racecam_network_manager.py

#!/usr/bin/env python3
import subprocess
import time
import logging

logging.basicConfig(level=logging.INFO, format='%(asctime)s - NetworkManager - %(message)s')

def run_cmd(cmd):
    """Runs a command, logging errors but not stopping the script."""
    try:
        result = subprocess.run(cmd, shell=True, check=True, capture_output=True, text=True)
        return result.stdout.strip()
    except subprocess.CalledProcessError as e:
        logging.error(f"Command '{cmd}' failed: {e.stderr.strip()}")
        return ""

def is_wifi_connected():
    """
    Checks if there is an active Wi-Fi connection on the wlan0 interface.
    A more reliable check is to see if an active connection profile exists on the device.
    """
    try:
        # We use subprocess.run directly to check the return code, which is cleaner.
        # A return code of 0 from grep means a match was found.
        subprocess.run("nmcli -t -f DEVICE connection show --active | grep -q '^wlan0$'", shell=True, check=True)
        logging.info("Active Wi-Fi connection found on wlan0.")
        return True
    except subprocess.CalledProcessError:
        # This error means grep returned a non-zero code (no match found).
        logging.info("No active Wi-Fi connection found on wlan0.")
        return False

def set_ap_mode(enable=True):
    """Enables or disables the Wi-Fi Access Point mode."""
    if enable:
        logging.info("No Wi-Fi connection. Enabling Access Point (AP) mode.")
        # Stop NetworkManager from managing wlan0 so hostapd can use it.
        run_cmd("sudo nmcli device set wlan0 managed no")
        run_cmd("sudo systemctl start hostapd.service")
        run_cmd("sudo systemctl start dnsmasq.service")
    else:
        logging.info("Wi-Fi connection detected. Disabling Access Point (AP) mode.")
        run_cmd("sudo systemctl stop hostapd.service")
        run_cmd("sudo systemctl stop dnsmasq.service")
        # Give control of wlan0 back to NetworkManager.
        run_cmd("sudo nmcli device set wlan0 managed yes")

def main():
    """Main logic to check network status and switch modes."""
    logging.info("Starting network mode check...")
    # Give NetworkManager a moment to establish a connection at boot.
    time.sleep(15)

    if is_wifi_connected():
        set_ap_mode(enable=False)
    else:
        set_ap_mode(enable=True)
    
    logging.info("Network mode check complete.")

if __name__ == "__main__":
    main()