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? 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. > >>> >
