snmp_sess_api(3)

NAME

snmp_sess_init, snmp_sess_open, snmp_sess_session,
snmp_sess_send, snmp_sess_async_send,
snmp_sess_select_info, snmp_sess_read, snmp_sess_timeout,
snmp_sess_close, snmp_sess_error - session functions

SYNOPSIS

#include <sys/types>
#include <netinet/in.h>
#include <sys/time.h>
#include <ucd-snmp/snmp.h>
#include <ucd-snmp/snmp_impl.h>
#include <ucd-snmp/asn1.h>
#include <ucd-snmp/snmp_api.h>
void snmp_sess_init ( struct snmp_session * );
void * snmp_sess_open ( struct snmp_session * );
struct snmp_session * snmp_sess_session ( void * );
int snmp_sess_send ( void * opaque,
       struct snmp_pdu *pdu );
int snmp_sess_async_send ( void * opaque,
       struct snmp_pdu *pdu,
       snmp_callback callback, void * callbackData );
int snmp_sess_select_info ( void * opaque,
       int *numfds, fd_set *fdset,
       struct timeval *timeout, int *block );
void snmp_sess_read ( void * opaque, fd_set *fdset );
void snmp_sess_timeout ( void * opaque );
int snmp_sess_close ( void * opaque );
void snmp_sess_error ( void * opaque,
       int *pcliberr, int *psnmperr, char **pperrstring );

DESCRIPTION

These functions define a subset of the API that can be
used to manage single SNMP sessions in a multi-threaded
application. Except for snmp_sess_session, these func tions are single session versions of the traditional SNMP
library API.

Note that these functions use an Opaque pointer to iden
tify a single session in lieu of a session pointer.

Snmp_sess_init prepares a struct snmp_session that sources transport characteristics and common information that will
be used for a set of SNMP transactions. After this struc
ture is passed to snmp_open to create an SNMP session, the structure is not used.

SNMP sessions that are created with snmp_sess_open are not affected by and should not be used with snmp_select_info, snmp_read, snmp_timeout, nor snmp_close. Use the other functions described here with similar capabilities.

Snmp_sess_init and snmp_sess_open each take as input a pointer to a struct snmp_session object. This structure
contains information for a set of transactions that will
share similar transport characteristics. Snmp_sess_ses_ sion takes the opaque session handle and returns a pointer
to its associated struct snmp_session.

Snmp_sess_send and snmp_sess_async_send each take as input an additional pointer to a struct snmp_pdu object. This
structure contains information that describes a transac
tion that will be performed over an open session.

Consult snmp_api.h for the definitions of these struc
tures.

Snmp_sess_select_info, snmp_sess_read, and snmp_sess_time_ out provide an interface for the use of the select(2) sys tem call so that SNMP transactions for a single session
can occur asynchronously.

Snmp_sess_select_info is given the information that would have been passed to select in the absence of SNMP. For example, this might include window update information.
This information is modified so that SNMP will get the
service it requires from the call to select. In this case, numfds, fdset, and timeout correspond to the nfds, readfds, and timeout arguments to select, respectively. The only exception is that timeout must always point to an
allocated (but perhaps uninitialized) struct timeval. If timeout would have been passed as NULL, block is set to true, and timeout is treated as undefined. This same rule applies upon return from snmp_select_info.

After calling snmp_sess_select_info, select is called with the returned data. When select returns, snmp_sess_read is called with the fd_set returned from select. This will read any input from this session's SNMP socket. If select times out, snmp_sess_timeout should be called to see if the timeout was intended for SNMP.

DIAGNOSTICS

Error return status from snmp_sess_open is indicated by return of a null pointer. Error return status from
snmp_sess_close and snmp_sess_send is indicated by return of 0. A successful status will return a 1.

Further information can be obtained by using
snmp_sess_error to see what type of error has occurred. This function returns the SNMP "snmp_errno" variable, the
value of the system "errno" variable, and a string inter
pretation of both variables. The string must be freed
after use by the caller.

For errors returned by snmp_sess_open, use the correspond ing function snmp_error instead of snmp_sess_error.

Consult snmp_api.h for the complete set of SNMP library
error values. The SNMP library error value snmperr can be one of the following values:

SNMPERR_GENERR A generic error occurred.

SNMPERR_BAD_LOCPORT The local port was bad because

it had already been allocated
or permission was denied.

SNMPERR_BAD_ADDRESS The host name or address given

was not useable.

SNMPERR_BAD_SESSION The specified session was not

open.

SNMPERR_TOO_LONG

SNMPERR_NO_SOCKET

SNMPERR_V2_IN_V1

SNMPERR_V1_IN_V2

SNMPERR_BAD_REPEATERS

SNMPERR_BAD_REPETITIONS

SNMPERR_BAD_ASN1_BUILD

SNMPERR_BAD_SENDTO

SNMPERR_BAD_RCVFROM

SNMPERR_BAD_PARSE

SNMPERR_BAD_VERSION

SNMPERR_BAD_COMMUNITY

SNMPERR_NOAUTH_DESPRIV

SNMPERR_ABORT

SNMPERR_UNKNOWN_PDU

SNMPERR_TIMEOUT

SEE ALSO

select(2), snmp_api(3), snmp_api.h

21 Oct 1999 SNMP_SESS_API(3)