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



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".

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 linux vnet ibm com>
> IBM Linux Technology Center
>
> --
> libvir-list mailing list
> libvir-list redhat com
> https://www.redhat.com/mailman/listinfo/libvir-list

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