Building OpenWRT under FreeBSD
As part of our research into using
OpenWRT
for
traffic
classification and other tasks on embedded devices, our group is documenting an approach to building OpenWRT images natively under
FreeBSD. This approach has been
confirmed to work inside a FreeBSD 8.x jail and a
PCBSD 9.1
jail.
OpenWRT
OpenWRT is a Linux distribution for embedded devices. It
is commonly used to replace the factory firmware found on residential
Internet routers. By replacing the factory firmware, users gain access
to additional configuration options and are able to extend the
functionality of the router by installing new software. Our "Diffuse for OpenWRT"
project released an Ubuntu-based
VirtualBox VM
suitable for building OpenWRT, but we also wanted to build OpenWRT
natively under FreeBSD. The challenge is to install the GNU tools
required by OpenWRT's build system.
Configuring FreeBSD to build OpenWRT
The key is
this script,
which installs any required-but-missing FreeBSD utilities (building
each one from source using the Ports system) and creates a set of
symlinks to ensure OpenWRT utilises GNU utilities in preference to
their BSD cousins where required.
The following example assumes we are installing OpenWRT's trunk branch
into local directory
/usr/home/openwrt.
The steps are:
- As your regular user, download and
install OpenWRT trunk to /usr/home/openwrt
(you will need subversion)
- e.g. svn co
svn://svn.openwrt.org/openwrt/trunk/
- Change directory to /usr/home/openwrt/trunk
- A number of FreeBSD Ports will most likely be
built and installed, including GNU versions of a number of tools
- Symlinks will added under ./bin-gnu
- You will be
told to pre-pend your environment's PATH variable with /usr/home/openwrt/trunk/bin-gnu
before trying to build OpenWRT in the next step as a regular user
Assuming everthing has run smoothly, you should now have a functional
OpenWRT build system able to run natively under FreeBSD.
- As your regular user, from within
/usr/home/openwrt/trunk
- Pre-pend your environment's PATH variable with /usr/home/openwrt/trunk/bin-gnu
- Run 'gmake menuconfig'
to launch OpenWRT's build system configuration menu
- Run 'gmake' to
start building OpenWRT (tools, toolchain and then your desired release
image)
Tested cases
We have successfully created OpenWRT trunk (
r35515), attitude_adjustment (
r35400) under a PCBSD 9.1 x64 Jail and a
FreeBSD 8-STABLE x64
ezjail
jail (using the Ports tree as of late January 2013 in each case), and
then built default sets of packages and working
images for the following Target Systems & Profiles:
- Cavium CNS21XX (e.g. for the NS-K330) [squashfs image, OpenWRT trunk only]
- Cavium CNS3XXX [squashfs image]
- Atheros AR7xxx/AR9xxx (TP-Link WR1043ND & WR703N) [squashfs image]
- ARM Ltd. Realview board (qemu) [elf image]
Notes
We came across at least one OpenWRT package (
package/mac80211) that is
hardwired to assume bash exists at
/bin/bash.
Our script assumes this is not generally true in a FreeBSD host, and
thus installs bash from Ports and symlinks
/bin/bash
to
/usr/local/bin/bash.
When installing inside a FreeBSD jail, check whether you have write
permission to
/bin
-- some jail tools (like ezjail) initially create
/bin as a
symlink to a read-only
/basejail/bin
directory tree. You'll need to remove the symlink, copy
/basejail/bin
to a new
/bin,
then restart our script to instantiate the bash symlink.
Our script also prevents OpenWRT from compiling its own
e2fsprogs
and
mtd-utils
build tools (they currently don't compile properly under
FreeBSD). These are different to any similarly-named packages that
might be added to an OpenWRT image, and their absence means you cannot
build
ext4 root filesystem images. (This is an acceptable limitation
for our purposes, as we only want squashfs or ramdisk images.)
Authors
Grenville Armitage and
Chris Holman
