snmp__screenos: first version of a plugin to monitor Juniper ScreenOS Resources

Right now this produces two graphs: memory and session allocation. CPU
time will be added shortly.

plugins/snmp/snmp__screenos

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+#!/usr/bin/perl -w
+# -*- perl -*-
+
+=head1 NAME
+
+snmp__screenos_ - SNMP plugin to monitor Juniper ScreenOS based routers
+
+=head1 APPLICABLE SYSTEMS
+
+This has been developed against a Juniper SSG5-Serial router, but
+should work with any ScreenOS-based router as manufactured by Juniper.
+
+Using a command such as "munin-node-configure --snmp
+switch.langfeldt.net --snmpversion 2c --snmpcommunity public | sh -x"
+should identify whether this plugin can apply.
+
+
+=head1 CONFIGURATION
+
+As a rule SNMP plugins need site specific configuration.  The default
+configuration (shown here) will only work on insecure sites/devices:
+
+   [snmp_*]
+	env.version 2
+        env.community public
+
+In general SNMP is not very secure at all unless you use SNMP version
+3 which supports authentication and privacy (encryption).  But in any
+case the community string for your devices should not be "public".
+
+Please see 'perldoc Munin::Plugin::SNMP' for further configuration
+information.
+
+=head1 MIB INFORMATION
+
+This plugin requires NETSCREEN-RESOURCE-MIB information.
+
+=head1 MAGIC MARKERS
+
+  #%# family=snmpauto
+  #%# capabilities=snmpconf
+
+=head1 AUTHOR
+
+Copyright (C) 2012 Diego Elio Pettenò.
+
+=head1 LICENSE
+
+GPLv2
+
+=cut
+
+use strict;
+use Munin::Plugin;
+use Munin::Plugin::SNMP;
+
+# This corresponds to NETSCREEN-SMI::netscreenResource
+my $oidBase = '1.3.6.1.4.1.3224.16';
+
+my $oidMemAllocate = $oidBase . '.2.1';
+my $oidMemLeft = $oidBase . '.2.2';
+my $oidSessAllocate = $oidBase . '.3.2';
+my $oidSessMaximum = $oidBase . '.3.3';
+my $oidSessFailed = $oidBase . '.3.4';
+
+if (defined $ARGV[0] and $ARGV[0] eq "snmpconf") {
+    print "require $oidBase.[23].[13].0";
+}
+
+my $session = Munin::Plugin::SNMP->session();
+my $data = $session->get_entries(-columns => [ $oidMemAllocate,
+					       $oidMemLeft,
+					       $oidSessAllocate,
+					       $oidSessMaximum,
+					       $oidSessFailed ]);
+
+if ($ARGV[0] and $ARGV[0] eq "config") {
+  my ($host) = Munin::Plugin::SNMP->config_session();
+
+  my $memTotal = $data->{"$oidMemAllocate.0"} + $data->{"$oidMemLeft.0"};
+
+  # this is the closet I can get to the yellow/red on the ScreenOS
+  # interface.
+  my $memWarning = int($memTotal * 0.75 + 0.5);
+  my $memCritical = int($memTotal * 0.85 + 0.5);
+  my $sessWarning = int($data->{"$oidSessMaximum.0"} * 0.75 + 0.5);
+  my $sessCritical = int($data->{"$oidSessMaximum.0"} * 0.85 + 0.5);
+
+  print <<END;
+host_name $host
+
+multigraph screenos_memory
+graph_title Memory allocation
+graph_vlabel bytes
+graph_args --base 1024
+graph_category system
+
+memory.label Memory
+memory.min 0
+memory.max $memTotal
+memory.warning $memWarning
+memory.critical $memCritical
+
+multigraph screenos_sessions
+graph_title Sessions allocation
+graph_vlabel Count
+graph_category system
+
+sessions.label Active Sessions
+sessions.min 0
+sessions.max $data->{"$oidSessMaximum.0"}
+sessions.warning $sessWarning
+sessions.critical $sessCritical
+failed.label Failed Sessions
+failed.min 0
+failed.critical 1
+END
+
+  exit 0;
+}
+
+print <<END;
+multigraph screenos_memory
+memory.value $data->{"$oidMemAllocate.0"}
+
+multigraph screenos_sessions
+sessions.value $data->{"$oidSessAllocate.0"}
+failed.value $data->{"$oidSessFailed.0"}
+END