List Google Cloud Platform IP Address Ranges - Golang

main.go

/*
	This package contains a simple Go code
	for acquiring the IP Address Ranges utilised by Google Cloud Platform.
	This process is based on documentation provided by Google
	see: https://cloud.google.com/compute/docs/faq#find_ip_range

	Author: Shaun Remekie
	Email: [email protected]
*/

package main

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

const (
	gcpLookupAddr = "_cloud-netblocks.googleusercontent.com"
)

// GoogleCloudIPR - type used to store ip ranges
type GoogleCloudIPR []string

// lookup - recursively lookup and read TXT records to
// identify google cloud IP address ranges
func (g *GoogleCloudIPR) lookup(addr string) error {
	records, err := net.LookupTXT(addr)
	if err != nil {
		return err
	}

	for _, txt := range records {
		for _, r := range strings.Split(txt, " ") {

			switch {
			case strings.HasPrefix(r, "include:"):
				if err := g.lookup(strings.ReplaceAll(r, "include:", "")); err != nil {
					return err
				}
			case strings.HasPrefix(r, "ip4:"):
				*g = append(*g, strings.ReplaceAll(r, "ip4:", ""))
			default:
				continue
			}
		}
	}
	return nil
}

func main() {
	gcp := GoogleCloudIPR{}
	if err := gcp.lookup(gcpLookupAddr); err != nil {
		log.Fatalf("failed lookup: %s", err)
	}

	for _, ip := range gcp {
		fmt.Println(ip)
	}
}