Virtualbox host networking and WIFI

Virtualbox > 2.1.4 and Jaunty. Virtualbox does that on its own now. Select host interface (or bridge network in 2.2) and then your wifi card. No need for this lengthy howto anymore...

Scope of this howto

While being connected to your router (thus the Internet) via your computer WIFI card, enable host networking on a different subnet by bridging your unused ethernet card.

Your Virtualbox machines will be connected to the Internet as well.

The tutorial is constructed as follows:
similar settings for Vbox > 2.1.0 and Vbox < 2.1.0
Vbox > 2.1.0
Vbox < 2.1.0
Guest configuration

Tested and working with the following:
Virtualbox 1.5.6, 1.6.0, 1.6.2 Ubuntu 8.04 Hardy Heron
Virtualbox 2.0.4, 2.0.6 Ubuntu 8.10 Intrepid Ibex
Virtualbox > 2.1.0 Ubuntu 8.10 Intrepid Ibex

Pre-requisites

One computer with:
WIFI controller eth0
ethernet controller eth1
Virtualbox
Internet connection thru eth0

All the bridge creation and host interface creation knowledge comes from Virtualbox help contents. (see chapter Host Interface Networking and bridging on Linux hosts)

How to - by example

Consider a connection to the internet via eth0 (WIFI) with IP 192.168.0.2 .
The bridge IP address will be 192.168.1.254 (note the difference of subnet between the wifi and the bridge).
Bridge br0 will include eth1 (ethernet card) and host interface tap0.

I will assume that virtualbox is up and running for the user joe.

Similar settings for Vbox > 2.1.0 and Vbox < 2.1.0

sudo apt-get install bridge-utils

Modify /etc/network/interfaces

auto lo
iface lo inet loopback

auto br0
iface br0 inet static
address 192.168.0.2
netmask 255.255.255.0
    bridge_ports eth0
    bridge_maxwait 0

Restart networking

sudo invoke-rc.d networking restart

Enable ip_forwarding: modify /etc/sysctl.conf (line thirty eight)

net.ipv4.ip_forward=1

While it is not necessary to create a firewall service to enable masquerading, it will be much easier to activate if you do so. You can use ufw if you prefer.

sudo vi /etc/init.d/firewall
#/bin/bash

start() {
        echo "Creating iptables rule"
        iptables -t nat -A POSTROUTING -o eth1 -j MASQUERADE
}

stop() {
        echo "Flushing iptables"
        iptables -P INPUT ACCEPT
        iptables -P FORWARD ACCEPT
        iptables -P OUTPUT ACCEPT
        iptables -t nat -P PREROUTING ACCEPT
        iptables -t nat -P POSTROUTING ACCEPT
        iptables -t nat -P OUTPUT ACCEPT
        iptables -F
        iptables -t nat -F
        iptables -X
        iptables -t nat -X
}

case $1 in
        start)  start;;
        stop)   stop;;
        restart)        stop
                        start;;
        status) /sbin/iptables -L
                /sbin/iptables -t nat -L
                exit 0;;
        *)      echo "Usage: firewall {start|stop|restart|status}"
                exit 1
esac
exit

Make the script executable

sudo chmod u+x /etc/init.d/firewall

Create links for the service to be started/stopped automatically

sudo update-rc.d firewall defaults

Start the service to enable masquerading

sudo invoke-rc.d firewall start

VBox 2.1.0

The configuration is almost over.
You just need to select host interface in the virtual machine settings and choose br0.

VBox < 2.1.0

sudo apt-get install uml-utilities
sudo gpasswd -a uml-net $USER
sudo chgrp uml-net /lib/udev/devices/net/tun
sudo chmod g+rw /lib/udev/devices/net/tun

(reboot necessary unless someone has another solution. You can change the ownership of /dev/net/tun right away and wait for a later reboot)

If you want to create a permanent host interface
change /etc/network/interfaces to

auto lo
iface lo inet loopback

auto tap0
iface tap0 inet manual
up ifconfig $IFACE 0.0.0.0 up
down ifconfig $IFACE down
tunctl_user joe    ###replace joe with the name of your user member of vboxusers and uml-net groups##

auto br0
iface br0 inet static
address 192.168.0.2
netmask 255.255.255.0
    bridge_ports eth0 tap0 #tap1 tap2 ...
    bridge_maxwait 0

Add as many host interfaces (tap1 tap2 ...) as desired on the same principle. If you do so, don't forget to add them to the bridge.
Restart networking

sudo invoke-rc.d networking restart

Assign tap0 (tap1 ...) as a host interface to your virtual machine.

I prefer dynamic host interfaces
To create dynamic tap interfaces (from the virtualbox help, 6.7.2. Creating interfaces dynamically when a virtual machine starts up):
* create a start up script (wherever you want, just remember where), replace joe with your user member of vboxusers and uml-net groups

cat > /home/joe/addtap.sh <<eof
#!/bin/bash

# Create an new TAP interface for the user 'joe' and remember its name.
interface=\`VBoxTunctl -b -u joe\`## replace joe with your user

# If for some reason the interface could not be created, return 1 to
# tell this to VirtualBox.
if [ -z "\$interface" ]; then
exit 1
fi

# Write the name of the interface to the standard output.
echo \$interface

# Bring up the interface.
ifconfig \$interface up

# And add it to the bridge.
brctl addif br0 \$interface
eof

chmod u+x /home/joe/addtap.sh

* create an end script

cat > /home/joe/deltap.sh <<eof
#!/bin/bash

# Remove the interface from the bridge.  The second script parameter is
# the interface name.
brctl delif br0 \$2

# And use VBoxTunctl to remove the interface.
VBoxTunctl -d \$2
eof

chmod u+x /home/joe/deltap.sh

In the virtual machine network settings, do the following changes
attached to: host interface
interface name: (nothing, leave it empty)
setup application: gksudo /home/joe/addtap.sh
terminate application: gksudo /home/joe/deltap.sh

if you wish to avoid typing your password when the tap interface is created, add the following line to your sudoers file

sudo visudo
%vboxusers ALL=(ALL) NOPASSWD: /home/joe/addtap.sh, /home/joe/deltap.sh

Guest configuration

1) No DHCP server

If you have no dhcp server serving the 192.168.0.0 range, you will need to assign an IP address in the 192.168.0.0 range to your virtual machine once it is started.

sudo ifconfig eth0 192.168.0.3

It will be necessary to add 192.168.0.2 as a default route as well

sudo route add default gw 192.168.0.2

If you want to make it permanent, edit /etc/network/interfaces of your virtual machine.

auto eth0
iface eth0 inet static
address 192.168.0.3
netmask 255.255.255.0
gateway 192.168.0.2

2) DHCP server

You have a dhcp server serving on the 192.168.0.0 range
either locally (laptop):
make sure the "option routers" given by dhcp is the IP of your bridge br0 (192.168.0.2)

or on your ethernet LAN connection:
nothing to do (in that case, your access to the internet will occur thru ethernet most certainly and not thru WIFI)

James Dupin http://hmbconcepts.fr
ventes de savons et bougies parfumés et de serviettes 100% coton roulées en forme de gâteau

CategoryNetworking