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45 lines
1.2 KiB
45 lines
1.2 KiB
package parser
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import (
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"encoding/binary"
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"fmt"
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)
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type UDP struct {
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BaseLayer
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SrcPort, DstPort uint16 // 源端口（可选）、目标端口
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Length uint16 // 数据包总长（header+payload）
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Checksum uint16 // 校验和（ipv4下可选）
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}
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func (U *UDP) LayerType() int {
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return LayerTypeUDP
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}
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func DecodeUDP(data []byte) (*UDP, error) {
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if len(data) < 8 {
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return nil, fmt.Errorf("[UDP] 无效数据包长度: %d bytes, 至少需要8 bytes", len(data))
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}
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udp := UDP{}
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udp.SrcPort = binary.BigEndian.Uint16(data[0:2])
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udp.DstPort = binary.BigEndian.Uint16(data[2:4])
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udp.Length = binary.BigEndian.Uint16(data[4:6])
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udp.Checksum = binary.BigEndian.Uint16(data[6:8])
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udp.Header = data[:8]
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switch {
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case udp.Length >= 8:
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hlen := int(udp.Length)
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if hlen > len(data) {
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hlen = len(data)
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}
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udp.Payload = data[8:hlen]
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case udp.Length == 0: // IPv6 Jumbogram, 剩下的所有数据都认为是payload
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udp.Payload = data[8:]
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default:
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return nil, fmt.Errorf("[UDP] 数据包太小：%d bytes", udp.Length)
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}
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return &udp, nil
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}
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