man/sd_bus_negotiate_fds.xml

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