Dear list,
I am a question about the best use of bridge, vlan trunk and libvirt.
When dealing with virtual machies bound to specific vlan, I generally
use a straightforward approach:
eth -> bridge -> vm (for untagged traffic)
eth -> eth.10 -> bridge -> vm
eth -> eth.nn -> bridge -> vm
Now I am faced with enabling vlan trunking for a specific vm (a
virtualized firewall). The simpler approach would be:
eth -> bridge -> vm (for the vm needing trunk)
eth -> bridge.10 -> macvtap -> vm
The issue with the above method is that any VM on the main untagged vlan
needs to be bound to the "plain" bridge, having access to *any* traffic
of *any* other vlan. If this is ok (and the desired behavior) for the
firewall, it is clearly wrong for the other VMs.
A simple fix would be to use ebtables to block/drop vlan tagged traffic
on the main bridge for any virtual adapter except the required one (ie:
the firewall virtual interface). It works, but I wounder if other
preferred approaches exists.
For example, I tested another more convoluted setup:
eth -> bridge -> firewall vm
eth -> bridge.10 -> macvtap -> vm
eth -> bridge -> veth0 -> veth1 -> other bridge with vlan filtering on
-> vm
The last row show the use of veth virtual interface, configurable via ip
link. Enabling vlan filtering on the second bridge (rather than on the
first) is to keep vlan filtering simple: rathen than enabling all
required vlan on the first bridge, I simply enable only untagged traffic
on the second one.
Does libvirt support bridge vlan filtering natively? Reading the docs,
it seems to the supported only on OpenVSwitch or SRV-IO based adapter.
Thanks.
--
Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. - www.assyoma.it
email: g.danti@xxxxxxxxxx - info@xxxxxxxxxx
GPG public key ID: FF5F32A8
