snmp_select_info(3)

1SESSION_API(3)                     Net-SNMP                     SESSION_API(3)
2
3
4

NAME

6       snmp_sess_init,   snmp_open,  snmp_send,  snmp_select_info,  snmp_read,
7       snmp_timeout, snmp_close,  snmp_perror,  snmp_sess_perror,  snmp_error,
8       snmp_api_errstring - session_api functions
9

SYNOPSIS

11       #include <net-snmp/session_api.h>
12
13       void snmp_sess_init ( struct snmp_session * );
14
15       struct snmp_session * snmp_open ( struct snmp_session *);
16              /* Input parameter not used in active sessions */
17
18       int snmp_send ( struct snmp_session *session,
19              struct snmp_pdu *pdu );
20
21       int snmp_select_info ( int *numfds, fd_set *fdset,
22              struct timeval *timeout, int *block );
23
24       void snmp_read ( fd_set *fdset );
25
26       void snmp_timeout ( void );
27
28       int snmp_close ( struct snmp_session *session );
29
30       void snmp_error ( struct snmp_session *session,
31              int *pcliberr, int *psnmperr, char **pperrstring );
32
33       char *snmp_api_errstring ( int snmperr );
34
35       void snmp_perror ( char * msg );
36              /* for parsing errors only */
37
38       void snmp_sess_perror (char * msg, struct snmp_session *);
39              /* all other SNMP library errors */
40

DESCRIPTION

42       Snmp_sess_init  prepares  a  struct snmp_session that sources transport
43       characteristics and common information that will be used for a  set  of
44       SNMP transactions.  After this structure is passed to snmp_open to cre‐
45       ate an SNMP session, the structure is not used.
46
47       Snmp_open returns a  pointer  to  a  newly-formed  struct  snmp_session
48       object,  which  the  application  must use to reference the active SNMP
49       session.
50
51       Snmp_send takes as input a pointer to a struct snmp_pdu  object.   This
52       structure  contains  information that describes a transaction that will
53       be performed over an open session.
54
55       Consult snmp_api.h for the definitions of these structures.
56
57       Snmp_read, snmp_select_info, and snmp_timeout provide an interface  for
58       the  use  of  the  select(2)  system call so that SNMP transactions can
59       occur asynchronously.
60
61       Snmp_select_info is given the information that would have  been  passed
62       to select in the absence of SNMP.  For example, this might include win‐
63       dow update information.  This information is modified so that SNMP will
64       get  the  service  it  requires from the call to select.  In this case,
65       numfds, fdset, and timeout correspond to the nfds, readfds, and timeout
66       arguments  to select, respectively.  The only exception is that timeout
67       must always point to an allocated (but  perhaps  uninitialized)  struct
68       timeval.   If  timeout  would have been passed as NULL, block is set to
69       true, and timeout is treated as undefined.  This same rule applies upon
70       return from snmp_select_info.
71
72       After  calling  snmp_select_info,  select  is  called with the returned
73       data.  When select returns, snmp_read should be called with the  fd_set
74       returned  from  select  to  read  each  SNMP socket that has input.  If
75       select times out, snmp_timeout should be called to see if  the  timeout
76       was intended for SNMP.
77

DIAGNOSTICS

79       Previous versions of the library used snmp_get_errno to read the global
80       variable snmp_errno which may have held the  error  status  within  the
81       SNMP  library.   The  existing method snmp_perror should be used to log
82       ASN.1 coding errors only.
83
84       The new method snmp_sess_perror is  provided  to  capture  errors  that
85       occur   during   the   processing   of   a   particular  SNMP  session.
86       Snmp_sess_perror calls snmp_error function to obtain  the  "C"  library
87       error  errno  ,  the  SNMP library error snmperr , and the SNMP library
88       detailed error message that is associated with an error  that  occurred
89       during a given session.
90
91       Note  that  in  all cases except one, snmp_sess_perror should be handed
92       the  struct  snmp_session  *  pointer  returned  from  snmp_open.    If
93       snmp_open  returns a null pointer, pass the INPUT struct snmp_session *
94       pointer used to call snmp_open.
95
96       Error return status from  snmp_close  and  snmp_send  is  indicated  by
97       return  of  0.   A successful status will return a 1 for snmp_close and
98       the request id of the packet for  snmp_send.   Upon  successful  return
99       from snmp_send the pdu will be freed by the library.
100
101       Consult  snmp_api.h  for the complete set of SNMP library error values.
102       The SNMP library error value snmperr can be one of the  following  val‐
103       ues:
104
105         SNMPERR_GENERR           A generic error occurred.
106
107         SNMPERR_BAD_LOCPORT      The  local  port  was  bad  because  it  had
108                                  already been  allocated  or  permission  was
109                                  denied.
110
111         SNMPERR_BAD_ADDRESS      The  host name or address given was not use‐
112                                  able.
113
114         SNMPERR_BAD_SESSION      The specified session was not open.
115
116         SNMPERR_TOO_LONG
117
118         SNMPERR_NO_SOCKET
119
120         SNMPERR_V2_IN_V1
121
122         SNMPERR_V1_IN_V2
123
124         SNMPERR_BAD_REPEATERS
125
126         SNMPERR_BAD_REPETITIONS
127
128         SNMPERR_BAD_ASN1_BUILD
129
130         SNMPERR_BAD_SENDTO
131
132         SNMPERR_BAD_PARSE
133
134         SNMPERR_BAD_VERSION
135
136         SNMPERR_NOAUTH_DESPRIV
137
138         SNMPERR_ABORT
139
140         SNMPERR_UNKNOWN_PDU
141
142         SNMPERR_TIMEOUT
143
144       A string  representation  of  the  error  code  can  be  obtained  with
145       snmp_api_errstring,  and  a standard error message may be printed using
146       snmp_perror that functions like the perror standard routine.
147

NAME

SYNOPSIS

DESCRIPTION

DIAGNOSTICS

SEE ALSO