Squashed commit of the following:

commit 92eaf8a
Merge: 5f7f49b a60ffba
Author: canewsin <[email protected]>
Date:   Fri Dec 10 14:55:10 2021 +0530

    Merge branch 'relay-v2' of https://github.com/mxinden/rust-libp2p into pr/9

commit a60ffba
Author: Max Inden <[email protected]>
Date:   Thu Dec 9 21:59:03 2021 +0100

    protocols/relay/src/v2: Renew reservation after 3/4 of expiration

commit bfd92a1
Author: Max Inden <[email protected]>
Date:   Thu Dec 9 20:42:09 2021 +0100

    protocols/relay/src/v2: Fix typo

commit 08d6637
Author: Max Inden <[email protected]>
Date:   Thu Dec 9 20:38:27 2021 +0100

    protocols/relay/src/v2: Use OrTransport

commit 746c75e
Author: Max Inden <[email protected]>
Date:   Thu Dec 9 15:16:19 2021 +0100

    protocols/relay/src/v2/: Document pending_error and send_error_futs

commit c0c0880
Author: Max Inden <[email protected]>
Date:   Thu Dec 9 14:55:20 2021 +0100

    protocols/relay/src/v2/client: Extend unreacheable! text

commit 5f7f49b
Merge: 2de96d6 c88cff1
Author: canewsin <[email protected]>
Date:   Thu Dec 9 13:23:34 2021 +0530

    Merge branch 'relay-v2' into pr/9

commit c88cff1
Author: Max Inden <[email protected]>
Date:   Mon Nov 1 11:18:58 2021 +0100

    Cargo.toml: Remove rc suffix

commit 0cf7e96
Author: Max Inden <[email protected]>
Date:   Mon Nov 1 11:16:59 2021 +0100

    *: Prepare v0.40.0 release (libp2p#2323)

Author: canewsin

misc/metrics/Cargo.toml

@@ -3,7 +3,7 @@ name = "libp2p-metrics"
 edition = "2021"
 rust-version = "1.56.1"
 description = "Metrics for libp2p"
-version = "0.3.0"
+version = "0.1.0"
 authors = ["Max Inden <[email protected]>"]
 license = "MIT"
 repository = "https://github.com/libp2p/rust-libp2p"

protocols/gossipsub/CHANGELOG.md

@@ -1,25 +1,3 @@
-# 0.35.0 [unreleased]
-
-- Update dependencies.
-
-- Migrate to Rust edition 2021 (see [PR 2339]).
-
-[PR 2339]: https://github.com/libp2p/rust-libp2p/pull/2339
-
-# 0.34.0 [2021-11-16]
-
-- Add topic and mesh metrics (see [PR 2316]).
-
-- Fix bug in internal peer's topics tracking (see [PR 2325]).
-
-- Use `instant` and `futures-timer` instead of `wasm-timer` (see [PR 2245]).
-
-- Update dependencies.
-
-[PR 2245]: https://github.com/libp2p/rust-libp2p/pull/2245
-[PR 2325]: https://github.com/libp2p/rust-libp2p/pull/2325
-[PR 2316]: https://github.com/libp2p/rust-libp2p/pull/2316
-
 # 0.33.0 [2021-11-01]
 
 - Add an event to register peers that do not support the gossipsub protocol

protocols/identify/CHANGELOG.md

@@ -1,21 +1,3 @@
-# 0.33.0 [unreleased]
-
-- Update dependencies.
-
-- Migrate to Rust edition 2021 (see [PR 2339]).
-
-[PR 2339]: https://github.com/libp2p/rust-libp2p/pull/2339
-
-# 0.32.0 [2021-11-16]
-
-- Use `futures-timer` instead of `wasm-timer` (see [PR 2245]).
-- Filter invalid peers from cache used in `addresses_of_peer` – [PR 2338].
-
-- Update dependencies.
-
-[PR 2245]: https://github.com/libp2p/rust-libp2p/pull/2245
-[PR 2338]: https://github.com/libp2p/rust-libp2p/pull/2338
-
 # 0.31.0 [2021-11-01]
 
 - Make default features of `libp2p-core` optional.

protocols/kad/CHANGELOG.md

@@ -1,27 +1,3 @@
-# 0.34.0 [unreleased]
-
-- Update dependencies.
-
-- Migrate to Rust edition 2021 (see [PR 2339]).
-
-[PR 2339]: https://github.com/libp2p/rust-libp2p/pull/2339
-
-# 0.33.0 [2021-11-16]
-
-- Use `instant` and `futures-timer` instead of `wasm-timer` (see [PR 2245]).
-
-- Rename `KademliaEvent::InboundRequestServed` to `KademliaEvent::InboundRequest` and move
-  `InboundPutRecordRequest` into `InboundRequest::PutRecord` and `InboundAddProviderRequest` into
-  `InboundRequest::AddProvider` (see [PR 2297]).
-
-- Populate the `key` field when converting `KadRequestMsg::PutValue` to `proto::Message` (see [PR 2309]).
-
-- Update dependencies.
-
-[PR 2245]: https://github.com/libp2p/rust-libp2p/pull/2245
-[PR 2297]: https://github.com/libp2p/rust-libp2p/pull/2297
-[PR 2309]: https://github.com/libp2p/rust-libp2p/pull/2309
-
 # 0.32.0 [2021-11-01]
 
 - Make default features of `libp2p-core` optional.

protocols/relay/CHANGELOG.md

@@ -1,19 +1,3 @@
-# 0.6.0 [unreleased]
-
-- Update dependencies.
-
-- Migrate to Rust edition 2021 (see [PR 2339]).
-
-[PR 2339]: https://github.com/libp2p/rust-libp2p/pull/2339
-
-# 0.5.0 [2021-11-16]
-
-- Use `instant` instead of `wasm-timer` (see [PR 2245]).
-
-- Update dependencies.
-
-[PR 2245]: https://github.com/libp2p/rust-libp2p/pull/2245
-
 # 0.4.0 [2021-11-01]
 
 - Make default features of `libp2p-core` optional.

protocols/relay/src/v2/client.rs

@@ -21,7 +21,7 @@
 //! [`NetworkBehaviour`] to act as a circuit relay v2 **client**.
 
 mod handler;
-mod transport;
+pub mod transport;
 
 use crate::v2::protocol::inbound_stop;
 use bytes::Bytes;
@@ -32,7 +32,7 @@ use futures::io::{AsyncRead, AsyncWrite};
 use futures::ready;
 use futures::stream::StreamExt;
 use libp2p_core::connection::{ConnectedPoint, ConnectionId};
-use libp2p_core::{Multiaddr, PeerId, Transport};
+use libp2p_core::{Multiaddr, PeerId};
 use libp2p_swarm::dial_opts::DialOpts;
 use libp2p_swarm::{
     DialError, NegotiatedSubstream, NetworkBehaviour, NetworkBehaviourAction, NotifyHandler,
@@ -84,11 +84,10 @@ pub struct Client {
 }
 
 impl Client {
-    pub fn new_transport_and_behaviour<T: Transport + Clone>(
+    pub fn new_transport_and_behaviour(
         local_peer_id: PeerId,
-        transport: T,
-    ) -> (transport::ClientTransport<T>, Self) {
-        let (transport, from_transport) = transport::ClientTransport::new(transport);
+    ) -> (transport::ClientTransport, Self) {
+        let (transport, from_transport) = transport::ClientTransport::new();
         let behaviour = Client {
             local_peer_id,
             from_transport,
@@ -323,7 +322,9 @@ impl NetworkBehaviour for Client {
                 }
                 Poll::Ready(None) => unreachable!(
                     "`Relay` `NetworkBehaviour` polled after channel from \
-                     `RelayTransport` has been closed.",
+                     `RelayTransport` has been closed. Unreachable under \
+                     the assumption that the `Client` is never polled after \
+                     `ClientTransport` is dropped.",
                 ),
                 Poll::Pending => break,
             }

protocols/relay/src/v2/client/handler.rs

@@ -126,6 +126,7 @@ pub struct Handler {
     local_peer_id: PeerId,
     remote_peer_id: PeerId,
     remote_addr: Multiaddr,
+    /// A pending fatal error that results in the connection being closed.
     pending_error: Option<
         ProtocolsHandlerUpgrErr<
             EitherError<inbound_stop::UpgradeError, outbound_hop::UpgradeError>,
@@ -158,6 +159,10 @@ pub struct Handler {
 
     circuit_deny_futs: FuturesUnordered<BoxFuture<'static, (PeerId, Result<(), std::io::Error>)>>,
 
+    /// Futures that try to send errors to the transport.
+    ///
+    /// We may drop errors if this handler ends up in a terminal state (by returning
+    /// [`ProtocolsHandlerEvent::Close`]).
     send_error_futs: FuturesUnordered<BoxFuture<'static, ()>>,
 }
 
@@ -392,14 +397,19 @@ impl ProtocolsHandler for Handler {
                     }
                 }
 
-                self.send_error_futs.push(
-                    async move {
-                        let _ = to_listener
-                            .send(transport::ToListenerMsg::Reservation(Err(())))
-                            .await;
-                    }
-                    .boxed(),
-                );
+                if self.pending_error.is_none() {
+                    self.send_error_futs.push(
+                        async move {
+                            let _ = to_listener
+                                .send(transport::ToListenerMsg::Reservation(Err(())))
+                                .await;
+                        }
+                        .boxed(),
+                    );
+                } else {
+                    // Fatal error occured, thus handler is closing as quickly as possible.
+                    // Transport is notified through dropping `to_listener`.
+                }
 
                 self.queued_events.push_back(ProtocolsHandlerEvent::Custom(
                     Event::ReservationReqFailed { renewal },