Buildroot

make menuconfig to configure.
Checked options:

• Target Architecture = x86_64 (Target options)
• Enable C++ support (apperently needed by iperf3) (Toolchain)
• Disable 'Enable root login with password' (System configuration)
• Disable 'Run a getty (login prompt) after boot' (System configuration)
• Disable Linux Kernel (Kernel)
• Enable iperf3 (Target packages -> Networking applications)
• Enable ext2/3/4 root filesystem (Filesystem images)
  • ext4 variant
• Disable 'tar the root filesystem' (Filesystem images)

Copy init scripts to rootfs (maybe have to do one make before this):

cp inittab buildroot/output/target/etc/inittab 
cp setup_client_net_ns.sh buildroot/output/target/etc/init.d/S41network_qemu
cp -p enable_events.sh buildroot/output/target/
cp -p toggle_skb_zeroing.sh buildroot/output/target/
cd buildroot
make

Networking

Create tap between host and client called qemu_tap (no outside connection) on subnet 192.168.111.0/24. The host ip is 192.168.111.1 and the client 192.168.111.2.

Run setup_host_net.sh to setup host network (create tap, assign ip and routing).
Run delete_host_net.sh to remove the host network (remove tap and routing). The script setup_client_net.sh is run during by the init script in qemu on boot which sets up ip and routing on the client

Need to enable this driver in the kernel for -device rtl8139 to work. (Device Drivers -> Network device support -> Ethernet driver support -> RealTek RTL-8139 C+ PCI Fast Ethernet Adapter support)

Linux Kernel

mkdir linux-x86-build
cd linux

# Default configuration
make O=../linux-x86-build defconfig
make O=../linux-x86-build kvm_guest.config

# Further configuration
make O=../linux-x86-build menuconfig

# Build
make O=../linux-x86-build -j8