fix: properly detect requests without body

Related: socketio/socket.io#4786

index.js

@@ -97,13 +97,11 @@ const setupMaster = (httpServer, opts) => {
         return;
       }
       workerId = computeWorkerId(data);
-      const mayHaveMultipleChunks = !(
-        data.startsWith("GET") ||
-        data
-          .substring(0, data.indexOf("\r\n\r\n"))
-          .includes("pgrade: websocket")
-      );
-      socket.pause();
+
+      const head = data.substring(0, data.indexOf("\r\n\r\n")).toLowerCase();
+      const mayHaveMultipleChunks =
+        head.includes("content-length:") || head.includes("transfer-encoding:");
+
       if (mayHaveMultipleChunks) {
         connectionId = randomId();
       }

test/fixtures/cors.js

@@ -0,0 +1,71 @@
+const cluster = require("cluster");
+const { createServer, request } = require("http");
+const { Server } = require("socket.io");
+const { setupMaster, setupWorker } = require("../..");
+const assert = require("assert").strict;
+
+if (cluster.isWorker) {
+  const httpServer = createServer();
+  const io = new Server(httpServer, {
+    cors: {
+      origin: true,
+    },
+  });
+  setupWorker(io);
+
+  io.on("connection", (socket) => {
+    socket.on("foo", (val) => {
+      socket.emit("bar", val);
+    });
+  });
+
+  return;
+}
+
+const WORKER_COUNT = 3;
+
+for (let i = 0; i < WORKER_COUNT; i++) {
+  cluster.fork();
+}
+
+const httpServer = createServer();
+
+setupMaster(httpServer, {
+  loadBalancingMethod: process.env.LB_METHOD || "least-connection",
+});
+
+const waitFor = (emitter, event) => {
+  return new Promise((resolve) => {
+    emitter.once(event, resolve);
+  });
+};
+
+httpServer.listen(async () => {
+  const port = httpServer.address().port;
+
+  const res = await sendRequest({
+    port,
+    method: "options",
+    path: "/socket.io/",
+    headers: {
+      origin: "https://example.com",
+    },
+  });
+
+  assert.equal(res.statusCode, 204);
+
+  assert.equal(
+    res.headers["access-control-allow-origin"],
+    "https://example.com"
+  );
+
+  // cleanup
+  for (const id in cluster.workers) {
+    cluster.workers[id].kill();
+  }
+  httpServer.close();
+});
+
+function sendRequest(options) {
+  return new Promise((resolve) => request(options, resolve).end());
+}

test/index.js

@@ -43,8 +43,8 @@ describe("@socket.io/sticky", () => {
     exec(fixture("connection.js"), { env: { TRANSPORT: "polling" } }, done);
   });
 
-  it("should work with HTTP long-polling only", (done) => {
-    exec(fixture("connection.js"), { env: { TRANSPORT: "polling" } }, done);
+  it("should work with CORS", (done) => {
+    exec(fixture("cors.js"), done);
   });
 
   it("should return a 503 error when no worker is available (polling)", (done) => {