Problem Description

Accessing a HTTP3 reverse proxy using its IP does not work via firefox but works if we access using localhost
refs #7025

Steps to reproduce the behavior:

1. Start a http3 reverse proxy: mitmdump --mode reverse:https://http3.is@443 --mode reverse:http3://http3.is@443
2. Ensure that http3 reverse proxy works by accessing it using https://localhost via firefox
3. Visit https://127.0.0.1:443 using firefox

We get a Client QUIC handshake failed. unknown error (0x12a)

System Information

Mitmproxy: 11.0.0.dev (+17, commit be4ba11)
Python: 3.11.3
OpenSSL: OpenSSL 3.2.2 4 Jun 2024
Platform: Windows-10-10.0.22631-SP0