[UPDATED!] USING YOUR NEW RASPBERRY PI 3 AS A WIFI ACCESS POINT WITH HOSTAPD

转自：https://frillip.com/using-your-raspberry-pi-3-as-a-wifi-access-point-with-hostapd/

There's a new Raspberry Pi. This is exciting. It also has on-board WiFi. This makes it doubly exciting!
One of my first thoughts was, can I use it as a SoftAP for some ESP8266 sensor nodes? As it turns out, you can, and it's not that difficult, as the BCM43438 chip
is supported by the open-source 

brcmfmac

 driver!

PACKAGES

The first step is to install the required packages: 

sudo
apt-get install dnsmasq hostapd

I'll go into a little detail about the two:
hostapd - This is the package that allows you to use the built in WiFi as an access point
dnsmasq - This is a combined DHCP and DNS server that's very easy to configure
If you want something a little more 'heavyweight', you can use the 

isc-dhcp-server

 and 

bind9

 packages
for DHCP and DNS respectively, but for our purposes, 

dnsmasq

 works just
fine.

CONFIGURE YOUR INTERFACES

The first thing you'll need to do is to configure your 

wlan0

 interface
with a static IP.
If you're connected to the Pi via WiFi, connect via ethernet/serial/keyboard first.
In newer Raspian versions, interface configuration is handled by 

dhcpcd

 by
default. We need to tell it to ignore 

wlan0

, as we will be configuring
it with a static IP address elsewhere. So open up the 

dhcpcd

 configuration
file with 

sudo nano /etc/dhcpcd.conf

 and add the following line to the
bottom of the file:

denyinterfaces wlan0

Note: This must be ABOVE any 

interface

 lines
you may have added!
Now we need to configure our static IP. To do this open up the interface configuration file with 

sudo
nano /etc/network/interfaces

 and edit the 

wlan0

section so that
it looks like this:

allow-hotplug wlan0
iface wlan0 inet static
address 172.24.1.1
netmask 255.255.255.0
network 172.24.1.0
broadcast 172.24.1.255
#    wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

Restart 

dhcpcd

 with 

sudo
service dhcpcd restart

 and then reload the configuration for 

wlan0

 with 

sudo
ifdown wlan0; sudo ifup wlan0

.

CONFIGURE HOSTAPD

Next, we need to configure 

hostapd

.
Create a new configuration file with 

sudo nano /etc/hostapd/hostapd.conf

 with
the following contents:

# This is the name of the WiFi interface we configured above
interface=wlan0

# Use the nl80211 driver with the brcmfmac driver
driver=nl80211

# This is the name of the network
ssid=Pi3-AP

# Use the 2.4GHz band
hw_mode=g

# Use channel 6
channel=6

# Enable 802.11n
ieee80211n=1

# Enable WMM
wmm_enabled=1

# Enable 40MHz channels with 20ns guard interval
ht_capab=[HT40][SHORT-GI-20][DSSS_CCK-40]

# Accept all MAC addresses
macaddr_acl=0

# Use WPA authentication
auth_algs=1

# Require clients to know the network name
ignore_broadcast_ssid=0

# Use WPA2
wpa=2

# Use a pre-shared key
wpa_key_mgmt=WPA-PSK

# The network passphrase
wpa_passphrase=raspberry

# Use AES, instead of TKIP
rsn_pairwise=CCMP

We can check if it's working at this stage by running 

sudo
/usr/sbin/hostapd /etc/hostapd/hostapd.conf

. If it's all gone well thus far, you should be able to see to the network Pi3-AP! If you try connecting to it, you will see some output from the Pi, but you won't receive
and IP address until we set up dnsmasq in the next step. Use Ctrl+C to stop it.
We aren't quite done yet, because we also need to tell hostapd where to look for the config file when it starts up on boot. Open up the default configuration file with 

sudo
nano /etc/default/hostapd

 and find the line 

#DAEMON_CONF=""

 and
replace it with 

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

.

CONFIGURE DNSMASQ

The shipped 

dnsmasq

 config
file contains a wealth of information on how to use it, but the majority of it is largely redundant for our purposes. I'd advise moving it (rather than deleting it), and creating a new one with

sudo mv /etc/dnsmasq.conf /etc/dnsmasq.conf.orig
sudo nano /etc/dnsmasq.conf

Paste the following into the new file:

interface=wlan0      # Use interface wlan0
listen-address=172.24.1.1 # Explicitly specify the address to listen on
bind-interfaces      # Bind to the interface to make sure we aren't sending things elsewhere
server=8.8.8.8       # Forward DNS requests to Google DNS
domain-needed        # Don't forward short names
bogus-priv           # Never forward addresses in the non-routed address spaces.
dh
a9d5
cp-range=172.24.1.50,172.24.1.150,12h # Assign IP addresses between 172.24.1.50 and 172.24.1.150 with a 12 hour lease time

SET UP IPV4 FORWARDING

One of the last things that we need to do before we send traffic anywhere is to enable packet forwarding.
To do this, open up the 

sysctl.conf

 file
with 

sudo nano /etc/sysctl.conf

, and remove the 

#

 from
the beginning of the line containing 

net.ipv4.ip_forward=1

. This will
enable it on the next reboot, but because we are impatient, activate it immediately with : 

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

We also need to share our Pi's internet connection to our devices connected over WiFi by the configuring a NAT between our 

wlan0

 interface
and our 

eth0

interface. We can do this using the following commands:

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

However, we need these rules to be applied every time we reboot the Pi, so run 

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

 to save the rules to the file 

/etc/iptables.ipv4.nat

.
Now we need to run this after each reboot, so open the 

rc.local

 file
with 

sudo nano /etc/rc.local

 and just above the line 

exit
0

, add the following line:

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

WE'RE ALMOST THERE!

Now we just need to start our services:

sudo service hostapd start
sudo service dnsmasq start

And that's it! You should now be able to connect to the internet through your Pi, via the on-board WiFi!
To double check we have got everything configured correctly, reboot with 

sudo
reboot

.
EDIT: Thanks to Justin for helping iron out some of the errors in this post!
EDIT2: Thanks to Ashok for several performance related enhancements!
EDIT3: Thanks to Lasse for some amendments to the dnsmasq configuration!
EDIT4: Fixed race condition between dhcpcd and dnsmasq, wlan0 is no longer configured by dhcpcd.

PHIL MARTIN

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