selftests: mlxsw: Add a TBF selftest

Add a test that runs traffic across a port throttled with TBF. The test
checks that the observed throughput is within +-5% from the installed
shaper.

To allow checking both the software datapath and the offloaded one, make
the test suitable for inclusion from driver-specific wrapper. Introduce
such wrappers for mlxsw.

Signed-off-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

@@ -0,0 +1,33 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+ALL_TESTS="
+	ping_ipv4
+	tbf_test
+"
+: ${lib_dir:=.}
+source $lib_dir/sch_tbf_core.sh
+
+tbf_test_one()
+{
+	local bs=$1; shift
+
+	tc qdisc replace dev $swp2 root handle 108: tbf \
+	   rate 400Mbit burst $bs limit 1M
+	do_tbf_test 10 400 $bs
+}
+
+tbf_test()
+{
+	tbf_test_one 128K
+	tc qdisc del dev $swp2 root
+}
+
+trap cleanup EXIT
+
+setup_prepare
+setup_wait
+
+tests_run
+
+exit $EXIT_STATUS