core, eth, trie: direct state trie synchronization

core/blockchain.go

@@ -37,6 +37,7 @@ import (
 	"github.com/ethereum/go-ethereum/metrics"
 	"github.com/ethereum/go-ethereum/pow"
 	"github.com/ethereum/go-ethereum/rlp"
+	"github.com/ethereum/go-ethereum/trie"
 	"github.com/hashicorp/golang-lru"
 )
 
@@ -246,6 +247,26 @@ func (bc *BlockChain) SetHead(head uint64) {
 	bc.loadLastState()
 }
 
+// FastSyncCommitHead sets the current head block to the one defined by the hash
+// irrelevant what the chain contents were prior.
+func (self *BlockChain) FastSyncCommitHead(hash common.Hash) error {
+	// Make sure that both the block as well at it's state trie exists
+	block := self.GetBlock(hash)
+	if block == nil {
+		return fmt.Errorf("non existent block [%x…]", hash[:4])
+	}
+	if _, err := trie.NewSecure(block.Root(), self.chainDb); err != nil {
+		return err
+	}
+	// If all checks out, manually set the head block
+	self.mu.Lock()
+	self.currentBlock = block
+	self.mu.Unlock()
+
+	glog.V(logger.Info).Infof("committed block #%d [%x…] as new head", block.Number(), hash[:4])
+	return nil
+}
+
 func (self *BlockChain) GasLimit() *big.Int {
 	self.mu.RLock()
 	defer self.mu.RUnlock()
@@ -721,10 +742,6 @@ func (self *BlockChain) InsertReceiptChain(blockChain types.Blocks, receiptChain
 	self.wg.Add(1)
 	defer self.wg.Done()
 
-	// Make sure only one thread manipulates the chain at once
-	self.chainmu.Lock()
-	defer self.chainmu.Unlock()
-
 	// Collect some import statistics to report on
 	stats := struct{ processed, ignored int }{}
 	start := time.Now()

core/state/sync.go

@@ -0,0 +1,98 @@
+// Copyright 2015 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package state
+
+import (
+	"bytes"
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/crypto/sha3"
+	"github.com/ethereum/go-ethereum/ethdb"
+	"github.com/ethereum/go-ethereum/rlp"
+	"github.com/ethereum/go-ethereum/trie"
+)
+
+type StateSync struct {
+	db          ethdb.Database
+	sync        *trie.TrieSync
+	codeReqs    map[common.Hash]struct{} // requested but not yet written to database
+	codeReqList []common.Hash            // requested since last Missing
+}
+
+var sha3_nil = common.BytesToHash(sha3.NewKeccak256().Sum(nil))
+
+func NewStateSync(root common.Hash, db ethdb.Database) *StateSync {
+	ss := &StateSync{
+		db:       db,
+		codeReqs: make(map[common.Hash]struct{}),
+	}
+	ss.codeReqs[sha3_nil] = struct{}{} // never request the nil hash
+	ss.sync = trie.NewTrieSync(root, db, ss.leafFound)
+	return ss
+}
+
+func (self *StateSync) leafFound(leaf []byte, parent common.Hash) error {
+	var obj struct {
+		Nonce    uint64
+		Balance  *big.Int
+		Root     common.Hash
+		CodeHash []byte
+	}
+	if err := rlp.Decode(bytes.NewReader(leaf), &obj); err != nil {
+		return err
+	}
+	self.sync.AddSubTrie(obj.Root, 64, parent, nil)
+
+	codehash := common.BytesToHash(obj.CodeHash)
+	if _, ok := self.codeReqs[codehash]; !ok {
+		code, _ := self.db.Get(obj.CodeHash)
+		if code == nil {
+			self.codeReqs[codehash] = struct{}{}
+			self.codeReqList = append(self.codeReqList, codehash)
+		}
+	}
+	return nil
+}
+
+func (self *StateSync) Missing(max int) []common.Hash {
+	cr := len(self.codeReqList)
+	gh := 0
+	if max != 0 {
+		if cr > max {
+			cr = max
+		}
+		gh = max - cr
+	}
+	list := append(self.sync.Missing(gh), self.codeReqList[:cr]...)
+	self.codeReqList = self.codeReqList[cr:]
+	return list
+}
+
+func (self *StateSync) Process(list []trie.SyncResult) error {
+	for i := 0; i < len(list); i++ {
+		if _, ok := self.codeReqs[list[i].Hash]; ok { // code data, not a node
+			self.db.Put(list[i].Hash[:], list[i].Data)
+			delete(self.codeReqs, list[i].Hash)
+			list[i] = list[len(list)-1]
+			list = list[:len(list)-1]
+			i--
+		}
+	}
+	_, err := self.sync.Process(list)
+	return err
+}

core/state/sync_test.go

@@ -0,0 +1,238 @@
+// Copyright 2015 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package state
+
+import (
+	"bytes"
+	"math/big"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/ethdb"
+	"github.com/ethereum/go-ethereum/trie"
+)
+
+// testAccount is the data associated with an account used by the state tests.
+type testAccount struct {
+	address common.Address
+	balance *big.Int
+	nonce   uint64
+	code    []byte
+}
+
+// makeTestState create a sample test state to test node-wise reconstruction.
+func makeTestState() (ethdb.Database, common.Hash, []*testAccount) {
+	// Create an empty state
+	db, _ := ethdb.NewMemDatabase()
+	state := New(common.Hash{}, db)
+
+	// Fill it with some arbitrary data
+	accounts := []*testAccount{}
+	for i := byte(0); i < 255; i++ {
+		obj := state.GetOrNewStateObject(common.BytesToAddress([]byte{i}))
+		acc := &testAccount{address: common.BytesToAddress([]byte{i})}
+
+		obj.AddBalance(big.NewInt(int64(11 * i)))
+		acc.balance = big.NewInt(int64(11 * i))
+
+		obj.SetNonce(uint64(42 * i))
+		acc.nonce = uint64(42 * i)
+
+		if i%3 == 0 {
+			obj.SetCode([]byte{i, i, i, i, i})
+			acc.code = []byte{i, i, i, i, i}
+		}
+		state.UpdateStateObject(obj)
+		accounts = append(accounts, acc)
+	}
+	root, _ := state.Commit()
+
+	// Return the generated state
+	return db, root, accounts
+}
+
+// checkStateAccounts cross references a reconstructed state with an expected
+// account array.
+func checkStateAccounts(t *testing.T, db ethdb.Database, root common.Hash, accounts []*testAccount) {
+	state := New(root, db)
+	for i, acc := range accounts {
+
+		if balance := state.GetBalance(acc.address); balance.Cmp(acc.balance) != 0 {
+			t.Errorf("account %d: balance mismatch: have %v, want %v", i, balance, acc.balance)
+		}
+		if nonce := state.GetNonce(acc.address); nonce != acc.nonce {
+			t.Errorf("account %d: nonce mismatch: have %v, want %v", i, nonce, acc.nonce)
+		}
+		if code := state.GetCode(acc.address); bytes.Compare(code, acc.code) != 0 {
+			t.Errorf("account %d: code mismatch: have %x, want %x", i, code, acc.code)
+		}
+	}
+}
+
+// Tests that an empty state is not scheduled for syncing.
+func TestEmptyStateSync(t *testing.T) {
+	empty := common.HexToHash("56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421")
+	db, _ := ethdb.NewMemDatabase()
+	if req := NewStateSync(empty, db).Missing(1); len(req) != 0 {
+		t.Errorf("content requested for empty state: %v", req)
+	}
+}
+
+// Tests that given a root hash, a state can sync iteratively on a single thread,
+// requesting retrieval tasks and returning all of them in one go.
+func TestIterativeStateSyncIndividual(t *testing.T) { testIterativeStateSync(t, 1) }
+func TestIterativeStateSyncBatched(t *testing.T)    { testIterativeStateSync(t, 100) }
+
+func testIterativeStateSync(t *testing.T, batch int) {
+	// Create a random state to copy
+	srcDb, srcRoot, srcAccounts := makeTestState()
+
+	// Create a destination state and sync with the scheduler
+	dstDb, _ := ethdb.NewMemDatabase()
+	sched := NewStateSync(srcRoot, dstDb)
+
+	queue := append([]common.Hash{}, sched.Missing(batch)...)
+	for len(queue) > 0 {
+		results := make([]trie.SyncResult, len(queue))
+		for i, hash := range queue {
+			data, err := srcDb.Get(hash.Bytes())
+			if err != nil {
+				t.Fatalf("failed to retrieve node data for %x: %v", hash, err)
+			}
+			results[i] = trie.SyncResult{hash, data}
+		}
+		if err := sched.Process(results); err != nil {
+			t.Fatalf("failed to process results: %v", err)
+		}
+		queue = append(queue[:0], sched.Missing(batch)...)
+	}
+	// Cross check that the two states are in sync
+	checkStateAccounts(t, dstDb, srcRoot, srcAccounts)
+}
+
+// Tests that the trie scheduler can correctly reconstruct the state even if only
+// partial results are returned, and the others sent only later.
+func TestIterativeDelayedStateSync(t *testing.T) {
+	// Create a random state to copy
+	srcDb, srcRoot, srcAccounts := makeTestState()
+
+	// Create a destination state and sync with the scheduler
+	dstDb, _ := ethdb.NewMemDatabase()
+	sched := NewStateSync(srcRoot, dstDb)
+
+	queue := append([]common.Hash{}, sched.Missing(0)...)
+	for len(queue) > 0 {
+		// Sync only half of the scheduled nodes
+		results := make([]trie.SyncResult, len(queue)/2+1)
+		for i, hash := range queue[:len(results)] {
+			data, err := srcDb.Get(hash.Bytes())
+			if err != nil {
+				t.Fatalf("failed to retrieve node data for %x: %v", hash, err)
+			}
+			results[i] = trie.SyncResult{hash, data}
+		}
+		if err := sched.Process(results); err != nil {
+			t.Fatalf("failed to process results: %v", err)
+		}
+		queue = append(queue[len(results):], sched.Missing(0)...)
+	}
+	// Cross check that the two states are in sync
+	checkStateAccounts(t, dstDb, srcRoot, srcAccounts)
+}
+
+// Tests that given a root hash, a trie can sync iteratively on a single thread,
+// requesting retrieval tasks and returning all of them in one go, however in a
+// random order.
+func TestIterativeRandomStateSyncIndividual(t *testing.T) { testIterativeRandomStateSync(t, 1) }
+func TestIterativeRandomStateSyncBatched(t *testing.T)    { testIterativeRandomStateSync(t, 100) }
+
+func testIterativeRandomStateSync(t *testing.T, batch int) {
+	// Create a random state to copy
+	srcDb, srcRoot, srcAccounts := makeTestState()
+
+	// Create a destination state and sync with the scheduler
+	dstDb, _ := ethdb.NewMemDatabase()
+	sched := NewStateSync(srcRoot, dstDb)
+
+	queue := make(map[common.Hash]struct{})
+	for _, hash := range sched.Missing(batch) {
+		queue[hash] = struct{}{}
+	}
+	for len(queue) > 0 {
+		// Fetch all the queued nodes in a random order
+		results := make([]trie.SyncResult, 0, len(queue))
+		for hash, _ := range queue {
+			data, err := srcDb.Get(hash.Bytes())
+			if err != nil {
+				t.Fatalf("failed to retrieve node data for %x: %v", hash, err)
+			}
+			results = append(results, trie.SyncResult{hash, data})
+		}
+		// Feed the retrieved results back and queue new tasks
+		if err := sched.Process(results); err != nil {
+			t.Fatalf("failed to process results: %v", err)
+		}
+		queue = make(map[common.Hash]struct{})
+		for _, hash := range sched.Missing(batch) {
+			queue[hash] = struct{}{}
+		}
+	}
+	// Cross check that the two states are in sync
+	checkStateAccounts(t, dstDb, srcRoot, srcAccounts)
+}
+
+// Tests that the trie scheduler can correctly reconstruct the state even if only
+// partial results are returned (Even those randomly), others sent only later.
+func TestIterativeRandomDelayedStateSync(t *testing.T) {
+	// Create a random state to copy
+	srcDb, srcRoot, srcAccounts := makeTestState()
+
+	// Create a destination state and sync with the scheduler
+	dstDb, _ := ethdb.NewMemDatabase()
+	sched := NewStateSync(srcRoot, dstDb)
+
+	queue := make(map[common.Hash]struct{})
+	for _, hash := range sched.Missing(0) {
+		queue[hash] = struct{}{}
+	}
+	for len(queue) > 0 {
+		// Sync only half of the scheduled nodes, even those in random order
+		results := make([]trie.SyncResult, 0, len(queue)/2+1)
+		for hash, _ := range queue {
+			delete(queue, hash)
+
+			data, err := srcDb.Get(hash.Bytes())
+			if err != nil {
+				t.Fatalf("failed to retrieve node data for %x: %v", hash, err)
+			}
+			results = append(results, trie.SyncResult{hash, data})
+
+			if len(results) >= cap(results) {
+				break
+			}
+		}
+		// Feed the retrieved results back and queue new tasks
+		if err := sched.Process(results); err != nil {
+			t.Fatalf("failed to process results: %v", err)
+		}
+		for _, hash := range sched.Missing(0) {
+			queue[hash] = struct{}{}
+		}
+	}
+	// Cross check that the two states are in sync
+	checkStateAccounts(t, dstDb, srcRoot, srcAccounts)
+}

eth/downloader/downloader.go

@@ -19,7 +19,6 @@ package downloader
 
 import (
 	"errors"
-	"fmt"
 	"math"
 	"math/big"
 	"strings"
@@ -29,9 +28,11 @@ import (
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/logger"
 	"github.com/ethereum/go-ethereum/logger/glog"
+	"github.com/rcrowley/go-metrics"
 )
 
 var (
@@ -39,8 +40,8 @@ var (
 	MaxBlockFetch   = 128 // Amount of blocks to be fetched per retrieval request
 	MaxHeaderFetch  = 192 // Amount of block headers to be fetched per retrieval request
 	MaxBodyFetch    = 128 // Amount of block bodies to be fetched per retrieval request
-	MaxStateFetch   = 384 // Amount of node state values to allow fetching per request
 	MaxReceiptFetch = 256 // Amount of transaction receipts to allow fetching per request
+	MaxStateFetch   = 384 // Amount of node state values to allow fetching per request
 
 	hashTTL        = 5 * time.Second    // [eth/61] Time it takes for a hash request to time out
 	blockSoftTTL   = 3 * time.Second    // [eth/61] Request completion threshold for increasing or decreasing a peer's bandwidth
@@ -49,10 +50,13 @@ var (
 	bodySoftTTL    = 3 * time.Second    // [eth/62] Request completion threshold for increasing or decreasing a peer's bandwidth
 	bodyHardTTL    = 3 * bodySoftTTL    // [eth/62] Maximum time allowance before a block body request is considered expired
 	receiptSoftTTL = 3 * time.Second    // [eth/63] Request completion threshold for increasing or decreasing a peer's bandwidth
-	receiptHardTTL = 3 * receiptSoftTTL // [eth/63] Maximum time allowance before a block body request is considered expired
+	receiptHardTTL = 3 * receiptSoftTTL // [eth/63] Maximum time allowance before a receipt request is considered expired
+	stateSoftTTL   = 2 * time.Second    // [eth/63] Request completion threshold for increasing or decreasing a peer's bandwidth
+	stateHardTTL   = 3 * stateSoftTTL   // [eth/63] Maximum time allowance before a node data request is considered expired
 
 	maxQueuedHashes   = 256 * 1024 // [eth/61] Maximum number of hashes to queue for import (DOS protection)
 	maxQueuedHeaders  = 256 * 1024 // [eth/62] Maximum number of headers to queue for import (DOS protection)
+	maxQueuedStates   = 256 * 1024 // [eth/63] Maximum number of state requests to queue (DOS protection)
 	maxResultsProcess = 256        // Number of download results to import at once into the chain
 
 	headerCheckFrequency = 64   // Verification frequency of the downloaded headers during fast sync
@@ -84,98 +88,6 @@ var (
 	errNoSyncActive       = errors.New("no sync active")
 )
 
-// headerCheckFn is a callback type for verifying a header's presence in the local chain.
-type headerCheckFn func(common.Hash) bool
-
-// blockCheckFn is a callback type for verifying a block's presence in the local chain.
-type blockCheckFn func(common.Hash) bool
-
-// headerRetrievalFn is a callback type for retrieving a header from the local chain.
-type headerRetrievalFn func(common.Hash) *types.Header
-
-// blockRetrievalFn is a callback type for retrieving a block from the local chain.
-type blockRetrievalFn func(common.Hash) *types.Block
-
-// headHeaderRetrievalFn is a callback type for retrieving the head header from the local chain.
-type headHeaderRetrievalFn func() *types.Header
-
-// headBlockRetrievalFn is a callback type for retrieving the head block from the local chain.
-type headBlockRetrievalFn func() *types.Block
-
-// headFastBlockRetrievalFn is a callback type for retrieving the head fast block from the local chain.
-type headFastBlockRetrievalFn func() *types.Block
-
-// tdRetrievalFn is a callback type for retrieving the total difficulty of a local block.
-type tdRetrievalFn func(common.Hash) *big.Int
-
-// headerChainInsertFn is a callback type to insert a batch of headers into the local chain.
-type headerChainInsertFn func([]*types.Header, bool) (int, error)
-
-// blockChainInsertFn is a callback type to insert a batch of blocks into the local chain.
-type blockChainInsertFn func(types.Blocks) (int, error)
-
-// receiptChainInsertFn is a callback type to insert a batch of receipts into the local chain.
-type receiptChainInsertFn func(types.Blocks, []types.Receipts) (int, error)
-
-// peerDropFn is a callback type for dropping a peer detected as malicious.
-type peerDropFn func(id string)
-
-// dataPack is a data message returned by a peer for some query.
-type dataPack interface {
-	PeerId() string
-	Empty() bool
-	Stats() string
-}
-
-// hashPack is a batch of block hashes returned by a peer (eth/61).
-type hashPack struct {
-	peerId string
-	hashes []common.Hash
-}
-
-// blockPack is a batch of blocks returned by a peer (eth/61).
-type blockPack struct {
-	peerId string
-	blocks []*types.Block
-}
-
-// headerPack is a batch of block headers returned by a peer.
-type headerPack struct {
-	peerId  string
-	headers []*types.Header
-}
-
-// bodyPack is a batch of block bodies returned by a peer.
-type bodyPack struct {
-	peerId       string
-	transactions [][]*types.Transaction
-	uncles       [][]*types.Header
-}
-
-// PeerId retrieves the origin peer who sent this block body packet.
-func (p *bodyPack) PeerId() string { return p.peerId }
-
-// Empty returns whether the no block bodies were delivered.
-func (p *bodyPack) Empty() bool { return len(p.transactions) == 0 || len(p.uncles) == 0 }
-
-// Stats creates a textual stats report for logging purposes.
-func (p *bodyPack) Stats() string { return fmt.Sprintf("%d:%d", len(p.transactions), len(p.uncles)) }
-
-// receiptPack is a batch of receipts returned by a peer.
-type receiptPack struct {
-	peerId   string
-	receipts [][]*types.Receipt
-}
-
-// PeerId retrieves the origin peer who sent this receipt packet.
-func (p *receiptPack) PeerId() string { return p.peerId }
-
-// Empty returns whether the no receipts were delivered.
-func (p *receiptPack) Empty() bool { return len(p.receipts) == 0 }
-
-// Stats creates a textual stats report for logging purposes.
-func (p *receiptPack) Stats() string { return fmt.Sprintf("%d", len(p.receipts)) }
-
 type Downloader struct {
 	mode SyncMode       // Synchronisation mode defining the strategies used
 	mux  *event.TypeMux // Event multiplexer to announce sync operation events
@@ -186,8 +98,10 @@ type Downloader struct {
 	interrupt int32 // Atomic boolean to signal termination
 
 	// Statistics
-	syncStatsOrigin uint64       // Origin block number where syncing started at
+	syncStatsChainOrigin uint64       // Origin block number where syncing started at
-	syncStatsHeight uint64       // Highest block number known when syncing started
+	syncStatsChainHeight uint64       // Highest block number known when syncing started
+	syncStatsStateTotal  uint64       // Total number of node state entries known so far
+	syncStatsStateDone   uint64       // Number of state trie entries already pulled
 	syncStatsLock        sync.RWMutex // Lock protecting the sync stats fields
 
 	// Callbacks
@@ -198,6 +112,7 @@ type Downloader struct {
 	headHeader      headHeaderRetrievalFn    // Retrieves the head header from the chain
 	headBlock       headBlockRetrievalFn     // Retrieves the head block from the chain
 	headFastBlock   headFastBlockRetrievalFn // Retrieves the head fast-sync block from the chain
+	commitHeadBlock headBlockCommitterFn     // Commits a manually assembled block as the chain head
 	getTd           tdRetrievalFn            // Retrieves the TD of a block from the chain
 	insertHeaders   headerChainInsertFn      // Injects a batch of headers into the chain
 	insertBlocks    blockChainInsertFn       // Injects a batch of blocks into the chain
@@ -212,14 +127,16 @@ type Downloader struct {
 
 	// Channels
 	newPeerCh     chan *peer
-	hashCh        chan hashPack   // [eth/61] Channel receiving inbound hashes
+	hashCh        chan dataPack // [eth/61] Channel receiving inbound hashes
-	blockCh       chan blockPack  // [eth/61] Channel receiving inbound blocks
+	blockCh       chan dataPack // [eth/61] Channel receiving inbound blocks
-	headerCh      chan headerPack // [eth/62] Channel receiving inbound block headers
+	headerCh      chan dataPack // [eth/62] Channel receiving inbound block headers
 	bodyCh        chan dataPack // [eth/62] Channel receiving inbound block bodies
 	receiptCh     chan dataPack // [eth/63] Channel receiving inbound receipts
+	stateCh       chan dataPack // [eth/63] Channel receiving inbound node state data
 	blockWakeCh   chan bool     // [eth/61] Channel to signal the block fetcher of new tasks
 	bodyWakeCh    chan bool     // [eth/62] Channel to signal the block body fetcher of new tasks
 	receiptWakeCh chan bool     // [eth/63] Channel to signal the receipt fetcher of new tasks
+	stateWakeCh   chan bool     // [eth/63] Channel to signal the state fetcher of new tasks
 
 	cancelCh   chan struct{} // Channel to cancel mid-flight syncs
 	cancelLock sync.RWMutex  // Lock to protect the cancel channel in delivers
@@ -232,14 +149,15 @@ type Downloader struct {
 }
 
 // New creates a new downloader to fetch hashes and blocks from remote peers.
-func New(mode SyncMode, mux *event.TypeMux, hasHeader headerCheckFn, hasBlock blockCheckFn, getHeader headerRetrievalFn, getBlock blockRetrievalFn,
+func New(mode SyncMode, stateDb ethdb.Database, mux *event.TypeMux, hasHeader headerCheckFn, hasBlock blockCheckFn, getHeader headerRetrievalFn,
-	headHeader headHeaderRetrievalFn, headBlock headBlockRetrievalFn, headFastBlock headFastBlockRetrievalFn, getTd tdRetrievalFn,
+	getBlock blockRetrievalFn, headHeader headHeaderRetrievalFn, headBlock headBlockRetrievalFn, headFastBlock headFastBlockRetrievalFn,
-	insertHeaders headerChainInsertFn, insertBlocks blockChainInsertFn, insertReceipts receiptChainInsertFn, dropPeer peerDropFn) *Downloader {
+	commitHeadBlock headBlockCommitterFn, getTd tdRetrievalFn, insertHeaders headerChainInsertFn, insertBlocks blockChainInsertFn,
+	insertReceipts receiptChainInsertFn, dropPeer peerDropFn) *Downloader {
 
 	return &Downloader{
 		mode:            mode,
 		mux:             mux,
-		queue:          newQueue(),
+		queue:           newQueue(stateDb),
 		peers:           newPeerSet(),
 		hasHeader:       hasHeader,
 		hasBlock:        hasBlock,
@@ -248,20 +166,23 @@ func New(mode SyncMode, mux *event.TypeMux, hasHeader headerCheckFn, hasBlock bl
 		headHeader:      headHeader,
 		headBlock:       headBlock,
 		headFastBlock:   headFastBlock,
+		commitHeadBlock: commitHeadBlock,
 		getTd:           getTd,
 		insertHeaders:   insertHeaders,
 		insertBlocks:    insertBlocks,
 		insertReceipts:  insertReceipts,
 		dropPeer:        dropPeer,
 		newPeerCh:       make(chan *peer, 1),
-		hashCh:         make(chan hashPack, 1),
+		hashCh:          make(chan dataPack, 1),
-		blockCh:        make(chan blockPack, 1),
+		blockCh:         make(chan dataPack, 1),
-		headerCh:       make(chan headerPack, 1),
+		headerCh:        make(chan dataPack, 1),
 		bodyCh:          make(chan dataPack, 1),
 		receiptCh:       make(chan dataPack, 1),
+		stateCh:         make(chan dataPack, 1),
 		blockWakeCh:     make(chan bool, 1),
 		bodyWakeCh:      make(chan bool, 1),
 		receiptWakeCh:   make(chan bool, 1),
+		stateWakeCh:     make(chan bool, 1),
 	}
 }
 
@@ -272,7 +193,7 @@ func (d *Downloader) Boundaries() (uint64, uint64) {
 	d.syncStatsLock.RLock()
 	defer d.syncStatsLock.RUnlock()
 
-	return d.syncStatsOrigin, d.syncStatsHeight
+	return d.syncStatsChainOrigin, d.syncStatsChainHeight
 }
 
 // Synchronising returns whether the downloader is currently retrieving blocks.
@@ -284,10 +205,11 @@ func (d *Downloader) Synchronising() bool {
 // used for fetching hashes and blocks from.
 func (d *Downloader) RegisterPeer(id string, version int, head common.Hash,
 	getRelHashes relativeHashFetcherFn, getAbsHashes absoluteHashFetcherFn, getBlocks blockFetcherFn, // eth/61 callbacks, remove when upgrading
-	getRelHeaders relativeHeaderFetcherFn, getAbsHeaders absoluteHeaderFetcherFn, getBlockBodies blockBodyFetcherFn, getReceipts receiptFetcherFn) error {
+	getRelHeaders relativeHeaderFetcherFn, getAbsHeaders absoluteHeaderFetcherFn, getBlockBodies blockBodyFetcherFn,
+	getReceipts receiptFetcherFn, getNodeData stateFetcherFn) error {
 
 	glog.V(logger.Detail).Infoln("Registering peer", id)
-	if err := d.peers.Register(newPeer(id, version, head, getRelHashes, getAbsHashes, getBlocks, getRelHeaders, getAbsHeaders, getBlockBodies, getReceipts)); err != nil {
+	if err := d.peers.Register(newPeer(id, version, head, getRelHashes, getAbsHashes, getBlocks, getRelHeaders, getAbsHeaders, getBlockBodies, getReceipts, getNodeData)); err != nil {
 		glog.V(logger.Error).Infoln("Register failed:", err)
 		return err
 	}
@@ -357,12 +279,18 @@ func (d *Downloader) synchronise(id string, hash common.Hash, td *big.Int) error
 	d.queue.Reset()
 	d.peers.Reset()
 
-	for _, ch := range []chan bool{d.blockWakeCh, d.bodyWakeCh, d.receiptWakeCh} {
+	for _, ch := range []chan bool{d.blockWakeCh, d.bodyWakeCh, d.receiptWakeCh, d.stateWakeCh} {
 		select {
 		case <-ch:
 		default:
 		}
 	}
+	// Reset and ephemeral sync statistics
+	d.syncStatsLock.Lock()
+	d.syncStatsStateTotal = 0
+	d.syncStatsStateDone = 0
+	d.syncStatsLock.Unlock()
+
 	// Create cancel channel for aborting mid-flight
 	d.cancelLock.Lock()
 	d.cancelCh = make(chan struct{})
@@ -414,17 +342,17 @@ func (d *Downloader) syncWithPeer(p *peer, hash common.Hash, td *big.Int) (err e
 			return err
 		}
 		d.syncStatsLock.Lock()
-		if d.syncStatsHeight <= origin || d.syncStatsOrigin > origin {
+		if d.syncStatsChainHeight <= origin || d.syncStatsChainOrigin > origin {
-			d.syncStatsOrigin = origin
+			d.syncStatsChainOrigin = origin
 		}
-		d.syncStatsHeight = latest
+		d.syncStatsChainHeight = latest
 		d.syncStatsLock.Unlock()
 
 		// Initiate the sync using a  concurrent hash and block retrieval algorithm
 		if d.syncInitHook != nil {
 			d.syncInitHook(origin, latest)
 		}
-		d.queue.Prepare(origin+1, 1)
+		d.queue.Prepare(origin+1, d.mode, 0)
 
 		errc := make(chan error, 2)
 		go func() { errc <- d.fetchHashes61(p, td, origin+1) }()
@@ -449,26 +377,27 @@ func (d *Downloader) syncWithPeer(p *peer, hash common.Hash, td *big.Int) (err e
 			return err
 		}
 		d.syncStatsLock.Lock()
-		if d.syncStatsHeight <= origin || d.syncStatsOrigin > origin {
+		if d.syncStatsChainHeight <= origin || d.syncStatsChainOrigin > origin {
-			d.syncStatsOrigin = origin
+			d.syncStatsChainOrigin = origin
 		}
-		d.syncStatsHeight = latest
+		d.syncStatsChainHeight = latest
 		d.syncStatsLock.Unlock()
 
 		// Initiate the sync using a  concurrent header and content retrieval algorithm
-		parts := 1
+		pivot := uint64(0)
-		if d.mode == FastSync {
+		if latest > uint64(minFullBlocks) {
-			parts = 2 // receipts are fetched too
+			pivot = latest - uint64(minFullBlocks)
 		}
-		d.queue.Prepare(origin+1, parts)
+		d.queue.Prepare(origin+1, d.mode, pivot)
 
 		if d.syncInitHook != nil {
 			d.syncInitHook(origin, latest)
 		}
-		errc := make(chan error, 3)
+		errc := make(chan error, 4)
 		go func() { errc <- d.fetchHeaders(p, td, origin+1) }() // Headers are always retrieved
+		go func() { errc <- d.fetchBodies(origin + 1) }()       // Bodies are retrieved during normal and fast sync
 		go func() { errc <- d.fetchReceipts(origin + 1) }()     // Receipts are retrieved during fast sync
-		go func() { errc <- d.fetchBodies(origin + 1) }()       // Bodies are retrieved during normal sync
+		go func() { errc <- d.fetchNodeData() }()               // Node state data is retrieved during fast sync
 
 		// If any fetcher fails, cancel the others
 		var fail error
@@ -538,14 +467,14 @@ func (d *Downloader) fetchHeight61(p *peer) (uint64, error) {
 		case <-d.hashCh:
 			// Out of bounds hashes received, ignore them
 
-		case blockPack := <-d.blockCh:
+		case packet := <-d.blockCh:
 			// Discard anything not from the origin peer
-			if blockPack.peerId != p.id {
+			if packet.PeerId() != p.id {
-				glog.V(logger.Debug).Infof("Received blocks from incorrect peer(%s)", blockPack.peerId)
+				glog.V(logger.Debug).Infof("Received blocks from incorrect peer(%s)", packet.PeerId())
 				break
 			}
 			// Make sure the peer actually gave something valid
-			blocks := blockPack.blocks
+			blocks := packet.(*blockPack).blocks
 			if len(blocks) != 1 {
 				glog.V(logger.Debug).Infof("%v: invalid number of head blocks: %d != 1", p, len(blocks))
 				return 0, errBadPeer
@@ -584,14 +513,14 @@ func (d *Downloader) findAncestor61(p *peer) (uint64, error) {
 		case <-d.cancelCh:
 			return 0, errCancelHashFetch
 
-		case hashPack := <-d.hashCh:
+		case packet := <-d.hashCh:
 			// Discard anything not from the origin peer
-			if hashPack.peerId != p.id {
+			if packet.PeerId() != p.id {
-				glog.V(logger.Debug).Infof("Received hashes from incorrect peer(%s)", hashPack.peerId)
+				glog.V(logger.Debug).Infof("Received hashes from incorrect peer(%s)", packet.PeerId())
 				break
 			}
 			// Make sure the peer actually gave something valid
-			hashes := hashPack.hashes
+			hashes := packet.(*hashPack).hashes
 			if len(hashes) == 0 {
 				glog.V(logger.Debug).Infof("%v: empty head hash set", p)
 				return 0, errEmptyHashSet
@@ -639,14 +568,14 @@ func (d *Downloader) findAncestor61(p *peer) (uint64, error) {
 			case <-d.cancelCh:
 				return 0, errCancelHashFetch
 
-			case hashPack := <-d.hashCh:
+			case packet := <-d.hashCh:
 				// Discard anything not from the origin peer
-				if hashPack.peerId != p.id {
+				if packet.PeerId() != p.id {
-					glog.V(logger.Debug).Infof("Received hashes from incorrect peer(%s)", hashPack.peerId)
+					glog.V(logger.Debug).Infof("Received hashes from incorrect peer(%s)", packet.PeerId())
 					break
 				}
 				// Make sure the peer actually gave something valid
-				hashes := hashPack.hashes
+				hashes := packet.(*hashPack).hashes
 				if len(hashes) != 1 {
 					glog.V(logger.Debug).Infof("%v: invalid search hash set (%d)", p, len(hashes))
 					return 0, errBadPeer
@@ -716,17 +645,17 @@ func (d *Downloader) fetchHashes61(p *peer, td *big.Int, from uint64) error {
 		case <-d.bodyCh:
 			// Out of bounds eth/62 block bodies received, ignore them
 
-		case hashPack := <-d.hashCh:
+		case packet := <-d.hashCh:
 			// Make sure the active peer is giving us the hashes
-			if hashPack.peerId != p.id {
+			if packet.PeerId() != p.id {
-				glog.V(logger.Debug).Infof("Received hashes from incorrect peer(%s)", hashPack.peerId)
+				glog.V(logger.Debug).Infof("Received hashes from incorrect peer(%s)", packet.PeerId())
 				break
 			}
 			hashReqTimer.UpdateSince(request)
 			timeout.Stop()
 
 			// If no more hashes are inbound, notify the block fetcher and return
-			if len(hashPack.hashes) == 0 {
+			if packet.Items() == 0 {
 				glog.V(logger.Debug).Infof("%v: no available hashes", p)
 
 				select {
@@ -751,12 +680,13 @@ func (d *Downloader) fetchHashes61(p *peer, td *big.Int, from uint64) error {
 				return nil
 			}
 			gotHashes = true
+			hashes := packet.(*hashPack).hashes
 
 			// Otherwise insert all the new hashes, aborting in case of junk
-			glog.V(logger.Detail).Infof("%v: scheduling %d hashes from #%d", p, len(hashPack.hashes), from)
+			glog.V(logger.Detail).Infof("%v: scheduling %d hashes from #%d", p, len(hashes), from)
 
-			inserts := d.queue.Schedule61(hashPack.hashes, true)
+			inserts := d.queue.Schedule61(hashes, true)
-			if len(inserts) != len(hashPack.hashes) {
+			if len(inserts) != len(hashes) {
 				glog.V(logger.Debug).Infof("%v: stale hashes", p)
 				return errBadPeer
 			}
@@ -776,7 +706,7 @@ func (d *Downloader) fetchHashes61(p *peer, td *big.Int, from uint64) error {
 				return nil
 			}
 			// Queue not yet full, fetch the next batch
-			from += uint64(len(hashPack.hashes))
+			from += uint64(len(hashes))
 			getHashes(from)
 
 		case <-timeout.C:
@@ -813,16 +743,17 @@ func (d *Downloader) fetchBlocks61(from uint64) error {
 		case <-d.bodyCh:
 			// Out of bounds eth/62 block bodies received, ignore them
 
-		case blockPack := <-d.blockCh:
+		case packet := <-d.blockCh:
 			// If the peer was previously banned and failed to deliver it's pack
 			// in a reasonable time frame, ignore it's message.
-			if peer := d.peers.Peer(blockPack.peerId); peer != nil {
+			if peer := d.peers.Peer(packet.PeerId()); peer != nil {
 				// Deliver the received chunk of blocks, and demote in case of errors
-				err := d.queue.Deliver61(blockPack.peerId, blockPack.blocks)
+				blocks := packet.(*blockPack).blocks
+				err := d.queue.DeliverBlocks(peer.id, blocks)
 				switch err {
 				case nil:
 					// If no blocks were delivered, demote the peer (need the delivery above)
-					if len(blockPack.blocks) == 0 {
+					if len(blocks) == 0 {
 						peer.Demote()
 						peer.SetBlocksIdle()
 						glog.V(logger.Detail).Infof("%s: no blocks delivered", peer)
@@ -831,7 +762,7 @@ func (d *Downloader) fetchBlocks61(from uint64) error {
 					// All was successful, promote the peer and potentially start processing
 					peer.Promote()
 					peer.SetBlocksIdle()
-					glog.V(logger.Detail).Infof("%s: delivered %d blocks", peer, len(blockPack.blocks))
+					glog.V(logger.Detail).Infof("%s: delivered %d blocks", peer, len(blocks))
 					go d.process()
 
 				case errInvalidChain:
@@ -891,7 +822,7 @@ func (d *Downloader) fetchBlocks61(from uint64) error {
 				return errNoPeers
 			}
 			// Check for block request timeouts and demote the responsible peers
-			for _, pid := range d.queue.Expire61(blockHardTTL) {
+			for _, pid := range d.queue.ExpireBlocks(blockHardTTL) {
 				if peer := d.peers.Peer(pid); peer != nil {
 					peer.Demote()
 					glog.V(logger.Detail).Infof("%s: block delivery timeout", peer)
@@ -907,7 +838,7 @@ func (d *Downloader) fetchBlocks61(from uint64) error {
 			}
 			// Send a download request to all idle peers, until throttled
 			throttled := false
-			idles, total := d.peers.BlockIdlePeers(61)
+			idles, total := d.peers.BlockIdlePeers()
 
 			for _, peer := range idles {
 				// Short circuit if throttling activated
@@ -918,7 +849,7 @@ func (d *Downloader) fetchBlocks61(from uint64) error {
 				// Reserve a chunk of hashes for a peer. A nil can mean either that
 				// no more hashes are available, or that the peer is known not to
 				// have them.
-				request := d.queue.Reserve61(peer, peer.BlockCapacity())
+				request := d.queue.ReserveBlocks(peer, peer.BlockCapacity())
 				if request == nil {
 					continue
 				}
@@ -928,7 +859,7 @@ func (d *Downloader) fetchBlocks61(from uint64) error {
 				// Fetch the chunk and make sure any errors return the hashes to the queue
 				if err := peer.Fetch61(request); err != nil {
 					glog.V(logger.Error).Infof("%v: fetch failed, rescheduling", peer)
-					d.queue.Cancel61(request)
+					d.queue.CancelBlocks(request)
 				}
 			}
 			// Make sure that we have peers available for fetching. If all peers have been tried
@@ -954,14 +885,14 @@ func (d *Downloader) fetchHeight(p *peer) (uint64, error) {
 		case <-d.cancelCh:
 			return 0, errCancelBlockFetch
 
-		case headerPack := <-d.headerCh:
+		case packet := <-d.headerCh:
 			// Discard anything not from the origin peer
-			if headerPack.peerId != p.id {
+			if packet.PeerId() != p.id {
-				glog.V(logger.Debug).Infof("Received headers from incorrect peer(%s)", headerPack.peerId)
+				glog.V(logger.Debug).Infof("Received headers from incorrect peer(%s)", packet.PeerId())
 				break
 			}
 			// Make sure the peer actually gave something valid
-			headers := headerPack.headers
+			headers := packet.(*headerPack).headers
 			if len(headers) != 1 {
 				glog.V(logger.Debug).Infof("%v: invalid number of head headers: %d != 1", p, len(headers))
 				return 0, errBadPeer
@@ -1014,14 +945,14 @@ func (d *Downloader) findAncestor(p *peer) (uint64, error) {
 		case <-d.cancelCh:
 			return 0, errCancelHashFetch
 
-		case headerPack := <-d.headerCh:
+		case packet := <-d.headerCh:
 			// Discard anything not from the origin peer
-			if headerPack.peerId != p.id {
+			if packet.PeerId() != p.id {
-				glog.V(logger.Debug).Infof("Received headers from incorrect peer(%s)", headerPack.peerId)
+				glog.V(logger.Debug).Infof("Received headers from incorrect peer(%s)", packet.PeerId())
 				break
 			}
 			// Make sure the peer actually gave something valid
-			headers := headerPack.headers
+			headers := packet.(*headerPack).headers
 			if len(headers) == 0 {
 				glog.V(logger.Debug).Infof("%v: empty head header set", p)
 				return 0, errEmptyHeaderSet
@@ -1069,14 +1000,14 @@ func (d *Downloader) findAncestor(p *peer) (uint64, error) {
 			case <-d.cancelCh:
 				return 0, errCancelHashFetch
 
-			case headerPack := <-d.headerCh:
+			case packer := <-d.headerCh:
 				// Discard anything not from the origin peer
-				if headerPack.peerId != p.id {
+				if packer.PeerId() != p.id {
-					glog.V(logger.Debug).Infof("Received headers from incorrect peer(%s)", headerPack.peerId)
+					glog.V(logger.Debug).Infof("Received headers from incorrect peer(%s)", packer.PeerId())
 					break
 				}
 				// Make sure the peer actually gave something valid
-				headers := headerPack.headers
+				headers := packer.(*headerPack).headers
 				if len(headers) != 1 {
 					glog.V(logger.Debug).Infof("%v: invalid search header set (%d)", p, len(headers))
 					return 0, errBadPeer
@@ -1150,20 +1081,20 @@ func (d *Downloader) fetchHeaders(p *peer, td *big.Int, from uint64) error {
 		case <-d.blockCh:
 			// Out of bounds eth/61 blocks received, ignore them
 
-		case headerPack := <-d.headerCh:
+		case packet := <-d.headerCh:
 			// Make sure the active peer is giving us the headers
-			if headerPack.peerId != p.id {
+			if packet.PeerId() != p.id {
-				glog.V(logger.Debug).Infof("Received headers from incorrect peer (%s)", headerPack.peerId)
+				glog.V(logger.Debug).Infof("Received headers from incorrect peer (%s)", packet.PeerId())
 				break
 			}
 			headerReqTimer.UpdateSince(request)
 			timeout.Stop()
 
 			// If no more headers are inbound, notify the content fetchers and return
-			if len(headerPack.headers) == 0 {
+			if packet.Items() == 0 {
 				glog.V(logger.Debug).Infof("%v: no available headers", p)
 
-				for _, ch := range []chan bool{d.bodyWakeCh, d.receiptWakeCh} {
+				for _, ch := range []chan bool{d.bodyWakeCh, d.receiptWakeCh, d.stateWakeCh} {
 					select {
 					case ch <- false:
 					case <-d.cancelCh:
@@ -1187,26 +1118,27 @@ func (d *Downloader) fetchHeaders(p *peer, td *big.Int, from uint64) error {
 				return nil
 			}
 			gotHeaders = true
+			headers := packet.(*headerPack).headers
 
 			// Otherwise insert all the new headers, aborting in case of junk
-			glog.V(logger.Detail).Infof("%v: schedule %d headers from #%d", p, len(headerPack.headers), from)
+			glog.V(logger.Detail).Infof("%v: schedule %d headers from #%d", p, len(headers), from)
 
 			if d.mode == FastSync || d.mode == LightSync {
-				if n, err := d.insertHeaders(headerPack.headers, false); err != nil {
+				if n, err := d.insertHeaders(headers, false); err != nil {
-					glog.V(logger.Debug).Infof("%v: invalid header #%d [%x…]: %v", p, headerPack.headers[n].Number, headerPack.headers[n].Hash().Bytes()[:4], err)
+					glog.V(logger.Debug).Infof("%v: invalid header #%d [%x…]: %v", p, headers[n].Number, headers[n].Hash().Bytes()[:4], err)
 					return errInvalidChain
 				}
 			}
 			if d.mode == FullSync || d.mode == FastSync {
-				inserts := d.queue.Schedule(headerPack.headers, from, d.mode == FastSync)
+				inserts := d.queue.Schedule(headers, from)
-				if len(inserts) != len(headerPack.headers) {
+				if len(inserts) != len(headers) {
 					glog.V(logger.Debug).Infof("%v: stale headers", p)
 					return errBadPeer
 				}
 			}
 			// Notify the content fetchers of new headers, but stop if queue is full
 			cont := d.queue.PendingBlocks() < maxQueuedHeaders || d.queue.PendingReceipts() < maxQueuedHeaders
-			for _, ch := range []chan bool{d.bodyWakeCh, d.receiptWakeCh} {
+			for _, ch := range []chan bool{d.bodyWakeCh, d.receiptWakeCh, d.stateWakeCh} {
 				if cont {
 					// We still have headers to fetch, send continuation wake signal (potential)
 					select {
@@ -1223,7 +1155,7 @@ func (d *Downloader) fetchHeaders(p *peer, td *big.Int, from uint64) error {
 				}
 			}
 			// Queue not yet full, fetch the next batch
-			from += uint64(len(headerPack.headers))
+			from += uint64(len(headers))
 			getHeaders(from)
 
 		case <-timeout.C:
@@ -1233,7 +1165,7 @@ func (d *Downloader) fetchHeaders(p *peer, td *big.Int, from uint64) error {
 			d.dropPeer(p.id)
 
 			// Finish the sync gracefully instead of dumping the gathered data though
-			for _, ch := range []chan bool{d.bodyWakeCh, d.receiptWakeCh} {
+			for _, ch := range []chan bool{d.bodyWakeCh, d.receiptWakeCh, d.stateWakeCh} {
 				select {
 				case ch <- false:
 				case <-d.cancelCh:
@@ -1251,19 +1183,19 @@ func (d *Downloader) fetchBodies(from uint64) error {
 	glog.V(logger.Debug).Infof("Downloading block bodies from #%d", from)
 
 	var (
-		deliver = func(packet interface{}) error {
+		deliver = func(packet dataPack) error {
 			pack := packet.(*bodyPack)
-			return d.queue.DeliverBlocks(pack.peerId, pack.transactions, pack.uncles)
+			return d.queue.DeliverBodies(pack.peerId, pack.transactions, pack.uncles)
 		}
-		expire   = func() []string { return d.queue.ExpireBlocks(bodyHardTTL) }
+		expire   = func() []string { return d.queue.ExpireBodies(bodyHardTTL) }
 		fetch    = func(p *peer, req *fetchRequest) error { return p.FetchBodies(req) }
 		capacity = func(p *peer) int { return p.BlockCapacity() }
-		getIdles = func() ([]*peer, int) { return d.peers.BlockIdlePeers(62) }
+		getIdles = func() ([]*peer, int) { return d.peers.BodyIdlePeers() }
 		setIdle  = func(p *peer) { p.SetBlocksIdle() }
 	)
-	err := d.fetchParts(from, errCancelBodyFetch, d.bodyCh, deliver, d.bodyWakeCh, expire,
+	err := d.fetchParts(errCancelBodyFetch, d.bodyCh, deliver, d.bodyWakeCh, expire,
-		d.queue.PendingBlocks, d.queue.ThrottleBlocks, d.queue.ReserveBlocks, d.bodyFetchHook,
+		d.queue.PendingBlocks, d.queue.ThrottleBlocks, d.queue.ReserveBodies, d.bodyFetchHook,
-		fetch, d.queue.CancelBlocks, capacity, getIdles, setIdle, "Body")
+		fetch, d.queue.CancelBodies, capacity, getIdles, setIdle, "Body")
 
 	glog.V(logger.Debug).Infof("Block body download terminated: %v", err)
 	return err
@@ -1276,7 +1208,7 @@ func (d *Downloader) fetchReceipts(from uint64) error {
 	glog.V(logger.Debug).Infof("Downloading receipts from #%d", from)
 
 	var (
-		deliver = func(packet interface{}) error {
+		deliver = func(packet dataPack) error {
 			pack := packet.(*receiptPack)
 			return d.queue.DeliverReceipts(pack.peerId, pack.receipts)
 		}
@@ -1285,7 +1217,7 @@ func (d *Downloader) fetchReceipts(from uint64) error {
 		capacity = func(p *peer) int { return p.ReceiptCapacity() }
 		setIdle  = func(p *peer) { p.SetReceiptsIdle() }
 	)
-	err := d.fetchParts(from, errCancelReceiptFetch, d.receiptCh, deliver, d.receiptWakeCh, expire,
+	err := d.fetchParts(errCancelReceiptFetch, d.receiptCh, deliver, d.receiptWakeCh, expire,
 		d.queue.PendingReceipts, d.queue.ThrottleReceipts, d.queue.ReserveReceipts, d.receiptFetchHook,
 		fetch, d.queue.CancelReceipts, capacity, d.peers.ReceiptIdlePeers, setIdle, "Receipt")
 
@@ -1293,10 +1225,46 @@ func (d *Downloader) fetchReceipts(from uint64) error {
 	return err
 }
 
+// fetchNodeData iteratively downloads the scheduled state trie nodes, taking any
+// available peers, reserving a chunk of nodes for each, waiting for delivery and
+// also periodically checking for timeouts.
+func (d *Downloader) fetchNodeData() error {
+	glog.V(logger.Debug).Infof("Downloading node state data")
+
+	var (
+		deliver = func(packet dataPack) error {
+			start := time.Now()
+			done, found, err := d.queue.DeliverNodeData(packet.PeerId(), packet.(*statePack).states)
+
+			d.syncStatsLock.Lock()
+			totalDone, totalKnown := d.syncStatsStateDone+uint64(done), d.syncStatsStateTotal+uint64(found)
+			d.syncStatsStateDone, d.syncStatsStateTotal = totalDone, totalKnown
+			d.syncStatsLock.Unlock()
+
+			glog.V(logger.Info).Infof("imported %d [%d / %d] state entries in %v.", done, totalDone, totalKnown, time.Since(start))
+			return err
+		}
+		expire   = func() []string { return d.queue.ExpireNodeData(stateHardTTL) }
+		throttle = func() bool { return false }
+		reserve  = func(p *peer, count int) (*fetchRequest, bool, error) {
+			return d.queue.ReserveNodeData(p, count), false, nil
+		}
+		fetch    = func(p *peer, req *fetchRequest) error { return p.FetchNodeData(req) }
+		capacity = func(p *peer) int { return p.NodeDataCapacity() }
+		setIdle  = func(p *peer) { p.SetNodeDataIdle() }
+	)
+	err := d.fetchParts(errCancelReceiptFetch, d.stateCh, deliver, d.stateWakeCh, expire,
+		d.queue.PendingNodeData, throttle, reserve, nil, fetch, d.queue.CancelNodeData,
+		capacity, d.peers.ReceiptIdlePeers, setIdle, "State")
+
+	glog.V(logger.Debug).Infof("Node state data download terminated: %v", err)
+	return err
+}
+
 // fetchParts iteratively downloads scheduled block parts, taking any available
 // peers, reserving a chunk of fetch requests for each, waiting for delivery and
 // also periodically checking for timeouts.
-func (d *Downloader) fetchParts(from uint64, errCancel error, deliveryCh chan dataPack, deliver func(packet interface{}) error, wakeCh chan bool,
+func (d *Downloader) fetchParts(errCancel error, deliveryCh chan dataPack, deliver func(packet dataPack) error, wakeCh chan bool,
 	expire func() []string, pending func() int, throttle func() bool, reserve func(*peer, int) (*fetchRequest, bool, error), fetchHook func([]*types.Header),
 	fetch func(*peer, *fetchRequest) error, cancel func(*fetchRequest), capacity func(*peer) int, idle func() ([]*peer, int), setIdle func(*peer), kind string) error {
 
@@ -1327,7 +1295,7 @@ func (d *Downloader) fetchParts(from uint64, errCancel error, deliveryCh chan da
 				switch err := deliver(packet); err {
 				case nil:
 					// If no blocks were delivered, demote the peer (need the delivery above to clean internal queue!)
-					if packet.Empty() {
+					if packet.Items() == 0 {
 						peer.Demote()
 						setIdle(peer)
 						glog.V(logger.Detail).Infof("%s: no %s delivered", peer, strings.ToLower(kind))
@@ -1441,7 +1409,11 @@ func (d *Downloader) fetchParts(from uint64, errCancel error, deliveryCh chan da
 					continue
 				}
 				if glog.V(logger.Detail) {
+					if len(request.Headers) > 0 {
 						glog.Infof("%s: requesting %d %s(s), first at #%d", peer, len(request.Headers), strings.ToLower(kind), request.Headers[0].Number)
+					} else {
+						glog.Infof("%s: requesting %d %s(s)", peer, len(request.Hashes), strings.ToLower(kind))
+					}
 				}
 				// Fetch the chunk and make sure any errors return the hashes to the queue
 				if fetchHook != nil {
@@ -1528,7 +1500,9 @@ func (d *Downloader) process() {
 					blocks = append(blocks, types.NewBlockWithHeader(result.Header).WithBody(result.Transactions, result.Uncles))
 				case d.mode == FastSync:
 					blocks = append(blocks, types.NewBlockWithHeader(result.Header).WithBody(result.Transactions, result.Uncles))
+					if result.Header.Number.Uint64() <= d.queue.fastSyncPivot {
 						receipts = append(receipts, result.Receipts)
+					}
 				case d.mode == LightSync:
 					headers = append(headers, result.Header)
 				}
@@ -1539,12 +1513,16 @@ func (d *Downloader) process() {
 				index int
 			)
 			switch {
-			case d.mode == FullSync:
+			case len(headers) > 0:
-				index, err = d.insertBlocks(blocks)
-			case d.mode == FastSync:
-				index, err = d.insertReceipts(blocks, receipts)
-			case d.mode == LightSync:
 				index, err = d.insertHeaders(headers, true)
+
+			case len(receipts) > 0:
+				index, err = d.insertReceipts(blocks, receipts)
+				if err == nil && blocks[len(blocks)-1].NumberU64() == d.queue.fastSyncPivot {
+					err = d.commitHeadBlock(blocks[len(blocks)-1].Hash())
+				}
+			default:
+				index, err = d.insertBlocks(blocks)
 			}
 			if err != nil {
 				glog.V(logger.Debug).Infof("Result #%d [%x…] processing failed: %v", results[index].Header.Number, results[index].Header.Hash().Bytes()[:4], err)
@@ -1557,125 +1535,47 @@ func (d *Downloader) process() {
 	}
 }
 
-// DeliverHashes61 injects a new batch of hashes received from a remote node into
+// DeliverHashes injects a new batch of hashes received from a remote node into
 // the download schedule. This is usually invoked through the BlockHashesMsg by
 // the protocol handler.
-func (d *Downloader) DeliverHashes61(id string, hashes []common.Hash) (err error) {
+func (d *Downloader) DeliverHashes(id string, hashes []common.Hash) (err error) {
-	// Update the delivery metrics for both good and failed deliveries
+	return d.deliver(id, d.hashCh, &hashPack{id, hashes}, hashInMeter, hashDropMeter)
-	hashInMeter.Mark(int64(len(hashes)))
-	defer func() {
-		if err != nil {
-			hashDropMeter.Mark(int64(len(hashes)))
-		}
-	}()
-	// Make sure the downloader is active
-	if atomic.LoadInt32(&d.synchronising) == 0 {
-		return errNoSyncActive
-	}
-	// Deliver or abort if the sync is canceled while queuing
-	d.cancelLock.RLock()
-	cancel := d.cancelCh
-	d.cancelLock.RUnlock()
-
-	select {
-	case d.hashCh <- hashPack{id, hashes}:
-		return nil
-
-	case <-cancel:
-		return errNoSyncActive
-	}
 }
 
-// DeliverBlocks61 injects a new batch of blocks received from a remote node.
+// DeliverBlocks injects a new batch of blocks received from a remote node.
 // This is usually invoked through the BlocksMsg by the protocol handler.
-func (d *Downloader) DeliverBlocks61(id string, blocks []*types.Block) (err error) {
+func (d *Downloader) DeliverBlocks(id string, blocks []*types.Block) (err error) {
-	// Update the delivery metrics for both good and failed deliveries
+	return d.deliver(id, d.blockCh, &blockPack{id, blocks}, blockInMeter, blockDropMeter)
-	blockInMeter.Mark(int64(len(blocks)))
-	defer func() {
-		if err != nil {
-			blockDropMeter.Mark(int64(len(blocks)))
-		}
-	}()
-	// Make sure the downloader is active
-	if atomic.LoadInt32(&d.synchronising) == 0 {
-		return errNoSyncActive
-	}
-	// Deliver or abort if the sync is canceled while queuing
-	d.cancelLock.RLock()
-	cancel := d.cancelCh
-	d.cancelLock.RUnlock()
-
-	select {
-	case d.blockCh <- blockPack{id, blocks}:
-		return nil
-
-	case <-cancel:
-		return errNoSyncActive
-	}
 }
 
 // DeliverHeaders injects a new batch of blck headers received from a remote
 // node into the download schedule.
 func (d *Downloader) DeliverHeaders(id string, headers []*types.Header) (err error) {
-	// Update the delivery metrics for both good and failed deliveries
+	return d.deliver(id, d.headerCh, &headerPack{id, headers}, headerInMeter, headerDropMeter)
-	headerInMeter.Mark(int64(len(headers)))
-	defer func() {
-		if err != nil {
-			headerDropMeter.Mark(int64(len(headers)))
-		}
-	}()
-	// Make sure the downloader is active
-	if atomic.LoadInt32(&d.synchronising) == 0 {
-		return errNoSyncActive
-	}
-	// Deliver or abort if the sync is canceled while queuing
-	d.cancelLock.RLock()
-	cancel := d.cancelCh
-	d.cancelLock.RUnlock()
-
-	select {
-	case d.headerCh <- headerPack{id, headers}:
-		return nil
-
-	case <-cancel:
-		return errNoSyncActive
-	}
 }
 
 // DeliverBodies injects a new batch of block bodies received from a remote node.
 func (d *Downloader) DeliverBodies(id string, transactions [][]*types.Transaction, uncles [][]*types.Header) (err error) {
-	// Update the delivery metrics for both good and failed deliveries
+	return d.deliver(id, d.bodyCh, &bodyPack{id, transactions, uncles}, bodyInMeter, bodyDropMeter)
-	bodyInMeter.Mark(int64(len(transactions)))
-	defer func() {
-		if err != nil {
-			bodyDropMeter.Mark(int64(len(transactions)))
-		}
-	}()
-	// Make sure the downloader is active
-	if atomic.LoadInt32(&d.synchronising) == 0 {
-		return errNoSyncActive
-	}
-	// Deliver or abort if the sync is canceled while queuing
-	d.cancelLock.RLock()
-	cancel := d.cancelCh
-	d.cancelLock.RUnlock()
-
-	select {
-	case d.bodyCh <- &bodyPack{id, transactions, uncles}:
-		return nil
-
-	case <-cancel:
-		return errNoSyncActive
-	}
 }
 
 // DeliverReceipts injects a new batch of receipts received from a remote node.
 func (d *Downloader) DeliverReceipts(id string, receipts [][]*types.Receipt) (err error) {
+	return d.deliver(id, d.receiptCh, &receiptPack{id, receipts}, receiptInMeter, receiptDropMeter)
+}
+
+// DeliverNodeData injects a new batch of node state data received from a remote node.
+func (d *Downloader) DeliverNodeData(id string, data [][]byte) (err error) {
+	return d.deliver(id, d.stateCh, &statePack{id, data}, stateInMeter, stateDropMeter)
+}
+
+// deliver injects a new batch of data received from a remote node.
+func (d *Downloader) deliver(id string, destCh chan dataPack, packet dataPack, inMeter, dropMeter metrics.Meter) (err error) {
 	// Update the delivery metrics for both good and failed deliveries
-	receiptInMeter.Mark(int64(len(receipts)))
+	inMeter.Mark(int64(packet.Items()))
 	defer func() {
 		if err != nil {
-			receiptDropMeter.Mark(int64(len(receipts)))
+			dropMeter.Mark(int64(packet.Items()))
 		}
 	}()
 	// Make sure the downloader is active
@@ -1688,7 +1588,7 @@ func (d *Downloader) DeliverReceipts(id string, receipts [][]*types.Receipt) (er
 	d.cancelLock.RUnlock()
 
 	select {
-	case d.receiptCh <- &receiptPack{id, receipts}:
+	case destCh <- packet:
 		return nil
 
 	case <-cancel:

eth/downloader/downloader_test.go

@@ -27,11 +27,13 @@ import (
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core"
+	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/params"
+	"github.com/ethereum/go-ethereum/trie"
 )
 
 var (
@@ -115,6 +117,7 @@ func makeChainFork(n, f int, parent *types.Block, parentReceipts types.Receipts)
 
 // downloadTester is a test simulator for mocking out local block chain.
 type downloadTester struct {
+	stateDb    ethdb.Database
 	downloader *Downloader
 
 	ownHashes   []common.Hash                  // Hash chain belonging to the tester
@@ -146,8 +149,10 @@ func newTester(mode SyncMode) *downloadTester {
 		peerReceipts: make(map[string]map[common.Hash]types.Receipts),
 		peerChainTds: make(map[string]map[common.Hash]*big.Int),
 	}
-	tester.downloader = New(mode, new(event.TypeMux), tester.hasHeader, tester.hasBlock, tester.getHeader, tester.getBlock,
+	tester.stateDb, _ = ethdb.NewMemDatabase()
-		tester.headHeader, tester.headBlock, tester.headFastBlock, tester.getTd, tester.insertHeaders, tester.insertBlocks, tester.insertReceipts, tester.dropPeer)
+	tester.downloader = New(mode, tester.stateDb, new(event.TypeMux), tester.hasHeader, tester.hasBlock, tester.getHeader,
+		tester.getBlock, tester.headHeader, tester.headBlock, tester.headFastBlock, tester.commitHeadBlock, tester.getTd,
+		tester.insertHeaders, tester.insertBlocks, tester.insertReceipts, tester.dropPeer)
 
 	return tester
 }
@@ -213,7 +218,7 @@ func (dl *downloadTester) headHeader() *types.Header {
 			return header
 		}
 	}
-	return nil
+	return genesis.Header()
 }
 
 // headBlock retrieves the current head block from the canonical chain.
@@ -223,10 +228,12 @@ func (dl *downloadTester) headBlock() *types.Block {
 
 	for i := len(dl.ownHashes) - 1; i >= 0; i-- {
 		if block := dl.getBlock(dl.ownHashes[i]); block != nil {
+			if _, err := dl.stateDb.Get(block.Root().Bytes()); err == nil {
 				return block
 			}
 		}
-	return nil
+	}
+	return genesis
 }
 
 // headFastBlock retrieves the current head fast-sync block from the canonical chain.
@@ -236,12 +243,20 @@ func (dl *downloadTester) headFastBlock() *types.Block {
 
 	for i := len(dl.ownHashes) - 1; i >= 0; i-- {
 		if block := dl.getBlock(dl.ownHashes[i]); block != nil {
-			if _, ok := dl.ownReceipts[block.Hash()]; ok {
 			return block
 		}
 	}
+	return genesis
+}
+
+// commitHeadBlock manually sets the head block to a given hash.
+func (dl *downloadTester) commitHeadBlock(hash common.Hash) error {
+	// For now only check that the state trie is correct
+	if block := dl.getBlock(hash); block != nil {
+		_, err := trie.NewSecure(block.Root(), dl.stateDb)
+		return err
 	}
-	return nil
+	return fmt.Errorf("non existent block: %x", hash[:4])
 }
 
 // getTd retrieves the block's total difficulty from the canonical chain.
@@ -283,6 +298,7 @@ func (dl *downloadTester) insertBlocks(blocks types.Blocks) (int, error) {
 		dl.ownHashes = append(dl.ownHashes, block.Hash())
 		dl.ownHeaders[block.Hash()] = block.Header()
 		dl.ownBlocks[block.Hash()] = block
+		dl.stateDb.Put(block.Root().Bytes(), []byte{})
 		dl.ownChainTd[block.Hash()] = dl.ownChainTd[block.ParentHash()]
 	}
 	return len(blocks), nil
@@ -321,13 +337,13 @@ func (dl *downloadTester) newSlowPeer(id string, version int, hashes []common.Ha
 	var err error
 	switch version {
 	case 61:
-		err = dl.downloader.RegisterPeer(id, version, hashes[0], dl.peerGetRelHashesFn(id, delay), dl.peerGetAbsHashesFn(id, delay), dl.peerGetBlocksFn(id, delay), nil, nil, nil, nil)
+		err = dl.downloader.RegisterPeer(id, version, hashes[0], dl.peerGetRelHashesFn(id, delay), dl.peerGetAbsHashesFn(id, delay), dl.peerGetBlocksFn(id, delay), nil, nil, nil, nil, nil)
 	case 62:
-		err = dl.downloader.RegisterPeer(id, version, hashes[0], nil, nil, nil, dl.peerGetRelHeadersFn(id, delay), dl.peerGetAbsHeadersFn(id, delay), dl.peerGetBodiesFn(id, delay), nil)
+		err = dl.downloader.RegisterPeer(id, version, hashes[0], nil, nil, nil, dl.peerGetRelHeadersFn(id, delay), dl.peerGetAbsHeadersFn(id, delay), dl.peerGetBodiesFn(id, delay), nil, nil)
 	case 63:
-		err = dl.downloader.RegisterPeer(id, version, hashes[0], nil, nil, nil, dl.peerGetRelHeadersFn(id, delay), dl.peerGetAbsHeadersFn(id, delay), dl.peerGetBodiesFn(id, delay), dl.peerGetReceiptsFn(id, delay))
+		err = dl.downloader.RegisterPeer(id, version, hashes[0], nil, nil, nil, dl.peerGetRelHeadersFn(id, delay), dl.peerGetAbsHeadersFn(id, delay), dl.peerGetBodiesFn(id, delay), dl.peerGetReceiptsFn(id, delay), dl.peerGetNodeDataFn(id, delay))
 	case 64:
-		err = dl.downloader.RegisterPeer(id, version, hashes[0], nil, nil, nil, dl.peerGetRelHeadersFn(id, delay), dl.peerGetAbsHeadersFn(id, delay), dl.peerGetBodiesFn(id, delay), dl.peerGetReceiptsFn(id, delay))
+		err = dl.downloader.RegisterPeer(id, version, hashes[0], nil, nil, nil, dl.peerGetRelHeadersFn(id, delay), dl.peerGetAbsHeadersFn(id, delay), dl.peerGetBodiesFn(id, delay), dl.peerGetReceiptsFn(id, delay), dl.peerGetNodeDataFn(id, delay))
 	}
 	if err == nil {
 		// Assign the owned hashes, headers and blocks to the peer (deep copy)
@@ -399,7 +415,7 @@ func (dl *downloadTester) peerGetRelHashesFn(id string, delay time.Duration) fun
 		// Delay delivery a bit to allow attacks to unfold
 		go func() {
 			time.Sleep(time.Millisecond)
-			dl.downloader.DeliverHashes61(id, result)
+			dl.downloader.DeliverHashes(id, result)
 		}()
 		return nil
 	}
@@ -424,7 +440,7 @@ func (dl *downloadTester) peerGetAbsHashesFn(id string, delay time.Duration) fun
 		// Delay delivery a bit to allow attacks to unfold
 		go func() {
 			time.Sleep(time.Millisecond)
-			dl.downloader.DeliverHashes61(id, result)
+			dl.downloader.DeliverHashes(id, result)
 		}()
 		return nil
 	}
@@ -447,7 +463,7 @@ func (dl *downloadTester) peerGetBlocksFn(id string, delay time.Duration) func([
 				result = append(result, block)
 			}
 		}
-		go dl.downloader.DeliverBlocks61(id, result)
+		go dl.downloader.DeliverBlocks(id, result)
 
 		return nil
 	}
@@ -553,17 +569,54 @@ func (dl *downloadTester) peerGetReceiptsFn(id string, delay time.Duration) func
 	}
 }
 
+// peerGetNodeDataFn constructs a getNodeData method associated with a particular
+// peer in the download tester. The returned function can be used to retrieve
+// batches of node state data from the particularly requested peer.
+func (dl *downloadTester) peerGetNodeDataFn(id string, delay time.Duration) func([]common.Hash) error {
+	return func(hashes []common.Hash) error {
+		time.Sleep(delay)
+
+		dl.lock.RLock()
+		defer dl.lock.RUnlock()
+
+		results := make([][]byte, 0, len(hashes))
+		for _, hash := range hashes {
+			if data, err := testdb.Get(hash.Bytes()); err == nil {
+				results = append(results, data)
+			}
+		}
+		go dl.downloader.DeliverNodeData(id, results)
+
+		return nil
+	}
+}
+
 // assertOwnChain checks if the local chain contains the correct number of items
 // of the various chain components.
 func assertOwnChain(t *testing.T, tester *downloadTester, length int) {
-	headers, blocks, receipts := length, length, length
+	assertOwnForkedChain(t, tester, 1, []int{length})
+}
+
+// assertOwnForkedChain checks if the local forked chain contains the correct
+// number of items of the various chain components.
+func assertOwnForkedChain(t *testing.T, tester *downloadTester, common int, lengths []int) {
+	// Initialize the counters for the first fork
+	headers, blocks, receipts := lengths[0], lengths[0], lengths[0]-minFullBlocks
+	if receipts < 0 {
+		receipts = 1
+	}
+	// Update the counters for each subsequent fork
+	for _, length := range lengths[1:] {
+		headers += length - common
+		blocks += length - common
+		receipts += length - common - minFullBlocks
+	}
 	switch tester.downloader.mode {
 	case FullSync:
 		receipts = 1
 	case LightSync:
 		blocks, receipts = 1, 1
 	}
-
 	if hs := len(tester.ownHeaders); hs != headers {
 		t.Fatalf("synchronised headers mismatch: have %v, want %v", hs, headers)
 	}
@@ -573,6 +626,14 @@ func assertOwnChain(t *testing.T, tester *downloadTester, length int) {
 	if rs := len(tester.ownReceipts); rs != receipts {
 		t.Fatalf("synchronised receipts mismatch: have %v, want %v", rs, receipts)
 	}
+	// Verify the state trie too for fast syncs
+	if tester.downloader.mode == FastSync {
+		if index := lengths[len(lengths)-1] - minFullBlocks - 1; index > 0 {
+			if statedb := state.New(tester.ownHeaders[tester.ownHashes[index]].Root, tester.stateDb); statedb == nil {
+				t.Fatalf("state reconstruction failed")
+			}
+		}
+	}
 }
 
 // Tests that simple synchronization against a canonical chain works correctly.
@@ -647,9 +708,11 @@ func testThrottling(t *testing.T, protocol int, mode SyncMode) {
 			cached = len(tester.downloader.queue.blockDonePool)
 			if mode == FastSync {
 				if receipts := len(tester.downloader.queue.receiptDonePool); receipts < cached {
+					if tester.downloader.queue.resultCache[receipts].Header.Number.Uint64() < tester.downloader.queue.fastSyncPivot {
 						cached = receipts
 					}
 				}
+			}
 			tester.downloader.queue.lock.RUnlock()
 
 			if cached == blockCacheLimit || len(tester.ownBlocks)+cached+int(atomic.LoadUint32(&blocked)) == targetBlocks+1 {
@@ -704,7 +767,7 @@ func testForkedSynchronisation(t *testing.T, protocol int, mode SyncMode) {
 	if err := tester.sync("fork B", nil); err != nil {
 		t.Fatalf("failed to synchronise blocks: %v", err)
 	}
-	assertOwnChain(t, tester, common+2*fork+1)
+	assertOwnForkedChain(t, tester, common+1, []int{common + fork + 1, common + fork + 1})
 }
 
 // Tests that an inactive downloader will not accept incoming hashes and blocks.
@@ -712,10 +775,10 @@ func TestInactiveDownloader61(t *testing.T) {
 	tester := newTester(FullSync)
 
 	// Check that neither hashes nor blocks are accepted
-	if err := tester.downloader.DeliverHashes61("bad peer", []common.Hash{}); err != errNoSyncActive {
+	if err := tester.downloader.DeliverHashes("bad peer", []common.Hash{}); err != errNoSyncActive {
 		t.Errorf("error mismatch: have %v, want %v", err, errNoSyncActive)
 	}
-	if err := tester.downloader.DeliverBlocks61("bad peer", []*types.Block{}); err != errNoSyncActive {
+	if err := tester.downloader.DeliverBlocks("bad peer", []*types.Block{}); err != errNoSyncActive {
 		t.Errorf("error mismatch: have %v, want %v", err, errNoSyncActive)
 	}
 }
@@ -809,14 +872,6 @@ func testMultiSynchronisation(t *testing.T, protocol int, mode SyncMode) {
 		id := fmt.Sprintf("peer #%d", i)
 		tester.newPeer(id, protocol, hashes[i*blockCacheLimit:], headers, blocks, receipts)
 	}
-	// Synchronise with the middle peer and make sure half of the blocks were retrieved
-	id := fmt.Sprintf("peer #%d", targetPeers/2)
-	if err := tester.sync(id, nil); err != nil {
-		t.Fatalf("failed to synchronise blocks: %v", err)
-	}
-	assertOwnChain(t, tester, len(tester.peerHashes[id]))
-
-	// Synchronise with the best peer and make sure everything is retrieved
 	if err := tester.sync("peer #0", nil); err != nil {
 		t.Fatalf("failed to synchronise blocks: %v", err)
 	}
@@ -870,8 +925,8 @@ func TestEmptyShortCircuit64Fast(t *testing.T)  { testEmptyShortCircuit(t, 64, F
 func TestEmptyShortCircuit64Light(t *testing.T) { testEmptyShortCircuit(t, 64, LightSync) }
 
 func testEmptyShortCircuit(t *testing.T, protocol int, mode SyncMode) {
-	// Create a small enough block chain to download
+	// Create a block chain to download
-	targetBlocks := blockCacheLimit - 15
+	targetBlocks := 2*blockCacheLimit - 15
 	hashes, headers, blocks, receipts := makeChain(targetBlocks, 0, genesis, nil)
 
 	tester := newTester(mode)
@@ -898,8 +953,8 @@ func testEmptyShortCircuit(t *testing.T, protocol int, mode SyncMode) {
 			bodiesNeeded++
 		}
 	}
-	for _, receipt := range receipts {
+	for hash, receipt := range receipts {
-		if mode == FastSync && len(receipt) > 0 {
+		if mode == FastSync && len(receipt) > 0 && headers[hash].Number.Uint64() <= uint64(targetBlocks-minFullBlocks) {
 			receiptsNeeded++
 		}
 	}

eth/downloader/metrics.go

@@ -47,4 +47,9 @@ var (
 	receiptReqTimer     = metrics.NewTimer("eth/downloader/receipts/req")
 	receiptDropMeter    = metrics.NewMeter("eth/downloader/receipts/drop")
 	receiptTimeoutMeter = metrics.NewMeter("eth/downloader/receipts/timeout")
+
+	stateInMeter      = metrics.NewMeter("eth/downloader/states/in")
+	stateReqTimer     = metrics.NewTimer("eth/downloader/states/req")
+	stateDropMeter    = metrics.NewMeter("eth/downloader/states/drop")
+	stateTimeoutMeter = metrics.NewMeter("eth/downloader/states/timeout")
 )

eth/downloader/peer.go

@@ -41,6 +41,7 @@ type relativeHeaderFetcherFn func(common.Hash, int, int, bool) error
 type absoluteHeaderFetcherFn func(uint64, int, int, bool) error
 type blockBodyFetcherFn func([]common.Hash) error
 type receiptFetcherFn func([]common.Hash) error
+type stateFetcherFn func([]common.Hash) error
 
 var (
 	errAlreadyFetching   = errors.New("already fetching blocks from peer")
@@ -55,12 +56,16 @@ type peer struct {
 
 	blockIdle   int32 // Current block activity state of the peer (idle = 0, active = 1)
 	receiptIdle int32 // Current receipt activity state of the peer (idle = 0, active = 1)
+	stateIdle   int32 // Current node data activity state of the peer (idle = 0, active = 1)
 	rep         int32 // Simple peer reputation
 
 	blockCapacity   int32 // Number of blocks (bodies) allowed to fetch per request
 	receiptCapacity int32 // Number of receipts allowed to fetch per request
+	stateCapacity   int32 // Number of node data pieces allowed to fetch per request
+
 	blockStarted   time.Time // Time instance when the last block (body)fetch was started
 	receiptStarted time.Time // Time instance when the last receipt fetch was started
+	stateStarted   time.Time // Time instance when the last node data fetch was started
 
 	ignored *set.Set // Set of hashes not to request (didn't have previously)
 
@@ -73,6 +78,7 @@ type peer struct {
 	getBlockBodies blockBodyFetcherFn      // [eth/62] Method to retrieve a batch of block bodies
 
 	getReceipts receiptFetcherFn // [eth/63] Method to retrieve a batch of block transaction receipts
+	getNodeData stateFetcherFn   // [eth/63] Method to retrieve a batch of state trie data
 
 	version int // Eth protocol version number to switch strategies
 }
@@ -82,12 +88,13 @@ type peer struct {
 func newPeer(id string, version int, head common.Hash,
 	getRelHashes relativeHashFetcherFn, getAbsHashes absoluteHashFetcherFn, getBlocks blockFetcherFn, // eth/61 callbacks, remove when upgrading
 	getRelHeaders relativeHeaderFetcherFn, getAbsHeaders absoluteHeaderFetcherFn, getBlockBodies blockBodyFetcherFn,
-	getReceipts receiptFetcherFn) *peer {
+	getReceipts receiptFetcherFn, getNodeData stateFetcherFn) *peer {
 	return &peer{
 		id:              id,
 		head:            head,
 		blockCapacity:   1,
 		receiptCapacity: 1,
+		stateCapacity:   1,
 		ignored:         set.New(),
 
 		getRelHashes: getRelHashes,
@@ -99,6 +106,7 @@ func newPeer(id string, version int, head common.Hash,
 		getBlockBodies: getBlockBodies,
 
 		getReceipts: getReceipts,
+		getNodeData: getNodeData,
 
 		version: version,
 	}
@@ -110,6 +118,7 @@ func (p *peer) Reset() {
 	atomic.StoreInt32(&p.receiptIdle, 0)
 	atomic.StoreInt32(&p.blockCapacity, 1)
 	atomic.StoreInt32(&p.receiptCapacity, 1)
+	atomic.StoreInt32(&p.stateCapacity, 1)
 	p.ignored.Clear()
 }
 
@@ -167,6 +176,24 @@ func (p *peer) FetchReceipts(request *fetchRequest) error {
 	return nil
 }
 
+// FetchNodeData sends a node state data retrieval request to the remote peer.
+func (p *peer) FetchNodeData(request *fetchRequest) error {
+	// Short circuit if the peer is already fetching
+	if !atomic.CompareAndSwapInt32(&p.stateIdle, 0, 1) {
+		return errAlreadyFetching
+	}
+	p.stateStarted = time.Now()
+
+	// Convert the hash set to a retrievable slice
+	hashes := make([]common.Hash, 0, len(request.Hashes))
+	for hash, _ := range request.Hashes {
+		hashes = append(hashes, hash)
+	}
+	go p.getNodeData(hashes)
+
+	return nil
+}
+
 // SetBlocksIdle sets the peer to idle, allowing it to execute new retrieval requests.
 // Its block retrieval allowance will also be updated either up- or downwards,
 // depending on whether the previous fetch completed in time or not.
@@ -188,6 +215,13 @@ func (p *peer) SetReceiptsIdle() {
 	p.setIdle(p.receiptStarted, receiptSoftTTL, receiptHardTTL, MaxReceiptFetch, &p.receiptCapacity, &p.receiptIdle)
 }
 
+// SetNodeDataIdle sets the peer to idle, allowing it to execute new retrieval
+// requests. Its node data retrieval allowance will also be updated either up- or
+// downwards, depending on whether the previous fetch completed in time or not.
+func (p *peer) SetNodeDataIdle() {
+	p.setIdle(p.stateStarted, stateSoftTTL, stateSoftTTL, MaxStateFetch, &p.stateCapacity, &p.stateIdle)
+}
+
 // setIdle sets the peer to idle, allowing it to execute new retrieval requests.
 // Its data retrieval allowance will also be updated either up- or downwards,
 // depending on whether the previous fetch completed in time or not.
@@ -230,6 +264,12 @@ func (p *peer) ReceiptCapacity() int {
 	return int(atomic.LoadInt32(&p.receiptCapacity))
 }
 
+// NodeDataCapacity retrieves the peers block download allowance based on its
+// previously discovered bandwidth capacity.
+func (p *peer) NodeDataCapacity() int {
+	return int(atomic.LoadInt32(&p.stateCapacity))
+}
+
 // Promote increases the peer's reputation.
 func (p *peer) Promote() {
 	atomic.AddInt32(&p.rep, 1)
@@ -340,39 +380,50 @@ func (ps *peerSet) AllPeers() []*peer {
 
 // BlockIdlePeers retrieves a flat list of all the currently idle peers within the
 // active peer set, ordered by their reputation.
-func (ps *peerSet) BlockIdlePeers(version int) ([]*peer, int) {
+func (ps *peerSet) BlockIdlePeers() ([]*peer, int) {
-	ps.lock.RLock()
+	idle := func(p *peer) bool {
-	defer ps.lock.RUnlock()
+		return atomic.LoadInt32(&p.blockIdle) == 0
-
-	idle, total := make([]*peer, 0, len(ps.peers)), 0
-	for _, p := range ps.peers {
-		if (version == 61 && p.version == 61) || (version >= 62 && p.version >= 62) {
-			if atomic.LoadInt32(&p.blockIdle) == 0 {
-				idle = append(idle, p)
-			}
-			total++
 	}
+	return ps.idlePeers(61, 61, idle)
+}
+
+// BodyIdlePeers retrieves a flat list of all the currently body-idle peers within
+// the active peer set, ordered by their reputation.
+func (ps *peerSet) BodyIdlePeers() ([]*peer, int) {
+	idle := func(p *peer) bool {
+		return atomic.LoadInt32(&p.blockIdle) == 0
 	}
-	for i := 0; i < len(idle); i++ {
+	return ps.idlePeers(62, 64, idle)
-		for j := i + 1; j < len(idle); j++ {
+}
-			if atomic.LoadInt32(&idle[i].rep) < atomic.LoadInt32(&idle[j].rep) {
+
-				idle[i], idle[j] = idle[j], idle[i]
+// ReceiptIdlePeers retrieves a flat list of all the currently receipt-idle peers
-			}
+// within the active peer set, ordered by their reputation.
+func (ps *peerSet) ReceiptIdlePeers() ([]*peer, int) {
+	idle := func(p *peer) bool {
+		return atomic.LoadInt32(&p.receiptIdle) == 0
 	}
+	return ps.idlePeers(63, 64, idle)
+}
+
+// NodeDataIdlePeers retrieves a flat list of all the currently node-data-idle
+// peers within the active peer set, ordered by their reputation.
+func (ps *peerSet) NodeDataIdlePeers() ([]*peer, int) {
+	idle := func(p *peer) bool {
+		return atomic.LoadInt32(&p.stateIdle) == 0
 	}
-	return idle, total
+	return ps.idlePeers(63, 64, idle)
 }
 
-// ReceiptIdlePeers retrieves a flat list of all the currently idle peers within the
+// idlePeers retrieves a flat list of all currently idle peers satisfying the
-// active peer set, ordered by their reputation.
+// protocol version constraints, using the provided function to check idleness.
-func (ps *peerSet) ReceiptIdlePeers() ([]*peer, int) {
+func (ps *peerSet) idlePeers(minProtocol, maxProtocol int, idleCheck func(*peer) bool) ([]*peer, int) {
 	ps.lock.RLock()
 	defer ps.lock.RUnlock()
 
 	idle, total := make([]*peer, 0, len(ps.peers)), 0
 	for _, p := range ps.peers {
-		if p.version >= 63 {
+		if p.version >= minProtocol && p.version <= maxProtocol {
-			if atomic.LoadInt32(&p.receiptIdle) == 0 {
+			if idleCheck(p) {
 				idle = append(idle, p)
 			}
 			total++

eth/downloader/queue.go

@@ -26,9 +26,13 @@ import (
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/logger"
 	"github.com/ethereum/go-ethereum/logger/glog"
+	"github.com/ethereum/go-ethereum/trie"
 	"github.com/rcrowley/go-metrics"
 	"gopkg.in/karalabe/cookiejar.v2/collections/prque"
 )
@@ -39,13 +43,14 @@ var (
 
 var (
 	errNoFetchesPending = errors.New("no fetches pending")
+	errStateSyncPending = errors.New("state trie sync already scheduled")
 	errStaleDelivery    = errors.New("stale delivery")
 )
 
 // fetchRequest is a currently running data retrieval operation.
 type fetchRequest struct {
 	Peer    *peer               // Peer to which the request was sent
-	Hashes  map[common.Hash]int // [eth/61] Requested block with their insertion index (priority)
+	Hashes  map[common.Hash]int // [eth/61] Requested hashes with their insertion index (priority)
 	Headers []*types.Header     // [eth/62] Requested headers, sorted by request order
 	Time    time.Time           // Time when the request was made
 }
@@ -64,6 +69,9 @@ type fetchResult struct {
 
 // queue represents hashes that are either need fetching or are being fetched
 type queue struct {
+	mode          SyncMode // Synchronisation mode to decide on the block parts to schedule for fetching
+	fastSyncPivot uint64   // Block number where the fast sync pivots into archive synchronisation mode
+
 	hashPool    map[common.Hash]int // [eth/61] Pending hashes, mapping to their insertion index (priority)
 	hashQueue   *prque.Prque        // [eth/61] Priority queue of the block hashes to fetch
 	hashCounter int                 // [eth/61] Counter indexing the added hashes to ensure retrieval order
@@ -80,15 +88,22 @@ type queue struct {
 	receiptPendPool  map[string]*fetchRequest      // [eth/63] Currently pending receipt retrieval operations
 	receiptDonePool  map[common.Hash]struct{}      // [eth/63] Set of the completed receipt fetches
 
+	stateTaskIndex int                      // [eth/63] Counter indexing the added hashes to ensure prioritized retrieval order
+	stateTaskPool  map[common.Hash]int      // [eth/63] Pending node data retrieval tasks, mapping to their priority
+	stateTaskQueue *prque.Prque             // [eth/63] Priority queue of the hashes to fetch the node data for
+	statePendPool  map[string]*fetchRequest // [eth/63] Currently pending node data retrieval operations
+
+	stateDatabase  ethdb.Database   // [eth/63] Trie database to populate during state reassembly
+	stateScheduler *state.StateSync // [eth/63] State trie synchronisation scheduler and integrator
+
 	resultCache  []*fetchResult // Downloaded but not yet delivered fetch results
 	resultOffset uint64         // Offset of the first cached fetch result in the block-chain
-	resultParts  int            // Number of fetch components required to complete an item
 
 	lock sync.RWMutex
 }
 
 // newQueue creates a new download queue for scheduling block retrieval.
-func newQueue() *queue {
+func newQueue(stateDb ethdb.Database) *queue {
 	return &queue{
 		hashPool:         make(map[common.Hash]int),
 		hashQueue:        prque.New(),
@@ -100,6 +115,10 @@ func newQueue() *queue {
 		receiptTaskQueue: prque.New(),
 		receiptPendPool:  make(map[string]*fetchRequest),
 		receiptDonePool:  make(map[common.Hash]struct{}),
+		stateTaskPool:    make(map[common.Hash]int),
+		stateTaskQueue:   prque.New(),
+		statePendPool:    make(map[string]*fetchRequest),
+		stateDatabase:    stateDb,
 		resultCache:      make([]*fetchResult, blockCacheLimit),
 	}
 }
@@ -109,6 +128,9 @@ func (q *queue) Reset() {
 	q.lock.Lock()
 	defer q.lock.Unlock()
 
+	q.mode = FullSync
+	q.fastSyncPivot = 0
+
 	q.hashPool = make(map[common.Hash]int)
 	q.hashQueue.Reset()
 	q.hashCounter = 0
@@ -125,9 +147,14 @@ func (q *queue) Reset() {
 	q.receiptPendPool = make(map[string]*fetchRequest)
 	q.receiptDonePool = make(map[common.Hash]struct{})
 
+	q.stateTaskIndex = 0
+	q.stateTaskPool = make(map[common.Hash]int)
+	q.stateTaskQueue.Reset()
+	q.statePendPool = make(map[string]*fetchRequest)
+	q.stateScheduler = nil
+
 	q.resultCache = make([]*fetchResult, blockCacheLimit)
 	q.resultOffset = 0
-	q.resultParts = 0
 }
 
 // PendingBlocks retrieves the number of block (body) requests pending for retrieval.
@@ -146,12 +173,20 @@ func (q *queue) PendingReceipts() int {
 	return q.receiptTaskQueue.Size()
 }
 
+// PendingNodeData retrieves the number of node data entries pending for retrieval.
+func (q *queue) PendingNodeData() int {
+	q.lock.RLock()
+	defer q.lock.RUnlock()
+
+	return q.stateTaskQueue.Size()
+}
+
 // InFlight retrieves the number of fetch requests currently in flight.
 func (q *queue) InFlight() int {
 	q.lock.RLock()
 	defer q.lock.RUnlock()
 
-	return len(q.blockPendPool) + len(q.receiptPendPool)
+	return len(q.blockPendPool) + len(q.receiptPendPool) + len(q.statePendPool)
 }
 
 // Idle returns if the queue is fully idle or has some data still inside. This
@@ -160,8 +195,8 @@ func (q *queue) Idle() bool {
 	q.lock.RLock()
 	defer q.lock.RUnlock()
 
-	queued := q.hashQueue.Size() + q.blockTaskQueue.Size() + q.receiptTaskQueue.Size()
+	queued := q.hashQueue.Size() + q.blockTaskQueue.Size() + q.receiptTaskQueue.Size() + q.stateTaskQueue.Size()
-	pending := len(q.blockPendPool) + len(q.receiptPendPool)
+	pending := len(q.blockPendPool) + len(q.receiptPendPool) + len(q.statePendPool)
 	cached := len(q.blockDonePool) + len(q.receiptDonePool)
 
 	return (queued + pending + cached) == 0
@@ -227,7 +262,7 @@ func (q *queue) Schedule61(hashes []common.Hash, fifo bool) []common.Hash {
 
 // Schedule adds a set of headers for the download queue for scheduling, returning
 // the new headers encountered.
-func (q *queue) Schedule(headers []*types.Header, from uint64, receipts bool) []*types.Header {
+func (q *queue) Schedule(headers []*types.Header, from uint64) []*types.Header {
 	q.lock.Lock()
 	defer q.lock.Unlock()
 
@@ -256,10 +291,21 @@ func (q *queue) Schedule(headers []*types.Header, from uint64, receipts bool) []
 		// Queue the header for content retrieval
 		q.blockTaskPool[hash] = header
 		q.blockTaskQueue.Push(header, -float32(header.Number.Uint64()))
-		if receipts {
+
+		if q.mode == FastSync && header.Number.Uint64() <= q.fastSyncPivot {
+			// Fast phase of the fast sync, retrieve receipts too
 			q.receiptTaskPool[hash] = header
 			q.receiptTaskQueue.Push(header, -float32(header.Number.Uint64()))
 		}
+		if q.mode == FastSync && header.Number.Uint64() == q.fastSyncPivot {
+			// Pivoting point of the fast sync, retrieve the state tries
+			q.stateScheduler = state.NewStateSync(header.Root, q.stateDatabase)
+			for _, hash := range q.stateScheduler.Missing(0) {
+				q.stateTaskPool[hash] = q.stateTaskIndex
+				q.stateTaskQueue.Push(hash, -float32(q.stateTaskIndex))
+				q.stateTaskIndex++
+			}
+		}
 		inserts = append(inserts, header)
 		q.headerHead = hash
 		from++
@@ -279,6 +325,9 @@ func (q *queue) GetHeadResult() *fetchResult {
 	if q.resultCache[0].Pending > 0 {
 		return nil
 	}
+	if q.mode == FastSync && q.resultCache[0].Header.Number.Uint64() == q.fastSyncPivot && len(q.stateTaskPool) > 0 {
+		return nil
+	}
 	return q.resultCache[0]
 }
 
@@ -291,9 +340,18 @@ func (q *queue) TakeResults() []*fetchResult {
 	// Accumulate all available results
 	results := []*fetchResult{}
 	for _, result := range q.resultCache {
+		// Stop if no more results are ready
 		if result == nil || result.Pending > 0 {
 			break
 		}
+		// The fast sync pivot block may only be processed after state fetch completes
+		if q.mode == FastSync && result.Header.Number.Uint64() == q.fastSyncPivot && len(q.stateTaskPool) > 0 {
+			break
+		}
+		// If we've just inserted the fast sync pivot, stop as the following batch needs different insertion
+		if q.mode == FastSync && result.Header.Number.Uint64() == q.fastSyncPivot+1 && len(results) > 0 {
+			break
+		}
 		results = append(results, result)
 
 		hash := result.Header.Hash()
@@ -312,31 +370,45 @@ func (q *queue) TakeResults() []*fetchResult {
 	return results
 }
 
-// Reserve61 reserves a set of hashes for the given peer, skipping any previously
+// ReserveBlocks reserves a set of block hashes for the given peer, skipping any
-// failed download.
+// previously failed download.
-func (q *queue) Reserve61(p *peer, count int) *fetchRequest {
+func (q *queue) ReserveBlocks(p *peer, count int) *fetchRequest {
+	return q.reserveHashes(p, count, q.hashQueue, q.blockPendPool, len(q.resultCache)-len(q.blockDonePool))
+}
+
+// ReserveNodeData reserves a set of node data hashes for the given peer, skipping
+// any previously failed download.
+func (q *queue) ReserveNodeData(p *peer, count int) *fetchRequest {
+	return q.reserveHashes(p, count, q.stateTaskQueue, q.statePendPool, 0)
+}
+
+// reserveHashes reserves a set of hashes for the given peer, skipping previously
+// failed ones.
+func (q *queue) reserveHashes(p *peer, count int, taskQueue *prque.Prque, pendPool map[string]*fetchRequest, maxPending int) *fetchRequest {
 	q.lock.Lock()
 	defer q.lock.Unlock()
 
 	// Short circuit if the pool has been depleted, or if the peer's already
 	// downloading something (sanity check not to corrupt state)
-	if q.hashQueue.Empty() {
+	if taskQueue.Empty() {
 		return nil
 	}
-	if _, ok := q.blockPendPool[p.id]; ok {
+	if _, ok := pendPool[p.id]; ok {
 		return nil
 	}
 	// Calculate an upper limit on the hashes we might fetch (i.e. throttling)
-	space := len(q.resultCache) - len(q.blockDonePool)
+	allowance := maxPending
-	for _, request := range q.blockPendPool {
+	if allowance > 0 {
-		space -= len(request.Hashes)
+		for _, request := range pendPool {
+			allowance -= len(request.Hashes)
+		}
 	}
 	// Retrieve a batch of hashes, skipping previously failed ones
 	send := make(map[common.Hash]int)
 	skip := make(map[common.Hash]int)
 
-	for proc := 0; proc < space && len(send) < count && !q.hashQueue.Empty(); proc++ {
+	for proc := 0; (allowance == 0 || proc < allowance) && len(send) < count && !taskQueue.Empty(); proc++ {
-		hash, priority := q.hashQueue.Pop()
+		hash, priority := taskQueue.Pop()
 		if p.ignored.Has(hash) {
 			skip[hash.(common.Hash)] = int(priority)
 		} else {
@@ -345,7 +417,7 @@ func (q *queue) Reserve61(p *peer, count int) *fetchRequest {
 	}
 	// Merge all the skipped hashes back
 	for hash, index := range skip {
-		q.hashQueue.Push(hash, float32(index))
+		taskQueue.Push(hash, float32(index))
 	}
 	// Assemble and return the block download request
 	if len(send) == 0 {
@@ -356,19 +428,19 @@ func (q *queue) Reserve61(p *peer, count int) *fetchRequest {
 		Hashes: send,
 		Time:   time.Now(),
 	}
-	q.blockPendPool[p.id] = request
+	pendPool[p.id] = request
 
 	return request
 }
 
-// ReserveBlocks reserves a set of body fetches for the given peer, skipping any
+// ReserveBodies reserves a set of body fetches for the given peer, skipping any
 // previously failed downloads. Beside the next batch of needed fetches, it also
 // returns a flag whether empty blocks were queued requiring processing.
-func (q *queue) ReserveBlocks(p *peer, count int) (*fetchRequest, bool, error) {
+func (q *queue) ReserveBodies(p *peer, count int) (*fetchRequest, bool, error) {
 	noop := func(header *types.Header) bool {
 		return header.TxHash == types.EmptyRootHash && header.UncleHash == types.EmptyUncleHash
 	}
-	return q.reserveFetch(p, count, q.blockTaskPool, q.blockTaskQueue, q.blockPendPool, q.blockDonePool, noop)
+	return q.reserveHeaders(p, count, q.blockTaskPool, q.blockTaskQueue, q.blockPendPool, q.blockDonePool, noop)
 }
 
 // ReserveReceipts reserves a set of receipt fetches for the given peer, skipping
@@ -378,13 +450,13 @@ func (q *queue) ReserveReceipts(p *peer, count int) (*fetchRequest, bool, error)
 	noop := func(header *types.Header) bool {
 		return header.ReceiptHash == types.EmptyRootHash
 	}
-	return q.reserveFetch(p, count, q.receiptTaskPool, q.receiptTaskQueue, q.receiptPendPool, q.receiptDonePool, noop)
+	return q.reserveHeaders(p, count, q.receiptTaskPool, q.receiptTaskQueue, q.receiptPendPool, q.receiptDonePool, noop)
 }
 
-// reserveFetch reserves a set of data download operations for a given peer,
+// reserveHeaders reserves a set of data download operations for a given peer,
 // skipping any previously failed ones. This method is a generic version used
 // by the individual special reservation functions.
-func (q *queue) reserveFetch(p *peer, count int, taskPool map[common.Hash]*types.Header, taskQueue *prque.Prque,
+func (q *queue) reserveHeaders(p *peer, count int, taskPool map[common.Hash]*types.Header, taskQueue *prque.Prque,
 	pendPool map[string]*fetchRequest, donePool map[common.Hash]struct{}, noop func(*types.Header) bool) (*fetchRequest, bool, error) {
 	q.lock.Lock()
 	defer q.lock.Unlock()
@@ -416,8 +488,12 @@ func (q *queue) reserveFetch(p *peer, count int, taskPool map[common.Hash]*types
 			return nil, false, errInvalidChain
 		}
 		if q.resultCache[index] == nil {
+			components := 1
+			if q.mode == FastSync && header.Number.Uint64() <= q.fastSyncPivot {
+				components = 2
+			}
 			q.resultCache[index] = &fetchResult{
-				Pending: q.resultParts,
+				Pending: components,
 				Header:  header,
 			}
 		}
@@ -456,30 +532,36 @@ func (q *queue) reserveFetch(p *peer, count int, taskPool map[common.Hash]*types
 	return request, progress, nil
 }
 
-// Cancel61 aborts a fetch request, returning all pending hashes to the queue.
+// CancelBlocks aborts a fetch request, returning all pending hashes to the queue.
-func (q *queue) Cancel61(request *fetchRequest) {
+func (q *queue) CancelBlocks(request *fetchRequest) {
-	q.cancel(request, nil, q.blockPendPool)
+	q.cancel(request, q.hashQueue, q.blockPendPool)
 }
 
-// CancelBlocks aborts a body fetch request, returning all pending hashes to the
+// CancelBodies aborts a body fetch request, returning all pending headers to the
 // task queue.
-func (q *queue) CancelBlocks(request *fetchRequest) {
+func (q *queue) CancelBodies(request *fetchRequest) {
 	q.cancel(request, q.blockTaskQueue, q.blockPendPool)
 }
 
-// CancelReceipts aborts a body fetch request, returning all pending hashes to
+// CancelReceipts aborts a body fetch request, returning all pending headers to
 // the task queue.
 func (q *queue) CancelReceipts(request *fetchRequest) {
 	q.cancel(request, q.receiptTaskQueue, q.receiptPendPool)
 }
 
+// CancelNodeData aborts a node state data fetch request, returning all pending
+// hashes to the task queue.
+func (q *queue) CancelNodeData(request *fetchRequest) {
+	q.cancel(request, q.stateTaskQueue, q.statePendPool)
+}
+
 // Cancel aborts a fetch request, returning all pending hashes to the task queue.
 func (q *queue) cancel(request *fetchRequest, taskQueue *prque.Prque, pendPool map[string]*fetchRequest) {
 	q.lock.Lock()
 	defer q.lock.Unlock()
 
 	for hash, index := range request.Hashes {
-		q.hashQueue.Push(hash, float32(index))
+		taskQueue.Push(hash, float32(index))
 	}
 	for _, header := range request.Headers {
 		taskQueue.Push(header, -float32(header.Number.Uint64()))
@@ -509,29 +591,41 @@ func (q *queue) Revoke(peerId string) {
 		}
 		delete(q.receiptPendPool, peerId)
 	}
+	if request, ok := q.statePendPool[peerId]; ok {
+		for hash, index := range request.Hashes {
+			q.stateTaskQueue.Push(hash, float32(index))
+		}
+		delete(q.statePendPool, peerId)
+	}
 }
 
-// Expire61 checks for in flight requests that exceeded a timeout allowance,
+// ExpireBlocks checks for in flight requests that exceeded a timeout allowance,
 // canceling them and returning the responsible peers for penalization.
-func (q *queue) Expire61(timeout time.Duration) []string {
+func (q *queue) ExpireBlocks(timeout time.Duration) []string {
-	return q.expire(timeout, q.blockPendPool, nil)
+	return q.expire(timeout, q.blockPendPool, q.hashQueue, blockTimeoutMeter)
 }
 
-// ExpireBlocks checks for in flight block body requests that exceeded a timeout
+// ExpireBodies checks for in flight block body requests that exceeded a timeout
 // allowance, canceling them and returning the responsible peers for penalization.
-func (q *queue) ExpireBlocks(timeout time.Duration) []string {
+func (q *queue) ExpireBodies(timeout time.Duration) []string {
-	return q.expire(timeout, q.blockPendPool, q.blockTaskQueue)
+	return q.expire(timeout, q.blockPendPool, q.blockTaskQueue, bodyTimeoutMeter)
 }
 
 // ExpireReceipts checks for in flight receipt requests that exceeded a timeout
 // allowance, canceling them and returning the responsible peers for penalization.
 func (q *queue) ExpireReceipts(timeout time.Duration) []string {
-	return q.expire(timeout, q.receiptPendPool, q.receiptTaskQueue)
+	return q.expire(timeout, q.receiptPendPool, q.receiptTaskQueue, receiptTimeoutMeter)
+}
+
+// ExpireNodeData checks for in flight node data requests that exceeded a timeout
+// allowance, canceling them and returning the responsible peers for penalization.
+func (q *queue) ExpireNodeData(timeout time.Duration) []string {
+	return q.expire(timeout, q.statePendPool, q.stateTaskQueue, stateTimeoutMeter)
 }
 
 // expire is the generic check that move expired tasks from a pending pool back
 // into a task pool, returning all entities caught with expired tasks.
-func (q *queue) expire(timeout time.Duration, pendPool map[string]*fetchRequest, taskQueue *prque.Prque) []string {
+func (q *queue) expire(timeout time.Duration, pendPool map[string]*fetchRequest, taskQueue *prque.Prque, timeoutMeter metrics.Meter) []string {
 	q.lock.Lock()
 	defer q.lock.Unlock()
 
@@ -540,14 +634,11 @@ func (q *queue) expire(timeout time.Duration, pendPool map[string]*fetchRequest,
 	for id, request := range pendPool {
 		if time.Since(request.Time) > timeout {
 			// Update the metrics with the timeout
-			if len(request.Hashes) > 0 {
+			timeoutMeter.Mark(1)
-				blockTimeoutMeter.Mark(1)
+
-			} else {
-				bodyTimeoutMeter.Mark(1)
-			}
 			// Return any non satisfied requests to the pool
 			for hash, index := range request.Hashes {
-				q.hashQueue.Push(hash, float32(index))
+				taskQueue.Push(hash, float32(index))
 			}
 			for _, header := range request.Headers {
 				taskQueue.Push(header, -float32(header.Number.Uint64()))
@@ -562,8 +653,8 @@ func (q *queue) expire(timeout time.Duration, pendPool map[string]*fetchRequest,
 	return peers
 }
 
-// Deliver61 injects a block retrieval response into the download queue.
+// DeliverBlocks injects a block retrieval response into the download queue.
-func (q *queue) Deliver61(id string, blocks []*types.Block) (err error) {
+func (q *queue) DeliverBlocks(id string, blocks []*types.Block) error {
 	q.lock.Lock()
 	defer q.lock.Unlock()
 
@@ -626,8 +717,8 @@ func (q *queue) Deliver61(id string, blocks []*types.Block) (err error) {
 	}
 }
 
-// DeliverBlocks injects a block (body) retrieval response into the results queue.
+// DeliverBodies injects a block body retrieval response into the results queue.
-func (q *queue) DeliverBlocks(id string, txLists [][]*types.Transaction, uncleLists [][]*types.Header) error {
+func (q *queue) DeliverBodies(id string, txLists [][]*types.Transaction, uncleLists [][]*types.Header) error {
 	reconstruct := func(header *types.Header, index int, result *fetchResult) error {
 		if types.DeriveSha(types.Transactions(txLists[index])) != header.TxHash || types.CalcUncleHash(uncleLists[index]) != header.UncleHash {
 			return errInvalidBody
@@ -717,14 +808,84 @@ func (q *queue) deliver(id string, taskPool map[common.Hash]*types.Header, taskQ
 	}
 }
 
+// DeliverNodeData injects a node state data retrieval response into the queue.
+func (q *queue) DeliverNodeData(id string, data [][]byte) (int, int, error) {
+	q.lock.Lock()
+	defer q.lock.Unlock()
+
+	// Short circuit if the data was never requested
+	request := q.statePendPool[id]
+	if request == nil {
+		return 0, 0, errNoFetchesPending
+	}
+	stateReqTimer.UpdateSince(request.Time)
+	delete(q.statePendPool, id)
+
+	// If no data was retrieved, mark them as unavailable for the origin peer
+	if len(data) == 0 {
+		for hash, _ := range request.Hashes {
+			request.Peer.ignored.Add(hash)
+		}
+	}
+	// Iterate over the downloaded data and verify each of them
+	errs := make([]error, 0)
+	processed := 0
+	for _, blob := range data {
+		// Skip any blocks that were not requested
+		hash := common.BytesToHash(crypto.Sha3(blob))
+		if _, ok := request.Hashes[hash]; !ok {
+			errs = append(errs, fmt.Errorf("non-requested state data %x", hash))
+			continue
+		}
+		// Inject the next state trie item into the database
+		if err := q.stateScheduler.Process([]trie.SyncResult{{hash, blob}}); err != nil {
+			errs = []error{err}
+			break
+		}
+		processed++
+
+		delete(request.Hashes, hash)
+		delete(q.stateTaskPool, hash)
+	}
+	// Return all failed or missing fetches to the queue
+	for hash, index := range request.Hashes {
+		q.stateTaskQueue.Push(hash, float32(index))
+	}
+	// Also enqueue any newly required state trie nodes
+	discovered := 0
+	if len(q.stateTaskPool) < maxQueuedStates {
+		for _, hash := range q.stateScheduler.Missing(4 * MaxStateFetch) {
+			q.stateTaskPool[hash] = q.stateTaskIndex
+			q.stateTaskQueue.Push(hash, -float32(q.stateTaskIndex))
+			q.stateTaskIndex++
+			discovered++
+		}
+	}
+	// If none of the data items were good, it's a stale delivery
+	switch {
+	case len(errs) == 0:
+		return processed, discovered, nil
+
+	case len(errs) == len(request.Hashes):
+		return processed, discovered, errStaleDelivery
+
+	default:
+		return processed, discovered, fmt.Errorf("multiple failures: %v", errs)
+	}
+}
+
 // Prepare configures the result cache to allow accepting and caching inbound
 // fetch results.
-func (q *queue) Prepare(offset uint64, parts int) {
+func (q *queue) Prepare(offset uint64, mode SyncMode, pivot uint64) {
 	q.lock.Lock()
 	defer q.lock.Unlock()
 
 	if q.resultOffset < offset {
 		q.resultOffset = offset
 	}
-	q.resultParts = parts
+	q.fastSyncPivot = 0
+	if mode == FastSync {
+		q.fastSyncPivot = pivot
+	}
+	q.mode = mode
 }

eth/downloader/types.go

@@ -0,0 +1,137 @@
+// Copyright 2015 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package downloader
+
+import (
+	"fmt"
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+)
+
+// headerCheckFn is a callback type for verifying a header's presence in the local chain.
+type headerCheckFn func(common.Hash) bool
+
+// blockCheckFn is a callback type for verifying a block's presence in the local chain.
+type blockCheckFn func(common.Hash) bool
+
+// headerRetrievalFn is a callback type for retrieving a header from the local chain.
+type headerRetrievalFn func(common.Hash) *types.Header
+
+// blockRetrievalFn is a callback type for retrieving a block from the local chain.
+type blockRetrievalFn func(common.Hash) *types.Block
+
+// headHeaderRetrievalFn is a callback type for retrieving the head header from the local chain.
+type headHeaderRetrievalFn func() *types.Header
+
+// headBlockRetrievalFn is a callback type for retrieving the head block from the local chain.
+type headBlockRetrievalFn func() *types.Block
+
+// headFastBlockRetrievalFn is a callback type for retrieving the head fast block from the local chain.
+type headFastBlockRetrievalFn func() *types.Block
+
+// headBlockCommitterFn is a callback for directly committing the head block to a certain entity.
+type headBlockCommitterFn func(common.Hash) error
+
+// tdRetrievalFn is a callback type for retrieving the total difficulty of a local block.
+type tdRetrievalFn func(common.Hash) *big.Int
+
+// headerChainInsertFn is a callback type to insert a batch of headers into the local chain.
+type headerChainInsertFn func([]*types.Header, bool) (int, error)
+
+// blockChainInsertFn is a callback type to insert a batch of blocks into the local chain.
+type blockChainInsertFn func(types.Blocks) (int, error)
+
+// receiptChainInsertFn is a callback type to insert a batch of receipts into the local chain.
+type receiptChainInsertFn func(types.Blocks, []types.Receipts) (int, error)
+
+// peerDropFn is a callback type for dropping a peer detected as malicious.
+type peerDropFn func(id string)
+
+// dataPack is a data message returned by a peer for some query.
+type dataPack interface {
+	PeerId() string
+	Items() int
+	Stats() string
+}
+
+// hashPack is a batch of block hashes returned by a peer (eth/61).
+type hashPack struct {
+	peerId string
+	hashes []common.Hash
+}
+
+func (p *hashPack) PeerId() string { return p.peerId }
+func (p *hashPack) Items() int     { return len(p.hashes) }
+func (p *hashPack) Stats() string  { return fmt.Sprintf("%d", len(p.hashes)) }
+
+// blockPack is a batch of blocks returned by a peer (eth/61).
+type blockPack struct {
+	peerId string
+	blocks []*types.Block
+}
+
+func (p *blockPack) PeerId() string { return p.peerId }
+func (p *blockPack) Items() int     { return len(p.blocks) }
+func (p *blockPack) Stats() string  { return fmt.Sprintf("%d", len(p.blocks)) }
+
+// headerPack is a batch of block headers returned by a peer.
+type headerPack struct {
+	peerId  string
+	headers []*types.Header
+}
+
+func (p *headerPack) PeerId() string { return p.peerId }
+func (p *headerPack) Items() int     { return len(p.headers) }
+func (p *headerPack) Stats() string  { return fmt.Sprintf("%d", len(p.headers)) }
+
+// bodyPack is a batch of block bodies returned by a peer.
+type bodyPack struct {
+	peerId       string
+	transactions [][]*types.Transaction
+	uncles       [][]*types.Header
+}
+
+func (p *bodyPack) PeerId() string { return p.peerId }
+func (p *bodyPack) Items() int {
+	if len(p.transactions) <= len(p.uncles) {
+		return len(p.transactions)
+	}
+	return len(p.uncles)
+}
+func (p *bodyPack) Stats() string { return fmt.Sprintf("%d:%d", len(p.transactions), len(p.uncles)) }
+
+// receiptPack is a batch of receipts returned by a peer.
+type receiptPack struct {
+	peerId   string
+	receipts [][]*types.Receipt
+}
+
+func (p *receiptPack) PeerId() string { return p.peerId }
+func (p *receiptPack) Items() int     { return len(p.receipts) }
+func (p *receiptPack) Stats() string  { return fmt.Sprintf("%d", len(p.receipts)) }
+
+// statePack is a batch of states returned by a peer.
+type statePack struct {
+	peerId string
+	states [][]byte
+}
+
+func (p *statePack) PeerId() string { return p.peerId }
+func (p *statePack) Items() int     { return len(p.states) }
+func (p *statePack) Stats() string  { return fmt.Sprintf("%d", len(p.states)) }

eth/handler.go

@@ -129,9 +129,9 @@ func NewProtocolManager(mode Mode, networkId int, mux *event.TypeMux, txpool txP
 	case LightMode:
 		syncMode = downloader.LightSync
 	}
-	manager.downloader = downloader.New(syncMode, manager.eventMux, blockchain.HasHeader, blockchain.HasBlock, blockchain.GetHeader,
+	manager.downloader = downloader.New(syncMode, chaindb, manager.eventMux, blockchain.HasHeader, blockchain.HasBlock, blockchain.GetHeader,
-		blockchain.GetBlock, blockchain.CurrentHeader, blockchain.CurrentBlock, blockchain.CurrentFastBlock, blockchain.GetTd,
+		blockchain.GetBlock, blockchain.CurrentHeader, blockchain.CurrentBlock, blockchain.CurrentFastBlock, blockchain.FastSyncCommitHead,
-		blockchain.InsertHeaderChain, blockchain.InsertChain, blockchain.InsertReceiptChain, manager.removePeer)
+		blockchain.GetTd, blockchain.InsertHeaderChain, blockchain.InsertChain, blockchain.InsertReceiptChain, manager.removePeer)
 
 	validator := func(block *types.Block, parent *types.Block) error {
 		return core.ValidateHeader(pow, block.Header(), parent.Header(), true, false)
@@ -220,8 +220,8 @@ func (pm *ProtocolManager) handle(p *peer) error {
 
 	// Register the peer in the downloader. If the downloader considers it banned, we disconnect
 	if err := pm.downloader.RegisterPeer(p.id, p.version, p.Head(),
-		p.RequestHashes, p.RequestHashesFromNumber, p.RequestBlocks,
+		p.RequestHashes, p.RequestHashesFromNumber, p.RequestBlocks, p.RequestHeadersByHash,
-		p.RequestHeadersByHash, p.RequestHeadersByNumber, p.RequestBodies, p.RequestReceipts); err != nil {
+		p.RequestHeadersByNumber, p.RequestBodies, p.RequestReceipts, p.RequestNodeData); err != nil {
 		return err
 	}
 	// Propagate existing transactions. new transactions appearing
@@ -307,7 +307,7 @@ func (pm *ProtocolManager) handleMsg(p *peer) error {
 			break
 		}
 		// Deliver them all to the downloader for queuing
-		err := pm.downloader.DeliverHashes61(p.id, hashes)
+		err := pm.downloader.DeliverHashes(p.id, hashes)
 		if err != nil {
 			glog.V(logger.Debug).Infoln(err)
 		}
@@ -353,7 +353,7 @@ func (pm *ProtocolManager) handleMsg(p *peer) error {
 		}
 		// Filter out any explicitly requested blocks, deliver the rest to the downloader
 		if blocks := pm.fetcher.FilterBlocks(blocks); len(blocks) > 0 {
-			pm.downloader.DeliverBlocks61(p.id, blocks)
+			pm.downloader.DeliverBlocks(p.id, blocks)
 		}
 
 	// Block header query, collect the requested headers and reply
@@ -515,6 +515,17 @@ func (pm *ProtocolManager) handleMsg(p *peer) error {
 		}
 		return p.SendNodeData(data)
 
+	case p.version >= eth63 && msg.Code == NodeDataMsg:
+		// A batch of node state data arrived to one of our previous requests
+		var data [][]byte
+		if err := msg.Decode(&data); err != nil {
+			return errResp(ErrDecode, "msg %v: %v", msg, err)
+		}
+		// Deliver all to the downloader
+		if err := pm.downloader.DeliverNodeData(p.id, data); err != nil {
+			glog.V(logger.Debug).Infof("failed to deliver node state data: %v", err)
+		}
+
 	case p.version >= eth63 && msg.Code == GetReceiptsMsg:
 		// Decode the retrieval message
 		msgStream := rlp.NewStream(msg.Payload, uint64(msg.Size))

eth/peer.go

@@ -191,7 +191,7 @@ func (p *peer) SendBlockBodiesRLP(bodies []rlp.RawValue) error {
 	return p2p.Send(p.rw, BlockBodiesMsg, bodies)
 }
 
-// SendNodeData sends a batch of arbitrary internal data, corresponding to the
+// SendNodeDataRLP sends a batch of arbitrary internal data, corresponding to the
 // hashes requested.
 func (p *peer) SendNodeData(data [][]byte) error {
 	return p2p.Send(p.rw, NodeDataMsg, data)

trie/sync.go

@@ -0,0 +1,233 @@
+// Copyright 2015 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package trie
+
+import (
+	"fmt"
+
+	"github.com/ethereum/go-ethereum/common"
+	"gopkg.in/karalabe/cookiejar.v2/collections/prque"
+)
+
+// request represents a scheduled or already in-flight state retrieval request.
+type request struct {
+	hash   common.Hash // Hash of the node data content to retrieve
+	data   []byte      // Data content of the node, cached until all subtrees complete
+	object *node       // Target node to populate with retrieved data (hashnode originally)
+
+	parents []*request // Parent state nodes referencing this entry (notify all upon completion)
+	depth   int        // Depth level within the trie the node is located to prioritize DFS
+	deps    int        // Number of dependencies before allowed to commit this node
+
+	callback TrieSyncLeafCallback // Callback to invoke if a leaf node it reached on this branch
+}
+
+// SyncResult is a simple list to return missing nodes along with their request
+// hashes.
+type SyncResult struct {
+	Hash common.Hash // Hash of the originally unknown trie node
+	Data []byte      // Data content of the retrieved node
+}
+
+// TrieSyncLeafCallback is a callback type invoked when a trie sync reaches a
+// leaf node. It's used by state syncing to check if the leaf node requires some
+// further data syncing.
+type TrieSyncLeafCallback func(leaf []byte, parent common.Hash) error
+
+// TrieSync is the main state trie synchronisation scheduler, which provides yet
+// unknown trie hashes to retrieve, accepts node data associated with said hashes
+// and reconstructs the trie steb by step until all is done.
+type TrieSync struct {
+	database Database                 // State database for storing all the assembled node data
+	requests map[common.Hash]*request // Pending requests pertaining to a key hash
+	queue    *prque.Prque             // Priority queue with the pending requests
+}
+
+// NewTrieSync creates a new trie data download scheduler.
+func NewTrieSync(root common.Hash, database Database, callback TrieSyncLeafCallback) *TrieSync {
+	ts := &TrieSync{
+		database: database,
+		requests: make(map[common.Hash]*request),
+		queue:    prque.New(),
+	}
+	ts.AddSubTrie(root, 0, common.Hash{}, callback)
+	return ts
+}
+
+// AddSubTrie registers a new trie to the sync code, rooted at the designated parent.
+func (s *TrieSync) AddSubTrie(root common.Hash, depth int, parent common.Hash, callback TrieSyncLeafCallback) {
+	// Short circuit if the trie is empty
+	if root == emptyRoot {
+		return
+	}
+	// Assemble the new sub-trie sync request
+	node := node(hashNode(root.Bytes()))
+	req := &request{
+		object:   &node,
+		hash:     root,
+		depth:    depth,
+		callback: callback,
+	}
+	// If this sub-trie has a designated parent, link them together
+	if parent != (common.Hash{}) {
+		ancestor := s.requests[parent]
+		if ancestor == nil {
+			panic(fmt.Sprintf("sub-trie ancestor not found: %x", parent))
+		}
+		ancestor.deps++
+		req.parents = append(req.parents, ancestor)
+	}
+	s.schedule(req)
+}
+
+// Missing retrieves the known missing nodes from the trie for retrieval.
+func (s *TrieSync) Missing(max int) []common.Hash {
+	requests := []common.Hash{}
+	for !s.queue.Empty() && (max == 0 || len(requests) < max) {
+		requests = append(requests, s.queue.PopItem().(common.Hash))
+	}
+	return requests
+}
+
+// Process injects a batch of retrieved trie nodes data.
+func (s *TrieSync) Process(results []SyncResult) (int, error) {
+	for i, item := range results {
+		// If the item was not requested, bail out
+		request := s.requests[item.Hash]
+		if request == nil {
+			return i, fmt.Errorf("not requested: %x", item.Hash)
+		}
+		// Decode the node data content and update the request
+		node, err := decodeNode(item.Data)
+		if err != nil {
+			return i, err
+		}
+		*request.object = node
+		request.data = item.Data
+
+		// Create and schedule a request for all the children nodes
+		requests, err := s.children(request)
+		if err != nil {
+			return i, err
+		}
+		if len(requests) == 0 && request.deps == 0 {
+			s.commit(request)
+			continue
+		}
+		request.deps += len(requests)
+		for _, child := range requests {
+			s.schedule(child)
+		}
+	}
+	return 0, nil
+}
+
+// schedule inserts a new state retrieval request into the fetch queue. If there
+// is already a pending request for this node, the new request will be discarded
+// and only a parent reference added to the old one.
+func (s *TrieSync) schedule(req *request) {
+	// If we're already requesting this node, add a new reference and stop
+	if old, ok := s.requests[req.hash]; ok {
+		old.parents = append(old.parents, req.parents...)
+		return
+	}
+	// Schedule the request for future retrieval
+	s.queue.Push(req.hash, float32(req.depth))
+	s.requests[req.hash] = req
+}
+
+// children retrieves all the missing children of a state trie entry for future
+// retrieval scheduling.
+func (s *TrieSync) children(req *request) ([]*request, error) {
+	// Gather all the children of the node, irrelevant whether known or not
+	type child struct {
+		node  *node
+		depth int
+	}
+	children := []child{}
+
+	switch node := (*req.object).(type) {
+	case shortNode:
+		children = []child{{
+			node:  &node.Val,
+			depth: req.depth + len(node.Key),
+		}}
+	case fullNode:
+		for i := 0; i < 17; i++ {
+			if node[i] != nil {
+				children = append(children, child{
+					node:  &node[i],
+					depth: req.depth + 1,
+				})
+			}
+		}
+	default:
+		panic(fmt.Sprintf("unknown node: %+v", node))
+	}
+	// Iterate over the children, and request all unknown ones
+	requests := make([]*request, 0, len(children))
+	for _, child := range children {
+		// Notify any external watcher of a new key/value node
+		if req.callback != nil {
+			if node, ok := (*child.node).(valueNode); ok {
+				if err := req.callback(node, req.hash); err != nil {
+					return nil, err
+				}
+			}
+		}
+		// If the child references another node, resolve or schedule
+		if node, ok := (*child.node).(hashNode); ok {
+			// Try to resolve the node from the local database
+			blob, _ := s.database.Get(node)
+			if local, err := decodeNode(blob); local != nil && err == nil {
+				*child.node = local
+				continue
+			}
+			// Locally unknown node, schedule for retrieval
+			requests = append(requests, &request{
+				object:   child.node,
+				hash:     common.BytesToHash(node),
+				parents:  []*request{req},
+				depth:    child.depth,
+				callback: req.callback,
+			})
+		}
+	}
+	return requests, nil
+}
+
+// commit finalizes a retrieval request and stores it into the database. If any
+// of the referencing parent requests complete due to this commit, they are also
+// committed themselves.
+func (s *TrieSync) commit(req *request) error {
+	// Write the node content to disk
+	if err := s.database.Put(req.hash[:], req.data); err != nil {
+		return err
+	}
+	delete(s.requests, req.hash)
+
+	// Check all parents for completion
+	for _, parent := range req.parents {
+		parent.deps--
+		if parent.deps == 0 {
+			if err := s.commit(parent); err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}

trie/sync_test.go

@@ -0,0 +1,257 @@
+// Copyright 2015 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package trie
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/ethdb"
+)
+
+// makeTestTrie create a sample test trie to test node-wise reconstruction.
+func makeTestTrie() (ethdb.Database, *Trie, map[string][]byte) {
+	// Create an empty trie
+	db, _ := ethdb.NewMemDatabase()
+	trie, _ := New(common.Hash{}, db)
+
+	// Fill it with some arbitrary data
+	content := make(map[string][]byte)
+	for i := byte(0); i < 255; i++ {
+		key, val := common.LeftPadBytes([]byte{1, i}, 32), []byte{i}
+		content[string(key)] = val
+		trie.Update(key, val)
+
+		key, val = common.LeftPadBytes([]byte{2, i}, 32), []byte{i}
+		content[string(key)] = val
+		trie.Update(key, val)
+	}
+	trie.Commit()
+
+	// Return the generated trie
+	return db, trie, content
+}
+
+// checkTrieContents cross references a reconstructed trie with an expected data
+// content map.
+func checkTrieContents(t *testing.T, db Database, root []byte, content map[string][]byte) {
+	trie, err := New(common.BytesToHash(root), db)
+	if err != nil {
+		t.Fatalf("failed to create trie at %x: %v", root, err)
+	}
+	for key, val := range content {
+		if have := trie.Get([]byte(key)); bytes.Compare(have, val) != 0 {
+			t.Errorf("entry %x: content mismatch: have %x, want %x", key, have, val)
+		}
+	}
+}
+
+// Tests that an empty trie is not scheduled for syncing.
+func TestEmptyTrieSync(t *testing.T) {
+	emptyA, _ := New(common.Hash{}, nil)
+	emptyB, _ := New(emptyRoot, nil)
+
+	for i, trie := range []*Trie{emptyA, emptyB} {
+		db, _ := ethdb.NewMemDatabase()
+		if req := NewTrieSync(common.BytesToHash(trie.Root()), db, nil).Missing(1); len(req) != 0 {
+			t.Errorf("test %d: content requested for empty trie: %v", i, req)
+		}
+	}
+}
+
+// Tests that given a root hash, a trie can sync iteratively on a single thread,
+// requesting retrieval tasks and returning all of them in one go.
+func TestIterativeTrieSyncIndividual(t *testing.T) { testIterativeTrieSync(t, 1) }
+func TestIterativeTrieSyncBatched(t *testing.T)    { testIterativeTrieSync(t, 100) }
+
+func testIterativeTrieSync(t *testing.T, batch int) {
+	// Create a random trie to copy
+	srcDb, srcTrie, srcData := makeTestTrie()
+
+	// Create a destination trie and sync with the scheduler
+	dstDb, _ := ethdb.NewMemDatabase()
+	sched := NewTrieSync(common.BytesToHash(srcTrie.Root()), dstDb, nil)
+
+	queue := append([]common.Hash{}, sched.Missing(batch)...)
+	for len(queue) > 0 {
+		results := make([]SyncResult, len(queue))
+		for i, hash := range queue {
+			data, err := srcDb.Get(hash.Bytes())
+			if err != nil {
+				t.Fatalf("failed to retrieve node data for %x: %v", hash, err)
+			}
+			results[i] = SyncResult{hash, data}
+		}
+		if index, err := sched.Process(results); err != nil {
+			t.Fatalf("failed to process result #%d: %v", index, err)
+		}
+		queue = append(queue[:0], sched.Missing(batch)...)
+	}
+	// Cross check that the two tries re in sync
+	checkTrieContents(t, dstDb, srcTrie.Root(), srcData)
+}
+
+// Tests that the trie scheduler can correctly reconstruct the state even if only
+// partial results are returned, and the others sent only later.
+func TestIterativeDelayedTrieSync(t *testing.T) {
+	// Create a random trie to copy
+	srcDb, srcTrie, srcData := makeTestTrie()
+
+	// Create a destination trie and sync with the scheduler
+	dstDb, _ := ethdb.NewMemDatabase()
+	sched := NewTrieSync(common.BytesToHash(srcTrie.Root()), dstDb, nil)
+
+	queue := append([]common.Hash{}, sched.Missing(10000)...)
+	for len(queue) > 0 {
+		// Sync only half of the scheduled nodes
+		results := make([]SyncResult, len(queue)/2+1)
+		for i, hash := range queue[:len(results)] {
+			data, err := srcDb.Get(hash.Bytes())
+			if err != nil {
+				t.Fatalf("failed to retrieve node data for %x: %v", hash, err)
+			}
+			results[i] = SyncResult{hash, data}
+		}
+		if index, err := sched.Process(results); err != nil {
+			t.Fatalf("failed to process result #%d: %v", index, err)
+		}
+		queue = append(queue[len(results):], sched.Missing(10000)...)
+	}
+	// Cross check that the two tries re in sync
+	checkTrieContents(t, dstDb, srcTrie.Root(), srcData)
+}
+
+// Tests that given a root hash, a trie can sync iteratively on a single thread,
+// requesting retrieval tasks and returning all of them in one go, however in a
+// random order.
+func TestIterativeRandomTrieSyncIndividual(t *testing.T) { testIterativeRandomTrieSync(t, 1) }
+func TestIterativeRandomTrieSyncBatched(t *testing.T)    { testIterativeRandomTrieSync(t, 100) }
+
+func testIterativeRandomTrieSync(t *testing.T, batch int) {
+	// Create a random trie to copy
+	srcDb, srcTrie, srcData := makeTestTrie()
+
+	// Create a destination trie and sync with the scheduler
+	dstDb, _ := ethdb.NewMemDatabase()
+	sched := NewTrieSync(common.BytesToHash(srcTrie.Root()), dstDb, nil)
+
+	queue := make(map[common.Hash]struct{})
+	for _, hash := range sched.Missing(batch) {
+		queue[hash] = struct{}{}
+	}
+	for len(queue) > 0 {
+		// Fetch all the queued nodes in a random order
+		results := make([]SyncResult, 0, len(queue))
+		for hash, _ := range queue {
+			data, err := srcDb.Get(hash.Bytes())
+			if err != nil {
+				t.Fatalf("failed to retrieve node data for %x: %v", hash, err)
+			}
+			results = append(results, SyncResult{hash, data})
+		}
+		// Feed the retrieved results back and queue new tasks
+		if index, err := sched.Process(results); err != nil {
+			t.Fatalf("failed to process result #%d: %v", index, err)
+		}
+		queue = make(map[common.Hash]struct{})
+		for _, hash := range sched.Missing(batch) {
+			queue[hash] = struct{}{}
+		}
+	}
+	// Cross check that the two tries re in sync
+	checkTrieContents(t, dstDb, srcTrie.Root(), srcData)
+}
+
+// Tests that the trie scheduler can correctly reconstruct the state even if only
+// partial results are returned (Even those randomly), others sent only later.
+func TestIterativeRandomDelayedTrieSync(t *testing.T) {
+	// Create a random trie to copy
+	srcDb, srcTrie, srcData := makeTestTrie()
+
+	// Create a destination trie and sync with the scheduler
+	dstDb, _ := ethdb.NewMemDatabase()
+	sched := NewTrieSync(common.BytesToHash(srcTrie.Root()), dstDb, nil)
+
+	queue := make(map[common.Hash]struct{})
+	for _, hash := range sched.Missing(10000) {
+		queue[hash] = struct{}{}
+	}
+	for len(queue) > 0 {
+		// Sync only half of the scheduled nodes, even those in random order
+		results := make([]SyncResult, 0, len(queue)/2+1)
+		for hash, _ := range queue {
+			data, err := srcDb.Get(hash.Bytes())
+			if err != nil {
+				t.Fatalf("failed to retrieve node data for %x: %v", hash, err)
+			}
+			results = append(results, SyncResult{hash, data})
+
+			if len(results) >= cap(results) {
+				break
+			}
+		}
+		// Feed the retrieved results back and queue new tasks
+		if index, err := sched.Process(results); err != nil {
+			t.Fatalf("failed to process result #%d: %v", index, err)
+		}
+		for _, result := range results {
+			delete(queue, result.Hash)
+		}
+		for _, hash := range sched.Missing(10000) {
+			queue[hash] = struct{}{}
+		}
+	}
+	// Cross check that the two tries re in sync
+	checkTrieContents(t, dstDb, srcTrie.Root(), srcData)
+}
+
+// Tests that a trie sync will not request nodes multiple times, even if they
+// have such references.
+func TestDuplicateAvoidanceTrieSync(t *testing.T) {
+	// Create a random trie to copy
+	srcDb, srcTrie, srcData := makeTestTrie()
+
+	// Create a destination trie and sync with the scheduler
+	dstDb, _ := ethdb.NewMemDatabase()
+	sched := NewTrieSync(common.BytesToHash(srcTrie.Root()), dstDb, nil)
+
+	queue := append([]common.Hash{}, sched.Missing(0)...)
+	requested := make(map[common.Hash]struct{})
+
+	for len(queue) > 0 {
+		results := make([]SyncResult, len(queue))
+		for i, hash := range queue {
+			data, err := srcDb.Get(hash.Bytes())
+			if err != nil {
+				t.Fatalf("failed to retrieve node data for %x: %v", hash, err)
+			}
+			if _, ok := requested[hash]; ok {
+				t.Errorf("hash %x already requested once", hash)
+			}
+			requested[hash] = struct{}{}
+
+			results[i] = SyncResult{hash, data}
+		}
+		if index, err := sched.Process(results); err != nil {
+			t.Fatalf("failed to process result #%d: %v", index, err)
+		}
+		queue = append(queue[:0], sched.Missing(0)...)
+	}
+	// Cross check that the two tries re in sync
+	checkTrieContents(t, dstDb, srcTrie.Root(), srcData)
+}