path: root/eth/peer.go

package eth

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

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/core/types"
    "github.com/ethereum/go-ethereum/eth/downloader"
    "github.com/ethereum/go-ethereum/logger"
    "github.com/ethereum/go-ethereum/logger/glog"
    "github.com/ethereum/go-ethereum/p2p"
    "gopkg.in/fatih/set.v0"
)

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

type statusMsgData struct {
    ProtocolVersion uint32
    NetworkId       uint32
    TD              *big.Int
    CurrentBlock    common.Hash
    GenesisBlock    common.Hash
}

type getBlockHashesMsgData struct {
    Hash   common.Hash
    Amount uint64
}

type peer struct {
    *p2p.Peer

    rw p2p.MsgReadWriter

    protv, netid int

    recentHash common.Hash
    id         string
    td         *big.Int

    genesis, ourHash common.Hash
    ourTd            *big.Int

    txHashes    *set.Set
    blockHashes *set.Set
}

func newPeer(protv, netid int, genesis, recentHash common.Hash, td *big.Int, p *p2p.Peer, rw p2p.MsgReadWriter) *peer {
    id := p.ID()

    return &peer{
        Peer:        p,
        rw:          rw,
        genesis:     genesis,
        ourHash:     recentHash,
        ourTd:       td,
        protv:       protv,
        netid:       netid,
        id:          fmt.Sprintf("%x", id[:8]),
        txHashes:    set.New(),
        blockHashes: set.New(),
    }
}

// sendTransactions sends transactions to the peer and includes the hashes
// in it's tx hash set for future reference. The tx hash will allow the
// manager to check whether the peer has already received this particular
// transaction
func (p *peer) sendTransactions(txs types.Transactions) error {
    for _, tx := range txs {
        p.txHashes.Add(tx.Hash())
    }

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

func (p *peer) sendBlockHashes(hashes []common.Hash) error {
    return p2p.Send(p.rw, BlockHashesMsg, hashes)
}

func (p *peer) sendBlocks(blocks []*types.Block) error {
    return p2p.Send(p.rw, BlocksMsg, blocks)
}

func (p *peer) sendNewBlock(block *types.Block) error {
    p.blockHashes.Add(block.Hash())

    return p2p.Send(p.rw, NewBlockMsg, []interface{}{block, block.Td})
}

func (p *peer) sendTransaction(tx *types.Transaction) error {
    p.txHashes.Add(tx.Hash())

    return p2p.Send(p.rw, TxMsg, []*types.Transaction{tx})
}

func (p *peer) requestHashes(from common.Hash) error {
    glog.V(logger.Debug).Infof("[%s] fetching hashes (%d) %x...\n", p.id, downloader.MaxHashFetch, from[:4])
    return p2p.Send(p.rw, GetBlockHashesMsg, getBlockHashesMsgData{from, downloader.MaxHashFetch})
}

func (p *peer) requestBlocks(hashes []common.Hash) error {
    glog.V(logger.Debug).Infof("[%s] fetching %v blocks\n", p.id, len(hashes))
    return p2p.Send(p.rw, GetBlocksMsg, hashes)
}

func (p *peer) handleStatus() error {
    errc := make(chan error, 1)
    go func() {
        errc <- p2p.Send(p.rw, StatusMsg, &statusMsgData{
            ProtocolVersion: uint32(p.protv),
            NetworkId:       uint32(p.netid),
            TD:              p.ourTd,
            CurrentBlock:    p.ourHash,
            GenesisBlock:    p.genesis,
        })
    }()

    // read and handle remote status
    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)
    }

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

    if status.GenesisBlock != p.genesis {
        return errResp(ErrGenesisBlockMismatch, "%x (!= %x)", status.GenesisBlock, p.genesis)
    }

    if int(status.NetworkId) != p.netid {
        return errResp(ErrNetworkIdMismatch, "%d (!= %d)", status.NetworkId, p.netid)
    }

    if int(status.ProtocolVersion) != p.protv {
        return errResp(ErrProtocolVersionMismatch, "%d (!= %d)", status.ProtocolVersion, p.protv)
    }
    // Set the total difficulty of the peer
    p.td = status.TD
    // set the best hash of the peer
    p.recentHash = status.CurrentBlock

    return <-errc
}

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

// 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.
func (ps *peerSet) Register(p *peer) error {
    ps.lock.Lock()
    defer ps.lock.Unlock()

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

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

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

// TxLackingPeers retrieves a list of peers that do not have a given transaction
// in their set of known hashes.
func (ps *peerSet) TxLackingPeers(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.txHashes.Has(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 best *peer
    for _, p := range ps.peers {
        if best == nil || p.td.Cmp(best.td) > 0 {
            best = p
        }
    }
    return best
}