awl/util/helpers.go

44 lines
1010 B
Go

// SPDX-License-Identifier: BSD-3-Clause
package util
import (
"errors"
"fmt"
"strings"
"github.com/miekg/dns"
)
// 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)
}