解读Bytom源码：P2P网络 地址簿

{ “Key”: “359be6d08bc0c6e21c84bbb2”, “Addrs”: [ { “Addr”: { “IP”: “122.224.11.144”, “Port”: 46657 }, “Src”: { “IP”: “198.74.61.131”, “Port”: 46657 }, “Attempts”: 0, “LastAttempt”: “2018-05-04T12:58:23.894057702+08:00”, “LastSuccess”: “0001-01-01T00:00:00Z”, “BucketType”: 1, “Buckets”: [ 181, 10 ] } ] }

const ( bucketTypeNew = 0x01 // 标识新地址，不可靠地址（未成功连接过）。只存储在一个bucket中 bucketTypeOld = 0x02 // 标识旧地址，可靠地址（已成功连接过）。可以存储在多个bucket中，最多为maxNewBucketsPerAddress个 )

type AddrBook struct { cmn.BaseService mtx sync.Mutex filePath string // 地址簿路径 routabilityStrict bool // 是否可路由，默认为true rand *rand.Rand key string // 地址簿标识，用于计算addrNew和addrOld的索引 ourAddrs map[string]*NetAddress // 存储本地网络地址，用于添加p2p地址时做排除使用 addrLookup map[string]*knownAddress // 存储新、旧地址集，用于查询 addrNew []map[string]*knownAddress // 存储新地址 addrOld []map[string]*knownAddress // 存储旧地址 wg sync.WaitGroup nOld int // 旧地址数量 nNew int // 新地址数量 }

type knownAddress struct { Addr *NetAddress // 已知peer的addr Src *NetAddress // 已知peer的addr的来源addr Attempts int32 // 连接peer的重试次数 LastAttempt time.Time // 最近一次尝试连接的时间 LastSuccess time.Time // 最近一次尝试成功连接的时间 BucketType byte // 地址的类型（表示可靠地址或不可靠地址） Buckets []int // 当前addr所属的buckets }

// NewAddrBook creates a new address book. // Use Start to begin processing asynchronous address updates. func NewAddrBook(filePath string, routabilityStrict bool) *AddrBook { am := &AddrBook{ rand: rand.New(rand.NewSource(time.Now().UnixNano())), ourAddrs: make(map[string]*NetAddress), addrLookup: make(map[string]*knownAddress), filePath: filePath, routabilityStrict: routabilityStrict, } am.init() am.BaseService = *cmn.NewBaseService(nil, “AddrBook”, am) return am } // When modifying this, dont forget to update loadFromFile() func (a *AddrBook) init() { // 地址簿唯一标识 a.key = crypto.CRandHex(24) // 24/2 * 8 = 96 bits // New addr buckets， 默认为256个大小 a.addrNew = make([]map[string]*knownAddress, newBucketCount) for i := range a.addrNew { a.addrNew[i] = make(map[string]*knownAddress) } // Old addr buckets，默认为64个大小 a.addrOld = make([]map[string]*knownAddress, oldBucketCount) for i := range a.addrOld { a.addrOld[i] = make(map[string]*knownAddress) } }

// OnStart implements Service. func (a *AddrBook) OnStart() error { a.BaseService.OnStart() a.loadFromFile(a.filePath) a.wg.Add(1) go a.saveRoutine() return nil } // Returns false if file does not exist. // cmn.Panics if file is corrupt. func (a *AddrBook) loadFromFile(filePath string) bool { // If doesnt exist, do nothing. // 如果本地地址簿不存在则直接返回 _, err := os.Stat(filePath) if os.IsNotExist(err) { return false } // 加载地址簿json内容 // Load addrBookJSON{} r, err := os.Open(filePath) if err != nil { cmn.PanicCrisis(cmn.Fmt(“Error opening file %s: %v”, filePath, err)) } defer r.Close() aJSON := &addrBookJSON{} dec := json.NewDecoder(r) err = dec.Decode(aJSON) if err != nil { cmn.PanicCrisis(cmn.Fmt(“Error reading file %s: %v”, filePath, err)) } // 填充addrNew、addrOld等 // Restore all the fields… // Restore the key a.key = aJSON.Key // Restore .addrNew & .addrOld for _, ka := range aJSON.Addrs { for _, bucketIndex := range ka.Buckets { bucket := a.getBucket(ka.BucketType, bucketIndex) bucket[ka.Addr.String()] = ka } a.addrLookup[ka.Addr.String()] = ka if ka.BucketType == bucketTypeNew { a.nNew++ } else { a.nOld++ } } return true }

func (a *AddrBook) saveRoutine() { dumpAddressTicker := time.NewTicker(dumpAddressInterval) out: for { select { case <-dumpAddressTicker.C: a.saveToFile(a.filePath) case <-a.Quit: break out } } dumpAddressTicker.Stop() a.saveToFile(a.filePath) a.wg.Done() log.Info(“Address handler done”) } func (a *AddrBook) saveToFile(filePath string) { log.WithField(“size”, a.Size()).Info(“Saving AddrBook to file”) a.mtx.Lock() defer a.mtx.Unlock() // Compile Addrs addrs := []*knownAddress{} for _, ka := range a.addrLookup { addrs = append(addrs, ka) } aJSON := &addrBookJSON{ Key: a.key, Addrs: addrs, } jsonBytes, err := json.MarshalIndent(aJSON, “”, “\t”) if err != nil { log.WithField(“err”, err).Error(“Failed to save AddrBook to file”) return } err = cmn.WriteFileAtomic(filePath, jsonBytes, 0644) if err != nil { log.WithFields(log.Fields{ “file”: filePath, “err”: err, }).Error(“Failed to save AddrBook to file”) } }

func (a *AddrBook) AddAddress(addr *NetAddress, src *NetAddress) { a.mtx.Lock() defer a.mtx.Unlock() log.WithFields(log.Fields{ “addr”: addr, “src”: src, }).Debug(“Add address to book”) a.addAddress(addr, src) } func (a *AddrBook) addAddress(addr, src *NetAddress) { // 验证地址是否为可路由地址 if a.routabilityStrict && !addr.Routable() { log.Error(cmn.Fmt(“Cannot add non-routable address %v”, addr)) return } // 验证地址是否为本地节点地址 if _, ok := a.ourAddrs[addr.String()]; ok { // Ignore our own listener address. return } // 验证地址是否存在地址集中 // 如果存在：则判断该地址是否为old可靠地址、是否超过了最大buckets中。否则根据该地址已经被ka.Buckets引用的个数来随机决定是否添加到地址集中 // 如果不存在：则添加到地址集中。并标识为bucketTypeNew地址类型 ka := a.addrLookup[addr.String()] if ka != nil { // Already old. if ka.isOld() { return } // Already in max new buckets. if len(ka.Buckets) == maxNewBucketsPerAddress { return } // The more entries we have, the less likely we are to add more. factor := int32(2 * len(ka.Buckets)) if a.rand.Int31n(factor) != 0 { return } } else { ka = newKnownAddress(addr, src) } // 找到该地址在地址集的索引位置并添加 bucket := a.calcNewBucket(addr, src) a.addToNewBucket(ka, bucket) log.Info(“Added new address “, “address:”, addr, ” total:”, a.size()) }

// Pick an address to connect to with new/old bias. func (a *AddrBook) PickAddress(newBias int) *NetAddress { a.mtx.Lock() defer a.mtx.Unlock() if a.size() == 0 { return nil } // newBias地址分数限制在0-100分数之间 if newBias > 100 { newBias = 100 } if newBias < 0 { newBias = 0 } // Bias between new and old addresses. oldCorrelation := math.Sqrt(float64(a.nOld)) * (100.0 – float64(newBias)) newCorrelation := math.Sqrt(float64(a.nNew)) * float64(newBias) // 根据地址分数计算是否从addrOld或addrNew中随机选择一个地址 if (newCorrelation+oldCorrelation)*a.rand.Float64() < oldCorrelation { // pick random Old bucket. var bucket map[string]*knownAddress = nil num := 0 for len(bucket) == 0 && num < oldBucketCount { bucket = a.addrOld[a.rand.Intn(len(a.addrOld))] num++ } if num == oldBucketCount { return nil } // pick a random ka from bucket. randIndex := a.rand.Intn(len(bucket)) for _, ka := range bucket { if randIndex == 0 { return ka.Addr } randIndex– } cmn.PanicSanity(“Should not happen”) } else { // pick random New bucket. var bucket map[string]*knownAddress = nil num := 0 for len(bucket) == 0 && num < newBucketCount { bucket = a.addrNew[a.rand.Intn(len(a.addrNew))] num++ } if num == newBucketCount { return nil } // pick a random ka from bucket. randIndex := a.rand.Intn(len(bucket)) for _, ka := range bucket { if randIndex == 0 { return ka.Addr } randIndex– } cmn.PanicSanity(“Should not happen”) } return nil }

func (a *AddrBook) MarkBad(addr *NetAddress) { a.RemoveAddress(addr) } // RemoveAddress removes the address from the book. func (a *AddrBook) RemoveAddress(addr *NetAddress) { a.mtx.Lock() defer a.mtx.Unlock() ka := a.addrLookup[addr.String()] if ka == nil { return } log.WithField(“addr”, addr).Info(“Remove address from book”) a.removeFromAllBuckets(ka) } func (a *AddrBook) removeFromAllBuckets(ka *knownAddress) { for _, bucketIdx := range ka.Buckets { bucket := a.getBucket(ka.BucketType, bucketIdx) delete(bucket, ka.Addr.String()) } ka.Buckets = nil if ka.BucketType == bucketTypeNew { a.nNew– } else { a.nOld– } delete(a.addrLookup, ka.Addr.String()) }