prevent sending data on a uTP socket after closing it

include/libtorrent/aux_/utp_stream.hpp

@@ -252,6 +252,7 @@ struct TORRENT_EXTRA_EXPORT utp_stream
 	void add_read_buffer(void* buf, int len);
 	void issue_read();
 	void add_write_buffer(void const* buf, int len);
+	bool check_fin_sent() const;
 	void issue_write();
 	std::size_t read_some(bool clear_buffers);
 	std::size_t write_some(bool clear_buffers);
@@ -379,6 +380,13 @@ struct TORRENT_EXTRA_EXPORT utp_stream
 			return 0;
 		}
 
+		if (check_fin_sent())
+		{
+			// we can't send more data after closing the socket
+			ec = boost::asio::error::broken_pipe;
+			return 0;
+		}
+
 #if TORRENT_USE_ASSERTS
 		size_t buf_size = 0;
 #endif
@@ -441,6 +449,14 @@ struct TORRENT_EXTRA_EXPORT utp_stream
 			return;
 		}
 
+		if (check_fin_sent())
+		{
+			// we can't send more data after closing the socket
+			post(m_io_service, std::bind<void>(std::move(handler)
+				, boost::asio::error::broken_pipe, std::size_t(0)));
+			return;
+		}
+
 		std::size_t bytes_added = 0;
 		for (auto i = buffer_sequence_begin(buffers)
 			, end(buffer_sequence_end(buffers)); i != end; ++i)
@@ -635,6 +651,8 @@ struct utp_socket_impl
 	void issue_read();
 	void issue_write();
 
+	bool check_fin_sent() const;
+
 	void do_connect(tcp::endpoint const& ep);
 
 	std::size_t read_some(bool const clear_buffers);

src/utp_stream.cpp

@@ -474,6 +474,12 @@ void utp_stream::add_write_buffer(void const* buf, int const len)
 	m_impl->add_write_buffer(buf, len);
 }
 
+bool utp_stream::check_fin_sent() const
+{
+	TORRENT_ASSERT(m_impl);
+	return m_impl->check_fin_sent();
+}
+
 // this is called when all user provided read buffers have been added
 // and it's time to execute the async operation. The first thing we
 // do is to copy any data stored in m_receive_buffer into the user
@@ -684,6 +690,11 @@ void utp_socket_impl::issue_write()
 	maybe_trigger_send_callback();
 }
 
+bool utp_socket_impl::check_fin_sent() const
+{
+	return state() == state_t::fin_sent;
+}
+
 std::size_t utp_socket_impl::write_some(bool const clear_buffers)
 {
 	m_written = 0;
@@ -1394,6 +1405,10 @@ bool utp_socket_impl::send_pkt(int const flags)
 		+ (sack ? sack + 2 : 0)
 		+ (close_reason ? 6 : 0);
 
+	// once we're in fin-sent mode, the write buffer should not be re-filled
+	// although, we may re-send packets, but those live in m_outbuf
+	TORRENT_ASSERT(state() != state_t::fin_sent || m_write_buffer_size == 0);
+
 	int payload_size = std::min(m_write_buffer_size
 		, effective_mtu - header_size);
 	TORRENT_ASSERT(payload_size >= 0);