refactor discover_device() away from upnp

include/libtorrent/upnp.hpp

@@ -182,7 +182,6 @@ struct TORRENT_EXTRA_EXPORT upnp final
 	bool get_mapping(port_mapping_t mapping_index, tcp::endpoint& local_ep, int& external_port
 		, portmap_protocol& protocol) const;
 
-	void discover_device();
 	void close();
 
 	// This is only available for UPnP routers. If the model is advertised by

src/session_impl.cpp

@@ -6657,8 +6657,6 @@ namespace aux {
 			, *this);
 		m_upnp->start();
 
-		m_upnp->discover_device();
-
 		for (auto& s : m_listen_sockets)
 		{
 			remap_ports(remap_upnp, *s);

src/upnp.cpp

@@ -119,21 +119,12 @@ void upnp::start()
 		, lt::get_io_service(m_refresh_timer), ec);
 
 	m_mappings.reserve(10);
-}
-
-upnp::~upnp() = default;
-
-void upnp::discover_device()
-{
-	TORRENT_ASSERT(is_single_thread());
-#ifndef TORRENT_DISABLE_LOGGING
-	if (m_socket.num_send_sockets() == 0)
-		log("No network interfaces to broadcast to");
-#endif
 
 	discover_device_impl();
 }
 
+upnp::~upnp() = default;
+
 #ifndef TORRENT_DISABLE_LOGGING
 bool upnp::should_log() const
 {

test/test_upnp.cpp

@@ -198,7 +198,6 @@ void run_upnp_test(char const* root_filename, char const* control_name, int igd_
 	upnp_callback cb;
 	auto upnp_handler = std::make_shared<upnp>(ios, user_agent, cb);
 	upnp_handler->start();
-	upnp_handler->discover_device();
 
 	for (int i = 0; i < 20; ++i)
 	{