Ethereumのトランザクションの流れ(2) バックエンド編 1. transaction受信編

[Ethereumのトランザクションの流れ(1) フロント編](https://qiita.com/t10471/items/73545e0f93ea63820953)の続きでノード側の処理を追っていきます。
v1.8.15ベースに解説します。

# transactionが発行されてbroadcastする流れ

## 前提

```go
// Backend gethで使うAPIのインタフェース
type Backend interface {
	// General Ethereum API
	Downloader() *downloader.Downloader
	ProtocolVersion() int
	SuggestPrice(ctx context.Context) (*big.Int, error)
	ChainDb() ethdb.Database
	EventMux() *event.TypeMux
	AccountManager() *accounts.Manager

	// BlockChain API
	SetHead(number uint64)
	HeaderByNumber(ctx context.Context, blockNr rpc.BlockNumber) (*types.Header, error)
	BlockByNumber(ctx context.Context, blockNr rpc.BlockNumber) (*types.Block, error)
	StateAndHeaderByNumber(ctx context.Context, blockNr rpc.BlockNumber) (*state.StateDB, *types.Header, error)
	GetBlock(ctx context.Context, blockHash common.Hash) (*types.Block, error)
	GetReceipts(ctx context.Context, blockHash common.Hash) (types.Receipts, error)
	GetTd(blockHash common.Hash) *big.Int
	GetEVM(ctx context.Context, msg core.Message, state *state.StateDB, header *types.Header, vmCfg vm.Config) (*vm.EVM, func() error, error)
	SubscribeChainEvent(ch chan<- core.ChainEvent) event.Subscription
	SubscribeChainHeadEvent(ch chan<- core.ChainHeadEvent) event.Subscription
	SubscribeChainSideEvent(ch chan<- core.ChainSideEvent) event.Subscription

	// TxPool API
	SendTx(ctx context.Context, signedTx *types.Transaction) error
	GetPoolTransactions() (types.Transactions, error)
	GetPoolTransaction(txHash common.Hash) *types.Transaction
	GetPoolNonce(ctx context.Context, addr common.Address) (uint64, error)
	Stats() (pending int, queued int)
	TxPoolContent() (map[common.Address]types.Transactions, map[common.Address]types.Transactions)
	SubscribeNewTxsEvent(chan<- core.NewTxsEvent) event.Subscription

	ChainConfig() *params.ChainConfig
	CurrentBlock() *types.Block
}

// Miner ブロックの生成を担当
type Miner struct {
	mux *event.TypeMux

	worker *worker

	coinbase common.Address
	mining   int32
	eth      Backend
	engine   consensus.Engine

	canStart    int32 // can start indicates whether we can start the mining operation
	shouldStart int32 // should start indicates whether we should start after sync
}

// トランザクションの受信ブロックの生成などをメインで行う
type worker struct {
	config *params.ChainConfig
	engine consensus.Engine

	mu sync.Mutex

	// update loop
	mux          *event.TypeMux
	txsCh        chan core.NewTxsEvent
	txsSub       event.Subscription
	chainHeadCh  chan core.ChainHeadEvent
	chainHeadSub event.Subscription
	chainSideCh  chan core.ChainSideEvent
	chainSideSub event.Subscription
	wg           sync.WaitGroup

	agents map[Agent]struct{}
	recv   chan *Result

	eth     Backend
	chain   *core.BlockChain
	proc    core.Validator
	chainDb ethdb.Database

	coinbase common.Address
	extra    []byte

	currentMu sync.Mutex
	current   *Work

	snapshotMu    sync.RWMutex
	snapshotBlock *types.Block
	snapshotState *state.StateDB

	uncleMu        sync.Mutex
	possibleUncles map[common.Hash]*types.Block

	unconfirmed *unconfirmedBlocks // set of locally mined blocks pending canonicalness confirmations

	// atomic status counters
	mining int32
	atWork int32
}

type NewTxsEvent struct{ Txs []*types.Transaction }

```

## ブロードキャストする側

http Json RPCサーバがデータを受信する(web3の場合)

`func (s *PublicTransactionPoolAPI) SendTransaction(ctx context.Context, args SendTxArgs) (common.Hash, error)`
か
`func (s *PublicTransactionPoolAPI) SendRawTransaction(ctx context.Context, encodedTx hexutil.Bytes) (common.Hash, error) {`
から受け取ります

トランザクションのハッシュとrecipient(トランザクションのTo)をログに出力します
```
INFO [06-15|21:23:57] Submitted transaction                    fullhash=0xaf8cc41bd9745db4f696f3e51d2013ec164523a7105eb95986b130c908519955 recipient=0x11A725282EE227fF2dDe2fD11055Cbe8F5961E39
```

```go
// 上のログを出力する前に　b.SendTx(ctx, tx)　を実行し、
func submitTransaction(ctx context.Context, b Backend, tx *types.Transaction) (common.Hash, error) {
	if err := b.SendTx(ctx, tx); err != nil {
		return common.Hash{}, err
	}
	...
}

func (b *EthAPIBackend) SendTx(ctx context.Context, signedTx *types.Transaction) error {
	return b.eth.txPool.AddLocal(signedTx)
}

func (pool *TxPool) AddLocal(tx *types.Transaction) error {
	return pool.addTx(tx, !pool.config.NoLocals)
}

func (pool *TxPool) addTx(tx *types.Transaction, local bool) error {
	pool.mu.Lock()
	defer pool.mu.Unlock()

	// Try to inject the transaction and update any state
	replace, err := pool.add(tx, local)
	if err != nil {
		return err
	}
	// If we added a new transaction, run promotion checks and return
	if !replace {
		from, _ := types.Sender(pool.signer, tx) // already validated
		pool.promoteExecutables([]common.Address{from})
	}
	return nil
}


func (pool *TxPool) add(tx *types.Transaction, local bool) (bool, error) {
	// If the transaction is already known, discard it
	hash := tx.Hash()
	if pool.all.Get(hash) != nil {
		log.Trace("Discarding already known transaction", "hash", hash)
		return false, fmt.Errorf("known transaction: %x", hash)
	}
	// If the transaction fails basic validation, discard it
	if err := pool.validateTx(tx, local); err != nil {
		log.Trace("Discarding invalid transaction", "hash", hash, "err", err)
		invalidTxCounter.Inc(1)
		return false, err
	}
	// If the transaction pool is full, discard underpriced transactions
	if uint64(pool.all.Count()) >= pool.config.GlobalSlots+pool.config.GlobalQueue {
		// If the new transaction is underpriced, don't accept it
		if !local && pool.priced.Underpriced(tx, pool.locals) {
			log.Trace("Discarding underpriced transaction", "hash", hash, "price", tx.GasPrice())
			underpricedTxCounter.Inc(1)
			return false, ErrUnderpriced
		}
		// New transaction is better than our worse ones, make room for it
		drop := pool.priced.Discard(pool.all.Count()-int(pool.config.GlobalSlots+pool.config.GlobalQueue-1), pool.locals)
		for _, tx := range drop {
			log.Trace("Discarding freshly underpriced transaction", "hash", tx.Hash(), "price", tx.GasPrice())
			underpricedTxCounter.Inc(1)
			pool.removeTx(tx.Hash(), false)
		}
	}
	// If the transaction is replacing an already pending one, do directly
	from, _ := types.Sender(pool.signer, tx) // already validated
	if list := pool.pending[from]; list != nil && list.Overlaps(tx) {
		// Nonce already pending, check if required price bump is met
		inserted, old := list.Add(tx, pool.config.PriceBump)
		if !inserted {
			pendingDiscardCounter.Inc(1)
			return false, ErrReplaceUnderpriced
		}
		// New transaction is better, replace old one
		if old != nil {
			pool.all.Remove(old.Hash())
			pool.priced.Removed()
			pendingReplaceCounter.Inc(1)
		}
		pool.all.Add(tx)
		pool.priced.Put(tx)
		pool.journalTx(from, tx)

		log.Trace("Pooled new executable transaction", "hash", hash, "from", from, "to", tx.To())

		// We've directly injected a replacement transaction, notify subsystems
		// ここでNewTxsEventを発行
		// worker update txsChの受信
		go pool.txFeed.Send(NewTxsEvent{types.Transactions{tx}})

		return old != nil, nil
	}
	// New transaction isn't replacing a pending one, push into queue
	replace, err := pool.enqueueTx(hash, tx)
	if err != nil {
		return false, err
	}
	// Mark local addresses and journal local transactions
	if local {
		pool.locals.add(from)
	}
	pool.journalTx(from, tx)

	log.Trace("Pooled new future transaction", "hash", hash, "from", from, "to", tx.To())
	return replace, nil
}
```

```go
type peer struct {
	id string

	*p2p.Peer
	rw p2p.MsgReadWriter

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

	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
	queuedTxs   chan []*types.Transaction // 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
}

func (pm *ProtocolManager) txBroadcastLoop() {
	for {
		select {
		case event := <-pm.txsCh:
			// トランザクションイベントを受信して他のノードにブロードキャストする
			pm.BroadcastTxs(event.Txs)

		// Err() channel will be closed when unsubscribing.
		case <-pm.txsSub.Err():
			return
		}
	}
}

func (pm *ProtocolManager) BroadcastTxs(txs types.Transactions) {
	var txset = make(map[*peer]types.Transactions)

	// Broadcast transactions to a batch of peers not knowing about it
	for _, tx := range txs {
		peers := pm.peers.PeersWithoutTx(tx.Hash())
		for _, peer := range peers {
			txset[peer] = append(txset[peer], tx)
		}
		log.Trace("Broadcast transaction", "hash", tx.Hash(), "recipients", len(peers))
	}
	// FIXME include this again: peers = peers[:int(math.Sqrt(float64(len(peers))))]
	for peer, txs := range txset {
		peer.AsyncSendTransactions(txs)
	}
}

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))
	}
}

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 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
		}
	}
}

func (p *peer) SendTransactions(txs types.Transactions) error {
	fmt.Println("peer SendTransactions")
	// If we reached the memory allowance, drop a previously known transaction hash
	for _, tx := range txs {
		p.knownTxs.Add(tx.Hash())
	}
	return p2p.Send(p.rw, TxMsg, txs)
}

func Send(w MsgWriter, msgcode uint64, data interface{}) error {
	size, r, err := rlp.EncodeToReader(data)
	if err != nil {
		return err
	}
	return w.WriteMsg(Msg{Code: msgcode, Size: uint32(size), Payload: r})
}

type protoRW struct {
	Protocol
	in     chan Msg        // receices read messages
	closed <-chan struct{} // receives when peer is shutting down
	wstart <-chan struct{} // receives when write may start
	werr   chan<- error    // for write results
	offset uint64
	w      MsgWriter
}

func (rw *protoRW) WriteMsg(msg Msg) (err error) {
	if msg.Code >= rw.Length {
		return newPeerError(errInvalidMsgCode, "not handled")
	}
	msg.Code += rw.offset
	select {
	case <-rw.wstart:
		err = rw.w.WriteMsg(msg)
		// Report write status back to Peer.run. It will initiate
		// shutdown if the error is non-nil and unblock the next write
		// otherwise. The calling protocol code should exit for errors
		// as well but we don't want to rely on that.
		rw.werr <- err
	case <-rw.closed:
		err = fmt.Errorf("shutting down")
	}
	return err
}

type rlpx struct {
	fd net.Conn

	rmu, wmu sync.Mutex
	rw       *rlpxFrameRW
}

func (t *rlpx) WriteMsg(msg Msg) error {
	t.wmu.Lock()
	defer t.wmu.Unlock()
	t.fd.SetWriteDeadline(time.Now().Add(frameWriteTimeout))
	return t.rw.WriteMsg(msg)
}

type rlpxFrameRW struct {
	conn io.ReadWriter
	enc  cipher.Stream
	dec  cipher.Stream

	macCipher  cipher.Block
	egressMAC  hash.Hash
	ingressMAC hash.Hash

	snappy bool
}

func (rw *rlpxFrameRW) WriteMsg(msg Msg) error {
	ptype, _ := rlp.EncodeToBytes(msg.Code)

	// if snappy is enabled, compress message now
	if rw.snappy {
		if msg.Size > maxUint24 {
			return errPlainMessageTooLarge
		}
		payload, _ := ioutil.ReadAll(msg.Payload)
		payload = snappy.Encode(nil, payload)

		msg.Payload = bytes.NewReader(payload)
		msg.Size = uint32(len(payload))
	}
	// write header
	headbuf := make([]byte, 32)
	fsize := uint32(len(ptype)) + msg.Size
	if fsize > maxUint24 {
		return errors.New("message size overflows uint24")
	}
	putInt24(fsize, headbuf) // TODO: check overflow
	copy(headbuf[3:], zeroHeader)
	rw.enc.XORKeyStream(headbuf[:16], headbuf[:16]) // first half is now encrypted

	// write header MAC
	copy(headbuf[16:], updateMAC(rw.egressMAC, rw.macCipher, headbuf[:16]))
	if _, err := rw.conn.Write(headbuf); err != nil {
		return err
	}

	// write encrypted frame, updating the egress MAC hash with
	// the data written to conn.
	tee := cipher.StreamWriter{S: rw.enc, W: io.MultiWriter(rw.conn, rw.egressMAC)}
	if _, err := tee.Write(ptype); err != nil {
		return err
	}
	if _, err := io.Copy(tee, msg.Payload); err != nil {
		return err
	}
	if padding := fsize % 16; padding > 0 {
		if _, err := tee.Write(zero16[:16-padding]); err != nil {
			return err
		}
	}

	// write frame MAC. egress MAC hash is up to date because
	// frame content was written to it as well.
	fmacseed := rw.egressMAC.Sum(nil)
	mac := updateMAC(rw.egressMAC, rw.macCipher, fmacseed)
	_, err := rw.conn.Write(mac)
	return err
}
```

ブロードキャストされる側

```go
func (rw *rlpxFrameRW) ReadMsg() (msg Msg, err error) {
	// read the header
	headbuf := make([]byte, 32)
	if _, err := io.ReadFull(rw.conn, headbuf); err != nil {
		return msg, err
	}
	// verify header mac
	shouldMAC := updateMAC(rw.ingressMAC, rw.macCipher, headbuf[:16])
	if !hmac.Equal(shouldMAC, headbuf[16:]) {
		return msg, errors.New("bad header MAC")
	}
	rw.dec.XORKeyStream(headbuf[:16], headbuf[:16]) // first half is now decrypted
	fsize := readInt24(headbuf)
	// ignore protocol type for now

	// read the frame content
	var rsize = fsize // frame size rounded up to 16 byte boundary
	if padding := fsize % 16; padding > 0 {
		rsize += 16 - padding
	}
	framebuf := make([]byte, rsize)
	if _, err := io.ReadFull(rw.conn, framebuf); err != nil {
		return msg, err
	}

	// read and validate frame MAC. we can re-use headbuf for that.
	rw.ingressMAC.Write(framebuf)
	fmacseed := rw.ingressMAC.Sum(nil)
	if _, err := io.ReadFull(rw.conn, headbuf[:16]); err != nil {
		return msg, err
	}
	shouldMAC = updateMAC(rw.ingressMAC, rw.macCipher, fmacseed)
	if !hmac.Equal(shouldMAC, headbuf[:16]) {
		return msg, errors.New("bad frame MAC")
	}

	// decrypt frame content
	rw.dec.XORKeyStream(framebuf, framebuf)

	// decode message code
	content := bytes.NewReader(framebuf[:fsize])
	if err := rlp.Decode(content, &msg.Code); err != nil {
		return msg, err
	}
	msg.Size = uint32(content.Len())
	msg.Payload = content

	// if snappy is enabled, verify and decompress message
	if rw.snappy {
		payload, err := ioutil.ReadAll(msg.Payload)
		if err != nil {
			return msg, err
		}
		size, err := snappy.DecodedLen(payload)
		if err != nil {
			return msg, err
		}
		if size > int(maxUint24) {
			return msg, errPlainMessageTooLarge
		}
		payload, err = snappy.Decode(nil, payload)
		if err != nil {
			return msg, err
		}
		msg.Size, msg.Payload = uint32(size), bytes.NewReader(payload)
	}
	return msg, nil
}

func (t *rlpx) ReadMsg() (Msg, error) {
	t.rmu.Lock()
	defer t.rmu.Unlock()
	t.fd.SetReadDeadline(time.Now().Add(frameReadTimeout))
	return t.rw.ReadMsg()
}

func (pm *ProtocolManager) handleMsg(p *peer) error {
	// Read the next message from the remote peer, and ensure it's fully consumed
	msg, err := p.rw.ReadMsg()
	if err != nil {
		return err
	}
	if msg.Size > ProtocolMaxMsgSize {
		return errResp(ErrMsgTooLarge, "%v > %v", msg.Size, ProtocolMaxMsgSize)
	}
	defer msg.Discard()

	// Handle the message depending on its contents
	switch {
	case msg.Code == StatusMsg:
		// Status messages should never arrive after the handshake
		return errResp(ErrExtraStatusMsg, "uncontrolled status message")

	// Block header query, collect the requested headers and reply
	case msg.Code == GetBlockHeadersMsg:
		// Decode the complex header query
		var query getBlockHeadersData
		if err := msg.Decode(&query); err != nil {
			return errResp(ErrDecode, "%v: %v", msg, err)
		}
		hashMode := query.Origin.Hash != (common.Hash{})
		first := true
		maxNonCanonical := uint64(100)

		// Gather headers until the fetch or network limits is reached
		var (
			bytes   common.StorageSize
			headers []*types.Header
			unknown bool
		)
		for !unknown && len(headers) < int(query.Amount) && bytes < softResponseLimit && len(headers) < downloader.MaxHeaderFetch {
			// Retrieve the next header satisfying the query
			var origin *types.Header
			if hashMode {
				if first {
					first = false
					origin = pm.blockchain.GetHeaderByHash(query.Origin.Hash)
					if origin != nil {
						query.Origin.Number = origin.Number.Uint64()
					}
				} else {
					origin = pm.blockchain.GetHeader(query.Origin.Hash, query.Origin.Number)
				}
			} else {
				origin = pm.blockchain.GetHeaderByNumber(query.Origin.Number)
			}
			if origin == nil {
				break
			}
			headers = append(headers, origin)
			bytes += estHeaderRlpSize

			// Advance to the next header of the query
			switch {
			case hashMode && query.Reverse:
				// Hash based traversal towards the genesis block
				ancestor := query.Skip + 1
				if ancestor == 0 {
					unknown = true
				} else {
					query.Origin.Hash, query.Origin.Number = pm.blockchain.GetAncestor(query.Origin.Hash, query.Origin.Number, ancestor, &maxNonCanonical)
					unknown = (query.Origin.Hash == common.Hash{})
				}
			case hashMode && !query.Reverse:
				// Hash based traversal towards the leaf block
				var (
					current = origin.Number.Uint64()
					next    = current + query.Skip + 1
				)
				if next <= current {
					infos, _ := json.MarshalIndent(p.Peer.Info(), "", "  ")
					p.Log().Warn("GetBlockHeaders skip overflow attack", "current", current, "skip", query.Skip, "next", next, "attacker", infos)
					unknown = true
				} else {
					if header := pm.blockchain.GetHeaderByNumber(next); header != nil {
						nextHash := header.Hash()
						expOldHash, _ := pm.blockchain.GetAncestor(nextHash, next, query.Skip+1, &maxNonCanonical)
						if expOldHash == query.Origin.Hash {
							query.Origin.Hash, query.Origin.Number = nextHash, next
						} else {
							unknown = true
						}
					} else {
						unknown = true
					}
				}
			case query.Reverse:
				// Number based traversal towards the genesis block
				if query.Origin.Number >= query.Skip+1 {
					query.Origin.Number -= query.Skip + 1
				} else {
					unknown = true
				}

			case !query.Reverse:
				// Number based traversal towards the leaf block
				query.Origin.Number += query.Skip + 1
			}
		}
		return p.SendBlockHeaders(headers)

	case msg.Code == BlockHeadersMsg:
		// A batch of headers arrived to one of our previous requests
		var headers []*types.Header
		if err := msg.Decode(&headers); err != nil {
			return errResp(ErrDecode, "msg %v: %v", msg, err)
		}
		// If no headers were received, but we're expending a DAO fork check, maybe it's that
		if len(headers) == 0 && p.forkDrop != nil {
			// Possibly an empty reply to the fork header checks, sanity check TDs
			verifyDAO := true

			// If we already have a DAO header, we can check the peer's TD against it. If
			// the peer's ahead of this, it too must have a reply to the DAO check
			if daoHeader := pm.blockchain.GetHeaderByNumber(pm.chainconfig.DAOForkBlock.Uint64()); daoHeader != nil {
				if _, td := p.Head(); td.Cmp(pm.blockchain.GetTd(daoHeader.Hash(), daoHeader.Number.Uint64())) >= 0 {
					verifyDAO = false
				}
			}
			// If we're seemingly on the same chain, disable the drop timer
			if verifyDAO {
				p.Log().Debug("Seems to be on the same side of the DAO fork")
				p.forkDrop.Stop()
				p.forkDrop = nil
				return nil
			}
		}
		// Filter out any explicitly requested headers, deliver the rest to the downloader
		filter := len(headers) == 1
		if filter {
			// If it's a potential DAO fork check, validate against the rules
			if p.forkDrop != nil && pm.chainconfig.DAOForkBlock.Cmp(headers[0].Number) == 0 {
				// Disable the fork drop timer
				p.forkDrop.Stop()
				p.forkDrop = nil

				// Validate the header and either drop the peer or continue
				if err := misc.VerifyDAOHeaderExtraData(pm.chainconfig, headers[0]); err != nil {
					p.Log().Debug("Verified to be on the other side of the DAO fork, dropping")
					return err
				}
				p.Log().Debug("Verified to be on the same side of the DAO fork")
				return nil
			}
			// Irrelevant of the fork checks, send the header to the fetcher just in case
			headers = pm.fetcher.FilterHeaders(p.id, headers, time.Now())
		}
		if len(headers) > 0 || !filter {
			err := pm.downloader.DeliverHeaders(p.id, headers)
			if err != nil {
				log.Debug("Failed to deliver headers", "err", err)
			}
		}

	case msg.Code == GetBlockBodiesMsg:
		// Decode the retrieval message
		msgStream := rlp.NewStream(msg.Payload, uint64(msg.Size))
		if _, err := msgStream.List(); err != nil {
			return err
		}
		// Gather blocks until the fetch or network limits is reached
		var (
			hash   common.Hash
			bytes  int
			bodies []rlp.RawValue
		)
		for bytes < softResponseLimit && len(bodies) < downloader.MaxBlockFetch {
			// Retrieve the hash of the next block
			if err := msgStream.Decode(&hash); err == rlp.EOL {
				break
			} else if err != nil {
				return errResp(ErrDecode, "msg %v: %v", msg, err)
			}
			// Retrieve the requested block body, stopping if enough was found
			if data := pm.blockchain.GetBodyRLP(hash); len(data) != 0 {
				bodies = append(bodies, data)
				bytes += len(data)
			}
		}
		return p.SendBlockBodiesRLP(bodies)

	case msg.Code == BlockBodiesMsg:
		// A batch of block bodies arrived to one of our previous requests
		var request blockBodiesData
		if err := msg.Decode(&request); err != nil {
			return errResp(ErrDecode, "msg %v: %v", msg, err)
		}
		// Deliver them all to the downloader for queuing
		transactions := make([][]*types.Transaction, len(request))
		uncles := make([][]*types.Header, len(request))

		for i, body := range request {
			transactions[i] = body.Transactions
			uncles[i] = body.Uncles
		}
		// Filter out any explicitly requested bodies, deliver the rest to the downloader
		filter := len(transactions) > 0 || len(uncles) > 0
		if filter {
			transactions, uncles = pm.fetcher.FilterBodies(p.id, transactions, uncles, time.Now())
		}
		if len(transactions) > 0 || len(uncles) > 0 || !filter {
			err := pm.downloader.DeliverBodies(p.id, transactions, uncles)
			if err != nil {
				log.Debug("Failed to deliver bodies", "err", err)
			}
		}

	case p.version >= eth63 && msg.Code == GetNodeDataMsg:
		// Decode the retrieval message
		msgStream := rlp.NewStream(msg.Payload, uint64(msg.Size))
		if _, err := msgStream.List(); err != nil {
			return err
		}
		// Gather state data until the fetch or network limits is reached
		var (
			hash  common.Hash
			bytes int
			data  [][]byte
		)
		for bytes < softResponseLimit && len(data) < downloader.MaxStateFetch {
			// Retrieve the hash of the next state entry
			if err := msgStream.Decode(&hash); err == rlp.EOL {
				break
			} else if err != nil {
				return errResp(ErrDecode, "msg %v: %v", msg, err)
			}
			// Retrieve the requested state entry, stopping if enough was found
			if entry, err := pm.blockchain.TrieNode(hash); err == nil {
				data = append(data, entry)
				bytes += len(entry)
			}
		}
		return p.SendNodeData(data)

	case p.version >= eth63 && msg.Code == NodeDataMsg:
		// A batch of node state data arrived to one of our previous requests
		var data [][]byte
		if err := msg.Decode(&data); err != nil {
			return errResp(ErrDecode, "msg %v: %v", msg, err)
		}
		// Deliver all to the downloader
		if err := pm.downloader.DeliverNodeData(p.id, data); err != nil {
			log.Debug("Failed to deliver node state data", "err", err)
		}

	case p.version >= eth63 && msg.Code == GetReceiptsMsg:
		// Decode the retrieval message
		msgStream := rlp.NewStream(msg.Payload, uint64(msg.Size))
		if _, err := msgStream.List(); err != nil {
			return err
		}
		// Gather state data until the fetch or network limits is reached
		var (
			hash     common.Hash
			bytes    int
			receipts []rlp.RawValue
		)
		for bytes < softResponseLimit && len(receipts) < downloader.MaxReceiptFetch {
			// Retrieve the hash of the next block
			if err := msgStream.Decode(&hash); err == rlp.EOL {
				break
			} else if err != nil {
				return errResp(ErrDecode, "msg %v: %v", msg, err)
			}
			// Retrieve the requested block's receipts, skipping if unknown to us
			results := pm.blockchain.GetReceiptsByHash(hash)
			if results == nil {
				if header := pm.blockchain.GetHeaderByHash(hash); header == nil || header.ReceiptHash != types.EmptyRootHash {
					continue
				}
			}
			// If known, encode and queue for response packet
			if encoded, err := rlp.EncodeToBytes(results); err != nil {
				log.Error("Failed to encode receipt", "err", err)
			} else {
				receipts = append(receipts, encoded)
				bytes += len(encoded)
			}
		}
		return p.SendReceiptsRLP(receipts)

	case p.version >= eth63 && msg.Code == ReceiptsMsg:
		// A batch of receipts arrived to one of our previous requests
		var receipts [][]*types.Receipt
		if err := msg.Decode(&receipts); err != nil {
			return errResp(ErrDecode, "msg %v: %v", msg, err)
		}
		// Deliver all to the downloader
		if err := pm.downloader.DeliverReceipts(p.id, receipts); err != nil {
			log.Debug("Failed to deliver receipts", "err", err)
		}

	case msg.Code == NewBlockHashesMsg:
		var announces newBlockHashesData
		if err := msg.Decode(&announces); err != nil {
			return errResp(ErrDecode, "%v: %v", msg, err)
		}
		// Mark the hashes as present at the remote node
		for _, block := range announces {
			p.MarkBlock(block.Hash)
		}
		// Schedule all the unknown hashes for retrieval
		unknown := make(newBlockHashesData, 0, len(announces))
		for _, block := range announces {
			if !pm.blockchain.HasBlock(block.Hash, block.Number) {
				unknown = append(unknown, block)
			}
		}
		for _, block := range unknown {
			pm.fetcher.Notify(p.id, block.Hash, block.Number, time.Now(), p.RequestOneHeader, p.RequestBodies)
		}

	case msg.Code == NewBlockMsg:
		// Retrieve and decode the propagated block
		var request newBlockData
		if err := msg.Decode(&request); err != nil {
			return errResp(ErrDecode, "%v: %v", msg, err)
		}
		request.Block.ReceivedAt = msg.ReceivedAt
		request.Block.ReceivedFrom = p

		// Mark the peer as owning the block and schedule it for import
		p.MarkBlock(request.Block.Hash())
		pm.fetcher.Enqueue(p.id, request.Block)

		// Assuming the block is importable by the peer, but possibly not yet done so,
		// calculate the head hash and TD that the peer truly must have.
		var (
			trueHead = request.Block.ParentHash()
			trueTD   = new(big.Int).Sub(request.TD, request.Block.Difficulty())
		)
		// Update the peers total difficulty if better than the previous
		if _, td := p.Head(); trueTD.Cmp(td) > 0 {
			p.SetHead(trueHead, trueTD)

			// Schedule a sync if above ours. Note, this will not fire a sync for a gap of
			// a singe block (as the true TD is below the propagated block), however this
			// scenario should easily be covered by the fetcher.
			currentBlock := pm.blockchain.CurrentBlock()
			if trueTD.Cmp(pm.blockchain.GetTd(currentBlock.Hash(), currentBlock.NumberU64())) > 0 {
				go pm.synchronise(p)
			}
		}

	case msg.Code == TxMsg:
		// Transactions arrived, make sure we have a valid and fresh chain to handle them
		if atomic.LoadUint32(&pm.acceptTxs) == 0 {
			break
		}
		// Transactions can be processed, parse all of them and deliver to the pool
		var txs []*types.Transaction
		if err := msg.Decode(&txs); err != nil {
			return errResp(ErrDecode, "msg %v: %v", msg, err)
		}
		for i, tx := range txs {
			// Validate and mark the remote transaction
			if tx == nil {
				return errResp(ErrDecode, "transaction %d is nil", i)
			}
			p.MarkTransaction(tx.Hash())
		}
		pm.txpool.AddRemotes(txs)

	default:
		return errResp(ErrInvalidMsgCode, "%v", msg.Code)
	}
	return nil
}

func (pm *ProtocolManager) handle(p *peer) error {
	// Ignore maxPeers if this is a trusted peer
	if pm.peers.Len() >= pm.maxPeers && !p.Peer.Info().Network.Trusted {
		return p2p.DiscTooManyPeers
	}
	p.Log().Debug("Ethereum peer connected", "name", p.Name())

	// Execute the Ethereum handshake
	var (
		genesis = pm.blockchain.Genesis()
		head    = pm.blockchain.CurrentHeader()
		hash    = head.Hash()
		number  = head.Number.Uint64()
		td      = pm.blockchain.GetTd(hash, number)
	)
	if err := p.Handshake(pm.networkId, td, hash, genesis.Hash()); err != nil {
		p.Log().Debug("Ethereum handshake failed", "err", err)
		return err
	}
	if rw, ok := p.rw.(*meteredMsgReadWriter); ok {
		rw.Init(p.version)
	}
	// Register the peer locally
	if err := pm.peers.Register(p); err != nil {
		p.Log().Error("Ethereum peer registration failed", "err", err)
		return err
	}
	defer pm.removePeer(p.id)

	// Register the peer in the downloader. If the downloader considers it banned, we disconnect
	if err := pm.downloader.RegisterPeer(p.id, p.version, p); err != nil {
		return err
	}
	// Propagate existing transactions. new transactions appearing
	// after this will be sent via broadcasts.
	pm.syncTransactions(p)

	// If we're DAO hard-fork aware, validate any remote peer with regard to the hard-fork
	if daoBlock := pm.chainconfig.DAOForkBlock; daoBlock != nil {
		// Request the peer's DAO fork header for extra-data validation
		if err := p.RequestHeadersByNumber(daoBlock.Uint64(), 1, 0, false); err != nil {
			return err
		}
		// Start a timer to disconnect if the peer doesn't reply in time
		p.forkDrop = time.AfterFunc(daoChallengeTimeout, func() {
			p.Log().Debug("Timed out DAO fork-check, dropping")
			pm.removePeer(p.id)
		})
		// Make sure it's cleaned up if the peer dies off
		defer func() {
			if p.forkDrop != nil {
				p.forkDrop.Stop()
				p.forkDrop = nil
			}
		}()
	}
	// main loop. handle incoming messages.
	for {
		if err := pm.handleMsg(p); err != nil {
			p.Log().Debug("Ethereum message handling failed", "err", err)
			return err
		}
	}
}

func NewProtocolManager(config *params.ChainConfig, mode downloader.SyncMode, networkId uint64, mux *event.TypeMux, txpool txPool, engine consensus.Engine, blockchain *core.BlockChain, chaindb ethdb.Database) (*ProtocolManager, error) {
	// Create the protocol manager with the base fields
	manager := &ProtocolManager{
		networkId:   networkId,
		eventMux:    mux,
		txpool:      txpool,
		blockchain:  blockchain,
		chainconfig: config,
		peers:       newPeerSet(),
		newPeerCh:   make(chan *peer),
		noMorePeers: make(chan struct{}),
		txsyncCh:    make(chan *txsync),
		quitSync:    make(chan struct{}),
	}
	// Figure out whether to allow fast sync or not
	if mode == downloader.FastSync && blockchain.CurrentBlock().NumberU64() > 0 {
		log.Warn("Blockchain not empty, fast sync disabled")
		mode = downloader.FullSync
	}
	if mode == downloader.FastSync {
		manager.fastSync = uint32(1)
	}
	// Initiate a sub-protocol for every implemented version we can handle
	manager.SubProtocols = make([]p2p.Protocol, 0, len(ProtocolVersions))
	for i, version := range ProtocolVersions {
		// Skip protocol version if incompatible with the mode of operation
		if mode == downloader.FastSync && version < eth63 {
			continue
		}
		// Compatible; initialise the sub-protocol
		version := version // Closure for the run
		manager.SubProtocols = append(manager.SubProtocols, p2p.Protocol{
			Name:    ProtocolName,
			Version: version,
			Length:  ProtocolLengths[i],
			Run: func(p *p2p.Peer, rw p2p.MsgReadWriter) error {
				peer := manager.newPeer(int(version), p, rw)
				select {
				case manager.newPeerCh <- peer:
					manager.wg.Add(1)
					defer manager.wg.Done()
					return manager.handle(peer)
				case <-manager.quitSync:
					return p2p.DiscQuitting
				}
			},
			NodeInfo: func() interface{} {
				return manager.NodeInfo()
			},
			PeerInfo: func(id discover.NodeID) interface{} {
				if p := manager.peers.Peer(fmt.Sprintf("%x", id[:8])); p != nil {
					return p.Info()
				}
				return nil
			},
		})
	}
	if len(manager.SubProtocols) == 0 {
		return nil, errIncompatibleConfig
	}
	// Construct the different synchronisation mechanisms
	manager.downloader = downloader.New(mode, chaindb, manager.eventMux, blockchain, nil, manager.removePeer)

	validator := func(header *types.Header) error {
		return engine.VerifyHeader(blockchain, header, true)
	}
	heighter := func() uint64 {
		return blockchain.CurrentBlock().NumberU64()
	}
	inserter := func(blocks types.Blocks) (int, error) {
		// If fast sync is running, deny importing weird blocks
		if atomic.LoadUint32(&manager.fastSync) == 1 {
			log.Warn("Discarded bad propagated block", "number", blocks[0].Number(), "hash", blocks[0].Hash())
			return 0, nil
		}
		atomic.StoreUint32(&manager.acceptTxs, 1) // Mark initial sync done on any fetcher import
		return manager.blockchain.InsertChain(blocks)
	}
	manager.fetcher = fetcher.New(blockchain.GetBlockByHash, validator, manager.BroadcastBlock, heighter, inserter, manager.removePeer)

	return manager, nil
}

// 受信したことを記録する
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)
}

// 下の2つは送信側と同じ
// 1.他に伝搬するための処理
// 2.トランザクション受信イベントを受け取る
```