CODEWITHSUNDEEP
goipv6
Saint Night
Saint Night

Reputation: 343

Getting number of IPv6 addresses from Ipv6 CIDR in GO

Is there anyway to retrieve the maximum numbers of IPv6 from a CIDR range? Currently I have this code:

package main

import (
    "fmt"
    "log"
    "net"
)

func main() {
    ip, ipnet, err := net.ParseCIDR("2001:200:905::/49")
    var ips []string
    if err != nil {
        log.Fatal(err)
    }
    for ip := ip.Mask(ipnet.Mask); ipnet.Contains(ip); inc(ip) {
        ips = append(ips, ip.String())
    }
    fmt.Println(len(ips))
}

func inc(ip net.IP) {
    for j := len(ip)-1; j>=0; j-- {
        ip[j]++
        if ip[j] > 0 {
            break
        }
    }
}

But this process runs so slow. Is there any efficient way of retrieving the total number of ip addresses?

Upvotes: 0

Views: 1372

Answers (1)

Sean F
Sean F

Reputation: 4615

The IPAddress Go library can do this (get the count, starting point, end, or any address in the middle) with a few lines of polymorphic code that works with both IPv4 and IPv6 addresses. Repository here. Disclaimer: I am the project manager.

func details(addrStr string) {
    addr := ipaddr.NewIPAddressString(addrStr).GetAddress()
    lower, upper := addr.GetLower(), addr.GetUpper()
    count := addr.GetCount()
    fmt.Printf("%s has size %d,\n\tranging from %v to %v\n",
        addr, count, lower, upper)
    fmt.Println("\thundredth address is", addr.Increment(100))
}

Using your IPv6 example as well as an IPv4 subnet:

details("2001:200:905::/49")
details("192.168.10.0/24")

Output:

2001:200:905::/49 has size 604462909807314587353088,
        ranging from 2001:200:905::/49 to 2001:200:905:7fff:ffff:ffff:ffff:ffff/49
        hundredth address is 2001:200:905::64/49
192.168.10.0/24 has size 256,
        ranging from 192.168.10.0/24 to 192.168.10.255/24
        hundredth address is 192.168.10.100/24

Upvotes: 1

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