Return-path: Received: from mail-wi0-f178.google.com ([209.85.212.178]:37484 "EHLO mail-wi0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756149AbbGQJf4 convert rfc822-to-8bit (ORCPT ); Fri, 17 Jul 2015 05:35:56 -0400 Received: by wibud3 with SMTP id ud3so37792406wib.0 for ; Fri, 17 Jul 2015 02:35:55 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <1437124199.1933.6.camel@sipsolutions.net> References: <1435823996-32510-1-git-send-email-michal.kazior@tieto.com> <1437123955.1933.3.camel@sipsolutions.net> <1437124038.1933.4.camel@sipsolutions.net> <1437124199.1933.6.camel@sipsolutions.net> Date: Fri, 17 Jul 2015 11:35:55 +0200 Message-ID: (sfid-20150717_113600_735242_68C0B8E1) Subject: Re: [PATCH] mac80211: don't clear all tx flags when requeing From: Michal Kazior To: Johannes Berg Cc: linux-wireless Content-Type: text/plain; charset=UTF-8 Sender: linux-wireless-owner@vger.kernel.org List-ID: On 17 July 2015 at 11:09, Johannes Berg wrote: > On Fri, 2015-07-17 at 11:07 +0200, Johannes Berg wrote: >> >> > > Once (a) is not stripped (b) becomes important >> > > because it's the main condition to clear the >> > > Service Period bit of the station when Tx status >> > > for the released frame is reported back. >> > > >> > > This problem was observed with ath9k acting as P2P >> > > GO in some testing scenarios but isn't limited to >> > > it. AP operation with mac80211 based Tx A-MPDU >> > > control combined with clients using PS-Poll frames >> > > is subject to this race. >> > >> > I'm not sure I quite understand - how is the aggregation teardown >> > causing frame filtering? >> > >> >> Never mind, I was looking at the wrong code. I'll apply this. >> > > However, I'd like to ask you to look at this again - I can see how it > fixes the problem now, but it seems like a fairly unreliable fix since > the frame is sent through TX processing again, and you're relying on > that preserving a flag that's otherwise marked temporary... > > So I think it may be better to adjust the station flags in this case to > let a new (the same) frame be the ps-poll response again. Hmm.. I did contemplate on clearing the station flag. I didn't explore the idea thoroughly but my feeling was it could introduce new u-APSD corner-case bug(s) since you'd be changing the station state before it'd normally be done and hence would behave differently when handling Rx. I'll look into it more. Michał