From 9d40fb40fca7407237b9c2cbb32d5138599faeea Mon Sep 17 00:00:00 2001
From: Daniel Liu <139250065@qq.com>
Date: Mon, 3 Nov 2025 18:45:48 +0800
Subject: [PATCH] engine_v2: verify gap number in UpdateMasternodes, close
 XFN-11 (#1622)

---
 consensus/XDPoS/engines/engine_v1/engine.go |  5 +--
 consensus/XDPoS/engines/engine_v2/engine.go |  5 ++-
 consensus/tests/engine_v2_tests/api_test.go |  2 +-
 consensus/tests/engine_v2_tests/helper.go   | 38 ++++++++++-----------
 4 files changed, 26 insertions(+), 24 deletions(-)

diff --git a/consensus/XDPoS/engines/engine_v1/engine.go b/consensus/XDPoS/engines/engine_v1/engine.go
index bdc2c92012..2c1d73d3e0 100644
--- a/consensus/XDPoS/engines/engine_v1/engine.go
+++ b/consensus/XDPoS/engines/engine_v1/engine.go
@@ -790,6 +790,9 @@ func (x *XDPoS_v1) Prepare(chain consensus.ChainReader, header *types.Header) er
 
 // Update masternodes into snapshot. In V1, truncating ms[:MaxMasternodes] is done in this function.
 func (x *XDPoS_v1) UpdateMasternodes(chain consensus.ChainReader, header *types.Header, ms []utils.Masternode) error {
+	number := header.Number.Uint64()
+	log.Trace("take snapshot", "number", number, "hash", header.Hash())
+
 	var maxMasternodes int
 	// check if block number is increase ms checkpoint
 	if x.chainConfig.IsTIPIncreaseMasternodes(header.Number) || (x.config.V2.SwitchBlock != nil && header.Number.Cmp(x.config.V2.SwitchBlock) == 1) {
@@ -802,8 +805,6 @@ func (x *XDPoS_v1) UpdateMasternodes(chain consensus.ChainReader, header *types.
 	if len(ms) > maxMasternodes {
 		ms = ms[:maxMasternodes]
 	}
-	number := header.Number.Uint64()
-	log.Trace("take snapshot", "number", number, "hash", header.Hash())
 	// get snapshot
 	snap, err := x.snapshot(chain, number, header.Hash(), nil, header)
 	if err != nil {
diff --git a/consensus/XDPoS/engines/engine_v2/engine.go b/consensus/XDPoS/engines/engine_v2/engine.go
index 0469d3aec8..56d4d16412 100644
--- a/consensus/XDPoS/engines/engine_v2/engine.go
+++ b/consensus/XDPoS/engines/engine_v2/engine.go
@@ -509,7 +509,10 @@ func (x *XDPoS_v2) GetSnapshot(chain consensus.ChainReader, header *types.Header
 
 func (x *XDPoS_v2) UpdateMasternodes(chain consensus.ChainReader, header *types.Header, ms []utils.Masternode) error {
 	number := header.Number.Uint64()
-	log.Trace("[UpdateMasternodes]")
+	log.Trace("[UpdateMasternodes]", "number", number, "hash", header.Hash())
+	if number%x.config.Epoch != x.config.Epoch-x.config.Gap {
+		return fmt.Errorf("[UpdateMasternodes] not gap block, number: %d, epoch: %d,gap: %d", number, x.config.Epoch, x.config.Gap)
+	}
 
 	masterNodes := []common.Address{}
 	for _, m := range ms {
diff --git a/consensus/tests/engine_v2_tests/api_test.go b/consensus/tests/engine_v2_tests/api_test.go
index d02790d894..4c65a52a29 100644
--- a/consensus/tests/engine_v2_tests/api_test.go
+++ b/consensus/tests/engine_v2_tests/api_test.go
@@ -86,7 +86,7 @@ func TestGetMissedRoundsInEpochByBlockNum(t *testing.T) {
 	}
 
 	// Update Signer as there is no previous signer assigned
-	err = UpdateSigner(blockchain)
+	blockchain.UpdateM1()
 	if err != nil {
 		t.Fatal(err)
 	}
diff --git a/consensus/tests/engine_v2_tests/helper.go b/consensus/tests/engine_v2_tests/helper.go
index e07a02a0b2..d351421a04 100644
--- a/consensus/tests/engine_v2_tests/helper.go
+++ b/consensus/tests/engine_v2_tests/helper.go
@@ -295,11 +295,6 @@ func signingTxWithSignerFn(header *types.Header, nonce uint64, signer common.Add
 	return signedTx, nil
 }
 
-func UpdateSigner(bc *core.BlockChain) error {
-	err := bc.UpdateM1()
-	return err
-}
-
 func GetSnapshotSigner(bc *core.BlockChain, header *types.Header) (signersList, error) {
 	engine := bc.Engine().(*XDPoS.XDPoS)
 	snap, err := engine.GetSnapshot(bc, header)
@@ -425,12 +420,13 @@ func PrepareXDCTestBlockChainForV2Engine(t *testing.T, numOfBlocks int, chainCon
 		}
 
 		currentBlock = block
-	}
 
-	// Update Signer as there is no previous signer assigned
-	err = UpdateSigner(blockchain)
-	if err != nil {
-		t.Fatal(err)
+		if uint64(i)%chainConfig.XDPoS.Epoch == chainConfig.XDPoS.Epoch-chainConfig.XDPoS.Gap {
+			err := blockchain.UpdateM1()
+			if err != nil {
+				t.Fatal(err)
+			}
+		}
 	}
 
 	return blockchain, backend, currentBlock, signer, signFn, currentForkBlock
@@ -476,12 +472,13 @@ func PrepareXDCTestBlockChainWithPenaltyForV2Engine(t *testing.T, numOfBlocks in
 			t.Fatal(err)
 		}
 		currentBlock = block
-	}
 
-	// Update Signer as there is no previous signer assigned
-	err = UpdateSigner(blockchain)
-	if err != nil {
-		t.Fatal(err)
+		if uint64(i)%chainConfig.XDPoS.Epoch == chainConfig.XDPoS.Epoch-chainConfig.XDPoS.Gap {
+			err := blockchain.UpdateM1()
+			if err != nil {
+				t.Fatal(err)
+			}
+		}
 	}
 
 	return blockchain, backend, currentBlock, signer, signFn
@@ -539,12 +536,13 @@ func PrepareXDCTestBlockChainWith128Candidates(t *testing.T, numOfBlocks int, ch
 		}
 
 		currentBlock = block
-	}
 
-	// Update Signer as there is no previous signer assigned
-	err = UpdateSigner(blockchain)
-	if err != nil {
-		t.Fatal(err)
+		if uint64(i)%chainConfig.XDPoS.Epoch == chainConfig.XDPoS.Epoch-chainConfig.XDPoS.Gap {
+			err := blockchain.UpdateM1()
+			if err != nil {
+				t.Fatal(err)
+			}
+		}
 	}
 
 	return blockchain, backend, currentBlock, signer, signFn