On Ubuntu Lucid (vino 2.28.2) and Natty (vino 2.32.1), when you set the /desktop/gnome/remote_access/network_interfaces gconf key to "lo", Vino will accept VNC connections only for the first desktop session. If you switch user, opening a new session as a different one, it is impossible to connect to that session. It works as expected when the network_interfaces gconf key is not set.

= Step to reproduce =

1. On the target machine, open a session as one user, then switch to a second user.

2. From another machine, witness that you can cannot connect to both session by VNC:

    $ vncviewer target:0 # VNC client screen remain black (session is locked), but connection is possible
    $ vncviewer target:1 # Connection ok

3. On the target machine, set the /desktop/gnome/remote_access/network_interface gconf key to default to "lo". I think you need to reboot the machine at that point, as it seems that Vino continue to accept connection on non-lo interfaces (but that is not german to this bug).

4. Try to connect remotely using ssh tunneling:

    $ vncviewer -via target localhost:0 # VNC client screen remain black (session is locked), but connection otherwise work
    $ vncviewer -via target localhost:1 # Connection is refused

= Expected behavior =

Vino should allow incoming connection to the current foreground session, whether directly or through an ssh tunnel when network_interfaces is set to "lo".

This is tracked downstream in Ubuntu as https://bugs.launchpad.net/ubuntu/+source/vino/+bug/707705