Derek解读Bytom源码-P2P网络 地址簿

摘要：作者简介地址地址本章介绍代码网络中地址簿作者使用操作系统，其他平台也大同小异介绍用于存储网络中保留最近的对端节点地址在下，默认的地址簿路径存储在地址簿格式地址类型在中存储的地址有两种标识新地址，不可靠地址未成功连接过。

作者：Derek

Github地址：https://github.com/Bytom/bytom

Gitee地址：https://gitee.com/BytomBlockc...

本章介绍bytom代码P2P网络中addrbook地址簿

作者使用MacOS操作系统，其他平台也大同小异
Golang Version: 1.8

addrbook用于存储P2P网络中保留最近的对端节点地址
在MacOS下，默认的地址簿路径存储在~/Library/Bytom/addrbook.json

~/Library/Bytom/addrbook.json

{
    "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
            ]
        }
    ]
}

在addrbook中存储的地址有两种：
p2p/addrbook.go

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
)

注意: 一个地址的类型变更不在此文章中做介绍，后期的文章会讨论该问题

地址簿

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
}

已知地址

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
}

routabilityStrict参数表示地址簿是否存储的ip是否可路由。可路由是根据RFC划分，具体参考资料：RFC标准

// 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, don"t 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)
    }
}

loadFromFile在bytomd启动时，首先会加载本地的地址簿

// 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 doesn"t 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
}

bytomd会定时更新本地地址簿，默认2分钟一次

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, "", "	")
    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")
    }
}

当peer之间交换addr时，节点会收到对端节点已知的地址信息，这些信息会被当前节点添加到地址簿中

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())
}

地址簿中存储众多地址，在p2p网络中需选择最优的地址去连接
PickAddress(newBias int)函数中newBias是由pex_reactor产生的地址评分。如何计算地址分数在其他章节中再讲
根据地址评分随机选择地址可增加区块链安全性

// 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
}

当一个地址被标记为Bad时则从地址集中移除。目前bytomd的代码版本并未调用过

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())
}