path: root/eth/handler.go

package eth

// XXX Fair warning, most of the code is re-used from the old protocol. Please be aware that most of this will actually change
// The idea is that most of the calls within the protocol will become synchronous.
// Block downloading and block processing will be complete seperate processes
/*
# Possible scenarios

// Synching scenario
// Use the best peer to synchronise
blocks, err := pm.downloader.Synchronise()
if err != nil {
    // handle
    break
}
pm.chainman.InsertChain(blocks)

// Receiving block with known parent
if parent_exist {
    if err := pm.chainman.InsertChain(block); err != nil {
        // handle
        break
    }
    pm.BroadcastBlock(block)
}

// Receiving block with unknown parent
blocks, err := pm.downloader.SynchroniseWithPeer(peer)
if err != nil {
    // handle
    break
}
pm.chainman.InsertChain(blocks)

*/

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

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/core"
    "github.com/ethereum/go-ethereum/core/types"
    "github.com/ethereum/go-ethereum/eth/downloader"
    "github.com/ethereum/go-ethereum/event"
    "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"
)

const (
    peerCountTimeout    = 12 * time.Second // Amount of time it takes for the peer handler to ignore minDesiredPeerCount
    minDesiredPeerCount = 5                // Amount of peers desired to start syncing
)

func errResp(code errCode, format string, v ...interface{}) error {
    return fmt.Errorf("%v - %v", code, fmt.Sprintf(format, v...))
}

type hashFetcherFn func(common.Hash) error
type blockFetcherFn func([]common.Hash) error

// extProt is an interface which is passed around so we can expose GetHashes and GetBlock without exposing it to the rest of the protocol
// extProt is passed around to peers which require to GetHashes and GetBlocks
type extProt struct {
    getHashes hashFetcherFn
    getBlocks blockFetcherFn
}

func (ep extProt) GetHashes(hash common.Hash) error    { return ep.getHashes(hash) }
func (ep extProt) GetBlock(hashes []common.Hash) error { return ep.getBlocks(hashes) }

type ProtocolManager struct {
    protVer, netId int
    txpool         txPool
    chainman       *core.ChainManager
    downloader     *downloader.Downloader

    pmu   sync.Mutex
    peers map[string]*peer

    SubProtocol p2p.Protocol

    eventMux      *event.TypeMux
    txSub         event.Subscription
    minedBlockSub event.Subscription

    newPeerCh chan *peer
    quitSync  chan struct{}
}

// NewProtocolManager returns a new ethereum sub protocol manager. The Ethereum sub protocol manages peers capable
// with the ethereum network.
func NewProtocolManager(protocolVersion, networkId int, mux *event.TypeMux, txpool txPool, chainman *core.ChainManager, downloader *downloader.Downloader) *ProtocolManager {
    manager := &ProtocolManager{
        eventMux:   mux,
        txpool:     txpool,
        chainman:   chainman,
        downloader: downloader,
        peers:      make(map[string]*peer),
        newPeerCh:  make(chan *peer, 1),
        quitSync:   make(chan struct{}),
    }

    manager.SubProtocol = p2p.Protocol{
        Name:    "eth",
        Version: uint(protocolVersion),
        Length:  ProtocolLength,
        Run: func(p *p2p.Peer, rw p2p.MsgReadWriter) error {
            peer := manager.newPeer(protocolVersion, networkId, p, rw)

            manager.newPeerCh <- peer

            return manager.handle(peer)
        },
    }

    return manager
}

func (pm *ProtocolManager) removePeer(peer *peer) {
    pm.pmu.Lock()
    defer pm.pmu.Unlock()
    delete(pm.peers, peer.id)
}

func (pm *ProtocolManager) syncHandler() {
    // itimer is used to determine when to start ignoring `minDesiredPeerCount`
    itimer := time.NewTimer(peerCountTimeout)
out:
    for {
        select {
        case <-pm.newPeerCh:
            // Meet the `minDesiredPeerCount` before we select our best peer
            if len(pm.peers) < minDesiredPeerCount {
                break
            }

            // Find the best peer
            peer := getBestPeer(pm.peers)
            if peer == nil {
                glog.V(logger.Debug).Infoln("Sync attempt cancelled. No peers available")
            }

            itimer.Stop()
            go pm.synchronise(peer)
        case <-itimer.C:
            // The timer will make sure that the downloader keeps an active state
            // in which it attempts to always check the network for highest td peers
            // Either select the peer or restart the timer if no peers could
            // be selected.
            if peer := getBestPeer(pm.peers); peer != nil {
                go pm.synchronise(peer)
            } else {
                itimer.Reset(5 * time.Second)
            }
        case <-pm.quitSync:
            break out
        }
    }
}

func (pm *ProtocolManager) synchronise(peer *peer) {
    // Make sure the peer's TD is higher than our own. If not drop.
    if peer.td.Cmp(pm.chainman.Td()) <= 0 {
        return
    }
    // Check downloader if it's busy so it doesn't show the sync message
    // for every attempty
    if pm.downloader.IsBusy() {
        return
    }

    glog.V(logger.Info).Infof("Synchronisation attempt using %s TD=%v\n", peer.id, peer.td)
    // Get the hashes from the peer (synchronously)
    err := pm.downloader.Synchronise(peer.id, peer.recentHash)
    if err != nil && err == downloader.ErrBadPeer {
        glog.V(logger.Debug).Infoln("removed peer from peer set due to bad action")
        pm.removePeer(peer)
    } else if err != nil {
        // handle error
        glog.V(logger.Debug).Infoln("error downloading:", err)
    }
}

func (pm *ProtocolManager) Start() {
    // broadcast transactions
    pm.txSub = pm.eventMux.Subscribe(core.TxPreEvent{})
    go pm.txBroadcastLoop()

    // broadcast mined blocks
    pm.minedBlockSub = pm.eventMux.Subscribe(core.NewMinedBlockEvent{})
    go pm.minedBroadcastLoop()

    // sync handler
    go pm.syncHandler()
}

func (pm *ProtocolManager) Stop() {
    pm.txSub.Unsubscribe()         // quits txBroadcastLoop
    pm.minedBlockSub.Unsubscribe() // quits blockBroadcastLoop
    close(pm.quitSync)             // quits the sync handler
}

func (pm *ProtocolManager) newPeer(pv, nv int, p *p2p.Peer, rw p2p.MsgReadWriter) *peer {

    td, current, genesis := pm.chainman.Status()

    return newPeer(pv, nv, genesis, current, td, p, rw)
}

func (pm *ProtocolManager) handle(p *peer) error {
    if err := p.handleStatus(); err != nil {
        return err
    }
    pm.pmu.Lock()
    pm.peers[p.id] = p
    pm.pmu.Unlock()

    pm.downloader.RegisterPeer(p.id, p.recentHash, p.requestHashes, p.requestBlocks)
    defer func() {
        pm.downloader.UnregisterPeer(p.id)
        pm.removePeer(p)
    }()

    // propagate existing transactions. new transactions appearing
    // after this will be sent via broadcasts.
    if err := p.sendTransactions(pm.txpool.GetTransactions()); err != nil {
        return err
    }

    // main loop. handle incoming messages.
    for {
        if err := pm.handleMsg(p); err != nil {
            return err
        }
    }

    return nil
}

func (self *ProtocolManager) handleMsg(p *peer) error {
    msg, err := p.rw.ReadMsg()
    if err != nil {
        return err
    }
    if msg.Size > ProtocolMaxMsgSize {
        return errResp(ErrMsgTooLarge, "%v > %v", msg.Size, ProtocolMaxMsgSize)
    }
    // make sure that the payload has been fully consumed
    defer msg.Discard()

    switch msg.Code {
    case GetTxMsg: // ignore
    case StatusMsg:
        return errResp(ErrExtraStatusMsg, "uncontrolled status message")

    case TxMsg:
        // TODO: rework using lazy RLP stream
        var txs []*types.Transaction
        if err := msg.Decode(&txs); err != nil {
            return errResp(ErrDecode, "msg %v: %v", msg, err)
        }
        for i, tx := range txs {
            if tx == nil {
                return errResp(ErrDecode, "transaction %d is nil", i)
            }
            jsonlogger.LogJson(&logger.EthTxReceived{
                TxHash:   tx.Hash().Hex(),
                RemoteId: p.ID().String(),
            })
        }
        self.txpool.AddTransactions(txs)

    case GetBlockHashesMsg:
        var request getBlockHashesMsgData
        if err := msg.Decode(&request); err != nil {
            return errResp(ErrDecode, "->msg %v: %v", msg, err)
        }

        if request.Amount > maxHashes {
            request.Amount = maxHashes
        }

        hashes := self.chainman.GetBlockHashesFromHash(request.Hash, request.Amount)

        if glog.V(logger.Debug) {
            if len(hashes) == 0 {
                glog.Infof("invalid block hash %x", request.Hash.Bytes()[:4])
            }
        }

        // returns either requested hashes or nothing (i.e. not found)
        return p.sendBlockHashes(hashes)
    case BlockHashesMsg:
        msgStream := rlp.NewStream(msg.Payload, uint64(msg.Size))

        var hashes []common.Hash
        if err := msgStream.Decode(&hashes); err != nil {
            break
        }
        err := self.downloader.AddHashes(p.id, hashes)
        if err != nil {
            glog.V(logger.Debug).Infoln(err)
        }

    case GetBlocksMsg:
        var blocks []*types.Block

        msgStream := rlp.NewStream(msg.Payload, uint64(msg.Size))
        if _, err := msgStream.List(); err != nil {
            return err
        }
        var i int
        for {
            i++
            var hash common.Hash
            err := msgStream.Decode(&hash)
            if err == rlp.EOL {
                break
            } else if err != nil {
                return errResp(ErrDecode, "msg %v: %v", msg, err)
            }

            block := self.chainman.GetBlock(hash)
            if block != nil {
                blocks = append(blocks, block)
            }
            if i == maxBlocks {
                break
            }
        }
        return p.sendBlocks(blocks)
    case BlocksMsg:
        var blocks []*types.Block

        msgStream := rlp.NewStream(msg.Payload, uint64(msg.Size))
        if err := msgStream.Decode(&blocks); err != nil {
            glog.V(logger.Detail).Infoln("Decode error", err)
            blocks = nil
        }
        self.downloader.DeliverChunk(p.id, blocks)

    case NewBlockMsg:
        var request newBlockMsgData
        if err := msg.Decode(&request); err != nil {
            return errResp(ErrDecode, "%v: %v", msg, err)
        }
        if err := request.Block.ValidateFields(); err != nil {
            return errResp(ErrDecode, "block validation %v: %v", msg, err)
        }
        request.Block.ReceivedAt = msg.ReceivedAt

        hash := request.Block.Hash()
        // Add the block hash as a known hash to the peer. This will later be used to determine
        // who should receive this.
        p.blockHashes.Add(hash)

        _, chainHead, _ := self.chainman.Status()

        jsonlogger.LogJson(&logger.EthChainReceivedNewBlock{
            BlockHash:     hash.Hex(),
            BlockNumber:   request.Block.Number(), // this surely must be zero
            ChainHeadHash: chainHead.Hex(),
            BlockPrevHash: request.Block.ParentHash().Hex(),
            RemoteId:      p.ID().String(),
        })

        // Make sure the block isn't already known. If this is the case simply drop
        // the message and move on. If the TD is < currentTd; drop it as well. If this
        // chain at some point becomes canonical, the downloader will fetch it.
        if self.chainman.HasBlock(hash) {
            break
        }
        if self.chainman.Td().Cmp(request.TD) > 0 && new(big.Int).Add(request.Block.Number(), big.NewInt(7)).Cmp(self.chainman.CurrentBlock().Number()) < 0 {
            glog.V(logger.Debug).Infof("[%s] dropped block %v due to low TD %v\n", p.id, request.Block.Number(), request.TD)
            break
        }

        // Attempt to insert the newly received by checking if the parent exists.
        // if the parent exists we process the block and propagate to our peers
        // if the parent does not exists we delegate to the downloader.
        if self.chainman.HasBlock(request.Block.ParentHash()) {
            if _, err := self.chainman.InsertChain(types.Blocks{request.Block}); err != nil {
                glog.V(logger.Error).Infoln("removed peer (", p.id, ") due to block error")

                self.removePeer(p)

                return nil
            }
            self.BroadcastBlock(hash, request.Block)
        } else {
            // adding blocks is synchronous
            go func() {
                err := self.downloader.AddBlock(p.id, request.Block, request.TD)
                if err != nil && err == downloader.ErrBadPeer {
                    glog.V(logger.Error).Infoln("removed peer (", p.id, ") with err:", err)

                    self.removePeer(p)
                    return
                } else if err != nil {
                    glog.V(logger.Detail).Infoln("downloader err:", err)
                    return
                }
                self.BroadcastBlock(hash, request.Block)
            }()
        }
    default:
        return errResp(ErrInvalidMsgCode, "%v", msg.Code)
    }
    return nil
}

// BroadcastBlock will propagate the block to its connected peers. It will sort
// out which peers do not contain the block in their block set and will do a
// sqrt(peers) to determine the amount of peers we broadcast to.
func (pm *ProtocolManager) BroadcastBlock(hash common.Hash, block *types.Block) {
    pm.pmu.Lock()
    defer pm.pmu.Unlock()

    // Find peers who don't know anything about the given hash. Peers that
    // don't know about the hash will be a candidate for the broadcast loop
    var peers []*peer
    for _, peer := range pm.peers {
        if !peer.blockHashes.Has(hash) {
            peers = append(peers, peer)
        }
    }
    // Broadcast block to peer set
    peers = peers[:int(math.Sqrt(float64(len(peers))))]
    for _, peer := range peers {
        peer.sendNewBlock(block)
    }
    glog.V(logger.Detail).Infoln("broadcast block to", len(peers), "peers. Total propagation time:", time.Since(block.ReceivedAt))
}

// BroadcastTx will propagate the block to its connected peers. It will sort
// out which peers do not contain the block in their block set and will do a
// sqrt(peers) to determine the amount of peers we broadcast to.
func (pm *ProtocolManager) BroadcastTx(hash common.Hash, tx *types.Transaction) {
    pm.pmu.Lock()
    defer pm.pmu.Unlock()

    // Find peers who don't know anything about the given hash. Peers that
    // don't know about the hash will be a candidate for the broadcast loop
    var peers []*peer
    for _, peer := range pm.peers {
        if !peer.txHashes.Has(hash) {
            peers = append(peers, peer)
        }
    }
    // Broadcast block to peer set
    peers = peers[:int(math.Sqrt(float64(len(peers))))]
    for _, peer := range peers {
        peer.sendTransaction(tx)
    }
    glog.V(logger.Detail).Infoln("broadcast tx to", len(peers), "peers")
}

// Mined broadcast loop
func (self *ProtocolManager) minedBroadcastLoop() {
    // automatically stops if unsubscribe
    for obj := range self.minedBlockSub.Chan() {
        switch ev := obj.(type) {
        case core.NewMinedBlockEvent:
            self.BroadcastBlock(ev.Block.Hash(), ev.Block)
        }
    }
}

func (self *ProtocolManager) txBroadcastLoop() {
    // automatically stops if unsubscribe
    for obj := range self.txSub.Chan() {
        event := obj.(core.TxPreEvent)
        self.BroadcastTx(event.Tx.Hash(), event.Tx)
    }
}