Cannot connect to usb-wifi dongle as Hotspot using nmcli

Question

My setup consists of a pi5 running latest Bookworm $ uname -a Linux rpi5 6.6.31+rpt-rpi-2712 #1 SMP PREEMPT Debian 1:6.6.31-1+rpt1 (2024-05-29) aarch64 GNU/Linux. On-board wifi is set to the usual wlan0. I then added a Realtek usb-wifi dongle, which successfully appeared as wlan1. My Hotspot.nmconnection file looks as follows.

[connection]
id=Hotspot
uuid=6614cb3b-a24f-4da6-bd1e-5766a9e6c750
type=wifi
autoconnect=false
interface-name=wlan1
timestamp=1717672802

[wifi]
mode=ap
ssid=A0123

[wifi-security]
key-mgmt=wpa-psk
psk=my_plaintext_password

[ipv4]
method=shared

[ipv6]
addr-gen-mode=default
method=ignore

[proxy]

From my macbook I can see SSID A0123 being advertised as an available network. However on attempting to connect to it, I keep getting the dialog box for entering the password.

I have tested this wifi dongle to act as a standard wifi interface, which works perfectly, it can connect to home wifi router, get a DHCP address and I can ssh into the pi5 at the dongle's address. I have also tried setting the hotspot without the password and it fails with unable to join the network message.

Changing the Hotspot.nmconnection entry to interface-name=wlan0(i.e. pointing it to the on-board wifi NIC) I can connect to A0123 not a problem.

nmcli -f WIFI-PROPERTIES.AP device show wlan1 confirms the dongle supports AP. Am I missing something obvious or Bookworm's Realtek drivers can't do AP?

PS: This is not a question about setting a Hotspot/AP on wlan0.

Answer 1

You have failed to specify band. I am not sure what is absolutely necessary but mine contains:-

[wifi]
band=bg
mode=ap
ssid=…

[wifi-security]
group=ccmp;
key-mgmt=wpa-psk
pairwise=ccmp;
proto=rsn;
psk=…

PS using wlan1 rather than Predictable Network Interface Names is unreliable.

Answer 2

The following steps enabled the Realtek usb wifi dongle to work as the Hotspot in my case.

Chipset identification lsusb Bus 003 Device 002: ID 0bda:c811 Realtek Semiconductor Corp. 802.11ac NIC corresponds to 8821cu at https://linux-hardware.org/?id=usb:0bda-c811

sudo apt update && sudo apt upgrade
sudo apt install -y raspberrypi-kernel-headers build-essential bc dkms git
mkdir -p ~/src
cd ~/src
git clone https://github.com/morrownr/8821cu-20210916.git
cd ~/src/8821cu-20210916

GCC version verification

cat /proc/version
gcc --version

GCC major versions must match

sudo ./install-driver.sh 

reboot, plugged in the Realtek wifi dongle. sudo nmcli c up Hotspot. The Hotspot profile existed in my case, otherwise it has to be created:

sudo nmcli d wifi hotspot ifname wlan1 ssid A0123 password 12345678
sudo nmcli conn up Hotspot

Over to macbook, A0123 can be connected with now.

This install blacklists the native rtw88_8821cu driver. The repo includes remove-driver.sh in case this driver is no longer required.