#!/bin/bash
# chkconfig: 2345 99 10
# description: Auto assigns free EIP
# processname: ipassign
# Provides:             ipassign
# Required-Start:       
# Required-Stop:        
# Default-Start:        2 3 4 5
# Default-Stop:         
# Short-Description:    Set Public IP from ElasticIP pool during start-up

OUTPUT="text"
REGION="eu-west-1"
IPLOGFILE="/var/log/ipassign.log"
export PATH=/usr/share/pear:/usr/local/bin:/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/sbin:/opt/aws/bin:/home/ec2-user/bin

timestamp() {
  TIMESTAMP=`date -u +"%Y-%m-%dT%H:%M:%S.000Z"`
}

usage() {
  echo "$0 {start|stop|status}"
  exit 255
}

write_log() {
  timestamp
  echo "${TIMESTAMP} - ${LOG}" >> ${IPLOGFILE}
}

valid_ip() {
  RX='([1-9]?[0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])'
  
  if [[ ${EC2PUBLICIP} =~ ^${RX}\.${RX}\.${RX}\.${RX}$ ]]
  then
    VALIDIP=1
  else
    VALIDIP=0
  fi
}

check_ec2metadata() {
  ec2-metadata >/dev/null 2>&1
  if [ $? -eq 0 ]
  then
    # Amazon Linux ec2-metadata command found
    EC2INSTANCE=`ec2-metadata -i | awk '{ print $NF; }'`
    EC2PUBLICIP=`ec2-metadata -v | awk '{ print $NF; }'`
  else
    # Checking ec2metadata command
    ec2metadata >/dev/null 2>&1
    if [ $? -eq 0 ]
    then
      # ec2metadata command found
      EC2INSTANCE=`ec2metadata --instance-id`
      EC2PUBLICIP=`ec2metadata --public-ipv4`
    else
      # No ec2metadata command found
      LOG="ERROR: No ec2metadata or ec2-metadata command found"; write_log
      exit 127
    fi
  fi
}

check_awscli() {
  aws ec2 describe-addresses >/dev/null 2>&1
  
  if [ $? -ne 0 ]
  then
    # Incorrect instance role or no valid AWS CLI configuration found
    LOG="ERROR: AWS CLI commands not available. Check AWS CLI installation or configuration"; write_log
    exit 128
  fi
}

start() {
  # EC2 metadata: public IP and Instance ID
  check_ec2metadata

  # Checking if any Public IP is assigned
  valid_ip

  if [ ${VALIDIP} -eq 0 ]
  then
    # No Public IP available. Can't execute AWS CLI command
    LOG="ERROR: There is no Public IP address assigned. Can't run AWS CLI commands"; write_log
    exit 3
  fi
  
  # Check if AWS CLI commands are available
  check_awscli

  # Checking if instance has a public IP from Elastic pool assigned
  PUBLICIPASSIGNED=`aws ec2 describe-addresses --output ${OUTPUT} --region ${REGION} | grep ${EC2INSTANCE} | wc -l`

  if [ ${PUBLICIPASSIGNED} -gt 0 ]
  then
    # Instance has at least one Pulic IP associated from Elastic pool
    IP=`aws ec2 describe-addresses --output ${OUTPUT} --region ${REGION} | grep ${EC2INSTANCE} | head -1 | awk '{ print $NF; }'`
    LOG="Instance ${EC2INSTANCE} has a Public IP address from Elastic pool in ${REGION} region (${IP})"; write_log
    exit 4
  else
    # Get IP address from Elastic pool
    IP=`aws ec2 describe-addresses --output ${OUTPUT} --region ${REGION} | grep -v 'i-' | head -1 | awk '{ print $NF; }'`

    if [ "${IP}" = "" ]
    then
      # No unassigned Public IP on pool
      LOG="ERROR: No free Public IP from Elastic pool in ${REGION} region available"; write_log
      exit 5
    else
      # Attach Public IP from Elastic pool
      BOOL=0
      aws ec2 associate-address --output ${OUTPUT} --region ${REGION} --instance-id ${EC2INSTANCE} --public-ip ${IP} >/dev/null 2>&1
      EXITCODE=$?

      if [ ${EXITCODE} -eq 0 ]
      then
        LOG="${IP} Public IP from pool assigned to ${EC2INSTANCE} instance"; write_log
      else
        LOG="ERROR: (${EXITCODE}) Unable to associate ${IP} Public IP from Elastic pool to ${EC2INSTANCE} instance"; write_log
        BOOL=1
      fi

      if [ ${BOOL} -eq 0 ]
      then
        # Detaching default Public IP
        aws ec2 disassociate-address --output ${OUTPUT} --region ${REGION} --instance-id ${EC2INSTANCE} --public-ip ${EC2PUBLICIP} >/dev/null 2>&1
        EXITCODE=$?

        if [ ${EXITCODE} -eq 0 ] || [ ${EXITCODE} -eq 255 ]
        then
          LOG="Default public IP ${EC2PUBLICIP} not from pool disassociated in ${EC2INSTANCE} instance"; write_log
        else
          LOG="ERROR: (${EXITCODE}) Unable to disassociate default public IP ${EC2PUBLICIP} in ${EC2INSTANCE} instance"; write_log
          BOOL=2
        fi
      fi
      exit ${BOOL}
    fi
  fi
}

stop() {
  exit 6
}

status () {
  check_ec2metadata
  valid_ip

  if [ ${VALIDIP} -eq 0 ]
  then
    echo "No Public IP address assigned to ${EC2INSTANCE} instance."
    exit 1
  fi
  
  check_awscli
  IPPRESENTINPOOL=`aws ec2 describe-addresses --output ${OUTPUT} --region ${REGION} | grep "${EC2INSTANCE}" | grep ${EC2PUBLICIP} | wc -l`
  
  if [ ${IPPRESENTINPOOL} -eq 1 ]
  then
    echo "Public IP ${EC2PUBLICIP} assigned to ${EC2INSTANCE} instance is part of the ElasticIP pool"
    exit 0
  else
    echo "Public IP ${EC2PUBLICIP} assigned to ${EC2INSTANCE} instance is a generic public IP NOT present in ElasticIP pool"
    exit 2
  fi
}

case "$1" in
  start)
        start
        ;;
  stop)
        stop
        ;;
  status)
        status
        ;;
  *)
        usage
        ;;
esac