netfilter: nf_conntrack: remove dead code

The following code is not used in current upstream code.
Some of this seems to be old hooks, other might be used by some
out of tree module (which I don't care about breaking), and
the need_ipv4_conntrack was used by old NAT code but no longer
called.

Signed-off-by: Stephen Hemminger <[e-mail]>
Signed-off-by: Pablo Neira Ayuso <[e-mail]>

include/net/netfilter/ipv4/nf_conntrack_ipv4.h

···
 int nf_conntrack_ipv4_compat_init(void);
 void nf_conntrack_ipv4_compat_fini(void);
 
-void need_ipv4_conntrack(void);
-
 #endif /*_NF_CONNTRACK_IPV4_H*/

include/net/netfilter/nf_conntrack_l3proto.h

···
 void nf_ct_l3proto_unregister(struct nf_conntrack_l3proto *proto);
 
 struct nf_conntrack_l3proto *nf_ct_l3proto_find_get(u_int16_t l3proto);
-void nf_ct_l3proto_put(struct nf_conntrack_l3proto *p);
 
 /* Existing built-in protocols */
 extern struct nf_conntrack_l3proto nf_conntrack_l3proto_generic;

net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c

···
 
 module_init(nf_conntrack_l3proto_ipv4_init);
 module_exit(nf_conntrack_l3proto_ipv4_fini);
-
-void need_ipv4_conntrack(void)
-{
-	return;
-}
-EXPORT_SYMBOL_GPL(need_ipv4_conntrack);

net/netfilter/nf_conntrack_core.c

···
 				      const struct nlattr *attr) __read_mostly;
 EXPORT_SYMBOL_GPL(nfnetlink_parse_nat_setup_hook);
 
-int (*nf_nat_seq_adjust_hook)(struct sk_buff *skb,
-			      struct nf_conn *ct,
-			      enum ip_conntrack_info ctinfo,
-			      unsigned int protoff);
-EXPORT_SYMBOL_GPL(nf_nat_seq_adjust_hook);
-
 DEFINE_SPINLOCK(nf_conntrack_lock);
 EXPORT_SYMBOL_GPL(nf_conntrack_lock);
 
···
 
 	return NULL;
 }
-
-struct nf_conntrack_tuple_hash *
-__nf_conntrack_find(struct net *net, u16 zone,
-		    const struct nf_conntrack_tuple *tuple)
-{
-	return ____nf_conntrack_find(net, zone, tuple,
-				     hash_conntrack_raw(tuple, zone));
-}
-EXPORT_SYMBOL_GPL(__nf_conntrack_find);
 
 /* Find a connection corresponding to a tuple. */
 static struct nf_conntrack_tuple_hash *

net/netfilter/nf_conntrack_proto.c

···
 }
 EXPORT_SYMBOL_GPL(nf_ct_l3proto_find_get);
 
-void nf_ct_l3proto_put(struct nf_conntrack_l3proto *p)
-{
-	module_put(p->me);
-}
-EXPORT_SYMBOL_GPL(nf_ct_l3proto_put);
-
 int
 nf_ct_l3proto_try_module_get(unsigned short l3proto)
 {