1、
系统环境：
opensuse 11.3
2、
需要安装的net-snmp包：
net-snmp
net-snmp-devel
perl-SNMP
snmp-mibs
libsnmp20
可以使用 zypper 安装来解决包依赖问题(zypper install net-snmp 和 net-snmp-devel)。
3、
写一个MIB库：(参照ASN.1抽象标记语言生成SMI、MIB)
MyMIB DEFINITIONS::=BEGIN
IMPORTS
enterprises,OBJECT-TYPE,Integer32,TimeTicks
FROM SNMPv2-SMI
.....
4、编译
MIB库存放路径：/usr/share/snmp/mibs/mymib.mib
配置文件路径： /etc/snmp/mymib.conf
指令：
env MIBS="+/usr/share/snmp/mibs/mymib.mib" mib2c mymib
利用向导生成.c文件
步骤如下： (选2)Net-SNMP style code --> (选1) destroyed independently of the SNMP agent -->
(选2)mib2c -c mib2c.iterate_access.conf mymib -->看到提示：
**********************************************************************
NOTE: The only files you MUST modify should be the following:
mymib_access.c
mymib_access.h
mymib_checkfns_local.h
mymib_checkfns_local.c
**********************************************************************
则生成成功。
5、修改部分代码：
修改mymib.c mymibIfTable_handler函数
修改点1：
138 case MODE_GET:
// 不采用链表方式，可以注释掉这里。
139 /* data_context = netsnmp_extract_iterator_context(request);
140 if (data_context == NULL) {
141 netsnmp_set_request_error(reqinfo, request,
142 SNMP_NOSUCHINSTANCE);
143 continue;
144 }*/
145 break;
修改点2：
switch(reqinfo->mode) {
161 case MODE_GET:
162 switch(table_info->colnum) {
163 case COLUMN_IFINDEX:
164 {
// 这里就是查询返回值的地方：get_ifIndex就是节点对应的函数。
// 可以根据自己的需要修改get_ifIndex函数即可。
165 long *retval;
166 size_t retval_len = 0;
167 retval = get_ifIndex(data_context, &retval_len);
168 if (retval)
169 snmp_set_var_typed_value(var, ASN_INTEGER,
170 retval,
171 retval_len);
172 FREEPTR(retval);
173 }
174 break;
修改mymib_access.c
修改点3：
mymibIfTable_get_first_data_point中
37 netsnmp_variable_list *vptr;
38
39 //*my_loop_context = /** XXX */;
40 //*my_data_context = /** XXX */;
41
42 vptr = put_index_data;
43
44 //snmp_set_var_value(vptr, /** XXX: ifIndex data */, /** XXX: length of ifIndex data */);
snmp_set_var_value(vptr, NULL, 0);
45 vptr = vptr->next_variable;
修改点4：
57 netsnmp_variable_list *
58 tosIfTable_get_next_data_point(void **my_loop_context, void **my_data_context,
59 netsnmp_variable_list *put_index_data,
60 netsnmp_iterator_info *mydata)
61 {
62
63 netsnmp_variable_list *vptr;
64
65 *my_loop_context = /** XXX */;
66 *my_data_context = /** XXX */;
67
68 vptr = put_index_data;
69
70 snmp_set_var_value(vptr, /** XXX: ifIndex data */, /** XXX: length of ifIndex data */);
71 vptr = vptr->next_variable;
72
73 return put_index_data;
74 }
===》
57 netsnmp_variable_list *
58 tosIfTable_get_next_data_point(void **my_loop_context, void **my_data_context,
59 netsnmp_variable_list *put_index_data,
60 netsnmp_iterator_info *mydata)
61 {
62 mydata = NULL;
63 put_index_data = NULL;
64 return put_index_data;
65 }
修改点5：
122 /** XXX: return a data pointer to the data for the ifIndex column and set
123 ret_len to its proper size in bytes. */
124 long *get_ifIndex(void *data_context, size_t *ret_len) {
125 return NULL; /** XXX: replace this with a pointer to a real value */
126 }
===》
219 long *get_ifIndex(void *data_context, size_t *ret_len)
220 {
221 long *pagent = (long *)calloc( 4, 2);
222 pagent[0] = 100;
223 data_context = pagent;
224 *ret_len = 4;
225 return data_context; /** XXX: replace this with a pointer to a real value */
226 }
6、编译链接
gcc -g -o mymib mymib_new.c mymib.c mymib_access.c -I/usr/include -L/usr/lib/ -lnetsnmp -lnetsnmpagent -lnetsnmpmibs -lnetsnmphelpers
7、配置
修改/etc/snmp/snmpd.conf
添加以下参数：
// 允许启动监听705
15 agentxsocket tcp:localhost:705
16 master agentx
// 允许访问的客户端IP,以及密码
18 # These really aren't meant for production use. They include all MIBS
19 # and can use considerable resources. See snmpd.conf(5) for information
20 # on setting up groups and limiting MIBS.
21 rocommunity public 127.0.0.1
22 rocommunity public 192.168.71.237
23 rocommunity public 192.168.71.238
24 rocommunity public 127.0.0.1
8、启动服务
主代理服务：
service snmpd start
子代理服务
./mymib
看到提示：NET-SNMP version 5.5 AgentX subagent connected，表示子代理已经连接上主代理.
9、客户端
snmpget -v 2c -c public 192.168.71.237 .1.3.6.1.4.1.14331.5.5.1.5.1.2.0
就可以看到代理信息。
附件 (主程序框架)：
1 /*主函数：mymib_new.c */
2 #include <net-snmp/net-snmp-config.h>
3 #include <net-snmp/net-snmp-includes.h>
4 #include <net-snmp/agent/net-snmp-agent-includes.h>
5 #include <signal.h>
6
7
8 #include "mymib.h"
9 static int keep_running;
10
11 RETSIGTYPE stop_server(int a)
12 {
13 keep_running = 0;
14 }
15
16
17
18 int main (int argc, char **argv)
19 {
20
21 int agentx_subagent=1; /* change this if you want to be a SNMP master agent */
22 int background = 0; /* change this if you want to run in the background */
23 int syslog = 0; /* change this if you want to use syslog */
24
25 /* print log errors to syslog or stderr */
26 if (syslog)
27 snmp_enable_calllog();
28 else
29 snmp_enable_stderrlog();
30
31 /* we're an agentx subagent? */
32 if (agentx_subagent)
33 {
34 /* make us a agentx client. */
35 netsnmp_ds_set_boolean(NETSNMP_DS_APPLICATION_ID, NETSNMP_DS_AGENT_ROLE, 1);
36
37
38 netsnmp_ds_set_string(NETSNMP_DS_APPLICATION_ID, NETSNMP_DS_AGENT_X_SOCKET,
39 "tcp:localhost:705");
40 }
41
42
43 /* run in background, if requested */
44 if (background && netsnmp_daemonize(1, !syslog))
45 exit(1);
46
47 /* Initialize tcpip, if necessary */
48 SOCK_STARTUP;
49
50 /* Initialize the agent library */
51 int nret = init_agent("mymib-daemon");
52
53 /* Initialize our mib code here */
54 init_mymib();
55
56 /* initialize vacm/usm access control */
57 if (!agentx_subagent)
58 {
59 void init_vacm_vars();
60 void init_usmUser();
61 }
62
63 //init_mib_internals();
64
65 /* Example-demon will be used to read example-demon.conf files. */
66 init_snmp("mymib-daemon");
67
68 /* If we're going to be a snmp master agent, initial the ports */
69 if (!agentx_subagent)
70 init_master_agent(); /* open the port to listen on (defaults to udp:161) */
71
72 /* In case we recevie a request to stop (kill -TERM or kill -INT) */
73 keep_running = 1;
74 signal(SIGTERM, stop_server);
75 signal(SIGINT, stop_server);
76 snmp_log(LOG_INFO,"mymib-daemon is up and running./n");
77
78 /* your main loop here... */
79 while(keep_running)
80 {
81 /* if you use select(), see snmp_select_info() in snmp_api(3) */
82 /* --- OR --- */
83 agent_check_and_process(1); /* 0 == don't block */
84 }
85
86
87 /* at shutdown time */
88 snmp_shutdown("mymibsec-daemon");
89 SOCK_CLEANUP;
90
91 return 0;
92 }
93
参考：
网管SNMP Agent的快速开发
http://www.wangchao.net.cn/bbsdetail_53491.html
用NET-SNMP软件包开发简单客户端代理
http://bibu.blogchina.com/inc/net_snmp_doc.htm
How can I run AgentX with a different socket address?
http://net-snmp.sourceforge.net/wiki/index.php/FAQ:Agent_12
Re: working with tables... - SNMP
http://fixunix.com/snmp/382842-re-working-tables.html