netdev - Re: 2.6.35 -> 2.6.36 panic when vlan and promisc with tg3

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Date:	Wed, 1 Dec 2010 11:17:16 +0100
From:	Michael Leun <lkml20101129@...ton.leun.net>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Ben Greear <greearb@...delatech.com>, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org
Subject: Re: 2.6.35 -> 2.6.36 panic when vlan and promisc with tg3

On Tue, 30 Nov 2010 10:20:09 +0100
Eric Dumazet <eric.dumazet@...il.com> wrote:

> Le mardi 30 novembre 2010 à 09:59 +0100, Michael Leun a écrit :
> > On Mon, 29 Nov 2010 16:19:06 -0800
> > Ben Greear <greearb@...delatech.com> wrote:
> > 
> > > On 11/29/2010 11:17 AM, Michael Leun wrote:
> > > > UG: unable to handle kernel paging request at 01cc921c
> > > > IP: [<c034bfce>] vlan_hwaccel_do_receive+0x59/0xd0
> > > > *pdpt = 0000000036a2a001 *pde = 0000000000000000
> > > > Oops: 0002 [#1] SMP
> > > > last sysfs
> > > >
> > > > Then machine dead.
> > > >
> > > > In 2.6.35.x this did not happen (but vlans broken - cannot see
> > > > vlan tags with tcpdump),
> > > 
> > > Try this patch:
> > > 
> > > http://permalink.gmane.org/gmane.linux.network/176566
> > > 
> > > It looks like this hasn't made it into stable yet?
> > 
> > > > To reproduce:
> > > >
> > > > ip link set eth0 up
> > > > vconfig add eth0 2
> > > > ip link set eth0 promisc on
> > 
> > It makes it better - it does not crash anymore on this commands -
> > but if you add an "tcpdump -i eth0 -n" at the end it does. So,
> > unfortunately no real solution.
> > 
> > I guess, "dropping packet no one is interested in" (as noted in the
> > patch) does not work very well if tcpdump is actually interested?
> > 
> 
> Could you try with following patch instead, for net/core/dev.c 
> 
> (and keep the net/8021q/vlan_core.c part)
> 
> --- net/core/dev.c.orig
> +++ net/core/dev.c
> @@ -2891,6 +2891,9 @@
>  ncls:
>  #endif
>  
> +	if (unlikely(vlan_tx_tag_present(skb)))
> +		goto bypass;
> +
>  	/* Handle special case of bridge or macvlan */
>  	rx_handler = rcu_dereference(skb->dev->rx_handler);
>  	if (rx_handler) {
> @@ -2927,6 +2930,7 @@
>  		}
>  	}
>  
> +bypass:
>  	if (pt_prev) {
>  		ret = pt_prev->func(skb, skb->dev, pt_prev,
> orig_dev); } else {
> 
> 

Yup, from what I've tested this works (and tcpdump sees broadcast
packets even for vlans not configured at the moment including vlan tag
- yipee!).

-- 
MfG,

Michael Leun

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