added cheatsheet mobile-hotspot-setup

cheatsheets/networking/mobile-hotspot-setup.md

@@ -0,0 +1,73 @@
+---
+title: Mobile Setup with VPN
+categories: [cheatsheets]
+tags: [networking, hotspot, mobile]
+---
+
+# Mobile Setup with VPN
+
+## Hotspot
+
+**Tools needed:**
+
+- hostapd
+- dnsmasq
+- iptables
+
+### Configure dnsmasq and hostapd
+
+* hostapd (`/etc/hostapd.conf`)
+```
+interface=wlan0
+driver=nl80211
+ssid=sectest
+# Set access point harware mode to 802.11n
+hw_mode=g
+ieee80211n=1
+channel=6
+```
+
+* DNSmasq (`/etc/dnsmasq.conf`)
+```
+# Bind to only one interface
+bind-interfaces
+interface=wlan0
+dhcp-range=192.168.150.2,192.168.150.10
+```
+
+### Setup Hotspot
+
+* run `hotspot.sh`
+```
+#!/bin/bash
+# Starting
+sudo service wpa_supplicant stop
+sudo pkill wpa_supplicant
+
+sudo ifconfig wlan0 192.168.150.1
+sudo service dnsmasq restart
+sudo sysctl net.ipv4.ip_forward=1
+sudo iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
+sudo hostapd /etc/hostapd.conf
+
+# Stopping
+sudo iptables -D POSTROUTING -t nat -o eth0 -j MASQUERADE
+sudo sysctl net.ipv4.ip_forward=0
+sudo service dnsmasq stop
+sudo service hostapd stop
+sudo service wpa_supplicant start
+```
+
+* In case of **Failure**: `stop service wpa_supplicant && pkill wpa_supplicant`
+
+
+## Forwarding Traffic to VPN
+
+* Use the following iptables rules:
+```
+# wlan0 = AP interface
+# tun0  = VPN interface
+iptables -A FORWARD -i wlan0 -o tun0 -j ACCEPT
+iptables -A FORWARD -i tun0 -o wlan0 -m state --state ESTABLISHED,RELATED -j ACCEPT
+iptables -t nat -A POSTROUTING -o tun0 -j MASQUERADE
+```