From: Harlan Stenn <stenn@ntp.org>
Date: Sat, 19 Jun 2010 06:32:32 +0000 (-0400)
Subject: [Bug 1570] serial clock drivers get outdated input from kernel tty line buffer after... 
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=b03a2d2ce2218575a231552409c7172d7e03485d;p=thirdparty%2Fntp.git

[Bug 1570] serial clock drivers get outdated input from kernel tty line buffer after startup

bk: 4c1c6480p9KkoYffPgfUrNpHpBdzNQ
---

diff --git a/ChangeLog b/ChangeLog
index 0a510f5d0c..4fd868def4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,7 @@
 ---
 
+* [Bug 1570] serial clock drivers get outdated input from kernel tty
+  line buffer after startup
 * [Bug 1575] use 'snprintf' with LIB_BUFLENGTH in inttoa.c, tvtoa.c and
   utvtoa.c
 * [Bug 1576] sys/sysctl.h depends on sys/param.h on OpenBSD.
diff --git a/ntpd/ntp_refclock.c b/ntpd/ntp_refclock.c
index d299903a8b..1250570116 100644
--- a/ntpd/ntp_refclock.c
+++ b/ntpd/ntp_refclock.c
@@ -742,6 +742,9 @@ refclock_open(
 {
 	int	fd;
 	int	omode;
+#ifdef O_NONBLOCK
+	char    trash[128];	/* litter bin for old input data */
+#endif
 
 	/*
 	 * Open serial port and set default options
@@ -768,6 +771,16 @@ refclock_open(
 		close(fd);
 		return (0);
 	}
+#ifdef O_NONBLOCK
+	/*
+	 * We want to make sure there is no pending trash in the input
+	 * buffer. Since we have non-blocking IO available, this is a
+	 * good moment to read and dump all available outdated stuff
+	 * that might have become toxic for the driver.
+	 */
+	while (read(fd, trash, sizeof(trash)) > 0 || errno == EINTR)
+		/*NOP*/;
+#endif
 	return (fd);
 }
 
@@ -863,6 +876,14 @@ refclock_setup(
 		    "refclock_setup fd %d TCSANOW: %m", fd);
 		return (0);
 	}
+
+	/*
+	 * flush input and output buffers to discard any outdated stuff
+	 * that might have become toxic for the driver. Failing to do so
+	 * is logged, but we keep our fingers crossed otherwise.
+	 */
+	if (tcflush(fd, TCIOFLUSH) < 0)
+		msyslog(LOG_ERR, "refclock_setup fd %d tcflush(): %m", fd);
 #endif /* HAVE_TERMIOS */
 
 #ifdef HAVE_SYSV_TTYS