Send FIN even if remote station has not yet acknowledged all sent data

The TCP Stack shall send a FIN signal to the remote station, even in the case that data which was sent to the remote station is still unacknowledged.

The current implementation sends the FIN signal only if all data is acknowledged by the remote station. This behavior has the following disadvantages:

• If network is interrupted (e.g. cable pulled) and at the same time there is unacknowledged data, the TCP stack will never reject/close the connection to the remote station on its own, since the remote station will never acknowledge the data. In that scenario the application is required to close the TCP socket internally.
• A requested FIN signal from the application (by closing the socket) will be delayed if there is unacknowledged data present. The remote station may delay the acknowledgment of data (typical 250 millisecond) to avoid unnecessary data traffic on the bus.