fixup hostname for vpn

nixos/modules/ddns.nix

@@ -0,0 +1,47 @@
+{ config, pkgs, lib, ... }:
+with lib;
+let
+  cfg = config.dadada.ddns;
+  ddnsConfig = hostNames: {
+    systemd.timers = listToAttrs (forEach hostNames (hostname: nameValuePair "ddns-${hostname}"
+    { 
+      wantedBy = [ "timers.target" ];
+      partOf = [ "ddns-${hostname}.service" ];
+      timerConfig.OnCalendar = "hourly";
+    }));
+
+    systemd.services = listToAttrs (forEach hostNames (hostname: nameValuePair "ddns-${hostname}"
+    {
+      serviceConfig.Type = "oneshot";
+      script = ''
+        function url() {
+        echo "https://svc.joker.com/nic/update?username=$1&password=$2&hostname=$3"
+        }
+
+        IFS=':'
+        read -r user password < /var/lib/ddns/credentials
+        unset IFS
+
+        curl_url=$(url "$user" "$password" ${hostname})
+
+        ${pkgs.curl}/bin/curl -4 "$curl_url"
+        ${pkgs.curl}/bin/curl -6 "$curl_url"
+      '';
+    }));
+  };
+in {
+  options = {
+    dadada.ddns.domains = mkOption {
+      type = types.listOf types.str;
+      description = ''
+          Enables DDNS for these domains.
+      '';
+      example = ''
+        [ "example.com" ]
+      '';
+      default = [];
+    };
+  };
+
+  config = ddnsConfig cfg.domains;
+}