Add test exercising duplicate leaves.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 tools/testing/selftests/drivers/net/shaper.py | 25 +++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/drivers/net/shaper.py b/tools/testing/selftests/drivers/net/shaper.py
index 11310f19bfa0..f7872c931bf6 100755
--- a/tools/testing/selftests/drivers/net/shaper.py
+++ b/tools/testing/selftests/drivers/net/shaper.py
@@ -1,7 +1,10 @@
 #!/usr/bin/env python3
 # SPDX-License-Identifier: GPL-2.0
 
-from lib.py import ksft_run, ksft_exit, ksft_eq, ksft_true, KsftSkipEx
+import errno
+
+from lib.py import ksft_run, ksft_exit
+from lib.py import ksft_eq, ksft_raises, ksft_true, KsftSkipEx
 from lib.py import EthtoolFamily, NetshaperFamily
 from lib.py import NetDrvEnv
 from lib.py import NlError
@@ -438,6 +441,21 @@ from lib.py import cmd
         nl_shaper.delete({'ifindex': cfg.ifindex,
                           'handle': {'scope': 'queue', 'id': i}})
 
+def dup_leaves(cfg, nl_shaper) -> None:
+    """ Ensure that the kernel rejects duplicate leaves. """
+    if not cfg.groups:
+        raise KsftSkipEx("device does not support node scope")
+
+    with ksft_raises(NlError) as cm:
+        nl_shaper.group({
+                   'ifindex': cfg.ifindex,
+                   'leaves':[{'handle': {'scope': 'queue', 'id': 0}},
+                             {'handle': {'scope': 'queue', 'id': 0}}],
+                   'handle': {'scope':'node'},
+                   'metric': 'bps',
+                   'bw-max': 10000})
+    ksft_eq(cm.exception.error, errno.EINVAL)
+
 def main() -> None:
     with NetDrvEnv(__file__, queue_count=4) as cfg:
         cfg.queues = False
@@ -453,7 +471,10 @@ from lib.py import cmd
                   basic_groups,
                   qgroups,
                   delegation,
-                  queue_update], args=(cfg, NetshaperFamily()))
+                  queue_update,
+                  dup_leaves
+                  ],
+                 args=(cfg, NetshaperFamily()))
     ksft_exit()
 
 
-- 
2.54.0