package parser

import (
    "encoding/binary"
    "errors"
)

type ICMP struct {
    BaseLayer
    TypeCode uint16
    Checksum uint16
    Id       uint16
    Seq      uint16
}

func (I *ICMP) LayerType() int {
    return LayerTypeICMP
}

func DecodeICMP(data []byte) (*ICMP, error) {
    icmp := ICMP{}
    if len(data) < 8 {
        return nil, errors.New("ICMP数据包头部少于8字节")
    }

    icmp.TypeCode = binary.BigEndian.Uint16(data[0:2])
    icmp.Checksum = binary.BigEndian.Uint16(data[2:4])
    icmp.Id = binary.BigEndian.Uint16(data[4:6])
    icmp.Seq = binary.BigEndian.Uint16(data[6:8])
    icmp.BaseLayer = BaseLayer{data[:8], data[8:]}

    return &icmp, nil
}