[PATCH net-next v3 1/3] selftests: net-drv: exercise queue stats when the device is down

[Stanislav Fomichev <sdf@fomichev.me>]

Verify that total device stats don't decrease after it has been turned down.
Also make sure the device doesn't crash when we access per-queue stats
when it's down (in case it tries to access some pointers that are NULL).

  KTAP version 1
  1..5
  ok 1 stats.check_pause
  ok 2 stats.check_fec
  ok 3 stats.pkt_byte_sum
  ok 4 stats.qstat_by_ifindex
  ok 5 stats.check_down
  # Totals: pass:5 fail:0 xfail:0 xpass:0 skip:0 error:0

v3:
- use errno.EOPNOTSUPP (Petr)
- move qstat[0] under try (Petr)

v2:
- KTAP output formatting (Jakub)
- defer instead of try/finally (Jakub)
- disappearing stats is an error (Jakub)
- ksft_ge instead of open coding (Jakub)

Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
--
Cc: Shuah Khan <shuah@kernel.org>
Cc: Joe Damato <jdamato@fastly.com>
Cc: Petr Machata <petrm@nvidia.com>
Cc: linux-kselftest@vger.kernel.org
---
 tools/testing/selftests/drivers/net/stats.py | 25 +++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/drivers/net/stats.py b/tools/testing/selftests/drivers/net/stats.py
index 820b8e0a22c6..2fdde8cf0307 100755
--- a/tools/testing/selftests/drivers/net/stats.py
+++ b/tools/testing/selftests/drivers/net/stats.py
@@ -1,10 +1,12 @@
 #!/usr/bin/env python3
 # SPDX-License-Identifier: GPL-2.0
 
+import errno
 from lib.py import ksft_run, ksft_exit, ksft_pr
 from lib.py import ksft_ge, ksft_eq, ksft_in, ksft_true, ksft_raises, KsftSkipEx, KsftXfailEx
 from lib.py import EthtoolFamily, NetdevFamily, RtnlFamily, NlError
 from lib.py import NetDrvEnv
+from lib.py import ip, defer
 
 ethnl = EthtoolFamily()
 netfam = NetdevFamily()
@@ -133,9 +135,30 @@ rtnl = RtnlFamily()
     ksft_eq(cm.exception.nl_msg.extack['bad-attr'], '.ifindex')
 
 
+def check_down(cfg) -> None:
+    try:
+        qstat = netfam.qstats_get({"ifindex": cfg.ifindex}, dump=True)[0]
+    except NlError as e:
+        if e.error == errno.EOPNOTSUPP:
+            raise KsftSkipEx("qstats not supported by the device")
+        raise
+
+    ip(f"link set dev {cfg.dev['ifname']} down")
+    defer(ip, f"link set dev {cfg.dev['ifname']} up")
+
+    qstat2 = netfam.qstats_get({"ifindex": cfg.ifindex}, dump=True)[0]
+    for k, v in qstat.items():
+        ksft_ge(qstat2[k], qstat[k], comment=f"{k} went backwards on device down")
+
+    # exercise per-queue API to make sure that "device down" state
+    # is handled correctly and doesn't crash
+    netfam.qstats_get({"ifindex": cfg.ifindex, "scope": "queue"}, dump=True)
+
+
 def main() -> None:
     with NetDrvEnv(__file__) as cfg:
-        ksft_run([check_pause, check_fec, pkt_byte_sum, qstat_by_ifindex],
+        ksft_run([check_pause, check_fec, pkt_byte_sum, qstat_by_ifindex,
+                  check_down],
                  args=(cfg, ))
     ksft_exit()
 
-- 
2.45.2