When BT started by default scanning for devices getting continuous events in btmon logs

[gadekula1]

When BT started by default scanning for devices
getting continuous events in btmon logs

@ MGMT Event: Device Found (0x0012) plen 45 {0x0002} [hci0] 7652141.947641
LE Address: 58:4B:6D:AE:70:A4 (Resolvable)
RSSI: -70 dBm (0xba)
Flags: 0x00000004
Not Connectable
Data length: 31
Company: Apple, Inc. (76)
Type: Unknown (7)
Data: 0124200b998f110005225636c595b2d05c5837a0f166c9a440

bluetoothctl show
Controller D8:3A:DD:1A:7E:23 (public)
Manufacturer: 0x0131 (305)
Version: 0x09 (9)
Name: BlueZ 5.72
Alias: BlueZ 5.72
Class: 0x003c0000 (3932160)
Powered: yes
Discoverable: no
DiscoverableTimeout: 0x000000b4 (180)
Pairable: yes
UUID: A/V Remote Control (0000110e-0000-1000-8000-00805f9b34fb)
UUID: PnP Information (00001200-0000-1000-8000-00805f9b34fb)
UUID: Message Access Server (00001132-0000-1000-8000-00805f9b34fb)
UUID: Audio Sink (0000110b-0000-1000-8000-00805f9b34fb)
UUID: Message Notification Se.. (00001133-0000-1000-8000-00805f9b34fb)
UUID: A/V Remote Control Target (0000110c-0000-1000-8000-00805f9b34fb)
UUID: Generic Access Profile (00001800-0000-1000-8000-00805f9b34fb)
UUID: Phonebook Access Server (0000112f-0000-1000-8000-00805f9b34fb)
UUID: Generic Attribute Profile (00001801-0000-1000-8000-00805f9b34fb)
UUID: OBEX File Transfer (00001106-0000-1000-8000-00805f9b34fb)
UUID: Device Information (0000180a-0000-1000-8000-00805f9b34fb)
UUID: IrMC Sync (00001104-0000-1000-8000-00805f9b34fb)
UUID: Handsfree (0000111e-0000-1000-8000-00805f9b34fb)
UUID: OBEX Object Push (00001105-0000-1000-8000-00805f9b34fb)
UUID: Audio Source (0000110a-0000-1000-8000-00805f9b34fb)
Modalias: usb:v1D6Bp0246d0548
Discovering: no
Roles: central
Roles: peripheral
Advertising Features:
ActiveInstances: 0x00 (0)
SupportedInstances: 0x05 (5)
SupportedIncludes: tx-power
SupportedIncludes: appearance
SupportedIncludes: local-name

tried to stop using blutoothctl
but not stopping and getting error
bluetoothctl scan off
Failed to stop discovery: org.bluez.Error.Failed

dbus logs

method call time=1736136478.502259 sender=:1.24 -> destination=org.bluez serial=30 path=/org/bluez/hci0; interface=org.bluez.Adapter1; member=StopDiscovery
error time=1736136478.502972 sender=:1.7 -> destination=:1.24 error_name=org.bluez.Error.InProgress reply_serial=30

btmon logs during power on BT

HCI Event: Command Complete (0x0e) plen 4 #94 [hci0] 14.637294
Write Extended Inquiry Response (0x03|0x0052) ncmd 1
Status: Success (0x00)
@ MGMT Event: Command Complete (0x0001) plen 7 {0x0002} [hci0] 14.637493
Set Powered (0x0005) plen 4
Status: Success (0x00)
Current settings: 0x00000ad1
Powered
Bondable
Secure Simple Pairing
BR/EDR
Low Energy
Secure Connections
@ MGMT Event: New Settings (0x0006) plen 4 {0x0003} [hci0] 14.637514
Current settings: 0x00000ad1
Powered
Bondable
Secure Simple Pairing
BR/EDR
Low Energy
Secure Connections
@ MGMT Event: New Settings (0x0006) plen 4 {0x0001} [hci0] 14.637514
Current settings: 0x00000ad1
Powered
Bondable
Secure Simple Pairing
BR/EDR
Low Energy
Secure Connections
< HCI Command: LE Set Scan Parameters (0x08|0x000b) plen 7 #95 [hci0] 14.637573
Type: Passive (0x00)
Interval: 60.000 msec (0x0060)
Window: 30.000 msec (0x0030)
Own address type: Public (0x00)
Filter policy: Accept all advertisement (0x00)
HCI Event: Command Complete (0x0e) plen 4 #96 [hci0] 14.638034
LE Set Scan Parameters (0x08|0x000b) ncmd 1
Status: Success (0x00)
< HCI Command: LE Set Scan Enable (0x08|0x000c) plen 2 #97 [hci0] 14.638175
Scanning: Enabled (0x01)
Filter duplicates: Disabled (0x00)
HCI Event: Command Complete (0x0e) plen 4 #98 [hci0] 14.639111
LE Set Scan Enable (0x08|0x000c) ncmd 1
Status: Success (0x00)
@ MGMT Event: Discovering (0x0013) plen 2 {0x0003} [hci0] 14.639157
Address type: 0x00
Discovery: Enabled (0x01)
@ MGMT Event: Discovering (0x0013) plen 2 {0x0002} [hci0] 14.639157
Address type: 0x00
Discovery: Enabled (0x01)
@ MGMT Event: Discovering (0x0013) plen 2 {0x0001} [hci0] 14.639157
Address type: 0x00
Discovery: Enabled (0x01)
HCI Event: LE Meta Event (0x3e) plen 43 #99 [hci0] 14.647959
LE Advertising Report (0x02)
Num reports: 1
Event type: Non connectable undirected - ADV_NONCONN_IND (0x03)
Address type: Random (0x01)
Address: 0F:C0:BE:91:50:14 (Non-Resolvable)
Data length: 31
Company: Microsoft (6)
Data: 01092002a3dc622c612f35c009d4f258c2889cbcef9852d2fb374a
RSSI: -70 dBm (0xba)
@ MGMT Event: Device Found (0x0012) plen 45 {0x0003} [hci0] 14.648009
LE Address: 0F:C0:BE:91:50:14 (Non-Resolvable)
RSSI: -70 dBm (0xba)
Flags: 0x00000004
Not Connectable
Data length: 31
Company: Microsoft (6)
Data: 01092002a3dc622c612f35c009d4f258c2889cbcef9852d2fb374a

[Vudentz]

Is it really active scanning or passive? That is important difference, passive (aka. background) scanning is used to detect peripherals that where previously connected/paired and were marked to auto-connect, which is what seems to be the case:

< HCI Command: LE Set Scan Parameters (0x08|0x000b) plen 714.637573
Type: Passive (0x00)
Interval: 60.000 msec (0x0060)
Window: 30.000 msec (0x0030)
Own address type: Public (0x00)
Filter policy: Accept all advertisement (0x00)

There is the possibility of using the so called accept list in the controller and then set a Filter policy so only devices in that list would be notified, that requires controller support though since sometimes devices use Privacy feature (Resolvable Private Addresses - RPA) thus the controller needs to be able to resolve them, which perhaps is why the command above don't use it.