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bluetooth_monitor#

Description#

This node monitors a Bluetooth connection to a wireless device by using L2ping.
L2ping generates PING echo command on Bluetooth L2CAP layer, and it is able to receive and check echo response from a wireless device.

Block diagram#

L2ping is only allowed for root by default, so this package provides the following approach to minimize security risks as much as possible:

  • Provide a small program named l2ping_service which performs L2ping and provides wireless device information to bluetooth_monitor by using socket programming.
  • bluetooth_monitor is able to know wireless device information and L2ping status as an unprivileged user since those information are sent by socket communication.

block_diagram

Output#

bluetooth_monitor: bluetooth_connection#

[summary]

level message
OK OK
WARN RTT warning
ERROR Lost
Function error

[values]

key value (example)
Device [0-9]: Status OK / RTT warning / Verify error / Lost / Ping rejected / Function error
Device [0-9]: Name Wireless Controller
Device [0-9]: Manufacturer MediaTek, Inc.
Device [0-9]: Address AA:BB:CC:DD:EE:FF
Device [0-9]: RTT 0.00ms
  • The following key will be added when bluetooth_monitor reports Function error.
    ex.) The connect system call failed.
key (example) value (example)
Device [0-9]: connect No such file or directory

Parameters#

Name Type Description Default Range
addresses array Bluetooth addresses of the device to monitor ['4C:B9:9B:6E:7F:9A'] N/A
port integer Port number to connect to L2ping service on the host 7640 N/A
timeout integer Time in seconds to wait for a response from the device 5 N/A
rtt_warn float Time in seconds to warn if the round trip time is greater than this value 0.1 N/A

  • rtt_warn

    • 0.00(zero): Disable checking RTT
    • otherwise: Check RTT with specified seconds
  • addresses
    • *: All connected devices
    • AA:BB:CC:DD:EE:FF: You can specify a device to monitor by setting a Bluetooth address

Instructions before starting#

  • You can skip this instructions if you run l2ping_service as root user.

  1. Assign capability to l2ping_service since L2ping requires cap_net_raw+eip capability.

    sudo setcap 'cap_net_raw+eip' ./build/bluetooth_monitor/l2ping_service

  2. Run l2ping_service and bluetooth_monitor.

    ./build/bluetooth_monitor/l2ping_service
ros2 launch bluetooth_monitor bluetooth_monitor.launch.xml

Known limitations and issues#

None.