Sam Therapy
4c9221ee29
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:^) Signed-off-by: Sam Therapy <sam@samtherapy.net>
57 lines
1.2 KiB
Go
57 lines
1.2 KiB
Go
// SPDX-License-Identifier: BSD-3-Clause
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package util
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import (
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"fmt"
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"strings"
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"github.com/miekg/dns"
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)
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type errReverseDNS struct {
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addr string
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}
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func (e *errReverseDNS) Error() string {
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return fmt.Sprintf("reverseDNS: invalid value %s given", e.addr)
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}
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// ReverseDNS is given an IP or phone number and returns a canonical string to be queried.
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func ReverseDNS(address string, querInt uint16) (string, error) {
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query := dns.TypeToString[querInt]
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if query == "PTR" {
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str, err := dns.ReverseAddr(address)
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if err != nil {
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return "", fmt.Errorf("PTR reverse: %w", err)
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}
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return str, nil
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} else if query == "NAPTR" {
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// get rid of characters not needed
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replacer := strings.NewReplacer("+", "", " ", "", "-", "")
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address = replacer.Replace(address)
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// reverse the order of the string
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address = reverse(address)
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var arpa strings.Builder
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// Make it canonical
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for _, c := range address {
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fmt.Fprintf(&arpa, "%c.", c)
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}
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arpa.WriteString("e164.arpa.")
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return arpa.String(), nil
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}
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return "", &errReverseDNS{address}
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}
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// Reverse a string, return the string in reverse.
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func reverse(s string) string {
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rns := []rune(s)
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for i, j := 0, len(rns)-1; i < j; i, j = i+1, j-1 {
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rns[i], rns[j] = rns[j], rns[i]
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}
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return string(rns)
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}
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