> On 19. May 2021, at 20:44, Xin Long <lucien.xin@xxxxxxxxx> 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. > sysctl is always used for the default value for future sockets. > and the socket option should be added for a socket/asoc's setting. > > SCTP_PTMUD_METHOD? OK. > 0: PTB one I don't know what the above would mean. Not sure anything is really specified. > 1. PLPMTUD I guess you would need an struct sctp_assoc_value here. Maybe some constants such as: SCTP_PMTU_CLASSIC SCTP_PMTU_NEW or SCTP_PMTU_RFC_8899 Best regards Michael > >> >> 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. >>>>> >>
