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// Copyright 2017 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package dnsmessage_test
import (
"fmt"
"net"
"strings"
"golang.org/x/net/dns/dnsmessage"
)
func ExampleParser() {
msg := dnsmessage.Message{
Header: dnsmessage.Header{Response: true, Authoritative: true},
Questions: []dnsmessage.Question{
{
Name: dnsmessage.MustNewName("foo.bar.example.com."),
Type: dnsmessage.TypeA,
Class: dnsmessage.ClassINET,
},
{
Name: dnsmessage.MustNewName("bar.example.com."),
Type: dnsmessage.TypeA,
Class: dnsmessage.ClassINET,
},
},
Answers: []dnsmessage.Resource{
{
Header: dnsmessage.ResourceHeader{
Name: dnsmessage.MustNewName("foo.bar.example.com."),
Type: dnsmessage.TypeA,
Class: dnsmessage.ClassINET,
},
Body: &dnsmessage.AResource{A: [4]byte{127, 0, 0, 1}},
},
{
Header: dnsmessage.ResourceHeader{
Name: dnsmessage.MustNewName("bar.example.com."),
Type: dnsmessage.TypeA,
Class: dnsmessage.ClassINET,
},
Body: &dnsmessage.AResource{A: [4]byte{127, 0, 0, 2}},
},
},
}
buf, err := msg.Pack()
if err != nil {
panic(err)
}
wantName := "bar.example.com."
var p dnsmessage.Parser
if _, err := p.Start(buf); err != nil {
panic(err)
}
for {
q, err := p.Question()
if err == dnsmessage.ErrSectionDone {
break
}
if err != nil {
panic(err)
}
if q.Name.String() != wantName {
continue
}
fmt.Println("Found question for name", wantName)
if err := p.SkipAllQuestions(); err != nil {
panic(err)
}
break
}
var gotIPs []net.IP
for {
h, err := p.AnswerHeader()
if err == dnsmessage.ErrSectionDone {
break
}
if err != nil {
panic(err)
}
if (h.Type != dnsmessage.TypeA && h.Type != dnsmessage.TypeAAAA) || h.Class != dnsmessage.ClassINET {
continue
}
if !strings.EqualFold(h.Name.String(), wantName) {
if err := p.SkipAnswer(); err != nil {
panic(err)
}
continue
}
switch h.Type {
case dnsmessage.TypeA:
r, err := p.AResource()
if err != nil {
panic(err)
}
gotIPs = append(gotIPs, r.A[:])
case dnsmessage.TypeAAAA:
r, err := p.AAAAResource()
if err != nil {
panic(err)
}
gotIPs = append(gotIPs, r.AAAA[:])
}
}
fmt.Printf("Found A/AAAA records for name %s: %v\n", wantName, gotIPs)
// Output:
// Found question for name bar.example.com.
// Found A/AAAA records for name bar.example.com.: [127.0.0.2]
}
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