path: root/support/dktools/dk4dmt.ctr

%%	options

copyright owner	=	Dirk Krause
copyright year	=	2016-xxxx
license		=	bsd

%%	header

/**	@file	dk4dmt.h	Daemon tools.

The functions in this module can be used in standing daemons.

In the original process, call the
dk4dmt_parent_before_fork() function to close all file descriptors
above 2, reset all signal handlers to defaults, unblock all signals
and check whether a PID file already exists.
If you plan to give up root privileges in the child processes
(use setgid() and setuid() to change effective user and group),
do not use /var/run/<i>program</i>.pid as PID file name, better
use /var/run/<i>program</i>/<i>program</i>.pid instead and make
sure to set ownership and group on /var/run/<i>program</i>
to the unprivileged user and group used by the child process.
User and group need write permission to the directory, so the unprivileged
child process can remove the PID file when exiting.

In the intermediate process after the first fork call
dk4dmt_intermediate_before_fork(). Among other things this function
completely decouples the process from the terminal.

In the final process (after forking again) call
dk4dmt_daemon_after_fork()
to set up things before starting service. This function creates the PID
file, connects file descriptors 0, 1 and 2 to /dev/null, resets
the umask and changes into the / directory.

After finishing service call
dk4dmt_daemon_end() before exiting. This function removes the PID
file.
*/

#ifdef __cplusplus
extern "C" {
#endif

/**	Activities in parent process before calling fork().
	* Close all file descriptors above 2.
	* Reset all signal actions to default handlers.
	* Unblock all signals.
	* Check whether PID file already exists.
	Use this function to check whether the initial process
	can run fork().
	@param	prgname		Program name.
	@param	pidfilename	PID file name.
	@param	logstderr	Flag: Logging to stderr allowed.
	@param	slf		Syslog feature.
	@return	1 on success (can call fork), 0 on error (abort).
*/
int
dk4dmt_parent_before_fork(
  const char *prgname, const char *pidfilename, int logstderr, int slf
);


/**	Activities in first child before calling fork() again.
	* Decouple completely from terminal.
	Use this function to check whether the first child process
	can run fork() again.
	@param	prgname	Program name.
	@param	slf	Syslog feature.
	@return	1 on success (can call fork), 0 on error (abort).
*/
int
dk4dmt_intermediate_before_fork(const char *prgname, int slf);

/**	Activities in final daemon process.
	* Create PID file.
	* Connect file descriptors 0, 1 and 2 to /dev/null.
	* Reset umask.
	* Change into / directory.
	@param	prgname		Program name.
	@param	pidfilename	File name for PID file.
	@param	slf		Syslog feature.
	@return	1 on success, 0 on error.
*/
int
dk4dmt_daemon_after_fork(const char *prgname, const char *pidfilename, int slf);

/**	End of daemon, remove PID file.
	@param	prgname		Program name.
	@param	pidfilename	PID file name.
	@param	slf		Syslog feature.
*/
void
dk4dmt_daemon_end(const char *prgname, const char *pidfilename, int slf);

#ifdef __cplusplus
}
#endif

%%	module


#include "dk4conf.h"

#include <stdio.h>

#if	DK4_HAVE_SYS_TYPES_H
#ifndef	SYS_TYPES_H_INCLUDED
#include <sys/types.h>
#define	SYS_TYPES_H_INCLUDED 1
#endif
#endif

#if	DK4_HAVE_SYS_STAT_H
#ifndef	SYS_STAT_H_INCLUDED
#include <sys/stat.h>
#define	SYS_STAT_H_INCLUDED 1
#endif
#endif

#if	DK4_HAVE_STDLIB_H
#ifndef	STDLIB_H_INCLUDED
#include <stdlib.h>
#define	STDLIB_H_INCLUDED 1
#endif
#endif

#if	DK4_HAVE_UNISTD_H
#ifndef	UNISTD_H_INCLUDED
#include <unistd.h>
#define	UNISTD_H_INCLUDED 1
#endif
#endif

#if	DK4_HAVE_FCNTL_H
#ifndef	FCNTL_H_INCLUDED
#include <fcntl.h>
#define	FCNTL_H_INCLUDED 1
#endif
#endif

#if	DK4_HAVE_SIGNAL_H
#ifndef	SIGNAL_H_INCLUDED
#include <signal.h>
#define	SIGNAL_H_INCLUDED 1
#endif
#endif

#if	DK4_HAVE_IO_H
#ifndef	IO_H_INCLUDED
#include <io.h>
#define	IO_H_INCLUDED 1
#endif
#endif

#if	DK4_HAVE_SYSLOG_H
#ifndef	SYSLOG_H_INCLUDED
#include <syslog.h>
#define	SYSLOG_H_INCLUDED 1
#endif
#endif

#include "dk4types.h"
#include "dk4dmt.h"
#include "dk4mem.h"
#include "dk4mao8d.h"
#include "dk4stat8.h"
#include "dk4str8.h"
#include "dk4fopc8.h"
#include "dk4mkdh8.h"



$!trace-include



static const char * const	dk4dmt_kw[] = {
$!string-table
#
#	0	Newline
#
\n
#
#	1	Separator after program name
#
: 
#
#	2
#
Failed to create background process!
#
#	3
#
Failed to detach from terminal (missing setsid()/setpgpr())!
#
#	4
#
Failed to detach from terminal (setsid() failed)!
#
#	5
#
Failed to create daemon process!
#
#	6
#
Failed to reset signal handlers (sigemptyset)!
#
#	7
#
Failed to reset signal handlers (sigaction)!
#
#	8
#
Neither sigaction() nor sigset() available!
#
#	9
#
Failed to unblock signals (sigemptyset)!
#
#	10
#
Failed to unblock signals (sigprocmask)!
#
#	11 12
#
PID file already exists:\n"
"!
#
#	13
#
Neither setsid() nor setpgrp() available!
#
#	14
#
Failed to detach from terminal (setsid)!
#
#	15 16
#
Failed to write PID file: "
"!
#
#	17
#
dk4dmt
#
#	18
#
Failed to open /dev/null for read access!
#
#	19
#
Failed to duplicate /dev/null to standard input!
#
#	20
#
Failed to open /dev/null for write access!
#
#	21 22
#
Failed to duplicate /dev/null to standard output!
Failed to duplicate /dev/null to standard error output!
#
#	23
#
Failed to change into root directory!
#
#	24 25
#
Failed to remove PID file "
"!
$!end
};



static
void
dk4dmt_syslog_1(const char *prgname, int slf, size_t idx)
{
#if DK4_HAVE_SYSLOG
  openlog(((NULL != prgname) ? (prgname) : (dk4dmt_kw[17])), LOG_PID, slf);
  syslog(LOG_ERR, "%s", dk4dmt_kw[idx]);
  closelog();
#endif
}



static
void
dk4dmt_syslog_3(
  const char *prgname, int slf, size_t i1, size_t i2, const char *str
)
{
#if DK4_HAVE_SYSLOG
  openlog(((NULL != prgname) ? (prgname) : (dk4dmt_kw[17])), LOG_PID, slf);
  if (NULL != str) {
    syslog(LOG_ERR, "%s%s%s", dk4dmt_kw[i1], str, dk4dmt_kw[i2]);
  } else {
    syslog(LOG_ERR, "%s%s", dk4dmt_kw[i1], dk4dmt_kw[i2]);
  }
  closelog();
#endif
}



static
void
dk4dmt_log_1(const char *prgname, int slf, int lse, size_t i)
{
  if (0 != lse) {
    if (NULL != prgname) {
      fputs(prgname, stderr);
      fputs(dk4dmt_kw[1], stderr);
    }
    fputs(dk4dmt_kw[i], stderr);
    fputs(dk4dmt_kw[0], stderr);
    fflush(stderr);
  } else {
    dk4dmt_syslog_1(prgname, slf, i);
  }
}



static
void
dk4dmt_log_3(
  const char *prgname, int slf, int lse, size_t i1, size_t i2, const char *str
)
{
  if (0 != lse) {
    if (NULL != prgname) {
      fputs(prgname, stderr);
      fputs(dk4dmt_kw[1], stderr);
    }
    fputs(dk4dmt_kw[i1], stderr);
    if (NULL != str) { fputs(str, stderr); }
    fputs(dk4dmt_kw[i2], stderr);
    fputs(dk4dmt_kw[0], stderr);
    fflush(stderr);
  } else {
    dk4dmt_syslog_3(prgname, slf, i1, i2, str);
  }
}



/**	Reset all signals to SIG_DFL.
	@param	reason	Address of error code variable
	(1=sigemptyset failed, 2=sigaction failed, 3=no signal handling).
	@return	1 on success, 0 on error.
*/
static
int
dk4dmt_reset_all_signals(int *reason)
{
  $? "+ dk4dmt_reset_all_signals"
#if	DK4_HAVE_SIGACTION
  struct sigaction	sigact;		/* Signal information for sigaction() */
#endif
  int	back	= 1;			/* Function result */
  int	maxsig;				/* Maximum signal + 1 */
  int	i;				/* Current signal to modify */
  int	go;

#ifdef _NSIG
  maxsig = _NSIG;
#else
  maxsig = 16;
#endif

  for (i = 1; ((i < maxsig) && (1 == back)); i++) {
    go = 1;
#ifdef SIGKILL
    if (SIGKILL == i)	{ go = 0; }
#else
    if (9 == i)		{ go = 0; }
#endif
#ifdef SIGSTOP
    if (SIGSTOP == i)	{ go = 0; }
#else
    if (19 == i)	{ go = 0; }
#endif
    $? ". signo = %d   go = %d", i, go
    if (0 != go) {
#if	DK4_HAVE_SIGACTION
      DK4_MEMRES(&sigact, sizeof(sigact));
      sigact.sa_handler = SIG_DFL;
      sigact.sa_flags   = 0;
      if (0 != sigemptyset(&(sigact.sa_mask))) {
        if (16 > i) {
          back = 0;
	  if (NULL != reason) {	$? "! sigemptyset"
	    *reason = 1;
	  }
	}
      }
      if (0 != sigaction(i, &sigact, NULL)) {
        if (16 > i) {
          back = 0;
	  if (NULL != reason) {	$? "! sigaction"
	    *reason = 2;
	  }
	}
      }
#else
#if	DK4_HAVE_SIGSET
      sigset(i, SIG_DFL);
#else
#if	DK4_HAVE_SIGNAL
      signal(i, SIG_DFL);
#else
      back = 0;
      if (NULL != reason) { *reason = 3; }
#endif
#endif
#endif
    }
  }
  $? "- dk4dmt_reset_all_signals %d", back
  return back;
}



/**	Obtain maximum file descriptor number.
	@return	Maximum file descriptor.
*/
static
int
dk4dmt_max_file_descriptor(void)
{
#if DK4_HAVE_SYS_RESOURCE_H && DK4_HAVE_GETRLIMIT && defined(RLIMIT_NOFILE)
  struct rlimit		 rl;
#endif
  int		 back	= 1024;
#if DK4_HAVE_SYS_RESOURCE_H && DK4_HAVE_GETRLIMIT && defined(RLIMIT_NOFILE)
  if (0 == getrlimit(RLIMIT_NOFILE, &rl)) {
#if defined(RLIM_INFINITY)
    if (RLIM_INFINITY != rl.rlim_max) {
#endif
      back = rl.rlim_max;
#if defined(RLIM_INFINITY)
    }
#endif
  }
#endif
  return back;
}



/**	Close all file descriptors except 0 (stdin), 1 (stdout) and 2 (stderr).
*/
static
void
dk4dmt_close_non_std_file_descriptors(void)
{
  int	maxfd;
  int	fd;

  maxfd = dk4dmt_max_file_descriptor();
  for (fd = 3; fd < maxfd; fd++) {
    (void)close(fd);
  }
}



/**	Unblock all signals.
	@param	reason	Address of error code variable
	(1=sigemptyset failed, 2=sigprocmask failed).
	@return	1 on success, 0 on error.
*/
static
int
dk4dmt_unblock_all_signals(int *reason)
{
  sigset_t	set;
  int		back	= 1;
  if (0 != sigemptyset(&set)) {
    back = 0;
    if (NULL != reason) { *reason = 1; }
  }
  if (0 != sigprocmask(SIG_SETMASK, &set, NULL)) {
    back = 0;
    if (NULL != reason) { *reason = 2; }
  }
  return back;
}



int
dk4dmt_parent_before_fork(
  const char *prgname, const char *pidfilename, int logstderr, int slf
)
{
  dk4_stat_t	 stb;
  int		 reason	= 0;
  int		 back	= 1;

  /* Close file descriptors except 0, 1 and 2 */
  dk4dmt_close_non_std_file_descriptors();

  /* Reset all signal actions to default handlers */
  if (0 == dk4dmt_reset_all_signals(&reason)) {
    back = 0;
    if (0 != logstderr) {
      switch (reason) {
        case 1: {
	  /* ERROR: sigemptyset() failed */
	  dk4dmt_log_1(prgname, slf, logstderr, 6);
        } break;
        case 2: {
	  /* ERROR: sigaction() failed */
	  dk4dmt_log_1(prgname, slf, logstderr, 7);
        } break;
        default: {
	  /* ERROR: No sigaction()/sigset()/signal() function */
	  dk4dmt_log_1(prgname, slf, logstderr, 8);
        } break;
      }
    }
  }

  /* Unblock all signals */
  if (0 == dk4dmt_unblock_all_signals(&reason)) {
    back = 0;
    if (0 != logstderr) {
      switch (reason) {
        case 1: {
	  /* ERROR: sigemptyset() failed */
	  dk4dmt_log_1(prgname, slf, logstderr, 9);
	} break;
	case 2: {
	  /* ERROR: sigprocmask() failed */
	  dk4dmt_log_1(prgname, slf, logstderr, 10);
	} break;
      }
    }
  }

  if ((0 != back) && (NULL != pidfilename)) {
    if (0 != dk4stat_c8(&stb, pidfilename, NULL)) {
      back = 0;
      /* ERROR: PID file exists */
      dk4dmt_log_3(prgname, slf, logstderr, 11, 12, pidfilename);
    }
  }

  return back;
}


int
dk4dmt_intermediate_before_fork(const char *prgname, int slf)
{
  int		 back	= 1;
#if	DK4_HAVE_SETSID
  if ((pid_t)(-1) == setsid()) {
    back = 0;
    dk4dmt_syslog_1(prgname, slf, 14);
  }
#else
#if	DK4_HAVE_SETPGRP
  setpgrp();
#else
  back = 0;
  dk4dmt_syslog_1(prgname, slf, 13);
#endif
#endif
  return back;
}



int
dk4dmt_daemon_after_fork(const char *prgname, const char *pidfilename, int slf)
{
  char		 pidbuf[16*sizeof(dk4_um_t)];
  FILE		*fipo;
  int		 fdin;		/* File descriptor for input */
  int		 fdout;		/* File descriptor for output */
  int		 res;		/* Operation result */
  int		 back	= 1;

  if (NULL != pidfilename) {
    res = dk4ma_write_c8_decimal_unsigned(
      pidbuf, sizeof(pidbuf), (dk4_um_t)getpid(), 0, NULL
    );
    if (0 != res) {
      if (0 != dk4str8_cat_s(pidbuf, sizeof(pidbuf), dk4dmt_kw[0], NULL)) {
        (void)dk4mkdir_hierarchy_c8(pidfilename, 0, NULL);
        fipo = dk4fopen_c8(pidfilename, "w", DK4_FOPEN_SC_PRIVILEGED, NULL);
        if (NULL != fipo) {
          fputs(pidbuf, fipo);
          fclose(fipo);
        } else {
          dk4dmt_syslog_3(prgname, slf, 15, 16, pidfilename);
	  back = 0;
	}
      }
    }
  }

  /*	Connect /dev/null to stdin stout stderr or close them
  */
  fdin = open("/dev/null", O_RDONLY);
  if (-1 < fdin) {
    if (-1 == dup2(fdin, 0)) {
      back = 0;
      dk4dmt_syslog_1(prgname, slf, 19);
    }
    close(fdin);
  } else {
    back = 0;
    dk4dmt_syslog_1(prgname, slf, 18);
  }
  fdout = open("/dev/null", O_WRONLY);
  if (-1 < fdout) {
    if (-1 == dup2(fdout, 1)) {
      back = 0;
      dk4dmt_syslog_1(prgname, slf, 21);
    }
    if (-1 == dup2(fdout, 2)) {
      back = 0;
      dk4dmt_syslog_1(prgname, slf, 22);
    }
    close(fdout);
  } else {
    back = 0;
    dk4dmt_syslog_1(prgname, slf, 20);
  }

  /*	Use exact permissions when creating new files or directories.
  */
  umask(0);

  /*	Change to root directory, so the previous current directory
	can be unmounted without blocking.
  */
  if (0 != chdir("/")) {
    back = 0;
    dk4dmt_syslog_1(prgname, slf, 23);
  }

  /*	Indicate success or error.
  */
  return back;
}



void
dk4dmt_daemon_end(const char *prgname, const char *pidfilename, int slf)
{
  if (NULL != pidfilename) {
    if (0 != unlink(pidfilename)) {
      dk4dmt_syslog_3(prgname, slf, 24, 25, pidfilename);
    }
  }
}