169 lines
7.5 KiB
XML
169 lines
7.5 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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SPDX-License-Identifier: LGPL-2.1+
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This file is part of systemd.
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Copyright 2014 Lennart Poettering
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-->
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<refentry id="sd_bus_negotiate_fds">
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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_timestamp</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>mask</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
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it. Note that not all transports and servers support file
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descriptor passing. In particular, networked transports generally
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do not support file descriptor passing. To find out whether file
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descriptor passing is available 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><function>sd_bus_negotiate_timestamp()</function> controls whether implicit sender
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timestamps shall be attached automatically to all incoming messages. Takes a bus object and a
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boolean, which, when true, enables timestamping, and, when false, disables it. Use
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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_seqnum</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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to query the timestamps of incoming messages. If negotiation is disabled or not supported, these
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calls will fail with <constant>-ENODATA</constant>. Note that currently no transports support
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timestamping of messages. By default, message timestamping is not negotiated for
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connections.</para>
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<para><function>sd_bus_negotiate_creds()</function> controls whether and which implicit sender
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credentials shall be attached automatically to all incoming messages. Takes a bus object and a
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boolean indicating whether to enable or disable the credential parts encoded in the bit mask
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value argument. Note that not all transports support attaching sender credentials to messages,
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or do not support all types of sender credential parameters, or might suppress them under
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certain circumstances for individual messages. Specifically, dbus1 only supports
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<constant>SD_BUS_CREDS_UNIQUE_NAME</constant>. The sender credentials are suitable for
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authorization decisions. By default, only <constant>SD_BUS_CREDS_WELL_KNOWN_NAMES</constant> and
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<constant>SD_BUS_CREDS_UNIQUE_NAME</constant> are enabled. In fact, these two credential fields
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are always sent along and cannot be turned off.</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> may also 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 return 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_fds()</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_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_message_get_seqnum</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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</para>
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</refsect1>
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</refentry>
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