SNMP_SESS_API(3)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
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SNMP_SESS_API(3)SNMP_SESS_API(3)
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.
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SNMP_SESS_API(3)SNMP_SESS_API(3)
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
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SNMP_SESS_API(3)SNMP_SESS_API(3)
SNMPERR_UNKNOWN_PDU
SNMPERR_TIMEOUT
SEE ALSOselect(2), snmp_api(3), snmp_api.h
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