get_module_node, snmp_set_mib_warnings, snmp_set_save_descriptions,
shutdown_mib, print_mib, print_variable, fprint_variable, snprint_vari-
able, sprint_realloc_variable, print_value, fprint_value,
snprint_value, sprint_realloc_value, print_objid, fprint_objid,
snprint_objid, sprint_realloc_objid, print_description, fprint_descrip-
tion - mib_api functions
SYNOPSIS
#include <net-snmp/mib_api.h>
void init_mib(void);
int add_mibdir(char *dirname);
int add_module_replacement(char *old_module, char *new_module, char
*tag, int len);
void init_mib_internals(void);
struct tree *read_module(char *name);
struct tree *read_mib(char *filename);
struct tree *read_all_mibs(void);
void shutdown_mib(void);
void print_mib(FILE *fp);
int read_objid(char *input, oid *output, size_t *out_len);
int get_module_node(const char *name, const char *module, oid *objid,
size_t *objidlen);
void print_variable(const oid *objid, size_t objidlen, const net-
snmp_variable_list *variable);
void fprint_variable(FILE *fp, const oid *objid, size_t objidlen, const
netsnmp_variable_list *variable);
int snprint_variable(char *buf, size_t len, const oid *objid, size_t
objidlen, const netsnmp_variable_list *variable);
int sprint_realloc_variable(u_char **buf, size_t *buf_len, size_t
*out_len, int allow_realloc, const oid *objid, size_t objidlen, const
netsnmp_variable_list *variable);
void print_value(oid *objid, size_t objidlen, const netsnmp_vari-
able_list *variable)
void fprint_value(FILE *fp, const oid *objid, size_t objidlen, const
netsnmp_variable_list *variable);
int snprint_value(char *buf, size_t len, const oid *objid, size_t obji-
dlen, const netsnmp_variable_list *variable);
int sprint_realloc_value(u_char **buf, size_t *buf_len, size_t
*out_len, int allow_realloc, const oid *objid, size_t objidlen, const
netsnmp_variable_list *variable);
void print_objid(const oid *objid, size_t objidlen);
void fprint_objid(FILE *fp, const oid *objid, size_t objidlen);
int snprint_objid(char *buf, size_t len, const oid *objid, size_t obji-
dlen);
int sprint_realloc_objid(u_char **buf, size_t *buf_len, size_t
Initialisation and Shutdown
init_mib is a convenience function that handles all calls to add_mib-
dir, read_module and read_mib for standard applications. It should be
called before any other routine that manipulates or accesses the MIB
tree. This routine sets up various internal structures, as well as
reading in the default MIB modules, as detailed below.
add_mibdir is used to define the range of directory locations which are
searched for files containing MIB modules (one module per file). By
default, this will be set to the directory /usr/share/mibs but this can
be overridden by setting the environment variable MIBDIRS to a (colon-
separated) list of directories to search. Note that this does not
actually load the MIB modules located in that directory, but is an ini-
tialisation step to make them available. This function returns a count
of files found in the directory, or a -1 if there is an error.
init_mib_internals sets up the internal structures, preparatory to
reading in MIB modules. It should be called after all calls to
add_mibdir, and before and calls to read_module. This is called auto-
matically if init_mib is used.
shutdown_mib will clear the information that was gathered by read_mod-
ule, add_mibdir and add_module_replacement. It is strongly recommended
that one does not invoke shutdown_mib while there are SNMP sessions
being actively managed.
Reading and Parsing MIBs
add_module_replacement can be used to allow new MIB modules to obsolete
older ones, without needing to amend the imports clauses of other mod-
ules. It takes the names of the old and new modules, together with an
indication of which portions of the old module are affected.
tag len load the new module when:
NULL 0 always (the old module is a strict subset of the new)
name 0 for the given tag only
name non-0 for any identifier with this prefix
It can also be used to handle errors in the module identifiers used in
MIB import clauses (such as referring to RFC1213 instead of
RFC1213-MIB).
read_module locates and parses the module specified, together with any
modules that it imports from, and adds the contents of these modules to
the active MIB tree. Note that add_mibdir must first be called to add
the directory containing the file with the module definition, if this
is not in the standard path.
By default, the following MIB modules will be loaded: IP-MIB, IF-MIB,
TCP-MIB, UDP-MIB, SNMPv2-MIB, RFC1213-MIB, UCD-SNMP-MIB. This can be
overridden by setting the environment variable MIBS to a (colon-sepa-
rated) list of modules to load. If this variable starts with a plus
character, then the specified modules are added to the default list.
Otherwise only those modules listed are loaded (together with any oth-
identifier (in either numeric or descriptor form), and transforms this
into the corresponding list of sub-identifiers. This is returned in
the output parameter, with the number of sub-identifiers returned via
out_len. When called, out_len must hold the maximum length of the out-
put array. This function returns a value of 1 if it succeeds in pars-
ing the string and 0 otherwise.
Searching the MIB Tree
get_module_node takes a descriptor and the name of a module, and
returns the corresponding oid list, in the same way as read_objid
above.
If the module name is specified as "ANY", then this routine will assume
that the descriptor given is unique within the tree, and will return
the matching entry. If this assumption is invalid, then the behaviour
as to which variable is returned is implementation dependent.
Output
print_mib will print out a representation of the currently active MIB
tree to the specified FILE pointer.
print_variable will take an object identifier (as returned by
read_objid or get_module_node) and an instance of such a variable, and
prints to the standard output the textual form of the object identifier
together with the value of the variable. fprint_variable does the
same, but prints to the FILE pointer specified by the initial parame-
ter.
snprint_variable prints the same information into the buffer pointed to
by buf which is of length len and returns either the number of charac-
ters printed, or -1 if the buffer was not large enough. In the latter
case, buf will typically contained a truncated version of the informa-
tion (but this behaviour is not guaranteed). This function replaces
the obsolete function sprint_variable.
sprint_realloc_variable is the low-level function used to implement all
these functions. It prints to a specified offset in a string buffer.
The buf parameter points to a pointer to that buffer; buf_len points to
a variable holding the current size of that buffer, and out_len points
to a variable holding the offset to which to print. out_len will be
updated to hold the offset of the character following the last one
added to the buffer. If allow_realloc is 1, the buffer will be dynami-
cally expanded, as necessary, to hold the output; the variables pointed
to by buf and buf_len will be updated. If allow_realloc is 0, the
buffer will not be dynamically expanded. sprint_realloc_variable
returns 0 if allow_realloc is 1 and an attempt to allocate memory to
expand the buffer fails, or if allow_realloc is 0 and the output
wouldn't fit in the buffer. Otherwise it returns 1. When using this
function you should be careful to call free(3) on *buf when you have
finished with it.
print_value, fprint_value, snprint_value and sprint_realloc_value do
the same as the equivalent print_variable routines, but only displaying
the value of the variable, without the corresponding object identifier.
In general the parser is silent about what strangenesses it sees in the
MIB files. To get warnings reported, call snmp_set_mib_warnings with a
level of 1 (or 2 for even more warnings).
ENVIRONMENT VARIABLES
MIBDIRS A colon separated list of directories to search for MIB mod-
ules. Default: /usr/share/snmp/mibs
MIBFILES A colon separated list of files to load. Default: (none)
MIBS A colon separated list of MIB modules to load. Default: IP-
MIB:IF-MIB:TCP-MIB:UDP-MIB:SNMPv2-MIB:RFC1213-MIB:UCD-SNMP-
MIB.
SEE ALSO
snmp_api(3)
4.2 Berkeley Distribution 06 Mar 2002 MIB_API(3)
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