[PATCH 2/2] leds: trigger: netdev: refactor netdev_event_requires_handling()

If there are network devices with the same name in different
namespaces, ledtrig-netdev gets confused easily and switches between
these devices whenever there are NETDEV_CHANGENAME/NETDEV_REGISTER
notifications.  This happens since ledtrig-netdev only checks for
device name equality regardless of previous associations with another
network device with the same name.

Real world example: eth0 is the primary physical network interface and
ledltrig-netdev is associated with that interface. If now Docker creates
a virtual Ethernet interface (vethXXXX), moves it to the
container's net namespace and renames it to eth0, ledtrig-netdev
switches to this device and the LED no longer blinks for the original
(physical) network device.

Fix this by refactoring the conditions under which to handle netdev
events:

- For processing NETDEV_REGISTER events, the device name has to match
  and no association with a net_dev must exist.

- For processing NETDEV_CHANGENAME events, the associated and notified
  network device have to match. Alternatively the device name has to
  match and no association with a net_dev must exist.

- For all other events, the associated and notified network device have
  to match.

Signed-off-by: Tobias Junghans <redacted>
---
 drivers/leds/trigger/ledtrig-netdev.c | 29 +++++++++++++++++++--------
 1 file changed, 21 insertions(+), 8 deletions(-)

diff --git a/drivers/leds/trigger/ledtrig-netdev.c b/drivers/leds/trigger/ledtrig-netdev.c
index 6e16619719fe..a3f30e6f74b4 100644
--- a/drivers/leds/trigger/ledtrig-netdev.c
+++ b/drivers/leds/trigger/ledtrig-netdev.c

@@ -578,15 +578,28 @@ static const struct attribute_group *netdev_trig_groups[] = {
 static bool netdev_event_requires_handling(unsigned long evt, struct net_device *dev,
 					   struct led_netdev_data *trigger_data)
 {
-	if (evt != NETDEV_UP && evt != NETDEV_DOWN && evt != NETDEV_CHANGE
-	    && evt != NETDEV_REGISTER && evt != NETDEV_UNREGISTER
-	    && evt != NETDEV_CHANGENAME)
-		return false;
-
-	if (!(dev == trigger_data->net_dev ||
-	     (evt == NETDEV_CHANGENAME && !strcmp(dev->name, trigger_data->device_name)) ||
-	     (evt == NETDEV_REGISTER && !strcmp(dev->name, trigger_data->device_name))))
+	switch (evt) {
+	case NETDEV_REGISTER:
+		if (trigger_data->net_dev ||
+		    strcmp(dev->name, trigger_data->device_name))
+			return false;
+		break;
+	case NETDEV_CHANGENAME:
+		if (trigger_data->net_dev != dev &&
+		    (trigger_data->net_dev ||
+		     strcmp(dev->name, trigger_data->device_name)))
+			return false;
+		break;
+	case NETDEV_UNREGISTER:
+	case NETDEV_UP:
+	case NETDEV_DOWN:
+	case NETDEV_CHANGE:
+		if (trigger_data->net_dev != dev)
+			return false;
+		break;
+	default:
 		return false;
+	}
 
 	return true;
 }

-- 
2.43.0