How to kill TCP connection in LAST_ACK state

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2 total messages Started by Peter Miles Fri, 27 May 1994 08:42

#15522

Author: Peter Miles
Date: Fri, 27 May 1994 08:42

18 lines
1400 bytes

It is possible (and if so how?) to kill off, manually or otheriwse, a tcp 
connection which is the LAST_ACK state (as shown by netstat)? 

The client side does not appear to be sending a FIN before closing 
its side of a telnet/rlogin connection. This is leaving the server with a 
number of connections in LAST_ACK state with sometimes 30K each of bytes 
in the Send-Q (again, according netstat).

I'd like to find a way to zap these connections (with out shutting down 
the rest of tcp/ip). (Unfortunately, I can't do anything about the client 
side of the connection).

This is on a system running SCO UNIX and SCO TCP 1.2.1.

		-- Pete
-- 
Pete Miles			pmiles@dircon.co.uk
				...pipex!dircon!pmiles

Re: How to kill TCP connection in LAST_ACK state

#15523

Author: Lance Visser
Date: Sun, 29 May 1994 02:35

24 lines
1740 bytes

In <2s4bqf$lup@tdc.dircon.co.uk> pmiles@tdc.dircon.co.uk (Peter Miles) writes:

+>It is possible (and if so how?) to kill off, manually or otheriwse, a tcp 
+>connection which is the LAST_ACK state (as shown by netstat)? 

	LAST_ACK means both sides of the connection have sent FINs
to each other.  The side in LAST_ACK is waiting for the FIN it sent
to be ack'ed.

	The only way I can think to kill it off is to somehow forge
a TCP packet with the reset bit set and send it to the connection
stuck in FIN_WAIT from another host.  You could build a command
that would take the necessary ip addresses and tcp ports as arguements
to do it if you had raw access to the network.  It could be done, but
it would be a pain to write.




+>The client side does not appear to be sending a FIN before closing 
+>its side of a telnet/rlogin connection. 

	If that were the case, you would be in ESTABLISHED, FIN_WAIT_1
or FIN_WAIT_2, not LAST_ACK.

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