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128 lines
2.1 KiB
Go
128 lines
2.1 KiB
Go
// +build unix
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package main
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import (
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"fmt"
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"github.com/miekg/dns"
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"log"
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"time"
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)
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var clientConfig *dns.ClientConfig
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var dnsClient *dns.Client
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func lookupHost(host string) ([]string, error) {
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var result = []string{}
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var err error
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ret, err1 := getAAAA(host)
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if err1 == nil {
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result = append(result, ret...)
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} else {
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err = err1
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}
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ret1, err2 := getA(host)
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if err2 == nil {
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result = append(result, ret1...)
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} else {
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err = err2
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}
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if len(result) > 0 {
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return result, nil
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}
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if err == nil {
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return nil, fmt.Errorf("dns lookup failed for %s", host)
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}
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return nil, err
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}
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func getA(host string) ([]string, error) {
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var err error
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var msg *dns.Msg
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var result = []string{}
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m := new(dns.Msg)
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m.SetQuestion(dns.Fqdn(host), dns.TypeA)
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for _, srv := range clientConfig.Servers {
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dnsserver := fmt.Sprintf("%s:%s", srv, clientConfig.Port)
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msg, _, err = dnsClient.Exchange(m, dnsserver)
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if err == nil {
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break
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} else {
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log.Println(err)
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}
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}
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if err != nil {
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return result, err
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}
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for _, rr := range msg.Answer {
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if a, ok := rr.(*dns.A); ok {
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result = append(result, a.A.String())
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}
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}
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return result, nil
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}
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func getAAAA(host string) ([]string, error) {
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var err error
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var msg *dns.Msg
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var result = []string{}
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m := new(dns.Msg)
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m.SetQuestion(dns.Fqdn(host), dns.TypeAAAA)
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for _, srv := range clientConfig.Servers {
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dnsserver := fmt.Sprintf("%s:%s", srv, clientConfig.Port)
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msg, _, err = dnsClient.Exchange(m, dnsserver)
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if err == nil {
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break
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} else {
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log.Println(err)
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}
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}
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if err != nil {
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return result, err
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}
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for _, rr := range msg.Answer {
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if aaaa, ok := rr.(*dns.AAAA); ok {
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result = append(result, aaaa.AAAA.String())
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}
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}
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return result, nil
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}
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func init() {
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var err error
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clientConfig, err = dns.ClientConfigFromFile("/etc/resolv.conf")
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if err != nil {
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clientConfig = &dns.ClientConfig{
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Servers: []string{"8.8.8.8", "4.2.2.2"},
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Port: "53",
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Ndots: 1,
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Timeout: 2,
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Attempts: 3,
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}
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}
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//clientConfig.Port = "53"
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dnsClient = &dns.Client{
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Net: "udp",
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Timeout: time.Duration(clientConfig.Timeout) * time.Second,
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UDPSize: 4096,
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}
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}
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