Orbit Pro HKM281: Auto Restart WWAN Interface OpenWRT

check_wwan.sh

#!/bin/sh

# =============================================================================
#
# OpenWrt LTE/Cellular Connection Watchdog
# Created by: Indra L.N.
#
# =============================================================================
#
# PURPOSE:
# This script monitors an OpenWrt cellular connection that uses a virtual
# interface (common with NCM, QMI, and MBIM protocols) to get an IP address.
# It is designed to solve a common problem where the modem appears connected,
# but the virtual IP interface disappears, cutting off internet access.
#
# When a failure is detected, this script automatically restarts the main
# modem interface to re-establish a working connection.
#
# =============================================================================
#
# HOW TO USE:
#
# 1. CUSTOMIZE VARIABLES (If Necessary)
#    - Edit the VIRTUAL_IF and MODEM_IF variables below to match your
#      interface names as they appear in LuCI or from the `ifconfig` command.
#
# 2. UPLOAD SCRIPT TO YOUR ROUTER
#    - Copy this file to the /usr/bin/ directory on your OpenWrt router.
#    - Example using scp from your computer:
#      scp ./check_wwan.sh [email protected]:/usr/bin/
#
# 3. MAKE THE SCRIPT EXECUTABLE
#    - SSH into your router and run the following command:
#      chmod +x /usr/bin/check_wwan.sh
#
# 4. SCHEDULE THE SCRIPT WITH CRON
#    - On your router, edit the root user's crontab file:
#      vi /etc/crontabs/root
#    - Add the following line to the file. This will run the script
#      every 5 minutes. Ensure the file ends with a blank newline.
#
#      */5 * * * * /usr/bin/check_wwan.sh
#
# 5. ENABLE AND START THE CRON SERVICE
#    - Run these commands to make sure the scheduler is active and
#      will start automatically on reboot:
#      /etc/init.d/cron enable
#      /etc/init.d/cron start
#
# =============================================================================
#
# VERIFICATION:
# The script is silent and will only produce output when it detects a problem.
# To see if it's working, you can monitor the system log:
#
#   logread -f
#
# When your connection drops, a message like this will appear in the log:
# "Watchdog: Interface wwan_4 not found. Restarting wwan..."
#
# =============================================================================

# --- Script Configuration ---

# The virtual interface that gets the IP address (the one to check)
VIRTUAL_IF="wwan_4"

# The main modem interface (the one to restart)
MODEM_IF="wwan"

# --- Script Logic ---

# Check if the virtual interface exists and is up.
ifstatus $VIRTUAL_IF >/dev/null 2>&1

# Check the exit code of the last command ($?). A non-zero code means
# ifstatus failed, which tells us the interface is down or doesn't exist.
if [ $? -ne 0 ]; then
    # The virtual interface is down.
    # Now, let's validate the main modem interface before we restart it.
    uci show network.$MODEM_IF >/dev/null 2>&1

    if [ $? -eq 0 ]; then
        # This condition is true if the wwan interface exists in the configuration.
        logger "Watchdog: Interface $VIRTUAL_IF not found. Restarting $MODEM_IF..."
        ifdown $MODEM_IF && ifup $MODEM_IF
    else
        # This condition is true if the wwan interface does NOT exist in the configuration.
        logger "Watchdog: Interface $VIRTUAL_IF not found, but main interface $MODEM_IF is not configured. Taking no action."
    fi
fi