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OpenDaylight Controller:Netconf:Design

Netconf subsystem

This page contains documented design for the netconf subsystem.

Component diagram for Netconf subsystem

Server

Netconf server was designed as an extensible generic netconf server using Netty for async IO. The core is implemented in netconf-impl module with 2 extensions: config-netconf-connector providing RPC handles for config subsystem and netconf-monitoring providing a small set of support handles regarding ietf-netconf-monitoring. On top of netconf-impl, there are 2 interfaces for outside world: netconf-tcp providing a pure TCP netconf server endpoint and netconf-ssh providing SSH netconf server endpoint.

Netconf extensions

Netconf server is just a generic, dynamic handler that delegates rpc execution to a collection of specific handlers provided by extensions like config-netconf-connector. Arbitrary amount of these extensions can be supplied for the netconf server. The discovery mechanism for such extensions is following:

  1. Extension registers an instance of NetconfOperationServiceFactory into OSGi service registry
  2. Netconf server listens on new registrations and retrieves every instance
  3. Netconf server retrieves a list of capabilities and a list of operation handlers from that instance
  4. Capabilities are added to server hello (those with schema are also added to netconf-monitoring#get-schema operation handler in netconf-monitoring)
  5. Operations are added to the generic operation handler as delegates

Note: The capabilities and handlers are retrieved at the time a new netconf connection is established, so even though the server is dynamic(extensions can appear at any time), it seems static from the netconf user point of view.

Netconf interfaces

Netconf server binds itself just to a local address (local address is not accessible from the outside of a VM) and allows additional interfaces (accessible from the outside) to be provided on top of it.

UML Component diagram

Netconf server components

Util

There are two modules that contain utility classes: netconf-util and netconf-netty-util.

Netconf-util

Contains utilities for:

  • Xml handling
  • Abstract Netconf operation handlers implementation
  • Netconf message utilities

Netconf-netty-util

Contains netty channel handler implementations for:

  • Encoders/Decoders
  • Aggregators/Chunkers
  • EXI handlers
  • SSH handlers

Netconf to config mapping

Config-netconf-connector is an extension for the netconf server and provides handlers for editing and reading the data in config subsystem. It translates the netconf rpcs into java calls on config-subsystem.

The connector connects to config subsystem using JMX interface, where it looks for ConfigRegistry and uses it to edit the current state of configured modules.

Mapping

Since we are using JMX, there needs to be a mapping performed between XML and JMX open type objects. Config-netconf-connector implements custom mapping between these types using parsed SchemaContext that is available in the controller.

UML Component Diagram

Config Netconf Connector components

Auth

The default netconf transport protocol is SSH using username/password authentication. The authentication process is extracted from the netconf SSH server into a plugin that provides authentication.

Authentication API

Authentication service API definition is located in netconf-auth bundle. This bundle contains only one interface called AuthProvider.

Netconf SSH server cooperation

Netconf SSH server requires an implementation of AuthProvider to be able to authenticate its users. There is no direct dependency on any auth implementation from SSH server. The server picks up the implementation from OSGi service registry after its started. In case there is no implementation available, the server will reject every user. In case there are multiple implementations registered, server will choose just one of them and the choice depends on an attribute associated with every registered implementation called: org.opendaylight.controller.netconf.auth.AuthConstants.SERVICE_PREFERENCE_KEY. This attribute contains a numerical value and the higher the value, the higher the preference for netconf server to pick that implementation.

Authentication Implementations

Currently there are 2 implementations for netconf authentication.

Usermanager

Deprecated implementation using authentication mechanism provided by AD-SAL called UserManager. This implementation requires AD-SAL infrastructure in order to provide authentication for netconf. This implementation is deprecated in favor of AAA implementation. Located in bundle netconf-usermanager and part of netconf subsystem in controller project.

AAA project

Current implementation using authentication mechanism provided by the AAA project. Located in bundle aaa-authn-odl-plugin and part of AAA project.

Uml Component Diagram

Netconf Auth components

Monitoring

Netconf-monitoring is an extension for the netconf server and provides ietf-netconf-monitoring capability as well as handlers for get-schema(this handler is still located in netconf-impl module, needs to be moved) and get operation.

Note: Get operation handler is also provided by config-netconf-connector, but netconf server allows multiple operations to take part in forming of the response. Get from netconf monitoring just adds the netconf-state subtree to the response.

Netconf monitoring current netconf server state retrieval

Netconf-monitoring module provides information about current state of the netconf server e.g. sessions. However these information needs to be retrieved first from the netconf server. Netconf server exposes such information with a service named NetconfMonitoringService. This service is registered into OSGi service registry and located by the netconf monitoring when its started.

Ietf netconf monitoring

Modules ietf-netconf-monitoring and ietf-netconf-monitoring-extension contain yang modules for ietf-netconf-monitoring with a small extension and generated java classes.

UML Component Diagram

Netconf Monitoring components

Config persister impl

Config persister is component responsible for loading initial configuration and persisting changed configuration in the controller. Detailed information about persister implementation can be found at Initial config documentation.

Only the implementation config-persister-impl is part of netconf-subsystem. The rest of the components is located in config-subsystem. The reason is that config-persister-impl hooks to netconf for receiving notifications about changed config.

UML Component Diagram

Config persister components

Cli

Cli is a prototype for netconf cli using existing code from netconf-client as well as sal-netconf-connector. Its development is on hold.

Testtool

The testtool is just a small application that produces executable jar file. It is built using existing code for netconf-server.