if the cookie in the received packet doesn't match discard it silently;

the logging was useful for development but is a bad idea in production
use as a remote attacker could flood your logs

src/usr.sbin/ntpd/client.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: client.c,v 1.12 2004/07/07 01:01:27 henning Exp $ */
+/*	$OpenBSD: client.c,v 1.13 2004/07/07 06:50:40 henning Exp $ */
 
 /*
  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -113,11 +113,8 @@ client_dispatch(struct ntp_peer *p)
 	ntp_getmsg(buf, size, &msg);
 
 	if (msg.orgtime.int_part != p->query->msg.xmttime.int_part ||
-	    msg.orgtime.fraction != p->query->msg.xmttime.fraction) {
-		log_warnx("received packet from %s without correct cookie, "
-		    "discarding", log_sockaddr((struct sockaddr *)&fsa));
+	    msg.orgtime.fraction != p->query->msg.xmttime.fraction)
 		return (0);
-	}
 
 	/* 
 	 * From RFC 2030: