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 #include "utils.h"
  35
  36 rmode_t routing_mode = RMODE_ROUTER;
  37 fmode_t forwarding_mode = FMODE_INTERNAL;
  38 bmode_t broadcast_mode = BMODE_MST;
  39 bool decrement_ttl = false;
  40 bool directonly = false;
  41 bool priorityinheritance = false;
  42 int macexpire = 600;
  43 bool overwrite_mac = false;
  44 mac_t mymac = {{0xFE, 0xFD, 0, 0, 0, 0}};
  45 bool pcap = false;
  46
  47 /* Sizes of various headers */
  48
  49 static const size_t ether_size = sizeof(struct ether_header);
  50 static const size_t arp_size = sizeof(struct ether_arp);
  51 static const size_t ip_size = sizeof(struct ip);
  52 static const size_t icmp_size = sizeof(struct icmp) - sizeof(struct ip);
  53 static const size_t ip6_size = sizeof(struct ip6_hdr);
  54 static const size_t icmp6_size = sizeof(struct icmp6_hdr);
  55 static const size_t ns_size = sizeof(struct nd_neighbor_solicit);
  56 static const size_t opt_size = sizeof(struct nd_opt_hdr);
  57
  58 #ifndef MAX
  59 #define MAX(a, b) ((a) > (b) ? (a) : (b))
  60 #endif
  61
  62 volatile int dummy;
  63 static timeout_t age_subnets_timeout;
  64
  65 /* RFC 1071 */
  66
  67 static uint16_t inet_checksum(void *data, int len, uint16_t prevsum) {
  68         uint16_t *p = data;
  69         uint32_t checksum = prevsum ^ 0xFFFF;
  70
  71         while(len >= 2) {
  72                 checksum += *p++;
  73                 len -= 2;
  74         }
  75
  76         if(len) {
  77                 checksum += *(uint8_t *)p;
  78         }
  79
  80         while(checksum >> 16) {
  81                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
  82         }
  83
  84         // Work around a compiler optimization bug.
  85         if(checksum) {
  86                 dummy = 1;
  87         }
  88
  89         return ~checksum;
  90 }
  91
  92 static bool ratelimit(int frequency) {
  93         static time_t lasttime = 0;
  94         static int count = 0;
  95
  96         if(lasttime == now.tv_sec) {
  97                 if(count >= frequency) {
  98                         return true;
  99                 }
 100         } else {
 101                 lasttime = now.tv_sec;
 102                 count = 0;
 103         }
 104
 105         count++;
 106         return false;
 107 }
 108
 109 static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
 110         if(packet->len < length) {
 111                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Got too short packet from %s (%s)", source->name, source->hostname);
 112                 return false;
 113         } else {
 114                 return true;
 115         }
 116 }
 117
 118 static void swap_mac_addresses(vpn_packet_t *packet) {
 119         mac_t tmp;
 120         memcpy(&tmp, &DATA(packet)[0], sizeof(tmp));
 121         memcpy(&DATA(packet)[0], &DATA(packet)[6], sizeof(tmp));
 122         memcpy(&DATA(packet)[6], &tmp, sizeof(tmp));
 123 }
 124
 125 /* RFC 792 */
 126
 127 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, uint8_t type, uint8_t code) {
 128         struct ip ip = {0};
 129         struct icmp icmp = {0};
 130
 131         struct in_addr ip_src;
 132         struct in_addr ip_dst;
 133         uint32_t oldlen;
 134
 135         if(ratelimit(3)) {
 136                 return;
 137         }
 138
 139         /* Swap Ethernet source and destination addresses */
 140
 141         swap_mac_addresses(packet);
 142
 143         /* Copy headers from packet into properly aligned structs on the stack */
 144
 145         memcpy(&ip, DATA(packet) + ether_size, ip_size);
 146
 147         /* Remember original source and destination */
 148
 149         ip_src = ip.ip_src;
 150         ip_dst = ip.ip_dst;
 151
 152         /* Try to reply with an IP address assigned to the local machine */
 153
 154         if(type == ICMP_TIME_EXCEEDED && code == ICMP_EXC_TTL) {
 155                 int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
 156
 157                 if(sockfd != -1) {
 158                         struct sockaddr_in addr;
 159                         memset(&addr, 0, sizeof(addr));
 160                         addr.sin_family = AF_INET;
 161                         addr.sin_addr = ip.ip_src;
 162
 163                         if(!connect(sockfd, (const struct sockaddr *) &addr, sizeof(addr))) {
 164                                 memset(&addr, 0, sizeof(addr));
 165                                 addr.sin_family = AF_INET;
 166                                 socklen_t addrlen = sizeof(addr);
 167
 168                                 if(!getsockname(sockfd, (struct sockaddr *) &addr, &addrlen) && (size_t)addrlen <= sizeof(addr)) {
 169                                         ip_dst = addr.sin_addr;
 170                                 }
 171                         }
 172
 173                         close(sockfd);
 174                 }
 175         }
 176
 177         oldlen = packet->len - ether_size;
 178
 179         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) {
 180                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 181         }
 182
 183         if(oldlen >= IP_MSS - ip_size - icmp_size) {
 184                 oldlen = IP_MSS - ip_size - icmp_size;
 185         }
 186
 187         /* Copy first part of original contents to ICMP message */
 188
 189         memmove(DATA(packet) + ether_size + ip_size + icmp_size, DATA(packet) + ether_size, oldlen);
 190
 191         /* Fill in IPv4 header */
 192
 193         ip.ip_v = 4;
 194         ip.ip_hl = ip_size / 4;
 195         ip.ip_tos = 0;
 196         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 197         ip.ip_id = 0;
 198         ip.ip_off = 0;
 199         ip.ip_ttl = 255;
 200         ip.ip_p = IPPROTO_ICMP;
 201         ip.ip_sum = 0;
 202         ip.ip_src = ip_dst;
 203         ip.ip_dst = ip_src;
 204
 205         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 206
 207         /* Fill in ICMP header */
 208
 209         icmp.icmp_type = type;
 210         icmp.icmp_code = code;
 211         icmp.icmp_cksum = 0;
 212
 213         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 214         icmp.icmp_cksum = inet_checksum(DATA(packet) + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 215
 216         /* Copy structs on stack back to packet */
 217
 218         memcpy(DATA(packet) + ether_size, &ip, ip_size);
 219         memcpy(DATA(packet) + ether_size + ip_size, &icmp, icmp_size);
 220
 221         packet->len = ether_size + ip_size + icmp_size + oldlen;
 222
 223         send_packet(source, packet);
 224 }
 225
 226 /* RFC 2463 */
 227
 228 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, uint8_t type, uint8_t code) {
 229         struct ip6_hdr ip6;
 230         struct icmp6_hdr icmp6 = {0};
 231         uint16_t checksum;
 232
 233         struct {
 234                 struct in6_addr ip6_src;        /* source address */
 235                 struct in6_addr ip6_dst;        /* destination address */
 236                 uint32_t length;
 237                 uint32_t next;
 238         } pseudo;
 239
 240         if(ratelimit(3)) {
 241                 return;
 242         }
 243
 244         /* Swap Ethernet source and destination addresses */
 245
 246         swap_mac_addresses(packet);
 247
 248         /* Copy headers from packet to structs on the stack */
 249
 250         memcpy(&ip6, DATA(packet) + ether_size, ip6_size);
 251
 252         /* Remember original source and destination */
 253
 254         pseudo.ip6_src = ip6.ip6_dst;
 255         pseudo.ip6_dst = ip6.ip6_src;
 256
 257         /* Try to reply with an IP address assigned to the local machine */
 258
 259         if(type == ICMP6_TIME_EXCEEDED && code == ICMP6_TIME_EXCEED_TRANSIT) {
 260                 int sockfd = socket(AF_INET6, SOCK_DGRAM, 0);
 261
 262                 if(sockfd != -1) {
 263                         struct sockaddr_in6 addr;
 264                         memset(&addr, 0, sizeof(addr));
 265                         addr.sin6_family = AF_INET6;
 266                         addr.sin6_addr = ip6.ip6_src;
 267
 268                         if(!connect(sockfd, (const struct sockaddr *) &addr, sizeof(addr))) {
 269                                 memset(&addr, 0, sizeof(addr));
 270                                 addr.sin6_family = AF_INET6;
 271                                 socklen_t addrlen = sizeof(addr);
 272
 273                                 if(!getsockname(sockfd, (struct sockaddr *) &addr, &addrlen) && (size_t)addrlen <= sizeof(addr)) {
 274                                         pseudo.ip6_src = addr.sin6_addr;
 275                                 }
 276                         }
 277
 278                         close(sockfd);
 279                 }
 280         }
 281
 282         pseudo.length = packet->len - ether_size;
 283
 284         if(type == ICMP6_PACKET_TOO_BIG) {
 285                 icmp6.icmp6_mtu = htonl(pseudo.length);
 286         }
 287
 288         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size) {
 289                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 290         }
 291
 292         /* Copy first part of original contents to ICMP message */
 293
 294         memmove(DATA(packet) + ether_size + ip6_size + icmp6_size, DATA(packet) + ether_size, pseudo.length);
 295
 296         /* Fill in IPv6 header */
 297
 298         ip6.ip6_flow = htonl(0x60000000UL);
 299         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 300         ip6.ip6_nxt = IPPROTO_ICMPV6;
 301         ip6.ip6_hlim = 255;
 302         ip6.ip6_src = pseudo.ip6_src;
 303         ip6.ip6_dst = pseudo.ip6_dst;
 304
 305         /* Fill in ICMP header */
 306
 307         icmp6.icmp6_type = type;
 308         icmp6.icmp6_code = code;
 309         icmp6.icmp6_cksum = 0;
 310
 311         /* Create pseudo header */
 312
 313         pseudo.length = htonl(icmp6_size + pseudo.length);
 314         pseudo.next = htonl(IPPROTO_ICMPV6);
 315
 316         /* Generate checksum */
 317
 318         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 319         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 320         checksum = inet_checksum(DATA(packet) + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 321
 322         icmp6.icmp6_cksum = checksum;
 323
 324         /* Copy structs on stack back to packet */
 325
 326         memcpy(DATA(packet) + ether_size, &ip6, ip6_size);
 327         memcpy(DATA(packet) + ether_size + ip6_size, &icmp6, icmp6_size);
 328
 329         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 330
 331         send_packet(source, packet);
 332 }
 333
 334 static bool do_decrement_ttl(node_t *source, vpn_packet_t *packet) {
 335         uint16_t type = DATA(packet)[12] << 8 | DATA(packet)[13];
 336         length_t ethlen = ether_size;
 337
 338         if(type == ETH_P_8021Q) {
 339                 type = DATA(packet)[16] << 8 | DATA(packet)[17];
 340                 ethlen += 4;
 341         }
 342
 343         switch(type) {
 344         case ETH_P_IP:
 345                 if(!checklength(source, packet, ethlen + ip_size)) {
 346                         return false;
 347                 }
 348
 349                 if(DATA(packet)[ethlen + 8] <= 1) {
 350                         if(DATA(packet)[ethlen + 11] != IPPROTO_ICMP || DATA(packet)[ethlen + 32] != ICMP_TIME_EXCEEDED) {
 351                                 route_ipv4_unreachable(source, packet, ethlen, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL);
 352                         }
 353
 354                         return false;
 355                 }
 356
 357                 uint16_t old = DATA(packet)[ethlen + 8] << 8 | DATA(packet)[ethlen + 9];
 358                 DATA(packet)[ethlen + 8]--;
 359                 uint16_t new = DATA(packet)[ethlen + 8] << 8 | DATA(packet)[ethlen + 9];
 360
 361                 uint32_t checksum = DATA(packet)[ethlen + 10] << 8 | DATA(packet)[ethlen + 11];
 362                 checksum += old + (~new & 0xFFFF);
 363
 364                 while(checksum >> 16) {
 365                         checksum = (checksum & 0xFFFF) + (checksum >> 16);
 366                 }
 367
 368                 DATA(packet)[ethlen + 10] = checksum >> 8;
 369                 DATA(packet)[ethlen + 11] = checksum & 0xff;
 370
 371                 return true;
 372
 373         case ETH_P_IPV6:
 374                 if(!checklength(source, packet, ethlen + ip6_size)) {
 375                         return false;
 376                 }
 377
 378                 if(DATA(packet)[ethlen + 7] <= 1) {
 379                         if(DATA(packet)[ethlen + 6] != IPPROTO_ICMPV6 || DATA(packet)[ethlen + 40] != ICMP6_TIME_EXCEEDED) {
 380                                 route_ipv6_unreachable(source, packet, ethlen, ICMP6_TIME_EXCEEDED, ICMP6_TIME_EXCEED_TRANSIT);
 381                         }
 382
 383                         return false;
 384                 }
 385
 386                 DATA(packet)[ethlen + 7]--;
 387
 388                 return true;
 389
 390         default:
 391                 return true;
 392         }
 393 }
 394
 395 static void clamp_mss(const node_t *source, const node_t *via, vpn_packet_t *packet) {
 396         if(!source || !via || !(via->options & OPTION_CLAMP_MSS)) {
 397                 return;
 398         }
 399
 400         uint16_t mtu = source->mtu;
 401
 402         if(via != myself && via->mtu < mtu) {
 403                 mtu = via->mtu;
 404         }
 405
 406         /* Find TCP header */
 407         int start = ether_size;
 408         uint16_t type = DATA(packet)[12] << 8 | DATA(packet)[13];
 409
 410         if(type == ETH_P_8021Q) {
 411                 start += 4;
 412                 type = DATA(packet)[16] << 8 | DATA(packet)[17];
 413         }
 414
 415         /* IP in IP (RFC 2003) packet */
 416         if(type == ETH_P_IP && DATA(packet)[start + 9] == 4) {
 417                 start += 20;
 418         }
 419
 420         if(packet->len <= start + 20) {
 421                 return;
 422         }
 423
 424         if(type == ETH_P_IP && DATA(packet)[start + 9] == 6) {
 425                 start += (DATA(packet)[start] & 0xf) * 4;
 426         } else if(type == ETH_P_IPV6 && DATA(packet)[start + 6] == 6) {
 427                 start += 40;
 428         } else {
 429                 return;
 430         }
 431
 432         if(packet->len <= start + 20) {
 433                 return;
 434         }
 435
 436         /* Use data offset field to calculate length of options field */
 437         int len = ((DATA(packet)[start + 12] >> 4) - 5) * 4;
 438
 439         if(packet->len < start + 20 + len) {
 440                 return;
 441         }
 442
 443         /* Search for MSS option header */
 444         for(int i = 0; i < len;) {
 445                 if(DATA(packet)[start + 20 + i] == 0) {
 446                         break;
 447                 }
 448
 449                 if(DATA(packet)[start + 20 + i] == 1) {
 450                         i++;
 451                         continue;
 452                 }
 453
 454                 if(i > len - 2 || i > len - DATA(packet)[start + 21 + i]) {
 455                         break;
 456                 }
 457
 458                 if(DATA(packet)[start + 20 + i] != 2) {
 459                         if(DATA(packet)[start + 21 + i] < 2) {
 460                                 break;
 461                         }
 462
 463                         i += DATA(packet)[start + 21 + i];
 464                         continue;
 465                 }
 466
 467                 if(DATA(packet)[start + 21] != 4) {
 468                         break;
 469                 }
 470
 471                 /* Found it */
 472                 uint16_t oldmss = DATA(packet)[start + 22 + i] << 8 | DATA(packet)[start + 23 + i];
 473                 uint16_t newmss = mtu - start - 20;
 474                 uint32_t csum = DATA(packet)[start + 16] << 8 | DATA(packet)[start + 17];
 475
 476                 if(oldmss <= newmss) {
 477                         break;
 478                 }
 479
 480                 logger(DEBUG_TRAFFIC, LOG_INFO, "Clamping MSS of packet from %s to %s to %d", source->name, via->name, newmss);
 481
 482                 /* Update the MSS value and the checksum */
 483                 DATA(packet)[start + 22 + i] = newmss >> 8;
 484                 DATA(packet)[start + 23 + i] = newmss & 0xff;
 485                 csum ^= 0xffff;
 486                 csum += oldmss ^ 0xffff;
 487                 csum += newmss;
 488                 csum = (csum & 0xffff) + (csum >> 16);
 489                 csum += csum >> 16;
 490                 csum ^= 0xffff;
 491                 DATA(packet)[start + 16] = csum >> 8;
 492                 DATA(packet)[start + 17] = csum;
 493                 break;
 494         }
 495 }
 496
 497 static void age_subnets(void *data) {
 498         (void)data;
 499         bool left = false;
 500
 501         for splay_each(subnet_t, s, myself->subnet_tree) {
 502                 if(s->expires && s->expires < now.tv_sec) {
 503                         if(debug_level >= DEBUG_TRAFFIC) {
 504                                 char netstr[MAXNETSTR];
 505
 506                                 if(net2str(netstr, sizeof(netstr), s)) {
 507                                         logger(DEBUG_TRAFFIC, LOG_INFO, "Subnet %s expired", netstr);
 508                                 }
 509                         }
 510
 511                         for list_each(connection_t, c, connection_list)
 512                                 if(c->edge) {
 513                                         send_del_subnet(c, s);
 514                                 }
 515
 516                         subnet_del(myself, s);
 517                 } else {
 518                         if(s->expires) {
 519                                 left = true;
 520                         }
 521                 }
 522         }
 523
 524         if(left)
 525                 timeout_set(&age_subnets_timeout, &(struct timeval) {
 526                 10, rand() % 100000
 527         });
 528 }
 529
 530 static void learn_mac(mac_t *address) {
 531         subnet_t *subnet = lookup_subnet_mac(myself, address);
 532
 533         /* If we don't know this MAC address yet, store it */
 534
 535         if(!subnet) {
 536                 logger(DEBUG_TRAFFIC, LOG_INFO, "Learned new MAC address %x:%x:%x:%x:%x:%x",
 537                        address->x[0], address->x[1], address->x[2], address->x[3],
 538                        address->x[4], address->x[5]);
 539
 540                 subnet = new_subnet();
 541                 subnet->type = SUBNET_MAC;
 542                 subnet->expires = now.tv_sec + macexpire;
 543                 subnet->net.mac.address = *address;
 544                 subnet->weight = 10;
 545                 subnet_add(myself, subnet);
 546                 subnet_update(myself, subnet, true);
 547
 548                 /* And tell all other tinc daemons it's our MAC */
 549
 550                 for list_each(connection_t, c, connection_list)
 551                         if(c->edge) {
 552                                 send_add_subnet(c, subnet);
 553                         }
 554
 555                 timeout_add(&age_subnets_timeout, age_subnets, NULL, &(struct timeval) {
 556                         10, rand() % 100000
 557                 });
 558         } else {
 559                 if(subnet->expires) {
 560                         subnet->expires = now.tv_sec + macexpire;
 561                 }
 562         }
 563 }
 564
 565 static void route_broadcast(node_t *source, vpn_packet_t *packet) {
 566         if(decrement_ttl && source != myself)
 567                 if(!do_decrement_ttl(source, packet)) {
 568                         return;
 569                 }
 570
 571         broadcast_packet(source, packet);
 572 }
 573
 574 /* RFC 791 */
 575
 576 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet, length_t ether_size) {
 577         struct ip ip;
 578         vpn_packet_t fragment;
 579         int maxlen, todo;
 580         uint8_t *offset;
 581         uint16_t ip_off, origf;
 582
 583         memcpy(&ip, DATA(packet) + ether_size, ip_size);
 584         fragment.priority = packet->priority;
 585         fragment.offset = DEFAULT_PACKET_OFFSET;
 586
 587         if(ip.ip_hl != ip_size / 4) {
 588                 return;
 589         }
 590
 591         todo = ntohs(ip.ip_len) - ip_size;
 592
 593         if(ether_size + ip_size + todo != packet->len) {
 594                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Length of packet (%d) doesn't match length in IPv4 header (%d)", packet->len, (int)(ether_size + ip_size + todo));
 595                 return;
 596         }
 597
 598         logger(DEBUG_TRAFFIC, LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname);
 599
 600         offset = DATA(packet) + ether_size + ip_size;
 601         maxlen = (MAX(dest->mtu, 590) - ether_size - ip_size) & ~0x7;
 602         ip_off = ntohs(ip.ip_off);
 603         origf = ip_off & ~IP_OFFMASK;
 604         ip_off &= IP_OFFMASK;
 605
 606         while(todo) {
 607                 int len = todo > maxlen ? maxlen : todo;
 608                 memcpy(DATA(&fragment) + ether_size + ip_size, offset, len);
 609                 todo -= len;
 610                 offset += len;
 611
 612                 ip.ip_len = htons(ip_size + len);
 613                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 614                 ip.ip_sum = 0;
 615                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 616                 memcpy(DATA(&fragment), DATA(packet), ether_size);
 617                 memcpy(DATA(&fragment) + ether_size, &ip, ip_size);
 618                 fragment.len = ether_size + ip_size + len;
 619
 620                 send_packet(dest, &fragment);
 621
 622                 ip_off += len / 8;
 623         }
 624 }
 625
 626 static void route_ipv4(node_t *source, vpn_packet_t *packet) {
 627         if(!checklength(source, packet, ether_size + ip_size)) {
 628                 return;
 629         }
 630
 631         subnet_t *subnet;
 632         node_t *via;
 633         ipv4_t dest;
 634
 635         memcpy(&dest, &DATA(packet)[30], sizeof(dest));
 636         subnet = lookup_subnet_ipv4(&dest);
 637
 638         if(!subnet) {
 639                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d",
 640                        source->name, source->hostname,
 641                        dest.x[0],
 642                        dest.x[1],
 643                        dest.x[2],
 644                        dest.x[3]);
 645
 646                 route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 647                 return;
 648         }
 649
 650         if(!subnet->owner) {
 651                 route_broadcast(source, packet);
 652                 return;
 653         }
 654
 655         if(subnet->owner == source) {
 656                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 657                 return;
 658         }
 659
 660         if(!subnet->owner->status.reachable) {
 661                 route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 662                 return;
 663         }
 664
 665         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself) {
 666                 route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 667                 return;
 668         }
 669
 670         if(decrement_ttl && source != myself && subnet->owner != myself)
 671                 if(!do_decrement_ttl(source, packet)) {
 672                         return;
 673                 }
 674
 675         if(priorityinheritance) {
 676                 packet->priority = DATA(packet)[15];
 677         }
 678
 679         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 680
 681         if(via == source) {
 682                 logger(DEBUG_TRAFFIC, LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 683                 return;
 684         }
 685
 686         if(directonly && subnet->owner != via) {
 687                 route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 688                 return;
 689         }
 690
 691         if(via && packet->len > MAX(via->mtu, 590) && via != myself) {
 692                 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);
 693
 694                 if(DATA(packet)[20] & 0x40) {
 695                         packet->len = MAX(via->mtu, 590);
 696                         route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 697                 } else {
 698                         fragment_ipv4_packet(via, packet, ether_size);
 699                 }
 700
 701                 return;
 702         }
 703
 704         clamp_mss(source, via, packet);
 705
 706         send_packet(subnet->owner, packet);
 707 }
 708
 709 static void route_neighborsol(node_t *source, vpn_packet_t *packet);
 710
 711 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 712         if(!checklength(source, packet, ether_size + ip6_size)) {
 713                 return;
 714         }
 715
 716         if(DATA(packet)[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && DATA(packet)[54] == ND_NEIGHBOR_SOLICIT) {
 717                 route_neighborsol(source, packet);
 718                 return;
 719         }
 720
 721         subnet_t *subnet;
 722         node_t *via;
 723         ipv6_t dest;
 724
 725         memcpy(&dest, &DATA(packet)[38], sizeof(dest));
 726         subnet = lookup_subnet_ipv6(&dest);
 727
 728         if(!subnet) {
 729                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 730                        source->name, source->hostname,
 731                        ntohs(dest.x[0]),
 732                        ntohs(dest.x[1]),
 733                        ntohs(dest.x[2]),
 734                        ntohs(dest.x[3]),
 735                        ntohs(dest.x[4]),
 736                        ntohs(dest.x[5]),
 737                        ntohs(dest.x[6]),
 738                        ntohs(dest.x[7]));
 739
 740                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 741                 return;
 742         }
 743
 744         if(!subnet->owner) {
 745                 route_broadcast(source, packet);
 746                 return;
 747         }
 748
 749         if(subnet->owner == source) {
 750                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 751                 return;
 752         }
 753
 754         if(!subnet->owner->status.reachable) {
 755                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 756                 return;
 757         }
 758
 759         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself) {
 760                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 761                 return;
 762         }
 763
 764         if(decrement_ttl && source != myself && subnet->owner != myself)
 765                 if(!do_decrement_ttl(source, packet)) {
 766                         return;
 767                 }
 768
 769         if(priorityinheritance) {
 770                 packet->priority = ((DATA(packet)[14] & 0x0f) << 4) | (DATA(packet)[15] >> 4);
 771         }
 772
 773         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 774
 775         if(via == source) {
 776                 logger(DEBUG_TRAFFIC, LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 777                 return;
 778         }
 779
 780         if(directonly && subnet->owner != via) {
 781                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 782                 return;
 783         }
 784
 785         if(via && packet->len > MAX(via->mtu, 1294) && via != myself) {
 786                 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);
 787                 packet->len = MAX(via->mtu, 1294);
 788                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_PACKET_TOO_BIG, 0);
 789                 return;
 790         }
 791
 792         clamp_mss(source, via, packet);
 793
 794         send_packet(subnet->owner, packet);
 795 }
 796
 797 /* RFC 2461 */
 798
 799 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 800         struct ip6_hdr ip6;
 801         struct nd_neighbor_solicit ns;
 802         struct nd_opt_hdr opt;
 803         subnet_t *subnet;
 804         uint16_t checksum;
 805         bool has_opt;
 806
 807         struct {
 808                 struct in6_addr ip6_src;
 809                 struct in6_addr ip6_dst;
 810                 uint32_t length;
 811                 uint32_t next;
 812         } pseudo;
 813
 814         if(!checklength(source, packet, ether_size + ip6_size + ns_size)) {
 815                 return;
 816         }
 817
 818         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 819
 820         if(source != myself) {
 821                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname);
 822                 return;
 823         }
 824
 825         /* Copy headers from packet to structs on the stack */
 826
 827         memcpy(&ip6, DATA(packet) + ether_size, ip6_size);
 828         memcpy(&ns, DATA(packet) + ether_size + ip6_size, ns_size);
 829
 830         if(has_opt) {
 831                 memcpy(&opt, DATA(packet) + ether_size + ip6_size + ns_size, opt_size);
 832         }
 833
 834         /* First, snatch the source address from the neighbor solicitation packet */
 835
 836         if(overwrite_mac) {
 837                 memcpy(mymac.x, DATA(packet) + ETH_ALEN, ETH_ALEN);
 838         }
 839
 840         /* Check if this is a valid neighbor solicitation request */
 841
 842         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 843                         (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 844                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request");
 845                 return;
 846         }
 847
 848         /* Create pseudo header */
 849
 850         pseudo.ip6_src = ip6.ip6_src;
 851         pseudo.ip6_dst = ip6.ip6_dst;
 852
 853         if(has_opt) {
 854                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 855         } else {
 856                 pseudo.length = htonl(ns_size);
 857         }
 858
 859         pseudo.next = htonl(IPPROTO_ICMPV6);
 860
 861         /* Generate checksum */
 862
 863         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 864         checksum = inet_checksum(&ns, ns_size, checksum);
 865
 866         if(has_opt) {
 867                 checksum = inet_checksum(&opt, opt_size, checksum);
 868                 checksum = inet_checksum(DATA(packet) + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 869         }
 870
 871         if(checksum) {
 872                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request");
 873                 return;
 874         }
 875
 876         /* Check if the IPv6 address exists on the VPN */
 877
 878         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 879
 880         if(!subnet) {
 881                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 882                        ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 883                        ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 884                        ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 885                        ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 886                        ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 887                        ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 888                        ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 889                        ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 890
 891                 return;
 892         }
 893
 894         /* Check if it is for our own subnet */
 895
 896         if(subnet->owner == myself) {
 897                 return;        /* silently ignore */
 898         }
 899
 900         if(decrement_ttl)
 901                 if(!do_decrement_ttl(source, packet)) {
 902                         return;
 903                 }
 904
 905         /* Create neighbor advertation reply */
 906
 907         memcpy(DATA(packet), DATA(packet) + ETH_ALEN, ETH_ALEN); /* copy destination address */
 908         DATA(packet)[ETH_ALEN * 2 - 1] ^= 0xFF;                  /* mangle source address so it looks like it's not from us */
 909
 910         ip6.ip6_dst = ip6.ip6_src;                               /* swap destination and source protocol address */
 911         ip6.ip6_src = ns.nd_ns_target;
 912
 913         if(has_opt) {
 914                 memcpy(DATA(packet) + ether_size + ip6_size + ns_size + opt_size, DATA(packet) + ETH_ALEN, ETH_ALEN);        /* add fake source hard addr */
 915         }
 916
 917         ns.nd_ns_cksum = 0;
 918         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 919         ns.nd_ns_reserved = htonl(0x40000000UL);                 /* Set solicited flag */
 920         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 921
 922         /* Create pseudo header */
 923
 924         pseudo.ip6_src = ip6.ip6_src;
 925         pseudo.ip6_dst = ip6.ip6_dst;
 926
 927         if(has_opt) {
 928                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 929         } else {
 930                 pseudo.length = htonl(ns_size);
 931         }
 932
 933         pseudo.next = htonl(IPPROTO_ICMPV6);
 934
 935         /* Generate checksum */
 936
 937         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 938         checksum = inet_checksum(&ns, ns_size, checksum);
 939
 940         if(has_opt) {
 941                 checksum = inet_checksum(&opt, opt_size, checksum);
 942                 checksum = inet_checksum(DATA(packet) + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 943         }
 944
 945         ns.nd_ns_hdr.icmp6_cksum = checksum;
 946
 947         /* Copy structs on stack back to packet */
 948
 949         memcpy(DATA(packet) + ether_size, &ip6, ip6_size);
 950         memcpy(DATA(packet) + ether_size + ip6_size, &ns, ns_size);
 951
 952         if(has_opt) {
 953                 memcpy(DATA(packet) + ether_size + ip6_size + ns_size, &opt, opt_size);
 954         }
 955
 956         send_packet(source, packet);
 957 }
 958
 959 /* RFC 826 */
 960
 961 static void route_arp(node_t *source, vpn_packet_t *packet) {
 962         struct ether_arp arp;
 963         subnet_t *subnet;
 964         struct in_addr addr;
 965
 966         if(!checklength(source, packet, ether_size + arp_size)) {
 967                 return;
 968         }
 969
 970         if(source != myself) {
 971                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname);
 972                 return;
 973         }
 974
 975         /* First, snatch the source address from the ARP packet */
 976
 977         if(overwrite_mac) {
 978                 memcpy(mymac.x, DATA(packet) + ETH_ALEN, ETH_ALEN);
 979         }
 980
 981         /* Copy headers from packet to structs on the stack */
 982
 983         memcpy(&arp, DATA(packet) + ether_size, arp_size);
 984
 985         /* Check if this is a valid ARP request */
 986
 987         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 988                         arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof(addr) || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 989                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: received unknown type ARP request");
 990                 return;
 991         }
 992
 993         /* Check if the IPv4 address exists on the VPN */
 994
 995         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 996
 997         if(!subnet) {
 998                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d",
 999                        arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
1000                        arp.arp_tpa[3]);
1001                 return;
1002         }
1003
1004         /* Check if it is for our own subnet */
1005
1006         if(subnet->owner == myself) {
1007                 return;        /* silently ignore */
1008         }
1009
1010         if(decrement_ttl)
1011                 if(!do_decrement_ttl(source, packet)) {
1012                         return;
1013                 }
1014
1015         memcpy(&addr, arp.arp_tpa, sizeof(addr));                 /* save protocol addr */
1016         memcpy(arp.arp_tpa, arp.arp_spa, sizeof(addr));           /* swap destination and source protocol address */
1017         memcpy(arp.arp_spa, &addr, sizeof(addr));                 /* ... */
1018
1019         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);              /* set target hard/proto addr */
1020         memcpy(arp.arp_sha, DATA(packet) + ETH_ALEN, ETH_ALEN);  /* set source hard/proto addr */
1021         arp.arp_sha[ETH_ALEN - 1] ^= 0xFF;                       /* for consistency with route_packet() */
1022         arp.arp_op = htons(ARPOP_REPLY);
1023
1024         /* Copy structs on stack back to packet */
1025
1026         memcpy(DATA(packet) + ether_size, &arp, arp_size);
1027
1028         send_packet(source, packet);
1029 }
1030
1031 static void route_mac(node_t *source, vpn_packet_t *packet) {
1032         subnet_t *subnet;
1033         mac_t dest;
1034
1035         /* Learn source address */
1036
1037         if(source == myself) {
1038                 mac_t src;
1039                 memcpy(&src, &DATA(packet)[6], sizeof(src));
1040                 learn_mac(&src);
1041         }
1042
1043         /* Lookup destination address */
1044
1045         memcpy(&dest, &DATA(packet)[0], sizeof(dest));
1046         subnet = lookup_subnet_mac(NULL, &dest);
1047
1048         if(!subnet || !subnet->owner) {
1049                 route_broadcast(source, packet);
1050                 return;
1051         }
1052
1053         if(subnet->owner == source) {
1054                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
1055                 return;
1056         }
1057
1058         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself) {
1059                 return;
1060         }
1061
1062         if(decrement_ttl && source != myself && subnet->owner != myself)
1063                 if(!do_decrement_ttl(source, packet)) {
1064                         return;
1065                 }
1066
1067         uint16_t type = DATA(packet)[12] << 8 | DATA(packet)[13];
1068
1069         if(priorityinheritance) {
1070                 if(type == ETH_P_IP && packet->len >= ether_size + ip_size) {
1071                         packet->priority = DATA(packet)[15];
1072                 } else if(type == ETH_P_IPV6 && packet->len >= ether_size + ip6_size) {
1073                         packet->priority = ((DATA(packet)[14] & 0x0f) << 4) | (DATA(packet)[15] >> 4);
1074                 }
1075         }
1076
1077         // Handle packets larger than PMTU
1078
1079         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
1080
1081         if(directonly && subnet->owner != via) {
1082                 return;
1083         }
1084
1085         if(via && packet->len > via->mtu && via != myself) {
1086                 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);
1087                 length_t ethlen = 14;
1088
1089                 if(type == ETH_P_8021Q) {
1090                         type = DATA(packet)[16] << 8 | DATA(packet)[17];
1091                         ethlen += 4;
1092                 }
1093
1094                 if(type == ETH_P_IP && packet->len > 576 + ethlen) {
1095                         if(DATA(packet)[6 + ethlen] & 0x40) {
1096                                 packet->len = via->mtu;
1097                                 route_ipv4_unreachable(source, packet, ethlen, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
1098                         } else {
1099                                 fragment_ipv4_packet(via, packet, ethlen);
1100                         }
1101
1102                         return;
1103                 } else if(type == ETH_P_IPV6 && packet->len > 1280 + ethlen) {
1104                         packet->len = via->mtu;
1105                         route_ipv6_unreachable(source, packet, ethlen, ICMP6_PACKET_TOO_BIG, 0);
1106                         return;
1107                 }
1108         }
1109
1110         clamp_mss(source, via, packet);
1111
1112         send_packet(subnet->owner, packet);
1113 }
1114
1115 static void send_pcap(vpn_packet_t *packet) {
1116         pcap = false;
1117
1118         for list_each(connection_t, c, connection_list) {
1119                 if(!c->status.pcap) {
1120                         continue;
1121                 }
1122
1123                 pcap = true;
1124                 int len = packet->len;
1125
1126                 if(c->outmaclength && c->outmaclength < len) {
1127                         len = c->outmaclength;
1128                 }
1129
1130                 if(send_request(c, "%d %d %d", CONTROL, REQ_PCAP, len)) {
1131                         send_meta(c, (char *)DATA(packet), len);
1132                 }
1133         }
1134 }
1135
1136 void route(node_t *source, vpn_packet_t *packet) {
1137         if(pcap) {
1138                 send_pcap(packet);
1139         }
1140
1141         if(forwarding_mode == FMODE_KERNEL && source != myself) {
1142                 send_packet(myself, packet);
1143                 return;
1144         }
1145
1146         if(!checklength(source, packet, ether_size)) {
1147                 return;
1148         }
1149
1150         uint16_t type = DATA(packet)[12] << 8 | DATA(packet)[13];
1151
1152         switch(routing_mode) {
1153         case RMODE_ROUTER:
1154                 switch(type) {
1155                 case ETH_P_ARP:
1156                         route_arp(source, packet);
1157                         break;
1158
1159                 case ETH_P_IP:
1160                         route_ipv4(source, packet);
1161                         break;
1162
1163                 case ETH_P_IPV6:
1164                         route_ipv6(source, packet);
1165                         break;
1166
1167                 default:
1168                         logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type);
1169                         break;
1170                 }
1171
1172                 break;
1173
1174         case RMODE_SWITCH:
1175                 route_mac(source, packet);
1176                 break;
1177
1178         case RMODE_HUB:
1179                 route_broadcast(source, packet);
1180                 break;
1181         }
1182 }