path: root/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"
    "errors"
    "fmt"
    "math/big"
    "net"
    "sync"
    "time"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/consensus"
    "github.com/ethereum/go-ethereum/core"
    "github.com/ethereum/go-ethereum/core/state"
    "github.com/ethereum/go-ethereum/core/types"
    "github.com/ethereum/go-ethereum/eth"
    "github.com/ethereum/go-ethereum/eth/downloader"
    "github.com/ethereum/go-ethereum/ethdb"
    "github.com/ethereum/go-ethereum/event"
    "github.com/ethereum/go-ethereum/log"
    "github.com/ethereum/go-ethereum/p2p"
    "github.com/ethereum/go-ethereum/p2p/discover"
    "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
    MaxHeaderProofsFetch = 64  // Amount of merkle proofs to be fetched per retrieval request
    MaxTxSend            = 64  // Amount of transactions to be send per request

    disableClientRemovePeer = false
)

// errIncompatibleConfig is returned if the requested protocols and configs are
// not compatible (low protocol version restrictions and high requirements).
var errIncompatibleConfig = errors.New("incompatible configuration")

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

type BlockChain interface {
    HasHeader(hash common.Hash, number uint64) bool
    GetHeader(hash common.Hash, number uint64) *types.Header
    GetHeaderByHash(hash common.Hash) *types.Header
    CurrentHeader() *types.Header
    GetTdByHash(hash common.Hash) *big.Int
    InsertHeaderChain(chain []*types.Header, checkFreq int) (int, error)
    Rollback(chain []common.Hash)
    Status() (td *big.Int, currentBlock common.Hash, genesisBlock common.Hash)
    GetHeaderByNumber(number uint64) *types.Header
    GetBlockHashesFromHash(hash common.Hash, max uint64) []common.Hash
    LastBlockHash() common.Hash
    Genesis() *types.Block
    SubscribeChainHeadEvent(ch chan<- core.ChainHeadEvent) event.Subscription
}

type txPool interface {
    // AddRemotes should add the given transactions to the pool.
    AddRemotes([]*types.Transaction) error
}

type ProtocolManager struct {
    lightSync   bool
    txpool      txPool
    txrelay     *LesTxRelay
    networkId   uint64
    chainConfig *params.ChainConfig
    blockchain  BlockChain
    chainDb     ethdb.Database
    odr         *LesOdr
    server      *LesServer
    serverPool  *serverPool
    lesTopic    discv5.Topic
    reqDist     *requestDistributor
    retriever   *retrieveManager

    downloader *downloader.Downloader
    fetcher    *lightFetcher
    peers      *peerSet

    SubProtocols []p2p.Protocol

    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, lightSync bool, networkId uint64, mux *event.TypeMux, engine consensus.Engine, peers *peerSet, blockchain BlockChain, txpool txPool, chainDb ethdb.Database, odr *LesOdr, txrelay *LesTxRelay, quitSync chan struct{}, wg *sync.WaitGroup) (*ProtocolManager, error) {
    // Create the protocol manager with the base fields
    manager := &ProtocolManager{
        lightSync:   lightSync,
        eventMux:    mux,
        blockchain:  blockchain,
        chainConfig: chainConfig,
        chainDb:     chainDb,
        odr:         odr,
        networkId:   networkId,
        txpool:      txpool,
        txrelay:     txrelay,
        peers:       peers,
        newPeerCh:   make(chan *peer),
        quitSync:    quitSync,
        wg:          wg,
        noMorePeers: make(chan struct{}),
    }
    if odr != nil {
        manager.retriever = odr.retriever
        manager.reqDist = odr.retriever.dist
    }
    // Initiate a sub-protocol for every implemented version we can handle
    manager.SubProtocols = make([]p2p.Protocol, 0, len(ProtocolVersions))
    for i, version := range ProtocolVersions {
        // Compatible, initialize the sub-protocol
        version := version // Closure for the run
        manager.SubProtocols = append(manager.SubProtocols, p2p.Protocol{
            Name:    "les",
            Version: version,
            Length:  ProtocolLengths[i],
            Run: func(p *p2p.Peer, rw p2p.MsgReadWriter) error {
                var entry *poolEntry
                peer := manager.newPeer(int(version), networkId, p, rw)
                if manager.serverPool != nil {
                    addr := p.RemoteAddr().(*net.TCPAddr)
                    entry = manager.serverPool.connect(peer, addr.IP, uint16(addr.Port))
                }
                peer.poolEntry = entry
                select {
                case manager.newPeerCh <- peer:
                    manager.wg.Add(1)
                    defer manager.wg.Done()
                    err := manager.handle(peer)
                    if entry != nil {
                        manager.serverPool.disconnect(entry)
                    }
                    return err
                case <-manager.quitSync:
                    if entry != nil {
                        manager.serverPool.disconnect(entry)
                    }
                    return p2p.DiscQuitting
                }
            },
            NodeInfo: func() interface{} {
                return manager.NodeInfo()
            },
            PeerInfo: func(id discover.NodeID) interface{} {
                if p := manager.peers.Peer(fmt.Sprintf("%x", id[:8])); p != nil {
                    return p.Info()
                }
                return nil
            },
        })
    }
    if len(manager.SubProtocols) == 0 {
        return nil, errIncompatibleConfig
    }

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

    if lightSync {
        manager.downloader = downloader.New(downloader.LightSync, 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) {
    pm.peers.Unregister(id)
}

func (pm *ProtocolManager) Start() {
    if pm.lightSync {
        go pm.syncer()
    } else {
        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

    // 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")
}

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

    // Execute the LES handshake
    td, head, genesis := pm.blockchain.Status()
    headNum := core.GetBlockNumber(pm.chainDb, head)
    if err := p.Handshake(td, head, headNum, genesis, pm.server); err != nil {
        p.Log().Debug("Light Ethereum handshake failed", "err", err)
        return err
    }
    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)
        }
    }

    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, GetProofsMsg, SendTxMsg, GetHeaderProofsMsg}

// 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")

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

        // 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 {
                origin = pm.blockchain.GetHeaderByHash(query.Origin.Hash)
            } else {
                origin = pm.blockchain.GetHeaderByNumber(query.Origin.Number)
            }
            if origin == nil {
                break
            }
            number := origin.Number.Uint64()
            headers = append(headers, origin)
            bytes += estHeaderRlpSize

            // Advance to the next header of the query
            switch {
            case query.Origin.Hash != (common.Hash{}) && query.Reverse:
                // Hash based traversal towards the genesis block
                for i := 0; i < int(query.Skip)+1; i++ {
                    if header := pm.blockchain.GetHeader(query.Origin.Hash, number); header != nil {
                        query.Origin.Hash = header.ParentHash
                        number--
                    } else {
                        unknown = true
                        break
                    }
                }
            case query.Origin.Hash != (common.Hash{}) && !query.Reverse:
                // Hash based traversal towards the leaf block
                if header := pm.blockchain.GetHeaderByNumber(origin.Number.Uint64() + query.Skip + 1); header != nil {
                    if pm.blockchain.GetBlockHashesFromHash(header.Hash(), query.Skip+1)[query.Skip] == query.Origin.Hash {
                        query.Origin.Hash = header.Hash()
                    } 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 data := core.GetBodyRLP(pm.chainDb, hash, core.GetBlockNumber(pm.chainDb, hash)); 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 header := core.GetHeader(pm.chainDb, req.BHash, core.GetBlockNumber(pm.chainDb, req.BHash)); header != nil {
                if trie, _ := trie.New(header.Root, pm.chainDb); trie != nil {
                    sdata := trie.Get(req.AccKey)
                    var acc state.Account
                    if err := rlp.DecodeBytes(sdata, &acc); err == nil {
                        entry, _ := pm.chainDb.Get(acc.CodeHash)
                        if bytes+len(entry) >= softResponseLimit {
                            break
                        }
                        data = append(data, entry)
                        bytes += len(entry)
                    }
                }
            }
        }
        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
            results := core.GetBlockReceipts(pm.chainDb, hash, core.GetBlockNumber(pm.chainDb, hash))
            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 GetProofsMsg:
        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 {
            if bytes >= softResponseLimit {
                break
            }
            // Retrieve the requested state entry, stopping if enough was found
            if header := core.GetHeader(pm.chainDb, req.BHash, core.GetBlockNumber(pm.chainDb, req.BHash)); header != nil {
                if tr, _ := trie.New(header.Root, pm.chainDb); tr != nil {
                    if len(req.AccKey) > 0 {
                        sdata := tr.Get(req.AccKey)
                        tr = nil
                        var acc state.Account
                        if err := rlp.DecodeBytes(sdata, &acc); err == nil {
                            tr, _ = trie.New(acc.Root, pm.chainDb)
                        }
                    }
                    if tr != nil {
                        proof := tr.Prove(req.Key)
                        proofs = append(proofs, proof)
                        bytes += len(proof)
                    }
                }
            }
        }
        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 ProofsMsg:
        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      [][]rlp.RawValue
        }
        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: MsgProofs,
            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), MaxHeaderProofsFetch) {
            return errResp(ErrRequestRejected, "")
        }
        for _, req := range req.Reqs {
            if bytes >= softResponseLimit {
                break
            }

            if header := pm.blockchain.GetHeaderByNumber(req.BlockNum); header != nil {
                if root := getChtRoot(pm.chainDb, req.ChtNum); root != (common.Hash{}) {
                    if tr, _ := trie.New(root, pm.chainDb); tr != nil {
                        var encNumber [8]byte
                        binary.BigEndian.PutUint64(encNumber[:], req.BlockNum)
                        proof := tr.Prove(encNumber[:])
                        proofs = append(proofs, ChtResp{Header: header, Proof: proof})
                        bytes += len(proof) + estHeaderRlpSize
                    }
                }
            }
        }
        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 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 SendTxMsg:
        if pm.txpool == nil {
            return errResp(ErrUnexpectedResponse, "")
        }
        // 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, "")
        }

        if err := pm.txpool.AddRemotes(txs); err != nil {
            return errResp(ErrUnexpectedResponse, "msg: %v", err)
        }

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

    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
}

// NodeInfo retrieves some protocol metadata about the running host node.
func (self *ProtocolManager) NodeInfo() *eth.EthNodeInfo {
    return &eth.EthNodeInfo{
        Network:    self.networkId,
        Difficulty: self.blockchain.GetTdByHash(self.blockchain.LastBlockHash()),
        Genesis:    self.blockchain.Genesis().Hash(),
        Head:       self.blockchain.LastBlockHash(),
    }
}

// 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 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 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)
}