Embed Size (px)
Citation preview
SNMP::Class!Athanasios Douitsis
Very Brief SNMP Intro
• SNMP agent (daemon - responding to requests) • SNMP management station (making of requests) • UDP, port 161 • SNMP PDUs: SNMP GET , GET-NEXT, GETBULK,
notifications, SNMP-SET, etc o Basic Encoding Rules (BER)
• Structure of Management Information (SMIv2, ASN.1 subset) o Types (integer, string, etc) o MIBs (standard, vendor-specific)
Managed Object Semantics Managed Object Hierarchy
2 SNMP::Class
Very Brief SNMP Intro Example
Piece of knowledge: .1.3.6.1.2.1.2.2.1.5.15 = 100000000 (k-v pair)
• Object ID (OID): .1.3.6.1.2.1.2.2.1.5.15 o Object: .1.3.6.1.2.1.2.2.1.5 or .iso(1).org(3).dod(6).internet
(1).mgmt(2).mib-2(1).interfaces(2).ifTable(2).ifEntry(1).ifSpeed(5) or simply ifSpeed Semantics: "the speed of an interface" Type: Gauge32 (32-bit integer)
o Instance: .15 (row 15 in interface table)
• Value: 100.000.000 (100M) === 100Mbps for ifSpeed
3 SNMP::Class
Writing network management tools
Network management tools using SNMP:
• Small complexity, i.e. a nagios plugin
• Medium complexity, i.e. a topology discovery tool
• (Very) High complexity, i.e. a Network Management System (NMS) (mostly commercial systems)
Burden of using SNMP properly for small or medium size software
4 SNMP::Class
Problem Statement
• Perl : Availability of high performance, high quality libraries for SNMP o Net-SNMP: SNMP.pm (XS, very fast, used by
SNMP::Class) o Net::SNMP (pure Perl)
• Usage of SNMP libraries for querying managed devices (routers, switches, servers, etc)
• Typical network management tool: 1. retrieval of info from device(s) by library 2. organization of library returned data into suitable
structure 3. Conversions of data as necessary 4. Processing, calculations on data
5 SNMP::Class
Problem Statement (2) Impedance mismatch between the programming language (not just Perl) and the SNMP-SMI world
Issues: • OIDs returned in various forms (ifType, .1.3.6...) • Data types of values returned not always directly usable
o IP addresses, Mac addresses, Gauges, Enumerations o Varying between libraries
• Error codes from library (end of mib, timeout, etc) • SNMP agents
o Bugs in older implementations missing OIDs broken loops, etc
o Difference between GET-NEXT and GET-BULK • Usability of structure of returned data (array, hash, etc) --->
considerable effort 6 SNMP::Class
Problem Statemement (3) Some examples of cumbersomeness:
my ($instance) = ($key =~ /^ifSpeed.(\d+)$/)my ($instance) = ($key =~ /^\.1\.3\.6\.1\.2\.1\.2\.2\.1\.5\.(\d+)$/)
my $bridge_id = uc join(':',(unpack 'n(H2)*',$value)[1..6]);
for my $key (%kv) { if ($key =~ /^ifDescr.(\d+)$/) { $descriptions{$1} = $kv{$key}; }}for my $key (%kv) { if ($key =~ /^ifType.(\d+)$/) { say "interface ".$descriptions{$1}." is a ".$kv{$key} }}
7 SNMP::Class
SNMP::Class goals
• Usage of existing excellent libraries for Perl • Minimization of programmer-required knowledge of SNMP
esoteric (and arcane) details • Brief syntax for clarity and brevity, DWIM as much as
possible • Easy connection setup with agents, provision of sensible
defaults • Automatic optimization of communication with agents,
automatic handling of agent bugs • Orthogonal error reporting, proper usage of exceptions • Effortless navigation/querying of structure of returned data
from agents • Automatic encapsulation of values, taking into account
OID semantics, type (MIB and PDU), display-hint • Ultimately, complete encapsulation of SNMP
8 SNMP::Class
Library Overview - Connection Setup
my $c = SNMP::Class->new('myrouter.mydomain');
• Probing of SNMP version (try 2, then 1) • Querying of sysName.0
9 SNMP::Class
Library Overview - OIDs • OID: A series of integers
o representable by a label (example: 'ifType') • Complete encapsulation of the OID (creation, addition,
comparing, etc)
my $oid1 = SNMP::Class::OID->new('.1.3.6.1.4.1');
my $oid2 = SNMP::Class::OID->new('interfaces');
$oid2->contains('ifDescr'); #true
my $oid3 = SNMP::Class::OID->new('ifDescr')->add(15); #ifDescr.15
• Also, automatic separation of instance when possible
$oid3->get_instance_oid; #returns a .15 oid
10 SNMP::Class
Library Overview - Varbinds • Varbind: An OID with a value (SNMP::Class::Varbind) • Value connected with the specific OID semantically! • Attribute raw_value for all varbinds
o Just the bytes, completely unprocessed • Method value for most varbinds
o What is expected by a human • Varbind enhancement methods
• depending on OID semantics • Automatically available
Examples: $iftype->raw_value #6$iftype->value #'ethernetCsmacd', enum of 6
$designated_bridge->raw_value; #8 bytes,unprintable $bridge_id->value; # '80:00:00:06:28:84:D7:40'$bridge_id->mac_address #'00:06:28:84:D7:40'$bridge_id->priority #32768
11 SNMP::Class
Library Overview - Querying of agent
$c->add('system','interfaces');
• Walking of system and intefaces trees on agent o If SNMPv2 available, usage of GETBULK
• Query result storage inside $c (separate result objects possible as well) o $c: connection object and result object
12 SNMP::Class
Library Overview - The ResultSet ResultSet - a set of OID-value pairs (varbinds) • Filtering of set through methods
$rs->filter_label('ifSpeed'); #keep only ifSpeed OIDs
• Method chaining (returning of new ResultSets)
$rs->filter_label('ifSpeed')->filter_instance(3)
• Method autoloading with OID label names
$rs->ifSpeed(3) #same as previous, more clear• Generic filter (grep) available: $rs->filter(sub { return 1 if $_->get_label eq 'ifSpeed'; return});
13 SNMP::Class
Library Overview - The ResultSet (2)
• More advanced filtering
#Find speed of interface 'eth0'say $rs->filter_label('ifSpeed')->filter_instance($rs->filter_label('ifDescr')->filter_value('eth0')->get_instance_oid)->value;#the same, much more clearly and briefly:say $rs->find('ifDescr' => 'eth0')->ifSpeed->value;#Keep the instance for which the ifDescr equals 'eth0', then keep only the ifSpeed.
14 SNMP::Class
Library Overview - The ResultSet (3) • Iteration over contents, detection of list context
#print the description of each interfacefor($rs->ifDescr) { say $_->value }• Filter and map methods
o Used exactly as list grep and map with BLOCK
my $new_rs = $rs->filter(sub { ..... });my $new_rs = $rs->map(sub { ..... });
15 SNMP::Class
Library Overview - The ResultSet (4)
• Final touch: Resultset with 1 varbind:
$rs->ifDescr(3)->item(0)->value;#the same:$rs->ifDescr(3)->value;Varbind methods valid on 1-item ResultSets.
• Overloading also possible, but: o Awkward behavior when using list context o Awkward behavior when using operators like '.'
16 SNMP::Class
Library Implementation (so far) Built using Moose.pm Class & Role Hierarchy: • Classes:
o SNMP::Class - Session object (mostly empty, gaining functionality from Role::ResultSet and Role::Implementation::Net-SNMP)
o SNMP::Class::ResultSet - Results object (ditto) o SNMP::Class::OID - An OID
SNMP::Class::Varbind - A varbind (OID+value) • Roles:
o SNMP::Class::Role::ResultSet - resultset behavior o SNMP::Class::Role::Implementation - SNMP Instrumentation (abstract
part, not usable by itself) SNMP::Class::Role::Implementation::NetSNMP - Instrumentation
lower part using Net-SNMP (applied to SNMP::Class objects) SNMP::Class::Role::Implementation::Dummy - Another
instrumentation, dummy this time o SNMP::Class::Varbind::XXXXX - Varbind enhancement roles, (application
to plain varbinds)
17 SNMP::Class
Library Roles (2) SNMP::Class is-a: • SNMP::Class::Role::Implementation::NetSNMP • SNMP::Class::Role::ResultSet
Hence, full usability (SNMP Session + Result) available through a single object. my $s = SNMP::Class->new('myhost');$s->add('system');say $s->sysName->value;#orsay SNMP::Class->new('myhost')->add('system')->sysName->value;
18 SNMP::Class
Varbind Enhancement Roles Added functionality (new methods or override methods) for SNMP::Class::Varbind objects through SNMP::Class::Varbind:: roles Example:
#coming from SNMP::Class::Varbind$bridge_id->raw_value; #8 bytes,unprintable $bridge_id->value; # '80:00:00:06:28:84:D7:40'#coming from SNMP::Class::Varbind::BridgeId$bridge_id->mac_address #'00:06:28:84:D7:40'$bridge_id->priority #32768 • Applying of role at runtime, trigger when OID and value of Varbind
are known __PACKAGE__->meta->apply($_[0]);• Applying of multiple roles possible • Default Varbind 'value' method and other methods overridable by
roles 19 SNMP::Class
Code!
https://github.com/aduitsis/snmp-class
• Stuff in current presentation almost fully implemented • Many many varbind enhancement roles missing
(implementation on a need basis) • Only instrumentation so far from Net-SNMP • MIB parsing also from Net-SNMP • Obviously, bugs present • Built with Moose • Usage of Log::Log4Perl for logging • Test suite - but not 100% coverage
20 SNMP::Class
Future Directions
• Second instrumentation wrapper from Net::SNMP (Pure Perl)
• MIB parser other than from Net-SNMP • More Varbind enhancement roles • More performance fixes • Fix any bugs observed • Need to address snmpset functionality • Encapsulation of entire MIBs, hide SNMP completely.
o (also see the very good SNMP::Info module on CPAN)
21 SNMP::Class
