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

Sheldon shaohef at linux.vnet.ibm.com
Fri Jan 24 07:00:31 UTC 2014


On 01/24/2014 02:40 PM, Jincheng Miao wrote:
> ----- Original Message -----
>> 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>
>> """
> This interface xml is partial, and it is not recommended according to 'man virsh':
> "
> Note: using of partial device definition XML files may lead to
> unexpected results as some fields may be autogenerated and thus
> match devices other than expected.
> "
>
> And there is a way to find out the mac address specified by libvirt,
> we can check /var/lib/libvirt/dnsmasq/default.leases, newer one is on top
> # cat /var/lib/libvirt/dnsmasq/default.leases
> 1390549166 52:54:00:ea:9f:58 192.168.122.106 * *
> 1390547957 52:54:00:9d:43:38 192.168.122.134 * *
> 1390547828 52:54:00:0b:2f:ec 192.168.122.76 localhost *
>
> But seems there is some latency, :(
yes, but only the vm is running, we can get the mac and IP.

>
>
>> dom.attachDeviceFlags(xml, libvirt.VIR_DOMAIN_AFFECT_CURRENT)
>> # now I want to get the mac, how to get it?
>>
>>
>> I have check libvirt use this code to generate a mac address.
>> does libvirt can gurantee that the MAC address generated is unique?
> yes, I also have this question.
>
>>
>> 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
>>
>> --
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>> 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




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