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=-0.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 E96A9C47254 for ; Wed, 6 May 2020 01:28:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B3E6A20721 for ; Wed, 6 May 2020 01:28:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="llRy4LTG" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729621AbgEFB2z (ORCPT ); Tue, 5 May 2020 21:28:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41522 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1728609AbgEFB2z (ORCPT ); Tue, 5 May 2020 21:28:55 -0400 Received: from mail-lj1-x230.google.com (mail-lj1-x230.google.com [IPv6:2a00:1450:4864:20::230]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6DB94C061A0F for ; Tue, 5 May 2020 18:28:53 -0700 (PDT) Received: by mail-lj1-x230.google.com with SMTP id f18so552932lja.13 for ; Tue, 05 May 2020 18:28:53 -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=76OtenGWAkSDUJEhLpkCek93MkRcPxXTbg0Sd3kqU9Q=; b=llRy4LTG3ab/lk6swDQC1la+cYHFSg133H9CpXMSVMeOr5VwQO5sAtLB0HcYpnhLJj +WKljabFc2WgUU9hpKaCZBuG82q5WJwfZ7bHFWe6eygGCantbbBsFCvtNCGFFUWOotX4 j96LZryxQXd8s3e9mtUxYsiwRlk4lSN25i8osVS7ryWouWCEUeaj56leUxzb0TaMcyXK 4QiJI12OuEfX8nepdgN8cVWGDQfHRAzFYIxEyAWT9P99b0BZpzp6OhrOpog3R2PyHapD nsQu9Taa4QYoNVicZQ34il/20GpkC7yjzyTwLpxRYuJ8gQlWZUn1Vin3fHGQ+9RgTJIF 7ghA== 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=76OtenGWAkSDUJEhLpkCek93MkRcPxXTbg0Sd3kqU9Q=; b=nvrl5ArrvwRYZgUvos1h/PvcI+ZMlnyPJdbq3x06h1mBjrRB5i1uv4Hly5a5oFMNLg JZvUZ1uRpdqP56HJ/n3BD56P7iWYlHJclKYHsGN36blC1NcGzlZ3TrJ9rtxspExPMnz6 qXqAmzpBXj5RDhHHSMYcctw1KV+RUPhAMzV7ug24T7MNcdeI1TP6vrLKuJ508lAAgIWK D7gPD6uf/07fy6H7AVZchu5lKa1YYcr6UIh7kQN5eovJpLVI7vPxiczkVP5nmc8Ev4gC MjgZOLuxMAeq8hOWkaDVnQW2abFuIk4mywTvHlB6N7zKX6mOPDxRjh1QWWsP+PZSu8NA Tl2g== X-Gm-Message-State: AGi0PuZuIdLuUFIbjyuofzAUOz2oo5YvL7RdT/CnPuJQv8jr6xoInHCj HVDFq05tpvwnoTl2oG/g47HOUXcT1mO7jH2wG8Y= X-Google-Smtp-Source: APiQypLcnnXMl0Z+H3hJ1JWH0v+st7MclJWLk4ZZP0Lph4Ze3BwD3+bUyp9IY7RDxA2tx2PCW5p7IrB5WbJvcwxrN2E= X-Received: by 2002:a2e:9011:: with SMTP id h17mr3561792ljg.138.1588728531943; Tue, 05 May 2020 18:28:51 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Alexei Starovoitov Date: Tue, 5 May 2020 18:28:40 -0700 Message-ID: Subject: Re: Checksum behaviour of bpf_redirected packets To: Lorenz Bauer Cc: bpf , kernel-team 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 Mon, May 4, 2020 at 9:12 AM Lorenz Bauer wrote: > > In our TC classifier cls_redirect [1], we use the following sequence > of helper calls to > decapsulate a GUE (basically IP + UDP + custom header) encapsulated packet: > > skb_adjust_room(skb, -encap_len, > BPF_ADJ_ROOM_MAC, BPF_F_ADJ_ROOM_FIXED_GSO) > bpf_redirect(skb->ifindex, BPF_F_INGRESS) > > It seems like some checksums of the inner headers are not validated in > this case. > For example, a TCP SYN packet with invalid TCP checksum is still accepted by the > network stack and elicits a SYN ACK. > > Is this known but undocumented behaviour or a bug? In either case, is > there a work > around I'm not aware of? I thought inner and outer csums are covered by different flags and driver suppose to set the right one depending on level of in-hw checking it did.