can't start remote X programs

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I have two computers running Linux and openssh-4.1p1.

They are connect to each other through an OpenVPN tunnel.

If I connect from BROKEN to GOOD using ssh -X ..., I can start remote X
programs without problems (for example, xclock).

When I connect from GOOD to BROKEN, I can't start remote X programs:

$ ssh -l user BROKEN -v -X

$ xclock
debug1: client_input_channel_open: ctype x11 rchan 3 win 65536 max 16384
debug1: client_request_x11: request from 1535
debug1: channel 1: new [x11]
debug1: confirm x11

And I can wait forever, but xclock is not started on my local machine.
I can't kill it with ctrl+C.

When I do "ps x" on BROKEN, it shows xclock is running.
When I kill it (killall xclock), I can't use the terminal on which I
started anymore.

Has anyone seen this before?

What should I look for?

I noticed that when I try to start "xclock" on BROKEN, there are some
packets going on lo interface (this is captured with iptraf):

localhost:1363    =      10       760      -PA-          lo
localhost:6013    =       8      1016      --A-          lo

Any ideas?


Re: can't start remote X programs

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Worth a try:

but my money is on this:

(Richard: perhaps add "PPPoE" and "VPN" as common contributors to this?)

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I'll bet if you do a "netstat" on both ends and find you ssh connection
you'll see a constant or increasing number int he "Send-Q" at the ssh
server end.

Darren Tucker (dtucker at
GPG key 8FF4FA69 / D9A3 86E9 7EEE AF4B B2D4  37C9 C982 80C7 8FF4 FA69
    Good judgement comes with experience. Unfortunately, the experience
usually comes from bad judgement.

Re: can't start remote X programs

Darren Tucker schrieb:
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you were right, it has something to do with the mtu / VPN connection;
thanks for the hint!


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