bytom源码分析-p2p网络-地址簙

bytom源码分析-P2P网络-地址簿

简介

https://github.com/Bytom/bytom

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介绍

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

地址簿格式

~/Library/Bytom/addrbook.json

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{
"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
]
}
]
}

地址类型

在addrbook中存储的地址有两种:
p2p/addrbook.go

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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

地址簿相关结构体

地址簿

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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

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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

初始化地址簿

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// 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)
}
}

bytomd启动时加载本地地址簿

loadFromFile在bytomd启动时,首先会加载本地的地址簿

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// 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
}

定时更新地址簿

bytomd会定时更新本地地址簿,默认2分钟一次

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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")
}
}

添加新地址

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

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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())
}

选择最优节点

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

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// 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
}

移除一个地址

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

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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())
}

转载链接:https://shanhuhai5739.github.io/2018/04/28/bytom%E6%BA%90%E7%A0%81%E5%88%86%E6%9E%90-P2P%E7%BD%91%E7%BB%9C-%E5%9C%B0%E5%9D%80%E7%B0%BF/

-------------本文结束感谢您的阅读-------------

本文标题:bytom源码分析-p2p网络-地址簙

文章作者:Wuman

发布时间:2018年11月10日 - 15:11

最后更新:2018年11月10日 - 16:11

原始链接:http://yoursite.com/2018/11/10/bytom源码分析-p2p网络-地址簙/

许可协议: 署名-非商业性使用-禁止演绎 4.0 国际 转载请保留原文链接及作者。