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

   1 /*
   2     route.c -- routing
   3     Copyright (C) 2000-2005 Ivo Timmermans,
   4                   2000-2010 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 "splay_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 bool directonly = false;
  38 bool priorityinheritance = false;
  39 int macexpire = 600;
  40 bool overwrite_mac = false;
  41 mac_t mymac = {{0xFE, 0xFD, 0, 0, 0, 0}};
  42
  43 /* Sizes of various headers */
  44
  45 static const size_t ether_size = sizeof(struct ether_header);
  46 static const size_t arp_size = sizeof(struct ether_arp);
  47 static const size_t ip_size = sizeof(struct ip);
  48 static const size_t icmp_size = sizeof(struct icmp) - sizeof(struct ip);
  49 static const size_t ip6_size = sizeof(struct ip6_hdr);
  50 static const size_t icmp6_size = sizeof(struct icmp6_hdr);
  51 static const size_t ns_size = sizeof(struct nd_neighbor_solicit);
  52 static const size_t opt_size = sizeof(struct nd_opt_hdr);
  53
  54 #ifndef MAX
  55 #define MAX(a, b) ((a) > (b) ? (a) : (b))
  56 #endif
  57
  58 static struct event age_subnets_event;
  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         time_t now = time(NULL);
  84
  85         if(lasttime == now) {
  86                 if(++count > frequency)
  87                         return true;
  88         } else {
  89                 lasttime = now;
  90                 count = 0;
  91         }
  92
  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 = 0;
 114         uint16_t type = packet->data[12] << 8 | packet->data[13];
 115
 116         if(type == ETH_P_IP && packet->data[23] == 6)
 117                 start = 14 + (packet->data[14] & 0xf) * 4;
 118         else if(type == ETH_P_IPV6 && packet->data[20] == 6)
 119                 start = 14 + 40;
 120
 121         if(!start || packet->len <= start + 20)
 122                 return;
 123
 124         /* Use data offset field to calculate length of options field */
 125         int len = ((packet->data[start + 12] >> 4) - 5) * 4;
 126
 127         if(packet->len < start + 20 + len)
 128                 return;
 129
 130         /* Search for MSS option header */
 131         for(int i = 0; i < len;) {
 132                 if(packet->data[start + 20 + i] == 0)
 133                         break;
 134
 135                 if(packet->data[start + 20 + i] == 1) {
 136                         i++;
 137                         continue;
 138                 }
 139
 140                 if(i > len - 2 || i > len - packet->data[start + 21 + i])
 141                         break;
 142
 143                 if(packet->data[start + 20 + i] != 2) {
 144                         if(packet->data[start + 21 + i] < 2)
 145                                 break;
 146                         i += packet->data[start + 21 + i];
 147                         continue;
 148                 }
 149
 150                 if(packet->data[start + 21] != 4)
 151                         break;
 152
 153                 /* Found it */
 154                 uint16_t oldmss = packet->data[start + 22 + i] << 8 | packet->data[start + 23 + i];
 155                 uint16_t newmss = mtu - start - 20;
 156                 uint16_t csum = packet->data[start + 16] << 8 | packet->data[start + 17];
 157
 158                 if(oldmss <= newmss)
 159                         break;
 160
 161                 ifdebug(TRAFFIC) logger(LOG_INFO, "Clamping MSS of packet from %s to %s to %d", source->name, via->name, newmss);
 162
 163                 /* Update the MSS value and the checksum */
 164                 packet->data[start + 22 + i] = newmss >> 8;
 165                 packet->data[start + 23 + i] = newmss & 0xff;
 166                 csum ^= 0xffff;
 167                 csum -= oldmss;
 168                 csum += newmss;
 169                 csum ^= 0xffff;
 170                 packet->data[start + 16] = csum >> 8;
 171                 packet->data[start + 17] = csum & 0xff;
 172                 break;
 173         }
 174 }
 175
 176 static void swap_mac_addresses(vpn_packet_t *packet) {
 177         mac_t tmp;
 178         memcpy(&tmp, &packet->data[0], sizeof tmp);
 179         memcpy(&packet->data[0], &packet->data[6], sizeof tmp);
 180         memcpy(&packet->data[6], &tmp, sizeof tmp);
 181 }
 182
 183 static void age_subnets(int fd, short events, void *data) {
 184         subnet_t *s;
 185         connection_t *c;
 186         splay_node_t *node, *next, *node2;
 187         bool left = false;
 188         time_t now = time(NULL);
 189
 190         for(node = myself->subnet_tree->head; node; node = next) {
 191                 next = node->next;
 192                 s = node->data;
 193                 if(s->expires && s->expires < now) {
 194                         ifdebug(TRAFFIC) {
 195                                 char netstr[MAXNETSTR];
 196                                 if(net2str(netstr, sizeof netstr, s))
 197                                         logger(LOG_INFO, "Subnet %s expired", netstr);
 198                         }
 199
 200                         for(node2 = connection_tree->head; node2; node2 = node2->next) {
 201                                 c = node2->data;
 202                                 if(c->status.active)
 203                                         send_del_subnet(c, s);
 204                         }
 205
 206                         subnet_del(myself, s);
 207                 } else {
 208                         if(s->expires)
 209                                 left = true;
 210                 }
 211         }
 212
 213         if(left)
 214                 event_add(&age_subnets_event, &(struct timeval){10, 0});
 215 }
 216
 217 static void learn_mac(mac_t *address) {
 218         subnet_t *subnet;
 219         splay_node_t *node;
 220         connection_t *c;
 221
 222         subnet = lookup_subnet_mac(myself, address);
 223
 224         /* If we don't know this MAC address yet, store it */
 225
 226         if(!subnet) {
 227                 ifdebug(TRAFFIC) logger(LOG_INFO, "Learned new MAC address %hx:%hx:%hx:%hx:%hx:%hx",
 228                                    address->x[0], address->x[1], address->x[2], address->x[3],
 229                                    address->x[4], address->x[5]);
 230
 231                 subnet = new_subnet();
 232                 subnet->type = SUBNET_MAC;
 233                 subnet->expires = time(NULL) + macexpire;
 234                 subnet->net.mac.address = *address;
 235                 subnet->weight = 10;
 236                 subnet_add(myself, subnet);
 237                 subnet_update(myself, subnet, true);
 238
 239                 /* And tell all other tinc daemons it's our MAC */
 240
 241                 for(node = connection_tree->head; node; node = node->next) {
 242                         c = node->data;
 243                         if(c->status.active)
 244                                 send_add_subnet(c, subnet);
 245                 }
 246
 247                 if(!timeout_initialized(&age_subnets_event))
 248                         timeout_set(&age_subnets_event, age_subnets, NULL);
 249                 event_add(&age_subnets_event, &(struct timeval){10, 0});
 250         } else {
 251                 if(subnet->expires)
 252                         subnet->expires = time(NULL) + macexpire;
 253         }
 254 }
 255
 256 /* RFC 792 */
 257
 258 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 259         struct ip ip = {0};
 260         struct icmp icmp = {0};
 261
 262         struct in_addr ip_src;
 263         struct in_addr ip_dst;
 264         uint32_t oldlen;
 265
 266         if(ratelimit(3))
 267                 return;
 268
 269         /* Swap Ethernet source and destination addresses */
 270
 271         swap_mac_addresses(packet);
 272
 273         /* Copy headers from packet into properly aligned structs on the stack */
 274
 275         memcpy(&ip, packet->data + ether_size, ip_size);
 276
 277         /* Remember original source and destination */
 278
 279         ip_src = ip.ip_src;
 280         ip_dst = ip.ip_dst;
 281
 282         oldlen = packet->len - ether_size;
 283
 284         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 285                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 286
 287         if(oldlen >= IP_MSS - ip_size - icmp_size)
 288                 oldlen = IP_MSS - ip_size - icmp_size;
 289
 290         /* Copy first part of original contents to ICMP message */
 291
 292         memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
 293
 294         /* Fill in IPv4 header */
 295
 296         ip.ip_v = 4;
 297         ip.ip_hl = ip_size / 4;
 298         ip.ip_tos = 0;
 299         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 300         ip.ip_id = 0;
 301         ip.ip_off = 0;
 302         ip.ip_ttl = 255;
 303         ip.ip_p = IPPROTO_ICMP;
 304         ip.ip_sum = 0;
 305         ip.ip_src = ip_dst;
 306         ip.ip_dst = ip_src;
 307
 308         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 309
 310         /* Fill in ICMP header */
 311
 312         icmp.icmp_type = type;
 313         icmp.icmp_code = code;
 314         icmp.icmp_cksum = 0;
 315
 316         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 317         icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 318
 319         /* Copy structs on stack back to packet */
 320
 321         memcpy(packet->data + ether_size, &ip, ip_size);
 322         memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
 323
 324         packet->len = ether_size + ip_size + icmp_size + oldlen;
 325
 326         send_packet(source, packet);
 327 }
 328
 329 /* RFC 791 */
 330
 331 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet) {
 332         struct ip ip;
 333         vpn_packet_t fragment;
 334         int len, maxlen, todo;
 335         uint8_t *offset;
 336         uint16_t ip_off, origf;
 337
 338         memcpy(&ip, packet->data + ether_size, ip_size);
 339         fragment.priority = packet->priority;
 340
 341         if(ip.ip_hl != ip_size / 4)
 342                 return;
 343
 344         todo = ntohs(ip.ip_len) - ip_size;
 345
 346         if(ether_size + ip_size + todo != packet->len) {
 347                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Length of packet (%d) doesn't match length in IPv4 header (%zd)", packet->len, ether_size + ip_size + todo);
 348                 return;
 349         }
 350
 351         ifdebug(TRAFFIC) logger(LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname);
 352
 353         offset = packet->data + ether_size + ip_size;
 354         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 355         ip_off = ntohs(ip.ip_off);
 356         origf = ip_off & ~IP_OFFMASK;
 357         ip_off &= IP_OFFMASK;
 358
 359         while(todo) {
 360                 len = todo > maxlen ? maxlen : todo;
 361                 memcpy(fragment.data + ether_size + ip_size, offset, len);
 362                 todo -= len;
 363                 offset += len;
 364
 365                 ip.ip_len = htons(ip_size + len);
 366                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 367                 ip.ip_sum = 0;
 368                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 369                 memcpy(fragment.data, packet->data, ether_size);
 370                 memcpy(fragment.data + ether_size, &ip, ip_size);
 371                 fragment.len = ether_size + ip_size + len;
 372
 373                 send_packet(dest, &fragment);
 374
 375                 ip_off += len / 8;
 376         }
 377 }
 378
 379 static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet) {
 380         subnet_t *subnet;
 381         node_t *via;
 382         ipv4_t dest;
 383
 384         memcpy(&dest, &packet->data[30], sizeof dest);
 385         subnet = lookup_subnet_ipv4(&dest);
 386
 387         if(!subnet) {
 388                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d",
 389                                 source->name, source->hostname,
 390                                 dest.x[0],
 391                                 dest.x[1],
 392                                 dest.x[2],
 393                                 dest.x[3]);
 394
 395                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 396                 return;
 397         }
 398
 399         if(subnet->owner == source) {
 400                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 401                 return;
 402         }
 403
 404         if(!subnet->owner->status.reachable)
 405                 return route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 406
 407         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 408                 return route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 409
 410         if(priorityinheritance)
 411                 packet->priority = packet->data[15];
 412
 413         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 414
 415         if(directonly && subnet->owner != via)
 416                 return route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 417
 418         if(via && packet->len > MAX(via->mtu, 590) && via != myself) {
 419                 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);
 420                 if(packet->data[20] & 0x40) {
 421                         packet->len = MAX(via->mtu, 590);
 422                         route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 423                 } else {
 424                         fragment_ipv4_packet(via, packet);
 425                 }
 426
 427                 return;
 428         }
 429
 430         clamp_mss(source, via, packet);
 431
 432         send_packet(subnet->owner, packet);
 433 }
 434
 435 static void route_ipv4(node_t *source, vpn_packet_t *packet) {
 436         if(!checklength(source, packet, ether_size + ip_size))
 437                 return;
 438
 439         if(((packet->data[30] & 0xf0) == 0xe0) || (
 440                         packet->data[30] == 255 &&
 441                         packet->data[31] == 255 &&
 442                         packet->data[32] == 255 &&
 443                         packet->data[33] == 255))
 444                 broadcast_packet(source, packet);
 445         else
 446                 route_ipv4_unicast(source, packet);
 447 }
 448
 449 /* RFC 2463 */
 450
 451 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 452         struct ip6_hdr ip6;
 453         struct icmp6_hdr icmp6 = {0};
 454         uint16_t checksum;
 455
 456         struct {
 457                 struct in6_addr ip6_src;        /* source address */
 458                 struct in6_addr ip6_dst;        /* destination address */
 459                 uint32_t length;
 460                 uint32_t next;
 461         } pseudo;
 462
 463         if(ratelimit(3))
 464                 return;
 465
 466         /* Swap Ethernet source and destination addresses */
 467
 468         swap_mac_addresses(packet);
 469
 470         /* Copy headers from packet to structs on the stack */
 471
 472         memcpy(&ip6, packet->data + ether_size, ip6_size);
 473
 474         /* Remember original source and destination */
 475
 476         pseudo.ip6_src = ip6.ip6_dst;
 477         pseudo.ip6_dst = ip6.ip6_src;
 478
 479         pseudo.length = packet->len - ether_size;
 480
 481         if(type == ICMP6_PACKET_TOO_BIG)
 482                 icmp6.icmp6_mtu = htonl(pseudo.length);
 483
 484         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 485                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 486
 487         /* Copy first part of original contents to ICMP message */
 488
 489         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 490
 491         /* Fill in IPv6 header */
 492
 493         ip6.ip6_flow = htonl(0x60000000UL);
 494         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 495         ip6.ip6_nxt = IPPROTO_ICMPV6;
 496         ip6.ip6_hlim = 255;
 497         ip6.ip6_src = pseudo.ip6_src;
 498         ip6.ip6_dst = pseudo.ip6_dst;
 499
 500         /* Fill in ICMP header */
 501
 502         icmp6.icmp6_type = type;
 503         icmp6.icmp6_code = code;
 504         icmp6.icmp6_cksum = 0;
 505
 506         /* Create pseudo header */
 507
 508         pseudo.length = htonl(icmp6_size + pseudo.length);
 509         pseudo.next = htonl(IPPROTO_ICMPV6);
 510
 511         /* Generate checksum */
 512
 513         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 514         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 515         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 516
 517         icmp6.icmp6_cksum = checksum;
 518
 519         /* Copy structs on stack back to packet */
 520
 521         memcpy(packet->data + ether_size, &ip6, ip6_size);
 522         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 523
 524         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 525
 526         send_packet(source, packet);
 527 }
 528
 529 static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet) {
 530         subnet_t *subnet;
 531         node_t *via;
 532         ipv6_t dest;
 533
 534         memcpy(&dest, &packet->data[38], sizeof dest);
 535         subnet = lookup_subnet_ipv6(&dest);
 536
 537         if(!subnet) {
 538                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 539                                 source->name, source->hostname,
 540                                 ntohs(dest.x[0]),
 541                                 ntohs(dest.x[1]),
 542                                 ntohs(dest.x[2]),
 543                                 ntohs(dest.x[3]),
 544                                 ntohs(dest.x[4]),
 545                                 ntohs(dest.x[5]),
 546                                 ntohs(dest.x[6]),
 547                                 ntohs(dest.x[7]));
 548
 549                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 550                 return;
 551         }
 552
 553         if(subnet->owner == source) {
 554                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 555                 return;
 556         }
 557
 558         if(!subnet->owner->status.reachable)
 559                 return route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 560
 561         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 562                 return route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 563
 564         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 565
 566         if(directonly && subnet->owner != via)
 567                 return route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 568
 569         if(via && packet->len > MAX(via->mtu, 1294) && via != myself) {
 570                 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);
 571                 packet->len = MAX(via->mtu, 1294);
 572                 route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 573                 return;
 574         }
 575
 576         clamp_mss(source, via, packet);
 577
 578         send_packet(subnet->owner, packet);
 579 }
 580
 581 /* RFC 2461 */
 582
 583 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 584         struct ip6_hdr ip6;
 585         struct nd_neighbor_solicit ns;
 586         struct nd_opt_hdr opt;
 587         subnet_t *subnet;
 588         uint16_t checksum;
 589         bool has_opt;
 590
 591         struct {
 592                 struct in6_addr ip6_src;        /* source address */
 593                 struct in6_addr ip6_dst;        /* destination address */
 594                 uint32_t length;
 595                 uint32_t next;
 596         } pseudo;
 597
 598         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 599                 return;
 600
 601         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 602
 603         if(source != myself) {
 604                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname);
 605                 return;
 606         }
 607
 608         /* Copy headers from packet to structs on the stack */
 609
 610         memcpy(&ip6, packet->data + ether_size, ip6_size);
 611         memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
 612         if(has_opt)
 613                 memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 614
 615         /* First, snatch the source address from the neighbor solicitation packet */
 616
 617         if(overwrite_mac)
 618                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 619
 620         /* Check if this is a valid neighbor solicitation request */
 621
 622         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 623            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 624                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request");
 625                 return;
 626         }
 627
 628         /* Create pseudo header */
 629
 630         pseudo.ip6_src = ip6.ip6_src;
 631         pseudo.ip6_dst = ip6.ip6_dst;
 632         if(has_opt)
 633                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 634         else
 635                 pseudo.length = htonl(ns_size);
 636         pseudo.next = htonl(IPPROTO_ICMPV6);
 637
 638         /* Generate checksum */
 639
 640         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 641         checksum = inet_checksum(&ns, ns_size, checksum);
 642         if(has_opt) {
 643                 checksum = inet_checksum(&opt, opt_size, checksum);
 644                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 645         }
 646
 647         if(checksum) {
 648                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request");
 649                 return;
 650         }
 651
 652         /* Check if the IPv6 address exists on the VPN */
 653
 654         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 655
 656         if(!subnet) {
 657                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 658                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 659                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 660                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 661                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 662                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 663                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 664                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 665                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 666
 667                 return;
 668         }
 669
 670         /* Check if it is for our own subnet */
 671
 672         if(subnet->owner == myself)
 673                 return;                                 /* silently ignore */
 674
 675         /* Create neighbor advertation reply */
 676
 677         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 678         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 679
 680         ip6.ip6_dst = ip6.ip6_src;                      /* swap destination and source protocoll address */
 681         ip6.ip6_src = ns.nd_ns_target;
 682
 683         if(has_opt)
 684                 memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 685
 686         ns.nd_ns_cksum = 0;
 687         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 688         ns.nd_ns_reserved = htonl(0x40000000UL);        /* Set solicited flag */
 689         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 690
 691         /* Create pseudo header */
 692
 693         pseudo.ip6_src = ip6.ip6_src;
 694         pseudo.ip6_dst = ip6.ip6_dst;
 695         if(has_opt)
 696                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 697         else
 698                 pseudo.length = htonl(ns_size);
 699         pseudo.next = htonl(IPPROTO_ICMPV6);
 700
 701         /* Generate checksum */
 702
 703         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 704         checksum = inet_checksum(&ns, ns_size, checksum);
 705         if(has_opt) {
 706                 checksum = inet_checksum(&opt, opt_size, checksum);
 707                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 708         }
 709
 710         ns.nd_ns_hdr.icmp6_cksum = checksum;
 711
 712         /* Copy structs on stack back to packet */
 713
 714         memcpy(packet->data + ether_size, &ip6, ip6_size);
 715         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 716         if(has_opt)
 717                 memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 718
 719         send_packet(source, packet);
 720 }
 721
 722 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 723         if(!checklength(source, packet, ether_size + ip6_size))
 724                 return;
 725
 726         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 727                 route_neighborsol(source, packet);
 728                 return;
 729         }
 730
 731         if(packet->data[38] == 255)
 732                 broadcast_packet(source, packet);
 733         else
 734                 route_ipv6_unicast(source, packet);
 735 }
 736
 737 /* RFC 826 */
 738
 739 static void route_arp(node_t *source, vpn_packet_t *packet) {
 740         struct ether_arp arp;
 741         subnet_t *subnet;
 742         struct in_addr addr;
 743
 744         if(!checklength(source, packet, ether_size + arp_size))
 745                 return;
 746
 747         if(source != myself) {
 748                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname);
 749                 return;
 750         }
 751
 752         /* First, snatch the source address from the ARP packet */
 753
 754         if(overwrite_mac)
 755                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 756
 757         /* Copy headers from packet to structs on the stack */
 758
 759         memcpy(&arp, packet->data + ether_size, arp_size);
 760
 761         /* Check if this is a valid ARP request */
 762
 763         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 764            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof addr || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 765                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type ARP request");
 766                 return;
 767         }
 768
 769         /* Check if the IPv4 address exists on the VPN */
 770
 771         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 772
 773         if(!subnet) {
 774                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d",
 775                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 776                                    arp.arp_tpa[3]);
 777                 return;
 778         }
 779
 780         /* Check if it is for our own subnet */
 781
 782         if(subnet->owner == myself)
 783                 return;                                 /* silently ignore */
 784
 785         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 786         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 787
 788         memcpy(&addr, arp.arp_tpa, sizeof addr);        /* save protocol addr */
 789         memcpy(arp.arp_tpa, arp.arp_spa, sizeof addr);  /* swap destination and source protocol address */
 790         memcpy(arp.arp_spa, &addr, sizeof addr);        /* ... */
 791
 792         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);     /* set target hard/proto addr */
 793         memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN); /* add fake source hard addr */
 794         arp.arp_op = htons(ARPOP_REPLY);
 795
 796         /* Copy structs on stack back to packet */
 797
 798         memcpy(packet->data + ether_size, &arp, arp_size);
 799
 800         send_packet(source, packet);
 801 }
 802
 803 static void route_mac(node_t *source, vpn_packet_t *packet) {
 804         subnet_t *subnet;
 805         mac_t dest;
 806
 807         /* Learn source address */
 808
 809         if(source == myself) {
 810                 mac_t src;
 811                 memcpy(&src, &packet->data[6], sizeof src);
 812                 learn_mac(&src);
 813         }
 814
 815         /* Lookup destination address */
 816
 817         memcpy(&dest, &packet->data[0], sizeof dest);
 818         subnet = lookup_subnet_mac(NULL, &dest);
 819
 820         if(!subnet) {
 821                 broadcast_packet(source, packet);
 822                 return;
 823         }
 824
 825         if(subnet->owner == source) {
 826                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 827                 return;
 828         }
 829
 830         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 831                 return;
 832
 833         // Handle packets larger than PMTU
 834
 835         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 836
 837         if(directonly && subnet->owner != via)
 838                 return;
 839
 840         if(via && packet->len > via->mtu && via != myself) {
 841                 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);
 842                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 843                 if(type == ETH_P_IP && packet->len > 590) {
 844                         if(packet->data[20] & 0x40) {
 845                                 packet->len = via->mtu;
 846                                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 847                         } else {
 848                                 fragment_ipv4_packet(via, packet);
 849                         }
 850                         return;
 851                 } else if(type == ETH_P_IPV6 && packet->len > 1294) {
 852                         packet->len = via->mtu;
 853                         route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 854                         return;
 855                 }
 856         }
 857
 858         clamp_mss(source, via, packet);
 859
 860         send_packet(subnet->owner, packet);
 861 }
 862
 863 void route(node_t *source, vpn_packet_t *packet) {
 864         if(forwarding_mode == FMODE_KERNEL && source != myself) {
 865                 send_packet(myself, packet);
 866                 return;
 867         }
 868
 869         if(!checklength(source, packet, ether_size))
 870                 return;
 871
 872         switch (routing_mode) {
 873                 case RMODE_ROUTER:
 874                         {
 875                                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 876
 877                                 switch (type) {
 878                                         case ETH_P_ARP:
 879                                                 route_arp(source, packet);
 880                                                 break;
 881
 882                                         case ETH_P_IP:
 883                                                 route_ipv4(source, packet);
 884                                                 break;
 885
 886                                         case ETH_P_IPV6:
 887                                                 route_ipv6(source, packet);
 888                                                 break;
 889
 890                                         default:
 891                                                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type);
 892                                                 break;
 893                                 }
 894                         }
 895                         break;
 896
 897                 case RMODE_SWITCH:
 898                         route_mac(source, packet);
 899                         break;
 900
 901                 case RMODE_HUB:
 902                         broadcast_packet(source, packet);
 903                         break;
 904         }
 905 }