netfilter: conntrack: Introduce tcp offload timeout configuration

TCP connections may be offloaded from nf conntrack to nf flow table.
Offloaded connections are aged after 30 seconds of inactivity.
Once aged, ownership is returned to conntrack with a hard coded pickup
time of 120 seconds, after which the connection may be deleted.
eted. The current aging intervals may be too aggressive for some users.

Provide users with the ability to control the nf flow table offload
aging and pickup time intervals via sysctl parameter as a pre-step for
configuring the nf flow table GC timeout intervals.
Signed-off-by: Oz Shlomo <ozsh@nvidia.com>
Reviewed-by: Paul Blakey <paulb@nvidia.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/net/netns/conntrack.h

@@ -27,6 +27,10 @@ struct nf_tcp_net {
 	u8 tcp_loose;
 	u8 tcp_be_liberal;
 	u8 tcp_max_retrans;
+#if IS_ENABLED(CONFIG_NF_FLOW_TABLE)
+	unsigned int offload_timeout;
+	unsigned int offload_pickup;
+#endif
 };
 
 enum udp_conntrack {

net/netfilter/nf_conntrack_proto_tcp.c

@@ -1441,6 +1441,11 @@ void nf_conntrack_tcp_init_net(struct net *net)
 	 * will be started.
 	 */
 	tn->tcp_max_retrans = 3;
+
+#if IS_ENABLED(CONFIG_NF_FLOW_TABLE)
+	tn->offload_timeout = 30 * HZ;
+	tn->offload_pickup = 120 * HZ;
+#endif
 }
 
 const struct nf_conntrack_l4proto nf_conntrack_l4proto_tcp =

net/netfilter/nf_conntrack_standalone.c

@@ -573,6 +573,10 @@ enum nf_ct_sysctl_index {
 	NF_SYSCTL_CT_PROTO_TIMEOUT_TCP_CLOSE,
 	NF_SYSCTL_CT_PROTO_TIMEOUT_TCP_RETRANS,
 	NF_SYSCTL_CT_PROTO_TIMEOUT_TCP_UNACK,
+#if IS_ENABLED(CONFIG_NF_FLOW_TABLE)
+	NF_SYSCTL_CT_PROTO_TIMEOUT_TCP_OFFLOAD,
+	NF_SYSCTL_CT_PROTO_TIMEOUT_TCP_OFFLOAD_PICKUP,
+#endif
 	NF_SYSCTL_CT_PROTO_TCP_LOOSE,
 	NF_SYSCTL_CT_PROTO_TCP_LIBERAL,
 	NF_SYSCTL_CT_PROTO_TCP_MAX_RETRANS,
@@ -760,6 +764,20 @@ static struct ctl_table nf_ct_sysctl_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec_jiffies,
 	},
+#if IS_ENABLED(CONFIG_NF_FLOW_TABLE)
+	[NF_SYSCTL_CT_PROTO_TIMEOUT_TCP_OFFLOAD] = {
+		.procname	= "nf_flowtable_tcp_timeout",
+		.maxlen		= sizeof(unsigned int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_jiffies,
+	},
+	[NF_SYSCTL_CT_PROTO_TIMEOUT_TCP_OFFLOAD_PICKUP] = {
+		.procname	= "nf_flowtable_tcp_pickup",
+		.maxlen		= sizeof(unsigned int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_jiffies,
+	},
+#endif
 	[NF_SYSCTL_CT_PROTO_TCP_LOOSE] = {
 		.procname	= "nf_conntrack_tcp_loose",
 		.maxlen		= sizeof(u8),
@@ -969,6 +987,12 @@ static void nf_conntrack_standalone_init_tcp_sysctl(struct net *net,
 	XASSIGN(LIBERAL, &tn->tcp_be_liberal);
 	XASSIGN(MAX_RETRANS, &tn->tcp_max_retrans);
 #undef XASSIGN
+
+#if IS_ENABLED(CONFIG_NF_FLOW_TABLE)
+	table[NF_SYSCTL_CT_PROTO_TIMEOUT_TCP_OFFLOAD].data = &tn->offload_timeout;
+	table[NF_SYSCTL_CT_PROTO_TIMEOUT_TCP_OFFLOAD_PICKUP].data = &tn->offload_pickup;
+#endif
+
 }
 
 static void nf_conntrack_standalone_init_sctp_sysctl(struct net *net,