Re: [Qemu-devel] [RFC PATCH 0/2] make mac programming for virtio net more robust

[John Fastabend]

On 1/10/2013 11:46 PM, Michael S. Tsirkin wrote:
> On Fri, Jan 11, 2013 at 12:53:07PM +1030, Rusty Russell wrote:
> > "Michael S. Tsirkin" <address@hidden> writes:
> >
> > > On Thu, Jan 10, 2013 at 10:45:39PM +0800, address@hidden wrote:
> > > > From: Amos Kong <address@hidden>
> > > >
> > > > Currenly mac is programmed byte by byte. This means that we
> > > > have an intermediate step where mac is wrong.
> > > >
> > > > Second patch introduced a new vq control command to set mac
> > > > address in one time.
> > >
> > > As you mention we could alternatively do it without
> > > new commands, simply add a feature bit that says that MACs are
> > > in the mac table.
> > > This would be a much bigger patch, and I'm fine with either way.
> > > Rusty what do you think?
> >
> > Hmm, mac filtering and "my mac address" are not quite the same thing.  I
> > don't know if it matters for anyone: does it?
> > The mac address is abused
> > for things like identifying machines, etc.
>
> I don't know either. I think net core differentiates between mac and
> uc_list because linux has to know which mac to use when building
> up packets, so at some level, I agree it might be useful to identify the
> machine.
>
> BTW netdev/davem should have been copied on this, Amos I think it's a
> good idea to remember to do it next time you post.
>
> > If we keep it as a separate concept, Amos' patch seems to make sense.
>
> Yes. It also keeps the patch small, I just thought I'd mention the
> option.
>
> > Cheers,
> > Rusty.

Don't have the entire context here but if you implement the
ndo_fdb_dump() probably hooking it up to ndo_dflt_fdb_dump() you could
use the 'bridge' tool dump the uc_list.

Then use ndo_fdb_add() and ndo_fdb_del() to add and remove entries
from the uc_list. We do this today in macvlan and the ixgbe driver when
it is in SR-IOV mode and the embedded switch needs to be programmed.

fdb is "forwarding database" its a bit different then mac filtering
in that its telling the "switch" how to forward mac addresses, in
ixgbe and macvlan at least we have been overloading it a bit to also
stop filtering the mac address. I think this makes sense if you setup
forwarding to a port it doesn't make much sense to then drop them.

Maybe its not entirely applicable here just thought I would mention it.

Thanks,
John