P2P: allow to limit the size of protocols

src/lib_base/protocol.ml

@@ -53,6 +53,11 @@ let encoding =
        (req "expected_env_version" env_version_encoding)
        (req "components" (list component_encoding)))
 
+let bounded_encoding ?max_size () =
+  match max_size with
+  | None -> encoding
+  | Some max_size -> Data_encoding.check_size max_size encoding
+
 let pp ppf op =
   Data_encoding.Json.pp ppf
     (Data_encoding.Json.construct encoding op)

src/lib_base/protocol.mli

@@ -29,6 +29,8 @@ include S.HASHABLE with type t := t
                     and type hash := Protocol_hash.t
 val of_bytes_exn: MBytes.t -> t
 
+val bounded_encoding: ?max_size:int -> unit -> t Data_encoding.t
+
 module Meta: sig
 
   type t = {

src/lib_shell/distributed_db_message.ml

@@ -83,6 +83,16 @@ module Bounded_encoding = struct
   let operation_list = delayed (fun () -> !operation_list_cache)
   let operation_hash_list = delayed (fun () -> !operation_hash_list_cache)
 
+  let protocol_max_size = ref None
+  let protocol_cache =
+    ref (Protocol.bounded_encoding ?max_size:!protocol_max_size ())
+  let update_protocol_encoding () =
+    protocol_cache :=
+      Protocol.bounded_encoding ?max_size:!protocol_max_size ()
+  let set_protocol_max_size max =
+    protocol_max_size := max
+  let protocol = delayed (fun () -> !protocol_cache)
+
 end
 
 type t =
@@ -207,7 +217,7 @@ let encoding =
 
     case ~tag:0x41
       ~title:"Protocol"
-      (obj1 (req "protocol" Protocol.encoding))
+      (obj1 (req "protocol" Bounded_encoding.protocol))
       (function Protocol proto -> Some proto  | _ -> None)
       (fun proto -> Protocol proto);
 

src/lib_shell/distributed_db_message.mli

@@ -47,4 +47,5 @@ module Bounded_encoding : sig
   val set_operation_list_max_size: int option -> unit
   val set_operation_list_max_length: int option -> unit
   val set_operation_max_pass: int option -> unit
+  val set_protocol_max_size: int option -> unit
 end