/** * Copyright © 2015 Mattias Andrée * * 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. * * This file is copied from . */ #include "daemonise.h" #include #include #include #include #include #include #include #include #include /** * The process's environment variables. */ extern char** environ; /** * The pidfile created by `daemonise`. */ static char* __pidfile = NULL; /** * Daemonise the process. This means to: * * - close all file descritors except for those to * stdin, stdout, and stderr, * * - remove all custom signal handlers, and apply * the default handlers. * * - unblock all signals, * * - remove all malformatted entries in the * environment (this not containing an '=',) * * - set the umask to zero, to be ensure that all * file permissions are set as specified, * * - change directory to '/', to ensure that the * process does not block any mountpoint from being * unmounted, * * - fork to become a background process, * * - temporarily become a session leader to ensure * that the process does not have a controlling * terminal. * * - fork again to become a child of the daemon * supervisor, (subreaper could however be in the * say, so one should not merely rely on this when * writing a daemon supervisor,) (the first child * shall exit after this,) * * - create, exclusively, a PID file to stop the daemon * to be being run twice concurrently, and to let * the daemon supervicer know the process ID of the * daemon, * * - redirect stdin and stdout to /dev/null, * as well as stderr if it is currently directed * to a terminal, and * * - exit in the original process to let the daemon * supervisor know that the daemon has been * initialised. * * Before calling this function, you should remove any * environment variable that could negatively impact * the runtime of the process. * * After calling this function, you should remove * unnecessary privileges. * * Do not try do continue the process in failure unless * you make sure to only do this in the original process. * But not that things will not necessarily be as when * you make the function call. The process can have become * partially deamonised. * * If $XDG_RUNTIME_DIR is set and is not empty, its value * should be used instead of /run for the runtime data-files * directory, in which the PID file is stored. * * This is a slibc extension. * * @etymology (Daemonise) the process! * * @param name The name of the daemon. Use a hardcoded value, * not the process name. Must not be `NULL`. * @param flags Flags to modify the behaviour of the function. * A bitwise OR combination of the constants: * - `DAEMONISE_NO_CLOSE` * - `DAEMONISE_NO_SIG_DFL` * - `DAEMONISE_KEEP_SIGMASK` * - `DAEMONISE_KEEP_ENVIRON` * - `DAEMONISE_KEEP_UMASK` * - `DAEMONISE_NO_PID_FILE` * - `DAEMONISE_KEEP_STDERR` * - `DAEMONISE_CLOSE_STDERR` * - `DAEMONISE_KEEP_STDIN` * - `DAEMONISE_KEEP_STDOUT` * @return Zero on success, -1 on error. * * @throws EEXIST The PID file already exists on the system. * Unless your daemon supervisor removs old * PID files, this could mean that the daemon * has exited without removing the PID file. * @throws Any error specified for signal(3). * @throws Any error specified for sigemptyset(3). * @throws Any error specified for sigprocmask(3). * @throws Any error specified for chdir(3). * @throws Any error specified for pipe(3). * @throws Any error specified for dup2(3). * @throws Any error specified for fork(3). * @throws Any error specified for setsid(3). * @throws Any error specified for open(3). * * @since Always. */ int daemonise(const char* name, int flags) { #define t(...) do { if (__VA_ARGS__) goto fail; } while (0) struct rlimit rlimit; int pipe_rw[2] = { -1, -1 }; sigset_t set; char** r; char** w; char* run; int i, closeerr, fd = -1; pid_t pid; int saved_errno; /* Validate flags. */ if (flags & ~1023) return errno = EINVAL, -1; if (flags & DAEMONISE_KEEP_STDERR) if (flags & DAEMONISE_CLOSE_STDERR) return errno = EINVAL, -1; /* Close all files except stdin, stdout, and stderr. */ if ((flags & DAEMONISE_NO_CLOSE) == 0) { if (getrlimit(RLIMIT_NOFILE, &rlimit)) rlimit.rlim_cur = 4 << 10; for (i = 3; (rlim_t)i < rlimit.rlim_cur; i++) /* File descriptors with numbers above and including * `rlimit.rlim_cur` cannot be created. They cause EBADF. */ close(i); } /* Reset all signal handlers. */ if ((flags & DAEMONISE_NO_SIG_DFL) == 0) for (i = 1; i < _NSIG; i++) t (signal(i, SIG_DFL) == SIG_ERR); /* Set signal mask. */ if ((flags & DAEMONISE_KEEP_SIGMASK) == 0) { t (sigemptyset(&set)); t (sigprocmask(SIG_SETMASK, &set, NULL)); } /* Remove malformatted environment entires. */ if (((flags & DAEMONISE_KEEP_ENVIRON) == 0) && (environ != NULL)) { for (r = w = environ; *r; r++) if (strchr(*r, '=')) /* It happens that this is not the case! (Thank you PAM!) */ *w++ = *r; *w = NULL; } /* Zero umask. */ if ((flags & DAEMONISE_KEEP_UMASK) == 0) umask(0); /* Change current working directory to '/'. */ t (chdir("/")); /* Create a channel for letting the original process know when to exit. */ if (pipe(pipe_rw)) t ((pipe_rw[0] = pipe_rw[1] = -1)); t (dup2(pipe_rw[0], 10) == -1); close(pipe_rw[0]); pipe_rw[0] = 10; t (dup2(pipe_rw[1], 11) == -1); close(pipe_rw[1]); pipe_rw[1] = 11; /* Become a background process. */ t (pid = fork(), pid == -1); close(pipe_rw[!!pid]), pipe_rw[!!pid] = 1; if (pid) exit(read(pipe_rw[0], &fd, (size_t)1) <= 0); /* Temporarily become session leader. */ t (setsid() == -1); /* Fork again. */ t (pid = fork(), pid == -1); if (pid > 0) exit(0); /* Create PID file. */ if (flags & DAEMONISE_NO_PID_FILE) goto no_pid_file; run = getenv("XDG_RUNTIME_DIR"); if (run && *run) { __pidfile = malloc(sizeof("/.pid") + (strlen(run) + strlen(name)) * sizeof(char)); t (__pidfile == NULL); stpcpy(stpcpy(stpcpy(stpcpy(__pidfile, run), "/"), name), ".pid"); } else { __pidfile = malloc(sizeof("/run/.pid") + strlen(name) * sizeof(char)); t (__pidfile == NULL); stpcpy(stpcpy(stpcpy(__pidfile, "/run/"), name), ".pid"); } fd = open(__pidfile, O_WRONLY | O_CREAT | O_EXCL, 0644); if (fd == -1) { saved_errno = errno; free(__pidfile), __pidfile = NULL; errno = saved_errno; goto fail; } pid = getpid(); t (dprintf(fd, "%lli\n", (long long int)pid) < 0); t (close(fd) && (errno != EINTR)); no_pid_file: /* Redirect to '/dev/null'. */ if (flags & DAEMONISE_KEEP_STDERR) closeerr = 0; else if (flags & DAEMONISE_CLOSE_STDERR) closeerr = 1; else closeerr = (isatty(2) || (errno == EBADF)); t (fd = open("/dev/null", O_RDWR), fd == -1); if ((flags & DAEMONISE_KEEP_STDIN) == 0) if (fd != 0) close(0); if ((flags & DAEMONISE_KEEP_STDOUT) == 0) if (fd != 1) close(1); if (closeerr) if (fd != 2) close(2); if ((flags & DAEMONISE_KEEP_STDIN) == 0) t (dup2(fd, 0) == -1); if ((flags & DAEMONISE_KEEP_STDOUT) == 0) t (dup2(fd, 1) == -1); if (closeerr) t (dup2(fd, 2) == -1); if (fd > 2) close(fd); fd = -1; /* We are done! Let the original process exit. */ if ((write(pipe_rw[1], &fd, (size_t)1) <= 0) || (close(pipe_rw[1]) && (errno != EINTR))) { if (flags & DAEMONISE_KEEP_STDERR) return -1; undaemonise(); abort(); /* Do not overcomplicate things, just abort in this unlikely event. */ } return 0; fail: saved_errno = errno; if (pipe_rw[0] >= 0) close(pipe_rw[0]); if (pipe_rw[1] >= 0) close(pipe_rw[1]); if (fd >= 0) close(fd); errno = saved_errno; return -1; } /** * Remove the PID file created by `daemonise`. This shall * always be called before exiting after calling `daemonise`, * even if it failed. * * This is a slibc extension. * * @etymology (Un)link PID file created by `(daemonise)`! * * @return Zero on success, -1 on error. * * @throws Any error specified for unlink(3). * * @since Always. */ int undaemonise(void) { int r, saved_errno; if (__pidfile == NULL) return 0; r = unlink(__pidfile); saved_errno = errno; free(__pidfile), __pidfile = NULL; errno = saved_errno; return r; }