Message-ID: <48884451.1090703@trash.net> (sfid-20080724_105907_896330_043B457A)
Date: Thu, 24 Jul 2008 10:58:57 +0200
From: Patrick McHardy <kaber@trash.net>
MIME-Version: 1.0
To: David Miller <davem@davemloft.net>
CC: francois.valenduc@tvcablenet.be, akpm@linux-foundation.org,
	bugme-daemon@bugzilla.kernel.org, linux-wireless@vger.kernel.org,
	linville@tuxdriver.com, netdev@vger.kernel.org,
	jussi.kivilinna@mbnet.fi
Subject: Re: [Bugme-new] [Bug 11144] New: dhcp doesn't work with iwl4965
References: <4887550B.2070704@tvcablenet.be>	<4887555A.30605@trash.net>	<48875B8C.2090800@trash.net> <20080723.142147.61941255.davem@davemloft.net>
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Sender: linux-wireless-owner@vger.kernel.org

David Miller wrote:
> From: Patrick McHardy <kaber@trash.net>
> Date: Wed, 23 Jul 2008 18:25:48 +0200
> 
>> We can't fit them into the cb together, I don't see a way to
>> shrink ieee80211_tx_info.
>>
>> Maybe one of the wireless folks can suggest something? Is it
>> really necessary to pass the full struct ieee80211_tx_info
>> through the qdisc layer, or could the struct be split? It
>> needs to find a way to co-exist peacefully with qdiscs'
>> skb->cb usage.
> 
> This is another area that got mangled up in the ->select_queue()
> conversion of the WME bits, but in another aspect this problem
> existed beforehand as well.
> 
> Specifically, when RX packets get requeued out to transmit in
> the code in net/mac80211/rx.c that resends packets back out the
> wireless device by setting a bit in the SKB CB then calling
> dev_queue_xmit().
> 
> That's completely illegal :-)

It seems its doing even more illegal things that were also
present previously. The ieee80211_master_start_xmit function
expects to get a valid IEEE80211_SKB_CB, which means it
expects it to survive through the entire qdisc layer. I'm
not sure how packets get to the master device from the
subifs though, so I might be wrong.