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eth/downloader: implement concurrent header downloads

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This commit is contained in:
Péter Szilágyi
2016-02-25 18:36:42 +02:00
parent fe532a98f9
commit b40dc8a1da
4 changed files with 584 additions and 211 deletions
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480
eth/downloader/downloader.go
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@ -42,6 +42,7 @@ var (
MaxHashFetch = 512 // Amount of hashes to be fetched per retrieval request
MaxBlockFetch = 128 // Amount of blocks to be fetched per retrieval request
MaxHeaderFetch = 192 // Amount of block headers to be fetched per retrieval request
MaxSkeletonSize = 128 // Number of header fetches to need for a skeleton assembly
MaxBodyFetch = 128 // Amount of block bodies to be fetched per retrieval request
MaxReceiptFetch = 256 // Amount of transaction receipts to allow fetching per request
MaxStateFetch = 384 // Amount of node state values to allow fetching per request
@ -52,7 +53,8 @@ var (
blockTargetRTT = 3 * time.Second / 2 // [eth/61] Target time for completing a block retrieval request
blockTTL = 3 * blockTargetRTT // [eth/61] Maximum time allowance before a block request is considered expired
headerTTL = 3 * time.Second // [eth/62] Time it takes for a header request to time out
headerTargetRTT = time.Second // [eth/62] Target time for completing a header retrieval request (only for measurements for now)
headerTTL = 2 * time.Second // [eth/62] Time it takes for a header request to time out
bodyTargetRTT = 3 * time.Second / 2 // [eth/62] Target time for completing a block body retrieval request
bodyTTL = 3 * bodyTargetRTT // [eth/62] Maximum time allowance before a block body request is considered expired
receiptTargetRTT = 3 * time.Second / 2 // [eth/63] Target time for completing a receipt retrieval request
@ -60,9 +62,10 @@ var (
stateTargetRTT = 2 * time.Second / 2 // [eth/63] Target time for completing a state trie retrieval request
stateTTL = 3 * stateTargetRTT // [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)
maxResultsProcess = 256 // Number of download results to import at once into the chain
maxQueuedHashes = 32 * 1024 // [eth/61] Maximum number of hashes to queue for import (DOS protection)
maxQueuedHeaders = 32 * 1024 // [eth/62] Maximum number of headers to queue for import (DOS protection)
maxHeadersProcess = 2048 // Number of header download results to import at once into the chain
maxResultsProcess = 4096 // Number of content download results to import at once into the chain
fsHeaderCheckFrequency = 100 // Verification frequency of the downloaded headers during fast sync
fsHeaderSafetyNet = 2048 // Number of headers to discard in case a chain violation is detected
@ -72,29 +75,30 @@ var (
)
var (
errBusy = errors.New("busy")
errUnknownPeer = errors.New("peer is unknown or unhealthy")
errBadPeer = errors.New("action from bad peer ignored")
errStallingPeer = errors.New("peer is stalling")
errNoPeers = errors.New("no peers to keep download active")
errTimeout = errors.New("timeout")
errEmptyHashSet = errors.New("empty hash set by peer")
errEmptyHeaderSet = errors.New("empty header set by peer")
errPeersUnavailable = errors.New("no peers available or all tried for download")
errAlreadyInPool = errors.New("hash already in pool")
errInvalidAncestor = errors.New("retrieved ancestor is invalid")
errInvalidChain = errors.New("retrieved hash chain is invalid")
errInvalidBlock = errors.New("retrieved block is invalid")
errInvalidBody = errors.New("retrieved block body is invalid")
errInvalidReceipt = errors.New("retrieved receipt is invalid")
errCancelHashFetch = errors.New("hash download canceled (requested)")
errCancelBlockFetch = errors.New("block download canceled (requested)")
errCancelHeaderFetch = errors.New("block header download canceled (requested)")
errCancelBodyFetch = errors.New("block body download canceled (requested)")
errCancelReceiptFetch = errors.New("receipt download canceled (requested)")
errCancelStateFetch = errors.New("state data download canceled (requested)")
errCancelProcessing = errors.New("processing canceled (requested)")
errNoSyncActive = errors.New("no sync active")
errBusy = errors.New("busy")
errUnknownPeer = errors.New("peer is unknown or unhealthy")
errBadPeer = errors.New("action from bad peer ignored")
errStallingPeer = errors.New("peer is stalling")
errNoPeers = errors.New("no peers to keep download active")
errTimeout = errors.New("timeout")
errEmptyHashSet = errors.New("empty hash set by peer")
errEmptyHeaderSet = errors.New("empty header set by peer")
errPeersUnavailable = errors.New("no peers available or all tried for download")
errAlreadyInPool = errors.New("hash already in pool")
errInvalidAncestor = errors.New("retrieved ancestor is invalid")
errInvalidChain = errors.New("retrieved hash chain is invalid")
errInvalidBlock = errors.New("retrieved block is invalid")
errInvalidBody = errors.New("retrieved block body is invalid")
errInvalidReceipt = errors.New("retrieved receipt is invalid")
errCancelHashFetch = errors.New("hash download canceled (requested)")
errCancelBlockFetch = errors.New("block download canceled (requested)")
errCancelHeaderFetch = errors.New("block header download canceled (requested)")
errCancelBodyFetch = errors.New("block body download canceled (requested)")
errCancelReceiptFetch = errors.New("receipt download canceled (requested)")
errCancelStateFetch = errors.New("state data download canceled (requested)")
errCancelHeaderProcessing = errors.New("header processing canceled (requested)")
errCancelContentProcessing = errors.New("content processing canceled (requested)")
errNoSyncActive = errors.New("no sync active")
)
type Downloader struct {
@ -137,16 +141,17 @@ type Downloader struct {
// Channels
newPeerCh chan *peer
hashCh chan dataPack // [eth/61] Channel receiving inbound hashes
blockCh chan dataPack // [eth/61] Channel receiving inbound blocks
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
hashCh chan dataPack // [eth/61] Channel receiving inbound hashes
blockCh chan dataPack // [eth/61] Channel receiving inbound blocks
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
headerProcCh chan []*types.Header // [eth/62] Channel to feed the header processor new tasks
cancelCh chan struct{} // Channel to cancel mid-flight syncs
cancelLock sync.RWMutex // Lock to protect the cancel channel in delivers
@ -194,6 +199,7 @@ func New(stateDb ethdb.Database, mux *event.TypeMux, hasHeader headerCheckFn, ha
bodyWakeCh: make(chan bool, 1),
receiptWakeCh: make(chan bool, 1),
stateWakeCh: make(chan bool, 1),
headerProcCh: make(chan []*types.Header, 1),
}
}
@ -308,6 +314,13 @@ func (d *Downloader) synchronise(id string, hash common.Hash, td *big.Int, mode
default:
}
}
for empty := false; !empty; {
select {
case <-d.headerProcCh:
default:
empty = true
}
}
// Reset any ephemeral sync statistics
d.syncStatsLock.Lock()
d.syncStatsStateTotal = 0
@ -373,7 +386,7 @@ func (d *Downloader) syncWithPeer(p *peer, hash common.Hash, td *big.Int) (err e
if d.syncInitHook != nil {
d.syncInitHook(origin, latest)
}
return d.spawnSync(
return d.spawnSync(origin+1,
func() error { return d.fetchHashes61(p, td, origin+1) },
func() error { return d.fetchBlocks61(origin + 1) },
)
@ -423,11 +436,12 @@ func (d *Downloader) syncWithPeer(p *peer, hash common.Hash, td *big.Int) (err e
if d.syncInitHook != nil {
d.syncInitHook(origin, latest)
}
return d.spawnSync(
func() error { return d.fetchHeaders(p, td, origin+1) }, // Headers are always retrieved
func() error { return d.fetchBodies(origin + 1) }, // Bodies are retrieved during normal and fast sync
func() error { return d.fetchReceipts(origin + 1) }, // Receipts are retrieved during fast sync
func() error { return d.fetchNodeData() }, // Node state data is retrieved during fast sync
return d.spawnSync(origin+1,
func() error { return d.fetchHeaders(p, origin+1) }, // Headers are always retrieved
func() error { return d.processHeaders(origin+1, td) }, // Headers are always retrieved
func() error { return d.fetchBodies(origin + 1) }, // Bodies are retrieved during normal and fast sync
func() error { return d.fetchReceipts(origin + 1) }, // Receipts are retrieved during fast sync
func() error { return d.fetchNodeData() }, // Node state data is retrieved during fast sync
)
default:
@ -439,11 +453,11 @@ func (d *Downloader) syncWithPeer(p *peer, hash common.Hash, td *big.Int) (err e
// spawnSync runs d.process and all given fetcher functions to completion in
// separate goroutines, returning the first error that appears.
func (d *Downloader) spawnSync(fetchers ...func() error) error {
func (d *Downloader) spawnSync(origin uint64, fetchers ...func() error) error {
var wg sync.WaitGroup
errc := make(chan error, len(fetchers)+1)
wg.Add(len(fetchers) + 1)
go func() { defer wg.Done(); errc <- d.process() }()
go func() { defer wg.Done(); errc <- d.processContent() }()
for _, fn := range fetchers {
fn := fn
go func() { defer wg.Done(); errc <- fn() }()
@ -1149,55 +1163,38 @@ func (d *Downloader) findAncestor(p *peer, height uint64) (uint64, error) {
return start, nil
}
// fetchHeaders keeps retrieving headers from the requested number, until no more
// are returned, potentially throttling on the way.
//
// 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 {
glog.V(logger.Debug).Infof("%v: downloading headers from #%d", p, from)
// fetchHeaders keeps retrieving headers concurrently from the number
// requested, until no more are returned, potentially throttling on the way. To
// facilitate concurrency but still protect against malicious nodes sending bad
// headers, we construct a header chain skeleton using the "origin" peer we are
// syncing with, and fill in the missing headers using anyone else. Headers from
// other peers are only accepted if they map cleanly to the skeleton. If noone
// can fill in the skeleton - not even the origin peer - it's assumed invalid and
// the origin is dropped.
func (d *Downloader) fetchHeaders(p *peer, from uint64) error {
glog.V(logger.Debug).Infof("%v: directing header downloads from #%d", p, from)
defer glog.V(logger.Debug).Infof("%v: header download terminated", p)
// Calculate the pivoting point for switching from fast to slow sync
pivot := d.queue.FastSyncPivot()
// Keep a count of uncertain headers to roll back
rollback := []*types.Header{}
defer func() {
if len(rollback) > 0 {
// Flatten the headers and roll them back
hashes := make([]common.Hash, len(rollback))
for i, header := range rollback {
hashes[i] = header.Hash()
}
lh, lfb, lb := d.headHeader().Number, d.headFastBlock().Number(), d.headBlock().Number()
d.rollback(hashes)
glog.V(logger.Warn).Infof("Rolled back %d headers (LH: %d->%d, FB: %d->%d, LB: %d->%d)",
len(hashes), lh, d.headHeader().Number, lfb, d.headFastBlock().Number(), lb, d.headBlock().Number())
// If we're already past the pivot point, this could be an attack, disable fast sync
if rollback[len(rollback)-1].Number.Uint64() > pivot {
d.noFast = true
}
}
}()
// Create a timeout timer, and the associated hash fetcher
request := time.Now() // time of the last fetch request
// Create a timeout timer, and the associated header fetcher
skeleton := true // Skeleton assembly phase or finishing up
request := time.Now() // time of the last skeleton fetch request
timeout := time.NewTimer(0) // timer to dump a non-responsive active peer
<-timeout.C // timeout channel should be initially empty
defer timeout.Stop()
getHeaders := func(from uint64) {
glog.V(logger.Detail).Infof("%v: fetching %d headers from #%d", p, MaxHeaderFetch, from)
go p.getAbsHeaders(from, MaxHeaderFetch, 0, false)
if skeleton {
glog.V(logger.Detail).Infof("%v: fetching %d skeleton headers from #%d", p, MaxHeaderFetch, from)
go p.getAbsHeaders(from+uint64(MaxHeaderFetch)-1, MaxSkeletonSize, MaxHeaderFetch-1, false)
} else {
glog.V(logger.Detail).Infof("%v: fetching %d full headers from #%d", p, MaxHeaderFetch, from)
go p.getAbsHeaders(from, MaxHeaderFetch, 0, false)
}
request = time.Now()
timeout.Reset(headerTTL)
}
// Start pulling headers, until all are exhausted
// Start pulling the header chain skeleton until all is done
getHeaders(from)
gotHeaders := false
for {
select {
@ -1205,115 +1202,44 @@ func (d *Downloader) fetchHeaders(p *peer, td *big.Int, from uint64) error {
return errCancelHeaderFetch
case packet := <-d.headerCh:
// Make sure the active peer is giving us the headers
// Make sure the active peer is giving us the skeleton headers
if packet.PeerId() != p.id {
glog.V(logger.Debug).Infof("Received headers from incorrect peer (%s)", packet.PeerId())
glog.V(logger.Debug).Infof("Received skeleton headers from incorrect peer (%s)", packet.PeerId())
break
}
headerReqTimer.UpdateSince(request)
timeout.Stop()
// If the skeleton's finished, pull any remaining head headers directly from the origin
if packet.Items() == 0 && skeleton {
skeleton = false
getHeaders(from)
continue
}
// 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)
for _, ch := range []chan bool{d.bodyWakeCh, d.receiptWakeCh, d.stateWakeCh} {
select {
case ch <- false:
case <-d.cancelCh:
}
}
// If no headers were retrieved at all, the peer violated it's TD promise that it had a
// better chain compared to ours. The only exception is if it's promised blocks were
// already imported by other means (e.g. fetcher):
//
// R <remote peer>, L <local node>: Both at block 10
// R: Mine block 11, and propagate it to L
// L: Queue block 11 for import
// L: Notice that R's head and TD increased compared to ours, start sync
// L: Import of block 11 finishes
// L: Sync begins, and finds common ancestor at 11
// L: Request new headers up from 11 (R's TD was higher, it must have something)
// R: Nothing to give
if !gotHeaders && td.Cmp(d.getTd(d.headBlock().Hash())) > 0 {
return errStallingPeer
}
// If fast or light syncing, ensure promised headers are indeed delivered. This is
// needed to detect scenarios where an attacker feeds a bad pivot and then bails out
// of delivering the post-pivot blocks that would flag the invalid content.
//
// This check cannot be executed "as is" for full imports, since blocks may still be
// queued for processing when the header download completes. However, as long as the
// peer gave us something useful, we're already happy/progressed (above check).
if d.mode == FastSync || d.mode == LightSync {
if td.Cmp(d.getTd(d.headHeader().Hash())) > 0 {
return errStallingPeer
}
}
rollback = nil
d.headerProcCh <- nil
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(headers), from)
if d.mode == FastSync || d.mode == LightSync {
// 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 := fsHeaderCheckFrequency
if headers[len(headers)-1].Number.Uint64()+uint64(fsHeaderForceVerify) > pivot {
frequency = 1
}
if n, err := d.insertHeaders(headers, frequency); err != nil {
// If some headers were inserted, add them too to the rollback list
if n > 0 {
rollback = append(rollback, headers[:n]...)
}
glog.V(logger.Debug).Infof("%v: invalid header #%d [%x…]: %v", p, headers[n].Number, headers[n].Hash().Bytes()[:4], err)
// If we received a skeleton batch, resolve internals concurrently
if skeleton {
filled, err := d.fillHeaderSkeleton(from, headers)
if err != nil {
glog.V(logger.Debug).Infof("%v: skeleton chain invalid: %v", p, err)
return errInvalidChain
}
// All verifications passed, store newly found uncertain headers
rollback = append(rollback, unknown...)
if len(rollback) > fsHeaderSafetyNet {
rollback = append(rollback[:0], rollback[len(rollback)-fsHeaderSafetyNet:]...)
}
headers = filled
}
if d.mode == FullSync || d.mode == FastSync {
inserts := d.queue.Schedule(headers, from)
if len(inserts) != len(headers) {
glog.V(logger.Debug).Infof("%v: stale headers", p)
return errBadPeer
}
// Insert all the new headers and fetch the next batch
glog.V(logger.Detail).Infof("%v: schedule %d headers from #%d", p, len(headers), from)
select {
case d.headerProcCh <- headers:
case <-d.cancelCh:
return errCancelHeaderFetch
}
// 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, d.stateWakeCh} {
if cont {
// We still have headers to fetch, send continuation wake signal (potential)
select {
case ch <- true:
default:
}
} else {
// Header limit reached, send a termination wake signal (enforced)
select {
case ch <- false:
case <-d.cancelCh:
}
}
}
if !cont {
return nil
}
// Queue not yet full, fetch the next batch
from += uint64(len(headers))
getHeaders(from)
@ -1330,7 +1256,11 @@ func (d *Downloader) fetchHeaders(p *peer, td *big.Int, from uint64) error {
case <-d.cancelCh:
}
}
return nil
select {
case d.headerProcCh <- nil:
case <-d.cancelCh:
}
return errBadPeer
case <-d.hashCh:
case <-d.blockCh:
@ -1340,6 +1270,34 @@ func (d *Downloader) fetchHeaders(p *peer, td *big.Int, from uint64) error {
}
}
// fillHeaderSkeleton concurrently retrieves headers from all our available peers
// and maps them to the provided skeleton header chain.
func (d *Downloader) fillHeaderSkeleton(from uint64, skeleton []*types.Header) ([]*types.Header, error) {
glog.V(logger.Debug).Infof("Filling up skeleton from #%d", from)
d.queue.ScheduleSkeleton(from, skeleton)
var (
deliver = func(packet dataPack) (int, error) {
pack := packet.(*headerPack)
return d.queue.DeliverHeaders(pack.peerId, pack.headers)
}
expire = func() map[string]int { return d.queue.ExpireHeaders(headerTTL) }
throttle = func() bool { return false }
reserve = func(p *peer, count int) (*fetchRequest, bool, error) {
return d.queue.ReserveHeaders(p, count), false, nil
}
fetch = func(p *peer, req *fetchRequest) error { return p.FetchHeaders(req.From, MaxHeaderFetch) }
capacity = func(p *peer) int { return p.HeaderCapacity() }
setIdle = func(p *peer, accepted int) { p.SetHeadersIdle(accepted) }
)
err := d.fetchParts(errCancelHeaderFetch, d.headerCh, deliver, d.queue.headerContCh, expire,
d.queue.PendingHeaders, d.queue.InFlightHeaders, throttle, reserve,
nil, fetch, d.queue.CancelHeaders, capacity, d.peers.HeaderIdlePeers, setIdle, "Header")
glog.V(logger.Debug).Infof("Skeleton fill terminated: %v", err)
return d.queue.RetrieveHeaders(), err
}
// fetchBodies iteratively downloads the scheduled block bodies, taking any
// available peers, reserving a chunk of blocks for each, waiting for delivery
// and also periodically checking for timeouts.
@ -1398,6 +1356,11 @@ func (d *Downloader) fetchNodeData() error {
deliver = func(packet dataPack) (int, error) {
start := time.Now()
return d.queue.DeliverNodeData(packet.PeerId(), packet.(*statePack).states, func(err error, delivered int) {
// If the peer gave us nothing, stalling fast sync, drop
if delivered == 0 {
glog.V(logger.Debug).Infof("peer %s: stalling state delivery, dropping", packet.PeerId())
d.dropPeer(packet.PeerId())
}
if err != nil {
// If the node data processing failed, the root hash is very wrong, abort
glog.V(logger.Error).Infof("peer %d: state processing failed: %v", packet.PeerId(), err)
@ -1554,7 +1517,9 @@ func (d *Downloader) fetchParts(errCancel error, deliveryCh chan dataPack, deliv
continue
}
if glog.V(logger.Detail) {
if len(request.Headers) > 0 {
if request.From > 0 {
glog.Infof("%s: requesting %s(s) from #%d", peer, strings.ToLower(kind), request.From)
} else 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))
@ -1588,9 +1553,162 @@ func (d *Downloader) fetchParts(errCancel error, deliveryCh chan dataPack, deliv
}
}
// process takes fetch results from the queue and tries to import them into the
// chain. The type of import operation will depend on the result contents.
func (d *Downloader) process() error {
// processHeaders takes batches of retrieved headers from an input channel and
// keeps processing and scheduling them into the header chain and downloader's
// queue until the stream ends or a failure occurs.
func (d *Downloader) processHeaders(origin uint64, td *big.Int) error {
// Calculate the pivoting point for switching from fast to slow sync
pivot := d.queue.FastSyncPivot()
// Keep a count of uncertain headers to roll back
rollback := []*types.Header{}
defer func() {
if len(rollback) > 0 {
// Flatten the headers and roll them back
hashes := make([]common.Hash, len(rollback))
for i, header := range rollback {
hashes[i] = header.Hash()
}
lh, lfb, lb := d.headHeader().Number, d.headFastBlock().Number(), d.headBlock().Number()
d.rollback(hashes)
glog.V(logger.Warn).Infof("Rolled back %d headers (LH: %d->%d, FB: %d->%d, LB: %d->%d)",
len(hashes), lh, d.headHeader().Number, lfb, d.headFastBlock().Number(), lb, d.headBlock().Number())
// If we're already past the pivot point, this could be an attack, disable fast sync
if rollback[len(rollback)-1].Number.Uint64() > pivot {
d.noFast = true
}
}
}()
// Wait for batches of headers to process
gotHeaders := false
for {
select {
case <-d.cancelCh:
return errCancelHeaderProcessing
case headers := <-d.headerProcCh:
// Terminate header processing if we synced up
if len(headers) == 0 {
// Notify everyone that headers are fully processed
for _, ch := range []chan bool{d.bodyWakeCh, d.receiptWakeCh, d.stateWakeCh} {
select {
case ch <- false:
case <-d.cancelCh:
}
}
// If no headers were retrieved at all, the peer violated it's TD promise that it had a
// better chain compared to ours. The only exception is if it's promised blocks were
// already imported by other means (e.g. fecher):
//
// R <remote peer>, L <local node>: Both at block 10
// R: Mine block 11, and propagate it to L
// L: Queue block 11 for import
// L: Notice that R's head and TD increased compared to ours, start sync
// L: Import of block 11 finishes
// L: Sync begins, and finds common ancestor at 11
// L: Request new headers up from 11 (R's TD was higher, it must have something)
// R: Nothing to give
if !gotHeaders && td.Cmp(d.getTd(d.headBlock().Hash())) > 0 {
return errStallingPeer
}
// If fast or light syncing, ensure promised headers are indeed delivered. This is
// needed to detect scenarios where an attacker feeds a bad pivot and then bails out
// of delivering the post-pivot blocks that would flag the invalid content.
//
// This check cannot be executed "as is" for full imports, since blocks may still be
// queued for processing when the header download completes. However, as long as the
// peer gave us something useful, we're already happy/progressed (above check).
if d.mode == FastSync || d.mode == LightSync {
if td.Cmp(d.getTd(d.headHeader().Hash())) > 0 {
return errStallingPeer
}
}
// Disable any rollback and return
rollback = nil
return nil
}
// Otherwise split the chunk of headers into batches and process them
gotHeaders = true
for len(headers) > 0 {
// Terminate if something failed in between processing chunks
select {
case <-d.cancelCh:
return errCancelHeaderProcessing
default:
}
// Select the next chunk of headers to import
limit := maxHeadersProcess
if limit > len(headers) {
limit = len(headers)
}
chunk := headers[:limit]
// In case of header only syncing, validate the chunk immediately
if d.mode == FastSync || d.mode == LightSync {
// Collect the yet unknown headers to mark them as uncertain
unknown := make([]*types.Header, 0, len(headers))
for _, header := range chunk {
if !d.hasHeader(header.Hash()) {
unknown = append(unknown, header)
}
}
// If we're importing pure headers, verify based on their recentness
frequency := fsHeaderCheckFrequency
if chunk[len(chunk)-1].Number.Uint64()+uint64(fsHeaderForceVerify) > pivot {
frequency = 1
}
if n, err := d.insertHeaders(chunk, frequency); err != nil {
// If some headers were inserted, add them too to the rollback list
if n > 0 {
rollback = append(rollback, chunk[:n]...)
}
glog.V(logger.Debug).Infof("invalid header #%d [%x…]: %v", chunk[n].Number, chunk[n].Hash().Bytes()[:4], err)
return errInvalidChain
}
// All verifications passed, store newly found uncertain headers
rollback = append(rollback, unknown...)
if len(rollback) > fsHeaderSafetyNet {
rollback = append(rollback[:0], rollback[len(rollback)-fsHeaderSafetyNet:]...)
}
}
// 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
for d.queue.PendingBlocks() >= maxQueuedHeaders || d.queue.PendingReceipts() >= maxQueuedHeaders {
select {
case <-d.cancelCh:
return errCancelHeaderProcessing
case <-time.After(time.Second):
}
}
// Otherwise insert the headers for content retrieval
inserts := d.queue.Schedule(chunk, origin)
if len(inserts) != len(chunk) {
glog.V(logger.Debug).Infof("stale headers")
return errBadPeer
}
}
headers = headers[limit:]
origin += uint64(limit)
}
// Signal the content downloaders of the availablility of new tasks
for _, ch := range []chan bool{d.bodyWakeCh, d.receiptWakeCh, d.stateWakeCh} {
select {
case ch <- true:
default:
}
}
}
}
}
// processContent takes fetch results from the queue and tries to import them
// into the chain. The type of import operation will depend on the result contents.
func (d *Downloader) processContent() error {
pivot := d.queue.FastSyncPivot()
for {
results := d.queue.WaitResults()
@ -1608,7 +1726,7 @@ func (d *Downloader) process() error {
for len(results) != 0 {
// Check for any termination requests
if atomic.LoadInt32(&d.interrupt) == 1 {
return errCancelProcessing
return errCancelContentProcessing
}
// Retrieve the a batch of results to import
var (