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