Re: mac80211 : fix unaligned rx skb

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

matthieu castet wrote:
> 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.
> 
Do you want more explanation ?

Matthieu