man: document sd_bus_track objects

And while ware at it, also drop some references to kdbus, and stop claiming
sd-bus wasn't stable yet. Also order man page references in the main sd-bus man
page alphabetically.

3 files changed, 545 insertions, 30 deletions

diff --git a/man/sd-bus.xml b/man/sd-bus.xml
index 336dd33ea0..66b1c96c15 100644
--- a/man/sd-bus.xml
+++ b/man/sd-bus.xml
@@ -44,7 +44,7 @@
 
   <refnamediv>
     <refname>sd-bus</refname>
-    <refpurpose>A lightweight D-Bus and kdbus client library</refpurpose>
+    <refpurpose>A lightweight D-Bus IPC client library</refpurpose>
   </refnamediv>
 
   <refsynopsisdiv>
@@ -61,49 +61,40 @@
   <refsect1>
     <title>Description</title>
 
-    <para><filename>sd-bus.h</filename> provides an implementation
-    of a D-Bus client. It can interoperate both with the traditional
-    <citerefentry project='man-pages'><refentrytitle>dbus-daemon</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
-    and with kdbus. See
+    <para><filename>sd-bus.h</filename> provides an implementation of a D-Bus IPC client. See
     <ulink url="http://www.freedesktop.org/software/dbus/" />
-    for more information about the big picture.
+    for more information about D-Bus IPC.
     </para>
 
-    <important>
-      <para>Interfaces described here have not been declared stable yet,
-      and are not accessible from <filename>libsystemd.so</filename>.
-      This documentation is provided in hope it might be useful for
-      developers, without any guarantees of availability or stability.
-      </para>
-    </important>
-
     <para>See
+    <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+    <citerefentry><refentrytitle>sd_bus_creds_get_pid</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+    <citerefentry><refentrytitle>sd_bus_creds_new_from_pid</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
     <citerefentry><refentrytitle>sd_bus_default</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
-    <citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
-    <citerefentry><refentrytitle>sd_bus_request_name</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
-    <citerefentry><refentrytitle>sd_bus_start</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+    <citerefentry><refentrytitle>sd_bus_error</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+    <citerefentry><refentrytitle>sd_bus_error_add_map</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+    <citerefentry><refentrytitle>sd_bus_get_name_creds</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+    <citerefentry><refentrytitle>sd_bus_get_owner_creds</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
     <citerefentry><refentrytitle>sd_bus_message_append</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
-    <citerefentry><refentrytitle>sd_bus_message_append_basic</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
     <citerefentry><refentrytitle>sd_bus_message_append_array</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+    <citerefentry><refentrytitle>sd_bus_message_append_basic</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
     <citerefentry><refentrytitle>sd_bus_message_append_string_memfd</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
     <citerefentry><refentrytitle>sd_bus_message_append_strv</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
     <citerefentry><refentrytitle>sd_bus_message_can_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
     <citerefentry><refentrytitle>sd_bus_message_get_cookie</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
     <citerefentry><refentrytitle>sd_bus_message_get_monotonic_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+    <citerefentry><refentrytitle>sd_bus_negotiate_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+    <citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+    <citerefentry><refentrytitle>sd_bus_path_encode</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+    <citerefentry><refentrytitle>sd_bus_request_name</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
     <citerefentry><refentrytitle>sd_bus_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
     <citerefentry><refentrytitle>sd_bus_set_address</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+    <citerefentry><refentrytitle>sd_bus_set_allow_interactive_authorization</refentrytitle><manvolnum>3</manvolnum></citerefentry>
     <citerefentry><refentrytitle>sd_bus_set_description</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
     <citerefentry><refentrytitle>sd_bus_set_prepare</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
-    <citerefentry><refentrytitle>sd_bus_creds_get_pid</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
-    <citerefentry><refentrytitle>sd_bus_creds_new_from_pid</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
-    <citerefentry><refentrytitle>sd_bus_get_name_creds</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
-    <citerefentry><refentrytitle>sd_bus_get_owner_creds</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
-    <citerefentry><refentrytitle>sd_bus_negotiate_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
-    <citerefentry><refentrytitle>sd_bus_path_encode</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
-    <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
-    <citerefentry><refentrytitle>sd_bus_error</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
-    <citerefentry><refentrytitle>sd_bus_error_add_map</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
-    <citerefentry><refentrytitle>sd_bus_set_allow_interactive_authorization</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+    <citerefentry><refentrytitle>sd_bus_start</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+    <citerefentry><refentrytitle>sd_bus_track_add_name</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+    <citerefentry><refentrytitle>sd_bus_track_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
     for more information about the functions available.</para>
   </refsect1>
 
@@ -114,9 +105,9 @@
     <para>
       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
       <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>busctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
       <citerefentry project='man-pages'><refentrytitle>dbus-daemon</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
-      <citerefentry project='man-pages'><refentrytitle>dbus-send</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
-      <ulink url="https://developer.gnome.org/gio/stable/gdbus.html">gdbus</ulink>
+      <citerefentry project='man-pages'><refentrytitle>dbus-send</refentrytitle><manvolnum>1</manvolnum></citerefentry>
     </para>
   </refsect1>
 
diff --git a/man/sd_bus_track_add_name.xml b/man/sd_bus_track_add_name.xml
new file mode 100644
index 0000000000..6a5e344cb1
--- /dev/null
+++ b/man/sd_bus_track_add_name.xml
@@ -0,0 +1,261 @@
+<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+
+<!--
+  This file is part of systemd.
+
+  Copyright 2016 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+-->
+
+<refentry id="sd_bus_track_add_name">
+
+  <refentryinfo>
+    <title>sd_bus_track_add_name</title>
+    <productname>systemd</productname>
+
+    <authorgroup>
+      <author>
+        <contrib>Developer</contrib>
+        <firstname>Lennart</firstname>
+        <surname>Poettering</surname>
+        <email>lennart@poettering.net</email>
+      </author>
+    </authorgroup>
+  </refentryinfo>
+
+  <refmeta>
+    <refentrytitle>sd_bus_track_add_name</refentrytitle>
+    <manvolnum>3</manvolnum>
+  </refmeta>
+
+  <refnamediv>
+    <refname>sd_bus_track_add_name</refname>
+    <refname>sd_bus_track_add_sender</refname>
+    <refname>sd_bus_track_remove_name</refname>
+    <refname>sd_bus_track_remove_sender</refname>
+    <refname>sd_bus_track_count</refname>
+    <refname>sd_bus_track_count_sender</refname>
+    <refname>sd_bus_track_count_name</refname>
+    <refname>sd_bus_track_contains</refname>
+    <refname>sd_bus_track_first</refname>
+    <refname>sd_bus_track_next</refname>
+
+    <refpurpose>Add, remove and retrieve bus peers tracked in a bus peer tracking object</refpurpose>
+  </refnamediv>
+
+  <refsynopsisdiv>
+    <funcsynopsis>
+      <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
+
+      <funcprototype>
+        <funcdef>int <function>sd_bus_track_add_name</function></funcdef>
+        <paramdef>sd_bus_track* <parameter>t</parameter></paramdef>
+        <paramdef>const char* <parameter>name</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_bus_track_add_sender</function></funcdef>
+        <paramdef>sd_bus_track* <parameter>t</parameter></paramdef>
+        <paramdef>sd_bus_message* <parameter>message</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_bus_track_remove_name</function></funcdef>
+        <paramdef>sd_bus_track* <parameter>t</parameter></paramdef>
+        <paramdef>const char* <parameter>name</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_bus_track_remove_sender</function></funcdef>
+        <paramdef>sd_bus_track* <parameter>t</parameter></paramdef>
+        <paramdef>sd_bus_message* <parameter>message</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>unsigned <function>sd_bus_track_count</function></funcdef>
+        <paramdef>sd_bus_track* <parameter>t</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_bus_track_count_name</function></funcdef>
+        <paramdef>sd_bus_track* <parameter>t</parameter></paramdef>
+        <paramdef>const char* <parameter>name</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_bus_track_count_sender</function></funcdef>
+        <paramdef>sd_bus_track* <parameter>t</parameter></paramdef>
+        <paramdef>sd_bus_message* <parameter>message</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_bus_track_contains</function></funcdef>
+        <paramdef>sd_bus_track* <parameter>t</parameter></paramdef>
+        <paramdef>const char* <parameter>name</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>const char* <function>sd_bus_track_first</function></funcdef>
+        <paramdef>sd_bus_track* <parameter>t</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>const char* <function>sd_bus_track_next</function></funcdef>
+        <paramdef>sd_bus_track* <parameter>t</parameter></paramdef>
+      </funcprototype>
+
+    </funcsynopsis>
+  </refsynopsisdiv>
+
+  <refsect1>
+    <title>Description</title>
+
+    <para><function>sd_bus_track_add_name()</function> adds a peer to track to a bus peer tracking object. The first
+    argument should refer to a bus peer tracking object created with
+    <citerefentry><refentrytitle>sd_bus_track_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>, the second
+    name should refer to a D-Bus peer name to track, either in unique or well-known service format. If the name is not
+    tracked yet it will be added to the list of names to track. If it already is being tracked and non-recursive mode
+    is enabled, no operation is executed by this call. If recursive mode is enabled a per-name counter is increased by
+    one each time this call is invoked, and <function>sd_bus_track_remove_name()</function> has to be called as many
+    times as <function>sd_bus_track_add_name()</function> was invoked before in order to stop tracking of the name. Use
+    <citerefentry><refentrytitle>sd_bus_track_set_recursive</refentrytitle><manvolnum>3</manvolnum></citerefentry> to
+    switch from the default non-recursive mode to recursive mode, or back. Note that the specified name is tracked as
+    it is, well-known names are not resolved to unique names by this call. Note that multiple bus peer tracking objects
+    may track the same name.</para>
+
+    <para><function>sd_bus_track_remove_name()</function> undoes the effect of
+    <function>sd_bus_track_add_name()</function> and removes a bus peer name from the list of peers to watch. Depending
+    on whether non-recursive or recursive mode is enabled for the bus peer tracking object this call will either remove
+    the name fully from the tracking object, or will simply decrement the per-name counter by one, removing the name
+    only when the counter reaches zero (see above). Note that a bus peer disconnecting from the bus will implicitly
+    remove its names fully from the bus peer tracking object, regardless of the current per-name counter.</para>
+
+    <para><function>sd_bus_track_add_sender()</function> and <function>sd_bus_track_remove_sender()</function> are
+    similar to <function>sd_bus_track_add_name()</function> and <function>sd_bus_track_remove_name()</function> but
+    take a bus message as argument. The sender of this bus message is determined and added to/removed from the bus peer
+    tracking object. As messages always originate from unique names, and never from well-known names this means that
+    this call will effectively only add unique names to the bus peer tracking object.</para>
+
+    <para><function>sd_bus_track_count()</function> returns the number of names currently being tracked by the
+    specified bus peer tracking object. Note that this function always returns the actual number of names tracked, and
+    hence if <function>sd_bus_track_add_name()</function> has been invoked multiple times for the same name it is only
+    counted as one, regardless if recursive mode is used or not.</para>
+
+    <para><function>sd_bus_track_count_name()</function> returns the current per-name counter for the specified
+    name. If non-recursive mode is used this returns either 1 or 0, depending on whether the specified name has been
+    added to the tracking object before, or not. If recursive mode has been enabled, values larger than 1 may be
+    returned too, in case <function>sd_bus_track_add_name()</function> has been called multiple times for the same
+    name.</para>
+
+    <para><function>sd_bus_track_count_sender()</function> is similar to
+    <function>sd_bus_track_count_name()</function>, but takes a bus message object and returns the per-name counter
+    matching the sender of the message.</para>
+
+    <para><function>sd_bus_track_contains()</function> may be used to determine whether the specified name has been
+    added at least once to the specified bus peer tracking object.</para>
+
+    <para><function>sd_bus_track_first()</function> and <function>sd_bus_track_next()</function> may be used to
+    enumerate all names currently being tracked by the passed bus peer tracking
+    object. <function>sd_bus_track_first()</function> returns the first entry in the object, and resets an internally
+    maintained read index. Each subsequent invocation of <function>sd_bus_track_next()</function> returns the next name
+    contained in the bus object. If the end is reached <constant>NULL</constant> is returned. If no names have been
+    added to the object yet <function>sd_bus_track_first()</function> will return <constant>NULL</constant>
+    immediately. The order in which names are returned is undefined; in particular which name is considered the first
+    returned is not defined. If recursive mode is enabled and the same name has been added multiple times to the bus
+    peer tracking object it is only returned once by this enumeration. If new names are added to or existing names
+    removed from the bus peer tracking object while it is being enumerated the enumeration ends on the next invocation
+    of <function>sd_bus_track_next()</function> as <constant>NULL</constant> is returned.</para>
+  </refsect1>
+
+  <refsect1>
+    <title>Return Value</title>
+
+    <para>On success, <function>sd_bus_track_add_name()</function> and <function>sd_bus_track_add_sender()</function>
+    return 0 if the specified name has already been added to the bus peer tracking object before and positive if it
+    hasn't. On failure, they return a negative errno-style error code.</para>
+
+    <para><function>sd_bus_track_remove_name()</function> and <function>sd_bus_track_remove_sender()</function> return
+    positive if the specified name was previously tracked by the bus peer tracking object and has now been removed. In
+    non-recursive mode, 0 is returned if the specified name was not being tracked yet. In recursive mode
+    <constant>-EUNATCH</constant> is returned in this case. On failure, they return a negative errno-style error
+    code.</para>
+
+    <para><function>sd_bus_track_count()</function> returns the number of names currently being tracked, or 0 on
+    failure.</para>
+
+    <para><function>sd_bus_track_count_name()</function> and <function>sd_bus_track_count_sender()</function> return
+    the current per-name counter for the specified name or the sender of the specified message. Zero is returned for
+    names that are not being tracked yet, a positive value for names added at least once. Larger values than 1 are only
+    returned in recursive mode. On failure, a negative errno-style error code is returned.</para>
+
+    <para><function>sd_bus_track_contains()</function> returns the passed name if it exists in the bus peer tracking
+    object. On failure, and if the name has not been added yet <constant>NULL</constant> is returned.</para>
+
+    <para><function>sd_bus_track_first()</function> and <function>sd_bus_track_next()</function> return the first/next
+    name contained in the bus peer tracking object, and <constant>NULL</constant> if the end of the enumeration is
+    reached and on error.</para>
+  </refsect1>
+
+  <refsect1>
+    <title>Errors</title>
+
+    <para>Returned errors may indicate the following problems:</para>
+
+    <variablelist>
+
+      <varlistentry>
+        <term><constant>-EUNATCH</constant></term>
+
+        <listitem><para><function>sd_bus_track_remove_name()</function> or
+        <function>sd_bus_track_remove_sender()</function> have been invoked for a name not previously added to the bus
+        peer object.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-EINVAL</constant></term>
+
+        <listitem><para>Specified parameter is invalid.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-ENOMEM</constant></term>
+
+        <listitem><para>Memory allocation failed.</para></listitem>
+      </varlistentry>
+
+    </variablelist>
+  </refsect1>
+
+  <refsect1>
+    <title>Notes</title>
+
+    <para><function>sd_bus_track_add_name()</function> and the other calls described here are available as a shared library,
+    which can be compiled and linked to with the <constant>libsystemd</constant> <citerefentry
+    project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> file.</para>
+  </refsect1>
+
+  <refsect1>
+    <title>See Also</title>
+
+    <para>
+      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd_bus_track_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+    </para>
+  </refsect1>
+
+</refentry>
diff --git a/man/sd_bus_track_new.xml b/man/sd_bus_track_new.xml
new file mode 100644
index 0000000000..60e2e77f75
--- /dev/null
+++ b/man/sd_bus_track_new.xml
@@ -0,0 +1,263 @@
+<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+
+<!--
+  This file is part of systemd.
+
+  Copyright 2016 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+-->
+
+<refentry id="sd_bus_track_new">
+
+  <refentryinfo>
+    <title>sd_bus_track_new</title>
+    <productname>systemd</productname>
+
+    <authorgroup>
+      <author>
+        <contrib>Developer</contrib>
+        <firstname>Lennart</firstname>
+        <surname>Poettering</surname>
+        <email>lennart@poettering.net</email>
+      </author>
+    </authorgroup>
+  </refentryinfo>
+
+  <refmeta>
+    <refentrytitle>sd_bus_track_new</refentrytitle>
+    <manvolnum>3</manvolnum>
+  </refmeta>
+
+  <refnamediv>
+    <refname>sd_bus_track_new</refname>
+    <refname>sd_bus_track_ref</refname>
+    <refname>sd_bus_track_unref</refname>
+    <refname>sd_bus_track_unrefp</refname>
+    <refname>sd_bus_track_set_recursive</refname>
+    <refname>sd_bus_track_get_recursive</refname>
+    <refname>sd_bus_track_get_bus</refname>
+    <refname>sd_bus_track_get_userdata</refname>
+    <refname>sd_bus_track_set_userdata</refname>
+
+    <refpurpose>Track bus peers</refpurpose>
+  </refnamediv>
+
+  <refsynopsisdiv>
+    <funcsynopsis>
+      <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
+
+      <funcprototype>
+        <funcdef>int <function>sd_bus_track_new</function></funcdef>
+        <paramdef>sd_bus* <parameter>bus</parameter></paramdef>
+        <paramdef>sd_bus_track** <parameter>ret</parameter></paramdef>
+        <paramdef>sd_bus_track_handler_t <parameter>handler</parameter></paramdef>
+        <paramdef>void* <parameter>userdata</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>sd_bus_track *<function>sd_bus_track_ref</function></funcdef>
+        <paramdef>sd_bus_track *<parameter>t</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>sd_bus_track *<function>sd_bus_track_unref</function></funcdef>
+        <paramdef>sd_bus_track *<parameter>t</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>void <function>sd_bus_track_unrefp</function></funcdef>
+        <paramdef>sd_bus_track **<parameter>t</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_bus_track_get_recursive</function></funcdef>
+        <paramdef>sd_bus_track *<parameter>t</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_bus_track_set_recursive</function></funcdef>
+        <paramdef>sd_bus_track *<parameter>t</parameter></paramdef>
+        <paramdef>int <parameter>b</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>sd_bus* <function>sd_bus_track_get_bus</function></funcdef>
+        <paramdef>sd_bus_track *<parameter>t</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>void* <function>sd_bus_track_get_userdata</function></funcdef>
+        <paramdef>sd_bus_track *<parameter>t</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>void* <function>sd_bus_track_set_userdata</function></funcdef>
+        <paramdef>sd_bus_track *<parameter>t</parameter></paramdef>
+        <paramdef>void *userdata</paramdef>
+      </funcprototype>
+
+    </funcsynopsis>
+  </refsynopsisdiv>
+
+  <refsect1>
+    <title>Description</title>
+
+    <para><function>sd_bus_track_new()</function> creates a new bus peer tracking object. The object is allocated for
+    the specified bus, and returned in the <parameter>*ret</parameter> parameter. After use, the object should be freed
+    again by dropping the acquired reference with <function>sd_bus_track_unref()</function> (see below). A bus peer
+    tracking object may be used to keep track of peers on a specific IPC bus, for cases where peers are making use of
+    one or more local objects, in order to control the lifecycle of the local objects and ensure they stay around as
+    long as the peers needing them are around, and unreferenced (and possibly destroyed) as soon as all relevant peers
+    have vanished. Each bus peer tracking object may be used to track zero, one or more peers add a time. References to
+    specific bus peers are added via
+    <citerefentry><refentrytitle>sd_bus_track_add_name</refentrytitle><manvolnum>3</manvolnum></citerefentry> or
+    <function>sd_bus_track_add_sender()</function>. They may be dropped again via
+    <function>sd_bus_track_remove_name()</function> and
+    <function>sd_bus_track_remove_sender()</function>. Alternatively, references on peers are removed automatically
+    when they disconnect from the bus.  If non-NULL the <parameter>handler</parameter> may specify a function that is
+    invoked whenever the last reference is dropped, regardless whether the reference is dropped explicitly via
+    <function>sd_bus_track_remove_name()</function> or implicitly because the peer disconnected from the bus. The final
+    argument <parameter>userdata</parameter> may be used to attach a generic user data pointer to the object. This
+    pointer is passed to the handler callback when it is invoked.</para>
+
+    <para><function>sd_bus_track_ref()</function> creates a new reference to a bus peer tracking object. This object
+    will not be destroyed until <function>sd_bus_track_unref()</function> has been called as many times plus once
+    more. Once the reference count has dropped to zero, the specified object cannot be used anymore, further calls to
+    <function>sd_bus_track_ref()</function> or <function>sd_bus_track_unref()</function> on the same object are
+    illegal.</para>
+
+    <para><function>sd_bus_track_unref()</function> destroys a reference to a bus peer tracking object.</para>
+
+    <para><function>sd_bus_track_unrefp()</function> is similar to <function>sd_bus_track_unref()</function> but takes
+    a pointer to a pointer to an <type>sd_bus_track</type> object. This call is useful in conjunction with GCC's and
+    LLVM's <ulink url="https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up Variable
+    Attribute</ulink>. Note that this function is defined as inline function.</para>
+
+    <para><function>sd_bus_track_ref()</function>, <function>sd_bus_track_unref()</function> and
+    <function>sd_bus_track_unrefp()</function> execute no operation if the passed in bus peer tracking object is
+    <constant>NULL</constant>.</para>
+
+    <para>Bus peer tracking objects may exist in two modes: by default they operate in non-recursive mode, but may
+    optionally be switched into recursive mode. If operating in the default non-recursive mode a peer is either tracked
+    or not tracked. In this mode invoking <function>sd_bus_track_add_name()</function> multiple times in a row for the
+    same peer is fully equivalent to calling it just once, as the call adds the peer to the set of tracked peers if
+    necessary, and executes no operation if the peer is already being tracked. A single invocation of
+    <function>sd_bus_track_remove_name()</function> removes the reference on the peer again, regardless how many times
+    <function>sd_bus_track_add_name()</function> was called before. If operating in recursive mode, the number of times
+    <function>sd_bus_track_add_name()</function> is invoked for the same peer name is counted and
+    <function>sd_bus_track_remove_name()</function> must be called the same number of times before the peer is not
+    tracked anymore, with the exception when the tracked peer vanishes from the bus, in which case the count is
+    irrelevant and the tracking of the specific peer is immediately
+    removed. <function>sd_bus_track_get_recursive()</function> may be used to determine whether the bus peer tracking
+    object is operating in recursive mode. <function>sd_bus_track_set_recursive()</function> may be used to enable or
+    disable recursive mode. By default a bus peer tracking object operates in non-recursive mode, and
+    <function>sd_bus_track_get_recursive()</function> for a newly allocated object hence returns a value equal to
+    zero. Use <function>sd_bus_track_set_recursive()</function> to enable recursive mode, right after allocation. It
+    takes a boolean argument to enable or disable recursive mode. Note that tracking objects for which
+    <function>sd_bus_track_add_name()</function> was already invoked at least once (and which hence track already one
+    or more peers) may not be switched from recursive to non-recursive mode anymore.</para>
+
+    <para><function>sd_bus_track_get_bus()</function> returns the bus object the bus peer tracking object belongs
+    to. It returns the bus object initially passed to <function>sd_bus_track_new()</function> when the object was
+    allocated.</para>
+
+    <para><function>sd_bus_track_get_userdata()</function> returns the generic user data pointer set on the bus peer
+    tracking object at the time of creation using <function>sd_bus_track_new()</function> or at a later time, using
+    <function>sd_bus_track_set_userdata()</function>.</para>
+  </refsect1>
+
+  <refsect1>
+    <title>Return Value</title>
+
+    <para>On success, <function>sd_bus_track_new()</function> and <function>sd_bus_track_set_recursive()</function>
+    return 0 or a positive integer. On failure, they return a negative errno-style error code.</para>
+
+    <para><function>sd_bus_track_ref()</function> always returns the argument.</para>
+
+    <para><function>sd_bus_track_unref()</function> always returns <constant>NULL</constant>.</para>
+
+    <para><function>sd_bus_track_get_recursive()</function> returns 0 if non-recursive mode is selected (default), and
+    greater than 0 if recursive mode is selected. On failure a negative errno-style error code is returned.</para>
+
+    <para><function>sd_bus_track_get_bus()</function> returns the bus object associated to the bus peer tracking
+    object.</para>
+
+    <para><function>sd_bus_track_get_userdata()</function> returns the generic user data pointer associated with the
+    bus peer tracking object. <function>sd_bus_track_set_userdata()</function> returns the previous user data pointer
+    set.</para>
+
+  </refsect1>
+
+  <refsect1>
+    <title>Reference ownership</title>
+
+    <para>The <function>sd_bus_track_new()</function> function creates a new object and the caller owns the sole
+    reference. When not needed anymore, this reference should be destroyed with
+    <function>sd_bus_track_unref()</function>.
+    </para>
+  </refsect1>
+
+  <refsect1>
+    <title>Errors</title>
+
+    <para>Returned errors may indicate the following problems:</para>
+
+    <variablelist>
+
+      <varlistentry>
+        <term><constant>-EBUSY</constant></term>
+
+        <listitem><para>Bus peers have already been added to the bus peer tracking object and
+        <function>sd_bus_track_set_recursive()</function> was called to change tracking mode.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-EINVAL</constant></term>
+
+        <listitem><para>Specified parameter is invalid
+        (<constant>NULL</constant> in case of output
+        parameters).</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-ENOMEM</constant></term>
+
+        <listitem><para>Memory allocation failed.</para></listitem>
+      </varlistentry>
+
+    </variablelist>
+  </refsect1>
+
+  <refsect1>
+    <title>Notes</title>
+
+    <para><function>sd_bus_track_new()</function> and the other calls described here are available as a shared library,
+    which can be compiled and linked to with the <constant>libsystemd</constant> <citerefentry
+    project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> file.</para>
+  </refsect1>
+
+  <refsect1>
+    <title>See Also</title>
+
+    <para>
+      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+      <citerefentry><refentrytitle>sd_bus_track_add_name</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+    </para>
+  </refsect1>
+
+</refentry>