On Wed, May 19, 2021 at 6:24 PM <mleitner@xxxxxxxxxx> wrote: > > On Tue, May 18, 2021 at 09:19:21PM +0200, Michael Tuexen wrote: > > > > > > > On 18. May 2021, at 20:33, 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? > > > 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? > > Yes. I think testing for connectivity is conceptually different > > from testing a particular PMTU. When testing for PMTU, I think > > about sending probe packets. Not that they consist of a HB chunk > > bundled with a PAD chunk. > > > As the HB for PLPMTUD probe might get lost, which we don't want to > > > affect the link's > > > connectivity. > > Yes, I agree completely. > > With this, Xin, seems we should have a separate timer for the > PROBE_TIMER, other than the heartbeat one. > > Otherwise, converging the two logics into one single timer is not > worth the hassle for saving a timer. For example, we would have to > have it fire on the active transport but to send only the probe. > Also, considering they can and (AFAIU the RFC) should have different > expire timeouts from time to time. > > With a separate timer, we won't have issues converging the > user-selectable heartbeat interval to the recommended 600s > PMTU_RAISE_TIMER, for example. > > Maybe I am missing something. But it seems the hassle for reusing the > timer here is just not worth it. Thoughts? You're right, when I was doing testing, I had to set the hb_interval to 5s. the common value of hb_interval really doesn't fit in the probe_interval. I will try adding a new timer, but at the same time a probe_interval by sysctl/sockopt may be needed, or we can use a value equal to (hb_interval / n) for it? > > Best, > Marcelo > > > > > Best regards > > Michael > > > > > >> > > >> Best regards > > >> Michael > > >>> > > >>> Thanks. > > >> > > >
