In this post, we setup a wireguard VPN based RasberryPi Wifi Hotspot/AP that uses hostapd and dnsmasq on Ubuntu 20.04. I needed this for my parents who want to be able to connect to our home network, they would connect to the AP and the AP is connected to the home network over VPN.

Let’s start by installing the dependencies

apt-get update
apt-get install wireguard wireguard-tools dnsmasq hostapd

Wireguard VPN

I’m skipping how to configure Wireguard server and client. For quick reference, here’s what you need to do on the Ubuntu 20.04 RaspberryPi AP host where the wireguard client is configured:

$ cat /etc/wireguard/wg0.conf
[Interface]
PrivateKey = <your client's private key>
Address = <wg client ip>/24
DNS = 8.8.8.8, 8.8.4.4

[Peer]
PublicKey = <wg server public key>
PresharedKey = <wg server psk>
Endpoint = <wg server IP or domain>:51820
AllowedIPs = 0.0.0.0/0, ::0/0
PersistentKeepalive = 15

$ systemctl enable --now wg-quick@wg0

# Now to quick check that the interface is UP
$ wg
interface: wg0
  public key: <hidden>
  private key: (hidden)
  listening port: <hidden>
  fwmark: 0xca6c

peer: <hidden>
  preshared key: (hidden)
  endpoint: <wg server IP here>:51820
  allowed ips: 0.0.0.0/0, ::/0
  latest handshake: 1 minute, 36 seconds ago
  transfer: 1.52 MiB received, 501.10 KiB sent
  persistent keepalive: every 15 seconds

Wireless AP

In my case, I’ve used here 192.168.4.1/24 for the hotspot/ap network.

$ cat /etc/netplan/01-netplan.yaml
network:
  version: 2
  renderer: networkd
  ethernets:
    eth0:
    dhcp4: no
    addresses: [192.168.1.5/24]
    gateway4: 192.168.1.1
    nameservers:
      addresses: [8.8.8.8,8.8.4.4]
    wlan0:
      dhcp4: false
      addresses:
      - 192.168.4.1/24
$ netplan generate
$ netplan apply

Next, setup hostapd:

$ cat /etc/default/hostapd 
DAEMON_CONF="/etc/hostapd/hostapd.conf"

$ cat /etc/hostapd/hostapd.conf
interface=wlan0
driver=nl80211
ssid=<Wifi Name Here>
hw_mode=g
channel=6
ieee80211n=1
wmm_enabled=1
ht_capab=[HT40][SHORT-GI-20][DSSS_CCK-40]

country_code=IN
macaddr_acl=0
auth_algs=1
ignore_broadcast_ssid=0
wpa=2
wpa_key_mgmt=WPA-PSK
wpa_passphrase=<password here>
wpa_pairwise=TKIP
rsn_pairwise=CCMP

$ systemctl unmask hostapd
$ systemctl enable --now hostapd

Next, configure dnsmasq which allocate IPs to clients on the AP:

$ cat /etc/dnsmasq.conf
interface=wlan0
listen-address=192.168.4.1
dhcp-range=192.168.4.2,192.168.4.50,255.255.255.0,24h
bind-dynamic 
domain-needed
bogus-priv
$ cat /etc/resolv.conf
cat /etc/resolv.conf
nameserver 8.8.8.8
nameserver 8.8.4.4

$ systemctl stop systemd-resolved
$ systemctl mask systemd-resolved
$ systemctl restart dnsmasq

VPN based HotSpot/AP

Enable host to be able to forward packets:

# Uncomment the following in /etc/sysctl.conf
net.ipv4.ip_forward=1

Verify and apply the configuration:

$ sysctl -p
net.ipv4.ip_forward = 1

Finally, allow IP masquerading by enabling following rules to tunnel Wifi/AP traffic via the wireguard wg0 interface and persist rules on reboot:

$ iptables -t nat -A POSTROUTING -o wg0 -j MASQUERADE
$ iptables -A FORWARD -i wlan0 -o wg0 -j ACCEPT
$ iptables -A FORWARD -i wg0 -o wlan0 -m state --state RELATED,ESTABLISHED -j ACCEPT
$ apt-get install iptables-persistent
$ reboot