1<?xml version='1.0'?> 2<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" 3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> 4<!-- SPDX-License-Identifier: LGPL-2.1-or-later --> 5 6<refentry id="sd_bus_negotiate_fds" xmlns:xi="http://www.w3.org/2001/XInclude"> 7 8 <refentryinfo> 9 <title>sd_bus_negotiate_fds</title> 10 <productname>systemd</productname> 11 </refentryinfo> 12 13 <refmeta> 14 <refentrytitle>sd_bus_negotiate_fds</refentrytitle> 15 <manvolnum>3</manvolnum> 16 </refmeta> 17 18 <refnamediv> 19 <refname>sd_bus_negotiate_fds</refname> 20 <refname>sd_bus_negotiate_timestamp</refname> 21 <refname>sd_bus_negotiate_creds</refname> 22 <refname>sd_bus_get_creds_mask</refname> 23 24 <refpurpose>Control feature negotiation on bus connections</refpurpose> 25 </refnamediv> 26 27 <refsynopsisdiv> 28 <funcsynopsis> 29 <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> 30 31 <funcprototype> 32 <funcdef>int <function>sd_bus_negotiate_fds</function></funcdef> 33 <paramdef>sd_bus *<parameter>bus</parameter></paramdef> 34 <paramdef>int <parameter>b</parameter></paramdef> 35 </funcprototype> 36 37 <funcprototype> 38 <funcdef>int <function>sd_bus_negotiate_timestamp</function></funcdef> 39 <paramdef>sd_bus *<parameter>bus</parameter></paramdef> 40 <paramdef>int <parameter>b</parameter></paramdef> 41 </funcprototype> 42 43 <funcprototype> 44 <funcdef>int <function>sd_bus_negotiate_creds</function></funcdef> 45 <paramdef>sd_bus *<parameter>bus</parameter></paramdef> 46 <paramdef>int <parameter>b</parameter></paramdef> 47 <paramdef>uint64_t <parameter>mask</parameter></paramdef> 48 </funcprototype> 49 50 <funcprototype> 51 <funcdef>int <function>sd_bus_get_creds_mask</function></funcdef> 52 <paramdef>sd_bus *<parameter>bus</parameter></paramdef> 53 <paramdef>uint64_t *<parameter>mask</parameter></paramdef> 54 </funcprototype> 55 </funcsynopsis> 56 </refsynopsisdiv> 57 58 <refsect1> 59 <title>Description</title> 60 61 <para><function>sd_bus_negotiate_fds()</function> controls whether file descriptor passing shall be 62 negotiated for the specified bus connection. It takes a bus object and a boolean, which, when true, 63 enables file descriptor passing, and, when false, disables it. Note that not all transports and servers 64 support file descriptor passing. In particular, networked transports generally do not support file 65 descriptor passing. To find out whether file descriptor passing is available after negotiation, use 66 <citerefentry><refentrytitle>sd_bus_can_send</refentrytitle><manvolnum>3</manvolnum></citerefentry> 67 and pass <constant>SD_BUS_TYPE_UNIX_FD</constant>. Note that file descriptor passing is always enabled 68 for both sending and receiving or for neither, but never only in one direction. By default, file 69 descriptor passing is negotiated for all connections.</para> 70 71 <para><function>sd_bus_negotiate_timestamp()</function> controls whether implicit sender timestamps shall 72 be attached automatically to all incoming messages. Takes a bus object and a boolean, which, when true, 73 enables timestamping, and, when false, disables it. Use 74 <citerefentry><refentrytitle>sd_bus_message_get_monotonic_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>, 75 <citerefentry><refentrytitle>sd_bus_message_get_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>, 76 <citerefentry><refentrytitle>sd_bus_message_get_seqnum</refentrytitle><manvolnum>3</manvolnum></citerefentry> 77 to query the timestamps of incoming messages. If negotiation is disabled or not supported, these calls 78 will fail with <constant>-ENODATA</constant>. Note that currently no transports support timestamping of 79 messages. By default, message timestamping is not negotiated for connections.</para> 80 81 <para><function>sd_bus_negotiate_creds()</function> controls whether and which implicit sender 82 credentials shall be attached automatically to all incoming messages. Takes a bus object and a boolean 83 indicating whether to enable or disable the credential parts encoded in the bit mask value argument. Note 84 that not all transports support attaching sender credentials to messages, or do not support all types of 85 sender credential parameters, or might suppress them under certain circumstances for individual messages. 86 Specifically, dbus1 only supports <constant>SD_BUS_CREDS_UNIQUE_NAME</constant>. The sender credentials 87 are suitable for authorization decisions. By default, only 88 <constant>SD_BUS_CREDS_WELL_KNOWN_NAMES</constant> and <constant>SD_BUS_CREDS_UNIQUE_NAME</constant> are 89 enabled. In fact, these two credential fields are always sent along and cannot be turned off.</para> 90 91 <para><function>sd_bus_get_creds_mask()</function> returns the set of sender credentials that was 92 negotiated to be attached to all incoming messages in <parameter>mask</parameter>. This value is an 93 upper boundary only. Hence, always make sure to explicitly check which credentials are attached to a 94 specific message before using it.</para> 95 96 <para>The <function>sd_bus_negotiate_fds()</function> function may be called only before the connection 97 has been started with 98 <citerefentry><refentrytitle>sd_bus_start</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Both 99 <function>sd_bus_negotiate_timestamp()</function> and <function>sd_bus_negotiate_creds()</function> may 100 also be called after a connection has been set up. Note that, when operating on a connection that is 101 shared between multiple components of the same program (for example via 102 <citerefentry><refentrytitle>sd_bus_default</refentrytitle><manvolnum>3</manvolnum></citerefentry>), it 103 is highly recommended to only enable additional per message metadata fields, but never disable them 104 again, in order not to disable functionality needed by other components.</para> 105 </refsect1> 106 107 <refsect1> 108 <title>Return Value</title> 109 110 <para>On success, these functions return a non-negative integer. On failure, they return a negative 111 errno-style error code.</para> 112 113 <refsect2> 114 <title>Errors</title> 115 116 <para>Returned errors may indicate the following problems:</para> 117 118 <variablelist> 119 <varlistentry> 120 <term><constant>-EPERM</constant></term> 121 122 <listitem><para>The bus connection has already been started.</para></listitem> 123 </varlistentry> 124 125 <varlistentry> 126 <term><constant>-EINVAL</constant></term> 127 128 <listitem><para>An argument is invalid.</para></listitem> 129 </varlistentry> 130 131 <varlistentry> 132 <term><constant>-ENOPKG</constant></term> 133 134 <listitem><para>The bus cannot be resolved.</para></listitem> 135 </varlistentry> 136 137 <varlistentry> 138 <term><constant>-ECHILD</constant></term> 139 140 <listitem><para>The bus was created in a different process.</para></listitem> 141 </varlistentry> 142 </variablelist> 143 </refsect2> 144 </refsect1> 145 146 <xi:include href="libsystemd-pkgconfig.xml" /> 147 148 <refsect1> 149 <title>See Also</title> 150 151 <para> 152 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, 153 <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, 154 <citerefentry><refentrytitle>sd_bus_start</refentrytitle><manvolnum>3</manvolnum></citerefentry>, 155 <citerefentry><refentrytitle>sd_bus_can_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>, 156 <citerefentry><refentrytitle>sd_bus_message_get_monotonic_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>, 157 <citerefentry><refentrytitle>sd_bus_message_get_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>, 158 <citerefentry><refentrytitle>sd_bus_message_get_seqnum</refentrytitle><manvolnum>3</manvolnum></citerefentry>, 159 <citerefentry><refentrytitle>sd_bus_message_get_creds</refentrytitle><manvolnum>3</manvolnum></citerefentry> 160 </para> 161 </refsect1> 162 163</refentry> 164