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

   1 /*
   2     route.c -- routing
   3     Copyright (C) 2000-2005 Ivo Timmermans,
   4                   2000-2009 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 bool priorityinheritance = false;
  37 int macexpire = 600;
  38 bool overwrite_mac = false;
  39 mac_t mymac = {{0xFE, 0xFD, 0, 0, 0, 0}};
  40
  41 /* Sizes of various headers */
  42
  43 static const size_t ether_size = sizeof(struct ether_header);
  44 static const size_t arp_size = sizeof(struct ether_arp);
  45 static const size_t ip_size = sizeof(struct ip);
  46 static const size_t icmp_size = sizeof(struct icmp) - sizeof(struct ip);
  47 static const size_t ip6_size = sizeof(struct ip6_hdr);
  48 static const size_t icmp6_size = sizeof(struct icmp6_hdr);
  49 static const size_t ns_size = sizeof(struct nd_neighbor_solicit);
  50 static const size_t opt_size = sizeof(struct nd_opt_hdr);
  51 #define max(a, b) ((a) > (b) ? (a) : (b))
  52
  53 /* RFC 1071 */
  54
  55 static uint16_t inet_checksum(void *data, int len, uint16_t prevsum) {
  56         uint16_t *p = data;
  57         uint32_t checksum = prevsum ^ 0xFFFF;
  58
  59         while(len >= 2) {
  60                 checksum += *p++;
  61                 len -= 2;
  62         }
  63
  64         if(len)
  65                 checksum += *(uint8_t *)p;
  66
  67         while(checksum >> 16)
  68                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
  69
  70         return ~checksum;
  71 }
  72
  73 static bool ratelimit(int frequency) {
  74         static time_t lasttime = 0;
  75         static int count = 0;
  76
  77         if(lasttime == now) {
  78                 if(++count > frequency)
  79                         return true;
  80         } else {
  81                 lasttime = now;
  82                 count = 0;
  83         }
  84
  85         return false;
  86 }
  87
  88 static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
  89         if(packet->len < length) {
  90                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got too short packet from %s (%s)", source->name, source->hostname);
  91                 return false;
  92         } else
  93                 return true;
  94 }
  95
  96 static void clamp_mss(const node_t *source, const node_t *via, vpn_packet_t *packet) {
  97         if(!via || via == myself || !(via->options & OPTION_CLAMP_MSS))
  98                 return;
  99
 100         /* Find TCP header */
 101         int start = 0;
 102         uint16_t type = packet->data[12] << 8 | packet->data[13];
 103
 104         if(type == ETH_P_IP && packet->data[23] == 6)
 105                 start = 14 + (packet->data[14] & 0xf) * 4;
 106         else if(type == ETH_P_IPV6 && packet->data[20] == 6)
 107                 start = 14 + 40;
 108
 109         if(!start || packet->len <= start + 20)
 110                 return;
 111
 112         /* Use data offset field to calculate length of options field */
 113         int len = ((packet->data[start + 12] >> 4) - 5) * 4;
 114
 115         if(packet->len < start + 20 + len)
 116                 return;
 117
 118         /* Search for MSS option header */
 119         for(int i = 0; i < len;) {
 120                 if(packet->data[start + 20 + i] == 0)
 121                         break;
 122
 123                 if(packet->data[start + 20 + i] == 1) {
 124                         i++;
 125                         continue;
 126                 }
 127
 128                 if(i > len - 2 || i > len - packet->data[start + 21 + i])
 129                         break;
 130
 131                 if(packet->data[start + 20 + i] != 2) {
 132                         if(packet->data[start + 21 + i] < 2)
 133                                 break;
 134                         i += packet->data[start + 21 + i];
 135                         continue;
 136                 }
 137
 138                 if(packet->data[start + 21] != 4)
 139                         break;
 140
 141                 /* Found it */
 142                 uint16_t oldmss = packet->data[start + 22 + i] << 8 | packet->data[start + 23 + i];
 143                 uint16_t newmss = via->mtu - start - 20;
 144                 uint16_t csum = packet->data[start + 16] << 8 | packet->data[start + 17];
 145
 146                 if(oldmss <= newmss)
 147                         break;
 148
 149                 ifdebug(TRAFFIC) logger(LOG_INFO, "Clamping MSS of packet from %s to %s to %d", source->name, via->name, newmss);
 150
 151                 /* Update the MSS value and the checksum */
 152                 packet->data[start + 22 + i] = newmss >> 8;
 153                 packet->data[start + 23 + i] = newmss & 0xff;
 154                 csum ^= 0xffff;
 155                 csum -= oldmss;
 156                 csum += newmss;
 157                 csum ^= 0xffff;
 158                 packet->data[start + 16] = csum >> 8;
 159                 packet->data[start + 17] = csum & 0xff;
 160                 break;
 161         }
 162 }
 163
 164 static void swap_mac_addresses(vpn_packet_t *packet) {
 165         mac_t tmp;
 166         memcpy(&tmp, &packet->data[0], sizeof tmp);
 167         memcpy(&packet->data[0], &packet->data[6], sizeof tmp);
 168         memcpy(&packet->data[6], &tmp, sizeof tmp);
 169 }
 170
 171 static void learn_mac(mac_t *address) {
 172         subnet_t *subnet;
 173         avl_node_t *node;
 174         connection_t *c;
 175
 176         subnet = lookup_subnet_mac(myself, address);
 177
 178         /* If we don't know this MAC address yet, store it */
 179
 180         if(!subnet) {
 181                 ifdebug(TRAFFIC) logger(LOG_INFO, "Learned new MAC address %hx:%hx:%hx:%hx:%hx:%hx",
 182                                    address->x[0], address->x[1], address->x[2], address->x[3],
 183                                    address->x[4], address->x[5]);
 184
 185                 subnet = new_subnet();
 186                 subnet->type = SUBNET_MAC;
 187                 subnet->expires = now + macexpire;
 188                 subnet->net.mac.address = *address;
 189                 subnet->weight = 10;
 190                 subnet_add(myself, subnet);
 191
 192                 /* And tell all other tinc daemons it's our MAC */
 193
 194                 for(node = connection_tree->head; node; node = node->next) {
 195                         c = node->data;
 196                         if(c->status.active)
 197                                 send_add_subnet(c, subnet);
 198                 }
 199         }
 200
 201         if(subnet->expires)
 202                 subnet->expires = now + macexpire;
 203 }
 204
 205 void age_subnets(void) {
 206         subnet_t *s;
 207         connection_t *c;
 208         avl_node_t *node, *next, *node2;
 209
 210         for(node = myself->subnet_tree->head; node; node = next) {
 211                 next = node->next;
 212                 s = node->data;
 213                 if(s->expires && s->expires < now) {
 214                         ifdebug(TRAFFIC) {
 215                                 char netstr[MAXNETSTR];
 216                                 if(net2str(netstr, sizeof netstr, s))
 217                                         logger(LOG_INFO, "Subnet %s expired", netstr);
 218                         }
 219
 220                         for(node2 = connection_tree->head; node2; node2 = node2->next) {
 221                                 c = node2->data;
 222                                 if(c->status.active)
 223                                         send_del_subnet(c, s);
 224                         }
 225
 226                         subnet_del(myself, s);
 227                 }
 228         }
 229 }
 230
 231 /* RFC 792 */
 232
 233 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 234         struct ip ip = {0};
 235         struct icmp icmp = {0};
 236
 237         struct in_addr ip_src;
 238         struct in_addr ip_dst;
 239         uint32_t oldlen;
 240
 241         if(ratelimit(3))
 242                 return;
 243
 244         /* Swap Ethernet source and destination addresses */
 245
 246         swap_mac_addresses(packet);
 247
 248         /* Copy headers from packet into properly aligned structs on the stack */
 249
 250         memcpy(&ip, packet->data + ether_size, ip_size);
 251
 252         /* Remember original source and destination */
 253
 254         ip_src = ip.ip_src;
 255         ip_dst = ip.ip_dst;
 256
 257         oldlen = packet->len - ether_size;
 258
 259         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 260                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 261
 262         if(oldlen >= IP_MSS - ip_size - icmp_size)
 263                 oldlen = IP_MSS - ip_size - icmp_size;
 264
 265         /* Copy first part of original contents to ICMP message */
 266
 267         memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
 268
 269         /* Fill in IPv4 header */
 270
 271         ip.ip_v = 4;
 272         ip.ip_hl = ip_size / 4;
 273         ip.ip_tos = 0;
 274         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 275         ip.ip_id = 0;
 276         ip.ip_off = 0;
 277         ip.ip_ttl = 255;
 278         ip.ip_p = IPPROTO_ICMP;
 279         ip.ip_sum = 0;
 280         ip.ip_src = ip_dst;
 281         ip.ip_dst = ip_src;
 282
 283         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 284
 285         /* Fill in ICMP header */
 286
 287         icmp.icmp_type = type;
 288         icmp.icmp_code = code;
 289         icmp.icmp_cksum = 0;
 290
 291         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 292         icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 293
 294         /* Copy structs on stack back to packet */
 295
 296         memcpy(packet->data + ether_size, &ip, ip_size);
 297         memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
 298
 299         packet->len = ether_size + ip_size + icmp_size + oldlen;
 300
 301         send_packet(source, packet);
 302 }
 303
 304 /* RFC 791 */
 305
 306 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet) {
 307         struct ip ip;
 308         vpn_packet_t fragment;
 309         int len, maxlen, todo;
 310         uint8_t *offset;
 311         uint16_t ip_off, origf;
 312
 313         memcpy(&ip, packet->data + ether_size, ip_size);
 314         fragment.priority = packet->priority;
 315
 316         if(ip.ip_hl != ip_size / 4)
 317                 return;
 318
 319         todo = ntohs(ip.ip_len) - ip_size;
 320
 321         if(ether_size + ip_size + todo != packet->len) {
 322                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Length of packet (%d) doesn't match length in IPv4 header (%zd)", packet->len, ether_size + ip_size + todo);
 323                 return;
 324         }
 325
 326         ifdebug(TRAFFIC) logger(LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname);
 327
 328         offset = packet->data + ether_size + ip_size;
 329         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 330         ip_off = ntohs(ip.ip_off);
 331         origf = ip_off & ~IP_OFFMASK;
 332         ip_off &= IP_OFFMASK;
 333
 334         while(todo) {
 335                 len = todo > maxlen ? maxlen : todo;
 336                 memcpy(fragment.data + ether_size + ip_size, offset, len);
 337                 todo -= len;
 338                 offset += len;
 339
 340                 ip.ip_len = htons(ip_size + len);
 341                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 342                 ip.ip_sum = 0;
 343                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 344                 memcpy(fragment.data, packet->data, ether_size);
 345                 memcpy(fragment.data + ether_size, &ip, ip_size);
 346                 fragment.len = ether_size + ip_size + len;
 347
 348                 send_packet(dest, &fragment);
 349
 350                 ip_off += len / 8;
 351         }
 352 }
 353
 354 static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet) {
 355         subnet_t *subnet;
 356         node_t *via;
 357         ipv4_t dest;
 358
 359         memcpy(&dest, &packet->data[30], sizeof dest);
 360         subnet = lookup_subnet_ipv4(&dest);
 361
 362         if(!subnet) {
 363                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d",
 364                                 source->name, source->hostname,
 365                                 dest.x[0],
 366                                 dest.x[1],
 367                                 dest.x[2],
 368                                 dest.x[3]);
 369
 370                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 371                 return;
 372         }
 373
 374         if(subnet->owner == source) {
 375                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 376                 return;
 377         }
 378
 379         if(!subnet->owner->status.reachable)
 380                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 381
 382         if(priorityinheritance)
 383                 packet->priority = packet->data[15];
 384
 385         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 386
 387         if(via && packet->len > max(via->mtu, 590) && via != myself) {
 388                 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);
 389                 if(packet->data[20] & 0x40) {
 390                         packet->len = max(via->mtu, 590);
 391                         route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 392                 } else {
 393                         fragment_ipv4_packet(via, packet);
 394                 }
 395
 396                 return;
 397         }
 398
 399         clamp_mss(source, via, packet);
 400
 401         send_packet(subnet->owner, packet);
 402 }
 403
 404 static void route_ipv4(node_t *source, vpn_packet_t *packet) {
 405         if(!checklength(source, packet, ether_size + ip_size))
 406                 return;
 407
 408         if(((packet->data[30] & 0xf0) == 0xe0) || (
 409                         packet->data[30] == 255 &&
 410                         packet->data[31] == 255 &&
 411                         packet->data[32] == 255 &&
 412                         packet->data[33] == 255))
 413                 broadcast_packet(source, packet);
 414         else
 415                 route_ipv4_unicast(source, packet);
 416 }
 417
 418 /* RFC 2463 */
 419
 420 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 421         struct ip6_hdr ip6;
 422         struct icmp6_hdr icmp6 = {0};
 423         uint16_t checksum;
 424
 425         struct {
 426                 struct in6_addr ip6_src;        /* source address */
 427                 struct in6_addr ip6_dst;        /* destination address */
 428                 uint32_t length;
 429                 uint32_t next;
 430         } pseudo;
 431
 432         if(ratelimit(3))
 433                 return;
 434
 435         /* Swap Ethernet source and destination addresses */
 436
 437         swap_mac_addresses(packet);
 438
 439         /* Copy headers from packet to structs on the stack */
 440
 441         memcpy(&ip6, packet->data + ether_size, ip6_size);
 442
 443         /* Remember original source and destination */
 444
 445         pseudo.ip6_src = ip6.ip6_dst;
 446         pseudo.ip6_dst = ip6.ip6_src;
 447
 448         pseudo.length = packet->len - ether_size;
 449
 450         if(type == ICMP6_PACKET_TOO_BIG)
 451                 icmp6.icmp6_mtu = htonl(pseudo.length);
 452
 453         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 454                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 455
 456         /* Copy first part of original contents to ICMP message */
 457
 458         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 459
 460         /* Fill in IPv6 header */
 461
 462         ip6.ip6_flow = htonl(0x60000000UL);
 463         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 464         ip6.ip6_nxt = IPPROTO_ICMPV6;
 465         ip6.ip6_hlim = 255;
 466         ip6.ip6_src = pseudo.ip6_src;
 467         ip6.ip6_dst = pseudo.ip6_dst;
 468
 469         /* Fill in ICMP header */
 470
 471         icmp6.icmp6_type = type;
 472         icmp6.icmp6_code = code;
 473         icmp6.icmp6_cksum = 0;
 474
 475         /* Create pseudo header */
 476
 477         pseudo.length = htonl(icmp6_size + pseudo.length);
 478         pseudo.next = htonl(IPPROTO_ICMPV6);
 479
 480         /* Generate checksum */
 481
 482         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 483         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 484         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 485
 486         icmp6.icmp6_cksum = checksum;
 487
 488         /* Copy structs on stack back to packet */
 489
 490         memcpy(packet->data + ether_size, &ip6, ip6_size);
 491         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 492
 493         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 494
 495         send_packet(source, packet);
 496 }
 497
 498 static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet) {
 499         subnet_t *subnet;
 500         node_t *via;
 501         ipv6_t dest;
 502
 503         memcpy(&dest, &packet->data[38], sizeof dest);
 504         subnet = lookup_subnet_ipv6(&dest);
 505
 506         if(!subnet) {
 507                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 508                                 source->name, source->hostname,
 509                                 ntohs(dest.x[0]),
 510                                 ntohs(dest.x[1]),
 511                                 ntohs(dest.x[2]),
 512                                 ntohs(dest.x[3]),
 513                                 ntohs(dest.x[4]),
 514                                 ntohs(dest.x[5]),
 515                                 ntohs(dest.x[6]),
 516                                 ntohs(dest.x[7]));
 517
 518                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 519                 return;
 520         }
 521
 522         if(subnet->owner == source) {
 523                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 524                 return;
 525         }
 526
 527         if(!subnet->owner->status.reachable)
 528                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 529
 530         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 531
 532         if(via && packet->len > max(via->mtu, 1294) && via != myself) {
 533                 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);
 534                 packet->len = max(via->mtu, 1294);
 535                 route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 536                 return;
 537         }
 538
 539         clamp_mss(source, via, packet);
 540
 541         send_packet(subnet->owner, packet);
 542 }
 543
 544 /* RFC 2461 */
 545
 546 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 547         struct ip6_hdr ip6;
 548         struct nd_neighbor_solicit ns;
 549         struct nd_opt_hdr opt;
 550         subnet_t *subnet;
 551         uint16_t checksum;
 552         bool has_opt;
 553
 554         struct {
 555                 struct in6_addr ip6_src;        /* source address */
 556                 struct in6_addr ip6_dst;        /* destination address */
 557                 uint32_t length;
 558                 uint32_t next;
 559         } pseudo;
 560
 561         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 562                 return;
 563
 564         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 565
 566         if(source != myself) {
 567                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname);
 568                 return;
 569         }
 570
 571         /* Copy headers from packet to structs on the stack */
 572
 573         memcpy(&ip6, packet->data + ether_size, ip6_size);
 574         memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
 575         if(has_opt)
 576                 memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 577
 578         /* First, snatch the source address from the neighbor solicitation packet */
 579
 580         if(overwrite_mac)
 581                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 582
 583         /* Check if this is a valid neighbor solicitation request */
 584
 585         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 586            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 587                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request");
 588                 return;
 589         }
 590
 591         /* Create pseudo header */
 592
 593         pseudo.ip6_src = ip6.ip6_src;
 594         pseudo.ip6_dst = ip6.ip6_dst;
 595         if(has_opt)
 596                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 597         else
 598                 pseudo.length = htonl(ns_size);
 599         pseudo.next = htonl(IPPROTO_ICMPV6);
 600
 601         /* Generate checksum */
 602
 603         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 604         checksum = inet_checksum(&ns, ns_size, checksum);
 605         if(has_opt) {
 606                 checksum = inet_checksum(&opt, opt_size, checksum);
 607                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 608         }
 609
 610         if(checksum) {
 611                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request");
 612                 return;
 613         }
 614
 615         /* Check if the IPv6 address exists on the VPN */
 616
 617         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 618
 619         if(!subnet) {
 620                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 621                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 622                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 623                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 624                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 625                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 626                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 627                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 628                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 629
 630                 return;
 631         }
 632
 633         /* Check if it is for our own subnet */
 634
 635         if(subnet->owner == myself)
 636                 return;                                 /* silently ignore */
 637
 638         /* Create neighbor advertation reply */
 639
 640         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 641         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 642
 643         ip6.ip6_dst = ip6.ip6_src;                      /* swap destination and source protocoll address */
 644         ip6.ip6_src = ns.nd_ns_target;
 645
 646         if(has_opt)
 647                 memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 648
 649         ns.nd_ns_cksum = 0;
 650         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 651         ns.nd_ns_reserved = htonl(0x40000000UL);        /* Set solicited flag */
 652         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 653
 654         /* Create pseudo header */
 655
 656         pseudo.ip6_src = ip6.ip6_src;
 657         pseudo.ip6_dst = ip6.ip6_dst;
 658         if(has_opt)
 659                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 660         else
 661                 pseudo.length = htonl(ns_size);
 662         pseudo.next = htonl(IPPROTO_ICMPV6);
 663
 664         /* Generate checksum */
 665
 666         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 667         checksum = inet_checksum(&ns, ns_size, checksum);
 668         if(has_opt) {
 669                 checksum = inet_checksum(&opt, opt_size, checksum);
 670                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 671         }
 672
 673         ns.nd_ns_hdr.icmp6_cksum = checksum;
 674
 675         /* Copy structs on stack back to packet */
 676
 677         memcpy(packet->data + ether_size, &ip6, ip6_size);
 678         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 679         if(has_opt)
 680                 memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 681
 682         send_packet(source, packet);
 683 }
 684
 685 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 686         if(!checklength(source, packet, ether_size + ip6_size))
 687                 return;
 688
 689         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 690                 route_neighborsol(source, packet);
 691                 return;
 692         }
 693
 694         if(packet->data[38] == 255)
 695                 broadcast_packet(source, packet);
 696         else
 697                 route_ipv6_unicast(source, packet);
 698 }
 699
 700 /* RFC 826 */
 701
 702 static void route_arp(node_t *source, vpn_packet_t *packet) {
 703         struct ether_arp arp;
 704         subnet_t *subnet;
 705         struct in_addr addr;
 706
 707         if(!checklength(source, packet, ether_size + arp_size))
 708                 return;
 709
 710         if(source != myself) {
 711                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname);
 712                 return;
 713         }
 714
 715         /* First, snatch the source address from the ARP packet */
 716
 717         if(overwrite_mac)
 718                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 719
 720         /* Copy headers from packet to structs on the stack */
 721
 722         memcpy(&arp, packet->data + ether_size, arp_size);
 723
 724         /* Check if this is a valid ARP request */
 725
 726         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 727            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof(addr) || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 728                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type ARP request");
 729                 return;
 730         }
 731
 732         /* Check if the IPv4 address exists on the VPN */
 733
 734         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 735
 736         if(!subnet) {
 737                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d",
 738                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 739                                    arp.arp_tpa[3]);
 740                 return;
 741         }
 742
 743         /* Check if it is for our own subnet */
 744
 745         if(subnet->owner == myself)
 746                 return;                                 /* silently ignore */
 747
 748         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 749         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 750
 751         memcpy(&addr, arp.arp_tpa, sizeof(addr));       /* save protocol addr */
 752         memcpy(arp.arp_tpa, arp.arp_spa, sizeof(addr)); /* swap destination and source protocol address */
 753         memcpy(arp.arp_spa, &addr, sizeof(addr));       /* ... */
 754
 755         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);     /* set target hard/proto addr */
 756         memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN); /* add fake source hard addr */
 757         arp.arp_op = htons(ARPOP_REPLY);
 758
 759         /* Copy structs on stack back to packet */
 760
 761         memcpy(packet->data + ether_size, &arp, arp_size);
 762
 763         send_packet(source, packet);
 764 }
 765
 766 static void route_mac(node_t *source, vpn_packet_t *packet) {
 767         subnet_t *subnet;
 768         mac_t dest;
 769
 770         /* Learn source address */
 771
 772         if(source == myself) {
 773                 mac_t src;
 774                 memcpy(&src, &packet->data[6], sizeof src);
 775                 learn_mac(&src);
 776         }
 777
 778         /* Lookup destination address */
 779
 780         memcpy(&dest, &packet->data[0], sizeof dest);
 781         subnet = lookup_subnet_mac(NULL, &dest);
 782
 783         if(!subnet) {
 784                 broadcast_packet(source, packet);
 785                 return;
 786         }
 787
 788         if(subnet->owner == source) {
 789                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 790                 return;
 791         }
 792
 793         // Handle packets larger than PMTU
 794
 795         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 796
 797         if(via && packet->len > via->mtu && via != myself) {
 798                 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);
 799                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 800                 if(type == ETH_P_IP && packet->len > 590) {
 801                         if(packet->data[20] & 0x40) {
 802                                 packet->len = via->mtu;
 803                                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 804                         } else {
 805                                 fragment_ipv4_packet(via, packet);
 806                         }
 807                         return;
 808                 } else if(type == ETH_P_IPV6 && packet->len > 1294) {
 809                         packet->len = via->mtu;
 810                         route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 811                         return;
 812                 }
 813         }
 814
 815         clamp_mss(source, via, packet);
 816
 817         send_packet(subnet->owner, packet);
 818 }
 819
 820 void route(node_t *source, vpn_packet_t *packet) {
 821         if(!checklength(source, packet, ether_size))
 822                 return;
 823
 824         switch (routing_mode) {
 825                 case RMODE_ROUTER:
 826                         {
 827                                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 828
 829                                 switch (type) {
 830                                         case ETH_P_ARP:
 831                                                 route_arp(source, packet);
 832                                                 break;
 833
 834                                         case ETH_P_IP:
 835                                                 route_ipv4(source, packet);
 836                                                 break;
 837
 838                                         case ETH_P_IPV6:
 839                                                 route_ipv6(source, packet);
 840                                                 break;
 841
 842                                         default:
 843                                                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type);
 844                                                 break;
 845                                 }
 846                         }
 847                         break;
 848
 849                 case RMODE_SWITCH:
 850                         route_mac(source, packet);
 851                         break;
 852
 853                 case RMODE_HUB:
 854                         broadcast_packet(source, packet);
 855                         break;
 856         }
 857 }