udev/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/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 #ifndef _sd_hidden_
  79 #if (__GNUC__ >= 4) && !defined(SD_EXPORT_SYMBOLS)
  80 #define _sd_hidden_ __attribute__ ((visibility("hidden")))
  81 #else
  82 #define _sd_hidden_
  83 #endif
  84 #endif
  85
  86 /*
  87   Log levels for usage on stderr:
  88
  89           fprintf(stderr, SD_NOTICE "Hello World!\n");
  90
  91   This is similar to printk() usage in the kernel.
  92 */
  93 #define SD_EMERG   "<0>"  /* system is unusable */
  94 #define SD_ALERT   "<1>"  /* action must be taken immediately */
  95 #define SD_CRIT    "<2>"  /* critical conditions */
  96 #define SD_ERR     "<3>"  /* error conditions */
  97 #define SD_WARNING "<4>"  /* warning conditions */
  98 #define SD_NOTICE  "<5>"  /* normal but significant condition */
  99 #define SD_INFO    "<6>"  /* informational */
 100 #define SD_DEBUG   "<7>"  /* debug-level messages */
 101
 102 /* The first passed file descriptor is fd 3 */
 103 #define SD_LISTEN_FDS_START 3
 104
 105 /*
 106   Returns how many file descriptors have been passed, or a negative
 107   errno code on failure. Optionally, removes the $LISTEN_FDS and
 108   $LISTEN_PID file descriptors from the environment (recommended, but
 109   problematic in threaded environments). If r is the return value of
 110   this function you'll find the file descriptors passed as fds
 111   SD_LISTEN_FDS_START to SD_LISTEN_FDS_START+r-1. Returns a negative
 112   errno style error code on failure. This function call ensures that
 113   the FD_CLOEXEC flag is set for the passed file descriptors, to make
 114   sure they are not passed on to child processes. If FD_CLOEXEC shall
 115   not be set, the caller needs to unset it after this call for all file
 116   descriptors that are used.
 117
 118   See sd_listen_fds(3) for more information.
 119 */
 120 int sd_listen_fds(int unset_environment) _sd_hidden_;
 121
 122 /*
 123   Helper call for identifying a passed file descriptor. Returns 1 if
 124   the file descriptor is a FIFO in the file system stored under the
 125   specified path, 0 otherwise. If path is NULL a path name check will
 126   not be done and the call only verifies if the file descriptor
 127   refers to a FIFO. Returns a negative errno style error code on
 128   failure.
 129
 130   See sd_is_fifo(3) for more information.
 131 */
 132 int sd_is_fifo(int fd, const char *path) _sd_hidden_;
 133
 134 /*
 135   Helper call for identifying a passed file descriptor. Returns 1 if
 136   the file descriptor is a socket of the specified family (AF_INET,
 137   ...) and type (SOCK_DGRAM, SOCK_STREAM, ...), 0 otherwise. If
 138   family is 0 a socket family check will not be done. If type is 0 a
 139   socket type check will not be done and the call only verifies if
 140   the file descriptor refers to a socket. If listening is > 0 it is
 141   verified that the socket is in listening mode. (i.e. listen() has
 142   been called) If listening is == 0 it is verified that the socket is
 143   not in listening mode. If listening is < 0 no listening mode check
 144   is done. Returns a negative errno style error code on failure.
 145
 146   See sd_is_socket(3) for more information.
 147 */
 148 int sd_is_socket(int fd, int family, int type, int listening) _sd_hidden_;
 149
 150 /*
 151   Helper call for identifying a passed file descriptor. Returns 1 if
 152   the file descriptor is an Internet socket, of the specified family
 153   (either AF_INET or AF_INET6) and the specified type (SOCK_DGRAM,
 154   SOCK_STREAM, ...), 0 otherwise. If version is 0 a protocol version
 155   check is not done. If type is 0 a socket type check will not be
 156   done. If port is 0 a socket port check will not be done. The
 157   listening flag is used the same way as in sd_is_socket(). Returns a
 158   negative errno style error code on failure.
 159
 160   See sd_is_socket_inet(3) for more information.
 161 */
 162 int sd_is_socket_inet(int fd, int family, int type, int listening, uint16_t port) _sd_hidden_;
 163
 164 /*
 165   Helper call for identifying a passed file descriptor. Returns 1 if
 166   the file descriptor is an AF_UNIX socket of the specified type
 167   (SOCK_DGRAM, SOCK_STREAM, ...) and path, 0 otherwise. If type is 0
 168   a socket type check will not be done. If path is NULL a socket path
 169   check will not be done. For normal AF_UNIX sockets set length to
 170   0. For abstract namespace sockets set length to the length of the
 171   socket name (including the initial 0 byte), and pass the full
 172   socket path in path (including the initial 0 byte). The listening
 173   flag is used the same way as in sd_is_socket(). Returns a negative
 174   errno style error code on failure.
 175
 176   See sd_is_socket_unix(3) for more information.
 177 */
 178 int sd_is_socket_unix(int fd, int type, int listening, const char *path, size_t length) _sd_hidden_;
 179
 180 /*
 181   Informs systemd about changed daemon state. This takes a number of
 182   newline separated environment-style variable assignments in a
 183   string. The following variables are known:
 184
 185      READY=1      Tells systemd that daemon startup is finished (only
 186                   relevant for services of Type=notify). The passed
 187                   argument is a boolean "1" or "0". Since there is
 188                   little value in signaling non-readiness the only
 189                   value daemons should send is "READY=1".
 190
 191      STATUS=...   Passes a single-line status string back to systemd
 192                   that describes the daemon state. This is free-from
 193                   and can be used for various purposes: general state
 194                   feedback, fsck-like programs could pass completion
 195                   percentages and failing programs could pass a human
 196                   readable error message. Example: "STATUS=Completed
 197                   66% of file system check..."
 198
 199      ERRNO=...    If a daemon fails, the errno-style error code,
 200                   formatted as string. Example: "ERRNO=2" for ENOENT.
 201
 202      BUSERROR=... If a daemon fails, the D-Bus error-style error
 203                   code. Example: "BUSERROR=org.freedesktop.DBus.Error.TimedOut"
 204
 205      MAINPID=...  The main pid of a daemon, in case systemd did not
 206                   fork off the process itself. Example: "MAINPID=4711"
 207
 208   Daemons can choose to send additional variables. However, it is
 209   recommended to prefix variable names not listed above with X_.
 210
 211   Returns a negative errno-style error code on failure. Returns > 0
 212   if systemd could be notified, 0 if it couldn't possibly because
 213   systemd is not running.
 214
 215   Example: When a daemon finished starting up, it could issue this
 216   call to notify systemd about it:
 217
 218      sd_notify(0, "READY=1");
 219
 220   See sd_notifyf() for more complete examples.
 221
 222   See sd_notify(3) for more information.
 223 */
 224 int sd_notify(int unset_environment, const char *state) _sd_hidden_;
 225
 226 /*
 227   Similar to sd_notify() but takes a format string.
 228
 229   Example 1: A daemon could send the following after initialization:
 230
 231      sd_notifyf(0, "READY=1\n"
 232                    "STATUS=Processing requests...\n"
 233                    "MAINPID=%lu",
 234                    (unsigned long) getpid());
 235
 236   Example 2: A daemon could send the following shortly before
 237   exiting, on failure:
 238
 239      sd_notifyf(0, "STATUS=Failed to start up: %s\n"
 240                    "ERRNO=%i",
 241                    strerror(errno),
 242                    errno);
 243
 244   See sd_notifyf(3) for more information.
 245 */
 246 int sd_notifyf(int unset_environment, const char *format, ...) _sd_printf_attr_(2,3) _sd_hidden_;
 247
 248 /*
 249   Returns > 0 if the system was booted with systemd. Returns < 0 on
 250   error. Returns 0 if the system was not booted with systemd. Note
 251   that all of the functions above handle non-systemd boots just
 252   fine. You should NOT protect them with a call to this function. Also
 253   note that this function checks whether the system, not the user
 254   session is controlled by systemd. However the functions above work
 255   for both user and system services.
 256
 257   See sd_booted(3) for more information.
 258 */
 259 int sd_booted(void) _sd_hidden_;
 260
 261 #ifdef __cplusplus
 262 }
 263 #endif
 264
 265 #endif