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// Copyright 2011 Miek Gieben. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Chaos is a small program that prints the version.bind and hostname.bind
// for each address of the nameserver given as argument.
package main
import (
"fmt"
"github.com/miekg/dns"
"net"
"os"
)
func main() {
if len(os.Args) != 2 {
fmt.Printf("%s NAMESERVER\n", os.Args[0])
os.Exit(1)
}
conf, _ := dns.ClientConfigFromFile("/etc/resolv.conf")
m := new(dns.Msg)
m.Question = make([]dns.Question, 1)
c := new(dns.Client)
addr := addresses(conf, c, os.Args[1])
if len(addr) == 0 {
fmt.Printf("No address found for %s\n", os.Args[1])
os.Exit(1)
}
for _, a := range addr {
m.Question[0] = dns.Question{"version.bind.", dns.TypeTXT, dns.ClassCHAOS}
in, rtt, _ := c.Exchange(m, a)
if in != nil && len(in.Answer) > 0 {
fmt.Printf("(time %.3d µs) %v\n", rtt/1e3, in.Answer[0])
}
m.Question[0] = dns.Question{"hostname.bind.", dns.TypeTXT, dns.ClassCHAOS}
in, rtt, _ = c.Exchange(m, a)
if in != nil && len(in.Answer) > 0 {
fmt.Printf("(time %.3d µs) %v\n", rtt/1e3, in.Answer[0])
}
}
}
func do(t chan *dns.Msg, c *dns.Client, m *dns.Msg, addr string) {
go func() {
r, _, err := c.Exchange(m, addr)
if err != nil {
//print error stuff
t <- nil
}
t <- r
}()
}
func addresses(conf *dns.ClientConfig, c *dns.Client, name string) (ips []string) {
m4 := new(dns.Msg)
m4.SetQuestion(dns.Fqdn(os.Args[1]), dns.TypeA)
m6 := new(dns.Msg)
m6.SetQuestion(dns.Fqdn(os.Args[1]), dns.TypeAAAA)
t := make(chan *dns.Msg)
defer close(t)
do(t, c, m4, net.JoinHostPort(conf.Servers[0], conf.Port))
do(t, c, m6, net.JoinHostPort(conf.Servers[0], conf.Port))
i := 2 // two outstanding queries
forever:
for {
select {
case d := <-t:
i--
if d == nil {
continue
}
if i == 0 {
break forever
}
if d.Rcode == dns.RcodeSuccess {
for _, a := range d.Answer {
switch a.(type) {
case *dns.A:
ips = append(ips,
net.JoinHostPort(a.(*dns.A).A.String(), "53"))
case *dns.AAAA:
ips = append(ips,
net.JoinHostPort(a.(*dns.AAAA).AAAA.String(), "53"))
}
}
}
}
}
return ips
}
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