Re: Traps/Informs

On 21/07/2010 06:05, Gaurav Chaturvedi wrote:
> Hi Martin,
>
> Please use the following code after your mentioned part of code.
>
> You need to call "snmp_sess_select_info", "select" and 
> "snmp_sess_read" after snmp_sess_read() function. These functions help 
> in reading the data from socket and call the callback function.
>
> Also, there is no issue in using localhost in snmptrap/snmpinform 
> commands.
>
> if (transport = netsnmp_tdomain_transport(port, 1, "udp")) {
>         ss = snmp_sess_add(&session, transport, NULL, NULL);
>     }
>
>     while (1) {
>         numfds = 0;
>         FD_ZERO(&fdset);
>         block = 1;    /* note: will be set by snmp_sess_select_info */
>         tvp = &timeout;
>
>         if (block) timerclear(tvp);
>
>         snmp_sess_select_info(ss,&numfds, &fdset, tvp, &block);
>
>         if (block == 1) {
>             tvp = NULL;
>         }
>
>
>         count = select(numfds, &fdset, 0, 0, tvp);
>
>             if (count > 0) {
>                 snmp_sess_read (ss,&fdset);
>             } else
>         ....
>         ....
>     } /* End of while */
>
>     if (ss) {
>         snmp_sess_close(ss);
>         ss = NULL;
>     }
>
>
> Thanks
> Gaurav Chaturvedi
>
> On Tue, Jul 20, 2010 at 10:13 PM, Martin Townsend 
> <[email protected] 
> <mailto:[email protected]>> wrote:
>
>     Hi,
>
>     I'm having problems processing traps in my management application,
>     After
>     looking through the snmptrapd code I've added calls to
>     netsnmp_transport_open_server(app_name, "udp:162");
>     and then initialise a session with
>     snmp_sess_init
>     with the following initialisation
>         session_p->peername = SNMP_DEFAULT_PEERNAME;  /* Original code had
>     NULL here */
>         session_p->version = SNMP_DEFAULT_VERSION;
>         session_p->community_len = SNMP_DEFAULT_COMMUNITY_LEN;
>         session_p->retries = SNMP_DEFAULT_RETRIES;
>         session_p->timeout = SNMP_DEFAULT_TIMEOUT;
>         session_p->callback = snmp_input;
>         session_p->callback_magic = (void *) transport_trap_server_p;
>         session_p->authenticator = NULL;
>         session_p->isAuthoritative = SNMP_SESS_UNKNOWNAUTH;
>
>     which sets up the callback snmp_input.
>     then snmp_add to add the session to the opened transport server.
>
>     In snmp_input I have a printf to make sure that the routine is getting
>     called that will output the operation_id value.
>
>     Then using snmptrap or snmpinform send the trap, e.g.
>     snmpinform -v2c -c public localhost ""
>     PO-RECTIFIER-TEST-MIB::alarmMajorHighBattVoltTrapPO
>     PO-RECTIFIER-TEST-M
>     IB::alarmMajorHighBattVoltPO.0 i 1
>     snmpinform: Timeout
>
>     with no success.
>
>     Is it ok to use snmpinform/trap with localhost and will the code above
>     receive the trap PDU on localhost?
>     My application runs as a process that waits for commands to arrive
>     over
>     a socket so it will be blocked, would this cause problems?
>     Any other ideas/things to try out?
>
>     Many Thanks in advance,
>     Martin.
>
>
>
>
>
>
>
>
>
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>

Thank you Gaurav, using the single session api I now have a separate 
pthread to handle the traps.  Just in case anyone else tries this be 
warned that you must store the opaque session pointer returned from 
snmp_sess_add (or maybe pass it via the callback_magic field) as it is 
different to the one passed to the snmp_input callback routine of the 
session structure.   In the snmp_input routine I was trying to use 
snmp_sess_send to send the INFORM reply message using the session 
pointer that was passed as an input parameter which caused a seg fault.  
After stepping through the code I could see that the opaque session 
pointer is acutally a struct session_list * as returned by 
snmp_sess_add_ex.

PS does anyone know if there's a routine that takes an OID and returns 
the name/description from the MIB?

Cheers,
Martin.

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