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sd-bus objects use hashmaps, which use module-global state, so it is not safe to pass a sd-bus object created by a module instance to another module instance (e.g.: when two libraries static linking sd-bus are pulled in a single process). Initialize a random per-module origin id and store it in the object, and compare it when entering a public API, and error out if they don't match, together with the PID.
110 lines
4.4 KiB
XML
110 lines
4.4 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/4.2/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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<refentry id="sd_bus_set_connected_signal"
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xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>sd_bus_set_connected_signal</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_set_connected_signal</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_set_connected_signal</refname>
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<refname>sd_bus_get_connected_signal</refname>
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<refpurpose>Control emission of local connection establishment signal 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_set_connected_signal</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_get_connected_signal</function></funcdef>
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<paramdef>sd_bus *<parameter>bus</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_set_connected_signal()</function> may be used to control whether a local, synthetic
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<function>Connected()</function> signal message shall be generated and enqueued for dispatching when the connection
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is fully established. If the <parameter>b</parameter> parameter is zero the message is not generated (the default),
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otherwise it is generated.</para>
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<para><function>sd_bus_get_connected_signal()</function> may be used to query whether this feature is enabled. It
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returns zero if not, positive otherwise.</para>
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<para>The <function>Connected()</function> signal message is generated from the
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<literal>org.freedesktop.DBus.Local</literal> service and interface, and
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<literal>/org/freedesktop/DBus/Local</literal> object path. Use
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<citerefentry><refentrytitle>sd_bus_match_signal_async</refentrytitle><manvolnum>3</manvolnum></citerefentry> to
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match on this signal.</para>
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<para>This message is particularly useful on slow transports where connections take a long time to be
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established. This is especially the case when
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<citerefentry><refentrytitle>sd_bus_set_watch_bind</refentrytitle><manvolnum>3</manvolnum></citerefentry> is
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used. The signal is generated when the
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<citerefentry><refentrytitle>sd_bus_is_ready</refentrytitle><manvolnum>3</manvolnum></citerefentry> returns
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positive for the first time.</para>
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<para>The <function>Connected()</function> signal corresponds with the <function>Disconnected()</function> signal
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that is synthesized locally when the connection is terminated. The latter is generated unconditionally however,
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unlike the former which needs to be enabled explicitly before it is generated, with
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<function>sd_bus_set_connected_signal()</function>.</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 positive 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>-ECHILD</constant></term>
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<listitem><para>The bus connection has been created in a different process, library or module instance.</para></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>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_match_signal_async</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_set_watch_bind</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_is_ready</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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