ipv4: Delete routing cache.

The ipv4 routing cache is non-deterministic, performance wise, and is
subject to reasonably easy to launch denial of service attacks.

The routing cache works great for well behaved traffic, and the world
was a much friendlier place when the tradeoffs that led to the routing
cache's design were considered.

What it boils down to is that the performance of the routing cache is
a product of the traffic patterns seen by a system rather than being a
product of the contents of the routing tables.  The former of which is
controllable by external entitites.

Even for "well behaved" legitimate traffic, high volume sites can see
hit rates in the routing cache of only ~%10.

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 0 insertions, 5 deletions

diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index b83203658ee3..f277cf0e6321 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -1072,11 +1072,6 @@ static int fib_netdev_event(struct notifier_block *this, unsigned long event, vo
                 rt_cache_flush(dev_net(dev), 0);
                 break;
         case NETDEV_UNREGISTER_BATCH:
-                /* The batch unregister is only called on the first
-                 * device in the list of devices being unregistered.
-                 * Therefore we should not pass dev_net(dev) in here.
-                 */
-                rt_cache_flush_batch(NULL);
                 break;
         }
         return NOTIFY_DONE;