go ethereum之p2p

简介

p2p是以太坊节点网络层的骨架，夹在底层 TCP/UDP 和应用协议（eth、snap、les）之间，管三件事：节点发现（谁在线）、连接管理（怎么连上、怎么断）、消息多路复用（连上了跑什么协议）

重要结构

主要有

• Server
• Peer：表示一个连接

Server结构定义为

typeServerstruct{// Config fields may not be modified while the server is running.Config// Hooks for testing. These are useful because we can inhibit// the whole protocol stack.newTransportfunc(net.Conn,*ecdsa.PublicKey)transport newPeerHookfunc(*Peer)listenFuncfunc(network,addrstring)(net.Listener,error)lock sync.Mutex// protects runningrunningboollistener net.Listener ourHandshake*protoHandshake loopWG sync.WaitGroup// loop, listenLooppeerFeed event.Feed log log.Logger nodedb*enode.DB localnode*enode.LocalNode discv4*discover.UDPv4 discv5*discover.UDPv5 discmix*enode.FairMix dialsched*dialScheduler// This is read by the NAT port mapping loop.portMappingRegisterchan*portMapping// Channels into the run loop.quitchanstruct{}addtrustedchan*enode.Node removetrustedchan*enode.Node peerOpchanpeerOpFunc peerOpDonechanstruct{}delpeerchanpeerDrop checkpointPostHandshakechan*conn checkpointAddPeerchan*conn// State of run loop and listenLoop.inboundHistory expHeap}

Config：p2p服务端配置
listener：监听器，接受连接
discv4,discv5,discmix：节点发现
dialsched：向外连接
peerOp：对接操作
localnode：结点的ENR

Peer结构定义为

typePeerstruct{rw*conn runningmap[string]*protoRW log log.Logger created mclock.AbsTime wg sync.WaitGroup protoErrchanerrorclosedchanstruct{}pingRecvchanstruct{}discchanDiscReason// events receives message send / receive events if setevents*event.Feed testPipe*MsgPipeRW// for testing}

启动

通过Start启动p2p,主要作以下事项

• setupLocalNode：创建dev2p handshake和localnode
• setupPortMapping：开启端口映射循环，根据NAT配置执行不同的协程
• setupListening：开启监听协程listenLoop处理外部连接
• setupDiscovery：开启节点发现，根据配置开启发现服务discv4,discv5
• setupDialScheduler：开启拨号调度器dialScheduler，开启两个协程readNodes和loop
• srv.run()：处理通道事件，如新连接等