Re: [PATCH net-next v6 2/5] net/lapb: support netdev events

[Martin Schiller]

On 2020-11-25 22:49, Jakub Kicinski wrote:
> On Tue, 24 Nov 2020 10:39:35 +0100 Martin Schiller wrote:
> > This patch allows layer2 (LAPB) to react to netdev events itself and
> > avoids the detour via layer3 (X.25).
> >
> > 1. Establish layer2 on NETDEV_UP events, if the carrier is already up.
> >
> > 2. Call lapb_disconnect_request() on NETDEV_GOING_DOWN events to 
> > signal
> >    the peer that the connection will go down.
> >    (Only when the carrier is up.)
> >
> > 3. When a NETDEV_DOWN event occur, clear all queues, enter state
> >    LAPB_STATE_0 and stop all timers.
> >
> > 4. The NETDEV_CHANGE event makes it possible to handle carrier loss 
> > and
> >    detection.
> >
> >    In case of Carrier Loss, clear all queues, enter state LAPB_STATE_0
> >    and stop all timers.
> >
> >    In case of Carrier Detection, we start timer t1 on a DCE interface,
> >    and on a DTE interface we change to state LAPB_STATE_1 and start
> >    sending SABM(E).
> >
> > Signed-off-by: Martin Schiller <ms@xxxxxxxxxx>
>
> > +/* Handle device status changes. */
> > +static int lapb_device_event(struct notifier_block *this, unsigned 
> > long event,
> > +			     void *ptr)
> > +{
> > +	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
> > +	struct lapb_cb *lapb;
> > +
> > +	if (!net_eq(dev_net(dev), &init_net))
> > +		return NOTIFY_DONE;
> > +
> > +	if (dev->type == ARPHRD_X25) {
>
> Flip condition, save indentation.
>
> 	if (dev->type != ARPHRD_X25)
> 		return NOTIFY_DONE;
>
> You can also pull out of all the cases:
>
> 	lapb = lapb_devtostruct(dev);
> 	if (!lapb)
> 		return NOTIFY_DONE;
>
> right?
>
> > +		switch (event) {
> > +		case NETDEV_UP:
> > +			lapb_dbg(0, "(%p) Interface up: %s\n", dev,
> > +				 dev->name);
> > +
> > +			if (netif_carrier_ok(dev)) {
> > +				lapb = lapb_devtostruct(dev);
> > +				if (!lapb)
> > +					break;
>
> >  static int __init lapb_init(void)
> >  {
> > +	register_netdevice_notifier(&lapb_dev_notifier);
>
> This can fail, so:
>
> 	return register_netdevice_notifier(&lapb_dev_notifier);
>
> >  	return 0;
> >  }
> >
> >  static void __exit lapb_exit(void)
> >  {
> >  	WARN_ON(!list_empty(&lapb_list));
> > +
> > +	unregister_netdevice_notifier(&lapb_dev_notifier);
> >  }
> >
> >  MODULE_AUTHOR("Jonathan Naylor <g4klx@xxxxxxxxxxxxxxxxx>");

Thanks for your hints! I will send an update.