src/systemd/sd-daemon.h

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 #ifndef foosddaemonhfoo
   3 #define foosddaemonhfoo
   4
   5 /***
   6   systemd is free software; you can redistribute it and/or modify it
   7   under the terms of the GNU Lesser General Public License as published by
   8   the Free Software Foundation; either version 2.1 of the License, or
   9   (at your option) any later version.
  10
  11   systemd is distributed in the hope that it will be useful, but
  12   WITHOUT ANY WARRANTY; without even the implied warranty of
  13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  14   Lesser General Public License for more details.
  15
  16   You should have received a copy of the GNU Lesser General Public License
  17   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  18 ***/
  19
  20 #include <inttypes.h>
  21 #include <sys/types.h>
  22 #include <sys/socket.h>
  23
  24 #include "_sd-common.h"
  25
  26 _SD_BEGIN_DECLARATIONS;
  27
  28 /*
  29   The following functionality is provided:
  30
  31   - Support for logging with log levels on stderr
  32   - File descriptor passing for socket-based activation
  33   - Daemon startup and status notification
  34   - Detection of systemd boots
  35
  36   See sd-daemon(3) for more information.
  37 */
  38
  39 /*
  40   Log levels for usage on stderr:
  41
  42           fprintf(stderr, SD_NOTICE "Hello World!\n");
  43
  44   This is similar to printk() usage in the kernel.
  45 */
  46 #define SD_EMERG   "<0>"  /* system is unusable */
  47 #define SD_ALERT   "<1>"  /* action must be taken immediately */
  48 #define SD_CRIT    "<2>"  /* critical conditions */
  49 #define SD_ERR     "<3>"  /* error conditions */
  50 #define SD_WARNING "<4>"  /* warning conditions */
  51 #define SD_NOTICE  "<5>"  /* normal but significant condition */
  52 #define SD_INFO    "<6>"  /* informational */
  53 #define SD_DEBUG   "<7>"  /* debug-level messages */
  54
  55 /* The first passed file descriptor is fd 3 */
  56 #define SD_LISTEN_FDS_START 3
  57
  58 /*
  59   Returns how many file descriptors have been passed, or a negative
  60   errno code on failure. Optionally, removes the $LISTEN_FDS and
  61   $LISTEN_PID file descriptors from the environment (recommended, but
  62   problematic in threaded environments). If r is the return value of
  63   this function you'll find the file descriptors passed as fds
  64   SD_LISTEN_FDS_START to SD_LISTEN_FDS_START+r-1. Returns a negative
  65   errno style error code on failure. This function call ensures that
  66   the FD_CLOEXEC flag is set for the passed file descriptors, to make
  67   sure they are not passed on to child processes. If FD_CLOEXEC shall
  68   not be set, the caller needs to unset it after this call for all file
  69   descriptors that are used.
  70
  71   See sd_listen_fds(3) for more information.
  72 */
  73 int sd_listen_fds(int unset_environment);
  74
  75 int sd_listen_fds_with_names(int unset_environment, char ***names);
  76
  77 /*
  78   Helper call for identifying a passed file descriptor. Returns 1 if
  79   the file descriptor is a FIFO in the file system stored under the
  80   specified path, 0 otherwise. If path is NULL a path name check will
  81   not be done and the call only verifies if the file descriptor
  82   refers to a FIFO. Returns a negative errno style error code on
  83   failure.
  84
  85   See sd_is_fifo(3) for more information.
  86 */
  87 int sd_is_fifo(int fd, const char *path);
  88
  89 /*
  90   Helper call for identifying a passed file descriptor. Returns 1 if
  91   the file descriptor is a special character device on the file
  92   system stored under the specified path, 0 otherwise.
  93   If path is NULL a path name check will not be done and the call
  94   only verifies if the file descriptor refers to a special character.
  95   Returns a negative errno style error code on failure.
  96
  97   See sd_is_special(3) for more information.
  98 */
  99 int sd_is_special(int fd, const char *path);
 100
 101 /*
 102   Helper call for identifying a passed file descriptor. Returns 1 if
 103   the file descriptor is a socket of the specified family (AF_INET,
 104   ...) and type (SOCK_DGRAM, SOCK_STREAM, ...), 0 otherwise. If
 105   family is 0 a socket family check will not be done. If type is 0 a
 106   socket type check will not be done and the call only verifies if
 107   the file descriptor refers to a socket. If listening is > 0 it is
 108   verified that the socket is in listening mode. (i.e. listen() has
 109   been called) If listening is == 0 it is verified that the socket is
 110   not in listening mode. If listening is < 0 no listening mode check
 111   is done. Returns a negative errno style error code on failure.
 112
 113   See sd_is_socket(3) for more information.
 114 */
 115 int sd_is_socket(int fd, int family, int type, int listening);
 116
 117 /*
 118   Helper call for identifying a passed file descriptor. Returns 1 if
 119   the file descriptor is an Internet socket, of the specified family
 120   (either AF_INET or AF_INET6) and the specified type (SOCK_DGRAM,
 121   SOCK_STREAM, ...), 0 otherwise. If version is 0 a protocol version
 122   check is not done. If type is 0 a socket type check will not be
 123   done. If port is 0 a socket port check will not be done. The
 124   listening flag is used the same way as in sd_is_socket(). Returns a
 125   negative errno style error code on failure.
 126
 127   See sd_is_socket_inet(3) for more information.
 128 */
 129 int sd_is_socket_inet(int fd, int family, int type, int listening, uint16_t port);
 130
 131 /*
 132   Helper call for identifying a passed file descriptor. Returns 1 if the
 133   file descriptor is an Internet socket of the specified type
 134   (SOCK_DGRAM, SOCK_STREAM, ...), and if the address of the socket is
 135   the same as the address specified by addr. The listening flag is used
 136   the same way as in sd_is_socket(). Returns a negative errno style
 137   error code on failure.
 138
 139   See sd_is_socket_sockaddr(3) for more information.
 140 */
 141 int sd_is_socket_sockaddr(int fd, int type, const struct sockaddr* addr, unsigned addr_len, int listening);
 142
 143 /*
 144   Helper call for identifying a passed file descriptor. Returns 1 if
 145   the file descriptor is an AF_UNIX socket of the specified type
 146   (SOCK_DGRAM, SOCK_STREAM, ...) and path, 0 otherwise. If type is 0
 147   a socket type check will not be done. If path is NULL a socket path
 148   check will not be done. For normal AF_UNIX sockets set length to
 149   0. For abstract namespace sockets set length to the length of the
 150   socket name (including the initial 0 byte), and pass the full
 151   socket path in path (including the initial 0 byte). The listening
 152   flag is used the same way as in sd_is_socket(). Returns a negative
 153   errno style error code on failure.
 154
 155   See sd_is_socket_unix(3) for more information.
 156 */
 157 int sd_is_socket_unix(int fd, int type, int listening, const char *path, size_t length);
 158
 159 /*
 160   Helper call for identifying a passed file descriptor. Returns 1 if
 161   the file descriptor is a POSIX Message Queue of the specified name,
 162   0 otherwise. If path is NULL a message queue name check is not
 163   done. Returns a negative errno style error code on failure.
 164
 165   See sd_is_mq(3) for more information.
 166 */
 167 int sd_is_mq(int fd, const char *path);
 168
 169 /*
 170   Informs systemd about changed daemon state. This takes a number of
 171   newline separated environment-style variable assignments in a
 172   string. The following variables are known:
 173
 174      MAINPID=...  The main PID of a daemon, in case systemd did not
 175                   fork off the process itself. Example: "MAINPID=4711"
 176
 177      READY=1      Tells systemd that daemon startup or daemon reload
 178                   is finished (only relevant for services of Type=notify).
 179                   The passed argument is a boolean "1" or "0". Since there
 180                   is little value in signaling non-readiness the only
 181                   value daemons should send is "READY=1".
 182
 183      RELOADING=1  Tell systemd that the daemon began reloading its
 184                   configuration. When the configuration has been
 185                   reloaded completely, READY=1 should be sent to inform
 186                   systemd about this.
 187
 188      STOPPING=1   Tells systemd that the daemon is about to go down.
 189
 190      STATUS=...   Passes a single-line status string back to systemd
 191                   that describes the daemon state. This is free-form
 192                   and can be used for various purposes: general state
 193                   feedback, fsck-like programs could pass completion
 194                   percentages and failing programs could pass a human
 195                   readable error message. Example: "STATUS=Completed
 196                   66% of file system check..."
 197
 198      ERRNO=...    If a daemon fails, the errno-style error code,
 199                   formatted as string. Example: "ERRNO=2" for ENOENT.
 200
 201      BUSERROR=... If a daemon fails, the D-Bus error-style error
 202                   code. Example: "BUSERROR=org.freedesktop.DBus.Error.TimedOut"
 203
 204      WATCHDOG=1   Tells systemd to update the watchdog timestamp.
 205                   Services using this feature should do this in
 206                   regular intervals. A watchdog framework can use the
 207                   timestamps to detect failed services. Also see
 208                   sd_watchdog_enabled() below.
 209
 210      WATCHDOG_USEC=...
 211                   Reset watchdog_usec value during runtime.
 212                   To reset watchdog_usec value, start the service again.
 213                   Example: "WATCHDOG_USEC=20000000"
 214
 215      FDSTORE=1    Store the file descriptors passed along with the
 216                   message in the per-service file descriptor store,
 217                   and pass them to the main process again on next
 218                   invocation. This variable is only supported with
 219                   sd_pid_notify_with_fds().
 220
 221      FDSTOREREMOVE=1
 222                   Remove one or more file descriptors from the file
 223                   descriptor store, identified by the name specified
 224                   in FDNAME=, see below.
 225
 226      FDNAME=      A name to assign to new file descriptors stored in the
 227                   file descriptor store, or the name of the file descriptors
 228                   to remove in case of FDSTOREREMOVE=1.
 229
 230   Daemons can choose to send additional variables. However, it is
 231   recommended to prefix variable names not listed above with X_.
 232
 233   Returns a negative errno-style error code on failure. Returns > 0
 234   if systemd could be notified, 0 if it couldn't possibly because
 235   systemd is not running.
 236
 237   Example: When a daemon finished starting up, it could issue this
 238   call to notify systemd about it:
 239
 240      sd_notify(0, "READY=1");
 241
 242   See sd_notifyf() for more complete examples.
 243
 244   See sd_notify(3) for more information.
 245 */
 246 int sd_notify(int unset_environment, const char *state);
 247
 248 /*
 249   Similar to sd_notify() but takes a format string.
 250
 251   Example 1: A daemon could send the following after initialization:
 252
 253      sd_notifyf(0, "READY=1\n"
 254                    "STATUS=Processing requests...\n"
 255                    "MAINPID=%lu",
 256                    (unsigned long) getpid());
 257
 258   Example 2: A daemon could send the following shortly before
 259   exiting, on failure:
 260
 261      sd_notifyf(0, "STATUS=Failed to start up: %s\n"
 262                    "ERRNO=%i",
 263                    strerror(errno),
 264                    errno);
 265
 266   See sd_notifyf(3) for more information.
 267 */
 268 int sd_notifyf(int unset_environment, const char *format, ...) _sd_printf_(2,3);
 269
 270 /*
 271   Similar to sd_notify(), but send the message on behalf of another
 272   process, if the appropriate permissions are available.
 273 */
 274 int sd_pid_notify(pid_t pid, int unset_environment, const char *state);
 275
 276 /*
 277   Similar to sd_notifyf(), but send the message on behalf of another
 278   process, if the appropriate permissions are available.
 279 */
 280 int sd_pid_notifyf(pid_t pid, int unset_environment, const char *format, ...) _sd_printf_(3,4);
 281
 282 /*
 283   Similar to sd_pid_notify(), but also passes the specified fd array
 284   to the service manager for storage. This is particularly useful for
 285   FDSTORE=1 messages.
 286 */
 287 int sd_pid_notify_with_fds(pid_t pid, int unset_environment, const char *state, const int *fds, unsigned n_fds);
 288
 289 /*
 290   Returns > 0 if synchronization with systemd succeeded.  Returns < 0
 291   on error. Returns 0 if $NOTIFY_SOCKET was not set. Note that the
 292   timeout parameter of this function call takes the timeout in µs, and
 293   will be passed to ppoll(2), hence the behaviour will be similar to
 294   ppoll(2). This function can be called after sending a status message
 295   to systemd, if one needs to synchronize against reception of the
 296   status messages sent before this call is made. Therefore, this
 297   cannot be used to know if the status message was processed
 298   successfully, but to only synchronize against its consumption.
 299 */
 300 int sd_notify_barrier(int unset_environment, uint64_t timeout);
 301
 302 /*
 303   Returns > 0 if the system was booted with systemd. Returns < 0 on
 304   error. Returns 0 if the system was not booted with systemd. Note
 305   that all of the functions above handle non-systemd boots just
 306   fine. You should NOT protect them with a call to this function. Also
 307   note that this function checks whether the system, not the user
 308   session is controlled by systemd. However the functions above work
 309   for both user and system services.
 310
 311   See sd_booted(3) for more information.
 312 */
 313 int sd_booted(void);
 314
 315 /*
 316   Returns > 0 if the service manager expects watchdog keep-alive
 317   events to be sent regularly via sd_notify(0, "WATCHDOG=1"). Returns
 318   0 if it does not expect this. If the usec argument is non-NULL
 319   returns the watchdog timeout in µs after which the service manager
 320   will act on a process that has not sent a watchdog keep alive
 321   message. This function is useful to implement services that
 322   recognize automatically if they are being run under supervision of
 323   systemd with WatchdogSec= set. It is recommended for clients to
 324   generate keep-alive pings via sd_notify(0, "WATCHDOG=1") every half
 325   of the returned time.
 326
 327   See sd_watchdog_enabled(3) for more information.
 328 */
 329 int sd_watchdog_enabled(int unset_environment, uint64_t *usec);
 330
 331 _SD_END_DECLARATIONS;
 332
 333 #endif