A YANG Data Model for Syslog
ConfigurationCisco Systems Inc.170 West Tasman DriveSan JoseCA95134US+1 408 527-2672cwildes@cisco.comVerizon Wireless500 W Dove Rd.SouthlakeTX76092US+1 512 650-0210kirankoushik.agraharasreenivasa@verizonwireless.com
General
NETMOD WGThis document defines a YANG data model for the configuration of a
syslog process. It is intended this model be used by vendors who
implement syslog in their systems.This draft contains many placeholder values that need to be replaced
with finalized values at the time of publication. This note summarizes
all of the substitutions that are needed. No other RFC Editor
instructions are specified elsewhere in this document.Artwork in this document contains shorthand references to drafts in
progress. Please apply the following replacements: xxxx --> the assigned RFC value
for draft-ietf-netconf-keystoreyyyy --> the assigned RFC value
for draft-ietf-netconf-tls-client-serverzzzz --> the assigned RFC value
for this draftOperating 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 message.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 them.
The processing may involve logging to a local file, and/or displaying on
console, 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 in this RFC.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 and .The term "originator" is defined in : an
"originator" generates syslog content to be carried in a message.The term "relay" is defined in : a "relay"
forwards messages, accepting messages from originators or other relays
and sending them to collectors or other relaysThe term "collectors" is defined in : a
"collector" gathers syslog content for further analysis.The term "action" refers to the processing that takes place for
each syslog message received.A simplified graphical representation of the data models is used in
this document. The meaning of the symbols in these diagrams is as
follows:Brackets "[" and "]" enclose list keys.Braces "{" and "}" enclose feature names, and indicate that the
named feature must be present for the subtree to be
present.Abbreviations before data node names: "rw" means configuration
(read-write) and "ro" state data (read-only).Symbols after data node names: "?" means an optional node, "!"
means a presence container, and "*" denotes a list and
leaf-list.Parentheses enclose choice and case nodes, and case nodes are
also marked with a colon (":").Ellipsis ("...") stands for contents of subtrees that are not
shown.This document defines a YANG 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 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.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. This model is designed to be very simple for
maximum flexibility.Some optional features are defined in this document to specify
functionality that is present in specific vendor configurations.Syslog consists of originators and collectors. The following diagram
shows syslog messages flowing from an originator, to collectors where
filtering can take place.Figure 1. Syslog Processing FlowCollectors are configured using the leaves in the syslog model
"actions" container which correspond to each message collector:consolelog file(s)remote relay(s)/collector(s)Within each action, a selector is used to filter syslog messages. A
selector consists of a list of 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 field.A syslog message is processed if: The facility is one of a specific syslog-facility, or all
facilities.The severity is one of type syslog-severity, all severities, or none.
None is a special case that can be used to disable a filter. When
filtering severity, the default comparison is that messages of the
specified severity and higher are selected to be logged. This is shown
in the model as "default equals-or-higher". This behavior can be altered
if the select-adv-compare feature is enabled to specify a compare
operation and an action. Compare operations are: "equals" to select
messages with this single severity, or "equals-or-higher" to select
messages of the specified severity and higher. Actions are used to log
the message or block the message from being logged.Many vendors extend the list of facilities available for logging in
their implementation. An example is included in Extending Facilities
(Appendix A.1).A simplified graphical representation of the data model is used in
this document. Please see Section 1.3 for tree diagram notation.Figure 2. ietf-syslog Module TreeThis module imports typedefs from [RFC6021], [RFC7223], groupings
from [RFC yyyy], and [RFC xxxx],
and it references [RFC5424],
[RFC5425],
[RFC5426],
[RFC6587],
and [RFC5848]. file "ietf-syslog.yang"
module ietf-syslog {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-syslog";
prefix syslog;
import ietf-inet-types {
prefix inet;
reference
"RFC 6991: INET Types Model";
}
import ietf-interfaces {
prefix if;
reference
"RFC 7223: Interfaces Model";
}
import ietf-tls-client {
prefix tlsc;
reference
"RFC xxxx: Keystore Model";
}
import ietf-keystore {
prefix ks;
reference
"RFC yyyy: TLS Client and Server Models";
}
organization "IETF
NETMOD (Network Modeling) Working Group";
contact
"WG Web:
WG List:
Editor: Kiran Agrahara Sreenivasa
Editor: Clyde Wildes
";
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 zzzz
(http://tools.ietf.org/html/rfczzzz); see the RFC itself for
full legal notices.";
revision 2017-09-08 {
description
"Initial Revision";
reference
"RFC zzzz: Syslog YANG Model";
}
feature console-action {
description
"This feature indicates that the local console action is
supported.";
}
feature file-action {
description
"This feature indicates that the local file action is
supported.";
}
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 remote-action {
description
"This feature indicates that the remote server action is
supported.";
}
feature remote-source-interface {
description
"This feature indicates that source-interface is supported
supported for the remote-action.";
}
feature select-adv-compare {
description
"This feature represents the ability to select messages
using the additional comparison operators 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.";
}
typedef syslog-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.";
}
grouping severity-filter {
description
"This grouping defines the processing used to select
log messages by comparing syslog message severity using
the following processing rules:
- if 'none', do not match.
- if 'all', match.
- else compare message severity with the specified severity
according to the default compare rule (all messages of the
specified severity and greater match) or if the
select-adv-compare feature is present, the advance-compare
rule.";
leaf severity {
type union {
type syslog-severity;
type enumeration {
enum none {
value 2147483647;
description
"This enum describes the case where no severities
are selected.";
}
enum all {
value -2147483648;
description
"This enum describes the case where all severities
are selected.";
}
}
}
mandatory true;
description
"This leaf specifies the syslog message severity.";
}
container advanced-compare {
when '../severity != "all" and
../severity != "none"' {
description
"The advanced compare container is not applicable for
severity 'all' or severity 'none'";
}
if-feature select-adv-compare;
leaf compare {
type enumeration {
enum equals {
description
"This enum specifies that the severity comparison
operation will be equals.";
}
enum equals-or-higher {
description
"This enum specifies that the severity comparison
operation will be equals or higher.";
}
}
default equals-or-higher;
description
"The compare can be used to specify the comparison
operator that should be used to compare the syslog message
severity with the specified severity.";
}
leaf action {
type enumeration {
enum log {
description
"This enum specifies that if the compare operation is
true the message will be logged.";
}
enum block {
description
"This enum specifies that if the compare operation is
true the message will not be logged.";
}
}
default log;
description
"The action can be used to spectify if the message should
be logged or blocked based on the outcome of the compare
operation.";
}
description
"This container describes additional severity compare
operations that can be used in place of the default
severity comparison. The compare leaf specifies the type of
the compare that is done and the action leaf specifies the
intended result.
Example: compare->equals and action->no-match means
messages that have a severity that is not equal to the
specified severity will be logged.";
}
}
grouping selector {
description
"This grouping defines a syslog selector which is used to
select log messages for the log-actions (console, file,
remote, etc.). Choose one or both of the following:
facility [...]
pattern-match regular-expression-match-string
If both facility and pattern-match are specified, both must
match in order for a log message to be selected.";
container facility-filter {
description
"This container describes the syslog filter parameters.";
list facility-list {
key "facility severity";
ordered-by user;
description
"This list describes a collection of syslog
facilities and severities.";
leaf facility {
type union {
type identityref {
base 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 severity-filter;
}
}
leaf pattern-match {
if-feature select-match;
type string;
description
"This leaf describes 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 RFC 5424; 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 {
if-feature console-action;
presence "Enables logging to the console";
description
"This container describes the configuration parameters
for console logging.";
uses selector;
}
container file {
if-feature file-action;
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;
default 1;
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 uint32;
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 uint32;
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 {
if-feature remote-action;
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.";
}
}
}
case tls {
container tls {
description
"This container describes the TLS transport
options.";
reference
"RFC 5425: Transport Layer Security (TLS)
Transport Mapping for Syslog ";
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 6514;
description
"TCP port 6514 has been allocated as the default
port for syslog over TLS.";
}
uses tlsc:tls-client-grouping;
}
}
}
uses selector;
uses structured-data;
leaf facility-override {
type identityref {
base 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 {
if-feature remote-source-interface;
type if:interface-ref;
description
"This leaf sets the source interface to be used to
send messages 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";
container cert-signers {
description
"This container describes the signing certificate
configuration for Signature Group 0 which covers
the case for administrators who want all Signature
Blocks to be sent to a single destination.";
list cert-signer {
key "name";
description
"This list describes a collection of syslog
message signers.";
leaf name {
type string;
description
"This leaf specifies the name of the syslog
message signer.";
}
leaf certificate {
type leafref {
path "/ks:keystore/ks:keys/ks:key/ks:certificates"
+ "/ks:certificate/ks:name";
}
description
"This is the certificate that is periodically
sent to the remote receiver. Selection of the
certificate also implicitly selects the private
key used to sign the syslog messages.";
}
leaf hash-algorithm {
type enumeration {
enum SHA1 {
value 1;
description
"This enum describes the SHA1 algorithm.";
}
enum SHA256 {
value 2;
description
"This enum describes the SHA256 algorithm.";
}
}
description
"This leaf describes the syslog signer hash
algorithm used.";
}
}
leaf cert-initial-repeat {
type uint32;
default 3;
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 uint32;
units "seconds";
default 3600;
description
"This leaf specifies the maximum time delay in
seconds until resending the Certificate Block.";
}
leaf cert-resend-count {
type uint32;
default 0;
description
"This leaf specifies the maximum number of other
syslog messages to send until resending the
Certificate Block.";
}
leaf sig-max-delay {
type uint32;
units "seconds";
default 60;
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 sig-number-resends {
type uint32;
default 0;
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 RFC 5426 is used.).";
}
leaf sig-resend-delay {
type uint32;
units "seconds";
default 5;
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 sig-resend-count {
type uint32;
default 0;
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. A value of 0 means
that you don't resend based on the number of
messages.";
}
}
}
}
}
}
}
}
]]>Figure 3. ietf-syslog Moduleallcritical
Enable remote logging of syslogs to udp destination 2001:db8:a0b:12f0::1
for facility auth, severity error
remote1
2001:db8:a0b:12f0::1
autherror
]]>Figure 4. ietf-syslog ExamplesThe authors wish to thank the following who commented on this
proposal:Andy BiermanMartin BjorklundAlex CampbellAlex ClemmJim GibsonJeffrey HaasJohn HeasleyGiles HeronLisa HuangMahesh JethanandaniJeffrey K LangeJan LindbladChris LonvickTom PetchJuergen SchoenwaelderPhil ShaferJason SternePeter Van HorneKent WatsenBert WijnenDale R WorleyAleksandr ZhdankinThis document registers one URI in the IETF XML registry . Following the format in ,
the following registration is requested:This document registers one YANG module in the YANG Module Names
registry />. Following the format in />, the the following registration is
requested:The YANG module defined in this document is designed to be accessed
via YANG based management protocols, such as NETCONF and RESTCONF . Both of these
protocols have mandatory-to- implement secure transport layers (e.g.,
SSH, TLS) with mutual authentication.The NETCONF access control model (NACM)
provides the means to restrict access for particular users to a
pre-configured subset of all available protocol operations and
content.There are a number of data nodes defined in this YANG module that 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.It is the responsibility of the network administrator to ensure
that the configured message flow does not overwhelm system
resources.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 messages are actually going to the intended recipients."Chapter 9: Regular Expressions". The Open Group Base
Specifications Issue 6, IEEE Std 1003.1-2008, 2016 Edition.The Open GroupMany 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):