net-snmp扩展trap类型的私有mib

注：本文介绍的是静态编译的方法扩展的私有mib，别的方法请看本人整理的《net-snmp
agent开发（用net-snmp扩展MIB库）》

1. 首先创建一个简单的含有table变量的mib文件取名test-trap.mib，后缀名也可以是.txt 实际操作没有区别；

TEST-TRAP-MIB DEFINITIONS ::= BEGIN

IMPORTS
MODULE-IDENTITY, OBJECT-TYPE, TimeTicks FROM SNMPv2-SMI
DisplayString, FROM SNMPv2-TC
enterprises
FROM RFC1155-SMI;
test OBJECT IDENTIFIER ::= { enterprises 1000 }
TestTraps OBJECT IDENTIFIER ::= { test 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 }

END
注：其中TestTrapDescription是trap触发时上送的信息，内容可以自定义，trap cpuRatioHigh中object{ }中可以添加多个对象，都将是trap触发时上送的信息；

2. 将创建好的mib文件放入默认目录中，一般默认目录为/usr/local/net-snmp, 或者放到别的目录中，在配置文件snmpd.conf中增加mibs +/home//mibs/mytrap
test-trap.mib，或者直接修改默认的mib路径。

3.使用mib2c -c mib2c.notify.conf TEST-TRAP-MIB::TestTraps命令生成相应的.c和.h文件，如果该命令出错（ERROR: You don't have the SNMP perl module installed.  Please obtain

this by getting the latest source release of the net-snmp toolkit from
http://www.net-snmp.org/download/ .  Once you download the source and

unpack it, the perl module is contained in the perl/SNMP directory.

See the README file there for instructions.）请正常make    make install重新安装net-snmp，原因未知。

生成的.c文件如下

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

#include <net-snmp/net-snmp-config.h>
#include <net-snmp/net-snmp-includes.h>
#include <net-snmp/agent/net-snmp-agent-includes.h>
#include "TestTraps.h"

extern const oid snmptrap_oid[];
extern const size_t snmptrap_oid_len;

int
send_cpuRatioHigh_trap( void )
{
netsnmp_variable_list *var_list = NULL;
const oid cpuRatioHigh_oid[] = { 1,3,6,1,4,1,1000,1,1 };
const oid TestTrapDescription_oid[] = { 1,3,6,1,4,1,1000,1,2,1, 0 };

/*
* 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,
TestTrapDescription_oid, OID_LENGTH(TestTrapDescription_oid),
ASN_OCTET_STR,
/* Set an appropriate value for TestTrapDescription */
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;
}


4.修改.c文件，添加函数读取cpu实际使用率和判断是否产生告警函数，每过5秒产生一次报警，这里就直接将cpu使用率定为90，判断告警触发函数写成80，添加初始化函数，注册函数每过一秒读取一下cpu使用率，修改.h文件声明读取cpu使用率函数，修改后的.c函数如下：

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

#include <net-snmp/net-snmp-config.h>
#include <net-snmp/net-snmp-includes.h>
#include <net-snmp/agent/net-snmp-agent-includes.h>
#include "TestTraps.h"

extern const oid snmptrap_oid[] = {1,3,6,1,6,3,1,1,4,1,0};
const size_t snmptrap_oid_len = OID_LENGTH(snmptrap_oid);

void init_TestTraps(void)
{
DEBUGMSGTL(("TestTraps","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[] = { 1,3,6,1,4,1,1000,1,1 };
const oid TestTrapDescription_oid[] = { 1,3,6,1,4,1,1000,1,2,1, 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,
TestTrapDescription_oid, OID_LENGTH(TestTrapDescription_oid),
ASN_OCTET_STR,
/* Set an appropriate value for TestTrapDescription */
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);
}

5..然后把相应的.c和.h文件添加到net-snmp源码里的 agent/mibgroup路径下，在configure的时候添加 --with-mib-modules="TestTrap"选项，如果有多个table，则可以再mibgroup中创建一个文件夹例如testMIB文件夹，然后把相应的.c和.h文件都移到testMIB文件夹下，然后在mibgroup路径下新建一个test.h文件，添加config_require(testMIB/TestTable);依次添加，编译的时候添加configure选项为--weith-mib-modules="test"
 则可以一次全部编译；最后make   make install

6. 配置trap触发环境，在snmpd.conf添加trap2sink localhost或者trap2sink 127.0.0.1:162，重新启动snmpd 并用-c执行snmpd.conf

    然后新建snmptrapd的配置文件snmptrapd.conf添加authcommunity log,execute,net public，为了能清楚看到trap的打印消息用命令

snmptrapd -d -f -Lo -c snmptrapd.conf启动snmptrapd 

  则每过5秒可以看到trap返回来的告警信息；

注：本人的一点见解，不足之处可以多多交流指正；