Index: usr.sbin/daemon/daemon.c
===================================================================
--- usr.sbin/daemon/daemon.c	(revision 231014)
+++ usr.sbin/daemon/daemon.c	(working copy)
@@ -32,30 +32,36 @@
 __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
+#include <sys/wait.h>
 
 #include <err.h>
 #include <errno.h>
-#include <pwd.h>
 #include <libutil.h>
 #include <login_cap.h>
+#include <pwd.h>
+#include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
 
+static void dummy_sighandler(int);
 static void restrict_process(const char *);
+static int  wait_child(pid_t, sigset_t *);
 static void usage(void);
 
 int
 main(int argc, char *argv[])
 {
 	struct pidfh *pfh = NULL;
-	int ch, nochdir, noclose, errcode;
+	sigset_t mask, oldmask;
+	int ch, nochdir, noclose, restart;
 	const char *pidfile, *user;
-	pid_t otherpid;
+	pid_t otherpid, pid;
 
 	nochdir = noclose = 1;
+	restart = 0;
 	pidfile = user = NULL;
-	while ((ch = getopt(argc, argv, "-cfp:u:")) != -1) {
+	while ((ch = getopt(argc, argv, "-cfp:ru:")) != -1) {
 		switch (ch) {
 		case 'c':
 			nochdir = 0;
@@ -66,6 +72,9 @@ main(int argc, char *argv[])
 		case 'p':
 			pidfile = optarg;
 			break;
+		case 'r':
+			restart = 1;
+			break;
 		case 'u':
 			user = optarg;
 			break;
@@ -79,14 +88,12 @@ main(int argc, char *argv[])
 	if (argc == 0)
 		usage();
 
-	if (user != NULL)
-		restrict_process(user);
-
+	pfh = NULL;
 	/*
 	 * Try to open the pidfile before calling daemon(3),
 	 * to be able to report the error intelligently
 	 */
-	if (pidfile) {
+	if (pidfile != NULL) {
 		pfh = pidfile_open(pidfile, 0600, &otherpid);
 		if (pfh == NULL) {
 			if (errno == EEXIST) {
@@ -99,26 +106,83 @@ main(int argc, char *argv[])
 
 	if (daemon(nochdir, noclose) == -1)
 		err(1, NULL);
+	/*
+	 * If pidfile or restart option is specified the daemon
+	 * executes the command in a forked process and wait on child
+	 * exit to remove the pidfile or restart the command.
+	 * Normally we don't want the monitoring daemon to be
+	 * terminated leaving the running process and the stale
+	 * pidfile, so we catch SIGTERM and pass it to the children
+	 * expecting to get SIGCHLD eventually.
+	 */
+	pid = -1;
+	if (pidfile != NULL || restart) {
+		/*
+		 * Restore default action for SIGTERM in case the
+		 * parent process decided to ignore it.
+		 */
+		if (signal(SIGTERM, SIG_DFL) == SIG_ERR)
+			err(1, "signal");
+		/*
+		 * Because SIGCHLD is ignored by default, setup dummy handler
+		 * for it, so we can mask it.
+		 */
+		if (signal(SIGCHLD, dummy_sighandler) == SIG_ERR)
+			err(1, "signal");
+		/*
+		 * Block interesting signals.
+		 */
+		sigemptyset(&mask);
+		sigaddset(&mask, SIGTERM);
+		sigaddset(&mask, SIGCHLD);
+		if (sigprocmask(SIG_SETMASK, &mask, &oldmask) == -1)
+			err(1, "sigprocmask");
+restart:
+		/*
+		 * Spawn a child to exec the command, so in the parent
+		 * we could wait for it to exit and remove pidfile.
+		 */
+		pid = fork();
+		if (pid == -1) {
+			pidfile_remove(pfh);
+			err(1, "fork");
+		}
+	}
+	if (pid <= 0) {
+		if (pid == 0) {
+			/* Restore old sigmask in the child. */
+			if (sigprocmask(SIG_SETMASK, &oldmask, NULL) == -1)
+				err(1, "sigprocmask");
+		}
 
-	/* Now that we are the child, write out the pid */
-	if (pidfile)
+		/* Now that we are the child, write out the pid. */
 		pidfile_write(pfh);
 
-	execvp(argv[0], argv);
+		if (user != NULL)
+			restrict_process(user);
 
-	/*
-	 * execvp() failed -- unlink pidfile if any, and
-	 * report the error
-	 */
-	errcode = errno; /* Preserve errcode -- unlink may reset it */
-	if (pidfile)
-		pidfile_remove(pfh);
+		execvp(argv[0], argv);
 
-	/* The child is now running, so the exit status doesn't matter. */
-	errc(1, errcode, "%s", argv[0]);
+		/*
+		 * execvp() failed -- report the error. The child is
+		 * now running, so the exit status doesn't matter.
+		 */
+		err(1, "%s", argv[0]);
+	}
+	setproctitle("%s[%d]", argv[0], pid);
+	if (wait_child(pid, &mask) == 0 && restart)
+		goto restart;
+	pidfile_remove(pfh);
+	exit(0); /* Exit status does not matter. */
 }
 
 static void
+dummy_sighandler(int sig __unused)
+{
+	/* Nothing to do. */
+}
+
+static void
 restrict_process(const char *user)
 {
 	struct passwd *pw = NULL;
@@ -131,11 +195,42 @@ restrict_process(const char *user)
 		errx(1, "failed to set user environment");
 }
 
+static int
+wait_child(pid_t pid, sigset_t *mask)
+{
+	int terminate;
+	int signo;
+
+	terminate = 0;
+	for (;;) {
+		signo = sigwaitinfo(mask, NULL);
+		switch (signo) {
+		case SIGCHLD:
+			return terminate;
+		case SIGTERM:
+			terminate = 1;
+			if (kill(pid, signo) == -1) {
+				warn("kill");
+				return -1;
+			}
+			continue;
+		case -1:
+			if (errno == EINTR)
+				continue;
+			warn("sigwaitinfo");
+			return -1;
+		default:
+			warnx("sigwaitinfo: invalid signal: %d", signo);
+			return -1;
+		}
+	}
+}
+
 static void
 usage(void)
 {
 	(void)fprintf(stderr,
-	    "usage: daemon [-cf] [-p pidfile] [-u user] command "
+	    "usage: daemon [-cfr] [-p pidfile] [-u user] command "
 		"arguments ...\n");
 	exit(1);
 }