ng_ip_input use case

Brooks Davis brooks at one-eyed-alien.net
Thu Oct 2 16:05:21 PDT 2003


On Thu, Oct 02, 2003 at 03:45:47PM -0700, Julian Elischer wrote:
> On Thu, 2 Oct 2003, Vincent Jardin wrote:
> 
> > I read the man of ng_ip_input and the source code. However I do not
> > understand what the use cases could be. Who is using it and what's
> > for ?
>
> I have no idea what it is used for.. similar effect can be made by
> using the ng_iface node, but I think that they didn't want a separate
> interface for each packet source..
>
> I suggest we ask brooks..(cc'd).  I could imagine it somehow connected
> with the 300 processor FreeBSD based cluster that he is working on at
> hos job (especially as it has their copyright).

It was for a network emulator we were trying to build to allow us to
run real, unmodified programs in an environment where each program
was assumed to be an independent agent and the communication topology
between agents changed in realtime.  Each agent was to bind to the IP
address of an IP-over-IP tunnel (gif on the FreeBSD end).  We would then
take the packets, mangle them slightly and send them off to the emulator
(I think part of the goal was to let us use more or less off the shelf
emulation gear in the middle without needing a workstation for each
agent).  When we got them back, we'd remanged them and stuff them back
into the IP stack with ng_ip_input so it could decide which gif tunnel
to send it back down.  The emulation part of the project died when our
funding for it dried up so we've not actually using this module for
anything.

-- Brooks

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