guest programmable mac/vlan filtering with macvtap
This would be nice to have to be able to do bridging or use macvlan inside the guest.
We neet to be able to:
- change mac address of the guest virtio-net interface.
- create a vlan device on the guest virtio-net device
- set promiscuous mode on guest virtio-net device
- all this controllable by host admin
- There's a patch  proposed by Alex Williamson to do TX mac filtering in TUN. It's still in RFC state, no recent activity in thread. Try rewrite based on comments.
- Implement filtering in macvtap. The filtering information will be received through TUNSETTXFILTER ioctl (by above patch).
- Implement promiscuous mode in guest virtio-net driver. No ideas here, yet.
- Control should be done via qemu/virtio features. Need a way to disable access that qemu can't override unless it has net admin capability.
- Amos Kong works on QEMU side  to add event notification when guest change rx-filter config (main-mac, rx-mode, mac-table, vlan-table). Libvirt will query the rx-filter config from monitor (query-rx-filter), then sync the change to host device.