www.tinc-vpn.org Git - tinc/blob - src/route.c

   1 /*
   2     route.c -- routing
   3     Copyright (C) 2000-2005 Ivo Timmermans,
   4                   2000-2013 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 "connection.h"
  24 #include "control_common.h"
  25 #include "ethernet.h"
  26 #include "ipv4.h"
  27 #include "ipv6.h"
  28 #include "logger.h"
  29 #include "meta.h"
  30 #include "net.h"
  31 #include "protocol.h"
  32 #include "route.h"
  33 #include "subnet.h"
  34 #include "utils.h"
  35
  36 rmode_t routing_mode = RMODE_ROUTER;
  37 fmode_t forwarding_mode = FMODE_INTERNAL;
  38 bmode_t broadcast_mode = BMODE_MST;
  39 bool decrement_ttl = false;
  40 bool directonly = false;
  41 bool priorityinheritance = false;
  42 int macexpire = 600;
  43 bool overwrite_mac = false;
  44 mac_t mymac = {{0xFE, 0xFD, 0, 0, 0, 0}};
  45 bool pcap = false;
  46
  47 /* Sizes of various headers */
  48
  49 static const size_t ether_size = sizeof(struct ether_header);
  50 static const size_t arp_size = sizeof(struct ether_arp);
  51 static const size_t ip_size = sizeof(struct ip);
  52 static const size_t icmp_size = sizeof(struct icmp) - sizeof(struct ip);
  53 static const size_t ip6_size = sizeof(struct ip6_hdr);
  54 static const size_t icmp6_size = sizeof(struct icmp6_hdr);
  55 static const size_t ns_size = sizeof(struct nd_neighbor_solicit);
  56 static const size_t opt_size = sizeof(struct nd_opt_hdr);
  57
  58 #ifndef MAX
  59 #define MAX(a, b) ((a) > (b) ? (a) : (b))
  60 #endif
  61
  62 static timeout_t age_subnets_timeout;
  63
  64 /* RFC 1071 */
  65
  66 static uint16_t inet_checksum(void *data, int len, uint16_t prevsum) {
  67         uint16_t *p = data;
  68         uint32_t checksum = prevsum ^ 0xFFFF;
  69
  70         while(len >= 2) {
  71                 checksum += *p++;
  72                 len -= 2;
  73         }
  74
  75         if(len)
  76                 checksum += *(uint8_t *)p;
  77
  78         while(checksum >> 16)
  79                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
  80
  81         return ~checksum;
  82 }
  83
  84 static bool ratelimit(int frequency) {
  85         static time_t lasttime = 0;
  86         static int count = 0;
  87
  88         if(lasttime == now.tv_sec) {
  89                 if(count >= frequency)
  90                         return true;
  91         } else {
  92                 lasttime = now.tv_sec;
  93                 count = 0;
  94         }
  95
  96         count++;
  97         return false;
  98 }
  99
 100 static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
 101         if(packet->len < length) {
 102                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Got too short packet from %s (%s)", source->name, source->hostname);
 103                 return false;
 104         } else
 105                 return true;
 106 }
 107
 108 static void swap_mac_addresses(vpn_packet_t *packet) {
 109         mac_t tmp;
 110         memcpy(&tmp, &DATA(packet)[0], sizeof tmp);
 111         memcpy(&DATA(packet)[0], &DATA(packet)[6], sizeof tmp);
 112         memcpy(&DATA(packet)[6], &tmp, sizeof tmp);
 113 }
 114
 115 /* RFC 792 */
 116
 117 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, uint8_t type, uint8_t code) {
 118         struct ip ip = {0};
 119         struct icmp icmp = {0};
 120
 121         struct in_addr ip_src;
 122         struct in_addr ip_dst;
 123         uint32_t oldlen;
 124
 125         if(ratelimit(3))
 126                 return;
 127
 128         /* Swap Ethernet source and destination addresses */
 129
 130         swap_mac_addresses(packet);
 131
 132         /* Copy headers from packet into properly aligned structs on the stack */
 133
 134         memcpy(&ip, DATA(packet) + ether_size, ip_size);
 135
 136         /* Remember original source and destination */
 137
 138         ip_src = ip.ip_src;
 139         ip_dst = ip.ip_dst;
 140
 141         /* Try to reply with an IP address assigned to the local machine */
 142
 143         if (type == ICMP_TIME_EXCEEDED && code == ICMP_EXC_TTL) {
 144                 int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
 145                 if (sockfd != -1) {
 146                         struct sockaddr_in addr;
 147                         memset(&addr, 0, sizeof(addr));
 148                         addr.sin_family = AF_INET;
 149                         addr.sin_addr = ip.ip_src;
 150                         if (!connect(sockfd, (const struct sockaddr*) &addr, sizeof(addr))) {
 151                                 memset(&addr, 0, sizeof(addr));
 152                                 addr.sin_family = AF_INET;
 153                                 socklen_t addrlen = sizeof(addr);
 154                                 if (!getsockname(sockfd, (struct sockaddr*) &addr, &addrlen) && addrlen <= sizeof(addr)) {
 155                                         ip_dst = addr.sin_addr;
 156                                 }
 157                         }
 158                         close(sockfd);
 159                 }
 160         }
 161
 162         oldlen = packet->len - ether_size;
 163
 164         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 165                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 166
 167         if(oldlen >= IP_MSS - ip_size - icmp_size)
 168                 oldlen = IP_MSS - ip_size - icmp_size;
 169
 170         /* Copy first part of original contents to ICMP message */
 171
 172         memmove(DATA(packet) + ether_size + ip_size + icmp_size, DATA(packet) + ether_size, oldlen);
 173
 174         /* Fill in IPv4 header */
 175
 176         ip.ip_v = 4;
 177         ip.ip_hl = ip_size / 4;
 178         ip.ip_tos = 0;
 179         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 180         ip.ip_id = 0;
 181         ip.ip_off = 0;
 182         ip.ip_ttl = 255;
 183         ip.ip_p = IPPROTO_ICMP;
 184         ip.ip_sum = 0;
 185         ip.ip_src = ip_dst;
 186         ip.ip_dst = ip_src;
 187
 188         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 189
 190         /* Fill in ICMP header */
 191
 192         icmp.icmp_type = type;
 193         icmp.icmp_code = code;
 194         icmp.icmp_cksum = 0;
 195
 196         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 197         icmp.icmp_cksum = inet_checksum(DATA(packet) + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 198
 199         /* Copy structs on stack back to packet */
 200
 201         memcpy(DATA(packet) + ether_size, &ip, ip_size);
 202         memcpy(DATA(packet) + ether_size + ip_size, &icmp, icmp_size);
 203
 204         packet->len = ether_size + ip_size + icmp_size + oldlen;
 205
 206         send_packet(source, packet);
 207 }
 208
 209 /* RFC 2463 */
 210
 211 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, uint8_t type, uint8_t code) {
 212         struct ip6_hdr ip6;
 213         struct icmp6_hdr icmp6 = {0};
 214         uint16_t checksum;
 215
 216         struct {
 217                 struct in6_addr ip6_src;        /* source address */
 218                 struct in6_addr ip6_dst;        /* destination address */
 219                 uint32_t length;
 220                 uint32_t next;
 221         } pseudo;
 222
 223         if(ratelimit(3))
 224                 return;
 225
 226         /* Swap Ethernet source and destination addresses */
 227
 228         swap_mac_addresses(packet);
 229
 230         /* Copy headers from packet to structs on the stack */
 231
 232         memcpy(&ip6, DATA(packet) + ether_size, ip6_size);
 233
 234         /* Remember original source and destination */
 235
 236         pseudo.ip6_src = ip6.ip6_dst;
 237         pseudo.ip6_dst = ip6.ip6_src;
 238
 239         /* Try to reply with an IP address assigned to the local machine */
 240
 241         if (type == ICMP6_TIME_EXCEEDED && code == ICMP6_TIME_EXCEED_TRANSIT) {
 242                 int sockfd = socket(AF_INET6, SOCK_DGRAM, 0);
 243                 if (sockfd != -1) {
 244                         struct sockaddr_in6 addr;
 245                         memset(&addr, 0, sizeof(addr));
 246                         addr.sin6_family = AF_INET6;
 247                         addr.sin6_addr = ip6.ip6_src;
 248                         if (!connect(sockfd, (const struct sockaddr*) &addr, sizeof(addr))) {
 249                                 memset(&addr, 0, sizeof(addr));
 250                                 addr.sin6_family = AF_INET6;
 251                                 socklen_t addrlen = sizeof(addr);
 252                                 if (!getsockname(sockfd, (struct sockaddr*) &addr, &addrlen) && addrlen <= sizeof(addr)) {
 253                                         pseudo.ip6_src = addr.sin6_addr;
 254                                 }
 255                         }
 256                         close(sockfd);
 257                 }
 258         }
 259
 260         pseudo.length = packet->len - ether_size;
 261
 262         if(type == ICMP6_PACKET_TOO_BIG)
 263                 icmp6.icmp6_mtu = htonl(pseudo.length);
 264
 265         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 266                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 267
 268         /* Copy first part of original contents to ICMP message */
 269
 270         memmove(DATA(packet) + ether_size + ip6_size + icmp6_size, DATA(packet) + ether_size, pseudo.length);
 271
 272         /* Fill in IPv6 header */
 273
 274         ip6.ip6_flow = htonl(0x60000000UL);
 275         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 276         ip6.ip6_nxt = IPPROTO_ICMPV6;
 277         ip6.ip6_hlim = 255;
 278         ip6.ip6_src = pseudo.ip6_src;
 279         ip6.ip6_dst = pseudo.ip6_dst;
 280
 281         /* Fill in ICMP header */
 282
 283         icmp6.icmp6_type = type;
 284         icmp6.icmp6_code = code;
 285         icmp6.icmp6_cksum = 0;
 286
 287         /* Create pseudo header */
 288
 289         pseudo.length = htonl(icmp6_size + pseudo.length);
 290         pseudo.next = htonl(IPPROTO_ICMPV6);
 291
 292         /* Generate checksum */
 293
 294         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 295         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 296         checksum = inet_checksum(DATA(packet) + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 297
 298         icmp6.icmp6_cksum = checksum;
 299
 300         /* Copy structs on stack back to packet */
 301
 302         memcpy(DATA(packet) + ether_size, &ip6, ip6_size);
 303         memcpy(DATA(packet) + ether_size + ip6_size, &icmp6, icmp6_size);
 304
 305         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 306
 307         send_packet(source, packet);
 308 }
 309
 310 static bool do_decrement_ttl(node_t *source, vpn_packet_t *packet) {
 311         uint16_t type = DATA(packet)[12] << 8 | DATA(packet)[13];
 312         length_t ethlen = ether_size;
 313
 314         if(type == ETH_P_8021Q) {
 315                 type = DATA(packet)[16] << 8 | DATA(packet)[17];
 316                 ethlen += 4;
 317         }
 318
 319         switch (type) {
 320                 case ETH_P_IP:
 321                         if(!checklength(source, packet, ethlen + ip_size))
 322                                 return false;
 323
 324                         if(DATA(packet)[ethlen + 8] <= 1) {
 325                                 if(DATA(packet)[ethlen + 11] != IPPROTO_ICMP || DATA(packet)[ethlen + 32] != ICMP_TIME_EXCEEDED)
 326                                         route_ipv4_unreachable(source, packet, ethlen, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL);
 327                                 return false;
 328                         }
 329
 330                         uint16_t old = DATA(packet)[ethlen + 8] << 8 | DATA(packet)[ethlen + 9];
 331                         DATA(packet)[ethlen + 8]--;
 332                         uint16_t new = DATA(packet)[ethlen + 8] << 8 | DATA(packet)[ethlen + 9];
 333
 334                         uint32_t checksum = DATA(packet)[ethlen + 10] << 8 | DATA(packet)[ethlen + 11];
 335                         checksum += old + (~new & 0xFFFF);
 336                         while(checksum >> 16)
 337                                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
 338                         DATA(packet)[ethlen + 10] = checksum >> 8;
 339                         DATA(packet)[ethlen + 11] = checksum & 0xff;
 340
 341                         return true;
 342
 343                 case ETH_P_IPV6:
 344                         if(!checklength(source, packet, ethlen + ip6_size))
 345                                 return false;
 346
 347                         if(DATA(packet)[ethlen + 7] <= 1) {
 348                                 if(DATA(packet)[ethlen + 6] != IPPROTO_ICMPV6 || DATA(packet)[ethlen + 40] != ICMP6_TIME_EXCEEDED)
 349                                         route_ipv6_unreachable(source, packet, ethlen, ICMP6_TIME_EXCEEDED, ICMP6_TIME_EXCEED_TRANSIT);
 350                                 return false;
 351                         }
 352
 353                         DATA(packet)[ethlen + 7]--;
 354
 355                         return true;
 356
 357                 default:
 358                         return true;
 359         }
 360 }
 361
 362 static void clamp_mss(const node_t *source, const node_t *via, vpn_packet_t *packet) {
 363         if(!source || !via || !(via->options & OPTION_CLAMP_MSS))
 364                 return;
 365
 366         uint16_t mtu = source->mtu;
 367         if(via != myself && via->mtu < mtu)
 368                 mtu = via->mtu;
 369
 370         /* Find TCP header */
 371         int start = ether_size;
 372         uint16_t type = DATA(packet)[12] << 8 | DATA(packet)[13];
 373
 374         if(type == ETH_P_8021Q) {
 375                 start += 4;
 376                 type = DATA(packet)[16] << 8 | DATA(packet)[17];
 377         }
 378
 379         if(type == ETH_P_IP && DATA(packet)[start + 9] == 6)
 380                 start += (DATA(packet)[start] & 0xf) * 4;
 381         else if(type == ETH_P_IPV6 && DATA(packet)[start + 6] == 6)
 382                 start += 40;
 383         else
 384                 return;
 385
 386         if(packet->len <= start + 20)
 387                 return;
 388
 389         /* Use data offset field to calculate length of options field */
 390         int len = ((DATA(packet)[start + 12] >> 4) - 5) * 4;
 391
 392         if(packet->len < start + 20 + len)
 393                 return;
 394
 395         /* Search for MSS option header */
 396         for(int i = 0; i < len;) {
 397                 if(DATA(packet)[start + 20 + i] == 0)
 398                         break;
 399
 400                 if(DATA(packet)[start + 20 + i] == 1) {
 401                         i++;
 402                         continue;
 403                 }
 404
 405                 if(i > len - 2 || i > len - DATA(packet)[start + 21 + i])
 406                         break;
 407
 408                 if(DATA(packet)[start + 20 + i] != 2) {
 409                         if(DATA(packet)[start + 21 + i] < 2)
 410                                 break;
 411                         i += DATA(packet)[start + 21 + i];
 412                         continue;
 413                 }
 414
 415                 if(DATA(packet)[start + 21] != 4)
 416                         break;
 417
 418                 /* Found it */
 419                 uint16_t oldmss = DATA(packet)[start + 22 + i] << 8 | DATA(packet)[start + 23 + i];
 420                 uint16_t newmss = mtu - start - 20;
 421                 uint32_t csum = DATA(packet)[start + 16] << 8 | DATA(packet)[start + 17];
 422
 423                 if(oldmss <= newmss)
 424                         break;
 425
 426                 logger(DEBUG_TRAFFIC, LOG_INFO, "Clamping MSS of packet from %s to %s to %d", source->name, via->name, newmss);
 427
 428                 /* Update the MSS value and the checksum */
 429                 DATA(packet)[start + 22 + i] = newmss >> 8;
 430                 DATA(packet)[start + 23 + i] = newmss & 0xff;
 431                 csum ^= 0xffff;
 432                 csum += oldmss ^ 0xffff;
 433                 csum += newmss;
 434                 csum = (csum & 0xffff) + (csum >> 16);
 435                 csum += csum >> 16;
 436                 csum ^= 0xffff;
 437                 DATA(packet)[start + 16] = csum >> 8;
 438                 DATA(packet)[start + 17] = csum;
 439                 break;
 440         }
 441 }
 442
 443 static void age_subnets(void *data) {
 444         bool left = false;
 445
 446         for splay_each(subnet_t, s, myself->subnet_tree) {
 447                 if(s->expires && s->expires < now.tv_sec) {
 448                         if(debug_level >= DEBUG_TRAFFIC) {
 449                                 char netstr[MAXNETSTR];
 450                                 if(net2str(netstr, sizeof netstr, s))
 451                                         logger(DEBUG_TRAFFIC, LOG_INFO, "Subnet %s expired", netstr);
 452                         }
 453
 454                         for list_each(connection_t, c, connection_list)
 455                                 if(c->edge)
 456                                         send_del_subnet(c, s);
 457
 458                         subnet_del(myself, s);
 459                 } else {
 460                         if(s->expires)
 461                                 left = true;
 462                 }
 463         }
 464
 465         if(left)
 466                 timeout_set(&age_subnets_timeout, &(struct timeval){10, rand() % 100000});
 467 }
 468
 469 static void learn_mac(mac_t *address) {
 470         subnet_t *subnet = lookup_subnet_mac(myself, address);
 471
 472         /* If we don't know this MAC address yet, store it */
 473
 474         if(!subnet) {
 475                 logger(DEBUG_TRAFFIC, LOG_INFO, "Learned new MAC address %x:%x:%x:%x:%x:%x",
 476                                    address->x[0], address->x[1], address->x[2], address->x[3],
 477                                    address->x[4], address->x[5]);
 478
 479                 subnet = new_subnet();
 480                 subnet->type = SUBNET_MAC;
 481                 subnet->expires = now.tv_sec + macexpire;
 482                 subnet->net.mac.address = *address;
 483                 subnet->weight = 10;
 484                 subnet_add(myself, subnet);
 485                 subnet_update(myself, subnet, true);
 486
 487                 /* And tell all other tinc daemons it's our MAC */
 488
 489                 for list_each(connection_t, c, connection_list)
 490                         if(c->edge)
 491                                 send_add_subnet(c, subnet);
 492
 493                 timeout_add(&age_subnets_timeout, age_subnets, NULL, &(struct timeval){10, rand() % 100000});
 494         } else {
 495                 if(subnet->expires)
 496                         subnet->expires = now.tv_sec + macexpire;
 497         }
 498 }
 499
 500 static void route_broadcast(node_t *source, vpn_packet_t *packet) {
 501         if(decrement_ttl && source != myself)
 502                 if(!do_decrement_ttl(source, packet))
 503                         return;
 504
 505         broadcast_packet(source, packet);
 506 }
 507
 508 /* RFC 791 */
 509
 510 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet, length_t ether_size) {
 511         struct ip ip;
 512         vpn_packet_t fragment;
 513         int len, maxlen, todo;
 514         uint8_t *offset;
 515         uint16_t ip_off, origf;
 516
 517         memcpy(&ip, DATA(packet) + ether_size, ip_size);
 518         fragment.priority = packet->priority;
 519         fragment.offset = DEFAULT_PACKET_OFFSET;
 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                 logger(DEBUG_TRAFFIC, 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         logger(DEBUG_TRAFFIC, LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname);
 532
 533         offset = DATA(packet) + 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(DATA(&fragment) + 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(DATA(&fragment), DATA(packet), ether_size);
 550                 memcpy(DATA(&fragment) + 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(node_t *source, vpn_packet_t *packet) {
 560         if(!checklength(source, packet, ether_size + ip_size))
 561                 return;
 562
 563         subnet_t *subnet;
 564         node_t *via;
 565         ipv4_t dest;
 566
 567         memcpy(&dest, &DATA(packet)[30], sizeof dest);
 568         subnet = lookup_subnet_ipv4(&dest);
 569
 570         if(!subnet) {
 571                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d",
 572                                 source->name, source->hostname,
 573                                 dest.x[0],
 574                                 dest.x[1],
 575                                 dest.x[2],
 576                                 dest.x[3]);
 577
 578                 route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 579                 return;
 580         }
 581
 582         if (!subnet->owner) {
 583                 route_broadcast(source, packet);
 584                 return;
 585         }
 586
 587         if(subnet->owner == source) {
 588                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 589                 return;
 590         }
 591
 592         if(!subnet->owner->status.reachable)
 593                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 594
 595         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 596                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 597
 598         if(decrement_ttl && source != myself && subnet->owner != myself)
 599                 if(!do_decrement_ttl(source, packet))
 600                         return;
 601
 602         if(priorityinheritance)
 603                 packet->priority = DATA(packet)[15];
 604
 605         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 606
 607         if(via == source) {
 608                 logger(DEBUG_TRAFFIC, LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 609                 return;
 610         }
 611
 612         if(directonly && subnet->owner != via)
 613                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 614
 615         if(via && packet->len > MAX(via->mtu, 590) && via != myself) {
 616                 logger(DEBUG_TRAFFIC, LOG_INFO, "Packet for %s (%s) length %d larger than MTU %d", subnet->owner->name, subnet->owner->hostname, packet->len, via->mtu);
 617                 if(DATA(packet)[20] & 0x40) {
 618                         packet->len = MAX(via->mtu, 590);
 619                         route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 620                 } else {
 621                         fragment_ipv4_packet(via, packet, ether_size);
 622                 }
 623
 624                 return;
 625         }
 626
 627         clamp_mss(source, via, packet);
 628
 629         send_packet(subnet->owner, packet);
 630 }
 631
 632 static void route_neighborsol(node_t *source, vpn_packet_t *packet);
 633
 634 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 635         if(!checklength(source, packet, ether_size + ip6_size))
 636                 return;
 637
 638         if(DATA(packet)[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && DATA(packet)[54] == ND_NEIGHBOR_SOLICIT) {
 639                 route_neighborsol(source, packet);
 640                 return;
 641         }
 642
 643         subnet_t *subnet;
 644         node_t *via;
 645         ipv6_t dest;
 646
 647         memcpy(&dest, &DATA(packet)[38], sizeof dest);
 648         subnet = lookup_subnet_ipv6(&dest);
 649
 650         if(!subnet) {
 651                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 652                                 source->name, source->hostname,
 653                                 ntohs(dest.x[0]),
 654                                 ntohs(dest.x[1]),
 655                                 ntohs(dest.x[2]),
 656                                 ntohs(dest.x[3]),
 657                                 ntohs(dest.x[4]),
 658                                 ntohs(dest.x[5]),
 659                                 ntohs(dest.x[6]),
 660                                 ntohs(dest.x[7]));
 661
 662                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 663                 return;
 664         }
 665
 666         if (!subnet->owner) {
 667                 route_broadcast(source, packet);
 668                 return;
 669         }
 670
 671         if(subnet->owner == source) {
 672                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 673                 return;
 674         }
 675
 676         if(!subnet->owner->status.reachable)
 677                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 678
 679         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 680                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 681
 682         if(decrement_ttl && source != myself && subnet->owner != myself)
 683                 if(!do_decrement_ttl(source, packet))
 684                         return;
 685
 686         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 687
 688         if(via == source) {
 689                 logger(DEBUG_TRAFFIC, LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 690                 return;
 691         }
 692
 693         if(directonly && subnet->owner != via)
 694                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 695
 696         if(via && packet->len > MAX(via->mtu, 1294) && via != myself) {
 697                 logger(DEBUG_TRAFFIC, LOG_INFO, "Packet for %s (%s) length %d larger than MTU %d", subnet->owner->name, subnet->owner->hostname, packet->len, via->mtu);
 698                 packet->len = MAX(via->mtu, 1294);
 699                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_PACKET_TOO_BIG, 0);
 700                 return;
 701         }
 702
 703         clamp_mss(source, via, packet);
 704
 705         send_packet(subnet->owner, packet);
 706 }
 707
 708 /* RFC 2461 */
 709
 710 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 711         struct ip6_hdr ip6;
 712         struct nd_neighbor_solicit ns;
 713         struct nd_opt_hdr opt;
 714         subnet_t *subnet;
 715         uint16_t checksum;
 716         bool has_opt;
 717
 718         struct {
 719                 struct in6_addr ip6_src;
 720                 struct in6_addr ip6_dst;
 721                 uint32_t length;
 722                 uint32_t next;
 723         } pseudo;
 724
 725         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 726                 return;
 727
 728         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 729
 730         if(source != myself) {
 731                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname);
 732                 return;
 733         }
 734
 735         /* Copy headers from packet to structs on the stack */
 736
 737         memcpy(&ip6, DATA(packet) + ether_size, ip6_size);
 738         memcpy(&ns, DATA(packet) + ether_size + ip6_size, ns_size);
 739         if(has_opt)
 740                 memcpy(&opt, DATA(packet) + ether_size + ip6_size + ns_size, opt_size);
 741
 742         /* First, snatch the source address from the neighbor solicitation packet */
 743
 744         if(overwrite_mac)
 745                 memcpy(mymac.x, DATA(packet) + ETH_ALEN, ETH_ALEN);
 746
 747         /* Check if this is a valid neighbor solicitation request */
 748
 749         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 750            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 751                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request");
 752                 return;
 753         }
 754
 755         /* Create pseudo header */
 756
 757         pseudo.ip6_src = ip6.ip6_src;
 758         pseudo.ip6_dst = ip6.ip6_dst;
 759         if(has_opt)
 760                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 761         else
 762                 pseudo.length = htonl(ns_size);
 763         pseudo.next = htonl(IPPROTO_ICMPV6);
 764
 765         /* Generate checksum */
 766
 767         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 768         checksum = inet_checksum(&ns, ns_size, checksum);
 769         if(has_opt) {
 770                 checksum = inet_checksum(&opt, opt_size, checksum);
 771                 checksum = inet_checksum(DATA(packet) + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 772         }
 773
 774         if(checksum) {
 775                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request");
 776                 return;
 777         }
 778
 779         /* Check if the IPv6 address exists on the VPN */
 780
 781         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 782
 783         if(!subnet) {
 784                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 785                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 786                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 787                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 788                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 789                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 790                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 791                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 792                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 793
 794                 return;
 795         }
 796
 797         /* Check if it is for our own subnet */
 798
 799         if(subnet->owner == myself)
 800                 return;                                          /* silently ignore */
 801
 802         if(decrement_ttl)
 803                 if(!do_decrement_ttl(source, packet))
 804                         return;
 805
 806         /* Create neighbor advertation reply */
 807
 808         memcpy(DATA(packet), DATA(packet) + ETH_ALEN, ETH_ALEN); /* copy destination address */
 809         DATA(packet)[ETH_ALEN * 2 - 1] ^= 0xFF;                  /* mangle source address so it looks like it's not from us */
 810
 811         ip6.ip6_dst = ip6.ip6_src;                               /* swap destination and source protocoll address */
 812         ip6.ip6_src = ns.nd_ns_target;
 813
 814         if(has_opt)
 815                 memcpy(DATA(packet) + ether_size + ip6_size + ns_size + opt_size, DATA(packet) + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 816
 817         ns.nd_ns_cksum = 0;
 818         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 819         ns.nd_ns_reserved = htonl(0x40000000UL);                 /* Set solicited flag */
 820         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 821
 822         /* Create pseudo header */
 823
 824         pseudo.ip6_src = ip6.ip6_src;
 825         pseudo.ip6_dst = ip6.ip6_dst;
 826         if(has_opt)
 827                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 828         else
 829                 pseudo.length = htonl(ns_size);
 830         pseudo.next = htonl(IPPROTO_ICMPV6);
 831
 832         /* Generate checksum */
 833
 834         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 835         checksum = inet_checksum(&ns, ns_size, checksum);
 836         if(has_opt) {
 837                 checksum = inet_checksum(&opt, opt_size, checksum);
 838                 checksum = inet_checksum(DATA(packet) + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 839         }
 840
 841         ns.nd_ns_hdr.icmp6_cksum = checksum;
 842
 843         /* Copy structs on stack back to packet */
 844
 845         memcpy(DATA(packet) + ether_size, &ip6, ip6_size);
 846         memcpy(DATA(packet) + ether_size + ip6_size, &ns, ns_size);
 847         if(has_opt)
 848                 memcpy(DATA(packet) + ether_size + ip6_size + ns_size, &opt, opt_size);
 849
 850         send_packet(source, packet);
 851 }
 852
 853 /* RFC 826 */
 854
 855 static void route_arp(node_t *source, vpn_packet_t *packet) {
 856         struct ether_arp arp;
 857         subnet_t *subnet;
 858         struct in_addr addr;
 859
 860         if(!checklength(source, packet, ether_size + arp_size))
 861                 return;
 862
 863         if(source != myself) {
 864                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname);
 865                 return;
 866         }
 867
 868         /* First, snatch the source address from the ARP packet */
 869
 870         if(overwrite_mac)
 871                 memcpy(mymac.x, DATA(packet) + ETH_ALEN, ETH_ALEN);
 872
 873         /* Copy headers from packet to structs on the stack */
 874
 875         memcpy(&arp, DATA(packet) + ether_size, arp_size);
 876
 877         /* Check if this is a valid ARP request */
 878
 879         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 880            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof addr || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 881                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: received unknown type ARP request");
 882                 return;
 883         }
 884
 885         /* Check if the IPv4 address exists on the VPN */
 886
 887         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 888
 889         if(!subnet) {
 890                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d",
 891                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 892                                    arp.arp_tpa[3]);
 893                 return;
 894         }
 895
 896         /* Check if it is for our own subnet */
 897
 898         if(subnet->owner == myself)
 899                 return;                                          /* silently ignore */
 900
 901         if(decrement_ttl)
 902                 if(!do_decrement_ttl(source, packet))
 903                         return;
 904
 905         memcpy(&addr, arp.arp_tpa, sizeof addr);                 /* save protocol addr */
 906         memcpy(arp.arp_tpa, arp.arp_spa, sizeof addr);           /* swap destination and source protocol address */
 907         memcpy(arp.arp_spa, &addr, sizeof addr);                 /* ... */
 908
 909         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);              /* set target hard/proto addr */
 910         memcpy(arp.arp_sha, DATA(packet) + ETH_ALEN, ETH_ALEN);  /* set source hard/proto addr */
 911         arp.arp_sha[ETH_ALEN - 1] ^= 0xFF;                       /* for consistency with route_packet() */
 912         arp.arp_op = htons(ARPOP_REPLY);
 913
 914         /* Copy structs on stack back to packet */
 915
 916         memcpy(DATA(packet) + ether_size, &arp, arp_size);
 917
 918         send_packet(source, packet);
 919 }
 920
 921 static void route_mac(node_t *source, vpn_packet_t *packet) {
 922         subnet_t *subnet;
 923         mac_t dest;
 924
 925         /* Learn source address */
 926
 927         if(source == myself) {
 928                 mac_t src;
 929                 memcpy(&src, &DATA(packet)[6], sizeof src);
 930                 learn_mac(&src);
 931         }
 932
 933         /* Lookup destination address */
 934
 935         memcpy(&dest, &DATA(packet)[0], sizeof dest);
 936         subnet = lookup_subnet_mac(NULL, &dest);
 937
 938         if(!subnet || !subnet->owner) {
 939                 route_broadcast(source, packet);
 940                 return;
 941         }
 942
 943         if(subnet->owner == source) {
 944                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 945                 return;
 946         }
 947
 948         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 949                 return;
 950
 951         if(decrement_ttl && source != myself && subnet->owner != myself)
 952                 if(!do_decrement_ttl(source, packet))
 953                         return;
 954
 955         uint16_t type = DATA(packet)[12] << 8 | DATA(packet)[13];
 956
 957         if(priorityinheritance && type == ETH_P_IP && packet->len >= ether_size + ip_size)
 958                 packet->priority = DATA(packet)[15];
 959
 960         // Handle packets larger than PMTU
 961
 962         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 963
 964         if(directonly && subnet->owner != via)
 965                 return;
 966
 967         if(via && packet->len > via->mtu && via != myself) {
 968                 logger(DEBUG_TRAFFIC, LOG_INFO, "Packet for %s (%s) length %d larger than MTU %d", subnet->owner->name, subnet->owner->hostname, packet->len, via->mtu);
 969                 length_t ethlen = 14;
 970
 971                 if(type == ETH_P_8021Q) {
 972                         type = DATA(packet)[16] << 8 | DATA(packet)[17];
 973                         ethlen += 4;
 974                 }
 975
 976                 if(type == ETH_P_IP && packet->len > 576 + ethlen) {
 977                         if(DATA(packet)[6 + ethlen] & 0x40) {
 978                                 packet->len = via->mtu;
 979                                 route_ipv4_unreachable(source, packet, ethlen, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 980                         } else {
 981                                 fragment_ipv4_packet(via, packet, ethlen);
 982                         }
 983                         return;
 984                 } else if(type == ETH_P_IPV6 && packet->len > 1280 + ethlen) {
 985                         packet->len = via->mtu;
 986                         route_ipv6_unreachable(source, packet, ethlen, ICMP6_PACKET_TOO_BIG, 0);
 987                         return;
 988                 }
 989         }
 990
 991         clamp_mss(source, via, packet);
 992
 993         send_packet(subnet->owner, packet);
 994 }
 995
 996 static void send_pcap(vpn_packet_t *packet) {
 997         pcap = false;
 998
 999         for list_each(connection_t, c, connection_list) {
1000                 if(!c->status.pcap)
1001                         continue;
1002
1003                 pcap = true;
1004                 int len = packet->len;
1005                 if(c->outmaclength && c->outmaclength < len)
1006                         len = c->outmaclength;
1007
1008                 if(send_request(c, "%d %d %d", CONTROL, REQ_PCAP, len))
1009                         send_meta(c, (char *)DATA(packet), len);
1010         }
1011 }
1012
1013 void route(node_t *source, vpn_packet_t *packet) {
1014         if(pcap)
1015                 send_pcap(packet);
1016
1017         if(forwarding_mode == FMODE_KERNEL && source != myself) {
1018                 send_packet(myself, packet);
1019                 return;
1020         }
1021
1022         if(!checklength(source, packet, ether_size))
1023                 return;
1024
1025         uint16_t type = DATA(packet)[12] << 8 | DATA(packet)[13];
1026
1027         switch (routing_mode) {
1028                 case RMODE_ROUTER:
1029                         switch (type) {
1030                                 case ETH_P_ARP:
1031                                         route_arp(source, packet);
1032                                         break;
1033
1034                                 case ETH_P_IP:
1035                                         route_ipv4(source, packet);
1036                                         break;
1037
1038                                 case ETH_P_IPV6:
1039                                         route_ipv6(source, packet);
1040                                         break;
1041
1042                                 default:
1043                                         logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type);
1044                                         break;
1045                         }
1046                         break;
1047
1048                 case RMODE_SWITCH:
1049                         route_mac(source, packet);
1050                         break;
1051
1052                 case RMODE_HUB:
1053                         route_broadcast(source, packet);
1054                         break;
1055         }
1056 }