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From Cliff Skolnick <>
Subject Re: Finish 1.2!
Date Fri, 10 Jan 1997 07:38:37 GMT
On Thu, 9 Jan 1997, Brian Behlendorf wrote:
> > I'm wondering if the FIN_WAIT_2 thing may start causing a lot of problems
> > after release?  There are a good number of people having tons of
> > connections stuck in FIN_WAIT_2 that they didn't have before 1.2 but do
> > with 1.2.  
> I wish we knew more about what may be causing this.  Certainly adding a note to
> the docs suggesting toggling the lingering close code may be appropriate, yet I
> haven't seen conclusive evidence that that's the problem.  For what it's worth
> it's not been a problem on any of the servers I watch (Solaris with 1.5 mill
> hits/day, BSDI with ~150K, SGI with ~40K).

Well this is actually a well known TCP/IP bug.  If I remember correctly 
it had something to do with the client "disappearing" from the net (like 
hanging up their ISP) and not letting the socket fully close.  I thought 
a while about why this could be worse with 1.2, and the only two things I 
come up with are:

	1) They were always there, and people are just noticing them.  The
	people who downgraded and still saw them said nothing, but the people
	who downgraded and did not see them spoke up really loudly.  The only
	real cause was the random there/not there factor.  I know I have
	always seen these until I applied a patch to get rid of them
	after a while, this was a kernel thing since these sockets are not
	tied to a user process.

	2) Sockets are gettting stuck in 1.2, increasing the chance that
	this may happen.  If the server does not close the connection and
	lets it timeout I can guess there may be a greater chance of a
	FIN_WAIT2 when the server starts timing stuff out and you have a
	bunch of dialup users logging of the net.

Any other thoughts?  Maybe we should ask the people to send the error_log and
see if there are more timeouts reported for 1.2 that 1.1?  Way to test 
for #2.


Cliff Skolnick, Technical Consultant
Steam Tunnel Operations, 415.297.5938

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