Package: opal-bridge — true layer-2 WiFi→Ethernet bridge for the Opal (GL-SFT1200)

Router
1

The Opal's "Repeater" mode is WISP: it NATs, and wired clients land on an
isolated 192.168.8.0/24. If you ever wanted the Opal to behave like a real
bridge — wired clients getting DHCP from the upstream router, same subnet,
broadcast/mDNS passing — the stock firmware has no mode for it.

I built a package that adds it:

What it does

  • True L2 bridge (relayd + a firewall fix for the hairpin-NAT problem that
    makes naive relayd setups randomly lose packets — full write-up in the
    repo's docs/ARCHITECTURE.md).
  • The physical slide switch selects the mode: toward the dot = bridge,
    away = stock router. Read at boot, and flipping it while running switches
    modes live (bridge→router takes ~4 s, router→bridge ~1 min).
  • Zero hardcoded IPs: the bridge discovers whatever subnet the upstream WiFi
    provides and adapts — including when you move it between networks (home,
    phone hotspot). Management IP is persisted and announced as opal.local
    (optional, one extra command).
  • The LED tells you what's happening: blue = bridge (blinking while
    converging, solid when up), white = router, blue/white alternating = error.
  • Clean uninstall: opkg remove opal-bridge puts everything back to stock.
    Nothing is reflashed.

Install

On a stock device: do the initial setup, join your upstream WiFi from the
Repeater page, and install LuCI from System → Advanced Settings (that is
what enables SSH). Then, with the .ipk from the
Releases page:

scp -O -o HostKeyAlgorithms=+ssh-rsa -o PubkeyAcceptedKeyTypes=+ssh-rsa \
    opal-bridge_0.1.0-1_all.ipk root@192.168.8.1:/tmp/
ssh -o HostKeyAlgorithms=+ssh-rsa -o PubkeyAcceptedKeyTypes=+ssh-rsa \
    root@192.168.8.1 "opkg update && opkg install /tmp/opal-bridge_0.1.0-1_all.ipk"

Set the switch toward the dot and reboot — the LED goes blinking blue, then
solid blue when the bridge is up (~2 min).

Honest limitations

  • Throughput is bounded by the WiFi uplink and software forwarding on the
    MIPS SoC — fine for IoT/SSH/web/moderate transfers, not wire-speed gigabit.
  • After a mode flip, wired clients keep their old DHCP lease until they renew
    (replug the cable). The Ethernet PHYs can't be bounced in software on this
    switch chip.
  • It's a proxy-ARP relay, not 802.11 4-addr WDS: IPv4/DHCP/broadcast/mDNS
    work; exotic non-IP protocols may not.

Tested on stock firmware 4.8.3. Feedback and issues welcome

3

Hi,

Thank you very much for developing and sharing this project with the community!

This provides a useful community solution for Opal users who need wired devices to connect through the upstream Wi-Fi network while remaining on the same subnet.
We especially appreciate the work you have put into dynamic subnet detection, hardware switch-based mode selection, status indication, configuration restoration, and the detailed documentation of the implementation and its limitations.

Thank you again for the time and effort you have put into developing, testing, documenting, and sharing this project. Your contribution is greatly appreciated!