Internet Engineering Task Force M. Veillette, Ed.
Internet-Draft Trilliant Networks Inc.
Intended status: Standards Track November 30, 2016
Expires: June 3, 2017

Constrained YANG Module Library
draft-veillette-core-cool-library-00

Abstract

This document describes a library, which provides information about all YANG modules implemented by a CoOL server endpoint. A simple caching mechanism is provided to minimize retrieval of this information by CoOL clients.

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at http://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."

This Internet-Draft will expire on June 3, 2017.

Copyright Notice

Copyright (c) 2016 IETF Trust and the persons identified as the document authors. All rights reserved.

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.


Table of Contents

1. Introduction

The YANG module defined in this meno is available to CoOL clients to discover the different YANG data models supported by a CoOL server endpoint. The following YANG module information is needed by client applications to fully utilize the YANG data modeling language:

2. Terminology and Notation

The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in [RFC2119].

The following terms are defined in [I-D.ietf-netmod-rfc6020bis]:

The following terms are defined in [I-D.somaraju-core-sid]:

The following terms are defined in [I-D.veillette-core-cool]:

The following terms are used within this document:

3. Overview

The “ietf-cool-library” module provides information about the YANG library used by a server endpoint. This module is defined using YANG version 1, but it supports the description of YANG modules written in any revision of YANG.

3.1. Tree diagram

A simplified graphical representation of the YANG module specified in this document (ietf-cool-library) is provided below. The meaning of the symbols in this diagram is as follows:

module: ietf-cool-library
   +--ro modules-state
      +--ro module-set-id    union
      +--ro module* [sid revision]
         +--ro sid                 sid
         +--ro revision            revision
         +--ro feature*            sid
         +--ro deviation* [sid revision]
         |  +--ro sid         sid
         |  +--ro revision    revision
         +--ro conformance-type    enumeration
         +--ro submodule* [sid revision]
            +--ro sid         sid
            +--ro revision    revision
notifications:
   +---n cool-library-change
      +--ro module-set-id    -> /modules-state/module-set-id

3.2. Description

3.2.1. modules-state

This mandatory container holds the module set identifier and the list of modules supported by the server endpoint.

3.2.2. modules-state/module-set-id

This mandatory leaf contains an identifier representing the current set of modules and submodules used by a server endpoint. This identifier is endpoint-specific when implemented as unit32 or shared between multiple endpoints on one or multiple servers when implemented as identityref. The value of this leaf MUST change whenever the set of modules and submodules in the library changes. There is no requirement that the same set always results in the same module-set-id value.

This leaf allows a client to fetch the module list once, cache it, and only re-fetch it if the value of this leaf has been changed.

If the value of this leaf changes, the server also generates a “cool-library-change” notification, with the new value of “module-set-id”.

3.2.3. modules-state/module

This mandatory list contains one entry for each YANG module supported by the server endpoint. There MUST be an entry in this list for each revision of each YANG module that is used by the server.

4. YANG Module “ietf-cool-library”

RFC Ed.: update the date below with the date of RFC publication and remove this note.

<CODE BEGINS> file "ietf-cool-library@2016-06-01.yang"
module ietf-cool-library {
  namespace "urn:ietf:params:xml:ns:yang:ietf-cool-library";
  prefix "coollib";

  organization
    "IETF CORE (Constrained RESTful Environments) Working Group";

  contact
    "WG Web:   <http://datatracker.ietf.org/wg/core/>
    
     WG List:  <mailto:core@ietf.org>

     WG Chair: Carsten Bormann 
               <mailto:cabo@tzi.org>

     WG Chair: Jaime Jimenez 
               <mailto:jaime.jimenez@ericsson.com>

     Editor:   Michel Veillette
               <mailto:michel.veillette@trilliantinc.com>";

  description
    "This module contains the list of YANG modules and submodules
    implemented by a CoOL server endpoint.

     Copyright (c) 2016 IETF Trust and the persons identified as
     authors of the code.  All rights reserved.

     Redistribution and use in source and binary forms, with or
     without modification, is permitted pursuant to, and subject
     to the license terms contained in, the Simplified BSD License
     set forth in Section 4.c of the IETF Trust's Legal Provisions
     Relating to IETF Documents
     (http://trustee.ietf.org/license-info).

     This version of this YANG module is part of RFC XXXX; see
     the RFC itself for full legal notices.";

  // RFC Ed.: replace XXXX with actual RFC number and remove
  // this note.

  // RFC Ed.: update the date below with the date of the RFC
  // publication and remove this note.

  // RFC Ed.: update [I-D.somaraju-core-sid] with actual RFC
  // number and remove this note.
  
  revision 2016-06-01 {
    description
      "Initial revision.";
    reference
      "RFC XXXX: Contrained YANG Module Library.";
  }

  /*
   * Typedefs
   */

  typedef revision {
    type binary {
      length "4";
    }
    description
      "Revision date encoded as a binary string as follow:
      - First byte = Century
      - Second byte = Year (0 to 99)
      - Third byte = Month (1 = January to 12 = december)
      - Forth byte = Day (1 to 31)";
  }

  typedef sid {
    type uint32;
    description
      "Unique identifier assigned to different YANG items
      such as data nodes, RPCs and actions, notifications,
      modules, sub-modules, features and deviations. The SID
      registration process is defined in
      [I-D.somaraju-core-sid].";
  }
  
  /*
   * Groupings
   */

  grouping identification-info {
    description
      "YANG modules and submodules identification information.";

    leaf sid {
      type sid;
      mandatory true;
      description
        "SID assigned to this module or submodule.";
    }
    
    leaf revision {
      type revision;
      description
        "Revision date assigned to this module or submodule.
        A zero-length binary string is used if no revision statement
        is present in the YANG module or submodule.";
    }
  }
  
  identity module-set {
      description
        "Base identity from which shared module-set identifiers
        are derived.";
    }
  
  /*
   * Operational state data nodes
   */

  container modules-state {
    config false;
    description
      "Contain information about the different data models
      implement by a CoOL endpoint.";
    
    leaf module-set-id {
      type union {
        type uint32;
        type identityref {
          base "coollib:module-set";
        }
      }
      mandatory true;
      description
        "Identifier representing the current set of modules
        and submodules listed in the 'module' list. This
        identifier is endpoint-specific when implemented as
        unit32 or shared between multiple endpoints on one
        or multiple servers when implemented as identityref.
        The server MUST change the value of this leaf each
        time the information represented by the 'module'
        list instance changes.";
    }

    list module {
      key "sid revision";
      description
        "Each entry represents one revision of one module
         currently supported by the server endpoint.";

      uses identification-info;
      
      leaf-list feature {
        type sid;
        description
          "List of YANG features from this module that are
          supported by the server endpoint, regardless whether
          they are defined in the module or any included
          submodule.";
      }
      
      list deviation {
        key "sid revision";
        description
          "List of YANG deviation modules used by this server
          endpoint to modify the conformance of the module
          associated with this entry.  Note that the same module
          can be used for deviations for multiple modules, so the
          same entry MAY appear within multiple 'module' entries.

          The deviation module MUST be present in the 'module'
          list, with the same sid and revision values.
          The 'conformance-type' value will be 'implement' for
          the deviation module.";
          
        uses identification-info;
      }
      
      leaf conformance-type {
        type enumeration {
          enum implement {
            value 0;
            description
              "Indicates that the server endpoint implements one or
              more protocol-accessible objects defined in the YANG
              module identified in this entry.  This includes
              deviation statements defined in the module.

              For YANG version 1.1 modules, there is at most one
              module entry with conformance type 'implement' for a
              particular module, since YANG 1.1 requires that
              at most one revision of a module is implemented.

              For YANG version 1 modules, there SHOULD NOT be more
              than one module entry for a particular module.";
          }
          enum import {
            value 1;
            description
              "Indicates that the server endpoint imports reusable
              definitions from the specified revision of the module,
              but does not implement any protocol accessible objects
              from this revision.

              Multiple module entries for the same module MAY
              exist. This can occur if multiple modules import the
              same module, but specify different revision-dates in
              the import statements.";
          }
        }
        mandatory true;
        description
          "Indicates the type of conformance the server endpoint is
          claiming for the YANG module identified by this entry.";
      }
      
      list submodule {
        key "sid revision";
        description
          "Each entry represents one submodule within the
           parent module.";
        uses identification-info;
      }
    }
  }

  /*
   * Notifications
   */

  notification cool-library-change {
    description
      "Generated when the set of modules and submodules supported
      by the server endpoint has changed.";
      
    leaf module-set-id {
      type leafref {
        path "/coollib:modules-state/coollib:module-set-id";
      }
      mandatory true;
      description
        "Contains the module-set-id value representing the
        set of modules and submodules supported at the server
        endpoint at the time the notification is generated.";
    }
  }
}
<CODE ENDS>

5. IANA Considerations

5.1. YANG Module Registry

This document registers one YANG module in the YANG Module Names registry [I-D.ietf-netmod-rfc6020bis].

name: ietf-cool-library

namespace: urn:ietf:params:xml:ns:yang:ietf-cool-library

prefix: coollib

reference: RFC XXXX

// RFC Ed.: replace XXXX with RFC number and remove this note

6. Security Considerations

This YANG module is designed to be accessed via the CoOL protocol [I-D.veillette-core-cool]. Some of the readable data nodes in this YANG module may be considered sensitive or vulnerable in some network environments. It is thus important to control read access to these data nodes.

Specifically, the ‘module’ list may help an attacker identify the server capabilities and server implementations with known bugs. Server vulnerabilities may be specific to particular modules, module revisions, module features, or even module deviations. This information is included in each module entry. For example, if a particular operation on a particular data node is known to cause a server to crash or significantly degrade device performance, then the module list information will help an attacker identify server implementations with such a defect, in order to launch a denial of service attack on the device.

7. Acknowledgments

The YANG module defined by this memo have been derived from an already existing YANG module targeting the RESTconf protocol [I-D.ietf-netconf-restconf]. We will like to thank the authors of this prior work [I-D.ietf-netconf-yang-library] which have been essential for the development of “ietf-cool-library” targeting the Constrained Objects Language [I-D.veillette-core-cool] protocol. The authors would also like to thank Andy Bierman for his recommendations and his review of the resulting YANG module.

8. References

8.1. Normative References

[I-D.ietf-netmod-rfc6020bis] Bjorklund, M., "The YANG 1.1 Data Modeling Language", Internet-Draft draft-ietf-netmod-rfc6020bis-14, June 2016.
[I-D.somaraju-core-sid] Somaraju, A., Veillette, M., Pelov, A., Turner, R. and A. Minaburo, "Structure Identifier (SID)", Internet-Draft draft-somaraju-core-sid-01, July 2016.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.

8.2. Informative References

[I-D.ietf-netconf-restconf] Bierman, A., Bjorklund, M. and K. Watsen, "RESTCONF Protocol", Internet-Draft draft-ietf-netconf-restconf-18, October 2016.
[I-D.ietf-netconf-yang-library] Bierman, A., Bjorklund, M. and K. Watsen, "YANG Module Library", Internet-Draft draft-ietf-netconf-yang-library-06, April 2016.
[I-D.veillette-core-cool] Veillette, M., Pelov, A., Somaraju, A., Turner, R. and A. Minaburo, "Constrained Objects Language", Internet-Draft draft-veillette-core-cool-02, July 2016.

Author's Address

Michel Veillette (editor) Trilliant Networks Inc. 610 Rue du Luxembourg Granby, Quebec J2J 2V2 Canada Phone: +14503750556 EMail: michel.veillette@trilliantinc.com
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