[Bug 989817] Re: Cannot change bluetooth device name

[TJ]

To permanently change the adapter device name using a bluez tool we have
to use DBus to set the name using org.bluez.Adaptor.SetProperty  which
is handled by set_name(), which results in a call to adapter_set_name()
which in turn calls write_local_name().

dbus-send --print-reply --system --dest=org.bluez /org/bluez/$(pidof
bluetoothd)/hci0 org.bluez.Adapter.SetProperty string:'Name'
variant:string:'adapter_name'

$ dbus-send --print-reply --system --dest=org.bluez /org/bluez/$(pidof bluetoothd)/hci0 org.bluez.Adapter.SetProperty string:'Name' variant:string:'adapter_name'
method return sender=:1.164 -> dest=:1.189 reply_serial=2

$ cat /var/lib/bluetooth/00\:1F\:E1\:E0\:EB\:96/config 
name adapter_name
pairable yes
class 0x6e0100
onmode discoverable
mode discoverable

'bluetoothd' reads "/etc/bluetooth/main.conf" where we have "Name =
%h-%d" which should be expanded to "<host>-<adapter_id>".

This is passed to the 'adaptername' plugin function adaptername_probe()
which calls read_pretty_host_name(). This function looks for a systemd-
specific text file "/etc/machine-info" and if found reads the file then
looks for a line with the prefix "PRETTY_HOSTNAME=" and uses the name
assigned there.

If no name has been set at this point read_local_name() is called to get
the name from "/var/lib/bluetooth/$MAC/config". If no name is obtained
from that file expand_name(,,"%h-%d",) is called and a name created from
the machine hostname and bluetooth adapter id, e.g. "hostname-0".

This is later written out to "/var/lib/bluetooth/$MAC/config".

It appears to me that "ubuntu-0" is created during installation from a
liveISO environment where the default machine name is always "ubuntu".
Bluetooth starts in the live environment and assigns the "ubuntu-0" name
to the adapter. Later, when bluetoothd is installed in the target the
configuration file is probably copied over, or otherwise generated based
on the live environment.

Once there is a name entry in "/var/lib/bluetooth/$MAC/config" the
bluetoothd adaptername plugin will not generate a new name.

---- debug with "name adapter_name" setting in /var/lib/bluetooth/$MAC/config ----
bluetoothd[11119]: src/main.c:parse_config() name=%h-%d
bluetoothd[11119]: src/plugin.c:add_plugin() Loading adaptername plugin
bluetoothd[11119]: plugins/hciops.c:read_local_name_complete() hci0 status 0
bluetoothd[11119]: plugins/hciops.c:read_local_name_complete() Got name for hci0
bluetoothd[11119]: plugins/adaptername.c:adaptername_probe() Setting name 'adapter_name' for device 'hci0'
bluetoothd[11119]: plugins/hciops.c:hciops_set_name() hci0, name adapter_name


-- debug with no "name" setting in /var/lib/bluetooth/$MAC/config ----
bluetoothd[11425]: src/main.c:parse_config() name=%h-%d
bluetoothd[11425]: src/plugin.c:add_plugin() Loading adaptername plugin
bluetoothd[11425]: plugins/hciops.c:read_local_name_complete() hci0 status 0
bluetoothd[11425]: plugins/hciops.c:read_local_name_complete() Got name for hci0
bluetoothd[11425]: plugins/adaptername.c:adaptername_probe() Setting name 'XPSm1530-0' for device 'hci0'
bluetoothd[11425]: plugins/hciops.c:hciops_set_name() hci0, name XPSm1530-0

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https://bugs.launchpad.net/bugs/989817

Title:
  Cannot change bluetooth device name

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