Date:	Sun, 25 Oct 2009 21:30:09 -0700 (PDT)
From:	Gertjan Hofman <gertjan_hofman@...oo.com>
To:	Matt Carlson <mcarlson@...adcom.com>
Cc:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Benny Amorsen <benny+usenet@...rsen.dk>
Subject: Re: VLAN and ARP failure on tg3 drivers

Dear Matt, Eric, Benny,

Sorry about the slow response to your fast replies. I think Benny is correct, the 'problem' lies in the fact that we were using a VLAN ID of 0, without knowing its special significance. User error.

I tested it with other VLAN id's (>0) and it appears to work fine. We are not entirely sure we understand  why it used to work with VLAN ID 0 on the Broadcom chips and still does with a number of different cards (with >2.6.27 kernels).  What is the 'correct' behaviour for this incorrect usage ? When a PC returns the ARP response to the machine with the BroadCom card, it will have the destination address of the VLAN device, but presumably the VLAN ID tag set to zero.  Hmmm. I can live with not knowing the answer I guess.


Thanks again,

Gertjan



 

--- On Fri, 10/23/09, Matt Carlson <mcarlson@...adcom.com> wrote:

> From: Matt Carlson <mcarlson@...adcom.com>
> Subject: Re: VLAN and ARP failure on tg3 drivers
> To: "Gertjan Hofman" <gertjan_hofman@...oo.com>
> Cc: "netdev@...r.kernel.org" <netdev@...r.kernel.org>
> Date: Friday, October 23, 2009, 3:35 PM
> On Thu, Oct 22, 2009 at 09:52:42PM
> -0700, Gertjan Hofman wrote:
> > Dear Kernel developers,
> > 
> > A couple of weeks ago we tried to migrate from a
> 2.6.24? kernel to a 2.6.29 kernel and noticed our VLAN
> application no longer works.? The problem is easy to
> replicate:
> > 
> > 1. connect 2 PC's with a cross-over cable
> > 2. set up a fixed IP address to both PC's? (say
> 192.168.0.[1,2])
> > 3. create a vlan:? vconfig? add eth0 0.
> > 4. set IP addresses on the VLAN devices? (say
> 192.168.1.[1,2])
> > 5. try ping one machine from the other.
> > 
> > I tried to dig into the problem by using un-patched
> kernel.org kernels with Ubuntu .config files.? Kernels up to
> 2.6.26 work fine, kernels after and including 2.6.27 fail.
> The problem is that ARP messages are being dropped. If the
> ARP table is updated by hand on each machine, the
> communication across the VLAN works fine.
> > 
> > At first I thought the kernel VLAN code was the
> problem (we had an earlier issue with a regression in
> 2.6.24) but it looks like the problem is actually with the
> tg3 driver.? Our system uses Broadcom ethernet chips. I
> tried the same experiments with combination of boards that
> have Broadcom and none-Broadcom and the only time I see it
> fail is with the tg3? driver loaded.
> > 
> > Snooping with WireShark shows that a ARP request from
> the non-Broadcom machine is seen and even answered, but
> never appears back on the network. If the Broadcom machine
> orginates the ARP message, it never arrives at the
> destination. I tried lowering the size of the MTU to 1492 as
> well as giving each VLAN device a different MAC. No deal.
> > 
> > I tried to look at tg3 patch changes from 2.6.26 to
> 2.6.27 but I am not familiar enough with the Git system to
> extract the appropiate changes.? I am a bit surprised that I
> am not seeing any references to this on the web, the
> combination of >2.6.27 kernels, Broadcom and VLAN cant be
> that uncommon.
> > 
> > I would be happy to provide more information and to
> try tests if any one can suggest them.
> > 
> > Sincerely,
> > 
> > Gertjan
> 
> I don't see any reason why your setup should fail, but it
> doesn't hurt
> to gather more info about the problem.
> 
> What device are you experiencing this problem with? 
> Is management
> firmware enabled?  (`ethtool -i ethx`)
> 
>






      
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