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: #31543
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

Author: rustyconover

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;
 };

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({