Re: mac80211 : fix unaligned rx skb

[matthieu castet <castet.matthieu@free.fr>]

Michael Buesch wrote:
> On Thursday 04 June 2009 23:16:13 Georgy Berdyshev wrote:
>> Hi,
>>
>> that's the inline version:
>> -------
>> mac80211 is checking is the skb is aligned on 32 bit boundary.
>> But it is checking against ethernet header, whereas Linux expect IP
>> header aligned.
>> And ethernet ether size is 6*2+2=14, so aligning ethernet header make
>> IP header unaligned.
>>
>> Signed-off-by: Matthieu CASTET <castet.matthieu@free.fr>
>> diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
>> index 9776f73..0845fb3 100644
>> --- a/net/mac80211/rx.c
>> +++ b/net/mac80211/rx.c
>> @@ -1397,7 +1397,7 @@ ieee80211_deliver_skb(struct ieee80211_rx_data *rx)
>>  		 * mac80211. That also explains the __skb_push()
>>  		 * below.
>>  		 */
>> -		align = (unsigned long)skb->data & 3;
>> +		align = ((unsigned long)(skb->data + sizeof(struct ethhdr))) & 3;
>>  		if (align) {
>>  			if (WARN_ON(skb_headroom(skb) < 3)) {
>>  				dev_kfree_skb(skb);
> 
> Uhm, can you give a more verbose explanation? Without that I'd say this patch is plain wrong.
> What the hell does struct ethhdr have to do with wireless?
 > This is not ethernet. It's 802.11. There is no such thing as an
 > ethernet header in a 802.11 packet.
 >
Where are in ieee80211_deliver_skb that is called after 
ieee80211_data_to_8023. So it is not 802.11.

Matthieu