From 34bab9524eb6d1b5e3fa96be7ed2602d71f25dd9 Mon Sep 17 00:00:00 2001
From: Michael Jumper <mjumper@apache.org>
Date: Thu, 6 Sep 2018 19:57:29 -0700
Subject: [PATCH] GUACAMOLE-567: Regularly test connection stability of HTTP
 tunnel.

Unlike the WebSocket tunnel, where a manual ping request/response must
be explicitly implemented, we can rely on HTTP's own request/response
to verify stability.
---
 .../src/main/webapp/modules/Tunnel.js         | 29 +++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/guacamole-common-js/src/main/webapp/modules/Tunnel.js b/guacamole-common-js/src/main/webapp/modules/Tunnel.js
index 827dd6cd4..24ffaa860 100644
--- a/guacamole-common-js/src/main/webapp/modules/Tunnel.js
+++ b/guacamole-common-js/src/main/webapp/modules/Tunnel.js
@@ -258,6 +258,25 @@ Guacamole.HTTPTunnel = function(tunnelURL, crossDomain, extraTunnelHeaders) {
      */
     var unstableTimeout = null;
 
+    /**
+     * The current connection stability test ping interval ID, if any. This
+     * will only be set upon successful connection.
+     *
+     * @private
+     * @type {Number}
+     */
+    var pingInterval = null;
+
+    /**
+     * The number of milliseconds to wait between connection stability test
+     * pings.
+     *
+     * @private
+     * @constant
+     * @type {Number}
+     */
+    var PING_FREQUENCY = 500;
+
     /**
      * Additional headers to be sent in tunnel requests. This dictionary can be
      * populated with key/value header pairs to pass information such as authentication
@@ -327,6 +346,9 @@ Guacamole.HTTPTunnel = function(tunnelURL, crossDomain, extraTunnelHeaders) {
         window.clearTimeout(receive_timeout);
         window.clearTimeout(unstableTimeout);
 
+        // Cease connection test pings
+        window.clearInterval(pingInterval);
+
         // Ignore if already closed
         if (tunnel.state === Guacamole.Tunnel.State.CLOSED)
             return;
@@ -413,6 +435,8 @@ Guacamole.HTTPTunnel = function(tunnelURL, crossDomain, extraTunnelHeaders) {
             message_xmlhttprequest.onreadystatechange = function() {
                 if (message_xmlhttprequest.readyState === 4) {
 
+                    reset_timeout();
+
                     // If an error occurs during send, handle it
                     if (message_xmlhttprequest.status !== 200)
                         handleHTTPTunnelError(message_xmlhttprequest);
@@ -687,6 +711,11 @@ Guacamole.HTTPTunnel = function(tunnelURL, crossDomain, extraTunnelHeaders) {
             // Mark as open
             tunnel.setState(Guacamole.Tunnel.State.OPEN);
 
+            // Ping tunnel endpoint regularly to test connection stability
+            pingInterval = setInterval(function sendPing() {
+                tunnel.sendMessage("nop");
+            }, PING_FREQUENCY);
+
             // Start reading data
             handleResponse(makeRequest());