path: root/dex/peer.go

// Copyright 2018 The dexon-consensus Authors
// This file is part of the dexon-consensus library.
//
// The dexon-consensus 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 dexon-consensus 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 dexon-consensus library. If not, see
// <http://www.gnu.org/licenses/>.

// Copyright 2015 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package dex

import (
    "encoding/hex"
    "errors"
    "fmt"
    "sync"
    "time"

    mapset "github.com/deckarep/golang-set"
    coreCommon "github.com/dexon-foundation/dexon-consensus/common"
    coreTypes "github.com/dexon-foundation/dexon-consensus/core/types"
    dkgTypes "github.com/dexon-foundation/dexon-consensus/core/types/dkg"

    "github.com/dexon-foundation/dexon/common"
    "github.com/dexon-foundation/dexon/core/types"
    "github.com/dexon-foundation/dexon/crypto"
    "github.com/dexon-foundation/dexon/log"
    "github.com/dexon-foundation/dexon/p2p"
    "github.com/dexon-foundation/dexon/p2p/enode"
    "github.com/dexon-foundation/dexon/rlp"
)

var (
    errClosed            = errors.New("peer set is closed")
    errAlreadyRegistered = errors.New("peer is already registered")
    errNotRegistered     = errors.New("peer is not registered")
)

const (
    maxKnownTxs    = 32768 // Maximum transactions hashes to keep in the known list (prevent DOS)
    maxKnownBlocks = 1024  // Maximum block hashes to keep in the known list (prevent DOS)

    maxKnownDKGPrivateShares = 1024 // this related to DKG Size

    // maxQueuedTxs is the maximum number of transaction lists to queue up before
    // dropping broadcasts. This is a sensitive number as a transaction list might
    // contain a single transaction, or thousands.
    maxQueuedTxs = 1024

    // maxQueuedProps is the maximum number of block propagations to queue up before
    // dropping broadcasts. There's not much point in queueing stale blocks, so a few
    // that might cover uncles should be enough.
    maxQueuedProps = 4

    // maxQueuedAnns is the maximum number of block announcements to queue up before
    // dropping broadcasts. Similarly to block propagations, there's no point to queue
    // above some healthy uncle limit, so use that.
    maxQueuedAnns = 4

    maxQueuedCoreBlocks           = 16
    maxQueuedVotes                = 128
    maxQueuedAgreements           = 16
    maxQueuedDKGPrivateShare      = 16
    maxQueuedDKGParitialSignature = 16
    maxQueuedPullBlocks           = 128
    maxQueuedPullVotes            = 128
    maxQueuedPullRandomness       = 128

    handshakeTimeout = 5 * time.Second

    groupConnNum     = 3
    groupConnTimeout = 3 * time.Minute
)

// PeerInfo represents a short summary of the Ethereum sub-protocol metadata known
// about a connected peer.
type PeerInfo struct {
    Version int    `json:"version"` // Ethereum protocol version negotiated
    Number  uint64 `json:"number"`  // Number the peer's blockchain
    Head    string `json:"head"`    // SHA3 hash of the peer's best owned block
}

type setType uint32

const (
    notaryset = iota
)

type peerLabel struct {
    set   setType
    round uint64
}

func (p peerLabel) String() string {
    var t string
    switch p.set {
    case notaryset:
        t = fmt.Sprintf("NotarySet round: %d", p.round)
    }
    return t
}

type peer struct {
    id string

    *p2p.Peer
    rw p2p.MsgReadWriter

    version int // Protocol version negotiated

    head   common.Hash
    number uint64
    lock   sync.RWMutex

    lastKnownAgreementPositionLock sync.RWMutex
    lastKnownAgreementPosition     coreTypes.Position // The position of latest agreement to be known by this peer
    knownTxs                       mapset.Set         // Set of transaction hashes known to be known by this peer
    knownBlocks                    mapset.Set         // Set of block hashes known to be known by this peer
    knownAgreements                mapset.Set
    knownDKGPrivateShares          mapset.Set
    queuedTxs                      chan []*types.Transaction // Queue of transactions to broadcast to the peer
    queuedProps                    chan *types.Block         // Queue of blocks to broadcast to the peer
    queuedAnns                     chan *types.Block         // Queue of blocks to announce to the peer
    queuedCoreBlocks               chan []*coreTypes.Block
    queuedVotes                    chan []*coreTypes.Vote
    queuedAgreements               chan *coreTypes.AgreementResult
    queuedDKGPrivateShares         chan *dkgTypes.PrivateShare
    queuedDKGPartialSignatures     chan *dkgTypes.PartialSignature
    queuedPullBlocks               chan coreCommon.Hashes
    queuedPullVotes                chan coreTypes.Position
    queuedPullRandomness           chan coreCommon.Hashes
    term                           chan struct{} // Termination channel to stop the broadcaster
}

func newPeer(version int, p *p2p.Peer, rw p2p.MsgReadWriter) *peer {
    return &peer{
        Peer:                       p,
        rw:                         rw,
        version:                    version,
        id:                         p.ID().String(),
        knownTxs:                   mapset.NewSet(),
        knownBlocks:                mapset.NewSet(),
        knownAgreements:            mapset.NewSet(),
        knownDKGPrivateShares:      mapset.NewSet(),
        queuedTxs:                  make(chan []*types.Transaction, maxQueuedTxs),
        queuedProps:                make(chan *types.Block, maxQueuedProps),
        queuedAnns:                 make(chan *types.Block, maxQueuedAnns),
        queuedCoreBlocks:           make(chan []*coreTypes.Block, maxQueuedCoreBlocks),
        queuedVotes:                make(chan []*coreTypes.Vote, maxQueuedVotes),
        queuedAgreements:           make(chan *coreTypes.AgreementResult, maxQueuedAgreements),
        queuedDKGPrivateShares:     make(chan *dkgTypes.PrivateShare, maxQueuedDKGPrivateShare),
        queuedDKGPartialSignatures: make(chan *dkgTypes.PartialSignature, maxQueuedDKGParitialSignature),
        queuedPullBlocks:           make(chan coreCommon.Hashes, maxQueuedPullBlocks),
        queuedPullVotes:            make(chan coreTypes.Position, maxQueuedPullVotes),
        queuedPullRandomness:       make(chan coreCommon.Hashes, maxQueuedPullRandomness),
        term:                       make(chan struct{}),
    }
}

// broadcast is a write loop that multiplexes block propagations, announcements,
// transaction broadcasts into the remote peer.
// The goal is to have an async writer that does not lock up node internals.
func (p *peer) broadcast() {
    queuedVotes := make([]*coreTypes.Vote, 0, maxQueuedVotes)
    for {
    PriorityBroadcastVote:
        for {
            select {
            case votes := <-p.queuedVotes:
                queuedVotes = append(queuedVotes, votes...)
            default:
                break PriorityBroadcastVote
            }
        }
        if len(queuedVotes) != 0 {
            if err := p.SendVotes(queuedVotes); err != nil {
                return
            }
            p.Log().Trace("Broadcast votes", "count", len(queuedVotes))
            queuedVotes = queuedVotes[:0]
        }
        select {
        case block := <-p.queuedProps:
            if err := p.SendNewBlock(block); err != nil {
                return
            }
            p.Log().Trace("Propagated block", "number", block.Number(), "hash", block.Hash())

        case block := <-p.queuedAnns:
            if err := p.SendNewBlockHashes([]common.Hash{block.Hash()}, []uint64{block.NumberU64()}); err != nil {
                return
            }
            p.Log().Trace("Announced block", "number", block.Number(), "hash", block.Hash())
        case blocks := <-p.queuedCoreBlocks:
            if err := p.SendCoreBlocks(blocks); err != nil {
                return
            }
            p.Log().Trace("Broadcast core blocks", "count", len(blocks))
        case votes := <-p.queuedVotes:
            if err := p.SendVotes(votes); err != nil {
                return
            }
            p.Log().Trace("Broadcast votes", "count", len(votes))
        case agreement := <-p.queuedAgreements:
            if err := p.SendAgreement(agreement); err != nil {
                return
            }
            p.Log().Trace("Broadcast agreement")
        case privateShare := <-p.queuedDKGPrivateShares:
            if err := p.SendDKGPrivateShare(privateShare); err != nil {
                return
            }
            p.Log().Trace("Broadcast DKG private share")
        case psig := <-p.queuedDKGPartialSignatures:
            if err := p.SendDKGPartialSignature(psig); err != nil {
                return
            }
            p.Log().Trace("Broadcast DKG partial signature")
        case hashes := <-p.queuedPullBlocks:
            if err := p.SendPullBlocks(hashes); err != nil {
                return
            }
            p.Log().Trace("Pulling Blocks", "hashes", hashes)
        case pos := <-p.queuedPullVotes:
            if err := p.SendPullVotes(pos); err != nil {
                return
            }
            p.Log().Trace("Pulling Votes", "position", pos)
        case <-p.term:
            return
        case <-time.After(100 * time.Millisecond):
        }
        select {
        case txs := <-p.queuedTxs:
            if err := p.SendTransactions(txs); err != nil {
                return
            }
            p.Log().Trace("Broadcast transactions", "count", len(txs))
        default:
        }
    }
}

// close signals the broadcast goroutine to terminate.
func (p *peer) close() {
    close(p.term)
}

// Info gathers and returns a collection of metadata known about a peer.
func (p *peer) Info() *PeerInfo {
    hash, number := p.Head()

    return &PeerInfo{
        Version: p.version,
        Number:  number,
        Head:    hash.Hex(),
    }
}

// Head retrieves a copy of the current head hash and number of the
// peer.
func (p *peer) Head() (hash common.Hash, number uint64) {
    p.lock.RLock()
    defer p.lock.RUnlock()

    copy(hash[:], p.head[:])
    return hash, p.number
}

// SetHead updates the head hash and number of the peer.
func (p *peer) SetHead(hash common.Hash, number uint64) {
    p.lock.Lock()
    defer p.lock.Unlock()

    copy(p.head[:], hash[:])
    p.number = number
}

// MarkBlock marks a block as known for the peer, ensuring that the block will
// never be propagated to this particular peer.
func (p *peer) MarkBlock(hash common.Hash) {
    // If we reached the memory allowance, drop a previously known block hash
    for p.knownBlocks.Cardinality() >= maxKnownBlocks {
        p.knownBlocks.Pop()
    }
    p.knownBlocks.Add(hash)
}

// MarkTransaction marks a transaction as known for the peer, ensuring that it
// will never be propagated to this particular peer.
func (p *peer) MarkTransaction(hash common.Hash) {
    // If we reached the memory allowance, drop a previously known transaction hash
    for p.knownTxs.Cardinality() >= maxKnownTxs {
        p.knownTxs.Pop()
    }
    p.knownTxs.Add(hash)
}

func (p *peer) MarkAgreement(position coreTypes.Position) bool {
    p.lastKnownAgreementPositionLock.Lock()
    defer p.lastKnownAgreementPositionLock.Unlock()
    if position.Newer(p.lastKnownAgreementPosition) {
        p.lastKnownAgreementPosition = position
        return true
    }
    return false
}

func (p *peer) MarkDKGPrivateShares(hash common.Hash) {
    for p.knownDKGPrivateShares.Cardinality() >= maxKnownDKGPrivateShares {
        p.knownDKGPrivateShares.Pop()
    }
    p.knownDKGPrivateShares.Add(hash)
}

func (p *peer) isAgreementKnown(position coreTypes.Position) bool {
    p.lastKnownAgreementPositionLock.RLock()
    defer p.lastKnownAgreementPositionLock.RUnlock()
    return !p.lastKnownAgreementPosition.Older(position)
}

func (p *peer) logSend(err error, code uint64) error {
    if err != nil {
        p.Log().Error("Failed to send peer message", "code", code, "err", err)
    }
    return err
}

// SendTransactions sends transactions to the peer and includes the hashes
// in its transaction hash set for future reference.
func (p *peer) SendTransactions(txs types.Transactions) error {
    for _, tx := range txs {
        p.knownTxs.Add(tx.Hash())
    }
    return p.logSend(p2p.Send(p.rw, TxMsg, txs), TxMsg)
}

// AsyncSendTransactions queues list of transactions propagation to a remote
// peer. If the peer's broadcast queue is full, the event is silently dropped.
func (p *peer) AsyncSendTransactions(txs []*types.Transaction) {
    select {
    case p.queuedTxs <- txs:
        for _, tx := range txs {
            p.knownTxs.Add(tx.Hash())
        }
    default:
        p.Log().Debug("Dropping transaction propagation", "count", len(txs))
    }
}

// SendNewBlockHashes announces the availability of a number of blocks through
// a hash notification.
func (p *peer) SendNewBlockHashes(hashes []common.Hash, numbers []uint64) error {
    for _, hash := range hashes {
        p.knownBlocks.Add(hash)
    }
    request := make(newBlockHashesData, len(hashes))
    for i := 0; i < len(hashes); i++ {
        request[i].Hash = hashes[i]
        request[i].Number = numbers[i]
    }
    return p.logSend(p2p.Send(p.rw, NewBlockHashesMsg, request), NewBlockHashesMsg)
}

// AsyncSendNewBlockHash queues the availability of a block for propagation to a
// remote peer. If the peer's broadcast queue is full, the event is silently
// dropped.
func (p *peer) AsyncSendNewBlockHash(block *types.Block) {
    select {
    case p.queuedAnns <- block:
        p.knownBlocks.Add(block.Hash())
    default:
        p.Log().Debug("Dropping block announcement", "number", block.NumberU64(), "hash", block.Hash())
    }
}

// SendNewBlock propagates an entire block to a remote peer.
func (p *peer) SendNewBlock(block *types.Block) error {
    p.knownBlocks.Add(block.Hash())
    return p.logSend(p2p.Send(p.rw, NewBlockMsg, block), NewBlockMsg)
}

// AsyncSendNewBlock queues an entire block for propagation to a remote peer. If
// the peer's broadcast queue is full, the event is silently dropped.
func (p *peer) AsyncSendNewBlock(block *types.Block) {
    select {
    case p.queuedProps <- block:
        p.knownBlocks.Add(block.Hash())
    default:
        p.Log().Debug("Dropping block propagation", "number", block.NumberU64(), "hash", block.Hash())
    }
}

func (p *peer) SendCoreBlocks(blocks []*coreTypes.Block) error {
    return p.logSend(p2p.Send(p.rw, CoreBlockMsg, blocks), CoreBlockMsg)
}

func (p *peer) AsyncSendCoreBlocks(blocks []*coreTypes.Block) {
    select {
    case p.queuedCoreBlocks <- blocks:
    default:
        p.Log().Debug("Dropping core block propagation")
    }
}

func (p *peer) SendVotes(votes []*coreTypes.Vote) error {
    return p.logSend(p2p.Send(p.rw, VoteMsg, votes), VoteMsg)
}

func (p *peer) AsyncSendVotes(votes []*coreTypes.Vote) {
    select {
    case p.queuedVotes <- votes:
    default:
        p.Log().Debug("Dropping vote propagation")
    }
}

func (p *peer) SendAgreement(agreement *coreTypes.AgreementResult) error {
    p.knownAgreements.Add(rlpHash(agreement))
    return p.logSend(p2p.Send(p.rw, AgreementMsg, agreement), AgreementMsg)
}

func (p *peer) AsyncSendAgreement(agreement *coreTypes.AgreementResult) {
    select {
    case p.queuedAgreements <- agreement:
        p.knownAgreements.Add(rlpHash(agreement))
    default:
        p.Log().Debug("Dropping agreement result")
    }
}

func (p *peer) SendDKGPrivateShare(privateShare *dkgTypes.PrivateShare) error {
    p.knownDKGPrivateShares.Add(rlpHash(privateShare))
    return p.logSend(p2p.Send(p.rw, DKGPrivateShareMsg, privateShare), DKGPrivateShareMsg)
}

func (p *peer) AsyncSendDKGPrivateShare(privateShare *dkgTypes.PrivateShare) {
    select {
    case p.queuedDKGPrivateShares <- privateShare:
        p.knownDKGPrivateShares.Add(rlpHash(privateShare))
    default:
        p.Log().Debug("Dropping DKG private share")
    }
}

func (p *peer) SendDKGPartialSignature(psig *dkgTypes.PartialSignature) error {
    return p.logSend(p2p.Send(p.rw, DKGPartialSignatureMsg, psig), DKGPartialSignatureMsg)
}

func (p *peer) AsyncSendDKGPartialSignature(psig *dkgTypes.PartialSignature) {
    select {
    case p.queuedDKGPartialSignatures <- psig:
    default:
        p.Log().Debug("Dropping DKG partial signature")
    }
}

func (p *peer) SendPullBlocks(hashes coreCommon.Hashes) error {
    return p.logSend(p2p.Send(p.rw, PullBlocksMsg, hashes), PullBlocksMsg)
}

func (p *peer) AsyncSendPullBlocks(hashes coreCommon.Hashes) {
    select {
    case p.queuedPullBlocks <- hashes:
    default:
        p.Log().Debug("Dropping Pull Blocks")
    }
}

func (p *peer) SendPullVotes(pos coreTypes.Position) error {
    return p.logSend(p2p.Send(p.rw, PullVotesMsg, pos), PullVotesMsg)
}

func (p *peer) AsyncSendPullVotes(pos coreTypes.Position) {
    select {
    case p.queuedPullVotes <- pos:
    default:
        p.Log().Debug("Dropping Pull Votes")
    }
}

// SendBlockHeaders sends a batch of block headers to the remote peer.
func (p *peer) SendBlockHeaders(flag uint8, headers []*types.HeaderWithGovState) error {
    return p.logSend(p2p.Send(p.rw, BlockHeadersMsg, headersData{Flag: flag, Headers: headers}), BlockHeadersMsg)
}

// SendBlockBodiesRLP sends a batch of block contents to the remote peer from
// an already RLP encoded format.
func (p *peer) SendBlockBodiesRLP(flag uint8, bodies []rlp.RawValue) error {
    return p.logSend(p2p.Send(p.rw, BlockBodiesMsg, blockBodiesDataRLP{Flag: flag, Bodies: bodies}), BlockBodiesMsg)
}

// SendNodeDataRLP sends a batch of arbitrary internal data, corresponding to the
// hashes requested.
func (p *peer) SendNodeData(data [][]byte) error {
    return p.logSend(p2p.Send(p.rw, NodeDataMsg, data), NodeDataMsg)
}

// SendReceiptsRLP sends a batch of transaction receipts, corresponding to the
// ones requested from an already RLP encoded format.
func (p *peer) SendReceiptsRLP(receipts []rlp.RawValue) error {
    return p.logSend(p2p.Send(p.rw, ReceiptsMsg, receipts), ReceiptsMsg)
}

func (p *peer) SendGovState(govState *types.GovState) error {
    return p.logSend(p2p.Send(p.rw, GovStateMsg, govState), GovStateMsg)
}

// RequestOneHeader is a wrapper around the header query functions to fetch a
// single header. It is used solely by the fetcher.
func (p *peer) RequestOneHeader(hash common.Hash) error {
    p.Log().Debug("Fetching single header", "hash", hash)
    return p2p.Send(p.rw, GetBlockHeadersMsg, &getBlockHeadersData{Origin: hashOrNumber{Hash: hash}, Amount: uint64(1), Skip: uint64(0), Reverse: false, WithGov: false, Flag: fetcherReq})
}

// RequestHeadersByHash fetches a batch of blocks' headers corresponding to the
// specified header query, based on the hash of an origin block.
func (p *peer) RequestHeadersByHash(origin common.Hash, amount int, skip int, reverse, withGov bool) error {
    p.Log().Debug("Fetching batch of headers", "count", amount, "fromhash", origin, "skip", skip, "reverse", reverse, "withgov", withGov, "flag", downloaderReq)
    return p2p.Send(p.rw, GetBlockHeadersMsg, &getBlockHeadersData{Origin: hashOrNumber{Hash: origin}, Amount: uint64(amount), Skip: uint64(skip), Reverse: reverse, WithGov: withGov, Flag: downloaderReq})
}

// RequestHeadersByNumber fetches a batch of blocks' headers corresponding to the
// specified header query, based on the number of an origin block.
func (p *peer) RequestHeadersByNumber(origin uint64, amount int, skip int, reverse, withGov bool) error {
    p.Log().Debug("Fetching batch of headers", "count", amount, "fromnum", origin, "skip", skip, "reverse", reverse, "withgov", withGov, "flag", downloaderReq)
    return p2p.Send(p.rw, GetBlockHeadersMsg, &getBlockHeadersData{Origin: hashOrNumber{Number: origin}, Amount: uint64(amount), Skip: uint64(skip), Reverse: reverse, WithGov: withGov, Flag: downloaderReq})
}

func (p *peer) RequestWhitelistHeader(origin uint64) error {
    p.Log().Debug("Fetching whitelist header", "number", origin, "flag", whitelistReq)
    return p2p.Send(p.rw, GetBlockHeadersMsg, &getBlockHeadersData{Origin: hashOrNumber{Number: origin}, Amount: 1, Skip: 0, Reverse: false, WithGov: false, Flag: whitelistReq})
}

func (p *peer) RequestGovStateByHash(hash common.Hash) error {
    p.Log().Debug("Fetching one gov state", "hash", hash)
    return p2p.Send(p.rw, GetGovStateMsg, hash)
}

// RequestBodies fetches a batch of blocks' bodies corresponding to the hashes
// specified.
func (p *peer) RequestBodies(flag uint8, hashes []common.Hash) error {
    p.Log().Debug("Fetching batch of block bodies", "count", len(hashes), "flag", flag)
    return p2p.Send(p.rw, GetBlockBodiesMsg, []interface{}{flag, hashes})
}

func (p *peer) FetchBodies(hashes []common.Hash) error {
    return p.RequestBodies(fetcherReq, hashes)
}

func (p *peer) DownloadBodies(hashes []common.Hash) error {
    return p.RequestBodies(downloaderReq, hashes)
}

// RequestNodeData fetches a batch of arbitrary data from a node's known state
// data, corresponding to the specified hashes.
func (p *peer) RequestNodeData(hashes []common.Hash) error {
    p.Log().Debug("Fetching batch of state data", "count", len(hashes))
    return p2p.Send(p.rw, GetNodeDataMsg, hashes)
}

// RequestReceipts fetches a batch of transaction receipts from a remote node.
func (p *peer) RequestReceipts(hashes []common.Hash) error {
    p.Log().Debug("Fetching batch of receipts", "count", len(hashes))
    return p2p.Send(p.rw, GetReceiptsMsg, hashes)
}

// Handshake executes the eth protocol handshake, negotiating version number,
// network IDs, difficulties, head and genesis blocks.
func (p *peer) Handshake(network uint64, number uint64, head common.Hash, genesis common.Hash) error {
    // Send out own handshake in a new thread
    errc := make(chan error, 2)
    var status statusData // safe to read after two values have been received from errc

    go func() {
        errc <- p2p.Send(p.rw, StatusMsg, &statusData{
            ProtocolVersion: uint32(p.version),
            NetworkId:       network,
            Number:          number,
            CurrentBlock:    head,
            GenesisBlock:    genesis,
        })
    }()
    go func() {
        errc <- p.readStatus(network, &status, genesis)
    }()
    timeout := time.NewTimer(handshakeTimeout)
    defer timeout.Stop()
    for i := 0; i < 2; i++ {
        select {
        case err := <-errc:
            if err != nil {
                return err
            }
        case <-timeout.C:
            return p2p.DiscReadTimeout
        }
    }
    p.number, p.head = status.Number, status.CurrentBlock
    return nil
}

func (p *peer) readStatus(network uint64, status *statusData, genesis common.Hash) (err error) {
    msg, err := p.rw.ReadMsg()
    if err != nil {
        return err
    }
    if msg.Code != StatusMsg {
        return errResp(ErrNoStatusMsg, "first msg has code %x (!= %x)", msg.Code, StatusMsg)
    }
    if msg.Size > ProtocolMaxMsgSize {
        return errResp(ErrMsgTooLarge, "%v > %v", msg.Size, ProtocolMaxMsgSize)
    }
    // Decode the handshake and make sure everything matches
    if err := msg.Decode(&status); err != nil {
        return errResp(ErrDecode, "msg %v: %v", msg, err)
    }
    if status.GenesisBlock != genesis {
        return errResp(ErrGenesisBlockMismatch, "%x (!= %x)", status.GenesisBlock[:8], genesis[:8])
    }
    if status.NetworkId != network {
        return errResp(ErrNetworkIdMismatch, "%d (!= %d)", status.NetworkId, network)
    }
    if int(status.ProtocolVersion) != p.version {
        return errResp(ErrProtocolVersionMismatch, "%d (!= %d)", status.ProtocolVersion, p.version)
    }
    return nil
}

// String implements fmt.Stringer.
func (p *peer) String() string {
    return fmt.Sprintf("Peer %s [%s]", p.id,
        fmt.Sprintf("dex/%2d", p.version),
    )
}

// peerSet represents the collection of active peers currently participating in
// the Ethereum sub-protocol.
type peerSet struct {
    peers  map[string]*peer
    lock   sync.RWMutex
    closed bool
    selfPK string

    srvr p2pServer
    gov  governance

    label2Nodes    map[peerLabel]map[string]*enode.Node
    directConn     map[peerLabel]struct{}
    groupConnPeers map[peerLabel]map[string]time.Time
    allDirectPeers map[string]map[peerLabel]struct{}
}

// newPeerSet creates a new peer set to track the active participants.
func newPeerSet(gov governance, srvr p2pServer) *peerSet {
    return &peerSet{
        peers:          make(map[string]*peer),
        gov:            gov,
        srvr:           srvr,
        selfPK:         hex.EncodeToString(crypto.FromECDSAPub(&srvr.GetPrivateKey().PublicKey)),
        label2Nodes:    make(map[peerLabel]map[string]*enode.Node),
        directConn:     make(map[peerLabel]struct{}),
        groupConnPeers: make(map[peerLabel]map[string]time.Time),
        allDirectPeers: make(map[string]map[peerLabel]struct{}),
    }
}

// Register injects a new peer into the working set, or returns an error if the
// peer is already known. If a new peer it registered, its broadcast loop is also
// started.
func (ps *peerSet) Register(p *peer) error {
    ps.lock.Lock()
    defer ps.lock.Unlock()

    if ps.closed {
        return errClosed
    }
    if _, ok := ps.peers[p.id]; ok {
        return errAlreadyRegistered
    }
    ps.peers[p.id] = p
    go p.broadcast()

    return nil
}

// Unregister removes a remote peer from the active set, disabling any further
// actions to/from that particular entity.
func (ps *peerSet) Unregister(id string) error {
    ps.lock.Lock()
    defer ps.lock.Unlock()

    p, ok := ps.peers[id]
    if !ok {
        return errNotRegistered
    }
    delete(ps.peers, id)
    p.close()

    return nil
}

// Peer retrieves the registered peer with the given id.
func (ps *peerSet) Peer(id string) *peer {
    ps.lock.RLock()
    defer ps.lock.RUnlock()

    return ps.peers[id]
}

// Len returns if the current number of peers in the set.
func (ps *peerSet) Len() int {
    ps.lock.RLock()
    defer ps.lock.RUnlock()

    return len(ps.peers)
}

// Peers retrieves all of the peers.
func (ps *peerSet) Peers() []*peer {
    ps.lock.RLock()
    defer ps.lock.RUnlock()

    list := make([]*peer, 0, len(ps.peers))
    for _, p := range ps.peers {
        list = append(list, p)
    }
    return list
}

// PeersWithoutBlock retrieves a list of peers that do not have a given block in
// their set of known hashes.
func (ps *peerSet) PeersWithoutBlock(hash common.Hash) []*peer {
    ps.lock.RLock()
    defer ps.lock.RUnlock()

    list := make([]*peer, 0, len(ps.peers))
    for _, p := range ps.peers {
        if !p.knownBlocks.Contains(hash) {
            list = append(list, p)
        }
    }
    return list
}

func (ps *peerSet) PeersWithLabel(label peerLabel) []*peer {
    ps.lock.RLock()
    defer ps.lock.RUnlock()
    list := make([]*peer, 0, len(ps.label2Nodes[label]))
    for id := range ps.label2Nodes[label] {
        if p, ok := ps.peers[id]; ok {
            list = append(list, p)
        }
    }
    return list
}

func (ps *peerSet) PeersWithoutLabel(label peerLabel) []*peer {
    ps.lock.RLock()
    defer ps.lock.RUnlock()
    length := len(ps.peers) - len(ps.label2Nodes[label])
    if length <= 0 {
        return []*peer{}
    }
    list := make([]*peer, 0, len(ps.peers)-len(ps.label2Nodes[label]))
    peersWithLabel := ps.label2Nodes[label]
    for id, p := range ps.peers {
        if _, exist := peersWithLabel[id]; !exist {
            list = append(list, p)
        }
    }
    return list
}

func (ps *peerSet) PeersWithoutAgreement(position coreTypes.Position) []*peer {
    ps.lock.RLock()
    defer ps.lock.RUnlock()
    list := make([]*peer, 0, len(ps.peers))
    for _, p := range ps.peers {
        if !p.isAgreementKnown(position) {
            list = append(list, p)
        }
    }
    return list
}

func (ps *peerSet) PeersWithoutDKGPrivateShares(hash common.Hash) []*peer {
    ps.lock.RLock()
    defer ps.lock.RUnlock()
    list := make([]*peer, 0, len(ps.peers))
    for _, p := range ps.peers {
        if !p.knownDKGPrivateShares.Contains(hash) {
            list = append(list, p)
        }
    }
    return list
}

// BestPeer retrieves the known peer with the currently highest total difficulty.
func (ps *peerSet) BestPeer() *peer {
    ps.lock.RLock()
    defer ps.lock.RUnlock()

    var (
        bestPeer   *peer
        bestNumber uint64
    )
    for _, p := range ps.peers {
        if _, number := p.Head(); bestPeer == nil || number > bestNumber {
            bestPeer, bestNumber = p, number
        }
    }
    return bestPeer
}

// Close disconnects all peers.
// No new peers can be registered after Close has returned.
func (ps *peerSet) Close() {
    ps.lock.Lock()
    defer ps.lock.Unlock()

    for _, p := range ps.peers {
        p.Disconnect(p2p.DiscQuitting)
    }
    ps.closed = true
}

func (ps *peerSet) BuildConnection(round uint64) {
    ps.lock.Lock()
    defer ps.lock.Unlock()

    log.Info("Build connection", "round", round)

    notaryLabel := peerLabel{set: notaryset, round: round}
    if _, ok := ps.label2Nodes[notaryLabel]; !ok {
        notaryPKs, err := ps.gov.NotarySet(round)
        if err != nil {
            log.Error("get notary set fail", "round", round, "err", err)
            return
        }

        nodes := ps.pksToNodes(notaryPKs)
        ps.label2Nodes[notaryLabel] = nodes

        if _, exists := nodes[ps.srvr.Self().ID().String()]; exists {
            ps.buildDirectConn(notaryLabel)
        } else {
            ps.buildGroupConn(notaryLabel)
        }
    }
}

func (ps *peerSet) ForgetLabelConnection(label peerLabel) {
    ps.lock.Lock()
    defer ps.lock.Unlock()

    log.Debug("Forget label connection", "label", label)
    ps.forgetDirectConn(label)
    ps.forgetGroupConn(label)
    delete(ps.directConn, label)
    delete(ps.groupConnPeers, label)
    delete(ps.label2Nodes, label)
}

func (ps *peerSet) ForgetConnection(round uint64) {
    ps.lock.Lock()
    defer ps.lock.Unlock()

    log.Debug("Forget connection", "round", round)

    for label := range ps.directConn {
        if label.round <= round {
            ps.forgetDirectConn(label)
        }
    }

    for label := range ps.groupConnPeers {
        if label.round <= round {
            ps.forgetGroupConn(label)
        }
    }

    for label := range ps.label2Nodes {
        if label.round <= round {
            delete(ps.label2Nodes, label)
        }
    }
}

func (ps *peerSet) EnsureGroupConn() {
    ps.lock.Lock()
    defer ps.lock.Unlock()

    now := time.Now()
    for label, peers := range ps.groupConnPeers {
        // Remove timeout group conn peer.
        for id, addtime := range peers {
            if ps.peers[id] == nil && time.Since(addtime) > groupConnTimeout {
                ps.removeDirectPeer(id, label)
                delete(ps.groupConnPeers[label], id)
            }
        }

        // Add new group conn peer.
        for id := range ps.label2Nodes[label] {
            if len(ps.groupConnPeers[label]) >= groupConnNum {
                break
            }
            ps.groupConnPeers[label][id] = now
            ps.addDirectPeer(id, label)
        }
    }
}

func (ps *peerSet) buildDirectConn(label peerLabel) {
    ps.directConn[label] = struct{}{}
    for id := range ps.label2Nodes[label] {
        ps.addDirectPeer(id, label)
    }
}

func (ps *peerSet) forgetDirectConn(label peerLabel) {
    for id := range ps.label2Nodes[label] {
        ps.removeDirectPeer(id, label)
    }
    delete(ps.directConn, label)
}

func (ps *peerSet) buildGroupConn(label peerLabel) {
    peers := make(map[string]time.Time)
    now := time.Now()
    for id := range ps.label2Nodes[label] {
        peers[id] = now
        ps.addDirectPeer(id, label)
        if len(peers) >= groupConnNum {
            break
        }
    }
    ps.groupConnPeers[label] = peers
}

func (ps *peerSet) forgetGroupConn(label peerLabel) {
    for id := range ps.groupConnPeers[label] {
        ps.removeDirectPeer(id, label)
    }
    delete(ps.groupConnPeers, label)
}

func (ps *peerSet) addDirectPeer(id string, label peerLabel) {
    if len(ps.allDirectPeers[id]) > 0 {
        ps.allDirectPeers[id][label] = struct{}{}
        return
    }
    ps.allDirectPeers[id] = map[peerLabel]struct{}{label: {}}
    node := ps.label2Nodes[label][id]
    ps.srvr.AddDirectPeer(node)
}

func (ps *peerSet) removeDirectPeer(id string, label peerLabel) {
    if len(ps.allDirectPeers[id]) == 0 {
        return
    }

    delete(ps.allDirectPeers[id], label)
    if len(ps.allDirectPeers[id]) == 0 {
        ps.srvr.RemoveDirectPeer(ps.label2Nodes[label][id])
        delete(ps.allDirectPeers, id)
    }
}

func (ps *peerSet) pksToNodes(pks map[string]struct{}) map[string]*enode.Node {
    nodes := map[string]*enode.Node{}
    for pk := range pks {
        n := ps.newEmptyNode(pk)
        if n.ID() == ps.srvr.Self().ID() {
            n = ps.srvr.Self()
        }
        nodes[n.ID().String()] = n
    }
    return nodes
}

func (ps *peerSet) newEmptyNode(pk string) *enode.Node {
    b, err := hex.DecodeString(pk)
    if err != nil {
        panic(err)
    }

    pubkey, err := crypto.UnmarshalPubkey(b)
    if err != nil {
        panic(err)
    }
    return enode.NewV4(pubkey, nil, 0, 0)
}

func (ps *peerSet) Status() {
    ps.lock.Lock()
    defer ps.lock.Unlock()
    for label := range ps.directConn {
        l := label.String()
        for id := range ps.label2Nodes[label] {
            _, ok := ps.peers[id]
            log.Debug("direct conn", "label", l, "id", id, "connected", ok)
        }
    }

    for label, peers := range ps.groupConnPeers {
        l := label.String()
        for id := range peers {
            _, ok := ps.peers[id]
            log.Debug("group conn", "label", l, "id", id, "connected", ok)
        }
    }

    connected := 0
    for id := range ps.allDirectPeers {
        if _, ok := ps.peers[id]; ok {
            connected++
        }
    }
    log.Debug("all direct peers",
        "connected", connected, "all", len(ps.allDirectPeers))
}