selftests: devlink_lib: Add devlink port helpers

Add two devlink port helpers:
 * devlink port get by netdev
 * devlink cpu port get
Signed-off-by: Shalom Toledo <shalomt@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

tools/testing/selftests/net/forwarding/devlink_lib.sh

@@ -419,3 +419,19 @@ devlink_trap_drop_cleanup()
 	kill $mz_pid && wait $mz_pid &> /dev/null
 	tc filter del dev $dev egress protocol $proto pref $pref handle $handle flower
 }
+
+devlink_port_by_netdev()
+{
+	local if_name=$1
+
+	devlink -j port show $if_name | jq -e '.[] | keys' | jq -r '.[]'
+}
+
+devlink_cpu_port_get()
+{
+	local cpu_dl_port_num=$(devlink port list | grep "$DEVLINK_DEV" |
+				grep cpu | cut -d/ -f3 | cut -d: -f1 |
+				sed -n '1p')
+
+	echo "$DEVLINK_DEV/$cpu_dl_port_num"
+}