Re: D-BUS and Xforwarding.

2006/8/7, Davyd Madeley <davyd madeley id au>:
On Sun, Aug 06, 2006 at 04:20:58PM -0400, Havoc Pennington wrote:

I think we're going onto another topic here, but one that really
needs to be addressed.

X forwarding is incredibly useful and a lot of people are using it.
While D-BUS at the moment will work for the LTSP and straight
Xterminal case, it doesn't currently handle the so called 'fat
client' case, where my local workstation does most of my day to day
desktop needs, and I can log into a remote server to run my CPU
intensive/pain in the neck to license application (I don't feel this
is an edge case we shouldn't design for).

I have customers who have choosen an rdesktop (windows) based solution instead linux because there are no clean way to integrate usb peripherals (scanners, pendrives...) with the desktop session. A networked dbus plus libusb would be great here.

The increased use of D-BUS for IPC of things that are tied into the
X session (screensaver inhibiting, power management control, program status
[mathusalem], &c.) means we need a way to extend the bus across the
network. Ideally, we should be able to do this securely, and without
having to change too much stuff.

I have pondered the idea of a Dbus-over-X bridge. That is, when
attempting to connect to the session bus, it detects that DISPLAY
implies you're on a remote machine, and then uses X11 to communicate
with the same machine that is running your X server via a bus proxy
back to the session daemon.

This is exactly what rdesktop does, it has an encapsulation of IPC and data stream (at least for USB AFAIK).

This seems a bit crack, but has the advantage of being secure,
relatively easy to implement (I think), requiring no additional
authentication mechanisms and working as expected in the case of
multiple users from multiple machines having multiple connections to
the remote machine all using the same username (this happens!).

I have seen that configuration scheme often, mostly for computer rooms for free access, like universities.

As with X11, the value of DISPLAY becomes the key to make it work.

Unfortunately, as it stands, this is going to break some important
cases, the Xterminal case, where DISPLAY is scully:0, but _all_
processes are running on the remote machine, won't be able to find a
bus daemon, but I'm sure this can be addressed.

That is what  LTSP uses to set the ESPEAKER var for esound for example, in order to connect sound from the server to the workstation.


Davyd Madeley
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Un saludo,
Alberto Ruiz

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