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

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

On Sat, Jun 6, 2009 at 2:48 PM, Michael S. Tsirkin<mst@redhat.com> wrote:
> On Fri, Jun 05, 2009 at 02:47:18PM -0600, Alex Williamson wrote:
>> Add a few new RX modes to better control the receive_filter.  These
>> are all fairly obvious features that hardware could provide.
>
> Could you add a bit more detail on motivation for these
> features please?

Sure, e1000 offers RX controls which separate unicast and multicast
promiscuous, these are replicated with allmulti, which has a direct
mapping for Linux, and thus already exists, and alluni, to accept all
unicast packets.  With these we could actually do away with
promiscuous, but since we have to dig into the header to determine the
type of packet, I chose to leave promiscuous separate.  Promiscuous
also filters before vlan filtering, so has a slightly different
meaning (maybe all-multi/uni should too?).

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,

Alex