The state of the session.
sessionSetupInit: The initiation of the session.
sessionSetupReq: The initiator requests to negotiate the SA and
so on of the session.
sessionSetupSuccess: The session has been built successfully.
sessionRekeyReq: The initiator requests to renegotiate the SA.
sessionRekeyRep: The passive side replies with a SA renegotiation
response packet successfully.