avoid a race by installing SIGCHLD handler before fork() is called.

ok henning@ ckuethe@

src/usr.sbin/ntpd/ntp.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: ntp.c,v 1.87 2006/06/17 18:40:42 otto Exp $ */
+/*	$OpenBSD: ntp.c,v 1.88 2006/06/21 07:42:00 otto Exp $ */
 
 /*
  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -139,6 +139,7 @@ ntp_main(int pipe_prnt[2], struct ntpd_conf *nconf)
 	signal(SIGINT, ntp_sighdlr);
 	signal(SIGPIPE, SIG_IGN);
 	signal(SIGHUP, SIG_IGN);
+	signal(SIGCHLD, SIG_DFL);
 
 	close(pipe_prnt[0]);
 	if ((ibuf_main = malloc(sizeof(struct imsgbuf))) == NULL)

src/usr.sbin/ntpd/ntpd.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: ntpd.c,v 1.43 2006/06/17 18:40:42 otto Exp $ */
+/*	$OpenBSD: ntpd.c,v 1.44 2006/06/21 07:42:00 otto Exp $ */
 
 /*
  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -137,6 +137,7 @@ main(int argc, char *argv[])
 	if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, pipe_chld) == -1)
 		fatal("socketpair");
 
+	signal(SIGCHLD, sighdlr);
 	/* fork child process */
 	chld_pid = ntp_main(pipe_chld, &conf);
 
@@ -144,7 +145,6 @@ main(int argc, char *argv[])
 
 	signal(SIGTERM, sighdlr);
 	signal(SIGINT, sighdlr);
-	signal(SIGCHLD, sighdlr);
 	signal(SIGHUP, sighdlr);
 
 	close(pipe_chld[1]);