man/sd_bus_negotiate_fds.xml

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   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4
   5 <!--
   6   SPDX-License-Identifier: LGPL-2.1+
   7
   8   This file is part of systemd.
   9
  10   Copyright 2014 Lennart Poettering
  11 -->
  12
  13 <refentry id="sd_bus_negotiate_fds" xmlns:xi="http://www.w3.org/2001/XInclude">
  14
  15   <refentryinfo>
  16     <title>sd_bus_negotiate_fds</title>
  17     <productname>systemd</productname>
  18
  19     <authorgroup>
  20       <author>
  21         <contrib>Developer</contrib>
  22         <firstname>Lennart</firstname>
  23         <surname>Poettering</surname>
  24         <email>lennart@poettering.net</email>
  25       </author>
  26     </authorgroup>
  27   </refentryinfo>
  28
  29   <refmeta>
  30     <refentrytitle>sd_bus_negotiate_fds</refentrytitle>
  31     <manvolnum>3</manvolnum>
  32   </refmeta>
  33
  34   <refnamediv>
  35     <refname>sd_bus_negotiate_fds</refname>
  36     <refname>sd_bus_negotiate_timestamp</refname>
  37     <refname>sd_bus_negotiate_creds</refname>
  38
  39     <refpurpose>Control feature negotiation on bus connections</refpurpose>
  40   </refnamediv>
  41
  42   <refsynopsisdiv>
  43     <funcsynopsis>
  44       <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
  45
  46       <funcprototype>
  47         <funcdef>int <function>sd_bus_negotiate_fds</function></funcdef>
  48         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  49         <paramdef>int <parameter>b</parameter></paramdef>
  50       </funcprototype>
  51
  52       <funcprototype>
  53         <funcdef>int <function>sd_bus_negotiate_timestamp</function></funcdef>
  54         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  55         <paramdef>int <parameter>b</parameter></paramdef>
  56       </funcprototype>
  57
  58       <funcprototype>
  59         <funcdef>int <function>sd_bus_negotiate_creds</function></funcdef>
  60         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  61         <paramdef>int <parameter>b</parameter></paramdef>
  62         <paramdef>uint64_t <parameter>mask</parameter></paramdef>
  63       </funcprototype>
  64     </funcsynopsis>
  65   </refsynopsisdiv>
  66
  67   <refsect1>
  68     <title>Description</title>
  69
  70     <para><function>sd_bus_negotiate_fds()</function> controls whether
  71     file descriptor passing shall be negotiated for the specified bus
  72     connection. It takes a bus object and a boolean, which, when true,
  73     enables file descriptor passing, and, when false, disables
  74     it. Note that not all transports and servers support file
  75     descriptor passing. In particular, networked transports generally
  76     do not support file descriptor passing. To find out whether file
  77     descriptor passing is available after negotiation, use
  78     <citerefentry><refentrytitle>sd_bus_can_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  79     and pass <constant>SD_BUS_TYPE_UNIX_FD</constant>. Note that file
  80     descriptor passing is always enabled for both sending and
  81     receiving or for neither, but never only in one direction. By
  82     default, file descriptor passing is negotiated for all
  83     connections.</para>
  84
  85     <para><function>sd_bus_negotiate_timestamp()</function> controls whether implicit sender
  86     timestamps shall be attached automatically to all incoming messages. Takes a bus object and a
  87     boolean, which, when true, enables timestamping, and, when false, disables it.  Use
  88     <citerefentry><refentrytitle>sd_bus_message_get_monotonic_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  89     <citerefentry><refentrytitle>sd_bus_message_get_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  90     <citerefentry><refentrytitle>sd_bus_message_get_seqnum</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  91     to query the timestamps of incoming messages. If negotiation is disabled or not supported, these
  92     calls will fail with <constant>-ENODATA</constant>. Note that currently no transports support
  93     timestamping of messages. By default, message timestamping is not negotiated for
  94     connections.</para>
  95
  96     <para><function>sd_bus_negotiate_creds()</function> controls whether and which implicit sender
  97     credentials shall be attached automatically to all incoming messages. Takes a bus object and a
  98     boolean indicating whether to enable or disable the credential parts encoded in the bit mask
  99     value argument. Note that not all transports support attaching sender credentials to messages,
 100     or do not support all types of sender credential parameters, or might suppress them under
 101     certain circumstances for individual messages. Specifically, dbus1 only supports
 102     <constant>SD_BUS_CREDS_UNIQUE_NAME</constant>. The sender credentials are suitable for
 103     authorization decisions. By default, only <constant>SD_BUS_CREDS_WELL_KNOWN_NAMES</constant> and
 104     <constant>SD_BUS_CREDS_UNIQUE_NAME</constant> are enabled. In fact, these two credential fields
 105     are always sent along and cannot be turned off.</para>
 106
 107     <para>The <function>sd_bus_negotiate_fds()</function> function may
 108     be called only before the connection has been started with
 109     <citerefentry><refentrytitle>sd_bus_start</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Both
 110     <function>sd_bus_negotiate_timestamp()</function> and
 111     <function>sd_bus_negotiate_creds()</function> may also be called
 112     after a connection has been set up. Note that, when operating on a
 113     connection that is shared between multiple components of the same
 114     program (for example via
 115     <citerefentry><refentrytitle>sd_bus_default</refentrytitle><manvolnum>3</manvolnum></citerefentry>),
 116     it is highly recommended to only enable additional per message
 117     metadata fields, but never disable them again, in order not to
 118     disable functionality needed by other components.</para>
 119   </refsect1>
 120
 121   <refsect1>
 122     <title>Return Value</title>
 123
 124     <para>On success, these functions return 0 or a
 125     positive integer. On failure, they return a negative errno-style
 126     error code.</para>
 127   </refsect1>
 128
 129   <refsect1>
 130     <title>Errors</title>
 131
 132     <para>Returned errors may indicate the following problems:</para>
 133
 134     <variablelist>
 135       <varlistentry>
 136         <term><constant>-EPERM</constant></term>
 137
 138         <listitem><para>The bus connection has already been started.</para></listitem>
 139       </varlistentry>
 140     </variablelist>
 141   </refsect1>
 142
 143   <xi:include href="libelogind-pkgconfig.xml" />
 144
 145   <refsect1>
 146     <title>See Also</title>
 147
 148     <para>
 149       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 150       <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 151       <citerefentry><refentrytitle>sd_bus_start</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 152       <citerefentry><refentrytitle>sd_bus_message_can_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 153       <citerefentry><refentrytitle>sd_bus_message_get_monotonic_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 154       <citerefentry><refentrytitle>sd_bus_message_get_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 155       <citerefentry><refentrytitle>sd_bus_message_get_seqnum</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 156       <citerefentry><refentrytitle>sd_bus_message_get_creds</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 157     </para>
 158   </refsect1>
 159
 160 </refentry>