www.tinc-vpn.org Git - tinc/blob - 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 static bool do_decrement_ttl(node_t *source, vpn_packet_t *packet);
  57
  58 #ifndef MAX
  59 #define MAX(a, b) ((a) > (b) ? (a) : (b))
  60 #endif
  61
  62 /* RFC 1071 */
  63
  64 static uint16_t inet_checksum(void *data, int len, uint16_t prevsum) {
  65         uint16_t *p = data;
  66         uint32_t checksum = prevsum ^ 0xFFFF;
  67
  68         while(len >= 2) {
  69                 checksum += *p++;
  70                 len -= 2;
  71         }
  72
  73         if(len)
  74                 checksum += *(uint8_t *)p;
  75
  76         while(checksum >> 16)
  77                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
  78
  79         return ~checksum;
  80 }
  81
  82 static bool ratelimit(int frequency) {
  83         static time_t lasttime = 0;
  84         static int count = 0;
  85
  86         if(lasttime == now) {
  87                 if(count >= frequency)
  88                         return true;
  89         } else {
  90                 lasttime = now;
  91                 count = 0;
  92         }
  93
  94         count++;
  95         return false;
  96 }
  97
  98 static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
  99         if(packet->len < length) {
 100                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got too short packet from %s (%s)", source->name, source->hostname);
 101                 return false;
 102         } else
 103                 return true;
 104 }
 105
 106 static void clamp_mss(const node_t *source, const node_t *via, vpn_packet_t *packet) {
 107         if(!source || !via || !(via->options & OPTION_CLAMP_MSS))
 108                 return;
 109
 110         uint16_t mtu = source->mtu;
 111         if(via != myself && via->mtu < mtu)
 112                 mtu = via->mtu;
 113
 114         /* Find TCP header */
 115         int start = ether_size;
 116         uint16_t type = packet->data[12] << 8 | packet->data[13];
 117
 118         if(type == ETH_P_8021Q) {
 119                 start += 4;
 120                 type = packet->data[16] << 8 | packet->data[17];
 121         }
 122
 123         if(type == ETH_P_IP && packet->data[start + 9] == 6)
 124                 start += (packet->data[start] & 0xf) * 4;
 125         else if(type == ETH_P_IPV6 && packet->data[start + 6] == 6)
 126                 start += 40;
 127         else
 128                 return;
 129
 130         if(packet->len <= start + 20)
 131                 return;
 132
 133         /* Use data offset field to calculate length of options field */
 134         int len = ((packet->data[start + 12] >> 4) - 5) * 4;
 135
 136         if(packet->len < start + 20 + len)
 137                 return;
 138
 139         /* Search for MSS option header */
 140         for(int i = 0; i < len;) {
 141                 if(packet->data[start + 20 + i] == 0)
 142                         break;
 143
 144                 if(packet->data[start + 20 + i] == 1) {
 145                         i++;
 146                         continue;
 147                 }
 148
 149                 if(i > len - 2 || i > len - packet->data[start + 21 + i])
 150                         break;
 151
 152                 if(packet->data[start + 20 + i] != 2) {
 153                         if(packet->data[start + 21 + i] < 2)
 154                                 break;
 155                         i += packet->data[start + 21 + i];
 156                         continue;
 157                 }
 158
 159                 if(packet->data[start + 21] != 4)
 160                         break;
 161
 162                 /* Found it */
 163                 uint16_t oldmss = packet->data[start + 22 + i] << 8 | packet->data[start + 23 + i];
 164                 uint16_t newmss = mtu - start - 20;
 165                 uint32_t csum = packet->data[start + 16] << 8 | packet->data[start + 17];
 166
 167                 if(oldmss <= newmss)
 168                         break;
 169
 170                 ifdebug(TRAFFIC) logger(LOG_INFO, "Clamping MSS of packet from %s to %s to %d", source->name, via->name, newmss);
 171
 172                 /* Update the MSS value and the checksum */
 173                 packet->data[start + 22 + i] = newmss >> 8;
 174                 packet->data[start + 23 + i] = newmss & 0xff;
 175                 csum ^= 0xffff;
 176                 csum += oldmss ^ 0xffff;
 177                 csum += newmss;
 178                 csum = (csum & 0xffff) + (csum >> 16);
 179                 csum += csum >> 16;
 180                 csum ^= 0xffff;
 181                 packet->data[start + 16] = csum >> 8;
 182                 packet->data[start + 17] = csum;
 183                 break;
 184         }
 185 }
 186
 187 static void swap_mac_addresses(vpn_packet_t *packet) {
 188         mac_t tmp;
 189         memcpy(&tmp, &packet->data[0], sizeof tmp);
 190         memcpy(&packet->data[0], &packet->data[6], sizeof tmp);
 191         memcpy(&packet->data[6], &tmp, sizeof tmp);
 192 }
 193
 194 static void learn_mac(mac_t *address) {
 195         subnet_t *subnet;
 196         avl_node_t *node;
 197         connection_t *c;
 198
 199         subnet = lookup_subnet_mac(myself, address);
 200
 201         /* If we don't know this MAC address yet, store it */
 202
 203         if(!subnet) {
 204                 ifdebug(TRAFFIC) logger(LOG_INFO, "Learned new MAC address %x:%x:%x:%x:%x:%x",
 205                                    address->x[0], address->x[1], address->x[2], address->x[3],
 206                                    address->x[4], address->x[5]);
 207
 208                 subnet = new_subnet();
 209                 subnet->type = SUBNET_MAC;
 210                 subnet->expires = now + macexpire;
 211                 subnet->net.mac.address = *address;
 212                 subnet->weight = 10;
 213                 subnet_add(myself, subnet);
 214                 subnet_update(myself, subnet, true);
 215
 216                 /* And tell all other tinc daemons it's our MAC */
 217
 218                 for(node = connection_tree->head; node; node = node->next) {
 219                         c = node->data;
 220                         if(c->status.active)
 221                                 send_add_subnet(c, subnet);
 222                 }
 223         }
 224
 225         if(subnet->expires)
 226                 subnet->expires = now + macexpire;
 227 }
 228
 229 void age_subnets(void) {
 230         subnet_t *s;
 231         connection_t *c;
 232         avl_node_t *node, *next, *node2;
 233
 234         for(node = myself->subnet_tree->head; node; node = next) {
 235                 next = node->next;
 236                 s = node->data;
 237                 if(s->expires && s->expires <= now) {
 238                         ifdebug(TRAFFIC) {
 239                                 char netstr[MAXNETSTR];
 240                                 if(net2str(netstr, sizeof netstr, s))
 241                                         logger(LOG_INFO, "Subnet %s expired", netstr);
 242                         }
 243
 244                         for(node2 = connection_tree->head; node2; node2 = node2->next) {
 245                                 c = node2->data;
 246                                 if(c->status.active)
 247                                         send_del_subnet(c, s);
 248                         }
 249
 250                         subnet_update(myself, s, false);
 251                         subnet_del(myself, s);
 252                 }
 253         }
 254 }
 255
 256 static void broadcast_packet_helper(node_t *source, vpn_packet_t *packet) {
 257         if(decrement_ttl && source != myself)
 258                 if(!do_decrement_ttl(source, packet))
 259                         return;
 260
 261         broadcast_packet(source, packet);
 262 }
 263
 264 /* RFC 792 */
 265
 266 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, uint8_t type, uint8_t code) {
 267         struct ip ip = {0};
 268         struct icmp icmp = {0};
 269
 270         struct in_addr ip_src;
 271         struct in_addr ip_dst;
 272         uint32_t oldlen;
 273
 274         if(ratelimit(3))
 275                 return;
 276
 277         /* Swap Ethernet source and destination addresses */
 278
 279         swap_mac_addresses(packet);
 280
 281         /* Copy headers from packet into properly aligned structs on the stack */
 282
 283         memcpy(&ip, packet->data + ether_size, ip_size);
 284
 285         /* Remember original source and destination */
 286
 287         ip_src = ip.ip_src;
 288         ip_dst = ip.ip_dst;
 289
 290         /* Try to reply with an IP address assigned to the local machine */
 291
 292         if (type == ICMP_TIME_EXCEEDED && code == ICMP_EXC_TTL) {
 293                 int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
 294                 if (sockfd != -1) {
 295                         struct sockaddr_in addr;
 296                         memset(&addr, 0, sizeof(addr));
 297                         addr.sin_family = AF_INET;
 298                         addr.sin_addr = ip.ip_src;
 299                         if (!connect(sockfd, (const struct sockaddr*) &addr, sizeof(addr))) {
 300                                 memset(&addr, 0, sizeof(addr));
 301                                 addr.sin_family = AF_INET;
 302                                 socklen_t addrlen = sizeof(addr);
 303                                 if (!getsockname(sockfd, (struct sockaddr*) &addr, &addrlen) && addrlen <= sizeof(addr)) {
 304                                         ip_dst = addr.sin_addr;
 305                                 }
 306                         }
 307                         close(sockfd);
 308                 }
 309         }
 310
 311         oldlen = packet->len - ether_size;
 312
 313         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 314                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 315
 316         if(oldlen >= IP_MSS - ip_size - icmp_size)
 317                 oldlen = IP_MSS - ip_size - icmp_size;
 318
 319         /* Copy first part of original contents to ICMP message */
 320
 321         memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
 322
 323         /* Fill in IPv4 header */
 324
 325         ip.ip_v = 4;
 326         ip.ip_hl = ip_size / 4;
 327         ip.ip_tos = 0;
 328         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 329         ip.ip_id = 0;
 330         ip.ip_off = 0;
 331         ip.ip_ttl = 255;
 332         ip.ip_p = IPPROTO_ICMP;
 333         ip.ip_sum = 0;
 334         ip.ip_src = ip_dst;
 335         ip.ip_dst = ip_src;
 336
 337         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 338
 339         /* Fill in ICMP header */
 340
 341         icmp.icmp_type = type;
 342         icmp.icmp_code = code;
 343         icmp.icmp_cksum = 0;
 344
 345         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 346         icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 347
 348         /* Copy structs on stack back to packet */
 349
 350         memcpy(packet->data + ether_size, &ip, ip_size);
 351         memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
 352
 353         packet->len = ether_size + ip_size + icmp_size + oldlen;
 354
 355         send_packet(source, packet);
 356 }
 357
 358 /* RFC 791 */
 359
 360 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet, length_t ether_size) {
 361         struct ip ip;
 362         vpn_packet_t fragment;
 363         int len, maxlen, todo;
 364         uint8_t *offset;
 365         uint16_t ip_off, origf;
 366
 367         memcpy(&ip, packet->data + ether_size, ip_size);
 368         fragment.priority = packet->priority;
 369
 370         if(ip.ip_hl != ip_size / 4)
 371                 return;
 372
 373         todo = ntohs(ip.ip_len) - ip_size;
 374
 375         if(ether_size + ip_size + todo != packet->len) {
 376                 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));
 377                 return;
 378         }
 379
 380         ifdebug(TRAFFIC) logger(LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname);
 381
 382         offset = packet->data + ether_size + ip_size;
 383         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 384         ip_off = ntohs(ip.ip_off);
 385         origf = ip_off & ~IP_OFFMASK;
 386         ip_off &= IP_OFFMASK;
 387
 388         while(todo) {
 389                 len = todo > maxlen ? maxlen : todo;
 390                 memcpy(fragment.data + ether_size + ip_size, offset, len);
 391                 todo -= len;
 392                 offset += len;
 393
 394                 ip.ip_len = htons(ip_size + len);
 395                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 396                 ip.ip_sum = 0;
 397                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 398                 memcpy(fragment.data, packet->data, ether_size);
 399                 memcpy(fragment.data + ether_size, &ip, ip_size);
 400                 fragment.len = ether_size + ip_size + len;
 401
 402                 send_packet(dest, &fragment);
 403
 404                 ip_off += len / 8;
 405         }
 406 }
 407
 408 static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet) {
 409         subnet_t *subnet;
 410         node_t *via;
 411         ipv4_t dest;
 412
 413         memcpy(&dest, &packet->data[30], sizeof dest);
 414         subnet = lookup_subnet_ipv4(&dest);
 415
 416         if(!subnet) {
 417                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d",
 418                                 source->name, source->hostname,
 419                                 dest.x[0],
 420                                 dest.x[1],
 421                                 dest.x[2],
 422                                 dest.x[3]);
 423
 424                 route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 425                 return;
 426         }
 427
 428         if(subnet->owner == source) {
 429                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 430                 return;
 431         }
 432
 433         if(!subnet->owner->status.reachable)
 434                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 435
 436         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 437                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 438
 439         if(decrement_ttl && source != myself && subnet->owner != myself)
 440                 if(!do_decrement_ttl(source, packet))
 441                         return;
 442
 443         if(priorityinheritance)
 444                 packet->priority = packet->data[15];
 445
 446         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 447
 448         if(via == source) {
 449                 ifdebug(TRAFFIC) logger(LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 450                 return;
 451         }
 452
 453         if(directonly && subnet->owner != via)
 454                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 455
 456         if(via && packet->len > MAX(via->mtu, 590) && via != myself) {
 457                 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);
 458                 if(packet->data[20] & 0x40) {
 459                         packet->len = MAX(via->mtu, 590);
 460                         route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 461                 } else {
 462                         fragment_ipv4_packet(via, packet, ether_size);
 463                 }
 464
 465                 return;
 466         }
 467
 468         clamp_mss(source, via, packet);
 469
 470         send_packet(subnet->owner, packet);
 471 }
 472
 473 static void route_ipv4(node_t *source, vpn_packet_t *packet) {
 474         if(!checklength(source, packet, ether_size + ip_size))
 475                 return;
 476
 477         if(broadcast_mode && (((packet->data[30] & 0xf0) == 0xe0) || (
 478                         packet->data[30] == 255 &&
 479                         packet->data[31] == 255 &&
 480                         packet->data[32] == 255 &&
 481                         packet->data[33] == 255)))
 482                 broadcast_packet_helper(source, packet);
 483         else
 484                 route_ipv4_unicast(source, packet);
 485 }
 486
 487 /* RFC 2463 */
 488
 489 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, uint8_t type, uint8_t code) {
 490         struct ip6_hdr ip6;
 491         struct icmp6_hdr icmp6 = {0};
 492         uint16_t checksum;
 493
 494         struct {
 495                 struct in6_addr ip6_src;        /* source address */
 496                 struct in6_addr ip6_dst;        /* destination address */
 497                 uint32_t length;
 498                 uint32_t next;
 499         } pseudo;
 500
 501         if(ratelimit(3))
 502                 return;
 503
 504         /* Swap Ethernet source and destination addresses */
 505
 506         swap_mac_addresses(packet);
 507
 508         /* Copy headers from packet to structs on the stack */
 509
 510         memcpy(&ip6, packet->data + ether_size, ip6_size);
 511
 512         /* Remember original source and destination */
 513
 514         pseudo.ip6_src = ip6.ip6_dst;
 515         pseudo.ip6_dst = ip6.ip6_src;
 516
 517         /* Try to reply with an IP address assigned to the local machine */
 518
 519         if (type == ICMP6_TIME_EXCEEDED && code == ICMP6_TIME_EXCEED_TRANSIT) {
 520                 int sockfd = socket(AF_INET6, SOCK_DGRAM, 0);
 521                 if (sockfd != -1) {
 522                         struct sockaddr_in6 addr;
 523                         memset(&addr, 0, sizeof(addr));
 524                         addr.sin6_family = AF_INET6;
 525                         addr.sin6_addr = ip6.ip6_src;
 526                         if (!connect(sockfd, (const struct sockaddr*) &addr, sizeof(addr))) {
 527                                 memset(&addr, 0, sizeof(addr));
 528                                 addr.sin6_family = AF_INET6;
 529                                 socklen_t addrlen = sizeof(addr);
 530                                 if (!getsockname(sockfd, (struct sockaddr*) &addr, &addrlen) && addrlen <= sizeof(addr)) {
 531                                         pseudo.ip6_src = addr.sin6_addr;
 532                                 }
 533                         }
 534                         close(sockfd);
 535                 }
 536         }
 537
 538         pseudo.length = packet->len - ether_size;
 539
 540         if(type == ICMP6_PACKET_TOO_BIG)
 541                 icmp6.icmp6_mtu = htonl(pseudo.length);
 542
 543         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 544                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 545
 546         /* Copy first part of original contents to ICMP message */
 547
 548         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 549
 550         /* Fill in IPv6 header */
 551
 552         ip6.ip6_flow = htonl(0x60000000UL);
 553         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 554         ip6.ip6_nxt = IPPROTO_ICMPV6;
 555         ip6.ip6_hlim = 255;
 556         ip6.ip6_src = pseudo.ip6_src;
 557         ip6.ip6_dst = pseudo.ip6_dst;
 558
 559         /* Fill in ICMP header */
 560
 561         icmp6.icmp6_type = type;
 562         icmp6.icmp6_code = code;
 563         icmp6.icmp6_cksum = 0;
 564
 565         /* Create pseudo header */
 566
 567         pseudo.length = htonl(icmp6_size + pseudo.length);
 568         pseudo.next = htonl(IPPROTO_ICMPV6);
 569
 570         /* Generate checksum */
 571
 572         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 573         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 574         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 575
 576         icmp6.icmp6_cksum = checksum;
 577
 578         /* Copy structs on stack back to packet */
 579
 580         memcpy(packet->data + ether_size, &ip6, ip6_size);
 581         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 582
 583         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 584
 585         send_packet(source, packet);
 586 }
 587
 588 static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet) {
 589         subnet_t *subnet;
 590         node_t *via;
 591         ipv6_t dest;
 592
 593         memcpy(&dest, &packet->data[38], sizeof dest);
 594         subnet = lookup_subnet_ipv6(&dest);
 595
 596         if(!subnet) {
 597                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 598                                 source->name, source->hostname,
 599                                 ntohs(dest.x[0]),
 600                                 ntohs(dest.x[1]),
 601                                 ntohs(dest.x[2]),
 602                                 ntohs(dest.x[3]),
 603                                 ntohs(dest.x[4]),
 604                                 ntohs(dest.x[5]),
 605                                 ntohs(dest.x[6]),
 606                                 ntohs(dest.x[7]));
 607
 608                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 609                 return;
 610         }
 611
 612         if(subnet->owner == source) {
 613                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 614                 return;
 615         }
 616
 617         if(!subnet->owner->status.reachable)
 618                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 619
 620         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 621                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 622
 623         if(decrement_ttl && source != myself && subnet->owner != myself)
 624                 if(!do_decrement_ttl(source, packet))
 625                         return;
 626
 627         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 628
 629         if(via == source) {
 630                 ifdebug(TRAFFIC) logger(LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 631                 return;
 632         }
 633
 634         if(directonly && subnet->owner != via)
 635                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 636
 637         if(via && packet->len > MAX(via->mtu, 1294) && via != myself) {
 638                 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);
 639                 packet->len = MAX(via->mtu, 1294);
 640                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_PACKET_TOO_BIG, 0);
 641                 return;
 642         }
 643
 644         clamp_mss(source, via, packet);
 645
 646         send_packet(subnet->owner, packet);
 647 }
 648
 649 /* RFC 2461 */
 650
 651 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 652         struct ip6_hdr ip6;
 653         struct nd_neighbor_solicit ns;
 654         struct nd_opt_hdr opt;
 655         subnet_t *subnet;
 656         uint16_t checksum;
 657         bool has_opt;
 658
 659         struct {
 660                 struct in6_addr ip6_src;        /* source address */
 661                 struct in6_addr ip6_dst;        /* destination address */
 662                 uint32_t length;
 663                 uint32_t next;
 664         } pseudo;
 665
 666         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 667                 return;
 668
 669         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 670
 671         if(source != myself) {
 672                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname);
 673                 return;
 674         }
 675
 676         /* Copy headers from packet to structs on the stack */
 677
 678         memcpy(&ip6, packet->data + ether_size, ip6_size);
 679         memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
 680         if(has_opt)
 681                 memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 682
 683         /* First, snatch the source address from the neighbor solicitation packet */
 684
 685         if(overwrite_mac)
 686                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 687
 688         /* Check if this is a valid neighbor solicitation request */
 689
 690         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 691            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 692                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request");
 693                 return;
 694         }
 695
 696         /* Create pseudo header */
 697
 698         pseudo.ip6_src = ip6.ip6_src;
 699         pseudo.ip6_dst = ip6.ip6_dst;
 700         if(has_opt)
 701                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 702         else
 703                 pseudo.length = htonl(ns_size);
 704         pseudo.next = htonl(IPPROTO_ICMPV6);
 705
 706         /* Generate checksum */
 707
 708         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 709         checksum = inet_checksum(&ns, ns_size, checksum);
 710         if(has_opt) {
 711                 checksum = inet_checksum(&opt, opt_size, checksum);
 712                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 713         }
 714
 715         if(checksum) {
 716                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request");
 717                 return;
 718         }
 719
 720         /* Check if the IPv6 address exists on the VPN */
 721
 722         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 723
 724         if(!subnet) {
 725                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 726                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 727                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 728                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 729                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 730                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 731                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 732                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 733                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 734
 735                 return;
 736         }
 737
 738         /* Check if it is for our own subnet */
 739
 740         if(subnet->owner == myself)
 741                 return;                                 /* silently ignore */
 742
 743         if(decrement_ttl)
 744                 if(!do_decrement_ttl(source, packet))
 745                         return;
 746
 747         /* Create neighbor advertation reply */
 748
 749         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 750         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 751
 752         ip6.ip6_dst = ip6.ip6_src;                      /* swap destination and source protocoll address */
 753         ip6.ip6_src = ns.nd_ns_target;
 754
 755         if(has_opt)
 756                 memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 757
 758         ns.nd_ns_cksum = 0;
 759         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 760         ns.nd_ns_reserved = htonl(0x40000000UL);        /* Set solicited flag */
 761         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 762
 763         /* Create pseudo header */
 764
 765         pseudo.ip6_src = ip6.ip6_src;
 766         pseudo.ip6_dst = ip6.ip6_dst;
 767         if(has_opt)
 768                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 769         else
 770                 pseudo.length = htonl(ns_size);
 771         pseudo.next = htonl(IPPROTO_ICMPV6);
 772
 773         /* Generate checksum */
 774
 775         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 776         checksum = inet_checksum(&ns, ns_size, checksum);
 777         if(has_opt) {
 778                 checksum = inet_checksum(&opt, opt_size, checksum);
 779                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 780         }
 781
 782         ns.nd_ns_hdr.icmp6_cksum = checksum;
 783
 784         /* Copy structs on stack back to packet */
 785
 786         memcpy(packet->data + ether_size, &ip6, ip6_size);
 787         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 788         if(has_opt)
 789                 memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 790
 791         send_packet(source, packet);
 792 }
 793
 794 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 795         if(!checklength(source, packet, ether_size + ip6_size))
 796                 return;
 797
 798         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 799                 route_neighborsol(source, packet);
 800                 return;
 801         }
 802
 803         if(broadcast_mode && packet->data[38] == 255)
 804                 broadcast_packet_helper(source, packet);
 805         else
 806                 route_ipv6_unicast(source, packet);
 807 }
 808
 809 /* RFC 826 */
 810
 811 static void route_arp(node_t *source, vpn_packet_t *packet) {
 812         struct ether_arp arp;
 813         subnet_t *subnet;
 814         struct in_addr addr;
 815
 816         if(!checklength(source, packet, ether_size + arp_size))
 817                 return;
 818
 819         if(source != myself) {
 820                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname);
 821                 return;
 822         }
 823
 824         /* First, snatch the source address from the ARP packet */
 825
 826         if(overwrite_mac)
 827                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 828
 829         /* Copy headers from packet to structs on the stack */
 830
 831         memcpy(&arp, packet->data + ether_size, arp_size);
 832
 833         /* Check if this is a valid ARP request */
 834
 835         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 836            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof(addr) || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 837                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type ARP request");
 838                 return;
 839         }
 840
 841         /* Check if the IPv4 address exists on the VPN */
 842
 843         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 844
 845         if(!subnet) {
 846                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d",
 847                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 848                                    arp.arp_tpa[3]);
 849                 return;
 850         }
 851
 852         /* Check if it is for our own subnet */
 853
 854         if(subnet->owner == myself)
 855                 return;                                 /* silently ignore */
 856
 857         if(decrement_ttl)
 858                 if(!do_decrement_ttl(source, packet))
 859                         return;
 860
 861         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 862         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 863
 864         memcpy(&addr, arp.arp_tpa, sizeof(addr));       /* save protocol addr */
 865         memcpy(arp.arp_tpa, arp.arp_spa, sizeof(addr)); /* swap destination and source protocol address */
 866         memcpy(arp.arp_spa, &addr, sizeof(addr));       /* ... */
 867
 868         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);     /* set target hard/proto addr */
 869         memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN); /* add fake source hard addr */
 870         arp.arp_op = htons(ARPOP_REPLY);
 871
 872         /* Copy structs on stack back to packet */
 873
 874         memcpy(packet->data + ether_size, &arp, arp_size);
 875
 876         send_packet(source, packet);
 877 }
 878
 879 static void route_mac(node_t *source, vpn_packet_t *packet) {
 880         subnet_t *subnet;
 881         mac_t dest;
 882
 883         /* Learn source address */
 884
 885         if(source == myself) {
 886                 mac_t src;
 887                 memcpy(&src, &packet->data[6], sizeof src);
 888                 learn_mac(&src);
 889         }
 890
 891         /* Lookup destination address */
 892
 893         memcpy(&dest, &packet->data[0], sizeof dest);
 894         subnet = lookup_subnet_mac(NULL, &dest);
 895
 896         if(!subnet) {
 897                 broadcast_packet_helper(source, packet);
 898                 return;
 899         }
 900
 901         if(subnet->owner == source) {
 902                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 903                 return;
 904         }
 905
 906         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 907                 return;
 908
 909         if(decrement_ttl && source != myself && subnet->owner != myself)
 910                 if(!do_decrement_ttl(source, packet))
 911                         return;
 912
 913         uint16_t type = packet->data[12] << 8 | packet->data[13];
 914
 915         if(priorityinheritance && type == ETH_P_IP && packet->len >= ether_size + ip_size)
 916                 packet->priority = packet->data[15];
 917
 918         // Handle packets larger than PMTU
 919
 920         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 921
 922         if(directonly && subnet->owner != via)
 923                 return;
 924
 925         if(via && packet->len > via->mtu && via != myself) {
 926                 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);
 927                 length_t ethlen = 14;
 928
 929                 if(type == ETH_P_8021Q) {
 930                         type = packet->data[16] << 8 | packet->data[17];
 931                         ethlen += 4;
 932                 }
 933
 934                 if(type == ETH_P_IP && packet->len > 576 + ethlen) {
 935                         if(packet->data[6 + ethlen] & 0x40) {
 936                                 packet->len = via->mtu;
 937                                 route_ipv4_unreachable(source, packet, ethlen, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 938                         } else {
 939                                 fragment_ipv4_packet(via, packet, ethlen);
 940                         }
 941                         return;
 942                 } else if(type == ETH_P_IPV6 && packet->len > 1280 + ethlen) {
 943                         packet->len = via->mtu;
 944                         route_ipv6_unreachable(source, packet, ethlen, ICMP6_PACKET_TOO_BIG, 0);
 945                         return;
 946                 }
 947         }
 948
 949         clamp_mss(source, via, packet);
 950
 951         send_packet(subnet->owner, packet);
 952 }
 953
 954 static bool do_decrement_ttl(node_t *source, vpn_packet_t *packet) {
 955         uint16_t type = packet->data[12] << 8 | packet->data[13];
 956         length_t ethlen = ether_size;
 957
 958         if(type == ETH_P_8021Q) {
 959                 type = packet->data[16] << 8 | packet->data[17];
 960                 ethlen += 4;
 961         }
 962
 963         switch (type) {
 964                 case ETH_P_IP:
 965                         if(!checklength(source, packet, ethlen + ip_size))
 966                                 return false;
 967
 968                         if(packet->data[ethlen + 8] <= 1) {
 969                                 if(packet->data[ethlen + 11] != IPPROTO_ICMP || packet->data[ethlen + 32] != ICMP_TIME_EXCEEDED)
 970                                         route_ipv4_unreachable(source, packet, ethlen, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL);
 971                                 return false;
 972                         }
 973
 974                         uint16_t old = packet->data[ethlen + 8] << 8 | packet->data[ethlen + 9];
 975                         packet->data[ethlen + 8]--;
 976                         uint16_t new = packet->data[ethlen + 8] << 8 | packet->data[ethlen + 9];
 977
 978                         uint32_t checksum = packet->data[ethlen + 10] << 8 | packet->data[ethlen + 11];
 979                         checksum += old + (~new & 0xFFFF);
 980                         while(checksum >> 16)
 981                                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
 982                         packet->data[ethlen + 10] = checksum >> 8;
 983                         packet->data[ethlen + 11] = checksum & 0xff;
 984
 985                         return true;
 986
 987                 case ETH_P_IPV6:
 988                         if(!checklength(source, packet, ethlen + ip6_size))
 989                                 return false;
 990
 991                         if(packet->data[ethlen + 7] <= 1) {
 992                                 if(packet->data[ethlen + 6] != IPPROTO_ICMPV6 || packet->data[ethlen + 40] != ICMP6_TIME_EXCEEDED)
 993                                         route_ipv6_unreachable(source, packet, ethlen, ICMP6_TIME_EXCEEDED, ICMP6_TIME_EXCEED_TRANSIT);
 994                                 return false;
 995                         }
 996
 997                         packet->data[ethlen + 7]--;
 998
 999                         return true;
1000
1001                 default:
1002                         return true;
1003         }
1004 }
1005
1006 void route(node_t *source, vpn_packet_t *packet) {
1007         if(forwarding_mode == FMODE_KERNEL && source != myself) {
1008                 send_packet(myself, packet);
1009                 return;
1010         }
1011
1012         if(!checklength(source, packet, ether_size))
1013                 return;
1014
1015         switch (routing_mode) {
1016                 case RMODE_ROUTER:
1017                         {
1018                                 uint16_t type = packet->data[12] << 8 | packet->data[13];
1019
1020                                 switch (type) {
1021                                         case ETH_P_ARP:
1022                                                 route_arp(source, packet);
1023                                                 break;
1024
1025                                         case ETH_P_IP:
1026                                                 route_ipv4(source, packet);
1027                                                 break;
1028
1029                                         case ETH_P_IPV6:
1030                                                 route_ipv6(source, packet);
1031                                                 break;
1032
1033                                         default:
1034                                                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type);
1035                                                 break;
1036                                 }
1037                         }
1038                         break;
1039
1040                 case RMODE_SWITCH:
1041                         route_mac(source, packet);
1042                         break;
1043
1044                 case RMODE_HUB:
1045                         broadcast_packet_helper(source, packet);
1046                         break;
1047         }
1048 }