From 56afb7b481db26ec6f86dcd3806c8bfafe78e40e Mon Sep 17 00:00:00 2001
From: Ouyang Yadong <oyydoibh@gmail.com>
Date: Sat, 27 Oct 2018 15:44:50 +0800
Subject: [PATCH] net: `net.Server.listen()` avoid operations on `null` when
 fail

When `net.Server` fails to create a new handle, an error shall be
emitted in the next tick. Therefore, we make `net.Server.listen()`
directly  return to avoid following operations on `null`
`this._handle`.

Fixes: https://github.com/nodejs/node/issues/23917

PR-URL: https://github.com/nodejs/node/pull/23920
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
---
 lib/net.js                                   |  7 +++++++
 test/parallel/test-net-server-listen-path.js | 20 ++++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/lib/net.js b/lib/net.js
index cc048eccbbd85b..48a8bc069901e2 100644
--- a/lib/net.js
+++ b/lib/net.js
@@ -1435,6 +1435,13 @@ Server.prototype.listen = function(...args) {
     backlog = options.backlog || backlogFromArgs;
     listenInCluster(this, pipeName, -1, -1,
                     backlog, undefined, options.exclusive);
+
+    if (!this._handle) {
+      // Failed and an error shall be emitted in the next tick.
+      // Therefore, we directly return.
+      return this;
+    }
+
     let mode = 0;
     if (options.readableAll === true)
       mode |= PipeConstants.UV_READABLE;
diff --git a/test/parallel/test-net-server-listen-path.js b/test/parallel/test-net-server-listen-path.js
index cc73c3fd438abe..cc7c6678b04224 100644
--- a/test/parallel/test-net-server-listen-path.js
+++ b/test/parallel/test-net-server-listen-path.js
@@ -69,3 +69,23 @@ function randomPipePath() {
       srv.close();
     }));
 }
+
+// Test should emit "error" events when listening fails.
+{
+  const handlePath = randomPipePath();
+  const srv1 = net.createServer().listen({ path: handlePath }, () => {
+    // As the handlePath is in use, binding to the same address again should
+    // make the server emit an 'EADDRINUSE' error.
+    const srv2 = net.createServer()
+      .listen({
+        path: handlePath,
+        writableAll: true,
+      }, common.mustNotCall());
+
+    srv2.on('error', common.mustCall((err) => {
+      srv1.close();
+      assert.strictEqual(err.code, 'EADDRINUSE');
+      assert(/^listen EADDRINUSE: address already in use/.test(err.message));
+    }));
+  });
+}