How to share Android "Reverse-tethered" internet via Android WiFi?
I managed to make it work.  Here is an "OSI-like" diagram of my setup, if it makes sense:

 ____________________   ______________________________    ____________
|   LinuxVM &lt;----+  |  |                              |  |            |
|  VirtualBox    |  |  |                              |  |            |
| Windows7(host) |  |  | +--&gt; AndroidPhone &lt;-------+  |  | +--&gt;Laptop |
|  (USB)         +-------+   (USB)  (wifi-HotSpot) +-------+   (wifi) |
|___________________|  |______________________________|  |____________|


The script is located at the XDA forum: http://forum.xda-developers.com/showpost.php?p=50236807&amp;postcount=9

## 0.a. Connect android-phone to PC through USB.
## 0.b Enable Settings|...|Tethering 
##  (so that the device gets detected by the PC's kernel, you should see the following with 'dmsg':
##         [    3.976599] rndis_host 1-1:1.0 usb0: register 'rndis_host' at usb-0000:00:0b.0-1, RNDIS device, 4e:d5:8c:7b:4f:5a
## Enable Settings|...|Wifi-Hotspot


## Setup usb reverse-tethering.
#  from: http://forum.xda-developers.com/show....php?t=2287494
#
#  Yours device might be 'rndis0' or something else.  Check by just typing 'netcfg'.
#
netcfg usb0 dhcp
busybox route add default gw 10.42.0.1 dev usb0


## Disable mobile-data.
#
busybox ifconfig rmnet_usb0  0.0.0.0


## Masquerade through USB.
#
echo 1 &gt; /proc/sys/net/ipv4/ip_forward
iptables -t nat -F
iptables -t nat -A POSTROUTING -o usb0 -j MASQUERADE
iptables -P FORWARD ACCEPT


## Set DNS (if neccessary, ie google's 8.8.4.4).
#
setprop net.dns1 XX.YY.ZZ.WW