plugin/etcd: propagate recursion flag properly (#2254)

When fetching records via the etcd plugin, the recursion flag was never
set properly according to if the caller requested an exact record match
or not. This cause problems especially in CNAME lookups, where recursion
took place and a random RR was returned instead of the one that was
specifically added for this key. Even when there is no service attached
on the given path, it is still wrong to return a random one from the
recursion.

Fixing by using the `exact` flag to decide if recursion should be done.

plugin/etcd/cname_test.go

@@ -57,6 +57,7 @@ var servicesCname = []*msg.Service{
 	{Host: "cname5.region2.skydns.test", Key: "cname4.region2.skydns.test."},
 	{Host: "cname6.region2.skydns.test", Key: "cname5.region2.skydns.test."},
 	{Host: "endpoint.region2.skydns.test", Key: "cname6.region2.skydns.test."},
+	{Host: "mainendpoint.region2.skydns.test", Key: "region2.skydns.test."},
 	{Host: "10.240.0.1", Key: "endpoint.region2.skydns.test."},
 }
 
@@ -76,4 +77,10 @@ var dnsTestCasesCname = []test.Case{
 			test.A("endpoint.region2.skydns.test.	300	IN	A	10.240.0.1"),
 		},
 	},
+	{
+		Qname: "region2.skydns.test.", Qtype: dns.TypeCNAME,
+		Answer: []dns.RR{
+			test.CNAME("region2.skydns.test.	300	IN	CNAME	mainendpoint.region2.skydns.test."),
+		},
+	},
 }

plugin/etcd/etcd.go

@@ -75,7 +75,7 @@ func (e *Etcd) Records(state request.Request, exact bool) ([]msg.Service, error)
 	name := state.Name()
 
 	path, star := msg.PathWithWildcard(name, e.PathPrefix)
-	r, err := e.get(path, true)
+	r, err := e.get(path, !exact)
 	if err != nil {
 		return nil, err
 	}