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