X-Git-Url: http://git.meshlink.io/?a=blobdiff_plain;f=src%2Fmeshlink.c;h=1d682c40b53b2d8bb9911450f9ab61d41c18572e;hb=e80127addf7a0a0a67e54bac9b19d0922b50e67e;hp=b8fb5055a41ed82a9ae740492f72cf0ab7e2b6b1;hpb=1da7f28315be17a4ed854cdceb97a870f16a511e;p=meshlink

diff --git a/src/meshlink.c b/src/meshlink.c
index b8fb5055..1d682c40 100644
--- a/src/meshlink.c
+++ b/src/meshlink.c
@@ -1,6 +1,6 @@
 /*
     meshlink.c -- Implementation of the MeshLink API.
-    Copyright (C) 2014 Guus Sliepen <guus@meshlink.io>
+    Copyright (C) 2014, 2017 Guus Sliepen <guus@meshlink.io>
 
     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
@@ -48,8 +48,6 @@ typedef struct {
 #define MSG_NOSIGNAL 0
 #endif
 
-static pthread_mutex_t global_mutex;
-
 __thread meshlink_errno_t meshlink_errno;
 meshlink_log_cb_t global_log_cb;
 meshlink_log_level_t global_log_level;
@@ -503,8 +501,10 @@ static bool finalize_join(meshlink_handle_t *mesh) {
 	}
 
 	char *b64key = ecdsa_get_base64_public_key(mesh->self->connection->ecdsa);
-	if(!b64key)
+	if(!b64key) {
+		fclose(fh);
 		return false;
+		}
 
 	fprintf(fh, "ECDSAPublicKey = %s\n", b64key);
 	fprintf(fh, "Port = %s\n", mesh->myport);
@@ -554,6 +554,7 @@ static bool invitation_receive(void *handle, uint8_t type, const void *msg, uint
 			break;
 
 		case 1:
+			mesh->thedatalen = 0;
 			return finalize_join(mesh);
 
 		case 2:
@@ -659,7 +660,7 @@ static bool ecdsa_keygen(meshlink_handle_t *mesh) {
 		logger(mesh, MESHLINK_DEBUG, "Done.\n");
 
 	snprintf(privname, sizeof privname, "%s" SLASH "ecdsa_key.priv", mesh->confbase);
-	f = fopen(privname, "w");
+	f = fopen(privname, "wb");
 
 	if(!f) {
 		meshlink_errno = MESHLINK_ESTORAGE;
@@ -698,6 +699,78 @@ static bool ecdsa_keygen(meshlink_handle_t *mesh) {
 	return true;
 }
 
+static struct timeval idle(event_loop_t *loop, void *data) {
+	meshlink_handle_t *mesh = data;
+	struct timeval t, tmin = {3600, 0};
+	for splay_each(node_t, n, mesh->nodes) {
+		if(!n->utcp)
+			continue;
+		t = utcp_timeout(n->utcp);
+		if(timercmp(&t, &tmin, <))
+			tmin = t;
+	}
+	return tmin;
+}
+
+// Find out what local address a socket would use if we connect to the given address.
+// We do this using connect() on a UDP socket, so the kernel has to resolve the address
+// of both endpoints, but this will actually not send any UDP packet.
+static bool getlocaladdrname(char *destaddr, char *host, socklen_t hostlen) {
+	struct addrinfo *rai = NULL;
+	const struct addrinfo hint = {
+		.ai_family = AF_UNSPEC,
+		.ai_socktype = SOCK_DGRAM,
+		.ai_protocol = IPPROTO_UDP,
+	};
+
+	if(getaddrinfo(destaddr, "80", &hint, &rai) || !rai)
+		return false;
+
+	int sock = socket(rai->ai_family, rai->ai_socktype, rai->ai_protocol);
+	if(sock == -1) {
+		freeaddrinfo(rai);
+		return false;
+	}
+
+	if(connect(sock, rai->ai_addr, rai->ai_addrlen) && !sockwouldblock(errno)) {
+		freeaddrinfo(rai);
+		return false;
+	}
+
+	freeaddrinfo(rai);
+
+	struct sockaddr_storage sn;
+	socklen_t sl = sizeof sn;
+
+	if(getsockname(sock, (struct sockaddr *)&sn, &sl))
+		return false;
+
+	if(getnameinfo((struct sockaddr *)&sn, sl, host, hostlen, NULL, 0, NI_NUMERICHOST | NI_NUMERICSERV))
+		return false;
+
+	return true;
+}
+
+// Get our local address(es) by simulating connecting to an Internet host.
+static void add_local_addresses(meshlink_handle_t *mesh) {
+	char host[NI_MAXHOST];
+	char entry[MAX_STRING_SIZE];
+
+	// IPv4 example.org
+
+	if(getlocaladdrname("93.184.216.34", host, sizeof host)) {
+		snprintf(entry, sizeof entry, "%s %s", host, mesh->myport);
+		append_config_file(mesh, mesh->name, "Address", entry);
+	}
+
+	// IPv6 example.org
+
+	if(getlocaladdrname("2606:2800:220:1:248:1893:25c8:1946", host, sizeof host)) {
+		snprintf(entry, sizeof entry, "%s %s", host, mesh->myport);
+		append_config_file(mesh, mesh->name, "Address", entry);
+	}
+}
+
 static bool meshlink_setup(meshlink_handle_t *mesh) {
 	if(mkdir(mesh->confbase, 0777) && errno != EEXIST) {
 		logger(mesh, MESHLINK_DEBUG, "Could not create directory %s: %s\n", mesh->confbase, strerror(errno));
@@ -742,14 +815,11 @@ static bool meshlink_setup(meshlink_handle_t *mesh) {
 	return true;
 }
 
-meshlink_handle_t *meshlink_open(const char *confbase, const char *name, const char* appname) {
-	return meshlink_open_with_size(confbase, name, appname, sizeof(meshlink_handle_t));
-}
-
-meshlink_handle_t *meshlink_open_with_size(const char *confbase, const char *name, const char* appname, size_t size) {
-
+meshlink_handle_t *meshlink_open(const char *confbase, const char *name, const char* appname, dev_class_t devclass) {
 	// Validate arguments provided by the application
 	bool usingname = false;
+	
+	logger(NULL, MESHLINK_DEBUG, "meshlink_open called\n");
 
 	if(!confbase || !*confbase) {
 		logger(NULL, MESHLINK_ERROR, "No confbase given!\n");
@@ -776,11 +846,24 @@ meshlink_handle_t *meshlink_open_with_size(const char *confbase, const char *nam
 		} else { usingname = true;}
 	}
 
-	meshlink_handle_t *mesh = xzalloc(size);
+	if(devclass < 0 || devclass > _DEV_CLASS_MAX) {
+		logger(NULL, MESHLINK_ERROR, "Invalid devclass given!\n");
+		meshlink_errno = MESHLINK_EINVAL;
+		return NULL;
+	}
+
+	meshlink_handle_t *mesh = xzalloc(sizeof(meshlink_handle_t));
 	mesh->confbase = xstrdup(confbase);
 	mesh->appname = xstrdup(appname);
+	mesh->devclass = devclass;
 	if (usingname) mesh->name = xstrdup(name);
-	pthread_mutex_init ( &(mesh->nodes_mutex), NULL);
+
+	// initialize mutex
+	pthread_mutexattr_t attr;
+	pthread_mutexattr_init(&attr);
+	pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
+	pthread_mutex_init(&(mesh->mesh_mutex), &attr);
+	
 	mesh->threadstarted = false;
 	event_loop_init(&mesh->loop);
 	mesh->loop.data = mesh;
@@ -829,29 +912,39 @@ meshlink_handle_t *meshlink_open_with_size(const char *confbase, const char *nam
 		return NULL;
 	}
 
+	add_local_addresses(mesh);
+
+	idle_set(&mesh->loop, idle, mesh);
+
+	logger(NULL, MESHLINK_DEBUG, "meshlink_open returning\n");
 	return mesh;
 }
 
 static void *meshlink_main_loop(void *arg) {
 	meshlink_handle_t *mesh = arg;
 
+	pthread_mutex_lock(&(mesh->mesh_mutex));
+
 	try_outgoing_connections(mesh);
 
 	logger(mesh, MESHLINK_DEBUG, "Starting main_loop...\n");
 	main_loop(mesh);
 	logger(mesh, MESHLINK_DEBUG, "main_loop returned.\n");
 
+	pthread_mutex_unlock(&(mesh->mesh_mutex));
 	return NULL;
 }
 
 bool meshlink_start(meshlink_handle_t *mesh) {
-
-	logger(mesh, MESHLINK_DEBUG, "meshlink_start called\n");
-
 	if(!mesh) {
 		meshlink_errno = MESHLINK_EINVAL;
 		return false;
 	}
+	pthread_mutex_lock(&(mesh->mesh_mutex));
+	
+	logger(mesh, MESHLINK_DEBUG, "meshlink_start called\n");
+
+	mesh->thedatalen = 0;
 
 	// TODO: open listening sockets first
 
@@ -859,6 +952,7 @@ bool meshlink_start(meshlink_handle_t *mesh) {
 	if(!mesh->name ) {
 		logger(mesh, MESHLINK_DEBUG, "No name given!\n");
 		meshlink_errno = MESHLINK_EINVAL;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return false;
 	}
 
@@ -868,6 +962,7 @@ bool meshlink_start(meshlink_handle_t *mesh) {
 		logger(mesh, MESHLINK_DEBUG, "Could not start thread: %s\n", strerror(errno));
 		memset(&mesh->thread, 0, sizeof mesh->thread);
 		meshlink_errno = MESHLINK_EINTERNAL;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return false;
 	}
 
@@ -875,18 +970,19 @@ bool meshlink_start(meshlink_handle_t *mesh) {
 
 	discovery_start(mesh);
 
+	pthread_mutex_unlock(&(mesh->mesh_mutex));
 	return true;
 }
 
 void meshlink_stop(meshlink_handle_t *mesh) {
-
-	logger(mesh, MESHLINK_DEBUG, "meshlink_stop called\n");
-	
 	if(!mesh) {
 		meshlink_errno = MESHLINK_EINVAL;
 		return;
 	}
 
+	pthread_mutex_lock(&(mesh->mesh_mutex));
+	logger(mesh, MESHLINK_DEBUG, "meshlink_stop called\n");
+
 	// Stop discovery
 	discovery_stop(mesh);
 
@@ -896,8 +992,10 @@ void meshlink_stop(meshlink_handle_t *mesh) {
 	shutdown(s->tcp.fd, SHUT_RDWR);
 
 	// Wait for the main thread to finish
-
+	pthread_mutex_unlock(&(mesh->mesh_mutex));
 	pthread_join(mesh->thread, NULL);
+	pthread_mutex_lock(&(mesh->mesh_mutex));
+
 	mesh->threadstarted = false;
 
 	// Fix the socket
@@ -909,6 +1007,8 @@ void meshlink_stop(meshlink_handle_t *mesh) {
 		logger(mesh, MESHLINK_ERROR, "Could not repair listenen socket!");
 	else
 		io_add(&mesh->loop, &s->tcp, handle_new_meta_connection, s, s->tcp.fd, IO_READ);
+	
+	pthread_mutex_unlock(&(mesh->mesh_mutex));
 }
 
 void meshlink_close(meshlink_handle_t *mesh) {
@@ -917,6 +1017,12 @@ void meshlink_close(meshlink_handle_t *mesh) {
 		return;
 	}
 
+	// stop can be called even if mesh has not been started
+	meshlink_stop(mesh);
+
+	// lock is not released after this
+	pthread_mutex_lock(&(mesh->mesh_mutex));
+
 	// Close and free all resources used.
 
 	close_network_connections(mesh);
@@ -934,20 +1040,67 @@ void meshlink_close(meshlink_handle_t *mesh) {
 	ecdsa_free(mesh->invitation_key);
 
 	free(mesh->name);
+	free(mesh->appname);
 	free(mesh->confbase);
+	pthread_mutex_destroy(&(mesh->mesh_mutex));
 
 	memset(mesh, 0, sizeof *mesh);
 
 	free(mesh);
 }
 
+static void deltree(const char *dirname) {
+	DIR *d = opendir(dirname);
+	if(d) {
+		struct dirent *ent;
+		while((ent = readdir(d))) {
+			if(ent->d_name[0] == '.')
+				continue;
+			char filename[PATH_MAX];
+			snprintf(filename, sizeof filename, "%s" SLASH "%s", dirname, ent->d_name);
+			if(unlink(filename))
+				deltree(filename);
+		}
+		closedir(d);
+	}
+	rmdir(dirname);
+	return;
+}
+
+bool meshlink_destroy(const char *confbase) {
+	if(!confbase) {
+		meshlink_errno = MESHLINK_EINVAL;
+		return false;
+	}
+
+	char filename[PATH_MAX];
+	snprintf(filename, sizeof filename, "%s" SLASH "meshlink.conf", confbase);
+
+	if(unlink(filename)) {
+		if(errno == ENOENT) {
+			meshlink_errno = MESHLINK_ENOENT;
+			return false;
+		} else {
+			logger(NULL, MESHLINK_ERROR, "Cannot delete %s: %s\n", filename, strerror(errno));
+			meshlink_errno = MESHLINK_ESTORAGE;
+			return false;
+		}
+	}
+
+	deltree(confbase);
+
+	return true;
+}
+
 void meshlink_set_receive_cb(meshlink_handle_t *mesh, meshlink_receive_cb_t cb) {
 	if(!mesh) {
 		meshlink_errno = MESHLINK_EINVAL;
 		return;
 	}
 
+	pthread_mutex_lock(&(mesh->mesh_mutex));
 	mesh->receive_cb = cb;
+	pthread_mutex_unlock(&(mesh->mesh_mutex));
 }
 
 void meshlink_set_node_status_cb(meshlink_handle_t *mesh, meshlink_node_status_cb_t cb) {
@@ -956,13 +1109,17 @@ void meshlink_set_node_status_cb(meshlink_handle_t *mesh, meshlink_node_status_c
 		return;
 	}
 
+	pthread_mutex_lock(&(mesh->mesh_mutex));
 	mesh->node_status_cb = cb;
+	pthread_mutex_unlock(&(mesh->mesh_mutex));
 }
 
 void meshlink_set_log_cb(meshlink_handle_t *mesh, meshlink_log_level_t level, meshlink_log_cb_t cb) {
 	if(mesh) {
+		pthread_mutex_lock(&(mesh->mesh_mutex));
 		mesh->log_cb = cb;
 		mesh->log_level = cb ? level : 0;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 	} else {
 		global_log_cb = cb;
 		global_log_level = cb ? level : 0;
@@ -970,7 +1127,10 @@ void meshlink_set_log_cb(meshlink_handle_t *mesh, meshlink_log_level_t level, me
 }
 
 bool meshlink_send(meshlink_handle_t *mesh, meshlink_node_t *destination, const void *data, size_t len) {
-	if(!mesh || !destination) {
+	meshlink_packethdr_t *hdr;
+
+	// Validate arguments
+	if(!mesh || !destination || len >= MAXSIZE - sizeof *hdr) {
 		meshlink_errno = MESHLINK_EINVAL;
 		return false;
 	}
@@ -983,46 +1143,47 @@ bool meshlink_send(meshlink_handle_t *mesh, meshlink_node_t *destination, const
 		return false;
 	}
 
-	//add packet to the queue
-	outpacketqueue_t *packet_in_queue = xzalloc(sizeof *packet_in_queue);
-	packet_in_queue->destination=destination;
-	packet_in_queue->data=data;
-	packet_in_queue->len=len;
-	if(!meshlink_queue_push(&mesh->outpacketqueue, packet_in_queue)) {
-		free(packet_in_queue);
+	// Prepare the packet
+	vpn_packet_t *packet = malloc(sizeof *packet);
+	if(!packet) {
+		meshlink_errno = MESHLINK_ENOMEM;
 		return false;
 	}
 
-	//notify event loop
-	signal_trigger(&(mesh->loop),&(mesh->datafromapp));
-	return true;
-}
+	packet->probe = false;
+	packet->tcp = false;
+	packet->len = len + sizeof *hdr;
 
-void meshlink_send_from_queue(event_loop_t* el,meshlink_handle_t *mesh) {
-	vpn_packet_t packet;
-	meshlink_packethdr_t *hdr = (meshlink_packethdr_t *)packet.data;
+	hdr = (meshlink_packethdr_t *)packet->data;
+	memset(hdr, 0, sizeof *hdr);
+	// leave the last byte as 0 to make sure strings are always
+	// null-terminated if they are longer than the buffer
+	strncpy(hdr->destination, destination->name, (sizeof hdr->destination) - 1);
+	strncpy(hdr->source, mesh->self->name, (sizeof hdr->source) -1 );
 
-	outpacketqueue_t* p = meshlink_queue_pop(&mesh->outpacketqueue);
-	if(!p)
-		return;
+	memcpy(packet->data + sizeof *hdr, data, len);
 
-	if (sizeof(meshlink_packethdr_t) + p->len > MAXSIZE) {
-		//log something
-		return ;
+	// Queue it
+	if(!meshlink_queue_push(&mesh->outpacketqueue, packet)) {
+		free(packet);
+		meshlink_errno = MESHLINK_ENOMEM;
+		return false;
 	}
 
-	packet.probe = false;
-	memset(hdr, 0, sizeof *hdr);
-	memcpy(hdr->destination, p->destination->name, sizeof hdr->destination);
-	memcpy(hdr->source, mesh->self->name, sizeof hdr->source);
+	// Notify event loop
+	signal_trigger(&(mesh->loop),&(mesh->datafromapp));
+	
+	return true;
+}
 
-	packet.len = sizeof *hdr + p->len;
-	memcpy(packet.data + sizeof *hdr, p->data, p->len);
+void meshlink_send_from_queue(event_loop_t *loop, meshlink_handle_t *mesh) {
+	vpn_packet_t *packet = meshlink_queue_pop(&mesh->outpacketqueue);
+	if(!packet)
+		return;
 
-        mesh->self->in_packets++;
-        mesh->self->in_bytes += packet.len;
-        route(mesh, mesh->self, &packet);
-	return ;
+	mesh->self->in_packets++;
+	mesh->self->in_bytes += packet->len;
+	route(mesh, mesh->self, packet);
 }
 
 ssize_t meshlink_get_pmtu(meshlink_handle_t *mesh, meshlink_node_t *destination) {
@@ -1030,14 +1191,22 @@ ssize_t meshlink_get_pmtu(meshlink_handle_t *mesh, meshlink_node_t *destination)
 		meshlink_errno = MESHLINK_EINVAL;
 		return -1;
 	}
+	pthread_mutex_lock(&(mesh->mesh_mutex));
 
 	node_t *n = (node_t *)destination;
-	if(!n->status.reachable)
+	if(!n->status.reachable) {
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return 0;
-	else if(n->mtuprobes > 30 && n->minmtu)
+	
+	}
+	else if(n->mtuprobes > 30 && n->minmtu) {
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return n->minmtu;
-	else
+	}
+	else {
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return MTU;
+	}
 }
 
 char *meshlink_get_fingerprint(meshlink_handle_t *mesh, meshlink_node_t *node) {
@@ -1045,11 +1214,13 @@ char *meshlink_get_fingerprint(meshlink_handle_t *mesh, meshlink_node_t *node) {
 		meshlink_errno = MESHLINK_EINVAL;
 		return NULL;
 	}
+	pthread_mutex_lock(&(mesh->mesh_mutex));
 
 	node_t *n = (node_t *)node;
 
 	if(!node_read_ecdsa_public_key(mesh, n) || !n->ecdsa) {
 		meshlink_errno = MESHLINK_EINTERNAL;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return false;
 	}
 
@@ -1058,16 +1229,31 @@ char *meshlink_get_fingerprint(meshlink_handle_t *mesh, meshlink_node_t *node) {
 	if(!fingerprint)
 		meshlink_errno = MESHLINK_EINTERNAL;
 
+	pthread_mutex_unlock(&(mesh->mesh_mutex));
 	return fingerprint;
 }
 
+meshlink_node_t *meshlink_get_self(meshlink_handle_t *mesh) {
+	if(!mesh) {
+		meshlink_errno = MESHLINK_EINVAL;
+		return NULL;
+	}
+
+	return (meshlink_node_t *)mesh->self;
+}
+
 meshlink_node_t *meshlink_get_node(meshlink_handle_t *mesh, const char *name) {
 	if(!mesh || !name) {
 		meshlink_errno = MESHLINK_EINVAL;
 		return NULL;
 	}
 
-	return (meshlink_node_t *)lookup_node(mesh, (char *)name); // TODO: make lookup_node() use const
+	meshlink_node_t *node = NULL;
+
+	pthread_mutex_lock(&(mesh->mesh_mutex));
+	node = (meshlink_node_t *)lookup_node(mesh, (char *)name); // TODO: make lookup_node() use const
+	pthread_mutex_unlock(&(mesh->mesh_mutex));
+	return node;
 }
 
 meshlink_node_t **meshlink_get_all_nodes(meshlink_handle_t *mesh, meshlink_node_t **nodes, size_t *nmemb) {
@@ -1079,7 +1265,7 @@ meshlink_node_t **meshlink_get_all_nodes(meshlink_handle_t *mesh, meshlink_node_
 	meshlink_node_t **result;
 
 	//lock mesh->nodes
-	pthread_mutex_lock(&(mesh->nodes_mutex));
+	pthread_mutex_lock(&(mesh->mesh_mutex));
 
 	*nmemb = mesh->nodes->count;
 	result = realloc(nodes, *nmemb * sizeof *nodes);
@@ -1094,7 +1280,7 @@ meshlink_node_t **meshlink_get_all_nodes(meshlink_handle_t *mesh, meshlink_node_
 		meshlink_errno = MESHLINK_ENOMEM;
 	}
 
-	pthread_mutex_unlock(&(mesh->nodes_mutex));
+	pthread_mutex_unlock(&(mesh->mesh_mutex));
 
 	return result;
 }
@@ -1110,12 +1296,16 @@ bool meshlink_sign(meshlink_handle_t *mesh, const void *data, size_t len, void *
 		return false;
 	}
 
+	pthread_mutex_lock(&(mesh->mesh_mutex));
+
 	if(!ecdsa_sign(mesh->self->connection->ecdsa, data, len, signature)) {
 		meshlink_errno = MESHLINK_EINTERNAL;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return false;
 	}
 
 	*siglen = MESHLINK_SIGLEN;
+	pthread_mutex_unlock(&(mesh->mesh_mutex));
 	return true;
 }
 
@@ -1130,23 +1320,32 @@ bool meshlink_verify(meshlink_handle_t *mesh, meshlink_node_t *source, const voi
 		return false;
 	}
 
+	pthread_mutex_lock(&(mesh->mesh_mutex));
+
+	bool rval = false;
+
 	struct node_t *n = (struct node_t *)source;
 	node_read_ecdsa_public_key(mesh, n);
 	if(!n->ecdsa) {
 		meshlink_errno = MESHLINK_EINTERNAL;
-		return false;
+		rval = false;
+	} else {
+		rval = ecdsa_verify(((struct node_t *)source)->ecdsa, data, len, signature);
 	}
-
-	return ecdsa_verify(((struct node_t *)source)->ecdsa, data, len, signature);
+	pthread_mutex_unlock(&(mesh->mesh_mutex));
+	return rval;
 }
 
 static bool refresh_invitation_key(meshlink_handle_t *mesh) {
 	char filename[PATH_MAX];
+	
+	pthread_mutex_lock(&(mesh->mesh_mutex));
 
 	snprintf(filename, sizeof filename, "%s" SLASH "invitations", mesh->confbase);
 	if(mkdir(filename, 0700) && errno != EEXIST) {
 		logger(mesh, MESHLINK_DEBUG, "Could not create directory %s: %s\n", filename, strerror(errno));
 		meshlink_errno = MESHLINK_ESTORAGE;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return false;
 	}
 
@@ -1155,6 +1354,7 @@ static bool refresh_invitation_key(meshlink_handle_t *mesh) {
 	if(!dir) {
 		logger(mesh, MESHLINK_DEBUG, "Could not read directory %s: %s\n", filename, strerror(errno));
 		meshlink_errno = MESHLINK_ESTORAGE;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return false;
 	}
 
@@ -1184,6 +1384,7 @@ static bool refresh_invitation_key(meshlink_handle_t *mesh) {
 		logger(mesh, MESHLINK_DEBUG, "Error while reading directory %s: %s\n", filename, strerror(errno));
 		closedir(dir);
 		meshlink_errno = MESHLINK_ESTORAGE;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return false;
 	}
 
@@ -1200,15 +1401,18 @@ static bool refresh_invitation_key(meshlink_handle_t *mesh) {
 		}
 	}
 
-	if(mesh->invitation_key)
+	if(mesh->invitation_key) {
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return true;
+	}
 
 	// Create a new key if necessary.
-	FILE *f = fopen(filename, "r");
+	FILE *f = fopen(filename, "rb");
 	if(!f) {
 		if(errno != ENOENT) {
 			logger(mesh, MESHLINK_DEBUG, "Could not read %s: %s\n", filename, strerror(errno));
 			meshlink_errno = MESHLINK_ESTORAGE;
+			pthread_mutex_unlock(&(mesh->mesh_mutex));
 			return false;
 		}
 
@@ -1216,12 +1420,14 @@ static bool refresh_invitation_key(meshlink_handle_t *mesh) {
 		if(!mesh->invitation_key) {
 			logger(mesh, MESHLINK_DEBUG, "Could not generate a new key!\n");
 			meshlink_errno = MESHLINK_EINTERNAL;
+			pthread_mutex_unlock(&(mesh->mesh_mutex));
 			return false;
 		}
-		f = fopen(filename, "w");
+		f = fopen(filename, "wb");
 		if(!f) {
 			logger(mesh, MESHLINK_DEBUG, "Could not write %s: %s\n", filename, strerror(errno));
 			meshlink_errno = MESHLINK_ESTORAGE;
+			pthread_mutex_unlock(&(mesh->mesh_mutex));
 			return false;
 		}
 		chmod(filename, 0600);
@@ -1236,6 +1442,7 @@ static bool refresh_invitation_key(meshlink_handle_t *mesh) {
 		}
 	}
 
+	pthread_mutex_unlock(&(mesh->mesh_mutex));
 	return mesh->invitation_key;
 }
 
@@ -1244,16 +1451,23 @@ bool meshlink_add_address(meshlink_handle_t *mesh, const char *address) {
 		meshlink_errno = MESHLINK_EINVAL;
 		return false;
 	}
+	
+	bool rval = false;
+
+	pthread_mutex_lock(&(mesh->mesh_mutex));
 
 	for(const char *p = address; *p; p++) {
 		if(isalnum(*p) || *p == '-' || *p == '.' || *p == ':')
 			continue;
 		logger(mesh, MESHLINK_DEBUG, "Invalid character in address: %s\n", address);
 		meshlink_errno = MESHLINK_EINVAL;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return false;
 	}
 
-	return append_config_file(mesh, mesh->self->name, "Address", address);
+	rval = append_config_file(mesh, mesh->self->name, "Address", address);
+	pthread_mutex_unlock(&(mesh->mesh_mutex));
+	return rval;
 }
 
 char *meshlink_invite(meshlink_handle_t *mesh, const char *name) {
@@ -1261,11 +1475,14 @@ char *meshlink_invite(meshlink_handle_t *mesh, const char *name) {
 		meshlink_errno = MESHLINK_EINVAL;
 		return NULL;
 	}
+	
+	pthread_mutex_lock(&(mesh->mesh_mutex));
 
 	// Check validity of the new node's name
 	if(!check_id(name)) {
 		logger(mesh, MESHLINK_DEBUG, "Invalid name for node.\n");
 		meshlink_errno = MESHLINK_EINVAL;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return NULL;
 	}
 
@@ -1275,6 +1492,7 @@ char *meshlink_invite(meshlink_handle_t *mesh, const char *name) {
 	if(!access(filename, F_OK)) {
 		logger(mesh, MESHLINK_DEBUG, "A host config file for %s already exists!\n", name);
 		meshlink_errno = MESHLINK_EEXIST;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return NULL;
 	}
 
@@ -1282,6 +1500,7 @@ char *meshlink_invite(meshlink_handle_t *mesh, const char *name) {
 	if(meshlink_get_node(mesh, name)) {
 		logger(mesh, MESHLINK_DEBUG, "A node with name %s is already known!\n", name);
 		meshlink_errno = MESHLINK_EEXIST;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return NULL;
 	}
 
@@ -1290,11 +1509,13 @@ char *meshlink_invite(meshlink_handle_t *mesh, const char *name) {
 	if(!address) {
 		logger(mesh, MESHLINK_DEBUG, "No Address known for ourselves!\n");
 		meshlink_errno = MESHLINK_ERESOLV;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return NULL;
 	}
 
 	if(!refresh_invitation_key(mesh)) {
 		meshlink_errno = MESHLINK_EINTERNAL;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return NULL;
 	}
 
@@ -1327,6 +1548,7 @@ char *meshlink_invite(meshlink_handle_t *mesh, const char *name) {
 	if(!ifd) {
 		logger(mesh, MESHLINK_DEBUG, "Could not create invitation file %s: %s\n", filename, strerror(errno));
 		meshlink_errno = MESHLINK_ESTORAGE;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return NULL;
 	}
 	FILE *f = fdopen(ifd, "w");
@@ -1357,6 +1579,7 @@ char *meshlink_invite(meshlink_handle_t *mesh, const char *name) {
 	} else {
 		logger(mesh, MESHLINK_DEBUG, "Could not create %s: %s\n", filename, strerror(errno));
 		meshlink_errno = MESHLINK_ESTORAGE;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return NULL;
 	}
 
@@ -1372,6 +1595,7 @@ char *meshlink_invite(meshlink_handle_t *mesh, const char *name) {
 	xasprintf(&url, "%s/%s%s", address, hash, cookie);
 	free(address);
 
+	pthread_mutex_unlock(&(mesh->mesh_mutex));
 	return url;
 }
 
@@ -1380,6 +1604,8 @@ bool meshlink_join(meshlink_handle_t *mesh, const char *invitation) {
 		meshlink_errno = MESHLINK_EINVAL;
 		return false;
 	}
+	
+	pthread_mutex_lock(&(mesh->mesh_mutex));
 
 	//TODO: think of a better name for this variable, or of a different way to tokenize the invitation URL.
 	char copy[strlen(invitation) + 1];
@@ -1422,6 +1648,7 @@ bool meshlink_join(meshlink_handle_t *mesh, const char *invitation) {
 	ecdsa_t *key = ecdsa_generate();
 	if(!key) {
 		meshlink_errno = MESHLINK_EINTERNAL;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return false;
 	}
 
@@ -1436,6 +1663,7 @@ bool meshlink_join(meshlink_handle_t *mesh, const char *invitation) {
 	struct addrinfo *ai = str2addrinfo(address, port, SOCK_STREAM);
 	if(!ai) {
 		meshlink_errno = MESHLINK_ERESOLV;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return false;
 	}
 
@@ -1444,6 +1672,7 @@ bool meshlink_join(meshlink_handle_t *mesh, const char *invitation) {
 		logger(mesh, MESHLINK_DEBUG, "Could not open socket: %s\n", strerror(errno));
 		freeaddrinfo(ai);
 		meshlink_errno = MESHLINK_ENETWORK;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return false;
 	}
 
@@ -1452,6 +1681,7 @@ bool meshlink_join(meshlink_handle_t *mesh, const char *invitation) {
 		closesocket(mesh->sock);
 		freeaddrinfo(ai);
 		meshlink_errno = MESHLINK_ENETWORK;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return false;
 	}
 
@@ -1467,6 +1697,7 @@ bool meshlink_join(meshlink_handle_t *mesh, const char *invitation) {
 		logger(mesh, MESHLINK_DEBUG, "Error sending request to %s port %s: %s\n", address, port, strerror(errno));
 		closesocket(mesh->sock);
 		meshlink_errno = MESHLINK_ENETWORK;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return false;
 	}
 
@@ -1479,6 +1710,7 @@ bool meshlink_join(meshlink_handle_t *mesh, const char *invitation) {
 		logger(mesh, MESHLINK_DEBUG, "Cannot read greeting from peer\n");
 		closesocket(mesh->sock);
 		meshlink_errno = MESHLINK_ENETWORK;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return false;
 	}
 
@@ -1488,11 +1720,13 @@ bool meshlink_join(meshlink_handle_t *mesh, const char *invitation) {
 	if(sha512(fingerprint, strlen(fingerprint), hishash)) {
 		logger(mesh, MESHLINK_DEBUG, "Could not create hash\n%s\n", mesh->line + 2);
 		meshlink_errno = MESHLINK_EINTERNAL;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return false;
 	}
 	if(memcmp(hishash, mesh->hash, 18)) {
 		logger(mesh, MESHLINK_DEBUG, "Peer has an invalid key!\n%s\n", mesh->line + 2);
 		meshlink_errno = MESHLINK_EPEER;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return false;
 
 	}
@@ -1500,18 +1734,21 @@ bool meshlink_join(meshlink_handle_t *mesh, const char *invitation) {
 	ecdsa_t *hiskey = ecdsa_set_base64_public_key(fingerprint);
 	if(!hiskey) {
 		meshlink_errno = MESHLINK_EINTERNAL;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return false;
 	}
 
 	// Start an SPTPS session
 	if(!sptps_start(&mesh->sptps, mesh, true, false, key, hiskey, "meshlink invitation", 15, invitation_send, invitation_receive)) {
 		meshlink_errno = MESHLINK_EINTERNAL;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return false;
 	}
 
 	// Feed rest of input buffer to SPTPS
 	if(!sptps_receive_data(&mesh->sptps, mesh->buffer, mesh->blen)) {
 		meshlink_errno = MESHLINK_EPEER;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return false;
 	}
 
@@ -1523,11 +1760,13 @@ bool meshlink_join(meshlink_handle_t *mesh, const char *invitation) {
 				continue;
 			logger(mesh, MESHLINK_DEBUG, "Error reading data from %s port %s: %s\n", address, port, strerror(errno));
 			meshlink_errno = MESHLINK_ENETWORK;
+			pthread_mutex_unlock(&(mesh->mesh_mutex));
 			return false;
 		}
 
 		if(!sptps_receive_data(&mesh->sptps, mesh->line, len)) {
 			meshlink_errno = MESHLINK_EPEER;
+			pthread_mutex_unlock(&(mesh->mesh_mutex));
 			return false;
 		}
 	}
@@ -1540,14 +1779,17 @@ bool meshlink_join(meshlink_handle_t *mesh, const char *invitation) {
 	if(!mesh->success) {
 		logger(mesh, MESHLINK_DEBUG, "Connection closed by peer, invitation cancelled.\n");
 		meshlink_errno = MESHLINK_EPEER;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return false;
 	}
 
+	pthread_mutex_unlock(&(mesh->mesh_mutex));
 	return true;
 
 invalid:
 	logger(mesh, MESHLINK_DEBUG, "Invalid invitation URL or you are already connected to a Mesh ?\n");
 	meshlink_errno = MESHLINK_EINVAL;
+	pthread_mutex_unlock(&(mesh->mesh_mutex));
 	return false;
 }
 
@@ -1557,12 +1799,15 @@ char *meshlink_export(meshlink_handle_t *mesh) {
 		return NULL;
 	}
 
+	pthread_mutex_lock(&(mesh->mesh_mutex));
+	
 	char filename[PATH_MAX];
 	snprintf(filename, sizeof filename, "%s" SLASH "hosts" SLASH "%s", mesh->confbase, mesh->self->name);
 	FILE *f = fopen(filename, "r");
 	if(!f) {
 		logger(mesh, MESHLINK_DEBUG, "Could not open %s: %s\n", filename, strerror(errno));
 		meshlink_errno = MESHLINK_ESTORAGE;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return NULL;
 	}
 
@@ -1577,11 +1822,14 @@ char *meshlink_export(meshlink_handle_t *mesh) {
 		logger(mesh, MESHLINK_DEBUG, "Error reading from %s: %s\n", filename, strerror(errno));
 		fclose(f);
 		meshlink_errno = MESHLINK_ESTORAGE;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return NULL;
 	}
 
 	fclose(f);
 	buf[len - 1] = 0;
+	
+	pthread_mutex_unlock(&(mesh->mesh_mutex));
 	return buf;
 }
 
@@ -1590,10 +1838,13 @@ bool meshlink_import(meshlink_handle_t *mesh, const char *data) {
 		meshlink_errno = MESHLINK_EINVAL;
 		return false;
 	}
+	
+	pthread_mutex_lock(&(mesh->mesh_mutex));
 
 	if(strncmp(data, "Name = ", 7)) {
 		logger(mesh, MESHLINK_DEBUG, "Invalid data\n");
 		meshlink_errno = MESHLINK_EPEER;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return false;
 	}
 
@@ -1601,6 +1852,7 @@ bool meshlink_import(meshlink_handle_t *mesh, const char *data) {
 	if(!end) {
 		logger(mesh, MESHLINK_DEBUG, "Invalid data\n");
 		meshlink_errno = MESHLINK_EPEER;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return false;
 	}
 
@@ -1611,6 +1863,7 @@ bool meshlink_import(meshlink_handle_t *mesh, const char *data) {
 	if(!check_id(name)) {
 		logger(mesh, MESHLINK_DEBUG, "Invalid Name\n");
 		meshlink_errno = MESHLINK_EPEER;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return false;
 	}
 
@@ -1619,12 +1872,14 @@ bool meshlink_import(meshlink_handle_t *mesh, const char *data) {
 	if(!access(filename, F_OK)) {
 		logger(mesh, MESHLINK_DEBUG, "File %s already exists, not importing\n", filename);
 		meshlink_errno = MESHLINK_EEXIST;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return false;
 	}
 
 	if(errno != ENOENT) {
 		logger(mesh, MESHLINK_DEBUG, "Error accessing %s: %s\n", filename, strerror(errno));
 		meshlink_errno = MESHLINK_ESTORAGE;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return false;
 	}
 
@@ -1632,6 +1887,7 @@ bool meshlink_import(meshlink_handle_t *mesh, const char *data) {
 	if(!f) {
 		logger(mesh, MESHLINK_DEBUG, "Could not create %s: %s\n", filename, strerror(errno));
 		meshlink_errno = MESHLINK_ESTORAGE;
+		pthread_mutex_unlock(&(mesh->mesh_mutex));
 		return false;
 	}
 
@@ -1640,6 +1896,7 @@ bool meshlink_import(meshlink_handle_t *mesh, const char *data) {
 
 	load_all_nodes(mesh);
 
+	pthread_mutex_unlock(&(mesh->mesh_mutex));
 	return true;
 }
 
@@ -1649,6 +1906,8 @@ void meshlink_blacklist(meshlink_handle_t *mesh, meshlink_node_t *node) {
 		return;
 	}
 
+	pthread_mutex_lock(&(mesh->mesh_mutex));
+	
 	node_t *n;
 	n = (node_t*)node;
 	n->status.blacklisted=true;
@@ -1657,6 +1916,7 @@ void meshlink_blacklist(meshlink_handle_t *mesh, meshlink_node_t *node) {
 	//Make blacklisting persistent in the config file
 	append_config_file(mesh, n->name, "blacklisted", "yes");
 
+	pthread_mutex_unlock(&(mesh->mesh_mutex));
 	return;
 }
 
@@ -1666,54 +1926,297 @@ void meshlink_whitelist(meshlink_handle_t *mesh, meshlink_node_t *node) {
 		return;
 	}
 
+	pthread_mutex_lock(&(mesh->mesh_mutex));
+	
 	node_t *n = (node_t *)node;
 	n->status.blacklisted = false;
 
 	//TODO: remove blacklisted = yes from the config file
 
+	pthread_mutex_unlock(&(mesh->mesh_mutex));
 	return;
 }
 
+void meshlink_set_default_blacklist(meshlink_handle_t *mesh, bool blacklist) {
+	mesh->default_blacklist = blacklist;
+}
+
 /* Hint that a hostname may be found at an address
  * See header file for detailed comment.
  */
-extern void meshlink_hint_address(meshlink_handle_t *mesh, meshlink_node_t *node, struct sockaddr *addr) {
+void meshlink_hint_address(meshlink_handle_t *mesh, meshlink_node_t *node, const struct sockaddr *addr) {
 	if(!mesh || !node || !addr)
 		return;
-	
-	char *addr_str = malloc(MAX_ADDRESS_LENGTH*sizeof(char));
-	memset(addr_str, 0, MAX_ADDRESS_LENGTH*sizeof(char));
-
-	char *port_str = malloc(MAX_PORT_LENGTH*sizeof(char));
-	memset(port_str, 0, MAX_PORT_LENGTH*sizeof(char));
-	
-	// extra byte for a space, and one to make sure string is null-terminated
-	int full_addr_len = MAX_ADDRESS_LENGTH + MAX_PORT_LENGTH + 2;
 
-	char *full_addr_str = malloc(full_addr_len*sizeof(char));
-	memset(full_addr_str, 0, full_addr_len*sizeof(char));
+	// Ignore hints about ourself.
+	if((node_t *)node == mesh->self)
+		return;
 	
-	// get address and port number
-	if(!get_ip_str(addr, addr_str, MAX_ADDRESS_LENGTH))
-		goto fail;
-	if(!get_port_str(addr, port_str, MAX_ADDRESS_LENGTH))
-		goto fail;
-
-	// append_config_file expects an address, a space, and then a port number
-	strcat(full_addr_str, addr_str);
-	strcat(full_addr_str, " ");
-	strcat(full_addr_str, port_str);
+	pthread_mutex_lock(&(mesh->mesh_mutex));
 	
-	append_config_file(mesh, node->name, "Address", full_addr_str);
+	char *host = NULL, *port = NULL, *str = NULL;
+	sockaddr2str((const sockaddr_t *)addr, &host, &port);
 
-fail:
-	free(addr_str);
-	free(port_str);
-	free(full_addr_str);
+	if(host && port) {
+		xasprintf(&str, "%s %s", host, port);
+		if ( (strncmp ("fe80",host,4) != 0) && ( strncmp("127.",host,4) != 0 ) && ( strcmp("localhost",host) !=0 ) )
+			append_config_file(mesh, node->name, "Address", str);
+		else
+			logger(mesh, MESHLINK_DEBUG, "Not adding Link Local IPv6 Address to config\n");
+	}
 
+	free(str);
+	free(host);
+	free(port);
+
+	pthread_mutex_unlock(&(mesh->mesh_mutex));
 	// @TODO do we want to fire off a connection attempt right away?
 }
 
+/* Return an array of edges in the current network graph.
+ * Data captures the current state and will not be updated.
+ * Caller must deallocate data when done.
+ */
+meshlink_edge_t **meshlink_get_all_edges_state(meshlink_handle_t *mesh, meshlink_edge_t **edges, size_t *nmemb) {
+	if(!mesh || !nmemb || (*nmemb && !edges)) {
+		meshlink_errno = MESHLINK_EINVAL;
+		return NULL;
+	}
+
+	pthread_mutex_lock(&(mesh->mesh_mutex));
+	
+	meshlink_edge_t **result = NULL;
+	meshlink_edge_t *copy = NULL;
+	int result_size = 0;
+
+	result_size = mesh->edges->count;
+
+	// if result is smaller than edges, we have to dealloc all the excess meshlink_edge_t
+	if(result_size > *nmemb) {
+		result = realloc(edges, result_size * sizeof (meshlink_edge_t*));
+	} else {
+		result = edges;
+	}
+
+	if(result) {
+		meshlink_edge_t **p = result;
+		int n = 0;
+		for splay_each(edge_t, e, mesh->edges) {
+			// skip edges that do not represent a two-directional connection
+			if((!e->reverse) || (e->reverse->to != e->from)) {
+				result_size--;
+				continue;
+			}
+			n++;
+			// the first *nmemb members of result can be re-used
+			if(n > *nmemb) {
+				copy = xzalloc(sizeof *copy);
+			}
+			else {
+				copy = *p;
+			}
+			copy->from = (meshlink_node_t*)e->from;
+			copy->to = (meshlink_node_t*)e->to;
+			copy->address = e->address.storage;
+			copy->options = e->options;
+			copy->weight = e->weight;
+			*p++ = copy;
+		}
+		// shrink result to the actual amount of memory used
+		for(int i = *nmemb; i > result_size; i--) {
+			free(result[i - 1]);
+		}
+		result = realloc(result, result_size * sizeof (meshlink_edge_t*));
+		*nmemb = result_size;
+	} else {
+		*nmemb = 0;
+		free(result);
+		meshlink_errno = MESHLINK_ENOMEM;
+	}
+
+	pthread_mutex_unlock(&(mesh->mesh_mutex));
+
+	return result;
+}
+
+static bool channel_pre_accept(struct utcp *utcp, uint16_t port) {
+	//TODO: implement
+	return true;
+}
+
+static ssize_t channel_recv(struct utcp_connection *connection, const void *data, size_t len) {
+	meshlink_channel_t *channel = connection->priv;
+	if(!channel)
+		abort();
+	node_t *n = channel->node;
+	meshlink_handle_t *mesh = n->mesh;
+	if(!channel->receive_cb)
+		return -1;
+	else {
+		channel->receive_cb(mesh, channel, data, len);
+		return len;
+	}
+}
+
+static void channel_accept(struct utcp_connection *utcp_connection, uint16_t port) {
+	node_t *n = utcp_connection->utcp->priv;
+	if(!n)
+		abort();
+	meshlink_handle_t *mesh = n->mesh;
+	if(!mesh->channel_accept_cb)
+		return;
+	meshlink_channel_t *channel = xzalloc(sizeof *channel);
+	channel->node = n;
+	channel->c = utcp_connection;
+	if(mesh->channel_accept_cb(mesh, channel, port, NULL, 0))
+		utcp_accept(utcp_connection, channel_recv, channel);
+	else
+		free(channel);
+}
+
+static ssize_t channel_send(struct utcp *utcp, const void *data, size_t len) {
+	node_t *n = utcp->priv;
+	meshlink_handle_t *mesh = n->mesh;
+	char hex[len * 2 + 1];
+	bin2hex(data, hex, len);
+	logger(mesh, MESHLINK_WARNING, "channel_send(%p, %p, %zu): %s\n", utcp, data, len, hex);
+	return meshlink_send(mesh, (meshlink_node_t *)n, data, len) ? len : -1;
+}
+
+void meshlink_set_channel_receive_cb(meshlink_handle_t *mesh, meshlink_channel_t *channel, meshlink_channel_receive_cb_t cb) {
+	if(!mesh || !channel) {
+		meshlink_errno = MESHLINK_EINVAL;
+		return;
+	}
+
+	channel->receive_cb = cb;
+}
+
+static void channel_receive(meshlink_handle_t *mesh, meshlink_node_t *source, const void *data, size_t len) {
+	node_t *n = (node_t *)source;
+	if(!n->utcp)
+		abort();
+	char hex[len * 2 + 1];
+	bin2hex(data, hex, len);
+	logger(mesh, MESHLINK_WARNING, "channel_receive(%p, %p, %zu): %s\n", n->utcp, data, len, hex);
+	utcp_recv(n->utcp, data, len);
+}
+
+static void channel_poll(struct utcp_connection *connection, size_t len) {
+	meshlink_channel_t *channel = connection->priv;
+	if(!channel)
+		abort();
+	node_t *n = channel->node;
+	meshlink_handle_t *mesh = n->mesh;
+	if(channel->poll_cb)
+		channel->poll_cb(mesh, channel, len);
+}
+
+void meshlink_set_channel_poll_cb(meshlink_handle_t *mesh, meshlink_channel_t *channel, meshlink_channel_poll_cb_t cb) {
+	channel->poll_cb = cb;
+	utcp_set_poll_cb(channel->c, cb ? channel_poll : NULL);
+}
+
+void meshlink_set_channel_accept_cb(meshlink_handle_t *mesh, meshlink_channel_accept_cb_t cb) {
+	if(!mesh) {
+		meshlink_errno = MESHLINK_EINVAL;
+		return;
+	}
+
+	pthread_mutex_lock(&mesh->mesh_mutex);
+	mesh->channel_accept_cb = cb;
+	mesh->receive_cb = channel_receive;
+	for splay_each(node_t, n, mesh->nodes) {
+		if(!n->utcp && n != mesh->self) {
+			logger(mesh, MESHLINK_WARNING, "utcp_init on node %s", n->name);
+			n->utcp = utcp_init(channel_accept, channel_pre_accept, channel_send, n);
+		}
+	}
+	pthread_mutex_unlock(&mesh->mesh_mutex);
+}
+
+meshlink_channel_t *meshlink_channel_open(meshlink_handle_t *mesh, meshlink_node_t *node, uint16_t port, meshlink_channel_receive_cb_t cb, const void *data, size_t len) {
+	if(!mesh || !node) {
+		meshlink_errno = MESHLINK_EINVAL;
+		return NULL;
+	}
+
+	logger(mesh, MESHLINK_WARNING, "meshlink_channel_open(%p, %s, %u, %p, %p, %zu)\n", mesh, node->name, port, cb, data, len);
+	node_t *n = (node_t *)node;
+	if(!n->utcp) {
+		n->utcp = utcp_init(channel_accept, channel_pre_accept, channel_send, n);
+		mesh->receive_cb = channel_receive;
+		if(!n->utcp) {
+			meshlink_errno = errno == ENOMEM ? MESHLINK_ENOMEM : MESHLINK_EINTERNAL;
+			return NULL;
+		}
+	}
+	meshlink_channel_t *channel = xzalloc(sizeof *channel);
+	channel->node = n;
+	channel->receive_cb = cb;
+	channel->c = utcp_connect(n->utcp, port, channel_recv, channel);
+	if(!channel->c) {
+		meshlink_errno = errno == ENOMEM ? MESHLINK_ENOMEM : MESHLINK_EINTERNAL;
+		free(channel);
+		return NULL;
+	}
+	return channel;
+}
+
+void meshlink_channel_shutdown(meshlink_handle_t *mesh, meshlink_channel_t *channel, int direction) {
+	if(!mesh || !channel) {
+		meshlink_errno = MESHLINK_EINVAL;
+		return;
+	}
+
+	utcp_shutdown(channel->c, direction);
+}
+
+void meshlink_channel_close(meshlink_handle_t *mesh, meshlink_channel_t *channel) {
+	if(!mesh || !channel) {
+		meshlink_errno = MESHLINK_EINVAL;
+		return;
+	}
+
+	utcp_close(channel->c);
+	free(channel);
+}
+
+ssize_t meshlink_channel_send(meshlink_handle_t *mesh, meshlink_channel_t *channel, const void *data, size_t len) {
+	if(!mesh || !channel) {
+		meshlink_errno = MESHLINK_EINVAL;
+		return -1;
+	}
+
+	if(!len)
+		return 0;
+
+	if(!data) {
+		meshlink_errno = MESHLINK_EINVAL;
+		return -1;
+	}
+
+	// TODO: more finegrained locking.
+	// Ideally we want to put the data into the UTCP connection's send buffer.
+	// Then, preferrably only if there is room in the receiver window,
+	// kick the meshlink thread to go send packets.
+
+	pthread_mutex_lock(&mesh->mesh_mutex);
+	ssize_t retval = utcp_send(channel->c, data, len);
+	pthread_mutex_unlock(&mesh->mesh_mutex);
+
+	if(retval < 0)
+		meshlink_errno = MESHLINK_ENETWORK;
+	return retval;
+}
+
+void update_node_status(meshlink_handle_t *mesh, node_t *n) {
+	if(n->status.reachable && mesh->channel_accept_cb && !n->utcp)
+		n->utcp = utcp_init(channel_accept, channel_pre_accept, channel_send, n);
+	if(mesh->node_status_cb)
+		mesh->node_status_cb(mesh, (meshlink_node_t *)n, n->status.reachable);
+}
+
 static void __attribute__((constructor)) meshlink_init(void) {
 	crypto_init();
 }
@@ -1721,3 +2224,11 @@ static void __attribute__((constructor)) meshlink_init(void) {
 static void __attribute__((destructor)) meshlink_exit(void) {
 	crypto_exit();
 }
+
+/// Device class traits
+dev_class_traits_t dev_class_traits[_DEV_CLASS_MAX +1] = {
+	{ .min_connects = 3, .max_connects = 10000, .edge_weight = 1 },	// DEV_CLASS_BACKBONE
+	{ .min_connects = 3, .max_connects = 100, .edge_weight = 3 },	// DEV_CLASS_STATIONARY
+	{ .min_connects = 3, .max_connects = 3, .edge_weight = 6 },		// DEV_CLASS_PORTABLE
+	{ .min_connects = 1, .max_connects = 1, .edge_weight = 9 },		// DEV_CLASS_UNKNOWN
+};