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