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[Linux] Creating a WiFi hotspot using hostapd and dnsmasq

Note that this does not consider sharing internet with the devices yet.

Prerequisites

Packages Required

First off, make sure you know which interface/card you are using. This can be done using a combination of ip link and lspci -v. I'll be using wlp4s0 throughout.

Now make sure you're interface supports AP mode. This can be seen using iw list. Under "Supported interface modes:", "AP" should be listed.

Setting up hostapd

Here is a configuration which sets up WPA2 - you'll need to edit the password, ssid, interface, and possibly country code. 

# /usr/share/doc/hostapd/hostapd.conf
# http://wireless.kernel.org/en/users/Documentation/hostapd

ctrl_interface=/var/run/hostapd
ctrl_interface_group=wheel

# Some usable default settings...
macaddr_acl=0
auth_algs=1
ignore_broadcast_ssid=0

# WPA2 with preshared key (passphrase).
wpa=2
wpa_key_mgmt=WPA-PSK
wpa_pairwise=TKIP
rsn_pairwise=CCMP

# TODO
wpa_passphrase=

# Most modern wireless drivers in the kernel need driver=nl80211
driver=nl80211

# Customize these for your local configuration...
interface=wlp4s0
hw_mode=g
channel=1
country_code=US
ssid=TODO

Setting up dnsmasq

In `/etc/dnsmasq.conf`, add the line 

interface=wlp4s0
and 
dhcp-range=10.0.0.2,10.0.0.5,12h
Adjust the second entry in the range if you plan on hosting more than three devices.

Putting it all together

  1. Mark your interface as the router: ip addr add 10.0.0.1/24 dev wlp4s0.
  2. Start dnsmasq: systemctl start dnsmasq
  3. Start hostapd: systemctl start hostapd

Gotchas

On Fedora, selinux can cause some pain. As per https://bugzilla.redhat.com/show_bug.cgi?id=1891152, do the following if you encounter AVC denials for comm="hostapd" in journalctl -xe.

  1. ausearch -c 'hostapd' --raw | audit2allow -M my-hostapd
  2. semanage -i my-hostapd.pp