ipv4: inetdev_by_index() switch to RCU

Use dev_get_by_index_rcu() instead of __dev_get_by_index() and
dev_base_lock rwlock
Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/devinet.c

@@ -405,11 +405,12 @@ struct in_device *inetdev_by_index(struct net *net, int ifindex)
 {
 	struct net_device *dev;
 	struct in_device *in_dev = NULL;
-	read_lock(&dev_base_lock);
-	dev = __dev_get_by_index(net, ifindex);
+
+	rcu_read_lock();
+	dev = dev_get_by_index_rcu(net, ifindex);
 	if (dev)
 		in_dev = in_dev_get(dev);
-	read_unlock(&dev_base_lock);
+	rcu_read_unlock();
 	return in_dev;
 }