netfilter: xtables: generate initial table on-demand

The static initial tables are pretty large, and after the net
namespace has been instantiated, they just hang around for nothing.
This commit removes them and creates tables on-demand at runtime when
needed.

Size shrinks by 7735 bytes (x86_64).

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>

include/linux/netfilter_arp/arp_tables.h

@@ -258,6 +258,7 @@ struct arpt_error {
 	.target.errorname = "ERROR",					       \
 }
 
+extern void *arpt_alloc_initial_table(const struct xt_table *);
 extern struct xt_table *arpt_register_table(struct net *net,
 					    const struct xt_table *table,
 					    const struct arpt_replace *repl);

include/linux/netfilter_ipv4/ip_tables.h

@@ -282,6 +282,7 @@ struct ipt_error {
 	.target.errorname = "ERROR",					       \
 }
 
+extern void *ipt_alloc_initial_table(const struct xt_table *);
 extern unsigned int ipt_do_table(struct sk_buff *skb,
 				 unsigned int hook,
 				 const struct net_device *in,

include/linux/netfilter_ipv6/ip6_tables.h

@@ -297,6 +297,7 @@ ip6t_get_target(struct ip6t_entry *e)
 #include <linux/init.h>
 extern void ip6t_init(void) __init;
 
+extern void *ip6t_alloc_initial_table(const struct xt_table *);
 extern struct xt_table *ip6t_register_table(struct net *net,
 					    const struct xt_table *table,
 					    const struct ip6t_replace *repl);