various fixes for potential shutdown freezes

include/libtorrent/udp_socket.hpp

@@ -134,6 +134,7 @@ namespace libtorrent
 		int m_queue_size_limit;
 		int m_rate_limit;
 		int m_quota;
+		bool m_abort;
 		ptime m_last_tick;
 		std::list<queued_packet> m_queue;
 	};

src/natpmp.cpp

@@ -299,9 +299,16 @@ void natpmp::send_map_request(int i)
 	m_socket.send_to(asio::buffer(buf, 12), m_nat_endpoint, 0, ec);
 	m.map_sent = true;
 	// linear back-off instead of exponential
-	++m_retry_count;
-	m_send_timer.expires_from_now(milliseconds(250 * m_retry_count), ec);
-	m_send_timer.async_wait(bind(&natpmp::resend_request, self(), i, _1));
+	if (m_abort)
+	{
+		try_next_mapping(i);
+	}
+	else
+	{
+		++m_retry_count;
+		m_send_timer.expires_from_now(milliseconds(250 * m_retry_count), ec);
+		m_send_timer.async_wait(bind(&natpmp::resend_request, self(), i, _1));
+	}
 }
 
 void natpmp::resend_request(int i, error_code const& e)

src/udp_socket.cpp

@@ -539,6 +539,7 @@ rate_limited_udp_socket::rate_limited_udp_socket(io_service& ios
 	, m_queue_size_limit(200)
 	, m_rate_limit(4000)
 	, m_quota(4000)
+	, m_abort(false)
 	, m_last_tick(time_now())
 {
 	error_code ec;
@@ -569,6 +570,7 @@ bool rate_limited_udp_socket::send(udp::endpoint const& ep, char const* p, int l
 void rate_limited_udp_socket::on_tick(error_code const& e)
 {
 	if (e) return;
+	if (m_abort) return;
 	error_code ec;
 	ptime now = time_now();
 	m_timer.expires_at(now + seconds(1), ec);
@@ -593,6 +595,7 @@ void rate_limited_udp_socket::on_tick(error_code const& e)
 void rate_limited_udp_socket::close()
 {
 	error_code ec;
+	m_abort = true;
 	m_timer.cancel(ec);
 	udp_socket::close();
 }

src/upnp.cpp

@@ -246,6 +246,8 @@ void upnp::resend_request(error_code const& e)
 
 	mutex_t::scoped_lock l(m_mutex);
 
+	if (m_closing) return;
+
 	if (m_retry_count < 12
 		&& (m_devices.empty() || m_retry_count < 4))
 	{