I bought a Raspberry Pi 4. So, I put Arch Linux in the SD card.

I didn't buy the LED separately this time, but it will be operated in its original state, but there is one problem,

** It is troublesome to check where you are connected **

Basically, DHCP is used and there is no monitor, so it is troublesome to go to check the IP address regardless of whether it is a wired connection or a wireless connection. So, this time, as the title suggests, I decided to "get the connection information from myself when the network connection is established".

Summary

Environmental information

Case: Raspberry Pi 4
OS: ArchLinux (ARM version)
Network management: NetworkManager
Python 3.8.0

The code I wrote

`py:/etc/NetworkManager/dispatcher.d/notify-connection-information.py`


#!/usr/bin/env python
import json
import os
import sys
from urllib.request import urlopen


WEBHOOK_URL = 'https://hooks.slack.com/services/THISIS/SLACK/WEBHOOK'


def main(conn_id, ip_addr):
    payload = {
        'username': 'info',
        'icon_emoji': ':strawberry:',
        'text': f'*attakei-pi* has connected to {conn_id}\n IP address is `{ip_addr}`',
        'channel': '@attakei',
    }
    urlopen(WEBHOOK_URL, json.dumps(payload).encode())


if __name__ == '__main__':
    argv = sys.argv[1:]
    # if argv[0] != 'wlan0' or argv[1] != 'up':
    if argv[1] != 'up':
        sys.exit(0)
    ip_addr = os.environ['DHCP4_IP_ADDRESS']
    conn_id = os.environ['CONNECTION_ID']
    main(conn_id, ip_addr)

Completion notification

NetworkManager story

What is NetworkManager?

It is a daemon (+ tool) for managing various things related to network connection. It manages the SSID and automatically connects to the already registered SSID.

There are also systemd-networkd etc., but for the time being I am currently using this.

NetworkManager dispatch function

Now, NetworkManager has a dispatcher feature that allows you to" execute a command to divide a network as an event. " In the sample etc. posted on the ArchLinux Wiki, examples such as "Disable wireless when making a wired connection (+ vice versa)" and "Continue to VPN connection when connecting to a specific network" are written. I am. This time, referring to these scripts, I made the above script "Declare the used SSID and ʻIP address to the specified Slack channel when connecting to the network".

What the dispatcher receives

As far as I know by actually using it, Disptcher will pass the following information when executing the command.

As a command argument
The name of the network device where the event occurred
What event occurred (eg ʻup` = connected)
As an environment variable
Various information associated with the above events
Connection setting name
IP address
etc

Align information and dispatch

Based on the conditions you want to trigger, organize where to get information and behavior.

"When connecting to the network"
=> Refer to the second argument of the command. Ignore all but ʻup`
"To the specified Slack channel"
=> Since it is not the management area of NetworkManager-dispacher, the script is written directly for the time being.
" Used SSID "
=> See the environment variable CONNECTION_ID
"ʻIP address` "
=> Since most of IPv4 is used for the time being, refer to the environment variable DHCP4_IP_ADDRESS.

Now that you have the information you need, you can write the code. Please refer to the code as it was written first.

Supplement

Don't forget to shebang and grant execute permissions as the script will be called directly.

I became "that" with this, and I was about to search for an IP address of a system that I would do my best.

URLs

https://wiki.gnome.org/Projects/NetworkManager
https://wiki.archlinux.org/index.php/NetworkManager
https://wiki.archlinux.jp/index.php/NetworkManager
https://developer.gnome.org/NetworkManager/stable/NetworkManager.html

[PYTHON] I want to be notified of the connection environment when the Raspberry Pi connects to the network