[PATCH net-next] selftests: drv-net: assume stats refresh is 0 if no ethtool -c support

[Jakub Kicinski <kuba@kernel.org>]

Tests using HW stats wait for them to stabilize, using data from
ethtool -c as the delay. Not all drivers implement ethtool -c
so handle the errors gracefully.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
CC: shuah@kernel.org
CC: willemb@google.com
CC: petrm@nvidia.com
CC: linux-kselftest@vger.kernel.org
---
 tools/testing/selftests/drivers/net/lib/py/env.py | 9 +++++++--
 tools/testing/selftests/net/lib/py/utils.py       | 6 ++++--
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/drivers/net/lib/py/env.py b/tools/testing/selftests/drivers/net/lib/py/env.py
index 1ea9bb695e94..fea343f209ea 100644
--- a/tools/testing/selftests/drivers/net/lib/py/env.py
+++ b/tools/testing/selftests/drivers/net/lib/py/env.py
@@ -5,7 +5,7 @@ import time
 from pathlib import Path
 from lib.py import KsftSkipEx, KsftXfailEx
 from lib.py import ksft_setup
-from lib.py import cmd, ethtool, ip
+from lib.py import cmd, ethtool, ip, CmdExitFailure
 from lib.py import NetNS, NetdevSimDev
 from .remote import Remote
 
@@ -234,7 +234,12 @@ from .remote import Remote
         Good drivers will tell us via ethtool what their sync period is.
         """
         if self._stats_settle_time is None:
-            data = ethtool("-c " + self.ifname, json=True)[0]
+            data = {}
+            try:
+                data = ethtool("-c " + self.ifname, json=True)[0]
+            except CmdExitFailure as e:
+                if "Operation not supported" not in e.cmd.stderr:
+                    raise
 
             self._stats_settle_time = 0.025 + \
                 data.get('stats-block-usecs', 0) / 1000 / 1000
diff --git a/tools/testing/selftests/net/lib/py/utils.py b/tools/testing/selftests/net/lib/py/utils.py
index 72590c3f90f1..9e3bcddcf3e8 100644
--- a/tools/testing/selftests/net/lib/py/utils.py
+++ b/tools/testing/selftests/net/lib/py/utils.py
@@ -10,7 +10,9 @@ import time
 
 
 class CmdExitFailure(Exception):
-    pass
+    def __init__(self, msg, cmd_obj):
+        super().__init__(msg)
+        self.cmd = cmd_obj
 
 
 class cmd:
@@ -48,7 +50,7 @@ import time
             if len(stderr) > 0 and stderr[-1] == "\n":
                 stderr = stderr[:-1]
             raise CmdExitFailure("Command failed: %s\nSTDOUT: %s\nSTDERR: %s" %
-                                 (self.proc.args, stdout, stderr))
+                                 (self.proc.args, stdout, stderr), self)
 
 
 class bkg(cmd):
-- 
2.47.1