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 functions are single session versions of the traditional SNMP library API.

Note that these functions use an Opaque pointer to identify 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 structure 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_session 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 transaction that will be performed over an open session.

Consult snmp_api.h for the definitions of these structures.

Snmp_sess_select_info, snmp_sess_read, and snmp_sess_timeout provide an interface for the use of the select(2) system 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 interpretation of both variables. The string must be freed after use by the caller.

For errors returned by snmp_sess_open, use the corresponding 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