On Fri, Jan 29, 2016 at 12:36:05AM +0100, Michael Tuexen wrote: > > > On 28 Jan 2016, at 22:03, Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx> wrote: > > > > On Thu, Jan 28, 2016 at 06:54:06PM +0100, Michael Tuexen wrote: > >>> On 28 Jan 2016, at 14:51, David Laight <David.Laight@xxxxxxxxxx> wrote: > >>> > >>> From: Marcelo Ricardo Leitner > >>>> Sent: 27 January 2016 17:07 > >>>> This patchset is merely a RFC for the moment. There are some > >>>> controversial points that I'd like to discuss before actually proposing > >>>> the patches. > >>> > >>> You also need to look at how a 'user' can actually get SCTP to > >>> merge data chunks in the first place. > >>> > >>> With Nagle disabled (and it probably has to be since the data flow > >>> is unlikely to be 'command-response' or 'unidirectional bulk') > >>> it is currently almost impossible to get more than one chunk > >>> into an ethernet frame. > >>> > >>> Support for MSG_MORE would help. > >> What about adding support for the explicit EOR mode as specified in > >> https://tools.ietf.org/html/rfc6458#section-8.1.26 > > > > Seizing the moment to clarify my understanding on that. :) > > Such multiple calls to send system calls will result in a single data > > chunk. Is that so? That's what I get from that text and also from this > No. It results in a single user message. This means you can send > a user message larger than the send buffer size. How the user message > is fragmented in DATA chunks is transparent to the upper layer. > > Does this make things clearer? I think so, yes. So it allows delaying setting the Ending fragment bit until the application set SCTP_EOR. All the rest before this stays as before: first send() will generate a chunk with Beginning bit set and may generate some other middle-fragments (no B nor E bit set) if necessary, second to N-1 call to send will generate only middle fragments, while the last send, with SCTP_EOF, will then set the Ending fragment in the last one. Right? Thanks, Marcelo > > Best regards > Michael > > snippet: > > "Sending a message using sendmsg() is atomic unless explicit end of > > record (EOR) marking is enabled on the socket specified by sd (see > > Section 8.1.26)." > > > > Best regards, > > Marcelo > > > >> Best regards > >> Michael > >>> > >>> Given the current implementation you can get almost the required > >>> behaviour by turning nagle off and on repeatedly. > >>> > >>> I did wonder whether the queued data could actually be picked up > >>> be a Heartbeat chunk that is probing a different remote address > >>> (which would be bad news). > >>> > >>> David > >>> > >>> -- > >>> To unsubscribe from this list: send the line "unsubscribe linux-sctp" in > >>> the body of a message to majordomo@xxxxxxxxxxxxxxx > >>> More majordomo info at http://vger.kernel.org/majordomo-info.html > >>> > >> > > > -- To unsubscribe from this list: send the line "unsubscribe linux-sctp" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
