netdev - Re: [PATCH net-next 1/7] openvswitch: Use inverted tuple in ovs_ct_find

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Date:   Sun, 05 Feb 2017 17:28:24 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     jarno@....org
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH net-next 1/7] openvswitch: Use inverted tuple in
 ovs_ct_find_existing() if NATted.

From: Jarno Rajahalme <jarno@....org>
Date: Thu,  2 Feb 2017 17:10:00 -0800

> This does not match either of the conntrack tuples above.  Normally
> this does not matter, as the conntrack lookup was already done using
> the tuple (B,A), but if the current packet does not match any flow in
> the OVS datapath, the packet is sent to userspace via an upcall,
> during which the packet's skb is freed, and the conntrack entry
> pointer in the skb is lost.

This is the real bug.

If the metadata for a packet is important, as it obviously is here,
then upcalls should preserve that metadata across the upcall.  This
is exactly how NF_QUEUE handles this problem and so should OVS.