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=-1.0 required=3.0 tests=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 268A3C433DF for ; Tue, 23 Jun 2020 13:17:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0715620723 for ; Tue, 23 Jun 2020 13:17:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732651AbgFWNRe convert rfc822-to-8bit (ORCPT ); Tue, 23 Jun 2020 09:17:34 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([207.82.80.151]:29316 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732618AbgFWNRe (ORCPT ); Tue, 23 Jun 2020 09:17:34 -0400 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-80-PPSv6GeNNhSUDZXNTs6kBQ-1; Tue, 23 Jun 2020 14:17:29 +0100 X-MC-Unique: PPSv6GeNNhSUDZXNTs6kBQ-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) by AcuMS.aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Tue, 23 Jun 2020 14:17:28 +0100 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Tue, 23 Jun 2020 14:17:28 +0100 From: David Laight To: 'Marcelo Ricardo Leitner' , Michael Tuexen CC: "minyard@acm.org" , Xin Long , "Vlad Yasevich" , Neil Horman , "linux-sctp@vger.kernel.org" , LKML Subject: RE: Strange problem with SCTP+IPv6 Thread-Topic: Strange problem with SCTP+IPv6 Thread-Index: AQHWSMOQnCXngLNhqU+XPiIQcbDSR6jmLNPQ Date: Tue, 23 Jun 2020 13:17:28 +0000 Message-ID: References: <20200621155604.GA23135@minyard.net> <20200622165759.GA3235@minyard.net> <4B68D06C-00F4-42C3-804A-B5531AABCE21@lurchi.franken.de> <20200622183253.GQ2491@localhost.localdomain> In-Reply-To: <20200622183253.GQ2491@localhost.localdomain> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Marcelo Ricardo Leitner > Sent: 22 June 2020 19:33 > On Mon, Jun 22, 2020 at 08:01:24PM +0200, Michael Tuexen wrote: > > > On 22. Jun 2020, at 18:57, Corey Minyard wrote: > > > > > > On Mon, Jun 22, 2020 at 08:01:23PM +0800, Xin Long wrote: > > >> On Sun, Jun 21, 2020 at 11:56 PM Corey Minyard wrote: > > >>> > > >>> I've stumbled upon a strange problem with SCTP and IPv6. If I create an > > >>> sctp listening socket on :: and set the IPV6_V6ONLY socket option on it, > > >>> then I make a connection to it using ::1, the connection will drop after > > >>> 2.5 seconds with an ECONNRESET error. > > >>> > > >>> It only happens on SCTP, it doesn't have the issue if you connect to a > > >>> full IPv6 address instead of ::1, and it doesn't happen if you don't > > >>> set IPV6_V6ONLY. I have verified current end of tree kernel.org. > > >>> I tried on an ARM system and x86_64. > > >>> > > >>> I haven't dug into the kernel to see if I could find anything yet, but I > > >>> thought I would go ahead and report it. I am attaching a reproducer. > > >>> Basically, compile the following code: > > >> The code only set IPV6_V6ONLY on server side, so the client side will > > >> still bind all the local ipv4 addresses (as you didn't call bind() to > > >> bind any specific addresses ). Then after the connection is created, > > >> the client will send HB on the v4 paths to the server. The server > > >> will abort the connection, as it can't support v4. > > >> > > >> So you can work around it by either: > > >> > > >> - set IPV6_V6ONLY on client side. > > >> > > >> or > > >> > > >> - bind to the specific v6 addresses on the client side. > > >> > > >> I don't see RFC said something about this. > > >> So it may not be a good idea to change the current behaviour > > >> to not establish the connection in this case, which may cause regression. > > > > > > Ok, I understand this. It's a little strange, but I see why it works > > > this way. > > I don't. I would expect it to work as I described in my email. > > Could someone explain me how and why it is behaving different from > > my expectation? > > It looks like a bug to me. Testing with this test app here, I can see > the INIT_ACK being sent with a bunch of ipv4 addresses in it and > that's unexpected for a v6only socket. As is, it's the server saying > "I'm available at these other addresses too, but not." Does it even make sense to mix IPv4 and IPv6 addresses on the same connection? I don't remember ever seeing both types of address in a message, but may not have looked. I also wonder whether the connection should be dropped for an error response on a path that has never been validated. OTOH the whole 'multi-homing' part of SCTP sucks. The IP addresses a server needs to bind to depend on where the incoming connection will come from. A local connection may be able to use a 192.168.x.x address but a remote connection must not - as it may be defined locally at the remote system. But both connections can come into the public (routable) address. We have to tell customers to explicitly configure the local IP addresses - which means the application has to know what they are. Fortunately these apps are pretty static - usually M3UA. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)