rt2x00: Further L2 padding fixes.

Fix a couple of more bugs in the L2 padding code:
1. Compute the amount of L2 padding correctly (in 3 places).
2. Trim the skb correctly when the L2 padding has been applied.

Also introduce a central macro the compute the L2 padding size.

Signed-off-by: Gertjan van Wingerde <gwingerde@gmail.com>
Acked-by: Ivo van Doorn <ivdoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

2 files changed, 11 insertions, 3 deletions

diff --git a/drivers/net/wireless/rt2x00/rt2x00.h b/drivers/net/wireless/rt2x00/rt2x00.h
index 4d841c07c970..194dae01d0c3 100644
--- a/drivers/net/wireless/rt2x00/rt2x00.h
+++ b/drivers/net/wireless/rt2x00/rt2x00.h
@@ -104,6 +104,12 @@
 #define GET_DURATION_RES(__size, __rate)(((__size) * 8 * 10) % (__rate))
 
 /*
+ * Determine the number of L2 padding bytes required between the header and
+ * the payload.
+ */
+#define L2PAD_SIZE(__hdrlen)    (-(__hdrlen) & 3)
+
+/*
  * Determine the alignment requirement,
  * to make sure the 802.11 payload is padded to a 4-byte boundrary
  * we must determine the address of the payload and calculate the
diff --git a/drivers/net/wireless/rt2x00/rt2x00queue.c b/drivers/net/wireless/rt2x00/rt2x00queue.c
index b8f09547787d..21d58769a1a7 100644
--- a/drivers/net/wireless/rt2x00/rt2x00queue.c
+++ b/drivers/net/wireless/rt2x00/rt2x00queue.c
@@ -181,7 +181,7 @@ void rt2x00queue_insert_l2pad(struct sk_buff *skb, unsigned int header_length)
         unsigned int frame_length = skb->len;
         unsigned int header_align = ALIGN_SIZE(skb, 0);
         unsigned int payload_align = ALIGN_SIZE(skb, header_length);
-        unsigned int l2pad = 4 - (payload_align - header_align);
+        unsigned int l2pad = L2PAD_SIZE(header_length);
 
         if (header_align == payload_align) {
                 /*
@@ -216,6 +216,7 @@ void rt2x00queue_insert_l2pad(struct sk_buff *skb, unsigned int header_length)
                 memmove(skb->data + header_length + l2pad,
                         skb->data + header_length + l2pad + payload_align,
                         frame_length - header_length);
+                skb_trim(skb, frame_length + l2pad);
                 skbdesc->flags |= SKBDESC_L2_PADDED;
         }
 }
@@ -223,7 +224,7 @@ void rt2x00queue_insert_l2pad(struct sk_buff *skb, unsigned int header_length)
 void rt2x00queue_remove_l2pad(struct sk_buff *skb, unsigned int header_length)
 {
         struct skb_frame_desc *skbdesc = get_skb_frame_desc(skb);
-        unsigned int l2pad = 4 - (header_length & 3);
+        unsigned int l2pad = L2PAD_SIZE(header_length);
 
         if (!l2pad || (skbdesc->flags & SKBDESC_L2_PADDED))
                 return;
@@ -346,7 +347,8 @@ static void rt2x00queue_create_tx_descriptor(struct queue_entry *entry,
          * Header and alignment information.
          */
         txdesc->header_length = ieee80211_get_hdrlen_from_skb(entry->skb);
-        txdesc->l2pad = ALIGN_SIZE(entry->skb, txdesc->header_length);
+        if (test_bit(DRIVER_REQUIRE_L2PAD, &rt2x00dev->flags))
+                txdesc->l2pad = L2PAD_SIZE(txdesc->header_length);
 
         /*
          * Check whether this frame is to be acked.