ieee802154: add security bit check function

ieee802154_is_secen checks if the 802.15.4 security bit is set in the
frame control field.
Signed-off-by: Alexander Aring <aar@pengutronix.de>
Signed-off-by: Alexandre Macabies <web+oss@zopieux.com>
Reviewed-by: Stefan Schmidt <stefan@osg.samsung.com>
Acked-by: Alan Ott <alan@signal11.us>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

include/linux/ieee802154.h

@@ -218,6 +218,7 @@ enum {
 /* frame control handling */
 #define IEEE802154_FCTL_FTYPE		0x0003
 #define IEEE802154_FCTL_ACKREQ		0x0020
+#define IEEE802154_FCTL_SECEN		0x0004
 #define IEEE802154_FCTL_INTRA_PAN	0x0040
 
 #define IEEE802154_FTYPE_DATA		0x0001
@@ -232,6 +233,15 @@ static inline int ieee802154_is_data(__le16 fc)
 		cpu_to_le16(IEEE802154_FTYPE_DATA);
 }
 
+/**
+ * ieee802154_is_secen - check if Security bit is set
+ * @fc: frame control bytes in little-endian byteorder
+ */
+static inline bool ieee802154_is_secen(__le16 fc)
+{
+	return fc & cpu_to_le16(IEEE802154_FCTL_SECEN);
+}
+
 /**
  * ieee802154_is_ackreq - check if acknowledgment request bit is set
  * @fc: frame control bytes in little-endian byteorder