net/mlx5: use meter color register for connection tracking

Based on the capacity, 3 registers could be used. Due to the register
allocation, only the one REG_C_3 for meter color could be reused
right now.

Then in the same flow, no more than one ASO action can be supported.

Signed-off-by: Bing Zhao <bingz@nvidia.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>

doc/guides/nics/mlx5.rst

@@ -434,6 +434,10 @@ Limitations
       or
       flow create 0 ingress pattern integrity level is 0 value mask l4_ok value spec 0 / eth / ipv4 proto is udp / end …
 
+- Connection tracking:
+
+  - Cannot co-exist with ASO meter, ASO age action in a single flow rule.
+
 Statistics
 ----------
 

drivers/net/mlx5/mlx5_flow.c

@@ -759,7 +759,9 @@ mlx5_flow_get_reg_id(struct rte_eth_dev *dev,
 			return priv->mtr_color_reg != REG_C_2 ? REG_C_2 :
 			       REG_C_3;
 	case MLX5_MTR_COLOR:
-	case MLX5_ASO_FLOW_HIT: /* Both features use the same REG_C. */
+	case MLX5_ASO_FLOW_HIT:
+	case MLX5_ASO_CONNTRACK:
+		/* All features use the same REG_C. */
 		MLX5_ASSERT(priv->mtr_color_reg != REG_NON);
 		return priv->mtr_color_reg;
 	case MLX5_COPY_MARK:

drivers/net/mlx5/mlx5_flow.h

@@ -85,6 +85,7 @@ enum mlx5_feature_name {
 	MLX5_MTR_COLOR,
 	MLX5_MTR_ID,
 	MLX5_ASO_FLOW_HIT,
+	MLX5_ASO_CONNTRACK,
 };
 
 /* Default queue number. */