tc-testing: Add command timeout feature to tdc

Using an attribute set in the tdc_config.py file, limit the
amount of time tdc will wait for an executed command to
complete and prevent the script from hanging entirely.

This timeout will be applied to all executed commands.
Signed-off-by: Lucas Bates <lucasb@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

tools/testing/selftests/tc-testing/tdc.py

@@ -131,12 +131,16 @@ def exec_cmd(args, pm, stage, command):
         stdout=subprocess.PIPE,
         stderr=subprocess.PIPE,
         env=ENVIR)
-    (rawout, serr) = proc.communicate()
 
-    if proc.returncode != 0 and len(serr) > 0:
-        foutput = serr.decode("utf-8", errors="ignore")
-    else:
-        foutput = rawout.decode("utf-8", errors="ignore")
+    try:
+        (rawout, serr) = proc.communicate(timeout=NAMES['TIMEOUT'])
+        if proc.returncode != 0 and len(serr) > 0:
+            foutput = serr.decode("utf-8", errors="ignore")
+        else:
+            foutput = rawout.decode("utf-8", errors="ignore")
+    except subprocess.TimeoutExpired:
+        foutput = "Command \"{}\" timed out\n".format(command)
+        proc.returncode = 255
 
     proc.stdout.close()
     proc.stderr.close()
@@ -438,6 +442,8 @@ def check_default_settings(args, remaining, pm):
         NAMES['TC'] = args.path
     if args.device != None:
         NAMES['DEV2'] = args.device
+    if 'TIMEOUT' not in NAMES:
+        NAMES['TIMEOUT'] = None
     if not os.path.isfile(NAMES['TC']):
         print("The specified tc path " + NAMES['TC'] + " does not exist.")
         exit(1)

tools/testing/selftests/tc-testing/tdc_config.py

@@ -15,6 +15,8 @@ NAMES = {
           'DEV1': 'v0p1',
           'DEV2': '',
           'BATCH_FILE': './batch.txt',
+          # Length of time in seconds to wait before terminating a command
+          'TIMEOUT': 12,
           # Name of the namespace to use
           'NS': 'tcut',
           # Directory containing eBPF test programs