RFC: automatic _NET_WM_PID setting for local clients

[Carsten Haitzler (The Rasterman)]

On Tue, 23 Jul 2019 13:57:01 -0700 xorg at pengaru.com said:

it'd be much more reliable to set _NET_STARTUP_ID to the content of whatever
the DESKTOP_STARTUP_ID env var has and enforce this in xlib itself. this can be
inherited down the chain through your launching/containers/whatever and passed
in for that launch instance. assuming your wm of course can do this and track
every launch instance it started off and map it back to that instance... but it
can know reliably then "THIS action of launching here resulted in that window
over there". much better than _NET_WM_PID because the pid here may not be the
pid of whatever was forked - but some other child process or even unrelated
other pid.

> Hello folks,
> 
> I'd like to propose that Xorg set the _NET_WM_PID property on new
> windows for local clients @ window create time whenever possible.  
> 
> This is something I added localy years ago to more reliably have this
> property set with uncooperative clients that didn't set it.  My window
> manager integrates client process monitoring and relies on this property
> for acquiring the PID of connected clients.
> 
> At the time, it was just a few X clients that were problematic, stuff
> like xpdf and other smaller programs using less popular toolkits or no
> toolkit at all.  It wasn't such a big deal, so I promptly forgot about
> it and stopped building my own Xorg debs with the patch, living with the
> absent monitoring overlays on those windows.
> 
> Fast-forward to today; I'm using systemd-nspawn for running X clients -
> particularly network-facing clients like FireFox where I _strongly_
> prefer isolating the client from accessing things like my home directory
> for obvious reasons (ssh keys, etc).
> 
> These programs are cooperative and set _NET_WM_PID, but the PID they set
> is from the perspective of the container namespace.  The display server
> is running in the global host namespace, where this PID has zero
> relevance.  The same goes for my window manager, it to runs in the
> host's namespace, so when it gets this PID and tries to monitor the
> process subtree rooted at that PID in /proc, it either finds nothing or
> the entirely wrong tree.
> 
> So again I'm wishing the display server would just set this property for
> local clients immediately when creating the window, which would not only
> make the property more reliable but now it would also set it from the
> PIDNS of the Xorg server, that I would argue is far more meaningful.
> 
> I happened to still have the old patch I was using to do this back in
> the day, and have attached it as-is for discussion purposes.
> 
> Thanks,
> Vito Caputo


-- 
------------- Codito, ergo sum - "I code, therefore I am" --------------
Carsten Haitzler - raster at rasterman.com