Revert "Revert "Switching from UNAUTHENTICATED to UNAVAILABLE for auth metadata failure""

src/core/lib/security/transport/client_auth_filter.cc

@@ -112,7 +112,7 @@ static void on_credentials_metadata(void* arg, grpc_error* input_error) {
     grpc_call_next_op(elem, batch);
   } else {
     error = grpc_error_set_int(error, GRPC_ERROR_INT_GRPC_STATUS,
-                               GRPC_STATUS_UNAUTHENTICATED);
+                               GRPC_STATUS_UNAVAILABLE);
     grpc_transport_stream_op_batch_finish_with_failure(batch, error,
                                                        calld->call_combiner);
   }

test/cpp/end2end/end2end_test.cc

@@ -1609,7 +1609,7 @@ TEST_P(SecureEnd2endTest, AuthMetadataPluginKeyFailure) {
 
   Status s = stub_->Echo(&context, request, &response);
   EXPECT_FALSE(s.ok());
-  EXPECT_EQ(s.error_code(), StatusCode::UNAUTHENTICATED);
+  EXPECT_EQ(s.error_code(), StatusCode::UNAVAILABLE);
 }
 
 TEST_P(SecureEnd2endTest, AuthMetadataPluginValueFailure) {
@@ -1626,7 +1626,7 @@ TEST_P(SecureEnd2endTest, AuthMetadataPluginValueFailure) {
 
   Status s = stub_->Echo(&context, request, &response);
   EXPECT_FALSE(s.ok());
-  EXPECT_EQ(s.error_code(), StatusCode::UNAUTHENTICATED);
+  EXPECT_EQ(s.error_code(), StatusCode::UNAVAILABLE);
 }
 
 TEST_P(SecureEnd2endTest, NonBlockingAuthMetadataPluginFailure) {
@@ -1644,7 +1644,7 @@ TEST_P(SecureEnd2endTest, NonBlockingAuthMetadataPluginFailure) {
 
   Status s = stub_->Echo(&context, request, &response);
   EXPECT_FALSE(s.ok());
-  EXPECT_EQ(s.error_code(), StatusCode::UNAUTHENTICATED);
+  EXPECT_EQ(s.error_code(), StatusCode::UNAVAILABLE);
   EXPECT_EQ(s.error_message(),
             grpc::string("Getting metadata from plugin failed with error: ") +
                 kTestCredsPluginErrorMsg);
@@ -1705,7 +1705,7 @@ TEST_P(SecureEnd2endTest, BlockingAuthMetadataPluginFailure) {
 
   Status s = stub_->Echo(&context, request, &response);
   EXPECT_FALSE(s.ok());
-  EXPECT_EQ(s.error_code(), StatusCode::UNAUTHENTICATED);
+  EXPECT_EQ(s.error_code(), StatusCode::UNAVAILABLE);
   EXPECT_EQ(s.error_message(),
             grpc::string("Getting metadata from plugin failed with error: ") +
                 kTestCredsPluginErrorMsg);