mac80211: add utility function to get header length

Take a __le16 directly rather than a host-endian value.

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

2 files changed, 38 insertions, 0 deletions

diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index f9b391faaf76..7ab4ff6159a2 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -1548,6 +1548,12 @@ unsigned int ieee80211_get_hdrlen_from_skb(const struct sk_buff *skb);
 int ieee80211_get_hdrlen(u16 fc);
 
 /**
+ * ieee80211_hdrlen - get header length in bytes from frame control
+ * @fc: frame control field in little-endian format
+ */
+unsigned int ieee80211_hdrlen(__le16 fc);
+
+/**
  * ieee80211_get_tkip_key - get a TKIP rc4 for skb
  *
  * This function computes a TKIP rc4 key for an skb. It computes
diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index f3c30d00b21e..9f365a3af96f 100644
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -133,6 +133,38 @@ int ieee80211_get_hdrlen(u16 fc)
 }
 EXPORT_SYMBOL(ieee80211_get_hdrlen);
 
+unsigned int ieee80211_hdrlen(__le16 fc)
+{
+        unsigned int hdrlen = 24;
+
+        if (ieee80211_is_data(fc)) {
+                if (ieee80211_has_a4(fc))
+                        hdrlen = 30;
+                if (ieee80211_is_data_qos(fc))
+                        hdrlen += IEEE80211_QOS_CTL_LEN;
+                goto out;
+        }
+
+        if (ieee80211_is_ctl(fc)) {
+                /*
+                 * ACK and CTS are 10 bytes, all others 16. To see how
+                 * to get this condition consider
+                 *   subtype mask:   0b0000000011110000 (0x00F0)
+                 *   ACK subtype:    0b0000000011010000 (0x00D0)
+                 *   CTS subtype:    0b0000000011000000 (0x00C0)
+                 *   bits that matter:         ^^^      (0x00E0)
+                 *   value of those: 0b0000000011000000 (0x00C0)
+                 */
+                if ((fc & cpu_to_le16(0x00E0)) == cpu_to_le16(0x00C0))
+                        hdrlen = 10;
+                else
+                        hdrlen = 16;
+        }
+out:
+        return hdrlen;
+}
+EXPORT_SYMBOL(ieee80211_hdrlen);
+
 unsigned int ieee80211_get_hdrlen_from_skb(const struct sk_buff *skb)
 {
         const struct ieee80211_hdr *hdr = (const struct ieee80211_hdr *)skb->data;