virsh domifaddr --domain domname --source {lease, arp} not showing results with ipv6
Michal Prívozník
mprivozn at redhat.com
Tue Mar 21 17:05:05 UTC 2023
On 3/21/23 16:50, Natxo Asenjo wrote:
> hi,
>
> On Tue, Mar 21, 2023 at 3:40 PM Michal Prívozník <mprivozn at redhat.com
> <mailto:mprivozn at redhat.com>> wrote:
>
> On 3/19/23 20:21, Natxo Asenjo wrote:
> > hi,
> >
> > I have configured a routed network on my laptop with a ipv6 subnet and
> > dnsmasq is handing out ipv6 addresses to my vms and it works
> really wel,
> > but finding out which ips have been used is not as easy as with ipv4.
> >
> > [root at lenovo ~]# virsh domifaddr --domain wec --source lease
> > Name MAC address Protocol Address
> >
> -------------------------------------------------------------------------------
> >
> > [root at lenovo ~]# virsh domifaddr --domain wec --source arp
> > Name MAC address Protocol Address
> >
> -------------------------------------------------------------------------------
> >
> > When using a ipv4 network, this works:
> >
> > root at lenovo ~]# virsh domifaddr --domain evenng --source arp
> > Name MAC address Protocol Address
> >
> -------------------------------------------------------------------------------
> > vnet2 52:54:00:4c:83:98 ipv4 192.168.122.229/0
> <http://192.168.122.229/0>
> > <http://192.168.122.229/0 <http://192.168.122.229/0>>
> >
> > [root at lenovo ~]# virsh domifaddr --domain evenng --source lease
> > Name MAC address Protocol Address
> >
> -------------------------------------------------------------------------------
> > vnet2 52:54:00:4c:83:98 ipv4 192.168.122.229/24
> <http://192.168.122.229/24>
> > <http://192.168.122.229/24 <http://192.168.122.229/24>>
> >
> > I can obviously look into the leases file and find out the
> address, but
> > it would be nice to be able to use the virt tooling.
>
> Looks like you won't find any info for IPv6 there, because that's
> exactly what '--source lease' is doing. Are you sure that your IPv6
> address is not autoconfigured and it indeed is libvirt spawned dnsmasq
> that's assigning the IPv6 address?
>
>
> this is the xml:
>
> # cat networks/ipv6.xml
> <!--
> WARNING: THIS IS AN AUTO-GENERATED FILE. CHANGES TO IT ARE LIKELY TO BE
> OVERWRITTEN AND LOST. Changes to this xml configuration should be made
> using:
> virsh net-edit ipv6
> or other application using the libvirt API.
> -->
>
> <network>
> <name>ipv6</name>
> <uuid>49957183-e4e4-4541-8746-11be67f0a511</uuid>
> <forward mode='open'/>
> <bridge name='virbr1' stp='on' delay='0'/>
> <mac address='52:54:00:09:8e:66'/>
> <domain name='ipv6'/>
> <ip family='ipv6' address='2a02:xxx:xx:7::1' prefix='64'>
> <dhcp>
> <range start='2a02:xxx:xx:7::100' end='2a02:xxx:xx:7::1ff'/>
> </dhcp>
> </ip>
> </network>
>
> so it looks like a dhcp server to me ;-)
Yep. That's fine. The only thing missing now is how's the <interface/>
configured in domain XML. Because '--source leases' is designed to work
only with <interface type='network'/>. Any other type (e.g.
type='bridge') is ignored.
>
> I just found out about virsh net-dhcp-leases and that one lists the leases:
>
> # virsh net-dhcp-leases --network ipv6
> Expiry Time MAC address Protocol IP address
> Hostname Client ID or DUID
> ---------------------------------------------------------------------------------------------------------------------------------------------
> 2023-03-22 16:35:44 52:54:00:0e:ee:da ipv6
> 2a02:xxx:xx:7::1ba/64 WIN-C0HD8RH61MI
> 00:01:00:01:2b:a7:05:c5:52:54:00:0e:ee:da
And the fact that you can see some leases but virsh doesn't report any
suggests that you may be using type='bridge'.
>
>
> For the '--source arp' case - libvirt reads the arp table (effectively
> the same info is exposed under /proc/net/arp file) and finds a matching
> entry there, based on the MAC address. Can you see whether there's a
> match?
>
>
> No, that only entry right now there is my router:
>
> ]# cat /proc/net/arp
> IP address HW type Flags HW address Mask
> Device
> xx.x.x.1 0x1 0x2 cafebabecafe * wifi0
Yeah, this is why '--source arp' doesn't display anything. And I just
realized that IPv6 doesn't use ARP, so that won't work :-)
> And lastly - there's '--source agent' which is most likely to return
> useful information, but that requires guest agent running inside.
>
>
> Indeed, no agent running on the vm, could add it.
>
>
If you want to get most consistent answer then that's probably the way
to go.
Michal
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