Date:	Tue, 17 Sep 2013 17:12:32 +0900
From:	Toshiaki Makita <makita.toshiaki@....ntt.co.jp>
To:	vyasevic@...hat.com
Cc:	Toshiaki Makita <toshiaki.makita1@...il.com>,
	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	Fernando Luis Vazquez Cao <fernando_b1@....ntt.co.jp>,
	Patrick McHardy <kaber@...sh.net>
Subject: Re: [PATCH net 0/4] bridge: Fix problems around the PVID

On Mon, 2013-09-16 at 13:49 -0400, Vlad Yasevich wrote:
> On 09/13/2013 08:06 AM, Toshiaki Makita wrote:
> > On Thu, 2013-09-12 at 16:00 -0400, David Miller wrote:
> >> From: Toshiaki Makita <makita.toshiaki@....ntt.co.jp>
> >> Date: Tue, 10 Sep 2013 19:27:54 +0900
> >>
> >>> There seem to be some undesirable behaviors related with PVID.
> >>> 1. It has no effect assigning PVID to a port. PVID cannot be applied
> >>> to any frame regardless of whether we set it or not.
> >>> 2. FDB entries learned via frames applied PVID are registered with
> >>> VID 0 rather than VID value of PVID.
> >>> 3. We can set 0 or 4095 as a PVID that are not allowed in IEEE 802.1Q.
> >>> This leads interoperational problems such as sending frames with VID
> >>> 4095, which is not allowed in IEEE 802.1Q, and treating frames with VID
> >>> 0 as they belong to VLAN 0, which is expected to be handled as they have
> >>> no VID according to IEEE 802.1Q.
> >>>
> >>> Note: 2nd and 3rd problems are potential and not exposed unless 1st problem
> >>> is fixed, because we cannot activate PVID due to it.
> >>
> >> Please work out the issues in patch #2 with Vlad and resubmit this
> >> series.
> >>
> >> Thank you.
> >
> > I'm hovering between whether we should fix the issue by changing vlan 0
> > interface behavior in 8021q module or enabling a bridge port to sending
> > priority-tagged frames, or another better way.
> >
> > If you could comment it, I'd appreciate it :)
> >
> >
> > BTW, I think what is discussed in patch #2 is another problem about
> > handling priority-tags, and it exists without this patch set applied.
> > It looks like that we should prepare another patch set than this to fix
> > that problem.
> >
> > Should I include patches that fix the priority-tags problem in this
> > patch set and resubmit them all together?
> >
> 
> I am thinking that we might need to do it in bridge and it looks like
> the simplest way to do it is to have default priority regeneration table
> (table 6-5 from 802.1Q doc).
> 
> That way I think we would conform to the spec.
> 
> -vlad

Unfortunately I don't think the default priority regeneration table
resolves the problem because IEEE 802.1Q says that a VLAN-aware bridge
can transmit untagged or VLAN-tagged frames only (the end of section 7.5
and 8.1.7).

No mechanism to send priority-tagged frames is found as far as I can see
the standard. I think the regenerated priority is used for outgoing PCP
field only if egress policy is not untagged (i.e. transmitting as
VLAN-tagged), and unused if untagged (Section 6.9.2 3rd/4th Paragraph).

If we want to transmit priority-tagged frames from a bridge port, I
think we need to implement a new (optional) feature that is above the
standard, as I stated previously.

How do you feel about adding a per-port policy that enables a bridge to
send priority-tagged frames instead of untagged frames when egress
policy for the port is untagged?
With this change, we can transmit frames for a given vlan as either all
untagged, all priority-tagged or all VLAN-tagged.

Thanks,

Toshiaki Makita

> 
> >
> > Thanks,
> >
> > Toshiaki Makita
> >
> >>
> >> --
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> >
> >
> >


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