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

   1 /*
   2     route.c -- routing
   3     Copyright (C) 2000-2005 Ivo Timmermans,
   4                   2000-2017 Guus Sliepen <guus@tinc-vpn.org>
   5                   2015-2016 Vittorio Gambaletta
   6
   7     This program is free software; you can redistribute it and/or modify
   8     it under the terms of the GNU General Public License as published by
   9     the Free Software Foundation; either version 2 of the License, or
  10     (at your option) any later version.
  11
  12     This program is distributed in the hope that it will be useful,
  13     but WITHOUT ANY WARRANTY; without even the implied warranty of
  14     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15     GNU General Public License for more details.
  16
  17     You should have received a copy of the GNU General Public License along
  18     with this program; if not, write to the Free Software Foundation, Inc.,
  19     51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  20 */
  21
  22 #include "system.h"
  23
  24 #include "avl_tree.h"
  25 #include "connection.h"
  26 #include "ethernet.h"
  27 #include "ipv4.h"
  28 #include "ipv6.h"
  29 #include "logger.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
  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 /* RFC 1071 */
  62
  63 static uint16_t inet_checksum(void *data, int len, uint16_t prevsum) {
  64         uint16_t *p = data;
  65         uint32_t checksum = prevsum ^ 0xFFFF;
  66
  67         while(len >= 2) {
  68                 checksum += *p++;
  69                 len -= 2;
  70         }
  71
  72         if(len) {
  73                 checksum += *(uint8_t *)p;
  74         }
  75
  76         while(checksum >> 16) {
  77                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
  78         }
  79
  80         return ~checksum;
  81 }
  82
  83 static bool ratelimit(int frequency) {
  84         static time_t lasttime = 0;
  85         static int count = 0;
  86
  87         if(lasttime == now) {
  88                 if(count >= frequency) {
  89                         return true;
  90                 }
  91         } else {
  92                 lasttime = now;
  93                 count = 0;
  94         }
  95
  96         count++;
  97         return false;
  98 }
  99
 100 static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
 101         if(packet->len < length) {
 102                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got too short packet from %s (%s)", source->name, source->hostname);
 103                 return false;
 104         } else {
 105                 return true;
 106         }
 107 }
 108
 109 static void swap_mac_addresses(vpn_packet_t *packet) {
 110         mac_t tmp;
 111         memcpy(&tmp, &packet->data[0], sizeof(tmp));
 112         memcpy(&packet->data[0], &packet->data[6], sizeof(tmp));
 113         memcpy(&packet->data[6], &tmp, sizeof(tmp));
 114 }
 115
 116 /* RFC 792 */
 117
 118 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, uint8_t type, uint8_t code) {
 119         struct ip ip = {};
 120         struct icmp icmp = {};
 121
 122         struct in_addr ip_src;
 123         struct in_addr ip_dst;
 124         uint32_t oldlen;
 125
 126         if(ratelimit(3)) {
 127                 return;
 128         }
 129
 130         /* Swap Ethernet source and destination addresses */
 131
 132         swap_mac_addresses(packet);
 133
 134         /* Copy headers from packet into properly aligned structs on the stack */
 135
 136         memcpy(&ip, packet->data + ether_size, ip_size);
 137
 138         /* Remember original source and destination */
 139
 140         ip_src = ip.ip_src;
 141         ip_dst = ip.ip_dst;
 142
 143         /* Try to reply with an IP address assigned to the local machine */
 144
 145         if(type == ICMP_TIME_EXCEEDED && code == ICMP_EXC_TTL) {
 146                 int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
 147
 148                 if(sockfd != -1) {
 149                         struct sockaddr_in addr;
 150                         memset(&addr, 0, sizeof(addr));
 151                         addr.sin_family = AF_INET;
 152                         addr.sin_addr = ip.ip_src;
 153
 154                         if(!connect(sockfd, (const struct sockaddr *) &addr, sizeof(addr))) {
 155                                 memset(&addr, 0, sizeof(addr));
 156                                 addr.sin_family = AF_INET;
 157                                 socklen_t addrlen = sizeof(addr);
 158
 159                                 if(!getsockname(sockfd, (struct sockaddr *) &addr, &addrlen) && addrlen <= sizeof(addr)) {
 160                                         ip_dst = addr.sin_addr;
 161                                 }
 162                         }
 163
 164                         close(sockfd);
 165                 }
 166         }
 167
 168         oldlen = packet->len - ether_size;
 169
 170         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) {
 171                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 172         }
 173
 174         if(oldlen >= IP_MSS - ip_size - icmp_size) {
 175                 oldlen = IP_MSS - ip_size - icmp_size;
 176         }
 177
 178         /* Copy first part of original contents to ICMP message */
 179
 180         memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
 181
 182         /* Fill in IPv4 header */
 183
 184         ip.ip_v = 4;
 185         ip.ip_hl = ip_size / 4;
 186         ip.ip_tos = 0;
 187         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 188         ip.ip_id = 0;
 189         ip.ip_off = 0;
 190         ip.ip_ttl = 255;
 191         ip.ip_p = IPPROTO_ICMP;
 192         ip.ip_sum = 0;
 193         ip.ip_src = ip_dst;
 194         ip.ip_dst = ip_src;
 195
 196         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 197
 198         /* Fill in ICMP header */
 199
 200         icmp.icmp_type = type;
 201         icmp.icmp_code = code;
 202         icmp.icmp_cksum = 0;
 203
 204         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 205         icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 206
 207         /* Copy structs on stack back to packet */
 208
 209         memcpy(packet->data + ether_size, &ip, ip_size);
 210         memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
 211
 212         packet->len = ether_size + ip_size + icmp_size + oldlen;
 213
 214         send_packet(source, packet);
 215 }
 216
 217 /* RFC 2463 */
 218
 219 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, uint8_t type, uint8_t code) {
 220         struct ip6_hdr ip6;
 221         struct icmp6_hdr icmp6 = {};
 222         uint16_t checksum;
 223
 224         struct {
 225                 struct in6_addr ip6_src;        /* source address */
 226                 struct in6_addr ip6_dst;        /* destination address */
 227                 uint32_t length;
 228                 uint32_t next;
 229         } pseudo;
 230
 231         if(ratelimit(3)) {
 232                 return;
 233         }
 234
 235         /* Swap Ethernet source and destination addresses */
 236
 237         swap_mac_addresses(packet);
 238
 239         /* Copy headers from packet to structs on the stack */
 240
 241         memcpy(&ip6, packet->data + ether_size, ip6_size);
 242
 243         /* Remember original source and destination */
 244
 245         pseudo.ip6_src = ip6.ip6_dst;
 246         pseudo.ip6_dst = ip6.ip6_src;
 247
 248         /* Try to reply with an IP address assigned to the local machine */
 249
 250         if(type == ICMP6_TIME_EXCEEDED && code == ICMP6_TIME_EXCEED_TRANSIT) {
 251                 int sockfd = socket(AF_INET6, SOCK_DGRAM, 0);
 252
 253                 if(sockfd != -1) {
 254                         struct sockaddr_in6 addr;
 255                         memset(&addr, 0, sizeof(addr));
 256                         addr.sin6_family = AF_INET6;
 257                         addr.sin6_addr = ip6.ip6_src;
 258
 259                         if(!connect(sockfd, (const struct sockaddr *) &addr, sizeof(addr))) {
 260                                 memset(&addr, 0, sizeof(addr));
 261                                 addr.sin6_family = AF_INET6;
 262                                 socklen_t addrlen = sizeof(addr);
 263
 264                                 if(!getsockname(sockfd, (struct sockaddr *) &addr, &addrlen) && addrlen <= sizeof(addr)) {
 265                                         pseudo.ip6_src = addr.sin6_addr;
 266                                 }
 267                         }
 268
 269                         close(sockfd);
 270                 }
 271         }
 272
 273         pseudo.length = packet->len - ether_size;
 274
 275         if(type == ICMP6_PACKET_TOO_BIG) {
 276                 icmp6.icmp6_mtu = htonl(pseudo.length);
 277         }
 278
 279         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size) {
 280                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 281         }
 282
 283         /* Copy first part of original contents to ICMP message */
 284
 285         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 286
 287         /* Fill in IPv6 header */
 288
 289         ip6.ip6_flow = htonl(0x60000000UL);
 290         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 291         ip6.ip6_nxt = IPPROTO_ICMPV6;
 292         ip6.ip6_hlim = 255;
 293         ip6.ip6_src = pseudo.ip6_src;
 294         ip6.ip6_dst = pseudo.ip6_dst;
 295
 296         /* Fill in ICMP header */
 297
 298         icmp6.icmp6_type = type;
 299         icmp6.icmp6_code = code;
 300         icmp6.icmp6_cksum = 0;
 301
 302         /* Create pseudo header */
 303
 304         pseudo.length = htonl(icmp6_size + pseudo.length);
 305         pseudo.next = htonl(IPPROTO_ICMPV6);
 306
 307         /* Generate checksum */
 308
 309         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 310         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 311         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 312
 313         icmp6.icmp6_cksum = checksum;
 314
 315         /* Copy structs on stack back to packet */
 316
 317         memcpy(packet->data + ether_size, &ip6, ip6_size);
 318         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 319
 320         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 321
 322         send_packet(source, packet);
 323 }
 324
 325 static bool do_decrement_ttl(node_t *source, vpn_packet_t *packet) {
 326         uint16_t type = packet->data[12] << 8 | packet->data[13];
 327         length_t ethlen = ether_size;
 328
 329         if(type == ETH_P_8021Q) {
 330                 type = packet->data[16] << 8 | packet->data[17];
 331                 ethlen += 4;
 332         }
 333
 334         switch(type) {
 335         case ETH_P_IP:
 336                 if(!checklength(source, packet, ethlen + ip_size)) {
 337                         return false;
 338                 }
 339
 340                 if(packet->data[ethlen + 8] <= 1) {
 341                         if(packet->data[ethlen + 11] != IPPROTO_ICMP || packet->data[ethlen + 32] != ICMP_TIME_EXCEEDED) {
 342                                 route_ipv4_unreachable(source, packet, ethlen, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL);
 343                         }
 344
 345                         return false;
 346                 }
 347
 348                 uint16_t old = packet->data[ethlen + 8] << 8 | packet->data[ethlen + 9];
 349                 packet->data[ethlen + 8]--;
 350                 uint16_t new = packet->data[ethlen + 8] << 8 | packet->data[ethlen + 9];
 351
 352                 uint32_t checksum = packet->data[ethlen + 10] << 8 | packet->data[ethlen + 11];
 353                 checksum += old + (~new & 0xFFFF);
 354
 355                 while(checksum >> 16) {
 356                         checksum = (checksum & 0xFFFF) + (checksum >> 16);
 357                 }
 358
 359                 packet->data[ethlen + 10] = checksum >> 8;
 360                 packet->data[ethlen + 11] = checksum & 0xff;
 361
 362                 return true;
 363
 364         case ETH_P_IPV6:
 365                 if(!checklength(source, packet, ethlen + ip6_size)) {
 366                         return false;
 367                 }
 368
 369                 if(packet->data[ethlen + 7] <= 1) {
 370                         if(packet->data[ethlen + 6] != IPPROTO_ICMPV6 || packet->data[ethlen + 40] != ICMP6_TIME_EXCEEDED) {
 371                                 route_ipv6_unreachable(source, packet, ethlen, ICMP6_TIME_EXCEEDED, ICMP6_TIME_EXCEED_TRANSIT);
 372                         }
 373
 374                         return false;
 375                 }
 376
 377                 packet->data[ethlen + 7]--;
 378
 379                 return true;
 380
 381         default:
 382                 return true;
 383         }
 384 }
 385
 386 static void clamp_mss(const node_t *source, const node_t *via, vpn_packet_t *packet) {
 387         if(!source || !via || !(via->options & OPTION_CLAMP_MSS)) {
 388                 return;
 389         }
 390
 391         uint16_t mtu = source->mtu;
 392
 393         if(via != myself && via->mtu < mtu) {
 394                 mtu = via->mtu;
 395         }
 396
 397         /* Find TCP header */
 398         int start = ether_size;
 399         uint16_t type = packet->data[12] << 8 | packet->data[13];
 400
 401         if(type == ETH_P_8021Q) {
 402                 start += 4;
 403                 type = packet->data[16] << 8 | packet->data[17];
 404         }
 405
 406         if(type == ETH_P_IP && packet->data[start + 9] == 6) {
 407                 start += (packet->data[start] & 0xf) * 4;
 408         } else if(type == ETH_P_IPV6 && packet->data[start + 6] == 6) {
 409                 start += 40;
 410         } else {
 411                 return;
 412         }
 413
 414         if(packet->len <= start + 20) {
 415                 return;
 416         }
 417
 418         /* Use data offset field to calculate length of options field */
 419         int len = ((packet->data[start + 12] >> 4) - 5) * 4;
 420
 421         if(packet->len < start + 20 + len) {
 422                 return;
 423         }
 424
 425         /* Search for MSS option header */
 426         for(int i = 0; i < len;) {
 427                 if(packet->data[start + 20 + i] == 0) {
 428                         break;
 429                 }
 430
 431                 if(packet->data[start + 20 + i] == 1) {
 432                         i++;
 433                         continue;
 434                 }
 435
 436                 if(i > len - 2 || i > len - packet->data[start + 21 + i]) {
 437                         break;
 438                 }
 439
 440                 if(packet->data[start + 20 + i] != 2) {
 441                         if(packet->data[start + 21 + i] < 2) {
 442                                 break;
 443                         }
 444
 445                         i += packet->data[start + 21 + i];
 446                         continue;
 447                 }
 448
 449                 if(packet->data[start + 21] != 4) {
 450                         break;
 451                 }
 452
 453                 /* Found it */
 454                 uint16_t oldmss = packet->data[start + 22 + i] << 8 | packet->data[start + 23 + i];
 455                 uint16_t newmss = mtu - start - 20;
 456                 uint32_t csum = packet->data[start + 16] << 8 | packet->data[start + 17];
 457
 458                 if(oldmss <= newmss) {
 459                         break;
 460                 }
 461
 462                 ifdebug(TRAFFIC) logger(LOG_INFO, "Clamping MSS of packet from %s to %s to %d", source->name, via->name, newmss);
 463
 464                 /* Update the MSS value and the checksum */
 465                 packet->data[start + 22 + i] = newmss >> 8;
 466                 packet->data[start + 23 + i] = newmss & 0xff;
 467                 csum ^= 0xffff;
 468                 csum += oldmss ^ 0xffff;
 469                 csum += newmss;
 470                 csum = (csum & 0xffff) + (csum >> 16);
 471                 csum += csum >> 16;
 472                 csum ^= 0xffff;
 473                 packet->data[start + 16] = csum >> 8;
 474                 packet->data[start + 17] = csum;
 475                 break;
 476         }
 477 }
 478
 479 static void learn_mac(mac_t *address) {
 480         subnet_t *subnet;
 481         avl_node_t *node;
 482         connection_t *c;
 483
 484         subnet = lookup_subnet_mac(myself, address);
 485
 486         /* If we don't know this MAC address yet, store it */
 487
 488         if(!subnet) {
 489                 ifdebug(TRAFFIC) logger(LOG_INFO, "Learned new MAC address %x:%x:%x:%x:%x:%x",
 490                                         address->x[0], address->x[1], address->x[2], address->x[3],
 491                                         address->x[4], address->x[5]);
 492
 493                 subnet = new_subnet();
 494                 subnet->type = SUBNET_MAC;
 495                 subnet->expires = now + macexpire;
 496                 subnet->net.mac.address = *address;
 497                 subnet->weight = 10;
 498                 subnet_add(myself, subnet);
 499                 subnet_update(myself, subnet, true);
 500
 501                 /* And tell all other tinc daemons it's our MAC */
 502
 503                 for(node = connection_tree->head; node; node = node->next) {
 504                         c = node->data;
 505
 506                         if(c->status.active) {
 507                                 send_add_subnet(c, subnet);
 508                         }
 509                 }
 510         }
 511
 512         if(subnet->expires) {
 513                 subnet->expires = now + macexpire;
 514         }
 515 }
 516
 517 void age_subnets(void) {
 518         subnet_t *s;
 519         connection_t *c;
 520         avl_node_t *node, *next, *node2;
 521
 522         for(node = myself->subnet_tree->head; node; node = next) {
 523                 next = node->next;
 524                 s = node->data;
 525
 526                 if(s->expires && s->expires <= now) {
 527                         ifdebug(TRAFFIC) {
 528                                 char netstr[MAXNETSTR];
 529
 530                                 if(net2str(netstr, sizeof(netstr), s)) {
 531                                         logger(LOG_INFO, "Subnet %s expired", netstr);
 532                                 }
 533                         }
 534
 535                         for(node2 = connection_tree->head; node2; node2 = node2->next) {
 536                                 c = node2->data;
 537
 538                                 if(c->status.active) {
 539                                         send_del_subnet(c, s);
 540                                 }
 541                         }
 542
 543                         subnet_update(myself, s, false);
 544                         subnet_del(myself, s);
 545                 }
 546         }
 547 }
 548
 549 static void route_broadcast(node_t *source, vpn_packet_t *packet) {
 550         if(decrement_ttl && source != myself)
 551                 if(!do_decrement_ttl(source, packet)) {
 552                         return;
 553                 }
 554
 555         broadcast_packet(source, packet);
 556 }
 557
 558 /* RFC 791 */
 559
 560 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet, length_t ether_size) {
 561         struct ip ip;
 562         vpn_packet_t fragment;
 563         int len, maxlen, todo;
 564         uint8_t *offset;
 565         uint16_t ip_off, origf;
 566
 567         memcpy(&ip, packet->data + ether_size, ip_size);
 568         fragment.priority = packet->priority;
 569
 570         if(ip.ip_hl != ip_size / 4) {
 571                 return;
 572         }
 573
 574         todo = ntohs(ip.ip_len) - ip_size;
 575
 576         if(ether_size + ip_size + todo != packet->len) {
 577                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Length of packet (%d) doesn't match length in IPv4 header (%d)", packet->len, (int)(ether_size + ip_size + todo));
 578                 return;
 579         }
 580
 581         ifdebug(TRAFFIC) logger(LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname);
 582
 583         offset = packet->data + ether_size + ip_size;
 584         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 585         ip_off = ntohs(ip.ip_off);
 586         origf = ip_off & ~IP_OFFMASK;
 587         ip_off &= IP_OFFMASK;
 588
 589         while(todo) {
 590                 len = todo > maxlen ? maxlen : todo;
 591                 memcpy(fragment.data + ether_size + ip_size, offset, len);
 592                 todo -= len;
 593                 offset += len;
 594
 595                 ip.ip_len = htons(ip_size + len);
 596                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 597                 ip.ip_sum = 0;
 598                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 599                 memcpy(fragment.data, packet->data, ether_size);
 600                 memcpy(fragment.data + ether_size, &ip, ip_size);
 601                 fragment.len = ether_size + ip_size + len;
 602
 603                 send_packet(dest, &fragment);
 604
 605                 ip_off += len / 8;
 606         }
 607 }
 608
 609 static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet) {
 610         subnet_t *subnet;
 611         node_t *via;
 612         ipv4_t dest;
 613
 614         memcpy(&dest, &packet->data[30], sizeof(dest));
 615         subnet = lookup_subnet_ipv4(&dest);
 616
 617         if(!subnet) {
 618                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d",
 619                                         source->name, source->hostname,
 620                                         dest.x[0],
 621                                         dest.x[1],
 622                                         dest.x[2],
 623                                         dest.x[3]);
 624
 625                 route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 626                 return;
 627         }
 628
 629         if(subnet->owner == source) {
 630                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 631                 return;
 632         }
 633
 634         if(!subnet->owner->status.reachable) {
 635                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 636         }
 637
 638         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself) {
 639                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 640         }
 641
 642         if(decrement_ttl && source != myself && subnet->owner != myself)
 643                 if(!do_decrement_ttl(source, packet)) {
 644                         return;
 645                 }
 646
 647         if(priorityinheritance) {
 648                 packet->priority = packet->data[15];
 649         }
 650
 651         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 652
 653         if(via == source) {
 654                 ifdebug(TRAFFIC) logger(LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 655                 return;
 656         }
 657
 658         if(directonly && subnet->owner != via) {
 659                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 660         }
 661
 662         if(via && packet->len > MAX(via->mtu, 590) && via != myself) {
 663                 ifdebug(TRAFFIC) logger(LOG_INFO, "Packet for %s (%s) length %d larger than MTU %d", subnet->owner->name, subnet->owner->hostname, packet->len, via->mtu);
 664
 665                 if(packet->data[20] & 0x40) {
 666                         packet->len = MAX(via->mtu, 590);
 667                         route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 668                 } else {
 669                         fragment_ipv4_packet(via, packet, ether_size);
 670                 }
 671
 672                 return;
 673         }
 674
 675         clamp_mss(source, via, packet);
 676
 677         send_packet(subnet->owner, packet);
 678 }
 679
 680 static void route_ipv4(node_t *source, vpn_packet_t *packet) {
 681         if(!checklength(source, packet, ether_size + ip_size)) {
 682                 return;
 683         }
 684
 685         if(broadcast_mode && (((packet->data[30] & 0xf0) == 0xe0) || (
 686                                       packet->data[30] == 255 &&
 687                                       packet->data[31] == 255 &&
 688                                       packet->data[32] == 255 &&
 689                                       packet->data[33] == 255))) {
 690                 route_broadcast(source, packet);
 691         } else {
 692                 route_ipv4_unicast(source, packet);
 693         }
 694 }
 695
 696 static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet) {
 697         subnet_t *subnet;
 698         node_t *via;
 699         ipv6_t dest;
 700
 701         memcpy(&dest, &packet->data[38], sizeof(dest));
 702         subnet = lookup_subnet_ipv6(&dest);
 703
 704         if(!subnet) {
 705                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 706                                         source->name, source->hostname,
 707                                         ntohs(dest.x[0]),
 708                                         ntohs(dest.x[1]),
 709                                         ntohs(dest.x[2]),
 710                                         ntohs(dest.x[3]),
 711                                         ntohs(dest.x[4]),
 712                                         ntohs(dest.x[5]),
 713                                         ntohs(dest.x[6]),
 714                                         ntohs(dest.x[7]));
 715
 716                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 717                 return;
 718         }
 719
 720         if(subnet->owner == source) {
 721                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 722                 return;
 723         }
 724
 725         if(!subnet->owner->status.reachable) {
 726                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 727         }
 728
 729         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself) {
 730                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 731         }
 732
 733         if(decrement_ttl && source != myself && subnet->owner != myself)
 734                 if(!do_decrement_ttl(source, packet)) {
 735                         return;
 736                 }
 737
 738         if(priorityinheritance) {
 739                 packet->priority = ((packet->data[14] & 0x0f) << 4) | (packet->data[15] >> 4);
 740         }
 741
 742         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 743
 744         if(via == source) {
 745                 ifdebug(TRAFFIC) logger(LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 746                 return;
 747         }
 748
 749         if(directonly && subnet->owner != via) {
 750                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 751         }
 752
 753         if(via && packet->len > MAX(via->mtu, 1294) && via != myself) {
 754                 ifdebug(TRAFFIC) logger(LOG_INFO, "Packet for %s (%s) length %d larger than MTU %d", subnet->owner->name, subnet->owner->hostname, packet->len, via->mtu);
 755                 packet->len = MAX(via->mtu, 1294);
 756                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_PACKET_TOO_BIG, 0);
 757                 return;
 758         }
 759
 760         clamp_mss(source, via, packet);
 761
 762         send_packet(subnet->owner, packet);
 763 }
 764
 765 /* RFC 2461 */
 766
 767 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 768         struct ip6_hdr ip6;
 769         struct nd_neighbor_solicit ns;
 770         struct nd_opt_hdr opt;
 771         subnet_t *subnet;
 772         uint16_t checksum;
 773         bool has_opt;
 774
 775         struct {
 776                 struct in6_addr ip6_src;        /* source address */
 777                 struct in6_addr ip6_dst;        /* destination address */
 778                 uint32_t length;
 779                 uint32_t next;
 780         } pseudo;
 781
 782         if(!checklength(source, packet, ether_size + ip6_size + ns_size)) {
 783                 return;
 784         }
 785
 786         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 787
 788         if(source != myself) {
 789                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname);
 790                 return;
 791         }
 792
 793         /* Copy headers from packet to structs on the stack */
 794
 795         memcpy(&ip6, packet->data + ether_size, ip6_size);
 796         memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
 797
 798         if(has_opt) {
 799                 memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 800         }
 801
 802         /* First, snatch the source address from the neighbor solicitation packet */
 803
 804         if(overwrite_mac) {
 805                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 806         }
 807
 808         /* Check if this is a valid neighbor solicitation request */
 809
 810         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 811                         (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 812                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request");
 813                 return;
 814         }
 815
 816         /* Create pseudo header */
 817
 818         pseudo.ip6_src = ip6.ip6_src;
 819         pseudo.ip6_dst = ip6.ip6_dst;
 820
 821         if(has_opt) {
 822                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 823         } else {
 824                 pseudo.length = htonl(ns_size);
 825         }
 826
 827         pseudo.next = htonl(IPPROTO_ICMPV6);
 828
 829         /* Generate checksum */
 830
 831         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 832         checksum = inet_checksum(&ns, ns_size, checksum);
 833
 834         if(has_opt) {
 835                 checksum = inet_checksum(&opt, opt_size, checksum);
 836                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 837         }
 838
 839         if(checksum) {
 840                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request");
 841                 return;
 842         }
 843
 844         /* Check if the IPv6 address exists on the VPN */
 845
 846         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 847
 848         if(!subnet) {
 849                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 850                                         ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 851                                         ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 852                                         ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 853                                         ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 854                                         ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 855                                         ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 856                                         ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 857                                         ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 858
 859                 return;
 860         }
 861
 862         /* Check if it is for our own subnet */
 863
 864         if(subnet->owner == myself) {
 865                 return;        /* silently ignore */
 866         }
 867
 868         if(decrement_ttl)
 869                 if(!do_decrement_ttl(source, packet)) {
 870                         return;
 871                 }
 872
 873         /* Create neighbor advertation reply */
 874
 875         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 876         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 877
 878         ip6.ip6_dst = ip6.ip6_src;                      /* swap destination and source protocoll address */
 879         ip6.ip6_src = ns.nd_ns_target;
 880
 881         if(has_opt) {
 882                 memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);        /* add fake source hard addr */
 883         }
 884
 885         ns.nd_ns_cksum = 0;
 886         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 887         ns.nd_ns_reserved = htonl(0x40000000UL);        /* Set solicited flag */
 888         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 889
 890         /* Create pseudo header */
 891
 892         pseudo.ip6_src = ip6.ip6_src;
 893         pseudo.ip6_dst = ip6.ip6_dst;
 894
 895         if(has_opt) {
 896                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 897         } else {
 898                 pseudo.length = htonl(ns_size);
 899         }
 900
 901         pseudo.next = htonl(IPPROTO_ICMPV6);
 902
 903         /* Generate checksum */
 904
 905         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 906         checksum = inet_checksum(&ns, ns_size, checksum);
 907
 908         if(has_opt) {
 909                 checksum = inet_checksum(&opt, opt_size, checksum);
 910                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 911         }
 912
 913         ns.nd_ns_hdr.icmp6_cksum = checksum;
 914
 915         /* Copy structs on stack back to packet */
 916
 917         memcpy(packet->data + ether_size, &ip6, ip6_size);
 918         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 919
 920         if(has_opt) {
 921                 memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 922         }
 923
 924         send_packet(source, packet);
 925 }
 926
 927 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 928         if(!checklength(source, packet, ether_size + ip6_size)) {
 929                 return;
 930         }
 931
 932         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 933                 route_neighborsol(source, packet);
 934                 return;
 935         }
 936
 937         if(broadcast_mode && packet->data[38] == 255) {
 938                 route_broadcast(source, packet);
 939         } else {
 940                 route_ipv6_unicast(source, packet);
 941         }
 942 }
 943
 944 /* RFC 826 */
 945
 946 static void route_arp(node_t *source, vpn_packet_t *packet) {
 947         struct ether_arp arp;
 948         subnet_t *subnet;
 949         struct in_addr addr;
 950
 951         if(!checklength(source, packet, ether_size + arp_size)) {
 952                 return;
 953         }
 954
 955         if(source != myself) {
 956                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname);
 957                 return;
 958         }
 959
 960         /* First, snatch the source address from the ARP packet */
 961
 962         if(overwrite_mac) {
 963                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 964         }
 965
 966         /* Copy headers from packet to structs on the stack */
 967
 968         memcpy(&arp, packet->data + ether_size, arp_size);
 969
 970         /* Check if this is a valid ARP request */
 971
 972         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 973                         arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof(addr) || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 974                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type ARP request");
 975                 return;
 976         }
 977
 978         /* Check if the IPv4 address exists on the VPN */
 979
 980         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 981
 982         if(!subnet) {
 983                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d",
 984                                         arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 985                                         arp.arp_tpa[3]);
 986                 return;
 987         }
 988
 989         /* Check if it is for our own subnet */
 990
 991         if(subnet->owner == myself) {
 992                 return;        /* silently ignore */
 993         }
 994
 995         if(decrement_ttl)
 996                 if(!do_decrement_ttl(source, packet)) {
 997                         return;
 998                 }
 999
1000         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
1001         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
1002
1003         memcpy(&addr, arp.arp_tpa, sizeof(addr));       /* save protocol addr */
1004         memcpy(arp.arp_tpa, arp.arp_spa, sizeof(addr)); /* swap destination and source protocol address */
1005         memcpy(arp.arp_spa, &addr, sizeof(addr));       /* ... */
1006
1007         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);     /* set target hard/proto addr */
1008         memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN); /* add fake source hard addr */
1009         arp.arp_op = htons(ARPOP_REPLY);
1010
1011         /* Copy structs on stack back to packet */
1012
1013         memcpy(packet->data + ether_size, &arp, arp_size);
1014
1015         send_packet(source, packet);
1016 }
1017
1018 static void route_mac(node_t *source, vpn_packet_t *packet) {
1019         subnet_t *subnet;
1020         mac_t dest;
1021
1022         /* Learn source address */
1023
1024         if(source == myself) {
1025                 mac_t src;
1026                 memcpy(&src, &packet->data[6], sizeof(src));
1027                 learn_mac(&src);
1028         }
1029
1030         /* Lookup destination address */
1031
1032         memcpy(&dest, &packet->data[0], sizeof(dest));
1033         subnet = lookup_subnet_mac(NULL, &dest);
1034
1035         if(!subnet) {
1036                 route_broadcast(source, packet);
1037                 return;
1038         }
1039
1040         if(subnet->owner == source) {
1041                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
1042                 return;
1043         }
1044
1045         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself) {
1046                 return;
1047         }
1048
1049         if(decrement_ttl && source != myself && subnet->owner != myself)
1050                 if(!do_decrement_ttl(source, packet)) {
1051                         return;
1052                 }
1053
1054         uint16_t type = packet->data[12] << 8 | packet->data[13];
1055
1056         if(priorityinheritance) {
1057                 if(type == ETH_P_IP && packet->len >= ether_size + ip_size) {
1058                         packet->priority = packet->data[15];
1059                 } else if(type == ETH_P_IPV6 && packet->len >= ether_size + ip6_size) {
1060                         packet->priority = ((packet->data[14] & 0x0f) << 4) | (packet->data[15] >> 4);
1061                 }
1062         }
1063
1064         // Handle packets larger than PMTU
1065
1066         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
1067
1068         if(directonly && subnet->owner != via) {
1069                 return;
1070         }
1071
1072         if(via && packet->len > via->mtu && via != myself) {
1073                 ifdebug(TRAFFIC) logger(LOG_INFO, "Packet for %s (%s) length %d larger than MTU %d", subnet->owner->name, subnet->owner->hostname, packet->len, via->mtu);
1074                 length_t ethlen = 14;
1075
1076                 if(type == ETH_P_8021Q) {
1077                         type = packet->data[16] << 8 | packet->data[17];
1078                         ethlen += 4;
1079                 }
1080
1081                 if(type == ETH_P_IP && packet->len > 576 + ethlen) {
1082                         if(packet->data[6 + ethlen] & 0x40) {
1083                                 packet->len = via->mtu;
1084                                 route_ipv4_unreachable(source, packet, ethlen, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
1085                         } else {
1086                                 fragment_ipv4_packet(via, packet, ethlen);
1087                         }
1088
1089                         return;
1090                 } else if(type == ETH_P_IPV6 && packet->len > 1280 + ethlen) {
1091                         packet->len = via->mtu;
1092                         route_ipv6_unreachable(source, packet, ethlen, ICMP6_PACKET_TOO_BIG, 0);
1093                         return;
1094                 }
1095         }
1096
1097         clamp_mss(source, via, packet);
1098
1099         send_packet(subnet->owner, packet);
1100 }
1101
1102 void route(node_t *source, vpn_packet_t *packet) {
1103         if(forwarding_mode == FMODE_KERNEL && source != myself) {
1104                 send_packet(myself, packet);
1105                 return;
1106         }
1107
1108         if(!checklength(source, packet, ether_size)) {
1109                 return;
1110         }
1111
1112         switch(routing_mode) {
1113         case RMODE_ROUTER: {
1114                 uint16_t type = packet->data[12] << 8 | packet->data[13];
1115
1116                 switch(type) {
1117                 case ETH_P_ARP:
1118                         route_arp(source, packet);
1119                         break;
1120
1121                 case ETH_P_IP:
1122                         route_ipv4(source, packet);
1123                         break;
1124
1125                 case ETH_P_IPV6:
1126                         route_ipv6(source, packet);
1127                         break;
1128
1129                 default:
1130                         ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type);
1131                         break;
1132                 }
1133         }
1134         break;
1135
1136         case RMODE_SWITCH:
1137                 route_mac(source, packet);
1138                 break;
1139
1140         case RMODE_HUB:
1141                 route_broadcast(source, packet);
1142                 break;
1143         }
1144 }