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=-2.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 99BFBC433ED for ; Thu, 20 May 2021 15:13:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7361A61163 for ; Thu, 20 May 2021 15:13:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232434AbhETPPM (ORCPT ); Thu, 20 May 2021 11:15:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37660 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232348AbhETPPL (ORCPT ); Thu, 20 May 2021 11:15:11 -0400 Received: from mail-wr1-x42b.google.com (mail-wr1-x42b.google.com [IPv6:2a00:1450:4864:20::42b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0B3ABC061574 for ; Thu, 20 May 2021 08:13:49 -0700 (PDT) Received: by mail-wr1-x42b.google.com with SMTP id r12so18068315wrp.1 for ; Thu, 20 May 2021 08:13:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=0bPmHYyl8QxCLfhtZIq65woICBYsW2OqgoD7ojR90/Q=; b=qgFs8CFf7S/AYEgF8F1eGvEESmsFyVcZZujlNHwJQ/WWzjarGIEeJxk8K1fdN4UDwY YkQrJn4iGe05B/585iSSvGpXtj7y+dd4AArR5kLMtWtU6sN1XfJaOy3crn8vv8rKXN/i +1eNtghiCBiaG2a5PK814njS5MBIDAhQoVC6S2oaxNi3MUjjcmqdoTr9J6L0XFg+EXni rvtwu4HxnyzknUcNV8jEvJ9sK8FmGA+J38pPav3q6Sh8HAH4d2wc++S/3fEVKjEd4DLq jvd1gbNxVtrZ/V+vWWcRz8rQPKKCVFYreoFsaZ3h+IR3zHyoh2CGqBHsOmPDtakUQFDi FkhQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=0bPmHYyl8QxCLfhtZIq65woICBYsW2OqgoD7ojR90/Q=; b=UoyN/fia6f9w9Z3wSjh7126U58+Rqj+aKb5HvsUxWkzN3Zn1QqYfbYQTi1+Avv8a7v 3t6mAX8LWLgTkB9mRtiTtMfsJCKP8TpTwn7LoqnFuFrIstTvxVvotlvLKRGvwigaiYEi UU5wfDzjwFe/jSDhpcTCHdUT+v+YZipkuWKHprrAIE5SiJB5Pg9TmSB6/VkLIRZtLI73 EjYug+CsBdujOWS0bGHP7Hc3oKQmrbt1zDB2DQeQ0Kzys2bHebQRh4BZa4hGUaQdLFaR joRuWjjPzt7ECXsctA8BJACUUHmmiv6Ylg4V7NSY/L1+U1cU/guoYwLJdz1yK22wOrkz KHug== X-Gm-Message-State: AOAM530bwpWpMcu54n4NNkDBggnDwYLF+y0yo/KjexIju0G4VrCz7h9U gGIc3CSFPbVaxPvwx4dDz+C0u6HHK27WBU3FPn6BYd6uafENJ4DN X-Google-Smtp-Source: ABdhPJw4eiksYP5Wy+f4nY3ZTLwLKbaohw0C71tsZnlwhKdv7lGaQR3HNGKa1Gq1mSrdF1uzAcokp0FdV6gKEgRmrF4= X-Received: by 2002:adf:b64b:: with SMTP id i11mr4882267wre.157.1621523627554; Thu, 20 May 2021 08:13:47 -0700 (PDT) MIME-Version: 1.0 References: <81B0ED00-D281-445B-83C7-7BE65DC0FD8E@freebsd.org> <364C37C5-5828-401C-BDD0-F345B288CE81@freebsd.org> In-Reply-To: <364C37C5-5828-401C-BDD0-F345B288CE81@freebsd.org> From: Xin Long Date: Thu, 20 May 2021 11:13:35 -0400 Message-ID: Subject: Re: add SPP_PLPMTUD_ENABLE/DISABLE flag for spp_flags To: Michael Tuexen Cc: Marcelo Ricardo Leitner , "linux-sctp @ vger . kernel . org" , =?UTF-8?B?VGltbyBWw7Zsa2Vy?= Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-sctp@vger.kernel.org On Thu, May 20, 2021 at 3:06 AM wrote: > > > On 20. May 2021, at 04:05, Xin Long wrote: > > > > On Wed, May 19, 2021 at 6:24 PM wrote: > >> > >> On Tue, May 18, 2021 at 09:19:21PM +0200, Michael Tuexen wrote: > >>> > >>> > >>>> On 18. May 2021, at 20:33, 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? > >>>> 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? > >>> Yes. I think testing for connectivity is conceptually different > >>> from testing a particular PMTU. When testing for PMTU, I think > >>> about sending probe packets. Not that they consist of a HB chunk > >>> bundled with a PAD chunk. > >>>> As the HB for PLPMTUD probe might get lost, which we don't want to > >>>> affect the link's > >>>> connectivity. > >>> Yes, I agree completely. > >> > >> With this, Xin, seems we should have a separate timer for the > >> PROBE_TIMER, other than the heartbeat one. > >> > >> Otherwise, converging the two logics into one single timer is not > >> worth the hassle for saving a timer. For example, we would have to > >> have it fire on the active transport but to send only the probe. > >> Also, considering they can and (AFAIU the RFC) should have different > >> expire timeouts from time to time. > >> > >> With a separate timer, we won't have issues converging the > >> user-selectable heartbeat interval to the recommended 600s > >> PMTU_RAISE_TIMER, for example. > >> > >> Maybe I am missing something. But it seems the hassle for reusing the > >> timer here is just not worth it. Thoughts? > > You're right, when I was doing testing, I had to set the hb_interval to 5s. > > the common value of hb_interval really doesn't fit in the probe_interval. > > I will try adding a new timer, but at the same time a probe_interval > > by sysctl/sockopt may be needed, or we can use a value equal to > > (hb_interval / n) for it? > Yeah, this is why I did not write a socket API section for RFC 8899. I think > when implementing it, one will find some parameters which can or should > be controlled by the application. So I guess there will be more than this > one. > > Timo (CCed) is working on some algorithmic explorations, since RFC 8899, gives > you some freedom. Right now, his work is done in a simulation environment, but > once that is finished and he came to some conclusions, we will implement this. > > So what about: > > * Try to implement PLPMTUD and figure out what you need as user controllable > parameters. > * Bring this up for discussion and we can agree on them and also on how > to control them via socket options. > * Then you get the code into the Linux tree. > > That way we would know what parameters are really needed in an implementation > and we would have a common interface. Makes sense. > > Does that make sense to you and sounds like an acceptable plan? That sounds a good plan, :-) Thanks. > > Best regards > Michael > > > >> > >> Best, > >> Marcelo > >> > >>> > >>> Best regards > >>> Michael > >>>> > >>>>> > >>>>> Best regards > >>>>> Michael > >>>>>> > >>>>>> Thanks. > >>>>> > >>> > >> >