#!/bin/bash
###########################################################
# check_network_link Nagios Linux plugin V1.0 11/01/2008  #
# Watch ethernet interface link status using ethtool      #
#                                                         #
# Originally by Markus Walther which used mii-tool        #
# Reworked by Dmitry Vayntrub to use ethtool              #
###########################################################
#                                                         #
# Usage:                                                  #
#  1. Copy this script to the nagios plugin-directory     #
#  2. Set the exec-rights (chmod a+x check_network_link)  #
#  3. If missing, install "ethtool"                       #
#  4. Allow user nagios execute ethtool in /etc/sudoers:  #
#	 Defaults:nagios !requiretty                        #
#      nagios ALL=NOPASSWD:/sbin/ethtool                  #
#  5. commands.cfg:    $USER1$/check_network_link $ARG1$  #
#  6. services.cfg:    check_network_link!eth0            #
#                                                         #
###########################################################
#
# Exit-Codes:
# 0 = $STATE_OK
# 1 = $STATE_WARNING
# 2 = $STATE_CRITICAL
# 3 = $STATE_UNKNOWN

# Reading the command-input, defaults to eth0 if undefined
NIC=$1
ETHTOOL_REPORT="`sudo /sbin/ethtool ${NIC:-eth0} 2>&1`"

LINK_STATUS=`echo "$ETHTOOL_REPORT" | grep Link | cut -d \  -f 3`

if [ "$LINK_STATUS" = "yes" ]
    then
	LINK_SPEED_RPT=`echo "$ETHTOOL_REPORT" | grep "Speed:"`
	  if [ -z `echo $LINK_SPEED_RPT | grep -v 100` ]
	then
        # Interface works fine
	echo "LINK OK - carrier ok, $LINK_SPEED_RPT"
		exit 0
	else
        # Interface works, but the link speed is slow or unexpected
	echo "LINK WARNING - carrier ok, but slow or unexpected link speed - $LINK_SPEED_RPT"
		exit 1
	  fi
  elif [ "$LINK_STATUS" = "no" ]
    then
        # Link Down - Critical
	echo "LINK CRITICAL - carrier not detected"
		exit 2
  elif [ -n "`echo $ETHTOOL_REPORT | grep link | grep 'No such device'`" ]
    then
        echo "$ETHTOOL_REPORT" #| grep link
	# Interface not found
		exit 2
  elif [ -n "`echo $ETHTOOL_REPORT | grep sudo`" ]
    then
	echo "Add \"Defaults:nagios !requiretty\" in /etc/sudoers"
	# Unknown if there is no tty for nagios
		exit 3
  else  echo "$ETHTOOL_REPORT"
	echo "Unknown error"
        # Another error?
		exit 3
fi