start torrent on incoming connection feature

ChangeLog

@@ -14,6 +14,8 @@
 	* support variable number of optimistic unchoke slots and to dynamically
 	  adjust based on the total number of unchoke slots
 	* support for BitTyrant choker algorithm
+	* support for automatically start torrents when they receive an
+	  incoming connection
 
 0.15 release
 

bindings/python/src/session_settings.cpp

@@ -113,6 +113,7 @@ void bind_session_settings()
         .def_readwrite("udp_tracker_token_expiry", &session_settings::udp_tracker_token_expiry)
         .def_readwrite("volatile_read_cache", &session_settings::volatile_read_cache)
         .def_readwrite("guided_read_cache", &session_settings::guided_read_cache)
+        .def_readwrite("incoming_starts_queued_torrents", &session_settings::incoming_starts_queued_torrents)
     ;
 
     enum_<proxy_settings::proxy_type>("proxy_type")
@@ -129,7 +130,7 @@ void bind_session_settings()
         .value("largest_contiguous", session_settings::largest_contiguous)
     ;
 
-    enum_<session_settings::disk_cache_algo_t>("choking_algorithm_t")
+    enum_<session_settings::choking_algorithm_t>("choking_algorithm_t")
         .value("fixed_slots_choker", session_settings::fixed_slots_choker)
         .value("auto_expand_choker", session_settings::auto_expand_choker)
         .value("rate_based_choker", session_settings::rate_based_choker)

docs/manual.rst

@@ -3764,6 +3764,8 @@ session_settings
 		bool volatile_read_cache;
 		bool guided_read_cache;
 		bool default_min_cache_age;
+
+		bool incoming_starts_queued_torrents;
 	};
 
 ``user_agent`` this is the client identification to the tracker.
@@ -4294,6 +4296,16 @@ fewer packets have to be sent to the UDP tracker. In order for higher
 values to work, the tracker needs to be configured to match the
 expiration time for tokens.
 
+``incoming_starts_queued_torrents`` defaults to false. If a torrent
+has been paused by the auto managed feature in libtorrent, i.e.
+the torrent is paused and auto managed, this feature affects whether
+or not it is automatically started on an incoming connection. The
+main reason to queue torrents, is not to make them unavailable, but
+to save on the overhead of announcing to the trackers, the DHT and to
+avoid spreading one's unchoke slots too thin. If a peer managed to
+find us, even though we're no in the torrent anymore, this setting
+can make us start the torrent and serve it.
+
 pe_settings
 ===========
 

include/libtorrent/session_settings.hpp

@@ -200,6 +200,7 @@ namespace libtorrent
 			, default_est_reciprocation_rate(16000)
 			, increase_est_reciprocation_rate(20)
 			, decrease_est_reciprocation_rate(3)
+			, incoming_starts_queued_torrents(false)
 		{}
 
 		// this is the user agent that will be sent to the tracker
@@ -752,6 +753,10 @@ namespace libtorrent
 		// our estimate of the reciprocation rate, since we might have
 		// over-estimated it
 		int decrease_est_reciprocation_rate;
+
+		// if set to true, an incoming connection to a torrent that's
+		// paused and auto-managed will make the torrent start.
+		bool incoming_starts_queued_torrents;
 	};
 
 #ifndef TORRENT_DISABLE_DHT

src/peer_connection.cpp

@@ -1071,10 +1071,15 @@ namespace libtorrent
 			return;
 		}
 
-		if (t->is_paused())
+		if (t->is_paused() && (!t->is_auto_managed()
+			|| !m_ses.m_settings.incoming_starts_queued_torrents
+			|| t->has_error()))
 		{
 			// paused torrents will not accept
-			// incoming connections
+			// incoming connections unless they are auto managed
+			// and inconing_starts_queued_torrents is true
+			// torrents that have errors should always reject
+			// incoming peers
 #if defined TORRENT_VERBOSE_LOGGING || defined TORRENT_ERROR_LOGGING
 			(*m_logger) << " rejected connection to paused torrent\n";
 #endif
@@ -1097,6 +1102,13 @@ namespace libtorrent
 #endif // TORRENT_USE_I2P
 
 		TORRENT_ASSERT(m_torrent.expired());
+
+		if (t->is_paused())
+		{
+			TORRENT_ASSERT(m_ses.m_settings.incoming_starts_queued_torrents);
+			t->resume();
+		}
+
 		// check to make sure we don't have another connection with the same
 		// info_hash and peer_id. If we do. close this connection.
 		t->attach_peer(this);

src/session_impl.cpp

@@ -1524,6 +1524,13 @@ namespace aux {
 		  	return;
 		}
 
+		// if we don't have any active torrents, there's no
+		// point in accepting this connection. If, however,
+		// the setting to start up queued torrents when they
+		// get an incoming connection is enabled, we cannot
+		// perform this check.
+		if (!m_settings.incoming_starts_queued_torrents)
+		{
 			bool has_active_torrent = false;
 			for (torrent_map::iterator i = m_torrents.begin()
 				, end(m_torrents.end()); i != end; ++i)
@@ -1541,6 +1548,7 @@ namespace aux {
 #endif
 			  	return;
 			}
+		}
 
 		setup_socket_buffers(*s);