Merge pull request #24521 from yang-g/ip46

Check localhost is resolved to ipv4 or ipv6 and update test accordingly.

CMakeLists.txt

@@ -2087,6 +2087,7 @@ add_library(grpc_test_util
   test/core/util/port_isolated_runtime_environment.cc
   test/core/util/port_server_client.cc
   test/core/util/reconnect_server.cc
+  test/core/util/resolve_localhost_ip46.cc
   test/core/util/slice_splitter.cc
   test/core/util/subprocess_posix.cc
   test/core/util/subprocess_windows.cc
@@ -2158,6 +2159,7 @@ add_library(grpc_test_util_unsecure
   test/core/util/port_isolated_runtime_environment.cc
   test/core/util/port_server_client.cc
   test/core/util/reconnect_server.cc
+  test/core/util/resolve_localhost_ip46.cc
   test/core/util/slice_splitter.cc
   test/core/util/subprocess_posix.cc
   test/core/util/subprocess_windows.cc
@@ -15072,6 +15074,7 @@ if(_gRPC_PLATFORM_LINUX OR _gRPC_PLATFORM_MAC OR _gRPC_PLATFORM_POSIX)
     test/core/util/port_isolated_runtime_environment.cc
     test/core/util/port_server_client.cc
     test/core/util/reconnect_server.cc
+    test/core/util/resolve_localhost_ip46.cc
     test/core/util/slice_splitter.cc
     test/core/util/subprocess_posix.cc
     test/core/util/subprocess_windows.cc

build_autogenerated.yaml

@@ -1416,6 +1416,7 @@ libs:
   - test/core/util/port.h
   - test/core/util/port_server_client.h
   - test/core/util/reconnect_server.h
+  - test/core/util/resolve_localhost_ip46.h
   - test/core/util/slice_splitter.h
   - test/core/util/subprocess.h
   - test/core/util/test_config.h
@@ -1438,6 +1439,7 @@ libs:
   - test/core/util/port_isolated_runtime_environment.cc
   - test/core/util/port_server_client.cc
   - test/core/util/reconnect_server.cc
+  - test/core/util/resolve_localhost_ip46.cc
   - test/core/util/slice_splitter.cc
   - test/core/util/subprocess_posix.cc
   - test/core/util/subprocess_windows.cc
@@ -1472,6 +1474,7 @@ libs:
   - test/core/util/port.h
   - test/core/util/port_server_client.h
   - test/core/util/reconnect_server.h
+  - test/core/util/resolve_localhost_ip46.h
   - test/core/util/slice_splitter.h
   - test/core/util/subprocess.h
   - test/core/util/test_config.h
@@ -1494,6 +1497,7 @@ libs:
   - test/core/util/port_isolated_runtime_environment.cc
   - test/core/util/port_server_client.cc
   - test/core/util/reconnect_server.cc
+  - test/core/util/resolve_localhost_ip46.cc
   - test/core/util/slice_splitter.cc
   - test/core/util/subprocess_posix.cc
   - test/core/util/subprocess_windows.cc
@@ -7667,6 +7671,7 @@ targets:
   - test/core/util/port.h
   - test/core/util/port_server_client.h
   - test/core/util/reconnect_server.h
+  - test/core/util/resolve_localhost_ip46.h
   - test/core/util/slice_splitter.h
   - test/core/util/subprocess.h
   - test/core/util/test_config.h
@@ -7692,6 +7697,7 @@ targets:
   - test/core/util/port_isolated_runtime_environment.cc
   - test/core/util/port_server_client.cc
   - test/core/util/reconnect_server.cc
+  - test/core/util/resolve_localhost_ip46.cc
   - test/core/util/slice_splitter.cc
   - test/core/util/subprocess_posix.cc
   - test/core/util/subprocess_windows.cc

gRPC-Core.podspec

@@ -2021,6 +2021,8 @@ Pod::Spec.new do |s|
                       'test/core/util/port_server_client.h',
                       'test/core/util/reconnect_server.cc',
                       'test/core/util/reconnect_server.h',
+                      'test/core/util/resolve_localhost_ip46.cc',
+                      'test/core/util/resolve_localhost_ip46.h',
                       'test/core/util/slice_splitter.cc',
                       'test/core/util/slice_splitter.h',
                       'test/core/util/subprocess.h',

grpc.gyp

@@ -1007,6 +1007,7 @@
         'test/core/util/port_isolated_runtime_environment.cc',
         'test/core/util/port_server_client.cc',
         'test/core/util/reconnect_server.cc',
+        'test/core/util/resolve_localhost_ip46.cc',
         'test/core/util/slice_splitter.cc',
         'test/core/util/subprocess_posix.cc',
         'test/core/util/subprocess_windows.cc',
@@ -1044,6 +1045,7 @@
         'test/core/util/port_isolated_runtime_environment.cc',
         'test/core/util/port_server_client.cc',
         'test/core/util/reconnect_server.cc',
+        'test/core/util/resolve_localhost_ip46.cc',
         'test/core/util/slice_splitter.cc',
         'test/core/util/subprocess_posix.cc',
         'test/core/util/subprocess_windows.cc',

test/core/util/BUILD

@@ -51,6 +51,7 @@ grpc_cc_library(
         "port_isolated_runtime_environment.cc",
         "port_server_client.cc",
         "reconnect_server.cc",
+        "resolve_localhost_ip46.cc",
         "slice_splitter.cc",
         "subprocess_posix.cc",
         "subprocess_windows.cc",
@@ -73,6 +74,7 @@ grpc_cc_library(
         "port.h",
         "port_server_client.h",
         "reconnect_server.h",
+        "resolve_localhost_ip46.h",
         "slice_splitter.h",
         "subprocess.h",
         "test_config.h",
@@ -94,6 +96,7 @@ grpc_cc_library(
     deps = [
         ":grpc_debugger_macros",
         "//:gpr",
+        "//:grpc_base_c",
         "//:grpc_common",
     ],
 )

test/core/util/resolve_localhost_ip46.cc

@@ -0,0 +1,58 @@
+//
+//
+// Copyright 2020 gRPC authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+//
+
+#include "test/core/util/resolve_localhost_ip46.h"
+
+#include <grpc/support/log.h>
+
+#include "src/core/lib/iomgr/port.h"
+#include "src/core/lib/iomgr/resolve_address.h"
+#include "src/core/lib/iomgr/sockaddr.h"
+
+namespace grpc_core {
+namespace {
+
+bool localhost_to_ipv4 = false;
+bool localhost_to_ipv6 = false;
+gpr_once g_resolve_localhost_ipv46 = GPR_ONCE_INIT;
+
+void InitResolveLocalhost() {
+  grpc_resolved_addresses* addresses;
+  grpc_error* err =
+      grpc_blocking_resolve_address("localhost", "https", &addresses);
+  GPR_ASSERT(err == GRPC_ERROR_NONE);
+  for (size_t i = 0; i < addresses->naddrs; i++) {
+    grpc_sockaddr* addr =
+        reinterpret_cast<grpc_sockaddr*>(addresses->addrs[i].addr);
+    if (addr->sa_family == GRPC_AF_INET) {
+      localhost_to_ipv4 = true;
+    } else if (addr->sa_family == GRPC_AF_INET6) {
+      localhost_to_ipv6 = true;
+    }
+  }
+  grpc_resolved_addresses_destroy(addresses);
+}
+}  // namespace
+
+void LocalhostResolves(bool* ipv4, bool* ipv6) {
+  gpr_once_init(&g_resolve_localhost_ipv46, InitResolveLocalhost);
+  *ipv4 = localhost_to_ipv4;
+  *ipv6 = localhost_to_ipv6;
+}
+
+}  // namespace grpc_core

test/core/util/resolve_localhost_ip46.h

@@ -0,0 +1,29 @@
+//
+//
+// Copyright 2020 gRPC authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+//
+
+#ifndef GRPC_TEST_CORE_UTIL_RESOLVE_LOCALHOST_IP46_H_
+#define GRPC_TEST_CORE_UTIL_RESOLVE_LOCALHOST_IP46_H_
+
+namespace grpc_core {
+
+// Test whether localhost resolves to ipv4 and/or ipv6
+void LocalhostResolves(bool* ipv4, bool* ipv6);
+
+}  // namespace grpc_core
+
+#endif  // GRPC_TEST_CORE_UTIL_RESOLVE_LOCALHOST_IP46_H_

test/cpp/end2end/client_lb_end2end_test.cc

@@ -59,6 +59,7 @@
 #include "src/proto/grpc/testing/echo.grpc.pb.h"
 #include "src/proto/grpc/testing/xds/orca_load_report_for_test.pb.h"
 #include "test/core/util/port.h"
+#include "test/core/util/resolve_localhost_ip46.h"
 #include "test/core/util/test_config.h"
 #include "test/core/util/test_lb_policies.h"
 #include "test/cpp/end2end/test_service_impl.h"
@@ -152,12 +153,14 @@ class MyTestServiceImpl : public TestServiceImpl {
 
 class FakeResolverResponseGeneratorWrapper {
  public:
-  FakeResolverResponseGeneratorWrapper()
+  explicit FakeResolverResponseGeneratorWrapper(bool ipv6_only)
-      : response_generator_(grpc_core::MakeRefCounted<
+      : ipv6_only_(ipv6_only),
+        response_generator_(grpc_core::MakeRefCounted<
                             grpc_core::FakeResolverResponseGenerator>()) {}
 
   FakeResolverResponseGeneratorWrapper(
       FakeResolverResponseGeneratorWrapper&& other) noexcept {
+    ipv6_only_ = other.ipv6_only_;
     response_generator_ = std::move(other.response_generator_);
   }
 
@@ -167,13 +170,22 @@ class FakeResolverResponseGeneratorWrapper {
       std::unique_ptr<grpc_core::ServerAddress::AttributeInterface> attribute =
           nullptr) {
     grpc_core::ExecCtx exec_ctx;
-    response_generator_->SetResponse(BuildFakeResults(
+    // This is a dummy log line as a workaround for
-        ports, service_config_json, attribute_key, std::move(attribute)));
+    // https://github.com/grpc/grpc/issues/24550. It should be removed once the
+    // testing infrastructure updates compiler for MacOS.
+    if (service_config_json != nullptr) {
+      gpr_log(GPR_INFO, "SetNextResolution with service_config_json: %s",
+              service_config_json);
+    }
+    response_generator_->SetResponse(
+        BuildFakeResults(ipv6_only_, ports, service_config_json, attribute_key,
+                         std::move(attribute)));
   }
 
   void SetNextResolutionUponError(const std::vector<int>& ports) {
     grpc_core::ExecCtx exec_ctx;
-    response_generator_->SetReresolutionResponse(BuildFakeResults(ports));
+    response_generator_->SetReresolutionResponse(
+        BuildFakeResults(ipv6_only_, ports));
   }
 
   void SetFailureOnReresolution() {
@@ -187,13 +199,15 @@ class FakeResolverResponseGeneratorWrapper {
 
  private:
   static grpc_core::Resolver::Result BuildFakeResults(
-      const std::vector<int>& ports, const char* service_config_json = nullptr,
+      bool ipv6_only, const std::vector<int>& ports,
+      const char* service_config_json = nullptr,
       const char* attribute_key = nullptr,
       std::unique_ptr<grpc_core::ServerAddress::AttributeInterface> attribute =
           nullptr) {
     grpc_core::Resolver::Result result;
     for (const int& port : ports) {
-      std::string lb_uri_str = absl::StrCat("ipv4:127.0.0.1:", port);
+      std::string lb_uri_str =
+          absl::StrCat(ipv6_only ? "ipv6:[::1]:" : "ipv4:127.0.0.1:", port);
       grpc_uri* lb_uri = grpc_uri_parse(lb_uri_str.c_str(), true);
       GPR_ASSERT(lb_uri != nullptr);
       grpc_resolved_address address;
@@ -216,6 +230,7 @@ class FakeResolverResponseGeneratorWrapper {
     return result;
   }
 
+  bool ipv6_only_ = false;
   grpc_core::RefCountedPtr<grpc_core::FakeResolverResponseGenerator>
       response_generator_;
 };
@@ -238,7 +253,14 @@ class ClientLbEnd2endTest : public ::testing::Test {
 #endif
   }
 
-  void SetUp() override { grpc_init(); }
+  void SetUp() override {
+    grpc_init();
+    bool localhost_resolves_to_ipv4 = false;
+    bool localhost_resolves_to_ipv6 = false;
+    grpc_core::LocalhostResolves(&localhost_resolves_to_ipv4,
+                                 &localhost_resolves_to_ipv6);
+    ipv6_only_ = !localhost_resolves_to_ipv4 && localhost_resolves_to_ipv6;
+  }
 
   void TearDown() override {
     for (size_t i = 0; i < servers_.size(); ++i) {
@@ -278,7 +300,7 @@ class ClientLbEnd2endTest : public ::testing::Test {
   }
 
   FakeResolverResponseGeneratorWrapper BuildResolverResponseGenerator() {
-    return FakeResolverResponseGeneratorWrapper();
+    return FakeResolverResponseGeneratorWrapper(ipv6_only_);
   }
 
   std::unique_ptr<grpc::testing::EchoTestService::Stub> BuildStub(
@@ -468,6 +490,7 @@ class ClientLbEnd2endTest : public ::testing::Test {
   std::vector<std::unique_ptr<ServerData>> servers_;
   const std::string kRequestMessage_;
   std::shared_ptr<ChannelCredentials> creds_;
+  bool ipv6_only_ = false;
 };
 
 TEST_F(ClientLbEnd2endTest, ChannelStateConnectingWhenResolving) {
@@ -1969,8 +1992,9 @@ TEST_F(ClientLbAddressTest, Basic) {
   // Make sure that the attributes wind up on the subchannels.
   std::vector<std::string> expected;
   for (const int port : GetServersPorts()) {
-    expected.emplace_back(absl::StrCat(
+    expected.emplace_back(
-        "127.0.0.1:", port, " args={} attributes={", kAttributeKey, "=foo}"));
+        absl::StrCat(ipv6_only_ ? "[::1]:" : "127.0.0.1:", port,
+                     " args={} attributes={", kAttributeKey, "=foo}"));
   }
   EXPECT_EQ(addresses_seen(), expected);
 }

test/cpp/end2end/end2end_test.cc

@@ -350,7 +350,7 @@ class End2endTest : public ::testing::TestWithParam<TestScenario> {
   void StartServer(const std::shared_ptr<AuthMetadataProcessor>& processor) {
     int port = grpc_pick_unused_port_or_die();
     first_picked_port_ = port;
-    server_address_ << "127.0.0.1:" << port;
+    server_address_ << "localhost:" << port;
     // Setup server
     BuildAndStartServer(processor);
   }
@@ -1414,7 +1414,7 @@ TEST_P(End2endTest, ChannelStateTimeout) {
   }
   int port = grpc_pick_unused_port_or_die();
   std::ostringstream server_address;
-  server_address << "127.0.0.1:" << port;
+  server_address << "localhost:" << port;
   // Channel to non-existing server
   auto channel =
       grpc::CreateChannel(server_address.str(), InsecureChannelCredentials());

test/cpp/end2end/grpclb_end2end_test.cc

@@ -53,6 +53,7 @@
 #include "src/cpp/server/secure_server_credentials.h"
 
 #include "test/core/util/port.h"
+#include "test/core/util/resolve_localhost_ip46.h"
 #include "test/core/util/test_config.h"
 #include "test/cpp/end2end/test_service_impl.h"
 
@@ -184,6 +185,12 @@ std::string Ip4ToPackedString(const char* ip_str) {
   return std::string(reinterpret_cast<const char*>(&ip4), sizeof(ip4));
 }
 
+std::string Ip6ToPackedString(const char* ip_str) {
+  struct in6_addr ip6;
+  GPR_ASSERT(inet_pton(AF_INET6, ip_str, &ip6) == 1);
+  return std::string(reinterpret_cast<const char*>(&ip6), sizeof(ip6));
+}
+
 struct ClientStats {
   size_t num_calls_started = 0;
   size_t num_calls_finished = 0;
@@ -321,28 +328,6 @@ class BalancerServiceImpl : public BalancerService {
     gpr_log(GPR_INFO, "LB[%p]: shut down", this);
   }
 
-  static LoadBalanceResponse BuildResponseForBackends(
-      const std::vector<int>& backend_ports,
-      const std::map<std::string, size_t>& drop_token_counts) {
-    LoadBalanceResponse response;
-    for (const auto& drop_token_count : drop_token_counts) {
-      for (size_t i = 0; i < drop_token_count.second; ++i) {
-        auto* server = response.mutable_server_list()->add_servers();
-        server->set_drop(true);
-        server->set_load_balance_token(drop_token_count.first);
-      }
-    }
-    for (const int& backend_port : backend_ports) {
-      auto* server = response.mutable_server_list()->add_servers();
-      server->set_ip_address(Ip4ToPackedString("127.0.0.1"));
-      server->set_port(backend_port);
-      static int token_count = 0;
-      server->set_load_balance_token(
-          absl::StrFormat("token%03d", ++token_count));
-    }
-    return response;
-  }
-
   ClientStats WaitForLoadReport() {
     grpc::internal::MutexLock lock(&mu_);
     grpc::internal::CondVar cv;
@@ -418,6 +403,11 @@ class GrpclbEnd2endTest : public ::testing::Test {
   static void TearDownTestCase() { grpc_shutdown(); }
 
   void SetUp() override {
+    bool localhost_resolves_to_ipv4 = false;
+    bool localhost_resolves_to_ipv6 = false;
+    grpc_core::LocalhostResolves(&localhost_resolves_to_ipv4,
+                                 &localhost_resolves_to_ipv6);
+    ipv6_only_ = !localhost_resolves_to_ipv4 && localhost_resolves_to_ipv6;
     response_generator_ =
         grpc_core::MakeRefCounted<grpc_core::FakeResolverResponseGenerator>();
     // Start the backends.
@@ -546,11 +536,12 @@ class GrpclbEnd2endTest : public ::testing::Test {
     std::string balancer_name;
   };
 
-  static grpc_core::ServerAddressList CreateLbAddressesFromAddressDataList(
+  grpc_core::ServerAddressList CreateLbAddressesFromAddressDataList(
       const std::vector<AddressData>& address_data) {
     grpc_core::ServerAddressList addresses;
     for (const auto& addr : address_data) {
-      std::string lb_uri_str = absl::StrCat("ipv4:127.0.0.1:", addr.port);
+      std::string lb_uri_str = absl::StrCat(
+          ipv6_only_ ? "ipv6:[::1]:" : "ipv4:127.0.0.1:", addr.port);
       grpc_uri* lb_uri = grpc_uri_parse(lb_uri_str.c_str(), true);
       GPR_ASSERT(lb_uri != nullptr);
       grpc_resolved_address address;
@@ -565,7 +556,7 @@ class GrpclbEnd2endTest : public ::testing::Test {
     return addresses;
   }
 
-  static grpc_core::Resolver::Result MakeResolverResult(
+  grpc_core::Resolver::Result MakeResolverResult(
       const std::vector<AddressData>& balancer_address_data,
       const std::vector<AddressData>& backend_address_data = {},
       const char* service_config_json = kDefaultServiceConfig) {
@@ -628,6 +619,29 @@ class GrpclbEnd2endTest : public ::testing::Test {
     balancers_[i]->service_.add_response(response, delay_ms);
   }
 
+  LoadBalanceResponse BuildResponseForBackends(
+      const std::vector<int>& backend_ports,
+      const std::map<std::string, size_t>& drop_token_counts) {
+    LoadBalanceResponse response;
+    for (const auto& drop_token_count : drop_token_counts) {
+      for (size_t i = 0; i < drop_token_count.second; ++i) {
+        auto* server = response.mutable_server_list()->add_servers();
+        server->set_drop(true);
+        server->set_load_balance_token(drop_token_count.first);
+      }
+    }
+    for (const int& backend_port : backend_ports) {
+      auto* server = response.mutable_server_list()->add_servers();
+      server->set_ip_address(ipv6_only_ ? Ip6ToPackedString("::1")
+                                        : Ip4ToPackedString("127.0.0.1"));
+      server->set_port(backend_port);
+      static int token_count = 0;
+      server->set_load_balance_token(
+          absl::StrFormat("token%03d", ++token_count));
+    }
+    return response;
+  }
+
   Status SendRpc(EchoResponse* response = nullptr, int timeout_ms = 1000,
                  bool wait_for_ready = false,
                  const Status& expected_status = Status::OK) {
@@ -726,6 +740,7 @@ class GrpclbEnd2endTest : public ::testing::Test {
   const size_t num_backends_;
   const size_t num_balancers_;
   const int client_load_reporting_interval_seconds_;
+  bool ipv6_only_ = false;
   std::shared_ptr<Channel> channel_;
   std::unique_ptr<grpc::testing::EchoTestService::Stub> stub_;
   std::vector<std::unique_ptr<ServerThread<BackendServiceImpl>>> backends_;
@@ -745,8 +760,7 @@ TEST_F(SingleBalancerTest, Vanilla) {
   SetNextResolutionAllBalancers();
   const size_t kNumRpcsPerAddress = 100;
   ScheduleResponseForBalancer(
-      0, BalancerServiceImpl::BuildResponseForBackends(GetBackendPorts(), {}),
+      0, BuildResponseForBackends(GetBackendPorts(), {}), 0);
-      0);
   // Make sure that trying to connect works without a call.
   channel_->GetState(true /* try_to_connect */);
   // We need to wait for all backends to come online.
@@ -771,8 +785,7 @@ TEST_F(SingleBalancerTest, Vanilla) {
 TEST_F(SingleBalancerTest, ReturnServerStatus) {
   SetNextResolutionAllBalancers();
   ScheduleResponseForBalancer(
-      0, BalancerServiceImpl::BuildResponseForBackends(GetBackendPorts(), {}),
+      0, BuildResponseForBackends(GetBackendPorts(), {}), 0);
-      0);
   // We need to wait for all backends to come online.
   WaitForAllBackends();
   // Send a request that the backend will fail, and make sure we get
@@ -793,8 +806,7 @@ TEST_F(SingleBalancerTest, SelectGrpclbWithMigrationServiceConfig) {
       "  ]\n"
       "}");
   ScheduleResponseForBalancer(
-      0, BalancerServiceImpl::BuildResponseForBackends(GetBackendPorts(), {}),
+      0, BuildResponseForBackends(GetBackendPorts(), {}), 0);
-      0);
   CheckRpcSendOk(1, 1000 /* timeout_ms */, true /* wait_for_ready */);
   balancers_[0]->service_.NotifyDoneWithServerlists();
   // The balancer got a single request.
@@ -841,8 +853,7 @@ TEST_F(SingleBalancerTest, UsePickFirstChildPolicy) {
       "  ]\n"
       "}");
   ScheduleResponseForBalancer(
-      0, BalancerServiceImpl::BuildResponseForBackends(GetBackendPorts(), {}),
+      0, BuildResponseForBackends(GetBackendPorts(), {}), 0);
-      0);
   const size_t kNumRpcs = num_backends_ * 2;
   CheckRpcSendOk(kNumRpcs, 1000 /* timeout_ms */, true /* wait_for_ready */);
   balancers_[0]->service_.NotifyDoneWithServerlists();
@@ -872,8 +883,7 @@ TEST_F(SingleBalancerTest, SwapChildPolicy) {
       "  ]\n"
       "}");
   ScheduleResponseForBalancer(
-      0, BalancerServiceImpl::BuildResponseForBackends(GetBackendPorts(), {}),
+      0, BuildResponseForBackends(GetBackendPorts(), {}), 0);
-      0);
   const size_t kNumRpcs = num_backends_ * 2;
   CheckRpcSendOk(kNumRpcs, 1000 /* timeout_ms */, true /* wait_for_ready */);
   // Check that all requests went to the first backend.  This verifies
@@ -908,8 +918,7 @@ TEST_F(SingleBalancerTest, SameBackendListedMultipleTimes) {
   ports.push_back(backends_[0]->port_);
   ports.push_back(backends_[0]->port_);
   const size_t kNumRpcsPerAddress = 10;
-  ScheduleResponseForBalancer(
+  ScheduleResponseForBalancer(0, BuildResponseForBackends(ports, {}), 0);
-      0, BalancerServiceImpl::BuildResponseForBackends(ports, {}), 0);
   // We need to wait for the backend to come online.
   WaitForBackend(0);
   // Send kNumRpcsPerAddress RPCs per server.
@@ -927,8 +936,7 @@ TEST_F(SingleBalancerTest, SecureNaming) {
   SetNextResolution({AddressData{balancers_[0]->port_, "lb"}});
   const size_t kNumRpcsPerAddress = 100;
   ScheduleResponseForBalancer(
-      0, BalancerServiceImpl::BuildResponseForBackends(GetBackendPorts(), {}),
+      0, BuildResponseForBackends(GetBackendPorts(), {}), 0);
-      0);
   // Make sure that trying to connect works without a call.
   channel_->GetState(true /* try_to_connect */);
   // We need to wait for all backends to come online.
@@ -970,8 +978,7 @@ TEST_F(SingleBalancerTest, InitiallyEmptyServerlist) {
   ScheduleResponseForBalancer(0, LoadBalanceResponse(), 0);
   // Send non-empty serverlist only after kServerlistDelayMs
   ScheduleResponseForBalancer(
-      0, BalancerServiceImpl::BuildResponseForBackends(GetBackendPorts(), {}),
+      0, BuildResponseForBackends(GetBackendPorts(), {}), kServerlistDelayMs);
-      kServerlistDelayMs);
   const auto t0 = system_clock::now();
   // Client will block: LB will initially send empty serverlist.
   CheckRpcSendOk(1, kCallDeadlineMs, true /* wait_for_ready */);
@@ -997,8 +1004,7 @@ TEST_F(SingleBalancerTest, AllServersUnreachableFailFast) {
   for (size_t i = 0; i < kNumUnreachableServers; ++i) {
     ports.push_back(grpc_pick_unused_port_or_die());
   }
-  ScheduleResponseForBalancer(
+  ScheduleResponseForBalancer(0, BuildResponseForBackends(ports, {}), 0);
-      0, BalancerServiceImpl::BuildResponseForBackends(ports, {}), 0);
   const Status status = SendRpc();
   // The error shouldn't be DEADLINE_EXCEEDED.
   EXPECT_EQ(StatusCode::UNAVAILABLE, status.error_code());
@@ -1027,7 +1033,7 @@ TEST_F(SingleBalancerTest, Fallback) {
   // Send non-empty serverlist only after kServerlistDelayMs.
   ScheduleResponseForBalancer(
       0,
-      BalancerServiceImpl::BuildResponseForBackends(
+      BuildResponseForBackends(
           GetBackendPorts(kNumBackendsInResolution /* start_index */), {}),
       kServerlistDelayMs);
 
@@ -1096,7 +1102,7 @@ TEST_F(SingleBalancerTest, FallbackUpdate) {
   // Send non-empty serverlist only after kServerlistDelayMs.
   ScheduleResponseForBalancer(
       0,
-      BalancerServiceImpl::BuildResponseForBackends(
+      BuildResponseForBackends(
           GetBackendPorts(kNumBackendsInResolution +
                           kNumBackendsInResolutionUpdate /* start_index */),
           {}),
@@ -1201,9 +1207,8 @@ TEST_F(SingleBalancerTest,
     balancer_addresses.emplace_back(AddressData{balancers_[i]->port_, ""});
   }
   SetNextResolution(balancer_addresses, backend_addresses);
-  ScheduleResponseForBalancer(0,
+  ScheduleResponseForBalancer(
-                              BalancerServiceImpl::BuildResponseForBackends(
+      0, BuildResponseForBackends(GetBackendPorts(kNumFallbackBackends), {}),
-                                  GetBackendPorts(kNumFallbackBackends), {}),
       0);
   // Try to connect.
   channel_->GetState(true /* try_to_connect */);
@@ -1234,9 +1239,8 @@ TEST_F(SingleBalancerTest,
   // Now start the balancer again.  This should cause us to exit
   // fallback mode.
   balancers_[0]->Start(server_host_);
-  ScheduleResponseForBalancer(0,
+  ScheduleResponseForBalancer(
-                              BalancerServiceImpl::BuildResponseForBackends(
+      0, BuildResponseForBackends(GetBackendPorts(kNumFallbackBackends), {}),
-                                  GetBackendPorts(kNumFallbackBackends), {}),
       0);
   WaitForAllBackends(1 /* num_requests_multiple_of */,
                      kNumFallbackBackends /* start_index */);
@@ -1256,9 +1260,8 @@ TEST_F(SingleBalancerTest,
     balancer_addresses.emplace_back(AddressData{balancers_[i]->port_, ""});
   }
   SetNextResolution(balancer_addresses, backend_addresses);
-  ScheduleResponseForBalancer(0,
+  ScheduleResponseForBalancer(
-                              BalancerServiceImpl::BuildResponseForBackends(
+      0, BuildResponseForBackends(GetBackendPorts(kNumFallbackBackends), {}),
-                                  GetBackendPorts(kNumFallbackBackends), {}),
       0);
   // Try to connect.
   channel_->GetState(true /* try_to_connect */);
@@ -1287,9 +1290,8 @@ TEST_F(SingleBalancerTest,
   // Now start the balancer again.  This should cause us to exit
   // fallback mode.
   balancers_[0]->Start(server_host_);
-  ScheduleResponseForBalancer(0,
+  ScheduleResponseForBalancer(
-                              BalancerServiceImpl::BuildResponseForBackends(
+      0, BuildResponseForBackends(GetBackendPorts(kNumFallbackBackends), {}),
-                                  GetBackendPorts(kNumFallbackBackends), {}),
       0);
   WaitForAllBackends(1 /* num_requests_multiple_of */,
                      kNumFallbackBackends /* start_index */);
@@ -1358,7 +1360,7 @@ TEST_F(SingleBalancerTest, FallbackControlledByBalancer_AfterFirstServerlist) {
   // then sends the serverlist again.
   // The serverlist points to backend 1.
   LoadBalanceResponse serverlist_resp =
-      BalancerServiceImpl::BuildResponseForBackends({backends_[1]->port_}, {});
+      BuildResponseForBackends({backends_[1]->port_}, {});
   LoadBalanceResponse fallback_resp;
   fallback_resp.mutable_fallback_response();
   ScheduleResponseForBalancer(0, serverlist_resp, 0);
@@ -1375,8 +1377,7 @@ TEST_F(SingleBalancerTest, BackendsRestart) {
   SetNextResolutionAllBalancers();
   const size_t kNumRpcsPerAddress = 100;
   ScheduleResponseForBalancer(
-      0, BalancerServiceImpl::BuildResponseForBackends(GetBackendPorts(), {}),
+      0, BuildResponseForBackends(GetBackendPorts(), {}), 0);
-      0);
   // Make sure that trying to connect works without a call.
   channel_->GetState(true /* try_to_connect */);
   // Send kNumRpcsPerAddress RPCs per server.
@@ -1406,8 +1407,7 @@ TEST_F(SingleBalancerTest, ServiceNameFromLbPolicyConfig) {
 
   SetNextResolutionAllBalancers(kServiceConfigWithTarget);
   ScheduleResponseForBalancer(
-      0, BalancerServiceImpl::BuildResponseForBackends(GetBackendPorts(), {}),
+      0, BuildResponseForBackends(GetBackendPorts(), {}), 0);
-      0);
   // Make sure that trying to connect works without a call.
   channel_->GetState(true /* try_to_connect */);
   // We need to wait for all backends to come online.
@@ -1424,10 +1424,10 @@ TEST_F(UpdatesTest, UpdateBalancersButKeepUsingOriginalBalancer) {
   SetNextResolutionAllBalancers();
   const std::vector<int> first_backend{GetBackendPorts()[0]};
   const std::vector<int> second_backend{GetBackendPorts()[1]};
-  ScheduleResponseForBalancer(
+  ScheduleResponseForBalancer(0, BuildResponseForBackends(first_backend, {}),
-      0, BalancerServiceImpl::BuildResponseForBackends(first_backend, {}), 0);
+                              0);
-  ScheduleResponseForBalancer(
+  ScheduleResponseForBalancer(1, BuildResponseForBackends(second_backend, {}),
-      1, BalancerServiceImpl::BuildResponseForBackends(second_backend, {}), 0);
+                              0);
 
   // Wait until the first backend is ready.
   WaitForBackend(0);
@@ -1482,10 +1482,10 @@ TEST_F(UpdatesTest, UpdateBalancersRepeated) {
   const std::vector<int> first_backend{GetBackendPorts()[0]};
   const std::vector<int> second_backend{GetBackendPorts()[0]};
 
-  ScheduleResponseForBalancer(
+  ScheduleResponseForBalancer(0, BuildResponseForBackends(first_backend, {}),
-      0, BalancerServiceImpl::BuildResponseForBackends(first_backend, {}), 0);
+                              0);
-  ScheduleResponseForBalancer(
+  ScheduleResponseForBalancer(1, BuildResponseForBackends(second_backend, {}),
-      1, BalancerServiceImpl::BuildResponseForBackends(second_backend, {}), 0);
+                              0);
 
   // Wait until the first backend is ready.
   WaitForBackend(0);
@@ -1555,10 +1555,10 @@ TEST_F(UpdatesTest, UpdateBalancersDeadUpdate) {
   const std::vector<int> first_backend{GetBackendPorts()[0]};
   const std::vector<int> second_backend{GetBackendPorts()[1]};
 
-  ScheduleResponseForBalancer(
+  ScheduleResponseForBalancer(0, BuildResponseForBackends(first_backend, {}),
-      0, BalancerServiceImpl::BuildResponseForBackends(first_backend, {}), 0);
+                              0);
-  ScheduleResponseForBalancer(
+  ScheduleResponseForBalancer(1, BuildResponseForBackends(second_backend, {}),
-      1, BalancerServiceImpl::BuildResponseForBackends(second_backend, {}), 0);
+                              0);
 
   // Start servers and send 10 RPCs per server.
   gpr_log(GPR_INFO, "========= BEFORE FIRST BATCH ==========");
@@ -1688,10 +1688,10 @@ class UpdatesWithClientLoadReportingTest : public GrpclbEnd2endTest {
 TEST_F(UpdatesWithClientLoadReportingTest, ReresolveDeadBalancer) {
   const std::vector<int> first_backend{GetBackendPorts()[0]};
   const std::vector<int> second_backend{GetBackendPorts()[1]};
-  ScheduleResponseForBalancer(
+  ScheduleResponseForBalancer(0, BuildResponseForBackends(first_backend, {}),
-      0, BalancerServiceImpl::BuildResponseForBackends(first_backend, {}), 0);
+                              0);
-  ScheduleResponseForBalancer(
+  ScheduleResponseForBalancer(1, BuildResponseForBackends(second_backend, {}),
-      1, BalancerServiceImpl::BuildResponseForBackends(second_backend, {}), 0);
+                              0);
 
   // Ask channel to connect to trigger resolver creation.
   channel_->GetState(true);
@@ -1767,7 +1767,7 @@ TEST_F(SingleBalancerTest, Drop) {
   const int num_total_addresses = num_backends_ + num_of_drop_addresses;
   ScheduleResponseForBalancer(
       0,
-      BalancerServiceImpl::BuildResponseForBackends(
+      BuildResponseForBackends(
           GetBackendPorts(),
           {{"rate_limiting", num_of_drop_by_rate_limiting_addresses},
            {"load_balancing", num_of_drop_by_load_balancing_addresses}}),
@@ -1806,7 +1806,7 @@ TEST_F(SingleBalancerTest, DropAllFirst) {
   const int num_of_drop_by_load_balancing_addresses = 1;
   ScheduleResponseForBalancer(
       0,
-      BalancerServiceImpl::BuildResponseForBackends(
+      BuildResponseForBackends(
           {}, {{"rate_limiting", num_of_drop_by_rate_limiting_addresses},
                {"load_balancing", num_of_drop_by_load_balancing_addresses}}),
       0);
@@ -1818,13 +1818,12 @@ TEST_F(SingleBalancerTest, DropAllFirst) {
 TEST_F(SingleBalancerTest, DropAll) {
   SetNextResolutionAllBalancers();
   ScheduleResponseForBalancer(
-      0, BalancerServiceImpl::BuildResponseForBackends(GetBackendPorts(), {}),
+      0, BuildResponseForBackends(GetBackendPorts(), {}), 0);
-      0);
   const int num_of_drop_by_rate_limiting_addresses = 1;
   const int num_of_drop_by_load_balancing_addresses = 1;
   ScheduleResponseForBalancer(
       0,
-      BalancerServiceImpl::BuildResponseForBackends(
+      BuildResponseForBackends(
           {}, {{"rate_limiting", num_of_drop_by_rate_limiting_addresses},
                {"load_balancing", num_of_drop_by_load_balancing_addresses}}),
       1000);
@@ -1850,8 +1849,7 @@ TEST_F(SingleBalancerWithClientLoadReportingTest, Vanilla) {
   SetNextResolutionAllBalancers();
   const size_t kNumRpcsPerAddress = 100;
   ScheduleResponseForBalancer(
-      0, BalancerServiceImpl::BuildResponseForBackends(GetBackendPorts(), {}),
+      0, BuildResponseForBackends(GetBackendPorts(), {}), 0);
-      0);
   // Wait until all backends are ready.
   int num_ok = 0;
   int num_failure = 0;
@@ -1892,8 +1890,7 @@ TEST_F(SingleBalancerWithClientLoadReportingTest, BalancerRestart) {
   // Balancer returns backends starting at index 1.
   ScheduleResponseForBalancer(
       0,
-      BalancerServiceImpl::BuildResponseForBackends(
+      BuildResponseForBackends(GetBackendPorts(0, kNumBackendsFirstPass), {}),
-          GetBackendPorts(0, kNumBackendsFirstPass), {}),
       0);
   // Wait until all backends returned by the balancer are ready.
   int num_ok = 0;
@@ -1922,9 +1919,8 @@ TEST_F(SingleBalancerWithClientLoadReportingTest, BalancerRestart) {
   }
   // Now restart the balancer, this time pointing to all backends.
   balancers_[0]->Start(server_host_);
-  ScheduleResponseForBalancer(0,
+  ScheduleResponseForBalancer(
-                              BalancerServiceImpl::BuildResponseForBackends(
+      0, BuildResponseForBackends(GetBackendPorts(kNumBackendsFirstPass), {}),
-                                  GetBackendPorts(kNumBackendsFirstPass), {}),
       0);
   // Wait for queries to start going to one of the new backends.
   // This tells us that we're now using the new serverlist.
@@ -1955,7 +1951,7 @@ TEST_F(SingleBalancerWithClientLoadReportingTest, Drop) {
   const int num_total_addresses = num_backends_ + num_of_drop_addresses;
   ScheduleResponseForBalancer(
       0,
-      BalancerServiceImpl::BuildResponseForBackends(
+      BuildResponseForBackends(
           GetBackendPorts(),
           {{"rate_limiting", num_of_drop_by_rate_limiting_addresses},
            {"load_balancing", num_of_drop_by_load_balancing_addresses}}),

test/cpp/end2end/server_early_return_test.cc

@@ -115,7 +115,7 @@ class ServerEarlyReturnTest : public ::testing::Test {
   void SetUp() override {
     int port = grpc_pick_unused_port_or_die();
     picked_port_ = port;
-    server_address_ << "127.0.0.1:" << port;
+    server_address_ << "localhost:" << port;
     ServerBuilder builder;
     builder.AddListeningPort(server_address_.str(),
                              InsecureServerCredentials());

test/cpp/end2end/service_config_end2end_test.cc

@@ -57,6 +57,7 @@
 
 #include "src/proto/grpc/testing/echo.grpc.pb.h"
 #include "test/core/util/port.h"
+#include "test/core/util/resolve_localhost_ip46.h"
 #include "test/core/util/test_config.h"
 #include "test/cpp/end2end/test_service_impl.h"
 
@@ -131,6 +132,11 @@ class ServiceConfigEnd2endTest : public ::testing::Test {
     grpc_init();
     response_generator_ =
         grpc_core::MakeRefCounted<grpc_core::FakeResolverResponseGenerator>();
+    bool localhost_resolves_to_ipv4 = false;
+    bool localhost_resolves_to_ipv6 = false;
+    grpc_core::LocalhostResolves(&localhost_resolves_to_ipv4,
+                                 &localhost_resolves_to_ipv6);
+    ipv6_only_ = !localhost_resolves_to_ipv4 && localhost_resolves_to_ipv6;
   }
 
   void TearDown() override {
@@ -169,7 +175,8 @@ class ServiceConfigEnd2endTest : public ::testing::Test {
   grpc_core::Resolver::Result BuildFakeResults(const std::vector<int>& ports) {
     grpc_core::Resolver::Result result;
     for (const int& port : ports) {
-      std::string lb_uri_str = absl::StrCat("ipv4:127.0.0.1:", port);
+      std::string lb_uri_str =
+          absl::StrCat(ipv6_only_ ? "ipv6:[::1]:" : "ipv4:127.0.0.1:", port);
       grpc_uri* lb_uri = grpc_uri_parse(lb_uri_str.c_str(), true);
       GPR_ASSERT(lb_uri != nullptr);
       grpc_resolved_address address;
@@ -422,6 +429,7 @@ class ServiceConfigEnd2endTest : public ::testing::Test {
     return "{\"version\": \"invalid_default\"";
   }
 
+  bool ipv6_only_ = false;
   const std::string server_host_;
   std::unique_ptr<grpc::testing::EchoTestService::Stub> stub_;
   std::vector<std::unique_ptr<ServerData>> servers_;

test/cpp/ext/filters/census/stats_plugin_end2end_test.cc

@@ -81,7 +81,7 @@ class StatsPluginEnd2EndTest : public ::testing::Test {
     server_ = builder.BuildAndStart();
     ASSERT_NE(nullptr, server_);
     ASSERT_NE(0, port);
-    server_address_ = absl::StrCat("0.0.0.0:", port);
+    server_address_ = absl::StrCat("localhost:", port);
     server_thread_ = std::thread(&StatsPluginEnd2EndTest::RunServerLoop, this);
 
     stub_ = EchoTestService::NewStub(::grpc::CreateChannel(