#!/bin/bash
# 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 3 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see .
# ----------------------------------------------------------------------------
#
# Written by Tom Molin to count the number of half-open SYN connections.
# Lessons learnt from Anonymous big SYN Flood attack 2012-09-03
# Exit levels:
OK=0
WARN=1
ERROR=2
UNKNOWN=3
function usage
{
echo "Usage: Count number of half open tcp connections with netstat.
-w --warnlevel NUM
-c --criticallevel NUM
-L LABEL"
}
# Parse input parameters
until [ -z "$1" ]; do
case "$1" in
-w|--warnlevel)
WARNLEVEL="$2"
shift
;;
-c|--criticallevel)
CRITLEVEL="$2"
shift
;;
-L)
LBL="$2"
shift
;;
*)
usage
exit 1
;;
esac
shift
done
if [[ -z "$WARNLEVEL" ]] || [[ -z "$CRITLEVEL" ]] || [[ -z "$LBL" ]]
then
echo "Missing argument"
usage
exit 1
fi
STATUS=$(/bin/netstat -n -p TCP tcp | grep SYN_R | wc -l)
LABEL="| ${LBL}=${STATUS};$WARNLEVEL;$CRITLEVEL;0;"
if [ "$STATUS" -lt "$WARNLEVEL" ];then
echo "OK - $STATUS $LABEL"
exit $OK
fi
if [ "$STATUS" -ge "$WARNLEVEL" -a "$STATUS" -lt "$CRITLEVEL" ];then
echo "WARNING - $STATUS $LABEL"
exit $WARN
fi
if [ "$STATUS" -ge "$CRITLEVEL" ];then
echo "CRITICAL - $STATUS $LABEL"
exit $ERROR
fi
echo "UNKNOWN ERROR status ($STATUS)!"
exit $UNKNOWN