Test for cloudflare IP

cloudflare.go

package main

import (
	"net"
	"os"
	"fmt"
)

var cidrs = []string{
	"103.21.244.0/22",
	"103.22.200.0/22",
	"103.31.4.0/22",
	"104.16.0.0/12",
	"108.162.192.0/18",
	"131.0.72.0/22",
	"141.101.64.0/18",
	"162.158.0.0/15",
	"172.64.0.0/13",
	"173.245.48.0/20",
	"188.114.96.0/20",
	"190.93.240.0/20",
	"197.234.240.0/22",
	"198.41.128.0/17",
	"199.27.128.0/21",
}

func main() {

	host := os.Args[1]

	ips, _ := net.LookupIP(host)

	for _, cidr := range cidrs {
		_, ipNet, _ := net.ParseCIDR(cidr)

		for _, ip := range ips {
			if ipNet.Contains(ip) {
				fmt.Printf("%s found in a cloudflare ip range\n", ip)
			}
		}
	}
}