From 0d30546329e3fde5b798736817b4a5fcdb7b87ec Mon Sep 17 00:00:00 2001
From: Rusty Conover <rusty@conover.me>
Date: Mon, 27 Jan 2020 22:09:23 -0500
Subject: [PATCH] net: track state of setNoDelay() and prevent unnecessary
 system calls

The state of .setNoDelay() is now tracked and code will prevent repeated
system calls to setsockopt() when the value has already been set to the
desired value for the socket.

Change and expand the appropriate test.

PR-URL: https://github.com/nodejs/node/pull/31543
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
---
 lib/net.js                                  | 10 +++++++---
 test/parallel/test-net-socket-setnodelay.js | 12 ++++++++++--
 2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/lib/net.js b/lib/net.js
index b32937f224b873..21d17702b53798 100644
--- a/lib/net.js
+++ b/lib/net.js
@@ -257,7 +257,7 @@ function initSocketHandle(self) {
 
 const kBytesRead = Symbol('kBytesRead');
 const kBytesWritten = Symbol('kBytesWritten');
-
+const kSetNoDelay = Symbol('kSetNoDelay');
 
 function Socket(options) {
   if (!(this instanceof Socket)) return new Socket(options);
@@ -271,6 +271,7 @@ function Socket(options) {
   this[kHandle] = null;
   this._parent = null;
   this._host = null;
+  this[kSetNoDelay] = false;
   this[kLastWriteQueueSize] = 0;
   this[kTimeout] = null;
   this[kBuffer] = null;
@@ -487,8 +488,11 @@ Socket.prototype.setNoDelay = function(enable) {
   }
 
   // Backwards compatibility: assume true when `enable` is omitted
-  if (this._handle.setNoDelay)
-    this._handle.setNoDelay(enable === undefined ? true : !!enable);
+  const newValue = enable === undefined ? true : !!enable;
+  if (this._handle.setNoDelay && newValue !== this[kSetNoDelay]) {
+    this[kSetNoDelay] = newValue;
+    this._handle.setNoDelay(newValue);
+  }
 
   return this;
 };
diff --git a/test/parallel/test-net-socket-setnodelay.js b/test/parallel/test-net-socket-setnodelay.js
index 55b4c773fa5bf7..e11d89daec58de 100644
--- a/test/parallel/test-net-socket-setnodelay.js
+++ b/test/parallel/test-net-socket-setnodelay.js
@@ -20,18 +20,26 @@ socket.setNoDelay();
 
 socket = new net.Socket({
   handle: {
-    setNoDelay: common.mustCall(genSetNoDelay(true), truthyValues.length)
+    setNoDelay: common.mustCall(genSetNoDelay(true), 1)
   }
 });
 truthyValues.forEach((testVal) => socket.setNoDelay(testVal));
 
 socket = new net.Socket({
   handle: {
-    setNoDelay: common.mustCall(genSetNoDelay(false), falseyValues.length)
+    setNoDelay: common.mustNotCall()
   }
 });
 falseyValues.forEach((testVal) => socket.setNoDelay(testVal));
 
+socket = new net.Socket({
+  handle: {
+    setNoDelay: common.mustCall(() => {}, 3)
+  }
+});
+truthyValues.concat(falseyValues).concat(truthyValues)
+  .forEach((testVal) => socket.setNoDelay(testVal));
+
 // If a handler doesn't have a setNoDelay function it shouldn't be called.
 // In the case below, if it is called an exception will be thrown
 socket = new net.Socket({