nfp: flower-ct: add nft callback stubs

Add register/unregister of the nft callback. For now just add
stub code to accept the flows, but don't do anything with it.
Decided to accept the flows since netfilter will keep on trying
to offload a flow if it was rejected, which is quite noisy.
Follow-up patches will start implementing the functions to add
nft flows to the relevant tables.
Signed-off-by: Louis Peens <louis.peens@corigine.com>
Signed-off-by: Yinjun Zhang <yinjun.zhang@corigine.com>
Signed-off-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/netronome/nfp/flower/conntrack.c

@@ -384,6 +384,7 @@ int nfp_fl_ct_handle_pre_ct(struct nfp_flower_priv *priv,
 	struct flow_action_entry *ct_act, *ct_goto;
 	struct nfp_fl_ct_flow_entry *ct_entry;
 	struct nfp_fl_ct_zone_entry *zt;
+	int err;
 
 	ct_act = get_flow_act(flow, FLOW_ACTION_CT);
 	if (!ct_act) {
@@ -406,8 +407,15 @@ int nfp_fl_ct_handle_pre_ct(struct nfp_flower_priv *priv,
 		return PTR_ERR(zt);
 	}
 
-	if (!zt->nft)
+	if (!zt->nft) {
 		zt->nft = ct_act->ct.flow_table;
+		err = nf_flow_table_offload_add_cb(zt->nft, nfp_fl_ct_handle_nft_flow, zt);
+		if (err) {
+			NL_SET_ERR_MSG_MOD(extack,
+					   "offload error: Could not register nft_callback");
+			return err;
+		}
+	}
 
 	/* Add entry to pre_ct_list */
 	ct_entry = nfp_fl_ct_add_flow(zt, netdev, flow, extack);
@@ -489,6 +497,42 @@ int nfp_fl_ct_handle_post_ct(struct nfp_flower_priv *priv,
 	return 0;
 }
 
+static int
+nfp_fl_ct_offload_nft_flow(struct nfp_fl_ct_zone_entry *zt, struct flow_cls_offload *flow)
+{
+	ASSERT_RTNL();
+
+	switch (flow->command) {
+	case FLOW_CLS_REPLACE:
+		return 0;
+	case FLOW_CLS_DESTROY:
+		return 0;
+	case FLOW_CLS_STATS:
+		return 0;
+	default:
+		break;
+	}
+	return -EINVAL;
+}
+
+int nfp_fl_ct_handle_nft_flow(enum tc_setup_type type, void *type_data, void *cb_priv)
+{
+	struct flow_cls_offload *flow = type_data;
+	struct nfp_fl_ct_zone_entry *zt = cb_priv;
+	int err = -EOPNOTSUPP;
+
+	switch (type) {
+	case TC_SETUP_CLSFLOWER:
+		rtnl_lock();
+		err = nfp_fl_ct_offload_nft_flow(zt, flow);
+		rtnl_unlock();
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+	return err;
+}
+
 int nfp_fl_ct_del_flow(struct nfp_fl_ct_map_entry *ct_map_ent)
 {
 	struct nfp_fl_ct_flow_entry *ct_entry;
@@ -506,6 +550,23 @@ int nfp_fl_ct_del_flow(struct nfp_fl_ct_map_entry *ct_map_ent)
 				       nfp_ct_map_params);
 		nfp_fl_ct_clean_flow_entry(ct_entry);
 		kfree(ct_map_ent);
+
+		/* If this is the last pre_ct_rule it means that it is
+		 * very likely that the nft table will be cleaned up next,
+		 * as this happens on the removal of the last act_ct flow.
+		 * However we cannot deregister the callback on the removal
+		 * of the last nft flow as this runs into a deadlock situation.
+		 * So deregister the callback on removal of the last pre_ct flow
+		 * and remove any remaining nft flow entries. We also cannot
+		 * save this state and delete the callback later since the
+		 * nft table would already have been freed at that time.
+		 */
+		if (!zt->pre_ct_count) {
+			nf_flow_table_offload_del_cb(zt->nft,
+						     nfp_fl_ct_handle_nft_flow,
+						     zt);
+			zt->nft = NULL;
+		}
 		break;
 	case CT_TYPE_POST_CT:
 		zt->post_ct_count--;

drivers/net/ethernet/netronome/nfp/flower/conntrack.h

@@ -4,6 +4,7 @@
 #ifndef __NFP_FLOWER_CONNTRACK_H__
 #define __NFP_FLOWER_CONNTRACK_H__ 1
 
+#include <net/netfilter/nf_flow_table.h>
 #include "main.h"
 
 #define NFP_FL_CT_NO_TUN	0xff
@@ -158,4 +159,14 @@ void nfp_fl_ct_clean_flow_entry(struct nfp_fl_ct_flow_entry *entry);
  * @ct_map_ent:	ct map entry for the flow that needs deleting
  */
 int nfp_fl_ct_del_flow(struct nfp_fl_ct_map_entry *ct_map_ent);
+
+/**
+ * nfp_fl_ct_handle_nft_flow() - Handle flower flow callbacks for nft table
+ * @type:	Type provided by callback
+ * @type_data:	Callback data
+ * @cb_priv:	Pointer to data provided when registering the callback, in this
+ *		case it's the zone table.
+ */
+int nfp_fl_ct_handle_nft_flow(enum tc_setup_type type, void *type_data,
+			      void *cb_priv);
 #endif