transport.h

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/*
 *
 * 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_CORE_LIB_TRANSPORT_TRANSPORT_H
#define GRPC_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 "absl/status/status.h"
#include "absl/strings/string_view.h"
#include "absl/types/optional.h"
 
#include <grpc/impl/codegen/connectivity_state.h>
#include <grpc/slice.h>
#include <grpc/status.h>
#include <grpc/support/atm.h>
#include <grpc/support/log.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/iomgr/pollset.h"
#include "src/core/lib/promise/arena_promise.h"
#include "src/core/lib/promise/context.h"
#include "src/core/lib/promise/latch.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/transport/connectivity_state.h"
#include "src/core/lib/transport/metadata_batch.h"
#include "src/core/lib/transport/transport_fwd.h"
 
struct grpc_transport_stream_op_batch_payload;
 
/* 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"
 
#define GRPC_WRITE_INTERNAL_COMPRESS (0x80000000u)
 
#define GRPC_WRITE_INTERNAL_TEST_ONLY_WAS_COMPRESSED (0x40000000u)
 
#define GRPC_WRITE_INTERNAL_USED_MASK \
  (GRPC_WRITE_INTERNAL_COMPRESS | GRPC_WRITE_INTERNAL_TEST_ONLY_WAS_COMPRESSED)
 
namespace grpc_core {
// TODO(ctiller): eliminate once MetadataHandle is constructable directly.
namespace promise_filter_detail {
class BaseCallData;
}
 
// Small unowned "handle" type to ensure one accessor at a time to metadata.
// The focus here is to get promises to use the syntax we'd like - we'll
// probably substitute some other smart pointer later.
template <typename T>
class MetadataHandle {
 public:
  MetadataHandle() = default;
 
  MetadataHandle(const MetadataHandle&) = delete;
  MetadataHandle& operator=(const MetadataHandle&) = delete;
 
  MetadataHandle(MetadataHandle&& other) noexcept : handle_(other.handle_) {
    other.handle_ = nullptr;
  }
  MetadataHandle& operator=(MetadataHandle&& other) noexcept {
    handle_ = other.handle_;
    other.handle_ = nullptr;
    return *this;
  }
 
  explicit MetadataHandle(const absl::Status& status) {
    handle_ = GetContext<Arena>()->New<T>(GetContext<Arena>());
    handle_->Set(GrpcStatusMetadata(),
                 static_cast<grpc_status_code>(status.code()));
    if (status.ok()) return;
    handle_->Set(GrpcMessageMetadata(),
                 Slice::FromCopiedString(status.message()));
  }
 
  T* operator->() const { return handle_; }
  bool has_value() const { return handle_ != nullptr; }
  T* get() const { return handle_; }
 
  static MetadataHandle TestOnlyWrap(T* p) { return MetadataHandle(p); }
 
 private:
  friend class promise_filter_detail::BaseCallData;
 
  explicit MetadataHandle(T* handle) : handle_(handle) {}
  T* Unwrap() {
    T* result = handle_;
    handle_ = nullptr;
    return result;
  }
 
  T* handle_ = nullptr;
};
 
// Server metadata type
// TODO(ctiller): This should be a bespoke instance of MetadataMap<>
using ServerMetadata = grpc_metadata_batch;
using ServerMetadataHandle = MetadataHandle<ServerMetadata>;
 
// 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;
}
 
// Client initial metadata type
// TODO(ctiller): This should be a bespoke instance of MetadataMap<>
using ClientMetadata = grpc_metadata_batch;
using ClientMetadataHandle = MetadataHandle<ClientMetadata>;
 
// Server initial metadata type
// TODO(ctiller): This should be a bespoke instance of MetadataMap<>
using ServerMetadataHandle = MetadataHandle<grpc_metadata_batch>;
 
struct CallArgs {
  ClientMetadataHandle client_initial_metadata;
  Latch<ServerMetadata*>* server_initial_metadata;
};
 
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;
};
 
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) {}
 
  grpc_closure* on_complete = nullptr;
 
  grpc_transport_stream_op_batch_payload* payload = nullptr;
 
  bool send_initial_metadata : 1;
 
  bool send_trailing_metadata : 1;
 
  bool send_message : 1;
 
  bool recv_initial_metadata : 1;
 
  bool recv_message : 1;
 
  bool recv_trailing_metadata : 1;
 
  bool cancel_stream : 1;
 
  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;
    uint32_t send_initial_metadata_flags = 0;
    // If non-NULL, will be set by the transport to the peer string (a char*).
    // The transport retains ownership of the string.
    // Note: This pointer may be used by the transport after the
    // send_initial_metadata op is completed.  It must remain valid
    // until the call is destroyed.
    gpr_atm* peer_string = 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;
    // Flags are used only on the server side.  If non-null, will be set to
    // a bitfield of the GRPC_INITIAL_METADATA_xxx macros (e.g., to
    // indicate if the call is idempotent).
    uint32_t* recv_flags = nullptr;
    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;
    // If non-NULL, will be set by the transport to the peer string (a char*).
    // The transport retains ownership of the string.
    // Note: This pointer may be used by the transport after the
    // recv_initial_metadata op is completed.  It must remain valid
    // until the call is destroyed.
    gpr_atm* peer_string = 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;
    grpc_closure* recv_message_ready = nullptr;
  } recv_message;
 
  struct {
    grpc_metadata_batch* recv_trailing_metadata = nullptr;
    grpc_transport_stream_stats* collect_stats = nullptr;
    grpc_closure* recv_trailing_metadata_ready = nullptr;
  } recv_trailing_metadata;
 
  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 = GRPC_ERROR_NONE;
  } cancel_stream;
 
  /* Indexes correspond to grpc_context_index enum values */
  grpc_call_context_element* context;
};
 
typedef struct grpc_transport_op {
  grpc_closure* on_consumed = nullptr;
  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;
  grpc_error_handle disconnect_with_error = GRPC_ERROR_NONE;
  grpc_error_handle goaway_error = GRPC_ERROR_NONE;
  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;
  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;
  grpc_pollset* bind_pollset = nullptr;
  grpc_pollset_set* bind_pollset_set = nullptr;
  struct {
    grpc_closure* on_initiate = nullptr;
    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);
 
std::string grpc_transport_stream_op_batch_string(
    grpc_transport_stream_op_batch* op);
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_CORE_LIB_TRANSPORT_TRANSPORT_H */