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Cake day: July 5th, 2023

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  • 0 4   *   *   *    /usr/sbin/reboot
    

    Adjust interval as needed.

    Or if you want something a bit faster and less disruptive:

    #!/bin/sh
    
    NAME="$0"
    
    logger_cmd () {
      echo $@
      logger -p daemon.info -t "$NAME[$$]" $@
    }
    
    if ! which ncat 1>/dev/null
    then
      logger_cmd "ncat not found, installing..."
      opkg update && opkg install ncat
    fi
    
    chk_conn () {
      echo "Checking connectivity to $@"
      if ncat --send-only --recv-only -w 334ms $@ 2>/dev/null; then
        return 0
      fi
    
      logger_cmd "Cannot reach $@"
      return 1
    }
    
    restart_network_iface() {
        # TODO: Don't restart every minute
    
        COOLDOWN_LOCK=/tmp/internet-connectivity-watchcat.tmp
        COOLDOWN_SECONDS=300
    
        cooldown_time_end=$(cat $COOLDOWN_LOCK || echo 0)
    
        time_now="$(cat /proc/uptime)"
        time_now="${time_now%%.*}"
    
        cooldown_time_left=$((cooldown_time_end - time_now))
    
        if [ "$cooldown_time_left" -lt "1" ]
        then
            logger_cmd "Restarting network interface: \"$1\"."
            ifdown "$1"
            ifup "$1"
    
            cooldown_time_end=$((time_now + COOLDOWN_SECONDS))
            echo $cooldown_time_end > $COOLDOWN_LOCK
        else
            logger_cmd "Skipping interface \"$1\" restart due to cooldown. Cooldown left: $cooldown_time_left seconds"
        fi
    }
    
    
    logger_cmd "Checking internet connectivity..."
    
    if   chk_conn google.com 443 \
      || chk_conn amazon.com 443 \
      || chk_conn facebook.com 443 \
      || chk_conn cloudflare.com 443 \
      || chk_conn telekom.de 443
    then
      logger_cmd "Connected to internet."
    else
      logger_cmd  "Not connected to internet."
      restart_network_iface "$1"
    fi
    

    In restart_network_iface use /usr/sbin/reboot instead of interface up/down and run the script every few minutes via cron or systemd timer. This was written for OpenWrt so if you use that you can use it as-is. For other systems you’d also have to adjust the logger_cmd.

    You can place that on another machine and send a signal to a smart plug instead if you’re worried of a locked up / frozen router. That said if your router freezes like that, you should probably change it and you should be able to run this script on it.