Hi Anderson/Johan,
On 11/8/2011 3:39 AM, Anderson Lizardo wrote:
Hi Johan/Brian,
On Tue, Nov 8, 2011 at 4:52 AM, Johan Hedberg<johan.hedberg@xxxxxxxxx> wrote:
Hi Brian,
On Mon, Nov 07, 2011, Brian Gix wrote:
+#define MGMT_ADDR_BREDR 0x00
+#define MGMT_ADDR_LE 0x01
+#define MGMT_ADDR_BREDR_LE 0x02
+#define MGMT_ADDR_INVALID 0xff
What would you think about overloading this Address type with the
Public/Random flag?
We are already seeing devices in the marketplace with Random
Addresses, effectively giving LE addresses 7 significant octets of
address information, rather than the standard 6 octet "MAC"
addresses.
+
+struct mgmt_addr_info {
+ bdaddr_t bdaddr;
+ __u8 type;
I would also support adding an additional octet here, which would be
essentially the "Address Type" as used in the HCI LE Connect
Command, and in the SMP LE Pairing protocol.
Brian: note that this address type is being used only on mgmt
messages. So it will be mostly useful (in LE context) for discovery
command and events.
For creating connections, we still do not have a way to indicate the
address type from userspace (currently we rely on the advertising
cache).
In the solution we have been working on here, we are storing the
(Public/Random) address type with the LTK, both in the BlueZ database,
and with the keys that we send back to the kernel which on the reworked
MGMT interface is the command "Load Long Term Keys". We still rely on
the Advertising cache when pairing, but once paired can then reconnect
to LE devices (and know their Public/Random setting) via the LTK list.
Also remember that when we get around to supporting the LE GAP
Privacy/Reconnection (Vol 3, Part C, Sections 12.3 & 12.4), and SMP
Identity information (Vol 3, Part H, Sections 3.6.4 & 3.6.5) we will
need to track this (Public/Random) information as part of the overall
identity of remote peripherals. We will be unable to connect to
"Private" devices without the Public/Random info, because they will be
invisible to an LE Discovery scan.
Plus Also: other than for Pairing, I think that forcing an LE Discovery
each time you want to connect to a previously known device to be inelegant.
I have stated elsewhere, that I think this to be crucial information
to store with Long Term KEYs (LTKs) as well as future LE Signing
keys, and in future Address Resolution solutions. The earlier we get
this bit of information into the MGMT interface, the better IMO.
This is the same impression I got also when looking into this several
months ago. Thanks for reminding me!
The BREDR_LE option is there for the updated start_discovery command.
You'll be able to specify whether you want BR/EDR-only, LE-only or
interleaved discovery. I wouldn't add a completely new octet for public
vs random information though but reuse the existing one instead. To be
able to reuse our address type definitions for all purposes, how about
making each value orthogonal to the others, e.g.:
ADDR_BREDR 0x01
ADDR_LE_PUBLIC 0x02
ADDR_LE_RANDOM 0x04
For events like connected, found, etc you'd only have one of the bits
set whereas for the start_discovery you could have any (but at least
one).
Johan: how would link_to_mgmt() in your code work in this case?
I see this will help simplifying how do we identify LE devices on
BlueZ (currently it is done by parsing AD flags, but broken devices
may lack the correct "BR/EDR not supported" flag, and thus we
incorrectly identify then as BR/EDR). Unfortunately, it will still not
allow us to correctly connect to LE devices without relying on the
kernel's advertising cache.
Regards,
--
Brian Gix
bgix@xxxxxxxxxxxxxx
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum
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