CIDR to ip range

hostsb4.go

// before 1.18
package main

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

func Hosts(cidr string) ([]string, error) {
	ip, ipnet, err := net.ParseCIDR(cidr)
	if err != nil {
		return nil, err
	}

	var ips []string
	for ip := ip.Mask(ipnet.Mask); ipnet.Contains(ip); inc(ip) {
		ips = append(ips, ip.String())
	}
	// remove network address and broadcast address
	if len(ips) > 1 {
		return ips[1 : len(ips)-1], nil
	}
	return ips, nil
}

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

func main() {
	tmp, err := Hosts("192.168.1.3/32")
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println(tmp)

	tmp, err = Hosts("10.168.0.0/16")
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println(tmp)

}

main.go

// after 1.18
package main

import (
	"fmt"
	"log"
	"net/netip"
)

func Hosts(cidr string) ([]netip.Addr, error) {
	prefix, err := netip.ParsePrefix(cidr)
	if err != nil {
		panic(err)
	}

	var ips []netip.Addr
	for addr := prefix.Addr(); prefix.Contains(addr); addr = addr.Next() {
		ips = append(ips, addr)
	}

	if len(ips) < 2 {
		return ips, nil
	}

	return ips[1 : len(ips)-1], nil
}

func main() {
	tmp, err := Hosts("192.168.1.3/32")
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println(tmp)
	
	tmp, err = Hosts("10.168.0.0/16")
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println(tmp)
}