Error with Go program ( Bettercap 2 ) depending on which bluetooth dongle I use on Ubuntu/Raspberry Pi OS when running ble scan

I use this on Ubuntu 20.04 and Raspberry Pi OS 5.10 but this is not a Linux related issue.

I'm having an issue with a Go program called Bettercap 2 ( https://www.bettercap.org/ and the repository: https://github.com/bettercap/bettercap ) when I use its function to scan bluetooth devices "ble.recon on" with a different bluetooth dongle.

When I use it with a dongle using Realtek RTL8761b drivers ( MPOW MPBH456AB ) you can find on amazon it works well, but when I use a NordicSemi nrf52840 dongle ( https://www.nordicsemi.com/Products/Development-hardware/nrf52840-dongle ) which is my goal, flashed with Zephyr RTOS' hci_usb sample ( https://github.com/zephyrproject-rtos/zephyr/tree/main/samples/bluetooth/hci_usb ) which is supposed to turn any micro controller using bluetooth into a regular bluetooth dongle that any computer is supposed to recognize as, it throws this error:

>> ble.recon on
   panic: runtime error: slice bounds out of range [:1] with capacity 0

   goroutine 1 [running]:
   github.com/bettercap/gatt/linux/cmd.(*Cmd).SendAndCheckResp(0x1c637c0, 0xa0c760, 0x1c64fe8, 0x1c6501c, 0x1, 0x1, 0x0, 0x0)
    /home/pi/go/pkg/mod/github.com/bettercap/gatt@v0.0.0-20210514133428-df6e615f2f67/linux/cmd/cmd.go:98 +0x1b4
   github.com/bettercap/gatt/linux.(*HCI).resetDevice(0x18ac0a0, 0x93dc10, 0x18ac0a0)
    /home/pi/go/pkg/mod/github.com/bettercap/gatt@v0.0.0-20210514133428-df6e615f2f67/linux/hci.go:273 +0x2f0
   github.com/bettercap/gatt/linux.NewHCI(0xffffffff, 0x184fd01, 0xff, 0x2, 0x0, 0x0)
    /home/pi/go/pkg/mod/github.com/bettercap/gatt@v0.0.0-20210514133428-df6e615f2f67/linux/hci.go:90 +0x4c0
   github.com/bettercap/gatt.NewDevice(0x184fd1c, 0x2, 0x2, 0x3c, 0x184fd24, 0x1, 0x1)
    /home/pi/go/pkg/mod/github.com/bettercap/gatt@v0.0.0-20210514133428-df6e615f2f67/device_linux.go:57 +0x114
   github.com/bettercap/bettercap/modules/ble.(*BLERecon).Configure(0x18a2780, 0x0, 0x4)
    /home/pi/go/pkg/mod/github.com/bettercap/bettercap@v2.24.1+incompatible/modules/ble/ble_recon.go:165 +0x1cc
   github.com/bettercap/bettercap/modules/ble.(*BLERecon).Start(0x18a2780, 0x1, 0x1b2c001)
    /home/pi/go/pkg/mod/github.com/bettercap/bettercap@v2.24.1+incompatible/modules/ble/ble_recon.go:183 +0x1c
   github.com/bettercap/bettercap/modules/ble.NewBLERecon.func1(0x0, 0x0, 0x0, 0x84f358, 0xc)
    /home/pi/go/pkg/mod/github.com/bettercap/bettercap@v2.24.1+incompatible/modules/ble/ble_recon.go:56 +0x1c
   github.com/bettercap/bettercap/session.(*ModuleHandler).Exec(0x1b2c0c0, 0x0, 0x0, 0x0, 0x0, 0x0)
    /home/pi/go/pkg/mod/github.com/bettercap/bettercap@v2.24.1+incompatible/session/module_handler.go:74 +0x80
   github.com/bettercap/bettercap/session.(*Session).Run(0x18fb2c0, 0x1c64e30, 0xc, 0x1, 0x1)
    /home/pi/go/pkg/mod/github.com/bettercap/bettercap@v2.24.1+incompatible/session/session.go:416 +0x284
   main.main()
    /home/pi/go/pkg/mod/github.com/bettercap/bettercap@v2.24.1+incompatible/main.go:94 +0x8c8

I have no idea what it means as I'm not a Go developer and have never used this language, I've looked at the error and it seems to be in the code but not knowing Go, I prefer to ask before I modify anything.

The problem is only when I'm using the nrf dongle, otherwise it works with the host's bluetooth and the other realtek dongle.

The nrf dongle works with the BlueZ stack, here are the results:

bluetoothctl ( has a BD address )
Scan does work

$ sudo bluetoothctl
  Agent registered
  [bluetooth]# list
  Controller EB:XX:XX:XX:XX:XX BlueZ 5.50 [default]

btmgmt ( finds the controller )
Scan does work

$ sudo btmgmt --index 0
   [hci0]# auto-power
   Found controller with index 0
   [hci0]# find -l

But, although deprecated, hciconfig and hcitool recognize the realtek dongle but for this one, here are the results:

hciconfig ( no BD address )

$ hciconfig
  hci0:   Type: Primary  Bus: USB
    BD Address: 00:00:00:00:00:00  ACL MTU: 27:7  SCO MTU: 0:0
    UP RUNNING
    RX bytes:1593 acl:0 sco:0 events:88 errors:0
    TX bytes:285 acl:0 sco:0 commands:51 errors:0

hcitool ( Doesn't find the controller )

$ hcitool scan
  Scanning ...
  Inquiry failed: Operation not supported

So, I assume the dongle works well with BlueZ, being the Linux official bluetooth stack it's a good sign, but I thought that Bettercap was also using BlueZ and in that sense the dongle should work.

I don't think there are any drivers to install for the dongle as of the fact that when it is flashed ( J-Link ) it turns into a generic bluetooth dongle.

Do you have any idea what the problem could be ?

I believe the error is coming from https://github.com/bettercap/gatt/blob/master/linux/cmd/cmd.go#L98

The program is attempting to write something to the device and expects that it will receive a response as long as there was no error sending. But apparently the Send call is successful but receives an empty response.

I'd suggest opening an issue over there and asking your question.