[RFC] LE based Remote Name Request

[Brian Gix <bgix@codeaurora.org>]

LE does not have a Remote Name Request like BR/EDR has.  It does have 
the ability to fairly efficiently request the remote device name, 
however, which we should implement.  Currently the only support we offer 
for obtaining the remote device name is to pluck it out of the 
Advertising packets (Formatted identically to EIR) which works for most 
devices, but as with BR/EDR, there is no requirement that devices 
include their name in their advertising data.

The Device Name characteristic is Mandatory, and may only exist once for 
a device.  If it is less than 20 bytes may therefore be read with a 
single ReadByType GATT command (uuid16: 0x2a00) over the full 1-0xFFFF 
range. It must also be readable without security, so can be done without 
first going through SMP.

We may not want to featurize this particular functionality at all, since 
all of the components to obtain this info is already available: We just 
need to set up an ATT socket in BlueZ, and make the request.  However, 
when we talk about Scanning for devices, and automatically forwarding 
the Remote Name via a MGMT evevnt, the precedence is there to supply it 
from the kernel.  And if we were to go down that path, we would also 
want to simultaneously offer access to the equally Mandatory and 
Unsecured "Appearance" Characteristic (uuid16: 0x2a01) which is LE's 
sort-of equivilent to the BR/EDR Class-Of-Device.

So: What are the feelings about doing Remote Name (And Appearance) 
discovery in the kernel, probably as part of the LE Discovery mechanism? 
  I favor putting it in the kernel, due to the equivalent functionality 
available to BR/EDR there.

Also, there is no coincidence that I offer this RFC at the same time as 
I bring up the Write Signed Command functionality from earlier today. 
Both concern usages of GATT (or at least ATT) in a way not currently 
supported. It is also a case where ideally, we would use a low-latency 
connect-read-disconnect methodology.

-- 
Brian Gix
bgix@codeaurora.org
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum