Matejunkie » netstat

Update 1.1: UDP Packet Loss Check Plugin for Nagios

Mike Adolphs — Mon, 11 May 2009 09:36:39 +0000

I’ve changed the small UDP packet loss script yesterday so that it’s now showing the total requests, requests sent to an unknown port and receive errors per check interval. That means, if you’d choose a check interval of 5 minutes, the script shows the amount of the previous mentioned for this time frame. It now creates two temporary files in a directory which you may define via -t/–path-tmp. The file is automatically deleted when it’s size got over 32Kb.
Feel free to grab it from MonitoringExchange (they’ve changed their name due to legal problems with Nagios Enterprises and because of Nagios’ new fork Icinga), via svn or copy’n'paste below.

user@host ~ $ svn co https://svn.matejunkie.com/svn/nagios-plugins/stable/check_udp-packet-loss/ check_udp-packet-loss/

#!/bin/sh
 
#   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 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., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 
PROGNAME=`basename $0`
VERSION="Version 1.1,"
AUTHOR="2009, Mike Adolphs (http://www.matejunkie.com/)"
 
ST_OK=0
ST_WR=1
ST_CR=2
ST_UK=3
 
path_tmp="/tmp"
 
print_version() {
    echo "$VERSION $AUTHOR"
}
 
print_help() {
    print_version $PROGNAME $VERSION
    echo ""
    echo "$PROGNAME is a Nagios plugin to monitor the UDP packet"
    echo "loss via netstat. It writes a temporary file to a configurable"
	echo "directory and compares it's values against the ones from the check"
	echo "before."
	echo "That means the actual result shows the amount of overall packets,"
	echo "received, receive errors and/or packets recieved to unknown port"
	echo "for the last check interval you've chosen."
    echo ""
    echo "$PROGNAME check_udp-packet-loss.sh"
    echo ""
    echo "Options:"
    echo "  --warning|-w)"
    echo "    Sets a warning level for packet receive errors. Default is:"
    echo "    off"
    echo "  --critical|-c)"
    echo "    Sets a critical level for packet receive errors. Default is:"
    echo "    off"
    echo "  --path-tmp|-t)"
    echo "    Sets the path for the temporary file. Default is: /tmp"
    exit $ST_UK
}
 
while test -n "$1"; do
    case "$1" in
        --help|-h)
            print_help
            exit $ST_UK
            ;;
        --version|-v)
            print_version $PROGNAME $VERSION
            exit $ST_UK
            ;;
        --path-tmp|-t)
            path_tmp=$2
            shift
            ;;
        --warning|-w)
            warn=$2
            shift
            ;;
        --critical|-c)
            crit=$2
            shift
            ;;
        *)
            echo "Unknown argument: $1"
            print_help
            exit $ST_UK
            ;;
    esac
    shift
done
 
check_filesize() {
    if [ -f $path_tmp/udp-errors.log ]
    then
        size=`du $path_tmp/udp-errors.log | awk '{print $1}'`
	if [ $size -gt 32 ]
        then
            rm $path_tmp/udp-errors.log
            touch $path_tmp/udp-errors.log
        fi
    else
        touch $path_tmp/udp-errors.log
    fi   
}
 
get_packet_loss() {
	date_beg=`date`
	echo "+++ $date_beg +++" >> $path_tmp/udp-errors.log
    netstat -us|grep 'packets received' >> $path_tmp/udp-errors.log
    netstat -us|grep 'to unknown port' >> $path_tmp/udp-errors.log
    netstat -us|grep 'packet receive errors' >> $path_tmp/udp-errors.log
	date_end=`date`
	echo "--- $date_end ---" >> $path_tmp/udp-errors.log
	tac /tmp/udp-errors.log | awk '/---/{p=1} p{print} /+++/{p=0;if \
(count++==1) exit}' > $path_tmp/udp-errors.log.tmp
}
 
chk_packet_loss() {
	p_receive_1st=`tac $path_tmp/udp-errors.log.tmp | grep -m1 'packets \
received' | awk '{print $1}'`
	p_receive_2nd=`tac $path_tmp/udp-errors.log.tmp | grep 'packets \
received' | sort -r | grep -m1 'packets received' | awk '{print $1}'`
	p_unknown_1st=`tac $path_tmp/udp-errors.log.tmp | grep -m1 'to unknown \
port' | awk '{print $1}'`
	p_unknown_2nd=`tac $path_tmp/udp-errors.log.tmp | grep 'to unknown \
port' | sort -r | grep -m1 'to unknown port' | awk '{print $1}'`
	p_errors_1st=`tac $path_tmp/udp-errors.log.tmp | grep -m1 'receive \
errors' | awk '{print $1}'`
	p_errors_2nd=`tac $path_tmp/udp-errors.log.tmp | grep 'receive errors' \
| sort -r | grep -m1 'receive errors' | awk '{print $1}'`
 
	if [ ! $p_receive_2nd = 0 ]
	then
		p_receive=`expr $p_receive_2nd - $p_receive_1st`
	else
		p_receive=0
	fi
 
	if [ ! "$p_unknown_2nd" = 0 ]
	then
		p_unknown=`expr $p_unknown_2nd - $p_unknown_1st`
	else
		p_unknown=0
	fi
 
	if [ ! "$p_errors_2nd" = 0 ]
	then
		p_errors=`expr $p_errors_2nd - $p_errors_1st`
	else
		p_errors=0
	fi
}
 
val_wcdiff() {
    if [ ${warn} -gt ${crit} ]
    then
        wcdiff=1
    fi
}
 
check_filesize
get_packet_loss
chk_packet_loss
 
if [ -n "$warn" -a -n "$crit" ]
then
    val_wcdiff
    if [ "$wcdiff" = 1 ]
    then
        echo "The warning level should be lower than the critical level. \
Please adjust them."
        exit $ST_UK
    fi
fi
 
if [ -n "$warn" -a -n "$crit" ]
then
    if [ "$p_unknown" -ge "$warn" -a "$p_unknown" -lt "$crit" ]
    then
        echo "WARNING - $p_receive total packets received, $p_unknown \ 
went to unknown port, $p_errors receive errors! | \
'received'=$p_receive 'unknown_port'=$p_unknown 'errors'=$p_errors"
        exit $ST_WR
    elif [ "$p_unknown" -ge "$crit" ]
    then
        echo "CRITICAL - $p_receive total packets received, $p_unknown \
went to unknown port, $p_errors receive errors! | \
'received'=$p_receive 'unknown_port'=$p_unknown 'errors'=$p_errors"
        exit $ST_CR
    else
        echo "OK - $p_receive total packets received, $p_unknown \
went to unknown port, $p_errors receive errors! | \
'received'=$p_receive 'unknown_port'=$p_unknown 'errors'=$p_errors"
        exit $ST_OK
    fi
else
    echo "OK - $p_receive total packets received, $p_unknown went to unknown \
port, $p_errors receive errors! | 'received'=$p_receive \
'unknown_port'=$p_unknown 'errors'=$p_errors"
    exit $ST_OK
fi

UDP Packet Loss Check Plugin for Nagios

Mike Adolphs — Tue, 05 May 2009 22:20:10 +0000

I just needed to rewrite a small check plugin I’ve written a few months ago to check possible UDP data loss on a host which serves an application that constantly has to process tens of thousand UDP packets at a time. Otherwise we just wouldn’t know in time when the application or the host’s network stack become somewhat limited because of UDP’s stateless nature and that’s what you better wanna know for sure if the transmitted data is valuable for the company.

The script

As always, the script is downloadable from NagiosExchange, via svn directly from here or the copy’n'paste way below.

user@host ~ $ svn co https://svn.matejunkie.com/svn/nagios-plugins/stable/check_udp-packet-loss/ check_udp-packet-loss/

It makes use of netstat to check for packets received to an unknown port or receive errors and to monitor the overall count of UDP packets received. This information is being put into a file in a temporary directory which is not being used at all for now, I must confess. The idea behind that is to rather monitor UDP packet receive errors over a period of time instead of its total count, but since there’s other heavy stuff going on at the moment, I just don’t have the time to finish this at the moment. I’ll do this within the next weeks.
The script checks by itselfs whether the file grows over 32K, then deletes and re-creates it. So no worries about broken hard drives here.

The term “packets to unknown port received” is explained as the following: “Displays the total number of UDP datagrams received for which there was no application at the destination port” which means that e.g. those will increase when you’d temporarily shutdown your application. “packet receive errors” will mostly occur when the host’s buffer is bursting. For additional information I’d suggest reading “UDP Buffer sizing” at 29west.com and UDP’s man page at kernel.org.

#!/bin/sh
 
#   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 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., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 
PROGNAME=`basename $0`
VERSION="Version 1.0,"
AUTHOR="2009, Mike Adolphs (http://www.matejunkie.com/)"
 
ST_OK=0
ST_WR=1
ST_CR=2
ST_UK=3
 
path_tmp="/tmp"
 
print_version() {
    echo "$VERSION $AUTHOR"
}
 
print_help() {
    print_version $PROGNAME $VERSION
    echo ""
    echo "$PROGNAME is a Nagios plugin to monitor the UDP packet loss via"
    echo "netstat."
    echo ""
    echo "$PROGNAME check_udp-packet-loss.sh"
    echo ""
    echo "Options:"
    echo "  --warning|-w)"
    echo "    Sets a warning level for packet receive errors. Default is:"
    echo "    off"
    echo "  --critical|-c)"
    echo "    Sets a critical level for packet receive errors. Default is:"
    echo "    off"
    echo "  --path-tmp|-t)"
    echo "    Sets the path for the temporary file. Default is: /tmp"
    exit $ST_UK
}
 
while test -n "$1"; do
    case "$1" in
        --help|-h)
            print_help
            exit $ST_UK
            ;;
        --version|-v)
            print_version $PROGNAME $VERSION
            exit $ST_UK
            ;;
        --path-tmp|-t)
            path_tmp=$2
            shift
            ;;
        --warning|-w)
            warn=$2
            shift
            ;;
        --critical|-c)
            crit=$2
            shift
            ;;
        *)
            echo "Unknown argument: $1"
            print_help
            exit $ST_UK
            ;;
    esac
    shift
done
 
check_filesize() {
    if [ -f $path_tmp/check_udp-packet-errors.log ]
    then
        size=`du $path_tmp/check_udp-packet-errors.log | awk '{print $1}'`
	if [ $size -gt 32 ]
        then
            rm $path_tmp/check_udp-packet-errors.log
            touch $path_tmp/check_udp-packet-errors.log
        fi
    else
        touch $path_tmp/check_udp-packet-errors.log
    fi
}
 
check_packet_loss() {
    p_receive=`netstat -us|grep 'packets received'|awk '{print $1}'`
    echo "Received: $p_receive" >> $path_tmp/check_udp-packet-errors.log
    p_unknown=`netstat -us|grep 'to unknown port'|awk '{print $1}'`
    echo "Unknown: $p_unknown" >> $path_tmp/check_udp-packet-errors.log
    p_errors=`netstat -us|grep 'packet receive errors'|awk '{print $1}'`
    echo "Errors: $p_errors" >> $path_tmp/check_udp-packet-errors.log
}
 
val_wcdiff() {
    if [ ${warn} -gt ${crit} ]
    then
        wcdiff=1
    fi
}
 
check_filesize
check_packet_loss
 
if [ -n "$warn" -a -n "$crit" ]
then
    val_wcdiff
    if [ "$wcdiff" = 1 ]
    then
        echo "The warning level should be lower than the critical level. Please adjust them."
        exit $ST_UK
    fi
fi
 
if [ -n "$warn" -a -n "$crit" ]
then
    if [ "$p_unknown" -ge "$warn" -a "$p_unknown" -lt "$crit" ]
    then
        echo "WARNING - $p_receive total packets received, $p_unknown went to unknown port, $p_errors receive errors! | 'received'=$p_receive 'unknown_port'=$p_unknown 'errors'=$p_errors"
        exit $ST_WR
    elif [ "$p_unknown" -ge "$crit" ]
    then
        echo "CRITICAL - $p_receive total packets received, $p_unknown went to unknown port, $p_errors receive errors! | 'received'=$p_receive 'unknown_port'=$p_unknown 'errors'=$p_errors"
        exit $ST_CR
    else
        echo "OK - $p_receive total packets received, $p_unknown went to unknown port, $p_errors receive errors! | 'received'=$p_receive 'unknown_port'=$p_unknown 'errors'=$p_errors"
        exit $ST_OK
    fi
else
    echo "OK - $p_receive total packets received, $p_unknown went to unknown port, $p_errors receive errors! | 'received'=$p_receive 'unknown_port'=$p_unknown 'errors'=$p_errors"
    exit $ST_OK
fi

The License

As always this little script is ment to be sh-compliant and released under the terms of the GPL Version 2 only. Feel free to subscribe via rss to get updates on this one. More options will be added in the future.