nodejs · aduh95 · Feb 2, 2026 · Jan 24, 2026 · Jan 24, 2026 · Jan 24, 2026
diff --git a/doc/api/net.md b/doc/api/net.md
@@ -1461,6 +1461,45 @@ 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.
+
+Note that `setTOS()` may be called before the socket is connected; the value
+will be cached and applied when the socket establishes a connection. `getTOS()`
+will return the currently set value even before connection.
+
+On some platforms (e.g., Linux), certain TOS/ECN bits may be masked or ignored,
+and behavior can differ between IPv4 and IPv6 or dual-stack sockets. Callers
+should verify platform-specific semantics.
+
+### `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.
+
+Note that `setTOS()` may be called before the socket is connected; the value
+will be cached and applied when the socket establishes a connection. `getTOS()`
+will return the currently set value even before connection.
+
+On some platforms (e.g., Linux), certain TOS/ECN bits may be masked or ignored,
+and behavior can differ between IPv4 and IPv6 or dual-stack sockets. Callers
+should verify platform-specific semantics.
+
 ### `socket.timeout`
 
 <!-- YAML

diff --git a/lib/net.js b/lib/net.js
@@ -57,6 +57,7 @@ const {
 const assert = require('internal/assert');
 const {
   UV_EADDRINUSE,
+  UV_EBADF,
   UV_EINVAL,
   UV_ENOTCONN,
   UV_ECANCELED,
@@ -358,6 +359,7 @@ 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 +475,10 @@ function Socket(options) {
   this[kSetNoDelay] = Boolean(options.noDelay);
   this[kSetKeepAlive] = Boolean(options.keepAlive);
   this[kSetKeepAliveInitialDelay] = ~~(options.keepAliveInitialDelay / 1000);
+  if (options.tos !== undefined) {
+    validateInt32(options.tos, 'options.tos', 0, 255);
+  }
+  this[kSetTOS] = options.tos;
 
   // Shut down the socket when we're finished with it.
   this.on('end', onReadableStreamEnd);
@@ -652,6 +658,52 @@ 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) {
+    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 cached value if set, otherwise default to 0
+    return this[kSetTOS] !== undefined ? this[kSetTOS] : 0;
+  }
+
+  if (!this._handle.getTOS) {
+    return this[kSetTOS] !== undefined ? this[kSetTOS] : 0;
+  }
+
+  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 +1671,13 @@ function afterConnect(status, handle, req, readable, writable) {
       self._handle.setKeepAlive(true, self[kSetKeepAliveInitialDelay]);
     }
 
+    if (self[kSetTOS] !== undefined && self._handle.setTOS) {
+      const err = self._handle.setTOS(self[kSetTOS]);
+      if (err && err !== UV_EBADF) {
+        self.emit('error', new ErrnoException(err, 'setTOS'));
+      }
+    }
+
     self.emit('connect');
     self.emit('ready');
 

diff --git a/src/tcp_wrap.cc b/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 +217,135 @@ 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 = 0;
+  if (!args[0]->Int32Value(env->context()).To(&tos)) return;
+
+  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;
+  }
+
+  // 1. Detect the socket family (IPv4 vs IPv6)
+  sockaddr_storage storage;
+  int addrlen = sizeof(storage);
+  int sock_err = uv_tcp_getsockname(&wrap->handle_,
+                                    reinterpret_cast<sockaddr*>(&storage),
+                                    &addrlen);
+
+  // If we can't determine the family (e.g. closed socket), fail gracefully.
+  if (sock_err != 0) {
+    args.GetReturnValue().Set(sock_err);
+    return;
+  }
+
+  // 2. Select the correct protocol level and option name
+  int level;
+  int option;
+
+  if (storage.ss_family == AF_INET) {
+    level = IPPROTO_IP;
+    option = IP_TOS;
+  } else if (storage.ss_family == AF_INET6) {
+    level = IPPROTO_IPV6;
+    option = IPV6_TCLASS;
+  } else {
+    // Unsupported socket family (e.g. AF_UNIX)
+    args.GetReturnValue().Set(UV_EINVAL);
+    return;
+  }
+
+  // 3. Perform the system call (Platform specific casting)
+#ifdef _WIN32
+  if (setsockopt(reinterpret_cast<SOCKET>(fd),
+                 level,
+                 option,
+                 reinterpret_cast<const char*>(&tos),
+                 static_cast<int>(sizeof(tos))) == 0) {
+    args.GetReturnValue().Set(0);
+  } else {
+    args.GetReturnValue().Set(uv_translate_sys_error(WSAGetLastError()));
+  }
+#else
+  if (setsockopt(fd, level, option, &tos, sizeof(tos)) == 0) {
+    args.GetReturnValue().Set(0);
+  } else {
+    args.GetReturnValue().Set(uv_translate_sys_error(errno));
+  }
+#endif
+}
+
+void TCPWrap::GetTOS(const FunctionCallbackInfo<Value>& args) {
+  TCPWrap* wrap;
+  ASSIGN_OR_RETURN_UNWRAP(
+      &wrap, args.This(), args.GetReturnValue().Set(UV_EBADF));
+
+  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;
+  }
+
+  // Detect socket family explicitly
+  sockaddr_storage storage;
+  int addrlen = sizeof(storage);
+  int sock_err = uv_tcp_getsockname(&wrap->handle_,
+                                    reinterpret_cast<sockaddr*>(&storage),
+                                    &addrlen);
+
+  int level;
+  int option;
+
+  // Select the correct constant based on family
+  if (sock_err == 0) {
+    if (storage.ss_family == AF_INET) {
+      level = IPPROTO_IP;
+      option = IP_TOS;
+    } else if (storage.ss_family == AF_INET6) {
+      level = IPPROTO_IPV6;
+      option = IPV6_TCLASS;
+    } else {
+      // Unknown or unsupported family
+      args.GetReturnValue().Set(UV_EINVAL);
+      return;
+    }
+  } else {
+    // If we can't determine the family, we can't safely get the TOS
+    args.GetReturnValue().Set(sock_err);
+    return;
+  }
+
+  int tos = 0;
+
+  // Perform the system call with platform-specific casting
+#ifdef _WIN32
+  int len = sizeof(tos);
+  if (getsockopt(reinterpret_cast<SOCKET>(fd),
+                 level,
+                 option,
+                 reinterpret_cast<char*>(&tos),
+                 &len) == 0) {
+    args.GetReturnValue().Set(tos);
+  } else {
+    args.GetReturnValue().Set(uv_translate_sys_error(WSAGetLastError()));
+  }
+#else
+  socklen_t len = sizeof(tos);
+  if (getsockopt(fd, level, option, &tos, &len) == 0) {
+    args.GetReturnValue().Set(tos);
+  } else {
+    args.GetReturnValue().Set(uv_translate_sys_error(errno));
+  }
+#endif
+}
 
 #ifdef _WIN32
 void TCPWrap::SetSimultaneousAccepts(const FunctionCallbackInfo<Value>& args) {

diff --git a/src/tcp_wrap.h b/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);