#!/bin/bash

# ============================== SUMMARY =====================================
#Author : Ken Roulamellah
#Date : 19/07/2018
#Version : 1.0
# Licence : GPL
# ===================== INFORMATION ABOUT THIS PLUGIN ========================
#
# This plugin checks the average RX and TX bandwidth utilisation. It use
# kbytes as measure unite.
#
# ========================== START OF PROGRAM CODE ===========================

STATE_OK=0
STATE_WARNING=1
STATE_CRITICAL=2
STATE_UNKNOWN=3

interface=$( ip route | grep default | awk '{print $5}' | head -n1)
function print_usage()
{
  echo "Usage :"
  echo "$0 [ -i=INTERFACE]  [ -ct=COUNT ] -w WARNING -c CRITICAL"
  echo "This script calculate the average bandwith usage."
  echo "Default values | interface: ${interface}, counter: 10"
}

counter=10
warning=-1
critical=-1

sum_rx=0
sum_tx=0
avg_rx=
avg_tx=
i=


if [[ $# -lt 4 ]];
then
	echo "Error: Arguments are missing"
	print_usage
	exit $STATE_UNKNOWN
fi

while [[ $# -gt 0 ]]; do
    case "$1" in
        -i=*)
            interface="$(cut -d'=' -f2 <<<"$1")"
            shift
        ;;
        -ct=*)
            counter="$(cut -d'=' -f2 <<<"$1")"
            shift
        ;;
        -w)
            warning=$2
            shift 2
        ;;
        -c)
            critical=$2
            shift 2
        ;;
        *)
            printf "\nError: Invalid option '$1'"
            print_usage
            exit $STATE_UNKNOWN
        ;;
    esac
done

if [ $warning -lt 0 ] || [ $critical -lt 0 ];
then
	echo "Error: You need to specify a warning and critical treshold"
	print_usage
    exit $STATE_UNKNOWN
fi

grep -q "up" /sys/class/net/$interface/operstate || exec echo "$interface: no such device or down"

read rx <"/sys/class/net/$interface/statistics/rx_bytes"
read tx <"/sys/class/net/$interface/statistics/tx_bytes"

i=$counter
while [ $i -gt 0 ]; do
    sleep 1
    read newrx <"/sys/class/net/$interface/statistics/rx_bytes"
    read newtx <"/sys/class/net/$interface/statistics/tx_bytes"

    #echo "old rx :$rx"
    #echo "new rx :$newrx"
    rx_cal=$(bc <<< "scale=2; ($newrx-$rx) / 1000")
    tx_cal=$(bc <<< "scale=2; ($newtx-$tx) / 1000")

    sum_rx=$(bc <<< "scale=2;$sum_rx+$rx_cal")
    sum_tx=$(bc <<< "scale=2;$sum_tx+$tx_cal")

    #echo  "$interface {rx: $rx_cal ko/s, tx: $tx_cal ko/s}"
    rx=$newrx
    tx=$newtx
    ((i --))
done

avg_rx=$(bc <<< "scale=2;$sum_rx/$counter")
avg_tx=$(bc <<< "scale=2;$sum_tx/$counter")

#echo "$avg_rx"
#echo "$avg_tx"


if [ $(bc <<< "$avg_rx > $critical || $avg_tx > $critical") -eq 1 ]; then
	echo "$interface CRITICAL - AVG_RX: $avg_rx kb/s,  AVG_TX:
        $avg_tx kb/s | RX="$avg_rx"kbps;0;0;0; TX="$avg_tx"kbps;0;0;0;"
	exit $STATE_CRITICAL
elif [ $(bc <<< "$avg_rx > $warning || $avg_tx > $warning") -eq 1 ]; then
	echo "$interface WARNING - AVG_RX: $avg_rx kb/s,  AVG_TX: $avg_tx kb/s | RX="$avg_rx"kbps;0;0;0; TX="$avg_tx"kbps;0;0;0;"
	exit $STATE_WARNING
else
	echo "$interface - OK AVG_RX: $avg_rx kb/s,  AVG_TX: $avg_tx kb/s | RX="$avg_rx"kbps;0;0;0; TX="$avg_tx"kbps;0;0;0;"
	exit $STATE_OK
fi
exit 3