selftests: net: py: check process exit code in bkg() and background cmd()

JIRA: https://issues.redhat.com/browse/RHEL-57764

commit e1bb5e6
Author: Jakub Kicinski <kuba@kernel.org>
Date:   Wed May 1 19:53:25 2024 -0700

    selftests: net: py: check process exit code in bkg() and background cmd()

    We're a bit too loose with error checking for background
    processes. cmd() completely ignores the fail argument
    passed to the constructor if background is True.
    Default to checking for errors if process is not terminated
    explicitly. Caller can override with True / False.

    For bkg() the processing step is called magically by __exit__
    so record the value passed in the constructor.

    Reported-by: Willem de Bruijn <willemb@google.com>
    Tested-by: Willem de Bruijn <willemb@google.com>
    Link: https://lore.kernel.org/r/20240502025325.1924923-1-kuba@kernel.org
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Signed-off-by: Ivan Vecera <ivecera@redhat.com>

Author: ivecera

tools/testing/selftests/net/lib/py/utils.py

@@ -26,6 +26,9 @@ def __init__(self, comm, shell=True, fail=True, ns=None, background=False, host=
             self.process(terminate=False, fail=fail)
 
     def process(self, terminate=True, fail=None):
+        if fail is None:
+            fail = not terminate
+
         if terminate:
             self.proc.terminate()
         stdout, stderr = self.proc.communicate(timeout=5)
@@ -42,17 +45,18 @@ def process(self, terminate=True, fail=None):
 
 
 class bkg(cmd):
-    def __init__(self, comm, shell=True, fail=True, ns=None, host=None,
+    def __init__(self, comm, shell=True, fail=None, ns=None, host=None,
                  exit_wait=False):
         super().__init__(comm, background=True,
                          shell=shell, fail=fail, ns=ns, host=host)
         self.terminate = not exit_wait
+        self.check_fail = fail
 
     def __enter__(self):
         return self
 
     def __exit__(self, ex_type, ex_value, ex_tb):
-        return self.process(terminate=self.terminate)
+        return self.process(terminate=self.terminate, fail=self.check_fail)
 
 
 def ip(args, json=None, ns=None, host=None):