以太坊 p2p Server 原理及实现
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2022-07-01 15:29:22
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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：https://github.com/ethereum/go-ethereum/tree/master/p2p
Kademlia算法：https://en.wikipedia.org/wiki/Kademlia
转自：（魂祭心） https://my.oschina.net/hunjixin/blog/1803029
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