Wi-Fi hotspot

Bliss OS and other Android-x86 based systems offer a smooth and refined experience for desktop and laptop users, but they sometimes lack features present in a conformant OEM Android device. One such feature is the Wi-Fi hotspot functionality. While awaiting for Bliss OS developers to implement it properly, I discovered a workaround to allow users enabling Wi-Fi hotspot functionality using the hostapd HAL binaries extracted from Google’s cuttlefish system images available at Android CI.

Prerequisites

Before you begin, ensure you have:

A Bliss OS or Android-x86 system installed.
Unpacked system.sfs to allow modification: https://docs.blissos.org/knowledgebase/troubleshooting/remount-system-as-read-write/.
Extract the required files from cuttlefish images: Android CI or download a .zip.
A high degree of Linux terminal skills, as it involves complex file manipulations and system modifications.

Steps to Enable Wi-Fi Hotspot

1. Download the Required Files

The .zip file contains the necessary files:

com.android.wifi.hal.apex_payload
com.google.cf.wifi.rc
system/init/init.cutf_cvm.rc
vendor/vintf/manifest/android.hardware.wifi.hostapd.xml

2. Prepare the System Image

Resize the System Partition

Unpack the system.sfs file as mentioned before: https://docs.blissos.org/knowledgebase/troubleshooting/remount-system-as-read-write/.
Resize the system.img file using the resize2fs command. Currently it is around 4GB in size, so we will increase its size to 5GB to accommodate the new files:

resize2fs system.img 5G

Mount the System Image

Mount the resized system.img to a directory:

mkdir /tmp/system_img
mount -o loop system.img /tmp/system_img

3. Install the Apex Payload containing the hostapd HAL

Prepare the Directory

Create the necessary directory for the Apex payload:

mkdir -p /tmp/system_img/system/apex/com.android.wifi.hal

Mount the Apex Payload

Loop mount com.android.wifi.hal.apex_payload read-only and copy its contents preserving permissions and SELinux context:

mkdir /tmp/apex_payload
mount -o loop,ro com.android.wifi.hal.apex_payload /mnt/apex_payload
cp -a /mnt/apex_payload/* /tmp/system_img/system/apex/com.android.wifi.hal/

4. Edit init.rc files

init.cutf_cvm.rc contains the lines to be added to init.bliss_x86_64.rc for creating the necessary directories required for hostapd to function.
com.google.cf.wifi.rc contains the lines to be added to init.bliss_x86_64.rc to start a hostapd service.

Edit /tmp/system_img/init.bliss_x86_64.rc to include the hostapd service

...
service hostapd /apex/com.android.wifi.hal/bin/hw/hostapd
   interface aidl android.hardware.wifi.hostapd.IHostapd/default
   class main
   capabilities NET_ADMIN NET_RAW
   user wifi
   group wifi net_raw net_admin
   disabled
   oneshot
...

Edit /tmp/system_img/init.bliss_x86_64.rc to add the code for creating /data/vendor/wifi/hostapd/sockets

on post-fs-data
   # Create the directories used by the Wireless subsystem
   mkdir /data/vendor/wifi 0771 wifi wifi

   mkdir /data/vendor/wifi/hostapd 0770 wifi wifi
   mkdir /data/vendor/wifi/hostapd/sockets 0770 wifi wifi

   mkdir /data/vendor/wifi/wpa 0770 wifi wifi
   mkdir /data/vendor/wifi/wpa/sockets 0770 wifi wifi
   mkdir /data/misc/dhcp 0770 dhcp dhcp
   mkdir /data/misc/hcid 0770 bluetooth bluetooth

Modify the system VINTF Manifest

Copy android.hardware.wifi.hostapd.xml to the VINTF manifest directory:

cp vendor/vintf/manifest/android.hardware.wifi.hostapd.xml /tmp/system_img/system/vendor/etc/vintf/manifest/android.hardware.wifi.hostapd.xml

5. Apply Changes and Reboot

Unmount and Repack
- Unmount the system image:
  Terminal window
```
umount /tmp/system_img
```
- Repack system.img if necessary.
Reboot Your System
- Restart your system for the changes to take effect. After rebooting, you should be able to use the Wi-Fi hotspot feature.

This workaround provides a temporary solution for enabling Wi-Fi hotspot functionality on Bliss OS and Android-x86 systems till it is fixed. This is written solely for the purpose of sharing knowledge.

Hardware Limitations

This workaround allows you to share a connection not being used by your Wi-Fi adapter, such as Ethernet or mobile data. However, not all hardware supports sharing the same Wi-Fi connection on the same adapter. Not all Wi-Fi adapters can function as both a station (client) and an access point (AP) simultaneously with Linux drivers.
To potentially overcome this limitation, hostapd can be configured to use a different Wi-Fi interface (e.gwlan1 instead of wlan0). This can be done by modifying the configuration file provided to hostapd. It is yet to be investigated. https://source.android.com/docs/core/connect/wifi-sta-ap-concurrency