netdev - Re: [PATCH 1/2] vlan: only create special VLAN 0 once

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Date:	Tue, 7 Jun 2011 18:41:36 +0200
From:	Jiri Bohac <jbohac@...e.cz>
To:	Patrick McHardy <kaber@...sh.net>
Cc:	David Miller <davem@...emloft.net>, jbohac@...e.cz,
	netdev@...r.kernel.org, pedro.netdev@...devamos.com
Subject: Re: [PATCH 1/2] vlan: only create special VLAN 0 once

On Tue, Jun 07, 2011 at 05:17:27PM +0200, Patrick McHardy wrote:
> On 05.06.2011 23:28, David Miller wrote:
> > I am pretty sure that the hardware device driver methods that
> > implement ndo_vlan_rx_add_vid() assume that the device is up.
> > Because most drivers completely reset the chip when the
> > interface is brought up and this will likely clear out the
> > VLAN ID tables in the chip.
> > 
> 
> Good point.
> 
> I don't think this approach works very well at all since
> some drivers don't do incremental updates, but iterate over
> the registered VLAN group when constructing filters. The
> group is not created until the first real VLAN device is
> registered however.
> 
> Based on a quick grep (may have missed some):
> 
> - via_velocity, mlx4, starfire: will do nothing
> 
> - benet, igb, vxge, igbvf, ixgbevf, e1000e: would oops on
>   rx_kill_vid due to unnecessary vlan_group_set_device()

which approach do you mean? David's or mine? I suppose you mean
David's, because I did not call rx_kill_vid().

> The assumption of the drivers that a VLAN group exists
> before the first VID is configured is reasonable in my
> opinion, a lot of them also don't even configure VLAN
> filtering until the VLAN group is registered.

So this is broken already since ad1afb00 :(
The assumption broke the bonding driver and this got fixed by
f35188fa, btw.

> So I think a good solution would be to make sure all
> drivers don't enable VLAN filtering before the first
> VLAN is actually registered and do the automatic
> registration of VID 0 once the first real VLAN device
> is created.

But this behaviour is not what was intended by ad1afb00.
The VID 0 needs to be registered by default, to make 8021p work.
Even without any real VLAN devices created.

-- 
Jiri Bohac <jbohac@...e.cz>
SUSE Labs, SUSE CZ

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