netdev - Re: [PATCH] igb: Fix VLAN tag stripping on Intel i350

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Date:	Wed, 27 Jan 2016 11:25:22 -0800
From:	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
To:	Corinna Vinschen <vinschen@...hat.com>,
	intel-wired-lan@...ts.osuosl.org
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH] igb: Fix VLAN tag stripping on Intel i350

On Wed, 2016-01-27 at 14:28 +0100, Corinna Vinschen wrote:
> Problem: When switching off VLAN offloading on an i350, the VLAN
> interface gets unusable.  For testing, set up a VLAN on an i350
> and some remote machine, e.g.:
> 
>   $ ip link add link eth0 name eth0.42 type vlan id 42
>   $ ip addr add 192.168.42.1/24 dev eth0.42
>   $ ip link set dev eth0.42 up
> 
> Offloading is switched on by default:
> 
>   $ ethtool -k eth0 | grep vlan-offload
>   rx-vlan-offload: on
>   tx-vlan-offload: on
> 
>   $ ping -c 3 -I eth0.42 192.168.42.2
>   [...works as usual...]
> 
> Now switch off VLAN offloading and try again:
> 
>   $ ethtool -K eth0 rxvlan off
>   Actual changes:
>   rx-vlan-offload: off
>   tx-vlan-offload: off [requested on]
>   $ ping -c 3 -I eth0.42 192.168.42.2
>   PING 192.168.42.2 (192.168.42.2) from 192.168.42.1 eth0.42: 56(84)
> bytes of data.
> 
>   --- 192.168.42.2 ping statistics ---
>   3 packets transmitted, 0 received, 100% packet loss, time 1999ms
> 
> I can only reproduce it on an i350, the above works fine on a 82580.
> 
> While inspecting the igb source, I came across the code in
> igb_set_vmolr
> which sets the E1000_VMOLR_STRVLAN/E1000_DVMOLR_STRVLAN flags once
> and
> for all, and in all of the igb code there's no other place where the
> STRVLAN is set or cleared.  Thus, VLAN stripping is enabled in igb
> unconditionally, independently of the offloading setting.
> 
> I compared that to the latest Intel igb-5.3.3.5 driver from
> http://sourceforge.net/projects/e1000/ which in fact sets and clears
> the
> STRVLAN flag independently from igb_set_vmolr in its own function
> igb_set_vf_vlan_strip, depending on the vlan settings.
> 
> So I included the STRVLAN handling from the igb-5.3.3.5 driver into
> our
> current igb driver and tested the above scenario again.  This time
> ping
> still works after switching off VLAN offloading.
> 
> Tested on i350, with and without addtional VFs, as well as on 82580
> successfully.
> 
> Signed-off-by: Corinna Vinschen <vinschen@...hat.com>
> ---
>  drivers/net/ethernet/intel/igb/igb_main.c | 39
> ++++++++++++++++++++++++-------
>  1 file changed, 31 insertions(+), 8 deletions(-)

I tried applying your patch to my tree for review and validation, but
due to patches already applied against the igb driver in my tree, your
patch does not apply cleanly.

Can you please update your patch to apply cleanly to my tree?
git://git.kernel.org/pub/scm/linux/kernel/git/jkirsher/next-queue.git
dev-queue

(next-queue tree and dev-queue branch)
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