man/sd_bus_negotiate_fds.xml

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  23
  24 <refentry id="sd_bus_negotiate_fds" conditional="ENABLE_KDBUS">
  25
  26   <refentryinfo>
  27     <title>sd_bus_negotiate_fds</title>
  28     <productname>systemd</productname>
  29
  30     <authorgroup>
  31       <author>
  32         <contrib>Developer</contrib>
  33         <firstname>Lennart</firstname>
  34         <surname>Poettering</surname>
  35         <email>lennart@poettering.net</email>
  36       </author>
  37     </authorgroup>
  38   </refentryinfo>
  39
  40   <refmeta>
  41     <refentrytitle>sd_bus_negotiate_fds</refentrytitle>
  42     <manvolnum>3</manvolnum>
  43   </refmeta>
  44
  45   <refnamediv>
  46     <refname>sd_bus_negotiate_fds</refname>
  47     <refname>sd_bus_negotiate_timestamps</refname>
  48     <refname>sd_bus_negotiate_creds</refname>
  49
  50     <refpurpose>Control feature negotiation on bus connections</refpurpose>
  51   </refnamediv>
  52
  53   <refsynopsisdiv>
  54     <funcsynopsis>
  55       <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
  56
  57       <funcprototype>
  58         <funcdef>int <function>sd_bus_negotiate_fds</function></funcdef>
  59         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  60         <paramdef>int <parameter>b</parameter></paramdef>
  61       </funcprototype>
  62
  63       <funcprototype>
  64         <funcdef>int <function>sd_bus_negotiate_timestamp</function></funcdef>
  65         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  66         <paramdef>int <parameter>b</parameter></paramdef>
  67       </funcprototype>
  68
  69       <funcprototype>
  70         <funcdef>int <function>sd_bus_negotiate_creds</function></funcdef>
  71         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  72         <paramdef>int <parameter>b</parameter></paramdef>
  73       </funcprototype>
  74     </funcsynopsis>
  75   </refsynopsisdiv>
  76
  77   <refsect1>
  78     <title>Description</title>
  79
  80     <para><function>sd_bus_negotiate_fds()</function> controls whether
  81     file descriptor passing shall be negotiated for the specified bus
  82     connection. It takes a bus object and a boolean, which, when true,
  83     enables file descriptor passing, and, when false, disables it. Note
  84     that not all transports and servers support file descriptor
  85     passing. To find out whether file descriptor passing is available
  86     after negotiation, use
  87     <citerefentry><refentrytitle>sd_bus_can_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  88     and pass <constant>SD_BUS_TYPE_UNIX_FD</constant>. Note that file
  89     descriptor passing is always enabled for both sending and
  90     receiving or for neither, but never only in one direction. By
  91     default, file descriptor passing is negotiated for all
  92     connections.</para>
  93
  94     <para>Note that when bus activation is used, it is highly
  95     recommended to set the <option>AcceptFileDescriptors=</option>
  96     setting in the <filename>.busname</filename> unit file to the same
  97     setting as negotiated by the program ultimately activated. By
  98     default, file descriptor passing is enabled for both.</para>
  99
 100     <para><function>sd_bus_negotiate_timestamps()</function> controls
 101     whether implicit sender timestamps shall be attached automatically
 102     to all incoming messages. Takes a bus object and a boolean, which,
 103     when true, enables timestamping, and, when false, disables it. If
 104     this is disabled,
 105     <citerefentry><refentrytitle>sd_bus_message_get_monotonic_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 106     <citerefentry><refentrytitle>sd_bus_message_get_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 107     <citerefentry><refentrytitle>sd_bus_message_get_seqno</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 108     fail with <constant>-ENODATA</constant> on incoming messages. Note
 109     that not all transports support timestamping of messages. On local
 110     transports, the timestamping is applied by the kernel and cannot be
 111     manipulated by userspace.</para>
 112
 113     <para><function>sd_bus_negotiate_creds()</function> controls
 114     whether implicit sender credentials shall be attached
 115     automatically to all incoming messages. Takes a bus object and a
 116     bit mask value, which controls which credential parameters are
 117     attached. If this is not used,
 118     <citerefentry><refentrytitle>sd_bus_message_get_creds</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 119     fails with <constant>-ENODATA</constant> on incoming
 120     messages. Note that not all transports support attaching sender
 121     credentials to messages, or do not support all types of sender
 122     credential parameters. On local transports, the sender credentials
 123     are attached by the kernel and cannot be manipulated by
 124     userspace. By default, no sender credentials are attached.</para>
 125
 126     <para>These functions may be called only before the connection has
 127     been started with
 128     <citerefentry><refentrytitle>sd_bus_start</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
 129   </refsect1>
 130
 131   <refsect1>
 132     <title>Return Value</title>
 133
 134     <para>On success, these functions returns 0 or a
 135     positive integer. On failure, they return a negative errno-style
 136     error code.</para>
 137   </refsect1>
 138
 139   <refsect1>
 140     <title>Errors</title>
 141
 142     <para>Returned errors may indicate the following problems:</para>
 143
 144     <variablelist>
 145       <varlistentry>
 146         <term><varname>-EPERM</varname></term>
 147
 148         <listitem><para>The bus connection has already been started.</para></listitem>
 149       </varlistentry>
 150     </variablelist>
 151   </refsect1>
 152
 153   <refsect1>
 154     <title>Notes</title>
 155
 156     <para><function>sd_bus_negotiate_fs()</function> and the other
 157     functions described here are available as a shared library, which
 158     can be compiled and linked to with the
 159     <constant>libsystemd</constant> <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 160     file.</para>
 161   </refsect1>
 162
 163   <refsect1>
 164     <title>See Also</title>
 165
 166     <para>
 167       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 168       <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 169       <citerefentry><refentrytitle>sd_bus_start</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 170       <citerefentry><refentrytitle>sd_bus_message_can_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 171       <citerefentry><refentrytitle>sd_bus_message_get_monotonic_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 172       <citerefentry><refentrytitle>sd_bus_message_get_creds</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 173     </para>
 174   </refsect1>
 175
 176 </refentry>