net: do not inherit the no-half-open enforcer

lib/_stream_duplex.js

@@ -29,33 +29,15 @@
 module.exports = Duplex;
 
 const util = require('util');
-const Readable = require('_stream_readable');
-const Writable = require('_stream_writable');
-
-util.inherits(Duplex, Readable);
-
-{
-  // avoid scope creep, the keys array can then be collected
-  const keys = Object.keys(Writable.prototype);
-  for (var v = 0; v < keys.length; v++) {
-    const method = keys[v];
-    if (!Duplex.prototype[method])
-      Duplex.prototype[method] = Writable.prototype[method];
-  }
-}
+const DuplexBase = require('internal/streams/duplex_base');
+
+util.inherits(Duplex, DuplexBase);
 
 function Duplex(options) {
   if (!(this instanceof Duplex))
     return new Duplex(options);
 
-  Readable.call(this, options);
-  Writable.call(this, options);
-
-  if (options && options.readable === false)
-    this.readable = false;
-
-  if (options && options.writable === false)
-    this.writable = false;
+  DuplexBase.call(this, options);
 
   this.allowHalfOpen = true;
   if (options && options.allowHalfOpen === false) {

lib/internal/streams/duplex_base.js

@@ -0,0 +1,30 @@
+'use strict';
+
+const util = require('util');
+const Readable = require('_stream_readable');
+const Writable = require('_stream_writable');
+
+function DuplexBase(options) {
+  Readable.call(this, options);
+  Writable.call(this, options);
+
+  if (options && options.readable === false)
+    this.readable = false;
+
+  if (options && options.writable === false)
+    this.writable = false;
+}
+
+util.inherits(DuplexBase, Readable);
+
+{
+  // Avoid scope creep, the keys array can then be collected.
+  const keys = Object.keys(Writable.prototype);
+  for (var v = 0; v < keys.length; v++) {
+    const method = keys[v];
+    if (!DuplexBase.prototype[method])
+      DuplexBase.prototype[method] = Writable.prototype[method];
+  }
+}
+
+module.exports = DuplexBase;

lib/net.js

@@ -64,6 +64,7 @@ const {
   ERR_SOCKET_BAD_PORT,
   ERR_SOCKET_CLOSED
 } = errors.codes;
+const DuplexBase = require('internal/streams/duplex_base');
 const dns = require('dns');
 
 const kLastWriteQueueSize = Symbol('lastWriteQueueSize');
@@ -238,7 +239,11 @@ function Socket(options) {
   // For backwards compat do not emit close on destroy.
   options.emitClose = false;
 
-  stream.Duplex.call(this, options);
+  // `DuplexBase` is just a slimmed down constructor for `Duplex` which allow
+  // us to not inherit the "no-half-open enforcer" as there is already one in
+  // place. Instances of `Socket` are still instances of `Duplex`, that is,
+  // `socket instanceof Duplex === true`.
+  DuplexBase.call(this, options);
 
   if (options.handle) {
     this._handle = options.handle; // private
@@ -263,8 +268,6 @@ function Socket(options) {
       this._writev = null;
       this._write = makeSyncWrite(fd);
     }
-    this.readable = options.readable !== false;
-    this.writable = options.writable !== false;
   } else {
     // these will be set once there is a connection
     this.readable = this.writable = false;
@@ -282,7 +285,7 @@ function Socket(options) {
   this._writableState.decodeStrings = false;
 
   // default to *not* allowing half open sockets
-  this.allowHalfOpen = options && options.allowHalfOpen || false;
+  this.allowHalfOpen = options.allowHalfOpen || false;
 
   // if we have a handle, then start the flow of data into the
   // buffer.  if not, then this will happen when we connect

node.gyp

@@ -146,6 +146,7 @@
       'lib/internal/streams/lazy_transform.js',
       'lib/internal/streams/async_iterator.js',
       'lib/internal/streams/BufferList.js',
+      'lib/internal/streams/duplex_base.js',
       'lib/internal/streams/duplexpair.js',
       'lib/internal/streams/legacy.js',
       'lib/internal/streams/destroy.js',

test/parallel/test-http-connect.js

@@ -75,12 +75,7 @@ server.listen(0, common.mustCall(() => {
     assert.strictEqual(socket.listeners('connect').length, 0);
     assert.strictEqual(socket.listeners('data').length, 0);
     assert.strictEqual(socket.listeners('drain').length, 0);
-
-    // the stream.Duplex onend listener
-    // allow 0 here, so that i can run the same test on streams1 impl
-    assert(socket.listenerCount('end') <= 2,
-           `Found ${socket.listenerCount('end')} end listeners`);
-
+    assert.strictEqual(socket.listeners('end').length, 1);
     assert.strictEqual(socket.listeners('free').length, 0);
     assert.strictEqual(socket.listeners('close').length, 0);
     assert.strictEqual(socket.listeners('error').length, 0);

test/parallel/test-net-socket-no-halfopen-enforcer.js

@@ -0,0 +1,11 @@
+'use strict';
+require('../common');
+
+// This test ensures that `net.Socket` does not inherit the no-half-open
+// enforcer from `stream.Duplex`.
+
+const { Socket } = require('net');
+const { strictEqual } = require('assert');
+
+const socket = new Socket({ allowHalfOpen: false });
+strictEqual(socket.listenerCount('end'), 1);