Added NS requests.

config.json.sample

@@ -18,5 +18,6 @@
   "dnson": true,
   "httpon": true,
   "httpport": 8123,
-  "externalon": true
+  "externalon": true,
+  "recurseon": true
 }

docs/docs/configuration-parameters.md

@@ -70,3 +70,4 @@ It is sufficient to specify just one of the `zk` or `masters` field. If both are
 
 `SOAMinttl` is the minimum TTL field in the SOA record for the Mesos domain. For details, see the [RFC-2308](https://tools.ietf.org/html/rfc2308). The default value is `60`.
 
+`recurseon` controls if the DNS replies for names in the Mesos domain will indicate that recursion is available. The default value is `true`. 

docs/docs/naming.md

@@ -48,16 +48,21 @@ _search._tcp.marathon.mesos.	60 IN SRV 0 0 31302 10.254.132.41.
 
 SRV records are generated only for tasks that have been allocated a specific port through Mesos. 
 
+## Other Records
+
+Mesos-DNS generates a few special records. Specifically, it creates a set of records for the leading master (A record for `leader.domain` and SRV records for `_leader._tcp.domain` and `_leader._udp.domain`). It also creates creates A records (`master.domain`) and SRV records (`_master._tcp.domain` and `_master._udp.domain`) for every Mesos master it knows about. Note that, if you configure Mesos-DNS to detect the leading master through Zookeeper, then this is the only master it knows about. If you configure Mesos-DNS using the `masters` field, it will generate master records for every master in the list. Also note that there is inherent delay between the election of a new master and the update of leader/master records in Mesos-DNS. 
+
+Mesos-DNS generates A records for itself that list all the IP addresses that Mesos-DNS is listening to. The name for Mesos-DNS can be selected using the `SOARname` [configuration parameter](configuration-parameters.html). The default name is `ns1.mesos`. 
+
+In addition to A and SRV records for Mesos tasks, Mesos-DNS supports requests for SOA and NS records for the Mesos domain. DNS requests for records of other types in the Mesos domain will return `NXDOMAIN`. Mesos-DNS does not support PTR records needed fo reserve lookups. 
 
 ## Notes
 
 If a framework launches multiple tasks with the same name, the DNS lookup will return multiple records, one per task. Mesos-DNS randomly shuffles the order of records to provide rudimentary load balancing between these tasks. 
 
-Mesos-DNS does not support other types of DNS records at this point, including the PTR records needed for reverse lookups. DNS requests for records of type`ANY`, `A`, or `SRV` will return any A or SRV records found. DNS requests for records of other types in the Mesos domain will return `NXDOMAIN`.
+Mesos-DNS follows [RFC 952](https://tools.ietf.org/html/rfc952) for name formatting. All fields used to construct hostnames for A records and service names for SRV records must be up to 24 characters and drawn from the alphabet (A-Z), digits (0-9) and minus sign (-). No distinction is made between upper and lower case. If the task name does not comply with these constraints, Mesos-DNS will trim it, remove all invalid characters, and replace period (.) with sign (-) for task names. For framework names, we allow period (.) but all other constraints apply.  For example, a task named `apiserver.myservice` launch by framework `marathon.prod`, will have A records associated with the name `apiserver-myservice.marathon.prod.mesos` and SRV records associated with name `_apiserver-myservice._tcp.marathon.prod.mesos`. 
 
 Some frameworks register with longer, less friendly names. For example, earlier versions of marathon may register with names like `marathon-0.7.5`, which will lead to names like `search.marathon-0.7.5.mesos`. Make sure your framework registers with the desired name. For instance, you can launch marathon with ` --framework_name marathon` to get the framework registered as `marathon`.  
 
-## Special Records
 
-Mesos-DNS generates a few special records. Specifically, it creates a set of records for the leading master (A record for `leader.domain` and SRV records for `_leader._tcp.domain` and `_leader._udp.domain`). It also creates creates A records (`master.domain`) and SRV records (`_master._tcp.domain` and `_master._udp.domain`) for every Mesos master it knows about. Note that, if you configure Mesos-DNS to detect the leading master through Zookeeper, then this is the only master it knows about. If you configure Mesos-DNS using the `masters` field, it will generate master records for every master in the list. Also not that the is inherent delay between the election of a new master and the update of leader/master records in Mesos-DNS. Finally Mesos-DNS generates A records for itself (`mesos-dns.domain`) that list all the IP addresses that Mesos-DNS is listening to. 
 

records/config.go

@@ -54,6 +54,9 @@ type Config struct {
 	SOAExpire  uint32  // expiration time
 	SOAMinttl  uint32  // minimum TTL
 
+	// Value of RecursionAvailable for responses in Mesos domain
+	RecurseOn bool 
+
 	// ListenAddr is the server listener address
 	Listener string
 
@@ -89,6 +92,7 @@ func SetConfig(cjson string) (c Config) {
 		DnsOn:          true,
 		HttpOn:         true,
 	        ExternalOn:     true,
+	        RecurseOn:      true,
 	}
 
 	// read configuration file
@@ -164,6 +168,7 @@ func SetConfig(cjson string) (c Config) {
 	logging.Verbose.Println("   - SOARetry: ", c.SOARetry)
 	logging.Verbose.Println("   - SOAExpire: ", c.SOAExpire)
 	logging.Verbose.Println("   - SOAExpire: ", c.SOAMinttl)
+	logging.Verbose.Println("   - RecurseOn: ", c.RecurseOn)
 	logging.Verbose.Println("   - HttpPort: ", c.HttpPort)
 	logging.Verbose.Println("   - HttpOn: ", c.HttpOn)
 	logging.Verbose.Println("   - ConfigFile: ", c.File)

records/generator.go

@@ -80,7 +80,7 @@ func (rg *RecordGenerator) ParseState(leader string, c Config) error {
 	}
 
 	// insert state
-	rg.InsertState(sj, c.Domain, c.SOAMname, c.Listener, c.Masters)
+	rg.InsertState(sj, c.Domain, c.SOARname, c.Listener, c.Masters)
 	return nil
 }
 

resolver/resolver.go

@@ -227,8 +227,8 @@ func (res *Resolver) formatSOA(dom string) (*dns.SOA, error) {
 			Class:  dns.ClassINET,
 			Ttl:    ttl,
 		},
-		Ns:      res.config.SOAMname,
-		Mbox:    res.config.SOARname,
+		Ns:      res.config.SOARname,
+		Mbox:    res.config.SOAMname,
 		Serial:  res.config.SOASerial,
 		Refresh: res.config.SOARefresh,
 		Retry:   res.config.SOARetry,
@@ -237,6 +237,23 @@ func (res *Resolver) formatSOA(dom string) (*dns.SOA, error) {
 	}, nil
 }
 
+// formatNS returns the NS  record for the mesos domain
+func (res *Resolver) formatNS(dom string) (*dns.NS, error) {
+	ttl := uint32(res.config.TTL)
+
+	return &dns.NS{
+		Hdr: dns.RR_Header{
+			Name:   dom,
+			Rrtype: dns.TypeNS,
+			Class:  dns.ClassINET,
+			Ttl:    ttl,
+		},
+		Ns:      res.config.SOAMname,
+	}, nil
+}
+
+
+
 // reorders answers for very basic load balancing
 func shuffleAnswers(answers []dns.RR) []dns.RR {
 	rand.Seed(time.Now().UTC().UnixNano())
@@ -315,7 +332,7 @@ func (res *Resolver) HandleMesos(w dns.ResponseWriter, r *dns.Msg) {
 
 	m := new(dns.Msg)
 	m.Authoritative = true
-	m.RecursionAvailable = false
+	m.RecursionAvailable = res.config.RecurseOn
 	m.SetReply(r)
 
 	rs := res.records()
@@ -357,10 +374,7 @@ func (res *Resolver) HandleMesos(w dns.ResponseWriter, r *dns.Msg) {
 	}
 
 	// SOA requests
-	if qType == dns.TypeSOA {
-		m = new(dns.Msg)
-		m.SetReply(r)
-
+	if (qType == dns.TypeSOA)  || (qType == dns.TypeANY) {
 		rr, err := res.formatSOA(r.Question[0].Name)
 		if err != nil {
 			logging.Error.Println(err)
@@ -369,6 +383,17 @@ func (res *Resolver) HandleMesos(w dns.ResponseWriter, r *dns.Msg) {
 		}
 	}
 
+	// NS requests
+	if (qType == dns.TypeNS)  || (qType == dns.TypeANY) {
+		rr, err := res.formatNS(r.Question[0].Name)
+		logging.Error.Println("NS request")
+		if err != nil {
+			logging.Error.Println(err)
+		} else {
+			m.Ns = append(m.Ns, rr)
+		}
+	}
+
 	// shuffle answers
 	m.Answer = shuffleAnswers(m.Answer)
 	// tracing info
@@ -378,16 +403,14 @@ func (res *Resolver) HandleMesos(w dns.ResponseWriter, r *dns.Msg) {
 		logging.CurLog.MesosFailed.Inc()
 	} else if (qType == dns.TypeAAAA) && (len(rs.SRVs[dom]) > 0 || len(rs.As[dom]) > 0) {
 		// correct handling of AAAA if there are A or SRV records
-		m = new(dns.Msg)
 		m.Authoritative = true
 		// set NOERROR
 		m.SetRcode(r, 0)
 		// leave answer empty (NOERROR --> NODATA)
 
 	} else {
 		// no answers but not a {SOA,SRV} request
-		if len(m.Answer) == 0 && (qType != dns.TypeSOA) && (qType != dns.TypeSRV) {
-			m = new(dns.Msg)
+		if len(m.Answer) == 0 && (qType != dns.TypeSOA)  && (qType != dns.TypeNS) && (qType != dns.TypeSRV) {
 			// set NXDOMAIN
 			m.SetRcode(r, 3)
 

resolver/resolver_test.go

@@ -180,15 +180,26 @@ func TestHandler(t *testing.T) {
 	}
 
 	// test SOA
-	m, err2 := fakeMsg("non-existing.mesos.", dns.TypeSOA, "udp")
-	if err2 != nil {
-		t.Error(err2)
+	m, err := fakeMsg("non-existing.mesos.", dns.TypeSOA, "udp")
+	if err != nil {
+		t.Error(err)
 	}
 
 	if m.Ns == nil {
 		t.Error("not serving up SOA")
 	}
 
+	// test NS
+	m, err = fakeMsg("non-existing2.mesos.", dns.TypeNS, "udp")
+	if err != nil {
+		t.Error(err)
+	}
+
+	if m.Ns == nil {
+		t.Error("not serving up NS")
+	}
+
+
 	// test non-existing host
 	m, err = fakeMsg("missing.mesos.", dns.TypeA, "udp")
 	if err != nil {