Use an Android phone as a WiFi extender
- Many Android phones have WiFi hardware capabilities required for extending WiFi.
- Some of them, however, have software restrictions to be used as such. My Nokia G20 for example, loses this capability when upgraded to Android 13 (when hotspot is enabled, WiFi is automatically disabled).
- Here, we will be bypassing Android restrictions and interface directly with the Linux kernel to extend a WiFi network.
- This method follows roughly how OpenWRT implements WiFi extender.
- In theory, this method can also be adapted for PC or single board computers running Linux as long as the WiFi hardware has the capabilities.
- Android phone (rooted) - I am using Xiaomi Redmi 4x with the latest MIUI
available.
- Find tutorial online on how to root your specific Android phone.
- Termux with Termux:Boot installed on the Android phone so that wake-lock
and sshd can be started automatically when the phone is turned on.
- https://wiki.termux.com/wiki/Termux:Boot#:~:text=Example%3A%20to%20start%20an%20ssh d%20server%20and%20prevent%20the%20device%20from%20sleeping%20at%20boot%2C %20create%20the%20following%20file%20at
- Connect to to the phone via SSH to perform the steps.
- Nice to have:
- Battery management script to manage the battery when the phone is plugged 24 hours so that it does not overcharge.
- Install tools for compiling from source
We will need these to compile and install libubox and relayd (from OpenWRT
git).
$ pkg install git clang cmake $ pkg install stow # This is nice to have because we want to be able to install binaries and libraries compiled from source cleanly $ mkdir /usr/stow - Compile and install
libuboxRequired to be able to compilerelaydafter this.$ pkg install lua5.1 json-c $ git clone git://git.openwrt.org/project/libubox.git $ cd libubox $ mkdir build $ cd build $ cmake -DCMAKE_INSTALL_PREFIX=/data/data/com.termux/files/usr/stow/libubox .. $ make # Fix lua related compile error by fixing lua*.h includes in uloop.c $ make install $ cd /data/data/com.termux/files/usr/stow $ stow libubox - Compile and install
relaydSoftware bridge between 2 network interface.$ git clone https://git.openwrt.org/project/relayd.git $ cd relayd $ mkdir build $ cd build $ cmake -DCMAKE_INSTALL_PREFIX=/data/data/com.termux/files/usr/stow/relayd -DCMAKE_C_FLAGS=-D_BSD_SOURCE .. $ make # Fix compile error by removing #define NLMSG_ALIGN(len) in route.c $ make install $ cd /data/data/com.termux/files/usr/stow $ stow relayd - Disable WiFi multicast filter
- Redmi 4x uses Snapdragon SOC - Edit
/data/misc/wifi/WCNSS_qcom_cfg.iniand reboot the phone.--- WCNSS_qcom_cfg.ini.orig 2023-10-03 19:37:29.598680264 +0700 +++ WCNSS_qcom_cfg.ini 2023-10-03 19:38:05.328680250 +0700 @@ -24,7 +24,7 @@ # 1: Enable standby, 2: Enable Deep sleep, 3: Enable Mcast/Bcast Filter -gEnableSuspend=3 +gEnableSuspend=2 # Phy Mode (auto, b, g, n, etc) @@ -81,7 +81,7 @@ # 2: Filter all Broadcast. 3: Filter all Mcast abd Bcast -McastBcastFilter=3 +McastBcastFilter=0 #Flag to enable HostARPOffload feature or not - Alternatively, you can force the Android phone to keep screen on when plugged to a charger - WiFi multicast filter will never be engaged.
# svc power Control the power manager usage: svc power stayon [true|false|usb|ac|wireless] Set the 'keep awake while plugged in' setting. svc power reboot [reason] Perform a runtime shutdown and reboot device with specified reason. svc power shutdown Perform a runtime shutdown and power off the device. # svc power stayon true
- Redmi 4x uses Snapdragon SOC - Edit
- Configure WiFi interface, forwarding, and
iptables.# iw dev wlan0 interface add wlan0-ap type __ap # Quirk: the name needs to be wlan0-ap or it will not work (at least for Redmi 4x) # ip link set up dev wlan0-ap # ip addr add 192.168.169.169/24 dev wlan0-ap # FIXME Arbitrary IP address outside wlan0 subnet # echo 1 > /proc/sys/net/ipv4/ip_forward # Enable ip forwarding and arp filter # echo 1 > /proc/sys/net/ipv4/conf/wlan0/arp_filter # echo 1 > /proc/sys/net/ipv4/conf/wlan0-ap/arp_filter # iptables -I FORWARD -i wlan0-ap -j ACCEPT -s 192.168.1.0/24 # iptables -I FORWARD -i wlan0 -j ACCEPT -d 192.168.1.0/24 - Run
hostapd# mkdir tmp # cd tmp # cat << EOF > hostapd.conf # network interface to listen on interface=wlan0-ap # wi-fi driver driver=nl80211 # WLAN channel to use channel=11 # 802.11n support ieee80211n=1 # QoS support, also required for full speed on 802.11n/ac/ax wmm_enabled=1 # ser operation mode, what frequency to use hw_mode=g # network name ssid=myssid # enforce Wireless Protected Access (WPA) wpa=2 # passphrase to use for protected access wpa_passphrase=mypassword # WPA protocol wpa_key_mgmt=WPA-PSK rsn_pairwise=CCMP EOF # hostapd hostapd.conf # Quirk: hostapd.conf must be alone in the current directory (maybe SELinux restriction?) - Run
relayd# relayd Usage: relayd <options> Options: -d Enable debug messages -i <ifname> Add an interface for relaying -I <ifname> Same as -i, except with ARP cache and host route management You need to specify at least two interfaces -G <ip> Set a gateway IP for clients -R <gateway>:<net>/<mask> Add a static route for <net>/<mask> via <gateway> -t <timeout> Host entry expiry timeout -p <tries> Number of ARP ping attempts before considering a host dead -T <table> Set routing table number for automatically added routes -B Enable broadcast forwarding -D Enable DHCP forwarding -P Disable DHCP options parsing -L <ipaddr> Enable local access using <ipaddr> as source address # relayd -I wlan0 -I wlan0-ap -D -B -d - Extended WiFi is ready to use.
- https://android.stackexchange.com/questions/201024/how-to-use-wi-fi-and-hotspot-at-the-same-time-on-android/202335#202335
- https://forums.raspberrypi.com/viewtopic.php?t=1763
- https://clockworkbird9.wordpress.com/2020/02/16/install-libubox-and-ubus-on-ubuntu/
- https://forum.fairphone.com/t/rom-unofficial-lineageos-16-0-for-fp3/59849/218?page=12