[NETFILTER] x_tables: Abstraction layer for {ip,ip6,arp}_tables

This monster-patch tries to do the best job for unifying the data
structures and backend interfaces for the three evil clones ip_tables,
ip6_tables and arp_tables.  In an ideal world we would never have
allowed this kind of copy+paste programming... but well, our world
isn't (yet?) ideal.

o introduce a new x_tables module
o {ip,arp,ip6}_tables depend on this x_tables module
o registration functions for tables, matches and targets are only
  wrappers around x_tables provided functions
o all matches/targets that are used from ip_tables and ip6_tables
  are now implemented as xt_FOOBAR.c files and provide module aliases
  to ipt_FOOBAR and ip6t_FOOBAR
o header files for xt_matches are in include/linux/netfilter/,
  include/linux/netfilter_{ipv4,ipv6} contains compatibility wrappers
  around the xt_FOOBAR.h headers

Based on this patchset we're going to further unify the code,
gradually getting rid of all the layer 3 specific assumptions.

Signed-off-by: Harald Welte <laforge@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/netfilter_ipv4/ipt_MARK.h b/include/linux/netfilter_ipv4/ipt_MARK.h
index f474857..697a486 100644
--- a/include/linux/netfilter_ipv4/ipt_MARK.h
+++ b/include/linux/netfilter_ipv4/ipt_MARK.h
@@ -1,20 +1,18 @@
 #ifndef _IPT_MARK_H_target
 #define _IPT_MARK_H_target
 
+/* Backwards compatibility for old userspace */
+
+#include <linux/netfilter/xt_MARK.h>
+
 /* Version 0 */
-struct ipt_mark_target_info {
-	unsigned long mark;
-};
+#define ipt_mark_target_info xt_mark_target_info
 
 /* Version 1 */
-enum {
-	IPT_MARK_SET=0,
-	IPT_MARK_AND,
-	IPT_MARK_OR
-};
+#define IPT_MARK_SET	XT_MARK_SET
+#define IPT_MARK_AND	XT_MARK_AND
+#define	IPT_MARK_OR	XT_MARK_OR
 
-struct ipt_mark_target_info_v1 {
-	unsigned long mark;
-	u_int8_t mode;
-};
+#define ipt_mark_target_info_v1 xt_mark_target_info_v1
+
 #endif /*_IPT_MARK_H_target*/