package util import ( "errors" "fmt" "strings" "time" "github.com/miekg/dns" ) type Response struct { Answers Answers `json:"Response"` // These be DNS query answers } // The Answers struct is the basic structure of a DNS request // to be returned to the user upon making a request type Answers struct { Server string `json:"Server"` // The server to make the DNS request from Request uint16 `json:"Request"` // The type of request Name string `json:"Name"` // The domain name to make a DNS request for RTT time.Duration `json:"RTT"` // The time it took to make the DNS query } // Given an IP or phone number, return a canonical string to be queried func ReverseDNS(address string, query string) (string, error) { if query == "PTR" { return dns.ReverseAddr(address) } else if query == "NAPTR" { // get rid of characters not needed replacer := strings.NewReplacer("+", "", " ", "", "-", "") address = replacer.Replace(address) // reverse the order of the string address = reverse(address) var arpa strings.Builder // Make it canonical for _, c := range address { fmt.Fprintf(&arpa, "%c.", c) } arpa.WriteString("e164.arpa.") return arpa.String(), nil } return "", errors.New("ReverseDNS: -x flag given but no IP found") } // Reverse a string, return the string in reverse func reverse(s string) string { rns := []rune(s) for i, j := 0, len(rns)-1; i < j; i, j = i+1, j-1 { rns[i], rns[j] = rns[j], rns[i] } return string(rns) }