// Copyright 2016 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 les implements the Light Ethereum Subprotocol.
package les
import (
"math/big"
"sync"
"time"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/common/mclock"
"github.com/ethereum/go-ethereum/core"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/light"
"github.com/ethereum/go-ethereum/logger"
"github.com/ethereum/go-ethereum/logger/glog"
)
const (
blockDelayTimeout = time.Second * 10 // timeout for a peer to announce a head that has already been confirmed by others
maxNodeCount = 20 // maximum number of fetcherTreeNode entries remembered for each peer
)
// lightFetcher
type lightFetcher struct {
pm *ProtocolManager
odr *LesOdr
chain *light.LightChain
maxConfirmedTd *big.Int
peers map[*peer]*fetcherPeerInfo
lastUpdateStats *updateStatsEntry
lock sync.Mutex // qwerqwerqwe
deliverChn chan fetchResponse
reqMu sync.RWMutex
requested map[uint64]fetchRequest
timeoutChn chan uint64
requestChn chan bool // true if initiated from outside
syncing bool
syncDone chan *peer
}
// fetcherPeerInfo holds fetcher-specific information about each active peer
type fetcherPeerInfo struct {
root, lastAnnounced *fetcherTreeNode
nodeCnt int
confirmedTd *big.Int
bestConfirmed *fetcherTreeNode
nodeByHash map[common.Hash]*fetcherTreeNode
firstUpdateStats *updateStatsEntry
}
// fetcherTreeNode is a node of a tree that holds information about blocks recently
// announced and confirmed by a certain peer. Each new announce message from a peer
// adds nodes to the tree, based on the previous announced head and the reorg depth.
// There are three possible states for a tree node:
// - announced: not downloaded (known) yet, but we know its head, number and td
// - intermediate: not known, hash and td are empty, they are filled out when it becomes known
// - known: both announced by this peer and downloaded (from any peer).
// This structure makes it possible to always know which peer has a certain block,
// which is necessary for selecting a suitable peer for ODR requests and also for
// canonizing new heads. It also helps to always download the minimum necessary
// amount of headers with a single request.
type fetcherTreeNode struct {
hash common.Hash
number uint64
td *big.Int
known, requested bool
parent *fetcherTreeNode
children []*fetcherTreeNode
}
// fetchRequest represents a header download request
type fetchRequest struct {
hash common.Hash
amount uint64
peer *peer
sent mclock.AbsTime
timeout bool
}
// fetchResponse represents a header download response
type fetchResponse struct {
reqID uint64
headers []*types.Header
peer *peer
}
// newLightFetcher creates a new light fetcher
func newLightFetcher(pm *ProtocolManager) *lightFetcher {
f := &lightFetcher{
pm: pm,
chain: pm.blockchain.(*light.LightChain),
odr: pm.odr,
peers: make(map[*peer]*fetcherPeerInfo),
deliverChn: make(chan fetchResponse, 100),
requested: make(map[uint64]fetchRequest),
timeoutChn: make(chan uint64),
requestChn: make(chan bool, 100),
syncDone: make(chan *peer),
maxConfirmedTd: big.NewInt(0),
}
go f.syncLoop()
return f
}
// syncLoop is the main event loop of the light fetcher
func (f *lightFetcher) syncLoop() {
f.pm.wg.Add(1)
defer f.pm.wg.Done()
requestStarted := false
for {
select {
case <-f.pm.quitSync:
return
// when a new announce is received, request loop keeps running until
// no further requests are necessary or possible
case newAnnounce := <-f.requestChn:
f.lock.Lock()
s := requestStarted
requestStarted = false
if !f.syncing && !(newAnnounce && s) {
if peer, node, amount := f.nextRequest(); node != nil {
requestStarted = true
reqID, started := f.request(peer, node, amount)
if started {
go func() {
time.Sleep(softRequestTimeout)
f.reqMu.Lock()
req, ok := f.requested[reqID]
if ok {
req.timeout = true
f.requested[reqID] = req
}
f.reqMu.Unlock()
// keep starting new requests while possible
f.requestChn <- false
}()
}
}
}
f.lock.Unlock()
case reqID := <-f.timeoutChn:
f.reqMu.Lock()
req, ok := f.requested[reqID]
if ok {
delete(f.requested, reqID)
}
f.reqMu.Unlock()
if ok {
f.pm.serverPool.adjustResponseTime(req.peer.poolEntry, time.Duration(mclock.Now()-req.sent), true)
glog.V(logger.Debug).Infof("hard timeout by peer %v", req.peer.id)
go f.pm.removePeer(req.peer.id)
}
case resp := <-f.deliverChn:
f.reqMu.Lock()
req, ok := f.requested[resp.reqID]
if ok && req.peer != resp.peer {
ok = false
}
if ok {
delete(f.requested, resp.reqID)
}
f.reqMu.Unlock()
if ok {
f.pm.serverPool.adjustResponseTime(req.peer.poolEntry, time.Duration(mclock.Now()-req.sent), req.timeout)
}
f.lock.Lock()
if !ok || !(f.syncing || f.processResponse(req, resp)) {
glog.V(logger.Debug).Infof("failed processing response by peer %v", resp.peer.id)
go f.pm.removePeer(resp.peer.id)
}
f.lock.Unlock()
case p := <-f.syncDone:
f.lock.Lock()
glog.V(logger.Debug).Infof("done synchronising with peer %v", p.id)
f.checkSyncedHeaders(p)
f.syncing = false
f.lock.Unlock()
}
}
}
// addPeer adds a new peer to the fetcher's peer set
func (f *lightFetcher) addPeer(p *peer) {
p.lock.Lock()
p.hasBlock = func(hash common.Hash, number uint64) bool {
return f.peerHasBlock(p, hash, number)
}
p.lock.Unlock()
f.lock.Lock()
defer f.lock.Unlock()
f.peers[p] = &fetcherPeerInfo{nodeByHash: make(map[common.Hash]*fetcherTreeNode)}
}
// removePeer removes a new peer from the fetcher's peer set
func (f *lightFetcher) removePeer(p *peer) {
p.lock.Lock()
p.hasBlock = nil
p.lock.Unlock()
f.lock.Lock()
defer f.lock.Unlock()
// check for potential timed out block delay statistics
f.checkUpdateStats(p, nil)
delete(f.peers, p)
}
// announce processes a new announcement message received from a peer, adding new
// nodes to the peer's block tree and removing old nodes if necessary
func (f *lightFetcher) announce(p *peer, head *announceData) {
f.lock.Lock()
defer f.lock.Unlock()
glog.V(logger.Debug).Infof("received announce from peer %v #%d %016x reorg: %d", p.id, head.Number, head.Hash[:8], head.ReorgDepth)
fp := f.peers[p]
if fp == nil {
glog.V(logger.Debug).Infof("announce: unknown peer")
return
}
if fp.lastAnnounced != nil && head.Td.Cmp(fp.lastAnnounced.td) <= 0 {
// announced tds should be strictly monotonic
glog.V(logger.Debug).Infof("non-monotonic Td from peer %v", p.id)
go f.pm.removePeer(p.id)
return
}
n := fp.lastAnnounced
for i := uint64(0); i < head.ReorgDepth; i++ {
if n == nil {
break
}
n = n.parent
}
if n != nil {
// n is now the reorg common ancestor, add a new branch of nodes
// check if the node count is too high to add new nodes
locked := false
for uint64(fp.nodeCnt)+head.Number-n.number > maxNodeCount && fp.root != nil {
if !locked {
f.chain.LockChain()
defer f.chain.UnlockChain()
locked = true
}
// if one of root's children is canonical, keep it, delete other branches and root itself
var newRoot *fetcherTreeNode
for i, nn := range fp.root.children {
if core.GetCanonicalHash(f.pm.chainDb, nn.number) == nn.hash {
fp.root.children = append(fp.root.children[:i], fp.root.children[i+1:]...)
nn.parent = nil
newRoot = nn
break
}
}
fp.deleteNode(fp.root)
if n == fp.root {
n = newRoot
}
fp.root = newRoot
if newRoot == nil || !f.checkKnownNode(p, newRoot) {
fp.bestConfirmed = nil
fp.confirmedTd = nil
}
if n == nil {
break
}
}
if n != nil {
for n.number < head.Number {
nn := &fetcherTreeNode{number: n.number + 1, parent: n}
n.children = append(n.children, nn)
n = nn
fp.nodeCnt++
}
n.hash = head.Hash
n.td = head.Td
fp.nodeByHash[n.hash] = n
}
}
if n == nil {
// could not find reorg common ancestor or had to delete entire tree, a new root and a resync is needed
if fp.root != nil {
fp.deleteNode(fp.root)
}
n = &fetcherTreeNode{hash: head.Hash, number: head.Number, td: head.Td}
fp.root = n
fp.nodeCnt++
fp.nodeByHash[n.hash] = n
fp.bestConfirmed = nil
fp.confirmedTd = nil
}
f.checkKnownNode(p, n)
p.lock.Lock()
p.headInfo = head
fp.lastAnnounced = n
p.lock.Unlock()
f.checkUpdateStats(p, nil)
f.requestChn <- true
}
// peerHasBlock returns true if we can assume the peer knows the given block
// based on its announcements
func (f *lightFetcher) peerHasBlock(p *peer, hash common.Hash, number uint64) bool {
f.lock.Lock()
defer f.lock.Unlock()
fp := f.peers[p]
if fp == nil || fp.root == nil {
return false
}
if number >= fp.root.number {
// it is recent enough that if it is known, is should be in the peer's block tree
return fp.nodeByHash[hash] != nil
}
f.chain.LockChain()
defer f.chain.UnlockChain()
// if it's older than the peer's block tree root but it's in the same canonical chain
// than the root, we can still be sure the peer knows it
return core.GetCanonicalHash(f.pm.chainDb, fp.root.number) == fp.root.hash && core.GetCanonicalHash(f.pm.chainDb, number) == hash
}
// request initiates a header download request from a certain peer
func (f *lightFetcher) request(p *peer, n *fetcherTreeNode, amount uint64) (uint64, bool) {
fp := f.peers[p]
if fp == nil {
glog.V(logger.Debug).Infof("request: unknown peer")
return 0, false
}
if fp.bestConfirmed == nil || fp.root == nil || !f.checkKnownNode(p, fp.root) {
f.syncing = true
go func() {
glog.V(logger.Debug).Infof("synchronising with peer %v", p.id)
f.pm.synchronise(p)
f.syncDone <- p
}()
return 0, false
}
reqID := getNextReqID()
n.requested = true
cost := p.GetRequestCost(GetBlockHeadersMsg, int(amount))
p.fcServer.SendRequest(reqID, cost)
f.reqMu.Lock()
f.requested[reqID] = fetchRequest{hash: n.hash, amount: amount, peer: p, sent: mclock.Now()}
f.reqMu.Unlock()
go p.RequestHeadersByHash(reqID, cost, n.hash, int(amount), 0, true)
go func() {
time.Sleep(hardRequestTimeout)
f.timeoutChn <- reqID
}()
return reqID, true
}
// requestAmount calculates the amount of headers to be downloaded starting
// from a certain head backwards
func (f *lightFetcher) requestAmount(p *peer, n *fetcherTreeNode) uint64 {
amount := uint64(0)
nn := n
for nn != nil && !f.checkKnownNode(p, nn) {
nn = nn.parent
amount++
}
if nn == nil {
amount = n.number
}
return amount
}
// requestedID tells if a certain reqID has been requested by the fetcher
func (f *lightFetcher) requestedID(reqID uint64) bool {
f.reqMu.RLock()
_, ok := f.requested[reqID]
f.reqMu.RUnlock()
return ok
}
// nextRequest selects the peer and announced head to be requested next, amount
// to be downloaded starting from the head backwards is also returned
func (f *lightFetcher) nextRequest() (*peer, *fetcherTreeNode, uint64) {
var (
bestHash common.Hash
bestAmount uint64
)
bestTd := f.maxConfirmedTd
for p, fp := range f.peers {
for hash, n := range fp.nodeByHash {
if !f.checkKnownNode(p, n) && !n.requested && (bestTd == nil || n.td.Cmp(bestTd) >= 0) {
amount := f.requestAmount(p, n)
if bestTd == nil || n.td.Cmp(bestTd) > 0 || amount < bestAmount {
bestHash = hash
bestAmount = amount
bestTd = n.td
}
}
}
}
if bestTd == f.maxConfirmedTd {
return nil, nil, 0
}
peer := f.pm.serverPool.selectPeer(func(p *peer) (bool, uint64) {
fp := f.peers[p]
if fp == nil || fp.nodeByHash[bestHash] == nil {
return false, 0
}
return true, p.fcServer.CanSend(p.GetRequestCost(GetBlockHeadersMsg, int(bestAmount)))
})
var node *fetcherTreeNode
if peer != nil {
node = f.peers[peer].nodeByHash[bestHash]
}
return peer, node, bestAmount
}
// deliverHeaders delivers header download request responses for processing
func (f *lightFetcher) deliverHeaders(peer *peer, reqID uint64, headers []*types.Header) {
f.deliverChn <- fetchResponse{reqID: reqID, headers: headers, peer: peer}
}
// processResponse processes header download request responses
func (f *lightFetcher) processResponse(req fetchRequest, resp fetchResponse) bool {
if uint64(len(resp.headers)) != req.amount || resp.headers[0].Hash() != req.hash {
return false
}
headers := make([]*types.Header, req.amount)
for i, header := range resp.headers {
headers[int(req.amount)-1-i] = header
}
if _, err := f.chain.InsertHeaderChain(headers, 1); err != nil {
return false
}
tds := make([]*big.Int, len(headers))
for i, header := range headers {
td := f.chain.GetTd(header.Hash(), header.Number.Uint64())
if td == nil {
return false
}
tds[i] = td
}
f.newHeaders(headers, tds)
return true
}
// newHeaders updates the block trees of all active peers according to a newly
// downloaded and validated batch or headers
func (f *lightFetcher) newHeaders(headers []*types.Header, tds []*big.Int) {
var maxTd *big.Int
for p, fp := range f.peers {
if !f.checkAnnouncedHeaders(fp, headers, tds) {
glog.V(logger.Debug).Infof("announce inconsistency by peer %v", p.id)
go f.pm.removePeer(p.id)
}
if fp.confirmedTd != nil && (maxTd == nil || maxTd.Cmp(fp.confirmedTd) > 0) {
maxTd = fp.confirmedTd
}
}
if maxTd != nil {
f.updateMaxConfirmedTd(maxTd)
}
}
// checkAnnouncedHeaders updates peer's block tree if necessary after validating
// a batch of headers. It searches for the latest header in the batch that has a
// matching tree node (if any), and if it has not been marked as known already,
// sets it and its parents to known (even those which are older than the currently
// validated ones). Return value shows if all hashes, numbers and Tds matched
// correctly to the announced values (otherwise the peer should be dropped).
func (f *lightFetcher) checkAnnouncedHeaders(fp *fetcherPeerInfo, headers []*types.Header, tds []*big.Int) bool {
var (
n *fetcherTreeNode
header *types.Header
td *big.Int
)
for i := len(headers) - 1; ; i-- {
if i < 0 {
if n == nil {
// no more headers and nothing to match
return true
}
// we ran out of recently delivered headers but have not reached a node known by this peer yet, continue matching
td = f.chain.GetTd(header.ParentHash, header.Number.Uint64()-1)
header = f.chain.GetHeader(header.ParentHash, header.Number.Uint64()-1)
} else {
header = headers[i]
td = tds[i]
}
hash := header.Hash()
number := header.Number.Uint64()
if n == nil {
n = fp.nodeByHash[hash]
}
if n != nil {
if n.td == nil {
// node was unannounced
if nn := fp.nodeByHash[hash]; nn != nil {
// if there was already a node with the same hash, continue there and drop this one
nn.children = append(nn.children, n.children...)
n.children = nil
fp.deleteNode(n)
n = nn
} else {
n.hash = hash
n.td = td
fp.nodeByHash[hash] = n
}
}
// check if it matches the header
if n.hash != hash || n.number != number || n.td.Cmp(td) != 0 {
// peer has previously made an invalid announcement
return false
}
if n.known {
// we reached a known node that matched our expectations, return with success
return true
}
n.known = true
if fp.confirmedTd == nil || td.Cmp(fp.confirmedTd) > 0 {
fp.confirmedTd = td
fp.bestConfirmed = n
}
n = n.parent
if n == nil {
return true
}
}
}
}
// checkSyncedHeaders updates peer's block tree after synchronisation by marking
// downloaded headers as known. If none of the announced headers are found after
// syncing, the peer is dropped.
func (f *lightFetcher) checkSyncedHeaders(p *peer) {
fp := f.peers[p]
if fp == nil {
glog.V(logger.Debug).Infof("checkSyncedHeaders: unknown peer")
return
}
n := fp.lastAnnounced
var td *big.Int
for n != nil {
if td = f.chain.GetTd(n.hash, n.number); td != nil {
break
}
n = n.parent
}
// now n is the latest downloaded header after syncing
if n == nil {
glog.V(logger.Debug).Infof("synchronisation failed with peer %v", p.id)
go f.pm.removePeer(p.id)
} else {
header := f.chain.GetHeader(n.hash, n.number)
f.newHeaders([]*types.Header{header}, []*big.Int{td})
}
}
// checkKnownNode checks if a block tree node is known (downloaded and validated)
// If it was not known previously but found in the database, sets its known flag
func (f *lightFetcher) checkKnownNode(p *peer, n *fetcherTreeNode) bool {
if n.known {
return true
}
td := f.chain.GetTd(n.hash, n.number)
if td == nil {
return false
}
fp := f.peers[p]
if fp == nil {
glog.V(logger.Debug).Infof("checkKnownNode: unknown peer")
return false
}
header := f.chain.GetHeader(n.hash, n.number)
if !f.checkAnnouncedHeaders(fp, []*types.Header{header}, []*big.Int{td}) {
glog.V(logger.Debug).Infof("announce inconsistency by peer %v", p.id)
go f.pm.removePeer(p.id)
}
if fp.confirmedTd != nil {
f.updateMaxConfirmedTd(fp.confirmedTd)
}
return n.known
}
// deleteNode deletes a node and its child subtrees from a peer's block tree
func (fp *fetcherPeerInfo) deleteNode(n *fetcherTreeNode) {
if n.parent != nil {
for i, nn := range n.parent.children {
if nn == n {
n.parent.children = append(n.parent.children[:i], n.parent.children[i+1:]...)
break
}
}
}
for {
if n.td != nil {
delete(fp.nodeByHash, n.hash)
}
fp.nodeCnt--
if len(n.children) == 0 {
return
}
for i, nn := range n.children {
if i == 0 {
n = nn
} else {
fp.deleteNode(nn)
}
}
}
}
// updateStatsEntry items form a linked list that is expanded with a new item every time a new head with a higher Td
// than the previous one has been downloaded and validated. The list contains a series of maximum confirmed Td values
// and the time these values have been confirmed, both increasing monotonically. A maximum confirmed Td is calculated
// both globally for all peers and also for each individual peer (meaning that the given peer has announced the head
// and it has also been downloaded from any peer, either before or after the given announcement).
// The linked list has a global tail where new confirmed Td entries are added and a separate head for each peer,
// pointing to the next Td entry that is higher than the peer's max confirmed Td (nil if it has already confirmed
// the current global head).
type updateStatsEntry struct {
time mclock.AbsTime
td *big.Int
next *updateStatsEntry
}
// updateMaxConfirmedTd updates the block delay statistics of active peers. Whenever a new highest Td is confirmed,
// adds it to the end of a linked list together with the time it has been confirmed. Then checks which peers have
// already confirmed a head with the same or higher Td (which counts as zero block delay) and updates their statistics.
// Those who have not confirmed such a head by now will be updated by a subsequent checkUpdateStats call with a
// positive block delay value.
func (f *lightFetcher) updateMaxConfirmedTd(td *big.Int) {
if f.maxConfirmedTd == nil || td.Cmp(f.maxConfirmedTd) > 0 {
f.maxConfirmedTd = td
newEntry := &updateStatsEntry{
time: mclock.Now(),
td: td,
}
if f.lastUpdateStats != nil {
f.lastUpdateStats.next = newEntry
}
f.lastUpdateStats = newEntry
for p, _ := range f.peers {
f.checkUpdateStats(p, newEntry)
}
}
}
// checkUpdateStats checks those peers who have not confirmed a certain highest Td (or a larger one) by the time it
// has been confirmed by another peer. If they have confirmed such a head by now, their stats are updated with the
// block delay which is (this peer's confirmation time)-(first confirmation time). After blockDelayTimeout has passed,
// the stats are updated with blockDelayTimeout value. In either case, the confirmed or timed out updateStatsEntry
// items are removed from the head of the linked list.
// If a new entry has been added to the global tail, it is passed as a parameter here even though this function
// assumes that it has already been added, so that if the peer's list is empty (all heads confirmed, head is nil),
// it can set the new head to newEntry.
func (f *lightFetcher) checkUpdateStats(p *peer, newEntry *updateStatsEntry) {
now := mclock.Now()
fp := f.peers[p]
if fp == nil {
glog.V(logger.Debug).Infof("checkUpdateStats: unknown peer")
return
}
if newEntry != nil && fp.firstUpdateStats == nil {
fp.firstUpdateStats = newEntry
}
for fp.firstUpdateStats != nil && fp.firstUpdateStats.time <= now-mclock.AbsTime(blockDelayTimeout) {
f.pm.serverPool.adjustBlockDelay(p.poolEntry, blockDelayTimeout)
fp.firstUpdateStats = fp.firstUpdateStats.next
}
if fp.confirmedTd != nil {
for fp.firstUpdateStats != nil && fp.firstUpdateStats.td.Cmp(fp.confirmedTd) <= 0 {
f.pm.serverPool.adjustBlockDelay(p.poolEntry, time.Duration(now-fp.firstUpdateStats.time))
fp.firstUpdateStats = fp.firstUpdateStats.next
}
}
}
