worker: add double sign check for safety. (bnb-chain#1201)

* worker: add double sign check for safety.

And for corner cases, such as reorg after reorg...
use slice to record all broadcast blocks's parents to avoid overwritten.

miner/worker.go

@@ -38,6 +38,7 @@ import (
 	"github.com/ethereum/go-ethereum/metrics"
 	"github.com/ethereum/go-ethereum/params"
 	"github.com/ethereum/go-ethereum/trie"
+	lru "github.com/hashicorp/golang-lru"
 )
 
 const (
@@ -63,6 +64,10 @@ const (
 
 	// staleThreshold is the maximum depth of the acceptable stale block.
 	staleThreshold = 11
+
+	// the current 4 mining loops could have asynchronous risk of mining block with
+	// save height, keep recently mined blocks to avoid double sign for safety,
+	recentMinedCacheLimit = 20
 )
 
 var (
@@ -226,13 +231,15 @@ type worker struct {
 	isLocalBlock func(header *types.Header) bool // Function used to determine whether the specified block is mined by local miner.
 
 	// Test hooks
-	newTaskHook  func(*task)                        // Method to call upon receiving a new sealing task.
-	skipSealHook func(*task) bool                   // Method to decide whether skipping the sealing.
-	fullTaskHook func()                             // Method to call before pushing the full sealing task.
-	resubmitHook func(time.Duration, time.Duration) // Method to call upon updating resubmitting interval.
+	newTaskHook       func(*task)                        // Method to call upon receiving a new sealing task.
+	skipSealHook      func(*task) bool                   // Method to decide whether skipping the sealing.
+	fullTaskHook      func()                             // Method to call before pushing the full sealing task.
+	resubmitHook      func(time.Duration, time.Duration) // Method to call upon updating resubmitting interval.
+	recentMinedBlocks *lru.Cache
 }
 
 func newWorker(config *Config, chainConfig *params.ChainConfig, engine consensus.Engine, eth Backend, mux *event.TypeMux, isLocalBlock func(header *types.Header) bool, init bool) *worker {
+	recentMinedBlocks, _ := lru.New(recentMinedCacheLimit)
 	worker := &worker{
 		prefetcher:         core.NewStatePrefetcher(chainConfig, eth.BlockChain(), engine),
 		config:             config,
@@ -256,6 +263,7 @@ func newWorker(config *Config, chainConfig *params.ChainConfig, engine consensus
 		exitCh:             make(chan struct{}),
 		startCh:            make(chan struct{}, 1),
 		resubmitIntervalCh: make(chan time.Duration),
+		recentMinedBlocks:  recentMinedBlocks,
 	}
 	// Subscribe NewTxsEvent for tx pool
 	worker.txsSub = eth.TxPool().SubscribeNewTxsEvent(worker.txsCh)
@@ -661,6 +669,30 @@ func (w *worker) resultLoop() {
 				logs = append(logs, receipt.Logs...)
 			}
 
+			if prev, ok := w.recentMinedBlocks.Get(block.NumberU64()); ok {
+				doubleSign := false
+				prevParents, _ := prev.([]common.Hash)
+				for _, prevParent := range prevParents {
+					if prevParent == block.ParentHash() {
+						log.Error("Reject Double Sign!!", "block", block.NumberU64(),
+							"hash", block.Hash(),
+							"root", block.Root(),
+							"ParentHash", block.ParentHash())
+						doubleSign = true
+						break
+					}
+				}
+				if doubleSign {
+					continue
+				}
+				prevParents = append(prevParents, block.ParentHash())
+				w.recentMinedBlocks.Add(block.NumberU64(), prevParents)
+			} else {
+				// Add() will call removeOldest internally to remove the oldest element
+				// if the LRU Cache is full
+				w.recentMinedBlocks.Add(block.NumberU64(), []common.Hash{block.ParentHash()})
+			}
+
 			// Broadcast the block and announce chain insertion event
 			w.mux.Post(core.NewMinedBlockEvent{Block: block})