Xen users - May 2008 - Find domID from domU

Hello,

I am trying to write a script to add to the proper bridge any vif that  
is brought up trying to use a domU as a backend.

After much researching, I don''t know if I have found the proper  
solution but, at least, a viable one.

I see that I can read the bridge name in xenstore from the following  
key:

/local/domain/<domid>/backend/vif/<vif num>/bridge

But I have found two obstacles to this solution.

First, by default a domU cannot list /local/domain, so the only way to  
find my domID would be to guess, up to the maximum number of domain  
IDs that Xen can have, which is a horrid solution. I can change the  
permissions so that key can be listed, and then I can try to read the  
different domain IDs until one succeeds, which would be a better way  
of guessing my own domID.

So my question is. Is there a deterministic way of reading the proper  
key /local/domain/<domid>/backend/vif/<vif num>/bridge from the
domU,
or a way to determine my domID in a deterministic fashion or change  
the the default permissions, so that if I ever reboot my dom0 I can  
bring everything back automatically.

Thanks,
Pepe

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On Thu, May 8, 2008 at 4:38 PM, Pepe Barbe <elventear@gmail.com>
wrote:
> Hello,
>
>  I am trying to write a script to add to the proper bridge any vif that is
> brought up trying to use a domU as a backend.
>
>  After much researching, I don''t know if I have found the proper
solution
> but, at least, a viable one.
>
>  I see that I can read the bridge name in xenstore from the following key:
>
>  /local/domain/<domid>/backend/vif/<vif num>/bridge
>
>  But I have found two obstacles to this solution.
>
>  First, by default a domU cannot list /local/domain, so the only way to
find
> my domID would be to guess, up to the maximum number of domain IDs that Xen
> can have, which is a horrid solution. I can change the permissions so that
> key can be listed, and then I can try to read the different domain IDs
until
> one succeeds, which would be a better way of guessing my own domID.
>
>  So my question is. Is there a deterministic way of reading the proper key
> /local/domain/<domid>/backend/vif/<vif num>/bridge from the
domU, or a way
> to determine my domID in a deterministic fashion or change the the default
> permissions, so that if I ever reboot my dom0 I can bring everything back
> automatically.
>
I am not sure if this exactly answers your question, but might be along the
lines that you are looking for.

http://lists.xensource.com/archives/html/xen-users/2005-08/msg00089.html

Regards,
Todd

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