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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 521DAC433F5 for ; Tue, 12 Apr 2022 13:50:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344633AbiDLNw1 (ORCPT ); Tue, 12 Apr 2022 09:52:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45842 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238580AbiDLNwY (ORCPT ); Tue, 12 Apr 2022 09:52:24 -0400 Received: from nbd.name (nbd.name [IPv6:2a01:4f8:221:3d45::2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 66CC350B0A; Tue, 12 Apr 2022 06:50:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=nbd.name; s=20160729; h=Content-Transfer-Encoding:Content-Type:In-Reply-To:Subject: From:References:Cc:To:MIME-Version:Date:Message-ID:Sender:Reply-To:Content-ID :Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To: Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe :List-Post:List-Owner:List-Archive; bh=DqKc8iJWKXFesV4tUBomdbYhQAx3J3hZZcgttBI4x2Y=; b=lUcIljzLQVkGDAXHQvO3ekCQ9M JW4E1mqnOh350Gj+Eo1iyNXxUT+ph4jRyeLYG3/8bpC3qR5mSIBj1whJKWuTaAsjmIKKYhUDNBrnj 06RlAEIaL8dX8lKiR47oFmu0ZI/9BKYRTXp8vJ4av43r3Y3xyLnM47QGCmqTDWbqLZK8=; Received: from p57a6f1f9.dip0.t-ipconnect.de ([87.166.241.249] helo=nf.local) by ds12 with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.89) (envelope-from ) id 1neGu0-00074w-2t; Tue, 12 Apr 2022 15:49:52 +0200 Message-ID: Date: Tue, 12 Apr 2022 15:49:51 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Thunderbird/91.7.0 Content-Language: en-US To: Andrew Lunn Cc: netdev@vger.kernel.org, John Crispin , Sean Wang , Mark Lee , "David S. Miller" , Jakub Kicinski , Paolo Abeni , Matthias Brugger , linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org, Jiri Pirko , Ido Schimmel , Florian Fainelli , Vladimir Oltean References: <20220405195755.10817-1-nbd@nbd.name> <20220405195755.10817-15-nbd@nbd.name> From: Felix Fietkau Subject: Re: [PATCH v2 14/14] net: ethernet: mtk_eth_soc: support creating mac address based offload entries In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 12.04.22 15:07, Andrew Lunn wrote: >> > > > > I'm trying to understand the architecture here. >> > > > > We have an Ethernet interface and a Wireless interface. The slow >> > > path >> > > > is that frames ingress from one of these interfaces, Linux decides >> > > > what to do with them, either L2 or L3, and they then egress probably >> > > > out the other interface. >> > > > > The hardware will look at the frames and try to spot flows? It >> > > will >> > > > then report any it finds. You can then add an offload, telling it for >> > > > a flow it needs to perform L2 or L3 processing, and egress out a >> > > > specific port? Linux then no longer sees the frame, the hardware >> > > > handles it, until the flow times out? >> > > Yes, the hw handles it until either the flow times out, or the corresponding >> > > offload entry is removed. >> > > >> > > For OpenWrt I also wrote a daemon that uses tc classifier BPF to accelerate >> > > the software bridge and create hardware offload entries as well via hardware >> > > TC flower rules: https://github.com/nbd168/bridger >> > > It works in combination with these changes. >> > >> > What about the bridge? In Linux, it is the software bridge which >> > controls all this at L2, and it should be offloading the flows, via >> > switchdev. The egress port you derive here is from the software bridge >> > FDB? > >> My code uses netlink to fetch and monitor the bridge configuration, >> including fdb, port state, vlans, etc. and it uses that for the offload path >> - no extra configuration needed. > > So this is where we get into architecture issues. Do we really want > Linux to have two ways for setting up L2 networking? It was decided > that users should not need to know about how to use an accelerator, > they should not use additional tools, it should just look like > linux. The user should just add the WiFi netdev to the bridge and > switchdev will do the rest to offload L2 switching to the hardware. > > You appear to be saying you need a daemon in userspace. That is not > how every other accelerate works in Linux networking. > > We the Linux network community need to decided if we want this? The problem here is that it can't be fully transparent. Enabling hardware offload for LAN -> WiFi comes at a cost of bypassing airtime fairness and mac80211's bufferbloat mitigation. Some people want this anyway (often but not always for benchmark/marketing purposes), but it's not something that I would want to have enabled by default simply by a wifi netdev to a bridge. Initially, I wanted to put more of the state tracking code in the kernel. I made the first implementation of my acceleration code as a patch to the network bridge - speeding up bridge unicast forwarding significantly for any device regardless of hardware support. I wanted to build on that to avoid putting a lot of FDB/VLAN related tracking directly into the driver. That approach was immediately rejected and I was told to use BPF instead. That said, I really don't think it's a good idea to put all the code for tracking the bridge state, and all possible forwarding destinations into the driver directly. I believe the combination of doing the bridge state tracking in user space + using the standard TC API for programming offloading rules into the hardware is a reasonable compromise. - Felix