Remove libp2p dependency from sc-network-sync (#4974)

## Issue
https://github.com/paritytech/polkadot-sdk/issues/4858

## Description
This PR removes `libp2p::request_response::OutboundFailure` from
`substrate/client/network/sync/src/engine.rs`. This way, the dependency
with the library `libp2p` is removed from `sc-network-sync`.

---------

Co-authored-by: Bastian Köcher <git@kchr.de>
Co-authored-by: command-bot <>
Co-authored-by: Dmitry Markin <dmitry@markin.tech>
Co-authored-by: Alexandru Vasile <60601340+lexnv@users.noreply.github.com>

Cargo.lock

@@ -19275,7 +19275,6 @@ dependencies = [
  "fork-tree",
  "futures",
  "futures-timer",
- "libp2p",
  "log",
  "mockall 0.11.4",
  "parity-scale-codec",

prdoc/pr_4974.prdoc

+# Schema: Polkadot SDK PRDoc Schema (prdoc) v1.0.0
+# See doc at https://raw.githubusercontent.com/paritytech/polkadot-sdk/master/prdoc/schema_user.json
+
+title: "Remove libp2p dependency from sc-network-sync"
+
+doc:
+  - audience: Node Dev
+    description: |
+      This PR removes `libp2p::request_response::OutboundFailure` from `substrate/client/network/sync/src/engine.rs`.
+
+crates: 
+  - name: sc-network
+    bump: patch
+  - name: sc-network-sync
+    bump: patch

substrate/client/network/src/request_responses.rs

@@ -64,7 +64,69 @@ use std::{
 	time::{Duration, Instant},
 };
 
-pub use libp2p::request_response::{Config, InboundFailure, OutboundFailure, RequestId};
+pub use libp2p::request_response::{Config, RequestId};
+
+/// Possible failures occurring in the context of sending an outbound request and receiving the
+/// response.
+#[derive(Debug, thiserror::Error)]
+pub enum OutboundFailure {
+	/// The request could not be sent because a dialing attempt failed.
+	#[error("Failed to dial the requested peer")]
+	DialFailure,
+	/// The request timed out before a response was received.
+	#[error("Timeout while waiting for a response")]
+	Timeout,
+	/// The connection closed before a response was received.
+	#[error("Connection was closed before a response was received")]
+	ConnectionClosed,
+	/// The remote supports none of the requested protocols.
+	#[error("The remote supports none of the requested protocols")]
+	UnsupportedProtocols,
+}
+
+impl From<request_response::OutboundFailure> for OutboundFailure {
+	fn from(out: request_response::OutboundFailure) -> Self {
+		match out {
+			request_response::OutboundFailure::DialFailure => OutboundFailure::DialFailure,
+			request_response::OutboundFailure::Timeout => OutboundFailure::Timeout,
+			request_response::OutboundFailure::ConnectionClosed =>
+				OutboundFailure::ConnectionClosed,
+			request_response::OutboundFailure::UnsupportedProtocols =>
+				OutboundFailure::UnsupportedProtocols,
+		}
+	}
+}
+
+/// Possible failures occurring in the context of receiving an inbound request and sending a
+/// response.
+#[derive(Debug, thiserror::Error)]
+pub enum InboundFailure {
+	/// The inbound request timed out, either while reading the incoming request or before a
+	/// response is sent
+	#[error("Timeout while receiving request or sending response")]
+	Timeout,
+	/// The connection closed before a response could be send.
+	#[error("Connection was closed before a response could be sent")]
+	ConnectionClosed,
+	/// The local peer supports none of the protocols requested by the remote.
+	#[error("The local peer supports none of the protocols requested by the remote")]
+	UnsupportedProtocols,
+	/// The local peer failed to respond to an inbound request
+	#[error("The response channel was dropped without sending a response to the remote")]
+	ResponseOmission,
+}
+
+impl From<request_response::InboundFailure> for InboundFailure {
+	fn from(out: request_response::InboundFailure) -> Self {
+		match out {
+			request_response::InboundFailure::ResponseOmission => InboundFailure::ResponseOmission,
+			request_response::InboundFailure::Timeout => InboundFailure::Timeout,
+			request_response::InboundFailure::ConnectionClosed => InboundFailure::ConnectionClosed,
+			request_response::InboundFailure::UnsupportedProtocols =>
+				InboundFailure::UnsupportedProtocols,
+		}
+	}
+}
 
 /// Error in a request.
 #[derive(Debug, thiserror::Error)]
@@ -808,7 +870,9 @@ impl NetworkBehaviour for RequestResponsesBehaviour {
 								}) => {
 									// Try using the fallback request if the protocol was not
 									// supported.
-									if let OutboundFailure::UnsupportedProtocols = error {
+									if let request_response::OutboundFailure::UnsupportedProtocols =
+										error
+									{
 										if let Some((fallback_request, fallback_protocol)) =
 											fallback_request
 										{
@@ -829,7 +893,7 @@ impl NetworkBehaviour for RequestResponsesBehaviour {
 									}
 
 									if response_tx
-										.send(Err(RequestFailure::Network(error.clone())))
+										.send(Err(RequestFailure::Network(error.clone().into())))
 										.is_err()
 									{
 										log::debug!(
@@ -856,7 +920,7 @@ impl NetworkBehaviour for RequestResponsesBehaviour {
 								peer,
 								protocol: protocol.clone(),
 								duration: started.elapsed(),
-								result: Err(RequestFailure::Network(error)),
+								result: Err(RequestFailure::Network(error.into())),
 							};
 
 							return Poll::Ready(ToSwarm::GenerateEvent(out))
@@ -873,7 +937,7 @@ impl NetworkBehaviour for RequestResponsesBehaviour {
 							let out = Event::InboundRequest {
 								peer,
 								protocol: protocol.clone(),
-								result: Err(ResponseFailure::Network(error)),
+								result: Err(ResponseFailure::Network(error.into())),
 							};
 							return Poll::Ready(ToSwarm::GenerateEvent(out))
 						},

substrate/client/network/sync/Cargo.toml

@@ -25,7 +25,6 @@ async-trait = { workspace = true }
 codec = { features = ["derive"], workspace = true, default-features = true }
 futures = { workspace = true }
 futures-timer = { workspace = true }
-libp2p = { workspace = true }
 log = { workspace = true, default-features = true }
 mockall = { workspace = true }
 prost = { workspace = true }

substrate/client/network/sync/src/engine.rs

@@ -42,7 +42,6 @@ use crate::{
 
 use codec::{Decode, DecodeAll, Encode};
 use futures::{channel::oneshot, FutureExt, StreamExt};
-use libp2p::request_response::OutboundFailure;
 use log::{debug, error, trace, warn};
 use prometheus_endpoint::{
 	register, Counter, Gauge, MetricSource, Opts, PrometheusError, Registry, SourcedGauge, U64,
@@ -56,7 +55,7 @@ use sc_consensus::{import_queue::ImportQueueService, IncomingBlock};
 use sc_network::{
 	config::{FullNetworkConfiguration, NotificationHandshake, ProtocolId, SetConfig},
 	peer_store::PeerStoreProvider,
-	request_responses::{IfDisconnected, RequestFailure},
+	request_responses::{IfDisconnected, OutboundFailure, RequestFailure},
 	service::{
 		traits::{Direction, NotificationConfig, NotificationEvent, ValidationResult},
 		NotificationMetrics,