create a natpmp instance for each listen socket

include/libtorrent/aux_/session_impl.hpp

@@ -201,6 +201,8 @@ namespace aux {
 		// time on handler allocation every time we read again.
 		aux::handler_storage<TORRENT_READ_HANDLER_MAX_SIZE> udp_handler_storage;
 
+		std::shared_ptr<natpmp> natpmp_mapper;
+
 		// the key is an id that is used to identify the
 		// client with the tracker only.
 		std::uint32_t tracker_key = 0;
@@ -636,7 +638,7 @@ namespace aux {
 
 			void start_ip_notifier();
 			void start_lsd();
-			natpmp* start_natpmp();
+			void start_natpmp();
 			upnp* start_upnp();
 
 			void stop_ip_notifier();
@@ -777,6 +779,8 @@ namespace aux {
 
 			void on_lsd_peer(tcp::endpoint const& peer, sha1_hash const& ih) override;
 
+			void start_natpmp(aux::listen_socket_t& s);
+
 			void set_external_address(std::shared_ptr<listen_socket_t> const& sock, address const& ip
 				, ip_source_t source_type, address const& source);
 
@@ -1136,7 +1140,6 @@ namespace aux {
 			// this is deducted from the connect speed
 			int m_boost_connections = 0;
 
-			std::shared_ptr<natpmp> m_natpmp;
 			std::shared_ptr<upnp> m_upnp;
 			std::shared_ptr<lsd> m_lsd;
 

include/libtorrent/enum_net.hpp

@@ -94,7 +94,9 @@ namespace libtorrent {
 	TORRENT_EXTRA_EXPORT bool in_local_network(std::vector<ip_interface> const& net
 		, address const& addr);
 
-	TORRENT_EXTRA_EXPORT address get_default_gateway(io_service& ios, error_code& ec);
+	// returns the first default gateway found if device is empty
+	TORRENT_EXTRA_EXPORT address get_default_gateway(io_service& ios
+		, string_view device, bool v6, error_code& ec);
 
 	// attempt to bind socket to the device with the specified name. For systems
 	// that don't support SO_BINDTODEVICE the socket will be bound to one of the

include/libtorrent/natpmp.hpp

@@ -51,7 +51,7 @@ struct TORRENT_EXTRA_EXPORT natpmp
 {
 	natpmp(io_service& ios, aux::portmap_callback& cb);
 
-	void start();
+	void start(address const& local_address, std::string device);
 
 	// maps the ports, if a port is set to 0
 	// it will not be mapped

src/enum_net.cpp

@@ -846,11 +846,17 @@ int _System __libsocket_sysctl(int* mib, u_int namelen, void *oldp, size_t *oldl
 		return ret;
 	}
 
-	address get_default_gateway(io_service& ios, error_code& ec)
+	address get_default_gateway(io_service& ios
+		, string_view device, bool v6, error_code& ec)
 	{
 		std::vector<ip_route> ret = enum_routes(ios, ec);
 		auto const i = std::find_if(ret.begin(), ret.end()
-			, [](ip_route const& r) { return r.destination == address(); });
+			, [device,v6](ip_route const& r)
+		{
+			return r.destination.is_unspecified()
+				&& r.destination.is_v6() == v6
+				&& (device.empty() || r.name == device);
+		});
 		if (i == ret.end()) return address();
 		return i->gateway;
 	}

src/natpmp.cpp

@@ -76,19 +76,31 @@ natpmp::natpmp(io_service& ios
 	m_mappings.reserve(10);
 }
 
-void natpmp::start()
+void natpmp::start(address const& local_address, std::string device)
 {
 	TORRENT_ASSERT(is_single_thread());
 
 	error_code ec;
-	address const gateway = get_default_gateway(m_socket.get_io_service(), ec);
-	if (ec)
+
+	// we really want a device name to get the right default gateway
+	// try to find one even if the listen socket isn't bound to a device
+	if (device.empty())
+	{
+		device = device_for_address(local_address, m_socket.get_io_service(), ec);
+		// if this failes fall back to using the first default gateway in the
+		// routing table
+		ec.clear();
+	}
+
+	address const gateway = get_default_gateway(m_socket.get_io_service()
+		, device, local_address.is_v6(), ec);
+	if (ec || gateway.is_unspecified())
 	{
 #ifndef TORRENT_DISABLE_LOGGING
 		if (should_log())
 		{
-			log("failed to find default route: %s"
-				, convert_from_native(ec.message()).c_str());
+			log("failed to find default route for %s: %s"
+				, local_address.to_string().c_str(), convert_from_native(ec.message()).c_str());
 		}
 #endif
 		disable(ec);
@@ -109,13 +121,13 @@ void natpmp::start()
 	}
 #endif
 
-	m_socket.open(udp::v4(), ec);
+	m_socket.open(local_address.is_v4() ? udp::v4() : udp::v6(), ec);
 	if (ec)
 	{
 		disable(ec);
 		return;
 	}
-	m_socket.bind({address_v4::any(), 0}, ec);
+	m_socket.bind({local_address, 0}, ec);
 	if (ec)
 	{
 		disable(ec);

src/session_impl.cpp

@@ -1859,6 +1859,7 @@ namespace aux {
 #endif
 			if ((*remove_iter)->sock) (*remove_iter)->sock->close(ec);
 			if ((*remove_iter)->udp_sock) (*remove_iter)->udp_sock->sock.close();
+			if ((*remove_iter)->natpmp_mapper) (*remove_iter)->natpmp_mapper->close();
 			remove_iter = m_listen_sockets.erase(remove_iter);
 		}
 
@@ -1879,9 +1880,11 @@ namespace aux {
 
 				TORRENT_ASSERT((s->incoming == duplex::accept_incoming) == bool(s->sock));
 				if (s->sock) async_accept(s->sock, s->ssl);
+				if (m_settings.get_bool(settings_pack::enable_natpmp))
+					start_natpmp(*s);
 				// since this is a new socket it needs to map ports
 				// even if the caller did not request re-mapping
-				if (!map_ports) remap_ports(remap_natpmp_and_upnp, *s);
+				if (!map_ports) remap_ports(remap_upnp, *s);
 			}
 		}
 
@@ -2126,10 +2129,10 @@ namespace aux {
 		tcp::endpoint const tcp_ep = s.sock ? s.sock->local_endpoint() : tcp::endpoint();
 		udp::endpoint const udp_ep = s.udp_sock ? s.udp_sock->sock.local_endpoint() : udp::endpoint();
 
-		if ((mask & remap_natpmp) && m_natpmp)
+		if ((mask & remap_natpmp) && s.natpmp_mapper)
 		{
-			map_port(*m_natpmp, portmap_protocol::tcp, tcp_ep, s.tcp_port_mapping[0]);
-			map_port(*m_natpmp, portmap_protocol::udp, to_tcp(udp_ep), s.udp_port_mapping[0]);
+			map_port(*s.natpmp_mapper, portmap_protocol::tcp, tcp_ep, s.tcp_port_mapping[0]);
+			map_port(*s.natpmp_mapper, portmap_protocol::udp, to_tcp(udp_ep), s.udp_port_mapping[0]);
 		}
 		if ((mask & remap_upnp) && m_upnp)
 		{
@@ -5450,6 +5453,23 @@ namespace aux {
 			m_alerts.emplace_alert<lsd_peer_alert>(t->get_handle(), peer);
 	}
 
+	void session_impl::start_natpmp(aux::listen_socket_t& s)
+	{
+		// don't create mappings for local IPv6 addresses
+		// they can't be reached from outside of the local network anyways
+		if (is_v6(s.local_endpoint) && is_local(s.local_endpoint.address()))
+			return;
+
+		if (!s.natpmp_mapper)
+		{
+			// the natpmp constructor may fail and call the callbacks
+			// into the session_impl.
+			s.natpmp_mapper = std::make_shared<natpmp>(m_io_service, *this);
+			s.natpmp_mapper->start(s.local_endpoint.address(), s.device);
+		}
+		remap_ports(remap_natpmp, s);
+	}
+
 	namespace {
 		bool find_tcp_port_mapping(portmap_transport const transport
 			, port_mapping_t mapping, std::shared_ptr<listen_socket_t> const& ls)
@@ -6646,22 +6666,11 @@ namespace aux {
 			m_alerts.emplace_alert<lsd_error_alert>(ec);
 	}
 
-	natpmp* session_impl::start_natpmp()
+	void session_impl::start_natpmp()
 	{
 		INVARIANT_CHECK;
-
-		if (m_natpmp) return m_natpmp.get();
-
-		// the natpmp constructor may fail and call the callbacks
-		// into the session_impl.
-		m_natpmp = std::make_shared<natpmp>(m_io_service, *this);
-		m_natpmp->start();
-
 		for (auto& s : m_listen_sockets)
-		{
-			remap_ports(remap_natpmp, *s);
-		}
-		return m_natpmp.get();
+			start_natpmp(*s);
 	}
 
 	upnp* session_impl::start_upnp()
@@ -6694,15 +6703,21 @@ namespace aux {
 		port_mapping_t ret{-1};
 		if (m_upnp) ret = m_upnp->add_mapping(t, external_port
 			, tcp::endpoint({}, static_cast<std::uint16_t>(local_port)));
-		if (m_natpmp) ret = m_natpmp->add_mapping(t, external_port
-			, tcp::endpoint({}, static_cast<std::uint16_t>(local_port)));
+		for (auto& s : m_listen_sockets)
+		{
+			if (s->natpmp_mapper) ret = s->natpmp_mapper->add_mapping(t, external_port
+				, tcp::endpoint({}, static_cast<std::uint16_t>(local_port)));
+		}
 		return ret;
 	}
 
 	void session_impl::delete_port_mapping(port_mapping_t handle)
 	{
 		if (m_upnp) m_upnp->delete_mapping(handle);
-		if (m_natpmp) m_natpmp->delete_mapping(handle);
+		for (auto& s : m_listen_sockets)
+		{
+			if (s->natpmp_mapper) s->natpmp_mapper->delete_mapping(handle);
+		}
 	}
 
 	void session_impl::stop_ip_notifier()
@@ -6722,16 +6737,14 @@ namespace aux {
 
 	void session_impl::stop_natpmp()
 	{
-		if (!m_natpmp) return;
-
-		m_natpmp->close();
 		for (auto& s : m_listen_sockets)
 		{
 			s->tcp_port_mapping[0] = port_mapping_t{-1};
 			s->udp_port_mapping[0] = port_mapping_t{-1};
+			if (!s->natpmp_mapper) continue;
+			s->natpmp_mapper->close();
+			s->natpmp_mapper.reset();
 		}
-
-		m_natpmp.reset();
 	}
 
 	void session_impl::stop_upnp()

test/enum_if.cpp

@@ -42,7 +42,7 @@ int main()
 	io_service ios;
 	error_code ec;
 
-	address def_gw = get_default_gateway(ios, ec);
+	address def_gw = get_default_gateway(ios, "", false, ec);
 	if (ec)
 	{
 		std::printf("%s\n", ec.message().c_str());