devlink: Add 'mirror' trap action

The action is used by control traps such as IGMP query. The packet is
flooded by the device, but also trapped to the CPU in order for the
software bridge to mark the receiving port as a multicast router port.
Such packets are marked with 'skb->offload_fwd_mark = 1' in order to
prevent the software bridge from flooding them again.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/devlink/devlink-trap.rst

@@ -108,6 +108,8 @@ The ``devlink-trap`` mechanism supports the following packet trap actions:
   * ``trap``: The sole copy of the packet is sent to the CPU.
   * ``drop``: The packet is dropped by the underlying device and a copy is not
     sent to the CPU.
+  * ``mirror``: The packet is forwarded by the underlying device and a copy is
+    sent to the CPU.
 
 Generic Packet Traps
 ====================

include/uapi/linux/devlink.h

@@ -233,10 +233,13 @@ enum {
  * @DEVLINK_TRAP_ACTION_DROP: Packet is dropped by the device and a copy is not
  *                            sent to the CPU.
  * @DEVLINK_TRAP_ACTION_TRAP: The sole copy of the packet is sent to the CPU.
+ * @DEVLINK_TRAP_ACTION_MIRROR: Packet is forwarded by the device and a copy is
+ *                              sent to the CPU.
  */
 enum devlink_trap_action {
 	DEVLINK_TRAP_ACTION_DROP,
 	DEVLINK_TRAP_ACTION_TRAP,
+	DEVLINK_TRAP_ACTION_MIRROR,
 };
 
 /**

net/core/devlink.c

@@ -5869,7 +5869,8 @@ devlink_trap_action_get_from_info(struct genl_info *info,
 	val = nla_get_u8(info->attrs[DEVLINK_ATTR_TRAP_ACTION]);
 	switch (val) {
 	case DEVLINK_TRAP_ACTION_DROP: /* fall-through */
-	case DEVLINK_TRAP_ACTION_TRAP:
+	case DEVLINK_TRAP_ACTION_TRAP: /* fall-through */
+	case DEVLINK_TRAP_ACTION_MIRROR:
 		*p_trap_action = val;
 		break;
 	default: