Re: [Qemu-devel] [PATCH 6/7] virtio-net: Add new RX filter controls

[Alex Williamson <alex.williamson@hp.com>]

On Mon, Jun 8, 2009 at 1:18 PM, Anthony Liguori<anthony@codemonkey.ws> wrote:
> Alex Williamson wrote:
>>
>> e1000 also allows the driver to selectively enable/disable RX of
>> packets to the broadcast address.  This is replicated with the
>> all/no-bcast options.  Finally, there may be cases where we want to
>> receive only unicast or only multicast address for special purpose
>> network devices.  This is provided by the nouni and nomulti options.
>> A proprietary guest know as DMX intends to make use of these extra
>> modes.  Are there any other interesting, useful and lightweight packet
>> filters we could implement?  Thanks,
>>
>
> I've been thinking about whether doing VLAN filtering/tagging within QEMU
> would make sense.  It could potentially simplify bridge setups tremendously.
>  Today, if you want to isolate VMs on separate vlans, it involves creating
> multiple bridges which gets ugly quickly.

IIRC, you have to be careful that the host NIC doesn't strip the VLAN
tag itself, which means you want the VLAN guests on a non-VLAN bridge.
 It's all rather confusing and I wouldn't be surprised if there's some
dependency on how much offloading the host NIC does.  We do have VLAN
filtering in virtio-net today, but of course it would be better if it
was done at a generic network level in QEMU or pushed deeper into the
host.  Tagging doesn't make much sense at the level we're doing it
now.

Alex