Golang Msg.SetQuestion方法代碼示例

// LookupCAA uses a DNSSEC-enabled query to find all CAA records associated with
// the provided hostname. If the query fails due to DNSSEC, error will be
// set to ErrorDNSSEC.
func (dnsResolver *DNSResolver) LookupCAA(domain string, alias bool) ([]*dns.CAA, error) {
	if alias {
		// Check if there is a CNAME record for domain
		canonName, err := dnsResolver.LookupCNAME(domain)
		if err != nil {
			return nil, err
		}
		if canonName == "" || canonName == domain {
			return []*dns.CAA{}, nil
		}
		domain = canonName
	}

	m := new(dns.Msg)
	m.SetQuestion(dns.Fqdn(domain), dns.TypeCAA)

	r, _, err := dnsResolver.LookupDNSSEC(m)
	if err != nil {
		return nil, err
	}

	var CAAs []*dns.CAA
	for _, answer := range r.Answer {
		if answer.Header().Rrtype == dns.TypeCAA {
			caaR, ok := answer.(*dns.CAA)
			if !ok {
				err = errors.New("Badly formatted record")
				return nil, err
			}
			CAAs = append(CAAs, caaR)
		}
	}

	return CAAs, nil
}

// LookupHost uses a DNSSEC-enabled query to find all A/AAAA records associated with
// the provided hostname. If the query fails due to DNSSEC, error will be
// set to ErrorDNSSEC.
func (dnsResolver *DNSResolver) LookupHost(hostname string) ([]net.IP, time.Duration, error) {
	var addrs []net.IP
	var answers []dns.RR

	m := new(dns.Msg)
	m.SetQuestion(dns.Fqdn(hostname), dns.TypeA)
	r, aRtt, err := dnsResolver.LookupDNSSEC(m)
	if err != nil {
		return addrs, aRtt, err
	}
	answers = append(answers, r.Answer...)

	m.SetQuestion(dns.Fqdn(hostname), dns.TypeAAAA)
	r, aaaaRtt, err := dnsResolver.LookupDNSSEC(m)
	if err != nil {
		return addrs, aRtt + aaaaRtt, err
	}
	answers = append(answers, r.Answer...)

	for _, answer := range answers {
		if answer.Header().Rrtype == dns.TypeA {
			a := answer.(*dns.A)
			addrs = append(addrs, a.A)
		} else if answer.Header().Rrtype == dns.TypeAAAA {
			aaaa := answer.(*dns.AAAA)
			addrs = append(addrs, aaaa.AAAA)
		}
	}

	return addrs, aRtt + aaaaRtt, nil
}

// exchangeOne performs a single DNS exchange with a randomly chosen server
// out of the server list, returning the response, time, and error (if any).
// This method sets the DNSSEC OK bit on the message to true before sending
// it to the resolver in case validation isn't the resolvers default behaviour.
func (dnsResolver *DNSResolverImpl) exchangeOne(hostname string, qtype uint16, msgStats metrics.Scope) (rsp *dns.Msg, err error) {
	m := new(dns.Msg)
	// Set question type
	m.SetQuestion(dns.Fqdn(hostname), qtype)
	// Set DNSSEC OK bit for resolver
	m.SetEdns0(4096, true)

	if len(dnsResolver.Servers) < 1 {
		err = fmt.Errorf("Not configured with at least one DNS Server")
		return
	}

	dnsResolver.stats.Inc("Rate", 1)

	// Randomly pick a server
	chosenServer := dnsResolver.Servers[rand.Intn(len(dnsResolver.Servers))]

	msg, rtt, err := dnsResolver.DNSClient.Exchange(m, chosenServer)
	msgStats.TimingDuration("RTT", rtt)
	if err == nil {
		msgStats.Inc("Successes", 1)
	} else {
		msgStats.Inc("Errors", 1)
	}
	return msg, err
}

func TestDNSDuplicateServers(t *testing.T) {
	obj := NewDNSResolver(time.Second*10, []string{"8.8.8.8:53", "8.8.8.8:53"})

	m := new(dns.Msg)
	m.SetQuestion("letsencrypt.org.", dns.TypeSOA)
	_, _, err := obj.ExchangeOne(m)

	test.AssertNotError(t, err, "No message")
}

// exchangeOne performs a single DNS exchange with a randomly chosen server
// out of the server list, returning the response, time, and error (if any).
// This method sets the DNSSEC OK bit on the message to true before sending
// it to the resolver in case validation isn't the resolvers default behaviour.
func (dnsResolver *DNSResolverImpl) exchangeOne(ctx context.Context, hostname string, qtype uint16, msgStats metrics.Scope) (*dns.Msg, error) {
	m := new(dns.Msg)
	// Set question type
	m.SetQuestion(dns.Fqdn(hostname), qtype)
	// Set DNSSEC OK bit for resolver
	m.SetEdns0(4096, true)

	if len(dnsResolver.Servers) < 1 {
		return nil, fmt.Errorf("Not configured with at least one DNS Server")
	}

	dnsResolver.stats.Inc("Rate", 1)

	// Randomly pick a server
	chosenServer := dnsResolver.Servers[rand.Intn(len(dnsResolver.Servers))]

	client := dnsResolver.DNSClient

	tries := 1
	start := dnsResolver.clk.Now()
	msgStats.Inc("Calls", 1)
	defer msgStats.TimingDuration("Latency", dnsResolver.clk.Now().Sub(start))
	for {
		msgStats.Inc("Tries", 1)
		ch := make(chan dnsResp, 1)

		go func() {
			rsp, rtt, err := client.Exchange(m, chosenServer)
			msgStats.TimingDuration("SingleTryLatency", rtt)
			ch <- dnsResp{m: rsp, err: err}
		}()
		select {
		case <-ctx.Done():
			msgStats.Inc("Cancels", 1)
			msgStats.Inc("Errors", 1)
			return nil, ctx.Err()
		case r := <-ch:
			if r.err != nil {
				msgStats.Inc("Errors", 1)
				operr, ok := r.err.(*net.OpError)
				isRetryable := ok && operr.Temporary()
				hasRetriesLeft := tries < dnsResolver.maxTries
				if isRetryable && hasRetriesLeft {
					tries++
					continue
				} else if isRetryable && !hasRetriesLeft {
					msgStats.Inc("RanOutOfTries", 1)
				}
			} else {
				msgStats.Inc("Successes", 1)
			}
			return r.m, r.err
		}
	}
}

// ExchangeOne performs a single DNS exchange with a randomly chosen server
// out of the server list, returning the response, time, and error (if any).
// This method sets the DNSSEC OK bit on the message to true before sending
// it to the resolver in case validation isn't the resolvers default behaviour.
func (dnsResolver *DNSResolverImpl) ExchangeOne(hostname string, qtype uint16) (rsp *dns.Msg, rtt time.Duration, err error) {
	m := new(dns.Msg)
	// Set question type
	m.SetQuestion(dns.Fqdn(hostname), qtype)
	// Set DNSSEC OK bit for resolver
	m.SetEdns0(4096, true)

	if len(dnsResolver.Servers) < 1 {
		err = fmt.Errorf("Not configured with at least one DNS Server")
		return
	}

	// Randomly pick a server
	chosenServer := dnsResolver.Servers[rand.Intn(len(dnsResolver.Servers))]

	return dnsResolver.DNSClient.Exchange(m, chosenServer)
}

// LookupCNAME uses a DNSSEC-enabled query to  records for domain and returns either
// the target, "", or a if the query fails due to DNSSEC, error will be set to
// ErrorDNSSEC.
func (dnsResolver *DNSResolver) LookupCNAME(domain string) (string, error) {
	m := new(dns.Msg)
	m.SetQuestion(dns.Fqdn(domain), dns.TypeCNAME)

	r, _, err := dnsResolver.LookupDNSSEC(m)
	if err != nil {
		return "", err
	}

	for _, answer := range r.Answer {
		if cname, ok := answer.(*dns.CNAME); ok {
			return cname.Target, nil
		}
	}

	return "", nil
}

// LookupTXT uses a DNSSEC-enabled query to find all TXT records associated with
// the provided hostname. If the query fails due to DNSSEC, error will be
// set to ErrorDNSSEC.
func (dnsResolver *DNSResolver) LookupTXT(hostname string) ([]string, time.Duration, error) {
	var txt []string

	m := new(dns.Msg)
	m.SetQuestion(dns.Fqdn(hostname), dns.TypeTXT)
	r, rtt, err := dnsResolver.LookupDNSSEC(m)

	if err != nil {
		return nil, 0, err
	}

	for _, answer := range r.Answer {
		if answer.Header().Rrtype == dns.TypeTXT {
			txtRec := answer.(*dns.TXT)
			for _, field := range txtRec.Txt {
				txt = append(txt, field)
			}
		}
	}

	return txt, rtt, err
}

func TestDNSSEC(t *testing.T) {
	goodServer := NewDNSResolver(time.Second*10, []string{"8.8.8.8:53"})

	m := new(dns.Msg)
	m.SetQuestion(dns.Fqdn("sigfail.verteiltesysteme.net"), dns.TypeA)

	_, _, err := goodServer.LookupDNSSEC(m)
	test.AssertError(t, err, "DNSSEC failure")
	_, ok := err.(DNSSECError)
	test.Assert(t, ok, "Should have been a DNSSECError")

	m.SetQuestion(dns.Fqdn("sigok.verteiltesysteme.net"), dns.TypeA)

	_, _, err = goodServer.LookupDNSSEC(m)
	test.AssertNotError(t, err, "DNSSEC should have worked")

	badServer := NewDNSResolver(time.Second*10, []string{"127.0.0.1:99"})

	_, _, err = badServer.LookupDNSSEC(m)
	test.AssertError(t, err, "Should have failed")
	_, ok = err.(DNSSECError)
	test.Assert(t, !ok, "Shouldn't have been a DNSSECError")

}