Once the normal flow of operation is assumed, i.e. either the TAO or the 3-Way Handshake has been completed successfully, the CC options are used to determine if the packet arrived is for the correct connection.
If the CC value in the received packet is not equal to the value expected (sk->cc_recv) then the packet is discarded. If it is, then the segment can be accepted and dropped into the normal TCP/IP processing that performs other validation such as bad sequence numbers.