xds: force ipv4 for localhost to workaround ipv6 issue in docker compose (#819)

internal/controlplane/xds_cluster_test.go

@@ -271,4 +271,34 @@ func Test_buildCluster(t *testing.T) {
 			}
 		`, cluster)
 	})
+	t.Run("localhost", func(t *testing.T) {
+		cluster := buildCluster("example", mustParseURL("http://localhost"), nil, true)
+		testutil.AssertProtoJSONEqual(t, `
+			{
+				"name": "example",
+				"type": "STATIC",
+				"connectTimeout": "10s",
+				"respectDnsTtl": true,
+				"http2ProtocolOptions": {
+					"allowConnect": true
+				},
+				"loadAssignment": {
+					"clusterName": "example",
+					"endpoints": [{
+						"lbEndpoints": [{
+							"endpoint": {
+								"address": {
+									"socketAddress": {
+										"address": "127.0.0.1",
+										"ipv4Compat": true,
+										"portValue": 80
+									}
+								}
+							}
+						}]
+					}]
+				}
+			}
+		`, cluster)
+	})
 }

internal/controlplane/xds_clusters.go

@@ -4,6 +4,7 @@ import (
 	"encoding/base64"
 	"net"
 	"net/url"
+	"strings"
 	"time"
 
 	envoy_config_cluster_v3 "github.com/envoyproxy/go-control-plane/envoy/config/cluster/v3"
@@ -185,6 +186,13 @@ func buildCluster(
 		defaultPort = 443
 	}
 
+	if endpoint.Hostname() == "localhost" {
+		u := new(url.URL)
+		*u = *endpoint
+		u.Host = strings.Replace(endpoint.Host, "localhost", "127.0.0.1", -1)
+		endpoint = u
+	}
+
 	cluster := &envoy_config_cluster_v3.Cluster{
 		Name:           name,
 		ConnectTimeout: ptypes.DurationProto(time.Second * 10),