nixos/modules/desktop/ssh.nix

{home-manager, ...}: {
  # https://nix-community.github.io/home-manager/options.html

  home-manager.users.caspervk = {
    programs.ssh = {
      enable = true;
      # ControlMaster enables the sharing of multiple sessions over a single
      # network connection. When enabled, additional sessions to the same host
      # will reuse the master session's connection rather than initiating a new
      # one. This is especially useful when using SCP.
      controlMaster = "yes";
      # ISPs in Denmark prefer the simplicity of CG-NAT and stateful firewalls
      # to the mess that is IPv6. Force keepalive packets to avoid sessions
      # dying. See https://news.ycombinator.com/item?id=25737611.
      serverAliveInterval = 25;
      matchBlocks = {
        # Lambda exposes ssh on port 222 to allow git ssh on 22.
        "lambda" = {
          port = 222;
        };
      };
      # TODO: use addKeysToAgent attribute in Home Manager 24.04 instead of
      # extraConfig.
      extraConfig = ''
        # Add ssh keys to the agent the first time we unlock them so we don't
        # have to type the password all the time.
        AddKeysToAgent yes
      '';
    };
  };

  programs.ssh = {
    startAgent = true;
  };
}