net: core: Use csum_replace_by_diff() and csum_sub() instead of opencoding

Open coded calculation can be avoided and replaced by the
equivalent csum_replace_by_diff() and csum_sub().

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/utils.c b/net/core/utils.c
index 1f31a39236d52fea76eb4925e5c43636c7e9477f..938495bc1d348b4c865cf129b6be51275a730871 100644 (file)
--- a/net/core/utils.c
+++ b/net/core/utils.c
@@ -476,9 +476,9 @@ void inet_proto_csum_replace_by_diff(__sum16 *sum, struct sk_buff *skb,
                                     __wsum diff, bool pseudohdr)
 {
        if (skb->ip_summed != CHECKSUM_PARTIAL) {
-               *sum = csum_fold(csum_add(diff, ~csum_unfold(*sum)));
+               csum_replace_by_diff(sum, diff);
                if (skb->ip_summed == CHECKSUM_COMPLETE && pseudohdr)
-                       skb->csum = ~csum_add(diff, ~skb->csum);
+                       skb->csum = ~csum_sub(diff, skb->csum);
        } else if (pseudohdr) {
                *sum = ~csum_fold(csum_add(diff, csum_unfold(*sum)));
        }