net: Reset secmark when scrubbing packet

net: Reset secmark when scrubbing packet

skb_scrub_packet() is called when a packet switches between a context
such as between underlay and overlay, between namespaces, or between
L3 subnets.

While we already scrub the packet mark, connection tracking entry,
and cached destination, the security mark/context is left intact.

It seems wrong to inherit the security context of a packet when going
from overlay to underlay or across forwarding paths.

Signed-off-by: Thomas Graf <[email protected]>
Acked-by: Flavio Leitner <[email protected]>
Signed-off-by: David S. Miller <[email protected]>