sd-daemon.h

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/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/

#pragma once

/***
  Copyright 2010 Lennart Poettering

  Permission is hereby granted, free of charge, to any person
  obtaining a copy of this software and associated documentation files
  (the "Software"), to deal in the Software without restriction,
  including without limitation the rights to use, copy, modify, merge,
  publish, distribute, sublicense, and/or sell copies of the Software,
  and to permit persons to whom the Software is furnished to do so,
  subject to the following conditions:

  The above copyright notice and this permission notice shall be
  included in all copies or substantial portions of the Software.

  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
  BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  SOFTWARE.
***/

#include <sys/types.h>
#include <inttypes.h>

#ifdef __cplusplus
extern "C" {
#endif

/*
  Reference implementation of a few systemd related interfaces for
  writing daemons. These interfaces are trivial to implement. To
  simplify porting we provide this reference implementation.
  Applications are welcome to reimplement the algorithms described
  here if they do not want to include these two source files.

  The following functionality is provided:

  - Support for logging with log levels on stderr
  - File descriptor passing for socket-based activation
  - Daemon startup and status notification
  - Detection of systemd boots

  You may compile this with -DDISABLE_SYSTEMD to disable systemd
  support. This makes all those calls NOPs that are directly related to
  systemd (i.e. only sd_is_xxx() will stay useful).

  Since this is drop-in code we don't want any of our symbols to be
  exported in any case. Hence we declare hidden visibility for all of
  them.

  You may find an up-to-date version of these source files online:

  https://cgit.freedesktop.org/systemd/plain/src/sd-daemon.h
  https://cgit.freedesktop.org/systemd/plain/src/sd-daemon.c

  This should compile on non-Linux systems, too, but with the
  exception of the sd_is_xxx() calls all functions will become NOPs.

  See sd-daemon(7) for more information.
*/

#ifndef _sd_printf_attr_
#if __GNUC__ >= 4
#define _sd_printf_attr_(a, b) __attribute__((format(printf, a, b)))
#else
#define _sd_printf_attr_(a, b)
#endif
#endif

#ifndef _sd_hidden_
#if (__GNUC__ >= 4) && !defined(SD_EXPORT_SYMBOLS)
#define _sd_hidden_ __attribute__((visibility("hidden")))
#else
#define _sd_hidden_
#endif
#endif

/*
  Log levels for usage on stderr:

          fprintf(stderr, SD_NOTICE "Hello World!\n");

  This is similar to printk() usage in the kernel.
*/
#define SD_EMERG "<0>"   /* system is unusable */
#define SD_ALERT "<1>"   /* action must be taken immediately */
#define SD_CRIT "<2>"    /* critical conditions */
#define SD_ERR "<3>"     /* error conditions */
#define SD_WARNING "<4>" /* warning conditions */
#define SD_NOTICE "<5>"  /* normal but significant condition */
#define SD_INFO "<6>"    /* informational */
#define SD_DEBUG "<7>"   /* debug-level messages */

/* The first passed file descriptor is fd 3 */
#define SD_LISTEN_FDS_START 3

/*
  Returns how many file descriptors have been passed, or a negative
  errno code on failure. Optionally, removes the $LISTEN_FDS and
  $LISTEN_PID file descriptors from the environment (recommended, but
  problematic in threaded environments). If r is the return value of
  this function you'll find the file descriptors passed as fds
  SD_LISTEN_FDS_START to SD_LISTEN_FDS_START+r-1. Returns a negative
  errno style error code on failure. This function call ensures that
  the FD_CLOEXEC flag is set for the passed file descriptors, to make
  sure they are not passed on to child processes. If FD_CLOEXEC shall
  not be set, the caller needs to unset it after this call for all file
  descriptors that are used.

  See sd_listen_fds(3) for more information.
*/
int sd_listen_fds(int unset_environment) _sd_hidden_;

/*
  Helper call for identifying a passed file descriptor. Returns 1 if
  the file descriptor is a FIFO in the file system stored under the
  specified path, 0 otherwise. If path is NULL a path name check will
  not be done and the call only verifies if the file descriptor
  refers to a FIFO. Returns a negative errno style error code on
  failure.

  See sd_is_fifo(3) for more information.
*/
int sd_is_fifo(int fd, const char *path) _sd_hidden_;

/*
  Helper call for identifying a passed file descriptor. Returns 1 if
  the file descriptor is a socket of the specified family (AF_INET,
  ...) and type (SOCK_DGRAM, SOCK_STREAM, ...), 0 otherwise. If
  family is 0 a socket family check will not be done. If type is 0 a
  socket type check will not be done and the call only verifies if
  the file descriptor refers to a socket. If listening is > 0 it is
  verified that the socket is in listening mode. (i.e. listen() has
  been called) If listening is == 0 it is verified that the socket is
  not in listening mode. If listening is < 0 no listening mode check
  is done. Returns a negative errno style error code on failure.

  See sd_is_socket(3) for more information.
*/
int sd_is_socket(int fd, int family, int type, int listening) _sd_hidden_;

/*
  Helper call for identifying a passed file descriptor. Returns 1 if
  the file descriptor is an Internet socket, of the specified family
  (either AF_INET or AF_INET6) and the specified type (SOCK_DGRAM,
  SOCK_STREAM, ...), 0 otherwise. If version is 0 a protocol version
  check is not done. If type is 0 a socket type check will not be
  done. If port is 0 a socket port check will not be done. The
  listening flag is used the same way as in sd_is_socket(). Returns a
  negative errno style error code on failure.

  See sd_is_socket_inet(3) for more information.
*/
int sd_is_socket_inet(int fd, int family, int type, int listening, uint16_t port) _sd_hidden_;

/*
  Helper call for identifying a passed file descriptor. Returns 1 if
  the file descriptor is an AF_UNIX socket of the specified type
  (SOCK_DGRAM, SOCK_STREAM, ...) and path, 0 otherwise. If type is 0
  a socket type check will not be done. If path is NULL a socket path
  check will not be done. For normal AF_UNIX sockets set length to
  0. For abstract namespace sockets set length to the length of the
  socket name (including the initial 0 byte), and pass the full
  socket path in path (including the initial 0 byte). The listening
  flag is used the same way as in sd_is_socket(). Returns a negative
  errno style error code on failure.

  See sd_is_socket_unix(3) for more information.
*/
int sd_is_socket_unix(int fd, int type, int listening, const char *path, size_t length) _sd_hidden_;

/*
  Informs systemd about changed daemon state. This takes a number of
  newline separated environment-style variable assignments in a
  string. The following variables are known:

     READY=1      Tells systemd that daemon startup is finished (only
                  relevant for services of Type=notify). The passed
                  argument is a boolean "1" or "0". Since there is
                  little value in signaling non-readiness the only
                  value daemons should send is "READY=1".

     STATUS=...   Passes a single-line status string back to systemd
                  that describes the daemon state. This is free-from
                  and can be used for various purposes: general state
                  feedback, fsck-like programs could pass completion
                  percentages and failing programs could pass a human
                  readable error message. Example: "STATUS=Completed
                  66% of file system check..."

     ERRNO=...    If a daemon fails, the errno-style error code,
                  formatted as string. Example: "ERRNO=2" for ENOENT.

     BUSERROR=... If a daemon fails, the D-Bus error-style error
                  code. Example: "BUSERROR=org.freedesktop.DBus.Error.TimedOut"

     MAINPID=...  The main pid of a daemon, in case systemd did not
                  fork off the process itself. Example: "MAINPID=4711"

  Daemons can choose to send additional variables. However, it is
  recommended to prefix variable names not listed above with X_.

  Returns a negative errno-style error code on failure. Returns > 0
  if systemd could be notified, 0 if it couldn't possibly because
  systemd is not running.

  Example: When a daemon finished starting up, it could issue this
  call to notify systemd about it:

     sd_notify(0, "READY=1");

  See sd_notifyf() for more complete examples.

  See sd_notify(3) for more information.
*/
int sd_notify(int unset_environment, const char *state) _sd_hidden_;

/*
  Similar to sd_notify() but takes a format string.

  Example 1: A daemon could send the following after initialization:

     sd_notifyf(0, "READY=1\n"
                   "STATUS=Processing requests...\n"
                   "MAINPID=%lu",
                   (unsigned long) getpid());

  Example 2: A daemon could send the following shortly before
  exiting, on failure:

     sd_notifyf(0, "STATUS=Failed to start up: %s\n"
                   "ERRNO=%i",
                   strerror(errno),
                   errno);

  See sd_notifyf(3) for more information.
*/
int sd_notifyf(int unset_environment, const char *format, ...) _sd_printf_attr_(2, 3) _sd_hidden_;

/*
  Returns > 0 if the system was booted with systemd. Returns < 0 on
  error. Returns 0 if the system was not booted with systemd. Note
  that all of the functions above handle non-systemd boots just
  fine. You should NOT protect them with a call to this function. Also
  note that this function checks whether the system, not the user
  session is controlled by systemd. However the functions above work
  for both user and system services.

  See sd_booted(3) for more information.
*/
int sd_booted(void) _sd_hidden_;

#ifdef __cplusplus
}
#endif