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Date:      Sun, 10 Mar 2002 14:40:45 -0500
From:      Matt Impett <M.Impett@flarion.com>
To:        "'freebsd-net@freebsd.org'" <freebsd-net@freebsd.org>
Subject:   FW: policy routing to tunnels..
Message-ID:  <8C92E23A3E87FB479988285F9E22BE460235FB@ftmail>

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> Hello.. I am working on a mobileIP implementation on freeBSD, and I have a
> question about how to do something with the freeBSD IP networking stack.
> This is the jist:
> 
> Basically, what I want to be able to do is to add a policy route to a
> freebsd router so that it will take packets with specific source addresses
> and pass them to a tunnel.  Now, I have seen examples of the ipfw command
> that would handle this, but I don't think they apply to me. This is why:
> 
> I have created a gif tunnel and have set the physsrc and physdest
> addresses of the tunnel but I have not actually given the point to point
> interface its addresses (ie, with the ifconfig command, or something
> similar).  The reason why is that for the majority of the tunnel lifetime,
> I do not want to transmit any packets on it, but only receive.  Therefore,
> I want no route to the tunnel for any IP addresses.  However, at some
> point during the tunnel lifetime, I may want to redirect packets with
> particular source addresses into the tunnel.
> 
> Now, if I had a routing table entry which pointed to the tunnel, something
> like this:
> Destination		Gateway	Netif
> a.b.c.d			gif0		gif0
> 
> then I guess I could do something like this with ipfw:
> ipfw add fwd a.b.c.d ip from <my src addr that I want tunnelled> to any
> 
> However, I have no routes in my routing table for this tunnel.  The reason
> why is there is no destination address which I always want to tunnel for.
> I really only want to tunnel based on source address.  (As I side note,
> would the above work?? I ask because I guess a hack to make this work
> would be to make up a dummy private IP and put a route in for it using my
> tunnel as outgoing interface, then I could use the firewalling code to
> direct packets to that "fake route".. ugh..)
> 
> My question then is it is possible to route packets with particular source
> addresses directly to a particular interface?? Or, is there some other way
> I could accomplish this same thing??
> 
> Now, for anyone familiar with mobileIP and wondering what exactly I am
> trying to do with all this craziness, I am trying to implement mobileIP
> reverse tunneling (RFC 2344).
> 
> Also, I have never posted here before, so I don't really know the
> protocol, but here is some (potentially) useful info:
> FreeBSD version: 4.4-RC5
> 
> thanks for your time,
> matt

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