caddy-frontend: Improve QUIC notes

software/caddy-frontend/README.caddy_frontend.rst

@@ -456,11 +456,13 @@ the proxy::
 QUIC Protocol
 =============
 
-Experimental QUIC available in Caddy is not configurable, thus it is required to open port ``udp:11443`` on the machine, like::
+Note: QUIC support in Caddy is really experimental. It can result with silently having problems with QUIC connections or hanging Caddy process. So in case of QUIC error ``QUIC_NETWORK_IDLE_TIMEOUT`` or ``QUIC_PEER_GOING_AWAY`` it is required to restart caddy process.
 
-  iptables -I INPUT -p udp --dport 11443 --destination ${ip} -j ACCEPT
+Experimental QUIC available in Caddy is not configurable. If caddy is configured to bind to HTTPS port ``${port}``, QUIC is going to be advertised on this port only. It is not possible to configure another public port in case of port rewriting.
 
-where ``${ip}`` is the IP of the partition with running caddy process.
+So it is required to ``DNAT`` from ``${public IP}`` of the computer to the computer partition running caddy ``${local IP}`` with configured port::
+
+  iptables -A DNAT -d ${public IP}/32 -p udp -m udp --dport ${port} -j DNAT --to-destination ${local IP}:${port}
 
 
 Notes