/* * 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 #include #include #include #include #ifdef HAVE_SYS_WAIT_H #include #endif #ifdef HAVE_FCNTL_H #include #else /* !HAVE_FCNTL_H */ #ifdef HAVE_SYS_FCNTL_H #include #endif /* HAVE_SYS_FCNTL_H */ #endif /* !HAVE_FCNTL_H */ #include /* get umask(2) prototyped */ #if defined(HAVE_UNISTD_H) #include #endif #if defined(STDC_HEADERS) #include #endif #if defined(QNX) #include #endif #if !defined(HAVE_SETSID) && defined(SIGTSTP) #if defined(HAVE_TERMIOS_H) # include /* for TIOCNOTTY under Linux */ #endif #if !defined(TIOCNOTTY) && defined(HAVE_SGTTY_H) # include /* 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); } /* move to root directory, so we don't prevent filesystem unmounts */ chdir("/"); /* 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 */