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178 lines
8.7 KiB
XML
178 lines
8.7 KiB
XML
<?xml version='1.0'?>
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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<refentry id="sd_bus_negotiate_fds" xmlns:xi="http://www.w3.org/2001/XInclude">
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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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</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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<refname>sd_bus_get_creds_mask</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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<funcprototype>
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<funcdef>int <function>sd_bus_get_creds_mask</function></funcdef>
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<paramdef>sd_bus *<parameter>bus</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 file descriptor passing shall be
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negotiated for the specified bus 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 that not all transports and servers
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support file descriptor passing. In particular, networked transports generally do not support file
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descriptor passing. To find out whether file 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 descriptor passing is always enabled
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for both sending and receiving or for neither, but never only in one direction. By default, file
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descriptor passing is negotiated for all connections.</para>
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<para><function>sd_bus_negotiate_timestamp()</function> controls whether implicit sender timestamps shall
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be attached automatically to all incoming messages. Takes a bus object and a boolean, which, when true,
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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 calls
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will fail with <constant>-ENODATA</constant>. Note that currently no transports support timestamping of
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messages. By default, message timestamping is not negotiated for 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 boolean
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indicating whether to enable or disable the credential parts encoded in the bit mask value argument. Note
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that not all transports support attaching sender credentials to messages, or do not support all types of
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sender credential parameters, or might suppress them under certain circumstances for individual messages.
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Specifically, dbus1 only supports <constant>SD_BUS_CREDS_UNIQUE_NAME</constant>. The sender credentials
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are suitable for authorization decisions. By default, only
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<constant>SD_BUS_CREDS_WELL_KNOWN_NAMES</constant> and <constant>SD_BUS_CREDS_UNIQUE_NAME</constant> are
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enabled. In fact, these two credential fields are always sent along and cannot be turned off.</para>
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<para><function>sd_bus_get_creds_mask()</function> returns the set of sender credentials that was
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negotiated to be attached to all incoming messages in <parameter>mask</parameter>. This value is an
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upper boundary only. Hence, always make sure to explicitly check which credentials are attached to a
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specific message before using it.</para>
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<para>The <function>sd_bus_negotiate_fds()</function> function may be called only before the connection
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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 <function>sd_bus_negotiate_creds()</function> may
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also be called after a connection has been set up. Note that, when operating on a connection that is
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shared between multiple components of the same program (for example via
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<citerefentry><refentrytitle>sd_bus_default</refentrytitle><manvolnum>3</manvolnum></citerefentry>), it
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is highly recommended to only enable additional per message metadata fields, but never disable them
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again, in order not to 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 a non-negative integer. On failure, they return a negative
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errno-style error code.</para>
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<refsect2>
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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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<varlistentry>
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<term><constant>-EINVAL</constant></term>
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<listitem><para>An argument is invalid.</para>
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<xi:include href="version-info.xml" xpointer="v246"/></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-ENOPKG</constant></term>
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<listitem><para>The bus cannot be resolved.</para>
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<xi:include href="version-info.xml" xpointer="v246"/></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-ECHILD</constant></term>
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<listitem><para>The bus was created in a different process, library or module instance.</para>
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<xi:include href="version-info.xml" xpointer="v246"/></listitem>
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</varlistentry>
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</variablelist>
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</refsect2>
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</refsect1>
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<xi:include href="libsystemd-pkgconfig.xml" />
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<refsect1>
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<title>History</title>
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<para><function>sd_bus_negotiate_fds()</function>,
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<function>sd_bus_negotiate_timestamp()</function>, and
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<function>sd_bus_negotiate_creds()</function> were added in version 212.</para>
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<para><function>sd_bus_get_creds_mask()</function> was added in version 246.</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para><simplelist type="inline">
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<member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>sd_bus_start</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>sd_bus_can_send</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>sd_bus_message_get_monotonic_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>sd_bus_message_get_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>sd_bus_message_get_seqnum</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>sd_bus_message_get_creds</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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</simplelist></para>
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</refsect1>
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</refentry>
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