netdev - Re: issues with vxlan RX checksum offload under OVS datapath

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Date:	Tue, 21 Jan 2014 23:43:58 +0200
From:	Or Gerlitz <or.gerlitz@...il.com>
To:	Joseph Gasparakis <joseph.gasparakis@...el.com>
Cc:	Pravin Shelar <pshelar@...ira.com>,
	Or Gerlitz <ogerlitz@...lanox.com>,
	netdev <netdev@...r.kernel.org>
Subject: Re: issues with vxlan RX checksum offload under OVS datapath

On Tue, Jan 21, 2014, Joseph Gasparakis <joseph.gasparakis@...el.com> wrote:
> On Tue, 21 Jan 2014, Or Gerlitz wrote:

>> To be a bit more precise/concrete here, do we agree that the both paths must >>    skb->encapsulation = 0;
>> which is done now only by the non-ovs path

> Originally skb->encapsulation had (and still has) the meaning of "does
> this skb have outer *and* (valid) inner headers? If so, it is an
> encapsulated packet".
> So based on this skb->encapsulation should be set as soon an (inner)
> packet gets encapsulated and unset when decapsulation takes place, and
> ideally this should happen in the ovs path too.

I would say critically not ideally... e.g when the packet is
destinat-ed to a VM and goes through tap netdevice plugged to OVS --
without this de-assignment weird things happen after the point in time
where the ovs TX path calls dev_queue_xmit() in
net/openvswitch/vport-netdev.c

> Together with skb->encapsulation the inner headers should be correctly set.

That's interesting point, what might break if this isn't done?
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