forked from libp2p/rust-libp2p
/
muxing.rs
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/
muxing.rs
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// Copyright 2018 Parity Technologies (UK) Ltd.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//! Muxing is the process of splitting a connection into multiple substreams.
//!
//! The main item of this module is the `StreamMuxer` trait. An implementation of `StreamMuxer`
//! has ownership of a connection, lets you open and close substreams, and read/write data
//! on open substreams.
//!
//! > **Note**: You normally don't need to use the methods of the `StreamMuxer` directly, as this
//! > is managed by the library's internals.
//!
//! Each substream of a connection is an isolated stream of data. All the substreams are muxed
//! together so that the data read from or written to each substream doesn't influence the other
//! substreams.
//!
//! In the context of libp2p, each substream can use a different protocol. Contrary to opening a
//! connection, opening a substream is almost free in terms of resources. This means that you
//! shouldn't hesitate to rapidly open and close substreams, and to design protocols that don't
//! require maintaining long-lived channels of communication.
//!
//! > **Example**: The Kademlia protocol opens a new substream for each request it wants to
//! > perform. Multiple requests can be performed simultaneously by opening multiple
//! > substreams, without having to worry about associating responses with the
//! > right request.
//!
//! # Implementing a muxing protocol
//!
//! In order to implement a muxing protocol, create an object that implements the `UpgradeInfo`,
//! `InboundUpgrade` and `OutboundUpgrade` traits. See the `upgrade` module for more information.
//! The `Output` associated type of the `InboundUpgrade` and `OutboundUpgrade` traits should be
//! identical, and should be an object that implements the `StreamMuxer` trait.
//!
//! The upgrade process will take ownership of the connection, which makes it possible for the
//! implementation of `StreamMuxer` to control everything that happens on the wire.
use futures::{future, prelude::*, task::Context, task::Poll};
use multiaddr::Multiaddr;
use std::{fmt, io, ops::Deref, pin::Pin};
pub use self::boxed::StreamMuxerBox;
pub use self::singleton::SingletonMuxer;
mod boxed;
mod singleton;
/// Implemented on objects that can open and manage substreams.
///
/// The state of a muxer, as exposed by this API, is the following:
///
/// - A connection to the remote. The `poll_event`, `flush_all` and `close` methods operate
/// on this.
/// - A list of substreams that are open. The `poll_outbound`, `read_substream`, `write_substream`,
/// `flush_substream`, `shutdown_substream` and `destroy_substream` methods allow controlling
/// these entries.
/// - A list of outbound substreams being opened. The `open_outbound`, `poll_outbound` and
/// `destroy_outbound` methods allow controlling these entries.
///
pub trait StreamMuxer {
/// Type of the object that represents the raw substream where data can be read and written.
type Substream;
/// Future that will be resolved when the outgoing substream is open.
type OutboundSubstream;
/// Error type of the muxer
type Error: Into<io::Error>;
/// Polls for a connection-wide event.
///
/// This function behaves the same as a `Stream`.
///
/// If `Pending` is returned, then the current task will be notified once the muxer
/// is ready to be polled, similar to the API of `Stream::poll()`.
/// Only the latest task that was used to call this method may be notified.
///
/// It is permissible and common to use this method to perform background
/// work, such as processing incoming packets and polling timers.
///
/// An error can be generated if the connection has been closed.
fn poll_event(
&self,
cx: &mut Context<'_>,
) -> Poll<Result<StreamMuxerEvent<Self::Substream>, Self::Error>>;
/// Opens a new outgoing substream, and produces the equivalent to a future that will be
/// resolved when it becomes available.
///
/// The API of `OutboundSubstream` is totally opaque, and the object can only be interfaced
/// through the methods on the `StreamMuxer` trait.
fn open_outbound(&self) -> Self::OutboundSubstream;
/// Polls the outbound substream.
///
/// If `Pending` is returned, then the current task will be notified once the substream
/// is ready to be polled, similar to the API of `Future::poll()`.
/// However, for each individual outbound substream, only the latest task that was used to
/// call this method may be notified.
///
/// May panic or produce an undefined result if an earlier polling of the same substream
/// returned `Ready` or `Err`.
fn poll_outbound(
&self,
cx: &mut Context<'_>,
s: &mut Self::OutboundSubstream,
) -> Poll<Result<Self::Substream, Self::Error>>;
/// Destroys an outbound substream future. Use this after the outbound substream has finished,
/// or if you want to interrupt it.
fn destroy_outbound(&self, s: Self::OutboundSubstream);
/// Reads data from a substream. The behaviour is the same as `futures::AsyncRead::poll_read`.
///
/// If `Pending` is returned, then the current task will be notified once the substream
/// is ready to be read. However, for each individual substream, only the latest task that
/// was used to call this method may be notified.
///
/// If `Async::Ready(0)` is returned, the substream has been closed by the remote and should
/// no longer be read afterwards.
///
/// An error can be generated if the connection has been closed, or if a protocol misbehaviour
/// happened.
fn read_substream(
&self,
cx: &mut Context<'_>,
s: &mut Self::Substream,
buf: &mut [u8],
) -> Poll<Result<usize, Self::Error>>;
/// Write data to a substream. The behaviour is the same as `futures::AsyncWrite::poll_write`.
///
/// If `Pending` is returned, then the current task will be notified once the substream
/// is ready to be read. For each individual substream, only the latest task that was used to
/// call this method may be notified.
///
/// Calling `write_substream` does not guarantee that data will arrive to the remote. To
/// ensure that, you should call `flush_substream`.
///
/// It is incorrect to call this method on a substream if you called `shutdown_substream` on
/// this substream earlier.
fn write_substream(
&self,
cx: &mut Context<'_>,
s: &mut Self::Substream,
buf: &[u8],
) -> Poll<Result<usize, Self::Error>>;
/// Flushes a substream. The behaviour is the same as `futures::AsyncWrite::poll_flush`.
///
/// After this method has been called, data written earlier on the substream is guaranteed to
/// be received by the remote.
///
/// If `Pending` is returned, then the current task will be notified once the substream
/// is ready to be read. For each individual substream, only the latest task that was used to
/// call this method may be notified.
///
/// > **Note**: This method may be implemented as a call to `flush_all`.
fn flush_substream(
&self,
cx: &mut Context<'_>,
s: &mut Self::Substream,
) -> Poll<Result<(), Self::Error>>;
/// Attempts to shut down the writing side of a substream. The behaviour is similar to
/// `AsyncWrite::poll_close`.
///
/// Contrary to `AsyncWrite::poll_close`, shutting down a substream does not imply
/// `flush_substream`. If you want to make sure that the remote is immediately informed about
/// the shutdown, use `flush_substream` or `flush_all`.
///
/// After this method has been called, you should no longer attempt to write to this substream.
///
/// An error can be generated if the connection has been closed, or if a protocol misbehaviour
/// happened.
fn shutdown_substream(
&self,
cx: &mut Context<'_>,
s: &mut Self::Substream,
) -> Poll<Result<(), Self::Error>>;
/// Destroys a substream.
fn destroy_substream(&self, s: Self::Substream);
/// Closes this `StreamMuxer`.
///
/// After this has returned `Poll::Ready(Ok(()))`, the muxer has become useless. All
/// subsequent reads must return either `EOF` or an error. All subsequent writes, shutdowns,
/// or polls must generate an error or be ignored.
///
/// Calling this method implies `flush_all`.
///
/// > **Note**: You are encouraged to call this method and wait for it to return `Ready`, so
/// > that the remote is properly informed of the shutdown. However, apart from
/// > properly informing the remote, there is no difference between this and
/// > immediately dropping the muxer.
fn poll_close(&self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>>;
}
/// Event about a connection, reported by an implementation of [`StreamMuxer`].
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum StreamMuxerEvent<T> {
/// Remote has opened a new substream. Contains the substream in question.
InboundSubstream(T),
/// Address to the remote has changed. The previous one is now obsolete.
///
/// > **Note**: This can for example happen when using the QUIC protocol, where the two nodes
/// > can change their IP address while retaining the same QUIC connection.
AddressChange(Multiaddr),
}
impl<T> StreamMuxerEvent<T> {
/// If `self` is a [`StreamMuxerEvent::InboundSubstream`], returns the content. Otherwise
/// returns `None`.
pub fn into_inbound_substream(self) -> Option<T> {
if let StreamMuxerEvent::InboundSubstream(s) = self {
Some(s)
} else {
None
}
}
}
/// Polls for an event from the muxer and, if an inbound substream, wraps this substream in an
/// object that implements `Read`/`Write`/`AsyncRead`/`AsyncWrite`.
pub fn event_from_ref_and_wrap<P>(
muxer: P,
) -> impl Future<Output = Result<StreamMuxerEvent<SubstreamRef<P>>, <P::Target as StreamMuxer>::Error>>
where
P: Deref + Clone,
P::Target: StreamMuxer,
{
let muxer2 = muxer.clone();
future::poll_fn(move |cx| muxer.poll_event(cx)).map_ok(|event| match event {
StreamMuxerEvent::InboundSubstream(substream) => {
StreamMuxerEvent::InboundSubstream(substream_from_ref(muxer2, substream))
}
StreamMuxerEvent::AddressChange(addr) => StreamMuxerEvent::AddressChange(addr),
})
}
/// Same as `outbound_from_ref`, but wraps the output in an object that
/// implements `Read`/`Write`/`AsyncRead`/`AsyncWrite`.
pub fn outbound_from_ref_and_wrap<P>(muxer: P) -> OutboundSubstreamRefWrapFuture<P>
where
P: Deref + Clone,
P::Target: StreamMuxer,
{
let inner = outbound_from_ref(muxer);
OutboundSubstreamRefWrapFuture { inner }
}
/// Future returned by `outbound_from_ref_and_wrap`.
pub struct OutboundSubstreamRefWrapFuture<P>
where
P: Deref + Clone,
P::Target: StreamMuxer,
{
inner: OutboundSubstreamRefFuture<P>,
}
impl<P> Future for OutboundSubstreamRefWrapFuture<P>
where
P: Deref + Clone,
P::Target: StreamMuxer,
{
type Output = Result<SubstreamRef<P>, <P::Target as StreamMuxer>::Error>;
fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
match Future::poll(Pin::new(&mut self.inner), cx) {
Poll::Ready(Ok(substream)) => {
let out = substream_from_ref(self.inner.muxer.clone(), substream);
Poll::Ready(Ok(out))
}
Poll::Pending => Poll::Pending,
Poll::Ready(Err(err)) => Poll::Ready(Err(err)),
}
}
}
/// Builds a new future for an outbound substream, where the muxer is a reference.
pub fn outbound_from_ref<P>(muxer: P) -> OutboundSubstreamRefFuture<P>
where
P: Deref,
P::Target: StreamMuxer,
{
let outbound = muxer.open_outbound();
OutboundSubstreamRefFuture {
muxer,
outbound: Some(outbound),
}
}
/// Future returned by `outbound_from_ref`.
pub struct OutboundSubstreamRefFuture<P>
where
P: Deref,
P::Target: StreamMuxer,
{
muxer: P,
outbound: Option<<P::Target as StreamMuxer>::OutboundSubstream>,
}
impl<P> Unpin for OutboundSubstreamRefFuture<P>
where
P: Deref,
P::Target: StreamMuxer,
{
}
impl<P> Future for OutboundSubstreamRefFuture<P>
where
P: Deref,
P::Target: StreamMuxer,
{
type Output = Result<<P::Target as StreamMuxer>::Substream, <P::Target as StreamMuxer>::Error>;
fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
// We use a `this` because the compiler isn't smart enough to allow mutably borrowing
// multiple different fields from the `Pin` at the same time.
let this = &mut *self;
this.muxer
.poll_outbound(cx, this.outbound.as_mut().expect("outbound was empty"))
}
}
impl<P> Drop for OutboundSubstreamRefFuture<P>
where
P: Deref,
P::Target: StreamMuxer,
{
fn drop(&mut self) {
self.muxer
.destroy_outbound(self.outbound.take().expect("outbound was empty"))
}
}
/// Builds an implementation of `Read`/`Write`/`AsyncRead`/`AsyncWrite` from an `Arc` to the
/// muxer and a substream.
pub fn substream_from_ref<P>(
muxer: P,
substream: <P::Target as StreamMuxer>::Substream,
) -> SubstreamRef<P>
where
P: Deref,
P::Target: StreamMuxer,
{
SubstreamRef {
muxer,
substream: Some(substream),
shutdown_state: ShutdownState::Shutdown,
}
}
/// Stream returned by `substream_from_ref`.
pub struct SubstreamRef<P>
where
P: Deref,
P::Target: StreamMuxer,
{
muxer: P,
substream: Option<<P::Target as StreamMuxer>::Substream>,
shutdown_state: ShutdownState,
}
enum ShutdownState {
Shutdown,
Flush,
Done,
}
impl<P> fmt::Debug for SubstreamRef<P>
where
P: Deref,
P::Target: StreamMuxer,
<P::Target as StreamMuxer>::Substream: fmt::Debug,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
write!(f, "Substream({:?})", self.substream)
}
}
impl<P> Unpin for SubstreamRef<P>
where
P: Deref,
P::Target: StreamMuxer,
{
}
impl<P> AsyncRead for SubstreamRef<P>
where
P: Deref,
P::Target: StreamMuxer,
{
fn poll_read(
mut self: Pin<&mut Self>,
cx: &mut Context<'_>,
buf: &mut [u8],
) -> Poll<Result<usize, io::Error>> {
// We use a `this` because the compiler isn't smart enough to allow mutably borrowing
// multiple different fields from the `Pin` at the same time.
let this = &mut *self;
let s = this.substream.as_mut().expect("substream was empty");
this.muxer.read_substream(cx, s, buf).map_err(|e| e.into())
}
}
impl<P> AsyncWrite for SubstreamRef<P>
where
P: Deref,
P::Target: StreamMuxer,
{
fn poll_write(
mut self: Pin<&mut Self>,
cx: &mut Context<'_>,
buf: &[u8],
) -> Poll<Result<usize, io::Error>> {
// We use a `this` because the compiler isn't smart enough to allow mutably borrowing
// multiple different fields from the `Pin` at the same time.
let this = &mut *self;
let s = this.substream.as_mut().expect("substream was empty");
this.muxer.write_substream(cx, s, buf).map_err(|e| e.into())
}
fn poll_close(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), io::Error>> {
// We use a `this` because the compiler isn't smart enough to allow mutably borrowing
// multiple different fields from the `Pin` at the same time.
let this = &mut *self;
let s = this.substream.as_mut().expect("substream was empty");
loop {
match this.shutdown_state {
ShutdownState::Shutdown => match this.muxer.shutdown_substream(cx, s) {
Poll::Ready(Ok(())) => this.shutdown_state = ShutdownState::Flush,
Poll::Ready(Err(err)) => return Poll::Ready(Err(err.into())),
Poll::Pending => return Poll::Pending,
},
ShutdownState::Flush => match this.muxer.flush_substream(cx, s) {
Poll::Ready(Ok(())) => this.shutdown_state = ShutdownState::Done,
Poll::Ready(Err(err)) => return Poll::Ready(Err(err.into())),
Poll::Pending => return Poll::Pending,
},
ShutdownState::Done => {
return Poll::Ready(Ok(()));
}
}
}
}
fn poll_flush(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), io::Error>> {
// We use a `this` because the compiler isn't smart enough to allow mutably borrowing
// multiple different fields from the `Pin` at the same time.
let this = &mut *self;
let s = this.substream.as_mut().expect("substream was empty");
this.muxer.flush_substream(cx, s).map_err(|e| e.into())
}
}
impl<P> Drop for SubstreamRef<P>
where
P: Deref,
P::Target: StreamMuxer,
{
fn drop(&mut self) {
self.muxer
.destroy_substream(self.substream.take().expect("substream was empty"))
}
}