# libnetconf2 – The NETCONF protocol library

[![BSD license](https://img.shields.io/badge/License-BSD-blue.svg)](https://opensource.org/licenses/BSD-3-Clause)
[![Build Status](https://secure.travis-ci.org/CESNET/libnetconf2.png?branch=master)](http://travis-ci.org/CESNET/libnetconf2)
[![Coverity Scan Build Status](https://scan.coverity.com/projects/7642/badge.svg)](https://scan.coverity.com/projects/7642)

**libnetconf2** is a NETCONF library in C intended for building NETCONF clients
and servers. NETCONF is the [NETwork CONFiguration protocol](http://trac.tools.ietf.org/wg/netconf/trac/wiki)
introduced by IETF.

**libnetconf2** is a NETCONF library in C handling NETCONF authentication and all NETCONF RPC communication both server
and client-side. Note that NETCONF datastore implementation is not a part of this library. The library supports both
NETCONF 1.0 ([RFC 4741](https://tools.ietf.org/html/rfc4741)) as well as NETCONF 1.1
([RFC 6241](https://tools.ietf.org/html/rfc6241)). The main features include:

* NETCONF over SSH ([RFC 4742](https://tools.ietf.org/html/rfc4742), [RFC 6242](https://tools.ietf.org/html/rfc6242)),
  using [libssh](https://www.libssh.org/).
* NETCONF over TLS ([RFC 7589](https://tools.ietf.org/html/rfc7589)), using [OpenSSL](https://www.openssl.org/).
  * DNSSEC SSH Key Fingerprints ([RFC 4255](https://tools.ietf.org/html/rfc4255))
* NETCONF over pre-established transport sessions (using this mechanism the communication can be tunneled through
  sshd(8), for instance).
* NETCONF Call Home ([RFC 8071](https://tools.ietf.org/html/rfc8071)).
* NETCONF Event Notifications ([RFC 5277](https://tools.ietf.org/html/rfc5277)),

**libnetconf2** is maintained and further developed by the [Tools for
Monitoring and Configuration](https://www.liberouter.org/) department of
[CESNET](http://www.ces.net/). Any testing or improving/fixing the library
is welcome. Please inform us about your experiences with using **libnetconf2**
via the [issue tracker](https://github.com/CESNET/libnetconf/issues).

Besides the [**libyang**](https://github.com/CESNET/libyang), **libnetconf2** is
another basic building block for the [**Netopeer2** toolset](https://github.com/CESNET/Netopeer2).
For a reference implementation of NETCONF client and server, check the
**Netopeer2** project.

## Branches

The project uses 2 main branches `master` and `devel`. Other branches should not be cloned. In `master` there are files of the
last official *release*. Any latest improvements and changes, which were tested at least briefly are found in `devel`. On every
new *release*, `devel` is merged into `master`.

This means that when only stable official releases are to be used, either `master` can be used or specific *releases* downloaded.
If all the latest bugfixes should be applied, `devel` branch is the  one to be used. Note that whenever **a new issue is created**
and it occurs on the `master` branch, the **first response will likely be** to use `devel` before any further provided support.

## Packages

We are using openSUSE Build Service to automaticaly prepare binary packages for number of GNU/Linux distros.
The [libnetconf2](https://software.opensuse.org//download.html?project=home%3Aliberouter&package=libnetconf2)
packages are always build from current `master` branch (latest release). If you are interested in any other packages
(such as *devel*), you can browse
[all packages](https://download.opensuse.org/repositories/home:/liberouter/) from our repository.

## libnetconf vs libnetconf2

**libnetconf2** is being developed with experiences gained from the development
of the [**libnetconf**](https://github.com/CESNET/libnetconf) library. Here are the
main differences between the both libraries that would help you to decide which
of them is more suitable for your needs.

### libxml2 vs libyang

To represent the schema and data trees, **libnetconf** uses libxml2, which is
intended for different purposes - schema and data trees connected with YANG
have specific needs and restrictions in comparison to more generic XML.
Therefore, in **libnetconf2**, we have completely replaced libxml2 by
[libyang](https://github.com/CESNET/libyang). It is much more efficient in work
with YANG modeled data (which is the case of NETCONF messages) and this advantage
then applies also to **libnetconf2**. The library connects data with the YANG
schemas, so for example the data validation according to the provided YANG
schemas is done internally by libyang instead of using external and extremely
slow DSDL tools (as it was in the first generation of libnetconf).

### Datastore

**libnetconf** was trying to be all-in-one, so besides the NETCONF transport,
it also implements configuration datastores, NETCONF Access Control Module or
the NETCONF Event Notification storage. In contrast, to allow better design of
the NETCONF servers, **libnetconf2** is focused strictly to the NETCONF
transport and message manipulation.

Therefore, all the features from **libnetconf** that are connected to the
datastore implementation are not available in **libnetconf2**. In the case of
the Netopeer2 server, all these features (and much more) are implemented as
part of the server itself or its datastore implementation -
[**sysrepo**](https://github.com/sysrepo/sysrepo).

### Notifications

While **libnetconf2** is able to send (on the server side) and receive (on the
client side) the NETCONF Event Notification messages, its generation and storage
is left up to the server implementation. In case of the Netopeer2 server, the
Notifications implementation is split between the server itself (managing
subscriptions) and sysrepo (Events storage).

### Call Home

Similarly as in case of Notifications, **libnetconf2** provides supporting
functions implementing the Call Home mechanism, but its management (setting the
connection parameters) is supposed to be done in the server. Again, as a
reference implementation, you can check the Netopeer2 server.

In contrast to **libnetconf**, **libnetconf2** actually implements more of the
Call Home functionality.

# Installation

## Required Dependencies

Install the following libraries and tools the libnetconf2 depends on.

### libyang
Follow the [libyang instructions](https://github.com/CESNET/libyang/blob/master/README.md),
in short:
```
$ git clone https://github.com/CESNET/libyang.git
$ cd libyang; mkdir build; cd build
$ cmake ..
$ make
# make install
```

### libssh
Required version is at least 0.6.4. This dependency can be removed by disabling
SSH support (see the [Build Options](#build-options) section). Below si the basic
sequence of commands for compiling and installing it from source. However, there
are packages for certain Linux distributions available [here](https://www.libssh.org/get-it/).
```
$ git clone http://git.libssh.org/projects/libssh.git
$ cd libssh; mkdir build; cd build
$ cmake ..
$ make
# make install
```

### OpenSSL
This dependency is required when the TLS support is enabled, which it is by
default but libssh requires it too. So, to remove this dependency, you need
to disable both SSH and TLS (see the [Build Options](#build-options) section).

OpenSSL is a standard part of the most distribution, so ask your package
manager for OpenSSL package including the necessary development files
(usually -dev or -devel package).

## Optional Dependencies

### libval (part of the DNSSEC-Tools suite)
It is required only if DNSSEC SSHFP retrieval is enabled (it is disabled by
default, see the [Build Options](#build-options) section).

The easier way of installing it is as the libval-dev package (or a part of
the dnssec-tools package), if you can find it for your distribution. Packages
for some distributions or the source can be downloaded from [here](https://www.dnssec-tools.org/download/).

### cmocka
For running the tests (see the [Tests](#tests) section for more information).
```
$ git clone git://git.cryptomilk.org/projects/cmocka.git
$ cd cmocka
$ git checkout tags/cmocka-1.0.1
$ mkdir build; cd build
$ cmake ..
$ make
# make install
```

### Doxygen
For building the library documentation.

Doxygen is a standard part of the most distribution, so ask your package
manager for doxygen package.

## Building libnetconf2

```
$ mkdir build; cd build
$ cmake ..
$ make
# install
```

The library documentation can be generated directly from the source codes using
Doxygen tool:
```
$ make doc
```

## Build Options

There are various options to change result of building.

### Changing Compiler

Set `CC` environment variable:

```
$ CC=/usr/bin/clang cmake ..
```

### Installation Prefix

By default, the library is installed with the `/usr/local` prefix, to change
it, use the following option:
```
$ cmake -DCMAKE_INSTALL_PREFIX:PATH=/usr ..
```

### Transport Protocol Support

The NETCONF protocol specification allows to use the protocol on top of
several transport protocols. **libnetconf2** provides support for SSH and
TLS transport. By default, both SSH and TLS transport is enabled. Disabling
and enabling both the transport protocols can be made
in the same way. The following command has actually the same effect as
specifying no option since it specifies the default settings.
```
$ cmake -DENABLE_TLS=ON -DENABLE_SSH=ON ..
```

### DNSSEC SSHFP Retrieval

In SSH connections, if the remote NETCONF server supports it and it is
enabled, it is possible to safely retrieve server host key fingerprints
using DNSSEC and automatically consider them to be trusted without any
interaction. Enable it with the following command.
```
$ cmake -DENABLE_DNSSEC=ON ..
```

### Build Modes

There are two build modes:
* Release.
  This generates library for the production use without any debug information.
* Debug.
  This generates library with the debug information and disables optimization
  of the code.

The `Debug` mode is currently used as the default one. to switch to the
`Release` mode, enter at the command line:
```
$ cmake -D CMAKE_BUILD_TYPE:String="Release" ..
```

### Inactive Read Timeout

It is possible to adjust inactive read timeout. It is used when a new message is
being read and no new data had arrived for this amount of seconds. 20 is the default value.

```
$ cmake -D READ_INACTIVE_TIMEOUT:String="20" ..
```

### Active Read Timeout

Active read timeout is used to limit the maximum number of seconds a message is given
to arrive in its entirety once a beginning is read. The default is 300 (5 minutes).

```
$ cmake -D READ_ACTIVE_TIMEOUT:String="300" ..
```

### PSPoll Thread Count

This value limits the maximum number of threads that can concurrently access
(wait for access) a single pspoll structure. To simplify, how many threads could
simultaneously call a function whose parameter is one and the same pspoll structure.
If using **netopeer2-server**, it will warn that this value needs to be adjusted if
too small.

```
$ cmake -D MAX_PSPOLL_THREAD_COUNT:String="6" ..
```

### CMake Notes

Note that, with CMake, if you want to change the compiler or its options after
you already ran CMake, you need to clear its cache first - the most simple way
to do it is to remove all content from the 'build' directory.

## Tests

The repository includes several tests built with [cmocka](https://cmocka.org/).
The tests can be found in `tests` subdirectory and they are designed for
checking library functionality after code changes.

The tests are by default built in the `Debug` build mode by running
```
$ make
```

In case of the `Release` mode, the tests are not built by default (it requires
additional dependency), but it can be enabled via cmake option:
```
$ cmake -DENABLE_BUILD_TESTS=ON ..
```

Note that if the necessary [cmocka](https://cmocka.org/) headers are not present
in the system include paths, tests are not available despite the build mode or
cmake's options.

Tests can be run by the make's `test` target:
```
$ make test
```

