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=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS 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 B42D7C43381 for ; Mon, 25 Feb 2019 16:39:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7361520684 for ; Mon, 25 Feb 2019 16:39:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="qmKrCewy" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728138AbfBYQjb (ORCPT ); Mon, 25 Feb 2019 11:39:31 -0500 Received: from mail-pf1-f194.google.com ([209.85.210.194]:38011 "EHLO mail-pf1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728076AbfBYQja (ORCPT ); Mon, 25 Feb 2019 11:39:30 -0500 Received: by mail-pf1-f194.google.com with SMTP id n125so4751249pfn.5 for ; Mon, 25 Feb 2019 08:39:30 -0800 (PST) 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=DJebk0VDOz7KMQ6CPWGfqiFTVPVm05W8cBYcRHeOn5M=; b=qmKrCewygVdaO4gbcvTmbcnKOz3z63+yIdmxpkPfg1F5DFvK18idq9rjAYo1/A+bMe npc7ZZsPMOgDLu3qBPUA698uyYK3qkNIfTKc2ai1fDSLxbv9/O6im8O2iV5NNdiGqmvV kfdD3lO1Cxu8Y7M/CVPvOmNOIfDz7XlsWHYgIcT4GqxQV1FaSbPVT9uUJ/obE0ZkT3dV AzIVEwtaH1YvaEl5Gi7ogtSB6/CQekV95QaZlMGjUP1UQHidw0Jg2IyGqYha84CG1h16 o1WJACRq58P9m4rrXYa9ZUH8T3SIZHWIGeEG1Ur4h6pQwlZvtti53Vl50xtx8ln8DmPA VSXg== 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=DJebk0VDOz7KMQ6CPWGfqiFTVPVm05W8cBYcRHeOn5M=; b=jquBqjVQLZuv0Efh5ZKjYB69eobb7wVpbhIbNzl9k8J4CV0erYNsmyjYcAS6zDPlpN kAV3DeOd7YMefzpFPVDjttKUq8Zk/pVVp2qXGECBEo5nTS3/0KT4mGXY2JVAFB3uEdtn bOl/Kg5hrgcVsyq8vZFFTYZWHwAjDMe1LpNksI+crsEZUAGKAWI0kkuvpgz1R1vcJZc5 t7X4GIAsSrcs2g9Gw5tAj3Q5OMsyEDR+8KO4D2gmHFYKz/nmCj687kZG614vx/EesRsP +R9imqHcsh90KPQ9Wl+394vGnoOnhNmTXa/5pvoZuWU78OZvfJFO0cv8h6PVpcfFgnFN FFdg== X-Gm-Message-State: AHQUAuZL2wKWl18UdvzisxtA7xXV4oPKcIUiA2hTjojW15FYb1souWGm cRuB1cNzImXkSjzp4MJ/YW4= X-Google-Smtp-Source: AHgI3IZpRC1MfJmu+nT8PSmTfAtxtop7jShF3d12CVyrohpNpV0qv8NcIhmRasWFZBdFpc5U1V7HCw== X-Received: by 2002:a63:8341:: with SMTP id h62mr20106318pge.254.1551112769707; Mon, 25 Feb 2019 08:39:29 -0800 (PST) Received: from ?IPv6:2620:15c:2c1:200:55c7:81e6:c7d8:94b? ([2620:15c:2c1:200:55c7:81e6:c7d8:94b]) by smtp.gmail.com with ESMTPSA id n4sm15896663pfh.8.2019.02.25.08.39.28 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 25 Feb 2019 08:39:28 -0800 (PST) Subject: Re: [PATCH net] sit: use ipv6_mod_enabled to check if ipv6 is disabled To: Hangbin Liu Cc: netdev@vger.kernel.org, Stefano Brivio , "David S . Miller" , David Ahern References: <20190225041243.9753-1-liuhangbin@gmail.com> <7c0f5c9c-d918-de27-643d-416509576be4@gmail.com> <20190225081759.GP10051@dhcp-12-139.nay.redhat.com> From: Eric Dumazet Message-ID: <1dd57d9d-fed2-67b8-ac28-7ef3681eeed2@gmail.com> Date: Mon, 25 Feb 2019 08:39:27 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20190225081759.GP10051@dhcp-12-139.nay.redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 02/25/2019 12:17 AM, Hangbin Liu wrote: > On Sun, Feb 24, 2019 at 08:24:51PM -0800, Eric Dumazet wrote: >> >> >> On 02/24/2019 08:12 PM, Hangbin Liu wrote: >>> ipv6_mod_enabled() is more safe and gentle to check if ipv6 is disabled >>> at running time. >>> >> >> >> Why is it better exactly ? >> >> IPv6 can be enabled on the host, but disabled per device >> >> /proc/sys/net/ipv6/conf/{name}/disable_ipv6 > > Sorry, it looks I didn't make it clear in the commit description. > This issue only occurs when IPv6 is disabled at boot time as there is > no IPv6 route entry. Disable ipv6 on specific interface is not affected. > So check ipv6_mod_enabled() is enough and we don't need to worry about > the rcu_read_lock or the dev status. > > Should I update the commit description? Certainly. Are you telling us skb->dev could be NULL here ? Because rcu_read_lock() should already be asserted.