> On 29 Jan 2016, at 12:26, Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx> wrote: > > On Fri, Jan 29, 2016 at 11:57:46AM +0100, Michael Tuexen wrote: >>> On 29 Jan 2016, at 02:18, Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx> wrote: >>> >>> 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? >> Yes. But there are no restrictions on the user data provided in send() >> calls and DATA chunks. So you can >> send(100000 byte, no SCTP_EOR) >> resulting in one DATA chunk with the B bit, several with no B and no E bit. >> send(100000 byte, no SCTP_EOR) >> resulting in several chunks with no B and no E bit. >> send(100000 byte, SCTP_EOR) >> resulting in several chunks with no B and no E bit and one (the last) chunk >> with the E bit. >> >> On the other hand you can do >> send(1 byte, no SCTP_EOR) >> resulting in a single DATA chunk with the E bit set. >> send(1 byte, no SCTP_EOR) >> send(1 byte, no SCTP_EOR) >> send(1 byte, no SCTP_EOR) >> send(1 byte, no SCTP_EOR) >> send(1 byte, no SCTP_EOR) >> All resulting in a single DATA chunk with 5 bytes user data and no B or E bit. >> (For example if Nagle is enabled and only after the last send call the SACK arrives). >> send(1 byte, SCTP_EOR) >> results in a single DATA chunk with the E bist set. > > Cool, thanks Michael. It will be quite fun to mix this with MSG_MORE > logic, I think :) Don't know. In FreeBSD we do support SCTP_EOR, but not MSG_MORE, which seems to be Linux specific. Best regards Michael > > Best regards, > Marcelo > > -- 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
