net: use reciprocal_scale() helper

Replace open codings of (((u64) <x> * <y>) >> 32) with reciprocal_scale().

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/inet_hashtables.c

@@ -229,7 +229,7 @@ begin:
 			}
 		} else if (score == hiscore && reuseport) {
 			matches++;
-			if (((u64)phash * matches) >> 32 == 0)
+			if (reciprocal_scale(phash, matches) == 0)
 				result = sk;
 			phash = next_pseudo_random32(phash);
 		}

net/ipv4/netfilter/ipt_CLUSTERIP.c

@@ -285,7 +285,7 @@ clusterip_hashfn(const struct sk_buff *skb,
 	}
 
 	/* node numbers are 1..n, not 0..n */
-	return (((u64)hashval * config->num_total_nodes) >> 32) + 1;
+	return reciprocal_scale(hashval, config->num_total_nodes) + 1;
 }
 
 static inline int

net/ipv4/udp.c

@@ -224,7 +224,7 @@ int udp_lib_get_port(struct sock *sk, unsigned short snum,
 		remaining = (high - low) + 1;
 
 		rand = prandom_u32();
-		first = (((u64)rand * remaining) >> 32) + low;
+		first = reciprocal_scale(rand, remaining) + low;
 		/*
 		 * force rand to be an odd multiple of UDP_HTABLE_SIZE
 		 */
@@ -448,7 +448,7 @@ begin:
 			}
 		} else if (score == badness && reuseport) {
 			matches++;
-			if (((u64)hash * matches) >> 32 == 0)
+			if (reciprocal_scale(hash, matches) == 0)
 				result = sk;
 			hash = next_pseudo_random32(hash);
 		}
@@ -529,7 +529,7 @@ begin:
 			}
 		} else if (score == badness && reuseport) {
 			matches++;
-			if (((u64)hash * matches) >> 32 == 0)
+			if (reciprocal_scale(hash, matches) == 0)
 				result = sk;
 			hash = next_pseudo_random32(hash);
 		}