Zabbix

/*

** Copyright (C) 2001-2025 Zabbix SIA

**

** This program is free software: you can redistribute it and/or modify it under the terms of

** the GNU Affero General Public License as published by the Free Software Foundation, version 3.

**

** 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 Affero General Public License for more details.

**

** You should have received a copy of the GNU Affero General Public License along with this program.

** If not, see <https://www.gnu.org/licenses/>.

**/

​

#include "checks_snmp.h"

#include "zbxcacheconfig.h"

#include "zbxip.h"

​

#ifdef HAVE_NETSNMP

​

#define SNMP_NO_DEBUGGING

​

#include "zbxasyncpoller.h"

#include "async_poller.h"

#include "zbxpoller.h"

​

#include "zbxcomms.h"

#include "zbxalgo.h"

#include "zbxjson.h"

#include "zbxparam.h"

#include "zbxsysinfo.h"

#include "zbxdbhigh.h"

#include "zbxexpr.h"

#include "zbxstr.h"

​

#include <event2/event.h>

#include <event2/util.h>

#include <event2/dns.h>

#include <net-snmp/net-snmp-config.h>

#include <net-snmp/net-snmp-includes.h>

#include <net-snmp/library/large_fd_set.h>

#include "zbxself.h"

​

#ifndef EVDNS_BASE_INITIALIZE_NAMESERVERS

#   define EVDNS_BASE_INITIALIZE_NAMESERVERS    1

#endif

​

/*

 * SNMP Dynamic Index Cache

 * ========================

 *

 * Description

 * -----------

 *

 * Zabbix caches the whole index table for the particular OID separately based on:

 *   * IP address;

 *   * port;

 *   * community string (SNMPv2c);

 *   * context, security name (SNMPv3).

 *

 * Zabbix revalidates each index before using it to get a value and rebuilds the index cache for the OID if the

 * index is invalid.

 *

 * Example

 * -------

 *

 * OID for getting memory usage of process by PID (index):

 *   HOST-RESOURCES-MIB::hrSWRunPerfMem:<PID>

 *

 * OID for getting PID (index) by process name (value):

 *   HOST-RESOURCES-MIB::hrSWRunPath:<PID> <NAME>

 *

 * SNMP OID as configured in Zabbix to get memory usage of "snmpd" process:

 *   HOST-RESOURCES-MIB::hrSWRunPerfMem["index","HOST-RESOURCES-MIB::hrSWRunPath","snmpd"]

 *

 * 1. Zabbix walks hrSWRunPath table and caches all <PID> and <NAME> pairs of particular SNMP agent/user.

 * 2. Before each GET request Zabbix revalidates the cached <PID> by getting its <NAME> from hrSWRunPath table.

 * 3. If the names match then Zabbix uses the cached <PID> in the GET request for the hrSWRunPerfMem.

 *    Otherwise Zabbix rebuilds the hrSWRunPath cache for the particular agent/user (see 1.).

 *

 * Implementation

 * --------------

 *

 * The cache is implemented using hash tables. In ERD:

 * zbx_snmpidx_main_key_t -------------------------------------------0< zbx_snmpidx_mapping_t

 * (OID, host, <v2c: community|v3: (context, security name)>)           (index, value)

 */

​

/******************************************************************************

 *                                                                            *

 * This is zbx_snmp_walk() callback function prototype.                       *