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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 590D5C433E0 for ; Tue, 16 Jun 2020 10:26:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2AC5720767 for ; Tue, 16 Jun 2020 10:26:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726856AbgFPK0O (ORCPT ); Tue, 16 Jun 2020 06:26:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52864 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725843AbgFPKZe (ORCPT ); Tue, 16 Jun 2020 06:25:34 -0400 X-Greylist: delayed 513 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Tue, 16 Jun 2020 03:25:34 PDT Received: from simonwunderlich.de (packetmixer.de [IPv6:2001:4d88:2000:24::c0de]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1817CC08C5C2 for ; Tue, 16 Jun 2020 03:25:33 -0700 (PDT) Received: from [IPv6:2003:c5:9716:5300:7e76:35ff:fe14:e6d7] (p200300c5971653007e7635fffe14e6d7.dip0.t-ipconnect.de [IPv6:2003:c5:9716:5300:7e76:35ff:fe14:e6d7]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by simonwunderlich.de (Postfix) with ESMTPSA id 95F6762055; Tue, 16 Jun 2020 12:16:51 +0200 (CEST) Subject: Re: [PATCH] mac80211: mesh: add mesh_param "mesh_nolearn" to skip path discovery To: =?UTF-8?Q?Linus_L=c3=bcssing?= , Johannes Berg Cc: linux-wireless@vger.kernel.org, b.a.t.m.a.n@lists.open-mesh.org, Sven Eckelmann , Simon Wunderlich References: <20200616095358.20143-1-linus.luessing@c0d3.blue> From: =?UTF-8?Q?Linus_L=c3=bcssing?= Message-ID: Date: Tue, 16 Jun 2020 12:16:51 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <20200616095358.20143-1-linus.luessing@c0d3.blue> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-wireless-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org > The new mesh_nolearn parameter allows to skip the PREQ/PREP exchange in > this scenario, leading to a reduced delay, reduced packet buffering and > simplifies HWMP in general. Also another small remark regarding the simplification: Next to the timer re-arming bug / crash [0] we also stumbled over another bug when using encryption on the 802.11s interfaces which we could quite solve yet: We are seeing packet loss every four seconds due to a "DECRYPT CRC ERR". We could narrow this down to the PREQ. This somehow makes the receiver unable to decrypt the packet in hardware and also the fallback to software decryption fails as the hardware has messed up the encrypted data (looks completely different than what we saw in the air with a third device in monitor mode, unencrypted headers looked ok though). Furthermore, the hardware still sends ACKs for this frame... so no retries on the 802.11 layer, leading to ugly packet loss for one UDP packet every four seconds. The hardware we were having this issue with is a Lima board with a QCA4531. Setting ath9k nohwcrypt=1 on the sender side helps. And avoiding PREQs with this patch also helped in our batman-adv setup which had mesh_fwding disabled already anyway. Regards, Linus PS/Disclaimer: This bug was observed on an old LEDE version. [0]: https://patchwork.kernel.org/patch/11566011/