controller: echo ip address if destination service receives ip (#186)

Signed-off-by: Sean McArthur <sean@seanmonstar.com>

controller/destination/server.go

@@ -109,6 +109,13 @@ func (s *server) Get(dest *common.Destination, stream pb.Destination_GetServer)
 		}
 	}
 
+	// If this is an IP address, echo it back
+	isIP, ip := isIPAddress(host)
+	if isIP {
+		echoIPDestination(ip, port, stream)
+		return nil
+	}
+
 	id, err := s.localKubernetesServiceIdFromDNSName(host)
 	if err != nil {
 		log.Error(err)
@@ -126,6 +133,34 @@ func (s *server) Get(dest *common.Destination, stream pb.Destination_GetServer)
 	return err
 }
 
+func isIPAddress(host string) (bool, *common.IPAddress) {
+	ip, err := util.ParseIPV4(host)
+	return err == nil, ip
+}
+
+func echoIPDestination(ip *common.IPAddress, port int, stream pb.Destination_GetServer) bool {
+	update := &pb.Update{
+		Update: &pb.Update_Add{
+			Add: &pb.WeightedAddrSet{
+				Addrs: []*pb.WeightedAddr{
+					&pb.WeightedAddr{
+						Addr: &common.TcpAddress{
+							Ip:   ip,
+							Port: uint32(port),
+						},
+						Weight: 1,
+					},
+				},
+			},
+		},
+	}
+	stream.Send(update)
+
+	<-stream.Context().Done()
+
+	return true
+}
+
 func (s *server) resolveKubernetesService(id string, port int, stream pb.Destination_GetServer) error {
 	listener := endpointListener{stream: stream}
 

controller/destination/server_test.go

@@ -2,8 +2,9 @@ package destination
 
 import (
 	"fmt"
-	"github.com/stretchr/testify/assert"
 	"testing"
+
+	"github.com/stretchr/testify/assert"
 )
 
 func TestLocalKubernetesServiceIdFromDNSName(t *testing.T) {
@@ -12,7 +13,7 @@ func TestLocalKubernetesServiceIdFromDNSName(t *testing.T) {
 	testCases := []struct {
 		k8sDNSZone string
 		host       string
-		result     *string
+		result    *string
 		resultErr  bool
 	}{
 		{"cluster.local", "", nil, true},
@@ -88,3 +89,22 @@ func TestSplitDNSName(t *testing.T) {
 		})
 	}
 }
+
+func TestIsIPAddress(t *testing.T) {
+	testCases := []struct {
+		host   string
+		result bool
+	}{
+		{"8.8.8.8", true},
+		{"example.com", false},
+	}
+
+	for i, tc := range testCases {
+		t.Run(fmt.Sprintf("%d: %+v", i, tc.host), func(t *testing.T) {
+			isIP, _ := isIPAddress(tc.host)
+			if isIP != tc.result {
+				t.Fatalf("Unexpected result: %+v", isIP)
+			}
+		})
+	}
+}