mac80211: allow drivers to access key sequence counter

In order to implement GTK rekeying, the device needs
to be able to encrypt frames with the right PN/IV and
check the PN/IV in RX frames. To be able to tell it
about all those counters, we need to be able to get
them from mac80211, this adds the required API.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/key.h b/net/mac80211/key.h
index beb9c20..86b216b 100644
--- a/net/mac80211/key.h
+++ b/net/mac80211/key.h
@@ -28,6 +28,7 @@
 #define CCMP_PN_LEN		6
 #define TKIP_IV_LEN		8
 #define TKIP_ICV_LEN		4
+#define CMAC_PN_LEN		6
 
 #define NUM_RX_DATA_QUEUES	16
 
@@ -89,13 +90,13 @@
 			 * frames and the last counter is used with Robust
 			 * Management frames.
 			 */
-			u8 rx_pn[NUM_RX_DATA_QUEUES + 1][6];
+			u8 rx_pn[NUM_RX_DATA_QUEUES + 1][CCMP_PN_LEN];
 			struct crypto_cipher *tfm;
 			u32 replays; /* dot11RSNAStatsCCMPReplays */
 		} ccmp;
 		struct {
 			atomic64_t tx_pn;
-			u8 rx_pn[6];
+			u8 rx_pn[CMAC_PN_LEN];
 			struct crypto_cipher *tfm;
 			u32 replays; /* dot11RSNAStatsCMACReplays */
 			u32 icverrors; /* dot11RSNAStatsCMACICVErrors */