[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 02:37:20 UTC 2014

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'/>
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?

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:

Thanks and best regards!

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

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