Seems to be almost working

lib/types/network-definition.nix

@@ -7,6 +7,7 @@ let
       service = {
         type = str;
         description = "Service name of SRV record.";
+        default = service;
       };
 
       priority = mkOption {
@@ -15,6 +16,13 @@ let
         default = 0;
       };
 
+      weight = mkOption {
+        type = int;
+        description =
+          "Weight to give this record, among records of equivalent priority.";
+        default = 5;
+      };
+
       port = mkOption {
         type = port;
         description = "Port for service on this host.";
@@ -29,7 +37,7 @@ let
     };
   };
 
-  hostOpts = { hostname, ... }: {
+  networkHostOpts = { hostname, ... }: {
     options = with types; {
       hostname = mkOption {
         type = str;
@@ -40,22 +48,18 @@ let
 
       ipv4-address = mkOption {
         type = nullOr str;
-        description = ''
-          The V4 IP of a given host, if any.
-        '';
+        description = "The V4 IP of a given host, if any.";
         default = null;
       };
 
       ipv6-address = mkOption {
         type = nullOr str;
-        description = ''
-          The V6 IP of a given host, if any.
-        '';
+        description = "The V6 IP of a given host, if any.";
         default = null;
       };
 
       mac-address = mkOption {
-        type = with types; nullOr types.str;
+        type = nullOr types.str;
         description =
           "The MAC address of a given host, if desired for IP reservation.";
         default = null;
@@ -65,16 +69,22 @@ let
 
 in {
   options = with types; {
-    hosts = {
-      type = attrsOf networkHostOpts;
+    hosts = mkOption {
+      type = attrsOf (submodule networkHostOpts);
       description = "Hosts on the local network, with relevant settings.";
+      example = {
+        my-host = {
+          ipv4-address = "192.168.0.1";
+          mac-address = "aa:aa:aa:aa:aa";
+        };
+      };
       default = { };
     };
 
-    srv-records = {
-      type = attrsOf (attrsOf (listOf (submodule protocolSrvRecords)));
+    srv-records = mkOption {
+      type = attrsOf (attrsOf (listOf (submodule srvRecordOpts)));
       description = "SRV records for the network.";
-      default = {
+      example = {
         tcp = {
           kerberos = {
             port = 88;
@@ -82,6 +92,7 @@ in {
           };
         };
       };
+      default = { };
     };
 
     aliases = mkOption {
@@ -121,5 +132,11 @@ in {
       description = "A list of mail servers serving this domain.";
       default = [ ];
     };
+
+    gssapi-realm = mkOption {
+      type = nullOr str;
+      description = "Kerberos GSSAPI realm of the network.";
+      default = null;
+    };
   };
 }