MT7921 - IPv6 no longer working (Not receiving Multicast)

[Rudi Daemen]

After updating to kernel linux-image-6.5.0-14-generic, IPv6 stopped working with the MT7921 wifi card.
No errors are logged, but when using tcpdump / wireshark to capture traffic, I can see the MT7921 card no longer appears to receive IPv6 Multicast (thus it never receives the Router Advertisements, etc.).

Booting back to the previous kernel image (linux-image-6.2.0-39-generic) resolves the issue and IPv6 Multicast works fine and IPv6 connectivity works fine again.

The system is configured to use the 22.04 HWE kernel to better support the AMD Advantage Platform hardware (ASUS ROG Strix G513QY).

Steps to reproduce:
1. Have Ubuntu 22.04 LTS installed on a laptop with MT7921 Wifi adapter and connect it to a Dual-stack network leveraging Router Advertisements for IPv6.

2. Run it with HWE Kernel image linux-image-6.2.0-39-generic and observe the following:
- IPv6 stateless autoconfiguration works and a public/global address is assigned.
- Inbound IPv6 Multicast packets are seen when using tcpdump/wireshark.

3. Update the HWE Kernel to linux-image-6.5.0-14-generic and observe the following:
- IPv6 only configures link-local address (fe80::) and no public/global address.
- No inbound IPv6 multicast packets are seen when using tcpdump/wireshark.

fludizz@pauwel:~$ lsb_release -rd
Description: Ubuntu 22.04.3 LTS
Release: 22.04

Network card in question:
05:00.0 Network controller: MEDIATEK Corp. MT7921 802.11ax PCI Express Wireless Network Adapter
 Subsystem: AzureWave Device 4680
 Flags: bus master, fast devsel, latency 0, IRQ 83, IOMMU group 14
 Memory at fc30300000 (64-bit, prefetchable) [size=1M]
 Memory at fc30400000 (64-bit, prefetchable) [size=16K]
 Memory at fc30404000 (64-bit, prefetchable) [size=4K]
 Capabilities: [80] Express Endpoint, MSI 00
 Capabilities: [e0] MSI: Enable+ Count=1/32 Maskable+ 64bit+
 Capabilities: [f8] Power Management version 3
 Capabilities: [100] Vendor Specific Information: ID=1556 Rev=1 Len=008 <?>
 Capabilities: [108] Latency Tolerance Reporting
 Capabilities: [110] L1 PM Substates
 Capabilities: [200] Advanced Error Reporting
 Kernel driver in use: mt7921e
 Kernel modules: mt7921e

fludizz@pauwel:~$ apt-cache policy linux-image-6.5.0-14-generic
linux-image-6.5.0-14-generic:
  Installed: 6.5.0-14.14~22.04.1
  Candidate: 6.5.0-14.14~22.04.1
  Version table:
 *** 6.5.0-14.14~22.04.1 500
        500 http://nl.archive.ubuntu.com/ubuntu jammy-updates/main amd64 Packages
        500 http://security.ubuntu.com/ubuntu jammy-security/main amd64 Packages
        100 /var/lib/dpkg/status

Note: The WiFi device is using the same firmware version on both kernels.

[Rudi Daemen (fludizz)]

Correcting "affecting" value.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.