consensus: get rid of 1st validator from snap.Recents when check rece…

consensus/parlia/parlia.go

@@ -656,13 +656,8 @@ func (p *Parlia) verifySeal(chain consensus.ChainHeaderReader, header *types.Hea
 		return fmt.Errorf("parlia.verifySeal: headerNum=%d, validator=%x, %w", header.Number.Uint64(), signer.Bytes(), errUnauthorizedValidator)
 	}
 
-	for seen, recent := range snap.Recents {
-		if recent == signer {
-			// Signer is among recents, only fail if the current block doesn't shift it out
-			if limit := uint64(len(snap.Validators)/2 + 1); seen > number-limit {
-				return errRecentlySigned
-			}
-		}
+	if snap.signedRecently(signer) {
+		return errRecentlySigned
 	}
 
 	// Ensure that the difficulty corresponds to the turn-ness of the signer
@@ -988,10 +983,16 @@ func (p *Parlia) finalize(header *types.Header, state *state.IntraBlockState, tx
 	if header.Difficulty.Cmp(diffInTurn) != 0 {
 		spoiledVal := snap.supposeValidator()
 		signedRecently := false
-		for _, recent := range snap.Recents {
-			if recent == spoiledVal {
+		if p.chainConfig.IsPlato(header.Number.Uint64()) {
+			if snap.signedRecently(spoiledVal) {
 				signedRecently = true
-				break
+			}
+		} else {
+			for _, recent := range snap.Recents {
+				if recent == spoiledVal {
+					signedRecently = true
+					break
+				}
 			}
 		}
 		if !signedRecently {

consensus/parlia/snapshot.go

@@ -377,6 +377,17 @@ func (s *Snapshot) supposeValidator() common.Address {
 	return validators[index]
 }
 
+func (s *Snapshot) signedRecently(validator common.Address) bool {
+	for seen, recent := range s.Recents {
+		if recent == validator {
+			if limit := uint64(len(s.Validators)/2 + 1); s.Number+1 < limit || seen > s.Number+1-limit {
+				return true
+			}
+		}
+	}
+	return false
+}
+
 func parseValidators(header *types.Header, chainConfig *chain.Config, parliaConfig *chain.ParliaConfig) ([]libcommon.Address, []types.BLSPublicKey, error) {
 	validatorsBytes := getValidatorBytesFromHeader(header, chainConfig, parliaConfig)
 	if len(validatorsBytes) == 0 {