How to send v2 traps in net snmp using c

Question

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.

Answer 1

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);
}