1NETSNMP_SESSION_API(3) Net-SNMP NETSNMP_SESSION_API(3)
2
6 snmp_sess_init, snmp_open, snmp_send, snmp_async_send,
7 snmp_select_info, snmp_read, snmp_timeout, snmp_synch_response,
8 snmp_close, snmp_perror, snmp_sess_perror, snmp_error,
9 snmp_api_errstring - netsnmp_session_api functions
10
12 #include <net-snmp/session_api.h>
13 void snmp_sess_init ( netsnmp_session*sess);
15 netsnmp_session* snmp_open ( netsnmp_session *sess);
17 /* Input parameter not used in active sessions */
18 int snmp_send ( netsnmp_session *session,
20 netsnmp_pdu *pdu);
21 int snmp_async_send ( netsnmp_session *session,
23 netsnmp_pdu *pdu,
24 snmp_callback callback,
25 void *callbackData);
26 int snmp_select_info ( int * numfds,fd_set *fdset,
28 struct timeval *timeout,int *block);
29 void snmp_read ( fd_set *fdset);
31 void snmp_timeout ( void );
33 int snmp_synch_response ( netsnmp_session *session,
35 netsnmp_pdu *pdu,
36 netsnmp_pdu **response);
37 int snmp_close ( netsnmp_session *session);
39 int snmp_close_sessions ( void );
40 Error Reporting
42 (Move to output_api(3))
43 void snmp_error ( netsnmp_session *session,
44 int *pcliberr,int *psnmperr,char **pperrstring);
45 char *snmp_api_errstring ( intsnmperr);
47 void snmp_perror ( char *msg);
49 /* for parsing errors only */
50 void snmp_sess_perror (char *msg,netsnmp_session *sess);
52 /* all other SNMP library errors */
53
55 Snmp_sess_init prepares a netsnmp_session that sources transport char‐
56 acteristics and common information that will be used for a set of SNMP
57 transactions. After this structure is passed to snmp_open to create an
58 SNMP session, the structure is not used.
59 Snmp_open returns a pointer to a newly-formed netsnmp_session object,
61 which the application must use to reference the active SNMP session.
62 snmp_send and snmp_async_send() each take as input a pointer to a net‐
64 snmp_pdu object. This structure contains information that describes a
65 transaction that will be performed over an open session.
66 Consult snmp_api.h for the definitions of these structures.
68 With the snmp_async_send() call, snmp_read will invoke the specified
70 callback when the response is received.
71 Snmp_read, snmp_select_info, and snmp_timeout provide an interface for
73 the use of the select(2) system call so that SNMP transactions can
74 occur asynchronously.
75 Snmp_select_info is given the information that would have been passed
77 to select in the absence of SNMP. For example, this might include win‐
78 dow update information. This information is modified so that SNMP will
79 get the service it requires from the call to select. In this case,
80 numfds, fdset, and timeout correspond to the nfds, readfds, and timeout
81 arguments to select, respectively. The only exception is that timeout
82 must always point to an allocated (but perhaps uninitialized) struct
83 timeval. If timeout would have been passed as NULL, block is set to
84 true, and timeout is treated as undefined. This same rule applies upon
85 return from snmp_select_info.
86 After calling snmp_select_info, select is called with the returned
88 data. When select returns, snmp_read should be called with the fd_set
89 returned from select to read each SNMP socket that has input. If
90 select times out, snmp_timeout should be called to see if the timeout
91 was intended for SNMP.
92 snmp_synch_response is a convenience routine that will send the
94 request, wait for the response and process it before returning. See
95 the descriptions of snmp_send , snmp_read etc for details.
96
98 Previous versions of the library used snmp_get_errno to read the global
99 variable snmp_errno which may have held the error status within the
100 SNMP library. The existing method snmp_perror should be used to log
101 ASN.1 coding errors only.
102 The new method snmp_sess_perror is provided to capture errors that
104 occur during the processing of a particular SNMP session.
105 Snmp_sess_perror calls snmp_error function to obtain the "C" library
106 error errno , the SNMP library error snmperr , and the SNMP library
107 detailed error message that is associated with an error that occurred
108 during a given session.
109 Note that in all cases except one, snmp_sess_perror should be handed
111 the netsnmp_session * pointer returned from snmp_open. If snmp_open
112 returns a null pointer, pass the INPUT netsnmp_session * pointer used
113 to call snmp_open.
114 Error return status from snmp_close and snmp_send is indicated by
116 return of 0. A successful status will return a 1 for snmp_close and
117 the request id of the packet for snmp_send. Upon successful return
118 from snmp_send the pdu will be freed by the library.
119 Consult snmp_api.h for the complete set of SNMP library error values.
121 The SNMP library error value snmperr can be one of the following val‐
122 ues:
123 SNMPERR_GENERR A generic error occurred.
125 SNMPERR_BAD_LOCPORT The local port was bad because it had
127 already been allocated or permission was
128 denied.
129 SNMPERR_BAD_ADDRESS The host name or address given was not use‐
131 able.
132 SNMPERR_BAD_SESSION The specified session was not open.
134 SNMPERR_TOO_LONG
136 SNMPERR_NO_SOCKET
138 SNMPERR_V2_IN_V1
140 SNMPERR_V1_IN_V2
142 SNMPERR_BAD_REPEATERS
144 SNMPERR_BAD_REPETITIONS
146 SNMPERR_BAD_ASN1_BUILD
148 SNMPERR_BAD_SENDTO
150 SNMPERR_BAD_PARSE
152 SNMPERR_BAD_VERSION
154 SNMPERR_NOAUTH_DESPRIV
156 SNMPERR_ABORT
158 SNMPERR_UNKNOWN_PDU
160 SNMPERR_TIMEOUT
162 A string representation of the error code can be obtained with
164 snmp_api_errstring, and a standard error message may be printed using
165 snmp_perror that functions like the perror standard routine.
166
168 select(2), netsnmp_sess_api(3), netsnmp_mib_api(3), netsnmp_pdu_api(3),
169 netsnmp_varbind_api(3), snmp_api.h
170V5.8 19 May 2011 NETSNMP_SESSION_API(3)