src/systemd/sd-daemon.h

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 #ifndef foosddaemonhfoo
   3 #define foosddaemonhfoo
   4
   5 /***
   6   Copyright 2013 Lennart Poettering
   7
   8   systemd is free software; you can redistribute it and/or modify it
   9   under the terms of the GNU Lesser General Public License as published by
  10   the Free Software Foundation; either version 2.1 of the License, or
  11   (at your option) any later version.
  12
  13   systemd is distributed in the hope that it will be useful, but
  14   WITHOUT ANY WARRANTY; without even the implied warranty of
  15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16   Lesser General Public License for more details.
  17
  18   You should have received a copy of the GNU Lesser General Public License
  19   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  20 ***/
  21
  22 #include <inttypes.h>
  23 #include <sys/types.h>
  24 #include <sys/socket.h>
  25
  26 #include "_sd-common.h"
  27
  28 _SD_BEGIN_DECLARATIONS;
  29
  30 /*
  31   The following functionality is provided:
  32
  33   - Support for logging with log levels on stderr
  34   - File descriptor passing for socket-based activation
  35   - Daemon startup and status notification
  36   - Detection of systemd boots
  37
  38   See sd-daemon(3) for more information.
  39 */
  40
  41 /*
  42   Log levels for usage on stderr:
  43
  44           fprintf(stderr, SD_NOTICE "Hello World!\n");
  45
  46   This is similar to printk() usage in the kernel.
  47 */
  48 #define SD_EMERG   "<0>"  /* system is unusable */
  49 #define SD_ALERT   "<1>"  /* action must be taken immediately */
  50 #define SD_CRIT    "<2>"  /* critical conditions */
  51 #define SD_ERR     "<3>"  /* error conditions */
  52 #define SD_WARNING "<4>"  /* warning conditions */
  53 #define SD_NOTICE  "<5>"  /* normal but significant condition */
  54 #define SD_INFO    "<6>"  /* informational */
  55 #define SD_DEBUG   "<7>"  /* debug-level messages */
  56
  57 /* The first passed file descriptor is fd 3 */
  58 #define SD_LISTEN_FDS_START 3
  59
  60 /*
  61   Returns how many file descriptors have been passed, or a negative
  62   errno code on failure. Optionally, removes the $LISTEN_FDS and
  63   $LISTEN_PID file descriptors from the environment (recommended, but
  64   problematic in threaded environments). If r is the return value of
  65   this function you'll find the file descriptors passed as fds
  66   SD_LISTEN_FDS_START to SD_LISTEN_FDS_START+r-1. Returns a negative
  67   errno style error code on failure. This function call ensures that
  68   the FD_CLOEXEC flag is set for the passed file descriptors, to make
  69   sure they are not passed on to child processes. If FD_CLOEXEC shall
  70   not be set, the caller needs to unset it after this call for all file
  71   descriptors that are used.
  72
  73   See sd_listen_fds(3) for more information.
  74 */
  75 int sd_listen_fds(int unset_environment);
  76
  77 int sd_listen_fds_with_names(int unset_environment, char ***names);
  78
  79 /*
  80   Helper call for identifying a passed file descriptor. Returns 1 if
  81   the file descriptor is a FIFO in the file system stored under the
  82   specified path, 0 otherwise. If path is NULL a path name check will
  83   not be done and the call only verifies if the file descriptor
  84   refers to a FIFO. Returns a negative errno style error code on
  85   failure.
  86
  87   See sd_is_fifo(3) for more information.
  88 */
  89 int sd_is_fifo(int fd, const char *path);
  90
  91 /*
  92   Helper call for identifying a passed file descriptor. Returns 1 if
  93   the file descriptor is a special character device on the file
  94   system stored under the specified path, 0 otherwise.
  95   If path is NULL a path name check will not be done and the call
  96   only verifies if the file descriptor refers to a special character.
  97   Returns a negative errno style error code on failure.
  98
  99   See sd_is_special(3) for more information.
 100 */
 101 int sd_is_special(int fd, const char *path);
 102
 103 /*
 104   Helper call for identifying a passed file descriptor. Returns 1 if
 105   the file descriptor is a socket of the specified family (AF_INET,
 106   ...) and type (SOCK_DGRAM, SOCK_STREAM, ...), 0 otherwise. If
 107   family is 0 a socket family check will not be done. If type is 0 a
 108   socket type check will not be done and the call only verifies if
 109   the file descriptor refers to a socket. If listening is > 0 it is
 110   verified that the socket is in listening mode. (i.e. listen() has
 111   been called) If listening is == 0 it is verified that the socket is
 112   not in listening mode. If listening is < 0 no listening mode check
 113   is done. Returns a negative errno style error code on failure.
 114
 115   See sd_is_socket(3) for more information.
 116 */
 117 int sd_is_socket(int fd, int family, int type, int listening);
 118
 119 /*
 120   Helper call for identifying a passed file descriptor. Returns 1 if
 121   the file descriptor is an Internet socket, of the specified family
 122   (either AF_INET or AF_INET6) and the specified type (SOCK_DGRAM,
 123   SOCK_STREAM, ...), 0 otherwise. If version is 0 a protocol version
 124   check is not done. If type is 0 a socket type check will not be
 125   done. If port is 0 a socket port check will not be done. The
 126   listening flag is used the same way as in sd_is_socket(). Returns a
 127   negative errno style error code on failure.
 128
 129   See sd_is_socket_inet(3) for more information.
 130 */
 131 int sd_is_socket_inet(int fd, int family, int type, int listening, uint16_t port);
 132
 133 /*
 134   Helper call for identifying a passed file descriptor. Returns 1 if the
 135   file descriptor is an Internet socket of the specified type
 136   (SOCK_DGRAM, SOCK_STREAM, ...), and if the address of the socket is
 137   the same as the address specified by addr. The listening flag is used
 138   the same way as in sd_is_socket(). Returns a negative errno style
 139   error code on failure.
 140
 141   See sd_is_socket_sockaddr(3) for more information.
 142 */
 143 int sd_is_socket_sockaddr(int fd, int type, const struct sockaddr* addr, unsigned addr_len, int listening);
 144
 145 /*
 146   Helper call for identifying a passed file descriptor. Returns 1 if
 147   the file descriptor is an AF_UNIX socket of the specified type
 148   (SOCK_DGRAM, SOCK_STREAM, ...) and path, 0 otherwise. If type is 0
 149   a socket type check will not be done. If path is NULL a socket path
 150   check will not be done. For normal AF_UNIX sockets set length to
 151   0. For abstract namespace sockets set length to the length of the
 152   socket name (including the initial 0 byte), and pass the full
 153   socket path in path (including the initial 0 byte). The listening
 154   flag is used the same way as in sd_is_socket(). Returns a negative
 155   errno style error code on failure.
 156
 157   See sd_is_socket_unix(3) for more information.
 158 */
 159 int sd_is_socket_unix(int fd, int type, int listening, const char *path, size_t length);
 160
 161 /*
 162   Helper call for identifying a passed file descriptor. Returns 1 if
 163   the file descriptor is a POSIX Message Queue of the specified name,
 164   0 otherwise. If path is NULL a message queue name check is not
 165   done. Returns a negative errno style error code on failure.
 166
 167   See sd_is_mq(3) for more information.
 168 */
 169 int sd_is_mq(int fd, const char *path);
 170
 171 /*
 172   Informs systemd about changed daemon state. This takes a number of
 173   newline separated environment-style variable assignments in a
 174   string. The following variables are known:
 175
 176      MAINPID=...  The main PID of a daemon, in case systemd did not
 177                   fork off the process itself. Example: "MAINPID=4711"
 178
 179      READY=1      Tells systemd that daemon startup or daemon reload
 180                   is finished (only relevant for services of Type=notify).
 181                   The passed argument is a boolean "1" or "0". Since there
 182                   is little value in signaling non-readiness the only
 183                   value daemons should send is "READY=1".
 184
 185      RELOADING=1  Tell systemd that the daemon began reloading its
 186                   configuration. When the configuration has been
 187                   reloaded completely, READY=1 should be sent to inform
 188                   systemd about this.
 189
 190      STOPPING=1   Tells systemd that the daemon is about to go down.
 191
 192      STATUS=...   Passes a single-line status string back to systemd
 193                   that describes the daemon state. This is free-form
 194                   and can be used for various purposes: general state
 195                   feedback, fsck-like programs could pass completion
 196                   percentages and failing programs could pass a human
 197                   readable error message. Example: "STATUS=Completed
 198                   66% of file system check..."
 199
 200      ERRNO=...    If a daemon fails, the errno-style error code,
 201                   formatted as string. Example: "ERRNO=2" for ENOENT.
 202
 203      BUSERROR=... If a daemon fails, the D-Bus error-style error
 204                   code. Example: "BUSERROR=org.freedesktop.DBus.Error.TimedOut"
 205
 206      WATCHDOG=1   Tells systemd to update the watchdog timestamp.
 207                   Services using this feature should do this in
 208                   regular intervals. A watchdog framework can use the
 209                   timestamps to detect failed services. Also see
 210                   sd_watchdog_enabled() below.
 211
 212      WATCHDOG_USEC=...
 213                   Reset watchdog_usec value during runtime.
 214                   To reset watchdog_usec value, start the service again.
 215                   Example: "WATCHDOG_USEC=20000000"
 216
 217      FDSTORE=1    Store the file descriptors passed along with the
 218                   message in the per-service file descriptor store,
 219                   and pass them to the main process again on next
 220                   invocation. This variable is only supported with
 221                   sd_pid_notify_with_fds().
 222
 223      FDSTOREREMOVE=1
 224                   Remove one or more file descriptors from the file
 225                   descriptor store, identified by the name specified
 226                   in FDNAME=, see below.
 227
 228      FDNAME=      A name to assign to new file descriptors stored in the
 229                   file descriptor store, or the name of the file descriptors
 230                   to remove in case of FDSTOREREMOVE=1.
 231
 232   Daemons can choose to send additional variables. However, it is
 233   recommended to prefix variable names not listed above with X_.
 234
 235   Returns a negative errno-style error code on failure. Returns > 0
 236   if systemd could be notified, 0 if it couldn't possibly because
 237   systemd is not running.
 238
 239   Example: When a daemon finished starting up, it could issue this
 240   call to notify systemd about it:
 241
 242      sd_notify(0, "READY=1");
 243
 244   See sd_notifyf() for more complete examples.
 245
 246   See sd_notify(3) for more information.
 247 */
 248 int sd_notify(int unset_environment, const char *state);
 249
 250 /*
 251   Similar to sd_notify() but takes a format string.
 252
 253   Example 1: A daemon could send the following after initialization:
 254
 255      sd_notifyf(0, "READY=1\n"
 256                    "STATUS=Processing requests...\n"
 257                    "MAINPID=%lu",
 258                    (unsigned long) getpid());
 259
 260   Example 2: A daemon could send the following shortly before
 261   exiting, on failure:
 262
 263      sd_notifyf(0, "STATUS=Failed to start up: %s\n"
 264                    "ERRNO=%i",
 265                    strerror(errno),
 266                    errno);
 267
 268   See sd_notifyf(3) for more information.
 269 */
 270 int sd_notifyf(int unset_environment, const char *format, ...) _sd_printf_(2,3);
 271
 272 /*
 273   Similar to sd_notify(), but send the message on behalf of another
 274   process, if the appropriate permissions are available.
 275 */
 276 int sd_pid_notify(pid_t pid, int unset_environment, const char *state);
 277
 278 /*
 279   Similar to sd_notifyf(), but send the message on behalf of another
 280   process, if the appropriate permissions are available.
 281 */
 282 int sd_pid_notifyf(pid_t pid, int unset_environment, const char *format, ...) _sd_printf_(3,4);
 283
 284 /*
 285   Similar to sd_pid_notify(), but also passes the specified fd array
 286   to the service manager for storage. This is particularly useful for
 287   FDSTORE=1 messages.
 288 */
 289 int sd_pid_notify_with_fds(pid_t pid, int unset_environment, const char *state, const int *fds, unsigned n_fds);
 290
 291 /*
 292   Returns > 0 if the system was booted with systemd. Returns < 0 on
 293   error. Returns 0 if the system was not booted with systemd. Note
 294   that all of the functions above handle non-systemd boots just
 295   fine. You should NOT protect them with a call to this function. Also
 296   note that this function checks whether the system, not the user
 297   session is controlled by systemd. However the functions above work
 298   for both user and system services.
 299
 300   See sd_booted(3) for more information.
 301 */
 302 int sd_booted(void);
 303
 304 /*
 305   Returns > 0 if the service manager expects watchdog keep-alive
 306   events to be sent regularly via sd_notify(0, "WATCHDOG=1"). Returns
 307   0 if it does not expect this. If the usec argument is non-NULL
 308   returns the watchdog timeout in µs after which the service manager
 309   will act on a process that has not sent a watchdog keep alive
 310   message. This function is useful to implement services that
 311   recognize automatically if they are being run under supervision of
 312   systemd with WatchdogSec= set. It is recommended for clients to
 313   generate keep-alive pings via sd_notify(0, "WATCHDOG=1") every half
 314   of the returned time.
 315
 316   See sd_watchdog_enabled(3) for more information.
 317 */
 318 int sd_watchdog_enabled(int unset_environment, uint64_t *usec);
 319
 320 _SD_END_DECLARATIONS;
 321
 322 #endif