1SNMP_SESS_API(3) Net-SNMP SNMP_SESS_API(3)
2
6 snmp_sess_init, snmp_sess_open, snmp_sess_session, snmp_sess_send,
7 snmp_sess_async_send, snmp_sess_select_info, snmp_sess_read,
8 snmp_sess_timeout, snmp_sess_close, snmp_sess_error - session functions
9
11 #include <net-snmp/session_api.h>
12 void snmp_sess_init(struct snmp_session *session);
14 void *snmp_sess_open(struct snmp_session *session);
16 struct snmp_session *snmp_sess_session(void *handle);
18 int snmp_sess_send(void *handle, struct snmp_pdu *pdu);
20 int snmp_sess_async_send(void *handle,
22 struct snmp_pdu *pdu,
23 snmp_callback callback,
24 void *callbackData);
25 int snmp_sess_select_info(void *handle,
27 int *numfds, fd_set *fdset,
28 struct timeval *timeout,
29 int *block);
30 int snmp_sess_read(void *handle, fd_set *fdset);
32 void snmp_sess_timeout(void *handle);
34 int snmp_sess_close(void *handle);
36 void snmp_sess_error(void *handle, int *pcliberr,
38 int *psnmperr, char **pperrstring);
39
41 These functions define a subset of the API that can be used to manage
42 single SNMP sessions in a multi-threaded application. Except for
43 snmp_sess_session(), these functions are single session versions of the
44 traditional SNMP library API.
45 Note that these functions use an opaque pointer (handle in the above
47 prototypes) to identify a single session in lieu of a session pointer
48 (as in the traditional API).
49 snmp_sess_init() prepares a struct snmp_session that sources transport
51 characteristics and common information that will be used for a set of
52 SNMP transactions. After this structure is passed to snmp_sess_open()
53 to create an SNMP session, the structure is no longer used. Instead
54 the opaque pointer returned by snmp_sess_open() is used to refer to
55 that session henceforth.
56 SNMP sessions that are created with snmp_sess_open() are not affected
58 by, and SHOULD NOT BE USED WITH, snmp_select_info(), snmp_read(),
59 snmp_timeout() nor snmp_close(). Rather the equivalent single session
60 functions described here should be used.
61 snmp_sess_init() and snmp_sess_open() each take as input a pointer to a
63 struct snmp_session object. This structure contains information for a
64 set of transactions that will share similar transport characteristics.
65 snmp_sess_session() takes the opaque session handle and returns a
66 pointer to its associated struct snmp_session.
67 snmp_sess_send() and snmp_sess_async_send() each take a pdu parameter,
69 which points to a struct snmp_pdu object containing information that
70 describes a transaction that will be performed over an open session.
71 Consult snmp_api.h for the definitions of these structures.
73 snmp_sess_select_info(), snmp_sess_read() and snmp_sess_timeout() pro‐
75 vide an interface for the use of the select(2) system call so that SNMP
76 transactions for a single session can occur asynchronously.
77 snmp_sess_select_info() is passed the information that would have been
79 passed to select(2) in the absence of SNMP. For example, this might
80 include file descriptors associated with the main loop of a graphical
81 application. This information is modified so that SNMP will get the
82 service it requires from the call to select(2). In this case, numfds,
83 fdset and timeout correspond to the nfds, readfds and timeout arguments
84 to select(2) respectively. The only exception is that timeout must
85 ALWAYS point to an allocated (but perhaps uninitialized) struct timeval
86 (it cannot be NULL as for select(2)). If timeout would have been
87 passed as NULL, block is instead set to true, and timeout is treated as
88 undefined. This same rule applies upon return from snmp_select_info().
89 After calling snmp_sess_select_info() , select(2) should be called with
91 the returned data. When it returns, snmp_sess_read() should then be
92 called with the fd_set returned from select(2). This will read any
93 input from this session's SNMP socket. If select(2) times out (that
94 is, it returns zero), snmp_sess_timeout() should be called to see if a
95 timeout has occurred on the SNMP session.
96
98 Error return status from snmp_sess_open() is indicated by return of a
99 NULL pointer. Error return status from snmp_sess_close() and
100 snmp_sess_send() is indicated by a return value of 0. A successful
101 status will return 1.
102 Further information can be obtained by using snmp_sess_error() to see
104 what type of error has occurred. This function returns the SNMP
105 snmp_errno variable, the value of the system errno variable, and a
106 string interpretation of both variables. The string must be freed
107 after use by the caller.
108 For errors returned by snmp_sess_open(), use the corresponding function
110 snmp_error() instead of snmp_sess_error().
111 Consult snmp_api.h for the complete set of SNMP library error values.
113 The SNMP library error value snmperr can be one of the following val‐
114 ues:
115 SNMPERR_GENERR A generic error occurred.
117 SNMPERR_BAD_LOCPORT The local port was bad because it had
119 already been allocated or permission was
120 denied.
121 SNMPERR_BAD_ADDRESS The host name or address given was not use‐
123 able.
124 SNMPERR_BAD_SESSION The specified session was not open.
126 SNMPERR_TOO_LONG
128 SNMPERR_NO_SOCKET
130 SNMPERR_V2_IN_V1
132 SNMPERR_V1_IN_V2
134 SNMPERR_BAD_REPEATERS
136 SNMPERR_BAD_REPETITIONS
138 SNMPERR_BAD_ASN1_BUILD
140 SNMPERR_BAD_SENDTO
142 SNMPERR_BAD_RCVFROM
144 SNMPERR_BAD_PARSE
146 SNMPERR_BAD_VERSION
148 SNMPERR_BAD_COMMUNITY
150 SNMPERR_NOAUTH_DESPRIV
152 SNMPERR_ABORT
154 SNMPERR_UNKNOWN_PDU
156 SNMPERR_TIMEOUT
158
160 select(2), snmp_api(3), snmp_api.h
1614.2 Berkeley Distribution 07 Mar 2002 SNMP_SESS_API(3)