Date: Wed, 10 Apr 2002 23:18:51 -0700 From: "Crist J. Clark" <cjc@FreeBSD.ORG> To: Paulius Bulotas <paulius@kaktusas.org> Cc: freebsd-net@FreeBSD.ORG Subject: Re: strange network conversation Message-ID: <20020410231851.B37066@blossom.cjclark.org> In-Reply-To: <20020410090644.GB8914@kaktusas.org>; from paulius@kaktusas.org on Wed, Apr 10, 2002 at 11:06:44AM %2B0200 References: <20020410090644.GB8914@kaktusas.org>
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On Wed, Apr 10, 2002 at 11:06:44AM +0200, Paulius Bulotas wrote:
> Hello list,
>
> I'm seeing strange? networking behaviour with my FreeBSD server, and it
> seems that this list is tne right to ask ;)
> Suppose, there is outgoing connection for whom dynamic rule is created
> (that's how I noticed it - ipfw logs denied packets). My 4.4-Release
> FreeBSD is hostA, something on the next end is hostB - smtp server.
> That's how the end of smtp session looks:
>
> _Host tcpflags seq nseq ack data_
> hostA ( [PSH,ACK], seq1, nseq1, ack1, "QUIT" )
> hostA ( [FIN,ACK], nseq1, -- , ack1 )
> hostB ( [[ACK], ack1, -- , nseq1)
> hostB ( [PSH,ACK], ack1, nseq2, nseq1, "221 Bye")
> hostA ( [RST], nseq1, -- , -- )
> hostB ( [FIN,ACK], nseq2, -- , nseq1)
> hostB ( [ACK], nseq2+1, -- , nseq1+1)
> hostB ( [FIN,PSH,ACK], ack1, nseq2, nseq1+1)
> ...
>
> I'm wondering, why FreeBSD sends RST so early and hostB tries to send
> something back (and that didn't match dynamic rule, which is destroyed
> upon RST (I suspect))?
Is that _really_ what happens because,
> hostA ( [PSH,ACK], seq1, nseq1, ack1, "QUIT" )
> hostA ( [FIN,ACK], nseq1, -- , ack1 )
> hostB ( [[ACK], ack1, -- , nseq1)
^^^^^
Should be, nseq1 + 1. But I think that would explain the RST.
> Is it possible to change this? (so that conversation between hostA and
> hostB ended normally)
If hostB's stack is really broken, not sure what to do to fix it.
--
Crist J. Clark | cjclark@alum.mit.edu
| cjclark@jhu.edu
http://people.freebsd.org/~cjc/ | cjc@freebsd.org
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