removed the reuse-address flag on the listen socket

ChangeLog

@@ -1,3 +1,4 @@
+	* made the reuse-address flag configurable on the listen socket
 	* moved UDP trackers over to use a single socket
 	* added feature to make asserts log to a file instead of breaking the process
 	  (production asserts)
@@ -32,6 +33,7 @@
 	  incoming connection
 	* added more detailed instrumentation of the disk I/O thread
 
+	* removed the reuse-address flag on the listen socket
 	* fixed bug where local peer discovery and DHT wouldn't be announced to without trackers
 	* fixed bug in bdecoder when decoding invalid messages
 	* added build warning when building with UNICODE but the standard library

docs/manual.rst

@@ -207,9 +207,12 @@ The ``session`` class has the following synopsis::
 
 		bool is_listening() const;
 		unsigned short listen_port() const;
+
+		enum { listen_reuse_address = 1 };
 		bool listen_on(
 			std::pair<int, int> const& port_range
-			, char const* interface = 0);
+			, char const* interface = 0
+			, int flags = 0);
 
 		std::auto_ptr<alert> pop_alert();
 		alert const* wait_for_alert(time_duration max_wait);
@@ -917,7 +920,8 @@ is_listening() listen_port() listen_on()
 		unsigned short listen_port() const;
 		bool listen_on(
 			std::pair<int, int> const& port_range
-			, char const* interface = 0);
+			, char const* interface = 0
+			, int flags = 0);
 
 ``is_listening()`` will tell you whether or not the session has successfully
 opened a listening port. If it hasn't, this function will return false, and
@@ -946,6 +950,11 @@ listen on multiple interfaces (typically 0.0.0.0 and ::). This means that if you
 IPv6 interface doesn't work, you may still see a listen_failed_alert_, even though
 the IPv4 port succeeded.
 
+The ``flags`` parameter can either be 0 or ``session::listen_reuse_address``, which
+will set the reuse address socket option on the listen socket(s). By default, the
+listen socket does not use reuse address. If you're running a service that needs
+to run on a specific port no matter if it's in use, set this flag.
+
 If you're also starting the DHT, it is a good idea to do that after you've called
 ``listen_on()``, since the default listen port for the DHT is the same as the tcp
 listen socket. If you start the DHT first, it will assume the tcp port is free and

include/libtorrent/aux_/session_impl.hpp

@@ -161,7 +161,7 @@ namespace libtorrent
 #endif
 			void main_thread();
 
-			void open_listen_port();
+			void open_listen_port(bool reuse_address);
 
 			// if we are listening on an IPv6 interface
 			// this will return one of the IPv6 addresses on this
@@ -236,7 +236,8 @@ namespace libtorrent
 
 			bool listen_on(
 				std::pair<int, int> const& port_range
-				, const char* net_interface = 0);
+				, const char* net_interface = 0
+				, int flags = 0);
 			bool is_listening() const;
 
 			torrent_handle add_torrent(add_torrent_params const&, error_code& ec);
@@ -580,7 +581,8 @@ namespace libtorrent
 			boost::shared_ptr<socket_type> m_i2p_listen_socket;
 #endif
 
-			listen_socket_t setup_listener(tcp::endpoint ep, int retries, bool v6_only = false);
+			listen_socket_t setup_listener(tcp::endpoint ep, int retries
+				, bool v6_only, bool reuse_address);
 
 			// the settings for the client
 			session_settings m_settings;

include/libtorrent/session.hpp

@@ -322,9 +322,12 @@ namespace libtorrent
 		// this function will return false on failure.
 		// If it fails, it will also generate alerts describing
 		// the error. It will return true on success.
+		enum { listen_reuse_address = 1 };
+
 		bool listen_on(
 			std::pair<int, int> const& port_range
-			, const char* net_interface = 0);
+			, const char* net_interface = 0
+			, int flags = 0);
 
 		// returns the port we ended up listening on
 		unsigned short listen_port() const;

src/session.cpp

@@ -548,10 +548,10 @@ namespace libtorrent
 
 	bool session::listen_on(
 		std::pair<int, int> const& port_range
-		, const char* net_interface)
+		, const char* net_interface, int flags)
 	{
 		mutex::scoped_lock l(m_impl->m_mutex);
-		return m_impl->listen_on(port_range, net_interface);
+		return m_impl->listen_on(port_range, net_interface, flags);
 	}
 
 	unsigned short session::listen_port() const

src/session_impl.cpp

@@ -744,7 +744,8 @@ namespace aux {
 			boost::bind(&session_impl::on_dht_announce, this, _1));
 #endif
 
-		open_listen_port();
+		// no reuse_address
+		open_listen_port(false);
 
 		m_thread.reset(new thread(boost::bind(&session_impl::main_thread, this)));
 	}
@@ -1304,12 +1305,13 @@ namespace aux {
 	}
 
 	session_impl::listen_socket_t session_impl::setup_listener(tcp::endpoint ep
-		, int retries, bool v6_only)
+		, int retries, bool v6_only, bool reuse_address)
 	{
 		error_code ec;
 		listen_socket_t s;
 		s.sock.reset(new socket_acceptor(m_io_service));
 		s.sock->open(ep.protocol(), ec);
+		if (reuse_address)
 			s.sock->set_option(socket_acceptor::reuse_address(true), ec);
 #if TORRENT_USE_IPV6
 		if (ep.protocol() == tcp::v6())
@@ -1380,7 +1382,7 @@ namespace aux {
 		return s;
 	}
 	
-	void session_impl::open_listen_port()
+	void session_impl::open_listen_port(bool reuse_address)
 	{
 		// close the open listen sockets
 		m_listen_sockets.clear();
@@ -1396,7 +1398,7 @@ namespace aux {
 		
 			listen_socket_t s = setup_listener(
 				tcp::endpoint(address_v4::any(), m_listen_interface.port())
-				, m_listen_port_retries);
+				, m_listen_port_retries, false, reuse_address);
 
 			if (s.sock)
 			{
@@ -1420,7 +1422,7 @@ namespace aux {
 			{
 				s = setup_listener(
 					tcp::endpoint(address_v6::any(), m_listen_interface.port())
-					, m_listen_port_retries, true);
+					, m_listen_port_retries, true, reuse_address);
 
 				if (s.sock)
 				{
@@ -1450,7 +1452,7 @@ namespace aux {
 			// binds to the given interface
 
 			listen_socket_t s = setup_listener(
-				m_listen_interface, m_listen_port_retries);
+				m_listen_interface, m_listen_port_retries, false, reuse_address);
 
 			if (s.sock)
 			{
@@ -3193,7 +3195,7 @@ namespace aux {
 
 	bool session_impl::listen_on(
 		std::pair<int, int> const& port_range
-		, const char* net_interface)
+		, const char* net_interface, int flags)
 	{
 		INVARIANT_CHECK;
 
@@ -3223,7 +3225,7 @@ namespace aux {
 
 		m_listen_interface = new_interface;
 
-		open_listen_port();
+		open_listen_port(flags & session::listen_reuse_address);
 
 #if defined TORRENT_VERBOSE_LOGGING || defined TORRENT_LOGGING || defined TORRENT_ERROR_LOGGING
 		m_logger = create_log("main_session", listen_port(), false);
@@ -3430,7 +3432,7 @@ namespace aux {
 		INVARIANT_CHECK;
 
 		if (m_listen_interface.port() != 0)
-			open_listen_port();
+			open_listen_port(false);
 
 		if (m_dht)
 		{