tinc-vpn.org Git - tinc/blob - src/net_packet.c

   1 /*
   2     net_packet.c -- Handles in- and outgoing VPN packets
   3     Copyright (C) 1998-2005 Ivo Timmermans,
   4                   2000-2010 Guus Sliepen <guus@tinc-vpn.org>
   5                   2010      Timothy Redaelli <timothy@redaelli.eu>
   6                   2010      Brandon Black <blblack@gmail.com>
   7
   8     This program is free software; you can redistribute it and/or modify
   9     it under the terms of the GNU General Public License as published by
  10     the Free Software Foundation; either version 2 of the License, or
  11     (at your option) any later version.
  12
  13     This program is distributed in the hope that it will be useful,
  14     but WITHOUT ANY WARRANTY; without even the implied warranty of
  15     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16     GNU General Public License for more details.
  17
  18     You should have received a copy of the GNU General Public License along
  19     with this program; if not, write to the Free Software Foundation, Inc.,
  20     51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  21 */
  22
  23 #include "system.h"
  24
  25 #include <openssl/rand.h>
  26 #include <openssl/err.h>
  27 #include <openssl/evp.h>
  28 #include <openssl/pem.h>
  29 #include <openssl/hmac.h>
  30
  31 #ifdef HAVE_ZLIB
  32 #include <zlib.h>
  33 #endif
  34
  35 #ifdef HAVE_LZO
  36 #include LZO1X_H
  37 #endif
  38
  39 #include "splay_tree.h"
  40 #include "cipher.h"
  41 #include "conf.h"
  42 #include "connection.h"
  43 #include "crypto.h"
  44 #include "digest.h"
  45 #include "device.h"
  46 #include "ethernet.h"
  47 #include "graph.h"
  48 #include "list.h"
  49 #include "logger.h"
  50 #include "net.h"
  51 #include "netutl.h"
  52 #include "protocol.h"
  53 #include "process.h"
  54 #include "route.h"
  55 #include "utils.h"
  56 #include "xalloc.h"
  57
  58 int keylifetime = 0;
  59 int keyexpires = 0;
  60 #ifdef HAVE_LZO
  61 static char lzo_wrkmem[LZO1X_999_MEM_COMPRESS > LZO1X_1_MEM_COMPRESS ? LZO1X_999_MEM_COMPRESS : LZO1X_1_MEM_COMPRESS];
  62 #endif
  63
  64 static void send_udppacket(node_t *, vpn_packet_t *);
  65
  66 unsigned replaywin = 16;
  67
  68 #define MAX_SEQNO 1073741824
  69
  70 // mtuprobes == 1..30: initial discovery, send bursts with 1 second interval
  71 // mtuprobes ==    31: sleep pinginterval seconds
  72 // mtuprobes ==    32: send 1 burst, sleep pingtimeout second
  73 // mtuprobes ==    33: no response from other side, restart PMTU discovery process
  74
  75 static void send_mtu_probe_handler(void *data) {
  76         node_t *n = data;
  77         vpn_packet_t packet;
  78         int len, i;
  79         int timeout = 1;
  80
  81         n->mtuprobes++;
  82
  83         if(!n->status.reachable || !n->status.validkey) {
  84                 ifdebug(TRAFFIC) logger(LOG_INFO, "Trying to send MTU probe to unreachable or rekeying node %s (%s)", n->name, n->hostname);
  85                 n->mtuprobes = 0;
  86                 return;
  87         }
  88
  89         if(n->mtuprobes > 32) {
  90                 ifdebug(TRAFFIC) logger(LOG_INFO, "%s (%s) did not respond to UDP ping, restarting PMTU discovery", n->name, n->hostname);
  91                 n->mtuprobes = 1;
  92                 n->minmtu = 0;
  93                 n->maxmtu = MTU;
  94         }
  95
  96         if(n->mtuprobes >= 10 && !n->minmtu) {
  97                 ifdebug(TRAFFIC) logger(LOG_INFO, "No response to MTU probes from %s (%s)", n->name, n->hostname);
  98                 n->mtuprobes = 0;
  99                 return;
 100         }
 101
 102         if(n->mtuprobes == 30 || (n->mtuprobes < 30 && n->minmtu >= n->maxmtu)) {
 103                 if(n->minmtu > n->maxmtu)
 104                         n->minmtu = n->maxmtu;
 105                 else
 106                         n->maxmtu = n->minmtu;
 107                 n->mtu = n->minmtu;
 108                 ifdebug(TRAFFIC) logger(LOG_INFO, "Fixing MTU of %s (%s) to %d after %d probes", n->name, n->hostname, n->mtu, n->mtuprobes);
 109                 n->mtuprobes = 31;
 110         }
 111
 112         if(n->mtuprobes == 31) {
 113                 timeout = pinginterval;
 114                 goto end;
 115         } else if(n->mtuprobes == 32) {
 116                 timeout = pingtimeout;
 117         }
 118
 119         for(i = 0; i < 3; i++) {
 120                 if(n->maxmtu <= n->minmtu)
 121                         len = n->maxmtu;
 122                 else
 123                         len = n->minmtu + 1 + rand() % (n->maxmtu - n->minmtu);
 124
 125                 if(len < 64)
 126                         len = 64;
 127
 128                 memset(packet.data, 0, 14);
 129                 randomize(packet.data + 14, len - 14);
 130                 packet.len = len;
 131                 packet.priority = 0;
 132
 133                 ifdebug(TRAFFIC) logger(LOG_INFO, "Sending MTU probe length %d to %s (%s)", len, n->name, n->hostname);
 134
 135                 send_udppacket(n, &packet);
 136         }
 137
 138 end:
 139         n->mtuevent.time = time(NULL) + timeout;
 140         event_add(&n->mtuevent);
 141 }
 142
 143 void send_mtu_probe(node_t *n) {
 144         event_del(&n->mtuevent);
 145         n->mtuevent.handler = send_mtu_probe_handler;
 146         n->mtuevent.data = n;
 147         send_mtu_probe_handler(n);
 148 }
 149
 150 void mtu_probe_h(node_t *n, vpn_packet_t *packet, length_t len) {
 151         ifdebug(TRAFFIC) logger(LOG_INFO, "Got MTU probe length %d from %s (%s)", packet->len, n->name, n->hostname);
 152
 153         if(!packet->data[0]) {
 154                 packet->data[0] = 1;
 155                 send_udppacket(n, packet);
 156         } else {
 157                 if(len > n->maxmtu)
 158                         len = n->maxmtu;
 159                 if(n->minmtu < len)
 160                         n->minmtu = len;
 161                 if(n->mtuprobes > 30)
 162                         n->mtuprobes = 30;
 163         }
 164 }
 165
 166 static length_t compress_packet(uint8_t *dest, const uint8_t *source, length_t len, int level) {
 167         if(level == 0) {
 168                 memcpy(dest, source, len);
 169                 return len;
 170         } else if(level == 10) {
 171 #ifdef HAVE_LZO
 172                 lzo_uint lzolen = MAXSIZE;
 173                 lzo1x_1_compress(source, len, dest, &lzolen, lzo_wrkmem);
 174                 return lzolen;
 175 #else
 176                 return -1;
 177 #endif
 178         } else if(level < 10) {
 179 #ifdef HAVE_ZLIB
 180                 unsigned long destlen = MAXSIZE;
 181                 if(compress2(dest, &destlen, source, len, level) == Z_OK)
 182                         return destlen;
 183                 else
 184 #endif
 185                         return -1;
 186         } else {
 187 #ifdef HAVE_LZO
 188                 lzo_uint lzolen = MAXSIZE;
 189                 lzo1x_999_compress(source, len, dest, &lzolen, lzo_wrkmem);
 190                 return lzolen;
 191 #else
 192                 return -1;
 193 #endif
 194         }
 195
 196         return -1;
 197 }
 198
 199 static length_t uncompress_packet(uint8_t *dest, const uint8_t *source, length_t len, int level) {
 200         if(level == 0) {
 201                 memcpy(dest, source, len);
 202                 return len;
 203         } else if(level > 9) {
 204 #ifdef HAVE_LZO
 205                 lzo_uint lzolen = MAXSIZE;
 206                 if(lzo1x_decompress_safe(source, len, dest, &lzolen, NULL) == LZO_E_OK)
 207                         return lzolen;
 208                 else
 209 #endif
 210                         return -1;
 211         }
 212 #ifdef HAVE_ZLIB
 213         else {
 214                 unsigned long destlen = MAXSIZE;
 215                 if(uncompress(dest, &destlen, source, len) == Z_OK)
 216                         return destlen;
 217                 else
 218                         return -1;
 219         }
 220 #endif
 221
 222         return -1;
 223 }
 224
 225 /* VPN packet I/O */
 226
 227 static void receive_packet(node_t *n, vpn_packet_t *packet) {
 228         ifdebug(TRAFFIC) logger(LOG_DEBUG, "Received packet of %d bytes from %s (%s)",
 229                            packet->len, n->name, n->hostname);
 230
 231         route(n, packet);
 232 }
 233
 234 static bool try_mac(node_t *n, const vpn_packet_t *inpkt) {
 235         if(!digest_active(&n->indigest) || inpkt->len < sizeof inpkt->seqno + digest_length(&n->indigest))
 236                 return false;
 237
 238         return digest_verify(&n->indigest, &inpkt->seqno, inpkt->len - n->indigest.maclength, (const char *)&inpkt->seqno + inpkt->len - n->indigest.maclength);
 239 }
 240
 241 static void receive_udppacket(node_t *n, vpn_packet_t *inpkt) {
 242         vpn_packet_t pkt1, pkt2;
 243         vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
 244         int nextpkt = 0;
 245         vpn_packet_t *outpkt = pkt[0];
 246         size_t outlen;
 247         int i;
 248
 249         if(!cipher_active(&n->incipher)) {
 250                 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got packet from %s (%s) but he hasn't got our key yet",
 251                                         n->name, n->hostname);
 252                 return;
 253         }
 254
 255         /* Check packet length */
 256
 257         if(inpkt->len < sizeof inpkt->seqno + digest_length(&n->indigest)) {
 258                 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got too short packet from %s (%s)",
 259                                         n->name, n->hostname);
 260                 return;
 261         }
 262
 263         /* Check the message authentication code */
 264
 265         if(digest_active(&n->indigest)) {
 266                 inpkt->len -= n->indigest.maclength;
 267                 if(!digest_verify(&n->indigest, &inpkt->seqno, inpkt->len, (const char *)&inpkt->seqno + inpkt->len)) {
 268                         ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got unauthenticated packet from %s (%s)", n->name, n->hostname);
 269                         return;
 270                 }
 271         }
 272         /* Decrypt the packet */
 273
 274         if(cipher_active(&n->incipher)) {
 275                 outpkt = pkt[nextpkt++];
 276                 outlen = MAXSIZE;
 277
 278                 if(!cipher_decrypt(&n->incipher, &inpkt->seqno, inpkt->len, &outpkt->seqno, &outlen, true)) {
 279                         ifdebug(TRAFFIC) logger(LOG_DEBUG, "Error decrypting packet from %s (%s)", n->name, n->hostname);
 280                         return;
 281                 }
 282
 283                 outpkt->len = outlen;
 284                 inpkt = outpkt;
 285         }
 286
 287         /* Check the sequence number */
 288
 289         inpkt->len -= sizeof inpkt->seqno;
 290         inpkt->seqno = ntohl(inpkt->seqno);
 291
 292         if(replaywin) {
 293                 if(inpkt->seqno != n->received_seqno + 1) {
 294                         if(inpkt->seqno >= n->received_seqno + replaywin * 8) {
 295                                 if(n->farfuture++ < replaywin >> 2) {
 296                                         logger(LOG_WARNING, "Packet from %s (%s) is %d seqs in the future, dropped (%u)",
 297                                                 n->name, n->hostname, inpkt->seqno - n->received_seqno - 1, n->farfuture);
 298                                         return;
 299                                 }
 300                                 logger(LOG_WARNING, "Lost %d packets from %s (%s)",
 301                                                 inpkt->seqno - n->received_seqno - 1, n->name, n->hostname);
 302                                 memset(n->late, 0, replaywin);
 303                         } else if (inpkt->seqno <= n->received_seqno) {
 304                                 if((n->received_seqno >= replaywin * 8 && inpkt->seqno <= n->received_seqno - replaywin * 8) || !(n->late[(inpkt->seqno / 8) % replaywin] & (1 << inpkt->seqno % 8))) {
 305                                         logger(LOG_WARNING, "Got late or replayed packet from %s (%s), seqno %d, last received %d",
 306                                                 n->name, n->hostname, inpkt->seqno, n->received_seqno);
 307                                         return;
 308                                 }
 309                         } else {
 310                                 for(i = n->received_seqno + 1; i < inpkt->seqno; i++)
 311                                         n->late[(i / 8) % replaywin] |= 1 << i % 8;
 312                         }
 313                 }
 314
 315                 n->farfuture = 0;
 316                 n->late[(inpkt->seqno / 8) % replaywin] &= ~(1 << inpkt->seqno % 8);
 317         }
 318
 319         if(inpkt->seqno > n->received_seqno)
 320                 n->received_seqno = inpkt->seqno;
 321
 322         if(n->received_seqno > MAX_SEQNO)
 323                 regenerate_key();
 324
 325         /* Decompress the packet */
 326
 327         length_t origlen = inpkt->len;
 328
 329         if(n->incompression) {
 330                 outpkt = pkt[nextpkt++];
 331
 332                 if((outpkt->len = uncompress_packet(outpkt->data, inpkt->data, inpkt->len, n->incompression)) < 0) {
 333                         ifdebug(TRAFFIC) logger(LOG_ERR, "Error while uncompressing packet from %s (%s)",
 334                                                  n->name, n->hostname);
 335                         return;
 336                 }
 337
 338                 inpkt = outpkt;
 339
 340                 origlen -= MTU/64 + 20;
 341         }
 342
 343         inpkt->priority = 0;
 344
 345         if(!inpkt->data[12] && !inpkt->data[13])
 346                 mtu_probe_h(n, inpkt, origlen);
 347         else
 348                 receive_packet(n, inpkt);
 349 }
 350
 351 void receive_tcppacket(connection_t *c, char *buffer, int len) {
 352         vpn_packet_t outpkt;
 353
 354         outpkt.len = len;
 355         if(c->options & OPTION_TCPONLY)
 356                 outpkt.priority = 0;
 357         else
 358                 outpkt.priority = -1;
 359         memcpy(outpkt.data, buffer, len);
 360
 361         receive_packet(c->node, &outpkt);
 362 }
 363
 364 static void send_udppacket(node_t *n, vpn_packet_t *origpkt) {
 365         vpn_packet_t pkt1, pkt2;
 366         vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
 367         vpn_packet_t *inpkt = origpkt;
 368         int nextpkt = 0;
 369         vpn_packet_t *outpkt;
 370         int origlen;
 371         size_t outlen;
 372 #if defined(SOL_IP) && defined(IP_TOS)
 373         static int priority = 0;
 374 #endif
 375         int origpriority;
 376         int sock;
 377
 378         if(!n->status.reachable) {
 379                 ifdebug(TRAFFIC) logger(LOG_INFO, "Trying to send UDP packet to unreachable node %s (%s)", n->name, n->hostname);
 380                 return;
 381         }
 382
 383         /* Make sure we have a valid key */
 384
 385         if(!n->status.validkey) {
 386                 time_t now = time(NULL);
 387
 388                 ifdebug(TRAFFIC) logger(LOG_INFO,
 389                                    "No valid key known yet for %s (%s), forwarding via TCP",
 390                                    n->name, n->hostname);
 391
 392                 if(n->last_req_key + 10 < now) {
 393                         send_req_key(n);
 394                         n->last_req_key = now;
 395                 }
 396
 397                 send_tcppacket(n->nexthop->connection, origpkt);
 398
 399                 return;
 400         }
 401
 402         if(n->options & OPTION_PMTU_DISCOVERY && inpkt->len > n->minmtu && (inpkt->data[12] | inpkt->data[13])) {
 403                 ifdebug(TRAFFIC) logger(LOG_INFO,
 404                                 "Packet for %s (%s) larger than minimum MTU, forwarding via %s",
 405                                 n->name, n->hostname, n != n->nexthop ? n->nexthop->name : "TCP");
 406
 407                 if(n != n->nexthop)
 408                         send_packet(n->nexthop, origpkt);
 409                 else
 410                         send_tcppacket(n->nexthop->connection, origpkt);
 411
 412                 return;
 413         }
 414
 415         origlen = inpkt->len;
 416         origpriority = inpkt->priority;
 417
 418         /* Compress the packet */
 419
 420         if(n->outcompression) {
 421                 outpkt = pkt[nextpkt++];
 422
 423                 if((outpkt->len = compress_packet(outpkt->data, inpkt->data, inpkt->len, n->outcompression)) < 0) {
 424                         ifdebug(TRAFFIC) logger(LOG_ERR, "Error while compressing packet to %s (%s)",
 425                                    n->name, n->hostname);
 426                         return;
 427                 }
 428
 429                 inpkt = outpkt;
 430         }
 431
 432         /* Add sequence number */
 433
 434         inpkt->seqno = htonl(++(n->sent_seqno));
 435         inpkt->len += sizeof inpkt->seqno;
 436
 437         /* Encrypt the packet */
 438
 439         if(cipher_active(&n->outcipher)) {
 440                 outpkt = pkt[nextpkt++];
 441                 outlen = MAXSIZE;
 442
 443                 if(!cipher_encrypt(&n->outcipher, &inpkt->seqno, inpkt->len, &outpkt->seqno, &outlen, true)) {
 444                         ifdebug(TRAFFIC) logger(LOG_ERR, "Error while encrypting packet to %s (%s)", n->name, n->hostname);
 445                         goto end;
 446                 }
 447
 448                 outpkt->len = outlen;
 449                 inpkt = outpkt;
 450         }
 451
 452         /* Add the message authentication code */
 453
 454         if(digest_active(&n->outdigest)) {
 455                 digest_create(&n->outdigest, &inpkt->seqno, inpkt->len, (char *)&inpkt->seqno + inpkt->len);
 456                 inpkt->len += digest_length(&n->outdigest);
 457         }
 458
 459         /* Determine which socket we have to use */
 460
 461         for(sock = 0; sock < listen_sockets; sock++)
 462                 if(n->address.sa.sa_family == listen_socket[sock].sa.sa.sa_family)
 463                         break;
 464
 465         if(sock >= listen_sockets)
 466                 sock = 0;                               /* If none is available, just use the first and hope for the best. */
 467
 468         /* Send the packet */
 469
 470 #if defined(SOL_IP) && defined(IP_TOS)
 471         if(priorityinheritance && origpriority != priority
 472            && listen_socket[sock].sa.sa.sa_family == AF_INET) {
 473                 priority = origpriority;
 474                 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Setting outgoing packet priority to %d", priority);
 475                 if(setsockopt(listen_socket[sock].udp, SOL_IP, IP_TOS, &priority, sizeof priority))     /* SO_PRIORITY doesn't seem to work */
 476                         logger(LOG_ERR, "System call `%s' failed: %s", "setsockopt", strerror(errno));
 477         }
 478 #endif
 479
 480         if(sendto(listen_socket[sock].udp, (char *) &inpkt->seqno, inpkt->len, 0, &(n->address.sa), SALEN(n->address.sa)) < 0 && !sockwouldblock(sockerrno)) {
 481                 if(sockmsgsize(sockerrno)) {
 482                         if(n->maxmtu >= origlen)
 483                                 n->maxmtu = origlen - 1;
 484                         if(n->mtu >= origlen)
 485                                 n->mtu = origlen - 1;
 486                 } else
 487                         logger(LOG_ERR, "Error sending packet to %s (%s): %s", n->name, n->hostname, sockstrerror(sockerrno));
 488         }
 489
 490 end:
 491         origpkt->len = origlen;
 492 }
 493
 494 /*
 495   send a packet to the given vpn ip.
 496 */
 497 void send_packet(const node_t *n, vpn_packet_t *packet) {
 498         node_t *via;
 499
 500         if(n == myself) {
 501                 if(overwrite_mac)
 502                          memcpy(packet->data, mymac.x, ETH_ALEN);
 503                 write_packet(packet);
 504                 return;
 505         }
 506
 507         ifdebug(TRAFFIC) logger(LOG_ERR, "Sending packet of %d bytes to %s (%s)",
 508                            packet->len, n->name, n->hostname);
 509
 510         if(!n->status.reachable) {
 511                 ifdebug(TRAFFIC) logger(LOG_INFO, "Node %s (%s) is not reachable",
 512                                    n->name, n->hostname);
 513                 return;
 514         }
 515
 516         via = (packet->priority == -1 || n->via == myself) ? n->nexthop : n->via;
 517
 518         if(via != n)
 519                 ifdebug(TRAFFIC) logger(LOG_INFO, "Sending packet to %s via %s (%s)",
 520                            n->name, via->name, n->via->hostname);
 521
 522         if(packet->priority == -1 || ((myself->options | via->options) & OPTION_TCPONLY)) {
 523                 if(!send_tcppacket(via->connection, packet))
 524                         terminate_connection(via->connection, true);
 525         } else
 526                 send_udppacket(via, packet);
 527 }
 528
 529 /* Broadcast a packet using the minimum spanning tree */
 530
 531 void broadcast_packet(const node_t *from, vpn_packet_t *packet) {
 532         splay_node_t *node;
 533         connection_t *c;
 534
 535         ifdebug(TRAFFIC) logger(LOG_INFO, "Broadcasting packet of %d bytes from %s (%s)",
 536                            packet->len, from->name, from->hostname);
 537
 538         if(from != myself) {
 539                 send_packet(myself, packet);
 540
 541                 // In TunnelServer mode, do not forward broadcast packets.
 542                 // The MST might not be valid and create loops.
 543                 if(tunnelserver)
 544                         return;
 545         }
 546
 547         for(node = connection_tree->head; node; node = node->next) {
 548                 c = node->data;
 549
 550                 if(c->status.active && c->status.mst && c != from->nexthop->connection)
 551                         send_packet(c->node, packet);
 552         }
 553 }
 554
 555 static node_t *try_harder(const sockaddr_t *from, const vpn_packet_t *pkt) {
 556         splay_node_t *node;
 557         node_t *n, *found = NULL;
 558         static time_t last_hard_try = 0;
 559         time_t now = time(NULL);
 560
 561         if(last_hard_try == now)
 562                 return NULL;
 563         else
 564                 last_hard_try = now;
 565
 566         for(node = node_tree->head; node; node = node->next) {
 567                 n = node->data;
 568
 569                 if(n == myself || !n->status.reachable || !digest_active(&n->indigest))
 570                         continue;
 571
 572                 if(try_mac(n, pkt)) {
 573                         found = n;
 574                         break;
 575                 }
 576         }
 577
 578         return found;
 579 }
 580
 581 void handle_incoming_vpn_data(void *arg) {
 582         listen_socket_t *l = arg;
 583         vpn_packet_t pkt;
 584         char *hostname;
 585         sockaddr_t from;
 586         socklen_t fromlen = sizeof from;
 587         node_t *n;
 588         int len;
 589
 590         while(true) {
 591                 len = recvfrom(l->udp, (char *) &pkt.seqno, MAXSIZE, 0, &from.sa, &fromlen);
 592
 593                 if(len <= 0 || len > MAXSIZE) {
 594                         logger(LOG_ERR, "Receiving packet failed: %s", sockstrerror(sockerrno));
 595                         return;
 596                 }
 597
 598                 pkt.len = len;
 599
 600                 sockaddrunmap(&from);           /* Some braindead IPv6 implementations do stupid things. */
 601
 602                 mutex_lock(&mutex);
 603                 n = lookup_node_udp(&from);
 604
 605                 if(!n) {
 606                         n = try_harder(&from, &pkt);
 607                         if(n)
 608                                 update_node_udp(n, &from);
 609                 }
 610
 611                 if(n) {
 612                         receive_udppacket(n, &pkt);
 613                 } else {
 614                         ifdebug(PROTOCOL) {
 615                                 hostname = sockaddr2hostname(&from);
 616                                 logger(LOG_WARNING, "Received UDP packet from unknown source %s", hostname);
 617                                 free(hostname);
 618                         }
 619                 }
 620
 621                 mutex_unlock(&mutex);
 622         }
 623 }
 624
 625 void handle_device_data(int sock, short events, void *data) {
 626         vpn_packet_t packet;
 627
 628         if(read_packet(&packet))
 629                 route(myself, &packet);
 630 }