net: add setTOS and getTOS to Socket #61503

amyssnippet · 2026-01-24T11:11:33Z

this PR implements socket.setTOS(tos) and socket.getTOS() in net.Socket. it needed this to support DSCP tagging (QoS) for traffic prioritization, which wasn't previously exposed in the JS API. for the implementation:

I added the logic in tcp_wrap.cc to attempt IP_TOS first, and fallback to IPV6_TCLASS if that fails. This handles both IPv4 and IPv6 sockets automatically without needing a separate flag.
Windows returns UV_ENOSYS for now since the headers/implementation differ there.
Added a new test file (test-net-socket-tos.js) to verify input validation and ensure the values are actually set on supported platforms.

Fixes: #61489

nodejs-github-bot · 2026-01-24T11:11:39Z

Review requested:

@nodejs/net

mcollina

Good work. Can you add the documentation?

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

doc/api/net.md

src/tcp_wrap.cc

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

amyssnippet · 2026-01-24T16:03:04Z

Thanks @mcollina , is this ready to be merged? Please let me know if there is anything else you need me to adjust.

src/tcp_wrap.cc

nodejs-github-bot · 2026-01-25T07:11:32Z

CI: https://ci.nodejs.org/job/node-test-pull-request/71012/

ronag · 2026-01-25T10:53:10Z

@mcollina I'm confused by the CI failures. Any ideas? Or just flaky?

amyssnippet · 2026-01-25T11:25:54Z

@ronag and @mcollina , it's all my fault, as things work for the linux better, on which i worked on, and i observed most of failures are for windows and very few or i guess only 1 or 2 for macos, and thats completely the code fault written by me. And the reason is platform incompatiblity. Some constants worked for Linux and macos but not for windows. Gimme some time I will fix all of them and get back with solutions soon. Thanks!

amyssnippet · 2026-01-25T12:18:23Z

@ronag and @mcollina i guess all errors are fixed, its because of windows incompatibility, so now lets rerun the checks.

and rest this below picture of macos failures are flake i read the console output

https://ci.nodejs.org/job/node-test-commit-osx/68706/nodes=macos15-arm64/

nodejs-github-bot · 2026-01-25T12:54:08Z

CI: https://ci.nodejs.org/job/node-test-pull-request/71022/

amyssnippet · 2026-01-25T18:07:18Z

@ryan and @mcollina , i think all changes are good, please have a look to the changes, i have setted up everything to be proper for all machine OS. if anything needs change, i am here. and many test runs in ci pipeline are flaky, and not proper, so have a look at them too. Thanks!

Copilot

Pull request overview

This PR adds setTOS() and getTOS() methods to net.Socket and dgram.Socket to enable DSCP tagging for QoS traffic prioritization. The implementation handles both IPv4 (IP_TOS) and IPv6 (IPV6_TCLASS) sockets automatically with fallback logic.

Changes:

Implemented native C++ methods in tcp_wrap.cc and udp_wrap.cc to set/get TOS values using appropriate socket options
Added JavaScript API methods in lib/net.js and lib/dgram.js with validation and deferred application logic
Created comprehensive test coverage across multiple scenarios (validation, implicit bind/connect, connected state)

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
test/parallel/test-tcp-setTOS.js	Tests basic TCP setTOS/getTOS functionality with validation
test/parallel/test-tcp-setTOS-implicit-connect.js	Tests TCP TOS setting before connect
test/parallel/test-net-socket-tos.js	Comprehensive TCP socket TOS validation tests
test/parallel/test-dgram-setTOS.js	Tests basic UDP setTOS/getTOS with validation
test/parallel/test-dgram-setTOS-implicit-bind.js	Tests UDP TOS setting before bind
test/parallel/test-dgram-setTOS-connect.js	Tests UDP TOS with connected datagram socket
src/udp_wrap.h	Declares SetTOS and GetTOS methods for UDP
src/udp_wrap.cc	Implements UDP TOS get/set with IPv4/IPv6 handling
src/tcp_wrap.h	Declares SetTOS and GetTOS methods for TCP
src/tcp_wrap.cc	Implements TCP TOS get/set with IPv4/IPv6 handling and header includes
lib/net.js	Adds Socket.prototype.setTOS/getTOS with deferred application logic
lib/dgram.js	Adds Socket.prototype.setTOS/getTOS with deferred application logic
doc/api/net.md	Documents the new setTOS and getTOS methods

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Copilot · 2026-01-26T06:34:06Z

src/tcp_wrap.cc

+#ifdef __linux__
+#include <netinet/ip6.h>
+#else
+#include <netinet/ip6.h>
+#endif


The conditional include is redundant - both branches include the same header <netinet/ip6.h>. Either remove the conditional entirely if the header is universally available, or use it to conditionally include different headers if platform-specific handling is needed.

Suggested change

#ifdef __linux__

#include <netinet/ip6.h>

#else

#include <netinet/ip6.h>

#endif

#include <netinet/ip6.h>

Copilot · 2026-01-26T06:34:07Z

lib/net.js

+
+  // TOS must be an integer in the range 0..255.
+  if (!Number.isInteger(tos) || tos < 0 || tos > 255) {
+    throw new ErrnoException(UV_EINVAL, 'setTOS');


This validation error uses ErrnoException with UV_EINVAL, but validation errors for out-of-range values typically use ERR_OUT_OF_RANGE for consistency with the rest of the codebase and to provide clearer error messages. Consider using ERR_OUT_OF_RANGE for the range validation instead.

Suggested change

throw new ErrnoException(UV_EINVAL, 'setTOS');

throw new ERR_OUT_OF_RANGE('tos', '>= 0 && <= 255', tos);

Copilot · 2026-01-26T06:34:07Z

lib/dgram.js

+  if (!Number.isInteger(tos) || tos < 0 || tos > 255) {
+    throw new ErrnoException(UV_EINVAL, 'setTOS');
+  }


This validation error uses ErrnoException with UV_EINVAL, but validation errors for out-of-range values typically use ERR_OUT_OF_RANGE for consistency with the rest of the codebase and to provide clearer error messages. Consider using ERR_OUT_OF_RANGE for the range validation instead.

Copilot · 2026-01-26T06:34:07Z

doc/api/net.md

+* 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.


Corrected capitalization of 'Packets' to 'packets'.

Suggested change

Packets sent from this socket. This can be used to prioritize network traffic.

packets sent from this socket. This can be used to prioritize network traffic.

ronag · 2026-01-26T06:45:24Z

lib/dgram.js

+  if (socket[kSetTOS] !== undefined && state.handle && state.handle.setTOS) {
+    const err = state.handle.setTOS(socket[kSetTOS]);
+    if (err && err !== UV_EBADF) {
+      // Non-fatal: surface error to the socket
+      socket.emit('error', new ErrnoException(err, 'setTOS'));
+    }
+  }


Isn't it better to always defer to on listening?

ronag · 2026-01-26T06:47:03Z

lib/dgram.js

+    // Ignore EBADF: on some platforms the underlying fd may not be
+    // fully initialized yet even though a handle exists. In that case
+    // defer applying the setting to when the socket is actually bound
+    // (handled by bind/replaceHandle).


This seems rather hacky... isn't there a way to know when the handle is initialized?

amyssnippet · 2026-01-26T07:42:23Z

@ronag, i request that this pr should only address the tcp or is udp required?? if we push the udp in next update, then it will be easy to rollback changes on crashes

amyssnippet · 2026-01-26T07:43:46Z

as the errors were found only in the dgram which is an udp related work, so we can do 2 different work. one for tcp and one for udp

ronag · 2026-01-26T08:03:57Z

IMHO, tcp is sufficient

Copilot

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

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Copilot · 2026-01-26T08:05:09Z

lib/net.js

  this[kSetNoDelay] = Boolean(options.noDelay);
  this[kSetKeepAlive] = Boolean(options.keepAlive);
  this[kSetKeepAliveInitialDelay] = ~~(options.keepAliveInitialDelay / 1000);
+  this[kSetTOS] = options.TOS;


The option name 'TOS' uses inconsistent casing compared to other options ('noDelay', 'keepAlive'). Consider using 'tos' (lowercase) instead of 'TOS' for consistency with the method names and other socket options.

Suggested change

this[kSetTOS] = options.TOS;

this[kSetTOS] = options.tos;

Copilot · 2026-01-26T08:05:09Z

lib/net.js

+  }
+
+  if (!this._handle.getTOS) {
+    return this[kSetTOS];


When getTOS() is called and the handle exists but doesn't support getTOS, the method returns the cached kSetTOS value which could be undefined. This creates inconsistent behavior compared to line 683 where undefined is explicitly converted to 0. The return should be: return this[kSetTOS] !== undefined ? this[kSetTOS] : 0;

Suggested change

return this[kSetTOS];

// Return cached value if set, otherwise default to 0

return this[kSetTOS] !== undefined ? this[kSetTOS] : 0;

Copilot · 2026-01-26T08:05:09Z

src/tcp_wrap.cc

+  }
+
+  // If both failed, return the negative errno
+  args.GetReturnValue().Set(-errno);


Using errno directly after failed getsockopt calls is unreliable because errno may have been modified by intervening operations. The errno value should be captured immediately after the getsockopt call fails before any other operations occur.

ronag · 2026-01-26T08:47:25Z

src/tcp_wrap.cc

+#ifdef _WIN32
+  // Windows: Try IPv4
+  if (setsockopt(reinterpret_cast<SOCKET>(fd),
+                 IPPROTO_IP,
+                 IP_TOS,
+                 reinterpret_cast<const char*>(&tos),
+                 static_cast<int>(sizeof(tos))) == 0) {
+    successful_at_least_once = true;
+  }
+  // Windows: Try IPv6 (Best effort)
+  if (setsockopt(reinterpret_cast<SOCKET>(fd),
+                 IPPROTO_IPV6,
+                 IPV6_TCLASS,
+                 reinterpret_cast<const char*>(&tos),
+                 static_cast<int>(sizeof(tos))) == 0) {
+    successful_at_least_once = true;
+  }
+#else
+  // POSIX (Linux/macOS): Try IPv4
+  if (setsockopt(fd, IPPROTO_IP, IP_TOS, &tos, sizeof(tos)) == 0) {
+    successful_at_least_once = true;
+  }
+  // POSIX (Linux/macOS): Try IPv6
+  if (setsockopt(fd, IPPROTO_IPV6, IPV6_TCLASS, &tos, sizeof(tos)) == 0) {
+    successful_at_least_once = true;
+  }
+#endif


Isn't there a way to check if a socket is ipv4 or ipv6 before doing this? Rather than relying on fallback on any error?

you re absolutely right, i have refractored the implementation to detect whether the socket is ipv4 or 6, and performs a single targeted call with correct constant

net: add setTOS and getTOS to Socket

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amyssnippet added 3 commits January 24, 2026 19:08

added doc

9e7a183

fixed some lint issues

14b3fb0

already complete with validation and platform specific tests

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socket.setTOS #61489

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amyssnippet added 2 commits January 24, 2026 19:52

added: REPLACEME

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common.mustCall used

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Type of Service (IP prioritization) nodejs/undici#4765

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undo: unrelated header was removed irrelevantly

c0407b2

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Feature Request - Allow setting ToS on socket (rather; wrap getNativeHandle() and let you apply whatever options you wish) uNetworking/uWebSockets.js#1205

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fix: resolve windows compilation and linter issues

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ronag requested a review from mcollina January 26, 2026 06:48

rollback to tcp only

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	throw new ErrnoException(UV_EINVAL, 'setTOS');
	throw new ERR_OUT_OF_RANGE('tos', '>= 0 && <= 255', tos);

	Packets sent from this socket. This can be used to prioritize network traffic.
	packets sent from this socket. This can be used to prioritize network traffic.

	return this[kSetTOS];
	// Return cached value if set, otherwise default to 0
	return this[kSetTOS] !== undefined ? this[kSetTOS] : 0;

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net: add setTOS and getTOS to Socket #61503

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net: add setTOS and getTOS to Socket #61503

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amyssnippet commented Jan 24, 2026 •

edited by mcollina

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