src/route.c

   1 /*
   2     route.c -- routing
   3     Copyright (C) 2000-2005 Ivo Timmermans,
   4                   2000-2014 Guus Sliepen <guus@tinc-vpn.org>
   5                   2015      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         while(checksum >> 16)
  76                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
  77
  78         return ~checksum;
  79 }
  80
  81 static bool ratelimit(int frequency) {
  82         static time_t lasttime = 0;
  83         static int count = 0;
  84
  85         if(lasttime == now) {
  86                 if(count >= frequency)
  87                         return true;
  88         } else {
  89                 lasttime = now;
  90                 count = 0;
  91         }
  92
  93         count++;
  94         return false;
  95 }
  96
  97 static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
  98         if(packet->len < length) {
  99                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got too short packet from %s (%s)", source->name, source->hostname);
 100                 return false;
 101         } else
 102                 return true;
 103 }
 104
 105 static void swap_mac_addresses(vpn_packet_t *packet) {
 106         mac_t tmp;
 107         memcpy(&tmp, &packet->data[0], sizeof tmp);
 108         memcpy(&packet->data[0], &packet->data[6], sizeof tmp);
 109         memcpy(&packet->data[6], &tmp, sizeof tmp);
 110 }
 111
 112 /* RFC 792 */
 113
 114 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, uint8_t type, uint8_t code) {
 115         struct ip ip = {0};
 116         struct icmp icmp = {0};
 117
 118         struct in_addr ip_src;
 119         struct in_addr ip_dst;
 120         uint32_t oldlen;
 121
 122         if(ratelimit(3))
 123                 return;
 124
 125         /* Swap Ethernet source and destination addresses */
 126
 127         swap_mac_addresses(packet);
 128
 129         /* Copy headers from packet into properly aligned structs on the stack */
 130
 131         memcpy(&ip, packet->data + ether_size, ip_size);
 132
 133         /* Remember original source and destination */
 134
 135         ip_src = ip.ip_src;
 136         ip_dst = ip.ip_dst;
 137
 138         /* Try to reply with an IP address assigned to the local machine */
 139
 140         if (type == ICMP_TIME_EXCEEDED && code == ICMP_EXC_TTL) {
 141                 int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
 142                 if (sockfd != -1) {
 143                         struct sockaddr_in addr;
 144                         memset(&addr, 0, sizeof(addr));
 145                         addr.sin_family = AF_INET;
 146                         addr.sin_addr = ip.ip_src;
 147                         if (!connect(sockfd, (const struct sockaddr*) &addr, sizeof(addr))) {
 148                                 memset(&addr, 0, sizeof(addr));
 149                                 addr.sin_family = AF_INET;
 150                                 socklen_t addrlen = sizeof(addr);
 151                                 if (!getsockname(sockfd, (struct sockaddr*) &addr, &addrlen) && addrlen <= sizeof(addr)) {
 152                                         ip_dst = addr.sin_addr;
 153                                 }
 154                         }
 155                         close(sockfd);
 156                 }
 157         }
 158
 159         oldlen = packet->len - ether_size;
 160
 161         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 162                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 163
 164         if(oldlen >= IP_MSS - ip_size - icmp_size)
 165                 oldlen = IP_MSS - ip_size - icmp_size;
 166
 167         /* Copy first part of original contents to ICMP message */
 168
 169         memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
 170
 171         /* Fill in IPv4 header */
 172
 173         ip.ip_v = 4;
 174         ip.ip_hl = ip_size / 4;
 175         ip.ip_tos = 0;
 176         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 177         ip.ip_id = 0;
 178         ip.ip_off = 0;
 179         ip.ip_ttl = 255;
 180         ip.ip_p = IPPROTO_ICMP;
 181         ip.ip_sum = 0;
 182         ip.ip_src = ip_dst;
 183         ip.ip_dst = ip_src;
 184
 185         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 186
 187         /* Fill in ICMP header */
 188
 189         icmp.icmp_type = type;
 190         icmp.icmp_code = code;
 191         icmp.icmp_cksum = 0;
 192
 193         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 194         icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 195
 196         /* Copy structs on stack back to packet */
 197
 198         memcpy(packet->data + ether_size, &ip, ip_size);
 199         memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
 200
 201         packet->len = ether_size + ip_size + icmp_size + oldlen;
 202
 203         send_packet(source, packet);
 204 }
 205
 206 /* RFC 2463 */
 207
 208 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, uint8_t type, uint8_t code) {
 209         struct ip6_hdr ip6;
 210         struct icmp6_hdr icmp6 = {0};
 211         uint16_t checksum;
 212
 213         struct {
 214                 struct in6_addr ip6_src;        /* source address */
 215                 struct in6_addr ip6_dst;        /* destination address */
 216                 uint32_t length;
 217                 uint32_t next;
 218         } pseudo;
 219
 220         if(ratelimit(3))
 221                 return;
 222
 223         /* Swap Ethernet source and destination addresses */
 224
 225         swap_mac_addresses(packet);
 226
 227         /* Copy headers from packet to structs on the stack */
 228
 229         memcpy(&ip6, packet->data + ether_size, ip6_size);
 230
 231         /* Remember original source and destination */
 232
 233         pseudo.ip6_src = ip6.ip6_dst;
 234         pseudo.ip6_dst = ip6.ip6_src;
 235
 236         /* Try to reply with an IP address assigned to the local machine */
 237
 238         if (type == ICMP6_TIME_EXCEEDED && code == ICMP6_TIME_EXCEED_TRANSIT) {
 239                 int sockfd = socket(AF_INET6, SOCK_DGRAM, 0);
 240                 if (sockfd != -1) {
 241                         struct sockaddr_in6 addr;
 242                         memset(&addr, 0, sizeof(addr));
 243                         addr.sin6_family = AF_INET6;
 244                         addr.sin6_addr = ip6.ip6_src;
 245                         if (!connect(sockfd, (const struct sockaddr*) &addr, sizeof(addr))) {
 246                                 memset(&addr, 0, sizeof(addr));
 247                                 addr.sin6_family = AF_INET6;
 248                                 socklen_t addrlen = sizeof(addr);
 249                                 if (!getsockname(sockfd, (struct sockaddr*) &addr, &addrlen) && addrlen <= sizeof(addr)) {
 250                                         pseudo.ip6_src = addr.sin6_addr;
 251                                 }
 252                         }
 253                         close(sockfd);
 254                 }
 255         }
 256
 257         pseudo.length = packet->len - ether_size;
 258
 259         if(type == ICMP6_PACKET_TOO_BIG)
 260                 icmp6.icmp6_mtu = htonl(pseudo.length);
 261
 262         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 263                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 264
 265         /* Copy first part of original contents to ICMP message */
 266
 267         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 268
 269         /* Fill in IPv6 header */
 270
 271         ip6.ip6_flow = htonl(0x60000000UL);
 272         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 273         ip6.ip6_nxt = IPPROTO_ICMPV6;
 274         ip6.ip6_hlim = 255;
 275         ip6.ip6_src = pseudo.ip6_src;
 276         ip6.ip6_dst = pseudo.ip6_dst;
 277
 278         /* Fill in ICMP header */
 279
 280         icmp6.icmp6_type = type;
 281         icmp6.icmp6_code = code;
 282         icmp6.icmp6_cksum = 0;
 283
 284         /* Create pseudo header */
 285
 286         pseudo.length = htonl(icmp6_size + pseudo.length);
 287         pseudo.next = htonl(IPPROTO_ICMPV6);
 288
 289         /* Generate checksum */
 290
 291         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 292         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 293         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 294
 295         icmp6.icmp6_cksum = checksum;
 296
 297         /* Copy structs on stack back to packet */
 298
 299         memcpy(packet->data + ether_size, &ip6, ip6_size);
 300         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 301
 302         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 303
 304         send_packet(source, packet);
 305 }
 306
 307 static bool do_decrement_ttl(node_t *source, vpn_packet_t *packet) {
 308         uint16_t type = packet->data[12] << 8 | packet->data[13];
 309         length_t ethlen = ether_size;
 310
 311         if(type == ETH_P_8021Q) {
 312                 type = packet->data[16] << 8 | packet->data[17];
 313                 ethlen += 4;
 314         }
 315
 316         switch (type) {
 317                 case ETH_P_IP:
 318                         if(!checklength(source, packet, ethlen + ip_size))
 319                                 return false;
 320
 321                         if(packet->data[ethlen + 8] <= 1) {
 322                                 if(packet->data[ethlen + 11] != IPPROTO_ICMP || packet->data[ethlen + 32] != ICMP_TIME_EXCEEDED)
 323                                         route_ipv4_unreachable(source, packet, ethlen, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL);
 324                                 return false;
 325                         }
 326
 327                         uint16_t old = packet->data[ethlen + 8] << 8 | packet->data[ethlen + 9];
 328                         packet->data[ethlen + 8]--;
 329                         uint16_t new = packet->data[ethlen + 8] << 8 | packet->data[ethlen + 9];
 330
 331                         uint32_t checksum = packet->data[ethlen + 10] << 8 | packet->data[ethlen + 11];
 332                         checksum += old + (~new & 0xFFFF);
 333                         while(checksum >> 16)
 334                                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
 335                         packet->data[ethlen + 10] = checksum >> 8;
 336                         packet->data[ethlen + 11] = checksum & 0xff;
 337
 338                         return true;
 339
 340                 case ETH_P_IPV6:
 341                         if(!checklength(source, packet, ethlen + ip6_size))
 342                                 return false;
 343
 344                         if(packet->data[ethlen + 7] <= 1) {
 345                                 if(packet->data[ethlen + 6] != IPPROTO_ICMPV6 || packet->data[ethlen + 40] != ICMP6_TIME_EXCEEDED)
 346                                         route_ipv6_unreachable(source, packet, ethlen, ICMP6_TIME_EXCEEDED, ICMP6_TIME_EXCEED_TRANSIT);
 347                                 return false;
 348                         }
 349
 350                         packet->data[ethlen + 7]--;
 351
 352                         return true;
 353
 354                 default:
 355                         return true;
 356         }
 357 }
 358
 359 static void clamp_mss(const node_t *source, const node_t *via, vpn_packet_t *packet) {
 360         if(!source || !via || !(via->options & OPTION_CLAMP_MSS))
 361                 return;
 362
 363         uint16_t mtu = source->mtu;
 364         if(via != myself && via->mtu < mtu)
 365                 mtu = via->mtu;
 366
 367         /* Find TCP header */
 368         int start = ether_size;
 369         uint16_t type = packet->data[12] << 8 | packet->data[13];
 370
 371         if(type == ETH_P_8021Q) {
 372                 start += 4;
 373                 type = packet->data[16] << 8 | packet->data[17];
 374         }
 375
 376         if(type == ETH_P_IP && packet->data[start + 9] == 6)
 377                 start += (packet->data[start] & 0xf) * 4;
 378         else if(type == ETH_P_IPV6 && packet->data[start + 6] == 6)
 379                 start += 40;
 380         else
 381                 return;
 382
 383         if(packet->len <= start + 20)
 384                 return;
 385
 386         /* Use data offset field to calculate length of options field */
 387         int len = ((packet->data[start + 12] >> 4) - 5) * 4;
 388
 389         if(packet->len < start + 20 + len)
 390                 return;
 391
 392         /* Search for MSS option header */
 393         for(int i = 0; i < len;) {
 394                 if(packet->data[start + 20 + i] == 0)
 395                         break;
 396
 397                 if(packet->data[start + 20 + i] == 1) {
 398                         i++;
 399                         continue;
 400                 }
 401
 402                 if(i > len - 2 || i > len - packet->data[start + 21 + i])
 403                         break;
 404
 405                 if(packet->data[start + 20 + i] != 2) {
 406                         if(packet->data[start + 21 + i] < 2)
 407                                 break;
 408                         i += packet->data[start + 21 + i];
 409                         continue;
 410                 }
 411
 412                 if(packet->data[start + 21] != 4)
 413                         break;
 414
 415                 /* Found it */
 416                 uint16_t oldmss = packet->data[start + 22 + i] << 8 | packet->data[start + 23 + i];
 417                 uint16_t newmss = mtu - start - 20;
 418                 uint32_t csum = packet->data[start + 16] << 8 | packet->data[start + 17];
 419
 420                 if(oldmss <= newmss)
 421                         break;
 422
 423                 ifdebug(TRAFFIC) logger(LOG_INFO, "Clamping MSS of packet from %s to %s to %d", source->name, via->name, newmss);
 424
 425                 /* Update the MSS value and the checksum */
 426                 packet->data[start + 22 + i] = newmss >> 8;
 427                 packet->data[start + 23 + i] = newmss & 0xff;
 428                 csum ^= 0xffff;
 429                 csum += oldmss ^ 0xffff;
 430                 csum += newmss;
 431                 csum = (csum & 0xffff) + (csum >> 16);
 432                 csum += csum >> 16;
 433                 csum ^= 0xffff;
 434                 packet->data[start + 16] = csum >> 8;
 435                 packet->data[start + 17] = csum;
 436                 break;
 437         }
 438 }
 439
 440 static void learn_mac(mac_t *address) {
 441         subnet_t *subnet;
 442         avl_node_t *node;
 443         connection_t *c;
 444
 445         subnet = lookup_subnet_mac(myself, address);
 446
 447         /* If we don't know this MAC address yet, store it */
 448
 449         if(!subnet) {
 450                 ifdebug(TRAFFIC) logger(LOG_INFO, "Learned new MAC address %x:%x:%x:%x:%x:%x",
 451                                    address->x[0], address->x[1], address->x[2], address->x[3],
 452                                    address->x[4], address->x[5]);
 453
 454                 subnet = new_subnet();
 455                 subnet->type = SUBNET_MAC;
 456                 subnet->expires = now + macexpire;
 457                 subnet->net.mac.address = *address;
 458                 subnet->weight = 10;
 459                 subnet_add(myself, subnet);
 460                 subnet_update(myself, subnet, true);
 461
 462                 /* And tell all other tinc daemons it's our MAC */
 463
 464                 for(node = connection_tree->head; node; node = node->next) {
 465                         c = node->data;
 466                         if(c->status.active)
 467                                 send_add_subnet(c, subnet);
 468                 }
 469         }
 470
 471         if(subnet->expires)
 472                 subnet->expires = now + macexpire;
 473 }
 474
 475 void age_subnets(void) {
 476         subnet_t *s;
 477         connection_t *c;
 478         avl_node_t *node, *next, *node2;
 479
 480         for(node = myself->subnet_tree->head; node; node = next) {
 481                 next = node->next;
 482                 s = node->data;
 483                 if(s->expires && s->expires <= now) {
 484                         ifdebug(TRAFFIC) {
 485                                 char netstr[MAXNETSTR];
 486                                 if(net2str(netstr, sizeof netstr, s))
 487                                         logger(LOG_INFO, "Subnet %s expired", netstr);
 488                         }
 489
 490                         for(node2 = connection_tree->head; node2; node2 = node2->next) {
 491                                 c = node2->data;
 492                                 if(c->status.active)
 493                                         send_del_subnet(c, s);
 494                         }
 495
 496                         subnet_update(myself, s, false);
 497                         subnet_del(myself, s);
 498                 }
 499         }
 500 }
 501
 502 static void route_broadcast(node_t *source, vpn_packet_t *packet) {
 503         if(decrement_ttl && source != myself)
 504                 if(!do_decrement_ttl(source, packet))
 505                         return;
 506
 507         broadcast_packet(source, packet);
 508 }
 509
 510 /* RFC 791 */
 511
 512 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet, length_t ether_size) {
 513         struct ip ip;
 514         vpn_packet_t fragment;
 515         int len, maxlen, todo;
 516         uint8_t *offset;
 517         uint16_t ip_off, origf;
 518
 519         memcpy(&ip, packet->data + ether_size, ip_size);
 520         fragment.priority = packet->priority;
 521
 522         if(ip.ip_hl != ip_size / 4)
 523                 return;
 524
 525         todo = ntohs(ip.ip_len) - ip_size;
 526
 527         if(ether_size + ip_size + todo != packet->len) {
 528                 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));
 529                 return;
 530         }
 531
 532         ifdebug(TRAFFIC) logger(LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname);
 533
 534         offset = packet->data + ether_size + ip_size;
 535         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 536         ip_off = ntohs(ip.ip_off);
 537         origf = ip_off & ~IP_OFFMASK;
 538         ip_off &= IP_OFFMASK;
 539
 540         while(todo) {
 541                 len = todo > maxlen ? maxlen : todo;
 542                 memcpy(fragment.data + ether_size + ip_size, offset, len);
 543                 todo -= len;
 544                 offset += len;
 545
 546                 ip.ip_len = htons(ip_size + len);
 547                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 548                 ip.ip_sum = 0;
 549                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 550                 memcpy(fragment.data, packet->data, ether_size);
 551                 memcpy(fragment.data + ether_size, &ip, ip_size);
 552                 fragment.len = ether_size + ip_size + len;
 553
 554                 send_packet(dest, &fragment);
 555
 556                 ip_off += len / 8;
 557         }
 558 }
 559
 560 static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet) {
 561         subnet_t *subnet;
 562         node_t *via;
 563         ipv4_t dest;
 564
 565         memcpy(&dest, &packet->data[30], sizeof dest);
 566         subnet = lookup_subnet_ipv4(&dest);
 567
 568         if(!subnet) {
 569                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d",
 570                                 source->name, source->hostname,
 571                                 dest.x[0],
 572                                 dest.x[1],
 573                                 dest.x[2],
 574                                 dest.x[3]);
 575
 576                 route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 577                 return;
 578         }
 579
 580         if(subnet->owner == source) {
 581                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 582                 return;
 583         }
 584
 585         if(!subnet->owner->status.reachable)
 586                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 587
 588         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 589                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 590
 591         if(decrement_ttl && source != myself && subnet->owner != myself)
 592                 if(!do_decrement_ttl(source, packet))
 593                         return;
 594
 595         if(priorityinheritance)
 596                 packet->priority = packet->data[15];
 597
 598         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 599
 600         if(via == source) {
 601                 ifdebug(TRAFFIC) logger(LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 602                 return;
 603         }
 604
 605         if(directonly && subnet->owner != via)
 606                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 607
 608         if(via && packet->len > MAX(via->mtu, 590) && via != myself) {
 609                 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);
 610                 if(packet->data[20] & 0x40) {
 611                         packet->len = MAX(via->mtu, 590);
 612                         route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 613                 } else {
 614                         fragment_ipv4_packet(via, packet, ether_size);
 615                 }
 616
 617                 return;
 618         }
 619
 620         clamp_mss(source, via, packet);
 621
 622         send_packet(subnet->owner, packet);
 623 }
 624
 625 static void route_ipv4(node_t *source, vpn_packet_t *packet) {
 626         if(!checklength(source, packet, ether_size + ip_size))
 627                 return;
 628
 629         if(broadcast_mode && (((packet->data[30] & 0xf0) == 0xe0) || (
 630                         packet->data[30] == 255 &&
 631                         packet->data[31] == 255 &&
 632                         packet->data[32] == 255 &&
 633                         packet->data[33] == 255)))
 634                 route_broadcast(source, packet);
 635         else
 636                 route_ipv4_unicast(source, packet);
 637 }
 638
 639 static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet) {
 640         subnet_t *subnet;
 641         node_t *via;
 642         ipv6_t dest;
 643
 644         memcpy(&dest, &packet->data[38], sizeof dest);
 645         subnet = lookup_subnet_ipv6(&dest);
 646
 647         if(!subnet) {
 648                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 649                                 source->name, source->hostname,
 650                                 ntohs(dest.x[0]),
 651                                 ntohs(dest.x[1]),
 652                                 ntohs(dest.x[2]),
 653                                 ntohs(dest.x[3]),
 654                                 ntohs(dest.x[4]),
 655                                 ntohs(dest.x[5]),
 656                                 ntohs(dest.x[6]),
 657                                 ntohs(dest.x[7]));
 658
 659                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 660                 return;
 661         }
 662
 663         if(subnet->owner == source) {
 664                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 665                 return;
 666         }
 667
 668         if(!subnet->owner->status.reachable)
 669                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 670
 671         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 672                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 673
 674         if(decrement_ttl && source != myself && subnet->owner != myself)
 675                 if(!do_decrement_ttl(source, packet))
 676                         return;
 677
 678         if(priorityinheritance)
 679                 packet->priority = ((packet->data[14] & 0x0f) << 4) | (packet->data[15] >> 4);
 680
 681         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 682
 683         if(via == source) {
 684                 ifdebug(TRAFFIC) logger(LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 685                 return;
 686         }
 687
 688         if(directonly && subnet->owner != via)
 689                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 690
 691         if(via && packet->len > MAX(via->mtu, 1294) && via != myself) {
 692                 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);
 693                 packet->len = MAX(via->mtu, 1294);
 694                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_PACKET_TOO_BIG, 0);
 695                 return;
 696         }
 697
 698         clamp_mss(source, via, packet);
 699
 700         send_packet(subnet->owner, packet);
 701 }
 702
 703 /* RFC 2461 */
 704
 705 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 706         struct ip6_hdr ip6;
 707         struct nd_neighbor_solicit ns;
 708         struct nd_opt_hdr opt;
 709         subnet_t *subnet;
 710         uint16_t checksum;
 711         bool has_opt;
 712
 713         struct {
 714                 struct in6_addr ip6_src;        /* source address */
 715                 struct in6_addr ip6_dst;        /* destination address */
 716                 uint32_t length;
 717                 uint32_t next;
 718         } pseudo;
 719
 720         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 721                 return;
 722
 723         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 724
 725         if(source != myself) {
 726                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname);
 727                 return;
 728         }
 729
 730         /* Copy headers from packet to structs on the stack */
 731
 732         memcpy(&ip6, packet->data + ether_size, ip6_size);
 733         memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
 734         if(has_opt)
 735                 memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 736
 737         /* First, snatch the source address from the neighbor solicitation packet */
 738
 739         if(overwrite_mac)
 740                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 741
 742         /* Check if this is a valid neighbor solicitation request */
 743
 744         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 745            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 746                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request");
 747                 return;
 748         }
 749
 750         /* Create pseudo header */
 751
 752         pseudo.ip6_src = ip6.ip6_src;
 753         pseudo.ip6_dst = ip6.ip6_dst;
 754         if(has_opt)
 755                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 756         else
 757                 pseudo.length = htonl(ns_size);
 758         pseudo.next = htonl(IPPROTO_ICMPV6);
 759
 760         /* Generate checksum */
 761
 762         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 763         checksum = inet_checksum(&ns, ns_size, checksum);
 764         if(has_opt) {
 765                 checksum = inet_checksum(&opt, opt_size, checksum);
 766                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 767         }
 768
 769         if(checksum) {
 770                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request");
 771                 return;
 772         }
 773
 774         /* Check if the IPv6 address exists on the VPN */
 775
 776         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 777
 778         if(!subnet) {
 779                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 780                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 781                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 782                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 783                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 784                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 785                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 786                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 787                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 788
 789                 return;
 790         }
 791
 792         /* Check if it is for our own subnet */
 793
 794         if(subnet->owner == myself)
 795                 return;                                 /* silently ignore */
 796
 797         if(decrement_ttl)
 798                 if(!do_decrement_ttl(source, packet))
 799                         return;
 800
 801         /* Create neighbor advertation reply */
 802
 803         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 804         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 805
 806         ip6.ip6_dst = ip6.ip6_src;                      /* swap destination and source protocoll address */
 807         ip6.ip6_src = ns.nd_ns_target;
 808
 809         if(has_opt)
 810                 memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 811
 812         ns.nd_ns_cksum = 0;
 813         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 814         ns.nd_ns_reserved = htonl(0x40000000UL);        /* Set solicited flag */
 815         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 816
 817         /* Create pseudo header */
 818
 819         pseudo.ip6_src = ip6.ip6_src;
 820         pseudo.ip6_dst = ip6.ip6_dst;
 821         if(has_opt)
 822                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 823         else
 824                 pseudo.length = htonl(ns_size);
 825         pseudo.next = htonl(IPPROTO_ICMPV6);
 826
 827         /* Generate checksum */
 828
 829         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 830         checksum = inet_checksum(&ns, ns_size, checksum);
 831         if(has_opt) {
 832                 checksum = inet_checksum(&opt, opt_size, checksum);
 833                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 834         }
 835
 836         ns.nd_ns_hdr.icmp6_cksum = checksum;
 837
 838         /* Copy structs on stack back to packet */
 839
 840         memcpy(packet->data + ether_size, &ip6, ip6_size);
 841         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 842         if(has_opt)
 843                 memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 844
 845         send_packet(source, packet);
 846 }
 847
 848 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 849         if(!checklength(source, packet, ether_size + ip6_size))
 850                 return;
 851
 852         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 853                 route_neighborsol(source, packet);
 854                 return;
 855         }
 856
 857         if(broadcast_mode && packet->data[38] == 255)
 858                 route_broadcast(source, packet);
 859         else
 860                 route_ipv6_unicast(source, packet);
 861 }
 862
 863 /* RFC 826 */
 864
 865 static void route_arp(node_t *source, vpn_packet_t *packet) {
 866         struct ether_arp arp;
 867         subnet_t *subnet;
 868         struct in_addr addr;
 869
 870         if(!checklength(source, packet, ether_size + arp_size))
 871                 return;
 872
 873         if(source != myself) {
 874                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname);
 875                 return;
 876         }
 877
 878         /* First, snatch the source address from the ARP packet */
 879
 880         if(overwrite_mac)
 881                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 882
 883         /* Copy headers from packet to structs on the stack */
 884
 885         memcpy(&arp, packet->data + ether_size, arp_size);
 886
 887         /* Check if this is a valid ARP request */
 888
 889         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 890            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof(addr) || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 891                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type ARP request");
 892                 return;
 893         }
 894
 895         /* Check if the IPv4 address exists on the VPN */
 896
 897         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 898
 899         if(!subnet) {
 900                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d",
 901                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 902                                    arp.arp_tpa[3]);
 903                 return;
 904         }
 905
 906         /* Check if it is for our own subnet */
 907
 908         if(subnet->owner == myself)
 909                 return;                                 /* silently ignore */
 910
 911         if(decrement_ttl)
 912                 if(!do_decrement_ttl(source, packet))
 913                         return;
 914
 915         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 916         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 917
 918         memcpy(&addr, arp.arp_tpa, sizeof(addr));       /* save protocol addr */
 919         memcpy(arp.arp_tpa, arp.arp_spa, sizeof(addr)); /* swap destination and source protocol address */
 920         memcpy(arp.arp_spa, &addr, sizeof(addr));       /* ... */
 921
 922         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);     /* set target hard/proto addr */
 923         memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN); /* add fake source hard addr */
 924         arp.arp_op = htons(ARPOP_REPLY);
 925
 926         /* Copy structs on stack back to packet */
 927
 928         memcpy(packet->data + ether_size, &arp, arp_size);
 929
 930         send_packet(source, packet);
 931 }
 932
 933 static void route_mac(node_t *source, vpn_packet_t *packet) {
 934         subnet_t *subnet;
 935         mac_t dest;
 936
 937         /* Learn source address */
 938
 939         if(source == myself) {
 940                 mac_t src;
 941                 memcpy(&src, &packet->data[6], sizeof src);
 942                 learn_mac(&src);
 943         }
 944
 945         /* Lookup destination address */
 946
 947         memcpy(&dest, &packet->data[0], sizeof dest);
 948         subnet = lookup_subnet_mac(NULL, &dest);
 949
 950         if(!subnet) {
 951                 route_broadcast(source, packet);
 952                 return;
 953         }
 954
 955         if(subnet->owner == source) {
 956                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 957                 return;
 958         }
 959
 960         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 961                 return;
 962
 963         if(decrement_ttl && source != myself && subnet->owner != myself)
 964                 if(!do_decrement_ttl(source, packet))
 965                         return;
 966
 967         uint16_t type = packet->data[12] << 8 | packet->data[13];
 968
 969         if(priorityinheritance) {
 970                 if(type == ETH_P_IP && packet->len >= ether_size + ip_size)
 971                         packet->priority = packet->data[15];
 972                 else if(type == ETH_P_IPV6 && packet->len >= ether_size + ip6_size)
 973                         packet->priority = ((packet->data[14] & 0x0f) << 4) | (packet->data[15] >> 4);
 974         }
 975
 976         // Handle packets larger than PMTU
 977
 978         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 979
 980         if(directonly && subnet->owner != via)
 981                 return;
 982
 983         if(via && packet->len > via->mtu && via != myself) {
 984                 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);
 985                 length_t ethlen = 14;
 986
 987                 if(type == ETH_P_8021Q) {
 988                         type = packet->data[16] << 8 | packet->data[17];
 989                         ethlen += 4;
 990                 }
 991
 992                 if(type == ETH_P_IP && packet->len > 576 + ethlen) {
 993                         if(packet->data[6 + ethlen] & 0x40) {
 994                                 packet->len = via->mtu;
 995                                 route_ipv4_unreachable(source, packet, ethlen, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 996                         } else {
 997                                 fragment_ipv4_packet(via, packet, ethlen);
 998                         }
 999                         return;
1000                 } else if(type == ETH_P_IPV6 && packet->len > 1280 + ethlen) {
1001                         packet->len = via->mtu;
1002                         route_ipv6_unreachable(source, packet, ethlen, ICMP6_PACKET_TOO_BIG, 0);
1003                         return;
1004                 }
1005         }
1006
1007         clamp_mss(source, via, packet);
1008
1009         send_packet(subnet->owner, packet);
1010 }
1011
1012 void route(node_t *source, vpn_packet_t *packet) {
1013         if(forwarding_mode == FMODE_KERNEL && source != myself) {
1014                 send_packet(myself, packet);
1015                 return;
1016         }
1017
1018         if(!checklength(source, packet, ether_size))
1019                 return;
1020
1021         switch (routing_mode) {
1022                 case RMODE_ROUTER:
1023                         {
1024                                 uint16_t type = packet->data[12] << 8 | packet->data[13];
1025
1026                                 switch (type) {
1027                                         case ETH_P_ARP:
1028                                                 route_arp(source, packet);
1029                                                 break;
1030
1031                                         case ETH_P_IP:
1032                                                 route_ipv4(source, packet);
1033                                                 break;
1034
1035                                         case ETH_P_IPV6:
1036                                                 route_ipv6(source, packet);
1037                                                 break;
1038
1039                                         default:
1040                                                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type);
1041                                                 break;
1042                                 }
1043                         }
1044                         break;
1045
1046                 case RMODE_SWITCH:
1047                         route_mac(source, packet);
1048                         break;
1049
1050                 case RMODE_HUB:
1051                         route_broadcast(source, packet);
1052                         break;
1053         }
1054 }