I have pcaps from Cisco2960 span port and found some tcp handshake has weird order 3-way handshake.
It seems first packet order between sessions is not guaranted for cisco span. maybe.
Current state transition is
INIT -- syn --> SYN1 -- syn&ack --> SYN2 -- ack --> ESTABLISHED
New state transition starts with SYN1 or SYN2 and adds(revive actually)
STATE_ACK to handle both cases.
case1 : INIT -- syn --> SYN1 -- syn&ack -->ACK -- ack --> ESTABLISHED (normal)
case2 : INIT -- syn&ack --> SYN2 -- syn -->ACK -- ack --> ESTABLISHED
(weird)