core/muxing: Flatten StreamMuxer interface to poll_{inbound,outbound,address_change,close} (#2724)

Instead of having a mix of `poll_event`, `poll_outbound` and `poll_close`, we
flatten the entire interface of `StreamMuxer` into 4 individual functions:

- `poll_inbound`
- `poll_outbound`
- `poll_address_change`
- `poll_close`

This design is closer to the design of other async traits like `AsyncRead` and
`AsyncWrite`. It also allows us to delete the `StreamMuxerEvent`.

Cargo.toml

@@ -78,25 +78,25 @@ instant = "0.1.11" # Explicit dependency to be used in `wasm-bindgen` feature
 lazy_static = "1.2"
 
 libp2p-autonat = { version = "0.6.0", path = "protocols/autonat", optional = true }
-libp2p-core = { version = "0.34.0", path = "core",  default-features = false }
+libp2p-core = { version = "0.35.0", path = "core",  default-features = false }
 libp2p-dcutr = { version = "0.5.0", path = "protocols/dcutr",  optional = true }
 libp2p-floodsub = { version = "0.38.0", path = "protocols/floodsub", optional = true }
 libp2p-identify = { version = "0.38.0", path = "protocols/identify", optional = true }
 libp2p-kad = { version = "0.39.0", path = "protocols/kad", optional = true }
 libp2p-metrics = { version = "0.8.0", path = "misc/metrics", optional = true }
-libp2p-mplex = { version = "0.34.0", path = "muxers/mplex", optional = true }
+libp2p-mplex = { version = "0.35.0", path = "muxers/mplex", optional = true }
-libp2p-noise = { version = "0.37.0", path = "transports/noise", optional = true }
+libp2p-noise = { version = "0.38.0", path = "transports/noise", optional = true }
 libp2p-ping = { version = "0.38.0", path = "protocols/ping", optional = true }
-libp2p-plaintext = { version = "0.34.0", path = "transports/plaintext", optional = true }
+libp2p-plaintext = { version = "0.35.0", path = "transports/plaintext", optional = true }
 libp2p-pnet = { version = "0.22.0", path = "transports/pnet", optional = true }
 libp2p-relay = { version = "0.11.0", path = "protocols/relay", optional = true }
 libp2p-rendezvous = { version = "0.8.0", path = "protocols/rendezvous", optional = true }
 libp2p-request-response = { version = "0.20.0", path = "protocols/request-response", optional = true }
 libp2p-swarm = { version = "0.38.0", path = "swarm" }
 libp2p-swarm-derive = { version = "0.28.0", path = "swarm-derive" }
-libp2p-uds = { version = "0.33.0", path = "transports/uds", optional = true }
+libp2p-uds = { version = "0.34.0", path = "transports/uds", optional = true }
-libp2p-wasm-ext = { version = "0.34.0", path = "transports/wasm-ext", default-features = false, optional = true }
+libp2p-wasm-ext = { version = "0.35.0", path = "transports/wasm-ext", default-features = false, optional = true }
-libp2p-yamux = { version = "0.38.0", path = "muxers/yamux", optional = true }
+libp2p-yamux = { version = "0.39.0", path = "muxers/yamux", optional = true }
 multiaddr = { version = "0.14.0" }
 parking_lot = "0.12.0"
 pin-project = "1.0.0"
@@ -104,11 +104,11 @@ rand = "0.7.3" # Explicit dependency to be used in `wasm-bindgen` feature
 smallvec = "1.6.1"
 
 [target.'cfg(not(any(target_os = "emscripten", target_os = "wasi", target_os = "unknown")))'.dependencies]
-libp2p-deflate = { version = "0.34.0", path = "transports/deflate", optional = true }
+libp2p-deflate = { version = "0.35.0", path = "transports/deflate", optional = true }
-libp2p-dns = { version = "0.34.0", path = "transports/dns", optional = true, default-features = false }
+libp2p-dns = { version = "0.35.0", path = "transports/dns", optional = true, default-features = false }
 libp2p-mdns = { version = "0.39.0", path = "protocols/mdns", optional = true }
 libp2p-tcp = { version = "0.34.0", path = "transports/tcp", default-features = false, optional = true }
-libp2p-websocket = { version = "0.36.0", path = "transports/websocket", optional = true }
+libp2p-websocket = { version = "0.37.0", path = "transports/websocket", optional = true }
 
 [target.'cfg(not(target_os = "unknown"))'.dependencies]
 libp2p-gossipsub = { version = "0.40.0", path = "protocols/gossipsub", optional = true }

core/CHANGELOG.md

@@ -1,6 +1,12 @@
+# 0.35.0 [unreleased]
+
+- Remove `StreamMuxer::poll_event` in favor of individual functions: `poll_inbound`, `poll_outbound`
+  and `poll_address_change`. Consequently, `StreamMuxerEvent` is also removed. See [PR 2724].
+
+[PR 2724]: https://github.com/libp2p/rust-libp2p/pull/2724
+
 # 0.34.0
 
-- Introduce `StreamMuxerEvent::map_inbound_stream`. See [PR 2691].
 - Remove `{read,write,flush,shutdown,destroy}_substream` functions from `StreamMuxer` trait
   in favor of forcing `StreamMuxer::Substream` to implement `AsyncRead + AsyncWrite`. See [PR 2707].
 - Replace `Into<std::io::Error>` bound on `StreamMuxer::Error` with `std::error::Error`. See [PR 2710].

core/Cargo.toml

@@ -3,7 +3,7 @@ name = "libp2p-core"
 edition = "2021"
 rust-version = "1.56.1"
 description = "Core traits and structs of libp2p"
-version = "0.34.0"
+version = "0.35.0"
 authors = ["Parity Technologies <admin@parity.io>"]
 license = "MIT"
 repository = "https://github.com/libp2p/rust-libp2p"

core/src/either.rs

@@ -19,7 +19,7 @@
 // DEALINGS IN THE SOFTWARE.
 
 use crate::{
-    muxing::{StreamMuxer, StreamMuxerEvent},
+    muxing::StreamMuxer,
     transport::{ListenerId, Transport, TransportError, TransportEvent},
     Multiaddr, ProtocolName,
 };
@@ -202,60 +202,38 @@ where
     B: StreamMuxer,
 {
     type Substream = EitherOutput<A::Substream, B::Substream>;
-    type OutboundSubstream = EitherOutbound<A, B>;
     type Error = EitherError<A::Error, B::Error>;
 
-    fn poll_event(
+    fn poll_inbound(&self, cx: &mut Context<'_>) -> Poll<Result<Self::Substream, Self::Error>> {
-        &self,
-        cx: &mut Context<'_>,
-    ) -> Poll<Result<StreamMuxerEvent<Self::Substream>, Self::Error>> {
         match self {
             EitherOutput::First(inner) => inner
-                .poll_event(cx)
+                .poll_inbound(cx)
-                .map_err(EitherError::A)
+                .map_ok(EitherOutput::First)
-                .map_ok(|event| event.map_inbound_stream(EitherOutput::First)),
-            EitherOutput::Second(inner) => inner
-                .poll_event(cx)
-                .map_err(EitherError::B)
-                .map_ok(|event| event.map_inbound_stream(EitherOutput::Second)),
-        }
-    }
-
-    fn open_outbound(&self) -> Self::OutboundSubstream {
-        match self {
-            EitherOutput::First(inner) => EitherOutbound::A(inner.open_outbound()),
-            EitherOutput::Second(inner) => EitherOutbound::B(inner.open_outbound()),
-        }
-    }
-
-    fn poll_outbound(
-        &self,
-        cx: &mut Context<'_>,
-        substream: &mut Self::OutboundSubstream,
-    ) -> Poll<Result<Self::Substream, Self::Error>> {
-        match (self, substream) {
-            (EitherOutput::First(ref inner), EitherOutbound::A(ref mut substream)) => inner
-                .poll_outbound(cx, substream)
-                .map(|p| p.map(EitherOutput::First))
                 .map_err(EitherError::A),
-            (EitherOutput::Second(ref inner), EitherOutbound::B(ref mut substream)) => inner
+            EitherOutput::Second(inner) => inner
-                .poll_outbound(cx, substream)
+                .poll_inbound(cx)
-                .map(|p| p.map(EitherOutput::Second))
+                .map_ok(EitherOutput::Second)
                 .map_err(EitherError::B),
-            _ => panic!("Wrong API usage"),
         }
     }
 
-    fn destroy_outbound(&self, substream: Self::OutboundSubstream) {
+    fn poll_outbound(&self, cx: &mut Context<'_>) -> Poll<Result<Self::Substream, Self::Error>> {
         match self {
-            EitherOutput::First(inner) => match substream {
+            EitherOutput::First(inner) => inner
-                EitherOutbound::A(substream) => inner.destroy_outbound(substream),
+                .poll_outbound(cx)
-                _ => panic!("Wrong API usage"),
+                .map_ok(EitherOutput::First)
-            },
+                .map_err(EitherError::A),
-            EitherOutput::Second(inner) => match substream {
+            EitherOutput::Second(inner) => inner
-                EitherOutbound::B(substream) => inner.destroy_outbound(substream),
+                .poll_outbound(cx)
-                _ => panic!("Wrong API usage"),
+                .map_ok(EitherOutput::Second)
-            },
+                .map_err(EitherError::B),
+        }
+    }
+
+    fn poll_address_change(&self, cx: &mut Context<'_>) -> Poll<Result<Multiaddr, Self::Error>> {
+        match self {
+            EitherOutput::First(inner) => inner.poll_address_change(cx).map_err(EitherError::A),
+            EitherOutput::Second(inner) => inner.poll_address_change(cx).map_err(EitherError::B),
         }
     }
 
@@ -267,13 +245,6 @@ where
     }
 }
 
-#[derive(Debug, Copy, Clone)]
-#[must_use = "futures do nothing unless polled"]
-pub enum EitherOutbound<A: StreamMuxer, B: StreamMuxer> {
-    A(A::OutboundSubstream),
-    B(B::OutboundSubstream),
-}
-
 /// Implements `Future` and dispatches all method calls to either `First` or `Second`.
 #[pin_project(project = EitherFutureProj)]
 #[derive(Debug, Copy, Clone)]

core/src/muxing.rs

@@ -63,62 +63,25 @@ mod singleton;
 /// Provides multiplexing for a connection by allowing users to open substreams.
 ///
 /// A substream created by a [`StreamMuxer`] is a type that implements [`AsyncRead`] and [`AsyncWrite`].
-///
+/// The [`StreamMuxer`] itself is modelled closely after [`AsyncWrite`]. It features `poll`-style
-/// Inbound substreams are reported via [`StreamMuxer::poll_event`].
+/// functions that allow the implementation to make progress on various tasks.
-/// Outbound substreams can be opened via [`StreamMuxer::open_outbound`] and subsequent polling via
-/// [`StreamMuxer::poll_outbound`].
 pub trait StreamMuxer {
     /// Type of the object that represents the raw substream where data can be read and written.
     type Substream: AsyncRead + AsyncWrite;
 
-    /// Future that will be resolved when the outgoing substream is open.
-    type OutboundSubstream;
-
     /// Error type of the muxer
     type Error: std::error::Error;
 
-    /// Polls for a connection-wide event.
+    /// Poll for new inbound substreams.
-    ///
+    fn poll_inbound(&self, cx: &mut Context<'_>) -> Poll<Result<Self::Substream, Self::Error>>;
-    /// 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
+    /// Poll for a new, outbound substream.
-    /// resolved when it becomes available.
+    fn poll_outbound(&self, cx: &mut Context<'_>) -> Poll<Result<Self::Substream, Self::Error>>;
-    ///
-    /// 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.
+    /// Poll for an address change of the underlying connection.
     ///
-    /// If `Pending` is returned, then the current task will be notified once the substream
+    /// Not all implementations may support this feature.
-    /// is ready to be polled, similar to the API of `Future::poll()`.
+    fn poll_address_change(&self, cx: &mut Context<'_>) -> Poll<Result<Multiaddr, Self::Error>>;
-    /// 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);
 
     /// Closes this `StreamMuxer`.
     ///
@@ -132,38 +95,3 @@ pub trait StreamMuxer {
     /// >           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
-        }
-    }
-
-    /// Map the stream within [`StreamMuxerEvent::InboundSubstream`] to a new type.
-    pub fn map_inbound_stream<O>(self, map: impl FnOnce(T) -> O) -> StreamMuxerEvent<O> {
-        match self {
-            StreamMuxerEvent::InboundSubstream(stream) => {
-                StreamMuxerEvent::InboundSubstream(map(stream))
-            }
-            StreamMuxerEvent::AddressChange(addr) => StreamMuxerEvent::AddressChange(addr),
-        }
-    }
-}

core/src/muxing/boxed.rs

@@ -1,23 +1,16 @@
-use crate::muxing::StreamMuxerEvent;
 use crate::StreamMuxer;
-use fnv::FnvHashMap;
+use futures::{AsyncRead, AsyncWrite};
-use futures::{ready, AsyncRead, AsyncWrite};
+use multiaddr::Multiaddr;
-use parking_lot::Mutex;
 use std::error::Error;
 use std::fmt;
 use std::io;
 use std::io::{IoSlice, IoSliceMut};
 use std::pin::Pin;
-use std::sync::atomic::{AtomicUsize, Ordering};
 use std::task::{Context, Poll};
 
 /// Abstract `StreamMuxer`.
 pub struct StreamMuxerBox {
-    inner: Box<
+    inner: Box<dyn StreamMuxer<Substream = SubstreamBox, Error = io::Error> + Send + Sync>,
-        dyn StreamMuxer<Substream = SubstreamBox, OutboundSubstream = usize, Error = io::Error>
-            + Send
-            + Sync,
-    >,
 }
 
 /// Abstract type for asynchronous reading and writing.
@@ -31,8 +24,6 @@ where
     T: StreamMuxer,
 {
     inner: T,
-    outbound: Mutex<FnvHashMap<usize, T::OutboundSubstream>>,
-    next_outbound: AtomicUsize,
 }
 
 impl<T> StreamMuxer for Wrap<T>
@@ -42,54 +33,30 @@ where
     T::Error: Send + Sync + 'static,
 {
     type Substream = SubstreamBox;
-    type OutboundSubstream = usize; // TODO: use a newtype
     type Error = io::Error;
 
-    #[inline]
-    fn poll_event(
-        &self,
-        cx: &mut Context<'_>,
-    ) -> Poll<Result<StreamMuxerEvent<Self::Substream>, Self::Error>> {
-        let event = ready!(self.inner.poll_event(cx).map_err(into_io_error)?)
-            .map_inbound_stream(SubstreamBox::new);
-
-        Poll::Ready(Ok(event))
-    }
-
-    #[inline]
-    fn open_outbound(&self) -> Self::OutboundSubstream {
-        let outbound = self.inner.open_outbound();
-        let id = self.next_outbound.fetch_add(1, Ordering::Relaxed);
-        self.outbound.lock().insert(id, outbound);
-        id
-    }
-
-    #[inline]
-    fn poll_outbound(
-        &self,
-        cx: &mut Context<'_>,
-        substream: &mut Self::OutboundSubstream,
-    ) -> Poll<Result<Self::Substream, Self::Error>> {
-        let mut list = self.outbound.lock();
-        let stream = ready!(self
-            .inner
-            .poll_outbound(cx, list.get_mut(substream).unwrap())
-            .map_err(into_io_error)?);
-
-        Poll::Ready(Ok(SubstreamBox::new(stream)))
-    }
-
-    #[inline]
-    fn destroy_outbound(&self, substream: Self::OutboundSubstream) {
-        let mut list = self.outbound.lock();
-        self.inner
-            .destroy_outbound(list.remove(&substream).unwrap())
-    }
-
     #[inline]
     fn poll_close(&self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
         self.inner.poll_close(cx).map_err(into_io_error)
     }
+
+    fn poll_inbound(&self, cx: &mut Context<'_>) -> Poll<Result<Self::Substream, Self::Error>> {
+        self.inner
+            .poll_inbound(cx)
+            .map_ok(SubstreamBox::new)
+            .map_err(into_io_error)
+    }
+
+    fn poll_outbound(&self, cx: &mut Context<'_>) -> Poll<Result<Self::Substream, Self::Error>> {
+        self.inner
+            .poll_outbound(cx)
+            .map_ok(SubstreamBox::new)
+            .map_err(into_io_error)
+    }
+
+    fn poll_address_change(&self, cx: &mut Context<'_>) -> Poll<Result<Multiaddr, Self::Error>> {
+        self.inner.poll_address_change(cx).map_err(into_io_error)
+    }
 }
 
 fn into_io_error<E>(err: E) -> io::Error
@@ -104,15 +71,10 @@ impl StreamMuxerBox {
     pub fn new<T>(muxer: T) -> StreamMuxerBox
     where
         T: StreamMuxer + Send + Sync + 'static,
-        T::OutboundSubstream: Send,
         T::Substream: Send + Unpin + 'static,
         T::Error: Send + Sync + 'static,
     {
-        let wrap = Wrap {
+        let wrap = Wrap { inner: muxer };
-            inner: muxer,
-            outbound: Mutex::new(Default::default()),
-            next_outbound: AtomicUsize::new(0),
-        };
 
         StreamMuxerBox {
             inner: Box::new(wrap),
@@ -122,40 +84,24 @@ impl StreamMuxerBox {
 
 impl StreamMuxer for StreamMuxerBox {
     type Substream = SubstreamBox;
-    type OutboundSubstream = usize; // TODO: use a newtype
     type Error = io::Error;
 
-    #[inline]
-    fn poll_event(
-        &self,
-        cx: &mut Context<'_>,
-    ) -> Poll<Result<StreamMuxerEvent<Self::Substream>, Self::Error>> {
-        self.inner.poll_event(cx)
-    }
-
-    #[inline]
-    fn open_outbound(&self) -> Self::OutboundSubstream {
-        self.inner.open_outbound()
-    }
-
-    #[inline]
-    fn poll_outbound(
-        &self,
-        cx: &mut Context<'_>,
-        s: &mut Self::OutboundSubstream,
-    ) -> Poll<Result<Self::Substream, Self::Error>> {
-        self.inner.poll_outbound(cx, s)
-    }
-
-    #[inline]
-    fn destroy_outbound(&self, substream: Self::OutboundSubstream) {
-        self.inner.destroy_outbound(substream)
-    }
-
     #[inline]
     fn poll_close(&self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
         self.inner.poll_close(cx)
     }
+
+    fn poll_inbound(&self, cx: &mut Context<'_>) -> Poll<Result<Self::Substream, Self::Error>> {
+        self.inner.poll_inbound(cx)
+    }
+
+    fn poll_outbound(&self, cx: &mut Context<'_>) -> Poll<Result<Self::Substream, Self::Error>> {
+        self.inner.poll_outbound(cx)
+    }
+
+    fn poll_address_change(&self, cx: &mut Context<'_>) -> Poll<Result<Multiaddr, Self::Error>> {
+        self.inner.poll_address_change(cx)
+    }
 }
 
 impl SubstreamBox {

core/src/muxing/singleton.rs

@@ -18,12 +18,10 @@
 // FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 // DEALINGS IN THE SOFTWARE.
 
-use crate::{
+use crate::{connection::Endpoint, muxing::StreamMuxer};
-    connection::Endpoint,
-    muxing::{StreamMuxer, StreamMuxerEvent},
-};
 
 use futures::prelude::*;
+use multiaddr::Multiaddr;
 use std::cell::Cell;
 use std::{io, task::Context, task::Poll};
 
@@ -52,55 +50,36 @@ impl<TSocket> SingletonMuxer<TSocket> {
     }
 }
 
-/// Outbound substream attempt of the `SingletonMuxer`.
-pub struct OutboundSubstream {}
-
 impl<TSocket> StreamMuxer for SingletonMuxer<TSocket>
 where
     TSocket: AsyncRead + AsyncWrite + Unpin,
 {
     type Substream = TSocket;
-    type OutboundSubstream = OutboundSubstream;
     type Error = io::Error;
 
-    fn poll_event(
+    fn poll_inbound(&self, _: &mut Context<'_>) -> Poll<Result<Self::Substream, Self::Error>> {
-        &self,
-        _: &mut Context<'_>,
-    ) -> Poll<Result<StreamMuxerEvent<Self::Substream>, io::Error>> {
         match self.endpoint {
-            Endpoint::Dialer => return Poll::Pending,
+            Endpoint::Dialer => Poll::Pending,
-            Endpoint::Listener => {}
+            Endpoint::Listener => match self.inner.replace(None) {
-        }
+                None => Poll::Pending,
-
+                Some(stream) => Poll::Ready(Ok(stream)),
-        if let Some(stream) = self.inner.replace(None) {
+            },
-            Poll::Ready(Ok(StreamMuxerEvent::InboundSubstream(stream)))
-        } else {
-            Poll::Pending
         }
     }
 
-    fn open_outbound(&self) -> Self::OutboundSubstream {
+    fn poll_outbound(&self, _: &mut Context<'_>) -> Poll<Result<Self::Substream, Self::Error>> {
-        OutboundSubstream {}
-    }
-
-    fn poll_outbound(
-        &self,
-        _: &mut Context<'_>,
-        _: &mut Self::OutboundSubstream,
-    ) -> Poll<Result<Self::Substream, io::Error>> {
         match self.endpoint {
-            Endpoint::Listener => return Poll::Pending,
+            Endpoint::Listener => Poll::Pending,
-            Endpoint::Dialer => {}
+            Endpoint::Dialer => match self.inner.replace(None) {
-        }
+                None => Poll::Pending,
-
+                Some(stream) => Poll::Ready(Ok(stream)),
-        if let Some(stream) = self.inner.replace(None) {
+            },
-            Poll::Ready(Ok(stream))
-        } else {
-            Poll::Pending
         }
     }
 
-    fn destroy_outbound(&self, _: Self::OutboundSubstream) {}
+    fn poll_address_change(&self, _: &mut Context<'_>) -> Poll<Result<Multiaddr, Self::Error>> {
+        Poll::Pending
+    }
 
     fn poll_close(&self, _cx: &mut Context<'_>) -> Poll<Result<(), io::Error>> {
         Poll::Ready(Ok(()))

core/src/transport/upgrade.rs

@@ -301,7 +301,6 @@ impl<T> Multiplexed<T> {
         T::Error: Send + Sync,
         M: StreamMuxer + Send + Sync + 'static,
         M::Substream: Send + Unpin + 'static,
-        M::OutboundSubstream: Send + 'static,
         M::Error: Send + Sync + 'static,
     {
         boxed(self.map(|(i, m), _| (i, StreamMuxerBox::new(m))))

misc/keygen/Cargo.toml

@@ -13,5 +13,5 @@ clap = {version = "3.1.6", features = ["derive"]}
 zeroize = "1"
 serde = { version = "1.0.136", features = ["derive"] }
 serde_json = "1.0.79"
-libp2p-core = { path = "../../core", default-features = false, version = "0.34.0"}
+libp2p-core = { path = "../../core", default-features = false, version = "0.35.0"}
 base64 = "0.13.0"

misc/metrics/CHANGELOG.md

@@ -14,6 +14,8 @@
 
 - Track number of connected nodes supporting a specific protocol via the identify protocol. See [PR 2734].
 
+- Update to `libp2p-core` `v0.35.0`.
+
 [PR 2734]: https://github.com/libp2p/rust-libp2p/pull/2734/
 
 # 0.7.0

misc/metrics/Cargo.toml

@@ -19,7 +19,7 @@ relay = ["libp2p-relay"]
 dcutr = ["libp2p-dcutr"]
 
 [dependencies]
-libp2p-core = { version = "0.34.0", path = "../../core", default-features = false }
+libp2p-core = { version = "0.35.0", path = "../../core", default-features = false }
 libp2p-dcutr =  { version = "0.5.0", path = "../../protocols/dcutr", optional = true }
 libp2p-identify = { version = "0.38.0", path = "../../protocols/identify", optional = true }
 libp2p-kad = { version = "0.39.0", path = "../../protocols/kad", optional = true }

muxers/mplex/CHANGELOG.md

@@ -1,3 +1,7 @@
+# 0.35.0 [unreleased]
+
+- Update to `libp2p-core` `v0.35.0`
+
 # 0.34.0
 
 - `Substream` now implements `AsyncRead` and `AsyncWrite`. See [PR 2706].

muxers/mplex/Cargo.toml

@@ -3,7 +3,7 @@ name = "libp2p-mplex"
 edition = "2021"
 rust-version = "1.56.1"
 description = "Mplex multiplexing protocol for libp2p"
-version = "0.34.0"
+version = "0.35.0"
 authors = ["Parity Technologies <admin@parity.io>"]
 license = "MIT"
 repository = "https://github.com/libp2p/rust-libp2p"
@@ -14,7 +14,7 @@ categories = ["network-programming", "asynchronous"]
 bytes = "1"
 futures = "0.3.1"
 asynchronous-codec = "0.6"
-libp2p-core = { version = "0.34.0", path = "../../core", default-features = false }
+libp2p-core = { version = "0.35.0", path = "../../core", default-features = false }
 log = "0.4"
 nohash-hasher = "0.2"
 parking_lot = "0.12"

muxers/mplex/benches/split_send_size.rs

@@ -114,11 +114,9 @@ fn run(
                 }
                 transport::TransportEvent::Incoming { upgrade, .. } => {
                     let (_peer, conn) = upgrade.await.unwrap();
-                    let mut s = poll_fn(|cx| conn.poll_event(cx))
+                    let mut s = poll_fn(|cx| conn.poll_inbound(cx))
                         .await
-                        .expect("unexpected error")
+                        .expect("unexpected error");
-                        .into_inbound_substream()
-                        .expect("Unexpected muxer event");
 
                     let mut buf = vec![0u8; payload_len];
                     let mut off = 0;
@@ -143,10 +141,7 @@ fn run(
     let sender = async move {
         let addr = addr_receiver.await.unwrap();
         let (_peer, conn) = sender_trans.dial(addr).unwrap().await.unwrap();
-        let mut handle = conn.open_outbound();
+        let mut stream = poll_fn(|cx| conn.poll_outbound(cx)).await.unwrap();
-        let mut stream = poll_fn(|cx| conn.poll_outbound(cx, &mut handle))
-            .await
-            .unwrap();
         let mut off = 0;
         loop {
             let n = poll_fn(|cx| Pin::new(&mut stream).poll_write(cx, &payload[off..]))

muxers/mplex/src/lib.rs

@@ -28,9 +28,8 @@ use bytes::Bytes;
 use codec::LocalStreamId;
 use futures::{future, prelude::*, ready};
 use libp2p_core::{
-    muxing::StreamMuxerEvent,
     upgrade::{InboundUpgrade, OutboundUpgrade, UpgradeInfo},
-    StreamMuxer,
+    Multiaddr, StreamMuxer,
 };
 use parking_lot::Mutex;
 use std::{cmp, iter, pin::Pin, sync::Arc, task::Context, task::Poll};
@@ -75,9 +74,6 @@ where
 }
 
 /// Multiplexer. Implements the `StreamMuxer` trait.
-///
-/// This implementation isn't capable of detecting when the underlying socket changes its address,
-/// and no [`StreamMuxerEvent::AddressChange`] event is ever emitted.
 pub struct Multiplex<C> {
     io: Arc<Mutex<io::Multiplexed<C>>>,
 }
@@ -87,33 +83,24 @@ where
     C: AsyncRead + AsyncWrite + Unpin,
 {
     type Substream = Substream<C>;
-    type OutboundSubstream = OutboundSubstream;
     type Error = io::Error;
 
-    fn poll_event(
+    fn poll_inbound(&self, cx: &mut Context<'_>) -> Poll<Result<Self::Substream, Self::Error>> {
-        &self,
+        self.io
-        cx: &mut Context<'_>,
+            .lock()
-    ) -> Poll<io::Result<StreamMuxerEvent<Self::Substream>>> {
+            .poll_next_stream(cx)
-        let stream_id = ready!(self.io.lock().poll_next_stream(cx))?;
+            .map_ok(|stream_id| Substream::new(stream_id, self.io.clone()))
-        let stream = Substream::new(stream_id, self.io.clone());
-        Poll::Ready(Ok(StreamMuxerEvent::InboundSubstream(stream)))
     }
 
-    fn open_outbound(&self) -> Self::OutboundSubstream {
+    fn poll_outbound(&self, cx: &mut Context<'_>) -> Poll<Result<Self::Substream, Self::Error>> {
-        OutboundSubstream {}
+        self.io
+            .lock()
+            .poll_open_stream(cx)
+            .map_ok(|stream_id| Substream::new(stream_id, self.io.clone()))
     }
 
-    fn poll_outbound(
+    fn poll_address_change(&self, _: &mut Context<'_>) -> Poll<Result<Multiaddr, Self::Error>> {
-        &self,
+        Poll::Pending
-        cx: &mut Context<'_>,
-        _: &mut Self::OutboundSubstream,
-    ) -> Poll<Result<Self::Substream, io::Error>> {
-        let stream_id = ready!(self.io.lock().poll_open_stream(cx))?;
-        Poll::Ready(Ok(Substream::new(stream_id, self.io.clone())))
-    }
-
-    fn destroy_outbound(&self, _substream: Self::OutboundSubstream) {
-        // Nothing to do, since `open_outbound` creates no new local state.
     }
 
     fn poll_close(&self, cx: &mut Context<'_>) -> Poll<Result<(), io::Error>> {
@@ -121,9 +108,6 @@ where
     }
 }
 
-/// Active attempt to open an outbound substream.
-pub struct OutboundSubstream {}
-
 impl<C> AsyncRead for Substream<C>
 where
     C: AsyncRead + AsyncWrite + Unpin,

muxers/mplex/tests/async_write.rs

@@ -60,10 +60,7 @@ fn async_write() {
             .await
             .unwrap();
 
-        let mut outbound_token = client.open_outbound();
+        let mut outbound = poll_fn(|cx| client.poll_outbound(cx)).await.unwrap();
-        let mut outbound = poll_fn(|cx| client.poll_outbound(cx, &mut outbound_token))
-            .await
-            .unwrap();
 
         let mut buf = Vec::new();
         outbound.read_to_end(&mut buf).await.unwrap();
@@ -76,15 +73,7 @@ fn async_write() {
             .and_then(move |c, e| upgrade::apply(c, mplex, e, upgrade::Version::V1));
 
         let client = Arc::new(transport.dial(rx.await.unwrap()).unwrap().await.unwrap());
-        let mut inbound = loop {
+        let mut inbound = poll_fn(|cx| client.poll_inbound(cx)).await.unwrap();
-            if let Some(s) = poll_fn(|cx| client.poll_event(cx))
-                .await
-                .unwrap()
-                .into_inbound_substream()
-            {
-                break s;
-            }
-        };
         inbound.write_all(b"hello world").await.unwrap();
 
         // The test consists in making sure that this flushes the substream.

muxers/mplex/tests/two_peers.rs

@@ -60,10 +60,7 @@ fn client_to_server_outbound() {
             .await
             .unwrap();
 
-        let mut outbound_token = client.open_outbound();
+        let mut outbound = poll_fn(|cx| client.poll_outbound(cx)).await.unwrap();
-        let mut outbound = poll_fn(|cx| client.poll_outbound(cx, &mut outbound_token))
-            .await
-            .unwrap();
 
         let mut buf = Vec::new();
         outbound.read_to_end(&mut buf).await.unwrap();
@@ -77,15 +74,7 @@ fn client_to_server_outbound() {
             .boxed();
 
         let client = Arc::new(transport.dial(rx.await.unwrap()).unwrap().await.unwrap());
-        let mut inbound = loop {
+        let mut inbound = poll_fn(|cx| client.poll_inbound(cx)).await.unwrap();
-            if let Some(s) = poll_fn(|cx| client.poll_event(cx))
-                .await
-                .unwrap()
-                .into_inbound_substream()
-            {
-                break s;
-            }
-        };
         inbound.write_all(b"hello world").await.unwrap();
         inbound.close().await.unwrap();
 
@@ -131,15 +120,7 @@ fn client_to_server_inbound() {
                 .unwrap(),
         );
 
-        let mut inbound = loop {
+        let mut inbound = poll_fn(|cx| client.poll_inbound(cx)).await.unwrap();
-            if let Some(s) = poll_fn(|cx| client.poll_event(cx))
-                .await
-                .unwrap()
-                .into_inbound_substream()
-            {
-                break s;
-            }
-        };
 
         let mut buf = Vec::new();
         inbound.read_to_end(&mut buf).await.unwrap();
@@ -154,10 +135,7 @@ fn client_to_server_inbound() {
 
         let client = transport.dial(rx.await.unwrap()).unwrap().await.unwrap();
 
-        let mut outbound_token = client.open_outbound();
+        let mut outbound = poll_fn(|cx| client.poll_outbound(cx)).await.unwrap();
-        let mut outbound = poll_fn(|cx| client.poll_outbound(cx, &mut outbound_token))
-            .await
-            .unwrap();
         outbound.write_all(b"hello world").await.unwrap();
         outbound.close().await.unwrap();
 
@@ -199,10 +177,7 @@ fn protocol_not_match() {
             .await
             .unwrap();
 
-        let mut outbound_token = client.open_outbound();
+        let mut outbound = poll_fn(|cx| client.poll_outbound(cx)).await.unwrap();
-        let mut outbound = poll_fn(|cx| client.poll_outbound(cx, &mut outbound_token))
-            .await
-            .unwrap();
 
         let mut buf = Vec::new();
         outbound.read_to_end(&mut buf).await.unwrap();

muxers/yamux/CHANGELOG.md

@@ -1,3 +1,7 @@
+# 0.39.0 [unreleased]
+
+- Update to `libp2p-core` `v0.35.0`
+
 # 0.38.0
 
 - Update to `libp2p-core` `v0.34.0`.

muxers/yamux/Cargo.toml

@@ -3,7 +3,7 @@ name = "libp2p-yamux"
 edition = "2021"
 rust-version = "1.56.1"
 description = "Yamux multiplexing protocol for libp2p"
-version = "0.38.0"
+version = "0.39.0"
 authors = ["Parity Technologies <admin@parity.io>"]
 license = "MIT"
 repository = "https://github.com/libp2p/rust-libp2p"
@@ -12,7 +12,7 @@ categories = ["network-programming", "asynchronous"]
 
 [dependencies]
 futures = "0.3.1"
-libp2p-core = { version = "0.34.0", path = "../../core", default-features = false }
+libp2p-core = { version = "0.35.0", path = "../../core", default-features = false }
 parking_lot = "0.12"
 thiserror = "1.0"
 yamux = "0.10.0"

muxers/yamux/src/lib.rs

@@ -24,11 +24,11 @@
 use futures::{
     future,
     prelude::*,
-    ready,
     stream::{BoxStream, LocalBoxStream},
 };
-use libp2p_core::muxing::{StreamMuxer, StreamMuxerEvent};
+use libp2p_core::muxing::StreamMuxer;
 use libp2p_core::upgrade::{InboundUpgrade, OutboundUpgrade, UpgradeInfo};
+use libp2p_core::Multiaddr;
 use parking_lot::Mutex;
 use std::{
     fmt, io, iter, mem,
@@ -36,6 +36,7 @@ use std::{
     task::{Context, Poll},
 };
 use thiserror::Error;
+use yamux::ConnectionError;
 
 /// A Yamux connection.
 pub struct Yamux<S>(Mutex<Inner<S>>);
@@ -97,44 +98,35 @@ where
 
 pub type YamuxResult<T> = Result<T, YamuxError>;
 
-/// > **Note**: This implementation never emits [`StreamMuxerEvent::AddressChange`] events.
 impl<S> StreamMuxer for Yamux<S>
 where
     S: Stream<Item = Result<yamux::Stream, YamuxError>> + Unpin,
 {
     type Substream = yamux::Stream;
-    type OutboundSubstream = OpenSubstreamToken;
     type Error = YamuxError;
 
-    fn poll_event(
+    fn poll_inbound(&self, cx: &mut Context<'_>) -> Poll<Result<Self::Substream, Self::Error>> {
-        &self,
+        self.0
-        c: &mut Context<'_>,
+            .lock()
-    ) -> Poll<YamuxResult<StreamMuxerEvent<Self::Substream>>> {
+            .incoming
-        let mut inner = self.0.lock();
+            .poll_next_unpin(cx)
-        match ready!(inner.incoming.poll_next_unpin(c)) {
+            .map(|maybe_stream| {
-            Some(Ok(s)) => Poll::Ready(Ok(StreamMuxerEvent::InboundSubstream(s))),
+                let stream = maybe_stream
-            Some(Err(e)) => Poll::Ready(Err(e)),
+                    .transpose()?
-            None => Poll::Ready(Err(yamux::ConnectionError::Closed.into())),
+                    .ok_or(YamuxError(ConnectionError::Closed))?;
-        }
+
+                Ok(stream)
+            })
     }
 
-    fn open_outbound(&self) -> Self::OutboundSubstream {
+    fn poll_outbound(&self, cx: &mut Context<'_>) -> Poll<Result<Self::Substream, Self::Error>> {
-        OpenSubstreamToken(())
+        Pin::new(&mut self.0.lock().control)
-    }
+            .poll_open_stream(cx)
-
-    fn poll_outbound(
-        &self,
-        c: &mut Context<'_>,
-        _: &mut OpenSubstreamToken,
-    ) -> Poll<YamuxResult<Self::Substream>> {
-        let mut inner = self.0.lock();
-        Pin::new(&mut inner.control)
-            .poll_open_stream(c)
             .map_err(YamuxError)
     }
 
-    fn destroy_outbound(&self, _: Self::OutboundSubstream) {
+    fn poll_address_change(&self, _: &mut Context<'_>) -> Poll<Result<Multiaddr, Self::Error>> {
-        self.0.lock().control.abort_open_stream()
+        Poll::Pending
     }
 
     fn poll_close(&self, c: &mut Context<'_>) -> Poll<YamuxResult<()>> {

protocols/autonat/CHANGELOG.md

@@ -4,6 +4,8 @@
 
 - Update to `libp2p-request-response` `v0.20.0`.
 
+- Update to `libp2p-core` `v0.35.0`.
+
 # 0.5.0
 
 - Update to `libp2p-core` `v0.34.0`.

protocols/autonat/Cargo.toml

@@ -18,7 +18,7 @@ async-trait = "0.1"
 futures = "0.3"
 futures-timer = "3.0"
 instant = "0.1"
-libp2p-core = { version = "0.34.0", path = "../../core", default-features = false }
+libp2p-core = { version = "0.35.0", path = "../../core", default-features = false }
 libp2p-swarm = { version = "0.38.0", path = "../../swarm" }
 libp2p-request-response = { version = "0.20.0", path = "../request-response" }
 log = "0.4"

protocols/dcutr/CHANGELOG.md

@@ -4,6 +4,8 @@
 
 - Expose `PROTOCOL_NAME`. See [PR 2734].
 
+- Update to `libp2p-core` `v0.35.0`.
+
 [PR 2734]: https://github.com/libp2p/rust-libp2p/pull/2734/
 
 # 0.4.0

protocols/dcutr/Cargo.toml

@@ -17,7 +17,7 @@ either = "1.6.0"
 futures = "0.3.1"
 futures-timer = "3.0"
 instant = "0.1.11"
-libp2p-core = { version = "0.34.0", path = "../../core" }
+libp2p-core = { version = "0.35.0", path = "../../core" }
 libp2p-swarm = { version = "0.38.0", path = "../../swarm" }
 log = "0.4"
 prost-codec = { version = "0.1", path = "../../misc/prost-codec" }

protocols/floodsub/CHANGELOG.md

@@ -2,6 +2,8 @@
 
 - Update to `libp2p-swarm` `v0.38.0`.
 
+- Update to `libp2p-core` `v0.35.0`.
+
 # 0.37.0
 
 - Update to `libp2p-core` `v0.34.0`.

protocols/floodsub/Cargo.toml

@@ -14,7 +14,7 @@ categories = ["network-programming", "asynchronous"]
 cuckoofilter = "0.5.0"
 fnv = "1.0"
 futures = "0.3.1"
-libp2p-core = { version = "0.34.0", path = "../../core", default-features = false }
+libp2p-core = { version = "0.35.0", path = "../../core", default-features = false }
 libp2p-swarm = { version = "0.38.0", path = "../../swarm" }
 log = "0.4"
 prost = "0.10"

protocols/gossipsub/CHANGELOG.md

@@ -2,6 +2,8 @@
 
 - Update to `libp2p-swarm` `v0.38.0`.
 
+- Update to `libp2p-core` `v0.35.0`.
+
 # 0.39.0
 
 - Update to `libp2p-core` `v0.34.0`.

protocols/gossipsub/Cargo.toml

@@ -12,7 +12,7 @@ categories = ["network-programming", "asynchronous"]
 
 [dependencies]
 libp2p-swarm = { version = "0.38.0", path = "../../swarm" }
-libp2p-core = { version = "0.34.0", path = "../../core", default-features = false }
+libp2p-core = { version = "0.35.0", path = "../../core", default-features = false }
 bytes = "1.0"
 byteorder = "1.3.4"
 fnv = "1.0.7"

protocols/identify/CHANGELOG.md

@@ -4,6 +4,8 @@
 
 - Expose `PROTOCOL_NAME` and `PUSH_PROTOCOL_NAME`. See [PR 2734].
 
+- Update to `libp2p-core` `v0.35.0`.
+
 [PR 2734]: https://github.com/libp2p/rust-libp2p/pull/2734/
 
 # 0.37.0

protocols/identify/Cargo.toml

@@ -14,7 +14,7 @@ categories = ["network-programming", "asynchronous"]
 asynchronous-codec = "0.6"
 futures = "0.3.1"
 futures-timer = "3.0.2"
-libp2p-core = { version = "0.34.0", path = "../../core", default-features = false }
+libp2p-core = { version = "0.35.0", path = "../../core", default-features = false }
 libp2p-swarm = { version = "0.38.0", path = "../../swarm" }
 log = "0.4.1"
 lru = "0.7.2"

protocols/kad/CHANGELOG.md

@@ -2,6 +2,8 @@
 
 - Update to `libp2p-swarm` `v0.38.0`.
 
+- Update to `libp2p-core` `v0.35.0`.
+
 # 0.38.0
 
 - Update to `libp2p-core` `v0.34.0`.

protocols/kad/Cargo.toml

@@ -18,7 +18,7 @@ fnv = "1.0"
 asynchronous-codec = "0.6"
 futures = "0.3.1"
 log = "0.4"
-libp2p-core = { version = "0.34.0", path = "../../core", default-features = false }
+libp2p-core = { version = "0.35.0", path = "../../core", default-features = false }
 libp2p-swarm = { version = "0.38.0", path = "../../swarm" }
 prost = "0.10"
 rand = "0.7.2"

protocols/mdns/CHANGELOG.md

@@ -2,6 +2,8 @@
 
 - Update to `libp2p-swarm` `v0.38.0`.
 
+- Update to `libp2p-core` `v0.35.0`.
+
 # 0.38.0
 
 - Update to `libp2p-core` `v0.34.0`.

protocols/mdns/Cargo.toml

@@ -17,7 +17,7 @@ dns-parser = "0.8.0"
 futures = "0.3.13"
 if-watch = "1.0.0"
 lazy_static = "1.4.0"
-libp2p-core = { version = "0.34.0", path = "../../core", default-features = false }
+libp2p-core = { version = "0.35.0", path = "../../core", default-features = false }
 libp2p-swarm = { version = "0.38.0", path = "../../swarm" }
 log = "0.4.14"
 rand = "0.8.3"

protocols/ping/CHANGELOG.md

@@ -4,6 +4,8 @@
 
 - Expose `PROTOCOL_NAME`. See [PR 2734].
 
+- Update to `libp2p-core` `v0.35.0`.
+
 [PR 2734]: https://github.com/libp2p/rust-libp2p/pull/2734/
 
 # 0.37.0

protocols/ping/Cargo.toml

@@ -14,7 +14,7 @@ categories = ["network-programming", "asynchronous"]
 futures = "0.3.1"
 futures-timer = "3.0.2"
 instant = "0.1.11"
-libp2p-core = { version = "0.34.0", path = "../../core", default-features = false }
+libp2p-core = { version = "0.35.0", path = "../../core", default-features = false }
 libp2p-swarm = { version = "0.38.0", path = "../../swarm" }
 log = "0.4.1"
 rand = "0.7.2"

protocols/relay/CHANGELOG.md

@@ -4,6 +4,8 @@
 
 - Expose `HOP_PROTOCOL_NAME` and `STOP_PROTOCOL_NAME`. See [PR 2734].
 
+- Update to `libp2p-core` `v0.35.0`.
+
 [PR 2734]: https://github.com/libp2p/rust-libp2p/pull/2734/
 
 # 0.10.0

protocols/relay/Cargo.toml

@@ -17,7 +17,7 @@ either = "1.6.0"
 futures = "0.3.1"
 futures-timer = "3"
 instant = "0.1.11"
-libp2p-core = { version = "0.34.0", path = "../../core", default-features = false }
+libp2p-core = { version = "0.35.0", path = "../../core", default-features = false }
 libp2p-swarm = { version = "0.38.0", path = "../../swarm" }
 log = "0.4"
 pin-project = "1"

protocols/rendezvous/CHANGELOG.md

@@ -2,6 +2,8 @@
 
 - Update to `libp2p-swarm` `v0.38.0`.
 
+- Update to `libp2p-core` `v0.35.0`.
+
 # 0.7.0
 
 - Update to `libp2p-core` `v0.34.0`.

protocols/rendezvous/Cargo.toml

@@ -12,7 +12,7 @@ categories = ["network-programming", "asynchronous"]
 
 [dependencies]
 asynchronous-codec = "0.6"
-libp2p-core = { version = "0.34.0", path = "../../core", default-features = false }
+libp2p-core = { version = "0.35.0", path = "../../core", default-features = false }
 libp2p-swarm = { version = "0.38.0", path = "../../swarm" }
 prost = "0.10"
 void = "1"

protocols/request-response/CHANGELOG.md

@@ -2,6 +2,8 @@
 
 - Update to `libp2p-swarm` `v0.38.0`.
 
+- Update to `libp2p-core` `v0.35.0`.
+
 # 0.19.0
 
 - Update to `libp2p-core` `v0.34.0`.

protocols/request-response/Cargo.toml

@@ -15,7 +15,7 @@ async-trait = "0.1"
 bytes = "1"
 futures = "0.3.1"
 instant = "0.1.11"
-libp2p-core = { version = "0.34.0", path = "../../core", default-features = false  }
+libp2p-core = { version = "0.35.0", path = "../../core", default-features = false  }
 libp2p-swarm = { version = "0.38.0", path = "../../swarm" }
 log = "0.4.11"
 rand = "0.7"

swarm/CHANGELOG.md

@@ -2,6 +2,8 @@
 
 - Update dial address concurrency factor to `8`, thus dialing up to 8 addresses concurrently for a single connection attempt. See `Swarm::dial_concurrency_factor` and [PR 2741].
 
+- Update to `libp2p-core` `v0.35.0`.
+
 [PR 2741]: https://github.com/libp2p/rust-libp2p/pull/2741/
 
 # 0.37.0

swarm/Cargo.toml

@@ -16,7 +16,7 @@ fnv = "1.0"
 futures = "0.3.1"
 futures-timer = "3.0.2"
 instant = "0.1.11"
-libp2p-core = { version = "0.34.0", path = "../core", default-features = false }
+libp2p-core = { version = "0.35.0", path = "../core", default-features = false }
 log = "0.4"
 pin-project = "1.0.0"
 rand = "0.7"

swarm/src/connection.rs

@@ -20,7 +20,6 @@
 
 mod error;
 mod handler_wrapper;
-mod substream;
 
 pub(crate) mod pool;
 
@@ -30,18 +29,19 @@ pub use error::{
 };
 pub use pool::{ConnectionCounters, ConnectionLimits};
 pub use pool::{EstablishedConnection, PendingConnection};
-pub use substream::{Close, SubstreamEndpoint};
 
 use crate::handler::ConnectionHandler;
 use crate::IntoConnectionHandler;
+use futures::future::poll_fn;
 use handler_wrapper::HandlerWrapper;
 use libp2p_core::connection::ConnectedPoint;
 use libp2p_core::multiaddr::Multiaddr;
 use libp2p_core::muxing::StreamMuxerBox;
-use libp2p_core::upgrade;
 use libp2p_core::PeerId;
-use std::{error::Error, fmt, pin::Pin, task::Context, task::Poll};
+use libp2p_core::{upgrade, StreamMuxer};
-use substream::{Muxing, SubstreamEvent};
+use std::collections::VecDeque;
+use std::future::Future;
+use std::{error::Error, fmt, io, pin::Pin, task::Context, task::Poll};
 
 /// Information about a successfully established connection.
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -52,6 +52,13 @@ pub struct Connected {
     pub peer_id: PeerId,
 }
 
+/// Endpoint for a received substream.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub enum SubstreamEndpoint<TDialInfo> {
+    Dialer(TDialInfo),
+    Listener,
+}
+
 /// Event generated by a [`Connection`].
 #[derive(Debug, Clone)]
 pub enum Event<T> {
@@ -67,19 +74,22 @@ where
     THandler: ConnectionHandler,
 {
     /// Node that handles the muxing.
-    muxing: substream::Muxing<StreamMuxerBox, handler_wrapper::OutboundOpenInfo<THandler>>,
+    muxing: StreamMuxerBox,
     /// Handler that processes substreams.
     handler: HandlerWrapper<THandler>,
+    /// List of "open_info" that is waiting for new outbound substreams.
+    open_info: VecDeque<handler_wrapper::OutboundOpenInfo<THandler>>,
 }
 
 impl<THandler> fmt::Debug for Connection<THandler>
 where
     THandler: ConnectionHandler + fmt::Debug,
+    THandler::OutboundOpenInfo: fmt::Debug,
 {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_struct("Connection")
-            .field("muxing", &self.muxing)
             .field("handler", &self.handler)
+            .field("open_info", &self.open_info)
             .finish()
     }
 }
@@ -108,8 +118,9 @@ where
             max_negotiating_inbound_streams,
         );
         Connection {
-            muxing: Muxing::new(muxer),
+            muxing: muxer,
             handler: wrapped_handler,
+            open_info: VecDeque::with_capacity(8),
         }
     }
 
@@ -120,10 +131,10 @@ where
 
     /// Begins an orderly shutdown of the connection, returning the connection
     /// handler and a `Future` that resolves when connection shutdown is complete.
-    pub fn close(self) -> (THandler, Close<StreamMuxerBox>) {
+    pub fn close(self) -> (THandler, impl Future<Output = io::Result<()>>) {
         (
             self.handler.into_connection_handler(),
-            self.muxing.close().0,
+            poll_fn(move |cx| self.muxing.poll_close(cx)),
         )
     }
 
@@ -138,38 +149,38 @@ where
             match self.handler.poll(cx)? {
                 Poll::Pending => {}
                 Poll::Ready(handler_wrapper::Event::OutboundSubstreamRequest(user_data)) => {
-                    self.muxing.open_substream(user_data);
+                    self.open_info.push_back(user_data);
-                    continue;
+                    continue; // Poll handler until exhausted.
                 }
                 Poll::Ready(handler_wrapper::Event::Custom(event)) => {
                     return Poll::Ready(Ok(Event::Handler(event)));
                 }
             }
 
-            // Perform I/O on the connection through the muxer, informing the handler
+            if !self.open_info.is_empty() {
-            // of new substreams.
+                if let Poll::Ready(substream) = self.muxing.poll_outbound(cx)? {
-            match self.muxing.poll(cx)? {
+                    let user_data = self
-                Poll::Pending => {}
+                        .open_info
-                Poll::Ready(SubstreamEvent::InboundSubstream { substream }) => {
+                        .pop_front()
-                    self.handler
+                        .expect("`open_info` is not empty");
-                        .inject_substream(substream, SubstreamEndpoint::Listener);
-                    continue;
-                }
-                Poll::Ready(SubstreamEvent::OutboundSubstream {
-                    user_data,
-                    substream,
-                }) => {
                     let endpoint = SubstreamEndpoint::Dialer(user_data);
                     self.handler.inject_substream(substream, endpoint);
-                    continue;
+                    continue; // Go back to the top, handler can potentially make progress again.
-                }
-                Poll::Ready(SubstreamEvent::AddressChange(address)) => {
-                    self.handler.inject_address_change(&address);
-                    return Poll::Ready(Ok(Event::AddressChange(address)));
                 }
             }
 
-            return Poll::Pending;
+            if let Poll::Ready(substream) = self.muxing.poll_inbound(cx)? {
+                self.handler
+                    .inject_substream(substream, SubstreamEndpoint::Listener);
+                continue; // Go back to the top, handler can potentially make progress again.
+            }
+
+            if let Poll::Ready(address) = self.muxing.poll_address_change(cx)? {
+                self.handler.inject_address_change(&address);
+                return Poll::Ready(Ok(Event::AddressChange(address)));
+            }
+
+            return Poll::Pending; // Nothing can make progress, return `Pending`.
         }
     }
 }

swarm/src/connection/substream.rs

@@ -1,252 +0,0 @@
-// 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.
-
-use futures::prelude::*;
-use libp2p_core::multiaddr::Multiaddr;
-use libp2p_core::muxing::{StreamMuxer, StreamMuxerEvent};
-use smallvec::SmallVec;
-use std::sync::Arc;
-use std::{fmt, pin::Pin, task::Context, task::Poll};
-
-/// Endpoint for a received substream.
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
-pub enum SubstreamEndpoint<TDialInfo> {
-    Dialer(TDialInfo),
-    Listener,
-}
-
-/// Implementation of `Stream` that handles substream multiplexing.
-///
-/// The stream will receive substreams and can be used to open new outgoing substreams. Destroying
-/// the `Muxing` will **not** close the existing substreams.
-///
-/// The stream will close once both the inbound and outbound channels are closed, and no more
-/// outbound substream attempt is pending.
-pub struct Muxing<TMuxer, TUserData>
-where
-    TMuxer: StreamMuxer,
-{
-    /// The muxer used to manage substreams.
-    inner: Arc<TMuxer>,
-    /// List of substreams we are currently opening.
-    outbound_substreams: SmallVec<[(TUserData, TMuxer::OutboundSubstream); 8]>,
-}
-
-/// Future that signals the remote that we have closed the connection.
-pub struct Close<TMuxer> {
-    /// Muxer to close.
-    muxer: Arc<TMuxer>,
-}
-
-/// Event that can happen on the `Muxing`.
-pub enum SubstreamEvent<TMuxer, TUserData>
-where
-    TMuxer: StreamMuxer,
-{
-    /// A new inbound substream arrived.
-    InboundSubstream {
-        /// The newly-opened substream. Will return EOF of an error if the `Muxing` is
-        /// destroyed or `close_graceful` is called.
-        substream: TMuxer::Substream,
-    },
-
-    /// An outbound substream has successfully been opened.
-    OutboundSubstream {
-        /// User data that has been passed to the `open_substream` method.
-        user_data: TUserData,
-        /// The newly-opened substream. Will return EOF of an error if the `Muxing` is
-        /// destroyed or `close_graceful` is called.
-        substream: TMuxer::Substream,
-    },
-
-    /// 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),
-}
-
-/// Identifier for a substream being opened.
-#[derive(Debug, Copy, Clone, Hash, PartialEq, Eq, PartialOrd, Ord)]
-pub struct OutboundSubstreamId(usize);
-
-impl<TMuxer, TUserData> Muxing<TMuxer, TUserData>
-where
-    TMuxer: StreamMuxer,
-{
-    /// Creates a new node events stream.
-    pub fn new(muxer: TMuxer) -> Self {
-        Muxing {
-            inner: Arc::new(muxer),
-            outbound_substreams: SmallVec::new(),
-        }
-    }
-
-    /// Starts the process of opening a new outbound substream.
-    ///
-    /// After calling this method, polling the stream should eventually produce either an
-    /// `OutboundSubstream` event or an `OutboundClosed` event containing the user data that has
-    /// been passed to this method.
-    pub fn open_substream(&mut self, user_data: TUserData) {
-        let raw = self.inner.open_outbound();
-        self.outbound_substreams.push((user_data, raw));
-    }
-
-    /// Destroys the node stream and returns all the pending outbound substreams, plus an object
-    /// that signals the remote that we shut down the connection.
-    #[must_use]
-    pub fn close(mut self) -> (Close<TMuxer>, Vec<TUserData>) {
-        let substreams = self.cancel_outgoing();
-        let close = Close {
-            muxer: self.inner.clone(),
-        };
-        (close, substreams)
-    }
-
-    /// Destroys all outbound streams and returns the corresponding user data.
-    pub fn cancel_outgoing(&mut self) -> Vec<TUserData> {
-        let mut out = Vec::with_capacity(self.outbound_substreams.len());
-        for (user_data, outbound) in self.outbound_substreams.drain(..) {
-            out.push(user_data);
-            self.inner.destroy_outbound(outbound);
-        }
-        out
-    }
-
-    /// Provides an API similar to `Future`.
-    pub fn poll(
-        &mut self,
-        cx: &mut Context<'_>,
-    ) -> Poll<Result<SubstreamEvent<TMuxer, TUserData>, TMuxer::Error>> {
-        // Polling inbound substream.
-        match self.inner.poll_event(cx) {
-            Poll::Ready(Ok(StreamMuxerEvent::InboundSubstream(substream))) => {
-                return Poll::Ready(Ok(SubstreamEvent::InboundSubstream { substream }));
-            }
-            Poll::Ready(Ok(StreamMuxerEvent::AddressChange(addr))) => {
-                return Poll::Ready(Ok(SubstreamEvent::AddressChange(addr)))
-            }
-            Poll::Ready(Err(err)) => return Poll::Ready(Err(err)),
-            Poll::Pending => {}
-        }
-
-        // Polling outbound substreams.
-        // We remove each element from `outbound_substreams` one by one and add them back.
-        for n in (0..self.outbound_substreams.len()).rev() {
-            let (user_data, mut outbound) = self.outbound_substreams.swap_remove(n);
-            match self.inner.poll_outbound(cx, &mut outbound) {
-                Poll::Ready(Ok(substream)) => {
-                    self.inner.destroy_outbound(outbound);
-                    return Poll::Ready(Ok(SubstreamEvent::OutboundSubstream {
-                        user_data,
-                        substream,
-                    }));
-                }
-                Poll::Pending => {
-                    self.outbound_substreams.push((user_data, outbound));
-                }
-                Poll::Ready(Err(err)) => {
-                    self.inner.destroy_outbound(outbound);
-                    return Poll::Ready(Err(err));
-                }
-            }
-        }
-
-        // Nothing happened. Register our task to be notified and return.
-        Poll::Pending
-    }
-}
-
-impl<TMuxer, TUserData> fmt::Debug for Muxing<TMuxer, TUserData>
-where
-    TMuxer: StreamMuxer,
-{
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
-        f.debug_struct("Muxing")
-            .field("outbound_substreams", &self.outbound_substreams.len())
-            .finish()
-    }
-}
-
-impl<TMuxer, TUserData> Drop for Muxing<TMuxer, TUserData>
-where
-    TMuxer: StreamMuxer,
-{
-    fn drop(&mut self) {
-        // The substreams that were produced will continue to work, as the muxer is held in an Arc.
-        // However we will no longer process any further inbound or outbound substream, and we
-        // therefore close everything.
-        for (_, outbound) in self.outbound_substreams.drain(..) {
-            self.inner.destroy_outbound(outbound);
-        }
-    }
-}
-
-impl<TMuxer> Future for Close<TMuxer>
-where
-    TMuxer: StreamMuxer,
-{
-    type Output = Result<(), TMuxer::Error>;
-
-    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
-        match self.muxer.poll_close(cx) {
-            Poll::Pending => Poll::Pending,
-            Poll::Ready(Ok(())) => Poll::Ready(Ok(())),
-            Poll::Ready(Err(err)) => Poll::Ready(Err(err)),
-        }
-    }
-}
-
-impl<TMuxer> fmt::Debug for Close<TMuxer>
-where
-    TMuxer: StreamMuxer,
-{
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
-        f.debug_struct("Close").finish()
-    }
-}
-
-impl<TMuxer, TUserData> fmt::Debug for SubstreamEvent<TMuxer, TUserData>
-where
-    TMuxer: StreamMuxer,
-    TMuxer::Substream: fmt::Debug,
-    TUserData: fmt::Debug,
-{
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match self {
-            SubstreamEvent::InboundSubstream { substream } => f
-                .debug_struct("SubstreamEvent::OutboundClosed")
-                .field("substream", substream)
-                .finish(),
-            SubstreamEvent::OutboundSubstream {
-                user_data,
-                substream,
-            } => f
-                .debug_struct("SubstreamEvent::OutboundSubstream")
-                .field("user_data", user_data)
-                .field("substream", substream)
-                .finish(),
-            SubstreamEvent::AddressChange(address) => f
-                .debug_struct("SubstreamEvent::AddressChange")
-                .field("address", address)
-                .finish(),
-        }
-    }
-}

transports/deflate/CHANGELOG.md

@@ -1,3 +1,7 @@
+# 0.35.0 [unreleased]
+
+- Update to `libp2p-core` `v0.35.0`.
+
 # 0.34.0
 
 - Update to `libp2p-core` `v0.34.0`.

transports/deflate/Cargo.toml

@@ -3,7 +3,7 @@ name = "libp2p-deflate"
 edition = "2021"
 rust-version = "1.56.1"
 description = "Deflate encryption protocol for libp2p"
-version = "0.34.0"
+version = "0.35.0"
 authors = ["Parity Technologies <admin@parity.io>"]
 license = "MIT"
 repository = "https://github.com/libp2p/rust-libp2p"
@@ -12,7 +12,7 @@ categories = ["network-programming", "asynchronous"]
 
 [dependencies]
 futures = "0.3.1"
-libp2p-core = { version = "0.34.0", path = "../../core", default-features = false  }
+libp2p-core = { version = "0.35.0", path = "../../core", default-features = false  }
 flate2 = "1.0"
 
 [dev-dependencies]

transports/dns/CHANGELOG.md

@@ -1,3 +1,7 @@
+# 0.35.0 [unreleased]
+
+- Update to `libp2p-core` `v0.35.0`.
+
 # 0.34.0
 
 - Update to `libp2p-core` `v0.34.0`.

transports/dns/Cargo.toml

@@ -3,7 +3,7 @@ name = "libp2p-dns"
 edition = "2021"
 rust-version = "1.56.1"
 description = "DNS transport implementation for libp2p"
-version = "0.34.0"
+version = "0.35.0"
 authors = ["Parity Technologies <admin@parity.io>"]
 license = "MIT"
 repository = "https://github.com/libp2p/rust-libp2p"
@@ -11,7 +11,7 @@ keywords = ["peer-to-peer", "libp2p", "networking"]
 categories = ["network-programming", "asynchronous"]
 
 [dependencies]
-libp2p-core = { version = "0.34.0", path = "../../core", default-features = false  }
+libp2p-core = { version = "0.35.0", path = "../../core", default-features = false  }
 log = "0.4.1"
 futures = "0.3.1"
 async-std-resolver = { version = "0.21", optional = true }

transports/noise/CHANGELOG.md

@@ -1,3 +1,7 @@
+# 0.38.0 [unreleased]
+
+- Update to `libp2p-core` `v0.35.0`.
+
 # 0.37.0
 
 - Update to `libp2p-core` `v0.34.0`.

transports/noise/Cargo.toml

@@ -3,7 +3,7 @@ name = "libp2p-noise"
 edition = "2021"
 rust-version = "1.56.1"
 description = "Cryptographic handshake protocol using the noise framework."
-version = "0.37.0"
+version = "0.38.0"
 authors = ["Parity Technologies <admin@parity.io>"]
 license = "MIT"
 repository = "https://github.com/libp2p/rust-libp2p"
@@ -13,7 +13,7 @@ bytes = "1"
 curve25519-dalek = "3.0.0"
 futures = "0.3.1"
 lazy_static = "1.2"
-libp2p-core = { version = "0.34.0", path = "../../core", default-features = false  }
+libp2p-core = { version = "0.35.0", path = "../../core", default-features = false  }
 log = "0.4"
 prost = "0.10"
 rand = "0.8.3"

transports/plaintext/CHANGELOG.md

@@ -1,3 +1,7 @@
+# 0.35.0 [unreleased]
+
+- Update to `libp2p-core` `v0.35.0`.
+
 # 0.34.0
 
 - Update to `libp2p-core` `v0.34.0`.

transports/plaintext/Cargo.toml

@@ -3,7 +3,7 @@ name = "libp2p-plaintext"
 edition = "2021"
 rust-version = "1.56.1"
 description = "Plaintext encryption dummy protocol for libp2p"
-version = "0.34.0"
+version = "0.35.0"
 authors = ["Parity Technologies <admin@parity.io>"]
 license = "MIT"
 repository = "https://github.com/libp2p/rust-libp2p"
@@ -14,7 +14,7 @@ categories = ["network-programming", "asynchronous"]
 bytes = "1"
 futures = "0.3.1"
 asynchronous-codec = "0.6"
-libp2p-core = { version = "0.34.0", path = "../../core", default-features = false  }
+libp2p-core = { version = "0.35.0", path = "../../core", default-features = false  }
 log = "0.4.8"
 prost = "0.10"
 unsigned-varint = { version = "0.7", features = ["asynchronous_codec"] }

transports/tcp/Cargo.toml

@@ -18,7 +18,7 @@ if-watch = { version = "1.0.0", optional = true }
 if-addrs = { version = "0.7.0", optional = true }
 ipnet = "2.0.0"
 libc = "0.2.80"
-libp2p-core = { version = "0.34.0", path = "../../core", default-features = false  }
+libp2p-core = { version = "0.35.0", path = "../../core", default-features = false  }
 log = "0.4.11"
 socket2 = { version = "0.4.0", features = ["all"] }
 tokio-crate = { package = "tokio", version = "1.19.0", default-features = false, features = ["net"], optional = true }

transports/uds/CHANGELOG.md

@@ -1,3 +1,7 @@
+# 0.34.0 [unreleased]
+
+- Update to `libp2p-core` `v0.35.0`.
+
 # 0.33.0
 
 - Update dependencies.

transports/uds/Cargo.toml

@@ -3,7 +3,7 @@ name = "libp2p-uds"
 edition = "2021"
 rust-version = "1.56.1"
 description = "Unix domain sockets transport for libp2p"
-version = "0.33.0"
+version = "0.34.0"
 authors = ["Parity Technologies <admin@parity.io>"]
 license = "MIT"
 repository = "https://github.com/libp2p/rust-libp2p"
@@ -12,7 +12,7 @@ categories = ["network-programming", "asynchronous"]
 
 [target.'cfg(all(unix, not(target_os = "emscripten")))'.dependencies]
 async-std = { version = "1.6.2", optional = true }
-libp2p-core = { version = "0.34.0", path = "../../core", default-features = false  }
+libp2p-core = { version = "0.35.0", path = "../../core", default-features = false  }
 log = "0.4.1"
 futures = "0.3.1"
 tokio = { version = "1.15", default-features = false, features = ["net"], optional = true }

transports/wasm-ext/CHANGELOG.md

@@ -1,3 +1,7 @@
+# 0.35.0 [unreleased]
+
+- Update to `libp2p-core` `v0.35.0`.
+
 # 0.34.0
 
 - Update to `libp2p-core` `v0.34.0`.

transports/wasm-ext/Cargo.toml

@@ -3,7 +3,7 @@ name = "libp2p-wasm-ext"
 edition = "2021"
 rust-version = "1.56.1"
 description = "Allows passing in an external transport in a WASM environment"
-version = "0.34.0"
+version = "0.35.0"
 authors = ["Pierre Krieger <pierre.krieger1708@gmail.com>"]
 license = "MIT"
 repository = "https://github.com/libp2p/rust-libp2p"
@@ -13,7 +13,7 @@ categories = ["network-programming", "asynchronous"]
 [dependencies]
 futures = "0.3.1"
 js-sys = "0.3.50"
-libp2p-core = { version = "0.34.0", path = "../../core", default-features = false  }
+libp2p-core = { version = "0.35.0", path = "../../core", default-features = false  }
 parity-send-wrapper = "0.1.0"
 wasm-bindgen = "0.2.42"
 wasm-bindgen-futures = "0.4.4"

transports/websocket/CHANGELOG.md

@@ -1,3 +1,7 @@
+# 0.37.0 [unreleased]
+
+- Update to `libp2p-core` `v0.35.0`.
+
 # 0.36.0
 
 - Update to `libp2p-core` `v0.34.0`.

transports/websocket/Cargo.toml

@@ -3,7 +3,7 @@ name = "libp2p-websocket"
 edition = "2021"
 rust-version = "1.56.1"
 description = "WebSocket transport for libp2p"
-version = "0.36.0"
+version = "0.37.0"
 authors = ["Parity Technologies <admin@parity.io>"]
 license = "MIT"
 repository = "https://github.com/libp2p/rust-libp2p"
@@ -14,7 +14,7 @@ categories = ["network-programming", "asynchronous"]
 futures-rustls = "0.22"
 either = "1.5.3"
 futures = "0.3.1"
-libp2p-core = { version = "0.34.0", path = "../../core", default-features = false  }
+libp2p-core = { version = "0.35.0", path = "../../core", default-features = false  }
 log = "0.4.8"
 parking_lot = "0.12.0"
 quicksink = "0.1"