[openbox] openbox connected to remote display doesn't know X server gone

[Xavier Toth]

On Thu, Sep 24, 2009 at 9:47 AM, txtoth <txtoth at gmail.com> wrote:
> On Thu, Sep 24, 2009 at 1:57 AM, Anthony Thyssen
> <A.Thyssen at griffith.edu.au> wrote:
>> On Wed, 23 Sep 2009 16:13:10 -0500
>> Xavier Toth <txtoth at gmail.com> wrote:
>>
>> | I'm running an X server for remote display purposes (some might call
>> | it an X terminal). The X client starts an openbox session when a user
>> | logs in. If I power off the X server box (something that shouldn't
>> | happen but can) when a user is logged in and then do a ps on the X
>> | client I see that openbox and a number of other processes started by
>> | the openbox session continue to run indefinitely. It appears that
>> | openbox doesn't know that it's X connection has been lost. Is there
>> | anything that can be done to cleanup these dead sessions?
>> |
>> Many internet connections don't die when the remote server dies.
>> Basically it cant't tell if the host has disappeared, or is just
>> not talking.
>>
>> When the host comes back online usally such connections get a error
>> about no such connection from the rebooted host, and the clients
>> die.  But only when the host comes back.
>>
>> This is especially the case with X window UDP packets.
>>
>> The other solution is that the socket connection be setup with a
>> 'keepalive' flag.  This checks the connection for response, and
>> closed dead connections when the remote client 'dissapears'.
>>
>> X windows via SSH tunneling encryption is the standard way X window
>> connections are handled these days.   And SSH has options to use
>> 'keepalive' socket techniques.
>>
>> In the system ssh_config or your personal $HOME/.ssh/config
>> add the following...
>>
>> ----------8<--------------
>> Host *
>>  TCPKeepAlive yes
>>  ServerAliveInterval 1800
>> ----------8<--------------
>>
>> the second item is not really needed, but sends an "I'm here"
>> type packet every 5 mins to prevent some firewalls and routers
>> from killing 'unused connections'.  that takes care of the opposite
>> problems.   connections dying when you aren't using them even though
>> nothing is wrong at either end.
>>
>> Both flags are worth it.
>>
>> PS: to ensure X windows is passed with SSH by default also include a
>>   ForwardX11 yes
>> in the above.
>>
>>
>>  Anthony Thyssen ( System Programmer )    <A.Thyssen at griffith.edu.au>
>>  -----------------------------------------------------------------------------
>>            Graffito in a MIT lavatory...
>>                   Heisenberg might have been here
>>  -----------------------------------------------------------------------------
>>     Anthony's Home is his Castle     http://www.cit.gu.edu.au/~anthony/
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>>
>
> We are using an ipsec.The X library is supposedly setting SO_KEEPALIVE
> on connections it creates so I'll try setting
> /proc/sys/net/ipv4/tcp_keepalive_time and see if that helps. Thanks
>
> Ted
>

I set the time in  /proc/sys/net/ipv4/tcp_keepalive_time to 1800 but
still openbox never realizes that the X server it was connected to is
no longer running. This causes a real problem because besides openbox
there are a number of its children and eventually you can have a box
running with a number of zombies, not good in a production
environment.

Ted