nix-config/lib/default.nix

# This module is for use by all C3D2 machines.
# That includes physical servers, VMs, containers, and personal machines.
#

{ config, lib, ... }:

let
  hqPrefix64 = "fd23:42:c3d2:523";
  # TODO: Is this stable? Is there a better place to specifiy this?

  # Generate a deterministic IPv6 address for a 64 bit prefix
  # and seed string. Prefix must not contain trailing ':'.
  toIpv6Address = prefix64: seed:
    with builtins;
    let
      digest = builtins.hashString "sha256" seed;
      hextets = map (i: substring (4 * i) 4 digest) [ 0 1 2 3 ];
    in concatStringsSep ":" ([ prefix64 ] ++ hextets);

  # Generate a deterministic public IPv6 addresses
  # for the HQ networking using a seed string.
  toHqPrivateAddress = toIpv6Address hqPrefix64;

  /* # Generate a deterministic public IPv6 addresses
     # for the HQ networking using a seed string.
     toHqPublicAddress = toIpv6Address publicPrefix64;

     # Generate a deterministic public IPv6 addresses
     # for the HQ networking using a seed string.
     toserver7YggdrasilAddress = toIpv6Address server7YggrasilPrefix64;
  */

  cfg = config.c3d2;

in {

  options.c3d2 = with lib;
    with lib.types; {

      isInHq = mkEnableOption "HQ presence";

      enableMotd = mkOption {
        type = bool;
        default = cfg.isInHq;
        defaultText = literalExample "config.c3d2.isInHq";
      };

      mapPublicHosts = mkOption {
        type = bool;
        default = false;
        description = ''
          Whether to add all external HQ host mappings to /etc/hosts.
        '';
      };

      mapHqHosts = mkOption {
        type = bool;
        default = false;
        description = ''
          Whether to add all internal HQ host mappings to /etc/hosts.
        '';
      };

      hq = {

        /* externalInterface = mkOption {
             type = nullOr str;
             default = null;
             example = "eth0";
             description = ''
               Configure the given interface name with an external IP address.
             '';
           };
        */

        interface = mkOption {
          type = nullOr str;
          default = null;
          example = "eth0";
          description = ''
            Configure the given interface name with an internal IP address.
          '';
        };

        statistics = { enable = mkEnableOption "statistics collection"; };

      };

    };

  config = let
    cfg = config.c3d2;
    hostRegistry = import ../host-registry.nix;
    mkIfIsInHq = lib.mkIf cfg.isInHq;
  in {

    assertions = [{
      assertion = let
        check = hostName: hostName == config.networking.hostName;
        checkRegistry = list: builtins.any check list;
      in cfg.isInHq -> checkRegistry hostRegistry.hqPrivate;
      message = "${config.networking.hostName} is not registered in ${
          toString ../host-registry.nix
        }";
    }];

    networking.defaultGateway = mkIfIsInHq "172.22.99.4";

    networking.domain = mkIfIsInHq "hq.c3d2.de";

    users.motd = lib.mkIf cfg.enableMotd (builtins.readFile ./motd);

    networking.hosts = let
      mapHostsNamesToAttrs = f: list: builtins.listToAttrs (map f list);

      /* hqPublicHosts = mapHostsNamesToAttrs (hostName: {
           name = toHqPublicAddress hostName;
           value = [ "${hostName}.hq.c3d2.de" hostName ];
         }) hostRegistry.hqPublic;
      */

      hqPrivateHosts = mapHostsNamesToAttrs (hostName: {
        name = toHqPrivateAddress hostName;
        value = [ "${hostName}.hq" hostName ];
      }) hostRegistry.hqPrivate;

    in if cfg.mapHqHosts then hqPrivateHosts else { };

    networking.interfaces =
      /* (if cfg.hq.externalInterface == null then
           { }
         else {
           "${cfg.hq.externalInterface}" = {
             ipv6.addresses = [{
               address = toHqPublicAddress config.networking.hostName;
               prefixLength = 64;
             }];
           };
         }) //
      */
      (if cfg.hq.interface == null then
        { }
      else {
        "${cfg.hq.interface}" = {
          ipv6.addresses = [{
            address = toHqPrivateAddress config.networking.hostName;
            prefixLength = 64;
          }];
        };
      });

    programs.ssh.knownHosts = with builtins;
      let
        hostNames = hostRegistry.hqPrivate;
        intersectKeys = intersectAttrs {
          publicKey = null;
          publicKeyFile = null;
        };
        list = map (name:
          let sshAttrs = intersectKeys (getAttr name hostRegistry.hosts);
          in if sshAttrs == { } then
            null
          else {
            inherit name;
            value = {
              publicKey = null;
              publicKeyFile = null;
              hostNames = [
                (toHqPrivateAddress name)
                "${name}.hq.c3d2.de"
                "${name}.hq"
                name
              ];
            } // sshAttrs;
          }) hostNames;
        keyedHosts = filter (x: x != null) list;
      in listToAttrs keyedHosts;

    services.collectd = lib.mkIf cfg.hq.statistics.enable {
      enable = true;
      autoLoadPlugin = true;
      extraConfig = ''
        HostName "${config.networking.hostName}"
        FQDNLookup false
        Interval 10

        LoadPlugin network
        <Plugin "network">
          Server "grafana.hq" "25826"
        </Plugin>
      '';
    };

  };

  meta.maintainers = with lib.maintainers; [ ehmry ];
}