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

`Socket.prototype.destroySoon()` is called as soon as `UV_EOF` is read
if the `allowHalfOpen` option is disabled. This already works as a
"no-half-open enforcer" so there is no need to inherit another from
`stream.Duplex`.

PR-URL: https://github.com/nodejs/node/pull/18974
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Chen Gang <gangc.cxy@foxmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

1 files changed, 7 insertions, 4 deletions

diff --git a/lib/net.js b/lib/net.js
index f2cb423f30..7fa1e20aed 100644
--- a/lib/net.js
+++ b/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