Initial VNC Fence implementation

[TeofilisMartisius]

Add basic ServerFence/ClientFence implementation, which is required to work with shared tigervnc #322

[pmhahn]

Looks okay from reading the code/PR.
I would find it clearer to add a class FencFlags(IntFlag), which improves type safety and debugging and future additions to implement Fence for real.

I've no yet run any tests.

[coder111111]

Hi, thanks for your comments, I'll try to fix this as soon as I have some time.

[pmhahn]

Functional test is failing: make test-func – more exactly: all 3 tests from tests/functional/test_proxy.py.

For debugging: PATH=$PATH:.vncdo/libvncserver-LibVNCServer-0.9.14/examples python3 -m unittest discover -s tests/functional -t . -p test_proxy.py -k test_key_alpha -v

If I remember correctly vncdotool/loggingproxy.py functions as a pass-through proxy, e.g. all traffic between any client and server goes completely through it. As such it also must be able to understand/parse the new fence messages completely – handle the variable length payload – to pass the message from server-to-client and client-to-server.

I've lost most of my knowledge about this project in the last 2 years, so maybe @sibson can help and knows, where the proxy must be extended.

[pmhahn]

Functional test is failing: make test-func – more exactly: all 3 tests from tests/functional/test_proxy.py.

diff --git a/vncdotool/loggingproxy.py b/vncdotool/loggingproxy.py
index 37b0177..c51ec7d 100644
--- a/vncdotool/loggingproxy.py
+++ b/vncdotool/loggingproxy.py
@@ -171,6 +171,8 @@ class RFBServer(Protocol):  # type: ignore[misc]
             else:
                 log.debug("Unhandled subtype %r", QemuClientMessage.lookup(subtype))
                 raise ProtocolError(subtype)
+        elif ptype == MsgC2S.CLIENT_FENCE:
+            pass
         else:
             log.debug("Unhandled response %r", MsgC2S.lookup(ptype))
             raise ProtocolError(ptype)
@@ -342,6 +344,7 @@ class VNCLoggingServerFactory(portforward.ProxyFactory):  # type: ignore[misc]
     pseudodesktop = True
     qemu_extended_key = True
     last_rect = True
+    fence = False
     force_caps = False
 
     password_required = False

The 2nd hunk is the missing one; the 1st one should be the location, where proper handling for CLIENT_FENCE should go in if FENCE should be handled, too.

[pmhahn]

vncdotool/loggingproxy.py at least needs fence = False; more work if True.