B.A.T.M.A.N. OpenWrt configuration

This page showcases some basic batman-adv configurations on OpenWrt including wireless & network setups. However, the goal is to provide not more than a starting point. For a full reference of the OpenWrt uci system please visit the official OpenWrt uci documentation.

The configuration for the following common example is provided: One AP with a wireless “adhoc” interface is supposed to run batman-adv (essentially, the setup explained in our Quick-start-guide).

Network Configuration

The batman-adv OpenWrt support provides three different protos:

batadv_hardif
- network interface used by batadv meshif to transport the batman-adv packets
- it is assigned to the batadv meshif
batadv (meshif/softif)
- virtual interface that emulates a normal 802.3 interface on top
- encapsulates traffic and forwards it via the batadv hardifs
batadv_vlan
- potential VLAN ID on top of batadv meshif
- allows filtering of traffic from specific VIDs

The first step is to create the “batadv” mesh interface (in our case “bat0”) in /etc/config/network with the optional list of options:

config interface 'bat0'
      option proto 'batadv'
      ## optional settings to override the defaults:
      option routing_algo 'BATMAN_IV'
      option aggregated_ogms 1
      option ap_isolation 0
      option bonding 0
      option fragmentation 1
      option gw_mode 'off'
      #option gw_bandwidth '10000/2000'
      #option gw_sel_class 20
      option log_level 0
      option orig_interval 1000
      option bridge_loop_avoidance 1
      option distributed_arp_table 1
      option multicast_mode 1
      option multicast_fanout 16
      option network_coding 0
      option hop_penalty 30
      option isolation_mark '0x00000000/0x00000000'

The next step is to add actual network device has “batadv_hardif” to the “bat0” batadv meshif. This is done by specifying a “batadv_hardif” interface section per network device. Here we add eth0 and the mesh0 (from /etc/config/wireless) to bat0. It is important to adjust the MTU of the batadv_hardif devices to avoid fragmentation.:

# add *single* wifi-iface with network bat0_hardif_mesh0 as hardif to bat0
config interface 'bat0_hardif_mesh0'
      option proto 'batadv_hardif'
      option master 'bat0'
      option mtu '1536'
      # option ifname is filled out by the wifi-iface

# add eth0 as hardif to bat0
config interface 'bat0_hardif_eth0'
      option proto 'batadv_hardif'
      option master 'bat0'
      option mtu '1536'
      option ifname 'eth0'
      option hop_penalty 15
      # change throughput_override to 0 to use automatic detection; also allows kbit suffix
      option 'throughput_override' '1mbit'

The “bat0” batadv meshif can then be used like any other network device. It can be added to bridges by adding “bat0” to the list of “ifnames” of the bridge like this:

# add bat0 to the lan bridge
config interface 'client'
      option type 'bridge'
      list ifname 'bat0'
      ...

Or an IP can be configured using:

# configure IP on bat0
config interface 'bat0_lan'
      option ifname 'bat0'
      option proto 'static'
      option ipaddr '192.168.1.1'
      option netmask '255.255.255.0'
      option ip6assign '60'

VLAN specific options have to be configured in a separated stanza having protocol ‘batadv_vlan’.

In this particular section the user has to specify the name of the VLAN interface (that will be automatically created by netifd) and then list all the wanted options. At the moment the only available option for this section is ‘ap_isolation’:

config interface 'my_bat_vlan1'
      option proto 'batadv_vlan'
      option ifname 'bat0.1'
      option ap_isolation '1'

Any VLAN specific option can still be listed in the batadv meshif configuration for ‘bat0’ and in that case they will affect the behaviour only for the plain mesh interface (i.e. bat0 - the untagged LAN).

Wireless configuration

batman-adv is not requiring a specific wireless interface. But it is nowadays often used with so called meshpoint interfaces with disabled forwarding. Such an interface can be configured in ‘/etc/config/wireless’:

config wifi-device 'radio0'
      option [..]

config wifi-iface 'wmesh'
      option device 'radio0'
      option ifname 'mesh0'
      option network 'bat0_hardif_mesh0' # automatically configure interface as shown in bat0_hardif_mesh0 /etc/config/network block
      option mode 'mesh'
      option mesh_id 'mesh'
      option mesh_fwding '0'
      option mesh_ttl '1'
      option 'mcast_rate' '24000'

It is assumed you configured the ‘wifi-device’ depending on your requirements and your hardware. The interesting part is the ‘wifi-iface’ stanza with its options:

device: points back to your radio (wifi-device) interface
ifname: allows you to specify an arbitrary name for your adhoc/meshpoint interface
network: points to the corresponding stanza in ‘/etc/config/network’
mode: defines the wifi mode - 802.11s mesh(point) in our case
mcast_rate: helps to avoid low bandwidth routes (routes with a lower throughput rate than the mcast rate will not be visible to batman-adv)
mesh_id: is a basic wireless settings (like an SSID) you might want to set to your liking

If bat0 was added to the ‘lan’ bridge in the network configuration, then it is possible to just add another AP to the same bridge and let batman-adv transfer data from the AP interface over the mesh:

config wifi-iface 'client_radio0'
      option device 'radio0'
      option ifname 'client0'
      option network 'lan'
      option mode 'ap'
      option ssid 'my_test_network'
      ...

More information can be found in the OpenWrt wireless configuration