cdc_ncm: fix short packet issue on some devices

The default maximum transmit length for NCM USB frames should be so
that a short packet happens at the end if the device supports a length
greater than the defined maximum. This is achieved by adding 4 bytes
to the maximum length so that the existing logic can fit a short
packet there.

Signed-off-by: Hans Petter Selasky <hselasky@c2i.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/cdc_ncm.c

@@ -54,13 +54,13 @@
 #include <linux/usb/usbnet.h>
 #include <linux/usb/cdc.h>
 
-#define	DRIVER_VERSION				"7-Feb-2011"
+#define	DRIVER_VERSION				"23-Apr-2011"
 
 /* CDC NCM subclass 3.2.1 */
 #define USB_CDC_NCM_NDP16_LENGTH_MIN		0x10
 
 /* Maximum NTB length */
-#define	CDC_NCM_NTB_MAX_SIZE_TX			16384	/* bytes */
+#define	CDC_NCM_NTB_MAX_SIZE_TX			(16384 + 4) /* bytes, must be short terminated */
 #define	CDC_NCM_NTB_MAX_SIZE_RX			16384	/* bytes */
 
 /* Minimum value for MaxDatagramSize, ch. 6.2.9 */