3 files changed, 48 insertions, 0 deletions
diff --git a/core/vm/oracle_contract_abi.go b/core/vm/oracle_contract_abi.go
index af0affece..f0845eb7b 100644
--- a/core/vm/oracle_contract_abi.go
+++ b/core/vm/oracle_contract_abi.go
@@ -659,6 +659,23 @@ const GovernanceABIJSON = `
         "type": "address"
       },
       {
+        "indexed": true,
+        "name": "NewOwnerAddress",
+        "type": "address"
+      }
+    ],
+    "name": "NodeOwnershipTransfered",
+    "type": "event"
+  },
+  {
+    "anonymous": false,
+    "inputs": [
+      {
+        "indexed": true,
+        "name": "NodeAddress",
+        "type": "address"
+      },
+      {
         "indexed": false,
         "name": "Amount",
         "type": "uint256"
diff --git a/core/vm/oracle_contracts.go b/core/vm/oracle_contracts.go
index 62261a36b..f21700d86 100644
--- a/core/vm/oracle_contracts.go
+++ b/core/vm/oracle_contracts.go
@@ -1058,6 +1058,16 @@ func (s *GovernanceState) emitCRSProposed(round *big.Int, crs common.Hash) {
 	})
 }
 
+// event NodeOwnershipTransfered(address indexed NodeAddress, address indexed NewOwnerAddress);
+func (s *GovernanceState) emitNodeOwnershipTransfered(nodeAddr, newNodeAddr common.Address) {
+	s.StateDB.AddLog(&types.Log{
+		Address: GovernanceContractAddress,
+		Topics: []common.Hash{GovernanceABI.Events["NodeOwnershipTransfered"].Id(),
+			nodeAddr.Hash(), newNodeAddr.Hash()},
+		Data: []byte{},
+	})
+}
+
 // event Staked(address indexed NodeAddress, uint256 Amount);
 func (s *GovernanceState) emitStaked(nodeAddr common.Address, amount *big.Int) {
 	s.StateDB.AddLog(&types.Log{
@@ -2373,6 +2383,11 @@ func (g *GovernanceContract) transferNodeOwnership(newOwner common.Address) ([]b
 		return nil, errExecutionReverted
 	}
 
+	newOffset := g.state.NodesOffsetByAddress(newOwner)
+	if newOffset.Cmp(big.NewInt(0)) >= 0 {
+		return nil, errExecutionReverted
+	}
+
 	node := g.state.Node(offset)
 	g.state.PutNodeOffsets(node, big.NewInt(0))
 
@@ -2380,6 +2395,8 @@ func (g *GovernanceContract) transferNodeOwnership(newOwner common.Address) ([]b
 	g.state.PutNodeOffsets(node, offset)
 	g.state.UpdateNode(offset, node)
 
+	g.state.emitNodeOwnershipTransfered(caller, newOwner)
+
 	return nil, nil
 }
 
diff --git a/core/vm/oracle_contracts_test.go b/core/vm/oracle_contracts_test.go
index 69e13e1a1..4b25b39da 100644
--- a/core/vm/oracle_contracts_test.go
+++ b/core/vm/oracle_contracts_test.go
@@ -271,6 +271,20 @@ func (g *OracleContractsTestSuite) TestTransferNodeOwnership() {
 	g.Require().Equal(uint64(0), g.s.NodesOffsetByNodeKeyAddress(nodeKeyAddr).Uint64())
 	g.Require().Equal(offset.Uint64(), g.s.NodesOffsetByAddress(newAddr).Uint64())
 	g.Require().Equal(offset.Uint64(), g.s.NodesOffsetByNodeKeyAddress(newNodeKeyAddr).Uint64())
+
+	// Call with owner.
+	privKey2, addr2 := g.newPrefundAccount()
+	pk2 := crypto.FromECDSAPub(&privKey2.PublicKey)
+	input, err = GovernanceABI.ABI.Pack("register", pk2, "Test2", "test1@dexon.org", "Taipei", "https://dexon.org")
+	g.Require().NoError(err)
+	_, err = g.call(GovernanceContractAddress, addr2, input, amount)
+	g.Require().NoError(err)
+
+	// Transfer to duplicate owner address.
+	input, err = GovernanceABI.ABI.Pack("transferNodeOwnership", addr2)
+	g.Require().NoError(err)
+	_, err = g.call(GovernanceContractAddress, newAddr, input, amount)
+	g.Require().Error(err)
 }
 
 func (g *OracleContractsTestSuite) TestStakingMechanism() {