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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,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 AAE56C35280 for ; Fri, 8 May 2020 00:30:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8FFF1208E4 for ; Fri, 8 May 2020 00:30:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726797AbgEHAaG convert rfc822-to-8bit (ORCPT ); Thu, 7 May 2020 20:30:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58230 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1726480AbgEHAaG (ORCPT ); Thu, 7 May 2020 20:30:06 -0400 Received: from shards.monkeyblade.net (shards.monkeyblade.net [IPv6:2620:137:e000::1:9]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 586ABC05BD43 for ; Thu, 7 May 2020 17:30:06 -0700 (PDT) Received: from localhost (unknown [IPv6:2601:601:9f00:477::d71]) (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 D9EC61193B1AA; Thu, 7 May 2020 17:30:05 -0700 (PDT) Date: Thu, 07 May 2020 17:30:04 -0700 (PDT) Message-Id: <20200507.173004.1881498730999455740.davem@davemloft.net> To: zenczykowski@gmail.com Cc: maze@google.com, netdev@vger.kernel.org, edumazet@google.com, willemb@google.com, lucien.xin@gmail.com, hannes@stressinduktion.org Subject: Re: [PATCH] Revert "ipv6: add mtu lock check in __ip6_rt_update_pmtu" From: David Miller In-Reply-To: <20200505185723.191944-1-zenczykowski@gmail.com> References: <20200505185723.191944-1-zenczykowski@gmail.com> X-Mailer: Mew version 6.8 on Emacs 26.3 Mime-Version: 1.0 Content-Type: Text/Plain; charset=iso-8859-2 Content-Transfer-Encoding: 8BIT X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Thu, 07 May 2020 17:30:06 -0700 (PDT) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Maciej Żenczykowski Date: Tue, 5 May 2020 11:57:23 -0700 > From: Maciej Żenczykowski > > This reverts commit 19bda36c4299ce3d7e5bce10bebe01764a655a6d: > > | ipv6: add mtu lock check in __ip6_rt_update_pmtu > | > | Prior to this patch, ipv6 didn't do mtu lock check in ip6_update_pmtu. > | It leaded to that mtu lock doesn't really work when receiving the pkt > | of ICMPV6_PKT_TOOBIG. > | > | This patch is to add mtu lock check in __ip6_rt_update_pmtu just as ipv4 > | did in __ip_rt_update_pmtu. > > The above reasoning is incorrect. IPv6 *requires* icmp based pmtu to work. > There's already a comment to this effect elsewhere in the kernel: > > $ git grep -p -B1 -A3 'RTAX_MTU lock' > net/ipv6/route.c=4813= > > static int rt6_mtu_change_route(struct fib6_info *f6i, void *p_arg) > ... > /* In IPv6 pmtu discovery is not optional, > so that RTAX_MTU lock cannot disable it. > We still use this lock to block changes > caused by addrconf/ndisc. > */ > > This reverts to the pre-4.9 behaviour. > > Signed-off-by: Maciej Żenczykowski > Fixes: 19bda36c4299 ("ipv6: add mtu lock check in __ip6_rt_update_pmtu") I've thought about this some more and decided to apply this and queue it up for -stable, thank you.