Add ipv4 and ipv6 functions to Expr

nftables.ml

@@ -66,6 +66,9 @@ module Expr = struct
     | Range : 'a t * 'a t -> 'a t
     | Payload : 'a Payload.t -> 'a t
 
+  let ipv4 x = Ipv4 x
+  let ipv6 x = Ipv6 x
+
   let rec to_json : type a. a t -> Yojson.Basic.t = function
     | String str -> `String str
     | Number num -> `Int num