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Date:      Sun, 25 Mar 2007 23:33:07 +1000 (EST)
From:      Ian Smith <smithi@nimnet.asn.au>
To:        Richard <rleippe@bellsouth.net>
Cc:        freebsd-questions@freebsd.org
Subject:   [OT] Re: TCP conection problems IBM VM -> FreeBSD
Message-ID:  <Pine.BSF.3.96.1070325225506.19711A-100000@gaia.nimnet.asn.au>
In-Reply-To: <20070324120023.91CC916A4D6@hub.freebsd.org>

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On Sat, 24 Mar 2007 07:40:50 -0400 Richard reckons:
[..]
 > 	Then I started thinking (always a fruitless endeavor), why would a *BSD
 > based firewall/"IP stack" drop the corresponding SYN-ACK when it was
 > activated?  And that thought just fucking bugged me to no end.  I could
 > accept some crazy IBM "IP stack" not dealing with *BSD, but this was
 > *BSD box to *BSD box on the return path that dropped the packet. Also,
 > according to the original poster bang.swox.se has no problems
 > communicating with other systems and he has no problems communicating to
 > vm.se.lsoft.com.

I can't help with the Real Problem here, hence Subject change, but ..

[..]
 > 	** After looking through "Stevens TCP/IP Illustrated" I can find no
 > reference to what sequence number a RST packet should have if a SYN-ACK
 > precedes it.  I'm unsure whether the RST should ACK the SYN + 1, as a
 > SYN consumes a byte in normal operation, or return the ISN to the
 > sending host. But as sending a RST in response to a SYN-ACK is not
 > normal operation; such ambiguities would likely be left to the
 > programmers discretion.  In this case IBM not a stack derived from *BSD.

Secondly, the IBM TCP/IP stack and most userland network utilities were
declaredly BSD-derived at least through the '90s OS/2 times - and likely
much earlier, but I've not played with an IBM mainframe since '73 :)

But firstly, I wonder why you'd expect IBM to run 'some crazy' stack?

 > this now opens a whole new box of worms?!?!?

Hopefully not ..

Cheers, Ian




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