net: Add inet_proto_csum_replace_by_diff utility function
This function updates a checksum field value and skb->csum based on
a value which is the difference between the old and new checksum.
Signed-off-by: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/checksum.h b/include/net/checksum.h
index 619f344..9fcaedf 100644
--- a/include/net/checksum.h
+++ b/include/net/checksum.h
@@ -144,6 +144,8 @@
void inet_proto_csum_replace16(__sum16 *sum, struct sk_buff *skb,
const __be32 *from, const __be32 *to,
bool pseudohdr);
+void inet_proto_csum_replace_by_diff(__sum16 *sum, struct sk_buff *skb,
+ __wsum diff, bool pseudohdr);
static inline void inet_proto_csum_replace2(__sum16 *sum, struct sk_buff *skb,
__be16 from, __be16 to,