diff mbox series

[v1,07/13] ui: correctly reset framebuffer update state after processing dirty regions

Message ID 20171218191228.31018-8-berrange@redhat.com
State New
Headers show
Series Fix VNC server unbounded memory usage | expand

Commit Message

Daniel P. Berrangé Dec. 18, 2017, 7:12 p.m. UTC 
According to the RFB protocol, a client sends one or more framebuffer update
requests to the server. The server can reply with a single framebuffer update
response, that covers all previously received requests. Once the client has
read this update from the server, it may send further framebuffer update
requests to monitor future changes. The client is free to delay sending the
framebuffer update request if it needs to throttle the amount of data it is
reading from the server.

The QEMU VNC server, however, has never correctly handled the framebuffer
update requests. Once QEMU has received an update request, it will continue to
send client updates forever, even if the client hasn't asked for further
updates. This prevents the client from throttling back data it gets from the
server. This change fixes the flawed logic such that after a set of updates are
sent out, QEMU waits for a further update request before sending more data.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
---
 ui/vnc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
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Patch

diff --git a/ui/vnc.c b/ui/vnc.c
index d3b04f1166..51fbf0449d 100644
--- a/ui/vnc.c
+++ b/ui/vnc.c
@@ -1031,7 +1031,7 @@  static int vnc_update_client(VncState *vs, int has_dirty)
     }
 
     vnc_job_push(job);
-    vs->update = VNC_STATE_UPDATE_INCREMENTAL;
+    vs->update = VNC_STATE_UPDATE_NONE;
     vs->has_dirty = 0;
     return n;
 }