[SPAM] Re: TLS over SCTP
sdecugis at nict.go.jp
Mon Aug 4 03:16:16 CEST 2008
Thank you for your answer. Please see my comments below.
> A layer that would demultiplex the streams before should be needed.
> That's correct.
>> I am considering to implement such support in the gnutls library, either
>> as a new session object ("gnutls_session_multistream_t") or as an
>> extension of the current session object (adding new fields to it).
>> Basically, the differences are:
>> -> ability to define a number of independent communication channels
>> (bi-directional streams) in the object.
>> -> storage for this same number of sessions states (the current
>> -> different prototype of the push and pull transport callbacks, that
>> take an additional parameter (the stream id on which to send / on which
>> the message was received)
> Can't this be achieved by having a layer of demultiplexing before gnutls
> that will use separate pull/push functions and a custom transport
> pointer? That we could include in gnutls as helper functions for SCTP.
I understand your point. My first attempt was to come up with such
intermediate layer that would provide these two functions:
send_to_stream(message, length, streamid);
recv_from_stream(message, length, streamid);
It would be quite straight-forward to use the user pointer from the
session, or the connection object, to retrieve the stream id of a session.
Unfortunately, whereas the send function can be written quite easily, I
cannot figure out how to write the recv function. Using the SCTP socket
API , we do not specify the stream on which we are listening for a
new message. Instead, we are listening for the next message from any
stream, and when we receive it we can also get its stream id. That is a
fundamental difference between a multistream SCTP association, and many
That is the reason for my previous proposal. An alternate approach would
be to be able to change the current TLS session from inside the
transport handler, but I don't think this is a good approach, if
possible at all.
What do you think, is there another possibility to solve the problem
that I cannot see?
Thank you in advance,
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