Disabling MAC layer ACKs

Disabling MAC layer ACKs

[Andrew Wygle]

Hello,

I'm trying to disable MAC layer ACKs for some testing I'm doing. I can't 
seem to pin down the best way to do this, though.

 From some mailing list posts it seems I should be able to set the NoAck 
flag on any frames I send from a fairly high level of the networking 
stack. I can't seem to figure out where I'd do this, or what interface I 
should be using to do so - sockets don't know anything about MAC layers, 
and that's as low as I know how to go in userspace.

Coming at it from the other side, I found mac80211_tx_control_flags has 
a field called IEEE80211_TX_CTL_NO_ACK, which one could presumably set 
to achieve this effect. However my (admittedly limited) understanding is 
that mac80211 is at the driver level, or at least not in userspace, so I 
don't know where/when this would get set.

I was hoping that iw's noack_map command would work for me, although I 
didn't really understand what a TID meant in this context, but when I 
try to run it I get "command failed: Operation not supported (-95)". I 
suppose it's possible my hardware just doesn't support 802.11e, but as 
far as I can tell it does. Is that the only reason one should expect to 
see that error? Is it possibly related to the fact that I had to compile 
iw 3.3 myself on Ubuntu 12.04, which ships with 3.2 which doesn't have 
noack_map, and I didn't upgrade any libraries or anything when I did so?

Finally, I noted from a mailing list post from 2011 that this can be 
done for Atheros chips (which this is) by adding REG_SET_BIT(ah, 
AR_DIAG_SW, AR_DIAG_ACK_DIS) into the ath5k/9k code. I suppose I could 
do this, but I'd be glad to avoid a custom driver if at all possible.

Can anyone point me in the right direction?

Thanks,

~Andrew Wygle