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Date:      Tue, 26 Jun 2001 01:31:17 -0700
From:      Terry Lambert <tlambert2@mindspring.com>
To:        Mike Silbersack <silby@silby.com>
Cc:        Gilbert Gong <ggong@cal.alumni.berkeley.edu>, hackers@FreeBSD.ORG
Subject:   Re: strange tcp behavior?
Message-ID:  <3B384855.341FB05E@mindspring.com>
References:  <20010625213923.V43878-100000@achilles.silby.com>

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Mike Silbersack wrote:
> On Mon, 25 Jun 2001, Gilbert Gong wrote:
> > If I am not mistaken, this should not happen..
> > I'm also relatively certain the TIME_WAIT is not from a
> > previously closed connection..
> >
> > Any ideas what might cause this, or hints on how I can
> > further investigate this?
> 
> That's a known bug with our current tcp sequence number
> generation scheme.  It may be some time before a new scheme
> is put in place, so you'll have to live with it for a while.

The problem is that the number doesn't increment monotonically.

You don't get an RST if the sequence number is less.  The
idea that broke this was an attempt to make things "safer"
by making the sequence number non-predictable, to prevent
session hijack.

If the sequence number is higher, then the previous connection
is reset, and the new connection is established in its place.

-- Terry

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