Bad version specified

Question

I'm currently writing an asynchronous application in C but despite the examples on the web site I still get the error:

snmp_send: Bad version specified

Here is the code:

/* initialize library */
init_snmp("scanagent");
SOCK_STARTUP;
struct snmp_session *session;
struct snmp_pdu *pdu;
oid anOID[MAX_OID_LEN];
size_t anOID_len = MAX_OID_LEN;

char *peer_ip = malloc(sizeof(char) * (strlen(pool->prefix) + 5));
if(peer_ip != NULL){

  /* PDU creation */
  pdu = snmp_pdu_create(SNMP_MSG_GETNEXT);
  if (!snmp_parse_oid(".1.3.6.1.2.1.1.1.0", anOID, &anOID_len)) {
     snmp_perror(".1.3.6.1.2.1.1.1.0");
     SOCK_CLEANUP;
     exit(1);
  }

  snmp_add_null_var(pdu, anOID, anOID_len);
  /* startup all hosts */
  int i;
  for (i = pool->start_ip; i <= pool->length; ++i) {
     /* Check the next ip */

     char ip[3];
     sprintf(ip, ".%d", i);
     strcpy(peer_ip, pool->prefix);
     strcat(peer_ip, ip);

     int j;
     for (j = 0; j < pool->snmp_length; ++j) {
        struct snmp_session sess;
        snmp_info *info = pool->info[j];    /* Get the information */

        char *protocol_ip = malloc(sizeof(char) * (strlen(peer_ip) + 5));
        strcpy(protocol_ip, peer_ip);
        strcat(protocol_ip, ":");
        strcat(protocol_ip, info->port);

        snmp_sess_init(&sess);
        sess.peername = strdup(protocol_ip);
        sess.callback = asynch_response;      /* default callback */
        sess.callback_magic = session;

        switch(info->SNMPv) {
           case 1:
              set_snmp_v1(info, &sess);
              break;
           case 2:
              set_snmp_v2(info, &sess);
              break;
           case 3:
              set_snmp_v3(info, &sess);
              break;
        }

        if (!(session = snmp_open(&sess))) {
           snmp_perror("snmp_open");
           continue;
        }

         if (snmp_send(session, pdu)) {
         } else {
           snmp_perror("snmp_send");
         }

        free(protocol_ip);
     }
  }
  snmp_free_pdu(pdu);
  free(peer_ip);

The code of set_snmp_v2:

void set_snmp_v2(snmp_info *info, struct snmp_session *sess){
  sess->version = SNMP_VERSION_2c;
  sess->community = strdup(info->community);
  sess->community_len = strlen(sess->community);
}

I have this error for the version 3 too (similar to the one above). For the version 1 there is no problem but the version 2c and 3 seems to trigger the errors. Can someone enlighten me about this error ?

Note: the purpose of the code is to scan a given network and detect all the snmp agent given iformations. The first code is just the copy of the inside of the async_request function.

EDIT: I forgot to put my include in the post.

#include <stdlib.h>
#include <stdio.h>
#include <regex.h>        
#include <math.h>
#include <net-snmp/net-snmp-config.h>
#include <net-snmp/net-snmp-includes.h>

Answer 1

I resolved it! The problem was that each time I attempt to open a session I have to create a new pdu :

            /* Openning the session */
        if (!(session = snmp_open(&sess))) {
           snmp_perror("snmp_open");
           continue;
        }

        /* PDU creation */
        pdu = snmp_pdu_create(SNMP_MSG_GETNEXT);
        snmp_add_null_var(pdu, anOID, anOID_len);

        /* Sending the request */
        if (!snmp_send(session, pdu)) {
          snmp_perror("snmp_send");
          snmp_free_pdu(pdu);
        }

But I'm puzzled because as it work I see that the request are not asynchronous and wait for a timeout to make the next request.