If vlan dev was created with reorder_hdr off and hw offload both
off but up with hw offload on, it will trigger a skb_panic bug in
vlan_dev_hard_header().

Add a test to automatically catch re-occurrence of the issue.

Suggested-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Chen Zhen <chenzhen126@huawei.com>
---
 tools/testing/selftests/net/Makefile          |  1 +
 .../testing/selftests/net/vlan_hw_offload.sh  | 31 +++++++++++++++++++
 2 files changed, 32 insertions(+)
 create mode 100755 tools/testing/selftests/net/vlan_hw_offload.sh

diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile
index b66ba04f19d9..8b50448a01cd 100644
--- a/tools/testing/selftests/net/Makefile
+++ b/tools/testing/selftests/net/Makefile
@@ -113,6 +113,7 @@ TEST_PROGS := \
 	veth.sh \
 	vlan_bridge_binding.sh \
 	vlan_hw_filter.sh \
+	vlan_hw_offload.sh \
 	vrf-xfrm-tests.sh \
 	vrf_route_leaking.sh \
 	vrf_strict_mode_test.sh \
diff --git a/tools/testing/selftests/net/vlan_hw_offload.sh b/tools/testing/selftests/net/vlan_hw_offload.sh
new file mode 100755
index 000000000000..ac7140539d95
--- /dev/null
+++ b/tools/testing/selftests/net/vlan_hw_offload.sh
@@ -0,0 +1,31 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# shellcheck disable=SC2329
+
+setup() {
+	ip link add veth0 type veth peer name veth1
+	ip link set veth0 up
+	ip link set veth1 up
+}
+
+cleanup() {
+	ip link delete veth0 2>/dev/null
+}
+
+# turn on hw offload and set up vlan dev with reorder_hdr off
+test_vlan_hw_offload_toggle_crash() {
+	ethtool -K veth0 tx-vlan-hw-insert off
+	ip link add link veth0 name veth0.10 type vlan id 10 reorder_hdr off
+	ethtool -K veth0 tx-vlan-hw-insert on
+
+	# set up vlan dev and it will trigger ndisc
+	ip link set veth0.10 up
+	ip -6 route show dev veth0.10
+}
+
+trap cleanup EXIT
+
+setup
+test_vlan_hw_offload_toggle_crash
+
+exit 0
-- 
2.33.0