nixos/networking: use mkIfs on the inner attributes

      address = forEach (interfaceIps i)

        (ip: "${ip.address}/${toString ip.prefixLength}");

      routes = forEach (interfaceRoutes i)

        (route: mkMerge [

        (route: {

          # Most of these route options have not been tested.

          # Please fix or report any mistakes you may find.

          (mkIf (route.address != null && route.prefixLength != null) {

            Destination = "${route.address}/${toString route.prefixLength}";

          })

          (mkIf (route.options ? fastopen_no_cookie) {

            FastOpenNoCookie = route.options.fastopen_no_cookie;

          })

          (mkIf (route.via != null) {

            Gateway = route.via;

          })

          (mkIf (route.type != null) {

            Type = route.type;

          })

          (mkIf (route.options ? onlink) {

            GatewayOnLink = true;

          })

          (mkIf (route.options ? initrwnd) {

            InitialAdvertisedReceiveWindow = route.options.initrwnd;

          })

          (mkIf (route.options ? initcwnd) {

            InitialCongestionWindow = route.options.initcwnd;

          })

          (mkIf (route.options ? pref) {

            IPv6Preference = route.options.pref;

          })

          (mkIf (route.options ? mtu) {

            MTUBytes = route.options.mtu;

          })

          (mkIf (route.options ? metric) {

            Metric = route.options.metric;

          })

          (mkIf (route.options ? src) {

            PreferredSource = route.options.src;

          })

          (mkIf (route.options ? protocol) {

            Protocol = route.options.protocol;

          })

          (mkIf (route.options ? quickack) {

            QuickAck = route.options.quickack;

          })

          (mkIf (route.options ? scope) {

            Scope = route.options.scope;

          })

          (mkIf (route.options ? from) {

            Source = route.options.from;

          })

          (mkIf (route.options ? table) {

            Table = route.options.table;

          })

          (mkIf (route.options ? advmss) {

            TCPAdvertisedMaximumSegmentSize = route.options.advmss;

          })

          (mkIf (route.options ? ttl-propagate) {

            TTLPropagate = route.options.ttl-propagate == "enabled";

          })

        ]);

          Destination = mkIf (route.address != null && route.prefixLength != null) "${route.address}/${toString route.prefixLength}";

          FastOpenNoCookie = mkIf (route.options ? fastopen_no_cookie) route.options.fastopen_no_cookie;

          Gateway = mkIf (route.via != null) route.via;

          Type = mkIf (route.type != null) route.type;

          GatewayOnLink = mkIf (route.options ? onlink) true;

          InitialAdvertisedReceiveWindow = mkIf (route.options ? initrwnd) route.options.initrwnd;

          InitialCongestionWindow = mkIf (route.options ? initcwnd) route.options.initcwnd;

          IPv6Preference = mkIf (route.options ? pref) route.options.pref;

          MTUBytes = mkIf (route.options ? mtu) route.options.mtu;

          Metric = mkIf (route.options ? metric) route.options.metric;

          PreferredSource = mkIf (route.options ? src) route.options.src;

          Protocol = mkIf (route.options ? protocol) route.options.protocol;

          QuickAck = mkIf (route.options ? quickack) route.options.quickack;

          Scope = mkIf (route.options ? scope) route.options.scope;

          Source = mkIf (route.options ? from) route.options.from;

          Table = mkIf (route.options ? table) route.options.table;

          TCPAdvertisedMaximumSegmentSize = mkIf (route.options ? advmss) route.options.advmss;

          TTLPropagate = mkIf (route.options ? ttl-propagate) route.options.ttl-propagate == "enabled";

        });

      networkConfig.IPv6PrivacyExtensions = "kernel";

      linkConfig = optionalAttrs (i.macAddress != null) {

        MACAddress = i.macAddress;