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docs/libnm: add some more documentation

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Lubomir Rintel
2017-03-15 14:28:23 +01:00
parent 374abc3f50
commit a1cf9f4339
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docs/libnm/libnm-docs.xml
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@@ -48,24 +48,130 @@
<chapter id="ref-overview">
<title>Overview</title>
<para>
libnm maps fairly closely to the actual D-Bus API that NetworkManager
provides, wrapping the remote D-Bus objects as native GObjects,
mapping D-Bus signals and properties to GObject signals and properties,
and providing helpful accessor and utility functions. However, unlike
the old libnm-util/libnm-glib API, the mapping to the D-Bus API is not
exact, and various inconveniences and historical anomolies of the D-Bus
API are papered over.
</para>
<para>
The following is a rough overview of the libnm object structure and
how to use the various parts of it:
<mediaobject id="libnm-overview">
<imageobject>
<imagedata fileref="libnm.png" format="PNG"/>
</imageobject>
</mediaobject>
</para>
<section id="intro">
<title>Introduction to libnm</title>
<para>
libnm is a client library for NetworkManager, the standard Linux network
management service. NetworkManager supports a wide variety of network
configuration scenarios, hardware devices and protocol families. Most of
the functionality is exposed on a
<ulink url="https://developer.gnome.org/NetworkManager/stable/spec.html">D-Bus API</ulink>,
allowing other tools to use the functionality provided by NetworkManager.
</para>
<para>
libnm provides C language bindings for functionality provided by
NetworkManager, optionally useful from other language runtimes as well.
</para>
<para>
libnm maps fairly closely to the actual D-Bus API that NetworkManager
provides, wrapping the remote D-Bus objects as native GObjects,
mapping D-Bus signals and properties to GObject signals and properties,
and providing helpful accessor and utility functions. However, unlike
the old libnm-util/libnm-glib API, the mapping to the D-Bus API is not
exact, and various inconveniences and historical anomolies of the D-Bus
API are papered over.
</para>
<para>
The following is a rough overview of the libnm object structure and
how to use the various parts of it:
<mediaobject id="libnm-overview">
<imageobject>
<imagedata fileref="libnm.png" format="PNG"/>
</imageobject>
</mediaobject>
</para>
</section>
<section id="usage">
<title>Using libnm</title>
<simplesect>
<title>When to use libnm</title>
<para>
libnm is fairly simple to use from C. It's based on glib and GObject.
If your project uses these already you'll find integration libnm with your
project rather convenient. In fact, the <command>nmcli</command> tool shipped
with NetworkManager is based on libnm.
</para>
<para>
libnm should be also the way to go if your project does something non-trivial
with NetworkManager, such as manipulating the connection profiles.
That is, if you're writing a specialized networking control tool or a desktop
environment, libnm is probably the right choice. The popular desktop
environments in fact all use libnm directly or with nm-applet and
nm-connection-editor that are all based on libnm.
</para>
<para>
An alternative to use of libnm is the use of the
<ulink url="https://developer.gnome.org/NetworkManager/stable/spec.html">D-Bus API</ulink>
directly. This gives you larger flexibility and reduces the overhead of linking
with the libnm library. This makes sense if your task is simple and you have a good
D-Bus library at your disposal. Activating a particular connection profile
from a Python script is a good example of a task that is perfectly simple
without using libnm.
</para>
</simplesect>
<simplesect>
<title>How to use libnm</title>
<para>
You can use the libnm's C API directly. To do so, all libnm programs need to
include <filename>NetworkManager.h</filename> that provides necessary definitions.
The rest of the API is documented in the reference manual.
</para>
<informalexample><programlisting><![CDATA[#include <glib.h>
#include <NetworkManager.h>
int
main (int argc, char *argv[])
{
NMClient *client;
client = nm_client_new (NULL, NULL);
if (client)
g_print ("NetworkManager version: %s\n", nm_client_get_version (client));
}]]></programlisting></informalexample>
<para>
Use <command>pkg-config</command> for <varname>libnm</varname> to discover the necessary
compiler flags.
</para>
<screen><prompt>$ </prompt><userinput>cc $(pkg-config --libs --cflags libnm) -o hello-nm hello-nm.c</userinput>
<prompt>$ </prompt><userinput>./hello-nm</userinput>
NetworkManager version: &version;
<prompt>$ </prompt></screen>
<para>
Utilize the <varname>PKG_CHECK_MODULES</varname> macro to integrate with an
autoconf-based build system. It's also recommended to use
<varname>NM_VERSION_MIN_REQUIRED</varname> and <varname>NM_VERSION_MAX_ALLOWED</varname>
macros to tell libnm headers which API version does your application need to work with.
If you use them, the compiler will warn you when you use functionality that is not
available in the versions you specified.
</para>
<informalexample><programlisting><![CDATA[PKG_CHECK_MODULES(LIBNM, libnm >= 1.8)
LIBNM_CFLAGS="$LIBNM_CFLAGS -DNM_VERSION_MIN_REQUIRED=NM_VERSION_1_8"
LIBNM_CFLAGS="$LIBNM_CFLAGS -DNM_VERSION_MAX_ALLOWED=NM_VERSION_1_8"]]></programlisting></informalexample>
<para>
You can use libnm from other languages than C with the use of GObject introspection.
This includes Perl, Python, Javascript, Lua, Ruby and more. The example below shows what the
typical libnm use in Python would look like.
</para>
<informalexample><programlisting><![CDATA[import gi
gi.require_version('NM', '1.0')
from gi.repository import NM
client = NM.Client.new(None)
print ("NetworkManager version " + client.get_version())]]></programlisting></informalexample>
<para>
There's <ulink url="https://lazka.github.io/pgi-docs/#NM-1.0">NM-1.0 Python API Reference</ulink>
maintained a third party that is generated from the introspection metadata.
</para>
<para>
In general, the C API documentation applies to the use GObject introspection
from other languages, with the calling convention respecting the language's
customs. Consult the source tree for
<ulink url="https://cgit.freedesktop.org/NetworkManager/NetworkManager/tree/examples">some examples</ulink>.
</para>
</simplesect>
</section>
</chapter>
<chapter>