From 2a13ddffd4dc71c58c36c05a790cee70828997d2 Mon Sep 17 00:00:00 2001
From: Mark Spanbroek <mark@spanbroek.net>
Date: Tue, 29 Oct 2024 13:05:38 +0100
Subject: [PATCH] refuse a proposal that was already received

---
 mysticeti/validator.nim                    | 2 ++
 tests/mysticeti/validator/testMultiple.nim | 6 ++++++
 2 files changed, 8 insertions(+)

diff --git a/mysticeti/validator.nim b/mysticeti/validator.nim
index a27d115..e39ba41 100644
--- a/mysticeti/validator.nim
+++ b/mysticeti/validator.nim
@@ -114,6 +114,8 @@ func check*(validator: Validator, signed: SignedBlock): auto =
         missing.add(parent)
   if missing.len > 0:
     return BlockCheck.incomplete(missing)
+  if validator.rounds.latest.find(signed.blck.id).isSome:
+    return BlockCheck.invalid("block already received")
   BlockCheck.correct(signed)
 
 func receive*(validator: Validator, correct: CorrectBlock) =
diff --git a/tests/mysticeti/validator/testMultiple.nim b/tests/mysticeti/validator/testMultiple.nim
index c8b3d22..7795877 100644
--- a/tests/mysticeti/validator/testMultiple.nim
+++ b/tests/mysticeti/validator/testMultiple.nim
@@ -176,6 +176,12 @@ suite "Multiple Validators":
     check checked.verdict == BlockVerdict.invalid
     check checked.reason == "block has a round number that is too high"
 
+  test "refuses a proposal that was already received":
+    let proposals = exchangeProposals()
+    let checked = validators[1].check(proposals[0])
+    check checked.verdict == BlockVerdict.invalid
+    check checked.reason == "block already received"
+
   test "skips blocks that are ignored by >2f validators":
     # first round: other validators do not receive proposal from first validator
     let proposals = exchangeProposals {