPV6:
 914                         if(!checklength(source, packet, ethlen + ip6_size))
 915                                 return false;
 916
 917                         if(packet->data[ethlen + 7] < 1) {
 918                                 if(packet->data[ethlen + 6] != IPPROTO_ICMPV6 || packet->data[ethlen + 40] != ICMP6_TIME_EXCEEDED)
 919                                         route_ipv6_unreachable(source, packet, ethlen, ICMP6_TIME_EXCEEDED, ICMP6_TIME_EXCEED_TRANSIT);
 920                                 return false;
 921                         }
 922
 923                         packet->data[ethlen + 7]--;
 924
 925                         return true;
 926
 927                 default:
 928                         return true;
 929         }
 930 }
 931
 932 void route(node_t *source, vpn_packet_t *packet) {
 933         if(forwarding_mode == FMODE_KERNEL && source != myself) {
 934                 send_packet(myself, packet);
 935                 return;
 936         }
 937
 938         if(!checklength(source, packet, ether_size))
 939                 return;
 940
 941         if(decrement_ttl && source != myself)
 942                 if(!do_decrement_ttl(source, packet))
 943                         return;
 944
 945         switch (routing_mode) {
 946                 case RMODE_ROUTER:
 947                         {
 948                                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 949
 950                                 switch (type) {
 951                                         case ETH_P_ARP:
 952                                                 route_arp(source, packet);
 953                                                 break;
 954
 955                                         case ETH_P_IP:
 956                                                 route_ipv4(source, packet);
 957                                                 break;
 958
 959                                         case ETH_P_IPV6:
 960                                                 route_ipv6(source, packet);
 961                                                 break;
 962
 963                                         default:
 964                                                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type);
 965                                                 break;
 966                                 }
 967                         }
 968                         break;
 969
 970                 case RMODE_SWITCH:
 971                         route_mac(source, packet);
 972                         break;
 973
 974                 case RMODE_HUB:
 975                         broadcast_packet(source, packet);
 976                         break;
 977         }
 978 }