1 This directory holds the implementation of individual MIB groups.
2 Currently, this contains the eight MIB-2 groups, plus a basic template
3 for new MIB groups (examples/example.c and examples/example.h)
5 Additionally, you may wish to check out the 'mib2c' perl script in the
6 SRCDIR/local directory that can convert a written mib into C template
7 files for use with this package as mib modules.
9 Each group consists of two files:
11 examples/example.h: interface information
13 - declaration of the initialisation function 'init_example'
15 - declaration of the function(s) for retrieving variable
16 information 'var_example'
17 - declaration of the function(s) for setting variable
18 information (if appropriate)
20 - declaration of the function(s) for parsing the snmpd.conf file
22 - a call to config_parse_dot_conf() to explain to the .conf
23 parser which tokens we want to parse.
26 - definitions of the MIB group 'magic numbers'
27 declarations of the 'public' functions
29 - a list of the variables in the group, including
30 type information, mapping between magic numbers
31 and OID sub-identifiers within the group,
32 accessibility information, and the relevant
33 function for retrieving this variable's value.
34 They *must* be listed in the mib-descending order.
35 - a call to 'config_load_mib', identifying the location of
36 this MIB group within the general MIB structure.
37 - a call to 'config_require' to identify any other files
38 that are required by the implementation of this group.
41 (these last three are only visible within the 'glue' file 'snmp_vars.c'
42 (if at all), but are declared here for ease of maintainance)
46 examples/example.c: implementation code
47 (can be non-existant if only the .h file is needed)
49 - a list of kernel information needed to report
51 - an initialisation function (optional)
52 - a routine to parse an snmpd.conf line.
53 - a routine to free resources from above and return to
55 - 'header' function(s) to map the OID requested
56 to the next appropriate OID
57 (and similar system-independent setup)
58 - function(s) (possibly system-specific) to
59 determine and return the value of the
61 - (optionally) functions used to set values
62 - other functions used internally
65 To implement a new MIB group, copy the two files 'example.c'
66 and 'example.h' to appropriate new files ({MODULENAME}.c and {MODULENAME}.h),
67 and edit them as follows:
70 globally change "example" to the new module name
71 and update the initial comment.
72 replace the EXAMPLE* defines with the list of
73 variables within this new group
74 fill in the 'MODULENAME_variables' structure with these
75 new variables, updating the type, accessibility
76 and sub-identifier information as appropriate.
77 replace 'variableN' with the maximum size of the
78 returned OID (omitting the group prefix).
79 For non-table values, this will probably be one
80 greater than the length of the sub-identifier.
81 update or remove the 'config_parse_dot_conf' call if
82 you need to handle lines in the snmpd.conf files.
83 update the 'config_load_mib' call with the appropriate
84 location within the global MIB structure, and
85 its length (note that 'MIB' has length 6)
86 provide a suitable 'config_require' call if this
87 code uses routines from any other files within
88 the 'mibgroup' directory (such as 'util_funcs.c')
93 globally change "example" to the new module name
94 and update the initial comment.
95 replace the 'MODULENAME_nl' name list with any necessary
96 kernel variables, and update the associated #define's
97 replace the name length definition within the 'header'
98 function with the length of the requesting OID
99 (i.e. the sum of the lengths given in the subtree
100 definition, and the variable structure above).
101 replace the basic 'switch' structure within the
102 'var_MODULENAME' function with the necessary code
103 to calculate the required information.
104 (plus any other internal functions as needed).
106 It will then be necessary to (re-)run the configure script with the
108 --with-mib-modules="MODULENAME"
110 (where MODULENAME matches the name of the .c/.h file pair exactly).
111 Note that if anything in the config_* macros changes, or the init function
112 is added or removed, then the configure script will need to be re-run.