remove functionality to initiate MTU based on the MTU on the nic (this is error prone and has questionable value)

include/libtorrent/settings_pack.hpp

@@ -477,16 +477,6 @@ namespace libtorrent
 			// libtorrent API.
 			report_web_seed_downloads,
 
-			// controls if the uTP socket manager is allowed to increase the
-			// socket buffer if a network interface with a large MTU is used (such
-			// as loopback or ethernet jumbo frames). This defaults to true and
-			// might improve uTP throughput. For RAM constrained systems,
-			// disabling this typically saves around 30kB in user space and
-			// probably around 400kB in kernel socket buffers (it adjusts the send
-			// and receive buffer size on the kernel socket, both for IPv4 and
-			// IPv6).
-			utp_dynamic_sock_buf,
-
 			// set to true if uTP connections should be rate limited This option
 			// is *DEPRECATED*, please use set_peer_class_filter() instead.
 #ifndef TORRENT_NO_DEPRECATE

include/libtorrent/utp_socket_manager.hpp

@@ -87,7 +87,6 @@ namespace libtorrent
 		int connect_timeout() const { return m_sett.get_int(settings_pack::utp_connect_timeout); }
 		int min_timeout() const { return m_sett.get_int(settings_pack::utp_min_timeout); }
 		int loss_multiplier() const { return m_sett.get_int(settings_pack::utp_loss_multiplier); }
-		bool allow_dynamic_sock_buf() const { return m_sett.get_bool(settings_pack::utp_dynamic_sock_buf); }
 
 		void mtu_for_dest(address const& addr, int& link_mtu, int& utp_mtu);
 		void set_sock_buf(int size);

src/session.cpp

@@ -167,9 +167,6 @@ namespace libtorrent
 		// whole pieces
 		set.set_bool(settings_pack::coalesce_reads, false);
 		set.set_bool(settings_pack::coalesce_writes, false);
-
-		// disallow the buffer size to grow for the uTP socket
-		set.set_bool(settings_pack::utp_dynamic_sock_buf, false);
 	}
 
 	TORRENT_EXPORT void high_performance_seed(settings_pack& set)
@@ -281,9 +278,6 @@ namespace libtorrent
 		// connect to us if they want to
 		set.set_int(settings_pack::max_failcount, 1);
 
-		// allow the buffer size to grow for the uTP socket
-		set.set_bool(settings_pack::utp_dynamic_sock_buf, true);
-
 		// we're likely to have more than 4 cores on a high
 		// performance machine. One core is needed for the
 		// network thread

src/settings_pack.cpp

@@ -185,7 +185,6 @@ namespace libtorrent
 		SET(no_recheck_incomplete_resume, false, 0),
 		SET(anonymous_mode, false, &session_impl::update_anonymous_mode),
 		SET(report_web_seed_downloads, true, &session_impl::update_report_web_seed_downloads),
-		SET(utp_dynamic_sock_buf, true, 0),
 		DEPRECATED_SET(rate_limit_utp, false, &session_impl::update_rate_limit_utp),
 		SET(announce_double_nat, false, 0),
 		SET(seeding_outgoing_connections, true, 0),

src/utp_socket_manager.cpp

@@ -90,34 +90,10 @@ namespace libtorrent
 
 	void utp_socket_manager::mtu_for_dest(address const& addr, int& link_mtu, int& utp_mtu)
 	{
-		if (aux::time_now() - seconds(60) > m_last_route_update)
-		{
-			m_last_route_update = aux::time_now();
-			error_code ec;
-			m_routes = enum_routes(m_sock.get_io_service(), ec);
-		}
 
 		int mtu = 0;
-		if (!m_routes.empty())
-		{
-			for (std::vector<ip_route>::iterator i = m_routes.begin()
-				, end(m_routes.end()); i != end; ++i)
-			{
-				if (!match_addr_mask(addr, i->destination, i->netmask)) continue;
-
-				// assume that we'll actually use the route with the largest
-				// MTU (seems like a reasonable assumption).
-				// this could however be improved by using the route metrics
-				// and the prefix length of the netmask to order the matches
-				if (mtu < i->mtu) mtu = i->mtu;
-			}
-		}
-
-		if (mtu == 0)
-		{
 		if (is_teredo(addr)) mtu = TORRENT_TEREDO_MTU;
 		else mtu = TORRENT_ETHERNET_MTU;
-		}
 
 #if defined __APPLE__
 		// apple has a very strange loopback. It appears you can't

src/utp_stream.cpp

@@ -2646,17 +2646,7 @@ void utp_socket_impl::init_mtu(int link_mtu, int utp_mtu)
 {
 	INVARIANT_CHECK;
 
-	// if we're in a RAM constrained environment, don't increase
+	if (link_mtu > TORRENT_ETHERNET_MTU)
-	// the buffer size for interfaces with large MTUs. Just stick
-	// to ethernet frame sizes
-	if (m_sm->allow_dynamic_sock_buf())
-	{
-		// Make sure that we have enough socket buffer space
-		// for sending and receiving packets of this size
-		// add 10% for smaller ACKs and other overhead
-		m_sm->set_sock_buf(link_mtu * 11 / 10);
-	}
-	else if (link_mtu > TORRENT_ETHERNET_MTU)
 	{
 		// we can't use larger packets than this since we're
 		// not allocating any more memory for socket buffers

test/test_utp.cpp

@@ -81,7 +81,6 @@ void test_transfer()
 	pack.set_bool(settings_pack::announce_to_all_trackers, true);
 	pack.set_bool(settings_pack::announce_to_all_tiers, true);
 	pack.set_bool(settings_pack::prefer_udp_trackers, false);
-	pack.set_bool(settings_pack::utp_dynamic_sock_buf, true);
 	pack.set_int(settings_pack::min_reconnect_time, 1);
 	pack.set_str(settings_pack::listen_interfaces, "0.0.0.0:48885");
 	lt::session ses1(pack);