simplify natpmp by requiring it to be tied to a specific network, and use get_gateway() and remove unused get_default_route() functions

include/libtorrent/enum_net.hpp

@@ -107,13 +107,6 @@ namespace libtorrent {
 	TORRENT_EXTRA_EXPORT boost::optional<address> get_gateway(
 		ip_interface const& iface, span<ip_route const> routes);
 
-	TORRENT_EXTRA_EXPORT boost::optional<ip_route> get_default_route(io_service& ios
-		, string_view device, bool v6, 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
 	// IP addresses of the specified device. In this case it is necessary to

include/libtorrent/natpmp.hpp

@@ -42,6 +42,7 @@ POSSIBILITY OF SUCH DAMAGE.
 #include "libtorrent/debug.hpp"
 #include "libtorrent/aux_/portmap.hpp"
 #include "libtorrent/aux_/vector.hpp"
+#include "libtorrent/enum_net.hpp" // for ip_interface
 
 namespace libtorrent {
 
@@ -85,7 +86,7 @@ struct TORRENT_EXTRA_EXPORT natpmp
 {
 	natpmp(io_service& ios, aux::portmap_callback& cb);
 
-	void start(address local_address, std::string device);
+	void start(ip_interface const& ip);
 
 	// maps the ports, if a port is set to 0
 	// it will not be mapped

src/enum_net.cpp

@@ -817,28 +817,6 @@ int _System __libsocket_sysctl(int* mib, u_int namelen, void *oldp, size_t *oldl
 		return {};
 	}
 
-	boost::optional<ip_route> get_default_route(io_service& ios
-		, string_view const device, bool const v6, error_code& ec)
-	{
-		std::vector<ip_route> const ret = enum_routes(ios, ec);
-		auto const i = std::find_if(ret.begin(), ret.end()
-			, [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 boost::none;
-		return *i;
-	}
-
-	address get_default_gateway(io_service& ios
-		, string_view const device, bool const v6, error_code& ec)
-	{
-		auto const default_route = get_default_route(ios, device, v6, ec);
-		return default_route ? default_route->gateway : address();
-	}
-
 	std::vector<ip_route> enum_routes(io_service& ios, error_code& ec)
 	{
 		std::vector<ip_route> ret;

src/natpmp.cpp

@@ -146,28 +146,31 @@ natpmp::natpmp(io_service& ios
 	m_mappings.reserve(10);
 }
 
-void natpmp::start(address local_address, std::string device)
+void natpmp::start(ip_interface const& ip)
 {
 	TORRENT_ASSERT(is_single_thread());
 
-	error_code ec;
-
 	// assume servers support PCP and fall back to NAT-PMP
 	// if necessary
 	m_version = version_pcp;
 
-	// we really want a device name to get the right default gateway
+	address const& local_address = ip.interface_address;
-	// try to find one even if the listen socket isn't bound to a device
+
-	if (device.empty())
+	error_code ec;
+	auto const routes = enum_routes(get_io_service(m_socket), ec);
+	if (ec)
 	{
-		device = device_for_address(local_address, get_io_service(m_socket), ec);
+#ifndef TORRENT_DISABLE_LOGGING
-		// if this fails fall back to using the first default gateway in the
+		if (should_log())
-		// routing table
+		{
-		ec.clear();
+			log("failed to enumerate routes: %s"
+				, convert_from_native(ec.message()).c_str());
+		}
+#endif
+		disable(ec);
 	}
 
-	auto const route = get_default_route(get_io_service(m_socket)
+	auto const route = get_gateway(ip, routes);
-		, device, local_address.is_v6(), ec);
 
 	if (!route)
 	{
@@ -175,7 +178,7 @@ void natpmp::start(address local_address, std::string device)
 		if (should_log())
 		{
 			log("failed to find default route for \"%s\" %s: %s"
-				, device.c_str(), local_address.to_string().c_str()
+				, ip.name, local_address.to_string().c_str()
 				, convert_from_native(ec.message()).c_str());
 		}
 #endif
@@ -183,65 +186,16 @@ void natpmp::start(address local_address, std::string device)
 		return;
 	}
 
-	if (device.empty()) device = route->name;
-
-	TORRENT_ASSERT(!device.empty());
-
-	// PCP requires reporting the source address at the application
-	// layer so the socket MUST be bound to a specific address
-	// if the caller didn't specify one then get the first suitable
-	// address from the OS
-	if (local_address.is_unspecified())
-	{
-		std::vector<ip_interface> const net = enum_net_interfaces(
-			get_io_service(m_socket), ec);
-
-		auto const it = std::find_if(net.begin(), net.end(), [&](ip_interface const& i)
-		{
-			return i.interface_address.is_v4() == local_address.is_v4()
-				&& (i.interface_address.is_v4() || !is_local(i.interface_address))
-				&& i.name == device;
-		});
-
-		if (it != net.end())
-		{
-			local_address = it->interface_address;
-		}
-		else
-		{
-			// if we can't get a specific address to bind to we'll have
-			// to fall back to NAT-PMP
-			// but NAT-PMP doesn't support IPv6 so if that's what is being
-			// requested we can't do anything
-			if (local_address.is_v6())
-			{
-				if (!ec) ec = boost::asio::error::address_family_not_supported;
-#ifndef TORRENT_DISABLE_LOGGING
-				if (should_log())
-				{
-					log("cannot map IPv6 without a local address, %s"
-						, convert_from_native(ec.message()).c_str());
-				}
-#endif
-				disable(ec);
-				return;
-			}
-
-			m_version = version_natpmp;
-			ec.clear();
-		}
-	}
-
 	m_disabled = false;
 
-	udp::endpoint const nat_endpoint(route->gateway, 5351);
+	udp::endpoint const nat_endpoint(*route, 5351);
 	if (nat_endpoint == m_nat_endpoint) return;
 	m_nat_endpoint = nat_endpoint;
 
 #ifndef TORRENT_DISABLE_LOGGING
 	if (should_log())
 	{
-		log("found router at: %s"
+		log("found gateway at: %s"
 			, print_address(m_nat_endpoint.address()).c_str());
 	}
 #endif

src/session_impl.cpp

@@ -5464,7 +5464,11 @@ namespace aux {
 			// 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);
+			ip_interface ip;
+			ip.interface_address = s.local_endpoint.address();
+			ip.netmask = s.netmask;
+			std::strncpy(ip.name, s.device.c_str(), sizeof(ip.name));
+			s.natpmp_mapper->start(ip);
 		}
 	}
 

test/enum_if.cpp

@@ -42,15 +42,6 @@ int main()
 	io_service ios;
 	error_code ec;
 
-	address def_gw = get_default_gateway(ios, "", false, ec);
-	if (ec)
-	{
-		std::printf("%s\n", ec.message().c_str());
-		return 1;
-	}
-
-	std::printf("Default gateway: %s\n", def_gw.to_string(ec).c_str());
-
 	std::printf("=========== Routes ===========\n");
 	auto const routes = enum_routes(ios, ec);
 	if (ec)