arm net-snmp使用

参考MIB如下（该参考MIB主要获取ARM的时间和状态）：
MIB简述参考：https://blog.csdn.net/shanzhizi/article/details/15340305


```c
-- RSU-STATE-MIB.my
    RSU-STATE-MIB DEFINITIONS ::= BEGIN
 
        IMPORTS
            OBJECT-GROUP, MODULE-COMPLIANCE, NOTIFICATION-GROUP    
                FROM SNMPv2-CONF    
            enterprises, Integer32, Unsigned32, OBJECT-TYPE, MODULE-IDENTITY, 
            NOTIFICATION-TYPE    
                FROM SNMPv2-SMI    
            DisplayString    
                FROM SNMPv2-TC;
    
-- October 09, 2002 at 14:50 GMT
        -- 1.3.6.1.4.1.16535
        RSU-state MODULE-IDENTITY 
            LAST-UPDATED "202007161450Z"        -- October 09, 2002 at 14:50 GMT
            ORGANIZATION 
                "DEMO"  
            CONTACT-INFO 
                "Basic state of antenna"  
            DESCRIPTION 
                "RSU's Server MIB."
            ::= { enterprises 16535 }
    
--  Node definitions
-- This part will include all details about the RSU-state.
        -- 1.3.6.1.4.1.16535.1
        Time OBJECT IDENTIFIER ::= { RSU-state 1 } 
        -- 1.3.6.1.4.1.16535.1.1
        GetTime OBJECT-TYPE
            SYNTAX DisplayString (SIZE (0..100))
            MAX-ACCESS read-only
            STATUS current
            DESCRIPTION
                "Example : 2013/4/11"
            ::= { Time 1 }
		
		
		-- 1.3.6.1.4.1.16535.2
        state OBJECT IDENTIFIER ::= { RSU-state 2 } 
        -- 1.3.6.1.4.1.16535.2.1
        GetState OBJECT-TYPE
            SYNTAX DisplayString (SIZE (0..100))
            MAX-ACCESS read-only
            STATUS current
            DESCRIPTION
                "Example : normal"
            ::= { state 1 }
    END
 
-- RSU-STATE-MIB.my

编写好后使用 snmptranslate -Tp -IR RSU-STATE-MIB::RSU-state 检查MIB是否有问题，如下：
在这里插入图片描述
运行命令生成RSU_state.h，RSU_state.c文件
命令：env MIBS="+/usr/local/net-snmp/share/snmp/mibs/RSU-STATE-MIB.txt" mib2c RSU-state
注意：RSU-STATE-MIB.txt要拷贝到安装目录去，生成的文件也在哪里，运行命令的时候会要求选择，依次输入2,1就行。

修改生成的C文件：
未修改前：

/*
 * 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 "RSU_state.h"

/** Initializes the RSU_state module */
void
init_RSU_state(void)
{
    const oid GetTime_oid[] = { 1,3,6,1,4,1,16535,1,1 };
    const oid GetState_oid[] = { 1,3,6,1,4,1,16535,2,1 };

  DEBUGMSGTL(("RSU_state", "Initializing\n"));

    netsnmp_register_scalar(
        netsnmp_create_handler_registration("GetTime", handle_GetTime,
                               GetTime_oid, OID_LENGTH(GetTime_oid),
                               HANDLER_CAN_RONLY
        ));
    netsnmp_register_scalar(
        netsnmp_create_handler_registration("GetState", handle_GetState,
                               GetState_oid, OID_LENGTH(GetState_oid),
                               HANDLER_CAN_RONLY
        ));
}

int
handle_GetTime(netsnmp_mib_handler *handler,
                          netsnmp_handler_registration *reginfo,
                          netsnmp_agent_request_info   *reqinfo,
                          netsnmp_request_info         *requests)
{
    /* We are never called for a GETNEXT if it's registered as a
       "instance", as it's "magically" handled for us.  */

    /* a instance handler also only hands us one request at a time, so
       we don't need to loop over a list of requests; we'll only get one. */
    
    switch(reqinfo->mode) {

        case MODE_GET:
            snmp_set_var_typed_value(requests->requestvb, ASN_OCTET_STR,
                                     /* XXX: a pointer to the scalar's data */,
                                     /* XXX: the length of the data in bytes */);
            break;


        default:
            /* we should never get here, so this is a really bad error */
            snmp_log(LOG_ERR, "unknown mode (%d) in handle_GetTime\n", reqinfo->mode );
            return SNMP_ERR_GENERR;
    }

    return SNMP_ERR_NOERROR;
}
int
handle_GetState(netsnmp_mib_handler *handler,
                          netsnmp_handler_registration *reginfo,
                          netsnmp_agent_request_info   *reqinfo,
                          netsnmp_request_info         *requests)
{
    /* We are never called for a GETNEXT if it's registered as a
       "instance", as it's "magically" handled for us.  */

    /* a instance handler also only hands us one request at a time, so
       we don't need to loop over a list of requests; we'll only get one. */
    
    switch(reqinfo->mode) {

        case MODE_GET:
            snmp_set_var_typed_value(requests->requestvb, ASN_OCTET_STR,
                                     /* XXX: a pointer to the scalar's data */,
                                     /* XXX: the length of the data in bytes */);
            break;


        default:
            /* we should never get here, so this is a really bad error */
            snmp_log(LOG_ERR, "unknown mode (%d) in handle_GetState\n", reqinfo->mode );
            return SNMP_ERR_GENERR;
    }

    return SNMP_ERR_NOERROR;
}

修改后：

/*
 * 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 "RSU_state.h"
#include <time.h>
#include <string.h>

/** Initializes the RSU_state module */
void
init_RSU_state(void)
{
    const oid GetTime_oid[] = { 1,3,6,1,4,1,16535,1,1 };
    const oid GetState_oid[] = { 1,3,6,1,4,1,16535,2,1 };

  DEBUGMSGTL(("RSU_state", "Initializing\n"));

    netsnmp_register_scalar(
        netsnmp_create_handler_registration("GetTime", handle_GetTime,
                               GetTime_oid, OID_LENGTH(GetTime_oid),
                               HANDLER_CAN_RONLY
        ));
    netsnmp_register_scalar(
        netsnmp_create_handler_registration("GetState", handle_GetState,
                               GetState_oid, OID_LENGTH(GetState_oid),
                               HANDLER_CAN_RONLY
        ));
}

int
handle_GetTime(netsnmp_mib_handler *handler,
                          netsnmp_handler_registration *reginfo,
                          netsnmp_agent_request_info   *reqinfo,
                          netsnmp_request_info         *requests)
{
    /* We are never called for a GETNEXT if it's registered as a
       "instance", as it's "magically" handled for us.  */

    /* a instance handler also only hands us one request at a time, so
       we don't need to loop over a list of requests; we'll only get one. */
    
	time_t t;
	
    switch(reqinfo->mode) {

        case MODE_GET:
			time(&t);
			char szTime[100]={0};
			snprintf(szTime,100,"%s",ctime(&t));
            snmp_set_var_typed_value(requests->requestvb, ASN_OCTET_STR,
                                     szTime,
                                     strlen(szTime));
            break;


        default:
            /* we should never get here, so this is a really bad error */
            snmp_log(LOG_ERR, "unknown mode (%d) in handle_GetTime\n", reqinfo->mode );
            return SNMP_ERR_GENERR;
    }

    return SNMP_ERR_NOERROR;
}
int
handle_GetState(netsnmp_mib_handler *handler,
                          netsnmp_handler_registration *reginfo,
                          netsnmp_agent_request_info   *reqinfo,
                          netsnmp_request_info         *requests)
{
    /* We are never called for a GETNEXT if it's registered as a
       "instance", as it's "magically" handled for us.  */

    /* a instance handler also only hands us one request at a time, so
       we don't need to loop over a list of requests; we'll only get one. */
    char srustate[100]={0};
	strcpy(srustate,"normal");  //测试 直接赋值了
    switch(reqinfo->mode) {

        case MODE_GET:
            snmp_set_var_typed_value(requests->requestvb, ASN_OCTET_STR,
                                     srustate,
                                     strlen(srustate));
            break;


        default:
            /* we should never get here, so this is a really bad error */
            snmp_log(LOG_ERR, "unknown mode (%d) in handle_GetState\n", reqinfo->mode );
            return SNMP_ERR_GENERR;
    }

    return SNMP_ERR_NOERROR;
}

将生成的.c .h拷贝到源码目录 net-snmp-5.7.3/agent/mibgroup下

./configure --host=arm-linux --build=i686-linux --with-cc=arm-linux-gnueabihf-gcc --with-ar=arm-linux-gnueabihf-ar --with-endianness=little --disable-embedded-perl --disable-shared --prefix=/my_file/share/net-snmp-5.7.3/my_lib --with-mib-modules=RSU-state

make

make install

将生成的snmpd应用替换ARM里面的就行了，重启ARM

启动snmpd:
snmpd -c /usr/local/share/snmp/snmpd.conf -f -Le -d -M /usr/local/share/snmp/mibs/

测试：
snmpwalk -v 1或2c(代表SNMP版本) -c SNMP读团体密码 IP地址 OID(对象标示符)
snmpwalk -v 2c -c public localhost 1.3.6.1.4.1.16535.2.1
在这里插入图片描述