From: Juergen Perlinger <perlinger@ntp.org>
Date: Fri, 4 Jun 2010 06:34:03 +0000 (+0200)
Subject: [Bug 1580] Purge tty line buffers so serial refclocks do not get outdated data immedi... 
X-Git-Tag: NTP_4_2_7P34~4^2~1
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=014f0516e9fa4ae56f0342cb3285821fcc008e4e;p=thirdparty%2Fntp.git

[Bug 1580] Purge tty line buffers so serial refclocks do not get outdated data immediately after startup.

bk: 4c089e5bk23LbkYfv9bbtczpXywTWQ
---

diff --git a/ntpd/ntp_refclock.c b/ntpd/ntp_refclock.c
index 9e47f58c6..249c998c4 100644
--- a/ntpd/ntp_refclock.c
+++ b/ntpd/ntp_refclock.c
@@ -714,6 +714,9 @@ 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
@@ -740,6 +743,16 @@ 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 none-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+	 * moment to read and dump all available outdated stuff that might have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)
+		/*NOP*/;
+#endif
 	return (fd);
 }
 
@@ -835,6 +848,15 @@ 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+	 * flush input and output buffers to discard any outdated stuff that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