I don't know of any real TCP stacks that accept all RSTs with no validation checks. The trend has definitely been in the opposite direction... That TCP impleme

I don't know of any real TCP stacks that accept all RSTs with no validation checks. The trend has definitely been in the opposite direction... That TCP implementations are interoperable almost all the time is a major feat of design and engineering. For the specific case of RST handling, there's two reasons why it does. First, the RSTs sent in reply to packets received on closed sockets allow the system to converge. That's a clever bit of design, and if it's taken out (as appears to have been the case in the last example), the teardown becomes fragile. Second, if a connection doesn't get closed properly all that happens normally is some resource wastage. The main purpose of the connection (transfering data) worked correctly, so the failure after that won't get noticed.