diff --git a/eth/downloader/downloader.go b/eth/downloader/downloader.go
index f6dbb4610f5d8cdb5e8d7b8ec1565170548c2b45..0bc8b4acf1440f8823099e77f4abcfd75a612a9e 100644
--- a/eth/downloader/downloader.go
+++ b/eth/downloader/downloader.go
@@ -73,6 +73,7 @@ var (
fsHeaderForceVerify = 24 // Number of headers to verify before and after the pivot to accept it
fsPivotInterval = 512 // Number of headers out of which to randomize the pivot point
fsMinFullBlocks = 1024 // Number of blocks to retrieve fully even in fast sync
+ fsCriticalTrials = 10 // Number of times to retry in the cricical section before bailing
)
var (
@@ -103,13 +104,15 @@ var (
)
type Downloader struct {
- mode SyncMode // Synchronisation mode defining the strategy used (per sync cycle)
- noFast bool // Flag to disable fast syncing in case of a security error
- mux *event.TypeMux // Event multiplexer to announce sync operation events
+ mode SyncMode // Synchronisation mode defining the strategy used (per sync cycle)
+ mux *event.TypeMux // Event multiplexer to announce sync operation events
queue *queue // Scheduler for selecting the hashes to download
peers *peerSet // Set of active peers from which download can proceed
+ fsPivotLock *types.Header // Pivot header on critical section entry (cannot change between retries)
+ fsPivotFails int // Number of fast sync failures in the critical section
+
interrupt int32 // Atomic boolean to signal termination
// Statistics
@@ -314,6 +317,15 @@ func (d *Downloader) synchronise(id string, hash common.Hash, td *big.Int, mode
default:
}
}
+ for _, ch := range []chan dataPack{d.hashCh, d.blockCh, d.headerCh, d.bodyCh, d.receiptCh, d.stateCh} {
+ for empty := false; !empty; {
+ select {
+ case <-ch:
+ default:
+ empty = true
+ }
+ }
+ }
for empty := false; !empty; {
select {
case <-d.headerProcCh:
@@ -330,7 +342,7 @@ func (d *Downloader) synchronise(id string, hash common.Hash, td *big.Int, mode
// Set the requested sync mode, unless it's forbidden
d.mode = mode
- if d.mode == FastSync && d.noFast {
+ if d.mode == FastSync && d.fsPivotFails >= fsCriticalTrials {
d.mode = FullSync
}
// Retrieve the origin peer and initiate the downloading process
@@ -413,12 +425,17 @@ func (d *Downloader) syncWithPeer(p *peer, hash common.Hash, td *big.Int) (err e
pivot = height
case FastSync:
// Calculate the new fast/slow sync pivot point
- pivotOffset, err := rand.Int(rand.Reader, big.NewInt(int64(fsPivotInterval)))
- if err != nil {
- panic(fmt.Sprintf("Failed to access crypto random source: %v", err))
- }
- if height > uint64(fsMinFullBlocks)+pivotOffset.Uint64() {
- pivot = height - uint64(fsMinFullBlocks) - pivotOffset.Uint64()
+ if d.fsPivotLock == nil {
+ pivotOffset, err := rand.Int(rand.Reader, big.NewInt(int64(fsPivotInterval)))
+ if err != nil {
+ panic(fmt.Sprintf("Failed to access crypto random source: %v", err))
+ }
+ if height > uint64(fsMinFullBlocks)+pivotOffset.Uint64() {
+ pivot = height - uint64(fsMinFullBlocks) - pivotOffset.Uint64()
+ }
+ } else {
+ // Pivot point locked in, use this and do not pick a new one!
+ pivot = d.fsPivotLock.Number.Uint64()
}
// If the point is below the origin, move origin back to ensure state download
if pivot < origin {
@@ -1218,8 +1235,12 @@ func (d *Downloader) fetchHeaders(p *peer, from uint64) error {
// If no more headers are inbound, notify the content fetchers and return
if packet.Items() == 0 {
glog.V(logger.Debug).Infof("%v: no available headers", p)
- d.headerProcCh <- nil
- return nil
+ select {
+ case d.headerProcCh <- nil:
+ return nil
+ case <-d.cancelCh:
+ return errCancelHeaderFetch
+ }
}
headers := packet.(*headerPack).headers
@@ -1611,9 +1632,18 @@ func (d *Downloader) processHeaders(origin uint64, td *big.Int) error {
glog.V(logger.Warn).Infof("Rolled back %d headers (LH: %d->%d, FB: %d->%d, LB: %d->%d)",
len(hashes), lastHeader, d.headHeader().Number, lastFastBlock, d.headFastBlock().Number(), lastBlock, d.headBlock().Number())
- // If we're already past the pivot point, this could be an attack, disable fast sync
+ // If we're already past the pivot point, this could be an attack, thread carefully
if rollback[len(rollback)-1].Number.Uint64() > pivot {
- d.noFast = true
+ // If we didn't ever fail, lock in te pivot header (must! not! change!)
+ if d.fsPivotFails == 0 {
+ for _, header := range rollback {
+ if header.Number.Uint64() == pivot {
+ glog.V(logger.Warn).Infof("Fast-sync critical section failure, locked pivot to header #%d [%x…]", pivot, header.Hash().Bytes()[:4])
+ d.fsPivotLock = header
+ }
+ }
+ }
+ d.fsPivotFails++
}
}
}()
@@ -1712,6 +1742,13 @@ func (d *Downloader) processHeaders(origin uint64, td *big.Int) error {
rollback = append(rollback[:0], rollback[len(rollback)-fsHeaderSafetyNet:]...)
}
}
+ // If we're fast syncing and just pulled in the pivot, make sure it's the one locked in
+ if d.mode == FastSync && d.fsPivotLock != nil && chunk[0].Number.Uint64() <= pivot && chunk[len(chunk)-1].Number.Uint64() >= pivot {
+ if pivot := chunk[int(pivot-chunk[0].Number.Uint64())]; pivot.Hash() != d.fsPivotLock.Hash() {
+ glog.V(logger.Warn).Infof("Pivot doesn't match locked in version: have #%v [%x…], want #%v [%x…]", pivot.Number, pivot.Hash().Bytes()[:4], d.fsPivotLock.Number, d.fsPivotLock.Hash().Bytes()[:4])
+ return errInvalidChain
+ }
+ }
// Unless we're doing light chains, schedule the headers for associated content retrieval
if d.mode == FullSync || d.mode == FastSync {
// If we've reached the allowed number of pending headers, stall a bit
diff --git a/eth/downloader/downloader_test.go b/eth/downloader/downloader_test.go
index 1cf0e7cd31913f42f7a03c94f2a4271ead3de6e4..f3a0e38f1ae506ef88220d29ad8d9b58c2e6122e 100644
--- a/eth/downloader/downloader_test.go
+++ b/eth/downloader/downloader_test.go
@@ -149,22 +149,25 @@ type downloadTester struct {
peerReceipts map[string]map[common.Hash]types.Receipts // Receipts belonging to different test peers
peerChainTds map[string]map[common.Hash]*big.Int // Total difficulties of the blocks in the peer chains
+ peerMissingStates map[string]map[common.Hash]bool // State entries that fast sync should not return
+
lock sync.RWMutex
}
// newTester creates a new downloader test mocker.
func newTester() *downloadTester {
tester := &downloadTester{
- ownHashes: []common.Hash{genesis.Hash()},
- ownHeaders: map[common.Hash]*types.Header{genesis.Hash(): genesis.Header()},
- ownBlocks: map[common.Hash]*types.Block{genesis.Hash(): genesis},
- ownReceipts: map[common.Hash]types.Receipts{genesis.Hash(): nil},
- ownChainTd: map[common.Hash]*big.Int{genesis.Hash(): genesis.Difficulty()},
- peerHashes: make(map[string][]common.Hash),
- peerHeaders: make(map[string]map[common.Hash]*types.Header),
- peerBlocks: make(map[string]map[common.Hash]*types.Block),
- peerReceipts: make(map[string]map[common.Hash]types.Receipts),
- peerChainTds: make(map[string]map[common.Hash]*big.Int),
+ ownHashes: []common.Hash{genesis.Hash()},
+ ownHeaders: map[common.Hash]*types.Header{genesis.Hash(): genesis.Header()},
+ ownBlocks: map[common.Hash]*types.Block{genesis.Hash(): genesis},
+ ownReceipts: map[common.Hash]types.Receipts{genesis.Hash(): nil},
+ ownChainTd: map[common.Hash]*big.Int{genesis.Hash(): genesis.Difficulty()},
+ peerHashes: make(map[string][]common.Hash),
+ peerHeaders: make(map[string]map[common.Hash]*types.Header),
+ peerBlocks: make(map[string]map[common.Hash]*types.Block),
+ peerReceipts: make(map[string]map[common.Hash]types.Receipts),
+ peerChainTds: make(map[string]map[common.Hash]*big.Int),
+ peerMissingStates: make(map[string]map[common.Hash]bool),
}
tester.stateDb, _ = ethdb.NewMemDatabase()
tester.stateDb.Put(genesis.Root().Bytes(), []byte{0x00})
@@ -408,6 +411,7 @@ func (dl *downloadTester) newSlowPeer(id string, version int, hashes []common.Ha
dl.peerBlocks[id] = make(map[common.Hash]*types.Block)
dl.peerReceipts[id] = make(map[common.Hash]types.Receipts)
dl.peerChainTds[id] = make(map[common.Hash]*big.Int)
+ dl.peerMissingStates[id] = make(map[common.Hash]bool)
genesis := hashes[len(hashes)-1]
if header := headers[genesis]; header != nil {
@@ -648,7 +652,9 @@ func (dl *downloadTester) peerGetNodeDataFn(id string, delay time.Duration) func
results := make([][]byte, 0, len(hashes))
for _, hash := range hashes {
if data, err := testdb.Get(hash.Bytes()); err == nil {
- results = append(results, data)
+ if !dl.peerMissingStates[id][hash] {
+ results = append(results, data)
+ }
}
}
go dl.downloader.DeliverNodeData(id, results)
@@ -1288,7 +1294,7 @@ func testInvalidHeaderRollback(t *testing.T, protocol int, mode SyncMode) {
tester.newPeer("withhold-attack", protocol, hashes, headers, blocks, receipts)
missing = 3*fsHeaderSafetyNet + MaxHeaderFetch + 1
- tester.downloader.noFast = false
+ tester.downloader.fsPivotFails = 0
tester.downloader.syncInitHook = func(uint64, uint64) {
for i := missing; i <= len(hashes); i++ {
delete(tester.peerHeaders["withhold-attack"], hashes[len(hashes)-i])
@@ -1307,6 +1313,8 @@ func testInvalidHeaderRollback(t *testing.T, protocol int, mode SyncMode) {
t.Errorf("fast sync pivot block #%d not rolled back", head)
}
}
+ tester.downloader.fsPivotFails = fsCriticalTrials
+
// Synchronise with the valid peer and make sure sync succeeds. Since the last
// rollback should also disable fast syncing for this process, verify that we
// did a fresh full sync. Note, we can't assert anything about the receipts
@@ -1749,3 +1757,41 @@ func testDeliverHeadersHang(t *testing.T, protocol int, mode SyncMode) {
}
}
}
+
+// Tests that if fast sync aborts in the critical section, it can restart a few
+// times before giving up.
+func TestFastCriticalRestarts63(t *testing.T) { testFastCriticalRestarts(t, 63) }
+func TestFastCriticalRestarts64(t *testing.T) { testFastCriticalRestarts(t, 64) }
+
+func testFastCriticalRestarts(t *testing.T, protocol int) {
+ t.Parallel()
+
+ // Create a large enough blockchin to actually fast sync on
+ targetBlocks := fsMinFullBlocks + 2*fsPivotInterval - 15
+ hashes, headers, blocks, receipts := makeChain(targetBlocks, 0, genesis, nil, false)
+
+ // Create a tester peer with the critical section state roots missing (force failures)
+ tester := newTester()
+ tester.newPeer("peer", protocol, hashes, headers, blocks, receipts)
+
+ for i := 0; i < fsPivotInterval; i++ {
+ tester.peerMissingStates["peer"][headers[hashes[fsMinFullBlocks+i]].Root] = true
+ }
+ // Synchronise with the peer a few times and make sure they fail until the retry limit
+ for i := 0; i < fsCriticalTrials; i++ {
+ // Attempt a sync and ensure it fails properly
+ if err := tester.sync("peer", nil, FastSync); err == nil {
+ t.Fatalf("failing fast sync succeeded: %v", err)
+ }
+ // If it's the first failure, pivot should be locked => reenable all others to detect pivot changes
+ if i == 0 {
+ tester.peerMissingStates["peer"] = map[common.Hash]bool{tester.downloader.fsPivotLock.Root: true}
+ }
+ time.Sleep(100 * time.Millisecond) // Make sure no in-flight requests remain
+ }
+ // Retry limit exhausted, downloader will switch to full sync, should succeed
+ if err := tester.sync("peer", nil, FastSync); err != nil {
+ t.Fatalf("failed to synchronise blocks in slow sync: %v", err)
+ }
+ assertOwnChain(t, tester, targetBlocks+1)
+}