Raspberry PI Access Point Setup and Configuration

If you follow the steps in this document, and read carefully, the end result will be a fully functioning highly customizable raspberry-pi access point that you can use for a myriad of entertaining and useful tasks.

If you've ever wanted to see what a computer was doing while connected to an access point, or see how different applications behave in slow or overcrowded networks, this document, and the related commands in other files in this project can show you how to have an entire WIFI test suite at your disposal.

Build this doc as HTML

1. Install docutils: sudo apt-get install python-docutils
2. Build to HTML: rst2html howto.txt howto.html --stylesheet-path=docutils.css

Note:	If rst2html isn't present try: rst2html.py

IP Addresses

In this tutorial I'm going to assume you will be creating a new network and subnet in the 192.168.1.xxx range.

I'm also going to assume you already have an existing LAN network that is in the

10.0.10.xxx range.

If your LAN is using 192.168.1.1 and you want the Raspberry PI to use

10.x.x.x range, you should switch around the commands as you see fit.

Note:	I will eventually add some scripts to help build the configs automatically.

Installing Raspbian

Raspbian is the default and best linux distribution currently available to use with your raspberry pi. Our raspberry pi came with a bootable memory card with a program called NOOBS on it. You can use NOOBS to install Raspbian (it gives you several other options).

From Noobs

• Plug in your keyboard and monitor (hdmi)
• Plug in the USB power cable
• The Raspberry PI will begin booting (you'll see lights on the board lit) A list of the different operating systems will appear. Tick the box next to Raspbian and select install.
• The install process wil begin (this will take awhile)
• raspi-config is automatically started when install finishes. You can set the region time, date, etc from this menu.

Restoring/Installing from Disk Image

• Insert the memory card into a memory card reader and connect it to your linux desktop.
• Use dd command line tool to copy your disk image to the raspberry pi.
• You're done.

Logging In to the Raspberry PI

When connected directly to the raspberry pi or over ssh you can use default credentials.

Note: you won't see any characters appear when you're typing (this is a security feature of linux)

Default Credentials:

username: pi
password: raspberry

Login:

ssh pi@10.0.10.48

Installing and Configuring

Configs

Configuration files we'll be creating or editing.

Copies of some of these are located in the configs directory within the github repository containing this code based on exactly the configurations detailed here.

• /etc/sysctl.conf
• /etc/default/hostapd
• /etc/dnsmasq.conf
• /etc/hostapd/hostapd.conf
• /etc/network/interfaces

Setup the wlan0 interface

We need the wireless hardware interface setup and configured in such a way that it can act as an access point. To do this we'll need to do a few things.

1. Edit /etc/network/interfaces

2. Comment out these lines:

   #allow-hotplug wlan0
   #wpa-roam /etc/wpa_supplicant/wpa_supplicant.conf
   #iface default inet dhcp
   

3. Add these lines (editing the iface wlan0 interface if it's already there):

   iface wlan0 inet static
     address 192.168.1.1
     netmask 255.255.255.0
   

Install hostapd

hostapd will act as the actual access point software. It will manage the wireless device and broadcast the wireless network.

WIFI Adapter Note:

Many Raspberry PI use Wifi Adapter Realtek 8188CU (same chip used by the Edimax EW-7811Un) This ADAPTER is Not supported and will not run in AP mode!

There are mentions of a patch to hostapd that allows this chip to work, but it was unsuccessful for me.

1. Verify AP Support:

   Verify by sudo apt-get install iw and executing iw list.

   If you see nl80211 not found. your device doesn't support AP mode.

   At SpotOn we purchased Panda Mid-Range Wireless N USB Adapter's - these worked great.

2. sudo apt-get install hostapd

3. Edit the file /etc/default/hostapd edit and uncomment the existing line in the file so you end up with...

   DAEMON_CONF="/etc/hostapd/hostapd.conf"

4. Create/Edit the file /etc/hostapd/hostapd.conf

5. Change/Add the line driver=nl80211 to the hostapd.conf file.

6. Add the following configuration options to hostapd.conf

   change ssid to a reasonable name

   and wpa-passphrase to something unique.

   Change wlan0 to the name of your wireless interface.

   driver=nl80211
   interface=wlan0
   country_code=US
   #ctrl_interface=eth0
   #ctrl_interface_group=0
   ssid=rpi1-at-10-0-10-48
   hw_mode=g
   channel=1
   ignore_broadcast_ssid=0
   wpa=2
   wpa_passphrase=password
   wpa_key_mgmt=WPA-PSK
   wpa_pairwise=TKIP
   rsn_pairwise=CCMP
   beacon_int=100
   auth_algs=3
   macaddr_acl=0
   wmm_enabled=1
   eap_reauth_period=360000000
   logger_stdout=1
   logger_stdout_level=0
   logger_syslog=-1
   logger_syslog_level=0
   

7. Start hostapd

   sudo service hostapd start ... (or)

   sudo hostapd /etc/hostapd/hostapd.conf to run interactively (view errors)
8. optional step

   Add the line ifconfig wlan0 192.168.1.1 to the file

   /etc/init.d/hostapd immediately before the exit 0 at the bottom.

   
   

   When hostapd is restarted, the IP address on the WIFI (wlan0) interface is lost.

   Now the command service hostapd restart will function properly.

Install dnsmasq

1. sudo apt-get install dnsmasq

2. edit the file /etc/dnsmasq.conf

   uncomment and set interface=wlan0

   uncomment and set dhcp-range=192.168.1.50,192.168.1.150,255.255.255.0,12h

   uncomment and set dhcp-authoritative

Setup connection sharing

Assumptions:

• You have a wired connection to a private network behind a router as interface eth0.
• You have a wireless connection configured as wlan0.

IpTables Note:

• You can check iptablets and the current ruleset with the command sudo iptables -nvL

• You can flush and reset iptables (to defaults) with these commands:

  iptables -F
  iptables -X
  iptables -t nat -F
  iptables -t nat -X
  iptables -t mangle -F
  iptables -t mangle -X
  iptables -t raw -F
  iptables -t raw -X
  iptables -t security -F
  iptables -t security -X
  iptables -P INPUT ACCEPT
  iptables -P FORWARD ACCEPT
  iptables -P OUTPUT ACCEPT
  

1. Enable NETWORK ADDRESS TRANSLATION (NAT) to share the internet on eth0 with wlan0...:

   sudo sh -c "echo 1 > /proc/sys/net/ipv4/ip_forward"
   

2. Persist NAT after boot - Edit /etc/sysctl.conf adding this line at the bottom:

   net.ipv4.ip_forward=1
   

3. Enable NAT/forwarding in the kernel:

   sudo iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
   sudo iptables -A FORWARD -i wlan0 -o eth0 -j ACCEPT
   sudo iptables -A FORWARD -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
   

4. Persist the changes to iptables:

   sudo sh -c "iptables-save > /etc/iptables.ipv4.nat"
   

5. Now edit the file /etc/network/interfaces and add the following line at the bottom

   This will cause iptables to be restored from config when the interface comes up::

   up iptables-restore < /etc/iptables.ipv4.nat

Services Configuration

We want hostapd, and dnsmasq to start with the device by default.:

sudo update-rc.d hostapd enable
sudo update-rc.d dnsmasq enable

Networking Tests

• See the file tc.rst for poor network quality simulation options (packet loss, out-of-order, etc)
• See the file iptables.rst for network failure simulation commands.
• See the file dnsredirection.rst for controlling how DNS requests for specific domains are handled.

References

The most Relevant tutorial specifically for RPI and using dnsmasq and hostap

• http://sirlagz.net/2012/08/09/how-to-use-the-raspberry-pi-as-a-wireless-access-pointrouter-part-1/
• http://sirlagz.net/2012/08/10/how-to-use-the-raspberry-pi-as-a-wireless-access-pointrouter-part-2/
• http://sirlagz.net/2012/08/11/how-to-use-the-raspberry-pi-as-a-wireless-access-pointrouter-part-3/

Other stuff

• http://elinux.org/RPI-Wireless-Hotspot
• http://www.daveconroy.com/turn-your-raspberry-pi-into-a-wifi-hotspot-with-edimax-nano-usb-ew-7811un-rtl8188cus-chipset/
• http://blog.sip2serve.com/post/48420162196/howto-setup-rtl8188cus-on-rpi-as-an-access-point
• https://github.com/previ/coderbot/wiki/Realtek-8188-Wi-Fi-adapter
• http://www.raspberrypi.org/forums/viewtopic.php?p=462982#p462982
• http://www.andybev.com/index.php/Using_iptables_and_PHP_to_create_a_captive_portal
• http://ftp.netbsd.org/pub/NetBSD/NetBSD-current/src/external/bsd/wpa/dist/hostapd/hostapd.conf

forwarding between networks

• http://serverfault.com/questions/267580/linux-routing-traffic-between-two-networks-with-iptables

The best article on configuring NAT with dnsmasq and access point.

• https://wiki.archlinux.org/index.php/Software_access_point