[NETFILTER]: conntrack: add fixed timeout flag in connection tracking

Add a flag in a connection status to have a non updated timeout.
This permits to have connection that automatically die at a given
time.

Signed-off-by: Eric Leblond <eric@inl.fr>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index f9b83f9..bc2bd4c 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -1396,6 +1396,12 @@
 
 	write_lock_bh(&nf_conntrack_lock);
 
+	/* Only update if this is not a fixed timeout */
+	if (test_bit(IPS_FIXED_TIMEOUT_BIT, &ct->status)) {
+		write_unlock_bh(&nf_conntrack_lock);
+		return;
+	}
+
 	/* If not in hash table, timer will not be active yet */
 	if (!nf_ct_is_confirmed(ct)) {
 		ct->timeout.expires = extra_jiffies;