Timeouts silent incoming connections

Timeouts silent incoming connections
Adds new stat counters:
- tcp_silent_connection_drop
- tcp_io_timeout_drop

nano/core_test/socket.cpp

@@ -351,6 +351,34 @@ TEST (socket, disabled_max_peers_per_ip)
 	node->stop ();
 }
 
+TEST (socket, disconnection_of_silent_connections)
+{
+	nano::system system;
+	auto node = system.add_node ();
+	auto socket = std::make_shared<nano::socket> (*node);
+	// Classify the socket type as real-time as the disconnections are done only for this connection type.
+	socket->type_set (nano::socket::type_t::realtime);
+	// Silent connections are connections open by external peers that don't contribute with any data.
+	socket->set_silent_connection_tolerance_time (std::chrono::seconds{ 5 });
+	auto bootstrap_endpoint = node->bootstrap.endpoint ();
+	std::atomic<bool> connected{ false };
+	// Opening a connection that will be closed because it remains silent during the tolerance time.
+	socket->async_connect (bootstrap_endpoint, [socket, &connected] (boost::system::error_code const & ec) {
+		ASSERT_FALSE (ec);
+		connected = true;
+	});
+	ASSERT_TIMELY (4s, connected);
+	// Checking the connection was closed.
+	ASSERT_TIMELY (10s, socket->is_closed ());
+
+	auto get_tcp_silent_connection_drops = [&node] () {
+		return node->stats.count (nano::stat::type::tcp, nano::stat::detail::tcp_silent_connection_drop, nano::stat::dir::in);
+	};
+	ASSERT_EQ (1, get_tcp_silent_connection_drops ());
+
+	node->stop ();
+}
+
 TEST (socket, drop_policy)
 {
 	auto node_flags = nano::inactive_node_flag_defaults ();

nano/lib/config.hpp

@@ -156,6 +156,7 @@ class network_constants
 		request_interval_ms = is_dev_network () ? 20 : 500;
 		cleanup_period = is_dev_network () ? std::chrono::seconds (1) : std::chrono::seconds (60);
 		idle_timeout = is_dev_network () ? cleanup_period * 15 : cleanup_period * 2;
+		silent_connection_tolerance_time = std::chrono::seconds (120);
 		syn_cookie_cutoff = std::chrono::seconds (5);
 		bootstrap_interval = std::chrono::seconds (15 * 60);
 		max_peers_per_ip = is_dev_network () ? 10 : 5;
@@ -189,6 +190,7 @@ class network_constants
 	}
 	/** Default maximum idle time for a socket before it's automatically closed */
 	std::chrono::seconds idle_timeout;
+	std::chrono::seconds silent_connection_tolerance_time;
 	std::chrono::seconds syn_cookie_cutoff;
 	std::chrono::seconds bootstrap_interval;
 	/** Maximum number of peers per IP. It is also the max number of connections per IP */

nano/node/bootstrap/bootstrap_server.cpp

@@ -749,5 +749,5 @@ bool nano::bootstrap_server::is_bootstrap_connection ()
 
 bool nano::bootstrap_server::is_realtime_connection ()
 {
-	return socket->type () == nano::socket::type_t::realtime || socket->type () == nano::socket::type_t::realtime_response_server;
+	return socket->is_realtime_connection ();
 }

nano/node/socket.cpp

@@ -21,7 +21,9 @@ nano::socket::socket (nano::node & node_a) :
 	node{ node_a },
 	next_deadline{ std::numeric_limits<uint64_t>::max () },
 	last_completion_time{ 0 },
-	io_timeout{ node_a.config.tcp_io_timeout }
+	last_receive_time{ 0 },
+	io_timeout{ node_a.config.tcp_io_timeout },
+	silent_connection_tolerance_time{ node_a.network_params.network.silent_connection_tolerance_time }
 {
 }
 
@@ -58,6 +60,7 @@ void nano::socket::async_read (std::shared_ptr<std::vector<uint8_t>> const & buf
 				[this_l, buffer_a, callback_a] (boost::system::error_code const & ec, std::size_t size_a) {
 					this_l->node.stats.add (nano::stat::type::traffic_tcp, nano::stat::dir::in, size_a);
 					this_l->stop_timer ();
+					this_l->update_last_receive_time ();
 					callback_a (ec, size_a);
 				}));
 			}));
@@ -124,14 +127,30 @@ void nano::socket::stop_timer ()
 	last_completion_time = nano::seconds_since_epoch ();
 }
 
+void nano::socket::update_last_receive_time ()
+{
+	last_receive_time = nano::seconds_since_epoch ();
+}
+
 void nano::socket::checkup ()
 {
 	std::weak_ptr<nano::socket> this_w (shared_from_this ());
 	node.workers.add_timed_task (std::chrono::steady_clock::now () + std::chrono::seconds (2), [this_w] () {
 		if (auto this_l = this_w.lock ())
 		{
 			uint64_t now (nano::seconds_since_epoch ());
+			auto condition_to_disconnect{ false };
+			if (this_l->is_realtime_connection () && now - this_l->last_receive_time > this_l->silent_connection_tolerance_time.count ())
+			{
+				this_l->node.stats.inc (nano::stat::type::tcp, nano::stat::detail::tcp_silent_connection_drop, nano::stat::dir::in);
+				condition_to_disconnect = true;
+			}
 			if (this_l->next_deadline != std::numeric_limits<uint64_t>::max () && now - this_l->last_completion_time > this_l->next_deadline)
+			{
+				this_l->node.stats.inc (nano::stat::type::tcp, nano::stat::detail::tcp_io_timeout_drop, nano::stat::dir::in);
+				condition_to_disconnect = true;
+			}
+			if (condition_to_disconnect)
 			{
 				if (this_l->node.config.logging.network_timeout_logging ())
 				{
@@ -164,6 +183,14 @@ void nano::socket::timeout_set (std::chrono::seconds io_timeout_a)
 	io_timeout = io_timeout_a;
 }
 
+void nano::socket::set_silent_connection_tolerance_time (std::chrono::seconds tolerance_time_a)
+{
+	auto this_l (shared_from_this ());
+	boost::asio::dispatch (strand, boost::asio::bind_executor (strand, [this_l, tolerance_time_a] () {
+		this_l->silent_connection_tolerance_time = tolerance_time_a;
+	}));
+}
+
 void nano::socket::close ()
 {
 	auto this_l (shared_from_this ());

nano/node/socket.hpp

@@ -72,6 +72,7 @@ class socket : public std::enable_shared_from_this<nano::socket>
 	/** This can be called to change the maximum idle time, e.g. based on the type of traffic detected. */
 	void timeout_set (std::chrono::seconds io_timeout_a);
 	void start_timer (std::chrono::seconds deadline_a);
+	void set_silent_connection_tolerance_time (std::chrono::seconds tolerance_time_a);
 	bool max () const
 	{
 		return queue_size >= queue_size_max;
@@ -88,6 +89,14 @@ class socket : public std::enable_shared_from_this<nano::socket>
 	{
 		type_m = type_a;
 	}
+	bool is_realtime_connection ()
+	{
+		return type () == nano::socket::type_t::realtime || type () == nano::socket::type_t::realtime_response_server;
+	}
+	bool is_closed ()
+	{
+		return closed;
+	}
 
 protected:
 	/** Holds the buffer and callback for queued writes */
@@ -107,8 +116,10 @@ class socket : public std::enable_shared_from_this<nano::socket>
 
 	std::atomic<uint64_t> next_deadline;
 	std::atomic<uint64_t> last_completion_time;
+	std::atomic<uint64_t> last_receive_time;
 	std::atomic<bool> timed_out{ false };
 	std::atomic<std::chrono::seconds> io_timeout;
+	std::chrono::seconds silent_connection_tolerance_time;
 	std::atomic<std::size_t> queue_size{ 0 };
 
 	/** Set by close() - completion handlers must check this. This is more reliable than checking
@@ -117,6 +128,7 @@ class socket : public std::enable_shared_from_this<nano::socket>
 	void close_internal ();
 	void start_timer ();
 	void stop_timer ();
+	void update_last_receive_time ();
 	void checkup ();
 
 private: