%% 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/program.pid as PID file name, better use /var/run/program/program.pid instead and make sure to set ownership and group on /var/run/program 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 #if DK4_HAVE_SYS_TYPES_H #ifndef SYS_TYPES_H_INCLUDED #include #define SYS_TYPES_H_INCLUDED 1 #endif #endif #if DK4_HAVE_SYS_STAT_H #ifndef SYS_STAT_H_INCLUDED #include #define SYS_STAT_H_INCLUDED 1 #endif #endif #if DK4_HAVE_STDLIB_H #ifndef STDLIB_H_INCLUDED #include #define STDLIB_H_INCLUDED 1 #endif #endif #if DK4_HAVE_UNISTD_H #ifndef UNISTD_H_INCLUDED #include #define UNISTD_H_INCLUDED 1 #endif #endif #if DK4_HAVE_FCNTL_H #ifndef FCNTL_H_INCLUDED #include #define FCNTL_H_INCLUDED 1 #endif #endif #if DK4_HAVE_SIGNAL_H #ifndef SIGNAL_H_INCLUDED #include #define SIGNAL_H_INCLUDED 1 #endif #endif #if DK4_HAVE_IO_H #ifndef IO_H_INCLUDED #include #define IO_H_INCLUDED 1 #endif #endif #if DK4_HAVE_SYSLOG_H #ifndef SYSLOG_H_INCLUDED #include #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); } } }