Check if IP address is in private network space

Question

I have a program in go which accepts URLs from clients and gets them using the net/http package. Before doing further processing, I would like to check if the URL maps to privat

Answer 1

It seems there's no better way to accomplish than the one I described. Combining code from @MichaelHausenblas with the suggestion from @JimB, my code ended up kind of like this.

func privateIP(ip string) (bool, error) {
    var err error
    private := false
    IP := net.ParseIP(ip)
    if IP == nil {
        err = errors.New("Invalid IP")
    } else {
        _, private24BitBlock, _ := net.ParseCIDR("10.0.0.0/8")
        _, private20BitBlock, _ := net.ParseCIDR("172.16.0.0/12")
        _, private16BitBlock, _ := net.ParseCIDR("192.168.0.0/16")
        private = private24BitBlock.Contains(IP) || private20BitBlock.Contains(IP) || private16BitBlock.Contains(IP)
    }
    return private, err
}