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