selftests: net: add scaffolding for Netlink tests in Python

Add glue code for accessing the YNL library which lives under
tools/net and YAML spec files from under Documentation/.
Automatically figure out if tests are run in tree or not.
Since we'll want to use this library both from net and
drivers/net test targets make the library a target as well,
and automatically include it when net or drivers/net are
included. Making net/lib a target ensures that we end up
with only one copy of it, and saves us some path guessing.

Add a tiny bit of formatting support to be able to output KTAP
from the start.

Reviewed-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 47 insertions, 0 deletions

diff --git a/tools/testing/selftests/net/lib/py/utils.py b/tools/testing/selftests/net/lib/py/utils.py
new file mode 100644
index 000000000000..f0d425731fd4
--- /dev/null
+++ b/tools/testing/selftests/net/lib/py/utils.py
@@ -0,0 +1,47 @@
+# SPDX-License-Identifier: GPL-2.0
+
+import json as _json
+import subprocess
+
+class cmd:
+    def __init__(self, comm, shell=True, fail=True, ns=None, background=False):
+        if ns:
+            if isinstance(ns, NetNS):
+                ns = ns.name
+            comm = f'ip netns exec {ns} ' + comm
+
+        self.stdout = None
+        self.stderr = None
+        self.ret = None
+
+        self.comm = comm
+        self.proc = subprocess.Popen(comm, shell=shell, stdout=subprocess.PIPE,
+                                     stderr=subprocess.PIPE)
+        if not background:
+            self.process(terminate=False, fail=fail)
+
+    def process(self, terminate=True, fail=None):
+        if terminate:
+            self.proc.terminate()
+        stdout, stderr = self.proc.communicate()
+        self.stdout = stdout.decode("utf-8")
+        self.stderr = stderr.decode("utf-8")
+        self.proc.stdout.close()
+        self.proc.stderr.close()
+        self.ret = self.proc.returncode
+
+        if self.proc.returncode != 0 and fail:
+            if len(stderr) > 0 and stderr[-1] == "\n":
+                stderr = stderr[:-1]
+            raise Exception("Command failed: %s\n%s" % (self.proc.args, stderr))
+
+
+def ip(args, json=None, ns=None):
+    cmd_str = "ip "
+    if json:
+        cmd_str += '-j '
+    cmd_str += args
+    cmd_obj = cmd(cmd_str, ns=ns)
+    if json:
+        return _json.loads(cmd_obj.stdout)
+    return cmd_obj