[Libvir] Proposed remote protocol (XDR source file qemud/remote_protocol.x)

Richard W.M. Jones rjones at redhat.com
Tue May 1 10:07:22 UTC 2007

Daniel P. Berrange wrote:
> On Mon, Apr 30, 2007 at 06:42:01PM +0100, Richard W.M. Jones wrote:
>> Attached are the args (*_args) and return structures (*_ret) for all the 
>> calls covered by the remote protocol, that is to say everything except 
>> Save, Restore and CoreDump (see previous email).
>> The only problem area are the upper limits imposed on the lengths of 
>> various strings and arrays.  The upper limits seem to be required for 
>> safely decoding messages from untrusted sources.  Some of them however 
>> would impose limits on such things as the number of CPUs supported, and 
>> perhaps those limits are too low (or too high)?  I don't really have any 
>> experience of the sort of huge machines that people might be running 
>> libvirt on.
> SGI did a preso at the Xen summit about their 1024 CPU monster ia64
> box. So given that such a thing already exists, we need biggger to
> account for future developments.
> One thing I'm not clear - are these limits actually applied at the
> protocol level, or is the protocol completely variable length and
> these limits enforced during decoding ?  If the latter, then this
> isn't so critical to get perfect, because we can do updates without
> breaking back-compat.

The latter, so yeah afaics we should be able to increase them later 
without any harmful effects on ABI compatibility.

I've bumped up some of the limits in response to your comments.


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