The Perl5 'SNMP' Extension Module v4.2.0
		      for the Net-SNMP Library
	       G.S. Marzot (gmarzot@nortelnetworks.com)

Contents:
   Introduction:
   Availability:
   Contact:
   Supported Platforms:
   Release Notes:
   Installation:
   Operational Description:
   Trouble Shooting:
   Acknowledgments:
   History:
   Copyright:

Introduction:

This is the Perl5 'SNMP' extension module. The SNMP module provides a
full featured, tri-lingual SNMP (SNMPv3, SNMPv2c, SNMPv1) API. The
SNMP module also provides an interface to the SMI MIB parse-tree for
run-time access to parsed MIB data.  The SNMP module internals rely on
the Net-SNMP toolkit library (previously known as ucd-snmp). For
information on the Net-SNMP library see the documentation provided
with the Net-SNMP distribution or the project web page available on
'Source Forge':

http://sourceforge.net/projects/net-snmp

Availability:

The most recent release of the Perl5 SNMP module can be found bundled
with the latest Net-SNMP distibution available from:
http://sourceforge.net/projects/net-snmp 

(Note: The perl SNMP distribution obtained this way has the highest
chance of being up to date and compatible with the Net-SNMP version
with which it is bundled.)

A seperately bundled package of the SNMP module can be obtained from CPAN.

Development and older releases may be found at the following FTP site:
ftp://ftp-east.baynetworks.com/netman/snmp/perl5

(Note: In previous releases this module was compatible with the CMU
SNMP library. Starting with Perl5/SNMP-1.7 this module will *only*
work with the Net-SNMP (aka ucd-snmp) library due to dependence on new
features)

Contact:
	the following forums may be helpful:

	comp.lang.perl.modules
	net-snmp-coders@lists.sourceforge.net mail list
	(see http://sourceforge.net/projects/net-snmp to subscribe)
        gmarzot@nortelnetworks.com (last resort)

Supported Platforms:
	Linux 1.2.x, 2.x
	Solaris 2.x
	Many other UNIX variants
	Win9x/NT

Release Notes:

SNMP module version 4.2.0 is being developed against NET-SNMP-4.2.0
see http://sourceforge.net/projects/net-snmp for details.

Compatibility with earlier or later versions of Net-SNMP or UCD-SNMP
is not guaranteed due to the dynamic nature of open software
development :).

the previous stable release is SNMP-3.1.0 and ucd-snmp-4.1.2.

Yes, I skipped some versions, do not be alarmed.

KNOWN BUGS:

(none?)

Installation:

Build and install the Net-SNMP package - see Net-SNMP README and
INSTALL docs.

(Note: To ensure that any previous Net-SNMP, ucd-snmp or cmu snmp
installation's library or headers are not used by mistake, use the
-NET-SNMP-PATH directive to explicitly set the default path)

Unix:

perl Makefile.PL [-NET-SNMP-PATH=/usr/local]
make
make test
make install

Win32:

This package only builds on NT as far as I know. Thes directions are
fo VC++ 5.0-6.0 (I will be interested to hear of success with cygwin).

First  run vcvars32.bat

for ActiveState Perl  (tested with AS Perl5.005_03 (515))

perl Makefile.PL CAPI=TRUE [-NET-SNMP-PATH=/usr]
nmake
nmake test
nmake install

OpenSSL note: see the net-snmp/README.win32 to compile libsnmp with
              libeay32 and see that libeay.lib is in usr\lib

for the older perl5.004_02 distribution by gsarathy

perl Makefile.PL
nmake
nmake test
nmake install


Win32 Testing Note:

'nmake test' requires that an agent(snmpd) and trap receiver (snmptrapd)
are running. Before running 'nmake test' start these servers using the
config file provided (t/snmpd.conf). You will be asked for the test host
and port numbers by Makefile.PL

Operational Description:

The basic operations of the SNMP protocol are provided by this module
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' and other method calls. The methods take a variety of input
argument formats and support both synchronous and asynchronous
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]
 RemotePort  - default '161', allow remote UDP port to be overridden
 Timeout     - default '1000000', micro-seconds before retry
 Retries     - default '5', retries before failure
 RetryNoSuch - default '0', if enabled NOSUCH errors in 'get' pdus will
               be repaired, removing the varbind in error, and resent -
               undef will be returned for all NOSUCH varbinds, when set
               to '0' this feature is disabled and the entire get request
               will fail on any NOSUCH error (applies to v1 only)
 SecName     - default 'initial', security name (v3)
 SecLevel    - default 'noAuthNoPriv', security level [noAuthNoPriv,
               authNoPriv, authPriv] (v3)
 SecEngineId - default <none>, security engineID, will be probed if not
               supplied (v3)
 ContextEngineId - default <SecEngineId>, context engineID, will be
                   probed if not supplied (v3)
 Context     - default '', context name (v3)
 AuthProto   - default 'MD5', authentication protocol [MD5, SHA] (v3)
 AuthPass    - default <none>, authentication passphrase
 PrivProto   - default 'DES', privacy protocol [DES] (v3)
 PrivPass    - default <none>, privacy passphrase (v3)
 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
 UseNumeric  - defaults to the value of SNMP::use_numeric at time of session
               creation. set to non-zero to have <tags> returned by the 'get'
               methods untranslated (i.e. dotted-decimal).  Setting the
               UseLongNames value for the session is highly recommended.
 TimeStamp   - defaults to the value of SNMP::timestamp_vars at time of
               session creation. set to non-zero to add an additional element
               to each Varbind, containing a time(2) timestamp.  Reference
               the Varbind timestamp through the $varbind_ref->stamp() method.
	       Do not modify a timestamp value -- it is shared between all
	       variables that were received at the same time.

 ErrorStr    - read-only, holds the error message assoc. w/ last request
 ErrorNum    - read-only, holds the snmp_err or status 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 constructor 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 synchronous operation <vars> will be updated
                   with value(s) and type(s) and will also return
                   retrieved value(s). If <callback> supplied method
                   will operate asynchronously
 fget(<vars>[,<callback>])
                 - do SNMP GET like 'get' and format the values according
                   the handlers specified in $sess->{VarFormats} and
                   $sess->{TypeFormats}. Async *not supported*
 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 asynchronously
 fgetnext(<vars>[,<callback>])
                 - do SNMP GETNEXT like getnext and format the values according
                   the handlers specified in $sess->{VarFormats} and
                   $sess->{TypeFormats}. Async *not supported*
 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 true on success or undef on error. If <callback>
                   supplied method will operate asynchronously
 getbulk(<non-repeaters>, <max-repeaters>, <vars> [, <callback>])
                 - do an SNMP GETBULK, from the list of Varbinds, the single
                   next lexico instance is fetched for the first n Varbinds
                   as defined by <non-repeaters>. For remaining Varbinds,
                   the m lexico instances are retrieved each of the remaining
                   Varbinds, where m is <max-repeaters>.
 bulkwalk(<non-repeaters>, <max-repeaters>, <vars> [, <callback>])
                 - do an "SNMP bulkwalk" on the given variables.  Bulkwalk is
                   implemented by sending an SNMP GETBULK request to fetch the
                   variables.  Objects are copied to the return list until the
                   sub-tree is exited.  If the request is not completed at the
                   end of a packet, a new request is created, starting where
                   the previous packet left off.  This implementation is able
                   to handle multiple repeated vars, as well as non-repeaters.
                   Returns a list (or, in scalar context, a reference to a
                   list) of arrays of VarBinds.  The VarBinds consist of the
                   responses for each requested variable.  bulkwalk() leaves
                   the original Varbinds list intact to facilitate querying
                   of multiple devices.

SNMP::TrapSession - supports all applicable fields from SNMP::Session
                    (see above)
methods:
 new(<fields>)   - Constructs a new SNMP::TrapSession object. The fields are
                   passed to the constructor 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(oid, uptime, <vars>)
    $sess->trap(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 needs to populate this
                            field when passing to a 'set' operation. this
                            field need not be supplied when the 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> field 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 a
SNMP::VarList reference. In case of timeout the last argument
will be undef.

SNMP package variables and functions:

 $SNMP::VERSION       - the current version specifier (e.g., 3.1.0)

 $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 Net-SNMP 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::use_numeric   - default '0', set to non-zero to return tags as numeric
                        OID's, instead of translating them.  Also setting
                        $SNMP::use_long_names to non-zero is highly recommended.

 $SNMP::timestamp_vars - default '0', set to non-zero to add an additional
			time(2)-style timestamp element to each returned 
			Varbind (as array element 4).  Do not modify a 
			timestamp value -- it is shared between all variables
			that were received at the same time.

 $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', controls 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 structure of the
                        MIB (i.e., schema)). The hash returns blessed
                        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 application type (see getType for values)
        access        - returns ACCESS (ReadOnly, ReadWrite, WriteOnly,
                        NoAccess, Notify, Create)
        status        - returns STATUS (Mandatory, Optional, Obsolete,
                        Deprecated, Current)
        syntax        - returns 'textualConvention' if defined else 'type'
        textualConvention - returns TEXTUAL-CONVENTION
        units         - returns UNITS
        hint          - returns HINT
        enums         - returns hash ref {tag => num, ...}
        ranges        - returns array ref [[low1, high1], [low2, high2], ...]
        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 environment
                         variables. called with no args acts like initMib,
                         loading MIBs indicated by environment variables (see
                         Net-SNMP 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 Net-SNMP
                        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 identifier 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 enumeration 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([<timeout>, [<callback>]])
                   - 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.
                     If no args supplied this function enters an infinite loop
                     so program must be exited in a callback or externally
                     interrupted. If <timeout

 &SNMP::finish()
		   - This function, when called from an SNMP::MainLoop() 
		     callback function, will cause the current SNMP::MainLoop
		     to return after the callback is completed. finish() can
		     be used to terminate an otherwise-infinite MainLoop. A
		     new MainLoop() instance can then be started to handle
		     further requests.

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 Net-SNMP installation
independently from the Perl5 SNMP interface.

Try running the apps from the Net-SNMP distribution.

Make sure your agent (snmpd) is running and properly configured with
read-write access for the community you are using.

Ensure that your MIBs are installed and environment variables are set
appropriately (see man mib_api)

Be sure to ensure headers and libraries from old CMU installations are
not being used by mistake (see -NET-SNMP-PATH).

If the problem occurs during compilation/linking check that the snmp
library being linked is actually the Net-SNMP 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 Net-SNMP library with
'position-independent-code' enabled is required (HPUX specifically).

If you cannot resolve the problem you can post to
comp.lang.perl.modules or email net-snmp-coders@lists.sourceforge.net.

please give sufficient information to analyze the problem (OS type,
versions for OS/Perl/net-SNMP/compiler, complete error output, etc.)

Acknowledgments:

Many thanks to all those who supplied patches, suggestions and
feedback.

Wes Hardaker and the net-snmp-coders
Dave Perkins
Marcel Wiget
David Blackburn
John Stofell
Gary Hayward
Claire Harrison
Achim Bohnet
Doug Kingston
Jacques Vidrine
Carl Jacobsen
Wayne Marquette
Scott Schumate
Michael Slifcak
Srivathsan Srinivasagopalan
Bill Fenner
Jef Peeraer
Daniel Hagerty
Karl "Rat" Schilke and Electric Lightwave, Inc.
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.

------
History:

Bugs fixed and changes in 3.1.0
1) update to ucd-snmp-4.1.0

2) support much of SNMPv3

3) add support for getbulk - Thanks Daniel

4) further regularize error return codes - will return undef on error
for most cases except where values are expected from a varbind (will
themselves be undef)

5) fix bug where session deletion inadvertently occurred with async calls
if calling Session went out of scope - a reference is saved which will
not destruct until after async callback completes

6) pass protocol errors to callbacks

7) added lower level async API so SNMP events can be integrated with
arbitrary event loop (Event.pm?) - thanks Jef

8) Major enhancement to 'make test' - thanks Sri

9) POD documentation - thanks Bill

10) fix OBJECTID translations (unsigned long)

11) display Mib info on 'status' and 'indexes'


Bugs fixed and changes in 1.8.2
1) minor bug fix

Bugs fixed and changes in 1.8.1

1) updated docs

2) fixed #defines from MAX_NAME_LEN to MAX_OID_LEN (mslifcak)

3) reverted __tag2oid to use read_objid rather than get_node. this
gives full name resolution provided by libsnmp and no longer creates
problems on failure since 3.6.2 removes the call to 'exit' in
read_objid

4) fixed Makefile.PL to use win32 'type' vs. 'cat'

Bugs fixed and changes in 1.8

1) added async API (async api should be considered beta -
   potential changes are most likely in the event loop integration
   area - would like to integrate with Event.pm)

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 dynamically 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

19) fixed bug when setting values of type OBJID (thanks Scott Schumate)

20) *WARNING* RetryNoSuch in session creation had a bug which prevented
    it from being disabled. It now defaults to being disabled - this may
    break code *WARNING*


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 initialization 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 attribute names and numeric OIDs are now valid <obj>
   definitions.

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

Copyright:

     Copyright (c) 1995-2000 G. S. Marzot. All rights reserved.
     This program is free software; you can redistribute it and/or
     modify it under the same terms as Perl itself.