mirror of
https://github.com/impact-eintr/netstack.git
synced 2025-10-21 11:49:25 +08:00
145 lines
4.1 KiB
Go
145 lines
4.1 KiB
Go
package fdbased
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import (
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"netstack/tcpip"
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"netstack/tcpip/buffer"
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"netstack/tcpip/header"
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"netstack/tcpip/link/rawfile"
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"netstack/tcpip/stack"
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"syscall"
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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{1<<7, 1<<8, 1<<8, 1<<9, 1<<10, 1<<11, 1<<12, 1<<13, 1<<14, 1<<15}
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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 func(*tcpip.Error)
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iovers []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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handleLocal bool
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}
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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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// 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) // 初始化
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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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iovers: 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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func (e *endpoint) Capabilities() stack.LinkEndpointCapabilities {
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return e.caps
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}
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// 返回当前以太网头部信息长度
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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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// 返回当前MAC地址
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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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// 将上层的报文经过链路层封装，写入网卡中，如果写入失败则丢弃该报文
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func (e *endpoint) WritePacket(r *stack.Route, hdr buffer.Prependable,
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payload buffer.VectorisedView, protocol tcpip.NetworkProtocolNumber) *tcpip.Error {
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// 如果目标地址是设备自己 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) // 添加报文头
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e.dispatcher.DeliverNetworkPacket(e, r.RemoteLinkAddress, r.LocalLinkAddress,
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protocol, vv) // 分发数据报
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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)) // 分配14B的内存
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ethHdr := &header.EthernetFields{ // 配置以太帧信息
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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
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// 如果没有，则使用本网卡的地址
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if r.LocalLinkAddress != "" {
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ethHdr.SrcAddr = r.LocalLinkAddress // 源网卡地址 说明这是一个转发报文
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} else {
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ethHdr.SrcAddr = e.addr // 说明这是一个原始报文
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}
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eth.Encode(ethHdr) // 将以太帧信息作为报文头编入
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// 写入网卡中
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if payload.Size() == 0 {
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return rawfile
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}
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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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