WiFi hotspot through VPN

I had been using Bluetooth and USB DUN on my Miix, because WiFi hotspot could not go through a VPN connection on the phone. Well, this problem has been solved, thanking to this XDA post! Here I summarize the process:

• Start the VPN connection.
• Start WiFi hotspot.
• Open a terminal or ADB shell, run the following commands as su -:

iptables -t filter -F FORWARD
iptables -t nat -F POSTROUTING
iptables -t filter -A FORWARD -j ACCEPT
iptables -t nat -A POSTROUTING -j MASQUERADE 

thantos_mehak also posted his source code that makes above last step a simple click. I edited the code with above commands, compiled it and it worked fine. Note：

• Your phone must be root.
• You don't need to run VPN on other devices that are tethered to the phone.
• If other devices still cannot connect, but ping 8.8.8.8 is successful, then change their DNS servers to, say, 8.8.8.8 and 8.8.4.4. Or add another commands:

iptables -t nat -A PREROUTING -p udp --dport 53 -j DNAT --to 8.8.8.8

PS:  WiFi Tether Router by Fabio Grasso works through VPN on its own (i.e. no need of above iptables commands). It is also the most featured among such apps I've seen. The only missing feature is auto WiFi channel. It works fine on my Galaxy S4 (root stock 4.3 ROM) but does not on my Pantech Burst.

PPS: Works for native Android Bluetooth PAN and USB tether too, and for proxy too (might need some extra routing work).

PPPS: For KitKat 4.4.2, some ip routes must be added as described in this XDA post:

ip rule add from 192.168.43.0/24 lookup 61
ip route add default dev tun0 scope link table 61
ip route add 192.168.43.0/24 dev wlan0 scope link table 61
ip route add broadcast 255.255.255.255 dev wlan0 scope link table 61

PPPPS：For some phones, even earlier than 4.4, the added lookup 61 will be removed randomly, hence need to be added again and again. Sometimes it is 60 instead of 61.