Fix transition protocol schedule (#4078)

* Fix to return pre-merge protocol schedule when block difficulty is less that TTD

Signed-off-by: Fabio Di Fabio <fabio.difabio@consensys.net>

CHANGELOG.md

@@ -8,6 +8,7 @@
 - Return the correct latest valid hash in case of bad block when calling engine methods [#4056](https://github.com/hyperledger/besu/pull/4056)
 - Add a PoS block header rule to check that the current block is more recent than its parent [#4066](https://github.com/hyperledger/besu/pull/4066)
 - Fixed a trie log layer issue on bonsai during reorg [#4069](https://github.com/hyperledger/besu/pull/4069)
+- Fix transition protocol schedule to return the pre Merge schedule when reorg pre TTD [#4078](https://github.com/hyperledger/besu/pull/4078)
 
 ## 22.7.0-RC1
 

consensus/merge/src/main/java/org/hyperledger/besu/consensus/merge/TransitionProtocolSchedule.java

@@ -86,8 +86,7 @@ public class TransitionProtocolSchedule extends TransitionUtils<ProtocolSchedule
           () -> thisDifficulty);
 
       // if this block is pre-merge or a TTD block
-      if ((thisDifficulty.lessOrEqualThan(terminalDifficulty)
-              && thisDifficulty.greaterThan(parentDifficulty))
+      if (thisDifficulty.lessThan(terminalDifficulty)
           || TransitionUtils.isTerminalProofOfWorkBlock(blockHeader, protocolContext)) {
         debugLambda(
             LOG,

consensus/merge/src/test/java/org/hyperledger/besu/consensus/merge/TransitionProtocolScheduleTest.java

@@ -0,0 +1,150 @@
+/*
+ * Copyright Hyperledger Besu Contributors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package org.hyperledger.besu.consensus.merge;
+
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoInteractions;
+import static org.mockito.Mockito.when;
+
+import org.hyperledger.besu.datatypes.Hash;
+import org.hyperledger.besu.ethereum.ProtocolContext;
+import org.hyperledger.besu.ethereum.chain.MutableBlockchain;
+import org.hyperledger.besu.ethereum.core.BlockHeader;
+import org.hyperledger.besu.ethereum.core.Difficulty;
+import org.hyperledger.besu.ethereum.mainnet.ProtocolSchedule;
+
+import java.util.Optional;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.junit.MockitoJUnitRunner;
+
+@RunWith(MockitoJUnitRunner.class)
+public class TransitionProtocolScheduleTest {
+
+  @Mock ProtocolContext protocolContext;
+  @Mock MutableBlockchain blockchain;
+  @Mock MergeContext mergeContext;
+  @Mock ProtocolSchedule preMergeProtocolSchedule;
+  @Mock ProtocolSchedule postMergeProtocolSchedule;
+  @Mock BlockHeader blockHeader;
+
+  private static final Difficulty TTD = Difficulty.of(100L);
+  private static final long BLOCK_NUMBER = 29L;
+  private TransitionProtocolSchedule transitionProtocolSchedule;
+
+  @Before
+  public void setUp() {
+    when(protocolContext.getBlockchain()).thenReturn(blockchain);
+    when(protocolContext.getConsensusContext(MergeContext.class)).thenReturn(mergeContext);
+    when(mergeContext.getTerminalTotalDifficulty()).thenReturn(TTD);
+
+    transitionProtocolSchedule =
+        new TransitionProtocolSchedule(
+            preMergeProtocolSchedule, postMergeProtocolSchedule, mergeContext);
+  }
+
+  @Test
+  public void returnPostMergeIfFinalizedExists() {
+    when(mergeContext.getFinalized()).thenReturn(Optional.of(mock(BlockHeader.class)));
+    when(blockHeader.getNumber()).thenReturn(BLOCK_NUMBER);
+
+    transitionProtocolSchedule.getByBlockHeader(protocolContext, blockHeader);
+
+    verifyPostMergeProtocolScheduleReturned();
+  }
+
+  @Test
+  public void returnPreMergeIfBeforeMerge() {
+    when(mergeContext.getFinalized()).thenReturn(Optional.empty());
+    when(mergeContext.isPostMerge()).thenReturn(false);
+
+    when(blockHeader.getNumber()).thenReturn(BLOCK_NUMBER);
+
+    transitionProtocolSchedule.getByBlockHeader(protocolContext, blockHeader);
+
+    verifyPreMergeProtocolScheduleReturned();
+  }
+
+  @Test
+  public void returnPreMergeIfTerminalPoWBlock() {
+
+    when(mergeContext.getFinalized()).thenReturn(Optional.empty());
+    when(mergeContext.isPostMerge()).thenReturn(true);
+
+    final Hash parentHash = Hash.fromHexStringLenient("0xabc123");
+
+    when(blockHeader.getNumber()).thenReturn(BLOCK_NUMBER);
+    when(blockHeader.getParentHash()).thenReturn(parentHash);
+    when(blockHeader.getDifficulty()).thenReturn(Difficulty.of(10L));
+    when(blockchain.getTotalDifficultyByHash(parentHash))
+        .thenReturn(Optional.of(Difficulty.of(95L)));
+
+    transitionProtocolSchedule.getByBlockHeader(protocolContext, blockHeader);
+
+    verifyPreMergeProtocolScheduleReturned();
+  }
+
+  @Test
+  public void returnPreMergeIfAfterMergeButReorgPreTTD() {
+
+    when(mergeContext.getFinalized()).thenReturn(Optional.empty());
+    when(mergeContext.isPostMerge()).thenReturn(true);
+
+    final Hash parentHash = Hash.fromHexStringLenient("0xabc123");
+
+    when(blockHeader.getNumber()).thenReturn(BLOCK_NUMBER);
+    when(blockHeader.getParentHash()).thenReturn(parentHash);
+    when(blockHeader.getDifficulty()).thenReturn(Difficulty.of(2L));
+    when(blockchain.getTotalDifficultyByHash(parentHash))
+        .thenReturn(Optional.of(Difficulty.of(95L)));
+
+    transitionProtocolSchedule.getByBlockHeader(protocolContext, blockHeader);
+
+    verifyPreMergeProtocolScheduleReturned();
+  }
+
+  @Test
+  public void returnPostMergeIfAfterMergeButReorgPostTTD() {
+
+    when(mergeContext.getFinalized()).thenReturn(Optional.empty());
+    when(mergeContext.isPostMerge()).thenReturn(true);
+
+    final Hash parentHash = Hash.fromHexStringLenient("0xabc123");
+
+    when(blockHeader.getNumber()).thenReturn(BLOCK_NUMBER);
+    when(blockHeader.getParentHash()).thenReturn(parentHash);
+    when(blockHeader.getDifficulty()).thenReturn(Difficulty.ZERO);
+    when(blockchain.getTotalDifficultyByHash(parentHash))
+        .thenReturn(Optional.of(Difficulty.of(105L)));
+
+    transitionProtocolSchedule.getByBlockHeader(protocolContext, blockHeader);
+
+    verifyPostMergeProtocolScheduleReturned();
+  }
+
+  private void verifyPreMergeProtocolScheduleReturned() {
+    verify(preMergeProtocolSchedule).getByBlockNumber(BLOCK_NUMBER);
+    verifyNoInteractions(postMergeProtocolSchedule);
+  }
+
+  private void verifyPostMergeProtocolScheduleReturned() {
+    verify(postMergeProtocolSchedule).getByBlockNumber(BLOCK_NUMBER);
+    verifyNoInteractions(preMergeProtocolSchedule);
+  }
+}