src/route.c

   1 /*
   2     route.c -- routing
   3     Copyright (C) 2000-2005 Ivo Timmermans,
   4                   2000-2014 Guus Sliepen <guus@tinc-vpn.org>
   5
   6     This program is free software; you can redistribute it and/or modify
   7     it under the terms of the GNU General Public License as published by
   8     the Free Software Foundation; either version 2 of the License, or
   9     (at your option) any later version.
  10
  11     This program is distributed in the hope that it will be useful,
  12     but WITHOUT ANY WARRANTY; without even the implied warranty of
  13     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14     GNU General Public License for more details.
  15
  16     You should have received a copy of the GNU General Public License along
  17     with this program; if not, write to the Free Software Foundation, Inc.,
  18     51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  19 */
  20
  21 #include "system.h"
  22
  23 #include "avl_tree.h"
  24 #include "connection.h"
  25 #include "ethernet.h"
  26 #include "ipv4.h"
  27 #include "ipv6.h"
  28 #include "logger.h"
  29 #include "net.h"
  30 #include "protocol.h"
  31 #include "route.h"
  32 #include "subnet.h"
  33 #include "utils.h"
  34
  35 rmode_t routing_mode = RMODE_ROUTER;
  36 fmode_t forwarding_mode = FMODE_INTERNAL;
  37 bmode_t broadcast_mode = BMODE_MST;
  38 bool decrement_ttl = false;
  39 bool directonly = false;
  40 bool priorityinheritance = false;
  41 int macexpire = 600;
  42 bool overwrite_mac = false;
  43 mac_t mymac = {{0xFE, 0xFD, 0, 0, 0, 0}};
  44
  45 /* Sizes of various headers */
  46
  47 static const size_t ether_size = sizeof(struct ether_header);
  48 static const size_t arp_size = sizeof(struct ether_arp);
  49 static const size_t ip_size = sizeof(struct ip);
  50 static const size_t icmp_size = sizeof(struct icmp) - sizeof(struct ip);
  51 static const size_t ip6_size = sizeof(struct ip6_hdr);
  52 static const size_t icmp6_size = sizeof(struct icmp6_hdr);
  53 static const size_t ns_size = sizeof(struct nd_neighbor_solicit);
  54 static const size_t opt_size = sizeof(struct nd_opt_hdr);
  55
  56 #ifndef MAX
  57 #define MAX(a, b) ((a) > (b) ? (a) : (b))
  58 #endif
  59
  60 /* RFC 1071 */
  61
  62 static uint16_t inet_checksum(void *data, int len, uint16_t prevsum) {
  63         uint16_t *p = data;
  64         uint32_t checksum = prevsum ^ 0xFFFF;
  65
  66         while(len >= 2) {
  67                 checksum += *p++;
  68                 len -= 2;
  69         }
  70
  71         if(len)
  72                 checksum += *(uint8_t *)p;
  73
  74         while(checksum >> 16)
  75                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
  76
  77         return ~checksum;
  78 }
  79
  80 static bool ratelimit(int frequency) {
  81         static time_t lasttime = 0;
  82         static int count = 0;
  83
  84         if(lasttime == now) {
  85                 if(count >= frequency)
  86                         return true;
  87         } else {
  88                 lasttime = now;
  89                 count = 0;
  90         }
  91
  92         count++;
  93         return false;
  94 }
  95
  96 static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
  97         if(packet->len < length) {
  98                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got too short packet from %s (%s)", source->name, source->hostname);
  99                 return false;
 100         } else
 101                 return true;
 102 }
 103
 104 static void clamp_mss(const node_t *source, const node_t *via, vpn_packet_t *packet) {
 105         if(!source || !via || !(via->options & OPTION_CLAMP_MSS))
 106                 return;
 107
 108         uint16_t mtu = source->mtu;
 109         if(via != myself && via->mtu < mtu)
 110                 mtu = via->mtu;
 111
 112         /* Find TCP header */
 113         int start = ether_size;
 114         uint16_t type = packet->data[12] << 8 | packet->data[13];
 115
 116         if(type == ETH_P_8021Q) {
 117                 start += 4;
 118                 type = packet->data[16] << 8 | packet->data[17];
 119         }
 120
 121         if(type == ETH_P_IP && packet->data[start + 9] == 6)
 122                 start += (packet->data[start] & 0xf) * 4;
 123         else if(type == ETH_P_IPV6 && packet->data[start + 6] == 6)
 124                 start += 40;
 125         else
 126                 return;
 127
 128         if(packet->len <= start + 20)
 129                 return;
 130
 131         /* Use data offset field to calculate length of options field */
 132         int len = ((packet->data[start + 12] >> 4) - 5) * 4;
 133
 134         if(packet->len < start + 20 + len)
 135                 return;
 136
 137         /* Search for MSS option header */
 138         for(int i = 0; i < len;) {
 139                 if(packet->data[start + 20 + i] == 0)
 140                         break;
 141
 142                 if(packet->data[start + 20 + i] == 1) {
 143                         i++;
 144                         continue;
 145                 }
 146
 147                 if(i > len - 2 || i > len - packet->data[start + 21 + i])
 148                         break;
 149
 150                 if(packet->data[start + 20 + i] != 2) {
 151                         if(packet->data[start + 21 + i] < 2)
 152                                 break;
 153                         i += packet->data[start + 21 + i];
 154                         continue;
 155                 }
 156
 157                 if(packet->data[start + 21] != 4)
 158                         break;
 159
 160                 /* Found it */
 161                 uint16_t oldmss = packet->data[start + 22 + i] << 8 | packet->data[start + 23 + i];
 162                 uint16_t newmss = mtu - start - 20;
 163                 uint16_t csum = packet->data[start + 16] << 8 | packet->data[start + 17];
 164
 165                 if(oldmss <= newmss)
 166                         break;
 167
 168                 ifdebug(TRAFFIC) logger(LOG_INFO, "Clamping MSS of packet from %s to %s to %d", source->name, via->name, newmss);
 169
 170                 /* Update the MSS value and the checksum */
 171                 packet->data[start + 22 + i] = newmss >> 8;
 172                 packet->data[start + 23 + i] = newmss & 0xff;
 173                 csum ^= 0xffff;
 174                 csum -= oldmss;
 175                 csum += newmss;
 176                 csum ^= 0xffff;
 177                 packet->data[start + 16] = csum >> 8;
 178                 packet->data[start + 17] = csum & 0xff;
 179                 break;
 180         }
 181 }
 182
 183 static void swap_mac_addresses(vpn_packet_t *packet) {
 184         mac_t tmp;
 185         memcpy(&tmp, &packet->data[0], sizeof tmp);
 186         memcpy(&packet->data[0], &packet->data[6], sizeof tmp);
 187         memcpy(&packet->data[6], &tmp, sizeof tmp);
 188 }
 189
 190 static void learn_mac(mac_t *address) {
 191         subnet_t *subnet;
 192         avl_node_t *node;
 193         connection_t *c;
 194
 195         subnet = lookup_subnet_mac(myself, address);
 196
 197         /* If we don't know this MAC address yet, store it */
 198
 199         if(!subnet) {
 200                 ifdebug(TRAFFIC) logger(LOG_INFO, "Learned new MAC address %x:%x:%x:%x:%x:%x",
 201                                    address->x[0], address->x[1], address->x[2], address->x[3],
 202                                    address->x[4], address->x[5]);
 203
 204                 subnet = new_subnet();
 205                 subnet->type = SUBNET_MAC;
 206                 subnet->expires = now + macexpire;
 207                 subnet->net.mac.address = *address;
 208                 subnet->weight = 10;
 209                 subnet_add(myself, subnet);
 210                 subnet_update(myself, subnet, true);
 211
 212                 /* And tell all other tinc daemons it's our MAC */
 213
 214                 for(node = connection_tree->head; node; node = node->next) {
 215                         c = node->data;
 216                         if(c->status.active)
 217                                 send_add_subnet(c, subnet);
 218                 }
 219         }
 220
 221         if(subnet->expires)
 222                 subnet->expires = now + macexpire;
 223 }
 224
 225 void age_subnets(void) {
 226         subnet_t *s;
 227         connection_t *c;
 228         avl_node_t *node, *next, *node2;
 229
 230         for(node = myself->subnet_tree->head; node; node = next) {
 231                 next = node->next;
 232                 s = node->data;
 233                 if(s->expires && s->expires <= now) {
 234                         ifdebug(TRAFFIC) {
 235                                 char netstr[MAXNETSTR];
 236                                 if(net2str(netstr, sizeof netstr, s))
 237                                         logger(LOG_INFO, "Subnet %s expired", netstr);
 238                         }
 239
 240                         for(node2 = connection_tree->head; node2; node2 = node2->next) {
 241                                 c = node2->data;
 242                                 if(c->status.active)
 243                                         send_del_subnet(c, s);
 244                         }
 245
 246                         subnet_update(myself, s, false);
 247                         subnet_del(myself, s);
 248                 }
 249         }
 250 }
 251
 252 /* RFC 792 */
 253
 254 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, uint8_t type, uint8_t code) {
 255         struct ip ip = {0};
 256         struct icmp icmp = {0};
 257
 258         struct in_addr ip_src;
 259         struct in_addr ip_dst;
 260         uint32_t oldlen;
 261
 262         if(ratelimit(3))
 263                 return;
 264
 265         /* Swap Ethernet source and destination addresses */
 266
 267         swap_mac_addresses(packet);
 268
 269         /* Copy headers from packet into properly aligned structs on the stack */
 270
 271         memcpy(&ip, packet->data + ether_size, ip_size);
 272
 273         /* Remember original source and destination */
 274
 275         ip_src = ip.ip_src;
 276         ip_dst = ip.ip_dst;
 277
 278         /* Try to reply with an IP address assigned to the local machine */
 279
 280         if (type == ICMP_TIME_EXCEEDED && code == ICMP_EXC_TTL) {
 281                 int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
 282                 if (sockfd != -1) {
 283                         struct sockaddr_in addr;
 284                         memset(&addr, 0, sizeof(addr));
 285                         addr.sin_family = AF_INET;
 286                         addr.sin_addr = ip.ip_src;
 287                         if (!connect(sockfd, (const struct sockaddr*) &addr, sizeof(addr))) {
 288                                 memset(&addr, 0, sizeof(addr));
 289                                 addr.sin_family = AF_INET;
 290                                 socklen_t addrlen = sizeof(addr);
 291                                 if (!getsockname(sockfd, (struct sockaddr*) &addr, &addrlen) && addrlen <= sizeof(addr)) {
 292                                         ip_dst = addr.sin_addr;
 293                                 }
 294                         }
 295                         close(sockfd);
 296                 }
 297         }
 298
 299         oldlen = packet->len - ether_size;
 300
 301         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 302                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 303
 304         if(oldlen >= IP_MSS - ip_size - icmp_size)
 305                 oldlen = IP_MSS - ip_size - icmp_size;
 306
 307         /* Copy first part of original contents to ICMP message */
 308
 309         memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
 310
 311         /* Fill in IPv4 header */
 312
 313         ip.ip_v = 4;
 314         ip.ip_hl = ip_size / 4;
 315         ip.ip_tos = 0;
 316         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 317         ip.ip_id = 0;
 318         ip.ip_off = 0;
 319         ip.ip_ttl = 255;
 320         ip.ip_p = IPPROTO_ICMP;
 321         ip.ip_sum = 0;
 322         ip.ip_src = ip_dst;
 323         ip.ip_dst = ip_src;
 324
 325         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 326
 327         /* Fill in ICMP header */
 328
 329         icmp.icmp_type = type;
 330         icmp.icmp_code = code;
 331         icmp.icmp_cksum = 0;
 332
 333         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 334         icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 335
 336         /* Copy structs on stack back to packet */
 337
 338         memcpy(packet->data + ether_size, &ip, ip_size);
 339         memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
 340
 341         packet->len = ether_size + ip_size + icmp_size + oldlen;
 342
 343         send_packet(source, packet);
 344 }
 345
 346 /* RFC 791 */
 347
 348 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet, length_t ether_size) {
 349         struct ip ip;
 350         vpn_packet_t fragment;
 351         int len, maxlen, todo;
 352         uint8_t *offset;
 353         uint16_t ip_off, origf;
 354
 355         memcpy(&ip, packet->data + ether_size, ip_size);
 356         fragment.priority = packet->priority;
 357
 358         if(ip.ip_hl != ip_size / 4)
 359                 return;
 360
 361         todo = ntohs(ip.ip_len) - ip_size;
 362
 363         if(ether_size + ip_size + todo != packet->len) {
 364                 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));
 365                 return;
 366         }
 367
 368         ifdebug(TRAFFIC) logger(LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname);
 369
 370         offset = packet->data + ether_size + ip_size;
 371         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 372         ip_off = ntohs(ip.ip_off);
 373         origf = ip_off & ~IP_OFFMASK;
 374         ip_off &= IP_OFFMASK;
 375
 376         while(todo) {
 377                 len = todo > maxlen ? maxlen : todo;
 378                 memcpy(fragment.data + ether_size + ip_size, offset, len);
 379                 todo -= len;
 380                 offset += len;
 381
 382                 ip.ip_len = htons(ip_size + len);
 383                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 384                 ip.ip_sum = 0;
 385                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 386                 memcpy(fragment.data, packet->data, ether_size);
 387                 memcpy(fragment.data + ether_size, &ip, ip_size);
 388                 fragment.len = ether_size + ip_size + len;
 389
 390                 send_packet(dest, &fragment);
 391
 392                 ip_off += len / 8;
 393         }
 394 }
 395
 396 static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet) {
 397         subnet_t *subnet;
 398         node_t *via;
 399         ipv4_t dest;
 400
 401         memcpy(&dest, &packet->data[30], sizeof dest);
 402         subnet = lookup_subnet_ipv4(&dest);
 403
 404         if(!subnet) {
 405                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d",
 406                                 source->name, source->hostname,
 407                                 dest.x[0],
 408                                 dest.x[1],
 409                                 dest.x[2],
 410                                 dest.x[3]);
 411
 412                 route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 413                 return;
 414         }
 415
 416         if(subnet->owner == source) {
 417                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 418                 return;
 419         }
 420
 421         if(!subnet->owner->status.reachable)
 422                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 423
 424         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 425                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 426
 427         if(priorityinheritance)
 428                 packet->priority = packet->data[15];
 429
 430         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 431
 432         if(via == source) {
 433                 ifdebug(TRAFFIC) logger(LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 434                 return;
 435         }
 436
 437         if(directonly && subnet->owner != via)
 438                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 439
 440         if(via && packet->len > MAX(via->mtu, 590) && via != myself) {
 441                 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);
 442                 if(packet->data[20] & 0x40) {
 443                         packet->len = MAX(via->mtu, 590);
 444                         route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 445                 } else {
 446                         fragment_ipv4_packet(via, packet, ether_size);
 447                 }
 448
 449                 return;
 450         }
 451
 452         clamp_mss(source, via, packet);
 453
 454         send_packet(subnet->owner, packet);
 455 }
 456
 457 static void route_ipv4(node_t *source, vpn_packet_t *packet) {
 458         if(!checklength(source, packet, ether_size + ip_size))
 459                 return;
 460
 461         if(broadcast_mode && (((packet->data[30] & 0xf0) == 0xe0) || (
 462                         packet->data[30] == 255 &&
 463                         packet->data[31] == 255 &&
 464                         packet->data[32] == 255 &&
 465                         packet->data[33] == 255)))
 466                 broadcast_packet(source, packet);
 467         else
 468                 route_ipv4_unicast(source, packet);
 469 }
 470
 471 /* RFC 2463 */
 472
 473 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, uint8_t type, uint8_t code) {
 474         struct ip6_hdr ip6;
 475         struct icmp6_hdr icmp6 = {0};
 476         uint16_t checksum;
 477
 478         struct {
 479                 struct in6_addr ip6_src;        /* source address */
 480                 struct in6_addr ip6_dst;        /* destination address */
 481                 uint32_t length;
 482                 uint32_t next;
 483         } pseudo;
 484
 485         if(ratelimit(3))
 486                 return;
 487
 488         /* Swap Ethernet source and destination addresses */
 489
 490         swap_mac_addresses(packet);
 491
 492         /* Copy headers from packet to structs on the stack */
 493
 494         memcpy(&ip6, packet->data + ether_size, ip6_size);
 495
 496         /* Remember original source and destination */
 497
 498         pseudo.ip6_src = ip6.ip6_dst;
 499         pseudo.ip6_dst = ip6.ip6_src;
 500
 501         /* Try to reply with an IP address assigned to the local machine */
 502
 503         if (type == ICMP6_TIME_EXCEEDED && code == ICMP6_TIME_EXCEED_TRANSIT) {
 504                 int sockfd = socket(AF_INET6, SOCK_DGRAM, 0);
 505                 if (sockfd != -1) {
 506                         struct sockaddr_in6 addr;
 507                         memset(&addr, 0, sizeof(addr));
 508                         addr.sin6_family = AF_INET6;
 509                         addr.sin6_addr = ip6.ip6_src;
 510                         if (!connect(sockfd, (const struct sockaddr*) &addr, sizeof(addr))) {
 511                                 memset(&addr, 0, sizeof(addr));
 512                                 addr.sin6_family = AF_INET6;
 513                                 socklen_t addrlen = sizeof(addr);
 514                                 if (!getsockname(sockfd, (struct sockaddr*) &addr, &addrlen) && addrlen <= sizeof(addr)) {
 515                                         pseudo.ip6_src = addr.sin6_addr;
 516                                 }
 517                         }
 518                         close(sockfd);
 519                 }
 520         }
 521
 522         pseudo.length = packet->len - ether_size;
 523
 524         if(type == ICMP6_PACKET_TOO_BIG)
 525                 icmp6.icmp6_mtu = htonl(pseudo.length);
 526
 527         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 528                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 529
 530         /* Copy first part of original contents to ICMP message */
 531
 532         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 533
 534         /* Fill in IPv6 header */
 535
 536         ip6.ip6_flow = htonl(0x60000000UL);
 537         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 538         ip6.ip6_nxt = IPPROTO_ICMPV6;
 539         ip6.ip6_hlim = 255;
 540         ip6.ip6_src = pseudo.ip6_src;
 541         ip6.ip6_dst = pseudo.ip6_dst;
 542
 543         /* Fill in ICMP header */
 544
 545         icmp6.icmp6_type = type;
 546         icmp6.icmp6_code = code;
 547         icmp6.icmp6_cksum = 0;
 548
 549         /* Create pseudo header */
 550
 551         pseudo.length = htonl(icmp6_size + pseudo.length);
 552         pseudo.next = htonl(IPPROTO_ICMPV6);
 553
 554         /* Generate checksum */
 555
 556         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 557         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 558         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 559
 560         icmp6.icmp6_cksum = checksum;
 561
 562         /* Copy structs on stack back to packet */
 563
 564         memcpy(packet->data + ether_size, &ip6, ip6_size);
 565         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 566
 567         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 568
 569         send_packet(source, packet);
 570 }
 571
 572 static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet) {
 573         subnet_t *subnet;
 574         node_t *via;
 575         ipv6_t dest;
 576
 577         memcpy(&dest, &packet->data[38], sizeof dest);
 578         subnet = lookup_subnet_ipv6(&dest);
 579
 580         if(!subnet) {
 581                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 582                                 source->name, source->hostname,
 583                                 ntohs(dest.x[0]),
 584                                 ntohs(dest.x[1]),
 585                                 ntohs(dest.x[2]),
 586                                 ntohs(dest.x[3]),
 587                                 ntohs(dest.x[4]),
 588                                 ntohs(dest.x[5]),
 589                                 ntohs(dest.x[6]),
 590                                 ntohs(dest.x[7]));
 591
 592                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 593                 return;
 594         }
 595
 596         if(subnet->owner == source) {
 597                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 598                 return;
 599         }
 600
 601         if(!subnet->owner->status.reachable)
 602                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 603
 604         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 605                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 606
 607         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 608
 609         if(via == source) {
 610                 ifdebug(TRAFFIC) logger(LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 611                 return;
 612         }
 613
 614         if(directonly && subnet->owner != via)
 615                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 616
 617         if(via && packet->len > MAX(via->mtu, 1294) && via != myself) {
 618                 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);
 619                 packet->len = MAX(via->mtu, 1294);
 620                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_PACKET_TOO_BIG, 0);
 621                 return;
 622         }
 623
 624         clamp_mss(source, via, packet);
 625
 626         send_packet(subnet->owner, packet);
 627 }
 628
 629 /* RFC 2461 */
 630
 631 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 632         struct ip6_hdr ip6;
 633         struct nd_neighbor_solicit ns;
 634         struct nd_opt_hdr opt;
 635         subnet_t *subnet;
 636         uint16_t checksum;
 637         bool has_opt;
 638
 639         struct {
 640                 struct in6_addr ip6_src;        /* source address */
 641                 struct in6_addr ip6_dst;        /* destination address */
 642                 uint32_t length;
 643                 uint32_t next;
 644         } pseudo;
 645
 646         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 647                 return;
 648
 649         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 650
 651         if(source != myself) {
 652                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname);
 653                 return;
 654         }
 655
 656         /* Copy headers from packet to structs on the stack */
 657
 658         memcpy(&ip6, packet->data + ether_size, ip6_size);
 659         memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
 660         if(has_opt)
 661                 memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 662
 663         /* First, snatch the source address from the neighbor solicitation packet */
 664
 665         if(overwrite_mac)
 666                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 667
 668         /* Check if this is a valid neighbor solicitation request */
 669
 670         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 671            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 672                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request");
 673                 return;
 674         }
 675
 676         /* Create pseudo header */
 677
 678         pseudo.ip6_src = ip6.ip6_src;
 679         pseudo.ip6_dst = ip6.ip6_dst;
 680         if(has_opt)
 681                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 682         else
 683                 pseudo.length = htonl(ns_size);
 684         pseudo.next = htonl(IPPROTO_ICMPV6);
 685
 686         /* Generate checksum */
 687
 688         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 689         checksum = inet_checksum(&ns, ns_size, checksum);
 690         if(has_opt) {
 691                 checksum = inet_checksum(&opt, opt_size, checksum);
 692                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 693         }
 694
 695         if(checksum) {
 696                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request");
 697                 return;
 698         }
 699
 700         /* Check if the IPv6 address exists on the VPN */
 701
 702         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 703
 704         if(!subnet) {
 705                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 706                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 707                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 708                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 709                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 710                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 711                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 712                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 713                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 714
 715                 return;
 716         }
 717
 718         /* Check if it is for our own subnet */
 719
 720         if(subnet->owner == myself)
 721                 return;                                 /* silently ignore */
 722
 723         /* Create neighbor advertation reply */
 724
 725         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 726         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 727
 728         ip6.ip6_dst = ip6.ip6_src;                      /* swap destination and source protocoll address */
 729         ip6.ip6_src = ns.nd_ns_target;
 730
 731         if(has_opt)
 732                 memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 733
 734         ns.nd_ns_cksum = 0;
 735         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 736         ns.nd_ns_reserved = htonl(0x40000000UL);        /* Set solicited flag */
 737         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 738
 739         /* Create pseudo header */
 740
 741         pseudo.ip6_src = ip6.ip6_src;
 742         pseudo.ip6_dst = ip6.ip6_dst;
 743         if(has_opt)
 744                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 745         else
 746                 pseudo.length = htonl(ns_size);
 747         pseudo.next = htonl(IPPROTO_ICMPV6);
 748
 749         /* Generate checksum */
 750
 751         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 752         checksum = inet_checksum(&ns, ns_size, checksum);
 753         if(has_opt) {
 754                 checksum = inet_checksum(&opt, opt_size, checksum);
 755                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 756         }
 757
 758         ns.nd_ns_hdr.icmp6_cksum = checksum;
 759
 760         /* Copy structs on stack back to packet */
 761
 762         memcpy(packet->data + ether_size, &ip6, ip6_size);
 763         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 764         if(has_opt)
 765                 memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 766
 767         send_packet(source, packet);
 768 }
 769
 770 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 771         if(!checklength(source, packet, ether_size + ip6_size))
 772                 return;
 773
 774         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 775                 route_neighborsol(source, packet);
 776                 return;
 777         }
 778
 779         if(broadcast_mode && packet->data[38] == 255)
 780                 broadcast_packet(source, packet);
 781         else
 782                 route_ipv6_unicast(source, packet);
 783 }
 784
 785 /* RFC 826 */
 786
 787 static void route_arp(node_t *source, vpn_packet_t *packet) {
 788         struct ether_arp arp;
 789         subnet_t *subnet;
 790         struct in_addr addr;
 791
 792         if(!checklength(source, packet, ether_size + arp_size))
 793                 return;
 794
 795         if(source != myself) {
 796                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname);
 797                 return;
 798         }
 799
 800         /* First, snatch the source address from the ARP packet */
 801
 802         if(overwrite_mac)
 803                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 804
 805         /* Copy headers from packet to structs on the stack */
 806
 807         memcpy(&arp, packet->data + ether_size, arp_size);
 808
 809         /* Check if this is a valid ARP request */
 810
 811         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 812            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof(addr) || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 813                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type ARP request");
 814                 return;
 815         }
 816
 817         /* Check if the IPv4 address exists on the VPN */
 818
 819         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 820
 821         if(!subnet) {
 822                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d",
 823                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 824                                    arp.arp_tpa[3]);
 825                 return;
 826         }
 827
 828         /* Check if it is for our own subnet */
 829
 830         if(subnet->owner == myself)
 831                 return;                                 /* silently ignore */
 832
 833         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 834         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 835
 836         memcpy(&addr, arp.arp_tpa, sizeof(addr));       /* save protocol addr */
 837         memcpy(arp.arp_tpa, arp.arp_spa, sizeof(addr)); /* swap destination and source protocol address */
 838         memcpy(arp.arp_spa, &addr, sizeof(addr));       /* ... */
 839
 840         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);     /* set target hard/proto addr */
 841         memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN); /* add fake source hard addr */
 842         arp.arp_op = htons(ARPOP_REPLY);
 843
 844         /* Copy structs on stack back to packet */
 845
 846         memcpy(packet->data + ether_size, &arp, arp_size);
 847
 848         send_packet(source, packet);
 849 }
 850
 851 static void route_mac(node_t *source, vpn_packet_t *packet) {
 852         subnet_t *subnet;
 853         mac_t dest;
 854
 855         /* Learn source address */
 856
 857         if(source == myself) {
 858                 mac_t src;
 859                 memcpy(&src, &packet->data[6], sizeof src);
 860                 learn_mac(&src);
 861         }
 862
 863         /* Lookup destination address */
 864
 865         memcpy(&dest, &packet->data[0], sizeof dest);
 866         subnet = lookup_subnet_mac(NULL, &dest);
 867
 868         if(!subnet) {
 869                 broadcast_packet(source, packet);
 870                 return;
 871         }
 872
 873         if(subnet->owner == source) {
 874                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 875                 return;
 876         }
 877
 878         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 879                 return;
 880
 881         uint16_t type = packet->data[12] << 8 | packet->data[13];
 882
 883         if(priorityinheritance && type == ETH_P_IP && packet->len >= ether_size + ip_size)
 884                 packet->priority = packet->data[15];
 885
 886         // Handle packets larger than PMTU
 887
 888         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 889
 890         if(directonly && subnet->owner != via)
 891                 return;
 892
 893         if(via && packet->len > via->mtu && via != myself) {
 894                 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);
 895                 length_t ethlen = 14;
 896
 897                 if(type == ETH_P_8021Q) {
 898                         type = packet->data[16] << 8 | packet->data[17];
 899                         ethlen += 4;
 900                 }
 901
 902                 if(type == ETH_P_IP && packet->len > 576 + ethlen) {
 903                         if(packet->data[6 + ethlen] & 0x40) {
 904                                 packet->len = via->mtu;
 905                                 route_ipv4_unreachable(source, packet, ethlen, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 906                         } else {
 907                                 fragment_ipv4_packet(via, packet, ethlen);
 908                         }
 909                         return;
 910                 } else if(type == ETH_P_IPV6 && packet->len > 1280 + ethlen) {
 911                         packet->len = via->mtu;
 912                         route_ipv6_unreachable(source, packet, ethlen, ICMP6_PACKET_TOO_BIG, 0);
 913                         return;
 914                 }
 915         }
 916
 917         clamp_mss(source, via, packet);
 918
 919         send_packet(subnet->owner, packet);
 920 }
 921
 922 static bool do_decrement_ttl(node_t *source, vpn_packet_t *packet) {
 923         uint16_t type = packet->data[12] << 8 | packet->data[13];
 924         length_t ethlen = ether_size;
 925
 926         if(type == ETH_P_8021Q) {
 927                 type = packet->data[16] << 8 | packet->data[17];
 928                 ethlen += 4;
 929         }
 930
 931         switch (type) {
 932                 case ETH_P_IP:
 933                         if(!checklength(source, packet, ethlen + ip_size))
 934                                 return false;
 935
 936                         if(packet->data[ethlen + 8] <= 1) {
 937                                 if(packet->data[ethlen + 11] != IPPROTO_ICMP || packet->data[ethlen + 32] != ICMP_TIME_EXCEEDED)
 938                                         route_ipv4_unreachable(source, packet, ethlen, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL);
 939                                 return false;
 940                         }
 941
 942                         uint16_t old = packet->data[ethlen + 8] << 8 | packet->data[ethlen + 9];
 943                         packet->data[ethlen + 8]--;
 944                         uint16_t new = packet->data[ethlen + 8] << 8 | packet->data[ethlen + 9];
 945
 946                         uint32_t checksum = packet->data[ethlen + 10] << 8 | packet->data[ethlen + 11];
 947                         checksum += old + (~new & 0xFFFF);
 948                         while(checksum >> 16)
 949                                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
 950                         packet->data[ethlen + 10] = checksum >> 8;
 951                         packet->data[ethlen + 11] = checksum & 0xff;
 952
 953                         return true;
 954
 955                 case ETH_P_IPV6:
 956                         if(!checklength(source, packet, ethlen + ip6_size))
 957                                 return false;
 958
 959                         if(packet->data[ethlen + 7] <= 1) {
 960                                 if(packet->data[ethlen + 6] != IPPROTO_ICMPV6 || packet->data[ethlen + 40] != ICMP6_TIME_EXCEEDED)
 961                                         route_ipv6_unreachable(source, packet, ethlen, ICMP6_TIME_EXCEEDED, ICMP6_TIME_EXCEED_TRANSIT);
 962                                 return false;
 963                         }
 964
 965                         packet->data[ethlen + 7]--;
 966
 967                         return true;
 968
 969                 default:
 970                         return true;
 971         }
 972 }
 973
 974 void route(node_t *source, vpn_packet_t *packet) {
 975         if(forwarding_mode == FMODE_KERNEL && source != myself) {
 976                 send_packet(myself, packet);
 977                 return;
 978         }
 979
 980         if(!checklength(source, packet, ether_size))
 981                 return;
 982
 983         if(decrement_ttl && source != myself)
 984                 if(!do_decrement_ttl(source, packet))
 985                         return;
 986
 987         switch (routing_mode) {
 988                 case RMODE_ROUTER:
 989                         {
 990                                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 991
 992                                 switch (type) {
 993                                         case ETH_P_ARP:
 994                                                 route_arp(source, packet);
 995                                                 break;
 996
 997                                         case ETH_P_IP:
 998                                                 route_ipv4(source, packet);
 999                                                 break;
1000
1001                                         case ETH_P_IPV6:
1002                                                 route_ipv6(source, packet);
1003                                                 break;
1004
1005                                         default:
1006                                                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type);
1007                                                 break;
1008                                 }
1009                         }
1010                         break;
1011
1012                 case RMODE_SWITCH:
1013                         route_mac(source, packet);
1014                         break;
1015
1016                 case RMODE_HUB:
1017                         broadcast_packet(source, packet);
1018                         break;
1019         }
1020 }