github.com/linapex/ethereum-go-chinese@v0.0.0-20190316121929-f8b7a73c3fa1/eth/handler.go

//<developer>
//    <name>linapex 曹一峰</name>
//    <email>linapex@163.com</email>
//    <wx>superexc</wx>
//    <qqgroup>128148617</qqgroup>
//    <url>https://jsq.ink</url>
//    <role>pku engineer</role>
//    <date>2019-03-16 19:16:37</date>
//</624450089162641408>


package eth

import (
	"encoding/json"
	"errors"
	"fmt"
	"math"
	"math/big"
	"sync"
	"sync/atomic"
	"time"

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/consensus"
	"github.com/ethereum/go-ethereum/consensus/misc"
	"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/eth/fetcher"
	"github.com/ethereum/go-ethereum/ethdb"
	"github.com/ethereum/go-ethereum/event"
	"github.com/ethereum/go-ethereum/log"
	"github.com/ethereum/go-ethereum/p2p"
	"github.com/ethereum/go-ethereum/p2p/enode"
	"github.com/ethereum/go-ethereum/params"
	"github.com/ethereum/go-ethereum/rlp"
)

const (
softResponseLimit = 2 * 1024 * 1024 //返回的块、头或节点数据的目标最大大小。
estHeaderRlpSize  = 500             //RLP编码块头的近似大小

//txchanSize是侦听newtxSevent的频道的大小。
//该数字是根据Tx池的大小引用的。
	txChanSize = 4096

//minimim number of peers to broadcast new blocks to
	minBroadcastPeers = 4
)

var (
daoChallengeTimeout = 15 * time.Second //允许节点响应DAO握手挑战的时间
)

//如果请求的协议和配置为
//不兼容（低协议版本限制和高要求）。
var errIncompatibleConfig = errors.New("incompatible configuration")

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

type ProtocolManager struct {
	networkID uint64

fastSync  uint32 //标记是否启用快速同步（如果已经有块，则禁用）
acceptTxs uint32 //标记是否被认为是同步的（启用事务处理）

	txpool      txPool
	blockchain  *core.BlockChain
	chainconfig *params.ChainConfig
	maxPeers    int

	downloader *downloader.Downloader
	fetcher    *fetcher.Fetcher
	peers      *peerSet

	SubProtocols []p2p.Protocol

	eventMux      *event.TypeMux
	txsCh         chan core.NewTxsEvent
	txsSub        event.Subscription
	minedBlockSub *event.TypeMuxSubscription

	whitelist map[uint64]common.Hash

//获取器、同步器、TxSyncLoop的通道
	newPeerCh   chan *peer
	txsyncCh    chan *txsync
	quitSync    chan struct{}
	noMorePeers chan struct{}

//wait group is used for graceful shutdowns during downloading
//加工
	wg sync.WaitGroup
}

//NewProtocolManager返回新的以太坊子协议管理器。以太坊子协议管理对等端
//with the Ethereum network.
func NewProtocolManager(config *params.ChainConfig, mode downloader.SyncMode, networkID uint64, mux *event.TypeMux, txpool txPool, engine consensus.Engine, blockchain *core.BlockChain, chaindb ethdb.Database, whitelist map[uint64]common.Hash) (*ProtocolManager, error) {
//使用基本字段创建协议管理器
	manager := &ProtocolManager{
		networkID:   networkID,
		eventMux:    mux,
		txpool:      txpool,
		blockchain:  blockchain,
		chainconfig: config,
		peers:       newPeerSet(),
		whitelist:   whitelist,
		newPeerCh:   make(chan *peer),
		noMorePeers: make(chan struct{}),
		txsyncCh:    make(chan *txsync),
		quitSync:    make(chan struct{}),
	}
//确定是否允许快速同步
	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)
	}
//为我们能处理的每个实现版本启动一个子协议
	manager.SubProtocols = make([]p2p.Protocol, 0, len(ProtocolVersions))
	for i, version := range ProtocolVersions {
//如果与操作模式不兼容，则跳过协议版本
		if mode == downloader.FastSync && version < eth63 {
			continue
		}
//兼容；初始化子协议
version := version //跑步结束
		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 enode.ID) 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
	}
//构建不同的同步机制
	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) {
//如果快速同步正在运行，则拒绝导入奇怪的块
		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) //在任何获取器导入上标记初始同步完成
		return manager.blockchain.InsertChain(blocks)
	}
	manager.fetcher = fetcher.New(blockchain.GetBlockByHash, validator, manager.BroadcastBlock, heighter, inserter, manager.removePeer)

	return manager, nil
}

func (pm *ProtocolManager) removePeer(id string) {
//如果对等点已被删除，则短路
	peer := pm.peers.Peer(id)
	if peer == nil {
		return
	}
	log.Debug("Removing Ethereum peer", "peer", id)

//从下载程序和以太坊对等集注销对等。
	pm.downloader.UnregisterPeer(id)
	if err := pm.peers.Unregister(id); err != nil {
		log.Error("Peer removal failed", "peer", id, "err", err)
	}
//网络层硬断开
	if peer != nil {
		peer.Peer.Disconnect(p2p.DiscUselessPeer)
	}
}

func (pm *ProtocolManager) Start(maxPeers int) {
	pm.maxPeers = maxPeers

//广播事务
	pm.txsCh = make(chan core.NewTxsEvent, txChanSize)
	pm.txsSub = pm.txpool.SubscribeNewTxsEvent(pm.txsCh)
	go pm.txBroadcastLoop()

//广播挖掘块
	pm.minedBlockSub = pm.eventMux.Subscribe(core.NewMinedBlockEvent{})
	go pm.minedBroadcastLoop()

//启动同步处理程序
	go pm.syncer()
	go pm.txsyncLoop()
}

func (pm *ProtocolManager) Stop() {
	log.Info("Stopping Ethereum protocol")

pm.txsSub.Unsubscribe()        //退出TxBroadcastLoop
pm.minedBlockSub.Unsubscribe() //退出BlockBroadcastLoop

//退出同步循环。
//完成此发送后，将不接受任何新对等方。
	pm.noMorePeers <- struct{}{}

//Quit fetcher, txsyncLoop.
	close(pm.quitSync)

//断开现有会话。
//这也会关闭对等集上任何新注册的入口。
//sessions which are already established but not added to pm.peers yet
//当他们尝试注册时将退出。
	pm.peers.Close()

//等待所有对等处理程序Goroutines和循环出现。
	pm.wg.Wait()

	log.Info("Ethereum protocol stopped")
}

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

//handle是为管理ETH对等机的生命周期而调用的回调。什么时候？
//此函数终止，对等端断开连接。
func (pm *ProtocolManager) handle(p *peer) error {
//如果这是受信任的对等，则忽略MaxPeers
	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)
	}
//在本地注册对等机
	if err := pm.peers.Register(p); err != nil {
		p.Log().Error("Ethereum peer registration failed", "err", err)
		return err
	}
	defer pm.removePeer(p.id)

//在下载程序中注册对等点。如果下载者认为它是被禁止的，我们会断开
	if err := pm.downloader.RegisterPeer(p.id, p.version, p); err != nil {
		return err
	}
//传播现有事务。出现新交易
//之后将通过广播发送。
	pm.syncTransactions(p)

//如果我们知道DAO Hard Fork，请验证与Hard Fork相关的任何远程对等。
	if daoBlock := pm.chainconfig.DAOForkBlock; daoBlock != nil {
//请求对等端的DAO分叉头进行额外的数据验证
		if err := p.RequestHeadersByNumber(daoBlock.Uint64(), 1, 0, false); err != nil {
			return err
		}
//如果对等端没有及时回复，启动计时器断开连接
		p.forkDrop = time.AfterFunc(daoChallengeTimeout, func() {
			p.Log().Debug("Timed out DAO fork-check, dropping")
			pm.removePeer(p.id)
		})
//如果同伴死了，一定要把它清理干净。
		defer func() {
			if p.forkDrop != nil {
				p.forkDrop.Stop()
				p.forkDrop = nil
			}
		}()
	}
//如果我们有任何显式的白名单块哈希，请请求它们
	for number := range pm.whitelist {
		if err := p.RequestHeadersByNumber(number, 1, 0, false); err != nil {
			return err
		}
	}
//处理传入消息，直到断开连接
	for {
		if err := pm.handleMsg(p); err != nil {
			p.Log().Debug("Ethereum message handling failed", "err", err)
			return err
		}
	}
}

//每当从远程服务器接收到入站消息时，将调用handlemsg。
//同龄人。返回任何错误时，远程连接被断开。
func (pm *ProtocolManager) handleMsg(p *peer) error {
//从远程对等端读取下一条消息，并确保它被完全消耗掉。
	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()

//根据消息的内容处理消息
	switch {
	case msg.Code == StatusMsg:
//状态消息不应在握手后到达
		return errResp(ErrExtraStatusMsg, "uncontrolled status message")

//阻止头查询，收集请求的头并答复
	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)

//收集邮件头，直到达到提取或网络限制
		var (
			bytes   common.StorageSize
			headers []*types.Header
			unknown bool
		)
		for !unknown && len(headers) < int(query.Amount) && bytes < softResponseLimit && len(headers) < downloader.MaxHeaderFetch {
//检索满足查询的下一个标题
			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

//前进到查询的下一个标题
			switch {
			case hashMode && query.Reverse:
//向Genesis块的基于哈希的遍历
				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:
//基于哈希的叶块遍历
				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:
//朝向Genesis区块的基于数字的遍历
				if query.Origin.Number >= query.Skip+1 {
					query.Origin.Number -= query.Skip + 1
				} else {
					unknown = true
				}

			case !query.Reverse:
//面向叶块的基于数字的遍历
				query.Origin.Number += query.Skip + 1
			}
		}
		return p.SendBlockHeaders(headers)

	case msg.Code == BlockHeadersMsg:
//我们以前的一个请求收到了一批头文件
		var headers []*types.Header
		if err := msg.Decode(&headers); err != nil {
			return errResp(ErrDecode, "msg %v: %v", msg, err)
		}
//如果没有收到报头，但我们要花费一张刀叉支票，也许是这样
		if len(headers) == 0 && p.forkDrop != nil {
//可能是对分叉头检查的空回复，健全性检查TDS
			verifyDAO := true

//如果我们已经有了一个DAO头，我们可以对照它检查对等端的TD。如果
//同行在前面，它也必须对DAO检查有答复
			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
				}
			}
//如果我们看起来是在同一条链上，请禁用掉计时。
			if verifyDAO {
				p.Log().Debug("Seems to be on the same side of the DAO fork")
				p.forkDrop.Stop()
				p.forkDrop = nil
				return nil
			}
		}
//过滤掉任何显式请求的头，将其余的传递给下载程序
		filter := len(headers) == 1
		if filter {
//如果这是一个潜在的DAO分叉检查，请根据规则验证
			if p.forkDrop != nil && pm.chainconfig.DAOForkBlock.Cmp(headers[0].Number) == 0 {
//禁用拨叉下降计时器
				p.forkDrop.Stop()
				p.forkDrop = nil

//验证头并删除对等端或继续
				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
			}
//否则，如果它是一个白名单块，请根据集合进行验证
			if want, ok := pm.whitelist[headers[0].Number.Uint64()]; ok {
				if hash := headers[0].Hash(); want != hash {
					p.Log().Info("Whitelist mismatch, dropping peer", "number", headers[0].Number.Uint64(), "hash", hash, "want", want)
					return errors.New("whitelist block mismatch")
				}
				p.Log().Debug("Whitelist block verified", "number", headers[0].Number.Uint64(), "hash", want)
			}
//与fork检查无关，将header发送到gether，以防万一。
			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:
//解码检索消息
		msgStream := rlp.NewStream(msg.Payload, uint64(msg.Size))
		if _, err := msgStream.List(); err != nil {
			return err
		}
//收集块，直到达到获取或网络限制
		var (
			hash   common.Hash
			bytes  int
			bodies []rlp.RawValue
		)
		for bytes < softResponseLimit && len(bodies) < downloader.MaxBlockFetch {
//检索下一个块的哈希
			if err := msgStream.Decode(&hash); err == rlp.EOL {
				break
			} else if err != nil {
				return errResp(ErrDecode, "msg %v: %v", msg, err)
			}
//检索请求的块体，如果找到足够的块体，则停止
			if data := pm.blockchain.GetBodyRLP(hash); len(data) != 0 {
				bodies = append(bodies, data)
				bytes += len(data)
			}
		}
		return p.SendBlockBodiesRLP(bodies)

	case msg.Code == BlockBodiesMsg:
//我们以前的一个要求得到了一批尸体。
		var request blockBodiesData
		if err := msg.Decode(&request); err != nil {
			return errResp(ErrDecode, "msg %v: %v", msg, err)
		}
//把它们全部送到下载者那里排队
		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
		}
//过滤掉任何明确要求的主体，把其余的交付给下载者。
		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:
//解码检索消息
		msgStream := rlp.NewStream(msg.Payload, uint64(msg.Size))
		if _, err := msgStream.List(); err != nil {
			return err
		}
//收集状态数据，直到达到提取或网络限制
		var (
			hash  common.Hash
			bytes int
			data  [][]byte
		)
		for bytes < softResponseLimit && len(data) < downloader.MaxStateFetch {
//检索下一个状态项的哈希
			if err := msgStream.Decode(&hash); err == rlp.EOL {
				break
			} else if err != nil {
				return errResp(ErrDecode, "msg %v: %v", msg, err)
			}
//检索请求的状态项，如果找到足够的，则停止
			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:
//一批节点状态数据到达了我们以前的一个请求
		var data [][]byte
		if err := msg.Decode(&data); err != nil {
			return errResp(ErrDecode, "msg %v: %v", msg, err)
		}
//将所有内容发送到下载程序
		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:
//解码检索消息
		msgStream := rlp.NewStream(msg.Payload, uint64(msg.Size))
		if _, err := msgStream.List(); err != nil {
			return err
		}
//收集状态数据，直到达到提取或网络限制
		var (
			hash     common.Hash
			bytes    int
			receipts []rlp.RawValue
		)
		for bytes < softResponseLimit && len(receipts) < downloader.MaxReceiptFetch {
//检索下一个块的哈希
			if err := msgStream.Decode(&hash); err == rlp.EOL {
				break
			} else if err != nil {
				return errResp(ErrDecode, "msg %v: %v", msg, err)
			}
//检索请求块的收据，如果我们不知道，则跳过
			results := pm.blockchain.GetReceiptsByHash(hash)
			if results == nil {
				if header := pm.blockchain.GetHeaderByHash(hash); header == nil || header.ReceiptHash != types.EmptyRootHash {
					continue
				}
			}
//如果已知，则对响应数据包进行编码和排队
			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:
//我们以前的一个请求收到了一批收据
		var receipts [][]*types.Receipt
		if err := msg.Decode(&receipts); err != nil {
			return errResp(ErrDecode, "msg %v: %v", msg, err)
		}
//将所有内容发送到下载程序
		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)
		}
//将哈希标记为在远程节点上存在
		for _, block := range announces {
			p.MarkBlock(block.Hash)
		}
//计划所有未知哈希以便检索
		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:
//检索并解码传播的块
		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

//将对等机标记为拥有该块并计划导入
		p.MarkBlock(request.Block.Hash())
		pm.fetcher.Enqueue(p.id, request.Block)

//假设该块可由对等机导入，但可能尚未导入，
//计算对等端真正必须拥有的头散列和td。
		var (
			trueHead = request.Block.ParentHash()
			trueTD   = new(big.Int).Sub(request.TD, request.Block.Difficulty())
		)
//如果优于前一个，则更新同伴的总难度
		if _, td := p.Head(); trueTD.Cmp(td) > 0 {
			p.SetHead(trueHead, trueTD)

//如果高于我们的，则安排同步。注意，对于间隔为
//一个单独的块（因为真正的td低于传播的块），但是
//场景应该很容易被获取器覆盖。
			currentBlock := pm.blockchain.CurrentBlock()
			if trueTD.Cmp(pm.blockchain.GetTd(currentBlock.Hash(), currentBlock.NumberU64())) > 0 {
				go pm.synchronise(p)
			}
		}

	case msg.Code == TxMsg:
//交易已到达，请确保我们有一个有效且新鲜的链来处理它们。
		if atomic.LoadUint32(&pm.acceptTxs) == 0 {
			break
		}
//可以处理事务，解析所有事务并将其传递到池
		var txs []*types.Transaction
		if err := msg.Decode(&txs); err != nil {
			return errResp(ErrDecode, "msg %v: %v", msg, err)
		}
		for i, tx := range txs {
//验证并标记远程事务
			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
}

//BroadcastBlock将把一个块传播到它的一个子集的对等端，或者
//只会宣布它的可用性（取决于请求的内容）。
func (pm *ProtocolManager) BroadcastBlock(block *types.Block, propagate bool) {
	hash := block.Hash()
	peers := pm.peers.PeersWithoutBlock(hash)

//如果请求传播，则发送到对等机的一个子集
	if propagate {
//计算块的td（尚未导入，因此块.td无效）
		var td *big.Int
		if parent := pm.blockchain.GetBlock(block.ParentHash(), block.NumberU64()-1); parent != nil {
			td = new(big.Int).Add(block.Difficulty(), pm.blockchain.GetTd(block.ParentHash(), block.NumberU64()-1))
		} else {
			log.Error("Propagating dangling block", "number", block.Number(), "hash", hash)
			return
		}
//将块发送到对等节点的一个子集
		transferLen := int(math.Sqrt(float64(len(peers))))
		if transferLen < minBroadcastPeers {
			transferLen = minBroadcastPeers
		}
		if transferLen > len(peers) {
			transferLen = len(peers)
		}
		transfer := peers[:transferLen]
		for _, peer := range transfer {
			peer.AsyncSendNewBlock(block, td)
		}
		log.Trace("Propagated block", "hash", hash, "recipients", len(transfer), "duration", common.PrettyDuration(time.Since(block.ReceivedAt)))
		return
	}
//否则，如果该块确实在外链中，则将其公布。
	if pm.blockchain.HasBlock(hash, block.NumberU64()) {
		for _, peer := range peers {
			peer.AsyncSendNewBlockHash(block)
		}
		log.Trace("Announced block", "hash", hash, "recipients", len(peers), "duration", common.PrettyDuration(time.Since(block.ReceivedAt)))
	}
}

//BroadcastTXS将把一批事务传播到所有未知的对等端
//已经有给定的事务。
func (pm *ProtocolManager) BroadcastTxs(txs types.Transactions) {
	var txset = make(map[*peer]types.Transactions)

//将事务广播给一批不知道它的对等方
	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再次包括：peers=peers[：int（math.sqrt（float64（len（peers）））]
	for peer, txs := range txset {
		peer.AsyncSendTransactions(txs)
	}
}

//地雷广播回路
func (pm *ProtocolManager) minedBroadcastLoop() {
//如果取消订阅，则自动停止
	for obj := range pm.minedBlockSub.Chan() {
		if ev, ok := obj.Data.(core.NewMinedBlockEvent); ok {
pm.BroadcastBlock(ev.Block, true)  //首先将块传播到对等端
pm.BroadcastBlock(ev.Block, false) //然后向其他人宣布
		}
	}
}

func (pm *ProtocolManager) txBroadcastLoop() {
	for {
		select {
		case event := <-pm.txsCh:
			pm.BroadcastTxs(event.Txs)

//err（）取消订阅时通道将关闭。
		case <-pm.txsSub.Err():
			return
		}
	}
}

//nodeinfo表示以太坊子协议元数据的简短摘要
//了解主机对等机。
type NodeInfo struct {
Network    uint64              `json:"network"`    //以太坊网络ID（1=前沿，2=现代，Ropsten=3，Rinkeby=4）
Difficulty *big.Int            `json:"difficulty"` //主机区块链的总难度
Genesis    common.Hash         `json:"genesis"`    //寄主创世纪区块的沙3哈希
Config     *params.ChainConfig `json:"config"`     //分叉规则的链配置
Head       common.Hash         `json:"head"`       //主机最好拥有的块的sha3哈希
}

//nodeinfo检索有关正在运行的主机节点的一些协议元数据。
func (pm *ProtocolManager) NodeInfo() *NodeInfo {
	currentBlock := pm.blockchain.CurrentBlock()
	return &NodeInfo{
		Network:    pm.networkID,
		Difficulty: pm.blockchain.GetTd(currentBlock.Hash(), currentBlock.NumberU64()),
		Genesis:    pm.blockchain.Genesis().Hash(),
		Config:     pm.blockchain.Config(),
		Head:       currentBlock.Hash(),
	}
}