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

On 01/24/2014 05:30 PM, Martin Kletzander wrote: > On Fri, Jan 24, 2014 at 04:34:12PM +0800, Sheldon wrote: >> 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? >> > Yes, exactly. You may be trying how the systems behave when MAC > addresses clash, you may have different subnets which are not > connected and you want have the same MAC address, but libvirt will > never know if you want to connect them together, you may have two > machines defined with slight differences (one with numa one without) > and run the one you want each time, etc. And libvirt can't possibly > know about this. IIRC, virt-manager can do the thing you want, but > that's probably not applicable for you, so you'll have to go through > the list of VMs you don't want the addresses to clash and check > whether the MAC is ok or not. Or assign a MAC using a function > according to some unique element of yours and you don't have to check > anything. > >> I wonder can libvirt support a API to generate mac address? >> > Patches are welcome :-) libvirt.virDomain.macAddrGenerate() or libvirt.virConnect.macAddrGenerate() ?