netdev - Re: [PATCH] vlan: allow VLAN ID 0 to be used

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Date:	Tue, 27 Oct 2009 10:52:41 +0100
From:	Benny Amorsen <benny+usenet@...rsen.dk>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	unlisted-recipients:; (no To-header on input)
	Gertjan Hofman <gertjan_hofman@...oo.com>,
	Matt Carlson <mcarlson@...adcom.com>,
	"netdev\@vger.kernel.org" <netdev@...r.kernel.org>,
	Patrick McHardy <kaber@...sh.net>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH] vlan: allow VLAN ID 0 to be used

Eric Dumazet <eric.dumazet@...il.com> writes:

> Here is the patch I cooked that permitted VLAN 0 to be used with tg3
> (and other HW accelerated vlan nics I suppose)
>
> [PATCH] vlan: allow VLAN ID 0 to be used
>
> We currently use a 16 bit field (vlan_tci) to store VLAN ID on a skb.
>
> 0 value is used a special value, meaning VLAN ID not set.
> This forbids use of VLAN ID 0

Are you sure you actually want to do this?

VLAN 0 IS special. Frames received on VLAN 0 should be treated just as
if they had no VLAN tag at all, except that they have an 802.1p value.

Sending frames with VLAN 0 should have something to do with whether
the sender wants to use 802.1p, which doesn't really have much to do
with VLAN's at all...

It would be nice if the unsuspecting user was at least warned that their
use of VLAN 0 is non-standard and may cause surprising results like
leakage into the "native" VLAN. That could be done in /sbin/ip or
/sbin/vconfig, of course.

/Benny

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