See a “fixed” issue. The point is that reusing IPv6 socket for IPv4 is causing trouble for ocserv’s udp bind & connect. Don’t know how to fix it in code, but there is a walk-round by seperately listen on IPv4 and IPv6’s global address.
Another thought: Maybe SO_REUSEPORT is also an option, but alas, I set
ReusePort to true (without seperating IPv4 and IPv6), and the error remained
the same.
sudo systemctl edit ocserv.socket[Socket] ListenStream= ListenDatagram= ListenStream=0.0.0.0:443 ListenStream=[::]:443 ListenDatagram=0.0.0.0:443 ListenDatagram=[::]:443 BindIPv6Only=ipv6-only