snmp_sess_init, snmp_open, snmp_send, snmp_free_pdu,
snmp_select_info, snmp_read, snmp_timeout, snmp_close,
snmp_perror, snmp_sess_perror, snmp_error,
snmp_api_errstring - send and receive SNMP messages
SYNOPSIS
#include <sys/types>
#include <netinet/in.h>
#include <sys/time.h>
#include <netdb.h>
#include <ucd-snmp/asn1.h>
#include <ucd-snmp/snmp.h>
#include <ucd-snmp/snmp_api.h>
void snmp_sess_init ( struct snmp_session * );
struct snmp_session * snmp_open ( struct snmp_session *);
/* Input parameter not used in active sessions */
int snmp_send ( struct snmp_session *session,
struct snmp_pdu *pdu );
int snmp_select_info ( int *numfds, fd_set *fdset,
struct timeval *timeout, int *block );
void snmp_read ( fd_set *fdset );
void snmp_timeout ( void );
int snmp_close ( struct snmp_session *session );
void snmp_free_pdu ( struct snmp_pdu *pdu );
void snmp_error ( struct snmp_session *session,
int *pcliberr, int *psnmperr, char **pperrstring );
char *snmp_api_errstring ( int snmperr );
void snmp_perror ( char * msg );
/* for parsing errors only */
void snmp_sess_perror (char * msg, struct snmp_session *);
/* all other SNMP library errors */
DESCRIPTION
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_open returns a pointer to a newly-formed struct
reference the active SNMP session.
Snmp_send and snmp_free_pdu each take as input a pointer
to a struct snmp_pdu object. This structure contains
information that describes a transaction that will be per
formed over an open session.
Consult snmp_api.h for the definitions of these struc
tures.
Snmp_read, snmp_select_info, and snmp_timeout provide an
interface for the use of the select(2) system call so that
SNMP transactions can occur asynchronously.
Snmp_select_info is given the information that would have
been passed to select in the absence of SNMP. For exam
ple, 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_select_info, select is called with the
returned data. When select returns, snmp_read should be
called with the fd_set returned from select to read each
SNMP socket that has input. If select times out,
snmp_timeout should be called to see if the timeout was
intended for SNMP.
DIAGNOSTICS
Previous versions of the library used snmp_get_errno to
read the global variable snmp_errno which may have held
the error status within the SNMP library. The existing
method snmp_perror should be used to log ASN.1 coding
errors only.
The new method snmp_sess_perror is provided to capture
errors that occur during the processing of a particular
SNMP session. Snmp_sess_perror calls snmp_error function
to obtain the "C" library error errno , the SNMP library
error snmperr , and the SNMP library detailed error mes
sage that is associated with an error that occurred during
a given session.
Note that in all cases except one, snmp_sess_perror should
be handed the struct snmp_session * pointer returned from
snmp_open. If snmp_open returns a null pointer, pass the
INPUT struct snmp_session * pointer used to call
Error return status from snmp_close and snmp_send is indi
cated by return of 0. A successful status will return a 1
for snmp_close and then request id of the packet for
snmp_send. Upon successful return from snmp_send the pdu
will be freed by the library.
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_PARSE
SNMPERR_BAD_VERSION
SNMPERR_NOAUTH_DESPRIV
SNMPERR_ABORT
SNMPERR_UNKNOWN_PDU
SNMPERR_TIMEOUT
A string representation of the error code can be obtained
with snmp_api_errstring, and a standard error message may
ror standard routine.
SEE ALSO
select(2), snmp_api.h
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