github.com/Blockdaemon/celo-blockchain@v0.0.0-20200129231733-e667f6b08419/les/handler.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 implements the Light Ethereum Subprotocol.
package les

import (
	"encoding/binary"
	"encoding/json"
	"fmt"
	"math"
	"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"
	"github.com/ethereum/go-ethereum/core/rawdb"
	"github.com/ethereum/go-ethereum/core/state"
	"github.com/ethereum/go-ethereum/core/types"
	"github.com/ethereum/go-ethereum/eth/downloader"
	"github.com/ethereum/go-ethereum/ethdb"
	"github.com/ethereum/go-ethereum/event"
	"github.com/ethereum/go-ethereum/light"
	"github.com/ethereum/go-ethereum/log"
	"github.com/ethereum/go-ethereum/p2p"
	"github.com/ethereum/go-ethereum/p2p/discv5"
	"github.com/ethereum/go-ethereum/params"
	"github.com/ethereum/go-ethereum/rlp"
	"github.com/ethereum/go-ethereum/trie"
)

const (
	softResponseLimit = 2 * 1024 * 1024 // Target maximum size of returned blocks, headers or node data.
	estHeaderRlpSize  = 500             // Approximate size of an RLP encoded block header

	ethVersion = 63 // equivalent eth version for the downloader

	MaxHeaderFetch           = 192 // Amount of block headers to be fetched per retrieval request
	MaxBodyFetch             = 32  // Amount of block bodies to be fetched per retrieval request
	MaxReceiptFetch          = 128 // Amount of transaction receipts to allow fetching per request
	MaxCodeFetch             = 64  // Amount of contract codes to allow fetching per request
	MaxProofsFetch           = 64  // Amount of merkle proofs to be fetched per retrieval request
	MaxHelperTrieProofsFetch = 64  // Amount of merkle proofs to be fetched per retrieval request
	MaxTxSend                = 64  // Amount of transactions to be send per request
	MaxTxStatus              = 256 // Amount of transactions to queried per request

	disableClientRemovePeer = false
)

func errResp(code errCode, format string, v ...interface{}) error {
	return fmt.Errorf("%v - %v", code, fmt.Sprintf(format, v...))
}

type BlockChain interface {
	Config() *params.ChainConfig
	HasHeader(hash common.Hash, number uint64) bool
	GetHeader(hash common.Hash, number uint64) *types.Header
	GetHeaderByHash(hash common.Hash) *types.Header
	CurrentHeader() *types.Header
	GetTd(hash common.Hash, number uint64) *big.Int
	State() (*state.StateDB, error)
	InsertHeaderChain(chain []*types.Header, checkFreq int, contiguousHeaders bool) (int, error)
	Rollback(chain []common.Hash, fullHeaderChainAvailable bool)
	GetHeaderByNumber(number uint64) *types.Header
	GetAncestor(hash common.Hash, number, ancestor uint64, maxNonCanonical *uint64) (common.Hash, uint64)
	Genesis() *types.Block
	SubscribeChainHeadEvent(ch chan<- core.ChainHeadEvent) event.Subscription
}

type txPool interface {
	AddRemotes(txs []*types.Transaction) []error
	Status(hashes []common.Hash) []core.TxStatus
}

type ProtocolManager struct {
	lightSync   bool
	txpool      txPool
	txrelay     *LesTxRelay
	networkId   uint64
	chainConfig *params.ChainConfig
	iConfig     *light.IndexerConfig
	blockchain  BlockChain
	chainDb     ethdb.Database
	odr         *LesOdr
	server      *LesServer
	serverPool  *serverPool
	clientPool  *freeClientPool
	lesTopic    discv5.Topic
	reqDist     *requestDistributor
	retriever   *retrieveManager
	etherbase   common.Address
	gatewayFee  *big.Int

	downloader *downloader.Downloader
	fetcher    *lightFetcher
	peers      *peerSet
	maxPeers   int

	eventMux *event.TypeMux

	// channels for fetcher, syncer, txsyncLoop
	newPeerCh   chan *peer
	quitSync    chan struct{}
	noMorePeers chan struct{}

	// wait group is used for graceful shutdowns during downloading
	// and processing
	wg *sync.WaitGroup
}

// NewProtocolManager returns a new ethereum sub protocol manager. The Ethereum sub protocol manages peers capable
// with the ethereum network.
func NewProtocolManager(chainConfig *params.ChainConfig, indexerConfig *light.IndexerConfig,
	syncMode downloader.SyncMode, networkId uint64, mux *event.TypeMux, engine consensus.Engine,
	peers *peerSet, blockchain BlockChain, txpool txPool, chainDb ethdb.Database,
	odr *LesOdr, txrelay *LesTxRelay, serverPool *serverPool, quitSync chan struct{},
	wg *sync.WaitGroup, etherbase common.Address, gatewayFee *big.Int) (*ProtocolManager, error) {
	lightSync := !syncMode.SyncFullBlockChain()
	// Create the protocol manager with the base fields
	manager := &ProtocolManager{
		lightSync:   lightSync,
		eventMux:    mux,
		blockchain:  blockchain,
		chainConfig: chainConfig,
		iConfig:     indexerConfig,
		chainDb:     chainDb,
		odr:         odr,
		networkId:   networkId,
		txpool:      txpool,
		txrelay:     txrelay,
		serverPool:  serverPool,
		peers:       peers,
		newPeerCh:   make(chan *peer),
		quitSync:    quitSync,
		wg:          wg,
		noMorePeers: make(chan struct{}),
		etherbase:   etherbase,
		gatewayFee:  gatewayFee,
	}
	if odr != nil {
		manager.retriever = odr.retriever
		manager.reqDist = odr.retriever.dist
	}

	removePeer := manager.removePeer
	if disableClientRemovePeer {
		removePeer = func(id string) {}
	}

	if lightSync {
		manager.downloader = downloader.New(syncMode, chainDb, manager.eventMux, nil, blockchain, removePeer)
		manager.peers.notify((*downloaderPeerNotify)(manager))
		manager.fetcher = newLightFetcher(manager)
	}

	return manager, nil
}

// removePeer initiates disconnection from a peer by removing it from the peer set
func (pm *ProtocolManager) removePeer(id string) {
	log.Debug("Removing Ethereum Light peer", "peer", id)

	if peer := pm.peers.Peer(id); peer == nil {
		log.Debug("Attempt to remove light peer which has been already removed", "peer", id)
		return
	}

	if err := pm.peers.Unregister(id); err != nil {
		log.Error("Removing light peer failed", "peer", id, "err", err)
	}
}

func (pm *ProtocolManager) Start(maxPeers int) {
	pm.maxPeers = maxPeers

	if pm.lightSync {
		go pm.syncer()
	} else {
		pm.clientPool = newFreeClientPool(pm.chainDb, maxPeers, 10000, mclock.System{})
		go func() {
			for range pm.newPeerCh {
			}
		}()
	}
}

func (pm *ProtocolManager) Stop() {
	// Showing a log message. During download / process this could actually
	// take between 5 to 10 seconds and therefor feedback is required.
	log.Info("Stopping light Ethereum protocol")

	// Quit the sync loop.
	// After this send has completed, no new peers will be accepted.
	pm.noMorePeers <- struct{}{}

	close(pm.quitSync) // quits syncer, fetcher
	if pm.clientPool != nil {
		pm.clientPool.stop()
	}

	// Disconnect existing sessions.
	// This also closes the gate for any new registrations on the peer set.
	// sessions which are already established but not added to pm.peers yet
	// will exit when they try to register.
	pm.peers.Close()

	// Wait for any process action
	pm.wg.Wait()

	log.Info("Light Ethereum protocol stopped")
}

// runPeer is the p2p protocol run function for the given version.
func (pm *ProtocolManager) runPeer(version uint, p *p2p.Peer, rw p2p.MsgReadWriter) error {
	var entry *poolEntry
	peer := pm.newPeer(int(version), pm.networkId, p, rw)
	if pm.serverPool != nil {
		entry = pm.serverPool.connect(peer, peer.Node())
	}
	peer.poolEntry = entry
	select {
	case pm.newPeerCh <- peer:
		pm.wg.Add(1)
		defer pm.wg.Done()
		err := pm.handle(peer)
		if entry != nil {
			pm.serverPool.disconnect(entry)
		}
		return err
	case <-pm.quitSync:
		if entry != nil {
			pm.serverPool.disconnect(entry)
		}
		return p2p.DiscQuitting
	}
}

func (pm *ProtocolManager) newPeer(pv int, nv uint64, p *p2p.Peer, rw p2p.MsgReadWriter) *peer {
	return newPeer(pv, nv, p, newMeteredMsgWriter(rw))
}

// handle is the callback invoked to manage the life cycle of a les peer. When
// this function terminates, the peer is disconnected.
func (pm *ProtocolManager) handle(p *peer) error {
	// Ignore maxPeers if this is a trusted peer
	// In server mode we try to check into the client pool after handshake
	if pm.lightSync && pm.peers.Len() >= pm.maxPeers && !p.Peer.Info().Network.Trusted {
		return p2p.DiscTooManyPeers
	}

	p.Log().Debug("Light Ethereum peer connected", "name", p.Name())

	// Execute the LES handshake
	var (
		genesis = pm.blockchain.Genesis()
		head    = pm.blockchain.CurrentHeader()
		hash    = head.Hash()
		number  = head.Number.Uint64()
		td      = pm.blockchain.GetTd(hash, number)
	)
	if err := p.Handshake(td, hash, number, genesis.Hash(), pm.server); err != nil {
		p.Log().Debug("Light Ethereum handshake failed", "err", err)
		return err
	}

	if !pm.lightSync && !p.Peer.Info().Network.Trusted {
		// geth upstream uses the IP address for the client pool to protect against malicious clients, in here we'll just use the peer's ID which can be changed but allows us to circumvent:
		// 1. Kubernetes internal networking putting clients on the "same IP"
		// 2. Light clients being on the same Wifi network
		if !pm.clientPool.connect(p.id, func() { go pm.removePeer(p.id) }) {
			p.Log().Debug(fmt.Sprintf("Unable to connect peer to client pool"))
			return p2p.DiscTooManyPeers
		}
		defer pm.clientPool.disconnect(p.id)
	}

	if rw, ok := p.rw.(*meteredMsgReadWriter); ok {
		rw.Init(p.version)
	}
	// Register the peer locally
	if err := pm.peers.Register(p); err != nil {
		p.Log().Error("Light Ethereum peer registration failed", "err", err)
		return err
	}
	defer func() {
		if pm.server != nil && pm.server.fcManager != nil && p.fcClient != nil {
			p.fcClient.Remove(pm.server.fcManager)
		}
		pm.removePeer(p.id)
	}()
	// Register the peer in the downloader. If the downloader considers it banned, we disconnect
	if pm.lightSync {
		p.lock.Lock()
		head := p.headInfo
		p.lock.Unlock()
		if pm.fetcher != nil {
			pm.fetcher.announce(p, head)
		}

		if p.poolEntry != nil {
			pm.serverPool.registered(p.poolEntry)
		}

		// If we're strictly a light node, loop until we receive a RequestEtherbase response or timeout.
		go func() {
			maxRequests := 10
			requests := 0
			for {
				p.Log().Trace("Requesting etherbase from new peer")
				reqID := genReqID()
				cost := p.GetRequestCost(GetEtherbaseMsg, int(1))
				err := p.RequestEtherbase(reqID, cost)
				requests++
				if err != nil {
					p.Log().Warn("Unable to request etherbase from peer", "err", err)
				}
				time.Sleep(time.Duration(math.Pow(2, float64(requests))/2) * time.Second)
				if pm.peers.isEtherbaseSet(p) || requests == maxRequests {
					return
				}
			}
		}()
	}

	stop := make(chan struct{})
	defer close(stop)
	go func() {
		// new block announce loop
		for {
			select {
			case announce := <-p.announceChn:
				p.SendAnnounce(announce)
			case <-stop:
				return
			}
		}
	}()

	// main loop. handle incoming messages.
	for {
		if err := pm.handleMsg(p); err != nil {
			p.Log().Debug("Light Ethereum message handling failed", "err", err)
			return err
		}
	}
}

var reqList = []uint64{GetBlockHeadersMsg, GetBlockBodiesMsg, GetCodeMsg, GetReceiptsMsg, GetProofsV1Msg, SendTxMsg, SendTxV2Msg, GetTxStatusMsg, GetHeaderProofsMsg, GetProofsV2Msg, GetHelperTrieProofsMsg, GetEtherbaseMsg}

func (pm *ProtocolManager) verifyGatewayFee(gatewayFeeRecipient *common.Address, gatewayFee *big.Int) error {
	// If this node does not specify an etherbase, accept any GatewayFeeRecipient. Otherwise,
	// reject transactions that don't pay gas fees to this node.
	if (pm.etherbase != common.Address{}) {
		if gatewayFeeRecipient == nil {
			return fmt.Errorf("gateway fee recipient must be %s, got <nil>", pm.etherbase.String())
		}
		if *gatewayFeeRecipient != pm.etherbase {
			return fmt.Errorf("gateway fee recipient must be %s, got %s", pm.etherbase.String(), (*gatewayFeeRecipient).String())
		}

		// Check that the value of the supplied gateway fee is at least the minimum.
		if pm.gatewayFee != nil && pm.gatewayFee.Cmp(common.Big0) > 0 {
			if gatewayFee == nil || gatewayFee.Cmp(pm.gatewayFee) < 0 {
				return fmt.Errorf("gateway fee value must be at least %s, got %s", pm.gatewayFee, gatewayFee)
			}
		}
	}
	return nil
}

// handleMsg is invoked whenever an inbound message is received from a remote
// peer. The remote connection is torn down upon returning any error.
func (pm *ProtocolManager) handleMsg(p *peer) error {
	// Read the next message from the remote peer, and ensure it's fully consumed
	msg, err := p.rw.ReadMsg()
	if err != nil {
		return err
	}
	p.Log().Trace("Light Ethereum message arrived", "code", msg.Code, "bytes", msg.Size)

	costs := p.fcCosts[msg.Code]
	reject := func(reqCnt, maxCnt uint64) bool {
		if p.fcClient == nil || reqCnt > maxCnt {
			return true
		}
		bufValue, _ := p.fcClient.AcceptRequest()
		cost := costs.baseCost + reqCnt*costs.reqCost
		if cost > pm.server.defParams.BufLimit {
			cost = pm.server.defParams.BufLimit
		}
		if cost > bufValue {
			recharge := time.Duration((cost - bufValue) * 1000000 / pm.server.defParams.MinRecharge)
			p.Log().Error("Request came too early", "recharge", common.PrettyDuration(recharge))
			return true
		}
		return false
	}

	if msg.Size > ProtocolMaxMsgSize {
		return errResp(ErrMsgTooLarge, "%v > %v", msg.Size, ProtocolMaxMsgSize)
	}
	defer msg.Discard()

	var deliverMsg *Msg

	// Handle the message depending on its contents
	switch msg.Code {
	case StatusMsg:
		p.Log().Trace("Received status message")
		// Status messages should never arrive after the handshake
		return errResp(ErrExtraStatusMsg, "uncontrolled status message")

	// Block header query, collect the requested headers and reply
	case AnnounceMsg:
		p.Log().Trace("Received announce message")
		if p.requestAnnounceType == announceTypeNone {
			return errResp(ErrUnexpectedResponse, "")
		}

		var req announceData
		if err := msg.Decode(&req); err != nil {
			return errResp(ErrDecode, "%v: %v", msg, err)
		}

		if p.requestAnnounceType == announceTypeSigned {
			if err := req.checkSignature(p.ID()); err != nil {
				p.Log().Trace("Invalid announcement signature", "err", err)
				return err
			}
			p.Log().Trace("Valid announcement signature")
		}

		p.Log().Trace("Announce message content", "number", req.Number, "hash", req.Hash, "td", req.Td, "reorg", req.ReorgDepth)
		if pm.fetcher != nil {
			pm.fetcher.announce(p, &req)
		}

	case GetBlockHeadersMsg:
		p.Log().Trace("Received block header request")
		// Decode the complex header query
		var req struct {
			ReqID uint64
			Query getBlockHeadersData
		}
		if err := msg.Decode(&req); err != nil {
			return errResp(ErrDecode, "%v: %v", msg, err)
		}

		query := req.Query
		if reject(query.Amount, MaxHeaderFetch) {
			return errResp(ErrRequestRejected, "")
		}

		hashMode := query.Origin.Hash != (common.Hash{})
		first := true
		maxNonCanonical := uint64(100)

		// Gather headers until the fetch or network limits is reached
		var (
			bytes   common.StorageSize
			headers []*types.Header
			unknown bool
		)
		for !unknown && len(headers) < int(query.Amount) && bytes < softResponseLimit {
			// Retrieve the next header satisfying the query
			var origin *types.Header
			if hashMode {
				if first {
					first = false
					origin = pm.blockchain.GetHeaderByHash(query.Origin.Hash)
					if origin != nil {
						query.Origin.Number = origin.Number.Uint64()
					}
				} else {
					origin = pm.blockchain.GetHeader(query.Origin.Hash, query.Origin.Number)
				}
			} else {
				origin = pm.blockchain.GetHeaderByNumber(query.Origin.Number)
			}
			if origin == nil {
				break
			}
			headers = append(headers, origin)
			bytes += estHeaderRlpSize

			// Advance to the next header of the query
			switch {
			case hashMode && query.Reverse:
				// Hash based traversal towards the genesis block
				ancestor := query.Skip + 1
				if ancestor == 0 {
					unknown = true
				} else {
					query.Origin.Hash, query.Origin.Number = pm.blockchain.GetAncestor(query.Origin.Hash, query.Origin.Number, ancestor, &maxNonCanonical)
					unknown = (query.Origin.Hash == common.Hash{})
				}
			case hashMode && !query.Reverse:
				// Hash based traversal towards the leaf block
				var (
					current = origin.Number.Uint64()
					next    = current + query.Skip + 1
				)
				if next <= current {
					infos, _ := json.MarshalIndent(p.Peer.Info(), "", "  ")
					p.Log().Warn("GetBlockHeaders skip overflow attack", "current", current, "skip", query.Skip, "next", next, "attacker", infos)
					unknown = true
				} else {
					if header := pm.blockchain.GetHeaderByNumber(next); header != nil {
						nextHash := header.Hash()
						expOldHash, _ := pm.blockchain.GetAncestor(nextHash, next, query.Skip+1, &maxNonCanonical)
						if expOldHash == query.Origin.Hash {
							query.Origin.Hash, query.Origin.Number = nextHash, next
						} else {
							unknown = true
						}
					} else {
						unknown = true
					}
				}
			case query.Reverse:
				// Number based traversal towards the genesis block
				if query.Origin.Number >= query.Skip+1 {
					query.Origin.Number -= query.Skip + 1
				} else {
					unknown = true
				}

			case !query.Reverse:
				// Number based traversal towards the leaf block
				query.Origin.Number += query.Skip + 1
			}
		}

		bv, rcost := p.fcClient.RequestProcessed(costs.baseCost + query.Amount*costs.reqCost)
		pm.server.fcCostStats.update(msg.Code, query.Amount, rcost)
		return p.SendBlockHeaders(req.ReqID, bv, headers)

	case BlockHeadersMsg:
		if pm.downloader == nil {
			return errResp(ErrUnexpectedResponse, "")
		}

		p.Log().Trace("Received block header response message")
		// A batch of headers arrived to one of our previous requests
		var resp struct {
			ReqID, BV uint64
			Headers   []*types.Header
		}
		if err := msg.Decode(&resp); err != nil {
			return errResp(ErrDecode, "msg %v: %v", msg, err)
		}
		p.fcServer.GotReply(resp.ReqID, resp.BV)
		if pm.fetcher != nil && pm.fetcher.requestedID(resp.ReqID) {
			pm.fetcher.deliverHeaders(p, resp.ReqID, resp.Headers)
		} else {
			err := pm.downloader.DeliverHeaders(p.id, resp.Headers)
			if err != nil {
				log.Debug(fmt.Sprint(err))
			}
		}

	case GetBlockBodiesMsg:
		p.Log().Trace("Received block bodies request")
		// Decode the retrieval message
		var req struct {
			ReqID  uint64
			Hashes []common.Hash
		}
		if err := msg.Decode(&req); err != nil {
			return errResp(ErrDecode, "msg %v: %v", msg, err)
		}
		// Gather blocks until the fetch or network limits is reached
		var (
			bytes  int
			bodies []rlp.RawValue
		)
		reqCnt := len(req.Hashes)
		if reject(uint64(reqCnt), MaxBodyFetch) {
			return errResp(ErrRequestRejected, "")
		}
		for _, hash := range req.Hashes {
			if bytes >= softResponseLimit {
				break
			}
			// Retrieve the requested block body, stopping if enough was found
			if number := rawdb.ReadHeaderNumber(pm.chainDb, hash); number != nil {
				if data := rawdb.ReadBodyRLP(pm.chainDb, hash, *number); len(data) != 0 {
					bodies = append(bodies, data)
					bytes += len(data)
				}
			}
		}
		bv, rcost := p.fcClient.RequestProcessed(costs.baseCost + uint64(reqCnt)*costs.reqCost)
		pm.server.fcCostStats.update(msg.Code, uint64(reqCnt), rcost)
		return p.SendBlockBodiesRLP(req.ReqID, bv, bodies)

	case BlockBodiesMsg:
		if pm.odr == nil {
			return errResp(ErrUnexpectedResponse, "")
		}

		p.Log().Trace("Received block bodies response")
		// A batch of block bodies arrived to one of our previous requests
		var resp struct {
			ReqID, BV uint64
			Data      []*types.Body
		}
		if err := msg.Decode(&resp); err != nil {
			return errResp(ErrDecode, "msg %v: %v", msg, err)
		}
		p.fcServer.GotReply(resp.ReqID, resp.BV)
		deliverMsg = &Msg{
			MsgType: MsgBlockBodies,
			ReqID:   resp.ReqID,
			Obj:     resp.Data,
		}

	case GetCodeMsg:
		p.Log().Trace("Received code request")
		// Decode the retrieval message
		var req struct {
			ReqID uint64
			Reqs  []CodeReq
		}
		if err := msg.Decode(&req); err != nil {
			return errResp(ErrDecode, "msg %v: %v", msg, err)
		}
		// Gather state data until the fetch or network limits is reached
		var (
			bytes int
			data  [][]byte
		)
		reqCnt := len(req.Reqs)
		if reject(uint64(reqCnt), MaxCodeFetch) {
			return errResp(ErrRequestRejected, "")
		}
		for _, req := range req.Reqs {
			// Retrieve the requested state entry, stopping if enough was found
			if number := rawdb.ReadHeaderNumber(pm.chainDb, req.BHash); number != nil {
				if header := rawdb.ReadHeader(pm.chainDb, req.BHash, *number); header != nil {
					statedb, err := pm.blockchain.State()
					if err != nil {
						continue
					}
					account, err := pm.getAccount(statedb, header.Root, common.BytesToHash(req.AccKey))
					if err != nil {
						continue
					}
					code, _ := statedb.Database().TrieDB().Node(common.BytesToHash(account.CodeHash))

					data = append(data, code)
					if bytes += len(code); bytes >= softResponseLimit {
						break
					}
				}
			}
		}
		bv, rcost := p.fcClient.RequestProcessed(costs.baseCost + uint64(reqCnt)*costs.reqCost)
		pm.server.fcCostStats.update(msg.Code, uint64(reqCnt), rcost)
		return p.SendCode(req.ReqID, bv, data)

	case CodeMsg:
		if pm.odr == nil {
			return errResp(ErrUnexpectedResponse, "")
		}

		p.Log().Trace("Received code response")
		// A batch of node state data arrived to one of our previous requests
		var resp struct {
			ReqID, BV uint64
			Data      [][]byte
		}
		if err := msg.Decode(&resp); err != nil {
			return errResp(ErrDecode, "msg %v: %v", msg, err)
		}
		p.fcServer.GotReply(resp.ReqID, resp.BV)
		deliverMsg = &Msg{
			MsgType: MsgCode,
			ReqID:   resp.ReqID,
			Obj:     resp.Data,
		}

	case GetReceiptsMsg:
		p.Log().Trace("Received receipts request")
		// Decode the retrieval message
		var req struct {
			ReqID  uint64
			Hashes []common.Hash
		}
		if err := msg.Decode(&req); err != nil {
			return errResp(ErrDecode, "msg %v: %v", msg, err)
		}
		// Gather state data until the fetch or network limits is reached
		var (
			bytes    int
			receipts []rlp.RawValue
		)
		reqCnt := len(req.Hashes)
		if reject(uint64(reqCnt), MaxReceiptFetch) {
			return errResp(ErrRequestRejected, "")
		}
		for _, hash := range req.Hashes {
			if bytes >= softResponseLimit {
				break
			}
			// Retrieve the requested block's receipts, skipping if unknown to us
			var results types.Receipts
			if number := rawdb.ReadHeaderNumber(pm.chainDb, hash); number != nil {
				results = rawdb.ReadReceipts(pm.chainDb, hash, *number)
			}
			if results == nil {
				if header := pm.blockchain.GetHeaderByHash(hash); header == nil || header.ReceiptHash != types.EmptyRootHash {
					continue
				}
			}
			// If known, encode and queue for response packet
			if encoded, err := rlp.EncodeToBytes(results); err != nil {
				log.Error("Failed to encode receipt", "err", err)
			} else {
				receipts = append(receipts, encoded)
				bytes += len(encoded)
			}
		}
		bv, rcost := p.fcClient.RequestProcessed(costs.baseCost + uint64(reqCnt)*costs.reqCost)
		pm.server.fcCostStats.update(msg.Code, uint64(reqCnt), rcost)
		return p.SendReceiptsRLP(req.ReqID, bv, receipts)

	case ReceiptsMsg:
		if pm.odr == nil {
			return errResp(ErrUnexpectedResponse, "")
		}

		p.Log().Trace("Received receipts response")
		// A batch of receipts arrived to one of our previous requests
		var resp struct {
			ReqID, BV uint64
			Receipts  []types.Receipts
		}
		if err := msg.Decode(&resp); err != nil {
			return errResp(ErrDecode, "msg %v: %v", msg, err)
		}
		p.fcServer.GotReply(resp.ReqID, resp.BV)
		deliverMsg = &Msg{
			MsgType: MsgReceipts,
			ReqID:   resp.ReqID,
			Obj:     resp.Receipts,
		}

	case GetProofsV1Msg:
		p.Log().Trace("Received proofs request")
		// Decode the retrieval message
		var req struct {
			ReqID uint64
			Reqs  []ProofReq
		}
		if err := msg.Decode(&req); err != nil {
			return errResp(ErrDecode, "msg %v: %v", msg, err)
		}
		// Gather state data until the fetch or network limits is reached
		var (
			bytes  int
			proofs proofsData
		)
		reqCnt := len(req.Reqs)
		if reject(uint64(reqCnt), MaxProofsFetch) {
			return errResp(ErrRequestRejected, "")
		}
		for _, req := range req.Reqs {
			// Retrieve the requested state entry, stopping if enough was found
			if number := rawdb.ReadHeaderNumber(pm.chainDb, req.BHash); number != nil {
				if header := rawdb.ReadHeader(pm.chainDb, req.BHash, *number); header != nil {
					statedb, err := pm.blockchain.State()
					if err != nil {
						continue
					}
					var trie state.Trie
					if len(req.AccKey) > 0 {
						account, err := pm.getAccount(statedb, header.Root, common.BytesToHash(req.AccKey))
						if err != nil {
							continue
						}
						trie, _ = statedb.Database().OpenStorageTrie(common.BytesToHash(req.AccKey), account.Root)
					} else {
						trie, _ = statedb.Database().OpenTrie(header.Root)
					}
					if trie != nil {
						var proof light.NodeList
						trie.Prove(req.Key, 0, &proof)

						proofs = append(proofs, proof)
						if bytes += proof.DataSize(); bytes >= softResponseLimit {
							break
						}
					}
				}
			}
		}
		bv, rcost := p.fcClient.RequestProcessed(costs.baseCost + uint64(reqCnt)*costs.reqCost)
		pm.server.fcCostStats.update(msg.Code, uint64(reqCnt), rcost)
		return p.SendProofs(req.ReqID, bv, proofs)

	case GetProofsV2Msg:
		p.Log().Trace("Received les/2 proofs request")
		// Decode the retrieval message
		var req struct {
			ReqID uint64
			Reqs  []ProofReq
		}
		if err := msg.Decode(&req); err != nil {
			return errResp(ErrDecode, "msg %v: %v", msg, err)
		}
		// Gather state data until the fetch or network limits is reached
		var (
			lastBHash common.Hash
			statedb   *state.StateDB
			root      common.Hash
		)
		reqCnt := len(req.Reqs)
		if reject(uint64(reqCnt), MaxProofsFetch) {
			return errResp(ErrRequestRejected, "")
		}

		nodes := light.NewNodeSet()

		for _, req := range req.Reqs {
			// Look up the state belonging to the request
			if statedb == nil || req.BHash != lastBHash {
				statedb, root, lastBHash = nil, common.Hash{}, req.BHash

				if number := rawdb.ReadHeaderNumber(pm.chainDb, req.BHash); number != nil {
					if header := rawdb.ReadHeader(pm.chainDb, req.BHash, *number); header != nil {
						statedb, _ = pm.blockchain.State()
						root = header.Root
					}
				}
			}
			if statedb == nil {
				continue
			}
			// Pull the account or storage trie of the request
			var trie state.Trie
			if len(req.AccKey) > 0 {
				account, err := pm.getAccount(statedb, root, common.BytesToHash(req.AccKey))
				if err != nil {
					continue
				}
				trie, _ = statedb.Database().OpenStorageTrie(common.BytesToHash(req.AccKey), account.Root)
			} else {
				trie, _ = statedb.Database().OpenTrie(root)
			}
			if trie == nil {
				continue
			}
			// Prove the user's request from the account or stroage trie
			trie.Prove(req.Key, req.FromLevel, nodes)
			if nodes.DataSize() >= softResponseLimit {
				break
			}
		}
		bv, rcost := p.fcClient.RequestProcessed(costs.baseCost + uint64(reqCnt)*costs.reqCost)
		pm.server.fcCostStats.update(msg.Code, uint64(reqCnt), rcost)
		return p.SendProofsV2(req.ReqID, bv, nodes.NodeList())

	case ProofsV1Msg:
		if pm.odr == nil {
			return errResp(ErrUnexpectedResponse, "")
		}

		p.Log().Trace("Received proofs response")
		// A batch of merkle proofs arrived to one of our previous requests
		var resp struct {
			ReqID, BV uint64
			Data      []light.NodeList
		}
		if err := msg.Decode(&resp); err != nil {
			return errResp(ErrDecode, "msg %v: %v", msg, err)
		}
		p.fcServer.GotReply(resp.ReqID, resp.BV)
		deliverMsg = &Msg{
			MsgType: MsgProofsV1,
			ReqID:   resp.ReqID,
			Obj:     resp.Data,
		}

	case ProofsV2Msg:
		if pm.odr == nil {
			return errResp(ErrUnexpectedResponse, "")
		}

		p.Log().Trace("Received les/2 proofs response")
		// A batch of merkle proofs arrived to one of our previous requests
		var resp struct {
			ReqID, BV uint64
			Data      light.NodeList
		}
		if err := msg.Decode(&resp); err != nil {
			return errResp(ErrDecode, "msg %v: %v", msg, err)
		}
		p.fcServer.GotReply(resp.ReqID, resp.BV)
		deliverMsg = &Msg{
			MsgType: MsgProofsV2,
			ReqID:   resp.ReqID,
			Obj:     resp.Data,
		}

	case GetHeaderProofsMsg:
		p.Log().Trace("Received headers proof request")
		// Decode the retrieval message
		var req struct {
			ReqID uint64
			Reqs  []ChtReq
		}
		if err := msg.Decode(&req); err != nil {
			return errResp(ErrDecode, "msg %v: %v", msg, err)
		}
		// Gather state data until the fetch or network limits is reached
		var (
			bytes  int
			proofs []ChtResp
		)
		reqCnt := len(req.Reqs)
		if reject(uint64(reqCnt), MaxHelperTrieProofsFetch) {
			return errResp(ErrRequestRejected, "")
		}
		trieDb := trie.NewDatabase(ethdb.NewTable(pm.chainDb, light.ChtTablePrefix))
		for _, req := range req.Reqs {
			if header := pm.blockchain.GetHeaderByNumber(req.BlockNum); header != nil {
				sectionHead := rawdb.ReadCanonicalHash(pm.chainDb, req.ChtNum*pm.iConfig.ChtSize-1)
				if root := light.GetChtRoot(pm.chainDb, req.ChtNum-1, sectionHead); root != (common.Hash{}) {
					trie, err := trie.New(root, trieDb)
					if err != nil {
						continue
					}
					var encNumber [8]byte
					binary.BigEndian.PutUint64(encNumber[:], req.BlockNum)

					var proof light.NodeList
					trie.Prove(encNumber[:], 0, &proof)

					proofs = append(proofs, ChtResp{Header: header, Proof: proof})
					if bytes += proof.DataSize() + estHeaderRlpSize; bytes >= softResponseLimit {
						break
					}
				}
			}
		}
		bv, rcost := p.fcClient.RequestProcessed(costs.baseCost + uint64(reqCnt)*costs.reqCost)
		pm.server.fcCostStats.update(msg.Code, uint64(reqCnt), rcost)
		return p.SendHeaderProofs(req.ReqID, bv, proofs)

	case GetHelperTrieProofsMsg:
		p.Log().Trace("Received helper trie proof request")
		// Decode the retrieval message
		var req struct {
			ReqID uint64
			Reqs  []HelperTrieReq
		}
		if err := msg.Decode(&req); err != nil {
			return errResp(ErrDecode, "msg %v: %v", msg, err)
		}
		// Gather state data until the fetch or network limits is reached
		var (
			auxBytes int
			auxData  [][]byte
		)
		reqCnt := len(req.Reqs)
		if reject(uint64(reqCnt), MaxHelperTrieProofsFetch) {
			return errResp(ErrRequestRejected, "")
		}

		var (
			lastIdx  uint64
			lastType uint
			root     common.Hash
			auxTrie  *trie.Trie
		)
		nodes := light.NewNodeSet()
		for _, req := range req.Reqs {
			if auxTrie == nil || req.Type != lastType || req.TrieIdx != lastIdx {
				auxTrie, lastType, lastIdx = nil, req.Type, req.TrieIdx

				var prefix string
				if root, prefix = pm.getHelperTrie(req.Type, req.TrieIdx); root != (common.Hash{}) {
					auxTrie, _ = trie.New(root, trie.NewDatabase(ethdb.NewTable(pm.chainDb, prefix)))
				}
			}
			if req.AuxReq == auxRoot {
				var data []byte
				if root != (common.Hash{}) {
					data = root[:]
				}
				auxData = append(auxData, data)
				auxBytes += len(data)
			} else {
				if auxTrie != nil {
					auxTrie.Prove(req.Key, req.FromLevel, nodes)
				}
				if req.AuxReq != 0 {
					data := pm.getHelperTrieAuxData(req)
					auxData = append(auxData, data)
					auxBytes += len(data)
				}
			}
			if nodes.DataSize()+auxBytes >= softResponseLimit {
				break
			}
		}
		bv, rcost := p.fcClient.RequestProcessed(costs.baseCost + uint64(reqCnt)*costs.reqCost)
		pm.server.fcCostStats.update(msg.Code, uint64(reqCnt), rcost)
		return p.SendHelperTrieProofs(req.ReqID, bv, HelperTrieResps{Proofs: nodes.NodeList(), AuxData: auxData})

	case HeaderProofsMsg:
		if pm.odr == nil {
			return errResp(ErrUnexpectedResponse, "")
		}

		p.Log().Trace("Received headers proof response")
		var resp struct {
			ReqID, BV uint64
			Data      []ChtResp
		}
		if err := msg.Decode(&resp); err != nil {
			return errResp(ErrDecode, "msg %v: %v", msg, err)
		}
		p.fcServer.GotReply(resp.ReqID, resp.BV)
		deliverMsg = &Msg{
			MsgType: MsgHeaderProofs,
			ReqID:   resp.ReqID,
			Obj:     resp.Data,
		}

	case HelperTrieProofsMsg:
		if pm.odr == nil {
			return errResp(ErrUnexpectedResponse, "")
		}

		p.Log().Trace("Received helper trie proof response")
		var resp struct {
			ReqID, BV uint64
			Data      HelperTrieResps
		}
		if err := msg.Decode(&resp); err != nil {
			return errResp(ErrDecode, "msg %v: %v", msg, err)
		}

		p.fcServer.GotReply(resp.ReqID, resp.BV)
		deliverMsg = &Msg{
			MsgType: MsgHelperTrieProofs,
			ReqID:   resp.ReqID,
			Obj:     resp.Data,
		}

	case SendTxMsg:
		if pm.txpool == nil {
			return errResp(ErrRequestRejected, "")
		}
		// Transactions arrived, parse all of them and deliver to the pool
		var txs []*types.Transaction
		if err := msg.Decode(&txs); err != nil {
			return errResp(ErrDecode, "msg %v: %v", msg, err)
		}
		reqCnt := len(txs)
		if reject(uint64(reqCnt), MaxTxSend) {
			return errResp(ErrRequestRejected, "")
		}
		for _, tx := range txs {
			if err := pm.verifyGatewayFee(tx.GatewayFeeRecipient(), tx.GatewayFee()); err != nil {
				return errResp(ErrRequestRejected, "tx %v: %v", tx, err)
			}
		}
		pm.txpool.AddRemotes(txs)

		_, rcost := p.fcClient.RequestProcessed(costs.baseCost + uint64(reqCnt)*costs.reqCost)
		pm.server.fcCostStats.update(msg.Code, uint64(reqCnt), rcost)

	case SendTxV2Msg:
		if pm.txpool == nil {
			return errResp(ErrRequestRejected, "")
		}
		// Transactions arrived, parse all of them and deliver to the pool
		var req struct {
			ReqID uint64
			Txs   []*types.Transaction
		}
		if err := msg.Decode(&req); err != nil {
			return errResp(ErrDecode, "msg %v: %v", msg, err)
		}
		reqCnt := len(req.Txs)
		if reject(uint64(reqCnt), MaxTxSend) {
			return errResp(ErrRequestRejected, "")
		}

		hashes := make([]common.Hash, len(req.Txs))
		for i, tx := range req.Txs {
			hashes[i] = tx.Hash()
		}
		stats := pm.txStatus(hashes)
		for i, stat := range stats {
			if stat.Status == core.TxStatusUnknown {
				tx := req.Txs[i]
				if err := pm.verifyGatewayFee(tx.GatewayFeeRecipient(), tx.GatewayFee()); err != nil {
					stats[i].Error = err.Error()
					continue
				}
				if errs := pm.txpool.AddRemotes([]*types.Transaction{tx}); errs[0] != nil {
					stats[i].Error = errs[0].Error()
					continue
				}
				stats[i] = pm.txStatus([]common.Hash{hashes[i]})[0]
			}
		}

		bv, rcost := p.fcClient.RequestProcessed(costs.baseCost + uint64(reqCnt)*costs.reqCost)
		pm.server.fcCostStats.update(msg.Code, uint64(reqCnt), rcost)

		return p.SendTxStatus(req.ReqID, bv, stats)

	case GetTxStatusMsg:
		if pm.txpool == nil {
			return errResp(ErrUnexpectedResponse, "")
		}
		// Transactions arrived, parse all of them and deliver to the pool
		var req struct {
			ReqID  uint64
			Hashes []common.Hash
		}
		if err := msg.Decode(&req); err != nil {
			return errResp(ErrDecode, "msg %v: %v", msg, err)
		}
		reqCnt := len(req.Hashes)
		if reject(uint64(reqCnt), MaxTxStatus) {
			return errResp(ErrRequestRejected, "")
		}
		bv, rcost := p.fcClient.RequestProcessed(costs.baseCost + uint64(reqCnt)*costs.reqCost)
		pm.server.fcCostStats.update(msg.Code, uint64(reqCnt), rcost)

		return p.SendTxStatus(req.ReqID, bv, pm.txStatus(req.Hashes))

	case TxStatusMsg:
		if pm.odr == nil {
			return errResp(ErrUnexpectedResponse, "")
		}

		p.Log().Trace("Received tx status response")
		var resp struct {
			ReqID, BV uint64
			Status    []txStatus
		}
		if err := msg.Decode(&resp); err != nil {
			return errResp(ErrDecode, "msg %v: %v", msg, err)
		}

		p.fcServer.GotReply(resp.ReqID, resp.BV)

	case GetEtherbaseMsg:
		p.Log().Trace("Received etherbase request")
		// Transactions arrived, parse all of them and deliver to the pool
		var req struct {
			ReqID uint64
		}
		if err := msg.Decode(&req); err != nil {
			return errResp(ErrDecode, "msg %v: %v", msg, err)
		}
		bv, rcost := p.fcClient.RequestProcessed(costs.baseCost + costs.reqCost)
		pm.server.fcCostStats.update(msg.Code, 1, rcost)
		return p.SendEtherbaseRLP(req.ReqID, bv, pm.etherbase)

	case EtherbaseMsg:
		p.Log().Trace("Received etherbase response")
		// TODO(asa): do we need to do anything with flow control here?
		var resp struct {
			ReqID, BV uint64
			Etherbase common.Address
		}
		if err := msg.Decode(&resp); err != nil {
			return errResp(ErrDecode, "msg %v: %v", msg, err)
		}
		p.Log().Trace("Setting peer etherbase", "etherbase", resp.Etherbase, "Peer ID", p.ID)
		pm.peers.setEtherbase(p, resp.Etherbase)

	default:
		p.Log().Trace("Received unknown message", "code", msg.Code)
		return errResp(ErrInvalidMsgCode, "%v", msg.Code)
	}

	if deliverMsg != nil {
		err := pm.retriever.deliver(p, deliverMsg)
		if err != nil {
			p.responseErrors++
			if p.responseErrors > maxResponseErrors {
				return err
			}
		}
	}
	return nil
}

// getAccount retrieves an account from the state based at root.
func (pm *ProtocolManager) getAccount(statedb *state.StateDB, root, hash common.Hash) (state.Account, error) {
	trie, err := trie.New(root, statedb.Database().TrieDB())
	if err != nil {
		return state.Account{}, err
	}
	blob, err := trie.TryGet(hash[:])
	if err != nil {
		return state.Account{}, err
	}
	var account state.Account
	if err = rlp.DecodeBytes(blob, &account); err != nil {
		return state.Account{}, err
	}
	return account, nil
}

// getHelperTrie returns the post-processed trie root for the given trie ID and section index
func (pm *ProtocolManager) getHelperTrie(id uint, idx uint64) (common.Hash, string) {
	switch id {
	case htCanonical:
		idxV1 := (idx+1)*(pm.iConfig.PairChtSize/pm.iConfig.ChtSize) - 1
		sectionHead := rawdb.ReadCanonicalHash(pm.chainDb, (idxV1+1)*pm.iConfig.ChtSize-1)
		return light.GetChtRoot(pm.chainDb, idxV1, sectionHead), light.ChtTablePrefix
	case htBloomBits:
		sectionHead := rawdb.ReadCanonicalHash(pm.chainDb, (idx+1)*pm.iConfig.BloomTrieSize-1)
		return light.GetBloomTrieRoot(pm.chainDb, idx, sectionHead), light.BloomTrieTablePrefix
	}
	return common.Hash{}, ""
}

// getHelperTrieAuxData returns requested auxiliary data for the given HelperTrie request
func (pm *ProtocolManager) getHelperTrieAuxData(req HelperTrieReq) []byte {
	if req.Type == htCanonical && req.AuxReq == auxHeader && len(req.Key) == 8 {
		blockNum := binary.BigEndian.Uint64(req.Key)
		hash := rawdb.ReadCanonicalHash(pm.chainDb, blockNum)
		return rawdb.ReadHeaderRLP(pm.chainDb, hash, blockNum)
	}
	return nil
}

func (pm *ProtocolManager) txStatus(hashes []common.Hash) []txStatus {
	stats := make([]txStatus, len(hashes))
	for i, stat := range pm.txpool.Status(hashes) {
		// Save the status we've got from the transaction pool
		stats[i].Status = stat

		// If the transaction is unknown to the pool, try looking it up locally
		if stat == core.TxStatusUnknown {
			if block, number, index := rawdb.ReadTxLookupEntry(pm.chainDb, hashes[i]); block != (common.Hash{}) {
				stats[i].Status = core.TxStatusIncluded
				stats[i].Lookup = &rawdb.TxLookupEntry{BlockHash: block, BlockIndex: number, Index: index}
			}
		}
	}
	return stats
}

// downloaderPeerNotify implements peerSetNotify
type downloaderPeerNotify ProtocolManager

type peerConnection struct {
	manager *ProtocolManager
	peer    *peer
}

func (pc *peerConnection) Head() (common.Hash, *big.Int) {
	return pc.peer.HeadAndTd()
}

func (pc *peerConnection) RequestHeadersByHash(origin common.Hash, amount int, skip int, reverse bool) error {
	reqID := genReqID()
	rq := &distReq{
		getCost: func(dp distPeer) uint64 {
			peer := dp.(*peer)
			return peer.GetRequestCost(GetBlockHeadersMsg, amount)
		},
		canSend: func(dp distPeer) bool {
			return dp.(*peer) == pc.peer
		},
		request: func(dp distPeer) func() {
			peer := dp.(*peer)
			cost := peer.GetRequestCost(GetBlockHeadersMsg, amount)
			peer.fcServer.QueueRequest(reqID, cost)
			return func() { peer.RequestHeadersByHash(reqID, cost, origin, amount, skip, reverse) }
		},
	}
	_, ok := <-pc.manager.reqDist.queue(rq)
	if !ok {
		return light.ErrNoPeers
	}
	return nil
}

func (pc *peerConnection) RequestHeadersByNumber(origin uint64, amount int, skip int, reverse bool) error {
	reqID := genReqID()
	rq := &distReq{
		getCost: func(dp distPeer) uint64 {
			peer := dp.(*peer)
			return peer.GetRequestCost(GetBlockHeadersMsg, amount)
		},
		canSend: func(dp distPeer) bool {
			return dp.(*peer) == pc.peer
		},
		request: func(dp distPeer) func() {
			peer := dp.(*peer)
			cost := peer.GetRequestCost(GetBlockHeadersMsg, amount)
			peer.fcServer.QueueRequest(reqID, cost)
			return func() { peer.RequestHeadersByNumber(reqID, cost, origin, amount, skip, reverse) }
		},
	}
	_, ok := <-pc.manager.reqDist.queue(rq)
	if !ok {
		return light.ErrNoPeers
	}
	return nil
}

func (d *downloaderPeerNotify) registerPeer(p *peer) {
	pm := (*ProtocolManager)(d)
	pc := &peerConnection{
		manager: pm,
		peer:    p,
	}
	pm.downloader.RegisterLightPeer(p.id, ethVersion, pc)
}

func (d *downloaderPeerNotify) unregisterPeer(p *peer) {
	pm := (*ProtocolManager)(d)
	pm.downloader.UnregisterPeer(p.id)
}