Merge pull request #1153 from karalabe/downloader-banned-starvation-attack

eth/downloader: gather and ban hashes from invalid chains

eth/downloader/peer.go

@@ -94,7 +94,7 @@ func (p *peer) SetIdle() {
 	for {
 		// Calculate the new download bandwidth allowance
 		prev := atomic.LoadInt32(&p.capacity)
-		next := int32(math.Max(1, math.Min(MaxBlockFetch, float64(prev)*scale)))
+		next := int32(math.Max(1, math.Min(float64(MaxBlockFetch), float64(prev)*scale)))
 
 		// Try to update the old value
 		if atomic.CompareAndSwapInt32(&p.capacity, prev, next) {

eth/downloader/queue.go

@@ -16,7 +16,7 @@ import (
 	"gopkg.in/karalabe/cookiejar.v2/collections/prque"
 )
 
-const (
+var (
 	blockCacheLimit = 8 * MaxBlockFetch // Maximum number of blocks to cache before throttling the download
 )
 
@@ -54,6 +54,7 @@ func newQueue() *queue {
 		hashQueue:  prque.New(),
 		pendPool:   make(map[string]*fetchRequest),
 		blockPool:  make(map[common.Hash]int),
+		blockCache: make([]*Block, blockCacheLimit),
 	}
 }
 
@@ -70,7 +71,7 @@ func (q *queue) Reset() {
 
 	q.blockPool = make(map[common.Hash]int)
 	q.blockOffset = 0
-	q.blockCache = nil
+	q.blockCache = make([]*Block, blockCacheLimit)
 }
 
 // Size retrieves the number of hashes in the queue, returning separately for
@@ -208,7 +209,7 @@ func (q *queue) TakeBlocks() []*Block {
 
 // Reserve reserves a set of hashes for the given peer, skipping any previously
 // failed download.
-func (q *queue) Reserve(p *peer) *fetchRequest {
+func (q *queue) Reserve(p *peer, count int) *fetchRequest {
 	q.lock.Lock()
 	defer q.lock.Unlock()
 
@@ -229,8 +230,7 @@ func (q *queue) Reserve(p *peer) *fetchRequest {
 	send := make(map[common.Hash]int)
 	skip := make(map[common.Hash]int)
 
-	capacity := p.Capacity()
-	for proc := 0; proc < space && len(send) < capacity && !q.hashQueue.Empty(); proc++ {
+	for proc := 0; proc < space && len(send) < count && !q.hashQueue.Empty(); proc++ {
 		hash, priority := q.hashQueue.Pop()
 		if p.ignored.Has(hash) {
 			skip[hash.(common.Hash)] = int(priority)
@@ -345,20 +345,12 @@ func (q *queue) Deliver(id string, blocks []*types.Block) (err error) {
 	return nil
 }
 
-// Alloc ensures that the block cache is the correct size, given a starting
-// offset, and a memory cap.
-func (q *queue) Alloc(offset int) {
+// Prepare configures the block cache offset to allow accepting inbound blocks.
+func (q *queue) Prepare(offset int) {
 	q.lock.Lock()
 	defer q.lock.Unlock()
 
 	if q.blockOffset < offset {
 		q.blockOffset = offset
 	}
-	size := len(q.hashPool)
-	if size > blockCacheLimit {
-		size = blockCacheLimit
-	}
-	if len(q.blockCache) < size {
-		q.blockCache = append(q.blockCache, make([]*Block, size-len(q.blockCache))...)
-	}
 }

eth/handler.go

@@ -213,8 +213,8 @@ func (self *ProtocolManager) handleMsg(p *peer) error {
 			return errResp(ErrDecode, "->msg %v: %v", msg, err)
 		}
 
-		if request.Amount > downloader.MaxHashFetch {
-			request.Amount = downloader.MaxHashFetch
+		if request.Amount > uint64(downloader.MaxHashFetch) {
+			request.Amount = uint64(downloader.MaxHashFetch)
 		}
 
 		hashes := self.chainman.GetBlockHashesFromHash(request.Hash, request.Amount)

eth/peer.go

@@ -102,7 +102,7 @@ func (p *peer) sendTransaction(tx *types.Transaction) error {
 
 func (p *peer) requestHashes(from common.Hash) error {
 	glog.V(logger.Debug).Infof("[%s] fetching hashes (%d) %x...\n", p.id, downloader.MaxHashFetch, from[:4])
-	return p2p.Send(p.rw, GetBlockHashesMsg, getBlockHashesMsgData{from, downloader.MaxHashFetch})
+	return p2p.Send(p.rw, GetBlockHashesMsg, getBlockHashesMsgData{from, uint64(downloader.MaxHashFetch)})
 }
 
 func (p *peer) requestBlocks(hashes []common.Hash) error {