On Wed, Jun 24, 2020 at 5:48 AM Michael Tuexen <michael.tuexen@xxxxxxxxxxxxxxxxx> wrote: > > > On 23. Jun 2020, at 23:31, Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx> wrote: > > > > On Tue, Jun 23, 2020 at 11:24:59PM +0200, Michael Tuexen wrote: > >>> On 23. Jun 2020, at 23:21, Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx> wrote: > >>> > >>> On Tue, Jun 23, 2020 at 11:17:56AM -0500, Corey Minyard wrote: > >>>> On Tue, Jun 23, 2020 at 01:17:28PM +0000, David Laight wrote: > >>>>> 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 <minyard@xxxxxxx> 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 <minyard@xxxxxxx> 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. > >>>> > >>>> That's an interesting question. Do the RFCs say anything? I would > >>>> assume it was ok unless ipv6only was set. > >>>> > >>>>> > >>>>> I also wonder whether the connection should be dropped for an error > >>>>> response on a path that has never been validated. > >>>> > >>>> That actually bothered me a bit more. Shouldn't it stay up if any path > >>>> is up? That's kind of the whole point of multihoming. > >>> > >>> Michael explained it on the other email. What he described is what I > >>> observed in my tests. > >>> > >>>> > >>>>> > >>>>> OTOH the whole 'multi-homing' part of SCTP sucks. > >>>> > >>>> I don't think so. > >>>> > >>>>> 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. > >>>> > >>>> Umm, no, If you have a private address, it better be behind a firewall, > >>>> and the firewall should handle rewriting the packet to fix the addresses. > >>>> > >>>> It doesn't appear that Linux netfilter does this. There is a TODO in > >>>> the code for this. But that's how it *should* work. > >>> > >>> Right, we don't support SCTP aware NAT [1]. > >>> > >>> 1.https://tools.ietf.org/html/draft-stewart-behave-sctpnat-04 > >> The current version is: https://tools.ietf.org/html/draft-ietf-tsvwg-natsupp-16 > > > > Thanks! > > > >> > >> Another possibility for NAT traversal is UDP encapsulation... > > > > Also not supported.. :-] > But maybe someone wants to implement it. It is supported by FreeBSD, if you > need a peer for testing. Or the userland stack usrsctp supports it. Then you > do not need root privileges to run it. You mean SCTP_REMOTE_UDP_ENCAPS_PORT sockopt, right? We have this in our to-do list. I mixed rfc6951 with the userland one. Will prioritize this feature. Thanks. > > Best regards > Michael > > > > Best regards, > > Marcelo > > > >> > >> Best regards > >> Michael > >>> > >>> Marcelo > >>> > >>>> > >>>> -corey > >>>> > >>>>> > >>>>> David > >>>>> > >>>>> - > >>>>> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK > >>>>> Registration No: 1397386 (Wales) > >>>>> > >> >
