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Date:      Fri, 5 Apr 2002 16:28:37 -0700 (MST)
From:      Alex Rousskov <rousskov@measurement-factory.com>
To:        freebsd-net@FreeBSD.ORG
Subject:   Forcing packets to the wire
Message-ID:  <Pine.BSF.4.10.10204051543440.54230-100000@measurement-factory.com>

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Hi there,

	I have two Ethernet NICs inside a PC. I want TCP/IP packets to
leave one NIC, go on the wire, and eventually arrive at the other NIC.
I do not want the kernel to be smart and shortcut the path. I want the
outside world to see the packets and to think that my two NICs are two
PCs talking to each other.

	Could any networking guru answer the following questions:

	- Is it possible without kernel modifications? How?

	- If kernel modifications are required, how extensive
	  would they be (e.g., how many hours would it take a guru
	  to implement the required functionality)?

	I am flexible as far as IP addressing scheme is concerned,
though I would prefer to be able to put both NIC IP addresses on one
and on separate subnets (from the outside world point of view). Again,
I want the outside world think that these NICs are inside two PCs.

	If you want to know a "use case" for this strange requirement,
here it is: I am building an appliance to test HTTP proxies. I want an
appliance to have one NIC for the "client side" and one NIC for the
"server side". I want to be able to run no-proxy test through the
networking gear (a baseline experiment testing hubs/switches for
bottlenecks), and I want to test "transparent proxies" (clients think
they send requests directly to servers).


Thank you,

Alex.

P.S. So far, all attempts to make this work have failed. Even jail
environment does not go far enough and lets the "jailed" packet to
traverse the kernel instead of using the wires...


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