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=-3.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_NEOMUTT autolearn=ham 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 16D6AC169C4 for ; Wed, 6 Feb 2019 04:11:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D1EA720844 for ; Wed, 6 Feb 2019 04:11:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="bAlEzRvw" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726742AbfBFELR (ORCPT ); Tue, 5 Feb 2019 23:11:17 -0500 Received: from mail-pf1-f194.google.com ([209.85.210.194]:43095 "EHLO mail-pf1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726062AbfBFELR (ORCPT ); Tue, 5 Feb 2019 23:11:17 -0500 Received: by mail-pf1-f194.google.com with SMTP id w73so2497291pfk.10 for ; Tue, 05 Feb 2019 20:11:16 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=WnHeLt/WXE8qsZPQGxjMeEg4tU8DDzrJQoQKjaQontw=; b=bAlEzRvwqICcACo2JJ+S0m/5hR2SJ57AFvL0/nFnr8ecy7mGIi9E1FoNeTXN+uspA7 pa5cVdt+tVRrCmNFw4RU6OcNFuLy/cRK6PjESI6JYd1YkytdhtlGDv5J4SIP697hToVx zXHcDQ4Yu7C8KizHGIC7h6BRH9M8gTI217zUCLZ7GoCRvey86U73hSw0Gmuu06AlfJOo tTKyat5m4n4aGcdynpdV0nsEuaq3ZVNFzVmvRCYTq9mGAO5fstdkyil3JfWpxNRHWAf7 7Wq/1ilGTKWsJU7i+leJX6dKTMq/ZYeaOKcABdUB6O0FVRKdkGc+Z6oTB4H1ay9VfQeR gGfw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=WnHeLt/WXE8qsZPQGxjMeEg4tU8DDzrJQoQKjaQontw=; b=bYTvG+idb8wJQQKiLskIWNHkFs4x3ivICIpZumYrJ42as2wAiLWrTcYjdAU2vK09Ul 4AoqhVq637oMFuuP3pIMawAqf+4uP+68l+H2fozVp5mGh9CbU6cjQD1nRJwfEpKxG9qT AUTLdptO9VOdWu2efWGjcTrreGbuiVUWyRUzg7ICqRnKY3beX+pcujk0JnZmv8SBNB4E grArxETnHdgJvaCRNMXgUlg4fz3hgJS0nXhqbW/s+ceeB7gN6aWiMRmyGMzuOH/Whq3P q824iSbp06fCRUuURlwOpgCnUthoSoYG2GbMBfWZ0hW4OkvW6XdtG+tIMHeKBc9WJnGZ DuxQ== X-Gm-Message-State: AHQUAuY7HZrTr9b3bS4Gq1iesSHszu1cZHslwPMtLl0dpqdVg8a8Qv/0 PFwOEoOci0ExPo5vQRehZDg= X-Google-Smtp-Source: AHgI3IaWR0F5ct2NS7oONfqU/BBuTWz0EAJToqcQACeiDW8XK7I5ghhNoUkZF3e8SJl6NnIiv9ZsEg== X-Received: by 2002:a63:d450:: with SMTP id i16mr7671764pgj.246.1549426276330; Tue, 05 Feb 2019 20:11:16 -0800 (PST) Received: from ast-mbp ([2620:10d:c090:180::1:f6ef]) by smtp.gmail.com with ESMTPSA id c23sm5539400pfi.83.2019.02.05.20.11.14 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 05 Feb 2019 20:11:15 -0800 (PST) Date: Tue, 5 Feb 2019 20:11:13 -0800 From: Alexei Starovoitov To: Stanislav Fomichev Cc: Willem de Bruijn , Stanislav Fomichev , Network Development , David Miller , Alexei Starovoitov , Daniel Borkmann , simon.horman@netronome.com, Willem de Bruijn Subject: Re: [RFC bpf-next 0/7] net: flow_dissector: trigger BPF hook when called from eth_get_headlen Message-ID: <20190206041112.h3ccahimp2uerdfk@ast-mbp> References: <20190205173629.160717-1-sdf@google.com> <20190205204003.GB10769@mini-arch> <20190206004714.pz44evow5uwgvt4x@ast-mbp.dhcp.thefacebook.com> <20190206005931.GF10769@mini-arch> <20190206031215.qldeh7pfgqr3frg3@ast-mbp> <20190206035619.GG10769@mini-arch> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190206035619.GG10769@mini-arch> User-Agent: NeoMutt/20180223 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, Feb 05, 2019 at 07:56:19PM -0800, Stanislav Fomichev wrote: > On 02/05, Alexei Starovoitov wrote: > > On Tue, Feb 05, 2019 at 04:59:31PM -0800, Stanislav Fomichev wrote: > > > On 02/05, Alexei Starovoitov wrote: > > > > On Tue, Feb 05, 2019 at 12:40:03PM -0800, Stanislav Fomichev wrote: > > > > > On 02/05, Willem de Bruijn wrote: > > > > > > On Tue, Feb 5, 2019 at 12:57 PM Stanislav Fomichev wrote: > > > > > > > > > > > > > > Currently, when eth_get_headlen calls flow dissector, it doesn't pass any > > > > > > > skb. Because we use passed skb to lookup associated networking namespace > > > > > > > to find whether we have a BPF program attached or not, we always use > > > > > > > C-based flow dissector in this case. > > > > > > > > > > > > > > The goal of this patch series is to add new networking namespace argument > > > > > > > to the eth_get_headlen and make BPF flow dissector programs be able to > > > > > > > work in the skb-less case. > > > > > > > > > > > > > > The series goes like this: > > > > > > > 1. introduce __init_skb and __init_skb_shinfo; those will be used to > > > > > > > initialize temporary skb > > > > > > > 2. introduce skb_net which can be used to get networking namespace > > > > > > > associated with an skb > > > > > > > 3. add new optional network namespace argument to __skb_flow_dissect and > > > > > > > plumb through the callers > > > > > > > 4. add new __flow_bpf_dissect which constructs temporary on-stack skb > > > > > > > (using __init_skb) and calls BPF flow dissector program > > > > > > > > > > > > The main concern I see with this series is this cost of skb zeroing > > > > > > for every packet in the device driver receive routine, *independent* > > > > > > from the real skb allocation and zeroing which will likely happen > > > > > > later. > > > > > Yes, plus ~200 bytes on the stack for the callers. > > > > > > > > > > Not sure how visible this zeroing though, I can probably try to get some > > > > > numbers from BPF_PROG_TEST_RUN (running current version vs running with > > > > > on-stack skb). > > > > > > > > imo extra 256 byte memset for every packet is non starter. > > > We can put pre-allocated/initialized skbs without data into percpu or even > > > use pcpu_freelist_pop/pcpu_freelist_push to make sure we don't have to think > > > about having multiple percpu for irq/softirq/process contexts. > > > Any concerns with that approach? > > > Any other possible concerns with the overall series? > > > > I'm missing why the whole thing is needed. > > You're saying: > > " make BPF flow dissector programs be able to work in the skb-less case". > > What does it mean specifically? > > The only non-skb case is XDP. > > Are you saying you want flow_dissector prog to be run in XDP? > eth_get_headlen that drivers call on RX path on a chunk of data to > guesstimate the length of the headers calls flow dissector without an skb > (__skb_flow_dissect was a weird interface where it accepts skb or > data+len). Right now, there is no way to trigger BPF flow dissector > for this case (we don't have an skb to get associated namespace/etc/etc). > The patch series tries to fix that to make sure that we always trigger > BPF program if it's attached to a device's namespace. then why not to create flow_dissector prog type that works without skb? Why do you need to fake an skb? XDP progs work just fine without it.