以太坊p2p原理与实现
区块链技术的去中心依赖于底层组网技术，以太坊的底层实现了p2pServer，大约可以分为这样三层。
- 底层路由表。封装了kad路由，节点的数据结构以及计算记录，节点搜索，验证等功能。
- 中层peer抽象，message开放发送接口，server对外提供peer检测，初始化，事件订阅，peer状态查询，启动，停止等功能
- 以太坊最上层peer，peerset再封装，通过协议的Run函数，在中层启动peer时，获取peer，最终通过一个循环截取稳定peer，包装在peerset中使用。
底层路由表
这里简化问题仅讨论Node Discovery Protocol。 这一层维护了一个buckets桶，总共有17个桶，每个桶有16个节点和10个替换节点。 Node放入时先要计算hash和localNode的距离。再按距离选择一个桶放进去，取的时候逐个计算target和每个桶中对象的举例，详细参考closest函数，后面会贴出来。
距离公式满足：f(x,y)=256-8*n-map(x[n+1]^y[n+1]) 注：n为相同节点数量 map为一个负相关的映射关系。
简单来说就是相似越多，值越小。细节参考Node.go的logdist函数。 这里需要了解算法Kademlia，
.├── database.go //封装node数据库相关操作├── node.go //节点数据结构├── ntp.go //同步时间 ├── table.go //路由表├── udp.go //网络相关操作
其中最重要的就是table对象，table公共方法有：
- newTable 实例创建
- Self local节点获取
- ReadRandomNodes 随机读取几个节点
- Close 关闭
- Resolve 在周边查找某个节点
- Lookup 查找某个节点的邻近节点
逐个来分析这些方法：
newTable
- 1：生成对象实例（获取数据库客户端，LocalNode etc）
// If no node database was given, use an in-memory one db, err := newNodeDB(nodeDBPath, Version, ourID) if err != nil { return nil, err } tab := &Table{ net: t, db: db, self: NewNode(ourID, ourAddr.IP, uint16(ourAddr.Port), uint16(ourAddr.Port)), bonding: make(map[NodeID]*bondproc), bondslots: make(chan struct{}, maxBondingPingPongs), refreshReq: make(chan chan struct{}), initDone: make(chan struct{}), closeReq: make(chan struct{}), closed: make(chan struct{}), rand: mrand.New(mrand.NewSource(0)), ips: netutil.DistinctNetSet{Subnet: tableSubnet, Limit: tableIPLimit}, } - 2：载入引导节点，初始化k桶。
if err := tab.setFallbackNodes(bootnodes); err != nil { return nil, err } for i := 0; i < cap(tab.bondslots); i++ { tab.bondslots <- struct{}{} } for i := range tab.buckets { tab.buckets[i] = &bucket{ ips: netutil.DistinctNetSet{Subnet: bucketSubnet, Limit: bucketIPLimit}, } } - 3：将节点放入到桶里，生成一条协程用于刷新，验证节点。
tab.seedRand() tab.loadSeedNodes(false) //载入种子节点 // Start the background expiration goroutine after loading seeds so that the search for // seed nodes also considers older nodes that would otherwise be removed by the // expiration. tab.db.ensureExpirer() go tab.loop()
载入种子节点
func (tab *Table) loadSeedNodes(bond bool) { seeds := tab.db.querySeeds(seedCount, seedMaxAge) //数据库中的种子节点和引导节点合并 seeds = append(seeds, tab.nursery...) if bond { seeds = tab.bondall(seeds) //节点验证 } for i := range seeds { seed := seeds[i] age := log.Lazy{Fn: func() interface{} { return time.Since(tab.db.bondTime(seed.ID)) }} log.Debug("Found seed node in database", "id", seed.ID, "addr", seed.addr(), "age", age) tab.add(seed) //节点入桶 } } 节点入桶，同时也要检查ip等限制。
func (tab *Table) add(new *Node) { tab.mutex.Lock() defer tab.mutex.Unlock() b := tab.bucket(new.sha) //获取当前节点对应的桶 if !tab.bumpOrAdd(b, new) { // Node is not in table. Add it to the replacement list. tab.addReplacement(b, new) } } 桶的选择
func (tab *Table) bucket(sha common.Hash) *bucket { d := logdist(tab.self.sha, sha) //计算hash举例 if d <= bucketMinDistance { //这里按算法来看，只要hash前三位相等就会到第一个buckets return tab.buckets[0] } return tab.buckets[d-bucketMinDistance-1] } Resolve
根据Node的Id查找Node，先在当前的桶里面查找，查找一遍之后没找到就在周边的节点里面搜索一遍再找。
// Resolve searches for a specific node with the given ID. // It returns nil if the node could not be found. func (tab *Table) Resolve(targetID NodeID) *Node { // If the node is present in the local table, no // network interaction is required. hash := crypto.Keccak256Hash(targetID[:]) tab.mutex.Lock() //查找最近节点 cl := tab.closest(hash, 1) tab.mutex.Unlock() if len(cl.entries) > 0 && cl.entries[0].ID == targetID { return cl.entries[0] } // Otherwise, do a network lookup. //不存在 搜索邻居节点 result := tab.Lookup(targetID) for _, n := range result { if n.ID == targetID { return n } } return nil } 这里需要理解的函数是 closest，遍历所有桶的所有节点，查找最近的一个
// closest returns the n nodes in the table that are closest to the // given id. The caller must hold tab.mutex. func (tab *Table) closest(target common.Hash, nresults int) *nodesByDistance { // This is a very wasteful way to find the closest nodes but // obviously correct. I believe that tree-based buckets would make // this easier to implement efficiently. close := &nodesByDistance{target: target} for _, b := range tab.buckets { for _, n := range b.entries { close.push(n, nresults) } } return close } func (h *nodesByDistance) push(n *Node, maxElems int) { ix := sort.Search(len(h.entries), func(i int) bool { return distcmp(h.target, h.entries[i].sha, n.sha) > 0 }) if len(h.entries) < maxElems { h.entries = append(h.entries, n) } if ix == len(h.entries) { // farther away than all nodes we already have. // if there was room for it, the node is now the last element. } else { // slide existing entries down to make room // this will overwrite the entry we just appended. //近的靠前边 copy(h.entries[ix+1:], h.entries[ix:]) h.entries[ix] = n } } ReadRandomNodes
整体思路是先拷贝出来，再逐个桶的抽最上面的一个，剩下空桶移除，剩下的桶合并后，下一轮再抽桶的第一个节点，直到填满给定数据或者桶全部空掉。最后返回填到数组里面的数量。
// ReadRandomNodes fills the given slice with random nodes from the // table. It will not write the same node more than once. The nodes in // the slice are copies and can be modified by the caller. func (tab *Table) ReadRandomNodes(buf []*Node) (n int) { if !tab.isInitDone() { return 0 } tab.mutex.Lock() defer tab.mutex.Unlock() // Find all non-empty buckets and get a fresh slice of their entries. var buckets [][]*Node //拷贝节点 for _, b := range tab.buckets { if len(b.entries) > 0 { buckets = append(buckets, b.entries[:]) } } if len(buckets) == 0 { return 0 } // Shuffle the buckets. for i := len(buckets) - 1; i > 0; i-- { j := tab.rand.Intn(len(buckets)) buckets[i], buckets[j] = buckets[j], buckets[i] } // Move head of each bucket into buf, removing buckets that become empty. var i, j int for ; i < len(buf); i, j = i+1, (j+1)%len(buckets) { b := buckets[j] buf[i] = &(*b[0]) //取第一个节点 buckets[j] = b[1:] //移除第一个 if len(b) == 1 { //空桶移除 buckets = append(buckets[:j], buckets[j+1:]...) } if len(buckets) == 0 { break } } return i + 1 } Lookup
lookup会要求已知节点查找邻居节点，查找的邻居节点又递归的找它周边的节点
for { // ask the alpha closest nodes that we haven't asked yet for i := 0; i < len(result.entries) && pendingQueries < alpha; i++ { n := result.entries[i] if !asked[n.ID] { asked[n.ID] = true pendingQueries++ go func() { // Find potential neighbors to bond with r, err := tab.net.findnode(n.ID, n.addr(), targetID) if err != nil { // Bump the failure counter to detect and evacuate non-bonded entries fails := tab.db.findFails(n.ID) + 1 tab.db.updateFindFails(n.ID, fails) log.Trace("Bumping findnode failure counter", "id", n.ID, "failcount", fails) if fails >= maxFindnodeFailures { log.Trace("Too many findnode failures, dropping", "id", n.ID, "failcount", fails) tab.delete(n) } } reply <- tab.bondall(r) }() } } if pendingQueries == 0 { // we have asked all closest nodes, stop the search break } // wait for the next reply for _, n := range <-reply { //此处会阻塞请求 if n != nil && !seen[n.ID] { seen[n.ID] = true result.push(n, bucketSize) } } pendingQueries-- } 桶的维护
桶初始化完成后会进入一个循环逻辑，其中通过三个timer控制调整周期。
- 验证timer 间隔 10s左右
- 刷新timer 间隔 30 min
- 持久化timer 间隔 30s
revalidate = time.NewTimer(tab.nextRevalidateTime()) refresh = time.NewTicker(refreshInterval) copyNodes = time.NewTicker(copyNodesInterval)
刷新逻辑:重新加载种子节点，查找周边节点，随机三个节点，并查找这三个节点的周围节点。
func (tab *Table) doRefresh(done chan struct{}) { defer close(done) tab.loadSeedNodes(true) tab.lookup(tab.self.ID, false) for i := 0; i < 3; i++ { var target NodeID crand.Read(target[:]) tab.lookup(target, false) } } 验证逻辑:验证每个桶的最末尾节点，如果该节点通过验证则放到队首（验证过程是本地节点向它发送ping请求，如果回应pong则通过）
last, bi := tab.nodeToRevalidate() //取最后一个节点 if last == nil { // No non-empty bucket found. return } // Ping the selected node and wait for a pong. err := tab.ping(last.ID, last.addr()) //通信验证 tab.mutex.Lock() defer tab.mutex.Unlock() b := tab.buckets[bi] if err == nil { // The node responded, move it to the front. log.Debug("Revalidated node", "b", bi, "id", last.ID) b.bump(last) //提到队首 return } Peer/Server
相关文件
.├── dial.go //封装一个任务生成处理结构以及三种任务结构中（此处命名不太精确）├── message.go //定义一些数据的读写接口，以及对外的Send/SendItem函数├── peer.go //封装了Peer 包括消息读取 ├── rlpx.go //内部的握手协议├── server.go //初始化，维护Peer网络，还有一些对外的接口
这一层会不断的从路由中提取节点，提取出来的节点要经过身份验证，协议检查之后加入到peer里面，紧接着如果没有人使用这个peer，这个peer就会被删除，再重新选择一些节点出来继续这个流程，peer再其中是随生随销，这样做是为了平均的使用所有的节点，而不是仅仅依赖于特定的几个节点。因而这里从Server开始入手分析整个流程
Peers() //peer对象 PeerCount() //peer数量 AddPeer(node *discover.Node) //添加节点 RemovePeer(node *discover.Node) //删除节点 SubscribeEvents(ch chan *PeerEvent) //订阅内部的事件（节点的增加，删除） //以上四个属于对外的接口，不影响内部逻辑 Start() //server开始工作 SetupConn(fd net.Conn, flags connFlag, dialDest *discover.Node) //启动一个连接，经过两次验证之后，如果通过则加入到peer之中。
Start初始化
Start做了三件事，生成路由表于建立底层网络。生成DialState用于驱动维护本地peer的更新与死亡，监听本地接口用于信息应答。这里主要分析peer的维护过程。函数是run函数。
func (srv *Server) Start() (err error) { //**************初始化代码省略 if !srv.NoDiscovery && srv.DiscoveryV5 { unhandled = make(chan discover.ReadPacket, 100) sconn = &sharedUDPConn{conn, unhandled} } // node table if !srv.NoDiscovery { //路由表生成 cfg := discover.Config{ PrivateKey: srv.PrivateKey, AnnounceAddr: realaddr, NodeDBPath: srv.NodeDatabase, NetRestrict: srv.NetRestrict, Bootnodes: srv.BootstrapNodes, Unhandled: unhandled, } ntab, err := discover.ListenUDP(conn, cfg) if err != nil { return err } srv.ntab = ntab } if srv.DiscoveryV5 { //路由表生成 var ( ntab *discv5.Network err error ) if sconn != nil { ntab, err = discv5.ListenUDP(srv.PrivateKey, sconn, realaddr, "", srv.NetRestrict) //srv.NodeDatabase) } else { ntab, err = discv5.ListenUDP(srv.PrivateKey, conn, realaddr, "", srv.NetRestrict) //srv.NodeDatabase) } if err != nil { return err } if err := ntab.SetFallbackNodes(srv.BootstrapNodesV5); err != nil { return err } srv.DiscV5 = ntab } dynPeers := srv.maxDialedConns() //newDialState 对象生成，这个对象包含Peer的实际维护代码 dialer := newDialState(srv.StaticNodes, srv.BootstrapNodes, srv.ntab, dynPeers, srv.NetRestrict) // handshake 协议加载 srv.ourHandshake = &protoHandshake{Version: baseProtocolVersion, Name: srv.Name, ID: discover.PubkeyID(&srv.PrivateKey.PublicKey)} for _, p := range srv.Protocols { srv.ourHandshake.Caps = append(srv.ourHandshake.Caps, p.cap()) } // listen/dial //监听本地端口 if srv.ListenAddr != "" { if err := srv.startListening(); err != nil { return err } } if srv.NoDial && srv.ListenAddr == "" { srv.log.Warn("P2P server will be useless, neither dialing nor listening") } srv.loopWG.Add(1) //重要的一句，开个协程，在其中做peer的维护 go srv.run(dialer) srv.running = true return nil } run 开始peer的生成
该函数中定义了两个队列
runningTasks []task //正在执行的任务 queuedTasks []task //尚未执行的任务
定义了三个匿名函数
//从正在执行任务中删除任务 delTask := func(t task) { for i := range runningTasks { if runningTasks[i] == t { runningTasks = append(runningTasks[:i], runningTasks[i+1:]...) break } } } //开始一批任务 startTasks := func(ts []task) (rest []task) { i := 0 for ; len(runningTasks) < maxActiveDialTasks && i < len(ts); i++ { t := ts[i] srv.log.Trace("New dial task", "task", t) go func() { t.Do(srv); taskdone <- t }() runningTasks = append(runningTasks, t) } return ts[i:] } //启动开始一批任务再调用dialstate的newTasks函数生成一批任务，加载到任务队列里面 scheduleTasks := func() { // Start from queue first. queuedTasks = append(queuedTasks[:0], startTasks(queuedTasks)...) // Query dialer for new tasks and start as many as possible now. if len(runningTasks) < maxActiveDialTasks { nt := dialstate.newTasks(len(runningTasks)+len(queuedTasks), peers, time.Now()) queuedTasks = append(queuedTasks, startTasks(nt)...) } } 定义了一个循环，分不同的chanel执行对应的逻辑
for { //调度开始找生成任务 scheduleTasks() select { case <-srv.quit://退出 break running case n := <-srv.addstatic: //增加一个节点 该节点最终会生成一个dialTask //并在newTasks的时候加入到读列 srv.log.Debug("Adding static node", "node", n) dialstate.addStatic(n) case n := <-srv.removestatic: //直接删除该节点 节点不再参与维护，很快就会死掉了 dialstate.removeStatic(n) if p, ok := peers[n.ID]; ok { p.Disconnect(DiscRequested) } case op := <-srv.peerOp: // Peers 和 PeerCount 两个外部接口，只是读取peer信息 op(peers) srv.peerOpDone <- struct{}{} case t := <-taskdone: //task完成后会根据不同的任务类型进行相应的处理 srv.log.Trace("Dial task done", "task", t) dialstate.taskDone(t, time.Now()) delTask(t) case c := <-srv.posthandshake: //身份验证通过 if trusted[c.id] { // Ensure that the trusted flag is set before checking against MaxPeers. c.flags |= trustedConn } select { case c.cont <- srv.encHandshakeChecks(peers, inboundCount, c): case <-srv.quit: break running } case c := <-srv.addpeer: //身份协议验证通过 加入队列 err := srv.protoHandshakeChecks(peers, inboundCount, c) if err == nil { // The handshakes are done and it passed all checks. p := newPeer(c, srv.Protocols) // If message events are enabled, pass the peerFeed // to the peer if srv.EnableMsgEvents { p.events = &srv.peerFeed } name := truncateName(c.name) srv.log.Debug("Adding p2p peer", "name", name, "addr", c.fd.RemoteAddr(), "peers", len(peers)+1) go srv.runPeer(p) //触发事件 此处是最上层截取peer的位置，如果此物没有外部影响，那么这个peer很快就被销毁了 peerAdd++ fmt.Printf("--count %d--- add %d-- del %d--\n",len(peers),peerAdd,peerDel) peers[c.id] = p if p.Inbound() { inboundCount++ } } // The dialer logic relies on the assumption that // dial tasks complete after the peer has been added or // discarded. Unblock the task last. select { case c.cont <- err: case <-srv.quit: break running } case pd := <-srv.delpeer: //移除peer d := common.PrettyDuration(mclock.Now() - pd.created) pd.log.Debug("Removing p2p peer", "duration", d, "peers", len(peers)-1, "req", pd.requested, "err", pd.err) delete(peers, pd.ID()) peerDel++ fmt.Printf("--count %d--- add %d-- del %d--\n",len(peers),peerAdd,peerDel) if pd.Inbound() { inboundCount-- } } } 记住上面的代码，再来逐个的看：
scheduleTasks
scheduleTasks调度生成任务，生成的任务中有一种dialTask的任务，该任务结构如下
type dialTask struct { flags connFlag dest *discover.Node lastResolved time.Time resolveDelay time.Duration } func (t *dialTask) Do(srv *Server) { if t.dest.Incomplete() { if !t.resolve(srv) { return } } err := t.dial(srv, t.dest) //此处会调用到setupConn函数 if err != nil { log.Trace("Dial error", "task", t, "err", err) // Try resolving the ID of static nodes if dialing failed. if _, ok := err.(*dialError); ok && t.flags&staticDialedConn != 0 { if t.resolve(srv) { t.dial(srv, t.dest) } } } } dial最终回调用到setupConn函数，函数只保留重点的几句，篇幅有点长了
func (srv *Server) setupConn(c *conn, flags connFlag, dialDest *discover.Node) error { //身份验证码 获取设备，标识等信息 if c.id, err = c.doEncHandshake(srv.PrivateKey, dialDest); err != //此处会往chanel中添加连接对象，最终触发循环中的posthandshake分支 err = srv.checkpoint(c, srv.posthandshake) //协议验证 phs, err := c.doProtoHandshake(srv.ourHandshake) c.caps, c.name = phs.Caps, phs.Name //此处会往chanel中添加连接对象 最终触发循环中的addpeer分支 err = srv.checkpoint(c, srv.addpeer) } posthandshake 分支仅仅做了验证，addpeer做的事情就比较多了，重要的就是执行runPeer函数
func (srv *Server) runPeer(p *Peer) { // 广播 peer add srv.peerFeed.Send(&PeerEvent{ Type: PeerEventTypeAdd, Peer: p.ID(), }) // run the protocol remoteRequested, err := p.run() // // 广播 peer drop srv.peerFeed.Send(&PeerEvent{ Type: PeerEventTypeDrop, Peer: p.ID(), Error: err.Error(), }) //移除peer srv.delpeer <- peerDrop{p, err, remoteRequested} } func (p *Peer) run() (remoteRequested bool, err error) { //************* writeStart <- struct{}{} p.startProtocols(writeStart, writeErr) //************* //这一句阻塞性确保了peer的存活 p.wg.Wait() } func (p *Peer) startProtocols(writeStart <-chan struct{}, writeErr chan<- error) { p.wg.Add(len(p.running)) for _, proto := range p.running { proto := proto proto.closed = p.closed proto.wstart = writeStart proto.werr = writeErr var rw MsgReadWriter = proto if p.events != nil { rw = newMsgEventer(rw, p.events, p.ID(), proto.Name) } p.log.Trace(fmt.Sprintf("Starting protocol %s/%d", proto.Name, proto.Version)) go func() { //其他的都是为这一句做准备的，在以太坊中p2p就是靠这一句对上层暴露peer对象 err := proto.Run(p, rw) if err == nil { p.log.Trace(fmt.Sprintf("Protocol %s/%d returned", proto.Name, proto.Version)) err = errProtocolReturned } else if err != io.EOF { p.log.Trace(fmt.Sprintf("Protocol %s/%d failed", proto.Name, proto.Version), "err", err) } p.protoErr <- err p.wg.Done() }() } } 这样就可以可理出一条思路 scheduleTasks执行生成dialTask任务 dialTask任务执行过程中逐个填充posthandshake，addPeer这两个chanel。 addPeer执行时对上层暴露了Peer对象，完成后填充了delpeer，最后删除了Peer。
任务的生成
具体看代码中的注释
func (s *dialstate) newTasks(nRunning int, peers map[discover.NodeID]*Peer, now time.Time) []task { if s.start.IsZero() { s.start = now } var newtasks []task //这里声明了一个添加任务的函数 addDial := func(flag connFlag, n *discover.Node) bool { if err := s.checkDial(n, peers); err != nil { log.Trace("Skipping dial candidate", "id", n.ID, "addr", &net.TCPAddr{IP: n.IP, Port: int(n.TCP)}, "err", err) return false } s.dialing[n.ID] = flag //排除掉已经再测试的 newtasks = append(newtasks, &dialTask{flags: flag, dest: n}) return true } // Compute number of dynamic dials necessary at this point. needDynDials := s.maxDynDials //当前系统中最大连接数目 for _, p := range peers { //扣除已建立链接的peer if p.rw.is(dynDialedConn) { needDynDials-- } } for _, flag := range s.dialing { //扣除已建立链接的peer if flag&dynDialedConn != 0 { needDynDials-- } } //外部命令添加的节点 这种节点不占用needDynDials数目， //是为了保证手动加的节点能够起效 for id, t := range s.static { err := s.checkDial(t.dest, peers) switch err { case errNotWhitelisted, errSelf: log.Warn("Removing static dial candidate", "id", t.dest.ID, "addr", &net.TCPAddr{IP: t.dest.IP, Port: int(t.dest.TCP)}, "err", err) delete(s.static, t.dest.ID) case nil: s.dialing[id] = t.flags newtasks = append(newtasks, t) } } // If we don't have any peers whatsoever, try to dial a random bootnode. This // scenario is useful for the testnet (and private networks) where the discovery // table might be full of mostly bad peers, making it hard to find good ones. if len(peers) == 0 && len(s.bootnodes) > 0 && needDynDials > 0 && //检查引导节点 因为引导节点比搜索到的节点更大概率靠谱 因而比较靠前 now.Sub(s.start) > fallbackInterval { bootnode := s.bootnodes[0] s.bootnodes = append(s.bootnodes[:0], s.bootnodes[1:]...) s.bootnodes = append(s.bootnodes, bootnode) if addDial(dynDialedConn, bootnode) { needDynDials-- } } //随机的从路由中抽取最大节点的二分之一 randomCandidates := needDynDials / 2 if randomCandidates > 0 { n := s.ntab.ReadRandomNodes(s.randomNodes) for i := 0; i < randomCandidates && i < n; i++ { if addDial(dynDialedConn, s.randomNodes[i]) { needDynDials-- } } } // 从lookupbuf中抽取 i := 0 for ; i < len(s.lookupBuf) && needDynDials > 0; i++ { if addDial(dynDialedConn, s.lookupBuf[i]) { needDynDials-- } } s.lookupBuf = s.lookupBuf[:copy(s.lookupBuf, s.lookupBuf[i:])] // 如果还是不够，路由再去搜索节点 if len(s.lookupBuf) < needDynDials && !s.lookupRunning { s.lookupRunning = true newtasks = append(newtasks, &discoverTask{}) } // wait if nRunning == 0 && len(newtasks) == 0 && s.hist.Len() > 0 { t := &waitExpireTask{s.hist.min().exp.Sub(now)} newtasks = append(newtasks, t) } return newtasks } 消息发送
另一个是message中的Send，SendItem函数 实现了MsgWriter的对象都可以调用这个函数写入，觉得这里没什么必要，完全可以封装到peer里面去，不过它上层做广播的时候确实是调用的这两个函数。
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}) } func SendItems(w MsgWriter, msgcode uint64, elems ...interface{}) error { return Send(w, msgcode, elems) } 以太坊上层调用
Peer/PeerSet
文件：go-ethereum/eth/peer.go
定义了两个struct，Peer和PeerSet。Peer封装了底层的p2p.Peer,集成了一些和业务相关的方法，比如SendTransactions，SendNewBlock等。PeerSet是Peer的集合
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 } type peerSet struct { peers map[string]*peer lock sync.RWMutex closed bool } Peer注册/注销
文件：go-ethereum/eth/handler.go manager.handle在检查了peer后会把这个peer注册到peerset中，表示此peer可用，发生错误后peerset注销该peer，返回错误，最后再Server中销毁。
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() //此处如果顺利会进入for循环 如果失败返回错误我会销毁掉这个peer 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 }, }) } 参考
源码：
Kademlia算法：