watchdog-netroute.sh

#!/bin/bash

# Reboots if there is no network device for the global route.
#
# Hilmar Lapp <hlapp@drycafe.net>
#
# To the extent possible under law, I have waived all copyright and related
# or neighboring rights to this work under the CC0 1.0 Universal Public Domai
# Dedication. See https://creativecommons.org/publicdomain/zero/1.0

# log message level
#
# Log to standard output if in a terminal, and to syslog otherwise. Level
# defaults to info.
function log() {
    level=$2
    if [ -z "$level" -a ! -t 1 ] ; then
        level=info
    fi
    if [ -t 1 ] ; then
        if [ -n "$level" ] ; then
            level="${level}: "
        fi
        echo "$level$1"
    else
        logger -p local0.$level -t "watchdog" "$1"
    fi
}

# determine the network interface that was supposed to be connected
dev=$(ip route list scope global | cut -d" " -f5)

# if there's no device then reboot unless we're already rebooting
if [ -z "$dev" ] ; then
    if [ -e /tmp/reboot ] ; then
        log "No network device for global route. Rebooting already in progress?" error
        exit 0
    fi
    touch /tmp/reboot
    log "No network device for global route. Rebooting now." error
    (sleep 3 && /sbin/reboot) &
fi