netfilter: nf_conntrack: IPS_UNTRACKED bit

NOTRACK makes all cpus share a cache line on nf_conntrack_untracked
twice per packet. This is bad for performance.
__read_mostly annotation is also a bad choice.

This patch introduces IPS_UNTRACKED bit so that we can use later a
per_cpu untrack structure more easily.

A new helper, nf_ct_untracked_get() returns a pointer to
nf_conntrack_untracked.

Another one, nf_ct_untracked_status_or() is used by nf_nat_init() to add
IPS_NAT_DONE_MASK bits to untracked status.

nf_ct_is_untracked() prototype is changed to work on a nf_conn pointer.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>

include/linux/netfilter/nf_conntrack_common.h

@@ -76,6 +76,10 @@ enum ip_conntrack_status {
 	/* Conntrack is a template */
 	IPS_TEMPLATE_BIT = 11,
 	IPS_TEMPLATE = (1 << IPS_TEMPLATE_BIT),
+
+	/* Conntrack is a fake untracked entry */
+	IPS_UNTRACKED_BIT = 12,
+	IPS_UNTRACKED = (1 << IPS_UNTRACKED_BIT),
 };
 
 /* Connection tracking event types */