Extcap binary for capturing bluetooth packets from Android devices

Installation

```sh $ cargo install btsnoop-extcap

Running btsnoop-extcap from command line is not part of the normal workflow,

but it will print out installation instructions. For example:

$ btsnoop-extcap Unknown extcap phase. This is an extcap plugin meant to be used with Wireshark or tshark. To install this plugin for use with Wireshark, symlink or copy this executable to your Wireshark extcap directory

Run the symlink command in the error message (for Wireshark 4.1 or later)

$ mkdir -p "$HOME/.local/lib/wireshark/extcap/" && \ ln -s "$HOME/.cargo/bin/btsnoop-extcap" "$HOME/.local/lib/wireshark/extcap/btsnoop-extcap"

or for Wireshark 4.0 or before

$ mkdir -p "$HOME/.cargo/wireshark/extcap/" && \ ln -s "$HOME/.cargo/bin/btsnoop-extcap" "$HOME/.cargo/wireshark/extcap/btsnoop-extcap" ```

Root is required on the selected Android device.

This extcap plugin is designed to be used with Wireshark or tshark, and will show a live stream of Bluetooth HCI events from the selected device.

Detected devices are shown in Wireshark's Capture interface list.

Instructions to turn on btsnoop log capturing

1. Enable Developer options on the device.
2. In the Developer options menu, activate the Enable Bluetooth HCI snoop log toggle.
3. Restart Bluetooth for logging to take effect.
4. Run adb root

Relationship with androiddump

Wireshark has androiddump as one of the included extcap implementations. It is based on an old configuration in Android that forwarded the btsnoop logs to port 8872, which was disabled in 2015. While it can be turned back on by changing the source code, recompiling Android is incovenient in some cases.

Meanwhile, Android continues to provide the option to write the HCI logs to a local log file (in the /system partition, so root access is required to read it), and that is what this extcap uses as the packet source.