-<?xml version='1.0'?> <!--*-nxml-*-->
-<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
- "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
-<!ENTITY % entities SYSTEM "custom-entities.ent" >
-%entities;
-]>
-
-<!--
- This file is part of systemd.
-
- Copyright 2010 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.
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- WITHOUT ANY WARRANTY; without even the implied warranty of
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- 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/>.
--->
+<?xml version='1.0'?>
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
+ "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+<!-- SPDX-License-Identifier: LGPL-2.1+ -->
<refentry id="sd_listen_fds"
xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>sd_listen_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>
<refnamediv>
<refname>sd_listen_fds</refname>
+ <refname>sd_listen_fds_with_names</refname>
<refname>SD_LISTEN_FDS_START</refname>
<refpurpose>Check for file descriptors passed by the system manager</refpurpose>
</refnamediv>
<funcdef>int <function>sd_listen_fds</function></funcdef>
<paramdef>int <parameter>unset_environment</parameter></paramdef>
</funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_listen_fds_with_names</function></funcdef>
+ <paramdef>int <parameter>unset_environment</parameter></paramdef>
+ <paramdef>char*** <parameter>names</parameter></paramdef>
+ </funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
- <para><function>sd_listen_fds()</function> shall be called by a
- daemon to check for file descriptors passed by the init system as
- part of the socket-based activation logic.</para>
-
- <para>If the <parameter>unset_environment</parameter> parameter is
- non-zero, <function>sd_listen_fds()</function> will unset the
- <varname>$LISTEN_FDS</varname> and <varname>$LISTEN_PID</varname>
- environment variables before returning (regardless of whether the
- function call itself succeeded or not). Further calls to
- <function>sd_listen_fds()</function> will then fail, but the
- variables are no longer inherited by child processes.</para>
+ <para><function>sd_listen_fds()</function> may be invoked by a
+ daemon to check for file descriptors passed by the service manager as
+ part of the socket-based activation logic. It returns the number
+ of received file descriptors. If no file descriptors have been
+ received, zero is returned. The first file descriptor may be found
+ at file descriptor number 3
+ (i.e. <constant>SD_LISTEN_FDS_START</constant>), the remaining
+ descriptors follow at 4, 5, 6, …, if any.</para>
<para>If a daemon receives more than one file descriptor, they
will be passed in the same order as configured in the systemd
passed file descriptors to avoid further inheritance to children
of the calling process.</para>
- <para>If multiple socket units activate the same service the order
+ <para>If multiple socket units activate the same service, the order
of the file descriptors passed to its main process is undefined.
If additional file descriptors have been passed to the service
manager using
<literal>FDSTORE=1</literal> messages, these file descriptors are
passed last, in arbitrary order, and with duplicates
removed.</para>
+
+ <para>If the <parameter>unset_environment</parameter> parameter is
+ non-zero, <function>sd_listen_fds()</function> will unset the
+ <varname>$LISTEN_FDS</varname>, <varname>$LISTEN_PID</varname> and
+ <varname>$LISTEN_FDNAMES</varname> environment variables before
+ returning (regardless of whether the function call itself
+ succeeded or not). Further calls to
+ <function>sd_listen_fds()</function> will then return zero, but the
+ variables are no longer inherited by child processes.</para>
+
+ <para><function>sd_listen_fds_with_names()</function> is like
+ <function>sd_listen_fds()</function>, but optionally also returns
+ an array of strings with identification names for the passed file
+ descriptors, if that is available and the
+ <parameter>names</parameter> parameter is non-NULL. This
+ information is read from the <varname>$LISTEN_FDNAMES</varname>
+ variable, which may contain a colon-separated list of names. For
+ socket-activated services, these names may be configured with the
+ <varname>FileDescriptorName=</varname> setting in socket unit
+ files, see
+ <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ for details. For file descriptors pushed into the file descriptor
+ store (see above), the name is set via the
+ <varname>FDNAME=</varname> field transmitted via
+ <function>sd_pid_notify_with_fds()</function>. The primary usecase
+ for these names are services which accept a variety of file
+ descriptors which are not recognizable with functions like
+ <function>sd_is_socket()</function> alone, and thus require
+ identification via a name. It is recommended to rely on named file
+ descriptors only if identification via
+ <function>sd_is_socket()</function> and related calls is not
+ sufficient. Note that the names used are not unique in any
+ way. The returned array of strings has as many entries as file
+ descriptors have been received, plus a final NULL pointer
+ terminating the array. The caller needs to free the array itself
+ and each of its elements with libc's <function>free()</function>
+ call after use. If the <parameter>names</parameter> parameter is
+ NULL, the call is entirely equivalent to
+ <function>sd_listen_fds()</function>.</para>
+
+ <para>Under specific conditions, the following automatic file
+ descriptor names are returned:
+
+ <table>
+ <title>
+ <command>Special names</command>
+ </title>
+
+ <tgroup cols='2'>
+ <thead>
+ <row>
+ <entry>Name</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry><literal>unknown</literal></entry>
+ <entry>The process received no name for the specific file descriptor from the service manager.</entry>
+ </row>
+
+ <row>
+ <entry><literal>stored</literal></entry>
+ <entry>The file descriptor originates in the service manager's per-service file descriptor store, and the <varname>FDNAME=</varname> field was absent when the file descriptor was submitted to the service manager.</entry>
+ </row>
+
+ <row>
+ <entry><literal>connection</literal></entry>
+ <entry>The service was activated in per-connection style using <varname>Accept=yes</varname> in the socket unit file, and the file descriptor is the connection socket.</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+ </para>
</refsect1>
<refsect1>
<title>Return Value</title>
- <para>On failure, this call returns a negative errno-style error
+ <para>On failure, these calls returns a negative errno-style error
code. If
<varname>$LISTEN_FDS</varname>/<varname>$LISTEN_PID</varname> was
not set or was not correctly set for this daemon and hence no file
<xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/>
- <para>Internally, this function checks whether the
- <varname>$LISTEN_PID</varname> environment variable equals the
- daemon PID. If not, it returns immediately. Otherwise, it parses
- the number passed in the <varname>$LISTEN_FDS</varname>
+ <para>Internally, <function>sd_listen_fds()</function> checks
+ whether the <varname>$LISTEN_PID</varname> environment variable
+ equals the daemon PID. If not, it returns immediately. Otherwise,
+ it parses the number passed in the <varname>$LISTEN_FDS</varname>
environment variable, then sets the FD_CLOEXEC flag for the parsed
number of file descriptors starting from SD_LISTEN_FDS_START.
- Finally, it returns the parsed number.</para>
+ Finally, it returns the parsed
+ number. <function>sd_listen_fds_with_names()</function> does the
+ same but also parses <varname>$LISTEN_FDNAMES</varname> if
+ set.</para>
</refsect1>
<refsect1>
<varlistentry>
<term><varname>$LISTEN_PID</varname></term>
<term><varname>$LISTEN_FDS</varname></term>
-
- <listitem><para>Set by the init system
- for supervised processes that use
- socket-based activation. This
- environment variable specifies the
- data
- <function>sd_listen_fds()</function>
- parses. See above for
- details.</para></listitem>
+ <term><varname>$LISTEN_FDNAMES</varname></term>
+
+ <listitem><para>Set by the service manager for supervised
+ processes that use socket-based activation. This environment
+ variable specifies the data
+ <function>sd_listen_fds()</function> and
+ <function>sd_listen_fds_with_names()</function> parses. See
+ above for details.</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<citerefentry><refentrytitle>sd_is_socket</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_is_socket_inet</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_is_socket_unix</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_pid_notify_with_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>
projects / thirdparty / systemd.git / blobdiff