From owner-freebsd-net@freebsd.org Mon Dec 23 11:08:38 2019 Return-Path: Delivered-To: freebsd-net@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id BDB1C1ECAD6 for ; Mon, 23 Dec 2019 11:08:38 +0000 (UTC) (envelope-from eugen@grosbein.net) Received: from hz.grosbein.net (hz.grosbein.net [IPv6:2a01:4f8:c2c:26d8::2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "hz.grosbein.net", Issuer "hz.grosbein.net" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 47hGn11Ct3z4WVl; Mon, 23 Dec 2019 11:08:36 +0000 (UTC) (envelope-from eugen@grosbein.net) Received: from eg.sd.rdtc.ru (eg.sd.rdtc.ru [IPv6:2a03:3100:c:13:0:0:0:5]) by hz.grosbein.net (8.15.2/8.15.2) with ESMTPS id xBNB8SYX050679 (version=TLSv1.2 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 23 Dec 2019 11:08:31 GMT (envelope-from eugen@grosbein.net) X-Envelope-From: eugen@grosbein.net X-Envelope-To: bu7cher@yandex.ru Received: from [10.58.0.4] ([10.58.0.4]) by eg.sd.rdtc.ru (8.15.2/8.15.2) with ESMTPS id xBNB8OZr089706 (version=TLSv1.2 cipher=DHE-RSA-AES128-SHA bits=128 verify=NOT); Mon, 23 Dec 2019 18:08:24 +0700 (+07) (envelope-from eugen@grosbein.net) Subject: Re: IPSec transport mode, mtu, fragmentation... To: "Andrey V. Elsukov" , Victor Sudakov References: <20191220152314.GA55278@admin.sibptus.ru> <20191220160357.GB56081@admin.sibptus.ru> <20191220162233.GA56815@admin.sibptus.ru> <55eeca4c-9633-339a-f521-b0db462cc1d6@yandex.ru> <20191223100655.GA41651@admin.sibptus.ru> <3edbc7ad-a760-48c7-3222-202d7a835fe5@yandex.ru> <35fd51d5-c171-c97c-5bb2-529912d75844@grosbein.net> Cc: freebsd-net@freebsd.org, Michael Tuexen From: Eugene Grosbein Message-ID: Date: Mon, 23 Dec 2019 18:08:16 +0700 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=0.3 required=5.0 tests=BAYES_00,LOCAL_FROM, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.2 X-Spam-Report: * -2.3 BAYES_00 BODY: Bayes spam probability is 0 to 1% * [score: 0.0000] * -0.0 SPF_PASS SPF: sender matches SPF record * 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record * 2.6 LOCAL_FROM From my domains X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on hz.grosbein.net X-Rspamd-Queue-Id: 47hGn11Ct3z4WVl X-Spamd-Bar: --- Authentication-Results: mx1.freebsd.org; dkim=none; dmarc=none; spf=permerror (mx1.freebsd.org: domain of eugen@grosbein.net uses mechanism not recognized by this client) smtp.mailfrom=eugen@grosbein.net X-Spamd-Result: default: False [-3.82 / 15.00]; ARC_NA(0.00)[]; NEURAL_HAM_MEDIUM(-1.00)[-1.000,0]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_THREE(0.00)[4]; TO_DN_SOME(0.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000,0]; MIME_GOOD(-0.10)[text/plain]; DMARC_NA(0.00)[grosbein.net]; RCVD_COUNT_THREE(0.00)[3]; TO_MATCH_ENVRCPT_SOME(0.00)[]; R_SPF_PERMFAIL(0.00)[]; IP_SCORE(-1.72)[ip: (-4.59), ipnet: 2a01:4f8::/29(-2.43), asn: 24940(-1.55), country: DE(-0.02)]; FREEMAIL_TO(0.00)[yandex.ru]; FROM_EQ_ENVFROM(0.00)[]; R_DKIM_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; ASN(0.00)[asn:24940, ipnet:2a01:4f8::/29, country:DE]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_TLS_ALL(0.00)[] X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 23 Dec 2019 11:08:38 -0000 23.12.2019 18:00, Andrey V. Elsukov wrote: > On 23.12.2019 13:55, Eugene Grosbein wrote: >>> I think the real problem is that PMTUD doesn't work correctly with >>> IPsec. Linux has special sysctl variabl ip_no_pmtu_disc and flag >>> SADB_SAFLAGS_NOPMTUDISC for SA that can disable PMTUD for IPv4 and IP_DF >>> flag will not be set. We can add some similar quirks, but it would be >>> better to fix PMTUD. We already have hundreds sysctl in our system and >>> remembering all them is a problem too. >> >> It's true that PMTUD does not work with IPSec transport mode. >> >> I think we could just clear DF bit off encapsulated transport mode packets unconditionally, >> please take a look at last chunk of sample patch in the PR 242744: >> https://bz-attachments.freebsd.org/attachment.cgi?id=210122 >> >> Sample patch creates another sysctl but we should do it unconditionally, don't we? > > As I said I didn't find that other OSes do this. Linux has enabled by > PMTUD by default, strongswan doesn't set SADB_SAFLAGS_NOPMTUDISC flag, > OpenBSD hasn't such quirk. Why should we add this instead of try to fix > PMTUD? RFC 2401 Appendix B https://tools.ietf.org/html/rfc2401#page-1-48 states that packets generated by IPSec transport mode must be "fragmentable" over the path and this is incompatible with DF=1.