devlink: Add blackhole_nexthop trap

Add a packet trap to report packets that were dropped due to a
blackhole nexthop.

Signed-off-by: Ido Schimmel <[e-mail]>
Reviewed-by: Jiri Pirko <[e-mail]>
Signed-off-by: Jakub Kicinski <[e-mail]>

Documentation/networking/devlink/devlink-trap.rst

···
    * - ``esp_parsing``
      - ``drop``
      - Traps packets dropped due to an error in the ESP header parsing
+   * - ``blackhole_nexthop``
+     - ``drop``
+     - Traps packets that the device decided to drop in case they hit a
+       blackhole nexthop
 
 Driver-specific Packet Traps
 ============================

include/net/devlink.h

···
 	DEVLINK_TRAP_GENERIC_ID_DCCP_PARSING,
 	DEVLINK_TRAP_GENERIC_ID_GTP_PARSING,
 	DEVLINK_TRAP_GENERIC_ID_ESP_PARSING,
+	DEVLINK_TRAP_GENERIC_ID_BLACKHOLE_NEXTHOP,
 
 	/* Add new generic trap IDs above */
 	__DEVLINK_TRAP_GENERIC_ID_MAX,
···
 	"gtp_parsing"
 #define DEVLINK_TRAP_GENERIC_NAME_ESP_PARSING \
 	"esp_parsing"
-
+#define DEVLINK_TRAP_GENERIC_NAME_BLACKHOLE_NEXTHOP \
+	"blackhole_nexthop"
 
 #define DEVLINK_TRAP_GROUP_GENERIC_NAME_L2_DROPS \
 	"l2_drops"

net/core/devlink.c

···
 	DEVLINK_TRAP(DCCP_PARSING, DROP),
 	DEVLINK_TRAP(GTP_PARSING, DROP),
 	DEVLINK_TRAP(ESP_PARSING, DROP),
+	DEVLINK_TRAP(BLACKHOLE_NEXTHOP, DROP),
 };
 
 #define DEVLINK_TRAP_GROUP(_id)						      \