plugin/kubernetes: fix case preservation and add test (#2430)

* fix case preservation and add test
* only fix case in k8s

2 files changed, 74 insertions, 2 deletions

diff --git a/plugin/kubernetes/handler.go b/plugin/kubernetes/handler.go
index 4d70279b7..e829a5f78 100644
--- a/plugin/kubernetes/handler.go
+++ b/plugin/kubernetes/handler.go
@@ -18,11 +18,12 @@ func (k Kubernetes) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.M
 	m.SetReply(r)
 	m.Authoritative = true
 
-	zone := plugin.Zones(k.Zones).Matches(state.Name())
+	qname := state.QName()
+	zone := plugin.Zones(k.Zones).Matches(qname)
 	if zone == "" {
 		return plugin.NextOrFailure(k.Name(), k.Next, ctx, w, r)
 	}
-
+	zone = qname[len(qname)-len(zone):] // maintain case of original query
 	state.Zone = zone
 
 	var (
diff --git a/plugin/kubernetes/handler_case_test.go b/plugin/kubernetes/handler_case_test.go
new file mode 100644
index 000000000..e59f21166
--- /dev/null
+++ b/plugin/kubernetes/handler_case_test.go
@@ -0,0 +1,71 @@
+package kubernetes
+
+import (
+	"context"
+	"testing"
+
+	"github.com/coredns/coredns/plugin/pkg/dnstest"
+	"github.com/coredns/coredns/plugin/test"
+
+	"github.com/miekg/dns"
+)
+
+var dnsPreserveCaseCases = []test.Case{
+	// Negative response
+	{
+		Qname: "not-a-service.testns.svc.ClUsTeR.lOcAl.", Qtype: dns.TypeA,
+		Rcode: dns.RcodeNameError,
+		Ns: []dns.RR{
+			test.SOA("ClUsTeR.lOcAl.	30	IN	SOA	ns.dns.ClUsTeR.lOcAl. hostmaster.ClUsTeR.lOcAl. 1499347823 7200 1800 86400 60"),
+		},
+	},
+	// A Service
+	{
+		Qname: "SvC1.TeStNs.SvC.cLuStEr.LoCaL.", Qtype: dns.TypeA,
+		Rcode: dns.RcodeSuccess,
+		Answer: []dns.RR{
+			test.A("SvC1.TeStNs.SvC.cLuStEr.LoCaL.	5	IN	A	10.0.0.1"),
+		},
+	},
+	// SRV Service
+	{
+		Qname: "_HtTp._TcP.sVc1.TeStNs.SvC.cLuStEr.LoCaL.", Qtype: dns.TypeSRV,
+		Rcode: dns.RcodeSuccess,
+		Answer: []dns.RR{
+			test.SRV("_HtTp._TcP.sVc1.TeStNs.SvC.cLuStEr.LoCaL.	5	IN	SRV	0 100 80 svc1.testns.svc.cLuStEr.LoCaL."),
+		},
+		Extra: []dns.RR{
+			test.A("svc1.testns.svc.cLuStEr.LoCaL.	5	IN	A	10.0.0.1"),
+		},
+	},
+}
+
+func TestPreserveCase(t *testing.T) {
+	k := New([]string{"cluster.local."})
+	k.APIConn = &APIConnServeTest{}
+	k.opts.ignoreEmptyService = true
+	k.Next = test.NextHandler(dns.RcodeSuccess, nil)
+	ctx := context.TODO()
+
+	for i, tc := range dnsPreserveCaseCases {
+		r := tc.Msg()
+
+		w := dnstest.NewRecorder(&test.ResponseWriter{})
+
+		_, err := k.ServeDNS(ctx, w, r)
+		if err != tc.Error {
+			t.Errorf("Test %d expected no error, got %v", i, err)
+			return
+		}
+		if tc.Error != nil {
+			continue
+		}
+
+		resp := w.Msg
+		if resp == nil {
+			t.Fatalf("Test %d, got nil message and no error for %q", i, r.Question[0].Name)
+		}
+
+		test.SortAndCheck(t, resp, tc)
+	}
+}