From 47a7fe5d22fe2a6be783f6576070814fe951eaaf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C3=A9ter=20Szil=C3=A1gyi?= <peterke@gmail.com>
Date: Fri, 14 Aug 2015 21:25:41 +0300
Subject: eth: port the synchronisation algo to eth/62

---
 eth/downloader/downloader.go      | 674 ++++++++++++++++++++++++++++++++------
 eth/downloader/downloader_test.go | 337 ++++++++++++++-----
 eth/downloader/peer.go            |  92 +++++-
 eth/downloader/queue.go           | 239 ++++++++++++--
 4 files changed, 1125 insertions(+), 217 deletions(-)

(limited to 'eth/downloader')

diff --git a/eth/downloader/downloader.go b/eth/downloader/downloader.go
index b28879ee6..0e8529756 100644
--- a/eth/downloader/downloader.go
+++ b/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
-	blockSoftTTL    = 3 * time.Second  // Request completion threshold for increasing or decreasing a peer's bandwidth
-	blockHardTTL    = 3 * blockSoftTTL // Maximum time allowance before a block request is considered expired
-	crossCheckCycle = time.Second      // Period after which to check for expired cross checks
+	hashTTL      = 5 * time.Second  // [eth/61] Time it takes for a hash request to time out
+	blockSoftTTL = 3 * time.Second  // [eth/61] Request completion threshold for increasing or decreasing a peer's bandwidth
+	blockHardTTL = 3 * blockSoftTTL // [eth/61] Maximum time allowance before a block request is considered expired
+	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)
-	maxBannedHashes = 4096       // Number of bannable hashes before phasing old ones out
-	maxBlockProcess = 256        // Number of blocks to import at once into the chain
+	maxQueuedHashes  = 256 * 1024 // [eth/61] Maximum number of hashes to queue for import (DOS protection)
+	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
 )
 
 var (
-	errBusy             = errors.New("busy")
-	errUnknownPeer      = errors.New("peer is unknown or unhealthy")
-	errBadPeer          = errors.New("action from bad peer ignored")
-	errStallingPeer     = errors.New("peer is stalling")
-	errBannedHead       = errors.New("peer head hash already banned")
-	errNoPeers          = errors.New("no peers to keep download active")
-	errPendingQueue     = errors.New("pending items in queue")
-	errTimeout          = errors.New("timeout")
-	errEmptyHashSet     = errors.New("empty hash set by peer")
-	errPeersUnavailable = errors.New("no peers available or all peers tried for block download process")
-	errAlreadyInPool    = errors.New("hash already in pool")
-	errInvalidChain     = errors.New("retrieved hash chain is invalid")
-	errCrossCheckFailed = errors.New("block cross-check failed")
-	errCancelHashFetch  = errors.New("hash fetching canceled (requested)")
-	errCancelBlockFetch = errors.New("block downloading canceled (requested)")
-	errNoSyncActive     = errors.New("no sync active")
+	errBusy              = errors.New("busy")
+	errUnknownPeer       = errors.New("peer is unknown or unhealthy")
+	errBadPeer           = errors.New("action from bad peer ignored")
+	errStallingPeer      = errors.New("peer is stalling")
+	errNoPeers           = errors.New("no peers to keep download active")
+	errPendingQueue      = errors.New("pending items in queue")
+	errTimeout           = errors.New("timeout")
+	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")
+	errAlreadyInPool     = errors.New("hash already in pool")
+	errInvalidChain      = errors.New("retrieved hash chain is invalid")
+	errInvalidBody       = errors.New("retrieved block body is invalid")
+	errCancelHashFetch   = errors.New("hash fetching canceled (requested)")
+	errCancelBlockFetch  = errors.New("block downloading canceled (requested)")
+	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)
 
+// hashPack is a batch of block hashes returned by a peer (eth/61).
+type hashPack struct {
+	peerId string
+	hashes []common.Hash
+}
+
+// blockPack is a batch of blocks returned by a peer (eth/61).
 type blockPack struct {
 	peerId string
 	blocks []*types.Block
 }
 
-type hashPack struct {
-	peerId string
-	hashes []common.Hash
+// headerPack is a batch of block headers returned by a peer.
+type headerPack struct {
+	peerId  string
+	headers []*types.Header
 }
 
-type crossCheck struct {
-	expire time.Time
-	parent common.Hash
+// 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
-	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
+	queue *queue   // Scheduler for selecting the hashes to download
+	peers *peerSet // Set of active peers from which download can proceed
 
 	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
-	blockCh   chan blockPack // Channel receiving inbound blocks
-	processCh chan bool      // Channel to signal the block fetcher of new or finished work
+	hashCh    chan hashPack   // [eth/61] Channel receiving inbound hashes
+	blockCh   chan blockPack  // [eth/61] Channel receiving inbound blocks
+	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
-	downloader := &Downloader{
+	return &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 {
-	// If the peer wants to send a banned hash, reject
-	if d.banned.Has(head) {
-		glog.V(logger.Debug).Infoln("Register rejected, head hash banned:", id)
-		return errBannedHead
-	}
-	// Otherwise try to construct and register the peer
+func (d *Downloader) RegisterPeer(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) error {
+
 	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)
-	switch p.version {
-	case eth61:
+	glog.V(logger.Debug).Infof("Synchronising with the network using: %s [eth/%d]", p.id, p.version)
+	defer glog.V(logger.Debug).Infof("Synchronisation terminated")
+
+	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.fetchBlocks(number + 1) }()
+		go func() { errc <- d.fetchHeaders(p, td, 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
-// head blocks match), we do a binary search to find the common ancestor.
-func (d *Downloader) findAncestor(p *peer) (uint64, error) {
+// 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) 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
-// the download schedule. This is usually invoked through the BlockHashesMsg by
-// the protocol handler.
-func (d *Downloader) DeliverHashes(id string, hashes []common.Hash) error {
+// DeliverHeaders injects a new batch of blck headers received from a remote
+// node into the download schedule.
+func (d *Downloader) DeliverHeaders(id string, headers []*types.Header) 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:
diff --git a/eth/downloader/downloader_test.go b/eth/downloader/downloader_test.go
index 7e3456433..8d009b671 100644
--- a/eth/downloader/downloader_test.go
+++ b/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()
-	genesis   = core.GenesisBlockForTesting(testdb, common.Address{}, big.NewInt(0))
+	testdb, _   = ethdb.NewMemDatabase()
+	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
-// parent. the returned hash chain is ordered head->parent.
+// makeChain creates a chain of n blocks starting at and including parent.
+// the returned hash chain is ordered head->parent. In addition, every 3rd block
+// contains a transaction and every 5th an uncle to allow testing correct block
+// reassembly.
 func makeChain(n int, seed byte, parent *types.Block) ([]common.Hash, map[common.Hash]*types.Block) {
-	blocks := core.GenerateChain(parent, testdb, n, func(i int, gen *core.BlockGen) {
-		gen.SetCoinbase(common.Address{seed})
+	blocks := core.GenerateChain(parent, testdb, n, func(i int, block *core.BlockGen) {
+		block.SetCoinbase(common.Address{seed})
+
+		// If the block number is multiple of 3, send a bonus transaction to the miner
+		if parent == genesis && i%3 == 0 {
+			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)
-		for i := 0; i < limit && len(hashes)-int(head)-1-i >= 0; i++ {
+		result := make([]common.Hash, 0, count)
+		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)
-	tester.downloader.insertChain = func(blocks types.Blocks) (int, error) {
-		n, err := tester.insertChain(blocks)
-		done <- n
-		return n, err
+	blocked, proceed := uint32(0), make(chan struct{})
+	tester.downloader.chainInsertHook = func(blocks []*Block) {
+		atomic.StoreUint32(&blocked, uint32(len(blocks)))
+		<-proceed
 	}
 	// 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 {
-			t.Fatalf("block count mismatch: have %v, want %v", cached, blockCacheLimit)
+		if cached != blockCacheLimit && len(tester.ownBlocks)+cached+int(atomic.LoadUint32(&blocked)) != targetBlocks+1 {
+			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
-		for cached > maxBlockProcess {
-			cached -= <-done
+		// Permit the blocked blocks to import
+		if atomic.LoadUint32(&blocked) > 0 {
+			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 B", eth61, hashesB, blocksB)
+	tester.newPeer("fork A", protocol, hashesA, blocksA)
+	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.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.DeliverBlocks("bad peer", []*types.Block{}); 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()
-	if hashCount > 0 || blockCount > 0 {
-		t.Errorf("block or hash count mismatch: %d hashes, %d blocks, want 0", hashCount, blockCount)
+	downloading, importing := tester.downloader.queue.Size()
+	if downloading > 0 || importing > 0 {
+		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()
-	if hashCount > 0 || blockCount > 0 {
-		t.Errorf("block or hash count mismatch: %d hashes, %d blocks, want 0", hashCount, blockCount)
+	downloading, importing = tester.downloader.queue.Size()
+	if downloading > 0 || importing > 0 {
+		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
-		{errBusy, false},             // Sync is already in progress, no problem
-		{errUnknownPeer, false},      // Peer is unknown, was already dropped, don't double drop
-		{errBadPeer, true},           // Peer was deemed bad for some reason, 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
-		{errPendingQueue, false},     // There are blocks still cached, wait to exhaust, no issue
-		{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
-		{errPeersUnavailable, true},  // Nobody had the advertised blocks, drop the advertiser
-		{errInvalidChain, true},      // Hash chain was detected as invalid, definitely drop
-		{errCrossCheckFailed, true},  // Hash-origin failed to pass a block cross check, 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
+		{nil, false},                  // Sync succeeded, all is well
+		{errBusy, false},              // Sync is already in progress, no problem
+		{errUnknownPeer, false},       // Peer is unknown, was already dropped, don't double drop
+		{errBadPeer, true},            // Peer was deemed bad for some reason, drop it
+		{errStallingPeer, true},       // Peer was detected to be stalling, drop it
+		{errNoPeers, false},           // No peers to download from, soft race, 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
+		{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
+		{errInvalidChain, true},       // Hash chain was detected as invalid, definitely 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
+		{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 {
diff --git a/eth/downloader/peer.go b/eth/downloader/peer.go
index 4273b9168..8fd1f9a99 100644
--- a/eth/downloader/peer.go
+++ b/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
-	getAbsHashes absoluteHashFetcherFn // Method to retrieve a batch of hashes from an absolute position
-	getBlocks    blockFetcherFn        // Method to retrieve a batch of blocks
+	getRelHashes relativeHashFetcherFn // [eth/61] Method to retrieve a batch of hashes from an origin hash
+	getAbsHashes absoluteHashFetcherFn // [eth/61] Method to retrieve a batch of hashes from an absolute position
+	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,
-		head:         head,
-		capacity:     1,
+		id:       id,
+		head:     head,
+		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.
-func (p *peer) Fetch(request *fetchRequest) error {
+// Fetch61 sends a block retrieval request to the remote peer.
+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 {
diff --git a/eth/downloader/queue.go b/eth/downloader/queue.go
index 96e08e144..a527414ff 100644
--- a/eth/downloader/queue.go
+++ b/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
-	Hashes map[common.Hash]int // Requested hashes with their insertion index (priority)
-	Time   time.Time           // Time when the request was made
+	Peer    *peer               // Peer to which the request was sent
+	Hashes  map[common.Hash]int // [eth/61] Requested hashes with their insertion index (priority)
+	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)
-	hashQueue   *prque.Prque        // Priority queue of the block hashes to fetch
-	hashCounter int                 // Counter indexing the added hashes to ensure retrieval order
+	hashPool    map[common.Hash]int // [eth/61] Pending hashes, mapping to their insertion index (priority)
+	hashQueue   *prque.Prque        // [eth/61] Priority queue of the block hashes to fetch
+	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),
-		hashQueue:  prque.New(),
-		pendPool:   make(map[string]*fetchRequest),
-		blockPool:  make(map[common.Hash]uint64),
-		blockCache: make([]*Block, blockCacheLimit),
+		hashPool:    make(map[common.Hash]int),
+		hashQueue:   prque.New(),
+		headerPool:  make(map[common.Hash]*types.Header),
+		headerQueue: prque.New(),
+		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.
-func (q *queue) Deliver(id string, blocks []*types.Block) (err error) {
+// Deliver61 injects a block retrieval response into the download queue.
+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
-		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 block
-		q.blockCache[index] = &Block{
-			RawBlock:   block,
-			OriginPeer: id,
+		// Queue the block up for processing
+		if err := q.enqueue(id, block); err != nil {
+			return err
 		}
 		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()
-- 
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