Don't ban nodes for block created in early catchup

Problem: when a node is in early catchup and creates a block, it might
be considered worse than root and the node to be banned for gossiping
it.

Solution: if parent of the transition is in root history, do not ban.

Additionally, if we've seen gossip with the parent of transition and
its ancestor was in root history, do not ban. This one is implemented
heuristically via an LRU cache.

src/lib/transition_handler/dune

@@ -53,6 +53,7 @@
    kimchi_backend.pasta
    kimchi_backend.pasta.basic
    internal_tracing
+   transition_frontier_extensions
    )
  (instrumentation (backend bisect_ppx))
  (preprocess (pps ppx_mina ppx_version ppx_jane)))

src/lib/transition_handler/validator.ml

@@ -4,7 +4,6 @@ open Pipe_lib.Strict_pipe
 open Mina_base
 open Mina_state
 open Cache_lib
-open Mina_block
 open Network_peer
 
 module type CONTEXT = sig
@@ -87,6 +86,7 @@ let run ~context:(module Context : CONTEXT) ~trust_system ~time_controller
        Writer.t ) ~unprocessed_transition_cache =
   let open Context in
   let module Lru = Core_extended_cache.Lru in
+  let outdated_root_cache = Lru.create ~destruct:None 1000 in
   O1trace.background_thread "validate_blocks_against_frontier" (fun () ->
       Reader.iter transition_reader
         ~f:(fun (`Block transition_env, `Valid_cb vc) ->
@@ -118,8 +118,9 @@ let run ~context:(module Context : CONTEXT) ~trust_system ~time_controller
               in
               let transition_time =
                 Mina_block.header transition
-                |> Header.protocol_state |> Protocol_state.blockchain_state
-                |> Blockchain_state.timestamp |> Block_time.to_time_exn
+                |> Mina_block.Header.protocol_state
+                |> Protocol_state.blockchain_state |> Blockchain_state.timestamp
+                |> Block_time.to_time_exn
               in
               Perf_histograms.add_span
                 ~name:"accepted_transition_remote_latency"
@@ -143,18 +144,44 @@ let run ~context:(module Context : CONTEXT) ~trust_system ~time_controller
               [%log internal] "Failure"
                 ~metadata:[ ("reason", `String "Disconnected") ] ;
               Mina_metrics.(Counter.inc_one Rejected_blocks.worse_than_root) ;
+              let protocol_state =
+                Mina_block.Header.protocol_state (Mina_block.header transition)
+              in
               [%log error]
                 ~metadata:
                   [ ("state_hash", State_hash.to_yojson transition_hash)
                   ; ("reason", `String "not selected over current root")
                   ; ( "protocol_state"
-                    , Header.protocol_state (Mina_block.header transition)
-                      |> Protocol_state.value_to_yojson )
+                    , Protocol_state.value_to_yojson protocol_state )
                   ]
                 "Validation error: external transition with state hash \
                  $state_hash was rejected for reason $reason" ;
+              let is_in_root_history =
+                let open Transition_frontier.Extensions in
+                get_extension
+                  (Transition_frontier.extensions frontier)
+                  Root_history
+                |> Root_history.mem
+              in
+              let parent_hash =
+                Protocol_state.previous_state_hash protocol_state
+              in
+              let action =
+                if
+                  is_in_root_history transition_hash
+                  || Option.is_some
+                       (Lru.find outdated_root_cache transition_hash)
+                then Trust_system.Actions.Sent_old_gossip
+                else if
+                  is_in_root_history parent_hash
+                  || Option.is_some (Lru.find outdated_root_cache parent_hash)
+                then (
+                  Lru.add outdated_root_cache ~key:transition_hash ~data:() ;
+                  Sent_useless_gossip )
+                else Disconnected_chain
+              in
               Trust_system.record_envelope_sender trust_system logger sender
-                ( Trust_system.Actions.Disconnected_chain
+                ( action
                 , Some
                     ( "received transition that was not connected to our chain \
                        from $sender"