selftests: Add loopback test

Add selftest for loopback feature

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

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

@@ -0,0 +1,94 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+ALL_TESTS="loopback_test"
+NUM_NETIFS=2
+source tc_common.sh
+source lib.sh
+
+h1_create()
+{
+	simple_if_init $h1 192.0.2.1/24
+	tc qdisc add dev $h1 clsact
+}
+
+h1_destroy()
+{
+	tc qdisc del dev $h1 clsact
+	simple_if_fini $h1 192.0.2.1/24
+}
+
+h2_create()
+{
+	simple_if_init $h2
+}
+
+h2_destroy()
+{
+	simple_if_fini $h2
+}
+
+loopback_test()
+{
+	RET=0
+
+	tc filter add dev $h1 ingress protocol arp pref 1 handle 101 flower \
+		skip_hw arp_op reply arp_tip 192.0.2.1 action drop
+
+	$MZ $h1 -c 1 -t arp -q
+
+	tc_check_packets "dev $h1 ingress" 101 1
+	check_fail $? "Matched on a filter without loopback setup"
+
+	ethtool -K $h1 loopback on
+	check_err $? "Failed to enable loopback"
+
+	setup_wait_dev $h1
+
+	$MZ $h1 -c 1 -t arp -q
+
+	tc_check_packets "dev $h1 ingress" 101 1
+	check_err $? "Did not match on filter with loopback"
+
+	ethtool -K $h1 loopback off
+	check_err $? "Failed to disable loopback"
+
+	$MZ $h1 -c 1 -t arp -q
+
+	tc_check_packets "dev $h1 ingress" 101 2
+	check_fail $? "Matched on a filter after loopback was removed"
+
+	tc filter del dev $h1 ingress protocol arp pref 1 handle 101 flower
+
+	log_test "loopback"
+}
+
+setup_prepare()
+{
+	h1=${NETIFS[p1]}
+	h2=${NETIFS[p2]}
+
+	vrf_prepare
+
+	h1_create
+	h2_create
+}
+
+cleanup()
+{
+	pre_cleanup
+
+	h2_destroy
+	h1_destroy
+
+	vrf_cleanup
+}
+
+trap cleanup EXIT
+
+setup_prepare
+setup_wait
+
+tests_run
+
+exit $EXIT_STATUS