Internet tuning

Gateway

Batman offers to announce the avaibility of an internet connection. You can use the gateway class option ([STRIKEOUT:g down/up) to tell batman how much bandwidth is available. You can specify the download and upload speed] batman will choose the nearest gateway class to represent your speed and propagate it in the network. The following examples should illustrate the usage:

batmand -g 5000 [interface]

batmand -g 5000kbit [interface]

batmand -g 5mbit [interface]

batmand -g 5mbit/1024 [interface]

batmand -g 5mbit/1024kbit [interface]

batmand -g 5mbit/1mbit [interface]

The syntax is very flexible and allows all these values to become gateway class 49.

Of course, you should enter the values which represent your connection speeds.

Your gateway will open a new tunnel interface gate0 and sets up the correct routing entries. All batman internet clients will connect to the gateway which gives them a free IP for their own gate0 interface. The traffic to the gateway is encapsulated in UDP packets and sent to port 4306 (it should not be blocked by the firewall). On the way back from the internet the gateway also encapsulates the traffic.

That behaviour allows the gateway maintainer to distinguish between traffic inside the mesh and traffic which should go to the internet. All filtering / caching / traffic shaping can be done on the gate0 interface.

Additionally, you have to make sure that the gateway allows forwarding and that the firewall masquerades all traffic coming through gate0.

GatewayClient

You can tell batman to watch out for announced gateways and connect to them via the routing class option (-r). This option allows you to influence which gateway will be chosen. Currently, there are 3 modes available:

batmand -r 1 [interface]

This mode is called “fast internet connection” because it considers the link quality and the advertised gateway class before choosing the gateway. Once a gateway is chosen and the tunnel is established batman will try to keep the tunnel open as long as possible to not break your stateful connections.

batmand -r 2 [interface]

This mode only considers the link quality towards the gateway while choosing it. Therefore it is named “stable internet connection”. It also will keep the tunnel open as long as possible.

batmand -r 3 [interface]

This mode also considers the link quality only but it will destroy the established tunnel as soon as another gateway with a better link quality is found (fast-switching).

batmand -r (number between 3 and 256) [interface]

This mode also considers the link quality only but switches to another gateway as soon as this gateway has a TQ value which is $number better than the currently selected gateway (late-switching).

After a gateway is chosen batman will create a gate0 interface and tries to get an IP from the gateway. The tunnel architecture allows batman to observe the internet connection because all traffic is going through the tunnel. If batman notices that the currently selected gateway does not forward the traffic into the internet it will disconnect from that gateway and choose another gateway.

batman 0.3.1 and before

If you plan to attach non-batman clients to your batman internet client you have to masquerade all outgoing packets on interface gate0 (e.g. iptables).

batman 0.3.2 and later

The batman daemon will try to locate the iptables binary to setup the masquerading automatically. This behaviour can be turned off using the “–disable-client-nat” option. If the outgoing packets are not masqueraded (the iptables binary wasn’t found / the automatism deactivated) batman will switch to the “half tunnel” mode which operates without masquerading. Beware: This mode requires the gateway to have a routing entry for each client that accesses the internet (e.g. non-batman clients may be announced via HNA). Also, batman won’t be able to automatically detect whether the chosen gateway is connected to the internet or not as only outgoing packets go through gate0.

Tuning

To be more flexible and better integrate into different setups and environments batman has a runtime interface which you can connect to. You can change batmans behaviour on the fly and adapt to changing requirements.

For example you announce internet but you discover that your internet connection is down, so you can tell batman to stop announcing the gateway class:

batmand -c -g 0

You could even say: I try to get my internet over that mesh as well:

batmand -c -r 1

Later you deactivate it again and reactivate your gateway announcement:

batmand -c -r 0 && batmand -c -g 5000

Or in one step:

batmand -c -g 5000

If you know that you want to use a particular gateway you can use the preferred gateway option (-p) to specify it. If batman finds the given gateway it will use it otherwise it will choose a gateway according to the routing class (routing class 1 is default if none is given).

For example:

batmand -c -p 1.2.3.4

The preferred gateway option can also be given at startup time.

If you have many users connected to your gateway you will experience a higher CPU load on the gateway because it has to maintain tunnel connections to numerous gateway clients at the same time. To reduce the load you can use the batgat kernel module which will do the tunneling from within the kernel space. You can load it like any other kernel module. Have a look in your kernel logs to see its boot up messages:

batgat: [init_module:96] batgat loaded rv959
batgat: [init_module:97] I was assigned major number 252. To talk to
batgat: [init_module:98] the driver, create a dev file with 'mknod /dev/batgat c 252 0'.
batgat: [init_module:99] Remove the device file and module when done.

Now the module is loaded but inactive. When you start batmand the daemon will automatically look for a file ‘/dev/batgat’ to communicate with the kernel module in order to activate it. This file should be generated by the kernel if you have devfs (on linux 2.4) or udev (on linux 2.6) running. You can create the file by yourself as mentionned in the logs if it was not generated. When batmand finds this file the kernel module will be used.

Attention: Do not hardcode the major number in your scripts. This number is assigned by the kernel and may differ from system to system, even from boot to boot. You can retrieve the current number from the proc filesystem:

cat /proc/devices | grep batgat