Returns DNS Error NSDOMAIN when DC does not exists

agent/dns.go

@@ -818,6 +818,18 @@ func (d *DNSServer) trimDomain(query string) string {
 	return strings.TrimSuffix(query, shorter)
 }
 
+// computeRCode Return the DNS Error code from Consul Error
+func (d *DNSServer) computeRCode(err error) int {
+	if err == nil {
+		return dns.RcodeSuccess
+	}
+	dErr := err.Error()
+	if dErr == structs.ErrNoDCPath.Error() || dErr == consul.ErrQueryNotFound.Error() {
+		return dns.RcodeNameError
+	}
+	return dns.RcodeServerFailure
+}
+
 // nodeLookup is used to handle a node query
 func (d *DNSServer) nodeLookup(cfg *dnsConfig, network, datacenter, node string, req, resp *dns.Msg, maxRecursionLevel int) {
 	// Only handle ANY, A, AAAA, and TXT type requests
@@ -838,7 +850,11 @@ func (d *DNSServer) nodeLookup(cfg *dnsConfig, network, datacenter, node string,
 	out, err := d.lookupNode(cfg, args)
 	if err != nil {
 		d.logger.Error("rpc error", "error", err)
-		resp.SetRcode(req, dns.RcodeServerFailure)
+		rCode := d.computeRCode(err)
+		if rCode == dns.RcodeNameError {
+			d.addSOA(cfg, resp)
+		}
+		resp.SetRcode(req, rCode)
 		return
 	}
 
@@ -1202,7 +1218,11 @@ func (d *DNSServer) serviceLookup(cfg *dnsConfig, lookup serviceLookup, req, res
 	out, err := d.lookupServiceNodes(cfg, lookup)
 	if err != nil {
 		d.logger.Error("rpc error", "error", err)
-		resp.SetRcode(req, dns.RcodeServerFailure)
+		rCode := d.computeRCode(err)
+		if rCode == dns.RcodeNameError {
+			d.addSOA(cfg, resp)
+		}
+		resp.SetRcode(req, rCode)
 		return
 	}
 
@@ -1296,12 +1316,12 @@ func (d *DNSServer) preparedQueryLookup(cfg *dnsConfig, network, datacenter, que
 	// If they give a bogus query name, treat that as a name error,
 	// not a full on server error. We have to use a string compare
 	// here since the RPC layer loses the type information.
-	if err != nil && err.Error() == consul.ErrQueryNotFound.Error() {
-		d.addSOA(cfg, resp)
-		resp.SetRcode(req, dns.RcodeNameError)
-		return
-	} else if err != nil {
-		resp.SetRcode(req, dns.RcodeServerFailure)
+	if err != nil {
+		rCode := d.computeRCode(err)
+		if rCode == dns.RcodeNameError {
+			d.addSOA(cfg, resp)
+		}
+		resp.SetRcode(req, rCode)
 		return
 	}
 

agent/dns_test.go

@@ -5790,6 +5790,27 @@ func TestDNS_AddressLookupIPV6(t *testing.T) {
 	}
 }
 
+func TestDNS_NonExistingDC(t *testing.T) {
+	t.Parallel()
+	a := NewTestAgent(t, "")
+	defer a.Shutdown()
+	testrpc.WaitForLeader(t, a.RPC, "dc1")
+
+	// lookup a non-existing node, we should receive a SOA
+	m := new(dns.Msg)
+	m.SetQuestion("consul.dc2.consul.", dns.TypeANY)
+
+	c := new(dns.Client)
+	in, _, err := c.Exchange(m, a.DNSAddr())
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+
+	if in.Rcode != dns.RcodeNameError {
+		t.Fatalf("Expected RCode: %#v, had: %#v", dns.RcodeNameError, in.Rcode)
+	}
+}
+
 func TestDNS_NonExistingLookup(t *testing.T) {
 	t.Parallel()
 	a := NewTestAgent(t, "")