src/systemd/sd-daemon.h

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 #ifndef foosddaemonhfoo
   3 #define foosddaemonhfoo
   4
   5 /***
   6   This file is part of systemd.
   7
   8   Copyright 2013 Lennart Poettering
   9
  10   systemd is free software; you can redistribute it and/or modify it
  11   under the terms of the GNU Lesser General Public License as published by
  12   the Free Software Foundation; either version 2.1 of the License, or
  13   (at your option) any later version.
  14
  15   systemd is distributed in the hope that it will be useful, but
  16   WITHOUT ANY WARRANTY; without even the implied warranty of
  17   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  18   Lesser General Public License for more details.
  19
  20   You should have received a copy of the GNU Lesser General Public License
  21   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  22 ***/
  23
  24 #include <inttypes.h>
  25 #include <sys/types.h>
  26 #include <sys/socket.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 the
 137   file descriptor is an Internet socket of the specified type
 138   (SOCK_DGRAM, SOCK_STREAM, ...), and if the address of the socket is
 139   the same as the address specified by addr. The listening flag is used
 140   the same way as in sd_is_socket(). Returns a negative errno style
 141   error code on failure.
 142
 143   See sd_is_socket_sockaddr(3) for more information.
 144 */
 145 int sd_is_socket_sockaddr(int fd, int type, const struct sockaddr* addr, unsigned addr_len, int listening);
 146
 147 /*
 148   Helper call for identifying a passed file descriptor. Returns 1 if
 149   the file descriptor is an AF_UNIX socket of the specified type
 150   (SOCK_DGRAM, SOCK_STREAM, ...) and path, 0 otherwise. If type is 0
 151   a socket type check will not be done. If path is NULL a socket path
 152   check will not be done. For normal AF_UNIX sockets set length to
 153   0. For abstract namespace sockets set length to the length of the
 154   socket name (including the initial 0 byte), and pass the full
 155   socket path in path (including the initial 0 byte). The listening
 156   flag is used the same way as in sd_is_socket(). Returns a negative
 157   errno style error code on failure.
 158
 159   See sd_is_socket_unix(3) for more information.
 160 */
 161 int sd_is_socket_unix(int fd, int type, int listening, const char *path, size_t length);
 162
 163 /*
 164   Helper call for identifying a passed file descriptor. Returns 1 if
 165   the file descriptor is a POSIX Message Queue of the specified name,
 166   0 otherwise. If path is NULL a message queue name check is not
 167   done. Returns a negative errno style error code on failure.
 168
 169   See sd_is_mq(3) for more information.
 170 */
 171 int sd_is_mq(int fd, const char *path);
 172
 173 /*
 174   Informs systemd about changed daemon state. This takes a number of
 175   newline separated environment-style variable assignments in a
 176   string. The following variables are known:
 177
 178      READY=1      Tells systemd that daemon startup is finished (only
 179                   relevant for services of Type=notify). The passed
 180                   argument is a boolean "1" or "0". Since there is
 181                   little value in signaling non-readiness the only
 182                   value daemons should send is "READY=1".
 183
 184      STATUS=...   Passes a single-line status string back to systemd
 185                   that describes the daemon state. This is free-form
 186                   and can be used for various purposes: general state
 187                   feedback, fsck-like programs could pass completion
 188                   percentages and failing programs could pass a human
 189                   readable error message. Example: "STATUS=Completed
 190                   66% of file system check..."
 191
 192      ERRNO=...    If a daemon fails, the errno-style error code,
 193                   formatted as string. Example: "ERRNO=2" for ENOENT.
 194
 195      BUSERROR=... If a daemon fails, the D-Bus error-style error
 196                   code. Example: "BUSERROR=org.freedesktop.DBus.Error.TimedOut"
 197
 198      MAINPID=...  The main pid of a daemon, in case systemd did not
 199                   fork off the process itself. Example: "MAINPID=4711"
 200
 201      WATCHDOG=1   Tells systemd to update the watchdog timestamp.
 202                   Services using this feature should do this in
 203                   regular intervals. A watchdog framework can use the
 204                   timestamps to detect failed services. Also see
 205                   sd_watchdog_enabled() below.
 206
 207      FDSTORE=1    Store the file descriptors passed along with the
 208                   message in the per-service file descriptor store,
 209                   and pass them to the main process again on next
 210                   invocation. This variable is only supported with
 211                   sd_pid_notify_with_fds().
 212
 213      WATCHDOG_USEC=...
 214                   Reset watchdog_usec value during runtime.
 215                   To reset watchdog_usec value, start the service again.
 216                   Example: "WATCHDOG_USEC=20000000"
 217
 218   Daemons can choose to send additional variables. However, it is
 219   recommended to prefix variable names not listed above with X_.
 220
 221   Returns a negative errno-style error code on failure. Returns > 0
 222   if systemd could be notified, 0 if it couldn't possibly because
 223   systemd is not running.
 224
 225   Example: When a daemon finished starting up, it could issue this
 226   call to notify systemd about it:
 227
 228      sd_notify(0, "READY=1");
 229
 230   See sd_notifyf() for more complete examples.
 231
 232   See sd_notify(3) for more information.
 233 */
 234 int sd_notify(int unset_environment, const char *state);
 235
 236 /*
 237   Similar to sd_notify() but takes a format string.
 238
 239   Example 1: A daemon could send the following after initialization:
 240
 241      sd_notifyf(0, "READY=1\n"
 242                    "STATUS=Processing requests...\n"
 243                    "MAINPID=%lu",
 244                    (unsigned long) getpid());
 245
 246   Example 2: A daemon could send the following shortly before
 247   exiting, on failure:
 248
 249      sd_notifyf(0, "STATUS=Failed to start up: %s\n"
 250                    "ERRNO=%i",
 251                    strerror(errno),
 252                    errno);
 253
 254   See sd_notifyf(3) for more information.
 255 */
 256 int sd_notifyf(int unset_environment, const char *format, ...) _sd_printf_(2,3);
 257
 258 /*
 259   Similar to sd_notify(), but send the message on behalf of another
 260   process, if the appropriate permissions are available.
 261 */
 262 int sd_pid_notify(pid_t pid, int unset_environment, const char *state);
 263
 264 /*
 265   Similar to sd_notifyf(), but send the message on behalf of another
 266   process, if the appropriate permissions are available.
 267 */
 268 int sd_pid_notifyf(pid_t pid, int unset_environment, const char *format, ...) _sd_printf_(3,4);
 269
 270 /*
 271   Similar to sd_pid_notify(), but also passes the specified fd array
 272   to the service manager for storage. This is particularly useful for
 273   FDSTORE=1 messages.
 274 */
 275 int sd_pid_notify_with_fds(pid_t pid, int unset_environment, const char *state, const int *fds, unsigned n_fds);
 276
 277 /*
 278   Returns > 0 if the system was booted with systemd. Returns < 0 on
 279   error. Returns 0 if the system was not booted with systemd. Note
 280   that all of the functions above handle non-systemd boots just
 281   fine. You should NOT protect them with a call to this function. Also
 282   note that this function checks whether the system, not the user
 283   session is controlled by systemd. However the functions above work
 284   for both user and system services.
 285
 286   See sd_booted(3) for more information.
 287 */
 288 int sd_booted(void);
 289
 290 /*
 291   Returns > 0 if the service manager expects watchdog keep-alive
 292   events to be sent regularly via sd_notify(0, "WATCHDOG=1"). Returns
 293   0 if it does not expect this. If the usec argument is non-NULL
 294   returns the watchdog timeout in µs after which the service manager
 295   will act on a process that has not sent a watchdog keep alive
 296   message. This function is useful to implement services that
 297   recognize automatically if they are being run under supervision of
 298   systemd with WatchdogSec= set. It is recommended for clients to
 299   generate keep-alive pings via sd_notify(0, "WATCHDOG=1") every half
 300   of the returned time.
 301
 302   See sd_watchdog_enabled(3) for more information.
 303 */
 304 int sd_watchdog_enabled(int unset_environment, uint64_t *usec);
 305
 306 _SD_END_DECLARATIONS;
 307
 308 #endif