[libvirt] [PATCH] qemu: Allow empty script path to <interface/>

[Michal Privoznik]

On 02/02/2017 06:12 PM, Daniel P. Berrange wrote:
> On Thu, Feb 02, 2017 at 04:55:29PM +0100, Kashyap Chamarthy wrote:
>> On Thu, Feb 02, 2017 at 03:29:15PM +0000, Daniel P. Berrange wrote:
>>> On Thu, Feb 02, 2017 at 04:21:39PM +0100, Michal Privoznik wrote:
>>>> On 02/02/2017 02:56 PM, Daniel P. Berrange wrote:
>>>>> On Thu, Feb 02, 2017 at 02:49:48PM +0100, Michal Privoznik wrote:
>>>>>> Before 9c17d665fdc5f (v1.3.2 - I know, right?) it was possible to
>>>>>> have the following interface configuration:
>>>>>>
>>>>>>   <interface type='ethernet'/>
>>>>>>     <script path=''/>
>>>>>>   </interface>
>>>>>>
>>>>>> This resulted in -netdev tap,script=,.. Fortunately, qemu helped
>>>>>> us to get away with this as it just ignored the empty script
>>>>>> path. However, after the commit mentioned above it's libvirtd
>>>>>> who is executing the script. Unfortunately without special
>>>>>> case-ing empty script path.
>>>>>>
>>>>>> Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
>>>>>
>>>>> This was always invalid input and the fact that it happened
>>>>> to work in the past is just luck. Since this has been broken since
>>>>> 1.3.2 there's plenty of libvirt releases that reject this, and so
>>>>> any app realistically has to be fixed to omit the <script> entirely
>>>>> if they want any portability. As such I don't think we need to "fix"
>>>>> this.
>>>>
>>>> Fair enough. Although, 1.3.2 was not that long time ago (~a year). BTW:
>>>> it's openstack who is still using this.
>>>>
>>>> https://bugzilla.redhat.com/show_bug.cgi?id=1412834
>>
>> IIUC, this bug was filed to handle the case of _existing_ VMs that were
>> not launched with the patch that you point to below.
> 
> THat is only a problem if you have a running VM on libvirt < 1.3.2 and
> you want to migrate it to libvirt >= 1.3.2. That can be solved by
> removing the bogus script element prior to migration - nova already
> has code that modifies the XML prior to migration where such a fix
> could live

Question is - does it live there already? If not, we should fix it there
too.

Michal