core: perform shutdown before closing in control_connection::recv()

src/control_connection.cpp

@@ -183,6 +183,33 @@ reply control_connection::recv()
     {
         boost::system::error_code ec;
 
+        if (socket_->has_ssl_support())
+        {
+            socket_->ssl_shutdown(ec);
+        }
+        else
+        {
+            socket_->shutdown(boost::asio::ip::tcp::socket::shutdown_both, ec);
+        }
+
+        if (ec == boost::asio::error::not_connected)
+        {
+            /* Ignore 'not_connected' error. We could get ENOTCONN if a server side
+             * has already closed the control connection. This suits us, just close
+             * the socket.
+             */
+        }
+        else if (ec == boost::asio::error::eof)
+        {
+            /* Rationale:
+             * http://stackoverflow.com/questions/25587403/boost-asio-ssl-async-shutdown-always-finishes-with-an-error
+             */
+        }
+        else if (ec)
+        {
+            throw ftp_exception(ec, "Cannot close control connection");
+        }
+
         socket_->close(ec);
 
         if (ec)