netdev - Re: [PATCH 2.6.36] vlan: Avoid hwaccel vlan packets when vid not used

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Message-ID: <20110107032459.GA17959@mcarlson.broadcom.com>
Date:	Thu, 6 Jan 2011 19:24:59 -0800
From:	"Matt Carlson" <mcarlson@...adcom.com>
To:	"Jesse Gross" <jesse@...ira.com>
cc:	"Michael Leun" <lkml20101129@...ton.leun.net>,
	"Matthew Carlson" <mcarlson@...adcom.com>,
	"Michael Chan" <mchan@...adcom.com>,
	"Eric Dumazet" <eric.dumazet@...il.com>,
	"David Miller" <davem@...emloft.net>,
	"Ben Greear" <greearb@...delatech.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH 2.6.36] vlan: Avoid hwaccel vlan packets when vid
 not used

On Sat, Dec 18, 2010 at 07:38:00PM -0800, Jesse Gross wrote:
> On Tue, Dec 14, 2010 at 11:16 PM, Michael Leun
> <lkml20101129@...ton.leun.net> wrote:
> > OK - all tests done on that DL320G5:
> >
> > For completeness, 2.6.37-rc5 unpatched:
> >
> > eth0, no vlan configured: totally broken - see double tagged vlans
> > without tag, single or untagged packets missing at all
> 
> Random behavior?  This one is somewhat hard to explain - maybe there
> are some other factors.  eth0 has ASF on, so it always strips tags.  I
> would expect it to behave like the vlan configured case.
> 
> >
> > eth0, vlan configured: see packets without vlan tag (see double tagged
> > packets with one vlan tag)
> 
> Both ASF and vlan group configured cause tag stripping to be enabled.
> Missing tag.
> 
> >
> > eth1 same as originally reported:
> > without vlan configured see vlan tags (single and double tagged as
> > expected)
> 
> No ASF and no vlan group means tag stripping is disabled.  Have tag.
> 
> > with vlan configured: see packets without vlan tag (see double tagged
> > packets with one vlan tag)
> 
> Configuring vlan group causes stripping to be enabled.  Missing tag.
> 
> >
> >
> > 2.6.37-rc5, your tg3 use new vlan-code patch:
> >
> > eth0, no vlan configured: ?see packets without vlan tag (see double
> > tagged packets with one vlan tag)
> 
> ASF enables tag stripping.  Missing tag.
> 
> > eth1, no vlan configured: see vlan tags (single and double tagged as
> > expected)
> 
> No ASF, no vlan group means no stripping.  Have tag.
> 
> >
> >
> > eth0, vlan configured: as without vlan
> 
> ASF enables stripping.  Missing tag.
> 
> > eth1, vlan configured: as without vlan
> 
> With this patch vlan stripping is only enabled when ASF is on, so no
> stripping.  Have tag.
> 
> >
> > 2.6.37-rc5, your tg3 use new vlan-code patch with test patch ontop
> >
> > eth1 no vlan configured: see packets without vlan tag (see double tagged
> > packets with one vlan tag)
> 
> With the second patch, vlan stripping is always enabled.  Missing tag.
> 
> > eth1 with vlan: the same
> 
> Stripping still always enabled.  Missing tag.
> 
> The bottom line is whenever vlan stripping is enabled we're missing
> the outer tag.  It might be worth adding some debugging in the area
> before napi_gro_receive/vlan_gro_receive (depending on version).  My
> guess is that (desc->type_flags & RXD_FLAG_VLAN) is false even for
> vlan packets on this NIC.
> 
> You said that everything works on the 5752?  Matt, is it possible that
> the 5714 either has a problem with vlan stripping or a different way
> of reporting it?

I don't think this is a 5714 specific issue.  I think the problem is
rooted in the fact that the VLAN tag stripping is enabled.

Your RXD_FLAG_VLAN idea sounds unlikely to me, but it's worth a check.

The patch here is using __vlan_hwaccel_put_tag(), which informs the
stack a VLAN tag is present.  If this is indeed a reporting problem, I'm
not sure what else the driver should be doing.

> Also, why does ASF require vlan stripping?

This is a firmware limitation.

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