Is there anything missing when forwarding my X11 connections?

[Christophe Lohr]

Hello,
Please excuse the naivety of my question; I'm trying to understand how 
things work.

I try to forward a tcp X11 connection to the server's unix socket:
   $ socat TCP-LISTEN:6001,fork UNIX-CONNECT:/tmp/.X11-unix/X0

Then I can use it:
   $ DISPLAY=localhost:1 xeyes

It works well... but only for simple applications (xlogo xeyes xclock 
xmessage xnest...)
Surprisingly, this does not works for more complex applications (Xephyr 
wireshark ...)
These applications stop, seemingly waiting for an event that doesn't come.
Increasing socat's verbosity level doesn't help me to understand, nor 
does strace ltrace xtrace ...

Well, this seems relating to the MIT-SHM extension.
My assumption: If the server thinks the client is local (due to the use 
of a unix socket), it activates the MIT-SHM extension without further 
preliminary checks (and tries to send ancillary data (shm keys or file 
descriptor?) via the unix socket?). Right?

As a workarround, I have to generate an "untrusted" xauth cookie.
Is there a better way?

(Note: I'm a fan of network transparency!
A next time we'll talk about vsock;-) )

Best regards
Christophe
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