[B.A.T.M.A.N.] updated README

[Marek Lindner <lindner_marek@yahoo.de>]

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Hey,

Andrew pointed out that our README would need a little bit of love. I spent 
some time to get the text into a decent shape. I attached the full file for a 
review. Let me know if you find anything.  :)

Cheers,
Marek

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[state: 03-05-2010]

BATMAN-ADV
----------

Batman advanced is a new approach to wireless networking which does no longer
operate on the IP basis. Unlike the batman daemon, which exchanges
information using UDP packets and sets routing tables, batman-advanced operates
on ISO/OSI Layer 2 only and uses and routes (or better: bridges) Ethernet
Frames. It emulates a virtual network switch of all nodes participating.
Therefore all nodes appear to be link local, thus all higher operating
protocols won't be affected by any changes within the network. You can run
almost any protocol above batman advanced, prominent examples are: IPv4, IPv6,
DHCP, IPX.

Batman advanced was implemented as a Linux kernel driver to reduce the overhead
to a minimum. It does not depend on any (other) network driver, and can be used
on wifi as well as ethernet lan, vpn, etc ... (anything with ethernet-style
layer 2). It compiles against and should work with Linux 2.6.20 - 2.6.33.
Supporting older versions is not planned, but it's probably easy to backport it.
If you work on a backport, feel free to contact us.  :-)


COMPILE
-------
To compile against your currently installed kernel, just type:

# make

if you want to compile against some other kernel, use:

# make KERNELPATH=/path/to/kernel


CONFIGURATION
-------------

Load the batman-adv module into your kernel:

# insmod batman-adv.ko

The module is now waiting for activation. You must add some interfaces on which
batman can operate. After loading the module batman advanced will scan your
systems interfaces to search for compatible interfaces. Once found, it will
create subfolders in the /sys directories of each supported interface, e.g.

# ls /sys/class/net/eth0/batman_adv/

If an interface does not have the "batman_adv" subfolder it probably is not
supported. Not supported interfaces are: loopback, non-ethernet and batman's
own interfaces.

Note: After the module was loaded it will continuously watch for new interfaces
to verify the compatibility. There is no need to reload the module if you plug
your USB wifi adapter into your machine after batman advanced was initially
loaded.

To activate a given interface simply write "bat0" into its "mesh_iface" file
inside the batman_adv subfolder:

# echo bat0 > /sys/class/net/eth0/batman_adv/mesh_iface

Repeat this step for all interfaces you wish to add.
Now batman starts using/broadcasting on this/these interface(s).

By reading the "iface_status" file you can check its status:

# cat /sys/class/net/eth0/batman_adv/iface_status

To deactivate an interface you have to write "none" into its "mesh_iface" file:

# echo none > /sys/class/net/eth0/batman_adv/mesh_iface


All mesh wide settings can be found in batman's own interface folder:

# ls /sys/class/net/bat0/mesh/

Some of the files contain all sort of status information regarding the mesh
network. For exmaple, you can view the table of originators (mesh participants)
with:

# cat /sys/class/net/bat0/mesh/originators

Other files allow to change batman's behaviour to better fit your requirements.
For instance, you can check the current originator interval (value in
milliseconds which determines how often batman sends its broadcast packets):

# cat /sys/class/net/bat0/mesh/orig_interval

and also change its value:

# echo 3000 > /sys/class/net/bat0/mesh/orig_interval

In very mobile scenarios, you might want to adjust the originator interval to a
lower value. This will make the mesh more responsive to topology changes, but
will also increase the overhead.


USAGE
-----

To make use of your newly created mesh, batman advanced provides a new
interface "bat0" which you should use from this point on. All interfaces added
to batman advanced are not relevant any longer because batman handles them for
you. Basically, one "hands over" the data by using the batman interface and
batman will make sure it reaches its destination.

The "bat0" interface can be used like any other regular interface. It needs an
IP address which can be either statically configured or dynamically (by using
DHCP or similar services):

# NodeA: ifconfig bat0 192.168.0.1 up
# NodeB: ifconfig bat0 192.168.0.2 up
# NodeB: ping 192.168.0.1

Note: In order to avoid problems remove all IP addresses previously assigned to
interfaces now used by batman advanced, e.g.

# ifconfig eth0 0.0.0.0


VISUALIZATION
-------------

If you want topology visualization, at least one mesh node must be configured
as VIS-server:

# echo "server" > /sys/class/net/bat0/mesh/vis_mode

Each node is either configured as "server" or as "client" (default: "client").
Clients send their topology data to the server next to them, and server
synchronize with other servers. If there is no server configured (default)
within the mesh, no topology information will be transmitted. With these
"synchronizing servers", there can be 1 or more vis servers sharing the same
(or at least very similar) data.

When configured as server, you can get a topology snapshot of your mesh:

# cat /sys/class/net/bat0/mesh/vis_data

This raw output is intended to be easily parsable and convertable with other
tools. Have a look at the batctl README if you want a vis output in dot or json
format for instance and how those outputs could then be visualised in an image.

The raw format consists of comma seperated values per entry where each entry is
giving information about a certain source interface. Each entry can/has to have
the following values:
-> "mac" -> mac address of an originator's source interface
           (each line begins with it)
-> "TQ mac value" -> src mac's link quality towards mac address of a neighbor
                     originator's interface which is being used for routing
-> "HNA mac" -> HNA announced by source mac
-> "PRIMARY" -> this is a primary interface
-> "SEC mac" -> secondary mac address of source (requires preceeding PRIMARY)

The TQ value has a range from 4 to 255 with 255 being the best.
The HNA entries are showing which hosts are connected to the mesh via bat0
or being bridged into the mesh network.
The PRIMARY/SEC values are only applied on primary interfaces


LOGGING/DEBUGGING
-----------------

All error messages, warnings and information messages are sent to the kernel
log. Depending on your operating system distribution this can be read in one of
a number of ways. Try using the commands: dmesg, logread, or looking in the
files /var/log/kern.log or /var/log/syslog. All batman-adv messages are
prefixed with "batman-adv:" So to see just these messages try

# dmesg | grep batman-adv

When investigating problems with your mesh network it is sometimes necessary to
see more detail debug messages. This must be enabled when compiling the
batman-adv module. When building batman-adv as part of kernel, use
"make menuconfig" and enable the option "B.A.T.M.A.N. debugging". When
compiling outside of the kernel tree it is necessary to edit the file
Makefile.kbuild and uncomment the line

#EXTRA_CFLAGS += -DCONFIG_BATMAN_ADV_DEBUG

The additional debug output is by default disabled. It can be enabled either at
kernel modules load time or during run time. To enable debug output at module
load time, add the module parameter debug=<value>.
<value> can take one of four values.

0 - All debug output disabled
1 - Enable messages related to routing / flooding / broadcasting
2 - Enable route or hna added / changed / deleted
3 - Enable all messages

e.g.

# modprobe batman-adv debug=2

will load the module and enable debug messages for when routes or HNAs change.

The debug output can also be changed at runtime using the file
/sys/module/batman-adv/parameters/debug. e.g.

# echo 2 > /sys/module/batman-adv/parameters/debug

enables debug messages for when routes or HNAs

The debug output is sent to the kernel logs. So try dmesg, logread, etc to see
the debug messages.


BATCTL
------

As batman advanced operates on layer 2 all hosts participating in the virtual
switch are completely transparent for all  protocols above layer 2. Therefore
the common diagnosis tools do not work as expected. To overcome these problems
batctl was created. At the  moment the  batctl contains ping, traceroute,
tcpdump and interfaces to the kernel module settings.

For more information, please see the manpage (man batctl).

batctl is available on http://www.open-mesh.org/


CONTACT
-------

Please send us comments, experiences, questions, anything :)

IRC:             #batman on irc.freenode.org
Mailing-list:    b.a.t.m.a.n@open-mesh.net
(optional subscription at https://lists.open-mesh.org/mm/listinfo/b.a.t.m.a.n)

You can also contact the Authors:

Marek Lindner <lindner_marek@yahoo.de>
Simon Wunderlich <siwu@hrz.tu-chemnitz.de>