plugeth/les/fetcher.go
Felföldi Zsolt b4a2681120
les, les/lespay: implement new server pool (#20758)
This PR reimplements the light client server pool. It is also a first step
to move certain logic into a new lespay package. This package will contain
the implementation of the lespay token sale functions, the token buying and
selling logic and other components related to peer selection/prioritization
and service quality evaluation. Over the long term this package will be
reusable for incentivizing future protocols.

Since the LES peer logic is now based on enode.Iterator, it can now use
DNS-based fallback discovery to find servers.

This document describes the function of the new components:
https://gist.github.com/zsfelfoldi/3c7ace895234b7b345ab4f71dab102d4
2020-05-22 13:46:34 +02:00

888 lines
27 KiB
Go

// 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
import (
"math/big"
"sync"
"time"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/common/mclock"
"github.com/ethereum/go-ethereum/consensus"
"github.com/ethereum/go-ethereum/core/rawdb"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/light"
"github.com/ethereum/go-ethereum/log"
)
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
serverStateAvailable = 100 // number of recent blocks where state availability is assumed
)
// lightFetcher implements retrieval of newly announced headers. It also provides a peerHasBlock function for the
// ODR system to ensure that we only request data related to a certain block from peers who have already processed
// and announced that block.
type lightFetcher struct {
handler *clientHandler
chain *light.LightChain
softRequestTimeout func() time.Duration
lock sync.Mutex // lock protects access to the fetcher's internal state variables except sent requests
maxConfirmedTd *big.Int
peers map[*serverPeer]*fetcherPeerInfo
lastUpdateStats *updateStatsEntry
syncing bool
syncDone chan *serverPeer
reqMu sync.RWMutex // reqMu protects access to sent header fetch requests
requested map[uint64]fetchRequest
deliverChn chan fetchResponse
timeoutChn chan uint64
requestTriggered bool
requestTrigger chan struct{}
lastTrustedHeader *types.Header
closeCh chan struct{}
wg sync.WaitGroup
}
// 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 *serverPeer
sent mclock.AbsTime
timeout bool
}
// fetchResponse represents a header download response
type fetchResponse struct {
reqID uint64
headers []*types.Header
peer *serverPeer
}
// newLightFetcher creates a new light fetcher
func newLightFetcher(h *clientHandler, softRequestTimeout func() time.Duration) *lightFetcher {
f := &lightFetcher{
handler: h,
chain: h.backend.blockchain,
peers: make(map[*serverPeer]*fetcherPeerInfo),
deliverChn: make(chan fetchResponse, 100),
requested: make(map[uint64]fetchRequest),
timeoutChn: make(chan uint64),
requestTrigger: make(chan struct{}, 1),
syncDone: make(chan *serverPeer),
closeCh: make(chan struct{}),
maxConfirmedTd: big.NewInt(0),
softRequestTimeout: softRequestTimeout,
}
h.backend.peers.subscribe(f)
f.wg.Add(1)
go f.syncLoop()
return f
}
func (f *lightFetcher) close() {
close(f.closeCh)
f.wg.Wait()
}
// syncLoop is the main event loop of the light fetcher
func (f *lightFetcher) syncLoop() {
defer f.wg.Done()
for {
select {
case <-f.closeCh:
return
// request loop keeps running until no further requests are necessary or possible
case <-f.requestTrigger:
f.lock.Lock()
var (
rq *distReq
reqID uint64
syncing bool
)
if !f.syncing {
rq, reqID, syncing = f.nextRequest()
}
f.requestTriggered = rq != nil
f.lock.Unlock()
if rq != nil {
if _, ok := <-f.handler.backend.reqDist.queue(rq); ok {
if syncing {
f.lock.Lock()
f.syncing = true
f.lock.Unlock()
} else {
go func() {
time.Sleep(f.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.requestTrigger <- struct{}{}
}()
}
} else {
f.requestTrigger <- struct{}{}
}
}
case reqID := <-f.timeoutChn:
f.reqMu.Lock()
req, ok := f.requested[reqID]
if ok {
delete(f.requested, reqID)
}
f.reqMu.Unlock()
if ok {
req.peer.Log().Debug("Fetching data timed out hard")
go f.handler.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()
f.lock.Lock()
if !ok || !(f.syncing || f.processResponse(req, resp)) {
resp.peer.Log().Debug("Failed processing response")
go f.handler.removePeer(resp.peer.id)
}
f.lock.Unlock()
case p := <-f.syncDone:
f.lock.Lock()
p.Log().Debug("Done synchronising with peer")
f.checkSyncedHeaders(p)
f.syncing = false
f.lock.Unlock()
f.requestTrigger <- struct{}{} // f.requestTriggered is always true here
}
}
}
// registerPeer adds a new peer to the fetcher's peer set
func (f *lightFetcher) registerPeer(p *serverPeer) {
p.lock.Lock()
p.hasBlock = func(hash common.Hash, number uint64, hasState bool) bool {
return f.peerHasBlock(p, hash, number, hasState)
}
p.lock.Unlock()
f.lock.Lock()
defer f.lock.Unlock()
f.peers[p] = &fetcherPeerInfo{nodeByHash: make(map[common.Hash]*fetcherTreeNode)}
}
// unregisterPeer removes a new peer from the fetcher's peer set
func (f *lightFetcher) unregisterPeer(p *serverPeer) {
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 *serverPeer, head *announceData) {
f.lock.Lock()
defer f.lock.Unlock()
p.Log().Debug("Received new announcement", "number", head.Number, "hash", head.Hash, "reorg", head.ReorgDepth)
fp := f.peers[p]
if fp == nil {
p.Log().Debug("Announcement from unknown peer")
return
}
if fp.lastAnnounced != nil && head.Td.Cmp(fp.lastAnnounced.td) <= 0 {
// announced tds should be strictly monotonic
p.Log().Debug("Received non-monotonic td", "current", head.Td, "previous", fp.lastAnnounced.td)
go f.handler.removePeer(p.id)
return
}
n := fp.lastAnnounced
for i := uint64(0); i < head.ReorgDepth; i++ {
if n == nil {
break
}
n = n.parent
}
// n is now the reorg common ancestor, add a new branch of nodes
if n != nil && (head.Number >= n.number+maxNodeCount || head.Number <= n.number) {
// if announced head block height is lower or same as n or too far from it to add
// intermediate nodes then discard previous announcement info and trigger a resync
n = nil
fp.nodeCnt = 0
fp.nodeByHash = make(map[common.Hash]*fetcherTreeNode)
}
// check if the node count is too high to add new nodes, discard oldest ones if necessary
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 rawdb.ReadCanonicalHash(f.handler.backend.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 = blockInfo{Number: head.Number, Hash: head.Hash, Td: head.Td}
fp.lastAnnounced = n
p.lock.Unlock()
f.checkUpdateStats(p, nil)
if !f.requestTriggered {
f.requestTriggered = true
f.requestTrigger <- struct{}{}
}
}
// peerHasBlock returns true if we can assume the peer knows the given block
// based on its announcements
func (f *lightFetcher) peerHasBlock(p *serverPeer, hash common.Hash, number uint64, hasState bool) bool {
f.lock.Lock()
defer f.lock.Unlock()
fp := f.peers[p]
if fp == nil || fp.root == nil {
return false
}
if hasState {
if fp.lastAnnounced == nil || fp.lastAnnounced.number > number+serverStateAvailable {
return false
}
}
if f.syncing {
// always return true when syncing
// false positives are acceptable, a more sophisticated condition can be implemented later
return true
}
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
// as the root, we can still be sure the peer knows it
//
// when syncing, just check if it is part of the known chain, there is nothing better we
// can do since we do not know the most recent block hash yet
return rawdb.ReadCanonicalHash(f.handler.backend.chainDb, fp.root.number) == fp.root.hash && rawdb.ReadCanonicalHash(f.handler.backend.chainDb, number) == hash
}
// requestAmount calculates the amount of headers to be downloaded starting
// from a certain head backwards
func (f *lightFetcher) requestAmount(p *serverPeer, 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() (*distReq, uint64, bool) {
var (
bestHash common.Hash
bestAmount uint64
bestTd *big.Int
bestSyncing bool
)
bestHash, bestAmount, bestTd, bestSyncing = f.findBestRequest()
if bestTd == f.maxConfirmedTd {
return nil, 0, false
}
var rq *distReq
reqID := genReqID()
if bestSyncing {
rq = f.newFetcherDistReqForSync(bestHash)
} else {
rq = f.newFetcherDistReq(bestHash, reqID, bestAmount)
}
return rq, reqID, bestSyncing
}
// findBestRequest finds the best head to request that has been announced by but not yet requested from a known peer.
// It also returns the announced Td (which should be verified after fetching the head),
// the necessary amount to request and whether a downloader sync is necessary instead of a normal header request.
func (f *lightFetcher) findBestRequest() (bestHash common.Hash, bestAmount uint64, bestTd *big.Int, bestSyncing bool) {
bestTd = f.maxConfirmedTd
bestSyncing = false
for p, fp := range f.peers {
for hash, n := range fp.nodeByHash {
if f.checkKnownNode(p, n) || n.requested {
continue
}
// if ulc mode is disabled, isTrustedHash returns true
amount := f.requestAmount(p, n)
if (bestTd == nil || n.td.Cmp(bestTd) > 0 || amount < bestAmount) && (f.isTrustedHash(hash) || f.maxConfirmedTd.Int64() == 0) {
bestHash = hash
bestTd = n.td
bestAmount = amount
bestSyncing = fp.bestConfirmed == nil || fp.root == nil || !f.checkKnownNode(p, fp.root)
}
}
}
return
}
// isTrustedHash checks if the block can be trusted by the minimum trusted fraction.
func (f *lightFetcher) isTrustedHash(hash common.Hash) bool {
// If ultra light cliet mode is disabled, trust all hashes
if f.handler.ulc == nil {
return true
}
// Ultra light enabled, only trust after enough confirmations
var agreed int
for peer, info := range f.peers {
if peer.trusted && info.nodeByHash[hash] != nil {
agreed++
}
}
return 100*agreed/len(f.handler.ulc.keys) >= f.handler.ulc.fraction
}
func (f *lightFetcher) newFetcherDistReqForSync(bestHash common.Hash) *distReq {
return &distReq{
getCost: func(dp distPeer) uint64 {
return 0
},
canSend: func(dp distPeer) bool {
p := dp.(*serverPeer)
f.lock.Lock()
defer f.lock.Unlock()
if p.onlyAnnounce {
return false
}
fp := f.peers[p]
return fp != nil && fp.nodeByHash[bestHash] != nil
},
request: func(dp distPeer) func() {
if f.handler.ulc != nil {
// Keep last trusted header before sync
f.setLastTrustedHeader(f.chain.CurrentHeader())
}
go func() {
p := dp.(*serverPeer)
p.Log().Debug("Synchronisation started")
f.handler.synchronise(p)
f.syncDone <- p
}()
return nil
},
}
}
// newFetcherDistReq creates a new request for the distributor.
func (f *lightFetcher) newFetcherDistReq(bestHash common.Hash, reqID uint64, bestAmount uint64) *distReq {
return &distReq{
getCost: func(dp distPeer) uint64 {
p := dp.(*serverPeer)
return p.getRequestCost(GetBlockHeadersMsg, int(bestAmount))
},
canSend: func(dp distPeer) bool {
p := dp.(*serverPeer)
f.lock.Lock()
defer f.lock.Unlock()
if p.onlyAnnounce {
return false
}
fp := f.peers[p]
if fp == nil {
return false
}
n := fp.nodeByHash[bestHash]
return n != nil && !n.requested
},
request: func(dp distPeer) func() {
p := dp.(*serverPeer)
f.lock.Lock()
fp := f.peers[p]
if fp != nil {
n := fp.nodeByHash[bestHash]
if n != nil {
n.requested = true
}
}
f.lock.Unlock()
cost := p.getRequestCost(GetBlockHeadersMsg, int(bestAmount))
p.fcServer.QueuedRequest(reqID, cost)
f.reqMu.Lock()
f.requested[reqID] = fetchRequest{hash: bestHash, amount: bestAmount, peer: p, sent: mclock.Now()}
f.reqMu.Unlock()
go func() {
time.Sleep(hardRequestTimeout)
f.timeoutChn <- reqID
}()
return func() { p.requestHeadersByHash(reqID, bestHash, int(bestAmount), 0, true) }
},
}
}
// deliverHeaders delivers header download request responses for processing
func (f *lightFetcher) deliverHeaders(peer *serverPeer, reqID uint64, headers []*types.Header) {
f.deliverChn <- fetchResponse{reqID: reqID, headers: headers, peer: peer}
}
// processResponse processes header download request responses, returns true if successful
func (f *lightFetcher) processResponse(req fetchRequest, resp fetchResponse) bool {
if uint64(len(resp.headers)) != req.amount || resp.headers[0].Hash() != req.hash {
req.peer.Log().Debug("Response content mismatch", "requested", len(resp.headers), "reqfrom", resp.headers[0], "delivered", req.amount, "delfrom", 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 {
if err == consensus.ErrFutureBlock {
return true
}
log.Debug("Failed to insert header chain", "err", err)
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 {
log.Debug("Total difficulty not found for header", "index", i+1, "number", header.Number, "hash", header.Hash())
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) {
p.Log().Debug("Inconsistent announcement")
go f.handler.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
hash, number := header.ParentHash, header.Number.Uint64()-1
td = f.chain.GetTd(hash, number)
header = f.chain.GetHeader(hash, number)
if header == nil || td == nil {
log.Error("Missing parent of validated header", "hash", hash, "number", number)
return false
}
} 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 *serverPeer) {
fp := f.peers[p]
if fp == nil {
p.Log().Debug("Unknown peer to check sync headers")
return
}
var (
node = fp.lastAnnounced
td *big.Int
)
if f.handler.ulc != nil {
// Roll back untrusted blocks
h, unapproved := f.lastTrustedTreeNode(p)
f.chain.Rollback(unapproved)
node = fp.nodeByHash[h.Hash()]
}
// Find last valid block
for node != nil {
if td = f.chain.GetTd(node.hash, node.number); td != nil {
break
}
node = node.parent
}
// Now node is the latest downloaded/approved header after syncing
if node == nil {
p.Log().Debug("Synchronisation failed")
go f.handler.removePeer(p.id)
return
}
header := f.chain.GetHeader(node.hash, node.number)
f.newHeaders([]*types.Header{header}, []*big.Int{td})
}
// lastTrustedTreeNode return last approved treeNode and a list of unapproved hashes
func (f *lightFetcher) lastTrustedTreeNode(p *serverPeer) (*types.Header, []common.Hash) {
unapprovedHashes := make([]common.Hash, 0)
current := f.chain.CurrentHeader()
if f.lastTrustedHeader == nil {
return current, unapprovedHashes
}
canonical := f.chain.CurrentHeader()
if canonical.Number.Uint64() > f.lastTrustedHeader.Number.Uint64() {
canonical = f.chain.GetHeaderByNumber(f.lastTrustedHeader.Number.Uint64())
}
commonAncestor := rawdb.FindCommonAncestor(f.handler.backend.chainDb, canonical, f.lastTrustedHeader)
if commonAncestor == nil {
log.Error("Common ancestor of last trusted header and canonical header is nil", "canonical hash", canonical.Hash(), "trusted hash", f.lastTrustedHeader.Hash())
return current, unapprovedHashes
}
for current.Hash() == commonAncestor.Hash() {
if f.isTrustedHash(current.Hash()) {
break
}
unapprovedHashes = append(unapprovedHashes, current.Hash())
current = f.chain.GetHeader(current.ParentHash, current.Number.Uint64()-1)
}
return current, unapprovedHashes
}
func (f *lightFetcher) setLastTrustedHeader(h *types.Header) {
f.lock.Lock()
defer f.lock.Unlock()
f.lastTrustedHeader = h
}
// 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 *serverPeer, n *fetcherTreeNode) bool {
if n.known {
return true
}
td := f.chain.GetTd(n.hash, n.number)
if td == nil {
return false
}
header := f.chain.GetHeader(n.hash, n.number)
// check the availability of both header and td because reads are not protected by chain db mutex
// Note: returning false is always safe here
if header == nil {
return false
}
fp := f.peers[p]
if fp == nil {
p.Log().Debug("Unknown peer to check known nodes")
return false
}
if !f.checkAnnouncedHeaders(fp, []*types.Header{header}, []*big.Int{td}) {
p.Log().Debug("Inconsistent announcement")
go f.handler.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 *serverPeer, newEntry *updateStatsEntry) {
now := mclock.Now()
fp := f.peers[p]
if fp == nil {
p.Log().Debug("Unknown peer to check update stats")
return
}
if newEntry != nil && fp.firstUpdateStats == nil {
fp.firstUpdateStats = newEntry
}
for fp.firstUpdateStats != nil && fp.firstUpdateStats.time <= now-mclock.AbsTime(blockDelayTimeout) {
fp.firstUpdateStats = fp.firstUpdateStats.next
}
if fp.confirmedTd != nil {
for fp.firstUpdateStats != nil && fp.firstUpdateStats.td.Cmp(fp.confirmedTd) <= 0 {
fp.firstUpdateStats = fp.firstUpdateStats.next
}
}
}