selftests: drv-net: factor out parsing of the env

The tests with a remote end will use a different class,
for clarity, but will also need to parse the env.
So factor parsing the env out to a function.

Reviewed-by: Willem de Bruijn <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

tools/testing/selftests/drivers/net/lib/py/env.py

···
 from lib.py import ip
 from lib.py import NetdevSimDev
 
+
+def _load_env_file(src_path):
+    env = os.environ.copy()
+
+    src_dir = Path(src_path).parent.resolve()
+    if not (src_dir / "net.config").exists():
+        return env
+
+    lexer = shlex.shlex(open((src_dir / "net.config").as_posix(), 'r').read())
+    k = None
+    for token in lexer:
+        if k is None:
+            k = token
+            env[k] = ""
+        elif token == "=":
+            pass
+        else:
+            env[k] = token
+            k = None
+    return env
+
+
 class NetDrvEnv:
+    """
+    Class for a single NIC / host env, with no remote end
+    """
     def __init__(self, src_path):
         self._ns = None
 
-        self.env = os.environ.copy()
-        self._load_env_file(src_path)
+        self.env = _load_env_file(src_path)
 
         if 'NETIF' in self.env:
             self.dev = ip("link show dev " + self.env['NETIF'], json=True)[0]
···
             self._ns.remove()
             self._ns = None
 
-    def _load_env_file(self, src_path):
-        src_dir = Path(src_path).parent.resolve()
-        if not (src_dir / "net.config").exists():
-            return
 
-        lexer = shlex.shlex(open((src_dir / "net.config").as_posix(), 'r').read())
-        k = None
-        for token in lexer:
-            if k is None:
-                k = token
-                self.env[k] = ""
-            elif token == "=":
-                pass
-            else:
-                self.env[k] = token
-                k = None