Android tethering

What is Tethering

Tethering is a way to have Internet access on your PC through your smartphone using its network connection. USB and Wi-Fi access point tethering is natively supported from Android Froyo ( 2.2 ). Older versions of the Android OS, mostly unofficial roms have this option enabled.

Wi-Fi access point

Using an Android phone as a Wi-Fi access point (using 3G) has been accessible by default since Froyo (Android 2.2) without needing to root the phone. Moreover, this method will discharge the battery rapidly and tends to cause intense heating, unlike USB. See : menu/wireless & networks/Internet tethering/Wi-Fi access point

USB tethering

Tools Needed

• Root access to the phone (for old Android versions, Froyo (Android 2.2) and beyond can do it natively)
• USB connection cable from your phone to PC

Procedure

• Enable USB Debugging. This is usually done from Settings --> Applications --> Development --> USB debugging. Reboot the phone after checking this option to make sure USB debugging is enabled (if there is no such option, this step probably does not apply to your version of Android)
• Disconnect your computer from any wireless or wired networks
• Connect the phone to your computer using the USB cable (the USB connection mode -- Phone Portal, Memory Card or Charge only -- is not important, but please note that you will not be able to change the USB mode during tethering)
• Enable the tethering option from your phone. This is usually done from Settings --> Wireless & Networks --> Internet tethering (or Tethering & portable hotspot, for more recent versions)

(The following step may not be needed. usbnet module may not be necessary, do it only if you do not see a usb0 interface in the ifconfig step)

• Load the usbnet module(if it's not already loaded). You will need root access to do that

modprobe usbnet

• Make sure that the USB interface is recognized by the system by using the following command:

ifconfig -a

you should be able to see a usb0 device listed like this (notice the usb0 device):

# ifconfig -a

eth0      Link encap:Ethernet  HWaddr 00:16:36:FA:3E:31  
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:316435 errors:0 dropped:0 overruns:0 frame:0
          TX packets:316435 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:22875193 (21.8 Mb)  TX bytes:22875193 (21.8 Mb)

usb0      Link encap:Ethernet  HWaddr C2:5A:11:8D:43:F5  
          BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)

• Configure the new network device via DHCP using the following command:

ifconfig usb0 up && dhcpcd usb0

To configure the new network device using the iproute toolkit, issue the following as root:

ip link set usb0 up && dhcpcd usb0

To stop the network sharing, issue the command:

dhcpcd -x usb0

USB tethering with OpenVPN

This method works for any old Android version and does not requires root access nor modifications in the phone (it is also suitable for Android 2.2 and later, but no longer required).

It does not requires changes to your browser; in fact transparently handles all network traffic for any PC application (except ICMP pings). It is somewhat CPU intensive in the phone at high usage rates (a 500 kbyte/sec data transfer rate may take more than 50% of phone CPU on a powerful Acer Liquid).

Tools Needed

In Arch, you need to install the openvpn package. Is is also required the Android SDK installed (which can be obtained here). In the phone, the azilink application, a Java-based NAT that will communicate with OpenVPN in your computer.

Configuring the phone connection in Arch Linux

Once you have installed the Android SDK, in order to use the provided tools your phone must be properly set up in udev and your Linux user needs to be granted rights. Otherwise you may need root privileges to use the Android SDK, which is not recommended. To perform this configuration, turn on USB debugging on the phone (usually in Settings -> Applications -> Development -> USB debugging), connect it to the PC by the USB cable and run the lsusb command. The device should be listed. Example output for the Acer Liquid phone:

Bus 001 Device 006: ID 0502:3202 Acer, Inc. 

Then, create the following file, replacing ciri by your own Linux user name, and 0502 by the vendor ID of your own phone:

/etc/udev/rules.d/51-android.rules

SUBSYSTEM=="usb", ATTR(idVendor)=="0502", MODE="0666" OWNER="ciri"

As root run the udevadm control restart command (or reboot your computer) to make the change effective. Now run in your linux PC the adb shell command from the Android SDK as plain (non root) user: you should get a unix prompt in your phone.

Procedure

Run the AziLink application in the phone and select "About" at the bottom to receive instructions, which basically are:

1. You will have to enable USB debugging on the phone if it was not already enabled (usually in Settings -> Applications -> Development -> USB debugging).
2. Connect the phone with the USB cable to the PC.
3. Run AziLink and make sure that the Service active option at the top is checked.
4. Run the following commands in your Linux PC:
   1. As plain user: adb forward tcp:41927 tcp:41927 (requires Android SDK installed)
   2. As root: openvpn AziLink.ovpn

AziLink.ovpn

dev tun
remote 127.0.0.1 41927 tcp-client
ifconfig 192.168.56.2 192.168.56.1
route 0.0.0.0 128.0.0.0
route 128.0.0.0 128.0.0.0
socket-flags TCP_NODELAY
keepalive 10 30
dhcp-option DNS 192.168.56.1 

Tethering with proxy

With this method tethering is achieved by port forwarding from the phone to the PC. This is suitable only for browsing. For Firefox, you should set network.proxy.socks_remote_dns to true in about:config ( address bar )

Tools Needed

• Root access to the PC
• Android SDK which can be obtained here
• USB connection cable from your phone to PC
• Proxoid application(free download from the Android market)

Instructions

Follow the instructions demonstrated in the following link