datapath: Scrub skb between namespaces

datapath: Scrub skb between namespaces

If OVS receives a packet from another namespace, then the packet should
be scrubbed. However, people have already begun to rely on the behaviour
that skb->mark is preserved across namespaces, so retain this one field.

This is mainly to address information leakage between namespaces when
using OVS internal ports, but by placing it in ovs_vport_receive() it is
more generally applicable, meaning it should not be overlooked if other
port types are allowed to be moved into namespaces in future.

Upstream: 740dbc289155 ("openvswitch: Scrub skb between namespaces")
Signed-off-by: Joe Stringer <joestringer@nicira.com>
Acked-by: Pravin B Shelar <pshelar@nicira.com>