58 lines
1.2 KiB
Go
58 lines
1.2 KiB
Go
// SPDX-License-Identifier: BSD-3-Clause
|
|
|
|
package util
|
|
|
|
import (
|
|
"fmt"
|
|
"strings"
|
|
|
|
"github.com/miekg/dns"
|
|
)
|
|
|
|
type errReverseDNS struct {
|
|
addr string
|
|
}
|
|
|
|
func (e *errReverseDNS) Error() string {
|
|
return fmt.Sprintf("reverseDNS: invalid value %s given", e.addr)
|
|
}
|
|
|
|
// ReverseDNS is given an IP or phone number and returns a canonical string to be queried.
|
|
func ReverseDNS(address string, querInt uint16) (string, error) {
|
|
query := dns.TypeToString[querInt]
|
|
if query == "PTR" {
|
|
str, err := dns.ReverseAddr(address)
|
|
if err != nil {
|
|
return "", fmt.Errorf("PTR reverse: %w", err)
|
|
}
|
|
|
|
return str, nil
|
|
} 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 "", &errReverseDNS{address}
|
|
}
|
|
|
|
// 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)
|
|
}
|