#158 HandlePrackFSM doesn't handle multiple reliable provisional

[Eric]

As there can be multiple unacknowledged reliable responses within an INVITE transaction, B2buaInviteFSM has a machine array of HandlePrackFSM. However, HandlePrackFSM does not check that a received response to PRACK matches the PRACK it sent out in the following transitions:

110 transition AWAIT_PRACK_RESPONSE - callee ? PrackSuccessResponse / {

116 transition AWAIT_PRACK_RESPONSE - callee ? PrackErrorResponse / {

These transitions should have guards to check that the CSeq in response matches the CSeq in the PRACK sent earlier on the callee port.

[Eric]

Actually before the response to PRACK, this machine fragment should also match a received PRACK to the reliable provisional response sent in the following transition:

101 transition INIT - caller ? Prack / {

The RAck header in the PRACK should match the RSeq, CSeq and method in the reliable response. See RFC3262 bottom of page 4.