WSL2: DDS discovery between WSL containers and Windows host stopped working

[tim-schaechterle]

Hi,
I’m experiencing an issue where UDP‑based DDS discovery no longer works between WSL2 and the Windows host, although it still works inside WSL.
Full details are in my Fast DDS discussion:
👉 eProsima/Fast-DDS#6311

Setup

WSL2 (Ubuntu) running multiple DDS participants in Podman containers (hostNetwork: true)
Windows host running another DDS participant
All participants use the same Fast DDS configuration
WSL ↔ WSL discovery works
WSL ↔ Windows discovery used to work, but stopped about a week ago without any config changes

Observed

Windows occasionally sees WSL participants on the participant level (SPDP)
But no writers/readers appear (no SEDP)
Thus no topics and no data exchange
WSL‑internal DDS works perfectly

What I tested

UDP connectivity from WSL → Windows on ports 7400, 7401, 7402 works (tested via PowerShell UDP listener + nc -u)
So UDP is not globally blocked
Problem seems to be asymmetric or incomplete UDP forwarding between WSL and Windows

Question
Has there been any recent change in WSL2 networking (mirrored mode, loopback forwarding, UDP reflection, Hyper‑V NAT) that could affect multi‑stage UDP discovery protocols like DDS?
Any hints or confirmations would help a lot — this setup worked reliably before and suddenly stopped.
Thanks!