src/core/transport/chttp2/internal.h

/*
 *
 * Copyright 2015, Google Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *     * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

#ifndef GRPC_INTERNAL_CORE_CHTTP2_INTERNAL_H
#define GRPC_INTERNAL_CORE_CHTTP2_INTERNAL_H

#include "src/core/iomgr/endpoint.h"
#include "src/core/transport/chttp2/frame.h"
#include "src/core/transport/chttp2/frame_data.h"
#include "src/core/transport/chttp2/frame_goaway.h"
#include "src/core/transport/chttp2/frame_ping.h"
#include "src/core/transport/chttp2/frame_rst_stream.h"
#include "src/core/transport/chttp2/frame_settings.h"
#include "src/core/transport/chttp2/frame_window_update.h"
#include "src/core/transport/chttp2/hpack_parser.h"
#include "src/core/transport/chttp2/incoming_metadata.h"
#include "src/core/transport/chttp2/stream_encoder.h"
#include "src/core/transport/chttp2/stream_map.h"
#include "src/core/transport/connectivity_state.h"
#include "src/core/transport/transport_impl.h"

typedef struct grpc_chttp2_transport grpc_chttp2_transport;
typedef struct grpc_chttp2_stream grpc_chttp2_stream;

/* streams are kept in various linked lists depending on what things need to
   happen to them... this enum labels each list */
typedef enum {
  GRPC_CHTTP2_LIST_ALL_STREAMS,
  GRPC_CHTTP2_LIST_READ_WRITE_STATE_CHANGED,
  GRPC_CHTTP2_LIST_WRITABLE,
  GRPC_CHTTP2_LIST_WRITING,
  GRPC_CHTTP2_LIST_WRITTEN,
  GRPC_CHTTP2_LIST_WRITABLE_WINDOW_UPDATE,
  GRPC_CHTTP2_LIST_PARSING_SEEN,
  GRPC_CHTTP2_LIST_CLOSED_WAITING_FOR_PARSING,
  GRPC_CHTTP2_LIST_INCOMING_WINDOW_UPDATED,
  /** streams that are waiting to start because there are too many concurrent
      streams on the connection */
  GRPC_CHTTP2_LIST_WAITING_FOR_CONCURRENCY,
  STREAM_LIST_COUNT /* must be last */
} grpc_chttp2_stream_list_id;

/* deframer state for the overall http2 stream of bytes */
typedef enum {
  /* prefix: one entry per http2 connection prefix byte */
  GRPC_DTS_CLIENT_PREFIX_0 = 0,
  GRPC_DTS_CLIENT_PREFIX_1,
  GRPC_DTS_CLIENT_PREFIX_2,
  GRPC_DTS_CLIENT_PREFIX_3,
  GRPC_DTS_CLIENT_PREFIX_4,
  GRPC_DTS_CLIENT_PREFIX_5,
  GRPC_DTS_CLIENT_PREFIX_6,
  GRPC_DTS_CLIENT_PREFIX_7,
  GRPC_DTS_CLIENT_PREFIX_8,
  GRPC_DTS_CLIENT_PREFIX_9,
  GRPC_DTS_CLIENT_PREFIX_10,
  GRPC_DTS_CLIENT_PREFIX_11,
  GRPC_DTS_CLIENT_PREFIX_12,
  GRPC_DTS_CLIENT_PREFIX_13,
  GRPC_DTS_CLIENT_PREFIX_14,
  GRPC_DTS_CLIENT_PREFIX_15,
  GRPC_DTS_CLIENT_PREFIX_16,
  GRPC_DTS_CLIENT_PREFIX_17,
  GRPC_DTS_CLIENT_PREFIX_18,
  GRPC_DTS_CLIENT_PREFIX_19,
  GRPC_DTS_CLIENT_PREFIX_20,
  GRPC_DTS_CLIENT_PREFIX_21,
  GRPC_DTS_CLIENT_PREFIX_22,
  GRPC_DTS_CLIENT_PREFIX_23,
  /* frame header byte 0... */
  /* must follow from the prefix states */
  GRPC_DTS_FH_0,
  GRPC_DTS_FH_1,
  GRPC_DTS_FH_2,
  GRPC_DTS_FH_3,
  GRPC_DTS_FH_4,
  GRPC_DTS_FH_5,
  GRPC_DTS_FH_6,
  GRPC_DTS_FH_7,
  /* ... frame header byte 8 */
  GRPC_DTS_FH_8,
  /* inside a http2 frame */
  GRPC_DTS_FRAME
} grpc_chttp2_deframe_transport_state;

typedef enum {
  GRPC_WRITE_STATE_OPEN,
  GRPC_WRITE_STATE_QUEUED_CLOSE,
  GRPC_WRITE_STATE_SENT_CLOSE
} grpc_chttp2_write_state;

typedef enum {
  GRPC_DONT_SEND_CLOSED = 0,
  GRPC_SEND_CLOSED,
  GRPC_SEND_CLOSED_WITH_RST_STREAM
} grpc_chttp2_send_closed;

typedef struct {
  grpc_chttp2_stream *head;
  grpc_chttp2_stream *tail;
} grpc_chttp2_stream_list;

typedef struct {
  grpc_chttp2_stream *next;
  grpc_chttp2_stream *prev;
} grpc_chttp2_stream_link;

/* We keep several sets of connection wide parameters */
typedef enum {
  /* The settings our peer has asked for (and we have acked) */
  GRPC_PEER_SETTINGS = 0,
  /* The settings we'd like to have */
  GRPC_LOCAL_SETTINGS,
  /* The settings we've published to our peer */
  GRPC_SENT_SETTINGS,
  /* The settings the peer has acked */
  GRPC_ACKED_SETTINGS,
  GRPC_NUM_SETTING_SETS
} grpc_chttp2_setting_set;

/* Outstanding ping request data */
typedef struct grpc_chttp2_outstanding_ping {
  gpr_uint8 id[8];
  grpc_iomgr_closure *on_recv;
  struct grpc_chttp2_outstanding_ping *next;
  struct grpc_chttp2_outstanding_ping *prev;
} grpc_chttp2_outstanding_ping;

typedef struct {
  /** data to write next write */
  gpr_slice_buffer qbuf;
  /** queued callbacks */
  grpc_iomgr_closure *pending_closures;

  /** window available for us to send to peer */
  gpr_uint32 outgoing_window;
  /** window available for peer to send to us - updated after parse */
  gpr_uint32 incoming_window;
  /** how much window would we like to have for incoming_window */
  gpr_uint32 connection_window_target;

  /** have we seen a goaway */
  gpr_uint8 seen_goaway;

  /** is this transport a client? */
  gpr_uint8 is_client;
  /** are the local settings dirty and need to be sent? */
  gpr_uint8 dirtied_local_settings;
  /** have local settings been sent? */
  gpr_uint8 sent_local_settings;
  /** bitmask of setting indexes to send out */
  gpr_uint32 force_send_settings;
  /** settings values */
  gpr_uint32 settings[GRPC_NUM_SETTING_SETS][GRPC_CHTTP2_NUM_SETTINGS];

  /** what is the next stream id to be allocated by this peer?
      copied to next_stream_id in parsing when parsing commences */
  gpr_uint32 next_stream_id;

  /** last received stream id */
  gpr_uint32 last_incoming_stream_id;

  /** pings awaiting responses */
  grpc_chttp2_outstanding_ping pings;
  /** next payload for an outgoing ping */
  gpr_uint64 ping_counter;

  /** concurrent stream count: updated when not parsing,
      so this is a strict over-estimation on the client */
  gpr_uint32 concurrent_stream_count;
} grpc_chttp2_transport_global;

typedef struct {
  /** data to write now */
  gpr_slice_buffer outbuf;
  /** hpack encoding */
  grpc_chttp2_hpack_compressor hpack_compressor;
  /** is this a client? */
  gpr_uint8 is_client;
} grpc_chttp2_transport_writing;

struct grpc_chttp2_transport_parsing {
  /** is this transport a client? (boolean) */
  gpr_uint8 is_client;

  /** were settings updated? */
  gpr_uint8 settings_updated;
  /** was a settings ack received? */
  gpr_uint8 settings_ack_received;
  /** was a goaway frame received? */
  gpr_uint8 goaway_received;

  /** initial window change */
  gpr_int64 initial_window_update;

  /** data to write later - after parsing */
  gpr_slice_buffer qbuf;
  /* metadata object cache */
  grpc_mdstr *str_grpc_timeout;
  /** parser for headers */
  grpc_chttp2_hpack_parser hpack_parser;
  /** simple one shot parsers */
  union {
    grpc_chttp2_window_update_parser window_update;
    grpc_chttp2_settings_parser settings;
    grpc_chttp2_ping_parser ping;
    grpc_chttp2_rst_stream_parser rst_stream;
  } simple;
  /** parser for goaway frames */
  grpc_chttp2_goaway_parser goaway_parser;

  /** window available for peer to send to us */
  gpr_uint32 incoming_window;
  gpr_uint32 incoming_window_delta;

  /** next stream id available at the time of beginning parsing */
  gpr_uint32 next_stream_id;
  gpr_uint32 last_incoming_stream_id;

  /* deframing */
  grpc_chttp2_deframe_transport_state deframe_state;
  gpr_uint8 incoming_frame_type;
  gpr_uint8 incoming_frame_flags;
  gpr_uint8 header_eof;
  gpr_uint32 expect_continuation_stream_id;
  gpr_uint32 incoming_frame_size;
  gpr_uint32 incoming_stream_id;

  /* active parser */
  void *parser_data;
  grpc_chttp2_stream_parsing *incoming_stream;
  grpc_chttp2_parse_error (*parser)(
      void *parser_user_data, grpc_chttp2_transport_parsing *transport_parsing,
      grpc_chttp2_stream_parsing *stream_parsing, gpr_slice slice, int is_last);

  /* received settings */
  gpr_uint32 settings[GRPC_CHTTP2_NUM_SETTINGS];

  /* goaway data */
  grpc_status_code goaway_error;
  gpr_uint32 goaway_last_stream_index;
  gpr_slice goaway_text;

  gpr_uint64 outgoing_window_update;

  /** pings awaiting responses */
  grpc_chttp2_outstanding_ping pings;
};

struct grpc_chttp2_transport {
  grpc_transport base; /* must be first */
  grpc_endpoint *ep;
  grpc_mdctx *metadata_context;
  gpr_refcount refs;

  gpr_mu mu;

  /** is the transport destroying itself? */
  gpr_uint8 destroying;
  /** has the upper layer closed the transport? */
  gpr_uint8 closed;

  /** is a thread currently writing */
  gpr_uint8 writing_active;
  /** is a thread currently parsing */
  gpr_uint8 parsing_active;

  /** is there a read request to the endpoint outstanding? */
  gpr_uint8 endpoint_reading;

  /** various lists of streams */
  grpc_chttp2_stream_list lists[STREAM_LIST_COUNT];

  /** global state for reading/writing */
  grpc_chttp2_transport_global global;
  /** state only accessible by the chain of execution that
      set writing_active=1 */
  grpc_chttp2_transport_writing writing;
  /** state only accessible by the chain of execution that
      set parsing_active=1 */
  grpc_chttp2_transport_parsing parsing;

  /** maps stream id to grpc_chttp2_stream objects;
      owned by the parsing thread when parsing */
  grpc_chttp2_stream_map parsing_stream_map;

  /** streams created by the client (possibly during parsing);
      merged with parsing_stream_map during unlock when no
      parsing is occurring */
  grpc_chttp2_stream_map new_stream_map;

  /** closure to execute writing */
  grpc_iomgr_closure writing_action;
  /** closure to start reading from the endpoint */
  grpc_iomgr_closure reading_action;

  /** address to place a newly accepted stream - set and unset by
      grpc_chttp2_parsing_accept_stream; used by init_stream to
      publish the accepted server stream */
  grpc_chttp2_stream **accepting_stream;

  struct {
    /* accept stream callback */
    void (*accept_stream)(void *user_data, grpc_transport *transport,
                          const void *server_data);
    void *accept_stream_user_data;

    /** connectivity tracking */
    grpc_connectivity_state_tracker state_tracker;
  } channel_callback;
};

typedef struct {
  /** HTTP2 stream id for this stream, or zero if one has not been assigned */
  gpr_uint32 id;

  grpc_iomgr_closure *send_done_closure;
  grpc_iomgr_closure *recv_done_closure;

  /** window available for us to send to peer */
  gpr_int64 outgoing_window;
  /** window available for peer to send to us - updated after parse */
  gpr_uint32 incoming_window;
  /** stream ops the transport user would like to send */
  grpc_stream_op_buffer *outgoing_sopb;
  /** when the application requests writes be closed, the write_closed is
      'queued'; when the close is flow controlled into the send path, we are
      'sending' it; when the write has been performed it is 'sent' */
  grpc_chttp2_write_state write_state;
  /** is this stream closed (boolean) */
  gpr_uint8 read_closed;
  /** has this stream been cancelled? (boolean) */
  gpr_uint8 cancelled;
  grpc_status_code cancelled_status;
  /** have we told the upper layer that this stream is cancelled? */
  gpr_uint8 published_cancelled;
  /** is this stream in the stream map? (boolean) */
  gpr_uint8 in_stream_map;

  /** stream state already published to the upper layer */
  grpc_stream_state published_state;
  /** address to publish next stream state to */
  grpc_stream_state *publish_state;
  /** pointer to sop buffer to fill in with new stream ops */
  grpc_stream_op_buffer *publish_sopb;
  grpc_stream_op_buffer incoming_sopb;

  /** incoming metadata */
  grpc_chttp2_incoming_metadata_buffer incoming_metadata;
  grpc_chttp2_incoming_metadata_live_op_buffer outstanding_metadata;
} grpc_chttp2_stream_global;

typedef struct {
  /** HTTP2 stream id for this stream, or zero if one has not been assigned */
  gpr_uint32 id;
  /** sops that have passed flow control to be written */
  grpc_stream_op_buffer sopb;
  /** how strongly should we indicate closure with the next write */
  grpc_chttp2_send_closed send_closed;
} grpc_chttp2_stream_writing;

struct grpc_chttp2_stream_parsing {
  /** HTTP2 stream id for this stream, or zero if one has not been assigned */
  gpr_uint32 id;
  /** has this stream received a close */
  gpr_uint8 received_close;
  /** saw a rst_stream */
  gpr_uint8 saw_rst_stream;
  /** incoming_window has been reduced by this much during parsing */
  gpr_uint32 incoming_window_delta;
  /** window available for peer to send to us */
  gpr_uint32 incoming_window;
  /** parsing state for data frames */
  grpc_chttp2_data_parser data_parser;
  /** reason give to rst_stream */
  gpr_uint32 rst_stream_reason;
  /* amount of window given */
  gpr_uint64 outgoing_window_update;

  /** incoming metadata */
  grpc_chttp2_incoming_metadata_buffer incoming_metadata;
};

struct grpc_chttp2_stream {
  grpc_chttp2_stream_global global;
  grpc_chttp2_stream_writing writing;
  grpc_chttp2_stream_parsing parsing;

  grpc_chttp2_stream_link links[STREAM_LIST_COUNT];
  gpr_uint8 included[STREAM_LIST_COUNT];
};

/** Transport writing call flow:
    chttp2_transport.c calls grpc_chttp2_unlocking_check_writes to see if writes
   are required;
    if they are, chttp2_transport.c calls grpc_chttp2_perform_writes to do the
   writes.
    Once writes have been completed (meaning another write could potentially be
   started),
    grpc_chttp2_terminate_writing is called. This will call
   grpc_chttp2_cleanup_writing, at which
    point the write phase is complete. */

/** Someone is unlocking the transport mutex: check to see if writes
    are required, and schedule them if so */
int grpc_chttp2_unlocking_check_writes(grpc_chttp2_transport_global *global,
                                       grpc_chttp2_transport_writing *writing);
void grpc_chttp2_perform_writes(
    grpc_chttp2_transport_writing *transport_writing, grpc_endpoint *endpoint);
void grpc_chttp2_terminate_writing(
    grpc_chttp2_transport_writing *transport_writing, int success);
void grpc_chttp2_cleanup_writing(grpc_chttp2_transport_global *global,
                                 grpc_chttp2_transport_writing *writing);

void grpc_chttp2_prepare_to_read(grpc_chttp2_transport_global *global,
                                 grpc_chttp2_transport_parsing *parsing);
/** Process one slice of incoming data; return 1 if the connection is still
    viable after reading, or 0 if the connection should be torn down */
int grpc_chttp2_perform_read(grpc_chttp2_transport_parsing *transport_parsing,
                             gpr_slice slice);
void grpc_chttp2_publish_reads(grpc_chttp2_transport_global *global,
                               grpc_chttp2_transport_parsing *parsing);

/** Get a writable stream
    returns non-zero if there was a stream available */
void grpc_chttp2_list_add_writable_stream(
    grpc_chttp2_transport_global *transport_global,
    grpc_chttp2_stream_global *stream_global);
int grpc_chttp2_list_pop_writable_stream(
    grpc_chttp2_transport_global *transport_global,
    grpc_chttp2_transport_writing *transport_writing,
    grpc_chttp2_stream_global **stream_global,
    grpc_chttp2_stream_writing **stream_writing);

void grpc_chttp2_list_add_incoming_window_updated(
    grpc_chttp2_transport_global *transport_global,
    grpc_chttp2_stream_global *stream_global);
int grpc_chttp2_list_pop_incoming_window_updated(
    grpc_chttp2_transport_global *transport_global,
    grpc_chttp2_transport_parsing *transport_parsing,
    grpc_chttp2_stream_global **stream_global,
    grpc_chttp2_stream_parsing **stream_parsing);
void grpc_chttp2_list_remove_incoming_window_updated(
    grpc_chttp2_transport_global *transport_global,
    grpc_chttp2_stream_global *stream_global);

void grpc_chttp2_list_add_writing_stream(
    grpc_chttp2_transport_writing *transport_writing,
    grpc_chttp2_stream_writing *stream_writing);
int grpc_chttp2_list_have_writing_streams(
    grpc_chttp2_transport_writing *transport_writing);
int grpc_chttp2_list_pop_writing_stream(
    grpc_chttp2_transport_writing *transport_writing,
    grpc_chttp2_stream_writing **stream_writing);

void grpc_chttp2_list_add_written_stream(
    grpc_chttp2_transport_writing *transport_writing,
    grpc_chttp2_stream_writing *stream_writing);
int grpc_chttp2_list_pop_written_stream(
    grpc_chttp2_transport_global *transport_global,
    grpc_chttp2_transport_writing *transport_writing,
    grpc_chttp2_stream_global **stream_global,
    grpc_chttp2_stream_writing **stream_writing);

void grpc_chttp2_list_add_writable_window_update_stream(
    grpc_chttp2_transport_global *transport_global,
    grpc_chttp2_stream_global *stream_global);
int grpc_chttp2_list_pop_writable_window_update_stream(
    grpc_chttp2_transport_global *transport_global,
    grpc_chttp2_stream_global **stream_global);
void grpc_chttp2_list_remove_writable_window_update_stream(
    grpc_chttp2_transport_global *transport_global,
    grpc_chttp2_stream_global *stream_global);

void grpc_chttp2_list_add_parsing_seen_stream(
    grpc_chttp2_transport_parsing *transport_parsing,
    grpc_chttp2_stream_parsing *stream_parsing);
int grpc_chttp2_list_pop_parsing_seen_stream(
    grpc_chttp2_transport_global *transport_global,
    grpc_chttp2_transport_parsing *transport_parsing,
    grpc_chttp2_stream_global **stream_global,
    grpc_chttp2_stream_parsing **stream_parsing);

void grpc_chttp2_list_add_waiting_for_concurrency(
    grpc_chttp2_transport_global *transport_global,
    grpc_chttp2_stream_global *stream_global);
int grpc_chttp2_list_pop_waiting_for_concurrency(
    grpc_chttp2_transport_global *transport_global,
    grpc_chttp2_stream_global **stream_global);

void grpc_chttp2_list_add_closed_waiting_for_parsing(
    grpc_chttp2_transport_global *transport_global,
    grpc_chttp2_stream_global *stream_global);
int grpc_chttp2_list_pop_closed_waiting_for_parsing(
    grpc_chttp2_transport_global *transport_global,
    grpc_chttp2_stream_global **stream_global);

void grpc_chttp2_list_add_read_write_state_changed(
    grpc_chttp2_transport_global *transport_global,
    grpc_chttp2_stream_global *stream_global);
int grpc_chttp2_list_pop_read_write_state_changed(
    grpc_chttp2_transport_global *transport_global,
    grpc_chttp2_stream_global **stream_global);

/** schedule a closure to run without the transport lock taken */
void grpc_chttp2_schedule_closure(
    grpc_chttp2_transport_global *transport_global, grpc_iomgr_closure *closure,
    int success);

grpc_chttp2_stream_parsing *grpc_chttp2_parsing_lookup_stream(
    grpc_chttp2_transport_parsing *transport_parsing, gpr_uint32 id);
grpc_chttp2_stream_parsing *grpc_chttp2_parsing_accept_stream(
    grpc_chttp2_transport_parsing *transport_parsing, gpr_uint32 id);

void grpc_chttp2_add_incoming_goaway(
    grpc_chttp2_transport_global *transport_global, gpr_uint32 goaway_error,
    gpr_slice goaway_text);

void grpc_chttp2_register_stream(grpc_chttp2_transport *t,
                                 grpc_chttp2_stream *s);
void grpc_chttp2_unregister_stream(grpc_chttp2_transport *t,
                                   grpc_chttp2_stream *s);
void grpc_chttp2_for_all_streams(
    grpc_chttp2_transport_global *transport_global, void *user_data,
    void (*cb)(grpc_chttp2_transport_global *transport_global, void *user_data,
               grpc_chttp2_stream_global *stream_global));

void grpc_chttp2_parsing_become_skip_parser(
    grpc_chttp2_transport_parsing *transport_parsing);

#define GRPC_CHTTP2_CLIENT_CONNECT_STRING "PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n"
#define GRPC_CHTTP2_CLIENT_CONNECT_STRLEN \
  (sizeof(GRPC_CHTTP2_CLIENT_CONNECT_STRING) - 1)

extern int grpc_http_trace;
extern int grpc_flowctl_trace;

#define GRPC_CHTTP2_IF_TRACING(stmt) \
  if (!(grpc_http_trace))            \
    ;                                \
  else                               \
  stmt

#define GRPC_CHTTP2_FLOWCTL_TRACE_STREAM(reason, transport, context, var,      \
                                         delta)                                \
  if (!(grpc_flowctl_trace)) {                                                 \
  } else {                                                                     \
    grpc_chttp2_flowctl_trace(__FILE__, __LINE__, reason, #context, #var,      \
                              transport->is_client, context->id, context->var, \
                              delta);                                          \
  }

#define GRPC_CHTTP2_FLOWCTL_TRACE_TRANSPORT(reason, context, var, delta)   \
  if (!(grpc_flowctl_trace)) {                                             \
  } else {                                                                 \
    grpc_chttp2_flowctl_trace(__FILE__, __LINE__, reason, #context, #var,  \
                              context->is_client, 0, context->var, delta); \
  }

void grpc_chttp2_flowctl_trace(const char *file, int line, const char *reason,
                               const char *context, const char *var,
                               int is_client, gpr_uint32 stream_id,
                               gpr_int64 current_value, gpr_int64 delta);

#endif