bugfix: resend: fix serial_flush

[Wolfgang Walter]

serial_flush implements FlushFileBuffers for serial devices

FlushFileBuffers should write out any data not yet transmitted but
serial_flush instead discards any data not yet transmitted

This is because it uses tcflush() instead of tcdrain().

Regards,
-- 
Wolfgang Walter
Studentenwerk München
Anstalt des öffentlichen Rechts
Leiter EDV
Leopoldstraße 15
80802 München
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From 85c73f458dfe8a9ae4c64a27264f9d8de54b00c6 Mon Sep 17 00:00:00 2001
From: Wolfgang Walter <wine at stwm.de>
Date: Fri, 12 Dec 2008 12:54:55 +0100
Subject: serial: fix serial_flush

serial_flush implements FlushFileBuffers for serial devices

FlushFileBuffers should write out any data not yet transmitted but
serial_flush instead discards any data not yet transmitted

This is because it uses tcflush() instead of tcdrain().
---
 server/serial.c |   13 ++++++++++++-
 1 files changed, 12 insertions(+), 1 deletions(-)

diff --git a/server/serial.c b/server/serial.c
index d1b3822..04dc15e 100644
--- a/server/serial.c
+++ b/server/serial.c
@@ -33,6 +33,7 @@
 #include <sys/types.h>
 #include <time.h>
 #include <unistd.h>
+#include <errno.h>
 #ifdef HAVE_UTIME_H
 #include <utime.h>
 #endif
@@ -201,7 +202,17 @@ static void serial_flush( struct fd *fd, struct event **event )
     /* MSDN says: If hFile is a handle to a communications device,
      * the function only flushes the transmit buffer.
      */
-    if (tcflush( get_unix_fd(fd), TCOFLUSH ) == -1) file_set_error();
+    /* FlushFileBuffers does NOT have the semantics of tcflush.
+     * Whereas tcflush discards any data not yet transmitted
+     * FlushFileBuffers ensures they are written out.
+     * The POSIX equivalent is tcdrain
+     */
+    while (tcdrain( get_unix_fd(fd)) == -1) {
+    	if (errno != EINTR) {
+            file_set_error();
+            return;
+        }
+    }
 }
 
 DECL_HANDLER(get_serial_info)
-- 
1.5.6.5