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
   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 "avl_tree.h"
  24 #include "connection.h"
  25 #include "ethernet.h"
  26 #include "ipv4.h"
  27 #include "ipv6.h"
  28 #include "logger.h"
  29 #include "net.h"
  30 #include "protocol.h"
  31 #include "route.h"
  32 #include "subnet.h"
  33 #include "utils.h"
  34
  35 rmode_t routing_mode = RMODE_ROUTER;
  36 fmode_t forwarding_mode = FMODE_INTERNAL;
  37 bmode_t broadcast_mode = BMODE_MST;
  38 bool decrement_ttl = false;
  39 bool directonly = false;
  40 bool priorityinheritance = false;
  41 int macexpire = 600;
  42 bool overwrite_mac = false;
  43 mac_t mymac = {{0xFE, 0xFD, 0, 0, 0, 0}};
  44
  45 /* Sizes of various headers */
  46
  47 static const size_t ether_size = sizeof(struct ether_header);
  48 static const size_t arp_size = sizeof(struct ether_arp);
  49 static const size_t ip_size = sizeof(struct ip);
  50 static const size_t icmp_size = sizeof(struct icmp) - sizeof(struct ip);
  51 static const size_t ip6_size = sizeof(struct ip6_hdr);
  52 static const size_t icmp6_size = sizeof(struct icmp6_hdr);
  53 static const size_t ns_size = sizeof(struct nd_neighbor_solicit);
  54 static const size_t opt_size = sizeof(struct nd_opt_hdr);
  55
  56 #ifndef MAX
  57 #define MAX(a, b) ((a) > (b) ? (a) : (b))
  58 #endif
  59
  60 /* RFC 1071 */
  61
  62 static uint16_t inet_checksum(void *data, int len, uint16_t prevsum) {
  63         uint16_t *p = data;
  64         uint32_t checksum = prevsum ^ 0xFFFF;
  65
  66         while(len >= 2) {
  67                 checksum += *p++;
  68                 len -= 2;
  69         }
  70
  71         if(len)
  72                 checksum += *(uint8_t *)p;
  73
  74         while(checksum >> 16)
  75                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
  76
  77         return ~checksum;
  78 }
  79
  80 static bool ratelimit(int frequency) {
  81         static time_t lasttime = 0;
  82         static int count = 0;
  83
  84         if(lasttime == now) {
  85                 if(count >= frequency)
  86                         return true;
  87         } else {
  88                 lasttime = now;
  89                 count = 0;
  90         }
  91
  92         count++;
  93         return false;
  94 }
  95
  96 static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
  97         if(packet->len < length) {
  98                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got too short packet from %s (%s)", source->name, source->hostname);
  99                 return false;
 100         } else
 101                 return true;
 102 }
 103
 104 static void clamp_mss(const node_t *source, const node_t *via, vpn_packet_t *packet) {
 105         if(!source || !via || !(via->options & OPTION_CLAMP_MSS))
 106                 return;
 107
 108         uint16_t mtu = source->mtu;
 109         if(via != myself && via->mtu < mtu)
 110                 mtu = via->mtu;
 111
 112         /* Find TCP header */
 113         int start = ether_size;
 114         uint16_t type = packet->data[12] << 8 | packet->data[13];
 115
 116         if(type == ETH_P_8021Q) {
 117                 start += 4;
 118                 type = packet->data[16] << 8 | packet->data[17];
 119         }
 120
 121         if(type == ETH_P_IP && packet->data[start + 9] == 6)
 122                 start += (packet->data[start] & 0xf) * 4;
 123         else if(type == ETH_P_IPV6 && packet->data[start + 6] == 6)
 124                 start += 40;
 125         else
 126                 return;
 127
 128         if(packet->len <= start + 20)
 129                 return;
 130
 131         /* Use data offset field to calculate length of options field */
 132         int len = ((packet->data[start + 12] >> 4) - 5) * 4;
 133
 134         if(packet->len < start + 20 + len)
 135                 return;
 136
 137         /* Search for MSS option header */
 138         for(int i = 0; i < len;) {
 139                 if(packet->data[start + 20 + i] == 0)
 140                         break;
 141
 142                 if(packet->data[start + 20 + i] == 1) {
 143                         i++;
 144                         continue;
 145                 }
 146
 147                 if(i > len - 2 || i > len - packet->data[start + 21 + i])
 148                         break;
 149
 150                 if(packet->data[start + 20 + i] != 2) {
 151                         if(packet->data[start + 21 + i] < 2)
 152                                 break;
 153                         i += packet->data[start + 21 + i];
 154                         continue;
 155                 }
 156
 157                 if(packet->data[start + 21] != 4)
 158                         break;
 159
 160                 /* Found it */
 161                 uint16_t oldmss = packet->data[start + 22 + i] << 8 | packet->data[start + 23 + i];
 162                 uint16_t newmss = mtu - start - 20;
 163                 uint16_t csum = packet->data[start + 16] << 8 | packet->data[start + 17];
 164
 165                 if(oldmss <= newmss)
 166                         break;
 167
 168                 ifdebug(TRAFFIC) logger(LOG_INFO, "Clamping MSS of packet from %s to %s to %d", source->name, via->name, newmss);
 169
 170                 /* Update the MSS value and the checksum */
 171                 packet->data[start + 22 + i] = newmss >> 8;
 172                 packet->data[start + 23 + i] = newmss & 0xff;
 173                 csum ^= 0xffff;
 174                 csum -= oldmss;
 175                 csum += newmss;
 176                 csum ^= 0xffff;
 177                 packet->data[start + 16] = csum >> 8;
 178                 packet->data[start + 17] = csum & 0xff;
 179                 break;
 180         }
 181 }
 182
 183 static void swap_mac_addresses(vpn_packet_t *packet) {
 184         mac_t tmp;
 185         memcpy(&tmp, &packet->data[0], sizeof tmp);
 186         memcpy(&packet->data[0], &packet->data[6], sizeof tmp);
 187         memcpy(&packet->data[6], &tmp, sizeof tmp);
 188 }
 189
 190 static void learn_mac(mac_t *address) {
 191         subnet_t *subnet;
 192         avl_node_t *node;
 193         connection_t *c;
 194
 195         subnet = lookup_subnet_mac(myself, address);
 196
 197         /* If we don't know this MAC address yet, store it */
 198
 199         if(!subnet) {
 200                 ifdebug(TRAFFIC) logger(LOG_INFO, "Learned new MAC address %x:%x:%x:%x:%x:%x",
 201                                    address->x[0], address->x[1], address->x[2], address->x[3],
 202                                    address->x[4], address->x[5]);
 203
 204                 subnet = new_subnet();
 205                 subnet->type = SUBNET_MAC;
 206                 subnet->expires = now + macexpire;
 207                 subnet->net.mac.address = *address;
 208                 subnet->weight = 10;
 209                 subnet_add(myself, subnet);
 210                 subnet_update(myself, subnet, true);
 211
 212                 /* And tell all other tinc daemons it's our MAC */
 213
 214                 for(node = connection_tree->head; node; node = node->next) {
 215                         c = node->data;
 216                         if(c->status.active)
 217                                 send_add_subnet(c, subnet);
 218                 }
 219         }
 220
 221         if(subnet->expires)
 222                 subnet->expires = now + macexpire;
 223 }
 224
 225 void age_subnets(void) {
 226         subnet_t *s;
 227         connection_t *c;
 228         avl_node_t *node, *next, *node2;
 229
 230         for(node = myself->subnet_tree->head; node; node = next) {
 231                 next = node->next;
 232                 s = node->data;
 233                 if(s->expires && s->expires <= now) {
 234                         ifdebug(TRAFFIC) {
 235                                 char netstr[MAXNETSTR];
 236                                 if(net2str(netstr, sizeof netstr, s))
 237                                         logger(LOG_INFO, "Subnet %s expired", netstr);
 238                         }
 239
 240                         for(node2 = connection_tree->head; node2; node2 = node2->next) {
 241                                 c = node2->data;
 242                                 if(c->status.active)
 243                                         send_del_subnet(c, s);
 244                         }
 245
 246                         subnet_update(myself, s, false);
 247                         subnet_del(myself, s);
 248                 }
 249         }
 250 }
 251
 252 /* RFC 792 */
 253
 254 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, uint8_t type, uint8_t code) {
 255         struct ip ip = {0};
 256         struct icmp icmp = {0};
 257
 258         struct in_addr ip_src;
 259         struct in_addr ip_dst;
 260         uint32_t oldlen;
 261         int sockfd;
 262
 263         if(ratelimit(3))
 264                 return;
 265
 266         /* Swap Ethernet source and destination addresses */
 267
 268         swap_mac_addresses(packet);
 269
 270         /* Copy headers from packet into properly aligned structs on the stack */
 271
 272         memcpy(&ip, packet->data + ether_size, ip_size);
 273
 274         /* Remember original source and destination */
 275
 276         ip_src = ip.ip_src;
 277         ip_dst = ip.ip_dst;
 278
 279         /* Try to reply with an IP address assigned to the local machine */
 280
 281         sockfd = socket(AF_INET, SOCK_DGRAM, 0);
 282         if (sockfd != -1) {
 283                 struct sockaddr_in addr;
 284                 memset(&addr, 0, sizeof(addr));
 285                 addr.sin_family = AF_INET;
 286                 addr.sin_addr = ip.ip_src;
 287                 if (!connect(sockfd, (const struct sockaddr*) &addr, sizeof(addr))) {
 288                         memset(&addr, 0, sizeof(addr));
 289                         addr.sin_family = AF_INET;
 290                         socklen_t addrlen = sizeof(addr);
 291                         if (!getsockname(sockfd, (struct sockaddr*) &addr, &addrlen) && addrlen <= sizeof(addr)) {
 292                                 ip_dst = addr.sin_addr;
 293                         }
 294                 }
 295                 close(sockfd);
 296         }
 297
 298         oldlen = packet->len - ether_size;
 299
 300         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 301                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 302
 303         if(oldlen >= IP_MSS - ip_size - icmp_size)
 304                 oldlen = IP_MSS - ip_size - icmp_size;
 305
 306         /* Copy first part of original contents to ICMP message */
 307
 308         memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
 309
 310         /* Fill in IPv4 header */
 311
 312         ip.ip_v = 4;
 313         ip.ip_hl = ip_size / 4;
 314         ip.ip_tos = 0;
 315         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 316         ip.ip_id = 0;
 317         ip.ip_off = 0;
 318         ip.ip_ttl = 255;
 319         ip.ip_p = IPPROTO_ICMP;
 320         ip.ip_sum = 0;
 321         ip.ip_src = ip_dst;
 322         ip.ip_dst = ip_src;
 323
 324         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 325
 326         /* Fill in ICMP header */
 327
 328         icmp.icmp_type = type;
 329         icmp.icmp_code = code;
 330         icmp.icmp_cksum = 0;
 331
 332         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 333         icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 334
 335         /* Copy structs on stack back to packet */
 336
 337         memcpy(packet->data + ether_size, &ip, ip_size);
 338         memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
 339
 340         packet->len = ether_size + ip_size + icmp_size + oldlen;
 341
 342         send_packet(source, packet);
 343 }
 344
 345 /* RFC 791 */
 346
 347 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet, length_t ether_size) {
 348         struct ip ip;
 349         vpn_packet_t fragment;
 350         int len, maxlen, todo;
 351         uint8_t *offset;
 352         uint16_t ip_off, origf;
 353
 354         memcpy(&ip, packet->data + ether_size, ip_size);
 355         fragment.priority = packet->priority;
 356
 357         if(ip.ip_hl != ip_size / 4)
 358                 return;
 359
 360         todo = ntohs(ip.ip_len) - ip_size;
 361
 362         if(ether_size + ip_size + todo != packet->len) {
 363                 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));
 364                 return;
 365         }
 366
 367         ifdebug(TRAFFIC) logger(LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname);
 368
 369         offset = packet->data + ether_size + ip_size;
 370         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 371         ip_off = ntohs(ip.ip_off);
 372         origf = ip_off & ~IP_OFFMASK;
 373         ip_off &= IP_OFFMASK;
 374
 375         while(todo) {
 376                 len = todo > maxlen ? maxlen : todo;
 377                 memcpy(fragment.data + ether_size + ip_size, offset, len);
 378                 todo -= len;
 379                 offset += len;
 380
 381                 ip.ip_len = htons(ip_size + len);
 382                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 383                 ip.ip_sum = 0;
 384                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 385                 memcpy(fragment.data, packet->data, ether_size);
 386                 memcpy(fragment.data + ether_size, &ip, ip_size);
 387                 fragment.len = ether_size + ip_size + len;
 388
 389                 send_packet(dest, &fragment);
 390
 391                 ip_off += len / 8;
 392         }
 393 }
 394
 395 static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet) {
 396         subnet_t *subnet;
 397         node_t *via;
 398         ipv4_t dest;
 399
 400         memcpy(&dest, &packet->data[30], sizeof dest);
 401         subnet = lookup_subnet_ipv4(&dest);
 402
 403         if(!subnet) {
 404                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d",
 405                                 source->name, source->hostname,
 406                                 dest.x[0],
 407                                 dest.x[1],
 408                                 dest.x[2],
 409                                 dest.x[3]);
 410
 411                 route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 412                 return;
 413         }
 414
 415         if(subnet->owner == source) {
 416                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 417                 return;
 418         }
 419
 420         if(!subnet->owner->status.reachable)
 421                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 422
 423         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 424                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 425
 426         if(priorityinheritance)
 427                 packet->priority = packet->data[15];
 428
 429         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 430
 431         if(via == source) {
 432                 ifdebug(TRAFFIC) logger(LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 433                 return;
 434         }
 435
 436         if(directonly && subnet->owner != via)
 437                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 438
 439         if(via && packet->len > MAX(via->mtu, 590) && via != myself) {
 440                 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);
 441                 if(packet->data[20] & 0x40) {
 442                         packet->len = MAX(via->mtu, 590);
 443                         route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 444                 } else {
 445                         fragment_ipv4_packet(via, packet, ether_size);
 446                 }
 447
 448                 return;
 449         }
 450
 451         clamp_mss(source, via, packet);
 452
 453         send_packet(subnet->owner, packet);
 454 }
 455
 456 static void route_ipv4(node_t *source, vpn_packet_t *packet) {
 457         if(!checklength(source, packet, ether_size + ip_size))
 458                 return;
 459
 460         if(broadcast_mode && (((packet->data[30] & 0xf0) == 0xe0) || (
 461                         packet->data[30] == 255 &&
 462                         packet->data[31] == 255 &&
 463                         packet->data[32] == 255 &&
 464                         packet->data[33] == 255)))
 465                 broadcast_packet(source, packet);
 466         else
 467                 route_ipv4_unicast(source, packet);
 468 }
 469
 470 /* RFC 2463 */
 471
 472 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, uint8_t type, uint8_t code) {
 473         struct ip6_hdr ip6;
 474         struct icmp6_hdr icmp6 = {0};
 475         uint16_t checksum;
 476         int sockfd;
 477
 478         struct {
 479                 struct in6_addr ip6_src;        /* source address */
 480                 struct in6_addr ip6_dst;        /* destination address */
 481                 uint32_t length;
 482                 uint32_t next;
 483         } pseudo;
 484
 485         if(ratelimit(3))
 486                 return;
 487
 488         /* Swap Ethernet source and destination addresses */
 489
 490         swap_mac_addresses(packet);
 491
 492         /* Copy headers from packet to structs on the stack */
 493
 494         memcpy(&ip6, packet->data + ether_size, ip6_size);
 495
 496         /* Remember original source and destination */
 497
 498         pseudo.ip6_src = ip6.ip6_dst;
 499         pseudo.ip6_dst = ip6.ip6_src;
 500
 501         /* Try to reply with an IP address assigned to the local machine */
 502
 503         sockfd = socket(AF_INET6, SOCK_DGRAM, 0);
 504         if (sockfd != -1) {
 505                 struct sockaddr_in6 addr;
 506                 memset(&addr, 0, sizeof(addr));
 507                 addr.sin6_family = AF_INET6;
 508                 addr.sin6_addr = ip6.ip6_src;
 509                 if (!connect(sockfd, (const struct sockaddr*) &addr, sizeof(addr))) {
 510                         memset(&addr, 0, sizeof(addr));
 511                         addr.sin6_family = AF_INET6;
 512                         socklen_t addrlen = sizeof(addr);
 513                         if (!getsockname(sockfd, (struct sockaddr*) &addr, &addrlen) && addrlen <= sizeof(addr)) {
 514                                 pseudo.ip6_src = addr.sin6_addr;
 515                         }
 516                 }
 517                 close(sockfd);
 518         }
 519
 520         pseudo.length = packet->len - ether_size;
 521
 522         if(type == ICMP6_PACKET_TOO_BIG)
 523                 icmp6.icmp6_mtu = htonl(pseudo.length);
 524
 525         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 526                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 527
 528         /* Copy first part of original contents to ICMP message */
 529
 530         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 531
 532         /* Fill in IPv6 header */
 533
 534         ip6.ip6_flow = htonl(0x60000000UL);
 535         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 536         ip6.ip6_nxt = IPPROTO_ICMPV6;
 537         ip6.ip6_hlim = 255;
 538         ip6.ip6_src = pseudo.ip6_src;
 539         ip6.ip6_dst = pseudo.ip6_dst;
 540
 541         /* Fill in ICMP header */
 542
 543         icmp6.icmp6_type = type;
 544         icmp6.icmp6_code = code;
 545         icmp6.icmp6_cksum = 0;
 546
 547         /* Create pseudo header */
 548
 549         pseudo.length = htonl(icmp6_size + pseudo.length);
 550         pseudo.next = htonl(IPPROTO_ICMPV6);
 551
 552         /* Generate checksum */
 553
 554         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 555         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 556         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 557
 558         icmp6.icmp6_cksum = checksum;
 559
 560         /* Copy structs on stack back to packet */
 561
 562         memcpy(packet->data + ether_size, &ip6, ip6_size);
 563         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 564
 565         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 566
 567         send_packet(source, packet);
 568 }
 569
 570 static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet) {
 571         subnet_t *subnet;
 572         node_t *via;
 573         ipv6_t dest;
 574
 575         memcpy(&dest, &packet->data[38], sizeof dest);
 576         subnet = lookup_subnet_ipv6(&dest);
 577
 578         if(!subnet) {
 579                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 580                                 source->name, source->hostname,
 581                                 ntohs(dest.x[0]),
 582                                 ntohs(dest.x[1]),
 583                                 ntohs(dest.x[2]),
 584                                 ntohs(dest.x[3]),
 585                                 ntohs(dest.x[4]),
 586                                 ntohs(dest.x[5]),
 587                                 ntohs(dest.x[6]),
 588                                 ntohs(dest.x[7]));
 589
 590                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 591                 return;
 592         }
 593
 594         if(subnet->owner == source) {
 595                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 596                 return;
 597         }
 598
 599         if(!subnet->owner->status.reachable)
 600                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 601
 602         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 603                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 604
 605         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 606
 607         if(via == source) {
 608                 ifdebug(TRAFFIC) logger(LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 609                 return;
 610         }
 611
 612         if(directonly && subnet->owner != via)
 613                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 614
 615         if(via && packet->len > MAX(via->mtu, 1294) && via != myself) {
 616                 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);
 617                 packet->len = MAX(via->mtu, 1294);
 618                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_PACKET_TOO_BIG, 0);
 619                 return;
 620         }
 621
 622         clamp_mss(source, via, packet);
 623
 624         send_packet(subnet->owner, packet);
 625 }
 626
 627 /* RFC 2461 */
 628
 629 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 630         struct ip6_hdr ip6;
 631         struct nd_neighbor_solicit ns;
 632         struct nd_opt_hdr opt;
 633         subnet_t *subnet;
 634         uint16_t checksum;
 635         bool has_opt;
 636
 637         struct {
 638                 struct in6_addr ip6_src;        /* source address */
 639                 struct in6_addr ip6_dst;        /* destination address */
 640                 uint32_t length;
 641                 uint32_t next;
 642         } pseudo;
 643
 644         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 645                 return;
 646
 647         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 648
 649         if(source != myself) {
 650                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname);
 651                 return;
 652         }
 653
 654         /* Copy headers from packet to structs on the stack */
 655
 656         memcpy(&ip6, packet->data + ether_size, ip6_size);
 657         memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
 658         if(has_opt)
 659                 memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 660
 661         /* First, snatch the source address from the neighbor solicitation packet */
 662
 663         if(overwrite_mac)
 664                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 665
 666         /* Check if this is a valid neighbor solicitation request */
 667
 668         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 669            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 670                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request");
 671                 return;
 672         }
 673
 674         /* Create pseudo header */
 675
 676         pseudo.ip6_src = ip6.ip6_src;
 677         pseudo.ip6_dst = ip6.ip6_dst;
 678         if(has_opt)
 679                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 680         else
 681                 pseudo.length = htonl(ns_size);
 682         pseudo.next = htonl(IPPROTO_ICMPV6);
 683
 684         /* Generate checksum */
 685
 686         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 687         checksum = inet_checksum(&ns, ns_size, checksum);
 688         if(has_opt) {
 689                 checksum = inet_checksum(&opt, opt_size, checksum);
 690                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 691         }
 692
 693         if(checksum) {
 694                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request");
 695                 return;
 696         }
 697
 698         /* Check if the IPv6 address exists on the VPN */
 699
 700         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 701
 702         if(!subnet) {
 703                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 704                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 705                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 706                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 707                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 708                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 709                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 710                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 711                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 712
 713                 return;
 714         }
 715
 716         /* Check if it is for our own subnet */
 717
 718         if(subnet->owner == myself)
 719                 return;                                 /* silently ignore */
 720
 721         /* Create neighbor advertation reply */
 722
 723         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 724         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 725
 726         ip6.ip6_dst = ip6.ip6_src;                      /* swap destination and source protocoll address */
 727         ip6.ip6_src = ns.nd_ns_target;
 728
 729         if(has_opt)
 730                 memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 731
 732         ns.nd_ns_cksum = 0;
 733         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 734         ns.nd_ns_reserved = htonl(0x40000000UL);        /* Set solicited flag */
 735         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 736
 737         /* Create pseudo header */
 738
 739         pseudo.ip6_src = ip6.ip6_src;
 740         pseudo.ip6_dst = ip6.ip6_dst;
 741         if(has_opt)
 742                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 743         else
 744                 pseudo.length = htonl(ns_size);
 745         pseudo.next = htonl(IPPROTO_ICMPV6);
 746
 747         /* Generate checksum */
 748
 749         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 750         checksum = inet_checksum(&ns, ns_size, checksum);
 751         if(has_opt) {
 752                 checksum = inet_checksum(&opt, opt_size, checksum);
 753                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 754         }
 755
 756         ns.nd_ns_hdr.icmp6_cksum = checksum;
 757
 758         /* Copy structs on stack back to packet */
 759
 760         memcpy(packet->data + ether_size, &ip6, ip6_size);
 761         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 762         if(has_opt)
 763                 memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 764
 765         send_packet(source, packet);
 766 }
 767
 768 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 769         if(!checklength(source, packet, ether_size + ip6_size))
 770                 return;
 771
 772         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 773                 route_neighborsol(source, packet);
 774                 return;
 775         }
 776
 777         if(broadcast_mode && packet->data[38] == 255)
 778                 broadcast_packet(source, packet);
 779         else
 780                 route_ipv6_unicast(source, packet);
 781 }
 782
 783 /* RFC 826 */
 784
 785 static void route_arp(node_t *source, vpn_packet_t *packet) {
 786         struct ether_arp arp;
 787         subnet_t *subnet;
 788         struct in_addr addr;
 789
 790         if(!checklength(source, packet, ether_size + arp_size))
 791                 return;
 792
 793         if(source != myself) {
 794                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname);
 795                 return;
 796         }
 797
 798         /* First, snatch the source address from the ARP packet */
 799
 800         if(overwrite_mac)
 801                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 802
 803         /* Copy headers from packet to structs on the stack */
 804
 805         memcpy(&arp, packet->data + ether_size, arp_size);
 806
 807         /* Check if this is a valid ARP request */
 808
 809         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 810            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof(addr) || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 811                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type ARP request");
 812                 return;
 813         }
 814
 815         /* Check if the IPv4 address exists on the VPN */
 816
 817         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 818
 819         if(!subnet) {
 820                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d",
 821                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 822                                    arp.arp_tpa[3]);
 823                 return;
 824         }
 825
 826         /* Check if it is for our own subnet */
 827
 828         if(subnet->owner == myself)
 829                 return;                                 /* silently ignore */
 830
 831         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 832         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 833
 834         memcpy(&addr, arp.arp_tpa, sizeof(addr));       /* save protocol addr */
 835         memcpy(arp.arp_tpa, arp.arp_spa, sizeof(addr)); /* swap destination and source protocol address */
 836         memcpy(arp.arp_spa, &addr, sizeof(addr));       /* ... */
 837
 838         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);     /* set target hard/proto addr */
 839         memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN); /* add fake source hard addr */
 840         arp.arp_op = htons(ARPOP_REPLY);
 841
 842         /* Copy structs on stack back to packet */
 843
 844         memcpy(packet->data + ether_size, &arp, arp_size);
 845
 846         send_packet(source, packet);
 847 }
 848
 849 static void route_mac(node_t *source, vpn_packet_t *packet) {
 850         subnet_t *subnet;
 851         mac_t dest;
 852
 853         /* Learn source address */
 854
 855         if(source == myself) {
 856                 mac_t src;
 857                 memcpy(&src, &packet->data[6], sizeof src);
 858                 learn_mac(&src);
 859         }
 860
 861         /* Lookup destination address */
 862
 863         memcpy(&dest, &packet->data[0], sizeof dest);
 864         subnet = lookup_subnet_mac(NULL, &dest);
 865
 866         if(!subnet) {
 867                 broadcast_packet(source, packet);
 868                 return;
 869         }
 870
 871         if(subnet->owner == source) {
 872                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 873                 return;
 874         }
 875
 876         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 877                 return;
 878
 879         uint16_t type = packet->data[12] << 8 | packet->data[13];
 880
 881         if(priorityinheritance && type == ETH_P_IP && packet->len >= ether_size + ip_size)
 882                 packet->priority = packet->data[15];
 883
 884         // Handle packets larger than PMTU
 885
 886         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 887
 888         if(directonly && subnet->owner != via)
 889                 return;
 890
 891         if(via && packet->len > via->mtu && via != myself) {
 892                 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);
 893                 length_t ethlen = 14;
 894
 895                 if(type == ETH_P_8021Q) {
 896                         type = packet->data[16] << 8 | packet->data[17];
 897                         ethlen += 4;
 898                 }
 899
 900                 if(type == ETH_P_IP && packet->len > 576 + ethlen) {
 901                         if(packet->data[6 + ethlen] & 0x40) {
 902                                 packet->len = via->mtu;
 903                                 route_ipv4_unreachable(source, packet, ethlen, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 904                         } else {
 905                                 fragment_ipv4_packet(via, packet, ethlen);
 906                         }
 907                         return;
 908                 } else if(type == ETH_P_IPV6 && packet->len > 1280 + ethlen) {
 909                         packet->len = via->mtu;
 910                         route_ipv6_unreachable(source, packet, ethlen, ICMP6_PACKET_TOO_BIG, 0);
 911                         return;
 912                 }
 913         }
 914
 915         clamp_mss(source, via, packet);
 916
 917         send_packet(subnet->owner, packet);
 918 }
 919
 920 static bool do_decrement_ttl(node_t *source, vpn_packet_t *packet) {
 921         uint16_t type = packet->data[12] << 8 | packet->data[13];
 922         length_t ethlen = ether_size;
 923
 924         if(type == ETH_P_8021Q) {
 925                 type = packet->data[16] << 8 | packet->data[17];
 926                 ethlen += 4;
 927         }
 928
 929         switch (type) {
 930                 case ETH_P_IP:
 931                         if(!checklength(source, packet, ethlen + ip_size))
 932                                 return false;
 933
 934                         if(packet->data[ethlen + 8] <= 1) {
 935                                 if(packet->data[ethlen + 11] != IPPROTO_ICMP || packet->data[ethlen + 32] != ICMP_TIME_EXCEEDED)
 936                                         route_ipv4_unreachable(source, packet, ethlen, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL);
 937                                 return false;
 938                         }
 939
 940                         uint16_t old = packet->data[ethlen + 8] << 8 | packet->data[ethlen + 9];
 941                         packet->data[ethlen + 8]--;
 942                         uint16_t new = packet->data[ethlen + 8] << 8 | packet->data[ethlen + 9];
 943
 944                         uint32_t checksum = packet->data[ethlen + 10] << 8 | packet->data[ethlen + 11];
 945                         checksum += old + (~new & 0xFFFF);
 946                         while(checksum >> 16)
 947                                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
 948                         packet->data[ethlen + 10] = checksum >> 8;
 949                         packet->data[ethlen + 11] = checksum & 0xff;
 950
 951                         return true;
 952
 953                 case ETH_P_IPV6:
 954                         if(!checklength(source, packet, ethlen + ip6_size))
 955                                 return false;
 956
 957                         if(packet->data[ethlen + 7] <= 1) {
 958                                 if(packet->data[ethlen + 6] != IPPROTO_ICMPV6 || packet->data[ethlen + 40] != ICMP6_TIME_EXCEEDED)
 959                                         route_ipv6_unreachable(source, packet, ethlen, ICMP6_TIME_EXCEEDED, ICMP6_TIME_EXCEED_TRANSIT);
 960                                 return false;
 961                         }
 962
 963                         packet->data[ethlen + 7]--;
 964
 965                         return true;
 966
 967                 default:
 968                         return true;
 969         }
 970 }
 971
 972 void route(node_t *source, vpn_packet_t *packet) {
 973         if(forwarding_mode == FMODE_KERNEL && source != myself) {
 974                 send_packet(myself, packet);
 975                 return;
 976         }
 977
 978         if(!checklength(source, packet, ether_size))
 979                 return;
 980
 981         if(decrement_ttl && source != myself)
 982                 if(!do_decrement_ttl(source, packet))
 983                         return;
 984
 985         switch (routing_mode) {
 986                 case RMODE_ROUTER:
 987                         {
 988                                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 989
 990                                 switch (type) {
 991                                         case ETH_P_ARP:
 992                                                 route_arp(source, packet);
 993                                                 break;
 994
 995                                         case ETH_P_IP:
 996                                                 route_ipv4(source, packet);
 997                                                 break;
 998
 999                                         case ETH_P_IPV6:
1000                                                 route_ipv6(source, packet);
1001                                                 break;
1002
1003                                         default:
1004                                                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type);
1005                                                 break;
1006                                 }
1007                         }
1008                         break;
1009
1010                 case RMODE_SWITCH:
1011                         route_mac(source, packet);
1012                         break;
1013
1014                 case RMODE_HUB:
1015                         broadcast_packet(source, packet);
1016                         break;
1017         }
1018 }