ipv4和ipv6与int互转通用处理方式

记录一下ipv4和ipv6与int互转通用处理方式,由于ipv6转的int比较大,因此需要使用big.Int来保存
另外记录一下将ip返回转换为CIDR表达方式 点击运行

package main

import (
	"fmt"
	"math/big"
	"net/netip"
)

func IpRangeToCIDRRange(ipFrom, ipTo string) ([]string, error) {
	url := "https://www.ipaddressguide.com/cidr"
	if strings.IndexByte(ipFrom, '.') < 0 {
		url = "https://www.ipaddressguide.com/ipv6-cidr"
	}
	resp, err := http.Post(url, "application/x-www-form-urlencoded",
		strings.NewReader("mode=range&ipFrom="+ipFrom+"&ipTo="+ipTo))
	if err != nil {
		return nil, err
	}

	data, err := io.ReadAll(resp.Body)
	_ = resp.Body.Close()
	if err != nil {
		return nil, err
	}

	if e := bytes.Index(data, []byte("</code></pre></div>")); e > 0 {
		if s := bytes.LastIndexByte(data[:e], '>'); s > 0 {
			return strings.Split(string(data[s+1:e]), "\n"), nil
		}
	}
	return nil, errors.New("not find")
}

func InetNtoA(ip *big.Int, ipv4 int64) string {
	if ip == nil {
		return netip.AddrFrom4([4]byte{byte(ipv4 >> 24), byte(ipv4 >> 16),
			byte(ipv4 >> 8), byte(ipv4)}).String()
	}

	var (
		buf   [16]byte
		ipv6  = ip.Bytes()
		index = len(buf) - len(ipv6)
	)
	if index < 0 || index >= 16 {
		return ""
	}
	copy(buf[index:], ipv6)
	return netip.AddrFrom16(buf).String()
}

func InetAtoN(ip string) (*big.Int, int64, error) {
	addr, err := netip.ParseAddr(ip)
	if err != nil {
		return nil, 0, err
	}

	if addr.Is4() {
		ipv4 := addr.As4()
		return nil, int64(ipv4[0])<<24 | int64(ipv4[1])<<16 |
			int64(ipv4[2])<<8 | int64(ipv4[3]), nil
	}

	ipv6 := addr.As16()
	return new(big.Int).SetBytes(ipv6[:]), 0, nil
}

func main() {
	ipv6 := "f000:0000:0000:0000:0000:ffff:192.168.100.228"
	ipInt, ipv4, err := InetAtoN(ipv6)
	if err != nil {
		panic(err)
	}
	fmt.Println(ipInt, ipv4, InetNtoA(ipInt, ipv4))

	ip := "192.168.78.123"
	ipInt, ipv4, err = InetAtoN(ip)
	if err != nil {
		panic(err)
	}
	fmt.Println(ipInt, ipv4, InetNtoA(ipInt, ipv4))
}