View source for USB Networking

From Openmoko

Jump to: navigation, search

You do not have permission to edit this page, for the following reasons:

  • The action you have requested is limited to users in the group: Administrators.
  • You must confirm your email address before editing pages. Please set and validate your email address through your user preferences.

You can view and copy the source of this page:

Templates used on this page:

Return to USB Networking.

Personal tools

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 e.g. 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 (as root on your desktop, with FreeRunner attached via USB cable and booted properly, not at the Boot Menu). If it works, then you can add permanent configuration or use more sophisticated setups below.

iptables -A POSTROUTING -t nat -j MASQUERADE -s
sysctl -w net.ipv4.ip_forward=1
ip addr add dev usb0

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

ip addr add dev usb0

(This will just map the net from to onto usb0)

Then ifconfig usb0 up

Then (ideally, not as root):

ssh root@

The default password is blank.

Due to the fact that in most cases your Neo will use the same dns servers as your computer uses, you can automate the process of writing dns servers to your phone:

  1. !/bin/sh

/sbin/route add -host dev usb0
iptables -A POSTROUTING -t nat -j MASQUERADE -s
sysctl -w net.ipv4.ip_forward=1
su `whoami` -c "scp /etc/resolv.conf root@"

Again if your net already is, replace one statement with iptables -A POSTROUTING -t nat -j MASQUERADE -s

This simple script will set up routing for your Freerunner and than copy resolv.conf with dns addresses straight to the phone. All you have to do is connect phone to the computer, run the script and enjoy internet connection from your phone.

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


Device Drivers -> Network Device Support -> USB Network Adapters -> Multipurpose USB Networking Framework.

For more info see the usbnet driver homepage.

Masquerading options (tested on Linux are found in:

Networking ---> Networking options --->

To see the other options, enable

  • CONFIG_NETFILTER (Network packet filtering framework (Netfilter))

Then, from

Networking ---> Networking options ---> [*] Network packet filtering framework (Netfilter) ---> Core Netfilter Configuration --->

You need at least following options enabled as modules:

  • CONFIG_NF_CONNTRACK (Netfilter connection tracking support)
  • CONFIG_NF_CONNTRACK_FTP (FTP protocol support)
  • CONFIG_NETFILTER_XTABLES (Netfilter Xtables support)

Rest of the needed options are found from

Networking ---> Networking options ---> [*] Network packet filtering framework (Netfilter) ---> IP: Netfilter Configuration --->

You need to enable (again, as modules is fine):

  • CONFIG_NF_CONNTRACK_IPV4 (IPv4 connection tracking support (required for NAT))
  • CONFIG_IP_NF_IPTABLES (IP tables support (required for filtering/masq/NAT))

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.

You should add the IP address of the DNS servers as provided by your ISP. Check your router's or PC's network status for the nameserver IP addresses.

echo nameserver > /etc/resolv.conf

You can also add the public DNS server called openDNS: echo nameserver > /etc/resolv.conf echo nameserver >> /etc/resolv.conf

These settings will be lost on reboot. You can set the DNS for the next connect, by adding the following to the end of the usb0 setting in /etc/network/interfaces, right above the bluetooth networking section: up echo nameserver > /etc/resolv.conf up echo nameserver >> /etc/resolv.conf

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=`awk '$1 == "nameserver"{print $2; exit(0);}' /etc/resolv.conf`: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: ping

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.

Testing Your Connection

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

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

Try pinging the outside world (a Google IP address) ping 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: ping

OS or Distro Specific & Automatic Configuration

Based on Hotplugging usbnet by Marcin 'Hrw' Juszkiewicz. These instructions should keep you from having to run the Simple Manual Linux Configuration every time you plug in and want to connect to an Openmoko device. One run and then you're done!

If the Simple Manual Linux Configuration does not work for your OS or Distro (MacOS X, MS Windows, etc) there may be instructions here that work for you.


See MacOS X USB Networking.


See Windows USB Ethernet emulation for Neo1973.


You need to load the cdce kernel module (if it is not already linked into your kernel). As root do:

  1. kldload cdce

The Neo should then show up as cdce0 interface and you can handle the cdce0 interface just like the usb0 device under Linux. For more information see the cdce manpage. An easy way to assign the IP address to the cdce0 interface is using the devd(8) daemon. Create the following two files,

/usr/local/etc/devd/cdce.conf as:

notify 1 { match "system" "IFNET"; match "subsystem" "cdce0"; match "type" "ATTACH"; action "/usr/local/etc/devd/ $subsystem $type"; };

and /usr/local/etc/devd/ as:

  1. !/bin/sh

case $2 in 'ATTACH') ifconfig cdce0 netmask exit 0 ;

esac exit 0

Then restart the devd(8) daemon with:

  1. /etc/rc.d/devd restart

If you now plugin the FreeRunner into the USB port the cdce0 interface gets created and the IP addr will be assigned.

Debian, Ubuntu and others

Edit /etc/network/interfaces and add:

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

This is more sophisticated than the manual setup. The 'auto usb' stanza ties into the Linux hotplug system so that when the device appears and vanishes, as happens when the FreeRunner 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.

Another possible configuration that adds DNS forward and removes the iptables changes after unplugging:

in /etc/network/interfaces add

# freerunner
auto 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=$(awk '$1 == "nameserver"{print $2; exit(0);}' /etc/resolv.conf)

case "$1" in
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 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. Moving the DRIVERS=="*?" out of the top GOTO, to ACTION=="add" line fixes the problem.

SUBSYSTEM=="net", GOTO="net_start" GOTO="net_end"


  1. Bring devices up and down only if they're marked auto.
  2. Use start-stop-daemon so we don't wait on dhcp

ACTION=="add", DRIVERS=="?*", 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 DRIVERS variable isn't set at all when the device is unplugged.

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

Actually it appears that it's not fixed, but patching that file and disconnecting and reconnecting the phone works perfectly. --Johndoesacc 18:37, 20 August 2008 (UTC)


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

This didn't work for me (Mandriva 2008.1), giving errors from Shorewall. However, simply using MCC, Network->Sharing Internet Access worked fine. You need to connect Neo when starting it. --Alih 18:50, 22 September 2008 (UTC)



  1. 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


  1. USB configuration for PDAs (openmoko)
  2. from


Option B

This setup is probably over-complex:




  1. !/bin/bash

. /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:

  1. !/bin/bash

. /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

Option C - tested on F9

Plug in the usb cable. NetworkManager should detect the phone automatically but you should ignore it. Open Network Configuration tool (System -> Administration -> Network) and perform following steps:

  1. Click New button on top bar
  2. Click Forward
  3. Select OpenMoko from device list
  4. Click Forward
  5. Select 'Statically set IP address:' and enter address:, netmask (or use if you want only route ip range Leave gateway empty.
  6. Click Forward
  7. Click Apply to close add dialog
  8. Select newly added usb0 device from the device list.
  9. Click Edit button on top bar
  10. You might want to remove a tick from 'Activate device when computer starts' check box.
  11. Click Ok to close window dialog.

Save settings and close the window.

Open Firewall Configuration (System -> Administration -> Firewall) and enable masquerading:

  1. Select Masquerading from left panel
  2. Check device(s) which you'd like to share internet connection. Typically eth0 or wlan0.
  3. Click Apply and close application

Open terminal and perform (as root user):

  1. ifdown usb0
  2. ifup usb0

The first command will remove any existing settings given by the NetworkManager and second command brings the device up with appropriate settings.

Now you should be able to ping e.g. [] from OpenMoko. Configure /etc/resolv.conf and you should have full a internet access.


If Network Configuration tool cannot see the the usb0 try to unplug the usb cable for a few seconds and wait until the NetworkManager finds it again.

NetworkManager will assign a new ip address for the OpenMoko if link goes down for a while. You can fix this by issuing ifup usb0 again.

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:

  1. Neo

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

Create a new init script:

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

Manual Configuration

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

Automatic Configuration

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 }

Slackware (tested with 12.1)

Following is based on Enrico Zini's solution.

Create a new udev rules file /etc/udev/rules.d/91-openmoko.rules:

SUBSYSTEM=="net", ACTION=="add", ATTRS{idVendor}=="1457", ATTRS{idProduct}=="5122", RUN+="/etc/openmoko/openmoko-usb $env{INTERFACE} start" SUBSYSTEM=="net", ACTION=="remove", ENV{INTERFACE}=="usb[0-9]", RUN+="/etc/openmoko/openmoko-usb $env{INTERFACE} stop"

Then create the script /etc/openmoko/openmoko-usb:

  1. !/bin/sh


  1. udev fails silently when the script fails, e.g. due to commands not
  2. being found


case $ACTION in 'start')

  1. Put all your setup here


  1. Put all your tear down here
  • )

echo "Usage: $0 {start|stop}" exit 1


The INTERFACE will be usb0 in most cases.


Following is based on furester's solution.

Install package openmoko-usb-networking from AUR:

$ yaourt -S openmoko-usb-networking

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 adding a new line for every ssh host-key to your known_hosts you can add the following to the phone section in ~/.ssh/config (or see the snippet at : USB Networking#Changing_host_keys bellow)

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:

user@host$ 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:

root@phone# mkdir ~/.ssh

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

user@host$ scp ~/.ssh/ root@phone:~/.ssh/authorized_keys

You should now be able to ssh directly into the phone without a password prompt using a command like 'ssh root@phone' from the account user@host because the public key in the file user@host:~/.ssh/ is contained in the list of keys which have access in the file root@phone:~/.ssh/authorized_keys (since scp is used, only one key exists, but you can grant access to the phone from more than one account, for example user@host, user@laptop).

To make ssh login as root by default, add the following lines to ~/.ssh/config:

Host phone User root

Replace phone with the hostname or ip of your phone. You should now be able to ssh into the phone without having to type root@ every time.

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 HostName 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). Now you have set this, you can issue the following command to connect to your moko :

ssh root@moko

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 #(isn't the "env" redundant here?)

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 -

Automated setup network and mounting partitions

See Ubuntu bug report in launchpad.