mptcpd: init at 0.13

[nim65s]

Hi,

This add https://github.com/multipath-tcp/mptcpd

And take some inspiration from @teto in https://github.com/teto/mptcp-flake/blob/main/pkgs/mptcpd/default.nix

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 24.11 Release Notes (or backporting 23.11 and 24.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

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[mweinelt]

And the module please!

[nim65s]

Thanks for the review !
I added the requested changes

[mweinelt]

The module needs to go into a separate commit named "nixos/mptcpd: init".

[nim65s]

ok, done.
Thanks !

[mweinelt]

https://github.com/teto/mptcp-flake/blob/main/modules/mptcp/default.nix

[matttbe]

https://github.com/teto/mptcp-flake/blob/main/modules/mptcp/default.nix

@mweinelt Please note that this old nix module was designed for an old out-of-tree kernel supporting a different implementation of MPTCP than the one that is now in the upstream kernel. See this line:

Default mptcp kernel to use. For now the module works only with the out-of-tree module.

Most (all?) of the option and sysctl names I see there are for the previous out-of-tree, which are not needed. The routing modifications should not be needed as well.

[nim65s]

I probably won't be able to work on this until Sunday, but feel free to push here if you need @mweinelt

[teto]

I confirm @matttbe's remark. I think we could merge mptcpd and see for the module later. Testing it might need some work (I have never tested mptcpd in a multihomed setting). Ideally we would have a nixosTest for it but this means someone is using it and motivated enough to write and maintain it. @nim65s ar you going to use the module ?

[nim65s]

I wanted to try mptcp on top of multiple vpn (zerotier / tailscale / maybe mycelium), yes, but I have no idea where I'm going, so maybe this is foolish / useless.

[matttbe]

Hello,
It looks like most of the work has been done here (thanks for that and the reviews!), but I'm not sure what's missing to get this merged. Any help needed from "upstream"?

[mweinelt]

I'll defer to @teto and @nim65s.

[matttbe]

Hello,

@nim65s @teto : do you think the new module could be added later? It doesn't seem mandatory, right?

In this case, maybe this PR can be merged as it is, no? :)

[nim65s]

From my point of view this can be merged as it. I did not test it yet, but this looks simple enough, and we can always improve it later if needed

[teto]

I had planned to test it during holidays and completely forgot about it sry.
I built "mptcpd" but the bin/ folder doesn't contain mptcpd (the main program), just mptcpize (that I tried to run on a curl call without success, but maybe I used it wrong).
mptcpd allows to select a path management (how to create TCP subflows) via a plugin system so it would be nice to have at least one of them (I found 2 in the plugins folder anyway).
https://manpages.debian.org/testing/mptcpd/mptcpd.8.en.html

[matttbe]

@teto: thank you for having checked this!

I built "mptcpd" but the bin/ folder doesn't contain mptcpd (the main program)

By default, it should be in <prefix>/libexec. But I don't know how libexecdir is configured on NixOS.

just mptcpize (that I tried to run on a curl call without success, but maybe I used it wrong).

If the kernel supports MPTCP, libmptcpwrap.so.0.0.1 is installed at the right location (typically under <prefix>/lib/mptcpize/), and there are no middleboxes on the way explicitly blocking MPTCP, this command should tell you if MPTCP is supported or not:

mptcpize run curl https://check.mptcp.dev/ 

Note that it would be great to have the possibility to install only mptcpize, and not mptcpd (or not to start the service). Some people might not need mptcpd, e.g. if NM >= 1.40 is used, see here.

mptcpd allows to select a path management (how to create TCP subflows) via a plugin system so it would be nice to have at least one of them (I found 2 in the plugins folder anyway). https://manpages.debian.org/testing/mptcpd/mptcpd.8.en.html

Indeed, addr_adv.so and sspi.so should be built somewhere, typically installed in <prefix>/lib/mptcpd/

[teto]

ok my bad it lives in result/libexec/mptcpd indeed. Is libexec something standard I should know of ?
mptcpize run curl https://check.mptcp.dev/ worked as well. Let's merge. We can make mptcpd optional the day someone requires it but let's not preemptively optimize. Ty for the work.

[matttbe]

ok my bad it lives in result/libexec/mptcpd indeed. Is libexec something standard I should know of ?

Yes, it is standard:

The directory for installing executable programs to be run by other programs rather than by users.

According to: https://www.gnu.org/prep/standards/html_node/Directory-Variables.html

mptcpize run curl https://check.mptcp.dev/ worked as well. Let's merge. We can make mptcpd optional the day someone requires it but let's not preemptively optimize. Ty for the work.

Great, thank you for having merged this!

[teto]

interesting because this was a point of discussion for LSP servers as well huggingface/llm.nvim#64 (comment). I need to read more on it, as it looks quite brittle to me but this is not the place. Thanks for your effort on MPTCP