#!/bin/bash

# check_vpn - plugin for nagios to check whether a VPN is down, by verifying
#             that the private network is down and the public network is up
# Copyright (C) 2010 Ioannis Aslanidis <deathwing00 at deathwing00 dot org>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Library General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

# exit status will be:
# 0 if VPN is UP
# 1 if there is packet loss > 0% or the public network is down
#      the purpose of this check is to detect that the VPN is down, not the
#      public network, to be able to add dependencies accordingly to the VPN
# 2 if the VPN is down
# 3 if incorrectly used

declare -f f_ok
declare -f f_war
declare -f f_cri
declare -f f_unk
declare -f check_params
declare -i EXP_PARAMS
readonly EXP_PARAMS="3"
# Params:
# 1 - public ip address
# 2 - private ip address
# 3 - number of pings
function f_ok {
    echo "OK: "${1}
    exit 0
}
function f_war {
    echo "WARNING: "${1}
    exit 1
}
function f_cri {
    echo "CRITICAL: "${1}
    exit 2
}
function f_unk {
    echo "UNKNOWN: "${1}
    exit 3
}
function check_params {
    if [[ ${#} -ne ${EXP_PARAMS} ]];
    then
        f_unk "Expected ${EXP_PARAMS} parameters (pub addr, priv addr, # of pings) but got ${#}"
    fi
}
### MAIN ###
check_params ${*}
readonly PUBL_ADDR="${1}"
readonly PRIV_ADDR="${2}"
readonly MAX_PINGS="${3}"
publ_loss=`/bin/ping -c ${MAX_PINGS} -n -q ${PUBL_ADDR} | /bin/grep "% packet loss" | /usr/bin/cut -d ',' -f 3 | /usr/bin/cut -d '%' -f 1 | /usr/bin/xargs`
if [[ `echo "${publ_loss}" | /bin/grep -q "^[0-9]*$"; echo ${?}` -ne 0 ]];
then
    f_unk "The public address could not be pinged."
fi
priv_loss=`/bin/ping -c ${MAX_PINGS} -n -q ${PRIV_ADDR} | /bin/grep "% packet loss" | /usr/bin/cut -d ',' -f 3 | /usr/bin/cut -d '%' -f 1 | /usr/bin/xargs`
if [[ `echo "${priv_loss}" | /bin/grep -q "^[0-9]*$"; echo ${?}` -ne 0 ]];
then
    f_unk "The private address could not be pinged."
fi
if [[ "${publ_loss}" -lt 0 || "${priv_loss}" -lt 0 ]];
then
    f_unk "Negative packet loss detected."
elif [[ "${publ_loss}" -eq 0 && "${priv_loss}" -eq 0 ]];
then
    f_ok "The VPN is working correctly. 0% packet loss."
elif [[ "${publ_loss}" -eq 0 && "${priv_loss}" -lt 100 ]];
then
    f_war "The VPN is suffering ${priv_loss}% packet loss."
elif [[ "${publ_loss}" -lt 100 ]];
then
    f_war "The public network is suffering ${publ_loss}% packet loss. The VPN is suffering ${priv_loss}% packet loss."
elif [[ "${publ_loss}" -ge 100 ]];
then
    f_war "The public network is DOWN."
else
    f_cri "The VPN is DOWN."
fi
f_unk "Reached unreachable code"