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=-5.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS 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 B7399C43603 for ; Tue, 17 Dec 2019 08:46:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 85E16207FF for ; Tue, 17 Dec 2019 08:46:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="RHeQX14t" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726836AbfLQIqv (ORCPT ); Tue, 17 Dec 2019 03:46:51 -0500 Received: from us-smtp-1.mimecast.com ([205.139.110.61]:54383 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726716AbfLQIqv (ORCPT ); Tue, 17 Dec 2019 03:46:51 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1576572409; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=03mvPsY7xasEEB7ziDGo/lAPtpDV+P7ujRg7IbN9j1o=; b=RHeQX14tf4Kjz3+sdDvk4QzMGsstapo2BzX3ArO2HRLnoq7wVLNB4fDJYZga6m76FxYHaR ssGdDOQOhS6IzLPUZullSC927heRupx1wCDBWW3UuQJZGd+KVTtKjrMiktw5/F3BWCo7Jq O0K6A4QHZaseRbrkiyy/6HhnfBpgt9o= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-314-tUJVge8qMsuKt0ZXiec_SA-1; Tue, 17 Dec 2019 03:46:48 -0500 X-MC-Unique: tUJVge8qMsuKt0ZXiec_SA-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 18E381800D42; Tue, 17 Dec 2019 08:46:46 +0000 (UTC) Received: from carbon (ovpn-200-37.brq.redhat.com [10.40.200.37]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9E7FE5D9C9; Tue, 17 Dec 2019 08:46:37 +0000 (UTC) Date: Tue, 17 Dec 2019 09:46:35 +0100 From: Jesper Dangaard Brouer To: Luigi Rizzo Cc: "Jubran, Samih" , "Machulsky, Zorik" , Daniel Borkmann , David Miller , "Tzalik, Guy" , Ilias Apalodimas , Toke =?UTF-8?B?SMO4aWxhbmQtSsO4cmdlbnNl?= =?UTF-8?B?bg==?= , "Kiyanovski, Arthur" , Alexei Starovoitov , "netdev@vger.kernel.org" , David Ahern , brouer@redhat.com Subject: Re: XDP multi-buffer design discussion Message-ID: <20191217094635.7e4cac1c@carbon> In-Reply-To: References: <5FA3F980-29E6-4B91-8150-9F28C0E09C45@amazon.com> <20190823084704.075aeebd@carbon> <67C7F66A-A3F7-408F-9C9E-C53982BCCD40@amazon.com> <20191204155509.6b517f75@carbon> <20191216150728.38c50822@carbon> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Mon, 16 Dec 2019 20:15:12 -0800 Luigi Rizzo wrote: > On Mon, Dec 16, 2019 at 6:07 AM Jesper Dangaard Brouer > wrote: > > > > > > See answers inlined below (please get an email client that support > > inline replies... to interact with this community) > > > > On Sun, 15 Dec 2019 13:57:12 +0000 > > "Jubran, Samih" wrote: > ... > > > * Why should we provide the fragments to the bpf program if the > > > program doesn't access them? If validating the length is what > > > matters, we can provide only the full length info to the user with no > > > issues. > > > > My Proposal#1 (in [base-doc]) is that XDP only get access to the > > first-buffer. People are welcome to challenge this choice. > > > > There are a several sub-questions and challenges hidden inside this > > choice. > > > > As you hint, the total length... spawns some questions we should answer: > > > > (1) is it relevant to the BPF program to know this, explain the use-case. > > > > (2) if so, how does BPF prog access info (without slowdown baseline) > > For some use cases, the bpf program could deduct the total length > looking at the L3 header. Yes, that actually good insight. I guess the BPF-program could also use this to detect that it doesn't have access to the full-lineary packet this way(?) > It won't work for XDP_TX response though. The XDP_TX case also need to be discussed/handled. IMHO need to support XDP_TX for multi-buffer frames. XDP_TX *can* be driver specific, but most drivers choose to convert xdp_buff to xdp_frame, which makes it possible to use/share part of the XDP_REDIRECT code from ndo_xdp_xmit. We also need to handle XDP_REDIRECT, which becomes challenging, as the ndo_xdp_xmit functions of *all* drivers need to be updated (or introduce a flag to handle this incrementally). Sameeh, I know you have read the section[1] on "Storage space for multi-buffer references/segments", and you updated the doc in git-tree. So, you should understand that I want to keep this compatible with how SKB stores segments, which will make XDP_PASS a lot easier/faster. -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer [1] https://github.com/xdp-project/xdp-project/blob/master/areas/core/xdp-multi-buffer01-design.org#storage-space-for-multi-buffer-referencessegments