Update RX sequence number after refusing TCP FIN packet.

[ActoryOu]

Update RX sequence number after refusing TCP FIN packet.

Description

As FreeRTOS Forum TCP Refusing FIN mentioned, the expected RX sequence is not well handled in the stack when refusing FIN. Update the RX sequence number when hitting this scenario.

Test Steps

Refer to this forum post for the test result.

1. Create TCP connection.
2. Keep sending packets.
3. Receiving FIN packet.

Checklist:

• I have tested my changes. No regression in existing tests.
• [] I have modified and/or added unit-tests to cover the code changes in this Pull Request.

Related Issue

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[htibosch]

Thank you @ActoryOu for this PR. I already commented the case on the FreeRTOS forum.
I also agree with this extra check:

+    if( lDistance == 1 )
+    {
         pxTCPWindow->rx.ulCurrentSequenceNumber =
             pxTCPWindow->rx.ulFINSequenceNumber + 1U;
+    }
}

[mike919192]

Hi, I have backported the changes to TCP 3.1.0 for testing, using kernel 10.5.1 and Xilinx Zynq port. All appears to be working as expected. Let me know if there is any other information I can provide. Thanks for the great support!

Gain: Socket 6000 now has 1 / 1 child
prvSocketSetMSS: 1460 bytes for C0A81505ip:53356
Socket 6000 -> C0A81505ip:53356 State eCLOSED->eSYN_FIRST
prvWinScaleFactor: uxRxWinSize 2 MSS 1460 Factor 0
Socket 6000 -> C0A81505ip:53356 State eSYN_FIRST->eSYN_RECEIVED
TCP: passive 6000 => C0A81505ip:53356 set ESTAB (scaling 1)
Socket 6000 -> C0A81505ip:53356 State eSYN_RECEIVED->eESTABLISHED
Starting network tasks
Refusing FIN[6000,53356]: RxCompl 1 tx done 0
TCP: RST received from C0A81505ip:53356 for 6000
Socket 6000 -> C0A81505ip:53356 State eESTABLISHED->eCLOSED
error reading from socket
Notify txTask to shutdown
Tx task is deleting itself
Lost: Socket 6000 now has 0 / 1 children
FreeRTOS_closesocket[6000 to C0A81505ip:53356]: buffers 64 socks 1
Rx task is deleting itself