tcp_fsm.h: sending FIN or FIN+ACK in Closing state

[Vishal M]

Hello:

I have a question on Simulataneous TCP close.

According to the TCP state machine mentioned in
"TCP/IP Illustrated - Vol 2", pg 806; TCP stack is
supposed to just send out an ACK before transitioning
into CLOSING state.

However, according to tcp_outflags[] array shown on pg
807, fig #24.16; the associated flags are FIN+ACK.

I looked at 4.x FreeBSD codebase and it sends out
FIN+ACK while transitioning to CLOSING state (inside
tcp_outflags[] defined in tcp_fsm.h file).

Question:
- Could someone please let me know the correct
behavior i.e should we send out just an ACK or FIN+ACK
while transitioning into CLOSING state?
- Is there is legacy associated with freeBSD in such
scenario?

Thanks for your time and help.

Regards,
Vishal.



		
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