1 files changed, 20 insertions, 23 deletions

diff --git a/eth/downloader/queue.go b/eth/downloader/queue.go
index 40749698c..13ec9a520 100644
--- a/eth/downloader/queue.go
+++ b/eth/downloader/queue.go
@@ -122,24 +122,28 @@ func (q *queue) Has(hash common.Hash) bool {
 	return false
 }
 
-// Insert adds a set of hashes for the download queue for scheduling.
-func (q *queue) Insert(hashes []common.Hash) {
+// Insert adds a set of hashes for the download queue for scheduling, returning
+// the new hashes encountered.
+func (q *queue) Insert(hashes []common.Hash) []common.Hash {
 	q.lock.Lock()
 	defer q.lock.Unlock()
 
 	// Insert all the hashes prioritized in the arrival order
-	for i, hash := range hashes {
-		index := q.hashCounter + i
-
+	inserts := make([]common.Hash, 0, len(hashes))
+	for _, hash := range hashes {
+		// Skip anything we already have
 		if old, ok := q.hashPool[hash]; ok {
 			glog.V(logger.Warn).Infof("Hash %x already scheduled at index %v", hash, old)
 			continue
 		}
-		q.hashPool[hash] = index
-		q.hashQueue.Push(hash, float32(index)) // Highest gets schedules first
+		// Update the counters and insert the hash
+		q.hashCounter = q.hashCounter + 1
+		inserts = append(inserts, hash)
+
+		q.hashPool[hash] = q.hashCounter
+		q.hashQueue.Push(hash, float32(q.hashCounter)) // Highest gets schedules first
 	}
-	// Update the hash counter for the next batch of inserts
-	q.hashCounter += len(hashes)
+	return inserts
 }
 
 // GetHeadBlock retrieves the first block from the cache, or nil if it hasn't
@@ -172,17 +176,11 @@ func (q *queue) GetBlock(hash common.Hash) *types.Block {
 }
 
 // TakeBlocks retrieves and permanently removes a batch of blocks from the cache.
-// The head parameter is required to prevent a race condition where concurrent
-// takes may fail parent verifications.
-func (q *queue) TakeBlocks(head *types.Block) types.Blocks {
+func (q *queue) TakeBlocks() types.Blocks {
 	q.lock.Lock()
 	defer q.lock.Unlock()
 
-	// Short circuit if the head block's different
-	if len(q.blockCache) == 0 || q.blockCache[0] != head {
-		return nil
-	}
-	// Otherwise accumulate all available blocks
+	// Accumulate all available blocks
 	var blocks types.Blocks
 	for _, block := range q.blockCache {
 		if block == nil {
@@ -302,18 +300,17 @@ func (q *queue) Deliver(id string, blocks []*types.Block) (err error) {
 	// Iterate over the downloaded blocks and add each of them
 	errs := make([]error, 0)
 	for _, block := range blocks {
-		// Skip any blocks that fall outside the cache range
-		index := int(block.NumberU64()) - q.blockOffset
-		if index >= len(q.blockCache) || index < 0 {
-			//fmt.Printf("block cache overflown (N=%v O=%v, C=%v)", block.Number(), q.blockOffset, len(q.blockCache))
-			continue
-		}
 		// Skip any blocks that were not requested
 		hash := block.Hash()
 		if _, ok := request.Hashes[hash]; !ok {
 			errs = append(errs, fmt.Errorf("non-requested block %v", hash))
 			continue
 		}
+		// If a requested block falls out of the range, the hash chain is invalid
+		index := int(block.NumberU64()) - q.blockOffset
+		if index >= len(q.blockCache) || index < 0 {
+			return ErrInvalidChain
+		}
 		// Otherwise merge the block and mark the hash block
 		q.blockCache[index] = block