Example #1
0
// handleTest is used to handle DNS queries in the ".consul." domain
func (d *DNSServer) handleTest(resp dns.ResponseWriter, req *dns.Msg) {
	q := req.Question[0]
	defer func(s time.Time) {
		d.logger.Printf("[DEBUG] dns: request for %v (%v)", q, time.Now().Sub(s))
	}(time.Now())

	if !(q.Qtype == dns.TypeANY || q.Qtype == dns.TypeTXT) {
		return
	}
	if q.Name != testQuery {
		return
	}

	// Always respond with TXT "ok"
	m := new(dns.Msg)
	m.SetReply(req)
	m.Authoritative = true
	m.RecursionAvailable = true
	header := dns.RR_Header{Name: q.Name, Rrtype: dns.TypeTXT, Class: dns.ClassINET, Ttl: 0}
	txt := &dns.TXT{Hdr: header, Txt: []string{"ok"}}
	m.Answer = append(m.Answer, txt)
	d.addSOA(consulDomain, m)
	if err := resp.WriteMsg(m); err != nil {
		d.logger.Printf("[WARN] dns: failed to respond: %v", err)
	}
}
Example #2
0
// handlePtr is used to handle "reverse" DNS queries
func (d *DNSServer) handlePtr(resp dns.ResponseWriter, req *dns.Msg) {
	q := req.Question[0]
	defer func(s time.Time) {
		d.logger.Printf("[DEBUG] dns: request for %v (%v)", q, time.Now().Sub(s))
	}(time.Now())

	// Setup the message response
	m := new(dns.Msg)
	m.SetReply(req)
	m.Authoritative = true
	m.RecursionAvailable = (len(d.recursors) > 0)

	// Only add the SOA if requested
	if req.Question[0].Qtype == dns.TypeSOA {
		d.addSOA(d.domain, m)
	}

	datacenter := d.agent.config.Datacenter

	// Get the QName without the domain suffix
	qName := strings.ToLower(dns.Fqdn(req.Question[0].Name))

	args := structs.DCSpecificRequest{
		Datacenter:   datacenter,
		QueryOptions: structs.QueryOptions{AllowStale: d.config.AllowStale},
	}
	var out structs.IndexedNodes

	// TODO: Replace ListNodes with an internal RPC that can do the filter
	// server side to avoid transferring the entire node list.
	if err := d.agent.RPC("Catalog.ListNodes", &args, &out); err == nil {
		for _, n := range out.Nodes {
			arpa, _ := dns.ReverseAddr(n.Address)
			if arpa == qName {
				ptr := &dns.PTR{
					Hdr: dns.RR_Header{Name: q.Name, Rrtype: dns.TypePTR, Class: dns.ClassINET, Ttl: 0},
					Ptr: fmt.Sprintf("%s.node.%s.%s", n.Node, datacenter, d.domain),
				}
				m.Answer = append(m.Answer, ptr)
				break
			}
		}
	}

	// Write out the complete response
	if err := resp.WriteMsg(m); err != nil {
		d.logger.Printf("[WARN] dns: failed to respond: %v", err)
	}
}
Example #3
0
// handleQUery is used to handle DNS queries in the configured domain
func (d *DNSServer) handleQuery(resp dns.ResponseWriter, req *dns.Msg) {
	q := req.Question[0]
	defer func(s time.Time) {
		d.logger.Printf("[DEBUG] dns: request for %v (%v)", q, time.Now().Sub(s))
	}(time.Now())

	// Check if this is potentially a test query
	if q.Name == testQuery {
		d.handleTest(resp, req)
		return
	}

	// Switch to TCP if the client is
	network := "udp"
	if _, ok := resp.RemoteAddr().(*net.TCPAddr); ok {
		network = "tcp"
	}

	// Setup the message response
	m := new(dns.Msg)
	m.SetReply(req)
	m.Authoritative = true
	m.RecursionAvailable = (len(d.recursors) > 0)

	// Only add the SOA if requested
	if req.Question[0].Qtype == dns.TypeSOA {
		d.addSOA(d.domain, m)
	}

	// Dispatch the correct handler
	d.dispatch(network, req, m)

	// Write out the complete response
	if err := resp.WriteMsg(m); err != nil {
		d.logger.Printf("[WARN] dns: failed to respond: %v", err)
	}
}
Example #4
0
// handleRecurse is used to handle recursive DNS queries
func (d *DNSServer) handleRecurse(resp dns.ResponseWriter, req *dns.Msg) {
	q := req.Question[0]
	network := "udp"
	defer func(s time.Time) {
		d.logger.Printf("[DEBUG] dns: request for %v (%s) (%v)", q, network, time.Now().Sub(s))
	}(time.Now())

	// Switch to TCP if the client is
	if _, ok := resp.RemoteAddr().(*net.TCPAddr); ok {
		network = "tcp"
	}

	// Recursively resolve
	c := &dns.Client{Net: network}
	var r *dns.Msg
	var rtt time.Duration
	var err error
	for _, recursor := range d.recursors {
		r, rtt, err = c.Exchange(req, recursor)
		if err == nil {
			// Forward the response
			d.logger.Printf("[DEBUG] dns: recurse RTT for %v (%v)", q, rtt)
			if err := resp.WriteMsg(r); err != nil {
				d.logger.Printf("[WARN] dns: failed to respond: %v", err)
			}
			return
		}
		d.logger.Printf("[ERR] dns: recurse failed: %v", err)
	}

	// If all resolvers fail, return a SERVFAIL message
	d.logger.Printf("[ERR] dns: all resolvers failed for %v", q)
	m := &dns.Msg{}
	m.SetReply(req)
	m.RecursionAvailable = true
	m.SetRcode(req, dns.RcodeServerFailure)
	resp.WriteMsg(m)
}