Date: Mon, 8 Apr 2002 11:54:27 -0600 (MDT) From: Alex Rousskov <rousskov@measurement-factory.com> To: freebsd-net@FreeBSD.ORG Subject: Re: Forcing packets to the wire Message-ID: <Pine.BSF.4.10.10204081142050.59236-100000@measurement-factory.com> In-Reply-To: <Pine.BSF.4.10.10204051543440.54230-100000@measurement-factory.com>
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Hi, Thanks a lot to all those who replied on and off the list! The winner is Andrew R. Reiter <arr at FreeBSD dot org>. Here is a possible solution to the problem, inspired by his response: ifconfig fxp1 fxp1_IP netmask 255.255.255.255 ifconfig fxp2 fxp2_IP netmask 255.255.255.255 route add fxp1_IP -iface -link fxp2:fxp1_MAC_address route add fxp2_IP -iface -link fxp1:fxp2_MAC_address The subnet doesn not have to be /32 as long as the two IPs are in different subnets. We are now testing the throughput limits of the above configuration and contemplating its effect on the rest of our setup. Thank you, Alex. On Fri, 5 Apr 2002, Alex Rousskov wrote: > 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... > > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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