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