kairos/daemonize.c

/*
 * daemonize.c -- provides daemonize() function to daemonize a process
 * according to daemon(7) and given flags.
 */

#include <stdlib.h>
#include <stdint.h>
#include <stdbool.h>
#include <unistd.h>
#include <sys/resource.h>
#include <syslog.h>
#include <errno.h>
#include <signal.h>
#include <sys/stat.h>
#include <fcntl.h>

#include "daemonize.h"
#include "config.h"

#define unless(x) if(!((x)))

bool daemonize(uint32_t flags) {
	if (flags & NODAEMONIZE) return true;

	bool retval = true;

	unless (flags & NOCLOSEFD) {
		struct rlimit maxfd;
		if(getrlimit(RLIMIT_NOFILE, &maxfd) == -1) {
			//Shouldn't ever happen
			syslog(cfg_log_facility | LOG_WARNING, "daemonize: getrlimit failed: %m");
			retval = false;
		}
		for (rlim_t fd = 3; fd < maxfd.rlim_cur; fd++) {
			char tries = 0;
			while(close(fd) == -1) { // Try 3 times to close fd, retry only if interrupted
				unless (errno == EINTR) {
					break;
				}
				tries++;
				if (tries > 3) {
					syslog(cfg_log_facility | LOG_WARNING, "daemonize: could not close fd %d: %m", fd);
					retval = false;
					break;
				}
			}
		}
	}

	unless (flags & NORSTSIG) {
		for (int sig = 0; sig <= SIGRTMAX; sig++) { //FIXME: This may not be the best way
			signal(sig, SIG_DFL); //EINVAL is not important
		}
	}

	unless (flags & NORSTSIGMASK) {
		sigset_t *set = malloc(sizeof(sigset_t));
		if (set == NULL) {
			syslog(cfg_log_facility | LOG_WARNING, "daemonize: could not malloc sigset_t: %m");
			retval = false;
		}
		sigemptyset(set); //shall not have errors
		if (sigprocmask(SIG_SETMASK, set, NULL) == -1) { //Shall not fail
			syslog(cfg_log_facility | LOG_WARNING, "daemonize: sigprocmask failed: %m");
			retval = false;
		}
	}

	unless (flags & NOSANITY) {
		// We don't sanitize environment, the user does.
	}

	// Create pipe for notification in step 14
	int pipe_fds[2];
	if(pipe(pipe_fds) == -1) {
		syslog(cfg_log_facility | LOG_WARNING, "daemonize: could not create pipe: %m");
		retval = false;
	}

	unless (flags & NOBGFORK) {
		pid_t val = fork();
		if (val == -1) {
			syslog(cfg_log_facility | LOG_WARNING, "daemonize: fork failed: %m");
			retval = false;
		}
		if (val > 0) {
			// We're the grandparent
			// We only wait for report from our grandson and then exit.
			close(pipe_fds[1]);
			char buf[2] = {0,0};
			int tries = 0;
			while (read(pipe_fds[0], buf, 1) == -1) {
				tries++;
				if (errno == EINTR && tries <= 3) {
					continue;
				}
				syslog(cfg_log_facility | LOG_WARNING, "daemonize: grandpa: cannot receive data through pipe: %m");
				retval = false;
			}
			if (buf[0] != 'S') { //Not success
				syslog(cfg_log_facility | LOG_NOTICE, "daemonize: grandpa: grandson didn't report success");
				retval = false;
			}

			exit(retval?0:1);
		}
		// We're the parent and we continue running at this point.
		close(pipe_fds[0]);
	}

	unless(flags & NOSETSID) {
		if(setsid() == -1)
			syslog(cfg_log_facility | LOG_WARNING, "daemonize: father: setsid failed: %m");
	}

	unless (flags & NOSECONDFORK) {
		pid_t val = fork();
		if (val == -1) {
			syslog(cfg_log_facility | LOG_WARNING, "daemonize: second fork failed: %m");
			retval = false;
		}
		if (val > 0) {
			//We're the parent, we exit
			exit(0);
		}
		// We're the son and we continue running.
	}

	unless (flags & NOCONNECTIO) {
		int fd = open("/dev/null", O_RDWR);
		dup2(fd, STDIN_FILENO); //These shall not fail, maybe exept EINTR (FIXME)
		dup2(fd, STDOUT_FILENO);
		dup2(fd, STDERR_FILENO);
		close(fd);
	}

	unless(flags & NORSTUMASK) {
		umask(0000); //No errors are defined.
	}

	unless (flags & NOCHANGEWD) {
		chdir("/"); //No errors are applicable, maybe except EACCESS (FIXME)
	}

	unless (flags & NOPIDFILE) {
		// Not implemented
	}

	unless (flags & NOPRIVDROP) {
		// We don't drop privileges, as we want to exec programs with privileges of the user.
	}

	write(pipe_fds[1], retval?"S":"F", 1);
	syslog(cfg_log_facility | LOG_INFO, "Now runing as a daemon");
	close(pipe_fds[1]);

	return retval;
}