src/systemd/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/plain/src/systemd/sd-daemon.h
  62   http://cgit.freedesktop.org/systemd/plain/src/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(7) 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