[libvirt] [PATCH] qemu: Fix -chardev udp if parameters are omitted

[Eric Blake]

On 03/22/2011 02:36 PM, Cole Robinson wrote:
> The following XML:
> 
>     <serial type='udp'>
>       <source mode='connect' service='9999'/>
>     </serial>
> 
> is accepted by domain_conf.c but maps to the qemu command line:
> 
> -chardev udp,host=127.0.0.1,port=2222,localaddr=(null),localport=(null)
> 
> qemu can cope with everything omitting except the connection port, which
> seems to also be the intent of domain_conf validation, so let's not
> generate bogus command lines for that case.

In the past, I've been told that the qemu command line should be as
full-featured as possible - that is, if we know what qemu will be using
as a default, then we should explicitly provide that argument rather
than relying on the default (it helps us future-proof if not all
versions of qemu take the same defaults).

I agree that something needs to be done here to avoid the NULL
dereference (glibc is too kind by printing "(null)" instead of
crashing); but am not sure that making the qemu command line parameters
optional is right, if we instead know what qemu does when those
parameters are missing.

-- 
Eric Blake   eblake at redhat.com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org

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