openvswitch: add ct_clear action

This adds a ct_clear action for clearing conntrack state. ct_clear is
currently implemented in OVS userspace, but is not backed by an action
in the kernel datapath. This is useful for flows that may modify a
packet tuple after a ct lookup has already occurred.

Signed-off-by: Eric Garver <e@erig.me>
Acked-by: Pravin B Shelar <pshelar@ovn.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/openvswitch/flow_netlink.c b/net/openvswitch/flow_netlink.c
index fc0ca9a8..dc0d790 100644
--- a/net/openvswitch/flow_netlink.c
+++ b/net/openvswitch/flow_netlink.c
@@ -76,6 +76,7 @@ static bool actions_may_change_flow(const struct nlattr *actions)
 			break;
 
 		case OVS_ACTION_ATTR_CT:
+		case OVS_ACTION_ATTR_CT_CLEAR:
 		case OVS_ACTION_ATTR_HASH:
 		case OVS_ACTION_ATTR_POP_ETH:
 		case OVS_ACTION_ATTR_POP_MPLS:
@@ -2528,6 +2529,7 @@ static int __ovs_nla_copy_actions(struct net *net, const struct nlattr *attr,
 			[OVS_ACTION_ATTR_SAMPLE] = (u32)-1,
 			[OVS_ACTION_ATTR_HASH] = sizeof(struct ovs_action_hash),
 			[OVS_ACTION_ATTR_CT] = (u32)-1,
+			[OVS_ACTION_ATTR_CT_CLEAR] = 0,
 			[OVS_ACTION_ATTR_TRUNC] = sizeof(struct ovs_action_trunc),
 			[OVS_ACTION_ATTR_PUSH_ETH] = sizeof(struct ovs_action_push_eth),
 			[OVS_ACTION_ATTR_POP_ETH] = 0,
@@ -2669,6 +2671,9 @@ static int __ovs_nla_copy_actions(struct net *net, const struct nlattr *attr,
 			skip_copy = true;
 			break;
 
+		case OVS_ACTION_ATTR_CT_CLEAR:
+			break;
+
 		case OVS_ACTION_ATTR_PUSH_ETH:
 			/* Disallow pushing an Ethernet header if one
 			 * is already present */