Net-snmp总结(五)-net-snmp的MIBs扩展_添加trap

一、编写MIB文件

这里我们建立一个mib文件，命名为TEST-TRAP-MIB.txt，放在/usr/local/net-snmp/share/snmp/mibs/目录下因为这个目录是snmpd的默认目录，只要把MIB库放入该目录就可以自动加载MIB库，否则需要修改snmpd.conf文件，自定义的MIB文件如下：

--开始
TEST-TRAP-MIB DEFINITIONS ::= BEGIN

--引入部分
IMPORTS
    MODULE-IDENTITY, OBJECT-TYPE, TimeTicks FROM SNMPv2-SMI
       DisplayString, FROM SNMPv2-TC
    enterprises
        FROM RFC1155-SMI; --引用结束，用分号

--定义节点
--enterprises的OID是1.3.6.1.4
testTrap    OBJECT IDENTIFIER ::= { enterprises 12581 }

TestTraps OBJECT IDENTIFIER ::= { testTrap 1 }

cpuRatioHigh NOTIFICATION-TYPE
OBJECTS  {SystemTrapDescription}
STATUS  current
DESCRIPTION  "."
::= { TestTraps 1 }

TestDescription OBJECT IDENTIFIER ::= { TestTraps 2 }
TestTrapDescription  OBJECT-TYPE
SYNTAX  DisplayString (SIZE (0..256))
MAX-ACCESS read-only
STATUS current
DESCRIPTION "  "
::= { TestDescription 1 }

--结束定义
END

写完后我们测一个MIB库有没有问题，在linux机器上用snmptranslate-Tp -IR TEST-GET-MIB::testGet显示结果如下：（这个测试不需要启动snmpd进程）

[root@localhostbin]# ./snmptranslate -Tp -IR TEST-TRAP-MIB::testTrap

+--testTrap(12581)
   |
   +--TestTraps(1)
      |
      +--cpuRatioHigh(1)
      |
      +--TestDescription(2)
         |
         +-- -R-- String    TestTrapDescription(1)
                  Textual Convention: DisplayString
                  Size: 0..256

OK,snmp自动发现了这个MIB库， 有了自定义的OID，接下来开始添加处理程序。

二、生成源代码

执行envMIBS="+/usr/local/net-snmp/share/snmp/mibs/TEST-TRAP-MIB.txt" ./mib2ctestTRAP，会引导你逐渐生成testTrap.h和testTrap.c,先选2再选1然后再选y。

生成的testTrap.h如下

/*
 * Note: this file originally auto-generated by mib2c using
 *        $
 */
#ifndef TESTTRAP_H
#define TESTTRAP_H

/*
 * function declarations
 */
int             send_cpuRatioHigh_trap(void);

#endif                          /* TESTTRAP_H */

修改后 testTrap.c 文件代码如下：

/*
 * Note: this file originally auto-generated by mib2c using
 *        $
 */

#include 
#include 
#include 
#include "testTrap.h"

void read_cpudata_repeat(unsigned int clientreg, void *clientarg);
extern const oid snmptrap_oid[] = {1,3,6,1,6,3,1,1,4,1,0};
extern const size_t snmptrap_oid_len = OID_LENGTH(snmptrap_oid);

void init_testTrap(void)
{
    DEBUGMSGTL(("testTrap","Initializing\n"));
    snmp_alarm_register(1,SA_REPEAT,read_cpudata_repeat, NULL);
}

int
send_cpuRatioHigh_trap(void)
{
    netsnmp_variable_list *var_list = NULL;
    const oid       cpuRatioHigh_oid[] = { 1, 3, 6, 1, 4, 1, 12581, 1, 1 };
    const oid       SystemTrapDescription_oid[] ={ 1,3,6,1,4,1,12581,1,2,1, 0 };

        static char TestTrapDescription[50];
    strcpy(TestTrapDescription,"CPU使用率过高");
    /*
     * Set the snmpTrapOid.0 value
     */
    snmp_varlist_add_variable(&var_list,
                              snmptrap_oid, snmptrap_oid_len,
                              ASN_OBJECT_ID,
                              cpuRatioHigh_oid, sizeof(cpuRatioHigh_oid));

    /*
     * Add any objects from the trap definition
     */
    snmp_varlist_add_variable(&var_list,
                              SystemTrapDescription_oid,
                              OID_LENGTH(SystemTrapDescription_oid),
                                                          ASN_OCTET_STR,
                              /*
                               * Set an appropriate value for SystemTrapDescription
                               */
                              NULL, 0);

    /*
     * Add any extra (optional) objects here
     */

    /*
     * Send the trap to the list of configured destinations
     *  and clean up
     */
    send_v2trap(var_list);
    snmp_free_varbind(var_list);

    return SNMP_ERR_NOERROR;
}
void judge_send_cputrap(int cpu)
{
    static unsigned int cputrap_clientreg = 0;
    if(cpu > 80)
    {
        if(cputrap_clientreg == 0){
            send_cpuRatioHigh_trap();
            cputrap_clientreg = snmp_alarm_register(5,SA_REPEAT,send_cpuRatioHigh_trap,NULL);

        }
    }
    else
    {
        if(cputrap_clientreg != 0)
        {
            snmp_alarm_unregister(cputrap_clientreg);
            cputrap_clientreg = 0;
        }
    }
}

void read_cpudata_repeat(unsigned int clientreg, void *clientarg)
{
    int cpu = 90;
    judge_send_cputrap(cpu);
}

三、配置编译

把testGet.c和testGet.h复制到/net-snmp-5.7.3/agent/mibgroups/路径下

设置编译参数（红色部分即为加上我们自己的mib模块）

[[email protected]]# ./configure  --prefix=/usr/local/net-snmp    --with-mib-modules="testTrap

查看文件net-snmp-5.7.3/agent/mibgroup/mib_module_inits.h，发现已经添加到初始化中。

/*This file is automatically generated by configure.  Do not modify by hand. */

  if (should_init("testGet"))init_testTrap

编译并安装

[[email protected]]# make

[[email protected]]# make instal

四、测试新加的MIB

配置trap触发环境

在snmpd.conf添加trap2sink localhost或者trap2sink 127.0.0.1:162

新建snmptrapd的配置文件snmptrapd.conf添加authcommunity log,execute,net public

 

启动snmpd服务

[root@localhostsbin]# ./snmpd -f -Le

Turning on AgentXmaster support.

NET-SNMP version5.7.3

No Shmem line in/proc/meminfo

 

启动snmptrapd 服务

[root@localhostsbin]# ./snmptrapd -d -f -Lo -c snmptrapd.conf

 则每过5秒可以看到trap返回来的告警信息，说明我们添加自定义MIB trap操作成功!