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core, eth: roll back uncertain headers in failed fast syncs

This commit is contained in:
Péter Szilágyi 2015-10-09 16:21:47 +03:00
parent b97e34a8e4
commit a9d8dfc8e7
6 changed files with 180 additions and 15 deletions
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37
core/blockchain.go
View File

@ -245,7 +245,21 @@ func (bc *BlockChain) SetHead(head uint64) {
if bc.currentBlock == nil {
bc.currentBlock = bc.genesisBlock
}
bc.insert(bc.currentBlock)
if bc.currentHeader == nil {
bc.currentHeader = bc.genesisBlock.Header()
}
if bc.currentFastBlock == nil {
bc.currentFastBlock = bc.genesisBlock
}
if err := WriteHeadBlockHash(bc.chainDb, bc.currentBlock.Hash()); err != nil {
glog.Fatalf("failed to reset head block hash: %v", err)
}
if err := WriteHeadHeaderHash(bc.chainDb, bc.currentHeader.Hash()); err != nil {
glog.Fatalf("failed to reset head header hash: %v", err)
}
if err := WriteHeadFastBlockHash(bc.chainDb, bc.currentFastBlock.Hash()); err != nil {
glog.Fatalf("failed to reset head fast block hash: %v", err)
}
bc.loadLastState()
}
@ -790,6 +804,27 @@ func (self *BlockChain) InsertHeaderChain(chain []*types.Header, checkFreq int)
return 0, nil
}
// Rollback is designed to remove a chain of links from the database that aren't
// certain enough to be valid.
func (self *BlockChain) Rollback(chain []common.Hash) {
for i := len(chain) - 1; i >= 0; i-- {
hash := chain[i]
if self.currentHeader.Hash() == hash {
self.currentHeader = self.GetHeader(self.currentHeader.ParentHash)
WriteHeadHeaderHash(self.chainDb, self.currentHeader.Hash())
}
if self.currentFastBlock.Hash() == hash {
self.currentFastBlock = self.GetBlock(self.currentFastBlock.ParentHash())
WriteHeadFastBlockHash(self.chainDb, self.currentFastBlock.Hash())
}
if self.currentBlock.Hash() == hash {
self.currentBlock = self.GetBlock(self.currentBlock.ParentHash())
WriteHeadBlockHash(self.chainDb, self.currentBlock.Hash())
}
}
}
// InsertReceiptChain attempts to complete an already existing header chain with
// transaction and receipt data.
func (self *BlockChain) InsertReceiptChain(blockChain types.Blocks, receiptChain []types.Receipts) (int, error) {

15
core/blockchain_test.go
View File

@ -599,8 +599,8 @@ func testReorgBadHashes(t *testing.T, full bool) {
t.Errorf("last block gasLimit mismatch: have: %x, want %x", ncm.GasLimit(), blocks[2].Header().GasLimit)
}
} else {
if ncm.CurrentHeader().Hash() != genesis.Hash() {
t.Errorf("last header hash mismatch: have: %x, want %x", ncm.CurrentHeader().Hash(), genesis.Hash())
if ncm.CurrentHeader().Hash() != headers[2].Hash() {
t.Errorf("last header hash mismatch: have: %x, want %x", ncm.CurrentHeader().Hash(), headers[2].Hash())
}
}
}
@ -775,6 +775,11 @@ func TestLightVsFastVsFullChainHeads(t *testing.T) {
height := uint64(1024)
blocks, receipts := GenerateChain(genesis, gendb, int(height), nil)
// Configure a subchain to roll back
remove := []common.Hash{}
for _, block := range blocks[height/2:] {
remove = append(remove, block.Hash())
}
// Create a small assertion method to check the three heads
assert := func(t *testing.T, kind string, chain *BlockChain, header uint64, fast uint64, block uint64) {
if num := chain.CurrentBlock().NumberU64(); num != block {
@ -798,6 +803,8 @@ func TestLightVsFastVsFullChainHeads(t *testing.T) {
t.Fatalf("failed to process block %d: %v", n, err)
}
assert(t, "archive", archive, height, height, height)
archive.Rollback(remove)
assert(t, "archive", archive, height/2, height/2, height/2)
// Import the chain as a non-archive node and ensure all pointers are updated
fastDb, _ := ethdb.NewMemDatabase()
@ -816,6 +823,8 @@ func TestLightVsFastVsFullChainHeads(t *testing.T) {
t.Fatalf("failed to insert receipt %d: %v", n, err)
}
assert(t, "fast", fast, height, height, 0)
fast.Rollback(remove)
assert(t, "fast", fast, height/2, height/2, 0)
// Import the chain as a light node and ensure all pointers are updated
lightDb, _ := ethdb.NewMemDatabase()
@ -827,6 +836,8 @@ func TestLightVsFastVsFullChainHeads(t *testing.T) {
t.Fatalf("failed to insert header %d: %v", n, err)
}
assert(t, "light", light, height, 0, 0)
light.Rollback(remove)
assert(t, "light", light, height/2, 0, 0)
}
// Tests that chain reorganizations handle transaction removals and reinsertions.

60
eth/downloader/downloader.go
View File

@ -59,8 +59,8 @@ var (
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
minCheckedHeaders = 1024 // Number of headers to verify fully when approaching the chain head
headerCheckFrequency = 100 // Verification frequency of the downloaded headers during fast sync
minCheckedHeaders = 2048 // Number of headers to verify fully when approaching the chain head
minFullBlocks = 1024 // Number of blocks to retrieve fully even in fast sync
)
@ -117,6 +117,7 @@ type Downloader struct {
insertHeaders headerChainInsertFn // Injects a batch of headers into the chain
insertBlocks blockChainInsertFn // Injects a batch of blocks into the chain
insertReceipts receiptChainInsertFn // Injects a batch of blocks and their receipts into the chain
rollback chainRollbackFn // Removes a batch of recently added chain links
dropPeer peerDropFn // Drops a peer for misbehaving
// Status
@ -152,7 +153,7 @@ type Downloader struct {
func New(mode SyncMode, stateDb ethdb.Database, mux *event.TypeMux, hasHeader headerCheckFn, hasBlock blockCheckFn, getHeader headerRetrievalFn,
getBlock blockRetrievalFn, headHeader headHeaderRetrievalFn, headBlock headBlockRetrievalFn, headFastBlock headFastBlockRetrievalFn,
commitHeadBlock headBlockCommitterFn, getTd tdRetrievalFn, insertHeaders headerChainInsertFn, insertBlocks blockChainInsertFn,
insertReceipts receiptChainInsertFn, dropPeer peerDropFn) *Downloader {
insertReceipts receiptChainInsertFn, rollback chainRollbackFn, dropPeer peerDropFn) *Downloader {
return &Downloader{
mode: mode,
@ -171,6 +172,7 @@ func New(mode SyncMode, stateDb ethdb.Database, mux *event.TypeMux, hasHeader he
insertHeaders: insertHeaders,
insertBlocks: insertBlocks,
insertReceipts: insertReceipts,
rollback: rollback,
dropPeer: dropPeer,
newPeerCh: make(chan *peer, 1),
hashCh: make(chan dataPack, 1),
@ -383,7 +385,7 @@ func (d *Downloader) syncWithPeer(p *peer, hash common.Hash, td *big.Int) (err e
d.syncStatsChainHeight = latest
d.syncStatsLock.Unlock()
// Initiate the sync using a concurrent header and content retrieval algorithm
// Initiate the sync using a concurrent header and content retrieval algorithm
pivot := uint64(0)
if latest > uint64(minFullBlocks) {
pivot = latest - uint64(minFullBlocks)
@ -394,10 +396,10 @@ func (d *Downloader) syncWithPeer(p *peer, hash common.Hash, td *big.Int) (err e
d.syncInitHook(origin, latest)
}
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.fetchNodeData() }() // Node state data is retrieved during fast sync
go func() { errc <- d.fetchHeaders(p, td, origin+1, latest) }() // 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.fetchNodeData() }() // Node state data is retrieved during fast sync
// If any fetcher fails, cancel the others
var fail error
@ -1049,10 +1051,28 @@ func (d *Downloader) findAncestor(p *peer) (uint64, error) {
//
// The queue parameter can be used to switch between queuing headers for block
// body download too, or directly import as pure header chains.
func (d *Downloader) fetchHeaders(p *peer, td *big.Int, from uint64) error {
func (d *Downloader) fetchHeaders(p *peer, td *big.Int, from, latest uint64) error {
glog.V(logger.Debug).Infof("%v: downloading headers from #%d", p, from)
defer glog.V(logger.Debug).Infof("%v: header download terminated", p)
// Keep a count of uncertain headers to roll back
rollback := []*types.Header{}
defer func() {
if len(rollback) > 0 {
hashes := make([]common.Hash, len(rollback))
for i, header := range rollback {
hashes[i] = header.Hash()
}
d.rollback(hashes)
}
}()
// Calculate the pivoting point for switching from fast to slow sync
pivot := uint64(0)
if d.mode == FastSync && latest > uint64(minFullBlocks) {
pivot = latest - uint64(minFullBlocks)
} else if d.mode == LightSync {
pivot = latest
}
// Create a timeout timer, and the associated hash fetcher
request := time.Now() // time of the last fetch request
timeout := time.NewTimer(0) // timer to dump a non-responsive active peer
@ -1124,10 +1144,30 @@ func (d *Downloader) fetchHeaders(p *peer, td *big.Int, from uint64) error {
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(headers, headerCheckFrequency); err != nil {
// Collect the yet unknown headers to mark them as uncertain
unknown := make([]*types.Header, 0, len(headers))
for _, header := range headers {
if !d.hasHeader(header.Hash()) {
unknown = append(unknown, header)
}
}
// If we're importing pure headers, verify based on their recentness
frequency := headerCheckFrequency
if headers[len(headers)-1].Number.Uint64()+uint64(minCheckedHeaders) > pivot {
frequency = 1
}
if n, err := d.insertHeaders(headers, frequency); err != nil {
glog.V(logger.Debug).Infof("%v: invalid header #%d [%x…]: %v", p, headers[n].Number, headers[n].Hash().Bytes()[:4], err)
return errInvalidChain
}
// All verifications passed, store newly found uncertain headers
rollback = append(rollback, unknown...)
if len(rollback) > minCheckedHeaders {
rollback = append(rollback[:0], rollback[len(rollback)-minCheckedHeaders:]...)
}
if headers[len(headers)-1].Number.Uint64() >= pivot {
rollback = rollback[:0]
}
}
if d.mode == FullSync || d.mode == FastSync {
inserts := d.queue.Schedule(headers, from)

78
eth/downloader/downloader_test.go
View File

@ -152,7 +152,7 @@ func newTester(mode SyncMode) *downloadTester {
tester.stateDb, _ = ethdb.NewMemDatabase()
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)
tester.insertHeaders, tester.insertBlocks, tester.insertReceipts, tester.rollback, tester.dropPeer)
return tester
}
@ -272,6 +272,16 @@ func (dl *downloadTester) insertHeaders(headers []*types.Header, checkFreq int)
dl.lock.Lock()
defer dl.lock.Unlock()
// Do a quick check, as the blockchain.InsertHeaderChain doesn't insert anthing in case of errors
if _, ok := dl.ownHeaders[headers[0].ParentHash]; !ok {
return 0, errors.New("unknown parent")
}
for i := 1; i < len(headers); i++ {
if headers[i].ParentHash != headers[i-1].Hash() {
return i, errors.New("unknown parent")
}
}
// Do a full insert if pre-checks passed
for i, header := range headers {
if _, ok := dl.ownHeaders[header.Hash()]; ok {
continue
@ -322,6 +332,22 @@ func (dl *downloadTester) insertReceipts(blocks types.Blocks, receipts []types.R
return len(blocks), nil
}
// rollback removes some recently added elements from the chain.
func (dl *downloadTester) rollback(hashes []common.Hash) {
dl.lock.Lock()
defer dl.lock.Unlock()
for i := len(hashes) - 1; i >= 0; i-- {
if dl.ownHashes[len(dl.ownHashes)-1] == hashes[i] {
dl.ownHashes = dl.ownHashes[:len(dl.ownHashes)-1]
}
delete(dl.ownChainTd, hashes[i])
delete(dl.ownHeaders, hashes[i])
delete(dl.ownReceipts, hashes[i])
delete(dl.ownBlocks, hashes[i])
}
}
// newPeer registers a new block download source into the downloader.
func (dl *downloadTester) newPeer(id string, version int, hashes []common.Hash, headers map[common.Hash]*types.Header, blocks map[common.Hash]*types.Block, receipts map[common.Hash]types.Receipts) error {
return dl.newSlowPeer(id, version, hashes, headers, blocks, receipts, 0)
@ -1031,6 +1057,56 @@ func testShiftedHeaderAttack(t *testing.T, protocol int, mode SyncMode) {
assertOwnChain(t, tester, targetBlocks+1)
}
// Tests that upon detecting an invalid header, the recent ones are rolled back
func TestInvalidHeaderRollback63Fast(t *testing.T) { testInvalidHeaderRollback(t, 63, FastSync) }
func TestInvalidHeaderRollback64Fast(t *testing.T) { testInvalidHeaderRollback(t, 64, FastSync) }
func TestInvalidHeaderRollback64Light(t *testing.T) { testInvalidHeaderRollback(t, 64, LightSync) }
func testInvalidHeaderRollback(t *testing.T, protocol int, mode SyncMode) {
// Create a small enough block chain to download
targetBlocks := 3*minCheckedHeaders + minFullBlocks
hashes, headers, blocks, receipts := makeChain(targetBlocks, 0, genesis, nil)
tester := newTester(mode)
// Attempt to sync with an attacker that feeds junk during the fast sync phase
tester.newPeer("fast-attack", protocol, hashes, headers, blocks, receipts)
missing := minCheckedHeaders + MaxHeaderFetch + 1
delete(tester.peerHeaders["fast-attack"], hashes[len(hashes)-missing])
if err := tester.sync("fast-attack", nil); err == nil {
t.Fatalf("succeeded fast attacker synchronisation")
}
if head := tester.headHeader().Number.Int64(); int(head) > MaxHeaderFetch {
t.Fatalf("rollback head mismatch: have %v, want at most %v", head, MaxHeaderFetch)
}
// Attempt to sync with an attacker that feeds junk during the block import phase
tester.newPeer("block-attack", protocol, hashes, headers, blocks, receipts)
missing = 3*minCheckedHeaders + MaxHeaderFetch + 1
delete(tester.peerHeaders["block-attack"], hashes[len(hashes)-missing])
if err := tester.sync("block-attack", nil); err == nil {
t.Fatalf("succeeded block attacker synchronisation")
}
if mode == FastSync {
// Fast sync should not discard anything below the verified pivot point
if head := tester.headHeader().Number.Int64(); int(head) < 3*minCheckedHeaders {
t.Fatalf("rollback head mismatch: have %v, want at least %v", head, 3*minCheckedHeaders)
}
} else if mode == LightSync {
// Light sync should still discard data as before
if head := tester.headHeader().Number.Int64(); int(head) > 3*minCheckedHeaders {
t.Fatalf("rollback head mismatch: have %v, want at most %v", head, 3*minCheckedHeaders)
}
}
// Synchronise with the valid peer and make sure sync succeeds
tester.newPeer("valid", protocol, hashes, headers, blocks, receipts)
if err := tester.sync("valid", nil); err != nil {
t.Fatalf("failed to synchronise blocks: %v", err)
}
assertOwnChain(t, tester, targetBlocks+1)
}
// Tests that if a peer sends an invalid block piece (body or receipt) for a
// requested block, it gets dropped immediately by the downloader.
func TestInvalidContentAttack62(t *testing.T) { testInvalidContentAttack(t, 62, FullSync) }

3
eth/downloader/types.go
View File

@ -60,6 +60,9 @@ 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)
// chainRollbackFn is a callback type to remove a few recently added elements from the local chain.
type chainRollbackFn func([]common.Hash)
// peerDropFn is a callback type for dropping a peer detected as malicious.
type peerDropFn func(id string)

2
eth/handler.go
View File

@ -131,7 +131,7 @@ func NewProtocolManager(mode Mode, networkId int, mux *event.TypeMux, txpool txP
}
manager.downloader = downloader.New(syncMode, chaindb, manager.eventMux, blockchain.HasHeader, blockchain.HasBlock, blockchain.GetHeader,
blockchain.GetBlock, blockchain.CurrentHeader, blockchain.CurrentBlock, blockchain.CurrentFastBlock, blockchain.FastSyncCommitHead,
blockchain.GetTd, blockchain.InsertHeaderChain, blockchain.InsertChain, blockchain.InsertReceiptChain, manager.removePeer)
blockchain.GetTd, blockchain.InsertHeaderChain, blockchain.InsertChain, blockchain.InsertReceiptChain, blockchain.Rollback, manager.removePeer)
validator := func(block *types.Block, parent *types.Block) error {
return core.ValidateHeader(pow, block.Header(), parent.Header(), true, false)