linux/linux-5.4.31/Documentation/networking/batman-adv.rst

.. SPDX-License-Identifier: GPL-2.0

==========
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).


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-adv can operate. The batman-adv soft-interface can be created using the
iproute2 tool ``ip``::

  $ ip link add name bat0 type batadv

To activate a given interface simply attach it to the ``bat0`` interface::

  $ ip link set dev eth0 master bat0

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

To deactivate an interface you have to detach it from the "bat0" interface::

  $ ip link set dev eth0 nomaster

The same can also be done using the batctl interface subcommand::

  batctl -m bat0 interface create
  batctl -m bat0 interface add -M eth0

To detach eth0 and destroy bat0::

  batctl -m bat0 interface del -M eth0
  batctl -m bat0 interface destroy

There are additional settings for each batadv mesh interface, vlan and hardif
which can be modified using batctl. Detailed information about this can be found
in its manual.

For instance, you can check the current originator interval (value
in milliseconds which determines how often batman-adv sends its broadcast
packets)::

  $ batctl -M bat0 orig_interval
  1000

and also change its value::

  $ batctl -M bat0 orig_interval 3000

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.

Information about the current state can be accessed via the batadv generic
netlink family. batctl provides human readable version via its debug tables
subcommands.


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: ip link set up dev bat0
  NodeA: ip addr add 192.168.0.1/24 dev bat0

  NodeB: ip link set up dev bat0
  NodeB: ip addr add 192.168.0.2/24 dev bat0
  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.::

  $ ip addr flush dev eth0


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``
(``CONFIG_BATMAN_ADV_DEBUG=y``).

Those additional debug messages can be accessed using the perf infrastructure::

  $ trace-cmd stream -e batadv:batadv_dbg

The additional debug output is by default disabled. It can be enabled during
run time::

  $ batctl -m bat0 loglevel routes tt

will enable debug messages for when routes and translation table entries change.

Counters for different types of packets entering and leaving the batman-adv
module are available through ethtool::

  $ ethtool --statistics bat0


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 https://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.org (optional subscription at
  https://lists.open-mesh.org/mm/listinfo/b.a.t.m.a.n)

You can also contact the Authors:

* Marek Lindner <mareklindner@neomailbox.ch>
* Simon Wunderlich <sw@simonwunderlich.de>