+#if defined(NEED_CSUM_NORMALIZE) || LINUX_VERSION_CODE < KERNEL_VERSION(2,6,25)
+/* This is really compatibility code that belongs in the compat directory.
+ * However, it needs access to our normalized checksum values, so put it here.
+ */
+#define inet_proto_csum_replace4 rpl_inet_proto_csum_replace4
+static inline void inet_proto_csum_replace4(__sum16 *sum, struct sk_buff *skb,
+ __be32 from, __be32 to,
+ int pseudohdr)
+{
+ __be32 diff[] = { ~from, to };
+
+ if (get_ip_summed(skb) != OVS_CSUM_PARTIAL) {
+ *sum = csum_fold(csum_partial((char *)diff, sizeof(diff),
+ ~csum_unfold(*sum)));
+ if (get_ip_summed(skb) == OVS_CSUM_COMPLETE && pseudohdr)
+ skb->csum = ~csum_partial((char *)diff, sizeof(diff),
+ ~skb->csum);
+ } else if (pseudohdr)
+ *sum = ~csum_fold(csum_partial((char *)diff, sizeof(diff),
+ csum_unfold(*sum)));
+}
+#endif
+