@layus

It would be nice if we could have a simple nixos test for mptcp.

I have it mostly working, but for some reason mptcp is not detected by amiusingmptcp.de

here is my code

# mptcp.nix

{pkgs, ...}:
{
  imports = [ ./minimal.nix ];

  boot.kernelPackages = pkgs.linuxPackages_mptcp;

  environment.systemPackages = [
    pkgs.jshon
    pkgs.curl
  ];
  programs.bash.interactiveShellInit = with pkgs; ''
    amiusingmptcp() { ${curl.bin}/bin/curl 'http://amiusingmptcp.de/v1/check_connection' -qs | ${jshon}/bin/jshon -e proc -e mptcp; }
  '';

  virtualisation.qemu.networkingOptions = [
    # Replace virtio, otherwise mptcp is bypassed
    "-nic user,model=e1000"
    #"-net nic,netdev=user.0,model=virtio"
    #"-netdev user,id=user.0\${QEMU_NET_OPTS:+,$QEMU_NET_OPTS}"
  ];
}

# ./minimal.nix

{pkgs, lib, ...}:
{
  # Allow ssh
  services.openssh.enable = true;

  # Setup ssh key for root
  users.mutableUsers = false;
  users.extraUsers.root.password = "root";
  users.extraUsers.root.openssh.authorizedKeys.keyFiles = [
    ~/.ssh/id_ecdsa.pub
  ];

  #programs.zsh.enable = true;
  #users.defaultUserShell = "/var/run/current-system/sw/bin/zsh";

  # Disable X libs as this is a headless server
  environment.noXlibs = lib.mkDefault true;

  environment.systemPackages = [ pkgs.rxvt_unicode.terminfo ];

  # Define keymap for Qemu
  i18n = {
    consoleFont = "lat9w-16";
    consoleKeyMap = "be-latin1";
    defaultLocale = "en_US.UTF-8";
  };
}

nix-build ../nixpkgs/nixos -A vm -Q -I nixos-config=$PWD/mptcp.nix --show-trace

The issue is most probably with the virtualisation.qemu.networkingOptions where we need a proper interface emulation for mptcp to kick in.
If you manage to get this working, we would at least get some confidence that everything is working.

At the moment, I can affirm that your PR builds a working linux kernel :-).

oh that's great ! I've wanted to write a test for a long time but I can't get the time.
#59342 might force me to.

curling ttp://amiusingmptcp.de might not be reliable enough as proxies/middleboxes can block MPTCP. That's maybe what happens in your case ? You could check your network with tracebox (a UCL software).

to check I would be thinking of capturing MPTCP traffic with tshark (which has mptcp filter).

Merging this. Currently writing a test for nixos.

curling ttp://amiusingmptcp.de might not be reliable enough as proxies/middleboxes can block MPTCP. That's maybe what happens in your case ? You could check your network with tracebox (a UCL software).

It already dropped all mptcp headers when reaching eth0. It is most probably linked to qemu netdev emulation. I know for sure that virtio does not work (obviously) but the commands have changed since my last test years ago.