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Didj Network Bridging

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This page includes steps that describe an alternative method to enable your Didj to access to the wider Internet via the USB connection through the use of bridging.

They have been tested in Ubuntu 8.04 Hardy Heron (2.6.24-26 kernel), and are based on similar instructions for other handheld devices.

Prerequisites

  1. You have set up USB networking as per http://elinux.org/Didj_Networking_HOWTO
  2. The required tools are provided by the bridge-utils package:

sudo apt-get install bridge-utils


Configuring the Host

In this example, we assume that the host has an ethernet connectoion on eth0. (your own config may be different; for example, you may be using a Wifi adapter. In theory, aside from your LAN specific configuration, the steps outlined below should still work.)

The bridge will be made up of the host's usb ethernet link to the Didj usb0, combined with the ethernet connection eth0 in a virtual 'bridge' interface called br0.

The bridged interface br0 will be assigned the IP configuration for the PC.

(In later steps, you will assign the Didj an IP address on the same network).

Configure the host machine's /etc/network/interfaces file as follows (adjusting IP addresses as needed):

auto lo
iface lo inet loopback
auto eth0
iface eth0 inet dhcp
auto usb0
iface usb0 inet static
       address 192.168.0.199
       netmask 255.255.255.0
       up echo 1 > /proc/sys/net/ipv4/ip_forward
       up iptables -P FORWARD ACCEPT
       up iptables -A POSTROUTING -t nat -j MASQUERADE -s 192.168.0.0/24
       down echo 0 > /proc/sys/net/ipv4/ip_forward
       down iptables -t nat -F POSTROUTING
iface br0 inet dhcp
        pre-up   echo     "Adding ethernet bridge between Didj and LAN"
        pre-up   ifconfig eth0 0.0.0.0
        pre-up   brctl    addbr br0
        pre-up   brctl    setfd br0 0
        pre-up   brctl    stp br0 off
        pre-up   brctl    addif br0 eth0
        pre-down echo     "Removing ethernet bridge between Didj and LAN"
        post-down brctl    delif br0 eth0
        post-down brctl    delbr br0
        post-down ifdown eth0
        post-down ifup eth0

To apply these new settings:

On the Host:

sudo /etc/init.d/networking restart

(of course, rebooting the host will also work)


If you are using DHCP as we do in the above example, make a note of your br0 ip address by typing ifconfig.

Configuring the Didj

If you are using a standard Didj configuration and you have not yet done so, rmmod the g_file_storage kernel module and insmod the g_ether/ko module. (see http://elinux.org/Didj_Networking_HOWTO#Installing_g_ether.ko)

With the USB cable connected to your host, configure an IP address on the same subnet as the rest of your LAN

On the Didj:

ifconfig usb0 192.168.0.200 netmask 255.255.255.0

At this point, activate your bridge on the host by entering:

On the Host:

sudo ifup br0

Next, add a route from your Didj to the host (making it the gateway) using the ip address you found for br0 via running ifconfig on the host.

On the Didj:

route add default gw 192.168.0.116 usb0

Finally, add nameservers to your Didj's /etc/resolv.conf file (you can add the lines from this example which uses the OpenDNS servers)

nameserver 208.67.222.222
nameserver 208.61.220.220


At this point, assuming br0 is brought up on your host, your Didj is connected to the outside world - and a ping or a wget to yahoo or google should work.


References

http://wiki.maemo.org/USB_networking

http://wiki.openzaurus.org/HowTos/Bridging_with_Ubuntu