man/sd_bus_negotiate_fds.xml

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