Message-ID: <1ba2fa240804141139ua5f6f26k6920001ceb59443e@mail.gmail.com> (sfid-20080414_193921_655906_E45BE1E8)
Date: Mon, 14 Apr 2008 21:39:00 +0300
From: "Tomas Winkler" <tomasw@gmail.com>
To: "Ivo van Doorn" <ivdoorn@gmail.com>
Subject: Re: mac80211 hardware encryption
Cc: "Johannes Berg" <johannes@sipsolutions.net>,
	linux-wireless@vger.kernel.org
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On Mon, Apr 14, 2008 at 7:27 PM, Ivo van Doorn <ivdoorn@gmail.com> wrote:
> Hi,
>
> I've implemented the steps for hardware encryption
> including the part where the IV/EIV is being moved around.
>
> I now have a different problem, the hw_key_idx is u8,
> so is very limited to what can be stored in it. I am trying
> to find a solution for the following problem without increasing
> the size of hw_key_idx since it is also used in the ieee80211_tx_control
> structure which should remain as small as possible to fix in skb->cb.
>
> The problem is as follows:
> rt61pci, rt73usb, rt2800pci and rt2800usb support both shared keys
> as well as pairwise keys. When the "address" argument of set_key()
> is a valid MAC address, then the key is considered to be pairwise,
> otherwise it is a shared key.
>
> rt61pci and rt73usb supports:
> shared keys: 16 (4 per allowed virtual interface)
> pairwise keys: 64 (16 per allowed virtual interface)
>
> rt2800pci and rt2800usb supports:
> shared keys: 32 (4 per allowed virtual interface)
> pairwise keys: 256 (32 per allowed virtual interface)
>
> This means that the hw_key_idx with rt2800 hardware is already
> full when all keys are being supported. I am thinking of adding a flag
> to the key structure and ieee80211_tx_control structure to indicate
> if the key is shared or pairwise. This will safe 1 bit that otherwise has
> to be reserved from the hw_key_idx.
> Do you agree with such a flag addition, or should the driver not care
> about pairwise vs. shared.
>
> But now the fun part begins, the hardware needs the ieee80211_key_alg value
> for encryption (don't ask why, the algorithm is also stored in the register
> so it should be easy for the hardware to look it up directly).
> What should be the best way to obtain this algorithm, should a callback
> function be added, or should the driver keep a list in memory for all
> added keys (which would be memory duplication since mac80211 also
> has it in memory).
>
> Thanks,
>
>
Not sure what was intention for hw_key_idx but currently there are assignment
from key->conf.keyidx to hw_key_idx and visa versa.  keyidx is used
for 802.11 key index [1..4]
So it's quit risky to use it for something else
>
>
> Ivo
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