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=-3.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 60078C43331 for ; Thu, 2 Apr 2020 15:40:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 32B8E2080C for ; Thu, 2 Apr 2020 15:40:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="QiJY6vAF" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389349AbgDBPkh (ORCPT ); Thu, 2 Apr 2020 11:40:37 -0400 Received: from mail-lf1-f65.google.com ([209.85.167.65]:34162 "EHLO mail-lf1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388972AbgDBPkh (ORCPT ); Thu, 2 Apr 2020 11:40:37 -0400 Received: by mail-lf1-f65.google.com with SMTP id e7so3144533lfq.1; Thu, 02 Apr 2020 08:40:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=1+2erfkkbu3TLnQgP4FNOMyrP6eIdZu6/WJPUCTbdAA=; b=QiJY6vAFVaADxgmOmeE784cvy5UzSNFL7qXv9U7OiG/ZMEuwa2vEwY6vVWcaccQ7na GbAEDP+GKI/k7Z4eVfyfmSz10A/spb4g63pOAA3oq6T/nxAAd3YUVZOuzoqxoF3wW+PZ qFpyF74CkGNiCdMXkCbmmeBtF20TG/+rjyFJSvz4kQY/Euvsp7hRzDziIIm0nnx9VHw/ j37WbJT9HhQEk3LDifhUHXz33V1hGVfNvTalDT9wQtshYzrIjXb72WeZPCKw2+9LATR4 8/6cxXD8+ZnYsyxq2OTIkr6OKTFV3DJOYwoLKFDF0/QHs1li4pbHyfpO2TP66E/0SDuZ hxeQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=1+2erfkkbu3TLnQgP4FNOMyrP6eIdZu6/WJPUCTbdAA=; b=UWKsQ/EjjHANV9fLPgBni5oyPbDuTlHhQ7B8wH9bW+p1Q45etwe9a2FOLVkUNUMVwG W30k76KOx3JjcoffDPv7ki0pITqam0iQPabpmw5peoFqbgZoKsc2e3zLIOmWvnvVMcHj fLKazb0hpYPmrsuvJA7R5nWhb9trTj1ptwUGsZXSuU71n5GN2eZDT+XG0UvRgKyVYLxT Qtl4PH9QudOew7it/NY9BgHM0q1pSuFj/mJP7dlq7psaU5SRp3jhALwjwMbET3Z4ftGk 7TCNx26wLUSlpC9QPJJECnhhTt/6WaMDTB8RisjQLyr9h0lQw+6sPwHtinIjqy15PN4Y 5g0w== X-Gm-Message-State: AGi0PuaaMPw8GauXvn0zkVSKsxgM5ie5/7v0dnmfT58q5A6gOTCERg1I US9GSYayGON622+QjrYpVqotdirxuNQmKxKsZ88= X-Google-Smtp-Source: APiQypIdvYJc6O/exwVrWe6ToU6iOSXmBNO1FTBzi81ghhxfIzKlP+jfokCDAjIOMT0OgNS+I5in+pfDYpMcW1SGxZc= X-Received: by 2002:a19:40ca:: with SMTP id n193mr2503030lfa.196.1585842035185; Thu, 02 Apr 2020 08:40:35 -0700 (PDT) MIME-Version: 1.0 References: <20200331060641.79999-1-maowenan@huawei.com> <7a1d55ad-1427-67fe-f204-4d4a0ab2c4b1@gmail.com> <20200401181419.7acd2aa6@carbon> <20200402110619.48f31a63@carbon> In-Reply-To: <20200402110619.48f31a63@carbon> From: Alexei Starovoitov Date: Thu, 2 Apr 2020 08:40:23 -0700 Message-ID: Subject: Re: [PATCH net v2] veth: xdp: use head instead of hard_start To: Jesper Dangaard Brouer Cc: Toshiaki Makita , Mao Wenan , "David S. Miller" , Alexei Starovoitov , Daniel Borkmann , Jakub Kicinski , Jesper Dangaard Brouer , John Fastabend , Martin KaFai Lau , Song Liu , Yonghong Song , Andrii Nakryiko , jwi@linux.ibm.com, jianglidong3@jd.com, Eric Dumazet , Network Development , LKML , bpf , kernel-janitors@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Thu, Apr 2, 2020 at 2:06 AM Jesper Dangaard Brouer wrote: > > On Thu, 2 Apr 2020 09:47:03 +0900 > Toshiaki Makita wrote: > > > On 2020/04/02 1:15, Jesper Dangaard Brouer wrote: > > ... > > > [PATCH RFC net-next] veth: adjust hard_start offset on redirect XDP frames > > > > > > When native XDP redirect into a veth device, the frame arrives in the > > > xdp_frame structure. It is then processed in veth_xdp_rcv_one(), > > > which can run a new XDP bpf_prog on the packet. Doing so requires > > > converting xdp_frame to xdp_buff, but the tricky part is that > > > xdp_frame memory area is located in the top (data_hard_start) memory > > > area that xdp_buff will point into. > > > > > > The current code tried to protect the xdp_frame area, by assigning > > > xdp_buff.data_hard_start past this memory. This results in 32 bytes > > > less headroom to expand into via BPF-helper bpf_xdp_adjust_head(). > > > > > > This protect step is actually not needed, because BPF-helper > > > bpf_xdp_adjust_head() already reserve this area, and don't allow > > > BPF-prog to expand into it. Thus, it is safe to point data_hard_start > > > directly at xdp_frame memory area. > > > > > > Cc: Toshiaki Makita > > > > FYI: This mail address is deprecated. > > > > > Fixes: 9fc8d518d9d5 ("veth: Handle xdp_frames in xdp napi ring") > > > Reported-by: Mao Wenan > > > Signed-off-by: Jesper Dangaard Brouer > > > > FWIW, > > > > Acked-by: Toshiaki Makita > > Thanks. > > I have updated your email and added your ack in my patchset. I will > submit this officially once net-next opens up again[1], as part my > larger patchset for introducing XDP frame_sz. It looks like bug fix to me. The way I read it that behavior of bpf_xdp_adjust_head() is a bit buggy with veth netdev, so why wait ?