egg/with-sidecar.sh

@@ -31,6 +31,23 @@ for v in RUSTLINK_SERVER_ID RUSTLINK_WEB_TOKEN RUSTLINK_RETAIN_DAYS RUSTLINK_WEB
   if [ -z "$val" ]; then unset "$v"; fi
 done
 
+# The server id follows the PLUGIN's config once it exists. The plugin reads RUSTLINK_SERVER_ID only
+# when it writes its first config; after that the file is canonical and the website locks it (D150).
+# The sidecar refuses a plugin that names another server (D155), so a variable edited after the
+# first boot would otherwise take the bridge down instead of changing nothing. Stock framework paths,
+# the same ones the installer writes. `sed`, because the game image has no jq.
+for f in /home/container/oxide/config/RunicGateway.json /home/container/carbon/configs/RunicGateway.json; do
+  [ -f "$f" ] || continue
+  ID="$(sed -n 's/^[[:space:]]*"ServerId":[[:space:]]*"\([^"]*\)".*$/\1/p' "$f" | head -n 1)"
+  if [ -n "$ID" ]; then
+    if [ -n "${RUSTLINK_SERVER_ID-}" ] && [ "$RUSTLINK_SERVER_ID" != "$ID" ]; then
+      echo "[rust-link] RUSTLINK_SERVER_ID is '$RUSTLINK_SERVER_ID' but the plugin's config names '$ID'; using '$ID', the id the website knows. The variable is read once, at the first boot."
+    fi
+    export RUSTLINK_SERVER_ID="$ID"
+  fi
+  break
+done
+
 # The website-facing bind. Pterodactyl tells a container nothing about its extra allocations, so
 # the port is typed into the egg, and it must be one of this server's allocations — a port that is
 # not fails as a bind the website never reaches, which the lines below make visible (§34.1).

sidecar/src/app.rs

@@ -87,7 +87,8 @@ where
 
     // Game link: events in, commands out.
     let (event_tx, mut event_rx) = mpsc::unbounded_channel::<game::GameEvent>();
-    let (handle, _bound) = game::serve(&cfg.game.bind, event_tx).await?;
+    let (handle, _bound) =
+        game::serve(&cfg.game.bind, cfg.game.server_id.clone(), event_tx).await?;
 
     // Live feed: every game event fans out to all connected website WebSocket clients.
     let (bcast_tx, _) = broadcast::channel::<String>(1024);
@@ -145,7 +146,6 @@ where
     // waiting caller and stop. Everything else is filed by its `type`, and by its `type` alone:
     // that is what keeps this process a dumb forwarder while the catalogue grows (PROTOCOL.md
     // §8.1). Ten new event kinds are no change here.
-    let configured_server_id = cfg.game.server_id.clone();
     let feed_tx = bcast_tx.clone();
     let route_rpc = rpc.clone();
     let event_store = store.clone();
@@ -194,7 +194,6 @@ where
                     // `type` exists to prevent, and it is invisible until somebody wonders why the
                     // presence board has four thousand rows.
                     if ev.kind == store::SERVER_BOARD {
-                        check_server_id(&configured_server_id, &ev.value);
                         info!(kind = %ev.kind, "{}", line);
                     } else {
                         tracing::debug!(kind = %ev.kind, "board {}", line);
@@ -260,24 +259,6 @@ where
     Ok(())
 }
 
-/// The plugin's `serverId` is the authority; `[game].server_id` is a cross-check. A disagreement is
-/// almost always two game servers pointed at one sidecar by a copied config, which is silent in
-/// every other design and produces one server's history under another's name.
-fn check_server_id(configured: &str, hello: &serde_json::Value) {
-    if configured.is_empty() {
-        return;
-    }
-    let announced = hello.get("serverId").and_then(|v| v.as_str()).unwrap_or("");
-    if !announced.is_empty() && announced != configured {
-        warn!(
-            configured,
-            announced,
-            "the connected plugin announces a different serverId than this sidecar is configured \
-             for; keeping the plugin's. Two servers sharing one sidecar is the usual cause."
-        );
-    }
-}
-
 /// A frame's own timestamp, falling back to ours. The plugin stamps `t` at the moment the world was
 /// read, which is earlier than the moment we saw the line and is the one worth keeping.
 fn frame_t(value: &serde_json::Value) -> i64 {

sidecar/src/config.rs

@@ -17,9 +17,11 @@
 //! R8 makes the platform multi-server: one sidecar per game server, and every row the module
 //! stores carries the server it came from. The plugin declares its own `serverId` in `server.hello`
 //! and that is the authority. This setting is a **cross-check**, not a second source of truth: when
-//! both are set and they disagree, the sidecar logs the disagreement loudly and keeps the plugin's.
-//! Two servers pointed at one sidecar by a copy-pasted config is the mistake this catches, and it
-//! is silent in every other design.
+//! both are set and they disagree, the sidecar **refuses the plugin** — it closes the connection
+//! before the frame is filed, and logs both ids at ERROR (D155). Two servers dialling one sidecar is
+//! the mistake this catches, and it is silent in every other design. It was a warning that kept the
+//! plugin's id until the phase 18 walk showed what that costs: one server's history filed under
+//! another's name, visible on the website. Left blank, nothing is checked.
 
 use std::env;
 use std::fs;

sidecar/src/game.rs

@@ -23,7 +23,7 @@ use serde_json::Value;
 use tokio::io::{AsyncBufRead, AsyncBufReadExt, AsyncWriteExt, BufReader};
 use tokio::net::TcpListener;
 use tokio::sync::{mpsc, Mutex};
-use tracing::{info, warn};
+use tracing::{error, info, warn};
 
 /// The longest line the sidecar will accept from the plugin, in bytes.
 ///
@@ -181,8 +181,12 @@ impl GameHandle {
 /// The **bound** address is returned alongside the handle rather than assumed to be the one asked
 /// for: `127.0.0.1:0` is a legitimate thing to configure (and what the tests use), and a log line
 /// echoing the request rather than the result is the kind that is wrong exactly when it matters.
+///
+/// `server_id` is `[game].server_id`. When it is set, a plugin that names another server is
+/// refused — see [`foreign_server_id`].
 pub async fn serve(
     addr: &str,
+    server_id: String,
     event_tx: mpsc::UnboundedSender<GameEvent>,
 ) -> std::io::Result<(GameHandle, std::net::SocketAddr)> {
     let listener = TcpListener::bind(addr).await?;
@@ -197,7 +201,9 @@ pub async fn serve(
             match listener.accept().await {
                 Ok((stream, peer)) => {
                     info!(%peer, "plugin connected");
-                    if let Err(e) = handle_connection(stream, &event_tx, &accept_handle).await {
+                    if let Err(e) =
+                        handle_connection(stream, &server_id, &event_tx, &accept_handle).await
+                    {
                         warn!(error = %e, "plugin connection ended");
                     } else {
                         info!("plugin disconnected");
@@ -224,17 +230,44 @@ pub async fn serve(
     Ok((handle, bound))
 }
 
+/// The server a frame names, when it is not the one this sidecar is configured for.
+///
+/// `None` means the frame may pass: no `server_id` is configured, or the frame names none, or it
+/// names this one. The plugin stamps `serverId` on every frame, so the first line of a connection
+/// is enough to tell — and the check runs before that line reaches the store or the feed, because
+/// by the time it is filed, one server's history is already under another's name (D155). That is
+/// what the phase 18 walk saw when this was a warning: a second server's plugin, parked in this
+/// listener's backlog, was accepted the moment the first one reloaded, and the website showed the
+/// first server with the second's hostname and wipe.
+fn foreign_server_id<'a>(configured: &str, frame: &'a Value) -> Option<&'a str> {
+    if configured.is_empty() {
+        return None;
+    }
+    match frame.get("serverId").and_then(|v| v.as_str()) {
+        Some(announced) if !announced.is_empty() && announced != configured => Some(announced),
+        _ => None,
+    }
+}
+
 async fn handle_connection(
     stream: tokio::net::TcpStream,
+    server_id: &str,
     event_tx: &mpsc::UnboundedSender<GameEvent>,
     handle: &GameHandle,
 ) -> std::io::Result<()> {
     stream.set_nodelay(true).ok();
     let (read_half, mut write_half) = stream.into_split();
 
-    // Install the outbound command channel for this connection.
+    // The outbound command channel for this connection. With a `server_id` configured it is
+    // installed only once a frame has named this server: until then the peer could be a plugin
+    // about to be refused, and a command sent in that window — a permission grant, a world write —
+    // would land on the wrong server. `/health` reads the same handle, so it reports the plugin
+    // connected only from that moment too.
     let (cmd_tx, mut cmd_rx) = mpsc::unbounded_channel::<String>();
-    handle.set(Some(cmd_tx)).await;
+    let mut pending_tx = Some(cmd_tx);
+    if server_id.is_empty() {
+        handle.set(pending_tx.take()).await;
+    }
 
     let mut reader = BufReader::new(read_half);
     let mut lines = LineReader::default();
@@ -258,6 +291,24 @@ async fn handle_connection(
                         if !trimmed.is_empty() {
                             match serde_json::from_str::<Value>(trimmed) {
                                 Ok(value) => {
+                                    if let Some(announced) = foreign_server_id(server_id, &value) {
+                                        error!(
+                                            configured = server_id,
+                                            announced,
+                                            "refusing a plugin that names another server: this \
+                                             sidecar is '{server_id}', the plugin says \
+                                             '{announced}'. Two servers are dialling one game \
+                                             port — check each plugin config's Port against its \
+                                             sidecar's [game].bind"
+                                        );
+                                        return Ok(());
+                                    }
+                                    if pending_tx.is_some()
+                                        && value.get("serverId").and_then(|v| v.as_str())
+                                            == Some(server_id)
+                                    {
+                                        handle.set(pending_tx.take()).await;
+                                    }
                                     let kind = value
                                         .get("kind")
                                         .and_then(|k| k.as_str())
@@ -396,7 +447,7 @@ mod tests {
         use tokio::io::AsyncReadExt;
 
         let (tx, mut rx) = mpsc::unbounded_channel();
-        let (handle, addr) = serve("127.0.0.1:0", tx).await.unwrap();
+        let (handle, addr) = serve("127.0.0.1:0", String::new(), tx).await.unwrap();
 
         let mut client = tokio::net::TcpStream::connect(addr).await.unwrap();
         client
@@ -415,4 +466,67 @@ mod tests {
         let n = client.read(&mut buf).await.unwrap();
         assert_eq!(&buf[..n], b"{\"cmd\":\"ping\"}\n");
     }
+
+    #[test]
+    fn foreign_server_id_names_only_a_disagreement() {
+        let beta = serde_json::json!({ "kind": "server.hello", "serverId": "beta" });
+        let alpha = serde_json::json!({ "kind": "server.hello", "serverId": "alpha" });
+        let anonymous = serde_json::json!({ "kind": "pong" });
+        let blank = serde_json::json!({ "kind": "pong", "serverId": "" });
+
+        assert_eq!(foreign_server_id("alpha", &beta), Some("beta"));
+        assert_eq!(foreign_server_id("alpha", &alpha), None);
+        assert_eq!(foreign_server_id("alpha", &anonymous), None);
+        assert_eq!(foreign_server_id("alpha", &blank), None);
+        // Nothing configured: nothing to check against.
+        assert_eq!(foreign_server_id("", &beta), None);
+    }
+
+    /// D155, over a real socket: the plugin that names another server is closed on its first
+    /// frame, the frame is never forwarded, and no command could have reached it meanwhile.
+    #[tokio::test]
+    async fn a_plugin_naming_another_server_is_refused_before_anything_is_filed() {
+        use tokio::io::AsyncReadExt;
+
+        let (tx, mut rx) = mpsc::unbounded_channel();
+        let (handle, addr) = serve("127.0.0.1:0", "alpha".to_string(), tx).await.unwrap();
+
+        let mut client = tokio::net::TcpStream::connect(addr).await.unwrap();
+        // Accepted, but not yet vetted: no command may go to it.
+        tokio::time::sleep(std::time::Duration::from_millis(50)).await;
+        assert!(!handle.is_connected().await);
+
+        client
+            .write_all(b"{\"kind\":\"server.hello\",\"type\":\"board\",\"serverId\":\"beta\"}\n")
+            .await
+            .unwrap();
+
+        let mut buf = [0u8; 16];
+        let n = tokio::time::timeout(std::time::Duration::from_secs(2), client.read(&mut buf))
+            .await
+            .expect("the sidecar closes a refused plugin")
+            .unwrap_or(0);
+        assert_eq!(n, 0);
+
+        // The only thing forwarded is the listener's own link.down, never beta's hello.
+        let ev = rx.recv().await.unwrap();
+        assert_eq!(ev.kind, "link.down");
+        assert!(!handle.is_connected().await);
+    }
+
+    #[tokio::test]
+    async fn the_command_channel_opens_on_the_first_frame_naming_this_server() {
+        let (tx, mut rx) = mpsc::unbounded_channel();
+        let (handle, addr) = serve("127.0.0.1:0", "alpha".to_string(), tx).await.unwrap();
+
+        let mut client = tokio::net::TcpStream::connect(addr).await.unwrap();
+        client
+            .write_all(b"{\"kind\":\"server.hello\",\"serverId\":\"alpha\"}\n")
+            .await
+            .unwrap();
+
+        let ev = rx.recv().await.unwrap();
+        assert_eq!(ev.value["serverId"], "alpha");
+        assert!(handle.is_connected().await);
+    }
 }