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Clixon automatically generates interactive CLI, NETCONF, RESTCONF and embedded databases with transaction support from a YANG specification.

www.clicon.org/

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Clixon

Clixon is a YANG-based configuration manager, with interactive CLI, NETCONF and RESTCONF interfaces, an embedded database and transaction support.

Background

Clixon was implemented to provide an open-source generic configuration tool. The existing CLIgen tool was for command-lines only, while Clixon is a system with configuration database, xml and rest interfaces all defined by Yang. Most of the projects using Clixon are for embedded network and measuring devices. But Clixon can be used for other systems as well due to its modular and pluggable architecture.

Users of Clixon currently include:

See also Clicon project page.

Clixon runs on Linux, FreeBSD port and Mac/Apple. CPU architecures include x86_64, i686, ARM32.

Installation

A typical installation is as follows:

     configure	       	       # Configure clixon to platform
     make                      # Compile
     sudo make install         # Install libs, binaries, and config-files
     sudo make install-include # Install include files (for compiling)

One example application is provided, a IETF IP YANG datamodel with generated CLI, Netconf and restconf interface.

Licenses

Clixon is open-source and dual licensed. Either Apache License, Version 2.0 or GNU General Public License Version 2; you choose.

See LICENSE.md for the license.

Dependencies

Clixon depends on the following software packages, which need to exist on the target machine.

  • CLIgen If you need to build and install CLIgen:
    git clone https://github.com/olofhagsand/cligen.git
    cd cligen; configure; make; make install
  • Yacc/bison
  • Lex/Flex
  • Fcgi (if restconf is enabled)

Support

Clixon interaction is best done posting issues, pull requests, or joining the slack channel. Slack invite.

Extending

Clixon provides a core system and can be used as-is using available Yang specifications. However, an application very quickly needs to specialize functions. Clixon is extended by writing plugins for cli and backend. Extensions for netconf and restconf are also available.

Plugins are written in C and easiest is to look at example or consulting the FAQ.

Yang

YANG and XML is the heart of Clixon. Yang modules are used as a specification for handling XML configuration data. The YANG spec is used to generate an interactive CLI, netconf and restconf clients. It also manages an XML datastore.

Clixon follows:

However, the following YANG syntax modules are not implemented (reference to RFC7950 in parenthesis):

  • deviation (7.20.3)
  • action (7.15)
  • augment in a uses sub-clause (7.17) (module-level augment is implemented)
  • status (7.21.2)
  • extension (7.19)
  • YIN (13)
  • Yang extended Xpath functions: re-match(), deref)(), derived-from(), derived-from-or-self(), enum-value(), bit-is-set() (10.2-10.6)
  • Default values on leaf-lists are not supported (7.7.2)

Yang patterns

Yang type patterns use regexps defined in W3C XML XSD. XSD regexp:s are slightly different from POSIX regexp.

Clixon supports two regular expressions engines:

  • "Posix" which is the default method, which translates XSD regexp:s to posix before matching with the standard Linux regex engine. This translation is not complete but can be considered "good-enough" for most yang use-cases. For reference, all standard Yang models in [https://github.com/YangModels/yang] have been tested.
  • "Libxml2" which uses the XSD regex engine in Libxml2. This is a complete XSD engine but you need to compile and link with libxml2 which may add overhead.

To use libxml2 in clixon you need enable libxml2 in both cligen and clixon:

> ./configure --with-libxml2 # both cligen and clixon

You then need to set the following configure option:

  <CLICON_YANG_REGEXP>libxml2</CLICON_YANG_REGEXP>

XML

Clixon has its own implementation of XML and XPATH implementation.

The standards covered include:

Not supported:

  • !DOCTYPE (ie DTD)

Historically, Clixon has not until 3.9 made strict namespace enforcing. For example, the following non-strict netconf was previously accepted:

     <rpc><my-own-method/></rpc>

In 3.9, the same statement should be, for example:

     <rpc><my-own-method xmlns="urn:example:my-own"/></rpc>

Note that base netconf syntax is still not enforced but recommended:

     <rpc xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
        <my-own-method xmlns="urn:example:my-own"/>
     </rpc>

Netconf

Clixon implements the following NETCONF proposals or standards:

The following RFC6241 capabilities/features are hardcoded in Clixon:

  • :candidate (RFC6241 8.3)
  • :validate (RFC6241 8.6)
  • :xpath (RFC6241 8.9)
  • :notification: (RFC5277)

The following features are optional and can be enabled by setting CLICON_FEATURE:

  • :startup (RFC6241 8.7)

Clixon does not support the following netconf features:

  • :url capability
  • copy-config source config
  • edit-config testopts
  • edit-config erropts
  • edit-config config-text
  • edit-config operation

Some other deviations from the RFC:

  • edit-config xpath select statement does not support namespaces

Restconf

Clixon Restconf is a daemon based on FastCGI C-API. Instructions are available to run with NGINX. The implementatation is based on RFC 8040: RESTCONF Protocol.

The following features are supported:

  • OPTIONS, HEAD, GET, POST, PUT, DELETE
  • stream notifications (RFC8040 sec 6)
  • query parameters start-time and stop-time(RFC8040 section 4.9)

The following features are not implemented:

  • PATCH
  • query parameters other than start/stop-time.

See more detailed instructions.

Datastore

The Clixon datastore is a stand-alone XML based datastore. The idea is to be able to use different datastores backends with the same API. Currently only an XML plain text datastore is supported.

The datastore is primarily designed to be used by Clixon but can be used separately.

See more detailed instructions.

Auth

Authentication is managed outside Clixon using SSH, SSL, Oauth2, etc.

For CLI, login is typically made via SSH. For netconf, SSH netconf subsystem can be used.

Restconf however needs credentials. This is done by writing a credentials callback in a restconf plugin. See:

The clients send the ID of the user using a "username" attribute with the RPC calls to the backend. Note that the backend trusts the clients so the clients can in principle fake a username.

NACM

Clixon includes an experimental Network Configuration Access Control Model (NACM) according to RFC8341(NACM).

To enable NACM:

  • The CLICON_NACM_MODE config variable is by default disabled.
  • If the mode is internal`, NACM configurations are expected to be in the regular configuration, managed by regular candidate/runing/commit procedures. This mode may have some problems with bootstrapping.
  • If the mode is external, the CLICON_NACM_FILE yang config variable contains the name of a separate configuration file containing the NACM configurations. After changes in this file, the backend needs to be restarted.

The example contains a http basic auth and a NACM backend callback for mandatory state variables.

NACM is implemented in the backend with incoming RPC and data node access control points.

The functionality is as follows (references to sections in RFC8341):

  • Access control point support:
    • Incoming RPC Message validation is supported (3.4.4)
    • Data Node Access validation is supported (3.4.5), except:
      • rule-type data-node path is not supported
    • Outgoing noitification aithorization is not supported (3.4.6)
  • RPC:s are supported except:
    • copy-configfor other src/target combinations than running/startup (3.2.6)
    • commit - NACM is applied to candidate and running operations only (3.2.8)
  • Client-side RPC:s are not supported.

Runtime

clixon sdk

The figure shows the SDK runtime of Clixon.

Standard Compliance

This is work-in-progress on which standards Clixon supports:

  • RFC 6020 YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)
  • RFC7895 YANG Module Library
  • RFC7950 The YANG 1.1 Data Modeling Language
  • RFC7951 JSON Encoding of Data Modeled with YANG

Reference

Clixon uses Doxygen for reference documentation. You need to install doxygen and graphviz on your system. Build it in the doc directory and point the browser to .../clixon/doc/html/index.html as follows:

> cd doc
> make doc
> make graphs # detailed callgraphs

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Clixon automatically generates interactive CLI, NETCONF, RESTCONF and embedded databases with transaction support from a YANG specification.

www.clicon.org/

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