[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>

include/linux/netfilter/nf_conntrack_common.h

@@ -69,6 +69,10 @@ enum ip_conntrack_status {
 	/* Connection is dying (removed from lists), can not be unset. */
 	IPS_DYING_BIT = 9,
 	IPS_DYING = (1 << IPS_DYING_BIT),
+
+	/* Connection has fixed timeout. */
+	IPS_FIXED_TIMEOUT_BIT = 10,
+	IPS_FIXED_TIMEOUT = (1 << IPS_FIXED_TIMEOUT_BIT),
 };
 
 /* Connection tracking event bits */

net/ipv4/netfilter/ip_conntrack_core.c

@@ -1130,6 +1130,12 @@ void __ip_ct_refresh_acct(struct ip_conntrack *ct,
 
 	write_lock_bh(&ip_conntrack_lock);
 
+	/* Only update if this is not a fixed timeout */
+	if (test_bit(IPS_FIXED_TIMEOUT_BIT, &ct->status)) {
+		write_unlock_bh(&ip_conntrack_lock);
+		return;
+	}
+
 	/* If not in hash table, timer will not be active yet */
 	if (!is_confirmed(ct)) {
 		ct->timeout.expires = extra_jiffies;

net/netfilter/nf_conntrack_core.c

@@ -1396,6 +1396,12 @@ void __nf_ct_refresh_acct(struct nf_conn *ct,
 
 	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;