BRatWuRsT (aka 'Buildroot WRT') is a buildroot based home router firmware, similar in scope to OpenWrt.

Buildroot is used as it provides a means for very straight forward development and build cycles.

Development could be done directly on physical hardware, however:

1. it takes forever
2. QEMU supports simulating different architectures and platforms
3. of course QEMU handles Ethernet interfaces, however Linux also supports simulating:
   • ATM connections with ATM over TCP using atmtcp
   • wireless interfaces using mac80211_hwsim and palming hints from hwsim

So instead we use QEMU. It is this which I think makes this project special and different to other home router projects.

Related Links:

• Development and Contributing
• Issues

Features

• complete development supported within a QEMU VM
• includes a 'fake ISP' VM that emulates xDSL connectivity, the ISP and Internet
• PPPoA/PPPoE support
• full native IPv6 support
• including DHCPv6-PD to automatically assign IPv6 subnets locally
• 6to4 support so that those without native IPv6 do not miss out
• combined IPv6/IPv4 (inet) firewalling with nftables
• runit (tutorial) as PID 1
• DNS authoritative server, including reverse zones
• use the 6to4reverse form if you use 6to4
• client services:
• SSH with public keys
• DNS
• IPv6 RA
• DHCPv4

Supported Physical Targets

• Linksys WAG54G
• TP-Link TD-W8980 - currently not supported
• TP-Link TL-MR3020 - currently not supported

Preflight

You will need roughly 5GB of free disk space and to start off and to have git installed on your workstation.

The first stop is to fetch a copy of the project:

git clone https://github.com/jimdigriz/bratwurst.git
cd bratwurst

Help is available by running:

make help

Debian 'jessie' 8

You can install everything you need with:

sudo apt-get install --no-install-recommends \
	build-essential perl \
	wget ca-certificates cpio rsync vim-common \
	qemu-system-$(uname -m | sed 's/\(i[3456]86\|x86_64\)/x86/')

Fedora 20

N.B. this is untested

To install the dependencies you should just need to run:

sudo yum install \
	gcc gcc-c++ binutils make patch flex bison perl-Data-Dumper automake \
	wget ca-certificates rsync qemu-kvm qemu-system-mips
sudo yum update vim-minimal
sudo yum install vim-common

How to Use

Configuration

For a fresh build you will need a configuration file:

make defconfig

This creates the default bratwurst.config configuration file which contains inline documentation. Later this file is used during the firmware building process and installed on the target at /etc/bratwurst. Open this file in an editor and edit it to suit your environment, the defaults can be left as is if you just want to spin up the VM.

User Accounts

To slip user accounts into the build, at the top of the BRatWuRsT project directory you run:

mkdir users
cat ~bob/.ssh/id_rsa.pub > users/bob

Here we have added an account for 'bob' using the SSH keys from the local workstation.

Note that:

1. each all accounts are password-less
2. to add a password to an account, use passwd when logged into the device
3. password-less accounts can only log in via the serial port (SSH rejects password authentication)
4. only public key authentication is supported for SSH
5. root is never permitted to SSH in (as well as being password-less)
6. to become root you use su - when logged in at a terminal

N.B. on first boot the system has to generate SSH host keys which takes typically around five minutes to complete. Until this process is finished you will get 'Connection Refused' as the SSH server cannot start till this process completes

SSH Server Keys

To preserve the SSH server's keys across builds, you can copy the files /etc/dropbear/dropbear_{rsa,dsa,ecdsa}_host_key on the target into a directory called dropbear at the top of the BRatWuRsT project directory.

Alternatively you might want to consider adding the following to your ~/.ssh/config:

Host 192.168.*
        StrictHostKeyChecking no

Running

To build the qemu/mipsel board firmware and automatically start up QEMU instance of BRatWuRsT you run:

make bratwurst BOARD=qemu/mipsel

N.B. making bratwurst only works for qemu/* targets, whilst the default for BOARD is qemu/mipsel so can be omitted in the example above

On the first run, the build will take about 30 minutes (on an i7@3Ghz plus the time taken to download 250MB) whilst subsequent runs should take seconds. Once built, you will see a typical Linux kernel boot up which drops you at a login prompt; the username is root with no password. Use Ctrl-A ? to get some QEMU usage information, Ctrl-A x will exit the emulator and there is of course the QEMU Monitor Console instructions to help you out too.

Building

Building for other targets is just a case of reading the relevant page linked from Supported Physical Targets above to learn how to install the built firmware to your target. Building the firmware its-self is done just by typing:

make soc/board

For information on customising the build, read the Customising the Build.