www.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 mac_t mymac = {{0xFE, 0xFD, 0, 0, 0, 0}};
  43
  44 /* Sizes of various headers */
  45
  46 static const size_t ether_size = sizeof(struct ether_header);
  47 static const size_t arp_size = sizeof(struct ether_arp);
  48 static const size_t ip_size = sizeof(struct ip);
  49 static const size_t icmp_size = sizeof(struct icmp) - sizeof(struct ip);
  50 static const size_t ip6_size = sizeof(struct ip6_hdr);
  51 static const size_t icmp6_size = sizeof(struct icmp6_hdr);
  52 static const size_t ns_size = sizeof(struct nd_neighbor_solicit);
  53 static const size_t opt_size = sizeof(struct nd_opt_hdr);
  54
  55 #ifndef MAX
  56 #define MAX(a, b) ((a) > (b) ? (a) : (b))
  57 #endif
  58
  59 /* RFC 1071 */
  60
  61 static uint16_t inet_checksum(void *data, int len, uint16_t prevsum) {
  62         uint16_t *p = data;
  63         uint32_t checksum = prevsum ^ 0xFFFF;
  64
  65         while(len >= 2) {
  66                 checksum += *p++;
  67                 len -= 2;
  68         }
  69
  70         if(len)
  71                 checksum += *(uint8_t *)p;
  72
  73         while(checksum >> 16)
  74                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
  75
  76         return ~checksum;
  77 }
  78
  79 static bool ratelimit(int frequency) {
  80         static time_t lasttime = 0;
  81         static int count = 0;
  82
  83         if(lasttime == now) {
  84                 if(++count > frequency)
  85                         return true;
  86         } else {
  87                 lasttime = now;
  88                 count = 0;
  89         }
  90
  91         return false;
  92 }
  93
  94 static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
  95         if(packet->len < length) {
  96                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got too short packet from %s (%s)", source->name, source->hostname);
  97                 return false;
  98         } else
  99                 return true;
 100 }
 101
 102 static void clamp_mss(const node_t *source, const node_t *via, vpn_packet_t *packet) {
 103         if(!source || !via || !(via->options & OPTION_CLAMP_MSS))
 104                 return;
 105
 106         uint16_t mtu = source->mtu;
 107         if(via != myself && via->mtu < mtu)
 108                 mtu = via->mtu;
 109
 110         /* Find TCP header */
 111         int start = 0;
 112         uint16_t type = packet->data[12] << 8 | packet->data[13];
 113
 114         if(type == ETH_P_IP && packet->data[23] == 6)
 115                 start = 14 + (packet->data[14] & 0xf) * 4;
 116         else if(type == ETH_P_IPV6 && packet->data[20] == 6)
 117                 start = 14 + 40;
 118
 119         if(!start || packet->len <= start + 20)
 120                 return;
 121
 122         /* Use data offset field to calculate length of options field */
 123         int len = ((packet->data[start + 12] >> 4) - 5) * 4;
 124
 125         if(packet->len < start + 20 + len)
 126                 return;
 127
 128         /* Search for MSS option header */
 129         for(int i = 0; i < len;) {
 130                 if(packet->data[start + 20 + i] == 0)
 131                         break;
 132
 133                 if(packet->data[start + 20 + i] == 1) {
 134                         i++;
 135                         continue;
 136                 }
 137
 138                 if(i > len - 2 || i > len - packet->data[start + 21 + i])
 139                         break;
 140
 141                 if(packet->data[start + 20 + i] != 2) {
 142                         if(packet->data[start + 21 + i] < 2)
 143                                 break;
 144                         i += packet->data[start + 21 + i];
 145                         continue;
 146                 }
 147
 148                 if(packet->data[start + 21] != 4)
 149                         break;
 150
 151                 /* Found it */
 152                 uint16_t oldmss = packet->data[start + 22 + i] << 8 | packet->data[start + 23 + i];
 153                 uint16_t newmss = mtu - start - 20;
 154                 uint16_t csum = packet->data[start + 16] << 8 | packet->data[start + 17];
 155
 156                 if(oldmss <= newmss)
 157                         break;
 158
 159                 ifdebug(TRAFFIC) logger(LOG_INFO, "Clamping MSS of packet from %s to %s to %d", source->name, via->name, newmss);
 160
 161                 /* Update the MSS value and the checksum */
 162                 packet->data[start + 22 + i] = newmss >> 8;
 163                 packet->data[start + 23 + i] = newmss & 0xff;
 164                 csum ^= 0xffff;
 165                 csum -= oldmss;
 166                 csum += newmss;
 167                 csum ^= 0xffff;
 168                 packet->data[start + 16] = csum >> 8;
 169                 packet->data[start + 17] = csum & 0xff;
 170                 break;
 171         }
 172 }
 173
 174 static void swap_mac_addresses(vpn_packet_t *packet) {
 175         mac_t tmp;
 176         memcpy(&tmp, &packet->data[0], sizeof tmp);
 177         memcpy(&packet->data[0], &packet->data[6], sizeof tmp);
 178         memcpy(&packet->data[6], &tmp, sizeof tmp);
 179 }
 180
 181 static void learn_mac(mac_t *address) {
 182         subnet_t *subnet;
 183         avl_node_t *node;
 184         connection_t *c;
 185
 186         subnet = lookup_subnet_mac(myself, address);
 187
 188         /* If we don't know this MAC address yet, store it */
 189
 190         if(!subnet) {
 191                 ifdebug(TRAFFIC) logger(LOG_INFO, "Learned new MAC address %hx:%hx:%hx:%hx:%hx:%hx",
 192                                    address->x[0], address->x[1], address->x[2], address->x[3],
 193                                    address->x[4], address->x[5]);
 194
 195                 subnet = new_subnet();
 196                 subnet->type = SUBNET_MAC;
 197                 subnet->expires = now + macexpire;
 198                 subnet->net.mac.address = *address;
 199                 subnet->weight = 10;
 200                 subnet_add(myself, subnet);
 201                 subnet_update(myself, subnet, true);
 202
 203                 /* And tell all other tinc daemons it's our MAC */
 204
 205                 for(node = connection_tree->head; node; node = node->next) {
 206                         c = node->data;
 207                         if(c->status.active)
 208                                 send_add_subnet(c, subnet);
 209                 }
 210         }
 211
 212         if(subnet->expires)
 213                 subnet->expires = now + macexpire;
 214 }
 215
 216 void age_subnets(void) {
 217         subnet_t *s;
 218         connection_t *c;
 219         avl_node_t *node, *next, *node2;
 220
 221         for(node = myself->subnet_tree->head; node; node = next) {
 222                 next = node->next;
 223                 s = node->data;
 224                 if(s->expires && s->expires <= now) {
 225                         ifdebug(TRAFFIC) {
 226                                 char netstr[MAXNETSTR];
 227                                 if(net2str(netstr, sizeof netstr, s))
 228                                         logger(LOG_INFO, "Subnet %s expired", netstr);
 229                         }
 230
 231                         for(node2 = connection_tree->head; node2; node2 = node2->next) {
 232                                 c = node2->data;
 233                                 if(c->status.active)
 234                                         send_del_subnet(c, s);
 235                         }
 236
 237                         subnet_update(myself, s, false);
 238                         subnet_del(myself, s);
 239                 }
 240         }
 241 }
 242
 243 /* RFC 792 */
 244
 245 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 246         struct ip ip = {0};
 247         struct icmp icmp = {0};
 248
 249         struct in_addr ip_src;
 250         struct in_addr ip_dst;
 251         uint32_t oldlen;
 252
 253         if(ratelimit(3))
 254                 return;
 255
 256         /* Swap Ethernet source and destination addresses */
 257
 258         swap_mac_addresses(packet);
 259
 260         /* Copy headers from packet into properly aligned structs on the stack */
 261
 262         memcpy(&ip, packet->data + ether_size, ip_size);
 263
 264         /* Remember original source and destination */
 265
 266         ip_src = ip.ip_src;
 267         ip_dst = ip.ip_dst;
 268
 269         oldlen = packet->len - ether_size;
 270
 271         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 272                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 273
 274         if(oldlen >= IP_MSS - ip_size - icmp_size)
 275                 oldlen = IP_MSS - ip_size - icmp_size;
 276
 277         /* Copy first part of original contents to ICMP message */
 278
 279         memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
 280
 281         /* Fill in IPv4 header */
 282
 283         ip.ip_v = 4;
 284         ip.ip_hl = ip_size / 4;
 285         ip.ip_tos = 0;
 286         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 287         ip.ip_id = 0;
 288         ip.ip_off = 0;
 289         ip.ip_ttl = 255;
 290         ip.ip_p = IPPROTO_ICMP;
 291         ip.ip_sum = 0;
 292         ip.ip_src = ip_dst;
 293         ip.ip_dst = ip_src;
 294
 295         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 296
 297         /* Fill in ICMP header */
 298
 299         icmp.icmp_type = type;
 300         icmp.icmp_code = code;
 301         icmp.icmp_cksum = 0;
 302
 303         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 304         icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 305
 306         /* Copy structs on stack back to packet */
 307
 308         memcpy(packet->data + ether_size, &ip, ip_size);
 309         memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
 310
 311         packet->len = ether_size + ip_size + icmp_size + oldlen;
 312
 313         send_packet(source, packet);
 314 }
 315
 316 /* RFC 791 */
 317
 318 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet) {
 319         struct ip ip;
 320         vpn_packet_t fragment;
 321         int len, maxlen, todo;
 322         uint8_t *offset;
 323         uint16_t ip_off, origf;
 324
 325         memcpy(&ip, packet->data + ether_size, ip_size);
 326         fragment.priority = packet->priority;
 327
 328         if(ip.ip_hl != ip_size / 4)
 329                 return;
 330
 331         todo = ntohs(ip.ip_len) - ip_size;
 332
 333         if(ether_size + ip_size + todo != packet->len) {
 334                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Length of packet (%d) doesn't match length in IPv4 header (%zd)", packet->len, ether_size + ip_size + todo);
 335                 return;
 336         }
 337
 338         ifdebug(TRAFFIC) logger(LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname);
 339
 340         offset = packet->data + ether_size + ip_size;
 341         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 342         ip_off = ntohs(ip.ip_off);
 343         origf = ip_off & ~IP_OFFMASK;
 344         ip_off &= IP_OFFMASK;
 345
 346         while(todo) {
 347                 len = todo > maxlen ? maxlen : todo;
 348                 memcpy(fragment.data + ether_size + ip_size, offset, len);
 349                 todo -= len;
 350                 offset += len;
 351
 352                 ip.ip_len = htons(ip_size + len);
 353                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 354                 ip.ip_sum = 0;
 355                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 356                 memcpy(fragment.data, packet->data, ether_size);
 357                 memcpy(fragment.data + ether_size, &ip, ip_size);
 358                 fragment.len = ether_size + ip_size + len;
 359
 360                 send_packet(dest, &fragment);
 361
 362                 ip_off += len / 8;
 363         }
 364 }
 365
 366 static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet) {
 367         subnet_t *subnet;
 368         node_t *via;
 369         ipv4_t dest;
 370
 371         memcpy(&dest, &packet->data[30], sizeof dest);
 372         subnet = lookup_subnet_ipv4(&dest);
 373
 374         if(!subnet) {
 375                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d",
 376                                 source->name, source->hostname,
 377                                 dest.x[0],
 378                                 dest.x[1],
 379                                 dest.x[2],
 380                                 dest.x[3]);
 381
 382                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 383                 return;
 384         }
 385
 386         if(subnet->owner == source) {
 387                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 388                 return;
 389         }
 390
 391         if(!subnet->owner->status.reachable)
 392                 return route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 393
 394         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 395                 return route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 396
 397         if(priorityinheritance)
 398                 packet->priority = packet->data[15];
 399
 400         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 401
 402         if(directonly && subnet->owner != via)
 403                 return route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 404
 405         if(via && packet->len > MAX(via->mtu, 590) && via != myself) {
 406                 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);
 407                 if(packet->data[20] & 0x40) {
 408                         packet->len = MAX(via->mtu, 590);
 409                         route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 410                 } else {
 411                         fragment_ipv4_packet(via, packet);
 412                 }
 413
 414                 return;
 415         }
 416
 417         clamp_mss(source, via, packet);
 418
 419         send_packet(subnet->owner, packet);
 420 }
 421
 422 static void route_ipv4(node_t *source, vpn_packet_t *packet) {
 423         if(!checklength(source, packet, ether_size + ip_size))
 424                 return;
 425
 426         if(((packet->data[30] & 0xf0) == 0xe0) || (
 427                         packet->data[30] == 255 &&
 428                         packet->data[31] == 255 &&
 429                         packet->data[32] == 255 &&
 430                         packet->data[33] == 255))
 431                 broadcast_packet(source, packet);
 432         else
 433                 route_ipv4_unicast(source, packet);
 434 }
 435
 436 /* RFC 2463 */
 437
 438 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 439         struct ip6_hdr ip6;
 440         struct icmp6_hdr icmp6 = {0};
 441         uint16_t checksum;
 442
 443         struct {
 444                 struct in6_addr ip6_src;        /* source address */
 445                 struct in6_addr ip6_dst;        /* destination address */
 446                 uint32_t length;
 447                 uint32_t next;
 448         } pseudo;
 449
 450         if(ratelimit(3))
 451                 return;
 452
 453         /* Swap Ethernet source and destination addresses */
 454
 455         swap_mac_addresses(packet);
 456
 457         /* Copy headers from packet to structs on the stack */
 458
 459         memcpy(&ip6, packet->data + ether_size, ip6_size);
 460
 461         /* Remember original source and destination */
 462
 463         pseudo.ip6_src = ip6.ip6_dst;
 464         pseudo.ip6_dst = ip6.ip6_src;
 465
 466         pseudo.length = packet->len - ether_size;
 467
 468         if(type == ICMP6_PACKET_TOO_BIG)
 469                 icmp6.icmp6_mtu = htonl(pseudo.length);
 470
 471         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 472                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 473
 474         /* Copy first part of original contents to ICMP message */
 475
 476         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 477
 478         /* Fill in IPv6 header */
 479
 480         ip6.ip6_flow = htonl(0x60000000UL);
 481         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 482         ip6.ip6_nxt = IPPROTO_ICMPV6;
 483         ip6.ip6_hlim = 255;
 484         ip6.ip6_src = pseudo.ip6_src;
 485         ip6.ip6_dst = pseudo.ip6_dst;
 486
 487         /* Fill in ICMP header */
 488
 489         icmp6.icmp6_type = type;
 490         icmp6.icmp6_code = code;
 491         icmp6.icmp6_cksum = 0;
 492
 493         /* Create pseudo header */
 494
 495         pseudo.length = htonl(icmp6_size + pseudo.length);
 496         pseudo.next = htonl(IPPROTO_ICMPV6);
 497
 498         /* Generate checksum */
 499
 500         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 501         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 502         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 503
 504         icmp6.icmp6_cksum = checksum;
 505
 506         /* Copy structs on stack back to packet */
 507
 508         memcpy(packet->data + ether_size, &ip6, ip6_size);
 509         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 510
 511         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 512
 513         send_packet(source, packet);
 514 }
 515
 516 static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet) {
 517         subnet_t *subnet;
 518         node_t *via;
 519         ipv6_t dest;
 520
 521         memcpy(&dest, &packet->data[38], sizeof dest);
 522         subnet = lookup_subnet_ipv6(&dest);
 523
 524         if(!subnet) {
 525                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 526                                 source->name, source->hostname,
 527                                 ntohs(dest.x[0]),
 528                                 ntohs(dest.x[1]),
 529                                 ntohs(dest.x[2]),
 530                                 ntohs(dest.x[3]),
 531                                 ntohs(dest.x[4]),
 532                                 ntohs(dest.x[5]),
 533                                 ntohs(dest.x[6]),
 534                                 ntohs(dest.x[7]));
 535
 536                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 537                 return;
 538         }
 539
 540         if(subnet->owner == source) {
 541                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 542                 return;
 543         }
 544
 545         if(!subnet->owner->status.reachable)
 546                 return route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 547
 548         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 549                 return route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 550
 551         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 552
 553         if(directonly && subnet->owner != via)
 554                 return route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 555
 556         if(via && packet->len > MAX(via->mtu, 1294) && via != myself) {
 557                 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);
 558                 packet->len = MAX(via->mtu, 1294);
 559                 route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 560                 return;
 561         }
 562
 563         clamp_mss(source, via, packet);
 564
 565         send_packet(subnet->owner, packet);
 566 }
 567
 568 /* RFC 2461 */
 569
 570 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 571         struct ip6_hdr ip6;
 572         struct nd_neighbor_solicit ns;
 573         struct nd_opt_hdr opt;
 574         subnet_t *subnet;
 575         uint16_t checksum;
 576         bool has_opt;
 577
 578         struct {
 579                 struct in6_addr ip6_src;        /* source address */
 580                 struct in6_addr ip6_dst;        /* destination address */
 581                 uint32_t length;
 582                 uint32_t next;
 583         } pseudo;
 584
 585         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 586                 return;
 587
 588         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 589
 590         if(source != myself) {
 591                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname);
 592                 return;
 593         }
 594
 595         /* Copy headers from packet to structs on the stack */
 596
 597         memcpy(&ip6, packet->data + ether_size, ip6_size);
 598         memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
 599         if(has_opt)
 600                 memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 601
 602         /* First, snatch the source address from the neighbor solicitation packet */
 603
 604         if(overwrite_mac)
 605                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 606
 607         /* Check if this is a valid neighbor solicitation request */
 608
 609         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 610            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 611                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request");
 612                 return;
 613         }
 614
 615         /* Create pseudo header */
 616
 617         pseudo.ip6_src = ip6.ip6_src;
 618         pseudo.ip6_dst = ip6.ip6_dst;
 619         if(has_opt)
 620                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 621         else
 622                 pseudo.length = htonl(ns_size);
 623         pseudo.next = htonl(IPPROTO_ICMPV6);
 624
 625         /* Generate checksum */
 626
 627         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 628         checksum = inet_checksum(&ns, ns_size, checksum);
 629         if(has_opt) {
 630                 checksum = inet_checksum(&opt, opt_size, checksum);
 631                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 632         }
 633
 634         if(checksum) {
 635                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request");
 636                 return;
 637         }
 638
 639         /* Check if the IPv6 address exists on the VPN */
 640
 641         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 642
 643         if(!subnet) {
 644                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 645                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 646                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 647                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 648                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 649                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 650                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 651                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 652                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 653
 654                 return;
 655         }
 656
 657         /* Check if it is for our own subnet */
 658
 659         if(subnet->owner == myself)
 660                 return;                                 /* silently ignore */
 661
 662         /* Create neighbor advertation reply */
 663
 664         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 665         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 666
 667         ip6.ip6_dst = ip6.ip6_src;                      /* swap destination and source protocoll address */
 668         ip6.ip6_src = ns.nd_ns_target;
 669
 670         if(has_opt)
 671                 memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 672
 673         ns.nd_ns_cksum = 0;
 674         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 675         ns.nd_ns_reserved = htonl(0x40000000UL);        /* Set solicited flag */
 676         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 677
 678         /* Create pseudo header */
 679
 680         pseudo.ip6_src = ip6.ip6_src;
 681         pseudo.ip6_dst = ip6.ip6_dst;
 682         if(has_opt)
 683                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 684         else
 685                 pseudo.length = htonl(ns_size);
 686         pseudo.next = htonl(IPPROTO_ICMPV6);
 687
 688         /* Generate checksum */
 689
 690         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 691         checksum = inet_checksum(&ns, ns_size, checksum);
 692         if(has_opt) {
 693                 checksum = inet_checksum(&opt, opt_size, checksum);
 694                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 695         }
 696
 697         ns.nd_ns_hdr.icmp6_cksum = checksum;
 698
 699         /* Copy structs on stack back to packet */
 700
 701         memcpy(packet->data + ether_size, &ip6, ip6_size);
 702         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 703         if(has_opt)
 704                 memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 705
 706         send_packet(source, packet);
 707 }
 708
 709 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 710         if(!checklength(source, packet, ether_size + ip6_size))
 711                 return;
 712
 713         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 714                 route_neighborsol(source, packet);
 715                 return;
 716         }
 717
 718         if(packet->data[38] == 255)
 719                 broadcast_packet(source, packet);
 720         else
 721                 route_ipv6_unicast(source, packet);
 722 }
 723
 724 /* RFC 826 */
 725
 726 static void route_arp(node_t *source, vpn_packet_t *packet) {
 727         struct ether_arp arp;
 728         subnet_t *subnet;
 729         struct in_addr addr;
 730
 731         if(!checklength(source, packet, ether_size + arp_size))
 732                 return;
 733
 734         if(source != myself) {
 735                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname);
 736                 return;
 737         }
 738
 739         /* First, snatch the source address from the ARP packet */
 740
 741         if(overwrite_mac)
 742                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 743
 744         /* Copy headers from packet to structs on the stack */
 745
 746         memcpy(&arp, packet->data + ether_size, arp_size);
 747
 748         /* Check if this is a valid ARP request */
 749
 750         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 751            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof(addr) || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 752                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type ARP request");
 753                 return;
 754         }
 755
 756         /* Check if the IPv4 address exists on the VPN */
 757
 758         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 759
 760         if(!subnet) {
 761                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d",
 762                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 763                                    arp.arp_tpa[3]);
 764                 return;
 765         }
 766
 767         /* Check if it is for our own subnet */
 768
 769         if(subnet->owner == myself)
 770                 return;                                 /* silently ignore */
 771
 772         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 773         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 774
 775         memcpy(&addr, arp.arp_tpa, sizeof(addr));       /* save protocol addr */
 776         memcpy(arp.arp_tpa, arp.arp_spa, sizeof(addr)); /* swap destination and source protocol address */
 777         memcpy(arp.arp_spa, &addr, sizeof(addr));       /* ... */
 778
 779         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);     /* set target hard/proto addr */
 780         memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN); /* add fake source hard addr */
 781         arp.arp_op = htons(ARPOP_REPLY);
 782
 783         /* Copy structs on stack back to packet */
 784
 785         memcpy(packet->data + ether_size, &arp, arp_size);
 786
 787         send_packet(source, packet);
 788 }
 789
 790 static void route_mac(node_t *source, vpn_packet_t *packet) {
 791         subnet_t *subnet;
 792         mac_t dest;
 793
 794         /* Learn source address */
 795
 796         if(source == myself) {
 797                 mac_t src;
 798                 memcpy(&src, &packet->data[6], sizeof src);
 799                 learn_mac(&src);
 800         }
 801
 802         /* Lookup destination address */
 803
 804         memcpy(&dest, &packet->data[0], sizeof dest);
 805         subnet = lookup_subnet_mac(NULL, &dest);
 806
 807         if(!subnet) {
 808                 broadcast_packet(source, packet);
 809                 return;
 810         }
 811
 812         if(subnet->owner == source) {
 813                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 814                 return;
 815         }
 816
 817         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 818                 return;
 819
 820         // Handle packets larger than PMTU
 821
 822         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 823
 824         if(directonly && subnet->owner != via)
 825                 return;
 826
 827         if(via && packet->len > via->mtu && via != myself) {
 828                 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);
 829                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 830                 if(type == ETH_P_IP && packet->len > 590) {
 831                         if(packet->data[20] & 0x40) {
 832                                 packet->len = via->mtu;
 833                                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 834                         } else {
 835                                 fragment_ipv4_packet(via, packet);
 836                         }
 837                         return;
 838                 } else if(type == ETH_P_IPV6 && packet->len > 1294) {
 839                         packet->len = via->mtu;
 840                         route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 841                         return;
 842                 }
 843         }
 844
 845         clamp_mss(source, via, packet);
 846
 847         send_packet(subnet->owner, packet);
 848 }
 849
 850 static bool do_decrement_ttl(node_t *source, vpn_packet_t *packet) {
 851         uint16_t type = packet->data[12] << 8 | packet->data[13];
 852
 853         switch (type) {
 854                 case ETH_P_IP:
 855                         if(!checklength(source, packet, 14 + 32))
 856                                 return false;
 857
 858                         if(packet->data[22] < 1) {
 859                                 route_ipv4_unreachable(source, packet, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL);
 860                                 return false;
 861                         }
 862
 863                         uint16_t old = packet->data[22] << 8 | packet->data[23];
 864                         packet->data[22]--;
 865                         uint16_t new = packet->data[22] << 8 | packet->data[23];
 866
 867                         uint32_t checksum = packet->data[24] << 8 | packet->data[25];
 868                         checksum += old + (~new & 0xFFFF);
 869                         while(checksum >> 16)
 870                                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
 871                         packet->data[24] = checksum >> 8;
 872                         packet->data[25] = checksum & 0xff;
 873
 874                         return true;
 875
 876                 case ETH_P_IPV6:
 877                         if(!checklength(source, packet, 14 + 40))
 878                                 return false;
 879
 880                         if(packet->data[21] < 1) {
 881                                 route_ipv6_unreachable(source, packet, ICMP6_TIME_EXCEEDED, ICMP6_TIME_EXCEED_TRANSIT);
 882                                 return false;
 883                         }
 884
 885                         packet->data[21]--;
 886
 887                         return true;
 888
 889                 default:
 890                         return true;
 891         }
 892 }
 893
 894 void route(node_t *source, vpn_packet_t *packet) {
 895         if(forwarding_mode == FMODE_KERNEL && source != myself) {
 896                 send_packet(myself, packet);
 897                 return;
 898         }
 899
 900         if(!checklength(source, packet, ether_size))
 901                 return;
 902
 903         if(decrement_ttl && source != myself)
 904                 if(!do_decrement_ttl(source, packet))
 905                         return;
 906
 907         switch (routing_mode) {
 908                 case RMODE_ROUTER:
 909                         {
 910                                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 911
 912                                 switch (type) {
 913                                         case ETH_P_ARP:
 914                                                 route_arp(source, packet);
 915                                                 break;
 916
 917                                         case ETH_P_IP:
 918                                                 route_ipv4(source, packet);
 919                                                 break;
 920
 921                                         case ETH_P_IPV6:
 922                                                 route_ipv6(source, packet);
 923                                                 break;
 924
 925                                         default:
 926                                                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type);
 927                                                 break;
 928                                 }
 929                         }
 930                         break;
 931
 932                 case RMODE_SWITCH:
 933                         route_mac(source, packet);
 934                         break;
 935
 936                 case RMODE_HUB:
 937                         broadcast_packet(source, packet);
 938                         break;
 939         }
 940 }