snmp学习笔记之二trap——分析notification.c文件

需要文件:

NET-SNMP-EXAMPLES-MIB.txt
notification.c

这两个文件都在net-snmp源码包里，我的版本是5.4.1
NET-SNMP-EXAMPLES-MIB.txt net-snmp-5.4.1.2/mibs目录下
notification.c net-snmp-5.4.1.2/agent/mibgroup/examples目录下

安装notification:

./configure --with-mib-modules="examples/notification"
make
sudo make install

配置snmp.conf文件，在文件中增加NET-SNMP-EXAMPLES-MIB mib库

sudo vim /usr/local/share/snmp/snmp.conf
在文件中增加： mibs +NET-SNMP-EXAMPLES-MIB

验证netSnmpExampleNotifications mib库是否正常加载:

snmptranslate -IR -Tp netSnmpExampleNotifications
+--netSnmpExampleNotifications(3)
|
+--netSnmpExampleNotificationPrefix(0)
|  |
|  +--netSnmpExampleHeartbeatNotification(1)
|
+-- ---N String    netSnmpExampleNotification(1)
|        Textual Convention: SnmpAdminString
|        Size: 0..255
|
+--netSnmpExampleNotificationObjects(2)
|
+-- ---N Integer32 netSnmpExampleHeartbeatRate(1)
+-- ---N String    netSnmpExampleHeartbeatName(2)
Textual Convention: SnmpAdminString
Size: 0..255

配置snmptrapd.conf
建立/usr/share/snmp/snmptrapd.conf（我的机器上是这个，不同机器不同，可能有的放在/etc/snmp,/usr/local/share/snmp/下，视不同情况慢慢实验），加入以下一行:

authcommunity execute,log,net public

设置所有用户的访问权限：可执行，记录，传递，
如果相对接受到的信息处理可以增加:

traphandle .1.3.6.1.4.1.2021.251.2  page_me down
# 默认处理函数
traphandle default                  log_it

agent自动产生trap

配置agent的snmpd.conf，加入以下几行：(参考:
http://www.net-snmp.org/wiki/index.php/FAQ:Agent_17 ):

# From: http://www.net-snmp.org/wiki/index.php/FAQ:Agent_17 # send v1 traps
trapsink   127.0.0.1:162
# also send v2 traps
trap2sink  127.0.0.1:162
informsink 127.0.0.1:162

启动snmptrapd

sudo snmptrapd –d –f –Lo

启动snmpd

sudo snmpd -f -L

snmpd 会每隔30秒给snmptrapd发送一个信息。收到的信息如下:

Received 64 bytes from UDP: [127.0.0.1]:56929
0000: 30 3E 02 01  00 04 06 70  75 62 6C 69  63 A4 31 06    0>.....public.1.
0016: 09 2B 06 01  04 01 BF 08  02 03 40 04  AC 10 81 01    .+........@.....
0032: 02 01 06 02  01 01 43 03  03 CC BC 30  13 30 11 06    ......C....0.0..
0048: 0C 2B 06 01  04 01 BF 08  02 03 02 01  00 02 01 1E    .+..............

2008-11-11 15:43:11 172.16.129.1(via UDP: [127.0.0.1]:56929) TRAP, SNMP v1, community public
NET-SNMP-EXAMPLES-MIB::netSnmpExampleNotifications Enterprise Specific Trap
(NET-SNMP-EXAMPLES-MIB::netSnmpExampleHeartbeatNotification) Uptime: 0:41:30.20
NET-SNMP-EXAMPLES-MIB::netSnmpExampleHeartbeatRate.0 = INTEGER: 30

notification.c 源码如下:

/** @example notification.c
*  This example shows how to send a notification from inside the
*  agent.  In this case we do something really boring to decide
*  whether to send a notification or not: we simply sleep for 30
*  seconds and send it, then we sleep for 30 more and send it again.
*  We do this through the snmp_alarm mechanisms (which are safe to
*  use within the agent.  Don't use the system alarm() call, it won't
*  work properly).  Normally, you would probably want to do something
*  to test whether or not to send an alarm, based on the type of mib
*  module you were creating.
*
*  When this module is compiled into the agent (run configure with
*  --with-mib-modules="examples/notification") then it should send
*  out traps, which when received by the snmptrapd demon will look
*  roughly like:
*
*   可以通过 --with-mib-modules="examples/notification" 把这个模块
* 编译到agent模块中，snmptrapd可以接收到他发送的traps, 接收到的信息
* 如下:
*
*  2002-05-08 08:57:05 localhost.localdomain [udp:127.0.0.1:32865]:
*      sysUpTimeInstance = Timeticks: (3803) 0:00:38.03 /
*      snmpTrapOID.0 = OID: netSnmpExampleNotification
*
*/

/*
* start be including the appropriate header files
*/
#include <net-snmp/net-snmp-config.h>
#include <net-snmp/net-snmp-includes.h>
#include <net-snmp/agent/net-snmp-agent-includes.h>

/*
* contains prototypes
*/
#include "notification.h"

/*
* our initialization routine 初始化
* (to get called, the function name must match init_FILENAME()
* 函数的名字必须是 init_FILENAME() 这种格式
*/
void
init_notification(void)
{
DEBUGMSGTL(("example_notification",
"initializing (setting callback alarm)/n"));
snmp_alarm_register(30,     /* seconds, 秒 */
SA_REPEAT,      /* repeat (every 30 seconds). 每隔30秒发送一个trap*/
send_example_notification,      /* our callback 我们的回调函数 */
NULL    /* no callback data needed */
);
}

/** here we send a SNMP v2 trap (which can be sent through snmpv3 and
*  snmpv1 as well) and send it out.
*
*     The various "send_trap()" calls allow you to specify traps in different
*  formats.  And the various "trapsink" directives allow you to specify
*  destinations to receive different formats.
*  But *all* traps are sent to *all* destinations, regardless of how they
*  were specified.
*
*
*  I.e. it's
* @verbatim
*                                           ___  trapsink
*                                          /
*      send_easy_trap /___  [  Trap      ] ____  trap2sink
*                      ___  [ Generator  ]
*      send_v2trap    /     [            ] ----- informsink
*                                          /____
*                                                trapsess
*
*  *Not*
*       send_easy_trap  ------------------->  trapsink
*       send_v2trap     ------------------->  trap2sink
*       ????            ------------------->  informsink
*       ????            ------------------->  trapsess
* @endverbatim
*/
void
send_example_notification(unsigned int clientreg, void *clientarg)
{
/*
* define the OID for the notification we're going to send
* NET-SNMP-EXAMPLES-MIB::netSnmpExampleHeartbeatNotification
*/
oid             notification_oid[] =
{ 1, 3, 6, 1, 4, 1, 8072, 2, 3, 0, 1 };
size_t          notification_oid_len = OID_LENGTH(notification_oid);
static u_long count = 0;

/*
* In the notification, we have to assign our notification OID to
* the snmpTrapOID.0 object. Here is it's definition.
*/
oid             objid_snmptrap[] = { 1, 3, 6, 1, 6, 3, 1, 1, 4, 1, 0 };
size_t          objid_snmptrap_len = OID_LENGTH(objid_snmptrap);

/*
* define the OIDs for the varbinds we're going to include
*  with the notification -
* NET-SNMP-EXAMPLES-MIB::netSnmpExampleHeartbeatRate  and
* NET-SNMP-EXAMPLES-MIB::netSnmpExampleHeartbeatName
*/
oid      hbeat_rate_oid[]   = { 1, 3, 6, 1, 4, 1, 8072, 2, 3, 2, 1, 0 };
size_t   hbeat_rate_oid_len = OID_LENGTH(hbeat_rate_oid);
oid      hbeat_name_oid[]   = { 1, 3, 6, 1, 4, 1, 8072, 2, 3, 2, 2, 0 };
size_t   hbeat_name_oid_len = OID_LENGTH(hbeat_name_oid);

/*
* here is where we store the variables to be sent in the trap
*/
netsnmp_variable_list *notification_vars = NULL;
const char *heartbeat_name = "A girl named Maria";
#ifdef  RANDOM_HEARTBEAT
int  heartbeat_rate = rand() % 60;
#else
int  heartbeat_rate = 30;
#endif

DEBUGMSGTL(("example_notification", "defining the trap/n"));

/*
* add in the trap definition object
*/
snmp_varlist_add_variable(¬ification_vars,
/*
* the snmpTrapOID.0 variable
*/
objid_snmptrap, objid_snmptrap_len,
/*
* value type is an OID
*/
ASN_OBJECT_ID,
/*
* value contents is our notification OID
*/
(u_char *) notification_oid,
/*
* size in bytes = oid length * sizeof(oid)
*/
notification_oid_len * sizeof(oid));

/*
* add in the additional objects defined as part of the trap
*/

snmp_varlist_add_variable(¬ification_vars,
hbeat_rate_oid, hbeat_rate_oid_len,
ASN_INTEGER,
(u_char *)&heartbeat_rate,
sizeof(heartbeat_rate));

/*
* if we want to insert additional objects, we do it here
*/
if (heartbeat_rate < 30 ) {
snmp_varlist_add_variable(¬ification_vars,
hbeat_name_oid, hbeat_name_oid_len,
ASN_OCTET_STR,
heartbeat_name, strlen(heartbeat_name));
}

/*
* send the trap out.  This will send it to all registered
* receivers (see the "SETTING UP TRAP AND/OR INFORM DESTINATIONS"
* section of the snmpd.conf manual page.
*/
++count;
DEBUGMSGTL(("example_notification", "sending trap %ld/n",count));
send_v2trap(notification_vars); // 发送snmpv2的trap

/*
* free the created notification variable list
*/
DEBUGMSGTL(("example_notification", "cleaning up/n"));
snmp_free_varbind(notification_vars);
}

参考:
How can I get the agent to generate a trap http://www.net-snmp.org/wiki/index.php/FAQ:Coding_15

http://www.net-snmp.org/docs/mibs/NET-SNMP-EXAMPLES-MIB.txt

http://www.net-snmp.org/dev/agent/notification_8c-example.html

http://www.net-snmp.org/wiki/index.php/FAQ:Agent_17

By: Bian Jiang (borderj@gmail.com)

From: http://www.b0rder.com