64k streams not supported

64k streams not supported

[David Laight]

Isn't SCTP supposed to support 65536 data streams?
If I try to enable that many I get 10.
Not surprising since the number of streams gets stored in a u16.

The whole code base may need changing to save the highest
valid stream?

Since I don't actually need that many I'm not writing the patch.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

Re: 64k streams not supported

[Marcelo Ricardo Leitner]

On Fri, Aug 21, 2020 at 03:59:42PM +0000, David Laight wrote:
> Isn't SCTP supposed to support 65536 data streams?

Hm, no? Why?

https://tools.ietf.org/html/rfc4960#section-5.1.1
"After the association is initialized, the valid outbound stream
identifier range for either endpoint shall be 0 to min(local OS,
remote MIS)-1."

Section 3.3.2:
   Number of Outbound Streams (OS): 16 bits (unsigned integer)

      Defines the number of outbound streams the sender of this INIT
      chunk wishes to create in this association.  The value of 0 MUST
      NOT be used.

...

   Number of Inbound Streams (MIS): 16 bits (unsigned integer)


      Defines the maximum number of streams the sender of this INIT
      chunk allows the peer end to create in this association.  The
      value 0 MUST NOT be used.

  Marcelo

Re: 64k streams not supported

[Michael Tuexen]

> On 21. Aug 2020, at 17:59, David Laight <David.Laight@ACULAB.COM> wrote:
> 
> Isn't SCTP supposed to support 65536 data streams?
Since the number of streams is exchanged in the INIT and INIT-ACK chunks
and encoded in a uint16_t, the number is 65535, not 65536.
So an implementation should be able to use up to 65535 incoming and
outgoing streams.

Best regards
Michael
> If I try to enable that many I get 10.
> Not surprising since the number of streams gets stored in a u16.
> 
> The whole code base may need changing to save the highest
> valid stream?
> 
> Since I don't actually need that many I'm not writing the patch.
> 
> 	David
> 
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> Registration No: 1397386 (Wales)
> 

RE: 64k streams not supported

[David Laight]

From: Michael Tuexen
> Sent: 21 August 2020 21:10
> > On 21. Aug 2020, at 17:59, David Laight <David.Laight@ACULAB.COM> wrote:
> >
> > Isn't SCTP supposed to support 65536 data streams?
>
> Since the number of streams is exchanged in the INIT and INIT-ACK chunks
> and encoded in a uint16_t, the number is 65535, not 65536.
> So an implementation should be able to use up to 65535 incoming and
> outgoing streams.

Ah, I'd assumed that because the stream number was encoded
in 16 bits you could use stream numbers 0 through 65535.

At least no one needs to write the patch :-)

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)