Subject: Re: [PATCH v2 net] vlan: Mask off vlan acceleration features on vlan device.

From: Vlad Yasevich <[email-masked]>
Date: Wed, 26 Mar 2014 21:03:47 -0400

On 03/26/2014 05:10 PM, David Miller wrote:
> From: Vlad Yasevich <[email-masked]>
> Date: Wed, 26 Mar 2014 16:28:31 -0400
> 
>> Some drivers incorrectly assign vlan acceleration features to
>> vlan_features thus causing issues for Q-in-Q vlan configurations.
>> Prevent this once and for all by masking off acceleration features
>> for vlan devices until such time as we support stacked acceleration.
>>
>> Signed-off-by: Vlad Yasevich <[email-masked]>
> 
> So what if we do have chips that can offload Q-in-Q?  Will we use
> a new flag?
> 

If there are chips that can take both the inner and outer tags an put
both vlan headers on the packet, then we'll need a lot more then just
a new flag to support that since the skbs will need to carry 2 vlan_tci
values in that case.

With this patch you can still offload the outer tag, whether STAG and
or CTAG (old Q-in-Q), but the inner tag can't be offloaded.

-vlad