[NETFILTER] bridge: code rearrangement for clarity

Cleanup and rearrangement for better style and clarity:
	Split the function nf_bridge_maybe_copy_header into two pieces
	Move copy portion out of line.
	Use Ethernet header size macros.
	Use header file to handle CONFIG_NETFILTER_BRIDGE differences

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/netfilter_bridge.h b/include/linux/netfilter_bridge.h
index 427c67f..274fe4b 100644
--- a/include/linux/netfilter_bridge.h
+++ b/include/linux/netfilter_bridge.h
@@ -47,26 +47,12 @@
 
 
 /* Only used in br_forward.c */
-static inline
-int nf_bridge_maybe_copy_header(struct sk_buff *skb)
+extern int nf_bridge_copy_header(struct sk_buff *skb);
+static inline int nf_bridge_maybe_copy_header(struct sk_buff *skb)
 {
-	int err;
-
-	if (skb->nf_bridge) {
-		if (skb->protocol == __constant_htons(ETH_P_8021Q)) {
-			err = skb_cow(skb, 18);
-			if (err)
-				return err;
-			memcpy(skb->data - 18, skb->nf_bridge->data, 18);
-			skb_push(skb, 4);
-		} else {
-			err = skb_cow(skb, 16);
-			if (err)
-				return err;
-			memcpy(skb->data - 16, skb->nf_bridge->data, 16);
-		}
-	}
-	return 0;
+	if (skb->nf_bridge)
+		return nf_bridge_copy_header(skb);
+  	return 0;
 }
 
 /* This is called by the IP fragmenting code and it ensures there is
@@ -90,6 +76,8 @@
 };
 
 extern int brnf_deferred_hooks;
+#else
+#define nf_bridge_maybe_copy_header(skb)	(0)
 #endif /* CONFIG_BRIDGE_NETFILTER */
 
 #endif /* __KERNEL__ */