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