text: /***************************************************************************
   *                                  _   _ ____  _
   *  Project                     ___| | | |  _ \| |
   *                             / __| | | | |_) | |
   *                            | (__| |_| |  _ <| |___
   *                             \___|\___/|_| \_\_____|
   *
   * Copyright (C) 1998 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
   *
   * This software is licensed as described in the file COPYING, which
   * you should have received as part of this distribution. The terms
   * are also available at https://curl.haxx.se/docs/copyright.html.
   *
   * You may opt to use, copy, modify, merge, publish, distribute and/or sell
   * copies of the Software, and permit persons to whom the Software is
   * furnished to do so, under the terms of the COPYING file.
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
   * KIND, either express or implied.
   *
   ***************************************************************************/
  
  #include "curl_setup.h"
  
  #ifdef USE_NGHTTP2
  #include <nghttp2/nghttp2.h>
  #include "urldata.h"
  #include "http2.h"
  #include "http.h"
  #include "sendf.h"
  #include "select.h"
  #include "curl_base64.h"
  #include "strcase.h"
  #include "multiif.h"
  #include "url.h"
  #include "connect.h"
  #include "strtoofft.h"
  #include "strdup.h"
  /* The last 3 #include files should be in this order */
  #include "curl_printf.h"
  #include "curl_memory.h"
  #include "memdebug.h"
  
  #define H2_BUFSIZE 32768
  
  #if (NGHTTP2_VERSION_NUM < 0x010000)
  #error too old nghttp2 version, upgrade!
  #endif
  
  #if (NGHTTP2_VERSION_NUM > 0x010800)
  #define NGHTTP2_HAS_HTTP2_STRERROR 1
  #endif
  
  #if (NGHTTP2_VERSION_NUM >= 0x010900)
  /* nghttp2_session_callbacks_set_error_callback is present in nghttp2 1.9.0 or
     later */
  #define NGHTTP2_HAS_ERROR_CALLBACK 1
  #else
  #define nghttp2_session_callbacks_set_error_callback(x,y)
  #endif
  
  #if (NGHTTP2_VERSION_NUM >= 0x010c00)
  #define NGHTTP2_HAS_SET_LOCAL_WINDOW_SIZE 1
  #endif
  
  #define HTTP2_HUGE_WINDOW_SIZE (1 << 30)
  
  #ifdef DEBUG_HTTP2
  #define H2BUGF(x) x
  #else
  #define H2BUGF(x) do { } while(0)
  #endif
  
  
  static ssize_t http2_recv(struct connectdata *conn, int sockindex,
                            char *mem, size_t len, CURLcode *err);
  static bool http2_connisdead(struct connectdata *conn);
  static int h2_session_send(struct Curl_easy *data,
                             nghttp2_session *h2);
  static int h2_process_pending_input(struct connectdata *conn,
                                      struct http_conn *httpc,
                                      CURLcode *err);
  
  /*
   * Curl_http2_init_state() is called when the easy handle is created and
   * allows for HTTP/2 specific init of state.
   */
  void Curl_http2_init_state(struct UrlState *state)
  {
    state->stream_weight = NGHTTP2_DEFAULT_WEIGHT;
  }
  
  /*
   * Curl_http2_init_userset() is called when the easy handle is created and
   * allows for HTTP/2 specific user-set fields.
   */
  void Curl_http2_init_userset(struct UserDefined *set)
  {
    set->stream_weight = NGHTTP2_DEFAULT_WEIGHT;
  }
  
  static int http2_perform_getsock(const struct connectdata *conn,
                                   curl_socket_t *sock)
  {
    const struct http_conn *c = &conn->proto.httpc;
    struct SingleRequest *k = &conn->data->req;
    int bitmap = GETSOCK_BLANK;
  
    sock[0] = conn->sock[FIRSTSOCKET];
  
    /* in a HTTP/2 connection we can basically always get a frame so we should
       always be ready for one */
    bitmap |= GETSOCK_READSOCK(FIRSTSOCKET);
  
    /* we're still uploading or the HTTP/2 layer wants to send data */
    if(((k->keepon & (KEEP_SEND|KEEP_SEND_PAUSE)) == KEEP_SEND) ||
       nghttp2_session_want_write(c->h2))
      bitmap |= GETSOCK_WRITESOCK(FIRSTSOCKET);
  
    return bitmap;
  }
  
  static int http2_getsock(struct connectdata *conn,
                           curl_socket_t *socks)
  {
    return http2_perform_getsock(conn, socks);
  }
  
  /*
   * http2_stream_free() free HTTP2 stream related data
   */
  static void http2_stream_free(struct HTTP *http)
  {
    if(http) {
      Curl_add_buffer_free(&http->header_recvbuf);
      Curl_add_buffer_free(&http->trailer_recvbuf);
      for(; http->push_headers_used > 0; --http->push_headers_used) {
        free(http->push_headers[http->push_headers_used - 1]);
      }
      free(http->push_headers);
      http->push_headers = NULL;
    }
  }
  
  /*
   * Disconnects *a* connection used for HTTP/2. It might be an old one from the
   * connection cache and not the "main" one. Don't touch the easy handle!
   */
  
  static CURLcode http2_disconnect(struct connectdata *conn,
                                   bool dead_connection)
  {
    struct http_conn *c = &conn->proto.httpc;
    (void)dead_connection;
  
    H2BUGF(infof(conn->data, "HTTP/2 DISCONNECT starts now\n"));
  
    nghttp2_session_del(c->h2);
    Curl_safefree(c->inbuf);
  
    H2BUGF(infof(conn->data, "HTTP/2 DISCONNECT done\n"));
  
    return CURLE_OK;
  }
  
  /*
   * The server may send us data at any point (e.g. PING frames). Therefore,
   * we cannot assume that an HTTP/2 socket is dead just because it is readable.
   *
   * Instead, if it is readable, run Curl_connalive() to peek at the socket
   * and distinguish between closed and data.
   */
  static bool http2_connisdead(struct connectdata *conn)
  {
    int sval;
    bool dead = TRUE;
  
    if(conn->bits.close)
      return TRUE;
  
    sval = SOCKET_READABLE(conn->sock[FIRSTSOCKET], 0);
    if(sval == 0) {
      /* timeout */
      dead = FALSE;
    }
    else if(sval & CURL_CSELECT_ERR) {
      /* socket is in an error state */
      dead = TRUE;
    }
    else if(sval & CURL_CSELECT_IN) {
      /* readable with no error. could still be closed */
      dead = !Curl_connalive(conn);
      if(!dead) {
        /* This happens before we've sent off a request and the connection is
           not in use by any other transfer, there shouldn't be any data here,
           only "protocol frames" */
        CURLcode result;
        struct http_conn *httpc = &conn->proto.httpc;
        ssize_t nread = -1;
        if(httpc->recv_underlying)
          /* if called "too early", this pointer isn't setup yet! */
          nread = ((Curl_recv *)httpc->recv_underlying)(
            conn, FIRSTSOCKET, httpc->inbuf, H2_BUFSIZE, &result);
        if(nread != -1) {
          infof(conn->data,
                "%d bytes stray data read before trying h2 connection\n",
                (int)nread);
          httpc->nread_inbuf = 0;
          httpc->inbuflen = nread;
          (void)h2_process_pending_input(conn, httpc, &result);
        }
        else
          /* the read failed so let's say this is dead anyway */
          dead = TRUE;
      }
    }
  
    return dead;
  }
  
  static unsigned int http2_conncheck(struct connectdata *check,
                                      unsigned int checks_to_perform)
  {
    unsigned int ret_val = CONNRESULT_NONE;
    struct http_conn *c = &check->proto.httpc;
    int rc;
    bool send_frames = false;
  
    if(checks_to_perform & CONNCHECK_ISDEAD) {
      if(http2_connisdead(check))
        ret_val |= CONNRESULT_DEAD;
    }
  
    if(checks_to_perform & CONNCHECK_KEEPALIVE) {
      struct curltime now = Curl_now();
      timediff_t elapsed = Curl_timediff(now, check->keepalive);
  
      if(elapsed > check->upkeep_interval_ms) {
        /* Perform an HTTP/2 PING */
        rc = nghttp2_submit_ping(c->h2, 0, ZERO_NULL);
        if(!rc) {
          /* Successfully added a PING frame to the session. Need to flag this
             so the frame is sent. */
          send_frames = true;
        }
        else {
         failf(check->data, "nghttp2_submit_ping() failed: %s(%d)",
               nghttp2_strerror(rc), rc);
        }
  
        check->keepalive = now;
      }
    }
  
    if(send_frames) {
      rc = nghttp2_session_send(c->h2);
      if(rc)
        failf(check->data, "nghttp2_session_send() failed: %s(%d)",
              nghttp2_strerror(rc), rc);
    }
  
    return ret_val;
  }
  
  /* called from http_setup_conn */
  void Curl_http2_setup_req(struct Curl_easy *data)
  {
    struct HTTP *http = data->req.protop;
  
    http->nread_header_recvbuf = 0;
    http->bodystarted = FALSE;
    http->status_code = -1;
    http->pausedata = NULL;
    http->pauselen = 0;
    http->closed = FALSE;
    http->close_handled = FALSE;
    http->mem = data->state.buffer;
    http->len = data->set.buffer_size;
    http->memlen = 0;
  }
  
  /* called from http_setup_conn */
  void Curl_http2_setup_conn(struct connectdata *conn)
  {
    conn->proto.httpc.settings.max_concurrent_streams =
      DEFAULT_MAX_CONCURRENT_STREAMS;
    conn->proto.httpc.error_code = NGHTTP2_NO_ERROR;
  }
  
  /*
   * HTTP2 handler interface. This isn't added to the general list of protocols
   * but will be used at run-time when the protocol is dynamically switched from
   * HTTP to HTTP2.
   */
  static const struct Curl_handler Curl_handler_http2 = {
    "HTTP",                               /* scheme */
    ZERO_NULL,                            /* setup_connection */
    Curl_http,                            /* do_it */
    Curl_http_done,                       /* done */
    ZERO_NULL,                            /* do_more */
    ZERO_NULL,                            /* connect_it */
    ZERO_NULL,                            /* connecting */
    ZERO_NULL,                            /* doing */
    http2_getsock,                        /* proto_getsock */
    http2_getsock,                        /* doing_getsock */
    ZERO_NULL,                            /* domore_getsock */
    http2_perform_getsock,                /* perform_getsock */
    http2_disconnect,                     /* disconnect */
    ZERO_NULL,                            /* readwrite */
    http2_conncheck,                      /* connection_check */
    PORT_HTTP,                            /* defport */
    CURLPROTO_HTTP,                       /* protocol */
    PROTOPT_STREAM                        /* flags */
  };
  
  static const struct Curl_handler Curl_handler_http2_ssl = {
    "HTTPS",                              /* scheme */
    ZERO_NULL,                            /* setup_connection */
    Curl_http,                            /* do_it */
    Curl_http_done,                       /* done */
    ZERO_NULL,                            /* do_more */
    ZERO_NULL,                            /* connect_it */
    ZERO_NULL,                            /* connecting */
    ZERO_NULL,                            /* doing */
    http2_getsock,                        /* proto_getsock */
    http2_getsock,                        /* doing_getsock */
    ZERO_NULL,                            /* domore_getsock */
    http2_perform_getsock,                /* perform_getsock */
    http2_disconnect,                     /* disconnect */
    ZERO_NULL,                            /* readwrite */
    http2_conncheck,                      /* connection_check */
    PORT_HTTP,                            /* defport */
    CURLPROTO_HTTPS,                      /* protocol */
    PROTOPT_SSL | PROTOPT_STREAM          /* flags */
  };
  
  /*
   * Store nghttp2 version info in this buffer, Prefix with a space.  Return
   * total length written.
   */
  int Curl_http2_ver(char *p, size_t len)
  {
    nghttp2_info *h2 = nghttp2_version(0);
    return msnprintf(p, len, " nghttp2/%s", h2->version_str);
  }
  
  /* HTTP/2 error code to name based on the Error Code Registry.
  https://tools.ietf.org/html/rfc7540#page-77
  nghttp2_error_code enums are identical.
  */
  static const char *http2_strerror(uint32_t err)
  {
  #ifndef NGHTTP2_HAS_HTTP2_STRERROR
    const char *str[] = {
      "NO_ERROR",             /* 0x0 */
      "PROTOCOL_ERROR",       /* 0x1 */
      "INTERNAL_ERROR",       /* 0x2 */
      "FLOW_CONTROL_ERROR",   /* 0x3 */
      "SETTINGS_TIMEOUT",     /* 0x4 */
      "STREAM_CLOSED",        /* 0x5 */
      "FRAME_SIZE_ERROR",     /* 0x6 */
      "REFUSED_STREAM",       /* 0x7 */
      "CANCEL",               /* 0x8 */
      "COMPRESSION_ERROR",    /* 0x9 */
      "CONNECT_ERROR",        /* 0xA */
      "ENHANCE_YOUR_CALM",    /* 0xB */
      "INADEQUATE_SECURITY",  /* 0xC */
      "HTTP_1_1_REQUIRED"     /* 0xD */
    };
    return (err < sizeof(str) / sizeof(str[0])) ? str[err] : "unknown";
  #else
    return nghttp2_http2_strerror(err);
  #endif
  }
  
  /*
   * The implementation of nghttp2_send_callback type. Here we write |data| with
   * size |length| to the network and return the number of bytes actually
   * written. See the documentation of nghttp2_send_callback for the details.
   */
  static ssize_t send_callback(nghttp2_session *h2,
                               const uint8_t *data, size_t length, int flags,
                               void *userp)
  {
    struct connectdata *conn = (struct connectdata *)userp;
    struct http_conn *c = &conn->proto.httpc;
    ssize_t written;
    CURLcode result = CURLE_OK;
  
    (void)h2;
    (void)flags;
  
    if(!c->send_underlying)
      /* called before setup properly! */
      return NGHTTP2_ERR_CALLBACK_FAILURE;
  
    written = ((Curl_send*)c->send_underlying)(conn, FIRSTSOCKET,
                                               data, length, &result);
  
    if(result == CURLE_AGAIN) {
      return NGHTTP2_ERR_WOULDBLOCK;
    }
  
    if(written == -1) {
      failf(conn->data, "Failed sending HTTP2 data");
      return NGHTTP2_ERR_CALLBACK_FAILURE;
    }
  
    if(!written)
      return NGHTTP2_ERR_WOULDBLOCK;
  
    return written;
  }
  
  
  /* We pass a pointer to this struct in the push callback, but the contents of
     the struct are hidden from the user. */
  struct curl_pushheaders {
    struct Curl_easy *data;
    const nghttp2_push_promise *frame;
  };
  
  /*
   * push header access function. Only to be used from within the push callback
   */
  char *curl_pushheader_bynum(struct curl_pushheaders *h, size_t num)
  {
    /* Verify that we got a good easy handle in the push header struct, mostly to
       detect rubbish input fast(er). */
    if(!h || !GOOD_EASY_HANDLE(h->data))
      return NULL;
    else {
      struct HTTP *stream = h->data->req.protop;
      if(num < stream->push_headers_used)
        return stream->push_headers[num];
    }
    return NULL;
  }
  
  /*
   * push header access function. Only to be used from within the push callback
   */
  char *curl_pushheader_byname(struct curl_pushheaders *h, const char *header)
  {
    /* Verify that we got a good easy handle in the push header struct,
       mostly to detect rubbish input fast(er). Also empty header name
       is just a rubbish too. We have to allow ":" at the beginning of
       the header, but header == ":" must be rejected. If we have ':' in
       the middle of header, it could be matched in middle of the value,
       this is because we do prefix match.*/
    if(!h || !GOOD_EASY_HANDLE(h->data) || !header || !header[0] ||
       !strcmp(header, ":") || strchr(header + 1, ':'))
      return NULL;
    else {
      struct HTTP *stream = h->data->req.protop;
      size_t len = strlen(header);
      size_t i;
      for(i = 0; i<stream->push_headers_used; i++) {
        if(!strncmp(header, stream->push_headers[i], len)) {
          /* sub-match, make sure that it is followed by a colon */
          if(stream->push_headers[i][len] != ':')
            continue;
          return &stream->push_headers[i][len + 1];
        }
      }
    }
    return NULL;
  }
  
  /*
   * This specific transfer on this connection has been "drained".
   */
  static void drained_transfer(struct Curl_easy *data,
                               struct http_conn *httpc)
  {
    DEBUGASSERT(httpc->drain_total >= data->state.drain);
    httpc->drain_total -= data->state.drain;
    data->state.drain = 0;
  }
  
  /*
   * Mark this transfer to get "drained".
   */
  static void drain_this(struct Curl_easy *data,
                         struct http_conn *httpc)
  {
    data->state.drain++;
    httpc->drain_total++;
    DEBUGASSERT(httpc->drain_total >= data->state.drain);
  }
  
  static struct Curl_easy *duphandle(struct Curl_easy *data)
  {
    struct Curl_easy *second = curl_easy_duphandle(data);
    if(second) {
      /* setup the request struct */
      struct HTTP *http = calloc(1, sizeof(struct HTTP));
      if(!http) {
        (void)Curl_close(&second);
      }
      else {
        second->req.protop = http;
        http->header_recvbuf = Curl_add_buffer_init();
        if(!http->header_recvbuf) {
          free(http);
          (void)Curl_close(&second);
        }
        else {
          Curl_http2_setup_req(second);
          second->state.stream_weight = data->state.stream_weight;
        }
      }
    }
    return second;
  }
  
  
  static int push_promise(struct Curl_easy *data,
                          struct connectdata *conn,
                          const nghttp2_push_promise *frame)
  {
    int rv;
    H2BUGF(infof(data, "PUSH_PROMISE received, stream %u!\n",
                 frame->promised_stream_id));
    if(data->multi->push_cb) {
      struct HTTP *stream;
      struct HTTP *newstream;
      struct curl_pushheaders heads;
      CURLMcode rc;
      struct http_conn *httpc;
      size_t i;
      /* clone the parent */
      struct Curl_easy *newhandle = duphandle(data);
      if(!newhandle) {
        infof(data, "failed to duplicate handle\n");
        rv = 1; /* FAIL HARD */
        goto fail;
      }
  
      heads.data = data;
      heads.frame = frame;
      /* ask the application */
      H2BUGF(infof(data, "Got PUSH_PROMISE, ask application!\n"));
  
      stream = data->req.protop;
      if(!stream) {
        failf(data, "Internal NULL stream!\n");
        (void)Curl_close(&newhandle);
        rv = 1;
        goto fail;
      }
  
      Curl_set_in_callback(data, true);
      rv = data->multi->push_cb(data, newhandle,
                                stream->push_headers_used, &heads,
                                data->multi->push_userp);
      Curl_set_in_callback(data, false);
  
      /* free the headers again */
      for(i = 0; i<stream->push_headers_used; i++)
        free(stream->push_headers[i]);
      free(stream->push_headers);
      stream->push_headers = NULL;
      stream->push_headers_used = 0;
  
      if(rv) {
        /* denied, kill off the new handle again */
        http2_stream_free(newhandle->req.protop);
        newhandle->req.protop = NULL;
        (void)Curl_close(&newhandle);
        goto fail;
      }
  
      newstream = newhandle->req.protop;
      newstream->stream_id = frame->promised_stream_id;
      newhandle->req.maxdownload = -1;
      newhandle->req.size = -1;
  
      /* approved, add to the multi handle and immediately switch to PERFORM
         state with the given connection !*/
      rc = Curl_multi_add_perform(data->multi, newhandle, conn);
      if(rc) {
        infof(data, "failed to add handle to multi\n");
        http2_stream_free(newhandle->req.protop);
        newhandle->req.protop = NULL;
        Curl_close(&newhandle);
        rv = 1;
        goto fail;
      }
  
      httpc = &conn->proto.httpc;
      rv = nghttp2_session_set_stream_user_data(httpc->h2,
                                                frame->promised_stream_id,
                                                newhandle);
      if(rv) {
        infof(data, "failed to set user_data for stream %d\n",
              frame->promised_stream_id);
        DEBUGASSERT(0);
        goto fail;
      }
    }
    else {
      H2BUGF(infof(data, "Got PUSH_PROMISE, ignore it!\n"));
      rv = 1;
    }
    fail:
    return rv;
  }
  
  /*
   * multi_connchanged() is called to tell that there is a connection in
   * this multi handle that has changed state (multiplexing become possible, the
   * number of allowed streams changed or similar), and a subsequent use of this
   * multi handle should move CONNECT_PEND handles back to CONNECT to have them
   * retry.
   */
  static void multi_connchanged(struct Curl_multi *multi)
  {
    multi->recheckstate = TRUE;
  }
  
  static int on_frame_recv(nghttp2_session *session, const nghttp2_frame *frame,
                           void *userp)
  {
    struct connectdata *conn = (struct connectdata *)userp;
    struct http_conn *httpc = &conn->proto.httpc;
    struct Curl_easy *data_s = NULL;
    struct HTTP *stream = NULL;
    int rv;
    size_t left, ncopy;
    int32_t stream_id = frame->hd.stream_id;
    CURLcode result;
  
    if(!stream_id) {
      /* stream ID zero is for connection-oriented stuff */
      if(frame->hd.type == NGHTTP2_SETTINGS) {
        uint32_t max_conn = httpc->settings.max_concurrent_streams;
        H2BUGF(infof(conn->data, "Got SETTINGS\n"));
        httpc->settings.max_concurrent_streams =
          nghttp2_session_get_remote_settings(
            session, NGHTTP2_SETTINGS_MAX_CONCURRENT_STREAMS);
        httpc->settings.enable_push =
          nghttp2_session_get_remote_settings(
            session, NGHTTP2_SETTINGS_ENABLE_PUSH);
        H2BUGF(infof(conn->data, "MAX_CONCURRENT_STREAMS == %d\n",
                     httpc->settings.max_concurrent_streams));
        H2BUGF(infof(conn->data, "ENABLE_PUSH == %s\n",
                     httpc->settings.enable_push?"TRUE":"false"));
        if(max_conn != httpc->settings.max_concurrent_streams) {
          /* only signal change if the value actually changed */
          infof(conn->data,
                "Connection state changed (MAX_CONCURRENT_STREAMS == %u)!\n",
                httpc->settings.max_concurrent_streams);
          multi_connchanged(conn->data->multi);
        }
      }
      return 0;
    }
    data_s = nghttp2_session_get_stream_user_data(session, stream_id);
    if(!data_s) {
      H2BUGF(infof(conn->data,
                   "No Curl_easy associated with stream: %x\n",
                   stream_id));
      return 0;
    }
  
    stream = data_s->req.protop;
    if(!stream) {
      H2BUGF(infof(data_s, "No proto pointer for stream: %x\n",
                   stream_id));
      return NGHTTP2_ERR_CALLBACK_FAILURE;
    }
  
    H2BUGF(infof(data_s, "on_frame_recv() header %x stream %x\n",
                 frame->hd.type, stream_id));
  
    switch(frame->hd.type) {
    case NGHTTP2_DATA:
      /* If body started on this stream, then receiving DATA is illegal. */
      if(!stream->bodystarted) {
        rv = nghttp2_submit_rst_stream(session, NGHTTP2_FLAG_NONE,
                                       stream_id, NGHTTP2_PROTOCOL_ERROR);
  
        if(nghttp2_is_fatal(rv)) {
          return NGHTTP2_ERR_CALLBACK_FAILURE;
        }
      }
      break;
    case NGHTTP2_HEADERS:
      if(stream->bodystarted) {
        /* Only valid HEADERS after body started is trailer HEADERS.  We
           buffer them in on_header callback. */
        break;
      }
  
      /* nghttp2 guarantees that :status is received, and we store it to
         stream->status_code. Fuzzing has proven this can still be reached
         without status code having been set. */
      if(stream->status_code == -1)
        return NGHTTP2_ERR_CALLBACK_FAILURE;
  
      /* Only final status code signals the end of header */
      if(stream->status_code / 100 != 1) {
        stream->bodystarted = TRUE;
        stream->status_code = -1;
      }
  
      result = Curl_add_buffer(&stream->header_recvbuf, "\r\n", 2);
      if(result)
        return NGHTTP2_ERR_CALLBACK_FAILURE;
  
      left = stream->header_recvbuf->size_used - stream->nread_header_recvbuf;
      ncopy = CURLMIN(stream->len, left);
  
      memcpy(&stream->mem[stream->memlen],
             stream->header_recvbuf->buffer + stream->nread_header_recvbuf,
             ncopy);
      stream->nread_header_recvbuf += ncopy;
  
      H2BUGF(infof(data_s, "Store %zu bytes headers from stream %u at %p\n",
                   ncopy, stream_id, stream->mem));
  
      stream->len -= ncopy;
      stream->memlen += ncopy;
  
      drain_this(data_s, httpc);
      {
        /* get the pointer from userp again since it was re-assigned above */
        struct connectdata *conn_s = (struct connectdata *)userp;
  
        /* if we receive data for another handle, wake that up */
        if(conn_s->data != data_s)
          Curl_expire(data_s, 0, EXPIRE_RUN_NOW);
      }
      break;
    case NGHTTP2_PUSH_PROMISE:
      rv = push_promise(data_s, conn, &frame->push_promise);
      if(rv) { /* deny! */
        rv = nghttp2_submit_rst_stream(session, NGHTTP2_FLAG_NONE,
                                       frame->push_promise.promised_stream_id,
                                       NGHTTP2_CANCEL);
        if(nghttp2_is_fatal(rv)) {
          return rv;
        }
      }
      break;
    default:
      H2BUGF(infof(data_s, "Got frame type %x for stream %u!\n",
                   frame->hd.type, stream_id));
      break;
    }
    return 0;
  }
  
  static int on_data_chunk_recv(nghttp2_session *session, uint8_t flags,
                                int32_t stream_id,
                                const uint8_t *data, size_t len, void *userp)
  {
    struct HTTP *stream;
    struct Curl_easy *data_s;
    size_t nread;
    struct connectdata *conn = (struct connectdata *)userp;
    (void)session;
    (void)flags;
    (void)data;
  
    DEBUGASSERT(stream_id); /* should never be a zero stream ID here */
  
    /* get the stream from the hash based on Stream ID */
    data_s = nghttp2_session_get_stream_user_data(session, stream_id);
    if(!data_s)
      /* Receiving a Stream ID not in the hash should not happen, this is an
         internal error more than anything else! */
      return NGHTTP2_ERR_CALLBACK_FAILURE;
  
    stream = data_s->req.protop;
    if(!stream)
      return NGHTTP2_ERR_CALLBACK_FAILURE;
  
    nread = CURLMIN(stream->len, len);
    memcpy(&stream->mem[stream->memlen], data, nread);
  
    stream->len -= nread;
    stream->memlen += nread;
  
    drain_this(data_s, &conn->proto.httpc);
  
    /* if we receive data for another handle, wake that up */
    if(conn->data != data_s)
      Curl_expire(data_s, 0, EXPIRE_RUN_NOW);
  
    H2BUGF(infof(data_s, "%zu data received for stream %u "
                 "(%zu left in buffer %p, total %zu)\n",
                 nread, stream_id,
                 stream->len, stream->mem,
                 stream->memlen));
  
    if(nread < len) {
      stream->pausedata = data + nread;
      stream->pauselen = len - nread;
      H2BUGF(infof(data_s, "NGHTTP2_ERR_PAUSE - %zu bytes out of buffer"
                   ", stream %u\n",
                   len - nread, stream_id));
      data_s->conn->proto.httpc.pause_stream_id = stream_id;
  
      return NGHTTP2_ERR_PAUSE;
    }
  
    /* pause execution of nghttp2 if we received data for another handle
       in order to process them first. */
    if(conn->data != data_s) {
      data_s->conn->proto.httpc.pause_stream_id = stream_id;
  
      return NGHTTP2_ERR_PAUSE;
    }
  
    return 0;
  }
  
  static int on_stream_close(nghttp2_session *session, int32_t stream_id,
                             uint32_t error_code, void *userp)
  {
    struct Curl_easy *data_s;
    struct HTTP *stream;
    struct connectdata *conn = (struct connectdata *)userp;
    int rv;
    (void)session;
    (void)stream_id;
  
    if(stream_id) {
      struct http_conn *httpc;
      /* get the stream from the hash based on Stream ID, stream ID zero is for
         connection-oriented stuff */
      data_s = nghttp2_session_get_stream_user_data(session, stream_id);
      if(!data_s) {
        /* We could get stream ID not in the hash.  For example, if we
           decided to reject stream (e.g., PUSH_PROMISE). */
        return 0;
      }
      H2BUGF(infof(data_s, "on_stream_close(), %s (err %d), stream %u\n",
                   http2_strerror(error_code), error_code, stream_id));
      stream = data_s->req.protop;
      if(!stream)
        return NGHTTP2_ERR_CALLBACK_FAILURE;
  
      stream->closed = TRUE;
      httpc = &conn->proto.httpc;
      drain_this(data_s, httpc);
      Curl_expire(data_s, 0, EXPIRE_RUN_NOW);
      httpc->error_code = error_code;
  
      /* remove the entry from the hash as the stream is now gone */
      rv = nghttp2_session_set_stream_user_data(session, stream_id, 0);
      if(rv) {
        infof(data_s, "http/2: failed to clear user_data for stream %d!\n",
              stream_id);
        DEBUGASSERT(0);
      }
      if(stream_id == httpc->pause_stream_id) {
        H2BUGF(infof(data_s, "Stopped the pause stream!\n"));
        httpc->pause_stream_id = 0;
      }
      H2BUGF(infof(data_s, "Removed stream %u hash!\n", stream_id));
      stream->stream_id = 0; /* cleared */
    }
    return 0;
  }
  
  static int on_begin_headers(nghttp2_session *session,
                              const nghttp2_frame *frame, void *userp)
  {
    struct HTTP *stream;
    struct Curl_easy *data_s = NULL;
    (void)userp;
  
    data_s = nghttp2_session_get_stream_user_data(session, frame->hd.stream_id);
    if(!data_s) {
      return 0;
    }
  
    H2BUGF(infof(data_s, "on_begin_headers() was called\n"));
  
    if(frame->hd.type != NGHTTP2_HEADERS) {
      return 0;
    }
  
    stream = data_s->req.protop;
    if(!stream || !stream->bodystarted) {
      return 0;
    }
  
    if(!stream->trailer_recvbuf) {
      stream->trailer_recvbuf = Curl_add_buffer_init();
      if(!stream->trailer_recvbuf) {
        return NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE;
      }
    }
    return 0;
  }
  
  /* Decode HTTP status code.  Returns -1 if no valid status code was
     decoded. */
  static int decode_status_code(const uint8_t *value, size_t len)
  {
    int i;
    int res;
  
    if(len != 3) {
      return -1;
    }
  
    res = 0;
  
    for(i = 0; i < 3; ++i) {
      char c = value[i];
  
      if(c < '0' || c > '9') {
        return -1;
      }
  
      res *= 10;
      res += c - '0';
    }
  
    return res;
  }
  
  /* frame->hd.type is either NGHTTP2_HEADERS or NGHTTP2_PUSH_PROMISE */
  static int on_header(nghttp2_session *session, const nghttp2_frame *frame,
                       const uint8_t *name, size_t namelen,
                       const uint8_t *value, size_t valuelen,
                       uint8_t flags,
                       void *userp)
  {
    struct HTTP *stream;
    struct Curl_easy *data_s;
    int32_t stream_id = frame->hd.stream_id;
    struct connectdata *conn = (struct connectdata *)userp;
    CURLcode result;
    (void)flags;
  
    DEBUGASSERT(stream_id); /* should never be a zero stream ID here */
  
    /* get the stream from the hash based on Stream ID */
    data_s = nghttp2_session_get_stream_user_data(session, stream_id);
    if(!data_s)
      /* Receiving a Stream ID not in the hash should not happen, this is an
         internal error more than anything else! */
      return NGHTTP2_ERR_CALLBACK_FAILURE;
  
    stream = data_s->req.protop;
    if(!stream) {
      failf(data_s, "Internal NULL stream! 5\n");
      return NGHTTP2_ERR_CALLBACK_FAILURE;
    }
  
    /* Store received PUSH_PROMISE headers to be used when the subsequent
       PUSH_PROMISE callback comes */
    if(frame->hd.type == NGHTTP2_PUSH_PROMISE) {
      char *h;
  
      if(!strcmp(":authority", (const char *)name)) {
        /* pseudo headers are lower case */
        int rc = 0;
        char *check = aprintf("%s:%d", conn->host.name, conn->remote_port);
        if(!check)
          /* no memory */
          return NGHTTP2_ERR_CALLBACK_FAILURE;
        if(!Curl_strcasecompare(check, (const char *)value) &&
           ((conn->remote_port != conn->given->defport) ||
            !Curl_strcasecompare(conn->host.name, (const char *)value))) {
          /* This is push is not for the same authority that was asked for in
           * the URL. RFC 7540 section 8.2 says: "A client MUST treat a
           * PUSH_PROMISE for which the server is not authoritative as a stream
           * error of type PROTOCOL_ERROR."
           */
          (void)nghttp2_submit_rst_stream(session, NGHTTP2_FLAG_NONE,
                                          stream_id, NGHTTP2_PROTOCOL_ERROR);
          rc = NGHTTP2_ERR_CALLBACK_FAILURE;
        }
        free(check);
        if(rc)
          return rc;
      }
  
      if(!stream->push_headers) {
        stream->push_headers_alloc = 10;
        stream->push_headers = malloc(stream->push_headers_alloc *
                                      sizeof(char *));
        if(!stream->push_headers)
          return NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE;
        stream->push_headers_used = 0;
      }
      else if(stream->push_headers_used ==
              stream->push_headers_alloc) {
        char **headp;
        stream->push_headers_alloc *= 2;
        headp = Curl_saferealloc(stream->push_headers,
                                 stream->push_headers_alloc * sizeof(char *));
        if(!headp) {
          stream->push_headers = NULL;
          return NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE;
        }
        stream->push_headers = headp;
      }
      h = aprintf("%s:%s", name, value);
      if(h)
        stream->push_headers[stream->push_headers_used++] = h;
      return 0;
    }
  
    if(stream->bodystarted) {
      /* This is trailer fields. */
      /* 4 is for ": " and "\r\n". */
      uint32_t n = (uint32_t)(namelen + valuelen + 4);
  
      H2BUGF(infof(data_s, "h2 trailer: %.*s: %.*s\n", namelen, name, valuelen,
                   value));
  
      result = Curl_add_buffer(&stream->trailer_recvbuf, &n, sizeof(n));
      if(result)
        return NGHTTP2_ERR_CALLBACK_FAILURE;
      result = Curl_add_buffer(&stream->trailer_recvbuf, name, namelen);
      if(result)
        return NGHTTP2_ERR_CALLBACK_FAILURE;
      result = Curl_add_buffer(&stream->trailer_recvbuf, ": ", 2);
      if(result)
        return NGHTTP2_ERR_CALLBACK_FAILURE;
      result = Curl_add_buffer(&stream->trailer_recvbuf, value, valuelen);
      if(result)
        return NGHTTP2_ERR_CALLBACK_FAILURE;
      result = Curl_add_buffer(&stream->trailer_recvbuf, "\r\n\0", 3);
      if(result)
        return NGHTTP2_ERR_CALLBACK_FAILURE;
  
      return 0;
    }
  
    if(namelen == sizeof(":status") - 1 &&
       memcmp(":status", name, namelen) == 0) {
      /* nghttp2 guarantees :status is received first and only once, and
         value is 3 digits status code, and decode_status_code always
         succeeds. */
      stream->status_code = decode_status_code(value, valuelen);
      DEBUGASSERT(stream->status_code != -1);
  
      result = Curl_add_buffer(&stream->header_recvbuf, "HTTP/2 ", 7);
      if(result)
        return NGHTTP2_ERR_CALLBACK_FAILURE;
      result = Curl_add_buffer(&stream->header_recvbuf, value, valuelen);
      if(result)
        return NGHTTP2_ERR_CALLBACK_FAILURE;
      /* the space character after the status code is mandatory */
      result = Curl_add_buffer(&stream->header_recvbuf, " \r\n", 3);
      if(result)
        return NGHTTP2_ERR_CALLBACK_FAILURE;
      /* if we receive data for another handle, wake that up */
      if(conn->data != data_s)
        Curl_expire(data_s, 0, EXPIRE_RUN_NOW);
  
      H2BUGF(infof(data_s, "h2 status: HTTP/2 %03d (easy %p)\n",
                   stream->status_code, data_s));
      return 0;
    }
  
    /* nghttp2 guarantees that namelen > 0, and :status was already
       received, and this is not pseudo-header field . */
    /* convert to a HTTP1-style header */
    result = Curl_add_buffer(&stream->header_recvbuf, name, namelen);
    if(result)
      return NGHTTP2_ERR_CALLBACK_FAILURE;
    result = Curl_add_buffer(&stream->header_recvbuf, ": ", 2);
    if(result)
      return NGHTTP2_ERR_CALLBACK_FAILURE;
    result = Curl_add_buffer(&stream->header_recvbuf, value, valuelen);
    if(result)
      return NGHTTP2_ERR_CALLBACK_FAILURE;
    result = Curl_add_buffer(&stream->header_recvbuf, "\r\n", 2);
    if(result)
      return NGHTTP2_ERR_CALLBACK_FAILURE;
    /* if we receive data for another handle, wake that up */
    if(conn->data != data_s)
      Curl_expire(data_s, 0, EXPIRE_RUN_NOW);
  
    H2BUGF(infof(data_s, "h2 header: %.*s: %.*s\n", namelen, name, valuelen,
                 value));
  
    return 0; /* 0 is successful */
  }
  
  static ssize_t data_source_read_callback(nghttp2_session *session,
                                           int32_t stream_id,
                                           uint8_t *buf, size_t length,
                                           uint32_t *data_flags,
                                           nghttp2_data_source *source,
                                           void *userp)
  {
    struct Curl_easy *data_s;
    struct HTTP *stream = NULL;
    size_t nread;
    (void)source;
    (void)userp;
  
    if(stream_id) {
      /* get the stream from the hash based on Stream ID, stream ID zero is for
         connection-oriented stuff */
      data_s = nghttp2_session_get_stream_user_data(session, stream_id);
      if(!data_s)
        /* Receiving a Stream ID not in the hash should not happen, this is an
           internal error more than anything else! */
        return NGHTTP2_ERR_CALLBACK_FAILURE;
  
      stream = data_s->req.protop;
      if(!stream)
        return NGHTTP2_ERR_CALLBACK_FAILURE;
    }
    else
      return NGHTTP2_ERR_INVALID_ARGUMENT;
  
    nread = CURLMIN(stream->upload_len, length);
    if(nread > 0) {
      memcpy(buf, stream->upload_mem, nread);
      stream->upload_mem += nread;
      stream->upload_len -= nread;
      if(data_s->state.infilesize != -1)
        stream->upload_left -= nread;
    }
  
    if(stream->upload_left == 0)
      *data_flags = NGHTTP2_DATA_FLAG_EOF;
    else if(nread == 0)
      return NGHTTP2_ERR_DEFERRED;
  
    H2BUGF(infof(data_s, "data_source_read_callback: "
                 "returns %zu bytes stream %u\n",
                 nread, stream_id));
  
    return nread;
  }
  
  #if defined(NGHTTP2_HAS_ERROR_CALLBACK) &&      \
    !defined(CURL_DISABLE_VERBOSE_STRINGS)
  static int error_callback(nghttp2_session *session,
                            const char *msg,
                            size_t len,
                            void *userp)
  {
    struct connectdata *conn = (struct connectdata *)userp;
    (void)session;
    infof(conn->data, "http2 error: %.*s\n", len, msg);
    return 0;
  }
  #endif
  
  static void populate_settings(struct connectdata *conn,
                                struct http_conn *httpc)
  {
    nghttp2_settings_entry *iv = httpc->local_settings;
  
    iv[0].settings_id = NGHTTP2_SETTINGS_MAX_CONCURRENT_STREAMS;
    iv[0].value = (uint32_t)Curl_multi_max_concurrent_streams(conn->data->multi);
  
    iv[1].settings_id = NGHTTP2_SETTINGS_INITIAL_WINDOW_SIZE;
    iv[1].value = HTTP2_HUGE_WINDOW_SIZE;
  
    iv[2].settings_id = NGHTTP2_SETTINGS_ENABLE_PUSH;
    iv[2].value = conn->data->multi->push_cb != NULL;
  
    httpc->local_settings_num = 3;
  }
  
  void Curl_http2_done(struct connectdata *conn, bool premature)
  {
    struct Curl_easy *data = conn->data;
    struct HTTP *http = data->req.protop;
    struct http_conn *httpc = &conn->proto.httpc;
  
    /* there might be allocated resources done before this got the 'h2' pointer
       setup */
    if(http->header_recvbuf) {
      Curl_add_buffer_free(&http->header_recvbuf);
      Curl_add_buffer_free(&http->trailer_recvbuf);
      if(http->push_headers) {
        /* if they weren't used and then freed before */
        for(; http->push_headers_used > 0; --http->push_headers_used) {
          free(http->push_headers[http->push_headers_used - 1]);
        }
        free(http->push_headers);
        http->push_headers = NULL;
      }
    }
  
    if(!httpc->h2) /* not HTTP/2 ? */
      return;
  
    if(premature) {
      /* RST_STREAM */
      if(!nghttp2_submit_rst_stream(httpc->h2, NGHTTP2_FLAG_NONE,
                                    http->stream_id, NGHTTP2_STREAM_CLOSED))
        (void)nghttp2_session_send(httpc->h2);
  
      if(http->stream_id == httpc->pause_stream_id) {
        infof(data, "stopped the pause stream!\n");
        httpc->pause_stream_id = 0;
      }
    }
  
    if(data->state.drain)
      drained_transfer(data, httpc);
  
    /* -1 means unassigned and 0 means cleared */
    if(http->stream_id > 0) {
      int rv = nghttp2_session_set_stream_user_data(httpc->h2,
                                                    http->stream_id, 0);
      if(rv) {
        infof(data, "http/2: failed to clear user_data for stream %d!\n",
              http->stream_id);
        DEBUGASSERT(0);
      }
      http->stream_id = 0;
    }
  }
  
  /*
   * Initialize nghttp2 for a Curl connection
   */
  static CURLcode http2_init(struct connectdata *conn)
  {
    if(!conn->proto.httpc.h2) {
      int rc;
      nghttp2_session_callbacks *callbacks;
  
      conn->proto.httpc.inbuf = malloc(H2_BUFSIZE);
      if(conn->proto.httpc.inbuf == NULL)
        return CURLE_OUT_OF_MEMORY;
  
      rc = nghttp2_session_callbacks_new(&callbacks);
  
      if(rc) {
        failf(conn->data, "Couldn't initialize nghttp2 callbacks!");
        return CURLE_OUT_OF_MEMORY; /* most likely at least */
      }
  
      /* nghttp2_send_callback */
      nghttp2_session_callbacks_set_send_callback(callbacks, send_callback);
      /* nghttp2_on_frame_recv_callback */
      nghttp2_session_callbacks_set_on_frame_recv_callback
        (callbacks, on_frame_recv);
      /* nghttp2_on_data_chunk_recv_callback */
      nghttp2_session_callbacks_set_on_data_chunk_recv_callback
        (callbacks, on_data_chunk_recv);
      /* nghttp2_on_stream_close_callback */
      nghttp2_session_callbacks_set_on_stream_close_callback
        (callbacks, on_stream_close);
      /* nghttp2_on_begin_headers_callback */
      nghttp2_session_callbacks_set_on_begin_headers_callback
        (callbacks, on_begin_headers);
      /* nghttp2_on_header_callback */
      nghttp2_session_callbacks_set_on_header_callback(callbacks, on_header);
  
  #ifndef CURL_DISABLE_VERBOSE_STRINGS
      nghttp2_session_callbacks_set_error_callback(callbacks, error_callback);
  #endif
  
      /* The nghttp2 session is not yet setup, do it */
      rc = nghttp2_session_client_new(&conn->proto.httpc.h2, callbacks, conn);
  
      nghttp2_session_callbacks_del(callbacks);
  
      if(rc) {
        failf(conn->data, "Couldn't initialize nghttp2!");
        return CURLE_OUT_OF_MEMORY; /* most likely at least */
      }
    }
    return CURLE_OK;
  }
  
  /*
   * Append headers to ask for a HTTP1.1 to HTTP2 upgrade.
   */
  CURLcode Curl_http2_request_upgrade(Curl_send_buffer *req,
                                      struct connectdata *conn)
  {
    CURLcode result;
    ssize_t binlen;
    char *base64;
    size_t blen;
    struct SingleRequest *k = &conn->data->req;
    uint8_t *binsettings = conn->proto.httpc.binsettings;
    struct http_conn *httpc = &conn->proto.httpc;
  
    populate_settings(conn, httpc);
  
    /* this returns number of bytes it wrote */
    binlen = nghttp2_pack_settings_payload(binsettings, H2_BINSETTINGS_LEN,
                                           httpc->local_settings,
                                           httpc->local_settings_num);
    if(!binlen) {
      failf(conn->data, "nghttp2 unexpectedly failed on pack_settings_payload");
      Curl_add_buffer_free(&req);
      return CURLE_FAILED_INIT;
    }
    conn->proto.httpc.binlen = binlen;
  
    result = Curl_base64url_encode(conn->data, (const char *)binsettings, binlen,
                                   &base64, &blen);
    if(result) {
      Curl_add_buffer_free(&req);
      return result;
    }
  
    result = Curl_add_bufferf(&req,
                              "Connection: Upgrade, HTTP2-Settings\r\n"
                              "Upgrade: %s\r\n"
                              "HTTP2-Settings: %s\r\n",
                              NGHTTP2_CLEARTEXT_PROTO_VERSION_ID, base64);
    free(base64);
  
    k->upgr101 = UPGR101_REQUESTED;
  
    return result;
  }
  
  /*
   * Returns nonzero if current HTTP/2 session should be closed.
   */
  static int should_close_session(struct http_conn *httpc)
  {
    return httpc->drain_total == 0 && !nghttp2_session_want_read(httpc->h2) &&
      !nghttp2_session_want_write(httpc->h2);
  }
  
  /*
   * h2_process_pending_input() processes pending input left in
   * httpc->inbuf.  Then, call h2_session_send() to send pending data.
   * This function returns 0 if it succeeds, or -1 and error code will
   * be assigned to *err.
   */
  static int h2_process_pending_input(struct connectdata *conn,
                                      struct http_conn *httpc,
                                      CURLcode *err)
  {
    ssize_t nread;
    char *inbuf;
    ssize_t rv;
    struct Curl_easy *data = conn->data;
  
    nread = httpc->inbuflen - httpc->nread_inbuf;
    inbuf = httpc->inbuf + httpc->nread_inbuf;
  
    rv = nghttp2_session_mem_recv(httpc->h2, (const uint8_t *)inbuf, nread);
    if(rv < 0) {
      failf(data,
            "h2_process_pending_input: nghttp2_session_mem_recv() returned "
            "%zd:%s\n", rv, nghttp2_strerror((int)rv));
      *err = CURLE_RECV_ERROR;
      return -1;
    }
  
    if(nread == rv) {
      H2BUGF(infof(data,
                   "h2_process_pending_input: All data in connection buffer "
                   "processed\n"));
      httpc->inbuflen = 0;
      httpc->nread_inbuf = 0;
    }
    else {
      httpc->nread_inbuf += rv;
      H2BUGF(infof(data,
                   "h2_process_pending_input: %zu bytes left in connection "
                   "buffer\n",
                   httpc->inbuflen - httpc->nread_inbuf));
    }
  
    rv = h2_session_send(data, httpc->h2);
    if(rv != 0) {
      *err = CURLE_SEND_ERROR;
      return -1;
    }
  
    if(should_close_session(httpc)) {
      H2BUGF(infof(data,
                   "h2_process_pending_input: nothing to do in this session\n"));
      if(httpc->error_code)
        *err = CURLE_HTTP2;
      else {
        /* not an error per se, but should still close the connection */
        connclose(conn, "GOAWAY received");
        *err = CURLE_OK;
      }
      return -1;
    }
  
    return 0;
  }
  
  /*
   * Called from transfer.c:done_sending when we stop uploading.
   */
  CURLcode Curl_http2_done_sending(struct connectdata *conn)
  {
    CURLcode result = CURLE_OK;
  
    if((conn->handler == &Curl_handler_http2_ssl) ||
       (conn->handler == &Curl_handler_http2)) {
      /* make sure this is only attempted for HTTP/2 transfers */
  
      struct HTTP *stream = conn->data->req.protop;
  
      if(stream->upload_left) {
        /* If the stream still thinks there's data left to upload. */
        struct http_conn *httpc = &conn->proto.httpc;
        nghttp2_session *h2 = httpc->h2;
  
        stream->upload_left = 0; /* DONE! */
  
        /* resume sending here to trigger the callback to get called again so
           that it can signal EOF to nghttp2 */
        (void)nghttp2_session_resume_data(h2, stream->stream_id);
  
        (void)h2_process_pending_input(conn, httpc, &result);
      }
    }
    return result;
  }
  
  static ssize_t http2_handle_stream_close(struct connectdata *conn,
                                           struct Curl_easy *data,
                                           struct HTTP *stream, CURLcode *err)
  {
    char *trailer_pos, *trailer_end;
    CURLcode result;
    struct http_conn *httpc = &conn->proto.httpc;
  
    if(httpc->pause_stream_id == stream->stream_id) {
      httpc->pause_stream_id = 0;
    }
  
    drained_transfer(data, httpc);
  
    if(httpc->pause_stream_id == 0) {
      if(h2_process_pending_input(conn, httpc, err) != 0) {
        return -1;
      }
    }
  
    DEBUGASSERT(data->state.drain == 0);
  
    /* Reset to FALSE to prevent infinite loop in readwrite_data function. */
    stream->closed = FALSE;
    if(httpc->error_code == NGHTTP2_REFUSED_STREAM) {
      H2BUGF(infof(data, "REFUSED_STREAM (%d), try again on a new connection!\n",
                   stream->stream_id));
      connclose(conn, "REFUSED_STREAM"); /* don't use this anymore */
      data->state.refused_stream = TRUE;
      *err = CURLE_RECV_ERROR; /* trigger Curl_retry_request() later */
      return -1;
    }
    else if(httpc->error_code != NGHTTP2_NO_ERROR) {
      failf(data, "HTTP/2 stream %d was not closed cleanly: %s (err %u)",
            stream->stream_id, http2_strerror(httpc->error_code),
            httpc->error_code);
      *err = CURLE_HTTP2_STREAM;
      return -1;
    }
  
    if(!stream->bodystarted) {
      failf(data, "HTTP/2 stream %d was closed cleanly, but before getting "
            " all response header fields, treated as error",
            stream->stream_id);
      *err = CURLE_HTTP2_STREAM;
      return -1;
    }
  
    if(stream->trailer_recvbuf && stream->trailer_recvbuf->buffer) {
      trailer_pos = stream->trailer_recvbuf->buffer;
      trailer_end = trailer_pos + stream->trailer_recvbuf->size_used;
  
      for(; trailer_pos < trailer_end;) {
        uint32_t n;
        memcpy(&n, trailer_pos, sizeof(n));
        trailer_pos += sizeof(n);
  
        result = Curl_client_write(conn, CLIENTWRITE_HEADER, trailer_pos, n);
        if(result) {
          *err = result;
          return -1;
        }
  
        trailer_pos += n + 1;
      }
    }
  
    stream->close_handled = TRUE;
  
    H2BUGF(infof(data, "http2_recv returns 0, http2_handle_stream_close\n"));
    return 0;
  }
  
  /*
   * h2_pri_spec() fills in the pri_spec struct, used by nghttp2 to send weight
   * and dependency to the peer. It also stores the updated values in the state
   * struct.
   */
  
  static void h2_pri_spec(struct Curl_easy *data,
                          nghttp2_priority_spec *pri_spec)
  {
    struct HTTP *depstream = (data->set.stream_depends_on?
                              data->set.stream_depends_on->req.protop:NULL);
    int32_t depstream_id = depstream? depstream->stream_id:0;
    nghttp2_priority_spec_init(pri_spec, depstream_id, data->set.stream_weight,
                               data->set.stream_depends_e);
    data->state.stream_weight = data->set.stream_weight;
    data->state.stream_depends_e = data->set.stream_depends_e;
    data->state.stream_depends_on = data->set.stream_depends_on;
  }
  
  /*
   * h2_session_send() checks if there's been an update in the priority /
   * dependency settings and if so it submits a PRIORITY frame with the updated
   * info.
   */
  static int h2_session_send(struct Curl_easy *data,
                             nghttp2_session *h2)
  {
    struct HTTP *stream = data->req.protop;
    if((data->set.stream_weight != data->state.stream_weight) ||
       (data->set.stream_depends_e != data->state.stream_depends_e) ||
       (data->set.stream_depends_on != data->state.stream_depends_on) ) {
      /* send new weight and/or dependency */
      nghttp2_priority_spec pri_spec;
      int rv;
  
      h2_pri_spec(data, &pri_spec);
  
      H2BUGF(infof(data, "Queuing PRIORITY on stream %u (easy %p)\n",
                   stream->stream_id, data));
      DEBUGASSERT(stream->stream_id != -1);
      rv = nghttp2_submit_priority(h2, NGHTTP2_FLAG_NONE, stream->stream_id,
                                   &pri_spec);
      if(rv)
        return rv;
    }
  
    return nghttp2_session_send(h2);
  }
  
  static ssize_t http2_recv(struct connectdata *conn, int sockindex,
                            char *mem, size_t len, CURLcode *err)
  {
    CURLcode result = CURLE_OK;
    ssize_t rv;
    ssize_t nread;
    struct http_conn *httpc = &conn->proto.httpc;
    struct Curl_easy *data = conn->data;
    struct HTTP *stream = data->req.protop;
  
    (void)sockindex; /* we always do HTTP2 on sockindex 0 */
  
    if(should_close_session(httpc)) {
      H2BUGF(infof(data,
                   "http2_recv: nothing to do in this session\n"));
      if(conn->bits.close) {
        /* already marked for closure, return OK and we're done */
        *err = CURLE_OK;
        return 0;
      }
      *err = CURLE_HTTP2;
      return -1;
    }
  
    /* Nullify here because we call nghttp2_session_send() and they
       might refer to the old buffer. */
    stream->upload_mem = NULL;
    stream->upload_len = 0;
  
    /*
     * At this point 'stream' is just in the Curl_easy the connection
     * identifies as its owner at this time.
     */
  
    if(stream->bodystarted &&
       stream->nread_header_recvbuf < stream->header_recvbuf->size_used) {
      /* If there is body data pending for this stream to return, do that */
      size_t left =
        stream->header_recvbuf->size_used - stream->nread_header_recvbuf;
      size_t ncopy = CURLMIN(len, left);
      memcpy(mem, stream->header_recvbuf->buffer + stream->nread_header_recvbuf,
             ncopy);
      stream->nread_header_recvbuf += ncopy;
  
      H2BUGF(infof(data, "http2_recv: Got %d bytes from header_recvbuf\n",
                   (int)ncopy));
      return ncopy;
    }
  
    H2BUGF(infof(data, "http2_recv: easy %p (stream %u)\n",
                 data, stream->stream_id));
  
    if((data->state.drain) && stream->memlen) {
      H2BUGF(infof(data, "http2_recv: DRAIN %zu bytes stream %u!! (%p => %p)\n",
                   stream->memlen, stream->stream_id,
                   stream->mem, mem));
      if(mem != stream->mem) {
        /* if we didn't get the same buffer this time, we must move the data to
           the beginning */
        memmove(mem, stream->mem, stream->memlen);
        stream->len = len - stream->memlen;
        stream->mem = mem;
      }
      if(httpc->pause_stream_id == stream->stream_id && !stream->pausedata) {
        /* We have paused nghttp2, but we have no pause data (see
           on_data_chunk_recv). */
        httpc->pause_stream_id = 0;
        if(h2_process_pending_input(conn, httpc, &result) != 0) {
          *err = result;
          return -1;
        }
      }
    }
    else if(stream->pausedata) {
      DEBUGASSERT(httpc->pause_stream_id == stream->stream_id);
      nread = CURLMIN(len, stream->pauselen);
      memcpy(mem, stream->pausedata, nread);
  
      stream->pausedata += nread;
      stream->pauselen -= nread;
  
      infof(data, "%zd data bytes written\n", nread);
      if(stream->pauselen == 0) {
        H2BUGF(infof(data, "Unpaused by stream %u\n", stream->stream_id));
        DEBUGASSERT(httpc->pause_stream_id == stream->stream_id);
        httpc->pause_stream_id = 0;
  
        stream->pausedata = NULL;
        stream->pauselen = 0;
  
        /* When NGHTTP2_ERR_PAUSE is returned from
           data_source_read_callback, we might not process DATA frame
           fully.  Calling nghttp2_session_mem_recv() again will
           continue to process DATA frame, but if there is no incoming
           frames, then we have to call it again with 0-length data.
           Without this, on_stream_close callback will not be called,
           and stream could be hanged. */
        if(h2_process_pending_input(conn, httpc, &result) != 0) {
          *err = result;
          return -1;
        }
      }
      H2BUGF(infof(data, "http2_recv: returns unpaused %zd bytes on stream %u\n",
                   nread, stream->stream_id));
      return nread;
    }
    else if(httpc->pause_stream_id) {
      /* If a stream paused nghttp2_session_mem_recv previously, and has
         not processed all data, it still refers to the buffer in
         nghttp2_session.  If we call nghttp2_session_mem_recv(), we may
         overwrite that buffer.  To avoid that situation, just return
         here with CURLE_AGAIN.  This could be busy loop since data in
         socket is not read.  But it seems that usually streams are
         notified with its drain property, and socket is read again
         quickly. */
      if(stream->closed)
        /* closed overrides paused */
        return 0;
      H2BUGF(infof(data, "stream %x is paused, pause id: %x\n",
                   stream->stream_id, httpc->pause_stream_id));
      *err = CURLE_AGAIN;
      return -1;
    }
    else {
      char *inbuf;
      /* remember where to store incoming data for this stream and how big the
         buffer is */
      stream->mem = mem;
      stream->len = len;
      stream->memlen = 0;
  
      if(httpc->inbuflen == 0) {
        nread = ((Curl_recv *)httpc->recv_underlying)(
            conn, FIRSTSOCKET, httpc->inbuf, H2_BUFSIZE, &result);
  
        if(nread == -1) {
          if(result != CURLE_AGAIN)
            failf(data, "Failed receiving HTTP2 data");
          else if(stream->closed)
            /* received when the stream was already closed! */
            return http2_handle_stream_close(conn, data, stream, err);
  
          *err = result;
          return -1;
        }
  
        if(nread == 0) {
          H2BUGF(infof(data, "end of stream\n"));
          *err = CURLE_OK;
          return 0;
        }
  
        H2BUGF(infof(data, "nread=%zd\n", nread));
  
        httpc->inbuflen = nread;
        inbuf = httpc->inbuf;
      }
      else {
        nread = httpc->inbuflen - httpc->nread_inbuf;
        inbuf = httpc->inbuf + httpc->nread_inbuf;
  
        H2BUGF(infof(data, "Use data left in connection buffer, nread=%zd\n",
                     nread));
      }
      rv = nghttp2_session_mem_recv(httpc->h2, (const uint8_t *)inbuf, nread);
  
      if(nghttp2_is_fatal((int)rv)) {
        failf(data, "nghttp2_session_mem_recv() returned %zd:%s\n",
              rv, nghttp2_strerror((int)rv));
        *err = CURLE_RECV_ERROR;
        return -1;
      }
      H2BUGF(infof(data, "nghttp2_session_mem_recv() returns %zd\n", rv));
      if(nread == rv) {
        H2BUGF(infof(data, "All data in connection buffer processed\n"));
        httpc->inbuflen = 0;
        httpc->nread_inbuf = 0;
      }
      else {
        httpc->nread_inbuf += rv;
        H2BUGF(infof(data, "%zu bytes left in connection buffer\n",
                     httpc->inbuflen - httpc->nread_inbuf));
      }
      /* Always send pending frames in nghttp2 session, because
         nghttp2_session_mem_recv() may queue new frame */
      rv = h2_session_send(data, httpc->h2);
      if(rv != 0) {
        *err = CURLE_SEND_ERROR;
        return -1;
      }
  
      if(should_close_session(httpc)) {
        H2BUGF(infof(data, "http2_recv: nothing to do in this session\n"));
        *err = CURLE_HTTP2;
        return -1;
      }
    }
    if(stream->memlen) {
      ssize_t retlen = stream->memlen;
      H2BUGF(infof(data, "http2_recv: returns %zd for stream %u\n",
                   retlen, stream->stream_id));
      stream->memlen = 0;
  
      if(httpc->pause_stream_id == stream->stream_id) {
        /* data for this stream is returned now, but this stream caused a pause
           already so we need it called again asap */
        H2BUGF(infof(data, "Data returned for PAUSED stream %u\n",
                     stream->stream_id));
      }
      else if(!stream->closed) {
        drained_transfer(data, httpc);
      }
      else
        /* this stream is closed, trigger a another read ASAP to detect that */
        Curl_expire(data, 0, EXPIRE_RUN_NOW);
  
      return retlen;
    }
    /* If this stream is closed, return 0 to signal the http routine to close
       the connection */
    if(stream->closed)
      return 0;
    *err = CURLE_AGAIN;
    H2BUGF(infof(data, "http2_recv returns AGAIN for stream %u\n",
                 stream->stream_id));
    return -1;
  }
  
  /* Index where :authority header field will appear in request header
     field list. */
  #define AUTHORITY_DST_IDX 3
  
  /* USHRT_MAX is 65535 == 0xffff */
  #define HEADER_OVERFLOW(x) \
    (x.namelen > 0xffff || x.valuelen > 0xffff - x.namelen)
  
  /*
   * Check header memory for the token "trailers".
   * Parse the tokens as separated by comma and surrounded by whitespace.
   * Returns TRUE if found or FALSE if not.
   */
  static bool contains_trailers(const char *p, size_t len)
  {
    const char *end = p + len;
    for(;;) {
      for(; p != end && (*p == ' ' || *p == '\t'); ++p)
        ;
      if(p == end || (size_t)(end - p) < sizeof("trailers") - 1)
        return FALSE;
      if(strncasecompare("trailers", p, sizeof("trailers") - 1)) {
        p += sizeof("trailers") - 1;
        for(; p != end && (*p == ' ' || *p == '\t'); ++p)
          ;
        if(p == end || *p == ',')
          return TRUE;
      }
      /* skip to next token */
      for(; p != end && *p != ','; ++p)
        ;
      if(p == end)
        return FALSE;
      ++p;
    }
  }
  
  typedef enum {
    /* Send header to server */
    HEADERINST_FORWARD,
    /* Don't send header to server */
    HEADERINST_IGNORE,
    /* Discard header, and replace it with "te: trailers" */
    HEADERINST_TE_TRAILERS
  } header_instruction;
  
  /* Decides how to treat given header field. */
  static header_instruction inspect_header(const char *name, size_t namelen,
                                           const char *value, size_t valuelen) {
    switch(namelen) {
    case 2:
      if(!strncasecompare("te", name, namelen))
        return HEADERINST_FORWARD;
  
      return contains_trailers(value, valuelen) ?
             HEADERINST_TE_TRAILERS : HEADERINST_IGNORE;
    case 7:
      return strncasecompare("upgrade", name, namelen) ?
             HEADERINST_IGNORE : HEADERINST_FORWARD;
    case 10:
      return (strncasecompare("connection", name, namelen) ||
              strncasecompare("keep-alive", name, namelen)) ?
             HEADERINST_IGNORE : HEADERINST_FORWARD;
    case 16:
      return strncasecompare("proxy-connection", name, namelen) ?
             HEADERINST_IGNORE : HEADERINST_FORWARD;
    case 17:
      return strncasecompare("transfer-encoding", name, namelen) ?
             HEADERINST_IGNORE : HEADERINST_FORWARD;
    default:
      return HEADERINST_FORWARD;
    }
  }
  
  static ssize_t http2_send(struct connectdata *conn, int sockindex,
                            const void *mem, size_t len, CURLcode *err)
  {
    /*
     * Currently, we send request in this function, but this function is also
     * used to send request body. It would be nice to add dedicated function for
     * request.
     */
    int rv;
    struct http_conn *httpc = &conn->proto.httpc;
    struct HTTP *stream = conn->data->req.protop;
    nghttp2_nv *nva = NULL;
    size_t nheader;
    size_t i;
    size_t authority_idx;
    char *hdbuf = (char *)mem;
    char *end, *line_end;
    nghttp2_data_provider data_prd;
    int32_t stream_id;
    nghttp2_session *h2 = httpc->h2;
    nghttp2_priority_spec pri_spec;
  
    (void)sockindex;
  
    H2BUGF(infof(conn->data, "http2_send len=%zu\n", len));
  
    if(stream->stream_id != -1) {
      if(stream->close_handled) {
        infof(conn->data, "stream %d closed\n", stream->stream_id);
        *err = CURLE_HTTP2_STREAM;
        return -1;
      }
      else if(stream->closed) {
        return http2_handle_stream_close(conn, conn->data, stream, err);
      }
      /* If stream_id != -1, we have dispatched request HEADERS, and now
         are going to send or sending request body in DATA frame */
      stream->upload_mem = mem;
      stream->upload_len = len;
      rv = nghttp2_session_resume_data(h2, stream->stream_id);
      if(nghttp2_is_fatal(rv)) {
        *err = CURLE_SEND_ERROR;
        return -1;
      }
      rv = h2_session_send(conn->data, h2);
      if(nghttp2_is_fatal(rv)) {
        *err = CURLE_SEND_ERROR;
        return -1;
      }
      len -= stream->upload_len;
  
      /* Nullify here because we call nghttp2_session_send() and they
         might refer to the old buffer. */
      stream->upload_mem = NULL;
      stream->upload_len = 0;
  
      if(should_close_session(httpc)) {
        H2BUGF(infof(conn->data, "http2_send: nothing to do in this session\n"));
        *err = CURLE_HTTP2;
        return -1;
      }
  
      if(stream->upload_left) {
        /* we are sure that we have more data to send here.  Calling the
           following API will make nghttp2_session_want_write() return
           nonzero if remote window allows it, which then libcurl checks
           socket is writable or not.  See http2_perform_getsock(). */
        nghttp2_session_resume_data(h2, stream->stream_id);
      }
  
      H2BUGF(infof(conn->data, "http2_send returns %zu for stream %u\n", len,
                   stream->stream_id));
      return len;
    }
  
    /* Calculate number of headers contained in [mem, mem + len) */
    /* Here, we assume the curl http code generate *correct* HTTP header
       field block */
    nheader = 0;
    for(i = 1; i < len; ++i) {
      if(hdbuf[i] == '\n' && hdbuf[i - 1] == '\r') {
        ++nheader;
        ++i;
      }
    }
    if(nheader < 2)
      goto fail;
  
    /* We counted additional 2 \r\n in the first and last line. We need 3
       new headers: :method, :path and :scheme. Therefore we need one
       more space. */
    nheader += 1;
    nva = malloc(sizeof(nghttp2_nv) * nheader);
    if(nva == NULL) {
      *err = CURLE_OUT_OF_MEMORY;
      return -1;
    }
  
    /* Extract :method, :path from request line
       We do line endings with CRLF so checking for CR is enough */
    line_end = memchr(hdbuf, '\r', len);
    if(!line_end)
      goto fail;
  
    /* Method does not contain spaces */
    end = memchr(hdbuf, ' ', line_end - hdbuf);
    if(!end || end == hdbuf)
      goto fail;
    nva[0].name = (unsigned char *)":method";
    nva[0].namelen = strlen((char *)nva[0].name);
    nva[0].value = (unsigned char *)hdbuf;
    nva[0].valuelen = (size_t)(end - hdbuf);
    nva[0].flags = NGHTTP2_NV_FLAG_NONE;
    if(HEADER_OVERFLOW(nva[0])) {
      failf(conn->data, "Failed sending HTTP request: Header overflow");
      goto fail;
    }
  
    hdbuf = end + 1;
  
    /* Path may contain spaces so scan backwards */
    end = NULL;
    for(i = (size_t)(line_end - hdbuf); i; --i) {
      if(hdbuf[i - 1] == ' ') {
        end = &hdbuf[i - 1];
        break;
      }
    }
    if(!end || end == hdbuf)
      goto fail;
    nva[1].name = (unsigned char *)":path";
    nva[1].namelen = strlen((char *)nva[1].name);
    nva[1].value = (unsigned char *)hdbuf;
    nva[1].valuelen = (size_t)(end - hdbuf);
    nva[1].flags = NGHTTP2_NV_FLAG_NONE;
    if(HEADER_OVERFLOW(nva[1])) {
      failf(conn->data, "Failed sending HTTP request: Header overflow");
      goto fail;
    }
  
    nva[2].name = (unsigned char *)":scheme";
    nva[2].namelen = strlen((char *)nva[2].name);
    if(conn->handler->flags & PROTOPT_SSL)
      nva[2].value = (unsigned char *)"https";
    else
      nva[2].value = (unsigned char *)"http";
    nva[2].valuelen = strlen((char *)nva[2].value);
    nva[2].flags = NGHTTP2_NV_FLAG_NONE;
    if(HEADER_OVERFLOW(nva[2])) {
      failf(conn->data, "Failed sending HTTP request: Header overflow");
      goto fail;
    }
  
    authority_idx = 0;
    i = 3;
    while(i < nheader) {
      size_t hlen;
  
      hdbuf = line_end + 2;
  
      /* check for next CR, but only within the piece of data left in the given
         buffer */
      line_end = memchr(hdbuf, '\r', len - (hdbuf - (char *)mem));
      if(!line_end || (line_end == hdbuf))
        goto fail;
  
      /* header continuation lines are not supported */
      if(*hdbuf == ' ' || *hdbuf == '\t')
        goto fail;
  
      for(end = hdbuf; end < line_end && *end != ':'; ++end)
        ;
      if(end == hdbuf || end == line_end)
        goto fail;
      hlen = end - hdbuf;
  
      if(hlen == 4 && strncasecompare("host", hdbuf, 4)) {
        authority_idx = i;
        nva[i].name = (unsigned char *)":authority";
        nva[i].namelen = strlen((char *)nva[i].name);
      }
      else {
        nva[i].namelen = (size_t)(end - hdbuf);
        /* Lower case the header name for HTTP/2 */
        Curl_strntolower((char *)hdbuf, hdbuf, nva[i].namelen);
        nva[i].name = (unsigned char *)hdbuf;
      }
      hdbuf = end + 1;
      while(*hdbuf == ' ' || *hdbuf == '\t')
        ++hdbuf;
      end = line_end;
  
      switch(inspect_header((const char *)nva[i].name, nva[i].namelen, hdbuf,
                            end - hdbuf)) {
      case HEADERINST_IGNORE:
        /* skip header fields prohibited by HTTP/2 specification. */
        --nheader;
        continue;
      case HEADERINST_TE_TRAILERS:
        nva[i].value = (uint8_t*)"trailers";
        nva[i].valuelen = sizeof("trailers") - 1;
        break;
      default:
        nva[i].value = (unsigned char *)hdbuf;
        nva[i].valuelen = (size_t)(end - hdbuf);
      }
  
      nva[i].flags = NGHTTP2_NV_FLAG_NONE;
      if(HEADER_OVERFLOW(nva[i])) {
        failf(conn->data, "Failed sending HTTP request: Header overflow");
        goto fail;
      }
      ++i;
    }
  
    /* :authority must come before non-pseudo header fields */
    if(authority_idx != 0 && authority_idx != AUTHORITY_DST_IDX) {
      nghttp2_nv authority = nva[authority_idx];
      for(i = authority_idx; i > AUTHORITY_DST_IDX; --i) {
        nva[i] = nva[i - 1];
      }
      nva[i] = authority;
    }
  
    /* Warn stream may be rejected if cumulative length of headers is too large.
       It appears nghttp2 will not send a header frame larger than 64KB. */
  #define MAX_ACC 60000  /* <64KB to account for some overhead */
    {
      size_t acc = 0;
  
      for(i = 0; i < nheader; ++i) {
        acc += nva[i].namelen + nva[i].valuelen;
  
        H2BUGF(infof(conn->data, "h2 header: %.*s:%.*s\n",
                     nva[i].namelen, nva[i].name,
                     nva[i].valuelen, nva[i].value));
      }
  
      if(acc > MAX_ACC) {
        infof(conn->data, "http2_send: Warning: The cumulative length of all "
              "headers exceeds %zu bytes and that could cause the "
              "stream to be rejected.\n", MAX_ACC);
      }
    }
  
    h2_pri_spec(conn->data, &pri_spec);
  
    switch(conn->data->set.httpreq) {
    case HTTPREQ_POST:
    case HTTPREQ_POST_FORM:
    case HTTPREQ_POST_MIME:
    case HTTPREQ_PUT:
      if(conn->data->state.infilesize != -1)
        stream->upload_left = conn->data->state.infilesize;
      else
        /* data sending without specifying the data amount up front */
        stream->upload_left = -1; /* unknown, but not zero */
  
      data_prd.read_callback = data_source_read_callback;
      data_prd.source.ptr = NULL;
      stream_id = nghttp2_submit_request(h2, &pri_spec, nva, nheader,
                                         &data_prd, conn->data);
      break;
    default:
      stream_id = nghttp2_submit_request(h2, &pri_spec, nva, nheader,
                                         NULL, conn->data);
    }
  
    Curl_safefree(nva);
  
    if(stream_id < 0) {
      H2BUGF(infof(conn->data, "http2_send() send error\n"));
      *err = CURLE_SEND_ERROR;
      return -1;
    }
  
    infof(conn->data, "Using Stream ID: %x (easy handle %p)\n",
          stream_id, (void *)conn->data);
    stream->stream_id = stream_id;
  
    /* this does not call h2_session_send() since there can not have been any
     * priority upodate since the nghttp2_submit_request() call above */
    rv = nghttp2_session_send(h2);
  
    if(rv != 0) {
      *err = CURLE_SEND_ERROR;
      return -1;
    }
  
    if(should_close_session(httpc)) {
      H2BUGF(infof(conn->data, "http2_send: nothing to do in this session\n"));
      *err = CURLE_HTTP2;
      return -1;
    }
  
    /* If whole HEADERS frame was sent off to the underlying socket, the nghttp2
       library calls data_source_read_callback. But only it found that no data
       available, so it deferred the DATA transmission. Which means that
       nghttp2_session_want_write() returns 0 on http2_perform_getsock(), which
       results that no writable socket check is performed. To workaround this,
       we issue nghttp2_session_resume_data() here to bring back DATA
       transmission from deferred state. */
    nghttp2_session_resume_data(h2, stream->stream_id);
  
    return len;
  
  fail:
    free(nva);
    *err = CURLE_SEND_ERROR;
    return -1;
  }
  
  CURLcode Curl_http2_setup(struct connectdata *conn)
  {
    CURLcode result;
    struct http_conn *httpc = &conn->proto.httpc;
    struct HTTP *stream = conn->data->req.protop;
  
    stream->stream_id = -1;
  
    if(!stream->header_recvbuf) {
      stream->header_recvbuf = Curl_add_buffer_init();
      if(!stream->header_recvbuf)
        return CURLE_OUT_OF_MEMORY;
    }
  
    if((conn->handler == &Curl_handler_http2_ssl) ||
       (conn->handler == &Curl_handler_http2))
      return CURLE_OK; /* already done */
  
    if(conn->handler->flags & PROTOPT_SSL)
      conn->handler = &Curl_handler_http2_ssl;
    else
      conn->handler = &Curl_handler_http2;
  
    result = http2_init(conn);
    if(result) {
      Curl_add_buffer_free(&stream->header_recvbuf);
      return result;
    }
  
    infof(conn->data, "Using HTTP2, server supports multi-use\n");
    stream->upload_left = 0;
    stream->upload_mem = NULL;
    stream->upload_len = 0;
  
    httpc->inbuflen = 0;
    httpc->nread_inbuf = 0;
  
    httpc->pause_stream_id = 0;
    httpc->drain_total = 0;
  
    conn->bits.multiplex = TRUE; /* at least potentially multiplexed */
    conn->httpversion = 20;
    conn->bundle->multiuse = BUNDLE_MULTIPLEX;
  
    infof(conn->data, "Connection state changed (HTTP/2 confirmed)\n");
    multi_connchanged(conn->data->multi);
  
    return CURLE_OK;
  }
  
  CURLcode Curl_http2_switched(struct connectdata *conn,
                               const char *mem, size_t nread)
  {
    CURLcode result;
    struct http_conn *httpc = &conn->proto.httpc;
    int rv;
    ssize_t nproc;
    struct Curl_easy *data = conn->data;
    struct HTTP *stream = conn->data->req.protop;
  
    result = Curl_http2_setup(conn);
    if(result)
      return result;
  
    httpc->recv_underlying = conn->recv[FIRSTSOCKET];
    httpc->send_underlying = conn->send[FIRSTSOCKET];
    conn->recv[FIRSTSOCKET] = http2_recv;
    conn->send[FIRSTSOCKET] = http2_send;
  
    if(conn->data->req.upgr101 == UPGR101_RECEIVED) {
      /* stream 1 is opened implicitly on upgrade */
      stream->stream_id = 1;
      /* queue SETTINGS frame (again) */
      rv = nghttp2_session_upgrade(httpc->h2, httpc->binsettings,
                                   httpc->binlen, NULL);
      if(rv != 0) {
        failf(data, "nghttp2_session_upgrade() failed: %s(%d)",
              nghttp2_strerror(rv), rv);
        return CURLE_HTTP2;
      }
  
      rv = nghttp2_session_set_stream_user_data(httpc->h2,
                                                stream->stream_id,
                                                data);
      if(rv) {
        infof(data, "http/2: failed to set user_data for stream %d!\n",
              stream->stream_id);
        DEBUGASSERT(0);
      }
    }
    else {
      populate_settings(conn, httpc);
  
      /* stream ID is unknown at this point */
      stream->stream_id = -1;
      rv = nghttp2_submit_settings(httpc->h2, NGHTTP2_FLAG_NONE,
                                   httpc->local_settings,
                                   httpc->local_settings_num);
      if(rv != 0) {
        failf(data, "nghttp2_submit_settings() failed: %s(%d)",
              nghttp2_strerror(rv), rv);
        return CURLE_HTTP2;
      }
    }
  
  #ifdef NGHTTP2_HAS_SET_LOCAL_WINDOW_SIZE
    rv = nghttp2_session_set_local_window_size(httpc->h2, NGHTTP2_FLAG_NONE, 0,
                                               HTTP2_HUGE_WINDOW_SIZE);
    if(rv != 0) {
      failf(data, "nghttp2_session_set_local_window_size() failed: %s(%d)",
            nghttp2_strerror(rv), rv);
      return CURLE_HTTP2;
    }
  #endif
  
    /* we are going to copy mem to httpc->inbuf.  This is required since
       mem is part of buffer pointed by stream->mem, and callbacks
       called by nghttp2_session_mem_recv() will write stream specific
       data into stream->mem, overwriting data already there. */
    if(H2_BUFSIZE < nread) {
      failf(data, "connection buffer size is too small to store data following "
                  "HTTP Upgrade response header: buflen=%zu, datalen=%zu",
            H2_BUFSIZE, nread);
      return CURLE_HTTP2;
    }
  
    infof(conn->data, "Copying HTTP/2 data in stream buffer to connection buffer"
                      " after upgrade: len=%zu\n",
          nread);
  
    if(nread)
      memcpy(httpc->inbuf, mem, nread);
    httpc->inbuflen = nread;
  
    nproc = nghttp2_session_mem_recv(httpc->h2, (const uint8_t *)httpc->inbuf,
                                     httpc->inbuflen);
  
    if(nghttp2_is_fatal((int)nproc)) {
      failf(data, "nghttp2_session_mem_recv() failed: %s(%d)",
            nghttp2_strerror((int)nproc), (int)nproc);
      return CURLE_HTTP2;
    }
  
    H2BUGF(infof(data, "nghttp2_session_mem_recv() returns %zd\n", nproc));
  
    if((ssize_t)nread == nproc) {
      httpc->inbuflen = 0;
      httpc->nread_inbuf = 0;
    }
    else {
      httpc->nread_inbuf += nproc;
    }
  
    /* Try to send some frames since we may read SETTINGS already. */
    rv = h2_session_send(data, httpc->h2);
  
    if(rv != 0) {
      failf(data, "nghttp2_session_send() failed: %s(%d)",
            nghttp2_strerror(rv), rv);
      return CURLE_HTTP2;
    }
  
    if(should_close_session(httpc)) {
      H2BUGF(infof(data,
                   "nghttp2_session_send(): nothing to do in this session\n"));
      return CURLE_HTTP2;
    }
  
    return CURLE_OK;
  }
  
  CURLcode Curl_http2_add_child(struct Curl_easy *parent,
                                struct Curl_easy *child,
                                bool exclusive)
  {
    if(parent) {
      struct Curl_http2_dep **tail;
      struct Curl_http2_dep *dep = calloc(1, sizeof(struct Curl_http2_dep));
      if(!dep)
        return CURLE_OUT_OF_MEMORY;
      dep->data = child;
  
      if(parent->set.stream_dependents && exclusive) {
        struct Curl_http2_dep *node = parent->set.stream_dependents;
        while(node) {
          node->data->set.stream_depends_on = child;
          node = node->next;
        }
  
        tail = &child->set.stream_dependents;
        while(*tail)
          tail = &(*tail)->next;
  
        DEBUGASSERT(!*tail);
        *tail = parent->set.stream_dependents;
        parent->set.stream_dependents = 0;
      }
  
      tail = &parent->set.stream_dependents;
      while(*tail) {
        (*tail)->data->set.stream_depends_e = FALSE;
        tail = &(*tail)->next;
      }
  
      DEBUGASSERT(!*tail);
      *tail = dep;
    }
  
    child->set.stream_depends_on = parent;
    child->set.stream_depends_e = exclusive;
    return CURLE_OK;
  }
  
  void Curl_http2_remove_child(struct Curl_easy *parent, struct Curl_easy *child)
  {
    struct Curl_http2_dep *last = 0;
    struct Curl_http2_dep *data = parent->set.stream_dependents;
    DEBUGASSERT(child->set.stream_depends_on == parent);
  
    while(data && data->data != child) {
      last = data;
      data = data->next;
    }
  
    DEBUGASSERT(data);
  
    if(data) {
      if(last) {
        last->next = data->next;
      }
      else {
        parent->set.stream_dependents = data->next;
      }
      free(data);
    }
  
    child->set.stream_depends_on = 0;
    child->set.stream_depends_e = FALSE;
  }
  
  void Curl_http2_cleanup_dependencies(struct Curl_easy *data)
  {
    while(data->set.stream_dependents) {
      struct Curl_easy *tmp = data->set.stream_dependents->data;
      Curl_http2_remove_child(data, tmp);
      if(data->set.stream_depends_on)
        Curl_http2_add_child(data->set.stream_depends_on, tmp, FALSE);
    }
  
    if(data->set.stream_depends_on)
      Curl_http2_remove_child(data->set.stream_depends_on, data);
  }
  
  /* Only call this function for a transfer that already got a HTTP/2
     CURLE_HTTP2_STREAM error! */
  bool Curl_h2_http_1_1_error(struct connectdata *conn)
  {
    struct http_conn *httpc = &conn->proto.httpc;
    return (httpc->error_code == NGHTTP2_HTTP_1_1_REQUIRED);
  }
  
  #else /* !USE_NGHTTP2 */
  
  /* Satisfy external references even if http2 is not compiled in. */
  #include <curl/curl.h>
  
  char *curl_pushheader_bynum(struct curl_pushheaders *h, size_t num)
  {
    (void) h;
    (void) num;
    return NULL;
  }
  
  char *curl_pushheader_byname(struct curl_pushheaders *h, const char *header)
  {
    (void) h;
    (void) header;
    return NULL;
  }
  
  #endif /* USE_NGHTTP2 */
  