netdev - Re: Wrong padding of short packets send by a tagged-vlan interface?

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Date:	Mon, 7 Jul 2008 23:29:12 +0200 (CEST)
From:	Krzysztof Oledzki <olel@....pl>
To:	Ben Greear <greearb@...delatech.com>
cc:	netdev@...r.kernel.org, kaber@...sh.net
Subject: Re: Wrong padding of short packets send by a tagged-vlan interface?

On Mon, 7 Jul 2008, Ben Greear wrote:

> Krzysztof Oledzki wrote:
>> Hello,
>> 
>> I have a problem that I'm not able to connect from selected linux hosts to 
>> a newly installed Netware 6.5 server. After two days of debugging I 
>> discovered that the problem seems to be caused by an insufficient padding 
>> of a .1q tagged packets.
>
> Last time this came up I looked up the RFC and according to it
> there is no need to pad beyond the normal 60 + 4, vlan tag or
> not.
>
> This is a bug in your intervening switch and/or Netware unless you actually 
> see packets
> leaving Linux with less than 60 + 4 bytes.

Rather a Broadcom Corporation NetXtreme II driver "feature" as AFAIK 
Netware 6.5 does not support .1Q natively and vlans are implemented 
directly in network drivers, especially that everything worked with a 
previous hardware (Intel 82541GI based).

So yes, it may not be a Linux bug but it would be nice to make Linux more 
compatible with such configurations, of course if that is possible. Please 
also note that this problem does not exists with Netware<->Netware 
communication (both NetXtreme II<->NetXtreme II and 82541GI<->NetXtreme 
II) so it seems that both Intel and Broadcom supports the "extened" 
padding of .1Q packets in their Netware drivers.

Best regards,

 				Krzysztof Olędzki