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Return to USB Networking.

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OpenMoko Networking Setup

In order to communicate via TCP/IP to your FreeRunner, a basic understanding of the networking expectations is required. Each end of the USB connection forms a LAN (local area network) segment, with the FreeRunner's USB networking device at one end (default and your laptop or desktop at the other end ( in this guide).

Normally, your desktop machine will know how to reach the Internet, having had its gateway (the IP address of the machine or device which knows how to send packets to machines beyond your subnet) configured via DHCP or statically (probably via a router). For the FreeRunner to reach the Internet, your desktop will have to be configured to route and masquerade (NAT) packets from it.

Normally, none of this is an issue, but problems can arise when the subnet between the FreeRunner and your desktop overlap with the desktop to the router (which forms a second LAN), since your desktop might not know how to route traffic properly.

In other words: if your existing router and desktop have addresses 192.168.0.(something) changing them to eg 192.168.1.(something) might save you a lot of troubleshooting later. The guides to set up USB networking for your FreeRunner assume that your router/desktop IP range differs from the USB network IP range.

A discussion of this is here

Simple Manual Linux Configuration

Try this first. If it works, then you can add permanent configuration or use more sophisticated setups below:

(as root on your desktop):

iptables -A POSTROUTING -t nat -j MASQUERADE -s
sysctl -w net.ipv4.ip_forward=1
ifconfig usb0

If your Internet connection is also in the range 192.168.0.x then instead you might want to use:

ifconfig usb0 netmask

Then (ideally, not as root):

ssh root@

The default password is blank.

Linux Kernel Support

Your Linux desktop/laptop needs to have suitable support, in particular, you will need to have enabled full masquerading in the kernel and USB networking options enabled. For default kernels in many Linux distributions, this will already be the case. If not, you will need to enable:


Both USB networking options are available in the Device Drivers -> USB support -> USB Network Adapters or Device Drivers -> Network Device Support -> USB Network Adapters -> Multipurpose USB Networking Framework. For more info see the usbnet driver homepage.

It can be complex to set all the correct options for masquerading in the kernel if they are not turned on. This could be detailed further.

Firewall Issues

On some systems, you may have firewall rules which prevent this working - such as added by the iptables service on Fedora. You may care to stop these, and/or review any rules or policies you think might cause issues.

The most relevant table is the nat table, which controls translation of addresses:

iptables -L -t nat -v -n

Unless you have a special setup, you'll want to see only the MASQUERADE rule that you apply below, and ACCEPT as the default policy. Also look at the filter table:

iptables -L -t filter -v -n

If this contains anything in the FORWARD chain, then this may prevent passing packets. It can be flushed with:

iptables -t filter -F FORWARD


In addition to routing issues, to be practical, DNS will need to work. In some cases, you might already be running a DNS server on your desktop such as dnsmasq or bind9, which is the default assumption the FreeRunner makes. In other cases, you'll need to configure DNS to that of your router, or a DNS server further out on the internet such as that provided by your ISP.

Configure Default Neo DNS

DNS is configured in /etc/resolv.conf on your FreeRunner. It should contain:

If Desktop/Laptop has a DNS server or is proxying DNS:


or just put in another DNS Server - for example:


Some Linux and Windows systems have DNS servers, especially those configured as servers, but in general they do not. You can install packages such as bind9 or dnsmasq to run your own DNS server. If you have a DNS server then Test Your Connection. Otherwise you may want to proxy DNS from your Desktop/Laptop.

Proxying DNS from Desktop/Laptop

If you move about, making assumptions about the network may not be convenient, and it is possible to proxy DNS requests via your host laptop (which you are also taking with you), without running or installing a DNS server. There are a number of ways to do this:

Proxying with dnrd

The script is designed to use dnrd as the DNS proxy. The script and a copy of dnrd are available. The script also performs the initial setup of the connection as per the USB_Networking#Manual_method above.

Proxying with a UDP forwarder

Another easy setup is using a UDP forwarder like the one from - use it with the command"

udpf-elf -p=53-f=`cat /etc/resolv.conf|awk '$1 == "nameserver"{print $2; exit(0);}'`:53

Proxying with iptables

It is possible to forward DNS requests with iptables using the DNAT target:

iptables -t nat -A PREROUTING -p tcp -s -d --dport domain -j DNAT --to-destination
iptables -t nat -A PREROUTING -p udp -s -d --dport domain -j DNAT --to-destination

Where is the IP of your router.

Test if it works:


If so, then this is sufficient for most internet access. But manual changes to resolv.conf are usually lost later if for example one uses DHCP, especially for WiFi, and so may not be convenient to configure manually.


If you become tired of remembering and typing in the ip address of the Neo (for scp, telnet, SSH, SMB, or whatever), you can give it an easy to remember hostname.

Open and enter the following line in your desktop's /etc/hosts: openmoko

Now instead of typing the full ip address in commands like:


You can replace the full ip with the hostname like:

ssh root@openmoko

It may also be helpful to some to edit the Neo's /etc/hosts to use "desktop" or "laptop" instead of

Testing Your Connection

You should be able to connect to your Neo! Make sure you can ping your Neo to be sure.


Then log into your Neo using ssh:

ssh root@

The default password is blank (press enter).

You can also scp files back and forth. You can telnet, SSH, SMB or do whatever you want if you install software that enables you to set up TCP/IP network over your USB connection.

Now, make sure you can ping back to your desktop


(Note that some systems like Vista, don't respond to ICMP ping by default)

Try pinging the outside world (a Google IP address)


This demonstrates that masquerading is working - your desktop is sending/receiving packets to the wider internet.

Lastly, verify that DNS is correctly configured between the Neo & Network:


Make it Permanent

Based on Hotplugging usbnet by Marcin 'Hrw' Juszkiewicz.


See MacOS X USB Networking.


See Windows USB Ethernet emulation for Neo1973.

Debian, Ubuntu and others

Edit /etc/network/interfaces and add:

 allow-hotplug usb0
 iface usb0 inet static
        post-up iptables -A POSTROUTING -t nat -j MASQUERADE -s
        post-up echo 1 > /proc/sys/net/ipv4/ip_forward
        post-up iptables -P FORWARD ACCEPT
        pre-down iptables -D POSTROUTING -t nat -j MASQUERADE -s

This is more sophisticated than the manual setup. The allow-hotplug stanza ties into Linux hotplug system so that when the device appears and vanishes, as happens when the FreeRunner's is connected via USB, this is run.

In addition, the desktop-side netmask is limited to a much smaller range, so that overlapping subnets are less of a problem - Linux will use more specific routes first when deciding where to send packets.

An other possible configuration that adds DNS forward and removes the iptable changes after the unplugg.

in /etc/network/interfaces add

 # freerunner
 allow-hotplug usb0
 iface usb0 inet static
        post-up /etc/network/freerunner start
        pre-down /etc/network/freerunner stop

create file /etc/network/freerunner

 # configures the freerunner for internet


 # get first ip for dns
 DNSIP=$(cat /etc/resolv.conf | grep nameserver | awk '{ print $2 }' | head -n 1 )

 case "$1" in
        iptables -A POSTROUTING -t nat -j MASQUERADE -s $REMOTE_IPADDR
        iptables -A PREROUTING -t nat -p tcp -s $REMOTE_IPADDR -d $IPADDR --dport domain -j DNAT --to-destination $DNSIP
        iptables -A PREROUTING -t nat -p udp -s $REMOTE_IPADDR -d $IPADDR --dport domain -j DNAT --to-destination $DNSIP
        if [ "$(cat /proc/sys/net/ipv4/ip_forward)" = "0" ]; then
                echo "temoprarely allow ip_forward for openmoko" > /var/run/openmoko.ip_forward
                echo 1 > /proc/sys/net/ipv4/ip_forward
        iptables -D POSTROUTING -t nat -j MASQUERADE -s $REMOTE_IPADDR
        iptables -D PREROUTING -t nat -p tcp -s $REMOTE_IPADDR -d $IPADDR --dport domain -j DNAT --to-destination $DNSIP
        iptables -D PREROUTING -t nat -p udp -s $REMOTE_IPADDR -d  $IPADDR --dport domain -j DNAT --to-destination $DNSIP

        if [ -f /var/run/openmoko.ip_forward ]; then
                rm /var/run/openmoko.ip_forward
                echo 0 > /proc/sys/net/ipv4/ip_forward

Make /etc/network/freerunner executable with

chmod +x /etc/network/freerunner

Ubuntu Issues

Ubuntu Feisty, Gutsy and Hardy reportedly have a bug where ifdown is not run when the interface is unplugged, meaning this only works once after the system is booted. This is mentioned at

One can patch /etc/udev/rules.d/85-ifupdown.rules, editing the two lines at the end of the file:

SUBSYSTEM=="net", DRIVERS=="?*", GOTO="net_start"


# Bring devices up and down only if they're marked auto.
# Use start-stop-daemon so we don't wait on dhcp
ACTION=="add",          RUN+="/sbin/start-stop-daemon --start --background --pidfile /var/run/network/bogus --startas /sbin/ifup -- --allow auto $env{INTERFACE}"


ACTION=="remove",       RUN+="/sbin/start-stop-daemon --start --background --pidfile /var/run/network/bogus --startas /sbin/ifdown -- --allow auto $env{INTERFACE}"

The bug is that the LABEL="net_end" is at the wrong position

 This appears to be fixed in Ubuntu 8.04 Mattt 11:38, 30 July 2008 (UTC)


Tested with Mandriva 2008.1. The idea here is that we will carve out a small (8 hosts) subnet from the main subnet. So our netmask will be

This first file configures the network system for the usb0 interface. Any time you plug in the FreeRunner the interface will be configured.



This next file configures the static routes that we need to communicate to the subnet. Since it has "usb0" in the name, the system will automatically apply these static routes any time that the usb0 interface is configured. (i.e. when you connect the FreeRunner)



Now we need to restart the network system to pick up the changes.

service network restart



# USB configuration for PDAs (openmoko)

For more information on getting USB networking up using YaST, see USB Networking with openSUSE.


Option A - Tested with FC8 & FC5


# USB configuration for PDAs (openmoko)
# from

Option B

This setup is probably over-complex:





. /etc/init.d/functions

cd /etc/sysconfig/network-scripts
. ./network-functions

[ -f ../network ] && . ../network


need_config ${CONFIG}


NETBITS=`ipcalc -p ${IPADDR} ${NETMASK} | awk -F'=' '{print $2;}'`

/sbin/ip addr flush dev ${DEVICE} 2>/dev/null
/sbin/ip link set dev ${DEVICE} up
/sbin/ip addr add dev ${DEVICE} ${IPADDR}/${NETBITS}

/sbin/iptables -I POSTROUTING -t nat -j MASQUERADE -s ${IPADDR}/${NETBITS}
/sbin/sysctl net.ipv4.ip_forward=1
/sbin/iptables -I FORWARD -s ${IPADDR}/${NETBITS} -j ACCEPT
/sbin/iptables -I FORWARD -d ${IPADDR}/${NETBITS} -j ACCEPT

Set /etc/sysconfig/network-scripts/ifdown-usb:


. /etc/init.d/functions

cd /etc/sysconfig/network-scripts
. ./network-functions

[ -f ../network ] && . ../network


need_config ${CONFIG}


NETBITS=`ipcalc -p ${IPADDR} ${NETMASK} | awk -F'=' '{print $2;}'`

/sbin/iptables -D FORWARD -d ${IPADDR}/${NETBITS} -j ACCEPT
/sbin/iptables -D FORWARD -s ${IPADDR}/${NETBITS} -j ACCEPT
/sbin/sysctl net.ipv4.ip_forward=0
/sbin/iptables -D POSTROUTING -t nat -j MASQUERADE -s ${IPADDR}/${NETBITS}

/sbin/ip link set dev ${DEVICE} down
/sbin/ip addr flush dev ${DEVICE} 2>/dev/null

If you are using NetworkManager, restart it and enable the usb device from its menu, otherwise it will disable your connection shortly after you enable it.

/sbin/service NetworkManager restart

Red Hat or Similar (tested with Workstation 5)

Edit /etc/sysconfig/network-scripts/net.hotplug:

After this command:

    case $INTERFACE in
	# interfaces that are registered after being "up" (?)


		ifconfig usb0 netmask
		route add usb0
		iptables -I INPUT 1 -s -j ACCEPT
		iptables -I OUTPUT 1 -s -j ACCEPT
                iptables -A POSTROUTING -t nat -j MASQUERADE -s
                echo 1 > /proc/sys/net/ipv4/ip_forward
		exit 0


Open /etc/conf.d/net and add:

# Neo
config_usb0=( " netmask" )
routes_usb0=( " via" )

Create a new init script:

cd /etc/init.d
ln -s net.lo net.usb0

Put iptables into use:

iptables -I INPUT 1 -s -j ACCEPT
iptables -I OUTPUT 1 -s -j ACCEPT
iptables -A POSTROUTING -t nat -j MASQUERADE -s

Store them:

/etc/init.d/iptables save

If you want the routing by default:

rc-update add iptables default

You must also inform the kernel, to start forwarding.

echo 1 > /proc/sys/net/ipv4/ip_forward

One way to automate all this is to create /etc/conf.d/net.usb0 as follows. It sets IP forwarding and the iptables rules all in one go. It removes the iptables rules and disables ip forwarding when the FreeRunner is unplugged.

preup() {
       echo 1 > /proc/sys/net/ipv4/ip_forward
       iptables -I INPUT 1 -s -j ACCEPT
       iptables -I OUTPUT 1 -s -j ACCEPT
       iptables -A POSTROUTING -t nat -j MASQUERADE -s
       return 0

postdown() {
       echo 0 > /proc/sys/net/ipv4/ip_forward
       iptables -D INPUT -s -j ACCEPT
       iptables -D OUTPUT -s -j ACCEPT
       iptables -D POSTROUTING -t nat -j MASQUERADE -s
       return 0

SSH Extras

Reportedly, the ssh daemon (dropbear 0.49) on the FreeRunner appears to have a bug when sending the exit status back to the client. From time to time you receive an exit status of 255.

To avoid ssh added a new line for every ssh host-key to you known_hosts you can add the following to the phone section in ~/.ssh/config

 UserKnownHostsFile /dev/null

You might want to use keys to bypass the login prompt too.

SSH Keys

From desktop to FreeRunner

To generate ssh keys for use as a login mechanism type:

ssh-keygen -t rsa

When prompted for a password either hit enter for no password (not really a good idea) or enter a password for this key. ssh into the phone and create ~/.ssh:

# mkdir ~/.ssh

Then from your desktop copy the .pub file to the phone.

# scp ~/.ssh/ phone:.ssh/authorized_keys

You should now be able to ssh directly into the phone without a password prompt.

To disable password logins (after setting up key access) edit /etc/init.d/dropbear and change the following line:




You will need to restart dropbear for this to take effect.

From FreeRunner to Desktop

Generate the key:

 dropbearkey -t rsa -f id_rsa

The output will look something like this:

 Will output 1024 bit rsa secret key to 'id_rsa'
 Generating key, this may take a while...
 Public key portion is:
 ssh-rsa AAAAB3Nza[...]
 Fingerprint: md5 ca:e8:f0:b7:f6:7b:c2:b6:b9:71:e4:45:86:a9:ff:b8

Copy and paste the one line (in this example, starting with 'ssh-rsa' onto the end of the host's authorized_keys file (often in ~/.ssh/).

From the phone, ssh with -i:

 ssh -i id_rsa user@host

Changing host keys

If you reflash, your hosts keys will change. Try this ~/.ssh/config snippet:

Host moko
StrictHostKeyChecking no
UserKnownHostsFile /dev/null
User root

This is suggested because ssh on your desktop may complain if the key matching a certain IP changes (stored in .ssh/known_hosts).

GUI on desktop through SSH

To get the GUI on the FreeRunner onto the desktop via USB, you can use ssh as follows:

 ssh -l root -X -v

Using this, run openmoko-finger-demo for example, and it will open up on the desktop. To get landscape view, just resize the GUI window on the desktop.

If you get an error like this:

dbus.exceptions.DBusException: org.freedesktop.DBus.Error.Spawn.ExecFailed: dbus-launch failed to     
autolaunch D-Bus session: Autolaunch requested, but X11 support not compiled in.

you need to set the DBUS_SESSION_BUS_ADDRESS environment variable to the value on the Freerunner before launching the process from your desktop. You can find the value of this variable by using a command such as

ps auxwwwwe | grep -m 1 DBUS_SESSION_BUS_ADDRESS

Note that you must run that command on the Freerunner. Back on your desktop, run the process you want with the env command like this:

env DBUS_SESSION_BUS_ADDRESS=dbus_address process

Display Remote Applications on FreeRunner

To get desktop apps to show up on your FreeRunner, first log in:

 ssh -l root

Then run:

 DISPLAY=:0 xhost +

After this you can close the ssh session. Back on the desktop computer, run:

 DISPLAY=openmoko:0 xclock

Note that the xhost command will allow remote applications on to access the X server. It will allow anyone on the desktop machine to access the X server of the neo, including snooping anything you type on it. To disallow remote applications again, run this in the neo:

 DISPLAY=:0 xhost -