Feature: Detect incorrect proxy setups (GeyserMC#4941)

* Feature: Detect & warn about incorrect proxy setups on Spigot platforms

* Properly disable Geyser if we failed to load

bootstrap/bungeecord/src/main/java/org/geysermc/geyser/platform/bungeecord/GeyserBungeePlugin.java

@@ -71,9 +71,6 @@ public class GeyserBungeePlugin extends Plugin implements GeyserBootstrap {
     private IGeyserPingPassthrough geyserBungeePingPassthrough;
     private GeyserImpl geyser;
 
-    // We can't disable the plugin; hence we need to keep track of it manually
-    private boolean disabled;
-
     @Override
     public void onLoad() {
         onGeyserInitialize();
@@ -98,7 +95,6 @@ public void onGeyserInitialize() {
         }
 
         if (!this.loadConfig()) {
-            disabled = true;
             return;
         }
         this.geyserLogger.setDebug(geyserConfig.isDebugMode());
@@ -112,7 +108,7 @@ public void onGeyserInitialize() {
 
     @Override
     public void onEnable() {
-        if (disabled) {
+        if (geyser == null) {
             return; // Config did not load properly!
         }
         // Big hack - Bungee does not provide us an event to listen to, so schedule a repeating

bootstrap/mod/src/main/java/org/geysermc/geyser/platform/mod/GeyserModBootstrap.java

@@ -89,6 +89,11 @@ public void onGeyserInitialize() {
     }
 
     public void onGeyserEnable() {
+        // "Disabling" a mod isn't possible; so if we fail to initialize we need to manually stop here
+        if (geyser == null) {
+            return;
+        }
+
         if (GeyserImpl.getInstance().isReloading()) {
             if (!loadConfig()) {
                 return;

bootstrap/spigot/src/main/java/org/geysermc/geyser/platform/spigot/GeyserSpigotPlugin.java

@@ -117,7 +117,6 @@ public void onGeyserInitialize() {
             geyserLogger.error(GeyserLocale.getLocaleStringLog("geyser.bootstrap.unsupported_server.message", "1.13.2"));
             geyserLogger.error("");
             geyserLogger.error("*********************************************");
-            Bukkit.getPluginManager().disablePlugin(this);
             return;
         }
 
@@ -131,7 +130,6 @@ public void onGeyserInitialize() {
                 geyserLogger.error(GeyserLocale.getLocaleStringLog("geyser.bootstrap.unsupported_server_type.message", "Paper"));
                 geyserLogger.error("");
                 geyserLogger.error("*********************************************");
-                Bukkit.getPluginManager().disablePlugin(this);
                 return;
             }
         }
@@ -144,10 +142,25 @@ public void onGeyserInitialize() {
             geyserLogger.error("This version of Spigot is using an outdated version of netty. Please use Paper instead!");
             geyserLogger.error("");
             geyserLogger.error("*********************************************");
-            Bukkit.getPluginManager().disablePlugin(this);
             return;
         }
 
+        try {
+            // Check spigot config for BungeeCord mode
+            if (Bukkit.getServer().spigot().getConfig().getBoolean("settings.bungeecord")) {
+                warnInvalidProxySetups("BungeeCord");
+                return;
+            }
+
+            // Now: Check for velocity mode - deliberately after checking bungeecord because this is a paper only option
+            if (Bukkit.getServer().spigot().getPaperConfig().getBoolean("proxies.velocity.enabled")) {
+                warnInvalidProxySetups("Velocity");
+                return;
+            }
+        } catch (NoSuchMethodError e) {
+            // no-op
+        }
+
         if (!loadConfig()) {
             return;
         }
@@ -162,6 +175,11 @@ public void onGeyserInitialize() {
 
     @Override
     public void onEnable() {
+        // Disabling the plugin in onLoad() is not supported; we need to manually stop here
+        if (geyser == null) {
+            return;
+        }
+
         // Create command manager early so we can add Geyser extension commands
         var sourceConverter = new CommandSourceConverter<>(
                 CommandSender.class,
@@ -458,4 +476,13 @@ private boolean loadConfig() {
 
         return true;
     }
+
+    private void warnInvalidProxySetups(String platform) {
+        geyserLogger.error("*********************************************");
+        geyserLogger.error("");
+        geyserLogger.error(GeyserLocale.getLocaleStringLog("geyser.bootstrap.unsupported_proxy_backend", platform));
+        geyserLogger.error(GeyserLocale.getLocaleStringLog("geyser.bootstrap.setup_guide", "https://geysermc.org/wiki/geyser/setup/"));
+        geyserLogger.error("");
+        geyserLogger.error("*********************************************");
+    }
 }

bootstrap/velocity/src/main/java/org/geysermc/geyser/platform/velocity/GeyserVelocityPlugin.java

@@ -113,6 +113,10 @@ public void onGeyserInitialize() {
 
     @Override
     public void onGeyserEnable() {
+        // If e.g. the config failed to load, GeyserImpl was not loaded and we cannot start
+        if (geyser == null) {
+            return;
+        }
         if (GeyserImpl.getInstance().isReloading()) {
             if (!loadConfig()) {
                 return;

bootstrap/viaproxy/src/main/java/org/geysermc/geyser/platform/viaproxy/GeyserViaProxyPlugin.java

@@ -132,6 +132,10 @@ public void onGeyserInitialize() {
 
     @Override
     public void onGeyserEnable() {
+        // If e.g. the config failed to load, GeyserImpl was not loaded and we cannot start
+        if (geyser == null) {
+            return;
+        }
         boolean reloading = geyser.isReloading();
         if (reloading) {
             if (!this.loadConfig()) {