path: root/eth/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 eth

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

    "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"
    "github.com/ethereum/go-ethereum/rlp"
    "gopkg.in/fatih/set.v0"
)

var (
    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)
    handshakeTimeout = 5 * time.Second
)

// 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
}

type peer struct {
    id string

    *p2p.Peer
    rw p2p.MsgReadWriter

    version int // Protocol version negotiated
    head    common.Hash
    td      *big.Int
    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
}

func newPeer(version int, p *p2p.Peer, rw p2p.MsgReadWriter) *peer {
    id := p.ID()

    return &peer{
        Peer:        p,
        rw:          rw,
        version:     version,
        id:          fmt.Sprintf("%x", id[:8]),
        knownTxs:    set.New(),
        knownBlocks: set.New(),
    }
}

// Info gathers and returns a collection of metadata known about a peer.
func (p *peer) Info() *PeerInfo {
    return &PeerInfo{
        Version:    p.version,
        Difficulty: p.Td(),
        Head:       fmt.Sprintf("%x", p.Head()),
    }
}

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

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

// SetHead updates the head (most recent) hash of the peer.
func (p *peer) SetHead(hash common.Hash) {
    p.lock.Lock()
    defer p.lock.Unlock()

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

// Td retrieves the current total difficulty of a peer.
func (p *peer) Td() *big.Int {
    p.lock.RLock()
    defer p.lock.RUnlock()

    return new(big.Int).Set(p.td)
}

// SetTd updates the current total difficulty of a peer.
func (p *peer) SetTd(td *big.Int) {
    p.lock.Lock()
    defer p.lock.Unlock()

    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.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(txs types.Transactions) error {
    for _, tx := range txs {
        p.knownTxs.Add(tx.Hash())
    }
    return p2p.Send(p.rw, TxMsg, txs)
}

// SendBlockHashes sends a batch of known hashes to the remote peer.
func (p *peer) SendBlockHashes(hashes []common.Hash) error {
    return p2p.Send(p.rw, BlockHashesMsg, hashes)
}

// SendBlocks sends a batch of blocks to the remote peer.
func (p *peer) SendBlocks(blocks []*types.Block) error {
    return p2p.Send(p.rw, BlocksMsg, blocks)
}

// SendNewBlockHashes61 announces the availability of a number of blocks through
// a hash notification.
func (p *peer) SendNewBlockHashes61(hashes []common.Hash) error {
    for _, hash := range hashes {
        p.knownBlocks.Add(hash)
    }
    return p2p.Send(p.rw, NewBlockHashesMsg, hashes)
}

// 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)
}

// 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})
}

// 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)
}

// RequestHashes fetches a batch of hashes from a peer, starting at from, going
// towards the genesis block.
func (p *peer) RequestHashes(from common.Hash) error {
    glog.V(logger.Debug).Infof("%v fetching hashes (%d) from %x...", p, downloader.MaxHashFetch, from[:4])
    return p2p.Send(p.rw, GetBlockHashesMsg, getBlockHashesData{from, uint64(downloader.MaxHashFetch)})
}

// RequestHashesFromNumber fetches a batch of hashes from a peer, starting at
// the requested block number, going upwards towards the genesis block.
func (p *peer) RequestHashesFromNumber(from uint64, count int) error {
    glog.V(logger.Debug).Infof("%v fetching hashes (%d) from #%d...", p, count, from)
    return p2p.Send(p.rw, GetBlockHashesFromNumberMsg, getBlockHashesFromNumberData{from, uint64(count)})
}

// RequestBlocks fetches a batch of blocks corresponding to the specified hashes.
func (p *peer) RequestBlocks(hashes []common.Hash) error {
    glog.V(logger.Debug).Infof("%v fetching %v blocks", p, len(hashes))
    return p2p.Send(p.rw, GetBlocksMsg, hashes)
}

// RequestHeaders 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 {
    glog.V(logger.Debug).Infof("%v fetching a single header: %x", p, 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 {
    glog.V(logger.Debug).Infof("%v fetching %d headers from %x, skipping %d (reverse = %v)", p, amount, origin[:4], skip, 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 {
    glog.V(logger.Debug).Infof("%v fetching %d headers from #%d, skipping %d (reverse = %v)", p, amount, origin, skip, 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 {
    glog.V(logger.Debug).Infof("%v fetching %d block bodies", p, 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 {
    glog.V(logger.Debug).Infof("%v fetching %v state data", p, 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 {
    glog.V(logger.Debug).Infof("%v fetching %v receipts", p, 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 int, 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:       uint32(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 int, 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, genesis)
    }
    if int(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("eth/%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
}

// 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)
}

// 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
}

// 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.Td(); bestPeer == nil || td.Cmp(bestTd) > 0 {
            bestPeer, bestTd = p, td
        }
    }
    return bestPeer
}