net: add setTypeOfService and getTypeOfService to Socket

[amyssnippet]

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]

Review requested:

• @nodejs/net

[mcollina]

Good work. Can you add the documentation?

[amyssnippet]

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

[nodejs-github-bot]

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

[ronag]

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

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/71060/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/71069/

[amyssnippet]

i have fixed all issues from my side, on both linux and windows. all platforms are ready to get served with the 26 pre version. rest ci failures are flaky. Thanks!

[juanarbol]

I think windows may need a different implementation, with a different API.

Do not use. Type of Service (TOS) settings should only be set using the Quality of Service API. See Differentiated Services in the Quality of Service section of the Platform SDK for more information.

https://learn.microsoft.com/en-us/windows/win32/winsock/ipproto-ip-socket-options

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/71088/

[amyssnippet]

so is everything fine and ready to merge???

[mcollina]

lgtm but there are still a few comments to solve

[amyssnippet]

@mcollina likely the renaming ones right??

i have pushed the changes regarding the renaming ones, have a look at it, i was just waiting to see that all ci checks are running properly or not for all platforms.