Perl5 SNMP Extension Module v1.8
for the UCD SNMP Library
G.S. Marzot (gmarzot@baynetworks.com)
Contents:
Introduction:
Availability:
Supported Platforms:
Release Notes:
Installation:
Operational Description:
Trouble Shooting:
Acknowledments:
History:
Introduction:
This is a Perl5 extension module which provides a full featured SNMP
client side API. The SNMP module internals rely on the UCD SNMP
client library toolkit. The UCD SNMP library was originally based on
version 2.1.2.1 of the CMU SNMP library but has incorporated many
bugfixes and enhancements. For information on the UCD SNMP library see
the documentation provided with the UCD SNMP distribution or the
ucd-snmp project web page: http://www.ece.ucdavis.edu/ucd-snmp
(NOTE: In previous releases this module was compatible with both the
UCD and CMU SNMP libraries. Starting with Perl5/SNMP-1.7 this module
will *only* work with the UCD SNMP library due to dependence on new
features)
Availability:
The most recent release of the UCD SNMP Libray can be found at:
ftp://ftp.ece.ucdavis.edu/pub/snmp/ucd-snmp.tar.gz
The most recent release of the Perl5/SNMP module can be found at:
ftp:/ftp.wellfleet.com/netman/snmp/perl5/SNMP.tar.gz
(as well as the usual perl archives, CPAN)
Supported Platforms:
SunOS 4.1.x
Solaris 2.x
Linux 1.2.x, 2.0.x
Many other UNIX variants
Win95/NT
Release Notes:
version 1.8 is intended to compile w/ ucd-snmp-3.5 (1.8a1 was
targetted at ucd-snmp-3.4). Compatibility with later versions of
ucd-snmp is not guaranteed due to the dynamic nature of free software
development :). As of 1.8a2, 'make test' will fail session test 9 when
tested with the ucd-snmp agent due to a bug in the agent in which
'set's to read-only attributes appear to succeed. This 'make test'
failure can be safely ignored.
Installation:
build and install ucd-snmp-3.5
note: you should ensure that any previous ucd-snmp or cmu snmp
installation is located so that the wrong libsnmp or headers are not
used by mistake).
perl Makefile.PL
make
make test
make install
note: 'make test' requires that an agent is running to which you have
read/write access. For the ucd-snmp snmpd this may involve setting up
the snmpd.conf file with read-write access for 'private'
Operational Description:
The basic operations offered by the SNMP module are provided through
an object oriented interface for modularity and ease of use. The
primary class is SNMP::Session which encapsulates the persistent
aspects of a connection between the management application and the
managed agent. Internally the class is implemented as a blessed hash
reference. This class supplies 'get', 'getnext', 'set', 'fget', and
'fgetnext' method calls. The methods take a variety of input argument
formats and support both syncronous and asyncronous operation through
a polymorphic API (i.e., method behaviour varies dependent on args
passed - see below).
A description of the fields which can be specified when an
SNMP::Session object is created follows:
SNMP::Session
public:
DestHost - default 'localhost', hostname or ip addr of SNMP agent
Community - default 'public', SNMP community string (used for both R/W)
Version - default '1', [2 (same as 2c), 2c, 3 (not implemented)]
RemotePort - default '161', allow remote UDP port to be overriden
Timeout - default '1000000', micro-seconds before retry
Retries - default '5', retries before failure
RetryNoSuch - default '1', 'get' request NOSUCH errors in the pdu will
be repaired, removing the varbind in error, and resent -
undef will be returned for all NOSUCH varbinds, setting
to '0' disables this feature and the entire get request
will fail on any NOSUCH error (applies to v1 only)
VarFormats - default 'undef', used by 'fget[next]', holds an hash
reference of output value formatters, (e.g., {<obj> =>
<sub-ref>, ... }, <obj> must match the <obj> and format
used in the get operation. A special <obj>, '*', may be
used to apply all <obj>s, the supplied sub is called to
translate the value to a new format. The sub is called
passing the Varbind as the arg
TypeFormats - default 'undef', used by 'fget[next]', holds an hash
reference of output value formatters, (e.g., {<type> =>
<sub-ref>, ... }, the supplied sub is called to translate
the value to a new format, unless a VarFormat mathces first
(e.g., $session->{TypeFormats}{INTEGER} = \&mapEnum();
although this can be done more efficiently by enabling
$SNMP::use_enums or session creation param 'UseEnums')
UseLongNames - defaults to the value of SNMP::use_long_names at time
of session creation. set to non-zero to have <tags>
for 'getnext' methods generated preferring longer Mib name
convention (e.g., system.sysDescr vs just sysDescr)
UseSprintValue - defaults to the value of SNMP::use_sprint_value at time
of session creation. set to non-zero to have return values
for 'get' and 'getnext' methods formatted with the libraries
sprint_value function. This will result in certain data types
being returned in non-canonical format NOTE: values returned
with this option set may not be appropriate for 'set' operations
(see discussion of value formats in <vars> description section)
UseEnums - defaults to the value of SNMP::use_enums at time of session
creation. set to non-zero to have integer return values
converted to enumeration identifiers if possible, these values
will also be acceptable when supplied to 'set' operations
ErrorStr - read-only, holds the error message assoc. w/ last request
ErrorNum - read-only, holds the snmp_err or staus of last request
ErrorInd - read-only, holds the snmp_err_index when appropriate
private:
DestAddr - internal field used to hold the translated DestHost field
SessPtr - internal field used to cache a created session structure
methods:
new(<fields>) - Constructs a new SNMP::Session object. The fields are
passed to the contructor as a hash list
(e.g., $session = new SNMP::Session(DestHost => 'foo',
Community => 'private');), returns an object reference
or undef in case of error.
update(<fields>)- Updates the SNMP::Session object with the values fields
passed in as a hash list (similar to new(<fields>))
(WARNING! not fully implemented)
get(<vars>[,<callback>])
- do SNMP GET, multiple <vars> formats accepted,
for syncronous operation <vars> will be updated
with value(s) and type(s) and will return
retrieved value(s). If <callback> supplied method
will operate asyncronously
fget(<vars>[,<callback>])
- do SNMP GET like 'get' and format the values according
the handlers specified in $sess->{VarFormats} and
$sess->{TypeFormats}
getnext(<vars>[,<callback>])
- do SNMP GETNEXT, multiple <vars> formats accepted,
returns retrieved value(s), <vars> passed as arguments are
updated to indicate next lexicographical <obj>,<iid>,<val>,
and <type> NOTE: simple string <vars>,(e.g., 'sysDescr.0')
form is not updated. If <callback> supplied method
will operate asyncronously
fgetnext(<vars>[,<callback>])
- do SNMP GETNEXT like getnext and format the values according
the handlers specified in $sess->{VarFormats} and
$sess->{TypeFormats}
set(<vars>[,<callback>])
- do SNMP SET, multiple <vars> formats accepted,
the value field in all <vars> formats must be in a canonical
format (i.e., well known format) to ensure unambiguous
translation to SNMP MIB data value (see discussion of
canonical value format <vars> description section),
returns snmp_errno. If <callback> supplied method
will operate asyncronously
getbulk(<non-repeaters>, <max-repeaters>, <vars>)
- * Not Implemented *
SNMP::TrapSession - supports all aplicable fields from SNMP::Session
(see above)
methods:
new(<fields>) - Constructs a new SNMP::TrapSession object. The fields are
passed to the contructor as a hash list
(e.g., $trapsess = new SNMP::Session(DestHost => 'foo',
Community => 'private');), returns an object reference
or undef in case of error.
trap(enterprise, agent, generic, specific, uptime, <vars>)
$sess->trap(enterprise=>'.1.3.6.1.4.1.2021', # or 'ucdavis' [default]
agent => '127.0.0.1', # or 'localhost',[dflt 1st intf on host]
generic => specific, # can be omitted if 'specific' supplied
specific => 5, # can be omitted if 'generic' supplied
uptime => 1234, # dflt to localhost uptime (0 on win32)
[[ifIndex, 1, 1],[sysLocation, 0, "here"]]); # optional vars
# always last
or v2 format
trap(srcParty, dstParty, oid, uptime, <vars>) - * Not Implemented *
$sess->trap(srcParty => party1,
dstParty => party2,
oid => 'snmpRisingAlarm',
uptime => 1234,
[[ifIndex, 1, 1],[sysLocation, 0, "here"]]); # optional vars
# always last
Acceptable variable formats:
<vars> may be one of the following forms:
SNMP::VarList: - represents an array of MIB objects to get or set,
implemented as a blessed reference to an array of
SNMP::Varbinds, (e.g., [<varbind1>, <varbind2>, ...])
SNMP::Varbind: - represents a single MIB object to get or set, implemented as
a blessed reference to a 4 element array;
[<obj>, <iid>, <val>, <type>].
<obj> - one of the following forms:
1) leaf identifier (e.g., 'sysDescr') assumed to be
unique for practical purposes
2) fully qualified identifier (e.g.,
'.iso.org.dod.internet.mgmt.mib-2.system.sysDescr')
3) fully qualified, dotted-decimal, numeric OID (e.g.,
'.1.3.6.1.2.1.1.1')
<iid> - the dotted-decimal, instance identifier. for
scalar MIB objects use '0'
<val> - the SNMP data value retrieved from or being set
to the agents MIB. for (f)get(next) operations
<val> may have a variety of formats as determined by
session and package settings. However for set
operations the <val> format must be canonical to
ensure unambiguous translation. The canonical forms
are as follows:
OBJECTID => dotted-decimal (e.g., .1.3.6.1.2.1.1.1)
OCTETSTR => perl scalar containing octets,
INTEGER => decimal signed integer (or enum),
NETADDR => dotted-decimal,
IPADDR => dotted-decimal,
COUNTER => decimal unsigned integer,
COUNTER64 => decimal unsigned integer,
GAUGE, => decimal unsigned integer,
UINTEGER, => decimal unsigned integer,
TICKS, => decimal unsigned integer,
OPAQUE => perl scalar containing octets,
NULL, => perl scalar containing nothing,
<type> - SNMP data type (see list above), this field is
populated by 'get' and 'getnext' operations. In
some cases the programmer should populate this
field when passing to a 'set' operation. this
field need not be supplied when attribute
indicated by <tag> is already described by loaded
Mib modules. for 'set's, if a numeric OID is used
and the object is not currently in the loaded Mib,
the <type> fileds must be supplied
simple string - light weight form of <var> used to 'set' or 'get' a
single attribute without constructing an SNMP::Varbind.
stored in a perl scalar, has the form '<tag>.<iid>',
(e.g., 'sysDescr.0'). for 'set' operations the value
is passed as a second arg. NOTE: This argument form is
not updated in get[next] operations as are the other forms.
Acceptable callback formats:
<callback> may be one of the following forms:
without arguments:
\&subname
sub { ... }
or with arguments:
[ \&subname, $arg1, ... ]
[ sub { ... }, $arg1, ... ]
[ "method", $obj, $arg1, ... ]
callback will be called when response is received or timeout
occurs. the last argument passed to callback will be the
SNMP::VarList.
SNMP package variables and functions:
$SNMP::VERSION - the current version specifier (e.g., 1.8)
$SNMP::auto_init_mib - default '1', set to 0 to disable automatic reading
of the MIB upon session creation. set to non-zero
to call initMib at session creation which will result
in MIB loading according to UCD env. variables (see
man mib_api)
$SNMP::verbose - default '0', controls warning/info output of
SNMP module, 0 => no output, 1 => enables warning/info
output from SNMP module itself (is also controlled
by SNMP::debugging - see below)
$SNMP::use_long_names - default '0', set to non-zero to enable the use of
longer Mib identifiers. see translateObj. will also
influence the formatting of <tag> in varbinds returned
from 'getnext' operations. Can be set on a per session
basis (UseLongNames)
$SNMP::use_sprint_value - default '0', set to non-zero to enable formatting of
response values using the snmp libraries sprint_value
function. can also be set on a per session basis (see
UseSprintValue) NOTE: returned values may not be
suitable for 'set' operations
$SNMP::use_enums - default '0',set non-zero to return values as enums and
allow sets using enums where appropriate. integer data
will still be accepted for set operations. can also be
set on a per session basis (see UseEnums)
$SNMP::save_descriptions - default '0',set non-zero to have mib parser save
attribute descriptions. must be set prior to mib
initialization
$SNMP::debugging - default '0', controlls debugging output level
within SNMP module and libsnmp
1 => enables 'SNMP::verbose' (see above)
2 => level 1 plus snmp_set_do_debugging(1),
3 => level 2 plus snmp_set_dump_packet(1)
$SNMP::dump_packet - default '0', set [non-]zero to independently set
snmp_set_dump_packet()
%SNMP::MIB - a tied hash to access parsed MIB information. After
the MIB has been loaded this hash allows access to
to the parsed in MIB meta-data. The hash returns
references to SNMP::MIB::NODE objects which represent
a single MIB attribute. The nodes can be fetched with
multiple 'key' formats - the leaf name (e.g.,sysDescr)
or fully/partially qualified name (e.g.,
system.sysDescr) or fully qualified numeric OID. The
returned node object supports the following fields:
objectID - dotted decimal fully qualified OID
label - leaf textual identifier (e.g., 'sysDescr')
subID - leaf numeric OID component of objectID (e.g., '1')
moduleID - textual identifier for module (e.g., 'RFC1213-MIB')
parent - parent node
children - array reference of children nodes
nextNode - next lexico node (BUG!does not return in lexico order)
type - returns simple type (see getType for values)
access - returns ACCESS (ReadOnly, ReadWrite, WriteOnly,
NoAccess, Notify, Create)
status - returns STATUS (Mandatory, Optional, Obsolete,
Deprecated)
syntax - returns 'textualConvention' if defined else 'type'
textualConvention - returns TEXTUAL-CONVENTION
units - returns UNITS
hint - returns HINT
enums - returns hash ref {tag => num, ...}
description - returns DESCRIPTION ($SNMP::save_descriptions must
be set prior to MIB initialization/parsing)
&SNMP::setMib(<file>) - allows dynamic parsing of the mib and explicit
specification of mib file independent of enviroment
variables. called with no args acts like initMib,
loading MIBs indicated by environment variables (see
ucd mib_api docs). passing non-zero second arg
forces previous mib to be freed and replaced
(note: second arg not working since freeing previous
Mib is more involved than before).
&SNMP::initMib() - calls library init_mib function if Mib not already
loaded - does nothing if Mib already loaded. will
parse directories and load modules according to
environment variables described in UCD documentations.
(see man mib_api, MIBDIRS, MIBS, MIBFILE(S), etc.)
&SNMP::addMibDirs(<dir>,...) - calls library add_mibdir for each directory
supplied. will cause directory(s) to be added to
internal list and made available for searching in
subsequent loadModules calls
&SNMP::addMibFiles(<file>,...) - calls library read_mib function. The file(s)
supplied will be read and all Mib module definitions
contained therein will be added to internal mib tree
structure
&SNMP::loadModules(<mod>,...) - calls library read_module function. The
module(s) supplied will be searched for in the
current mibdirs and and added to internal mib tree
structure. Passing special <mod>, 'ALL', will cause
all known modules to be loaded.
&SNMP::unloadModules(<mod>,...) - *Not Implemented*
&SNMP::translateObj(<var>[,arg]) - will convert a text obj tag to an OID and
vice-versa. any iid suffix is retained numerically.
default behaviour when converting a numeric OID
to text form is to return leaf indentifier only
(e.g.,'sysDescr') but when $SNMP::use_long_names
is non-zero or a non-zero second arg is supplied
will return longer textual identifier. If no Mib
is loaded when called and $SNMP::auto_init_mib is
enabled then the Mib will be loaded. Will return
'undef' upon failure.
&SNMP::getType(<var>) - return SNMP data type for given textual identifier
OBJECTID, OCTETSTR, INTEGER, NETADDR, IPADDR, COUNTER
GAUGE, TIMETICKS, OPAQUE, or undef
&SNMP::mapEnum(<var>) - converts integer value to enumertion tag defined
in Mib or converts tag to integer depending on
input. the function will return the corresponding
integer value *or* tag for a given MIB attribute
and value. The function will sense which direction
to perform the conversion. Various arg formats are
supported
$val = SNMP::mapEnum($varbind);
# where $varbind is SNMP::Varbind or equiv
# note: $varbind will be updated
$val = SNMP::mapEnum('ipForwarding', 'forwarding');
$val = SNMP::mapEnum('ipForwarding', 1);
&SNMP::MainLoop() - to be used with async SNMP::Session
calls. MainLoop must be called after initial async calls
so return packets from the agent will not be processed.
This function enters an infinite loop so program must
be exited in a callback or externally interupted.
Exported SNMP utility functions
&snmp_get() - takes args of SNMP::Session::new followed by those of
SNMP::Session::get
&snmp_getnext() - takes args of SNMP::Session::new followed by those of
SNMP::Session::getnext
&snmp_set() - takes args of SNMP::Session::new followed by those of
SNMP::Session::set
&snmp_trap() - takes args of SNMP::TrapSession::new followed by those of
SNMP::TrapSession::trap
note: utility functions do not support async operation yet.
Trouble Shooting:
If problems occur there are number areas to look at to narrow down the
possibilities.
The first step should be to test the UCD installation independently from
the Perl5/SNMP interface.
Try running the apps from the UCD distribution.
Make sure your agent is running and properly configured with
read-write access for the community you are using
Ensure that your MIBs are installed and enviroment variables are set
appropriately (see man mib_api)
Be sure to remove old ucd-snmp installations and ensure headers and
libraries from old CMU installations are not being used by mistake
If the problem occurs during compilation/linking check that the snmp
library being linked is actually the UCD library (there have been name
conflicts with existing snmp libs).
Also check that the header files are correct and up to date.
Sometimes compiling the UCD snmp library with
'position-independent-code' enabled is required (HPUX specifically).
if you cannot resolve the problem you can email me at
gmarzot@baynetworks.com and/or ucd-snmp-coders@ece.ucdavis.edu.
and maybe I can help.
please give sufficient information to analyze the problem (OS type,
versions for OS/Perl/UCD/compiler, complete error output, etc.)
Acknowledments:
Many thanks to all those who supplied patches, suggestions and
feedback.
Wes Hardaker and the ucd-coders
Dave Perkins
Marcel Wiget
David Blackburn
John Stofell
Gary Hayward
Claire Harrison
Achim Bohnet
Doug Kingston
Jacques Vidrine
Carl Jacobsen
Wayne Marquette
Perl5 Porters
Apologies to any/all who's patch/feature/request was not mentioned or
included - most likely it was lost when paying work intruded on my
fun. Please try again if you do not see a desired feature. This may
actually turn out to be a decent package with such excellent help and
the fact that I have more time to work on it than in the past.
bugs, comments, questions to gmarzot@baynetworks.com
------
History:
Bugs fixed and changes in 1.8
1) added async API
2) added trap generation API (implemented v1 traps only for now)
3) added and exported non-OO utility API (snmp_get, snmp_set, etc.)
4) added $SNMP::debugging to dynmically control libsnmp debugging output
5) added $SNMP::save_descriptions to control libsnmp parsing/saving
of MIB descriptions
6) added $SNMP::dump_packet to control libsnmp packet dumping
7) implemented the SNMP::mapEnum function (thanks to Wayne Marquette)
8) officially added(documented) tied %SNMP::MIB hash to allow access
to parsed MIB meta-data (new support for textualConvention and syntax)
9) fixed bug related to AUTOLOAD recursion
10) fixed bug with SNMP::use_enums so 'set' (and trap) should now accept
enums as input values
11) fixed bug with fget[next] - formatted values are supplied as return
values as well as within args passed
12) fixed Makefile to link with -kstat on solaris
13) fixed bug when handling noSuchName returns for getnext calls with
varbinds w/ no iid supplied (__get_label_iid should not use the
FAIL_ON_NULL_IID flag)
14) fixed bug with uninitialized sprintval_flag
15) fixed bug when no val is passed to SNMP::Session::set - now
will not core or complain about uninitialized data
16) fixed bug with __translate_appl_type in case of NULL or empty string
17) eliminated the use of strtoul for portability - use sscanf(,"%lu",)
18) getType() supports all tag formats now
Bugs fixed and changes in 1.7
1) fixed seg fault on use of unknown/unparsed attribute in Varbind or
passed to translateObj
2) fixed truncation of last char of attribute name in translateObj
3) handles variable args to setMib without complaint
4) added SNMP::getType to query data type of a given attribute and
extended Varbind structure to return type wherever possible
5) added RemotePort to SNMP::Session initialation list to allow override
of port 161
6) removed noisy announcement of mib parse success unless verbose is set
*WARNING* *this may break existing scripts*
7) changed return format for IpAddress and ObjID data types - these are
now always returned as dotted decimal strings as opposed to the
packed binary forms in 1.6
*WARNING* *this may break existing scripts*
8) Session now sets ErrorInd (e.g., $session->{ErrorInd}) where appropriate
9) Support for ucd-snmp-3.2 (and greater) style of Mib loading
10) Fully qualified attriubute names and numeric OIDs are now valid <obj>
defintions.
11) Numeric OIDs can be used even if they have not been parsed in the
current Mib - Mib loading is now optional
12) Support for Win32 perl
13) Updated docs and examples
14) Reworked/extended the test harness to use the perl t/* facility
(thanks to jfs@fluent.com)
15) fixed up error handling to be more consistent with library and more
useful in general. Now returns both library API errors and snmp
protocol error numbers and strings.
16) added per object and per type formatting of returned values - more
control of value formatting with UseEnums and UseSprintValue