From: Juergen Perlinger <perlinger@ntp.org>
Date: Sun, 13 Nov 2022 08:47:08 +0000 (+0100)
Subject: [Bug 3640] sidekick: fixed "discard monitor" implementation
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=dc7838cb9b23915d1ba4ead9481e170693733d1d;p=thirdparty%2Fntp.git

[Bug 3640] sidekick: fixed "discard monitor" implementation

bk: 6370af0c2dixLDDTTrOHMhX27Qc33A
---

diff --git a/ChangeLog b/ChangeLog
index 3addb7b81..51a731231 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -37,6 +37,8 @@
 * [Bug 3672] fix biased selection in median cut <perlinger@ntp.org>
 * [Bug 3666] avoid unlimited receive buffer allocation <perlinger@ntp.org>
   - follow-up: fix inverted sense in check, reset shortfall counter
+* [Bug 3640] ntp.conf: missing documentation for "discard monitor" default value
+  - sidekick: fixed a bug in discard monitor implementation <perlingeræntp.org>
 * [Bug 3626] (SNTP) UTC offset calculation needs dst flag <perlinger@ntp.org>
   - applied patch by Gerry Garvey
 * [Bug 3432] refclocks that 'write()' should check the result <perlinger@ntp.org>
diff --git a/include/ntp_random.h b/include/ntp_random.h
index fa77f6553..931b21990 100644
--- a/include/ntp_random.h
+++ b/include/ntp_random.h
@@ -5,6 +5,7 @@ void ntp_crypto_srandom(void);
 int ntp_crypto_random_buf(void *buf, size_t nbytes);
 
 long ntp_random (void);
+double ntp_uurandom(void);
 void ntp_srandom (unsigned long);
 void ntp_srandomdev (void);
 char * ntp_initstate (unsigned long, 	/* seed for R.N.G. */
diff --git a/libntp/ntp_random.c b/libntp/ntp_random.c
index 0ada44f25..83806c420 100644
--- a/libntp/ntp_random.c
+++ b/libntp/ntp_random.c
@@ -497,3 +497,18 @@ ntp_random( void )
 	}
 	return(i);
 }
+
+/*
+ * ntp_uurandom()
+ *
+ * Generate a Uniform-distributed Unity based random number. Replaces a
+ * few locations where the transformation was made in an ad-hoc style
+ * (and in one instance, wrong...)
+ *
+ * returns a number in [0.0 .. 1.0], both ends inclusive
+ */
+double
+ntp_uurandom( void )
+{
+	return (double)ntp_random() / 0x7FFFFFFFu;
+}
diff --git a/libntp/systime.c b/libntp/systime.c
index a738c8d92..e2f07f71a 100644
--- a/libntp/systime.c
+++ b/libntp/systime.c
@@ -235,7 +235,7 @@ get_systime(
 	 * must scale up the result by 2.0 to cover the full fractional
 	 * range.
 	 */
-	dfuzz = ntp_random() * 2. / FRAC * sys_fuzz;
+	dfuzz = ntp_uurandom() * sys_fuzz;
 	DTOLFP(dfuzz, &lfpfuzz);
 	L_ADD(&result, &lfpfuzz);
 
diff --git a/ntpd/ntp_io.c b/ntpd/ntp_io.c
index c0dcea598..6b88f5e4d 100644
--- a/ntpd/ntp_io.c
+++ b/ntpd/ntp_io.c
@@ -3444,7 +3444,7 @@ fetch_timestamp(
 				break;
 #endif  /* HAVE_TIMESTAMP */
 			}
-			fuzz = ntp_random() * 2. / FRAC * sys_fuzz;
+			fuzz = ntp_uurandom() * sys_fuzz;
 			DTOLFP(fuzz, &lfpfuzz);
 			L_ADD(&nts, &lfpfuzz);
 #ifdef DEBUG_TIMING
diff --git a/ntpd/ntp_monitor.c b/ntpd/ntp_monitor.c
index a07a1aaef..5252794fd 100644
--- a/ntpd/ntp_monitor.c
+++ b/ntpd/ntp_monitor.c
@@ -459,7 +459,7 @@ ntp_monitor(
 				mon_getmoremem();
 			UNLINK_HEAD_SLIST(mon, mon_free, hash_next);
 		/* Preempt from the MRU list if old enough. */
-		} else if (ntp_random() / (2. * FRAC) >
+		} else if (ntp_uurandom() >
 			   (double)oldest_age / mon_age) {
 			return ~(RES_LIMITED | RES_KOD) & flags;
 		} else {
diff --git a/ntpd/ntp_proto.c b/ntpd/ntp_proto.c
index 898ff73ee..7992ef0f0 100644
--- a/ntpd/ntp_proto.c
+++ b/ntpd/ntp_proto.c
@@ -740,7 +740,7 @@ receive(
 	 * surviving packets.
 	 */
 	if (restrict_mask & RES_FLAKE) {
-		if ((double)ntp_random() / 0x7fffffff < .1) {
+		if (ntp_uurandom() < .1) {
 			DPRINTF(2, ("receive: drop: RES_FLAKE\n"));
 			sys_restricted++;
 			return;			/* no flakeway */