Re: [Sofia-sip-devel] SOA Media rejection question

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2008/6/16 Colin Whittaker <co...@oc...>:
> Still running 1.12.6, and it has been working great. Ran into a little
> hiccup in another interop.
>
> During a call, we get a re-INVITE with a new media descriptor. We have
> NOT included that media in our SDP, so the SOA task rejects it.
>
> Time 16:09:08: sipuad: soa_static(0x10b62588, soa_generate_answer): marking rejected media
>
>
> But, the response to the INVITE is 200 OK. This appears to be a problem
> for the switch, which is expecting a
>
> 415 Unsupported Media Type
>
>
> Now the problem I have in fixing this is the stack does not give me a
> chance to respond to the INVITE.
>
> So a couple of questions:
> 1. Can I get the stack to allow me to respond to re-INVITEs with a TAG
> or some other means ?

Include NUTAG_AUTOANSWER(0) in nua_handle_create() or initial
nua_respond(). I'm afraid this bug is documented there in the
NUTAG_AUTOANSWER() dox.

> 2. Can I get the rejected media to be responded to with 415 without
> tearing down the call ?

I think so.

> 3. Is the sofia SDP response technically correct ?

Yes... RFC 3261 section 21.4.13  describes how to handle unknown
session description with 415. IMO 415 is wrong - it is part of the
content negotation, ie, does your terminal support SDP-ng or just
plain SDP.

UA is expected to return a 488/606 response if there is something they
can not process in the SDP.  RFC 3264 section 8.1. describes how to
proceed with a new stream.

> The scenario is the switch is requesting a switch from a G.711 voice
> call to do T.38 Fax. Our endpoint does not support T.38, so we need to
> reject the INVITE without interrupting the call.

Then it is section 8.3.3. on RFC 3264. Unfortunately, RFC 3264 leaves
it open how a session is rejected. Sofia SIP now rejects each media,
which is the most portable way, or so we thought. Obviously, if a
re-offer replaces the only stream, the offer should be rejected with
488/606. (I'm afraid we were only concerned with a/v sessions, where
the offerer might be confused if his offer modifying audio and adding
a videeo stream was rejected.)

Please check the logic in soa and nua_session.c and propose improvements...

--Pekka

> Here are the SIP packets:
>
> =================================================================================
> 16:09:08.424918 10.2.21.2.5060 > 10.3.6.30.5060:  udp 714 (DF)
> INVITE sip:9992221161@10.3.6.30 SIP/2.0
> Call-ID:diceiiffcbjbhaac-diiddgdbcb
> CSeq:6002 INVITE
> Contact: sip:6662221007@10.2.21.2
> From: sip:6662221007@10.2.21.2;tag=difcebgfcbjbhaac-diiddgdbcb
> To:<sip:9992221161@10.2.21.2>;tag=S4tH4yDKj8ajg
> Via:SIP/2.0/UDP 10.2.21.2:5060
> Content-Length: 368
> Content-Type:application/sdp
> Max-Forwards:70
>
> v=0
> o=ast12345sg 2694309633 2694309633 IN IP4 10.2.21.6
> s=-
> c=IN IP4 10.2.21.6
> t=0 0
> a=sendrecv
> m=image 10032 UDPTL t38
> a=T38FaxVersion:0
> a=T38maxBitRate:14400
> a=T38FaxRateManagement:transferredTCF
> a=T38FaxMaxBuffer:800
> a=T38FaxMaxDatagram:213
> a=T38FaxUdpEC:t38UDPRedundancy
> a=T38FaxFillBitRemoval:0
> a=T38FaxTranscodingMMR:0
> a=T38FaxTranscodingJBIG:0
> =================================================================================
> 16:09:08.438768 10.3.6.30.5060 > 10.2.21.2.5060:  udp 632 (DF) [tos 0xb8]
> SIP/2.0 200 OK
> Via: SIP/2.0/UDP 10.2.21.2:5060
> From: <sip:6662221007@10.2.21.2>;tag=difcebgfcbjbhaac-diiddgdbcb
> To: <sip:9992221161@10.2.21.2>;tag=S4tH4yDKj8ajg
> Call-ID: diceiiffcbjbhaac-diiddgdbcb
> CSeq: 6002 INVITE
> Contact: <sip:9992221161@10.3.6.30;transport=udp>
> User-Agent: sofia-sip/1.12.6
> Accept: application/sdp
> Allow: INVITE, ACK, BYE, CANCEL, OPTIONS, REFER, UPDATE, NOTIFY, INFO
> Supported: timer
> Min-SE: 120
> Content-Type: application/sdp
> Content-Disposition: session
> Content-Length: 118
>
> v=0
> o=- 4381022568673842968 6575715192701033337 IN IP4 10.3.6.30
> s=-
> c=IN IP4 10.3.6.30
> t=0 0
> m=image 0 UDPTL 9
>
>
>
>
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-- 
Pekka.Pessi mail at nokia.com