Simplify shutdown process

On shutdown, there's no need to use kill(2) to kill the child
processes. Just closing the IPC sockets will make the children receive
an EOF, break out from the event loop and then exit.

This "pipe teardown" removes a PID reuse race condition, makes the code
simpler and allow us to remove "proc" from pledge.

OK and tweaks from claudio@

eigrpd.c

@@ -40,9 +40,8 @@
 
 void		main_sig_handler(int, short, void *);
 __dead void	usage(void);
-void		eigrpd_shutdown(void);
+__dead void	eigrpd_shutdown(void);
 pid_t		start_child(enum eigrpd_process, char *, int, int, int, char *);
-int		check_child(pid_t, const char *);
 
 void	main_dispatch_eigrpe(int, short, void *);
 void	main_dispatch_rde(int, short, void *);
@@ -65,29 +64,11 @@ pid_t			 rde_pid = 0;
 void
 main_sig_handler(int sig, short event, void *arg)
 {
-	/*
-	 * signal handler rules don't apply, libevent decouples for us
-	 */
-
-	int	die = 0;
-
+	/* signal handler rules don't apply, libevent decouples for us */
 	switch (sig) {
 	case SIGTERM:
 	case SIGINT:
-		die = 1;
-		/* FALLTHROUGH */
-	case SIGCHLD:
-		if (check_child(eigrpe_pid, "eigrp engine")) {
-			eigrpe_pid = 0;
-			die = 1;
-		}
-		if (check_child(rde_pid, "route decision engine")) {
-			rde_pid = 0;
-			die = 1;
-		}
-		if (die)
-			eigrpd_shutdown();
-		break;
+		eigrpd_shutdown();
 	case SIGHUP:
 		if (eigrp_reload() == -1)
 			log_warnx("configuration reload failed");
@@ -116,7 +97,7 @@ struct eigrpd_global global;
 int
 main(int argc, char *argv[])
 {
-	struct event		 ev_sigint, ev_sigterm, ev_sigchld, ev_sighup;
+	struct event		 ev_sigint, ev_sigterm, ev_sighup;
 	char			*saved_argv0;
 	int			 ch;
 	int			 debug = 0, rflag = 0, eflag = 0;
@@ -248,11 +229,9 @@ main(int argc, char *argv[])
 	/* setup signal handler */
 	signal_set(&ev_sigint, SIGINT, main_sig_handler, NULL);
 	signal_set(&ev_sigterm, SIGTERM, main_sig_handler, NULL);
-	signal_set(&ev_sigchld, SIGCHLD, main_sig_handler, NULL);
 	signal_set(&ev_sighup, SIGHUP, main_sig_handler, NULL);
 	signal_add(&ev_sigint, NULL);
 	signal_add(&ev_sigterm, NULL);
-	signal_add(&ev_sigchld, NULL);
 	signal_add(&ev_sighup, NULL);
 	signal(SIGPIPE, SIG_IGN);
 
@@ -287,42 +266,41 @@ main(int argc, char *argv[])
 	    eigrpd_conf->rdomain) == -1)
 		fatalx("kr_init failed");
 
-	if (pledge("inet rpath stdio proc sendfd", NULL) == -1)
+	if (pledge("inet rpath stdio sendfd", NULL) == -1)
 		fatal("pledge");
 
 	event_dispatch();
 
 	eigrpd_shutdown();
-	/* NOTREACHED */
-	return (0);
 }
 
-void
+__dead void
 eigrpd_shutdown(void)
 {
-	pid_t		 	 pid;
+	pid_t		 pid;
+	int		 status;
 
-	if (eigrpe_pid)
-		kill(eigrpe_pid, SIGTERM);
-
-	if (rde_pid)
-		kill(rde_pid, SIGTERM);
+	msgbuf_clear(&iev_eigrpe->ibuf.w);
+	free(iev_eigrpe);
+	iev_eigrpe = NULL;
+	msgbuf_clear(&iev_rde->ibuf.w);
+	free(iev_rde);
+	iev_rde = NULL;
 
+	config_clear(eigrpd_conf);
 	kr_shutdown();
 
 	do {
-		if ((pid = wait(NULL)) == -1 &&
-		    errno != EINTR && errno != ECHILD)
-			fatal("wait");
+		pid = wait(&status);
+		if (pid == -1) {
+			if (errno != EINTR && errno != ECHILD)
+				fatal("wait");
+		} else if (WIFSIGNALED(status))
+			log_warnx("%s terminated; signal %d",
+			    (pid == rde_pid) ? "route decision engine" :
+			    "eigrp engine", WTERMSIG(status));
 	} while (pid != -1 || (pid == -1 && errno == EINTR));
 
-	config_clear(eigrpd_conf);
-
-	msgbuf_clear(&iev_eigrpe->ibuf.w);
-	free(iev_eigrpe);
-	msgbuf_clear(&iev_rde->ibuf.w);
-	free(iev_rde);
-
 	log_info("terminating");
 	exit(0);
 }
@@ -373,26 +351,6 @@ start_child(enum eigrpd_process p, char *argv0, int fd, int debug, int verbose,
 	fatal("execvp");
 }
 
-int
-check_child(pid_t pid, const char *pname)
-{
-	int	status;
-
-	if (waitpid(pid, &status, WNOHANG) > 0) {
-		if (WIFEXITED(status)) {
-			log_warnx("lost child: %s exited", pname);
-			return (1);
-		}
-		if (WIFSIGNALED(status)) {
-			log_warnx("lost child: %s terminated; signal %d",
-			    pname, WTERMSIG(status));
-			return (1);
-		}
-	}
-
-	return (0);
-}
-
 /* imsg handling */
 /* ARGSUSED */
 void
@@ -535,18 +493,20 @@ main_dispatch_rde(int fd, short event, void *bula)
 	}
 }
 
-void
+int
 main_imsg_compose_eigrpe(int type, pid_t pid, void *data, uint16_t datalen)
 {
 	if (iev_eigrpe == NULL)
-		return;
-	imsg_compose_event(iev_eigrpe, type, 0, pid, -1, data, datalen);
+		return (-1);
+	return (imsg_compose_event(iev_eigrpe, type, 0, pid, -1, data, datalen));
 }
 
-void
+int
 main_imsg_compose_rde(int type, pid_t pid, void *data, uint16_t datalen)
 {
-	imsg_compose_event(iev_rde, type, 0, pid, -1, data, datalen);
+	if (iev_rde == NULL)
+		return (-1);
+	return (imsg_compose_event(iev_rde, type, 0, pid, -1, data, datalen));
 }
 
 void
@@ -660,9 +620,9 @@ eigrp_reload(void)
 int
 eigrp_sendboth(enum imsg_type type, void *buf, uint16_t len)
 {
-	if (imsg_compose_event(iev_eigrpe, type, 0, 0, -1, buf, len) == -1)
+	if (main_imsg_compose_eigrpe(type, 0, buf, len) == -1)
 		return (-1);
-	if (imsg_compose_event(iev_rde, type, 0, 0, -1, buf, len) == -1)
+	if (main_imsg_compose_rde(type, 0, buf, len) == -1)
 		return (-1);
 	return (0);
 }

eigrpd.h

@@ -481,8 +481,8 @@ void		 addscope(struct sockaddr_in6 *, uint32_t);
 void		 clearscope(struct in6_addr *);
 
 /* eigrpd.c */
-void		 main_imsg_compose_eigrpe(int, pid_t, void *, uint16_t);
-void		 main_imsg_compose_rde(int, pid_t, void *, uint16_t);
+int		 main_imsg_compose_eigrpe(int, pid_t, void *, uint16_t);
+int		 main_imsg_compose_rde(int, pid_t, void *, uint16_t);
 void		 merge_config(struct eigrpd_conf *, struct eigrpd_conf *);
 struct eigrpd_conf *config_new_empty(void);
 void		 config_clear(struct eigrpd_conf *);