netfilter: decouple nf_hook_entry and nf_hook_ops

During nfhook traversal we only need a very small subset of
nf_hook_ops members.

We need:
- next element
- hook function to call
- hook function priv argument

Bridge netfilter also needs 'thresh'; can be obtained via ->orig_ops.

nf_hook_entry struct is now 32 bytes on x86_64.

A followup patch will turn the run-time list into an array that only
stores hook functions plus their priv arguments, eliminating the ->next
element.
Suggested-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Aaron Conole <aconole@bytheb.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/linux/netfilter.h

@@ -75,7 +75,8 @@ struct nf_hook_ops {
 
 struct nf_hook_entry {
 	struct nf_hook_entry __rcu	*next;
-	struct nf_hook_ops		ops;
+	nf_hookfn			*hook;
+	void				*priv;
 	const struct nf_hook_ops	*orig_ops;
 };
 
@@ -83,21 +84,22 @@ static inline void
 nf_hook_entry_init(struct nf_hook_entry *entry,	const struct nf_hook_ops *ops)
 {
 	entry->next = NULL;
-	entry->ops = *ops;
+	entry->hook = ops->hook;
+	entry->priv = ops->priv;
 	entry->orig_ops = ops;
 }
 
 static inline int
 nf_hook_entry_priority(const struct nf_hook_entry *entry)
 {
-	return entry->ops.priority;
+	return entry->orig_ops->priority;
 }
 
 static inline int
 nf_hook_entry_hookfn(const struct nf_hook_entry *entry, struct sk_buff *skb,
 		     struct nf_hook_state *state)
 {
-	return entry->ops.hook(entry->ops.priv, skb, state);
+	return entry->hook(entry->priv, skb, state);
 }
 
 static inline const struct nf_hook_ops *