network: Avoid notifier re-creating in connect function

[xndcn]

No description provided.

[xndcn]

ping, thanks

[xndcn]

If network connect again without disconnect, current implementation will not re-create bus, but notifier will always be re-created. I think it is better to check the notifier in connect() and release it in disconnect, as well as the bus object.

[bizfsc]

The fix is correct – without this patch, calling connect() again without a prior disconnect() always re-creates the notifier, leaking the old one. The guard on self.bus already existed, so this makes the notifier handling symmetrical. Nice catch!

Two suggestions:

1. Simplify try/except/finally in disconnect()

The except Exception as e: raise e is a no-op and can be removed. This simplifies to:

try:
    self.check()
finally:
    self.notifier = None

2. Add regression tests

Consider adding tests to test/test_network.py to verify the new behavior:

def test_network_connect_does_not_recreate_notifier(self):
    self.network.connect(interface="virtual")
    self.addCleanup(self.network.disconnect)
    notifier1 = self.network.notifier
    self.assertIsNotNone(notifier1)
    # Calling connect() again should reuse the existing notifier
    self.network.connect(interface="virtual")
    self.assertIs(self.network.notifier, notifier1)

def test_network_disconnect_releases_notifier(self):
    self.network.connect(interface="virtual")
    self.assertIsNotNone(self.network.notifier)
    self.network.disconnect()
    self.assertIsNone(self.network.notifier)

def test_network_disconnect_releases_notifier_on_exception(self):
    self.network.connect(interface="virtual")

    class Custom(Exception):
        pass

    self.network.notifier.exception = Custom("fake")
    with self.assertRaises(Custom):
        with self.assertLogs(level=logging.ERROR):
            self.network.disconnect()
    # Notifier must be released even when check() raises
    self.assertIsNone(self.network.notifier)

I verified locally that all three tests pass with the patched code.