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11a1589223
Files which are installed as-is (any .service and other unit files, .conf files, .policy files, etc), are left as is. My assumption is that SPDX identifiers are not yet that well known, so it's better to retain the extended header to avoid any doubt. I also kept any copyright lines. We can probably remove them, but it'd nice to obtain explicit acks from all involved authors before doing that.
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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