From d10e6d02924c70207d4f7ffebbd9274abc41aaa9 Mon Sep 17 00:00:00 2001
From: Wim <wim@42.be>
Date: Mon, 21 May 2018 22:27:41 +0200
Subject: [PATCH] Do reverse service lookup only if address doesn't match node

---
 agent/dns.go | 41 ++++++++++++++++++++++-------------------
 1 file changed, 22 insertions(+), 19 deletions(-)

diff --git a/agent/dns.go b/agent/dns.go
index 7e4b816f96..27c14f429b 100644
--- a/agent/dns.go
+++ b/agent/dns.go
@@ -208,27 +208,30 @@ func (d *DNSServer) handlePtr(resp dns.ResponseWriter, req *dns.Msg) {
 		}
 	}
 
-	// lookup the service address
-	serviceAddress := dnsutil.ExtractAddressFromReverse(qName)
-	sargs := structs.ServiceSpecificRequest{
-		Datacenter: datacenter,
-		QueryOptions: structs.QueryOptions{
-			Token:      d.agent.tokens.UserToken(),
-			AllowStale: d.config.AllowStale,
-		},
-		ServiceAddress: serviceAddress,
-	}
+	// only look into the services if we didn't find a node
+	if len(m.Answer) == 0 {
+		// lookup the service address
+		serviceAddress := dnsutil.ExtractAddressFromReverse(qName)
+		sargs := structs.ServiceSpecificRequest{
+			Datacenter: datacenter,
+			QueryOptions: structs.QueryOptions{
+				Token:      d.agent.tokens.UserToken(),
+				AllowStale: d.config.AllowStale,
+			},
+			ServiceAddress: serviceAddress,
+		}
 
-	var sout structs.IndexedServiceNodes
-	if err := d.agent.RPC("Catalog.ServiceNodes", &sargs, &sout); err == nil {
-		for _, n := range sout.ServiceNodes {
-			if n.ServiceAddress == serviceAddress {
-				ptr := &dns.PTR{
-					Hdr: dns.RR_Header{Name: q.Name, Rrtype: dns.TypePTR, Class: dns.ClassINET, Ttl: 0},
-					Ptr: fmt.Sprintf("%s.service.%s", n.ServiceName, d.domain),
+		var sout structs.IndexedServiceNodes
+		if err := d.agent.RPC("Catalog.ServiceNodes", &sargs, &sout); err == nil {
+			for _, n := range sout.ServiceNodes {
+				if n.ServiceAddress == serviceAddress {
+					ptr := &dns.PTR{
+						Hdr: dns.RR_Header{Name: q.Name, Rrtype: dns.TypePTR, Class: dns.ClassINET, Ttl: 0},
+						Ptr: fmt.Sprintf("%s.service.%s", n.ServiceName, d.domain),
+					}
+					m.Answer = append(m.Answer, ptr)
+					break
 				}
-				m.Answer = append(m.Answer, ptr)
-				break
 			}
 		}
 	}