netdev - Re: [PATCH net v2] openvswitch: Fix pop_vlan action for double tagged frames

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Date:   Wed, 20 Dec 2017 13:13:41 -0500
From:   Eric Garver <e@...g.me>
To:     Jiri Benc <jbenc@...hat.com>
Cc:     netdev@...r.kernel.org, ovs-dev@...nvswitch.org
Subject: Re: [PATCH net v2] openvswitch: Fix pop_vlan action for double
 tagged frames

On Wed, Dec 20, 2017 at 06:41:17PM +0100, Jiri Benc wrote:
> On Wed, 20 Dec 2017 10:39:32 -0500, Eric Garver wrote:
> > +	if (is_flow_key_valid(key) && key->eth.vlan.tci && key->eth.cvlan.tci)
> 
> Maybe (key->eth.vlan.tci & htons(VLAN_TAG_PRESENT)) for consistency
> with the rest of the code? But it's just nitpicking.
> 
> The real problem here is when a double tagged packet leaves the ovs
> bridge, it won't have the skb->protocol that the kernel expects: it
> will be ethertype of the payload, while my understanding is it should
> be the inner tpid, right?

Right.

> 
> This patch fixes that nicely for the pop vlan case. But what about
> other cases? It seems to me that we need to add the logic to
> key_extract.
> 

The part I was missing is; before encap into the L3 tunnel all the VLAN
tags must be explicitly popped.

Setting skb->protocol to the TPID for double tagged frames means the pop
operations shift the payload ethertype into skb->protocol.

I'll send a v3 that does this is key_extract().