Tether your android phone to your PC using USB cable could share your 3g Internet connection with PC.
In other words, your PC could connect to the Internet through your android phone.
WHILE REVERSE TETHERING DOES EXACTLY THE OPPOSITE.

Background:

Say I have a very limited 3g data plan. And I don't always have access to wifi.

Since my PC is connected to the Internet, why not connect my android phone to my PC and try sharing my PC's Internet connection with my android phone.

Solution:

The following steps shall do that trick:

Turn off celluar data conection on the phone
Tether the phone to the PC
On the PC side, share the Internet connection with the network created by the Remote NDIS based Internet Sharing Device.
On the PC side, delete the route table item which makes android phone a gateway. (admin privilege needed)
```
route delete 0.0.0.0 192.168.42.*
```
　replace the last IP address with your phone's IP address that your PC can reach.
On the android phone side, open terminal, do the following operations(root privilege needed):
```
busybox route add default gw 192.168..*
```
　　replace the last IP address with PC's IP address that your phone can reach.
DONE. Do some test now. eg. ping an address and open a webpage.

Tested on my rooted android phone and PC.

Know Issues:

　　1. some apps will check wifi or celluar data connection and mistakenly report no Internet connection　

　　　　Partially solved: check out this guide here on xda, it still need a SIM card in the first place

　　　　though data won't go through cellular data connection.

Miscellaneous:

There's a app on Google Play namely Reverse Tether which might do the trick, you may try the trial version.

Unfortunately, it failed to complete setup on my Mi2s.

USB Reverse Tether (a dirty solution)-LMLPHP
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