Add vendor dir (#16) (#4)

* Add vendor dir so builds dont require dep * Pin specific version go-eth version
2018-01-29 13:44:18 -06:00
parent 82119b3c4b
commit 293dd2e848
4319 changed files with 1448696 additions and 26 deletions
@@ -0,0 +1,736 @@
+// Copyright 2015 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+// Package fetcher contains the block announcement based synchronisation.
+package fetcher
+
+import (
+	"errors"
+	"math/rand"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/consensus"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/log"
+	"gopkg.in/karalabe/cookiejar.v2/collections/prque"
+)
+
+const (
+	arriveTimeout = 500 * time.Millisecond // Time allowance before an announced block is explicitly requested
+	gatherSlack   = 100 * time.Millisecond // Interval used to collate almost-expired announces with fetches
+	fetchTimeout  = 5 * time.Second        // Maximum allotted time to return an explicitly requested block
+	maxUncleDist  = 7                      // Maximum allowed backward distance from the chain head
+	maxQueueDist  = 32                     // Maximum allowed distance from the chain head to queue
+	hashLimit     = 256                    // Maximum number of unique blocks a peer may have announced
+	blockLimit    = 64                     // Maximum number of unique blocks a peer may have delivered
+)
+
+var (
+	errTerminated = errors.New("terminated")
+)
+
+// blockRetrievalFn is a callback type for retrieving a block from the local chain.
+type blockRetrievalFn func(common.Hash) *types.Block
+
+// headerRequesterFn is a callback type for sending a header retrieval request.
+type headerRequesterFn func(common.Hash) error
+
+// bodyRequesterFn is a callback type for sending a body retrieval request.
+type bodyRequesterFn func([]common.Hash) error
+
+// headerVerifierFn is a callback type to verify a block's header for fast propagation.
+type headerVerifierFn func(header *types.Header) error
+
+// blockBroadcasterFn is a callback type for broadcasting a block to connected peers.
+type blockBroadcasterFn func(block *types.Block, propagate bool)
+
+// chainHeightFn is a callback type to retrieve the current chain height.
+type chainHeightFn func() uint64
+
+// chainInsertFn is a callback type to insert a batch of blocks into the local chain.
+type chainInsertFn func(types.Blocks) (int, error)
+
+// peerDropFn is a callback type for dropping a peer detected as malicious.
+type peerDropFn func(id string)
+
+// announce is the hash notification of the availability of a new block in the
+// network.
+type announce struct {
+	hash   common.Hash   // Hash of the block being announced
+	number uint64        // Number of the block being announced (0 = unknown | old protocol)
+	header *types.Header // Header of the block partially reassembled (new protocol)
+	time   time.Time     // Timestamp of the announcement
+
+	origin string // Identifier of the peer originating the notification
+
+	fetchHeader headerRequesterFn // Fetcher function to retrieve the header of an announced block
+	fetchBodies bodyRequesterFn   // Fetcher function to retrieve the body of an announced block
+}
+
+// headerFilterTask represents a batch of headers needing fetcher filtering.
+type headerFilterTask struct {
+	peer    string          // The source peer of block headers
+	headers []*types.Header // Collection of headers to filter
+	time    time.Time       // Arrival time of the headers
+}
+
+// headerFilterTask represents a batch of block bodies (transactions and uncles)
+// needing fetcher filtering.
+type bodyFilterTask struct {
+	peer         string                 // The source peer of block bodies
+	transactions [][]*types.Transaction // Collection of transactions per block bodies
+	uncles       [][]*types.Header      // Collection of uncles per block bodies
+	time         time.Time              // Arrival time of the blocks' contents
+}
+
+// inject represents a schedules import operation.
+type inject struct {
+	origin string
+	block  *types.Block
+}
+
+// Fetcher is responsible for accumulating block announcements from various peers
+// and scheduling them for retrieval.
+type Fetcher struct {
+	// Various event channels
+	notify chan *announce
+	inject chan *inject
+
+	blockFilter  chan chan []*types.Block
+	headerFilter chan chan *headerFilterTask
+	bodyFilter   chan chan *bodyFilterTask
+
+	done chan common.Hash
+	quit chan struct{}
+
+	// Announce states
+	announces  map[string]int              // Per peer announce counts to prevent memory exhaustion
+	announced  map[common.Hash][]*announce // Announced blocks, scheduled for fetching
+	fetching   map[common.Hash]*announce   // Announced blocks, currently fetching
+	fetched    map[common.Hash][]*announce // Blocks with headers fetched, scheduled for body retrieval
+	completing map[common.Hash]*announce   // Blocks with headers, currently body-completing
+
+	// Block cache
+	queue  *prque.Prque            // Queue containing the import operations (block number sorted)
+	queues map[string]int          // Per peer block counts to prevent memory exhaustion
+	queued map[common.Hash]*inject // Set of already queued blocks (to dedup imports)
+
+	// Callbacks
+	getBlock       blockRetrievalFn   // Retrieves a block from the local chain
+	verifyHeader   headerVerifierFn   // Checks if a block's headers have a valid proof of work
+	broadcastBlock blockBroadcasterFn // Broadcasts a block to connected peers
+	chainHeight    chainHeightFn      // Retrieves the current chain's height
+	insertChain    chainInsertFn      // Injects a batch of blocks into the chain
+	dropPeer       peerDropFn         // Drops a peer for misbehaving
+
+	// Testing hooks
+	announceChangeHook func(common.Hash, bool) // Method to call upon adding or deleting a hash from the announce list
+	queueChangeHook    func(common.Hash, bool) // Method to call upon adding or deleting a block from the import queue
+	fetchingHook       func([]common.Hash)     // Method to call upon starting a block (eth/61) or header (eth/62) fetch
+	completingHook     func([]common.Hash)     // Method to call upon starting a block body fetch (eth/62)
+	importedHook       func(*types.Block)      // Method to call upon successful block import (both eth/61 and eth/62)
+}
+
+// New creates a block fetcher to retrieve blocks based on hash announcements.
+func New(getBlock blockRetrievalFn, verifyHeader headerVerifierFn, broadcastBlock blockBroadcasterFn, chainHeight chainHeightFn, insertChain chainInsertFn, dropPeer peerDropFn) *Fetcher {
+	return &Fetcher{
+		notify:         make(chan *announce),
+		inject:         make(chan *inject),
+		blockFilter:    make(chan chan []*types.Block),
+		headerFilter:   make(chan chan *headerFilterTask),
+		bodyFilter:     make(chan chan *bodyFilterTask),
+		done:           make(chan common.Hash),
+		quit:           make(chan struct{}),
+		announces:      make(map[string]int),
+		announced:      make(map[common.Hash][]*announce),
+		fetching:       make(map[common.Hash]*announce),
+		fetched:        make(map[common.Hash][]*announce),
+		completing:     make(map[common.Hash]*announce),
+		queue:          prque.New(),
+		queues:         make(map[string]int),
+		queued:         make(map[common.Hash]*inject),
+		getBlock:       getBlock,
+		verifyHeader:   verifyHeader,
+		broadcastBlock: broadcastBlock,
+		chainHeight:    chainHeight,
+		insertChain:    insertChain,
+		dropPeer:       dropPeer,
+	}
+}
+
+// Start boots up the announcement based synchroniser, accepting and processing
+// hash notifications and block fetches until termination requested.
+func (f *Fetcher) Start() {
+	go f.loop()
+}
+
+// Stop terminates the announcement based synchroniser, canceling all pending
+// operations.
+func (f *Fetcher) Stop() {
+	close(f.quit)
+}
+
+// Notify announces the fetcher of the potential availability of a new block in
+// the network.
+func (f *Fetcher) Notify(peer string, hash common.Hash, number uint64, time time.Time,
+	headerFetcher headerRequesterFn, bodyFetcher bodyRequesterFn) error {
+	block := &announce{
+		hash:        hash,
+		number:      number,
+		time:        time,
+		origin:      peer,
+		fetchHeader: headerFetcher,
+		fetchBodies: bodyFetcher,
+	}
+	select {
+	case f.notify <- block:
+		return nil
+	case <-f.quit:
+		return errTerminated
+	}
+}
+
+// Enqueue tries to fill gaps the the fetcher's future import queue.
+func (f *Fetcher) Enqueue(peer string, block *types.Block) error {
+	op := &inject{
+		origin: peer,
+		block:  block,
+	}
+	select {
+	case f.inject <- op:
+		return nil
+	case <-f.quit:
+		return errTerminated
+	}
+}
+
+// FilterHeaders extracts all the headers that were explicitly requested by the fetcher,
+// returning those that should be handled differently.
+func (f *Fetcher) FilterHeaders(peer string, headers []*types.Header, time time.Time) []*types.Header {
+	log.Trace("Filtering headers", "peer", peer, "headers", len(headers))
+
+	// Send the filter channel to the fetcher
+	filter := make(chan *headerFilterTask)
+
+	select {
+	case f.headerFilter <- filter:
+	case <-f.quit:
+		return nil
+	}
+	// Request the filtering of the header list
+	select {
+	case filter <- &headerFilterTask{peer: peer, headers: headers, time: time}:
+	case <-f.quit:
+		return nil
+	}
+	// Retrieve the headers remaining after filtering
+	select {
+	case task := <-filter:
+		return task.headers
+	case <-f.quit:
+		return nil
+	}
+}
+
+// FilterBodies extracts all the block bodies that were explicitly requested by
+// the fetcher, returning those that should be handled differently.
+func (f *Fetcher) FilterBodies(peer string, transactions [][]*types.Transaction, uncles [][]*types.Header, time time.Time) ([][]*types.Transaction, [][]*types.Header) {
+	log.Trace("Filtering bodies", "peer", peer, "txs", len(transactions), "uncles", len(uncles))
+
+	// Send the filter channel to the fetcher
+	filter := make(chan *bodyFilterTask)
+
+	select {
+	case f.bodyFilter <- filter:
+	case <-f.quit:
+		return nil, nil
+	}
+	// Request the filtering of the body list
+	select {
+	case filter <- &bodyFilterTask{peer: peer, transactions: transactions, uncles: uncles, time: time}:
+	case <-f.quit:
+		return nil, nil
+	}
+	// Retrieve the bodies remaining after filtering
+	select {
+	case task := <-filter:
+		return task.transactions, task.uncles
+	case <-f.quit:
+		return nil, nil
+	}
+}
+
+// Loop is the main fetcher loop, checking and processing various notification
+// events.
+func (f *Fetcher) loop() {
+	// Iterate the block fetching until a quit is requested
+	fetchTimer := time.NewTimer(0)
+	completeTimer := time.NewTimer(0)
+
+	for {
+		// Clean up any expired block fetches
+		for hash, announce := range f.fetching {
+			if time.Since(announce.time) > fetchTimeout {
+				f.forgetHash(hash)
+			}
+		}
+		// Import any queued blocks that could potentially fit
+		height := f.chainHeight()
+		for !f.queue.Empty() {
+			op := f.queue.PopItem().(*inject)
+			if f.queueChangeHook != nil {
+				f.queueChangeHook(op.block.Hash(), false)
+			}
+			// If too high up the chain or phase, continue later
+			number := op.block.NumberU64()
+			if number > height+1 {
+				f.queue.Push(op, -float32(op.block.NumberU64()))
+				if f.queueChangeHook != nil {
+					f.queueChangeHook(op.block.Hash(), true)
+				}
+				break
+			}
+			// Otherwise if fresh and still unknown, try and import
+			hash := op.block.Hash()
+			if number+maxUncleDist < height || f.getBlock(hash) != nil {
+				f.forgetBlock(hash)
+				continue
+			}
+			f.insert(op.origin, op.block)
+		}
+		// Wait for an outside event to occur
+		select {
+		case <-f.quit:
+			// Fetcher terminating, abort all operations
+			return
+
+		case notification := <-f.notify:
+			// A block was announced, make sure the peer isn't DOSing us
+			propAnnounceInMeter.Mark(1)
+
+			count := f.announces[notification.origin] + 1
+			if count > hashLimit {
+				log.Debug("Peer exceeded outstanding announces", "peer", notification.origin, "limit", hashLimit)
+				propAnnounceDOSMeter.Mark(1)
+				break
+			}
+			// If we have a valid block number, check that it's potentially useful
+			if notification.number > 0 {
+				if dist := int64(notification.number) - int64(f.chainHeight()); dist < -maxUncleDist || dist > maxQueueDist {
+					log.Debug("Peer discarded announcement", "peer", notification.origin, "number", notification.number, "hash", notification.hash, "distance", dist)
+					propAnnounceDropMeter.Mark(1)
+					break
+				}
+			}
+			// All is well, schedule the announce if block's not yet downloading
+			if _, ok := f.fetching[notification.hash]; ok {
+				break
+			}
+			if _, ok := f.completing[notification.hash]; ok {
+				break
+			}
+			f.announces[notification.origin] = count
+			f.announced[notification.hash] = append(f.announced[notification.hash], notification)
+			if f.announceChangeHook != nil && len(f.announced[notification.hash]) == 1 {
+				f.announceChangeHook(notification.hash, true)
+			}
+			if len(f.announced) == 1 {
+				f.rescheduleFetch(fetchTimer)
+			}
+
+		case op := <-f.inject:
+			// A direct block insertion was requested, try and fill any pending gaps
+			propBroadcastInMeter.Mark(1)
+			f.enqueue(op.origin, op.block)
+
+		case hash := <-f.done:
+			// A pending import finished, remove all traces of the notification
+			f.forgetHash(hash)
+			f.forgetBlock(hash)
+
+		case <-fetchTimer.C:
+			// At least one block's timer ran out, check for needing retrieval
+			request := make(map[string][]common.Hash)
+
+			for hash, announces := range f.announced {
+				if time.Since(announces[0].time) > arriveTimeout-gatherSlack {
+					// Pick a random peer to retrieve from, reset all others
+					announce := announces[rand.Intn(len(announces))]
+					f.forgetHash(hash)
+
+					// If the block still didn't arrive, queue for fetching
+					if f.getBlock(hash) == nil {
+						request[announce.origin] = append(request[announce.origin], hash)
+						f.fetching[hash] = announce
+					}
+				}
+			}
+			// Send out all block header requests
+			for peer, hashes := range request {
+				log.Trace("Fetching scheduled headers", "peer", peer, "list", hashes)
+
+				// Create a closure of the fetch and schedule in on a new thread
+				fetchHeader, hashes := f.fetching[hashes[0]].fetchHeader, hashes
+				go func() {
+					if f.fetchingHook != nil {
+						f.fetchingHook(hashes)
+					}
+					for _, hash := range hashes {
+						headerFetchMeter.Mark(1)
+						fetchHeader(hash) // Suboptimal, but protocol doesn't allow batch header retrievals
+					}
+				}()
+			}
+			// Schedule the next fetch if blocks are still pending
+			f.rescheduleFetch(fetchTimer)
+
+		case <-completeTimer.C:
+			// At least one header's timer ran out, retrieve everything
+			request := make(map[string][]common.Hash)
+
+			for hash, announces := range f.fetched {
+				// Pick a random peer to retrieve from, reset all others
+				announce := announces[rand.Intn(len(announces))]
+				f.forgetHash(hash)
+
+				// If the block still didn't arrive, queue for completion
+				if f.getBlock(hash) == nil {
+					request[announce.origin] = append(request[announce.origin], hash)
+					f.completing[hash] = announce
+				}
+			}
+			// Send out all block body requests
+			for peer, hashes := range request {
+				log.Trace("Fetching scheduled bodies", "peer", peer, "list", hashes)
+
+				// Create a closure of the fetch and schedule in on a new thread
+				if f.completingHook != nil {
+					f.completingHook(hashes)
+				}
+				bodyFetchMeter.Mark(int64(len(hashes)))
+				go f.completing[hashes[0]].fetchBodies(hashes)
+			}
+			// Schedule the next fetch if blocks are still pending
+			f.rescheduleComplete(completeTimer)
+
+		case filter := <-f.headerFilter:
+			// Headers arrived from a remote peer. Extract those that were explicitly
+			// requested by the fetcher, and return everything else so it's delivered
+			// to other parts of the system.
+			var task *headerFilterTask
+			select {
+			case task = <-filter:
+			case <-f.quit:
+				return
+			}
+			headerFilterInMeter.Mark(int64(len(task.headers)))
+
+			// Split the batch of headers into unknown ones (to return to the caller),
+			// known incomplete ones (requiring body retrievals) and completed blocks.
+			unknown, incomplete, complete := []*types.Header{}, []*announce{}, []*types.Block{}
+			for _, header := range task.headers {
+				hash := header.Hash()
+
+				// Filter fetcher-requested headers from other synchronisation algorithms
+				if announce := f.fetching[hash]; announce != nil && announce.origin == task.peer && f.fetched[hash] == nil && f.completing[hash] == nil && f.queued[hash] == nil {
+					// If the delivered header does not match the promised number, drop the announcer
+					if header.Number.Uint64() != announce.number {
+						log.Trace("Invalid block number fetched", "peer", announce.origin, "hash", header.Hash(), "announced", announce.number, "provided", header.Number)
+						f.dropPeer(announce.origin)
+						f.forgetHash(hash)
+						continue
+					}
+					// Only keep if not imported by other means
+					if f.getBlock(hash) == nil {
+						announce.header = header
+						announce.time = task.time
+
+						// If the block is empty (header only), short circuit into the final import queue
+						if header.TxHash == types.DeriveSha(types.Transactions{}) && header.UncleHash == types.CalcUncleHash([]*types.Header{}) {
+							log.Trace("Block empty, skipping body retrieval", "peer", announce.origin, "number", header.Number, "hash", header.Hash())
+
+							block := types.NewBlockWithHeader(header)
+							block.ReceivedAt = task.time
+
+							complete = append(complete, block)
+							f.completing[hash] = announce
+							continue
+						}
+						// Otherwise add to the list of blocks needing completion
+						incomplete = append(incomplete, announce)
+					} else {
+						log.Trace("Block already imported, discarding header", "peer", announce.origin, "number", header.Number, "hash", header.Hash())
+						f.forgetHash(hash)
+					}
+				} else {
+					// Fetcher doesn't know about it, add to the return list
+					unknown = append(unknown, header)
+				}
+			}
+			headerFilterOutMeter.Mark(int64(len(unknown)))
+			select {
+			case filter <- &headerFilterTask{headers: unknown, time: task.time}:
+			case <-f.quit:
+				return
+			}
+			// Schedule the retrieved headers for body completion
+			for _, announce := range incomplete {
+				hash := announce.header.Hash()
+				if _, ok := f.completing[hash]; ok {
+					continue
+				}
+				f.fetched[hash] = append(f.fetched[hash], announce)
+				if len(f.fetched) == 1 {
+					f.rescheduleComplete(completeTimer)
+				}
+			}
+			// Schedule the header-only blocks for import
+			for _, block := range complete {
+				if announce := f.completing[block.Hash()]; announce != nil {
+					f.enqueue(announce.origin, block)
+				}
+			}
+
+		case filter := <-f.bodyFilter:
+			// Block bodies arrived, extract any explicitly requested blocks, return the rest
+			var task *bodyFilterTask
+			select {
+			case task = <-filter:
+			case <-f.quit:
+				return
+			}
+			bodyFilterInMeter.Mark(int64(len(task.transactions)))
+
+			blocks := []*types.Block{}
+			for i := 0; i < len(task.transactions) && i < len(task.uncles); i++ {
+				// Match up a body to any possible completion request
+				matched := false
+
+				for hash, announce := range f.completing {
+					if f.queued[hash] == nil {
+						txnHash := types.DeriveSha(types.Transactions(task.transactions[i]))
+						uncleHash := types.CalcUncleHash(task.uncles[i])
+
+						if txnHash == announce.header.TxHash && uncleHash == announce.header.UncleHash && announce.origin == task.peer {
+							// Mark the body matched, reassemble if still unknown
+							matched = true
+
+							if f.getBlock(hash) == nil {
+								block := types.NewBlockWithHeader(announce.header).WithBody(task.transactions[i], task.uncles[i])
+								block.ReceivedAt = task.time
+
+								blocks = append(blocks, block)
+							} else {
+								f.forgetHash(hash)
+							}
+						}
+					}
+				}
+				if matched {
+					task.transactions = append(task.transactions[:i], task.transactions[i+1:]...)
+					task.uncles = append(task.uncles[:i], task.uncles[i+1:]...)
+					i--
+					continue
+				}
+			}
+
+			bodyFilterOutMeter.Mark(int64(len(task.transactions)))
+			select {
+			case filter <- task:
+			case <-f.quit:
+				return
+			}
+			// Schedule the retrieved blocks for ordered import
+			for _, block := range blocks {
+				if announce := f.completing[block.Hash()]; announce != nil {
+					f.enqueue(announce.origin, block)
+				}
+			}
+		}
+	}
+}
+
+// rescheduleFetch resets the specified fetch timer to the next announce timeout.
+func (f *Fetcher) rescheduleFetch(fetch *time.Timer) {
+	// Short circuit if no blocks are announced
+	if len(f.announced) == 0 {
+		return
+	}
+	// Otherwise find the earliest expiring announcement
+	earliest := time.Now()
+	for _, announces := range f.announced {
+		if earliest.After(announces[0].time) {
+			earliest = announces[0].time
+		}
+	}
+	fetch.Reset(arriveTimeout - time.Since(earliest))
+}
+
+// rescheduleComplete resets the specified completion timer to the next fetch timeout.
+func (f *Fetcher) rescheduleComplete(complete *time.Timer) {
+	// Short circuit if no headers are fetched
+	if len(f.fetched) == 0 {
+		return
+	}
+	// Otherwise find the earliest expiring announcement
+	earliest := time.Now()
+	for _, announces := range f.fetched {
+		if earliest.After(announces[0].time) {
+			earliest = announces[0].time
+		}
+	}
+	complete.Reset(gatherSlack - time.Since(earliest))
+}
+
+// enqueue schedules a new future import operation, if the block to be imported
+// has not yet been seen.
+func (f *Fetcher) enqueue(peer string, block *types.Block) {
+	hash := block.Hash()
+
+	// Ensure the peer isn't DOSing us
+	count := f.queues[peer] + 1
+	if count > blockLimit {
+		log.Debug("Discarded propagated block, exceeded allowance", "peer", peer, "number", block.Number(), "hash", hash, "limit", blockLimit)
+		propBroadcastDOSMeter.Mark(1)
+		f.forgetHash(hash)
+		return
+	}
+	// Discard any past or too distant blocks
+	if dist := int64(block.NumberU64()) - int64(f.chainHeight()); dist < -maxUncleDist || dist > maxQueueDist {
+		log.Debug("Discarded propagated block, too far away", "peer", peer, "number", block.Number(), "hash", hash, "distance", dist)
+		propBroadcastDropMeter.Mark(1)
+		f.forgetHash(hash)
+		return
+	}
+	// Schedule the block for future importing
+	if _, ok := f.queued[hash]; !ok {
+		op := &inject{
+			origin: peer,
+			block:  block,
+		}
+		f.queues[peer] = count
+		f.queued[hash] = op
+		f.queue.Push(op, -float32(block.NumberU64()))
+		if f.queueChangeHook != nil {
+			f.queueChangeHook(op.block.Hash(), true)
+		}
+		log.Debug("Queued propagated block", "peer", peer, "number", block.Number(), "hash", hash, "queued", f.queue.Size())
+	}
+}
+
+// insert spawns a new goroutine to run a block insertion into the chain. If the
+// block's number is at the same height as the current import phase, if updates
+// the phase states accordingly.
+func (f *Fetcher) insert(peer string, block *types.Block) {
+	hash := block.Hash()
+
+	// Run the import on a new thread
+	log.Debug("Importing propagated block", "peer", peer, "number", block.Number(), "hash", hash)
+	go func() {
+		defer func() { f.done <- hash }()
+
+		// If the parent's unknown, abort insertion
+		parent := f.getBlock(block.ParentHash())
+		if parent == nil {
+			log.Debug("Unknown parent of propagated block", "peer", peer, "number", block.Number(), "hash", hash, "parent", block.ParentHash())
+			return
+		}
+		// Quickly validate the header and propagate the block if it passes
+		switch err := f.verifyHeader(block.Header()); err {
+		case nil:
+			// All ok, quickly propagate to our peers
+			propBroadcastOutTimer.UpdateSince(block.ReceivedAt)
+			go f.broadcastBlock(block, true)
+
+		case consensus.ErrFutureBlock:
+			// Weird future block, don't fail, but neither propagate
+
+		default:
+			// Something went very wrong, drop the peer
+			log.Debug("Propagated block verification failed", "peer", peer, "number", block.Number(), "hash", hash, "err", err)
+			f.dropPeer(peer)
+			return
+		}
+		// Run the actual import and log any issues
+		if _, err := f.insertChain(types.Blocks{block}); err != nil {
+			log.Debug("Propagated block import failed", "peer", peer, "number", block.Number(), "hash", hash, "err", err)
+			return
+		}
+		// If import succeeded, broadcast the block
+		propAnnounceOutTimer.UpdateSince(block.ReceivedAt)
+		go f.broadcastBlock(block, false)
+
+		// Invoke the testing hook if needed
+		if f.importedHook != nil {
+			f.importedHook(block)
+		}
+	}()
+}
+
+// forgetHash removes all traces of a block announcement from the fetcher's
+// internal state.
+func (f *Fetcher) forgetHash(hash common.Hash) {
+	// Remove all pending announces and decrement DOS counters
+	for _, announce := range f.announced[hash] {
+		f.announces[announce.origin]--
+		if f.announces[announce.origin] == 0 {
+			delete(f.announces, announce.origin)
+		}
+	}
+	delete(f.announced, hash)
+	if f.announceChangeHook != nil {
+		f.announceChangeHook(hash, false)
+	}
+	// Remove any pending fetches and decrement the DOS counters
+	if announce := f.fetching[hash]; announce != nil {
+		f.announces[announce.origin]--
+		if f.announces[announce.origin] == 0 {
+			delete(f.announces, announce.origin)
+		}
+		delete(f.fetching, hash)
+	}
+
+	// Remove any pending completion requests and decrement the DOS counters
+	for _, announce := range f.fetched[hash] {
+		f.announces[announce.origin]--
+		if f.announces[announce.origin] == 0 {
+			delete(f.announces, announce.origin)
+		}
+	}
+	delete(f.fetched, hash)
+
+	// Remove any pending completions and decrement the DOS counters
+	if announce := f.completing[hash]; announce != nil {
+		f.announces[announce.origin]--
+		if f.announces[announce.origin] == 0 {
+			delete(f.announces, announce.origin)
+		}
+		delete(f.completing, hash)
+	}
+}
+
+// forgetBlock removes all traces of a queued block from the fetcher's internal
+// state.
+func (f *Fetcher) forgetBlock(hash common.Hash) {
+	if insert := f.queued[hash]; insert != nil {
+		f.queues[insert.origin]--
+		if f.queues[insert.origin] == 0 {
+			delete(f.queues, insert.origin)
+		}
+		delete(f.queued, hash)
+	}
+}
@@ -0,0 +1,789 @@
+// Copyright 2015 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package fetcher
+
+import (
+	"errors"
+	"math/big"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/ethdb"
+	"github.com/ethereum/go-ethereum/params"
+)
+
+var (
+	testdb, _    = ethdb.NewMemDatabase()
+	testKey, _   = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
+	testAddress  = crypto.PubkeyToAddress(testKey.PublicKey)
+	genesis      = core.GenesisBlockForTesting(testdb, testAddress, big.NewInt(1000000000))
+	unknownBlock = types.NewBlock(&types.Header{GasLimit: params.GenesisGasLimit}, nil, nil, nil)
+)
+
+// makeChain creates a chain of n blocks starting at and including parent.
+// the returned hash chain is ordered head->parent. In addition, every 3rd block
+// contains a transaction and every 5th an uncle to allow testing correct block
+// reassembly.
+func makeChain(n int, seed byte, parent *types.Block) ([]common.Hash, map[common.Hash]*types.Block) {
+	blocks, _ := core.GenerateChain(params.TestChainConfig, parent, testdb, n, func(i int, block *core.BlockGen) {
+		block.SetCoinbase(common.Address{seed})
+
+		// If the block number is multiple of 3, send a bonus transaction to the miner
+		if parent == genesis && i%3 == 0 {
+			signer := types.MakeSigner(params.TestChainConfig, block.Number())
+			tx, err := types.SignTx(types.NewTransaction(block.TxNonce(testAddress), common.Address{seed}, big.NewInt(1000), new(big.Int).SetUint64(params.TxGas), nil, nil), signer, testKey)
+			if err != nil {
+				panic(err)
+			}
+			block.AddTx(tx)
+		}
+		// If the block number is a multiple of 5, add a bonus uncle to the block
+		if i%5 == 0 {
+			block.AddUncle(&types.Header{ParentHash: block.PrevBlock(i - 1).Hash(), Number: big.NewInt(int64(i - 1))})
+		}
+	})
+	hashes := make([]common.Hash, n+1)
+	hashes[len(hashes)-1] = parent.Hash()
+	blockm := make(map[common.Hash]*types.Block, n+1)
+	blockm[parent.Hash()] = parent
+	for i, b := range blocks {
+		hashes[len(hashes)-i-2] = b.Hash()
+		blockm[b.Hash()] = b
+	}
+	return hashes, blockm
+}
+
+// fetcherTester is a test simulator for mocking out local block chain.
+type fetcherTester struct {
+	fetcher *Fetcher
+
+	hashes []common.Hash                // Hash chain belonging to the tester
+	blocks map[common.Hash]*types.Block // Blocks belonging to the tester
+	drops  map[string]bool              // Map of peers dropped by the fetcher
+
+	lock sync.RWMutex
+}
+
+// newTester creates a new fetcher test mocker.
+func newTester() *fetcherTester {
+	tester := &fetcherTester{
+		hashes: []common.Hash{genesis.Hash()},
+		blocks: map[common.Hash]*types.Block{genesis.Hash(): genesis},
+		drops:  make(map[string]bool),
+	}
+	tester.fetcher = New(tester.getBlock, tester.verifyHeader, tester.broadcastBlock, tester.chainHeight, tester.insertChain, tester.dropPeer)
+	tester.fetcher.Start()
+
+	return tester
+}
+
+// getBlock retrieves a block from the tester's block chain.
+func (f *fetcherTester) getBlock(hash common.Hash) *types.Block {
+	f.lock.RLock()
+	defer f.lock.RUnlock()
+
+	return f.blocks[hash]
+}
+
+// verifyHeader is a nop placeholder for the block header verification.
+func (f *fetcherTester) verifyHeader(header *types.Header) error {
+	return nil
+}
+
+// broadcastBlock is a nop placeholder for the block broadcasting.
+func (f *fetcherTester) broadcastBlock(block *types.Block, propagate bool) {
+}
+
+// chainHeight retrieves the current height (block number) of the chain.
+func (f *fetcherTester) chainHeight() uint64 {
+	f.lock.RLock()
+	defer f.lock.RUnlock()
+
+	return f.blocks[f.hashes[len(f.hashes)-1]].NumberU64()
+}
+
+// insertChain injects a new blocks into the simulated chain.
+func (f *fetcherTester) insertChain(blocks types.Blocks) (int, error) {
+	f.lock.Lock()
+	defer f.lock.Unlock()
+
+	for i, block := range blocks {
+		// Make sure the parent in known
+		if _, ok := f.blocks[block.ParentHash()]; !ok {
+			return i, errors.New("unknown parent")
+		}
+		// Discard any new blocks if the same height already exists
+		if block.NumberU64() <= f.blocks[f.hashes[len(f.hashes)-1]].NumberU64() {
+			return i, nil
+		}
+		// Otherwise build our current chain
+		f.hashes = append(f.hashes, block.Hash())
+		f.blocks[block.Hash()] = block
+	}
+	return 0, nil
+}
+
+// dropPeer is an emulator for the peer removal, simply accumulating the various
+// peers dropped by the fetcher.
+func (f *fetcherTester) dropPeer(peer string) {
+	f.lock.Lock()
+	defer f.lock.Unlock()
+
+	f.drops[peer] = true
+}
+
+// makeHeaderFetcher retrieves a block header fetcher associated with a simulated peer.
+func (f *fetcherTester) makeHeaderFetcher(peer string, blocks map[common.Hash]*types.Block, drift time.Duration) headerRequesterFn {
+	closure := make(map[common.Hash]*types.Block)
+	for hash, block := range blocks {
+		closure[hash] = block
+	}
+	// Create a function that return a header from the closure
+	return func(hash common.Hash) error {
+		// Gather the blocks to return
+		headers := make([]*types.Header, 0, 1)
+		if block, ok := closure[hash]; ok {
+			headers = append(headers, block.Header())
+		}
+		// Return on a new thread
+		go f.fetcher.FilterHeaders(peer, headers, time.Now().Add(drift))
+
+		return nil
+	}
+}
+
+// makeBodyFetcher retrieves a block body fetcher associated with a simulated peer.
+func (f *fetcherTester) makeBodyFetcher(peer string, blocks map[common.Hash]*types.Block, drift time.Duration) bodyRequesterFn {
+	closure := make(map[common.Hash]*types.Block)
+	for hash, block := range blocks {
+		closure[hash] = block
+	}
+	// Create a function that returns blocks from the closure
+	return func(hashes []common.Hash) error {
+		// Gather the block bodies to return
+		transactions := make([][]*types.Transaction, 0, len(hashes))
+		uncles := make([][]*types.Header, 0, len(hashes))
+
+		for _, hash := range hashes {
+			if block, ok := closure[hash]; ok {
+				transactions = append(transactions, block.Transactions())
+				uncles = append(uncles, block.Uncles())
+			}
+		}
+		// Return on a new thread
+		go f.fetcher.FilterBodies(peer, transactions, uncles, time.Now().Add(drift))
+
+		return nil
+	}
+}
+
+// verifyFetchingEvent verifies that one single event arrive on an fetching channel.
+func verifyFetchingEvent(t *testing.T, fetching chan []common.Hash, arrive bool) {
+	if arrive {
+		select {
+		case <-fetching:
+		case <-time.After(time.Second):
+			t.Fatalf("fetching timeout")
+		}
+	} else {
+		select {
+		case <-fetching:
+			t.Fatalf("fetching invoked")
+		case <-time.After(10 * time.Millisecond):
+		}
+	}
+}
+
+// verifyCompletingEvent verifies that one single event arrive on an completing channel.
+func verifyCompletingEvent(t *testing.T, completing chan []common.Hash, arrive bool) {
+	if arrive {
+		select {
+		case <-completing:
+		case <-time.After(time.Second):
+			t.Fatalf("completing timeout")
+		}
+	} else {
+		select {
+		case <-completing:
+			t.Fatalf("completing invoked")
+		case <-time.After(10 * time.Millisecond):
+		}
+	}
+}
+
+// verifyImportEvent verifies that one single event arrive on an import channel.
+func verifyImportEvent(t *testing.T, imported chan *types.Block, arrive bool) {
+	if arrive {
+		select {
+		case <-imported:
+		case <-time.After(time.Second):
+			t.Fatalf("import timeout")
+		}
+	} else {
+		select {
+		case <-imported:
+			t.Fatalf("import invoked")
+		case <-time.After(10 * time.Millisecond):
+		}
+	}
+}
+
+// verifyImportCount verifies that exactly count number of events arrive on an
+// import hook channel.
+func verifyImportCount(t *testing.T, imported chan *types.Block, count int) {
+	for i := 0; i < count; i++ {
+		select {
+		case <-imported:
+		case <-time.After(time.Second):
+			t.Fatalf("block %d: import timeout", i+1)
+		}
+	}
+	verifyImportDone(t, imported)
+}
+
+// verifyImportDone verifies that no more events are arriving on an import channel.
+func verifyImportDone(t *testing.T, imported chan *types.Block) {
+	select {
+	case <-imported:
+		t.Fatalf("extra block imported")
+	case <-time.After(50 * time.Millisecond):
+	}
+}
+
+// Tests that a fetcher accepts block announcements and initiates retrievals for
+// them, successfully importing into the local chain.
+func TestSequentialAnnouncements62(t *testing.T) { testSequentialAnnouncements(t, 62) }
+func TestSequentialAnnouncements63(t *testing.T) { testSequentialAnnouncements(t, 63) }
+func TestSequentialAnnouncements64(t *testing.T) { testSequentialAnnouncements(t, 64) }
+
+func testSequentialAnnouncements(t *testing.T, protocol int) {
+	// Create a chain of blocks to import
+	targetBlocks := 4 * hashLimit
+	hashes, blocks := makeChain(targetBlocks, 0, genesis)
+
+	tester := newTester()
+	headerFetcher := tester.makeHeaderFetcher("valid", blocks, -gatherSlack)
+	bodyFetcher := tester.makeBodyFetcher("valid", blocks, 0)
+
+	// Iteratively announce blocks until all are imported
+	imported := make(chan *types.Block)
+	tester.fetcher.importedHook = func(block *types.Block) { imported <- block }
+
+	for i := len(hashes) - 2; i >= 0; i-- {
+		tester.fetcher.Notify("valid", hashes[i], uint64(len(hashes)-i-1), time.Now().Add(-arriveTimeout), headerFetcher, bodyFetcher)
+		verifyImportEvent(t, imported, true)
+	}
+	verifyImportDone(t, imported)
+}
+
+// Tests that if blocks are announced by multiple peers (or even the same buggy
+// peer), they will only get downloaded at most once.
+func TestConcurrentAnnouncements62(t *testing.T) { testConcurrentAnnouncements(t, 62) }
+func TestConcurrentAnnouncements63(t *testing.T) { testConcurrentAnnouncements(t, 63) }
+func TestConcurrentAnnouncements64(t *testing.T) { testConcurrentAnnouncements(t, 64) }
+
+func testConcurrentAnnouncements(t *testing.T, protocol int) {
+	// Create a chain of blocks to import
+	targetBlocks := 4 * hashLimit
+	hashes, blocks := makeChain(targetBlocks, 0, genesis)
+
+	// Assemble a tester with a built in counter for the requests
+	tester := newTester()
+	firstHeaderFetcher := tester.makeHeaderFetcher("first", blocks, -gatherSlack)
+	firstBodyFetcher := tester.makeBodyFetcher("first", blocks, 0)
+	secondHeaderFetcher := tester.makeHeaderFetcher("second", blocks, -gatherSlack)
+	secondBodyFetcher := tester.makeBodyFetcher("second", blocks, 0)
+
+	counter := uint32(0)
+	firstHeaderWrapper := func(hash common.Hash) error {
+		atomic.AddUint32(&counter, 1)
+		return firstHeaderFetcher(hash)
+	}
+	secondHeaderWrapper := func(hash common.Hash) error {
+		atomic.AddUint32(&counter, 1)
+		return secondHeaderFetcher(hash)
+	}
+	// Iteratively announce blocks until all are imported
+	imported := make(chan *types.Block)
+	tester.fetcher.importedHook = func(block *types.Block) { imported <- block }
+
+	for i := len(hashes) - 2; i >= 0; i-- {
+		tester.fetcher.Notify("first", hashes[i], uint64(len(hashes)-i-1), time.Now().Add(-arriveTimeout), firstHeaderWrapper, firstBodyFetcher)
+		tester.fetcher.Notify("second", hashes[i], uint64(len(hashes)-i-1), time.Now().Add(-arriveTimeout+time.Millisecond), secondHeaderWrapper, secondBodyFetcher)
+		tester.fetcher.Notify("second", hashes[i], uint64(len(hashes)-i-1), time.Now().Add(-arriveTimeout-time.Millisecond), secondHeaderWrapper, secondBodyFetcher)
+		verifyImportEvent(t, imported, true)
+	}
+	verifyImportDone(t, imported)
+
+	// Make sure no blocks were retrieved twice
+	if int(counter) != targetBlocks {
+		t.Fatalf("retrieval count mismatch: have %v, want %v", counter, targetBlocks)
+	}
+}
+
+// Tests that announcements arriving while a previous is being fetched still
+// results in a valid import.
+func TestOverlappingAnnouncements62(t *testing.T) { testOverlappingAnnouncements(t, 62) }
+func TestOverlappingAnnouncements63(t *testing.T) { testOverlappingAnnouncements(t, 63) }
+func TestOverlappingAnnouncements64(t *testing.T) { testOverlappingAnnouncements(t, 64) }
+
+func testOverlappingAnnouncements(t *testing.T, protocol int) {
+	// Create a chain of blocks to import
+	targetBlocks := 4 * hashLimit
+	hashes, blocks := makeChain(targetBlocks, 0, genesis)
+
+	tester := newTester()
+	headerFetcher := tester.makeHeaderFetcher("valid", blocks, -gatherSlack)
+	bodyFetcher := tester.makeBodyFetcher("valid", blocks, 0)
+
+	// Iteratively announce blocks, but overlap them continuously
+	overlap := 16
+	imported := make(chan *types.Block, len(hashes)-1)
+	for i := 0; i < overlap; i++ {
+		imported <- nil
+	}
+	tester.fetcher.importedHook = func(block *types.Block) { imported <- block }
+
+	for i := len(hashes) - 2; i >= 0; i-- {
+		tester.fetcher.Notify("valid", hashes[i], uint64(len(hashes)-i-1), time.Now().Add(-arriveTimeout), headerFetcher, bodyFetcher)
+		select {
+		case <-imported:
+		case <-time.After(time.Second):
+			t.Fatalf("block %d: import timeout", len(hashes)-i)
+		}
+	}
+	// Wait for all the imports to complete and check count
+	verifyImportCount(t, imported, overlap)
+}
+
+// Tests that announces already being retrieved will not be duplicated.
+func TestPendingDeduplication62(t *testing.T) { testPendingDeduplication(t, 62) }
+func TestPendingDeduplication63(t *testing.T) { testPendingDeduplication(t, 63) }
+func TestPendingDeduplication64(t *testing.T) { testPendingDeduplication(t, 64) }
+
+func testPendingDeduplication(t *testing.T, protocol int) {
+	// Create a hash and corresponding block
+	hashes, blocks := makeChain(1, 0, genesis)
+
+	// Assemble a tester with a built in counter and delayed fetcher
+	tester := newTester()
+	headerFetcher := tester.makeHeaderFetcher("repeater", blocks, -gatherSlack)
+	bodyFetcher := tester.makeBodyFetcher("repeater", blocks, 0)
+
+	delay := 50 * time.Millisecond
+	counter := uint32(0)
+	headerWrapper := func(hash common.Hash) error {
+		atomic.AddUint32(&counter, 1)
+
+		// Simulate a long running fetch
+		go func() {
+			time.Sleep(delay)
+			headerFetcher(hash)
+		}()
+		return nil
+	}
+	// Announce the same block many times until it's fetched (wait for any pending ops)
+	for tester.getBlock(hashes[0]) == nil {
+		tester.fetcher.Notify("repeater", hashes[0], 1, time.Now().Add(-arriveTimeout), headerWrapper, bodyFetcher)
+		time.Sleep(time.Millisecond)
+	}
+	time.Sleep(delay)
+
+	// Check that all blocks were imported and none fetched twice
+	if imported := len(tester.blocks); imported != 2 {
+		t.Fatalf("synchronised block mismatch: have %v, want %v", imported, 2)
+	}
+	if int(counter) != 1 {
+		t.Fatalf("retrieval count mismatch: have %v, want %v", counter, 1)
+	}
+}
+
+// Tests that announcements retrieved in a random order are cached and eventually
+// imported when all the gaps are filled in.
+func TestRandomArrivalImport62(t *testing.T) { testRandomArrivalImport(t, 62) }
+func TestRandomArrivalImport63(t *testing.T) { testRandomArrivalImport(t, 63) }
+func TestRandomArrivalImport64(t *testing.T) { testRandomArrivalImport(t, 64) }
+
+func testRandomArrivalImport(t *testing.T, protocol int) {
+	// Create a chain of blocks to import, and choose one to delay
+	targetBlocks := maxQueueDist
+	hashes, blocks := makeChain(targetBlocks, 0, genesis)
+	skip := targetBlocks / 2
+
+	tester := newTester()
+	headerFetcher := tester.makeHeaderFetcher("valid", blocks, -gatherSlack)
+	bodyFetcher := tester.makeBodyFetcher("valid", blocks, 0)
+
+	// Iteratively announce blocks, skipping one entry
+	imported := make(chan *types.Block, len(hashes)-1)
+	tester.fetcher.importedHook = func(block *types.Block) { imported <- block }
+
+	for i := len(hashes) - 1; i >= 0; i-- {
+		if i != skip {
+			tester.fetcher.Notify("valid", hashes[i], uint64(len(hashes)-i-1), time.Now().Add(-arriveTimeout), headerFetcher, bodyFetcher)
+			time.Sleep(time.Millisecond)
+		}
+	}
+	// Finally announce the skipped entry and check full import
+	tester.fetcher.Notify("valid", hashes[skip], uint64(len(hashes)-skip-1), time.Now().Add(-arriveTimeout), headerFetcher, bodyFetcher)
+	verifyImportCount(t, imported, len(hashes)-1)
+}
+
+// Tests that direct block enqueues (due to block propagation vs. hash announce)
+// are correctly schedule, filling and import queue gaps.
+func TestQueueGapFill62(t *testing.T) { testQueueGapFill(t, 62) }
+func TestQueueGapFill63(t *testing.T) { testQueueGapFill(t, 63) }
+func TestQueueGapFill64(t *testing.T) { testQueueGapFill(t, 64) }
+
+func testQueueGapFill(t *testing.T, protocol int) {
+	// Create a chain of blocks to import, and choose one to not announce at all
+	targetBlocks := maxQueueDist
+	hashes, blocks := makeChain(targetBlocks, 0, genesis)
+	skip := targetBlocks / 2
+
+	tester := newTester()
+	headerFetcher := tester.makeHeaderFetcher("valid", blocks, -gatherSlack)
+	bodyFetcher := tester.makeBodyFetcher("valid", blocks, 0)
+
+	// Iteratively announce blocks, skipping one entry
+	imported := make(chan *types.Block, len(hashes)-1)
+	tester.fetcher.importedHook = func(block *types.Block) { imported <- block }
+
+	for i := len(hashes) - 1; i >= 0; i-- {
+		if i != skip {
+			tester.fetcher.Notify("valid", hashes[i], uint64(len(hashes)-i-1), time.Now().Add(-arriveTimeout), headerFetcher, bodyFetcher)
+			time.Sleep(time.Millisecond)
+		}
+	}
+	// Fill the missing block directly as if propagated
+	tester.fetcher.Enqueue("valid", blocks[hashes[skip]])
+	verifyImportCount(t, imported, len(hashes)-1)
+}
+
+// Tests that blocks arriving from various sources (multiple propagations, hash
+// announces, etc) do not get scheduled for import multiple times.
+func TestImportDeduplication62(t *testing.T) { testImportDeduplication(t, 62) }
+func TestImportDeduplication63(t *testing.T) { testImportDeduplication(t, 63) }
+func TestImportDeduplication64(t *testing.T) { testImportDeduplication(t, 64) }
+
+func testImportDeduplication(t *testing.T, protocol int) {
+	// Create two blocks to import (one for duplication, the other for stalling)
+	hashes, blocks := makeChain(2, 0, genesis)
+
+	// Create the tester and wrap the importer with a counter
+	tester := newTester()
+	headerFetcher := tester.makeHeaderFetcher("valid", blocks, -gatherSlack)
+	bodyFetcher := tester.makeBodyFetcher("valid", blocks, 0)
+
+	counter := uint32(0)
+	tester.fetcher.insertChain = func(blocks types.Blocks) (int, error) {
+		atomic.AddUint32(&counter, uint32(len(blocks)))
+		return tester.insertChain(blocks)
+	}
+	// Instrument the fetching and imported events
+	fetching := make(chan []common.Hash)
+	imported := make(chan *types.Block, len(hashes)-1)
+	tester.fetcher.fetchingHook = func(hashes []common.Hash) { fetching <- hashes }
+	tester.fetcher.importedHook = func(block *types.Block) { imported <- block }
+
+	// Announce the duplicating block, wait for retrieval, and also propagate directly
+	tester.fetcher.Notify("valid", hashes[0], 1, time.Now().Add(-arriveTimeout), headerFetcher, bodyFetcher)
+	<-fetching
+
+	tester.fetcher.Enqueue("valid", blocks[hashes[0]])
+	tester.fetcher.Enqueue("valid", blocks[hashes[0]])
+	tester.fetcher.Enqueue("valid", blocks[hashes[0]])
+
+	// Fill the missing block directly as if propagated, and check import uniqueness
+	tester.fetcher.Enqueue("valid", blocks[hashes[1]])
+	verifyImportCount(t, imported, 2)
+
+	if counter != 2 {
+		t.Fatalf("import invocation count mismatch: have %v, want %v", counter, 2)
+	}
+}
+
+// Tests that blocks with numbers much lower or higher than out current head get
+// discarded to prevent wasting resources on useless blocks from faulty peers.
+func TestDistantPropagationDiscarding(t *testing.T) {
+	// Create a long chain to import and define the discard boundaries
+	hashes, blocks := makeChain(3*maxQueueDist, 0, genesis)
+	head := hashes[len(hashes)/2]
+
+	low, high := len(hashes)/2+maxUncleDist+1, len(hashes)/2-maxQueueDist-1
+
+	// Create a tester and simulate a head block being the middle of the above chain
+	tester := newTester()
+
+	tester.lock.Lock()
+	tester.hashes = []common.Hash{head}
+	tester.blocks = map[common.Hash]*types.Block{head: blocks[head]}
+	tester.lock.Unlock()
+
+	// Ensure that a block with a lower number than the threshold is discarded
+	tester.fetcher.Enqueue("lower", blocks[hashes[low]])
+	time.Sleep(10 * time.Millisecond)
+	if !tester.fetcher.queue.Empty() {
+		t.Fatalf("fetcher queued stale block")
+	}
+	// Ensure that a block with a higher number than the threshold is discarded
+	tester.fetcher.Enqueue("higher", blocks[hashes[high]])
+	time.Sleep(10 * time.Millisecond)
+	if !tester.fetcher.queue.Empty() {
+		t.Fatalf("fetcher queued future block")
+	}
+}
+
+// Tests that announcements with numbers much lower or higher than out current
+// head get discarded to prevent wasting resources on useless blocks from faulty
+// peers.
+func TestDistantAnnouncementDiscarding62(t *testing.T) { testDistantAnnouncementDiscarding(t, 62) }
+func TestDistantAnnouncementDiscarding63(t *testing.T) { testDistantAnnouncementDiscarding(t, 63) }
+func TestDistantAnnouncementDiscarding64(t *testing.T) { testDistantAnnouncementDiscarding(t, 64) }
+
+func testDistantAnnouncementDiscarding(t *testing.T, protocol int) {
+	// Create a long chain to import and define the discard boundaries
+	hashes, blocks := makeChain(3*maxQueueDist, 0, genesis)
+	head := hashes[len(hashes)/2]
+
+	low, high := len(hashes)/2+maxUncleDist+1, len(hashes)/2-maxQueueDist-1
+
+	// Create a tester and simulate a head block being the middle of the above chain
+	tester := newTester()
+
+	tester.lock.Lock()
+	tester.hashes = []common.Hash{head}
+	tester.blocks = map[common.Hash]*types.Block{head: blocks[head]}
+	tester.lock.Unlock()
+
+	headerFetcher := tester.makeHeaderFetcher("lower", blocks, -gatherSlack)
+	bodyFetcher := tester.makeBodyFetcher("lower", blocks, 0)
+
+	fetching := make(chan struct{}, 2)
+	tester.fetcher.fetchingHook = func(hashes []common.Hash) { fetching <- struct{}{} }
+
+	// Ensure that a block with a lower number than the threshold is discarded
+	tester.fetcher.Notify("lower", hashes[low], blocks[hashes[low]].NumberU64(), time.Now().Add(-arriveTimeout), headerFetcher, bodyFetcher)
+	select {
+	case <-time.After(50 * time.Millisecond):
+	case <-fetching:
+		t.Fatalf("fetcher requested stale header")
+	}
+	// Ensure that a block with a higher number than the threshold is discarded
+	tester.fetcher.Notify("higher", hashes[high], blocks[hashes[high]].NumberU64(), time.Now().Add(-arriveTimeout), headerFetcher, bodyFetcher)
+	select {
+	case <-time.After(50 * time.Millisecond):
+	case <-fetching:
+		t.Fatalf("fetcher requested future header")
+	}
+}
+
+// Tests that peers announcing blocks with invalid numbers (i.e. not matching
+// the headers provided afterwards) get dropped as malicious.
+func TestInvalidNumberAnnouncement62(t *testing.T) { testInvalidNumberAnnouncement(t, 62) }
+func TestInvalidNumberAnnouncement63(t *testing.T) { testInvalidNumberAnnouncement(t, 63) }
+func TestInvalidNumberAnnouncement64(t *testing.T) { testInvalidNumberAnnouncement(t, 64) }
+
+func testInvalidNumberAnnouncement(t *testing.T, protocol int) {
+	// Create a single block to import and check numbers against
+	hashes, blocks := makeChain(1, 0, genesis)
+
+	tester := newTester()
+	badHeaderFetcher := tester.makeHeaderFetcher("bad", blocks, -gatherSlack)
+	badBodyFetcher := tester.makeBodyFetcher("bad", blocks, 0)
+
+	imported := make(chan *types.Block)
+	tester.fetcher.importedHook = func(block *types.Block) { imported <- block }
+
+	// Announce a block with a bad number, check for immediate drop
+	tester.fetcher.Notify("bad", hashes[0], 2, time.Now().Add(-arriveTimeout), badHeaderFetcher, badBodyFetcher)
+	verifyImportEvent(t, imported, false)
+
+	tester.lock.RLock()
+	dropped := tester.drops["bad"]
+	tester.lock.RUnlock()
+
+	if !dropped {
+		t.Fatalf("peer with invalid numbered announcement not dropped")
+	}
+
+	goodHeaderFetcher := tester.makeHeaderFetcher("good", blocks, -gatherSlack)
+	goodBodyFetcher := tester.makeBodyFetcher("good", blocks, 0)
+	// Make sure a good announcement passes without a drop
+	tester.fetcher.Notify("good", hashes[0], 1, time.Now().Add(-arriveTimeout), goodHeaderFetcher, goodBodyFetcher)
+	verifyImportEvent(t, imported, true)
+
+	tester.lock.RLock()
+	dropped = tester.drops["good"]
+	tester.lock.RUnlock()
+
+	if dropped {
+		t.Fatalf("peer with valid numbered announcement dropped")
+	}
+	verifyImportDone(t, imported)
+}
+
+// Tests that if a block is empty (i.e. header only), no body request should be
+// made, and instead the header should be assembled into a whole block in itself.
+func TestEmptyBlockShortCircuit62(t *testing.T) { testEmptyBlockShortCircuit(t, 62) }
+func TestEmptyBlockShortCircuit63(t *testing.T) { testEmptyBlockShortCircuit(t, 63) }
+func TestEmptyBlockShortCircuit64(t *testing.T) { testEmptyBlockShortCircuit(t, 64) }
+
+func testEmptyBlockShortCircuit(t *testing.T, protocol int) {
+	// Create a chain of blocks to import
+	hashes, blocks := makeChain(32, 0, genesis)
+
+	tester := newTester()
+	headerFetcher := tester.makeHeaderFetcher("valid", blocks, -gatherSlack)
+	bodyFetcher := tester.makeBodyFetcher("valid", blocks, 0)
+
+	// Add a monitoring hook for all internal events
+	fetching := make(chan []common.Hash)
+	tester.fetcher.fetchingHook = func(hashes []common.Hash) { fetching <- hashes }
+
+	completing := make(chan []common.Hash)
+	tester.fetcher.completingHook = func(hashes []common.Hash) { completing <- hashes }
+
+	imported := make(chan *types.Block)
+	tester.fetcher.importedHook = func(block *types.Block) { imported <- block }
+
+	// Iteratively announce blocks until all are imported
+	for i := len(hashes) - 2; i >= 0; i-- {
+		tester.fetcher.Notify("valid", hashes[i], uint64(len(hashes)-i-1), time.Now().Add(-arriveTimeout), headerFetcher, bodyFetcher)
+
+		// All announces should fetch the header
+		verifyFetchingEvent(t, fetching, true)
+
+		// Only blocks with data contents should request bodies
+		verifyCompletingEvent(t, completing, len(blocks[hashes[i]].Transactions()) > 0 || len(blocks[hashes[i]].Uncles()) > 0)
+
+		// Irrelevant of the construct, import should succeed
+		verifyImportEvent(t, imported, true)
+	}
+	verifyImportDone(t, imported)
+}
+
+// Tests that a peer is unable to use unbounded memory with sending infinite
+// block announcements to a node, but that even in the face of such an attack,
+// the fetcher remains operational.
+func TestHashMemoryExhaustionAttack62(t *testing.T) { testHashMemoryExhaustionAttack(t, 62) }
+func TestHashMemoryExhaustionAttack63(t *testing.T) { testHashMemoryExhaustionAttack(t, 63) }
+func TestHashMemoryExhaustionAttack64(t *testing.T) { testHashMemoryExhaustionAttack(t, 64) }
+
+func testHashMemoryExhaustionAttack(t *testing.T, protocol int) {
+	// Create a tester with instrumented import hooks
+	tester := newTester()
+
+	imported, announces := make(chan *types.Block), int32(0)
+	tester.fetcher.importedHook = func(block *types.Block) { imported <- block }
+	tester.fetcher.announceChangeHook = func(hash common.Hash, added bool) {
+		if added {
+			atomic.AddInt32(&announces, 1)
+		} else {
+			atomic.AddInt32(&announces, -1)
+		}
+	}
+	// Create a valid chain and an infinite junk chain
+	targetBlocks := hashLimit + 2*maxQueueDist
+	hashes, blocks := makeChain(targetBlocks, 0, genesis)
+	validHeaderFetcher := tester.makeHeaderFetcher("valid", blocks, -gatherSlack)
+	validBodyFetcher := tester.makeBodyFetcher("valid", blocks, 0)
+
+	attack, _ := makeChain(targetBlocks, 0, unknownBlock)
+	attackerHeaderFetcher := tester.makeHeaderFetcher("attacker", nil, -gatherSlack)
+	attackerBodyFetcher := tester.makeBodyFetcher("attacker", nil, 0)
+
+	// Feed the tester a huge hashset from the attacker, and a limited from the valid peer
+	for i := 0; i < len(attack); i++ {
+		if i < maxQueueDist {
+			tester.fetcher.Notify("valid", hashes[len(hashes)-2-i], uint64(i+1), time.Now(), validHeaderFetcher, validBodyFetcher)
+		}
+		tester.fetcher.Notify("attacker", attack[i], 1 /* don't distance drop */, time.Now(), attackerHeaderFetcher, attackerBodyFetcher)
+	}
+	if count := atomic.LoadInt32(&announces); count != hashLimit+maxQueueDist {
+		t.Fatalf("queued announce count mismatch: have %d, want %d", count, hashLimit+maxQueueDist)
+	}
+	// Wait for fetches to complete
+	verifyImportCount(t, imported, maxQueueDist)
+
+	// Feed the remaining valid hashes to ensure DOS protection state remains clean
+	for i := len(hashes) - maxQueueDist - 2; i >= 0; i-- {
+		tester.fetcher.Notify("valid", hashes[i], uint64(len(hashes)-i-1), time.Now().Add(-arriveTimeout), validHeaderFetcher, validBodyFetcher)
+		verifyImportEvent(t, imported, true)
+	}
+	verifyImportDone(t, imported)
+}
+
+// Tests that blocks sent to the fetcher (either through propagation or via hash
+// announces and retrievals) don't pile up indefinitely, exhausting available
+// system memory.
+func TestBlockMemoryExhaustionAttack(t *testing.T) {
+	// Create a tester with instrumented import hooks
+	tester := newTester()
+
+	imported, enqueued := make(chan *types.Block), int32(0)
+	tester.fetcher.importedHook = func(block *types.Block) { imported <- block }
+	tester.fetcher.queueChangeHook = func(hash common.Hash, added bool) {
+		if added {
+			atomic.AddInt32(&enqueued, 1)
+		} else {
+			atomic.AddInt32(&enqueued, -1)
+		}
+	}
+	// Create a valid chain and a batch of dangling (but in range) blocks
+	targetBlocks := hashLimit + 2*maxQueueDist
+	hashes, blocks := makeChain(targetBlocks, 0, genesis)
+	attack := make(map[common.Hash]*types.Block)
+	for i := byte(0); len(attack) < blockLimit+2*maxQueueDist; i++ {
+		hashes, blocks := makeChain(maxQueueDist-1, i, unknownBlock)
+		for _, hash := range hashes[:maxQueueDist-2] {
+			attack[hash] = blocks[hash]
+		}
+	}
+	// Try to feed all the attacker blocks make sure only a limited batch is accepted
+	for _, block := range attack {
+		tester.fetcher.Enqueue("attacker", block)
+	}
+	time.Sleep(200 * time.Millisecond)
+	if queued := atomic.LoadInt32(&enqueued); queued != blockLimit {
+		t.Fatalf("queued block count mismatch: have %d, want %d", queued, blockLimit)
+	}
+	// Queue up a batch of valid blocks, and check that a new peer is allowed to do so
+	for i := 0; i < maxQueueDist-1; i++ {
+		tester.fetcher.Enqueue("valid", blocks[hashes[len(hashes)-3-i]])
+	}
+	time.Sleep(100 * time.Millisecond)
+	if queued := atomic.LoadInt32(&enqueued); queued != blockLimit+maxQueueDist-1 {
+		t.Fatalf("queued block count mismatch: have %d, want %d", queued, blockLimit+maxQueueDist-1)
+	}
+	// Insert the missing piece (and sanity check the import)
+	tester.fetcher.Enqueue("valid", blocks[hashes[len(hashes)-2]])
+	verifyImportCount(t, imported, maxQueueDist)
+
+	// Insert the remaining blocks in chunks to ensure clean DOS protection
+	for i := maxQueueDist; i < len(hashes)-1; i++ {
+		tester.fetcher.Enqueue("valid", blocks[hashes[len(hashes)-2-i]])
+		verifyImportEvent(t, imported, true)
+	}
+	verifyImportDone(t, imported)
+}
@@ -0,0 +1,43 @@
+// Copyright 2015 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+// Contains the metrics collected by the fetcher.
+
+package fetcher
+
+import (
+	"github.com/ethereum/go-ethereum/metrics"
+)
+
+var (
+	propAnnounceInMeter   = metrics.NewMeter("eth/fetcher/prop/announces/in")
+	propAnnounceOutTimer  = metrics.NewTimer("eth/fetcher/prop/announces/out")
+	propAnnounceDropMeter = metrics.NewMeter("eth/fetcher/prop/announces/drop")
+	propAnnounceDOSMeter  = metrics.NewMeter("eth/fetcher/prop/announces/dos")
+
+	propBroadcastInMeter   = metrics.NewMeter("eth/fetcher/prop/broadcasts/in")
+	propBroadcastOutTimer  = metrics.NewTimer("eth/fetcher/prop/broadcasts/out")
+	propBroadcastDropMeter = metrics.NewMeter("eth/fetcher/prop/broadcasts/drop")
+	propBroadcastDOSMeter  = metrics.NewMeter("eth/fetcher/prop/broadcasts/dos")
+
+	headerFetchMeter = metrics.NewMeter("eth/fetcher/fetch/headers")
+	bodyFetchMeter   = metrics.NewMeter("eth/fetcher/fetch/bodies")
+
+	headerFilterInMeter  = metrics.NewMeter("eth/fetcher/filter/headers/in")
+	headerFilterOutMeter = metrics.NewMeter("eth/fetcher/filter/headers/out")
+	bodyFilterInMeter    = metrics.NewMeter("eth/fetcher/filter/bodies/in")
+	bodyFilterOutMeter   = metrics.NewMeter("eth/fetcher/filter/bodies/out")
+)