Building B.A.T.M.A.N. Advanced with Openwrt
Many tutorials assume that you have batman-adv running on an Openwrt system without going into detail how to get the system built and configured. This documents aims to fill the gap by providing a step-by-step explanation how to get your Openwrt system up & running.
Getting the Openwrt build environment
First, you need to obtain a copy of the Openwrt build system which contains all the build information to compile & package a complete Linux system. You can either clone the sources via git or get tarballs from the Openwrt project website. The various versions of Openwrt (bleeding edge ‘trunk’, last stable release, previous release, etc) can be downloaded directly from the Openwrt repositories.
Once downloaded change into the Openwrt directory and configure the system to meet you needs (e.g. choose the platform and additional packages you intend to use).
cd openwrt
make menuconfig
Note: The batman-adv package is not there yet because it needs to be activated separately (see the following steps).
To build your images you always have to invoke the “make” command from within the Openwrt folder:
cd openwrt
make
The rest of the document will focus on the batman-adv package. It is assumed that you configured the system to work on your platform. If you require additional information on how to tweak your Openwrt system, please see the Openwrt project website.
Adding the batman-adv / batctl package
The standard Openwrt package feed contains a batman-adv and a batctl package which is intended to be used on a day to day basis, therefore it retrieves the latest batman-adv / batctl stable release. Since a lot of people want to experiment with the latest features or use Openwrt to test their own batman-adv patches we also provide an Openwrt package feed which contains the batman-adv development version.
stable version:
scripts/feeds update
scripts/feeds install kmod-batman-adv
scripts/feeds install batctl
developer version:
Append the following line to your Openwrt feed configuration file (either feeds.conf or feeds.conf.default):
src-git batman https://git.open-mesh.org/openwrt-feed-devel.git
Update the package information and add the development package:
scripts/feeds update
scripts/feeds install kmod-batman-adv-devel
scripts/feeds install batctl-devel
Configuring the batman-adv package
As soon as the batman-adv package has been added, it will show up in the Openwrt package menu:
stable version:
Kernel modules --->
Network Support --->
kmod-batman-adv
developer version:
Kernel modules --->
Network Support --->
kmod-batman-adv-devel
Once the package had been selected a number of suboptions will become visible. You can enable/disable the verbose debug logging as well as choose whether or not to include the batctl tool.
In addition, the batman-adv package comes with an init script which is installed per default. This script will run at boot time and can be used to configure your desired batman-adv options. It reads the batman-adv uci file to retrieve the settings which allows to specify interfaces, intervals, log level and more.
Basic configuration: batman-adv Openwrt config
Rebuilding the package
If you experience build problems or simply intend to rebuild the batman-adv package only, you can tell Openwrt to build a specific package and enable the debugging mode as follows:
stable version:
cd openwrt
make package/batman-adv/clean
make package/batman-adv/compile V=99
developer version:
cd openwrt
make package/batman-adv-devel/clean
make package/batman-adv-devel/compile V=99
Applying patches
The package offers an easy way to apply custom patches whenever batman-adv is built. Simply copy your patches into the “patches” folder inside the package directory (you have to create the folder in case it does not exist yet). Patch files having the string ‘batman’ in their name are applied to batman-adv whereas patches containing the string ‘batctl’ are applied to the batctl tool. The location of the folder depends on which package you want to patch:
stable version:
openwrt/feeds/packages/net/batman-adv/patches
developer version:
openwrt/feeds/batman/batman-adv-devel/patches
Changing the batman-adv / batctl version
It is also possible to modify the batman-adv version if you ever wanted to build an older/newer version than configured in the package:
stable version:
Adjust the PKG_VERSION variable configured in the package Makefile to download & build the stable release you are interested in.
cat openwrt/feeds/routing/batman-adv/Makefile
[..]
PKG_VERSION:=2013.4.0
[..]
you will probably want to change md5sum also:
[..]
PKG_MD5SUM:=1a2b3c4d5e6f7g # https://downloads.open-mesh.org/batman/releases/batman-adv-2013.4.0/batman-adv-2013.4.0.tar.gz.md5
[..]
And if you want to match batman-adv version with batctl version, do the similar thing for the next lines:
[..]
BATCTL_VERSION:=2013.4.0
[..]
[..]
PKG_MD5SUM:=1a2b3c4d5e6f7g # https://downloads.open-mesh.org/batman/releases/batman-adv-2013.4.0/batctl-2013.4.0.tar.gz.md5
[..]
And be careful when changing versions, your build may fail. Build with make V=99 so you can see what is going on, and if applying some batman-adv patch fails, locate it under /home/user/openwrt/feeds/routing/batman-adv/patches and remove it.
developer version:
Adjust the batman-adv & batctl git branch / tag via the Openwrt configuration menu (aka “make menuconfig”) to download & build the git revision you are interested in:
Kernel modules --->
Network Support --->
kmod-batman-adv-devel
batman-adv branch
Building from a different branch
The developer package offers a convenient way to select another branch to build from. This is particularly useful for testing features that have not been merged into the main branch yet. Simply enter the branch or git tag you wish to build in the Openwrt build menu.
Kernel crash debug
In case you experience kernel oopses it might prove helpful to enable the kernel symbol table which translates the cryptic numbers which are part of each kernel oops log into readable function names. This calltrace can help developers to analyze the problem. Use Openwrt’s config menu to enable the kernel symbol table and rebuild your image:
make menuconfig
Global build settings --->
Compile the kernel with symbol table information
If you can’t find this option you are using an older Openwrt version which doesn’t offer this config switch in the main menu. You have to modify the kernel settings directly:
make kernel_menuconfig
General setup --->
Configure standard kernel features (for small systems) --->
Load all symbols for debugging/ksymoops