The 802.11 header is only padded to 32-bit boundary when the frame has
a non-zero length payload. In other words, control frames (e.g., ACK)
do not have a padding and we should not try to remove it. This fixes
monitor mode for short control frames. In addition, the hdrlen&3 use
is described in more detail to make it easier to understand how the
padding length is calculated.
Signed-off-by: Jouni Malinen <jouni.malinen@xxxxxxxxxxx>
---
drivers/net/wireless/ath9k/recv.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
--- wireless-testing.orig/drivers/net/wireless/ath9k/recv.c 2008-12-11 11:35:56.000000000 +0200
+++ wireless-testing/drivers/net/wireless/ath9k/recv.c 2008-12-11 12:18:02.000000000 +0200
@@ -571,8 +571,16 @@ int ath_rx_tasklet(struct ath_softc *sc,
hdr = (struct ieee80211_hdr *)skb->data;
hdrlen = ieee80211_get_hdrlen_from_skb(skb);
- if (hdrlen & 3) {
- padsize = hdrlen % 4;
+ /* The MAC header is padded to have 32-bit boundary if the
+ * packet payload is non-zero. The general calculation for
+ * padsize would take into account odd header lengths:
+ * padsize = (4 - hdrlen % 4) % 4; However, since only
+ * even-length headers are used, padding can only be 0 or 2
+ * bytes and we can optimize this a bit. In addition, we must
+ * not try to remove padding from short control frames that do
+ * not have payload. */
+ padsize = hdrlen & 3;
+ if (padsize && hdrlen >= 24) {
memmove(skb->data + padsize, skb->data, hdrlen);
skb_pull(skb, padsize);
}
--
Jouni Malinen PGP id EFC895FA
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