-----Original Message-----
From: netdev-owner@vger.kernel.org [mailto:netdev-owner@vger.kernel.org] On
Behalf Of Eric Dumazet
Sent: Thursday, June 17, 2010 1:29 PM
To: Vladislav Zolotarov
Cc: Arnd Bergmann; Patrick McHardy; Pedro Garcia; netdev@vger.kernel.org; Ben
Hutchings
Subject: RE: [PATCH] vlan_dev: VLAN 0 should be treated as "no vlan tag"
(802.1p packet)

Le jeudi 17 juin 2010 à 01:56 -0700, Vladislav Zolotarov a écrit :

quoted

quoted

-----Original Message-----
From: netdev-owner@vger.kernel.org [mailto:netdev-owner@vger.kernel.org]

On

quoted

quoted

Behalf Of Eric Dumazet
Sent: Wednesday, June 16, 2010 9:58 PM
To: Arnd Bergmann
Cc: Patrick McHardy; Pedro Garcia; netdev@vger.kernel.org; Ben Hutchings
Subject: Re: [PATCH] vlan_dev: VLAN 0 should be treated as "no vlan tag"
(802.1p packet)

Le mercredi 16 juin 2010 à 20:26 +0200, Arnd Bergmann a écrit :

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On Wednesday 16 June 2010 17:28:23 Patrick McHardy wrote:

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Since we don't have any special VLAN handling in the bridging code, I
guess it comes down to optionally using a different ethertype value
(0x88a8) in the VLAN code. We probably also need some indication from
device drivers whether they are able to add these headers to avoid
trying to offload tagging in case they're not.

It's probably a little more than just supporting the new ethertype, but

not

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much. The outer tag can be handled like our current VLAN module does,
but the standard does not allow a regular frame to be encapsulated

directly,

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but rather requires one of

1. In 802.1ad: an 802.1Q VLAN tag (ethertype 0x8100) followed by the

frame

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2. In 802.1ah: A service tag (ethertype 0x88e7) followed by the 802.1Q

VLAN

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tag

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   and then the frame.

Maybe what we can do is extend the vlan code to understand all three

frame

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formats (q, ad and ah) or at least the first two so we configure both

the

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provider VID and the Customer VID for the interface in case of 802.1ad

but

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only the regular VID in 802.1Q.

Device drivers can then flag whether they support both formats or just
the regular Q tag.

	Arnd

Speaking of device drivers, I see bnx2 (hardware accelerated) is able to
insert a 8021q tag in case no vlgrp is defined (the 8201q tag that was
removed by NIC)... interesting ping pong games, since our 8021q stack
will remove it again, eventually.

So VLAN 0 'problem' on bnx2 could be solved with following patch
(avoiding this insert if vtag==0)

diff --git a/drivers/net/bnx2.c b/drivers/net/bnx2.c
index 522de9f..b5d4d05 100644
--- a/drivers/net/bnx2.c
+++ b/drivers/net/bnx2.c

@@ -3192,7 +3192,7 @@ bnx2_rx_int(struct bnx2 *bp, struct bnx2_napi

*bnapi,

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int budget)
 				hw_vlan = 1;
 			else
 #endif
-			{
+			if (vtag) {
 				struct vlan_ethhdr *ve = (struct vlan_ethhdr *)
 					__skb_push(skb, 4);



--

This way u will loose all the priority information that was on the VLAN

header.

16bits vtag = 0 : there is no priority information.

According to IEEE 802.1p PCP=0 is legal priority, CFI bit is usually zero. So, VTAG=0 would mark a priority tagged frame with a priority 0 and it should be handled differently than a frame with no priority at all and your patch will prevent it.

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