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=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 0555FC43470 for ; Thu, 20 May 2021 10:59:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DA8C6610A1 for ; Thu, 20 May 2021 10:59:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239785AbhETLA2 convert rfc822-to-8bit (ORCPT ); Thu, 20 May 2021 07:00:28 -0400 Received: from mail-n.franken.de ([193.175.24.27]:38870 "EHLO drew.franken.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S239033AbhETK5P (ORCPT ); Thu, 20 May 2021 06:57:15 -0400 Received: from smtpclient.apple (ip4d15f626.dynamic.kabel-deutschland.de [77.21.246.38]) (Authenticated sender: macmic) by mail-n.franken.de (Postfix) with ESMTPSA id 3A358721A5A7E; Thu, 20 May 2021 01:10:24 +0200 (CEST) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 14.0 \(3654.80.0.2.43\)) Subject: Re: add SPP_PLPMTUD_ENABLE/DISABLE flag for spp_flags From: Michael Tuexen In-Reply-To: Date: Thu, 20 May 2021 01:10:23 +0200 Cc: "linux-sctp @ vger . kernel . org" , Marcelo Ricardo Leitner Content-Transfer-Encoding: 8BIT Message-Id: <2C01CE13-6562-4B7C-A49B-4ADD2B6017A4@freebsd.org> References: <81B0ED00-D281-445B-83C7-7BE65DC0FD8E@freebsd.org> <8C3219EB-1BEF-4F96-B881-8BDCA2EC98EE@freebsd.org> To: Xin Long X-Mailer: Apple Mail (2.3654.80.0.2.43) Precedence: bulk List-ID: X-Mailing-List: linux-sctp@vger.kernel.org > On 19. May 2021, at 20:44, Xin Long wrote: > > On Wed, May 19, 2021 at 2:15 PM Michael Tuexen wrote: >> >>> On 19. May 2021, at 18:18, Xin Long wrote: >>> >>> On Tue, May 18, 2021 at 2:33 PM Xin Long wrote: >>>> >>>> On Tue, May 18, 2021 at 1:38 PM Michael Tuexen wrote: >>>>> >>>>>> On 18. May 2021, at 18:43, Xin Long wrote: >>>>>> >>>>>> Hi, Michael, >>>>>> >>>>>> We're implementing RFC8899 (PLPMTUD) on Linux SCTP recently, >>>>>> and to make this be controlled by setsockopt with >>>>>> SCTP_PEER_ADDR_PARAMS, as in >>>>>> >>>>>> https://datatracker.ietf.org/doc/html/rfc6458#section-8.1.12: >>>>>> >>>>>> we need another two flags to add for spp_flags: >>>>>> >>>>>> SPP_PLPMTUD_ENABLE >>>>>> SPP_PLPMTUD_DISABLE >>>>>> >>>>>> Do you think it makes sense? if yes, does the RFC6458 need to update? >>>>>> if not, do you have a better suggestion for it? >>>>> It is great new that you want to implement RFC 8899. I plan to do the >>>>> same for the FreeBSD stack. >>>>> >>>>> In my view, RFC 8899 is the right way to implement PMTU discovery. >>>>> So I will just use the SPP_PMTUD_ENABLE and SPP_PMTUD_DISABLE. I don't >>>>> think that the user needs to control which method is used. >>>>> I you want to support multiple versions, I would make that >>>>> controllable via a sysctl variable. But I think for FreeBSD, support >>>>> for RFC 8899 will be the only way of doing PMTU discovery. There >>>>> might be multiple choices for details like how to do the searching, >>>>> how long to wait for some events. These will be controllable via >>>>> sysctl. >>>>> >>>>> So in my view, there is no need to extend the socket API. What do you think? >>> I just noticed that with multiple versions supported, and without extending >>> this API, all applications will have to use the same version as it's >>> controlled by >>> sysctl. And when switching to another version by sysctl, all >>> applications will be >>> affected and have to do the switch. that seems not nice. >> That is true, but an application can not expect any specific behaviour >> right now when they are not disabling PMTUD. >> >> What about adding a sysctl variable, which defines the default >> algorithm and a socket option, which allows to get and set >> the algorithm being used. > yes, that's also what I'm thinking. > sysctl is always used for the default value for future sockets. > and the socket option should be added for a socket/asoc's setting. > > SCTP_PTMUD_METHOD? OK. > 0: PTB one I don't know what the above would mean. Not sure anything is really specified. > 1. PLPMTUD I guess you would need an struct sctp_assoc_value here. Maybe some constants such as: SCTP_PMTU_CLASSIC SCTP_PMTU_NEW or SCTP_PMTU_RFC_8899 Best regards Michael > >> >> Best regards >> Michael >>> >>>> OK, that makes sense to me. >>>> >>>> Another thing I want to know your opinion on is: do you think the HB >>>> should be created >>>> separately for PLPMTUD probe, instead of reusing the old HB that >>>> checks the link connectivity? >>>> As the HB for PLPMTUD probe might get lost, which we don't want to >>>> affect the link's >>>> connectivity. >>>> >>>>> >>>>> Best regards >>>>> Michael >>>>>> >>>>>> Thanks. >>>>> >>