[Linphone-users] INVITE with wrong SDP after a REFER if the transferee's call is already inactive

[Dario Santomaso]

Hello,
I am writing to signal this issue, which affects all the last linphone versions I've tested. The following releases have all the same behaviour:

• Linphone Android 3.2.7 - Core 3.11.1 - Belle-sip/1.6.1
• Linphone IOS 3.13.9 - Core 3.9.1
• Linphone Desktop 4.1.1 - Core 3.12.0

We are using our SIP proxy and our desktop softphone, which in this scenario is the transfer agent.
A (our softphone) is connected with B (linphone) and it wants to do an unattended transer to C (another Linphone). Sofphone A acts according to the RFC 5359. This is what happen:

1. A sends a reINVITE with audio inactive and puts B on hold
2. A sends a REFER to B
3. B then calls C, but the outgoing INVITE contains a wrong SDP without a valid audio media. C refuses the call.

It seems that Linphone is not able to build a valid SDP if this sequence occurs. Our softphone, as many others (ad es. SNOM), puts the other party on-hold before sending the REFER. I am aware this isn't the way Linphone handles the blind transfer, but could you please fix it or suggest a workaround?

Regards,
Dario Santomaso.

 

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