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   This file is part of systemd.
   8
   9   Copyright 2013 Lennart Poettering
  10
  11   systemd is free software; you can redistribute it and/or modify it
  12   under the terms of the GNU Lesser General Public License as published by
  13   the Free Software Foundation; either version 2.1 of the License, or
  14   (at your option) any later version.
  15
  16   systemd is distributed in the hope that it will be useful, but
  17   WITHOUT ANY WARRANTY; without even the implied warranty of
  18   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  19   Lesser General Public License for more details.
  20
  21   You should have received a copy of the GNU Lesser General Public License
  22   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  23 ***/
  24
  25 #include <inttypes.h>
  26 #include <sys/types.h>
  27
  28 #include "_sd-common.h"
  29
  30 _SD_BEGIN_DECLARATIONS;
  31
  32 /*
  33   The following functionality is provided:
  34
  35   - Support for logging with log levels on stderr
  36   - File descriptor passing for socket-based activation
  37   - Daemon startup and status notification
  38   - Detection of systemd boots
  39
  40   See sd-daemon(3) for more information.
  41 */
  42
  43 /*
  44   Log levels for usage on stderr:
  45
  46           fprintf(stderr, SD_NOTICE "Hello World!\n");
  47
  48   This is similar to printk() usage in the kernel.
  49 */
  50 #define SD_EMERG   "<0>"  /* system is unusable */
  51 #define SD_ALERT   "<1>"  /* action must be taken immediately */
  52 #define SD_CRIT    "<2>"  /* critical conditions */
  53 #define SD_ERR     "<3>"  /* error conditions */
  54 #define SD_WARNING "<4>"  /* warning conditions */
  55 #define SD_NOTICE  "<5>"  /* normal but significant condition */
  56 #define SD_INFO    "<6>"  /* informational */
  57 #define SD_DEBUG   "<7>"  /* debug-level messages */
  58
  59 /* The first passed file descriptor is fd 3 */
  60 #define SD_LISTEN_FDS_START 3
  61
  62 /*
  63   Returns how many file descriptors have been passed, or a negative
  64   errno code on failure. Optionally, removes the $LISTEN_FDS and
  65   $LISTEN_PID file descriptors from the environment (recommended, but
  66   problematic in threaded environments). If r is the return value of
  67   this function you'll find the file descriptors passed as fds
  68   SD_LISTEN_FDS_START to SD_LISTEN_FDS_START+r-1. Returns a negative
  69   errno style error code on failure. This function call ensures that
  70   the FD_CLOEXEC flag is set for the passed file descriptors, to make
  71   sure they are not passed on to child processes. If FD_CLOEXEC shall
  72   not be set, the caller needs to unset it after this call for all file
  73   descriptors that are used.
  74
  75   See sd_listen_fds(3) for more information.
  76 */
  77 int sd_listen_fds(int unset_environment);
  78
  79 int sd_listen_fds_with_names(int unset_environment, char ***names);
  80
  81 /*
  82   Helper call for identifying a passed file descriptor. Returns 1 if
  83   the file descriptor is a FIFO in the file system stored under the
  84   specified path, 0 otherwise. If path is NULL a path name check will
  85   not be done and the call only verifies if the file descriptor
  86   refers to a FIFO. Returns a negative errno style error code on
  87   failure.
  88
  89   See sd_is_fifo(3) for more information.
  90 */
  91 int sd_is_fifo(int fd, const char *path);
  92
  93 /*
  94   Helper call for identifying a passed file descriptor. Returns 1 if
  95   the file descriptor is a special character device on the file
  96   system stored under the specified path, 0 otherwise.
  97   If path is NULL a path name check will not be done and the call
  98   only verifies if the file descriptor refers to a special character.
  99   Returns a negative errno style error code on failure.
 100
 101   See sd_is_special(3) for more information.
 102 */
 103 int sd_is_special(int fd, const char *path);
 104
 105 /*
 106   Helper call for identifying a passed file descriptor. Returns 1 if
 107   the file descriptor is a socket of the specified family (AF_INET,
 108   ...) and type (SOCK_DGRAM, SOCK_STREAM, ...), 0 otherwise. If
 109   family is 0 a socket family check will not be done. If type is 0 a
 110   socket type check will not be done and the call only verifies if
 111   the file descriptor refers to a socket. If listening is > 0 it is
 112   verified that the socket is in listening mode. (i.e. listen() has
 113   been called) If listening is == 0 it is verified that the socket is
 114   not in listening mode. If listening is < 0 no listening mode check
 115   is done. Returns a negative errno style error code on failure.
 116
 117   See sd_is_socket(3) for more information.
 118 */
 119 int sd_is_socket(int fd, int family, int type, int listening);
 120
 121 /*
 122   Helper call for identifying a passed file descriptor. Returns 1 if
 123   the file descriptor is an Internet socket, of the specified family
 124   (either AF_INET or AF_INET6) and the specified type (SOCK_DGRAM,
 125   SOCK_STREAM, ...), 0 otherwise. If version is 0 a protocol version
 126   check is not done. If type is 0 a socket type check will not be
 127   done. If port is 0 a socket port check will not be done. The
 128   listening flag is used the same way as in sd_is_socket(). Returns a
 129   negative errno style error code on failure.
 130
 131   See sd_is_socket_inet(3) for more information.
 132 */
 133 int sd_is_socket_inet(int fd, int family, int type, int listening, uint16_t port);
 134
 135 /*
 136   Helper call for identifying a passed file descriptor. Returns 1 if
 137   the file descriptor is an AF_UNIX socket of the specified type
 138   (SOCK_DGRAM, SOCK_STREAM, ...) and path, 0 otherwise. If type is 0
 139   a socket type check will not be done. If path is NULL a socket path
 140   check will not be done. For normal AF_UNIX sockets set length to
 141   0. For abstract namespace sockets set length to the length of the
 142   socket name (including the initial 0 byte), and pass the full
 143   socket path in path (including the initial 0 byte). The listening
 144   flag is used the same way as in sd_is_socket(). Returns a negative
 145   errno style error code on failure.
 146
 147   See sd_is_socket_unix(3) for more information.
 148 */
 149 int sd_is_socket_unix(int fd, int type, int listening, const char *path, size_t length);
 150
 151 /*
 152   Helper call for identifying a passed file descriptor. Returns 1 if
 153   the file descriptor is a POSIX Message Queue of the specified name,
 154   0 otherwise. If path is NULL a message queue name check is not
 155   done. Returns a negative errno style error code on failure.
 156
 157   See sd_is_mq(3) for more information.
 158 */
 159 int sd_is_mq(int fd, const char *path);
 160
 161 /*
 162   Informs systemd about changed daemon state. This takes a number of
 163   newline separated environment-style variable assignments in a
 164   string. The following variables are known:
 165
 166      READY=1      Tells systemd that daemon startup is finished (only
 167                   relevant for services of Type=notify). The passed
 168                   argument is a boolean "1" or "0". Since there is
 169                   little value in signaling non-readiness the only
 170                   value daemons should send is "READY=1".
 171
 172      STATUS=...   Passes a single-line status string back to systemd
 173                   that describes the daemon state. This is free-form
 174                   and can be used for various purposes: general state
 175                   feedback, fsck-like programs could pass completion
 176                   percentages and failing programs could pass a human
 177                   readable error message. Example: "STATUS=Completed
 178                   66% of file system check..."
 179
 180      ERRNO=...    If a daemon fails, the errno-style error code,
 181                   formatted as string. Example: "ERRNO=2" for ENOENT.
 182
 183      BUSERROR=... If a daemon fails, the D-Bus error-style error
 184                   code. Example: "BUSERROR=org.freedesktop.DBus.Error.TimedOut"
 185
 186      MAINPID=...  The main pid of a daemon, in case systemd did not
 187                   fork off the process itself. Example: "MAINPID=4711"
 188
 189      WATCHDOG=1   Tells systemd to update the watchdog timestamp.
 190                   Services using this feature should do this in
 191                   regular intervals. A watchdog framework can use the
 192                   timestamps to detect failed services. Also see
 193                   sd_watchdog_enabled() below.
 194
 195      FDSTORE=1    Store the file descriptors passed along with the
 196                   message in the per-service file descriptor store,
 197                   and pass them to the main process again on next
 198                   invocation. This variable is only supported with
 199                   sd_pid_notify_with_fds().
 200
 201   Daemons can choose to send additional variables. However, it is
 202   recommended to prefix variable names not listed above with X_.
 203
 204   Returns a negative errno-style error code on failure. Returns > 0
 205   if systemd could be notified, 0 if it couldn't possibly because
 206   systemd is not running.
 207
 208   Example: When a daemon finished starting up, it could issue this
 209   call to notify systemd about it:
 210
 211      sd_notify(0, "READY=1");
 212
 213   See sd_notifyf() for more complete examples.
 214
 215   See sd_notify(3) for more information.
 216 */
 217 int sd_notify(int unset_environment, const char *state);
 218
 219 /*
 220   Similar to sd_notify() but takes a format string.
 221
 222   Example 1: A daemon could send the following after initialization:
 223
 224      sd_notifyf(0, "READY=1\n"
 225                    "STATUS=Processing requests...\n"
 226                    "MAINPID=%lu",
 227                    (unsigned long) getpid());
 228
 229   Example 2: A daemon could send the following shortly before
 230   exiting, on failure:
 231
 232      sd_notifyf(0, "STATUS=Failed to start up: %s\n"
 233                    "ERRNO=%i",
 234                    strerror(errno),
 235                    errno);
 236
 237   See sd_notifyf(3) for more information.
 238 */
 239 int sd_notifyf(int unset_environment, const char *format, ...) _sd_printf_(2,3);
 240
 241 /*
 242   Similar to sd_notify(), but send the message on behalf of another
 243   process, if the appropriate permissions are available.
 244 */
 245 int sd_pid_notify(pid_t pid, int unset_environment, const char *state);
 246
 247 /*
 248   Similar to sd_notifyf(), but send the message on behalf of another
 249   process, if the appropriate permissions are available.
 250 */
 251 int sd_pid_notifyf(pid_t pid, int unset_environment, const char *format, ...) _sd_printf_(3,4);
 252
 253 /*
 254   Similar to sd_pid_notify(), but also passes the specified fd array
 255   to the service manager for storage. This is particularly useful for
 256   FDSTORE=1 messages.
 257 */
 258 int sd_pid_notify_with_fds(pid_t pid, int unset_environment, const char *state, const int *fds, unsigned n_fds);
 259
 260 /*
 261   Returns > 0 if the system was booted with systemd. Returns < 0 on
 262   error. Returns 0 if the system was not booted with systemd. Note
 263   that all of the functions above handle non-systemd boots just
 264   fine. You should NOT protect them with a call to this function. Also
 265   note that this function checks whether the system, not the user
 266   session is controlled by systemd. However the functions above work
 267   for both user and system services.
 268
 269   See sd_booted(3) for more information.
 270 */
 271 int sd_booted(void);
 272
 273 /*
 274   Returns > 0 if the service manager expects watchdog keep-alive
 275   events to be sent regularly via sd_notify(0, "WATCHDOG=1"). Returns
 276   0 if it does not expect this. If the usec argument is non-NULL
 277   returns the watchdog timeout in µs after which the service manager
 278   will act on a process that has not sent a watchdog keep alive
 279   message. This function is useful to implement services that
 280   recognize automatically if they are being run under supervision of
 281   systemd with WatchdogSec= set. It is recommended for clients to
 282   generate keep-alive pings via sd_notify(0, "WATCHDOG=1") every half
 283   of the returned time.
 284
 285   See sd_watchdog_enabled(3) for more information.
 286 */
 287 int sd_watchdog_enabled(int unset_environment, uint64_t *usec);
 288
 289 _SD_END_DECLARATIONS;
 290
 291 #endif