Take IP from headers

package.json

@@ -22,6 +22,8 @@
     "compression": "^1.7.4",
     "dotenv": "^16.4.5",
     "express": "^4.19.2",
+    "forwarded-parse": "^2.1.2",
+    "is-ip": "^5.0.1",
     "is-mobile": "^4.0.0",
     "nipplejs": "^0.10.2",
     "socket.io": "^4.7.5",

server/index.ts

@@ -2,6 +2,7 @@ import { clampMagnitude } from "../common/vector";
 import { env } from "./env";
 import { disconnectPlayer, joinPlayer } from "./logic/logic";
 import { server } from "./server";
+import { getClientIp } from "./socket-utils";
 import { getLogger, initializeLogger } from "./utils/logger";
 import { getPlayer, getRoom } from "./world";
 
@@ -24,11 +25,13 @@ async function startServer() {
     });
 
     socket.on("requestJoin", async (event, callback) => {
+      const clientIp = getClientIp(socket);
+
       getLogger().stats({
         name: "user join request",
         unit: "count",
         extra: {
-          player_ip: socket.handshake.address,
+          player_ip: clientIp,
         },
         value: 1,
       });
@@ -42,7 +45,7 @@ async function startServer() {
       getLogger().info(
         `User ${socket.id} with name "${event.username}" joined room ${room.id}`,
         {
-          player_ip: socket.handshake.address,
+          player_ip: clientIp,
           player_id: player.id,
           room_id: `${room.id}`,
         },

server/socket-utils.ts

@@ -0,0 +1,43 @@
+import forwardedParse from "forwarded-parse";
+import { isIP } from "is-ip";
+import { Socket } from "socket.io";
+
+/**
+ * Given a socket, returns the IP address of the client.
+ *
+ * This function will try to find the most accurate IP address, based on headers and other data.
+ */
+export function getClientIp(socket: Socket): string {
+  return (
+    checkedIp(getXForwardedFor(socket)) ||
+    checkedIp(getForwarded(socket)) ||
+    checkedIp(getCloudflareHeaders(socket)) ||
+    socket.handshake.address
+  );
+}
+
+function checkedIp(ip: string | undefined) {
+  return ip && isIP(ip) ? ip : undefined;
+}
+
+function getXForwardedFor(socket: Socket) {
+  return [socket.handshake.headers["x-forwarded-for"] ?? []]
+    .flat()
+    .map((forwardedFor) => forwardedFor.split(",")[0]?.trim())
+    .filter(Boolean)[0];
+}
+
+function getForwarded(socket: Socket) {
+  try {
+    const forwardedHeader = socket.handshake.headers["forwarded"];
+    return forwardedHeader
+      ? forwardedParse(forwardedHeader)[0]?.for
+      : undefined;
+  } catch {
+    return undefined;
+  }
+}
+
+function getCloudflareHeaders(socket: Socket) {
+  return socket.handshake.headers["cf-connecting-ip"]?.[0];
+}