109 lines
2.9 KiB
Go
109 lines
2.9 KiB
Go
package gateway
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import (
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"encoding/binary"
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"errors"
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"fmt"
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"net"
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"strconv"
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)
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var packetIdentifier = []byte{0xDE, 0xAD, 0xBE, 0xEF}
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// MarshalGatewayOutPacket 将数据包转换为网关出网数据包
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// - | identifier(4) | ipv4(4) | port(2) | packet |
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func MarshalGatewayOutPacket(addr string, packet []byte) ([]byte, error) {
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host, portStr, err := net.SplitHostPort(addr)
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if err != nil {
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return nil, err
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}
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ipBytes := net.ParseIP(host).To4()
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if ipBytes == nil {
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return nil, errors.New("invalid IPv4 address")
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}
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port, err := strconv.Atoi(portStr)
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if err != nil || port < 0 || port > 65535 {
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return nil, errors.New("invalid port number")
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}
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portBytes := []byte{byte(port >> 8), byte(port & 0xFF)}
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result := append(packetIdentifier, ipBytes...)
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result = append(result, portBytes...)
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result = append(result, packet...)
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return result, nil
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}
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// UnmarshalGatewayOutPacket 将网关出网数据包转换为数据包
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// - | identifier(4) | ipv4(4) | port(2) | packet |
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func UnmarshalGatewayOutPacket(data []byte) (addr string, packet []byte, err error) {
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if len(data) < 10 {
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err = errors.New("data is too short to contain an IPv4 address and a port")
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return
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}
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if !compareBytes(data[:4], packetIdentifier) {
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err = errors.New("invalid identifier")
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return
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}
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ipAddr := net.IP(data[4:8]).String()
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port := uint16(data[8])<<8 | uint16(data[9])
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addr = fmt.Sprintf("%s:%d", ipAddr, port)
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packet = data[10:]
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return addr, packet, nil
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}
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// MarshalGatewayInPacket 将数据包转换为网关入网数据包
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// - | ipv4(4) | port(2) | cost(4) | packet |
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func MarshalGatewayInPacket(addr string, currentTime int64, packet []byte) ([]byte, error) {
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host, portStr, err := net.SplitHostPort(addr)
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if err != nil {
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return nil, err
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}
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ipBytes := net.ParseIP(host).To4()
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if ipBytes == nil {
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return nil, errors.New("invalid IPv4 address")
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}
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port, err := strconv.Atoi(portStr)
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if err != nil || port < 0 || port > 65535 {
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return nil, errors.New("invalid port number")
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}
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portBytes := []byte{byte(port >> 8), byte(port & 0xFF)}
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costBytes := make([]byte, 4)
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binary.BigEndian.PutUint32(costBytes, uint32(currentTime))
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result := append(ipBytes, portBytes...)
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result = append(result, costBytes...)
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result = append(result, packet...)
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return result, nil
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}
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// UnmarshalGatewayInPacket 将网关入网数据包转换为数据包
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// - | ipv4(4) | port(2) | cost(4) | packet |
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func UnmarshalGatewayInPacket(data []byte) (addr string, sendTime int64, packet []byte, err error) {
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if len(data) < 10 {
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err = errors.New("data is too short")
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return
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}
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ipAddr := net.IP(data[:4]).String()
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port := uint16(data[4])<<8 | uint16(data[5])
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addr = fmt.Sprintf("%s:%d", ipAddr, port)
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sendTime = int64(binary.BigEndian.Uint32(data[6:10]))
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packet = data[10:]
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return addr, sendTime, packet, nil
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}
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func compareBytes(a, b []byte) bool {
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if len(a) != len(b) {
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return false
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}
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for i := range a {
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if a[i] != b[i] {
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return false
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}
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}
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return true
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}
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