On Thu, May 20, 2021 at 08:59:49AM +0200, tuexen@xxxxxxxxxxx wrote: > > On 20. May 2021, at 02:45, Marcelo Ricardo Leitner <mleitner@xxxxxxxxxx> wrote: > > > > On Thu, May 20, 2021 at 01:16:38AM +0200, Michael Tuexen wrote: > >>> On 20. May 2021, at 00:44, mleitner@xxxxxxxxxx wrote: > >>> > >>> On Wed, May 19, 2021 at 02:44:20PM -0400, Xin Long wrote: > >>>> On Wed, May 19, 2021 at 2:15 PM Michael Tuexen <tuexen@xxxxxxxxxxx> wrote: > >>>>> > >>>>>> On 19. May 2021, at 18:18, Xin Long <lucien.xin@xxxxxxxxx> wrote: > >>>>>> > >>>>>> On Tue, May 18, 2021 at 2:33 PM Xin Long <lucien.xin@xxxxxxxxx> wrote: > >>>>>>> > >>>>>>> On Tue, May 18, 2021 at 1:38 PM Michael Tuexen <tuexen@xxxxxxxxxxx> wrote: > >>>>>>>> > >>>>>>>>> On 18. May 2021, at 18:43, Xin Long <lucien.xin@xxxxxxxxx> 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? > >>>>>> I just noticed that with multiple versions supported, and without extending > >>>>>> this API, all applications will have to use the same version as it's > >>>>>> controlled by > >>>>>> sysctl. And when switching to another version by sysctl, all > >>>>>> applications will be > >>>>>> affected and have to do the switch. that seems not nice. > >>>>> That is true, but an application can not expect any specific behaviour > >>>>> right now when they are not disabling PMTUD. > >>>>> > >>>>> What about adding a sysctl variable, which defines the default > >>>>> algorithm and a socket option, which allows to get and set > >>>>> the algorithm being used. > >>>> yes, that's also what I'm thinking. > >>> > >>> +1 > >>> > >>>> sysctl is always used for the default value for future sockets. > >>>> and the socket option should be added for a socket/asoc's setting. > >>> > >>> Speaking of inheritance, it should also use the SCTP_FUTURE_ASSOC / > >>> SCTP_CURRENT_ASSOC / SCTP_ALL_ASSOC mechanism. Like > >>> SCTP_PEER_ADDR_PARAMS, for example. > >> Yepp. > >>> > >>> The system can provide defaults but if the application requires > >>> something, it should have a good way of requesting it. > >>> > >>> Speaking of SCTP_PEER_ADDR_PARAMS, maybe reuse spp_pathmtu field? > >>> As in, if SPP_PMTUD_ENABLE is enabled, spp_pathmtu of "1" or "2" bytes > >>> doesn't make sense, and it could mean the algorithm used. Thing is, > >>> the field is currently ignored, and it could lead to some unexpected > >>> behavior change. It's probably safer to just add another sockopt, but > >>> wanted to share the idea anyway. > >> I leave it completely up to you what you implement in Linux. But I > >> would prefer to use a separate socket option instead of overloading > >> an existing one. > > > > Wait. Somehow I thought we were talking about extending the RFC with > > these new definitions here, no? Or at least agreeing on a common > > interface. It would be beneficial for the application to be able to > > use the same API on FreeBSD or Linux. > Hi Marcelo, Hi! > > sorry for not being clear. > > What I wanted to say: > > 1. I really appreciate the discussion and I agree that it would be great +1 > if we can agree on a common interface allowing to write portable > applications. > > 2. I don't like the idea of overloading the spp_pathmtu. Me neither. :D > > 3. I'm not in a position to put in a veto to what anyone is implementing > in any implementation (except maybe the FreeBSD implementation). > > Regarding the extension of the RFC. An RFC can't be changed. One can file > erratas, but I think we are discussing here an extension of the socket API > to cope with RFC 8899. So I don't think it is an errata. It would have been > appropriate to add a socket API section to RFC 8899, but it is too late for > that, too. > > So I guess we can discuss it here and come to an agreement how to extend > the socket API for RFC 8899. I'm more that happy to do this. Nice. Okay. > > I hope I expressed my view now clearer. Yep. On the same page now, thanks. :-) Best regards, Marcelo > > Best regards > Michael > > > > > > Thanks, > > Marcelo > > > >> > >> Best regards > >> Michael > >>> > >>>> > >>>> SCTP_PTMUD_METHOD? > >>> > >>> s/PTMUD/PMTUD/ :-) > >>> > >>>> 0: PTB one > >>>> 1. PLPMTUD > >>>> > >>>>> > >>>>> Best regards > >>>>> Michael > >>>>>> > >>>>>>> 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? > >>>>>>> As the HB for PLPMTUD probe might get lost, which we don't want to > >>>>>>> affect the link's > >>>>>>> connectivity. > >>>>>>> > >>>>>>>> > >>>>>>>> Best regards > >>>>>>>> Michael > >>>>>>>>> > >>>>>>>>> Thanks. > >>>>>>>> > >>>>> > >>>> > >>> > >> > > >
