本文作者：先河系统杨尉；原创作品，转载请注明出处
目录
6 filecoin源码协议层分析之hello握手协议
6.3.1 数据结构
6.3.2 方法
6.3.3 函数
6.3.4 实例化及业务逻辑
6.1 目的
6.2 源码信息
6.3 源码分析
6.1 目的
处理节点上线后的区块同步握手。
6.2 源码信息
version
master分支 619b0eb1（2019年３月２日）
package
hello
location
protocol/hello
node/node.go
6.3 源码分析
6.3.1 数据结构
定义协议名称
// Protocol is the libp2p protocol identifier for the hello protocol.const protocol = "/fil/hello/1.0.0"
定义hello协议消息体结构
TipSet切片
TipSet高度
创世区块cid
// Message is the data structure of a single message in the hello protocol.type Message struct {
HeaviestTipSetCids []cid.Cid
HeaviestTipSetHeight uint64
GenesisHash cid.Cid
}同步回调函数类型定义
type syncCallback func(from peer.ID, cids []cid.Cid, height uint64)
获取Tipset函数类型定义
type getTipSetFunc func() types.TipSet
Handler结构体,当连接到其他节点的时候，其一,会发送包含本节点信息的hello 消息给对端节点; 其二, 对端也会回复一个包含对端节点信息的消息体过来。
host 对应libp2p上的主机
创世区块cid
区块同步回调函数
获取TipSet的函数
// Handler implements the 'Hello' protocol handler. Upon connecting to a new// node, we send them a message containing some information about the state of// our chain, and receive the same information from them. This is used to// initiate a chainsync and detect connections to forks.type Handler struct {
host host.Host
genesis cid.Cid // chainSyncCB is called when new peers tell us about their chain
chainSyncCB syncCallback // getHeaviestTipSet is used to retrieve the current heaviest tipset
// for filling out our hello messages.
getHeaviestTipSet getTipSetFunc
}错误的创世区块
// ErrBadGenesis is the error returned when a missmatch in genesis blocks happens.var ErrBadGenesis = fmt.Errorf("bad genesis block")以上基本是作为hello客户端的一些定义，以下作为hello服务端的一些定义
// New peer connection notificationstype helloNotify Handler// 连接超时时间const helloTimeout = time.Second * 10
6.3.2 方法
6.3.2.1 Handler 方法
流函数处理，接收远端节点的hello消息
func (h *Handler) handleNewStream(s net.Stream) {
defer s.Close() // nolint: errcheck
//获取远端节点实例
from := s.Conn().RemotePeer() var hello Message // 读取流信息到hello结构体中
if err := cbu.NewMsgReader(s).ReadMsg(&hello); err != nil {
log.Warningf("bad hello message from peer %s: %s", from, err) return
} // 调用processHelloMessage方法对接收到的消息进行处理
switch err := h.processHelloMessage(from, &hello); err { // 如果创世区块不一样，关闭流连接退出，不予处理
case ErrBadGenesis:
log.Warningf("genesis cid: %s does not match: %s, disconnecting from peer: %s", &hello.GenesisHash, h.genesis, from)
s.Conn().Close() // nolint: errcheck
return
case nil: // ok, noop
default:
log.Error(err)
}
}处理hello消息
func (h *Handler) processHelloMessage(from peer.ID, msg *Message) error { // 如果创世区块不一样，报错
if !msg.GenesisHash.Equals(h.genesis) { return ErrBadGenesis
} // 调用区块同步方法
// 此回调函数实在node包实例化hello协议的时候中定义的
h.chainSyncCB(from, msg.HeaviestTipSetCids, msg.HeaviestTipSetHeight) return nil
}响应远端节点的连接，回复hello消息体
func (h *Handler) getOurHelloMessage() *Message {
heaviest := h.getHeaviestTipSet()
height, err := heaviest.Height() if err != nil {
panic("somehow heaviest tipset is empty")
} return &Message{
GenesisHash: h.genesis,
HeaviestTipSetCids: heaviest.ToSortedCidSet().ToSlice(),
HeaviestTipSetHeight: height,
}
}
func (h *Handler) sayHello(ctx context.Context, p peer.ID) error {
s, err := h.host.NewStream(ctx, p, protocol) if err != nil { return err
}
defer s.Close() // nolint: errcheck
//获取本节点的hello消息体
msg := h.getOurHelloMessage() //向远端节点发送消息体
return cbu.NewMsgWriter(s).WriteMsg(&msg)
}6.3.2.2 helloNotify方法
hello方法，返回一个handler实例
func (hn *helloNotify) hello() *Handler { return (*Handler)(hn)
}helloNotify实现了libp2p-net/interface.go中的Notifiee接口
func (hn *helloNotify) Connected(n net.Network, c net.Conn) { go func() {
ctx, cancel := context.WithTimeout(context.Background(), helloTimeout)
defer cancel()
p := c.RemotePeer() // 有其他节点连接的时候调用sayHello,发送hello消息体
if err := hn.hello().sayHello(ctx, p); err != nil { log.Warningf("failed to send hello handshake to peer %s: %s", p, err)
}
}()
}
func (hn *helloNotify) Listen(n net.Network, a ma.Multiaddr) {}
func (hn *helloNotify) ListenClose(n net.Network, a ma.Multiaddr) {}
func (hn *helloNotify) Disconnected(n net.Network, c net.Conn) {}
func (hn *helloNotify) OpenedStream(n net.Network, s net.Stream) {}
func (hn *helloNotify) ClosedStream(n net.Network, s net.Stream) {}6.3.3 函数
创建hello实例
// New creates a new instance of the hello protocol and registers it to// the given host, with the provided callbacks.func New(h host.Host, gen cid.Cid, syncCallback syncCallback, getHeaviestTipSet getTipSetFunc) *Handler {
hello := &Handler{
host: h,
genesis: gen,
chainSyncCB: syncCallback,
getHeaviestTipSet: getHeaviestTipSet,
} //设置流处理回调函数
h.SetStreamHandler(protocol, hello.handleNewStream) //注册网络状态改变通知回调函数
// register for connection notifications
h.Network().Notify((*helloNotify)(hello)) return hello
}//上文中的helloNotify 实现了libp2p-net/interface.go中的Notifiee接口// Notifiee is an interface for an object wishing to receive// notifications from a Network.type Notifiee interface {
Listen(Network, ma.Multiaddr) // called when network starts listening on an addr
ListenClose(Network, ma.Multiaddr) // called when network stops listening on an addr
Connected(Network, Conn) // called when a connection opened
Disconnected(Network, Conn) // called when a connection closed
OpenedStream(Network, Stream) // called when a stream opened
ClosedStream(Network, Stream) // called when a stream closed
// TODO
// PeerConnected(Network, peer.ID) // called when a peer connected
// PeerDisconnected(Network, peer.ID) // called when a peer disconnected}6.3.4 实例化及业务逻辑
location: node/node.go
Node节点中定义了hello服务
type Node struct {
......
HelloSvc *hello.Handler
......
}启动hello服务
// Start boots up the node.func (node *Node) Start(ctx context.Context) error {
...... // Start up 'hello' handshake service
// 定义区块同步的回调函数
syncCallBack := func(pid libp2ppeer.ID, cids []cid.Cid, height uint64) { // TODO it is possible the syncer interface should be modified to
// make use of the additional context not used here (from addr + height).
// To keep things simple for now this info is not used.
// 触发调用会启动同步区块的动作
err := node.Syncer.HandleNewBlocks(context.Background(), cids) if err != nil { log.Infof("error handling blocks: %s", types.NewSortedCidSet(cids...).String())
}
} //实例化hello服务
node.HelloSvc = hello.New(node.Host(), node.ChainReader.GenesisCid(), syncCallBack, node.ChainReader.Head)
......
}
作者：杨尉
链接：https://www.jianshu.com/p/6e40c4e6235b
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