/*- * SPDX-License-Identifier: BSD-3-Clause * * Copyright (c) 1999 Berkeley Software Design, Inc. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Berkeley Software Design Inc's name may not be used to endorse or * promote products derived from this software without specific prior * written permission. * * THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * From BSDI: daemon.c,v 1.2 1996/08/15 01:11:09 jch Exp */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define SYSLOG_NAMES #include #include #include #define LBUF_SIZE 4096 enum daemon_mode { MODE_DAEMON = 0, /* simply daemonize, no supervision */ MODE_SUPERVISE, /* initial supervision state */ MODE_TERMINATING, /* user requested termination */ MODE_NOCHILD, /* child is terminated, final state of the event loop */ }; struct daemon_state { int pipe_fd[2]; char **argv; const char *child_pidfile; const char *parent_pidfile; const char *output_filename; const char *syslog_tag; const char *title; const char *user; struct pidfh *parent_pidfh; struct pidfh *child_pidfh; enum daemon_mode mode; int pid; int keep_cur_workdir; int restart_delay; int stdmask; int syslog_priority; int syslog_facility; int keep_fds_open; int output_fd; bool restart_enabled; bool syslog_enabled; bool log_reopen; }; static void restrict_process(const char *); static int open_log(const char *); static void reopen_log(struct daemon_state *); static bool listen_child(int, struct daemon_state *); static int get_log_mapping(const char *, const CODE *); static void open_pid_files(struct daemon_state *); static void do_output(const unsigned char *, size_t, struct daemon_state *); static void daemon_sleep(struct daemon_state *); static void daemon_state_init(struct daemon_state *); static void daemon_eventloop(struct daemon_state *); static void daemon_terminate(struct daemon_state *); static void daemon_exec(struct daemon_state *); static bool daemon_is_child_dead(struct daemon_state *); static void daemon_set_child_pipe(struct daemon_state *); static const char shortopts[] = "+cfHSp:P:ru:o:s:l:t:m:R:T:h"; static const struct option longopts[] = { { "change-dir", no_argument, NULL, 'c' }, { "close-fds", no_argument, NULL, 'f' }, { "sighup", no_argument, NULL, 'H' }, { "syslog", no_argument, NULL, 'S' }, { "output-file", required_argument, NULL, 'o' }, { "output-mask", required_argument, NULL, 'm' }, { "child-pidfile", required_argument, NULL, 'p' }, { "supervisor-pidfile", required_argument, NULL, 'P' }, { "restart", no_argument, NULL, 'r' }, { "restart-delay", required_argument, NULL, 'R' }, { "title", required_argument, NULL, 't' }, { "user", required_argument, NULL, 'u' }, { "syslog-priority", required_argument, NULL, 's' }, { "syslog-facility", required_argument, NULL, 'l' }, { "syslog-tag", required_argument, NULL, 'T' }, { "help", no_argument, NULL, 'h' }, { NULL, 0, NULL, 0 } }; static _Noreturn void usage(int exitcode) { (void)fprintf(stderr, "usage: daemon [-cfHrS] [-p child_pidfile] [-P supervisor_pidfile]\n" " [-u user] [-o output_file] [-t title]\n" " [-l syslog_facility] [-s syslog_priority]\n" " [-T syslog_tag] [-m output_mask] [-R restart_delay_secs]\n" "command arguments ...\n"); (void)fprintf(stderr, " --change-dir -c Change the current working directory to root\n" " --close-fds -f Set stdin, stdout, stderr to /dev/null\n" " --sighup -H Close and re-open output file on SIGHUP\n" " --syslog -S Send output to syslog\n" " --output-file -o Append output of the child process to file\n" " --output-mask -m What to send to syslog/file\n" " 1=stdout, 2=stderr, 3=both\n" " --child-pidfile -p Write PID of the child process to file\n" " --supervisor-pidfile -P Write PID of the supervisor process to file\n" " --restart -r Restart child if it terminates (1 sec delay)\n" " --restart-delay -R Restart child if it terminates after N sec\n" " --title -t Set the title of the supervisor process\n" " --user -u <user> Drop privileges, run as given user\n" " --syslog-priority -s <prio> Set syslog priority\n" " --syslog-facility -l <flty> Set syslog facility\n" " --syslog-tag -T <tag> Set syslog tag\n" " --help -h Show this help\n"); exit(exitcode); } int main(int argc, char *argv[]) { char *p = NULL; int ch = 0; struct daemon_state state; daemon_state_init(&state); /* Signals are processed via kqueue */ signal(SIGHUP, SIG_IGN); signal(SIGTERM, SIG_IGN); /* * Supervision mode is enabled if one of the following options are used: * --child-pidfile -p * --supervisor-pidfile -P * --restart -r / --restart-delay -R * --syslog -S * --syslog-facility -l * --syslog-priority -s * --syslog-tag -T * * In supervision mode daemon executes the command in a forked process * and observes the child by waiting for SIGCHILD. In supervision mode * daemon must never exit before the child, this is necessary to prevent * orphaning the child and leaving a stale pid file. * To achieve this daemon catches SIGTERM and * forwards it to the child, expecting to get SIGCHLD eventually. */ while ((ch = getopt_long(argc, argv, shortopts, longopts, NULL)) != -1) { switch (ch) { case 'c': state.keep_cur_workdir = 0; break; case 'f': state.keep_fds_open = 0; break; case 'H': state.log_reopen = true; break; case 'l': state.syslog_facility = get_log_mapping(optarg, facilitynames); if (state.syslog_facility == -1) { errx(5, "unrecognized syslog facility"); } state.syslog_enabled = true; state.mode = MODE_SUPERVISE; break; case 'm': state.stdmask = strtol(optarg, &p, 10); if (p == optarg || state.stdmask < 0 || state.stdmask > 3) { errx(6, "unrecognized listening mask"); } break; case 'o': state.output_filename = optarg; /* * TODO: setting output filename doesn't have to turn * the supervision mode on. For non-supervised mode * daemon could open the specified file and set it's * descriptor as both stderr and stout before execve() */ state.mode = MODE_SUPERVISE; break; case 'p': state.child_pidfile = optarg; state.mode = MODE_SUPERVISE; break; case 'P': state.parent_pidfile = optarg; state.mode = MODE_SUPERVISE; break; case 'r': state.restart_enabled = true; state.mode = MODE_SUPERVISE; break; case 'R': state.restart_enabled = true; state.restart_delay = strtol(optarg, &p, 0); if (p == optarg || state.restart_delay < 1) { errx(6, "invalid restart delay"); } break; case 's': state.syslog_priority = get_log_mapping(optarg, prioritynames); if (state.syslog_priority == -1) { errx(4, "unrecognized syslog priority"); } state.syslog_enabled = true; state.mode = MODE_SUPERVISE; break; case 'S': state.syslog_enabled = true; state.mode = MODE_SUPERVISE; break; case 't': state.title = optarg; break; case 'T': state.syslog_tag = optarg; state.syslog_enabled = true; state.mode = MODE_SUPERVISE; break; case 'u': state.user = optarg; break; case 'h': usage(0); __builtin_unreachable(); default: usage(1); } } argc -= optind; argv += optind; state.argv = argv; if (argc == 0) { usage(1); } if (!state.title) { state.title = argv[0]; } if (state.output_filename) { state.output_fd = open_log(state.output_filename); if (state.output_fd == -1) { err(7, "open"); } } if (state.syslog_enabled) { openlog(state.syslog_tag, LOG_PID | LOG_NDELAY, state.syslog_facility); } /* * Try to open the pidfile before calling daemon(3), * to be able to report the error intelligently */ open_pid_files(&state); /* * TODO: add feature to avoid backgrounding * i.e. --foreground, -f */ if (daemon(state.keep_cur_workdir, state.keep_fds_open) == -1) { warn("daemon"); daemon_terminate(&state); } if (state.mode == MODE_DAEMON) { daemon_exec(&state); } /* Write out parent pidfile if needed. */ pidfile_write(state.parent_pidfh); do { state.mode = MODE_SUPERVISE; daemon_eventloop(&state); daemon_sleep(&state); } while (state.restart_enabled); daemon_terminate(&state); } static void daemon_exec(struct daemon_state *state) { pidfile_write(state->child_pidfh); if (state->user != NULL) { restrict_process(state->user); } /* Ignored signals remain ignored after execve, unignore them */ signal(SIGHUP, SIG_DFL); signal(SIGTERM, SIG_DFL); execvp(state->argv[0], state->argv); /* execvp() failed - report error and exit this process */ err(1, "%s", state->argv[0]); } /* Main event loop: fork the child and watch for events. * After SIGTERM is recieved and propagated to the child there are * several options on what to do next: * - read until EOF * - read until EOF but only for a while * - bail immediately * Currently the third option is used, because otherwise there is no * guarantee that read() won't block indefinitely if the child refuses * to depart. To handle the second option, a different approach * would be needed (procctl()?). */ static void daemon_eventloop(struct daemon_state *state) { struct kevent event; int kq; int ret; /* * Try to protect against pageout kill. Ignore the * error, madvise(2) will fail only if a process does * not have superuser privileges. */ (void)madvise(NULL, 0, MADV_PROTECT); if (pipe(state->pipe_fd)) { err(1, "pipe"); } kq = kqueuex(KQUEUE_CLOEXEC); EV_SET(&event, state->pipe_fd[0], EVFILT_READ, EV_ADD|EV_CLEAR, 0, 0, NULL); if (kevent(kq, &event, 1, NULL, 0, NULL) == -1) { err(EXIT_FAILURE, "failed to register kevent"); } EV_SET(&event, SIGHUP, EVFILT_SIGNAL, EV_ADD, 0, 0, NULL); if (kevent(kq, &event, 1, NULL, 0, NULL) == -1) { err(EXIT_FAILURE, "failed to register kevent"); } EV_SET(&event, SIGTERM, EVFILT_SIGNAL, EV_ADD, 0, 0, NULL); if (kevent(kq, &event, 1, NULL, 0, NULL) == -1) { err(EXIT_FAILURE, "failed to register kevent"); } EV_SET(&event, SIGCHLD, EVFILT_SIGNAL, EV_ADD, 0, 0, NULL); if (kevent(kq, &event, 1, NULL, 0, NULL) == -1) { err(EXIT_FAILURE, "failed to register kevent"); } memset(&event, 0, sizeof(struct kevent)); /* Spawn a child to exec the command. */ state->pid = fork(); /* fork failed, this can only happen when supervision is enabled */ switch (state->pid) { case -1: warn("fork"); state->mode = MODE_NOCHILD; return; /* fork succeeded, this is child's branch */ case 0: close(kq); daemon_set_child_pipe(state); daemon_exec(state); break; } /* case: pid > 0; fork succeeded */ close(state->pipe_fd[1]); state->pipe_fd[1] = -1; setproctitle("%s[%d]", state->title, (int)state->pid); setbuf(stdout, NULL); while (state->mode != MODE_NOCHILD) { ret = kevent(kq, NULL, 0, &event, 1, NULL); switch (ret) { case -1: if (errno == EINTR) continue; err(EXIT_FAILURE, "kevent wait"); case 0: continue; } if (event.flags & EV_ERROR) { errx(EXIT_FAILURE, "Event error: %s", strerror(event.data)); } switch (event.filter) { case EVFILT_SIGNAL: switch (event.ident) { case SIGCHLD: if (daemon_is_child_dead(state)) { /* child is dead, read all until EOF */ state->pid = -1; state->mode = MODE_NOCHILD; while (listen_child(state->pipe_fd[0], state)) ; } continue; case SIGTERM: if (state->mode != MODE_SUPERVISE) { /* user is impatient */ /* TODO: warn about repeated SIGTERM? */ continue; } state->mode = MODE_TERMINATING; state->restart_enabled = false; if (state->pid > 0) { kill(state->pid, SIGTERM); } /* * TODO set kevent timer to exit * unconditionally after some time */ continue; case SIGHUP: if (state->log_reopen && state->output_fd >= 0) { reopen_log(state); } continue; } break; case EVFILT_READ: /* * detecting EOF is no longer necessary * if child closes the pipe daemon will stop getting * EVFILT_READ events */ if (event.data > 0) { (void)listen_child(state->pipe_fd[0], state); } continue; default: continue; } } close(kq); close(state->pipe_fd[0]); state->pipe_fd[0] = -1; } static void daemon_sleep(struct daemon_state *state) { struct timespec ts = { state->restart_delay, 0 }; if (!state->restart_enabled) { return; } while (nanosleep(&ts, &ts) == -1) { if (errno != EINTR) { err(1, "nanosleep"); } } } static void open_pid_files(struct daemon_state *state) { pid_t fpid; int serrno; if (state->child_pidfile) { state->child_pidfh = pidfile_open(state->child_pidfile, 0600, &fpid); if (state->child_pidfh == NULL) { if (errno == EEXIST) { errx(3, "process already running, pid: %d", fpid); } err(2, "pidfile ``%s''", state->child_pidfile); } } /* Do the same for the actual daemon process. */ if (state->parent_pidfile) { state->parent_pidfh= pidfile_open(state->parent_pidfile, 0600, &fpid); if (state->parent_pidfh == NULL) { serrno = errno; pidfile_remove(state->child_pidfh); errno = serrno; if (errno == EEXIST) { errx(3, "process already running, pid: %d", fpid); } err(2, "ppidfile ``%s''", state->parent_pidfile); } } } static int get_log_mapping(const char *str, const CODE *c) { const CODE *cp; for (cp = c; cp->c_name; cp++) if (strcmp(cp->c_name, str) == 0) { return cp->c_val; } return -1; } static void restrict_process(const char *user) { struct passwd *pw = NULL; pw = getpwnam(user); if (pw == NULL) { errx(1, "unknown user: %s", user); } if (setusercontext(NULL, pw, pw->pw_uid, LOGIN_SETALL) != 0) { errx(1, "failed to set user environment"); } setenv("USER", pw->pw_name, 1); setenv("HOME", pw->pw_dir, 1); setenv("SHELL", *pw->pw_shell ? pw->pw_shell : _PATH_BSHELL, 1); } /* * We try to collect whole lines terminated by '\n'. Otherwise we collect a * full buffer, and then output it. * * Return value of false is assumed to mean EOF or error, and true indicates to * continue reading. * * TODO: simplify signature - state contains pipefd */ static bool listen_child(int fd, struct daemon_state *state) { static unsigned char buf[LBUF_SIZE]; static size_t bytes_read = 0; int rv; assert(state != NULL); assert(bytes_read < LBUF_SIZE - 1); rv = read(fd, buf + bytes_read, LBUF_SIZE - bytes_read - 1); if (rv > 0) { unsigned char *cp; bytes_read += rv; assert(bytes_read <= LBUF_SIZE - 1); /* Always NUL-terminate just in case. */ buf[LBUF_SIZE - 1] = '\0'; /* * Chomp line by line until we run out of buffer. * This does not take NUL characters into account. */ while ((cp = memchr(buf, '\n', bytes_read)) != NULL) { size_t bytes_line = cp - buf + 1; assert(bytes_line <= bytes_read); do_output(buf, bytes_line, state); bytes_read -= bytes_line; memmove(buf, cp + 1, bytes_read); } /* Wait until the buffer is full. */ if (bytes_read < LBUF_SIZE - 1) { return true; } do_output(buf, bytes_read, state); bytes_read = 0; return true; } else if (rv == -1) { /* EINTR should trigger another read. */ if (errno == EINTR) { return true; } else { warn("read"); return false; } } /* Upon EOF, we have to flush what's left of the buffer. */ if (bytes_read > 0) { do_output(buf, bytes_read, state); bytes_read = 0; } return false; } /* * The default behavior is to stay silent if the user wants to redirect * output to a file and/or syslog. If neither are provided, then we bounce * everything back to parent's stdout. */ static void do_output(const unsigned char *buf, size_t len, struct daemon_state *state) { assert(len <= LBUF_SIZE); assert(state != NULL); if (len < 1) { return; } if (state->syslog_enabled) { syslog(state->syslog_priority, "%.*s", (int)len, buf); } if (state->output_fd != -1) { if (write(state->output_fd, buf, len) == -1) warn("write"); } if (state->keep_fds_open && !state->syslog_enabled && state->output_fd == -1) { printf("%.*s", (int)len, buf); } } static int open_log(const char *outfn) { return open(outfn, O_CREAT | O_WRONLY | O_APPEND | O_CLOEXEC, 0600); } static void reopen_log(struct daemon_state *state) { int outfd; outfd = open_log(state->output_filename); if (state->output_fd >= 0) { close(state->output_fd); } state->output_fd = outfd; } static void daemon_state_init(struct daemon_state *state) { *state = (struct daemon_state) { .pipe_fd = { -1, -1 }, .argv = NULL, .parent_pidfh = NULL, .child_pidfh = NULL, .child_pidfile = NULL, .parent_pidfile = NULL, .title = NULL, .user = NULL, .mode = MODE_DAEMON, .restart_enabled = false, .pid = 0, .keep_cur_workdir = 1, .restart_delay = 1, .stdmask = STDOUT_FILENO | STDERR_FILENO, .syslog_enabled = false, .log_reopen = false, .syslog_priority = LOG_NOTICE, .syslog_tag = "daemon", .syslog_facility = LOG_DAEMON, .keep_fds_open = 1, .output_fd = -1, .output_filename = NULL, }; } static _Noreturn void daemon_terminate(struct daemon_state *state) { assert(state != NULL); if (state->output_fd >= 0) { close(state->output_fd); } if (state->pipe_fd[0] >= 0) { close(state->pipe_fd[0]); } if (state->pipe_fd[1] >= 0) { close(state->pipe_fd[1]); } if (state->syslog_enabled) { closelog(); } pidfile_remove(state->child_pidfh); pidfile_remove(state->parent_pidfh); /* * Note that the exit value here doesn't matter in the case of a clean * exit; daemon(3) already detached us from the caller, nothing is left * to care about this one. */ exit(1); } /* * Returns true if SIGCHILD came from state->pid * This function could hang if SIGCHILD was emittied for a reason other than * child dying (e.g., ptrace attach). */ static bool daemon_is_child_dead(struct daemon_state *state) { for (;;) { int who = waitpid(-1, NULL, WNOHANG); if (state->pid == who) { return true; } if (who == -1 && errno != EINTR) { warn("waitpid"); return false; } } } static void daemon_set_child_pipe(struct daemon_state *state) { if (state->stdmask & STDERR_FILENO) { if (dup2(state->pipe_fd[1], STDERR_FILENO) == -1) { err(1, "dup2"); } } if (state->stdmask & STDOUT_FILENO) { if (dup2(state->pipe_fd[1], STDOUT_FILENO) == -1) { err(1, "dup2"); } } if (state->pipe_fd[1] != STDERR_FILENO && state->pipe_fd[1] != STDOUT_FILENO) { close(state->pipe_fd[1]); } /* The child gets dup'd pipes. */ close(state->pipe_fd[0]); }