Official Go implementation of the Ethereum protocol
You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
 
 
 
 
 
 
go-ethereum/eth/downloader/downloader.go

1228 lines
40 KiB

// 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 contains the manual full chain synchronisation.
package downloader
import (
"bytes"
"errors"
"math"
"math/big"
"math/rand"
"sync"
"sync/atomic"
"time"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/core"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/event"
"github.com/ethereum/go-ethereum/logger"
"github.com/ethereum/go-ethereum/logger/glog"
"gopkg.in/fatih/set.v0"
)
const (
eth60 = 60 // Constant to check for old protocol support
eth61 = 61 // Constant to check for new protocol support
)
var (
MinHashFetch = 512 // Minimum amount of hashes to not consider a peer stalling
MaxHashFetch = 512 // Amount of hashes to be fetched per retrieval request
MaxBlockFetch = 128 // Amount of blocks to be fetched per retrieval request
hashTTL = 5 * time.Second // Time it takes for a hash request to time out
blockSoftTTL = 3 * time.Second // Request completion threshold for increasing or decreasing a peer's bandwidth
blockHardTTL = 3 * blockSoftTTL // Maximum time allowance before a block request is considered expired
crossCheckCycle = time.Second // Period after which to check for expired cross checks
maxQueuedHashes = 256 * 1024 // Maximum number of hashes to queue for import (DOS protection)
maxBannedHashes = 4096 // Number of bannable hashes before phasing old ones out
maxBlockProcess = 256 // Number of blocks to import at once into the chain
)
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")
errBannedHead = errors.New("peer head hash already banned")
errNoPeers = errors.New("no peers to keep download active")
errPendingQueue = errors.New("pending items in queue")
errTimeout = errors.New("timeout")
errEmptyHashSet = errors.New("empty hash set by peer")
errPeersUnavailable = errors.New("no peers available or all peers tried for block download process")
errAlreadyInPool = errors.New("hash already in pool")
errInvalidChain = errors.New("retrieved hash chain is invalid")
errCrossCheckFailed = errors.New("block cross-check failed")
errCancelHashFetch = errors.New("hash fetching canceled (requested)")
errCancelBlockFetch = errors.New("block downloading canceled (requested)")
errNoSyncActive = errors.New("no sync active")
)
// hashCheckFn is a callback type for verifying a hash's presence in the local chain.
type hashCheckFn func(common.Hash) bool
// blockRetrievalFn is a callback type for retrieving a block from the local chain.
type blockRetrievalFn func(common.Hash) *types.Block
// headRetrievalFn is a callback type for retrieving the head block from the local chain.
type headRetrievalFn func() *types.Block
// chainInsertFn is a callback type to insert a batch of blocks into the local chain.
type chainInsertFn func(types.Blocks) (int, error)
// peerDropFn is a callback type for dropping a peer detected as malicious.
type peerDropFn func(id string)
type blockPack struct {
peerId string
blocks []*types.Block
}
type hashPack struct {
peerId string
hashes []common.Hash
}
type crossCheck struct {
expire time.Time
parent common.Hash
}
type Downloader struct {
mux *event.TypeMux
queue *queue // Scheduler for selecting the hashes to download
peers *peerSet // Set of active peers from which download can proceed
checks map[common.Hash]*crossCheck // Pending cross checks to verify a hash chain
banned *set.Set // Set of hashes we've received and banned
interrupt int32 // Atomic boolean to signal termination
// Statistics
importStart time.Time // Instance when the last blocks were taken from the cache
importQueue []*Block // Previously taken blocks to check import progress
importDone int // Number of taken blocks already imported from the last batch
importLock sync.Mutex
// Callbacks
hasBlock hashCheckFn // Checks if a block is present in the chain
getBlock blockRetrievalFn // Retrieves a block from the chain
headBlock headRetrievalFn // Retrieves the head block from the chain
insertChain chainInsertFn // Injects a batch of blocks into the chain
dropPeer peerDropFn // Drops a peer for misbehaving
// Status
synchroniseMock func(id string, hash common.Hash) error // Replacement for synchronise during testing
synchronising int32
processing int32
notified int32
// Channels
newPeerCh chan *peer
hashCh chan hashPack // Channel receiving inbound hashes
blockCh chan blockPack // Channel receiving inbound blocks
processCh chan bool // Channel to signal the block fetcher of new or finished work
cancelCh chan struct{} // Channel to cancel mid-flight syncs
cancelLock sync.RWMutex // Lock to protect the cancel channel in delivers
}
// Block is an origin-tagged blockchain block.
type Block struct {
RawBlock *types.Block
OriginPeer string
}
// New creates a new downloader to fetch hashes and blocks from remote peers.
func New(mux *event.TypeMux, hasBlock hashCheckFn, getBlock blockRetrievalFn, headBlock headRetrievalFn, insertChain chainInsertFn, dropPeer peerDropFn) *Downloader {
// Create the base downloader
downloader := &Downloader{
mux: mux,
queue: newQueue(),
peers: newPeerSet(),
hasBlock: hasBlock,
getBlock: getBlock,
headBlock: headBlock,
insertChain: insertChain,
dropPeer: dropPeer,
newPeerCh: make(chan *peer, 1),
hashCh: make(chan hashPack, 1),
blockCh: make(chan blockPack, 1),
processCh: make(chan bool, 1),
}
// Inject all the known bad hashes
downloader.banned = set.New()
for hash, _ := range core.BadHashes {
downloader.banned.Add(hash)
}
return downloader
}
// Stats retrieves the current status of the downloader.
func (d *Downloader) Stats() (pending int, cached int, importing int, estimate time.Duration) {
// Fetch the download status
pending, cached = d.queue.Size()
// Figure out the import progress
d.importLock.Lock()
defer d.importLock.Unlock()
for len(d.importQueue) > 0 && d.hasBlock(d.importQueue[0].RawBlock.Hash()) {
d.importQueue = d.importQueue[1:]
d.importDone++
}
importing = len(d.importQueue)
// Make an estimate on the total sync
estimate = 0
if d.importDone > 0 {
estimate = time.Since(d.importStart) / time.Duration(d.importDone) * time.Duration(pending+cached+importing)
}
return
}
// Synchronising returns whether the downloader is currently retrieving blocks.
func (d *Downloader) Synchronising() bool {
return atomic.LoadInt32(&d.synchronising) > 0
}
// RegisterPeer injects a new download peer into the set of block source to be
// used for fetching hashes and blocks from.
func (d *Downloader) RegisterPeer(id string, version int, head common.Hash, getRelHashes relativeHashFetcherFn, getAbsHashes absoluteHashFetcherFn, getBlocks blockFetcherFn) error {
// If the peer wants to send a banned hash, reject
if d.banned.Has(head) {
glog.V(logger.Debug).Infoln("Register rejected, head hash banned:", id)
return errBannedHead
}
// Otherwise try to construct and register the peer
glog.V(logger.Detail).Infoln("Registering peer", id)
if err := d.peers.Register(newPeer(id, version, head, getRelHashes, getAbsHashes, getBlocks)); err != nil {
glog.V(logger.Error).Infoln("Register failed:", err)
return err
}
return nil
}
// UnregisterPeer remove a peer from the known list, preventing any action from
// the specified peer.
func (d *Downloader) UnregisterPeer(id string) error {
glog.V(logger.Detail).Infoln("Unregistering peer", id)
if err := d.peers.Unregister(id); err != nil {
glog.V(logger.Error).Infoln("Unregister failed:", err)
return err
}
return nil
}
// Synchronise tries to sync up our local block chain with a remote peer, both
// adding various sanity checks as well as wrapping it with various log entries.
func (d *Downloader) Synchronise(id string, head common.Hash, td *big.Int) {
glog.V(logger.Detail).Infof("Attempting synchronisation: %v, head 0x%x, TD %v", id, head[:4], td)
switch err := d.synchronise(id, head, td); err {
case nil:
glog.V(logger.Detail).Infof("Synchronisation completed")
case errBusy:
glog.V(logger.Detail).Infof("Synchronisation already in progress")
case errTimeout, errBadPeer, errStallingPeer, errBannedHead, errEmptyHashSet, errPeersUnavailable, errInvalidChain, errCrossCheckFailed:
glog.V(logger.Debug).Infof("Removing peer %v: %v", id, err)
d.dropPeer(id)
case errPendingQueue:
glog.V(logger.Debug).Infoln("Synchronisation aborted:", err)
default:
glog.V(logger.Warn).Infof("Synchronisation failed: %v", err)
}
}
// synchronise will select the peer and use it for synchronising. If an empty string is given
// it will use the best peer possible and synchronize if it's TD is higher than our own. If any of the
// checks fail an error will be returned. This method is synchronous
func (d *Downloader) synchronise(id string, hash common.Hash, td *big.Int) error {
// Mock out the synchonisation if testing
if d.synchroniseMock != nil {
return d.synchroniseMock(id, hash)
}
// Make sure only one goroutine is ever allowed past this point at once
if !atomic.CompareAndSwapInt32(&d.synchronising, 0, 1) {
return errBusy
}
defer atomic.StoreInt32(&d.synchronising, 0)
// If the head hash is banned, terminate immediately
if d.banned.Has(hash) {
return errBannedHead
}
// Post a user notification of the sync (only once per session)
if atomic.CompareAndSwapInt32(&d.notified, 0, 1) {
glog.V(logger.Info).Infoln("Block synchronisation started")
}
// Abort if the queue still contains some leftover data
if _, cached := d.queue.Size(); cached > 0 && d.queue.GetHeadBlock() != nil {
return errPendingQueue
}
// Reset the queue and peer set to clean any internal leftover state
d.queue.Reset()
d.peers.Reset()
d.checks = make(map[common.Hash]*crossCheck)
// Create cancel channel for aborting mid-flight
d.cancelLock.Lock()
d.cancelCh = make(chan struct{})
d.cancelLock.Unlock()
// Retrieve the origin peer and initiate the downloading process
p := d.peers.Peer(id)
if p == nil {
return errUnknownPeer
}
return d.syncWithPeer(p, hash, td)
}
// Has checks if the downloader knows about a particular hash, meaning that its
// either already downloaded of pending retrieval.
func (d *Downloader) Has(hash common.Hash) bool {
return d.queue.Has(hash)
}
// syncWithPeer starts a block synchronization based on the hash chain from the
// specified peer and head hash.
func (d *Downloader) syncWithPeer(p *peer, hash common.Hash, td *big.Int) (err error) {
d.mux.Post(StartEvent{})
defer func() {
// reset on error
if err != nil {
d.cancel()
d.mux.Post(FailedEvent{err})
} else {
d.mux.Post(DoneEvent{})
}
}()
glog.V(logger.Debug).Infof("Synchronizing with the network using: %s, eth/%d", p.id, p.version)
switch p.version {
case eth60:
// Old eth/60 version, use reverse hash retrieval algorithm
if err = d.fetchHashes60(p, hash); err != nil {
return err
}
if err = d.fetchBlocks60(); err != nil {
return err
}
case eth61:
// New eth/61, use forward, concurrent hash and block retrieval algorithm
number, err := d.findAncestor(p)
if err != nil {
return err
}
errc := make(chan error, 2)
go func() { errc <- d.fetchHashes(p, td, number+1) }()
go func() { errc <- d.fetchBlocks(number + 1) }()
// If any fetcher fails, cancel the other
if err := <-errc; err != nil {
d.cancel()
<-errc
return err
}
return <-errc
default:
// Something very wrong, stop right here
glog.V(logger.Error).Infof("Unsupported eth protocol: %d", p.version)
return errBadPeer
}
glog.V(logger.Debug).Infoln("Synchronization completed")
return nil
}
// cancel cancels all of the operations and resets the queue. It returns true
// if the cancel operation was completed.
func (d *Downloader) cancel() {
// Close the current cancel channel
d.cancelLock.Lock()
if d.cancelCh != nil {
select {
case <-d.cancelCh:
// Channel was already closed
default:
close(d.cancelCh)
}
}
d.cancelLock.Unlock()
// Reset the queue
d.queue.Reset()
}
// Terminate interrupts the downloader, canceling all pending operations.
func (d *Downloader) Terminate() {
atomic.StoreInt32(&d.interrupt, 1)
d.cancel()
}
// fetchHashes60 starts retrieving hashes backwards from a specific peer and hash,
// up until it finds a common ancestor. If the source peer times out, alternative
// ones are tried for continuation.
func (d *Downloader) fetchHashes60(p *peer, h common.Hash) error {
var (
start = time.Now()
active = p // active peer will help determine the current active peer
head = common.Hash{} // common and last hash
timeout = time.NewTimer(0) // timer to dump a non-responsive active peer
attempted = make(map[string]bool) // attempted peers will help with retries
crossTicker = time.NewTicker(crossCheckCycle) // ticker to periodically check expired cross checks
)
defer crossTicker.Stop()
defer timeout.Stop()
glog.V(logger.Debug).Infof("Downloading hashes (%x) from %s", h[:4], p.id)
<-timeout.C // timeout channel should be initially empty.
getHashes := func(from common.Hash) {
go active.getRelHashes(from)
timeout.Reset(hashTTL)
}
// Add the hash to the queue, and start hash retrieval.
d.queue.Insert([]common.Hash{h}, false)
getHashes(h)
attempted[p.id] = true
for finished := false; !finished; {
select {
case <-d.cancelCh:
return errCancelHashFetch
case hashPack := <-d.hashCh:
// Make sure the active peer is giving us the hashes
if hashPack.peerId != active.id {
glog.V(logger.Debug).Infof("Received hashes from incorrect peer(%s)", hashPack.peerId)
break
}
timeout.Stop()
// Make sure the peer actually gave something valid
if len(hashPack.hashes) == 0 {
glog.V(logger.Debug).Infof("Peer (%s) responded with empty hash set", active.id)
return errEmptyHashSet
}
for index, hash := range hashPack.hashes {
if d.banned.Has(hash) {
glog.V(logger.Debug).Infof("Peer (%s) sent a known invalid chain", active.id)
d.queue.Insert(hashPack.hashes[:index+1], false)
if err := d.banBlocks(active.id, hash); err != nil {
glog.V(logger.Debug).Infof("Failed to ban batch of blocks: %v", err)
}
return errInvalidChain
}
}
// Determine if we're done fetching hashes (queue up all pending), and continue if not done
done, index := false, 0
for index, head = range hashPack.hashes {
if d.hasBlock(head) || d.queue.GetBlock(head) != nil {
glog.V(logger.Debug).Infof("Found common hash %x", head[:4])
hashPack.hashes = hashPack.hashes[:index]
done = true
break
}
}
// Insert all the new hashes, but only continue if got something useful
inserts := d.queue.Insert(hashPack.hashes, false)
if len(inserts) == 0 && !done {
glog.V(logger.Debug).Infof("Peer (%s) responded with stale hashes", active.id)
return errBadPeer
}
if !done {
// Check that the peer is not stalling the sync
if len(inserts) < MinHashFetch {
return errStallingPeer
}
// Try and fetch a random block to verify the hash batch
// Skip the last hash as the cross check races with the next hash fetch
cross := rand.Intn(len(inserts) - 1)
origin, parent := inserts[cross], inserts[cross+1]
glog.V(logger.Detail).Infof("Cross checking (%s) with %x/%x", active.id, origin, parent)
d.checks[origin] = &crossCheck{
expire: time.Now().Add(blockSoftTTL),
parent: parent,
}
go active.getBlocks([]common.Hash{origin})
// Also fetch a fresh batch of hashes
getHashes(head)
continue
}
// We're done, prepare the download cache and proceed pulling the blocks
offset := uint64(0)
if block := d.getBlock(head); block != nil {
offset = block.NumberU64() + 1
}
d.queue.Prepare(offset)
finished = true
case blockPack := <-d.blockCh:
// Cross check the block with the random verifications
if blockPack.peerId != active.id || len(blockPack.blocks) != 1 {
continue
}
block := blockPack.blocks[0]
if check, ok := d.checks[block.Hash()]; ok {
if block.ParentHash() != check.parent {
return errCrossCheckFailed
}
delete(d.checks, block.Hash())
}
case <-crossTicker.C:
// Iterate over all the cross checks and fail the hash chain if they're not verified
for hash, check := range d.checks {
if time.Now().After(check.expire) {
glog.V(logger.Debug).Infof("Cross check timeout for %x", hash)
return errCrossCheckFailed
}
}
case <-timeout.C:
glog.V(logger.Debug).Infof("Peer (%s) didn't respond in time for hash request", p.id)
var p *peer // p will be set if a peer can be found
// Attempt to find a new peer by checking inclusion of peers best hash in our
// already fetched hash list. This can't guarantee 100% correctness but does
// a fair job. This is always either correct or false incorrect.
for _, peer := range d.peers.AllPeers() {
if d.queue.Has(peer.head) && !attempted[peer.id] {
p = peer
break
}
}
// if all peers have been tried, abort the process entirely or if the hash is
// the zero hash.
if p == nil || (head == common.Hash{}) {
return errTimeout
}
// set p to the active peer. this will invalidate any hashes that may be returned
// by our previous (delayed) peer.
active = p
getHashes(head)
glog.V(logger.Debug).Infof("Hash fetching switched to new peer(%s)", p.id)
}
}
glog.V(logger.Debug).Infof("Downloaded hashes (%d) in %v", d.queue.Pending(), time.Since(start))
return nil
}
// fetchBlocks60 iteratively downloads the entire schedules block-chain, taking
// any available peers, reserving a chunk of blocks for each, wait for delivery
// and periodically checking for timeouts.
func (d *Downloader) fetchBlocks60() error {
glog.V(logger.Debug).Infoln("Downloading", d.queue.Pending(), "block(s)")
start := time.Now()
// Start a ticker to continue throttled downloads and check for bad peers
ticker := time.NewTicker(20 * time.Millisecond)
defer ticker.Stop()
out:
for {
select {
case <-d.cancelCh:
return errCancelBlockFetch
case <-d.hashCh:
// Out of bounds hashes received, ignore them
case blockPack := <-d.blockCh:
// Short circuit if it's a stale cross check
if len(blockPack.blocks) == 1 {
block := blockPack.blocks[0]
if _, ok := d.checks[block.Hash()]; ok {
delete(d.checks, block.Hash())
break
}
}
// 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 {
// Deliver the received chunk of blocks, and demote in case of errors
err := d.queue.Deliver(blockPack.peerId, blockPack.blocks)
switch err {
case nil:
// If no blocks were delivered, demote the peer (need the delivery above)
if len(blockPack.blocks) == 0 {
peer.Demote()
peer.SetIdle()
glog.V(logger.Detail).Infof("%s: no blocks delivered", peer)
break
}
// All was successful, promote the peer and potentially start processing
peer.Promote()
peer.SetIdle()
glog.V(logger.Detail).Infof("%s: delivered %d blocks", peer, len(blockPack.blocks))
go d.process()
case errInvalidChain:
// The hash chain is invalid (blocks are not ordered properly), abort
return err
case errNoFetchesPending:
// Peer probably timed out with its delivery but came through
// in the end, demote, but allow to to pull from this peer.
peer.Demote()
peer.SetIdle()
glog.V(logger.Detail).Infof("%s: out of bound delivery", peer)
case errStaleDelivery:
// Delivered something completely else than requested, usually
// caused by a timeout and delivery during a new sync cycle.
// Don't set it to idle as the original request should still be
// in flight.
peer.Demote()
glog.V(logger.Detail).Infof("%s: stale delivery", peer)
default:
// Peer did something semi-useful, demote but keep it around
peer.Demote()
peer.SetIdle()
glog.V(logger.Detail).Infof("%s: delivery partially failed: %v", peer, err)
go d.process()
}
}
case <-ticker.C:
// Short circuit if we lost all our peers
if d.peers.Len() == 0 {
return errNoPeers
}
// Check for block request timeouts and demote the responsible peers
badPeers := d.queue.Expire(blockHardTTL)
for _, pid := range badPeers {
if peer := d.peers.Peer(pid); peer != nil {
peer.Demote()
glog.V(logger.Detail).Infof("%s: block delivery timeout", peer)
}
}
// If there are unrequested hashes left start fetching from the available peers
if d.queue.Pending() > 0 {
// Throttle the download if block cache is full and waiting processing
if d.queue.Throttle() {
break
}
// Send a download request to all idle peers, until throttled
idlePeers := d.peers.IdlePeers()
for _, peer := range idlePeers {
// Short circuit if throttling activated since above
if d.queue.Throttle() {
break
}
// Get a possible chunk. If nil is returned no chunk
// could be returned due to no hashes available.
request := d.queue.Reserve(peer, peer.Capacity())
if request == nil {
continue
}
if glog.V(logger.Detail) {
glog.Infof("%s: requesting %d blocks", peer, len(request.Hashes))
}
// Fetch the chunk and check for error. If the peer was somehow
// already fetching a chunk due to a bug, it will be returned to
// the queue
if err := peer.Fetch(request); err != nil {
glog.V(logger.Error).Infof("Peer %s received double work", peer.id)
d.queue.Cancel(request)
}
}
// Make sure that we have peers available for fetching. If all peers have been tried
// and all failed throw an error
if d.queue.InFlight() == 0 {
return errPeersUnavailable
}
} else if d.queue.InFlight() == 0 {
// When there are no more queue and no more in flight, We can
// safely assume we're done. Another part of the process will check
// for parent errors and will re-request anything that's missing
break out
}
}
}
glog.V(logger.Detail).Infoln("Downloaded block(s) in", time.Since(start))
return nil
}
// findAncestor tries to locate the common ancestor block of the local chain and
// a remote peers blockchain. In the general case when our node was in sync and
// on the correct chain, checking the top N blocks should already get us a match.
// In the rare scenario when we ended up on a long soft fork (i.e. none of the
// head blocks match), we do a binary search to find the common ancestor.
func (d *Downloader) findAncestor(p *peer) (uint64, error) {
glog.V(logger.Debug).Infof("%v: looking for common ancestor", p)
// Request out head blocks to short circuit ancestor location
head := d.headBlock().NumberU64()
from := int64(head) - int64(MaxHashFetch)
if from < 0 {
from = 0
}
go p.getAbsHashes(uint64(from), MaxHashFetch)
// Wait for the remote response to the head fetch
number, hash := uint64(0), common.Hash{}
timeout := time.After(hashTTL)
for finished := false; !finished; {
select {
case <-d.cancelCh:
return 0, errCancelHashFetch
case hashPack := <-d.hashCh:
// Discard anything not from the origin peer
if hashPack.peerId != p.id {
glog.V(logger.Debug).Infof("Received hashes from incorrect peer(%s)", hashPack.peerId)
break
}
// Make sure the peer actually gave something valid
hashes := hashPack.hashes
if len(hashes) == 0 {
glog.V(logger.Debug).Infof("%v: empty head hash set", p)
return 0, errEmptyHashSet
}
// Check if a common ancestor was found
finished = true
for i := len(hashes) - 1; i >= 0; i-- {
if d.hasBlock(hashes[i]) {
number, hash = uint64(from)+uint64(i), hashes[i]
break
}
}
case <-d.blockCh:
// Out of bounds blocks received, ignore them
case <-timeout:
glog.V(logger.Debug).Infof("%v: head hash timeout", p)
return 0, errTimeout
}
}
// If the head fetch already found an ancestor, return
if !common.EmptyHash(hash) {
glog.V(logger.Debug).Infof("%v: common ancestor: #%d [%x]", p, number, hash[:4])
return number, nil
}
// Ancestor not found, we need to binary search over our chain
start, end := uint64(0), head
for start+1 < end {
// Split our chain interval in two, and request the hash to cross check
check := (start + end) / 2
timeout := time.After(hashTTL)
go p.getAbsHashes(uint64(check), 1)
// Wait until a reply arrives to this request
for arrived := false; !arrived; {
select {
case <-d.cancelCh:
return 0, errCancelHashFetch
case hashPack := <-d.hashCh:
// Discard anything not from the origin peer
if hashPack.peerId != p.id {
glog.V(logger.Debug).Infof("Received hashes from incorrect peer(%s)", hashPack.peerId)
break
}
// Make sure the peer actually gave something valid
hashes := hashPack.hashes
if len(hashes) != 1 {
glog.V(logger.Debug).Infof("%v: invalid search hash set (%d)", p, len(hashes))
return 0, errBadPeer
}
arrived = true
// Modify the search interval based on the response
block := d.getBlock(hashes[0])
if block == nil {
end = check
break
}
if block.NumberU64() != check {
glog.V(logger.Debug).Infof("%v: non requested hash #%d [%x], instead of #%d", p, block.NumberU64(), block.Hash().Bytes()[:4], check)
return 0, errBadPeer
}
start = check
case <-d.blockCh:
// Out of bounds blocks received, ignore them
case <-timeout:
glog.V(logger.Debug).Infof("%v: search hash timeout", p)
return 0, errTimeout
}
}
}
return start, nil
}
// fetchHashes keeps retrieving hashes from the requested number, until no more
// are returned, potentially throttling on the way.
func (d *Downloader) fetchHashes(p *peer, td *big.Int, from uint64) error {
glog.V(logger.Debug).Infof("%v: downloading hashes from #%d", p, from)
// Create a timeout timer, and the associated hash fetcher
timeout := time.NewTimer(0) // timer to dump a non-responsive active peer
<-timeout.C // timeout channel should be initially empty
defer timeout.Stop()
getHashes := func(from uint64) {
glog.V(logger.Detail).Infof("%v: fetching %d hashes from #%d", p, MaxHashFetch, from)
go p.getAbsHashes(from, MaxHashFetch)
timeout.Reset(hashTTL)
}
// Start pulling hashes, until all are exhausted
getHashes(from)
gotHashes := false
for {
select {
case <-d.cancelCh:
return errCancelHashFetch
case hashPack := <-d.hashCh:
// Make sure the active peer is giving us the hashes
if hashPack.peerId != p.id {
glog.V(logger.Debug).Infof("Received hashes from incorrect peer(%s)", hashPack.peerId)
break
}
timeout.Stop()
// If no more hashes are inbound, notify the block fetcher and return
if len(hashPack.hashes) == 0 {
glog.V(logger.Debug).Infof("%v: no available hashes", p)
select {
case d.processCh <- false:
case <-d.cancelCh:
}
// If no hashes 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 hashes up from 11 (R's TD was higher, it must have something)
// R: Nothing to give
if !gotHashes && td.Cmp(d.headBlock().Td) > 0 {
return errStallingPeer
}
return nil
}
gotHashes = true
// Otherwise insert all the new hashes, aborting in case of junk
glog.V(logger.Detail).Infof("%v: inserting %d hashes from #%d", p, len(hashPack.hashes), from)
inserts := d.queue.Insert(hashPack.hashes, true)
if len(inserts) != len(hashPack.hashes) {
glog.V(logger.Debug).Infof("%v: stale hashes", p)
return errBadPeer
}
// Notify the block fetcher of new hashes, but stop if queue is full
cont := d.queue.Pending() < maxQueuedHashes
select {
case d.processCh <- cont:
default:
}
if !cont {
return nil
}
// Queue not yet full, fetch the next batch
from += uint64(len(hashPack.hashes))
getHashes(from)
case <-timeout.C:
glog.V(logger.Debug).Infof("%v: hash request timed out", p)
return errTimeout
}
}
}
// fetchBlocks iteratively downloads the scheduled hashes, taking any available
// peers, reserving a chunk of blocks for each, waiting for delivery and also
// periodically checking for timeouts.
func (d *Downloader) fetchBlocks(from uint64) error {
glog.V(logger.Debug).Infof("Downloading blocks from #%d", from)
defer glog.V(logger.Debug).Infof("Block download terminated")
// Create a timeout timer for scheduling expiration tasks
ticker := time.NewTicker(100 * time.Millisecond)
defer ticker.Stop()
update := make(chan struct{}, 1)
// Prepare the queue and fetch blocks until the hash fetcher's done
d.queue.Prepare(from)
finished := false
for {
select {
case <-d.cancelCh:
return errCancelBlockFetch
case blockPack := <-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 {
// Deliver the received chunk of blocks, and demote in case of errors
err := d.queue.Deliver(blockPack.peerId, blockPack.blocks)
switch err {
case nil:
// If no blocks were delivered, demote the peer (need the delivery above)
if len(blockPack.blocks) == 0 {
peer.Demote()
peer.SetIdle()
glog.V(logger.Detail).Infof("%s: no blocks delivered", peer)
break
}
// All was successful, promote the peer and potentially start processing
peer.Promote()
peer.SetIdle()
glog.V(logger.Detail).Infof("%s: delivered %d blocks", peer, len(blockPack.blocks))
go d.process()
case errInvalidChain:
// The hash chain is invalid (blocks are not ordered properly), abort
return err
case errNoFetchesPending:
// Peer probably timed out with its delivery but came through
// in the end, demote, but allow to to pull from this peer.
peer.Demote()
peer.SetIdle()
glog.V(logger.Detail).Infof("%s: out of bound delivery", peer)
case errStaleDelivery:
// Delivered something completely else than requested, usually
// caused by a timeout and delivery during a new sync cycle.
// Don't set it to idle as the original request should still be
// in flight.
peer.Demote()
glog.V(logger.Detail).Infof("%s: stale delivery", peer)
default:
// Peer did something semi-useful, demote but keep it around
peer.Demote()
peer.SetIdle()
glog.V(logger.Detail).Infof("%s: delivery partially failed: %v", peer, err)
go d.process()
}
}
// Blocks arrived, try to update the progress
select {
case update <- struct{}{}:
default:
}
case cont := <-d.processCh:
// The hash fetcher sent a continuation flag, check if it's done
if !cont {
finished = true
}
// Hashes arrive, try to update the progress
select {
case update <- struct{}{}:
default:
}
case <-ticker.C:
// Sanity check update the progress
select {
case update <- struct{}{}:
default:
}
case <-update:
// Short circuit if we lost all our peers
if d.peers.Len() == 0 {
return errNoPeers
}
// Check for block request timeouts and demote the responsible peers
for _, pid := range d.queue.Expire(blockHardTTL) {
if peer := d.peers.Peer(pid); peer != nil {
peer.Demote()
glog.V(logger.Detail).Infof("%s: block delivery timeout", peer)
}
}
// If there's noting more to fetch, wait or terminate
if d.queue.Pending() == 0 {
if d.queue.InFlight() == 0 && finished {
glog.V(logger.Debug).Infof("Block fetching completed")
return nil
}
break
}
// Send a download request to all idle peers, until throttled
for _, peer := range d.peers.IdlePeers() {
// Short circuit if throttling activated
if d.queue.Throttle() {
break
}
// 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.Reserve(peer, peer.Capacity())
if request == nil {
continue
}
if glog.V(logger.Detail) {
glog.Infof("%s: requesting %d blocks", peer, len(request.Hashes))
}
// Fetch the chunk and make sure any errors return the hashes to the queue
if err := peer.Fetch(request); err != nil {
glog.V(logger.Error).Infof("%v: fetch failed, rescheduling", peer)
d.queue.Cancel(request)
}
}
// Make sure that we have peers available for fetching. If all peers have been tried
// and all failed throw an error
if !d.queue.Throttle() && d.queue.InFlight() == 0 {
return errPeersUnavailable
}
}
}
}
// banBlocks retrieves a batch of blocks from a peer feeding us invalid hashes,
// and bans the head of the retrieved batch.
//
// This method only fetches one single batch as the goal is not ban an entire
// (potentially long) invalid chain - wasting a lot of time in the meanwhile -,
// but rather to gradually build up a blacklist if the peer keeps reconnecting.
func (d *Downloader) banBlocks(peerId string, head common.Hash) error {
glog.V(logger.Debug).Infof("Banning a batch out of %d blocks from %s", d.queue.Pending(), peerId)
// Ask the peer being banned for a batch of blocks from the banning point
peer := d.peers.Peer(peerId)
if peer == nil {
return nil
}
request := d.queue.Reserve(peer, MaxBlockFetch)
if request == nil {
return nil
}
if err := peer.Fetch(request); err != nil {
return err
}
// Wait a bit for the reply to arrive, and ban if done so
timeout := time.After(blockHardTTL)
for {
select {
case <-d.cancelCh:
return errCancelBlockFetch
case <-timeout:
return errTimeout
case <-d.hashCh:
// Out of bounds hashes received, ignore them
case blockPack := <-d.blockCh:
blocks := blockPack.blocks
// Short circuit if it's a stale cross check
if len(blocks) == 1 {
block := blocks[0]
if _, ok := d.checks[block.Hash()]; ok {
delete(d.checks, block.Hash())
break
}
}
// Short circuit if it's not from the peer being banned
if blockPack.peerId != peerId {
break
}
// Short circuit if no blocks were returned
if len(blocks) == 0 {
return errors.New("no blocks returned to ban")
}
// Reconstruct the original chain order and ensure we're banning the correct blocks
types.BlockBy(types.Number).Sort(blocks)
if bytes.Compare(blocks[0].Hash().Bytes(), head.Bytes()) != 0 {
return errors.New("head block not the banned one")
}
index := 0
for _, block := range blocks[1:] {
if bytes.Compare(block.ParentHash().Bytes(), blocks[index].Hash().Bytes()) != 0 {
break
}
index++
}
// Ban the head hash and phase out any excess
d.banned.Add(blocks[index].Hash())
for d.banned.Size() > maxBannedHashes {
var evacuate common.Hash
d.banned.Each(func(item interface{}) bool {
// Skip any hard coded bans
if core.BadHashes[item.(common.Hash)] {
return true
}
evacuate = item.(common.Hash)
return false
})
d.banned.Remove(evacuate)
}
glog.V(logger.Debug).Infof("Banned %d blocks from: %s", index+1, peerId)
return nil
}
}
}
// process takes blocks from the queue and tries to import them into the chain.
//
// The algorithmic flow is as follows:
// - The `processing` flag is swapped to 1 to ensure singleton access
// - The current `cancel` channel is retrieved to detect sync abortions
// - Blocks are iteratively taken from the cache and inserted into the chain
// - When the cache becomes empty, insertion stops
// - The `processing` flag is swapped back to 0
// - A post-exit check is made whether new blocks became available
// - This step is important: it handles a potential race condition between
// checking for no more work, and releasing the processing "mutex". In
// between these state changes, a block may have arrived, but a processing
// attempt denied, so we need to re-enter to ensure the block isn't left
// to idle in the cache.
func (d *Downloader) process() {
// Make sure only one goroutine is ever allowed to process blocks at once
if !atomic.CompareAndSwapInt32(&d.processing, 0, 1) {
return
}
// If the processor just exited, but there are freshly pending items, try to
// reenter. This is needed because the goroutine spinned up for processing
// the fresh blocks might have been rejected entry to to this present thread
// not yet releasing the `processing` state.
defer func() {
if atomic.LoadInt32(&d.interrupt) == 0 && d.queue.GetHeadBlock() != nil {
d.process()
}
}()
// Release the lock upon exit (note, before checking for reentry!), and set
// the import statistics to zero.
defer func() {
d.importLock.Lock()
d.importQueue = nil
d.importDone = 0
d.importLock.Unlock()
atomic.StoreInt32(&d.processing, 0)
}()
// Repeat the processing as long as there are blocks to import
for {
// Fetch the next batch of blocks
blocks := d.queue.TakeBlocks()
if len(blocks) == 0 {
return
}
// Reset the import statistics
d.importLock.Lock()
d.importStart = time.Now()
d.importQueue = blocks
d.importDone = 0
d.importLock.Unlock()
// Actually import the blocks
glog.V(logger.Debug).Infof("Inserting chain with %d blocks (#%v - #%v)\n", len(blocks), blocks[0].RawBlock.Number(), blocks[len(blocks)-1].RawBlock.Number())
for len(blocks) != 0 {
// Check for any termination requests
if atomic.LoadInt32(&d.interrupt) == 1 {
return
}
// Retrieve the first batch of blocks to insert
max := int(math.Min(float64(len(blocks)), float64(maxBlockProcess)))
raw := make(types.Blocks, 0, max)
for _, block := range blocks[:max] {
raw = append(raw, block.RawBlock)
}
// Try to inset the blocks, drop the originating peer if there's an error
index, err := d.insertChain(raw)
if err != nil {
glog.V(logger.Debug).Infof("Block #%d import failed: %v", raw[index].NumberU64(), err)
d.dropPeer(blocks[index].OriginPeer)
d.cancel()
return
}
blocks = blocks[max:]
}
}
}
// 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) DeliverBlocks(id string, blocks []*types.Block) error {
// 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
}
}
// 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) DeliverHashes(id string, hashes []common.Hash) error {
// 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
}
}