use __packed structs for the on-the-wire packets and just memcpy at once

instead of kind-of manual copyin/out. increases accuracy in server mode.
collecting dust in my tree for some time, result of a conversation with
somebody i really want to give credit to, but I can't find the mails now :(
okey dokey sez theo

src/usr.sbin/ntpd/ntp.h

@@ -1,4 +1,4 @@
-/*	$OpenBSD: ntp.h,v 1.11 2004/12/13 12:22:52 dtucker Exp $ */
+/*	$OpenBSD: ntp.h,v 1.12 2007/05/26 21:20:35 henning Exp $ */
 
 /*
  * Copyright (c) 2004 Henning Brauer <henning@openbsd.org>
@@ -105,9 +105,7 @@ struct ntp_msg {
 	struct l_fixedpt orgtime;
 	struct l_fixedpt rectime;
 	struct l_fixedpt xmttime;
-	u_int32_t keyid;
-	u_int8_t digest[NTP_DIGESTSIZE];
-};
+} __packed;
 
 struct ntp_query {
 	int			fd;

src/usr.sbin/ntpd/ntp_msg.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: ntp_msg.c,v 1.16 2006/07/01 18:52:46 otto Exp $ */
+/*	$OpenBSD: ntp_msg.c,v 1.17 2007/05/26 21:20:35 henning Exp $ */
 
 /*
  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -34,25 +34,7 @@ ntp_getmsg(struct sockaddr *sa, char *p, ssize_t len, struct ntp_msg *msg)
 		return (-1);
 	}
 
-#define	copyin(f,p)	memcpy(&(f), (p), sizeof(f)); (p) += sizeof(f)
-
-	copyin(msg->status, p);
-	copyin(msg->stratum, p);
-	copyin(msg->ppoll, p);
-	copyin(msg->precision, p);
-	copyin(msg->rootdelay.int_parts, p);
-	copyin(msg->rootdelay.fractions, p);
-	copyin(msg->dispersion.int_parts, p);
-	copyin(msg->dispersion.fractions, p);
-	copyin(msg->refid, p);
-	copyin(msg->reftime.int_partl, p);
-	copyin(msg->reftime.fractionl, p);
-	copyin(msg->orgtime.int_partl, p);
-	copyin(msg->orgtime.fractionl, p);
-	copyin(msg->rectime.int_partl, p);
-	copyin(msg->rectime.fractionl, p);
-	copyin(msg->xmttime.int_partl, p);
-	copyin(msg->xmttime.fractionl, p);
+	memcpy(msg, p, sizeof(*msg));
 
 	return (0);
 }
@@ -61,36 +43,16 @@ int
 ntp_sendmsg(int fd, struct sockaddr *sa, struct ntp_msg *msg, ssize_t len,
     int auth)
 {
-	char		 buf[NTP_MSGSIZE];
-	char		*p = buf;
 	socklen_t	sa_len;
-
-#define	copyout(p,f)	memcpy((p), &(f), sizeof(f)); p += sizeof(f)
-
-	copyout(p, msg->status);
-	copyout(p, msg->stratum);
-	copyout(p, msg->ppoll);
-	copyout(p, msg->precision);
-	copyout(p, msg->rootdelay.int_parts);
-	copyout(p, msg->rootdelay.fractions);
-	copyout(p, msg->dispersion.int_parts);
-	copyout(p, msg->dispersion.fractions);
-	copyout(p, msg->refid);
-	copyout(p, msg->reftime.int_partl);
-	copyout(p, msg->reftime.fractionl);
-	copyout(p, msg->orgtime.int_partl);
-	copyout(p, msg->orgtime.fractionl);
-	copyout(p, msg->rectime.int_partl);
-	copyout(p, msg->rectime.fractionl);
-	copyout(p, msg->xmttime.int_partl);
-	copyout(p, msg->xmttime.fractionl);
+	ssize_t		n;
 
 	if (sa != NULL)
 		sa_len = SA_LEN(sa);
 	else
 		sa_len = 0;
 
-	if (sendto(fd, &buf, len, 0, sa, sa_len) != len) {
+	n = sendto(fd, msg, sizeof(*msg), 0, sa, sa_len);
+	if (n == -1) {
 		if (errno == ENOBUFS || errno == EHOSTUNREACH ||
 		    errno == ENETDOWN || errno == EHOSTDOWN) {
 			/* logging is futile */
@@ -100,5 +62,11 @@ ntp_sendmsg(int fd, struct sockaddr *sa, struct ntp_msg *msg, ssize_t len,
 		return (-1);
 	}
 
+	if (n != sizeof(*msg)) {
+		log_warnx("ntp_sendmsg: only %ld of %ld bytes sent", n,
+		    sizeof(*msg));
+		return (-1);
+	}
+
 	return (0);
 }