Re: [rtcweb] Data channel: Handling of packets on unknown channels

Note that I started a thread about this last month:
https://mailarchive.ietf.org/arch/msg/rtcweb/lIuiu91_L2nOh935eAqifrs_ius

On Thu, Jun 28, 2018 at 8:19 AM, Michael Tuexen <
michael.tuexen@lurchi.franken.de> wrote:

>
>
> > On 28. Jun 2018, at 17:01, Harald Alvestrand <harald@alvestrand.no>
> wrote:
> >
> > Den 28. juni 2018 16:35, skrev Michael Tuexen:
> >>> On 28. Jun 2018, at 16:22, Harald Alvestrand <harald@alvestrand.no>
> wrote:
> >>>
> >>> Den 28. juni 2018 14:51, skrev Michael Tuexen:
> >>>>> On 28. Jun 2018, at 13:30, Harald Alvestrand <harald@alvestrand.no>
> wrote:
> >>>>>
> >>>>> In considering the datachannel API, we encountered one interesting
> race
> >>>>> condition:
> >>>>>
> >>>>> A: <configure for datachannel>
> >>>>>
> >>>>> A: CreateOffer(), SetLocalDescription(), send SDP
> >>>>>
> >>>>> B: SetRemoteDescription, CreateAnswer, SetLocalDescription, send SDP
> >>>>>
> >>>>> B: Configure an externally defined data channel, with #3249
> >>>>>
> >>>>> B: Send a message on #3249
> >>>>>
> >>>>> A: SetRemoteDescription
> >>>>>
> >>>>> A: Wait a while (THE PAUSE)
> >>>>>
> >>>>> A: Configure #3249
> >>>>>
> >>>>> Now, if a message comes in to A on #3249 during THE PAUSE, what is
> the
> >>>>> implementation to do?
> >>>> Isn't that some kind or error condition?
> >>>>
> >>>> If that it true, one could apply:
> >>>>
> >>>>  If a message with an unsupported PPID is received or some error
> >>>>  condition related to the received message is detected by the receiver
> >>>>  (for example, illegal ordering), the receiver SHOULD close the
> >>>>  corresponding data channel.  This implies in particular that
> >>>>  extensions using additional PPIDs can't be used without prior
> >>>>  negotiation.
> >>>
> >>>
> >>> The receiver can't close the datachannel if the datachannel doesn't
> >>> exist yet, so this doesn't work for that case.
> >> I was assuming that the SCTP receives a user message on a stream. When
> >> this message is delivered to its upper layer, doesn't this layer know
> >> that there is no data channel? I would assume that this layer triggers
> >> the stream reset procedure. I'm not saying that the user (for example
> >> via a JS API) is involved... I'm more talking about implementing this
> >> iside the browser..
> >
> >
> > Exactly, it could close the stream, but it can't close the data channel
> > since it doesn't exist.
> Well, I can run the procedure and the peer will get an indication that
> something isn't working well.
> >
> > I think closing the stream would be a mistake, since that would make the
> > outcome about whether you end up with the datachannel or not racy;
> > discarding data will give you a working datachannel once A gets around
> > to configuring it.
> But if the user configures a reliable data channel, the user does not
> get the service that was required...
>
> Best regards
> Michael
> >
>
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