mirror of
https://github.com/impact-eintr/netstack.git
synced 2025-10-05 12:56:55 +08:00
153 lines
3.7 KiB
Go
153 lines
3.7 KiB
Go
package tcp
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import (
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"fmt"
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"log"
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"netstack/logger"
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"netstack/tcpip/buffer"
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"netstack/tcpip/header"
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"netstack/tcpip/seqnum"
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"netstack/tcpip/stack"
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"strings"
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"sync/atomic"
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)
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// tcp 太复杂了 专门写一个协议解析器 segment 是有种类之分的
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// Flags that may be set in a TCP segment.
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const (
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flagFin = 1 << iota
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flagSyn
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flagRst
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flagPsh
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flagAck
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flagUrg
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)
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func flagString(flags uint8) string {
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var s []string
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if (flags & flagAck) != 0 {
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s = append(s, "ack")
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}
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if (flags & flagFin) != 0 {
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s = append(s, "fin")
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}
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if (flags & flagPsh) != 0 {
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s = append(s, "psh")
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}
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if (flags & flagRst) != 0 {
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s = append(s, "rst")
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}
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if (flags & flagSyn) != 0 {
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s = append(s, "syn")
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}
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if (flags & flagUrg) != 0 {
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s = append(s, "urg")
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}
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return strings.Join(s, "|")
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}
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// segment 表示一个 TCP 段。它保存有效负载和解析的 TCP 段信息，并且可以添加到侵入列表中
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type segment struct {
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segmentEntry
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refCnt int32 // 引用计数
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id stack.TransportEndpointID
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route stack.Route
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data buffer.VectorisedView
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// views is used as buffer for data when its length is large
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// enough to store a VectorisedView.
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views [8]buffer.View
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// TODO 需要解析
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viewToDeliver int
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sequenceNumber seqnum.Value // tcp序号 第一个字节在整个报文的位置
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ackNumber seqnum.Value // 确认号 希望继续获取的下一个字节序号
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flags uint8
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window seqnum.Size // NOTE 这里是本地的接收窗口大小 不是发送窗口
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// parsedOptions stores the parsed values from the options in the segment.
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parsedOptions header.TCPOptions
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options []byte
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}
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func newSegment(r *stack.Route, id stack.TransportEndpointID, vv buffer.VectorisedView) *segment {
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s := &segment{refCnt: 1, id: id, route: r.Clone()}
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s.data = vv.Clone(s.views[:])
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return s
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}
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func newSegmentFromView(r *stack.Route, id stack.TransportEndpointID, v buffer.View) *segment {
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s := &segment{
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refCnt: 1,
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id: id,
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route: r.Clone(),
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}
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s.views[0] = v
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s.data = buffer.NewVectorisedView(len(v), s.views[:1]) // TODO 为什么只复制1?
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return s
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}
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func (s *segment) clone() *segment {
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t := &segment{
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refCnt: 1,
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id: s.id,
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sequenceNumber: s.sequenceNumber,
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ackNumber: s.ackNumber,
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flags: s.flags,
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window: s.window,
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route: s.route.Clone(),
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viewToDeliver: s.viewToDeliver,
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}
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t.data = s.data.Clone(t.views[:])
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return t
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}
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func (s *segment) flagIsSet(flag uint8) bool {
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return (s.flags & flag) != 0
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}
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func (s *segment) decRef() {
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if atomic.AddInt32(&s.refCnt, -1) == 0 {
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s.route.Release()
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}
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}
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func (s *segment) incRef() {
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atomic.AddInt32(&s.refCnt, 1)
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}
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// logicalLen is the segment length in the sequence number space. It's defined
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// as the data length plus one for each of the SYN and FIN bits set.
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// 计算tcp段的逻辑长度，包括负载数据的长度，如果有控制标记，需要加1
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func (s *segment) logicalLen() seqnum.Size {
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l := seqnum.Size(s.data.Size())
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if s.flagIsSet(flagSyn) {
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l++
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}
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if s.flagIsSet(flagFin) {
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l++
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}
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return l
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}
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func (s *segment) parse() bool {
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h := header.TCP(s.data.First())
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offset := int(h.DataOffset())
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if offset < header.TCPMinimumSize || offset > len(h) {
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return false
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}
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s.options = h.Options()
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s.parsedOptions = header.ParseTCPOptions(s.options)
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logger.GetInstance().Info(logger.TCP, func() {
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log.Println(h)
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fmt.Println(s.parsedOptions)
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})
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s.data.TrimFront(offset)
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s.sequenceNumber = seqnum.Value(h.SequenceNumber())
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s.ackNumber = seqnum.Value(h.AckNumber())
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s.flags = h.Flags() // U|A|P|R|S|F
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s.window = seqnum.Size(h.WindowSize())
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return true
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}
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