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sd-daemon.h
1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
2
3 #ifndef foosddaemonhfoo
4 #define foosddaemonhfoo
5
6 /***
7 Copyright 2010 Lennart Poettering
8
9 Permission is hereby granted, free of charge, to any person
10 obtaining a copy of this software and associated documentation files
11 (the "Software"), to deal in the Software without restriction,
12 including without limitation the rights to use, copy, modify, merge,
13 publish, distribute, sublicense, and/or sell copies of the Software,
14 and to permit persons to whom the Software is furnished to do so,
15 subject to the following conditions:
16
17 The above copyright notice and this permission notice shall be
18 included in all copies or substantial portions of the Software.
19
20 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
21 EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
22 MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
23 NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
24 BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
25 ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
26 CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
27 SOFTWARE.
28 ***/
29
30 #include <sys/types.h>
31 #include <inttypes.h>
32
33 #ifdef __cplusplus
34 extern "C" {
35 #endif
36
37 /*
38 Reference implementation of a few systemd related interfaces for
39 writing daemons. These interfaces are trivial to implement. To
40 simplify porting we provide this reference implementation.
41 Applications are welcome to reimplement the algorithms described
42 here if they do not want to include these two source files.
43
44 The following functionality is provided:
45
46 - Support for logging with log levels on stderr
47 - File descriptor passing for socket-based activation
48 - Daemon startup and status notification
49 - Detection of systemd boots
50
51 You may compile this with -DDISABLE_SYSTEMD to disable systemd
52 support. This makes all those calls NOPs that are directly related to
53 systemd (i.e. only sd_is_xxx() will stay useful).
54
55 Since this is drop-in code we don't want any of our symbols to be
56 exported in any case. Hence we declare hidden visibility for all of
57 them.
58
59 You may find an up-to-date version of these source files online:
60
61 http://cgit.freedesktop.org/systemd/systemd/plain/src/systemd/sd-daemon.h
62 http://cgit.freedesktop.org/systemd/systemd/plain/src/libsystemd-daemon/sd-daemon.c
63
64 This should compile on non-Linux systems, too, but with the
65 exception of the sd_is_xxx() calls all functions will become NOPs.
66
67 See sd-daemon(3) for more information.
68 */
69
70 #ifndef _sd_printf_attr_
71 #if __GNUC__ >= 4
72 #define _sd_printf_attr_(a,b) __attribute__ ((format (printf, a, b)))
73 #else
74 #define _sd_printf_attr_(a,b)
75 #endif
76 #endif
77
78 /*
79 Log levels for usage on stderr:
80
81 fprintf(stderr, SD_NOTICE "Hello World!\n");
82
83 This is similar to printk() usage in the kernel.
84 */
85 #define SD_EMERG "<0>" /* system is unusable */
86 #define SD_ALERT "<1>" /* action must be taken immediately */
87 #define SD_CRIT "<2>" /* critical conditions */
88 #define SD_ERR "<3>" /* error conditions */
89 #define SD_WARNING "<4>" /* warning conditions */
90 #define SD_NOTICE "<5>" /* normal but significant condition */
91 #define SD_INFO "<6>" /* informational */
92 #define SD_DEBUG "<7>" /* debug-level messages */
93
94 /* The first passed file descriptor is fd 3 */
95 #define SD_LISTEN_FDS_START 3
96
97 /*
98 Returns how many file descriptors have been passed, or a negative
99 errno code on failure. Optionally, removes the $LISTEN_FDS and
100 $LISTEN_PID file descriptors from the environment (recommended, but
101 problematic in threaded environments). If r is the return value of
102 this function you'll find the file descriptors passed as fds
103 SD_LISTEN_FDS_START to SD_LISTEN_FDS_START+r-1. Returns a negative
104 errno style error code on failure. This function call ensures that
105 the FD_CLOEXEC flag is set for the passed file descriptors, to make
106 sure they are not passed on to child processes. If FD_CLOEXEC shall
107 not be set, the caller needs to unset it after this call for all file
108 descriptors that are used.
109
110 See sd_listen_fds(3) for more information.
111 */
112 int sd_listen_fds(int unset_environment);
113
114 /*
115 Helper call for identifying a passed file descriptor. Returns 1 if
116 the file descriptor is a FIFO in the file system stored under the
117 specified path, 0 otherwise. If path is NULL a path name check will
118 not be done and the call only verifies if the file descriptor
119 refers to a FIFO. Returns a negative errno style error code on
120 failure.
121
122 See sd_is_fifo(3) for more information.
123 */
124 int sd_is_fifo(int fd, const char *path);
125
126 /*
127 Helper call for identifying a passed file descriptor. Returns 1 if
128 the file descriptor is a special character device on the file
129 system stored under the specified path, 0 otherwise.
130 If path is NULL a path name check will not be done and the call
131 only verifies if the file descriptor refers to a special character.
132 Returns a negative errno style error code on failure.
133
134 See sd_is_special(3) for more information.
135 */
136 int sd_is_special(int fd, const char *path);
137
138 /*
139 Helper call for identifying a passed file descriptor. Returns 1 if
140 the file descriptor is a socket of the specified family (AF_INET,
141 ...) and type (SOCK_DGRAM, SOCK_STREAM, ...), 0 otherwise. If
142 family is 0 a socket family check will not be done. If type is 0 a
143 socket type check will not be done and the call only verifies if
144 the file descriptor refers to a socket. If listening is > 0 it is
145 verified that the socket is in listening mode. (i.e. listen() has
146 been called) If listening is == 0 it is verified that the socket is
147 not in listening mode. If listening is < 0 no listening mode check
148 is done. Returns a negative errno style error code on failure.
149
150 See sd_is_socket(3) for more information.
151 */
152 int sd_is_socket(int fd, int family, int type, int listening);
153
154 /*
155 Helper call for identifying a passed file descriptor. Returns 1 if
156 the file descriptor is an Internet socket, of the specified family
157 (either AF_INET or AF_INET6) and the specified type (SOCK_DGRAM,
158 SOCK_STREAM, ...), 0 otherwise. If version is 0 a protocol version
159 check is not done. If type is 0 a socket type check will not be
160 done. If port is 0 a socket port check will not be done. The
161 listening flag is used the same way as in sd_is_socket(). Returns a
162 negative errno style error code on failure.
163
164 See sd_is_socket_inet(3) for more information.
165 */
166 int sd_is_socket_inet(int fd, int family, int type, int listening, uint16_t port);
167
168 /*
169 Helper call for identifying a passed file descriptor. Returns 1 if
170 the file descriptor is an AF_UNIX socket of the specified type
171 (SOCK_DGRAM, SOCK_STREAM, ...) and path, 0 otherwise. If type is 0
172 a socket type check will not be done. If path is NULL a socket path
173 check will not be done. For normal AF_UNIX sockets set length to
174 0. For abstract namespace sockets set length to the length of the
175 socket name (including the initial 0 byte), and pass the full
176 socket path in path (including the initial 0 byte). The listening
177 flag is used the same way as in sd_is_socket(). Returns a negative
178 errno style error code on failure.
179
180 See sd_is_socket_unix(3) for more information.
181 */
182 int sd_is_socket_unix(int fd, int type, int listening, const char *path, size_t length);
183
184 /*
185 Helper call for identifying a passed file descriptor. Returns 1 if
186 the file descriptor is a POSIX Message Queue of the specified name,
187 0 otherwise. If path is NULL a message queue name check is not
188 done. Returns a negative errno style error code on failure.
189 */
190 int sd_is_mq(int fd, const char *path);
191
192 /*
193 Informs systemd about changed daemon state. This takes a number of
194 newline separated environment-style variable assignments in a
195 string. The following variables are known:
196
197 READY=1 Tells systemd that daemon startup is finished (only
198 relevant for services of Type=notify). The passed
199 argument is a boolean "1" or "0". Since there is
200 little value in signaling non-readiness the only
201 value daemons should send is "READY=1".
202
203 STATUS=... Passes a single-line status string back to systemd
204 that describes the daemon state. This is free-from
205 and can be used for various purposes: general state
206 feedback, fsck-like programs could pass completion
207 percentages and failing programs could pass a human
208 readable error message. Example: "STATUS=Completed
209 66% of file system check..."
210
211 ERRNO=... If a daemon fails, the errno-style error code,
212 formatted as string. Example: "ERRNO=2" for ENOENT.
213
214 BUSERROR=... If a daemon fails, the D-Bus error-style error
215 code. Example: "BUSERROR=org.freedesktop.DBus.Error.TimedOut"
216
217 MAINPID=... The main pid of a daemon, in case systemd did not
218 fork off the process itself. Example: "MAINPID=4711"
219
220 WATCHDOG=1 Tells systemd to update the watchdog timestamp.
221 Services using this feature should do this in
222 regular intervals. A watchdog framework can use the
223 timestamps to detect failed services.
224
225 Daemons can choose to send additional variables. However, it is
226 recommended to prefix variable names not listed above with X_.
227
228 Returns a negative errno-style error code on failure. Returns > 0
229 if systemd could be notified, 0 if it couldn't possibly because
230 systemd is not running.
231
232 Example: When a daemon finished starting up, it could issue this
233 call to notify systemd about it:
234
235 sd_notify(0, "READY=1");
236
237 See sd_notifyf() for more complete examples.
238
239 See sd_notify(3) for more information.
240 */
241 int sd_notify(int unset_environment, const char *state);
242
243 /*
244 Similar to sd_notify() but takes a format string.
245
246 Example 1: A daemon could send the following after initialization:
247
248 sd_notifyf(0, "READY=1\n"
249 "STATUS=Processing requests...\n"
250 "MAINPID=%lu",
251 (unsigned long) getpid());
252
253 Example 2: A daemon could send the following shortly before
254 exiting, on failure:
255
256 sd_notifyf(0, "STATUS=Failed to start up: %s\n"
257 "ERRNO=%i",
258 strerror(errno),
259 errno);
260
261 See sd_notifyf(3) for more information.
262 */
263 int sd_notifyf(int unset_environment, const char *format, ...) _sd_printf_attr_(2,3);
264
265 /*
266 Returns > 0 if the system was booted with systemd. Returns < 0 on
267 error. Returns 0 if the system was not booted with systemd. Note
268 that all of the functions above handle non-systemd boots just
269 fine. You should NOT protect them with a call to this function. Also
270 note that this function checks whether the system, not the user
271 session is controlled by systemd. However the functions above work
272 for both user and system services.
273
274 See sd_booted(3) for more information.
275 */
276 int sd_booted(void);
277
278 #ifdef __cplusplus
279 }
280 #endif
281
282 #endif