Hi,
Correct me if I'm wrong, but it seems you trying to use the AVPops to capture a time stamp of the very first INVITE of a transaction? To get this same information, I've used the acc module.
It's about accounting but requires some extra. I must generate a unique id and attach it in a specific header. Hint: RFC 3544, P-Charging-Vector.
For billing and user call logging purposes, I needed this info and have used: acc_db_request("CallStart", "acc"); in openser.cfg.
This logs a record to the acc table containing the sip_callid, timestamps, and in "sip_status" is the string "CallStart". I then had various scripts parse acc to the format I needed for the end user.
Thanks - anyhow, I'm afraid that this does not solve my problem. As stated already before: Inserting the call-id into an AVP and writing it to the SIP header is no problem. What makes the topic difficult is to store the content in a call-specific (and not contact-specific) way.
--Joachim