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  • 1. SNMP::Class! Athanasios Douitsis
  • 2. 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     SNMP::Class 2
  • 3. Very Brief SNMP Intro ExamplePiece 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  SNMP::Class 3
  • 4. Writing network management toolsNetwork 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 sizesoftware SNMP::Class 4
  • 5. 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 SNMP::Class 5
  • 6. Problem Statement (2)Impedance mismatch between the programming language (notjust Perl) and the SNMP-SMI worldIssues: •  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 SNMP::Class 6
  • 7. 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}     } } SNMP::Class 7
  • 8. 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 SNMP::Class 8
  • 9. Library Overview - Connection Setupmy $c = SNMP::Class->new(myrouter.mydomain); •  Probing of SNMP version (try 2, then 1)•  Querying of sysName.0 SNMP::Class 9
  • 10. 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 SNMP::Class 10
  • 11. 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 availableExamples:$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 $bridge_id->priority #32768 SNMP::Class 11
  • 12. Library Overview - Querying of agent$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  $c: connection object and result object SNMP::Class 12
  • 13. Library Overview - The ResultSetResultSet -  a set of OID-value pairs (varbinds)•  Filtering of set through methods$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 }); SNMP::Class 13
  • 14. 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 $rs->find(ifDescr => eth0)->ifSpeed->value; #Keep the instance for which the ifDescr equals eth0, thenkeep only the ifSpeed.  SNMP::Class 14
  • 15. Library Overview - The ResultSet (3) •  Iteration over contents, detection of list context#print the description of each interface for($rs->ifDescr) {      say $_->value  } •  Filter and map methods o  Used exactly as list grep and map with BLOCKmy $new_rs = $rs->filter(sub { ..... }); my $new_rs = $rs->map(sub { ..... });      SNMP::Class 15
  • 16. Library Overview - The ResultSet (4)•  Final touch: Resultset with 1 varbind:$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 . SNMP::Class 16
  • 17. 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) SNMP::Class 17
  • 18. Library Roles (2)SNMP::Class is-a: •  SNMP::Class::Role::Implementation::NetSNMP •  SNMP::Class::Role::ResultSetHence, full usability (SNMP Session + Result) available througha single object.my $s = SNMP::Class->new(myhost); $s->add(system); say $s->sysName->value; #or say SNMP::Class->new(myhost)->add(system)->sysName->value; SNMP::Class 18
  • 19. Varbind Enhancement Roles Added functionality (new methods or override methods) forSNMP::Class::Varbind objects through SNMP::Class::Varbind::rolesExample:#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 SNMP::Class 19
  • 20. 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 SNMP::Class 20
  • 21. 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)  SNMP::Class 21
  • 22. Thank you for your attention aduitsis@cpan.org