Failure to comply with RFC 3311

[SouradeepBera]

Describe the bug RFC 3311 states that If an UPDATE is received that contains an offer, and the UAS has generated an offer (in an UPDATE, PRACK or INVITE) to which it has not yet received an answer, the UAS MUST reject the UPDATE with a 491 response. FreeSWITCH sends a 500 Overlapping Offer/Answer response.

To Reproduce Using Sipp or any simulation tool, establish a session with FreeSWITCH. Decrease the session-timer and when FreeSWITCH sends a reINVITE, instead of responding to it with a final response, send an UPDATE request.

Expected behavior A 491 response is expected