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=-11.1 required=3.0 tests=BAYES_00,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 8337BC47087 for ; Fri, 28 May 2021 10:54:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5DBB1613D1 for ; Fri, 28 May 2021 10:54:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236450AbhE1K4b (ORCPT ); Fri, 28 May 2021 06:56:31 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:51215 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236445AbhE1K4b (ORCPT ); Fri, 28 May 2021 06:56:31 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1622199296; 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=vUHBlvf58/m1+0bdfopi5k6+RO92MQelPRuJ7bCd7+c=; b=XuFNV8FqRnbdlodLX6ib8itFcXsgb32vTq8aqzwkYqSPEEVlkVYonRBoZ+0kmDCZMrjuYd m9WiltMNBiftrnAYwAuN1usMG0HggzfMeqCredlxievwNOb6vhDMiNkIibEf3eNvmsqVHX dQ8vccUkHMmNq98sVYRyayj02024smo= Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-273-tdads_FmM_2UHmrVi1uQtA-1; Fri, 28 May 2021 06:54:53 -0400 X-MC-Unique: tdads_FmM_2UHmrVi1uQtA-1 Received: by mail-ed1-f72.google.com with SMTP id da10-20020a056402176ab029038f0fea1f51so1939680edb.13 for ; Fri, 28 May 2021 03:54:52 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:in-reply-to:references:date :message-id:mime-version:content-transfer-encoding; bh=vUHBlvf58/m1+0bdfopi5k6+RO92MQelPRuJ7bCd7+c=; b=QPw3ALKufewx2AqLXegbaXtikFLMyoxgmxJXrL5Kdevsr4SLpr4mrE5VIITRpXDhW1 AHcvFlXzdHBoZ8ECiaXkMRcFYYoqgrUYttHsKmHYbfzj5gEw+GffGblqr4exiNulUVpY H9NeDv5pzZDnktWPtb/C7bCIdDuTAoGBSnpZME6vytptg10fd5gSfX87aJy94I3UjPUg YlgJIIXwVUoygrRkCa64/FNHUaUhSStw8CggBtlJbFQlu4erBFp2Hqny+U00k5jKlxgi 4kCS/ZM8eDN8fQqjFO+0xG9fJDpZ102ov+aV2gGiiWRVk/cM3yNHtzCmh3ZiVzDd7ENu 6NtA== X-Gm-Message-State: AOAM5306BDDYnnl2e04IRaxj+Jo8zP2s6QPllsDY167eIPd1rMt9f18v hHgfHghhYIWYRRtY04llpgBj0cE9RnTWWP7x+y8DD5WR84qWIW6WOyx2wMxT50GT90CnmP6F/1N z1H+ps6vt/TcO X-Received: by 2002:a05:6402:1052:: with SMTP id e18mr9377866edu.366.1622199291652; Fri, 28 May 2021 03:54:51 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzKPlowlteoA21X2ExE/xl0e23P4UV6FzqNHeU7XLx84Ru2OTIy1r7dHfxTdFmCl/doCGsmkQ== X-Received: by 2002:a05:6402:1052:: with SMTP id e18mr9377820edu.366.1622199291229; Fri, 28 May 2021 03:54:51 -0700 (PDT) Received: from alrua-x1.borgediget.toke.dk ([2a0c:4d80:42:443::2]) by smtp.gmail.com with ESMTPSA id y20sm1259600ejd.33.2021.05.28.03.54.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 28 May 2021 03:54:50 -0700 (PDT) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id 0BD9A18071B; Fri, 28 May 2021 12:54:50 +0200 (CEST) From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= To: Daniel Borkmann , Magnus Karlsson , Jesper Dangaard Brouer Cc: Xuan Zhuo , Eelco Chaudron , Lorenzo Bianconi , =?utf-8?B?QmrDtnJuIFTDtnBlbA==?= , Magnus Karlsson , Jonathan Lemon , "David S. Miller" , Jakub Kicinski , Alexei Starovoitov , John Fastabend , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , KP Singh , Willem de Bruijn , Xie He , Eric Dumazet , John Ogness , Wang Hai , Tanner Love , Eyal Birger , Menglong Dong , Network Development , bpf Subject: Re: [PATCH bpf-next] xsk: support AF_PACKET In-Reply-To: References: <87im33grtt.fsf@toke.dk> <1622192521.5931044-1-xuanzhuo@linux.alibaba.com> <20210528115003.37840424@carbon> X-Clacks-Overhead: GNU Terry Pratchett Date: Fri, 28 May 2021 12:54:49 +0200 Message-ID: <87a6ofgmbq.fsf@toke.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Daniel Borkmann writes: > On 5/28/21 12:00 PM, Magnus Karlsson wrote: >> On Fri, May 28, 2021 at 11:52 AM Jesper Dangaard Brouer >> wrote: >>> On Fri, 28 May 2021 17:02:01 +0800 >>> Xuan Zhuo wrote: >>>> On Fri, 28 May 2021 10:55:58 +0200, Toke H=C3=B8iland-J=C3=B8rgensen <= toke@redhat.com> wrote: >>>>> Xuan Zhuo writes: >>>>> >>>>>> In xsk mode, users cannot use AF_PACKET(tcpdump) to observe the curr= ent >>>>>> rx/tx data packets. This feature is very important in many cases. So >>>>>> this patch allows AF_PACKET to obtain xsk packages. >>>>> >>>>> You can use xdpdump to dump the packets from the XDP program before it >>>>> gets redirected into the XSK: >>>>> https://github.com/xdp-project/xdp-tools/tree/master/xdp-dump >>>> >>>> Wow, this is a good idea. >>> >>> Yes, it is rather cool (credit to Eelco). Notice the extra info you >>> can capture from 'exit', like XDP return codes, if_index, rx_queue. >>> >>> The tool uses the perf ring-buffer to send/copy data to userspace. >>> This is actually surprisingly fast, but I still think AF_XDP will be >>> faster (but it usually 'steals' the packet). >>> >>> Another (crazy?) idea is to extend this (and xdpdump), is to leverage >>> Hangbin's recent XDP_REDIRECT extension e624d4ed4aa8 ("xdp: Extend >>> xdp_redirect_map with broadcast support"). We now have a >>> xdp_redirect_map flag BPF_F_BROADCAST, what if we create a >>> BPF_F_CLONE_PASS flag? >>> >>> The semantic meaning of BPF_F_CLONE_PASS flag is to copy/clone the >>> packet for the specified map target index (e.g AF_XDP map), but >>> afterwards it does like veth/cpumap and creates an SKB from the >>> xdp_frame (see __xdp_build_skb_from_frame()) and send to netstack. >>> (Feel free to kick me if this doesn't make any sense) >>=20 >> This would be a smooth way to implement clone support for AF_XDP. If >> we had this and someone added AF_XDP support to libpcap, we could both >> capture AF_XDP traffic with tcpdump (using this clone functionality in >> the XDP program) and speed up tcpdump for dumping traffic destined for >> regular sockets. Would that solve your use case Xuan? Note that I have >> not looked into the BPF_F_CLONE_PASS code, so do not know at this >> point what it would take to support this for XSKMAPs. > > Recently also ended up with something similar for our XDP LB to record pc= aps [0] ;) > My question is.. tcpdump doesn't really care where the packet data comes = from, > so why not extending libpcap's Linux-related internals to either capture = from > perf RB or BPF ringbuf rather than AF_PACKET sockets? Cloning is slow, an= d if > you need to end up creating an skb which is then cloned once again inside= AF_PACKET > it's even worse. Just relying and reading out, say, perf RB you don't nee= d any > clones at all. We discussed this when creating xdpdump and decided to keep it as a separate tool for the time being. I forget the details of the discussion, maybe Eelco remembers. Anyway, xdpdump does have a "pipe pcap to stdout" feature so you can do `xdpdump | tcpdump` and get the interactive output; and it will also save pcap information to disk, of course (using pcap-ng so it can also save metadata like XDP program name and return code). -Toke