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=-9.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 CAD8AC433B4 for ; Tue, 11 May 2021 03:06:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9981C6144F for ; Tue, 11 May 2021 03:06:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230005AbhEKDHF (ORCPT ); Mon, 10 May 2021 23:07:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36084 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229465AbhEKDHD (ORCPT ); Mon, 10 May 2021 23:07:03 -0400 Received: from mail-oi1-x22f.google.com (mail-oi1-x22f.google.com [IPv6:2607:f8b0:4864:20::22f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B0BD3C061574; Mon, 10 May 2021 20:05:57 -0700 (PDT) Received: by mail-oi1-x22f.google.com with SMTP id c3so17696719oic.8; Mon, 10 May 2021 20:05:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=JnHqVVEfRTu9JkoWKbT89biz9F5E98u3YQefU6ToVJs=; b=IHDqgZVX8rwjXdiEQWd77E0h7YLUDnGNSHmDHPDRPX8+EMCxTkKC32U3k1YJVV9YxG MmGR6aoMgrHvHafjfpNZD83B6pCe51ND0t91/NvETI/VJANZADGzAzrBKtGgW4GzwTUZ 69CLIp2DHIK0Y/yp254IPIM/FWsL0jyTqZYif2IncazNeCpBQ9szradgdIFLUTDdw1+d 0588UdAxo41V/3Rsikw6uwKVD5/2d9s0iANQ9emxlvgAAmmAdulVHvRFyc07a4JW7kgv YAGKQGMkvxZRo096wDGq5R+ad347kHBUF81JA56pnZBK8axyoeqmYv37PL0BUwCEzWqv x8sA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=JnHqVVEfRTu9JkoWKbT89biz9F5E98u3YQefU6ToVJs=; b=MK2PCJQAILwBi5SBS7qP9clIynLp288iz0IfABTrnwbflOi7qkg4c0gSXMKAW2rktY hwJzdIEs1kIBeV29jlT13VMp2ZEGzAMjvLSgmprYr1XRAhgj9lXn7B5Mvzdrv+uum5Sm BGQEIMVWupoEmQcp2IaSqNoD4IoTKvLqI0qhWMpnDBiXUGBWV9l5ZAYzlxL58P40GPTO CwLuWUBergWSFCNQcpOn4gVnEsRCLWFICnjIrTc1c3ZgXstp4KqE9nq5Sh8kSTByHJFJ IJ6YvfEAjGh2e7x0IBqyhtlb6Wqf+QNGiW1Ompk44VK6yMdwUGkMPIjQWddUnhS1F7bP VTtw== X-Gm-Message-State: AOAM533rDKjbo/rdCvmeV4ogrjKF5MwCqRwSmIpFsFQOY3WwOxurYE5H Zj4jcdwX9y2mteAKPr3C5EK4zmlxnvBmjg== X-Google-Smtp-Source: ABdhPJzrxBcF+IhTlgsq620YFfreAbh7Vmr1yslK2IAm/T1PEFwxTfAN3W5RsdH60tzMIFwGNzGMcQ== X-Received: by 2002:aca:d493:: with SMTP id l141mr1855190oig.51.1620702357025; Mon, 10 May 2021 20:05:57 -0700 (PDT) Received: from Davids-MacBook-Pro.local ([8.48.134.33]) by smtp.googlemail.com with ESMTPSA id z4sm3473871otq.65.2021.05.10.20.05.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 10 May 2021 20:05:56 -0700 (PDT) Subject: Re: [PATCH] net/ipv4/ip_fragment:fix missing Flags reserved bit set in iphdr To: meijusan , Jakub Kicinski Cc: davem@davemloft.net, yoshfuji@linux-ipv6.org, dsahern@kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20210506145905.3884-1-meijusan@163.com> <20210507155900.43cd8200@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> <1368d6c3.bd1.1795900a467.Coremail.meijusan@163.com> From: David Ahern Message-ID: <28dfa69f-2844-29c4-5405-421520711196@gmail.com> Date: Mon, 10 May 2021 21:05:54 -0600 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: <1368d6c3.bd1.1795900a467.Coremail.meijusan@163.com> Content-Type: text/plain; charset=gbk Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/10/21 7:18 PM, meijusan wrote: > > At 2021-05-08 06:59:00, "Jakub Kicinski" wrote: >> On Thu, 6 May 2021 22:59:05 +0800 meijusan wrote: >>> ip frag with the iphdr flags reserved bit set,via router,ip frag reasm or >>> fragment,causing the reserved bit is reset to zero. >>> >>> Keep reserved bit set is not modified in ip frag defrag or fragment. >>> >>> Signed-off-by: meijusan >> >> Could you please provide more background on why we'd want to do this? > >> Preferably with references to relevant (non-April Fools' Day) RFCs. > > [background] > the Simple network usage scenarios: the one PC software<--->linux router(L3)/linux bridege(L2,bridge-nf-call-iptables)<--->the other PC software > 1)the PC software send the ip packet with the iphdr flags reserved bit is set, when ip packet(not fragments ) via the one linux router/linux bridge,and the iphdr flags reserved bit is not modified; > 2)but the ip fragments via router,the linux IP reassembly or fragmentation ,causing the reserved bit is reset to zero,Which leads to The other PC software depending on the reserved bit set process the Packet failed. > [rfc] > RFC791 > Bit 0: reserved, must be zero > RFC3514 > Introduction This bit , but The scene seems different from usŁ¬we expect Keep reserved bit set is not modified when forward the linux router > > > > > Why process the packet at all? If a reserved bit must be 0 and it is not, drop the packet.