Re: [PATCH] mac80211: Allow NO_ACK flag overwrite for injected frames

[Johannes Berg <johannes@sipsolutions.net>]

On Thu, 2011-09-29 at 11:27 +0200, Helmut Schaa wrote:
> Allow injected unicast frames to be sent without having to wait
> for an ACK.
> 
> Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
> ---
> 
> Just in case you're interested in what's the intended purpose of this:
> 
> Some clients are staying on scanned channels for a very short period of
> time. hostapd sends out probe responses for each configured BSSID. Under
> some circumstances I can see that the client already left the channel
> while some probe responses are still sent out and thus retried. This 
> consumes quite some airtime. Commercial wireless APs (Aruba for example)
> seem to disable retries for probe responses to mitigate such issues.

Makes sense, but I wonder if we really should continue using
radiotap :-) Maybe mgmt-tx in nl80211 would be appropriate.

> @@ -1257,7 +1265,7 @@ ieee80211_tx_prepare(struct ieee80211_sub_if_data *sdata,
>  		tx->flags |= IEEE80211_TX_UNICAST;
>  		if (unlikely(local->wifi_wme_noack_test))
>  			info->flags |= IEEE80211_TX_CTL_NO_ACK;
> -		else
> +		else if (!(info->flags & IEEE80211_TX_CTL_NO_ACK))
>  			info->flags &= ~IEEE80211_TX_CTL_NO_ACK;

??

johannes