After IP route cache removal, multicast applications using
a lot of multicast addresses hit a O(N) behavior in ip_check_mc_rcu()
Add a per in_device hash table to get faster lookup.
This hash table is created only if the number of items in mc_list is
above 4.
Reported-by: Shawn Bohrer <sbohrer@rgmadvisors.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Tested-by: Shawn Bohrer <sbohrer@rgmadvisors.com>
Reviewed-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
e989707135