[SOLVED] Why is LE device connected automatically on HCI up?

Why is LE device connected automatically on HCI up?

Whenever I hit hciconfig hci0 up noscan, followed by hcitool con after a few seconds, my LE device is always connected automatically.

> hciconfig hci0
hci0:   Type: BR/EDR  Bus: USB
    BD Address: YY:YY:YY:YY:YY:YY  ACL MTU: 310:10  SCO MTU: 64:8
    DOWN
    RX bytes:494922 acl:12605 sco:0 events:8429 errors:0
    TX bytes:63543 acl:917 sco:0 commands:3692 errors:0
> hciconfig hci0 up

... (wait a few seconds)

> hcitool con
Connections:
    < LE XX:XX:XX:XX:XX:XX handle 70 state 1 lm MASTER AUTH ENCRYPT

I initially thought that only devices in White List will be connected automatically, but only then to figure out that the device is not in white list after I typed in the following command.

> hcitool lewlrm XX:XX:XX:XX:XX:XX
Can't remove from white list: Input/output error(5)

Question:

Why will my device connected automatically when it is not in the White List?

Environment:

Kernel Version: Linux 4.11.1
Bluez Version: 5.37

Solution

My solution is to use bluetoothctl to disconnect and remove it.

> bluetoothctl
[bluetooth] > disconnect XX:XX:XX:XX:XX:XX
[bluetooth] > remove XX:XX:XX:XX:XX:XX