mirror of
https://github.com/impact-eintr/netstack.git
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129 lines
4.5 KiB
Go
129 lines
4.5 KiB
Go
package ipv4
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import (
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"encoding/binary"
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"log"
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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/stack"
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)
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/*
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ICMP 的全称是 Internet Control Message Protocol 。与 IP 协议一样同属 TCP/IP 模型中的网络层，并且 ICMP 数据包是包裹在 IP 数据包中的
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0 1 2 3
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Type | Code | Checksum |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| |
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| 不同的Type和Code有不同的内容 |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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*/
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type echoRequest struct {
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r stack.Route
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v buffer.View
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}
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// handleControl处理ICMP数据包包含导致ICMP发送的原始数据包的标头的情况。
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// 此信息用于确定必须通知哪个传输端点有关ICMP数据包。
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func (e *endpoint) handleControl(typ stack.ControlType, extra uint32, vv buffer.VectorisedView) {
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h := header.IPv4(vv.First())
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// We don't use IsValid() here because ICMP only requires that the IP
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// header plus 8 bytes of the transport header be included. So it's
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// likely that it is truncated, which would cause IsValid to return
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// false.
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//
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// Drop packet if it doesn't have the basic IPv4 header or if the
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// original source address doesn't match the endpoint's address.
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if len(h) < header.IPv4MinimumSize || h.SourceAddress() != e.id.LocalAddress {
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return
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}
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hlen := int(h.HeaderLength())
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if vv.Size() < hlen || h.FragmentOffset() != 0 {
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// We won't be able to handle this if it doesn't contain the
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// full IPv4 header, or if it's a fragment not at offset 0
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// (because it won't have the transport header).
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return
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}
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// Skip the ip header, then deliver control message.
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vv.TrimFront(hlen)
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p := h.TransportProtocol()
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e.dispatcher.DeliverTransportControlPacket(e.id.LocalAddress, h.DestinationAddress(), ProtocolNumber, p, typ, extra, vv)
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}
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// 处理ICMP报文
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func (e *endpoint) handleICMP(r *stack.Route, vv buffer.VectorisedView) {
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v := vv.First()
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if len(v) < header.ICMPv4MinimumSize {
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return
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}
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h := header.ICMPv4(v)
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// 更具icmp的类型来进行相应的处理
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switch h.Type() {
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case header.ICMPv4Echo: // icmp echo请求
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if len(v) < header.ICMPv4EchoMinimumSize {
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return
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}
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log.Printf("ICMP echo")
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vv.TrimFront(header.ICMPv4MinimumSize) // 去掉头部
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req := echoRequest{r: r.Clone(), v: vv.ToView()}
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select {
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case e.echoRequests <- req: // 发送给echoReplier处理 在那里会重新组一个头部
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default:
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req.r.Release()
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}
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case header.ICMPv4EchoReply: // icmp echo响应
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if len(v) < header.ICMPv4EchoMinimumSize {
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return
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}
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e.dispatcher.DeliverTransportPacket(r, header.ICMPv4ProtocolNumber, vv)
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case header.ICMPv4DstUnreachable: // 目标不可达
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if len(v) < header.ICMPv4DstUnreachableMinimumSize {
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return
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}
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vv.TrimFront(header.ICMPv4DstUnreachableMinimumSize)
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switch h.Code() {
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case header.ICMPv4PortUnreachable: // 端口不可达
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e.handleControl(stack.ControlPortUnreachable, 0, vv)
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case header.ICMPv4FragmentationNeeded: // 需要进行分片但设置不分片标志
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mtu := uint32(binary.BigEndian.Uint16(v[header.ICMPv4DstUnreachableMinimumSize-2:]))
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e.handleControl(stack.ControlPacketTooBig, calculateMTU(mtu), vv)
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}
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}
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}
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// 处理icmp echo请求的goroutine
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func (e *endpoint) echoReplier() {
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for req := range e.echoRequests {
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sendPing4(&req.r, 0, req.v)
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req.r.Release()
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}
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}
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// 根据icmp echo请求，封装icmp echo响应报文，并传给ip层处理
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func sendPing4(r *stack.Route, code byte, data buffer.View) *tcpip.Error {
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hdr := buffer.NewPrependable(header.ICMPv4EchoMinimumSize + int(r.MaxHeaderLength()))
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icmpv4 := header.ICMPv4(hdr.Prepend(header.ICMPv4EchoMinimumSize))
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icmpv4.SetType(header.ICMPv4EchoReply)
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icmpv4.SetCode(code)
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copy(icmpv4[header.ICMPv4MinimumSize:], data)
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data = data[header.ICMPv4EchoMinimumSize-header.ICMPv4MinimumSize:]
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icmpv4.SetChecksum(^header.Checksum(icmpv4, header.Checksum(data, 0)))
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log.Printf("ICMP 回应报文组完 再次包装到IP报文")
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// 传给ip层处理
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return r.WritePacket(hdr, data.ToVectorisedView(), header.ICMPv4ProtocolNumber, r.DefaultTTL())
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}
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