Thinking about UDP and tunneling

Julian Elischer julian at
Wed Nov 19 11:14:45 PST 2008

Randall Stewart wrote:
> Dear All:
> I have been contemplating UDP and tunneling. One of the
> things that is a nice feature in MacOS is the ability of
> a kernel module/extension to open a kernel level socket
> and have the mbuf chain that arrives for that port be passed
> in via a function.

define "kernel level" and "mbuf chain that arrives [...] passed in via 
a function"

> We use this in our MacOS version of the SCTP stack to do the
> UDP de-tunneling of SCTP packets. This is becoming a more and
> more common thing i.e. having transport protocols like SCTP and DCCP
> be tunneled over UDP to get by NAT's.... this actually sucks that
> this is necessary .. but it is what it is....

I do that using netgraph..
set a point ot point ng_iface and hook the other end to
a netgraph ksocket which is bound/connaected where you want.

"just works"

> So, I am contemplating adding a similar sort of feature... basically
> provide an interface in UDP that a consumer (such as SCTP or DCCP) could
> use to "bind" a port and get UDP packets directly.
> What do you all think of the idea?

Well netgraph allows you to do it already

> That also reminds me.. who owns the ipfw code.. we actually
> have SCTP nat support that Jason But has done that we need to
> get in...
> I would be more than glad to shepherd this in if the owner
> of the code does not have the time...
> R
> ------------------------------
> Randall Stewart
> 803-317-4952 (cell)
> 803-345-0391(direct)
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