[NET]: Move netfilter checksum helpers to net/core/utils.c

This allows to get rid of the CONFIG_NETFILTER dependency of NET_ACT_NAT.
This patch redefines the old names to keep the noise low, the next patch
converts all users.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 16 insertions, 0 deletions

diff --git a/net/core/utils.c b/net/core/utils.c
index 0bf17da40d52..34459c4c740c 100644
--- a/net/core/utils.c
+++ b/net/core/utils.c
@@ -293,3 +293,19 @@ out:
 }
 
 EXPORT_SYMBOL(in6_pton);
+
+void inet_proto_csum_replace4(__sum16 *sum, struct sk_buff *skb,
+                              __be32 from, __be32 to, int pseudohdr)
+{
+        __be32 diff[] = { ~from, to };
+        if (skb->ip_summed != CHECKSUM_PARTIAL) {
+                *sum = csum_fold(csum_partial(diff, sizeof(diff),
+                                ~csum_unfold(*sum)));
+                if (skb->ip_summed == CHECKSUM_COMPLETE && pseudohdr)
+                        skb->csum = ~csum_partial(diff, sizeof(diff),
+                                                ~skb->csum);
+        } else if (pseudohdr)
+                *sum = ~csum_fold(csum_partial(diff, sizeof(diff),
+                                csum_unfold(*sum)));
+}
+EXPORT_SYMBOL(inet_proto_csum_replace4);