BeagleBone Access Point (and working around udhcpd)

Warning: it's easy to screw this stuff up and lose the ability to ssh into the beaglebone when you reboot.  Usually it was as simple as manually setting the IP address on my laptop, but you may not be so lucky.  You may not want to attempt this if you don't have a good handle on TCP/IP networking.

My Keebox W150NU seems to be doing a good job with a BeagleBone black as a wifi access point.  (I get about 3MB/s beaglebone -> laptop).  Beware that lots of other adapters (eg., Edimax and D-Link) work really poorly or not at all with the BeagleBone.

With a newer BeagleBone green, the W150NU was recognized out of the box, but on an older BBB with another adapter I had to update the kernel first:

Update kernel if your wifi adapter isn't detected (or if you just want to be up to date):

First I did 'sudo apt-get update ; sudo apt-get dist-upgrade'

Then I upgraded the kernel so it'd recognize the usb wifi adapter:

'cd /opt/scripts/tools ; git pull ; ./update_kernel.sh' 

On BeagleBone Green they tweaked a file to say "BBG" instead of "BBB", so I had to revert it with: 'cd /opt/scripts ; git checkout tools/eMMC/init-eMMC-flasher-v3.sh' then 'git pull' again before I could run the 'update_kernel.sh' script.

Rebooting, the W150NU appeared as wifi2.

Next, I followed the instructions here to set up hostapd.  

First, 'sudo apt-get install dnsmasq hostapd'

Here's my /etc/hostapd/hostapd.conf (beware leading and trailing spaces, or hostapd.conf will refuse to start):

### Wireless network name ###
interface=wlan0
#
### Set your bridge name ###
#bridge=br0

#driver
driver=nl80211

country_code=US

ssid=beaglebone

channel=7

hw_mode=g

# # Static WPA2 key configuration
# #1=wpa1, 2=wpa2, 3=both
wpa=2

wpa_passphrase=yourpassword

## Key management algorithms ##
wpa_key_mgmt=WPA-PSK
#
## Set cipher suites (encryption algorithms) ##
## TKIP = Temporal Key Integrity Protocol
## CCMP = AES in Counter mode with CBC-MAC
wpa_pairwise=TKIP
#rsn_pairwise=CCMP
#
## Shared Key Authentication ##
auth_algs=1
## Accept all MAC address ###
macaddr_acl=0
#enables/disables broadcasting the ssid
ignore_broadcast_ssid=0
# Needed for Windows clients
eapol_key_index_workaround=0

And don't forget to set this in /etc/defaults/hostapd:

DAEMON_CONF="/etc/hostapd/hostapd.conf"
I couldn't get dnsmasq or isc-dhcp-server to work consistently, though.  Turns out that 'netstat -nlp' showed udhcpd was binding to 0.0.0.0 on port 67 (which is a bug, since it ignores the "interface" option), so the other dhcp servers can't start.

Hint: /var/log/daemon.log is where a lot of the error messages show up.

I fixed that with 'mv /usr/sbin/udhcpd /usr/sbin/udhcpd.disabled', although it would probably have been better to 'apt-get purge udhcpd'.

Here's my /etc/dnsmasq.conf:

interface=usb0
dhcp-range=192.168.7.1,192.168.7.1,4h

interface=wlan0

dhcp-range=192.168.4.2,192.168.4.10,4h

And I also added this to /etc/network/interfaces:
auto wlan0
iface wlan0 inet static
    address 192.168.4.1
    netmask 255.255.255.0
    network 192.168.4.0
    gateway 192.168.4.1

That seems to do it, except that I have to "ifup wlan0" after startup on my BeagleBone Green.  The Black doesn't seem to need that for some reason I haven't figured out yet.