netdev - Re: regression: tethering fails in 3.5 with iwlwifi

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Date:	Thu, 20 Sep 2012 14:35:24 +0200
From:	Johannes Berg <johannes@...solutions.net>
To:	artem.bityutskiy@...ux.intel.com
Cc:	Eric Dumazet <edumazet@...gle.com>, linux-wireless@...r.kernel.org,
	netdev <netdev@...r.kernel.org>
Subject: Re: regression: tethering fails in 3.5 with iwlwifi

Hi,

> >             56138f5 iwlwifi: dont pull too much payload in skb head
> >             3edaf3e mac80211: manage AP netdev carrier state
> 
> The second patch (AP carrier state) actually exposed a connman issue
> which I fixed and submitted a connman patch:
> http://lists.connman.net/pipermail/connman/2012-September/011232.html
> 
> However, Eric's patch still causes tethering problems to me.


Let me recap a bit. Artem is using connman, which sets up the wifi
interface as part of a bridge. It runs wpa_supplicant to create an AP
(only AP and mesh mode interfaces can be bridged anyway).


Eric, you said:

> I would say some part of the stack assumes a header (I dont know wich
> one ?) is pulled in skb->head/data, and thats a bug.
> 
> Always use pskb_may_pull(skb, XXX) to make sure you can access XXX
> bytes in skb->data

I thought we'd figure out which part of the stack assumes a header, so I
asked Artem to test a one-line patch which adds "skb_linearize()" before
"netif_receive_skb()" in mac80211. This makes it work, but I'm not sure
where after that the bad assumption might be.

johannes

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