Re: [Qemu-devel] [PATCH 3/4] qemu:virtio-net: Add support for qemu_vlan_rxfilter

[Jamie Lokier]

Paul Brook wrote:
> > We could use a changed() function, but it would need to know the
> > direction of the change, which leads back to the same mechanics.  If
> > there's a better way, please suggest it.  Thanks,
> 
> I still don't see why the device needs to know what's changed. The response 
> should always be the same: Request a filter, and see if it works.

Well, you do need some way to notify a client that the filter which
used to work has been removed because it's no longer available, for
example when migrating between host kernels.

Or implement reliable filtering in the infrastructure which relays
packets internally in QEMU, so that each client can request a filter
and it always works, and the tap driver can tell the QEMU
infrastructure when kernel filtering is working and not, but each
client doesn't need to know that.

-- Jamie