nagios-nrpe : add a check dhcp_pool

CHANGELOG

@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - base: set the title of the terminal when connecting to a server
 - post-install: add a version number to motd-carp-state.sh
+- nagios-nrpe : add a check dhcp_pool
 
 ### Changed
 

roles/nagios-nrpe/files/plugins_bsd/check_dhcp_pool

@@ -0,0 +1,223 @@
+#!/usr/bin/perl -w
+#
+# Copyright (C) 2008 Rien Broekstra <rien@rename-it.nl>
+#
+# 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; version 2 dated June,
+# 1991.
+#
+# 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., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+#
+#
+# Configuration variables:
+#
+#       conffile     - path to dhcpd's configuration file (default "/etc/dhcpd.conf")
+#       leasefile    - path to dhcpd's leases file (default "/var/lib/dhcp/dhcpd.leases")
+#
+
+use POSIX;
+use Time::Local;
+use strict;
+
+my $CONFFILE = exists $ENV{'conffile'} ? $ENV{'conffile'} : "/etc/dhcpd.conf";
+my $LEASEFILE = exists $ENV{'leasefile'} ? $ENV{'leasefile'} : "/var/db/dhcpd.leases";
+my $WARNING_LEVEL = 70;
+my $CRITICAL_LEVEL = 90;
+
+my (@activeleases, %dhcp_pools, $pool_start, $pool_end, $pool_size, $pool_free, $pool_usage, $pool_status, $label, $lease, $nagios_return_code, $nagios_ok, $nagios_warning, $nagios_critical, @nagios_text, @nagios_perfdata);
+
+# Determine all leased IP addresses
+@activeleases = determine_active_leases();
+
+# Determine the available IP pools
+%dhcp_pools = determine_pools();
+
+# Nagios return code
+$nagios_return_code = 0;
+$nagios_ok = 0;
+$nagios_warning = 0;
+$nagios_critical = 0;
+
+# For each pool, count how many leases from that pool are currently active
+foreach $pool_start (keys %dhcp_pools) {
+    $pool_size = $dhcp_pools{$pool_start};
+    $pool_end = $pool_start+$pool_size-1;
+    $pool_free = $pool_size;
+
+    foreach $lease (@activeleases) {
+        if ($lease >= $pool_start && $lease <= $pool_end) {
+    		$pool_free--;
+        }
+    }
+
+    $label = ip2string($pool_start)."-".ip2string($pool_end);
+    $pool_usage = sprintf("%.1f", 100*($pool_size-$pool_free)/$pool_size);
+
+    if ($pool_usage >= $CRITICAL_LEVEL) {
+	$nagios_return_code = 2;
+	$nagios_critical++;
+	$pool_status = "CRITICAL";
+    } elsif ($pool_usage >= $WARNING_LEVEL) {
+	if ($nagios_return_code == 0 ) {
+            $nagios_return_code = 1; 
+	}
+	$nagios_warning++;
+	$pool_status = "WARNING";
+    }
+    else {
+	$nagios_ok++;
+	$pool_status = "OK";
+    }
+    
+    push(@nagios_text,     "$pool_status : $label - $pool_usage \n");
+    push(@nagios_perfdata, "$label=$pool_usage%;$WARNING_LEVEL%;$CRITICAL_LEVEL%;;" );
+    # 'label'=value[UOM];[warn];[crit];;
+
+}
+
+
+print nagios_code_2_txt($nagios_return_code)." - ".$nagios_critical." CRIT / ".$nagios_warning." WARN / ".$nagios_ok." OK \n\n";
+
+print grep(/CRITICAL/, @nagios_text);
+print grep(/WARNING/, @nagios_text);
+print grep(/OK/, @nagios_text);
+
+print "|@nagios_perfdata";
+
+exit $nagios_return_code;
+
+
+################
+###### FUNCTIONS 
+
+# Parse dhcpd.conf for range statements.
+#
+# Returns a hash with start IP -> size
+sub determine_pools {
+    my (%pools, @conffile, $line, $start, $end, $size);
+
+    open(CONFFILE, "<${CONFFILE}") || exit -1;
+    @conffile = <CONFFILE>;
+    close (CONFFILE);
+
+    foreach $line (@conffile) {
+	next if $line =~ /^\s*#/;
+
+	if ($line =~ /range[\s]+([\d]+\.[\d]+\.[\d]+\.[\d]+)[\s]+([\d]+\.[\d]+\.[\d]+\.[\d]+)/) {
+	    $start = string2ip($1);
+	    $end = string2ip($2);
+
+	    defined($start) || next;
+	    defined($end) || next;
+
+            # The range statement gives the lowest and highest IP addresses in a range.
+	    $size = $end - $start + 1;
+
+	    $pools{$start} = $size;
+	}
+    }
+    return %pools;
+}
+
+# Very simple parser for dhcpd.leases. This will break very easily if dhcpd decides to
+# format the file differently. Ideally a simple recursive-descent parser should be used.
+#
+# Returns an array with currently leased IP's
+sub determine_active_leases {
+    my (@leasefile, $startdate, $enddate, $lease, @activeleases, $mytz, $line, %saw);
+
+    open(LEASEFILE, "<${LEASEFILE}") || exit -1;
+    @leasefile = <LEASEFILE>;
+    close (LEASEFILE);
+
+    @activeleases = ();
+
+    # Portable way of converting a GMT date/time string to timestamp is setting TZ to UTC, and then calling mktime()
+    $mytz = $ENV{'TZ'};
+    $ENV{'TZ'} = 'UTC 0';
+    tzset();
+
+    foreach $line (@leasefile) {
+	if ($line =~ /lease ([\d]+\.[\d]+\.[\d]+\.[\d]+)/) {
+	    $lease = string2ip($1);
+	    defined($lease) || next;
+
+	    undef $startdate;
+	    undef $enddate;
+	}
+	elsif ($line =~ /starts \d ([\d]{4})\/([\d]{2})\/([\d]{2}) ([\d]{2}):([\d]{2}):([\d]{2})/) {
+	    $startdate = mktime($6, $5, $4, $3, $2-1, $1-1900, 0, 0);
+	}
+	elsif ($line =~ /ends \d ([\d]{4})\/([\d]{2})\/([\d]{2}) ([\d]{2}):([\d]{2}):([\d]{2})/) {
+	    $enddate = mktime($6, $5, $4, $3, $2-1, $1-1900, 0, 0);
+	}
+	elsif ($line !~ /abandoned/) {
+	    if (defined($enddate) && defined($startdate) && defined($lease)) {
+		if ($startdate < time() && $enddate > time()) {
+		    push (@activeleases, $lease);
+		}
+	    }
+	}
+
+    }
+
+    # Set TZ back to its original setting
+    if (defined($mytz)) {
+	$ENV{'TZ'} = $mytz;
+    }
+    else {
+	delete $ENV{'TZ'};
+    }
+    tzset();
+
+    # Sort the array, strip doubles, and return
+    return grep(!$saw{$_}++, @activeleases);
+}
+
+#
+# Helper routine to convert an IP address a.b.c.d into an integer
+#
+# Returns an integer representation of an IP address
+sub string2ip {
+    my $string = shift;
+    defined($string) || return undef;
+    if ($string =~ /([\d]+)\.([\d]+)\.([\d]+)\.([\d]+)/) {
+	if ($1 < 0 || $1 > 255 || $2 < 0 || $2 > 255 || $3 < 0 || $3 > 255 || $4 < 0 || $4 > 255) {
+	    return undef;
+	}
+	else {
+	    return $1 << 24 | $2 << 16 | $3 << 8 | $4;
+	}
+    }
+    return undef;
+}
+
+#
+# Returns a dotted quad notation of an
+#
+sub ip2string {
+    my $ip = shift;
+    defined ($ip) || return undef;
+    return sprintf ("%d.%d.%d.%d", ($ip >> 24) & 0xff, ($ip >> 16) & 0xff, ($ip >> 8) & 0xff, $ip & 0xff);
+}
+
+
+#
+# Return textual status of return code
+#
+sub nagios_code_2_txt{
+    my $code = shift;
+    defined ($code) || return undef;
+
+    if($code == 0 )     { return "OK"       }
+    elsif( $code == 1 ) { return "WARNING"  }
+    elsif( $code == 2 ) { return "CRITICAL" }
+}

roles/nagios-nrpe/tasks/main.yml

@@ -59,6 +59,7 @@
     - {name: 'check_packetfilter.sh', force: true}
     - {name: 'check_pf_states', force: false}
     - {name: 'check_mailq.pl', force: true}
+    - {name: 'check_dhcp_pool', force: false}
   notify: restart nrpe
 
 - name: Nagios plugins are installed - template

roles/nagios-nrpe/templates/evolix_bsd.cfg.j2

@@ -49,6 +49,7 @@ command[check_ospfd_simple]=doas /usr/local/libexec/nagios/plugins/check_ospfd_s
 #command[check_bgpd]=doas /usr/local/libexec/nagios/plugins/check_openbgpd -u
 command[check_connections_state]=doas /usr/local/libexec/nagios/plugins/check_connections_state.sh
 command[check_packetfilter]=doas /usr/local/libexec/nagios/plugins/check_packetfilter.sh
+command[check_dhcp_pool]=/usr/local/libexec/nagios/plugins/check_dhcp_pool
 
 # This is an Ansible managed file !
 # For local modifications use the /etc/nrpe.d/zzz_evolix.cfg file instead