Merge pull request #121 from glyptodon/improve-lag-compensation

GUAC-1389: Stretch RDP and VNC frames until client has caught up.

src/protocols/rdp/client.h

@@ -37,7 +37,7 @@
  * milliseconds. If the server is silent for at least this amount of time, the
  * frame will be considered finished.
  */
-#define GUAC_RDP_FRAME_TIMEOUT 10
+#define GUAC_RDP_FRAME_TIMEOUT 0
 
 /**
  * The amount of time to wait for a new message from the RDP server when

src/protocols/rdp/rdp.c

@@ -829,9 +829,10 @@ void* guac_rdp_client_thread(void* data) {
 
     /* Connection complete */
     rdp_client->rdp_inst = rdp_inst;
-
     rdpChannels* channels = rdp_inst->context->channels;
 
+    guac_timestamp last_frame_end = guac_timestamp_current();
+
     /* Handle messages from RDP server while client is running */
     while (client->state == GUAC_CLIENT_RUNNING) {
 
@@ -845,8 +846,13 @@ void* guac_rdp_client_thread(void* data) {
         /* Wait for data and construct a reasonable frame */
         int wait_result = rdp_guac_client_wait_for_messages(client,
                 GUAC_RDP_FRAME_START_TIMEOUT);
+        if (wait_result > 0) {
+
+            int processing_lag = guac_client_get_processing_lag(client);
             guac_timestamp frame_start = guac_timestamp_current();
-        while (wait_result > 0) {
+
+            /* Read server messages until frame is built */
+            do {
 
                 guac_timestamp frame_end;
                 int frame_remaining;
@@ -902,15 +908,26 @@ void* guac_rdp_client_thread(void* data) {
 
                 /* Calculate time remaining in frame */
                 frame_end = guac_timestamp_current();
-            frame_remaining = frame_start + GUAC_RDP_FRAME_DURATION - frame_end;
+                frame_remaining = frame_start + GUAC_RDP_FRAME_DURATION
+                                - frame_end;
+
+                /* Calculate time that client needs to catch up */
+                int time_elapsed = frame_end - last_frame_end;
+                int required_wait = processing_lag - time_elapsed;
+
+                /* Increase the duration of this frame if client is lagging */
+                if (required_wait > GUAC_RDP_FRAME_TIMEOUT)
+                    wait_result = rdp_guac_client_wait_for_messages(client,
+                            required_wait*1000);
 
                 /* Wait again if frame remaining */
-            if (frame_remaining > 0)
+                else if (frame_remaining > 0)
                     wait_result = rdp_guac_client_wait_for_messages(client,
                             GUAC_RDP_FRAME_TIMEOUT*1000);
                 else
                     break;
 
+            } while (wait_result > 0);
         }
 
         /* If an error occurred, fail */
@@ -923,6 +940,9 @@ void* guac_rdp_client_thread(void* data) {
         guac_client_end_frame(client);
         guac_socket_flush(client->socket);
 
+        /* Record end of frame */
+        last_frame_end = guac_timestamp_current();
+
     }
 
     guac_client_log(client, GUAC_LOG_INFO, "Internal RDP client disconnected");

src/protocols/vnc/client.h

@@ -36,7 +36,7 @@
  * milliseconds. If the server is silent for at least this amount of time, the
  * frame will be considered finished.
  */
-#define GUAC_VNC_FRAME_TIMEOUT 10
+#define GUAC_VNC_FRAME_TIMEOUT 0
 
 /**
  * The amount of time to wait for a new message from the VNC server when

src/protocols/vnc/vnc.c

@@ -345,6 +345,7 @@ void* guac_vnc_client_thread(void* data) {
                 GUAC_VNC_FRAME_START_TIMEOUT);
         if (wait_result > 0) {
 
+            int processing_lag = guac_client_get_processing_lag(client);
             guac_timestamp frame_start = guac_timestamp_current();
 
             /* Read server messages until frame is built */
@@ -366,8 +367,17 @@ void* guac_vnc_client_thread(void* data) {
                 frame_remaining = frame_start + GUAC_VNC_FRAME_DURATION
                                 - frame_end;
 
+                /* Calculate time that client needs to catch up */
+                int time_elapsed = frame_end - last_frame_end;
+                int required_wait = processing_lag - time_elapsed;
+
+                /* Increase the duration of this frame if client is lagging */
+                if (required_wait > GUAC_VNC_FRAME_TIMEOUT)
+                    wait_result = guac_vnc_wait_for_messages(rfb_client,
+                            required_wait*1000);
+
                 /* Wait again if frame remaining */
-                if (frame_remaining > 0)
+                else if (frame_remaining > 0)
                     wait_result = guac_vnc_wait_for_messages(rfb_client,
                             GUAC_VNC_FRAME_TIMEOUT*1000);
                 else
@@ -386,17 +396,8 @@ void* guac_vnc_client_thread(void* data) {
         guac_client_end_frame(client);
         guac_socket_flush(client->socket);
 
-        /* Calculate time since previous frame ended */
-        int current_frame_end = guac_timestamp_current();
-        int time_elapsed = current_frame_end - last_frame_end;
-        int processing_lag = guac_client_get_processing_lag(client);
-
-        /* Insert delays as necessary to allow client to catch up */
-        if (time_elapsed < processing_lag)
-            guac_timestamp_msleep(processing_lag - time_elapsed);
-
         /* Record end of frame */
-        last_frame_end = current_frame_end;
+        last_frame_end = guac_timestamp_current();
 
     }