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

   1 /*
   2     route.c -- routing
   3     Copyright (C) 2000-2005 Ivo Timmermans,
   4                   2000-2018 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 "connection.h"
  24 #include "control_common.h"
  25 #include "ethernet.h"
  26 #include "ipv4.h"
  27 #include "ipv6.h"
  28 #include "logger.h"
  29 #include "meta.h"
  30 #include "net.h"
  31 #include "protocol.h"
  32 #include "route.h"
  33 #include "subnet.h"
  34
  35 rmode_t routing_mode = RMODE_ROUTER;
  36 fmode_t forwarding_mode = FMODE_INTERNAL;
  37 bmode_t broadcast_mode = BMODE_MST;
  38 bool decrement_ttl = false;
  39 bool directonly = false;
  40 bool priorityinheritance = false;
  41 int macexpire = 600;
  42 bool overwrite_mac = false;
  43 mac_t mymac = {{0xFE, 0xFD, 0, 0, 0, 0}};
  44 bool pcap = false;
  45
  46 /* Sizes of various headers */
  47
  48 static const size_t ether_size = sizeof(struct ether_header);
  49 static const size_t arp_size = sizeof(struct ether_arp);
  50 static const size_t ip_size = sizeof(struct ip);
  51 static const size_t icmp_size = sizeof(struct icmp) - sizeof(struct ip);
  52 static const size_t ip6_size = sizeof(struct ip6_hdr);
  53 static const size_t icmp6_size = sizeof(struct icmp6_hdr);
  54 static const size_t ns_size = sizeof(struct nd_neighbor_solicit);
  55 static const size_t opt_size = sizeof(struct nd_opt_hdr);
  56
  57 #ifndef MAX
  58 #define MAX(a, b) ((a) > (b) ? (a) : (b))
  59 #endif
  60
  61 static timeout_t age_subnets_timeout;
  62
  63 /* RFC 1071 */
  64
  65 static uint16_t inet_checksum(void *vdata, size_t len, uint16_t prevsum) {
  66         uint8_t *data = vdata;
  67         uint16_t word;
  68         uint32_t checksum = prevsum ^ 0xFFFF;
  69
  70         while(len >= 2) {
  71                 memcpy(&word, data, sizeof(word));
  72                 checksum += word;
  73                 data += 2;
  74                 len -= 2;
  75         }
  76
  77         if(len) {
  78                 checksum += *data;
  79         }
  80
  81         while(checksum >> 16) {
  82                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
  83         }
  84
  85         return (uint16_t) ~checksum;
  86 }
  87
  88 static bool ratelimit(int frequency) {
  89         static time_t lasttime = 0;
  90         static int count = 0;
  91
  92         if(lasttime == now.tv_sec) {
  93                 if(count >= frequency) {
  94                         return true;
  95                 }
  96         } else {
  97                 lasttime = now.tv_sec;
  98                 count = 0;
  99         }
 100
 101         count++;
 102         return false;
 103 }
 104
 105 static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
 106         if(packet->len < length) {
 107                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Got too short packet from %s (%s)", source->name, source->hostname);
 108                 return false;
 109         } else {
 110                 return true;
 111         }
 112 }
 113
 114 static void swap_mac_addresses(vpn_packet_t *packet) {
 115         mac_t tmp;
 116         memcpy(&tmp, &DATA(packet)[0], sizeof(tmp));
 117         memcpy(&DATA(packet)[0], &DATA(packet)[6], sizeof(tmp));
 118         memcpy(&DATA(packet)[6], &tmp, sizeof(tmp));
 119 }
 120
 121 /* RFC 792 */
 122
 123 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, uint8_t type, uint8_t code) {
 124         struct ip ip = {0};
 125         struct icmp icmp = {0};
 126
 127         struct in_addr ip_src;
 128         struct in_addr ip_dst;
 129         uint32_t oldlen;
 130
 131         if(ratelimit(3)) {
 132                 return;
 133         }
 134
 135         /* Swap Ethernet source and destination addresses */
 136
 137         swap_mac_addresses(packet);
 138
 139         /* Copy headers from packet into properly aligned structs on the stack */
 140
 141         memcpy(&ip, DATA(packet) + ether_size, ip_size);
 142
 143         /* Remember original source and destination */
 144
 145         ip_src = ip.ip_src;
 146         ip_dst = ip.ip_dst;
 147
 148         /* Try to reply with an IP address assigned to the local machine */
 149
 150         if(type == ICMP_TIME_EXCEEDED && code == ICMP_EXC_TTL) {
 151                 int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
 152
 153                 if(sockfd != -1) {
 154                         struct sockaddr_in addr;
 155                         memset(&addr, 0, sizeof(addr));
 156                         addr.sin_family = AF_INET;
 157                         addr.sin_addr = ip.ip_src;
 158
 159                         if(!connect(sockfd, (const struct sockaddr *) &addr, sizeof(addr))) {
 160                                 memset(&addr, 0, sizeof(addr));
 161                                 addr.sin_family = AF_INET;
 162                                 socklen_t addrlen = sizeof(addr);
 163
 164                                 if(!getsockname(sockfd, (struct sockaddr *) &addr, &addrlen) && (size_t)addrlen <= sizeof(addr)) {
 165                                         ip_dst = addr.sin_addr;
 166                                 }
 167                         }
 168
 169                         close(sockfd);
 170                 }
 171         }
 172
 173         oldlen = packet->len - ether_size;
 174
 175         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) {
 176                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 177         }
 178
 179         if(oldlen >= IP_MSS - ip_size - icmp_size) {
 180                 oldlen = IP_MSS - ip_size - icmp_size;
 181         }
 182
 183         /* Copy first part of original contents to ICMP message */
 184
 185         memmove(DATA(packet) + ether_size + ip_size + icmp_size, DATA(packet) + ether_size, oldlen);
 186
 187         /* Fill in IPv4 header */
 188
 189         ip.ip_v = 4;
 190         ip.ip_hl = ip_size / 4;
 191         ip.ip_tos = 0;
 192         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 193         ip.ip_id = 0;
 194         ip.ip_off = 0;
 195         ip.ip_ttl = 255;
 196         ip.ip_p = IPPROTO_ICMP;
 197         ip.ip_sum = 0;
 198         ip.ip_src = ip_dst;
 199         ip.ip_dst = ip_src;
 200
 201         ip.ip_sum = inet_checksum(&ip, ip_size, 0xFFFF);
 202
 203         /* Fill in ICMP header */
 204
 205         icmp.icmp_type = type;
 206         icmp.icmp_code = code;
 207         icmp.icmp_cksum = 0;
 208
 209         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, 0xFFFF);
 210         icmp.icmp_cksum = inet_checksum(DATA(packet) + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 211
 212         /* Copy structs on stack back to packet */
 213
 214         memcpy(DATA(packet) + ether_size, &ip, ip_size);
 215         memcpy(DATA(packet) + ether_size + ip_size, &icmp, icmp_size);
 216
 217         packet->len = ether_size + ip_size + icmp_size + oldlen;
 218
 219         send_packet(source, packet);
 220 }
 221
 222 /* RFC 2463 */
 223
 224 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, uint8_t type, uint8_t code) {
 225         struct ip6_hdr ip6;
 226         struct icmp6_hdr icmp6 = {0};
 227         uint16_t checksum;
 228
 229         struct {
 230                 struct in6_addr ip6_src;        /* source address */
 231                 struct in6_addr ip6_dst;        /* destination address */
 232                 uint32_t length;
 233                 uint32_t next;
 234         } pseudo;
 235
 236         if(ratelimit(3)) {
 237                 return;
 238         }
 239
 240         /* Swap Ethernet source and destination addresses */
 241
 242         swap_mac_addresses(packet);
 243
 244         /* Copy headers from packet to structs on the stack */
 245
 246         memcpy(&ip6, DATA(packet) + ether_size, ip6_size);
 247
 248         /* Remember original source and destination */
 249
 250         pseudo.ip6_src = ip6.ip6_dst;
 251         pseudo.ip6_dst = ip6.ip6_src;
 252
 253         /* Try to reply with an IP address assigned to the local machine */
 254
 255         if(type == ICMP6_TIME_EXCEEDED && code == ICMP6_TIME_EXCEED_TRANSIT) {
 256                 int sockfd = socket(AF_INET6, SOCK_DGRAM, 0);
 257
 258                 if(sockfd != -1) {
 259                         struct sockaddr_in6 addr;
 260                         memset(&addr, 0, sizeof(addr));
 261                         addr.sin6_family = AF_INET6;
 262                         addr.sin6_addr = ip6.ip6_src;
 263
 264                         if(!connect(sockfd, (const struct sockaddr *) &addr, sizeof(addr))) {
 265                                 memset(&addr, 0, sizeof(addr));
 266                                 addr.sin6_family = AF_INET6;
 267                                 socklen_t addrlen = sizeof(addr);
 268
 269                                 if(!getsockname(sockfd, (struct sockaddr *) &addr, &addrlen) && (size_t)addrlen <= sizeof(addr)) {
 270                                         pseudo.ip6_src = addr.sin6_addr;
 271                                 }
 272                         }
 273
 274                         close(sockfd);
 275                 }
 276         }
 277
 278         pseudo.length = packet->len - ether_size;
 279
 280         if(type == ICMP6_PACKET_TOO_BIG) {
 281                 icmp6.icmp6_mtu = htonl(pseudo.length);
 282         }
 283
 284         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size) {
 285                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 286         }
 287
 288         /* Copy first part of original contents to ICMP message */
 289
 290         memmove(DATA(packet) + ether_size + ip6_size + icmp6_size, DATA(packet) + ether_size, pseudo.length);
 291
 292         /* Fill in IPv6 header */
 293
 294         ip6.ip6_flow = htonl(0x60000000UL);
 295         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 296         ip6.ip6_nxt = IPPROTO_ICMPV6;
 297         ip6.ip6_hlim = 255;
 298         ip6.ip6_src = pseudo.ip6_src;
 299         ip6.ip6_dst = pseudo.ip6_dst;
 300
 301         /* Fill in ICMP header */
 302
 303         icmp6.icmp6_type = type;
 304         icmp6.icmp6_code = code;
 305         icmp6.icmp6_cksum = 0;
 306
 307         /* Create pseudo header */
 308
 309         pseudo.length = htonl(icmp6_size + pseudo.length);
 310         pseudo.next = htonl(IPPROTO_ICMPV6);
 311
 312         /* Generate checksum */
 313
 314         checksum = inet_checksum(&pseudo, sizeof(pseudo), 0xFFFF);
 315         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 316         checksum = inet_checksum(DATA(packet) + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 317
 318         icmp6.icmp6_cksum = checksum;
 319
 320         /* Copy structs on stack back to packet */
 321
 322         memcpy(DATA(packet) + ether_size, &ip6, ip6_size);
 323         memcpy(DATA(packet) + ether_size + ip6_size, &icmp6, icmp6_size);
 324
 325         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 326
 327         send_packet(source, packet);
 328 }
 329
 330 static bool do_decrement_ttl(node_t *source, vpn_packet_t *packet) {
 331         uint16_t type = DATA(packet)[12] << 8 | DATA(packet)[13];
 332         length_t ethlen = ether_size;
 333
 334         if(type == ETH_P_8021Q) {
 335                 type = DATA(packet)[16] << 8 | DATA(packet)[17];
 336                 ethlen += 4;
 337         }
 338
 339         switch(type) {
 340         case ETH_P_IP:
 341                 if(!checklength(source, packet, ethlen + ip_size)) {
 342                         return false;
 343                 }
 344
 345                 if(DATA(packet)[ethlen + 8] <= 1) {
 346                         if(DATA(packet)[ethlen + 11] != IPPROTO_ICMP || DATA(packet)[ethlen + 32] != ICMP_TIME_EXCEEDED) {
 347                                 route_ipv4_unreachable(source, packet, ethlen, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL);
 348                         }
 349
 350                         return false;
 351                 }
 352
 353                 uint16_t old = DATA(packet)[ethlen + 8] << 8 | DATA(packet)[ethlen + 9];
 354                 DATA(packet)[ethlen + 8]--;
 355                 uint16_t new = DATA(packet)[ethlen + 8] << 8 | DATA(packet)[ethlen + 9];
 356
 357                 uint32_t checksum = DATA(packet)[ethlen + 10] << 8 | DATA(packet)[ethlen + 11];
 358                 checksum += old + (~new & 0xFFFF);
 359
 360                 while(checksum >> 16) {
 361                         checksum = (checksum & 0xFFFF) + (checksum >> 16);
 362                 }
 363
 364                 DATA(packet)[ethlen + 10] = checksum >> 8;
 365                 DATA(packet)[ethlen + 11] = checksum & 0xff;
 366
 367                 return true;
 368
 369         case ETH_P_IPV6:
 370                 if(!checklength(source, packet, ethlen + ip6_size)) {
 371                         return false;
 372                 }
 373
 374                 if(DATA(packet)[ethlen + 7] <= 1) {
 375                         if(DATA(packet)[ethlen + 6] != IPPROTO_ICMPV6 || DATA(packet)[ethlen + 40] != ICMP6_TIME_EXCEEDED) {
 376                                 route_ipv6_unreachable(source, packet, ethlen, ICMP6_TIME_EXCEEDED, ICMP6_TIME_EXCEED_TRANSIT);
 377                         }
 378
 379                         return false;
 380                 }
 381
 382                 DATA(packet)[ethlen + 7]--;
 383
 384                 return true;
 385
 386         default:
 387                 return true;
 388         }
 389 }
 390
 391 static void clamp_mss(const node_t *source, const node_t *via, vpn_packet_t *packet) {
 392         if(!source || !via || !(via->options & OPTION_CLAMP_MSS)) {
 393                 return;
 394         }
 395
 396         uint16_t mtu = source->mtu;
 397
 398         if(via != myself && via->mtu < mtu) {
 399                 mtu = via->mtu;
 400         }
 401
 402         /* Find TCP header */
 403         size_t start = ether_size;
 404         uint16_t type = DATA(packet)[12] << 8 | DATA(packet)[13];
 405
 406         if(type == ETH_P_8021Q) {
 407                 start += 4;
 408                 type = DATA(packet)[16] << 8 | DATA(packet)[17];
 409         }
 410
 411         /* IP in IP (RFC 2003) packet */
 412         if(type == ETH_P_IP && DATA(packet)[start + 9] == 4) {
 413                 start += 20;
 414         }
 415
 416         if(packet->len <= start + 20) {
 417                 return;
 418         }
 419
 420         if(type == ETH_P_IP && DATA(packet)[start + 9] == 6) {
 421                 start += (DATA(packet)[start] & 0xf) * 4;
 422         } else if(type == ETH_P_IPV6 && DATA(packet)[start + 6] == 6) {
 423                 start += 40;
 424         } else {
 425                 return;
 426         }
 427
 428         if(packet->len <= start + 20) {
 429                 return;
 430         }
 431
 432         /* Use data offset field to calculate length of options field */
 433         int len = ((DATA(packet)[start + 12] >> 4) - 5) * 4;
 434
 435         if(packet->len < start + 20 + len) {
 436                 return;
 437         }
 438
 439         /* Search for MSS option header */
 440         for(int i = 0; i < len;) {
 441                 if(DATA(packet)[start + 20 + i] == 0) {
 442                         break;
 443                 }
 444
 445                 if(DATA(packet)[start + 20 + i] == 1) {
 446                         i++;
 447                         continue;
 448                 }
 449
 450                 if(i > len - 2 || i > len - DATA(packet)[start + 21 + i]) {
 451                         break;
 452                 }
 453
 454                 if(DATA(packet)[start + 20 + i] != 2) {
 455                         if(DATA(packet)[start + 21 + i] < 2) {
 456                                 break;
 457                         }
 458
 459                         i += DATA(packet)[start + 21 + i];
 460                         continue;
 461                 }
 462
 463                 if(DATA(packet)[start + 21] != 4) {
 464                         break;
 465                 }
 466
 467                 /* Found it */
 468                 uint16_t oldmss = DATA(packet)[start + 22 + i] << 8 | DATA(packet)[start + 23 + i];
 469                 uint16_t newmss = mtu - start - 20;
 470                 uint32_t csum = DATA(packet)[start + 16] << 8 | DATA(packet)[start + 17];
 471
 472                 if(oldmss <= newmss) {
 473                         break;
 474                 }
 475
 476                 logger(DEBUG_TRAFFIC, LOG_INFO, "Clamping MSS of packet from %s to %s to %d", source->name, via->name, newmss);
 477
 478                 /* Update the MSS value and the checksum */
 479                 DATA(packet)[start + 22 + i] = newmss >> 8;
 480                 DATA(packet)[start + 23 + i] = newmss & 0xff;
 481                 csum ^= 0xffff;
 482                 csum += oldmss ^ 0xffff;
 483                 csum += newmss;
 484                 csum = (csum & 0xffff) + (csum >> 16);
 485                 csum += csum >> 16;
 486                 csum ^= 0xffff;
 487                 DATA(packet)[start + 16] = csum >> 8;
 488                 DATA(packet)[start + 17] = csum;
 489                 break;
 490         }
 491 }
 492
 493 static void age_subnets(void *data) {
 494         (void)data;
 495         bool left = false;
 496
 497         for splay_each(subnet_t, s, myself->subnet_tree) {
 498                 if(s->expires && s->expires < now.tv_sec) {
 499                         if(debug_level >= DEBUG_TRAFFIC) {
 500                                 char netstr[MAXNETSTR];
 501
 502                                 if(net2str(netstr, sizeof(netstr), s)) {
 503                                         logger(DEBUG_TRAFFIC, LOG_INFO, "Subnet %s expired", netstr);
 504                                 }
 505                         }
 506
 507                         for list_each(connection_t, c, &connection_list)
 508                                 if(c->edge) {
 509                                         send_del_subnet(c, s);
 510                                 }
 511
 512                         subnet_del(myself, s);
 513                 } else {
 514                         if(s->expires) {
 515                                 left = true;
 516                         }
 517                 }
 518         }
 519
 520         if(left)
 521                 timeout_set(&age_subnets_timeout, &(struct timeval) {
 522                 10, rand() % 100000
 523         });
 524 }
 525
 526 static void learn_mac(mac_t *address) {
 527         subnet_t *subnet = lookup_subnet_mac(myself, address);
 528
 529         /* If we don't know this MAC address yet, store it */
 530
 531         if(!subnet) {
 532                 logger(DEBUG_TRAFFIC, LOG_INFO, "Learned new MAC address %x:%x:%x:%x:%x:%x",
 533                        address->x[0], address->x[1], address->x[2], address->x[3],
 534                        address->x[4], address->x[5]);
 535
 536                 subnet = new_subnet();
 537                 subnet->type = SUBNET_MAC;
 538                 subnet->expires = now.tv_sec + macexpire;
 539                 subnet->net.mac.address = *address;
 540                 subnet->weight = 10;
 541                 subnet_add(myself, subnet);
 542                 subnet_update(myself, subnet, true);
 543
 544                 /* And tell all other tinc daemons it's our MAC */
 545
 546                 for list_each(connection_t, c, &connection_list)
 547                         if(c->edge) {
 548                                 send_add_subnet(c, subnet);
 549                         }
 550
 551                 timeout_add(&age_subnets_timeout, age_subnets, NULL, &(struct timeval) {
 552                         10, rand() % 100000
 553                 });
 554         } else {
 555                 if(subnet->expires) {
 556                         subnet->expires = now.tv_sec + macexpire;
 557                 }
 558         }
 559 }
 560
 561 static void route_broadcast(node_t *source, vpn_packet_t *packet) {
 562         if(decrement_ttl && source != myself)
 563                 if(!do_decrement_ttl(source, packet)) {
 564                         return;
 565                 }
 566
 567         broadcast_packet(source, packet);
 568 }
 569
 570 /* RFC 791 */
 571
 572 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet, length_t ether_size) {
 573         struct ip ip;
 574         vpn_packet_t fragment;
 575         size_t maxlen, todo;
 576         uint8_t *offset;
 577         uint16_t ip_off, origf;
 578
 579         memcpy(&ip, DATA(packet) + ether_size, ip_size);
 580         fragment.priority = packet->priority;
 581         fragment.offset = DEFAULT_PACKET_OFFSET;
 582
 583         if(ip.ip_hl != ip_size / 4) {
 584                 return;
 585         }
 586
 587         todo = ntohs(ip.ip_len) - ip_size;
 588
 589         if(ether_size + ip_size + todo != packet->len) {
 590                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Length of packet (%d) doesn't match length in IPv4 header (%zu)", packet->len, ether_size + ip_size + todo);
 591                 return;
 592         }
 593
 594         logger(DEBUG_TRAFFIC, LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname);
 595
 596         offset = DATA(packet) + ether_size + ip_size;
 597         maxlen = (MAX(dest->mtu, 590) - ether_size - ip_size) & ~0x7;
 598         ip_off = ntohs(ip.ip_off);
 599         origf = ip_off & ~IP_OFFMASK;
 600         ip_off &= IP_OFFMASK;
 601
 602         while(todo) {
 603                 size_t len = todo > maxlen ? maxlen : todo;
 604                 memcpy(DATA(&fragment) + ether_size + ip_size, offset, len);
 605                 todo -= len;
 606                 offset += len;
 607
 608                 ip.ip_len = htons(ip_size + len);
 609                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 610                 ip.ip_sum = 0;
 611                 ip.ip_sum = inet_checksum(&ip, ip_size, 0xFFFF);
 612                 memcpy(DATA(&fragment), DATA(packet), ether_size);
 613                 memcpy(DATA(&fragment) + ether_size, &ip, ip_size);
 614                 fragment.len = ether_size + ip_size + len;
 615
 616                 send_packet(dest, &fragment);
 617
 618                 ip_off += len / 8;
 619         }
 620 }
 621
 622 static void route_ipv4(node_t *source, vpn_packet_t *packet) {
 623         if(!checklength(source, packet, ether_size + ip_size)) {
 624                 return;
 625         }
 626
 627         subnet_t *subnet;
 628         node_t *via;
 629         ipv4_t dest;
 630
 631         memcpy(&dest, &DATA(packet)[30], sizeof(dest));
 632         subnet = lookup_subnet_ipv4(&dest);
 633
 634         if(!subnet) {
 635                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d",
 636                        source->name, source->hostname,
 637                        dest.x[0],
 638                        dest.x[1],
 639                        dest.x[2],
 640                        dest.x[3]);
 641
 642                 route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 643                 return;
 644         }
 645
 646         if(!subnet->owner) {
 647                 route_broadcast(source, packet);
 648                 return;
 649         }
 650
 651         if(subnet->owner == source) {
 652                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 653                 return;
 654         }
 655
 656         if(!subnet->owner->status.reachable) {
 657                 route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 658                 return;
 659         }
 660
 661         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself) {
 662                 route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 663                 return;
 664         }
 665
 666         if(decrement_ttl && source != myself && subnet->owner != myself)
 667                 if(!do_decrement_ttl(source, packet)) {
 668                         return;
 669                 }
 670
 671         if(priorityinheritance) {
 672                 packet->priority = DATA(packet)[15];
 673         }
 674
 675         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 676
 677         if(via == source) {
 678                 logger(DEBUG_TRAFFIC, LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 679                 return;
 680         }
 681
 682         if(directonly && subnet->owner != via) {
 683                 route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 684                 return;
 685         }
 686
 687         if(via && packet->len > MAX(via->mtu, 590) && via != myself) {
 688                 logger(DEBUG_TRAFFIC, LOG_INFO, "Packet for %s (%s) length %d larger than MTU %d", subnet->owner->name, subnet->owner->hostname, packet->len, via->mtu);
 689
 690                 if(DATA(packet)[20] & 0x40) {
 691                         packet->len = MAX(via->mtu, 590);
 692                         route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 693                 } else {
 694                         fragment_ipv4_packet(via, packet, ether_size);
 695                 }
 696
 697                 return;
 698         }
 699
 700         clamp_mss(source, via, packet);
 701
 702         send_packet(subnet->owner, packet);
 703 }
 704
 705 static void route_neighborsol(node_t *source, vpn_packet_t *packet);
 706
 707 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 708         if(!checklength(source, packet, ether_size + ip6_size)) {
 709                 return;
 710         }
 711
 712         if(DATA(packet)[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && DATA(packet)[54] == ND_NEIGHBOR_SOLICIT) {
 713                 route_neighborsol(source, packet);
 714                 return;
 715         }
 716
 717         subnet_t *subnet;
 718         node_t *via;
 719         ipv6_t dest;
 720
 721         memcpy(&dest, &DATA(packet)[38], sizeof(dest));
 722         subnet = lookup_subnet_ipv6(&dest);
 723
 724         if(!subnet) {
 725                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 726                        source->name, source->hostname,
 727                        ntohs(dest.x[0]),
 728                        ntohs(dest.x[1]),
 729                        ntohs(dest.x[2]),
 730                        ntohs(dest.x[3]),
 731                        ntohs(dest.x[4]),
 732                        ntohs(dest.x[5]),
 733                        ntohs(dest.x[6]),
 734                        ntohs(dest.x[7]));
 735
 736                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 737                 return;
 738         }
 739
 740         if(!subnet->owner) {
 741                 route_broadcast(source, packet);
 742                 return;
 743         }
 744
 745         if(subnet->owner == source) {
 746                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 747                 return;
 748         }
 749
 750         if(!subnet->owner->status.reachable) {
 751                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 752                 return;
 753         }
 754
 755         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself) {
 756                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 757                 return;
 758         }
 759
 760         if(decrement_ttl && source != myself && subnet->owner != myself)
 761                 if(!do_decrement_ttl(source, packet)) {
 762                         return;
 763                 }
 764
 765         if(priorityinheritance) {
 766                 packet->priority = ((DATA(packet)[14] & 0x0f) << 4) | (DATA(packet)[15] >> 4);
 767         }
 768
 769         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 770
 771         if(via == source) {
 772                 logger(DEBUG_TRAFFIC, LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 773                 return;
 774         }
 775
 776         if(directonly && subnet->owner != via) {
 777                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 778                 return;
 779         }
 780
 781         if(via && packet->len > MAX(via->mtu, 1294) && via != myself) {
 782                 logger(DEBUG_TRAFFIC, LOG_INFO, "Packet for %s (%s) length %d larger than MTU %d", subnet->owner->name, subnet->owner->hostname, packet->len, via->mtu);
 783                 packet->len = MAX(via->mtu, 1294);
 784                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_PACKET_TOO_BIG, 0);
 785                 return;
 786         }
 787
 788         clamp_mss(source, via, packet);
 789
 790         send_packet(subnet->owner, packet);
 791 }
 792
 793 /* RFC 2461 */
 794
 795 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 796         struct ip6_hdr ip6;
 797         struct nd_neighbor_solicit ns;
 798         struct nd_opt_hdr opt;
 799         subnet_t *subnet;
 800         uint16_t checksum;
 801         bool has_opt;
 802
 803         struct {
 804                 struct in6_addr ip6_src;
 805                 struct in6_addr ip6_dst;
 806                 uint32_t length;
 807                 uint32_t next;
 808         } pseudo;
 809
 810         if(!checklength(source, packet, ether_size + ip6_size + ns_size)) {
 811                 return;
 812         }
 813
 814         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 815
 816         if(source != myself) {
 817                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname);
 818                 return;
 819         }
 820
 821         /* Copy headers from packet to structs on the stack */
 822
 823         memcpy(&ip6, DATA(packet) + ether_size, ip6_size);
 824         memcpy(&ns, DATA(packet) + ether_size + ip6_size, ns_size);
 825
 826         if(has_opt) {
 827                 memcpy(&opt, DATA(packet) + ether_size + ip6_size + ns_size, opt_size);
 828         }
 829
 830         /* First, snatch the source address from the neighbor solicitation packet */
 831
 832         if(overwrite_mac) {
 833                 memcpy(mymac.x, DATA(packet) + ETH_ALEN, ETH_ALEN);
 834         }
 835
 836         /* Check if this is a valid neighbor solicitation request */
 837
 838         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 839                         (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 840                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request");
 841                 return;
 842         }
 843
 844         /* Create pseudo header */
 845
 846         pseudo.ip6_src = ip6.ip6_src;
 847         pseudo.ip6_dst = ip6.ip6_dst;
 848
 849         if(has_opt) {
 850                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 851         } else {
 852                 pseudo.length = htonl(ns_size);
 853         }
 854
 855         pseudo.next = htonl(IPPROTO_ICMPV6);
 856
 857         /* Generate checksum */
 858
 859         checksum = inet_checksum(&pseudo, sizeof(pseudo), 0xFFFF);
 860         checksum = inet_checksum(&ns, ns_size, checksum);
 861
 862         if(has_opt) {
 863                 checksum = inet_checksum(&opt, opt_size, checksum);
 864                 checksum = inet_checksum(DATA(packet) + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 865         }
 866
 867         if(checksum) {
 868                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request");
 869                 return;
 870         }
 871
 872         /* Check if the IPv6 address exists on the VPN */
 873
 874         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 875
 876         if(!subnet) {
 877                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 878                        ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 879                        ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 880                        ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 881                        ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 882                        ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 883                        ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 884                        ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 885                        ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 886
 887                 return;
 888         }
 889
 890         /* Check if it is for our own subnet */
 891
 892         if(subnet->owner == myself) {
 893                 return;        /* silently ignore */
 894         }
 895
 896         if(decrement_ttl)
 897                 if(!do_decrement_ttl(source, packet)) {
 898                         return;
 899                 }
 900
 901         /* Create neighbor advertation reply */
 902
 903         memcpy(DATA(packet), DATA(packet) + ETH_ALEN, ETH_ALEN); /* copy destination address */
 904         DATA(packet)[ETH_ALEN * 2 - 1] ^= 0xFF;                  /* mangle source address so it looks like it's not from us */
 905
 906         ip6.ip6_dst = ip6.ip6_src;                               /* swap destination and source protocol address */
 907         ip6.ip6_src = ns.nd_ns_target;
 908
 909         if(has_opt) {
 910                 memcpy(DATA(packet) + ether_size + ip6_size + ns_size + opt_size, DATA(packet) + ETH_ALEN, ETH_ALEN);        /* add fake source hard addr */
 911         }
 912
 913         ns.nd_ns_cksum = 0;
 914         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 915         ns.nd_ns_reserved = htonl(0x40000000UL);                 /* Set solicited flag */
 916         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 917
 918         /* Create pseudo header */
 919
 920         pseudo.ip6_src = ip6.ip6_src;
 921         pseudo.ip6_dst = ip6.ip6_dst;
 922
 923         if(has_opt) {
 924                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 925         } else {
 926                 pseudo.length = htonl(ns_size);
 927         }
 928
 929         pseudo.next = htonl(IPPROTO_ICMPV6);
 930
 931         /* Generate checksum */
 932
 933         checksum = inet_checksum(&pseudo, sizeof(pseudo), 0xFFFF);
 934         checksum = inet_checksum(&ns, ns_size, checksum);
 935
 936         if(has_opt) {
 937                 checksum = inet_checksum(&opt, opt_size, checksum);
 938                 checksum = inet_checksum(DATA(packet) + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 939         }
 940
 941         ns.nd_ns_hdr.icmp6_cksum = checksum;
 942
 943         /* Copy structs on stack back to packet */
 944
 945         memcpy(DATA(packet) + ether_size, &ip6, ip6_size);
 946         memcpy(DATA(packet) + ether_size + ip6_size, &ns, ns_size);
 947
 948         if(has_opt) {
 949                 memcpy(DATA(packet) + ether_size + ip6_size + ns_size, &opt, opt_size);
 950         }
 951
 952         send_packet(source, packet);
 953 }
 954
 955 /* RFC 826 */
 956
 957 static void route_arp(node_t *source, vpn_packet_t *packet) {
 958         struct ether_arp arp;
 959         subnet_t *subnet;
 960         struct in_addr addr;
 961
 962         if(!checklength(source, packet, ether_size + arp_size)) {
 963                 return;
 964         }
 965
 966         if(source != myself) {
 967                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname);
 968                 return;
 969         }
 970
 971         /* First, snatch the source address from the ARP packet */
 972
 973         if(overwrite_mac) {
 974                 memcpy(mymac.x, DATA(packet) + ETH_ALEN, ETH_ALEN);
 975         }
 976
 977         /* Copy headers from packet to structs on the stack */
 978
 979         memcpy(&arp, DATA(packet) + ether_size, arp_size);
 980
 981         /* Check if this is a valid ARP request */
 982
 983         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 984                         arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof(addr) || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 985                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: received unknown type ARP request");
 986                 return;
 987         }
 988
 989         /* Check if the IPv4 address exists on the VPN */
 990
 991         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 992
 993         if(!subnet) {
 994                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d",
 995                        arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 996                        arp.arp_tpa[3]);
 997                 return;
 998         }
 999
1000         /* Check if it is for our own subnet */
1001
1002         if(subnet->owner == myself) {
1003                 return;        /* silently ignore */
1004         }
1005
1006         if(decrement_ttl)
1007                 if(!do_decrement_ttl(source, packet)) {
1008                         return;
1009                 }
1010
1011         memcpy(&addr, arp.arp_tpa, sizeof(addr));                 /* save protocol addr */
1012         memcpy(arp.arp_tpa, arp.arp_spa, sizeof(addr));           /* swap destination and source protocol address */
1013         memcpy(arp.arp_spa, &addr, sizeof(addr));                 /* ... */
1014
1015         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);              /* set target hard/proto addr */
1016         memcpy(arp.arp_sha, DATA(packet) + ETH_ALEN, ETH_ALEN);  /* set source hard/proto addr */
1017         arp.arp_sha[ETH_ALEN - 1] ^= 0xFF;                       /* for consistency with route_packet() */
1018         arp.arp_op = htons(ARPOP_REPLY);
1019
1020         /* Copy structs on stack back to packet */
1021
1022         memcpy(DATA(packet) + ether_size, &arp, arp_size);
1023
1024         send_packet(source, packet);
1025 }
1026
1027 static void route_mac(node_t *source, vpn_packet_t *packet) {
1028         subnet_t *subnet;
1029         mac_t dest;
1030
1031         /* Learn source address */
1032
1033         if(source == myself) {
1034                 mac_t src;
1035                 memcpy(&src, &DATA(packet)[6], sizeof(src));
1036                 learn_mac(&src);
1037         }
1038
1039         /* Lookup destination address */
1040
1041         memcpy(&dest, &DATA(packet)[0], sizeof(dest));
1042         subnet = lookup_subnet_mac(NULL, &dest);
1043
1044         if(!subnet || !subnet->owner) {
1045                 route_broadcast(source, packet);
1046                 return;
1047         }
1048
1049         if(subnet->owner == source) {
1050                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
1051                 return;
1052         }
1053
1054         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself) {
1055                 return;
1056         }
1057
1058         if(decrement_ttl && source != myself && subnet->owner != myself)
1059                 if(!do_decrement_ttl(source, packet)) {
1060                         return;
1061                 }
1062
1063         uint16_t type = DATA(packet)[12] << 8 | DATA(packet)[13];
1064
1065         if(priorityinheritance) {
1066                 if(type == ETH_P_IP && packet->len >= ether_size + ip_size) {
1067                         packet->priority = DATA(packet)[15];
1068                 } else if(type == ETH_P_IPV6 && packet->len >= ether_size + ip6_size) {
1069                         packet->priority = ((DATA(packet)[14] & 0x0f) << 4) | (DATA(packet)[15] >> 4);
1070                 }
1071         }
1072
1073         // Handle packets larger than PMTU
1074
1075         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
1076
1077         if(directonly && subnet->owner != via) {
1078                 return;
1079         }
1080
1081         if(via && packet->len > via->mtu && via != myself) {
1082                 logger(DEBUG_TRAFFIC, LOG_INFO, "Packet for %s (%s) length %d larger than MTU %d", subnet->owner->name, subnet->owner->hostname, packet->len, via->mtu);
1083                 length_t ethlen = 14;
1084
1085                 if(type == ETH_P_8021Q) {
1086                         type = DATA(packet)[16] << 8 | DATA(packet)[17];
1087                         ethlen += 4;
1088                 }
1089
1090                 if(type == ETH_P_IP && packet->len > 576 + ethlen) {
1091                         if(DATA(packet)[6 + ethlen] & 0x40) {
1092                                 packet->len = via->mtu;
1093                                 route_ipv4_unreachable(source, packet, ethlen, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
1094                         } else {
1095                                 fragment_ipv4_packet(via, packet, ethlen);
1096                         }
1097
1098                         return;
1099                 } else if(type == ETH_P_IPV6 && packet->len > 1280 + ethlen) {
1100                         packet->len = via->mtu;
1101                         route_ipv6_unreachable(source, packet, ethlen, ICMP6_PACKET_TOO_BIG, 0);
1102                         return;
1103                 }
1104         }
1105
1106         clamp_mss(source, via, packet);
1107
1108         send_packet(subnet->owner, packet);
1109 }
1110
1111 static void send_pcap(vpn_packet_t *packet) {
1112         pcap = false;
1113
1114         for list_each(connection_t, c, &connection_list) {
1115                 if(!c->status.pcap) {
1116                         continue;
1117                 }
1118
1119                 pcap = true;
1120                 int len = packet->len;
1121
1122                 if(c->outmaclength && c->outmaclength < len) {
1123                         len = c->outmaclength;
1124                 }
1125
1126                 if(send_request(c, "%d %d %d", CONTROL, REQ_PCAP, len)) {
1127                         send_meta(c, DATA(packet), len);
1128                 }
1129         }
1130 }
1131
1132 void route(node_t *source, vpn_packet_t *packet) {
1133         if(pcap) {
1134                 send_pcap(packet);
1135         }
1136
1137         if(forwarding_mode == FMODE_KERNEL && source != myself) {
1138                 send_packet(myself, packet);
1139                 return;
1140         }
1141
1142         if(!checklength(source, packet, ether_size)) {
1143                 return;
1144         }
1145
1146         uint16_t type = DATA(packet)[12] << 8 | DATA(packet)[13];
1147
1148         switch(routing_mode) {
1149         case RMODE_ROUTER:
1150                 switch(type) {
1151                 case ETH_P_ARP:
1152                         route_arp(source, packet);
1153                         break;
1154
1155                 case ETH_P_IP:
1156                         route_ipv4(source, packet);
1157                         break;
1158
1159                 case ETH_P_IPV6:
1160                         route_ipv6(source, packet);
1161                         break;
1162
1163                 default:
1164                         logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type);
1165                         break;
1166                 }
1167
1168                 break;
1169
1170         case RMODE_SWITCH:
1171                 route_mac(source, packet);
1172                 break;
1173
1174         case RMODE_HUB:
1175                 route_broadcast(source, packet);
1176                 break;
1177         }
1178 }