[libvirt] [question]Is there a good way to get the mac of guest interface after I attached it to a guest

[Sheldon]

On 01/24/2014 03:55 PM, Martin Kletzander wrote:
> On Fri, Jan 24, 2014 at 10:37:20AM +0800, Sheldon wrote:
>> Now I working on a new KVM management tool base on html5 and libvirt
>>
>> we will support a REST API for detach and attach guest interface.
>>
>> we want to use mac as the identifier of the network interface.
>>
>> That meas we should get the mac after the user create a interface.
>> also other people may be doing the exact same thing at the exact same
>> time to create a interface.
>>
>>
>> Here are the demo codes:
>>
>> dom = self._get_vm(vm)
>> xml = """
>> <interface type='network'>
>> <source network='default'/>
>> </interface>
>> """
>> dom.attachDeviceFlags(xml, libvirt.VIR_DOMAIN_AFFECT_CURRENT)
>> # now I want to get the mac, how to get it?
>>
> You have to parse the XML back and find it.
>
>> I have check libvirt use this code to generate a mac address.
>> does libvirt can gurantee that the MAC address generated is unique?
>>
> No, as mentioned in the second subthread, the XML you provided is
> incomplete and can cause address clashing.
>
> So te best answer to your question in $SUBJ would be "generate it
> yourself and add it to the XML before attaching".


now I define a  mac address  generator in our management tool.
it will generate a mac and assign it xml before create the interface.

+        def randomMAC():
+            mac = [0x52, 0x54, 0x00,
+                   random.randint(0x00, 0x7f),
+                   random.randint(0x00, 0xff),
+                   random.randint(0x00, 0xff)]
+        mac = randomMAC()

+        xml = """
+        <interface type='network'>
+        <source network='default'/>
+        <mac address='%s' >
+        </interface>
+        """ % mac

should I gurantee that the MAC address generated is unique by myself?
check every interface mac of every guest, and make sure no address clashing?


I wonder can libvirt support a API to generate mac address?

>
> Martin
>
>> void virMacAddrGenerate(const unsigned char prefix[VIR_MAC_PREFIX_BUFLEN],
>> virMacAddrPtr addr)
>> {
>> addr->addr[0] = prefix[0];
>> addr->addr[1] = prefix[1];
>> addr->addr[2] = prefix[2];
>> addr->addr[3] = virRandomBits(8);
>> addr->addr[4] = virRandomBits(8);
>> addr->addr[5] = virRandomBits(8);
>> }
>> libvirt also use the KVM prefix as default as it's in the privately
>> administered range:
>> 52:54:00:XX:XX:XX
>>
>>
>>
>> --
>> Thanks and best regards!
>>
>> Sheldon Feng(冯少合)<shaohef at linux.vnet.ibm.com>
>> IBM Linux Technology Center
>>
>> --
>> libvir-list mailing list
>> libvir-list at redhat.com
>> https://www.redhat.com/mailman/listinfo/libvir-list


-- 
Thanks and best regards!

Sheldon Feng(冯少合)<shaohef at linux.vnet.ibm.com>
IBM Linux Technology Center