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-mail]>
Acked-by: Pravin B Shelar <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/uapi/linux/openvswitch.h

···
  * packet.
  * @OVS_ACTION_ATTR_POP_ETH: Pop the outermost Ethernet header off the
  * packet.
+ * @OVS_ACTION_ATTR_CT_CLEAR: Clear conntrack state from the packet.
  *
  * Only a single header can be set with a single %OVS_ACTION_ATTR_SET.  Not all
  * fields within a header are modifiable, e.g. the IPv4 protocol and fragment
···
 	OVS_ACTION_ATTR_TRUNC,        /* u32 struct ovs_action_trunc. */
 	OVS_ACTION_ATTR_PUSH_ETH,     /* struct ovs_action_push_eth. */
 	OVS_ACTION_ATTR_POP_ETH,      /* No argument. */
+	OVS_ACTION_ATTR_CT_CLEAR,     /* No argument. */
 
 	__OVS_ACTION_ATTR_MAX,	      /* Nothing past this will be accepted
 				       * from userspace. */

net/openvswitch/actions.c

···
 				return err == -EINPROGRESS ? 0 : err;
 			break;
 
+		case OVS_ACTION_ATTR_CT_CLEAR:
+			err = ovs_ct_clear(skb, key);
+			break;
+
 		case OVS_ACTION_ATTR_PUSH_ETH:
 			err = push_eth(skb, key, nla_data(a));
 			break;

net/openvswitch/conntrack.c

···
 	return err;
 }
 
+int ovs_ct_clear(struct sk_buff *skb, struct sw_flow_key *key)
+{
+	if (skb_nfct(skb)) {
+		nf_conntrack_put(skb_nfct(skb));
+		nf_ct_set(skb, NULL, IP_CT_UNTRACKED);
+		ovs_ct_fill_key(skb, key);
+	}
+
+	return 0;
+}
+
 static int ovs_ct_add_helper(struct ovs_conntrack_info *info, const char *name,
 			     const struct sw_flow_key *key, bool log)
 {

net/openvswitch/conntrack.h

···
 
 int ovs_ct_execute(struct net *, struct sk_buff *, struct sw_flow_key *,
 		   const struct ovs_conntrack_info *);
+int ovs_ct_clear(struct sk_buff *skb, struct sw_flow_key *key);
 
 void ovs_ct_fill_key(const struct sk_buff *skb, struct sw_flow_key *key);
 int ovs_ct_put_key(const struct sw_flow_key *swkey,
···
 				 const struct ovs_conntrack_info *info)
 {
 	kfree_skb(skb);
+	return -ENOTSUPP;
+}
+
+static inline int ovs_ct_clear(struct sk_buff *skb,
+			       struct sw_flow_key *key)
+{
 	return -ENOTSUPP;
 }
 

net/openvswitch/flow_netlink.c

···
 			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:
···
 			[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,
···
 			if (err)
 				return err;
 			skip_copy = true;
+			break;
+
+		case OVS_ACTION_ATTR_CT_CLEAR:
 			break;
 
 		case OVS_ACTION_ATTR_PUSH_ETH: