AES counter mode uses 8byte IV, not 16 bytes.

Obtained from:	NetBSD

sys/netinet6/esp_aesctr.c

@@ -59,7 +59,7 @@
 union cblock {
 	struct {
 		u_int8_t nonce[4];
-		u_int8_t iv[16];
+		u_int8_t iv[8];
 		u_int32_t ctr;
 	} v __attribute__((__packed__));
 	u_int8_t cblock[16];