4 files changed, 102 insertions, 3 deletions

diff --git a/include/grpcpp/impl/codegen/call_op_set.h b/include/grpcpp/impl/codegen/call_op_set.h
index b4c34a01c9..1f2b88e9e1 100644
--- a/include/grpcpp/impl/codegen/call_op_set.h
+++ b/include/grpcpp/impl/codegen/call_op_set.h
@@ -314,14 +314,19 @@ class CallOpSendMessage {
     // Flags are per-message: clear them after use.
     write_options_.Clear();
   }
-  void FinishOp(bool* status) { send_buf_.Clear(); }
+  void FinishOp(bool* status) {
+    send_buf_.Clear();
+    if (hijacked_ && failed_send_) {
+      *status = false;
+    }
+  }
 
   void SetInterceptionHookPoint(
       InterceptorBatchMethodsImpl* interceptor_methods) {
     if (!send_buf_.Valid()) return;
     interceptor_methods->AddInterceptionHookPoint(
         experimental::InterceptionHookPoints::PRE_SEND_MESSAGE);
-    interceptor_methods->SetSendMessage(&send_buf_);
+    interceptor_methods->SetSendMessage(&send_buf_, &failed_send_);
   }
 
   void SetFinishInterceptionHookPoint(
@@ -333,6 +338,7 @@ class CallOpSendMessage {
 
  private:
   bool hijacked_ = false;
+  bool failed_send_ = false;
   ByteBuffer send_buf_;
   WriteOptions write_options_;
 };
diff --git a/include/grpcpp/impl/codegen/interceptor.h b/include/grpcpp/impl/codegen/interceptor.h
index e449e44a23..47239332c8 100644
--- a/include/grpcpp/impl/codegen/interceptor.h
+++ b/include/grpcpp/impl/codegen/interceptor.h
@@ -118,6 +118,10 @@ class InterceptorBatchMethods {
   // only interceptors after the current interceptor are created from the
   // factory objects registered with the channel.
   virtual std::unique_ptr<ChannelInterface> GetInterceptedChannel() = 0;
+
+  // On a hijacked RPC/ to-be hijacked RPC, this can be called to fail a SEND
+  // MESSAGE op
+  virtual void FailHijackedSendMessage() = 0;
 };
 
 class Interceptor {
diff --git a/include/grpcpp/impl/codegen/interceptor_common.h b/include/grpcpp/impl/codegen/interceptor_common.h
index d0aa23cb0a..601a929afe 100644
--- a/include/grpcpp/impl/codegen/interceptor_common.h
+++ b/include/grpcpp/impl/codegen/interceptor_common.h
@@ -110,12 +110,21 @@ class InterceptorBatchMethodsImpl
 
   Status* GetRecvStatus() override { return recv_status_; }
 
+  void FailHijackedSendMessage() override {
+    GPR_CODEGEN_ASSERT(hooks_[static_cast<size_t>(
+        experimental::InterceptionHookPoints::PRE_SEND_MESSAGE)]);
+    *fail_send_message_ = true;
+  }
+
   std::multimap<grpc::string_ref, grpc::string_ref>* GetRecvTrailingMetadata()
       override {
     return recv_trailing_metadata_->map();
   }
 
-  void SetSendMessage(ByteBuffer* buf) { send_message_ = buf; }
+  void SetSendMessage(ByteBuffer* buf, bool* fail_send_message) {
+    send_message_ = buf;
+    fail_send_message_ = fail_send_message;
+  }
 
   void SetSendInitialMetadata(
       std::multimap<grpc::string, grpc::string>* metadata) {
@@ -334,6 +343,7 @@ class InterceptorBatchMethodsImpl
   std::function<void(void)> callback_;
 
   ByteBuffer* send_message_ = nullptr;
+  bool* fail_send_message_ = nullptr;
 
   std::multimap<grpc::string, grpc::string>* send_initial_metadata_;
 
@@ -451,6 +461,12 @@ class CancelInterceptorBatchMethods
                        "method which has a Cancel notification");
     return std::unique_ptr<ChannelInterface>(nullptr);
   }
+
+  void FailHijackedSendMessage() override {
+    GPR_CODEGEN_ASSERT(false &&
+                       "It is illegal to call FailHijackedSendMessage on a "
+                       "method which has a Cancel notification");
+  }
 };
 }  // namespace internal
 }  // namespace grpc
diff --git a/test/cpp/end2end/client_interceptors_end2end_test.cc b/test/cpp/end2end/client_interceptors_end2end_test.cc
index 0b34ec93ae..81efd15452 100644
--- a/test/cpp/end2end/client_interceptors_end2end_test.cc
+++ b/test/cpp/end2end/client_interceptors_end2end_test.cc
@@ -269,6 +269,49 @@ class HijackingInterceptorMakesAnotherCallFactory
   }
 };
 
+class ClientStreamingRpcHijackingInterceptor
+    : public experimental::Interceptor {
+ public:
+  ClientStreamingRpcHijackingInterceptor(experimental::ClientRpcInfo* info) {
+    info_ = info;
+  }
+  virtual void Intercept(experimental::InterceptorBatchMethods* methods) {
+    bool hijack = false;
+    if (methods->QueryInterceptionHookPoint(
+            experimental::InterceptionHookPoints::PRE_SEND_INITIAL_METADATA)) {
+      hijack = true;
+    }
+    if (methods->QueryInterceptionHookPoint(
+            experimental::InterceptionHookPoints::PRE_SEND_MESSAGE)) {
+      if (++count_ > 10) {
+        methods->FailHijackedSendMessage();
+      }
+    }
+    if (methods->QueryInterceptionHookPoint(
+            experimental::InterceptionHookPoints::PRE_RECV_STATUS)) {
+      auto* status = methods->GetRecvStatus();
+      *status = Status(StatusCode::UNAVAILABLE, "Done sending 10 messages");
+    }
+    if (hijack) {
+      methods->Hijack();
+    } else {
+      methods->Proceed();
+    }
+  }
+
+ private:
+  experimental::ClientRpcInfo* info_;
+  int count_ = 0;
+};
+class ClientStreamingRpcHijackingInterceptorFactory
+    : public experimental::ClientInterceptorFactoryInterface {
+ public:
+  virtual experimental::Interceptor* CreateClientInterceptor(
+      experimental::ClientRpcInfo* info) override {
+    return new ClientStreamingRpcHijackingInterceptor(info);
+  }
+};
+
 class LoggingInterceptor : public experimental::Interceptor {
  public:
   LoggingInterceptor(experimental::ClientRpcInfo* info) { info_ = info; }
@@ -535,6 +578,36 @@ TEST_F(ClientInterceptorsStreamingEnd2endTest, ServerStreamingTest) {
   EXPECT_EQ(DummyInterceptor::GetNumTimesRun(), 20);
 }
 
+TEST_F(ClientInterceptorsStreamingEnd2endTest, ClientStreamingHijackingTest) {
+  ChannelArguments args;
+  auto creators = std::unique_ptr<std::vector<
+      std::unique_ptr<experimental::ClientInterceptorFactoryInterface>>>(
+      new std::vector<
+          std::unique_ptr<experimental::ClientInterceptorFactoryInterface>>());
+  creators->push_back(
+      std::unique_ptr<ClientStreamingRpcHijackingInterceptorFactory>(
+          new ClientStreamingRpcHijackingInterceptorFactory()));
+  auto channel = experimental::CreateCustomChannelWithInterceptors(
+      server_address_, InsecureChannelCredentials(), args, std::move(creators));
+
+  auto stub = grpc::testing::EchoTestService::NewStub(channel);
+  ClientContext ctx;
+  EchoRequest req;
+  EchoResponse resp;
+  req.mutable_param()->set_echo_metadata(true);
+  req.set_message("Hello");
+  string expected_resp = "";
+  auto writer = stub->RequestStream(&ctx, &resp);
+  for (int i = 0; i < 10; i++) {
+    EXPECT_TRUE(writer->Write(req));
+    expected_resp += "Hello";
+  }
+  // Expect that the interceptor will reject the 11th message
+  EXPECT_FALSE(writer->Write(req));
+  Status s = writer->Finish();
+  EXPECT_EQ(s.ok(), false);
+}
+
 TEST_F(ClientInterceptorsStreamingEnd2endTest, BidiStreamingTest) {
   ChannelArguments args;
   DummyInterceptor::Reset();