Revert "Revert "[BinderTransport] Send correct version to server and verify it (#27990)" (#28090)" (#28168)

This reverts commit ea49e4c73a.

msan test failed before because the mock object returns uninitialized
value and the code tries to conditionally log when the value is wrong.

src/core/ext/transport/binder/server/binder_server.cc

@@ -196,7 +196,9 @@ class BinderServerListener : public Server::ListenerInterface {
       return status;
     }
     gpr_log(GPR_INFO, "BinderTransport client protocol version = %d", version);
-    // TODO(waynetu): Check supported version.
+    // TODO(mingcl): Make sure we only give client a version that is not newer
+    // than the version they specify. For now, we always tell client that we
+    // only support version=1.
     std::unique_ptr<grpc_binder::Binder> client_binder{};
     status = parcel->ReadBinder(&client_binder);
     if (!status.ok()) {

src/core/ext/transport/binder/wire_format/wire_reader_impl.cc

@@ -42,6 +42,8 @@
 namespace grpc_binder {
 namespace {
 
+const int32_t kWireFormatVersion = 1;
+
 absl::StatusOr<Metadata> parse_metadata(ReadableParcel* reader) {
   int num_header;
   RETURN_IF_ERROR(reader->ReadInt32(&num_header));
@@ -114,9 +116,8 @@ void WireReaderImpl::SendSetupTransport(Binder* binder) {
   gpr_log(GPR_INFO, "prepare transaction = %d",
           binder->PrepareTransaction().ok());
   WritableParcel* writable_parcel = binder->GetWritableParcel();
-  int32_t version = 77;
   gpr_log(GPR_INFO, "write int32 = %d",
-          writable_parcel->WriteInt32(version).ok());
+          writable_parcel->WriteInt32(kWireFormatVersion).ok());
   // The lifetime of the transaction receiver is the same as the wire writer's.
   // The transaction receiver is responsible for not calling the on-transact
   // callback when it's dead.
@@ -194,7 +195,15 @@ absl::Status WireReaderImpl::ProcessTransaction(transaction_code_t code,
 
       int version;
       RETURN_IF_ERROR(parcel->ReadInt32(&version));
-      gpr_log(GPR_INFO, "version = %d", version);
+      gpr_log(GPR_INFO, "The other end respond with version = %d", version);
+      // We only support this single lowest possible version, so server must
+      // respond that version too.
+      if (version != kWireFormatVersion) {
+        gpr_log(GPR_ERROR,
+                "The other end respond with version = %d, but we requested "
+                "version %d, trying to continue anyway",
+                version, kWireFormatVersion);
+      }
       std::unique_ptr<Binder> binder{};
       RETURN_IF_ERROR(parcel->ReadBinder(&binder));
       if (!binder) {

test/core/transport/binder/mock_objects.h

@@ -76,7 +76,13 @@ class MockTransactionReceiver : public TransactionReceiver {
  public:
   explicit MockTransactionReceiver(OnTransactCb transact_cb,
                                    BinderTransportTxCode code,
-                                   ReadableParcel* output) {
+                                   MockReadableParcel* output) {
+    if (code == BinderTransportTxCode::SETUP_TRANSPORT) {
+      EXPECT_CALL(*output, ReadInt32).WillOnce([](int32_t* version) {
+        *version = 1;
+        return absl::OkStatus();
+      });
+    }
     transact_cb(static_cast<transaction_code_t>(code), output, /*uid=*/0)
         .IgnoreError();
   }

test/core/transport/binder/wire_reader_test.cc

@@ -114,19 +114,7 @@ TEST_F(WireReaderTest, SetupTransport) {
   EXPECT_CALL(mock_binder_ref, GetWritableParcel);
 
   // Write version.
-  EXPECT_CALL(mock_binder_ref.GetWriter(), WriteInt32(77));
-
-  // The transaction receiver immediately informs the wire writer that the
-  // transport has been successfully set up.
-  EXPECT_CALL(mock_binder_ref, ConstructTxReceiver);
-
-  EXPECT_CALL(mock_binder_ref.GetReader(), ReadInt32);
-  EXPECT_CALL(mock_binder_ref.GetReader(), ReadBinder);
-
-  // Write transaction receiver.
-  EXPECT_CALL(mock_binder_ref.GetWriter(), WriteBinder);
-  // Perform transaction.
-  EXPECT_CALL(mock_binder_ref, Transact);
+  EXPECT_CALL(mock_binder_ref.GetWriter(), WriteInt32(1));
 
   wire_reader_.SetupTransport(std::move(mock_binder));
 }