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这个仓库代码量太大了 以读为主 不写了
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impact-eintr
@@ -1,245 +0,0 @@
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package fdbased
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import (
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"log"
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"syscall"
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"github.com/impact-eintr/netstack/tcpip"
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"github.com/impact-eintr/netstack/tcpip/buffer"
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"github.com/impact-eintr/netstack/tcpip/header"
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"github.com/impact-eintr/netstack/tcpip/link/rawfile"
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"github.com/impact-eintr/netstack/tcpip/stack"
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)
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// 负责底层网卡的io读写以及数据分发
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type endpoint struct {
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// 发送和接收数据的文件描述符
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fd int
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// 单个帧的最大长度
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mtu uint32
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// 以太网头部长度
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hdrSize int
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// 网卡地址
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addr tcpip.LinkAddress
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// 网卡的能力
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caps stack.LinkEndpointCapabilities
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// closed is a function to be called when the FD's peer (if any) closes
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// its end of the communication pipe.
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closed func(*tcpip.Error)
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// 为了提高从磁盘读取数据到内存的效率，引入了IO向量机制，IO向量即struct iovec，
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// 在API接口在readv和writev中使用，当然其他地方也较多的使用它。
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iovecs []syscall.Iovec
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views []buffer.View
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dispatcher stack.NetworkDispatcher
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// handleLocal指示发往自身的数据包是由内部netstack处理（true）还是转发到FD端点（false）。
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// Resend packets back to netstack if destined to itself
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// Add option to redirect packet back to netstack if it's destined to itself.
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// This fixes the problem where connecting to the local NIC address would
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// not work, e.g.:
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// echo bar | nc -l -p 8080 &
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// echo foo | nc 192.168.0.2 8080
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handleLocal bool
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}
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// 创建fdbase端的一些选项参数
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type Options struct {
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FD int
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MTU uint32
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ClosedFunc func(*tcpip.Error)
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Address tcpip.LinkAddress
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ResolutionRequired bool
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SaveRestore bool
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ChecksumOffload bool
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DisconnectOk bool
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HandleLocal bool
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TestLossPacket func(data []byte) bool
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}
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// 从NIC读取数据的多级缓存配置
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var BufConfig = []int{128, 256, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768}
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// 根据选项参数创建一个链路层的endpoint，并返回该endpoint的id
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func New(opts *Options) tcpip.LinkEndpointID {
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syscall.SetNonblock(opts.FD, true)
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caps := stack.LinkEndpointCapabilities(0)
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if opts.ResolutionRequired {
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caps |= stack.CapabilityResolutionRequired
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}
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if opts.ChecksumOffload {
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caps |= stack.CapabilityChecksumOffload
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}
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if opts.SaveRestore {
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caps |= stack.CapabilitySaveRestore
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}
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if opts.DisconnectOk {
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caps |= stack.CapabilityDisconnectOk
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}
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e := &endpoint{
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fd: opts.FD,
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mtu: opts.MTU,
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caps: caps,
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closed: opts.ClosedFunc,
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addr: opts.Address,
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hdrSize: header.EthernetMinimumSize,
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views: make([]buffer.View, len(BufConfig)),
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iovecs: make([]syscall.Iovec, len(BufConfig)),
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handleLocal: opts.HandleLocal,
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}
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// 全局注册链路层设备
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return stack.RegisterLinkEndpoint(e)
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}
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func (e *endpoint) MTU() uint32 {
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return e.mtu
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}
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// Attach 启动从文件描述符中读取数据包的goroutine 并通过提供的分发函数来分发数据报
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func (e *endpoint) Attach(dispatcher stack.NetworkDispatcher) {
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e.dispatcher = dispatcher
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// 链接端点不可靠 保存传输端点后 它们将停止发送传出数据包 并拒绝所有传入数据包
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go e.dispatchLoop()
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}
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func (e *endpoint) IsAttached() bool {
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return e.dispatcher != nil
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}
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func (e *endpoint) Capabilities() stack.LinkEndpointCapabilities {
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return e.caps
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}
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func (e *endpoint) MaxHeaderLength() uint16 {
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return uint16(e.hdrSize)
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}
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func (e *endpoint) LinkAddress() tcpip.LinkAddress {
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return e.addr
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}
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// 循环地从fd中读取数据 然后将数据包分发给协议栈
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func (e *endpoint) dispatchLoop() *tcpip.Error {
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for {
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cont, err := e.dispatch()
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if err != nil || !cont {
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e.closed(err)
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}
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return err
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}
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}
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// 从网卡中读取一个数据报
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func (e *endpoint) dispatch() (bool, *tcpip.Error) {
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// 读取数据缓存的分配
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e.allocateViews(BufConfig)
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// 从网卡中读取数据
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n, err := rawfile.BlockingReadv(e.fd, e.iovecs)
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if err != nil {
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return false, err
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}
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// 如果比头部长度还小 直接丢弃
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if n <= e.hdrSize {
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return false, err
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}
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var (
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p tcpip.NetworkProtocolNumber
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remoteLinkAddr, localLinkAddr tcpip.LinkAddress
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)
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// 获取以太网头部信息
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eth := header.Ethernet(e.views[0])
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p = eth.Type()
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remoteLinkAddr = eth.SourceAddress()
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localLinkAddr = eth.DestinationAddress()
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used := e.capViews(n, BufConfig)
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vv := buffer.NewVectorisedView(n, e.views[:used])
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// 将数据内容删除以太网头部信息 也就是将数据指针指向网络层的第一个字节
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vv.TrimFront(e.hdrSize)
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// 调用nic.DeliverNetworkPacket 来分发网络层数据
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log.Printf("read from nic %d byte", e.hdrSize+vv.Size())
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e.dispatcher.DeliverNetworkPacket(e, remoteLinkAddr, localLinkAddr, p, vv)
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for i := 0; i < used; i++ {
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e.views[i] = nil
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}
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return true, nil
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}
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// 按照bugConfig的长度分配内存大小
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// 注意e.views和e.iovecs共用相同的内存块
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func (e *endpoint) allocateViews(bufConfig []int) {
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for i, v := range e.views {
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if v != nil {
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break
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}
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b := buffer.NewView(bufConfig[i])
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e.views[i] = b
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e.iovecs[i] = syscall.Iovec{
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Base: &b[0],
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Len: uint64(len(b)),
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}
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}
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}
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func (e *endpoint) capViews(n int, buffers []int) int {
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c := 0
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for i, s := range buffers {
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c += s
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if c >= n {
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e.views[i].CapLength((s - (c - n)))
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return i + 1
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}
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}
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return len(buffers)
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}
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func (e *endpoint) WritePacket(r *stack.Route, hdr buffer.Prependable, payload buffer.VectorisedView,
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protocol tcpip.NetworkProtocolNumber) *tcpip.Error {
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// 如果目标地址就是设备本身自己 那么将报文重新返回给协议栈
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if e.handleLocal && r.LocalAddress != "" && r.LocalAddress == r.RemoteAddress {
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views := make([]buffer.View, 1, 1+len(payload.Views()))
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views[0] = hdr.View()
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views = append(views, payload.Views()...)
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vv := buffer.NewVectorisedView(len(views[0])+payload.Size(), views)
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e.dispatcher.DeliverNetworkPacket(e, r.RemoteLinkAddress, r.LocalLinkAddress, protocol, vv)
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return nil
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}
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// 封装增加以太网头部
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eth := header.Ethernet(hdr.Prepend(header.EthernetMinimumSize))
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ethHdr := &header.EthernetFields{
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DstAddr: r.RemoteLinkAddress,
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Type: protocol,
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}
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// 如果路由信息中有配置源MAC地址 那么使用该地址 如果没有则使用网卡的地址
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if r.LocalLinkAddress != "" {
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ethHdr.SrcAddr = r.LocalLinkAddress
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} else {
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ethHdr.SrcAddr = e.addr
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}
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eth.Encode(ethHdr)
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// 写入网卡中
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log.Printf("write to nic %d bytes", hdr.UsedLength()+payload.Size())
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if payload.Size() == 0 {
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return rawfile.NonBlockingWrite(e.fd, hdr.View())
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}
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return rawfile.NonBlockingWrite2(e.fd, hdr.View(), payload.ToView())
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}
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