Return-path: Received: from mail.atheros.com ([12.36.123.2]:63755 "EHLO mail.atheros.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751353AbYLLKYM (ORCPT ); Fri, 12 Dec 2008 05:24:12 -0500 Received: from mail.atheros.com ([10.10.20.107]) by sidewinder.atheros.com for ; Fri, 12 Dec 2008 02:24:12 -0800 Date: Fri, 12 Dec 2008 15:54:05 +0530 From: Senthil Balasubramanian To: Jouni Malinen CC: "John W. Linville" , "linux-wireless@vger.kernel.org" , "ath9k-devel@venema.h4ckr.net" Subject: Re: [PATCH] ath9k: Do not remove header padding on RX from short frames Message-ID: <20081212102405.GA10231@senthil-lnx.users.atheros.com> (sfid-20081212_112416_351937_202745FC) References: <20081211162213.GA28193@jm.kir.nu> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" In-Reply-To: <20081211162213.GA28193@jm.kir.nu> Sender: linux-wireless-owner@vger.kernel.org List-ID: On Thu, Dec 11, 2008 at 09:52:13PM +0530, Jouni Malinen wrote: > 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 > > --- > 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) { I think "if(padsize && hdrlen > 24)" should be sufficient here as padsize is anyway zero for hdlen==24. > memmove(skb->data + padsize, skb->data, hdrlen); > skb_pull(skb, padsize); > } > > -- > Jouni Malinen PGP id EFC895FA > -- > To unsubscribe from this list: send the line "unsubscribe linux-wireless" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html