eth: port the synchronisation algo to eth/62

cmd/utils/flags.go

@@ -140,7 +140,7 @@ var (
 	}
 	EthVersionFlag = cli.IntFlag{
 		Name:  "eth",
-		Value: 61,
+		Value: 62,
 		Usage: "Highest eth protocol to advertise (temporary, dev option)",
 	}
 

core/types/block.go

@@ -357,6 +357,20 @@ func (b *Block) WithMiningResult(nonce uint64, mixDigest common.Hash) *Block {
 	}
 }
 
+// WithBody returns a new block with the given transaction and uncle contents.
+func (b *Block) WithBody(transactions []*Transaction, uncles []*Header) *Block {
+	block := &Block{
+		header:       copyHeader(b.header),
+		transactions: make([]*Transaction, len(transactions)),
+		uncles:       make([]*Header, len(uncles)),
+	}
+	copy(block.transactions, transactions)
+	for i := range uncles {
+		block.uncles[i] = copyHeader(uncles[i])
+	}
+	return block
+}
+
 // Implement pow.Block
 
 func (b *Block) Hash() common.Hash {

eth/downloader/downloader.go

@@ -26,12 +26,10 @@ import (
 	"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/event"
 	"github.com/ethereum/go-ethereum/logger"
 	"github.com/ethereum/go-ethereum/logger/glog"
-	"gopkg.in/fatih/set.v0"
 )
 
 const (
@@ -40,40 +38,44 @@ const (
 )
 
 var (
-	MinHashFetch     = 512 // Minimum amount of hashes to not consider a peer stalling
 	MaxHashFetch     = 512 // Amount of hashes to be fetched per retrieval request
 	MaxBlockFetch    = 128 // Amount of blocks to be fetched per retrieval request
-	MaxHeaderFetch   = 256 // Amount of block headers to be fetched per retrieval request
+	MaxHeaderFetch   = 192 // Amount of block headers to be fetched per retrieval request
+	MaxBodyFetch     = 128 // Amount of block bodies to be fetched per retrieval request
 	MaxStateFetch    = 384 // Amount of node state values to allow fetching per request
 	MaxReceiptsFetch = 384 // Amount of transaction receipts to allow fetching per request
 
-	hashTTL         = 5 * time.Second  // Time it takes for a hash request to time out
+	hashTTL      = 5 * time.Second  // [eth/61] Time it takes for a hash request to time out
-	blockSoftTTL    = 3 * time.Second  // Request completion threshold for increasing or decreasing a peer's bandwidth
+	blockSoftTTL = 3 * time.Second  // [eth/61] Request completion threshold for increasing or decreasing a peer's bandwidth
-	blockHardTTL    = 3 * blockSoftTTL // Maximum time allowance before a block request is considered expired
+	blockHardTTL = 3 * blockSoftTTL // [eth/61] Maximum time allowance before a block request is considered expired
-	crossCheckCycle = time.Second      // Period after which to check for expired cross checks
+	headerTTL    = 5 * time.Second  // [eth/62] Time it takes for a header request to time out
+	bodySoftTTL  = 3 * time.Second  // [eth/62] Request completion threshold for increasing or decreasing a peer's bandwidth
+	bodyHardTTL  = 3 * bodySoftTTL  // [eth/62] Maximum time allowance before a block body request is considered expired
 
-	maxQueuedHashes = 256 * 1024 // Maximum number of hashes to queue for import (DOS protection)
+	maxQueuedHashes  = 256 * 1024 // [eth/61] Maximum number of hashes to queue for import (DOS protection)
-	maxBannedHashes = 4096       // Number of bannable hashes before phasing old ones out
+	maxQueuedHeaders = 256 * 1024 // [eth/62] Maximum number of headers to queue for import (DOS protection)
-	maxBlockProcess = 256        // Number of blocks to import at once into the chain
+	maxBlockProcess  = 256        // Number of blocks to import at once into the chain
 )
 
 var (
-	errBusy             = errors.New("busy")
+	errBusy              = errors.New("busy")
-	errUnknownPeer      = errors.New("peer is unknown or unhealthy")
+	errUnknownPeer       = errors.New("peer is unknown or unhealthy")
-	errBadPeer          = errors.New("action from bad peer ignored")
+	errBadPeer           = errors.New("action from bad peer ignored")
-	errStallingPeer     = errors.New("peer is stalling")
+	errStallingPeer      = errors.New("peer is stalling")
-	errBannedHead       = errors.New("peer head hash already banned")
+	errNoPeers           = errors.New("no peers to keep download active")
-	errNoPeers          = errors.New("no peers to keep download active")
+	errPendingQueue      = errors.New("pending items in queue")
-	errPendingQueue     = errors.New("pending items in queue")
+	errTimeout           = errors.New("timeout")
-	errTimeout          = errors.New("timeout")
+	errEmptyHashSet      = errors.New("empty hash set by peer")
-	errEmptyHashSet     = errors.New("empty hash set by peer")
+	errEmptyHeaderSet    = errors.New("empty header set by peer")
-	errPeersUnavailable = errors.New("no peers available or all peers tried for block download process")
+	errPeersUnavailable  = errors.New("no peers available or all peers tried for block download process")
-	errAlreadyInPool    = errors.New("hash already in pool")
+	errAlreadyInPool     = errors.New("hash already in pool")
-	errInvalidChain     = errors.New("retrieved hash chain is invalid")
+	errInvalidChain      = errors.New("retrieved hash chain is invalid")
-	errCrossCheckFailed = errors.New("block cross-check failed")
+	errInvalidBody       = errors.New("retrieved block body is invalid")
-	errCancelHashFetch  = errors.New("hash fetching canceled (requested)")
+	errCancelHashFetch   = errors.New("hash fetching canceled (requested)")
-	errCancelBlockFetch = errors.New("block downloading canceled (requested)")
+	errCancelBlockFetch  = errors.New("block downloading canceled (requested)")
-	errNoSyncActive     = errors.New("no sync active")
+	errCancelHeaderFetch = errors.New("block header fetching canceled (requested)")
+	errCancelBodyFetch   = errors.New("block body downloading canceled (requested)")
+	errNoSyncActive      = errors.New("no sync active")
 )
 
 // hashCheckFn is a callback type for verifying a hash's presence in the local chain.
@@ -91,28 +93,36 @@ type chainInsertFn func(types.Blocks) (int, error)
 // peerDropFn is a callback type for dropping a peer detected as malicious.
 type peerDropFn func(id string)
 
-type blockPack struct {
+// hashPack is a batch of block hashes returned by a peer (eth/61).
-	peerId string
-	blocks []*types.Block
-}
-
 type hashPack struct {
 	peerId string
 	hashes []common.Hash
 }
 
-type crossCheck struct {
+// blockPack is a batch of blocks returned by a peer (eth/61).
-	expire time.Time
+type blockPack struct {
-	parent common.Hash
+	peerId string
+	blocks []*types.Block
+}
+
+// headerPack is a batch of block headers returned by a peer.
+type headerPack struct {
+	peerId  string
+	headers []*types.Header
+}
+
+// bodyPack is a batch of block bodies returned by a peer.
+type bodyPack struct {
+	peerId       string
+	transactions [][]*types.Transaction
+	uncles       [][]*types.Header
 }
 
 type Downloader struct {
 	mux *event.TypeMux
 
-	queue  *queue                      // Scheduler for selecting the hashes to download
+	queue *queue   // Scheduler for selecting the hashes to download
-	peers  *peerSet                    // Set of active peers from which download can proceed
+	peers *peerSet // Set of active peers from which download can proceed
-	checks map[common.Hash]*crossCheck // Pending cross checks to verify a hash chain
-	banned *set.Set                    // Set of hashes we've received and banned
 
 	interrupt int32 // Atomic boolean to signal termination
 
@@ -137,12 +147,18 @@ type Downloader struct {
 
 	// Channels
 	newPeerCh chan *peer
-	hashCh    chan hashPack  // Channel receiving inbound hashes
+	hashCh    chan hashPack   // [eth/61] Channel receiving inbound hashes
-	blockCh   chan blockPack // Channel receiving inbound blocks
+	blockCh   chan blockPack  // [eth/61] Channel receiving inbound blocks
-	processCh chan bool      // Channel to signal the block fetcher of new or finished work
+	headerCh  chan headerPack // [eth/62] Channel receiving inbound block headers
+	bodyCh    chan bodyPack   // [eth/62] Channel receiving inbound block bodies
+	processCh chan bool       // Channel to signal the block fetcher of new or finished work
 
 	cancelCh   chan struct{} // Channel to cancel mid-flight syncs
 	cancelLock sync.RWMutex  // Lock to protect the cancel channel in delivers
+
+	// Testing hooks
+	bodyFetchHook   func([]*types.Header) // Method to call upon starting a block body fetch
+	chainInsertHook func([]*Block)        // Method to call upon inserting a chain of blocks (possibly in multiple invocations)
 }
 
 // Block is an origin-tagged blockchain block.
@@ -153,8 +169,7 @@ type Block struct {
 
 // New creates a new downloader to fetch hashes and blocks from remote peers.
 func New(mux *event.TypeMux, hasBlock hashCheckFn, getBlock blockRetrievalFn, headBlock headRetrievalFn, insertChain chainInsertFn, dropPeer peerDropFn) *Downloader {
-	// Create the base downloader
+	return &Downloader{
-	downloader := &Downloader{
 		mux:         mux,
 		queue:       newQueue(),
 		peers:       newPeerSet(),
@@ -166,14 +181,10 @@ func New(mux *event.TypeMux, hasBlock hashCheckFn, getBlock blockRetrievalFn, he
 		newPeerCh:   make(chan *peer, 1),
 		hashCh:      make(chan hashPack, 1),
 		blockCh:     make(chan blockPack, 1),
+		headerCh:    make(chan headerPack, 1),
+		bodyCh:      make(chan bodyPack, 1),
 		processCh:   make(chan bool, 1),
 	}
-	// Inject all the known bad hashes
-	downloader.banned = set.New()
-	for hash, _ := range core.BadHashes {
-		downloader.banned.Add(hash)
-	}
-	return downloader
 }
 
 // Stats retrieves the current status of the downloader.
@@ -206,15 +217,12 @@ func (d *Downloader) Synchronising() bool {
 
 // RegisterPeer injects a new download peer into the set of block source to be
 // used for fetching hashes and blocks from.
-func (d *Downloader) RegisterPeer(id string, version int, head common.Hash, getRelHashes relativeHashFetcherFn, getAbsHashes absoluteHashFetcherFn, getBlocks blockFetcherFn) error {
+func (d *Downloader) RegisterPeer(id string, version int, head common.Hash,
-	// If the peer wants to send a banned hash, reject
+	getRelHashes relativeHashFetcherFn, getAbsHashes absoluteHashFetcherFn, getBlocks blockFetcherFn, // eth/61 callbacks, remove when upgrading
-	if d.banned.Has(head) {
+	getRelHeaders relativeHeaderFetcherFn, getAbsHeaders absoluteHeaderFetcherFn, getBlockBodies blockBodyFetcherFn) error {
-		glog.V(logger.Debug).Infoln("Register rejected, head hash banned:", id)
+
-		return errBannedHead
-	}
-	// Otherwise try to construct and register the peer
 	glog.V(logger.Detail).Infoln("Registering peer", id)
-	if err := d.peers.Register(newPeer(id, version, head, getRelHashes, getAbsHashes, getBlocks)); err != nil {
+	if err := d.peers.Register(newPeer(id, version, head, getRelHashes, getAbsHashes, getBlocks, getRelHeaders, getAbsHeaders, getBlockBodies)); err != nil {
 		glog.V(logger.Error).Infoln("Register failed:", err)
 		return err
 	}
@@ -235,7 +243,7 @@ func (d *Downloader) UnregisterPeer(id string) error {
 // Synchronise tries to sync up our local block chain with a remote peer, both
 // adding various sanity checks as well as wrapping it with various log entries.
 func (d *Downloader) Synchronise(id string, head common.Hash, td *big.Int) {
-	glog.V(logger.Detail).Infof("Attempting synchronisation: %v, head 0x%x, TD %v", id, head[:4], td)
+	glog.V(logger.Detail).Infof("Attempting synchronisation: %v, head [%x…], TD %v", id, head[:4], td)
 
 	switch err := d.synchronise(id, head, td); err {
 	case nil:
@@ -244,7 +252,7 @@ func (d *Downloader) Synchronise(id string, head common.Hash, td *big.Int) {
 	case errBusy:
 		glog.V(logger.Detail).Infof("Synchronisation already in progress")
 
-	case errTimeout, errBadPeer, errStallingPeer, errBannedHead, errEmptyHashSet, errPeersUnavailable, errInvalidChain, errCrossCheckFailed:
+	case errTimeout, errBadPeer, errStallingPeer, errEmptyHashSet, errEmptyHeaderSet, errPeersUnavailable, errInvalidChain:
 		glog.V(logger.Debug).Infof("Removing peer %v: %v", id, err)
 		d.dropPeer(id)
 
@@ -270,10 +278,6 @@ func (d *Downloader) synchronise(id string, hash common.Hash, td *big.Int) error
 	}
 	defer atomic.StoreInt32(&d.synchronising, 0)
 
-	// If the head hash is banned, terminate immediately
-	if d.banned.Has(hash) {
-		return errBannedHead
-	}
 	// Post a user notification of the sync (only once per session)
 	if atomic.CompareAndSwapInt32(&d.notified, 0, 1) {
 		glog.V(logger.Info).Infoln("Block synchronisation started")
@@ -285,7 +289,6 @@ func (d *Downloader) synchronise(id string, hash common.Hash, td *big.Int) error
 	// Reset the queue and peer set to clean any internal leftover state
 	d.queue.Reset()
 	d.peers.Reset()
-	d.checks = make(map[common.Hash]*crossCheck)
 
 	// Create cancel channel for aborting mid-flight
 	d.cancelLock.Lock()
@@ -320,17 +323,37 @@ func (d *Downloader) syncWithPeer(p *peer, hash common.Hash, td *big.Int) (err e
 		}
 	}()
 
-	glog.V(logger.Debug).Infof("Synchronizing with the network using: %s, eth/%d", p.id, p.version)
+	glog.V(logger.Debug).Infof("Synchronising with the network using: %s [eth/%d]", p.id, p.version)
-	switch p.version {
+	defer glog.V(logger.Debug).Infof("Synchronisation terminated")
-	case eth61:
+
+	switch {
+	case p.version == eth61:
 		// Old eth/61, use forward, concurrent hash and block retrieval algorithm
+		number, err := d.findAncestor61(p)
+		if err != nil {
+			return err
+		}
+		errc := make(chan error, 2)
+		go func() { errc <- d.fetchHashes61(p, td, number+1) }()
+		go func() { errc <- d.fetchBlocks61(number + 1) }()
+
+		// If any fetcher fails, cancel the other
+		if err := <-errc; err != nil {
+			d.cancel()
+			<-errc
+			return err
+		}
+		return <-errc
+
+	case p.version >= eth62:
+		// New eth/62, use forward, concurrent header and block body retrieval algorithm
 		number, err := d.findAncestor(p)
 		if err != nil {
 			return err
 		}
 		errc := make(chan error, 2)
-		go func() { errc <- d.fetchHashes(p, td, number+1) }()
+		go func() { errc <- d.fetchHeaders(p, td, number+1) }()
-		go func() { errc <- d.fetchBlocks(number + 1) }()
+		go func() { errc <- d.fetchBodies(number + 1) }()
 
 		// If any fetcher fails, cancel the other
 		if err := <-errc; err != nil {
@@ -373,17 +396,17 @@ func (d *Downloader) Terminate() {
 	d.cancel()
 }
 
-// findAncestor tries to locate the common ancestor block of the local chain and
+// findAncestor61 tries to locate the common ancestor block of the local chain and
 // a remote peers blockchain. In the general case when our node was in sync and
 // on the correct chain, checking the top N blocks should already get us a match.
-// In the rare scenario when we ended up on a long soft fork (i.e. none of the
+// In the rare scenario when we ended up on a long reorganization (i.e. none of
-// head blocks match), we do a binary search to find the common ancestor.
+// the head blocks match), we do a binary search to find the common ancestor.
-func (d *Downloader) findAncestor(p *peer) (uint64, error) {
+func (d *Downloader) findAncestor61(p *peer) (uint64, error) {
 	glog.V(logger.Debug).Infof("%v: looking for common ancestor", p)
 
 	// Request out head blocks to short circuit ancestor location
 	head := d.headBlock().NumberU64()
-	from := int64(head) - int64(MaxHashFetch)
+	from := int64(head) - int64(MaxHashFetch) + 1
 	if from < 0 {
 		from = 0
 	}
@@ -422,6 +445,12 @@ func (d *Downloader) findAncestor(p *peer) (uint64, error) {
 		case <-d.blockCh:
 			// Out of bounds blocks received, ignore them
 
+		case <-d.headerCh:
+			// Out of bounds eth/62 block headers received, ignore them
+
+		case <-d.bodyCh:
+			// Out of bounds eth/62 block bodies received, ignore them
+
 		case <-timeout:
 			glog.V(logger.Debug).Infof("%v: head hash timeout", p)
 			return 0, errTimeout
@@ -429,7 +458,7 @@ func (d *Downloader) findAncestor(p *peer) (uint64, error) {
 	}
 	// If the head fetch already found an ancestor, return
 	if !common.EmptyHash(hash) {
-		glog.V(logger.Debug).Infof("%v: common ancestor: #%d [%x]", p, number, hash[:4])
+		glog.V(logger.Debug).Infof("%v: common ancestor: #%d [%x…]", p, number, hash[:4])
 		return number, nil
 	}
 	// Ancestor not found, we need to binary search over our chain
@@ -468,7 +497,7 @@ func (d *Downloader) findAncestor(p *peer) (uint64, error) {
 					break
 				}
 				if block.NumberU64() != check {
-					glog.V(logger.Debug).Infof("%v: non requested hash #%d [%x], instead of #%d", p, block.NumberU64(), block.Hash().Bytes()[:4], check)
+					glog.V(logger.Debug).Infof("%v: non requested hash #%d [%x…], instead of #%d", p, block.NumberU64(), block.Hash().Bytes()[:4], check)
 					return 0, errBadPeer
 				}
 				start = check
@@ -476,6 +505,12 @@ func (d *Downloader) findAncestor(p *peer) (uint64, error) {
 			case <-d.blockCh:
 				// Out of bounds blocks received, ignore them
 
+			case <-d.headerCh:
+				// Out of bounds eth/62 block headers received, ignore them
+
+			case <-d.bodyCh:
+				// Out of bounds eth/62 block bodies received, ignore them
+
 			case <-timeout:
 				glog.V(logger.Debug).Infof("%v: search hash timeout", p)
 				return 0, errTimeout
@@ -485,9 +520,9 @@ func (d *Downloader) findAncestor(p *peer) (uint64, error) {
 	return start, nil
 }
 
-// fetchHashes keeps retrieving hashes from the requested number, until no more
+// fetchHashes61 keeps retrieving hashes from the requested number, until no more
 // are returned, potentially throttling on the way.
-func (d *Downloader) fetchHashes(p *peer, td *big.Int, from uint64) error {
+func (d *Downloader) fetchHashes61(p *peer, td *big.Int, from uint64) error {
 	glog.V(logger.Debug).Infof("%v: downloading hashes from #%d", p, from)
 
 	// Create a timeout timer, and the associated hash fetcher
@@ -510,6 +545,12 @@ func (d *Downloader) fetchHashes(p *peer, td *big.Int, from uint64) error {
 		case <-d.cancelCh:
 			return errCancelHashFetch
 
+		case <-d.headerCh:
+			// Out of bounds eth/62 block headers received, ignore them
+
+		case <-d.bodyCh:
+			// Out of bounds eth/62 block bodies received, ignore them
+
 		case hashPack := <-d.hashCh:
 			// Make sure the active peer is giving us the hashes
 			if hashPack.peerId != p.id {
@@ -548,7 +589,7 @@ func (d *Downloader) fetchHashes(p *peer, td *big.Int, from uint64) error {
 			// Otherwise insert all the new hashes, aborting in case of junk
 			glog.V(logger.Detail).Infof("%v: inserting %d hashes from #%d", p, len(hashPack.hashes), from)
 
-			inserts := d.queue.Insert(hashPack.hashes, true)
+			inserts := d.queue.Insert61(hashPack.hashes, true)
 			if len(inserts) != len(hashPack.hashes) {
 				glog.V(logger.Debug).Infof("%v: stale hashes", p)
 				return errBadPeer
@@ -573,10 +614,10 @@ func (d *Downloader) fetchHashes(p *peer, td *big.Int, from uint64) error {
 	}
 }
 
-// fetchBlocks iteratively downloads the scheduled hashes, taking any available
+// fetchBlocks61 iteratively downloads the scheduled hashes, taking any available
 // peers, reserving a chunk of blocks for each, waiting for delivery and also
 // periodically checking for timeouts.
-func (d *Downloader) fetchBlocks(from uint64) error {
+func (d *Downloader) fetchBlocks61(from uint64) error {
 	glog.V(logger.Debug).Infof("Downloading blocks from #%d", from)
 	defer glog.V(logger.Debug).Infof("Block download terminated")
 
@@ -595,24 +636,30 @@ func (d *Downloader) fetchBlocks(from uint64) error {
 		case <-d.cancelCh:
 			return errCancelBlockFetch
 
+		case <-d.headerCh:
+			// Out of bounds eth/62 block headers received, ignore them
+
+		case <-d.bodyCh:
+			// Out of bounds eth/62 block bodies received, ignore them
+
 		case blockPack := <-d.blockCh:
 			// If the peer was previously banned and failed to deliver it's pack
 			// in a reasonable time frame, ignore it's message.
 			if peer := d.peers.Peer(blockPack.peerId); peer != nil {
 				// Deliver the received chunk of blocks, and demote in case of errors
-				err := d.queue.Deliver(blockPack.peerId, blockPack.blocks)
+				err := d.queue.Deliver61(blockPack.peerId, blockPack.blocks)
 				switch err {
 				case nil:
 					// If no blocks were delivered, demote the peer (need the delivery above)
 					if len(blockPack.blocks) == 0 {
 						peer.Demote()
-						peer.SetIdle()
+						peer.SetIdle61()
 						glog.V(logger.Detail).Infof("%s: no blocks delivered", peer)
 						break
 					}
 					// All was successful, promote the peer and potentially start processing
 					peer.Promote()
-					peer.SetIdle()
+					peer.SetIdle61()
 					glog.V(logger.Detail).Infof("%s: delivered %d blocks", peer, len(blockPack.blocks))
 					go d.process()
 
@@ -624,7 +671,7 @@ func (d *Downloader) fetchBlocks(from uint64) error {
 					// Peer probably timed out with its delivery but came through
 					// in the end, demote, but allow to to pull from this peer.
 					peer.Demote()
-					peer.SetIdle()
+					peer.SetIdle61()
 					glog.V(logger.Detail).Infof("%s: out of bound delivery", peer)
 
 				case errStaleDelivery:
@@ -638,7 +685,7 @@ func (d *Downloader) fetchBlocks(from uint64) error {
 				default:
 					// Peer did something semi-useful, demote but keep it around
 					peer.Demote()
-					peer.SetIdle()
+					peer.SetIdle61()
 					glog.V(logger.Detail).Infof("%s: delivery partially failed: %v", peer, err)
 					go d.process()
 				}
@@ -696,7 +743,7 @@ func (d *Downloader) fetchBlocks(from uint64) error {
 				// Reserve a chunk of hashes for a peer. A nil can mean either that
 				// no more hashes are available, or that the peer is known not to
 				// have them.
-				request := d.queue.Reserve(peer, peer.Capacity())
+				request := d.queue.Reserve61(peer, peer.Capacity())
 				if request == nil {
 					continue
 				}
@@ -704,7 +751,7 @@ func (d *Downloader) fetchBlocks(from uint64) error {
 					glog.Infof("%s: requesting %d blocks", peer, len(request.Hashes))
 				}
 				// Fetch the chunk and make sure any errors return the hashes to the queue
-				if err := peer.Fetch(request); err != nil {
+				if err := peer.Fetch61(request); err != nil {
 					glog.V(logger.Error).Infof("%v: fetch failed, rescheduling", peer)
 					d.queue.Cancel(request)
 				}
@@ -718,6 +765,401 @@ func (d *Downloader) fetchBlocks(from uint64) error {
 	}
 }
 
+// findAncestor tries to locate the common ancestor block of the local chain and
+// a remote peers blockchain. In the general case when our node was in sync and
+// on the correct chain, checking the top N blocks should already get us a match.
+// In the rare scenario when we ended up on a long reorganization (i.e. none of
+// the head blocks match), we do a binary search to find the common ancestor.
+func (d *Downloader) findAncestor(p *peer) (uint64, error) {
+	glog.V(logger.Debug).Infof("%v: looking for common ancestor", p)
+
+	// Request our head blocks to short circuit ancestor location
+	head := d.headBlock().NumberU64()
+	from := int64(head) - int64(MaxHeaderFetch) + 1
+	if from < 0 {
+		from = 0
+	}
+	go p.getAbsHeaders(uint64(from), MaxHeaderFetch, 0, false)
+
+	// Wait for the remote response to the head fetch
+	number, hash := uint64(0), common.Hash{}
+	timeout := time.After(hashTTL)
+
+	for finished := false; !finished; {
+		select {
+		case <-d.cancelCh:
+			return 0, errCancelHashFetch
+
+		case headerPack := <-d.headerCh:
+			// Discard anything not from the origin peer
+			if headerPack.peerId != p.id {
+				glog.V(logger.Debug).Infof("Received headers from incorrect peer(%s)", headerPack.peerId)
+				break
+			}
+			// Make sure the peer actually gave something valid
+			headers := headerPack.headers
+			if len(headers) == 0 {
+				glog.V(logger.Debug).Infof("%v: empty head header set", p)
+				return 0, errEmptyHeaderSet
+			}
+			// Check if a common ancestor was found
+			finished = true
+			for i := len(headers) - 1; i >= 0; i-- {
+				if d.hasBlock(headers[i].Hash()) {
+					number, hash = headers[i].Number.Uint64(), headers[i].Hash()
+					break
+				}
+			}
+
+		case <-d.bodyCh:
+			// Out of bounds block bodies received, ignore them
+
+		case <-d.hashCh:
+			// Out of bounds eth/61 hashes received, ignore them
+
+		case <-d.blockCh:
+			// Out of bounds eth/61 blocks received, ignore them
+
+		case <-timeout:
+			glog.V(logger.Debug).Infof("%v: head header timeout", p)
+			return 0, errTimeout
+		}
+	}
+	// If the head fetch already found an ancestor, return
+	if !common.EmptyHash(hash) {
+		glog.V(logger.Debug).Infof("%v: common ancestor: #%d [%x…]", p, number, hash[:4])
+		return number, nil
+	}
+	// Ancestor not found, we need to binary search over our chain
+	start, end := uint64(0), head
+	for start+1 < end {
+		// Split our chain interval in two, and request the hash to cross check
+		check := (start + end) / 2
+
+		timeout := time.After(hashTTL)
+		go p.getAbsHeaders(uint64(check), 1, 0, false)
+
+		// Wait until a reply arrives to this request
+		for arrived := false; !arrived; {
+			select {
+			case <-d.cancelCh:
+				return 0, errCancelHashFetch
+
+			case headerPack := <-d.headerCh:
+				// Discard anything not from the origin peer
+				if headerPack.peerId != p.id {
+					glog.V(logger.Debug).Infof("Received headers from incorrect peer(%s)", headerPack.peerId)
+					break
+				}
+				// Make sure the peer actually gave something valid
+				headers := headerPack.headers
+				if len(headers) != 1 {
+					glog.V(logger.Debug).Infof("%v: invalid search header set (%d)", p, len(headers))
+					return 0, errBadPeer
+				}
+				arrived = true
+
+				// Modify the search interval based on the response
+				block := d.getBlock(headers[0].Hash())
+				if block == nil {
+					end = check
+					break
+				}
+				if block.NumberU64() != check {
+					glog.V(logger.Debug).Infof("%v: non requested header #%d [%x…], instead of #%d", p, block.NumberU64(), block.Hash().Bytes()[:4], check)
+					return 0, errBadPeer
+				}
+				start = check
+
+			case <-d.bodyCh:
+				// Out of bounds block bodies received, ignore them
+
+			case <-d.hashCh:
+				// Out of bounds eth/61 hashes received, ignore them
+
+			case <-d.blockCh:
+				// Out of bounds eth/61 blocks received, ignore them
+
+			case <-timeout:
+				glog.V(logger.Debug).Infof("%v: search header timeout", p)
+				return 0, errTimeout
+			}
+		}
+	}
+	return start, nil
+}
+
+// fetchHeaders keeps retrieving headers from the requested number, until no more
+// are returned, potentially throttling on the way.
+func (d *Downloader) fetchHeaders(p *peer, td *big.Int, from uint64) error {
+	glog.V(logger.Debug).Infof("%v: downloading headers from #%d", p, from)
+	defer glog.V(logger.Debug).Infof("%v: header download terminated", p)
+
+	// Create a timeout timer, and the associated hash fetcher
+	timeout := time.NewTimer(0) // timer to dump a non-responsive active peer
+	<-timeout.C                 // timeout channel should be initially empty
+	defer timeout.Stop()
+
+	getHeaders := func(from uint64) {
+		glog.V(logger.Detail).Infof("%v: fetching %d headers from #%d", p, MaxHeaderFetch, from)
+
+		go p.getAbsHeaders(from, MaxHeaderFetch, 0, false)
+		timeout.Reset(headerTTL)
+	}
+	// Start pulling headers, until all are exhausted
+	getHeaders(from)
+	gotHeaders := false
+
+	for {
+		select {
+		case <-d.cancelCh:
+			return errCancelHeaderFetch
+
+		case <-d.hashCh:
+			// Out of bounds eth/61 hashes received, ignore them
+
+		case <-d.blockCh:
+			// Out of bounds eth/61 blocks received, ignore them
+
+		case headerPack := <-d.headerCh:
+			// Make sure the active peer is giving us the headers
+			if headerPack.peerId != p.id {
+				glog.V(logger.Debug).Infof("Received headers from incorrect peer (%s)", headerPack.peerId)
+				break
+			}
+			timeout.Stop()
+
+			// If no more headers are inbound, notify the body fetcher and return
+			if len(headerPack.headers) == 0 {
+				glog.V(logger.Debug).Infof("%v: no available headers", p)
+
+				select {
+				case d.processCh <- false:
+				case <-d.cancelCh:
+				}
+				// If no headers were retrieved at all, the peer violated it's TD promise that it had a
+				// better chain compared to ours. The only exception is if it's promised blocks were
+				// already imported by other means (e.g. fecher):
+				//
+				// R <remote peer>, L <local node>: Both at block 10
+				// R: Mine block 11, and propagate it to L
+				// L: Queue block 11 for import
+				// L: Notice that R's head and TD increased compared to ours, start sync
+				// L: Import of block 11 finishes
+				// L: Sync begins, and finds common ancestor at 11
+				// L: Request new headers up from 11 (R's TD was higher, it must have something)
+				// R: Nothing to give
+				if !gotHeaders && td.Cmp(d.headBlock().Td) > 0 {
+					return errStallingPeer
+				}
+				return nil
+			}
+			gotHeaders = true
+
+			// Otherwise insert all the new headers, aborting in case of junk
+			glog.V(logger.Detail).Infof("%v: inserting %d headers from #%d", p, len(headerPack.headers), from)
+
+			inserts := d.queue.Insert(headerPack.headers)
+			if len(inserts) != len(headerPack.headers) {
+				glog.V(logger.Debug).Infof("%v: stale headers", p)
+				return errBadPeer
+			}
+			// Notify the block fetcher of new headers, but stop if queue is full
+			cont := d.queue.Pending() < maxQueuedHeaders
+			select {
+			case d.processCh <- cont:
+			default:
+			}
+			if !cont {
+				return nil
+			}
+			// Queue not yet full, fetch the next batch
+			from += uint64(len(headerPack.headers))
+			getHeaders(from)
+
+		case <-timeout.C:
+			// Header retrieval timed out, consider the peer bad and drop
+			glog.V(logger.Debug).Infof("%v: header request timed out", p)
+			d.dropPeer(p.id)
+
+			// Finish the sync gracefully instead of dumping the gathered data though
+			select {
+			case d.processCh <- false:
+			default:
+			}
+			return nil
+		}
+	}
+}
+
+// fetchBodies iteratively downloads the scheduled block bodies, taking any
+// available peers, reserving a chunk of blocks for each, waiting for delivery
+// and also periodically checking for timeouts.
+func (d *Downloader) fetchBodies(from uint64) error {
+	glog.V(logger.Debug).Infof("Downloading block bodies from #%d", from)
+	defer glog.V(logger.Debug).Infof("Block body download terminated")
+
+	// Create a timeout timer for scheduling expiration tasks
+	ticker := time.NewTicker(100 * time.Millisecond)
+	defer ticker.Stop()
+
+	update := make(chan struct{}, 1)
+
+	// Prepare the queue and fetch block bodies until the block header fetcher's done
+	d.queue.Prepare(from)
+	finished := false
+
+	for {
+		select {
+		case <-d.cancelCh:
+			return errCancelBlockFetch
+
+		case <-d.hashCh:
+			// Out of bounds eth/61 hashes received, ignore them
+
+		case <-d.blockCh:
+			// Out of bounds eth/61 blocks received, ignore them
+
+		case bodyPack := <-d.bodyCh:
+			// If the peer was previously banned and failed to deliver it's pack
+			// in a reasonable time frame, ignore it's message.
+			if peer := d.peers.Peer(bodyPack.peerId); peer != nil {
+				// Deliver the received chunk of bodies, and demote in case of errors
+				err := d.queue.Deliver(bodyPack.peerId, bodyPack.transactions, bodyPack.uncles)
+				switch err {
+				case nil:
+					// If no blocks were delivered, demote the peer (need the delivery above)
+					if len(bodyPack.transactions) == 0 || len(bodyPack.uncles) == 0 {
+						peer.Demote()
+						peer.SetIdle()
+						glog.V(logger.Detail).Infof("%s: no block bodies delivered", peer)
+						break
+					}
+					// All was successful, promote the peer and potentially start processing
+					peer.Promote()
+					peer.SetIdle()
+					glog.V(logger.Detail).Infof("%s: delivered %d:%d block bodies", peer, len(bodyPack.transactions), len(bodyPack.uncles))
+					go d.process()
+
+				case errInvalidChain:
+					// The hash chain is invalid (blocks are not ordered properly), abort
+					return err
+
+				case errInvalidBody:
+					// The peer delivered something very bad, drop immediately
+					glog.V(logger.Error).Infof("%s: delivered invalid block, dropping", peer)
+					d.dropPeer(peer.id)
+
+				case errNoFetchesPending:
+					// Peer probably timed out with its delivery but came through
+					// in the end, demote, but allow to to pull from this peer.
+					peer.Demote()
+					peer.SetIdle()
+					glog.V(logger.Detail).Infof("%s: out of bound delivery", peer)
+
+				case errStaleDelivery:
+					// Delivered something completely else than requested, usually
+					// caused by a timeout and delivery during a new sync cycle.
+					// Don't set it to idle as the original request should still be
+					// in flight.
+					peer.Demote()
+					glog.V(logger.Detail).Infof("%s: stale delivery", peer)
+
+				default:
+					// Peer did something semi-useful, demote but keep it around
+					peer.Demote()
+					peer.SetIdle()
+					glog.V(logger.Detail).Infof("%s: delivery partially failed: %v", peer, err)
+					go d.process()
+				}
+			}
+			// Blocks assembled, try to update the progress
+			select {
+			case update <- struct{}{}:
+			default:
+			}
+
+		case cont := <-d.processCh:
+			// The header fetcher sent a continuation flag, check if it's done
+			if !cont {
+				finished = true
+			}
+			// Headers arrive, try to update the progress
+			select {
+			case update <- struct{}{}:
+			default:
+			}
+
+		case <-ticker.C:
+			// Sanity check update the progress
+			select {
+			case update <- struct{}{}:
+			default:
+			}
+
+		case <-update:
+			// Short circuit if we lost all our peers
+			if d.peers.Len() == 0 {
+				return errNoPeers
+			}
+			// Check for block body request timeouts and demote the responsible peers
+			for _, pid := range d.queue.Expire(bodyHardTTL) {
+				if peer := d.peers.Peer(pid); peer != nil {
+					peer.Demote()
+					glog.V(logger.Detail).Infof("%s: block body delivery timeout", peer)
+				}
+			}
+			// If there's noting more to fetch, wait or terminate
+			if d.queue.Pending() == 0 {
+				if d.queue.InFlight() == 0 && finished {
+					glog.V(logger.Debug).Infof("Block body fetching completed")
+					return nil
+				}
+				break
+			}
+			// Send a download request to all idle peers, until throttled
+			queuedEmptyBlocks, throttled := false, false
+			for _, peer := range d.peers.IdlePeers() {
+				// Short circuit if throttling activated
+				if d.queue.Throttle() {
+					throttled = true
+					break
+				}
+				// Reserve a chunk of hashes for a peer. A nil can mean either that
+				// no more hashes are available, or that the peer is known not to
+				// have them.
+				request, process, err := d.queue.Reserve(peer, peer.Capacity())
+				if err != nil {
+					return err
+				}
+				if process {
+					queuedEmptyBlocks = true
+					go d.process()
+				}
+				if request == nil {
+					continue
+				}
+				if glog.V(logger.Detail) {
+					glog.Infof("%s: requesting %d block bodies", peer, len(request.Headers))
+				}
+				// Fetch the chunk and make sure any errors return the hashes to the queue
+				if d.bodyFetchHook != nil {
+					d.bodyFetchHook(request.Headers)
+				}
+				if err := peer.Fetch(request); err != nil {
+					glog.V(logger.Error).Infof("%v: fetch failed, rescheduling", peer)
+					d.queue.Cancel(request)
+				}
+			}
+			// Make sure that we have peers available for fetching. If all peers have been tried
+			// and all failed throw an error
+			if !queuedEmptyBlocks && !throttled && d.queue.InFlight() == 0 {
+				return errPeersUnavailable
+			}
+		}
+	}
+}
+
 // process takes blocks from the queue and tries to import them into the chain.
 //
 // The algorithmic flow is as follows:
@@ -763,6 +1205,9 @@ func (d *Downloader) process() {
 		if len(blocks) == 0 {
 			return
 		}
+		if d.chainInsertHook != nil {
+			d.chainInsertHook(blocks)
+		}
 		// Reset the import statistics
 		d.importLock.Lock()
 		d.importStart = time.Now()
@@ -796,9 +1241,31 @@ func (d *Downloader) process() {
 	}
 }
 
-// DeliverBlocks injects a new batch of blocks received from a remote node.
+// DeliverHashes61 injects a new batch of hashes received from a remote node into
+// the download schedule. This is usually invoked through the BlockHashesMsg by
+// the protocol handler.
+func (d *Downloader) DeliverHashes61(id string, hashes []common.Hash) error {
+	// Make sure the downloader is active
+	if atomic.LoadInt32(&d.synchronising) == 0 {
+		return errNoSyncActive
+	}
+	// Deliver or abort if the sync is canceled while queuing
+	d.cancelLock.RLock()
+	cancel := d.cancelCh
+	d.cancelLock.RUnlock()
+
+	select {
+	case d.hashCh <- hashPack{id, hashes}:
+		return nil
+
+	case <-cancel:
+		return errNoSyncActive
+	}
+}
+
+// DeliverBlocks61 injects a new batch of blocks received from a remote node.
 // This is usually invoked through the BlocksMsg by the protocol handler.
-func (d *Downloader) DeliverBlocks(id string, blocks []*types.Block) error {
+func (d *Downloader) DeliverBlocks61(id string, blocks []*types.Block) error {
 	// Make sure the downloader is active
 	if atomic.LoadInt32(&d.synchronising) == 0 {
 		return errNoSyncActive
@@ -817,10 +1284,9 @@ func (d *Downloader) DeliverBlocks(id string, blocks []*types.Block) error {
 	}
 }
 
-// DeliverHashes injects a new batch of hashes received from a remote node into
+// DeliverHeaders injects a new batch of blck headers received from a remote
-// the download schedule. This is usually invoked through the BlockHashesMsg by
+// node into the download schedule.
-// the protocol handler.
+func (d *Downloader) DeliverHeaders(id string, headers []*types.Header) error {
-func (d *Downloader) DeliverHashes(id string, hashes []common.Hash) error {
 	// Make sure the downloader is active
 	if atomic.LoadInt32(&d.synchronising) == 0 {
 		return errNoSyncActive
@@ -831,7 +1297,27 @@ func (d *Downloader) DeliverHashes(id string, hashes []common.Hash) error {
 	d.cancelLock.RUnlock()
 
 	select {
-	case d.hashCh <- hashPack{id, hashes}:
+	case d.headerCh <- headerPack{id, headers}:
+		return nil
+
+	case <-cancel:
+		return errNoSyncActive
+	}
+}
+
+// DeliverBodies injects a new batch of block bodies received from a remote node.
+func (d *Downloader) DeliverBodies(id string, transactions [][]*types.Transaction, uncles [][]*types.Header) error {
+	// Make sure the downloader is active
+	if atomic.LoadInt32(&d.synchronising) == 0 {
+		return errNoSyncActive
+	}
+	// Deliver or abort if the sync is canceled while queuing
+	d.cancelLock.RLock()
+	cancel := d.cancelCh
+	d.cancelLock.RUnlock()
+
+	select {
+	case d.bodyCh <- bodyPack{id, transactions, uncles}:
 		return nil
 
 	case <-cancel:

eth/downloader/downloader_test.go

@@ -27,20 +27,39 @@ import (
 	"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/event"
+	"github.com/ethereum/go-ethereum/params"
 )
 
 var (
-	testdb, _ = ethdb.NewMemDatabase()
+	testdb, _   = ethdb.NewMemDatabase()
-	genesis   = core.GenesisBlockForTesting(testdb, common.Address{}, big.NewInt(0))
+	testKey, _  = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
+	testAddress = crypto.PubkeyToAddress(testKey.PublicKey)
+	genesis     = core.GenesisBlockForTesting(testdb, testAddress, big.NewInt(1000000000))
 )
 
-// makeChain creates a chain of n blocks starting at but not including
+// makeChain creates a chain of n blocks starting at and including parent.
-// parent. the returned hash chain is ordered head->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(parent, testdb, n, func(i int, gen *core.BlockGen) {
+	blocks := core.GenerateChain(parent, testdb, n, func(i int, block *core.BlockGen) {
-		gen.SetCoinbase(common.Address{seed})
+		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 {
+			tx, err := types.NewTransaction(block.TxNonce(testAddress), common.Address{seed}, big.NewInt(1000), params.TxGas, nil, nil).SignECDSA(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()
@@ -78,8 +97,6 @@ type downloadTester struct {
 	ownBlocks  map[common.Hash]*types.Block            // Blocks belonging to the tester
 	peerHashes map[string][]common.Hash                // Hash chain belonging to different test peers
 	peerBlocks map[string]map[common.Hash]*types.Block // Blocks belonging to different test peers
-
-	maxHashFetch int // Overrides the maximum number of retrieved hashes
 }
 
 // newTester creates a new downloader test mocker.
@@ -156,7 +173,9 @@ func (dl *downloadTester) newPeer(id string, version int, hashes []common.Hash,
 // specific delay time on processing the network packets sent to it, simulating
 // potentially slow network IO.
 func (dl *downloadTester) newSlowPeer(id string, version int, hashes []common.Hash, blocks map[common.Hash]*types.Block, delay time.Duration) error {
-	err := dl.downloader.RegisterPeer(id, version, hashes[0], dl.peerGetRelHashesFn(id, delay), dl.peerGetAbsHashesFn(id, version, delay), dl.peerGetBlocksFn(id, delay))
+	err := dl.downloader.RegisterPeer(id, version, hashes[0],
+		dl.peerGetRelHashesFn(id, delay), dl.peerGetAbsHashesFn(id, delay), dl.peerGetBlocksFn(id, delay),
+		nil, dl.peerGetAbsHeadersFn(id, delay), dl.peerGetBodiesFn(id, delay))
 	if err == nil {
 		// Assign the owned hashes and blocks to the peer (deep copy)
 		dl.peerHashes[id] = make([]common.Hash, len(hashes))
@@ -184,13 +203,9 @@ func (dl *downloadTester) peerGetRelHashesFn(id string, delay time.Duration) fun
 	return func(head common.Hash) error {
 		time.Sleep(delay)
 
-		limit := MaxHashFetch
-		if dl.maxHashFetch > 0 {
-			limit = dl.maxHashFetch
-		}
 		// Gather the next batch of hashes
 		hashes := dl.peerHashes[id]
-		result := make([]common.Hash, 0, limit)
+		result := make([]common.Hash, 0, MaxHashFetch)
 		for i, hash := range hashes {
 			if hash == head {
 				i++
@@ -204,7 +219,7 @@ func (dl *downloadTester) peerGetRelHashesFn(id string, delay time.Duration) fun
 		// Delay delivery a bit to allow attacks to unfold
 		go func() {
 			time.Sleep(time.Millisecond)
-			dl.downloader.DeliverHashes(id, result)
+			dl.downloader.DeliverHashes61(id, result)
 		}()
 		return nil
 	}
@@ -213,24 +228,20 @@ func (dl *downloadTester) peerGetRelHashesFn(id string, delay time.Duration) fun
 // peerGetAbsHashesFn constructs a GetHashesFromNumber function associated with
 // a particular peer in the download tester. The returned function can be used to
 // retrieve batches of hashes from the particularly requested peer.
-func (dl *downloadTester) peerGetAbsHashesFn(id string, version int, delay time.Duration) func(uint64, int) error {
+func (dl *downloadTester) peerGetAbsHashesFn(id string, delay time.Duration) func(uint64, int) error {
 	return func(head uint64, count int) error {
 		time.Sleep(delay)
 
-		limit := count
-		if dl.maxHashFetch > 0 {
-			limit = dl.maxHashFetch
-		}
 		// Gather the next batch of hashes
 		hashes := dl.peerHashes[id]
-		result := make([]common.Hash, 0, limit)
+		result := make([]common.Hash, 0, count)
-		for i := 0; i < limit && len(hashes)-int(head)-1-i >= 0; i++ {
+		for i := 0; i < count && len(hashes)-int(head)-1-i >= 0; i++ {
 			result = append(result, hashes[len(hashes)-int(head)-1-i])
 		}
 		// Delay delivery a bit to allow attacks to unfold
 		go func() {
 			time.Sleep(time.Millisecond)
-			dl.downloader.DeliverHashes(id, result)
+			dl.downloader.DeliverHashes61(id, result)
 		}()
 		return nil
 	}
@@ -249,7 +260,55 @@ func (dl *downloadTester) peerGetBlocksFn(id string, delay time.Duration) func([
 				result = append(result, block)
 			}
 		}
-		go dl.downloader.DeliverBlocks(id, result)
+		go dl.downloader.DeliverBlocks61(id, result)
+
+		return nil
+	}
+}
+
+// peerGetAbsHeadersFn constructs a GetBlockHeaders function based on a numbered
+// origin; associated with a particular peer in the download tester. The returned
+// function can be used to retrieve batches of headers from the particular peer.
+func (dl *downloadTester) peerGetAbsHeadersFn(id string, delay time.Duration) func(uint64, int, int, bool) error {
+	return func(origin uint64, amount int, skip int, reverse bool) error {
+		time.Sleep(delay)
+
+		// Gather the next batch of hashes
+		hashes := dl.peerHashes[id]
+		blocks := dl.peerBlocks[id]
+		result := make([]*types.Header, 0, amount)
+		for i := 0; i < amount && len(hashes)-int(origin)-1-i >= 0; i++ {
+			if block, ok := blocks[hashes[len(hashes)-int(origin)-1-i]]; ok {
+				result = append(result, block.Header())
+			}
+		}
+		// Delay delivery a bit to allow attacks to unfold
+		go func() {
+			time.Sleep(time.Millisecond)
+			dl.downloader.DeliverHeaders(id, result)
+		}()
+		return nil
+	}
+}
+
+// peerGetBodiesFn constructs a getBlockBodies method associated with a particular
+// peer in the download tester. The returned function can be used to retrieve
+// batches of block bodies from the particularly requested peer.
+func (dl *downloadTester) peerGetBodiesFn(id string, delay time.Duration) func([]common.Hash) error {
+	return func(hashes []common.Hash) error {
+		time.Sleep(delay)
+		blocks := dl.peerBlocks[id]
+
+		transactions := make([][]*types.Transaction, 0, len(hashes))
+		uncles := make([][]*types.Header, 0, len(hashes))
+
+		for _, hash := range hashes {
+			if block, ok := blocks[hash]; ok {
+				transactions = append(transactions, block.Transactions())
+				uncles = append(uncles, block.Uncles())
+			}
+		}
+		go dl.downloader.DeliverBodies(id, transactions, uncles)
 
 		return nil
 	}
@@ -258,13 +317,18 @@ func (dl *downloadTester) peerGetBlocksFn(id string, delay time.Duration) func([
 // Tests that simple synchronization against a canonical chain works correctly.
 // In this test common ancestor lookup should be short circuited and not require
 // binary searching.
-func TestCanonicalSynchronisation61(t *testing.T) {
+func TestCanonicalSynchronisation61(t *testing.T) { testCanonicalSynchronisation(t, 61) }
+func TestCanonicalSynchronisation62(t *testing.T) { testCanonicalSynchronisation(t, 62) }
+func TestCanonicalSynchronisation63(t *testing.T) { testCanonicalSynchronisation(t, 63) }
+func TestCanonicalSynchronisation64(t *testing.T) { testCanonicalSynchronisation(t, 64) }
+
+func testCanonicalSynchronisation(t *testing.T, protocol int) {
 	// Create a small enough block chain to download
 	targetBlocks := blockCacheLimit - 15
 	hashes, blocks := makeChain(targetBlocks, 0, genesis)
 
 	tester := newTester()
-	tester.newPeer("peer", eth61, hashes, blocks)
+	tester.newPeer("peer", protocol, hashes, blocks)
 
 	// Synchronise with the peer and make sure all blocks were retrieved
 	if err := tester.sync("peer", nil); err != nil {
@@ -277,7 +341,10 @@ func TestCanonicalSynchronisation61(t *testing.T) {
 
 // Tests that if a large batch of blocks are being downloaded, it is throttled
 // until the cached blocks are retrieved.
-func TestThrottling61(t *testing.T) { testThrottling(t, eth61) }
+func TestThrottling61(t *testing.T) { testThrottling(t, 61) }
+func TestThrottling62(t *testing.T) { testThrottling(t, 62) }
+func TestThrottling63(t *testing.T) { testThrottling(t, 63) }
+func TestThrottling64(t *testing.T) { testThrottling(t, 64) }
 
 func testThrottling(t *testing.T, protocol int) {
 	// Create a long block chain to download and the tester
@@ -288,11 +355,10 @@ func testThrottling(t *testing.T, protocol int) {
 	tester.newPeer("peer", protocol, hashes, blocks)
 
 	// Wrap the importer to allow stepping
-	done := make(chan int)
+	blocked, proceed := uint32(0), make(chan struct{})
-	tester.downloader.insertChain = func(blocks types.Blocks) (int, error) {
+	tester.downloader.chainInsertHook = func(blocks []*Block) {
-		n, err := tester.insertChain(blocks)
+		atomic.StoreUint32(&blocked, uint32(len(blocks)))
-		done <- n
+		<-proceed
-		return n, err
 	}
 	// Start a synchronisation concurrently
 	errc := make(chan error)
@@ -303,27 +369,25 @@ func testThrottling(t *testing.T, protocol int) {
 	for len(tester.ownBlocks) < targetBlocks+1 {
 		// Wait a bit for sync to throttle itself
 		var cached int
-		for start := time.Now(); time.Since(start) < 3*time.Second; {
+		for start := time.Now(); time.Since(start) < time.Second; {
 			time.Sleep(25 * time.Millisecond)
 
 			cached = len(tester.downloader.queue.blockPool)
-			if cached == blockCacheLimit || len(tester.ownBlocks)+cached == targetBlocks+1 {
+			if cached == blockCacheLimit || len(tester.ownBlocks)+cached+int(atomic.LoadUint32(&blocked)) == targetBlocks+1 {
 				break
 			}
 		}
 		// Make sure we filled up the cache, then exhaust it
 		time.Sleep(25 * time.Millisecond) // give it a chance to screw up
-		if cached != blockCacheLimit && len(tester.ownBlocks)+cached < targetBlocks+1 {
+		if cached != blockCacheLimit && len(tester.ownBlocks)+cached+int(atomic.LoadUint32(&blocked)) != targetBlocks+1 {
-			t.Fatalf("block count mismatch: have %v, want %v", cached, blockCacheLimit)
+			t.Fatalf("block count mismatch: have %v, want %v (owned %v, target %v)", cached, blockCacheLimit, len(tester.ownBlocks), targetBlocks+1)
 		}
-		<-done // finish previous blocking import
+		// Permit the blocked blocks to import
-		for cached > maxBlockProcess {
+		if atomic.LoadUint32(&blocked) > 0 {
-			cached -= <-done
+			atomic.StoreUint32(&blocked, uint32(0))
+			proceed <- struct{}{}
 		}
-		time.Sleep(25 * time.Millisecond) // yield to the insertion
 	}
-	<-done // finish the last blocking import
-
 	// Check that we haven't pulled more blocks than available
 	if len(tester.ownBlocks) > targetBlocks+1 {
 		t.Fatalf("target block count mismatch: have %v, want %v", len(tester.ownBlocks), targetBlocks+1)
@@ -336,14 +400,19 @@ func testThrottling(t *testing.T, protocol int) {
 // Tests that simple synchronization against a forked chain works correctly. In
 // this test common ancestor lookup should *not* be short circuited, and a full
 // binary search should be executed.
-func TestForkedSynchronisation61(t *testing.T) {
+func TestForkedSynchronisation61(t *testing.T) { testForkedSynchronisation(t, 61) }
+func TestForkedSynchronisation62(t *testing.T) { testForkedSynchronisation(t, 62) }
+func TestForkedSynchronisation63(t *testing.T) { testForkedSynchronisation(t, 63) }
+func TestForkedSynchronisation64(t *testing.T) { testForkedSynchronisation(t, 64) }
+
+func testForkedSynchronisation(t *testing.T, protocol int) {
 	// Create a long enough forked chain
 	common, fork := MaxHashFetch, 2*MaxHashFetch
 	hashesA, hashesB, blocksA, blocksB := makeChainFork(common+fork, fork, genesis)
 
 	tester := newTester()
-	tester.newPeer("fork A", eth61, hashesA, blocksA)
+	tester.newPeer("fork A", protocol, hashesA, blocksA)
-	tester.newPeer("fork B", eth61, hashesB, blocksB)
+	tester.newPeer("fork B", protocol, hashesB, blocksB)
 
 	// Synchronise with the peer and make sure all blocks were retrieved
 	if err := tester.sync("fork A", nil); err != nil {
@@ -362,20 +431,36 @@ func TestForkedSynchronisation61(t *testing.T) {
 }
 
 // Tests that an inactive downloader will not accept incoming hashes and blocks.
-func TestInactiveDownloader(t *testing.T) {
+func TestInactiveDownloader61(t *testing.T) {
 	tester := newTester()
 
 	// Check that neither hashes nor blocks are accepted
-	if err := tester.downloader.DeliverHashes("bad peer", []common.Hash{}); err != errNoSyncActive {
+	if err := tester.downloader.DeliverHashes61("bad peer", []common.Hash{}); err != errNoSyncActive {
 		t.Errorf("error mismatch: have %v, want %v", err, errNoSyncActive)
 	}
-	if err := tester.downloader.DeliverBlocks("bad peer", []*types.Block{}); err != errNoSyncActive {
+	if err := tester.downloader.DeliverBlocks61("bad peer", []*types.Block{}); err != errNoSyncActive {
+		t.Errorf("error mismatch: have %v, want %v", err, errNoSyncActive)
+	}
+}
+
+// Tests that an inactive downloader will not accept incoming block headers and bodies.
+func TestInactiveDownloader62(t *testing.T) {
+	tester := newTester()
+
+	// Check that neither block headers nor bodies are accepted
+	if err := tester.downloader.DeliverHeaders("bad peer", []*types.Header{}); err != errNoSyncActive {
+		t.Errorf("error mismatch: have %v, want %v", err, errNoSyncActive)
+	}
+	if err := tester.downloader.DeliverBodies("bad peer", [][]*types.Transaction{}, [][]*types.Header{}); err != errNoSyncActive {
 		t.Errorf("error mismatch: have %v, want %v", err, errNoSyncActive)
 	}
 }
 
 // Tests that a canceled download wipes all previously accumulated state.
-func TestCancel61(t *testing.T) { testCancel(t, eth61) }
+func TestCancel61(t *testing.T) { testCancel(t, 61) }
+func TestCancel62(t *testing.T) { testCancel(t, 62) }
+func TestCancel63(t *testing.T) { testCancel(t, 63) }
+func TestCancel64(t *testing.T) { testCancel(t, 64) }
 
 func testCancel(t *testing.T, protocol int) {
 	// Create a small enough block chain to download and the tester
@@ -383,6 +468,9 @@ func testCancel(t *testing.T, protocol int) {
 	if targetBlocks >= MaxHashFetch {
 		targetBlocks = MaxHashFetch - 15
 	}
+	if targetBlocks >= MaxHeaderFetch {
+		targetBlocks = MaxHeaderFetch - 15
+	}
 	hashes, blocks := makeChain(targetBlocks, 0, genesis)
 
 	tester := newTester()
@@ -390,27 +478,30 @@ func testCancel(t *testing.T, protocol int) {
 
 	// Make sure canceling works with a pristine downloader
 	tester.downloader.cancel()
-	hashCount, blockCount := tester.downloader.queue.Size()
+	downloading, importing := tester.downloader.queue.Size()
-	if hashCount > 0 || blockCount > 0 {
+	if downloading > 0 || importing > 0 {
-		t.Errorf("block or hash count mismatch: %d hashes, %d blocks, want 0", hashCount, blockCount)
+		t.Errorf("download or import count mismatch: %d downloading, %d importing, want 0", downloading, importing)
 	}
 	// Synchronise with the peer, but cancel afterwards
 	if err := tester.sync("peer", nil); err != nil {
 		t.Fatalf("failed to synchronise blocks: %v", err)
 	}
 	tester.downloader.cancel()
-	hashCount, blockCount = tester.downloader.queue.Size()
+	downloading, importing = tester.downloader.queue.Size()
-	if hashCount > 0 || blockCount > 0 {
+	if downloading > 0 || importing > 0 {
-		t.Errorf("block or hash count mismatch: %d hashes, %d blocks, want 0", hashCount, blockCount)
+		t.Errorf("download or import count mismatch: %d downloading, %d importing, want 0", downloading, importing)
 	}
 }
 
 // Tests that synchronisation from multiple peers works as intended (multi thread sanity test).
-func TestMultiSynchronisation61(t *testing.T) { testMultiSynchronisation(t, eth61) }
+func TestMultiSynchronisation61(t *testing.T) { testMultiSynchronisation(t, 61) }
+func TestMultiSynchronisation62(t *testing.T) { testMultiSynchronisation(t, 62) }
+func TestMultiSynchronisation63(t *testing.T) { testMultiSynchronisation(t, 63) }
+func TestMultiSynchronisation64(t *testing.T) { testMultiSynchronisation(t, 64) }
 
 func testMultiSynchronisation(t *testing.T, protocol int) {
 	// Create various peers with various parts of the chain
-	targetPeers := 16
+	targetPeers := 8
 	targetBlocks := targetPeers*blockCacheLimit - 15
 	hashes, blocks := makeChain(targetBlocks, 0, genesis)
 
@@ -436,45 +527,130 @@ func testMultiSynchronisation(t *testing.T, protocol int) {
 	}
 }
 
+// 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 small enough block chain to download
+	targetBlocks := blockCacheLimit - 15
+	hashes, blocks := makeChain(targetBlocks, 0, genesis)
+
+	tester := newTester()
+	tester.newPeer("peer", protocol, hashes, blocks)
+
+	// Instrument the downloader to signal body requests
+	requested := int32(0)
+	tester.downloader.bodyFetchHook = func(headers []*types.Header) {
+		atomic.AddInt32(&requested, int32(len(headers)))
+	}
+	// Synchronise with the peer and make sure all blocks were retrieved
+	if err := tester.sync("peer", nil); err != nil {
+		t.Fatalf("failed to synchronise blocks: %v", err)
+	}
+	if imported := len(tester.ownBlocks); imported != targetBlocks+1 {
+		t.Fatalf("synchronised block mismatch: have %v, want %v", imported, targetBlocks+1)
+	}
+	// Validate the number of block bodies that should have been requested
+	needed := 0
+	for _, block := range blocks {
+		if block != genesis && (len(block.Transactions()) > 0 || len(block.Uncles()) > 0) {
+			needed++
+		}
+	}
+	if int(requested) != needed {
+		t.Fatalf("block body retrieval count mismatch: have %v, want %v", requested, needed)
+	}
+}
+
+// Tests that if a peer sends an invalid body for a requested block, it gets
+// dropped immediately by the downloader.
+func TestInvalidBlockBodyAttack62(t *testing.T) { testInvalidBlockBodyAttack(t, 62) }
+func TestInvalidBlockBodyAttack63(t *testing.T) { testInvalidBlockBodyAttack(t, 63) }
+func TestInvalidBlockBodyAttack64(t *testing.T) { testInvalidBlockBodyAttack(t, 64) }
+
+func testInvalidBlockBodyAttack(t *testing.T, protocol int) {
+	// Create two peers, one feeding invalid block bodies
+	targetBlocks := 4*blockCacheLimit - 15
+	hashes, validBlocks := makeChain(targetBlocks, 0, genesis)
+
+	invalidBlocks := make(map[common.Hash]*types.Block)
+	for hash, block := range validBlocks {
+		invalidBlocks[hash] = types.NewBlockWithHeader(block.Header())
+	}
+
+	tester := newTester()
+	tester.newPeer("valid", protocol, hashes, validBlocks)
+	tester.newPeer("attack", protocol, hashes, invalidBlocks)
+
+	// Synchronise with the valid peer (will pull contents from the attacker too)
+	if err := tester.sync("valid", nil); err != nil {
+		t.Fatalf("failed to synchronise blocks: %v", err)
+	}
+	if imported := len(tester.ownBlocks); imported != len(hashes) {
+		t.Fatalf("synchronised block mismatch: have %v, want %v", imported, len(hashes))
+	}
+	// Make sure the attacker was detected and dropped in the mean time
+	if _, ok := tester.peerHashes["attack"]; ok {
+		t.Fatalf("block body attacker not detected/dropped")
+	}
+}
+
 // Tests that a peer advertising an high TD doesn't get to stall the downloader
 // afterwards by not sending any useful hashes.
-func TestHighTDStarvationAttack61(t *testing.T) {
+func TestHighTDStarvationAttack61(t *testing.T) { testHighTDStarvationAttack(t, 61) }
+func TestHighTDStarvationAttack62(t *testing.T) { testHighTDStarvationAttack(t, 62) }
+func TestHighTDStarvationAttack63(t *testing.T) { testHighTDStarvationAttack(t, 63) }
+func TestHighTDStarvationAttack64(t *testing.T) { testHighTDStarvationAttack(t, 64) }
+
+func testHighTDStarvationAttack(t *testing.T, protocol int) {
 	tester := newTester()
-	tester.newPeer("attack", eth61, []common.Hash{genesis.Hash()}, nil)
+	hashes, blocks := makeChain(0, 0, genesis)
+
+	tester.newPeer("attack", protocol, []common.Hash{hashes[0]}, blocks)
 	if err := tester.sync("attack", big.NewInt(1000000)); err != errStallingPeer {
 		t.Fatalf("synchronisation error mismatch: have %v, want %v", err, errStallingPeer)
 	}
 }
 
 // Tests that misbehaving peers are disconnected, whilst behaving ones are not.
-func TestHashAttackerDropping(t *testing.T) {
+func TestBlockHeaderAttackerDropping61(t *testing.T) { testBlockHeaderAttackerDropping(t, 61) }
+func TestBlockHeaderAttackerDropping62(t *testing.T) { testBlockHeaderAttackerDropping(t, 62) }
+func TestBlockHeaderAttackerDropping63(t *testing.T) { testBlockHeaderAttackerDropping(t, 63) }
+func TestBlockHeaderAttackerDropping64(t *testing.T) { testBlockHeaderAttackerDropping(t, 64) }
+
+func testBlockHeaderAttackerDropping(t *testing.T, protocol int) {
 	// Define the disconnection requirement for individual hash fetch errors
 	tests := []struct {
 		result error
 		drop   bool
 	}{
-		{nil, false},                 // Sync succeeded, all is well
+		{nil, false},                  // Sync succeeded, all is well
-		{errBusy, false},             // Sync is already in progress, no problem
+		{errBusy, false},              // Sync is already in progress, no problem
-		{errUnknownPeer, false},      // Peer is unknown, was already dropped, don't double drop
+		{errUnknownPeer, false},       // Peer is unknown, was already dropped, don't double drop
-		{errBadPeer, true},           // Peer was deemed bad for some reason, drop it
+		{errBadPeer, true},            // Peer was deemed bad for some reason, drop it
-		{errStallingPeer, true},      // Peer was detected to be stalling, drop it
+		{errStallingPeer, true},       // Peer was detected to be stalling, drop it
-		{errBannedHead, true},        // Peer's head hash is a known bad hash, drop it
+		{errNoPeers, false},           // No peers to download from, soft race, no issue
-		{errNoPeers, false},          // No peers to download from, soft race, no issue
+		{errPendingQueue, false},      // There are blocks still cached, wait to exhaust, no issue
-		{errPendingQueue, false},     // There are blocks still cached, wait to exhaust, no issue
+		{errTimeout, true},            // No hashes received in due time, drop the peer
-		{errTimeout, true},           // No hashes received in due time, drop the peer
+		{errEmptyHashSet, true},       // No hashes were returned as a response, drop as it's a dead end
-		{errEmptyHashSet, true},      // No hashes were returned as a response, drop as it's a dead end
+		{errEmptyHeaderSet, true},     // No headers were returned as a response, drop as it's a dead end
-		{errPeersUnavailable, true},  // Nobody had the advertised blocks, drop the advertiser
+		{errPeersUnavailable, true},   // Nobody had the advertised blocks, drop the advertiser
-		{errInvalidChain, true},      // Hash chain was detected as invalid, definitely drop
+		{errInvalidChain, true},       // Hash chain was detected as invalid, definitely drop
-		{errCrossCheckFailed, true},  // Hash-origin failed to pass a block cross check, drop
+		{errInvalidBody, false},       // A bad peer was detected, but not the sync origin
-		{errCancelHashFetch, false},  // Synchronisation was canceled, origin may be innocent, don't drop
+		{errCancelHashFetch, false},   // Synchronisation was canceled, origin may be innocent, don't drop
-		{errCancelBlockFetch, false}, // Synchronisation was canceled, origin may be innocent, don't drop
+		{errCancelBlockFetch, false},  // Synchronisation was canceled, origin may be innocent, don't drop
+		{errCancelHeaderFetch, false}, // Synchronisation was canceled, origin may be innocent, don't drop
+		{errCancelBodyFetch, false},   // Synchronisation was canceled, origin may be innocent, don't drop
 	}
 	// Run the tests and check disconnection status
 	tester := newTester()
 	for i, tt := range tests {
 		// Register a new peer and ensure it's presence
 		id := fmt.Sprintf("test %d", i)
-		if err := tester.newPeer(id, eth61, []common.Hash{genesis.Hash()}, nil); err != nil {
+		if err := tester.newPeer(id, protocol, []common.Hash{genesis.Hash()}, nil); err != nil {
 			t.Fatalf("test %d: failed to register new peer: %v", i, err)
 		}
 		if _, ok := tester.peerHashes[id]; !ok {
@@ -491,7 +667,12 @@ func TestHashAttackerDropping(t *testing.T) {
 }
 
 // Tests that feeding bad blocks will result in a peer drop.
-func TestBlockAttackerDropping(t *testing.T) {
+func TestBlockBodyAttackerDropping61(t *testing.T) { testBlockBodyAttackerDropping(t, 61) }
+func TestBlockBodyAttackerDropping62(t *testing.T) { testBlockBodyAttackerDropping(t, 62) }
+func TestBlockBodyAttackerDropping63(t *testing.T) { testBlockBodyAttackerDropping(t, 63) }
+func TestBlockBodyAttackerDropping64(t *testing.T) { testBlockBodyAttackerDropping(t, 64) }
+
+func testBlockBodyAttackerDropping(t *testing.T, protocol int) {
 	// Define the disconnection requirement for individual block import errors
 	tests := []struct {
 		failure bool
@@ -506,7 +687,7 @@ func TestBlockAttackerDropping(t *testing.T) {
 	for i, tt := range tests {
 		// Register a new peer and ensure it's presence
 		id := fmt.Sprintf("test %d", i)
-		if err := tester.newPeer(id, eth61, []common.Hash{common.Hash{}}, nil); err != nil {
+		if err := tester.newPeer(id, protocol, []common.Hash{common.Hash{}}, nil); err != nil {
 			t.Fatalf("test %d: failed to register new peer: %v", i, err)
 		}
 		if _, ok := tester.peerHashes[id]; !ok {

eth/downloader/peer.go

@@ -31,10 +31,16 @@ import (
 	"gopkg.in/fatih/set.v0"
 )
 
+// Hash and block fetchers belonging to eth/61 and below
 type relativeHashFetcherFn func(common.Hash) error
 type absoluteHashFetcherFn func(uint64, int) error
 type blockFetcherFn func([]common.Hash) error
 
+// Block header and body fethers belonging to eth/62 and above
+type relativeHeaderFetcherFn func(common.Hash, int, int, bool) error
+type absoluteHeaderFetcherFn func(uint64, int, int, bool) error
+type blockBodyFetcherFn func([]common.Hash) error
+
 var (
 	errAlreadyFetching   = errors.New("already fetching blocks from peer")
 	errAlreadyRegistered = errors.New("peer is already registered")
@@ -54,25 +60,37 @@ type peer struct {
 
 	ignored *set.Set // Set of hashes not to request (didn't have previously)
 
-	getRelHashes relativeHashFetcherFn // Method to retrieve a batch of hashes from an origin hash
+	getRelHashes relativeHashFetcherFn // [eth/61] Method to retrieve a batch of hashes from an origin hash
-	getAbsHashes absoluteHashFetcherFn // Method to retrieve a batch of hashes from an absolute position
+	getAbsHashes absoluteHashFetcherFn // [eth/61] Method to retrieve a batch of hashes from an absolute position
-	getBlocks    blockFetcherFn        // Method to retrieve a batch of blocks
+	getBlocks    blockFetcherFn        // [eth/61] Method to retrieve a batch of blocks
+
+	getRelHeaders  relativeHeaderFetcherFn // [eth/62] Method to retrieve a batch of headers from an origin hash
+	getAbsHeaders  absoluteHeaderFetcherFn // [eth/62] Method to retrieve a batch of headers from an absolute position
+	getBlockBodies blockBodyFetcherFn      // [eth/62] Method to retrieve a batch of block bodies
 
 	version int // Eth protocol version number to switch strategies
 }
 
 // newPeer create a new downloader peer, with specific hash and block retrieval
 // mechanisms.
-func newPeer(id string, version int, head common.Hash, getRelHashes relativeHashFetcherFn, getAbsHashes absoluteHashFetcherFn, getBlocks blockFetcherFn) *peer {
+func newPeer(id string, version int, head common.Hash,
+	getRelHashes relativeHashFetcherFn, getAbsHashes absoluteHashFetcherFn, getBlocks blockFetcherFn, // eth/61 callbacks, remove when upgrading
+	getRelHeaders relativeHeaderFetcherFn, getAbsHeaders absoluteHeaderFetcherFn, getBlockBodies blockBodyFetcherFn) *peer {
 	return &peer{
-		id:           id,
+		id:       id,
-		head:         head,
+		head:     head,
-		capacity:     1,
+		capacity: 1,
+		ignored:  set.New(),
+
 		getRelHashes: getRelHashes,
 		getAbsHashes: getAbsHashes,
 		getBlocks:    getBlocks,
-		ignored:      set.New(),
+
-		version:      version,
+		getRelHeaders:  getRelHeaders,
+		getAbsHeaders:  getAbsHeaders,
+		getBlockBodies: getBlockBodies,
+
+		version: version,
 	}
 }
 
@@ -83,8 +101,8 @@ func (p *peer) Reset() {
 	p.ignored.Clear()
 }
 
-// Fetch sends a block retrieval request to the remote peer.
+// Fetch61 sends a block retrieval request to the remote peer.
-func (p *peer) Fetch(request *fetchRequest) error {
+func (p *peer) Fetch61(request *fetchRequest) error {
 	// Short circuit if the peer is already fetching
 	if !atomic.CompareAndSwapInt32(&p.idle, 0, 1) {
 		return errAlreadyFetching
@@ -101,10 +119,28 @@ func (p *peer) Fetch(request *fetchRequest) error {
 	return nil
 }
 
-// SetIdle sets the peer to idle, allowing it to execute new retrieval requests.
+// Fetch sends a block body retrieval request to the remote peer.
+func (p *peer) Fetch(request *fetchRequest) error {
+	// Short circuit if the peer is already fetching
+	if !atomic.CompareAndSwapInt32(&p.idle, 0, 1) {
+		return errAlreadyFetching
+	}
+	p.started = time.Now()
+
+	// Convert the header set to a retrievable slice
+	hashes := make([]common.Hash, 0, len(request.Headers))
+	for _, header := range request.Headers {
+		hashes = append(hashes, header.Hash())
+	}
+	go p.getBlockBodies(hashes)
+
+	return nil
+}
+
+// SetIdle61 sets the peer to idle, allowing it to execute new retrieval requests.
 // Its block retrieval allowance will also be updated either up- or downwards,
 // depending on whether the previous fetch completed in time or not.
-func (p *peer) SetIdle() {
+func (p *peer) SetIdle61() {
 	// Update the peer's download allowance based on previous performance
 	scale := 2.0
 	if time.Since(p.started) > blockSoftTTL {
@@ -131,6 +167,36 @@ func (p *peer) SetIdle() {
 	atomic.StoreInt32(&p.idle, 0)
 }
 
+// SetIdle sets the peer to idle, allowing it to execute new retrieval requests.
+// Its block body retrieval allowance will also be updated either up- or downwards,
+// depending on whether the previous fetch completed in time or not.
+func (p *peer) SetIdle() {
+	// Update the peer's download allowance based on previous performance
+	scale := 2.0
+	if time.Since(p.started) > bodySoftTTL {
+		scale = 0.5
+		if time.Since(p.started) > bodyHardTTL {
+			scale = 1 / float64(MaxBodyFetch) // reduces capacity to 1
+		}
+	}
+	for {
+		// Calculate the new download bandwidth allowance
+		prev := atomic.LoadInt32(&p.capacity)
+		next := int32(math.Max(1, math.Min(float64(MaxBodyFetch), float64(prev)*scale)))
+
+		// Try to update the old value
+		if atomic.CompareAndSwapInt32(&p.capacity, prev, next) {
+			// If we're having problems at 1 capacity, try to find better peers
+			if next == 1 {
+				p.Demote()
+			}
+			break
+		}
+	}
+	// Set the peer to idle to allow further block requests
+	atomic.StoreInt32(&p.idle, 0)
+}
+
 // Capacity retrieves the peers block download allowance based on its previously
 // discovered bandwidth capacity.
 func (p *peer) Capacity() int {

eth/downloader/queue.go

@@ -43,16 +43,20 @@ var (
 
 // fetchRequest is a currently running block retrieval operation.
 type fetchRequest struct {
-	Peer   *peer               // Peer to which the request was sent
+	Peer    *peer               // Peer to which the request was sent
-	Hashes map[common.Hash]int // Requested hashes with their insertion index (priority)
+	Hashes  map[common.Hash]int // [eth/61] Requested hashes with their insertion index (priority)
-	Time   time.Time           // Time when the request was made
+	Headers []*types.Header     // [eth/62] Requested headers, sorted by request order
+	Time    time.Time           // Time when the request was made
 }
 
 // queue represents hashes that are either need fetching or are being fetched
 type queue struct {
-	hashPool    map[common.Hash]int // Pending hashes, mapping to their insertion index (priority)
+	hashPool    map[common.Hash]int // [eth/61] Pending hashes, mapping to their insertion index (priority)
-	hashQueue   *prque.Prque        // Priority queue of the block hashes to fetch
+	hashQueue   *prque.Prque        // [eth/61] Priority queue of the block hashes to fetch
-	hashCounter int                 // Counter indexing the added hashes to ensure retrieval order
+	hashCounter int                 // [eth/61] Counter indexing the added hashes to ensure retrieval order
+
+	headerPool  map[common.Hash]*types.Header // [eth/62] Pending headers, mapping from their hashes
+	headerQueue *prque.Prque                  // [eth/62] Priority queue of the headers to fetch the bodies for
 
 	pendPool map[string]*fetchRequest // Currently pending block retrieval operations
 
@@ -66,11 +70,13 @@ type queue struct {
 // newQueue creates a new download queue for scheduling block retrieval.
 func newQueue() *queue {
 	return &queue{
-		hashPool:   make(map[common.Hash]int),
+		hashPool:    make(map[common.Hash]int),
-		hashQueue:  prque.New(),
+		hashQueue:   prque.New(),
-		pendPool:   make(map[string]*fetchRequest),
+		headerPool:  make(map[common.Hash]*types.Header),
-		blockPool:  make(map[common.Hash]uint64),
+		headerQueue: prque.New(),
-		blockCache: make([]*Block, blockCacheLimit),
+		pendPool:    make(map[string]*fetchRequest),
+		blockPool:   make(map[common.Hash]uint64),
+		blockCache:  make([]*Block, blockCacheLimit),
 	}
 }
 
@@ -83,6 +89,9 @@ func (q *queue) Reset() {
 	q.hashQueue.Reset()
 	q.hashCounter = 0
 
+	q.headerPool = make(map[common.Hash]*types.Header)
+	q.headerQueue.Reset()
+
 	q.pendPool = make(map[string]*fetchRequest)
 
 	q.blockPool = make(map[common.Hash]uint64)
@@ -90,21 +99,21 @@ func (q *queue) Reset() {
 	q.blockCache = make([]*Block, blockCacheLimit)
 }
 
-// Size retrieves the number of hashes in the queue, returning separately for
+// Size retrieves the number of blocks in the queue, returning separately for
 // pending and already downloaded.
 func (q *queue) Size() (int, int) {
 	q.lock.RLock()
 	defer q.lock.RUnlock()
 
-	return len(q.hashPool), len(q.blockPool)
+	return len(q.hashPool) + len(q.headerPool), len(q.blockPool)
 }
 
-// Pending retrieves the number of hashes pending for retrieval.
+// Pending retrieves the number of blocks pending for retrieval.
 func (q *queue) Pending() int {
 	q.lock.RLock()
 	defer q.lock.RUnlock()
 
-	return q.hashQueue.Size()
+	return q.hashQueue.Size() + q.headerQueue.Size()
 }
 
 // InFlight retrieves the number of fetch requests currently in flight.
@@ -124,7 +133,7 @@ func (q *queue) Throttle() bool {
 	// Calculate the currently in-flight block requests
 	pending := 0
 	for _, request := range q.pendPool {
-		pending += len(request.Hashes)
+		pending += len(request.Hashes) + len(request.Headers)
 	}
 	// Throttle if more blocks are in-flight than free space in the cache
 	return pending >= len(q.blockCache)-len(q.blockPool)
@@ -138,15 +147,18 @@ func (q *queue) Has(hash common.Hash) bool {
 	if _, ok := q.hashPool[hash]; ok {
 		return true
 	}
+	if _, ok := q.headerPool[hash]; ok {
+		return true
+	}
 	if _, ok := q.blockPool[hash]; ok {
 		return true
 	}
 	return false
 }
 
-// Insert adds a set of hashes for the download queue for scheduling, returning
+// Insert61 adds a set of hashes for the download queue for scheduling, returning
 // the new hashes encountered.
-func (q *queue) Insert(hashes []common.Hash, fifo bool) []common.Hash {
+func (q *queue) Insert61(hashes []common.Hash, fifo bool) []common.Hash {
 	q.lock.Lock()
 	defer q.lock.Unlock()
 
@@ -172,6 +184,29 @@ func (q *queue) Insert(hashes []common.Hash, fifo bool) []common.Hash {
 	return inserts
 }
 
+// Insert adds a set of headers for the download queue for scheduling, returning
+// the new headers encountered.
+func (q *queue) Insert(headers []*types.Header) []*types.Header {
+	q.lock.Lock()
+	defer q.lock.Unlock()
+
+	// Insert all the headers prioritized by the contained block number
+	inserts := make([]*types.Header, 0, len(headers))
+	for _, header := range headers {
+		// Make sure no duplicate requests are executed
+		hash := header.Hash()
+		if _, ok := q.headerPool[hash]; ok {
+			glog.V(logger.Warn).Infof("Header %x already scheduled", hash)
+			continue
+		}
+		// Queue the header for body retrieval
+		inserts = append(inserts, header)
+		q.headerPool[hash] = header
+		q.headerQueue.Push(header, -float32(header.Number.Uint64()))
+	}
+	return inserts
+}
+
 // GetHeadBlock retrieves the first block from the cache, or nil if it hasn't
 // been downloaded yet (or simply non existent).
 func (q *queue) GetHeadBlock() *Block {
@@ -227,9 +262,9 @@ func (q *queue) TakeBlocks() []*Block {
 	return blocks
 }
 
-// Reserve reserves a set of hashes for the given peer, skipping any previously
+// Reserve61 reserves a set of hashes for the given peer, skipping any previously
 // failed download.
-func (q *queue) Reserve(p *peer, count int) *fetchRequest {
+func (q *queue) Reserve61(p *peer, count int) *fetchRequest {
 	q.lock.Lock()
 	defer q.lock.Unlock()
 
@@ -276,6 +311,68 @@ func (q *queue) Reserve(p *peer, count int) *fetchRequest {
 	return request
 }
 
+// Reserve reserves a set of headers for the given peer, skipping any previously
+// failed download. Beside the next batch of needed fetches, it also returns a
+// flag whether empty blocks were queued requiring processing.
+func (q *queue) Reserve(p *peer, count int) (*fetchRequest, bool, error) {
+	q.lock.Lock()
+	defer q.lock.Unlock()
+
+	// Short circuit if the pool has been depleted, or if the peer's already
+	// downloading something (sanity check not to corrupt state)
+	if q.headerQueue.Empty() {
+		return nil, false, nil
+	}
+	if _, ok := q.pendPool[p.id]; ok {
+		return nil, false, nil
+	}
+	// Calculate an upper limit on the bodies we might fetch (i.e. throttling)
+	space := len(q.blockCache) - len(q.blockPool)
+	for _, request := range q.pendPool {
+		space -= len(request.Headers)
+	}
+	// Retrieve a batch of headers, skipping previously failed ones
+	send := make([]*types.Header, 0, count)
+	skip := make([]*types.Header, 0)
+
+	process := false
+	for proc := 0; proc < space && len(send) < count && !q.headerQueue.Empty(); proc++ {
+		header := q.headerQueue.PopItem().(*types.Header)
+
+		// If the header defines an empty block, deliver straight
+		if header.TxHash == types.DeriveSha(types.Transactions{}) && header.UncleHash == types.CalcUncleHash([]*types.Header{}) {
+			if err := q.enqueue("", types.NewBlockWithHeader(header)); err != nil {
+				return nil, false, errInvalidChain
+			}
+			delete(q.headerPool, header.Hash())
+			process, space, proc = true, space-1, proc-1
+			continue
+		}
+		// If it's a content block, add to the body fetch request
+		if p.ignored.Has(header.Hash()) {
+			skip = append(skip, header)
+		} else {
+			send = append(send, header)
+		}
+	}
+	// Merge all the skipped headers back
+	for _, header := range skip {
+		q.headerQueue.Push(header, -float32(header.Number.Uint64()))
+	}
+	// Assemble and return the block download request
+	if len(send) == 0 {
+		return nil, process, nil
+	}
+	request := &fetchRequest{
+		Peer:    p,
+		Headers: send,
+		Time:    time.Now(),
+	}
+	q.pendPool[p.id] = request
+
+	return request, process, nil
+}
+
 // Cancel aborts a fetch request, returning all pending hashes to the queue.
 func (q *queue) Cancel(request *fetchRequest) {
 	q.lock.Lock()
@@ -284,6 +381,9 @@ func (q *queue) Cancel(request *fetchRequest) {
 	for hash, index := range request.Hashes {
 		q.hashQueue.Push(hash, float32(index))
 	}
+	for _, header := range request.Headers {
+		q.headerQueue.Push(header, -float32(header.Number.Uint64()))
+	}
 	delete(q.pendPool, request.Peer.id)
 }
 
@@ -310,8 +410,8 @@ func (q *queue) Expire(timeout time.Duration) []string {
 	return peers
 }
 
-// Deliver injects a block retrieval response into the download queue.
+// Deliver61 injects a block retrieval response into the download queue.
-func (q *queue) Deliver(id string, blocks []*types.Block) (err error) {
+func (q *queue) Deliver61(id string, blocks []*types.Block) (err error) {
 	q.lock.Lock()
 	defer q.lock.Unlock()
 
@@ -337,19 +437,12 @@ func (q *queue) Deliver(id string, blocks []*types.Block) (err error) {
 			errs = append(errs, fmt.Errorf("non-requested block %x", hash))
 			continue
 		}
-		// If a requested block falls out of the range, the hash chain is invalid
+		// Queue the block up for processing
-		index := int(int64(block.NumberU64()) - int64(q.blockOffset))
+		if err := q.enqueue(id, block); err != nil {
-		if index >= len(q.blockCache) || index < 0 {
+			return err
-			return errInvalidChain
-		}
-		// Otherwise merge the block and mark the hash block
-		q.blockCache[index] = &Block{
-			RawBlock:   block,
-			OriginPeer: id,
 		}
 		delete(request.Hashes, hash)
 		delete(q.hashPool, hash)
-		q.blockPool[hash] = block.NumberU64()
 	}
 	// Return all failed or missing fetches to the queue
 	for hash, index := range request.Hashes {
@@ -365,6 +458,88 @@ func (q *queue) Deliver(id string, blocks []*types.Block) (err error) {
 	return nil
 }
 
+// Deliver injects a block body retrieval response into the download queue.
+func (q *queue) Deliver(id string, txLists [][]*types.Transaction, uncleLists [][]*types.Header) error {
+	q.lock.Lock()
+	defer q.lock.Unlock()
+
+	// Short circuit if the block bodies were never requested
+	request := q.pendPool[id]
+	if request == nil {
+		return errNoFetchesPending
+	}
+	delete(q.pendPool, id)
+
+	// If no block bodies were retrieved, mark them as unavailable for the origin peer
+	if len(txLists) == 0 || len(uncleLists) == 0 {
+		for hash, _ := range request.Headers {
+			request.Peer.ignored.Add(hash)
+		}
+	}
+	// Assemble each of the block bodies with their headers and queue for processing
+	errs := make([]error, 0)
+	for i, header := range request.Headers {
+		// Short circuit block assembly if no more bodies are found
+		if i >= len(txLists) || i >= len(uncleLists) {
+			break
+		}
+		// Reconstruct the next block if contents match up
+		if types.DeriveSha(types.Transactions(txLists[i])) != header.TxHash || types.CalcUncleHash(uncleLists[i]) != header.UncleHash {
+			errs = []error{errInvalidBody}
+			break
+		}
+		block := types.NewBlockWithHeader(header).WithBody(txLists[i], uncleLists[i])
+
+		// Queue the block up for processing
+		if err := q.enqueue(id, block); err != nil {
+			errs = []error{err}
+			break
+		}
+		request.Headers[i] = nil
+		delete(q.headerPool, header.Hash())
+	}
+	// Return all failed or missing fetches to the queue
+	for _, header := range request.Headers {
+		if header != nil {
+			q.headerQueue.Push(header, -float32(header.Number.Uint64()))
+		}
+	}
+	// If none of the blocks were good, it's a stale delivery
+	switch {
+	case len(errs) == 0:
+		return nil
+
+	case len(errs) == 1 && errs[0] == errInvalidBody:
+		return errInvalidBody
+
+	case len(errs) == 1 && errs[0] == errInvalidChain:
+		return errInvalidChain
+
+	case len(errs) == len(request.Headers):
+		return errStaleDelivery
+
+	default:
+		return fmt.Errorf("multiple failures: %v", errs)
+	}
+}
+
+// enqueue inserts a new block into the final delivery queue, waiting for pickup
+// by the processor.
+func (q *queue) enqueue(origin string, block *types.Block) error {
+	// If a requested block falls out of the range, the hash chain is invalid
+	index := int(int64(block.NumberU64()) - int64(q.blockOffset))
+	if index >= len(q.blockCache) || index < 0 {
+		return errInvalidChain
+	}
+	// Otherwise merge the block and mark the hash done
+	q.blockCache[index] = &Block{
+		RawBlock:   block,
+		OriginPeer: origin,
+	}
+	q.blockPool[block.Header().Hash()] = block.NumberU64()
+	return nil
+}
+
 // Prepare configures the block cache offset to allow accepting inbound blocks.
 func (q *queue) Prepare(offset uint64) {
 	q.lock.Lock()

eth/fetcher/fetcher.go

@@ -51,6 +51,12 @@ type blockRetrievalFn func(common.Hash) *types.Block
 // blockRequesterFn is a callback type for sending a block retrieval request.
 type blockRequesterFn func([]common.Hash) error
 
+// 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
+
 // blockValidatorFn is a callback type to verify a block's header for fast propagation.
 type blockValidatorFn func(block *types.Block, parent *types.Block) error
 
@@ -69,12 +75,30 @@ 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
+	hash   common.Hash   // Hash of the block being announced
-	number uint64      // Number of the block being announced (0 = unknown | old protocol)
+	number uint64        // Number of the block being announced (0 = unknown | old protocol)
-	time   time.Time   // Timestamp of the announcement
+	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
+	origin string // Identifier of the peer originating the notification
-	fetch  blockRequesterFn // Fetcher function to retrieve
+
+	fetch61     blockRequesterFn  // [eth/61] Fetcher function to retrieve an announced block
+	fetchHeader headerRequesterFn // [eth/62] Fetcher function to retrieve the header of an announced block
+	fetchBodies bodyRequesterFn   // [eth/62] Fetcher function to retrieve the body of an announced block
+}
+
+// headerFilterTask represents a batch of headers needing fetcher filtering.
+type headerFilterTask struct {
+	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 {
+	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.
@@ -89,14 +113,20 @@ type Fetcher struct {
 	// Various event channels
 	notify chan *announce
 	inject chan *inject
-	filter chan chan []*types.Block
+
-	done   chan common.Hash
+	blockFilter  chan chan []*types.Block
-	quit   chan struct{}
+	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
+	announces  map[string]int              // Per peer announce counts to prevent memory exhaustion
-	announced map[common.Hash][]*announce // Announced blocks, scheduled for fetching
+	announced  map[common.Hash][]*announce // Announced blocks, scheduled for fetching
-	fetching  map[common.Hash]*announce   // Announced blocks, currently 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)
@@ -112,8 +142,9 @@ type Fetcher struct {
 	dropPeer       peerDropFn         // Drops a peer for misbehaving
 
 	// Testing hooks
-	fetchingHook func([]common.Hash) // Method to call upon starting a block fetch
+	fetchingHook   func([]common.Hash) // Method to call upon starting a block (eth/61) or header (eth/62) fetch
-	importedHook func(*types.Block)  // Method to call upon successful block import
+	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.
@@ -121,12 +152,16 @@ func New(getBlock blockRetrievalFn, validateBlock blockValidatorFn, broadcastBlo
 	return &Fetcher{
 		notify:         make(chan *announce),
 		inject:         make(chan *inject),
-		filter:         make(chan chan []*types.Block),
+		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),
@@ -153,13 +188,17 @@ func (f *Fetcher) Stop() {
 
 // 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, fetcher blockRequesterFn) error {
+func (f *Fetcher) Notify(peer string, hash common.Hash, number uint64, time time.Time,
+	blockFetcher blockRequesterFn, // eth/61 specific whole block fetcher
+	headerFetcher headerRequesterFn, bodyFetcher bodyRequesterFn) error {
 	block := &announce{
-		hash:   hash,
+		hash:        hash,
-		number: number,
+		number:      number,
-		time:   time,
+		time:        time,
-		origin: peer,
+		origin:      peer,
-		fetch:  fetcher,
+		fetch61:     blockFetcher,
+		fetchHeader: headerFetcher,
+		fetchBodies: bodyFetcher,
 	}
 	select {
 	case f.notify <- block:
@@ -183,14 +222,16 @@ func (f *Fetcher) Enqueue(peer string, block *types.Block) error {
 	}
 }
 
-// Filter extracts all the blocks that were explicitly requested by the fetcher,
+// FilterBlocks extracts all the blocks that were explicitly requested by the fetcher,
 // returning those that should be handled differently.
-func (f *Fetcher) Filter(blocks types.Blocks) types.Blocks {
+func (f *Fetcher) FilterBlocks(blocks types.Blocks) types.Blocks {
+	glog.V(logger.Detail).Infof("[eth/61] filtering %d blocks", len(blocks))
+
 	// Send the filter channel to the fetcher
 	filter := make(chan []*types.Block)
 
 	select {
-	case f.filter <- filter:
+	case f.blockFilter <- filter:
 	case <-f.quit:
 		return nil
 	}
@@ -209,11 +250,69 @@ func (f *Fetcher) Filter(blocks types.Blocks) types.Blocks {
 	}
 }
 
+// FilterHeaders extracts all the headers that were explicitly requested by the fetcher,
+// returning those that should be handled differently.
+func (f *Fetcher) FilterHeaders(headers []*types.Header, time time.Time) []*types.Header {
+	glog.V(logger.Detail).Infof("[eth/62] filtering %d 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{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(transactions [][]*types.Transaction, uncles [][]*types.Header, time time.Time) ([][]*types.Transaction, [][]*types.Header) {
+	glog.V(logger.Detail).Infof("[eth/62] filtering %d:%d bodies", len(transactions), 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{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
-	fetch := time.NewTimer(0)
+	fetchTimer := time.NewTimer(0)
+	completeTimer := time.NewTimer(0)
+
 	for {
 		// Clean up any expired block fetches
 		for hash, announce := range f.fetching {
@@ -255,14 +354,25 @@ func (f *Fetcher) loop() {
 				glog.V(logger.Debug).Infof("Peer %s: exceeded outstanding announces (%d)", notification.origin, hashLimit)
 				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 {
+					glog.V(logger.Debug).Infof("[eth/62] Peer %s: discarded announcement #%d [%x…], distance %d", notification.origin, notification.number, notification.hash[:4], dist)
+					discardMeter.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 len(f.announced) == 1 {
-				f.reschedule(fetch)
+				f.rescheduleFetch(fetchTimer)
 			}
 
 		case op := <-f.inject:
@@ -275,7 +385,7 @@ func (f *Fetcher) loop() {
 			f.forgetHash(hash)
 			f.forgetBlock(hash)
 
-		case <-fetch.C:
+		case <-fetchTimer.C:
 			// At least one block's timer ran out, check for needing retrieval
 			request := make(map[string][]common.Hash)
 
@@ -292,30 +402,77 @@ func (f *Fetcher) loop() {
 					}
 				}
 			}
-			// Send out all block requests
+			// Send out all block (eth/61) or header (eth/62) requests
 			for peer, hashes := range request {
 				if glog.V(logger.Detail) && len(hashes) > 0 {
 					list := "["
 					for _, hash := range hashes {
-						list += fmt.Sprintf("%x, ", hash[:4])
+						list += fmt.Sprintf("%x…, ", hash[:4])
 					}
 					list = list[:len(list)-2] + "]"
 
-					glog.V(logger.Detail).Infof("Peer %s: fetching %s", peer, list)
+					if f.fetching[hashes[0]].fetch61 != nil {
+						glog.V(logger.Detail).Infof("[eth/61] Peer %s: fetching blocks %s", peer, list)
+					} else {
+						glog.V(logger.Detail).Infof("[eth/62] Peer %s: fetching headers %s", peer, list)
+					}
 				}
 				// Create a closure of the fetch and schedule in on a new thread
-				fetcher, hashes := f.fetching[hashes[0]].fetch, hashes
+				fetchBlocks, fetchHeader, hashes := f.fetching[hashes[0]].fetch61, f.fetching[hashes[0]].fetchHeader, hashes
 				go func() {
 					if f.fetchingHook != nil {
 						f.fetchingHook(hashes)
 					}
-					fetcher(hashes)
+					if fetchBlocks != nil {
+						// Use old eth/61 protocol to retrieve whole blocks
+						fetchBlocks(hashes)
+					} else {
+						// Use new eth/62 protocol to retrieve headers first
+						for _, hash := range hashes {
+							fetchHeader(hash) // Suboptimal, but protocol doesn't allow batch header retrievals
+						}
+					}
 				}()
 			}
 			// Schedule the next fetch if blocks are still pending
-			f.reschedule(fetch)
+			f.rescheduleFetch(fetchTimer)
 
-		case filter := <-f.filter:
+		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 {
+				if glog.V(logger.Detail) && len(hashes) > 0 {
+					list := "["
+					for _, hash := range hashes {
+						list += fmt.Sprintf("%x…, ", hash[:4])
+					}
+					list = list[:len(list)-2] + "]"
+
+					glog.V(logger.Detail).Infof("[eth/62] Peer %s: fetching bodies %s", peer, list)
+				}
+				// Create a closure of the fetch and schedule in on a new thread
+				if f.completingHook != nil {
+					f.completingHook(hashes)
+				}
+				go f.completing[hashes[0]].fetchBodies(hashes)
+			}
+			// Schedule the next fetch if blocks are still pending
+			f.rescheduleComplete(completeTimer)
+
+		case filter := <-f.blockFilter:
 			// Blocks arrived, extract any explicit fetches, return all else
 			var blocks types.Blocks
 			select {
@@ -352,12 +509,135 @@ func (f *Fetcher) loop() {
 					f.enqueue(announce.origin, block)
 				}
 			}
+
+		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
+			}
+			// 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 && 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 {
+						glog.V(logger.Detail).Infof("[eth/62] Peer %s: invalid block number for [%x…]: announced %d, provided %d", announce.origin, header.Hash().Bytes()[:4], announce.number, header.Number.Uint64())
+						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{}) {
+							glog.V(logger.Detail).Infof("[eth/62] Peer %s: block #%d [%x…] empty, skipping body retrieval", announce.origin, header.Number.Uint64(), header.Hash().Bytes()[:4])
+
+							complete = append(complete, types.NewBlockWithHeader(header))
+							f.completing[hash] = announce
+							continue
+						}
+						// Otherwise add to the list of blocks needing completion
+						incomplete = append(incomplete, announce)
+					} else {
+						glog.V(logger.Detail).Infof("[eth/62] Peer %s: block #%d [%x…] already imported, discarding header", announce.origin, header.Number.Uint64(), header.Hash().Bytes()[:4])
+						f.forgetHash(hash)
+					}
+				} else {
+					// Fetcher doesn't know about it, add to the return list
+					unknown = append(unknown, header)
+				}
+			}
+			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
+			}
+
+			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 {
+							// Mark the body matched, reassemble if still unknown
+							matched = true
+
+							if f.getBlock(hash) == nil {
+								blocks = append(blocks, types.NewBlockWithHeader(announce.header).WithBody(task.transactions[i], task.uncles[i]))
+							} 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
+				}
+			}
+
+			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)
+				}
+			}
 		}
 	}
 }
 
-// reschedule resets the specified fetch timer to the next announce timeout.
+// rescheduleFetch resets the specified fetch timer to the next announce timeout.
-func (f *Fetcher) reschedule(fetch *time.Timer) {
+func (f *Fetcher) rescheduleFetch(fetch *time.Timer) {
 	// Short circuit if no blocks are announced
 	if len(f.announced) == 0 {
 		return
@@ -372,6 +652,22 @@ func (f *Fetcher) reschedule(fetch *time.Timer) {
 	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) {
@@ -380,13 +676,15 @@ func (f *Fetcher) enqueue(peer string, block *types.Block) {
 	// Ensure the peer isn't DOSing us
 	count := f.queues[peer] + 1
 	if count > blockLimit {
-		glog.V(logger.Debug).Infof("Peer %s: discarded block #%d [%x], exceeded allowance (%d)", peer, block.NumberU64(), hash.Bytes()[:4], blockLimit)
+		glog.V(logger.Debug).Infof("Peer %s: discarded block #%d [%x…], exceeded allowance (%d)", peer, block.NumberU64(), hash.Bytes()[:4], blockLimit)
+		f.forgetHash(hash)
 		return
 	}
 	// Discard any past or too distant blocks
 	if dist := int64(block.NumberU64()) - int64(f.chainHeight()); dist < -maxUncleDist || dist > maxQueueDist {
-		glog.V(logger.Debug).Infof("Peer %s: discarded block #%d [%x], distance %d", peer, block.NumberU64(), hash.Bytes()[:4], dist)
+		glog.V(logger.Debug).Infof("Peer %s: discarded block #%d [%x…], distance %d", peer, block.NumberU64(), hash.Bytes()[:4], dist)
 		discardMeter.Mark(1)
+		f.forgetHash(hash)
 		return
 	}
 	// Schedule the block for future importing
@@ -400,7 +698,7 @@ func (f *Fetcher) enqueue(peer string, block *types.Block) {
 		f.queue.Push(op, -float32(block.NumberU64()))
 
 		if glog.V(logger.Debug) {
-			glog.Infof("Peer %s: queued block #%d [%x], total %v", peer, block.NumberU64(), hash.Bytes()[:4], f.queue.Size())
+			glog.Infof("Peer %s: queued block #%d [%x…], total %v", peer, block.NumberU64(), hash.Bytes()[:4], f.queue.Size())
 		}
 	}
 }
@@ -412,13 +710,14 @@ func (f *Fetcher) insert(peer string, block *types.Block) {
 	hash := block.Hash()
 
 	// Run the import on a new thread
-	glog.V(logger.Debug).Infof("Peer %s: importing block #%d [%x]", peer, block.NumberU64(), hash[:4])
+	glog.V(logger.Debug).Infof("Peer %s: importing block #%d [%x…]", peer, block.NumberU64(), hash[:4])
 	go func() {
 		defer func() { f.done <- hash }()
 
 		// If the parent's unknown, abort insertion
 		parent := f.getBlock(block.ParentHash())
 		if parent == nil {
+			glog.V(logger.Debug).Infof("Peer %s: parent []%x] of block #%d [%x…] unknown", block.ParentHash().Bytes()[:4], peer, block.NumberU64(), hash[:4])
 			return
 		}
 		// Quickly validate the header and propagate the block if it passes
@@ -434,13 +733,13 @@ func (f *Fetcher) insert(peer string, block *types.Block) {
 
 		default:
 			// Something went very wrong, drop the peer
-			glog.V(logger.Debug).Infof("Peer %s: block #%d [%x] verification failed: %v", peer, block.NumberU64(), hash[:4], err)
+			glog.V(logger.Debug).Infof("Peer %s: block #%d [%x…] verification failed: %v", peer, block.NumberU64(), hash[:4], err)
 			f.dropPeer(peer)
 			return
 		}
 		// Run the actual import and log any issues
 		if _, err := f.insertChain(types.Blocks{block}); err != nil {
-			glog.V(logger.Warn).Infof("Peer %s: block #%d [%x] import failed: %v", peer, block.NumberU64(), hash[:4], err)
+			glog.V(logger.Warn).Infof("Peer %s: block #%d [%x…] import failed: %v", peer, block.NumberU64(), hash[:4], err)
 			return
 		}
 		// If import succeeded, broadcast the block
@@ -474,9 +773,27 @@ func (f *Fetcher) forgetHash(hash common.Hash) {
 		}
 		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 frmo the fetcher's internal
+// 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 {

eth/fetcher/fetcher_test.go

@@ -27,21 +27,39 @@ import (
 	"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()
-	genesis      = core.GenesisBlockForTesting(testdb, common.Address{}, big.NewInt(0))
+	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.
+// 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(parent, testdb, n, func(i int, gen *core.BlockGen) {
+	blocks := core.GenerateChain(parent, testdb, n, func(i int, block *core.BlockGen) {
-		gen.SetCoinbase(common.Address{seed})
+		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 {
+			tx, err := types.NewTransaction(block.TxNonce(testAddress), common.Address{seed}, big.NewInt(1000), params.TxGas, nil, nil).SignECDSA(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()
@@ -60,6 +78,7 @@ type fetcherTester struct {
 
 	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
 }
@@ -69,6 +88,7 @@ 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.verifyBlock, tester.broadcastBlock, tester.chainHeight, tester.insertChain, tester.dropPeer)
 	tester.fetcher.Start()
@@ -122,12 +142,14 @@ func (f *fetcherTester) insertChain(blocks types.Blocks) (int, error) {
 	return 0, nil
 }
 
-// dropPeer is a nop placeholder for the peer removal.
+// dropPeer is an emulator for the peer removal, simply accumulating the various
+// peers dropped by the fetcher.
 func (f *fetcherTester) dropPeer(peer string) {
+	f.drops[peer] = true
 }
 
-// peerFetcher retrieves a fetcher associated with a simulated peer.
+// makeBlockFetcher retrieves a block fetcher associated with a simulated peer.
-func (f *fetcherTester) makeFetcher(blocks map[common.Hash]*types.Block) blockRequesterFn {
+func (f *fetcherTester) makeBlockFetcher(blocks map[common.Hash]*types.Block) blockRequesterFn {
 	closure := make(map[common.Hash]*types.Block)
 	for hash, block := range blocks {
 		closure[hash] = block
@@ -142,18 +164,105 @@ func (f *fetcherTester) makeFetcher(blocks map[common.Hash]*types.Block) blockRe
 			}
 		}
 		// Return on a new thread
-		go f.fetcher.Filter(blocks)
+		go f.fetcher.FilterBlocks(blocks)
 
 		return nil
 	}
 }
 
+// makeHeaderFetcher retrieves a block header fetcher associated with a simulated peer.
+func (f *fetcherTester) makeHeaderFetcher(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(headers, time.Now().Add(drift))
+
+		return nil
+	}
+}
+
+// makeBodyFetcher retrieves a block body fetcher associated with a simulated peer.
+func (f *fetcherTester) makeBodyFetcher(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(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) {
+func verifyImportEvent(t *testing.T, imported chan *types.Block, arrive bool) {
-	select {
+	if arrive {
-	case <-imported:
+		select {
-	case <-time.After(time.Second):
+		case <-imported:
-		t.Fatalf("import timeout")
+		case <-time.After(time.Second):
+			t.Fatalf("import timeout")
+		}
+	} else {
+		select {
+		case <-imported:
+			t.Fatalf("import invoked")
+		case <-time.After(10 * time.Millisecond):
+		}
 	}
 }
 
@@ -164,7 +273,7 @@ func verifyImportCount(t *testing.T, imported chan *types.Block, count int) {
 		select {
 		case <-imported:
 		case <-time.After(time.Second):
-			t.Fatalf("block %d: import timeout", i)
+			t.Fatalf("block %d: import timeout", i+1)
 		}
 	}
 	verifyImportDone(t, imported)
@@ -181,51 +290,78 @@ func verifyImportDone(t *testing.T, imported chan *types.Block) {
 
 // Tests that a fetcher accepts block announcements and initiates retrievals for
 // them, successfully importing into the local chain.
-func TestSequentialAnnouncements(t *testing.T) {
+func TestSequentialAnnouncements61(t *testing.T) { testSequentialAnnouncements(t, 61) }
+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()
-	fetcher := tester.makeFetcher(blocks)
+	blockFetcher := tester.makeBlockFetcher(blocks)
+	headerFetcher := tester.makeHeaderFetcher(blocks, -gatherSlack)
+	bodyFetcher := tester.makeBodyFetcher(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], 0, time.Now().Add(-arriveTimeout), fetcher)
+		if protocol < 62 {
-		verifyImportEvent(t, imported)
+			tester.fetcher.Notify("valid", hashes[i], 0, time.Now().Add(-arriveTimeout), blockFetcher, nil, nil)
+		} else {
+			tester.fetcher.Notify("valid", hashes[i], uint64(len(hashes)-i-1), time.Now().Add(-arriveTimeout), nil, 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 TestConcurrentAnnouncements(t *testing.T) {
+func TestConcurrentAnnouncements61(t *testing.T) { testConcurrentAnnouncements(t, 61) }
+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()
-	fetcher := tester.makeFetcher(blocks)
+	blockFetcher := tester.makeBlockFetcher(blocks)
+	headerFetcher := tester.makeHeaderFetcher(blocks, -gatherSlack)
+	bodyFetcher := tester.makeBodyFetcher(blocks, 0)
 
 	counter := uint32(0)
-	wrapper := func(hashes []common.Hash) error {
+	blockWrapper := func(hashes []common.Hash) error {
 		atomic.AddUint32(&counter, uint32(len(hashes)))
-		return fetcher(hashes)
+		return blockFetcher(hashes)
+	}
+	headerWrapper := func(hash common.Hash) error {
+		atomic.AddUint32(&counter, 1)
+		return headerFetcher(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], 0, time.Now().Add(-arriveTimeout), wrapper)
+		if protocol < 62 {
-		tester.fetcher.Notify("second", hashes[i], 0, time.Now().Add(-arriveTimeout+time.Millisecond), wrapper)
+			tester.fetcher.Notify("first", hashes[i], 0, time.Now().Add(-arriveTimeout), blockWrapper, nil, nil)
-		tester.fetcher.Notify("second", hashes[i], 0, time.Now().Add(-arriveTimeout-time.Millisecond), wrapper)
+			tester.fetcher.Notify("second", hashes[i], 0, time.Now().Add(-arriveTimeout+time.Millisecond), blockWrapper, nil, nil)
-
+			tester.fetcher.Notify("second", hashes[i], 0, time.Now().Add(-arriveTimeout-time.Millisecond), blockWrapper, nil, nil)
-		verifyImportEvent(t, imported)
+		} else {
+			tester.fetcher.Notify("first", hashes[i], uint64(len(hashes)-i-1), time.Now().Add(-arriveTimeout), nil, headerWrapper, bodyFetcher)
+			tester.fetcher.Notify("second", hashes[i], uint64(len(hashes)-i-1), time.Now().Add(-arriveTimeout+time.Millisecond), nil, headerWrapper, bodyFetcher)
+			tester.fetcher.Notify("second", hashes[i], uint64(len(hashes)-i-1), time.Now().Add(-arriveTimeout-time.Millisecond), nil, headerWrapper, bodyFetcher)
+		}
+		verifyImportEvent(t, imported, true)
 	}
 	verifyImportDone(t, imported)
 
@@ -237,56 +373,90 @@ func TestConcurrentAnnouncements(t *testing.T) {
 
 // Tests that announcements arriving while a previous is being fetched still
 // results in a valid import.
-func TestOverlappingAnnouncements(t *testing.T) {
+func TestOverlappingAnnouncements61(t *testing.T) { testOverlappingAnnouncements(t, 61) }
+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()
-	fetcher := tester.makeFetcher(blocks)
+	blockFetcher := tester.makeBlockFetcher(blocks)
+	headerFetcher := tester.makeHeaderFetcher(blocks, -gatherSlack)
+	bodyFetcher := tester.makeBodyFetcher(blocks, 0)
 
 	// Iteratively announce blocks, but overlap them continuously
-	fetching := make(chan []common.Hash)
+	overlap := 16
 	imported := make(chan *types.Block, len(hashes)-1)
-	tester.fetcher.fetchingHook = func(hashes []common.Hash) { fetching <- hashes }
+	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], 0, time.Now().Add(-arriveTimeout), fetcher)
+		if protocol < 62 {
+			tester.fetcher.Notify("valid", hashes[i], 0, time.Now().Add(-arriveTimeout), blockFetcher, nil, nil)
+		} else {
+			tester.fetcher.Notify("valid", hashes[i], uint64(len(hashes)-i-1), time.Now().Add(-arriveTimeout), nil, headerFetcher, bodyFetcher)
+		}
 		select {
-		case <-fetching:
+		case <-imported:
 		case <-time.After(time.Second):
-			t.Fatalf("hash %d: announce timeout", len(hashes)-i)
+			t.Fatalf("block %d: import timeout", len(hashes)-i)
 		}
 	}
 	// Wait for all the imports to complete and check count
-	verifyImportCount(t, imported, len(hashes)-1)
+	verifyImportCount(t, imported, overlap)
 }
 
 // Tests that announces already being retrieved will not be duplicated.
-func TestPendingDeduplication(t *testing.T) {
+func TestPendingDeduplication61(t *testing.T) { testPendingDeduplication(t, 61) }
+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()
-	fetcher := tester.makeFetcher(blocks)
+	blockFetcher := tester.makeBlockFetcher(blocks)
+	headerFetcher := tester.makeHeaderFetcher(blocks, -gatherSlack)
+	bodyFetcher := tester.makeBodyFetcher(blocks, 0)
 
 	delay := 50 * time.Millisecond
 	counter := uint32(0)
-	wrapper := func(hashes []common.Hash) error {
+	blockWrapper := func(hashes []common.Hash) error {
 		atomic.AddUint32(&counter, uint32(len(hashes)))
 
 		// Simulate a long running fetch
 		go func() {
 			time.Sleep(delay)
-			fetcher(hashes)
+			blockFetcher(hashes)
+		}()
+		return nil
+	}
+	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], 0, time.Now().Add(-arriveTimeout), wrapper)
+		if protocol < 62 {
+			tester.fetcher.Notify("repeater", hashes[0], 0, time.Now().Add(-arriveTimeout), blockWrapper, nil, nil)
+		} else {
+			tester.fetcher.Notify("repeater", hashes[0], 1, time.Now().Add(-arriveTimeout), nil, headerWrapper, bodyFetcher)
+		}
 		time.Sleep(time.Millisecond)
 	}
 	time.Sleep(delay)
@@ -302,14 +472,21 @@ func TestPendingDeduplication(t *testing.T) {
 
 // Tests that announcements retrieved in a random order are cached and eventually
 // imported when all the gaps are filled in.
-func TestRandomArrivalImport(t *testing.T) {
+func TestRandomArrivalImport61(t *testing.T) { testRandomArrivalImport(t, 61) }
+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()
-	fetcher := tester.makeFetcher(blocks)
+	blockFetcher := tester.makeBlockFetcher(blocks)
+	headerFetcher := tester.makeHeaderFetcher(blocks, -gatherSlack)
+	bodyFetcher := tester.makeBodyFetcher(blocks, 0)
 
 	// Iteratively announce blocks, skipping one entry
 	imported := make(chan *types.Block, len(hashes)-1)
@@ -317,25 +494,40 @@ func TestRandomArrivalImport(t *testing.T) {
 
 	for i := len(hashes) - 1; i >= 0; i-- {
 		if i != skip {
-			tester.fetcher.Notify("valid", hashes[i], 0, time.Now().Add(-arriveTimeout), fetcher)
+			if protocol < 62 {
+				tester.fetcher.Notify("valid", hashes[i], 0, time.Now().Add(-arriveTimeout), blockFetcher, nil, nil)
+			} else {
+				tester.fetcher.Notify("valid", hashes[i], uint64(len(hashes)-i-1), time.Now().Add(-arriveTimeout), nil, headerFetcher, bodyFetcher)
+			}
 			time.Sleep(time.Millisecond)
 		}
 	}
 	// Finally announce the skipped entry and check full import
-	tester.fetcher.Notify("valid", hashes[skip], 0, time.Now().Add(-arriveTimeout), fetcher)
+	if protocol < 62 {
+		tester.fetcher.Notify("valid", hashes[skip], 0, time.Now().Add(-arriveTimeout), blockFetcher, nil, nil)
+	} else {
+		tester.fetcher.Notify("valid", hashes[skip], uint64(len(hashes)-skip-1), time.Now().Add(-arriveTimeout), nil, 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 TestQueueGapFill(t *testing.T) {
+func TestQueueGapFill61(t *testing.T) { testQueueGapFill(t, 61) }
+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()
-	fetcher := tester.makeFetcher(blocks)
+	blockFetcher := tester.makeBlockFetcher(blocks)
+	headerFetcher := tester.makeHeaderFetcher(blocks, -gatherSlack)
+	bodyFetcher := tester.makeBodyFetcher(blocks, 0)
 
 	// Iteratively announce blocks, skipping one entry
 	imported := make(chan *types.Block, len(hashes)-1)
@@ -343,7 +535,11 @@ func TestQueueGapFill(t *testing.T) {
 
 	for i := len(hashes) - 1; i >= 0; i-- {
 		if i != skip {
-			tester.fetcher.Notify("valid", hashes[i], 0, time.Now().Add(-arriveTimeout), fetcher)
+			if protocol < 62 {
+				tester.fetcher.Notify("valid", hashes[i], 0, time.Now().Add(-arriveTimeout), blockFetcher, nil, nil)
+			} else {
+				tester.fetcher.Notify("valid", hashes[i], uint64(len(hashes)-i-1), time.Now().Add(-arriveTimeout), nil, headerFetcher, bodyFetcher)
+			}
 			time.Sleep(time.Millisecond)
 		}
 	}
@@ -354,13 +550,20 @@ func TestQueueGapFill(t *testing.T) {
 
 // Tests that blocks arriving from various sources (multiple propagations, hash
 // announces, etc) do not get scheduled for import multiple times.
-func TestImportDeduplication(t *testing.T) {
+func TestImportDeduplication61(t *testing.T) { testImportDeduplication(t, 61) }
+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()
-	fetcher := tester.makeFetcher(blocks)
+	blockFetcher := tester.makeBlockFetcher(blocks)
+	headerFetcher := tester.makeHeaderFetcher(blocks, -gatherSlack)
+	bodyFetcher := tester.makeBodyFetcher(blocks, 0)
 
 	counter := uint32(0)
 	tester.fetcher.insertChain = func(blocks types.Blocks) (int, error) {
@@ -374,7 +577,11 @@ func TestImportDeduplication(t *testing.T) {
 	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], 0, time.Now().Add(-arriveTimeout), fetcher)
+	if protocol < 62 {
+		tester.fetcher.Notify("valid", hashes[0], 0, time.Now().Add(-arriveTimeout), blockFetcher, nil, nil)
+	} else {
+		tester.fetcher.Notify("valid", hashes[0], 1, time.Now().Add(-arriveTimeout), nil, headerFetcher, bodyFetcher)
+	}
 	<-fetching
 
 	tester.fetcher.Enqueue("valid", blocks[hashes[0]])
@@ -391,35 +598,157 @@ func TestImportDeduplication(t *testing.T) {
 }
 
 // Tests that blocks with numbers much lower or higher than out current head get
-// discarded no prevent wasting resources on useless blocks from faulty peers.
+// discarded to prevent wasting resources on useless blocks from faulty peers.
-func TestDistantDiscarding(t *testing.T) {
+func TestDistantPropagationDiscarding(t *testing.T) {
-	// Create a long chain to import
+	// 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.hashes = []common.Hash{head}
 	tester.blocks = map[common.Hash]*types.Block{head: blocks[head]}
 
 	// Ensure that a block with a lower number than the threshold is discarded
-	tester.fetcher.Enqueue("lower", blocks[hashes[0]])
+	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[len(hashes)-1]])
+	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.hashes = []common.Hash{head}
+	tester.blocks = map[common.Hash]*types.Block{head: blocks[head]}
+
+	headerFetcher := tester.makeHeaderFetcher(blocks, -gatherSlack)
+	bodyFetcher := tester.makeBodyFetcher(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), nil, 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), nil, 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()
+	headerFetcher := tester.makeHeaderFetcher(blocks, -gatherSlack)
+	bodyFetcher := tester.makeBodyFetcher(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), nil, headerFetcher, bodyFetcher)
+	verifyImportEvent(t, imported, false)
+
+	if !tester.drops["bad"] {
+		t.Fatalf("peer with invalid numbered announcement not dropped")
+	}
+	// Make sure a good announcement passes without a drop
+	tester.fetcher.Notify("good", hashes[0], 1, time.Now().Add(-arriveTimeout), nil, headerFetcher, bodyFetcher)
+	verifyImportEvent(t, imported, true)
+
+	if tester.drops["good"] {
+		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(blocks, -gatherSlack)
+	bodyFetcher := tester.makeBodyFetcher(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), nil, 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 TestHashMemoryExhaustionAttack(t *testing.T) {
+func TestHashMemoryExhaustionAttack61(t *testing.T) { testHashMemoryExhaustionAttack(t, 61) }
+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()
 
@@ -429,17 +758,29 @@ func TestHashMemoryExhaustionAttack(t *testing.T) {
 	// Create a valid chain and an infinite junk chain
 	targetBlocks := hashLimit + 2*maxQueueDist
 	hashes, blocks := makeChain(targetBlocks, 0, genesis)
-	valid := tester.makeFetcher(blocks)
+	validBlockFetcher := tester.makeBlockFetcher(blocks)
+	validHeaderFetcher := tester.makeHeaderFetcher(blocks, -gatherSlack)
+	validBodyFetcher := tester.makeBodyFetcher(blocks, 0)
 
 	attack, _ := makeChain(targetBlocks, 0, unknownBlock)
-	attacker := tester.makeFetcher(nil)
+	attackerBlockFetcher := tester.makeBlockFetcher(nil)
+	attackerHeaderFetcher := tester.makeHeaderFetcher(nil, -gatherSlack)
+	attackerBodyFetcher := tester.makeBodyFetcher(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], 0, time.Now(), valid)
+			if protocol < 62 {
+				tester.fetcher.Notify("valid", hashes[len(hashes)-2-i], 0, time.Now(), validBlockFetcher, nil, nil)
+			} else {
+				tester.fetcher.Notify("valid", hashes[len(hashes)-2-i], uint64(i+1), time.Now(), nil, validHeaderFetcher, validBodyFetcher)
+			}
+		}
+		if protocol < 62 {
+			tester.fetcher.Notify("attacker", attack[i], 0, time.Now(), attackerBlockFetcher, nil, nil)
+		} else {
+			tester.fetcher.Notify("attacker", attack[i], 1 /* don't distance drop */, time.Now(), nil, attackerHeaderFetcher, attackerBodyFetcher)
 		}
-		tester.fetcher.Notify("attacker", attack[i], 0, time.Now(), attacker)
 	}
 	if len(tester.fetcher.announced) != hashLimit+maxQueueDist {
 		t.Fatalf("queued announce count mismatch: have %d, want %d", len(tester.fetcher.announced), hashLimit+maxQueueDist)
@@ -449,8 +790,12 @@ func TestHashMemoryExhaustionAttack(t *testing.T) {
 
 	// 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], 0, time.Now().Add(-arriveTimeout), valid)
+		if protocol < 62 {
-		verifyImportEvent(t, imported)
+			tester.fetcher.Notify("valid", hashes[i], 0, time.Now().Add(-arriveTimeout), validBlockFetcher, nil, nil)
+		} else {
+			tester.fetcher.Notify("valid", hashes[i], uint64(len(hashes)-i-1), time.Now().Add(-arriveTimeout), nil, validHeaderFetcher, validBodyFetcher)
+		}
+		verifyImportEvent(t, imported, true)
 	}
 	verifyImportDone(t, imported)
 }
@@ -498,7 +843,7 @@ func TestBlockMemoryExhaustionAttack(t *testing.T) {
 	// 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)
+		verifyImportEvent(t, imported, true)
 	}
 	verifyImportDone(t, imported)
 }

eth/handler.go

@@ -201,7 +201,9 @@ func (pm *ProtocolManager) handle(p *peer) error {
 	defer pm.removePeer(p.id)
 
 	// Register the peer in the downloader. If the downloader considers it banned, we disconnect
-	if err := pm.downloader.RegisterPeer(p.id, p.version, p.Head(), p.RequestHashes, p.RequestHashesFromNumber, p.RequestBlocks); err != nil {
+	if err := pm.downloader.RegisterPeer(p.id, p.version, p.Head(),
+		p.RequestHashes, p.RequestHashesFromNumber, p.RequestBlocks,
+		p.RequestHeadersByHash, p.RequestHeadersByNumber, p.RequestBodies); err != nil {
 		return err
 	}
 	// Propagate existing transactions. new transactions appearing
@@ -287,7 +289,7 @@ func (pm *ProtocolManager) handleMsg(p *peer) error {
 			break
 		}
 		// Deliver them all to the downloader for queuing
-		err := pm.downloader.DeliverHashes(p.id, hashes)
+		err := pm.downloader.DeliverHashes61(p.id, hashes)
 		if err != nil {
 			glog.V(logger.Debug).Infoln(err)
 		}
@@ -332,8 +334,8 @@ func (pm *ProtocolManager) handleMsg(p *peer) error {
 			block.ReceivedAt = msg.ReceivedAt
 		}
 		// Filter out any explicitly requested blocks, deliver the rest to the downloader
-		if blocks := pm.fetcher.Filter(blocks); len(blocks) > 0 {
+		if blocks := pm.fetcher.FilterBlocks(blocks); len(blocks) > 0 {
-			pm.downloader.DeliverBlocks(p.id, blocks)
+			pm.downloader.DeliverBlocks61(p.id, blocks)
 		}
 
 	// Block header query, collect the requested headers and reply
@@ -401,6 +403,46 @@ func (pm *ProtocolManager) handleMsg(p *peer) error {
 		}
 		return p.SendBlockHeaders(headers)
 
+	case p.version >= eth62 && msg.Code == BlockHeadersMsg:
+		// A batch of headers arrived to one of our previous requests
+		var headers []*types.Header
+		if err := msg.Decode(&headers); err != nil {
+			return errResp(ErrDecode, "msg %v: %v", msg, err)
+		}
+		// Filter out any explicitly requested headers, deliver the rest to the downloader
+		filter := len(headers) == 1
+		if filter {
+			headers = pm.fetcher.FilterHeaders(headers, time.Now())
+		}
+		if len(headers) > 0 || !filter {
+			err := pm.downloader.DeliverHeaders(p.id, headers)
+			if err != nil {
+				glog.V(logger.Debug).Infoln(err)
+			}
+		}
+
+	case p.version >= eth62 && msg.Code == BlockBodiesMsg:
+		// A batch of block bodies arrived to one of our previous requests
+		var request blockBodiesData
+		if err := msg.Decode(&request); err != nil {
+			return errResp(ErrDecode, "msg %v: %v", msg, err)
+		}
+		// Deliver them all to the downloader for queuing
+		trasactions := make([][]*types.Transaction, len(request))
+		uncles := make([][]*types.Header, len(request))
+
+		for i, body := range request {
+			trasactions[i] = body.Transactions
+			uncles[i] = body.Uncles
+		}
+		// Filter out any explicitly requested bodies, deliver the rest to the downloader
+		if trasactions, uncles := pm.fetcher.FilterBodies(trasactions, uncles, time.Now()); len(trasactions) > 0 || len(uncles) > 0 {
+			err := pm.downloader.DeliverBodies(p.id, trasactions, uncles)
+			if err != nil {
+				glog.V(logger.Debug).Infoln(err)
+			}
+		}
+
 	case p.version >= eth62 && msg.Code == GetBlockBodiesMsg:
 		// Decode the retrieval message
 		msgStream := rlp.NewStream(msg.Payload, uint64(msg.Size))
@@ -522,7 +564,11 @@ func (pm *ProtocolManager) handleMsg(p *peer) error {
 			}
 		}
 		for _, block := range unknown {
-			pm.fetcher.Notify(p.id, block.Hash, block.Number, time.Now(), p.RequestBlocks)
+			if p.version < eth62 {
+				pm.fetcher.Notify(p.id, block.Hash, block.Number, time.Now(), p.RequestBlocks, nil, nil)
+			} else {
+				pm.fetcher.Notify(p.id, block.Hash, block.Number, time.Now(), nil, p.RequestOneHeader, p.RequestBodies)
+			}
 		}
 
 	case msg.Code == NewBlockMsg:
@@ -612,7 +658,11 @@ func (pm *ProtocolManager) BroadcastBlock(block *types.Block, propagate bool) {
 	// Otherwise if the block is indeed in out own chain, announce it
 	if pm.chainman.HasBlock(hash) {
 		for _, peer := range peers {
-			peer.SendNewBlockHashes([]common.Hash{hash})
+			if peer.version < eth62 {
+				peer.SendNewBlockHashes61([]common.Hash{hash})
+			} else {
+				peer.SendNewBlockHashes([]common.Hash{hash}, []uint64{block.NumberU64()})
+			}
 		}
 		glog.V(logger.Detail).Infof("announced block %x to %d peers in %v", hash[:4], len(peers), time.Since(block.ReceivedAt))
 	}

eth/peer.go

@@ -145,15 +145,29 @@ func (p *peer) SendBlocks(blocks []*types.Block) error {
 	return p2p.Send(p.rw, BlocksMsg, blocks)
 }
 
-// SendNewBlockHashes announces the availability of a number of blocks through
+// SendNewBlockHashes61 announces the availability of a number of blocks through
 // a hash notification.
-func (p *peer) SendNewBlockHashes(hashes []common.Hash) error {
+func (p *peer) SendNewBlockHashes61(hashes []common.Hash) error {
 	for _, hash := range hashes {
 		p.knownBlocks.Add(hash)
 	}
 	return p2p.Send(p.rw, NewBlockHashesMsg, hashes)
 }
 
+// SendNewBlockHashes announces the availability of a number of blocks through
+// a hash notification.
+func (p *peer) SendNewBlockHashes(hashes []common.Hash, numbers []uint64) error {
+	for _, hash := range hashes {
+		p.knownBlocks.Add(hash)
+	}
+	request := make(newBlockHashesData, len(hashes))
+	for i := 0; i < len(hashes); i++ {
+		request[i].Hash = hashes[i]
+		request[i].Number = numbers[i]
+	}
+	return p2p.Send(p.rw, NewBlockHashesMsg, request)
+}
+
 // SendNewBlock propagates an entire block to a remote peer.
 func (p *peer) SendNewBlock(block *types.Block, td *big.Int) error {
 	p.knownBlocks.Add(block.Hash())
@@ -185,40 +199,61 @@ func (p *peer) SendReceipts(receipts []*types.Receipt) error {
 // RequestHashes fetches a batch of hashes from a peer, starting at from, going
 // towards the genesis block.
 func (p *peer) RequestHashes(from common.Hash) error {
-	glog.V(logger.Debug).Infof("%v fetching hashes (%d) from %x...\n", p, downloader.MaxHashFetch, from[:4])
+	glog.V(logger.Debug).Infof("%v fetching hashes (%d) from %x...", p, downloader.MaxHashFetch, from[:4])
 	return p2p.Send(p.rw, GetBlockHashesMsg, getBlockHashesData{from, uint64(downloader.MaxHashFetch)})
 }
 
 // RequestHashesFromNumber fetches a batch of hashes from a peer, starting at
 // the requested block number, going upwards towards the genesis block.
 func (p *peer) RequestHashesFromNumber(from uint64, count int) error {
-	glog.V(logger.Debug).Infof("%v fetching hashes (%d) from #%d...\n", p, count, from)
+	glog.V(logger.Debug).Infof("%v fetching hashes (%d) from #%d...", p, count, from)
 	return p2p.Send(p.rw, GetBlockHashesFromNumberMsg, getBlockHashesFromNumberData{from, uint64(count)})
 }
 
 // RequestBlocks fetches a batch of blocks corresponding to the specified hashes.
 func (p *peer) RequestBlocks(hashes []common.Hash) error {
-	glog.V(logger.Debug).Infof("%v fetching %v blocks\n", p, len(hashes))
+	glog.V(logger.Debug).Infof("%v fetching %v blocks", p, len(hashes))
 	return p2p.Send(p.rw, GetBlocksMsg, hashes)
 }
 
-// RequestHeaders fetches a batch of blocks' headers corresponding to the
+// RequestHeaders is a wrapper around the header query functions to fetch a
-// specified hashes.
+// single header. It is used solely by the fetcher.
-func (p *peer) RequestHeaders(hashes []common.Hash) error {
+func (p *peer) RequestOneHeader(hash common.Hash) error {
-	glog.V(logger.Debug).Infof("%v fetching %v headers\n", p, len(hashes))
+	glog.V(logger.Debug).Infof("%v fetching a single header: %x", p, hash)
-	return p2p.Send(p.rw, GetBlockHeadersMsg, hashes)
+	return p2p.Send(p.rw, GetBlockHeadersMsg, &getBlockHeadersData{Origin: hashOrNumber{Hash: hash}, Amount: uint64(1), Skip: uint64(0), Reverse: false})
+}
+
+// RequestHeadersByHash fetches a batch of blocks' headers corresponding to the
+// specified header query, based on the hash of an origin block.
+func (p *peer) RequestHeadersByHash(origin common.Hash, amount int, skip int, reverse bool) error {
+	glog.V(logger.Debug).Infof("%v fetching %d headers from %x, skipping %d (reverse = %v)", p, amount, origin[:4], skip, reverse)
+	return p2p.Send(p.rw, GetBlockHeadersMsg, &getBlockHeadersData{Origin: hashOrNumber{Hash: origin}, Amount: uint64(amount), Skip: uint64(skip), Reverse: reverse})
+}
+
+// RequestHeadersByNumber fetches a batch of blocks' headers corresponding to the
+// specified header query, based on the number of an origin block.
+func (p *peer) RequestHeadersByNumber(origin uint64, amount int, skip int, reverse bool) error {
+	glog.V(logger.Debug).Infof("%v fetching %d headers from #%d, skipping %d (reverse = %v)", p, amount, origin, skip, reverse)
+	return p2p.Send(p.rw, GetBlockHeadersMsg, &getBlockHeadersData{Origin: hashOrNumber{Number: origin}, Amount: uint64(amount), Skip: uint64(skip), Reverse: reverse})
+}
+
+// RequestBodies fetches a batch of blocks' bodies corresponding to the hashes
+// specified.
+func (p *peer) RequestBodies(hashes []common.Hash) error {
+	glog.V(logger.Debug).Infof("%v fetching %d block bodies", p, len(hashes))
+	return p2p.Send(p.rw, GetBlockBodiesMsg, hashes)
 }
 
 // RequestNodeData fetches a batch of arbitrary data from a node's known state
 // data, corresponding to the specified hashes.
 func (p *peer) RequestNodeData(hashes []common.Hash) error {
-	glog.V(logger.Debug).Infof("%v fetching %v state data\n", p, len(hashes))
+	glog.V(logger.Debug).Infof("%v fetching %v state data", p, len(hashes))
 	return p2p.Send(p.rw, GetNodeDataMsg, hashes)
 }
 
 // RequestReceipts fetches a batch of transaction receipts from a remote node.
 func (p *peer) RequestReceipts(hashes []common.Hash) error {
-	glog.V(logger.Debug).Infof("%v fetching %v receipts\n", p, len(hashes))
+	glog.V(logger.Debug).Infof("%v fetching %v receipts", p, len(hashes))
 	return p2p.Send(p.rw, GetReceiptsMsg, hashes)
 }