depot/cluster/services/dns/authoritative.nix

{ cluster, config, depot, lib, pkgs, ... }:

let
  inherit (config.reflection) interfaces;
  inherit (depot.lib.meta) domain;
  inherit (config.networking) hostName;

  link = cluster.config.hostLinks.${hostName}.dnsAuthoritative;
  patroni = cluster.config.links.patroni-pg-access;
  inherit (cluster.config.hostLinks.${hostName}) acmeDnsApi;

  otherDnsServers = lib.pipe (cluster.config.services.dns.otherNodes.authoritative hostName) [
    (map (node: cluster.config.hostLinks.${node}.dnsAuthoritative.tuple))
    (lib.concatStringsSep " ")
  ];

  recordsList = lib.mapAttrsToList (lib.const lib.id) cluster.config.dns.records;
  recordsPartitioned = lib.partition (record: record.rewrite.target == null) recordsList;

  staticRecords = let
    escape = type: {
      TXT = builtins.toJSON;
    }.${type} or lib.id;

    recordName = record: {
      "@" = "${record.root}.";
    }.${record.name} or "${record.name}.${record.root}.";
  in lib.flatten (
    map (record: map (target: "${recordName record} ${record.type} ${escape record.type target}") record.target) recordsPartitioned.right
  );

  rewrites = map (record: let
    maybeEscapeRegex = str: if record.rewrite.type == "regex" then "${lib.escapeRegex str}$" else str;
  in "rewrite stop name ${record.rewrite.type} ${record.name}${maybeEscapeRegex ".${record.root}."} ${record.rewrite.target}. answer auto") recordsPartitioned.wrong;

  rewriteConf = pkgs.writeText "coredns-rewrites.conf" ''
    rewrite stop type DS DS
    rewrite stop type NS NS
    rewrite stop type SOA SOA
    ${lib.concatStringsSep "\n" rewrites}
  '';
in {
  links.localAuthoritativeDNS = {};

  age.secrets = {
    acmeDnsDirectKey = {
      file = ./acme-dns-direct-key.age;
    };
  };

  networking.firewall = {
    allowedTCPPorts = [ 53 ];
    allowedUDPPorts = [ 53 ];
  };

  services.acme-dns = {
    enable = true;
    package = depot.packages.acme-dns;
    settings = {
      general = {
        listen = config.links.localAuthoritativeDNS.tuple;
        inherit domain;
        nsadmin = "hostmaster.${domain}";
        nsname = "eu1.ns.${domain}";
        records = staticRecords;
      };
      api = {
        ip = acmeDnsApi.ipv4;
        inherit (acmeDnsApi) port;
      };
      database = {
        engine = "postgres";
        connection = "postgres://acmedns@${patroni.tuple}/acmedns?sslmode=disable";
      };
    };
  };

  services.locksmith.waitForSecrets.acme-dns = [
    "patroni-acmedns"
  ];

  systemd.services.acme-dns.serviceConfig.EnvironmentFile = with config.age.secrets; [
    "/run/locksmith/patroni-acmedns"
    acmeDnsDirectKey.path
  ];

  services.coredns = {
    enable = true;
    config = ''
      .:${link.portStr} {
        bind ${interfaces.primary.addr}
        chaos "Private Void DNS" info@privatevoid.net
        cache {
          success 4000 86400
          denial 0
          prefetch 3
          serve_stale 86400s verify
        }
        template ANY DS {
          rcode NXDOMAIN
        }
        forward service.eu-central.sd-magic.${domain} 127.0.0.1:8600
        forward addr.eu-central.sd-magic.${domain} 127.0.0.1:8600
        import ${rewriteConf}
        forward . ${config.links.localAuthoritativeDNS.tuple} ${otherDnsServers} {
          policy sequential
        }
      }
    '';
  };

  systemd.services.coredns = {
    after = [ "acme-dns.service" ];
    serviceConfig = {
      MemoryMax = "200M";
      MemorySwapMax = "50M";
      CPUQuota = "25%";
    };
  };

  consul.services = {
    authoritative-dns = {
      unit = "acme-dns";
      definition = {
        name = "authoritative-dns-backend";
        address = config.links.localAuthoritativeDNS.ipv4;
        port = config.links.localAuthoritativeDNS.port;
        checks = lib.singleton {
          interval = "60s";
          tcp = config.links.localAuthoritativeDNS.tuple;
        };
      };
    };
    acme-dns.definition = {
      name = "acme-dns";
      address = acmeDnsApi.ipv4;
      port = acmeDnsApi.port;
      checks = lib.singleton {
        interval = "60s";
        http = "${acmeDnsApi.url}/health";
      };
    };
  };
}