merged changes from RC_1_0

ChangeLog

@@ -27,6 +27,7 @@
 	* almost completely changed the storage interface (for custom storage)
 	* added support for hashing pieces in multiple threads
 
+	* made uTP re-enter slow-start after time-out
 	* fixed uTP upload performance issue
 	* fix missing support for DHT put salt
 
@@ -96,6 +97,7 @@
 	* fix uTP edge case where udp socket buffer fills up
 	* fix nagle implementation in uTP
 
+	* fixed bug in add_torrent_alert::message for magnet links
 	* disable optimistic disconnects when connection limit is low
 	* improved error handling of session::listen_on
 	* suppress initial 'completed' announce to trackers added with replace_trackers

src/alert.cpp

@@ -522,19 +522,22 @@ namespace libtorrent {
 	std::string add_torrent_alert::message() const
 	{
 		char msg[600];
+		char info_hash[41];
+		char const* torrent_name = info_hash;
+		if (params.ti) torrent_name = params.ti->name().c_str();
+		else if (!params.name.empty()) torrent_name = params.name.c_str();
+		else if (!params.url.empty()) torrent_name = params.url.c_str();
+		else to_hex((const char*)&params.info_hash[0], 20, info_hash);
+
 		if (error)
 		{
-			snprintf(msg, sizeof(msg), "failed to add torrent: %s"
+			snprintf(msg, sizeof(msg), "failed to add torrent \"%s\": [%s] %s"
+				, torrent_name, error.category().name()
 				, convert_from_native(error.message()).c_str());
 		}
 		else
 		{
-			snprintf(msg, sizeof(msg), "added torrent: %s"
-				, !params.url.empty() ? params.url.c_str()
-				: params.ti ? params.ti->name().c_str()
-				: !params.name.empty() ? params.name.c_str()
-				: !params.uuid.empty() ? params.uuid.c_str()
-				: "");
+			snprintf(msg, sizeof(msg), "added torrent: %s", torrent_name);
 		}
 		return msg;
 	}

src/utp_stream.cpp

@@ -236,6 +236,7 @@ struct utp_socket_impl
 		, m_timeout(time_now_hires() + milliseconds(m_sm->connect_timeout()))
 		, m_last_history_step(time_now_hires())
 		, m_cwnd(TORRENT_ETHERNET_MTU << 16)
+		, m_ssthres(0)
 		, m_buffered_incoming_bytes(0)
 		, m_reply_micro(0)
 		, m_adv_wnd(TORRENT_ETHERNET_MTU)
@@ -438,6 +439,11 @@ struct utp_socket_impl
 	timestamp_history m_delay_hist;
 	timestamp_history m_their_delay_hist;
 
+	// the slow-start threshold. This is the congestion window size (m_cwnd)
+	// in bytes the last time we left slow-start mode. This is used as a
+	// threshold to leave slow-start earlier next time, to avoid packet-loss
+	boost::int32_t m_ssthres;
+
 	// the number of bytes we have buffered in m_inbuf
 	boost::int32_t m_buffered_incoming_bytes;
 
@@ -2153,6 +2159,14 @@ void utp_socket_impl::experienced_loss(int seq_nr)
 	// same packet again, ignore it.
 	if (compare_less_wrap(seq_nr, m_loss_seq_nr + 1, ACK_MASK)) return;
 	
+	// if we happen to be in slow-start mode, we need to leave it
+	if (m_slow_start)
+	{
+		m_ssthres = m_cwnd >> 16;
+		m_slow_start = false;
+		UTP_LOGV("%8p: experienced loss, slow_start -> 0\n", this);
+	}
+
 	// cut window size in 2
 	m_cwnd = (std::max)(m_cwnd * m_sm->loss_multiplier() / 100, boost::int64_t(m_mtu << 16));
 	m_loss_seq_nr = m_seq_nr;
@@ -2161,8 +2175,6 @@ void utp_socket_impl::experienced_loss(int seq_nr)
 	// the window size could go below one MMS here, if it does,
 	// we'll get a timeout in about one second
 	
-	// if we happen to be in slow-start mode, we need to leave it
-	m_slow_start = false;
 	m_sm->inc_stats_counter(counters::utp_packet_loss);
 }
 
@@ -3062,6 +3074,7 @@ bool utp_socket_impl::incoming_packet(boost::uint8_t const* buf, int size
 					"send_buffer:%d "
 					"recv_buffer:%d "
 					"fast_resend_seq_nr:%d "
+					"ssthres:%d "
 					"\n"
 					, this
 					, sample
@@ -3093,7 +3106,8 @@ bool utp_socket_impl::incoming_packet(boost::uint8_t const* buf, int size
 					, min_rtt / 1000
 					, m_write_buffer_size
 					, m_read_buffer_size
-					, m_fast_resend_seq_nr);
+					, m_fast_resend_seq_nr
+					, m_ssthres);
 			}
 #endif
 
@@ -3222,10 +3236,13 @@ void utp_socket_impl::do_ledbat(int acked_bytes, int delay, int in_flight)
 	if (delay >= target_delay)
 	{
 		if (m_slow_start)
+		{
 			UTP_LOGV("%8p: off_target: %d slow_start -> 0\n", this, target_delay - delay);
+			m_ssthres = m_cwnd >> 16;
+			m_slow_start = false;
+		}
 
 		m_sm->inc_stats_counter(counters::utp_samples_above_target);
-		m_slow_start = false;
 	}
 	else
 	{
@@ -3239,11 +3256,25 @@ void utp_socket_impl::do_ledbat(int acked_bytes, int delay, int in_flight)
 	// congestion window), don't adjust it at all.
 	if (cwnd_saturated)
 	{
+		boost::int64_t exponential_gain = boost::int64_t(acked_bytes) << 16;
 		if (m_slow_start)
 		{
 			// mimic TCP slow-start by adding the number of acked
 			// bytes to cwnd
-			scaled_gain = (std::max)(boost::int64_t(acked_bytes) << 16, linear_gain);
+			if (m_ssthres != 0 && ((m_cwnd + exponential_gain) >> 16) > m_ssthres)
+			{
+				// if we would exeed the slow start threshold by growing the cwnd
+				// exponentially, don't do it, and leave slow-start mode. This
+				// make us avoid causing more delay and/or packet loss by being too
+				// aggressive
+				m_slow_start = false;
+				scaled_gain = linear_gain;
+				UTP_LOGV("%8p: cwnd > ssthres (%d) slow_start -> 0\n", this, m_ssthres);
+			}
+			else
+			{
+				scaled_gain = (std::max)(exponential_gain, linear_gain);
+			}
 		}
 		else
 		{
@@ -3288,7 +3319,11 @@ void utp_socket_impl::do_ledbat(int acked_bytes, int delay, int in_flight)
 	}
 
 	if ((m_cwnd >> 16) >= m_adv_wnd)
+	{
 		m_slow_start = false;
+		UTP_LOGV("%8p: cwnd > advertized wnd (%d) slow_start -> 0\n"
+			, this, m_adv_wnd);
+	}
 }
 
 void utp_stream::bind(endpoint_type const& ep, error_code& ec) { }
@@ -3390,6 +3425,13 @@ void utp_socket_impl::tick(ptime now)
 		// timed out
 		m_loss_seq_nr = m_seq_nr;
 
+		// when we time out, the cwnd is reset to 1 MSS, which means we
+		// need to ramp it up quickly again. enter slow start mode. This time
+		// we're very likely to have an ssthres set, which will make us leave
+		// slow start before inducing more delay or loss.
+		m_slow_start = true;
+		UTP_LOGV("%8p: timeout slow_start -> 1\n", this);
+
 		// we need to go one past m_seq_nr to cover the case
 		// where we just sent a SYN packet and then adjusted for
 		// the uTorrent sequence number reuse

tools/parse_utp_log.py

@@ -71,6 +71,7 @@ metrics = {
 	'their_delay':['their delay (ms)', 'x1y2', delay_samples],
 	'get_microseconds':['clock (us)', 'x1y1', 'steps'],
 	'wnduser':['advertised window size (B)', 'x1y1', 'steps'],
+	'ssthres':['slow-start threshold (B)', 'x1y1', 'steps'],
 
 	'delay_base':['delay base (us)', 'x1y1', delay_base],
 	'their_delay_base':['their delay base (us)', 'x1y1', delay_base],
@@ -204,7 +205,7 @@ plot = [
 		'y2': 'Time (ms)'
 	},
 	{
-		'data': ['max_window', 'cur_window', 'our_delay', 'target_delay'],
+		'data': ['max_window', 'cur_window', 'our_delay', 'target_delay', 'ssthres'],
 		'title': 'cwnd',
 		'y1': 'Bytes',
 		'y2': 'Time (ms)'