[PATCH net-next v2 3/6] selftests: net: py: extract tool logic

[Jakub Kicinski <kuba@kernel.org>]

The main use of the ip() wrapper over cmd() is that it can parse JSON.
cmd("ip -j link show") will return stdout as a string, and test has
to call json.loads(). With ip("link show", json=True) the return value
will be already parsed.

More tools (ethtool, bpftool etc.) support the --json switch.
To avoid having to wrap all of them individually create a tool()
helper.

Switch from -j to --json (for ethtool).
While at it consume the netns attribute at the ip() level.

Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
v2:
 - use consistent quote type
 - use format string to force string conversion of NetNS class
---
 tools/testing/selftests/net/lib/py/utils.py | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/net/lib/py/utils.py b/tools/testing/selftests/net/lib/py/utils.py
index d3715e6c21f2..4930a90a64ea 100644
--- a/tools/testing/selftests/net/lib/py/utils.py
+++ b/tools/testing/selftests/net/lib/py/utils.py
@@ -56,10 +56,10 @@ import time
         return self.process(terminate=self.terminate)
 
 
-def ip(args, json=None, ns=None, host=None):
-    cmd_str = "ip "
+def tool(name, args, json=None, ns=None, host=None):
+    cmd_str = name + ' '
     if json:
-        cmd_str += '-j '
+        cmd_str += '--json '
     cmd_str += args
     cmd_obj = cmd(cmd_str, ns=ns, host=host)
     if json:
@@ -67,6 +67,12 @@ import time
     return cmd_obj
 
 
+def ip(args, json=None, ns=None, host=None):
+    if ns:
+        args = f'-netns {ns} ' + args
+    return tool('ip', args, json=json, host=host)
+
+
 def rand_port():
     """
     Get unprivileged port, for now just random, one day we may decide to check if used.
-- 
2.44.0