1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
use std::{
    convert::Infallible,
    future::Future,
    marker::PhantomData,
    pin::Pin,
    task::{Context, Poll},
    time::Duration,
};

use crate::rt::{Read, Write};
use bytes::Bytes;
use futures_channel::mpsc::{Receiver, Sender};
use futures_channel::{mpsc, oneshot};
use futures_util::future::{Either, FusedFuture, FutureExt as _};
use futures_util::ready;
use futures_util::stream::{StreamExt as _, StreamFuture};
use h2::client::{Builder, Connection, SendRequest};
use h2::SendStream;
use http::{Method, StatusCode};
use pin_project_lite::pin_project;

use super::ping::{Ponger, Recorder};
use super::{ping, H2Upgraded, PipeToSendStream, SendBuf};
use crate::body::{Body, Incoming as IncomingBody};
use crate::client::dispatch::{Callback, SendWhen, TrySendError};
use crate::common::io::Compat;
use crate::common::time::Time;
use crate::ext::Protocol;
use crate::headers;
use crate::proto::h2::UpgradedSendStream;
use crate::proto::Dispatched;
use crate::rt::bounds::Http2ClientConnExec;
use crate::upgrade::Upgraded;
use crate::{Request, Response};
use h2::client::ResponseFuture;

type ClientRx<B> = crate::client::dispatch::Receiver<Request<B>, Response<IncomingBody>>;

///// An mpsc channel is used to help notify the `Connection` task when *all*
///// other handles to it have been dropped, so that it can shutdown.
type ConnDropRef = mpsc::Sender<Infallible>;

///// A oneshot channel watches the `Connection` task, and when it completes,
///// the "dispatch" task will be notified and can shutdown sooner.
type ConnEof = oneshot::Receiver<Infallible>;

// Our defaults are chosen for the "majority" case, which usually are not
// resource constrained, and so the spec default of 64kb can be too limiting
// for performance.
const DEFAULT_CONN_WINDOW: u32 = 1024 * 1024 * 5; // 5mb
const DEFAULT_STREAM_WINDOW: u32 = 1024 * 1024 * 2; // 2mb
const DEFAULT_MAX_FRAME_SIZE: u32 = 1024 * 16; // 16kb
const DEFAULT_MAX_SEND_BUF_SIZE: usize = 1024 * 1024; // 1mb
const DEFAULT_MAX_HEADER_LIST_SIZE: u32 = 1024 * 16; // 16kb

// The maximum number of concurrent streams that the client is allowed to open
// before it receives the initial SETTINGS frame from the server.
// This default value is derived from what the HTTP/2 spec recommends as the
// minimum value that endpoints advertise to their peers. It means that using
// this value will minimize the chance of the failure where the local endpoint
// attempts to open too many streams and gets rejected by the remote peer with
// the `REFUSED_STREAM` error.
const DEFAULT_INITIAL_MAX_SEND_STREAMS: usize = 100;

#[derive(Clone, Debug)]
pub(crate) struct Config {
    pub(crate) adaptive_window: bool,
    pub(crate) initial_conn_window_size: u32,
    pub(crate) initial_stream_window_size: u32,
    pub(crate) initial_max_send_streams: usize,
    pub(crate) max_frame_size: u32,
    pub(crate) max_header_list_size: u32,
    pub(crate) keep_alive_interval: Option<Duration>,
    pub(crate) keep_alive_timeout: Duration,
    pub(crate) keep_alive_while_idle: bool,
    pub(crate) max_concurrent_reset_streams: Option<usize>,
    pub(crate) max_send_buffer_size: usize,
    pub(crate) max_pending_accept_reset_streams: Option<usize>,
}

impl Default for Config {
    fn default() -> Config {
        Config {
            adaptive_window: false,
            initial_conn_window_size: DEFAULT_CONN_WINDOW,
            initial_stream_window_size: DEFAULT_STREAM_WINDOW,
            initial_max_send_streams: DEFAULT_INITIAL_MAX_SEND_STREAMS,
            max_frame_size: DEFAULT_MAX_FRAME_SIZE,
            max_header_list_size: DEFAULT_MAX_HEADER_LIST_SIZE,
            keep_alive_interval: None,
            keep_alive_timeout: Duration::from_secs(20),
            keep_alive_while_idle: false,
            max_concurrent_reset_streams: None,
            max_send_buffer_size: DEFAULT_MAX_SEND_BUF_SIZE,
            max_pending_accept_reset_streams: None,
        }
    }
}

fn new_builder(config: &Config) -> Builder {
    let mut builder = Builder::default();
    builder
        .initial_max_send_streams(config.initial_max_send_streams)
        .initial_window_size(config.initial_stream_window_size)
        .initial_connection_window_size(config.initial_conn_window_size)
        .max_frame_size(config.max_frame_size)
        .max_header_list_size(config.max_header_list_size)
        .max_send_buffer_size(config.max_send_buffer_size)
        .enable_push(false);
    if let Some(max) = config.max_concurrent_reset_streams {
        builder.max_concurrent_reset_streams(max);
    }
    if let Some(max) = config.max_pending_accept_reset_streams {
        builder.max_pending_accept_reset_streams(max);
    }
    builder
}

fn new_ping_config(config: &Config) -> ping::Config {
    ping::Config {
        bdp_initial_window: if config.adaptive_window {
            Some(config.initial_stream_window_size)
        } else {
            None
        },
        keep_alive_interval: config.keep_alive_interval,
        keep_alive_timeout: config.keep_alive_timeout,
        keep_alive_while_idle: config.keep_alive_while_idle,
    }
}

pub(crate) async fn handshake<T, B, E>(
    io: T,
    req_rx: ClientRx<B>,
    config: &Config,
    mut exec: E,
    timer: Time,
) -> crate::Result<ClientTask<B, E, T>>
where
    T: Read + Write + Unpin,
    B: Body + 'static,
    B::Data: Send + 'static,
    E: Http2ClientConnExec<B, T> + Unpin,
    B::Error: Into<Box<dyn std::error::Error + Send + Sync>>,
{
    let (h2_tx, mut conn) = new_builder(config)
        .handshake::<_, SendBuf<B::Data>>(Compat::new(io))
        .await
        .map_err(crate::Error::new_h2)?;

    // An mpsc channel is used entirely to detect when the
    // 'Client' has been dropped. This is to get around a bug
    // in h2 where dropping all SendRequests won't notify a
    // parked Connection.
    let (conn_drop_ref, rx) = mpsc::channel(1);
    let (cancel_tx, conn_eof) = oneshot::channel();

    let conn_drop_rx = rx.into_future();

    let ping_config = new_ping_config(config);

    let (conn, ping) = if ping_config.is_enabled() {
        let pp = conn.ping_pong().expect("conn.ping_pong");
        let (recorder, ponger) = ping::channel(pp, ping_config, timer);

        let conn: Conn<_, B> = Conn::new(ponger, conn);
        (Either::Left(conn), recorder)
    } else {
        (Either::Right(conn), ping::disabled())
    };
    let conn: ConnMapErr<T, B> = ConnMapErr {
        conn,
        is_terminated: false,
    };

    exec.execute_h2_future(H2ClientFuture::Task {
        task: ConnTask::new(conn, conn_drop_rx, cancel_tx),
    });

    Ok(ClientTask {
        ping,
        conn_drop_ref,
        conn_eof,
        executor: exec,
        h2_tx,
        req_rx,
        fut_ctx: None,
        marker: PhantomData,
    })
}

pin_project! {
    struct Conn<T, B>
    where
        B: Body,
    {
        #[pin]
        ponger: Ponger,
        #[pin]
        conn: Connection<Compat<T>, SendBuf<<B as Body>::Data>>,
    }
}

impl<T, B> Conn<T, B>
where
    B: Body,
    T: Read + Write + Unpin,
{
    fn new(ponger: Ponger, conn: Connection<Compat<T>, SendBuf<<B as Body>::Data>>) -> Self {
        Conn { ponger, conn }
    }
}

impl<T, B> Future for Conn<T, B>
where
    B: Body,
    T: Read + Write + Unpin,
{
    type Output = Result<(), h2::Error>;

    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        let mut this = self.project();
        match this.ponger.poll(cx) {
            Poll::Ready(ping::Ponged::SizeUpdate(wnd)) => {
                this.conn.set_target_window_size(wnd);
                this.conn.set_initial_window_size(wnd)?;
            }
            Poll::Ready(ping::Ponged::KeepAliveTimedOut) => {
                debug!("connection keep-alive timed out");
                return Poll::Ready(Ok(()));
            }
            Poll::Pending => {}
        }

        Pin::new(&mut this.conn).poll(cx)
    }
}

pin_project! {
    struct ConnMapErr<T, B>
    where
        B: Body,
        T: Read,
        T: Write,
        T: Unpin,
    {
        #[pin]
        conn: Either<Conn<T, B>, Connection<Compat<T>, SendBuf<<B as Body>::Data>>>,
        #[pin]
        is_terminated: bool,
    }
}

impl<T, B> Future for ConnMapErr<T, B>
where
    B: Body,
    T: Read + Write + Unpin,
{
    type Output = Result<(), ()>;

    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        let mut this = self.project();

        if *this.is_terminated {
            return Poll::Pending;
        }
        let polled = this.conn.poll(cx);
        if polled.is_ready() {
            *this.is_terminated = true;
        }
        polled.map_err(|_e| {
            debug!(error = %_e, "connection error");
        })
    }
}

impl<T, B> FusedFuture for ConnMapErr<T, B>
where
    B: Body,
    T: Read + Write + Unpin,
{
    fn is_terminated(&self) -> bool {
        self.is_terminated
    }
}

pin_project! {
    pub struct ConnTask<T, B>
    where
        B: Body,
        T: Read,
        T: Write,
        T: Unpin,
    {
        #[pin]
        drop_rx: StreamFuture<Receiver<Infallible>>,
        #[pin]
        cancel_tx: Option<oneshot::Sender<Infallible>>,
        #[pin]
        conn: ConnMapErr<T, B>,
    }
}

impl<T, B> ConnTask<T, B>
where
    B: Body,
    T: Read + Write + Unpin,
{
    fn new(
        conn: ConnMapErr<T, B>,
        drop_rx: StreamFuture<Receiver<Infallible>>,
        cancel_tx: oneshot::Sender<Infallible>,
    ) -> Self {
        Self {
            drop_rx,
            cancel_tx: Some(cancel_tx),
            conn,
        }
    }
}

impl<T, B> Future for ConnTask<T, B>
where
    B: Body,
    T: Read + Write + Unpin,
{
    type Output = ();

    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        let mut this = self.project();

        if !this.conn.is_terminated() && this.conn.poll_unpin(cx).is_ready() {
            // ok or err, the `conn` has finished.
            return Poll::Ready(());
        }

        if !this.drop_rx.is_terminated() && this.drop_rx.poll_unpin(cx).is_ready() {
            // mpsc has been dropped, hopefully polling
            // the connection some more should start shutdown
            // and then close.
            trace!("send_request dropped, starting conn shutdown");
            drop(this.cancel_tx.take().expect("ConnTask Future polled twice"));
        }

        Poll::Pending
    }
}

pin_project! {
    #[project = H2ClientFutureProject]
    pub enum H2ClientFuture<B, T>
    where
        B: http_body::Body,
        B: 'static,
        B::Error: Into<Box<dyn std::error::Error + Send + Sync>>,
        T: Read,
        T: Write,
        T: Unpin,
    {
        Pipe {
            #[pin]
            pipe: PipeMap<B>,
        },
        Send {
            #[pin]
            send_when: SendWhen<B>,
        },
        Task {
            #[pin]
            task: ConnTask<T, B>,
        },
    }
}

impl<B, T> Future for H2ClientFuture<B, T>
where
    B: http_body::Body + 'static,
    B::Error: Into<Box<dyn std::error::Error + Send + Sync>>,
    T: Read + Write + Unpin,
{
    type Output = ();

    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> std::task::Poll<Self::Output> {
        let this = self.project();

        match this {
            H2ClientFutureProject::Pipe { pipe } => pipe.poll(cx),
            H2ClientFutureProject::Send { send_when } => send_when.poll(cx),
            H2ClientFutureProject::Task { task } => task.poll(cx),
        }
    }
}

struct FutCtx<B>
where
    B: Body,
{
    is_connect: bool,
    eos: bool,
    fut: ResponseFuture,
    body_tx: SendStream<SendBuf<B::Data>>,
    body: B,
    cb: Callback<Request<B>, Response<IncomingBody>>,
}

impl<B: Body> Unpin for FutCtx<B> {}

pub(crate) struct ClientTask<B, E, T>
where
    B: Body,
    E: Unpin,
{
    ping: ping::Recorder,
    conn_drop_ref: ConnDropRef,
    conn_eof: ConnEof,
    executor: E,
    h2_tx: SendRequest<SendBuf<B::Data>>,
    req_rx: ClientRx<B>,
    fut_ctx: Option<FutCtx<B>>,
    marker: PhantomData<T>,
}

impl<B, E, T> ClientTask<B, E, T>
where
    B: Body + 'static,
    E: Http2ClientConnExec<B, T> + Unpin,
    B::Error: Into<Box<dyn std::error::Error + Send + Sync>>,
    T: Read + Write + Unpin,
{
    pub(crate) fn is_extended_connect_protocol_enabled(&self) -> bool {
        self.h2_tx.is_extended_connect_protocol_enabled()
    }
}

pin_project! {
    pub struct PipeMap<S>
    where
        S: Body,
    {
        #[pin]
        pipe: PipeToSendStream<S>,
        #[pin]
        conn_drop_ref: Option<Sender<Infallible>>,
        #[pin]
        ping: Option<Recorder>,
    }
}

impl<B> Future for PipeMap<B>
where
    B: http_body::Body,
    B::Error: Into<Box<dyn std::error::Error + Send + Sync>>,
{
    type Output = ();

    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> std::task::Poll<Self::Output> {
        let mut this = self.project();

        match this.pipe.poll_unpin(cx) {
            Poll::Ready(result) => {
                if let Err(_e) = result {
                    debug!("client request body error: {}", _e);
                }
                drop(this.conn_drop_ref.take().expect("Future polled twice"));
                drop(this.ping.take().expect("Future polled twice"));
                return Poll::Ready(());
            }
            Poll::Pending => (),
        };
        Poll::Pending
    }
}

impl<B, E, T> ClientTask<B, E, T>
where
    B: Body + 'static + Unpin,
    B::Data: Send,
    E: Http2ClientConnExec<B, T> + Unpin,
    B::Error: Into<Box<dyn std::error::Error + Send + Sync>>,
    T: Read + Write + Unpin,
{
    fn poll_pipe(&mut self, f: FutCtx<B>, cx: &mut Context<'_>) {
        let ping = self.ping.clone();

        let send_stream = if !f.is_connect {
            if !f.eos {
                let mut pipe = PipeToSendStream::new(f.body, f.body_tx);

                // eagerly see if the body pipe is ready and
                // can thus skip allocating in the executor
                match Pin::new(&mut pipe).poll(cx) {
                    Poll::Ready(_) => (),
                    Poll::Pending => {
                        let conn_drop_ref = self.conn_drop_ref.clone();
                        // keep the ping recorder's knowledge of an
                        // "open stream" alive while this body is
                        // still sending...
                        let ping = ping.clone();

                        let pipe = PipeMap {
                            pipe,
                            conn_drop_ref: Some(conn_drop_ref),
                            ping: Some(ping),
                        };
                        // Clear send task
                        self.executor
                            .execute_h2_future(H2ClientFuture::Pipe { pipe });
                    }
                }
            }

            None
        } else {
            Some(f.body_tx)
        };

        self.executor.execute_h2_future(H2ClientFuture::Send {
            send_when: SendWhen {
                when: ResponseFutMap {
                    fut: f.fut,
                    ping: Some(ping),
                    send_stream: Some(send_stream),
                },
                call_back: Some(f.cb),
            },
        });
    }
}

pin_project! {
    pub(crate) struct ResponseFutMap<B>
    where
        B: Body,
        B: 'static,
    {
        #[pin]
        fut: ResponseFuture,
        #[pin]
        ping: Option<Recorder>,
        #[pin]
        send_stream: Option<Option<SendStream<SendBuf<<B as Body>::Data>>>>,
    }
}

impl<B> Future for ResponseFutMap<B>
where
    B: Body + 'static,
{
    type Output = Result<Response<crate::body::Incoming>, (crate::Error, Option<Request<B>>)>;

    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        let mut this = self.project();

        let result = ready!(this.fut.poll(cx));

        let ping = this.ping.take().expect("Future polled twice");
        let send_stream = this.send_stream.take().expect("Future polled twice");

        match result {
            Ok(res) => {
                // record that we got the response headers
                ping.record_non_data();

                let content_length = headers::content_length_parse_all(res.headers());
                if let (Some(mut send_stream), StatusCode::OK) = (send_stream, res.status()) {
                    if content_length.map_or(false, |len| len != 0) {
                        warn!("h2 connect response with non-zero body not supported");

                        send_stream.send_reset(h2::Reason::INTERNAL_ERROR);
                        return Poll::Ready(Err((
                            crate::Error::new_h2(h2::Reason::INTERNAL_ERROR.into()),
                            None::<Request<B>>,
                        )));
                    }
                    let (parts, recv_stream) = res.into_parts();
                    let mut res = Response::from_parts(parts, IncomingBody::empty());

                    let (pending, on_upgrade) = crate::upgrade::pending();
                    let io = H2Upgraded {
                        ping,
                        send_stream: unsafe { UpgradedSendStream::new(send_stream) },
                        recv_stream,
                        buf: Bytes::new(),
                    };
                    let upgraded = Upgraded::new(io, Bytes::new());

                    pending.fulfill(upgraded);
                    res.extensions_mut().insert(on_upgrade);

                    Poll::Ready(Ok(res))
                } else {
                    let res = res.map(|stream| {
                        let ping = ping.for_stream(&stream);
                        IncomingBody::h2(stream, content_length.into(), ping)
                    });
                    Poll::Ready(Ok(res))
                }
            }
            Err(err) => {
                ping.ensure_not_timed_out().map_err(|e| (e, None))?;

                debug!("client response error: {}", err);
                Poll::Ready(Err((crate::Error::new_h2(err), None::<Request<B>>)))
            }
        }
    }
}

impl<B, E, T> Future for ClientTask<B, E, T>
where
    B: Body + 'static + Unpin,
    B::Data: Send,
    B::Error: Into<Box<dyn std::error::Error + Send + Sync>>,
    E: Http2ClientConnExec<B, T> + Unpin,
    T: Read + Write + Unpin,
{
    type Output = crate::Result<Dispatched>;

    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        loop {
            match ready!(self.h2_tx.poll_ready(cx)) {
                Ok(()) => (),
                Err(err) => {
                    self.ping.ensure_not_timed_out()?;
                    return if err.reason() == Some(::h2::Reason::NO_ERROR) {
                        trace!("connection gracefully shutdown");
                        Poll::Ready(Ok(Dispatched::Shutdown))
                    } else {
                        Poll::Ready(Err(crate::Error::new_h2(err)))
                    };
                }
            };

            // If we were waiting on pending open
            // continue where we left off.
            if let Some(f) = self.fut_ctx.take() {
                self.poll_pipe(f, cx);
                continue;
            }

            match self.req_rx.poll_recv(cx) {
                Poll::Ready(Some((req, cb))) => {
                    // check that future hasn't been canceled already
                    if cb.is_canceled() {
                        trace!("request callback is canceled");
                        continue;
                    }
                    let (head, body) = req.into_parts();
                    let mut req = ::http::Request::from_parts(head, ());
                    super::strip_connection_headers(req.headers_mut(), true);
                    if let Some(len) = body.size_hint().exact() {
                        if len != 0 || headers::method_has_defined_payload_semantics(req.method()) {
                            headers::set_content_length_if_missing(req.headers_mut(), len);
                        }
                    }

                    let is_connect = req.method() == Method::CONNECT;
                    let eos = body.is_end_stream();

                    if is_connect
                        && headers::content_length_parse_all(req.headers())
                            .map_or(false, |len| len != 0)
                    {
                        warn!("h2 connect request with non-zero body not supported");
                        cb.send(Err(TrySendError {
                            error: crate::Error::new_h2(h2::Reason::INTERNAL_ERROR.into()),
                            message: None,
                        }));
                        continue;
                    }

                    if let Some(protocol) = req.extensions_mut().remove::<Protocol>() {
                        req.extensions_mut().insert(protocol.into_inner());
                    }

                    let (fut, body_tx) = match self.h2_tx.send_request(req, !is_connect && eos) {
                        Ok(ok) => ok,
                        Err(err) => {
                            debug!("client send request error: {}", err);
                            cb.send(Err(TrySendError {
                                error: crate::Error::new_h2(err),
                                message: None,
                            }));
                            continue;
                        }
                    };

                    let f = FutCtx {
                        is_connect,
                        eos,
                        fut,
                        body_tx,
                        body,
                        cb,
                    };

                    // Check poll_ready() again.
                    // If the call to send_request() resulted in the new stream being pending open
                    // we have to wait for the open to complete before accepting new requests.
                    match self.h2_tx.poll_ready(cx) {
                        Poll::Pending => {
                            // Save Context
                            self.fut_ctx = Some(f);
                            return Poll::Pending;
                        }
                        Poll::Ready(Ok(())) => (),
                        Poll::Ready(Err(err)) => {
                            f.cb.send(Err(TrySendError {
                                error: crate::Error::new_h2(err),
                                message: None,
                            }));
                            continue;
                        }
                    }
                    self.poll_pipe(f, cx);
                    continue;
                }

                Poll::Ready(None) => {
                    trace!("client::dispatch::Sender dropped");
                    return Poll::Ready(Ok(Dispatched::Shutdown));
                }

                Poll::Pending => match ready!(Pin::new(&mut self.conn_eof).poll(cx)) {
                    Ok(never) => match never {},
                    Err(_conn_is_eof) => {
                        trace!("connection task is closed, closing dispatch task");
                        return Poll::Ready(Ok(Dispatched::Shutdown));
                    }
                },
            }
        }
    }
}