[lwip-devel] [bug #34636] FIN_WAIT_2 - Incorrect shutdown of TCP pcb

[Amir Shalem]

Follow-up Comment #4, bug #34636 (project lwip):

Just to make sure,
The bug is when one side (server) sends lots of data and at the end
shutdown(SHUT_WR) - FIN.
The second side (client) receives data, and when it finishes to read all the
data, recv() should return 0, and the TCP will send ACK to the server (first
side).

The bug in question, which isn't that serious, is that although the server
still holds a socket, after the lwIP will receive the ACK, it will brutally
close the socket after 20ms.

I expected the behavior to be that the client can still send data - he didn't
SHUT_WR his side. And the server can still read data - he didn't SHUT_RD his
side (only SHUT_WR)

After I looked at the code I noticed that FIN_WAIT_2 is the reason for this
faulty behavior, and lwIP TCP uses FIN_WAIT_2 state only for this faulty
behavior - it has no other uses.


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