Subject: Re: [PATCH 4/5] virtio_net: Add a MAC filter table

From: Rusty Russell <[email-masked]>
Date: Fri, 30 Jan 2009 17:33:24 +1030

On Thursday 29 January 2009 16:47:55 David Stevens wrote:
> Also, if you can't keep all the MAC multicast addresses (ie,
> the limit is memory and not look-up speed), then getting
> out of multicast-promiscuous mode correctly isn't easy
> since you don't know what groups you "forgot". You could
> rebuild from the protocol memberships, if you know when
> you've left enough groups to fit, but otherwise the MAC
> multicast addresses you didn't keep of course won't work if you
> leave multicast-promiscuous mode and the filter doesn't
> have them.

The command is simply "set the filter", not "add" and "delete", so the host doesn't have this problem.

VLAN has more of an issue: that has add and del.  So the host can do a counting hash, or say remember 16 and then a count of overflows, but both will be suboptimal over time.

Cheers,
Rusty.