peer.go

// Copyright (c) 2018 The MATRIX Authors
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php

package man

import (
	"errors"
	"fmt"
	"github.com/MatrixAINetwork/go-matrix/common"
	"github.com/MatrixAINetwork/go-matrix/core/types"
	"github.com/MatrixAINetwork/go-matrix/log"
	"github.com/MatrixAINetwork/go-matrix/mc"
	"github.com/MatrixAINetwork/go-matrix/p2p"
	"github.com/MatrixAINetwork/go-matrix/params"
	"github.com/MatrixAINetwork/go-matrix/params/manversion"
	"github.com/MatrixAINetwork/go-matrix/rlp"
	"gopkg.in/fatih/set.v0"
	"math/big"
	"sync"
	"time"
)

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)

	// 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 = 128

	// 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

	handshakeTimeout = 5 * time.Second
)

// PeerInfo represents a short summary of the Matrix sub-protocol metadata known
// about a connected peer.
type PeerInfo struct {
	Version       int      `json:"version"`       // Matrix protocol version negotiated
	Difficulty    *big.Int `json:"difficulty"`    // Total difficulty of the peer's blockchain
	Head          string   `json:"head"`          // SHA3 hash of the peer's best owned block
	SuperBlockNum uint64   `json:"superBlockNum"` // SuperBlockHash
	SuperBlockSeq uint64   `json:"superBlockSeq"` // SuperBlockHash
	BlockTime     uint64   `json:"blockTime"`     // blockTime
	BlockHeight   uint64   `json:"blockHeight"`   // blockHeight
}

// propEvent is a block propagation, waiting for its turn in the broadcast queue.
type propEvent struct {
	block *types.Block
	td    *big.Int
	sbh   uint64 // SuperBlock  hash
	sbs   uint64 //SuperBlock  seq
}

type peer struct {
	id string

	*p2p.Peer
	//	rw p2p.MsgReadWriter
	rw p2p.MsgReadWriter

	version  int         // Protocol version negotiated
	forkDrop *time.Timer // Timed connection dropper if forks aren't validated in time

	head common.Hash
	bn   uint64
	sbn  uint64
	td   *big.Int
	bt   uint64
	sbs  uint64
	lock sync.RWMutex

	knownTxs    *set.Set                     // Set of transaction hashes known to be known by this peer
	knownBlocks *set.Set                     // Set of block hashes known to be known by this peer
	queuedTxs   chan []types.SelfTransaction // Queue of transactions to broadcast to the peer
	queuedProps chan *propEvent              // Queue of blocks to broadcast to the peer
	queuedAnns  chan *types.Block            // Queue of blocks to announce to the peer
	term        chan struct{}                // Termination channel to stop the broadcaster
	Msgcenter   *mc.Center
}

func newPeer(version int, p *p2p.Peer, rw p2p.MsgReadWriter) *peer {
	return &peer{
		Peer: p,
		//		rw:          rw,
		rw:          rw,
		version:     version,
		id:          fmt.Sprintf("%x", p.ID().Bytes()[:8]),
		knownTxs:    set.New(),
		knownBlocks: set.New(),
		queuedTxs:   make(chan []types.SelfTransaction, maxQueuedTxs),
		queuedProps: make(chan *propEvent, maxQueuedProps),
		queuedAnns:  make(chan *types.Block, maxQueuedAnns),
		term:        make(chan struct{}),
	}
}

// broadcast is a write loop that multiplexes block propagations, announcements
// and 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() {
	for {
		select {
		case txs := <-p.queuedTxs:
			log.Info("man/peer", "broadcast,addr", p2p.ServerP2p.ConvertIdToAddress(p.ID()).String(), "node id", p.ID().String()) //YY
			if err := p.SendTransactions(txs); err != nil {
				return
			}
			p.Log().Trace("Broadcast transactions", "count", len(txs))

		case prop := <-p.queuedProps:
			if err := p.SendNewBlock(prop.block, prop.td, prop.sbh, prop.sbs); err != nil {
				return
			}
			p.Log().Trace("Propagated block", "number", prop.block.Number(), "hash", prop.block.Hash(), "td", prop.td)

		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 <-p.term:
			return
		}
	}
}

// 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, td, sbs, sbHash, bt, bn := p.Head()

	return &PeerInfo{
		Version:       p.version,
		Difficulty:    td,
		Head:          hash.Hex(),
		SuperBlockNum: sbHash,
		SuperBlockSeq: sbs,
		BlockTime:     bt,
		BlockHeight:   bn,
	}
}

// Head retrieves a copy of the current head hash and total difficulty of the
// peer.
func (p *peer) Head() (hash common.Hash, td *big.Int, sbs uint64, sbHash uint64, uint64, bn uint64) {
	p.lock.RLock()
	defer p.lock.RUnlock()

	copy(hash[:], p.head[:])
	return hash, new(big.Int).Set(p.td), p.sbs, p.sbn, p.bt, p.bn
}
func (p *peer) SetHeadPart(hash common.Hash, bn uint64) {
	p.lock.Lock()
	defer p.lock.Unlock()

	copy(p.head[:], hash[:])
	//p.td.Set(td)
	p.bn = bn
}

// SetHead updates the head hash and total difficulty of the peer.
func (p *peer) SetHead(hash common.Hash, td *big.Int, sbs uint64, sbn uint64, bt uint64, bn uint64) {
	p.lock.Lock()
	defer p.lock.Unlock()

	copy(p.head[:], hash[:])
	p.td.Set(td)
	p.sbs = sbs
	p.sbn = sbn
	p.bn = bn
	p.bt = bt
}

// 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.Size() >= 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.Size() >= maxKnownTxs {
		p.knownTxs.Pop()
	}
	p.knownTxs.Add(hash)
}

// SendTransactions sends transactions to the peer and includes the hashes
// in its transaction hash set for future reference.
func (p *peer) SendTransactions(txser []types.SelfTransaction) error {
	tmptxs := make([]types.SelfTransaction, 0)
	for _, txer := range txser {
		p.knownTxs.Add(txer.Hash())
		switch txer.TxType() {
		case types.NormalTxIndex:
			tmptx, ok := txer.(*types.Transaction)
			if !ok {
				break
			}
			tx := *tmptx
			if nc := tx.Nonce(); nc >= params.NonceAddOne {
				nc = nc & params.NonceSubOne
				tx.SetNonce(nc)
			}
			tmptxs = append(tmptxs, &tx)
		default:
			log.Trace("man/peer.go", "SendTransactions()", "tx type unknown")
			break
		}
		log.Info("man/peer.go", "tcp SendTransactions,txHash", txer.Hash().String()) //YY
	}
	if len(tmptxs) <= 0 {
		log.Trace("man/peer.go", "SendTransactions()", "tmptxs length is 0")
	}
	return p2p.Send(p.rw, TxMsg, tmptxs)
}

// SendUdpTransactions
func SendUdpTransactions(txser []types.SelfTransaction) error {
	udptmptxs := make([]*types.Transaction_Mx, 0)
	for _, txer := range txser {
		switch txer.TxType() {
		case types.NormalTxIndex:
			tmptx, ok := txer.(*types.Transaction)
			if !ok {
				break
			}
			tx := *tmptx
			if nc := tx.Nonce(); nc >= params.NonceAddOne {
				nc = nc & params.NonceSubOne
				tx.SetNonce(nc)
			}
			// udp send
			udptx := types.ConvTxtoMxtx(&tx)
			udptmptxs = append(udptmptxs, udptx)
		default:
			log.Trace("man/peer.go", "SendUdpTransactions()", "tx type unknown")
			break
		}
		log.Info("man/peer.go", "udp SendUdpTransactions,txHash", txer.Hash().String()) //YY
	}
	p2p.UdpSend(udptmptxs)
	return nil
}

// 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.SelfTransaction) {
	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 p2p.Send(p.rw, NewBlockHashesMsg, request)
}

// 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, td *big.Int, sbh uint64, sbs uint64) error {
	p.knownBlocks.Add(block.Hash())
	return p2p.Send(p.rw, NewBlockMsg, []interface{}{block, td, sbh, sbs})
}

// 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, td *big.Int, sbh uint64, sbs uint64) {
	select {
	case p.queuedProps <- &propEvent{block: block, td: td, sbh: sbh, sbs: sbs}:
		p.knownBlocks.Add(block.Hash())
	default:
		p.Log().Debug("Dropping block propagation", "number", block.NumberU64(), "hash", block.Hash())
	}
}

// SendBlockHeaders sends a batch of block headers to the remote peer.
func (p *peer) SendBlockHeaders(headers []*types.Header) error {
	p.Log().Debug("download SendBlockHeaders", "len", len(headers))
	if len(headers) > 1 {
		for i, item := range headers {
			log.Info("test log", "index", i, "number", item.Number, "version", string(item.Version))
		}
	}

	return p2p.Send(p.rw, BlockHeadersMsg, headers)
}

// SendBlockBodies sends a batch of block contents to the remote peer.
func (p *peer) SendBlockBodies(bodies []*blockBody) error {
	return p2p.Send(p.rw, BlockBodiesMsg, blockBodiesData(bodies))
}

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

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

// 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 p2p.Send(p.rw, ReceiptsMsg, receipts)
}

// SendPongToBroad sends a pong msg to broadcast node to represent alive.
func (p *peer) SendPongToBroad(data []uint8) error {
	return p2p.Send(p.rw, common.BroadcastRespMsg, data)
}

// 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, blknum uint64) error {
	p.Log().Debug("Fetching single header", "blknum", blknum, "hash", hash)
	return p2p.Send(p.rw, GetBlockHeadersMsg, &getBlockHeadersData{Origin: hashOrNumber{Hash: hash}, Amount: uint64(1), Skip: uint64(0), Reverse: false})
}

// 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 bool) error {
	p.Log().Debug("peer Fetching batch of headers by hash[request header]", "count", amount, "fromhash", origin, "skip", skip, "reverse", reverse)
	return p2p.Send(p.rw, GetBlockHeadersMsg, &getBlockHeadersData{Origin: hashOrNumber{Hash: origin}, Amount: uint64(amount), Skip: uint64(skip), Reverse: reverse})
}

// 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 bool) error {
	p.Log().Debug("peer Fetching batch of headers RequestHeadersByNumber [request header]", "count", amount, "fromnum", origin, "skip", skip, "reverse", reverse)
	return p2p.Send(p.rw, GetBlockHeadersMsg, &getBlockHeadersData{Origin: hashOrNumber{Number: origin}, Amount: uint64(amount), Skip: uint64(skip), Reverse: reverse})
}

// RequestBodies fetches a batch of blocks' bodies corresponding to the hashes
// specified.
func (p *peer) RequestBodies(hashes []common.Hash) error {
	p.Log().Debug("peer Fetching batch of block bodies[request body]", "len count", len(hashes), "hashes[0]", hashes[0])
	return p2p.Send(p.rw, GetBlockBodiesMsg, 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("peer Fetching batch of state data[request node]", "len 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("peer Fetching batch of receipts[request receipts]", "len 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, td *big.Int, head common.Hash, sbs uint64, genesis common.Hash, sbh uint64) 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,
			SBS:             sbs,
			SBH:             sbh,
			TD:              td,
			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.td, p.head, p.sbs, p.sbn, p.bt, p.bn = status.TD, status.CurrentBlock, status.SBS, status.SBH, 0, 0
	return nil
}

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

	go func() {
		errc <- p2p.Send(p.rw, StatusMsg, &statusNewData{
			ProtocolVersion: uint32(p.version),
			NetworkId:       network,
			SBS:             sbs,
			SBH:             sbh,
			BN:              bn,
			BlockTime:       blockTime,
			CurrentBlock:    head,
			GenesisBlock:    genesis,
		})
	}()
	go func() {
		errc <- p.readNewStatus(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.bt, p.head, p.sbs, p.sbn, p.bn, p.td = status.BlockTime, status.CurrentBlock, status.SBS, status.SBH, status.BN, new(big.Int).SetUint64(0)
	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
}

func (p *peer) readNewStatus(network uint64, status *statusNewData, 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("man/%2d", p.version),
	)
}

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

// newPeerSet creates a new peer set to track the active participants.
func newPeerSet() *peerSet {
	return &peerSet{
		peers: make(map[string]*peer),
	}
}

// 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)
}

// 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.Has(hash) {
			list = append(list, p)
		}
	}
	return list
}

// PeersWithoutTx retrieves a list of peers that do not have a given transaction
// in their set of known hashes.
func (ps *peerSet) PeersWithoutTx(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.knownTxs.Has(hash) {
			list = append(list, p)
		}
	}
	return list
}

func (ps *peerSet) bestPeerA() *peer {

	var (
		bestPeer *peer
		bestTd   *big.Int
		bestBs   uint64
	)
	for _, p := range ps.peers {
		_, td, sb, _, _, _ := p.Head()
		if sb < bestBs {
			continue
		}
		//todo:bestTd
		if bestPeer == nil || sb > bestBs || td.Cmp(bestTd) > 0 {
			bestPeer, bestBs, bestTd = p, sb, td
		}
	}
	return bestPeer
}

func (ps *peerSet) bestPeerB() *peer {

	var (
		bestPeer *peer
		bestTime uint64
		bestBs   uint64
		bestBn   uint64
	)
	for _, p := range ps.peers {
		_, _, sb, _, bt, bn := p.Head()

		//todo:bestTd
		if bestPeer == nil || common.IsGreaterLink(common.LinkInfo{Sbs: sb, Bn: bn, Bt: bt}, common.LinkInfo{Sbs: bestBs, Bn: bestBn, Bt: bestTime}) {
			bestPeer, bestBs, bestTime, bestBn = p, sb, bt, bn
		}

	}
	return bestPeer
}

// BestPeer retrieves the known peer with the currently highest total difficulty.
func (ps *peerSet) BestPeer() *peer {
	ps.lock.RLock()
	defer ps.lock.RUnlock()
	if manversion.CanSwitchGammaCanonicalChain(time.Now().Unix()) {
		return ps.bestPeerB()
	} else {
		return ps.bestPeerA()
	}
}

// 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) PeersAll() []*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
}