disabled feature to drop requests after having been skipped too many times

ChangeLog

@@ -90,6 +90,7 @@
 	* only keeps one outstanding duplicate request per peer
 	  reduces waste download, specifically when streaming
 
+	* disabled feature to drop requests after having been skipped too many times
 	* fixed range request bug for files larger than 2 GB in web seeds
 
 release 0.14.8

docs/manual.rst

@@ -3711,6 +3711,8 @@ session_settings
 		bool disable_hash_check;
 
 		int max_suggest_pieces;
+
+		bool drop_skipped_requests;
 	};
 
 ``user_agent`` this is the client identification to the tracker.
@@ -4140,6 +4142,16 @@ bittorrent clients.
 from a peer that's remembered. If a peer floods suggest messages, this limit
 prevents libtorrent from using too much RAM. It defaults to 10.
 
+If ``drop_skipped_requests`` is set to true (it defaults to false), piece
+requests that have been skipped enough times when piece messages
+are received, will be considered lost. Requests are considered skipped
+when the returned piece messages are re-ordered compared to the order
+of the requests. This was an attempt to get out of dead-locks caused by
+BitComet peers silently ignoring some requests. It may cause problems
+at high rates, and high level of reordering in the uploading peer, that's
+why it's disabled by default.
+
+
 pe_settings
 ===========
 

include/libtorrent/session_settings.hpp

@@ -181,6 +181,7 @@ namespace libtorrent
 			, allow_reordered_disk_operations(true)
 			, allow_i2p_mixed(false)
 			, max_suggest_pieces(10)
+			, drop_skipped_requests(false)
 		{}
 
 		// this is the user agent that will be sent to the tracker
@@ -650,6 +651,11 @@ namespace libtorrent
 		// suggest to use before we start dropping
 		// previous suggested piece
 		int max_suggest_pieces;
+
+		// if set to true, requests that have have not been
+		// satisfied after the equivalence of the entire
+		// request queue has been received, will be considered lost
+		bool drop_skipped_requests;
 	};
 
 #ifndef TORRENT_DISABLE_DHT

src/peer_connection.cpp

@@ -2153,19 +2153,28 @@ namespace libtorrent
 #if defined TORRENT_VERBOSE_LOGGING || defined TORRENT_ERROR_LOGGING
 			(*m_logger) << time_now_string()
 				<< " *** SKIPPED_PIECE [ piece: " << qe.block.piece_index << " | "
-				"b: " << qe.block.block_index << " ] ***\n";
+				"b: " << qe.block.block_index << " | skip: " << qe.skipped << " | "
+				"dqs: " << int(m_desired_queue_size) << "] ***\n";
 #endif
 
 			++qe.skipped;
 			// if the number of times a block is skipped by out of order
 			// blocks exceeds the size of the outstanding queue, assume that
 			// the other end dropped the request.
-			if (qe.skipped > m_desired_queue_size * 2)
+			if (m_ses.m_settings.drop_skipped_requests
+				&& qe.skipped > m_desired_queue_size)
+			if (qe.skipped > m_desired_queue_size)
 			{
 				if (m_ses.m_alerts.should_post<request_dropped_alert>())
 					m_ses.m_alerts.post_alert(request_dropped_alert(t->get_handle()
 						, remote(), pid(), qe.block.block_index, qe.block.piece_index));
 
+#if defined TORRENT_VERBOSE_LOGGING || defined TORRENT_ERROR_LOGGING
+				(*m_logger) << time_now_string()
+					<< " *** DROPPED_PIECE [ piece: " << qe.block.piece_index << " | "
+					"b: " << qe.block.block_index << " | skip: " << qe.skipped << " | "
+					"dqs: " << int(m_desired_queue_size) << "] ***\n";
+#endif
 				if (!qe.timed_out && !qe.not_wanted)
 					picker.abort_download(qe.block);
 
@@ -2998,7 +3007,8 @@ namespace libtorrent
 				"s: " << r.start << " | "
 				"l: " << r.length << " | "
 				"ds: " << statistics().download_rate() << " B/s | "
-				"qs: " << int(m_desired_queue_size) << " "
+				"dqs: " << int(m_desired_queue_size) << " "
+				"rqs: " << int(m_download_queue.size()) << " "
 				"blk: " << (m_request_large_blocks?"large":"single") << " ]\n";
 #endif
 		}