[mesh-dev] Tackling the 10.0.0.0/8 problem

[Chris Stillson]

I don't see why it would be a problem. Won't NAT just deal with it?

c

Chris

On Sun, Feb 8, 2015 at 8:36 PM, Mitar <mitar at tnode.com> wrote:

> Hi!
>
> How much space do you need? Why not just choose one /16 subnet somewhere
> higher than 10.0.0.0? And then you can take another one /16 when you run
> out of it?
>
> Whole Germany manages to the whole /8. :-)
>
> http://wiki.freifunk.net/IP-Netze
>
>
> Mitar
>
> > One big issue that we will have to deal with before really launching is
> the
> > fact that several home routers use 10.0.0.0
> >
> > I honestly don't know if any of them use 10.0.0.0/8 or if they're all
> > 10.0.0.0/24 but either way it's a problem.
> >
> > There are two possible solutions.
> >
> > = We don't use 10.x.x.x for the mesh =
> >
> > There _are_ alternatives but one of them look great. Here are some I've
> > looked at.
> >
> > == 44.0.0.0/8 ==
> >
> > This is the HAM or AMPRnet subnet. It looks like it's very scarcely used,
> > if it's really used at all. It's for HAM packet radio and
> experimentation.
> > One the one hand I don't want to piss of the HAMs, but on the other hand
> > their entire subnet is in violation of net neutrality since they don't
> > allow commercial traffic on their subnet. This is definitely the easy
> > solution.
> >
> > Here's an overview of their allocations:
> >
> >   https://portal.ampr.org/networks.php
> >
> > I'm sure if we did a ping scan of the address space we'd see only very
> few
> > hosts. Anyone wanna take a stab at that?
> >
> > == 238.0.0.0/8 ==
> >
> > Using multicast address space as unicast unfortunately does not work.
> >
> > == 240.0.0.0/8 ==
> >
> > All of 240.0.0.0 and above is designated as "future use". However, an
> IETF
> > proposal to take it into use was rejected, apparently partially because
> > many IP stacks just outright reject or ignore any packets from this
> address
> > space. We'd need an overview of which systems are affected, but I don't
> > really think this is a viable option.
> >
> > = We use 10.x.x.x for the mesh =
> >
> > If we are to use 10.x.x.x for the mesh then we will have to do something
> > clever/ugly.
> >
> > A solution would contain the following parts:
> >
> > * The DHCP client would have to remap 10/8 DHCP responses on eth0 to a
> > different subnet (this could be 240/8) such that the interface takes on
> an
> > address different from the one provided by the DHCP server.
> > * ARP spoofing would have to be enabled on eth0 such that the node will
> > respond to ARP requests for the address it was assigned via DHCP.
> > * All incoming traffic on eth0 with a destination of 10/8 would have to
> be
> > remapped to 240/8 before routing happens
> > * All outgoing traffic on eth0 with a destination of 240/8 would have to
> be
> > remapped to 10/8 after routing happens
> >
> > To accomplish the DHCP fakery, a modification to the openwrt dhcp client
> > would have to be written. I don't foresee that being very difficult.
> > Depending on the ARP spoofing difficulty, it could be as simple as adding
> > support for a hook script that runs on dhcp lease acceptance.
> >
> > I'm not sure how best to do the ARP spoofing. There may be mechanisms
> built
> > into the Linux kernel. It may be that we can actually just assign the
> > 10.x.x.x address gotten from the dhcp server to eth0 in addition to the
> > 240.x.x.x address and just ensure that no mention of the 10.x.x.x address
> > appears in the routing table and that the kernel is configure to _not_
> > respond to ARP requests on interfaces other than the interface they are
> > inquiring about (the default is to always answer).
> >
> > It seems that the address remapping might already be possible. I haven't
> > yet tested if it works as expected, but the following commands seem to be
> > what we'd need:
> >
> > iptables -t nat -A PREROUTING -i eth0 -s 10.0.0.0/8 -j NETMAP --to
> > 239.0.0.0/8
> > iptables -t nat -A POSTROUTING -o eth0 -d 239.0.0.0/8 -j NETMAP --to
> > 10.0.0.0/8
> >
> > I'll try to set up a little experiment later tonight to see if this
> > remapping works as expected. Honestly though, using 44.0.0.0/8 seems
> really
> > attractive to me at this point.
> >
> >
> >
> > _______________________________________________
> > mesh-dev mailing list
> > mesh-dev at lists.sudoroom.org
> > https://lists.sudoroom.org/listinfo/mesh-dev
> >
>
> --
> http://mitar.tnode.com/
> https://twitter.com/mitar_m
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