Check ipv4 address is rfc1918

rfc1918.go

package main

import (
    "net"
    "fmt"
)

func IsPrivateIPv4(s string) bool {
    // RFC 1918 CIDRS
    var rfc1918_cidrs []string = []string{"10.0.0.0/8","172.16.0.0/12","192.168.0.0/16"}

    var ip net.IP = net.ParseIP(s)

    if ip == nil {
        return false
    }

    for _, cidr := range rfc1918_cidrs {
        _, net, _ := net.ParseCIDR(cidr)
        if net.Contains(ip) {
            return true
        }
    }

    return false
}

func main(){
    var addrs []string = []string{"10.1.1.1", "192.168.10.2", "20.202.1.1"}
    for _, addr := range addrs {
        fmt.Println("IsPrivateIPv4", addr, IsPrivateIPv4(addr))
    }
}