mirror of
https://github.com/systemd/systemd.git
synced 2024-11-24 18:53:33 +08:00
201 lines
8.9 KiB
XML
201 lines
8.9 KiB
XML
<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
|
||
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
|
||
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
|
||
|
||
<!--
|
||
This file is part of systemd.
|
||
|
||
Copyright 2014 Lennart Poettering
|
||
|
||
systemd is free software; you can redistribute it and/or modify it
|
||
under the terms of the GNU Lesser General Public License as published by
|
||
the Free Software Foundation; either version 2.1 of the License, or
|
||
(at your option) any later version.
|
||
|
||
systemd is distributed in the hope that it will be useful, but
|
||
WITHOUT ANY WARRANTY; without even the implied warranty of
|
||
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
||
Lesser General Public License for more details.
|
||
|
||
You should have received a copy of the GNU Lesser General Public License
|
||
along with systemd; If not, see <http://www.gnu.org/licenses/>.
|
||
-->
|
||
|
||
<refentry id="sd_bus_negotiate_fds">
|
||
|
||
<refentryinfo>
|
||
<title>sd_bus_negotiate_fds</title>
|
||
<productname>systemd</productname>
|
||
|
||
<authorgroup>
|
||
<author>
|
||
<contrib>Developer</contrib>
|
||
<firstname>Lennart</firstname>
|
||
<surname>Poettering</surname>
|
||
<email>lennart@poettering.net</email>
|
||
</author>
|
||
</authorgroup>
|
||
</refentryinfo>
|
||
|
||
<refmeta>
|
||
<refentrytitle>sd_bus_negotiate_fds</refentrytitle>
|
||
<manvolnum>3</manvolnum>
|
||
</refmeta>
|
||
|
||
<refnamediv>
|
||
<refname>sd_bus_negotiate_fds</refname>
|
||
<refname>sd_bus_negotiate_timestamp</refname>
|
||
<refname>sd_bus_negotiate_creds</refname>
|
||
|
||
<refpurpose>Control feature negotiation on bus connections</refpurpose>
|
||
</refnamediv>
|
||
|
||
<refsynopsisdiv>
|
||
<funcsynopsis>
|
||
<funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
|
||
|
||
<funcprototype>
|
||
<funcdef>int <function>sd_bus_negotiate_fds</function></funcdef>
|
||
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
|
||
<paramdef>int <parameter>b</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
<funcprototype>
|
||
<funcdef>int <function>sd_bus_negotiate_timestamp</function></funcdef>
|
||
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
|
||
<paramdef>int <parameter>b</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
<funcprototype>
|
||
<funcdef>int <function>sd_bus_negotiate_creds</function></funcdef>
|
||
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
|
||
<paramdef>int <parameter>b</parameter></paramdef>
|
||
<paramdef>uint64_t <parameter>mask</parameter></paramdef>
|
||
</funcprototype>
|
||
</funcsynopsis>
|
||
</refsynopsisdiv>
|
||
|
||
<refsect1>
|
||
<title>Description</title>
|
||
|
||
<para><function>sd_bus_negotiate_fds()</function> controls whether
|
||
file descriptor passing shall be negotiated for the specified bus
|
||
connection. It takes a bus object and a boolean, which, when true,
|
||
enables file descriptor passing, and, when false, disables
|
||
it. Note that not all transports and servers support file
|
||
descriptor passing. In particular, networked transports generally
|
||
do not support file descriptor passing. To find out whether file
|
||
descriptor passing is available after negotiation, use
|
||
<citerefentry><refentrytitle>sd_bus_can_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
||
and pass <constant>SD_BUS_TYPE_UNIX_FD</constant>. Note that file
|
||
descriptor passing is always enabled for both sending and
|
||
receiving or for neither, but never only in one direction. By
|
||
default, file descriptor passing is negotiated for all
|
||
connections.</para>
|
||
|
||
<para>Note that when bus activation is used, it is highly
|
||
recommended to set the <option>AcceptFileDescriptors=</option>
|
||
setting in the <filename>.busname</filename> unit file to the same
|
||
setting as negotiated by the program ultimately activated. By
|
||
default, file descriptor passing is enabled for both.</para>
|
||
|
||
<para><function>sd_bus_negotiate_timestamps()</function> controls
|
||
whether implicit sender timestamps shall be attached automatically
|
||
to all incoming messages. Takes a bus object and a boolean, which,
|
||
when true, enables timestamping, and, when false, disables it.
|
||
Use
|
||
<citerefentry><refentrytitle>sd_bus_message_get_monotonic_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>sd_bus_message_get_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>sd_bus_message_get_seqnum</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
||
to query the timestamps of incoming messages. If negotiation is
|
||
disabled or not supported, these calls will fail with
|
||
<constant>-ENODATA</constant>. Note that not all transports
|
||
support timestamping of messages. Specifically, timestamping is
|
||
only available on the kdbus transport, but not on dbus1. The
|
||
timestamping is applied by the kernel and cannot be manipulated by
|
||
userspace. By default, message timestamping is not negotiated for
|
||
connections.</para>
|
||
|
||
<para><function>sd_bus_negotiate_creds()</function> controls
|
||
whether and which implicit sender credentials shall be attached
|
||
automatically to all incoming messages. Takes a bus object and a
|
||
boolean indicating whether to enable or disable the credential
|
||
parts encoded in the bit mask value argument. Note that not all
|
||
transports support attaching sender credentials to messages, or do
|
||
not support all types of sender credential parameters, or might
|
||
suppress them under certain circumstances for individual
|
||
messages. Specifically, implicit sender credentials on messages
|
||
are only fully supported on kdbus transports, and dbus1 only
|
||
supports <constant>SD_BUS_CREDS_UNIQUE_NAME</constant>. The sender
|
||
credentials are attached by the kernel and cannot be manipulated
|
||
by userspace, and are thus suitable for authorization
|
||
decisions. By default, only
|
||
<constant>SD_BUS_CREDS_WELL_KNOWN_NAMES</constant> and
|
||
<constant>SD_BUS_CREDS_UNIQUE_NAME</constant> are enabled. In
|
||
fact, these two credential fields are always sent along and cannot
|
||
be turned off.</para>
|
||
|
||
<para>The <function>sd_bus_negotiate_fds()</function> function may
|
||
be called only before the connection has been started with
|
||
<citerefentry><refentrytitle>sd_bus_start</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Both
|
||
<function>sd_bus_negotiate_timestamp()</function> and
|
||
<function>sd_bus_negotiate_creds()</function> may also be called
|
||
after a connection has been set up. Note that, when operating on a
|
||
connection that is shared between multiple components of the same
|
||
program (for example via
|
||
<citerefentry><refentrytitle>sd_bus_default</refentrytitle><manvolnum>3</manvolnum></citerefentry>),
|
||
it is highly recommended to only enable additional per message
|
||
metadata fields, but never disable them again, in order not to
|
||
disable functionality needed by other components.</para>
|
||
</refsect1>
|
||
|
||
<refsect1>
|
||
<title>Return Value</title>
|
||
|
||
<para>On success, these functions return 0 or a
|
||
positive integer. On failure, they return a negative errno-style
|
||
error code.</para>
|
||
</refsect1>
|
||
|
||
<refsect1>
|
||
<title>Errors</title>
|
||
|
||
<para>Returned errors may indicate the following problems:</para>
|
||
|
||
<variablelist>
|
||
<varlistentry>
|
||
<term><constant>-EPERM</constant></term>
|
||
|
||
<listitem><para>The bus connection has already been started.</para></listitem>
|
||
</varlistentry>
|
||
</variablelist>
|
||
</refsect1>
|
||
|
||
<refsect1>
|
||
<title>Notes</title>
|
||
|
||
<para><function>sd_bus_negotiate_fds()</function> and the other
|
||
functions described here are available as a shared library, which
|
||
can be compiled and linked to with the
|
||
<constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
|
||
file.</para>
|
||
</refsect1>
|
||
|
||
<refsect1>
|
||
<title>See Also</title>
|
||
|
||
<para>
|
||
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>sd_bus_start</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>sd_bus_message_can_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>sd_bus_message_get_monotonic_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>sd_bus_message_get_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>sd_bus_message_get_seqnum</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>sd_bus_message_get_creds</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>systemd.busname</refentrytitle><manvolnum>5</manvolnum></citerefentry>
|
||
</para>
|
||
</refsect1>
|
||
|
||
</refentry>
|