From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3CE4AC3A5A0 for ; Mon, 19 Aug 2019 20:03:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0F83E2087E for ; Mon, 19 Aug 2019 20:03:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728177AbfHSUDb (ORCPT ); Mon, 19 Aug 2019 16:03:31 -0400 Received: from s3.sipsolutions.net ([144.76.43.62]:47150 "EHLO sipsolutions.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727970AbfHSUDb (ORCPT ); Mon, 19 Aug 2019 16:03:31 -0400 Received: by sipsolutions.net with esmtpsa (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1hznsG-0003hB-W0; Mon, 19 Aug 2019 22:03:29 +0200 Message-ID: <52914e64663283eeff9445b8b1fb37986c15223d.camel@sipsolutions.net> Subject: Re: [PATCH] iwlwifi: Extended Key ID support for mvm and dvm From: Johannes Berg To: Alexander Wetzel , luciano.coelho@intel.com Cc: linux-wireless@vger.kernel.org, linuxwifi@intel.com Date: Mon, 19 Aug 2019 22:03:27 +0200 In-Reply-To: References: <20190819180540.2855-1-alexander@wetzel-home.de> <204c346ab9fc71865e4cb5f5c29ec33ca05050e2.camel@sipsolutions.net> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.30.5 (3.30.5-1.fc29) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-wireless-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org On Mon, 2019-08-19 at 21:57 +0200, Alexander Wetzel wrote: > > > + > > > + /* The new Tx API does not allow to pass the key or keyid of a MPDU to > > > + * the hw, preventing us to control which key(id) to use per MPDU. > > > + * Till that's fixed we can't use Extended Key ID for the newer cards. > > > > Technically we still don't need per MPDU, we just need to switch which > > one to use for TX after installing it for RX already. > > The Extended Key ID API we finally merged in mac80211 is not notifying > the driver when to switch the key over to the other id. Oh, right, good point. > The current API provides the key/keyid per MPDU and let's mac80211 have > the full control what's the correct key for each frame. Yeah, but as you noticed we no longer have that control per MPDU with the new TX API in iwlmvm. > That's especially critical for drivers setting > IEEE80211_KEY_FLAG_GENERATE_IV and/or supporting A-MPDU's. Allowing the > driver to override the mac80211 decision is only safe when the > driver/card generates the PNs itself and also handles the A-MPDU key > borders correctly. Sure, the device does generate the PN itself now with the new TX API too. It doesn't care about A-MPDU key borders, but it probably could when taught to care about extended key ID. > While less desirable we still could get that working: The mvm driver > would have to detect the key borders and then tell the firmware to > switch over to the other key. But we would have to make sure to not > re-enable A-MPDU aggregation till the card really has switched. I'm not entirely sure off the top of my head how it works, but it seems possible that if we just assign a new PN to retransmits of the same frame but in a new A-MPDU after key switching, it wouldn't actually matter? But then again maybe somewhere it's stated that we must use the same key for all transmit attempts of a single frame? Not sure. I'm also not sure if we could actually assign a PN from the new key for the retransmit, the hardware has to store those back into memory normally. So probably you're right, and we'd have to disable A-MPDUs until we have no outstanding old-key-retransmits, but that seems manageable. johannes