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         if(priorityinheritance)
 687                 packet->priority = ((DATA(packet)[14] & 0x0f) << 4) | (DATA(packet)[15] >> 4);
 688
 689         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 690
 691         if(via == source) {
 692                 logger(DEBUG_TRAFFIC, LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 693                 return;
 694         }
 695
 696         if(directonly && subnet->owner != via)
 697                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 698
 699         if(via && packet->len > MAX(via->mtu, 1294) && via != myself) {
 700                 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);
 701                 packet->len = MAX(via->mtu, 1294);
 702                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_PACKET_TOO_BIG, 0);
 703                 return;
 704         }
 705
 706         clamp_mss(source, via, packet);
 707
 708         send_packet(subnet->owner, packet);
 709 }
 710
 711 /* RFC 2461 */
 712
 713 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 714         struct ip6_hdr ip6;
 715         struct nd_neighbor_solicit ns;
 716         struct nd_opt_hdr opt;
 717         subnet_t *subnet;
 718         uint16_t checksum;
 719         bool has_opt;
 720
 721         struct {
 722                 struct in6_addr ip6_src;
 723                 struct in6_addr ip6_dst;
 724                 uint32_t length;
 725                 uint32_t next;
 726         } pseudo;
 727
 728         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 729                 return;
 730
 731         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 732
 733         if(source != myself) {
 734                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname);
 735                 return;
 736         }
 737
 738         /* Copy headers from packet to structs on the stack */
 739
 740         memcpy(&ip6, DATA(packet) + ether_size, ip6_size);
 741         memcpy(&ns, DATA(packet) + ether_size + ip6_size, ns_size);
 742         if(has_opt)
 743                 memcpy(&opt, DATA(packet) + ether_size + ip6_size + ns_size, opt_size);
 744
 745         /* First, snatch the source address from the neighbor solicitation packet */
 746
 747         if(overwrite_mac)
 748                 memcpy(mymac.x, DATA(packet) + ETH_ALEN, ETH_ALEN);
 749
 750         /* Check if this is a valid neighbor solicitation request */
 751
 752         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 753            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 754                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request");
 755                 return;
 756         }
 757
 758         /* Create pseudo header */
 759
 760         pseudo.ip6_src = ip6.ip6_src;
 761         pseudo.ip6_dst = ip6.ip6_dst;
 762         if(has_opt)
 763                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 764         else
 765                 pseudo.length = htonl(ns_size);
 766         pseudo.next = htonl(IPPROTO_ICMPV6);
 767
 768         /* Generate checksum */
 769
 770         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 771         checksum = inet_checksum(&ns, ns_size, checksum);
 772         if(has_opt) {
 773                 checksum = inet_checksum(&opt, opt_size, checksum);
 774                 checksum = inet_checksum(DATA(packet) + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 775         }
 776
 777         if(checksum) {
 778                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request");
 779                 return;
 780         }
 781
 782         /* Check if the IPv6 address exists on the VPN */
 783
 784         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 785
 786         if(!subnet) {
 787                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 788                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 789                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 790                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 791                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 792                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 793                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 794                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 795                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 796
 797                 return;
 798         }
 799
 800         /* Check if it is for our own subnet */
 801
 802         if(subnet->owner == myself)
 803                 return;                                          /* silently ignore */
 804
 805         if(decrement_ttl)
 806                 if(!do_decrement_ttl(source, packet))
 807                         return;
 808
 809         /* Create neighbor advertation reply */
 810
 811         memcpy(DATA(packet), DATA(packet) + ETH_ALEN, ETH_ALEN); /* copy destination address */
 812         DATA(packet)[ETH_ALEN * 2 - 1] ^= 0xFF;                  /* mangle source address so it looks like it's not from us */
 813
 814         ip6.ip6_dst = ip6.ip6_src;                               /* swap destination and source protocoll address */
 815         ip6.ip6_src = ns.nd_ns_target;
 816
 817         if(has_opt)
 818                 memcpy(DATA(packet) + ether_size + ip6_size + ns_size + opt_size, DATA(packet) + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 819
 820         ns.nd_ns_cksum = 0;
 821         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 822         ns.nd_ns_reserved = htonl(0x40000000UL);                 /* Set solicited flag */
 823         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 824
 825         /* Create pseudo header */
 826
 827         pseudo.ip6_src = ip6.ip6_src;
 828         pseudo.ip6_dst = ip6.ip6_dst;
 829         if(has_opt)
 830                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 831         else
 832                 pseudo.length = htonl(ns_size);
 833         pseudo.next = htonl(IPPROTO_ICMPV6);
 834
 835         /* Generate checksum */
 836
 837         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 838         checksum = inet_checksum(&ns, ns_size, checksum);
 839         if(has_opt) {
 840                 checksum = inet_checksum(&opt, opt_size, checksum);
 841                 checksum = inet_checksum(DATA(packet) + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 842         }
 843
 844         ns.nd_ns_hdr.icmp6_cksum = checksum;
 845
 846         /* Copy structs on stack back to packet */
 847
 848         memcpy(DATA(packet) + ether_size, &ip6, ip6_size);
 849         memcpy(DATA(packet) + ether_size + ip6_size, &ns, ns_size);
 850         if(has_opt)
 851                 memcpy(DATA(packet) + ether_size + ip6_size + ns_size, &opt, opt_size);
 852
 853         send_packet(source, packet);
 854 }
 855
 856 /* RFC 826 */
 857
 858 static void route_arp(node_t *source, vpn_packet_t *packet) {
 859         struct ether_arp arp;
 860         subnet_t *subnet;
 861         struct in_addr addr;
 862
 863         if(!checklength(source, packet, ether_size + arp_size))
 864                 return;
 865
 866         if(source != myself) {
 867                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname);
 868                 return;
 869         }
 870
 871         /* First, snatch the source address from the ARP packet */
 872
 873         if(overwrite_mac)
 874                 memcpy(mymac.x, DATA(packet) + ETH_ALEN, ETH_ALEN);
 875
 876         /* Copy headers from packet to structs on the stack */
 877
 878         memcpy(&arp, DATA(packet) + ether_size, arp_size);
 879
 880         /* Check if this is a valid ARP request */
 881
 882         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 883            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof addr || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 884                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: received unknown type ARP request");
 885                 return;
 886         }
 887
 888         /* Check if the IPv4 address exists on the VPN */
 889
 890         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 891
 892         if(!subnet) {
 893                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d",
 894                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 895                                    arp.arp_tpa[3]);
 896                 return;
 897         }
 898
 899         /* Check if it is for our own subnet */
 900
 901         if(subnet->owner == myself)
 902                 return;                                          /* silently ignore */
 903
 904         if(decrement_ttl)
 905                 if(!do_decrement_ttl(source, packet))
 906                         return;
 907
 908         memcpy(&addr, arp.arp_tpa, sizeof addr);                 /* save protocol addr */
 909         memcpy(arp.arp_tpa, arp.arp_spa, sizeof addr);           /* swap destination and source protocol address */
 910         memcpy(arp.arp_spa, &addr, sizeof addr);                 /* ... */
 911
 912         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);              /* set target hard/proto addr */
 913         memcpy(arp.arp_sha, DATA(packet) + ETH_ALEN, ETH_ALEN);  /* set source hard/proto addr */
 914         arp.arp_sha[ETH_ALEN - 1] ^= 0xFF;                       /* for consistency with route_packet() */
 915         arp.arp_op = htons(ARPOP_REPLY);
 916
 917         /* Copy structs on stack back to packet */
 918
 919         memcpy(DATA(packet) + ether_size, &arp, arp_size);
 920
 921         send_packet(source, packet);
 922 }
 923
 924 static void route_mac(node_t *source, vpn_packet_t *packet) {
 925         subnet_t *subnet;
 926         mac_t dest;
 927
 928         /* Learn source address */
 929
 930         if(source == myself) {
 931                 mac_t src;
 932                 memcpy(&src, &DATA(packet)[6], sizeof src);
 933                 learn_mac(&src);
 934         }
 935
 936         /* Lookup destination address */
 937
 938         memcpy(&dest, &DATA(packet)[0], sizeof dest);
 939         subnet = lookup_subnet_mac(NULL, &dest);
 940
 941         if(!subnet || !subnet->owner) {
 942                 route_broadcast(source, packet);
 943                 return;
 944         }
 945
 946         if(subnet->owner == source) {
 947                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 948                 return;
 949         }
 950
 951         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 952                 return;
 953
 954         if(decrement_ttl && source != myself && subnet->owner != myself)
 955                 if(!do_decrement_ttl(source, packet))
 956                         return;
 957
 958         uint16_t type = DATA(packet)[12] << 8 | DATA(packet)[13];
 959
 960         if(priorityinheritance) {
 961                 if(type == ETH_P_IP && packet->len >= ether_size + ip_size)
 962                         packet->priority = DATA(packet)[15];
 963                 else if(type == ETH_P_IPV6 && packet->len >= ether_size + ip6_size)
 964                         packet->priority = ((DATA(packet)[14] & 0x0f) << 4) | (DATA(packet)[15] >> 4);
 965         }
 966
 967         // Handle packets larger than PMTU
 968
 969         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 970
 971         if(directonly && subnet->owner != via)
 972                 return;
 973
 974         if(via && packet->len > via->mtu && via != myself) {
 975                 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);
 976                 length_t ethlen = 14;
 977
 978                 if(type == ETH_P_8021Q) {
 979                         type = DATA(packet)[16] << 8 | DATA(packet)[17];
 980                         ethlen += 4;
 981                 }
 982
 983                 if(type == ETH_P_IP && packet->len > 576 + ethlen) {
 984                         if(DATA(packet)[6 + ethlen] & 0x40) {
 985                                 packet->len = via->mtu;
 986                                 route_ipv4_unreachable(source, packet, ethlen, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 987                         } else {
 988                                 fragment_ipv4_packet(via, packet, ethlen);
 989                         }
 990                         return;
 991                 } else if(type == ETH_P_IPV6 && packet->len > 1280 + ethlen) {
 992                         packet->len = via->mtu;
 993                         route_ipv6_unreachable(source, packet, ethlen, ICMP6_PACKET_TOO_BIG, 0);
 994                         return;
 995                 }
 996         }
 997
 998         clamp_mss(source, via, packet);
 999
1000         send_packet(subnet->owner, packet);
1001 }
1002
1003 static void send_pcap(vpn_packet_t *packet) {
1004         pcap = false;
1005
1006         for list_each(connection_t, c, connection_list) {
1007                 if(!c->status.pcap)
1008                         continue;
1009
1010                 pcap = true;
1011                 int len = packet->len;
1012                 if(c->outmaclength && c->outmaclength < len)
1013                         len = c->outmaclength;
1014
1015                 if(send_request(c, "%d %d %d", CONTROL, REQ_PCAP, len))
1016                         send_meta(c, (char *)DATA(packet), len);
1017         }
1018 }
1019
1020 void route(node_t *source, vpn_packet_t *packet) {
1021         if(pcap)
1022                 send_pcap(packet);
1023
1024         if(forwarding_mode == FMODE_KERNEL && source != myself) {
1025                 send_packet(myself, packet);
1026                 return;
1027         }
1028
1029         if(!checklength(source, packet, ether_size))
1030                 return;
1031
1032         uint16_t type = DATA(packet)[12] << 8 | DATA(packet)[13];
1033
1034         switch (routing_mode) {
1035                 case RMODE_ROUTER:
1036                         switch (type) {
1037                                 case ETH_P_ARP:
1038                                         route_arp(source, packet);
1039                                         break;
1040
1041                                 case ETH_P_IP:
1042                                         route_ipv4(source, packet);
1043                                         break;
1044
1045                                 case ETH_P_IPV6:
1046                                         route_ipv6(source, packet);
1047                                         break;
1048
1049                                 default:
1050                                         logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type);
1051                                         break;
1052                         }
1053                         break;
1054
1055                 case RMODE_SWITCH:
1056                         route_mac(source, packet);
1057                         break;
1058
1059                 case RMODE_HUB:
1060                         route_broadcast(source, packet);
1061                         break;
1062         }
1063 }