Currently Happy Eyeballs (IPv6 connection first, fallback to IPv4 connection if IPv6 fails within 300 ms) only works for TCP based outbounds. For QUIC based protocols such as Hysteria 2 or TUIC, if IPv6 traffic stalls, the connection simply hangs.
I created a script to reproduce this issue in a controlled environment (podman).
Currently Happy Eyeballs (IPv6 connection first, fallback to IPv4 connection if IPv6 fails within 300 ms) only works for TCP based outbounds. For QUIC based protocols such as Hysteria 2 or TUIC, if IPv6 traffic stalls, the connection simply hangs.
I created a script to reproduce this issue in a controlled environment (podman).