[Bug 291181] rtw-8821c Wi-Fi: bsdinstall auto-config fails, missing postinstall

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=291181

            Bug ID: 291181
           Summary: rtw-8821c Wi-Fi: bsdinstall auto-config fails, missing
                    postinstall
           Product: Base System
           Version: 15.0-RELEASE
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Some People
          Priority: ---
         Component: wireless
          Assignee: wireless@FreeBSD.org
          Reporter: fjachuf@gmail.com

Created attachment 265607
  --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=265607&action=edit
Explanation of the Wi-Fi issue with rtw-8821c, including screenshots

During the installation of FreeBSD 15.0-RC3, I encountered several issues
related to Wi-Fi configuration, especially when using DHCP through the
installer.


1. Initial Wi-Fi Adapter Configuration.

FreeBSD detected my Wi-Fi card as rtw-8821c.
First I clicked on automatic network configuration, where I was given the
option to add the IPv6 DNS servers.

I put in DNS #1 4.2.2.2 and continued, but then when I tried to download the
necessary packages to FreeBSD, it said there was no connection.
So I decided to go to the Shell station and sure enough there was no connection




2. Shell Test Using DHCP

I opened a shell during the installation and ran:
dhclient wlan0

With this command, the interface successfully obtained an IP address, and the
connection worked.
However, once I exited the shell and returned to the installer, the
configuration was not preserved, and Wi-Fi disconnected again.




3. Manual Configuration Without DHCP

I tried configuring the network again using the manual option (without DHCP),
entering the following values:
    • IP: 192.168.60.216
    • Mask: 255.255.255.0
    • Router: 192.168.60.1
With this manual configuration, the Wi-Fi connection worked correctly during
the installation.
The installation completed successfully using the appropriate firmware:
wifi-firmware-rtw88-kmod-rtw8821c



4. Post-Installation Behavior

After the installation, I only installed the following packages:
    • gnome
    • firefox
    • vim
    • drm-kmod
And I added the following entries to rc.conf:

dbus_enable="YES"
kld_list="amdgpu"

After the first reboot, Wi-Fi stopped working again.
However, after rebooting several more times, the Wi-Fi interface started
working on its own, without making any additional configuration changes.



5. Wi-Fi Performance Issue

Additionally, the Wi-Fi connection does not reach its expected throughput.
On other operating systems, this adapter normally achieves 90–130 Mbps, but on
FreeBSD I only get around 20 Mbps, even when the signal is strong. This
suggests a possible performance or driver-related issue with rtw88.



6. Summary

There appear to be reproducible issues with DHCP-based Wi-Fi configuration in
the FreeBSD 15.0-RC3 installer (bsdinstall):
    • DHCP sometimes fails or does not persist the configuration.
    • Manual network configuration works reliably.
    • After installation, the Wi-Fi interface may behave inconsistently until
it eventually initializes correctly.

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