np->mcast_oif is read locklessly in some contexts.
Make all accesses to this field lockless, adding appropriate
annotations.
This also makes setsockopt( IPV6_MULTICAST_IF ) lockless.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>