3790290c9b
miekg dependency was forking some of the golang standard library. We can fork it directly into the third_party folder respecting the LICENSE.
59 lines
1.6 KiB
Go
59 lines
1.6 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// This package is copied from Go library net.
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// https://golang.org/src/net/dnsclient.go
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// The original private function reverseaddr
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// is exported as public function.
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package net
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import "net"
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// Reverseaddr returns the in-addr.arpa. or ip6.arpa. hostname of the IP
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// address addr suitable for rDNS (PTR) record lookup or an error if it fails
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// to parse the IP address.
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func Reverseaddr(addr string) (arpa string, err error) {
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ip := net.ParseIP(addr)
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if ip == nil {
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return "", &net.DNSError{Err: "unrecognized address", Name: addr}
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}
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if ip.To4() != nil {
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return uitoa(uint(ip[15])) + "." + uitoa(uint(ip[14])) + "." + uitoa(uint(ip[13])) + "." + uitoa(uint(ip[12])) + ".in-addr.arpa.", nil
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}
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// Must be IPv6
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buf := make([]byte, 0, len(ip)*4+len("ip6.arpa."))
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// Add it, in reverse, to the buffer
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for i := len(ip) - 1; i >= 0; i-- {
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v := ip[i]
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buf = append(buf, hexDigit[v&0xF],
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'.',
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hexDigit[v>>4],
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'.')
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}
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// Append "ip6.arpa." and return (buf already has the final .)
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buf = append(buf, "ip6.arpa."...)
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return string(buf), nil
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}
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// Convert unsigned integer to decimal string.
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func uitoa(val uint) string {
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if val == 0 { // avoid string allocation
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return "0"
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}
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var buf [20]byte // big enough for 64bit value base 10
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i := len(buf) - 1
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for val >= 10 {
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q := val / 10
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buf[i] = byte('0' + val - q*10)
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i--
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val = q
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}
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// val < 10
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buf[i] = byte('0' + val)
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return string(buf[i:])
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}
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const hexDigit = "0123456789abcdef"
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