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Date: Sun, 29 Jun 2014 08:29:49 +0300
From: Johan Hedberg <johan.hedberg@gmail.com>
To: Ryan Press <ryan@presslab.us>,
	Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
	"linux-bluetooth@vger.kernel.org" <linux-bluetooth@vger.kernel.org>
Subject: Re: LE mouse reconnect problem
Message-ID: <20140629052949.GA32130@t440s>
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Hi,

On Sun, Jun 29, 2014, Johan Hedberg wrote:
> On Sat, Jun 28, 2014, Ryan Press wrote:
> > > It looks like Bluez is using random address and hcitool lescan is
> > > using public address.  I don't know why to use random or public.
> > >
> > > hcitool lescan:
> > >     own address: 0x00 (Public) policy: All
> > > bluetoothd:
> > >     own address: 0x01 (Random) policy: All
> > >
> > > And the advertise address from the mouse is the same.
> > >
> > > hcitool:
> > >     bdaddr C5:8C:97:E9:9C:81 (Random)
> > > bluetoothctl:
> > > [NEW] Device C5:8C:97:E9:9C:81 Arc Touch Mouse SE
> > >
> > >
> > > Thanks.
> > > Ryan
> > 
> > Hi Luiz,
> > 
> > I realized that 3.15+ kernel had the LE Privacy support, so I tried
> > 3.14 and my mouse reconnects just fine.  So somehow my mouse does not
> > work with the new LE Privacy in the kernel.
> > 
> > I couldn't find any way to disable this.  It seems that bluetoothd
> > just uses the default setting which is LE Privacy enabled.  And I
> > couldn't find any way in the kernel to disable it via a module option
> > or sysfs.  Is there some other way I can disable this?
> 
> What the kernel does is it actually uses a non-resolvable private
> address when doing active scanning. You should still be able to get
> advertising indications even though you don't get scan responses (as the
> remote can only choose to not send you the latter based on your
> address). So it's a bit strange you just get complete silence when doing
> active scanning with a non-resolvable private address.
> 
> It'd be interesting to know whether passive scanning discovers the
> device (it should). This is what we should be using, but as the kernel
> interface for it is not yet ready we're reusing the Start Discovery mgmt
> command which uses active instead of passive scanning.
> 
> Btw, it would be *much* better if you used btmon instead of hcidump for
> your investigation. It has much more complete decoding of all the
> various commands and events. Now we have to guess part of the parameters
> that you posted since hcidump doesn't show them.

One part I missed: it seems the mouse is using directed advertising:

2014-06-28 12:54:01.425141 > HCI Event: LE Meta Event (0x3e) plen 12
    LE Advertising Report
      ADV_DIRECT_IND - Connectable directed advertising (1)
      bdaddr C5:8C:97:E9:9C:81 (Random)
      RSSI: -35

It's possible that this makes your local controller filter out even the
indications as they don't match the local address.

Johan