src/core/lib/transport/transport.h

//
//
// Copyright 2015 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_SRC_CORE_LIB_TRANSPORT_TRANSPORT_H
#define GRPC_SRC_CORE_LIB_TRANSPORT_TRANSPORT_H

#include <grpc/support/port_platform.h>

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

#include <functional>
#include <string>
#include <utility>

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

#include <grpc/impl/connectivity_state.h>
#include <grpc/slice.h>
#include <grpc/status.h>
#include <grpc/support/log.h>
#include <grpc/support/time.h>

#include "src/core/lib/channel/context.h"
#include "src/core/lib/debug/trace.h"
#include "src/core/lib/gprpp/debug_location.h"
#include "src/core/lib/gprpp/orphanable.h"
#include "src/core/lib/gprpp/ref_counted.h"
#include "src/core/lib/iomgr/call_combiner.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/iomgr_fwd.h"
#include "src/core/lib/iomgr/polling_entity.h"
#include "src/core/lib/promise/arena_promise.h"
#include "src/core/lib/promise/context.h"
#include "src/core/lib/promise/detail/status.h"
#include "src/core/lib/promise/pipe.h"
#include "src/core/lib/resource_quota/arena.h"
#include "src/core/lib/slice/slice_buffer.h"
#include "src/core/lib/transport/connectivity_state.h"
#include "src/core/lib/transport/metadata_batch.h"
#include "src/core/lib/transport/transport_fwd.h"

// Minimum and maximum protocol accepted versions.
#define GRPC_PROTOCOL_VERSION_MAX_MAJOR 2
#define GRPC_PROTOCOL_VERSION_MAX_MINOR 1
#define GRPC_PROTOCOL_VERSION_MIN_MAJOR 2
#define GRPC_PROTOCOL_VERSION_MIN_MINOR 1

#define GRPC_ARG_TRANSPORT "grpc.internal.transport"

/// Internal bit flag for grpc_begin_message's \a flags signaling the use of
/// compression for the message. (Does not apply for stream compression.)
#define GRPC_WRITE_INTERNAL_COMPRESS (0x80000000u)
/// Internal bit flag for determining whether the message was compressed and had
/// to be decompressed by the message_decompress filter. (Does not apply for
/// stream compression.)
#define GRPC_WRITE_INTERNAL_TEST_ONLY_WAS_COMPRESSED (0x40000000u)
/// Mask of all valid internal flags.
#define GRPC_WRITE_INTERNAL_USED_MASK \
  (GRPC_WRITE_INTERNAL_COMPRESS | GRPC_WRITE_INTERNAL_TEST_ONLY_WAS_COMPRESSED)

namespace grpc_core {

// Server metadata type
// TODO(ctiller): This should be a bespoke instance of MetadataMap<>
using ServerMetadata = grpc_metadata_batch;
using ServerMetadataHandle = Arena::PoolPtr<ServerMetadata>;

// Client initial metadata type
// TODO(ctiller): This should be a bespoke instance of MetadataMap<>
using ClientMetadata = grpc_metadata_batch;
using ClientMetadataHandle = Arena::PoolPtr<ClientMetadata>;

class Message {
 public:
  Message() = default;
  ~Message() = default;
  Message(SliceBuffer payload, uint32_t flags)
      : payload_(std::move(payload)), flags_(flags) {}
  Message(const Message&) = delete;
  Message& operator=(const Message&) = delete;

  uint32_t flags() const { return flags_; }
  uint32_t& mutable_flags() { return flags_; }
  SliceBuffer* payload() { return &payload_; }
  const SliceBuffer* payload() const { return &payload_; }

 private:
  SliceBuffer payload_;
  uint32_t flags_ = 0;
};

using MessageHandle = Arena::PoolPtr<Message>;

// Ok/not-ok check for trailing metadata, so that it can be used as result types
// for TrySeq.
inline bool IsStatusOk(const ServerMetadataHandle& m) {
  return m->get(GrpcStatusMetadata()).value_or(GRPC_STATUS_UNKNOWN) ==
         GRPC_STATUS_OK;
}

ServerMetadataHandle ServerMetadataFromStatus(
    const absl::Status& status, Arena* arena = GetContext<Arena>());

template <>
struct StatusCastImpl<ServerMetadataHandle, absl::Status> {
  static ServerMetadataHandle Cast(const absl::Status& m) {
    return ServerMetadataFromStatus(m);
  }
};

template <>
struct StatusCastImpl<ServerMetadataHandle, const absl::Status&> {
  static ServerMetadataHandle Cast(const absl::Status& m) {
    return ServerMetadataFromStatus(m);
  }
};

template <>
struct StatusCastImpl<ServerMetadataHandle, absl::Status&> {
  static ServerMetadataHandle Cast(const absl::Status& m) {
    return ServerMetadataFromStatus(m);
  }
};

struct CallArgs {
  // Initial metadata from the client to the server.
  // During promise setup this can be manipulated by filters (and then
  // passed on to the next filter).
  ClientMetadataHandle client_initial_metadata;
  // Initial metadata from the server to the client.
  // Set once when it's available.
  // During promise setup filters can substitute their own latch for this
  // and consequently intercept the sent value and mutate/observe it.
  PipeSender<ServerMetadataHandle>* server_initial_metadata;
  // Messages travelling from the application to the transport.
  PipeReceiver<MessageHandle>* client_to_server_messages;
  // Messages travelling from the transport to the application.
  PipeSender<MessageHandle>* server_to_client_messages;
};

using NextPromiseFactory =
    std::function<ArenaPromise<ServerMetadataHandle>(CallArgs)>;

}  // namespace grpc_core

// forward declarations

// grpc_stream doesn't actually exist. It's used as a typesafe
// opaque pointer for whatever data the transport wants to track
// for a stream.
typedef struct grpc_stream grpc_stream;

extern grpc_core::DebugOnlyTraceFlag grpc_trace_stream_refcount;

typedef struct grpc_stream_refcount {
  grpc_core::RefCount refs;
  grpc_closure destroy;
#ifndef NDEBUG
  const char* object_type;
#endif
} grpc_stream_refcount;

#ifndef NDEBUG
void grpc_stream_ref_init(grpc_stream_refcount* refcount, int initial_refs,
                          grpc_iomgr_cb_func cb, void* cb_arg,
                          const char* object_type);
#define GRPC_STREAM_REF_INIT(rc, ir, cb, cb_arg, objtype) \
  grpc_stream_ref_init(rc, ir, cb, cb_arg, objtype)
#else
void grpc_stream_ref_init(grpc_stream_refcount* refcount, int initial_refs,
                          grpc_iomgr_cb_func cb, void* cb_arg);
#define GRPC_STREAM_REF_INIT(rc, ir, cb, cb_arg, objtype) \
  do {                                                    \
    grpc_stream_ref_init(rc, ir, cb, cb_arg);             \
    (void)(objtype);                                      \
  } while (0)
#endif

#ifndef NDEBUG
inline void grpc_stream_ref(grpc_stream_refcount* refcount,
                            const char* reason) {
  if (grpc_trace_stream_refcount.enabled()) {
    gpr_log(GPR_DEBUG, "%s %p:%p REF %s", refcount->object_type, refcount,
            refcount->destroy.cb_arg, reason);
  }
  refcount->refs.RefNonZero(DEBUG_LOCATION, reason);
}
#else
inline void grpc_stream_ref(grpc_stream_refcount* refcount) {
  refcount->refs.RefNonZero();
}
#endif

void grpc_stream_destroy(grpc_stream_refcount* refcount);

#ifndef NDEBUG
inline void grpc_stream_unref(grpc_stream_refcount* refcount,
                              const char* reason) {
  if (grpc_trace_stream_refcount.enabled()) {
    gpr_log(GPR_DEBUG, "%s %p:%p UNREF %s", refcount->object_type, refcount,
            refcount->destroy.cb_arg, reason);
  }
  if (GPR_UNLIKELY(refcount->refs.Unref(DEBUG_LOCATION, reason))) {
    grpc_stream_destroy(refcount);
  }
}
#else
inline void grpc_stream_unref(grpc_stream_refcount* refcount) {
  if (GPR_UNLIKELY(refcount->refs.Unref())) {
    grpc_stream_destroy(refcount);
  }
}
#endif

// Wrap a buffer that is owned by some stream object into a slice that shares
// the same refcount
grpc_slice grpc_slice_from_stream_owned_buffer(grpc_stream_refcount* refcount,
                                               void* buffer, size_t length);

struct grpc_transport_one_way_stats {
  uint64_t framing_bytes = 0;
  uint64_t data_bytes = 0;
  uint64_t header_bytes = 0;
};

struct grpc_transport_stream_stats {
  grpc_transport_one_way_stats incoming;
  grpc_transport_one_way_stats outgoing;
  gpr_timespec latency = gpr_inf_future(GPR_TIMESPAN);
};

void grpc_transport_move_one_way_stats(grpc_transport_one_way_stats* from,
                                       grpc_transport_one_way_stats* to);

void grpc_transport_move_stats(grpc_transport_stream_stats* from,
                               grpc_transport_stream_stats* to);

// This struct (which is present in both grpc_transport_stream_op_batch
// and grpc_transport_op_batch) is a convenience to allow filters or
// transports to schedule a closure related to a particular batch without
// having to allocate memory.  The general pattern is to initialize the
// closure with the callback arg set to the batch and extra_arg set to
// whatever state is associated with the handler (e.g., the call element
// or the transport stream object).
//
// Note that this can only be used by the current handler of a given
// batch on the way down the stack (i.e., whichever filter or transport is
// currently handling the batch).  Once a filter or transport passes control
// of the batch to the next handler, it cannot depend on the contents of
// this struct anymore, because the next handler may reuse it.
struct grpc_handler_private_op_data {
  void* extra_arg = nullptr;
  grpc_closure closure;
  grpc_handler_private_op_data() { memset(&closure, 0, sizeof(closure)); }
};

typedef struct grpc_transport_stream_op_batch_payload
    grpc_transport_stream_op_batch_payload;

// Transport stream op: a set of operations to perform on a transport
// against a single stream
struct grpc_transport_stream_op_batch {
  grpc_transport_stream_op_batch()
      : send_initial_metadata(false),
        send_trailing_metadata(false),
        send_message(false),
        recv_initial_metadata(false),
        recv_message(false),
        recv_trailing_metadata(false),
        cancel_stream(false),
        is_traced(false) {}

  /// Should be scheduled when all of the non-recv operations in the batch
  /// are complete.

  /// The recv ops (recv_initial_metadata, recv_message, and
  /// recv_trailing_metadata) each have their own callbacks.  If a batch
  /// contains both recv ops and non-recv ops, on_complete should be
  /// scheduled as soon as the non-recv ops are complete, regardless of
  /// whether or not the recv ops are complete.  If a batch contains
  /// only recv ops, on_complete can be null.
  grpc_closure* on_complete = nullptr;

  /// Values for the stream op (fields set are determined by flags above)
  grpc_transport_stream_op_batch_payload* payload = nullptr;

  /// Send initial metadata to the peer, from the provided metadata batch.
  bool send_initial_metadata : 1;

  /// Send trailing metadata to the peer, from the provided metadata batch.
  bool send_trailing_metadata : 1;

  /// Send message data to the peer, from the provided byte stream.
  bool send_message : 1;

  /// Receive initial metadata from the stream, into provided metadata batch.
  bool recv_initial_metadata : 1;

  /// Receive message data from the stream, into provided byte stream.
  bool recv_message : 1;

  /// Receive trailing metadata from the stream, into provided metadata batch.
  ///
  bool recv_trailing_metadata : 1;

  /// Cancel this stream with the provided error
  bool cancel_stream : 1;

  /// Is this stream traced
  bool is_traced : 1;

  //**************************************************************************
  // remaining fields are initialized and used at the discretion of the
  // current handler of the op

  grpc_handler_private_op_data handler_private;
};

struct grpc_transport_stream_op_batch_payload {
  explicit grpc_transport_stream_op_batch_payload(
      grpc_call_context_element* context)
      : context(context) {}
  struct {
    grpc_metadata_batch* send_initial_metadata = nullptr;
  } send_initial_metadata;

  struct {
    grpc_metadata_batch* send_trailing_metadata = nullptr;
    // Set by the transport to true if the stream successfully wrote the
    // trailing metadata. If this is not set but there was a send trailing
    // metadata op present, this can indicate that a server call can be marked
    // as  a cancellation (since the stream was write-closed before status could
    // be delivered).
    bool* sent = nullptr;
  } send_trailing_metadata;

  struct {
    // The transport (or a filter that decides to return a failure before
    // the op gets down to the transport) takes ownership.
    // The batch's on_complete will not be called until after the byte
    // stream is orphaned.
    grpc_core::SliceBuffer* send_message;
    uint32_t flags = 0;
    // Set by the transport if the stream has been closed for writes. If this
    // is set and send message op is present, we set the operation to be a
    // failure without sending a cancel OP down the stack. This is so that the
    // status of the call does not get overwritten by the Cancel OP, which would
    // be especially problematic if we had received a valid status from the
    // server.
    // For send_initial_metadata, it is fine for the status to be overwritten
    // because at that point, the client will not have received a status.
    // For send_trailing_metadata, we might overwrite the status if we have
    // non-zero metadata to send. This is fine because the API does not allow
    // the client to send trailing metadata.
    bool stream_write_closed = false;
  } send_message;

  struct {
    grpc_metadata_batch* recv_initial_metadata = nullptr;
    /// Should be enqueued when initial metadata is ready to be processed.
    grpc_closure* recv_initial_metadata_ready = nullptr;
    // If not NULL, will be set to true if trailing metadata is
    // immediately available. This may be a signal that we received a
    // Trailers-Only response. The retry filter checks this to know whether to
    // defer the decision to commit the call or not. The C++ callback API also
    // uses this to set the success flag of OnReadInitialMetadataDone()
    // callback.
    bool* trailing_metadata_available = nullptr;
  } recv_initial_metadata;

  struct {
    // Will be set by the transport to point to the byte stream containing a
    // received message. Will be nullopt if trailing metadata is received
    // instead of a message.
    absl::optional<grpc_core::SliceBuffer>* recv_message = nullptr;
    uint32_t* flags = nullptr;
    // Was this recv_message failed for reasons other than a clean end-of-stream
    bool* call_failed_before_recv_message = nullptr;
    /// Should be enqueued when one message is ready to be processed.
    grpc_closure* recv_message_ready = nullptr;
  } recv_message;

  struct {
    grpc_metadata_batch* recv_trailing_metadata = nullptr;
    grpc_transport_stream_stats* collect_stats = nullptr;
    /// Should be enqueued when trailing metadata is ready to be processed.
    grpc_closure* recv_trailing_metadata_ready = nullptr;
  } recv_trailing_metadata;

  /// Forcefully close this stream.
  /// The HTTP2 semantics should be:
  /// - server side: if cancel_error has
  /// grpc_core::StatusIntProperty::kRpcStatus, and trailing metadata has not
  /// been sent, send trailing metadata with status and message from
  /// cancel_error (use grpc_error_get_status) followed by a RST_STREAM with
  /// error=GRPC_CHTTP2_NO_ERROR to force a full close
  /// - at all other times: use grpc_error_get_status to get a status code, and
  ///   convert to a HTTP2 error code using
  ///   grpc_chttp2_grpc_status_to_http2_error. Send a RST_STREAM with this
  ///   error.
  struct {
    // Error contract: the transport that gets this op must cause cancel_error
    //                 to be unref'ed after processing it
    grpc_error_handle cancel_error;
  } cancel_stream;

  // Indexes correspond to grpc_context_index enum values
  grpc_call_context_element* context;
};

/// Transport op: a set of operations to perform on a transport as a whole
typedef struct grpc_transport_op {
  /// Called when processing of this op is done.
  grpc_closure* on_consumed = nullptr;
  /// connectivity monitoring - set connectivity_state to NULL to unsubscribe
  grpc_core::OrphanablePtr<grpc_core::ConnectivityStateWatcherInterface>
      start_connectivity_watch;
  grpc_connectivity_state start_connectivity_watch_state = GRPC_CHANNEL_IDLE;
  grpc_core::ConnectivityStateWatcherInterface* stop_connectivity_watch =
      nullptr;
  /// should the transport be disconnected
  /// Error contract: the transport that gets this op must cause
  ///                disconnect_with_error to be unref'ed after processing it
  grpc_error_handle disconnect_with_error;
  /// what should the goaway contain?
  /// Error contract: the transport that gets this op must cause
  ///                goaway_error to be unref'ed after processing it
  grpc_error_handle goaway_error;
  /// set the callback for accepting new streams;
  /// this is a permanent callback, unlike the other one-shot closures.
  /// If true, the callback is set to set_accept_stream_fn, with its
  /// user_data argument set to set_accept_stream_user_data
  bool set_accept_stream = false;
  void (*set_accept_stream_fn)(void* user_data, grpc_transport* transport,
                               const void* server_data) = nullptr;
  void* set_accept_stream_user_data = nullptr;
  /// set the callback for accepting new streams based upon promises;
  /// this is a permanent callback, unlike the other one-shot closures.
  /// If true, the callback is set to set_make_promise_fn, with its
  /// user_data argument set to set_make_promise_data
  bool set_make_promise = false;
  void (*set_make_promise_fn)(void* user_data, grpc_transport* transport,
                              const void* server_data) = nullptr;
  void* set_make_promise_user_data = nullptr;
  /// add this transport to a pollset
  grpc_pollset* bind_pollset = nullptr;
  /// add this transport to a pollset_set
  grpc_pollset_set* bind_pollset_set = nullptr;
  /// send a ping, if either on_initiate or on_ack is not NULL
  struct {
    /// Ping may be delayed by the transport, on_initiate callback will be
    /// called when the ping is actually being sent.
    grpc_closure* on_initiate = nullptr;
    /// Called when the ping ack is received
    grpc_closure* on_ack = nullptr;
  } send_ping;
  // If true, will reset the channel's connection backoff.
  bool reset_connect_backoff = false;

  //**************************************************************************
  // remaining fields are initialized and used at the discretion of the
  // transport implementation

  grpc_handler_private_op_data handler_private;
} grpc_transport_op;

// Returns the amount of memory required to store a grpc_stream for this
// transport
size_t grpc_transport_stream_size(grpc_transport* transport);

// Initialize transport data for a stream.

// Returns 0 on success, any other (transport-defined) value for failure.
// May assume that stream contains all-zeros.

// Arguments:
//   transport   - the transport on which to create this stream
//   stream      - a pointer to uninitialized memory to initialize
//   server_data - either NULL for a client initiated stream, or a pointer
//                 supplied from the accept_stream callback function
int grpc_transport_init_stream(grpc_transport* transport, grpc_stream* stream,
                               grpc_stream_refcount* refcount,
                               const void* server_data,
                               grpc_core::Arena* arena);

void grpc_transport_set_pops(grpc_transport* transport, grpc_stream* stream,
                             grpc_polling_entity* pollent);

// Destroy transport data for a stream.

// Requires: a recv_batch with final_state == GRPC_STREAM_CLOSED has been
// received by the up-layer. Must not be called in the same call stack as
// recv_frame.

// Arguments:
//   transport - the transport on which to create this stream
//   stream    - the grpc_stream to destroy (memory is still owned by the
//               caller, but any child memory must be cleaned up)
void grpc_transport_destroy_stream(grpc_transport* transport,
                                   grpc_stream* stream,
                                   grpc_closure* then_schedule_closure);

void grpc_transport_stream_op_batch_finish_with_failure(
    grpc_transport_stream_op_batch* batch, grpc_error_handle error,
    grpc_core::CallCombiner* call_combiner);
void grpc_transport_stream_op_batch_queue_finish_with_failure(
    grpc_transport_stream_op_batch* batch, grpc_error_handle error,
    grpc_core::CallCombinerClosureList* closures);
// Fail a batch from within the transport (i.e. without the activity lock/call
// combiner taken).
void grpc_transport_stream_op_batch_finish_with_failure_from_transport(
    grpc_transport_stream_op_batch* batch, grpc_error_handle error);

std::string grpc_transport_stream_op_batch_string(
    grpc_transport_stream_op_batch* op, bool truncate);
std::string grpc_transport_op_string(grpc_transport_op* op);

// Send a batch of operations on a transport

// Takes ownership of any objects contained in ops.

// Arguments:
//   transport - the transport on which to initiate the stream
//   stream    - the stream on which to send the operations. This must be
//               non-NULL and previously initialized by the same transport.
//   op        - a grpc_transport_stream_op_batch specifying the op to perform
//
void grpc_transport_perform_stream_op(grpc_transport* transport,
                                      grpc_stream* stream,
                                      grpc_transport_stream_op_batch* op);

void grpc_transport_perform_op(grpc_transport* transport,
                               grpc_transport_op* op);

// Send a ping on a transport

// Calls cb with user data when a response is received.
void grpc_transport_ping(grpc_transport* transport, grpc_closure* cb);

// Advise peer of pending connection termination.
void grpc_transport_goaway(grpc_transport* transport, grpc_status_code status,
                           grpc_slice debug_data);

// Destroy the transport
void grpc_transport_destroy(grpc_transport* transport);

// Get the endpoint used by \a transport
grpc_endpoint* grpc_transport_get_endpoint(grpc_transport* transport);

// Allocate a grpc_transport_op, and preconfigure the on_complete closure to
// \a on_complete and then delete the returned transport op
grpc_transport_op* grpc_make_transport_op(grpc_closure* on_complete);
// Allocate a grpc_transport_stream_op_batch, and preconfigure the on_complete
// closure
// to \a on_complete and then delete the returned transport op
grpc_transport_stream_op_batch* grpc_make_transport_stream_op(
    grpc_closure* on_complete);

namespace grpc_core {
// This is the key to be used for loading/storing keepalive_throttling in the
// absl::Status object.
constexpr const char* kKeepaliveThrottlingKey =
    "grpc.internal.keepalive_throttling";
}  // namespace grpc_core

#endif  // GRPC_SRC_CORE_LIB_TRANSPORT_TRANSPORT_H