Nexus S Android 4.1.1 share Ubuntu network via USB

Preparations:
1) Check the phone is root, because the phone needs to execute the su command to modify the Phone gateway, so must root, if there is no root reference (Nexus S 4.1.1) This address: http://www.teamandroid.com/2012/07/20/root-nexus-s-on-android-411-jelly-bean-jro03e-official-software-update/
2) install the terminal and busybox on the mobile phone through the market.

Step 1: System Setting-> wireless & networks-> more-> tethering & portables hotspot-> USB tethering check box

Step 2: run the ifconfig command on your computer to see that a USB 0 Nic is added to the PC. This is a network interface virtualized through the USB cable. Take my computer as an example, the IP address is 192.168.42.89. On the mobile terminal, enter the su command and run the busybox ifconfig command to view the IP address 192.168.42.129 corresponding to the PC, ping or buybox Ping can be used to ping each other, but the Internet is not available yet.

Step 3: Change the IP address 192.168.42.89 to 192.168.42.1.

 
Sudo ifconfig usb0 192.168.42.1 netmask 255.255.255.0
 

Step 4: Change the gateway on the mobile phone to 192.168.42.1.

 
Subusybox route add default GW 192.168.42.1setprop net. dns1 8.8.8.8
 

After this step, the mobile phone can ping the IP address of the real network card on the computer 172.16.2.181, but still cannot access the Internet.
To go through Ubuntu
Step 5: Set iptables
1) Check whether iptables Forwarding is enabled.

 
Sysctl net. ipv4.ip _ forward
 

"Net. ipv4.ip _ forward = 0" 0 => is printed, indicating that it is not enabled.
Or check whether the content of the/proc/sys/NET/IPv4/ip_forward file is 0 or 1, 0 => disabled, 1 => Enabled
2) if it is not enabled, set it to enable

 
Sysctl-W net. ipv4.ip _ forward = 1
 

Check whether the value of sysctl net. ipv4.ip _ forward is 1.
The above modification is temporary and will expire after restart. To save it permanently, you can modify the/etc/sysctl. conf file and cancel the OK operation on line net. ipv4.ip _ forward = 1.
3) Configure route forwarding, map the network address segments (192.168.42.1/24) of mobile phones connected through USB cables and PCs (UBUNTU) to the IP addresses on the network card, for example, 172.16.2.181.

 
Sudo iptables-T Nat-A postrouting-s 192.168.42.1/24-j snat -- to-source 172.16.2.181
 

Explanation: forward all packet requests sent from the class C network address 192.168.42.1/24 to 172.16.2.181.
Check the NAT table information of iptables to see if the command in the previous step has been successfully added.

Sudo iptables-T nat-vnl postrouting -- line-num
 

Then, you can access the Internet through a browser.
4) Save the changes made to iptables. Otherwise, restart the mobile phone. The changes just made to iptables are gone.

 
Sudo iptables-save
 

Refer:

Http://www.ducea.com/2006/08/01/how-to-enable-ip-forwarding-in-linux/

Http://hi.baidu.com/b1uecream/item/73d0df2110f47f112a0f1cdc