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61 lines
2.0 KiB
61 lines
2.0 KiB
package parser
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import (
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"encoding/binary"
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"fmt"
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"net"
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)
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// ARP ref: https://zh.wikipedia.org/zh-cn/%E5%9C%B0%E5%9D%80%E8%A7%A3%E6%9E%90%E5%8D%8F%E8%AE%AE#%E6%8A%A5%E6%96%87%E6%A0%BC%E5%BC%8F
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type ARP struct {
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BaseLayer
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HardwareType uint16 // 硬件类型
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ProtoType uint16 // 协议类型
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HwAddressSize uint8 // 硬件地址长度
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ProtoAddrSize uint8 // 协议地址长度
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Opcode uint16 // 操作码
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SrcHwAddress net.HardwareAddr // 源硬件地址
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SrcProtoAddress net.IP // 源协议地址
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DstHwAddress net.HardwareAddr // 目标硬件地址
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DstProtoAddress net.IP // 目标协议地址
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}
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func (A *ARP) LayerType() int {
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return LayerTypeARP
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}
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// DecodeARP ref: https://zh.wikipedia.org/zh-cn/%E5%9C%B0%E5%9D%80%E8%A7%A3%E6%9E%90%E5%8D%8F%E8%AE%AE#%E6%8A%A5%E6%96%87%E6%A0%BC%E5%BC%8F
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func DecodeARP(data []byte) (*ARP, error) {
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// 至少要有8bytes
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if len(data) < 8 {
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return nil, fmt.Errorf("[arp] 数据包太短: %d bytes", len(data))
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}
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arp := ARP{}
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arp.HardwareType = binary.BigEndian.Uint16(data[0:2])
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arp.ProtoType = binary.BigEndian.Uint16(data[2:4])
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arp.HwAddressSize = data[4]
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arp.ProtoAddrSize = data[5]
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arp.Opcode = binary.BigEndian.Uint16(data[6:8])
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arpLen := 8 + 2*arp.HwAddressSize + 2*arp.ProtoAddrSize
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if len(data) < int(arpLen) {
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return nil, fmt.Errorf("[arp] 实际长度小于声明长度：实际：%d，声明：%d", len(data), arpLen)
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}
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var offset uint8 = 8
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arp.SrcHwAddress = data[offset : offset+arp.HwAddressSize]
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offset += arp.HwAddressSize
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arp.SrcProtoAddress = data[offset : offset+arp.ProtoAddrSize]
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offset += arp.ProtoAddrSize
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arp.DstHwAddress = data[offset : offset+arp.HwAddressSize]
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offset += arp.HwAddressSize
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arp.DstProtoAddress = data[offset : offset+arp.ProtoAddrSize]
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arp.Header = data[:arpLen]
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arp.Payload = data[arpLen:]
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return &arp, nil
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}
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