#!/bin/bash
# Return Codes:
# 0 - Ok!       - Up
# 1 - Warning   - Flaky
# 2 - Critical  - Down
# 3 - Unknown   - Ummm... What happened?!

STATE=3

print_usage() {
        echo "Usage: check_twodns.sh [Master DNS] [Slave DNS] [Zone]"
}

#Parameter prüfen
if [ $# -ne 3 ]; then
  print_usage
  exit $STATE
fi

SerialMaster=$(/usr/bin/dig @${1} ${3} +short SOA | awk '{print $3}')
if [ $? -ne 0 ] || [ -z "$SerialMaster" ]; then
  echo "Error reading Serial from Master for Domain \"${3}\""
  exit 3
fi

SerialSlave=$(/usr/bin/dig @${2} ${3} +short SOA | awk '{print $3}')
if [ $? -ne 0 ] || [ -z "$SerialSlave" ]; then
  echo "Error reading Serial from Slave for Domain \"${3}\""
  exit 3
fi

if [ "$SerialMaster" -eq "$SerialSlave" ]; then
  Status="Serial for \"${3}\" is identical on both DNS-Servers: ${SerialMaster}"
  STATE=0
else
  echo "Serial for \"${3}\" is different. Master: ${SerialMaster}, Slave: ${SerialSlave}"
  STATE=2
fi

echo $Status
exit $STATE