path: root/dex/peer.go

// 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 (
    "errors"
    "fmt"
    "math/big"
    "sync"
    "time"

    mapset "github.com/deckarep/golang-set"
    "github.com/dexon-foundation/dexon/common"
    "github.com/dexon-foundation/dexon/core/types"
    "github.com/dexon-foundation/dexon/p2p"
    "github.com/dexon-foundation/dexon/p2p/discover"
    "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)
    maxKnownMetas  = 32768 // Maximum metas 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

    maxQueuedMetas = 512

    // 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

    groupNodeNum = 3
)

// 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
    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
}

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

type setType uint32

const (
    dkgset = iota
    notaryset
)

type peerLabel struct {
    set     setType
    chainID uint32
    round   uint64
}

type peer struct {
    id string

    *p2p.Peer
    rw p2p.MsgReadWriter

    version int // Protocol version negotiated
    labels  mapset.Set

    head common.Hash
    td   *big.Int
    lock sync.RWMutex

    knownTxs    mapset.Set                // Set of transaction hashes known to be known by this peer
    knownMetas  mapset.Set                // Set of node metas known to be known by this peer
    knownBlocks mapset.Set                // Set of block hashes known to be known by this peer
    queuedTxs   chan []*types.Transaction // Queue of transactions to broadcast to the peer
    queuedMetas chan []*NodeMeta          // Queue of node metas 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
}

func newPeer(version int, p *p2p.Peer, rw p2p.MsgReadWriter) *peer {
    return &peer{
        Peer:        p,
        rw:          rw,
        version:     version,
        labels:      mapset.NewSet(),
        id:          p.ID().String(),
        knownTxs:    mapset.NewSet(),
        knownMetas:  mapset.NewSet(),
        knownBlocks: mapset.NewSet(),
        queuedTxs:   make(chan []*types.Transaction, maxQueuedTxs),
        queuedMetas: make(chan []*NodeMeta, maxQueuedMetas),
        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,
// transaction and notary node metas 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:
            if err := p.SendTransactions(txs); err != nil {
                return
            }
            p.Log().Trace("Broadcast transactions", "count", len(txs))

        case metas := <-p.queuedMetas:
            if err := p.SendNodeMetas(metas); err != nil {
                return
            }
            p.Log().Trace("Broadcast node metas", "count", len(metas))

        case prop := <-p.queuedProps:
            if err := p.SendNewBlock(prop.block, prop.td); 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)
}

func (p *peer) addLabel(label peerLabel) {
    p.labels.Add(label)
}

func (p *peer) removeLabel(label peerLabel) {
    p.labels.Remove(label)
}

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

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

// 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) {
    p.lock.RLock()
    defer p.lock.RUnlock()

    copy(hash[:], p.head[:])
    return hash, new(big.Int).Set(p.td)
}

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

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

// 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) MarkNodeMeta(hash common.Hash) {
    for p.knownMetas.Cardinality() >= maxKnownMetas {
        p.knownMetas.Pop()
    }
    p.knownMetas.Add(hash)
}

// 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 p2p.Send(p.rw, TxMsg, txs)
}

// 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))
    }
}

// SendNodeMetas sends the metas to the peer and includes the hashes
// in its metas hash set for future reference.
func (p *peer) SendNodeMetas(metas []*NodeMeta) error {
    for _, meta := range metas {
        p.knownMetas.Add(meta.Hash())
    }
    return p2p.Send(p.rw, MetaMsg, metas)
}

// AsyncSendNodeMeta queues list of notary node meta propagation to a
// remote peer. If the peer's broadcast queue is full, the event is silently
// dropped.
func (p *peer) AsyncSendNodeMetas(metas []*NodeMeta) {
    select {
    case p.queuedMetas <- metas:
        for _, meta := range metas {
            p.knownMetas.Add(meta.Hash())
        }
    default:
        p.Log().Debug("Dropping node meta propagation", "count", len(metas))
    }
}

// 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) error {
    p.knownBlocks.Add(block.Hash())
    return p2p.Send(p.rw, NewBlockMsg, []interface{}{block, td})
}

// 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) {
    select {
    case p.queuedProps <- &propEvent{block: block, td: td}:
        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 {
    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)
}

// 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})
}

// 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("Fetching batch of headers", "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("Fetching batch of headers", "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("Fetching batch of block bodies", "count", len(hashes))
    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("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, td *big.Int, 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,
            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 = status.TD, 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
    tab    *nodeTable

    srvr          p2pServer
    gov           governance
    peerLabels    map[string]map[peerLabel]struct{}
    notaryHistory map[uint64]struct{}
    dkgHistory    map[uint64]struct{}
}

// newPeerSet creates a new peer set to track the active participants.
func newPeerSet(gov governance, srvr p2pServer, tab *nodeTable) *peerSet {
    return &peerSet{
        peers:         make(map[string]*peer),
        gov:           gov,
        srvr:          srvr,
        tab:           tab,
        peerLabels:    make(map[string]map[peerLabel]struct{}),
        notaryHistory: make(map[uint64]struct{}),
        dkgHistory:    make(map[uint64]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)
}

// 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
}

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

// PeersWithoutNodeMeta retrieves a list of peers that do not have a
// given meta in their set of known hashes.
func (ps *peerSet) PeersWithoutNodeMeta(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.knownMetas.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
        bestTd   *big.Int
    )
    for _, p := range ps.peers {
        if _, td := p.Head(); bestPeer == nil || td.Cmp(bestTd) > 0 {
            bestPeer, bestTd = p, td
        }
    }
    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) BuildNotaryConn(round uint64) {
    ps.lock.Lock()
    defer ps.lock.Unlock()

    if _, ok := ps.notaryHistory[round]; ok {
        return
    }

    ps.notaryHistory[round] = struct{}{}

    selfID := ps.srvr.Self().ID.String()
    for chainID := uint32(0); chainID < ps.gov.GetChainNum(round); chainID++ {
        s := ps.gov.GetNotarySet(chainID, round)

        // not in notary set, add group
        if _, ok := s[selfID]; !ok {
            var nodes []*discover.Node
            for id := range s {
                nodes = append(nodes, ps.newNode(id))
            }
            ps.srvr.AddGroup(notarySetName(chainID, round), nodes, groupNodeNum)
            continue
        }

        label := peerLabel{
            set:     notaryset,
            chainID: chainID,
            round:   round,
        }
        delete(s, selfID)
        for id := range s {
            ps.addDirectPeer(id, label)
        }
    }
}

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

    // forget all the rounds before the given round
    for r := range ps.notaryHistory {
        if r <= round {
            ps.forgetNotaryConn(r)
            delete(ps.notaryHistory, r)
        }
    }
}

func (ps *peerSet) forgetNotaryConn(round uint64) {
    selfID := ps.srvr.Self().ID.String()
    for chainID := uint32(0); chainID < ps.gov.GetChainNum(round); chainID++ {
        s := ps.gov.GetNotarySet(chainID, round)
        if _, ok := s[selfID]; !ok {
            ps.srvr.RemoveGroup(notarySetName(chainID, round))
            continue
        }

        label := peerLabel{
            set:     notaryset,
            chainID: chainID,
            round:   round,
        }
        delete(s, selfID)
        for id := range s {
            ps.removeDirectPeer(id, label)
        }
    }
}

func notarySetName(chainID uint32, round uint64) string {
    return fmt.Sprintf("%d-%d-notaryset", chainID, round)
}

func (ps *peerSet) BuildDKGConn(round uint64) {
    ps.lock.Lock()
    defer ps.lock.Unlock()
    selfID := ps.srvr.Self().ID.String()
    s := ps.gov.GetDKGSet(round)
    if _, ok := s[selfID]; !ok {
        return
    }
    ps.dkgHistory[round] = struct{}{}

    delete(s, selfID)
    for id := range s {
        ps.addDirectPeer(id, peerLabel{
            set:   dkgset,
            round: round,
        })
    }
}

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

    // forget all the rounds before the given round
    for r := range ps.dkgHistory {
        if r <= round {
            ps.forgetDKGConn(r)
            delete(ps.dkgHistory, r)
        }
    }
}

func (ps *peerSet) forgetDKGConn(round uint64) {
    selfID := ps.srvr.Self().ID.String()
    s := ps.gov.GetDKGSet(round)
    if _, ok := s[selfID]; !ok {
        return
    }

    delete(s, selfID)
    label := peerLabel{
        set:   dkgset,
        round: round,
    }
    for id := range s {
        ps.removeDirectPeer(id, label)
    }
}

// make sure the ps.lock is hold
func (ps *peerSet) addDirectPeer(id string, label peerLabel) {
    // if the peer exists add the label
    if p, ok := ps.peers[id]; ok {
        p.addLabel(label)
    }

    if _, ok := ps.peerLabels[id]; !ok {
        ps.peerLabels[id] = make(map[peerLabel]struct{})
    }

    ps.peerLabels[id][label] = struct{}{}
    ps.srvr.AddDirectPeer(ps.newNode(id))
}

// make sure the ps.lock is hold
func (ps *peerSet) removeDirectPeer(id string, label peerLabel) {
    if p, ok := ps.peers[id]; ok {
        p.removeLabel(label)
    }

    delete(ps.peerLabels[id], label)

    if len(ps.peerLabels[id]) == 0 {
        ps.srvr.RemoveDirectPeer(ps.newNode(id))
        delete(ps.peerLabels, id)
    }
}

func (ps *peerSet) newNode(id string) *enode.Node {
    nodeID := enode.HexID(id)
    meta := ps.tab.Get(enode.HexID(id))

    var r enr.Record
    r.Set(enr.ID(nodeID.String()))
    r.Set(enr.IP(meta.IP))
    r.Set(enr.TCP(meta.TCP))
    r.Set(enr.UDP(meta.UDP))

    n, err := enode.New(enode.ValidSchemes, &r)
    if err != nil {
        panic(err)
    }
    return n
}