[ovs-dev] [PATCH net-next] net: remove abuse of VLAN DEI/CFI bit

Michał Mirosław mirq-linux at rere.qmqm.pl
Wed Dec 14 02:03:05 UTC 2016

On Tue, Dec 13, 2016 at 05:21:18PM -0800, Stephen Hemminger wrote:
> On Sat,  3 Dec 2016 10:22:28 +0100 (CET)
> Michał Mirosław <mirq-linux at rere.qmqm.pl> wrote:
> > This All-in-one patch removes abuse of VLAN CFI bit, so it can be passed
> > intact through linux networking stack.
> > 
> > Signed-off-by: Michał Mirosław <michal.miroslaw at atendesoftware.pl>
> > ---
> > 
> > Dear NetDevs
> > 
> > I guess this needs to be split to the prep..convert[]..finish sequence,
> > but if you like it as is, then it's ready.
> > 
> > The biggest question is if the modified interface and vlan_present
> > is the way to go. This can be changed to use vlan_proto != 0 instead
> > of an extra flag bit.
> > 
> > As I can't test most of the driver changes, please look at them carefully.
> > OVS and bridge eyes are especially welcome.
> > 
> > Best Regards,
> > Michał Mirosław
> Is the motivation to support 802.1ad Drop Eligability Indicator (DEI)?
> If so then you need to be more verbose in the commit log, and lots more
> work is needed. You need to rename fields and validate every place a
> driver is using DEI bit to make sure it really does the right thing
> on that hardware. It is not just a mechanical change.

My main motivation is to be able to see the bit intact in tcpdump and be
able to pass it untouched through at least a veth pair. It would be great
if all devices didn't do something stupid with the bit, but it's not
something I am able to make happen.

Best Regards,
Michał Mirosław

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