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<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
This file is part of systemd.
Copyright 2014 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->
<refentry id="sd_bus_negotiate_fds" conditional="ENABLE_KDBUS">
<refentryinfo>
<title>sd_bus_negotiate_fds</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>Developer</contrib>
<firstname>Lennart</firstname>
<surname>Poettering</surname>
<email>lennart@poettering.net</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>sd_bus_negotiate_fds</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>sd_bus_negotiate_fds</refname>
<refname>sd_bus_negotiate_timestamps</refname>
<refname>sd_bus_negotiate_creds</refname>
<refpurpose>Control feature negotiation on bus connections</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
<funcprototype>
<funcdef>int <function>sd_bus_negotiate_fds</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>int <parameter>b</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_bus_negotiate_timestamp</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>int <parameter>b</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_bus_negotiate_creds</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>int <parameter>b</parameter></paramdef>
<paramdef>uint64_t <parameter>flags</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><function>sd_bus_negotiate_fds()</function> controls whether
file descriptor passing shall be negotiated for the specified bus
connection. It takes a bus object and a boolean, which, when true,
enables file descriptor passing, and, when false, disables it. Note
that not all transports and servers support file descriptor
passing. To find out whether file descriptor passing is available
after negotiation, use
<citerefentry><refentrytitle>sd_bus_can_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>
and pass <constant>SD_BUS_TYPE_UNIX_FD</constant>. Note that file
descriptor passing is always enabled for both sending and
receiving or for neither, but never only in one direction. By
default, file descriptor passing is negotiated for all
connections.</para>
<para>Note that when bus activation is used, it is highly
recommended to set the <option>AcceptFileDescriptors=</option>
setting in the <filename>.busname</filename> unit file to the same
setting as negotiated by the program ultimately activated. By
default, file descriptor passing is enabled for both.</para>
<para><function>sd_bus_negotiate_timestamps()</function> controls
whether implicit sender timestamps shall be attached automatically
to all incoming messages. Takes a bus object and a boolean, which,
when true, enables timestamping, and, when false, disables it. If
this is disabled,
<citerefentry><refentrytitle>sd_bus_message_get_monotonic_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_message_get_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_message_get_seqno</refentrytitle><manvolnum>3</manvolnum></citerefentry>
fail with <constant>-ENODATA</constant> on incoming messages. Note
that not all transports support timestamping of messages. On local
transports, the timestamping is applied by the kernel and cannot
be manipulated by userspace. By default, message timestamping is
not negotiated for all connections.</para>
<para><function>sd_bus_negotiate_creds()</function> controls
whether implicit sender credentials shall be attached
automatically to all incoming messages. Takes a bus object, a
boolean indicating whether to enable or disable the credential
parts encoded in the bit mask value argument. Note that not all
transports support attaching sender credentials to messages, or do
not support all types of sender credential parameters, or might
suppress them under certain circumstances for individual
messages. On local transports, the sender credentials are attached
by the kernel and cannot be manipulated by userspace. By default,
no sender credentials are attached.</para>
<para>The <function>sd_bus_negotiate_fds()</function> function may
be called only before the connection has been started with
<citerefentry><refentrytitle>sd_bus_start</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Both
<function>sd_bus_negotiate_timestamp()</function> and
<function>sd_bus_negotiate_creds()</function> also may be called
after a connection has been set up. Note that when operating on a
connection that is shared between multiple components of the same
program (for example via
<citerefentry><refentrytitle>sd_bus_default</refentrytitle><manvolnum>3</manvolnum></citerefentry>)
it is highly recommended to only enable additional per message
metadata fields, but never disable them again, in order not to
disable functionality needed by other components.</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para>On success, these functions returns 0 or a
positive integer. On failure, they return a negative errno-style
error code.</para>
</refsect1>
<refsect1>
<title>Errors</title>
<para>Returned errors may indicate the following problems:</para>
<variablelist>
<varlistentry>
<term><constant>-EPERM</constant></term>
<listitem><para>The bus connection has already been started.</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Notes</title>
<para><function>sd_bus_negotiate_fs()</function> and the other
functions described here are available as a shared library, which
can be compiled and linked to with the
<constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
file.</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_start</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_message_can_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_message_get_monotonic_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_message_get_creds</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.busname</refentrytitle><manvolnum>5</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
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