xref: /aosp_15_r20/external/grpc-grpc/src/core/ext/transport/inproc/legacy_inproc_transport.cc (revision cc02d7e222339f7a4f6ba5f422e6413f4bd931f2)

//
//
// Copyright 2017 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 <grpc/support/port_platform.h>

#include "src/core/ext/transport/inproc/legacy_inproc_transport.h"

#include <stddef.h>
#include <stdint.h>

#include <algorithm>
#include <memory>
#include <new>
#include <string>
#include <utility>

#include "absl/status/status.h"
#include "absl/status/statusor.h"
#include "absl/strings/str_cat.h"
#include "absl/strings/string_view.h"
#include "absl/types/optional.h"

#include <grpc/grpc.h>
#include <grpc/impl/channel_arg_names.h>
#include <grpc/impl/connectivity_state.h>
#include <grpc/status.h>
#include <grpc/support/alloc.h>
#include <grpc/support/log.h>
#include <grpc/support/sync.h>

#include "src/core/lib/channel/channel_args.h"
#include "src/core/lib/channel/channel_args_preconditioning.h"
#include "src/core/lib/channel/channelz.h"
#include "src/core/lib/config/core_configuration.h"
#include "src/core/lib/gprpp/debug_location.h"
#include "src/core/lib/gprpp/ref_counted_ptr.h"
#include "src/core/lib/gprpp/status_helper.h"
#include "src/core/lib/gprpp/time.h"
#include "src/core/lib/iomgr/closure.h"
#include "src/core/lib/iomgr/endpoint.h"
#include "src/core/lib/iomgr/error.h"
#include "src/core/lib/iomgr/exec_ctx.h"
#include "src/core/lib/iomgr/iomgr_fwd.h"
#include "src/core/lib/resource_quota/arena.h"
#include "src/core/lib/slice/slice.h"
#include "src/core/lib/slice/slice_buffer.h"
#include "src/core/lib/surface/api_trace.h"
#include "src/core/lib/surface/channel.h"
#include "src/core/lib/surface/channel_create.h"
#include "src/core/lib/surface/channel_stack_type.h"
#include "src/core/lib/surface/server.h"
#include "src/core/lib/transport/connectivity_state.h"
#include "src/core/lib/transport/metadata_batch.h"
#include "src/core/lib/transport/transport.h"

#define INPROC_LOG(...)                               \
  do {                                                \
    if (GRPC_TRACE_FLAG_ENABLED(grpc_inproc_trace)) { \
      gpr_log(__VA_ARGS__);                           \
    }                                                 \
  } while (0)

namespace {
struct inproc_stream;
bool cancel_stream_locked(inproc_stream* s, grpc_error_handle error);
void maybe_process_ops_locked(inproc_stream* s, grpc_error_handle error);
void op_state_machine_locked(inproc_stream* s, grpc_error_handle error);
void log_metadata(const grpc_metadata_batch* md_batch, bool is_client,
                  bool is_initial);
void fill_in_metadata(inproc_stream* s, const grpc_metadata_batch* metadata,
                      grpc_metadata_batch* out_md, bool* markfilled);

void ResetSendMessage(grpc_transport_stream_op_batch* batch) {
  std::exchange(batch->payload->send_message.send_message, nullptr)->Clear();
}

struct shared_mu {
  shared_mu() {
    // Share one lock between both sides since both sides get affected
    gpr_mu_init(&mu);
    gpr_ref_init(&refs, 2);
  }

  ~shared_mu() { gpr_mu_destroy(&mu); }

  gpr_mu mu;
  gpr_refcount refs;
};

struct inproc_transport final : public grpc_core::Transport,
                                public grpc_core::FilterStackTransport {
  inproc_transport(shared_mu* mu, bool is_client)
      : mu(mu),
        is_client(is_client),
        state_tracker(is_client ? "inproc_client" : "inproc_server",
                      GRPC_CHANNEL_READY) {
    // Start each side of transport with 2 refs since they each have a ref
    // to the other
    gpr_ref_init(&refs, 2);
  }

  ~inproc_transport() override {
    if (gpr_unref(&mu->refs)) {
      mu->~shared_mu();
      gpr_free(mu);
    }
  }

  grpc_core::FilterStackTransport* filter_stack_transport() override {
    return this;
  }

  grpc_core::ClientTransport* client_transport() override { return nullptr; }
  grpc_core::ServerTransport* server_transport() override { return nullptr; }

  absl::string_view GetTransportName() const override;
  void InitStream(grpc_stream* gs, grpc_stream_refcount* refcount,
                  const void* server_data, grpc_core::Arena* arena) override;
  void SetPollset(grpc_stream* stream, grpc_pollset* pollset) override;
  void SetPollsetSet(grpc_stream* stream,
                     grpc_pollset_set* pollset_set) override;
  void PerformOp(grpc_transport_op* op) override;
  grpc_endpoint* GetEndpoint() override;

  size_t SizeOfStream() const override;
  bool HackyDisableStreamOpBatchCoalescingInConnectedChannel() const override {
    return true;
  }

  void PerformStreamOp(grpc_stream* gs,
                       grpc_transport_stream_op_batch* op) override;
  void DestroyStream(grpc_stream* gs,
                     grpc_closure* then_schedule_closure) override;

  void Orphan() override;

  void ref() {
    INPROC_LOG(GPR_INFO, "ref_transport %p", this);
    gpr_ref(&refs);
  }

  void unref() {
    INPROC_LOG(GPR_INFO, "unref_transport %p", this);
    if (!gpr_unref(&refs)) {
      return;
    }
    INPROC_LOG(GPR_INFO, "really_destroy_transport %p", this);
    this->~inproc_transport();
    gpr_free(this);
  }

  shared_mu* mu;
  gpr_refcount refs;
  bool is_client;
  grpc_core::ConnectivityStateTracker state_tracker;
  void (*accept_stream_cb)(void* user_data, grpc_core::Transport* transport,
                           const void* server_data);
  void (*registered_method_matcher_cb)(
      void* user_data, grpc_core::ServerMetadata* metadata) = nullptr;
  void* accept_stream_data;
  bool is_closed = false;
  struct inproc_transport* other_side;
  struct inproc_stream* stream_list = nullptr;
};

struct inproc_stream {
  inproc_stream(inproc_transport* t, grpc_stream_refcount* refcount,
                const void* server_data, grpc_core::Arena* arena)
      : t(t), refs(refcount), arena(arena) {
    // Ref this stream right now for ctor and list.
    ref("inproc_init_stream:init");
    ref("inproc_init_stream:list");

    stream_list_prev = nullptr;
    gpr_mu_lock(&t->mu->mu);
    stream_list_next = t->stream_list;
    if (t->stream_list) {
      t->stream_list->stream_list_prev = this;
    }
    t->stream_list = this;
    gpr_mu_unlock(&t->mu->mu);

    if (!server_data) {
      t->ref();
      inproc_transport* st = t->other_side;
      st->ref();
      other_side = nullptr;  // will get filled in soon
      // Pass the client-side stream address to the server-side for a ref
      ref("inproc_init_stream:clt");  // ref it now on behalf of server
                                      // side to avoid destruction
      INPROC_LOG(GPR_INFO, "calling accept stream cb %p %p",
                 st->accept_stream_cb, st->accept_stream_data);
      (*st->accept_stream_cb)(st->accept_stream_data, t, this);
    } else {
      // This is the server-side and is being called through accept_stream_cb
      inproc_stream* cs = const_cast<inproc_stream*>(
          static_cast<const inproc_stream*>(server_data));
      other_side = cs;
      // Ref the server-side stream on behalf of the client now
      ref("inproc_init_stream:srv");

      // Now we are about to affect the other side, so lock the transport
      // to make sure that it doesn't get destroyed
      gpr_mu_lock(&t->mu->mu);
      cs->other_side = this;
      // Now transfer from the other side's write_buffer if any to the to_read
      // buffer
      if (cs->write_buffer_initial_md_filled) {
        fill_in_metadata(this, &cs->write_buffer_initial_md,
                         &to_read_initial_md, &to_read_initial_md_filled);
        deadline = std::min(deadline, cs->write_buffer_deadline);
        cs->write_buffer_initial_md.Clear();
        cs->write_buffer_initial_md_filled = false;
      }
      if (cs->write_buffer_trailing_md_filled) {
        fill_in_metadata(this, &cs->write_buffer_trailing_md,
                         &to_read_trailing_md, &to_read_trailing_md_filled);
        cs->write_buffer_trailing_md.Clear();
        cs->write_buffer_trailing_md_filled = false;
      }
      if (!cs->write_buffer_cancel_error.ok()) {
        cancel_other_error = cs->write_buffer_cancel_error;
        cs->write_buffer_cancel_error = absl::OkStatus();
        maybe_process_ops_locked(this, cancel_other_error);
      }

      gpr_mu_unlock(&t->mu->mu);
    }
  }

  ~inproc_stream() { t->unref(); }

#ifndef NDEBUG
#define STREAM_REF(refs, reason) grpc_stream_ref(refs, reason)
#define STREAM_UNREF(refs, reason) grpc_stream_unref(refs, reason)
#else
#define STREAM_REF(refs, reason) grpc_stream_ref(refs)
#define STREAM_UNREF(refs, reason) grpc_stream_unref(refs)
#endif
  void ref(const char* reason) {
    INPROC_LOG(GPR_INFO, "ref_stream %p %s", this, reason);
    STREAM_REF(refs, reason);
  }

  void unref(const char* reason) {
    INPROC_LOG(GPR_INFO, "unref_stream %p %s", this, reason);
    STREAM_UNREF(refs, reason);
  }
#undef STREAM_REF
#undef STREAM_UNREF

  inproc_transport* t;
  grpc_stream_refcount* refs;
  grpc_core::Arena* arena;

  grpc_metadata_batch to_read_initial_md;
  bool to_read_initial_md_filled = false;
  grpc_metadata_batch to_read_trailing_md;
  bool to_read_trailing_md_filled = false;
  bool ops_needed = false;
  // Write buffer used only during gap at init time when client-side
  // stream is set up but server side stream is not yet set up
  grpc_metadata_batch write_buffer_initial_md;
  bool write_buffer_initial_md_filled = false;
  grpc_core::Timestamp write_buffer_deadline =
      grpc_core::Timestamp::InfFuture();
  grpc_metadata_batch write_buffer_trailing_md;
  bool write_buffer_trailing_md_filled = false;
  grpc_error_handle write_buffer_cancel_error;

  struct inproc_stream* other_side;
  bool other_side_closed = false;               // won't talk anymore
  bool write_buffer_other_side_closed = false;  // on hold

  grpc_transport_stream_op_batch* send_message_op = nullptr;
  grpc_transport_stream_op_batch* send_trailing_md_op = nullptr;
  grpc_transport_stream_op_batch* recv_initial_md_op = nullptr;
  grpc_transport_stream_op_batch* recv_message_op = nullptr;
  grpc_transport_stream_op_batch* recv_trailing_md_op = nullptr;

  bool initial_md_sent = false;
  bool trailing_md_sent = false;
  bool initial_md_recvd = false;
  bool trailing_md_recvd = false;
  // The following tracks if the server-side only pretends to have received
  // trailing metadata since it no longer cares about the RPC. If that is the
  // case, it is still ok for the client to send trailing metadata (in which
  // case it will be ignored).
  bool trailing_md_recvd_implicit_only = false;

  bool closed = false;

  grpc_error_handle cancel_self_error;
  grpc_error_handle cancel_other_error;

  grpc_core::Timestamp deadline = grpc_core::Timestamp::InfFuture();

  bool listed = true;
  struct inproc_stream* stream_list_prev;
  struct inproc_stream* stream_list_next;
};

void log_metadata(const grpc_metadata_batch* md_batch, bool is_client,
                  bool is_initial) {
  std::string prefix = absl::StrCat(
      "INPROC:", is_initial ? "HDR:" : "TRL:", is_client ? "CLI:" : "SVR:");
  md_batch->Log([&prefix](absl::string_view key, absl::string_view value) {
    gpr_log(GPR_INFO, "%s", absl::StrCat(prefix, key, ": ", value).c_str());
  });
}

namespace {

class CopySink {
 public:
  explicit CopySink(grpc_metadata_batch* dst) : dst_(dst) {}

  void Encode(const grpc_core::Slice& key, const grpc_core::Slice& value) {
    dst_->Append(key.as_string_view(), value.AsOwned(),
                 [](absl::string_view, const grpc_core::Slice&) {});
  }

  template <class T, class V>
  void Encode(T trait, V value) {
    dst_->Set(trait, value);
  }

  template <class T>
  void Encode(T trait, const grpc_core::Slice& value) {
    dst_->Set(trait, value.AsOwned());
  }

 private:
  grpc_metadata_batch* dst_;
};

}  // namespace

void fill_in_metadata(inproc_stream* s, const grpc_metadata_batch* metadata,
                      grpc_metadata_batch* out_md, bool* markfilled) {
  if (GRPC_TRACE_FLAG_ENABLED(grpc_inproc_trace)) {
    log_metadata(metadata, s->t->is_client,
                 metadata->get_pointer(grpc_core::WaitForReady()) != nullptr);
  }

  if (markfilled != nullptr) {
    *markfilled = true;
  }

  // TODO(ctiller): copy the metadata batch, don't rely on a bespoke copy
  // function. Can only do this once mdelems are out of the way though, too
  // many edge cases otherwise.
  out_md->Clear();
  CopySink sink(out_md);
  metadata->Encode(&sink);
}

void inproc_transport::InitStream(grpc_stream* gs,
                                  grpc_stream_refcount* refcount,
                                  const void* server_data,
                                  grpc_core::Arena* arena) {
  INPROC_LOG(GPR_INFO, "init_stream %p %p %p", this, gs, server_data);
  new (gs) inproc_stream(this, refcount, server_data, arena);
}

void close_stream_locked(inproc_stream* s) {
  if (!s->closed) {
    // Release the metadata that we would have written out
    s->write_buffer_initial_md.Clear();
    s->write_buffer_trailing_md.Clear();

    if (s->listed) {
      inproc_stream* p = s->stream_list_prev;
      inproc_stream* n = s->stream_list_next;
      if (p != nullptr) {
        p->stream_list_next = n;
      } else {
        s->t->stream_list = n;
      }
      if (n != nullptr) {
        n->stream_list_prev = p;
      }
      s->listed = false;
      s->unref("close_stream:list");
    }
    s->closed = true;
    s->unref("close_stream:closing");
  }
}

// This function means that we are done talking/listening to the other side
void close_other_side_locked(inproc_stream* s, const char* reason) {
  if (s->other_side != nullptr) {
    // First release the metadata that came from the other side's arena
    s->to_read_initial_md.Clear();
    s->to_read_trailing_md.Clear();

    s->other_side->unref(reason);
    s->other_side_closed = true;
    s->other_side = nullptr;
  } else if (!s->other_side_closed) {
    s->write_buffer_other_side_closed = true;
  }
}

// Call the on_complete closure associated with this stream_op_batch if
// this stream_op_batch is only one of the pending operations for this
// stream. This is called when one of the pending operations for the stream
// is done and about to be NULLed out
void complete_if_batch_end_locked(inproc_stream* s, grpc_error_handle error,
                                  grpc_transport_stream_op_batch* op,
                                  const char* msg) {
  int is_sm = static_cast<int>(op == s->send_message_op);
  int is_stm = static_cast<int>(op == s->send_trailing_md_op);
  // TODO(vjpai): We should not consider the recv ops here, since they
  // have their own callbacks.  We should invoke a batch's on_complete
  // as soon as all of the batch's send ops are complete, even if there
  // are still recv ops pending.
  int is_rim = static_cast<int>(op == s->recv_initial_md_op);
  int is_rm = static_cast<int>(op == s->recv_message_op);
  int is_rtm = static_cast<int>(op == s->recv_trailing_md_op);

  if ((is_sm + is_stm + is_rim + is_rm + is_rtm) == 1) {
    INPROC_LOG(GPR_INFO, "%s %p %p %p %s", msg, s, op, op->on_complete,
               grpc_core::StatusToString(error).c_str());
    grpc_core::ExecCtx::Run(DEBUG_LOCATION, op->on_complete, error);
  }
}

void maybe_process_ops_locked(inproc_stream* s, grpc_error_handle error) {
  if (s && (!error.ok() || s->ops_needed)) {
    s->ops_needed = false;
    op_state_machine_locked(s, error);
  }
}

void fail_helper_locked(inproc_stream* s, grpc_error_handle error) {
  INPROC_LOG(GPR_INFO, "op_state_machine %p fail_helper", s);
  // If we're failing this side, we need to make sure that
  // we also send or have already sent trailing metadata
  if (!s->trailing_md_sent) {
    // Send trailing md to the other side indicating cancellation
    s->trailing_md_sent = true;

    grpc_metadata_batch fake_md;
    inproc_stream* other = s->other_side;
    grpc_metadata_batch* dest = (other == nullptr)
                                    ? &s->write_buffer_trailing_md
                                    : &other->to_read_trailing_md;
    bool* destfilled = (other == nullptr) ? &s->write_buffer_trailing_md_filled
                                          : &other->to_read_trailing_md_filled;
    fill_in_metadata(s, &fake_md, dest, destfilled);

    if (other != nullptr) {
      if (other->cancel_other_error.ok()) {
        other->cancel_other_error = error;
      }
      maybe_process_ops_locked(other, error);
    } else if (s->write_buffer_cancel_error.ok()) {
      s->write_buffer_cancel_error = error;
    }
  }
  if (s->recv_initial_md_op) {
    grpc_error_handle err;
    if (!s->t->is_client) {
      // If this is a server, provide initial metadata with a path and
      // authority since it expects that as well as no error yet
      grpc_metadata_batch fake_md;
      fake_md.Set(grpc_core::HttpPathMetadata(),
                  grpc_core::Slice::FromStaticString("/"));
      fake_md.Set(grpc_core::HttpAuthorityMetadata(),
                  grpc_core::Slice::FromStaticString("inproc-fail"));

      fill_in_metadata(s, &fake_md,
                       s->recv_initial_md_op->payload->recv_initial_metadata
                           .recv_initial_metadata,
                       nullptr);
      err = absl::OkStatus();
    } else {
      err = error;
    }
    if (s->recv_initial_md_op->payload->recv_initial_metadata
            .trailing_metadata_available != nullptr) {
      // Set to true unconditionally, because we're failing the call, so even
      // if we haven't actually seen the send_trailing_metadata op from the
      // other side, we're going to return trailing metadata anyway.
      *s->recv_initial_md_op->payload->recv_initial_metadata
           .trailing_metadata_available = true;
    }
    INPROC_LOG(GPR_INFO,
               "fail_helper %p scheduling initial-metadata-ready %s %s", s,
               grpc_core::StatusToString(error).c_str(),
               grpc_core::StatusToString(err).c_str());
    grpc_core::ExecCtx::Run(
        DEBUG_LOCATION,
        s->recv_initial_md_op->payload->recv_initial_metadata
            .recv_initial_metadata_ready,
        err);
    // Last use of err so no need to REF and then UNREF it

    complete_if_batch_end_locked(
        s, error, s->recv_initial_md_op,
        "fail_helper scheduling recv-initial-metadata-on-complete");
    s->recv_initial_md_op = nullptr;
  }
  if (s->recv_message_op) {
    INPROC_LOG(GPR_INFO, "fail_helper %p scheduling message-ready %s", s,
               grpc_core::StatusToString(error).c_str());
    if (s->recv_message_op->payload->recv_message
            .call_failed_before_recv_message != nullptr) {
      *s->recv_message_op->payload->recv_message
           .call_failed_before_recv_message = true;
    }
    grpc_core::ExecCtx::Run(
        DEBUG_LOCATION,
        s->recv_message_op->payload->recv_message.recv_message_ready, error);
    complete_if_batch_end_locked(
        s, error, s->recv_message_op,
        "fail_helper scheduling recv-message-on-complete");
    s->recv_message_op = nullptr;
  }
  if (s->send_message_op) {
    ResetSendMessage(s->send_message_op);
    complete_if_batch_end_locked(
        s, error, s->send_message_op,
        "fail_helper scheduling send-message-on-complete");
    s->send_message_op = nullptr;
  }
  if (s->send_trailing_md_op) {
    complete_if_batch_end_locked(
        s, error, s->send_trailing_md_op,
        "fail_helper scheduling send-trailng-md-on-complete");
    s->send_trailing_md_op = nullptr;
  }
  if (s->recv_trailing_md_op) {
    INPROC_LOG(GPR_INFO, "fail_helper %p scheduling trailing-metadata-ready %s",
               s, grpc_core::StatusToString(error).c_str());
    grpc_core::ExecCtx::Run(
        DEBUG_LOCATION,
        s->recv_trailing_md_op->payload->recv_trailing_metadata
            .recv_trailing_metadata_ready,
        error);
    INPROC_LOG(GPR_INFO, "fail_helper %p scheduling trailing-md-on-complete %s",
               s, grpc_core::StatusToString(error).c_str());
    complete_if_batch_end_locked(
        s, error, s->recv_trailing_md_op,
        "fail_helper scheduling recv-trailing-metadata-on-complete");
    s->recv_trailing_md_op = nullptr;
  }
  close_other_side_locked(s, "fail_helper:other_side");
  close_stream_locked(s);
}

// TODO(vjpai): It should not be necessary to drain the incoming byte
// stream and create a new one; instead, we should simply pass the byte
// stream from the sender directly to the receiver as-is.
//
// Note that fixing this will also avoid the assumption in this code
// that the incoming byte stream's next() call will always return
// synchronously.  That assumption is true today but may not always be
// true in the future.
void message_transfer_locked(inproc_stream* sender, inproc_stream* receiver) {
  *receiver->recv_message_op->payload->recv_message.recv_message =
      std::move(*sender->send_message_op->payload->send_message.send_message);
  *receiver->recv_message_op->payload->recv_message.flags =
      sender->send_message_op->payload->send_message.flags;

  INPROC_LOG(GPR_INFO, "message_transfer_locked %p scheduling message-ready",
             receiver);
  grpc_core::ExecCtx::Run(
      DEBUG_LOCATION,
      receiver->recv_message_op->payload->recv_message.recv_message_ready,
      absl::OkStatus());
  complete_if_batch_end_locked(
      sender, absl::OkStatus(), sender->send_message_op,
      "message_transfer scheduling sender on_complete");
  complete_if_batch_end_locked(
      receiver, absl::OkStatus(), receiver->recv_message_op,
      "message_transfer scheduling receiver on_complete");

  receiver->recv_message_op = nullptr;
  sender->send_message_op = nullptr;
}

void op_state_machine_locked(inproc_stream* s, grpc_error_handle error) {
  // This function gets called when we have contents in the unprocessed reads
  // Get what we want based on our ops wanted
  // Schedule our appropriate closures
  // and then return to ops_needed state if still needed

  grpc_error_handle new_err;

  bool needs_close = false;

  INPROC_LOG(GPR_INFO, "op_state_machine %p", s);
  // cancellation takes precedence
  inproc_stream* other = s->other_side;

  if (!s->cancel_self_error.ok()) {
    fail_helper_locked(s, s->cancel_self_error);
    goto done;
  } else if (!s->cancel_other_error.ok()) {
    fail_helper_locked(s, s->cancel_other_error);
    goto done;
  } else if (!error.ok()) {
    fail_helper_locked(s, error);
    goto done;
  }

  if (s->send_message_op && other) {
    if (other->recv_message_op) {
      message_transfer_locked(s, other);
      maybe_process_ops_locked(other, absl::OkStatus());
    } else if (!s->t->is_client && s->trailing_md_sent) {
      // A server send will never be matched if the server already sent status
      ResetSendMessage(s->send_message_op);
      complete_if_batch_end_locked(
          s, absl::OkStatus(), s->send_message_op,
          "op_state_machine scheduling send-message-on-complete case 1");
      s->send_message_op = nullptr;
    }
  }
  // Pause a send trailing metadata if there is still an outstanding
  // send message unless we know that the send message will never get
  // matched to a receive. This happens on the client if the server has
  // already sent status or on the server if the client has requested
  // status
  if (s->send_trailing_md_op &&
      (!s->send_message_op ||
       (s->t->is_client &&
        (s->trailing_md_recvd || s->to_read_trailing_md_filled)) ||
       (!s->t->is_client && other &&
        (other->trailing_md_recvd || other->to_read_trailing_md_filled ||
         other->recv_trailing_md_op)))) {
    grpc_metadata_batch* dest = (other == nullptr)
                                    ? &s->write_buffer_trailing_md
                                    : &other->to_read_trailing_md;
    bool* destfilled = (other == nullptr) ? &s->write_buffer_trailing_md_filled
                                          : &other->to_read_trailing_md_filled;
    if (*destfilled || s->trailing_md_sent) {
      // The buffer is already in use; that's an error!
      INPROC_LOG(GPR_INFO, "Extra trailing metadata %p", s);
      new_err = GRPC_ERROR_CREATE("Extra trailing metadata");
      fail_helper_locked(s, new_err);
      goto done;
    } else {
      if (!other || !other->closed) {
        fill_in_metadata(s,
                         s->send_trailing_md_op->payload->send_trailing_metadata
                             .send_trailing_metadata,
                         dest, destfilled);
      }
      s->trailing_md_sent = true;
      if (s->send_trailing_md_op->payload->send_trailing_metadata.sent) {
        *s->send_trailing_md_op->payload->send_trailing_metadata.sent = true;
      }
      if (!s->t->is_client && s->trailing_md_recvd && s->recv_trailing_md_op) {
        INPROC_LOG(GPR_INFO,
                   "op_state_machine %p scheduling trailing-metadata-ready", s);
        grpc_core::ExecCtx::Run(
            DEBUG_LOCATION,
            s->recv_trailing_md_op->payload->recv_trailing_metadata
                .recv_trailing_metadata_ready,
            absl::OkStatus());
        INPROC_LOG(GPR_INFO,
                   "op_state_machine %p scheduling trailing-md-on-complete", s);
        grpc_core::ExecCtx::Run(DEBUG_LOCATION,
                                s->recv_trailing_md_op->on_complete,
                                absl::OkStatus());
        s->recv_trailing_md_op = nullptr;
        needs_close = true;
      }
    }
    maybe_process_ops_locked(other, absl::OkStatus());
    complete_if_batch_end_locked(
        s, absl::OkStatus(), s->send_trailing_md_op,
        "op_state_machine scheduling send-trailing-metadata-on-complete");
    s->send_trailing_md_op = nullptr;
  }
  if (s->recv_initial_md_op) {
    if (s->initial_md_recvd) {
      new_err = GRPC_ERROR_CREATE("Already recvd initial md");
      INPROC_LOG(
          GPR_INFO,
          "op_state_machine %p scheduling on_complete errors for already "
          "recvd initial md %s",
          s, grpc_core::StatusToString(new_err).c_str());
      fail_helper_locked(s, new_err);
      goto done;
    }

    if (s->to_read_initial_md_filled) {
      s->initial_md_recvd = true;
      fill_in_metadata(s, &s->to_read_initial_md,
                       s->recv_initial_md_op->payload->recv_initial_metadata
                           .recv_initial_metadata,
                       nullptr);
      if (s->deadline != grpc_core::Timestamp::InfFuture()) {
        s->recv_initial_md_op->payload->recv_initial_metadata
            .recv_initial_metadata->Set(grpc_core::GrpcTimeoutMetadata(),
                                        s->deadline);
      }
      if (s->recv_initial_md_op->payload->recv_initial_metadata
              .trailing_metadata_available != nullptr) {
        *s->recv_initial_md_op->payload->recv_initial_metadata
             .trailing_metadata_available =
            (other != nullptr && other->send_trailing_md_op != nullptr);
      }
      s->to_read_initial_md.Clear();
      s->to_read_initial_md_filled = false;
      if (s->t->registered_method_matcher_cb != nullptr) {
        s->t->registered_method_matcher_cb(
            s->t->accept_stream_data,
            s->recv_initial_md_op->payload->recv_initial_metadata
                .recv_initial_metadata);
      }
      grpc_core::ExecCtx::Run(
          DEBUG_LOCATION,
          std::exchange(s->recv_initial_md_op->payload->recv_initial_metadata
                            .recv_initial_metadata_ready,
                        nullptr),
          absl::OkStatus());
      complete_if_batch_end_locked(
          s, absl::OkStatus(), s->recv_initial_md_op,
          "op_state_machine scheduling recv-initial-metadata-on-complete");
      s->recv_initial_md_op = nullptr;
    }
  }
  if (s->recv_message_op) {
    if (other && other->send_message_op) {
      message_transfer_locked(other, s);
      maybe_process_ops_locked(other, absl::OkStatus());
    }
  }
  if (s->to_read_trailing_md_filled) {
    if (s->trailing_md_recvd) {
      if (s->trailing_md_recvd_implicit_only) {
        INPROC_LOG(GPR_INFO,
                   "op_state_machine %p already implicitly received trailing "
                   "metadata, so ignoring new trailing metadata from client",
                   s);
        s->to_read_trailing_md.Clear();
        s->to_read_trailing_md_filled = false;
        s->trailing_md_recvd_implicit_only = false;
      } else {
        new_err = GRPC_ERROR_CREATE("Already recvd trailing md");
        INPROC_LOG(
            GPR_INFO,
            "op_state_machine %p scheduling on_complete errors for already "
            "recvd trailing md %s",
            s, grpc_core::StatusToString(new_err).c_str());
        fail_helper_locked(s, new_err);
        goto done;
      }
    }
    if (s->recv_message_op != nullptr) {
      // This message needs to be wrapped up because it will never be
      // satisfied
      s->recv_message_op->payload->recv_message.recv_message->reset();
      INPROC_LOG(GPR_INFO, "op_state_machine %p scheduling message-ready", s);
      grpc_core::ExecCtx::Run(
          DEBUG_LOCATION,
          s->recv_message_op->payload->recv_message.recv_message_ready,
          absl::OkStatus());
      complete_if_batch_end_locked(
          s, new_err, s->recv_message_op,
          "op_state_machine scheduling recv-message-on-complete");
      s->recv_message_op = nullptr;
    }
    if ((s->trailing_md_sent || s->t->is_client) && s->send_message_op) {
      // Nothing further will try to receive from this stream, so finish off
      // any outstanding send_message op
      ResetSendMessage(s->send_message_op);
      s->send_message_op->payload->send_message.stream_write_closed = true;
      complete_if_batch_end_locked(
          s, new_err, s->send_message_op,
          "op_state_machine scheduling send-message-on-complete case 2");
      s->send_message_op = nullptr;
    }
    if (s->recv_trailing_md_op != nullptr) {
      // We wanted trailing metadata and we got it
      s->trailing_md_recvd = true;
      fill_in_metadata(s, &s->to_read_trailing_md,
                       s->recv_trailing_md_op->payload->recv_trailing_metadata
                           .recv_trailing_metadata,
                       nullptr);
      s->to_read_trailing_md.Clear();
      s->to_read_trailing_md_filled = false;
      s->recv_trailing_md_op->payload->recv_trailing_metadata
          .recv_trailing_metadata->Set(grpc_core::GrpcStatusFromWire(), true);

      // We should schedule the recv_trailing_md_op completion if
      // 1. this stream is the client-side
      // 2. this stream is the server-side AND has already sent its trailing md
      //    (If the server hasn't already sent its trailing md, it doesn't
      //    have
      //     a final status, so don't mark this op complete)
      if (s->t->is_client || s->trailing_md_sent) {
        grpc_core::ExecCtx::Run(
            DEBUG_LOCATION,
            s->recv_trailing_md_op->payload->recv_trailing_metadata
                .recv_trailing_metadata_ready,
            absl::OkStatus());
        grpc_core::ExecCtx::Run(DEBUG_LOCATION,
                                s->recv_trailing_md_op->on_complete,
                                absl::OkStatus());
        s->recv_trailing_md_op = nullptr;
        needs_close = s->trailing_md_sent;
      }
    } else if (!s->trailing_md_recvd) {
      INPROC_LOG(
          GPR_INFO,
          "op_state_machine %p has trailing md but not yet waiting for it", s);
    }
  }
  if (!s->t->is_client && s->trailing_md_sent &&
      (s->recv_trailing_md_op != nullptr)) {
    // In this case, we don't care to receive the write-close from the client
    // because we have already sent status and the RPC is over as far as we
    // are concerned.
    INPROC_LOG(GPR_INFO, "op_state_machine %p scheduling trailing-md-ready %s",
               s, grpc_core::StatusToString(new_err).c_str());
    grpc_core::ExecCtx::Run(
        DEBUG_LOCATION,
        s->recv_trailing_md_op->payload->recv_trailing_metadata
            .recv_trailing_metadata_ready,
        new_err);
    complete_if_batch_end_locked(
        s, new_err, s->recv_trailing_md_op,
        "op_state_machine scheduling recv-trailing-md-on-complete");
    s->trailing_md_recvd = true;
    s->recv_trailing_md_op = nullptr;
    // Since we are only pretending to have received the trailing MD, it would
    // be ok (not an error) if the client actually sends it later.
    s->trailing_md_recvd_implicit_only = true;
  }
  if (s->trailing_md_recvd && s->recv_message_op) {
    // No further message will come on this stream, so finish off the
    // recv_message_op
    INPROC_LOG(GPR_INFO, "op_state_machine %p scheduling message-ready", s);
    s->recv_message_op->payload->recv_message.recv_message->reset();
    grpc_core::ExecCtx::Run(
        DEBUG_LOCATION,
        s->recv_message_op->payload->recv_message.recv_message_ready,
        absl::OkStatus());
    complete_if_batch_end_locked(
        s, new_err, s->recv_message_op,
        "op_state_machine scheduling recv-message-on-complete");
    s->recv_message_op = nullptr;
  }
  if (s->trailing_md_recvd && s->send_message_op && s->t->is_client) {
    // Nothing further will try to receive from this stream, so finish off
    // any outstanding send_message op
    ResetSendMessage(s->send_message_op);
    complete_if_batch_end_locked(
        s, new_err, s->send_message_op,
        "op_state_machine scheduling send-message-on-complete case 3");
    s->send_message_op = nullptr;
  }
  if (s->send_message_op || s->send_trailing_md_op || s->recv_initial_md_op ||
      s->recv_message_op || s->recv_trailing_md_op) {
    // Didn't get the item we wanted so we still need to get
    // rescheduled
    INPROC_LOG(
        GPR_INFO, "op_state_machine %p still needs closure %p %p %p %p %p", s,
        s->send_message_op, s->send_trailing_md_op, s->recv_initial_md_op,
        s->recv_message_op, s->recv_trailing_md_op);
    s->ops_needed = true;
  }
done:
  if (needs_close) {
    close_other_side_locked(s, "op_state_machine");
    close_stream_locked(s);
  }
}

bool cancel_stream_locked(inproc_stream* s, grpc_error_handle error) {
  bool ret = false;  // was the cancel accepted
  INPROC_LOG(GPR_INFO, "cancel_stream %p with %s", s,
             grpc_core::StatusToString(error).c_str());
  if (s->cancel_self_error.ok()) {
    ret = true;
    s->cancel_self_error = error;
    // Catch current value of other before it gets closed off
    inproc_stream* other = s->other_side;
    maybe_process_ops_locked(s, s->cancel_self_error);
    // Send trailing md to the other side indicating cancellation, even if we
    // already have
    s->trailing_md_sent = true;

    grpc_metadata_batch cancel_md;

    grpc_metadata_batch* dest = (other == nullptr)
                                    ? &s->write_buffer_trailing_md
                                    : &other->to_read_trailing_md;
    bool* destfilled = (other == nullptr) ? &s->write_buffer_trailing_md_filled
                                          : &other->to_read_trailing_md_filled;
    fill_in_metadata(s, &cancel_md, dest, destfilled);

    if (other != nullptr) {
      if (other->cancel_other_error.ok()) {
        other->cancel_other_error = s->cancel_self_error;
      }
      maybe_process_ops_locked(other, other->cancel_other_error);
    } else if (s->write_buffer_cancel_error.ok()) {
      s->write_buffer_cancel_error = s->cancel_self_error;
    }

    // if we are a server and already received trailing md but
    // couldn't complete that because we hadn't yet sent out trailing
    // md, now's the chance
    if (!s->t->is_client && s->trailing_md_recvd && s->recv_trailing_md_op) {
      grpc_core::ExecCtx::Run(
          DEBUG_LOCATION,
          s->recv_trailing_md_op->payload->recv_trailing_metadata
              .recv_trailing_metadata_ready,
          s->cancel_self_error);
      complete_if_batch_end_locked(
          s, s->cancel_self_error, s->recv_trailing_md_op,
          "cancel_stream scheduling trailing-md-on-complete");
      s->recv_trailing_md_op = nullptr;
    }
  }

  close_other_side_locked(s, "cancel_stream:other_side");
  close_stream_locked(s);

  return ret;
}

void inproc_transport::PerformStreamOp(grpc_stream* gs,
                                       grpc_transport_stream_op_batch* op) {
  INPROC_LOG(GPR_INFO, "perform_stream_op %p %p %p", this, gs, op);
  inproc_stream* s = reinterpret_cast<inproc_stream*>(gs);
  gpr_mu* mu = &s->t->mu->mu;  // save aside in case s gets closed
  gpr_mu_lock(mu);

  if (GRPC_TRACE_FLAG_ENABLED(grpc_inproc_trace)) {
    if (op->send_initial_metadata) {
      log_metadata(op->payload->send_initial_metadata.send_initial_metadata,
                   s->t->is_client, true);
    }
    if (op->send_trailing_metadata) {
      log_metadata(op->payload->send_trailing_metadata.send_trailing_metadata,
                   s->t->is_client, false);
    }
  }
  grpc_error_handle error;
  grpc_closure* on_complete = op->on_complete;
  // TODO(roth): This is a hack needed because we use data inside of the
  // closure itself to do the barrier calculation (i.e., to ensure that
  // we don't schedule the closure until all ops in the batch have been
  // completed).  This can go away once we move to a new C++ closure API
  // that provides the ability to create a barrier closure.
  if (on_complete == nullptr) {
    on_complete = op->on_complete =
        grpc_core::NewClosure([](grpc_error_handle) {});
  }

  if (op->cancel_stream) {
    // Call cancel_stream_locked without ref'ing the cancel_error because
    // this function is responsible to make sure that that field gets unref'ed
    cancel_stream_locked(s, op->payload->cancel_stream.cancel_error);
    // this op can complete without an error
  } else if (!s->cancel_self_error.ok()) {
    // already self-canceled so still give it an error
    error = s->cancel_self_error;
  } else {
    INPROC_LOG(GPR_INFO, "perform_stream_op %p %s%s%s%s%s%s%s", s,
               s->t->is_client ? "client" : "server",
               op->send_initial_metadata ? " send_initial_metadata" : "",
               op->send_message ? " send_message" : "",
               op->send_trailing_metadata ? " send_trailing_metadata" : "",
               op->recv_initial_metadata ? " recv_initial_metadata" : "",
               op->recv_message ? " recv_message" : "",
               op->recv_trailing_metadata ? " recv_trailing_metadata" : "");
  }

  inproc_stream* other = s->other_side;
  if (error.ok() && (op->send_initial_metadata || op->send_trailing_metadata)) {
    if (s->t->is_closed) {
      error = GRPC_ERROR_CREATE("Endpoint already shutdown");
    }
    if (error.ok() && op->send_initial_metadata) {
      grpc_metadata_batch* dest = (other == nullptr)
                                      ? &s->write_buffer_initial_md
                                      : &other->to_read_initial_md;
      bool* destfilled = (other == nullptr) ? &s->write_buffer_initial_md_filled
                                            : &other->to_read_initial_md_filled;
      if (*destfilled || s->initial_md_sent) {
        // The buffer is already in use; that's an error!
        INPROC_LOG(GPR_INFO, "Extra initial metadata %p", s);
        error = GRPC_ERROR_CREATE("Extra initial metadata");
      } else {
        if (!s->other_side_closed) {
          fill_in_metadata(
              s, op->payload->send_initial_metadata.send_initial_metadata, dest,
              destfilled);
        }
        if (s->t->is_client) {
          grpc_core::Timestamp* dl =
              (other == nullptr) ? &s->write_buffer_deadline : &other->deadline;
          *dl = std::min(
              *dl, op->payload->send_initial_metadata.send_initial_metadata
                       ->get(grpc_core::GrpcTimeoutMetadata())
                       .value_or(grpc_core::Timestamp::InfFuture()));
          s->initial_md_sent = true;
        }
      }
      maybe_process_ops_locked(other, error);
    }
  }

  if (error.ok() && (op->send_message || op->send_trailing_metadata ||
                     op->recv_initial_metadata || op->recv_message ||
                     op->recv_trailing_metadata)) {
    // Mark ops that need to be processed by the state machine
    if (op->send_message) {
      s->send_message_op = op;
    }
    if (op->send_trailing_metadata) {
      s->send_trailing_md_op = op;
    }
    if (op->recv_initial_metadata) {
      s->recv_initial_md_op = op;
    }
    if (op->recv_message) {
      s->recv_message_op = op;
    }
    if (op->recv_trailing_metadata) {
      s->recv_trailing_md_op = op;
    }

    // We want to initiate the state machine if:
    // 1. We want to send a message and the other side wants to receive
    // 2. We want to send trailing metadata and there isn't an unmatched send
    //    or the other side wants trailing metadata
    // 3. We want initial metadata and the other side has sent it
    // 4. We want to receive a message and there is a message ready
    // 5. There is trailing metadata, even if nothing specifically wants
    //    that because that can shut down the receive message as well
    if ((op->send_message && other && other->recv_message_op != nullptr) ||
        (op->send_trailing_metadata &&
         (!s->send_message_op || (other && other->recv_trailing_md_op))) ||
        (op->recv_initial_metadata && s->to_read_initial_md_filled) ||
        (op->recv_message && other && other->send_message_op != nullptr) ||
        (s->to_read_trailing_md_filled || s->trailing_md_recvd)) {
      op_state_machine_locked(s, error);
    } else {
      s->ops_needed = true;
    }
  } else {
    if (!error.ok()) {
      // Consume any send message that was sent here but that we are not
      // pushing to the other side
      if (op->send_message) {
        ResetSendMessage(op);
      }
      // Schedule op's closures that we didn't push to op state machine
      if (op->recv_initial_metadata) {
        if (op->payload->recv_initial_metadata.trailing_metadata_available !=
            nullptr) {
          // Set to true unconditionally, because we're failing the call, so
          // even if we haven't actually seen the send_trailing_metadata op
          // from the other side, we're going to return trailing metadata
          // anyway.
          *op->payload->recv_initial_metadata.trailing_metadata_available =
              true;
        }
        INPROC_LOG(
            GPR_INFO,
            "perform_stream_op error %p scheduling initial-metadata-ready %s",
            s, grpc_core::StatusToString(error).c_str());
        grpc_core::ExecCtx::Run(
            DEBUG_LOCATION,
            op->payload->recv_initial_metadata.recv_initial_metadata_ready,
            error);
      }
      if (op->recv_message) {
        INPROC_LOG(
            GPR_INFO,
            "perform_stream_op error %p scheduling recv message-ready %s", s,
            grpc_core::StatusToString(error).c_str());
        if (op->payload->recv_message.call_failed_before_recv_message !=
            nullptr) {
          *op->payload->recv_message.call_failed_before_recv_message = true;
        }
        grpc_core::ExecCtx::Run(DEBUG_LOCATION,
                                op->payload->recv_message.recv_message_ready,
                                error);
      }
      if (op->recv_trailing_metadata) {
        INPROC_LOG(GPR_INFO,
                   "perform_stream_op error %p scheduling "
                   "trailing-metadata-ready %s",
                   s, grpc_core::StatusToString(error).c_str());
        grpc_core::ExecCtx::Run(
            DEBUG_LOCATION,
            op->payload->recv_trailing_metadata.recv_trailing_metadata_ready,
            error);
      }
    }
    INPROC_LOG(GPR_INFO, "perform_stream_op %p scheduling on_complete %s", s,
               grpc_core::StatusToString(error).c_str());
    grpc_core::ExecCtx::Run(DEBUG_LOCATION, on_complete, error);
  }
  gpr_mu_unlock(mu);
}

void close_transport_locked(inproc_transport* t) {
  INPROC_LOG(GPR_INFO, "close_transport %p %d", t, t->is_closed);
  t->state_tracker.SetState(GRPC_CHANNEL_SHUTDOWN, absl::Status(),
                            "close transport");
  if (!t->is_closed) {
    t->is_closed = true;
    // Also end all streams on this transport
    while (t->stream_list != nullptr) {
      // cancel_stream_locked also adjusts stream list
      cancel_stream_locked(
          t->stream_list,
          grpc_error_set_int(GRPC_ERROR_CREATE("Transport closed"),
                             grpc_core::StatusIntProperty::kRpcStatus,
                             GRPC_STATUS_UNAVAILABLE));
    }
  }
}

void inproc_transport::PerformOp(grpc_transport_op* op) {
  INPROC_LOG(GPR_INFO, "perform_transport_op %p %p", this, op);
  gpr_mu_lock(&mu->mu);
  if (op->start_connectivity_watch != nullptr) {
    state_tracker.AddWatcher(op->start_connectivity_watch_state,
                             std::move(op->start_connectivity_watch));
  }
  if (op->stop_connectivity_watch != nullptr) {
    state_tracker.RemoveWatcher(op->stop_connectivity_watch);
  }
  if (op->set_accept_stream) {
    accept_stream_cb = op->set_accept_stream_fn;
    registered_method_matcher_cb = op->set_registered_method_matcher_fn;
    accept_stream_data = op->set_accept_stream_user_data;
  }
  if (op->on_consumed) {
    grpc_core::ExecCtx::Run(DEBUG_LOCATION, op->on_consumed, absl::OkStatus());
  }

  bool do_close = false;
  if (!op->goaway_error.ok()) {
    do_close = true;
  }
  if (!op->disconnect_with_error.ok()) {
    do_close = true;
  }

  if (do_close) {
    close_transport_locked(this);
  }
  gpr_mu_unlock(&mu->mu);
}

void inproc_transport::DestroyStream(grpc_stream* gs,
                                     grpc_closure* then_schedule_closure) {
  INPROC_LOG(GPR_INFO, "destroy_stream %p %p", gs, then_schedule_closure);
  inproc_stream* s = reinterpret_cast<inproc_stream*>(gs);
  gpr_mu_lock(&mu->mu);
  close_stream_locked(s);
  gpr_mu_unlock(&mu->mu);
  s->~inproc_stream();
  grpc_core::ExecCtx::Run(DEBUG_LOCATION, then_schedule_closure,
                          absl::OkStatus());
}

void inproc_transport::Orphan() {
  INPROC_LOG(GPR_INFO, "destroy_transport %p", this);
  gpr_mu_lock(&mu->mu);
  close_transport_locked(this);
  gpr_mu_unlock(&mu->mu);
  other_side->unref();
  unref();
}

//******************************************************************************
// INTEGRATION GLUE
//

size_t inproc_transport::SizeOfStream() const { return sizeof(inproc_stream); }

absl::string_view inproc_transport::GetTransportName() const {
  return "inproc";
}

void inproc_transport::SetPollset(grpc_stream* /*gs*/,
                                  grpc_pollset* /*pollset*/) {
  // Nothing to do here
}

void inproc_transport::SetPollsetSet(grpc_stream* /*gs*/,
                                     grpc_pollset_set* /*pollset_set*/) {
  // Nothing to do here
}

grpc_endpoint* inproc_transport::GetEndpoint() { return nullptr; }

//******************************************************************************
// Main inproc transport functions
//
void inproc_transports_create(grpc_core::Transport** server_transport,
                              grpc_core::Transport** client_transport) {
  INPROC_LOG(GPR_INFO, "inproc_transports_create");
  shared_mu* mu = new (gpr_malloc(sizeof(*mu))) shared_mu();
  inproc_transport* st =
      new (gpr_malloc(sizeof(*st))) inproc_transport(mu, /*is_client=*/false);
  inproc_transport* ct =
      new (gpr_malloc(sizeof(*ct))) inproc_transport(mu, /*is_client=*/true);
  st->other_side = ct;
  ct->other_side = st;
  *server_transport = reinterpret_cast<grpc_core::Transport*>(st);
  *client_transport = reinterpret_cast<grpc_core::Transport*>(ct);
}
}  // namespace

grpc_channel* grpc_legacy_inproc_channel_create(grpc_server* server,
                                                const grpc_channel_args* args,
                                                void* /*reserved*/) {
  GRPC_API_TRACE("grpc_inproc_channel_create(server=%p, args=%p)", 2,
                 (server, args));

  grpc_core::ExecCtx exec_ctx;

  grpc_core::Server* core_server = grpc_core::Server::FromC(server);
  // Remove max_connection_idle and max_connection_age channel arguments since
  // those do not apply to inproc transports.
  grpc_core::ChannelArgs server_args =
      core_server->channel_args()
          .Remove(GRPC_ARG_MAX_CONNECTION_IDLE_MS)
          .Remove(GRPC_ARG_MAX_CONNECTION_AGE_MS);

  // Add a default authority channel argument for the client
  grpc_core::ChannelArgs client_args =
      grpc_core::CoreConfiguration::Get()
          .channel_args_preconditioning()
          .PreconditionChannelArgs(args)
          .Set(GRPC_ARG_DEFAULT_AUTHORITY, "inproc.authority");
  grpc_core::Transport* server_transport;
  grpc_core::Transport* client_transport;
  inproc_transports_create(&server_transport, &client_transport);

  // TODO(ncteisen): design and support channelz GetSocket for inproc.
  grpc_error_handle error = core_server->SetupTransport(
      server_transport, nullptr, server_args, nullptr);
  grpc_channel* channel = nullptr;
  if (error.ok()) {
    auto new_channel = grpc_core::ChannelCreate(
        "inproc", client_args, GRPC_CLIENT_DIRECT_CHANNEL, client_transport);
    if (!new_channel.ok()) {
      GPR_ASSERT(!channel);
      gpr_log(GPR_ERROR, "Failed to create client channel: %s",
              grpc_core::StatusToString(error).c_str());
      intptr_t integer;
      grpc_status_code status = GRPC_STATUS_INTERNAL;
      if (grpc_error_get_int(error, grpc_core::StatusIntProperty::kRpcStatus,
                             &integer)) {
        status = static_cast<grpc_status_code>(integer);
      }
      // client_transport was destroyed when grpc_channel_create_internal saw an
      // error.
      server_transport->Orphan();
      channel = grpc_lame_client_channel_create(
          nullptr, status, "Failed to create client channel");
    } else {
      channel = new_channel->release()->c_ptr();
    }
  } else {
    GPR_ASSERT(!channel);
    gpr_log(GPR_ERROR, "Failed to create server channel: %s",
            grpc_core::StatusToString(error).c_str());
    intptr_t integer;
    grpc_status_code status = GRPC_STATUS_INTERNAL;
    if (grpc_error_get_int(error, grpc_core::StatusIntProperty::kRpcStatus,
                           &integer)) {
      status = static_cast<grpc_status_code>(integer);
    }
    client_transport->Orphan();
    server_transport->Orphan();
    channel = grpc_lame_client_channel_create(
        nullptr, status, "Failed to create server channel");
  }
  return channel;
}