nixos/promtheus-dnsmasq-exporter: add module

nixos/modules/services/monitoring/prometheus/exporters.nix

@@ -20,6 +20,7 @@ let
   exporterOpts = {
     blackbox  = import ./exporters/blackbox.nix  { inherit config lib pkgs; };
     collectd  = import ./exporters/collectd.nix  { inherit config lib pkgs; };
+    dnsmasq   = import ./exporters/dnsmasq.nix   { inherit config lib pkgs; };
     dovecot   = import ./exporters/dovecot.nix   { inherit config lib pkgs; };
     fritzbox  = import ./exporters/fritzbox.nix  { inherit config lib pkgs; };
     json      = import ./exporters/json.nix      { inherit config lib pkgs; };

nixos/modules/services/monitoring/prometheus/exporters/dnsmasq.nix

@@ -0,0 +1,39 @@
+{ config, lib, pkgs }:
+
+with lib;
+
+let
+  cfg = config.services.prometheus.exporters.dnsmasq;
+in
+{
+  port = 9153;
+  extraOpts = {
+    dnsmasqListenAddress = mkOption {
+      type = types.str;
+      default = "localhost:53";
+      description = ''
+        Address on which dnsmasq listens.
+      '';
+    };
+    leasesPath = mkOption {
+      type = types.path;
+      default = "/var/lib/misc/dnsmasq.leases";
+      example = "/var/lib/dnsmasq/dnsmasq.leases";
+      description = ''
+        Path to the <literal>dnsmasq.leases</literal> file.
+      '';
+    };
+  };
+  serviceOpts = {
+    serviceConfig = {
+      DynamicUser = true;
+      ExecStart = ''
+        ${pkgs.prometheus-dnsmasq-exporter}/bin/dnsmasq_exporter \
+          --listen ${cfg.listenAddress}:${toString cfg.port} \
+          --dnsmasq ${cfg.dnsmasqListenAddress} \
+          --leases_path ${cfg.leasesPath} \
+          ${concatStringsSep " \\\n  " cfg.extraFlags}
+      '';
+    };
+  };
+}