[Bluez] device: Fix device can't be scanned for 5 mins after reboot

From: Archie Pusaka <apusaka@chromium.org>

After the patches which limit the attempts of doing remote name
resolving, there's an issue which prevents BlueZ to RNR new devices
for 5 minutes after reboot. It's caused by failed_time is init to 0,
and is then treated as the timestamp when the device failed RNR.
However, actually there is no failure yet.

This CL fixes it by always allowing RNR when failed_time = 0.

Reviewed-by: Shuo-Peng Liao <deanliao@chromium.org>
---

 src/device.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

Hi Archie,

> After the patches which limit the attempts of doing remote name
> resolving, there's an issue which prevents BlueZ to RNR new devices
> for 5 minutes after reboot. It's caused by failed_time is init to 0,
> and is then treated as the timestamp when the device failed RNR.
> However, actually there is no failure yet.
> 
> This CL fixes it by always allowing RNR when failed_time = 0.
> 
> Reviewed-by: Shuo-Peng Liao <deanliao@chromium.org>
> ---
> 
> src/device.c | 11 ++++++++---
> 1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/src/device.c b/src/device.c
> index f2447c478e..16b1ed5bd3 100644
> --- a/src/device.c
> +++ b/src/device.c
> @@ -4487,10 +4487,15 @@ bool device_is_name_resolve_allowed(struct btd_device *device)
> 
> 	clock_gettime(CLOCK_MONOTONIC, &now);
> 
> -	/* If now < failed_time, it means the clock has somehow turned back,
> -	 * possibly because of system restart. Allow name request in this case.
> +	/* Allow name request for any of these cases:
> +	 * (1) failed_time is empty (0). Meaning no prior failure.
> +	 * (2) now < failed_time. Meaning the clock has somehow turned back,
> +	 *     possibly because of system restart. Allow just to be safe.
> +	 * (3) now >= failed_time + name_request_retry_delay. Meaning the
> +	 *     period of not sending name request is over.
> 	 */
> -	return now.tv_sec < device->name_resolve_failed_time ||
> +	return device->name_resolve_failed_time == 0 ||
> +		now.tv_sec < device->name_resolve_failed_time ||
> 		now.tv_sec >= device->name_resolve_failed_time +
> 					btd_opts.name_request_retry_delay;
> }

I have the feeling this becomes complex and hard to follow. I appreciate the comment above, but just for thoughts, would it be better to do something like this:

	/* failed_time is empty (0). Meaning no prior failure. */
	if (device->name_..failed_time == 0)
		return true;

	..

	return false;

Regards

Marcel

Hi Marcel,

On Thu, 13 Jan 2022 at 15:05, Marcel Holtmann <marcel@holtmann.org> wrote:
>
> Hi Archie,
>
> > After the patches which limit the attempts of doing remote name
> > resolving, there's an issue which prevents BlueZ to RNR new devices
> > for 5 minutes after reboot. It's caused by failed_time is init to 0,
> > and is then treated as the timestamp when the device failed RNR.
> > However, actually there is no failure yet.
> >
> > This CL fixes it by always allowing RNR when failed_time = 0.
> >
> > Reviewed-by: Shuo-Peng Liao <deanliao@chromium.org>
> > ---
> >
> > src/device.c | 11 ++++++++---
> > 1 file changed, 8 insertions(+), 3 deletions(-)
> >
> > diff --git a/src/device.c b/src/device.c
> > index f2447c478e..16b1ed5bd3 100644
> > --- a/src/device.c
> > +++ b/src/device.c
> > @@ -4487,10 +4487,15 @@ bool device_is_name_resolve_allowed(struct btd_device *device)
> >
> >       clock_gettime(CLOCK_MONOTONIC, &now);
> >
> > -     /* If now < failed_time, it means the clock has somehow turned back,
> > -      * possibly because of system restart. Allow name request in this case.
> > +     /* Allow name request for any of these cases:
> > +      * (1) failed_time is empty (0). Meaning no prior failure.
> > +      * (2) now < failed_time. Meaning the clock has somehow turned back,
> > +      *     possibly because of system restart. Allow just to be safe.
> > +      * (3) now >= failed_time + name_request_retry_delay. Meaning the
> > +      *     period of not sending name request is over.
> >        */
> > -     return now.tv_sec < device->name_resolve_failed_time ||
> > +     return device->name_resolve_failed_time == 0 ||
> > +             now.tv_sec < device->name_resolve_failed_time ||
> >               now.tv_sec >= device->name_resolve_failed_time +
> >                                       btd_opts.name_request_retry_delay;
> > }
>
> I have the feeling this becomes complex and hard to follow. I appreciate the comment above, but just for thoughts, would it be better to do something like this:
>
>         /* failed_time is empty (0). Meaning no prior failure. */
>         if (device->name_..failed_time == 0)
>                 return true;
>
>         ..
>
>         return false;
>

I actually prefer your suggestion, this makes the code much easier to read.
However it's not a very common pattern I observe so I went with the
previous approach.

I have sent a v2 to separate the big if, please take a look.

Thanks,
Archie

> Regards
>
> Marcel
>