snmp_max_oid per Os support and snmpv1 multi_oid fix (#9343)

* Added snmp_max_oid config at Os level.

* Added check for snmpv1 on multi_oid requests.

* Check  device_oid_limit on multi get

* Use array_chunk

* Update snmp.inc.php

* remove dump, unused variable and extra plodes

* per device settings should take priority over OS

* Update Settings.md

* don't discard the data :P

doc/Developing/os/Settings.md

@@ -47,14 +47,6 @@ ifalias: true
 ifindex: true
 ```
 
-### Disable snmpbulkwalk
-Some devices have buggy snmp implementations and don't respond well to the more efficient snmpbulkwalk.
-To disable snmpbulkwalk and only use snmpwalk for an os set the following.
-
-```yaml
-nobulk: true
-```
-
 ### Poller and Discovery Modules
 The various discovery and poller modules can be enabled or disabled per OS.  The defaults are usually reasonable, so likely you won't want to change more than a few.
 These modules can be enabled or disabled per-device in the webui and per os or globally in config.php.
@@ -67,11 +59,26 @@ discovery_modules:
     arp-table: false
 ```
 
+### SNMP Settings
+
+#### Disable snmpbulkwalk
+Some devices have buggy snmp implementations and don't respond well to the more efficient snmpbulkwalk.
+To disable snmpbulkwalk and only use snmpwalk for an os set the following.
+
+```yaml
+nobulk: true
+```
+
+#### Limit the oids per snmpget
+```yaml
+snmp_max_oid: 8
+```
+
 ### Storage Settings
 See also: [Global Storage Config](../../Support/Configuration.md#storage-configuration)
 
 ```yaml
-ignore_mount array: # exact match
+ignore_mount_array: # exact match
     - /var/run
 ignore_mount_string: # substring
     - run

includes/functions.php

@@ -2497,17 +2497,20 @@ function db_schema_is_current()
  */
 function get_device_oid_limit($device)
 {
-    global $config;
-
-    $max_oid = $device['snmp_max_oid'];
-
-    if (isset($max_oid) && $max_oid > 0) {
-        return $max_oid;
-    } elseif (isset($config['snmp']['max_oid']) && $config['snmp']['max_oid'] > 0) {
-        return $config['snmp']['max_oid'];
-    } else {
-        return 10;
+    // device takes priority
+    if ($device['snmp_max_oid'] > 0) {
+        return $device['snmp_max_oid'];
     }
+
+    // then os
+    $os_max = Config::getOsSetting($device['os'], 'snmp_max_oid', 0);
+    if ($os_max > 0) {
+        return $os_max;
+    }
+
+    // then global
+    $global_max = Config::get('snmp.max_oid', 10);
+    return $global_max > 0 ? $global_max : 10;
 }
 
 /**

includes/snmp.inc.php

@@ -221,17 +221,25 @@ function snmp_get_multi($device, $oids, $options = '-OQUs', $mib = null, $mibdir
 function snmp_get_multi_oid($device, $oids, $options = '-OUQn', $mib = null, $mibdir = null)
 {
     $time_start = microtime(true);
+    $oid_limit = get_device_oid_limit($device);
 
-    if (is_array($oids)) {
-        $oids = implode(' ', $oids);
+    if (!is_array($oids)) {
+        $oids = explode(" ", $oids);
     }
 
-    $cmd = gen_snmpget_cmd($device, $oids, $options, $mib, $mibdir);
-    $data = trim(external_exec($cmd));
+    $data = [];
+    foreach (array_chunk($oids, $oid_limit) as $chunk) {
+        $partial_oids = implode(' ', $chunk);
+        $cmd = gen_snmpget_cmd($device, $partial_oids, $options, $mib, $mibdir);
+        $result = trim(external_exec($cmd));
+        if ($result) {
+            $data = array_merge($data, explode("\n", $result));
+        }
+    }
 
     $array = array();
     $oid = '';
-    foreach (explode("\n", $data) as $entry) {
+    foreach ($data as $entry) {
         if (str_contains($entry, '=')) {
             list($oid,$value)  = explode('=', $entry, 2);
             $oid               = trim($oid);

misc/os_schema.json

@@ -339,6 +339,9 @@
         "nobulk": {
             "type": "boolean"
         },
+        "snmp_max_oid": {
+            "type": "string"
+        },
         "ifXmcbc": {
             "type": "boolean"
         },