netfilter: revert user-space expectation helper support

This patch partially reverts:
3d058d7 netfilter: rework user-space expectation helper support
that was applied during the 3.2 development cycle.

After this patch, the tree remains just like before patch bc01bef,
that initially added the preliminary infrastructure.

I decided to partially revert this patch because the approach
that I proposed to resolve this problem is broken in NAT setups.
Moreover, a new infrastructure will be submitted for the 3.3.x
development cycle that resolve the existing issues while
providing a neat solution.

Since nobody has been seriously using this infrastructure in
user-space, the removal of this feature should affect any know
FOSS project (to my knowledge).

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/linux/netfilter/nf_conntrack_common.h

@@ -83,10 +83,6 @@ enum ip_conntrack_status {
 	/* Conntrack is a fake untracked entry */
 	IPS_UNTRACKED_BIT = 12,
 	IPS_UNTRACKED = (1 << IPS_UNTRACKED_BIT),
-
-	/* Conntrack has a userspace helper. */
-	IPS_USERSPACE_HELPER_BIT = 13,
-	IPS_USERSPACE_HELPER = (1 << IPS_USERSPACE_HELPER_BIT),
 };
 
 /* Connection tracking event types */

include/linux/netfilter/xt_CT.h

@@ -3,8 +3,7 @@
 
 #include <linux/types.h>
 
-#define XT_CT_NOTRACK		0x1
-#define XT_CT_USERSPACE_HELPER	0x2
+#define XT_CT_NOTRACK	0x1
 
 struct xt_ct_target_info {
 	__u16 flags;