mDNS not working in firefox

[bitnapper]

Describe the bug

mDNS in general seems to be working fine. I can access mDNS addresses with SSH and other programs but not in firefox. I have no idea why it doesn't work there.

What did you expect to happen?

I expected 2 + 2 to equal 4, but instead 2 + 2 equaled 6!

Output of bootc status

● Booted image: ghcr.io/ublue-os/bluefin:gts
        Digest: sha256:2b95c34db2bd3badd3a3712c6ae2ca970a51d841fc5f6b60d9a154e4cbaa1d49 (amd64)
       Version: gts-41.20250824 (2025-08-24T05:57:57Z)

  Rollback image: ghcr.io/ublue-os/bluefin:gts
          Digest: sha256:94a56971d9cd7dab3aa22a468fe47e212d9dcc7acb206a1e69f04c96518dbb34 (amd64)
         Version: gts-41.20250706 (2025-07-06T05:58:14Z)

Output of groups

me wheel

Extra information or context

No response

[repires]

AI Generated:

This is a known issue: mDNS works in general on Bluefin (e.g., via SSH), but fails in Firefox. Other users have reported the same, and it can be hardware-related—especially if you use the MediaTek RZ717 WiFi module, which has kernel/driver bugs affecting mDNS over WiFi. Swapping to an Intel AX210 module resolved it for some users, and newer kernels may help, but the bug persists for some even after updates [source].

If your hardware isn't the issue, check if you're running Firefox as a Flatpak. Flatpak sandboxing can block mDNS/Avahi by default, so try the native Firefox package to see if it resolves .local addresses. Also, review Firefox's DNS settings: if DNS over HTTPS (DoH) is enabled (network.trr.mode set to 2 or higher in about:config), mDNS won't work—set it to 0 to use system DNS.

Make sure avahi-daemon is running and mDNS works in the console. If it does, but Firefox still fails, it's likely a Firefox or Flatpak sandboxing issue, not a Bluefin system bug. If you use the MediaTek RZ717, consider switching hardware or monitoring kernel updates for fixes.

[LorbusChris]

This is a limitation of flatpak (at the time of this writing). See also flatpak/xdg-desktop-portal#1365.

Firefox can be installed as an rpm (layered locally, which is not recommended, or in a derived image build) to work around this.

[repires]

@LorbusChris Hi did you find have any other findings for this issue?

[LorbusChris]

Not really. There are other issues with running flatpak'd too, e.g. breaking extensions like GSConnect. (The same also applies to IDEs like VSCode or Eclipse Theia). I build the Firefox rpm into my image to avoid that. Shipping Firefox as a flatpak is also tracked in Fedora here: https://gitlab.com/fedora/ostree/sig/-/issues/3

[dosubot]

Hi, @bitnapper. I'm Dosu, and I'm helping the bluefin team manage their backlog and am marking this issue as stale.

Recap

• You reported that mDNS hostnames resolve in SSH and other apps, but not in Firefox.
• The discussion pointed to a Flatpak limitation rather than a Bluefin-specific bug.
• A workaround was identified: using Firefox outside the Flatpak path can avoid the issue.
• Follow-up comments suggested the broader problem is being tracked elsewhere as well.

Next Steps

• If this is still relevant on the latest version of bluefin, please comment here to keep the discussion open.
• Otherwise, this issue will be automatically closed in 14 days.

Thanks for your understanding and contribution.

[Preisschild]

FYI you can work around this by enabling multicast dns in systemd-resolved

create /etc/systemd/resolved.conf.d/mdns.conf

[Resolve]
MulticastDNS=yes

systemctl restart systemd-resolved

Firefox flatpak can then resolve .local domains via the systemd-resolved resolv.conf stub iiuc