net: ipv4: refactor __ip_route_output_key_hash

A later patch wants access to the fib result on an output route lookup
with the rcu lock held. Refactor __ip_route_output_key_hash, pushing
the logic between rcu_read_lock ... rcu_read_unlock into a new helper
with the fib_result as an input arg.

To keep the name length under control remove the leading underscores
from the name and add _rcu to the name of the new helper indicating it
is called with the rcu read lock held.

Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/route.h b/include/net/route.h
index 2cc0e14..89e4028 100644
--- a/include/net/route.h
+++ b/include/net/route.h
@@ -113,13 +113,16 @@ struct in_device;
 int ip_rt_init(void);
 void rt_cache_flush(struct net *net);
 void rt_flush_dev(struct net_device *dev);
-struct rtable *__ip_route_output_key_hash(struct net *net, struct flowi4 *flp,
-					  const struct sk_buff *skb);
+struct rtable *ip_route_output_key_hash(struct net *net, struct flowi4 *flp,
+					const struct sk_buff *skb);
+struct rtable *ip_route_output_key_hash_rcu(struct net *net, struct flowi4 *flp,
+					    struct fib_result *res,
+					    const struct sk_buff *skb);
 
 static inline struct rtable *__ip_route_output_key(struct net *net,
 						   struct flowi4 *flp)
 {
-	return __ip_route_output_key_hash(net, flp, NULL);
+	return ip_route_output_key_hash(net, flp, NULL);
 }
 
 struct rtable *ip_route_output_flow(struct net *, struct flowi4 *flp,