improve dht error reporting

include/libtorrent/alert_types.hpp

@@ -1906,6 +1906,33 @@ namespace libtorrent
 		feed_item item;
 	};
 
+	// posted when something fails in the DHT. This is not necessarily a fatal
+	// error, but it could prevent proper operation
+	struct TORRENT_EXPORT dht_error_alert: alert
+	{
+		// internal
+		dht_error_alert(int op, error_code const& ec)
+			: error(ec), operation(op_t(op)) {}
+		
+		TORRENT_DEFINE_ALERT(dht_error_alert);
+
+		const static int static_category = alert::error_notification
+			| alert::dht_notification;
+		virtual std::string message() const;
+
+		// the error code
+		error_code error;
+
+		enum op_t
+		{
+			unknown,
+			hostname_lookup
+		};
+
+		// the operation that failed
+		op_t operation;
+	};
+
 
 #undef TORRENT_DEFINE_ALERT
 

src/alert.cpp

@@ -538,5 +538,26 @@ namespace libtorrent {
 			, error.category().name(), convert_from_native(error.message()).c_str());
 		return msg;
 	}
+
+	std::string dht_error_alert::message() const
+	{
+		const static char* const operation_names[] =
+		{
+			"unknown"
+			"hostname lookup"
+		};
+
+		int op = operation;
+		if (op < 0 || op > sizeof(operation_names)/sizeof(operation_names[0]))
+			op = 0;
+
+		char msg[600];
+		snprintf(msg, sizeof(msg), "DHT error [%s] (%d) %s"
+			, operation_names[op]
+			, error.value()
+			, convert_from_native(error.message()).c_str());
+		return msg;
+	}
+
 } // namespace libtorrent
 

src/session_impl.cpp

@@ -5750,8 +5750,14 @@ retry:
 #if defined TORRENT_ASIO_DEBUGGING
 		complete_async("session_impl::on_dht_router_name_lookup");
 #endif
-		// TODO: 1 report errors as alerts
-		if (e) return;
+		if (e)
+		{
+			if (m_alerts.should_post<dht_error_alert>())
+				m_alerts.post_alert(dht_error_alert(
+					dht_error_alert::hostname_lookup, e));
+			return;
+		}
+
 		while (host != tcp::resolver::iterator())
 		{
 			// router nodes should be added before the DHT is started (and bootstrapped)

src/utp_stream.cpp

@@ -1900,8 +1900,7 @@ bool utp_socket_impl::send_pkt(int flags)
 		m_mtu_ceiling = p->size - 1;
 		if (m_mtu_floor > m_mtu_ceiling) m_mtu_floor = m_mtu_ceiling;
 		update_mtu_limits();
-		// TODO: 2 we might want to do something else here
-		// as well, to resend the packet immediately without
+		// resend the packet immediately without
 		// it being an MTU probe
 		p->mtu_probe = false;
 		if (m_mtu_seq == m_ack_nr)