From 7b1e94ffe37e3f8e8ac3a7d3ba1ff5cfe4f60978 Mon Sep 17 00:00:00 2001
From: Pawan Dhananjay <pawandhananjay@gmail.com>
Date: Thu, 24 Aug 2023 05:54:37 +0000
Subject: [PATCH] Revive mplex (#4619)

N/A

In #4431 , we seem to have removed support for mplex as it is being deprecated in libp2p. See https://github.com/libp2p/specs/issues/553 . Related rust-libp2p PR https://github.com/libp2p/rust-libp2p/pull/3920
However, since this isn't part of the official [consensus specs](https://github.com/ethereum/consensus-specs/blob/dev/specs/phase0/p2p-interface.md#multiplexing), we still need to support mplex.

> Clients MUST support [mplex](https://github.com/libp2p/specs/tree/master/mplex) and MAY support [yamux](https://github.com/hashicorp/yamux/blob/master/spec.md).

This PR adds back mplex support as before.
---
 beacon_node/lighthouse_network/Cargo.toml           |  1 +
 beacon_node/lighthouse_network/src/service/utils.rs | 10 +++++++++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/beacon_node/lighthouse_network/Cargo.toml b/beacon_node/lighthouse_network/Cargo.toml
index f71845fed25..925d278ad62 100644
--- a/beacon_node/lighthouse_network/Cargo.toml
+++ b/beacon_node/lighthouse_network/Cargo.toml
@@ -44,6 +44,7 @@ prometheus-client = "0.21.0"
 unused_port = { path = "../../common/unused_port" }
 delay_map = "0.3.0"
 void = "1"
+libp2p-mplex = "0.40.0"
 
 [dependencies.libp2p]
 version = "0.52"
diff --git a/beacon_node/lighthouse_network/src/service/utils.rs b/beacon_node/lighthouse_network/src/service/utils.rs
index 9775f6028ff..65982ce941c 100644
--- a/beacon_node/lighthouse_network/src/service/utils.rs
+++ b/beacon_node/lighthouse_network/src/service/utils.rs
@@ -50,13 +50,21 @@ pub fn build_transport(
         transport.or_transport(libp2p::websocket::WsConfig::new(trans_clone))
     };
 
+    // mplex config
+    let mut mplex_config = libp2p_mplex::MplexConfig::new();
+    mplex_config.set_max_buffer_size(256);
+    mplex_config.set_max_buffer_behaviour(libp2p_mplex::MaxBufferBehaviour::Block);
+
     // yamux config
     let mut yamux_config = yamux::Config::default();
     yamux_config.set_window_update_mode(yamux::WindowUpdateMode::on_read());
     let (transport, bandwidth) = transport
         .upgrade(core::upgrade::Version::V1)
         .authenticate(generate_noise_config(&local_private_key))
-        .multiplex(yamux_config)
+        .multiplex(core::upgrade::SelectUpgrade::new(
+            yamux_config,
+            mplex_config,
+        ))
         .timeout(Duration::from_secs(10))
         .boxed()
         .with_bandwidth_logging();