support for adjusting the socket buffer sizes through session_settings

ChangeLog

@@ -1,3 +1,5 @@
+	* added support for changing socket buffer sizes through
+	  session_settings
 	* added support for merkle hash tree torrents (.merkle.torrent)
 	* added 'seed mode', which assumes that all files are complete
 	  and checks hashes lazily, as blocks are requested

docs/manual.rst

@@ -3357,6 +3357,9 @@ that will be sent to the tracker. The user-agent is a good way to identify your
 		bool lock_disk_cache;
 
 		int max_rejects;
+
+		int recv_socket_buffer_size;
+		int send_socket_buffer_size;
 	};
 
 ``user_agent`` this is the client identification to the tracker.
@@ -3702,6 +3705,13 @@ while a peer is choked before the peer is considered abusive and is
 disconnected.
 
 
+``recv_socket_buffer_size`` and ``send_socket_buffer_size`` specifies
+the buffer sizes set on peer sockets. 0 (which is the default) means
+the OS default (i.e. don't change the buffer sizes). The socket buffer
+sizes are changed using setsockopt() with SOL_SOCKET/SO_RCVBUF and
+SO_SNDBUFFER.
+
+
 pe_settings
 ===========
 

include/libtorrent/aux_/session_impl.hpp

@@ -346,6 +346,7 @@ namespace libtorrent
 			void dht_state_callback(boost::condition& c
 				, entry& e, bool& done) const;
 			void on_lsd_peer(tcp::endpoint peer, sha1_hash const& ih);
+			void setup_socket_buffers(socket_type& s);
 
 #ifndef TORRENT_DISABLE_POOL_ALLOCATOR
 			// this pool is used to allocate and recycle send

include/libtorrent/session_settings.hpp

@@ -161,6 +161,8 @@ namespace libtorrent
 			, lock_disk_cache(true)
 #endif
 			, max_rejects(50)
+			, recv_socket_buffer_size(0)
+			, send_socket_buffer_size(0)
 		{}
 
 		// this is the user agent that will be sent to the tracker
@@ -534,6 +536,11 @@ namespace libtorrent
 		// the number of times to reject requests while being
 		// choked before disconnecting a peer for being malicious
 		int max_rejects;
+
+		// sets the socket send and receive buffer sizes
+		// 0 means OS default
+		int recv_socket_buffer_size;
+		int send_socket_buffer_size;
 	};
 
 #ifndef TORRENT_DISABLE_DHT

src/session_impl.cpp

@@ -1006,6 +1006,8 @@ namespace aux {
 		  	return;
 		}
 
+		setup_socket_buffers(*s);
+
 		boost::intrusive_ptr<peer_connection> c(
 			new bt_peer_connection(*this, s, endp, 0));
 #ifdef TORRENT_DEBUG
@@ -1019,6 +1021,23 @@ namespace aux {
 		}
 	}
 
+	void session_impl::setup_socket_buffers(socket_type& s)
+	{
+		error_code ec;
+		if (m_settings.send_socket_buffer_size)
+		{
+			boost::asio::socket_base::send_buffer_size option(
+				m_settings.send_socket_buffer_size);
+			s.set_option(option, ec);
+		}
+		if (m_settings.recv_socket_buffer_size)
+		{
+			boost::asio::socket_base::receive_buffer_size option(
+				m_settings.recv_socket_buffer_size);
+			s.set_option(option, ec);
+		}
+	}
+
 	void session_impl::on_socks_accept(boost::shared_ptr<socket_type> const& s
 		, error_code const& e)
 	{

src/torrent.cpp

@@ -3519,6 +3519,8 @@ namespace libtorrent
 		(void)ret;
 		TORRENT_ASSERT(ret);
 
+		m_ses.setup_socket_buffers(*s);
+
 		boost::intrusive_ptr<peer_connection> c(new bt_peer_connection(
 			m_ses, shared_from_this(), s, a, peerinfo));