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_read, snmp_sess_select_info,
snmp_sess_timeout, snmp_sess_close, snmp_sess_error
SYNOPSIS
cc [ flag ... ] file ... -lsnmp [ library ... ]
#include <sys/types.h>
#include <snmp/snmp.h>
void snmp_sess_init (struct snmp_session * Session);
void *snmp_sess_open (struct snmp_session * Session);
struct snmp_session* snmp_sess_session (void * Opaque);
int snmp_sess_synch_response(void * Opaque, struct snmp_pdu * PDU,
struct snmp_pdu ** ResponsePDUP);
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 * syserrno, int * snmp_errno,
char ** errorString);
STRUCTURE
The snmp_session structure is:
int Version;/* SNMP Version for this session */
u_char * community;/* community for outgoing requests. */
int community_len;/* Length of community name. */
int retries;/* Number of retries before timeout. */
int timeout;/* uS 'til timeout, then exp. backoff */
char * peername;/* Default peer (name or IP) */
unsigned short remote_port;/* UDP port number of peer. */
unsigned short local_port;/* My UDP port number, 0 for default */
int (*callback)();/* Func. to interpret incoming data */
/* Pointer to data that the callback function may consider important */
void * callback_magic;
struct synch_state * snmp_synch_state;
int syserrno;/* copy of system errno */
int snmp_errno;/* copy of library errno */
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_init and snmp_sess_session, these functions are single ses‐
sion 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 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() initializes the input Session structure.
snmp_sess_open() opens the specified session.
snmp_sess_session() returns the pointer to Session structure.
snmp_sess_close() closes the specified session.
snmp_sess_synch_response() is a quick way to send PDU over session Ses‐
sion and wait for a response. The response will be pointed to by
ResponsePDUP.
snmp_sess_send() sends PDU over Session. If the PDU will receive a
response (GET, GETNEXT, INFORM, etc), the pending response is regis‐
tered, and the callback specified in the session will be called at the
appropriate time.
snmp_sess_read() will read all pending SNMP data from the ssession.
Once the packet is read, a PDU will be created, and if this response
was being waited for, the callback will be called.
snmp_sess_select_info() Returns info about what snmp requires from a
select statement. numfds is the number of fds in the list that are
significant. All file descriptors opened via this API are OR'd into
the fdset. If activity occurs on any of these file descriptors,
snmp_sess_read() should be called with that file descriptor set.
timeout is the latest time that the API can wait for a timeout. The
select should be done with the minimum time between timeout and any
other timeouts necessary. This should be checked upon each invocation
of select(). If a timeout is received, snmp_sess_timeout() should be
called to check if the timeout was for the SNMP API.
block is 1 if the select is requested to block indefinitely, rather
than time out. If block is input as 1, timeout will be treated as
undefined, but it must be available for setting in
snmp_sess_select_info(). On return, if block is true, the value of
timeout will be undefined.
snmp_sess_timeout() should be called whenever the timeout from select()
expires. It may also be polled (probably a cpu expensive proposition).
snmp_sess_timeout() checks to see if any of the sessions have an out‐
standing request that has timed out. If it finds one (or more), and
that pdu has more retries available, a new packet is formed from the
pdu and is resent. If there are no more retries available, the call‐
back for the session is used to alert the user of the timeout.
snmp_sess_error() returns a copy of the SNMP library "snmp_errno" vari‐
able, the system "errno" variable, and a string interpreting their val‐
ues. The string must be freed after use.
RETURN VALUESsnmp_sess_open() returns an Opaque pointer to the open session, or
NULL. If NULL is returned, more information can be had by calling
snmp_error().
snmp_sess_close() returns 1 upon success, 0 otherwise.
snmp_sess_send() Returns the Request ID of the generated packet if
applicable, otherwise 1. Returns 0 upon error.
snmp_sess_select_info() returns the number of open sockets.
snmp_sess_synch_response() returns either STAT_SUCCESS, STAT_TIMEOUT,
or STAT_ERROR.
RFCS
Related RFCs: 1065, 1066, 1067
Related SNMPv2 RFCs: 1901, 1902, 1902, 1904, 1905, 1906, 1907, 1908,
1909
RELATED URLS
CMU Networking Group: http://www.net.cmu.edu/
CMU SNMP Home Page: http://www.net.cmu.edu/projects/snmp
SEE ALSOsnmp_api(3), snmp_api_errors(3), snmp_client(3), snmp_coexistance(3),
snmp_error(3), snmp_extra(3), snmp_mib(3), snmp_mibii(3),
snmp_mini_client(3), snmp_msg(3), snmp_packet_dump(3), snmp_pdu(3),
snmp_sess_api(3), snmp_vars(3), snmp_version_info(3), snmp_oid(5)snmp(3)4th Berkeley Distribution Tue Sep 24 11:13:15 2002SNMP_SESS_API(3)
