NETMOD WG C. Wildes, Ed.
Internet-Draft K. Koushik, Ed.
Intended status: Standards Track Cisco Systems Inc.
Expires: May 17, 2017 November 13, 2016

A YANG Data Model for Syslog Configuration
draft-ietf-netmod-syslog-model-11

Abstract

This document describes a data model for the configuration of syslog.

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 May 17, 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

Operating systems, processes and applications generate messages indicating their own status or the occurrence of events. These messages are useful for managing and/or debugging the network and its services. The BSD syslog protocol is a widely adopted protocol that is used for transmission and processing of the messages.

Since each process, application and operating system was written somewhat independently, there is little uniformity to the content of syslog messages. For this reason, no assumption is made upon the formatting or contents of the messages. The protocol is simply designed to transport these event messages. No acknowledgement of the receipt is made.

Essentially, a syslog process receives messages (from the kernel, processes, applications or other syslog processes) and processes those. The processing involves logging to a local file, displaying on console, user terminal, and/or relaying to syslog processes on other machines. The processing is determined by the "facility" that originated the message and the "severity" assigned to the message by the facility.

We are using definitions of syslog protocol from [RFC5424] in this RFC.

1.1. Requirements Language

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 RFC 2119 [RFC2119].

1.2. Terminology

The term "originator" is defined in [RFC5424]: an "originator" generates syslog content to be carried in a message.

The terms "relay" and "collectors" are as defined in [RFC5424].

2. Problem Statement

This document defines a YANG [RFC6020] configuration data model that may be used to configure the syslog feature running on a system. YANG models can be used with network management protocols such as NETCONF [RFC6241] to install, manipulate, and delete the configuration of network devices.

The data model makes use of the YANG "feature" construct which allows implementations to support only those syslog features that lie within their capabilities.

This module can be used to configure the syslog application conceptual layers as implemented on the target system [RFC5424].

3. Design of the Syslog Model

The syslog model was designed by comparing various syslog features implemented by various vendors' in different implementations.

This draft addresses the common leafs between implementations and creates a common model, which can be augmented with proprietary features, if necessary. The base model is designed to be very simple for maximum flexibility.

Syslog consists of originators, and collectors. The following digram shows syslog messages flowing from an originator, to collectors where suppression filtering can take place.

Many vendors extend the list of facilities available for logging in their implementation. An example is included in Extending Facilities [extending_facilities].

Originators  
  +-------------+  +-------------+  +-------------+  +-------------+
  |  Various    |  |     OS      |  |             |  |   Remote    |
  | Components  |  |   Kernel    |  | Line Cards  |  |   Servers   |
  +-------------+  +-------------+  +-------------+  +-------------+  

  +-------------+  +-------------+  +-------------+  +-------------+
  |    SNMP     |  |  Interface  |  |   Standby   |  |   Syslog    |
  |   Events    |  |   Events    |  |  Supervisor |  |   Itself    |
  +-------------+  +-------------+  +-------------+  +-------------+

  |                                                                |
  +----------------------------------------------------------------+
               |
               |
               |
               |
       +-----------+------------+--------------+
       |           |            |              |
       v           v            v              |
Collectors                           |
  +----------+ +----------+ +----------+       |
  |          | |  Log     | | Log      |       |
  | Console  | |  Buffer  | | File(s)  |       |
  +----------+ +----------+ +----------+       |
                                               |
                                             +-+-------------+
                                             |               |                                   
                                             v               v
                                    
                                     +----------------+ +-----------+
                                     |Remote Relay(s)/| |User       |
                                     |Collectors(s)   | |Sessions(s)|
                                     +----------------+ +-----------+
       

Figure 1. Syslog Processing Flow

The leaves in the base syslog model actions container correspond to each message collector:

Within each action, a selector is used to filter syslog messages. A selector consists of two parts: one or more facility-severity matches, and if supported via the select-match feature, an optional regular expression pattern match that is performed on the SYSLOG-MSG field.

The facility is one of a specific syslogtypes:syslog-facility, none, or all facilities. None is a special case that can be used to disable an action.

The severity is one of syslogtypes:severity, all severities, or none. None is a special case that can be used to disable a facility. When filtering severity, the default comparison is that all messages of the specified severity and higher are logged. This is shown in the model as ?default equals-or-higher?. This behavior can be altered if the select-sev-compare feature is enabled to specify: ?equals? to specify only this single severity; ?not-equals? to ignore that severity; ?equals-or-higher? to specify all messages of the specified severity and higher.

Optional features are used to specified functionality that is present in specific vendor configurations.

3.1. Syslog Module

A simplified graphical representation of the complete data tree is presented here.

Each node is printed as:

<status> <flags> <name> <opts> <type> <if-features>

          +  for current
          x  for deprecated
          o  for obsolete
         

<status> is one of:

          rw  for configuration data
          ro  for non-configuration data
          -x  for rpcs
          -n  for notifications
         

<flags> is one of:

          (<name>) means that the node is a choice node
          :(<name>) means that the node is a case node
         

<name> is the name of the node

If the node is augmented into the tree from another module, its name is printed as <prefix>:<name>.

          ?  for an optional leaf or choice
          !  for a presence container
          *  for a leaf-list or list
          [<keys>] for a list's keys
         

<opts> is one of:

<type> is the name of the type for leafs and leaf-lists

If the type is a leafref, the type is printed as "-> TARGET", where TARGET is either the leafref path, with prefixed removed if possible.

<if-features> is the list of features this node depends on, printed within curly brackets and a question mark "{...}?"

module: ietf-syslog
   +--rw syslog!
      +--rw actions
         +--rw console!
         |  +--rw selector
         |     +--rw (selector-facility)
         |     |  +--:(facility)
         |     |  |  +--rw no-facilities?   empty
         |     |  +--:(name)
         |     |     +--rw facility-list* [facility]
         |     |        +--rw facility    union
         |     |        +--rw severity    union
         |     |        +--rw compare?    enumeration {select-sev-compare}?
         |     +--rw pattern-match?   string {select-match}?
         +--rw buffer {buffer-action}?
         |  +--rw selector
         |  |  +--rw (selector-facility)
         |  |  |  +--:(facility)
         |  |  |  |  +--rw no-facilities?   empty
         |  |  |  +--:(name)
         |  |  |     +--rw facility-list* [facility]
         |  |  |        +--rw facility    union
         |  |  |        +--rw severity    union
         |  |  |        +--rw compare?    enumeration {select-sev-compare}?
         |  |  +--rw pattern-match?   string {select-match}?
         |  +--rw structured-data?         boolean {structured-data}?
         |  +--rw buffer-limit-bytes?      uint64 {buffer-limit-bytes}?
         |  +--rw buffer-limit-messages?   uint64 {buffer-limit-messages}?
         +--rw file
         |  +--rw log-file* [name]
         |     +--rw name               inet:uri
         |     +--rw selector
         |     |  +--rw (selector-facility)
         |     |  |  +--:(facility)
         |     |  |  |  +--rw no-facilities?   empty
         |     |  |  +--:(name)
         |     |  |     +--rw facility-list* [facility]
         |     |  |        +--rw facility    union
         |     |  |        +--rw severity    union
         |     |  |        +--rw compare?    enumeration {select-sev-compare}?
         |     |  +--rw pattern-match?   string {select-match}?
         |     +--rw structured-data?   boolean {structured-data}?
         |     +--rw file-rotation
         |        +--rw number-of-files?   uint32 {file-limit-size}?
         |        +--rw max-file-size?     uint64 {file-limit-size}?
         |        +--rw rollover?          uint32 {file-limit-duration}?
         |        +--rw retention?         uint16 {file-limit-duration}?
         +--rw remote
         |  +--rw destination* [name]
         |     +--rw name                 string
         |     +--rw (transport)
         |     |  +--:(tcp)
         |     |  |  +--rw tcp
         |     |  |     +--rw address?   inet:host
         |     |  |     +--rw port?      inet:port-number
         |     |  +--:(udp)
         |     |     +--rw udp
         |     |        +--rw address?   inet:host
         |     |        +--rw port?      inet:port-number
         |     +--rw selector
         |     |  +--rw (selector-facility)
         |     |  |  +--:(facility)
         |     |  |  |  +--rw no-facilities?   empty
         |     |  |  +--:(name)
         |     |  |     +--rw facility-list* [facility]
         |     |  |        +--rw facility    union
         |     |  |        +--rw severity    union
         |     |  |        +--rw compare?    enumeration {select-sev-compare}?
         |     |  +--rw pattern-match?   string {select-match}?
         |     +--rw structured-data?     boolean {structured-data}?
         |     +--rw facility-override?   identityref
         |     +--rw source-interface?    if:interface-ref
         |     +--rw signing-options! {signed-messages}?
         |        +--rw cert-initial-repeat    uint16
         |        +--rw cert-resend-delay      uint16
         |        +--rw cert-resend-count      uint16
         |        +--rw max-delay              uint16
         |        +--rw number-resends         uint16
         |        +--rw resend-delay           uint16
         |        +--rw resend-count           uint16
         +--rw session
            +--rw all-users!
            |  +--rw selector
            |     +--rw (selector-facility)
            |     |  +--:(facility)
            |     |  |  +--rw no-facilities?   empty
            |     |  +--:(name)
            |     |     +--rw facility-list* [facility]
            |     |        +--rw facility    union
            |     |        +--rw severity    union
            |     |        +--rw compare?    enumeration {select-sev-compare}?
            |     +--rw pattern-match?   string {select-match}?
            +--rw user* [name]
               +--rw name        string
               +--rw selector
                  +--rw (selector-facility)
                  |  +--:(facility)
                  |  |  +--rw no-facilities?   empty
                  |  +--:(name)
                  |     +--rw facility-list* [facility]
                  |        +--rw facility    union
                  |        +--rw severity    union
                  |        +--rw compare?    enumeration {select-sev-compare}?
                  +--rw pattern-match?   string {select-match}?
         

Figure 2. ietf-syslog Module Tree

4. Syslog YANG Modules

4.1. The ietf-syslog-types Module

This module references [RFC5424].

<CODE BEGINS> file "ietf-syslog-types.yang"
module ietf-syslog-types {
  namespace "urn:ietf:params:xml:ns:yang:ietf-syslog-types";
  prefix syslogtypes;

  organization "IETF NETMOD (NETCONF Data Modeling Language) Working 
                Group";
  contact
    "WG Web:   <http://tools.ietf.org/wg/netmod/>
     WG List:  <mailto:netmod@ietf.org>
     
     WG Chair: Lou Berger
               <mailto:lberger@labn.net>
     
     WG Chair: Kent Watsen
               <mailto:kwatsen@juniper.net>
     
     Editor:   Kiran Agrahara Sreenivasa
               <mailto:kkoushik@cisco.com>
     
     Editor:   Clyde Wildes
               <mailto:cwildes@cisco.com>";
  description
    "This module contains a collection of YANG type definitions for 
     SYSLOG.

     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).

     The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
     NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY', and
     'OPTIONAL' in the module text are to be interpreted as described
     in RFC 2119 (http://tools.ietf.org/html/rfc2119).

     This version of this YANG module is part of RFC XXXX
     (http://tools.ietf.org/html/rfcXXXX); see the RFC itself for
     full legal notices.";

  reference
    "RFC 5424: The Syslog Protocol";

  revision 2016-11-13 {
    description
      "Initial Revision";
    reference
      "RFC XXXX: SYSLOG YANG Model";
  }

  typedef severity {
    type enumeration {
      enum "emergency" {
        value 0;
        description
          "The severity level 'Emergency' indicating that the system 
           is unusable.";
      }
      enum "alert" {
        value 1;
        description
          "The severity level 'Alert' indicating that an action must be 
           taken immediately.";
      }
      enum "critical" {
        value 2;
        description
          "The severity level 'Critical' indicating a critical condition.";
      }
      enum "error" {
        value 3;
        description
          "The severity level 'Error' indicating an error condition.";
      }
      enum "warning" {
        value 4;
        description
          "The severity level 'Warning' indicating a warning condition.";
      }
      enum "notice" {
        value 5;
        description
          "The severity level 'Notice' indicating a normal but significant 
           condition.";
      }
      enum "info" {
        value 6;
        description
          "The severity level 'Info' indicating an informational message.";
      }
      enum "debug" {
        value 7;
        description
          "The severity level 'Debug' indicating a debug-level message.";
      }
    }
    description
      "The definitions for Syslog message severity as per RFC 5424.";
  }

  identity syslog-facility {
    description
      "This identity is used as a base for all syslog facilities as
       per RFC 5424.";
  }

  identity kern {
    base syslog-facility;
    description
      "The facility for kernel messages (0) as defined in RFC 5424.";
  }

  identity user {
    base syslog-facility;
    description
      "The facility for user-level messages (1) as defined in RFC 5424.";
  }

  identity mail {
    base syslog-facility;
    description
      "The facility for the mail system (2) as defined in RFC 5424.";
  }

  identity daemon {
    base syslog-facility;
    description
      "The facility for the system daemons (3) as defined in RFC 5424.";
   }

  identity auth {
    base syslog-facility;
    description
      "The facility for security/authorization messages (4) as defined 
       in RFC 5424.";
  }

  identity syslog {
    base syslog-facility;
    description
      "The facility for messages generated internally by syslogd 
       facility (5) as defined in RFC 5424.";
  }

  identity lpr {
    base syslog-facility;
    description
      "The facility for the line printer subsystem (6) as defined in 
       RFC 5424.";
  }

  identity news {
    base syslog-facility;
    description
      "The facility for the network news subsystem (7) as defined in 
       RFC 5424.";
  }

  identity uucp {
    base syslog-facility;
    description
      "The facility for the UUCP subsystem (8) as defined in RFC 5424.";
  }

  identity cron {
    base syslog-facility;
    description
      "The facility for the clock daemon (9) as defined in RFC 5424.";
  }

  identity authpriv {
    base syslog-facility;
    description
      "The facility for privileged security/authorization messages (10) 
       as defined in RFC 5424.";
  }

  identity ftp {
    base syslog-facility;
    description
      "The facility for the FTP daemon (11) as defined in RFC 5424.";
  }

  identity ntp {
    base syslog-facility;
    description
      "The facility for the NTP subsystem (12) as defined in RFC 5424.";
  }

  identity audit {
    base syslog-facility;
    description
      "The facility for log audit messages (13) as defined in RFC 5424.";
  }

  identity console {
    base syslog-facility;
    description
      "The facility for log alert messages (14) as defined in RFC 5424.";
  }

  identity cron2 {
    base syslog-facility;
    description
      "The facility for the second clock daemon (15) as defined in 
       RFC 5424.";
  }

  identity local0 {
    base syslog-facility;
    description
      "The facility for local use 0 messages (16) as defined in 
       RFC 5424.";
  }

  identity local1 {
    base syslog-facility;
    description
      "The facility for local use 1 messages (17) as defined in 
       RFC 5424.";
  }

  identity local2 {
    base syslog-facility;
    description
      "The facility for local use 2 messages (18) as defined in 
       RFC 5424.";
  }

  identity local3 {
    base syslog-facility;
    description
      "The facility for local use 3 messages (19) as defined in 
       RFC 5424.";
  }

  identity local4 {
    base syslog-facility;
    description
      "The facility for local use 4 messages (20) as defined in 
       RFC 5424.";
  }

  identity local5 {
    base syslog-facility;
    description
      "The facility for local use 5 messages (21) as defined in 
       RFC 5424.";
  }

  identity local6 {
    base syslog-facility;
    description
      "The facility for local use 6 messages (22) as defined in 
       RFC 5424.";
  }

  identity local7 {
    base syslog-facility;
    description
      "The facility for local use 7 messages (23) as defined in 
       RFC 5424.";
  }
}
<CODE ENDS>
       

Figure 3. ietf-syslog-types Module

4.2. The ietf-syslog Module

This module imports typedefs from [RFC6021] and [RFC7223], and it references [RFC5424], [RFC5425], [RFC5426], [RFC6587], and [RFC5848].

<CODE BEGINS> file "ietf-syslog.yang"
module ietf-syslog {
  namespace "urn:ietf:params:xml:ns:yang:ietf-syslog";
  prefix syslog;

  import ietf-inet-types {
    prefix inet;
  }

  import ietf-interfaces {
    prefix if;
  }

  import ietf-syslog-types {
    prefix syslogtypes;
  }

  organization "IETF NETMOD (NETCONF Data Modeling Language) 
  Working Group";
  contact
    "WG Web:   <http://tools.ietf.org/wg/netmod/>
     WG List:  <mailto:netmod@ietf.org>
     
     WG Chair: Lou Berger
               <mailto:lberger@labn.net>
     
     WG Chair: Kent Watsen
               <mailto:kwatsen@juniper.net>
     
     Editor:   Kiran Agrahara Sreenivasa
               <mailto:kkoushik@cisco.com>
     
     Editor:   Clyde Wildes
               <mailto:cwildes@cisco.com>";
  description
    "This module contains a collection of YANG definitions 
     for syslog configuration.

     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).

     The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
     NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY', and
     'OPTIONAL' in the module text are to be interpreted as described
     in RFC 2119 (http://tools.ietf.org/html/rfc2119).

     This version of this YANG module is part of RFC XXXX
     (http://tools.ietf.org/html/rfcXXXX); see the RFC itself for
     full legal notices.";

  reference
    "RFC 5424: The Syslog Protocol
     RFC 5426: Transmission of Syslog Messages over UDP
     RFC 6587: Transmission of Syslog Messages over TCP
     RFC 5848: Signed Syslog Messages";

  revision 2016-11-13 {
    description
      "Initial Revision";
    reference
      "RFC XXXX: Syslog YANG Model";
  }

  feature buffer-action {
    description
      "This feature indicates that the local memory logging buffer
       action is supported.";
  }

  feature buffer-limit-bytes {
    description
      "This feature indicates that the local memory logging buffer
       is limited in size using a limit expressed in bytes.";
  }

  feature buffer-limit-messages {
    description
      "This feature indicates that the local memory logging buffer
       is limited in size using a limit expressed in number of log
       messages.";
  }

  feature file-limit-size {
    description
      "This feature indicates that file logging resources
       are managed using size and number limits.";
  }

  feature file-limit-duration {
    description
      "This feature indicates that file logging resources
       are managed using time based limits.";
  }

  feature select-sev-compare {
    description
      "This feature represents the ability to select messages 
       using the additional operators equal to, or not equal to 
       when comparing the syslog message severity.";
  }

  feature select-match {
    description
      "This feature represents the ability to select messages based
       on a Posix 1003.2 regular expression pattern match.";
  }

  feature structured-data {
    description
      "This feature represents the ability to log messages 
       in structured-data format as per RFC 5424.";
  }

  feature signed-messages {
    description
      "This feature represents the ability to configure signed 
       syslog messages according to RFC 5848.";
  }

  grouping log-severity {
    description
      "This grouping defines the severity value that is used to 
       select log messages.";
    leaf severity {
      type union {
        type syslogtypes:severity;
        type enumeration {
          enum none {
            value -2;
            description
              "This enum describes the case where no severities 
               are selected.";
          }
          enum all {
            value -1;
            description
              "This enum describes the case where all severities 
               are selected.";
          }
        }
      }
      mandatory true;
      description
        "This leaf specifies the syslog message severity. When 
         severity is specified, the default severity comparison 
         is all messages of the specified severity and greater are 
         selected. 'all' is a special case which means all severities
         are selected. 'none' is a special case which means that
         no selection should occur or disable this filter.";
    }
    leaf compare {
      when '../severity != "all" and
           ../severity != "none"' {
        description
          "The compare leaf is not applicable for severity 'all' or 
           severity 'none'";
      }
      if-feature select-sev-compare;
      type enumeration {
        enum equals-or-higher {
          description
            "This enum specifies all messages of the specified 
             severity and higher are logged according to the 
             given log-action";
        }
        enum equals {
          description
            "This enum specifies all messages that are for 
             the specified severity are logged according to the 
             given log-action";
        }
        enum not-equals {
          description
            "This enum specifies all messages that are not for 
             the specified severity are logged according to the 
             given log-action";
        }
      }
      default equals-or-higher;
      description
        "This leaf describes the option to specify how the 
         severity comparison is performed.";
    }
  }

  grouping selector {
    description
      "This grouping defines a syslog selector which is used to 
       select log messages for the log-action (console, file, 
       remote, etc). Choose one of the following:
         no-facility
         facility [<facility> <severity>...]";
    container selector {
      description
        "This container describes the log selector parameters 
         for syslog.";
      choice selector-facility {
        mandatory true;
        description
          "This choice describes the option to specify no 
           facilities, or a specific facility which can be
           all for all facilities.";
        case facility {
          description
            "This case specifies no facilities will match when 
             comparing the syslog message facility. This is a 
             method that can be used to effectively disable a 
             particular log-action (buffer, file, etc).";
          leaf no-facilities {
            type empty;
            description
            "This leaf specifies that no facilities are selected 
             for this log-action.";
          }
        }
        case name {
          description
            "This case specifies one or more specified facilities 
             will match when comparing the syslog message facility.";
          list facility-list {
            key facility;
            description
              "This list describes a collection of syslog 
               facilities and severities.";
            leaf facility {
              type union {
                type identityref {
                  base syslogtypes:syslog-facility;
                }
                type enumeration {
                  enum all {
                    description
                      "This enum describes the case where all 
                       facilities are requested.";
                  }
                }
              }
              description
                "The leaf uniquely identifies a syslog facility.";
            }
            uses log-severity;
          }
        }
      }
      leaf pattern-match {
        if-feature select-match;
        type string;
        description
          "This leaf desribes a Posix 1003.2 regular expression 
           string that can be used to select a syslog message for 
           logging. The match is performed on the RFC 5424 
           SYSLOG-MSG field.";
      }
    }
  }

  grouping structured-data {
    description
      "This grouping defines the syslog structured data option 
       which is used to select the format used to write log 
       messages.";
    leaf structured-data {
      if-feature structured-data;
      type boolean;
      default false;
      description
        "This leaf describes how log messages are written. 
         If true, messages will be written with one or more 
         STRUCTURED-DATA elements as per RFC5424; if false, 
         messages will be written with STRUCTURED-DATA = 
         NILVALUE.";
    }
  }

  container syslog {
    presence "Enables logging.";
    description
      "This container describes the configuration parameters for 
       syslog.";
    container actions {
      description
        "This container describes the log-action parameters 
         for syslog.";
      container console {
        presence "Enables logging console configuration";
        description
          "This container describes the configuration parameters for 
           console logging.";
        uses selector;
      }
      container buffer {
        if-feature buffer-action;
        description
          "This container describes the configuration parameters for 
           local memory buffer logging. The buffer is circular in 
           nature, so newer messages overwrite older messages after 
           the buffer is filled. The method used to read syslog messages
           from the buffer is supplied by the local implementation.";
        uses selector;
        uses structured-data;
        leaf buffer-limit-bytes {
          if-feature buffer-limit-bytes;
          type uint64;
          units "bytes";
          description
            "This leaf configures the amount of memory (in bytes) that 
             will be dedicated to the local memory logging buffer. 
             The default value varies by implementation.";
        }
        leaf buffer-limit-messages {
          if-feature buffer-limit-messages;
          type uint64;
          units "log messages";
          description
            "This leaf configures the number of log messages that 
             will be dedicated to the local memory logging buffer. 
             The default value varies by implementation.";
        }
      }
      container file {
        description
          "This container describes the configuration parameters for 
           file logging. If file-archive limits are not supplied, it
           is assumed that the local implementation defined limits will 
           be used.";
        list log-file {
          key "name";
          description
            "This list describes a collection of local logging 
             files.";
          leaf name {
            type inet:uri {
              pattern 'file:.*';
            }
            description
              "This leaf specifies the name of the log file which 
               MUST use the uri scheme file:.";
          }
          uses selector;
          uses structured-data;
          container file-rotation {
            description
              "This container describes the configuration 
               parameters for log file rotation.";
            leaf number-of-files {
              if-feature file-limit-size;
              type uint32;
              description
                "This leaf specifies the maximum number of log 
                 files retained. Specify 1 for implementations 
                 that only support one log file.";
            }
            leaf max-file-size {
              if-feature file-limit-size;
              type uint64;
              units "megabytes";
              description
                "This leaf specifies the maximum log file size.";
            }
            leaf rollover {
              if-feature file-limit-duration;
              type uint32;
              units "minutes";
              description
                "This leaf specifies the length of time that log 
                 events should be written to a specific log file. 
                 Log events that arrive after the rollover period 
                 cause the current log file to be closed and a new 
                 log file to be opened.";
            }
            leaf retention {
              if-feature file-limit-duration;
              type uint16;
              units "hours";
              description
                "This leaf specifies the length of time that 
                 completed/closed log event files should be stored 
                 in the file system before they are deleted.";
            }
          }
        }
      }
      container remote {
        description
          "This container describes the configuration parameters for 
           forwarding syslog messages to remote relays or collectors.";
        list destination {
          key "name";
          description
            "This list describes a collection of remote logging 
             destinations.";
          leaf name {
            type string;
            description
              "An arbitrary name for the endpoint to connect to.";
          }
          choice transport {
            mandatory true;
            description
              "This choice describes the transport option.";
            case tcp {
              container tcp {
                description
                  "This container describes the TCP transport
                   options.";
                reference
                  "RFC 6587: Transmission of Syslog Messages over TCP";
                leaf address {
                  type inet:host;
                  description
                    "The leaf uniquely specifies the address of 
                     the remote host. One of the following must 
                     be specified: an ipv4 address, an ipv6 
                     address, or a host name.";
                }
                leaf port {
                  type inet:port-number;
                  default 514;
                  description
                    "This leaf specifies the port number used to 
                     deliver messages to the remote server.";
                }
              }
            }
            case udp {
              container udp {
                description
                  "This container describes the UDP transport
                   options.";
                reference
                  "RFC 5426: Transmission of Syslog Messages over UDP";
                leaf address {
                  type inet:host;
                  description
                    "The leaf uniquely specifies the address of 
                     the remote host. One of the following must be 
                     specified: an ipv4 address, an ipv6 address, 
                     or a host name.";
                }
                leaf port {
                  type inet:port-number;
                  default 514;
                  description
                    "This leaf specifies the port number used to 
                     deliver messages to the remote server.";
                }
              }
            }
          }
          uses selector;
          uses structured-data;
          leaf facility-override {
            type identityref {
              base syslogtypes:syslog-facility;
            }
            description
              "If specified, this leaf specifies the facility used 
               to override the facility in messages delivered to the 
               remote server.";
          }
          leaf source-interface {
            type if:interface-ref;
            description
              "This leaf sets the source interface to be used to send 
               message to the remote syslog server. If not set, 
               messages sent to a remote syslog server will 
               contain the IP address of the interface the syslog 
               message uses to exit the network element";
          }
          container signing-options {
            if-feature signed-messages;
            presence
              "If present, syslog-signing options is activated.";
            description
              "This container describes the configuration 
               parameters for signed syslog messages as described 
               by RFC 5848.";
            reference
              "RFC 5848: Signed Syslog Messages";
            leaf cert-initial-repeat {
              type uint16;
              mandatory true;
              description
              "This leaf specifies the number of times each 
               Certificate Block should be sent before the first 
               message is sent.";
            }
            leaf cert-resend-delay {
              type uint16;
              units "seconds";
              mandatory true;
              description
                "This leaf specifies the maximum time delay in 
                 seconds until resending the Certificate Block.";
            }
            leaf cert-resend-count {
              type uint16;
              mandatory true;
              description
                "This leaf specifies the maximum number of other 
                 syslog messages to send until resending the 
                 Certificate Block.";
            }
            leaf max-delay {
              type uint16;
              units "seconds";
              mandatory true;
              description
                "This leaf specifies when to generate a new 
                 Signature Block. If this many seconds have 
                 elapsed since the message with the first message 
                 number of the Signature Block was sent, a new 
                 Signature Block should be generated.";
            }
            leaf number-resends {
              type uint16;
              mandatory true;
              description
                "This leaf specifies the number of times a 
                 Signature Block is resent. (It is recommended to 
                 select a value of greater than 0 in particular 
                 when the UDP transport [RFC5426] is used.).";
            }
            leaf resend-delay {
              type uint16;
              units "seconds";
              mandatory true;
              description
                "This leaf specifies when to send the next 
                 Signature Block transmission based on time. If 
                 this many seconds have elapsed since the previous 
                 sending of this Signature Block, resend it.";
            }
            leaf resend-count {
              type uint16;
              mandatory true;
              description
                "This leaf specifies when to send the next 
                 Signature Block transmission based on a count. 
                 If this many other syslog messages have been sent 
                 since the previous sending of this Signature 
                 Block, resend it.";
            }
          }
        }
      }
      container session {
        description
          "This container describes the configuration parameters for
           user CLI session logging configuration.";
        container all-users {
          presence "Enables logging to all user sessions.";
          description
            "This container describes the configuration
             parameters for all users.";
          uses selector;
        }
        list user {
          key "name";
          description
            "This list describes a collection of user names.";
          leaf name {
            type string;
            description
              "This leaf uniquely describes a user name which
               is the login name of the user whose session
               is to receive log messages.";
          }
          uses selector;
        }
      }
    }
  }
}
<CODE ENDS>
       

Figure 4. ietf-syslog Module

5. Usage Examples

   Requirement:
   Enable console logging of syslogs of severity critical
  
   Here is the example syslog configuration xml:
   <config xmlns:xc="urn:ietf:params:xml:ns:netconf:base:1.0">
     <syslog xmlns="urn:ietf:params:xml:ns:yang:ietf-syslog"
             xmlns:syslog="urn:ietf:params:xml:ns:yang:ietf-syslog">
       <actions>
         <console>
           <selector>
             <facility-list>
               <facility>all</facility>
               <severity>critical</severity>
             </facility>
           </selector>
         </console>
       </actions>
     </syslog>
   </config>

   Enable remote logging of syslogs to udp destination 2001:db8:a0b:12f0::1
   for facility auth, severity error

   <config xmlns:xc="urn:ietf:params:xml:ns:netconf:base:1.0">
     <syslog xmlns="urn:ietf:params:xml:ns:yang:ietf-syslog"
             xmlns:syslog="urn:ietf:params:xml:ns:yang:ietf-syslog">
       <actions>
         <remote>
           <destination>
             <name>remote1</name>
             <udp>
               <address>2001:db8:a0b:12f0::1</address>
             </udp>
             <selector>
               <facility-list>
                 <facility xmlns:syslogtypes=
                   "urn:ietf:params:xml:ns:yang:ietf-syslog-types">
                   syslogtypes:auth</facility>
                 <severity>error</severity>
               <facility>
             <selector>
           </destination>
         </remote>
       </actions>
     </syslog>
   </config>
       

Figure 5. ietf-syslog Examples

6. Acknowledgements

The authors wish to thank the following who commented on this proposal:

7. IANA Considerations

This document registers two URIs in the IETF XML registry [RFC3688].

Following the format in RFC 3688, the following registration is requested to be made:

URI: urn:ietf:params:xml:ns:yang:ietf-syslog-types

Registrant Contact: The IESG.

XML: N/A, the requested URI is an XML namespace.

This document registers a YANG module in the YANG Module Names registry [RFC6020].

name: ietf-syslog-types namespace: urn:ietf:params:xml:ns:yang:ietf-syslog-types

prefix: ietf-syslog-types reference: RFC XXXX

Following the format in RFC 3688, the following registration is requested to be made:

URI: urn:ietf:params:xml:ns:yang:ietf-syslog

Registrant Contact: The IESG.

XML: N/A, the requested URI is an XML namespace.

This document registers a YANG module in the YANG Module Names registry [RFC6020].

name: ietf-syslog namespace: urn:ietf:params:xml:ns:yang:ietf-syslog

prefix: ietf-syslog

reference: RFC XXXX

8. Security Considerations

The YANG module defined in this memo is designed to be accessed via the NETCONF protocol [RFC6241]. The lowest NETCONF layer is the secure transport layer and the mandatory-to-implement secure transport is SSH [RFC6242]. The NETCONF access control model [RFC6536] provides the means to restrict access for particular NETCONF users to a pre-configured subset of all available NETCONF protocol operations and content.

There are a number of data nodes defined in the YANG module which are writable/creatable/deletable (i.e., config true, which is the default). These data nodes may be considered sensitive or vulnerable in some network environments. Write operations (e.g., <edit-config>) to these data nodes without proper protection can have a negative effect on network operations.

8.1. Resource Constraints

Network administrators must take the time to estimate the appropriate memory limits caused by the configuration of actions/buffer using buffer-limit-bytes and/or buffer-limit-messages where necessary to limit the amount of memory used.

Network administrators must take the time to estimate the appropriate storage capacity caused by the configuration of actions/file using file-archive attributes to limit storage used.

It is the responsibility of the network administrator to ensure that the configured message flow does not overwhelm system resources.

8.2. Inappropriate Configuration

It is the responsibility of the network admisintrator to ensure that the messages are actually going to the intended recipients.

9. References

9.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.
[RFC5424] Gerhards, R., "The Syslog Protocol", RFC 5424, DOI 10.17487/RFC5424, March 2009.
[RFC5426] Okmianski, A., "Transmission of Syslog Messages over UDP", RFC 5426, DOI 10.17487/RFC5426, March 2009.
[RFC5848] Kelsey, J., Callas, J. and A. Clemm, "Signed Syslog Messages", RFC 5848, DOI 10.17487/RFC5848, May 2010.
[RFC6020] Bjorklund, M., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, DOI 10.17487/RFC6020, October 2010.
[RFC6021] Schoenwaelder, J., "Common YANG Data Types", RFC 6021, DOI 10.17487/RFC6021, October 2010.
[RFC6587] Gerhards, R. and C. Lonvick, "Transmission of Syslog Messages over TCP", RFC 6587, DOI 10.17487/RFC6587, April 2012.
[RFC7223] Bjorklund, M., "A YANG Data Model for Interface Management", RFC 7223, DOI 10.17487/RFC7223, May 2014.

9.2. Informative References

[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004.
[RFC6241] Enns, R., Bjorklund, M., Schoenwaelder, J. and A. Bierman, "Network Configuration Protocol (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011.
[RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011.

Appendix A. Implementor Guidelines

A.1. Extending Facilities

Many vendors extend the list of facilities available for logging in their implementation. Additional facilities may not work with the syslog protocol as defined in [RFC5424] and hence such facilities apply for local syslog-like logging functionality.

The following is an example that shows how additional facilities could be added to the list of available facilities (in this example two facilities are added):

module vendor-syslog-types-example {
  namespace "urn:vendor:params:xml:ns:yang:vendor-syslog-types";
  prefix vendor-syslogtypes;

  import ietf-syslog-types {
    prefix syslogtypes;
  }

  organization "Example, Inc.";
  contact
    "Example, Inc.
     Customer Service
     
     E-mail: syslog-yang@example.com";

  description
    "This module contains a collection of vendor-specific YANG type 
     definitions for SYSLOG.";

  revision 2016-11-13 {
    description
      "Version 1.0";
    reference
      "Vendor SYSLOG Types: SYSLOG YANG Model";
  }

  identity vendor_specific_type_1 {
    base syslogtypes:syslog-facility;
  }

  identity vendor_specific_type_2 {
    base syslogtypes:syslog-facility;
  }
}
         

Authors' Addresses

Clyde Wildes (editor) Cisco Systems Inc. 170 West Tasman Drive San Jose, CA 95134 US Phone: +1 408 527-2672 EMail: cwildes@cisco.com
Kiran Koushik (editor) Cisco Systems Inc. 12515Research Blvd., Building 4 Austin, TX 78759 US Phone: +1 512 378-1482 EMail: kkoushik@cisco.com