只是一个简单的计网课设
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eruhs/core/parser/arp.go

61 lines
2.0 KiB

package parser
import (
"encoding/binary"
"fmt"
"net"
)
// 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
type ARP struct {
BaseLayer
HardwareType uint16 // 硬件类型
ProtoType uint16 // 协议类型
HwAddressSize uint8 // 硬件地址长度
ProtoAddrSize uint8 // 协议地址长度
Opcode uint16 // 操作码
SrcHwAddress net.HardwareAddr // 源硬件地址
SrcProtoAddress net.IP // 源协议地址
DstHwAddress net.HardwareAddr // 目标硬件地址
DstProtoAddress net.IP // 目标协议地址
}
func (A *ARP) LayerType() int {
return LayerTypeARP
}
// 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
func DecodeARP(data []byte) (*ARP, error) {
// 至少要有8bytes
if len(data) < 8 {
return nil, fmt.Errorf("[arp] 数据包太短: %d bytes", len(data))
}
arp := ARP{}
arp.HardwareType = binary.BigEndian.Uint16(data[0:2])
arp.ProtoType = binary.BigEndian.Uint16(data[2:4])
arp.HwAddressSize = data[4]
arp.ProtoAddrSize = data[5]
arp.Opcode = binary.BigEndian.Uint16(data[6:8])
arpLen := 8 + 2*arp.HwAddressSize + 2*arp.ProtoAddrSize
if len(data) < int(arpLen) {
return nil, fmt.Errorf("[arp] 实际长度小于声明长度:实际:%d,声明:%d", len(data), arpLen)
}
var offset uint8 = 8
arp.SrcHwAddress = data[offset : offset+arp.HwAddressSize]
offset += arp.HwAddressSize
arp.SrcProtoAddress = data[offset : offset+arp.ProtoAddrSize]
offset += arp.ProtoAddrSize
arp.DstHwAddress = data[offset : offset+arp.HwAddressSize]
offset += arp.HwAddressSize
arp.DstProtoAddress = data[offset : offset+arp.ProtoAddrSize]
arp.Header = data[:arpLen]
arp.Payload = data[arpLen:]
return &arp, nil
}