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