> On 24. Jun 2020, at 09:25, Xin Long <lucien.xin@xxxxxxxxx> wrote: > > 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. Great to hear. When implementing RFC 6951 support, please take https://tools.ietf.org/html/draft-tuexen-tsvwg-sctp-udp-encaps-cons-02 into account. It is still valid and will be pushed further after RFC 4960bis is done. Best regards Michael > >> >> 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) >>>>>>> >>>> >>
