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=-8.5 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FROM_EXCESS_BASE64,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_IN_DEF_DKIM_WL 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 45656C282D7 for ; Thu, 31 Jan 2019 01:00:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 04DC520989 for ; Thu, 31 Jan 2019 01:00:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="KPUEbTMt" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729084AbfAaBAc (ORCPT ); Wed, 30 Jan 2019 20:00:32 -0500 Received: from mail-yb1-f177.google.com ([209.85.219.177]:44135 "EHLO mail-yb1-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725535AbfAaBAc (ORCPT ); Wed, 30 Jan 2019 20:00:32 -0500 Received: by mail-yb1-f177.google.com with SMTP id k189so626965yba.11 for ; Wed, 30 Jan 2019 17:00:31 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=0tVwBM/IYnl48we5vQ5ICn728BYjhpt7S0xNXioacaQ=; b=KPUEbTMtPopusPkV/VrmFOeFjOmyTpYbRdCl7yJ0T6Dvd2pcJnXkEHKi3oB1TA8x4i nCMs/zfEMEY4g5nDS5npn4tgn9UV0+pzDbXgoYyDp68hUyzc11Uy8fWt/KOtdTrVllp+ qeS1pcNQJEs81wKCrVCgjr3qoRXKDN0SAbF6c5d7+Ma8zRISIwPkiBPV3M+mNL1UN5qK oKpGgupR8ZhZ+HLWEADlAhe9SC//kx+zkISb+mqbb9yL22Knnvns5vbpgseFHuf4U3V8 dzAjdJm7pe86EaDw+sQHsxTHQNRjc7tur6CF+dp2OVhGlmzRi/hQlqRr1/EWgTUF49rp Aacg== 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:content-transfer-encoding; bh=0tVwBM/IYnl48we5vQ5ICn728BYjhpt7S0xNXioacaQ=; b=KKPxCie8O2Ld36szslMhXt7N2rxHi5Z1n6USaFEpNs89zN+9c2kSbqqv8tootwRiBe RoQlppStZKHE1PApEcLrGRTsxGJJ2WaF2xa7k1clKDwBh9kM1OohZuHWax8/jiXOynn/ /KG5OCpUMIMy+bsekjdx35P5LdPNSODlaLLNRuzJ1GRijpp02OuSVFHrhYevBi5IiMJn QY+N7Qa8qG6l6iH9gNAbZIyWMYTSEHnQKouRV4Ks+RisMpJk9mluOs7Y11P15RAjORre FOKDRAH7HvJgIbSuMsazcannVdM5XWgWQhdH4NoVQ+O8lSpTC1KQPYWJr3z5BZ7S5+jR wnXw== X-Gm-Message-State: AHQUAuburzby5KSE/CXBvi6Aj7eu4ZcKX2/FnANaCP09BFoCCZTdlR5y bN1A7D2aWw+dcjakMOlKJSisGBUMREE5gqAGmynIsw== X-Google-Smtp-Source: AHgI3IbFno6TnYYwsQwYi4qj8k4uyH5YnmfYfo6UusFliCKBpRJLiSosqrBg7NSUDeeim1ax26IJlj1uiOlANFnbyu0= X-Received: by 2002:a25:9d08:: with SMTP id i8mr2851463ybp.273.1548896430665; Wed, 30 Jan 2019 17:00:30 -0800 (PST) MIME-Version: 1.0 References: <874la1r0io.fsf@linkitivity.dja.id.au> In-Reply-To: From: =?UTF-8?B?TWFoZXNoIEJhbmRld2FyICjgpK7gpLngpYfgpLYg4KSs4KSC4KSh4KWH4KS14KS+4KSwKQ==?= Date: Wed, 30 Jan 2019 17:00:19 -0800 Message-ID: Subject: Re: Stack sends oversize UDP packet to the driver To: Michael Chan Cc: Daniel Axtens , Netdev , David Miller , Eric Dumazet , Willem de Bruijn Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, Jan 30, 2019 at 1:07 AM Michael Chan wr= ote: > > On Tue, Jan 22, 2019 at 10:29 AM Mahesh Bandewar (=E0=A4=AE=E0=A4=B9=E0= =A5=87=E0=A4=B6 =E0=A4=AC=E0=A4=82=E0=A4=A1=E0=A5=87=E0=A4=B5=E0=A4=BE=E0= =A4=B0) > wrote: > > > > > The idea behind the fix is very simple and it is to create a dst-only > > (unregistered) device with a very low MTU and use it instead of 'lo' > > while invalidating the dst. This would make it *not* forward packets > > to driver which might need fragmentation. > > > > We tested the 2 patches many times and including an overnight test. I > can confirm that the oversize UDP packets are no longer seen with the > patches applied. However, I don't see the blackhole xmit function > getting called to free the SKBs though. > Thanks for the confirmation Michael. The blackhole device mtu is really small, so I would assume the fragmentation code dropped those packets before calling the xmit function (in ip_fragment), you could verify that with icmp counters. > Thanks.