test proxy configuration

tailscale/rootfs/etc/s6-overlay/s6-rc.d/proxy/run

@@ -31,6 +31,13 @@ if bashio::var.true "$(bashio::core.ssl)"; then
   bashio::exit.nok
 fi
 
+# Test Home Assistant's HTTP reverse proxy configuration
+if (( 200 != $(curl -s -o /dev/null -w "%{http_code}" "http://127.0.0.1:$(bashio::core.port)" -H "X-Forwarded-For: 127.0.0.1") )); then
+  bashio::log.error "Unable to connect to Home Assistant on http://127.0.0.1:$(bashio::core.port)"
+  bashio::log.error "Please check your configuration based on the add-on's Documentation under \"Option: proxy\""
+  bashio::exit.nok
+fi
+
 # Set up proxy
 # Note: Configuration is persistent between reboots, though configuring the same value won't cause duplicate entries,
 #       but will overwite previous entry if core.port has been changed