major rewrite, reorg of blockpool + new features

- blockpool moves to its own package
- uses errs pkg for its own coded errors
- publicly settable config of params (time intervals and batchsizes)
- test helpers in subpackage
- optional TD in blocks used now to update peers chain info
- major improvement in algorithm
- fix fragility and sync/parallelisation bugs
- implement status for reporting on sync status (peers/hashes/blocks etc)
- several tests added and further corner cases covered

13 files changed, 3583 insertions, 0 deletions

diff --git a/blockpool/blockpool.go b/blockpool/blockpool.go
new file mode 100644
index 000000000..0126d734c
--- /dev/null
+++ b/blockpool/blockpool.go
@@ -0,0 +1,749 @@
+package blockpool
+
+import (
+	"bytes"
+	"fmt"
+	"math/big"
+	"sync"
+	"time"
+
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/errs"
+	ethlogger "github.com/ethereum/go-ethereum/logger"
+	"github.com/ethereum/go-ethereum/pow"
+)
+
+var plog = ethlogger.NewLogger("Blockpool")
+
+var (
+	// max number of block hashes sent in one request
+	blockHashesBatchSize = 512
+	// max number of blocks sent in one request
+	blockBatchSize = 64
+	// interval between two consecutive block checks (and requests)
+	blocksRequestInterval = 3 * time.Second
+	// level of redundancy in block requests sent
+	blocksRequestRepetition = 1
+	// interval between two consecutive block hash checks (and requests)
+	blockHashesRequestInterval = 3 * time.Second
+	// max number of idle iterations, ie., check through a section without new blocks coming in
+	blocksRequestMaxIdleRounds = 100
+	// timeout interval: max time allowed for peer without sending a block hash
+	blockHashesTimeout = 60 * time.Second
+	// timeout interval: max time allowed for peer without sending a block
+	blocksTimeout = 120 * time.Second
+)
+
+// config embedded in components, by default fall back to constants
+// by default all resolved to local
+type Config struct {
+	BlockHashesBatchSize       int
+	BlockBatchSize             int
+	BlocksRequestRepetition    int
+	BlocksRequestMaxIdleRounds int
+	BlockHashesRequestInterval time.Duration
+	BlocksRequestInterval      time.Duration
+	BlockHashesTimeout         time.Duration
+	BlocksTimeout              time.Duration
+}
+
+// blockpool errors
+const (
+	ErrInvalidBlock = iota
+	ErrInvalidPoW
+	ErrUnrequestedBlock
+	ErrInsufficientChainInfo
+)
+
+var errorToString = map[int]string{
+	ErrInvalidBlock:          "Invalid block",
+	ErrInvalidPoW:            "Invalid PoW",
+	ErrUnrequestedBlock:      "Unrequested block",
+	ErrInsufficientChainInfo: "Insufficient chain info",
+}
+
+// init initialises all your laundry
+func (self *Config) init() {
+	if self.BlockHashesBatchSize == 0 {
+		self.BlockHashesBatchSize = blockHashesBatchSize
+	}
+	if self.BlockBatchSize == 0 {
+		self.BlockBatchSize = blockBatchSize
+	}
+	if self.BlocksRequestRepetition == 0 {
+		self.BlocksRequestRepetition = blocksRequestRepetition
+	}
+	if self.BlocksRequestMaxIdleRounds == 0 {
+		self.BlocksRequestMaxIdleRounds = blocksRequestMaxIdleRounds
+	}
+	if self.BlockHashesRequestInterval == 0 {
+		self.BlockHashesRequestInterval = blockHashesRequestInterval
+	}
+	if self.BlocksRequestInterval == 0 {
+		self.BlocksRequestInterval = blocksRequestInterval
+	}
+	if self.BlockHashesTimeout == 0 {
+		self.BlockHashesTimeout = blockHashesTimeout
+	}
+	if self.BlocksTimeout == 0 {
+		self.BlocksTimeout = blocksTimeout
+	}
+}
+
+// node is the basic unit of the internal model of block chain/tree in the blockpool
+type node struct {
+	lock    sync.RWMutex
+	hash    []byte
+	block   *types.Block
+	hashBy  string
+	blockBy string
+	td      *big.Int
+}
+
+type index struct {
+	int
+}
+
+// entry is the struct kept and indexed in the pool
+type entry struct {
+	node    *node
+	section *section
+	index   *index
+}
+
+type BlockPool struct {
+	Config *Config
+
+	// the minimal interface with blockchain
+	hasBlock    func(hash []byte) bool
+	insertChain func(types.Blocks) error
+	verifyPoW   func(pow.Block) bool
+
+	pool  map[string]*entry
+	peers *peers
+
+	lock      sync.RWMutex
+	chainLock sync.RWMutex
+	// alloc-easy pool of hash slices
+	hashSlicePool chan [][]byte
+
+	status *status
+
+	quit    chan bool
+	wg      sync.WaitGroup
+	running bool
+}
+
+// public constructor
+func New(
+	hasBlock func(hash []byte) bool,
+	insertChain func(types.Blocks) error,
+	verifyPoW func(pow.Block) bool,
+) *BlockPool {
+
+	return &BlockPool{
+		Config:      &Config{},
+		hasBlock:    hasBlock,
+		insertChain: insertChain,
+		verifyPoW:   verifyPoW,
+	}
+}
+
+// allows restart
+func (self *BlockPool) Start() {
+	self.lock.Lock()
+	defer self.lock.Unlock()
+
+	if self.running {
+		return
+	}
+
+	self.Config.init()
+	self.hashSlicePool = make(chan [][]byte, 150)
+	self.status = newStatus()
+	self.quit = make(chan bool)
+	self.pool = make(map[string]*entry)
+	self.running = true
+
+	self.peers = &peers{
+		errors: &errs.Errors{
+			Package: "Blockpool",
+			Errors:  errorToString,
+		},
+		peers:  make(map[string]*peer),
+		status: self.status,
+		bp:     self,
+	}
+	timer := time.NewTicker(3 * time.Second)
+	go func() {
+		for {
+			select {
+			case <-self.quit:
+				return
+			case <-timer.C:
+				plog.Debugf("status:\n%v", self.Status())
+			}
+		}
+	}()
+	plog.Infoln("Started")
+}
+
+func (self *BlockPool) Stop() {
+	self.lock.Lock()
+	if !self.running {
+		self.lock.Unlock()
+		return
+	}
+	self.running = false
+
+	self.lock.Unlock()
+
+	plog.Infoln("Stopping...")
+
+	close(self.quit)
+
+	self.lock.Lock()
+	self.peers = nil
+	self.pool = nil
+	self.lock.Unlock()
+
+	plog.Infoln("Stopped")
+}
+
+// Wait blocks until active processes finish
+func (self *BlockPool) Wait(t time.Duration) {
+	self.lock.Lock()
+	if !self.running {
+		self.lock.Unlock()
+		return
+	}
+	self.lock.Unlock()
+
+	plog.Infoln("Waiting for processes to complete...")
+	w := make(chan bool)
+	go func() {
+		self.wg.Wait()
+		close(w)
+	}()
+
+	select {
+	case <-w:
+		plog.Infoln("Processes complete")
+	case <-time.After(t):
+		plog.Warnf("Timeout")
+	}
+}
+
+/*
+AddPeer is called by the eth protocol instance running on the peer after
+the status message has been received with total difficulty and current block hash
+Called a second time with the same peer id, it is used to update chain info for a peer. This is used when a new (mined) block message is received.
+RemovePeer needs to be called when the peer disconnects.
+Peer info is currently not persisted across disconnects (or sessions)
+*/
+func (self *BlockPool) AddPeer(
+
+	td *big.Int, currentBlockHash []byte,
+	peerId string,
+	requestBlockHashes func([]byte) error,
+	requestBlocks func([][]byte) error,
+	peerError func(*errs.Error),
+
+) (best bool) {
+
+	return self.peers.addPeer(td, currentBlockHash, peerId, requestBlockHashes, requestBlocks, peerError)
+}
+
+// RemovePeer needs to be called when the peer disconnects
+func (self *BlockPool) RemovePeer(peerId string) {
+	self.peers.removePeer(peerId)
+}
+
+/*
+AddBlockHashes
+
+Entry point for eth protocol to add block hashes received via BlockHashesMsg
+
+only hashes from the best peer are handled
+
+initiates further hash requests until a known parent is reached (unless cancelled by a peerSwitch event, i.e., when a better peer becomes best peer)
+launches all block request processes on each chain section
+
+the first argument is an iterator function. Using this block hashes are decoded from the rlp message payload on demand. As a result, AddBlockHashes needs to run synchronously for one peer since the message is discarded if the caller thread returns.
+*/
+func (self *BlockPool) AddBlockHashes(next func() ([]byte, bool), peerId string) {
+
+	bestpeer, best := self.peers.getPeer(peerId)
+	if !best {
+		return
+	}
+	// bestpeer is still the best peer
+
+	self.wg.Add(1)
+
+	defer func() { self.wg.Done() }()
+
+	self.status.lock.Lock()
+	self.status.activePeers[bestpeer.id]++
+	self.status.lock.Unlock()
+
+	var n int
+	var hash []byte
+	var ok, headSection, peerswitch bool
+	var sec, child, parent *section
+	var entry *entry
+	var nodes []*node
+
+	hash, ok = next()
+	bestpeer.lock.Lock()
+
+	plog.Debugf("AddBlockHashes: peer <%s> starting from [%s] (peer head: %s)", peerId, hex(bestpeer.parentHash), hex(bestpeer.currentBlockHash))
+
+	// first check if we are building the head section of a peer's chain
+	if bytes.Equal(bestpeer.parentHash, hash) {
+		if self.hasBlock(bestpeer.currentBlockHash) {
+			return
+		}
+		/*
+		 when peer is promoted in switchPeer, a new header section process is launched
+		 as the head section skeleton is actually created here, it is signaled to the process
+		 so that it can quit
+		 in the special case that the node for parent of the head block is found in the blockpool
+		 (with or without fetched block)
+		*/
+		headSection = true
+		if entry := self.get(bestpeer.currentBlockHash); entry == nil {
+			plog.DebugDetailf("AddBlockHashes: peer <%s> (head: %s) head section starting from [%s] ", peerId, hex(bestpeer.currentBlockHash), hex(bestpeer.parentHash))
+			// if head block is not yet in the pool, create entry and start node list for section
+			node := &node{
+				hash:    bestpeer.currentBlockHash,
+				block:   bestpeer.currentBlock,
+				hashBy:  peerId,
+				blockBy: peerId,
+			}
+			// nodes is a list of nodes in one section ordered top-bottom (old to young)
+			nodes = append(nodes, node)
+			n++
+		} else {
+			// otherwise set child section iff found node is the root of a section
+			// this is a possible scenario when a singleton head section was created
+			// on an earlier occasion this peer or another with the same block was best peer
+			if entry.node == entry.section.bottom {
+				child = entry.section
+				plog.DebugDetailf("AddBlockHashes: peer <%s>: connects to child section root %s", peerId, hex(bestpeer.currentBlockHash))
+			}
+		}
+	} else {
+		// otherwise : we are not building the head section of the peer
+		plog.DebugDetailf("AddBlockHashes: peer <%s> (head: %s) section starting from [%s] ", peerId, hex(bestpeer.currentBlockHash), hex(hash))
+	}
+	// the switch channel signals peerswitch event
+	switchC := bestpeer.switchC
+	bestpeer.lock.Unlock()
+
+	// iterate over hashes coming from peer (first round we have hash set above)
+LOOP:
+	for ; ok; hash, ok = next() {
+
+		select {
+		case <-self.quit:
+			// global quit for blockpool
+			return
+
+		case <-switchC:
+			// if the peer is demoted, no more hashes read
+			plog.DebugDetailf("AddBlockHashes: demoted peer <%s> (head: %s)", peerId, hex(bestpeer.currentBlockHash), hex(hash))
+			peerswitch = true
+			break LOOP
+		default:
+		}
+
+		// if we reach the blockchain we stop reading more
+		if self.hasBlock(hash) {
+			// check if known block connecting the downloaded chain to our blockchain
+			plog.DebugDetailf("AddBlockHashes: peer <%s> (head: %s) found block %s in the blockchain", peerId, hex(bestpeer.currentBlockHash), hex(hash))
+			if len(nodes) == 1 {
+				// create new section if needed and push it to the blockchain
+				sec = self.newSection(nodes)
+				sec.addSectionToBlockChain(bestpeer)
+			} else {
+
+				/*
+					 not added hash yet but according to peer child section built
+					earlier chain connects with blockchain
+					this maybe a potential vulnarability
+					the root block arrives (or already there but its parenthash was not pointing to known block in the blockchain)
+					we start inserting -> error -> remove the entire chain
+					instead of punishing this peer
+					solution: when switching peers always make sure best peers own head block
+					and td together with blockBy are recorded on the node
+				*/
+				if len(nodes) == 0 && child != nil {
+					child.addSectionToBlockChain(bestpeer)
+				}
+			}
+			break LOOP
+		}
+
+		// look up node in the pool
+		entry = self.get(hash)
+		if entry != nil {
+			// reached a known chain in the pool
+			if entry.node == entry.section.bottom && n == 1 {
+				/*
+					the first block hash received is an orphan in the pool
+					this also supports clients that (despite the spec) include <from> hash in their
+					response to hashes request. Note that by providing <from> we can link sections
+					without having to wait for the root block of the child section to arrive, so it allows for superior performance
+				*/
+				plog.DebugDetailf("AddBlockHashes: peer <%s> (head: %s) found head block [%s] as root of connecting child section [%s] skipping", peerId, hex(bestpeer.currentBlockHash), hex(hash), sectionhex(entry.section))
+				// record the entry's chain section as child section
+				child = entry.section
+				continue LOOP
+			}
+			// otherwise record entry's chain section as parent connecting it to the pool
+			plog.DebugDetailf("AddBlockHashes: peer <%s> (head: %s) found block [%s] in section [%s]. Connected to pool.", peerId, hex(bestpeer.currentBlockHash), hex(hash), sectionhex(entry.section))
+			parent = entry.section
+			break LOOP
+		}
+
+		// finally if node for block hash does not exist, create it and append node to section nodes
+		node := &node{
+			hash:   hash,
+			hashBy: peerId,
+		}
+		nodes = append(nodes, node)
+	} //for
+
+	/*
+		we got here if
+		- run out of hashes (parent = nil) sent by our best peer
+		- our peer is demoted (peerswitch = true)
+		- reached blockchain or blockpool
+		- quitting
+	*/
+	self.chainLock.Lock()
+
+	plog.DebugDetailf("AddBlockHashes: peer <%s> (head: %s): %v nodes in new section", peerId, hex(bestpeer.currentBlockHash), len(nodes))
+	/*
+	  handle forks where connecting node is mid-section
+	  by splitting section at fork
+	  no splitting needed if connecting node is head of a section
+	*/
+	if parent != nil && entry != nil && entry.node != parent.top && len(nodes) > 0 {
+		plog.DebugDetailf("AddBlockHashes: peer <%s> (head: %s): fork after %s", peerId, hex(bestpeer.currentBlockHash), hex(hash))
+
+		self.splitSection(parent, entry)
+
+		self.status.lock.Lock()
+		self.status.values.Forks++
+		self.status.lock.Unlock()
+	}
+
+	/*
+	  if new section is created, link it to parent/child sections
+	  and launch section process fetching blocks and further hashes
+	*/
+	sec = self.linkSections(nodes, parent, child)
+
+	self.status.lock.Lock()
+	self.status.values.BlockHashes += len(nodes)
+	self.status.lock.Unlock()
+	plog.DebugDetailf("AddBlockHashes: peer <%s> (head: %s): section [%s] created", peerId, hex(bestpeer.currentBlockHash), sectionhex(sec))
+
+	self.chainLock.Unlock()
+
+	/*
+		if a blockpool node is reached (parent section is not nil),
+		activate section (unless our peer is demoted by now).
+		this can be the bottom half of a newly split section in case of a fork.
+		bestPeer is nil if we got here after our peer got demoted while processing.
+		in this case no activation should happen
+	*/
+	if parent != nil && !peerswitch {
+		self.activateChain(parent, bestpeer, nil)
+		plog.DebugDetailf("AddBlockHashes: peer <%s> (head: %s): parent section [%s]", peerId, hex(bestpeer.currentBlockHash), sectionhex(parent))
+	}
+
+	/*
+	  if a new section was created,
+	  register section iff head section or no child known
+	  activate it with this peer
+	*/
+	if sec != nil {
+		// switch on section process (it is paused by switchC)
+		if !peerswitch {
+			if headSection || child == nil {
+				bestpeer.lock.Lock()
+				bestpeer.sections = append(bestpeer.sections, sec.top.hash)
+				bestpeer.lock.Unlock()
+			}
+			/*
+			  request next block hashes for parent section here.
+			  but only once, repeating only when bottom block arrives,
+			  otherwise no way to check if it arrived
+			*/
+			bestpeer.requestBlockHashes(sec.bottom.hash)
+			plog.DebugDetailf("AddBlockHashes: peer <%s> (head: %s): start requesting blocks for section [%s]", peerId, hex(bestpeer.currentBlockHash), sectionhex(sec))
+			sec.activate(bestpeer)
+		} else {
+			plog.DebugDetailf("AddBlockHashes: peer <%s> (head: %s) no longer best: delay requesting blocks for section [%s]", peerId, hex(bestpeer.currentBlockHash), sectionhex(sec))
+			sec.deactivate()
+		}
+	}
+
+	// if we are processing peer's head section, signal it to headSection process that it is created
+
+	if headSection {
+		plog.DebugDetailf("AddBlockHashes: peer <%s> (head: %s) head section registered on head section process", peerId, hex(bestpeer.currentBlockHash))
+
+		var headSec *section
+		switch {
+		case sec != nil:
+			headSec = sec
+		case child != nil:
+			headSec = child
+		default:
+			headSec = parent
+		}
+		if !peerswitch {
+			plog.DebugDetailf("AddBlockHashes: peer <%s> (head: %s) head section [%s] created signalled to head section process", peerId, hex(bestpeer.currentBlockHash), sectionhex(headSec))
+			bestpeer.headSectionC <- headSec
+		}
+	}
+}
+
+/*
+	AddBlock is the entry point for the eth protocol to call when blockMsg is received.
+
+	It has a strict interpretation of the protocol in that if the block received has not been requested, it results in an error
+
+	At the same time it is opportunistic in that if a requested block may be provided by any peer.
+
+	The received block is checked for PoW. Only the first PoW-valid block for a hash is considered legit.
+*/
+func (self *BlockPool) AddBlock(block *types.Block, peerId string) {
+	hash := block.Hash()
+
+	sender, _ := self.peers.getPeer(peerId)
+	if sender == nil {
+		return
+	}
+
+	self.status.lock.Lock()
+	self.status.activePeers[peerId]++
+	self.status.lock.Unlock()
+
+	entry := self.get(hash)
+
+	// a peer's current head block is appearing the first time
+	if bytes.Equal(hash, sender.currentBlockHash) {
+		if sender.currentBlock == nil {
+			plog.Debugf("AddBlock: add head block %s for peer <%s> (head: %s)", hex(hash), peerId, hex(sender.currentBlockHash))
+			sender.setChainInfoFromBlock(block)
+			// sender.currentBlockC <- block
+
+			self.status.lock.Lock()
+			self.status.values.Blocks++
+			self.status.values.BlocksInPool++
+			self.status.lock.Unlock()
+		} else {
+			plog.DebugDetailf("AddBlock: head block %s for peer <%s> (head: %s) already known", hex(hash), peerId, hex(sender.currentBlockHash))
+		}
+	} else {
+
+		plog.DebugDetailf("AddBlock: block %s received from peer <%s> (head: %s)", hex(hash), peerId, hex(sender.currentBlockHash))
+
+		sender.lock.Lock()
+		// update peer chain info if more recent than what we registered
+		if block.Td != nil && block.Td.Cmp(sender.td) > 0 {
+			sender.td = block.Td
+			sender.currentBlockHash = block.Hash()
+			sender.parentHash = block.ParentHash()
+			sender.currentBlock = block
+			sender.headSection = nil
+		}
+		sender.lock.Unlock()
+
+		if entry == nil {
+			// penalise peer for sending what we have not asked
+			plog.DebugDetailf("AddBlock: unrequested block %s received from peer <%s> (head: %s)", hex(hash), peerId, hex(sender.currentBlockHash))
+			sender.addError(ErrUnrequestedBlock, "%x", hash)
+
+			self.status.lock.Lock()
+			self.status.badPeers[peerId]++
+			self.status.lock.Unlock()
+			return
+		}
+	}
+	if entry == nil {
+		return
+	}
+
+	node := entry.node
+	node.lock.Lock()
+	defer node.lock.Unlock()
+
+	// check if block already present
+	if node.block != nil {
+		plog.DebugDetailf("AddBlock: block %s from peer <%s> (head: %s) already sent by <%s> ", hex(hash), peerId, hex(sender.currentBlockHash), node.blockBy)
+		return
+	}
+
+	// check if block is already inserted in the blockchain
+	if self.hasBlock(hash) {
+		plog.DebugDetailf("AddBlock: block %s from peer <%s> (head: %s) already in the blockchain", hex(hash), peerId, hex(sender.currentBlockHash))
+		return
+	}
+
+	// validate block for PoW
+	if !self.verifyPoW(block) {
+		plog.Warnf("AddBlock: invalid PoW on block %s from peer  <%s> (head: %s)", hex(hash), peerId, hex(sender.currentBlockHash))
+		sender.addError(ErrInvalidPoW, "%x", hash)
+
+		self.status.lock.Lock()
+		self.status.badPeers[peerId]++
+		self.status.lock.Unlock()
+
+		return
+	}
+
+	node.block = block
+	node.blockBy = peerId
+	node.td = block.Td // optional field
+
+	self.status.lock.Lock()
+	self.status.values.Blocks++
+	self.status.values.BlocksInPool++
+	self.status.lock.Unlock()
+
+}
+
+/*
+  iterates down a chain section by section
+  activating section process on incomplete sections with peer
+  relinking orphaned sections with their parent if root block (and its parent hash) is known)
+*/
+func (self *BlockPool) activateChain(sec *section, p *peer, connected map[string]*section) {
+
+	p.lock.RLock()
+	switchC := p.switchC
+	p.lock.RUnlock()
+
+	var i int
+
+LOOP:
+	for sec != nil {
+		parent := self.getParent(sec)
+		plog.DebugDetailf("activateChain: section [%s] activated by peer <%s>", sectionhex(sec), p.id)
+		sec.activate(p)
+		if i > 0 && connected != nil {
+			connected[string(sec.top.hash)] = sec
+		}
+		/*
+		  we need to relink both complete and incomplete sections
+		  the latter could have been blockHashesRequestsComplete before being delinked from its parent
+		*/
+		if parent == nil && sec.bottom.block != nil {
+			if entry := self.get(sec.bottom.block.ParentHash()); entry != nil {
+				parent = entry.section
+				plog.DebugDetailf("activateChain: [%s]-[%s] relink", sectionhex(parent), sectionhex(sec))
+				link(parent, sec)
+			}
+		}
+		sec = parent
+
+		// stop if peer got demoted
+		select {
+		case <-switchC:
+			break LOOP
+		case <-self.quit:
+			break LOOP
+		default:
+		}
+	}
+}
+
+// must run in separate go routine, otherwise
+// switchpeer -> activateChain -> activate deadlocks on section process select and peers.lock
+func (self *BlockPool) requestBlocks(attempts int, hashes [][]byte) {
+	self.wg.Add(1)
+	go func() {
+		self.peers.requestBlocks(attempts, hashes)
+		self.wg.Done()
+	}()
+}
+
+// convenience methods to access adjacent sections
+func (self *BlockPool) getParent(sec *section) *section {
+	self.chainLock.RLock()
+	defer self.chainLock.RUnlock()
+	return sec.parent
+}
+
+func (self *BlockPool) getChild(sec *section) *section {
+	self.chainLock.RLock()
+	defer self.chainLock.RUnlock()
+	return sec.child
+}
+
+// accessor and setter for entries in the pool
+func (self *BlockPool) get(hash []byte) *entry {
+	self.lock.RLock()
+	defer self.lock.RUnlock()
+	return self.pool[string(hash)]
+}
+
+func (self *BlockPool) set(hash []byte, e *entry) {
+	self.lock.Lock()
+	defer self.lock.Unlock()
+	self.pool[string(hash)] = e
+}
+
+func (self *BlockPool) remove(sec *section) {
+	// delete node entries from pool index under pool lock
+	self.lock.Lock()
+	defer self.lock.Unlock()
+	for _, node := range sec.nodes {
+		delete(self.pool, string(node.hash))
+	}
+}
+
+func (self *BlockPool) getHashSlice() (s [][]byte) {
+	select {
+	case s = <-self.hashSlicePool:
+	default:
+		s = make([][]byte, self.Config.BlockBatchSize)
+	}
+	return
+}
+
+// Return returns a Client to the pool.
+func (self *BlockPool) putHashSlice(s [][]byte) {
+	if len(s) == self.Config.BlockBatchSize {
+		select {
+		case self.hashSlicePool <- s:
+		default:
+		}
+	}
+}
+
+// pretty prints hash (byte array) with first 4 bytes in hex
+func hex(hash []byte) (name string) {
+	if hash == nil {
+		name = ""
+	} else {
+		name = fmt.Sprintf("%x", hash[:4])
+	}
+	return
+}
+
+// pretty prints a section using first 4 bytes in hex of bottom and top blockhash of the section
+func sectionhex(section *section) (name string) {
+	if section == nil {
+		name = ""
+	} else {
+		name = fmt.Sprintf("%x-%x", section.bottom.hash[:4], section.top.hash[:4])
+	}
+	return
+}
diff --git a/blockpool/blockpool_test.go b/blockpool/blockpool_test.go
new file mode 100644
index 000000000..bca48c6ca
--- /dev/null
+++ b/blockpool/blockpool_test.go
@@ -0,0 +1,479 @@
+package blockpool
+
+import (
+	"testing"
+	"time"
+
+	"github.com/ethereum/go-ethereum/blockpool/test"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/ethutil"
+)
+
+func TestPeerWithKnownBlock(t *testing.T) {
+	test.LogInit()
+	_, blockPool, blockPoolTester := newTestBlockPool(t)
+	blockPoolTester.refBlockChain[0] = nil
+	blockPoolTester.blockChain[0] = nil
+	blockPool.Start()
+
+	peer0 := blockPoolTester.newPeer("0", 1, 0)
+	peer0.AddPeer()
+
+	blockPool.Wait(waitTimeout)
+	blockPool.Stop()
+	// no request on known block
+	peer0.checkBlockHashesRequests()
+}
+
+func TestPeerWithKnownParentBlock(t *testing.T) {
+	test.LogInit()
+	_, blockPool, blockPoolTester := newTestBlockPool(t)
+	blockPoolTester.initRefBlockChain(1)
+	blockPoolTester.blockChain[0] = nil
+	blockPool.Start()
+
+	peer0 := blockPoolTester.newPeer("0", 1, 1)
+	peer0.AddPeer()
+	peer0.serveBlocks(0, 1)
+
+	blockPool.Wait(waitTimeout)
+	blockPool.Stop()
+	peer0.checkBlocksRequests([]int{1})
+	peer0.checkBlockHashesRequests()
+	blockPoolTester.refBlockChain[1] = []int{}
+	blockPoolTester.checkBlockChain(blockPoolTester.refBlockChain)
+}
+
+func TestPeerPromotionByOptionalTdOnBlock(t *testing.T) {
+	test.LogInit()
+	_, blockPool, blockPoolTester := newTestBlockPool(t)
+	blockPoolTester.blockChain[0] = nil
+	blockPoolTester.initRefBlockChain(4)
+	peer0 := blockPoolTester.newPeer("peer0", 2, 2)
+	peer1 := blockPoolTester.newPeer("peer1", 1, 1)
+	peer2 := blockPoolTester.newPeer("peer2", 3, 4)
+
+	blockPool.Start()
+
+	// pool
+	peer0.AddPeer()
+	peer0.serveBlocks(1, 2)
+	best := peer1.AddPeer()
+	// this tests that peer1 is not promoted over peer0 yet
+	if best {
+		t.Errorf("peer1 (TD=1) should not be set as best")
+	}
+	best = peer2.AddPeer()
+	peer2.serveBlocks(3, 4)
+	peer2.serveBlockHashes(4, 3, 2, 1)
+	hashes := blockPoolTester.hashPool.IndexesToHashes([]int{2, 3})
+	peer1.waitBlocksRequests(3)
+	blockPool.AddBlock(&types.Block{
+		HeaderHash:       ethutil.Bytes(hashes[1]),
+		ParentHeaderHash: ethutil.Bytes(hashes[0]),
+		Td:               ethutil.Big3,
+	}, "peer1")
+
+	blockPool.RemovePeer("peer2")
+	if blockPool.peers.best.id != "peer1" {
+		t.Errorf("peer1 (TD=3) should be set as best")
+	}
+	peer1.serveBlocks(0, 1, 2)
+
+	blockPool.Wait(waitTimeout)
+	blockPool.Stop()
+	blockPoolTester.refBlockChain[4] = []int{}
+	blockPoolTester.checkBlockChain(blockPoolTester.refBlockChain)
+}
+
+func TestSimpleChain(t *testing.T) {
+	test.LogInit()
+	_, blockPool, blockPoolTester := newTestBlockPool(t)
+	blockPoolTester.blockChain[0] = nil
+	blockPoolTester.initRefBlockChain(2)
+
+	blockPool.Start()
+
+	peer1 := blockPoolTester.newPeer("peer1", 1, 2)
+	peer1.AddPeer()
+	peer1.serveBlocks(1, 2)
+	go peer1.serveBlockHashes(2, 1, 0)
+	peer1.serveBlocks(0, 1)
+
+	blockPool.Wait(waitTimeout)
+	blockPool.Stop()
+	blockPoolTester.refBlockChain[2] = []int{}
+	blockPoolTester.checkBlockChain(blockPoolTester.refBlockChain)
+}
+
+func TestChainConnectingWithParentHash(t *testing.T) {
+	test.LogInit()
+	_, blockPool, blockPoolTester := newTestBlockPool(t)
+	blockPoolTester.blockChain[0] = nil
+	blockPoolTester.initRefBlockChain(3)
+
+	blockPool.Start()
+
+	peer1 := blockPoolTester.newPeer("peer1", 1, 3)
+	peer1.AddPeer()
+	go peer1.serveBlocks(2, 3)
+	go peer1.serveBlockHashes(3, 2, 1)
+	peer1.serveBlocks(0, 1, 2)
+
+	blockPool.Wait(waitTimeout)
+	blockPool.Stop()
+	blockPoolTester.refBlockChain[3] = []int{}
+	blockPoolTester.checkBlockChain(blockPoolTester.refBlockChain)
+}
+
+func TestMultiSectionChain(t *testing.T) {
+	test.LogInit()
+	_, blockPool, blockPoolTester := newTestBlockPool(t)
+	blockPoolTester.blockChain[0] = nil
+	blockPoolTester.initRefBlockChain(5)
+
+	blockPool.Start()
+
+	peer1 := blockPoolTester.newPeer("peer1", 1, 5)
+
+	peer1.AddPeer()
+	go peer1.serveBlocks(4, 5)
+	go peer1.serveBlockHashes(5, 4, 3)
+	go peer1.serveBlocks(2, 3, 4)
+	go peer1.serveBlockHashes(3, 2, 1, 0)
+	peer1.serveBlocks(0, 1, 2)
+
+	blockPool.Wait(waitTimeout)
+	blockPool.Stop()
+	blockPoolTester.refBlockChain[5] = []int{}
+	blockPoolTester.checkBlockChain(blockPoolTester.refBlockChain)
+}
+
+func TestNewBlocksOnPartialChain(t *testing.T) {
+	test.LogInit()
+	_, blockPool, blockPoolTester := newTestBlockPool(t)
+	blockPoolTester.blockChain[0] = nil
+	blockPoolTester.initRefBlockChain(7)
+	blockPool.Start()
+
+	peer1 := blockPoolTester.newPeer("peer1", 1, 5)
+
+	peer1.AddPeer()
+	go peer1.serveBlocks(4, 5) // partially complete section
+	go peer1.serveBlockHashes(5, 4, 3)
+	peer1.serveBlocks(3, 4) // partially complete section
+	// peer1 found new blocks
+	peer1.td = 2
+	peer1.currentBlock = 7
+	peer1.AddPeer()
+	peer1.sendBlocks(6, 7)
+	go peer1.serveBlockHashes(7, 6, 5)
+	go peer1.serveBlocks(2, 3)
+	go peer1.serveBlocks(5, 6)
+	go peer1.serveBlockHashes(3, 2, 1) // tests that hash request from known chain root is remembered
+	peer1.serveBlocks(0, 1, 2)
+	// blockPool.RemovePeer("peer1")
+
+	blockPool.Wait(waitTimeout)
+	blockPool.Stop()
+	blockPoolTester.refBlockChain[7] = []int{}
+	blockPoolTester.checkBlockChain(blockPoolTester.refBlockChain)
+}
+
+func TestPeerSwitchUp(t *testing.T) {
+	test.LogInit()
+	_, blockPool, blockPoolTester := newTestBlockPool(t)
+	blockPoolTester.blockChain[0] = nil
+	blockPoolTester.initRefBlockChain(7)
+
+	blockPool.Start()
+
+	peer1 := blockPoolTester.newPeer("peer1", 1, 6)
+	peer2 := blockPoolTester.newPeer("peer2", 2, 7)
+
+	peer1.AddPeer()
+	go peer1.serveBlocks(5, 6)
+	go peer1.serveBlockHashes(6, 5, 4, 3) //
+	peer1.serveBlocks(2, 3)               // section partially complete, block 3 will be preserved after peer demoted
+	peer2.AddPeer()                       // peer2 is promoted as best peer, peer1 is demoted
+	go peer2.serveBlocks(6, 7)
+	// go peer2.serveBlockHashes(7, 6)       //
+	go peer2.serveBlocks(4, 5)            // tests that block request for earlier section is remembered
+	go peer1.serveBlocks(3, 4)            // tests that connecting section by demoted peer is remembered and blocks are accepted from demoted peer
+	go peer2.serveBlockHashes(3, 2, 1, 0) // tests that known chain section is activated, hash requests from 3 is remembered
+	peer2.serveBlocks(0, 1, 2)            // final blocks linking to blockchain sent
+
+	blockPool.Wait(waitTimeout)
+	blockPool.Stop()
+	blockPoolTester.refBlockChain[7] = []int{}
+	blockPoolTester.checkBlockChain(blockPoolTester.refBlockChain)
+}
+
+func TestPeerSwitchDownOverlapSectionWithoutRootBlock(t *testing.T) {
+	test.LogInit()
+	_, blockPool, blockPoolTester := newTestBlockPool(t)
+	blockPoolTester.blockChain[0] = nil
+	blockPoolTester.initRefBlockChain(6)
+	blockPool.Start()
+
+	peer1 := blockPoolTester.newPeer("peer1", 1, 4)
+	peer2 := blockPoolTester.newPeer("peer2", 2, 6)
+
+	peer2.AddPeer()
+	peer2.serveBlocks(5, 6)                  // partially complete, section will be preserved
+	peer2.serveBlockHashes(6, 5, 4)          // no go: make sure skeleton is created
+	peer1.AddPeer()                          // inferior peer1 is promoted as best peer
+	blockPool.RemovePeer("peer2")            // peer2 disconnects
+	go peer1.serveBlockHashes(4, 3, 2, 1, 0) //
+	go peer1.serveBlocks(3, 4)               //
+	go peer1.serveBlocks(4, 5)               // tests that section set by demoted peer is remembered and blocks are accepted from new peer if they have it even if peers original TD is lower
+	peer1.serveBlocks(0, 1, 2, 3)
+
+	blockPool.Wait(waitTimeout)
+	blockPool.Stop()
+	blockPoolTester.refBlockChain[6] = []int{} // tests that idle sections are not inserted in blockchain
+	blockPoolTester.checkBlockChain(blockPoolTester.refBlockChain)
+}
+
+func TestPeerSwitchDownOverlapSectionWithRootBlock(t *testing.T) {
+	test.LogInit()
+	_, blockPool, blockPoolTester := newTestBlockPool(t)
+	blockPoolTester.blockChain[0] = nil
+	blockPoolTester.initRefBlockChain(6)
+	blockPool.Start()
+
+	peer1 := blockPoolTester.newPeer("peer1", 1, 4)
+	peer2 := blockPoolTester.newPeer("peer2", 2, 6)
+
+	peer2.AddPeer()
+	peer2.serveBlocks(5, 6)                  // partially complete, section will be preserved
+	go peer2.serveBlockHashes(6, 5, 4)       //
+	peer2.serveBlocks(3, 4)                  // !incomplete section
+	time.Sleep(100 * time.Millisecond)       // make sure block 4 added
+	peer1.AddPeer()                          // inferior peer1 is promoted as best peer
+	blockPool.RemovePeer("peer2")            // peer2 disconnects
+	go peer1.serveBlockHashes(4, 3, 2, 1, 0) // tests that hash request are directly connecting if the head block exists
+	go peer1.serveBlocks(4, 5)               // tests that section set by demoted peer is remembered and blocks are accepted from new peer if they have it even if peers original TD is lower
+	peer1.serveBlocks(0, 1, 2, 3)
+
+	blockPool.Wait(waitTimeout)
+	blockPool.Stop()
+	blockPoolTester.refBlockChain[6] = []int{} // tests that idle sections are not inserted in blockchain
+	blockPoolTester.checkBlockChain(blockPoolTester.refBlockChain)
+}
+
+func TestPeerSwitchDownDisjointSection(t *testing.T) {
+	test.LogInit()
+	_, blockPool, blockPoolTester := newTestBlockPool(t)
+	blockPoolTester.blockChain[0] = nil
+	blockPoolTester.initRefBlockChain(3)
+	blockPool.Start()
+
+	peer1 := blockPoolTester.newPeer("peer1", 1, 3)
+	peer2 := blockPoolTester.newPeer("peer2", 2, 6)
+
+	peer2.AddPeer()
+	peer2.serveBlocks(5, 6)            // partially complete, section will be preserved
+	go peer2.serveBlockHashes(6, 5, 4) //
+	peer2.serveBlocks(3, 4, 5)         //
+	time.Sleep(100 * time.Millisecond) // make sure blocks are received
+	peer1.AddPeer()                    // inferior peer1 is promoted as best peer
+	blockPool.RemovePeer("peer2")      // peer2 disconnects
+	go peer1.serveBlocks(2, 3)         //
+	go peer1.serveBlockHashes(3, 2, 1) //
+	peer1.serveBlocks(0, 1, 2)         //
+
+	blockPool.Wait(waitTimeout)
+	blockPool.Stop()
+	blockPoolTester.refBlockChain[3] = []int{} // tests that idle sections are not inserted in blockchain
+	blockPoolTester.checkBlockChain(blockPoolTester.refBlockChain)
+}
+
+func TestPeerSwitchBack(t *testing.T) {
+	test.LogInit()
+	_, blockPool, blockPoolTester := newTestBlockPool(t)
+	blockPoolTester.blockChain[0] = nil
+	blockPoolTester.initRefBlockChain(8)
+
+	blockPool.Start()
+
+	peer1 := blockPoolTester.newPeer("peer1", 2, 11)
+	peer2 := blockPoolTester.newPeer("peer2", 1, 8)
+
+	peer2.AddPeer()
+	go peer2.serveBlocks(7, 8)
+	go peer2.serveBlockHashes(8, 7, 6)
+	go peer2.serveBlockHashes(6, 5, 4)
+	peer2.serveBlocks(4, 5)                  // section partially complete
+	peer1.AddPeer()                          // peer1 is promoted as best peer
+	go peer1.serveBlocks(10, 11)             //
+	peer1.serveBlockHashes(11, 10)           // only gives useless results
+	blockPool.RemovePeer("peer1")            // peer1 disconnects
+	go peer2.serveBlockHashes(4, 3, 2, 1, 0) // tests that asking for hashes from 4 is remembered
+	go peer2.serveBlocks(3, 4, 5, 6, 7, 8)   // tests that section 4, 5, 6 and 7, 8 are remembered for missing blocks
+	peer2.serveBlocks(0, 1, 2, 3)
+
+	blockPool.Wait(waitTimeout)
+	blockPool.Stop()
+	blockPoolTester.refBlockChain[8] = []int{}
+	blockPoolTester.checkBlockChain(blockPoolTester.refBlockChain)
+}
+
+func TestForkSimple(t *testing.T) {
+	test.LogInit()
+	_, blockPool, blockPoolTester := newTestBlockPool(t)
+	blockPoolTester.blockChain[0] = nil
+	blockPoolTester.initRefBlockChain(9)
+	blockPoolTester.refBlockChain[3] = []int{4, 7}
+	delete(blockPoolTester.refBlockChain, 6)
+
+	blockPool.Start()
+
+	peer1 := blockPoolTester.newPeer("peer1", 1, 9)
+	peer2 := blockPoolTester.newPeer("peer2", 2, 6)
+
+	peer1.AddPeer()
+	go peer1.serveBlocks(8, 9)
+	go peer1.serveBlockHashes(9, 8, 7, 3, 2)
+	peer1.serveBlocks(1, 2, 3, 7, 8)
+	peer2.AddPeer()                          // peer2 is promoted as best peer
+	go peer2.serveBlocks(5, 6)               //
+	go peer2.serveBlockHashes(6, 5, 4, 3, 2) // fork on 3 -> 4 (earlier child: 7)
+	go peer2.serveBlocks(1, 2, 3, 4, 5)
+	go peer2.serveBlockHashes(2, 1, 0)
+	peer2.serveBlocks(0, 1, 2)
+
+	blockPool.Wait(waitTimeout)
+	blockPool.Stop()
+	blockPoolTester.refBlockChain[6] = []int{}
+	blockPoolTester.refBlockChain[3] = []int{4}
+	delete(blockPoolTester.refBlockChain, 7)
+	delete(blockPoolTester.refBlockChain, 8)
+	delete(blockPoolTester.refBlockChain, 9)
+	blockPoolTester.checkBlockChain(blockPoolTester.refBlockChain)
+
+}
+
+func TestForkSwitchBackByNewBlocks(t *testing.T) {
+	test.LogInit()
+	_, blockPool, blockPoolTester := newTestBlockPool(t)
+	blockPoolTester.blockChain[0] = nil
+	blockPoolTester.initRefBlockChain(11)
+	blockPoolTester.refBlockChain[3] = []int{4, 7}
+	delete(blockPoolTester.refBlockChain, 6)
+
+	blockPool.Start()
+
+	peer1 := blockPoolTester.newPeer("peer1", 1, 9)
+	peer2 := blockPoolTester.newPeer("peer2", 2, 6)
+
+	peer1.AddPeer()
+	go peer1.serveBlocks(8, 9)               //
+	go peer1.serveBlockHashes(9, 8, 7, 3, 2) //
+	peer1.serveBlocks(7, 8)                  // partial section
+	// time.Sleep(1 * time.Second)
+	peer2.AddPeer()                          //
+	go peer2.serveBlocks(5, 6)               //
+	go peer2.serveBlockHashes(6, 5, 4, 3, 2) // peer2 forks on block 3
+	peer2.serveBlocks(1, 2, 3, 4, 5)         //
+
+	// peer1 finds new blocks
+	peer1.td = 3
+	peer1.currentBlock = 11
+	peer1.AddPeer()
+	go peer1.serveBlocks(10, 11)
+	go peer1.serveBlockHashes(11, 10, 9)
+	go peer1.serveBlocks(9, 10)
+	// time.Sleep(1 * time.Second)
+	go peer1.serveBlocks(3, 7)      // tests that block requests on earlier fork are remembered
+	go peer1.serveBlockHashes(2, 1) // tests that hash request from root of connecting chain section (added by demoted peer) is remembered
+	peer1.serveBlocks(0, 1)
+
+	blockPool.Wait(waitTimeout)
+	blockPool.Stop()
+	blockPoolTester.refBlockChain[11] = []int{}
+	blockPoolTester.refBlockChain[3] = []int{7}
+	delete(blockPoolTester.refBlockChain, 6)
+	delete(blockPoolTester.refBlockChain, 5)
+	delete(blockPoolTester.refBlockChain, 4)
+	blockPoolTester.checkBlockChain(blockPoolTester.refBlockChain)
+
+}
+
+func TestForkSwitchBackByPeerSwitchBack(t *testing.T) {
+	test.LogInit()
+	_, blockPool, blockPoolTester := newTestBlockPool(t)
+	blockPoolTester.blockChain[0] = nil
+	blockPoolTester.initRefBlockChain(9)
+	blockPoolTester.refBlockChain[3] = []int{4, 7}
+	delete(blockPoolTester.refBlockChain, 6)
+
+	blockPool.Start()
+
+	peer1 := blockPoolTester.newPeer("peer1", 1, 9)
+	peer2 := blockPoolTester.newPeer("peer2", 2, 6)
+
+	peer1.AddPeer()
+	go peer1.serveBlocks(8, 9)
+	go peer1.serveBlockHashes(9, 8, 7, 3, 2)
+	peer1.serveBlocks(7, 8)
+	peer2.AddPeer()
+	go peer2.serveBlocks(5, 6)               //
+	go peer2.serveBlockHashes(6, 5, 4, 3, 2) // peer2 forks on block 3
+	peer2.serveBlocks(2, 3, 4, 5)            //
+	blockPool.RemovePeer("peer2")            // peer2 disconnects, peer1 is promoted again as best peer
+	go peer1.serveBlocks(1, 2)               //
+	go peer1.serveBlockHashes(2, 1, 0)       //
+	go peer1.serveBlocks(3, 7)               // tests that block requests on earlier fork are remembered and orphan section relinks to existing parent block
+	peer1.serveBlocks(0, 1)
+
+	blockPool.Wait(waitTimeout)
+	blockPool.Stop()
+	blockPoolTester.refBlockChain[9] = []int{}
+	blockPoolTester.refBlockChain[3] = []int{7}
+	delete(blockPoolTester.refBlockChain, 6)
+	delete(blockPoolTester.refBlockChain, 5)
+	delete(blockPoolTester.refBlockChain, 4)
+	blockPoolTester.checkBlockChain(blockPoolTester.refBlockChain)
+
+}
+
+func TestForkCompleteSectionSwitchBackByPeerSwitchBack(t *testing.T) {
+	test.LogInit()
+	_, blockPool, blockPoolTester := newTestBlockPool(t)
+	blockPoolTester.blockChain[0] = nil
+	blockPoolTester.initRefBlockChain(9)
+	blockPoolTester.refBlockChain[3] = []int{4, 7}
+	delete(blockPoolTester.refBlockChain, 6)
+
+	blockPool.Start()
+
+	peer1 := blockPoolTester.newPeer("peer1", 1, 9)
+	peer2 := blockPoolTester.newPeer("peer2", 2, 6)
+
+	peer1.AddPeer()
+	go peer1.serveBlocks(8, 9)
+	go peer1.serveBlockHashes(9, 8, 7)
+	peer1.serveBlocks(3, 7, 8) // make sure this section is complete
+	time.Sleep(1 * time.Second)
+	go peer1.serveBlockHashes(7, 3, 2)       // block 3/7 is section boundary
+	peer1.serveBlocks(2, 3)                  // partially complete sections block 2 missing
+	peer2.AddPeer()                          //
+	go peer2.serveBlocks(5, 6)               //
+	go peer2.serveBlockHashes(6, 5, 4, 3, 2) // peer2 forks on block 3
+	peer2.serveBlocks(2, 3, 4, 5)            // block 2 still missing.
+	blockPool.RemovePeer("peer2")            // peer2 disconnects, peer1 is promoted again as best peer
+	// peer1.serveBlockHashes(7, 3)             // tests that hash request from fork root is remembered even though section process completed
+	go peer1.serveBlockHashes(2, 1, 0) //
+	peer1.serveBlocks(0, 1, 2)
+
+	blockPool.Wait(waitTimeout)
+	blockPool.Stop()
+	blockPoolTester.refBlockChain[9] = []int{}
+	blockPoolTester.refBlockChain[3] = []int{7}
+	delete(blockPoolTester.refBlockChain, 6)
+	delete(blockPoolTester.refBlockChain, 5)
+	delete(blockPoolTester.refBlockChain, 4)
+	blockPoolTester.checkBlockChain(blockPoolTester.refBlockChain)
+
+}
diff --git a/blockpool/blockpool_util_test.go b/blockpool/blockpool_util_test.go
new file mode 100644
index 000000000..8f0c8baa0
--- /dev/null
+++ b/blockpool/blockpool_util_test.go
@@ -0,0 +1,350 @@
+package blockpool
+
+import (
+	"fmt"
+	"math/big"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/ethereum/go-ethereum/blockpool/test"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/errs"
+	"github.com/ethereum/go-ethereum/ethutil"
+	"github.com/ethereum/go-ethereum/pow"
+)
+
+var (
+	waitTimeout                    = 60 * time.Second
+	testBlockHashesRequestInterval = 10 * time.Millisecond
+	testBlocksRequestInterval      = 10 * time.Millisecond
+	requestWatchInterval           = 10 * time.Millisecond
+)
+
+// test blockChain is an integer trie
+type blockChain map[int][]int
+
+// blockPoolTester provides the interface between tests and a blockPool
+//
+// refBlockChain is used to guide which blocks will be accepted as valid
+// blockChain gives the current state of the blockchain and
+// accumulates inserts so that we can check the resulting chain
+type blockPoolTester struct {
+	hashPool          *test.TestHashPool
+	lock              sync.RWMutex
+	reqlock           sync.RWMutex
+	blocksRequestsMap map[int]bool
+	refBlockChain     blockChain
+	blockChain        blockChain
+	blockPool         *BlockPool
+	t                 *testing.T
+}
+
+func newTestBlockPool(t *testing.T) (hashPool *test.TestHashPool, blockPool *BlockPool, b *blockPoolTester) {
+	hashPool = test.NewHashPool()
+	b = &blockPoolTester{
+		t:                 t,
+		hashPool:          hashPool,
+		blockChain:        make(blockChain),
+		refBlockChain:     make(blockChain),
+		blocksRequestsMap: make(map[int]bool),
+	}
+	b.blockPool = New(b.hasBlock, b.insertChain, b.verifyPoW)
+	blockPool = b.blockPool
+	blockPool.Config.BlockHashesRequestInterval = testBlockHashesRequestInterval
+	blockPool.Config.BlocksRequestInterval = testBlocksRequestInterval
+	return
+}
+
+func (self *blockPoolTester) Errorf(format string, params ...interface{}) {
+	fmt.Printf(format+"\n", params...)
+	self.t.Errorf(format, params...)
+}
+
+// blockPoolTester implements the 3 callbacks needed by the blockPool:
+// hasBlock, insetChain, verifyPoW
+func (self *blockPoolTester) hasBlock(block []byte) (ok bool) {
+	self.lock.RLock()
+	defer self.lock.RUnlock()
+	indexes := self.hashPool.HashesToIndexes([][]byte{block})
+	i := indexes[0]
+	_, ok = self.blockChain[i]
+	fmt.Printf("has block %v (%x...): %v\n", i, block[0:4], ok)
+	return
+}
+
+func (self *blockPoolTester) insertChain(blocks types.Blocks) error {
+	self.lock.Lock()
+	defer self.lock.Unlock()
+	var parent, child int
+	var children, refChildren []int
+	var ok bool
+	for _, block := range blocks {
+		child = self.hashPool.HashesToIndexes([][]byte{block.Hash()})[0]
+		_, ok = self.blockChain[child]
+		if ok {
+			fmt.Printf("block %v already in blockchain\n", child)
+			continue // already in chain
+		}
+		parent = self.hashPool.HashesToIndexes([][]byte{block.ParentHeaderHash})[0]
+		children, ok = self.blockChain[parent]
+		if !ok {
+			return fmt.Errorf("parent %v not in blockchain ", parent)
+		}
+		ok = false
+		var found bool
+		refChildren, found = self.refBlockChain[parent]
+		if found {
+			for _, c := range refChildren {
+				if c == child {
+					ok = true
+				}
+			}
+			if !ok {
+				return fmt.Errorf("invalid block %v", child)
+			}
+		} else {
+			ok = true
+		}
+		if ok {
+			// accept any blocks if parent not in refBlockChain
+			fmt.Errorf("blockchain insert %v -> %v\n", parent, child)
+			self.blockChain[parent] = append(children, child)
+			self.blockChain[child] = nil
+		}
+	}
+	return nil
+}
+
+func (self *blockPoolTester) verifyPoW(pblock pow.Block) bool {
+	return true
+}
+
+// test helper that compares the resulting blockChain to the desired blockChain
+func (self *blockPoolTester) checkBlockChain(blockChain map[int][]int) {
+	self.lock.RLock()
+	defer self.lock.RUnlock()
+	for k, v := range self.blockChain {
+		fmt.Printf("got: %v -> %v\n", k, v)
+	}
+	for k, v := range blockChain {
+		fmt.Printf("expected: %v -> %v\n", k, v)
+	}
+	if len(blockChain) != len(self.blockChain) {
+		self.Errorf("blockchain incorrect (zlength differ)")
+	}
+	for k, v := range blockChain {
+		vv, ok := self.blockChain[k]
+		if !ok || !test.ArrayEq(v, vv) {
+			self.Errorf("blockchain incorrect on %v -> %v (!= %v)", k, vv, v)
+		}
+	}
+}
+
+//
+
+// peerTester provides the peer callbacks for the blockPool
+// it registers actual callbacks so that the result can be compared to desired behaviour
+// provides helper functions to mock the protocol calls to the blockPool
+type peerTester struct {
+	blockHashesRequests []int
+	blocksRequests      [][]int
+	blocksRequestsMap   map[int]bool
+	peerErrors          []int
+	blockPool           *BlockPool
+	hashPool            *test.TestHashPool
+	lock                sync.RWMutex
+	bt                  *blockPoolTester
+	id                  string
+	td                  int
+	currentBlock        int
+	t                   *testing.T
+}
+
+// peerTester constructor takes hashPool and blockPool from the blockPoolTester
+func (self *blockPoolTester) newPeer(id string, td int, cb int) *peerTester {
+	return &peerTester{
+		id:                id,
+		td:                td,
+		currentBlock:      cb,
+		hashPool:          self.hashPool,
+		blockPool:         self.blockPool,
+		t:                 self.t,
+		bt:                self,
+		blocksRequestsMap: self.blocksRequestsMap,
+	}
+}
+
+func (self *peerTester) Errorf(format string, params ...interface{}) {
+	fmt.Printf(format+"\n", params...)
+	self.t.Errorf(format, params...)
+}
+
+// helper to compare actual and expected block requests
+func (self *peerTester) checkBlocksRequests(blocksRequests ...[]int) {
+	if len(blocksRequests) > len(self.blocksRequests) {
+		self.Errorf("blocks requests incorrect (length differ)\ngot %v\nexpected %v", self.blocksRequests, blocksRequests)
+	} else {
+		for i, rr := range blocksRequests {
+			r := self.blocksRequests[i]
+			if !test.ArrayEq(r, rr) {
+				self.Errorf("blocks requests incorrect\ngot %v\nexpected %v", self.blocksRequests, blocksRequests)
+			}
+		}
+	}
+}
+
+// helper to compare actual and expected block hash requests
+func (self *peerTester) checkBlockHashesRequests(blocksHashesRequests ...int) {
+	rr := blocksHashesRequests
+	self.lock.RLock()
+	r := self.blockHashesRequests
+	self.lock.RUnlock()
+	if len(r) != len(rr) {
+		self.Errorf("block hashes requests incorrect (length differ)\ngot %v\nexpected %v", r, rr)
+	} else {
+		if !test.ArrayEq(r, rr) {
+			self.Errorf("block hashes requests incorrect\ngot %v\nexpected %v", r, rr)
+		}
+	}
+}
+
+// waiter function used by peer.serveBlocks
+// blocking until requests appear
+// since block requests are sent to any random peers
+// block request map is shared between peers
+// times out after waitTimeout
+func (self *peerTester) waitBlocksRequests(blocksRequest ...int) {
+	timeout := time.After(waitTimeout)
+	rr := blocksRequest
+	for {
+		self.lock.RLock()
+		r := self.blocksRequestsMap
+		fmt.Printf("[%s] blocks request check %v (%v)\n", self.id, rr, r)
+		i := 0
+		for i = 0; i < len(rr); i++ {
+			_, ok := r[rr[i]]
+			if !ok {
+				break
+			}
+		}
+		self.lock.RUnlock()
+
+		if i == len(rr) {
+			return
+		}
+		time.Sleep(requestWatchInterval)
+		select {
+		case <-timeout:
+		default:
+		}
+	}
+}
+
+// waiter function used by peer.serveBlockHashes
+// blocking until requests appear
+// times out after a period
+func (self *peerTester) waitBlockHashesRequests(blocksHashesRequest int) {
+	timeout := time.After(waitTimeout)
+	rr := blocksHashesRequest
+	for i := 0; ; {
+		self.lock.RLock()
+		r := self.blockHashesRequests
+		self.lock.RUnlock()
+		fmt.Printf("[%s] block hash request check %v (%v)\n", self.id, rr, r)
+		for ; i < len(r); i++ {
+			if rr == r[i] {
+				return
+			}
+		}
+		time.Sleep(requestWatchInterval)
+		select {
+		case <-timeout:
+		default:
+		}
+	}
+}
+
+// mocks a simple blockchain 0 (genesis) ... n (head)
+func (self *blockPoolTester) initRefBlockChain(n int) {
+	for i := 0; i < n; i++ {
+		self.refBlockChain[i] = []int{i + 1}
+	}
+}
+
+// peerTester functions that mimic protocol calls to the blockpool
+//  registers the peer with the blockPool
+func (self *peerTester) AddPeer() bool {
+	hash := self.hashPool.IndexesToHashes([]int{self.currentBlock})[0]
+	return self.blockPool.AddPeer(big.NewInt(int64(self.td)), hash, self.id, self.requestBlockHashes, self.requestBlocks, self.peerError)
+}
+
+// peer sends blockhashes if and when gets a request
+func (self *peerTester) serveBlockHashes(indexes ...int) {
+	fmt.Printf("ready to serve block hashes %v\n", indexes)
+
+	self.waitBlockHashesRequests(indexes[0])
+	self.sendBlockHashes(indexes...)
+}
+
+func (self *peerTester) sendBlockHashes(indexes ...int) {
+	fmt.Printf("adding block hashes %v\n", indexes)
+	hashes := self.hashPool.IndexesToHashes(indexes)
+	i := 1
+	next := func() (hash []byte, ok bool) {
+		if i < len(hashes) {
+			hash = hashes[i]
+			ok = true
+			i++
+		}
+		return
+	}
+	self.blockPool.AddBlockHashes(next, self.id)
+}
+
+// peer sends blocks if and when there is a request
+// (in the shared request store, not necessarily to a person)
+func (self *peerTester) serveBlocks(indexes ...int) {
+	fmt.Printf("ready to serve blocks %v\n", indexes[1:])
+	self.waitBlocksRequests(indexes[1:]...)
+	self.sendBlocks(indexes...)
+}
+
+func (self *peerTester) sendBlocks(indexes ...int) {
+	fmt.Printf("adding blocks %v \n", indexes)
+	hashes := self.hashPool.IndexesToHashes(indexes)
+	for i := 1; i < len(hashes); i++ {
+		fmt.Printf("adding block %v %x\n", indexes[i], hashes[i][:4])
+		self.blockPool.AddBlock(&types.Block{HeaderHash: ethutil.Bytes(hashes[i]), ParentHeaderHash: ethutil.Bytes(hashes[i-1])}, self.id)
+	}
+}
+
+// peer callbacks
+// -1 is special: not found (a hash never seen)
+// records block hashes requests by the blockPool
+func (self *peerTester) requestBlockHashes(hash []byte) error {
+	indexes := self.hashPool.HashesToIndexes([][]byte{hash})
+	fmt.Printf("[%s] block hash request %v %x\n", self.id, indexes[0], hash[:4])
+	self.lock.Lock()
+	defer self.lock.Unlock()
+	self.blockHashesRequests = append(self.blockHashesRequests, indexes[0])
+	return nil
+}
+
+// records block requests by the blockPool
+func (self *peerTester) requestBlocks(hashes [][]byte) error {
+	indexes := self.hashPool.HashesToIndexes(hashes)
+	fmt.Printf("blocks request %v %x...\n", indexes, hashes[0][:4])
+	self.bt.reqlock.Lock()
+	defer self.bt.reqlock.Unlock()
+	self.blocksRequests = append(self.blocksRequests, indexes)
+	for _, i := range indexes {
+		self.blocksRequestsMap[i] = true
+	}
+	return nil
+}
+
+// records the error codes of all the peerErrors found the blockPool
+func (self *peerTester) peerError(err *errs.Error) {
+	self.peerErrors = append(self.peerErrors, err.Code)
+}
diff --git a/blockpool/config_test.go b/blockpool/config_test.go
new file mode 100644
index 000000000..c06649024
--- /dev/null
+++ b/blockpool/config_test.go
@@ -0,0 +1,40 @@
+package blockpool
+
+import (
+	"testing"
+	"time"
+
+	"github.com/ethereum/go-ethereum/blockpool/test"
+)
+
+func TestBlockPoolConfig(t *testing.T) {
+	test.LogInit()
+	blockPool := &BlockPool{Config: &Config{}}
+	blockPool.Start()
+	c := blockPool.Config
+	test.CheckInt("BlockHashesBatchSize", c.BlockHashesBatchSize, blockHashesBatchSize, t)
+	test.CheckInt("BlockBatchSize", c.BlockBatchSize, blockBatchSize, t)
+	test.CheckInt("BlocksRequestRepetition", c.BlocksRequestRepetition, blocksRequestRepetition, t)
+	test.CheckInt("BlocksRequestMaxIdleRounds", c.BlocksRequestMaxIdleRounds, blocksRequestMaxIdleRounds, t)
+	test.CheckDuration("BlockHashesRequestInterval", c.BlockHashesRequestInterval, blockHashesRequestInterval, t)
+	test.CheckDuration("BlocksRequestInterval", c.BlocksRequestInterval, blocksRequestInterval, t)
+	test.CheckDuration("BlockHashesTimeout", c.BlockHashesTimeout, blockHashesTimeout, t)
+	test.CheckDuration("BlocksTimeout", c.BlocksTimeout, blocksTimeout, t)
+}
+
+func TestBlockPoolOverrideConfig(t *testing.T) {
+	test.LogInit()
+	blockPool := &BlockPool{Config: &Config{}}
+	c := &Config{128, 32, 1, 0, 300 * time.Millisecond, 100 * time.Millisecond, 90 * time.Second, 0}
+
+	blockPool.Config = c
+	blockPool.Start()
+	test.CheckInt("BlockHashesBatchSize", c.BlockHashesBatchSize, 128, t)
+	test.CheckInt("BlockBatchSize", c.BlockBatchSize, 32, t)
+	test.CheckInt("BlocksRequestRepetition", c.BlocksRequestRepetition, blocksRequestRepetition, t)
+	test.CheckInt("BlocksRequestMaxIdleRounds", c.BlocksRequestMaxIdleRounds, blocksRequestMaxIdleRounds, t)
+	test.CheckDuration("BlockHashesRequestInterval", c.BlockHashesRequestInterval, 300*time.Millisecond, t)
+	test.CheckDuration("BlocksRequestInterval", c.BlocksRequestInterval, 100*time.Millisecond, t)
+	test.CheckDuration("BlockHashesTimeout", c.BlockHashesTimeout, 90*time.Second, t)
+	test.CheckDuration("BlocksTimeout", c.BlocksTimeout, blocksTimeout, t)
+}
diff --git a/blockpool/errors_test.go b/blockpool/errors_test.go
new file mode 100644
index 000000000..65a161233
--- /dev/null
+++ b/blockpool/errors_test.go
@@ -0,0 +1,124 @@
+package blockpool
+
+import (
+	"testing"
+	"time"
+
+	"github.com/ethereum/go-ethereum/blockpool/test"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/pow"
+)
+
+func TestInvalidBlock(t *testing.T) {
+	test.LogInit()
+	_, blockPool, blockPoolTester := newTestBlockPool(t)
+	blockPoolTester.blockChain[0] = nil
+	blockPoolTester.initRefBlockChain(2)
+	blockPoolTester.refBlockChain[2] = []int{}
+
+	blockPool.Start()
+
+	peer1 := blockPoolTester.newPeer("peer1", 1, 3)
+	peer1.AddPeer()
+	go peer1.serveBlocks(2, 3)
+	go peer1.serveBlockHashes(3, 2, 1, 0)
+	peer1.serveBlocks(0, 1, 2)
+
+	blockPool.Wait(waitTimeout)
+	blockPool.Stop()
+	blockPoolTester.refBlockChain[2] = []int{}
+	blockPoolTester.checkBlockChain(blockPoolTester.refBlockChain)
+	if len(peer1.peerErrors) == 1 {
+		if peer1.peerErrors[0] != ErrInvalidBlock {
+			t.Errorf("wrong error, got %v, expected %v", peer1.peerErrors[0], ErrInvalidBlock)
+		}
+	} else {
+		t.Errorf("expected %v error, got %v", ErrInvalidBlock, peer1.peerErrors)
+	}
+}
+
+func TestVerifyPoW(t *testing.T) {
+	test.LogInit()
+	_, blockPool, blockPoolTester := newTestBlockPool(t)
+	blockPoolTester.blockChain[0] = nil
+	blockPoolTester.initRefBlockChain(3)
+	first := false
+	blockPoolTester.blockPool.verifyPoW = func(b pow.Block) bool {
+		bb, _ := b.(*types.Block)
+		indexes := blockPoolTester.hashPool.HashesToIndexes([][]byte{bb.Hash()})
+		if indexes[0] == 2 && !first {
+			first = true
+			return false
+		} else {
+			return true
+		}
+
+	}
+
+	blockPool.Start()
+
+	peer1 := blockPoolTester.newPeer("peer1", 1, 3)
+	peer2 := blockPoolTester.newPeer("peer2", 1, 3)
+	peer1.AddPeer()
+	peer2.AddPeer()
+	go peer1.serveBlocks(2, 3)
+	go peer1.serveBlockHashes(3, 2, 1, 0)
+	peer1.serveBlocks(0, 1, 2, 3)
+	blockPoolTester.blockPool.verifyPoW = func(b pow.Block) bool {
+		return true
+	}
+	peer2.serveBlocks(1, 2)
+
+	blockPool.Wait(waitTimeout)
+	blockPool.Stop()
+	blockPoolTester.refBlockChain[3] = []int{}
+	blockPoolTester.checkBlockChain(blockPoolTester.refBlockChain)
+	if len(peer1.peerErrors) == 1 {
+		if peer1.peerErrors[0] != ErrInvalidPoW {
+			t.Errorf("wrong error, expected %v, got %v", ErrInvalidPoW, peer1.peerErrors[0])
+		}
+	} else {
+		t.Errorf("expected %v error, got %v", ErrInvalidPoW, peer1.peerErrors)
+	}
+}
+
+func TestUnrequestedBlock(t *testing.T) {
+	test.LogInit()
+	_, blockPool, blockPoolTester := newTestBlockPool(t)
+	blockPoolTester.blockChain[0] = nil
+	blockPool.Start()
+
+	peer1 := blockPoolTester.newPeer("peer1", 1, 3)
+	peer1.AddPeer()
+	peer1.sendBlocks(1, 2)
+
+	// blockPool.Wait(waitTimeout)
+	blockPool.Stop()
+	if len(peer1.peerErrors) == 1 {
+		if peer1.peerErrors[0] != ErrUnrequestedBlock {
+			t.Errorf("wrong error, got %v, expected %v", peer1.peerErrors[0], ErrUnrequestedBlock)
+		}
+	} else {
+		t.Errorf("expected %v error, got %v", ErrUnrequestedBlock, peer1.peerErrors)
+	}
+}
+
+func TestErrInsufficientChainInfo(t *testing.T) {
+	test.LogInit()
+	_, blockPool, blockPoolTester := newTestBlockPool(t)
+	blockPool.Config.BlockHashesTimeout = 100 * time.Millisecond
+	blockPool.Start()
+
+	peer1 := blockPoolTester.newPeer("peer1", 1, 3)
+	peer1.AddPeer()
+
+	blockPool.Wait(waitTimeout)
+	blockPool.Stop()
+	if len(peer1.peerErrors) == 1 {
+		if peer1.peerErrors[0] != ErrInsufficientChainInfo {
+			t.Errorf("wrong error, got %v, expected %v", peer1.peerErrors[0], ErrInsufficientChainInfo)
+		}
+	} else {
+		t.Errorf("expected %v error, got %v", ErrInsufficientChainInfo, peer1.peerErrors)
+	}
+}
diff --git a/blockpool/peers.go b/blockpool/peers.go
new file mode 100644
index 000000000..5f1b2017c
--- /dev/null
+++ b/blockpool/peers.go
@@ -0,0 +1,536 @@
+package blockpool
+
+import (
+	"bytes"
+	"math/big"
+	"math/rand"
+	"sort"
+	"sync"
+	"time"
+
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/errs"
+	"github.com/ethereum/go-ethereum/ethutil"
+)
+
+type peer struct {
+	lock sync.RWMutex
+
+	// last known blockchain status
+	td               *big.Int
+	currentBlockHash []byte
+	currentBlock     *types.Block
+	parentHash       []byte
+	headSection      *section
+
+	id string
+
+	// peer callbacks
+	requestBlockHashes func([]byte) error
+	requestBlocks      func([][]byte) error
+	peerError          func(*errs.Error)
+	errors             *errs.Errors
+
+	sections [][]byte
+
+	// channels to push new head block and head section for peer a
+	currentBlockC chan *types.Block
+	headSectionC  chan *section
+
+	// channels to signal peers witch and peer quit
+	idleC   chan bool
+	switchC chan bool
+
+	quit chan bool
+	bp   *BlockPool
+
+	// timers for head section process
+	blockHashesRequestTimer <-chan time.Time
+	blocksRequestTimer      <-chan time.Time
+	suicide                 <-chan time.Time
+
+	idle bool
+}
+
+// peers is the component keeping a record of peers in a hashmap
+//
+type peers struct {
+	lock sync.RWMutex
+
+	bp     *BlockPool
+	errors *errs.Errors
+	peers  map[string]*peer
+	best   *peer
+	status *status
+}
+
+// peer constructor
+func (self *peers) newPeer(
+	td *big.Int,
+	currentBlockHash []byte,
+	id string,
+	requestBlockHashes func([]byte) error,
+	requestBlocks func([][]byte) error,
+	peerError func(*errs.Error),
+) (p *peer) {
+
+	p = &peer{
+		errors:             self.errors,
+		td:                 td,
+		currentBlockHash:   currentBlockHash,
+		id:                 id,
+		requestBlockHashes: requestBlockHashes,
+		requestBlocks:      requestBlocks,
+		peerError:          peerError,
+		currentBlockC:      make(chan *types.Block),
+		headSectionC:       make(chan *section),
+		bp:                 self.bp,
+		idle:               true,
+	}
+	// at creation the peer is recorded in the peer pool
+	self.peers[id] = p
+	return
+}
+
+// dispatches an error to a peer if still connected
+func (self *peers) peerError(id string, code int, format string, params ...interface{}) {
+	self.lock.RLock()
+	defer self.lock.RUnlock()
+	peer, ok := self.peers[id]
+	if ok {
+		peer.addError(code, format, params)
+	}
+	// blacklisting comes here
+}
+
+func (self *peer) addError(code int, format string, params ...interface{}) {
+	err := self.errors.New(code, format, params...)
+	self.peerError(err)
+}
+
+func (self *peer) setChainInfo(td *big.Int, c []byte) {
+	self.lock.Lock()
+	defer self.lock.Unlock()
+
+	self.td = td
+	self.currentBlockHash = c
+
+	self.currentBlock = nil
+	self.parentHash = nil
+	self.headSection = nil
+}
+
+func (self *peer) setChainInfoFromBlock(block *types.Block) {
+	self.lock.Lock()
+	defer self.lock.Unlock()
+	// use the optional TD to update peer td, this helps second best peer selection
+	// in case best peer is lost
+	if block.Td != nil && block.Td.Cmp(self.td) > 0 {
+		plog.DebugDetailf("setChainInfoFromBlock: update <%s> - head: %v->%v - TD: %v->%v", self.id, hex(self.currentBlockHash), hex(block.Hash()), self.td, block.Td)
+		self.td = block.Td
+		self.currentBlockHash = block.Hash()
+		self.parentHash = block.ParentHash()
+		self.currentBlock = block
+		self.headSection = nil
+	}
+	self.bp.wg.Add(1)
+	go func() {
+		self.currentBlockC <- block
+		self.bp.wg.Done()
+	}()
+}
+
+func (self *peers) requestBlocks(attempts int, hashes [][]byte) {
+	// distribute block request among known peers
+	self.lock.RLock()
+	defer self.lock.RUnlock()
+	peerCount := len(self.peers)
+	// on first attempt use the best peer
+	if attempts == 0 {
+		plog.DebugDetailf("request %v missing blocks from best peer <%s>", len(hashes), self.best.id)
+		self.best.requestBlocks(hashes)
+		return
+	}
+	repetitions := self.bp.Config.BlocksRequestRepetition
+	if repetitions > peerCount {
+		repetitions = peerCount
+	}
+	i := 0
+	indexes := rand.Perm(peerCount)[0:repetitions]
+	sort.Ints(indexes)
+
+	plog.DebugDetailf("request %v missing blocks from %v/%v peers", len(hashes), repetitions, peerCount)
+	for _, peer := range self.peers {
+		if i == indexes[0] {
+			plog.DebugDetailf("request length: %v", len(hashes))
+			plog.DebugDetailf("request %v missing blocks [%x/%x] from peer <%s>", len(hashes), hashes[0][:4], hashes[len(hashes)-1][:4], peer.id)
+			peer.requestBlocks(hashes)
+			indexes = indexes[1:]
+			if len(indexes) == 0 {
+				break
+			}
+		}
+		i++
+	}
+	self.bp.putHashSlice(hashes)
+}
+
+// addPeer implements the logic for blockpool.AddPeer
+// returns true iff peer is promoted as best peer in the pool
+func (self *peers) addPeer(
+	td *big.Int,
+	currentBlockHash []byte,
+	id string,
+	requestBlockHashes func([]byte) error,
+	requestBlocks func([][]byte) error,
+	peerError func(*errs.Error),
+) (best bool) {
+
+	var previousBlockHash []byte
+	self.lock.Lock()
+	p, found := self.peers[id]
+	if found {
+		if !bytes.Equal(p.currentBlockHash, currentBlockHash) {
+			previousBlockHash = p.currentBlockHash
+			plog.Debugf("addPeer: Update peer <%s> with td %v and current block %s (was %v)", id, td, hex(currentBlockHash), hex(previousBlockHash))
+			p.setChainInfo(td, currentBlockHash)
+			self.status.lock.Lock()
+			self.status.values.NewBlocks++
+			self.status.lock.Unlock()
+		}
+	} else {
+		p = self.newPeer(td, currentBlockHash, id, requestBlockHashes, requestBlocks, peerError)
+
+		self.status.lock.Lock()
+
+		self.status.peers[id]++
+		self.status.values.NewBlocks++
+		self.status.lock.Unlock()
+
+		plog.Debugf("addPeer: add new peer <%v> with td %v and current block %s", id, td, hex(currentBlockHash))
+	}
+	self.lock.Unlock()
+
+	// check peer current head
+	if self.bp.hasBlock(currentBlockHash) {
+		// peer not ahead
+		return false
+	}
+
+	if self.best == p {
+		// new block update for active current best peer -> request hashes
+		plog.Debugf("addPeer: <%s> already the best peer. Request new head section info from %s", id, hex(currentBlockHash))
+
+		if previousBlockHash != nil {
+			if entry := self.bp.get(previousBlockHash); entry != nil {
+				p.headSectionC <- nil
+				self.bp.activateChain(entry.section, p, nil)
+				p.sections = append(p.sections, previousBlockHash)
+			}
+		}
+		best = true
+	} else {
+		currentTD := ethutil.Big0
+		if self.best != nil {
+			currentTD = self.best.td
+		}
+		if td.Cmp(currentTD) > 0 {
+			self.status.lock.Lock()
+			self.status.bestPeers[p.id]++
+			self.status.lock.Unlock()
+			plog.Debugf("addPeer: peer <%v> promoted best peer", id)
+			self.bp.switchPeer(self.best, p)
+			self.best = p
+			best = true
+		}
+	}
+	return
+}
+
+// removePeer is called (via RemovePeer) by the eth protocol when the peer disconnects
+func (self *peers) removePeer(id string) {
+	self.lock.Lock()
+	defer self.lock.Unlock()
+
+	p, found := self.peers[id]
+	if !found {
+		return
+	}
+
+	delete(self.peers, id)
+	plog.Debugf("addPeer: remove peer <%v>", id)
+
+	// if current best peer is removed, need to find a better one
+	if self.best == p {
+		var newp *peer
+		// FIXME: own TD
+		max := ethutil.Big0
+		// peer with the highest self-acclaimed TD is chosen
+		for _, pp := range self.peers {
+			if pp.td.Cmp(max) > 0 {
+				max = pp.td
+				newp = pp
+			}
+		}
+		if newp != nil {
+			self.status.lock.Lock()
+			self.status.bestPeers[p.id]++
+			self.status.lock.Unlock()
+			plog.Debugf("addPeer: peer <%v> with td %v promoted best peer", newp.id, newp.td)
+		} else {
+			plog.Warnln("addPeer: no suitable peers found")
+		}
+		self.best = newp
+		self.bp.switchPeer(p, newp)
+	}
+}
+
+// switchPeer launches section processes based on information about
+// shared interest and legacy of peers
+func (self *BlockPool) switchPeer(oldp, newp *peer) {
+
+	// first quit AddBlockHashes, requestHeadSection and activateChain
+	if oldp != nil {
+		plog.DebugDetailf("<%s> quit peer processes", oldp.id)
+		close(oldp.switchC)
+	}
+	if newp != nil {
+		newp.idleC = make(chan bool)
+		newp.switchC = make(chan bool)
+		// if new best peer has no head section yet, create it and run it
+		// otherwise head section is an element of peer.sections
+		if newp.headSection == nil {
+			plog.DebugDetailf("[%s] head section for [%s] not created, requesting info", newp.id, hex(newp.currentBlockHash))
+
+			if newp.idle {
+				self.wg.Add(1)
+				newp.idle = false
+				self.syncing()
+			}
+
+			go func() {
+				newp.run()
+				if !newp.idle {
+					self.wg.Done()
+					newp.idle = true
+				}
+			}()
+
+		}
+
+		var connected = make(map[string]*section)
+		var sections [][]byte
+		for _, hash := range newp.sections {
+			plog.DebugDetailf("activate chain starting from section [%s]", hex(hash))
+			// if section not connected (ie, top of a contiguous sequence of sections)
+			if connected[string(hash)] == nil {
+				// if not deleted, then reread from pool (it can be orphaned top half of a split section)
+				if entry := self.get(hash); entry != nil {
+					self.activateChain(entry.section, newp, connected)
+					connected[string(hash)] = entry.section
+					sections = append(sections, hash)
+				}
+			}
+		}
+		plog.DebugDetailf("<%s> section processes (%v non-contiguous sequences, was %v before)", newp.id, len(sections), len(newp.sections))
+		// need to lock now that newp is exposed to section processes
+		newp.lock.Lock()
+		newp.sections = sections
+		newp.lock.Unlock()
+	}
+	// finally deactivate section process for sections where newp didnt activate
+	// newp activating section process changes the quit channel for this reason
+	if oldp != nil {
+		plog.DebugDetailf("<%s> quit section processes", oldp.id)
+		//
+		close(oldp.idleC)
+	}
+}
+
+func (self *peers) getPeer(id string) (p *peer, best bool) {
+	self.lock.RLock()
+	defer self.lock.RUnlock()
+	if self.best != nil && self.best.id == id {
+		return self.best, true
+	}
+	p = self.peers[id]
+	return
+}
+
+func (self *peer) handleSection(sec *section) {
+	self.lock.Lock()
+	defer self.lock.Unlock()
+
+	self.headSection = sec
+	self.blockHashesRequestTimer = nil
+
+	if sec == nil {
+		if self.idle {
+			self.idle = false
+			self.bp.wg.Add(1)
+			self.bp.syncing()
+		}
+
+		self.suicide = time.After(self.bp.Config.BlockHashesTimeout)
+
+		plog.DebugDetailf("HeadSection: <%s> head block hash changed (mined block received). New head %s", self.id, hex(self.currentBlockHash))
+	} else {
+		if !self.idle {
+			self.idle = true
+			self.suicide = nil
+			self.bp.wg.Done()
+		}
+		plog.DebugDetailf("HeadSection: <%s> head section [%s] created", self.id, sectionhex(sec))
+	}
+}
+
+func (self *peer) getCurrentBlock(currentBlock *types.Block) {
+	// called by update or after AddBlock signals that head block of current peer is received
+	if currentBlock == nil {
+		if entry := self.bp.get(self.currentBlockHash); entry != nil {
+			entry.node.lock.Lock()
+			currentBlock = entry.node.block
+			entry.node.lock.Unlock()
+		}
+		if currentBlock != nil {
+			plog.DebugDetailf("HeadSection: <%s> head block %s found in blockpool", self.id, hex(self.currentBlockHash))
+		} else {
+			plog.DebugDetailf("HeadSection: <%s> head block %s not found... requesting it", self.id, hex(self.currentBlockHash))
+			self.requestBlocks([][]byte{self.currentBlockHash})
+			self.blocksRequestTimer = time.After(self.bp.Config.BlocksRequestInterval)
+			return
+		}
+	} else {
+		plog.DebugDetailf("HeadSection: <%s> head block %s received (parent: %s)", self.id, hex(self.currentBlockHash), hex(currentBlock.ParentHash()))
+	}
+
+	self.lock.Lock()
+	defer self.lock.Unlock()
+	self.currentBlock = currentBlock
+	self.parentHash = currentBlock.ParentHash()
+	plog.DebugDetailf("HeadSection: <%s> head block %s found (parent: [%s])... requesting  hashes", self.id, hex(self.currentBlockHash), hex(self.parentHash))
+	self.blockHashesRequestTimer = time.After(0)
+	self.blocksRequestTimer = nil
+}
+
+func (self *peer) getBlockHashes() {
+	//if connecting parent is found
+	if self.bp.hasBlock(self.parentHash) {
+		plog.DebugDetailf("HeadSection: <%s> parent block %s found in blockchain", self.id, hex(self.parentHash))
+		err := self.bp.insertChain(types.Blocks([]*types.Block{self.currentBlock}))
+		if err != nil {
+			self.addError(ErrInvalidBlock, "%v", err)
+
+			self.bp.status.lock.Lock()
+			self.bp.status.badPeers[self.id]++
+			self.bp.status.lock.Unlock()
+		}
+	} else {
+		if parent := self.bp.get(self.parentHash); parent != nil {
+			if self.bp.get(self.currentBlockHash) == nil {
+				plog.DebugDetailf("HeadSection: <%s> connecting parent %s found in pool... creating singleton section", self.id, hex(self.parentHash))
+				n := &node{
+					hash:    self.currentBlockHash,
+					block:   self.currentBlock,
+					hashBy:  self.id,
+					blockBy: self.id,
+				}
+				self.bp.newSection([]*node{n}).activate(self)
+			} else {
+				plog.DebugDetailf("HeadSection: <%s> connecting parent %s found in pool...head section [%s] exists...not requesting hashes", self.id, hex(self.parentHash), sectionhex(parent.section))
+				self.bp.activateChain(parent.section, self, nil)
+			}
+		} else {
+			plog.DebugDetailf("HeadSection: <%s> section [%s] requestBlockHashes", self.id, sectionhex(self.headSection))
+			self.requestBlockHashes(self.currentBlockHash)
+			self.blockHashesRequestTimer = time.After(self.bp.Config.BlockHashesRequestInterval)
+			return
+		}
+	}
+	self.blockHashesRequestTimer = nil
+	if !self.idle {
+		self.idle = true
+		self.suicide = nil
+		self.bp.wg.Done()
+	}
+}
+
+// main loop for head section process
+func (self *peer) run() {
+
+	self.lock.RLock()
+	switchC := self.switchC
+	currentBlockHash := self.currentBlockHash
+	self.lock.RUnlock()
+
+	self.blockHashesRequestTimer = nil
+
+	self.blocksRequestTimer = time.After(0)
+	self.suicide = time.After(self.bp.Config.BlockHashesTimeout)
+
+	var quit chan bool
+
+	var ping = time.NewTicker(5 * time.Second)
+
+LOOP:
+	for {
+		select {
+		case <-ping.C:
+			plog.Debugf("HeadSection: <%s> section with head %s, idle: %v", self.id, hex(self.currentBlockHash), self.idle)
+
+		// signal from AddBlockHashes that head section for current best peer is created
+		// if sec == nil, it signals that chain info has updated (new block message)
+		case sec := <-self.headSectionC:
+			self.handleSection(sec)
+			// local var quit channel is linked to sections suicide channel so that
+			if sec == nil {
+				quit = nil
+			} else {
+				quit = sec.suicideC
+			}
+
+		// periodic check for block hashes or parent block/section
+		case <-self.blockHashesRequestTimer:
+			self.getBlockHashes()
+
+		// signal from AddBlock that head block of current best peer has been received
+		case currentBlock := <-self.currentBlockC:
+			self.getCurrentBlock(currentBlock)
+
+		// keep requesting until found or timed out
+		case <-self.blocksRequestTimer:
+			self.getCurrentBlock(nil)
+
+		// quitting on timeout
+		case <-self.suicide:
+			self.peerError(self.bp.peers.errors.New(ErrInsufficientChainInfo, "timed out without providing block hashes or head block", currentBlockHash))
+
+			self.bp.status.lock.Lock()
+			self.bp.status.badPeers[self.id]++
+			self.bp.status.lock.Unlock()
+			// there is no persistence here, so GC will just take care of cleaning up
+			break LOOP
+
+		// signal for peer switch, quit
+		case <-switchC:
+			var complete = "incomplete "
+			if self.idle {
+				complete = "complete"
+			}
+			plog.Debugf("HeadSection: <%s> section with head %s %s... quit request loop due to peer switch", self.id, hex(self.currentBlockHash), complete)
+			break LOOP
+
+		// global quit for blockpool
+		case <-self.bp.quit:
+			break LOOP
+
+		// quit
+		case <-quit:
+			break LOOP
+		}
+	}
+	if !self.idle {
+		self.idle = true
+		self.bp.wg.Done()
+	}
+}
diff --git a/blockpool/peers_test.go b/blockpool/peers_test.go
new file mode 100644
index 000000000..e53d7160b
--- /dev/null
+++ b/blockpool/peers_test.go
@@ -0,0 +1,120 @@
+package blockpool
+
+import (
+	"math/big"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/blockpool/test"
+)
+
+// the actual tests
+func TestAddPeer(t *testing.T) {
+	test.LogInit()
+	_, blockPool, blockPoolTester := newTestBlockPool(t)
+	peer0 := blockPoolTester.newPeer("peer0", 1, 0)
+	peer1 := blockPoolTester.newPeer("peer1", 2, 1)
+	peer2 := blockPoolTester.newPeer("peer2", 3, 2)
+	var bestpeer *peer
+
+	blockPool.Start()
+
+	// pool
+	best := peer0.AddPeer()
+	if !best {
+		t.Errorf("peer0 (TD=1) not accepted as best")
+	}
+	if blockPool.peers.best.id != "peer0" {
+		t.Errorf("peer0 (TD=1) not set as best")
+	}
+
+	best = peer2.AddPeer()
+	if !best {
+		t.Errorf("peer2 (TD=3) not accepted as best")
+	}
+	if blockPool.peers.best.id != "peer2" {
+		t.Errorf("peer2 (TD=3) not set as best")
+	}
+	peer2.waitBlocksRequests(2)
+
+	best = peer1.AddPeer()
+	if best {
+		t.Errorf("peer1 (TD=2) accepted as best")
+	}
+	if blockPool.peers.best.id != "peer2" {
+		t.Errorf("peer2 (TD=3) not set any more as best")
+	}
+	if blockPool.peers.best.td.Cmp(big.NewInt(int64(3))) != 0 {
+		t.Errorf("peer1 TD not set")
+	}
+
+	peer2.td = 4
+	peer2.currentBlock = 3
+	best = peer2.AddPeer()
+	if !best {
+		t.Errorf("peer2 (TD=4) not accepted as best")
+	}
+	if blockPool.peers.best.id != "peer2" {
+		t.Errorf("peer2 (TD=4) not set as best")
+	}
+	if blockPool.peers.best.td.Cmp(big.NewInt(int64(4))) != 0 {
+		t.Errorf("peer2 TD not updated")
+	}
+	peer2.waitBlocksRequests(3)
+
+	peer1.td = 3
+	peer1.currentBlock = 2
+	best = peer1.AddPeer()
+	if best {
+		t.Errorf("peer1 (TD=3) should not be set as best")
+	}
+	if blockPool.peers.best.id == "peer1" {
+		t.Errorf("peer1 (TD=3) should not be set as best")
+	}
+	bestpeer, best = blockPool.peers.getPeer("peer1")
+	if bestpeer.td.Cmp(big.NewInt(int64(3))) != 0 {
+		t.Errorf("peer1 TD should be updated")
+	}
+
+	blockPool.RemovePeer("peer2")
+	bestpeer, best = blockPool.peers.getPeer("peer2")
+	if bestpeer != nil {
+		t.Errorf("peer2 not removed")
+	}
+
+	if blockPool.peers.best.id != "peer1" {
+		t.Errorf("existing peer1 (TD=3) should be set as best peer")
+	}
+	peer1.waitBlocksRequests(2)
+
+	blockPool.RemovePeer("peer1")
+	bestpeer, best = blockPool.peers.getPeer("peer1")
+	if bestpeer != nil {
+		t.Errorf("peer1 not removed")
+	}
+
+	if blockPool.peers.best.id != "peer0" {
+		t.Errorf("existing peer0 (TD=1) should be set as best peer")
+	}
+	peer0.waitBlocksRequests(0)
+
+	blockPool.RemovePeer("peer0")
+	bestpeer, best = blockPool.peers.getPeer("peer0")
+	if bestpeer != nil {
+		t.Errorf("peer1 not removed")
+	}
+
+	// adding back earlier peer ok
+	peer0.currentBlock = 3
+	best = peer0.AddPeer()
+	if !best {
+		t.Errorf("peer0 (TD=1) should be set as best")
+	}
+
+	if blockPool.peers.best.id != "peer0" {
+		t.Errorf("peer0 (TD=1) should be set as best")
+	}
+	peer0.waitBlocksRequests(3)
+
+	blockPool.Stop()
+
+}
diff --git a/blockpool/section.go b/blockpool/section.go
new file mode 100644
index 000000000..48ea15d31
--- /dev/null
+++ b/blockpool/section.go
@@ -0,0 +1,677 @@
+package blockpool
+
+import (
+	"sync"
+	"time"
+
+	"github.com/ethereum/go-ethereum/core/types"
+)
+
+/*
+  section is the worker on each chain section in the block pool
+  - remove the section if there are blocks missing after an absolute time
+  - remove the section if there are maxIdleRounds of idle rounds of block requests with no response
+  - periodically polls the chain section for missing blocks which are then requested from peers
+  - registers the process controller on the peer so that if the peer is promoted as best peer the second time (after a disconnect of a better one), all active processes are switched back on unless they removed (inserted in blockchain, invalid or expired)
+  - when turned off (if peer disconnects and new peer connects with alternative chain), no blockrequests are made but absolute expiry timer is ticking
+  - when turned back on it recursively calls itself on the root of the next chain section
+*/
+type section struct {
+	lock sync.RWMutex
+
+	parent *section // connecting section back in time towards blockchain
+	child  *section // connecting section forward in time
+
+	top    *node // the topmost node = head node = youngest node within the chain section
+	bottom *node // the bottom node = root node = oldest node within the chain section
+	nodes  []*node
+
+	peer       *peer
+	parentHash []byte
+
+	blockHashes [][]byte
+
+	poolRootIndex int
+
+	bp *BlockPool
+
+	controlC  chan *peer     // to (de)register the current best peer
+	poolRootC chan *peer     // indicate connectedness to blockchain (well, known blocks)
+	offC      chan bool      // closed if process terminated
+	suicideC  chan bool      // initiate suicide on the section
+	quitInitC chan bool      // to signal end of initialisation
+	forkC     chan chan bool // freeze section process while splitting
+	switchC   chan bool      // switching
+	idleC     chan bool      // channel to indicate thai food
+	processC  chan *node     //
+	missingC  chan *node     //
+
+	blocksRequestTimer      <-chan time.Time
+	blockHashesRequestTimer <-chan time.Time
+	suicideTimer            <-chan time.Time
+
+	blocksRequests      int
+	blockHashesRequests int
+
+	blocksRequestsComplete      bool
+	blockHashesRequestsComplete bool
+	ready                       bool
+	same                        bool
+	initialised                 bool
+	active                      bool
+
+	step        int
+	idle        int
+	missing     int
+	lastMissing int
+	depth       int
+	invalid     bool
+	poolRoot    bool
+}
+
+//
+func (self *BlockPool) newSection(nodes []*node) *section {
+	sec := &section{
+		bottom:        nodes[len(nodes)-1],
+		top:           nodes[0],
+		nodes:         nodes,
+		poolRootIndex: len(nodes),
+		bp:            self,
+		controlC:      make(chan *peer),
+		poolRootC:     make(chan *peer),
+		offC:          make(chan bool),
+	}
+
+	for i, node := range nodes {
+		entry := &entry{node: node, section: sec, index: &index{i}}
+		self.set(node.hash, entry)
+	}
+
+	plog.DebugDetailf("[%s] setup section process", sectionhex(sec))
+
+	go sec.run()
+	return sec
+}
+
+func (self *section) addSectionToBlockChain(p *peer) {
+	self.bp.wg.Add(1)
+	go func() {
+
+		self.lock.Lock()
+		defer self.lock.Unlock()
+		defer func() {
+			self.bp.wg.Done()
+		}()
+
+		var node *node
+		var keys []string
+		var blocks []*types.Block
+		for self.poolRootIndex > 0 {
+			node = self.nodes[self.poolRootIndex-1]
+			node.lock.RLock()
+			block := node.block
+			node.lock.RUnlock()
+			if block == nil {
+				break
+			}
+			self.poolRootIndex--
+			keys = append(keys, string(node.hash))
+			blocks = append(blocks, block)
+		}
+
+		if len(blocks) == 0 {
+			return
+		}
+
+		self.bp.lock.Lock()
+		for _, key := range keys {
+			delete(self.bp.pool, key)
+		}
+		self.bp.lock.Unlock()
+
+		plog.Infof("[%s] insert %v blocks [%v/%v] into blockchain", sectionhex(self), len(blocks), hex(blocks[0].Hash()), hex(blocks[len(blocks)-1].Hash()))
+		err := self.bp.insertChain(blocks)
+		if err != nil {
+			self.invalid = true
+			self.bp.peers.peerError(node.blockBy, ErrInvalidBlock, "%v", err)
+			plog.Warnf("invalid block %x", node.hash)
+			plog.Warnf("penalise peers %v (hash), %v (block)", node.hashBy, node.blockBy)
+
+			// or invalid block and the entire chain needs to be removed
+			self.removeInvalidChain()
+		} else {
+			// if all blocks inserted in this section
+			// then need to try to insert blocks in child section
+			if self.poolRootIndex == 0 {
+				// if there is a child section, then recursively call itself:
+				// also if section process is not terminated,
+				// then signal blockchain connectivity with poolRootC
+				if child := self.bp.getChild(self); child != nil {
+					select {
+					case <-child.offC:
+						plog.DebugDetailf("[%s] add complete child section [%s] to the blockchain", sectionhex(self), sectionhex(child))
+					case child.poolRootC <- p:
+						plog.DebugDetailf("[%s] add incomplete child section [%s] to the blockchain", sectionhex(self), sectionhex(child))
+					}
+					child.addSectionToBlockChain(p)
+				} else {
+					plog.DebugDetailf("[%s] no child section in pool", sectionhex(self))
+				}
+				plog.DebugDetailf("[%s] section completely inserted to blockchain - remove", sectionhex(self))
+				// complete sections are removed. if called from within section process,
+				// this must run in its own go routine to avoid deadlock
+				self.remove()
+			}
+		}
+
+		self.bp.status.lock.Lock()
+		if err == nil {
+			headKey := string(blocks[0].ParentHash())
+			height := self.bp.status.chain[headKey] + len(blocks)
+			self.bp.status.chain[string(blocks[len(blocks)-1].Hash())] = height
+			if height > self.bp.status.values.LongestChain {
+				self.bp.status.values.LongestChain = height
+			}
+			delete(self.bp.status.chain, headKey)
+		}
+		self.bp.status.values.BlocksInChain += len(blocks)
+		self.bp.status.values.BlocksInPool -= len(blocks)
+		if err != nil {
+			self.bp.status.badPeers[node.blockBy]++
+		}
+		self.bp.status.lock.Unlock()
+
+	}()
+
+}
+
+func (self *section) run() {
+
+	// absolute time after which sub-chain is killed if not complete (some blocks are missing)
+	self.suicideC = make(chan bool)
+	self.forkC = make(chan chan bool)
+	self.suicideTimer = time.After(self.bp.Config.BlocksTimeout)
+
+	// node channels for the section
+	// container for missing block hashes
+	var checking bool
+	var ping = time.NewTicker(5 * time.Second)
+
+LOOP:
+	for !self.blockHashesRequestsComplete || !self.blocksRequestsComplete {
+
+		select {
+		case <-ping.C:
+			var name = "no peer"
+			if self.peer != nil {
+				name = self.peer.id
+			}
+			plog.DebugDetailf("[%s] peer <%s> active: %v", sectionhex(self), name, self.active)
+
+		// global quit from blockpool
+		case <-self.bp.quit:
+			break LOOP
+
+		// pause for peer switching
+		case <-self.switchC:
+			self.switchC = nil
+
+		case p := <-self.poolRootC:
+			// signal on pool root channel indicates that the blockpool is
+			// connected to the blockchain, insert the longest chain of blocks
+			// ignored in idle mode to avoid inserting chain sections of non-live peers
+			self.poolRoot = true
+			// switch off hash requests in case they were on
+			self.blockHashesRequestTimer = nil
+			self.blockHashesRequestsComplete = true
+			self.switchOn(p)
+
+		// peer quit or demoted, put section in idle mode
+		case <-self.idleC:
+			// peer quit or demoted, put section in idle mode
+			plog.Debugf("[%s] peer <%s> quit or demoted", sectionhex(self), self.peer.id)
+			self.switchOff()
+			self.idleC = nil
+
+		// timebomb - if section is not complete in time, nuke the entire chain
+		case <-self.suicideTimer:
+			self.suicide()
+			plog.Debugf("[%s] timeout. (%v total attempts): missing %v/%v/%v...suicide", sectionhex(self), self.blocksRequests, self.missing, self.lastMissing, self.depth)
+			self.suicideTimer = nil
+
+		// closing suicideC triggers section suicide: removes section nodes from pool and terminates section process
+		case <-self.suicideC:
+			plog.DebugDetailf("[%s] suicide", sectionhex(self))
+			self.unlink()
+			self.bp.remove(self)
+			plog.DebugDetailf("[%s] done", sectionhex(self))
+			break LOOP
+
+		// alarm for checking blocks in the section
+		case <-self.blocksRequestTimer:
+			plog.DebugDetailf("[%s] alarm: block request time", sectionhex(self))
+			self.processC = self.missingC
+
+		// alarm for checking parent of the section or sending out hash requests
+		case <-self.blockHashesRequestTimer:
+			plog.DebugDetailf("[%s] alarm: hash request time", sectionhex(self))
+			self.blockHashesRequest()
+
+		// activate this section process with a peer
+		case p := <-self.controlC:
+			if p == nil {
+				self.switchOff()
+			} else {
+				self.switchOn(p)
+			}
+			self.bp.wg.Done()
+		// blocks the process until section is split at the fork
+		case waiter := <-self.forkC:
+			<-waiter
+			self.initialised = false
+			self.quitInitC = nil
+
+		//
+		case n, ok := <-self.processC:
+			// channel closed, first iteration finished
+			if !ok && !self.initialised {
+				plog.DebugDetailf("[%s] section initalised: missing %v/%v/%v", sectionhex(self), self.missing, self.lastMissing, self.depth)
+				self.initialised = true
+				self.processC = nil
+				// self.processC = make(chan *node, self.missing)
+				self.checkRound()
+				checking = false
+				break
+			}
+			plog.DebugDetailf("[%s] section proc step %v: missing %v/%v/%v", sectionhex(self), self.step, self.missing, self.lastMissing, self.depth)
+			if !checking {
+				self.step = 0
+				self.missing = 0
+				checking = true
+			}
+			self.step++
+
+			n.lock.RLock()
+			block := n.block
+			n.lock.RUnlock()
+
+			// if node has no block, request it (buffer it for batch request)
+			// feed it to missingC channel for the next round
+			if block == nil {
+				pos := self.missing % self.bp.Config.BlockBatchSize
+				if pos == 0 {
+					if self.missing != 0 {
+						self.bp.requestBlocks(self.blocksRequests, self.blockHashes[:])
+					}
+					self.blockHashes = self.bp.getHashSlice()
+				}
+				self.blockHashes[pos] = n.hash
+				self.missing++
+				self.missingC <- n
+			} else {
+				// checking for parent block
+				if self.poolRoot {
+					// if node has got block (received via async AddBlock call from protocol)
+					if self.step == self.lastMissing {
+						// current root of the pool
+						plog.DebugDetailf("[%s] received block for current pool root %s", sectionhex(self), hex(n.hash))
+						self.addSectionToBlockChain(self.peer)
+					}
+				} else {
+					if self.parentHash == nil && n == self.bottom {
+						self.parentHash = block.ParentHash()
+						plog.DebugDetailf("[%s] got parent head block hash %s...checking", sectionhex(self), hex(self.parentHash))
+						self.blockHashesRequest()
+					}
+				}
+			}
+			if self.initialised && self.step == self.lastMissing {
+				plog.DebugDetailf("[%s] check if new blocks arrived (attempt %v): missing %v/%v/%v", sectionhex(self), self.blocksRequests, self.missing, self.lastMissing, self.depth)
+				self.checkRound()
+				checking = false
+			}
+		} // select
+	} // for
+
+	close(self.offC)
+	if self.peer != nil {
+		self.active = false
+		self.bp.wg.Done()
+	}
+
+	plog.DebugDetailf("[%s] section process terminated: %v blocks retrieved (%v attempts), hash requests complete on root (%v attempts).", sectionhex(self), self.depth, self.blocksRequests, self.blockHashesRequests)
+
+}
+
+func (self *section) switchOn(newpeer *peer) {
+
+	oldpeer := self.peer
+	// reset switchC/switchC to current best peer
+	self.idleC = newpeer.idleC
+	self.switchC = newpeer.switchC
+	self.peer = newpeer
+
+	if oldpeer != newpeer {
+		oldp := "no peer"
+		newp := "no peer"
+		if oldpeer != nil {
+			oldp = oldpeer.id
+		}
+		if newpeer != nil {
+			newp = newpeer.id
+		}
+
+		plog.DebugDetailf("[%s] active mode <%s> -> <%s>", sectionhex(self), oldp, newp)
+	}
+
+	// activate section with current peer
+	if oldpeer == nil {
+		self.bp.wg.Add(1)
+		self.active = true
+
+		if !self.blockHashesRequestsComplete {
+			self.blockHashesRequestTimer = time.After(0)
+		}
+		if !self.blocksRequestsComplete {
+			if !self.initialised {
+				if self.quitInitC != nil {
+					<-self.quitInitC
+				}
+				self.missingC = make(chan *node, self.bp.Config.BlockHashesBatchSize)
+				self.processC = make(chan *node, self.bp.Config.BlockHashesBatchSize)
+				self.quitInitC = make(chan bool)
+
+				self.step = 0
+				self.missing = 0
+				self.depth = len(self.nodes)
+				self.lastMissing = self.depth
+
+				self.feedNodes()
+			} else {
+				self.blocksRequestTimer = time.After(0)
+			}
+		}
+	}
+}
+
+// put the section to idle mode
+func (self *section) switchOff() {
+	// active -> idle
+	if self.peer != nil {
+		oldp := "no peer"
+		oldpeer := self.peer
+		if oldpeer != nil {
+			oldp = oldpeer.id
+		}
+		plog.DebugDetailf("[%s] idle mode peer <%s> -> <> (%v total attempts): missing %v/%v/%v", sectionhex(self), oldp, self.blocksRequests, self.missing, self.lastMissing, self.depth)
+
+		self.active = false
+		self.peer = nil
+		// turn off timers
+		self.blocksRequestTimer = nil
+		self.blockHashesRequestTimer = nil
+
+		if self.quitInitC != nil {
+			<-self.quitInitC
+			self.quitInitC = nil
+		}
+		self.processC = nil
+		self.bp.wg.Done()
+	}
+}
+
+// iterates through nodes of a section to feed processC
+// used to initialise chain section
+func (self *section) feedNodes() {
+	// if not run at least once fully, launch iterator
+	self.bp.wg.Add(1)
+	go func() {
+		self.lock.Lock()
+		defer self.lock.Unlock()
+		defer func() {
+			self.bp.wg.Done()
+		}()
+		var n *node
+	INIT:
+		for _, n = range self.nodes {
+			select {
+			case self.processC <- n:
+			case <-self.bp.quit:
+				break INIT
+			}
+		}
+		close(self.processC)
+		close(self.quitInitC)
+	}()
+}
+
+func (self *section) blockHashesRequest() {
+
+	if self.switchC != nil {
+		self.bp.chainLock.Lock()
+		parentSection := self.parent
+
+		if parentSection == nil {
+
+			// only link to new parent if not switching peers
+			// this protects against synchronisation issue where during switching
+			// a demoted peer's fork will be chosen over the best peer's chain
+			// because relinking the correct chain (activateChain) is overwritten here in
+			// demoted peer's section process just before the section is put to idle mode
+			if self.parentHash != nil {
+				if parent := self.bp.get(self.parentHash); parent != nil {
+					parentSection = parent.section
+					plog.DebugDetailf("[%s] blockHashesRequest: parent section [%s] linked\n", sectionhex(self), sectionhex(parentSection))
+					link(parentSection, self)
+				} else {
+					if self.bp.hasBlock(self.parentHash) {
+						self.poolRoot = true
+						plog.DebugDetailf("[%s] blockHashesRequest: parentHash known ... inserting section in blockchain", sectionhex(self))
+						self.addSectionToBlockChain(self.peer)
+						self.blockHashesRequestTimer = nil
+						self.blockHashesRequestsComplete = true
+					}
+				}
+			}
+		}
+		self.bp.chainLock.Unlock()
+
+		if !self.poolRoot {
+			if parentSection != nil {
+				//  activate parent section with this peer
+				// but only if not during switch mode
+				plog.DebugDetailf("[%s] parent section [%s] activated\n", sectionhex(self), sectionhex(parentSection))
+				self.bp.activateChain(parentSection, self.peer, nil)
+				// if not root of chain, switch off
+				plog.DebugDetailf("[%s] parent found, hash requests deactivated (after %v total attempts)\n", sectionhex(self), self.blockHashesRequests)
+				self.blockHashesRequestTimer = nil
+				self.blockHashesRequestsComplete = true
+			} else {
+				self.blockHashesRequests++
+				plog.DebugDetailf("[%s] hash request on root (%v total attempts)\n", sectionhex(self), self.blockHashesRequests)
+				self.peer.requestBlockHashes(self.bottom.hash)
+				self.blockHashesRequestTimer = time.After(self.bp.Config.BlockHashesRequestInterval)
+			}
+		}
+	}
+}
+
+// checks number of missing blocks after each round of request and acts accordingly
+func (self *section) checkRound() {
+	if self.missing == 0 {
+		// no missing blocks
+		plog.DebugDetailf("[%s] section checked: got all blocks. process complete (%v total blocksRequests): missing %v/%v/%v", sectionhex(self), self.blocksRequests, self.missing, self.lastMissing, self.depth)
+		self.blocksRequestsComplete = true
+		self.blocksRequestTimer = nil
+	} else {
+		// some missing blocks
+		plog.DebugDetailf("[%s] section checked: missing %v/%v/%v", sectionhex(self), self.missing, self.lastMissing, self.depth)
+		self.blocksRequests++
+		pos := self.missing % self.bp.Config.BlockBatchSize
+		if pos == 0 {
+			pos = self.bp.Config.BlockBatchSize
+		}
+		self.bp.requestBlocks(self.blocksRequests, self.blockHashes[:pos])
+
+		// handle idle rounds
+		if self.missing == self.lastMissing {
+			// idle round
+			if self.same {
+				// more than once
+				self.idle++
+				// too many idle rounds
+				if self.idle >= self.bp.Config.BlocksRequestMaxIdleRounds {
+					plog.DebugDetailf("[%s] block requests had %v idle rounds (%v total attempts): missing %v/%v/%v\ngiving up...", sectionhex(self), self.idle, self.blocksRequests, self.missing, self.lastMissing, self.depth)
+					self.suicide()
+				}
+			} else {
+				self.idle = 0
+			}
+			self.same = true
+		} else {
+			self.same = false
+		}
+		self.lastMissing = self.missing
+		// put processC offline
+		self.processC = nil
+		self.blocksRequestTimer = time.After(self.bp.Config.BlocksRequestInterval)
+	}
+}
+
+/*
+ link connects two sections via parent/child fields
+ creating a doubly linked list
+ caller must hold BlockPool chainLock
+*/
+func link(parent *section, child *section) {
+	if parent != nil {
+		exChild := parent.child
+		parent.child = child
+		if exChild != nil && exChild != child {
+			if child != nil {
+				// if child is nil it is not a real fork
+				plog.DebugDetailf("[%s] chain fork [%s] -> [%s]", sectionhex(parent), sectionhex(exChild), sectionhex(child))
+			}
+			exChild.parent = nil
+		}
+	}
+	if child != nil {
+		exParent := child.parent
+		if exParent != nil && exParent != parent {
+			if parent != nil {
+				// if parent is nil it is not a real fork, but suicide delinking section
+				plog.DebugDetailf("[%s] chain reverse fork [%s] -> [%s]", sectionhex(child), sectionhex(exParent), sectionhex(parent))
+			}
+			exParent.child = nil
+		}
+		child.parent = parent
+	}
+}
+
+/*
+  handle forks where connecting node is mid-section
+  by splitting section at fork
+  no splitting needed if connecting node is head of a section
+  caller must hold chain lock
+*/
+func (self *BlockPool) splitSection(parent *section, entry *entry) {
+	plog.DebugDetailf("[%s] split section at fork", sectionhex(parent))
+	parent.deactivate()
+	waiter := make(chan bool)
+	parent.wait(waiter)
+	chain := parent.nodes
+	parent.nodes = chain[entry.index.int:]
+	parent.top = parent.nodes[0]
+	parent.poolRootIndex -= entry.index.int
+	orphan := self.newSection(chain[0:entry.index.int])
+	link(orphan, parent.child)
+	close(waiter)
+	orphan.deactivate()
+}
+
+func (self *section) wait(waiter chan bool) {
+	self.forkC <- waiter
+}
+
+func (self *BlockPool) linkSections(nodes []*node, parent, child *section) (sec *section) {
+	// if new section is created, link it to parent/child sections
+	// and launch section process fetching block and further hashes
+	if len(nodes) > 0 {
+		sec = self.newSection(nodes)
+		plog.Debugf("[%s]->[%s](%v)->[%s] new chain section", sectionhex(parent), sectionhex(sec), len(nodes), sectionhex(child))
+		link(parent, sec)
+		link(sec, child)
+	} else {
+		// now this can only happen if we allow response to hash request to include <from> hash
+		// in this case we just link parent and child (without needing root block of child section)
+		plog.Debugf("[%s]->[%s] connecting known sections", sectionhex(parent), sectionhex(child))
+		link(parent, child)
+	}
+	return
+}
+
+func (self *section) activate(p *peer) {
+	self.bp.wg.Add(1)
+	select {
+	case <-self.offC:
+		self.bp.wg.Done()
+	case self.controlC <- p:
+		plog.DebugDetailf("[%s] activate section process for peer <%s>", sectionhex(self), p.id)
+	}
+}
+
+func (self *section) deactivate() {
+	self.bp.wg.Add(1)
+	self.controlC <- nil
+}
+
+func (self *section) suicide() {
+	select {
+	case <-self.suicideC:
+		return
+	default:
+	}
+	close(self.suicideC)
+}
+
+// removes this section exacly
+func (self *section) remove() {
+	select {
+	case <-self.offC:
+		// section is complete, no process
+		self.unlink()
+		self.bp.remove(self)
+		close(self.suicideC)
+		plog.DebugDetailf("[%s] remove: suicide", sectionhex(self))
+	case <-self.suicideC:
+		plog.DebugDetailf("[%s] remove: suicided already", sectionhex(self))
+	default:
+		plog.DebugDetailf("[%s] remove: suicide", sectionhex(self))
+		close(self.suicideC)
+	}
+	plog.DebugDetailf("[%s] removed section.", sectionhex(self))
+
+}
+
+// remove a section and all its descendents from the pool
+func (self *section) removeInvalidChain() {
+	// need to get the child before removeSection delinks the section
+	self.bp.chainLock.RLock()
+	child := self.child
+	self.bp.chainLock.RUnlock()
+
+	plog.DebugDetailf("[%s] remove invalid chain", sectionhex(self))
+	self.remove()
+	if child != nil {
+		child.removeInvalidChain()
+	}
+}
+
+// unlink a section from its parent/child
+func (self *section) unlink() {
+	// first delink from child and parent under chainlock
+	self.bp.chainLock.Lock()
+	link(nil, self)
+	link(self, nil)
+	self.bp.chainLock.Unlock()
+}
diff --git a/blockpool/status.go b/blockpool/status.go
new file mode 100644
index 000000000..0dd874232
--- /dev/null
+++ b/blockpool/status.go
@@ -0,0 +1,110 @@
+package blockpool
+
+import (
+	"fmt"
+	"sync"
+)
+
+type statusValues struct {
+	BlockHashes       int    // number of hashes fetched this session
+	BlockHashesInPool int    // number of hashes currently in  the pool
+	Blocks            int    // number of blocks fetched this session
+	BlocksInPool      int    // number of blocks currently in  the pool
+	BlocksInChain     int    // number of blocks inserted/connected to the blockchain this session
+	NewBlocks         int    // number of new blocks (received with new blocks msg) this session
+	Forks             int    // number of chain forks in the blockchain (poolchain) this session
+	LongestChain      int    // the longest chain inserted since the start of session (aka session blockchain height)
+	BestPeer          []byte //Pubkey
+	Syncing           bool   // requesting, updating etc
+	Peers             int    // cumulative number of all different registered peers since the start of this session
+	ActivePeers       int    // cumulative number of all different peers that contributed a hash or block since the start of this session
+	LivePeers         int    // number of live peers registered with the block pool (supposed to be redundant but good sanity check
+	BestPeers         int    // cumulative number of all peers that at some point were promoted as best peer (peer with highest TD status) this session
+	BadPeers          int    // cumulative number of all peers that violated the protocol (invalid block or pow, unrequested hash or block, etc)
+}
+
+type status struct {
+	lock        sync.Mutex
+	values      statusValues
+	chain       map[string]int
+	peers       map[string]int
+	bestPeers   map[string]int
+	badPeers    map[string]int
+	activePeers map[string]int
+}
+
+func newStatus() *status {
+	return &status{
+		chain:       make(map[string]int),
+		peers:       make(map[string]int),
+		bestPeers:   make(map[string]int),
+		badPeers:    make(map[string]int),
+		activePeers: make(map[string]int),
+	}
+}
+
+type Status struct {
+	statusValues
+}
+
+// blockpool status for reporting
+func (self *BlockPool) Status() *Status {
+	self.status.lock.Lock()
+	defer self.status.lock.Unlock()
+	self.status.values.BlockHashesInPool = len(self.pool)
+	self.status.values.ActivePeers = len(self.status.activePeers)
+	self.status.values.BestPeers = len(self.status.bestPeers)
+	self.status.values.BadPeers = len(self.status.badPeers)
+	self.status.values.LivePeers = len(self.peers.peers)
+	self.status.values.Peers = len(self.status.peers)
+	self.status.values.BlockHashesInPool = len(self.pool)
+	return &Status{self.status.values}
+}
+
+func (self *Status) String() string {
+	return fmt.Sprintf(`
+  Syncing:            %v
+  BlockHashes:        %v
+  BlockHashesInPool:  %v
+  Blocks:             %v
+  BlocksInPool:       %v
+  BlocksInChain:      %v
+  NewBlocks:          %v
+  Forks:              %v
+  LongestChain:       %v
+  Peers:              %v
+  LivePeers:          %v
+  ActivePeers:        %v
+  BestPeers:          %v
+  BadPeers:           %v
+`,
+		self.Syncing,
+		self.BlockHashes,
+		self.BlockHashesInPool,
+		self.Blocks,
+		self.BlocksInPool,
+		self.BlocksInChain,
+		self.NewBlocks,
+		self.Forks,
+		self.LongestChain,
+		self.Peers,
+		self.LivePeers,
+		self.ActivePeers,
+		self.BestPeers,
+		self.BadPeers,
+	)
+}
+
+func (self *BlockPool) syncing() {
+	self.status.lock.Lock()
+	defer self.status.lock.Unlock()
+	if !self.status.values.Syncing {
+		self.status.values.Syncing = true
+		go func() {
+			self.wg.Wait()
+			self.status.lock.Lock()
+			self.status.values.Syncing = false
+			self.status.lock.Unlock()
+		}()
+	}
+}
diff --git a/blockpool/status_test.go b/blockpool/status_test.go
new file mode 100644
index 000000000..7392f667a
--- /dev/null
+++ b/blockpool/status_test.go
@@ -0,0 +1,228 @@
+package blockpool
+
+import (
+	"fmt"
+	"testing"
+	// "time"
+
+	"github.com/ethereum/go-ethereum/blockpool/test"
+)
+
+var statusFields = []string{
+	"BlockHashes",
+	"BlockHashesInPool",
+	"Blocks",
+	"BlocksInPool",
+	"BlocksInChain",
+	"NewBlocks",
+	"Forks",
+	"LongestChain",
+	"Peers",
+	"LivePeers",
+	"ActivePeers",
+	"BestPeers",
+	"BadPeers",
+}
+
+func getStatusValues(s *Status) []int {
+	return []int{
+		s.BlockHashes,
+		s.BlockHashesInPool,
+		s.Blocks,
+		s.BlocksInPool,
+		s.BlocksInChain,
+		s.NewBlocks,
+		s.Forks,
+		s.LongestChain,
+		s.Peers,
+		s.LivePeers,
+		s.ActivePeers,
+		s.BestPeers,
+		s.BadPeers,
+	}
+}
+
+func checkStatus(t *testing.T, bp *BlockPool, syncing bool, expected []int) (err error) {
+	s := bp.Status()
+	if s.Syncing != syncing {
+		t.Errorf("status for Syncing incorrect. expected %v, got %v", syncing, s.Syncing)
+	}
+	got := getStatusValues(s)
+	for i, v := range expected {
+		err = test.CheckInt(statusFields[i], got[i], v, t)
+		if err != nil {
+			return err
+		}
+		fmt.Printf("%v: %v (%v)\n", statusFields[i], got[i], v)
+	}
+	return
+}
+
+// func TestBlockPoolStatus(t *testing.T) {
+// 	test.LogInit()
+// 	_, blockPool, blockPoolTester := newTestBlockPool(t)
+// 	blockPoolTester.blockChain[0] = nil
+// 	blockPoolTester.initRefBlockChain(12)
+// 	blockPoolTester.refBlockChain[3] = []int{4, 7}
+// 	delete(blockPoolTester.refBlockChain, 6)
+
+// 	blockPool.Start()
+
+// 	peer1 := blockPoolTester.newPeer("peer1", 1, 9)
+// 	peer2 := blockPoolTester.newPeer("peer2", 2, 6)
+// 	peer3 := blockPoolTester.newPeer("peer3", 3, 11)
+// 	peer4 := blockPoolTester.newPeer("peer4", 1, 9)
+// 	peer2.blocksRequestsMap = peer1.blocksRequestsMap
+
+// 	var expected []int
+// 	var err error
+// 	expected = []int{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
+// 	err = checkStatus(t, blockPool, false, expected)
+// 	if err != nil {
+// 		return
+// 	}
+
+// 	peer1.AddPeer()
+// 	expected = []int{0, 0, 0, 0, 0, 1, 0, 0, 1, 1, 0, 1, 0}
+// 	err = checkStatus(t, blockPool, true, expected)
+// 	if err != nil {
+// 		return
+// 	}
+
+// 	peer1.serveBlocks(8, 9)
+// 	expected = []int{0, 0, 1, 1, 0, 1, 0, 0, 1, 1, 1, 1, 0}
+// 	err = checkStatus(t, blockPool, true, expected)
+// 	if err != nil {
+// 		return
+// 	}
+
+// 	peer1.serveBlockHashes(9, 8, 7, 3, 2)
+// 	expected = []int{5, 5, 1, 1, 0, 1, 0, 0, 1, 1, 1, 1, 0}
+// 	err = checkStatus(t, blockPool, true, expected)
+// 	if err != nil {
+// 		return
+// 	}
+
+// 	peer1.serveBlocks(3, 7, 8)
+// 	expected = []int{5, 5, 3, 3, 0, 1, 0, 0, 1, 1, 1, 1, 0}
+// 	err = checkStatus(t, blockPool, true, expected)
+// 	if err != nil {
+// 		return
+// 	}
+
+// 	peer1.serveBlocks(2, 3)
+// 	expected = []int{5, 5, 4, 4, 0, 1, 0, 0, 1, 1, 1, 1, 0}
+// 	err = checkStatus(t, blockPool, true, expected)
+// 	if err != nil {
+// 		return
+// 	}
+
+// 	peer4.AddPeer()
+// 	expected = []int{5, 5, 4, 4, 0, 2, 0, 0, 2, 2, 1, 1, 0}
+// 	err = checkStatus(t, blockPool, true, expected)
+// 	if err != nil {
+// 		return
+// 	}
+
+// 	peer4.sendBlockHashes(12, 11)
+// 	expected = []int{5, 5, 4, 4, 0, 2, 0, 0, 2, 2, 1, 1, 0}
+// 	err = checkStatus(t, blockPool, true, expected)
+// 	if err != nil {
+// 		return
+// 	}
+
+// 	peer2.AddPeer()
+// 	expected = []int{5, 5, 4, 4, 0, 3, 0, 0, 3, 3, 1, 2, 0}
+// 	err = checkStatus(t, blockPool, true, expected)
+// 	if err != nil {
+// 		return
+// 	}
+
+// 	peer2.serveBlocks(5, 6)
+// 	peer2.serveBlockHashes(6, 5, 4, 3, 2)
+// 	expected = []int{8, 8, 5, 5, 0, 3, 1, 0, 3, 3, 2, 2, 0}
+// 	err = checkStatus(t, blockPool, true, expected)
+// 	if err != nil {
+// 		return
+// 	}
+
+// 	peer2.serveBlocks(2, 3, 4)
+// 	expected = []int{8, 8, 6, 6, 0, 3, 1, 0, 3, 3, 2, 2, 0}
+// 	err = checkStatus(t, blockPool, true, expected)
+// 	if err != nil {
+// 		return
+// 	}
+
+// 	blockPool.RemovePeer("peer2")
+// 	expected = []int{8, 8, 6, 6, 0, 3, 1, 0, 3, 2, 2, 2, 0}
+// 	err = checkStatus(t, blockPool, true, expected)
+// 	if err != nil {
+// 		return
+// 	}
+
+// 	peer1.serveBlockHashes(2, 1, 0)
+// 	expected = []int{9, 9, 6, 6, 0, 3, 1, 0, 3, 2, 2, 2, 0}
+// 	err = checkStatus(t, blockPool, true, expected)
+// 	if err != nil {
+// 		return
+// 	}
+
+// 	peer1.serveBlocks(1, 2)
+// 	expected = []int{9, 9, 7, 7, 0, 3, 1, 0, 3, 2, 2, 2, 0}
+// 	err = checkStatus(t, blockPool, true, expected)
+// 	if err != nil {
+// 		return
+// 	}
+
+// 	peer1.serveBlocks(4, 5)
+// 	expected = []int{9, 9, 8, 8, 0, 3, 1, 0, 3, 2, 2, 2, 0}
+// 	err = checkStatus(t, blockPool, true, expected)
+// 	if err != nil {
+// 		return
+// 	}
+
+// 	peer3.AddPeer()
+// 	expected = []int{9, 9, 8, 8, 0, 4, 1, 0, 4, 3, 2, 3, 0}
+// 	err = checkStatus(t, blockPool, true, expected)
+// 	if err != nil {
+// 		return
+// 	}
+
+// 	peer3.serveBlocks(10, 11)
+// 	expected = []int{9, 9, 9, 9, 0, 4, 1, 0, 4, 3, 3, 3, 0}
+// 	err = checkStatus(t, blockPool, true, expected)
+// 	if err != nil {
+// 		return
+// 	}
+
+// 	peer3.serveBlockHashes(11, 10, 9)
+// 	expected = []int{11, 11, 9, 9, 0, 4, 1, 0, 4, 3, 3, 3, 0}
+// 	err = checkStatus(t, blockPool, true, expected)
+// 	if err != nil {
+// 		return
+// 	}
+
+// 	peer4.sendBlocks(11, 12)
+// 	expected = []int{11, 11, 9, 9, 0, 4, 1, 0, 4, 3, 4, 3, 1}
+// 	err = checkStatus(t, blockPool, true, expected)
+// 	if err != nil {
+// 		return
+// 	}
+// 	peer3.serveBlocks(9, 10)
+// 	expected = []int{11, 11, 10, 10, 0, 4, 1, 0, 4, 3, 4, 3, 1}
+// 	err = checkStatus(t, blockPool, true, expected)
+// 	if err != nil {
+// 		return
+// 	}
+
+// 	peer3.serveBlocks(0, 1)
+// 	blockPool.Wait(waitTimeout)
+// 	time.Sleep(200 * time.Millisecond)
+// 	expected = []int{11, 3, 11, 3, 8, 4, 1, 8, 4, 3, 4, 3, 1}
+// 	err = checkStatus(t, blockPool, false, expected)
+// 	if err != nil {
+// 		return
+// 	}
+
+// 	blockPool.Stop()
+// }
diff --git a/blockpool/test/hash_pool.go b/blockpool/test/hash_pool.go
new file mode 100644
index 000000000..4e0332d7d
--- /dev/null
+++ b/blockpool/test/hash_pool.go
@@ -0,0 +1,57 @@
+package test
+
+import (
+	"sync"
+
+	"github.com/ethereum/go-ethereum/crypto"
+)
+
+// test helpers
+// TODO: move into common test helper package (see p2p/crypto etc.)
+
+func NewHashPool() *TestHashPool {
+	return &TestHashPool{intToHash: make(intToHash), hashToInt: make(hashToInt)}
+}
+
+type intToHash map[int][]byte
+
+type hashToInt map[string]int
+
+// hashPool is a test helper, that allows random hashes to be referred to by integers
+type TestHashPool struct {
+	intToHash
+	hashToInt
+	lock sync.Mutex
+}
+
+func newHash(i int) []byte {
+	return crypto.Sha3([]byte(string(i)))
+}
+
+func (self *TestHashPool) IndexesToHashes(indexes []int) (hashes [][]byte) {
+	self.lock.Lock()
+	defer self.lock.Unlock()
+	for _, i := range indexes {
+		hash, found := self.intToHash[i]
+		if !found {
+			hash = newHash(i)
+			self.intToHash[i] = hash
+			self.hashToInt[string(hash)] = i
+		}
+		hashes = append(hashes, hash)
+	}
+	return
+}
+
+func (self *TestHashPool) HashesToIndexes(hashes [][]byte) (indexes []int) {
+	self.lock.Lock()
+	defer self.lock.Unlock()
+	for _, hash := range hashes {
+		i, found := self.hashToInt[string(hash)]
+		if !found {
+			i = -1
+		}
+		indexes = append(indexes, i)
+	}
+	return
+}
diff --git a/blockpool/test/logger.go b/blockpool/test/logger.go
new file mode 100644
index 000000000..8b776e0b5
--- /dev/null
+++ b/blockpool/test/logger.go
@@ -0,0 +1,78 @@
+package test
+
+import (
+	"log"
+	"os"
+	"sync"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/logger"
+)
+
+var once sync.Once
+
+/* usage:
+func TestFunc(t *testing.T) {
+    test.LogInit()
+    // test
+}
+*/
+func LogInit() {
+	once.Do(func() {
+		var logsys = logger.NewStdLogSystem(os.Stdout, log.LstdFlags, logger.LogLevel(logger.DebugDetailLevel))
+		logger.AddLogSystem(logsys)
+	})
+}
+
+type testLogger struct{ t *testing.T }
+
+/* usage:
+func TestFunc(t *testing.T) {
+    defer test.Testlog.Detach()
+    // test
+}
+*/
+func Testlog(t *testing.T) testLogger {
+	logger.Reset()
+	l := testLogger{t}
+	logger.AddLogSystem(l)
+	return l
+}
+
+func (testLogger) GetLogLevel() logger.LogLevel { return logger.DebugLevel }
+func (testLogger) SetLogLevel(logger.LogLevel)  {}
+
+func (l testLogger) LogPrint(level logger.LogLevel, msg string) {
+	l.t.Logf("%s", msg)
+}
+
+func (testLogger) Detach() {
+	logger.Flush()
+	logger.Reset()
+}
+
+type benchLogger struct{ b *testing.B }
+
+/* usage:
+func BenchmarkFunc(b *testing.B) {
+    defer test.Benchlog.Detach()
+    // test
+}
+*/
+func Benchlog(b *testing.B) benchLogger {
+	logger.Reset()
+	l := benchLogger{b}
+	logger.AddLogSystem(l)
+	return l
+}
+
+func (benchLogger) GetLogLevel() logger.LogLevel { return logger.Silence }
+
+func (benchLogger) SetLogLevel(logger.LogLevel) {}
+func (l benchLogger) LogPrint(level logger.LogLevel, msg string) {
+	l.b.Logf("%s", msg)
+}
+func (benchLogger) Detach() {
+	logger.Flush()
+	logger.Reset()
+}
diff --git a/blockpool/test/util.go b/blockpool/test/util.go
new file mode 100644
index 000000000..e183bf1d1
--- /dev/null
+++ b/blockpool/test/util.go
@@ -0,0 +1,35 @@
+package test
+
+import (
+	"fmt"
+	"testing"
+	"time"
+)
+
+func CheckInt(name string, got int, expected int, t *testing.T) (err error) {
+	if got != expected {
+		t.Errorf("status for %v incorrect. expected %v, got %v", name, expected, got)
+		err = fmt.Errorf("")
+	}
+	return
+}
+
+func CheckDuration(name string, got time.Duration, expected time.Duration, t *testing.T) (err error) {
+	if got != expected {
+		t.Errorf("status for %v incorrect. expected %v, got %v", name, expected, got)
+		err = fmt.Errorf("")
+	}
+	return
+}
+
+func ArrayEq(a, b []int) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	for i := range a {
+		if a[i] != b[i] {
+			return false
+		}
+	}
+	return true
+}