Deferred instantiation of socket implmentations until registration.

Instantiating the implementations on plugin load was problematic
in case multiple socket plugins were loaded. Now, the first one
registered is instantiated.

src/libcharon/plugins/socket_default/socket_default_plugin.c

@@ -1,4 +1,6 @@
 /*
+ * Copyright (C) 2010 Tobias Brunner
+ * Hochschule fuer Technik Rapperswil
  * Copyright (C) 2010 Martin Willi
  * Copyright (C) 2010 revosec AG
  *
@@ -31,17 +33,13 @@ struct private_socket_default_plugin_t {
 	 */
 	socket_default_plugin_t public;
 
-	/**
-	 * Socket instance.
-	 */
-	socket_default_socket_t *socket;
 };
 
 METHOD(plugin_t, destroy, void,
 	private_socket_default_plugin_t *this)
 {
-	charon->socket->remove_socket(charon->socket, &this->socket->socket);
-	this->socket->destroy(this->socket);
+	charon->socket->remove_socket(charon->socket,
+						(socket_constructor_t)socket_default_socket_create);
 	free(this);
 }
 
@@ -58,15 +56,10 @@ plugin_t *socket_default_plugin_create()
 				.destroy = _destroy,
 			},
 		},
-		.socket = socket_default_socket_create(),
 	);
 
-	if (!this->socket)
-	{
-		free(this);
-		return NULL;
-	}
-	charon->socket->add_socket(charon->socket, &this->socket->socket);
+	charon->socket->add_socket(charon->socket,
+						(socket_constructor_t)socket_default_socket_create);
 
 	return &this->public.plugin;
 }

src/libcharon/plugins/socket_default/socket_default_socket.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2006-2009 Tobias Brunner
+ * Copyright (C) 2006-2010 Tobias Brunner
  * Copyright (C) 2006 Daniel Roethlisberger
  * Copyright (C) 2005-2010 Martin Willi
  * Copyright (C) 2005 Jan Hutter
@@ -546,7 +546,7 @@ static int open_socket(private_socket_default_socket_t *this,
 	return skt;
 }
 
-METHOD(socket_default_socket_t, destroy, void,
+METHOD(socket_t, destroy, void,
 	private_socket_default_socket_t *this)
 {
 	if (this->ipv4)
@@ -580,8 +580,8 @@ socket_default_socket_t *socket_default_socket_create()
 			.socket = {
 				.send = _sender,
 				.receive = _receiver,
+				.destroy = _destroy,
 			},
-			.destroy = _destroy,
 		},
 		.max_packet = lib->settings->get_int(lib->settings,
 										"charon.max_packet", MAX_PACKET),

src/libcharon/plugins/socket_default/socket_default_socket.h

@@ -35,10 +35,6 @@ struct socket_default_socket_t {
 	 */
 	socket_t socket;
 
-	/**
-	 * Destroy a socket_default_socket_t.
-	 */
-	void (*destroy)(socket_default_socket_t *this);
 };
 
 /**