[libvirt-users] Network hooks for ethernet interfaces

[Ruben Kerkhof]

On Wed, Apr 10, 2019 at 1:44 PM Laine Stump <laine at redhat.com> wrote:
>
> On 4/9/19 11:35 AM, Ruben Kerkhof wrote:
> > On Tue, Apr 9, 2019 at 5:10 PM Michal Privoznik <mprivozn at redhat.com> wrote:
> >>
> >> On 4/9/19 4:38 PM, Ruben Kerkhof wrote:
> >>> Hi all,
> >>>
> >>> I have a hook script, /etc/libvirt/hooks/network, that doesn't seem to
> >>> be called when I attach an interface with type 'ethernet' with this
> >>> xml snippet:
> >>>
> >>> <interface type='ethernet'>
> >>>       <model type="virtio"/>
> >>>       <source>
> >>>           <ip address="10.100.0.1" prefix="24" peer="10.100.0.10"/>
> >>>       </source>
> >>> </interface>
> >>>
> >>> https://www.libvirt.org/hooks.html#intro says
> >>> "A network is started or stopped or an interface is plugged/unplugged
> >>> to/from the network (since 1.2.2)".
> >>>
> >>> While I don't have a network defined in xml, I'd expect this to work
> >>> just as well for 'ethernet' type interfaces. Am I wrong?
> >>
> >>
> >> Hotplugging an 'ethernet' type of interface doesn't really relate to any
> >> libvirt network. Hence libvirt doesn't call 'network' hook script. If
> >> you'd continue reading you'll see what is the 'network' hook fed with
> >> (on stdin): info on domain in question AND network where the event
> >> ocurred. But there is no network, is it?
> >
> > No not in the libvirt sense there isn't, you're right.
> >>
> >> But maybe you can work around this by waiting for
> >> DEVICE_ADDED/DEVICE_REMOVED events? What is it that you're trying to solve?
> >
> > I'd like to enable proxy_arp on the interface among other things.
> > I can easily do this from the same script that adds the interface
> > though, so I have a workaround, but a hook that triggers on all
> > interface events felt cleaner.
>
> Also keep in mind that the hook scripts aren't an officially supported
> part of the API, and are thus liable to change without warning. As an
> example, danpb has proposed changing the network hook:
>
>   https://www.redhat.com/archives/libvir-list/2019-March/msg01280.html
>
> Once this goes in, any network hook script that uses the plugged and
> unplugged hooks will no longer work; you would instead need to use the
> port-created and port-deleted hooks.

That's good to know, thank you Laine.

In that case perhaps adding this functionality to libvirt itself would
make more sense?

Some background, I'm implementing
https://vincent.bernat.ch/en/blog/2018-l3-routing-hypervisor, so
announcing /32 host routes to our vms with BGP.
Our existing vms use /24 network addressing, and to keep that working,
I need to set proxy_arp on the interface.

Kind regards,

Ruben