start of adding basic support for the servertech sentry4 cdus

I agree to the conditions of the Contributor Agreement
    contained in doc/General/Contributing.md.

AUTHORS.md

@@ -106,6 +106,7 @@ LibreNMS contributors:
 - Marc Runkel <marc@runkel.org> (mrunkel)
 - Josh Driver <keeperofdakeys@gmail.com> (keeperofdakeys)
 - Felix Eckhofer <felix@eckhofer.com> (tribut)
+- Vikram Adukia <adukia@dropbox.com> (justmedude)
 
 [1]: http://observium.org/ "Observium web site"
 Observium was written by:

includes/definitions.inc.php

@@ -1401,6 +1401,13 @@ $config['os'][$os]['over'][0]['graph'] = 'device_current';
 $config['os'][$os]['over'][0]['text']  = 'Current';
 $config['os'][$os]['icon']             = 'servertech';
 
+$os = 'sentry4';
+$config['os'][$os]['text']             = 'ServerTech Sentry4';
+$config['os'][$os]['type']             = 'power';
+$config['os'][$os]['over'][0]['graph'] = 'device_current';
+$config['os'][$os]['over'][0]['text']  = 'Current';
+$config['os'][$os]['icon']             = 'servertech';
+
 $os = 'raritan';
 $config['os'][$os]['text']             = 'Raritan PDU';
 $config['os'][$os]['type']             = 'power';

includes/discovery/os/sentry3.inc.php

@@ -2,6 +2,18 @@
 
 if (!$os) {
     if (preg_match('/^Sentry\ (Switched|Smart) /', $sysDescr)) {
-        $os = 'sentry3';
+
+        // ServerTech doesn't have a way to distinguish between sentry3 and sentry4 devices
+        // Hopefully, we can use the version string to figure it out
+        $version = trim(snmp_get($device, 'Sentry3-MIB::serverTech.4.1.1.1.3.0', '-Osqnv'));
+        $version = explode(" ", $version)[1];
+        $version = intval($version);
+
+        // It appears that version 8 and up is good for sentry4
+        if ($version >= 8) {
+            $os = 'sentry4';
+        } else {
+            $os = 'sentry3';
+        }
     }
 }

includes/discovery/sensors/temperatures/sentry4.inc.php

@@ -0,0 +1,54 @@
+<?php
+
+/*
+ * Copyright (c) 2016 Dropbox, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+
+ *   http://www.apache.org/licenses/LICENSE-2.0
+
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+*/
+
+if ($device['os'] == 'sentry4') {
+    $oids = snmp_walk($device, 'st4TempSensorValue', '-Osqn', 'Sentry4-MIB');
+    d_echo($oids."\n");
+
+    $oids       = trim($oids);
+    $divisor    = '10';
+    $multiplier = '1';
+    if ($oids) {
+        echo 'ServerTech Sentry4 Temperature ';
+    }
+
+    foreach (explode("\n", $oids) as $data) {
+        $data = trim($data);
+        if ($data) {
+            list($oid,$descr) = explode(' ', $data, 2);
+            $split_oid        = explode('.', $oid);
+            $index            = $split_oid[(count($split_oid) - 1)];
+
+            // Sentry4-MIB::st4TempSensorValue
+            $temperature_oid = '1.3.6.1.4.1.1718.4.1.9.3.1.1.1.'.$index;
+            $descr           = 'Removable Sensor '.$index;
+            $low_warn_limit  = (snmp_get($device, "st4TempSensorLowWarning.1.$index", '-Ovq', 'Sentry4-MIB') / $divisor);
+            $low_limit       = (snmp_get($device, "st4TempSensorLowAlarm.1.$index", '-Ovq', 'Sentry4-MIB') / $divisor);
+            $high_warn_limit = (snmp_get($device, "st4TempSensorHighWarning.1.$index", '-Ovq', 'Sentry4-MIB') / $divisor);
+            $high_limit      = (snmp_get($device, "st4TempSensorHighAlarm.1.$index", '-Ovq', 'Sentry4-MIB') / $divisor);
+            $current         = (snmp_get($device, "$temperature_oid", '-Ovq', 'Sentry4-MIB') / $divisor);
+
+            if ($current >= 0) {
+                discover_sensor($valid['sensor'], 'temperature', $device,
+                    $temperature_oid, $index, 'sentry4',
+                    $descr, $divisor, $multiplier, $low_limit, $low_warn_limit,
+                    $high_warn_limit, $high_limit, $current);
+            }
+        }
+    }
+}