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