if (skb == NULL)
                return NULL;
 
-       if ((skb_headroom(skb) < crypt->ops->extra_prefix_len ||
-            skb_tailroom(skb) < crypt->ops->extra_postfix_len) &&
-           pskb_expand_head(skb, crypt->ops->extra_prefix_len,
-                            crypt->ops->extra_postfix_len, GFP_ATOMIC)) {
+       if ((skb_headroom(skb) < crypt->ops->extra_mpdu_prefix_len ||
+            skb_tailroom(skb) < crypt->ops->extra_mpdu_postfix_len) &&
+           pskb_expand_head(skb, crypt->ops->extra_mpdu_prefix_len,
+                            crypt->ops->extra_mpdu_postfix_len, GFP_ATOMIC)) {
                kfree_skb(skb);
                return NULL;
        }
 
        }
 
        skb = dev_alloc_skb(WLAN_AUTH_CHALLENGE_LEN +
-                           ap->crypt->extra_prefix_len +
-                           ap->crypt->extra_postfix_len);
+                           ap->crypt->extra_mpdu_prefix_len +
+                           ap->crypt->extra_mpdu_postfix_len);
        if (skb == NULL) {
                kfree(tmpbuf);
                return NULL;
        }
 
-       skb_reserve(skb, ap->crypt->extra_prefix_len);
+       skb_reserve(skb, ap->crypt->extra_mpdu_prefix_len);
        memset(skb_put(skb, WLAN_AUTH_CHALLENGE_LEN), 0,
               WLAN_AUTH_CHALLENGE_LEN);
        if (ap->crypt->encrypt_mpdu(skb, 0, ap->crypt_priv)) {
                return NULL;
        }
 
-       memcpy(tmpbuf, skb->data + ap->crypt->extra_prefix_len,
+       memcpy(tmpbuf, skb->data + ap->crypt->extra_mpdu_prefix_len,
               WLAN_AUTH_CHALLENGE_LEN);
        dev_kfree_skb(skb);