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// Copyright (c) 2018-2019 Parity Technologies (UK) Ltd.
//
// Licensed under the Apache License, Version 2.0 or MIT license, at your option.
//
// A copy of the Apache License, Version 2.0 is included in the software as
// LICENSE-APACHE and a copy of the MIT license is included in the software
// as LICENSE-MIT. You may also obtain a copy of the Apache License, Version 2.0
// at https://www.apache.org/licenses/LICENSE-2.0 and a copy of the MIT license
// at https://opensource.org/licenses/MIT.
use crate::frame::header::ACK;
use crate::{
chunks::Chunks,
connection::{self, StreamCommand},
frame::{
header::{Data, Header, StreamId, WindowUpdate},
Frame,
},
Config, WindowUpdateMode, DEFAULT_CREDIT,
};
use futures::{
channel::mpsc,
future::Either,
io::{AsyncRead, AsyncWrite},
ready, SinkExt,
};
use parking_lot::{Mutex, MutexGuard};
use std::convert::TryInto;
use std::{
fmt, io,
pin::Pin,
sync::Arc,
task::{Context, Poll, Waker},
};
/// The state of a Yamux stream.
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub enum State {
/// Open bidirectionally.
Open {
/// Whether the stream is acknowledged.
///
/// For outbound streams, this tracks whether the remote has acknowledged our stream.
/// For inbound streams, this tracks whether we have acknowledged the stream to the remote.
///
/// This starts out with `false` and is set to `true` when we receive or send an `ACK` flag for this stream.
/// We may also directly transition:
/// - from `Open` to `RecvClosed` if the remote immediately sends `FIN`.
/// - from `Open` to `Closed` if the remote immediately sends `RST`.
acknowledged: bool,
},
/// Open for incoming messages.
SendClosed,
/// Open for outgoing messages.
RecvClosed,
/// Closed (terminal state).
Closed,
}
impl State {
/// Can we receive messages over this stream?
pub fn can_read(self) -> bool {
!matches!(self, State::RecvClosed | State::Closed)
}
/// Can we send messages over this stream?
pub fn can_write(self) -> bool {
!matches!(self, State::SendClosed | State::Closed)
}
}
/// Indicate if a flag still needs to be set on an outbound header.
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub(crate) enum Flag {
/// No flag needs to be set.
None,
/// The stream was opened lazily, so set the initial SYN flag.
Syn,
/// The stream still needs acknowledgement, so set the ACK flag.
Ack,
}
/// A multiplexed Yamux stream.
///
/// Streams are created either outbound via [`crate::Connection::poll_new_outbound`]
/// or inbound via [`crate::Connection::poll_next_inbound`].
///
/// `Stream` implements [`AsyncRead`] and [`AsyncWrite`] and also
/// [`futures::stream::Stream`].
pub struct Stream {
id: StreamId,
conn: connection::Id,
config: Arc<Config>,
sender: mpsc::Sender<StreamCommand>,
flag: Flag,
shared: Arc<Mutex<Shared>>,
}
impl fmt::Debug for Stream {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.debug_struct("Stream")
.field("id", &self.id.val())
.field("connection", &self.conn)
.finish()
}
}
impl fmt::Display for Stream {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "(Stream {}/{})", self.conn, self.id.val())
}
}
impl Stream {
pub(crate) fn new_inbound(
id: StreamId,
conn: connection::Id,
config: Arc<Config>,
credit: u32,
sender: mpsc::Sender<StreamCommand>,
) -> Self {
Self {
id,
conn,
config: config.clone(),
sender,
flag: Flag::None,
shared: Arc::new(Mutex::new(Shared::new(DEFAULT_CREDIT, credit, config))),
}
}
pub(crate) fn new_outbound(
id: StreamId,
conn: connection::Id,
config: Arc<Config>,
window: u32,
sender: mpsc::Sender<StreamCommand>,
) -> Self {
Self {
id,
conn,
config: config.clone(),
sender,
flag: Flag::None,
shared: Arc::new(Mutex::new(Shared::new(window, DEFAULT_CREDIT, config))),
}
}
/// Get this stream's identifier.
pub fn id(&self) -> StreamId {
self.id
}
pub fn is_write_closed(&self) -> bool {
matches!(self.shared().state(), State::SendClosed)
}
pub fn is_closed(&self) -> bool {
matches!(self.shared().state(), State::Closed)
}
/// Whether we are still waiting for the remote to acknowledge this stream.
pub fn is_pending_ack(&self) -> bool {
self.shared().is_pending_ack()
}
/// Set the flag that should be set on the next outbound frame header.
pub(crate) fn set_flag(&mut self, flag: Flag) {
self.flag = flag
}
pub(crate) fn shared(&self) -> MutexGuard<'_, Shared> {
self.shared.lock()
}
pub(crate) fn clone_shared(&self) -> Arc<Mutex<Shared>> {
self.shared.clone()
}
fn write_zero_err(&self) -> io::Error {
let msg = format!("{}/{}: connection is closed", self.conn, self.id);
io::Error::new(io::ErrorKind::WriteZero, msg)
}
/// Set ACK or SYN flag if necessary.
fn add_flag(&mut self, header: &mut Header<Either<Data, WindowUpdate>>) {
match self.flag {
Flag::None => (),
Flag::Syn => {
header.syn();
self.flag = Flag::None
}
Flag::Ack => {
header.ack();
self.flag = Flag::None
}
}
}
/// Send new credit to the sending side via a window update message if
/// permitted.
fn send_window_update(&mut self, cx: &mut Context) -> Poll<io::Result<()>> {
// When using [`WindowUpdateMode::OnReceive`] window update messages are
// send early on data receival (see [`crate::Connection::on_frame`]).
#[allow(deprecated)]
if matches!(self.config.window_update_mode, WindowUpdateMode::OnReceive) {
return Poll::Ready(Ok(()));
}
let mut shared = self.shared.lock();
if let Some(credit) = shared.next_window_update() {
ready!(self
.sender
.poll_ready(cx)
.map_err(|_| self.write_zero_err())?);
shared.window += credit;
drop(shared);
let mut frame = Frame::window_update(self.id, credit).right();
self.add_flag(frame.header_mut());
let cmd = StreamCommand::SendFrame(frame);
self.sender
.start_send(cmd)
.map_err(|_| self.write_zero_err())?;
}
Poll::Ready(Ok(()))
}
}
/// Byte data produced by the [`futures::stream::Stream`] impl of [`Stream`].
#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct Packet(Vec<u8>);
impl AsRef<[u8]> for Packet {
fn as_ref(&self) -> &[u8] {
self.0.as_ref()
}
}
impl futures::stream::Stream for Stream {
type Item = io::Result<Packet>;
fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<Option<Self::Item>> {
if !self.config.read_after_close && self.sender.is_closed() {
return Poll::Ready(None);
}
match self.send_window_update(cx) {
Poll::Ready(Ok(())) => {}
Poll::Ready(Err(e)) => return Poll::Ready(Some(Err(e))),
// Continue reading buffered data even though sending a window update blocked.
Poll::Pending => {}
}
let mut shared = self.shared();
if let Some(bytes) = shared.buffer.pop() {
let off = bytes.offset();
let mut vec = bytes.into_vec();
if off != 0 {
// This should generally not happen when the stream is used only as
// a `futures::stream::Stream` since the whole point of this impl is
// to consume chunks atomically. It may perhaps happen when mixing
// this impl and the `AsyncRead` one.
log::debug!(
"{}/{}: chunk has been partially consumed",
self.conn,
self.id
);
vec = vec.split_off(off)
}
return Poll::Ready(Some(Ok(Packet(vec))));
}
// Buffer is empty, let's check if we can expect to read more data.
if !shared.state().can_read() {
log::debug!("{}/{}: eof", self.conn, self.id);
return Poll::Ready(None); // stream has been reset
}
// Since we have no more data at this point, we want to be woken up
// by the connection when more becomes available for us.
shared.reader = Some(cx.waker().clone());
Poll::Pending
}
}
// Like the `futures::stream::Stream` impl above, but copies bytes into the
// provided mutable slice.
impl AsyncRead for Stream {
fn poll_read(
mut self: Pin<&mut Self>,
cx: &mut Context,
buf: &mut [u8],
) -> Poll<io::Result<usize>> {
if !self.config.read_after_close && self.sender.is_closed() {
return Poll::Ready(Ok(0));
}
match self.send_window_update(cx) {
Poll::Ready(Ok(())) => {}
Poll::Ready(Err(e)) => return Poll::Ready(Err(e)),
// Continue reading buffered data even though sending a window update blocked.
Poll::Pending => {}
}
// Copy data from stream buffer.
let mut shared = self.shared();
let mut n = 0;
while let Some(chunk) = shared.buffer.front_mut() {
if chunk.is_empty() {
shared.buffer.pop();
continue;
}
let k = std::cmp::min(chunk.len(), buf.len() - n);
buf[n..n + k].copy_from_slice(&chunk.as_ref()[..k]);
n += k;
chunk.advance(k);
if n == buf.len() {
break;
}
}
if n > 0 {
log::trace!("{}/{}: read {} bytes", self.conn, self.id, n);
return Poll::Ready(Ok(n));
}
// Buffer is empty, let's check if we can expect to read more data.
if !shared.state().can_read() {
log::debug!("{}/{}: eof", self.conn, self.id);
return Poll::Ready(Ok(0)); // stream has been reset
}
// Since we have no more data at this point, we want to be woken up
// by the connection when more becomes available for us.
shared.reader = Some(cx.waker().clone());
Poll::Pending
}
}
impl AsyncWrite for Stream {
fn poll_write(
mut self: Pin<&mut Self>,
cx: &mut Context,
buf: &[u8],
) -> Poll<io::Result<usize>> {
ready!(self
.sender
.poll_ready(cx)
.map_err(|_| self.write_zero_err())?);
let body = {
let mut shared = self.shared();
if !shared.state().can_write() {
log::debug!("{}/{}: can no longer write", self.conn, self.id);
return Poll::Ready(Err(self.write_zero_err()));
}
if shared.credit == 0 {
log::trace!("{}/{}: no more credit left", self.conn, self.id);
shared.writer = Some(cx.waker().clone());
return Poll::Pending;
}
let k = std::cmp::min(shared.credit as usize, buf.len());
let k = std::cmp::min(k, self.config.split_send_size);
shared.credit = shared.credit.saturating_sub(k as u32);
Vec::from(&buf[..k])
};
let n = body.len();
let mut frame = Frame::data(self.id, body).expect("body <= u32::MAX").left();
self.add_flag(frame.header_mut());
log::trace!("{}/{}: write {} bytes", self.conn, self.id, n);
// technically, the frame hasn't been sent yet on the wire but from the perspective of this data structure, we've queued the frame for sending
// We are tracking this information:
// a) to be consistent with outbound streams
// b) to correctly test our behaviour around timing of when ACKs are sent. See `ack_timing.rs` test.
if frame.header().flags().contains(ACK) {
self.shared()
.update_state(self.conn, self.id, State::Open { acknowledged: true });
}
let cmd = StreamCommand::SendFrame(frame);
self.sender
.start_send(cmd)
.map_err(|_| self.write_zero_err())?;
Poll::Ready(Ok(n))
}
fn poll_flush(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<io::Result<()>> {
self.sender
.poll_flush_unpin(cx)
.map_err(|_| self.write_zero_err())
}
fn poll_close(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<io::Result<()>> {
if self.is_closed() {
return Poll::Ready(Ok(()));
}
ready!(self
.sender
.poll_ready(cx)
.map_err(|_| self.write_zero_err())?);
let ack = if self.flag == Flag::Ack {
self.flag = Flag::None;
true
} else {
false
};
log::trace!("{}/{}: close", self.conn, self.id);
let cmd = StreamCommand::CloseStream { ack };
self.sender
.start_send(cmd)
.map_err(|_| self.write_zero_err())?;
self.shared()
.update_state(self.conn, self.id, State::SendClosed);
Poll::Ready(Ok(()))
}
}
#[derive(Debug)]
pub(crate) struct Shared {
state: State,
pub(crate) window: u32,
pub(crate) credit: u32,
pub(crate) buffer: Chunks,
pub(crate) reader: Option<Waker>,
pub(crate) writer: Option<Waker>,
config: Arc<Config>,
}
impl Shared {
fn new(window: u32, credit: u32, config: Arc<Config>) -> Self {
Shared {
state: State::Open {
acknowledged: false,
},
window,
credit,
buffer: Chunks::new(),
reader: None,
writer: None,
config,
}
}
pub(crate) fn state(&self) -> State {
self.state
}
/// Update the stream state and return the state before it was updated.
pub(crate) fn update_state(
&mut self,
cid: connection::Id,
sid: StreamId,
next: State,
) -> State {
use self::State::*;
let current = self.state;
match (current, next) {
(Closed, _) => {}
(Open { .. }, _) => self.state = next,
(RecvClosed, Closed) => self.state = Closed,
(RecvClosed, Open { .. }) => {}
(RecvClosed, RecvClosed) => {}
(RecvClosed, SendClosed) => self.state = Closed,
(SendClosed, Closed) => self.state = Closed,
(SendClosed, Open { .. }) => {}
(SendClosed, RecvClosed) => self.state = Closed,
(SendClosed, SendClosed) => {}
}
log::trace!(
"{}/{}: update state: (from {:?} to {:?} -> {:?})",
cid,
sid,
current,
next,
self.state
);
current // Return the previous stream state for informational purposes.
}
/// Calculate the number of additional window bytes the receiving side
/// should grant the sending side via a window update message.
///
/// Returns `None` if too small to justify a window update message.
///
/// Note: Once a caller successfully sent a window update message, the
/// locally tracked window size needs to be updated manually by the caller.
pub(crate) fn next_window_update(&mut self) -> Option<u32> {
if !self.state.can_read() {
return None;
}
let new_credit = match self.config.window_update_mode {
#[allow(deprecated)]
WindowUpdateMode::OnReceive => {
debug_assert!(self.config.receive_window >= self.window);
self.config.receive_window.saturating_sub(self.window)
}
WindowUpdateMode::OnRead => {
debug_assert!(self.config.receive_window >= self.window);
let bytes_received = self.config.receive_window.saturating_sub(self.window);
let buffer_len: u32 = self.buffer.len().try_into().unwrap_or(std::u32::MAX);
bytes_received.saturating_sub(buffer_len)
}
};
// Send WindowUpdate message when half or more of the configured receive
// window can be granted as additional credit to the sender.
//
// See https://github.com/paritytech/yamux/issues/100 for a detailed
// discussion.
if new_credit >= self.config.receive_window / 2 {
Some(new_credit)
} else {
None
}
}
/// Whether we are still waiting for the remote to acknowledge this stream.
pub fn is_pending_ack(&self) -> bool {
matches!(
self.state(),
State::Open {
acknowledged: false
}
)
}
}