Use MTU probes to regularly ping other nodes over UDP.
[tinc] / src / net_packet.c
index 544bbde..7a73ef5 100644 (file)
     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.
-
-    $Id$
+    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 "system.h"
 
 int keylifetime = 0;
 int keyexpires = 0;
-EVP_CIPHER_CTX packet_ctx;
 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
 
-void send_mtu_probe(node_t *n)
-{
+// 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;
        
-       cp();
-
        n->mtuprobes++;
        n->mtuevent = NULL;
 
+       if(!n->status.reachable || !n->status.validkey) {
+               logger(LOG_DEBUG, "Trying to send MTU probe to unreachable 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);
+               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)) {
+               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->mtuprobes >= 30 || n->minmtu >= n->maxmtu) {
-                       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);
-                       return;
-               }
+               if(n->maxmtu <= n->minmtu)
+                       len = n->maxmtu;
+               else
+                       len = n->minmtu + 1 + rand() % (n->maxmtu - n->minmtu);
 
-               len = n->minmtu + 1 + random() % (n->maxmtu - n->minmtu);
                if(len < 64)
                        len = 64;
                
@@ -92,32 +117,36 @@ void send_mtu_probe(node_t *n)
                packet.len = len;
                packet.priority = 0;
 
-               ifdebug(TRAFFIC) logger(LOG_INFO, _("Sending MTU probe length %d to %s (%s)"), len, n->name, n->hostname);
+               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 + 1;
+       n->mtuevent->time = now + timeout;
        event_add(n->mtuevent);
 }
 
-void mtu_probe_h(node_t *n, vpn_packet_t *packet) {
-       ifdebug(TRAFFIC) logger(LOG_INFO, _("Got MTU probe length %d from %s (%s)"), packet->len, n->name, n->hostname);
+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_packet(n, packet);
        } else {
-               if(n->minmtu < packet->len)
-                       n->minmtu = packet->len;
+               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)
-{
+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);
@@ -137,8 +166,7 @@ static length_t compress_packet(uint8_t *dest, const uint8_t *source, length_t l
        return -1;
 }
 
-static length_t uncompress_packet(uint8_t *dest, const uint8_t *source, length_t len, int level)
-{
+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)
@@ -158,18 +186,25 @@ static length_t uncompress_packet(uint8_t *dest, const uint8_t *source, length_t
 
 /* VPN packet I/O */
 
-static void receive_packet(node_t *n, vpn_packet_t *packet)
-{
-       cp();
-
-       ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Received packet of %d bytes from %s (%s)"),
+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);
 }
 
-static void receive_udppacket(node_t *n, vpn_packet_t *inpkt)
-{
+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);
+}
+
+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;
@@ -178,25 +213,29 @@ static void receive_udppacket(node_t *n, vpn_packet_t *inpkt)
        unsigned char hmac[EVP_MAX_MD_SIZE];
        int i;
 
-       cp();
+       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) + myself->maclength) {
-               ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Got too short packet from %s (%s)"),
+       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(myself->digest && myself->maclength) {
-               inpkt->len -= myself->maclength;
-               HMAC(myself->digest, myself->key, myself->keylength,
+       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, myself->maclength)) {
-                       ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Got unauthenticated packet from %s (%s)"),
+               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;
                }
@@ -204,14 +243,14 @@ static void receive_udppacket(node_t *n, vpn_packet_t *inpkt)
 
        /* Decrypt the packet */
 
-       if(myself->cipher) {
+       if(n->incipher) {
                outpkt = pkt[nextpkt++];
 
-               if(!EVP_DecryptInit_ex(&packet_ctx, NULL, NULL, NULL, NULL)
-                               || !EVP_DecryptUpdate(&packet_ctx, (unsigned char *) &outpkt->seqno, &outlen,
+               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(&packet_ctx, (unsigned char *) &outpkt->seqno + outlen, &outpad)) {
-                       ifdebug(TRAFFIC) logger(LOG_DEBUG, _("Error decrypting packet from %s (%s): %s"),
+                               || !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;
                }
@@ -227,13 +266,13 @@ static void receive_udppacket(node_t *n, vpn_packet_t *inpkt)
 
        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)"),
+                       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"),
+                               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;
                        }
@@ -253,35 +292,33 @@ static void receive_udppacket(node_t *n, vpn_packet_t *inpkt)
 
        /* Decompress the packet */
 
-       if(myself->compression) {
+       length_t origlen = inpkt->len;
+
+       if(n->incompression) {
                outpkt = pkt[nextpkt++];
 
-               if((outpkt->len = uncompress_packet(outpkt->data, inpkt->data, inpkt->len, myself->compression)) < 0) {
-                       ifdebug(TRAFFIC) logger(LOG_ERR, _("Error while uncompressing packet from %s (%s)"),
+               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(n->connection)
-               n->connection->last_ping_time = now;
-
        if(!inpkt->data[12] && !inpkt->data[13])
-               mtu_probe_h(n, inpkt);
+               mtu_probe_h(n, inpkt, origlen);
        else
                receive_packet(n, inpkt);
 }
 
-void receive_tcppacket(connection_t *c, char *buffer, int len)
-{
+void receive_tcppacket(connection_t *c, char *buffer, int len) {
        vpn_packet_t outpkt;
 
-       cp();
-
        outpkt.len = len;
        if(c->options & OPTION_TCPONLY)
                outpkt.priority = 0;
@@ -292,8 +329,7 @@ void receive_tcppacket(connection_t *c, char *buffer, int len)
        receive_packet(c->node, &outpkt);
 }
 
-static void send_udppacket(node_t *n, vpn_packet_t *origpkt)
-{
+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;
@@ -305,17 +341,20 @@ static void send_udppacket(node_t *n, vpn_packet_t *origpkt)
        int origpriority;
        int sock;
 
-       cp();
+       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) {
                ifdebug(TRAFFIC) logger(LOG_INFO,
-                                  _("No valid key known yet for %s (%s), forwarding via TCP"),
+                                  "No valid key known yet for %s (%s), forwarding via TCP",
                                   n->name, n->hostname);
 
                if(!n->status.waitingforkey)
-                       send_req_key(n->nexthop->connection, myself, n);
+                       send_req_key(n);
 
                n->status.waitingforkey = true;
 
@@ -324,12 +363,14 @@ static void send_udppacket(node_t *n, vpn_packet_t *origpkt)
                return;
        }
 
-       if(!n->minmtu && (inpkt->data[12] | inpkt->data[13])) {
+       if(n->options & OPTION_PMTU_DISCOVERY && inpkt->len > n->minmtu && (inpkt->data[12] | inpkt->data[13])) {
                ifdebug(TRAFFIC) logger(LOG_INFO,
-                               _("No minimum MTU established yet for %s (%s), forwarding via TCP"),
+                               "Packet for %s (%s) larger than minimum MTU, forwarding via TCP",
                                n->name, n->hostname);
 
                send_tcppacket(n->nexthop->connection, origpkt);
+
+               return;
        }
 
        origlen = inpkt->len;
@@ -337,11 +378,11 @@ static void send_udppacket(node_t *n, vpn_packet_t *origpkt)
 
        /* Compress the packet */
 
-       if(n->compression) {
+       if(n->outcompression) {
                outpkt = pkt[nextpkt++];
 
-               if((outpkt->len = compress_packet(outpkt->data, inpkt->data, inpkt->len, n->compression)) < 0) {
-                       ifdebug(TRAFFIC) logger(LOG_ERR, _("Error while compressing packet to %s (%s)"),
+               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;
                }
@@ -356,14 +397,14 @@ static void send_udppacket(node_t *n, vpn_packet_t *origpkt)
 
        /* Encrypt the packet */
 
-       if(n->cipher) {
+       if(n->outcipher) {
                outpkt = pkt[nextpkt++];
 
-               if(!EVP_EncryptInit_ex(&n->packet_ctx, NULL, NULL, NULL, NULL)
-                               || !EVP_EncryptUpdate(&n->packet_ctx, (unsigned char *) &outpkt->seqno, &outlen,
+               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->packet_ctx, (unsigned char *) &outpkt->seqno + outlen, &outpad)) {
-                       ifdebug(TRAFFIC) logger(LOG_ERR, _("Error while encrypting packet to %s (%s): %s"),
+                               || !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;
                }
@@ -374,10 +415,10 @@ static void send_udppacket(node_t *n, vpn_packet_t *origpkt)
 
        /* Add the message authentication code */
 
-       if(n->digest && n->maclength) {
-               HMAC(n->digest, n->key, n->keylength, (unsigned char *) &inpkt->seqno,
+       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->maclength;
+               inpkt->len += n->outmaclength;
        }
 
        /* Determine which socket we have to use */
@@ -395,9 +436,9 @@ static void send_udppacket(node_t *n, vpn_packet_t *origpkt)
        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);
+               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));
+                       logger(LOG_ERR, "System call `%s' failed: %s", "setsockopt", strerror(errno));
        }
 #endif
 
@@ -408,7 +449,7 @@ static void send_udppacket(node_t *n, vpn_packet_t *origpkt)
                        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));
+                       logger(LOG_ERR, "Error sending packet to %s (%s): %s", n->name, n->hostname, strerror(errno));
        }
 
 end:
@@ -418,12 +459,9 @@ end:
 /*
   send a packet to the given vpn ip.
 */
-void send_packet(const node_t *n, vpn_packet_t *packet)
-{
+void send_packet(const node_t *n, vpn_packet_t *packet) {
        node_t *via;
 
-       cp();
-
        if(n == myself) {
                if(overwrite_mac)
                         memcpy(packet->data, mymac.x, ETH_ALEN);
@@ -431,11 +469,11 @@ void send_packet(const node_t *n, vpn_packet_t *packet)
                return;
        }
 
-       ifdebug(TRAFFIC) logger(LOG_ERR, _("Sending packet of %d bytes to %s (%s)"),
+       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"),
+               ifdebug(TRAFFIC) logger(LOG_INFO, "Node %s (%s) is not reachable",
                                   n->name, n->hostname);
                return;
        }
@@ -443,7 +481,7 @@ void send_packet(const node_t *n, vpn_packet_t *packet)
        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)"),
+               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)) {
@@ -455,19 +493,22 @@ void send_packet(const node_t *n, vpn_packet_t *packet)
 
 /* Broadcast a packet using the minimum spanning tree */
 
-void broadcast_packet(const node_t *from, vpn_packet_t *packet)
-{
+void broadcast_packet(const node_t *from, vpn_packet_t *packet) {
        avl_node_t *node;
        connection_t *c;
 
-       cp();
-
-       ifdebug(TRAFFIC) logger(LOG_INFO, _("Broadcasting packet of %d bytes from %s (%s)"),
+       ifdebug(TRAFFIC) logger(LOG_INFO, "Broadcasting packet of %d bytes from %s (%s)",
                           packet->len, from->name, from->hostname);
 
-       if(from != myself)
+       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;
 
@@ -476,20 +517,42 @@ void broadcast_packet(const node_t *from, vpn_packet_t *packet)
        }
 }
 
-void handle_incoming_vpn_data(int sock)
-{
+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;
+
+       for(node = edge_weight_tree->head; node; node = node->next) {
+               e = node->data;
+
+               if(sockaddrcmp_noport(from, &e->address))
+                       continue;
+
+               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;
 
-       cp();
-
        pkt.len = recvfrom(sock, (char *) &pkt.seqno, MAXSIZE, 0, &from.sa, &fromlen);
 
        if(pkt.len < 0) {
-               logger(LOG_ERR, _("Receiving packet failed: %s"), strerror(errno));
+               if(errno != EAGAIN && errno != EINTR)
+                       logger(LOG_ERR, "Receiving packet failed: %s", strerror(errno));
                return;
        }
 
@@ -498,11 +561,17 @@ void handle_incoming_vpn_data(int sock)
        n = lookup_node_udp(&from);
 
        if(!n) {
-               hostname = sockaddr2hostname(&from);
-               logger(LOG_WARNING, _("Received UDP packet from unknown source %s"),
-                          hostname);
-               free(hostname);
-               return;
+               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);