ipv6-test-backend/internal/pkg/utils/network.go

package utils

import (
	"encoding/hex"
	"errors"
	"fmt"
	"ipv6-test-node/internal/pkg/protocol"
	"net"
	"strings"
)

func GetIPVersion(ip net.IP) (protocol.IPVersion, error) {
	if ip == nil {
		return 0, errors.New("invalid IP address")
	}
	if ip.To4() != nil {
		return protocol.IPv4, nil
	} else if ip.To16() != nil {
		return protocol.IPv6, nil
	} else {
		return 0, errors.New("invalid IP address")
	}
}

func GetASN(ip protocol.IP) (string, error) {
	var query string
	if ip.Version == 4 {
		query = fmt.Sprintf("%sorigin.asn.cymru.com", reverseIPv4(ip.Address))
	} else if ip.Version == 6 {
		query = fmt.Sprintf("%sorigin6.asn.cymru.com", reverseIPv6(ip.Address))
	}

	txtRecords, err := net.LookupTXT(query)
	if err != nil {
		return "", err
	}

	if len(txtRecords) > 0 {
		parts := strings.Split(txtRecords[0], " | ")
		if len(parts) > 0 {
			return "AS" + parts[0], nil
		}
	}

	return "", fmt.Errorf("ASN not found")
}

func GetISPName(asn string) (string, error) {
	query := fmt.Sprintf("%s.asn.cymru.com", asn)
	txtRecords, err := net.LookupTXT(query)
	if err != nil {
		return "", err
	}

	if len(txtRecords) > 0 {
		parts := strings.Split(txtRecords[0], " | ")
		if len(parts) > 0 {
			return parts[4], nil
		}
	}

	return "", fmt.Errorf("ISP not found")
}

func ToIP(address net.IP) protocol.IP {
	version, err := GetIPVersion(address)
	if err != nil {
		return protocol.IP{}
	}
	return protocol.IP{Address: address, Version: version}
}

func reverseIPv4(ip net.IP) string {
	return fmt.Sprintf("%d.%d.%d.%d.", ip[3], ip[2], ip[1], ip[0])
}

func reverseIPv6(ip net.IP) string {
	var dst []byte
	dst = make([]byte, hex.EncodedLen(len(ip)))
	hex.Encode(dst, ip)

	var reversed string
	for i := len(dst) - 1; i >= 0; i-- {
		reversed = reversed + string(dst[i]) + "."
	}
	return reversed
}