linux-kernel - Re: [RFC] Bluetooth: Retry configure request if result is L2CAP_CONF

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Date:   Mon, 18 Feb 2019 20:57:53 -0800
From:   Andrey Smirnov <andrew.smirnov@...il.com>
To:     Marcel Holtmann <marcel@...tmann.org>
Cc:     linux-bluetooth@...r.kernel.org,
        "Pierre-Loup A . Griffais" <pgriffais@...vesoftware.com>,
        Florian Dollinger <dollinger.florian@....de>,
        Johan Hedberg <johan.hedberg@...il.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] Bluetooth: Retry configure request if result is L2CAP_CONF_UNKNOWN

On Mon, Feb 18, 2019 at 4:58 AM Marcel Holtmann <marcel@...tmann.org> wrote:
>
> Hi Andrey,
>
> > Due to:
> >
> > - current implementation of l2cap_config_rsp() dropping BT
> >   connection if sender of configuration response replied with unknown
> >   option failure (Result=0x0003/L2CAP_CONF_UNKNOWN)
> >
> > - current implementation of l2cap_build_conf_req() adding
> >   L2CAP_CONF_RFC(0x04) option to initial configure request sent by
> >   the Linux host.
> >
> > devices that do no recongninze L2CAP_CONF_RFC, such as Xbox One S
> > controllers, will get stuck in endless connect -> configure ->
> > disconnect loop, never connect and be generaly unusable.
> >
> > To avoid this problem add code to do the following:
> >
> > 1. Store a mask of supported conf option types per connection
> >
> > 2. Parse the body of response L2CAP_CONF_UNKNOWN and adjust
> >    connection's supported conf option types mask
> >
> > 3. Retry configuration step the same way it's done for
> >    L2CAP_CONF_UNACCEPT
> >
> > Signed-off-by: Andrey Smirnov <andrew.smirnov@...il.com>
> > Cc: Pierre-Loup A. Griffais <pgriffais@...vesoftware.com>
> > Cc: Florian Dollinger <dollinger.florian@....de>
> > Cc: Marcel Holtmann <marcel@...tmann.org>
> > Cc: Johan Hedberg <johan.hedberg@...il.com>
> > Cc: linux-bluetooth@...r.kernel.org
> > Cc: linux-kernel@...r.kernel.org
> > ---
> >
> > Everyone:
> >
> > I marked this as an RFC, since I don't have a lot of experience with
> > Bluetooth subsystem and don't have hight degree of confidence about
> > choices made in this patch. I do, however, thins is is good enough to
> > start a discussion about the problem.
>
> can you take a btmon -w trace.log protocol trace so that I can see where it fails. This seems a really odd behavior of the Xbox controller. We have to be careful in not breaking Bluetooth qualification to just workaround some buggy remote device.
>

Sure, n/p, both "failure" (behavior before this patch) and "success"
(behavior with the patch) cases on my machine are available here:

https://gist.github.com/ndreys/2b74094933601978e200af1ff0a55372

Let me know if that's not accessible to you.

Thanks,
Andrey Smirnov