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Creating snmp trap handlers

You must have a working snmptrapd. See SNMP TRAP HANDLER

Make sure the MIB is loaded from the trap you are adding. Edit /etc/systemd/system/snmptrapd.service.d/mibs.conf to add it then restart snmptrapd.

MIBDIRS option is not recursive, so you need to specify each directory individually.

Create a new class in LibreNMS\Snmptrap\Handlers that implements the LibreNMS\Interfaces\SnmptrapHandler interface. For example:

<?php
/**
 * ColdBoot.php
 *
 * Handles the SNMPv2-MIB::coldStart trap
 *
 * 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, either version 3 of the License, or
 * (at your option) any later version.
 *
 * 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, see <http://www.gnu.org/licenses/>.
 *
 * @package    LibreNMS
 * @link       http://librenms.org
 */

namespace LibreNMS\Snmptrap\Handlers;

use App\Models\Device;
use LibreNMS\Interfaces\SnmptrapHandler;
use LibreNMS\Snmptrap\Trap;
use Log;

class ColdBoot implements SnmptrapHandler
{
    /**
     * Handle snmptrap.
     * Data is pre-parsed and delivered as a Trap.
     *
     * @param Device $device
     * @param Trap $trap
     * @return void
     */
    public function handle(Device $device, Trap $trap)
    {
        Log::event('SNMP Trap: Device ' . $device->displayName() . ' cold booted', $device->device_id, 'reboot', 4);
    }
}

where number on the end of the row Log::event means color of the eventlog:

1 green
2 cyan
3 blue
4 yellow
5 red

Register the mapping in the config/snmptraps.php file. Make sure to use the full trap OID and correct class.

'SNMPv2-MIB::coldStart' => \LibreNMS\Snmptrap\Handlers\ColdBoot::class,

The handle function inside your new class will receive a LibreNMS/Snmptrap/Trap object containing the parsed trap. It is common to update the database and create event log entries within the handle function.

Getting information from the Trap

Source information

$trap->getDevice();   // gets Device model for the device associated with this trap
$trap->getHostname(); // gets hostname sent with the trap
$trap->getIp();       // gets source IP of this trap
$trap->getTrapOid();  // returns the string you registered your class with

Retrieving data from the Trap

$trap->getOidData('IF-MIB::ifDescr.114');

getOidData() requires the full name including any additional index. You can use these functions to search the OID keys.

$trap->findOid('ifDescr');  // returns the first oid key that contains the string
$trap->findOids('ifDescr'); // returns all oid keys containing the string

Advanced

If the above isn't adequate, you can get the entire trap text:

$trap->getRaw();

Source

Developing/SNMP-Traps.md