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Conclusion of this Project

  • The speed of the Wifi from Raspberry Pi is being capped by the Wifi Adapter present in Raspberry Pi 4B.
  • RPi 4B supports both 2.4 Ghz and 5Ghz; band of both 20 Mhz and 40 Mhz. But the porblem is that it doesn't support channel numbers : 34,38,42,46, etc. which are the allowed channels to use 40/80 MHz in India. That is why the speed is being capped at 54 Mb/s (Mb - Megabits) becuase we can use only 20MHz here. For complete list of allowed channels - https://en.wikipedia.org/wiki/List_of_WLAN_channels.
  • Still the speed should have been 100Mbps but it is capped mainly because the Wifi adapter shares the same bus as USB 2.0 ( according to some articles )
  • Possible Solution : Buy a USB 3.0 Wireless adapter which supports AP (Access Point) Mode, 802.11ac and 40 MHz at least.

Acheieved Goals:

  • Wifi connection at LBS:

ℹ️ This testing was done on Raspberry Pi 4 Model B Rev 1.1. The results may vary.

Device Before After After with Express Vpn
Android 16 Mbps 54 Mbps Roughly Same: 50 Mbps
Laptop 8 Mbps 54 Mbps Roughly Same: 50 Mbps
  • Able to run vpn on raspberry pi.
  • Generally to connect 3 different devices with VPN we need 3 different account connections ( for express vpn, my key obtained for free through some resources ). This lead to exhaustion of key + the slow wifi made it unusable. But now multiple devices can connect to the Pi and use vpn with just one account registered with Pi and that too with high speed!

Method:

The method is very trivial to understand, just the setup was a bit tough ( for me :D )

Tech Stack:

  • hostapd : for AP creation

  • dnsmasq : for DNS/DHCP configuration of clients

  • expressvpn : best possible choice out there.

  • Tutorial to set up AP in raspberry pi : here

Configs:

dhcpcd.conf

  • Location : /etc/dhcpcd.conf
interface wlan0			
    static ip_address=192.168.4.1/24
    nohook wpa_supplicant

routed-ap.conf

  • Location : /etc/sysctl.d/routed-ap.conf
# Enable IPv4 routing
net.ipv4.ip_forward=1

iptables config

  • Command : sudo iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
  • Command 2 : sudo iptables -t nat -A POSTROUTING -o tun0 -j MASQUERADE
  • -o eth0 : the outgoing interface ( in this case LAN )
  • -o tun0 : required for VPN for tunnel interface forwarding

dnsmasq config

  • Location : /etc/dnsmasq.conf
interface=wlan0 # Listening interface
dhcp-range=192.168.4.2,192.168.4.20,255.255.255.0,24h
                # Pool of IP addresses served via DHCP
domain=wlan     # Local wireless DNS domain
dhcp-option=6, 10.165.0.1
address=/gw.wlan/192.168.4.1
                # Alias for this router

hostapd config

  • Location : /etc/hostapd/hostapd.conf
country_code=IN
interface=wlan0
ssid=PiLan2

hw_mode=a
channel=36

macaddr_acl=0
auth_algs=1
ignore_broadcast_ssid=0
wpa=2
wpa_passphrase=SheharPi
wpa_key_mgmt=WPA-PSK
wpa_pairwise=TKIP
rsn_pairwise=CCMP

# N
ieee80211n=1

# AC
ieee80211ac=1

# Other
wmm_enabled=1 # QoS

interfaces config

  • Location : /etc/network/interfaces
# replace wlan0 with your adapter to be used. check output of iwconfig.
auto wlan0
allow-hotplug wlan0
iface wlan0 inet dhcp
wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf
wireless-power off              # turns power management off for the adapter
iface default inet dhcp
  • This is used to turn of the power management mode of inbuilt wifi

Know Issues and Bugs:

  • Express vpn DNS bug - Causes internet to not work. Can't connect to websites, but can ping to IP addresses. DNS servers were not being updated in /etc/resolv.conf due to the option force_vpn_dns=true.

Workaround :

  1. ExpressVPN, after connecting saves DNS addresses in file at /etc/resolv.conf.bak or similar ( can be verified by viewing the file, the address should be of the form 10.x.x.x ).
  2. Now replace the configs by executing sudo mv /etc/resolv.conf.bak /etc/resolv.conf. Here resolv.conf.bak is the name of file obtained above.
  3. To let the clients connected to VPN, access the internet - edit the following line in /etc/dnsmasq.conf
dhcp-option=6, <expressvpn dns server>

by adding the DNS server obtained in step 1. Reload the DNS service using sudo systemctl restart dnsmasq.service and finally disconnect and reconnect the clients.