Re: [osip-dev] How to resend final response?

[Aymeric Moizard]

Hi Roger,

There is no easy response to your question! The 200 ok and ACK

in rfc3261 are handled independantly of the osip_transaction_t. This

is very important because many 200 ok (with different tag, route, contact,

dialog information) can be received for one INVITE being sent.

That means that even if you receive a 200 ok and prepare one ACK

for it, you also need to be prepared to receiving other 200 ok and send

other ACK. For each of those 200 ok/ACK, you need to handle retransmission

if required, as you described.

I'm in the process of looking at a patch that I received last week: this patch

propose to implement inside osip, the newer rfc6026 which discuss this

topic and propose some additionnal finite state machine for handling 200ok/ACK:

http://sip.antisip.com/0007-Implement-rfc6026-Correct-Transaction-Handling-for-2.patch

I have not yet read the patch//I'm busy until march... but this is a patch I intend

to integrate for later version. It might be a reason to create osip 5.0 within the

next month or 2!

eXosip layer already does all job in a different way. rfc6026 is an alternative

way to make it easier.

Answer is basically yes: you need to call yourself cb_send_message()

you can check how I did in exosip (starting from) _eXosip_snd_message.

In theory, all 200ok needs to be sent to the same IP:PORT, and all ACK

needs to be sent to the same IP:PORT. (so you should not look at via the

second time, but instead, you need to re-use the exact ip:port you used

for first one)

Either the cb_send_message is taking care of this (as in exosip, mostly)

or your upper layer byu deciding the argument for cb_send_message...

Regards

Aymeric

2015-02-16 21:23 GMT+01:00 Roger Schreiter <address@hidden>:

Hello,

osip closes imho an IST as soon, as osip sends a
final response, e.g. 200 Ok.

In order to test, whether the client is sending the ACK,
I'm not removing the transaction immediately, when the
cb_kill_transaction is called, but I'm keeping the transaction
still for some seconds. When the ACK arrives, I look for the
matching transaction, remove it, and everythig is fine.

When the ACK is not arriving whithin half a second, imho I
should resend my last answer. osip_transaction_t is very useful for
that and storing my last answer. Thus most of the work is already done.

My problem is, how to send the response again?

Is there a function in osip, doing it?
(Imho, I cannot add a new event to the transaction for that task.)

Should I call my cb_send_message(), as I already did for sending
the ACK? In that case, I only would need a mean to figure out
the host and the port.
I wonder, if in osip_transaction_t "top_via" is indicating it.

Regards,
Roger.

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