Make maxmtu equal to minmtu when fixing the path MTU to a node.
[tinc] / src / net_packet.c
index 087df8a..3466f87 100644 (file)
@@ -1,7 +1,7 @@
 /*
     net_packet.c -- Handles in- and outgoing VPN packets
-    Copyright (C) 1998-2002 Ivo Timmermans <itimmermans@bigfoot.com>,
-                  2000-2002 Guus Sliepen <guus@sliepen.warande.net>
+    Copyright (C) 1998-2005 Ivo Timmermans,
+                  2000-2009 Guus Sliepen <guus@tinc-vpn.org>
 
     This program is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     GNU General Public License for more details.
 
-    You should have received a copy of the GNU General Public License
-    along with this program; if not, write to the Free Software
-    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
-
-    $Id: net_packet.c,v 1.2 2002/04/09 15:26:00 zarq Exp $
+    You should have received a copy of the GNU General Public License along
+    with this program; if not, write to the Free Software Foundation, Inc.,
+    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
 
-#include "config.h"
-
-#include <errno.h>
-#include <fcntl.h>
-#include <netdb.h>
-#include <netinet/in.h>
-#ifdef HAVE_LINUX
- #include <netinet/ip.h>
- #include <netinet/tcp.h>
-#endif
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-#include <signal.h>
-#include <sys/time.h>
-#include <sys/types.h>
-#include <syslog.h>
-#include <unistd.h>
-#include <sys/ioctl.h>
-/* SunOS really wants sys/socket.h BEFORE net/if.h,
-   and FreeBSD wants these lines below the rest. */
-#include <arpa/inet.h>
-#include <sys/socket.h>
-#include <net/if.h>
+#include "system.h"
 
 #include <openssl/rand.h>
+#include <openssl/err.h>
 #include <openssl/evp.h>
 #include <openssl/pem.h>
 #include <openssl/hmac.h>
 
-#ifndef HAVE_RAND_PSEUDO_BYTES
-#define RAND_pseudo_bytes RAND_bytes
-#endif
-
 #include <zlib.h>
+#include LZO1X_H
 
-#include <utils.h>
-#include <xalloc.h>
-#include <avl_tree.h>
-#include <list.h>
-
+#include "avl_tree.h"
 #include "conf.h"
 #include "connection.h"
-#include "meta.h"
+#include "device.h"
+#include "ethernet.h"
+#include "event.h"
+#include "graph.h"
+#include "list.h"
+#include "logger.h"
 #include "net.h"
 #include "netutl.h"
-#include "process.h"
 #include "protocol.h"
-#include "subnet.h"
-#include "graph.h"
 #include "process.h"
 #include "route.h"
-#include "device.h"
-#include "event.h"
+#include "utils.h"
+#include "xalloc.h"
 
-#include "system.h"
+#ifdef WSAEMSGSIZE
+#define EMSGSIZE WSAEMSGSIZE
+#endif
 
 int keylifetime = 0;
 int keyexpires = 0;
+static char lzo_wrkmem[LZO1X_999_MEM_COMPRESS > LZO1X_1_MEM_COMPRESS ? LZO1X_999_MEM_COMPRESS : LZO1X_1_MEM_COMPRESS];
+
+static void send_udppacket(node_t *, vpn_packet_t *);
 
 #define MAX_SEQNO 1073741824
 
+// mtuprobes == 1..30: initial discovery, send bursts with 1 second interval
+// mtuprobes ==    31: sleep pinginterval seconds
+// mtuprobes ==    32: send 1 burst, sleep pingtimeout second
+// mtuprobes ==    33: no response from other side, restart PMTU discovery process
+
+void send_mtu_probe(node_t *n) {
+       vpn_packet_t packet;
+       int len, i;
+       int timeout = 1;
+       
+       n->mtuprobes++;
+       n->mtuevent = NULL;
+
+       if(!n->status.reachable || !n->status.validkey) {
+               ifdebug(TRAFFIC) logger(LOG_INFO, "Trying to send MTU probe to unreachable or rekeying node %s (%s)", n->name, n->hostname);
+               n->mtuprobes = 0;
+               return;
+       }
+
+       if(n->mtuprobes > 32) {
+               ifdebug(TRAFFIC) logger(LOG_INFO, "%s (%s) did not respond to UDP ping, restarting PMTU discovery", n->name, n->hostname);
+               n->mtuprobes = 1;
+               n->minmtu = 0;
+               n->maxmtu = MTU;
+       }
+
+       if(n->mtuprobes >= 10 && !n->minmtu) {
+               ifdebug(TRAFFIC) logger(LOG_INFO, "No response to MTU probes from %s (%s)", n->name, n->hostname);
+               n->mtuprobes = 0;
+               return;
+       }
+
+       if(n->mtuprobes == 30 || (n->mtuprobes < 30 && n->minmtu >= n->maxmtu)) {
+               if(n->minmtu > n->maxmtu)
+                       n->minmtu = n->maxmtu;
+               else
+                       n->maxmtu = n->minmtu;
+               n->mtu = n->minmtu;
+               ifdebug(TRAFFIC) logger(LOG_INFO, "Fixing MTU of %s (%s) to %d after %d probes", n->name, n->hostname, n->mtu, n->mtuprobes);
+               n->mtuprobes = 31;
+       }
+
+       if(n->mtuprobes == 31) {
+               timeout = pinginterval;
+               goto end;
+       } else if(n->mtuprobes == 32) {
+               timeout = pingtimeout;
+       }
+
+       for(i = 0; i < 3; i++) {
+               if(n->maxmtu <= n->minmtu)
+                       len = n->maxmtu;
+               else
+                       len = n->minmtu + 1 + rand() % (n->maxmtu - n->minmtu);
+
+               if(len < 64)
+                       len = 64;
+               
+               memset(packet.data, 0, 14);
+               RAND_pseudo_bytes(packet.data + 14, len - 14);
+               packet.len = len;
+               packet.priority = 0;
+
+               ifdebug(TRAFFIC) logger(LOG_INFO, "Sending MTU probe length %d to %s (%s)", len, n->name, n->hostname);
+
+               send_udppacket(n, &packet);
+       }
+
+end:
+       n->mtuevent = new_event();
+       n->mtuevent->handler = (event_handler_t)send_mtu_probe;
+       n->mtuevent->data = n;
+       n->mtuevent->time = now + timeout;
+       event_add(n->mtuevent);
+}
+
+void mtu_probe_h(node_t *n, vpn_packet_t *packet, length_t len) {
+       ifdebug(TRAFFIC) logger(LOG_INFO, "Got MTU probe length %d from %s (%s)", packet->len, n->name, n->hostname);
+
+       if(!packet->data[0]) {
+               packet->data[0] = 1;
+               send_udppacket(n, packet);
+       } else {
+               if(len > n->maxmtu)
+                       len = n->maxmtu;
+               if(n->minmtu < len)
+                       n->minmtu = len;
+               if(n->mtuprobes > 30)
+                       n->mtuprobes = 30;
+       }
+}
+
+static length_t compress_packet(uint8_t *dest, const uint8_t *source, length_t len, int level) {
+       if(level == 10) {
+               lzo_uint lzolen = MAXSIZE;
+               lzo1x_1_compress(source, len, dest, &lzolen, lzo_wrkmem);
+               return lzolen;
+       } else if(level < 10) {
+               unsigned long destlen = MAXSIZE;
+               if(compress2(dest, &destlen, source, len, level) == Z_OK)
+                       return destlen;
+               else
+                       return -1;
+       } else {
+               lzo_uint lzolen = MAXSIZE;
+               lzo1x_999_compress(source, len, dest, &lzolen, lzo_wrkmem);
+               return lzolen;
+       }
+       
+       return -1;
+}
+
+static length_t uncompress_packet(uint8_t *dest, const uint8_t *source, length_t len, int level) {
+       if(level > 9) {
+               lzo_uint lzolen = MAXSIZE;
+               if(lzo1x_decompress_safe(source, len, dest, &lzolen, NULL) == LZO_E_OK)
+                       return lzolen;
+               else
+                       return -1;
+       } else {
+               unsigned long destlen = MAXSIZE;
+               if(uncompress(dest, &destlen, source, len) == Z_OK)
+                       return destlen;
+               else
+                       return -1;
+       }
+       
+       return -1;
+}
+
 /* VPN packet I/O */
 
-void receive_udppacket(node_t *n, vpn_packet_t *inpkt)
-{
-  vpn_packet_t pkt1, pkt2;
-  vpn_packet_t *pkt[] = {&pkt1, &pkt2, &pkt1, &pkt2};
-  int nextpkt = 0;
-  vpn_packet_t *outpkt = pkt[0];
-  int outlen, outpad;
-  long int complen = MTU + 12;
-  EVP_CIPHER_CTX ctx;
-  char hmac[EVP_MAX_MD_SIZE];
-cp
-  /* Check the message authentication code */
-
-  if(myself->digest && myself->maclength)
-    {
-      inpkt->len -= myself->maclength;
-      HMAC(myself->digest, myself->key, myself->keylength, (char *)&inpkt->seqno, inpkt->len, hmac, NULL);
-      if(memcmp(hmac, (char *)&inpkt->seqno + inpkt->len, myself->maclength))
-        {
-          if(debug_lvl >= DEBUG_TRAFFIC)
-            syslog(LOG_DEBUG, _("Got unauthenticated packet from %s (%s)"), n->name, n->hostname);
-          return;
-        }
-    }
-
-  /* Decrypt the packet */
-
-  if(myself->cipher)
-  {
-    outpkt = pkt[nextpkt++];
-
-    EVP_DecryptInit(&ctx, myself->cipher, myself->key, myself->key + myself->cipher->key_len);
-    EVP_DecryptUpdate(&ctx, (char *)&outpkt->seqno, &outlen, (char *)&inpkt->seqno, inpkt->len);
-    EVP_DecryptFinal(&ctx, (char *)&outpkt->seqno + outlen, &outpad);
-
-    outpkt->len = outlen + outpad;
-    inpkt = outpkt;
-  }
-
-  /* Check the sequence number */
-
-  inpkt->len -= sizeof(inpkt->seqno);
-  inpkt->seqno = ntohl(inpkt->seqno);
-
-  if(inpkt->seqno <= n->received_seqno)
-  {
-    if(debug_lvl >= DEBUG_TRAFFIC)
-      syslog(LOG_DEBUG, _("Got late or replayed packet from %s (%s), seqno %d"), n->name, n->hostname, inpkt->seqno);
-    return;
-  }
-  
-  n->received_seqno = inpkt->seqno;
-
-  if(n->received_seqno > MAX_SEQNO)
-    keyexpires = 0;
-
-  /* Decompress the packet */
-  
-  if(myself->compression)
-  {
-    outpkt = pkt[nextpkt++];
-
-    if(uncompress(outpkt->data, &complen, inpkt->data, inpkt->len) != Z_OK)
-    {
-      syslog(LOG_ERR, _("Error while uncompressing packet from %s (%s)"), n->name, n->hostname);
-      return;
-    }
-    
-    outpkt->len = complen;
-    inpkt = outpkt;
-  }
-
-  receive_packet(n, inpkt);
-cp
+static void receive_packet(node_t *n, vpn_packet_t *packet) {
+       ifdebug(TRAFFIC) logger(LOG_DEBUG, "Received packet of %d bytes from %s (%s)",
+                          packet->len, n->name, n->hostname);
+
+       route(n, packet);
 }
 
-void receive_tcppacket(connection_t *c, char *buffer, int len)
-{
-  vpn_packet_t outpkt;
-cp
-  outpkt.len = len;
-  memcpy(outpkt.data, buffer, len);
+static bool try_mac(const node_t *n, const vpn_packet_t *inpkt) {
+       unsigned char hmac[EVP_MAX_MD_SIZE];
+
+       if(!n->indigest || !n->inmaclength || !n->inkey || inpkt->len < sizeof inpkt->seqno + n->inmaclength)
+               return false;
+
+       HMAC(n->indigest, n->inkey, n->inkeylength, (unsigned char *) &inpkt->seqno, inpkt->len - n->inmaclength, (unsigned char *)hmac, NULL);
+
+       return !memcmp(hmac, (char *) &inpkt->seqno + inpkt->len - n->inmaclength, n->inmaclength);
+}
 
-  receive_packet(c->node, &outpkt);
-cp
+static void receive_udppacket(node_t *n, vpn_packet_t *inpkt) {
+       vpn_packet_t pkt1, pkt2;
+       vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
+       int nextpkt = 0;
+       vpn_packet_t *outpkt = pkt[0];
+       int outlen, outpad;
+       unsigned char hmac[EVP_MAX_MD_SIZE];
+       int i;
+
+       if(!n->inkey) {
+               ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got packet from %s (%s) but he hasn't got our key yet",
+                                       n->name, n->hostname);
+               return;
+       }
+
+       /* Check packet length */
+
+       if(inpkt->len < sizeof(inpkt->seqno) + n->inmaclength) {
+               ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got too short packet from %s (%s)",
+                                       n->name, n->hostname);
+               return;
+       }
+
+       /* Check the message authentication code */
+
+       if(n->indigest && n->inmaclength) {
+               inpkt->len -= n->inmaclength;
+               HMAC(n->indigest, n->inkey, n->inkeylength,
+                        (unsigned char *) &inpkt->seqno, inpkt->len, (unsigned char *)hmac, NULL);
+
+               if(memcmp(hmac, (char *) &inpkt->seqno + inpkt->len, n->inmaclength)) {
+                       ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got unauthenticated packet from %s (%s)",
+                                          n->name, n->hostname);
+                       return;
+               }
+       }
+
+       /* Decrypt the packet */
+
+       if(n->incipher) {
+               outpkt = pkt[nextpkt++];
+
+               if(!EVP_DecryptInit_ex(&n->inctx, NULL, NULL, NULL, NULL)
+                               || !EVP_DecryptUpdate(&n->inctx, (unsigned char *) &outpkt->seqno, &outlen,
+                                       (unsigned char *) &inpkt->seqno, inpkt->len)
+                               || !EVP_DecryptFinal_ex(&n->inctx, (unsigned char *) &outpkt->seqno + outlen, &outpad)) {
+                       ifdebug(TRAFFIC) logger(LOG_DEBUG, "Error decrypting packet from %s (%s): %s",
+                                               n->name, n->hostname, ERR_error_string(ERR_get_error(), NULL));
+                       return;
+               }
+               
+               outpkt->len = outlen + outpad;
+               inpkt = outpkt;
+       }
+
+       /* Check the sequence number */
+
+       inpkt->len -= sizeof(inpkt->seqno);
+       inpkt->seqno = ntohl(inpkt->seqno);
+
+       if(inpkt->seqno != n->received_seqno + 1) {
+               if(inpkt->seqno >= n->received_seqno + sizeof(n->late) * 8) {
+                       logger(LOG_WARNING, "Lost %d packets from %s (%s)",
+                                          inpkt->seqno - n->received_seqno - 1, n->name, n->hostname);
+                       
+                       memset(n->late, 0, sizeof(n->late));
+               } else if (inpkt->seqno <= n->received_seqno) {
+                       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))) {
+                               logger(LOG_WARNING, "Got late or replayed packet from %s (%s), seqno %d, last received %d",
+                                          n->name, n->hostname, inpkt->seqno, n->received_seqno);
+                               return;
+                       }
+               } else {
+                       for(i = n->received_seqno + 1; i < inpkt->seqno; i++)
+                               n->late[(i / 8) % sizeof(n->late)] |= 1 << i % 8;
+               }
+       }
+       
+       n->late[(inpkt->seqno / 8) % sizeof(n->late)] &= ~(1 << inpkt->seqno % 8);
+
+       if(inpkt->seqno > n->received_seqno)
+               n->received_seqno = inpkt->seqno;
+                       
+       if(n->received_seqno > MAX_SEQNO)
+               keyexpires = 0;
+
+       /* Decompress the packet */
+
+       length_t origlen = inpkt->len;
+
+       if(n->incompression) {
+               outpkt = pkt[nextpkt++];
+
+               if((outpkt->len = uncompress_packet(outpkt->data, inpkt->data, inpkt->len, n->incompression)) < 0) {
+                       ifdebug(TRAFFIC) logger(LOG_ERR, "Error while uncompressing packet from %s (%s)",
+                                                n->name, n->hostname);
+                       return;
+               }
+
+               inpkt = outpkt;
+
+               origlen -= MTU/64 + 20;
+       }
+
+       inpkt->priority = 0;
+
+       if(!inpkt->data[12] && !inpkt->data[13])
+               mtu_probe_h(n, inpkt, origlen);
+       else
+               receive_packet(n, inpkt);
 }
 
-void receive_packet(node_t *n, vpn_packet_t *packet)
-{
-cp
-  if(debug_lvl >= DEBUG_TRAFFIC)
-    syslog(LOG_DEBUG, _("Received packet of %d bytes from %s (%s)"), packet->len, n->name, n->hostname);
+void receive_tcppacket(connection_t *c, char *buffer, int len) {
+       vpn_packet_t outpkt;
 
-  route_incoming(n, packet);
-cp
+       outpkt.len = len;
+       if(c->options & OPTION_TCPONLY)
+               outpkt.priority = 0;
+       else
+               outpkt.priority = -1;
+       memcpy(outpkt.data, buffer, len);
+
+       receive_packet(c->node, &outpkt);
 }
 
-void send_udppacket(node_t *n, vpn_packet_t *inpkt)
-{
-  vpn_packet_t pkt1, pkt2;
-  vpn_packet_t *pkt[] = {&pkt1, &pkt2, &pkt1, &pkt2};
-  int nextpkt = 0;
-  vpn_packet_t *outpkt;
-  int origlen;
-  int outlen, outpad;
-  long int complen = MTU + 12;
-  EVP_CIPHER_CTX ctx;
-  vpn_packet_t *copy;
-  static int priority = 0;
-  int origpriority;
-  int sock;
-cp
-  /* Make sure we have a valid key */
+static void send_udppacket(node_t *n, vpn_packet_t *origpkt) {
+       vpn_packet_t pkt1, pkt2;
+       vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
+       vpn_packet_t *inpkt = origpkt;
+       int nextpkt = 0;
+       vpn_packet_t *outpkt;
+       int origlen;
+       int outlen, outpad;
+       static int priority = 0;
+       int origpriority;
+       int sock;
+
+       if(!n->status.reachable) {
+               ifdebug(TRAFFIC) logger(LOG_INFO, "Trying to send UDP packet to unreachable node %s (%s)", n->name, n->hostname);
+               return;
+       }
+
+       /* Make sure we have a valid key */
 
-  if(!n->status.validkey)
-    {
-      if(debug_lvl >= DEBUG_TRAFFIC)
-        syslog(LOG_INFO, _("No valid key known yet for %s (%s), queueing packet"),
-               n->name, n->hostname);
+       if(!n->status.validkey) {
+               ifdebug(TRAFFIC) logger(LOG_INFO,
+                                  "No valid key known yet for %s (%s), forwarding via TCP",
+                                  n->name, n->hostname);
 
-      /* Since packet is on the stack of handle_tap_input(),
-         we have to make a copy of it first. */
+               if(!n->status.waitingforkey)
+                       send_req_key(n);
 
-      copy = xmalloc(sizeof(vpn_packet_t));
-      memcpy(copy, inpkt, sizeof(vpn_packet_t));
+               n->status.waitingforkey = true;
 
-      list_insert_tail(n->queue, copy);
+               send_tcppacket(n->nexthop->connection, origpkt);
 
-      if(n->queue->count > MAXQUEUELENGTH)
-        list_delete_head(n->queue);
+               return;
+       }
 
-      if(!n->status.waitingforkey)
-        send_req_key(n->nexthop->connection, myself, n);
+       if(n->options & OPTION_PMTU_DISCOVERY && inpkt->len > n->minmtu && (inpkt->data[12] | inpkt->data[13])) {
+               ifdebug(TRAFFIC) logger(LOG_INFO,
+                               "Packet for %s (%s) larger than minimum MTU, forwarding via TCP",
+                               n->name, n->hostname);
 
-      n->status.waitingforkey = 1;
+               send_tcppacket(n->nexthop->connection, origpkt);
 
-      return;
-    }
+               return;
+       }
 
-  origlen = inpkt->len;
-  origpriority = inpkt->priority;
+       origlen = inpkt->len;
+       origpriority = inpkt->priority;
 
-  /* Compress the packet */
+       /* Compress the packet */
 
-  if(n->compression)
-  {
-    outpkt = pkt[nextpkt++];
+       if(n->outcompression) {
+               outpkt = pkt[nextpkt++];
 
-    if(compress2(outpkt->data, &complen, inpkt->data, inpkt->len, n->compression) != Z_OK)
-    {
-      syslog(LOG_ERR, _("Error while compressing packet to %s (%s)"), n->name, n->hostname);
-      return;
-    }
-    
-    outpkt->len = complen;
-    inpkt = outpkt;
-  }
+               if((outpkt->len = compress_packet(outpkt->data, inpkt->data, inpkt->len, n->outcompression)) < 0) {
+                       ifdebug(TRAFFIC) logger(LOG_ERR, "Error while compressing packet to %s (%s)",
+                                  n->name, n->hostname);
+                       return;
+               }
 
-  /* Add sequence number */
+               inpkt = outpkt;
+       }
 
-  inpkt->seqno = htonl(++(n->sent_seqno));
-  inpkt->len += sizeof(inpkt->seqno);
+       /* Add sequence number */
 
-  /* Encrypt the packet */
+       inpkt->seqno = htonl(++(n->sent_seqno));
+       inpkt->len += sizeof(inpkt->seqno);
 
-  if(n->cipher)
-  {
-    outpkt = pkt[nextpkt++];
+       /* Encrypt the packet */
 
-    EVP_EncryptInit(&ctx, n->cipher, n->key, n->key + n->cipher->key_len);
-    EVP_EncryptUpdate(&ctx, (char *)&outpkt->seqno, &outlen, (char *)&inpkt->seqno, inpkt->len);
-    EVP_EncryptFinal(&ctx, (char *)&outpkt->seqno + outlen, &outpad);
+       if(n->outcipher) {
+               outpkt = pkt[nextpkt++];
 
-    outpkt->len = outlen + outpad;
-    inpkt = outpkt;
-  }
+               if(!EVP_EncryptInit_ex(&n->outctx, NULL, NULL, NULL, NULL)
+                               || !EVP_EncryptUpdate(&n->outctx, (unsigned char *) &outpkt->seqno, &outlen,
+                                       (unsigned char *) &inpkt->seqno, inpkt->len)
+                               || !EVP_EncryptFinal_ex(&n->outctx, (unsigned char *) &outpkt->seqno + outlen, &outpad)) {
+                       ifdebug(TRAFFIC) logger(LOG_ERR, "Error while encrypting packet to %s (%s): %s",
+                                               n->name, n->hostname, ERR_error_string(ERR_get_error(), NULL));
+                       goto end;
+               }
 
-  /* Add the message authentication code */
+               outpkt->len = outlen + outpad;
+               inpkt = outpkt;
+       }
 
-  if(n->digest && n->maclength)
-    {
-      HMAC(n->digest, n->key, n->keylength, (char *)&inpkt->seqno, inpkt->len, (char *)&inpkt->seqno + inpkt->len, &outlen);
-      inpkt->len += n->maclength;
-    }
+       /* Add the message authentication code */
 
-  /* Determine which socket we have to use */
+       if(n->outdigest && n->outmaclength) {
+               HMAC(n->outdigest, n->outkey, n->outkeylength, (unsigned char *) &inpkt->seqno,
+                        inpkt->len, (unsigned char *) &inpkt->seqno + inpkt->len, NULL);
+               inpkt->len += n->outmaclength;
+       }
 
-  for(sock = 0; sock < listen_sockets; sock++)
-    if(n->address.sa.sa_family == listen_socket[sock].sa.sa.sa_family)
-      break;
+       /* Determine which socket we have to use */
 
-  if(sock >= listen_sockets)
-    sock = 0;  /* If none is available, just use the first and hope for the best. */
-  
-  /* Send the packet */
+       for(sock = 0; sock < listen_sockets; sock++)
+               if(n->address.sa.sa_family == listen_socket[sock].sa.sa.sa_family)
+                       break;
+
+       if(sock >= listen_sockets)
+               sock = 0;                               /* If none is available, just use the first and hope for the best. */
+
+       /* Send the packet */
 
 #if defined(SOL_IP) && defined(IP_TOS)
-  if(priorityinheritance && origpriority != priority && listen_socket[sock].sa.sa.sa_family == AF_INET)
-    {
-      priority = origpriority;
-      if(debug_lvl >= DEBUG_TRAFFIC)
-        syslog(LOG_DEBUG, _("Setting outgoing packet priority to %d"), priority);
-      if(setsockopt(sock, SOL_IP, IP_TOS, &priority, sizeof(priority))) /* SO_PRIORITY doesn't seem to work */
-       syslog(LOG_ERR, _("System call `%s' failed: %s"), "setsockopt", strerror(errno));
-    }
+       if(priorityinheritance && origpriority != priority
+          && listen_socket[sock].sa.sa.sa_family == AF_INET) {
+               priority = origpriority;
+               ifdebug(TRAFFIC) logger(LOG_DEBUG, "Setting outgoing packet priority to %d", priority);
+               if(setsockopt(listen_socket[sock].udp, SOL_IP, IP_TOS, &priority, sizeof(priority)))    /* SO_PRIORITY doesn't seem to work */
+                       logger(LOG_ERR, "System call `%s' failed: %s", "setsockopt", strerror(errno));
+       }
 #endif
 
-  if((sendto(listen_socket[sock].udp, (char *)&inpkt->seqno, inpkt->len, 0, &(n->address.sa), SALEN(n->address.sa))) < 0)
-    {
-      syslog(LOG_ERR, _("Error sending packet to %s (%s): %s"),
-             n->name, n->hostname, strerror(errno));
-      return;
-    }
-  
-  inpkt->len = origlen;
-cp
+       if((sendto(listen_socket[sock].udp, (char *) &inpkt->seqno, inpkt->len, 0, &(n->address.sa), SALEN(n->address.sa))) < 0) {
+               if(errno == EMSGSIZE) {
+                       if(n->maxmtu >= origlen)
+                               n->maxmtu = origlen - 1;
+                       if(n->mtu >= origlen)
+                               n->mtu = origlen - 1;
+               } else
+                       logger(LOG_ERR, "Error sending packet to %s (%s): %s", n->name, n->hostname, strerror(errno));
+       }
+
+end:
+       origpkt->len = origlen;
 }
 
 /*
   send a packet to the given vpn ip.
 */
-void send_packet(node_t *n, vpn_packet_t *packet)
-{
-  node_t *via;
-cp
-  if(debug_lvl >= DEBUG_TRAFFIC)
-    syslog(LOG_ERR, _("Sending packet of %d bytes to %s (%s)"),
-           packet->len, n->name, n->hostname);
-
-  if(n == myself)
-    {
-      if(debug_lvl >= DEBUG_TRAFFIC)
-        {
-          syslog(LOG_NOTICE, _("Packet is looping back to us!"));
-        }
-
-      return;
-    }
-  if(!n->status.reachable)
-    {
-      if(debug_lvl >= DEBUG_TRAFFIC)
-        syslog(LOG_INFO, _("Node %s (%s) is not reachable"),
-               n->name, n->hostname);
-      return;
-    }
-
-  via = (n->via == myself)?n->nexthop:n->via;
-
-  if(via != n && debug_lvl >= DEBUG_TRAFFIC)
-    syslog(LOG_ERR, _("Sending packet to %s via %s (%s)"),
-           n->name, via->name, n->via->hostname);
-
-  if((myself->options | via->options) & OPTION_TCPONLY)
-    {
-      if(send_tcppacket(via->connection, packet))
-        terminate_connection(via->connection, 1);
-    }
-  else
-    send_udppacket(via, packet);
+void send_packet(const node_t *n, vpn_packet_t *packet) {
+       node_t *via;
+
+       if(n == myself) {
+               if(overwrite_mac)
+                        memcpy(packet->data, mymac.x, ETH_ALEN);
+               write_packet(packet);
+               return;
+       }
+
+       ifdebug(TRAFFIC) logger(LOG_ERR, "Sending packet of %d bytes to %s (%s)",
+                          packet->len, n->name, n->hostname);
+
+       if(!n->status.reachable) {
+               ifdebug(TRAFFIC) logger(LOG_INFO, "Node %s (%s) is not reachable",
+                                  n->name, n->hostname);
+               return;
+       }
+
+       via = (packet->priority == -1 || n->via == myself) ? n->nexthop : n->via;
+
+       if(via != n)
+               ifdebug(TRAFFIC) logger(LOG_INFO, "Sending packet to %s via %s (%s)",
+                          n->name, via->name, n->via->hostname);
+
+       if(packet->priority == -1 || ((myself->options | via->options) & OPTION_TCPONLY)) {
+               if(!send_tcppacket(via->connection, packet))
+                       terminate_connection(via->connection, true);
+       } else
+               send_udppacket(via, packet);
 }
 
 /* Broadcast a packet using the minimum spanning tree */
 
-void broadcast_packet(node_t *from, vpn_packet_t *packet)
-{
-  avl_node_t *node;
-  connection_t *c;
-cp
-  if(debug_lvl >= DEBUG_TRAFFIC)
-    syslog(LOG_INFO, _("Broadcasting packet of %d bytes from %s (%s)"),
-           packet->len, from->name, from->hostname);
-
-  for(node = connection_tree->head; node; node = node->next)
-    {
-      c = (connection_t *)node->data;
-      if(c->status.active && c->status.mst && c != from->nexthop->connection)
-        send_packet(c->node, packet);
-    }
-cp
-}
+void broadcast_packet(const node_t *from, vpn_packet_t *packet) {
+       avl_node_t *node;
+       connection_t *c;
 
-void flush_queue(node_t *n)
-{
-  list_node_t *node, *next;
-cp
-  if(debug_lvl >= DEBUG_TRAFFIC)
-    syslog(LOG_INFO, _("Flushing queue for %s (%s)"), n->name, n->hostname);
-
-  for(node = n->queue->head; node; node = next)
-    {
-      next = node->next;
-      send_udppacket(n, (vpn_packet_t *)node->data);
-      list_delete_node(n->queue, node);
-    }
-cp
+       ifdebug(TRAFFIC) logger(LOG_INFO, "Broadcasting packet of %d bytes from %s (%s)",
+                          packet->len, from->name, from->hostname);
+
+       if(from != myself) {
+               send_packet(myself, packet);
+
+               // In TunnelServer mode, do not forward broadcast packets.
+                // The MST might not be valid and create loops.
+               if(tunnelserver)
+                       return;
+       }
+
+       for(node = connection_tree->head; node; node = node->next) {
+               c = node->data;
+
+               if(c->status.active && c->status.mst && c != from->nexthop->connection)
+                       send_packet(c->node, packet);
+       }
 }
 
-void handle_incoming_vpn_data(int sock)
-{
-  vpn_packet_t pkt;
-  int x, l = sizeof(x);
-  char *hostname;
-  sockaddr_t from;
-  socklen_t fromlen = sizeof(from);
-  node_t *n;
-cp
-  if(getsockopt(sock, SOL_SOCKET, SO_ERROR, &x, &l) < 0)
-    {
-      syslog(LOG_ERR, _("This is a bug: %s:%d: %d:%s"),
-             __FILE__, __LINE__, sock, strerror(errno));
-      cp_trace();
-      exit(1);
-    }
-  if(x)
-    {
-      syslog(LOG_ERR, _("Incoming data socket error: %s"), strerror(x));
-      return;
-    }
-
-  if((pkt.len = recvfrom(sock, (char *)&pkt.seqno, MAXSIZE, 0, &from.sa, &fromlen)) <= 0)
-    {
-      syslog(LOG_ERR, _("Receiving packet failed: %s"), strerror(errno));
-      return;
-    }
-
-  sockaddrunmap(&from);  /* Some braindead IPv6 implementations do stupid things. */
-
-  n = lookup_node_udp(&from);
-
-  if(!n)
-    {
-      hostname = sockaddr2hostname(&from);
-      syslog(LOG_WARNING, _("Received UDP packet from unknown source %s"), hostname);
-      free(hostname);
-      return;
-    }
-
-  if(n->connection)
-    n->connection->last_ping_time = now;
-
-  receive_udppacket(n, &pkt);
-cp
+static node_t *try_harder(const sockaddr_t *from, const vpn_packet_t *pkt) {
+       avl_node_t *node;
+       edge_t *e;
+       node_t *n = NULL;
+       static time_t last_hard_try = 0;
+
+       for(node = edge_weight_tree->head; node; node = node->next) {
+               e = node->data;
+
+               if(sockaddrcmp_noport(from, &e->address)) {
+                       if(last_hard_try == now)
+                               continue;
+                       last_hard_try = now;
+               }
+
+               if(!n)
+                       n = e->to;
+
+               if(!try_mac(e->to, pkt))
+                       continue;
+
+               n = e->to;
+               break;
+       }
+
+       return n;
 }
 
+void handle_incoming_vpn_data(int sock) {
+       vpn_packet_t pkt;
+       char *hostname;
+       sockaddr_t from;
+       socklen_t fromlen = sizeof(from);
+       node_t *n;
+
+       pkt.len = recvfrom(sock, (char *) &pkt.seqno, MAXSIZE, 0, &from.sa, &fromlen);
+
+       if(pkt.len < 0) {
+               if(errno != EAGAIN && errno != EINTR)
+                       logger(LOG_ERR, "Receiving packet failed: %s", strerror(errno));
+               return;
+       }
+
+       sockaddrunmap(&from);           /* Some braindead IPv6 implementations do stupid things. */
+
+       n = lookup_node_udp(&from);
+
+       if(!n) {
+               n = try_harder(&from, &pkt);
+               if(n)
+                       update_node_udp(n, &from);
+               else ifdebug(PROTOCOL) {
+                       hostname = sockaddr2hostname(&from);
+                       logger(LOG_WARNING, "Received UDP packet from unknown source %s", hostname);
+                       free(hostname);
+                       return;
+               }
+               else
+                       return;
+       }
+
+       receive_udppacket(n, &pkt);
+}