Title: A Raspberry Pi based batman-adv Mesh network node
Tags: english, nuug, freedombox, mesh network
Date: 2013-10-21 11:40

<p>The last few days I have been experimenting with the batman-adv
mech technology.  I want to gain some experience to see if it will fit
the Freedombox project, and try to build a mesh network around the
park where I live together with my neighbors.  Batman-adv is a layer 2
mesh system ("ethernet" in other words), where the mesh network appear
as if all the mesh clients are connected to the same switch.</p>

<p>My hardware of choice were the Linksys WRT54GL routers I had lying
around, but I've been unable to get them working with batman-adv.  So
instead, I started playing with a Raspberry Pi, and tried to get it
working as a mesh node.  My idea is to use it to create a mesh node
which function as a switch port, where everything connected to the
Raspberry Pi ethernet plug is connected to the mesh network.  This
allow me to hook a wifi base station like the Linksys WRT54GL to the
mesh by plugging it into a Raspberry Pi, and thus allow non-mesh
clients to hook up to the mesh.  This in turn is useful for Android
phones using <ahref="http://servalproject.org/">the Serval Project</a>
voip client, allowing every one around the playground to phone and
message each other for free.</p>

<p>To get this working, I've created a debian package
<ahref="https://github.com/petterreinholdtsen/meshfx-node">meshfx-node</a>
and a script
<ahref="https://github.com/petterreinholdtsen/meshfx-node/blob/master/build-rpi-mesh-node">build-rpi-mesh-node</a>
to create the Raspberry Pi boot image.  I'm using Debian Jessie (and
not Raspbian), to get more control over the packages available.
Unfortunately a huge binary blob need to be inserted into the boot
image to get it booting, but I'll ignore that for now.</p>

<p>To create an image, run the following with a sudo enabled user
after inserting the target SD card into the build machine:</p>

<p><pre>
% wget -O build-rpi-mesh-node \
    https://raw.github.com/petterreinholdtsen/meshfx-node/master/build-rpi-mesh-node
% sudo bash -x ./build-rpi-mesh-node > build.log 2>&1
% dd if=/root/rpi/rpi_basic_jessie_$(date +%Y%m%d).img of=/dev/mmcblk0 bs=1M
%
</pre></p>

<p>Booting with the resulting SD card on a Raspberry PI with a USB
wifi card inserted should give you a mesh node.  The default mesh
settings are the ones used by the Oslo mesh project at Hackeriet, as I
mentioned in
<ahref="http://people.skolelinux.org/pere/blog/Oslo_community_mesh_network___with_NUUG_and_Hackeriet_at_Hausmania.html">an
earlier blog post about this mesh testing</a>.</p>

<p>The mesh node was not horribly expensive either.  I bought
everything over the counter in shops nearby.  If I had ordered online
from the lowest bidder, the price should be significantly lower:</p>

<p><table>

<tr><th>Supplier</th><th>Model</th><th>NOK</th></tr>
<tr><td>Teknikkmagasinet</td><td>Raspberry Pi model B</td><td>349.90</td></tr>
<tr><td>Teknikkmagasinet</td><td>Raspberry Pi type B case</td><td>99.90</td></tr>
<tr><td>Lefdal</td><td>Jensen Air:Link 25150</td><td>295.-</td></tr>
<tr><td>Clas Ohlson</td><td>Kingston 16 GB SD card</td><td>199.-</td></tr>
<tr><td>Total cost</td><td></td><td>943.80</td></tr>

</table></p>

<p>Now my mesh network at home consist of one laptop in the basement
connected to my production network, one Raspberry Pi node on the 1th
floor that can be seen by my neighbor across the park, and one
play-node I use to develop the image building script.  I look forward
to figuring out what kind of latency the batman-adv setup will give,
and how much packet loss we will experience around the park. :)</p>