Nagios conntrack table monitor

check_conntrack

#!/usr/bin/env perl
#
# Script to check netfilter conntrack usage
# https://gist.github.com/gists/2885777
# emsearcy@osuosl.org
#
# Usage: check_conntrack -w WARN_USED% -c CRIT_USED%
#
# Returns:
#  UNKNOWN if no conntrack support found
#  CRITICAL if > CRIT_USED% table use
#  WARNING if > WARN_USED% table use
#  OK otherwise
#
use vars qw($conntrack_count, $conntrack_max);

my $conntrack_count = '';
my $conntrack_max = '';

# Some distros put this in different places. Deal with it in a sane manner
if (-e '/proc/sys/net/netfilter/nf_conntrack_count') {
    $conntrack_count = '/proc/sys/net/netfilter/nf_conntrack_count';
} elsif (-e '/proc/sys/net/ipv4/netfilter/ip_conntrack_count') {
    $conntrack_count = '/proc/sys/net/ipv4/netfilter/ip_conntrack_count';
}

if (-e '/proc/sys/net/netfilter/nf_conntrack_max') {
    $conntrack_max = '/proc/sys/net/netfilter/nf_conntrack_max';
} elsif (-e '/proc/sys/net/ipv4/netfilter/ip_conntrack_max') {
    $conntrack_max = '/proc/sys/net/ipv4/netfilter/ip_conntrack_max';
}

use Getopt::Std;
$Getopt::Std::STANDARD_HELP_VERSION = true;

sub VERSION_MESSAGE
{
    print "";
}

sub HELP_MESSAGE
{
    print "Usage: check_conntrack -w WARN_USED\% -c CRIT_USED\%\n";
}

my %options=();
getopts("hw:c:", \%options);

if (!(defined $options{w} && defined $options{c})) {
    HELP_MESSAGE();
    exit 1;
}

my $crit_thresh = int($options{c});
my $warn_thresh = int($options{w});

if ($warn_thresh > $crit_thresh) {
    print "CONNTRACK WARNING: " . 
        "Critical threshold must be higher than warning threshold!\n";
    exit 1;
}

open(COUNT, "< $conntrack_count") or print "CONNTRACK UNKNOWN: $! (count)\n" and exit 3;
open(MAX, "< $conntrack_max") or print "CONNTRACK UNKNOWN: $! (max)\n" and exit 3;

my $count = int(<COUNT>);
my $max = int(<MAX>);
my $used = 0;

if ($count && $max) {
    $used = int($count / ($max / 100));
} else {
    $used = -1;
}

if ($used == -1) {
    print "CONNTRACK UNKNOWN: unexpected contents in proc counters?\n";
    exit 3
} elsif ($used > $crit_thresh) {
    print "CONNTRACK CRITICAL: $used% used ($count of $max)\n";
    exit 2
} elsif ($used > $warn_thresh) {
    print "CONNTRACK WARNING: $used% used ($count of $max)\n";
    exit 1
} else {
    print "CONNTRACK OK: $used% used ($count of $max)\n";
    exit 0
}