Pekka Pessi wrote:
On 9/15/06, Colin Whittaker <[EMAIL PROTECTED]> wrote:
I'm not seeing any processing of the SDP when I receive multiple 183
replies to my INVITE.
Also, the 200 OK SDP is not being processes either.
Are those 183 100rel responses (iow, are they PRACKed)?
No, I have 100rel disabled.
This is a problem since my proxy is using this method to redirect a call
to a voice mail server.
I see a
nua(0x102db820): INVITE: ignoring duplicate SDP in 183 Session Progress
which I assume means the stack is not prepared for a new SDP after the
first one.
Is the proxy violating the spec ?
Yes. The can be only one answer to a single offer.
The proxy could fork the request, that is, it could respond from
another logical endpoint, the change would be visible from another tag
in the To header. However, that would bring other complications, like
how to tell UAC that the previous fork should be dropped. I just
yesterday called forking brain-dead. Not to mention that the nua stack
does not dig forking after it has received a 183.
If the proxy would like to keep existing dialog, it could send UPDATE
with a new offer in it.
I will report this as a bug to the proxy vendor. The proxy is a
Metaswitch, and they use the DC-SIP/2.0 stack.
Well, I wish I could say this might get fixed, but I'm not expecting
much.
Would it be difficult to modify the stack to support this ?
You could have peek in nua_session.c where the code now logs the
message about duplicate sdp.
However, you have to decide how to interpret the SDP. This is the most
difficult part, I'm afraid. Standard is no help because O/A model
tells us to ignore those SDP. Of course, you could peek in the
User-Agent header in the response and make decision based on that.
In the past we have interpreted these extra SDP in subsequent 183 or
200 as new offers, and sent answer in PRACK or ACK.
Well, I have PRACK disabled since this proxy expects authentication for
PRACK and sofia does not currently support this.
Seems like the SDP should be part of the sip object passed in the event
regardless of the status. If the packet has it why wouldn't the sip
object have it ?
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