X-forwarding stops working after a while

[Damien Miller]

On Fri, 1 Jan 2016, Yuri wrote:

> I connect from host into the guest VM with X-forwarding (ssh -X), so that
> programs launched in the VM will run on the host display.
> 
> X-forwarding works first, but after a while it stops working. Connection (from
> inside of the VM) on the corresponding port (6010 or similar) is immediately
> closed by the foreign host. Ssh connection itself is okay though. Reconnecting
> ssh helps, but later the same thing repeats.
> 
> Why would this be happening?

It's probably this: (ssh_config(5))

> ForwardX11Trusted
>     If this option is set to “yes”, remote X11 clients will have full
>     access to the original X11 display.
>
>     If this option is set to “no”, remote X11 clients will be consid‐
>     ered untrusted and prevented from stealing or tampering with data
>     belonging to trusted X11 clients.  Furthermore, the xauth(1)
>     token used for the session will be set to expire after 20 min‐
>     utes.  Remote clients will be refused access after this time.
>
>     The default is “no”.
>
>     See the X11 SECURITY extension specification for full details on
>     the restrictions imposed on untrusted clients.

You can use "ssh -Y" as a shortcut for ForwardX11Trusted=yes