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=-3.9 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 25FA2C65BAE for ; Thu, 13 Dec 2018 05:42:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E6B4120870 for ; Thu, 13 Dec 2018 05:42:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E6B4120870 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=davemloft.net Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726936AbeLMFmY (ORCPT ); Thu, 13 Dec 2018 00:42:24 -0500 Received: from shards.monkeyblade.net ([23.128.96.9]:47236 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726226AbeLMFmY (ORCPT ); Thu, 13 Dec 2018 00:42:24 -0500 Received: from localhost (unknown [IPv6:2601:601:9f80:35cd::bf5]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) (Authenticated sender: davem-davemloft) by shards.monkeyblade.net (Postfix) with ESMTPSA id 9D49814B3D316; Wed, 12 Dec 2018 21:42:23 -0800 (PST) Date: Wed, 12 Dec 2018 21:42:23 -0800 (PST) Message-Id: <20181212.214223.211216727717464391.davem@davemloft.net> To: mkubecek@suse.cz Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, posk@google.com, eric.dumazet@gmail.com, gfigueira@suse.com Subject: Re: [PATCH net] net: ipv4: do not handle duplicate fragments as overlapping From: David Miller In-Reply-To: <20181213022800.9D298E1116@unicorn.suse.cz> References: <20181213022800.9D298E1116@unicorn.suse.cz> X-Mailer: Mew version 6.8 on Emacs 26.1 Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Wed, 12 Dec 2018 21:42:23 -0800 (PST) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Michal Kubecek Date: Thu, 13 Dec 2018 03:28:00 +0100 (CET) > Since commit 7969e5c40dfd ("ip: discard IPv4 datagrams with overlapping > segments.") IPv4 reassembly code drops the whole queue whenever an > overlapping fragment is received. However, the test is written in a way > which detects duplicate fragments as overlapping so that in environments > with many duplicate packets, fragmented packets may be undeliverable. > > Add an extra test and for (potentially) duplicate fragment, only drop the > new fragment rather than the whole queue. Only starting offset and length > are checked, not the contents of the fragments as that would be too > expensive. Check for duplicity with last (tail) fragment first as in real > life scenarios this should be the most frequent case and we would have to > iterate through the whole "run" otherwise. > > Fixes: 7969e5c40dfd ("ip: discard IPv4 datagrams with overlapping segments.") > Signed-off-by: Michal Kubecek I'll give Eric a chance to review this, thanks Michal.