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Date:      Tue, 26 Nov 2002 11:03:13 -0500
From:      Don Bowman <don@sandvine.com>
To:        "'freebsd-net@freebsd.org'" <freebsd-net@freebsd.org>
Subject:   IPFW question with options and fwd rule
Message-ID:  <FE045D4D9F7AED4CBFF1B3B813C853370102303E@mail.sandvine.com>

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If I create a rule to 'fwd' packets with a particular TCP option 
set (or IP option) to a specific local port, and then I accept
on that port, will subsequent packets without that option work?

ie, I have this:

100 fwd localhost,9000 tcp from any to any 1234 tcpoptions ts recv interface

SYN (TCP option SACK=1), Dest port=5555, Dest ip = random-host
SYN/ACK
ACK (no TCP options)

will the first SYN reach me? (yes I think, even though the IP is not mine
and
the dest port is not me, the ipfw fwd magic takes care).
Will the ACK from the client reach me? (the dest ip is not me, so will the
stack discard, or will the already created PCB take care of this?)

I'd like to carry on a normal TCP conversation, but select the local port
that terminates it based on a TCP option. The destination IP will be
somewhere
else (its a transparent proxy application).

Thanks in advance.

--don (don@sandvine.com www.sandvine.com)

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