Discard replies with alarm flag set or invalid stratum; ok henning@

src/usr.sbin/ntpd/client.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: client.c,v 1.47 2004/12/09 20:24:46 mickey Exp $ */
+/*	$OpenBSD: client.c,v 1.48 2004/12/13 12:22:52 dtucker Exp $ */
 
 /*
  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -198,6 +198,10 @@ client_dispatch(struct ntp_peer *p, u_int8_t settime)
 	    msg.orgtime.fractionl != p->query->msg.xmttime.fractionl)
 		return (0);
 
+	if ((msg.status & LI_ALARM) == LI_ALARM || msg.stratum == 0 ||
+	    msg.stratum > NTP_MAXSTRATUM)
+		return (0);
+
 	/*
 	 * From RFC 2030 (with a correction to the delay math):
 	 *

src/usr.sbin/ntpd/ntp.h

@@ -1,4 +1,4 @@
-/*	$OpenBSD: ntp.h,v 1.10 2004/12/08 15:47:38 mickey Exp $ */
+/*	$OpenBSD: ntp.h,v 1.11 2004/12/13 12:22:52 dtucker Exp $ */
 
 /*
  * Copyright (c) 2004 Henning Brauer <henning@openbsd.org>
@@ -145,5 +145,6 @@ struct ntp_query {
 #define	JAN_1970	2208988800UL	/* 1970 - 1900 in seconds */
 
 #define	NTP_VERSION	4
+#define	NTP_MAXSTRATUM	15
 
 #endif	/* _NTP_H_ */