Conntrack offload and ingress_ifindex

[Edward Cree <ecree.xilinx@xxxxxxxxx>]

Pablo,

When developing a conntrack offload driver, I was quite surprised to find
 that CT entries passed to the driver's flow-block callback (as registered
 with nf_flow_table_offload_add_cb()) include a match on ingress_ifindex,
 with mask 0xffffffff and key 0.  This is especially confusing as AIUI 0 is
 not a valid ifindex.