Golang Msg.SetEdns0方法代碼示例

// LookupDNSSEC sends the provided DNS message to a randomly chosen server (see
// ExchangeOne) with DNSSEC enabled. If the lookup fails, this method sends a
// clarification query to determine if it's because DNSSEC was invalid or just
// a run-of-the-mill error. If it's because of DNSSEC, it returns ErrorDNSSEC.
func (dnsResolver *DNSResolver) LookupDNSSEC(m *dns.Msg) (*dns.Msg, time.Duration, error) {
	// Set DNSSEC OK bit
	m.SetEdns0(4096, true)
	r, rtt, err := dnsResolver.ExchangeOne(m)
	if err != nil {
		return r, rtt, err
	}

	if r.Rcode != dns.RcodeSuccess && r.Rcode != dns.RcodeNameError && r.Rcode != dns.RcodeNXRrset {
		if r.Rcode == dns.RcodeServerFailure {
			// Re-send query with +cd to see if SERVFAIL was caused by DNSSEC
			// validation failure at the resolver
			m.CheckingDisabled = true
			checkR, _, err := dnsResolver.ExchangeOne(m)
			if err != nil {
				return r, rtt, err
			}

			if checkR.Rcode != dns.RcodeServerFailure {
				// DNSSEC error, so we return the testable object.
				err = DNSSECError{}
				return r, rtt, err
			}
		}
		err = fmt.Errorf("Invalid response code: %d-%s", r.Rcode, dns.RcodeToString[r.Rcode])
		return r, rtt, err
	}

	return r, rtt, 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, 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
}

// 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)
}