[libvirt] [PATCH] Generate RFC4122 compliant UUIDs

[Eric Blake]

On 04/08/2013 10:45 AM, Daniel P. Berrange wrote:
> On Mon, Apr 08, 2013 at 12:35:40PM -0400, Milos Vyletel wrote:
>> Even though http://libvirt.org/formatdomain.html#elementsMetadata
>> states that it requires RFC4122 compliance UUIDs that are generated
>> by virUUIDGenerate() are not. Neither does virUUIDIsValid() check
>> for RFC4122 compliance. Following patch modifies virUUIDGenerate()
>> to generate valid UUIDs and adds check to virUUIDIsValid() to validate
>> UUIDs.
>>

>>  
>> +    /*
>> +     * RFC4122 defines version 1 to 5 (section 4.1.3)
>> +     * RFC4122 defined variant is desribed in section 4.1.1
>> +     */
>> +    version = (uuid[6] >> 4);
>> +    variant = (uuid[8] >> 6);
>> +    if (!(version > 0 && version <= 5) || variant != 2)
>> +        return 0;
>> +
>>      c = uuid[0];
>>  
>>      for (i = 1; i < VIR_UUID_BUFLEN; i++)
> 
> but NACk to this part
> 
> What you're checking here is just one possible valid scheme for UUIDs.
> We shouldn't reject UUIDs just because they use a different scheme than
> the one we do.

Furthermore, if we took this hunk, but a user is running a guest created
by a previous version of libvirt that happened to generate an invalid
UUID, we would lose the ability to manage that older guest.  It _might_
be appropriate to warn the user when a UUID is not valid according to
the schemes we recognize, but it must be a warning and not a fatal
error; furthermore, if we do add such a warning, we'd need to recognize
ALL of the schemes that are valid in the RFCs, not just the particular
scheme we use when generating a uuid ourselves, so as to minimize false
negative printouts of the warning.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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