CODEWITHSUNDEEP
c++clinuxsnmpnet-snmp
user2914066
user2914066

Reputation: 181

How to send v2 traps in net snmp using c

I have a the following configurations:

  1. Trap oid = .1.3.6.1.4.1.78945.1.1.1.1.1
  2. Trap variable oid = .1.3.6.1.4.1.78945.1.1.2.1.0, variable type = string
  3. Another Trap variable oid = .1.3.6.1.4.1.78945.1.1.2.4.0, variable type = integer.
  4. Trap listener ip and port = 192.168.4.10:1234

How can I send traps using C or C++ and net-snmp module in linux? I need a sample code. All sample codes at net-snmp site did not work for me.

my sample code:

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

oid             objid_id[] = { 1,3,6,1,4,1,78945,1,1,2,4,0};
oid             objid_name[] = { 1,3,6,1,4,1,78945,1,1,2,1,0};
oid           trap_oid[] = {1,3,6,1,4,1,78945,1,1,1,1,1};


int main()
{
    netsnmp_session session, *ss;
    netsnmp_pdu    *pdu, *response;

    char comm[] = "public";
    snmp_sess_init( &session );
    session.version = SNMP_VERSION_2c;
    session.community = comm;
    session.community_len = strlen(session.community);
    session.peername = "192.168.4.10:1234";
    ss = snmp_open(&session);
    if (!ss) {
      snmp_sess_perror("ack", &session);
      exit(1);
    }

    pdu = snmp_pdu_create(SNMP_MSG_TRAP2);
    pdu->community = comm;
    pdu->community_len = strlen(comm);
    pdu->enterprise = trap_oid;
    pdu->enterprise_length = sizeof(trap_oid) / sizeof(oid);
    pdu->trap_type = SNMP_TRAP_ENTERPRISESPECIFIC;
    snmp_add_var(pdu, objid_name, sizeof(objid_name) / sizeof(oid), 's', "Test Name");
    snmp_add_var(pdu, objid_id, sizeof(objid_id) / sizeof(oid), 'i', "5468");

    send_trap_to_sess (ss, pdu);
    snmp_close(ss);
    return (0);
}

The heartbeat notification example from net-snmp site confused me with where to give the listener details?

Thank you in advance.

Upvotes: 1

Views: 10901

Answers (2)

user2914066
user2914066

Reputation: 181

It looks like system uptime and trap oid are to be added as first variables in the pdu.

The following code did the trick:

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

oid             objid_sysuptime[] = { 1, 3, 6, 1, 2, 1, 1, 3, 0 };
oid             objid_id[] = { 1,3,6,1,4,1,78945,1,1,2,4,0};
oid             objid_name[] = { 1,3,6,1,4,1,78945,1,1,2,1,0};
oid              trap_oid[] = {1,3,6,1,4,1,78945,1,1,1,1,1};


int main()
{
    netsnmp_session session, *ss;
    netsnmp_pdu    *pdu, *response;
    char *trap = NULL;

    char comm[] = "public";
    snmp_sess_init( &session );
    session.version = SNMP_VERSION_2c;
    session.community = comm;
    session.community_len = strlen(session.community);
    session.peername = "192.168.4.10:1234";
    ss = snmp_open(&session);
    if (!ss) {
      snmp_sess_perror("ack", &session);
      exit(1);
    }

    pdu = snmp_pdu_create(SNMP_MSG_TRAP2);
    pdu->community = comm;
    pdu->community_len = strlen(comm);
    pdu->trap_type = SNMP_TRAP_ENTERPRISESPECIFIC;

    long sysuptime;
    char csysuptime [20];
    sysuptime = get_uptime ();
    sprintf (csysuptime, "%ld", sysuptime);
    trap = csysuptime;
    snmp_add_var (pdu, objid_sysuptime, sizeof (objid_sysuptime)/sizeof(oid),'t', trap);
    snmp_add_var(pdu, trap_oid, OID_LENGTH(trap_oid), 'o', "1.3.6.1.4.1.78945.1.1.1.1.1");
    snmp_add_var(pdu, objid_name, OID_LENGTH(objid_name), 's', "Test Name");
    snmp_add_var(pdu, objid_id, OID_LENGTH(objid_id) , 'i', "5468");

    send_trap_to_sess (ss, pdu);
    snmp_close(ss);
    return (0);
}

Upvotes: 1

user4991085
user4991085

Reputation: 11

Sample trap code (notification.c) in net-snmp won't work as a standalone application (i.e. call from your own main). You need to start a subagent (agentX) daemon as shown in the example-demon.c example in net-snmp. Inside the example-demon call the init_notification() defined in notification.c example code before while loop in example-demon.c

init_notification();
/* your main loop here... */
while(keep_running) {
/* if you use select(), see snmp_select_info() in snmp_api(3) */
/*     --- OR ---  */
agent_check_and_process(1); /* 0 == don't block */

}

which calls the 'send_example_notification(unsigned int clientreg, void *clientarg)' every 30 seconds which sends the trap using send_v2trap().

Compile and build notification.c and example-demon.c into an executable example-demon
gcc -I. `net-snmp-config --cflags`   -c -o notification.o notification.c
gcc -I. `net-snmp-config --cflags`   -c -o example-demon.o example-demon.c  
gcc -o example-demon notification.o example-demon.o `net-snmp-config --agent-libs`

Start the example-demon and you should see the v2 traps are sent every 30 seconds and received in your snmp manager (assuming you have the snmpsink etc set for your host IP in your snmpd.conf file).

What you have is also valid and another way of sending traps using your own code. "snmptrap" command can also be used to send traps as a standalone application or from a shell etc.

Upvotes: 1

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