Basic network configuration
Madwifi needs a network bridge to work. Fortunately for me, the atheros card has its bridge automatically set up when the interface is mounted. The card gets the ath0 interface, while the bridge is labelled wifi0.
With this card, I had to add an autocreate=ap option in modprobe. To do that :
echo "options ath_pci autocreate=ap" | sudo tee /etc/modprobe.d/ath_pci
Then I set ath0 in /etc/network/interfaces :
$ cat /etc/network/interfaces
auto lo
iface lo inet loopback
auto eth0
iface eth0 inet dhcp
auto ath0
iface ath0 inet static
wireless-mode master
wireless-channel 9
wireless-essid jonah
address 192.168.1.254
netmask 255.255.255.0
broadcast 192.168.1.255
I get my Internet connection through a router with a DHCP server on eth0.
Reload your network after you're done setting it up :
sudo /etc/init.d/networking restart
Setting up hostapd
Hostapd allows to set up a nice wifi access point with WPA authentication in a short time. Here is my configuration (ignoring empty and commented lines) :
cat /etc/default/hostapd | grep -v "^\(#\|$\)"
RUN_DAEMON="yes"
DAEMON_CONF="/etc/hostapd/hostapd.conf"
$ sudo cat /etc/hostapd/hostapd.conf | grep -v "^\(#\|$\)"
interface=ath0
bridge=wifi0
driver=madwifi
logger_syslog=-1
logger_syslog_level=2
logger_stdout=-1
logger_stdout_level=2
debug=0
dump_file=/tmp/hostapd.dump
ctrl_interface=/var/run/hostapd
ctrl_interface_group=0
ssid=jonah
hw_mode=g
channel=60
beacon_int=100
dtim_period=2
max_num_sta=255
rts_threshold=2347
fragm_threshold=2346
macaddr_acl=0
auth_algs=3
ignore_broadcast_ssid=0
wme_enabled=1
wme_ac_bk_cwmin=4
wme_ac_bk_cwmax=10
wme_ac_bk_aifs=7
wme_ac_bk_txop_limit=0
wme_ac_bk_acm=0
wme_ac_be_aifs=3
wme_ac_be_cwmin=4
wme_ac_be_cwmax=10
wme_ac_be_txop_limit=0
wme_ac_be_acm=0
wme_ac_vi_aifs=2
wme_ac_vi_cwmin=3
wme_ac_vi_cwmax=4
wme_ac_vi_txop_limit=94
wme_ac_vi_acm=0
wme_ac_vo_aifs=2
wme_ac_vo_cwmin=2
wme_ac_vo_cwmax=3
wme_ac_vo_txop_limit=47
wme_ac_vo_acm=0
eapol_key_index_workaround=0
eap_server=0
own_ip_addr=127.0.0.1
wpa=1
wpa_passphrase=My Great Passphrase for the Access Point
wpa_key_mgmt=WPA-PSK
wpa_pairwise=TKIP
wpa_group_rekey=600
wpa_gmk_rekey=86400
Don't forget to change the passphrase (up to 63 characters).
Check your conf with :
sudo hostapd -dd /etc/hostapd/hostapd.conf
I had problems there at first because my card wasn't able to be set to master mode (ap, see above for the modprobe.d hack). To set your card to master mode without rebooting, reload the driver :
sudo modprobe -r ath_pci
sudo modprobe ath_pci autocreate=ap
If hostapd works fine, you can launch it in the background :
sudo /etc/init.d/hostapd start
Once hostapd is set up, you should be able to connect to your AP by providing a manual IP address (in the right network). But you might want to go further, and set your AP as a DHCP server and router. These next steps are compiled from a post on Ubuntu Forums.
Setting up DHCP and DNS
The first thing you want is a DHCP server. Since the post on Ubuntu Forums gets us to install dnsmasq to forward the DNS requests, and that dnsmasq can also be used as a DHCP server, I didn't see the use for dhcp3-server, so I deactivated it. Here is my configuration for dnsmasq :
$ sudo cat /etc/default/dnsmasq | grep -v "^\(#\|$\)"
ENABLED=1
$ sudo cat /etc/dnsmasq.conf | grep -v "^\(#\|$\)"
dhcp-range=192.168.1.50,192.168.1.150,12h
Pretty easy, no? This will simply forward the DNS requests to the DNS servers listed in /etc/resolv.conf, and provide a very basic DHCP server serving addresses from 192.168.1.50 to 192.168.1.150.
We can now restart dnsmasq with :
sudo /etc/init.d/dnsmasq restart
This step should now let you connect to your AP without setting a static IP (using knetworkmanager for example). But you won't get really far from there, until you set up the NAT.
Setting up the NAT
This is the last step, setting up the NAT so that your AP can work as a router.
First, add IP forwarding settings to your sysctl.conf (to have it at next reboot) and activate it (for now) :
sudo iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
echo "net.ipv4.ip_forward = 1" | sudo tee -a /etc/sysctl.conf
echo 1 | sudo tee /proc/sys/net/ipv4/ip_forward"
Then set ipmasq to start up after services are started. This way, ipmasq will manage your iptables firewall after the interfaces are up and both dnsmasq and hostapd are up :
sudo dpkg-reconfigure dnsmasq
Warning: if you have static firewall rules, you should add them to the ipmasq settings (see "man ipmasq for more details).
Restart your AP host to make sure it still works after a reboot and enjoy.
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