Re: [Madwifi-devel] Atheros hardware key cache and multicast keys

[Benoit P. <ben...@fr...>]

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Benoit PAPILLAULT a écrit :
| Reading ath5k source code and current madwifi, I think I found something
| interesting. Your previous mail from referring to some multicast feature
| that needs to be enabled. Indeed, sc_mcastkey is inside a #if 0 section.
| ~From my reading, the ath_hal_getmcastkeysearch() function just check if
| the feature is enabled or not. There should be a corresponding
| ath_hal_setmcastkeysearch() probably since there is also a
| ath_hal_hastmcastkeysearch().
|
| Maybe if you try this that would work?

If have successfully enabled it. This means that
ath_hal_getmcastkeysearch() now returns 1!

|
| Moreover, I'd like to understand a bit further how the hardware is
| working. From ath5k, there is only one MAC address (if any...) in the
| hardware. From madwifi, it seems that up to 4 keys are created : RX/TX
| and MIC stuff (don't know what it is).
|
| So maybe we just need to know what proper combination of RX/TX keys we
| need to setup?

Further reading shows that TX key is selected when filling the TX
descriptor by ath_hal_setuptxdesc (see ath_tx_start).

I've been playing with the RX side using WEP and the following keycache:

[  0] keytype 0 [WEP40] mac 00:00:00:00:00:00
key:78563412-00000090-00000000-00000000-00000000
[  1] keytype 0 [WEP40] mac 00:00:00:00:00:00
key:78563412-00000090-00000000-00000000-00000000
[  2] keytype 0 [WEP40] mac 00:00:00:00:00:00
key:78563412-00000090-00000000-00000000-00000000
[  3] keytype 0 [WEP40] mac 06:0b:6b:37:a5:34
key:78563412-00000090-00000000-00000000-00000000
[  4] keytype 0 [WEP40] mac 00:00:00:00:00:00
key:78563412-00000090-00000000-00000000-00000000
[100] keytype 0 [WEP40] mac 06:0b:6b:56:6c:a5
key:78563412-00000090-00000000-00000000-00000000
[101] keytype 0 [WEP40] mac 86:0b:6b:56:6c:a5
key:78563412-00000090-00000000-00000000-00000000
[102] keytype 0 [WEP40] mac 06:0b:6b:37:a5:34
key:78563412-00000090-00000000-00000000-00000000
[103] keytype 0 [WEP40] mac 86:0b:6b:37:a5:34
key:78563412-00000090-00000000-00000000-00000000

The [] is the keycache index. When receiving unicast from
06:0b:6b:56:6c:a5, the keycache index 100 is selected and reported in
rs_keyix.

However, when receiving broadcast packets (the sending node use WEP Key
ID = 3), the keycache index 3 is still used and rs_keyix = 255 is
reported. I was expecting that keycache index 101 be used :-(

My fear is that nor current madwifi, nor the FreeBSD drived are using
this sc_mcastkey feature, so inline comments in code applies to source
code that has probably never be tested!

Regards,
Benoit
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