tc: handle packet mark of zero

tc: handle packet mark of zero

Openstack may set an skb mark of 0 in tunnel rules. This is considered to
be an unused/unset value. However, it prevents the rule from being
offloaded.

Check if the key value of the skb mark is 0 when it is in use (mask is
set to all ones). If it is then ignore the field and continue with TC offload.

Only the exact-match case is covered by this patch as it addresses the
Openstack use-case and seems most robust against feature evolution: f.e. in
future there may exist hardware offload scenarios where an operation, such
as a BPF offload, sets the SKB mark before proceeding tho the in-HW OVS.
datapath.

Signed-off-by: John Hurley <john.hurley@netronome.com>
Co-Authored-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: Simon Horman <simon.horman@netronome.com>
Acked-by: Aaron Conole <aconole@redhat.com>