#!/bin/sh
# this script looks up the IP address of system.@system[0].log_host
# if the DNS resolves succesfully (an IP address is found)
# and that IP address is different from current system.@system[0].log_ip
# it will set system.@system[0].log_ip to the new IP address
# and reload log daemon so that it reconnects to the new IP.
# sleep and repeat, every 5 minutes.

ip_from_host() {
  nslookup "$1" | grep 'Address 1' | awk '{print $3}'
}

while true; do
  log_host="$(uci -q get system.@system[0].log_host)"
  log_ip_old="$(uci -q get system.@system[0].log_ip)"
  log_ip_new="$(ip_from_host "$log_host")"

  if [ -n "$log_ip_new" ] && [ "$log_ip_old" != "$log_ip_new" ]; then
    uci set system.@system[0].log_ip="$log_ip_new"
    uci commit system
    /etc/init.d/log reload
  fi

  sleep 300  # 5 minutes
done