]>
Commit | Line | Data |
---|---|---|
8dd4c05b | 1 | <?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*--> |
f9378423 | 2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" |
12b42c76 | 3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
f9378423 LP |
4 | |
5 | <!-- | |
572eb058 ZJS |
6 | SPDX-License-Identifier: LGPL-2.1+ |
7 | ||
f9378423 LP |
8 | This file is part of systemd. |
9 | ||
10 | Copyright 2010 Lennart Poettering | |
11 | ||
12 | systemd is free software; you can redistribute it and/or modify it | |
5430f7f2 LP |
13 | under the terms of the GNU Lesser General Public License as published by |
14 | the Free Software Foundation; either version 2.1 of the License, or | |
f9378423 LP |
15 | (at your option) any later version. |
16 | ||
17 | systemd is distributed in the hope that it will be useful, but | |
18 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
5430f7f2 | 20 | Lesser General Public License for more details. |
f9378423 | 21 | |
5430f7f2 | 22 | You should have received a copy of the GNU Lesser General Public License |
f9378423 LP |
23 | along with systemd; If not, see <http://www.gnu.org/licenses/>. |
24 | --> | |
25 | ||
6a70f3aa | 26 | <refentry id="sd_listen_fds" |
798d3a52 ZJS |
27 | xmlns:xi="http://www.w3.org/2001/XInclude"> |
28 | ||
29 | <refentryinfo> | |
30 | <title>sd_listen_fds</title> | |
31 | <productname>systemd</productname> | |
32 | ||
33 | <authorgroup> | |
34 | <author> | |
35 | <contrib>Developer</contrib> | |
36 | <firstname>Lennart</firstname> | |
37 | <surname>Poettering</surname> | |
38 | <email>lennart@poettering.net</email> | |
39 | </author> | |
40 | </authorgroup> | |
41 | </refentryinfo> | |
42 | ||
43 | <refmeta> | |
44 | <refentrytitle>sd_listen_fds</refentrytitle> | |
45 | <manvolnum>3</manvolnum> | |
46 | </refmeta> | |
47 | ||
48 | <refnamediv> | |
49 | <refname>sd_listen_fds</refname> | |
8dd4c05b | 50 | <refname>sd_listen_fds_with_names</refname> |
798d3a52 ZJS |
51 | <refname>SD_LISTEN_FDS_START</refname> |
52 | <refpurpose>Check for file descriptors passed by the system manager</refpurpose> | |
53 | </refnamediv> | |
54 | ||
55 | <refsynopsisdiv> | |
56 | <funcsynopsis> | |
57 | <funcsynopsisinfo>#include <systemd/sd-daemon.h></funcsynopsisinfo> | |
58 | ||
59 | <funcsynopsisinfo>#define SD_LISTEN_FDS_START 3</funcsynopsisinfo> | |
60 | ||
61 | <funcprototype> | |
62 | <funcdef>int <function>sd_listen_fds</function></funcdef> | |
63 | <paramdef>int <parameter>unset_environment</parameter></paramdef> | |
64 | </funcprototype> | |
8dd4c05b LP |
65 | |
66 | <funcprototype> | |
67 | <funcdef>int <function>sd_listen_fds_with_names</function></funcdef> | |
68 | <paramdef>int <parameter>unset_environment</parameter></paramdef> | |
69 | <paramdef>char*** <parameter>names</parameter></paramdef> | |
70 | </funcprototype> | |
798d3a52 ZJS |
71 | </funcsynopsis> |
72 | </refsynopsisdiv> | |
73 | ||
74 | <refsect1> | |
75 | <title>Description</title> | |
76 | ||
8dd4c05b LP |
77 | <para><function>sd_listen_fds()</function> may be invoked by a |
78 | daemon to check for file descriptors passed by the service manager as | |
79 | part of the socket-based activation logic. It returns the number | |
80 | of received file descriptors. If no file descriptors have been | |
b938cb90 | 81 | received, zero is returned. The first file descriptor may be found |
8dd4c05b LP |
82 | at file descriptor number 3 |
83 | (i.e. <constant>SD_LISTEN_FDS_START</constant>), the remaining | |
1eecafb8 | 84 | descriptors follow at 4, 5, 6, …, if any.</para> |
798d3a52 ZJS |
85 | |
86 | <para>If a daemon receives more than one file descriptor, they | |
87 | will be passed in the same order as configured in the systemd | |
88 | socket unit file (see | |
89 | <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
90 | for details). Nonetheless, it is recommended to verify the correct | |
91 | socket types before using them. To simplify this checking, the | |
92 | functions | |
93 | <citerefentry><refentrytitle>sd_is_fifo</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
94 | <citerefentry><refentrytitle>sd_is_socket</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
95 | <citerefentry><refentrytitle>sd_is_socket_inet</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
96 | <citerefentry><refentrytitle>sd_is_socket_unix</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
97 | are provided. In order to maximize flexibility, it is recommended | |
98 | to make these checks as loose as possible without allowing | |
99 | incorrect setups. i.e. often, the actual port number a socket is | |
100 | bound to matters little for the service to work, hence it should | |
101 | not be verified. On the other hand, whether a socket is a datagram | |
102 | or stream socket matters a lot for the most common program logics | |
103 | and should be checked.</para> | |
104 | ||
105 | <para>This function call will set the FD_CLOEXEC flag for all | |
106 | passed file descriptors to avoid further inheritance to children | |
107 | of the calling process.</para> | |
108 | ||
b938cb90 | 109 | <para>If multiple socket units activate the same service, the order |
798d3a52 ZJS |
110 | of the file descriptors passed to its main process is undefined. |
111 | If additional file descriptors have been passed to the service | |
112 | manager using | |
113 | <citerefentry><refentrytitle>sd_pid_notify_with_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>'s | |
114 | <literal>FDSTORE=1</literal> messages, these file descriptors are | |
115 | passed last, in arbitrary order, and with duplicates | |
116 | removed.</para> | |
8dd4c05b LP |
117 | |
118 | <para>If the <parameter>unset_environment</parameter> parameter is | |
119 | non-zero, <function>sd_listen_fds()</function> will unset the | |
120 | <varname>$LISTEN_FDS</varname>, <varname>$LISTEN_PID</varname> and | |
121 | <varname>$LISTEN_FDNAMES</varname> environment variables before | |
122 | returning (regardless of whether the function call itself | |
123 | succeeded or not). Further calls to | |
124 | <function>sd_listen_fds()</function> will then return zero, but the | |
125 | variables are no longer inherited by child processes.</para> | |
126 | ||
127 | <para><function>sd_listen_fds_with_names()</function> is like | |
b938cb90 | 128 | <function>sd_listen_fds()</function>, but optionally also returns |
8dd4c05b | 129 | an array of strings with identification names for the passed file |
b938cb90 | 130 | descriptors, if that is available and the |
8dd4c05b LP |
131 | <parameter>names</parameter> parameter is non-NULL. This |
132 | information is read from the <varname>$LISTEN_FDNAMES</varname> | |
133 | variable, which may contain a colon-separated list of names. For | |
134 | socket-activated services, these names may be configured with the | |
135 | <varname>FileDescriptorName=</varname> setting in socket unit | |
136 | files, see | |
137 | <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
138 | for details. For file descriptors pushed into the file descriptor | |
b938cb90 | 139 | store (see above), the name is set via the |
8dd4c05b LP |
140 | <varname>FDNAME=</varname> field transmitted via |
141 | <function>sd_pid_notify_with_fds()</function>. The primary usecase | |
142 | for these names are services which accept a variety of file | |
143 | descriptors which are not recognizable with functions like | |
144 | <function>sd_is_socket()</function> alone, and thus require | |
145 | identification via a name. It is recommended to rely on named file | |
146 | descriptors only if identification via | |
147 | <function>sd_is_socket()</function> and related calls is not | |
148 | sufficient. Note that the names used are not unique in any | |
149 | way. The returned array of strings has as many entries as file | |
a8eaaee7 | 150 | descriptors have been received, plus a final NULL pointer |
8dd4c05b | 151 | terminating the array. The caller needs to free the array itself |
ba6bfc0d | 152 | and each of its elements with libc's <function>free()</function> |
8dd4c05b | 153 | call after use. If the <parameter>names</parameter> parameter is |
b938cb90 | 154 | NULL, the call is entirely equivalent to |
8dd4c05b LP |
155 | <function>sd_listen_fds()</function>.</para> |
156 | ||
b938cb90 | 157 | <para>Under specific conditions, the following automatic file |
8dd4c05b LP |
158 | descriptor names are returned: |
159 | ||
160 | <table> | |
161 | <title> | |
162 | <command>Special names</command> | |
163 | </title> | |
164 | ||
165 | <tgroup cols='2'> | |
166 | <thead> | |
167 | <row> | |
168 | <entry>Name</entry> | |
169 | <entry>Description</entry> | |
170 | </row> | |
171 | </thead> | |
172 | <tbody> | |
173 | <row> | |
174 | <entry><literal>unknown</literal></entry> | |
175 | <entry>The process received no name for the specific file descriptor from the service manager.</entry> | |
176 | </row> | |
177 | ||
178 | <row> | |
179 | <entry><literal>stored</literal></entry> | |
180 | <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> | |
181 | </row> | |
182 | ||
183 | <row> | |
184 | <entry><literal>connection</literal></entry> | |
185 | <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> | |
186 | </row> | |
187 | </tbody> | |
188 | </tgroup> | |
189 | </table> | |
190 | </para> | |
798d3a52 ZJS |
191 | </refsect1> |
192 | ||
193 | <refsect1> | |
194 | <title>Return Value</title> | |
195 | ||
8dd4c05b | 196 | <para>On failure, these calls returns a negative errno-style error |
798d3a52 ZJS |
197 | code. If |
198 | <varname>$LISTEN_FDS</varname>/<varname>$LISTEN_PID</varname> was | |
199 | not set or was not correctly set for this daemon and hence no file | |
200 | descriptors were received, 0 is returned. Otherwise, the number of | |
201 | file descriptors passed is returned. The application may find them | |
202 | starting with file descriptor SD_LISTEN_FDS_START, i.e. file | |
203 | descriptor 3.</para> | |
204 | </refsect1> | |
205 | ||
206 | <refsect1> | |
207 | <title>Notes</title> | |
208 | ||
209 | <xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/> | |
210 | ||
8dd4c05b LP |
211 | <para>Internally, <function>sd_listen_fds()</function> checks |
212 | whether the <varname>$LISTEN_PID</varname> environment variable | |
213 | equals the daemon PID. If not, it returns immediately. Otherwise, | |
214 | it parses the number passed in the <varname>$LISTEN_FDS</varname> | |
798d3a52 ZJS |
215 | environment variable, then sets the FD_CLOEXEC flag for the parsed |
216 | number of file descriptors starting from SD_LISTEN_FDS_START. | |
8dd4c05b LP |
217 | Finally, it returns the parsed |
218 | number. <function>sd_listen_fds_with_names()</function> does the | |
219 | same but also parses <varname>$LISTEN_FDNAMES</varname> if | |
220 | set.</para> | |
798d3a52 ZJS |
221 | </refsect1> |
222 | ||
223 | <refsect1> | |
224 | <title>Environment</title> | |
225 | ||
226 | <variablelist class='environment-variables'> | |
227 | <varlistentry> | |
228 | <term><varname>$LISTEN_PID</varname></term> | |
229 | <term><varname>$LISTEN_FDS</varname></term> | |
8dd4c05b | 230 | <term><varname>$LISTEN_FDNAMES</varname></term> |
798d3a52 | 231 | |
8dd4c05b LP |
232 | <listitem><para>Set by the service manager for supervised |
233 | processes that use socket-based activation. This environment | |
234 | variable specifies the data | |
235 | <function>sd_listen_fds()</function> and | |
236 | <function>sd_listen_fds_with_names()</function> parses. See | |
237 | above for details.</para></listitem> | |
798d3a52 ZJS |
238 | </varlistentry> |
239 | </variablelist> | |
240 | </refsect1> | |
241 | ||
242 | <refsect1> | |
243 | <title>See Also</title> | |
244 | ||
245 | <para> | |
246 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
247 | <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
248 | <citerefentry><refentrytitle>sd_is_fifo</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
249 | <citerefentry><refentrytitle>sd_is_socket</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
250 | <citerefentry><refentrytitle>sd_is_socket_inet</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
251 | <citerefentry><refentrytitle>sd_is_socket_unix</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
8dd4c05b | 252 | <citerefentry><refentrytitle>sd_pid_notify_with_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
798d3a52 ZJS |
253 | <citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>, |
254 | <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
255 | <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
256 | </para> | |
257 | </refsect1> | |
f9378423 LP |
258 | |
259 | </refentry> |