Add route53 plugin (#1390)

* Update vendor

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* Add route53 plugin

This fix adds route53 plugin so that it is possible to
query route53 record through CoreDNS.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

plugin/route53/route53_test.go

@@ -0,0 +1,81 @@
+package route53
+
+import (
+	"testing"
+
+	"github.com/coredns/coredns/plugin/pkg/dnstest"
+	"github.com/coredns/coredns/plugin/test"
+
+	"github.com/aws/aws-sdk-go/aws"
+	"github.com/aws/aws-sdk-go/service/route53"
+	"github.com/aws/aws-sdk-go/service/route53/route53iface"
+	"github.com/miekg/dns"
+	"golang.org/x/net/context"
+)
+
+type mockedRoute53 struct {
+	route53iface.Route53API
+}
+
+func (mockedRoute53) ListResourceRecordSets(input *route53.ListResourceRecordSetsInput) (*route53.ListResourceRecordSetsOutput, error) {
+	return &route53.ListResourceRecordSetsOutput{
+		ResourceRecordSets: []*route53.ResourceRecordSet{
+			{
+				ResourceRecords: []*route53.ResourceRecord{
+					{
+						Value: aws.String("10.2.3.4"),
+					},
+				},
+			},
+		},
+	}, nil
+}
+
+func TestRoute53(t *testing.T) {
+	r := Route53{
+		zones:  []string{"example.org."},
+		keys:   map[string]string{"example.org.": "1234567890"},
+		client: mockedRoute53{},
+	}
+
+	tests := []struct {
+		qname         string
+		qtype         uint16
+		expectedCode  int
+		expectedReply []string // ownernames for the records in the additional section.
+		expectedErr   error
+	}{
+		{
+			qname:         "example.org",
+			qtype:         dns.TypeA,
+			expectedCode:  dns.RcodeSuccess,
+			expectedReply: []string{"example.org."},
+			expectedErr:   nil,
+		},
+	}
+
+	ctx := context.TODO()
+
+	for i, tc := range tests {
+		req := new(dns.Msg)
+		req.SetQuestion(dns.Fqdn(tc.qname), tc.qtype)
+
+		rec := dnstest.NewRecorder(&test.ResponseWriter{})
+		code, err := r.ServeDNS(ctx, rec, req)
+
+		if err != tc.expectedErr {
+			t.Errorf("Test %d: Expected error %v, but got %v", i, tc.expectedErr, err)
+		}
+		if code != int(tc.expectedCode) {
+			t.Errorf("Test %d: Expected status code %d, but got %d", i, tc.expectedCode, code)
+		}
+		if len(tc.expectedReply) != 0 {
+			for i, expected := range tc.expectedReply {
+				actual := rec.Msg.Answer[i].Header().Name
+				if actual != expected {
+					t.Errorf("Test %d: Expected answer %s, but got %s", i, expected, actual)
+				}
+			}
+		}
+	}
+}