Clixon

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

• Background
• Frequently asked questions (FAQ)
• Installation
• Licenses
• Support
• Dependencies
• Extending
• XML and XPATH
• Yang
• Netconf
• Restconf
• Datastore
• Authentication
• NACM Access control
• Example
• Changelog
• Runtime
• Clixon project page
• Tests
• Docker
• Roadmap
• Reference manual

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:

• Netgate
• CloudMon360
• Grideye
• Netclean # only CLIgen
• Prosilient's PTAnalyzer # only CLIgen

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.

XML

Clixon has its own implementation of XML and XPATH implementation.

The standards covered include:

• XML 1.0
• Namespaces in XML 1.0
• XPATH 1.0

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> 

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:

• YANG 1.0 RFC 6020
• YANG 1.1 RFC 7950.
• RFC 7895: YANG module library

However, the following YANG syntax modules are not implemented:

• deviation
• min/max-elements
• unique
• action
• belongs-to

Restrictions on Yang types are as follows:

• The range statement for built-in integers does not support multiple values (RFC7950 9.2.4)
• The length statement for built-in strings does not support multiple values (RFC7950 9.4.4)
• Submodules cannot re-use a prefix in an import statement that is already used for another imported module in the module that the submodule belongs to. (see https://github.com/clicon/clixon/issues/60)
• default values on leaf-lists (RFC7950 7.7.2)

Netconf

Clixon implements the following NETCONF proposals or standards:

• RFC 6241: NETCONF Configuration Protocol
• RFC 6242: Using the NETCONF Configuration Protocol over Secure Shell (SSH)
• RFC 5277: NETCONF Event Notifications
• RFC 8341: Network Configuration Access Control Model

The following RFC6241 capabilities/features are hardcoded in Clixon:

• :candidate (RFC6241 8.3)
• :validate (RFC6241 8.6)
• :startup (RFC6241 8.7)
• :xpath (RFC6241 8.9)
• :notification: (RFC5277)

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:

• FAQ.
• Example has an example how to do this with HTTP basic auth.
• It has been done for other projects using Oauth2 or (https://github.com/CESNET/Netopeer2/tree/master/server/configuration)

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). It has limited functionality.

The support is as follows:

• There is a yang config variable CLICON_NACM_MODE to set whether NACM is disabled, uses internal(embedded) NACM configuration, or external configuration. (See yang/clixon-config.yang)
• If the mode is internal, NACM configurations is 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.
• There are two tests using internal and external NACM config
• The backend provides a limited NACM support (when enabled) described below

NACM is implemented in the backend and a single access check is made in from_client_msg() when an internal netconf RPC has just been received and decoded. The code is in nacm_access().

The functionality is as follows:

• Notification is not supported
• Groups are supported
• Rule-lists are supported
• Rules are supported as follows
  • module-name: fully supported
  • access-operations: only '*' and 'exec' supported
  • rpc-name: fully supported (eg edit-config/get-config, etc)
  • action: fully supported (permit/deny)

The tests outlines an example of three groups (taken from the RFC): admin, limited and guest:

• admin: Full access
• limited: Read access (get and get-config)
• guest: No access

Runtime

The figure shows the SDK runtime of Clixon.

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