[PATCHv2] selftests: net: devlink_port_split.py: skip test if no suitable device available

[Po-Hsu Lin <po-hsu.lin@xxxxxxxxxxxxx>]

The `devlink -j port show` command output may not contain the "flavour"
key, an example from s390x LPAR with Ubuntu 22.10 (5.19.0-37-generic),
iproute2-5.15.0:
  {"port":{"pci/0001:00:00.0/1":{"type":"eth","netdev":"ens301"},
           "pci/0001:00:00.0/2":{"type":"eth","netdev":"ens301d1"},
           "pci/0002:00:00.0/1":{"type":"eth","netdev":"ens317"},
           "pci/0002:00:00.0/2":{"type":"eth","netdev":"ens317d1"}}}

This will cause a KeyError exception.

Create a validate_devlink_output() to check for this "flavour" from
devlink command output to avoid this KeyError exception. Also let
it handle the check for `devlink -j dev show` output in main().

Apart from this, if the test was not started because of any reason
(e.g. "lanes" does not exist, max lanes is 0 or the flavour of the
designated device is not "physical" and etc.) The script will still
return 0 and thus causing a false-negative test result.

Use a test_ran flag to determine if these tests were skipped and
return KSFT_SKIP to make it more clear.

V2: factor out the skip logic from main(), update commit message and
    skip reasons accordingly.
Link: https://bugs.launchpad.net/bugs/1937133
Fixes: f3348a82e727 ("selftests: net: Add port split test")
Signed-off-by: Po-Hsu Lin <po-hsu.lin@xxxxxxxxxxxxx>
---
 tools/testing/selftests/net/devlink_port_split.py | 36 +++++++++++++++++++----
 1 file changed, 31 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/net/devlink_port_split.py b/tools/testing/selftests/net/devlink_port_split.py
index 2b5d6ff..749606c 100755
--- a/tools/testing/selftests/net/devlink_port_split.py
+++ b/tools/testing/selftests/net/devlink_port_split.py
@@ -59,6 +59,8 @@ class devlink_ports(object):
         assert stderr == ""
         ports = json.loads(stdout)['port']
 
+        validate_devlink_output(ports, 'flavour')
+
         for port in ports:
             if dev in port:
                 if ports[port]['flavour'] == 'physical':
@@ -220,6 +222,27 @@ def split_splittable_port(port, k, lanes, dev):
     unsplit(port.bus_info)
 
 
+def validate_devlink_output(devlink_data, target_property=None):
+    """
+    Determine if test should be skipped by checking:
+      1. devlink_data contains values
+      2. The target_property exist in devlink_data
+    """
+    skip_reason = None
+    if any(devlink_data.values()):
+        if target_property:
+            skip_reason = "{} not found in devlink output, test skipped".format(target_property)
+            for key in devlink_data:
+                if target_property in devlink_data[key]:
+                    skip_reason = None
+    else:
+        skip_reason = 'devlink output is empty, test skipped'
+
+    if skip_reason:
+        print(skip_reason)
+        sys.exit(KSFT_SKIP)
+
+
 def make_parser():
     parser = argparse.ArgumentParser(description='A test for port splitting.')
     parser.add_argument('--dev',
@@ -231,6 +254,7 @@ def make_parser():
 
 
 def main(cmdline=None):
+    test_ran = False
     parser = make_parser()
     args = parser.parse_args(cmdline)
 
@@ -240,12 +264,9 @@ def main(cmdline=None):
         stdout, stderr = run_command(cmd)
         assert stderr == ""
 
+        validate_devlink_output(json.loads(stdout))
         devs = json.loads(stdout)['dev']
-        if devs:
-            dev = list(devs.keys())[0]
-        else:
-            print("no devlink device was found, test skipped")
-            sys.exit(KSFT_SKIP)
+        dev = list(devs.keys())[0]
 
     cmd = "devlink dev show %s" % dev
     stdout, stderr = run_command(cmd)
@@ -277,6 +298,11 @@ def main(cmdline=None):
                 split_splittable_port(port, lane, max_lanes, dev)
 
                 lane //= 2
+        test_ran = True
+
+    if not test_ran:
+        print("Test not started, no suitable device for the test")
+        sys.exit(KSFT_SKIP)
 
 
 if __name__ == "__main__":
-- 
2.7.4