net: add setTOS and getTOS to Socket

doc/api/net.md

@@ -1461,6 +1461,29 @@ If `timeout` is 0, then the existing idle timeout is disabled.
 The optional `callback` parameter will be added as a one-time listener for the
 [`'timeout'`][] event.
 
+### `socket.getTOS()`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+* Returns: {integer} The current TOS value.
+
+Returns the current Type of Service (TOS) field for IPv4 packets or Traffic
+Class for IPv6 packets for this socket.
+
+### `socket.setTOS(tos)`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+* `tos` {integer} The TOS value to set (0-255).
+* Returns: {net.Socket} The socket itself.
+
+Sets the Type of Service (TOS) field for IPv4 packets or Traffic Class for IPv6
+Packets sent from this socket. This can be used to prioritize network traffic.
+
 ### `socket.timeout`
 
 <!-- YAML

lib/net.js

@@ -358,6 +358,7 @@ const kBytesWritten = Symbol('kBytesWritten');
 const kSetNoDelay = Symbol('kSetNoDelay');
 const kSetKeepAlive = Symbol('kSetKeepAlive');
 const kSetKeepAliveInitialDelay = Symbol('kSetKeepAliveInitialDelay');
+const kSetTOS = Symbol('kSetTOS');
 
 function Socket(options) {
   if (!(this instanceof Socket)) return new Socket(options);
@@ -473,6 +474,7 @@ function Socket(options) {
   this[kSetNoDelay] = Boolean(options.noDelay);
   this[kSetKeepAlive] = Boolean(options.keepAlive);
   this[kSetKeepAliveInitialDelay] = ~~(options.keepAliveInitialDelay / 1000);
+  this[kSetTOS] = options.TOS;
 
   // Shut down the socket when we're finished with it.
   this.on('end', onReadableStreamEnd);
@@ -652,6 +654,46 @@ Socket.prototype.setKeepAlive = function(enable, initialDelayMsecs) {
 };
 
 
+Socket.prototype.setTOS = function(tos) {
+  if (NumberIsNaN(tos)) {
+    throw new ERR_INVALID_ARG_TYPE('tos', 'number', tos);
+  }
+  validateInt32(tos, 'tos', 0, 255);
+
+  if (!this._handle) {
+    this[kSetTOS] = tos;
+    return this;
+  }
+
+  if (this._handle.setTOS && tos !== this[kSetTOS]) {
+    this[kSetTOS] = tos;
+    const err = this._handle.setTOS(tos);
+    if (err) {
+      throw new ErrnoException(err, 'setTOS');
+    }
+  }
+
+  return this;
+};
+
+
+Socket.prototype.getTOS = function() {
+  if (!this._handle) {
+    return this[kSetTOS];
+  }
+
+  if (!this._handle.getTOS) {
+    return this[kSetTOS];
+  }
+
+  const res = this._handle.getTOS();
+  if (typeof res === 'number' && res < 0) {
+    throw new ErrnoException(res, 'getTOS');
+  }
+  return res;
+};
+
+
 Socket.prototype.address = function() {
   return this._getsockname();
 };
@@ -1619,6 +1661,10 @@ function afterConnect(status, handle, req, readable, writable) {
       self._handle.setKeepAlive(true, self[kSetKeepAliveInitialDelay]);
     }
 
+    if (self[kSetTOS] !== undefined && self._handle.setTOS) {
+      self._handle.setTOS(self[kSetTOS]);
+    }
+
     self.emit('connect');
     self.emit('ready');
 

src/tcp_wrap.cc

@@ -20,7 +20,6 @@
 // USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 #include "tcp_wrap.h"
-
 #include "connect_wrap.h"
 #include "connection_wrap.h"
 #include "env-inl.h"
@@ -32,9 +31,15 @@
 #include "stream_base-inl.h"
 #include "stream_wrap.h"
 #include "util-inl.h"
-
+#include <cerrno>
 #include <cstdlib>
-
+#ifdef _WIN32
+#include <ws2tcpip.h>
+#endif
+#ifndef _WIN32
+#include <netinet/in.h>
+#include <sys/socket.h>
+#endif
 
 namespace node {
 
@@ -106,6 +111,8 @@ void TCPWrap::Initialize(Local<Object> target,
                  GetSockOrPeerName<TCPWrap, uv_tcp_getpeername>);
   SetProtoMethod(isolate, t, "setNoDelay", SetNoDelay);
   SetProtoMethod(isolate, t, "setKeepAlive", SetKeepAlive);
+  SetProtoMethod(isolate, t, "setTOS", SetTOS);
+  SetProtoMethod(isolate, t, "getTOS", GetTOS);
   SetProtoMethod(isolate, t, "reset", Reset);
 
 #ifdef _WIN32
@@ -145,6 +152,8 @@ void TCPWrap::RegisterExternalReferences(ExternalReferenceRegistry* registry) {
   registry->Register(GetSockOrPeerName<TCPWrap, uv_tcp_getpeername>);
   registry->Register(SetNoDelay);
   registry->Register(SetKeepAlive);
+  registry->Register(SetTOS);
+  registry->Register(GetTOS);
   registry->Register(Reset);
 #ifdef _WIN32
   registry->Register(SetSimultaneousAccepts);
@@ -208,6 +217,103 @@ void TCPWrap::SetKeepAlive(const FunctionCallbackInfo<Value>& args) {
   args.GetReturnValue().Set(err);
 }
 
+void TCPWrap::SetTOS(const FunctionCallbackInfo<Value>& args) {
+  TCPWrap* wrap;
+  ASSIGN_OR_RETURN_UNWRAP(
+      &wrap, args.This(), args.GetReturnValue().Set(UV_EBADF));
+  Environment* env = wrap->env();
+  int tos;
+  if (!args[0]->Int32Value(env->context()).To(&tos)) return;
+
+  // Use uv_os_fd_t (it handles int vs void* automatically)
+  uv_os_fd_t fd;
+  int err = uv_fileno(reinterpret_cast<uv_handle_t*>(&wrap->handle_), &fd);
+  if (err != 0) {
+    args.GetReturnValue().Set(err);
+    return;
+  }
+
+#ifdef _WIN32
+  // Windows implementation
+  // Windows setsockopt expects 'const char*' for value and 'SOCKET' for fd
+  if (setsockopt(reinterpret_cast<SOCKET>(fd),
+                 IPPROTO_IP,
+                 IP_TOS,
+                 reinterpret_cast<const char*>(&tos),
+                 sizeof(tos)) == 0) {
+    args.GetReturnValue().Set(0);
+    return;
+  }
+  // Windows does not typically support IPV6_TCLASS in the same way,
+  // or it might fallback. If you need IPv6 support on Windows,
+  // you often need explicit version checks or specific headers.
+  // For now, let's return the error if IPv4 failed.
+  args.GetReturnValue().Set(UV_EINVAL);
+#else
+  // Linux/macOS implementation
+  // Try IPv4 first
+  if (setsockopt(fd, IPPROTO_IP, IP_TOS, &tos, sizeof(tos)) == 0) {
+    args.GetReturnValue().Set(0);
+    return;
+  }
+
+  // If IPv4 failed, try IPv6
+  if (setsockopt(fd, IPPROTO_IPV6, IPV6_TCLASS, &tos, sizeof(tos)) == 0) {
+    args.GetReturnValue().Set(0);
+    return;
+  }
+
+  // If both failed, return the negative errno
+  args.GetReturnValue().Set(-errno);
+#endif
+}
+
+void TCPWrap::GetTOS(const FunctionCallbackInfo<Value>& args) {
+  TCPWrap* wrap;
+  ASSIGN_OR_RETURN_UNWRAP(
+      &wrap, args.This(), args.GetReturnValue().Set(UV_EBADF));
+
+  // Use uv_os_fd_t
+  uv_os_fd_t fd;
+  int err = uv_fileno(reinterpret_cast<uv_handle_t*>(&wrap->handle_), &fd);
+  if (err != 0) {
+    args.GetReturnValue().Set(err);
+    return;
+  }
+
+  int tos = 0;
+  socklen_t len = sizeof(tos);
+
+#ifdef _WIN32
+  // Windows implementation
+  // Windows getsockopt expects 'char*' and 'SOCKET'
+  if (getsockopt(reinterpret_cast<SOCKET>(fd),
+                 IPPROTO_IP,
+                 IP_TOS,
+                 reinterpret_cast<char*>(&tos),
+                 &len) == 0) {
+    args.GetReturnValue().Set(tos);
+    return;
+  }
+  args.GetReturnValue().Set(UV_EINVAL);
+#else
+  // Linux/macOS implementation
+  // Try IPv4 first
+  if (getsockopt(fd, IPPROTO_IP, IP_TOS, &tos, &len) == 0) {
+    args.GetReturnValue().Set(tos);
+    return;
+  }
+
+  // If IPv4 failed, try IPv6
+  if (getsockopt(fd, IPPROTO_IPV6, IPV6_TCLASS, &tos, &len) == 0) {
+    args.GetReturnValue().Set(tos);
+    return;
+  }
+
+  // If both failed, return the negative errno
+  args.GetReturnValue().Set(-errno);
+#endif
+}
 
 #ifdef _WIN32
 void TCPWrap::SetSimultaneousAccepts(const FunctionCallbackInfo<Value>& args) {

src/tcp_wrap.h

@@ -74,6 +74,8 @@ class TCPWrap : public ConnectionWrap<TCPWrap, uv_tcp_t> {
   static void New(const v8::FunctionCallbackInfo<v8::Value>& args);
   static void SetNoDelay(const v8::FunctionCallbackInfo<v8::Value>& args);
   static void SetKeepAlive(const v8::FunctionCallbackInfo<v8::Value>& args);
+  static void SetTOS(const v8::FunctionCallbackInfo<v8::Value>& args);
+  static void GetTOS(const v8::FunctionCallbackInfo<v8::Value>& args);
   static void Bind(const v8::FunctionCallbackInfo<v8::Value>& args);
   static void Bind6(const v8::FunctionCallbackInfo<v8::Value>& args);
   static void Listen(const v8::FunctionCallbackInfo<v8::Value>& args);

test/parallel/test-net-socket-tos.js

@@ -0,0 +1,72 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const net = require('net');
+
+const isWindows = common.isWindows;
+
+const server = net.createServer(
+  common.mustCall((socket) => {
+    socket.end();
+  }),
+);
+
+server.listen(
+  0,
+  common.mustCall(() => {
+    const port = server.address().port;
+    const client = net.connect(port);
+
+    client.on(
+      'connect',
+      common.mustCall(() => {
+        // TEST 1: setTOS validation
+        // Should throw if value is not a number or out of range
+        assert.throws(() => client.setTOS('invalid'), {
+          code: 'ERR_INVALID_ARG_TYPE',
+        });
+        assert.throws(() => client.setTOS(NaN), {
+          code: 'ERR_INVALID_ARG_TYPE',
+        });
+        assert.throws(() => client.setTOS(256), {
+          code: 'ERR_OUT_OF_RANGE',
+        });
+        assert.throws(() => client.setTOS(-1), {
+          code: 'ERR_OUT_OF_RANGE',
+        });
+
+        // TEST 2: setting and getting TOS
+        const tosValue = 0x10; // IPTOS_LOWDELAY (16)
+
+        if (isWindows) {
+          // On Windows, your implementation returns UV_ENOSYS, which throws in JS
+          assert.throws(() => client.setTOS(tosValue), {
+            code: 'ENOSYS',
+          });
+        } else {
+          // On POSIX (Linux/macOS), this should succeed
+          client.setTOS(tosValue);
+
+          // Verify values
+          // Note: Some OSs might mask the value (e.g. Linux sometimes masks ECN bits),
+          // but usually 0x10 should return 0x10.
+          const got = client.getTOS();
+          assert.strictEqual(
+            got,
+            tosValue,
+            `Expected TOS ${tosValue}, got ${got}`,
+          );
+        }
+
+        client.end();
+      }),
+    );
+
+    client.on(
+      'end',
+      common.mustCall(() => {
+        server.close();
+      }),
+    );
+  }),
+);