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 B4BCBC433ED for ; Tue, 18 May 2021 19:19:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8D18A61353 for ; Tue, 18 May 2021 19:19:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231236AbhERTUp convert rfc822-to-8bit (ORCPT ); Tue, 18 May 2021 15:20:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36584 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245640AbhERTUo (ORCPT ); Tue, 18 May 2021 15:20:44 -0400 Received: from drew.franken.de (drew.ipv6.franken.de [IPv6:2001:638:a02:a001:20e:cff:fe4a:feaa]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A8080C061573 for ; Tue, 18 May 2021 12:19:26 -0700 (PDT) Received: from smtpclient.apple (unknown [IPv6:2a02:8109:1140:c3d:e0c4:9f6d:2867:98f4]) (Authenticated sender: macmic) by drew.franken.de (Postfix) with ESMTPSA id EB24F721E2806; Tue, 18 May 2021 21:19:23 +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: Tue, 18 May 2021 21:19:21 +0200 Cc: "linux-sctp @ vger . kernel . org" , Marcelo Ricardo Leitner Content-Transfer-Encoding: 8BIT Message-Id: References: <81B0ED00-D281-445B-83C7-7BE65DC0FD8E@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 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. Best regards Michael > >> >> Best regards >> Michael >>> >>> Thanks. >>