/*

 * daemon.c -- turn a process into a daemon under POSIX, SYSV, BSD.

 *

 * For license terms, see the file COPYING in this directory.

 */

#include "config.h"

#include <stdio.h>

#include <errno.h>

#include <signal.h>

#include <string.h>

#include <sys/types.h>

#ifdef HAVE_SYS_WAIT_H

#include <sys/wait.h>

#endif

#ifdef HAVE_FCNTL_H

#include <fcntl.h>

#else /* !HAVE_FCNTL_H */

#ifdef HAVE_SYS_FCNTL_H

#include <sys/fcntl.h>

#endif /* HAVE_SYS_FCNTL_H */

#endif /* !HAVE_FCNTL_H */

#include <sys/stat.h>	/* get umask(2) prototyped */

#if defined(HAVE_UNISTD_H)

#include <unistd.h>

#endif

#if defined(STDC_HEADERS)

#include <stdlib.h>

#endif

#if defined(QNX)

#include <unix.h>

#endif

#if !defined(HAVE_SETSID) && defined(SIGTSTP)

#if defined(HAVE_TERMIOS_H)

#  include <termios.h>		/* for TIOCNOTTY under Linux */

#endif

#if !defined(TIOCNOTTY) && defined(HAVE_SGTTY_H)

#  include <sgtty.h>		/* for TIOCNOTTY under NEXTSTEP */

#endif

#endif /* !defined(HAVE_SETSID) && defined(SIGTSTP) */

/* BSD portability hack */

#if !defined(SIGCHLD) && defined(SIGCLD)

#define SIGCHLD	SIGCLD

#endif

#include "fetchmail.h"

#include "tunable.h"

static RETSIGTYPE

sigchld_handler (int sig)

/* process SIGCHLD to obtain the exit code of the terminating process */

{

#if 	defined(HAVE_WAITPID)				/* the POSIX way */

    int status;

    while (waitpid(-1, &status, WNOHANG) > 0)

	continue; /* swallow 'em up. */

#elif 	defined(HAVE_WAIT3)				/* the BSD way */

    pid_t pid;

#if defined(HAVE_UNION_WAIT) && !defined(__FreeBSD__)

    union wait status;

#else

    int status;

#endif

    while ((pid = wait3(&status, WNOHANG, 0)) > 0)

	continue; /* swallow 'em up. */

#else	/* Zooks! Nothing to do but wait(), and hope we don't block... */

    int status;

    wait(&status);

#endif

    lastsig = SIGCHLD;

    (void)sig;

}

RETSIGTYPE null_signal_handler(int sig) { (void)sig; }

SIGHANDLERTYPE set_signal_handler(int sig, SIGHANDLERTYPE handler)

/* 

 * This function is called by other parts of the program to

 * setup the signal handler after a change to the signal context.

 * This is done to improve robustness of the signal handling code.

 * It has the same prototype as signal(2).

 */

{

  SIGHANDLERTYPE rethandler;

#ifdef HAVE_SIGACTION

  struct sigaction sa_new, sa_old;

  memset (&sa_new, 0, sizeof sa_new);

  sigemptyset (&sa_new.sa_mask);

  sa_new.sa_handler = handler;

  sa_new.sa_flags = 0;

#ifdef SA_RESTART	/* SunOS 4.1 portability hack */

  /* system call should restart on all signals except SIGALRM */

  if (sig != SIGALRM)

      sa_new.sa_flags |= SA_RESTART;

#endif

#ifdef SA_NOCLDSTOP	/* SunOS 4.1 portability hack */

  if (sig == SIGCHLD)

      sa_new.sa_flags |= SA_NOCLDSTOP;

#endif

  sigaction(sig, &sa_new, &sa_old);

  rethandler = sa_old.sa_handler;

#if defined(SIGPWR)

  if (sig == SIGCHLD)

     sigaction(SIGPWR, &sa_new, NULL);

#endif

#else /* HAVE_SIGACTION */

  rethandler = signal(sig, handler);

#if defined(SIGPWR)

  if (sig == SIGCHLD)

      signal(SIGPWR, handler);

#endif

  /* system call should restart on all signals except SIGALRM */

  siginterrupt(sig, sig == SIGALRM);

#endif /* HAVE_SIGACTION */

  return rethandler;

}

void deal_with_sigchld(void)

{

  set_signal_handler(SIGCHLD, sigchld_handler);

}

int

daemonize (const char *logfile)

/* detach from control TTY, become process group leader, catch SIGCHLD */

{

  int fd, logfd;

  pid_t childpid;

  /* if we are started by init (process 1) via /etc/inittab we needn't 

     bother to detach from our process group context */

  if (getppid() == 1) 

    goto nottyDetach;

  /* Ignore BSD terminal stop signals */

#ifdef 	SIGTTOU

  set_signal_handler(SIGTTOU, SIG_IGN);

#endif

#ifdef	SIGTTIN

  set_signal_handler(SIGTTIN, SIG_IGN);

#endif

#ifdef	SIGTSTP

  set_signal_handler(SIGTSTP, SIG_IGN);

#endif

  /* In case we were not started in the background, fork and let

     the parent exit.  Guarantees that the child is not a process

     group leader */

  if ((childpid = fork()) < 0) {

    report(stderr, "fork (%s)\n", strerror(errno));

    return(PS_IOERR);

  }

  else if (childpid > 0) 

    exit(0);  /* parent */

  /* Make ourselves the leader of a new process group with no

     controlling terminal */

#if	defined(HAVE_SETSID)		/* POSIX */

  /* POSIX makes this soooo easy to do */

  if (setsid() < 0) {

    report(stderr, "setsid (%s)\n", strerror(errno));

    return(PS_IOERR);

  }

#elif	defined(SIGTSTP)		/* BSD */

  /* change process group */

#ifndef __EMX__

  setpgrp(0, getpid());

#endif

  /* lose controlling tty */

  if ((fd = open("/dev/tty", O_RDWR)) >= 0) {

    ioctl(fd, TIOCNOTTY, (char *) 0);

    close(fd);	/* not checking should be safe, there were no writes */

  }

#else					/* SVR3 and older */

  /* change process group */

#ifndef __EMX__

  setpgrp();

#endif

  /* lose controlling tty */

  set_signal_handler(SIGHUP, SIG_IGN);

  if ((childpid = fork()) < 0) {

    report(stderr, "fork (%s)\n", strerror(errno));

    return(PS_IOERR);

  }

  else if (childpid > 0) {

    exit(0); 	/* parent */

  }

#endif

nottyDetach:

  (void)close(0);

  /* Reopen stdin descriptor on /dev/null */

  if (open("/dev/null", O_RDWR) < 0) {   /* stdin */

    report(stderr, "cannot open /dev/null: %s\n", strerror(errno));

    return(PS_IOERR);

  }

  if (logfile)

  {

      if ((logfd = open(logfile, O_CREAT|O_WRONLY|O_APPEND, 0666)) < 0) {	/* stdout */

	  report(stderr, "cannot open %s: %s\n", logfile, strerror(errno));

	  return PS_IOERR;

      }

  } else

      logfd = 0;    /* else use /dev/null */

  /* Close any/all open file descriptors */

#if 	defined(HAVE_GETDTABLESIZE)

  fd = getdtablesize() - 1;

#elif	defined(NOFILE)

  fd = NOFILE - 1;

#else		/* make an educated guess */

  fd = 1023;

#endif

  while (fd >= 1) {

      if (fd != logfd)

	  close(fd);	/* not checking this should be safe, no writes */

      -- fd;

  }

  if (dup(logfd) < 0						/* stdout */

	  || ((logfd == 0 || logfd >= 3) && dup(logfd) < 0)) {	/* stderr */

      report(stderr, "dup (%s)\n", strerror(errno));

      return(PS_IOERR);

  }

#ifdef HAVE_GETCWD

  /* move to root directory, so we don't prevent filesystem unmounts */

  chdir("/");

#endif

  /* set our umask to something reasonable (we hope) */

#if defined(DEF_UMASK)

  umask(DEF_UMASK);

#else

  umask(022);

#endif

  deal_with_sigchld();

  return(0);

}

flag is_a_file(int fd)

/* is the given fd attached to a file? (used to control logging) */

{

    struct stat stbuf;

    /*

     * We'd like just to return 1 on (S_IFREG | S_IFBLK),

     * but weirdly enough, Linux ptys seem to have S_IFBLK

     * so this test would fail when run on an xterm.

     */

    if (isatty(fd) || fstat(fd, &stbuf))

	return(0);

    else if (stbuf.st_mode & (S_IFREG))

	return(1);

    return(0);

}

/* daemon.c ends here */